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  • 1
    Electronic Resource
    Electronic Resource
    A test of generalized van der Waals theory for confined fluids of rigid particles (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3022-3032 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The predictions of the generalized van der Waals (GvdW) theory for density profiles of hard rods and spheres confined between hard walls are considered as a function of chemical potential. The usual iterative solution of the stationarity condition of the functional becomes impractical at high μ and is replaced by a local steepest descent minimum search which is able to generate solutions with no apparent limit on μ. Further improvement can be achieved using the global method of simulated annealing to perform the combinatorial optimization and by consideration of the free-energy variation with the location of a test particle. The accuracy of the GvdW theory in one dimension is tested by comparison with exact results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461999
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  • 2
    Electronic Resource
    Electronic Resource
    A simple analysis of the classical hard-sphere one-component plasma. II. Density functional theory (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3102-3119 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The generalized van der Waals free energy density functional formalism of inhomogeneous fluids has been applied to study the thermodynamics and structural properties of a system of identical charged hard spheres neutralized by a uniform penetrating background. Nonlocal entropic effects are included through a simple density independent coarse-graining kernel and the hard-sphere truncation of the Coulomb interaction in the ionic atmosphere is accounted for within a mean-field approximation. In the first instance a parametric charge density of known form is introduced yielding essentially analytic results. Second, the functional is optimized with full variational flexibility to produce a theory directly analogous with the Poisson–Boltzmann approach to Coulomb fluids. A linearized version corresponding to a Debye–Hückel approximation is also discussed. The results compare favorably with Monte Carlo simulation in the regime of low to intermediate bulk density. At high volume fractions (〉0.1) the functional becomes ill conditioned as the excluded volume effect is exaggerated and the mean-field hole correction fails to account for the hard-sphere structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461955
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  • 3
    Electronic Resource
    Electronic Resource
    A simple analysis of ion–ion correlation in polyelectrolyte solutions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1915-1922 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the Poisson–Boltzmann theory of macroion screening in electrolyte solutions the chief simplifying assumption is the neglect of correlations within the ionic atmosphere. Using a generalized van der Waals density functional analysis incorporating ion–ion correlation in a local approximation we obtain a simple correlation corrected Poisson–Boltzmann theory. For point charges in the salt free case, this local correlation approximation leads to asymptotic instability (a "structuring catastrophe'') though the correction is well behaved to low orders in perturbation theory. Results in zeroth order and in a zeroth order field approximation are compared with an extended series of Monte Carlo simulations within a cell model (and a planar electrode model). An excellent agreement is found over a wide range of coupling strengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458022
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  • 4
    Electronic Resource
    Electronic Resource
    A simple analysis of the classical hard sphere one component plasma. I. Hole corrected Debye–Hückel theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2048-2055 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The principal simplifying assumptions in the description of Coulomb fluids are the neglect of correlations within the ionic atmosphere and the disregard of ion size effects. In order to account for short range repulsions, a straightforward heuristic approach is considered where a Debye–Hückel charge density is augmented with a central hard sphere and the possibility of an electrostatic exclusion zone is included to prevent an unphysical negative contact density. This approach leads to an analysis describing the relative competition between hard sphere and electrostatic mechanisms, which undergoes a well-defined interchange in the (γ,η) parameter space. While the structural information is, by construction, limited, thermodynamic properties agree remarkably well with both the rescaled mean spherical approximation and Monte Carlo simulations, up to moderate densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461004
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  • 5
    Electronic Resource
    Electronic Resource
    Ion–ion correlations in polyelectrolyte solutions: Hard sphere counterions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 497-514 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The intimately related mechanisms of macroion screening and ion–ion correlations in electrolyte solutions are investigated with the aim to explore the simplest theoretical estimations of the latter on the former. The Poisson–Boltzmann theory of macroion screening in electrolyte solutions was developed under two important assumptions. Specifically, the correlated motion of the mobile ions is ignored by identifying the mean field electrostatic potential with the potential of average force and, moreover, only point charges are considered so that finite size effects are not accounted for. Utilizing the generalized van der Waals free energy density functional formulation for inhomogeneous fluids, we obtain simple corrections to the Poisson–Boltzmann result where both these mechanisms are treated in local and nonlocal approximations. By incorporating a somewhat more realistic short range repulsive interaction, the asymptotic instability encountered in the point particle case is avoided and self-consistent density profiles can be computed. Nonlocal approximations are shown to be thermodynamically consistent in terms of the contact theorem for the osmotic pressure, and excellent agreement with Monte Carlo simulation is achieved even at high electrostatic coupling and with large particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465775
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  • 6
    Electronic Resource
    Electronic Resource
    Isolation of Bacillus megaterium Mutants That Produce High Levels of Heterologous Protein, and Their Use to Construct a Highly Mosquitocidal Strain (1997)
    Springer
    Current microbiology 35 (1997), S. 71 -76 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A xylose-regulated plasmid expression system for producing high levels of recombinant proteins in Bacillus megaterium has recently been described [Appl Microbiol Biotechnol 35:594, 1991]. Using an antibiotic resistance protein as the expressed protein, we have been able to select mutant plasmids that produce increased levels of heterologous protein. The mutant plasmids show increased segregational stability and have lost the ability to be transformed into Escherichia coli. The same selection protocol has been used to isolate a mutant strain producing high levels of the Bacillus sphaericus mosquitocidal binary toxin. This strain shows toxicity to Culex quinquefasciatus larvae that is comparable to B. sphaericus 2362 and higher than a B. megaterium strain with the original expression plasmid. This approach may be generally useful for high-level regulated protein expression in B. megaterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002849900215
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  • 7
    Electronic Resource
    Electronic Resource
    Cloning and heterologous expression of the violacein biosynthesis gene cluster fromChromobacterium violaceum (1991)
    Springer
    Current microbiology 22 (1991), S. 355-358 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The entire biosynthetic pathway for the synthesis of the antibiotic pigment violacein is encoded on a 14.5 kilobase (kb) fragment of theChromobacterium violaceum genome. When cloned intoEscherichia coli, pigment synthesis is strongly expressed, as it is in a wide range of Gram-negative bacteria. Transposon mutagenesis resulted in a number of different phenotypes that correlated with transposon insertion sites in the gene cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02092154
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  • 8
    Electronic Resource
    Electronic Resource
    A gene from the photosynthetic gene cluster ofRhodobacter sphaeroides inducestrans suppression of bacteriochlorophyll and carotenoid levels inR. sphaeroides andR. capsulatus (1991)
    Springer
    Current microbiology 23 (1991), S. 259-263 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract ARhodobacter sphaeroides gene (pps) inducestrans suppression of bacteriochlorophyll (Bch) and carotenoid (Crt) levels in bothR. sphaeroides andR. capsulatus. It also induces suppression of Crt levels in aParacoccus denitrificans strain carrying the Crt genes ofR. sphaeroides. The gene is located approximately 11 kilobases fromcrtA in the photosynthetic gene cluster. Crt suppression bypps is quantitatively different from that caused by an absence of mature Bch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02092027
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  • 9
    Electronic Resource
    Electronic Resource
    High-frequency electroporation and maintenance of pUC- and pBR-based cloning vectors inPseudomonas stutzeri (1992)
    Springer
    Current microbiology 25 (1992), S. 25-29 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A number ofEscherichia coli cloning vectors, based on ColE1-like replicons, were shown to be maintained inPseudomonas stutzeri ATCC 17588. A restrictionless mutant ofP. stutzeri was isolated, and this strain was used to develop an efficient electroporation system. With theE. coli cloning vector pHSG298, transformation frequencies of up to 2×107 transformants/μg DNA were achieved. This frequency is comparable to that obtained for CaCl2-mediated transformation ofE. coli; thus, direct cloning of DNA intoP. stutzeri is feasible. As will be discussed, this may prove useful for cloning DNA from high mol% G+C genera in cases in whichE. coli is not a suitable heterologous cloning host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570078
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  • 10
    Electronic Resource
    Electronic Resource
    A Sandwich Enzyme-Linked Immunosorbent Assay for the Bacillus sphaericus Binary Toxin (1998)
    Springer
    Current microbiology 36 (1998), S. 152-157 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Bacillus sphaericus (Bs) binary toxin was purified from recombinant E. coli DH5α harboring the recombinant plasmid pAR5, which carries a 3.6-kb DNA fragment of Bs 1593M encoding mosquito larvicidal activity. The binary toxin preparation, designated BsEcAg, contained mainly 51- and 42-kDa toxin proteins and was toxic to 50% of Culex quinquefasciatus larvae at a concentration of 9.22 ng toxin protein/ml. This preparation was used to raise antibodies in sheep and mice. The sandwich ELISA used sheep antitoxin antibody as primary antibody (coating antibody), mouse antitoxin antibody as second antibody, and goat antimouse antibody as an alkaline phosphatase-conjugated detecting antibody. The assay sensitivity was 200 ng/ml for both BsEcAg and binary toxin antigen (BsAg) from Bs 2362 cells. There is a significant correlation between toxin level determined by ELISA and bioassay. This procedure has also been used to monitor toxin levels in batch fermentations of Bs 2362.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006759
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