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  • 1
    Electronic Resource
    Electronic Resource
    The dissociative adsorption of hydrogen: Two-, three-, and four-dimensional quantum simulations (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2879-2884 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantum wave packet calculation for the activated dissociative adsorption of H2 is presented. Restricting the motion of the molecule to lie within a plane normal to the surface we have treated all four molecular degrees of freedom exactly. We compare results obtained using two-, three-, and four-dimensional simulations on the same potential and show that by restricting the molecular orientation, important dynamical effects are lost. The potential employed in the calculations has been obtained using the effective medium approximation. In the simulations it has been possible to treat dissociation, rotations and diffraction on an equal footing. By including a rotational degree of freedom, it is seen that strong orientational effects occur near to the transition state and result in an anisotropic selectivity in the dissociation. By examining the state-to-state scattering probabilities, it is possible to use the nonreacting (scattered) fraction to provide information on the reactive potential energy surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458873
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  • 2
    Electronic Resource
    Electronic Resource
    On the dynamics of the associative desorption of H2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4427-4439 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of activated associative desorption is discussed with particular reference to the system H2–Cu and to the partitioning of the energy released among the various product degrees of freedom. It is argued that a simple theory based on transition-state concepts should hold for this system because the potential energy surface (PES) divides naturally into reactant and product regions, separated by a "seam'' or "ridge'' at which it is reasonable to assume a thermal distribution of desorbing trajectories. Using a PES constructed in accordance with available electronic structure calculations we consider the angular distributions and translational, vibrational, and rotational energy distributions of the desorbing molecules. It is shown that, whereas the rotational energy reflects the surface temperature, the vibrational energy is markedly enhanced because the energetically low-lying regions of the ridge in the PES correspond to an H–H bond distance that is distended as compared with the gas-phase equilibrium separation. The enhancement is found to be a strong function of the surface temperature. The translational energy, however, is found to be only very weakly dependent on the temperature. These results are discussed in connection with available data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455689
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  • 3
    Electronic Resource
    Electronic Resource
    Bioactive aziridine derivatives of chrysanthemate insecticides (1986)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 34 (1986), S. 1057-1060 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00072a031
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of laser-induced desorption of ammonia from Cu(111): State-resolved dynamics, isotope effects, and selective surface photochemistry (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6720-6734 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A two-dimensional, two-state model is used to model the UV-laser-induced photodesorption dynamics of NH3 and ND3 from Cu(111) by solving the nuclear time-dependent Schrödinger equation. By projecting the asymptotic wave functions on the asymptotic ("umbrella'') eigenstates of NH3/ND3, we find that the molecules leave the surface vibrationally hot, in agreement with experimental data. Within individual asymptotic tunneling doublets, however, the desorbates are clearly non-Boltzmann with molecules of "gerade'' symmetry desorbing with increased probability. Our study correlates this parity selection with details of the electronic ground state potential energy surface. An experimentally observed strong isotope effect in the desorption yields for the different isotopomers is traced back mainly to differences between the vibrational frequencies of the "umbrella'' mode, in accord with earlier, classical models. Additionally, small tunneling and moderate zero-point contributions are observed. Finally, the possibility of bond and isotope selective photochemistry at surfaces, based on a two-photon IR+UV strategy is demonstrated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470351
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemistry of the prototype insecticide (2E,4E)-N-isobutyl-6-phenylhexa-2,4-dienamide (1988)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 36 (1988), S. 841-844 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00082a044
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  • 6
    Electronic Resource
    Electronic Resource
    Willingness to Help a Stranger: The Effects of Social Context and Opinion Similarity (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of applied social psychology 12 (1982), S. 0 
    Details
    ISSN: 1559-1816
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Psychology
    Notes: Two field experiments investigate how information about aspects of the social environment affects willingness to help others who are similar or dissimilar. Subjects were pedestrians who found a lost packet of materials containing information about the opinions of the packet's loser and a survey report which claimed that the quality of life in the neighborhood had either improved or deteriorated. In the fiist study, the opinions were varied in order to create different degrees of opinion similarity between the loser and subject. Results showed that relatively slight differences between the loser's and subject's opinions made subjects unwilling to help (return the lost packet) when information about the social environment suggested a negative state of affairs, e.g., quality of life deteriorating. However, when information about the social environment suggested a positive state of affairs, subjects were willing to help, even if there was little similarity of opinion. In the second study, subjects learned that the loser of the packet agreed with their views on one opinion but disagreed on another. In this study, one of the two opinions concerned the same social issue as the one described in the survey report. Results demonstrated that subjects helped when there was agreement on the social issue that was also highlighted in survey reports of a negative state of affairs in the social environment and withheld help when there was disagreement on this issue. There were trends for the same result with information about a positive state of affairs in the social world.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1559-1816.1982.tb00877.x
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetic properties of single sodium channels modified by fenvalerate in mouse neuroblastoma cells (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 613-621 
    Details
    ISSN: 1432-2013
    Keywords: Sodium channel ; Patch clamp ; Neuroblastoma ; Pyrethroid insecticide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract (1) The kinetic properties of single sodium channels modified by the pyrethroid fenvalerate have been analyzed by patch clamp techniques using the cultured mouse neuroblastoma cells. (2) Fenvalerate drastically prolonged the open time of single sodium channels from the normal value of 5 ms to several hundred milliseconds during a depolarizing pulse. The channels remained open after termination of a depolarizing pulse for as long as several seconds. (3) The channel lifetime varied with the membrane potential, attained a maximum at −70 mV, and decreased with hyperpolarization and depolarization from −70 mV. (4) Prolonged openings of the modified channels allowed a current-voltage curve for a single channel to be plotted by sweeping a ramp pulse. The single channel conductance had a value of 11 pS and was linear over potentials ranging from 0 to −100 mV. (5) Power density spectral analysis of the open channel current noise indicated a single Lorentzian curve with a cut-off frequency at 90 Hz, indicating that the increase in noise during channel opening resulted from a relatively slow kinetic process. (6) The probability of the channel being modified by fenvalerate was independent of the length of time during which the channel was opened. This observation suggests that channel modification had taken place before the channel opened. This study of the prolonged opening at the single channel level provides a new insight into open channel properties and the kinetics of channel modification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582125
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  • 8
    Electronic Resource
    Electronic Resource
    The catalytic group-I introns of the psbA gene of Chlamydomonas reinhardtii : core structures, ORFs and evolutionary implications (1999)
    Springer
    Current genetics 36 (1999), S. 69-78 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsChlamydomonas ; Chloroplast ; Evolution ; Group-I introns ; psbA gene ; Self-splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sequences and predicted secondary structures of the four catalytic group-I introns in the psbA gene of Chlamydomonas reinhardtii, Cr.psbA-1–Cr.psbA-4, have been determined. Cr.psbA-1 and Cr.psbA-4 are subgroup-IA1 introns and have similar secondary structures, except at the 3′ end where Cr.psbA-1 contains a large inverted-repeat domain. Cr.psbA-4 is closely related to intron 1 of the Chlamydomonas moewusii psbA gene, with which it shares the same location, high nucleotide identity in the core, and an identically placed ORF that shows 58% amino-acid identity. Cr.psbA-2 is a subgroup-IA3 intron, and shows similarities to the Chlamydomonas eugametos rRNA intron, Ce.LSU-1. Cr.psbA-3 is a subgroup-IA2 intron, and is remarkably similar to the T4 phage intron, sunY. Interestingly, a degenerate version of Cr.psbA-3 is located in the intergenic region between the chloroplast petA and petD genes. All four introns contain ORFs, which potentially code for basic proteins of 11–38 kDa. The ORFs in introns 2 and 3 contain variants of the GIY-YIG motif; however, the Cr.psbA-2 ORF is free-standing, whereas the Cr.psbA-3 ORF is contiguous and in-frame with the upstream exon. The Cr.psbA-4 ORF contains an H-N-H motif, and possibly a GIY-YIG motif. These data indicate that the C. reinhardtiipsbA introns have multiple origins, and illustrate some of the evolutionary DNA dynamics associated with group-I introns in Chlamydomonas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050474
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