Model-free methods for vapor—liquid equilibria calculations Binary systems

Existing methods for the calculation of vapor—liquid equilibria of binary systems by direct integration of the Gibbs—Duhem equation are classified and compared. Six new methods are proposed. All marching methods are found to give comparable results. Two simple marching methods are recommended for non-azeotropic systems. For azeotropic systems, values obtained from these two simple methods can be used with advantage to drastically reduce the number of iterations required by the more general method proposed by Mixon et al.     

Granular nature and superconductive coupling of YBa2Cu3O7 polycrystals observed by microwave absorption measurements

The results of measurements of the H-modulated microwave absorption of of YBa₂Cu₃O₇ ceramic in the transition temperature region and with fields in the range 0–10 kOe are presented. They give clear evidence of the weak-link inter-grain nature of the gross part of the dissipation and support the idea of stronger links, or microbridges of a more intrinsic species, involved in the high-field intra-grain absorption component. A semiquantitative analysis of the absorption process is suggested and applied to the derivative spectra in the T-swept form (at fixed external field). It allows to deduce information about T_c, the superconductive coupling, and the H- and T-dependences of the critical currents involved in the inter- and intra-grain regions. When applied to YBa₂Cu₃O₇ powders, obtained by finely grinding a ceramic pellet, it gives also evidence of a generalized suppression of coupling induced by the grinding process     

Expression of granulocyte-macrophage colony-stimulating factor receptors in human prostate cancer

This investigation examined the effects of NaHCO3 loading on lactate concentration ([La]), acid-base balance, and performance for a 603. 5-m sprint task. Ten greyhounds completed a NaHCO3 (300 mg/kg body weight) and control trial in a crossover design. Results are expressed as means +/- SE. Presprint differences (P < 0.05) were found for NaHCO3 vs. control, respectively, for blood pH (7.47 +/- 0.01 vs. 7.42 +/- 0.01), HCO-3 (28.4 +/- 0.4 vs. 23.5 +/- 0.3 meq/l), and base excess (5.0 +/- 0.3 vs. 0.2 +/- 0.3 meq/l). Peak blood [La] increased (P < 0.05) in NaHCO3 vs. control (20.4 +/- 1.6 vs. 16.9 +/- 1.3 mM, respectively). Relative to control, NaHCO3 produced a greater (P < 0.05) reduction in blood base excess (-18.5 +/- 1.4 vs. -14.1 +/- 0.8 meq/l) and HCO-3 (-17.4 +/- 1.2 vs. -12.8 +/- 0.7 meq/l) from presprint to postexercise. Postexercise peak muscle H+ concentration ([H+]) was higher (P < 0.05) in NaHCO3 vs. control (158.8 +/- 8.8 vs. 137.0 +/- 5.3 nM, respectively). Muscle [H+] recovery half-time (7.2 +/- 1.6 vs. 11.3 +/- 1.6 min) and time to predose values (22.2 +/- 2.4 vs. 32.9 +/- 4.0 min) were reduced (P < 0.05) in NaHCO3 vs. control, respectively. No differences were found in blood [H+] or blood [La] recovery curves or performance times. NaHCO3 increased postexercise blood [La] but did not reduce the muscle or blood acid-base disturbance associated with a 603.5-m sprint or significantly affect performance.     

Options for rural electrification in Mexico

The author summarizes a study which examined 19 commercially available options for electrifying remote communities in Mexico. Characteristics of a typical community were defined and, using seven of the technologies, power systems were designed capable of supporting this community. The performance of these systems was evaluated, with respect to their ability to satisfy 11 technical design objectives, five socioeconomic objectives, and their impact on the environment. A photovoltaic-diesel generator hybrid system with a wind generator option was recommended for the typical community     

Neuropsychological evaluation of everyday memory

The evaluation of everyday memory (EM) was reviewed and reconceptualized. EM has established new objectives of study and the development of new methods to reach these objectives. At the basic level, this approach has already produced important discoveries and the development of new principles about memory and functioning. At the clinical level, this new area of investigation has resulted in evaluating deficits of EM, which is defined as what daily life functions remain impaired after a deficit pathology has occurred. A type of evaluation has evolved that is oriented toward treatment and extremely useful in designing rehabilitation programs for individuals with alterations in memory.     

Energy Efficiency and Maintenance Costs of Pumping Systems for Groundwater Extraction

Sustainability and profitability of irrigation depends to a great extent on the energy efficiency of the pumping system, as water extraction from wells accounts for most of the energy consumption in irrigation activities all over the world. In this paper a methodology is presented intended to calculate and generalize total maintenance costs in well pumping systems. Likewise, the study has been conducted over 22 well pumping stations with the aim of analyzing the energy efficiency. The results show the essential role played by preventive maintenance works in the improvement of energy and economic efficiency.     

Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

Carbon nanofibers were produced by the catalytic CVD process by the floating catalyst method, in semi-industrial systems at temperatures above 1350 K. Iron-derived carbon nanofibers were produced from natural gas and xylene, using ferrocene as catalyst source, yielding a thickened submicron vapor grown carbon fibers with a core of multi-wall nanotubes. For the production of Ni derived nanofibers, natural gas was used as the carbon feedstock, and the Ni was added in a nickel compound solution. When no sulfur is used, only soot was obtained, but when sulfur is added to the reactive feedstock, a highly graphitic and very nice stacked-cup-type nanofibers with no free-CVD thickened layer were produced. TEM-EDS analysis confirms that this type of stacked-cup carbon nanofiber is produced only with a partially molten catalyst and methane as hydrocarbon source. In fact, very few fibers have either a particle tip at the end or trapped metal particle inside the wide hollow core of this type of produced carbon material.     

Small Strictly Convex Quadrilateral Meshes of Point Sets

In this paper we give upper and lower bounds on the number of Steiner points required to construct a strictly convex quadrilateral mesh for a planar point set. In particular, we show that 3\lfloorn/2\rfloor internal Steiner points are always sufficient for a convex quadrilateral mesh of n points in the plane. Furthermore, for any given n\geq 4, there are point sets for which \lceil(n–3)/2\rceil–1 Steiner points are necessary for a convex quadrilateral mesh.     

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