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  • 1995-1999  (440)
  • 1997  (440)
  • Industrial Chemistry and Chemical Engineering  (228)
  • Analytical Chemistry and Spectroscopy  (212)
  • Nuclear reactions
Material
Years
  • 1995-1999  (440)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 144-148 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the liquid phase hydrogenation of 4-tert-butylphenol to form cis- and trans- 4-tert-butylcyclohexanol at 1.0-10.0 MPa and 40°C in isopropanol over a Rh catalyst has been studied. The kinetic behavior of this parallel system is described by a proposed reaction network. Keto-enol tautomeric transformation of adsorbed 4-tert-butyltetrahydrophenol and 4-tert-butylcyclohexanone is thought to be a key step, which governs the stereoselectivity of the overall complex reaction of alkylphenol hydrogenation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 138-143 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The gas-phase hydrogenation of buta-1,3-diene to but-1-ene, trans- and cis-but-2-ene and butane has been performed over 0.5% Pd/γ-Al2O3 catalyst. The reaction has been investigated at atmospheric pressure and 0°C over a wide range of conversions. The kinetic model based on the present day knowledge of reaction mechanism has been advanced. The parameters of the kinetic model have been estimated through statistical data fitting. The kinetic model provides a fairly good description of selectivity in the whole range of conversions.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 149-161 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The following article concerns emulsification reaction in a continuous screw loop reactor. The influence of hydrodynamics on the emulsification process as well as the influence of some specific substances were examined. We produced oil/water model emulsions under different test conditions and we determined the correlations between the mixing behavior of the reactor and the characteristic features of the obtained emulsion. Special consideration was given to the droplet size and its distribution. Variable operating conditions of the reactor are the residence time and the rotational speed of the screw, both of which have a decisive influence on the recycle factor and the number of passages through the rotor/stator system. In addition we determined the dependence of the obtained droplet size distribution on the viscosity of the continuous and dispersed phase, on the interfacial surface tension and on the phase proportions. The influence of the specific type of emulsifying agent and its concentration has been examined as well. The positive effect of the mixing and of the recirculation on the emulsification in the screw loop reactor was particularly evident with low emulsifier concentrations and with emulsifiers with slow adsorption kinetics. The established theories for emulsion formation (Kolmogoroff, Taylor) were used for a quantitative description of the experimental results. The screw loop reactor was compared to an agitated tank reactor and a toothed-ring dispersing machine (Ultra Turrax) based on the comminution energy which is produced per unit volume of emulsion. The agitated tank reactor produced only coarsely dispersed emulsions through the entire rotational speed range, wheras the screw loop reactor and the Ultra Turrax, particularly at high rotational speeds and, therefore, high power densities, showed a similar emulsification and produced much finer dispersed emulsions.
    Additional Material: 18 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 162-170 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of an upflow packed-bed biofilm reactor has been analyzed under multisubstrate limitation by considering simultaneous carbon oxidation and nitrification reactions. The fasting shock load of inlet methanol concentration has a much more pronounced effect on the response of the system compared to that of inlet NH4+ -nitrogen concentration. The exit concentration of NH4+ -nitrogen drops very close to zero, thereby showing essentially complete nitrification during methanol fasting condition. Further, the concentration profiles of oxygen within the biofilm show significant variation during methanol fasting and nonfasting conditions whereas during NH4+ -nitrogen fasting conditions the oxygen concentration profile in the biofilm remains essentially unaffected.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 182-191 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The uncatalyzed esterification of acetic acid is described in the literature as a typical example of reactive distillation. Many rigorous models were validated using this esterification as an example. Process proposals for the production of pure ethyl acetate from ethanol and acetic acid have been determined using short-cut methods with the assumption of chemical equilibrium only. In this publication, the limitations of this esterification are clarified, using a rigorous model that was developed. The reasons why reactive distillation appears to be unfavorable for this esterification are explained. It is, however, theoretically possible to obtain ethyl acetate in high purity with different variants of the process. Different process variants are examined in this work. Construction variables that are important for the design of reactive columns, such as the number of reactive separation stages and the holdup in the column, are analyzed. Furthermore, the influence of variables dependent on the component system, such as the phase equilibrium of the reactive system and the reaction kinetics on the conversion in the column, are described. It can be shown that the short-cut methods published so far for reactive distillation, which assume chemical equilibrium, are inadequate.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 192-198 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two devices were developed, mechanical and electrical, to measure the mechanical power relative to superficial gas velocity and stirring speed in a mechanically agitated reactor. Two bubble regimes were demonstrated. The study of gas holdup, obtained from the residence time distribution, and the bubble size, determined by interfacial area measurement, confirm these two regimes of flow. Our results show that the gas holdup, the interfacial area, and the liquid-side mass transfer coefficient are increasing functions of the energy dissipated in the solution.
    Additional Material: 15 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 199-202 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide was used to study the rate of mass transfer inside a cubical cavity machined in the wall of a vertical rectangular duct. Variables studied were side length, physical properties of the solution and flow rate of the solution. The mass transfer coefficient was found to decrease with increasing cavity size; in all cases, the mass transfer coefficient inside the cavity was less than that at the duct wall. Mass transfer data inside the cavity were correlated by the equation Shc = 0.525 (Sc Re de/L)0.33. Comparison of the present results with the results obtained using other cavity geometries shows that cavity geometry plays an important role in determining the rate of mass transfer inside the cavity.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 203-207 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient heat transfer in a mechanically agitated vessel is studied in the case of an anchor and an helical ribbon impeller using Newtonian and shear thinning fluids. Temperature stratification is found more pronounced with the anchor, making this impeller clearly inadequate for heat transfer. The impact of natural convection is evaluated first using the classical Gr/Re2 ratio. It is shown that the use of this criterion in viscous mixing is somewhat misleading. A new Grashof number is then proposed to assess the significance of the viscous and buoyancy effects in non-isothermal, non-Newtonian mixing applications. It is shown that the interpretation of this new number is strongly related to the concept of process viscosity.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 208-211 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of a process analysis and an experimental exploratory study of supercritical water oxidation (SCWO) show that elements of combustion technology are suitable to overcome the technical problems of SCWO. The Film Cooled Hydrothermal Burner (FCHB) which operates at 25 MPa up to 2000 K in the reaction zone keeping wall temperature under stress at 300 to 400 K shows further development potential of the Wallcooled Hydrothermal Burner (WHB) concept for SCWO, a still promising waste treatment process.
    Additional Material: 6 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 212-219 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Subnetwork Corollary provides some sufficient conditions for which a complex reaction network could be determined to have capacity of admitting multiple positive steady-states, if it contains a subnetwork that also admit multiple positive steady-states. A family of reaction networks, involving catalytic reactions in an isothermal continuous flow stirred tank reactor (CFSTR), is determined to have the capacity to exhibit steady-state multiplicity by implementation of the Deficiency One Algorithm and the Subnetwork Corollary. A set of rate constants and two corresponding positive steady-states are constructed for several cases.
    Additional Material: 6 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 221-229 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To review mass transfer trays from a process point of view, the dependence of efficiency on the loadings, the loading range and the maximum loadings with an acceptable tray efficiency have to be known. Comparing the results taken from experiments on Dualflex trays and from other types of trays which have been in industrial applications for many years and which are recognized as “industrial standard”, has been evaluated in this review.
    Additional Material: 15 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 230-239 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this contribution, a new method is proposed for determining effective macropore diffusion coefficients in porous media by digitized microphotographs of porous support materials and random walk simulations. The method introduced allows calculation of the effective diffusion coefficient as a function of the mean free path length over a wide variety of values. A versatile method for the preparation of porous substances for light microscopy is described.The frequently applied model of an active shell, which is used to model particle/solid collisions, was found to give incorrect results in conjunction with the application of the first passage time algorithm, which was applied to save computing time in the simulation of gas diffusion. It was possible to show that more realistic results are obtained if a Knudsen layer is used to model particle/solid collisions. Furthermore, in investigating diffusion in two- and three-dimensional representations of capillary tubes, it was found that results of simulations performed to calculate transport properties of fluids in porous media, based on two-dimensional model systems, cannot in any case be transferred to the corresponding three-dimensional systems.
    Additional Material: 15 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 240-246 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of the homogenous exothermic hydrolysis reaction of acetic anhydride catalyzed by sulfric acid in solvent acetic acid was estimated from nonisothermal experimental batch reactor transient temperature data. Rate equations based on three different reaction mechanisms of hydrolysis published in the literature were fitted to the experimental rate data. The experimental results on runaway and limit cycle behavior obtained with this reaction were explained by using the mechanism-based rate equations for hydrolysis in the reactor dynamic models, and good agreement was obtained between the predicted and the experimental dynamic data.
    Additional Material: 6 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 247-258 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New uses of artificial selective membranes, particularly ion-exchange membranes, improve on traditional methods of treating liquid mixtures before, during or after chemical or biochemical reactions. With the correct choice of ion-exchange membrane in a membrane reactor, reactions can be performed in such a way that the main product is not contaminated by undesired byproducts. Recent examples, mainly in organic chemistry, are given for eight typical ion-exchange membrane reactors: electrodialysis (ED), electrometathesis (EMT), electro-ion substitution (EIS), electro-ion injection-extraction (EIIE), coupled counter-transport (CCT), electro-electrodialysis (EED), electrohydrolysis with bipolar membranes (EHBM), and catalysis with ion-exchange membrane (IEMC).
    Additional Material: 25 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 259-267 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this study, a scale-down approach has been used for the simulation of the imperfect mixing on the growth processes by considering several configurations of continuous stirred tank reactor (CSTR, aerated) and plug flow tubular reactor (PFTR, not aerated). The steady-state concentrations of biomass and enzyme in a continuous culture were calculated as a function of dilution rate using modified Monod growth kinetics. A mathematical model for each combination of two bioreactors was developed to account for growth, substrate utilization (oxygen and glucose) and enzyme synthesis and decay. The model was then used to investigate biomass production and enzyme expression in relation to the volumetric fraction Uf = VPFTR/(VCSTR + VPFTR) and the recirculation ratio R = fr/(f + fr) of the fermentation system. These two mixing parameters were found to be significant factors in the biomass and enzyme production from the fermentation system. This model was also compared with some of the existing models.
    Additional Material: 5 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 268-276 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As an alternative to the existing bioheat transfer models a new system of two energy equations is proposed by considering the human body as a deformable porous medium. One equation is developed for the blood and the other for the peripheral skeletal tissue. It includes such significant factors as the vascular geometry and size, the blood flow and direction, thermal diffusion and the local thermal nonequilibrium between the blood and peripheral tissue. Discussion and application of both equations are given.
    Additional Material: 5 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 282-284 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 277-281 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for cleaning inner surfaces of pipes was studied both theoretically and experimentally. The method is based on the phenomenon of a sphere rotating in a pipe (levitation), when the translational movement of the sphere is restricted and the sphere is subjected to fluid flow in the pipe. The high rotation velocity causes a vibration process, which may be exploited for cleaning sediments or rust from the inner surfaces of pipes. A simplified theoretical model for the determination of the relationships among the dimensionless parameters governing the rotation phenomenon was developed. The model was validated with experimental data and found to be appropriate for engineering design of the system. Application of the cleaning method was demonstrated by cleaning the sediments and rust off the inner surface of a one-inch nominal diameter pipe.
    Additional Material: 6 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 285-286 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ortho-experiment design and the analysis method of mathematical statistics are adopted to study the conversion of gypsum and potassium chloride to potassium sulfate in the system of K+, Ca2+, NH4+ ‖ Cl-, SO42- in H2O. Optimal reaction parameters and engineering mean are acquired to attain a conversion yield of potassium chloride of 94.52%.
    Additional Material: 2 Tab.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 414-418 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present work, we employ a fuzzy logic controller (FLC) to control the unstable state of a nonlinear biological reaction. The state variable vectors consist of cell density and substrate concentration. The dilution rate is used as a manipulated variable to control the reaction dynamics. An analytic form of FLC employing Zadeh AND logic along with Center of Mass defuzzification method is considered. Simulations reveal that for servo response test, the FLC shows satisfactory performance for natural unsteady states for which a conventional PI controller is known to fail. Further simulations also show that the FLC gives satisfactory regulatory response and is relatively insensitive to the deviations in model parameters.
    Additional Material: 8 Ill.
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  • 23
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A ‘carbon source controlled shift technique’ was developed for fermentation medium optimization in continuous culture with the objective to maximize growth rate and growth-linked product formation of a biological system. An automatic culture medium preparation system was operated together with 2 parallel stirred tank reactors and a HPLC system for on-line analysis of the carbon source concentration in the reactors. A genetic algorithm was applied for experimental design. The concentrations of 7 medium components (mineral salts and vitamins) were optimized automatically within 40 continuous experiments to result in a maximum growth rate of the methylotrophic yeast Candida boidinii and growth-linked production of the formate dehydrogenase enzyme (FDH). The specific growth rate of Candida boidinii and the specific activity of the FDH enzyme at a set-point of 420 mM methanol in the reactor were, thus, improved by 19% to 0.16 h-1 and 26% to 164 U g-1, respectively, compared to the previously used medium, which has already been previously optimized in shake flask experiments. The results of the continuous medium optimization were evaluated with a full second order seven-dimensional polynomial model (regression coefficient 96.8%).
    Additional Material: 7 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 419-423 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By applying the macroscopic conservation laws to a simplified jet downstream from a sudden enlargement, a new correlation of the two-phase subcritical pressure recovery is obtained. Comparisons with the set of existing data (air-water and steam-water subcritical flows) show that the predictions obtained by means of this formula are more accurate than the ones given by available analytical models. The proposed correlation presents an important improvement of the pressure recovery predictions in the case of small mass velocities. However, it can not be applied in the conditions of quality too close to one.
    Additional Material: 6 Ill.
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  • 25
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 424-428 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In paper coating make-down, a poor dispersion of pigments in coating colors may lead to coater runnability problems. This is manifested by coat defects at the paper surface, excessive coater blade wear, and an over-consumption of pigments. For this reason, high shear impellers operated at high speed are used, yielding a high energy consumption. A new method to disperse high solids mix at low energy consumption is presented. This method based on the use of a rod impeller scraping the fluid surface in the vessel, is tested on a slurry composed of calcined and delaminated clays up to a solids content of 66.7 wt.% without dispersing aids.
    Additional Material: 5 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 429-433 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When in contact with water, organoalkoxysilanes and other alkoxy metal compounds react to organofunctionalized polysiloxanes or heteropolysiloxanes. A new method for the continuous preparation of porous organopolysiloxane spheres was developed. Droplets of the precursor mixture are injected into the vertical reactor column. Movement of the gelating droplets is controlled by flow of the aqueous reaction medium. Advantages are adjustable residence time, minimized coalescence and low reactor height. An example shows typical product characteristics like narrow particle size distribution and macroporosity.
    Additional Material: 8 Ill.
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  • 28
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 435-444 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes how gain scheduling control is applied to a continuous stirred tank reactor model. The CSTR process, equipped with a cooling system, is modelled. Based on the resulting nonlinear model, a gain scheduling controller is designed. The gain scheduling follows a scheme denoted bias compensation. Compared to earlier reported gain scheduling schemes, the proposed scheme results in a controller that is less complex, which is advantageous in the controller implementation stage. Numerous simulations are performed, using the gain scheduling controller and two choices of control input to the reactor model. The simulation results indicate that a gain scheduling controller performs better than a linear controller. Simulations using different choices of control input to the reactor model indicate that proper process design is crucial for the controlled process performance.
    Additional Material: 9 Ill.
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  • 29
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 445-454 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two different layouts for the liquid-liquid extraction section of an industrial caprolactam process are evaluated. Laboratory mass transfer measurements on streams obtained from an industrial and a demonstration plant with different extraction sections are interpreted by a model describing the effect of surface contaminants on mass transfer coefficients. Indications of the impact of these layouts on the complexity of the extraction section, quality of products and efficiency of the extraction processes are given.
    Additional Material: 14 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 455-461 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A time- and space-dependent model based on the piston-dispersion-exchange model for liquid flow was developed to analyze the performance of two-phase upflow and downflow fixed bed reactors and was applied to the catalytic SO2 oxidation. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time-domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the PDE model was used to interpret the obtained RTD curves. Gas-liquid mass transfer parameters were determined by a stationary method based on the least square fit of the calculated concentration profiles in gas phase to the experimental values. It is shown that two-phase downflow fixed bed reactor performs better at low liquid flow rates, while two-phase downflow fixed bed reactor performs better at low liquid flow rates, while two-phase upflow performs better at high liquid flow rates.
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  • 31
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 462-468 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The autoxidation of aqueous sulfide solutions by dioxygen is studied at pH 9 and 14 and at initial sulfide concentrations between 1 and 100 mM. Disulfide as a primarary intermediate is proposed to enhance the sulfide oxidation by autocatalytically forming polysulfies. The postulate is supported by the observed acceleration of the process at increasing pH favoring the presence of disulfide rather than that of sulfur. The final reaction products thiosulfate and sulfate are proposed to result from the hydrolysis of the highly instable intermediate polythiosulfite in parallel parallel reaction pathways, assuming probabilities for breaking the sulfur chain at the α (sulfate) and β (thiosulfate) positions to be responsible for the selectivity. A reaction scheme is proposed, considering all experimental observations.
    Additional Material: 7 Ill.
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  • 32
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 469-474 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bubble columns are commonly used in industry for polluted gas treatment. Based on the same principle, the droplet column which is not widely known in the literature, uses much higher gas velocities, up to 14 m/s. This study concerns the hydrodynamics and mass transfer in this apparatus, in presence or absence of solid particles. Our results have demonstrated the impact of dusts on mass transfer performance giving rise to an increase in the kL aL coefficient with decreasing particle size. However, no influence of dust on the hydrodynamics of the column has been demonstrated within the studied particle size range.A study of liquid holdups obtained by three different methods is also carried out. Our results are comparable, thus validating the methods used.
    Additional Material: 11 Ill.
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  • 33
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 475-477 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple and new model for the prediction of drop velocity as a function of dispersed phase volume fraction has been proposed on the basis of experimental knowledge of onset time of complete separation between two phases as function of the initial hold-up.
    Additional Material: 1 Ill.
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  • 34
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 485-490 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model of the liquid fluidized bed containing two or more solid particle species of different size and density is presented. The model incorporates the particle mass transport mechanisms of the convection and the dispersion. The movement of the upper interface of the bed subject to a change in the liquid velocity is specified using the mass balance constraint. The particle velocities and dispersion coefficients are evaluated using correlations. The model is capable of describing the bed expansion, concentration profiles of the individual particle species, the bulk density profile, and the occurrence of layer inversion.
    Additional Material: 7 Ill.
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  • 35
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 491-494 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments were carried out in a conventional circulating fluidised bed to measure the axial pressure profile and total pressure drop, which covered a wide range of operating conditions. Material belonging to the Geldart A (fine material) as well as the Geldart B (course material) categories have been used in the present work. Slip velocity is determined from the total pressure drop and noticed that the slip velocity is much higher than the free fall velocity of single particle for Geldart A type material, while it is approximately equal to the free fall velocity of single particle for the Geldart B type materials.A model is developed for slip velocity taking into account all the hindrance effects: particle-particle, and particle-wall, and particle agglomeration. Predictions of the present model are validated with the data due to present study and the data reported in the literature.
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  • 36
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 478-484 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i-butane/n-butane distillation column equipped with two-pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one-pass and two-pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one-pass trays are higher than for two-pass trays. Obviously, this is caused by the longer liquid flowpath length of one-pass trays. The Murphree tray efficiencies are also calculated for an industrial-scale MTBE purification column. The column is equipped with two-pass trays in the stripping section and with one-pass trays in the rectifying section. The Murphree tray efficiencies of one-pass trays are considerably higher than the two-pass tray Murphree tray efficiencies.
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  • 37
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 495-501 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm for the computation of design variables in layer crystallisation processes is presented, based on an algebraic solution of the moving boundary equation for heat transfer, as well as on an expression for the concentration profile. The algorithm was applied to the discontinuous crystallisation of a NaCl-H2O solution around the wall of an internally cooled cylindrical tube. Good agreement between simulation results and laboratory experiments was observed. After input of experimentally measurable values of the distribution coefficient, the algorithm enables the prediction of the following process variables along the crystallisation time: layer thickness, temperature, and composition profiles across the layer, as well as the end-values of solid and liquid mass and concentrations. Multistage processes can be studied by the series association of crystallisation cycles, enabling the determination of the optimal number of stages that meets a specific design criterion.
    Additional Material: 9 Ill.
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  • 38
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 39
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 502-509 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosion hazard exists in plants and facilities wherever combustible dusts are hardled. Minimum explosible concentration of dust clouds is an important factor requiring special attention for hazard evaluation if any technological equipment is to be protected by inertisation. The mathematical models available for prediction of this parameter have been analysed for their application to organic dust clouds. Solution of the most general mode for determination of minimum explosible concentration of dust clouds proposed by Mitsui and Tanaka is presented, together with the comparison with experimental data. It has been found that the model is not successful in predicting the minimum explosible concentration for organic dusts. Recommendations on requirement of development of a new model for prediction of minimum explosible concentration of an organic dust such as polyethylen have been given.
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  • 40
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 511-521 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When working with disperse solid matter systems, one uses the effect of vibration in numerous processes. Solid matter mixing with vibration has only occurred in very simple units up to now. By means of the 3D-vibrational mixer from the company Kuston, Kleve, the influence of vibration on bulk materials and new mixing techniques are demonstrated. The 3D-vibrational mixer is suitable for liquids and solids, does not require mixing tools that need to be cleaned, and does not carry out rotary motions which would hinder incoming lines. It is used for mixing small amounts, where the mixing tank can be used simultaneously as the transportation container, so that a transfer is unnecessary.With the aid of 4 linear motors, the vibrational amplitudes and the frequencies can be varied within wide boundaries in all three spatial directions. By analyzing the vibrational system by means of Lissajous figures, it can be demonstrated that the optimal mixing effect occurs in the case of small frequency differences between the three axes. For freeflowing bulk materials, the best possible mixing state, the uniform coincidence mixing, is achieved after 2 min.
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  • 41
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 522-532 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intermixing of fluidizing gas between the compartments of a compartmented circulating gas fluidized bed fitted with a V-valve and riser combination has been experimentally studied. The intermixing of fluidizing gas that flows co-current (cross flow) as well as counter-current (back flow) to the circulating solids has been investigated. At low aerations, gas cross flow increased proportionally with the increase in solid circulation rate. But at high aerations, gas cross flow increased with aeration even when solid circulation decreased. Studies on back flow of gas revealed some interesting observations. At high fluidizing bed height on upstream side back flow of V-valve, gas has been negligible. But at low upstream bed heights and low aeration in V-valve and riser back flow of V-valve, gas has been substantial.
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  • 42
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    Chemical Engineering & Technology - CET 20 (1997), S. 17-22 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.
    Additional Material: 7 Ill.
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  • 43
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    Chemical Engineering & Technology - CET 20 (1997), S. 171-181 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrodynamic parameters have been determined in common equipment, i.e., same column and liquid and gas distributors, for cocurrent and countercurrent two-phase flow through fixed beds. The piston/dispersion exchange model (PDE) with usual Danckwerts' boundary conditions (closed/closed system) has been used to describe the liquid flow. A new imperfect pulse method has been used to estimate the PDE model parameters directly from the experimentally nonideal input and output response. The transition between trickle flow and pulse flow, for two-phase downflow, and the occurrence of flooding, for countercurrent flow, has been investigated using a macroscopic model for the two-phase flow.
    Additional Material: 10 Ill.
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  • 44
    ISSN: 0268-2605
    Keywords: sulphur ; alkyltin compounds ; GC-FPD interference ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Elemental sulphur, a common constituent of marine sediments, has been shown to give dialkyl sulphides with the Grignard reagents commonly used to derivatize alkyltin species before their determination by gas chromatography with flame photometric detection (GC-FPD). Further, it has been demonstrated that even with the red filter for 610 nm (normally used for organotin compounds) fitted to the detector, sulphur compounds do give rise to an emission signal, which may be mistaken for tin emission from a pentylated or propylated alkyltin compound, as the respective retention times are in some cases quite close. © 1997 by John Wiley & Sons, Ltd.
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  • 45
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    Applied Organometallic Chemistry 11 (1997), S. 67-67 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 46
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 67-67 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 47
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 153-161 
    ISSN: 0268-2605
    Keywords: polyimides ; solution polycondensation ; seven-membered cyclic polyimide intermediate ; polyimide-silica gel hybrids ; sol-gel reaction ; pyrolysis ; pore size ; surface area ; adsorption-desorption isotherms ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A facile preparation of polyimide-silica gel hybrids by the simultaneous in-situ formation of polyimides during the hydrolysis-condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2 and the seven-membered cyclic polyimide intermediate. The seven-membered cyclic intermediates, precursors of polyimides, were derived from the low-temperature polycondensation of dianhydrides [benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4-bis(hexafluoroisopropylidene)phthalic dianhydride (6FDA)] and di-isocyanates [isophorone di-isocyanate (IPDI), toluene di-isocyanate (TDI), hexamethylene di-isocyanate (HDI) and 4,4′-diphenylmethane di-isocyanate (MDI)]. These intermediates could readily be converted to the corresponding polyimides. Films were cast from the resulting mixtures and the solvent was gradually evaporated at 130 °C to result in the formation of clear, transparent, pale yellow or amber-colored hybrid films in which the salts were dispersed at the molecular level. Pyrolysis of polyimide-silica gel hybrids at 600 °C gave mesoporous silica. Silica gel obtained from hybrids HPI-8 (containing no salt) and HPI-11 (containing ZnCl2) had a pore radius (BJH method) of 2.9 nm, while that from hybrid HPI-9 (containing LiCl) had a pore radius of 11.4 nm. The surface areas (BET method) obtained were 203 m2 g-1, 19 m2 g-1 and 285 m2 g-1, while the pore volumes were 0.373 cm3 g-1, 0.158 cm3 g-1 and 0.387 cm3 g-1, respectively, for samples obtained from hybrids HPI-8, HPI-9 and HPI-11. © 1997 by John Wiley & Sons, Ltd.
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  • 48
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 565-575 
    ISSN: 0268-2605
    Keywords: complexes of furan oximes ; IMP dehydrogenase ; purine inhibitors ; cytotoxicity ; nucleic acid inhibitors ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copper complexes of furan oxime derivatives were found to be potent cytotoxic agents in both murine and human tissue cultured cell lines which were suspended as well as solid tumors. Mode of action studies in murine L1210 lymphoid leukemia cells showed that the compounds suppressed DNA, RNA and protein synthesis after 60 min at 100 μM. Inhibition of purine and pyrimidine de novo syntheses, as well as inhibition of ribonucleoside reductase and nucleoside kinase activities with DNA strand scission occurred. All of these effects of the drug probably added to its ability to cause cell death but most important was the inhibition of DNA topoisomerase II activity with IC50 values lower than those afforded by VP-16, the standard, which should cause apoptosis. © 1997 John Wiley & Sons, Ltd.
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  • 49
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    Applied Organometallic Chemistry 11 (1997), S. 591-600 
    ISSN: 0268-2605
    Keywords: organotin compounds ; lecithin liposome membrane ; Ca2+ and Pr3+ desorption ; 1H NMR ; radioactive tracer methods ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic compounds and surfactants constitute a potential threat to the environment. For that reason we have embarked on a study of their joint action on membranes. Model lecithin liposome membranes were modified with the cationic surfactant trimethyldodecylammonium bromide or the anionic surfactant sodium dodecylsulfonate, and the effect of tripropyltin chloride on the process of calcium (Ca2+) and praseodymium (Pr3+) desorption from the liposome membrane was studied.Kinetic constants for the process of Ca2+ ion desorption from lecithin liposome membranes were determined using the radiotracer method. The percentage of Pr3+ ion desorption from liposome membranes was measured by the 1H NMR method.Trimethyltin, triethyltin and tripropyltin alone caused increased Ca2+ and Pr3+ desorption from liposome membranes with increasing concentration of the compounds and alkyl chain length. For both the processes studied, a cationic surfactant brought about a lower effectiveness of tripropyltin and an anionic surfactant resulted in a higher effectiveness.The effect observed can be explained by changes in the surface charge of the membrane, induced by the surfactant modifiers and by the concomitant change in the partition coefficient of the organotin. The results obtained indicate a protective or harmful joint action of the surfactants used with tripropyltin on membranes. © 1997 John Wiley & Sons, Ltd.
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  • 50
    ISSN: 0268-2605
    Keywords: triorganotin(IV) ; L-homocysteic acid ; infrared ; Mössbauer ; NMR ; sea urchin ; Paracentrotus lividus (Echinodermata) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new triorganotin(IV) derivatives of L-homocysteic acid (L-HCAH) with formula R3Sn(L-HCA) (R=Me, nBu, Ph) have been synthesized. Their solid-state configurations were determined by IR and Mössbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes, with the L-homocysteic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The sulfonate (SO3-) and NH3+ groups of L-homocysteic acid maintain their free acid configuration and hence do not participate to the coordination of the tin(IV) atom. Coordination hypotheses have been checked through the correlation between the Mössbauer parameter isomer shift, δ, and partial atomic charge on the tin atoms, QSn, performed, for all the new organotin(IV) compounds, on the basis of an equalization procedure applied to idealized trigonal-bipyramidal structures for R3Sn(L-HCA).1H and 13C NMR spectra of the complexes show that pentacoordination of the tin atom, with R groups in the equatorial plane of a trigonal bipyramid, is retained in DMSO solution. The NMR data confirm also that the uncoordinated NH3+ group of the ligand is still present in solution.Results gathered after exposure of two- to four-cell embryos of the sea urchin Paracentrotus lividus (Echinodermata) to the triorganotin(IV) L-homocysteate derivatives as well as to the parent triorganotin(IV) chlorides document cytotoxicity of the complexes, while free L-homocysteic acid exerts no significant toxic activity. The trimethyltin(IV) L-homocysteate derivative seems to exert a lower cytotoxicity than the tributyl- and triphenyl-tin(IV) ones. Different structural lesions have been identified by comparative analysis of mitotic chromosomes from untreated embryos (negative controls) and embryos treated with triorganotin(IV) L-homocysteate derivatives, such as (1) suppression of the stretch among sister chromatids at the beginning of anaphase stage; (2) deeply stained zones mainly located at the telomeric regions of chromosomes; (3) arm breakages; and (4) chromosome bridges among daughter chromosomes at anaphase stage. A colchicine-like effect of triorganotin(IV) L-homocysteate derivatives was observed. © 1997 John Wiley & Sons, Ltd.
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  • 51
    ISSN: 0268-2605
    Keywords: palladium ; platinum ; imidazoline ; DNA ; cyclometallated complexes ; cytotoxic activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we describe the synthesis and chemical characterization of three new Pd(II)-imidazoline complexes: [PdCl2 (C6H5-CH2-C3H5N2)2] (2), [PdCl(SEt2) (C6H4-C3H5N2)] (5) and [Pd(C6H4-C3H5N2) (μ-Br)]2 (6). We have also analyzed the DNA modifications and in vitro antileukaemic activity of these compounds and of their previously reported analogs [Pd Cl2 (C6H5-C3H5N2)2] (1), [Pd (C6H4-C3H5N2) (μ-OAc)]2 (3), [Pd (C6H4-C3H5N2) (μ-Cl)]2 (4) and [Pt(C6H4-C3H5N2)(μ-Cl] (7). All these compounds modify the DNA secondary structure since they alter the melting temperature (Tm) of the DNA. Circular dichroism spectra indicated, moreover, that compounds 3, 5 and 6 induced higher modification on the double helix than compounds 1, 2 and 4. While compounds 1, 2 and 5 seem to induce slight changes in the electrophoretic mobility of the open and covalently closed circular forms of pUC8 DNA at high ri (input molar ratio of Pd or Pt to nucleotides), compounds 3, 6 and 7 do not modify at any ri the tertiary structure of the plasmid DNA. Antileukaemic tests suggest that compounds 1, 4 and 7 exhibit important cytotoxic activity since their IC50 values against HL-60 human leukaemic cells were below 10 μg ml-1. © 1997 John Wiley & Sons, Ltd.
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  • 52
    ISSN: 0268-2605
    Keywords: organotin compounds ; chemical speciation ; natural fluids ; biological fluids ; carboxylate complexes ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation by (CH3)2Sn2+ with acetate (ac), malonate (mal), 1,2,3-propane-tricarboxylate (tricarballylate, tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands in aqueous solution is reported. The study has been performed by potentiometry ([H+]-glass electrode) at T=25 °C, and in the 0≤I≤1 mol dm-3 ionic strength range. In order to evaluate the salt effects on the formation constants of the complex species, and to contribute to the definition of the chemical speciation of diorganotin(IV) compounds in natural waters where carboxylic ligands are naturally present, interactions of NaCl (which is the major component of all natural fluids), with the components of the systems under investigation have also been considered. A model for the ionic strength dependence of the formation constant was used in order to calculate the values of thermodynamic constants, at infinite dilution, for all the proposed species, by considering hydrolytic species too. A relationship between the charges on the different ligands considered and the stabilities of the complex species formed is also discussed. © 1997 John Wiley & Sons, Ltd.
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  • 53
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    Applied Organometallic Chemistry 11 (1997), S. 756-756 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 54
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    Applied Organometallic Chemistry 11 (1997), S. 743-749 
    ISSN: 0268-2605
    Keywords: methylarsonic acid ; dimethylarsinic acid ; trimethylarsine oxide ; mitotic arrest ; aneuploidy ; c-mitosis ; tetraploidy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inorganic arsenic is methylated in the mammalian body to methylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine oxide (TMA). To achieve a more precise understanding of arsenic carcinogenicity, we examined the genotoxic effects of organic arsenic compounds on human lymphocytes by assessing induction of mitotic arrest, sister chromatid exchange (SCE) and aneuploidy. MMA, DMA and TMA arrested mitosis, DMA induced hyperdiploid cells, and DMA and TMA induced tetraploid cells. Of the three arsenic metabolites tested, DMA had the strongest effects on cell mitosis and aneuploidy induction. DMA arrested mitosis and induced c-mitosis significantly. These results suggest that DMA arrests mitosis and induces aneuploidy through spindle disruptions similar to those observed with known spindle poisons, such as colchicine or vinblastine. Since aneuploidy has been thought to be associated with tumor induction or neoplastic transformation, induction of aneuploidy by organic metabolites of arsenic may play a major role in arsenic carcinogenesis in humans. © 1997 John Wiley & Sons, Ltd.
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  • 55
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    Applied Organometallic Chemistry 11 (1997), S. 805-811 
    ISSN: 0268-2605
    Keywords: [2+3] cycloaddition reaction ; silylisoxazolines ; silatrane ; pyridyl nitrile oxide ; vinylsilane ; vasodilating ; haemodynamic parameters ; antithrombotic properties ; acute toxicity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-(2-Pyridyl)-5-phenyldimethylsilylisoxazoline, 3-(3-pyridyl)-5-phenyldimethylsilylisoxazoline and 3-(4-pyridyl)-5-phenyldimethylsilylisoxazoline were obtained by the [2+3] cycloaddition reaction of pyridyl nitrile oxides to phenyldimethylvinylsilane. The condensation of 3-pyridyl-substituted 5-triethoxysilylisoxazolines with triethanolamine afforded 3-(2-pyridyl) -5-silatranylisoxazoline, 3-(3-pyridyl)-5-silatranylisoxazoline and 3-(4-pyridyl)-5-silatranylisoxazoline (12). In experiments in vivo and in vitro the vasodilating, antiarrhythmic and antithrombotic properties of pyridyl-substituted silylisoxazolines, their influence on the haemodynamic parameters in anaesthetized animals and their acute toxicity have been studied. It has been found that pyridyl-substituted silylisoxazolines possess vasodilating and antithrombotic properties. In experiments on the noradrenaline-preconstricted isolated rabbit ear artery, 3-(2-pyridyl)- and 3-(4-pyridyl)-5-phenyldimethylsilylisoxazoline exhibited pronounced vasodilating activity. 3-(2-Pyridyl)- and 3-(3-pyridyl)-5-phenyldimethylsilylisoxazoline and 3-(2-pyridyl)-5-silatranylisoxazoline prolonged blood coagulation time. © 1997 John Wiley & Sons, Ltd.
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  • 56
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    Applied Organometallic Chemistry 11 (1997), S. 889-901 
    ISSN: 0268-2605
    Keywords: alkyl-lead ; atmosphere ; phase partitioning ; wet deposition ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of alkyl-lead compounds in air and rain at rural and urban sites in central England during 1996 are reported. Vapour, aerosol and rain concentrations of individual tetra-, tri- and di-alkyl-lead species have been determined simultaneously at both sites, along with inorganic lead aerosol. The results show the predominance of vapour-phase over particle-associated species, with tetramethyl-lead being the most prevalent vapour-phase compound, with concentrations of up to 5.8 ng Pb m-3. Theoretical phase-partitioning coefficients for individual alkyl-lead compounds have been calculated and compared with measured values. Washout ratios for alkyl-lead compunds were found to be smaller than for inorganic lead. Atmospheric concentrations of both organic and inorganic lead appear to be falling, broadly in line with recent reductions in the use of alkyl-lead in gasoline. © 1997 John Wiley & Sons, Ltd.
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  • 57
    ISSN: 0268-2605
    Keywords: laser ablation molecular beam ; binuclear metal carbonyls ; chromium carbonyl ; bond dissociation energies ; density functional calculations ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the laser ablation-molecular beam (LAMB) method, laser ablation of metal substrates in vacuum is utilized for the formation of novel organometallic and metal complex compounds containing monopositive metal ions. Mixed-metal binuclear carbonyl ions [MCr(CO)n]+, n=0-6, are prepared in the gas phase by the reaction of laser-ablated metal ions (M+) and Cr(CO)6 in the molecular beam injected nearby. The relative abundance of these ions, for M=transition metals, can essentially be explained by the M+-Cr bond dissociation energies. Results of density functional calculation show that this is essentially valid. © 1997 John Wiley & Sons, Ltd.
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  • 58
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    Applied Organometallic Chemistry 11 (1997), S. 919-927 
    ISSN: 0268-2605
    Keywords: double alkoxides ; precursors ; Group II metal aluminates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Precursors to Group II metal aluminates (MAI2O4, M=Mg, Ca, Ba, Sr) are synthesized from inexpensive starting materials including Group II metal oxides/hydroxides, Al(OH)3, triethanolamine (TEA) and ethylene glycol, in a one-pot synthesis process. The precursors are soluble in common organic solvents and can be handled in moist air for a reasonable period of time. On pyrolysis in air to 1200 °C, all three precursors transform to the corresponding Group II metal aluminates. A termetallic double alkoxide, ‘ionomer-like’ structure is proposed, wherein the alkaline-earth metal is encapsulated by a TEA molecule bridging two alumatrane units. The precursors were characterized using TGA, NMR, mass spectroscopy and elemental analyses, and the pyrolysed precursors were briefly characterized using x-ray diffraction analysis. © 1997 John Wiley & Sons, Ltd.
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  • 59
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    Applied Organometallic Chemistry 11 (1997), S. 859-867 
    ISSN: 0268-2605
    Keywords: Formica sp. ; ants ; arsenobetaine ; arsenic compounds ; HPLC-HHPN-ICP-MS ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Total arsenic concentrations in the freeze-dried pulverized ants (Formica sp.) and material from an ant-hill collected at a former arsenic roasting facility were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion with nitric acid and hydrogen peroxide. The ants contained 12.6±0.9 mg As/kg dry mass, the ant-hill material 5420±90 mg As/kg dry mass. Total arsenic concentrations in needles of Picea abies and Larix decidua (spruce and larch needles) were also determined, because needles are the main constituents of the upper layer of ant-hill material. Needles of Picea abies contained 1.17 mg As/kg dry mass and needles of Larix decidua 3.71 mg As/kg. The Formica sp. and ant-hill material were extracted with water or methanol/water (9:1). The extracts were chromatographed on a cation-exchange and an anion-exchange column. Water extracted 20% of the arsenic from the ants and only 3% from the ant-hill material. With methanol/water (9:1) only 7% of the arsenic was released by the ants and 0.5% by the ant-hill material. The arsenic compounds in the column effluents that were introduced into the plasma via a hydraulic high-pressure nebulizer (HHPN) were quantified on-line by ICP-MS. Arsenite and arsenate were the major arsenic compounds in the extract. Dimethylarsinic acid and traces of methylarsonic acid and arsenobetaine were also detected. The extracts of the ant-hill material contained the same compounds. Additionally, traces of trimethylarsine oxide were found. The presence of arsenobetaine was confirmed by spiking an extract of the ants with synthetic arsenobetaine bromide. © 1997 John Wiley & Sons, Ltd.
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  • 60
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    Applied Organometallic Chemistry 11 (1997), S. 929-930 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 61
    ISSN: 0268-2605
    Keywords: organotin ; solid-state NMR ; crystal structure ; antitumor activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(dicyclohexylammonium) bis(2,6-pyridinedicarboxylato)dibutylstannate is assigned seven-fold coordination at tin on the basis of its 119Sn CP/MAS NMR chemical shift (δ=-424.9 ppm). The assignment has been corroborated by a crystal structure determination of its monohydrate, whose tin atom has the trans-C2SnNO4 pentagonal bipyramidal [Sn-C=2.040(9), 2.067(8) Å; C-Sn-C =168.9(5)°] geometry. One 2,6-pyridine- dicarboxylato group chelates to the tin atom (Sn-O=2.234(4), 2.260(4); Sn-N =2.279(5) Å) whereas the other binds through only one carboxyl -CO2 end (Sn-O=2.416(5), 2.441(5) Å). Hydrogen bonds link the cation and the stannate into a linear chain parallel to the b-axis. The lattice water molecule is hydrogen-bonded to the free carboxyl end. The anhydrous compound showed higher in vitro antitumor activity than those of carboplatin and cisplatin when screened against breast (MCF-7, EVSAT), colonic (WiDr), ovarian (IGROV) and renal (A498) carcinoma, and melanoma (M19 MEL) cell lines. © 1997 by John Wiley & Sons, Ltd.
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  • 62
    ISSN: 0268-2605
    Keywords: CdTiO3 ; sol-gel ; thin films ; powders ; Raman spectroscopy ; X-ray diffraction (XRD) ; scanning electron microscopy (SEM) ; electrical properties ; structural properties ; humidity sensors ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cadmium titanate, CdTiO3, was prepared by the sol-gel technique in bulk and in thin film form. The thermal evolution of the gels and the phase changes were studied by thermo- gravimetric analysis (TGA), X-ray diffractometry (XRD) and Raman and energy-dispersive (EDS) spectroscopies. The morphology of the samples was observed using scanning electron microscopy (SEM). Gels heated to 800 °C gave rise to powders with only the ilmenite-like phase. The orthorhombic perovskite phase is the only crystalline phase observed after a 4 h heat-treatment at 1100 °C. With respect to the conventional preparation method by solid-state reaction, by the sol-gel method it is possible to prepare the ilmenite phase at lower temperatures and the perovskite phase in a shorter time. Clear, homogeneous thin films were obtained by the dip-coating method. The refraction index and the thickness of the films were measured using ellipsometry. The humidity-sensitive electrical properties were measured for thin films deposited on alumina substrates with comb-type gold electrodes, heated to 200 °C and 450 °C. The films heated to 200 °C, which still contained organics, showed a variation of the resistance of six orders of magnitude in the relative humidity (RH) range tested (4-87% RH). The films heated to 450 °C, made of ilmenite-type CdTiO3, were nearly insensitive to RH. © 1997 by John Wiley & Sons, Ltd.
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  • 63
    ISSN: 0268-2605
    Keywords: sol-gel ; composite glass ; fiber ; dye laser ; optical power limiter ; nonlinear optics ; multiphasic nanostructured composites ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sol-gel-processed organic-inorganic hybrid materials combine the merits of inorganic glass and organic molecules, and are therefore a class of materials with good potential for photonics. In this review, two approaches which have shown promising results for producing useful materials for photonics are described: (i) a novel way to fabricate organically doped, multiphasic nanostructured composite monoliths and (ii) a method of fabrication of organically doped, sol-gel-derived optical fibers. For each approach, the preparation process is presented, together with selected applications such as multidye solid-state tunable laser, multiphasic optical power limiter, a micron-scale chemical-sensing and biosensing fibers and solid-state dye-doped fiber lasers. © 1997 by John Wiley & Sons Ltd.
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  • 64
    ISSN: 0268-2605
    Keywords: methylcyclopentadienylmanganese tricarbonyl (MMT) ; gas chromatography ; helium microwave plasma atomic emission ; air ; soil ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly sensitive and specific method is described for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography-plasma atomic emission detection (GC-AED). The procedure is simple, rapid and free from interferences. The absolute limit of detection is 0.5 fg of MMT (0.5×10-15 g) expressed as Mn. The precision for replicate injections (n=5) of an MMT solution (10 pg Mn) was 2.8% relative standard deviation (RSD). Applications of the method to analysis of gasoline (petrol), and preliminary results of the analyses of environmental samples such as air and roadside dirt, are given. © 1997 by John Wiley & Sons, Ltd.
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  • 65
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    Applied Organometallic Chemistry 11 (1997), S. 57-66 
    ISSN: 0268-2605
    Keywords: Chlorella sp. ; biomethylation ; arsenic ; HPLC-ICP-MS ; cadmium ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The growth of Chlorella Böhm, Chlorella kessleri and Chlorella 108 in media containing sodium arsenate at 200 or 2000 mg As dm-3 was investigated. The cell densities in the stationary phases were 40% higher for Chlorella Böhm (5.6×105 cells cm-3) and Chlorella kessleri (4.5×105 cells cm-3) grown in the 2000 mg As dm-3 arsenate media compared with the arsenic-free media. The growth of Chlorella 108 was depressed by arsenate. Dimethylarsinic acid (at concentrations never exceeding 1.2 mg As dm-3) and arsenite (≲0.2 mg As dm-3) were detected in the growth medium. The cells harvested during the stationary phase had 2400 mg arsenic associated with 1 kg dry mass. A water/methanol (80:20) mixture extracted all the arsenic from the cells. Most of the arsenic (99%) was arsenate. Arsenite, methylarsonic acid and dimethylarsinic acid accounted for the remaining arsenic. Cadmium in the arsenic-containing growth media (50 μg to 100 mg dm-3) reduced the yield of algal cells and induced the formation of an unidentified arsenic compound in Chlorella Böhm. © 1997 by John Wiley & Sons, Ltd.
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  • 66
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    Applied Organometallic Chemistry 11 (1997), S. 273-279 
    ISSN: 0268-2605
    Keywords: sediments ; adsorption ; desorption kinetics ; tributyltin ; dibutyltin ; zinc ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Adsorption-desorption equilibrium and de- sorption kinetic studies were conducted in order to assess desorption of tributyltin (TBT), dibutyltin (DBT) and zinc from resuspended sediment. Equilibria were described in terms of linear adsorption. Desorption kinetics were represented by a two-site model which assumed that desorption consisted of rapid desorption and first-order kinetic desorption. TBT desorbed the most easily. Desorption kinetic parameters were related to adsorption mechanisms. Some experimental results did not correspond with the theoretical model. This was thought to be caused by natural organic ligands originally held in the sediment. Zinc deviated the most, because it was affected by the natural organic ligands more strongly than butylins. For example the partition coefficient of zinc varied by up to 1000-fold, and re-adsorption to sediment of the zinc that had been discharged to the water took place. Release of chemicals induced by remedial dredging was assessed. Desorbed TBT may pose a high risk. Among remediation alternatives, capping or leaving the sediment to stand prior to in situ degradation are preferred. © 1997 by John Wiley & Sons, Ltd.
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  • 67
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    Applied Organometallic Chemistry 11 (1997), S. 297-304 
    ISSN: 0268-2605
    Keywords: freshwater biota ; freshwater fish ; freshwater algae ; organic arsenic ; arsenic ; arsenobetaine ; arsenosugar ; dimethylarsenic ; trimethylarsenic ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment. Water-soluble arsenic compounds in biological samples were extracted with 70% methanol. Samples containing arsenic compounds in the extracts were treated with 2 mol dm3 of sodium hydroxide and reduced with sodium borohydride. The detection of arsenic species was accomplished using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system. The major arsenic species in the river water, freshwater algae and fish are inorganic arsenic, dimethylarsenic and trimethylarsenic compounds, respectively. Trimethylarsenic compounds are also detected in aquatic macro-invertebrates. The freshwater unicellular alga Chlorella vulgaris, in a growth medium containing arsenate, accumulated arsenic and converted it to a dimethylarsenic compound. The water flea Daphnia magna, which was fed on arsenic-containing algae, converted it to a trimethylarsenic species. © 1997 by John Wiley & Sons, Ltd.
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  • 68
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    Applied Organometallic Chemistry 11 (1997), S. 249-249 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Issues 4 and 5 of Applied Organometallic Chemistry, vol. 11, 1997 consist of papers based on work presented at two Symposia held at the Pacifichem '95 Meeting in Honalulu, Hawaii. The papers published here were reviewed by the normal process of the Journal and are not verbatim accounts of the presentations themselves.
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  • 69
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    Applied Organometallic Chemistry 11 (1997), S. 458-458 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 70
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    Applied Organometallic Chemistry 11 (1997), S. 397-402 
    ISSN: 0268-2605
    Keywords: arsenic ; arsenate ; arsenite ; cacodylic acid ; NO production ; DNA ; cellular proliferation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exposure to arsenic, either through chronic consumption of contaminated water or inhalation, is associated with increased risk of cancer, yet the mechanism by which arsenicals promote neoplastic change remains undefined. The carcinogenic process involves the formation of heritable genetic changes in the DNA of normal cells and this process may be enhanced by environmental agents that increase cellular proliferation, increase DNA damage and decrease the ability to repair damage or cause immunosuppression. We describe the inhibition of cellular proliferation of C3H 10T1/2 murine fibroblasts in the presence of 1.0 μM arsenate or arsenite; yet cacodylic acid had no significant effect on cell growth in culture at this concentration. Both arsenate and cacodylate, at micromolar concentrations, slightly stimulated cell growth and cell density when cells were treated with interferon-γ/lipopolysaccharide (IFN-γ/LPS). At 1 μM, arsenate and cacodylate also slightly increased IFN-γ/LPS-induced nitric oxide (NO) synthesis in this cell line, consistent with the increase in cell number observed, whereas 1 μM arsenite significantly increased NO production on a per-cell basis. In contrast, arsenite significantly inhibited NO synthesis at concentrations above 10 μM arsenite as, to a lesser extent, did arsenate and cacodylate. These results suggest that ingestion of arsenicals could alter cellular generation of NO and interfere with its associated physiological functions. © 1997 by John Wiley & Sons, Ltd.
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  • 71
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    Applied Organometallic Chemistry 11 (1997), S. 369-379 
    ISSN: 0268-2605
    Keywords: efflux ; liposomes ; dimethylarsinic acid ; membrane modification ; egg phosphatidylcholine ; bilayer ; tributyltin chloride ; monobutyltin trichloride ; facilitated diffusion ; NMR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The efflux of dimethylarsinic acid (DMA) from liposomes formed from egg phosphatidylcholine (EPC) is increased when tributyltin chloride (TBT) is added to the extraliposomal compartment; however the addition of monobutyltin trichloride (MBT) slows down the efflux. When the liposomes are prepared from EPC and organotin compounds, different mechanisms for DMA efflux seem to operate: TBT-EPC liposomes show a mixture of facilitated and passive diffusion; MBT-EPC liposomes show only passive diffusion. The facilitated diffusion of DMA- seems to be stopped by the addition of TBT to the extraliposomal compartment. © 1997 by John Wiley & Sons, Ltd.
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  • 72
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    Applied Organometallic Chemistry 11 (1997), S. 353-368 
    ISSN: 0268-2605
    Keywords: dsorption ; disease ; environmental chemistry ; non-covalent surface interactions ; pathology ; silicone ; toxicity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While most organometallics enter the en- vironment through their industrial release, silicones are organometallic compounds purposefully introduced in high volume directly into healthy humans. A chemically centered study of the behavior of silicones in the biological environment reveals numerous de- gradative reactions and surface interactions that can produce bioreactive substances. Data from a variety of disciplines suggest that the preponderance of evidence supports the argument that silicone is a toxic organometallic. © 1997 by John Wiley & Sons, Ltd.
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  • 73
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    Applied Organometallic Chemistry 11 (1997), S. 540-540 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 74
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    Applied Organometallic Chemistry 11 (1997), S. 491-497 
    ISSN: 0268-2605
    Keywords: palladium ; complexes ; imidazole ; cyclometalation ; DNA ; intercalation ; drug ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, we show the synthesis of palladium(II) 4,5-phenylimidazole cyclometalated complexes. They have been characterized by IR, 1H- and 13C-NMR spectroscopy. The cyclometalated dimer compound 2 [Pd(C15H11N2)(μ-OAc)]2 and the cyclometalated monomer compound 5 [PdBr(SEt2)(C15H11N2)], having OAc and Br as leaving groups, interact with DNA, modifying its secondary structure (as measured by Tm and CD), without modifying its tertiary structure (as determined by measurement of the electrophoretic mobility in agarose gels). The monomeric compound 5 seems to be the one that induces the highest alterations in DNA secondary structure since it strongly modifies the CD spectrum of the DNA. Melting data of drug-DNA complexes suggest that, at low drug concentration, the 4,5-Imd ligand intercalates between the base pairs in the DNA molecule, increasing the Tm, while at high drug concentrations the palladium(II) centers destabilize the double helix, producing a lowering in Tm values. These results indicate that complexes containing planar structures might selectively bind to DNA that is not supercoiled, and that therefore it only has a secondary structure. © 1997 John Wiley & Sons, Ltd.
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  • 75
    ISSN: 0268-2605
    Keywords: organotin ; porphyrin ; structures ; Mössbauer ; infrared ; NMR ; biologial activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, the structural features and the in vivo biological activity of diorganotin(IV) and triorganotin(IV) derivatives of [meso-tetra(4-carboxyphenyl)porphine] (H4TPPC) are reported. Derivatives with general formula (R2Sn)2TPPC and (R3Sn)4TPPC (R=Me, Bu, and Ph) were obtained, and the main information extracted from the infrared and Mössbauer spectral data, in the solid state, was in favor of the occurrence of five-coordinated tin(IV) atoms, in a polymeric trigonal-bipyramidal configuration, attained through two differently coordinated, ester-type and chelating respectively, carboxylate anions in [R2Sn]2TPPC, while in [Alk3Sn]4TPPC five-coordination of the tin(IV) atom is reached through bridging carboxylate groups.1H and 13C NMR spectra, in DMSO-d6 or CDCl3 suggested that the soluble derivatives, at room temperature or at 342 K, were present in solution as simple monomers.The interactions of (trimethyltin)4[meso-tetra(4-carboxyphenyl)porphinate] (TMTPPC) and (tributyltin)4[meso-tetra(4-carboxyphenyl)porphinate] (TBTPPC) with Bluescript KS(+) plasmid and cultured 3T3 fibroblasts were studied.Both compounds have a clear inhibitory effect on the growth of cultured mouse embryonal fibroblasts (NIH-3T3), TBTPPC being much more active. No evidence was found, however, for DNA cleavage by the compounds at molar ratios as high as 1:10 (TMTPPC, TBTPPC/DNA base pairs).According to our observations, the cytotoxicity of TBTPPC and TMTPPC does not seem to be based on direct interaction with DNA. © 1997 John Wiley & Sons, Ltd.
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    Applied Organometallic Chemistry 11 (1997), S. 583-589 
    ISSN: 0268-2605
    Keywords: electroreduction ; di-n-hexyldichlorogermane ; poly(di-n-hexylgermane) ; sacrificial anode ; organic media ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of the nature of the electrodes (sacrificial anode and cathode) and of the solvent on the electroreduction of di-n-hexyldichlorogermane have been investigated. Several sacrificial anodes (magnesium, zinc and aluminium) and cathodes, including stainless steel, magnesium and aluminium, have been used in THF containing LiClO4. Monomodal and polymodal poly(di-n-hexylgermanes) were obtained with Al/Al and Mg/Mg electrode pairs, but the polymer yield was about twice as high with Al/Al (64%) as with Mg/Mg (30%). Various solvents (tetrahydrofuran, hexamethylphosphorotriamide, N,N-dimethylacetamide, acetonitrile and dimethylformamide) with LiClO4 have been used as electrolytic media. Monomodal PDHG with a relatively narrow molecular weight distribution ([M¯]w/[M¯]n=1.6) was obtained only in THF/HMPA with Al/stainless steel electrodes. © 1997 John Wiley & Sons, Ltd.
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  • 77
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    Applied Organometallic Chemistry 11 (1997), S. 705-706 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 78
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    Applied Organometallic Chemistry 11 (1997), S. 667-671 
    ISSN: 0268-2605
    Keywords: vinyl-substituted silanes ; allylsilanes ; short-chain alkenylsilanes ; silylalkenes ; ruthenium catalyst ; cross-metathesis ; dehydrogenative silylation ; olefins ; vinylsilane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the cross-metathesis reaction of tri(methyl, ethoxy)vinylsilanes with propene and/or 1-butene catalyzed by RuCl2(PPh3)3 activated in benzene at 115-130 °C, a series of l-alkenylsilanes of general formula CH3(CH2)mCH = CHSiMe3-n(OEt)n, where m=0, 1, and n=0-3 (1-silyl-1-alkenes), as well as of formula CH2=C(Me)SiMe3-n(OEt)n, where n=1, 2 (2-silyl-1-alkenes), were obtained. Additional products determined were allysilanes of general formula CH2=CHCH2SiMe3-n(OEt)n and CH3CH= CHCH2SiMe3-n(OEt)n, where n=1-3. © 1997 John Wiley & Sons, Ltd.
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  • 79
    ISSN: 0268-2605
    Keywords: organotin ; Grignard reagents ; sodium tetraethylborate ; mussels ; derivatization ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two different derivatization methods, alkylation with Grignard reagents, and ethylation with sodium tetraethylborate, were compared for the determination of organotin compounds, viz. tributyltin, dibutyltin, monobutyltin, triphenyltin, diphenyltin and monophenyltin, in mussel samples. Temperature, reaction time and concentration of Grignard reagents were optimized in the former method; in the latter the effect of pH, concentration of sodium tetraethylborate and reaction time were studied. In the derivatization with Grignard reagents hexyl, pentyl, propyl, ethyl and methyl were used as alkyl Grignard groups. A critical evaluation of the different derivatization methods is presented. © 1997 John Wiley & Sons, Ltd.
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  • 80
    ISSN: 0268-2605
    Keywords: activation ; catalyst ; palladium ; side chain ; ester ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective activation of the side-chain C-H bond of alkylbenzenes and methylcyclohexenes is achieved by a Pd(OAc)2/Sn(OAc)2 catalyst system. Under an oxygen atmosphere, various benzyl esters were obtained from the substrates and carboxylic anhydrides. The esters were obtained in more than 100% yield based on the amount of benzoic anhydride, and consumption of oxygen was observed. This suggests that oxygen may be incorporated to produce two moles of the benzoxyl group from one mole of benzoic anhydride. It is interesting that either 1-, 3- or 4-methylcyclohexene reacted with benzoic anhydride to give benzyl benzoate. These carboxylations proceeded at the side-chain alkyl group with high selectivity and no ring-carboxylated product or coupling product was detected. From these results, a mechanism involving the formation of a η3-benzylpalladium complex was proposed. © 1997 John Wiley & Sons, Ltd.
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  • 81
    ISSN: 0268-2605
    Keywords: polygermane copolymers ; micropatterning ; photo-oxidation ; heat treatment ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon ultraviolet irradiation of polygermane copolymers of methylphenylgermylene/phenylgermyne units (PhMeGe)n(PhGe)m in air, the germanium-germanium bond in the copolymer film changed into a digermoxane chain. Laser flash photolysis of the copolymer film showed the intermediacy of polygermyl radicals generated by Ge-Ge bond homolysis. The XPS showed the formation of germanium carbide (GeC) and germanium dioxide (GeO2) upon heating the unirradiated and irradiated copolymer (PhMeGe)n(PhGe)m films, respectively. A relatively high-resolution micro- pattern of GeC/GeO2 was obtained by combining the photochemical and thermal properties of the copolymers of methylphenylgermylene/phenylgermyne units. © 1997 John Wiley & Sons, Ltd.
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  • 82
    ISSN: 0268-2605
    Keywords: diorganotin(IV) halides ; N-methyl-2,2′-bisimidazole ; Mössbauer ; IR ; NMR ; cytostatic activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The compounds [SnR2X2(MBIm)] (MBIm=N-methyl-2,2′-bisimidazole; R=Me, Et, Bu, Ph; X=Cl or Br) have been synthesized and characterized by IR, Raman, Mössbauer and NMR spectroscopy, and their capacity to inhibit tumour cell division has been assayed. Measurements of conductivity in acetonitrile show the adducts to behave as non-ionogens in this solvent. The IR, Raman and Mössbauer data suggest that all the complexes have analogous pseudo-octahedral coordination geometries, with the R groups trans and MBIm bidentate. The 1H NMR spectra show the MBIm ligand to be partially dissociated in CDCl3. The most active compounds against the established cell line KB were the butyl derivatives. © 1997 John Wiley & Sons, Ltd.
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  • 83
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    Applied Organometallic Chemistry 11 (1997), S. 761-769 
    ISSN: 0268-2605
    Keywords: methylmercury ; dimethylmercury ; mercury speciation ; estuarine sediment ; sodium borohydride derivatization ; atomic fluorescence spectrometry ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a method capable of quantitatively separating sub-nanogram amounts of monomethylmercury cation (MeHg+) and dimethylmercury from sediments by vacuum distillation at 40 °C and 6 μm Hg pressure followed by hydride derivatization and atomic fluorescence spectrometric detection. Concentrations of MeHg+ in Great Bay Estuarine sediments ranged from 2.2 to 7.3 ng g-1 (dry weight) with a 4.7 ng g-1 average for samples taken over nine weeks of the 1996 summer. The RSD for replicate determinations of a homogenized estuarine sediment is typically less than 6%. The detection limit for the routine determinations on MeHg+ is 0.2 ng g-1 dry weight of sediment. We validated the method by determining MeHg+ concentration in reference sediment S-19, by confirming our method against an established extraction method, and by recovering 85% of 10 ng MeHgCl spiked into estuarine sediments. This paper also includes significant improvements in the hydride derivatization method for mercury compounds relative to previous work with respect to faster analysis time and lower detection limits. © 1997 John Wiley & Sons, Ltd.
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  • 84
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    Applied Organometallic Chemistry 11 (1997), S. 833-841 
    ISSN: 0268-2605
    Keywords: silylcarbodi-imide ; bis(trimethylsilyl)carbodi-imide ; poly(methylsilsesquicarbodi-imide) ; sol-gel ; pyrolysis ; thermal analysis ; mass spectra ; silicon carbonitride ; argon physisorption ; high-resolution transmission electron microscopy (HR TEM) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel polymeric organosilicon gel with the composition [MeSi(NCN)1.5]n synthesized by the reaction of MeSiCl3 with Me3Si-N=C=N-SiMe3 is reported. The reaction is performed without any solvent and with catalytic amounts of pyridine and provides highly cross-linked poly(methylsilsesquicarbodi-imide) in the form of a stable non-oxidic gel with unusual low open porosity (〈1 m2 g-1). The Si-C-N gel transforms to an amorphous silicon carbonitride ceramic, SiC1.1N1.6, by the thermally induced ceramization at 1200 °C in inert atmosphere (argon). The gel-derived silicon carbonitride is thermally stable up to 1450 °C. The synthesis, characterization and pyrolysis behavior of the new polyorganosilicon gel is discussed. © 1997 John Wiley & Sons, Ltd.
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  • 85
    ISSN: 0268-2605
    Keywords: metal colloids ; palladium ; Lindlar catalysts ; catalysis ; hydrogenation ; leaf alcohol ; XPS ; XANES ; TEM/EDX ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The performance of heterogeneous catalysts based on surfactant-stabilized palladium colloids is compared with conventional Pd/C and Lindlar catalysts in the partial hydrogenation of 3-hexyn-1-ol under optimized reaction conditions. The selectivity can be influenced by the protective shell as well as by the support and various promoters. The zwitterionic surfactant sulfobetaine-12 (N,N-dimethyldodecylammoniopropanesulfonate) appears to be best suited as a protective shell for highly selective palladium-colloid catalysts under the surfactants tested. The preferred support is CaCO3: the Pd(SB12) colloids supported on CaCO3 show the highest selectivities and activities of all tested catalysts. The best selectivity (98.1%) towards the desired cis-3-hexen-1-ol (leaf alcohol) is obtained with a lead-promoted palladium colloid supported on CaCO3. This catalyst is slightly (0.5%) better in selectivity and twice as active as a conventional Lindlar catalyst. © 1997 John Wiley & Sons, Ltd.
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  • 86
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    Applied Organometallic Chemistry 11 (1997), S. 813-832 
    ISSN: 0268-2605
    Keywords: cyclotetrasilazanes ; synthesis ; polymerization ; pyrolysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3,5,7-Tetrahydro-1,3,5,7-tetramethylcyclotetrasilazane and 1,3,5,7-tetrahydro-1,2,3,5,6,-7-hexamethylcyclotetrasilazane have been prepared by reaction of 1,3-dichloro-1,3-dihydro-1,3-dimethyldisilazane with ammonia and methylamine, respectively. The polymerization of these cyclotetrasilazanes by the action of catalytic quantities of potassium hydride and the pyrolysis of the resulting polymers in a stream of argon and in a stream of ammonia is reported. Comparisons are made with the polymers obtained by KH treatment of the ammonolysis product of CH3SiHCl2. © 1997 John Wiley & Sons, Ltd.
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  • 87
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    Applied Organometallic Chemistry 11 (1997), S. 903-912 
    ISSN: 0268-2605
    Keywords: tributyltin ; TBT ; butyltin ; organotin ; mussels ; zebra mussels ; environmental occurrence ; harbours and marinas ; Canada ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The presence of the highly toxic antifouling agent tributyltin (TBT) and its degradation products was determined in four species of mussels collected from 34 locations in fresh water in Ontario and in sea water on Canada's west and east coasts. The purpose of the study was to establish baseline information in order to assess TBT trends in mussels after the 1989 Canadian regulation of antifouling uses of TBT. In fresh water, concentrations of TBT were much higher in zebra mussels (Dreissena polymorpha) than in Elliptio complanata or Lampsilis radiata radiata. High concentrations of TBT were also found in Mytilus edulus in sea water. Residues of TBT in all species were similar to those that have been determined in other parts of the world before and after the regulation of antifouling uses of TBT in various countries. Analyses for degradation products indicated that zebra mussels metabolize TBT at about the same rate as L. radiata radiata and M. edulis, but more slowly than E. complanata. © 1997 John Wiley & Sons, Ltd.
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  • 88
    ISSN: 0268-2605
    Keywords: organotin ; pyridine-2-thiolate complexes ; pyrimidine-2-thiolate complexes ; crystal structure ; Mössbauer ; IR ; NMR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mono-organotin(IV) and tin(IV) derivatives of 2-mercaptopyridine (HSPy) and 2-mercaptopyrimidine (HSPym), RSnL3 (R=Me, n-Bu, Ph; L=SPy, SPym; R=Bz=benzyl, o-ClBz, o-ClC6H4, p-ClC6H4, o-tolyl, p-tolyl; L=SPy), RSnClL2 (R=Me, n-Bu, Ph; L=SPy, SPym), RSnCl2L (R=Me, n-Bu; L=SPy, SPym) and SnCl4-nLn (L=SPy, SPym; n=2, 4) were obtained from RSnCl3 or SnCl4 and NaL or by neutralization (R=Ph, p-tolyl; L=SPy, SPym). RSnClL2 and RSnCl2L were better prepared by comproportionation of RSnCl3 and RSnL3.MeSn(SPy)3 and PhSn(SPy)3·1.5CHCl3 crystals, as determined by single-crystal X-ray diffraction, are monoclinic. In the discrete monomeric RSn(SPy)3 units, three bidentate SPy ligands together with R form a distorted pentagonal bipyramid around tin. One S and the C(R) atom are in the axial positions. Two S atoms and three N atoms form the pentagonal plane.From 119Sn Mössbauer and IR data, analogous structures are inferred for the other solid RSnL3 compounds, except for R=Bz, o-ClBz, o-ClC6H4 and o-tolyl, in which tin would be hexacoordinated. In the compounds RSnClL2 and RSnCl2L, tin is at the center of an octahedron or a trigonal bipyramid, respectively. For Sn(SPym)4 and SnCl2(SPym)2, the same type of octahedral structure as was previously found for Sn(SPy)4·HSPy and SnCl2(SPy)2 is proposed.According to IR and 1H, 13C and 119Sn NMR data, the solid-state molecular structures are retained in chloroform and dimethyl sulfoxide solution. © 1997 John Wiley & Sons, Ltd.
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  • 89
    ISSN: 0268-2605
    Keywords: geometry ; relative stability ; organotin(IV) derivatives ; 4-acylpyrazol-5-onates ; fungicidal ; insecticidal ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fungicidal and insecticidal activities of the 4-acetyl (HPMAP) and 4-benzoyl (HPMBP) derivatives of 3-methyl-l-phenylpyrazol-5-one and their complexes with diorganotins [Bu2Sn(PMAP)2, Bu2Sn(PMBP)2, Ph2Sn(PMAP)2 and Ph2Sn(PMBP)2] and triorganotins [Bu3SnPMAP, Ph3SnPMAP, Bu3Sn(PMBP)(H2O) and Ph3SnPMBP] have been determined and their ED50 (fungicidal activity) and LC50 (insecticidal activity) values are reported. An attempt has been made to correlate the type of coordination geometry around the tin atom [based on published 119Sn NMR and 119Sn Mössbauer data as well as on the crystal structures of Bu2Sn(PMBP)2 and Bu3Sn(PMBP)(H2O)] and the relative stabilities with the observed bioactivities in these compounds. The diorganotin complexes are more effective than the triorganotins as insecticides. The effect of disproportionation of R3SnL to give R4Sn and R2SnL2 is discussed with respect to insecticidal activity. The stability constants of the diorganotin compounds are reported, and they suggest that these compounds are sufficiently stable to prevent appreciable ligand exchange before their assimilation into the living tissues of the insects. © 1997 by John Wiley & Sons, Ltd.
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  • 90
    ISSN: 0268-2605
    Keywords: organotin ; 2-thionaphthalene ; synthesis ; crystal structure ; biological activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of di- and tri-organotin complexes of 2-thionaphthalene of general formula RR′R″SnL (R=R′=R″=C6H5, CH3, n-C4H9, C6H11, C6H5CH2; R=R′=C6H5CH2, R″=Cl; R=R′=Me, R″=C10H7S and L=2-thio-naphthalene, C10H7S) have been prepared by the reaction of di-or tri-organotin chloride(s) with 2-thionaphthalene. All compounds have been characterized by elemental analysis, IR, MS, NMR (1H, 13C, 119Sn) and 119Sn Mössbauer spectroscopies. X-ray crystal structures of the representative compounds (C6H5)3SnL and (CH3)2SnL2 confirm a tetrahydral geometry about tin. The biological activities of these compounds against various bacteria and fungi have been investigated. © 1997 by John Wiley & Sons, Ltd.
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  • 91
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    Applied Organometallic Chemistry 11 (1997), S. 129-135 
    ISSN: 0268-2605
    Keywords: organic/inorganic gels ; interpenetrating networks ; polymer-impregnated gels ; organic-doped gels ; sol-gel process ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An attempt is made to classify transparent organic/inorganic materials synthesized by the sol-gel process. The chemical structures of the hybrids are the main criteria for this classification. Three main types of organic/inorganic gels are distinguished and their basic physico-chemical characteristics are outlined. © 1997 by John Wiley & Sons, Ltd.
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  • 92
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    Applied Organometallic Chemistry 11 (1997), S. 71-106 
    ISSN: 0268-2605
    Keywords: polysilane ; poly(carbosilane) ; disilane ; oligosilane ; SiC fiber ; SiC precursor ; dehalocoupling ; dehydropolymerization ; disproportionation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tailoring of polysilanes with given architectures and reactivities is a great challenge in the field of SiC pre-ceramic polymers. This paper reviews recent polysilane and related copolymer synthesis reactions.It is shown that the Wurtz-type polymerization of dichloro-, trichloro- or tetrachloro-silanes, so far the most extensively studied, enables access to a large variety of architectures ranging from one- to three-dimensional (3D) topologies, and based on secondary 〉SiR2, tertiary RSi(Si)3 or quaternary Si(Si)4 silicon units in the polymer backbone. These polysilanes usually present an intrinsic low reactivity, detrimental for fiber processing. Examples are given to illustrate how this reactivity can be increased by secondary substitution reactions, which create reactive entities that can favor further crosslinking reactions.Secondly a novel route involving heterogeneously catalyzed disproportionation of chloromethyldisilanes, developed in our laboratory, is reviewed which offers a direct access to polysilyne-type 3D architecture constituted by arrangements of fused rings. The Lewis-base catalyzed disproportionation mechanism is discussed and seems to involve donor-stabilized silylenes as key intermediates in the polymer formation process. The experimental results are supported by ab-initio quantum chemical calculations.Silylenes attack the Si sites of higher functionality causing a high regioselectivity for the exclusive formation of branched oligosilanes. The oligomers undergo thermally induced branching and crosslinking reactions leading to poly(chloromethylsilane)s. Obviously, there are analogies to the oligomer and polymer formation of the transition-metal complex catalyzed dehydropolymerzation of methyldisilanes. Poly(chloromethylsilane)s exhibit a high reactivity due to the presence of Si-Cl bonds.Disproportionation of chloromethyldisilanes in presence of olefins such as styrene provides promising polymer precursors for SiC fibers. Their rheological properties have been investigated for various styrene contents. The polymer fibers spun from melt are cured under ammonia, and then pyrolyzed to silicon carbide fibers, showing temperature resistance up to 1500 °C. © 1996 by John Wiley & Sons, Ltd.
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  • 93
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    Applied Organometallic Chemistry 11 (1997), S. 195-203 
    ISSN: 0268-2605
    Keywords: OMCVD ; ceramic ; thin films ; metallacycle ; titanium ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four-membered-ring heterocyclic molecule Cp2TiCH2Si(Me2)NSiMe3 (1; Cp=η-C5H5) was studied as a single-source precursor to titanium-based ceramic thin films. Its decomposition was studied at atmospheric and low pressure under nitrogen, argon and helium by TG-DTA-MS. Thin films containing the four elements of the metallacycle and oxygen were deposited on silicon substrates by low-pressure (20 Torr) chemical vapor deposition (CVD) between 773 and 923 K. Films were characterized by SEM-EDS, XPS, EPMA-WDS and XRD analyses. © 1997 by John Wiley & Sons, Ltd.
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  • 94
    ISSN: 0268-2605
    Keywords: laser fusion ; titanium ; metal-containing polymer ; titanocene ; carboxylic acid ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear, soluble copolymers containing titanium are of interest for use in targets for inertial-confinement fusion (ICF) experiments because the titanium is a useful spectroscopic probe for studying the nuclear fusion process. We have studied the reactions of dichloro- titanocene and diphenyltitanocene with carboxylic acids to determine if these can be used to prepare such polymers. Model reactions of dichlorotitanocene with p-toluic acid show that both mono- and di-carboxylates are formed. We have prepared a soluble titanium-containing copolymer via the reaction of poly(styrene-co-methacrylic acid) with an excess of dichlorotitanocene but attempts to remove the excess molecular titanocene from the copolymer result in crosslinking of the copolymer. Model reactions of benzoic and pivalic acids with diphenyltitanocene demonstrate that monosubstituted carboxylato(phenyl)titanocenes are formed but that these products are stable only at low temperatures and decompose readily at ambient temperature. Proton NMR studies of the reaction of diphenyltitanocene and benzoic acid at -20 °C indicate that this reaction is second order, suggesting that the reaction does not proceed through a benzyne intermediate. © 1997 by John Wiley & Sons, Ltd.
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  • 95
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    Applied Organometallic Chemistry 11 (1997), S. 289-296 
    ISSN: 0268-2605
    Keywords: mushrooms ; arsenic ; arsenobetaine ; arsenocholine ; hydraulic high-pressure nebulizer ; HPLC-HHPN-ICP-MS ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three mushroom species from two old arsenic smelter sites in Austria were analyzed for arsenic compounds. The total arsenic concentrations were determined by ICP-MS. Collybia maculata contained 30.0 mg, Collybia butyracea 10.9 mg and Amanita muscaria 21.9 mg As kg-1 dry mass. The arsenic compounds extracted with methanol/water (9:1) from the dried mushroom powders were separated by HPLC on anion-exchange and reversed-phase columns and detected by ICP-MS using a hydraulic high-pressure nebulizer. In Collybia maculata almost all arsenic is present as arsenobetaine. Collybia butyracea contained mainly arsenobetaine (8.8 mg As kg-1 dry mass) and dimethylarsinic acid (1.9 mg As kg-1). Amanita muscaria contained arsenobetaine (15.1 mg As kg-1), traces of arsenite, dimethylarsinic acid and arsenate, and surprisingly arsenocholine (2.6 mg As kg-1) and a tetramethylarsonium salt (0.8 mg As kg-1). © 1997 by John Wiley & Sons, Ltd.
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  • 96
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    Applied Organometallic Chemistry 11 (1997), S. 345-349 
    ISSN: 0268-2605
    Keywords: siloxones ; sedimentary ; geochronology ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selected samples of sediments from cores taken in the Ala Wai Canal (south-east Oahu, Hawaii) have been analyzed for organosilicon (silicone) content. Observed levels of silicone range from just above the detection limit (≈0.01 ppm) to over 1 ppm, and vertical distribution in the sediment column generally increases upwards, with the highest silicone content in the most contemporary sediments (dated independantly( by 210Pb and 137Cs measurements). Further, there is clear evidence of spike events (i.e. high levels of silicone in older, buried sediments) which appear to be associated with major, documented storm events on the island os Oahu. Silicone assay was by solvent extraction, and quantitative spectrophotometric measurement at 7.95 μm. The Ala Wai Canal is an anthropogenic hydorgraphic feature on Oahu. © 1997 by John Wiley & Sons, Ltd.
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  • 97
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    Applied Organometallic Chemistry 11 (1997), S. 327-335 
    ISSN: 0268-2605
    Keywords: arsenic ; urine ; HPLC-ICP-MS ; arsenobetaine ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsenic compounds were determined in 21 urine samples collected from a male volunteer. The volunteer was exposed to arsenic through either consumption of codfish or inhalation of small amounts of (CH3)3As present in the laboratory air. The arsenic compounds in the urine were separated and quantified with an HPLC-ICP-MS system equipped with a hydraulic high-pressure nebulizer. This method has a determination limit of 0.5 μg As dm-3 urine. To eliminate the influence of the density of the urine, creatinine was determined and all concentrations of arsenic compounds were expressed in μg As g-1 creatinine. The concentrations of arsenite, arsenate and methylarsonic acid in the urine were not influenced by the consumption of seafood. Exposure to trimethylarsine doubled the concentration of arsenate and increased the concentration of methylarsonic acid drastically (0.5 to 5 μg As g-1 creatinine). The concentration of dimethylarsinic acid was elevated after the first consumption of fish (2.8 to 4.3 μg As g-1 creatinine), after the second consumption of fish (4.9 to 26.5 μg As g-1 creatinine) and after exposure to trimethyl- arsine (2.9 to 9.6 μg As g-1 creatinine). As expected, the concentration of arsenobetaine in the urine increased 30- to 50-fold after the first consumption of codfish. Surprisingly, the concentration of arsenobetaine also increased after exposure to trimethylarsine, from a background of approximately 1 μg As g-1 creatinine up to 33.1 μg As g-1 creatinine. Arsenobetaine was detected in all the urine samples investigated. The arsenobetaine in the urine not ascribable to consumed seafood could come from food items of terrestrial origin that - unknown to us - contain arsenobetaine. The possibility that the human body is capable of metabolizing trimethyl- arsine to arsenobetaine must be considered. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 381-391 
    ISSN: 0268-2605
    Keywords: silicon-controlled ; bond formation ; cyclization ; allyltrimethylsilane ; 1,3-diketones ; β-ketoesters ; malonates ; ceric ammonium nitrate ; manganese(III) acetate ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of silicon on C-C bond formation between carbonyl compounds and allyltrimethylsilane was investigated. Treatment of 1,3-diketones, β-ketoesters or malonates with allyltrimethylsilane in the presence of ceric ammonium nitrate (CAN) in methanol produced the corresponding allylated products. Furthermore, introduction of Mn(OAc)3 · 2H2O into those reactions for replacement or assistance of CAN afforded silicon-containing cyclopentanes in 51-75% yields. A sequential process involving allylation, free-radical cyclization and elimination was also developed by use of CAN/Mn (OAc)3 · 2H2O/Cu(OAc)2 · H2O. Accordingly, β-ketoesters or malonates were allowed to react with allylsilanes in acetic acid to give silicon-containing cyclopentanes with an exo methylene unit in 52-71% yields. These reactions involved carbocationic and carboradical intermediates, of which formation and chemical activities were controlled by a β-silyl group. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 4 Tab.
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 451-455 
    ISSN: 0268-2605
    Keywords: imposex ; Japanese sea snails ; organotin pollution ; tributyltin (TBT) ; triphenyltin (TPT) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A country-wide survey and laboratory experiments on imposex (a superimposition of male sex organs on female sea snails) in Japanese sea snails were carried out: 38 species were observed to be affected by imposex. For the rock shell, Thais clavigera, the percentage occurrence of imposex was 100% at almost all sites surveyed. The degree of imposex seemed to be positively correlated with the concentrations of tributyltin (TBT) and triphenyltin (TPT) in the species. The results of laboratory experiments showed that imposex in T. clavigera was initiated and promoted by both TBT and TPT. Many oviduct-blocked individuals, which were thought to be sterile, were observed in T. clavigera at sites near marinas and harbours. The effects of organotin pollution on the population of T. clavigera were observed at the sites near marinas. From the results of the additional country-wide survey on imposex in T. clavigera during 1993-1995, serious organotin pollution and imposex symptoms in the species are still continuing in Japan. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 539-539 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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