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  • Electronic Resource  (1,463)
  • 1985-1989
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  • Electronic Resource  (1,463)
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  • 1975-1979  (1,463)
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  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 747-755 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations are presented for the [F-; e+] and [CN-; e+] complexes. Positron affinities of 4.99 and 3.79 eV are obtained for F- and CN-, respectively. The excitation energies to the low-lying excited states of the positron complexes are also calculated.
    Additional Material: 1 Ill.
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  • 102
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 757-766 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From the general formalism of elastic x-ray scattering and a few meaningful assumptions we have shown that for an atom, ∫ρ2dτ is an experimentally measurable quantity related to the intensity scattered by an element. We have labeled this quantity (p), the “average electron density.” If ψ obeys the virial theorem, within the Thomas-Fermi approximation we show (within a multiplicative constant) that 〈ρ〉 is a lower bound to (∑ ionization potentials )3/2. Thus, the scattered intensity of x rays is related quantitatively to the energy of the scattering atoms. Inequalities have been developed to express these relationships and have been confirmed for the more exact Hartree-Fock wave functions.
    Additional Material: 3 Tab.
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  • 103
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 767-777 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio molecular-orbital theory with the STO-3G and 4-31 G basis sets has been used to study the 1,3-sigmatropic hydrogen rearrangements: propene→propene, formic acid→formic acid, and vinyl alcohol→acetaldehyde, and the1,5-shifts:1,3-pentadiene→ 1,3-pentadiene and β-hydroxyacrolein→ β-hydroxyacrolein. Transition states have been determined using gradient procedures. Improved descriptions of the energies of the reactions have been obtained using 3 × 3 configuration interaction. In accord with expectations based on orbital-symmetry considerations, the calculated barriers are considerably greater for 1,3- than for 1,5-shifts. The forbidden pathway for the degenerate 1,3-shift in propene is predicted to require less activation energy than the allowed pathway, a result that can be rationalized in terms of interactions with subjacent and superjacent orbitals.
    Additional Material: 1 Ill.
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  • 104
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 801-813 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A multiple perturbation method for the study of molecular reactivity following multiple site interactions has been extended to trimolecular systems. The theory is reformulated by the many-body diagrammatic method. While adding no new physical content to the previous theory, the present formulation allows for a systematic way of evaluating higher-order energies. The additivity of perturbation contributions to the modification of molecular reactivity is tested on dihydrated adenine. The results compare favorably with supermolecule calculations.
    Additional Material: 3 Ill.
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  • 105
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 839-850 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo calculations for clusters consisting of 200 water molecules surrounding glycine in the neutral and zwitterionic forms were carried out at 300 K; all the relevant interaction potentials have been obtained by means of quantum-mechanical calculations. Water-water and amino acid-water energies were calculated, and the zwitterion was found to be strongly favored with respect to the neutral molecule, as expected. A detailed analysis of the energetic results yielded some information on the special extension of the solute-induced perturbation. The structural results were found to be in reasonable agreement with predictions that can be obtained by analyzing isoenergy contour maps, calculated for the two-body amino acid-water potential.
    Additional Material: 7 Ill.
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  • 106
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MODPOT/VRDDO calculations have been carried out on carcinogenic benzo(a)pyrene and its metabolites. The MODPOT/VRDDO method incorporates two very desirable options into our fast ab initio Gaussian programs: MODPOT - ab initio effective core model potentials - and a charge-conserving integral prescreening approximation which we named VRDDO (variable retention of diatomic differential overlap). For orbital energies and population analyses the MODPOT/VRDDO results agree to essentially three decimal places with completely ab initio calculations using the same valence atomic basis set. For this series of very closely related congeners a new MERGE technique was implemented that allows reuse of integrals of a common skeletal fragment. Since our program computes integrals efficiently by blocks, reusing information common to the block, it was more difficult to implement a MERGE technique than for integral programs which calculate the integrals one-byone. The MODPOT/VRDDO calculations were performed for benzo(a)pyrene (BP), BP oxides, BP dihydrodiols, and BP dihydrodiol epoxides. The metabolites investigated were BP-7,8-oxide, BP-4,5-oxide, BP-7,8-dihydrodiol [cis(e, a), cis(a, e), trans(e, e), and trans(a, a)], and BP-7,8-dihydrodiol-9,10-epoxide [β,β,β (the most stable), β,β,α; α,α,β, and α,α,α all derived from cis-BP-7,8-dihydrodiol and β,α,β; α,β,β and α,β,β derived from trans-BP-7,8-dihydrodiol]. Several different conformations were calculated for each of the BP dihydrodiols and BP dihydrodiol epoxides. Calculations were carried out for the opening of the C9 - O - C10 epoxide ring both toward C9 and C10 for the, most stable β,β,β isomer of BP-7,8-dihydrodiol-9,10-epoxide. Opening the epoxide ring between C10 and O leads to a more stable intermediate than opening the epoxide ring between C9 and C10. However, there is no buildup of positive charge in C10 as has been postulated by some cancer researchers, but rather the C10 becomes slightly more negative. Nor is there a buildup of negative charge on the O atom. rather it becomes slightly less negative. As the epoxide ring is opened further than 90° for the O - C9 - C10 or O - C10 - C9 angles, there appears to be a possible mixing of configurations that is being investigated further.
    Additional Material: 3 Ill.
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  • 107
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 779-791 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper reports an ab initio molecular-orbital (MO) study of binding of SH2 and SH- with ZnII. The mechanism of binding of ZnII with these ligands is investigated using a detailed analysis of the energy decomposition and of the electronic distribution. The dependence of the results on the choice of the basis set for sulfur (in particular the effect of incorporation of diffuses p and d orbitals) on the geometry of ligand binding, the binding energy, and the proton affinity of SH- are investigated. Comparison made with the corresponding results concerning the binding of OH2, OH-, and NH3 shows that sulfur binding is less favorable although more covalent. Both sulfur ligands show a marked preference for angular conformations for binding with the metal ion. The effect of ZnII binding on the ease of deprotonation of H2S is quite similar to the corresponding effect found earlier for H2O.
    Additional Material: 2 Ill.
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  • 108
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 815-838 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new theoretical approach to study the enthalpy variations occurring during an enzymatic reaction is presented. The structural modifications of the enzyme-substrate complex along the reaction path are distinguished as macro- and microdeformations. Macrodeformations, which concern primarily the approach of the substrate to the enzyme and the release of the reaction products and arise from nonbonded interactions, are treated with an empirical method for computing the energy of a macromolecule. Microdeformations, which are local displacements driven by variations of the electronic structure and its energy and involve only a limited portion of the complex, are treated with the ab initio SCF-LCAO-MO method. The reaction path is idealized as a sequence of major steps: at each step, first the empirical program REFINE is used to calculate the geometry of the system for that step, then the energy of an appropriate subsystem is computed ab initio with the program IBMOL, using the geometry provided by REFINE and applying small concerted atomic displacements. Thus along the entire reaction path one can obtain an energy profile computed with the ab initio method and compatible with the structure of the whole complex. This approach was applied here to the first steps of the reaction of proteolysis catalyzed by papain. The formation of an ion pair ImH+ …S- between the side chains of residues His-159 and Cys-25 was examined in detail. The results show that the instability of the ion pair decreases by ˜ 11.5 kcal/mol when the interactions with residues Asn-175 and Ala- 160 are taken into account; the instability is further decreased by ˜2 kcal/mol after a partial geometry optimization. The energies of the noncovalent enzyme-substrate complex and of the tetrahedral intermediate were computed, considering N-methyl acetamide (NMA) as model substrate and representing papain with the residues Cys-25, His-159, Gln-19, and Ala-160. The interaction energy of the noncovalent complex is -3.8 kcal/mol, compared to the value of +7.4 kcal/mol for the CH3S- -NMA complex. The tetrahedral intermediate is found to be less stable than the noncovalent complex by 27 and 38.5 kcal/mol, respectively, for the papain-NMA and the CH3S- -NMA systems. While these rather large energy differences are possibly due to the incorrect geometry of the tetrahedral intermediate and optimization of the structure is required, it appears that the interactions with the various protein residues represent a very important stabilization factor, which lowers the onthalpy variations during the reaction.
    Additional Material: 9 Ill.
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  • 109
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A MINDO/2 SCF MO geometry optimization of cytosine (C), thymine (T), uracil (U), the imino tautomer of cytosine (C*), the enol tautomer of thymine (T*), and the enol tautomer of uracil (U*)was made. The optimized geometries for cytosine, thymine, and uracil agree well with crystallographic data. The optimized geometries for the tautomers show the correct trends in bond lengthening and bond angle except for the C4 - O4 length and C4 - O4 - H angle of T* and U*. The energies of tautomerization were found to be 10.3, -9.0, and -14.2 kcal/mol for C⇌C*, T⇌T*, and U⇌U*, respectively, when optimized geometries are used. The overestimation of the C4 - O4 - H angle is speculated to arise because of an inadequacy in the parametrization of the one-center integrals in MINDO/2.
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  • 110
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    International Journal of Quantum Chemistry 13 (1978) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 111
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    International Journal of Quantum Chemistry 13 (1978), S. 27-39 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hamiltonian matrix elements between pairs of explicitly correlated Singer polymals are derived. A new method for 1/r12 matrix elements is found which avoids the 6 by 6 matrix inversion required at each quadrature point in the old method. The new formula requires about half the computer time of the old one. The electron repulsion and nuclear attraction matrix elements are shown to be related to incomplete elliptic integrals. Simplified formulas are derived for the special cases of cylindrical symmetry, spherical symmetry, and single-center expansions. An upper bound approximation formula for the purpose of neglecting matrix elements is derived. These bounds may be useful for single-center expansions but are found to be too high for the general case.
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  • 112
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    International Journal of Quantum Chemistry 13 (1978), S. 89-124 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of upper and lower ground state energy bounds for many-fermion systems is considered from the viewpoint of reduced density matrices. Model density matrices are used for upper bounds to, first uncoupled, then coupled fermions. Model Hamiltonians are developed for lower bounds in corresponding fashion. Both mathematical and physical models are constructed for setting up universally valid inequalities on density matrices. These are joined by both inequalities and equalities in which the explicit form of the system at hand is used. A few illustrative examples are presented.
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  • 113
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    International Journal of Quantum Chemistry 13 (1978), S. 143-148 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of determining idempotent one-densities which integrate to the exact or to a highly correlated particle density is considered. A method for obtaining the minimum energy idempotent one-density integrating to a given correlated particle density within a finite basis is described. The implications of this are twofold. First, Hartree-Fock accuracy can be exceeded in describing the electron density with an idempotent one-density; this is particularly relevant to the problem of constructing orbitals from experimental x-ray scattering data. Second, electron densities from analytic CI or MCSCF wave functions can be made available in a form as compact as the Hartree-Fock density by reporting the orbitals which define the correlated density via an idempotent one-density. A numerical example of the new method is given in which an accurate correlated density for He is “fitted” by an idempotent one-density represented in a finite (near Hartree-Fock) basis. Considering the deficiencies of the basis for this purpose, a technique is suggested for constructing basis sets optimized for prediction of one-electron properties rather than for energy.
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  • 114
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    International Journal of Quantum Chemistry 13 (1978) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 115
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    International Journal of Quantum Chemistry 13 (1978), S. 169-187 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic structure, potential energy curves, and radiative transition probabilities of excimer systems have been examined using quantum mechanical methods. These molecules are characterized by repulsive or weakly bound ground state potential curves and by bound, strongly ionic, or Rydberg, excited states. They constitute a very interesting class of molecules which offer the possibility for high power, high efficiency UV laser operation. Calculations have been carried out using the density functional SCF-Xα method, modified extensively to correct for well known errors arising from approximations to the potential and exchange terms. A limited number of ab initio calculations were also carried out for comparison purposes. For the ArF system we find that the lowest excited ionic state has symmetry 2∑½+, and that the dominant laser transition observed at 1933 Å should be assigned to B 2∑½+ → X 2∑½+. The C 2Π3/2 → X 2∑½+ transition is calculated to be two orders of magnitude smaller in emission intensity than the dominant transition, thus ruling out this assignment for the observed laser line in ArF. Preliminary calculations carried out for Ar2F indicate that the bound upper ionic state has 2B2 symmetry and that the most probable ground state also has 2B2 symmetry. This polyatomic system is predicted to exhibit a broadband emission spectrum with a relatively long radiative lifetime.
    Additional Material: 6 Ill.
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  • 116
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    International Journal of Quantum Chemistry 13 (1978), S. 227-233 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: General analytic formulas for derivatives of real Slater orbitals with respect to the Cartesian coordinates x and y have been derived. The application of this result to molecular geometry optimization or to the construction of a force constant matrix is briefly discussed.
    Additional Material: 2 Tab.
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  • 117
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    International Journal of Quantum Chemistry 13 (1978), S. 255-260 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The windows in the absorption spectrum of a harmonic oscillator coupled to a bath can be given a two-parameter form identical to the Fano windows in the absorption cross section of an atom with an autoionizing state.
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  • 118
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    International Journal of Quantum Chemistry 13 (1978), S. 297-310 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multipole expansions of Gaussian-lobe atomic orbitals around their centers are theoretically investigated in order to study the exact angular dependence of such functions. Analytical expressions of the multipole coefficients are derived for standard lobe orbitals. It is shown that the average-square values of multipole components are related to a unique orbital parameter λ. The numerical values of p- and d-components are given for selected λ and the choice of this parameter is discussed on the basis of symmetry and computational arguments. The transferability of optimized atomic exponents from harmonic (or Cartesian) functions to lobe functions is established so that the possibility of applying the Gaussian-lobe orbital approach in chemical studies is greatly extended.
    Additional Material: 1 Ill.
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  • 119
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    International Journal of Quantum Chemistry 13 (1978), S. 17-26 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A possible mode for the capture of a cation by the carrier molecule valinomycin has been simulated. The intramolecular nonbonded energy and the binding energy for a centrally located potassium ion at different stages in the capture process have been evaluated using a method proposed earlier. Contrary to intuitive expectations the open conformation of valinomycin is also found to have a strong affinity for K+. There appears to be a rather high potential barrier between the open and closed symmetric conformations.
    Additional Material: 3 Ill.
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  • 120
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    International Journal of Quantum Chemistry 13 (1978), S. 83-88 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most commonly the nonorthogonality of geminals is weakly expressed so that the exchange and overlap integrals ζ(η), ϕ(η) are negligible for large exchange parameters η. The conditions which allow the terms with large η to be discarded are considered. The integrals ζ(η), ϕ(η) are derived for η = 2, 3, 4.
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  • 121
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    International Journal of Quantum Chemistry 13 (1978), S. 155-158 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 122
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    International Journal of Quantum Chemistry 14 (1978) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 123
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    International Journal of Quantum Chemistry 14 (1978), S. 163-169 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The operators of dynamical observables of the crystal electron (velocity vector components. reciprocal mass tensor components and their functions) commute with the energy operator; hence, the averages of these observables can be adequately approximated by the eigenfunctions for the energy operator. Calculations of the averages were based on the LCAO eigenfunctions classified according to incompletely symmetric irreducible representations of the point group of the cubic crystal, and a similar classification was made for the averages.
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  • 124
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    International Journal of Quantum Chemistry 13 (1978), S. 263-263 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 125
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    International Journal of Quantum Chemistry 14 (1978), S. 127-152 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the studies on impure metals where the perturbation potential due to the impurity has symmetry of the point group of the crystal, subdivision of the electron density of the pure metal into irreducible representations of the point group is of significance. A method is presented for the calculation of wave functions of the perfect cubic crystal which transform according to the incompletely symmetric irreducible representations of the point group. The functions were evaluated in the LCAO approximation using s-type AOS for the face centered cubic lattice. These are in the form of standing waves, and their coefficient functions are linear combinations of the products of the cubic harmonics of a suitable type and the spherical Bessel functions. Properties of the solutions obtained were examined. Numerical calculations were made for four irreducible representations of the point group.
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  • 126
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    International Journal of Quantum Chemistry 13 (1978), S. 1-16 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using an STO-3G basis set, energy localized molecular orbitals (LMO) were determined for the ten electron series HF, H2O, NH3, and CH4 as well as for CH3OH and C2H2F2. The method of conjugate gradients is shown to be a viable alternative to other non-eigenvalue methods. The characterization of the LMO in terms of first and second moment measures indicates that the STO-3G basis set LMO may be accurately correlated to larger sp basis set LMO. Also, it is shown that the first and second moment measures display a good linear correlation with the classical concept of electronegativity.
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  • 127
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    International Journal of Quantum Chemistry 13 (1978), S. 41-65 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various forms of the unrestricted Hartree-Fock (UHF) scheme are studied for a simple three-electron model system, represented by the PPP (Pariser-Parr-Pople) π-electron model of the allyl radical. Both spin and space symmetry are violated in the UHF trial wave function, either individually or simultaneously. A comparison with the projected Hartree-Fock (PHF) schemes studied earlier is made and the effect of the order in which various symmetries are broken in both UHF and PHF schemes is studied. The effectiveness of various schemes follows from a comparison of the correlation energy and the wave function is obtained by various UHF (or projected UHF) and PHF schemes, in the whole range of the coupling constant, with the corresponding quantities given by the exact solution of the model. Finally, the implications of the stability of the restricted HF solutions for the behavior of various single- and multiparameter UHF and PHF schemes are briefly outlined and exemplified on the studied model.
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  • 128
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    International Journal of Quantum Chemistry 13 (1978), S. 149-153 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The homogeneity properties of the kinetic and potential energy operators are used to obtain expressions for the second derivatives of the energy expectation value. These are used to demonstrate that in atoms as well as in molecules in the neighborhood of the equilibrium geometry the variational energy cannot have maxima with respect to the non-linear parameters.
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  • 129
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    International Journal of Quantum Chemistry 13 (1978), S. 159-159 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 130
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    International Journal of Quantum Chemistry 13 (1978), S. 189-198 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We consider the “Hartree Problem,” here defined as the problem of finding the orthogonal one-electron states which in a single determinant minimize the electronic energy, excluding exchange contributions. These states may provide a useful basis for correlation-energy studies. It is shown how the “Hartree Problem,” although superficially not of pseudoeigenvalue form, can nevertheless be cast in such a form and solved by an iterative diagonalization process.
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  • 131
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    International Journal of Quantum Chemistry 13 (1978), S. 221-226 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary purpose of the present paper consists in obtaining a correction to Dingle's potential for a (point) impurity ion (embedded) in Si or Ge. This goal is accomplished by making use of a variational principle in taking into account the effect of the spatial variation of the dielectric constant in the respective medium. It is found that the resulting impurity-ion potential can be represented as the product of Dingle's potential and a factor which, with increasing distance from the charged impurity, approaches unity. The secondary purpose of the present paper consists in suggesting a way for the modification of an impurity-ion potential that has been obtained previously with a boundary condition, that, in retrospect, is open to criticism. It is shown that the modified impurity-ion potential can be represented as the product of the author's previous potential and a factor which, with increasing distance from the charged impurity, approaches unity.
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  • 132
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    International Journal of Quantum Chemistry 13 (1978), S. 261-262 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 133
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    International Journal of Quantum Chemistry 13 (1978), S. 265-270 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The perturbation contributions to the correlation energy of the H2 molecule are analyzed. This analysis is based on the computer solutions of several two-electron equations in the Gaussian geminal basis set. The pair equations differ by the choice of the two-electron interaction potential which may result from distinct infinite summations of correlation diagrams in Rayleigh-Schrödinger perturbation theory.
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  • 134
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    International Journal of Quantum Chemistry 13 (1978), S. 325-330 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis is presented that shows how the angular symmetry defects of lobe orbitals constructed from a polyhedric edifice can be accurately evaluated, and how these lobe orbitals can be related to harmonic Gaussian functions, the exponents being tranferred by a scale factor procedure.
    Additional Material: 2 Tab.
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  • 135
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    International Journal of Quantum Chemistry 13 (1978), S. 375-390 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the determination of the symmetry of first-order vectors in Hartree-Fock perturbation theory is developed. This leads to the definition of symmetry-adapted basis vectors to be employed at first order in the perturbation. It is shown that computer time can be saved, to some extent, in the calculation of second-order properties, by exploiting molecular symmetry. Specific examples are given for methane, ammonia, and water.
    Additional Material: 11 Tab.
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  • 136
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    International Journal of Quantum Chemistry 13 (1978), S. 443-454 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the method of alternant molecular orbitals (AMO), it is shown that the energies of AMOS (Ekσ) for an arbitrary heteronuclear alternant system, having a singlet ground state, are connected with the energies of MOS (ek(k)) obtained by means of the conventional Hartree-Fock (HF) method (SCF-LCAO-MO-PPP) via the formula: \documentclass{article}\pagestyle{empty}\begin{document}$$ E_{k\sigma } = {\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}\left( {e_k + e_{\bar k} + \delta _{1,k\sigma } } \right) \pm \sqrt {\left( {\frac{{e_k - e_{\bar k} }}{2} + \delta _{2,k\sigma } } \right)^2 + \delta _{3,k\sigma }^2 } $$\end{document} In the general case, the determination of the correlation corrections δi,kσ is connected with the solving of a complicated system of integral equations, which is considerably simplified if the Hubbard approximation is accepted for the electron interaction.The energy spectrum of a chain with two atoms in the elementary cell (AB)n is considered as an example. It is shown that if nontrivial solutions exist (δi,kσ ≠ 0), the correlation correction for AMOS of different spin are different (δi,kσ ≠ δi,kβ), from which it follows, that the width of the energy gap ΔE∞ for AMOS with different spin is different: ΔE∞,α ≠ ΔE∞,β.
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  • 137
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    International Journal of Quantum Chemistry 13 (1978), S. 553-562 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When considering the dynamical properties of a molecule in contact with an external medium whose degrees of freedom are at equilibrium, one can adopt either of two approaches to the problem. The equations of motion which govern the coupled molecule-medium system can be solved (or approximately solved), after which the initial values of the medium's coordinates are averaged over (with an equilibrium distribution function as weighting factor) to obtain the desired property of the molecule. In the second approach, which is the subject of the present work, the effects of the medium on the molecule of interest are incorporated into a time-dependent effective potential which contains the equilibrium average molecule-medium interaction as well as terms arising from fluctuations in the medium's coordinates about their equilibrium values. By introducing such an effective potential via the cumulant expansion technique, the problem of studying dynamical properties of the molecule is reduced to the study of a molecule which is in the presence of a time varying external field which no longer depends explicitly upon the coordinates of the medium. In addition to developing the basic method for treating such problems, applications of the method to interesting problems are briefly discussed.
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  • 138
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    International Journal of Quantum Chemistry 13 (1978), S. 619-626 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possibility of level crossings is discussed from a general multidimensional partitioning viewpoint. By extending the traditional motion of a self-adjoint Hamiltonian to a self-adjoint analytic family of operators, it is found that level intersections that appear fall into two mutually exclusive categories: the conventional diagonal one corresponding to Jordan blocks of order m = 1, and the nondiagonal one with m ≥ 2. Consequences with respect to some recent examples, such as Longuet-Higgins “sign-reversing loop” construction and the 1II near degeneracy in SiO, are discussed and examined.
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  • 139
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    International Journal of Quantum Chemistry 13 (1978) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 140
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    International Journal of Quantum Chemistry 13 (1978), S. 731-736 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some structural features of the diagonal problem of reduced density matrix theory are investigated by considering the cone Br introduced elsewhere. In some special cases, we discover a very tight connection between the group structure of Gr, the invariance group of Br, and the convex structure of Br. We also state a general theorem that relates the convex structure of Br to the group structure of Gr.
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  • 141
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    International Journal of Quantum Chemistry 13 (1978), S. 737-742 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is pointed out that the density matrices of the ground state contain valuable information concerning the calculation of particle-hole excited states. As an illustration, results on the nuclei 16O, 20Ne, and 28Si are presented, using small model spaces.
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  • 142
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The RPA, SCRPA, Tamm-Dancoff, and full CI methods are compared by analyzing their transition density matrices, oscillator strengths, and energy moments of oscillator strengths for the 1Sground - 1Podd transitions of the 4-electron B+ ion in the frozen K-shell approximation. It is found that the RPA gives transition density matrices that are aligned nearly as well as possible along those of the full CI, but have vector lengths that are significantly too long. The corresponding transition energies are significantly too small. These errors compensate to give oscillator strengths for the dominant transition that, for all forms of the oscillator strength, are within 1.6% of the corresponding full CI values. The SCRPA gives better transition density matrices than the RPA, but poorer oscillator strengths. The Tamm-Dancoff approximation gives very good values for the mixed length-velocity form of the oscillator strength. The RPA gives a static electric dipole polarizability that is nearly 20% larger than that of the full CI. The SCRPA gives a value 15% smaller than - and the Tamm-Dancoff approximation gives a mixed length-velocity value that is 11% larger than - that of the full CI. Other energy moments of oscillator strengths are also reported. Certain other approximations related to the RPA and the SCRPA are reported as well.
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  • 143
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    International Journal of Quantum Chemistry 14 (1978), S. 1-11 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The MCSCF wave functions of Das for Li2, and Das and Wahl for F2, have been analyzed in terms of Berlin's binding and antibinding regions. The effect of electronic correlation on the charge distributions in these regions is studied. The process of bond formation in going from separated atoms to the correlated molecule is also discussed with reference to Berlin's regions.
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  • 144
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    International Journal of Quantum Chemistry 14 (1978), S. 55-63 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Eckart frame is a frame of orthonormal vectors ei, i = 1, 2, 3, which follow a vibrating molecule while it rotates. The frame is orientated by the so-called Eckart condition, which Eckart found by requiring the Coriolis interaction to be minimal. In the present paper we shall see that Eckart's frame also can be characterized by a simple least squares property. Eckart showed how to construct the ei's by a certain orthonormalization of three vectors Fi, i = 1, 2, 3. We observe that this orthonormalization is in fact Löwdin's symmetric. Then we consider the least squares property in the light of the Carlson-Keller theorem - which is given a slightly different form. It is shown that the complete solution to Eckart's condition can be generated from the one of interest by C2 rotations around axes in an orthonormal set which originates from the Fi's by Löwdin's canonical Orthonormalization.
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  • 145
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    International Journal of Quantum Chemistry 14 (1978), S. 121-126 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is proved that two molecular symmetry-lobe orbitals, belonging to different irreducible representations, can have a non-negligible overlap. Using a previously reported multipolar analysis of Gaussian-lobe orbitals (GLOs), it is demonstrated that such defects occur when individual symmetry orbitals (SOs) are both contaminated in a given Y1m subspace, even if such contaminations are very small. A numerical application illustrates this result in the case of the NH3 molecule, and it is shown that axial-GLOs allow for the exact cancellation of the symmetry defects.
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  • 146
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    International Journal of Quantum Chemistry 14 (1978), S. 253-269 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is demonstrated for a spin-free, nonrelativistic, complete molecular Hamiltonian that there is an optimal solution to the separation of electronic and nuclear motions. The adiabatic approximation is obtained as a special limiting case. A fruitful interpretation of intermolecular correlation results from the assumption that such correlation involves the degeneracy of a molecular-energy state of one molecule with that of another chemical species, e.g., cubane and cyclooctatetraene. As a consequence, rigorous relationships are established for the influence of nodal patterns of the electronic functions on intermolecular correlation. Also derived are stringent symmetry rules which both electronic and nuclear functions involved in the correlation must obey. Throughout the treatment is a many-electron one.
    Additional Material: 3 Ill.
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  • 147
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    International Journal of Quantum Chemistry 14 (1978), S. 313-318 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method is presented for the variational calculation of a set of vectors under the condition that the metric of the vectors remains unchanged through the process of variation. Application of this method to typical measures (energy, overlap, distance, etc.) in quantum chemistry gives rise to new variational equations, for which the solution yields the Löwdin symmetric orthonormalization, the Kashiwagi-Sasaki generalization, the symmetric deorthogonalization, and the Adams localization, etc.
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  • 148
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    International Journal of Quantum Chemistry 14 (1978), S. 337-340 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 149
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    International Journal of Quantum Chemistry 14 (1978), S. 343-352 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex scaling method, also known as the complex coordinate or dilatation transformation method, is discussed in relation to the Stark effect and to the calculation of the position and width of resonant states of atoms or molecules. The significance of resonant scattering in atomic physics is briefly reviewed.
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  • 150
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    International Journal of Quantum Chemistry 14 (1978), S. 419-441 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 151
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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  • 152
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    International Journal of Quantum Chemistry 14 (1978), S. 613-621 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Even after completing a multiconfiguration self-consistent-field (MCSCF) calculation, one must often include additional configuration interaction (CI) to obtain quantitative or semiquantitative results. There is some question of whether the prior MCSCF calculation is worthwhile, if additional CI is needed later. We have developed a new MCSCF computational method, which, because of our assumptions about the nature of the configurations, yields one Fock-like operator for all the “filled” orbitals (high occupation numbers) and a second Fock-like operator for all the “virtual” orbitals (low occupation numbers). Since there are only two matrices to build, our method is considerably faster than other MCSCF approaches. Because of these similarities to standard molecular-orbital (MO) calculations, we have termed our approach generalized-molecular-orbital (GMO) theory. However, the “virtual” orbitals, unlike those of standard MO theory, are optimized to correlate the “filled” ones and can he used in a subsequent CI calculation. Results are presented for the correlation energy of H2O, the spectroscopic constants of N2, the singlet-triplet energy separations in CH2, and the nature of the chromium-chromium quadruple bond. Although these results are at a very low level of CI, the GMO approach appears to correct for the gross deficiencies of the single-determinant SCF procedure.
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  • 153
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    International Journal of Quantum Chemistry 14 (1978), S. 695-702 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper is a summary of a detailed treatment, given elsewhere, in which (gauge invariant), equations of change (at points in configuration space) of arbitrary dynamical properties of an N-particle quantum-mechanical system in the presence (or absence) of an arbitrary (time- and space-varying) classical electromagnetic field are derived for an arbitrary Hamiltonian by making use of both the Maxwell and the Schrödinger time-dependent equations. The properties at a point in configuration space are defined so as to be closely related to observables and the forces are related to their classical counterparts. The rates of change of linear momentum and angular momentum are closely related to the classical Lorentz force and the Lorentz torque, respectively. The rate of change of energy is the work done on the system by E(t), the time-dependent part of the external electromagnetic field. The reason for E(t) and its definition of the energy for a system in a time-varying electromagnetic field is explained. The Breit-Pauli Hamiltonian is required to treat “state-to-state” molecular problems and the detailed equations of change using this Hamiltonian are used as examples.
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  • 154
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    International Journal of Quantum Chemistry 14 (1978), S. 717-726 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio self-consistent-field (SCF) and configuration interaction (CI) calculations on the ground and excited states of carbonyl fluoride (F2CO) were carried out at its experimental ground-state equilibrium geometry. Vertical transition energies deduced from the CI results provide assignments for the electronic systems I-IV, experimentally observed by Workman and Duncan. The singlet excited state, 1A1 (π→π*), is found to be a mixed valence-Rydberg state and to he 1 to 1.2 eV above the suggested experimental value, irrespective of the choice of the basis used for the CI calculations.
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  • 155
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    International Journal of Quantum Chemistry 14 (1978), S. 727-736 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several aspects of the numerical application of the complex-coordinate method for calculating helium autoionizing resonances are discussed. A direct-search algorithm is used to locate resonance eigensolutions that satisfy the virial theorem, and the influence of the basis set on the accuracy of the calculated positions and widths is investigated. The complex-coordinate method is related to the stabilization method of Holøien and Midtdal.
    Additional Material: 7 Ill.
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  • 156
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    International Journal of Quantum Chemistry 14 (1978), S. 741-746 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Results of extended-basis SCF calculations indicate that BeF2- may exist as a metastable species. Comparison of results obtained from SCF calculations on neutral BeF2 with those of BeF2- shows that the orbital occupied by the electron of BeF2- is well approximated by the lowest unoccupied molecular orbital of neutral BeF2.
    Additional Material: 1 Ill.
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  • 157
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    Journal of Morphology 155 (1978), S. 35-61 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Projection microradiography was used to determine the density and orientation of the force transmitting structures, i.e., trabeculae and bone lying between approximately parallel vascular canals, within the bones of cat skulls. The organisation in the skulls was confirmed statistically for a total of ten cats. The results of the observations showed that within specific areas of the skull a high degree of structural orientation and an increased density of osseous structures was present. The distribution of these characters corresponded in contiguous bones such that a continuum of structural organisation was established between the alveolar region and the site of attachment of the temporalis and masseter muscles and the glenoid region.The patterns of force transmission during jaw closure were determined when a resistance was placed initially between the canines and then the carnassials. An analysis was first carried out on dry skulls using colophonium resin to determine the direction of the force distribution. The nature and the approximate magnitude of the forces were ascertained by replacing the resin with strain gauges. The basic similarities in the strain patterns recorded from the dry skulls and those from the ten anaesthetised cats in which strain gauges had been intra-vitally implanted, substantiated the recordings made on the dry skulls. Combination of the results from the three sets of experiments defined the patterns of force distribution in the cat skull during the closure of the mandible against a resistance. The results showed that: (1) the combined action of the temporalis and masseter muscles tended to reduce the overall strain in the skull bones, and that the deformations produced by the action of the masseter were greater than that exerted by the temporalis muscles; (2) during biting, whether the resistance was placed between the canines or carnassials, compressive forces predominated in the facial bones; (3) small movements observed between facial bones indicated the presence of a flexible component within the skull, thus allowing large forces to be exerted during biting without overstressing the facial bones; (4) the glenoid fossa is part of a force bearing joint; (5) forces generated during biting were resisted within the skull by forces of an opposite nature generated within the system, the incompressible nature of bone and by the effect of the soft tissues; (6) the nature and the magnitude of the strain altered when a resistance was placed at the canines and then at the carnassials; however, the pattern of force distribution within the skull remained the same; (7) there was a direct correspondence between the detailed structural organisation of the bones and the patterns of force distribution. This conclusion would appear to apply in general to mammalian skulls. The study also emphasises the importance, neglected hitherto, of carrying out a variety of experiments to determine the patterns of force distribution in bones.The Trajectorial Theory of bone organisation is discussed and, on the basis of the results obtained, a modified theory is proposed. This states that: the structural continuum is common to the compact and cancellous bone and comprises bony bars which are aligned in the optimum direction for the transmission of force to a region in the bone or bones where it is effectively resisted.
    Additional Material: 11 Ill.
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  • 158
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The tarsi of all three pairs of legs of both sexes of Aedes aegypti (L.) bear spine sensilla, five types of hair sensilla, which are designated A, B, C1, C2 and C3, and campaniform sensilla. Type A and B hairs, spines, and cam-paniform sensilla are innervated by one neuron with a tubular body, a characteristic of cuticular mechanoreceptors. In particular the hairs and spines are tactile receptors and the campaniform sensilla are proprioceptors. The C1, C2, and C3 hair sensilla have the morphological features of contact chemoreceptors. Type C1 and C3 hairs are innervated by five and four neurons, respectively, which extend to the tip of the hair. Type C2 is innervated by five neurons, one of which terminates at the base of the hair in a tubular body while the remaining four extend to the tip of the hair. The role of the type C hairs in oviposition behavior, nectar feeding, and recognition of conspecific females is discussed. Presumed efferent neurosecretory fibers occur near the spine and hair sensilla.
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  • 159
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    Journal of Morphology 155 (1978), S. 271-285 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The micro-anatomy of the corpuscles of Stannius of the toadfish, Opsanus tau, an aglomerular marine teleost, has been studied by light and electron microscopy. The corpuscles are composed of extensively anastomosed cords of epithelial cells which maintain intimate contact with blood capillaries. Most of the epithelial cells contain acidophilic granules which also show a positive reaction with the periodic acid-Schiff technique and aldehyde fuchsin. On the basis of fine structural criteria, three cell types can be recognized. The granular cells contain abundant quantities of granular endoplasmic reticulum, ribosomes, Golgi apparatus with prosecretory granules, coated vesicles, polymorphic mitochondria with lamellar cristae, filaments, microtubules, a cilium, a variety of lysosome-like dense bodies, glycogen particles, lipid droplets, secretory granules and intranuclear lipid-like inclusions. One variety of agranular cell (type I) is characterized by the total absence of secretory granules, but it contains large amounts of granular endoplasmic reticulum and ribosomes, conspicuous profiles of Golgi apparatus, coated vesicles and sometimes an abundance of glycogen. Another variety of agranular cell (type II) has poorly developed cytoplasmic organelles. The perivascular space between the capillary and parenchyma contains connective tissue cells and abundant nerve fibers. The different types of epithelial cells observed in the corpuscles of Stannius of this fish may represent functional stages of the secretory cycle in a single cell type.
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  • 160
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    Journal of Morphology 155 (1978), S. 311-325 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The nervous system of the maldanid polychaetes Clymenella torquata (Leidy) and Euclymene oerstedi (Claparede) (= Caesicirrus neglectus [Arwidsson, '11-'12]) retains its primitive association with the epidermis. It shows only slight metamerism in the presence of larger collections of neurones opposite the parapodia and of larger nerves at the segmental boundaries. Multicellular giant fibers are present in the ventral nerve cord; giant neurones which show a characteristic pattern of distribution in each species are also present. The cerebral ganglia supply nerves to the prostomial wall, nuchal grooves and the wall of the buccal cavity, and a pair of large nerves from the circumpharyngeal connectives also appear to join the buccal system. The organs of special sense are the elongated prostomial nuchal grooves, and prostomial ocelli in Euclymene but not in Clymenella. Statocysts are absent.Four pairs of nephromixia are present. They lie in the aseptate anterior trunk, in chaetigers 5-9 of Clymenella, and 6-10 of Euclymene. The nephridiopores lie at the ventral ends of the neuropodia of chaetigers 6-9 and 7-10, respectively. Each nephromixium consists of coelomostome, tubule and contractile bladder. The wall of the tubule and bladder consists of both excretory and ciliated cells. Most of the cytoplasm of the latter forms a bounding layer at the outer surface. The cytoplasm of the excretory cells contains lipid material and appears to synthesize lipofuscin. The tips of the excretory cells swell, fill with granules, and break off in the form of vesicles which are periodically expelled in clouds from the nephridiopores. Glycogen is present, especially in the ciliated cells of the tubule and coelomostome.Granules of a lipoid nature accumulate in (or between) cells of the nephridia, epidermis, and some regions of the gut, and may be excretory. Lipid granules also appear to be synthesized by coelomocytes which eventually end up in masses in the ventrolateral coelomic cavities of the tail.The nephridia act as gonoducts, but show no seasonal variation in either size or histological structure.
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  • 161
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    Journal of Morphology 156 (1978), S. 39-51 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ascophoran Pentapora foliacea was studied from epoxy sections of skeletal and soft (hard-soft) tissues. The basal wall is double, indicating the colony grew as two independent layers, back to back. The structure of the vertical walls and interzooidal communication organs indicates that zooids were budded in the usual way as in most encrusting cheilostomes. Secondary layers of the frontal wall are of acicular aragonite. The ovicell develops as a flattened cuticular bladder in early ontogeny; the aragonitic layer of the frontal wall later engulfs it. A median vesicle, an evagination of the vestibular wall, is present but the eggs may be supplied with sufficient yolk to nurture the embryo. The overall ovicell structure is similar to that of hyperstomial ovicells in other cheilostomes.
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  • 162
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This investigation describes the pre-natal morphogenesis of the type I pneumocyte subsequent to its differentiation from pulmonary epithelium. Cells lining subpleural alveolar septa were photographed from serial sections with the electron microscope, and a three-dimensional representation of each cell was obtained by transferring the contours of the cell membranes from montages to transparent plastic sheets which were then spaced to scale and stacked. The results of this study indicate that: The nascent blood-air barrier of a 50-day reconstructed cell was twice as thick as the average definitive barrier; definitive barrier thickness was observed in some areas in a 63-day reconstructed cell; the amorphous component of elastic tissue which appears peripherally in septal connective tissue during pre-natal morphogenesis may be directly juxtaposed to the basal lamina of the alveolar epithelium; the orientation of the cell junction between a pneumocyte and its neighboring cells, as observed in sections of alveolar septa, changes as the contour of the pneumocyte changes from simple abutment to overlapping patterns.
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  • 163
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    Journal of Morphology 156 (1978), S. 257-278 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the mid-gut musculature of the desert locust, Schistocerca gregaria is described and compared with that of the visceral muscles of other species. The gross morphology and fine structure of the nervous system which supplies the mid-gut muscle fibres is described.
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  • 164
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    Journal of Morphology 156 (1978), S. 293-315 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The integument of Paranthessius anemoniae has been studied with light and electron microscopy. A cuticle with clearly defined epicuticular, exocuticular and endocuticular regions overlies a cellular hypodermal layer. The distribution of carbohydrate, lipid and protein components of the cuticle were demonstrated histochemically. Parabolic striations in oblique sections of cuticle suggest that its molecular architecture fits a “twisted sheet” theory proposed for other species.Arthrodial membranes at body and limb joints have a homogeneous structure, lacking exocuticle and endocuticle. Subcuticular glands appear to secrete substances thought to be responsible for the immunity which Paranthessius seems to have to the nematocysts of its host. Small hairs, situated in cuticular cups which occur over the dorsal body surface are considered to function as rheoreceptors.
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  • 165
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    Journal of Morphology 157 (1978) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 166
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    Journal of Morphology 157 (1978), S. 21-31 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The larval epithelium of the sea urchin, Lytechinus pictus, consists of squamous cells and bands of columnar epithelial cells bearing cilia. During metamorphosis this tissue undergoes a series of rapid, complex changes. Through the scanning and transmission electron microscope, we describe and analyse these changes. The changes can be divided into three steps. (1) The larval arms bend away from the left side of the larva, exposing the urchin rudiment. Cells which are identical to smooth muscle cells are in a position to bring about this bending. (2) The squamous epithelial cells assume a cuboidal shape. This change in shape results in the collapse of the larval epithelium onto the presumptive aboral surface. These cells possess a subapical band of microfilaments. The cellular shape change but not the bending of the arms is reversibly inhibited by Cytochalasin B. These observations suggest a mechanism for this change. (3) The former lining of the vestibule of the urchin rudiment comes to lie over the collapsed larval tissue and forms the adult epithelium. At this point, after only one hour, the larva has assumed the external shape of an adult sea urchin.
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  • 167
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The mucous gland of the red-spotted newt, Notophthalamus viridescens viridescens, Rafinesque was examined by histochemical and ultrastructural techniques and its cytological responses to various hormonal conditions were studied. Its secretory epithelial cells produce and release in merocrine fashion a neutral, unsulphated mucosubstance. The secretory epithelium is bounded peripherally by a thin, but apparent non-functional, myo-epithelium. The duct of this mucous gland consists of a single keratinized tubular cell that extends from the neck region of the gland to the surface of the epidermis.Mucous secretion is absent or greatly reduced on the skins of newts maintained under laboratory conditions for a few weeks but reappears after injection of ovine prolactin. Mucous glands in laboratory conditioned animals show a 4-fold increase in volume brought about by the engorgement of their epithelial cells with secretory granules. Ovine prolactin reduces the volume of the glands to unconditioned levels with a corresponding reduction in granular content, suggesting that prolactin functions in the release of the granules. This view is reinforced by the findings that autotransplantation of the pituitary gland prevents the conditioning effect and that glandular volume increases in auto-transplanted animals given ergocornine. Granular accumulation begins also in hypophysectomized newts but ceases after a week, indicating the need for some hypophyseal factor in the synthesis as well as the release of the granules. Ovine prolactin restores mucous glands of hypophysectomized newts to the unconditioned state. Contrary to earlier findings, ovine prolactin induces a reduction in the volume of the mucous gland in thyroidectomized newts.
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  • 168
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    Journal of Morphology 157 (1978), S. 99-119 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The process of coelomic pouch formation in Pisaster ochraceus was studied with light microscopy, transmission and scanning electron microscopy and time-lapse cinemicrography as well as with the drug cytochalasin B. As in most asteroids, the paired coelomic pouches of Pisaster ochraceus are formed from outpocketing of the archenteron.Arrays of 50 Å microfilaments are found in the presumptive coelomic pouch cells at the apex of the archenteron as well as in the filopodia of the mesenchyme cells. Both cell types undergo active movements throughout the entire process. Treatment of embryos with cytochalasin B (CCB) during coelomic pouch formation results in the loss of cell movements and the regression of the coelomic pouches; this is accompanied by the loss of microfilament arrays in both cell types. Cell movements and microfilament arrays reappear on removal of CCB and coelomic pouch formation resumes.Our evidence suggests that the microfilaments in the presumptive coelomic pouch cells provide the main force for the outpocketing movement. The major role of the microfilament arrays in the filopodia of the mesenchyme cells associated with the coelomic pouches is to determine the definitive shape and location of the pouches.
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  • 169
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    Journal of Morphology 157 (1978), S. 161-179 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Morphological changes of the ovary of the Chinese cobra, Naja naja, throughout the annual reproductive cycle are described. A single clutch of between 6 and 22 eggs is produced in late June. From July to the following April the ovary remains quiescent and contains small previtellogenic, hydration stage follicles. The growth of an ovarian follicle from a primary oocyte to maturation and ovulation is estimated to take three years. The histology of the germinal epithelium and the follicular granulosa shows seasonal changes correlated with the growth of the oocyte. During the quiescent period, the germinal epithelium lacks mitotic activity, but during April, when yolk deposition and rapid growth of the preovulatory follicles take place, the germinal epithelium shows intense mitotic activity. The growth of the smallest hydration stage follicles, and the occurrence of cytoplasmic bridges between the pyriform cells of the granulosa and the developing oocyte, also appear to increase during this period. The possible function of the pyriform cell is discussed and the literature on the origin and fate of these cells in the squamate ovary is reviewed. Postovulatory follicles (corpora lutea) and two types of atresia are described and compared with what is known of these structures in other reptiles.
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  • 170
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    Journal of Morphology 157 (1978) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 171
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: An experiment was undertaken to determine which sensory structures of the mouse embryo inner ear developed from what portion of the mouse otocyst. Otocysts of gestation days 10, 11, 12 and 13 were divided by surgical dissection into six anatomical groups: dorsal, ventral, anterior, posterior, medial and lateral halves. They were organ cultured separately. After a period of ten days, the explanted tissues were harvested and processed histologically for microscopic analysis. The surgical control specimens fixed at the time of explanation were composed of undifferentiated ectodermal cells for tissues of gestation days 10, 11, and 12. Otocysts of gestation day ten showed no gross morphological differentiation. Otocysts of gestation days 11 and 12 showed, during the course of their subsequent growth, that the three semicircular ducts and their associated cristae developed from the dorsal and lateral halves. Only the anterior and posterior canals and cristae originated from the medial portion. The posterior half gave rise to the posterior crista and the anterior half provided for the development of the anterior and lateral cristae. The cochlear duct and its sensory epithelium developed in all the anatomical groups except the dorsal half. The utricle developed in the dorsal section of the middle third of the otocyst, while the utricular macula developed in the anterior half of the same section of the otocyst. The saccule and its macula differentiated from the ventral section of the middle third of the anterior half.
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  • 172
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The pineal-paraphyseal complex of sea turtles is an impressively large structure which projects dorsally and anteriorly above the prosencephalon. The complex was examined by light microscopy in several age classes of green sea turtles (Chelonia mydas) and from juvenile loggerhead turtles (Caretta caretta). The paraphysis is extensively fused to the distal portion of the pineal body, suggesting an interrelated function for these two tissues. No duct or canal was observed connecting the pineal lumen to the third ventricle. Two pineal cell types are described which appear to correspond to the neuroglial supportive cells and the secretory rudimentary photoreceptor cells of other amniotic vertebrates. A possible luminal secretion in the form of apical protrusions is produced by the latter cell type. No typical photoreceptive outer segments were observed.
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  • 173
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    Journal of Morphology 158 (1978), S. 243-273 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the wax gland of Anomoneura nymph and its metamorphic change were investigated. In the nymph, this organ encircles the anus, and consists of two kinds of cells, derived from epidermal cells: (1) very tall, slim wax cells, which produce and secrete the wax, and (2) flat interstitial cells found among the wax cells. The whole gland is covered by a wax-secreting cuticle with a delicate surface sculpture. Each wax cell has a long, wide duct which opens at the cuticle and penetrates the entire cell. Its cytoplasm is rich in mitochondria and smooth endoplasmic reticulum while that of interstitial cells contains rough endoplasmic reticulum. During each nymphal molt, the cluster of primordial wax gland cells  -  derived from the epidermis  -  proliferates rapidly and forms the gland of the next instar. The gland of the preceding instar meanwhile degenerates. Interstitial cells play an important role in cuticle formation and shedding at each molt. These cells alone produce and deposit the new cuticle of the next instar; the wax cells, specialized for wax production, cannot produce cuticle. The apical portion of the wax cell is cut off from the main cell body by growth of the surrounding interstitial cells. Thereafter, the wax cells degenerate, resulting in the rapid disappearance of the previous instar's wax gland. Adults lack this gland entirely.
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  • 174
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    Journal of Morphology 158 (1978), S. 291-322 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The dorsal ventricular ridge (DVR) is a subcortical, telencephalic structure in reptiles and birds that protrudes into the lateral ventricle. The structure of DVR has been studied in the red-eared turtle (Pseudemys scripta elegans) in Nissl and Golgi preparations. The DVR in Pseudemys is divided into the anterior dorsal ventricular ridge (ADVR) and the basal dorsal ventricular ridge (BDVR) by the dorsal branch of the middle ventricular sulcus. The structure of ADVR has been examined in detail.The ADVR is divided into four regions with distinct boundaries termed dorsal area, medial area, ventral area and central area. Dorsal area, medial area and ventral area border on the lateral ventricle; central area lies deep to the other areas. Three classes of neurons are found in Golgi preparations of ADVR. Juxtaependymal cells have somata near the perikarya of ependymal cells; their dendrites are found primarily in a periventricular fiber zone. Aspiny neurons were observed only in the dorsal half of ADVR and appear to be restricted to deep regions of the ridge. These multipolar neurons are rarely encountered in Golgi preparations, and the observed distribution may not represent their actual distribution in ADVR. The majority of the cells observed in ADVR are spiny neurons with dendritic fields that range from stellate to double-pyramidal. Cells in this class may be subdivided on the basis of axonal morphology into at least two groups, but further studies are needed to determine the range of axonal morphology exhibited by these neurons.An analysis of the distribution of these cell types in Golgi material shows that dorsal area, medial area and ventral area are organized in four zones concentric with the ventricular surface. Central area apparently lacks a concentric pattern of organization. Zone 1 is a periventricular fiber band that contains juxtaependymal neurons and ascending dendrites of zone 2 spiny neurons, and it may serve as a structural substrate for segregated input onto these cell populations. Zone 2 contains clusters of spiny neurons with apposed somata, which vary in size and distribution between areas. Dendrites of zone 4 neurons are also found in the deep half of zone 2. Zone 3 is a cell-poor region which lies at the center of a region of overlapping dendritic fields of zone 2 and zone 4 neurons. Zone 4 contains predominantly spiny neurons (aspiny neurons are found only in the dorsal half of ADVR) which are either isolated or in small clusters with apposed somata. Dendrites of zone 2 cells extend superficially into zone 4, so that the deep portions of zone 4 may be a substrate for segregated input to zone 4 neurons. These zones are differentially elaborated in each area. Central area, by contrast, consists of scattered spiny and aspiny neurons among fibers connecting ADVR and the lateral forebrain bundle.A comparison of these findings with the ADVR of snakes (Ulinski, '78a,b) shows both similarities and differences in DVR organization in the two taxa. Although snakes lack areal divisions, ADVR is organized in four concentric zones (zones A-D). Zones A and B resemble zones 1 and 2 in turtles, consisting of a superficial fiber zone and a subjacent cell cluster zone. The clusters are smaller in snakes than in turtles. However, snakes lack a cell-poor band deep to zone B, and dendrites of cells in zone C enter zone A. Thus, there are differences in both areal and zonal dimensions of ADVR organization in turtles and snakes.
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  • 175
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    Journal of Morphology 158 (1978), S. 109-153 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ultrathin sections of the nasal barbel of the channel catfish, Ictalurus punctatus, were studied in the electron microscope and the fine structure was compared to that of barbels of other teleosts and to the mandibular (dentary) barbels of I. punctatus. While the overall histology of the nasal barbel is similar to that of barbels described previously, this study revealed far greater cellular complexity and variability than was previously reported. A layer of stratified epidermal cells rests upon a connective tissue dermis containing a cartilage rod, a large number of nerve fibers and numerous blood vessels, fibroblasts and pigment cells. Taste buds are present in the epidermal layer. This layer was found to contain probably 16 kinds of cell types, several of which may represent transitional stages, in addition to taste bud cells. Observations were made pertaining to innervation and cell types in the taste buds. A new terminology for designating the barbels of I. punctatus is suggested.
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  • 176
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  • 177
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    Journal of Morphology 155 (1978), S. 181-192 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: New data on the brain of Latimeria indicate that previous estimates of the brain weight were too high by a factor of two. Our data suggest a brain weight of 1.1-1.5 grams for a specimen with a body weight of 30 kilograms. Quantitative data on major divisions of the brain are presented for the first time, and the relative size of the major brain divisions is similar to that of sturgeons and generalized sharks (such as hexanchids and squalids). Examination of brain component weight (s): body weight plots in a sample of non-teleost actinopterygian fishes indicates that all major divisions of the brain, except the telencephalon, are larger than in Latimeria. Brain component sizes in Latimeria are more similar to those extrapolated for amphibian brains than to those for actinopterygians. However, the cerebellum of Latimeria is considerably larger than that of amphibians.
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  • 178
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    Notes: The Champy-Maillet osmium tetroxide-zinc iodide technique and a new method using azur B-sodium thioglycolate were used to study the general nervous tissue structure in planarians. A subepidermal and a submuscular nerve plexus, partially reported by earlier authors, are described, and a gastrodermal plexus is reported for the first time in triclads. The possible functions for each one of these plexuses are discussed. By the Champy-Maillet method, the innervation within the parenchyma appears as an array of numerous single nerve fibers that course between the parenchyma cells making apparent synaptic contacts. The pharynx has outer and inner nerve nets similar in structure to the submuscular nerve plexus. Both nerve nets are connected to each other by radial nerves.The central nervous system has a sponge-like structure with many lacunae filled with cell bodies, dorso-ventral muscle fibers, parenchymal cell processes and excretory ducts. The existence of this sponge-like nervous tissue structure is discussed in relation to the still incomplete centralization of the nervous tissue in these organisms, to the lack of a true vascular system and to the acoelomate level of organization. A comparison with the nervous tissue structure of more advanced groups like polyclads and nemertines is suggested.
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  • 179
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  • 180
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    Journal of Morphology 156 (1978), S. 157-171 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Secretion in the salivary glands of Gromphadorhina portentosa involves three cell types: parietal cells, secretory cells, and duct cells. The organization and role of the parietal and secretory cells are here considered. Parietal cells have numerous mitochondria, indicating an active metabolic role and the subsequent production of ATP. Plasma membrane invaginations and intracellular ductules containing microvilli appear to function in the absorption of solutes from the hemolymph and finely-tapered ductules. Secretory cells contain abundant rough endoplasmic reticulum, the three forms (stacked, vesicular, and diffuse) of which appear to develop sequentially during maturation. Secretory vesicle formation is asynchronous between adjacent secretory cells, and apparently the large vesicles often coalesce. The secretory vesicles also show differing degrees of electron density, indicating distinct biochemical composition.
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  • 181
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    Notes: Studies were undertaken of the microcirculation and histology of the gill of Protopterus aethiopicus as a prerequisite for elucidating the function of the gills in a bimodal respiratory system. The lamellae of the gill-bearing arches (I, IV, V, VI) resembles the arborescent external gill of the larval amphibian rather than the gill of the teleost or selachian.The arterio-arterial system (a-a) of the gill consists of an afferent artery, a series of large capillaries, and an efferent artery on each of the primary, secondary and tertiary lamellae. There are no pillar cells and the loose capillaries are covered with a multilayered epithelium. While living in water, the minimum distance for gas exchange is of the order of 5 μ. An afferent-efferent arterial shunt at the base of each primary lamella may be involved in control of lamellar blood flow and the resistance of the gill vasculature.The arterio-venous system originates primarily from the efferent side of the arterio-arterial system and drains into large branchial veins. Numerous contractile cisternae, interposed between intercellular channels and veins, presumably function as micropumps that collect fluid from intercellular epithelial spaces and inject it into the venous circulation.During aestivation, the epithelial layer of the gill lamellae becomes thinner. The entire gill vasculature, including the capillaries and afferent-efferent shunts on arches IV-VI, are very dilated which presumably promotes blood flow through these gill arches to the lungs.
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  • 182
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    Journal of Morphology 156 (1978), S. 279-292 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The movements of the shoulder girdle of eight adult cats during overground stepping were studied, using standard slow motion cinematographic techniques. The patterns of activity of shoulder muscles were examined, using simultaneous intramuscular electromyography. Walking, trotting and galloping steps were analyzed from digitized single motion picture frame images. Angular movements of the shoulder girdle consist of biphasic flexion and extension of the shoulder joint and a monophasic flexion-extension alternation of the scapula on the thorax during each step cycle. In addition, the center of the scapula moves craniad during the swing phase and caudad during the stance phase with respect to a fixed reference point on the animal. Similar vertical movements of the center of the scapula also occur in each step cycle. Results of EMG studies of the 17 muscles capable of acting on the shoulder girdle indicate that three overall patterns of activity are found: (1) a pattern typical of extensor muscles, active during all the extension epochs; (2) a pattern typical of flexor muscles, active during the flexion epoch; and (3) a biphasic pattern of activity, active twice in each step. These data are used, along with a re-examination of previous models of the mechanics of the shoulder girdle of carnivores to examine the function and mechanics of shoulder motion. It is concluded that the rotary and translatory movements of the shoulder girdle during stepping combine to enhance step length.
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  • 183
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    Journal of Morphology 156 (1978), S. 367-379 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The most striking morphological feature of the ovarian epithelium of Cymatogaster is the presence of intercellular dilations during much of the year. These dilations increase markedly in volume during the several months prior to ovulation and fertilization, and decrease in volume during the months of embryogenesis and gestation. The epithelium then returns to its initial, relatively undifferentiated state. The extracellular material within the dilations likely is synthesized in the cells adjacent to or within the dilations. Apparently most of this material is released into the ovarian lumen when the apicolateral margins of adjacent epithelial cells pull apart; possibly it serves as nutrient for developing embryos.In addition to supporting embryogenesis, the ovarian epithelium also apparently is involved in sperm storage. Sperm are maintained within pockets in the ovarian epithelium for the several months between insemination and fertilization. The cells lining the sperm pocket do not develop the intercellular dilations characteristic of most of the ovarian epithelium, and sperm remain associated only with the sperm pocket cells.
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  • 184
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    Journal of Morphology 157 (1978), S. 1-19 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The antennae of Folsomia candida and Hypogastrura copiosa are provided with tactile hairs on all four segments and, in addition, with chemoreceptors on segments three and four. The cuticle of the thin-walled chemo-receptors of Folsomia, as in most other insects, is penetrated by many small pores uniformly distributed over the surface. In contrast, the cuticle of the thin-walled chemoreceptors of Hypogastrura is unusual in that a band of cuticle without perforations spirals around, or partly around, the hair. The cuticle between the spirals is very thin, and has extremely small openings in it. The tip of the antenna of Folsomia is thin, permeable to dyes in aqueous solution and apparently glandular. The antennal tip of Hypogastrura is definitely glandular.
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  • 185
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    Journal of Morphology 157 (1978) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 186
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: After hemisection of the spinal cord and medulla oblongata, a projection has been traced to the inner half of the tectal white of the tiger salamander, using Fink-Heimer degeneration staining. By microelectrode recording it was found that the tectal projection forms a topographic somatosensory map of the contralateral half of the body. This map is in register with the overlying retino-tectal visual projection. Using the Falck-Hillarp technique, it was found that the somatosensory tectal input is associated with yellow-fluorescing 5-hydroxytryptamine fibers.
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  • 187
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A comparative morphological study concerning typology and topography of chemoreceptors on the prothoracic legs of Calliphora vicina, Phormia terranovae and Musca domestica has been carried out. The typological criteria of Grabowski and Dethier ('54) and Hansen and Heumann ('71) were used. A single criterion, the shape of the tip, was used to define the different types of chemoreceptors.A-hairs have a rhombic pore at the side of the tip; B-hairs have an oval pore at the tip apex and D-hairs have a rectangular pore under an undulated, cap-like structure at the hair tip. A-, B-and D-hairs were found in the tarsomeres of Phormia; in Musca and Calliphora only B- and D-hairs were found. An opening and closing mechanism may operate on the pores of the tips of the chemoreceptors. Chemoreceptors were counted and a topographical map was completed, using SEM-techniques. Topographical maps are of value in electrophysiological and behavioural research, where only a limited optical magnification is possible.
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  • 188
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    Journal of Morphology 157 (1978), S. 281-299 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structures of the lantern tracheoles of three genera of flashing fireflies are compared. All three genera have stiff, reinforced tracheoles which resist folding or collapsing under conditions which flatten more typical tracheoles. This common specialization supports the hypothesis that the tracheoles play a major role in flash control in these fireflies, especially as the morphological basis of the stiffening is different in the three genera. Study of the tracheoles of other tissues reveals that there is great variety in structure and flexibility of these vessels from tissue to tissue and organism to organism, suggesting that tracheolar specialization may be a general phenomenon, with the fine structure of these air tubes being tailored to the particular demands and conditions of the tissues in which they are found.
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  • 189
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    Journal of Morphology 158 (1978), S. 21-29 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tibiotarsal segments of 12-day chick embryos homozygous for the crooked neck dwarf gene (cn/cn) were examined histologically following routine methods of preparation. The myogenic mass fails to divide into separate muscle bundles during the early stages of differentiation. Myoblasts and myotubes are observed, although the proportion favors the mononucleate cell population. Multinucleate myotubes are often wavy in appearance and many contain eosinophilic cytoplasmic inclusions. The entire tissue mass of mutants appears more compacted than in control limbs. Poor organization of muscle appears related to the lack of a suitable connective tissue system. Epimysia, perimysia, and subcutaneous connective tissue fail to develop properly. Tendons are poorly developed or absent. Comparisons between mutant and control embryos show no differences in peripheral innervation. Nerve fascicles penetrate deeply into the developing muscle of both species. The distribution of vascular elements is seemingly normal also. Skeletal muscle of cn/cn embryos is capable of differentiating to the myotube stage, after which it undergoes cellular degeneration without achieving a functional state. Comparisons of this mutant with alleged chemical phenocopies show important differences.
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  • 190
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    Journal of Morphology 158 (1978) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 191
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    Journal of Morphology 158 (1978), S. 155-167 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The histology and carbohydrate histochemistry of eight teleostean stomachs are compared. Three gross anatomical types of stomachs are described and their shapes appear to correlate somewhat with feeding habits. Each type can be divided histologically into a corpus and pylorus. Gastric glands, containing only one cell type, occur in the copora of all species, but are present in the pylori of esocids only. As a single cell can produce both enzymes and hydrochloric acid such cells may be comparable to those of amphibians but not mammals. Lamina propria and submucosa are indistinctly separated in corpora but better defined in pylori by an intervening muscularis mucosa. The arrangement of the muscularis into inner circular and outer longitudinal layers is the opposite of that seen in the esophagus. Gastric mucous cells show species variations in localization of epithelial mucosubstances, which in broad terms are recognized as sulfomucins, sialomucins and neutral mucosubstances. A piscivorous diet does not appear to demand any particular type of carbohydrate. Within the Centrarchidae, gastric pit cells vary in carbohydrate content from only neutral mucosubstance to only weakly acidic sulfomucin; two species contain both types. A positive PAS reaction on the surface of gastric epithelial cells is suggestive of a striated border and thus possibly absorptive function. The absence of stomachs in some teleosts and the evolutionary and dietary significances are discussed.
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  • 192
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    Journal of Morphology 158 (1978), S. 199-241 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The American cockroach has a total of 368 muscles inserting on the post-coxal segments of its legs. By using a narrow morphological definition for delimiting individual muscles, it is shown (i) that the protrochanteral musculatures (23 muscles/leg) differ from the essentially identical meso- and metatrochanteral musculatures (24 and 26 muscles/leg) in number and disposition of extensors and in having a completely different flexor composition, and (ii) that the musculatures of the more distal segments of the legs are completely serially homologous, there being 2 muscles for moving each femur, 23 for each tibia, 7 for each first tarsomere, and 5 for each of the paired pretarsal claws. In all six legs, the trochanteral and tibial musculatures each contain single slender muscles that may be acting proprioceptively to measure the angular displacements between, respectively, the coxas and trochanters, and the femurs and tibias. Neurological and phylogenetic considerations are used to demonstrate why a narrow morphological definition should be employed, and why the widely used functional definition of Snodgrass ('35) is not only fallacious on evolutionary grounds, but also leads to making erroneous conclusions regarding the manner in which insect musculature is controlled by the insect central nervous system. Finally, it is hypothesized that the physiological limitations imposed by having an open circulatory system and the problems inherent in the neural control of large muscles may have been major evolutionary factors in forcing insects to use many slender muscles to control their body movements.
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  • 193
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    Journal of Morphology 158 (1978), S. 323-360 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Among piscivorous cichlids consistent differences have been recorded between ambush and pursuit hunters with respect to electromyographic, kinematic, pressure and behavioral profiles during prey capture by high speed inertial suction. Piscivorous cichlids possess a repertoire of at least two patterns of prey capture, each of which is characterized by an extreme regularity of the kinematic, pressure, electromyographic and behavioral profiles. The nature and locomotory behavior of the prey, visually analyzed by the predator during the prestrike stalk, determine which of the two preprogrammed patterns is recruited. Agile and elusive prey invariably will elicit a preprogrammed motor output (stereotyped motor pattern) that produces the greatest suction velocities in both ambush and pursuit hunters. The greater the kinematic and suction velocities, the greater the overlap of the firing sequences of antagonistic muscle complexes. The opercular and branchiostegal apparati function as an exceedingly effective anti-backwash device, damping potential fluid oscillations within the oropharynx. Mastication occurs by triphasic movements and actions of muscles of the upper and lower pharyngeal jaws in both ambush and pursuit hunters. The lower pharyngeal jaw is acted upon by a force couple of which the fourth levator externus on one hand and the pharyngocleithralis externus and pharyngohyoideus on the other hand are the antagonistic components. Furthermore, the lower pharyngeal jaw is suspended by a muscular sling, the tension of which can be modified continuously. It is postulated that the switch from insectivorous to piscivorous feeding regimes (and perhaps vice versa) is accomplished by very minor structural and functional modifications, because the modulatory multiplicity and total range of repertories of the feeding machinery of the two trophic groups overlap significantly. Piscivorous cichlids may not have arisen by orthoselection in gradually-changing lineages, but represent the differential success of subsets from a random pool of speciation events. Adaptive features identified as characteristic for piscivory could have evolved in multiple and independent lineages at a punctuational mode and tempo.
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  • 194
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    Journal of Morphology 155 (1978), S. 1-17 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: There are two discrete lobes comprising the armadillo subman-dibular gland. These two lobes can be defined grossly, histochemically and morphologically with the light and electron microscope. The minor lobe stains more intensely with PAS and AB. When viewed in the electron microscope, the secretory granules of the acinar cells within this lobe appear mucous-like. The granules of the demilune cells are slightly different in appearance. The secretory granules of the acinar cells in the major lobe contain many dense foci embedded in a fibrillar matrix, a substructure not described previously. The demilune cells of this lobe contain secretory granules with a mucous-like structure which is consistent throughout the entire lobe. As in the minor lobe, these demilune cells stain very intensely with PAS and AB.
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  • 195
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    Journal of Morphology 155 (1978), S. 327-348 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: End-plate distributions have been determined for three frog muscles of different morphology in order to relate end-plate topography to spatial muscle structure and nerve branching. Koelle's cholinesterase technique was applied, both on whole muscles and frozen sections. The end-plates of the short parallel-fibered cutaneus pectoris muscle appeared to be located in short bands along the nerve branches. The nerve tree is restricted to a zonal area across the middle part of the muscle. Depending on the way the nerve branches, the end-plate bands form innervation patterns, varying from one single continuous band to multiple distributed bands. In the latter case one frequently observes that different end-plate bands do not run across the same longitudinal muscle fiber area, although the respective nerve branches run parallel across this area. The long parallel-fibered sartorius muscle has a wider nerve tree and exhibits the same phenomenon for close parallel nerve branches, but end-plate bands along parallel nerve branches far apart cover the same muscle fiber area. The end-plate distribution in the bipennate, short-fibered gastrocnemius is zonal throughout the muscle except in certain compartments containing tonic fibers. The end-plate zone centers around the inner aponeurosis about half-way between the muscle tendon junctions of the fibers and is visible only at the muscle surface where muscle fibers run over their entire length at that surface. The results are of general use in the electrophysiology of neuromuscular transmission because they illustrate how in certain twitch muscles neuromuscular morphology may help to localize end-plates.
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  • 196
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    Journal of Morphology 156 (1978), S. 1-37 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When a larva of Haplothrips verbasci is ready to feed, it grasps the surface of the leaf with its pretarsi, sinks down between its front legs, lifts its head, and places the tip of its mouthcone against the surface. It then shortens its mouthcone and punches a hole in the epidermis by rapidly and repeatedly protracting and retracting its left mandibular stylet. The thrips then inserts its two maxillary stylets as a unit into the wound with a series of rapid thrusts and withdrawals, salivating continuously while doing so. When a food source in the epidermis or mesophyll is found, probing and salivation stop and cibarial pumping begins. Cytoplasm is sucked into the opening at the tip of the protracted stylets, up the food canal between them and into the cibarium.Probing and feeding can occur without mandibular intervention but uptake of liquid seems to require use of the mutually coadapted maxillary stylets, even when these are fully retracted.Prior to molting, the larva protracts its maxillary stylets maximally and, in the pharate state, seems incapable of feeding or drinking.Structures used in feeding are fully described and are shown to resemble those of Hemiptera except for the presence of maxillary and labial palpi and the absence of the loral lobes, right mandible and of a salivary canal between the protracted maxillary stylets. Seven single and 18 paired muscles function in the feeding act, nine less than in adults of the same species.Differences in the feeding mechanism of terebrantian and tubuliferous thrips are discussed and evidence is presented to suggest that the simplified and more highly specialized mouthparts of the latter insects are adaptations for feeding in confining spaces.
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  • 197
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    Journal of Morphology 156 (1978), S. 53-125 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In contemporary entomology the morphological characters of insects are not always treated according to their phylogenetic rank. Fossil evidence often gives clues for different interpretations. All primitive Paleozoic pterygote nymphs are now known to have had articulated, freely movable wings reinforced by tubular veins. This suggests that the wings of early Pterygota were engaged in flapping movements, that the immobilized, fixed, veinless wing pads of Recent nymphs have resulted from a later adaptation affecting only juveniles, and that the paranotal theory of wing origin is not valid. The wings of Paleozoic nymphs were curved backwards in Paleoptera and were flexed backwards at will in Neoptera, in both to reduce resistance during forward movement. Therefore, the fixed oblique-backwards position of wing pads in all modern nymphs is secondary and is not homologous in Paleoptera and Neoptera. Primitive Paleozoic nymphs had articulated and movable prothoracic wings which became in some modern insects transformed into prothoracic lobes and shields. The nine pairs of abdominal gillplates of Paleozoic mayfly nymphs have a venation pattern, position, and development comparable to that in thoracic wings, to which they are serially homologous. Vestigial equivalents of wings and legs were present in the abdomen of all primitive Paleoptera and primitive Neoptera. The ontogenetic development of Paleozoic nymphs was confluent, with many nymphal and subimaginal instars, and the metamorphic instar was missing. The metamorphic instar originated by the merging together of several instars of old nymphs; it occurred in most orders only after the Paleozoic, separately and in parallel in all modern major lineages (at least twice in Paleoptera, in Ephemeroptera and Odonata; separately in hemipteroid, blattoid, orthopteroid, and plecopteroid lineages of exopterygote Neoptera; and once only in Endopterygota). Endopterygota evolved from ametabolous, not from hemimetabolous, exopterygote Neoptera.The full primitive wing venation consists of six symmetrical pairs of veins; in each pair, the first branch is always convex and the second always concave; therefore costa, subcosta, radius, media, cubitus, and anal are all primitively composed of two separate branches. Each pair arises from a single veinal base formed from a sclerotized blood sinus. In the most primitive wings the circulatory system was as follows: the costa did not encircle the wing, the axillary cord was missing, and the blood pulsed in and out of each of the six primary, convex-concave vein pair systems through the six basal blood sinuses. This type of circulation is found as an archaic feature in modern mayflies. Wing corrugation first appeared in preflight wings, and hence is considered primitive for early (paleopterous) Pterygota. Somewhat leveled corrugation of the central wing veins is primitive for Neoptera. Leveled corrugation in some modern Ephemeroptera, as well as accentuated corrugation in higher Neoptera, are both derived characters. The wing tracheation of Recent Ephemeroptera is not fully homologous to that of other insects and represents a more primitive, segmental stage of tracheal system.Morphology of an ancient articular region in Palaeodictyoptera shows that the primitive pterygote wing hinge in its simplest form was straight and composed of two separate but adjoining morphological units: the tergal, formed by the tegula and axillaries; and the alar, formed by six sclerotized blood sinuses, the basivenales. The tergal sclerites were derived from the tergum as follows: the lateral part of the tergum became incised into five lobes; the prealare, suralare, median lobe, postmedian lobe and posterior notal wing process. From the tips of these lobes, five slanted tergal sclerites separated along the deep paranotal sulcus: the tegula, first axillary, second axillary, median sclerite, and third axillary. Primitively, all pteralia were arranged in two parallel series on both sides of the hinge. In Paleoptera, the series stayed more or less straight; in Neoptera, the series became V-shaped. Pteralia in Paleoptera and Neoptera have been homologized on the basis of the fossil record.A differential diagnosis between Paleoptera and Neoptera is given. Fossil evidence indicates that the major steps in evolution, which led to the origin first of Pterygota, then of Neoptera and Endopterygota, were triggered by the origin and the diversification of flight apparatus. It is believed here that all above mentioned major events in pterygote evolution occurred first in the immature stages.
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  • 198
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    Journal of Morphology 155 (1978), S. 349-357 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Studies of the response of adult mammalian and amphibian ventricle to injury have indicated the formation of a connective tissue scar in the place of the wounded or amputated muscle. It has been demonstrated that amphibian myocytes adjacent to a wound surface, unlike mammalian myocytes, have a proliferative capacity. In the present study, a minced cardiac muscle graft was placed into the adult newt ventricle in order to increase the number of myocytes near a wound surface. With such an increased number of reactive myocytes, it was thought a new wall consisting primarily of muscle might be formed. One-sixteenth to one-eighth of the ventricular apex was removed, minced and returned to the amputation surface of the ventricle. General histological and autoradiographic studies were conducted on two sham-operated animals and on five experimental animals which were killed at 5, 10, 20, 30, 50 and 70 days after surgery. Major events of the repair and reorganization of minced cardiac muscle included blood clot formation followed by necrosis of the blood clot and much of the muscle graft. By ten days, an apparent coalescence of muscle fragments and continuity of ventricular and graft lumina were observed, although the graft area never formed an integrated unit with the wounded ventricular wall. The peak of mitotic activity (3.19%) and thymidine labeling (28.1%) of graft cells, including many cells which resembled cardiac myocytes, was observed at 20 days. At 30 days, the graft was observed as a continuous wall composed primarily of muscle fibers. Several 30-, 50- and 70-day grafts had rhythmic contractions. These results suggest that amphibian cardiac muscle has histogenetic and proliferative capacities not attributable to mammalian cardiac muscle.
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    Journal of Morphology 156 (1978), S. 209-235 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An ultrastructural comparison of mouse oocytes isolated at various stages of growth and meiotic competence has been carried out. Progressive changes in the nucleoli, ribosomes, mitochondria, endoplasmic reticulum, Golgi complex, and other organelles and inclusions of the oocyte have been examined as a function of oocyte size by transmission electron microscopy. The observations presented support the idea that growth of the mammalian oocyte involves not just tremendous enlargement of the cell, but extensive alterations in its overall metabolism as reflected in the ultrastructure of the oocyte at various stages of growth.
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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