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  • 1
    Digitale Medien
    Digitale Medien
    Instability versus bistability in electron-transfer problems: the conflict between electronic or nuclear relaxation and electronic delocalization (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 2162-2171 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100184a026
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  • 2
    Digitale Medien
    Digitale Medien
    Order parameter spatial variation and anchoring energy for nematic liquid crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6968-6973 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A spatial variation of the nematic scalar order parameter leads to a surface anchoring energy renormalization. This renormalization is a consequence of torque conservation and of the "macroscopic'' definition of the surface orientation. The order change comes from an assumed property of the boundary or from an external curvature constraint inducing surface melting. In both cases, the maximum effect leads to a surface extrapolation length comparable with the nematic-isotropic coherence length. Strong anchoring data should be remeasured and reinterpretated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347634
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  • 3
    Digitale Medien
    Digitale Medien
    Surface order transition in nematic liquid crystals induced by the flexoelectric polarization (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5549-5554 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of the flexoelectric polarization on the nematic surface energy is analyzed. It is shown that if the dielectric constant of the substrate is lower than a critical value the undistorted orientation is no more the one corresponding to lowest energy. The presence of a conducting substrate is also considered. In this case it is shown that by changing the thickness of the dielectric material deposited over the conducting material, a surface order transition is expected. Furthermore, the influence of a finite anchoring energy between nematic and substrate on the critical value of the dielectric constant is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347015
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  • 4
    Digitale Medien
    Digitale Medien
    Theoretical study of the electronic structure of Ar++2 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6085-6092 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The electronic states of the ionic excimer Ar++2 are calculated using ab initio multireference configuration interaction and effective core pseudopotentials. Among states dissociating into Ar+(2P)+Ar+(2P), all are found to be repulsive, except the ground state, which occurs to be quasibound near Re=4.1a0 with a well depth of ≥230 cm−1. All states originating from Ar++(3P,1D,1S)+Ar are bound with dissociation energies in the range 3200–4500 cm−1 and equilibrium distances between 5.6a0 and 6a0. Simulation emission spectra from bound excited states are derived from the calculated potentials and the possible contribution of the Ar++2 ion to the third continuum fluorescence is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.462650
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  • 5
    Digitale Medien
    Digitale Medien
    Theoretical study of the Rydberg excited electronic states of Ar+2 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6093-6103 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The first Rydberg states of the Ar+2 molecular ion dissociating into Ar+(3p5,2P) +Ar*(3p54s,3,1P) are calculated using multireference configuration interaction and effective core pseudopotentials. At long internuclear distance, their electronic structure is shown to be determined by resonance interaction and the magnitude of the Rydberg electron-transfer integral, inducing long-distance wells with De in the range 0.6–0.8 eV around Re(approximately-equal-to)9.0a0. In the short distance range, the electronic structure can be understood as resulting from an ionic Ar++ core with an outer Rydberg electron, and bound or quasibound Rydberg states are obtained around Re∼4a0. The fluorescence spectra of those states are simulated and the possible intervention of the Ar+2 system in the third continuum spectrum is considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.462651
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  • 6
    Digitale Medien
    Digitale Medien
    Structure and stability of Mg+n and Mg++n clusters (n≤7) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6225-6237 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present a nonempirical model Hamiltonian of the valence bond type for singly and doubly charged clusters of atoms which have a s2(1S) ground state configuration. This model includes delocalization, instantaneous polarization energies, interaction between induced dipoles, and Coulombic repulsion of the holes in doubly charged clusters; up to four-body terms are included. The model is applied to magnesium clusters. Comparisons with ab initio (configuration interaction) calculations show overall agreement for singly charged clusters, whereas doubly charged clusters suffer from the lack of collective p-type contributions in model calculations. For singly charged magnesium clusters, ground state geometries are found to be neutral atoms surrounding either a charged atom or a charged dimer. Considerations of shape and energy show that clusters are easily obtained by aggregation processes and analysis of vertical ionization potentials shows that they can also be obtained by direct ionization of neutral species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457389
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of an n-3 Fatty Acid-Deficient Diet on the Adenosine-Dependent Melatonin Release in Cultured Rat Pineal (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We studied the effect of a diet deficient in n-3 fatty acids on the adenosine-dependent melatonin release from cultured rat pineal gland after stimulation by 5′-N-ethylcarboxamidoadenosine (NECA), an A2 adenosine agonist. Experiments were conducted with 2-month-old rats raised on semipurified diets containing either peanut oil (n-3 deficients) or peanut plus rapeseed oil (controls). The proportion of docosahexaenoic acid (22:6 n-3) in the pineal total lipid fraction and in phosphatidylcholine and phosphatidylethanolamine was significantly decreased in n-3-deficient rats. This was compensated for partially by an increase in 22:4 n-6 and 22:5 n-6 levels. The activity of the cultured rat pineal, in terms of cyclic AMP content and N-acetylserotonin and melatonin release in the medium, was lower after stimulation by 10-5 mol/L NECA in the group fed peanut oil than in the group fed peanut plus rapeseed oil. The increased ratio of n-6/n-3 fatty acids in pineal total lipids and the major glycerophospholipids (phosphatidylcholine and phosphatidylethanolamine) may have an important influence on the rat pineal responses. The results are discussed in the context of changes in membrane-bound proteins, including enzymes and/or receptors involved in the rat pineal gland function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03620.x
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  • 8
    Digitale Medien
    Digitale Medien
    Alteration in Fatty Acid Composition of Adult Rat Brain Capillaries and Choroid Plexus Induced by a Diet Deficient in n-3 Fatty Acids: Slow Recovery After Substitution with a Nondeficient Diet (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Wistar rats were fed for three generations with a semisynthetic diet containing either 1.5% sunflower oil (940 mg% of C18:2n-6, 6 mg% of C18:3n-3) or 1.9% soya oil (940 mg% of C18:2n-6, 130 mg% of C18:3n-3). At 60 days of age, the male offspring of the third generation were killed. The fatty acyl composition of isolated capillaries and choroid plexus was determined. The major changes noted in the fatty acid profile of isolated capillaries were a reduction (threefold) in the level of docosahexaenoic acid and, consequently, a fourfold increase in docosapentaenoic acid in sunflower oil-fed animals. The total percentage of poly-unsaturated fatty acids was close to that in the soya oil-fed rats, but the ratio of n-3/n-6 fatty acids was reduced by threefold. In the choroid plexus, the C22:6n-3 content was also reduced, but by 2.6-fold, whereas the C22:5n-6 content was increased by 2.3-fold and the ratio of n-3/n-6 fatty acids was reduced by 2.4-fold. When the diet of sunflower oil-fed rats was replaced with a diet containing soya oil at 60 days of age, the recovery in content of n-6 and n-3 fatty acids started immediately after diet substitution; it progressed slowly to reach normal values after 2 months for C22:6n-5 and 2.5 months for C22:6n-3. The recovery in altered fatty acids of choroid plexus was also immediate and very fast. Recovery in content of C22:5n-6 and C22:6n-3 was complete by 46 days after diet substitution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb04833.x
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  • 9
    Digitale Medien
    Digitale Medien
    Recovery of Altered Fatty Acid Composition Induced by a Diet Devoid of n-3 Fatty Acids in Myelin, Synaptosomes, Mitochondria, and Microsomes of Developing Rat Brain (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Rats were fed a semisynthetic diet containing either sunflower oil or soya oil. Half the litter fed with sunflower oil diet was changed to a soya oil diet when the pups were 15 days old (during active myelination). Fatty acid analysis was then performed on subcellular fractions of the animals fed (a) soya oil, (b) sunflower oil, and (c) soya oil replacing sunflower oil from the 15th day, to determine the speed of the recovery. All material from animals fed sunflower oil showed an important reduction in docosahexaenoic acid (22:6 n-3), compensated by an increase in docosapentaenoic acid (22:5 n-6), whereas arachidonic acid (20:4 n-6) was not affected. In all fractions examined, when sunflower oil was replaced by soya oil in 15-day-old pups the recovery started from the very first day but lasted more than 2 months (this recovery was determined by the increase of 22:6 n-3 up to the normal value and decrease of the 22:5 n-6). In addition a delay was found for myelin recovery, starting only from the 25th day.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb12950.x
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  • 10
    Digitale Medien
    Digitale Medien
    Electrochirally controlled bistable surface switching in nematic liquid crystals (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2907-2909 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present an electrically controlled bistable surface switching for nematic liquid crystals, in cells with the usual display geometry. The surface bistability is controlled by means of an electrochiral effect, by doping a nematic with chiral ions. The alternate transient commutation between the two surface states is related to the sign of an applied pulsed electric field. The threshold behavior allows a writing surface time of 32 μs for a field of 21 V/1.3 μm. In the birefringence mode, the optical texture response time is 0.3 ms. The effect, comparable with the one used with ferroelectric smectic liquid crystals, could be used to realize high definition video passive matrix displays.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104718
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