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  • 1
    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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  • 2
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 37 (1986), S. 245-270 
    ISSN: 0066-426X
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6940-6942 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report molecular dynamics simulations of n-butane at the B1 state point of Ryckaert and Bellemans [Chem. Phys. Lett. 30, 23 (1975); Discuss. Chem. Soc. 6, 695 (1978)]. The results confirm those of Edberg et al. (preceding paper) in that we found 58.5±1.0% of the molecules in the trans state as opposed to the value of 54% reported by Ryckaert and Bellemans.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 43 (1986), S. 621-643 
    ISSN: 1572-9613
    Schlagwort(e): Wetting transition ; exact solution ; random walk ; S.O.S. model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A model of a binary mixture, showing a wetting transition, is examined. No prewetting phenomena are found. The scaling functions are obtained for the film thickness and for the correlation lengths.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 50 (1988), S. 813-838 
    ISSN: 1572-9613
    Schlagwort(e): Spherical model ; Coulombic systems ; correlation function decay ; Stillinger-Lovett relations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider simple cubic lattice systemsΛ ind dimensions with a continuous real charge variableq(n) at each lattice siten. These variables are subject t'o a mean spherical constraint forcing 〈∑n∈Λ q 2(n)〉=‖Λ‖Q 2, where ‖Λ‖ is the number of lattice sites inΛ andQ is an elementary charge. The energy of the charges comes from interactions with an electrostatic potential, which is the solution of a symmetric second-difference Poisson equation on the lattice. Two cases are considered, both of which allow the inclusion of the effects of a fixed, constant, external electric field. On the latticeΛ 1=[1,N]⊗d , a Neumann condition is imposed at the surface of the lattice. The latticeΛ 2=[1,N]⊗ [−M,M]⊗(d−1) is periodic in each direction ranging over [−M, M] and has a Dirichlet condition imposed at the other two surfaces. OnΛ 2 a finite electric field may be applied, while onΛ 2 a finite potential difference may be applied across the lattice. The models are exactly solvable. We study the distribution functions on each system and show that they satisfy appropriate forms of the first two Stillinger-Lovett moment conditions. The two charge distribution functions show screening behavior at high temperature and extreme short range at an intermediate temperatureT 0(d), and oscillate as they decay to zero forT〈T 0(d). Because of the continuous nature of the charge variables, there is no Kosterlitz-Thouless transition in two dimensions. In three dimensions the change in the decay behavior of the distribution functions atT〈T 0(d) is precursor to a phase transition to a charge ordered state.
    Materialart: Digitale Medien
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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 46 (1987), S. 179-190 
    ISSN: 1572-9613
    Schlagwort(e): Dipoles ; boundary conditions ; electrostatics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A microscopic derivation using the average Maxwell electric field is given for fluctuation formulas for the dielectric constant of a simulation sample for both periodic and reaction field boundary conditions. The reaction field case is for a spherical cavity reaction field. The derivations put both boundary conditions on an equal footing of microscopic theory and the only nonrigorous part of the derivation is the assumption that the region used to average the electric field is large enough. The fluctuation formula for reaction field boundary conditions is rather different from that used heretofore. The method is applied to a subregion of an isolated spherical system.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 55 (1989), S. 127-139 
    ISSN: 1572-9613
    Schlagwort(e): Spherical model ; Coulombic systems ; correlation function decay ; surface properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Studies of the mean spherical model with Coulomb interactions are continued, by considering a system on ad-dimensional lattice which is periodic ind−1 dimensions and has a free surface in the remaining dimension. It is shown explicitly that correlations along the free surface decay asy −d ind dimensions and show that the surface properties of this model are those expected for a charged system in its plasma phase.
    Materialart: Digitale Medien
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