Comparison between the binding of chlorpheniramine maleate to poly(sodium 4-styrenesulfonate) and the binding to other polyelectrolytes

The interactions of the antihistaminic drug chlorpheniramine maleate (CPM) with the negatively charged polyelectrolytes poly(sodium 4-styrenesulfonate) (PSS) and poly(acrylic acid) (PAA) are studied by the washing method of the diafiltration technique at conditions simulating those of the small intestine such as pH 7.5 and 0.13 M NaCl. The results are compared with those already reported involving other pharmacologically important polyelectrolytes such as alginic acid (ALG), carboxymethylcellulose (CMC), and κ- and ι-carrageenan (κ- and ι-CAR). As in the case of ALG, CMC, and CAR, interactions of CPM with PAA appear to be electrostatic and are cleaved in the presence of 0.13 M NaCl. On the contrary, apart from electrostatic interactions, additional interactions are found with PSS and residual interactions are kept in the presence of 0.13 M NaCl, a fact that may be attributed to π-π interactions and hydrophobic forces. The effect of the addition of 4 M urea, branched poly(ethyleneimine) (BPEI), and poly(vinylpyrrolidone) (PVP) is also studied. The addition of urea 4 M or 0.001 M BPEI produces a decrease on the amounts of counterions bound to PSS at infinite elution, while the addition of PVP does not produce any change on the diafiltration profiles.     

Age of acquisition: Its neural and computational mechanisms.

The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polymerization of ionic monomers in polar solvents: kinetics and mechanism of the free radical copolymerization of acrylamide/acrylic acid

A precise data set describing the kinetics of the free radical copolymerization of acrylamide/acrylic acid (AM/AA) in the range of low total monomer concentration as a function of the pH, total monomer concentration, initiator concentration, and comonomer ratio is presented. Strong impact on the reactivity ratios has been identified for the pH and total monomer concentration. Specifically, at constant total monomer concentration of 0.4 mol/l and T=313 K the reactivity ratio of AM increases from 0.54 at pH 1.8 to 3.04 at pH 12. Contrarily, the reactivity ratio of AA decreases from 1.48 to 0.32. The crossover occurs at pH≈4.2. Electrostatic effects due to the variation of the degree of ionization of AA are primarily suggested to influence the kinetics. When the total monomer concentration increases from 0.2 to 0.6 mol/l at constant pH=12, the reactivity ratios of AM and AA decrease from 4.01 to 2.13 and increase from 0.25 to 0.47, respectively. Reduction of electrostatic repulsion between the ionized monomer AA and partially charged growing polymer chain ends due to higher ionic strength at higher total monomer concentration serves as explanation of the effect. The precise data set is the prerequisite for a novel approach to calculate copolymer compositions in case of variable monomer reactivity.     

Experiments of Fast Learning with High Order Boltzmann Machines

This work reports the results obtained with the application of High Order Boltzmann Machines without hidden units to construct classifiers for some problems that represent different learning paradigms. The Boltzmann Machine weight updating algorithm remains the same even when some of the units can take values in a discrete set or in a continuous interval. The absence of hidden units and the restriction to classification problems allows for the estimation of the connection statistics, without the computational cost involved in the application of simulated annealing. In this setting, the learning process can be sped up several orders of magnitude with no appreciable loss of quality of the results obtained.     

2-Hydroxypropyl-beta-cyclodextrin enhances phorbol ester effects on glucose transport and/or protein kinase C-beta translocation to the plasma membrane in rat adipocytes and soleus muscles

In rat adipocytes and soleus muscles, 2-hydroxypropyl-beta-cyclodextrin (CD) was found to have a relatively small or no effect on basal or insulin-stimulated hexose uptake, but markedly enhanced hexose uptake effects of phorbol esters and/or diacylglycerol. In rat adipocytes, the CD-induced enhancement of hexose uptake during concurrent phorbol ester treatment was not associated with an increase in GLUT4 glucose transporter translocation to the plasma membrane, which was stimulated comparably by insulin and phorbol esters. Moreover, CD appeared to activate or facilitate the activation of glucose transporters subsequent to their translocation to the plasma membrane during ongoing phorbol ester treatment. In rat adipocytes, CD also enhanced the translocation of protein kinase C (PKC)-beta to the plasma membrane during the action of phorbol esters, which alone had little or no effect on this specific PKC translocation. Although it is uncertain how CD alters the function of plasma membranes to enhance the translocation of PKC-beta to, and the activation of glucose transporters within, this subcellular fraction during phorbol ester treatment, our findings provide direct support for a two-step model in the activation of glucose transport. In addition, it seems clear that, at least in some cell types, simple phorbol ester treatment does not necessarily serve as a ubiquitous activator of all activable PKC pools and all potential PKC-mediated responses.     

Electrical heat tracing: international harmonization-now and in thefuture

In the past, electrical heat tracing has been thought of as a minor addition to plant utilities. Today, it is recognized as a critical subsystem to be monitored and controlled. A marriage between process, mechanical, and electrical engineers must take place to ensure that optimum economic results are produced. The Internet, expert systems, and falling costs of instrumentation will all contribute to more reliable control systems and improved monitoring systems. There is a harmonization between Europe and North America that should facilitate design and installation using common components. The future holds many opportunities to optimize the design     

Controlled-Release Matrix of Acetaminophen-Ethylcellulose Solid Dispersion

In this study ethylcellulose was evaluated as a carrier for preparation of prolonged release acetaminophen tablets. Solid dispersions containing three levels of ethylcellulose and acetaminophen (1:3; 1:1; 3:1) were prepared by the solvent method. Also physical mixtures at the same level of ethylcellulose and acetaminophen were prepared. Systems composed of solid dispersion or physical mixture containing the equivalent weight of 50 mg acetaminophen, Lactose fast-flo as diluent and 1% magnesium stearate as lubricant were compressed into tablets and tested for dissolution. The dissolution data showed that the drug release decreased as the level of ethylcellulose increased in the solid dispersion formulations. The drug release from tablets prepared with solid dispersion followed the diffusion controlled model for inert porous matrix, while the drug release from tablets prepared with physical mixture followed the first-order kinetic model.     

High‐pressure processing effects on the mechanical,barrier and mass transfer properties of food packaging flexible structures: a critical review

Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.