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S Sokolowski

Publications and source records attributed to S Sokolowski.

At least 19 recordsLinked to original sources
PubMed2000

Adsorption of Fluids in Pores Formed between Two Hard Cylinders.

We study adsorption in pores with curved hard walls that are made of two uniaxial cylinders by using a density functional approach. Two cases are considered: adsorption of hard spheres and adsorption of a Lennard-Jones fluid. In the case of hard spheres, we perform a comparison with the results of grand canonical ensemble Monte Carlo data. This comparison indicates that the applied approach is capable of reproducing the fluid structure quite satisfactorily. For hard spheres, we also make a comparison of the total adsorption effect (expressed as the average density of a confined fluid) inside pores with curved walls with that evaluated for a slitlike pore. We have found that the differences between adsorption in pores with curved walls and in slits with the same wall-to-wall distance are quite low. The calculations for the Lennard-Jones fluid have been concerned with the investigation of the capillary evaporation and with the evaluation of phase diagrams for different pores, including slitlike pores. We have found that the curvature of the pore walls shifts the transition toward lower values of the chemical potential and increases slightly the value of the critical temperature in comparison with the values obtained for a slitlike pore. Copyright 2000 Academic Press.

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PubMed2000

Effects of Pore-Pore Correlations on Capillary Condensation in an Ensemble of Slit-like Pores: Application of a Density Functional Theory.

Using a density functional method we study how the correlations between particles adsorbed in neighboring pores, forming a network of slit-like pores, influence the capillary condensation and the structure of adsorbed Lennard-Jones fluid. The calculations indicate that if the distance between two pores is small enough, these correlations lead to pronounced changes in the density profiles, to an increase of the critical temperature, and to the modifications in the coexistence envelope. Copyright 2000 Academic Press.

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PubMed2000

Density Functional Theory and the Capillary Evaporation of a Liquid in a Slit.

Density functional theory is applied to a Lennard-Jones fluid near a single hard wall and in a slit formed by two walls. We use some simplified versions of the Weeks-Chandler-Andersen (WCA) and the Barker-Henderson (BH) theories. Only the most crude mean field version of the WCA theory, in which the hard-sphere correlation function is set equal to unity for all distances, seems useful. Use of the full WCA approximation is impractical because the effective hard-sphere diameter is density dependent. Generally, the best results are obtained using the BH macroscopic compressibility approximation. Our earlier study of "evaporation" of Lennard-Jones molecules in a slit is extended to other densities using the mean field theory. Copyright 2000 Academic Press.

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PubMed2000

Wetting of Crystalline Solids by Associating Fluids.

The wetting behavior of Lennard-Jones associating fluid on a crystalline surface is studied using Monte Carlo simulation in the isobaric-isothermal ensemble. We explore the structure of the adsorbed film, characterized by the distribution of all particles and the distributions of centers of mass of dimers, as well as by orientational distributions of the dimers. The simulations performed indicate the existence of a prewetting-like behavior of the adsorption isotherm. The results for a crystalline surface are compared with simular results obtained for a structureless surface. Finally, we present some density functional theory evaluations and compare them with the simulation results at a high temperature. Copyright 2000 Academic Press.

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PubMed1999

Application of the Replica Ornstein-Zernike Equations to Study Submonolayer Adsorption on Energetically Heterogeneous Surfaces.

Weapply the replica methodology and the replica Ornstein-Zernike equations to calculate adsorption isotherms on an energetically heterogeneous surface. The surface is modeled by quenching a two-dimensional "fluid of centers." After the quenching, we study gas adsorption using the replica Ornstein-Zernike equation with the hypernetted chain closure. The results of theoretical predictions are compared with the data obtained from the Grand Canonical Monte Carlo simulation, and the obtained agreement is satisfactory. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Adsorption of Nitrogen on Thermally Treated Peat Soils: The Role of Energetic and Geometric Heterogeneity.

We investigate adsorption isotherms of nitrogen at 80 K on several peat soils. In addition to natural soil samples we also study samples thermally treated at 50, 100, and 150 degrees C. The experimental adsorption isotherms are used to evaluate the surface fractal dimension and the energy distribution functions. Moreover, for some samples we have also determined the pore size distributions from mercury intrusion data. We compare the surface fractal dimensions evaluated from the mercury intrusion data and from adsorption isotherms and discuss how the thermal treatment changes the energetic heterogeneity of the samples. Copyright 1999 Academic Press.

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PubMed1999

Effective Interactions in a Quenched-Annealed Hard-Sphere Mixture Confined in a Narrow Slit-like Pore.

We consider a slit-like pore filled with a disordered hard-sphere matrix. The diameter of matrix species is chosen almost equal to the pore width. Another hard-sphere fluid species, of smaller diameter, enters, at a given chemical potential, into this confined quenched microporous medium. The model is similar to the experimental setup; see G. Cruz de Leon et al. Phys. Rev. Lett. 81, 1122 (1998). The model is solved by using the inhomogeneous replica Ornstein-Zernike equations with Percus-Yevick approximation. We discuss the effective interactions between species in a confined medium on the chemical potential and matrix microporosity. Copyright 1999 Academic Press.

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PubMed1999

Capillary Condensation of Associating Fluids in Slit-Like Pores: A Density Functional Theory.

Adsorption of associating particles interacting via the Lennard-Jones potential in slit-like pores is studied using the density functional theory. A model of association with one site per particle is considered. Capillary phase diagrams for three values of the association energy are evaluated. We show that the association shifts the entire diagram toward higher temperatures. The critical average densities of the confined fluid, however, are almost independent of the association energy. Our results also demonstrate that the association significantly influences the layering transitions. Copyright 1999 Academic Press.

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PubMed1997

Monte Carlo Study of Chemically Associating Polymerizing Two-Dimensional Fluids

NVT Monte Carlo simulations are reported for chemically associating two-dimensional fluids which can polymerize for certain interaction energies, due to the presence of two attractive sites per monomeric hard disc. The sites are fixed inside a hard core at a given valence angle and mutual penetration of discs is permitted. The type of products of polymerization depends on the parameters of the model; we observe the formation of small associates, as well as of extended chains, bent chains, and rings with different number of monomers. The values of valence angles and of association energy are of primary importance. The dependence of the structural properties of the model on fluid density and association energy is investigated. We performed detailed analysis of the clusters formed due to association in terms of fractions of singly and doubly bonded particles, of average numbers of chains and rings, and of their size. We also obtain the average end to end distance, the radius of gyration, and the persistent length of the products of polymerization. The pressure is calculated from the density profiles of particles of the polymerizing fluid near a hard "wall." The data can be used to develop the equation of state for chemically associating two-dimensional fluids. Copyright 1997 Academic Press. Copyright 1997Academic Press

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PubMed1992

Matching services to needs. Vocational services for substance abusers.

Problems with employment are common among individuals with substance use disorders, yet comprehensive vocational services are not generally available to them, and vocational interventions are often not matched to their specific needs. This article describes the wide range of vocational problems found among individuals with substance use disorders and the elements of a recently funded vocational program for patients in outpatient and residential drug and alcohol treatment programs. Data are presented describing program activity and documenting program effectiveness for the first 2 years of operation of the program. Three case histories are presented to illustrate the types of services delivered and the matching of services delivered to specific, identified client needs (see Case Histories).

Adult↗
PubMed1989

In vitro activity of CP-65,207, a new penem antimicrobial agent, in comparison with those of other agents.

CP-65,207 is a new parenteral penem antibiotic with a broad spectrum that includes gram-positive, gram-negative, and anaerobic microorganisms, with MICs for 90% (MIC90s) of the majority of 1,101 clinical pathogens tested being less than or equal to 1 microgram/ml. The compound was from 10- to 100-fold more active than cefoxitin and broad-spectrum cephalosporins against gram-positive bacteria and anaerobes. CP-65,207 was less active than imipenem for staphylococci, group A streptococci, and Enterococcus faecalis. Against members of the family Enterobacteriaceae, CP-65,207 was in general 100-fold more active than cefoxitin, 5- to 10-fold more active than broad-spectrum cephalosporins, and 2-fold more active than imipenem. Fresh clinical isolates that were resistant to broad-spectrum cephalosporins were highly susceptible to CP-65,207 and imipenem (MIC90, 1 microgram/ml). Isolates of Enterococcus faecalis, Serratia marcescens, and anaerobic Peptococcus spp. had MIC90s of 8, 2, and 3.12 micrograms/ml, respectively. CP-65,207 was not very active against methicillin-resistant staphylococci or Pseudomonas aeruginosa. Killing kinetics showed that against some strains CP-65,207 is rapidly bactericidal at concentrations well below those required to achieve a similar degree of killing with cefotaxime, ceftazidime, and ceftriaxone. CP-65,207 was only slightly susceptible to hydrolysis by type I cephalosporinases and TEM-1, SHV-1, and PSE-2 plasmid-encoded enzymes. It had the highest affinity for penicillin-binding proteins 2, 1A, 1B, and 3 in cell-free preparations of Escherichia coli W-7.

Anti-Bacterial Agents↗