832 research outputs found
Evaluation of effect of the primary particle size on compactibility of spray-dried lactoses
Spray-dried lactose is one of the most used filler-binders in direct compaction of tablets.
Spray-dried lactose is produced by spray-drying a suspension of α-lactose monohydrate
crystals in a saturated aqueous solution of lactoses. The resulting product is composed of
spherical particles, containing 80-85% crystals of α-lactose monohydrate (primary particles) and 15-20% amorphous lactose
The compactibility of two commercial spray-dried lactoses, Pharmatose® DCL 11
(DCL11), prepared from α-lactose monohydrate with a median primary particle size of 34
µm and a new product, Pharmatose® DCL 14 (DCL14), prepared from 20 µm primary
particles, were investigated
Topological methods for searching barriers and reaction paths
We present a family of algorithms for the fast determination of reaction
paths and barriers in phase space and the computation of the corresponding
rates. The method requires the reaction times be large compared to the
microscopic time, irrespective of the origin - energetic, entropic, cooperative
- of the timescale separation. It lends itself to temperature cycling as in
simulated annealing and to activation-relaxation routines. The dynamics is
ultimately based on supersymmetry methods used years ago to derive Morse
theory. Thus, the formalism automatically incorporates all relevant topological
information.Comment: 4 pages, 4 figures, RevTex
The Asakura-Oosawa model in the protein limit: the role of many-body interactions
We study the Asakura-Oosawa model in the "protein limit", where the
penetrable sphere radius is much greater than the hard sphere radius
. The phase behaviour and structure calculated with a full many-body
treatment show important qualitative differences when compared to a description
based on pair potentials alone. The overall effect of the many-body
interactions is repulsive.Comment: 9 pages and 11 figures, submitted to J. Phys.: Condensed Matter,
special issue "Effective many-body interactions and correlations in soft
matter
An integral equation approach to effective interactions between polymers in solution
We use the thread model for linear chains of interacting monomers, and the
``polymer reference interaction site model'' (PRISM) formalism to determine the
monomer-monomer pair correlation function for dilute and
semi-dilute polymer solutions, over a range of temperatures from very high
(where the chains behave as self-avoiding walks) to below the
temperature, where phase separation sets in. An inversion procedure, based on
the HNC integral equation, is used to extract the effective pair potential
between ``average'' monomers on different chains. An accurate relation between
, [the pair correlation function between the polymer
centers of mass (c.m.)], and the intramolecular form factors is then used to
determine , and subsequently extract the effective c.m.-c.m. pair
potential by a similar inversion procedure. depends on
temperature and polymer concentration, and the predicted variations are in
reasonable agreement with recent simulation data, except at very high
temperatures, and below the temperature.Comment: 13 pages, 13 figures, revtex ; revised versio
Proton Motive Force-Driven and ATP-Dependent Drug Extrusion Systems in Multidrug-Resistant Lactococcus lactis
Proton Motive Force-Driven and ATP-Dependent Drug Extrusion Systems in Multidrug-Resistant Lactococcus lactis
Proton Motive Force-Driven and ATP-Dependent Drug Extrusion Systems in Multidrug-Resistant Lactococcus lactis
Influence of polymer excluded volume on the phase behavior of colloid-polymer mixtures
We determine the depletion-induced phase-behavior of hard sphere colloids and
interacting polymers by large-scale Monte Carlo simulations using very accurate
coarse-graining techniques. A comparison with standard Asakura-Oosawa model
theories and simulations shows that including excluded volume interactions
between polymers leads to qualitative differences in the phase diagrams. These
effects become increasingly important for larger relative polymer size. Our
simulations results agree quantitatively with recent experiments.Comment: 5 pages, 4 figures submitted to Physical Review Letter
Phase behavior of a system of particles with core collapse
The pressure-temperature phase diagram of a one-component system, with
particles interacting through a spherically symmetric pair potential in two
dimensions is studied. The interaction consists of a hard core plus an
additional repulsion at low energies. It is shown that at zero temperature,
instead of the expected isostructural transition due to core collapse occurring
when increasing pressure, the system passes through a series of ground states
that are not triangular lattices. In particular, and depending on parameters,
structures with squares, chains, hexagons and even quasicrystalline ground
states are found. At finite temperatures the solid-fluid coexistence line
presents a zone with negative slope (which implies melting with decreasing in
volume) and the fluid phase has a temperature of maximum density, similar to
that in water.Comment: 11 pages, 15 figures included. To appear in PRE. Some figures in low
quality format. Better ones available upon request from [email protected]
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