Measurement of the concentration diffusion coefficient for Ne-Ar, Ne-Xe, Ne-H2, Xe-H2, H2-N2 and H2-O2 gas systems

The concentration diffusion coefficient, D ₁₂, is measured for the equimolar mixtures of Ne-Ar, Ne-Xe, Ne-H₂, Xe-H₂, H₂-N₂ and H₂-O₂ binary gas systems in a two-bulb metal apparatus in the temperature range 0 C to 100 C. These values are compared with the existing data on these systems and with the predictions of the kinetic theory in conjunction with the modified Buckingham exp-six potential. Unlike the thermal diffusion coefficient, with the simple theory it is possible to predict D ₁₂ within a few percent even for systems involving polyatomic gases. The smoothed experimental D ₁₂ values are also used to obtain data for the coefficients of viscosity and thermal conductivity at round temperatures and compositions for these systems.Nomenclature C ₂ ^t relative amount of a gas in the mixture in the bulb 2 at an instant t - C ₂ relative amount of the same gas in the mixture in the bulb 2 at equilibrium - D ₁₂ diffusion coefficient - X ₁ mole-fraction of the heavier component in the mixture - _mix viscosity coefficient - _mix thermal conductivity coefficient     

Phagocytosis of PLGA microparticles in rat peritoneal exudate cells: a time-dependent study.

With the purpose of enhancing the efficacy of microparticle-encapsulated therapeutic agents, in this study we evaluated the phagocytic ability of rat peritoneal exudate cells and the preferential location of poly(d,l-lactide-co-glycolic acid) (PLGA) microparticles inside these cells. The microparticles used were produced by a solvent evaporation method and were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Size distribution analysis using DLS and SEM showed that the particles were spherical, with diameters falling between 0.5 and 1.5 mum. Results from cell adhesion by SEM assay, indicated that the PLGA microparticles are not toxic to cells and do not cause any distinct damage to them as confirmed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Among the large variety of cell populations found in the peritoneal exudates (neutrophils, eosinophils, monocytes, and macrophages), TEM showed that only the latter phagocytosed PLGA microparticles, in a time-dependent manner. The results obtained indicate that the microparticles studied show merits as possible carriers of drugs for intracellular delivery.     

Sample path methods in the control of queues

Sample path methods are now among the most used techniques in the control of queueing systems. However, due to the lack of mathematical formalism, they may appear to be non-rigorous and even sometimes mysterious. The goal of this paper is threefold: to provide a general mathematical setting, to survey the most popular sample path methods including forward induction, backward induction and interchange arguments, and to illustrate our approach through the study of a number of classical scheduling and routing optimization problems arising in queueing theory.Z. Liu was supported in part by the CEC DG XIII under the ESPRIT BRA grants QMIPS.P. Nain was supported in part by NSF under grant NCR-9116183 and by the CEC DG XIII under the ESPRIT BRA grants QMIPS.D. Towsley was supported in part by NSF under grant NCR-9116183.     

Qualitative properties of the Erlang blocking model with heterogeneous user requirements

We study the effect of increasing the model parameters (e.g., arrival rates and traffic intensities) in the Erlang blocking model with heterogeneous user requirements. First-order (monotonicity) and second-order (concavity) qualitative results are obtained for the performance measures of interest (loss probabilities, throughput, channel occupancy, etc.) both in the transient and in the steady-state cases. Stochastic and likelihood-ratio orderings together with coupling techniques are used to indicate the effect of modifying the model parameters. Work performed while the author was visiting the Department of Systems Engineering of the University of Pennsylvania, Philadelphia, USA.     

Volumetric and Viscometric Studies in Binary Liquid Mixtures of 2-Methyl-2-propanol with Some Ketones at Different Temperatures

Densities, ??, and viscosities, ??, of binary mixtures of 2-methyl-2-propanol with acetone (AC), ethyl methyl ketone (EMK) and acetophenone (AP), including those of the pure liquids, were measured over the entire composition range at 298.15, 303.15 and 308.15?K. From these experimental data, the excess molar volume $V_{\mathrm{m}}^{\mathrm{E}}$ , deviation in viscosity ????, partial and apparent molar volumes ( $\overline{V}_{\mathrm{m},1}^{\,\circ }$ , $\overline{V}_{\mathrm{m},2}^{\,\circ }$ , $\overline{V}_{\phi ,1}^{\,\circ}$ and $\overline{V}_{\phi,2}^{\,\circ} $ ), and their excess values ( $\overline{V}_{\mathrm{m},1}^{\,\circ \mathrm{E}}$ , $\overline{V}_{\mathrm{m,2}}^{\,\circ \mathrm{ E}}$ , $\overline {V}_{\phi \mathrm{,1}}^{\,\circ \mathrm{ E}}$ and $\overline{V}_{\phi \mathrm{,2}}^{\,\circ \mathrm{ E}}$ ) of the components at infinite dilution were calculated. The interaction between the component molecules follows the order of AP > AC > EMK.     

Pyrrolidine-carbamate based new and efficient chiral organocatalyst for asymmetric Michael addition of ketones to nitroolefins

The novel ((S)-pyrrolidin-2-yl)methyl phenylcarbamate was synthesized and used as an efficient organocatalyst for the asymmetric Michael addition of cyclic/acyclic ketones to nitroolefins. Interestingly, the resulting Michael adducts were obtained in good to high yields (up to 96%) with excellent stereoselectivity (ee up to >99%, dr up to >99:1) without using any additive.     

Viscosities and Refractive Indices of Binary Mixtures of Dimethylsulphoxide with Some Aromatic Hydrocarbons at Different Temperatures: An Experimental and Theoretical Study

The viscosities, η, and refractive indices, n, of pure dimethylsulphoxide (DMSO), benzene, toluene, o‐xylene, m‐xylene, p‐xylene and mesitylene, and those of their 54 binary mixtures, with DMSO as common component, covering the whole composition range have been measured at 298.15, 303.15, 308.15, 313.15, and 318.15 K. From the experimental data, the deviations in viscosity, Δη and deviations in molar refraction, ΔR_m have been calculated. The variation of these parameters with composition and temperature of the mixtures have been discussed in terms of molecular interaction in these mixtures. The effect of the number and position of the methyl groups in these aromatic hydrocarbons on molecular interactions in these mixtures has also been discussed. The free energies, ΔG^*, enthalpies, ΔH^* and entropies, ΔS^* of activation of viscous flow have also been obtained by using Eyring viscosity equation. The ΔH^* values were found independent of temperature. The dependence of these thermodynamic parameters on composition of the mixtures has been discussed. Further, the viscosities and refractive indices of these binary mixtures were calculated theoretically from pure component data by using various empirical and semi‐empirical relations and the results were compared with the experimental findings.     

On the value function of a priority queue with an application to a controlled polling model

We give a closed-form expression for the discounted weighted queue length and switching costs of a two-class single-server queueing model under a preemptive priority rule. These expressions are used to do a single step of policy iteration in a polling model with a dynamically controlled switching rule, starting from the preemptive priority rule. Numerical experiments show that this leads to a policy that performs well.     

Improvement of organic solar cells by flexible substrate and ITO surface treatments

In this paper, surface treatments on polyethylene terephthalate with polymeric hard coating (PET-HC) substrates are described. The effect of the contact angle on the treatment is first investigated. It has been observed that detergent is quite effective in removing organic contamination on the flexible PET-HC substrates. Next, using a DC-reactive magnetron sputter, indium tin oxide (ITO) thin films of 90 nm are grown on a substrate treated by detergent. Then, various ITO surface treatments are made for improving the performance of the finally developed organic solar cells with structure Al/P3HT:PCBM/PEDOT:PSS/ITO/PET. It is found that the parameters of the ITO including resistivity, carrier concentration, transmittance, surface morphology, and work function depended on the surface treatments and significantly influence the solar cell performance. With the optimal conditions for detergent treatment on flexible PET substrates, the ITO film with a resistivity of 5.6 × 10⁻⁴ Ω cm and average optical transmittance of 84.1% in the visible region are obtained. The optimal ITO surface treated by detergent for 5 min and then by UV ozone for 20 min exhibits the best WF value of 5.22 eV. This improves about 8.30% in the WF compared with that of the untreated ITO film. In the case of optimal treatment with the organic photovoltaic device, meanwhile, 36.6% enhancement in short circuit current density (J_sc) and 92.7% enhancement in conversion efficiency (η) over the untreated solar cell are obtained.