Medical-grade acrylic adhesives for skin contact

Pressure-sensitive acrylic adhesives for application to skin are made from 2-ethylhexyl acrylate, isooctyl acrylate or n-butyl acrylate copolymerized with polar functional monomers such as acrylic acid, methacrylic acid, vinyl acetate, methyl acrylate, N-vinylcaprolactam, or hydroxyethyl methacrylate. Functional comonomers increase cohesive strength, provide surface polarity, and enhance wear performance. Tack, adhesion to skin, adhesive transfer to skin, and wear performance of the adhesive are governed by the molecular weight, glass transition temperature, and the viscoelastic behavior of the adhesive. Viscoelastic properties of the adhesive as measured by the Williams plasticity number (WPN), dynamic storage modulus (G′), dynamic loss modulus (G″), and tan δ are important polymer properties for good wear performance. Sweating skin, a moist environment, and physical activity are the most important factors influencing the failure of an adhesive tape during wear. A medicalgrade adhesive for application to human skin should be hypoallergenic. Medical-grade adhesives are utilized in making surgical tapes for holding dressings in place, adhesive bandages, adhesive dressings to cover wounds, and surgical operating drapes.     

Reversible or irreversible modification of [3H]PAF binding on rabbit platelet membranes differentiates various PAF receptor antagonists

[³H]Platelet-activating factor (PAF) binding to rabbit platelet membranes was examined before and after 20 min preincubation at 25°C in the presence of PAF, lysoPAF, or of five different PAF receptor antagonists (L 652731, BN 52021, WEB 2086, BN 52111 and BN 52115). When platelet membranes were not washed after preincubation with PAF or PAF antagonists, no significant specific binding of [³H]PAF was observed, which suggests full occupancy of the binding sites. When membranes were extensively washed, full recovery of specific [³H]PAF binding was attained with L 652731 and partial recoveries (60%, 55% and 30%) were reached with BN52021, WEB 2086 and PAF, respectively; no recovery was seen with the dioxolanes BN 52111 and BN 52115. Scatchard analysis of the binding data indicated that no significant change in the dissociation constant (K_d) and maximum number of binding sites (B_max) occurred after preincubation of platelet membrane with L 652731, whereas a reduction of B_max was observed when PAF and BN 52021 were measured. When platelet membranes were preincubated with WEB 2086, B_max and K_d significantly increased. The data suggest differing binding properties for PAF and the PAF antagonists. Some of the PAF antagonists may tightly bind to the PAF receptor site(s) and/or irreversibly modify or downregulate PAF recognition sites. Our results also suggest that the interaction of PAF receptor antagonists with PAF receptor can be divided into at least two components, namely a reversible component and an irreversible one. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Comparison between the effects of positive noncatastrophic HBM ESDstress in n-channel and p-channel power MOSFETs

The effect of noncatastrophic positive human body model (HBM) electrostatic discharge (ESD) stress on n-channel power MOSFETs is radically different from that on p-channel MOSFETs. In n-channel transistors, the stress causes negative shifts of the current-voltage characteristics indicative of positive charge trapping in the gate oxide. In p-channel transistors, the stress increases the drain-to-source leakage current, probably due to localized avalanche electron injection from the p-doped drain     

Effect of precyclic loading on stress-corrosion-cracking initiation in an X-65 pipeline steel exposed to near-neutral pH soil environment

A study was carried out to understand the effect of precyclic loading on stress-corrosion-crack initiation in an X-65 pipeline steel exposed to a near-neutral-pH soil environment. The test specimens were precyclically loaded before corrosion exposure to represent a service history of up to about 20 years, depending on the severity of pressure fluctuation. Microcracks had initiated on the polished surface of the X-65 pipeline steel after long-time exposure at open-circuit potential (OCP) in a near-neutral-pH synthetic soil solution. These microcracks were mostly initiated from pits at metallurgical discontinuities such as grain boundaries, pearlitic colonies, and banded phases in the steel. Strong preferential dissolution was observed along planes of the banded structures in the steel. The selective corrosion attack at these metallurgical discontinuities is attributed to the galvanic nature of those areas to their neighbors. Cyclic loading prior to corrosion exposure had significant effects on microcrack initiation and propagation during subsequent corrosion exposure. Cyclic loading prior to corrosion exposure either reduced or increased the probability of crack initiation and the rate of crack propagation, depending upon the magnitude of the stress cycles. The largest reduction was seen at a peak cyclic stress of about 0.8 of the yield strength. This cyclic-loading-dependent cracking behavior might be related to the alteration of the substructures and the residual stress in the steel as a result of precyclic loading.     

Narcissism, sexual refusal, and aggression: Testing a narcissistic reactance model of sexual coercion.

Laboratory analog studies investigated the theory that narcissism and reactance contribute to causing rape. In Study 1, narcissism correlated positively with rape-supportive beliefs and negatively with empathy for rape victims. In Study 2, narcissists reported more enjoyment than other men of film depictions that presented consensual, affectionate activity followed by rape (but not in response to either affection or rape alone). In Study 3, narcissists were more punitive than other men toward a female confederate who refused to read a sexually arousing passage aloud to them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metal-containing intermacromolecular complexes: Electrochemical and viscometric studies in DMF-methanol mixture

Summary Multicomponent intermacromolecular complexes have been prepared from some typical phenolic copolymers with a non-ionic polymer (e.g. PVP), and a polyelectrolyte (e.g. PAA). Some transition metal ions (e.g. Cu(II) and Ni (II)) have been incorporated in the complex through its unreacted co-ordinating groups. The formation of these complexes has been studied by several techniques, such as viscometry, conductometry, potentiometry, IR and UV spectrophotometry. A scheme has been presented to explain the mode of interaction of the various components.     

SURFACE ALLOYING OF MILD STEEL BY LASER MELTING OF AN ELECTROLESS NICKEL DEPOSIT CONTAINING CHROMIUM CARBIDES

It is possible to realize surface alloys by laser melting an electroless nickel layer containing chromium carbide particles predeposited on a mild steel substrate. By this way the surface alloy is expected to have not only a high nickel content but also an important chromium content in order to improve the corrosion resistance. The presence of chromium in solid solution results from the dissolution or melting of the carbide particles. Typical laser solidification microstructures are obtained. Dendrites consist of an austenitic Fe-Ni-Cr solid solution and interdendritic regions are constituted by an eutectic mixture containing the same austenitic solid solution and complex Fe, Ni, Cr carbides and phosphides. In comparison with a surface alloy obtained by laser melting of an electroless nickel layer without carbide particles, the corrosion resistance was slightly improved in saline aqueous solutions. The limited effect was due to the fact that the final chromium content in the present experimental conditions was not as high as that initially expected.     

Improved HF modem using convolutional coding

The paper describes the design of a digitally implemented modem for use over HF (2-30 MHz) radio channels. As a completely digital approach offers the prospect of a number of significant improvements, a new digital multifrequency-shift-keying (MFSK) modem has been developed that employs a novel digital processing procedure termed code-assisted bit synchronisation (CABS). Signal detection is achieved via a set of noncoherent correlators, whilst symbol synchronisation and error correction are performed using a soft-decision Viterbi decoder. Practical tests of modem show that it operates effectively under both additive white Gaussian noise and real HF channel conditions