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  • 1
    Electronic Resource
    Electronic Resource
    Sedimentation classification of silver colloids for surface-enhanced Raman scattering (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 1116-1119 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00297a030
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics of ion–molecule recombination. V. A study of energy transfer pathways (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8295-8306 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Li++H2O→Li+(H2O) association reaction is used as a model system to study translation to rotation (T→R) and translation to vibration (T→V) energy transfer pathways which lead to the formation of ion–molecule complexes. Classical trajectories are used to study the association probability vs H2O bend frequency, impact parameter, and rotational temperature. For low and high bend frequencies association only occurs by T→R energy transfer. For intermediate bend frequencies a T→V energy transfer pathway becomes available. There is a well-defined peak in the association probability vs bend frequency, which apparently arises from a resonance between the Li++H2O relative translational motion and the H2O bend. Energy transfer and association are affected by the orientation of the H2O dipole during the collision. There is considerable structure in an association probability contour map plotted vs impact parameter and rotational temperature. In contrast to ion–molecule capture which is most probable for an impact parameter of zero and a rotational temperature of 0 K, the formation of an ion–molecule complex by energy transfer is most probable for nonzero values of impact parameter and rotational temperature. Both short-range and long-range Li+(H2O) complexes are formed. The long-range complexes are important at large rotational temperatures and impact parameters. A discussion is given of the sensitivity of the trajectory results to the treatment of the zero point energy motion of H2O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462333
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  • 3
    Electronic Resource
    Electronic Resource
    Trajectory studies of SN2 nucleophilic substitution. II. Nonstatistical central barrier recrossing in the Cl−+CH3Cl system (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8275-8287 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: For the Cl−+CH3Cl SN2 nucleophilic substitution reaction transition-state theory predicts that crossing the central barrier region of the potential-energy surface is the rate-controlling step. In this work classical trajectories are initialized at the central barrier. Four different models are considered for the potential-energy surface. A significant amount of central barrier recrossing is observed in the trajectories, which suggests that transition-state theory is an incomplete model for calculating the Cl−+CH3Cl SN2 rate constant. Two types of recrossings are observed in the trajectories: intermediate recrossings in which trajectories linger near the central barrier and complex recrossings in which trajectories trapped in the Cl−⋅⋅⋅CH3Cl complex return to the central barrier region. Intermediate recrossings are important if, in the trajectory initial conditions, zero-point energy is added to the vibrational modes orthogonal to the reaction coordinate. Rice–Ramsperger–Kassel–Marcus (RRKM) theory predicts extensive dissociation of the Cl−⋅⋅⋅CH3Cl complex to Cl−+CH3Cl and negligible complex recrossings in the trajectory calculations. In contrast to this prediction, negligible Cl−+CH3Cl formation is observed and continual complex recrossings occur, on a time scale longer than the complex's RRKM lifetime. These results indicate the ergodic assumption is invalid for the Cl−⋅⋅⋅CH3Cl complex. Phase-space bottlenecks which give rise to the intermediate and complex recrossings are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462331
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  • 4
    Electronic Resource
    Electronic Resource
    Bond order simulation model: Coordination dependent bimetallic bonds (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5342-5349 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The variation of metal–metal bond strength or atomic site energy with number and type of atomic neighbors is described within a generalization of the bond order simulation (BOS) model, named the BOS-mixing model. The site energy for fixed coordination is expressed as a quadratic function of the number of existing mixed metal bonds. The three parameters in this functional form are (over)determined by the mixing energy as a function of composition for bulk bimetallic fcc systems. For the ten bimetallic alloys formed from Ni, Cu, Rh, Pd, and Ag, we find that the BOS-mixing model describes the composition dependence predicted by non-self-consistent electron density functional theory. Using the same BOS-mixing parameters obtained from this non-self-consistent electron density functional theory, the BOS-mixing model predicts accurately the microstructures (coordination arrangements) of clusters of Ni101Cu100, and Cu101Pd100 which are prototypical systems for bimetallic clusters. For Ni101Pd100 the BOS-mixing model displays some inaccuracies due to the atomic size mismatch of 10% which distorts the cluster shape from a perfect lattice structure. This is the same effect noted in previous applications of the BOS model and is thus expected. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469261
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of the reaction between hydroxyl and hydroperoxyl on the singlet potential energy surface (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 6784-6792 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100171a010
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of models for treating angular momentum in RRKM calculations with vibrator transition states: pressure and temperature dependence of chlorine atom + acetylene association (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 311-322 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100104a010
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  • 7
    Electronic Resource
    Electronic Resource
    A Model Multidimensional Analytic Potential Energy Function for the Cl- + CH3Br .fwdarw. ClCH3 + Br- Reaction (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 1608-1619 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100057a013
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of inhibiting melatonin biosynthesis on spatial memory retention and tau phosphorylation in rat (2004)
    Oxford, UK : Munksgaard International Publishers
    Journal of pineal research 37 (2004), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  We have found recently that melatonin protects SH-SY5Y neuroblastoma cells from calyculin A-induced neurofilament impairment and neurotoxicity. In the present study, we further investigated the in vivo effect of inhibiting melatonin biosynthesis on spatial memory retention and tau phosphorylation in rats and the potential underlying mechanisms by using haloperidol, a specific inhibitor of 5-hydroxyindole-O-methyltransferase, and a key enzyme in melatonin biosynthesis. We have found that injection of haloperidol into the lateral ventricle and into peritoneal cavity compromises spatial memory retention of rats and induces hyperphosphorylation of microtubule-associated protein tau at tau-1 (Ser199/Ser202) and PHF-1 (Ser396/Ser404) epitopes. At mean time, the activity of protein phosphatase-2A (PP-2A), a deficit phosphatase in the Alzheimer's disease brain and superoxide dismutase decreases with an elevated level of malondialdehyde. Supplementation with melatonin by prior injection for 1 wk and reinforcement during the haloperidol administration significantly improves memory retention deficits, arrests tau hyperphosphorylation and oxidative stress, and restores PP-2A activity. These results strongly support the involvement of decreased melatonin in Alzheimer-like spatial memory impairment and tau hyperphosphorylation, and PP-2A may play a role in mediating aberrant melatonin-induced lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.2004.00136.x
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  • 9
    Electronic Resource
    Electronic Resource
    Melatonin attenuates isoproterenol-induced protein kinase A overactivation and tau hyperphosphorylation in rat brain (2004)
    Oxford, UK : Munksgaard International Publishers
    Journal of pineal research 37 (2004), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  Hyperphosphorylation of microtubule-associated protein tau at specific sites is a recognized pathological process in Alzheimer's disease (AD), and protein kinase A (PKA) is a crucial kinase in AD-like tau hyperphosphorylation. In the present study, isoproterenol (ISO) was injected bilaterally into hippocampus of rat brain; ISO is a specific PKA activator and it induces tau hyperphosphorylation. With this system, melatonin (MT) was shown to protect against ISO-induced tau hyperphosphorylation. We found that hippocampal injection of ISO (0.02 μm) induced PKA overactivation and tau hyperphosphorylation at both paired helical filament (PHF)-1 and tau-1 sites. ISO injection also resulted in activation of superoxide dismutase (SOD) and elevation of malondialdehyde (MDA), parameters suggesting elevated oxidative stress. Preinfusion of MT intraperitoneally partially reversed ISO-induced tau hyperphosphorylation at the PHF-1 epitope (1 and 10 mg/kg continuously for 4 wk or 10 mg/kg for 1, 2 or 3 wk) and tau-1 epitope (10 mg/kg for 2 wk). Furthermore, MT (10 mg/kg for 2 wk) obviously antagonized ISO-induced PKA overactivation, as well as enhanced SOD activity and decreased the level of MDA. It is suggested from these data that ISO may induce abnormal hyperphosphorylation of tau through not only the activation of PKA but also because of the fact that it increases oxidative stress; MT may protect against ISO-induced tau hyperphosphorylation through suppression of both PKA overactivation and oxidative stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.2004.00130.x
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  • 10
    Electronic Resource
    Electronic Resource
    An analytic hindered rotor model for calculating microcanonical variational unimolecular rate constants from reaction path properties (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 407-419 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model is proposed for performing microcanonical variational transition state theory calculations which incorporates ideas from vibrator and flexible variational transition state models. Vibrational frequencies, moments of inertia, and potential energy for the variational transition state are found by reaction path following as for the vibrator model. However, the transitional modes are treated as hindered rotors using an analytic potential and an analytic density of states, which are fit to barriers for hindered rotation determined from reaction path following. The model proposed here differs from the flexible transition state model in that the density of states for the transitional modes is analytic and transitional modes and external rotational angular momenta are uncoupled. For the H + CH3 ⇌ CH4 system, rate constants calculated with this new model are only 6-23% smaller on average from those of the flexible transition state model for values of total angular momentum which correspond to average rotational temperatures of 0-2000 K. Harmonic frequencies calculated for the transitional modes from the hindered rotor Hamiltonian are in good agreement with the exact values found by a reaction path analysis. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550260404
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