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  • 1
    Digitale Medien
    Digitale Medien
    Peptide-induced parallel DNA duplexes for oligopyrimidines. Stereospecificity in complexation for oligo(L-lysine) and oligo(L-ornithine) (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 7838-7845 
    Details
    ISSN: 1520-4995
    Quelle: ACS Legacy Archives
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/bi00486a009
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  • 2
    Digitale Medien
    Digitale Medien
    Network Formation by Chain Polymerization of Liquid-Crystalline Monomer: A First Off-Lattice Monte Carlo Study (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 5632-5637 
    Details
    ISSN: 1520-5835
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ma00120a031
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  • 3
    Digitale Medien
    Digitale Medien
    Intermolecular effects on the radiogenic formation of electron-capture phosphorus-centered radicals. A single-crystal ESR study of diastereoisomeric precursors (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 938-944 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja00159a005
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  • 4
    Digitale Medien
    Digitale Medien
    Dynamical calculations on the photoisomerization of small polyenes in a nonadiabatic formalism (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4895-4909 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The dynamics of the cis–trans isomerization in 10° monopyramidalized ethylene, butadiene, and hexatriene has been studied in a nonadiabatic treatment including explicitly the twisting motion. The electronic energy curves, (transition) dipole moments, and nonadiabatic couplings have been obtained from ab initio CI calculations. An initially (Franck–Condon) excited wave function is constructed from the final vibrational eigenfunctions and energies. The appearance of the calculated prepared state is discussed in relation to the increasing line broadening vs decreasing chain length of the primary vibrational bands in the 1 1B+u absorption spectra of polyenes. It is found that this feature can be explained from the increasing tendency of shorter polyenes to be nonplanar in the excited state. The time evolution of the molecules is monitored by calculating the radiationless decay, the dipole moment, and the contributions of the electronic states to the total wave function. The role of the nonabsorbing 2 1A−g state is discussed. It is demonstrated that the dynamics of the cis–trans isomerization are directly correlated to the shape of the potential energy curve of the absorbing excited state. Ethylene is found to rotate once about the double bond in 0.075 ps and butadiene in 0.2 ps, whereas hexatriene is excited to an almost stationary wave function. Because of the limitations of the present model, the molecules do not show any substantial ("sudden'') polarization upon inclusion of the nonadiabatic coupling. For the same reason, the contribution of the electronic ground state to the total wave function is small.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.452776
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  • 5
    Digitale Medien
    Digitale Medien
    Electron capture phosphoranyl radicals in x-irradiated diphosphine disulfides. A single crystal ESR and ab initio quantum chemical study (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3694-3708 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: An electron spin resonance (ESR) study of phosphorus centered electron capture radicals trapped in single crystals of substituted diphosphine disulfides [R2P(S)P(S)R2, R=Me, Et, Ph] irradiated with x rays at 77 K is reported. The principal values and direction cosines of the hyperfine and g tensors were determined. It is shown that in all three compounds a three-electron P–P bond radical is formed. The unpaired electron is found to be symmetrically distributed over the two phosphorus atoms. The direction of the phosphorus hyperfine coupling makes an angle of 20°–30° with the P–P bond. The alkyl substituted diphosphine disulfides reveal furthermore a radical in which the unpaired electron is asymmetrically distributed over the two phosphorus atoms. The electronic configuration of these radicals is best described as trigonal bipyramidal (TBP) with a central phosphorus atom and the unpaired electron in an equatorial position (TBP-e). The second phosphorus atom and a sulfur substituent are located on the apical sites of the TBP. Irradiation yields for R=Et, Ph also a three-electron P–S bond radical and a number of dissociation products. Ab initio quantum chemical calculations of the isotropic and anisotropic hyperfine couplings for the three-electron P–P bond radicals are in good agreement with the experimental values and support the assignment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.450209
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  • 6
    Digitale Medien
    Digitale Medien
    Solving the discretized time-independent Schrödinger equation with the Lanczos procedure (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4374-4379 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A new method is presented to find bound state solutions of the one-, two-, or three-dimensional Schrödinger equation. The equation is turned into a sparse matrix eigenvalue problem by representing the potential energy surface and the wave function on a grid. The Laplacian is represented by a high (10th) order finite difference formula. Eigenvalues are found by the Lanczos procedure [J. Cullum and R. A. Willoughby, J. Comp. Phys. 44, 329 (1981)] and transition probabilities (Franck–Condon factors) are found by the recursive residue generation method [A. Nauts and R. E. Wyatt, Phys. Rev. Lett. 51, 2238 (1983)]. Examples are given for the 1D Morse oscillator and the 2D Hénon-Heiles potential. Numerical convergence can be checked easily and highly accurate results can be obtained. The algorithm is fast, easy to implement, and vectorizable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458575
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  • 7
    Digitale Medien
    Digitale Medien
    Efficiency of a combustion reaction in power production (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2730-2734 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We analyze a thermal engine in which the source of heat is the combustion reaction CH4+2O2→CO2+2H2O. The efficiency of the thermal engine is defined as the ratio of the power output of the engine to the power input. We compare the efficiency in two modes of operation, one in which the input and output of chemical species are constants and one in which their corresponding fluxes have an imposed oscillatory component of a given amplitude and frequency. The ratio of efficiency in the oscillatory mode to the stationary flux mode can be as high as 1.3 for an amplitude of variation of the input and output fluxes plus or minus 40% of the stationary value. At low amplitudes of variation (10%), a single peak is present in a plot of the ratio of efficiency vs frequency of the fluxes. For higher amplitudes there are two peaks in that plot. One peak is associated with a response of the system that has the same period as the fluxes and the other occurs in a frequency range for which the periodic response is twice that of the perturbation. We calculate plots of the oscillatory output flux and the power output divided by that flux, which is an analog of a thermodynamic force, as a function of time, to show the importance of both resonance effects and the phase relation between the flux and the thermodynamic force in determining the ratio of efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454003
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  • 8
    Digitale Medien
    Digitale Medien
    Semiclassical calculation of the vibrational structure of the B˜ 1Bu Rydberg state of trans-di-imide from ab initio configuration interaction potential energy surfaces (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3027-3035 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The applicability of the SDCI and CEPA methods to the excited state of the title molecule is investigated. Two basis sets are used, one of triple zeta quality extended with diffuse functions and another which also contained polarization functions. For the subsequent CI calculations closed shell as well as open shell, molecular orbitals are used. We investigate the Pople correction as a way to obtain size consistent results from the SDCI calculation. For each method, a two-dimensional potential energy surface of the 1(4ag,5bu) Rydberg state of trans-di-imide (HNNH) is calculated. The vibrational fine structure in the corresponding B˜←X˜ UV absorption spectrum is derived from these surfaces and the result is compared to the spectrum measured by Neudorfl et al. [P. S. Neudorfl, R. A. Back, and A. E. Douglas, Can. J. Chem. 59, 506 (1981)]. A semiclassical method [K. S. Sorbie, Mol. Phys. 32, 1577 (1976)] is used to obtain the vibrational frequencies. A slightly modified version of the Heller frozen Gaussian approximation [E. J. Heller, J. Chem. Phys. 75, 2923 (1981)] is proposed and used to obtain the intensities of the vibrational bands. We conclude that it is important to use the open shell molecular orbital basis and the SDCI plus Pople correction, or even better, the CEPA. Both methods give good results for the vertical transition energy and excited state geometry. The error in the vibrational frequencies is in the order of 10%, but the NN-stretch mode is best described by the CEPA method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456924
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  • 9
    Digitale Medien
    Digitale Medien
    Exact and moment equation modeling of electron transport in submicron structures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1743-1745 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We compare I-V characteristics of a semiconducting submicron n+nn+ diode as predicted by extended moment equation approximations to those obtained from the solution of the corresponding Boltzmann equation. All lower order models fail in the predominantly ballistic regime. Moreover, the conductance is inadequately predicted by these models, even in nonballistic cases due to the high build-in electric fields.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.106237
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  • 10
    Digitale Medien
    Digitale Medien
    GROUND WATER HYDRAULICS CONSIDERATIONS REGARDING LANDFILLS (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 27 (1991), S. 0 
    Details
    ISSN: 1752-1688
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie
    Notizen: : Landfill siting and design guidelines or regulations differ from state to state. Most include hydrogeological criteria, referring to hydraulic conductivities, aquifers, ground water flow patterns, contaminant travel times, and distance between landfill and sensitive targets for contaminants, etc. However, almost all of the existing hydrogeological guidelines are incomplete, inconsistent, or both. The aquitard between landfill and regional aquifer frequently offers less resistance to leachate migration than compliance with regulations may suggest. Residence times of leachate, that makes it through the landfill liner, is often overestimated. Monitoring wells in the regional aquifer are unreliable detectors of local leaks in a landfill. If a landfill does leak, costly aquifer restoration is called for. For traditional landfill designs, ground water monitoring considerations suggest the siting over homogeneous sand and gravel aquifers, rather than over complex till environments. An alternative landfill design criterion is suggested, which is based on a negative hydraulic gradient underneath the landfill. This design guarantees ground water protection, simplifies landfill monitoring, and generally enhances the landfill economy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1752-1688.1991.tb01477.x
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