Photodegradation of thermoplastic elastomeric rubber–polyethylene blends

The photodegradation of a new family of thermoplastic elastomers, based on blends of natural rubber and polyethylene, was studied with laboratory ultraviolet exposures in the unstrained state and under tensile strain (25 and 50%). Strained exposure caused reduction of the strain to failure in subsequent tensile tests. The blends were more resistant to degradation than the natural rubber homopolymer. The introduction of crosslinks (at a low concentration so that the thermoplastic nature of the blends was retained) changed the resistance to photo‐oxidation. Two different crosslinking systems were used. When dicumyl peroxide was used as the crosslinking agent, the resistance to degradation was reduced, whereas the compound containing a sulfur curing system showed improved resistance to photodegradation. Photo‐oxidation rather than ozone degradation was found to be the major cause of breakdown, even with samples held in tension. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2393–2402, 2002     

Studies on growth,structural carbohydrate and phytate in coriander (Coriandrum sativum) during seed development

Coriander (Coriandrum sativum L) is an important spice crop and is used in Indian diets. Physiological characters of plants and biochemical constituents like structural carbohydrate and phytate were studied in developing coriander (var Narnaul and Panth) seeds. Moisture decreased with advancement of seed development. Neutral detergent fibre, acid detergent fibre, hemicellulose, cellulose and lignin levels increased with maturation of seed in both coriander varieties. Significant variations were observed in biochemical constituents between varieties and during different stages of seed development. The presence of phytate did not vary at different stages of seed development. The height of plants varied from 134 to 139 cm with 10 branches. Umbels varied from 89 to 99 with an average of six umbellets. Narnaul seed weight was double that of the variety Panth.     

Things that go bump in the light: On the optical specification of contact severity.

Psychologists are intrigued with the idea that optical variables can specify not only the time until an object impacts an observer but also the severity of the impact. However, the mapping between the optical variables (τ and τ?) and the kinematic variables (velocity, acceleration) has been misstated, erroneously implying that there exist critical values of the optical variables used for locomotion and control. In this commentary, the mathematical relationship between the optical and kinematic variables is reexamined and the erroneous assumptions that have led to the proposal of critical values are shown. Also examined are the empirical data on deceleration to approach (particularly from active control paradigms) to assess whether the proposed optical variables are likely candidates for control strategies. Finally, problems associated with numerical approximations to dynamic systems, particularly when analytic solutions exist, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Separation of monoclonal IgM antibodies using tangential flow ultrafiltration

Experimental results are presented for the separation of monoclonal IgM antibodies from hybridoma cell cultures using tangential flow ultrafiltration with total recycle of the retentate. IgM antibodies are pentameric immunoglobulin molecules with a molar mass of 900 kDa and a tip-to-tip distance of 38 nm. The major impurity (foulant) in the supernatant sample was albumin, whose molar mass and diameter are 67 kDa and 7 nm, respectively. The antibody (product) recovery rate, variations in the permeation velocity and the time for a 90%-reduction in feed volume were investigated using 100 and 300 kDa NMWCO membranes at three transmembrane pressures and two tangential velocities. A model is also presented, in which the ultrafiltration process is divided into two regimes: the surface fouling regime (characterized by the adsorption of antibody molecules on the membrane surface) and the internal fouling regime (characterized by pore-blockage due to deposition of foulant protein molecules). Approximately 16% of the effective membrane area was blocked in the surface fouling regime. The model predictions are in satisfactory agreement with the experimental results.     

Hydrogenation of epoxidized natural rubber in the presence of palladium acetate catalyst

Expoxidized natural rubber has been selectively hydrogenated in the presence of a homogeneous palladium acetate catalyst. The hydrogenated product has been characterized by infra-red and nuclear magnetic resonance spectroscopies. No change is noted in the epoxy content of the polymer after the reaction. The catalyst is highly selective in reducing carbon-carbon double bonds in the presence of epoxy groups. Natural rubber has also been hydrogenated for a comparative study. The rate constant of hydrogenation is decreased with increase in epoxy content of the polymer.     

Dissolution of Sulphamethoxazole From Polyethlene Gylcols and Polyvinlpyrrolidone Solid Dispersions

Solid dispersions of sulphamethoxazole have been prepared by fusion and solvent methods using polyethylens glycols 6000 and 9000, and polyvinylpyrrolidone (mol.wt. 40,000) as water-soluble carriers. Coprecipitates with the latter were superior to other carriers in releasing the drug into solution. Melts with the solvent method. Solubility of the drug increased also with the former produced faster rates of dissolution of sulphamethoxazole than the coprecipitate from the solvent method. Solubility of the drug increased also with corresponding increase in the concetrations of these carriers.     

Differential human multiple myeloma cell line responsiveness to interferon-alpha. Analysis of transcription factor activation and interleukin 6 receptor expression

Although IFN-alpha is commonly used as maintenance treatment for multiple myeloma patients, its effectiveness is varied. In this study, we have used a panel of IL-6 responsive myeloma cell lines that vary remarkably in responsiveness to IFN-alpha. Three cell lines were growth arrested by IFN-alpha; however, IFN-alpha significantly stimulated growth of the fourth cell line, KAS-6/1. Our studies have focused on elucidating the mechanism of differential IFN-alpha responsiveness. First, we have shown that IFN-alpha-stimulated growth of the KAS-6/1 cells did not result from induction of autocrine IL-6 expression. Second, analysis of Stats 1, 2, and 3 and IFN regulatory factor-1 (IRF-1) and IRF-2 activation failed to reveal differences between the IFN-alpha growth-arrested or growth-stimulated cells. Third, although IFN-alpha treatment of the IFN-alpha growth-inhibited cell lines reduced IL-6 receptor (IL-6R) expression, IFN-alpha also reduced KAS-6/1 IL-6R expression. Finally, although IFN-alpha treatment reduced IL-6R numbers on each cell line, analysis of Stat protein activation revealed that the receptors were still functional. We conclude that myeloma cell responsiveness to IFN-alpha is heterogeneous and that mechanisms of IFN-alpha-mediated growth inhibition other than IL-6R downregulation must exist in myeloma. Identification of these mechanisms may allow development of agents that are more universally effective than IFN-alpha.     

Histopathological changes in aluminium phosphide poisoning

A total of thirty cases of aluminium phosphide poisoning were studied for gross and microscopic changes in various organs of the body ie, lungs, liver, kidneys, heart, brain, stomach and adrenals. The histopathological changes revealed varying degrees of congestion, oedema and leucocytic infiltration, changes suggestive of cellular hypoxia. The most dramatic effects were produced in lungs, kidneys and adrenals.     

Friction and part curvature in parallel- jaw grasping

When grasping a part with a parallel-jaw gripper, the part will generally rotate due to kinematic constraints. Predicting the part's final orientation is useful for grasping and for planning sequences of gripper motions to orient parts. For a given part geometry, the grasp function maps initial orientations to final orientations. Previously, we studied polygonal and algebraic parts in the absence of friction. This article considers how Coulomb friction affects the grasp function. We consider two models of Coulomb friction. For a deterministic model, we show that the grasp function of any polygonal part can be represented with a piecewise linear function that we call a step-ramp function. We then show that any step-ramp function is the grasp function of a curved part operating under zero friction. Both contain ranges of orientations where the part does not rotate when grasped. This yields our primary result, that any part with deterministic friction has equivalent grasp mechanics to a “dual” part under zero friction. We then apply previous results to derive grasp plans that orient parts in the presence of friction. We also give an algorithm for planning under a non-deterministic model of Coulomb friction, and give bounds on the friction coefficient needed to insure the existence of such plans. © 1995 John Wiley & Sons, Inc.