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  • 1
    Electronic Resource
    Electronic Resource
    A low energy crossed beam study of the reactions of C+ with CH4 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 2224-2237 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a crossed molecular beam study of the reactions of C+ with CH4 over the relative energy range from 0.66 to 2.38 eV. CH+3 production involves a direct rebound collision mechanism. Production of C2H+3 and C2H+2 proceeds through unimolecular decay of long-lived collision complexes. Hydrogen atom emission proceeds through a rotating ethylene cation and yields a polarized angular distribution of reaction products. The kinetic energy distributions for vinyl cation production place nearly three times as much of the available energy in translation as a statistical model predicts. At low collision energy, C2H+2 production proceeds through molecular hydrogen elimination and the angular distribution for reaction products is polarized perpendicularly to the initial relative velocity vector. At a higher collision energy of 2.38 eV, the complex decays in a fraction of a rotational period. The lifetime of 0.03 ps inferred from the asymmetry in the angular distribution is in good agreement with a statistical calculation incorporating nonadiabatic couplings among the excited and ground states of C2H+4. The recoil distribution at this energy is dramatically narrower than at the lower collision energy and is consistent with the sequential ejection of two hydrogen atoms through a metastable C2H+3 intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449315
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  • 2
    Electronic Resource
    Electronic Resource
    C–N bond formation in the gas phase reaction of C+ with NH3 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 127-134 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a study of the reaction of C+ with NH3 at collision energies near 2 eV. The reaction proceeds through a long lived intermediate which is hypothesized on the basis of ab initio calculations to be the nonclassical cation HCNH+2 produced by insertion of C+ into the N–H bond. Mass 28 production appears to proceed through a substantial exit channel barrier, suggesting that N–H bond cleavage in the intermediate complex yields HCNH+, hypothesized to be important in interstellar synthesis of large molecules. The recoil distribution is significantly broader than the predictions of phase space theory. Mass 27 production yields a recoil distribution which is also broader than predicted by a statistical theory and which appears to be a superposition of two channels releasing different amounts of kinetic energy. We hypothesize that the intermediate complex decays by (1,1) geminal elimination of H2 to yield HCN+, while HNC+ is also produced by (1,2) vicinal elimination from the same intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450187
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  • 3
    Electronic Resource
    Electronic Resource
    Collision complex formation in the reaction of C+ with H2O (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3958-3964 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A crossed beam study of the title reaction at collision energies of 0.62 and 2.14 eV demonstrates that the production of mass 29 ions, either HCO+ or COH+, occurs through the formation of a transient intermediate HCOH+ complex which lives approximately one rotational period at the lower collision energy. The asymmetry of the angular distribution at a relative energy of 0.62 eV indicates that the lifetime of the transient intermediate is ∼10−13 s. The widths of the kinetic energy distributions at both collision energies are consistent with production of a significant fraction ((approximately-greater-than)20%–30%) of the more stable formyl HCO+ isomer. These observations suggest the formation of a hydroxycarbene cation insertion complex at the lower energy which may decay by C–H cleavage to form isoformyl cation COH+ or by O–H bond cleavage to form the more stable formyl cation HCO+. At the higher collision energy, a smaller fraction of the mass 29 products are constrained to be HCO+. This observation and the form of the product flux distribution suggest the increasing dominance of a direct, "knockout'' mechanism at higher energy. The internal energy of the mass 29 product as inferred from the kinetic energy distributions is above the HCO+/COH+ isomerization barrier for approximately one-third of the products at the lower collision energy, and for two-thirds of the products at the higher energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449108
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction between hydrophobic surfaces with metastable intervening liquid (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 3873-3877 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular simulation is used to elucidate hydrophobic interaction at atmospheric pressure where liquid water between apolar walls is metastable with respect to capillary evaporation. The steep increase of the estimated activation barrier of evaporation with surface–surface separation explains the apparent stability of the liquid at distances more than an order of magnitude below the thermodynamic threshold of evaporation. Solvation by metastable liquid results in a short-ranged oscillatory repulsion which gives rise to an irreversible potential barrier between approaching walls. The barrier increases with external pressure in accord with measured pressure-induced slowing of conformational transitions of biopolymers with strong hydrophobic interactions. At a sufficiently small separation, the force abruptly turns attractive signaling nucleation of the vapor phase. This behavior is consistent with the cavitation-induced hysteresis observed in a number of surface–force measurements for strongly hydrophobic surfaces at ambient conditions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386926
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics of the reactions of C+ with C2H6 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 862-870 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a crossed beam study of the major reactive channels of C++C2H6 in the collision energy range between 0.8 and 1.6 eV. We find that C2H+5 formation proceeds as a direct hydride abstraction reaction with the accompanying CH product scattered in the forward hemisphere. The product recoil energy distribution shows a distinct Gaussian shape that we correlate with the nature of the potential energy surface for transfer of the light hydride ion between two heavy species. C2H+3 formation occurs through two pathways: the first and most important route is direct interaction of C+ with C2H6 to form a new C–C bond with the ejection of CH3 in a collinear interaction that leads to backward scattering of the ionic product. A second, and much less probable pathway involves formation of this product through a transient collision complex living a significant fraction of a rotational period. The condensation product C3H+3 is by far the most abundant C3 product observed in this collision energy range. The sideways-peaked angular distribution for its formation is consistent with a mechanism where the initially formed C3H+6 complex decays in a step in which a molecule of H2 is ejected in a direction perpendicular to the plane of rotation defined by the three carbon atoms. The kinetic energy distribution for this channel is significantly broader than the predictions of statistical phase space theory and underscores the importance of potential energy exit channel barriers in determining product recoil in such elimination processes. We discuss these results in the context of a schematic potential energy surface incorporating thermochemical data and results of ab initio calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456111
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  • 6
    Electronic Resource
    Electronic Resource
    Protein—Protein Interactions in Aqueous Ammonium Sulfate Solutions. Lysozyme and Bovine Serum Albumin (BSA) (2000)
    Springer
    Journal of solution chemistry 29 (2000), S. 699-718 
    Details
    ISSN: 1572-8927
    Keywords: Potential of mean force ; proteins ; salts ; intermolecular interactions ; precipitation ; crystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Osmotic pressures have been measured to determine lysozyme—lysozyme,BSA—BSA, and lysosyme—BSA interactions for protein concentrations to 100 g-L−1in an aqueous solution of ammonium sulfate at ambient temperature, as a functionof ionic strength and pH. Osmotic second virial coefficients for lysozyme, forBSA, and for a mixture of BSA and lysozyme were calculated from theosmotic-pressure data for protein concentrations to 40 g-L−1. The osmotic second virialcoefficient of lysozyme is slightly negative and becomes more negative withrising ionic strength and pH. The osmotic second virial coefficient for BSA isslightly positive, increasing with ionic strength and pH. The osmotic second virialcross coefficient of the mixture lies between the coefficients for lysozyme andBSA, indicating that the attractive forces for a lysozyme—BSA pair areintermediate between those for the lysozyme—lysozyme and BSA—BSA pairs. For proteinconcentrations less than 100 g-L−1, experimental osmotic-pressure data comparefavorably with results from an adhesive hard-sphere model, which has previouslybeen shown to fit osmotic compressibilities of lysozyme solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005112927213
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  • 7
    Electronic Resource
    Electronic Resource
    Second order effects in fluidmagnetic buoyancy (1974)
    Springer
    Flow, turbulence and combustion 29 (1974), S. 342-350 
    Details
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A non-magnetic solid object placed in a magnetically responsive fluid in the presence of a magnetic field gradient experiences a net buoyancy force of magnetic origin. A procedure is developed to account for the effects of magnetic field distortion due to the difference of magnetic permeability between the fluid and the solid and non-zero dependence of fluid magnetization on magnetic field strength. This procedure gives an expression for the magnetic buoyancy force correct to first order in the dimensionless magnetization of the fluid and in the dimensionless variation of fluid magnetization across the object. Calculations are performed for a sphere, cylinder and plate in an applied magnetic field where the field and field gradient are either aligned or at right angles in order to give an indication of the range of force variation due to a change of shape and due to a change of applied field geometry. Variations on the order of 10% can be expected in typical applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384157
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  • 8
    Electronic Resource
    Electronic Resource
    Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 11-21 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; salts ; intermolecular interactions ; potentials of mean force ; precipitation ; crystallization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 11-21, 1998.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 451-451 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 10
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    Unknown
    Second order effects in fluidmagnetic buoyancy (1974)
    Springer
    Details
    Publication Date: 1974-01-01
    Print ISSN: 1386-6184
    Electronic ISSN: 1573-1987
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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