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  • 1990-1994  (179)
  • 1970-1974
  • 1925-1929
  • 1910-1914
  • 1990  (179)
  • Biochemistry  (136)
  • Industrial Chemistry and Chemical Engineering
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  • 1990-1994  (179)
  • 1970-1974
  • 1925-1929
  • 1910-1914
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Histochemical and biochemical plasticity of muscle fibers in the little brown bat (Myotis lucifugus) (1990)
    Springer
    Journal of comparative physiology 160 (1990), S. 183-186 
    Details
    ISSN: 1432-136X
    Keywords: Histology ; Biochemistry ; Muscle physiology ; Hibernations ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fiber composition, and glycolytic and oxidative capacities of the pectoralis, gastrocnemius, and cardiac muscles from active and hibernating little brown bats (Myotis lucifugus) was studied. The data were used to test two hypotheses: First, since hibernating bats maintain the capability of flight and make use of leg muscles to maintain a roosting position all winter, the fiber composition of the pectoralis and gastrocnemius muscles should not change with season. Second, we tested the hypothesis of Ianuzzo et al. (in press), who propose that the oxidative potential of mammalian cardiac muscle should increase with increasing heart rate while glycolytic potential should not. Our results indicate that the fiber composition of the pectoralis muscle was uniformly fast-twitch oxidative (FO)_ regardless of the time of year, as predicted. However, the gastrocnemius muscle exhibited a change in FO composition from 83% in active to 61% in hibernating animals. Contrary to the variable change in histochemical properties with metabolic state, a trend of reduced maximal oxidative (CS) and glycolytic (PFK) potential during hibernation in both flight and leg muscles was apparent. The oxidative potential of flight and leg muscles decreased by 15.2% and 56.5%, respectively, while the glycolytic potential of the same muscles decreased by 23.5% and 60.5%, respectively. As predicted, the glycolytic potential of cardiac muscle remained constant between active and hibernating bats, although there was a significant decrease (22.0%) in oxidative potential during hibernation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300951
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  • 2
    Electronic Resource
    Electronic Resource
    The Linearity and Response of Focussed AperturesPresented at the 4th European Symposium Particle Characterization, PARTEC, Nürnberg (FRG), 19-21 April 1989. (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 1-5 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Practical experience of particle size analysers using the Coulter principle shows that for measurements made over a range of 2% to 60% of the aperture diameter, the aperture responds linearly to particle volume at least for spheres. In this paper it is shown that the response of a focussed aperture is not significantly different from an unfocussed aperture. It is also shown that a simple linear equation of response successfully applied to a COULTER COUNTER® model ZM in a previous paper, can be used to predict the calibration constant of a new wide range instrument, the COULTER® MULTISIZER.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070101
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  • 3
    Electronic Resource
    Electronic Resource
    A Single Expression of Common Particle Size Distribution (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 127-130 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new particle size distribution function based on a simple model is presented. Data generated by the normal, log-normal and Rosin-Rammler distribution functions were fitted with this new distribution function and the fitted curves were, for all practical purposes, indistinguishable from all three distributions.The new distribution function can replace all the three functions and thus a means of presenting and comparing the different size distribution patterns in terms of a single mathematical expression is obtained. Additionally, the new distribution function provides the possibility of developing the discussion on the physical meaning of the particle size distribution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070124
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  • 4
    Electronic Resource
    Electronic Resource
    Dispersion of Monosized Heavy Particles in Grid Turbulence Effects of Body Forces (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 136-143 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dispersion of monosized drops downstream a point injection in a grid-generated turbulence is studied. Influence of extra bodyforces is also investigated by use of ferrofluid drops and magnetic field. Datas are obtained through LDV and given for fluid and particles mean and fluctuant velocities. Presence probability repartition for particles downstream the injection is obtained by LDV counting.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070126
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of Particle Swelling of Materials of Pharmaceutical InterestPresented in part at the 4th European Symposium on Particle Characterization, PARTEC Nürnberg (FRG) 19-21 April 1989 (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 131-135 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method based on the employment of an electrical sensing zone instrument (Coulter Counter) has recently been proposed for the combined measurement of the increase in particle volume (particle swelling) and granulometric characterization of pharmaceutical tablet disintegrants. The performance of the method, as far as its applicability to limited swelling materials is concerned, has been assessed. Both inert materials (polystyrene latices) and limited swelling disintegrants (maize starch and crospovidone in different granulometric fractions) were examined for total particulate volume in aqueous media. The accuracy and repeatability of measurements of both total particulate volume and particle volume increase were defined. The results obtained indicate that the method may be adapted for measuring the increase in particle volume of so-called limited swelling disintegrants.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070125
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  • 6
    Electronic Resource
    Electronic Resource
    Aerosol Generation from the Sanding, Cutting, and Breaking of Floor Tiles (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 121-126 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various types of floor tile were tested in a controlled and isolated environment to determine quantitatively the wear rate and size characteristics of material generated from floor tile during operations of sanding, cutting, and breaking. Size characteristics were determined for the aerosolized fractions as well as the settled material worn from the tile surface. In addition to the vinyl composition tile, tests were also conducted with floor tile containing various amounts of glass fiber and sodium phosphate fibers. The tests were conducted in a specially designed glove box which allowed complete sampling and fractionization of the generated aerosol. Due to good measurement repeatability, aerosol generation differences from the various flooring types were determinable.A Frick-Taber accelerated wear machine was employed to establish comparative wear rates of the different flooring materials. Test results were repeatable and measured relative wear rates correlate well with published measurements. Results indicate that the presence of up to 13% glass fibers or phosphate fibers in the tile does not improve the tile's wear characteristics or significantly alter the size distribution of the generated material. Although asbestos-containing floor tile was not tested in this study, results from the simulant fiber tile tests may enable prediction of the behavior of vinyl-asbestos tile under the influence of similar wear mechanisms.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070123
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  • 7
    Electronic Resource
    Electronic Resource
    Congratulations to Prof. Dr.- Ing. Dr.-Ing. E. h. Kurt Leschonski on the occasion of his 60th birthday on 17 december 1990 (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 169-169 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070130
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  • 8
    Electronic Resource
    Electronic Resource
    Particle Dispersion in a Swirling Confined Jet FlowPresented at the 4th European Symposium Particle Characterization, PARTEC, Nürnberg (FRG), 19-21 April 1989. (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 16-24 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The characteristics of swirling single- and two-phase flows discharging into a sudden pipe expansion were studied in detail by the use of laser-Doppler anemometry. The results are compared with those for the comparable non-swirling case. The central recirculation zone established for a swirl number of 0.56 was found to have an annular shape, which was a result of the subcritical nature of the flow and the area contraction at the end of the test section.The behaviour of the particles in both swirling and non-swirling flow was studied by flow visualization, particle concentration and velocity measurements. Initially, the spreading of the particle jet is about the same for both cases owing to the particle inertia. In the middle of the recirculation bubble the particles start to spread more rapidly under the acting of centrifugal forces established in a swirling flow. This finally results in a high concentration of particles near the wall of the test section and a particle-free region in the core of the vortex. The numerical simulations of the non-swirling flow showed good agreement for both the gas and particle phases in comparison with the experimental results.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070104
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  • 9
    Electronic Resource
    Electronic Resource
    Use of the Laser Diffraction Technique for Particle Size Measurement at high suspension densitiesPresented at the 4th European Symposium Particle Characterization, PARTEC, Nürnberg (FRG), 19-21 April 1989. (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 25-29 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A laser diffraction technique for the on-line measurement of crystal growth rates was developed. The crystal growth experiments were executed in a fluidized bed apparatus with a specially designed measuring chamber. It is typical in crystallization from solutions to deal with non-spherically shaped particles at high suspension densities (3-25 Vol.-%). The results achieved in a first approach with commercially available instruments were not understandable. It was shown that the particle size distributions from experiments at high suspension densities depend on the volume concentration. This effect was examined by experiments with constant particle sizes and different volume concentrations.If the volume concentration is detected and used to correct the results achieved for the particle size distribution, understandable and reproducible results can be obtained.The necessary correlation function for the measurements at high suspension densities is introduced.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070105
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  • 10
    Electronic Resource
    Electronic Resource
    Technologically Relevant Particle Shape Analysis (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 30-35 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The current state in shape analysis is distinguished by a number of characterization methods, but the great variety of specific shapes complicates the selection of parameters that are relevant for a particular problem. Therefore, the preferred approach is to characterize single particles "free of presupposition" and to select technologically relevant parameters using cluster and discriminance algorithms.Parameter vectors including elongation, bulkiness, fractal dimension and area-equivalent diameter are calculated on the basis of image analysis. First applications to bacteria and agricultural freestuffs exemplify the concept and illustrate that technologically relevant particle shape analysis permits the classification of single particles and the quantification of property functions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070106
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  • 11
    Electronic Resource
    Electronic Resource
    Standard Media for Particle Size and Number-Density Calibrations in single, multiple and dependent scattering (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 36-43 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two kinds of standard media for particle size and number-density measurements and calibration are described. Although the main concern is multiple scattering situations, they might also be useful for single and dependent scattering. One medium is made of particles embedded in a solid polymer matrix and the other of particles embedded in a gel. Transmittance measurements at two wavelengths (visible and far-infrared) are used to exemplify the use of these media.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070107
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  • 12
    Electronic Resource
    Electronic Resource
    People. Arnold-Eucken-Medaille to Professor Dr.-Ing. Kurt Leschonski (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 44-44 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070108
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  • 13
    Electronic Resource
    Electronic Resource
    Particle size analysis (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 44-44 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070109
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  • 14
    Electronic Resource
    Electronic Resource
    Dual-Cylindrical Wave Method for Particle Sizing (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 45-53 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new laser Doppler method for particle sizing has been developed. In contrast to the standard phase Doppler technique, which uses scattering from plane waves for a measurement, the proposed method employs cylindrical waves of incident light. The main advantage is that signal frequency, instead of the signal phase, becomes a function of particle diameter and a standard frequency measuring device may be used as a signal processor. The advantages of spectrum analysis as the signal processing method are highlighted.The laws of geometrical optics applied to the present scattering problem provide a relationship for the frequency of the collected signal which is expressed as the sum of two terms, the conventional Doppler frequency and the "anisotropic frequency", which is directly dependent on the particle size. These theoretical assertions were examined experimentally. Measurements on glass and metal particles of known diameters showed good agreement with the theory.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070110
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  • 15
    Electronic Resource
    Electronic Resource
    Droplet Deposition from a Mist Flow on a Parallel Vertical Wall (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 70-73 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A primarily experimental investigation of the deposition of droplets from a turbulent two-phase suspension flow on a parallel vertical wall has been found to be closely related to the ratio of fluctuation velocity of the droplets to that of the flow and the size of the droplets. Data are obtained for an air-water mist flow parallel to a vertical flat plat at Re = 1.54 × 105 to 4.2 × 105 by the use of a particle-sizing two-dimensional reference-mode laser-Doppler anemometry technique. Although no rigorous theory can be formulated at present due to the complexities involved, however, an analytical attempt is made in the hope of providing an explanation to the physics of the phenomenon. It is based on an apparent turbulent viscosity of the fluid as felt by the moving particles in a turbulent two-phase suspension flow and the most energetic eddy frequency of the flow.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070113
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  • 16
    Electronic Resource
    Electronic Resource
    Calculated Characteristics of Droplet Size and Velocity Distributions in liquid sprays (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 54-59 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Predictions of the droplet size and velocity distributions in sprays under isothermal conditions are reported. The calculations are based on the maximum entropy formalism, complying with the conservation laws of liquid mass, momentum and energy. This theoretical approach considers only the macroscopic quantities about the atomization processes, without resorting to the details of the liquid breakup processes such as the onset and growth of instabilities. The derived joint droplet size and velocity distribution function depends on the Weber number as well as the liquid mass, momentum and energy source terms.These parameters represent the conditions under which the atomization occurs. The droplet velocity distributions are truncated Gaussian distributions for any specific sizes. The nondimensional Sauter mean diameter decreases slightly with the Weber number and then approaches an asymptotic constant. The calculated values of D21/D30 are very close to unity which agrees with the experimental observations. The computations also show that the atomization efficiency is very low; less than 2.6 percent.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070111
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  • 17
    Electronic Resource
    Electronic Resource
    Axial-View Measurements of Particle Motion in a Turbulent Pipe Flow (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 60-69 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes experimental measurements and numerical predictions of the motion of particles of size 500-800 m̈m diameter in a 20 m long (i. e. 620 pipe diameters) vertical tube. The numerical simulations suggest that the particles attain a fluctuating r.m.s. velocity in a direction normal to the axis of the tube which is at least one order of magnitude less than that of the gas phase turbulence fluctuations. However, the measured values are of the same order as the gas phase turbulence fluctuations (i. e. 0.5 to 1 m/s). This discrepancy is likely to occur because of particle/wall interactions and these were investigated in separate experiments. Although the cause of the measured coefficients of restitution in the normal direction being greater than unity was not finally demonstrated, the results indicated strongly that the effects were due to non-ideal bouncing of the particles in the presence of particle spin.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070112
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  • 18
    Electronic Resource
    Electronic Resource
    Use of One-Parameter Models for the Assessment of Particle Interactions by photon correlation spectroscopy (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 74-79 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of very simple one-parameter models of particle interactions for the analysis of the concentration dependence of the collective diffusion coefficient as determined by photon correlation spectroscopy is illustrated by measurements on two different systems. In one, a micro-emulsion, attractive interactions are dominant whereas in the other, a silica dispersion, repulsive interactions play the major role.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070114
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  • 19
    Electronic Resource
    Electronic Resource
    Sizing Nanoparticles by Means of Elliptically Polarized Scattered Light: A suggested method (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 107-112 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Given the paucity of optical methods for sizing nanoparticles (those between 1 and 100 nm), more methods are needed if, as has been predicted, such particles have a bright future. Linearly polarized light is transformed into elliptically polarized light upon scattering by small spheres at 90°. The resulting circular polarization increases as the fifth power of particle diameter and the shift of the azimuth of the vibration ellipse from the vertical increases as the square if the particles are negligibly absorbing. Titanium dioxide spheres (in air) with diameters between 20 and 120 nm give circular polarizations between about 10-5 and 10-1 for incident light of wavelength 450 nm. The corresponding azimuth shifts (in radians) lie between about 10-2 and 1. These values are within reach of experimental techniques based on polarization modulation. Metallic spheres yield much larger circular polarizations and azimuth shifts (with signs opposite those for negligibly absorbing spheres), both of which increase approximately as the square of particle diameter.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070120
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  • 20
    Electronic Resource
    Electronic Resource
    Velocity and Drop Size Measurements in Fuel Sprays in a direct injection diesel engine (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 160-168 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High-pressure injection fuel sprays have been investigated in a single-cylinder research Diesel engine using the laser and phase Doppler anemometry techniques to measure fuel droplet velocities and sizes and their spatial and temporal distributions within the spray. The measurements relate to the determination of the droplets' axial velocity component and diameter on the spray centre line between 75 and 100 nozzle diameters downstream from a single-hole injector nozzle. The experimental program covered the use of both Diesel and a non-combusting alcohol fuel. Measurements at radial locations in the spray and at different fuel loads were also taken for the alcohol fuel. Temporally resolved measurements of droplet velocity and size are presented together with time  -  averaged values in such a way as to isolate the contributions from the leading and trailing regions of each spray and identify two different break  -  up mechanisms occurring as suggested by a conceptual model of the spray behaviour.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070129
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  • 21
    Electronic Resource
    Electronic Resource
    Agglomeration and Solution of Particles During Sedimenation AnalysisPresented at the 4th European Symposium on Particle Technology, PARTEC, Nürnberg, 19-21 April 1989 (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 144-151 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A basic requirement of particle size analysis through sedimentation is the perfect dispersion of the particles in suspension. The dispersion must be perfect and stable. To ensure this, for a number of solids DIN 66111 specifies sedimentation liquids and suitable dispersing agents and defines an upper limit for the concentration of the solids in suspension. Some instruments require higher solids concentrations than are recommended in DIN 66111. However, there is no simple test to prove the stability of a dispersion with sedimenting particles.An effective method for testing the stability of a dispersion is to make a number of simultaneous sedimentation analyses, measuring the concentration of the particles at different distances from the surface of the liquid. If the dispersion remains perfect, identical particle concentrations have to be measured, when the measuring time is normalized to one distance from the surface (e.g. t1′ = t(h3/h1), t2′ = t(h3/h2) …). From the particle concentration, distance from the surface and time, the particle size distribution can be calculated.If the results of the lower (and hence later) measurement show a shift to the larger diameters, agglomeration has occurred. If the sensing technique is light extinction, then the effect is particularly pronounced.A photosedimentometer with three light beams at distances from the surface of 1.5, 15 and 150 mm was used to demonstrate the effect of agglomeration on particle size distribution and to optimize sedimentation liquids and dispersing agents. An attempt was made to determine the kinetics of agglomeration from the increase in transmission of a light beam through a suspension.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070127
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    Application of Laser/Phase Doppler Anemometer to Dispersed Two-Phase Jet Flow (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 152-159 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A confined jet flow involving glass particles was examined to clarify fundamental aspects of the turbulence structure of two-phase flow. Spherical glass particles of mean diameter 62.4 m̈m were loaded in a primary jet at a mass loading ratio of 0.3. The primary jet diameter was 13 mm and exit velocities at the centre line were set at 20 and 30 m/s. The confined pipe diameter was 60 mm and velocities were set at 10 and 15 m/s. The particle and gas flow characteristics, such as local mean velocities, their fluctuations and size distribution, are discussed for three flow conditions which were obtained by changing the velocities of primary and secondary flows.Laser Doppler anemometry was applied to measure the flows of both particles and tracer, discriminated by scattering light intensity, and the precise particle size, for examining the dependence of particle size on the flow, by phase Doppler anemometry. The signal processing of the phase Doppler anemometer was based on a fast Fourier transform method to detect not only Doppler frequency for velocity but also the phase shift of Doppler signals for particle sizing. The processing system consisted of conventional fast analogue to digital converters, multi-digital signal processor units and a host microcomputer.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070128
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  • 23
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    The Kinetics and Shape Factors of Ultrafine Dry Grinding in a laboratory tumbling ball mill (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 242-247 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of batch grinding quartz from a feed of 600 by 425 m̈m to a product of 80% less than 10 m̈m have been determined using screening and laser diffractometer sizing for size analysis. The specific rates of breakage decreased by a factor of about three when the material became less than about 100 m̈m in size, but the primary breakage distribution function also changed to give proportionately more fine material, so that the grinding efficiency expressed as the development of surface area (B.E.T.) per unit of energy input did not decrease. Analysis of the shape of the particles in the 25 × 38 m̈m size range showed that particles of this size produced by roll crushing or by 8 minutes of grinding of a 425 × 600 m̈m feed were not different but at long grinding times the particles were rounded. This suggests that the breakage mechanism changes to give more chipping and abrasion and less disintegrative fracture. As the material approached the ultrafine size range it adhered to the mill case and there was no further size reduction. However, a technique for striking the mill case to dislodge the particles was successful in allowing further grinding to 40% by weight less than 2 μm.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070139
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  • 24
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    Advances in particulate technology (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 256-256 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070142
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  • 25
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    Optical Levitation Experiments for generalized lorenz-mie theory validationDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 248-249 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generalized Lorenz-Mie theory (GLMT) is validated by comparisons between theoretical results and experimental optical levitation data. Selected results are presented.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070140
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  • 26
    Electronic Resource
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    International symposium on polymer analysis and characterization (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 256-256 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070143
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  • 27
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    Bipolar Ion and Electron Diffusion Charging of Aerosol Particles in high purity argon and nitrogenDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 250-255 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The bipolar diffusion charging process is studied theoretically for aerosol particles in high purity argon and nitrogen. The Fuchs theory is extended by the incorporation of the free electron charging of the aerosol particles. The ion parameters for positive and negative ions are assumed to be identical. The influence of the free electrons explains the differences between the mean mobility and mean mass of negative and positive ions. The ratio of the electron number concentration to the number concentration of negative ions is used to fit the curves, calculated by the extended model, to the experimentally determined bipolar charge distribution in argon and nitrogen. The extended Fuchs model was found to be rather insensitive to variations in the mobility and mass compared with the model with four different ion parameters. Further experimental studies of the bipolar charge distribution in a gas mixture of pure nitrogen and sulfur hexafluoride, SF6, indicate the importance of the free electrons in the bipolar diffusion charging process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070141
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  • 28
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    Improved Accuracy in the Measurement of Particle Size Distribution with a coulter counter equipped with a hydrodynamically focused aperture (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 6-10 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is well known that broadening of the observed particle size distribution occurs both at the finer end and at the coarser end of the distribution when using the Coulter Counter. This problem can partly be overcome with the aid of electronic pulse editing. However, it has been found that the accuracy can be further improved when the Coulter Counter is equipped with a hydrodynamically focused (HDF) aperture. The standard deviations of the main peaks of samples with diameters of 5.0, 10.2, 15.1 and 20.0 m̈m decreased by 21%-49% with HDF. HDF also prevents artefacts at the fine side of the main peak that originate from particles re-entering the sensing zone of a standard aperture after they have passed through it. In the experimental model used i.e. a silica sample with a diameter of 15.6 m̈m, the estimate of small particles (〉10 μm) decreased from 6.5% to 0.4%.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070102
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  • 29
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    Improved Resolution and Accuracy in Electrical Sensing Zone particle counters through hydrodynamic focussing (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 11-15 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The electrical sensing zone technique is long established, well researched and widely used. It is often used as a reference method against which others are compared or calibrated. This position should not be allowed to disguise the potential which exists for still greater accuracy and versatility. In this paper the use of the hydrodynamic focussing technique is evaluated and an experimental comparison is made with a normal Coulter stand for several samples. It is clearly shown that hydrodynamic focussing enables higher resolution and accuracy to be obtained for materials with narrow or unusual particle size distributions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070103
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  • 30
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    First Announcements and call for papers international conference on multiphase flows '91 (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 97-97 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070118
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  • 31
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    The Use of Simulated Fractals in Particle Characterization (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 87-92 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The principal focus in this paper is the development of a general method to simulate irregulary shaped particles whose perimeters are fractal. It is shown that this method can produce a particle of almost arbitrary fractal dimension. The Fourier components of these fractals are then computed. It is shown that these components were either independent of the fractal dimension or that any dependence is less important than other properties of the cluster such as symmetry and aspect ratio.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070116
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  • 32
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    Particle Size Analysis by Interaction of Charged Particles with an Alternating Electric Field (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 93-96 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical model for the interaction of charged particles with an alternating current field is developed. This model permits the determination of the particle size distribution by a numerical nonlinear iterative method. Results of numerical simulations are presented and discussed. Restrictions on the applicability of the model as an on-line measuring system are pointed out.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070117
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  • 33
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    Spectral Properties of the Regularized Inversion of the Laplace Transform (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 80-86 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Inversion of the Laplace integral equation, used in the laser scattering measurement of colloidal particle size distributions, presents sever numerical and experimental difficulties. In the presence of noise the variance of the inversion integral is infinite, indicating maximum uncertainty in the accuracy of the inversion. The regularized inversion of the Laplace intergral equation provides a convenient computational algorithm which requires no a priori knowledge of the unknown linewidth distribution. Using the eigenfunction decomposition of the Laplace kernel, the spectral properties of the regularized inversion may be seen.Regularized inversion represents a type of low pass filter which preserves the properties of the inversion spectrum at low frequencies, but provides a cutoff at a point controlled by the regularization parameter. This filtering reduces the variance of the inversion to a finite value. Regularized inversion is somewhere between optimal filtering and the abrupt truncation used in singular value decomposition and other similar methods. Two examples, a monodisperse and a bimodal linewidth distribution, are used to compare the performance of regularized inversion to that obtained through an optimal filter.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070115
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  • 34
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    Constraints On The Size And Shape Of The Receiving Aperture in a phase/doppler system (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 113-115 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using computations based on Mie scattering theory, the influence of the size and shape of the receiving aperture on the signal properties of a phase/Doppler system is examined. For circular apertures exceeding a certain size limit, it is shown that the signal phase is non-monotonic with respect to the particle diameter and exhibits abrupt changes of 180° at certain values of the diameter. This difficulty may be overcome by using rectangular apertures with appropriate aspect ratios.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070121
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  • 35
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    A Statistically Conditioned Averaging Formalism for Deriving Two-Phase Flow EquationsDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 191-202 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A statistical formalism overcoming some conceptual and practical difficulties arising in existing two-phase flow (2 PHF) formulations and modelling techniques is introduced. Basic theorems for the case of dispersed 2 PHF are presented. Phase interaction terms with a clear physical meaning enter the equations and this formalism provides some guidelines to avoid closure assumptions or to close those terms rationally. Continuous phase averaged continuity, momentum, turbulent kinetic energy and turbulence dissipation rate equations can be rigorously and systematically obtained with this methodology in a single step. These equations display a structure similar to that for single-phase flows. It is also assumed that the dispersed phase is well described by a "Boltzmann-type" equation and Eulerian "continuity", momentum and fluctuating kinetic energy equations for the dispersed phase are obtained. A k-ε turbulence model for the continuous phase is used. A gradient transport model is adopted for the dispersed phase fluctuating fluxes of momentum and kinetic energy. Closure assumptions are proposed for the phase interaction terms. This model is then used to predict the behaviour of an axisymmetric turbulent jet of air laden with solid particles varying in sizes and concentrations. Numerical results compare reasonably well with available experimental data.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070133
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  • 36
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    The Origin of Turbulence Acquired by Heavy Particles in a round, turbulent jetDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 203-208 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The paper describes the application of a stochastic separated flow model for the dispersed phase to the prediction of a particle-laden turbulent air jet discharging at 13 m/s from a 15 mm nozzle into stagnant surroundings. Emphasis is placed on the stochastic element of the Lagrangian particle tracking part of the model and on the importance of particle initial conditions over the first 20 jet diameters. Calculations are presented for 80 m̈m sized glass particles which clarify how particles with turbulent Stokes number less than unity acquire axial turbulence much larger than radial. Far from being only a response to the gas-phase turbulence as implied by the model, the axial turbulence is shown to be also produced by an interaction between particle radial turbulence fluctuations and cross-stream spatial gradients in particle mean velocity, here referred to as "fanspreading". In addition, initial particle turbulence levels remain identifiable for about 10 jet diameters; the initial radial turbulence reinforces the fan-spreading contribution and leads to extra generation of axial turbulence farther downstream. In general, the results agree well with experimental measurements.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070134
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  • 37
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    Drop Sizing by Laser Light Scattring Exploiting Intensity Angular Oscillation in the mie regimeDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 221-225 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intensity angular pattern of the light scattered by a drop at a scattering angle of ca. 90° is related to the size of the scattering drop. A simple relationship between the number of fringes per degree and the size is presented. The possibility of measuring the drop size through visualization of the fringe pattern is demonstrated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070136
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  • 38
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    Particle Dispersion in Turbulent Flow: The effect of particle size distributionDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 209-220 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The measured velocity fluctuation of particles in dispersed twophase flow systems is discussed and an interpretation of particle velocity statistics is given. Besides the turbulent velocity fluctuations resulting from the particle's response to the fluid turbulence, two additional apparent fluctuation components may be distinguished, caused by inertial effects of the particles and by a polydisperse particle phase.Especially for larger particles inertial effects may become important and therefore the particle motion in the flow field is strongly governed by the inlet conditions, namely the instantaneous particle velocity. Therefore, the measured axial particle velocity fluctuation at a given location may be considerably increased as particles from different starting locations with different initial velocities may cross the same measuring point. This dynamic particle behaviour is demonstrated by the numerical simulation of particle trajectories in a given flow field. The results show the importance of including appropriate inlet conditions for the numerical prediction of particulate two-phase flows.Further, in experimental realizations of particulate two-phase flows, the particles usually exhibit a certain size distribution. Owing to the different responses of the different sized particles to both the mean flow field and the turbulence characteristics of the flow, the measured particle velocity fluctuations are higher than in the comparable monodisperse case. Therefore, the particle size distribution was taken into account in the present numerical calculations in order to obtain results which are comparable to the corresponding experiments. In this numerical simulation the particle mean velocity and the rms value of the velocity fluctuation were obtained by averaging over the whole particle size distribution and then compared with the measured values. Calculations are presented for two different shaped particle size distributions with a different mean size and compared with calculations with a monosized particle material and experimental results.Further, the behaviour of the different sized particles in the particle size distribution is discussed by considering the changes in the particle size distribution and the particle velocity distribution throughout the flow field.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070135
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  • 39
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    Pulse Holography and Phase-Doppler Technique. A comparison when applied to swirl pressure-jet atomizersDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 226-232 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pulse holography and the phase-Doppler technique are two of the very few methods with which the size and velocity of individual particles within a two-phase flow may be simultaneously measured. This enables the two-dimensional frequency distributions of particle size and velocity to be compiled and allows the existence of mutual correlations to be verified.The application of both methods to investigations into water droplet collections within the hollow spray cone of a swirl pressure-jet atomizer is described. When comparing the results of measurements obtained by the two methods under identical conditions, one fundamental difference must be taken into account: whereas pulse holography delivers space-averaged concentration-dependent frequency distributions, those derived from the phase-Doppler technique are time-averaged fluxdependent. The methods hence deliver different, but equivalent, results. Since the possibility of conversion exists, both representations are always available. As far as the particle size distributions are concerned, the results obtained from the two methods confirm the expected differences, whilst verifying the compliance of the interconverted size distribution data. Regarding the velocity distributions, however, some unexplained discrepancies still remain.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070137
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  • 40
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    Mean Particle Diameters. Part I: Evaluation of definition systemsDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 233-241 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mean particle diameters are important for the science of particulate systems because they provide information on particlesize distributions in such a way that they can be related to physical or physiological processes or product properties. There are different notation systems for such mean diameters which may cause much confusion. This equally applies to their nomenclature. The present paper is concerned with comments on the “Moment-Ratio” and German (DIN) notations. The Moment-Ratio notation is recommended for standardization. A more extensive contribution of statistics to the science of particulate systems is recommended.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19900070138
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  • 41
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    Evaluation of a Commercial Instrument of Sedimentation Field Flow FractionationPresented at the 4th European Symposium on Particle Characterization, Nürnberg (FRG) 19-21 April 1989. (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 99-106 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The analysis of particles in the sub-micron range by sedimentation field flow fractionation (SFFF) is not new, but its commercial exploitation is recent. This inevitably will lead to a rigorous evaluation of the technique by many laboratories, for many applications, as well as to rapid development.This paper describes first an evaluation of the new commercial instrument using both ideal and real materials. These experiments lead to a discussion of the software package and of the influence of experimental conditions. A particular study is described of the combination of the SFFF technique with that of quasi-elastic light scattering. The paper concludes that SFFF now offers the technology for realistically measuring particle size distributions at high resolution in the submicron size range. The analysis time is in the order of one hour, but can be reduced at the expense of resolution.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070119
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  • 42
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    Alignment Errors in Phase Doppler Receiving Optics (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 116-120 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown that if the pinhole in a phase Doppler system' s collection optics is misaligned, even by a matter of micrometers, the effective collection aperture will be different from the aperture of the collection lens. This directly alters the phase characteristics of the resulting signal and can produce systematic and random errors in drop size measurements. The results of misalignment in a simple system are calculated, experimental evidence of the errors presented, and it is shown that replacing pinholes with vertiacl slits will reduce the sensitivity to such errors.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070122
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    Prediction of Gas-Particle Turbulent Free or Confined Jet FlowsDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 171-180 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Numerical predictions of two-phase turbulent gas-particle flows are reported for two test cases: for a plane jet and for an axisymmetric free jet. The numerical algorithm uses an Eulerian approach for the fluid phase and the particulate phase is described by using a Lagrangian stochastic model. The k-ε turbulence model was used to characterize the length and time scales of the fluid. In the plane confined jet the influence of the restitution coefficient on the statistical distribution of velocities was analysed. Particular attention was dedicated to the ε equation corrections regarding the problem of the free jet spreading rate overprediction. The influence of the particle tangential momentum equation on the prediction of particle concentration near the centre line in axisymmetric free jets was also analysed. Comparisons between predictions and experimental data are presented and shown to be satisfactory regarding the incomplete knowledge of turbulent multiphase flows.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070131
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    Lagrangian Stochastic-Deterministic (LSD) Predictions of Particle Dispersion in TurbulenceDedicated to Professor Kurt Leschonski on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 181-190 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Lagrangian model of particle motion in turbulence has been developed. The model is stochastic in the sense that the "instantaneous" fluid velocity field is generated from known turbulence energy and time scales of large eddies by using a random sampling. The particle motion during the interaction with the eddies is deterministic as being predicted from solutions of Lagrangian momentum equations. On the basis of a large number of calculated trajectories, the distributions of local particle mean and fluctuation velocity components and of the mean square particle displacement are evaluated in a flow domain. The results of the predictions for the case of particle dispersion in nearly homogeneous and isotropic turbulence behind a grid are compared with existing experimental data and satisfactory agreement is achieved. The model is also applied to the case of the particle dispersion from a point source in a nonhomogeneous turbulence of fully developed pipe flow. The agreement with experiments is satisfactory for both heavy and tracer particles. An explanation is given for the experimentally observed phenomenon that in some cases heavy particles disperse faster than fluid points.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19900070132
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990) 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110101
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  • 46
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    SCF, MP2, and CEPA-1 calculations on the OH ‥ O hydrogen bonded complexes (H2O)2 and (H2O-H2CO) (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1-18 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Counterpoise corrected ab initio calculations are reported for (H2O)2 and H2O-H2CO. Geometry searches were done in the moment-optimized basis DZP' at the SCF, MP2, and CEPA-1 levels of theory, followed by more accurate single-point calculations in basis ESPB, which includes bondfunctions to saturate the dispersion energy. The final equilibrium binding energies obtained are -4.7 ±0.3 kcal/mol for a near-linear (H2O)2 structure and -4.6 ±0.3 kcal/mol for a strongly bent HOH ‥ OCH2 structure. The energy difference between these systems is much smaller than in all previous ab initio work. Cyclic (C2h) and bifurcated (C2v) transition structures for (H2O)2 are located at 1.0 ±0.1 kcal/mol and 1.9 ±0.3 kcal/mol above the global minimum, respectively. A new partitioning scheme is presented that rigorously partitions the MP2 correlation interaction energy in intra and intermolecular (dispersion) contributions. These terms are large (up to 2 kcal/mol) but of opposite sign for most geometries studied and hence their overall effect upon the final structures is relatively small. The relative merits of the MP2 and CEPA-1 approaches are discussed are discussed and it is concluded that for economical reasons MP2 is to be preferred, especially for larger systems.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110102
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  • 47
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    A data compression method applicable to first-order convergent iterative procedures (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 45-57 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A data compression method is presented that is generally applicable to first-order convergent iterative procedures that employ subspace expansions or extrapolations based on successive correction vectors. This method is based on the truncation of insignificant information in successive correction vectors. Although the correction vectors themselves may be severely truncated with the proposed approach, the final solution vector may be represented to arbitrary accuracy. A feature of the proposed method is that more slowly convergent iterative procedures allow the correction vectors to be more severely truncated without affecting the overall convergence rate. The method is implemented and applied to the iterative Davidson diagonalization method. If the compressed representation of the expansion vectors can be held in main computer memory, then a significant reduction in the I/O requirements is achieved.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110105
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  • 48
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    Partial optimization of large molecules and clusters (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 67-75 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: By examining the displacement coordinate metric three modes of constrained optimization for large molecules and clusters are suggested. The first method corresponds to a conventional optimization using internal coordinates. The second mode has applications with respect to both internal and cartesian coordinates. The final mode is particularly interesting because it can result in computational savings. A mixture of both internal and cartesian coordinates is specified where these coordinates are usually a subset of the molecules or clusters total coordinate set. In the optimization only a subset of the energy derivatives need be evaluated reducing the computational effort associated with the gradient calculation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110108
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  • 49
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    Calculation of the nonlinear optical properties of molecules (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 82-87 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A finite-field method for the calculation of polarizabilities and hyperpolarizabilities is developed based on both an energy expansion and a dipole moment expansion. This procedure is implemented in the MOPAC semiempirical program. Values and components of the dipole moment (μ), polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) are calculated as an extension of the usual MOPAC run. Applications to benzene and substituted benzenes are shown as test cases utilizing both MNDO and AM1 Hamiltonians.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110110
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  • 50
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    Protein structure prediction using a combination of sequence homology and global energy minimization I. Global energy minimization of surface loops (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 121-151 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A procedure has been developed for global energy minimization of surface loops of proteins in the presence of a fixed core. The ECEPP potential function has been modified to allow more accurate representations of hydrogen bond interactions and intrinsic torsional energies. A computationally efficient representation of hydration free energy has been introduced. A local minimization procedure has been developed that uses a cutoff distance, minimization with respect to subsets of degrees of freedom, analytical second derivatives, and distance constraints between rigid segments to achieve efficiency in applications to surface loops. Efficient procedures have been developed for deforming segments of the initial backbone structure and for removing overlaps. Global energy minimization of a surface loop is accomplished by generating a sequence (or a trajectory) of local minima, the component steps of which are generated by searching collections of local minima obtained by deforming seven-residue segments of the surface loop. The search at each component step consists of the following calculations: (1) A large collection of backbone structures is generated by deforming a seven-residue segment of the initial backbone structure. (2) A collection of low-energy backbone structures is generated by applying local energy minimization to the resulting collection of backbone structures (interactions involving side chains that will be searched in this component step are not included in the energy). (3) One low-energy side-chain structure is generated for each of the resulting low-energy backbone structures. (4) A collection of low-energy local minima is generated by applying local energy minimization to the resulting collection of structures. (5) The local minimum with the lowest energy is retained as the next point of the trajectory. Applications of our global search procedure to surface segments of bovine pancreatic trypsin inhibitor (BPTI) and bovine trypsin suggest that component-step searches are reasonably complete. The computational efficiency of component-step searches is such that trajectories consisting of about 10 component steps are feasible using an FPS-5200 array processor. Our procedure for global energy minimization of surface loops is being used to identify and correct problems with the potential function and to calculate protein structure using a combination of sequence homology and global energy minimization.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110115
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    Comparative study of the molecular electrostatic potential obtained from different wavefunctions. Reliability of the semiempirical MNDO wavefunction (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 416-430 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A systematic analysis of the molecular electrostatic potential (MEP) is presented. This study has been performed with a twofold purpose: first, to study the MEP dependence with regard to the quality of the basis set used to compute the ab initio SCF wavefunction and second, to develop and to assess a new strategy for computing isoelectrostatic potential maps using the semiempirical MNDO wavefunction. The only differences between this procedure and the ab initio SCF MEP computation lie in the freezing of the inner electrons and in the origin of the first-order density matrix. The statistical analysis of MEPs computed for a large number of molecules from MNDO wavefunction and ab initio SCF wavefunctions obtained using STO-3G, 4-31G, 6-31G, 4-31G*, 6-31G*, and 6-31G** basis sets points out the ability of any wavefunction to reproduce the general topological characteristics of the MEP surfaces. Nevertheless, split-valence basis sets including polarization functions are necessary to obtain accurate MEP minimum energy values. MNDO wavefunction tends to overestimate the MEP minima depth by a constant factor and shows an excellent ability to reflect the relative variation of MEP minima energies derived from a rather sophisticated (6-31G*) basis set, lacking of the shortcomings detected in the semiempirical CNDO approximation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110403
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    Dynamics of peptides with fixed geometry: Kinetic energy terms and potential energy derivatives as functions of dihedral angles (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 487-492 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Expressions are derived for computing the kinetic energy of a peptide with fixed geometry, in terms of dihedral angles as generalized coordinates; other expressions required for the solution of Lagrange's equations are also presented. The peptide is regarded as held stationary at one end. We also outline the computations that are needed in calculating the components of the third derivative of a potential energy function that consists of a sum of pairwise interatomic interactions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110407
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    Combined application of pair potentials and the MM2 force field for the modeling of ionophores (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 819-828 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Complexes of alkali and alkaline earth cations with organic compounds are modeled by describing ionligand interaction energies with pair potentials and intraligand as well as interligand energies with the MM2 potential. New pair potentials for the interaction of Li+, Na+, K+, Mg2+, and Ca2+ ions are derived on the basis of 30,000 ab initio interaction energy values with 70 selected model ligand molecules. Various problems of the combination of these two basically different potentials are discussed. An application for the K+ complex of 18-crown-6 is presented. For more flexible ligands the introduction of three-body correction terms of the pair potentials seems necessary.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110705
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    Electronic structure and photoelectron spectra of Sb2 and Sb4 from local-spin-density calculations. Model potential for Sb (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 924-929 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry, electronic structure, and photoelectron spectra of Sb2 and Sb4 have been investigated employing the LCGTO-MP-LSD method. For both molecules the geometrical and spectroscopic constants computed using the VWN potential are in very good agreement with the available experimental data. The HeI photoelectron spectra were computed with different potentials (Xα, GL, HL, BH, and VWN). The calculated spectra are in excellent agreement with the experimental ones and the use of the VWN potential gives the most accurate results. The reliable results for molecules complement those for the Sb atom and show that the proposed LSD Model Potential is able to give an accurate description of the structural and spectroscopic properties of the title molecules.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110804
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    Monte Carlo simulations of liquid alkyl ethers with the OPLS potential functions (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 958-971 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Intermolecular potential functions have been developed for use in computer simulations of alkyl ethers. The simple OPLS model was adopted and parameterized to yield good descriptions of bimolecular and ion-molecule complexes as well as to reproduce experimental thermodynamic properties of liquid ethers. The principal testing featured Monte Carlo statistical mechanics simulations for liquid dimethyl ether (DME), ethyl methyl ether (EME), diethyl ether (DEE), and tetrahydrofuran (THF). Average errors of 1-3% are obtained for the computed densities and heats of vaporization including results for THF at pressures up to 5000 atm. The torsional motion about the central C—O bonds in EME and DEE was included in the simulations using rotational potential functions fit to results of molecular mechanics (MM2) calculations. The liquid-state environment is found to have negligible effect on the conformational equilibria.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110808
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    Concise, open-ended implementation of Rys polynomial evaluation of two-Electron integrals (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 972-977 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A quadrature-point-driven implementation of the standard Rys polynomial method for computing two-electron repulsion integrals of gaussian basis functions has been found to be both concise and openended with respect to the angular momentum of the gaussian functions (i.e., s,p,d,f,g,…). These are important features in certain applications, such as molecular properties and property gradients.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/jcc.540110809
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    Free energy perturbation calculations on models of active sites: Applications to adenosine deaminase inhibitors (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 994-1002 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Free energy perturbation calculations were performed to determine the free energy of binding associated with the presence of perhaps an unusual hydroxyl group in the transition state analog of nebularine, an inhibitor of the enzyme adenosine deaminase. The presence of a single hydroxyl group in this inhibitor has been found to contribute -9.8 kcal/mol to the free energy of binding, with a 108-fold increase in the binding affinity by the enzyme. In this work, we calculate the difference in solvation free energy for the 1,6-dihydropurine complex versus that of the 6-hydroxyl-1,6-dihydropurine complex to determine if this marked increase in binding affinity is attributed to an unusually hydrophobic hydroxyl group. The calculated ΔG associated for the solvation free energy is -11.8 kcal/mol. This large change in the solvation free energy suggests that this hydroxyl is instead unusually hydrophilic and that the difference in free energy of interaction for the two inhibitors to the enzyme must be at least ca. 20 kcal/mol. Although the crystal structure for adenosine deaminase is currently not known, we attempt to mimic the nature of the active site by constructing models which simulate the enzyme-inhibitor complex. We present a first attempt at determining the change in free energy of binding for a system in which structural data for the enzyme is incomplete. To do this, we construct what we believe is a minimal model of the binding between adenosine deaminase and an inhibitor. The active site is simulated as a single charged carboxyl group which can form a hydrogen bond with the hydroxyl group of the analog. Two different carboxyl anion models are used. In the first model, the association is modeled between an acetic acid anion and the modified inhibitor. The second model consists of a hydrophobic amino acid pocket with an interior Glu residue in the active site. From these models we calculate the change in free energy of association and the overall change in free energy of binding. We calculate the free energies of interaction both in the absence and presence of water. We conclude from this that the presence of a single suitably placed-CO-2 group probably cannot explain the binding effect of the-OH group and that additional interactions will be found in the adenosine deaminase active site.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110811
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    Pseudopotential calculations for methyl compounds of zinc and magnesium (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1029-1037 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Pseudopotentials and valence basis sets to be used in calculations for organometallic compounds of zinc and magnesium have been tested in calculations for the M(CH3)n (M = Zn, Mg; n = 1,2) molecules. Valence correlation effects are treated at the SDCI and CEPA levels. The capability of a polarization potential on zinc to account for the valence shell contracting effect of core valence correlation is studied. Properties considered are geometries, force constants, Mulliken populations, ionization potentials, atomization, and binding energies. Differences in bonding between the two dimethyl compounds are discussed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110905
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  • 59
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    AM1 study of acid-catalyzed hydrolysis of maleamic (4-amino-4-oxo-2-butenoic) acids (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1094-1100 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The acid-catalyzed hydrolysis mechanisms of maleamic (4-amino-4-oxo-2-butenoic) acids were studied using AM1 method. The reaction proceeded mainly in two steps: (1) nucleophilic attack of the undissociated carboxyl group on the adjacent aminocarbonyl carbon via a zwitterionic intermediate; and (2) the rate-determining proton transfer to form the zwitterionic tetrahedral intermediate. In each step, the hydration of water and hydronium ion molecules was important in stabilizing the polarized intermediates. The substituent effects at the amide moiety and the 2,3-positions of the maleamic acids were qualitatively estimated for each step.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110913
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990) 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540111001
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    The application of molecular similarity calculations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1139-1146 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A prescription for applying the method of molecular similarity calculations based on electrostatic potentials and fields is developed by consideration of a typical structure-activity series. Firm conclusions are drawn about the nature of the grid of points surrounding the molecules and about the choice of geometry, but options for point charges are less clearcut.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540111004
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    Combinatorial models and algorithms in chemistry. The expanded Wiener number - a novel topological index (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 899-908 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An expanded form of the Wiener number is suggested for characterization of molecular graphs and structure-property correlations. The simple, computer-oriented method for counting of the novel index is briefly discussed.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110802
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  • 63
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    Automated conformational analysis: Directed conformational search using the A* algorithm (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1193-1205 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A common requirement in conformational analysis is the identification of a molecule's lowest energy conformations. The application of the A* algorithm to this problem is examined. The algorithm uses heuristic information about the problem domain to direct the search and has been implemented in a system for performing automated conformational analysis. The method is detailed and sample results presented. Some limitations of the approach are identified.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540111012
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    Correlation of the acidity of substituted phenols, anilines, and benzoic acids calculated by MNDO, AM1, and PM3 with Hammett-type substituent constants (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1009-1016 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Heats of formation and net atomic charges of some 120 structures involving substituted phenols, anilines, and benzoic acids and the corresponding anions were calculated by MNDO, AM1, and PM3 semiempirical methods. The gas phase acidities of substituted phenols and anilines and the net atomic charges on the anionic heteroatoms of the corresponding anions have been successfully correlated with σ- constants. Moreover, good correlations with σ were found for the charges on the acidic hydrogens of substituted phenols and anilines. In contrast, the gas phase acidities of substituted benzoic acids and the charges on the anionic oxygens of the corresponding anions are better correlated with Taft σ° constants. Comparisons of these results with experimental data and ab initio theoretical calculations indicate that AM1 and PM3 methods are much better than MNDO in predicting the acidity of aromatic compounds.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110902
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    Comparative study of imidazole hydration: Ab initio and electrostatic calculations vs. Cambridge structural database analysis (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1038-1046 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We studied geometries and energies of complexes between water and neutral or protonated imidazole by ab initio molecular orbital calculations using the 4-31G basis set with and without the counterpoise correction. Positions of hydration sites and relative binding energies could be also estimated by using the electrostatic field map of imidazole as calculated by our bond increment method. The reliability of the calculations is confirmed by comparing the geometries of the imidazole-water complex to the experimental ones from the Cambridge Structural Database. These were obtained by X-ray diffraction studies on crystals with water bound to a molecule containing the imidazole fragment.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110906
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    Molecular mechanics calculations of several lanthanide complexes: An application of the random incremental pulse search (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1061-1071 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new method for the evaluation of metal complexes with molecular mechanics calculations is described. The method has been employed to determine the global minimum energy conformations of three seven-coordinate lanthanide complexes. The method searches the potential energy surface of the metal complexes for the global minimum structure using the recently reported Random Incremental Pulse Search (RIPS). The molecular mechanics calculations were performed using the MM2 metal-extended force field (MM2MX). This force field excludes 1-3 bending terms about the metal center and, instead, explicitly includes 1-3 nonbonded van der Waals interactions. This affords a model based mainly on steric interactions about the ligating atoms, and removes the necessity of specifying ligand-metal-ligand bond angles for seven-coordinate and higher metal complexes in which no preferred bond angle can be proficiently determined. The calculated minimum-energy structures were well known seven-coordinate conformations in all cases, and a comparison with X-ray crystallographic is presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110908
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    MRD-CI calculations of proton affinity within the ab initio method for approximation of the frozen molecular fragment (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1076-1079 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The method of approximation of the frozen molecular fragment (FMF) we derived has been applied to calculations of proton affinities. Results are in good agreement with experimental data and extended basis set calculations.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/jcc.540110910
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    Molecular mechanics study of myelin basic protein peptide 87-118: Some local energy minima (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1087-1093 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Myelin basic protein (MBP) is the major extrinsic protein of the myelin sheath in the central nervous system. It is this protein that is destroyed in such demyelinating diseases as multiple sclerosis. We have examined the predicted structures of one segment of MBP using the molecular mechanics program ECEPP83 developed by Scheraga and co-workers as modified by Chuman, Momany, and Schafer. We have focused upon a segment, 87-118, containing the Pro-Pro-Pro sequence (residues 100-102), which has been predicted from standard algorithms to exist in a hairpin loop connecting anti-parallel beta-strands. Several local energy minima have been found and reported. Tripoline sequences are not rare in proteins, but their structure and function is still uncertain.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110912
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    PRODEN: A new program for calculating integrated projected populations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1101-1110 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Two new computational methods for the evaluation and partitioning of projected, planar, and averaged slab electron densities, implemented in the program PRODEN, are presented. The new algorithms for the projection, demarcation, and integration of electron densities are described and evaluated in terms of speed and numerical accuracy. Integrated Projected Populations are analyzed and some of the advantages and limitations of the methods are discussed.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110914
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    The effect of diffuse functions on minimal basis set superposition errors for H-bonded dimers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 930-942 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The effect of the addition of diffuse functions of sp type on the first row atoms (and/or of d type on phosphorus) to a MINI-1 minimal basis set is evaluated by comparing the SCF description of the interaction energy and its decomposition, counterpoise (CP) corrected and uncorrected for basis set superposition errors (BSSEs), with that produced by extended basis sets (6-31G** and 3-21G+) as well as by basis sets (6-31G** + VPS and (2d)S), previously successfully tested, designed to minimize the BSSE. The systems considered are a few anions (F-, HCOO-, H2PO-4) H-bonded to water; the basis set performance on a different geometry (bifurcated instead of linear) of the phosphate-water adduct was also considered. An additional comparison with the interaction energy in a neutral dimer, (HF)2, was carried out. The addition of diffuse functions to the MINI-1 basis set, instead of resorting to extended basis sets, seems to be a sensible choice for anions. The equilibrium distance is shifted towards the reference basis set value at the CP corrected level as well as at the uncorrected one. The spread of the energy due to the basis set is hardly distinguishable when the CP corrected values are plotted. The description of the interaction energy in dimers involving phosphorus is improved using d type diffuse functions.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110805
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990) 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110901
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    Theoretical analysis of the electronic spectrum of GeH4 from ab initio CI calculations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1017-1020 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio CI calculations using pseudopotentials to describe germanium inner electrons are carried out on the low-lying excited singlet states (T2) of GeH4. A theoretical analysis of these states in terms of Mulliken population of Rydberg orbitals for each state and oscillator strengths allow us to reinterpret its experimental Vacuum UV electronic spectrum.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/jcc.540110903
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    GEPOL: An improved description of molecular surfaces. I. Building the spherical surface set (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1047-1060 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The algorithm used by the program GEPOL to compute the Molecular Surface (MS), as defined by Richards, is presented in detail. GEPOL starts like other algorithms from a set of spheres with van der Waals radii, centered on the atoms or group of atoms of the molecule. GEPOL computes the MS by first searching the spaces inaccessible to the solvent and consequently filling them with a new set of spheres. Here we study the behavior of the method with its parameters, presenting several examples of application.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110907
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    A boundary element method for molecular electrostatics with electrolyte effects (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1080-1086 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A boundary element method is developed to compute the electrostatic potential inside and around molecules in an electrolyte solution. A set of boundary integral equations are derived based on the integral formulations of the Poisson equation and the linearized Poisson-Boltzmann equation. The boundary integral equations are then solved numerically after discretizing the molecular surface into a number of flat triangular elements. The method is applied to a spherical molecule for which analytical solutions are available. Use is made of both constant and linearly varying unknowns over the boundary elements, and the method is tested for various values of parameters such as the dielectric constant of the molecule, ionic strength, and the location of the interior point charge. The use of the boundary integral method incorporating the nonlinear Poisson-Boltzmann equation is also briefly discussed.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110911
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    General quantum mechanical operators. An open-ended approach for one-electron integrals with Gaussian bases (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 105-111 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A universal computational approach for evaluating integrals over gaussian basis functions for general operators of the form \documentclass{article}\pagestyle{empty}\begin{document}$$x^{k_x } y^{k_y } z^{k_z } \{ (\frac{\partial }{{\partial x'}})^{l_x } (\frac{\partial }{{\partial y'}})^{l_y } (\frac{\partial }{{\partial z'}})^{l_z } \frac{1}{{r'}}\} (\frac{\partial }{{\partial x}})^{m_x } (\frac{\partial }{{\partial y}})^{m_y } (\frac{\partial }{{\partial z'}})^{m_z } x^{n_x } y^{n_y } z^{n_z }$$\end{document} is presented. The implementation is open-ended with respect to the types of basis functions (s, p, d, f, g, h…) and with respect to the integers that specify the operator. These one-electron integrals comprise operators associated with electrical and magnetic properties of molecules and include those needed to find multipole polarizabilities, multipole susceptibilities, chemical shifts, and so on. The scheme also generates the usual kinetic, nuclear attraction, and overlap operators.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110113
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    Computational chemistry applied to the design of chiral stationary phases for enantiomeric separation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 181-193 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A general computational scheme for the rational design of chiral stationary phases for the chromatographic separation of enantiomers has been established. The developed scheme was based on applying different interaction models (force field methods versus semi empirical quantum chemical methods), different docking algorithms (systematic grid search methods versus interactive methods guided by rules based on binding modes) and different levels of approximations (rigid versus flexible docking) to a representative test problem containing the 3,5-dinitrobenzoyl group. The computational methods in use covered the most sophisticated methods which could presently be applied to problems of such a size (about 80 atoms). It has been shown that the current computational approaches using rigid body approximations for the docked molecules and simple molecular mechanics (not taking pi-“effects” into account) are invalid in view of the required predictive precision of about 1-2 Kcal/mole for the differential binding energy. Another surprising result was the failure of the commonly used systematic search methods in determining the most favorable binding modes. Based on our calculations on the representative test problem we propose a new arrangement for the most stable complexes without parallel stacking of the aromatic pi-donor and the 3,5-dinitrobenzoyl pi-acceptor systems.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110204
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    On the enumeration and generation of polyhex hydrocarbons (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 223-235 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A novel efficient computer-oriented approach, based on the DAST (dualist angle-restricted spanning tree) code, is introduced for enumeration and generation of planar polyhex hydrocarbons. It is much faster than other approaches in the literature. The numbers of planar polyhex hydrocarbons with 14 hexagons are reported for the first time.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110208
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    Effects of computational variations for determining binding energies of diastereomeric complexes when using MM2 (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 242-248 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Variations of a procedure have been examined for minimization of the energies, calculated using MM2, of two docked molecules. After doing the intramolecular minimization of the individual molecules, randomized orientations of the rigid molecules were brought together to form complexes and the nonbonded energies of interaction were then minimized. Next, pairs having energies within 4.0 kcal/mol of the most stable pair were minimized further by atom-by-atom relaxation of the complex. Only two repetitions of the last two steps were found to give values within 0.001 kcal/mol in more than 90% of the cases. Compared to two other variations of the procedure, this method appeared to avoid erroneous (local, not global) minima. Finally, this overall procedure was tested against chromatographic data in the literature. Using only the most stable comformer of each species, the results appeared to be in qualitative agreement with fractionation data for enantiomeric aminoethanes on a chiral packing very similar to the one modeled here.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110210
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  • 79
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    η5-P- or η4-P-Coordination in apically oxygenated phosphoranes? An ab initio study of PH4O-, PH4O- · E (E = Li+, NH4+, and HF) and related fluorinated oxyphosphoranes (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 249-264 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Structural optimizations of the apically substituted isomer of PH4O- and the diapically substituted isomer of PH3FO- with diffuse-function augmented 3-21G* basis sets and with the 6-31 + G* and 6-31 + + G* basis sets result in P-η4-coordination in these anions. The structures obtained are those of a hydride or fluoride ion “solvated” by or complexed with phosphine oxide, rather than phosphoranes. In contrast, 3-21G* basis sets without diffuse functions on the atom in the trans-apical position with regard to the oxy-substituent yield P-η5-phosphorane structures that appear to be computational artifacts of the small basis set; the formation of the P-η4-geometries is curtailed by the insufficient functional description of the potential trans-apical nucleophilic leaving group. The overall neutral apical isomers of PH4O- · E(E = Li+, NH4+), the diapical isomer of PH3FO-Li+, as well as the model-solvated apical isomer of PH4O- · HF favor P-η5-phosphorane geometries at all of these computational levels. The mechanism by which the E-group alters the electronic structures within PH4Oa- is discussed based on the geometries, the molecular orbitals, and electron density analysis techniques.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110211
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    Theoretical study of adsorption of hydrocarbons on graphite (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 291-296 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The adsorption of methane, ethane, propane, n-butane, ethylene, propene, 1-butene, 1,3-butadiene, acetylene, benzene, toluene, naphthalene, anthracene, and pyrene on the basal plane of graphite has been studied by means of a semiempirical method proposed by Fraga based on a 1/R expansion of atom-atom pair potentials. The energies of interaction obtained agree reasonably well with experimental data and statistical calculations. The orientation of the adsorbed molecules relative to the graphite surface rendered by Fraga's method improves the picture provided by other calculations with empirical potentials. These results display Fraga's method as an economical alternative for the study of physisorption of hydrocarbons on the graphite surface.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110303
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    On the validity of polarization and correlation additivity in ab initio molecular orbital calculations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 311-313 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A common approximation used in ab initio molecular orbital calculations assumes that the changes in energy due to use of a larger basis set (as in the inclusion of polarization orbitals) and to allowance for electron correlation are additives. Thus, small basis sets may be used for correlated ab initio calculations, resulting in a great savings in time. While this approach has been shown to perform acceptably in some cases, a systematic study has not been published. We examined 35 species and computed the heats of reaction for 15 processes at the 6-31G level of theory using polarization and correlation correction up to the MP4 level. The same items were then treated by an additive procedure to attain the same level of theory. We also examined the conrotrary ring opening of cyclobutene. Our results indicate that the errors do cancel to some extent but that the uncertainty associated with open shell species is significantly larger than closed shell systems. This calls into question the use of the procedure in predicting the properties of transition states.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110305
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    First and second derivative matrix elements for linear and out-of-plane bending motion (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 336-345 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Simplified formulas for first and second derivatives of the internal coordinates with respect to Cartesian coordinates are reported for linear and out-of-plane bending motion. They are expressed in a local coordinate system and then rotated to a space-fixed Cartesian coordinate system. For linear motion the important points are: (1) the invariance of the energy with respect to translational and rotational coordinate transformations and (2) the presentation of derivatives of the energy in terms of (α - π)2 rather than (α - π), where α is the bond angle, to avoid indeterminant forms. By factoring the second derivatives of the energy with respect to (α - π) and sinα, analysis in this local coordinate system avoids division by sinα as α → π. The formulas describe linear systems without the need to project the motion onto two perpendicular planes. When the angle is exactly π two degenerate directions arise, and the coordinate axes perpendicular to the axis of the linear sequence of atoms may be chosen arbitrarily. Further refinements and clarifications of methods reported previously to obtain matrix elements for linear and out-of-plane motion are presented.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110308
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    On the use of series to integrate rate equations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 382-395 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The coefficients in power series, in the variable time, describing coupled nonlinear chemical reactions are easily obtained from a recursion relation. Since these series have a limited radius of convergence they are not very useful as such. If the series are inverted to give time as a function of the appropriate power of a progress variable, the new series converge over the entire time course of the reaction. If, further, the long-time asymptotic behavior, obtained from the linearized kinetic equations, is used, one can obtain a series expansion for a function that describes the correct short-time behavior. This function can be estimated very well using truncated series. The method works well for consecutive nonlinear reactions where the progress variables are monotonic functions of time; this includes many cases where the concentrations of intermediate species go through a maximum as the reaction progresses.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110313
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    Calculating electrostatic forces from grid-calculated potentials (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 401-409 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The accurate calculation of forces from finite difference potentials is very important, especially in the area of Brownian dynamics simulations. Test charge methods are typically used to calculate these forces. In these methods, the potential is calculated with one group of charges present, then the force on a second set of charges is calculated as the negative of the gradient of the potential times the charge. The test charge methods for calculating forces between solute molecules have been compared with more accurate methods and then regions of validity of the test charge methods explored. The test charge methods neglect certain reaction field effects. It is found for the simple charged systems studied that beyond a center-to-center separation of about twice the sum of the molecular radii the test charge approximations can be quite good. For polar molecules with no net charges, however, the corrections can be significant to even longer ranges.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/jcc.540110315
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    Atomic charges derived from semiempirical methods (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 431-439 
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: It is demonstrated that semiempirical methods give electrostatic potential (ESP) derived atomic point charges that are in reasonable agreement with ab initio ESP charges. Furthermore, we find that MNDO ESP charges are superior to AM1 ESP charges in correlating with ESP charges derived from the 6-31G* basis set. Thus, it is possible to obtain 6-31G* quality point charges by simply scaling MNDO ESP charges. The charges are scaled in a linear (y = Mx) manner to conserve charge. In this way researchers desiring to carry out force field simulations or minimizations can obtain charges by using MNDO, which requires much less computer time than the corresponding 6-31G* calculation.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110404
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  • 86
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    Variable step molecular dynamics: An exploratory technique for peptides with fixed geometry (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 468-486 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new algorithm is presented for performing molecular dynamics simulations of peptides with fixed geometry, with the aim of simulating conformational changes and of exploring conformational space. The principle of the method is to expand the potential energy as a Taylor's series in the coordinates around the current point, retaining the force and its first two derivatives, and obtain a series solution of the resulting differential equations using a method due to Lyapunov. By choosing the time step so that the second term in the series is small compared to the first, the true solution can in principle be approximated to any desired degree of accuracy. The algorithm has been used to solve numerically Lagrange's equations of motion for N-acetyl alanine amide and N-acetyl methionide amide, regarded as fixed at their C-termini, under the influence of the ECEPP/2 potential energy function, and time steps of 15-30 fsec have been achieved with little variation in the total energy. Possible directions for future development are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110406
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  • 87
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    Use of parallel processing in the study of protein. Ligand binding (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 314-325 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have undertaken an energy minimization study of the binding of a small ligand, water, to amino acid side-chains. These calculations have been performed on a Meiko Computing surface containing a small number of transputers and on a larger transputer array installed at Edinburgh University. The aim of this study is twofold. First, we wished to compare these potential energy maps for a given side-chain as a function of the local secondary structure and also of the neighboring residue types. Secondly, the energy maps are found to be in good agreement with experimental distributions on the binding of water molecules to amino acid side-chains. The use of our in-house Meiko computing surface increases the speed of these calculations by a factor of about 25 over a VAX 11/750. With larger arrays of transputers, such as that at Edinburgh “concurrent” Supercomputer Project, we achieve increases in speed of over 200 such that these energy maps can be calculated at interactive speeds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110306
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  • 88
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    A structural approach to calculate physical properties of pure organic substances: The critical temperature, critical volume and related properties (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 493-510 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new approach based on computation of the molecular surface interactions (MSI) to estimate several physical properties of pure organic substances is described. MSI are derived from molecular structural data and consist of total molecular surface area, electrostatic molecular surface interactions, and a hydrogen bonding term. This new approach estimates the critical temperature and the molar critical volume of pure organic substances with molecular weights in the range of 40-500 a.u‥ In addition, the following properties can be calculated: the critical pressure, the boiling temperature, the molar volume in liquid state at normal pressure and temperature. The method can be used to predict physical properties of compounds having flexible or rigid, symmetric or asymmetric, polar or nonpolar molecular structures, and compounds with or without hydrogen bonding groups.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110408
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  • 89
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    Theoretical studies on the alkaline hydrolysis of N-Methylcarbamates (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 524-530 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The reaction mechanisms of the alkaline hydrolysis of N-methylcarbamates were studied using the AM1 method by assuming two possible pathways: (1) nucleophilic attack of hydroxide ion on the carbonyl carbon to give a tetrahedral complex followed by its breakdown to carbamic acid (BAC2); and (2) proton abstraction by hydroxide ion at the nitrogen atom followed by elimination of the alkoxide ion to form N-methyl isocyanate (E1cB). Reaction coordinate analysis showed that the reaction mechanism is determined by both the stability of an intermediate and the energy barrier for elimination.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110411
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  • 90
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    Comments on a comparison of AM1 with the recently developed PM3 method (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 541-542 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A reparameterized version (PM3) of AM1 has recently been reported and the results for several hundred molecules compared with those from AM1 itself. The comparison implied that PM3 represents a significant improvement over the earlier treatment. The apparently poor performance of AM1 is, however, due to the inclusion of “AM1 results” for elements (A1,P,S) for which AM1 parameters were unavailable. If these are omitted, PM3 is seen to be only marginally better than AM1. Since this conclusion refers only to a specific set of stable molecules, it is not clear whether even this small improvement will apply to other species or studies of reactions. It is in any case insufficient to justify the confusion caused by the release of the new treatment.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110413
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  • 91
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    A new algorithm for solving large inhomogeneous linear system of algebraic equationsCommunication No. 652 from the Solid State and Structural Chemistry Unit. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 545-547 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An algorithm based on a small matrix approach to the solution of a system of inhomogeneous linear algebraic equations is developed and tested in this short communication. The solution is assumed to lie in an initial subspace and the dimension of the subspace is augmented iteratively by adding the component of the correction vector obtained from the Jacobi scheme on the coefficient matrix A (ATA, if the matrix A is nondefinite) that is orthogonal to the subspace. If the dimension of the subspace becomes inconveniently large, the iterative scheme can be restarted. The scheme is applicable to both symmetric and nonsymmetric matrices. The small matrix is symmetric (nonsymmetric), if the coefficient matrix is symmetric (nonsymmetric). The scheme has rapid convergence even for large nonsymmetric sparse systems.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110502
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  • 92
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    Electronic Resource
    Solvent effect and librational entropy calculations on N-acetylalanylglycine amide (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 573-575 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Entropy and solvent effects are calculated for some conformations of Ala-Gly. The inclusion of these effects in energy calculations show the βII type structure to be the most stable.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110506
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  • 93
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    Computing the electric potential of biomolecules: Application of a new method of molecular surface triangulation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 603-622 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new method is presented for defining a smooth, triangulated analytic surface for biological molecules. The surface produced by the algorithm is well-suited for use with a recently developed polarizationcharge technique1 for the computation of the electrostatic potential of solvated molecules, and may also be used for calculations of molecular surface areas and volumes. The new method employs Connolly's definitions of contact, reentrant and saddle surface,2 but includes modifications that preclude the presence of self-interesting reentrant surface, and also insure a rigorous decomposition of contact regions into curvilinear finite elements. The triangulation algorithm may be used in conjunction with the electrostatic methods described previously to compute the electric potential of molecules of arbitrary shape in solution. Applications include the estimation of hydration enthalpies, computation of the electrostatic forces associated with solvation, estimation of interactions between separate charged species in solution, and computation of the three-dimensional form of the molecular electric potential. Test calculations are presented for a double-stranded dinucleotide, the polypeptide enkephalin, and the protein ferredoxin.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110509
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  • 94
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    The anomeric effect: Ab-initio studies on molecules of the type X—CH2—O—CH3 (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 765-790 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The anomeric effect of the functional groups X = C≡N, C≡CH, COOH, COO-, O—CH3, NH2, and NH+3 has been studied with ab initio techniques. Geometry effects upon rotation around the central C—O bond in X—CH2—O—CH3 have been compared in the various compounds. The energy differences between the conformers with a gauche and trans (X—C—O—C) arrangement were calculated at the 6-31G* level in the fully optimized 4-21G geometries. Energy differences calculated at the 4-21G level appeared not to be reliable, especially for the groups X that contain non-sp3 hybridized atoms. The 6-31G* energy differences indicate a normal anomeric effect for X = COO-, O—CH3, and NH2(g+) (ca. 13 kJ/mol) and a small anomeric effect for X = COOH, C≡N, and C≡CH (ca. 6 kJ/mol). For X = NH2(t) and NH+3 a reverse anomeric effect occurs. These observations are in line with experimental results and evidence is given for a competition among various stereoelectronic interactions that occur at the same anomeric center. Geometry variations can be understood in terms of simple rules associated with anomeric orbital interactions. Trends followed when the group X is varied cannot be related in a straightforward way to the energy differences between the trans and the gauche forms in these compounds. Only the variation in the gauche torsion angle X—C—O—C follows roughly the same trend.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110702
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  • 95
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    Computer generation of distance polynomials of graphs (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 829-836 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computer program is developed to compute distance polynomials of graphs containing up to 200 vertices. The code also computes the eigenvalues and the eigenvectors of the distance matrix. It requires as input only the neighborhood information from which the program constructs the distance matrix. The eigenvalues and eigenvectors are computed using the Givens-Householder method while the characteristic polynomials of the distance matrix are constructed using the codes developed by the author before. The newly developed codes are tested out on many graphs containing large numbers of vertices. It is shown that some cyclic isospectral graphs are differentiated by their distance polynomials although distance polynomials themselves are in general not unique structural invariants.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110706
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  • 96
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    Diazonium ions. Topological electron density analysis of cyclopropeniumyldiazonium dications and of their stability toward dediazoniation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 663-679 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Results are presented of topological analyses of the electron density functions of cyclopropeniumyldiazonium dication, 1, of its 2,3-diamino derivative, 2, and of their products 3 and 4, respectively, formed by dediazoniative ring-opening. The new CN-bonding type in 1 and 2, recently realized synthetically in derivatives of 2, is compared to prototypical aliphatic diazonium ions with regard to electronic structure and thermodynamic stability, factors that both are crucial for the appreciation of the mechanisms of deamination reactions of chemical and biochemical significance. Association of the dication with N2 involves density accumulation in the CN bonding region, occurs without major overall charge transfer, and leads to an electrostatically favorable quadrupolar charge distribution in the diazonium ion. The CN-bonding model recently proposed for aliphatic diazonium ions also applies to these dications. 1 is thermodynamically stable while the dediazoniation of 2 is exothermic but kinetically hindered. Our best estimates for the reaction energies of the dediazoniations 1 → 3 + N2 and 2 → 4 + N2, respectively, are 65.5 and -7.2 kcal/mol, respectively. We have found that, in general, the cation is destabilized and that N2 is stabilized upon CN-bond cleavage. Cations force N2 to form diazonium ions. The remarkable difference between the stabilities of 1 and 2 is primarily due to the larger destabilization of the open dication 3 compared to 4. Push-pull interactions between the diazo- and the overall electron-withdrawing amino-functions characterize the electronic structure of 2. CN-Bonding and the overall electronic structure of 2 are incompatible with the usual Lewis resonance notations. Instead of dismissing the Lewis notations, it is shown that the topological description can be reconciled with the Lewis notations if the resonance forms are interpreted in a way that appropriately reflects the atom populations and first moments. Implications of the model with regard to reactivity are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110602
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  • 97
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    Design and application of a molecular mechanics force field for alkyl iodides including an electrostatic polarization model (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 734-742 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We describe a force field extending Boyd and Kesner's molecule mechanics treatment of alkyl chlorides, fluorides and bromides to alkyl iodides: accordingly, as well as parameters for the potential energy of bond stretching and bending and for interactions between nonbonded atoms, the field includes parameters taking into account permanent and induced C-I dipoles, whose values have been estimated by fitting the model to experimental dipole moment data. The results of applying this force field to 22 organic iodides comprising several substitution series are reported, and the structural and energy trends in the various series are discussed. These results agree satisfactorily with available experimental data and with those obtained by A. Y. Meyer using a different kind of force field.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110606
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  • 98
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    Computer generation of character tables of generalized wreath product groups (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 589-602 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Algorithms and computer codes in FORTRAN 77 are developed for the computation of characters of generalized wreath product groups through generating function methods. Characters of generalized wreath product groups of symmetric groups are computed in terms of the characters of much smaller composing groups using plethysms of S-functions. The developed codes were tested for many generalized wreath product groups. The character tables of generalized wreath products, S2[S3, S2, S2] (NMR group of hexane) and S4[S3] containing 576 and 31,104 elements, respectively, were constructed as examples.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110508
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  • 99
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    Electronic Resource
    Effect of basic set quality and electron correlation on the scale factors of a harmonic force field (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 623-628 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The completely optimized structure and harmonic force field of s-trans-buta-1,3-diene are reported at the MP2/6-31G and MP2/6-31G* levels of computation. Sets of empirical scale factors for the calculated force fields are derived and compared with the corresponding values computed at the RHF/4-31G and RHF/6-31G levels. Changes in the scale factors for this series of force fields are discussed. The vibrational frequencies are also reported for thirteen isotopomers of s-trans-buta-1,3-diene using the MP2/6-31G* force field. Some characteristics of the gauche and cis forms of buta-1,3-diene are also given.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110510
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  • 100
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    Masthead (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990) 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110601
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