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  • 1
    Electronic Resource
    Electronic Resource
    Polar solvation dynamics of polyatomic solutes: Simulation studies in acetonitrile and methanol (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3038-3060 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes results of simulations of solvation dynamics of a variety of solutes in two reference solvents, acetonitrile and methanol. Part of these studies involve attempts to realistically model the solvation dynamics observed experimentally with the fluorescence probe coumarin 153 (C153). After showing that linear response simulations afford a reliable route to the dynamics of interest, experimental and simulation results for C153 are compared. Agreement between the observed and calculated dynamics is found to be satisfactory in the case of acetonitrile but poor in the case of methanol. The latter failure is traced to a lack of realism in the dielectric properties of the methanol model employed. A number of further simulations are then reported for solvation of a number of atomic, diatomic, and benzenelike solutes which are used to elucidate what features of the solute are important for determining the time dependence of the solvation response. As far as large polyatomic solutes like C153 are concerned, the solute attribute of foremost importance is shown to be the "effective moment'' of its charge distribution (actually the difference between the S1 and S0 charge distributions). This effective moment, determined from consideration of continuum electrostatics, provides a simple measure of how rapidly the solute's electric field varies spatially in the important regions of the solvent. Simulations of fictitious excitations in a benzene solute show that this single quantity is able to correlate the dynamics observed in widely different solutes.Also explored is the effect of solute motion on its solvation dynamics. While of minor relevance for large solutes like C153, in small solutes of the size of benzene, solute motion can dramatically enhance the rate of solvation. A model based on independent solvent dynamics and solute rotational motion is able to account for the bulk of the observed effects. Finally, the influence of solute polarizability on solvation dynamics is considered. Simulations of diatomic molecules with a classical polarizability show that the rate of solvation decreases roughly in proportion to the polarizability of the solute. This dynamical effect can be understood in terms of the change that polarizability produces on the solvation force constant. These simulations indicate that the magnitude of the effect should be relatively small (10%–25%) in real systems, at least in the linear response limit. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470493
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  • 2
    Electronic Resource
    Electronic Resource
    Smart Monte Carlo for accurate simulation of rare-event dynamics: Diffusion of adsorbed species on solid surfaces (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 686-695 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We introduce a dynamical Smart Monte Carlo algorithm and assess its applicability for simulating the rare-event dynamics of adsorbate diffusion. Using the dynamical Smart Monte Carlo method, we simulate the self-diffusion of an adatom in the Cu/Cu(001) and Rh/Rh(111) systems and we compare the simulated diffusion coefficients to values arising from molecular dynamics and transition-state theory. We find that the accuracy of Smart Monte Carlo is sensitive to details of the potential-energy surface. For Cu/Cu(001), the agreement between dynamical Smart Monte Carlo, molecular dynamics, and transition-state theory is excellent. A similar comparison for the Rh/Rh(111) systems shows discrepancies between these three techniques. We find that the origins of the discrepancies in the Rh/Rh(111) system are transition-state recrossings, for small simulation time steps, and low escape rates of the adatom from the binding sites, at large time steps. We examine the sampling and dynamics in trajectories using a smaller time step for motion perpendicular to the surface than that for parallel motion. These studies show that low Smart Monte Carlo escape rates in the Rh/Rh(111) system can be correlated to excessive sampling, beyond the configurational space of the potential-energy minimum, at large time steps. Recrossings can be understood to arise from the absence of velocity correlations in the low-friction, transition-state region and can be minimized through the use of a large time step for parallel motion. With the appropriate choice of simulation time steps it is possible to improve the agreement between dynamical Smart Monte Carlo and more rigorous dynamical techniques. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471895
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  • 3
    Electronic Resource
    Electronic Resource
    The non-separability of "dielectric" and "mechanical" friction in molecular systems: A simulation study (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5370-5381 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Simulations of the time-dependent friction controlling rotational, translational, and vibrational motions of dipolar diatomic solutes in acetonitrile and methanol have been used to examine the nature of "dielectric" friction. The way in which electrical interactions increase the friction beyond that present in nonpolar systems is found to be rather different than what is anticipated by most theories of dielectric friction. Long-range electrostatic forces do not simply add an independent contribution to the friction due to short-ranged or "mechanical" sources (modeled here in terms of Lennard-Jones forces). Rather, the electrical and Lennard-Jones contributions are found to be strongly anticorrelated and not separable in any useful way. For some purposes, the mechanism by which electrical interactions increase friction is better viewed as a static electrostriction effect: electrical forces cause a subtle increase in atomic density in the solute's first solvation shell, which increases the amplitude of the force fluctuations derived from the Lennard-Jones interactions, i.e., the mechanical friction. However, electrical interactions also modify the dynamics of the friction, typically adding a long-time tail, which significantly increases the integral friction. Both of these effects must be included in a correct description of friction in the presence of polar interactions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481107
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  • 4
    Electronic Resource
    Electronic Resource
    Near-surface heating in the arabian sea during the pre-onset regime of MONEX-79 (1994)
    Springer
    Meteorology and atmospheric physics 53 (1994), S. 19-31 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary During the pre-onset regime of MONEX-79, the short period (1–2 weeks) time series measurements of surface meteorological elements, vertical profiles of temperature (BT) and salinity (Nansen casts) made from 5 former USSR and 2 Indian research vessels were utilised to investigate the observed near-surface heating rates at a few selected locations in the Arabian Sea. The influence of local surface heat fluxes on the upper ocean heat content variability is explored. The associated synoptic scale variability in the thermohaline structure of the upper layers is presented. The efficacy of a simple Kraus-Turner type one dimensional numerical model in simulating the observed variability of mixed layer heating rates is evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031902
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  • 5
    Electronic Resource
    Electronic Resource
    On the heat budget of the Arabian Sea (1997)
    Springer
    Meteorology and atmospheric physics 62 (1997), S. 215-224 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The rate of oceanic heat storage of the upper 200m of the Arabian Sea is explained in terms of net air-sea heat flux (Q F), heat change due to horizontal divergence and vertical motion (Q V) and heat change due to lateral advection (Q A). The analysis revealed that the heat storage of the Arabian Sea is mainly controlled byQ V while the effect ofQ A is much larger than expected. Parameterisation of summer cooling revealed that the depletion of energy from the mixed layer is mainly due to upwelling and horizontal advection though large amount of heat is accumulated due to net air-sea heat flux. The annual heat balance of the upper 200m of the Arabian Sea suggested large heat gain by air-sea exchange processes. About two third of this heat gain is compensated by horizontal advection and one third by vertical advection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029703
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  • 6
    Electronic Resource
    Electronic Resource
    Femtosecond solvation dynamics of water (1994)
    [s.l.] : Nature Publishing Group
    Nature 369 (1994), S. 471-473 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FIG. 1 Femtosecond fluorescence up-conversion data for coumarin 343 anion (sodium salt, 1CT4 M) in aqueous solution. The traces show data obtained at wavelengths ranging from 460 nm (bottom) to 570 nm (top) in steps of 10 nm. METHODS. A coherent Mira mode-locked Thsapphire laser operating at ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/369471a0
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  • 7
    Electronic Resource
    Electronic Resource
    Simultaneous degradation of 3-chlorobenzoate and phenolic compounds by a defined mixed culture ofPseudomonas spp. (1995)
    Springer
    World journal of microbiology and biotechnology 11 (1995), S. 148-152 
    Details
    ISSN: 1573-0972
    Keywords: 3-Chlorocatechol ; cresol ; phenol ; Pseudomonas aeruginosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A mixed culture of a chlorobenzoate-(3-CBA)-degradingPseudomonas aeruginosa, strain 3mT, and a phenol/cresols-degradingPseudomonas sp., strain CP4, simultaneously and efficiently degraded mixtures of 3-CBA and phenol/cresols. However, strains 3mT and CP4 usedortho- andmeta-ring cleavage pathways, respectively. Degradation of 3-CBA was complete when the 3-CBA was equal in amount to or less than that of phenol. CP4/3mT inoculum ratios (w/w) of 1:1 or 1:2 gave the most effective degradation of both the substrates in the mixture. The mixed culture degraded equimolar mixtures of 3-CBA/phenol up to 10mm. Equimolar mixtures of 3-CBA ando-, m- orp-cresol were also degraded by the mixed culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704636
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  • 8
    Electronic Resource
    Electronic Resource
    Somatic embryogenesis and plant regeneration from callus cultures of Aconitum heterophyllum Wall (1993)
    Springer
    Plant cell, tissue and organ culture 32 (1993), S. 213-218 
    Details
    ISSN: 1573-5044
    Keywords: Aconitum heterophyllum ; endangered medicinal plant ; somatic embryogenesis ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants were obtained via somatic embryogenesis in callus derived from in vitro raised leaf and petiole explants of Aconitum heterophyllum Wall. Callus was induced on a Murashige-Skoog medium supplemented with either 2,4-dichlorophenoxy acetic acid (2,4-d 1 mg l-1) and kinetin (KN 0.5 mg l-1) with coconut water (CW 10% v/v) or naphthalene acetic acid (NAA 5 mg l-1) and benzylaminopurine (BAP 1 mg l-1). Somatic embryos appeared after 2–3 months or 2 subculture passages when 2,4-d or NAA induced source of the callus was transferred to a MS medium containing BAP (1 mg l-1) and NAA (0.1 mg l-1). For successful plantlet formation, the somatic embryos were transferred to a medium containing 1/4 strength MS nutrient with indole-3-butyric acid (IBA 1 mg l-1). Alternatively, the somatic embryos were dipped in a concentrated solution of IBA for 5 min and placed on a hormone free medium. Complete plantlets were formed after 4 weeks and were transferred successfully to soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029845
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  • 9
    Electronic Resource
    Electronic Resource
    Insolation over the Arabian Sea during the southwest monsoon (1991)
    Springer
    Boundary layer meteorology 56 (1991), S. 197-203 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The relationship between monsoon cloud cover and incoming solar radiation in the Arabian Sea is examined utilising the available observations of daily mean total cloud amount and solar radiation collected during the summer monsoon. With these data sets, various cloud correction formulae are evaluated. For the estimation of solar radiation, the formulation of Laevastu (1960) is best, with a minimum error of -4%. A multiple polynomial regression equation based on cloud cover and noon altitude of the sun is developed for estimation of daily radiation. The error between estimated and observed radiation is -2%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119967
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