Blood Flow,Negative Pressure,and Hemolysis During Hemodialysis

Blood flow, measured by an ultrasound flowmeter, and the extent of hemolysis were assessed during a single, routine dialysis in 100 patients. Before and after the hemodialysis session, blood was drawn for measurements of haptoglobin (HPT), hemoglobin (HGB), albumin (ALB), and lactate dehydrogenase (LDH). The average values were as follows: pump speed 510 mL/ min, real blood flow 422 mL/min, arterial chamber pressure -350 mm Hg, and venous chamber pressure 279 mm Hg. Haptoglobin concentrations were higher in patients with central vein catheters compared to patients with arteriovenous access. The meaning of this finding is unclear. Mean HPT concentrations increased significantly less during hemodialysis (2.37%) than concentrations of ALB (11.3%), HGB (9.17%), and LDH (18.2%), indicating that some hemolysis is present in all dialyses. In dialyses with arterial chamber pressures more negative than -350 the median concentration of ALB (8.70%) increased significantly more than the median concentration of HGB (7.99%). This indicates significantly more hemolysis in dialyses with more negative pressures compared to those with less negative arterial chamber pressures. Median LDH increased more in dialyses with more negative prepump chamber pressures (16.19% vs 13.78%), but not significantly; however, LDH increases were significantly higher than either HGB or ALB, thus indicating significantly more hemolysis in dialyses with more negative pressures compared to those with less negative arterial chamber pressures. Erythropoietin dose was not significantly different in patients dialyzed with more or less negative arterial chamber pressures (17 645 ± 1226 U/week vs 16 308 ± 1506 U/week). We conclude that dialyses with negative arterial chamber pressures greater than -350 mm Hg cause slightly higher hemolysis than dialyses with less negative arterial chamber pressures, but this increased hemolysis is not associated with an increased requirement of erythropoietin dose. Whether this increased hemolysis is of clinical significance is uncertain.     

Grain Size and Wettability of TiO_2/SiO_2 Photocatalytic Composite Thin Filing

1 IntroductionTransparent super-hydrophilic self-cleaningTiO, thin films on glass substrates have highpotentialities for practical aPPlications such asmirrors, window glasses, windshields of automobiles, etc. The super-hydrophilic property ofthe surface allows water to spread completelyacross the surface rather than to remain asdroplets, Which malles the surface anti-foggingand easily washing. Recently, there are some research papers abollt the super-hydrOPhilic prOPerty of TiO, coating fi…     

Living anionic polymerization

For about 40 years living anionic polymerization has been the premier technique for the synthesis of model polymers of controlled architecture and narrow molecular weight distribution (MWD). Nowadays, despite the continuing development of new strategies for the synthesis of well-defined polymers and copolymers (e.g. group transfer polymerization, living radical polymerization, etc.), anionic polymerization continues to be the most reliable and versatile method for the synthesis of a wide variety of model polymers. The main reason for the broad utility of living anionic polymerization is that the conditions necessary for the efficient generation of polyanions that do not undergo termination or chain transfer reactions are well established for many monomers [Hsieh HL, Quirk RP. Anionic polymerization: principles and practical applications, New York: Marcel Dekker, 1996]. Despite these successes, significant challenges remain in the field of anionic polymerization. These challenges include extension of the strategies for anionic synthesis of polymers with controlled architectures (such as star and graft copolymers), further development of strategies for chain end functionalization, and mastering control over polymerization of (meth)acrylates. Recent advances in these areas are summarized in this article.     

NEW TECHNIQUES AND METHODS FOR THE STUDY OF AGGREGATION, ADSORPTION, AND SOLUBILITY OF ASPHALTENES. IMPACT OF THESE PROPERTIES ON COLLOIDAL STRUCTURE AND FLOCCULATION

The solubility of Furrial asphaltene in toluene was 57g L^-1. However, using a new technique, based on the precipitation of this sample by the phenol PNP, we found that a fraction [2], comprising 47% of the asphaltene, is of low solubility. This suggested that this material constitutes the colloidal phase, and the rest acts as the dispersing fraction. This technique allowed the fractionation of asphaltenes in fractions A₁, A₂, and A₃ according to solubility, going from practically insoluble (A₁) to low (A₂, 1 g L^-1) to high (A₃, around 57 g L^-1). The adsorption isotherms of asphaltenes on glass and silica in toluene consist of a sequence of steps or step-wise adsorption. The first layer or first step is formed by the adsorption of free asphaltene molecules and by small aggregates (aggregation number between 3 and 6) which saturate the glass or silica surface in the usual manner (L-type or H-type isotherms). However, we suggest that the second, third, and other asphaltene layers adsorb sequentially according to the above differences in solubility. The very slow changes with time and the negligible desorption from the surface measured for the above isotherms were interpreted as the effect of packing or the building up of a well packed layer. This would be achieved by the slow formation and rupture of bonds between neighboring molecules at the surface. Thus, molecules with difficulties to pack, adsorbed by a kinetically controlled process, are either rejected or relocated in a thermodynamic controlled process. The above results and ideas were used to improve the models for asphaltene and petroleum colloids and to underscore the importance of surfaces and colloid dispersants in asphaltene precipitation during the production of crude oils. For instance, the results described below suggest that colloids are constituted by a well packed and insoluble asphaltene core, impervious to the solvent, and by a loose packed periphery which, by allowing solvent penetration, keep the colloid in solution. According to this model, desorption of compounds in the above loosely packed periphery, such as the one promoted by a surface, would be the main cause of asphaltene precipitation from crude oils. In this case, solubility reductions caused by pressure drops during oil production would have a minor effect. Also, preliminary number average molecular weights M_n for four asphaltenes, obtained using a new procedure, are presented here. The M_n values obtained ranged from 780 to 1150 g/mol.     

Tensile Creep Behavior of a Vitreous-Bonded Aluminum Oxide under Static and Cyclic Loading

Creep deformation and rupture behavior of a vitreousbonded aluminum oxide was investigated under uniaxial static and cyclic tensile loadings at 1000°, 1100°, and 1175°C. The material was more creep resistant, i.e., having lower creep strain rates, under cyclic loading compared to that under static loading. For the same maximum applied stress, the ratio of steady-state creep rate under static loading to that under cyclic loading at 1100°C was approximately 100. However, the value of this ratio decreased to about 10 when the testing temperature was raised to 1175°C or lowered to 1000°C. Under static loading the material had more propensity to develop creep damage in the form of micro- and macrocracks, leading to early failure, whereas under cyclic loading the creep damage was more uniformly distributed in the form of cavities confined to the multigrain junctions. Viscous bridging by the grain boundary second phase may be the primary contributor to the lower creep deformation rate and improved lifetime under cyclic loading.     

Effect of Solvent Quality on Pure and Mixed Brushes

We investigate, theoretically and experimentally, the effect of solvent quality on pure, one-component, and two-component brushes. Both mean-field and self-consistent field models are developed, and their predictions compared to surface forces experiments on polystyrene and mixed polystyrene–polybutadiene brushes. We find that in pure brushes the structure and interactions between surfaces are highly sensitive to solvent quality. In a good solvent, the brush is extended and the interactions are repulsive, while in a poor solvent the brush is “collapsed” and the interactions are strongly attractive. Mixing two incompatible chains significantly reduces the sensitivity of the brush to solvent properties. While one of the chains collapses in a selective solvent, the other chain remains solvated, thus providing long-range repulsive interactions between surfaces. Our experiments show that the interactions between surfaces carrying a 1:1 mixed brush of styrene–butadiene are repulsive even in hexane, a poor solvent for polystyrene. Theoretically, we calculate that incorporating only 10% of an equi-molecular-weight chain into a collapsed brush can eliminate attractive interactions between surfaces.     

Women and AIDS-related concerns: Roles for psychologists in helping the worried well.

Acquired Immunodeficiency Syndrome (AIDS) has important implications for the practice of psychology. As the epidemic continues, the role of behavior change and psychosocial factors in the spread and transmission of Human Immunodeficiency Virus (HIV) infections assumes increasing significance. Psychologists, as behavior change experts, have a special and challenging role to play in educating the public, particularly women, about AIDS. This article examines AIDS- and HIV-related concerns in women with a focus on the personal dilemmas for the practicing psychologist, problems in health behavior advocacy, and methods and pitfalls in modifying sexual behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observation of crack-closure behavior after single overload cycles in 7075-T6 single-edge-notched specimens

Electrical potential and strain gage techniques were used to determine changes in crack-closure during the delay period after single overload cycles in 7075-T6 SEN specimens. For the specimen geometry (SEN), alloy (7075-T6), and instrumentation used, no significant changes in crack-closure were measured during propagation of the crack through the delay region after the overload cycle, even though some crack-closure was taking place during constant-amplitude cycling and changes in crack-closure loads were observed with changes in R values. The small change in crack-closure after the overload cycle was not enough to explain the delay. However, after relaxation for 16 hr, as well as after a high overload ratio, significant crack-closure was observed by the potential method. This crack-closure disappeared within 200 cycles. Thus, these results showed that the observed changes in crack-closure could not completely account for the observed number of delay cycles. These observations, which appear contrary to the crack-closure hypothesis, are in agreement with some of the other reported results. These results are applicable to the alloy, specimen geometry, thickness, and sensitivity of the instrumentation used in this investigation.     

Digital and analog signal applications of operational amplifiers I?Multiplexers and converters

This two-part article discusses the use of operational amplifiers in applications involving both digital and analog signals. In some cases the digital signals are used to control the acquisition of samples of analog signals. In other applications the digital signal is being converted into an analog voltage or, conversely, an analog is converted to a series of digital words. This first installment is concerned with multiplexer, D/A converter, and A/D converter circuits. Part II, scheduled to appear in the June issue, will be devoted to sample/hold modules, peak detectors, and comparators.