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  • Biochemistry  (79)
  • Occupational Health and Environmental Toxicology  (38)
  • Wiley-Blackwell  (117)
  • Cambridge University Press
  • 1980-1984  (117)
  • 1975-1979
  • 1983  (117)
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  • Wiley-Blackwell  (117)
  • Cambridge University Press
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  • 1980-1984  (117)
  • 1975-1979
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 1 (1983), S. 131-140 
    ISSN: 0263-6484
    Keywords: Biochemistry ; polyamines ; putrescine ; spermidine ; spermine ; ornithine decarboxylase ; biosynthesis ; cell proliferation ; oxidized polyamines ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The naturally-occurring polyamines exist in the free form, as N-acetyl derivatives and bound to protein. Their biosynthesis is subject to sensitive control, particularly of ornithine decarboxylase. This enzyme may be multifunctional and a key regulatory protein. Studies, principally with selective inhibitors, have elucidated the roles of polyamines in cell proliferation. Oxidized polyamines, in contrast, can be potent mitotic inhibitors. These effects are reviewed in terms of their chemistry and biochemistry. Their principal distinctions are that they can be made or degraded intracellularly, they can associate electrostatically with macromolecules by means of their spaced cationic groups, and these can be readily converted to covalent bonds.
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  • 2
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 181-186 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Gaussian basis sets, consisting of 15 s-type, 11 p-type, and 6 d-type functions, for the fourth-row main group elements, In-Xe, are presented. In order to compare these basis sets with larger ones, calculations have been performed in I2 and TeO2.
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  • 3
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 283-293 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Energetics and geometries for the hydrated gaseous halide anions have been computed from a simple model in which the molecular dipole of water was composed of two parts, one due to a lone pair on oxygen (60%) and the rest to formal charges on the nuclei. The calculations were made for both the symmetric and nonsymmetric structures. A variety of structures were used to compute potential energies and distances with up to six water molecules. The total energy consisted of a sum of electrostatic, polarization, dispersion, and repulsion terms. Various sets of repulsive potential parameters, ranging from those determined from molecular beam experiments to those determined using experimental ion-water distances or energies, have been employed to compute repulsive interaction energies. It was found that the range parameters play a significant role in deciding the magnitudes of the distances and energies, as the latter are most sensitive to them. It was also shown that with a simple correlation scheme the consistency of the experimental energies and distances can be tested separately without using repulsive potential parameters from other sources. It also suggests that a range of parameters can be used to compute repulsion energies. Despite the fact that the model is greatly simplified, the agreement of both the predicted ion-oxygen distances and energies with both experiment and other calculations is excellent. A detailed analysis of our calculation suggests that the negative ion clusters with one to three water molecules contain symmetric orientation of water molecules, while those with more than three may contain asymmetric orientations of water molecules or a mixture of both. From the log-log plots of hydration energies versus (R + radius of water molecule), we have proposed empirical expressions of the type ΔEn-1,n = 10·0x (R + 1.38)-y with both Pauling's and Ladd's radii for univalent ions with which stepwise hydration energies of the latter can be predicted if we know thier radii. The values predicted for the alkali cations are in excellent agreement with the experimental and theoretical values, indicating the consistency of the simple model.
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 345-349 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The tautomerism of the uracil-4-hydroxyuracil system is examined with the 3-21G basis set and full geometry optimization using gradient techniques. Single-point calculations at the 6-31G level were also done and the results compared with the 2-pyridone-2-hydroxypyridine system. The best ΔE(taut) obtained in this work is 74.1 kJ/mol.
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  • 5
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
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  • 6
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    Journal of Computational Chemistry 4 (1983), S. 1-8 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio SCF calculations of the equilibrium geometries have been carried out on nine possible isomers of MH2N2, where M = C or Si, and compared with the results of MNDO calculations. The results for the carbon compounds are in good agreement with available experimental data, but in the case of the silicon compounds, the molecules are predicted to be unstable with respect to decomposition to SiH2 and N2. The inclusion of electron correlation at the MP3 level does not alter the order of the relative stabilities, although the importance of the correlation contribution varies substantially between the different isomers.
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  • 7
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    Journal of Computational Chemistry 4 (1983), S. 23-32 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computer-oriented algorithm is developed for enumerating and generating all rigorously planar benzenoid hydrocarbons. An additional algorithm is also developed for identification and enumeration of carcinogenic bay regions. The results are reported for undisrupted benzenoid structures up to ten fused rings. The reported numbers of isomeric benzenoids do not agree with the results in the literature, because other authors included in their considerations some polyhexes which are not strictly planar structures (e.g., helicenes) or which represent rings of hexagons (e.g., circulenes). The reported results for enumeration of bay regions fully agree with those of Balasubramanian et al.
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  • 8
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    Journal of Computational Chemistry 4 (1983), S. 58-67 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A low-cost microcomputer and package of assembly language routines has been developed to emulate the structure and performance of a large analog computer. The advantages of the analog computer, as implemented in this scheme, include (1) a significant reduction in the programming effort involved in modeling complex dynamic systems and (2) the control of the simulation and model parameters in a completely interactive and flexible manner. The symbolic nomenclature and schematic representations involving devices, such as integrators, comparators, multipliers, and function generators, offers a powerful alternative to the more conventional numerical methods, that is, to provide very simply the solutions to large systems of differential equations. This approach invariably leads the user to a more thorough understanding of the dynamic character of the system. The technique is illustrated using a chemical kinetics example involving the simulation of laser-induced fluorescence. The results of this work have provided an assessment of a systematic error that occurs when using induced resonance fluorescence to measure OH concentrations in the troposphere of the earth.
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  • 9
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    Journal of Computational Chemistry 4 (1983), S. 104-109 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Approximate minimum energy reaction paths have been calculated for two thioketone-enethiol tautomeric systems using an ab initio SCF-MO method. The calculations indicate nearly equal stabil ties of the isolated tautomers in both systems and an energy barrier of ca. 85 kcal/mol for their interconversion. This barrier is expected to be significantly lower in solution as a result of solvent-solute interactions.
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  • 10
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    Journal of Computational Chemistry 4 (1983), S. 114-122 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The MM2 molecular mechanics force field, as modified for halogens, is able to predict the structures, dipole moments, and energies of the isomers of benzene hexachloride. For benzene tetrachloride and naphthalene tetrachloride the field exaggerates the stability of conformers with axial chlorine, but gives satisfactory results if the field is modified to allow for interaction between electronegative substituents and the π electrons.
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  • 11
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    Journal of Computational Chemistry 4 (1983), S. 124-124 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
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  • 12
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    Journal of Computational Chemistry 4 (1983), S. 127-135 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A relativistic effective core potential (REP) has been generated for the uranium atom and used in self-consistent-field calculations of the A states of UH, UF, and their ions. Energy curves were calculated at the base configuration level which ensures the dissociating atoms are described by Hartree-Fock wavefunctions. The electronic bonding of these molecules is found to be similar to that of comparable alkaline-earth hydrides and fluorides. The uranium 6p, 6d, and 5f orbitals retain their atomic character but the orbitals extend into the bonding region and are distorted by overlap repulsion and electrostatic effects. Nonetheless, the atomic energetic coupling determines that low energy states will have the maximum spin multiplicity and maximum orbital angular momentum projection consonant with the charge-transfer bonding.
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  • 13
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    Journal of Computational Chemistry 4 (1983), S. 154-157 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Following an earlier proposal to evaluate electron repulsion integrals over Gaussian basis functions by a numerical quadrature based on a set of orthogonal polynomials (Rys polynomials), \documentclass{article}\pagestyle{empty}\begin{document} $$ (\eta \eta \parallel \eta \eta) = 2(\rho/\pi)^{1/2} \sum\limits_{\alpha = 1, N} I_x(u_{\alpha})I_{y}(u_{\alpha}) I_z(u_{\alpha})W_{\alpha} $$ \end{document} a computational procedure is outlined for efficient evaluation of the two-dimensional integrals Ix, Iy, and Iz. Compact recurrence formulas for the integrals make the method particularly fitted to handle high-angular-momentum basis functions. The technique has been implemented in the HONDO molecular orbital program.
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  • 14
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    Journal of Computational Chemistry 4 (1983), S. 175-180 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: CNDO/Force and compliance constant methods were applied to define general quadratic potential functions for F2CO and HCOF. A satisfactory set of compliants was obtained by suitably scaling down the stretching and stretch-stretch elements of the initial force constant matrix, evaluated by the CNDO/force approach, followed by fitting the compliants to available experimental data.
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  • 15
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    Journal of Computational Chemistry 4 (1983), S. 218-225 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The problem of the determination of the vibration-rotation eigenvalue in diatomic molecules is considered. An eigenvalue equation totally independent from the eigenfunction is written for any potential, analytical or numerical. This equation uses uniquely the vibration-rotation canonical functions; its resolution is reduced to that of a simple and classical numerical problem. Examples of numerical applications for analytical (Morse) and numerical potentials are presented. It is shown that the vibrational eigenvalues deduced from the eigenvalue equation are within 10-6 cm-1 of the exact values. Comparison with conventional methods are presented and discussed.
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  • 16
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Symmetry methods employed in the ab initio polyatomic program HONDO are extended to the coupled perturbed Hartree-Fock (CPHF) formalism, a key step in the analytical computation of energy first derivatives for configuration interaction (CI) wavefunctions, and energy second derivatives for Hartree-Fock (HF) wavefunctions. One possible computational strategy is to construct Fock-like matrices for each nuclear coordinate in which the one- and two-electron integrals of the usual Fock matrix are replaced by the integral first derivatives. “Skeleton” matrices are constructed from the unique blocks of electron-repulsion integral derivatives. The correct matrices are generated by applying a symmetrization operator. The analysis is valid for many wavefunctions, including closed- or open-shell spin-restricted and spin-unrestricted HF wavefunctions. To illustrate the method, we compare the computer time required for setting up the coupled perturbed HF equations for eclipsed ethane using D3h symmetry point group and various subgroups of D3h. Computational times are roughly inversely proportional to the order of the point group.
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  • 17
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    Journal of Computational Chemistry 4 (1983), S. 276-282 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A scheme is presented that enables photographic representation of the (two-dimensional) surfaces of (three-dimensional) molecular orbitals and electron density functions. The algorithm has been implemented by a program which is completely general and computationally efficient.
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  • 18
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    Journal of Computational Chemistry 4 (1983), S. 308-312 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A force field has been developed, on the basis of available experimental and partial retention of diatomic differential overlap (PRDDO) data, to permit molecular mechanics calculations on azoxyalkanes. The calculated structures and enthalpies of formation are in fair agreement with experimental results. The calculated enthalpies of formation and strain energies are compared with the corresponding quantities for analogous azoalkanes.
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  • 19
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    Journal of Computational Chemistry 4 (1983), S. 337-344 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Interchange and many-body perturbation theory are applied to the calculation of the radiative lifetime of the 3B1 state of SO2. The radiative lifetime of 3B1 SO2 is predicted to be 7.6 msec, in excellent agreement with the experimental collision-free phosphorescence lifetime. As a separate calculation, interchange perturbation theory is used to determine the radiative lifetime of the 1A1 state of CH2.
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  • 20
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    Journal of Computational Chemistry 4 (1983), S. 333-336 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The nearest-neighbor exclusion model for intercalation was studied using an energetical approach. It was shown that creation of the intercalation site in the exclusion model corresponds to the same energetical destabilization of the structure as in the standard model of intercalation. The stability of the intercalation complex formed in the case of the exclusion model is lower by 68 kcal/mol as compared with the standard model, but geometrical structures of both complexes are very similar. The electrostatic molecular potential method was also used to further characterize the intercalation site formed within both models of intercalation.
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  • 21
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    Journal of Computational Chemistry 4 (1983), S. 350-361 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The major relativistic effects are included into the model potential (MP) method of Bonifacic and Huzinaga. The effects are incorporated on the level of Cowan and Griffin's relativistic Hartree-Fock (RHF) method. The model potential parameters are determined using the results of nonrelativistic Hartree-Fock (NHF) and RHF calculations. A new scheme of selection of the basis functions for use in atomic and molecular MP calculations is proposed. To obtain agreement with the Hartree-Fock calculations on AgH and Ag2, the 4p shell has to be included explicitly in the MP calculations. The explicit treatment of the 4p electrons and the resulting reduction of the core size are necessary in order to overcome difficulties with approximate representation of the large 4p-4d core-valence interactions on the MP level.
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  • 22
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    Journal of Computational Chemistry 4 (1983), S. 399-403 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Parameters have been derived so as to enable the inclusion of deuterium in the MM2 molecular mechanics force field. Several compounds were studied and the results are compared with experiment. The results are never qualitatively wrong, but the accuracy ranges from excellent to only fair. They are quite good for hydrocarbons, but less so for ketones.
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  • 23
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    Journal of Computational Chemistry 4 (1983), S. 404-409 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The radical cations H3PPH3+⋅, H3PSH2+⋅, H3PClH+·, and HClClH+· have been studied by ab initio molecular-orbital theory. An increasing tendency to adopt trigonal bipyramidal (TBP) gemoetries is observed for the phosphorus radicals with sulfur and chlorine ligands. The three-electron bond dissociation energies are calculated to be between 7 and 31 kcal mol-1. The dependence of these bond energies on the ionization potentials for the neutral hydrides is illustrated, and the deformation of phosphorus σ* radicals towards TBP structures is discussed.
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  • 24
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    Journal of Computational Chemistry 4 (1983), S. 428-437 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computer method for the calculation of the pseudorotational parameters in five-membered rings from vicinal proton spin-spin coupling constants is described. Some typical problems met in practice are discussed. Applications of the program in the conformational analysis of some substituted cyclopentanes are presented.
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  • 25
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    Journal of Computational Chemistry 4 (1983), S. 449-460 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: As a model reaction for peptide and bond formation, the SN2 reactions between glycine and ammonia have been studied with and without amine catalysis: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm NH}_3 + {\rm NH}_2 {\rm CH}_2 {\rm COOH} + ({\rm NH}_3 ) \to {\rm NH}_2 {\rm CH}_2 {\rm CONH}_2 + {\rm H}_2 {\rm O} + ({\rm NH}_3 )$$\end{document} using ab initio molecular-orbital methods. For each of the catalyzed and uncatalyzed reactions, two reaction mechanisms have been examined: a two-step and a concerted mechanism. The stationary points of each reaction, including intermediate and transition states, have been identified and free energies calculated for all geometry-optimized reaction species to determine the thermodynamics and kinetics of the reaction. The calculations demonstrate that a second ammonia molecule catalyzes amide bond formation, and that the two-step mechanism is more favorable than the concerted one for the catalyzed reaction, while for the uncatalyzed reaction both mechanisms are competitive.
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    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Basis-set balance parameters, defined in terms of various projections of an abstract force vector in the space spanned by the logarithms of orbital exponents, are evaluated for a sample of 100 Gaussian basis sets. These basis sets are taken from a random Gaussian distribution of bases, centered on the best energy, fully variational uniform quality (UQ) atomic orbital (AO) basis sets. With each basis geometry optimization has been carried out for model molecule dimethyl sulfoxide, the wavefunction of which molecule is exceptionally sensitive to basis-set errors. Correlations between the balance of basis sets and calculated molecular properties are analyzed.
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  • 27
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    Journal of Computational Chemistry 4 (1983), S. 513-523 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital theory has been used to probe the effect of the substituent X on the structures, strain energies, stabilization energies, inversion barriers, and proton affinities of carbanions CH3CX CH3- and cis-C3H4X-, where X = H, F, CN, and NC. All geometries have been optimized with a 3-21G basis set, and the parent anions (X = H) were also optimized with the same basis set with a diffuse function added (i.e. the 3-21 + G basis set). The anions, with the exception of the α-cyanoisopropyl anion, are pyramidal. The out-of-plane angle, α, for the pyramidal anions decreases in the order F 〉 H ≈ NC 〉 CN, and the barriers to inversion follow the same order with the cyclopropyl anions consistently having higher barriers than the isopropyl anions. The substituents strongly stabilize the anions with the stabilization energy following the order CN 〉 NC 〉 F. The cyano group slightly reduces the strain energy of cyclopropane, but the isocyano and fluoro substituents are weakly and strongly destabilizing, respectively. The pyramidal cyclopropyl anions are less strained than the cyclopropanes except when the substituent is a cyano group where the strain energies are reversed but are very similar. The planar anions all have higher strain energies than the cyclopropanes.
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  • 28
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    Journal of Computational Chemistry 4 (1983), S. 552-555 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A very simple yet effective device for reducing the number of self-consistent-field (SCF) cycles in central finite-difference calculations of molecular properties is presented. The efficiency of this is demonstrated by MINDO/2 calculations of the force constants of a variety of molecules. The device consists of using information about the wavefunction at two values of a perturbation parameter to provide an estimate of the wavefunction at a third. This estimate is then used as an initial guess in an SCF procedure. The underlying theory is discussed and applications to other problems are suggested.
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  • 29
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    Journal of Computational Chemistry 4 (1983), S. 567-577 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An ab initio computation procedure to obtain electronic transition wave numbers in solution is presented and discussed. The continuum description of the bulk solvent is adopted, and solute-solvent interaction is reduced to a closed-form interaction operator added to the solute Hamiltonian. The resulting Schrödinger equations are solved variationally. No limitations are imposed on the shape of the solvent cavity or on the level of accuracy of the ab initio procedure.
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    Journal of Computational Chemistry 4 (1983), S. 605-605 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
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  • 31
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    Journal of Computational Chemistry 4 (1983), S. 594-604 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Proton affinities (PA) of 80 neutral bases were calculated using the semiempirical molecular orbital procedure MNDO. These were compared with the corresponding experimental and, where available, ab initio STO-3G and 4-31G data. For the 12 bases studied which led to ions which were not hyperconjugatively stabilized, the mean absolute error between the calculated and experimental values was 7.2 kcal mol-1. However, a plot of these data revealed a clear tendency of MNDO to underestimate the PAs of the more basic molecules. Where hyperconjugative stabilization of the ion was possible, the calculated PAS were underestimated by a further 7-10 kcal mol-1 for each attached alkyl group. Calculated and observed methyl-and ethyl-cation affinities were compared for 18 bases with qualitatively similar results.
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  • 32
    ISSN: 0197-8462
    Keywords: Macaca monkeys ; electrocardiogram ; blood pressure ; stationary magnetic fields ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposures to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system.
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  • 33
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    Bioelectromagnetics 4 (1983), S. 21-42 
    ISSN: 0197-8462
    Keywords: biomolecules ; DNA ; microwave absorption ; optical method ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Direct determination of the microwave absorption characteristics of biological molecules in solution by an optical heterodyne technique is described. A visibly transparent sample is irradiated in a spatially nonuniform manner with pulsed microwaves, and the spatial variation in temperature increase measured by detecting the phase chirp impressed on a single-frequency He—Ne laser beam passing through the heated region. Results for several liquids and solutions such as water, methanol, various saline solutions, and solutions of DNA and DNA sodium salt in water are described. Where direct comparison is possible the results agree very well with published values. A significant increase in the absorption of DNA solutions compared with pure water has been observed that is consistent with microwave absorption by the longitudinal mode of the double helix.
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  • 34
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    Bioelectromagnetics 4 (1983) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 35
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    Bioelectromagnetics 4 (1983), S. 115-122 
    ISSN: 0197-8462
    Keywords: microwave biological effects ; hyperthermia ; B lymphocytes ; capping ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Normal mouse B lymphocytes were tested for the ability to cap plasma membrane antigenantibody complexes following exposure to 2.45-GHz continuous wave (CW) microwaves at power densities up to 100 mW/cm2 (45 W/kg specific absorption rate), at 37, 41, and 42.5 °C. After a 30-minute treatment, the irradiated cells and the nonirradiated controls were tested for capping by the direct immunofluorescence technique. First, the cells were incubated for nine minutes at 37 °C with fluorescein isothiocyanate-conjugated goat antimouse immunoglobulin. After fixing and washing, the percentage of capped cells was determined under a fluorescence microscope. The results show that for the nonirradiated controls, capping is reduced from 90% at 37 °C, to 52% 41 °C. to less than 5% for cells that were pretreated at 42.5 °C. There was no significant difference between the microwave-treated cells and the controls when both were maintained at the same temperature. In another experiment, there was no significant difference in the percentage of capping between controls and cells that were exposed to microwave radiation during capping, when the temperature in both preparations was kept at 38.5 °C. The results demonstrate that B-lymphocyte capping is sensitive to temperature in the range that is proposed for use in tumor therapy.
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  • 36
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    Bioelectromagnetics 4 (1983), S. 157-165 
    ISSN: 0197-8462
    Keywords: amplitude-modulated RF fields ; hyperthermia ; B lymphocytes ; capping ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: B lymphocytes collected from normal ICR Swiss mouse spleens were exposed in vitro in a Crawford cell to 147-MHz radiofrequency (RF) radiation, amplitude modulated by a 9-, 16-, or 60-Hz sine wave. The power densities ranged between 0.11 and 48 mW/cm2. The irradiated samples and the controls were maintained at 37 °C or 42 °C, with temperature variations less than 0.1 °C. Immediately after a 30-minute exposure, the distribution of antigen-antibody (Ag—Ab) complexes on the cell surface was evaluated at 37 °C by immunofluorescence. Under normal conditions (37 °C, no RF), Ag—Ab complexes are regrouped into a polar cap by an energy-dependent process. Our results demonstrate that the irradiated cells and the nonirradiated controls capped Ag—Ab complexes equally well after exposure at 37 °C. Capping was equally inhibited at 42 °C in both the controls and irradiated cells. No statistically significant differences in capping were observed between the RF-exposed and control samples at any of the modulation frequencies and power densities employed as long as both preparations were maintained at the same temperature.
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  • 37
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    Bioelectromagnetics 4 (1983), S. 167-180 
    ISSN: 0197-8462
    Keywords: air ions ; corona discharge inhalation system ; DC electric fields ; small animal exposure system ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Many previous problems in establishing the nature of biological and behavioral effects of small air ions have been due to poor control over the ion-inhalation microclimate, resulting in nonuniform electrical fields and highly uneven concentrations of small air ions. We have developed a corona discharge air ion-inhalation system for use with animals that incorporates rigorous control over the microclimate and produces highly uniform concentrations of small air ions throughout the exposure area.
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  • 38
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    Bioelectromagnetics 4 (1983), S. 193-204 
    ISSN: 0197-8462
    Keywords: microwaves ; immobilized peroxidase ; chemiluminescence ; luminol ; horseradish peroxidase ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Protein gels formed by crosslinking bovine serum albumin and horseradish peroxidase with glutaraldehyde were used to measure effects on peroxidase activity of 400-MHz (CW) radiofrequency radiation (RFR) at an average specific absorption rate (SAR) of 1.45 W/ kg. The enzyme activity was measured by luminol chemiluminescence recorded on photographic film after hydrogen peroxide activation. Activity was measured during RFR exposure of gels or after exposure of gels polymerized in the RFR field. During exposure, a significant (P 〈 .05) reversible increase occurred in overall mean peroxidase activity of gels activated with 0.88 M H2O2 but not in those activated with 8.8 M H2O2. Gels containing solubilized luminol and formed in the field showed no overall mean increase in peroxidase activity, but did display a highly significant (P 〈 .001) alteration in the distribution of local activities when compared to unexposed gels. These results are apparently due to changes in the rate of diffusion (concentration equilibration) of hydrogen peroxide in the gel.
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  • 39
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    Bioelectromagnetics 4 (1983), S. 249-255 
    ISSN: 0197-8462
    Keywords: radiofrequency radiation ; 27.12 MHz ; hyperthermia ; teratology ; rat ; embryo ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Five groups of pregnant Sprague-Dawley rats were either sham exposed or were irradiated in a 27.12-MHz radiofrequency (RF) field at 55 A/m and 300 V/m on gestation day 9. The absorbed power (approximately 11 W/kg) caused a relatively rapid increase in the rat's colonic temperature. Rats in group I were sham irradiated for 2.5 h at 0 A/m, 0 V/m. In group II RF irradiation was terminated after the rat's colonic temperature reached 41.0 °C. In group III the 41.0- °C temperature was maintained an additional 15 min by varying the field strength. At both temperatures the teratogenic and embryotoxic effects of the RF-induced hyperthermia increased as the exposure duration increased, but the increase was especially noticeable at 42.0 °C. The results indicate that the teratogenic and embryotoxic effects of RF-induced hyperthermia are related to both the temperature of the dam during exposure and the length of time the dam's temperature remains elevated.
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  • 40
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    Bioelectromagnetics 4 (1983), S. 267-279 
    ISSN: 0197-8462
    Keywords: mice ; specific absorption rate ; calorimetry ; TEM chamber ; 200-400 MHz CW ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A maximum of six live mice, mouse cadavers, prolate spheroids molded from muscle-equivalent tissue, or saline-filled culture flasks, were exposed to continuous wave radiation in a TEM cell at frequencies between 200 and 400 MHz. Whole-body average specific absorption rate (SAR) was determined from power meter measurements of incident, reflected, and transmitted powers. The SARs for both live mice and cadavers were approximately twice that for the prolate spheroid models, and when housed in Plexiglas restraining cages, about 2 1/2 times greater. An error multiplying factor is identified, that quantitatively expresses how SAR data obtained by the three -power-meter method becomes progressively more noisy as the irradiation frequency is lowered or as the TEM cell cross section is increased.
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  • 41
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    Bioelectromagnetics 4 (1983), S. 294-294 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 42
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    Bioelectromagnetics 4 (1983), S. 295-301 
    ISSN: 0197-8462
    Keywords: fusion reactors ; magnetic fields ; biological effects ; fertilization ; fish ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The sensitivity of trout ova and sperm to 1-T magnetic fields was investigated. It was determined that (1) overall test results combining seven independent Z-statistics demonstrated a significant (α 〈 0.0001) enhancement of fertilization when ova alone were exposed to the magnetic field prior to fertilization; (2) similarly, overall test results combining Z-statistics from eight independent experiments indicated a significant (α 〈 0.0004) enhancement when sperm alone were exposed; and (3) statistical analysis of nine independent experiments confirmed enhanced fertilization (α 〈 0.0001) when both ova and sperm were exposed to the magnetic field prior to fertilization. Although these data indicated that both ova and sperm were sensitive to magnetic fields, simultaneous exposure of both gametes did not have a greater total effect on fertilization rate than the sum of their individual effects.
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  • 43
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    Bioelectromagnetics 4 (1983), S. 341-355 
    ISSN: 0197-8462
    Keywords: microwaves ; microwave hyperthermia ; fever ; febrile convulsions ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: While convulsions associated with fever represent a serious problem in pediatric medicine, conventional animal models of febrile convulsions suffer numerous technical limitations. A microwave-hyperthermia model that eliminates these problems was tested. Microwave energy was used to increase the core temperature of 13- and 17-day-old rats, resulting in convulsions similar to febrile convulsions in human infants. Rats were irradiated for 10 min in circularly polarized waveguides at 918 MHz, CW (average SAR = 9.4 W/kg at 13 days and 18.0 W/kg at 17 days as determined by twin-well calorimetry). Day 17 irradiated rats were less susceptible to convulsions than were day 13 irradiated rats, indicating an age-dependent decline in susceptibility. Contrary to findings of earlier models using infrared or hot-oven heating, convulsions induced with microwave hyperthermia impaired neither brain growth nor subsequent performance during behavioral testing. Simultaneous measurement of brain and rectal temperatures during microwave irradiation revealed differential heating rates that favor thermal homeostasis in brain tissue.
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  • 44
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    Bioelectromagnetics 4 (1983), S. 141-155 
    ISSN: 0197-8462
    Keywords: microwave bioeffects ; hamster macrophages ; immunology ; viricidal macrophages ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Acute exposure of hamsters to microwave energy (2.45 GHz; 25 mW/cm2 for 60 min) resulted in activation of peritoneal macrophages that were significantly more viricidal to vaccinia virus as compared to sham-exposed or normal (minimum-handling) controls. Macrophages from microwave-exposed hamsters became activated as early as 6 h after exposure and remained activated for up to 12 days. The activation of macrophages by microwave exposure paralleled the macrophage activation after vaccinia virus immunization. Activated macrophages from vacciniaimmunized hamsters did not differ in their viricidal activity when the hamsters were microwave or sham-exposed. Exposure for 60 min at 15 mW/cm2 did not activate the macrophages while 40 mW/cm2 exposure was harmful to some hamsters. Average maximum core temperatures in the exposed (25 mW/cm2) and sham groups were 40.5 °C (±0.35 SD) and 38.4 °C (±0.5 SD), respectively. In vitro heating of macrophages to 40.5 °C was not as effective as in vivo microwave exposure in activating macrophages to the viricidal state. Macrophages from normal, shamexposed, and microwave-exposed hamsters were not morphologically different, and they all phagocytosed India ink particles. Moreover, immune macrophage cytotoxicity for virus-infected or noninfected target cells was not suppressed in the microwave-irradiated group (25 mW/cm2, 1 h) as compared to sham-exposed controls, indicating that peritoneal macrophages were not functionally suppressed or injured by microwave hyperthermia.
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  • 45
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    Bioelectromagnetics 4 (1983) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 46
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    Bioelectromagnetics 4 (1983), S. 215-247 
    ISSN: 0197-8462
    Keywords: electric field ; 60-Hz ; detection ; psychophysics ; rats ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rats partially deprived of food were trained individually to press a lever in the presence of a vertical, 60-Hz electric field and not to press in its absence. Correct detections that occurred during brief, 3- or 4-s trials occasionally produced a food pellet. The probability of detecting the field was found to increase as field strength increased. The threshold of detection, ie, the field strength required for detections at a probability of 0.5 after correction for errors, was generally between 4 and 10 kV/m. The range of field strengths between almost zero and almost 100% correctness of detection was approximately 8 kV/m. A logistic function provided a good description of the increase in the detection probability with increasing field strength. These performances occurred reliably in 19 rats, some of which were studied for 2 years. Control procedures showed that the behavior required that the rat be in the electric field; the behavior was not controlled by any of several potentially confounding variables.
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  • 47
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    Bioelectromagnetics 4 (1983), S. 257-265 
    ISSN: 0197-8462
    Keywords: shortwave ; diathermy applicators ; heating ; attenuation ; conductivity ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Tissue-substitute models consisting of layers of synthetic, electrically equivalent subcutaneous fat, muscle, and bone shaped in conformation with the normal anatomy are used for rapid determination of distribution of temperature and specific absorption rate throughout the tissues when exposed to electromagnetic radiation. The surfaces of the bisected models are approximated during a short exposure period, then separated and scanned with a thermograph. A method was developed to eliminate the electrical discontinuity at the bisected surfaces while allowing separation and subsequent thermographic scanning. A thin layer of silk screen wetted with propylene glycol saturated with sodium chloride was used at the fat interface and a 0.9% sodium chloride solution was used to wet the screen at the muscle interface to eliminate electrical discontinuity during exposure to 27.12-MHz diathermy. Tests showed that in the presence of an electrical discontinuity the heating pattern was grossly distorted. With the method used, the electrical discontinuity is minimized and the subsequent thermographic scanning reveals that the heating pattern is equivalent to that of an intact model.
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    Bioelectromagnetics 4 (1983) 
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    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 49
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    Bioelectromagnetics 4 (1983), S. 315-326 
    ISSN: 0197-8462
    Keywords: Drosophila ; ELF electromagnetic effects ; oviposition ; development ; viability ; magnetic fields ; DC magnetic fields ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Drosophila flies placed in a habitat with two lateral boxes demonstrated sensitivity to magnetic fields: Oviposition decreased by exposure to pulsated extremely low frequency (ELF) (100)Hz, 1.76 miliTesla (mT) and sinusosidal fields (50 Hz, 1 mT), while there was no initial effect of exposure to a static magnetic field (4.5 mT). Drosophila eggs treated for 48 h with the above described fields showed that (1) mortality of eggs was lower in controls than in eggs exposed to all tested magnetic fields; (2) mortality of larvae increased when a permanent magnet was used; (3) mortality of pupae was highest when a permanent magnet was used; and (4) general adult viability was highest in controls (67%) and diminished progressively when eggs were exposed to pulsated (55%), sinusoidal (45%), and static (35%) magnetic fields.
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  • 50
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    Bioelectromagnetics 4 (1983) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 51
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    Bioelectromagnetics 4 (1983), S. 11-19 
    ISSN: 0197-8462
    Keywords: electric field ; bone growth ; osteotomy repair ; rats ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rats were exposed to a 60-Hz electric field at an unperturbed field strength of 100 kV/m to determine its affect on bone growth and fracture repair. Exposure of immature male and female rats for 20 h/day for 30 days did not alter growth rate, cortical bone area, or medullary cavity area of the tibia. In another experiment, midfibular osteotomies were performed and the juvenile rats were exposed at 100 kV/m for 14 days. Evaluation by resistance to deformation and breaking strength indicated that fracture repair was not as advanced in the exposed animals as in the shamexposed animals. In another experiment measurements of resistance to deformation were made in adult rats at 16, 20, and 26 days after osteotmy. Fracture repair was slower in exposed compared to control animals at day 20 and, to a lesser extent, at day 16, but not at day 26.
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  • 52
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    Bioelectromagnetics 4 (1983), S. 55-62 
    ISSN: 0197-8462
    Keywords: 2880-MHz microwaves ; submaxillary salivary gland ; Na+ ; K+ ; Ca2+ ; flame photometry ; hyperthermia ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Na+, K+, and Ca2+ concentrations in the blood serum and submaxillary salivary gland (SSG) were investigated in adult, male rats exposed to 2880-MHz microwaves modulated with 1.5-μs pulses at a pulse repetition rate of 1000 Hz or in a hyperthermal environment. Rats were exposed, one at a time, for 30 min to microwaves producing a specific absorption rate (SAR) of: 4.2, 6.3,6.8,8.4, 10.8, or 12.6 W/kg, or were sham exposed under similar environmental conditions. In a second series, one group of rats was exposed singly for 15, 30, or 60 min to microwaves producing an SAR of 9.5 W/kg and other rats were exposed for similar periods at 40 °C; and 10 rats were sham exposed. Flame photometric analysis indicated that the thresholds of microwave radiation required to induce a change in Na+, K+, and Ca2+ concentrations in the salivary glands are 6.8, 6.8, and 6.3 W/kg, respectively. The directions of Na+, K+, and Ca2+ ion shifts in exposed rats' salivary glands are similar, whether affected by microwaves or hyperthermia. Greater changes in Na+ and K+ concentrations in SSG of rats exposed to microwaves for 15 and 30 min were found than in those exposed at 40 °C. On the other hand, exposure to hyperthermia at 40 °C or to microwaves for 1 h caused Na+ concentration to be increased by 68.7 and 59.5% and K+ concentration to be decreased by 29.6 and 21.7%, respectively.
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  • 53
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    Bioelectromagnetics 4 (1983), S. 63-77 
    ISSN: 0197-8462
    Keywords: microwaves ; exposure chamber ; dosimetry ; rabbit ; body mass ; food consumption ; blood chemistry ; pathology ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Two groups of 16 male New Zealand rabbits were exposed to 2450-MHz continuous wave microwave fields in two experiments of 90 days each. The incident power densities of the first and second experiment were 0.5 and 5 mW/cm2, respectively. During each study, 16 animals were adapted to a miniature anechoic chamber exposure system for at least 2 weeks, then 8 of them were exposed for 7 h daily, 5 days a week for 13 weeks, and the other 8 animals were sham exposed. The rabbits were placed in acrylic cages, and each was exposed from the top in an individual miniature anechoic chamber. Thermography showed a maximum specific absorption rate of 5.5 W/kg in the head and 7 W/kg in the back at 5-mW/cm2 incident power density. After each 7-h exposure session, the animals were returned to their home cages. Food consumption in the exposure chamber and body mass were measured daily. Blood samples were taken before exposure and monthly thereafter for hematological, morphological, chemical, protein electrophoresis, and lymphocyte blast transformation studies. Eyes were examined for cataract formation. Finally, pathological examinations of 28 specimens of organs and tissues of each rabbit were performed. Statistically, there was a significant (P 〈 .01) decrease only of food consumption during the 5-mW/cm2 exposure; other variables were not significantly different between exposed and control groups.
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  • 54
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    Bioelectromagnetics 4 (1983), S. 107-114 
    ISSN: 0197-8462
    Keywords: spermatogenesis ; microwave radiation ; germinal tissue ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Male Sprague-Dawley rats were exposed for 6 h per day for nine days to pulse-modulated microwave radiation (1.3 GHz, at 1-μs pulse width, 600 pulses per second). Exposures were carried out in cylindrical waveguide sections at a mean dose rate of 6.3 mW/g; sham controls were treated similarly and received no irradiation. At time periods corresponding to 0.5, 1.0, 2.0, and 4.0 cycles of the seminiferous epithelium, groups of four shamirradiated and four irradiated rats were killed and the testes removed for analysis. Net mass of the testes, epididymides, and seminal vesicles; daily sperm production (DSP) per testis and per gram of testis; sperm morphology; and the number of epididymal sperm were determined. There were no statistically significant differences between the shamirradiated and irradiated groups with respect to any measured variable. In a group of seven surrogate animals of similar body mass, the dose rate of 6.3 mW/g caused a net change in body temperature (via rectal probe) of 1.5 °C.
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    Bioelectromagnetics 4 (1983), S. 79-90 
    ISSN: 0197-8462
    Keywords: electric fields ; hematology ; serum chemistry ; rats ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Numerous hematologic and serum chemistry variables were examined in rats exposed to unperturbed 60-Hz electric fields at 100 kV/m for 15, 30, 60, or 120 days. Each study was replicated once. Rigorous statistical evaluations of these data did not detect any consistent effect of the electric field for exposures of up to 120 days. It was, however, not unusual in any individual study to detect certain variables that were significantly different between the exposed and shamexposed animals. This emphasizes the need for replicate designs and appropriate statistical analyses when investigating chemical or physical insults that may have minimal influence on biologic function.
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    Bioelectromagnetics 4 (1983), S. 91-101 
    ISSN: 0197-8462
    Keywords: reproductive hazards ; congenital malformations ; high voltage ; epidemiological study ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A retrospective study on reproductive hazards was performed among 542 employees at Swedish power plants. Questionnaires were answered by 89% of the employees. Data on pregnancies were checked by studying hospital case records. There was a statistically significant, decreased frequency of „normal“ pregnancy outcome, almost exclusively due to an increased frequency of congenital malformations, when the father was a high-voltage switchyard worker. The differences in pregnancy outcome could not be explained by any of the confounding factors analyzed. The total number of children with malformations (26) and the total number of pregnancies in this study, however, were very small.
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    Bioelectromagnetics 4 (1983), S. 293-293 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 58
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    Bioelectromagnetics 4 (1983), S. 303-314 
    ISSN: 0197-8462
    Keywords: DC electric fields ; exposure systems ; finite difference method (FDM) ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: In most previous 50/60-Hz experiments, subjects were placed in a dielectric cage and the electric field was applied from outside the cage. Although the field outside the cage was kept uniform in space and constant in time, the field inside the cage undergoes undesirable temporal and spatial variations. We have designed an electric-field exposure system that overcomes these problems by having a metal cage constitute a part of the field generating electrodes. The uniformity along the diameter of the cages for mice and cats are more than 84.2% and 74.3%, respectively.
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    Bioelectromagnetics 4 (1983), S. 327-339 
    ISSN: 0197-8462
    Keywords: 60-Hz electric fields ; perinatal exposure ; rat ; visual-evoked response ; central nervous system ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Two independent series of experiments were performed on 114 male Sprague-Dawley derived, albino rat pups, which represented 61 litters in experimental series I and 53 litters in experimental series II. Animals were exposed for 20 h/day from conception to testing (postnatal days 11-20) to a vertical, 65-kV/m, 60-Hz electric field or sham-exposed. Recordings of the visual-evoked response (VER) were obtained using a small silver ball electrode placed epidurally over the visual cortex. Visual stimuli consisted of 10-μS light flashes delivered at 0.2 Hz. Computer-averaged VERs were obtained and power spectral analyses (fast Fourier transform) were performed on the tapered (split cosine-bell window), averaged VERs. The expected age-related changes were clearly evident; however, a detailed analysis of VER component latencies, peak-to-peak amplitude, and power spectra failed to reveal any consistent, statistically significant effect of exposure to 60-Hz electric fields.
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    Bioelectromagnetics 4 (1983), S. 371-381 
    ISSN: 0197-8462
    Keywords: 2,450 MHz ; microwaves ; natural killer cells ; macrophages ; mice ; lymphocytes ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effect of 2,450-MHz CW microwaves on natural killer (NK) cell activity and lymphocyte responsiveness to mitogen stimulation was studied in mice. Groups of mice were irradiated at power densities of 5, 15, or 30 mW/cm2 (SAR = 3.5, 10.5, and 21 W/kg respectively) for 1.5 h on 2 or 9 consecutive days. NK cell activity was determined using an in vitro 51Cr release cytotoxicity assay and an in vivo tumor-cell clearance assay. No consistent change was observed in the mitogen response of spleen cells from sham compared with irradiated mice. A significant suppression of NK cell activity measured in vitro was observed for mice irradiated at 30 mW/cm2, but not at 15 or 5 mW/cm2. A significant suppression of NK cell activity, as determined using the in vivo tumor clearance assay, was also observed at 30 mW/cm2. NK cell activity, as determined using the in vitro assay, returned to normal within 24 h following the last irradiation. Treatment of mice with hydrocortisone caused suppression of NK cell activity measured in vitro and in vivo. Paradoxically, peritoneal macrophage phagocytosis was enhanced following irradiation at 30 mW/cm2, the power density at which NK activity was suppressed. The possible role that microwave heating plays in producing these effects is discussed.
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    Bioelectromagnetics 4 (1983), S. 383-396 
    ISSN: 0197-8462
    Keywords: hematology ; immunology ; mice ; pulsed microwaves ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Mice were exposed in the far field in an anechoic chamber to 2,880-MHz pulsed microwaves 3 to 7.5 h daily, 5 days/week for 60 to 360 h. Three experiments were performed at average power densities of 5 mW/cm2 and six at 10 mW/cm2, corresponding to averaged specific absorption rates (SARs) of 2.25 and 4.50 mW/g, respectively. Each experiment consisted of eight mice, with a concurrently sham-exposed group of eight. In two of three studies at 5 mW/cm2, there was a significant increase in bone marrow cellularity in the microwave-exposed groups compared to the sham-exposed groups. Significant differences were occasionally seen in erythrocyte, leukocyte, and platelet values from microwaveexposed groups, but were not consistently observed. In one of six groups exposed at 10 mW/cm2, mean bone marrow cellularity was reduced significantly in the microwaveexposed mice; in another group, the lymphocyte count was increased. In only one exposure (10 mW/cm2 for 360 h) was any significant effect noted on serum proteins: a reduction to 5.1 ± 0.3 g/dl in the exposed versus 5.6 ± 0.4 g/dl in the sham-exposed mice. This was due to a decrease in alpha and beta globulins, with no effect on albumin or gamma globulin concentrations. No effect on bone marrow granulocyte/macrophage colony-forming units (CFU) was revealed following exposure of mice to pulsed microwaves at 5 mW/cm2. In one of four exposures at 10 mW/cm2, there was a significant increase in CFU-agar colonies. No significant effects of exposures at 10 mW/cm2 were observed on in vivo and in vitro assays of cell-mediated immune functions. No exposure-related histopathologic lesions were found from examination of several tissues and organs. Results of these series of exposures of mice at SARs of 2.25 and 4.50 mW/g indicated no consistent effects on the hematologic, immunologic, or histopathologic variables examined.
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    Bioelectromagnetics 4 (1983), S. 357-370 
    ISSN: 0197-8462
    Keywords: Helmholtz coils ; electromagnetic fields ; induced currents ; saline media ; biological tissue ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The use of Helmholtz aiding coils to induce small electromagnetic (EM) fields in living tissue for both medical and research purposes has become quite common. While much progress has been made in showing that these induced EM signals can cause a variety of effects in tissues and individual cells, a satisfactory explanation of how the effects occur or how the EM signals couple to the tissue has not yet emerged. To address the latter problem adequately, it becomes necessary to know the spatial distribution of the induced fields inside a given set of boundaries. This paper examines the situation used for much in vitro research where a cylindrical culture dish is filled with a conducting solution and placed between the Helmholtz coils. Two cases are considered. The first assumes that the coils are above and below the culture dish (the planes of the coils are parallel with the top and bottom of the dish); the second assumes that the planes of the coils are parallel with the sides of the dish. A closed form solution is obtained for both cases, and it is shown that the induced EM field distribution is markedly different for the two cases.
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    Bioelectromagnetics 4 (1983), S. 397-400 
    ISSN: 0197-8462
    Keywords: acoustical imaging ; microwave-induced acoustics ; pulsed microwaves ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Pulsed 5.66-GHz microwave energy irradiated a model of a human hand that was positioned above a submerged planar array of 400 hydrophones. Hydrophone response data were analyzed by a computer that graphically reproduced the image.
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    Bioelectromagnetics 4 (1983), S. 103-106 
    ISSN: 0197-8462
    Keywords: Calcium efflux ; insulin ; secretion ; islets of Langerhans ; rabbit ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rabbit islets of Langerhans were exposed at 37 °C for 18 h to a low-frequency-pulsed magnetic field, generated in paired Helmholtz coils. Exposed islets showed a reduction of 26.1 ± 4.3% in 45Ca2+ content (P 〈 .004). a reduction of 25.1 ± 6.3% in 45Ca2+ efflux (P 〈 .006), and a reduction of 35.0 ± 8.7% (P 〈 .002) in insulin released during glucose stimulation when compared with appropriate controls.
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    Bioelectromagnetics 4 (1983), S. 123-139 
    ISSN: 0197-8462
    Keywords: microwave immunosuppression ; natural killer cells ; hamster immune system ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Hamsters were exposed to repeated or single doses of microwave energy and monitored for changes in core body temperature. circulating leukocyte profiles, serum corticosteroid levels, and natural killer (NK) cell activity in various tissues. NK cytotoxicity was measured in a 15Crrelease assay employing baby hamster kidney (BHK) targets or BHK infected with herpes simplex virus. Repeated exposure of hamsters at 15 mW/cm2 for 60 min/day had no significant effect on natural levels of spleen-cell NK activity against BHK targets. Similarly, repeated exposure at 15 mW/cm2 over a 5-day period had no demonstrable effect on the induction of spleen NK activity by vaccinia virus immunization, that is. comparable levels of NK were induced in untreated and microwave-treated animals. In contrast, treatment of hamsters with a single 60-min microwave exposure at 25 mW/cm2 caused a significant suppression in induced spleen NK activity. A similar but less marked decrease in spleen NK activity was observed in sham-exposed animals. Moreover, the sham effects on NK activity were not predictable and appeared to represent large individual animal variations in the response to stress factors. Depressed spleen NK activity was evident as early as 4 h postmicrowave treatment and returned to normal levels by 8 h. Hamsters exposed at 25 mW/cm2 showed an elevated temperature of 3.0-3.5 °C that returned to normal within 60 min after termination of microwave exposure. These animals also showed a marked lymphopenia and neutrophilia by 1 h posttreatment that returned to normal by 8-10 h. Serum glucocorticosteroids were elevated between 1 and 8 h after microwave treatment. Sham-exposed animals did not demonstrate significant changes in core body temperature. peripheral blood leukocyte (PBL) profile, or glucocorticosteroid levels as compared to minimum-handling controls.
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    Bioelectromagnetics 4 (1983), S. 181-191 
    ISSN: 0197-8462
    Keywords: 60-Hz electric fields ; arousal response ; electric field strength ; mice ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: White-footed mice, Peromyscus leucopus, were exposed to 60-Hz electric fields to study the relationship between field strength and three measures of the transient arousal response previously reported to occur with exposures at 100 kV/m. Five groups of 12 mice each were given a series of four 1-h exposures, separated by an hour, with each group exposed at one of the following field strengths: 75, 50, 35, 25, and 10 kV/m; 8 additional mice were sham-exposed with no voltage applied to the field generator. All mice were experimentally naive before the start of the experiment, and all exposures occurred during the inactive (lights-on) phase of the circadian cycle. The first exposure produced immediate increases in arousal measures, but subsequent exposures had no significant effect on any measure. These arousal responses were defined by significant increases of gross motor activity, carbon dioxide production, and oxygen consumption, and were frequently recorded with field strengths of 50 kV/m or higher. Significant arousal responses rarely occurred with exposures at lower field strengths. Responses of mice exposed at 75 and 50 kV/m were similar to previously described transient arousal responses in mice exposed to 100-kV/m electric fields. Less than half of the mice in each of the field strength groups below 50 kV/m showed arousal responses based on Z (standard) scores, but the arousals of the mice that did respond were similar to those of mice exposed at higher field strengths. Polynomial regression was used to calculate the field strength producing the greatest increases for each of the arousal measures. The results show that the amplitude of the transient arousal response is related to the strength of the electric field, but different measures of arousal may have different relationships to field strength.
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    Bioelectromagnetics 4 (1983), S. 205-214 
    ISSN: 0197-8462
    Keywords: microwaves ; apomorphine ; amphetamine ; morphine ; behavior ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of various psychoactive drugs were studied in rats exposed for 45 min in a circularly polarized, pulsed microwave field (2450 MHz; SAR 0.6 W/kg; 2-μs pulses, 500 pps). Apomorphine-induced hypothermia and stereotypy were enhanced by irradiation. Amphetamine-induced hyperthermia was attenuated while stereotypy was unaffected. Morphine-induced catalepsy and lethality were enhanced by irradiation at certain dosages of the drug. Since these drugs have different modes of action on central neural mechanisms and the effects of microwaves depend on the particular drug studied, these results show the complex nature of the effect of microwave irradiation on brain functions.
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    Bioelectromagnetics 4 (1983), S. 281-292 
    ISSN: 0197-8462
    Keywords: microwaves ; amplitude modulation ; murine allogeneic cytotoxicity ; T lymphocytes ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Significant inhibition of allogeneic cytotoxicity of the target cell MPC-11 by the murine cytotoxic T-lymphocyte line CTLL-1 was observed when the 4-h cytotoxicity assay was conducted in the presence of a 450-MHz field sinusoidally amplitude-modulated at 60 Hz. Exposure of the effector cells to the field prior to adding them to the target cells in the cytolytic assay resulted in a similar inhibition, suggesting a direct interaction of the field with the cytolytic T lymphocyte. The inhibition was preferentially expressed during the early allogeneic recognition phase. Fieldexposed cytolytic cells recovered their full cytolytic capacity in 12.5 h. A differential susceptibility was observed with modulation frequencies from 0 to 100 Hz. Peak suppression occurred at 60 Hz modulation, with progressively smaller effects at 40, 16, and 3 Hz. The unmodulated carrier wave did not affect the cytotoxicity. Effects with 80- and 100-Hz modulation were smaller than at 60 Hz. These results demonstrate an inhibitory but recoverable effect by certain amplitude modulations of weak nonionizing radiation upon the cell-mediated cytolytic immune response.
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    Bioelectromagnetics 4 (1983), S. 43-54 
    ISSN: 0197-8462
    Keywords: microwave radiation ; fertilizing capacity ; turkey sperm ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Turkey sperm were exposed to 2.45-GHz microwave radiation in a temperature-controlled waveguide apparatus. Temperature was maintained at either 25 or 40.5 °C. The sperm were exposed for 30 min at a specific absorption rate (SAR) of 10 or 50 mW/g. Following irradiation, the sperm were used to inseminate virgin turkey hens artificially. During the 9 weeks following the single insemination, the following were assessed: mean number of eggs, percentage of fertile eggs, rate of decrease in egg fertility, percentage of hatched eggs, and percentage of early and late deaths. These data demonstrate that, for the conditions used in these experiments, microwave radiation has no effect on the fertilizing capacity of turkey sperm.
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    Journal of Computational Chemistry 4 (1983), S. 9-14 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Koopmans' theorem ionization potentials have been calculated for a series of hydrides, methyls, and silyls HnX, (CH3)nX, and (SiH3)nX (X = F, Cl, n = 1; X = O, S, n = 2; X = N, P, n = 3), together with some mixed species (MH3)nXH3-n (X = N, P; M = C, Si) using ab initio SCF methods. The calculated values give excellent agreement with experimental values without the inclusion of d functions. For the chlorides, HCl, CH3Cl, and SiH3Cl, the values vary rather little over a wide range of basis sets, and are unaffected by the inclusion of d functions.
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    Journal of Computational Chemistry 4 (1983), S. 41-47 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A RHF energy minimization procedure based on the treatment outlined in Part I of this series of articles is presented. Test calculations performed on several closed- and open-shell systems show that the present procedure is definitely superior to the conventional SCF methods. In particular, the convergence of this procedure is ensured, the rate of convergency is high, and the computational cost of each cycle is low.
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    Journal of Computational Chemistry 4 (1983), S. 53-57 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Optimum geometries of planar and 90°-twisted C2v calicene are calculated with single-configuration STO-3G and 3-21-G wavefunctions. The barrier to ring-ring rotation is computed. Bond alternation is pronounced in the planar form and decreases in the twisted form, while dipolar character increases on twisting.
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    Journal of Computational Chemistry 4 (1983), S. 48-52 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The effect of basis functions on molecular one-electron property expectation values calculated by approximate methods is examined using weighted and unweighted least-squares Gaussian-type orbital function expansions of Slater-type orbital functions.
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    Journal of Computational Chemistry 4 (1983), S. 68-72 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry of a proposed intermediate (α-dialkylamino nitrite ester) of N-nitrosamine synthesis from nitrites is studied by ab initio SCF methods. The energy of a zwitterion is calculated and found to be high.
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
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    Notes: MNDO has been extended to sulfur, but without inclusion of 3d AOs. Calculations are reported for heats of formation, geometries, dipole moments, and ionization energies of a variety of sulfur-containing molecules. The average discrepancy between calculated and observed heats of formation is larger than for compounds of other elements, a difference probably due, at least partly, to the lower accuracy of the thermochemical data for sulfur compounds. The calculated dipole moments agree well with experiment as do the calculated ionization energies, except for those corresponding to ionization from sulfur “lone-pair” orbitals which are too high by ca. 1 eV, probably as a result of the neglect in NDDO of interactions between inner and valence shell orbitals. As in the case of other third-period elements, the calculated heats of formation of compounds of sulfur in its higher valence states (SIV, SVI) were too positive by large amounts, due presumably to the neglect of 3d AOs.
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    Journal of Computational Chemistry 4 (1983), S. 123-123 
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
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    Journal of Computational Chemistry 4 (1983), S. 150-153 
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The standard deviation in reduced errors (SDRE) quantitatively measures the similarity between an approximate and exact wavefunction. It is the Euclidean distance between the vector of the one-electron property expectation values calculated using the approximate and exact expectation values.
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    Journal of Computational Chemistry 4 (1983), S. 170-174 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Derivatives, with respect to the symmetry coordinates, of the components of the dipole polarizabilities of HF, H2O, and CH4 are calculated using the Kirkwood method and a generalization of that method. The results for the bond-stretching derivatives are in reasonable agreement with those found by finite field calculations; those for angle changes are of the correct sign, but their magnitudes are in poor agreement with the finite field ones. The results are also analyzed using a four-parameter bond polarizability model.
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    Journal of Computational Chemistry 4 (1983), S. 410-418 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Quantum chemical calculations with the semiempirical molecular orbital (MO) method SINDO1 were performed on excited states of the following five- and six-membered heterocycles containing nitrogen: imidazol, pyrazol, pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine. The geometries and adiabatic excitation energies of T1, S1, S2 were calculated. We also present charges, bond orders, and dipole moments. Consequences of these results for UV spectroscopic data are discussed.
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
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    Journal of Computational Chemistry 4 (1983), S. 461-469 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Conformational energy calculations are presented for the head-to-head dimerized β helices for Gramicidin A transmembrane channel structures. The calculations take into account both left- and right-handed β helices, and various side-chain conformations. The energetics of the dimerization is studied by considering various docking geometries. It is concluded from these vacuum-energy calculations that the lowest energy conformation for the channel dimer is that comprised of left-handed β helices.
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    Journal of Computational Chemistry 4 (1983), S. 15-22 
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: SCF wavefunctions with similar extended Gaussian bases for the series HCOX with X = H, OH (syn and anti), NH2, CN, and F yield closely similar charge deformation density maps in the formyl region of all six molecules. The differences, measured by moments of partitioned atomic deformation densities, correlate almost linearly with the Hammett substituent parameters σI and σR of the several substituents X. However, systematic deviations, especially in the carbon fragment, suggest the need for modified values of the inductive parameters σI for the correlation of these molecular charge densities.
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    Journal of Computational Chemistry 4 (1983), S. 33-40 
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    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present a new procedure for direct minimization of the RHF energy, which presents advantages over SCF methods with respect to convergence rate and computational cost. In this procedure we combine several techniques with the aim of obtaining best directions and step lengths for the iterative search for a minimum of the energy. In this article we develop the theory. Therefore, we analyze the variational function; we present a short description of the minimization techniques and we discuss in detail the way in which they are to be used. The computational aspects of the procedure will be treated in the following article.
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  • 85
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    Journal of Computational Chemistry 4 (1983), S. 73-83 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Structures XY⋅3XY⋅2XY3 of symmetry C2v (of which propane is an example) are examined and the rearrangement due to the internal rotation of the end groups XY3 studied. The isomerization graph is constructed, various forms of which are displayed and the symmetry of which has been determined. The order of the group is 72. There are nine prime (irreducible) representations (4A + E + 4G) with the following partitioning of the elements into classes: 1, 42, 62, 9, 122, 18. When the mechanism for rearrangement is generalized to include enantiomers, a duplex graph is produced with the order of the group 144 which is isomorphic to the group S2(S3,S2) (generalized wreath product of the symmetric group S2 and S3). The corresponding graph has been constructed and displayed in one of more symmetrical forms. Isomorphism of groups of order 144 is discussed and a procedure is outlined in which correspondence between distinctive combinatorial objects is established by inducing permutations of m elements from available permutations of n elements. The scheme is based on selection of suitable graph invariants in one system and their labeling as m objects which form the basis for representation of the symmetry for the other system.
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  • 86
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    Journal of Computational Chemistry 4 (1983), S. 110-113 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A rapid method is described for calculating the number of bonds on the shortest path between each two pairs of atoms of a molecule.
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  • 87
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    Journal of Computational Chemistry 4 (1983), S. 136-141 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: This article presents a general method and accurate algorithm for calculating the Cartesian coordinates (xa, ya, za) from an arbitrary triple of distances r(a,i), angles, θ(a,j,k), or dihedral angles φ(a,l,m,n), specifying the position of the nucleus a relative to nuclei i,⃜, n with known Cartesian coordinates. There is a brief discussion of the requirements on the 3N-6 geometric parameters in order for them to determine the shape of an N-atomic molecule.
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  • 88
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    Journal of Computational Chemistry 4 (1983), S. 142-149 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The conformational preferences of the molecule 1,4-pentadien-3-one (divinylketone) have been studied by ab initio molecular orbital calculations and discussed in terms of interaction between molecular fragments. The calculations predict a molecular ground state having a fully coplanar s-cis, s-cis conformation. In addition, we find three other structures that represent local minima on the energy surface. These are a fully coplanar s-cis, s-trans form, and two nonplanar s-trans, s-trans forms having symmetries C2 and C1h, respectively. The energies of these forms relative to the ground state are 7.5, 19.2, and 35.9 kJ/mol, respectively. The coplanar s-trans, s-trans form represents a saddle point on the energy surface. All conformers and the saddle point have been completely geometry optimized by the gradient technique. For the ground state a complete in-plane harmonic force field has been evaluated.
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  • 89
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    Journal of Computational Chemistry 4 (1983), S. 158-169 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: MNDO calculations of heats of formation, dipole moments, ionization potentials, and structures are reported for a wide range of compounds containing chlorine in its characteristic valence state (ClI) and one or more of the elements H, B, Be, C, N, O, and F. The calculated errors in the heats of formation and the dipole moments are not significantly greater than those previously reported for compounds containing no chlorine. First vertical ionization potentials were on average 0.95 eV too high. The ordering of higher cationic states was found to be correct, even for species such as Cl2O, Cl2, and HOCl, where ab initio-Koopmans' theorem calculations predict the incorrect ordering. The calculated energies and geometries of compounds such as CIF3 are qualitatively incorrect, probably because of the lack of 3d atomic orbitals in the orbital basis set.
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  • 90
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: CHARMM (Chemistry at HARvard Macromolecular Mechanics) is a highly flexible computer program which uses empirical energy functions to model macromolecular systems. The program can read or model build structures, energy minimize them by first- or second-derivative techniques, perform a normal mode or molecular dynamics simulation, and analyze the structural, equilibrium, and dynamic properties determined in these calculations. The operations that CHARMM can perform are described, and some implementation details are given. A set of parameters for the empirical energy function and a sample run are included.
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  • 91
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    Journal of Computational Chemistry 4 (1983), S. 241-251 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: STO-3G minimal basis sets for first- and second-row transition metals have been formulated and applied to the calculation of equilibrium geometries for a variety of inorganic systems, metal carbonyls, and organometallic compounds. While the overall level of agreement with experiment is not as good as that previously noted for main-group compounds, most trends and many subtle features in geometries are reproduced.
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  • 92
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    Journal of Computational Chemistry 4 (1983), S. 260-266 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Molecular orbital computations on the sign and magnitude of the Cotton effect of (-)-α-phellandrene (a conjugated diene) and the separate twisted butadiene chromophore were performed using configuration interaction (CI) and the random phase approximation (RPA) methods with a standard minimal basis set of STO/3G orbitals. The relative contributions to the rotatory strength of (-)-α-phellandrene which arise from a twist in the diene unit, the allylic axial bond, and nonplanarity of either one or both of the C=C double bonds were determined by examining various molecular geometries. This theoretical study confirms that the allylic axial substituent/bond provides the largest contribution to the longwavelength Cotton effect. It is found that the rotatory strength arising from distortion of the planar geometry of the double bonds tends to cancel the rotatory strength arising from the sense of twist of the diene unit. The computed energies suggest that molecular geometries where the trisubstituted bond is kept planar, and where twisting is allowed about the cis double bond, may be favored over geometries where torsion is allowed about both double bonds.
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  • 93
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    Journal of Computational Chemistry 4 (1983), S. 267-275 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A procedure has been devised to determine the automorphism partition and the automorphism group for nondirected graphs. The general approach is to reveal the permutational symmetry by means of its systematic destruction. Symmetry decomposition pathways are created by numerically weighting specific series of vertices. Each pathway leads to a discrete ordered vector. Each pair of pathways that match reveals an element of the automorphism group. Results are presented for two molecular graphs. Further potential applications of this approach to problems of isomorphism, canonical labeling, and structural indexing are discussed.
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  • 94
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    Journal of Computational Chemistry 4 (1983), S. 302-307 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Algorithms and computer programs are developed for generating the symmetry elements of nonrigid molecules. These programs are based on the wreath product formalism for the symmetry groups of nonrigid molecules developed by the present author. Several examples are given to illustrate the procedures. Applications to weakly bound van der Waal complexes synthesized by supersonic beam expansion are also presented.
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  • 95
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    Journal of Computational Chemistry 4 (1983), S. 313-332 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Computer simulation of the mechanics of molecular systems is a popular and powerful method for understanding chemical processes. The complexity of modeled chemical systems has advanced from hard spheres and rare gases to liquid solutions and biomolecules. Such simulations are computationally intensive and thus are limited by the speed of available computers. This article describes the use of specialized hardware, a high-speed floating-point array processor (AP), to dramatically speed up molecular mechanics, in other words molecular dynamics, Monte Carlo, and energy-minimization calculations. Although the array processor is a cost effective solution for computationally intensive problems in terms of hardware (full-time AP usage is equivalent to 2-8 h/day of Cray-1 time), its full speed comes at the expense of programming in a relatively difficult parallel assembly language. Since the architecture of the machine is dramatically different from conventional computers and utilizing its fast speed necessitates using this architecture on the assembly language level, the proper design and implementation of algorithms is critical. The molecular mechanics software design discussed here, consisting of 12,000 lines of C and 7000 lines of AP assembly language code, is quite general and has been used to study systems ranging from rare gases to biomolecules. This implementation yields effective speeds approximately 35 times faster than a dedicated DEC VAX 11/780 computer with floating-point accelerator and optimized VMS FORTRAN, thus allowing simulations to be run in one and a half weeks on the AP which would require a year of dedicated VAX time. The flexibility of the UNIX operating system, whose source code is accessible and can be modified to optimize performance, combined with the modern features of the C language, have made this implementation much easier by providing a convenient and powerful environment in which to imbed the hand-coded AP assembly language modules. Applications to date range from the molecular-dynamic calculation of infrared, Raman, and electronic spectra in gas and liquid solutions to the calculation of thermodynamic quantities for water and the simulation of the molecular dynamics of solution reactions and polypeptides.
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  • 96
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    Journal of Computational Chemistry 4 (1983), S. 366-378 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A technique to generate steric contours is developed and applied to the presentation of molecules that interact with DNA. The contours are generated by a Taylor's expansion in an extrapolation procedure designed to avoid infinite derivatives and correct for reversal in the direction of the drawing of the curve. A solution to the hidden line problem in computer graphics is presented for the case of steric contours ordered in parallel planes. The techniques developed in this article are demonstrated with stereographic orthographic projections for B-DNA, for intercalation complexes of lucanthone and actinomycin-D with DNA, and for the binding of benzo[a]pyrene diol epoxides (BPDEs) to guanine. The latter example illustrates the value of steric contours in demonstrating the lack of fit of BPDEs to B-DNA and by the need to unwind DNA to accommodate this molecule. Electrostatic contours in planes may be generated by this same procedure.
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  • 97
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    Journal of Computational Chemistry 4 (1983), S. 390-398 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Theoretical computations are performed of the interaction specificities of the monomethylammoniumion with double-stranded oligonucleotides (dPu)n·(dPy)n in the B-DNA conformation. The effects of base sequence and chain length are examined. In short oligomers (n = 2, 3), the interaction energies of the cation are larger in the major groove of (dG)n·(dC)n than in the minor groove of (dA)n·(dT)n. As a consequence of further shaping of the grooves and building up of the phosphates, a marked reversal in the affinities of the cation for the grooves occurs at the (dPu)5·(dPy)5 and the p(dPu)5p·p(dPy)5p levels: it is the binding in the minor groove of the adenine-thymine oligomers that provides then the most favorable interaction energies.It is also shown, at the level of the double helices built from dinucleoside monophosphates, that the interaction of monomethylammonium in the minor groove occurs in specific configurations involving the three NH bonds of the cation, and two successive bases on one strand; this binding is sequence-specific, the order of inherent preferences being (TpA) 〉 (TpT) 〉 (ApA) 〉 (ApT).
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  • 98
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    Journal of Computational Chemistry 4 (1983), S. 419-427 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Formamide, formamidic acid, and amidine water complexes were studied using 3-21G fully optimized structures and 6-31G energies. Hydrogen bonding and a water-mediated tautomerism mechanism were examined. The optimized complexes show that relaxation of the monomers has occurred. Hydrogen bond lengths and energies fall within the range of values found using other basis sets and other comparable systems.
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  • 99
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Theoretical studies are presented, aimed at the elucidation of through-space effects exerted by bridge-head oxygen and nitrogen atoms on cisoidal proton spin-spin coupling constants in 7-hetero-substituted norbornanes. The finite perturbation theory intermediate neglect of differential overlap (INDO) self-consistent field (SCF) molecular orbital (MO) method, modified according to the description given by Barfield [J. Am. Chem. Soc., 102, 1 (1980)], was employed. It is predicted that the known nonequivalence between Jendo-endo and Jexo-exo in norbornanes, which is in part mediated by the bridgehead methylene group (Barfield transmission effect), also occurs in 7-heteronorbornanes. A trend is recognized in which the nonequivalence induced by oxygen is rather smaller than that induced by the rear lobe of the N—H bond or by the nitrogen lone pair. It is shown that the Barfield effect also explains the observed nonequivalence between cisoidal H—Cβ—Cγ—H and H—Cγ—Cδ—H couplings in prolines. The calculations also predict similar, though smaller, effects on cisoidal couplings in the tetrahydrofuranyl ring system. Special attention was paid to the practical consequences of the existence of this effect with regard to the pseudorotation analysis of the five-membered sugar ring in nucleic acids. It is found that, in addition to the recently introduced correction for electronegativity and orientation of substituents [Haasnoot, de Leeuw, and Altona, Tetrahedron 36, 2783 (1980)], a cos2 dependency of 3Jcis upon the phase angle of pseudorotation must be taken into account, especially in the case of deoxyribofuranoses.
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  • 100
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    Journal of Computational Chemistry 4 (1983), S. 470-481 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Semiempirical and ab initio calculations for the diphenylmethyl anion and related species are reported. MINDO/3 calculations indicate a coplanar anion with an enlarged bond angle of ∼139° to counteract the steric repulsions. MNDO calculations reveal an expanded bond angle with somewhat greater twist (21°). The ab initio calculations (STO-3G level) reveal an expanded central bond angle with an intermediate degree of phenyl twist. The results are compared with experimental data for this and related anions.
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