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  • Inorganic Chemistry  (12)
  • Computational Chemistry and Molecular Modeling  (6)
  • 42.75
  • 1995-1999  (19)
  • 1
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    De edelherthorzel Cephenemyia auribarbis gekweekt (Diptera: Oestridae) (1999)
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.109
    Details
    Publication Date: 2007-01-10
    Description: The rearing of the botfly Cephenemyia auribarbis (Diptera: Oestridae) After several failures we finally succeeded in rearing botflies Cephenemyia from third-instar larvae. From a red deer shot at 13 March 1998 about one hundred larvae of Cephenemyia auribarbis (Meigen, 1824) were collected. Ten individuals reached the pupal stage. After 22 days, one fullgrown male died in the pupa, and two males emerged and lived for 17 and 18 days respectively. This is one of the few recorded succesful attempts to rear botflies.
    Keywords: Insecta ; Diptera ; Oestridae ; Cephenemyia auribarbis ; Nederland ; Verspreiding ; 42.75
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Utopia dielectrica (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 523-531 
    Details
    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 dielectric constant of a material is a macroscopic property that measures the reduction of the electrostatic forces between charged plates separated by the material, compared to a vacuum as intermediate material. It is next encountered as a scaling parameter in Coulomb's law for interacting charges, not only in the force, but also in the energy. In deriving the theory for dielectrics, the macroscopic nature is essential: Only then is the basic assumption that the dielectric material is homogeneous and isotropic a valid one. The appearance of the dielectric constant as a simple scaling factor in Coulomb's law has tempted many computational chemists to forget about the macroscopic nature of the dielectric and to apply the screened Coulomb's law between charges, supposedly in a low-dielectric medium such as proteins, in microscopic force fields. Optimization of force fields even led to distance-dependent “dielectric constants.” Another use of the dielectric constant appears in the dielectric continuum reaction field approaches for the computations of solvation energies and solvent effects. The solute is embedded in a cavity surrounded by the dielectric. Specific interactions between solvent molecules and solute are thus neglected. The cavity size and dielectric constants of interior and exterior are optimized for the model. The aim of this article is to show, by means of calculations on interacting point charges embedded in cavities surrounded by dielectrics and microscopic models of “low-dielectric” materials by explicit polarizabilities, that as far as the dielectric “constant” is concerned anything can happen, depending on the nature of the charges, the distance to the cavity boundary, the spatial arrangement of charges, and polarizabilities. Thus, a warning is issued to injudicious use of dielectric models in microscopic calculations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560855
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  • 3
    Electronic Resource
    Electronic Resource
    Implementation of reaction field methods in quantum chemistry computer codes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 1445-1446 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540161113
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  • 4
    Electronic Resource
    Electronic Resource
    Implementation of reaction field methods in quantum chemistry computer codes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 37-55 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The embedding of a quantum mechanically described subsystem by classical representations of its surroundings is reviewed. The choices for a distributed monopole representation and a distributed (group) polarizability representation, as well as the continuum approach to model bulk effects, are discussed. Focus is on the practical implementation of the classical description in quantum chemistry codes (in particular, HONDO8.1). Expressions are given for the self-consistent coupling between the classical partitions (dipole polarizabilities and boundary surface dipoles and charges) and for the coupling between classical and quantum partitions. The latter is mediated through expanded, rather than exact, potentials and fields. In this way, the computation of only a limited number of formal interactions between unit charge distributions located at the expansion centers suffices to evaluate the reaction field contributions. The electronic part of the coupling can be included in the Hamiltonian via the Fock matrix. The field operators, as well as the one- and two-electron matrix elements over the basis functions, are simple. The expressions for these are given explicitly.Nonequilibrium potentials and Monte Carlo sampling over classical degrees of freedom have been added to better mimic experimental conditions. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540160105
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  • 5
    Electronic Resource
    Electronic Resource
    Komplexe mit N,N,N′,N′-Tetrakis(2-hydroxybenzyl)ethylendiamin (H4tben). Kristallstruktur von Ti(tben) (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 671-674 
    Details
    ISSN: 0044-2313
    Keywords: N,N,N′,N′-Tetrakis(2-hydroxybenzyl)ethylenediamine ; Complexes of Titanium(IV), Vanadium(IV), Manganese(IV), Tin(IV) ; Mass Spectra ; Mössbauer Data ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Complexes with N,N,N′,N′-Tetrakis(2-hydroxybenzyl)ethylenediamine (H4tben). Crystal Structure of Ti(tben)The complexes of N,N,N′,N′-tetrakis(2-hydroxybenzyl)-ethylenediamine with titanium(IV), vanadium(IV), manganese(IV), and tin(IV) were synthesized and characterized by mass spectrometry. The Mössbauer date were evaluated for the tin compound. The molecular structure of the titanium(IV) complex was determined by X-ray structural analysis, crystallographic data see “Inhaltsübersicht”.
    Notes: Es wurden die Komplexe von N,N,N′,N′-Tetrakis(2-hydroxybenzyl)ethylendiamin mit Titan(IV), Vanadium(IV), Mangan(IV) und Zinn(IV) hergestellt und massenspektrometrisch charakterisiert. Für die Zinn-Verbindung wurden die Mössbauer-Daten ermittelt. Die Molekülstruktur des Titan(IV)-Komplexes wurde röntgenstrukturanalytisch bestimmt. N,N,N′,N′-Tetrakis(2-hydroxybenzyl)ethylendiaminato(4-)titan(IV): Raumgruppe P21/c (Nr. 14), Z = 4, 3949 Zahl der beobachteten Intensitäten, R = 0,0539, Gitterabmessung bei 20°C; a = 10,447(3) Å, b = 20,668(5) Å, c = 13,420(3) Å, b̃ = 101,93(5) Å
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210428
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  • 6
    Electronic Resource
    Electronic Resource
    Strukturverfeinerung und magnetische Messungen an Mn2SnS4 (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 1600-1604 
    Details
    ISSN: 0044-2313
    Keywords: Dimanganese tin tetrasulfide ; crystal structure ; magnetism ; IR ; Raman ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structure Redetermination and Magnetic Studies on Mn2SnS4The crystal structure of Mn2SnS4 was redetermined by single crystal and powder X-ray studies. It has a deficient NaCl superstructure crystallizing in the orthorhombic space group Cmmm proposed by Wintenberger and Jumas in 1980 (Z = 2, a = 740.7(1), b = 1047.5(1) and c = 366.7(2) pm, Rf = 1.4% for 266 unique reflections with I 〉 0σ1). Some additional reflections, which are not compatible with this cell, can be refined assuming formation of twinned trilling crystals. Mn2SnS4 undergoes antiferromagnetic ordering below 160 K. The effective magnetic moment μeff of Mn2+ is 5.92 B.M. The IR and Raman spectra display 5 and 3 bands in the range 150-320 cm-1, respectively.
    Notes: Die Kristallstruktur von Mn2SnS4 wurde mittels Röntgeneinkristall- und Röntgenpulver-Messungen nachbestimmt. Mn2SnS4 besitzt eine defiziente NaCl-Überstruktur und kristallisiert, wie von Wintenberger und Jumas [6] vorgeschlagen, in der orthorhombischen Raumgruppe Cmmm (Rf = 1,4% für 266 unabhängige Reflexe mit I 〉 0σ1). Die in dieser Zelle nicht indizierbaren Reflexe können unter der Annahme einer Mehrlingsbildung verfeinert werden. Das effektive magnetische Moment μeff von Mn2+ beträgt 5,92 B.M. Unterhalb 160 K liegt eine antiferromagnetische Ordnung vor. Die IR-und Raman-Spektren zeigen 5 bzw. 3 Banden im Bereich von 150-320 cm-1.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210927
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  • 7
    Electronic Resource
    Electronic Resource
    Kristallstrukturbestimmung an einer Strontium-hydrid-imid-nitrid-Phase - Sr2(H)N/SrNH bzw. Sr2(D)N/SrND - mit Röntgen-, Neutronen- und Synchrotron-Strahlung (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 414-422 
    Details
    ISSN: 0044-2313
    Keywords: Strontium hydride imide nitride ; preparation ; crystal structure determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Structure Determination of a Strontium Hydride Imide Nitride - Sr2(H)N/SrNH resp. Sr2(D)N/SrND - by X-Ray, Neutron, and Synchrotron RadiationStrontium reacts with nitrogen and hydrogen resp. deuterium under well defined conditions to a phase containing hydride, imide and nitride ions.Sr is evaporated at 1000°C. The Sr vapor reacts with N2 and H2 resp. D2 (p(N2) = p(H2/D2) = 50 mbar) in the gas phase. The product crystallizes as orange-yellow resp. black needles at 800°C.Neither X-ray single crystal nor X-ray and neutron powder diffraction data led to an acceptable model for the crystal structure. A high resolution diffraction experiment with synchrotron radiation gave the needed informations:Splitting of reflections led to a model in R3m with a = 3.870(1) Å and c = 18.958(3) Å. Further split reflections indicate, that the crystals contain areas where SrNH is a second phase besides Sr2(H)N. Neutron diffraction data (measured at 2 K, 10 K, 300 K and 505 K) were interpreted by a two phase model with Sr2(D)N/SrND: In a slightly distorted cubic close packing of Sr-atoms hydride and nitride resp imide ions occupy each by one third octahedral sites fully and in an ordered way.
    Notes: Strontium reagiert mit Stickstoff und Wasserstoff bzw. Deuterium unter definierten Bedingungen zu einer Phase, in der Hydrid-, Imid- und Nitridionen nebeneinander vorliegen.Sr wird bei bei 1000°C verdampft. Die Reaktion mit N2 und H2 bzw. D2 (p(N2) = p(H2/D2) = 50 mbar) findet in der Gasphase statt. Das Produkt kristallisiert als orange-gelbe bzw. schwarze Kristallnadeln bei 800°C.Weder aus Röntgen-Einkristall- noch aus Röntgen- oder Neutronenbeugungs-Pulverdaten konnte die Kristallstrukur eindeutig bestimmt werden. Erst ein hochauflösendes Beugungsexperiment mit Synchrotronstrahlung am Pulver gab entscheidende Hinweise auf ein Strukturmodell:Aufspaltungen von Reflexen können nur mit einem Modell in R3m mit a = 3,870(1) Å und c = 18,958(3) Å erklärt werden. Zusätzliche Reflexe zeigen, daß in den Kristallen neben Sr2(H)N Bereiche mit SrNH als zweiter Phase vorhanden sind. Die Verfeinerung von Neutronenbeugungsdaten (Messungen bei 2 K, 10 K, 300 K und 505 K) mit einem Zweiphasenmodell Sr2(D)N/SrND führt zu einem sinnvollen Ergebnis: In einer leicht verzerrten kubisch dichten Anordnung von Sr-Atomen besetzen schichtenweise in Domänen Hydrid- und Nitridionen bzw. Imidionen Oktaederlücken vollständig und geordnet jeweils zu einem Drittel.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230166
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  • 8
    Electronic Resource
    Electronic Resource
    Calculations of molecules, clusters, and solids with a simplified LCAO-DFT-LDA scheme (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 185-192 
    Details
    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 simplified LCAO-DFT-LDA scheme for calculations of structure and electronic structure of large molecules, clusters, and solids is presented. Forces on the atoms are calculated in a semiempirical way considering the electronic states. The small computational effort of this treatment allows one to perform molecular dynamics (MD) simulations of molecules and clusters up to a few hundred atoms as well as corresponding simulations of condensed systems within the Born-Oppenheimer approximation. The accuracy of the method is illustrated by the results of calculations for a series of small molecules and clusters. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Direct reaction field force field: A consistent way to connect and combine quantum-chemical and classical descriptions of molecules (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1111-1132 
    Details
    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 direct reaction field (DRF) force field gives a classical description of intermolecular interactions based on ab initio quantum-chemical descriptions of matter. The parameters of the DRF force field model molecular electrostatic and response properties, which are represented by distributed charges and dipole polarizabilities. The advantage of the DRF force field is that it can be combined transparently with quantum-chemical descriptions of a part of a large system, such as a molecule in solution or an active site in a protein. In this study, the theoretical basis for the derivation of the parameters is reviewed, paying special attention to the four interaction components: electrostatic, induction, dispersion, and repulsion. The ability of the force field to provide reliable intermolecular interactions is assessed, both in its mixed quantum-chemical-classical and fully classical usage. Specifically, the description of the water dimer and the solvation of water in water is scrutinized and seen to perform well. The force field is also applied to systems of a very different nature, viz. the benzene dimer and substituted-benzene dimers, as well as the acetonitrile and tetrachloromethane dimers. Finally, the solvation of a number of polar solutes in water is investigated. It is found that as far as the interaction energy is concerned, the DRF force field provides a reliable embedding scheme for molecular environments. The calculation of thermodynamic properties, such as solvation energy, requires better sampling of phase space than applied here. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Solvatochromism of the π* ← n transition of acetone by combined quantum mechanical - classical mechanical calculations (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 57 (1996), S. 1067-1076 
    Details
    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 solvent shift of the π* ← n transition of acetone in water, acetonitrile, and tetrachloromethane was calculated in a combined quantum mechanical - classical mechanical approach, using both dielectric continuum and explicit, polarizable molecular solvent models. The explicit modeling of solvent polarizability allows for a separate analysis of electrostatic, induction, and dispersion contributions to the shifts. The calculations confirm the qualitative theories about the mechanisms behind the blue shift in polar solvents and the red shift in nonpolar solvents, the solvation of the ground state due to electrostatic interactions being preferential in the former, and favorable dispersion interaction with the excited state, in the latter case. Good quantitative agreement for the solvent shift between experiment (+1,700, +400, and -350 cm-1 in water, acetonitrile, and tetrachloromethane, respectively) and the explicit solvent model (+1,821, +922, and -381 cm-1) was reached through a modest Monte Carlo sampling of the solvent degrees of freedom. A consistent treatment of the solvent could only be realized in the molecular solvent model. The dielectric-only model needs reparameterization for each solvent. © 1996 John Wiley & Sons, Inc.
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