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  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 76 (1954), S. 2283-2284 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 8870-8876 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The fast multipole method (FMM) has become an important alternative to traditional methods such as the Ewald method for computing the long-range interactions necessary to simulate charged or dipolar systems. In this paper, we present an improvement of this method, which we shall call the very fast multipole method (VFMM). The VFMM is shown to be a factor of about 1.2 faster than the FMM for two-dimensional systems and a factor about 2–3 times faster for three-dimensional systems without losing any accuracy for the worst case error.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 61 (1990), S. 187-201 
    ISSN: 1572-9613
    Schlagwort(e): Spherical model ; dipolar systems ; dielectric constant ; dipolar system simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A mean spherical model of classical dipoles on a simple cubic lattice of sideM=2N+1 sites is considered. Exact results are obtained for finite systems using periodic boundary conditions with an external dielectric constantɛ′ and using reaction field boundary conditions with a cutoff radiusR c ⩽N and an external dielectric constantɛ′. The dielectric constant in the disordered phase is calculated using a variety of fluctuation formulas commonly implemented in Monte Carlo and molecular dynamics simulations of dipolar systems. The coupling in the system is measured by the parametery=4πμ 2/9kT, whereμ 2 is the fixed mean square value of the dipole moments on the lattice. The system undergoes a phase transition aty≈2.8, so that very high dielectric constants cannot be obtained in the disordered phase. The results show clearly the effects of system size, cutoff radius, external dielectric constant, and different measuring techniques on a dielectric constant estimate. It is concluded that with periodic boundary conditions, the rate of approach of the dielectric constant estimate to its thermodynamic limit is asN −2/3 and depends only weakly onɛ′. Methods of implementing reaction field boundary conditions to give rapid convergence to the thermodynamic limit are discussed.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 39 (1990), S. 457-461 
    ISSN: 1432-1041
    Schlagwort(e): Vancomycin ; drug utilization ; drug usage evaluation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A prospective, two-phase, drug utilization review (DUR) was performed at the Royal Adelaide Hospital (RAH) to determine the extent and pattern of vancomycin use. For all patients commencing oral or parenteral vancomycin, treatment indication, route of administration, duration of therapy, results of culture and sensitivity tests, adverse drug reactions and results of therapeutic drug level monitoring were recorded. Vancomycin courses were classified as being for therapy or prophylaxis and compared with predetermined audit criteria to assess appropriateness of use. During the 8 week initial phase, data on 62 treatment courses in 59 patients were recorded, 50% for therapy and 50% for prophylaxis. Sixty four percent were classified as inappropriate, occurring in 32% of therapeutic courses and 97% of those for prophylaxis. During the 10 week re-evaluation, conducted 10 months later, data for 43 treatment courses in 43 patients were reviewed, 42% for therapy and 58% for prophylaxis. Sixty five percent were inappropriate occuring in 17% of therapeutic courses and 100% of the prophylactic courses. When compared with the initial phase, the re-evaluation demonstrated a decrease in the empirical use of vancomycin in the combination treatment of neutropaenic fever and also in the duration of vancomycin use for surgical prophylaxis. During both study phases, criteria contraventions were mostly due to inappropriate indication or duration of therapy. The cost of inappropriate vancomycin use was reduced by over 50% between survey phases, from $Aus11,500 or 55% of total vancomycin cost during the initial phase to $Aus3,600 or 25.7% during the re-evaluation. The most effective of the remedial strategies implemented after the initial phase was direct consultation with prescriber groups. The effectiveness of this DUR has provided the basis for an ongoing DUR programme at the RAH which has been met with general acceptance by hospital clinicians and administrators.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 77 (1994), S. 449-472 
    ISSN: 1572-9613
    Schlagwort(e): Virial theorem ; pressure ; periodic boundary conditions ; computer simulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Because it is not immediately clear how to write down a proper Hamiltonian for a system in periodic boundary conditions, particularly with Coulombic interactions, we consider a large, finite array of copies of a basic simulation cell containingN particles with some interaction between them. We also putN independent copy particles in each of the copy cells of the array and write down a constrained Lagrangian for the whole system. Constraints on the velocities of the particles of the whole array together with an appropriate initial condition implement the periodic structure in the cells of the array of copies. We derive a Hamiltonian for the whole system with constraints and then derive the equations of motion and a virial expression for the pressure tensor in terms of the forces on the system. In the limit as the array of cell copies becomes large, the equations of motion become the standard ones used in periodic-boundaryconditions simulations. The method also provides an unequivocal algorithm for the pressure in this limit in terms of a virial expression. Particular attention is paid to the case of Coulombic interactions.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 60 (1990), S. 529-549 
    ISSN: 1572-9613
    Schlagwort(e): Wetting transition ; finite-size scaling ; partition function zeros
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We derive a finite-size scaling representation for the partition function for an Onsager-Temperley string model with a wetting transition, and analyze the zeros of this partition function in the complex scaled coupling parameter of relevance. The system models the one-dimensional interface between two phases in a rectangular two-dimensional region (x, y) ∈ℝ2,−L ≤y⩽L,o≤x≤N. The two phases are at coexistence. The string or interface has a surface tension 2KkT per unit length and an extra Boltzmann weighta per unit length if it touches the surfaces aty=±L. There is a critical valuea c=1/2K and fora〉a c the string is confined to one of the surfaces, while fora ťa c the string moves roughly in the rectangular region. The finite-size scaling parameters are α=a c 2 N/L 2 and ζ=L(a−a c)/a c 2 . We find that for |ζ| large, the zeros of the scaled partition function lie close to the lines arg(ζ)=±π/4 with re(ζ)〉0. We discuss the motion of all the zeros as α changes by both analytic and numerical arguments.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 66 (1992), S. 233-247 
    ISSN: 1572-9613
    Schlagwort(e): Partition function zeros ; mean field transition ; one-dimensional plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the grand canonical partition function for the ordered one-dimensional, two-component plasma at fugacityζ in an applied electric fieldE with Dirichlet boundary conditions. The system has a phase transition from a low-coupling phase with equally spaced particles to a high-coupling phase with particles clustered into dipolar pairs. An exact expression for the partition function is developed. In zero applied field the zeros in theζ plane occupy the imaginary axis from −i∞ to −iζc and iζc to i∞ for some ζc. They also occupy the diamond shape of four straight lines from ±iζc to ζc and from ±iζc to −ζc. The fugacityζ acts like a temperature or coupling variable. The symmetry-breaking field is the applied electric fieldE. A finite-size scaling representation for the partition in scaled coupling and scaled electric field is developed. It has standard mean field form. When the scaled coupling is real, the zeros in the scaled field lie on the imaginary axis and pinch the real scaled field axis as the scaled coupling increases. The scaled partition function considered as a function of two complex variables, scaled coupling and scaled field, has zeros on a two-dimensional surface in a domain of four real variables. A numerical discussion of some of the properties of this surface is presented.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 72 (1993), S. 51-78 
    ISSN: 1572-9613
    Schlagwort(e): Partition function zeros ; Stokes phenomenon ; wetting transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the statistical mechanics of a fluctuating string (1D solid-on-solid model) ofN columns with a contact energy term displaying a critical wetting transition. For this model we derive a contour integral representation for the finite-size partition function. From this representation we derive a polynomial representation and obtain the Lee-Yang zeros forN ≲, 100. Through the asymptotic evaluation of the contour integral we evaluate the zeros for higherN. This asymptotic evaluation displays a Stokes phenomenon providing a different viewpoint of the mechanism by which a phase transition can arise, supplementing the picture of Lee and Yang. We also reproduce and extend somewhat the results of Smith for the finite-size scaling limit of the partition function.
    Materialart: Digitale Medien
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