Crosslink network rearrangement via reactive encapsulation of solvent in epoxy curing: A combined molecular simulation and experimental study

Encapsulation of solvent during cure is proposed as one way to alter the network topology of crosslinked polymers. We performed all-atom molecular dynamics simulations to study systems comprised of Epon828 epoxy resin and Jeffamine-D400 diamine crosslinkers cured with varying amounts of the inert solvent dichloromethane (0–50 wt%) and then dried and annealed. Densities, glass transition temperatures, and Young's moduli are observed to be insensitive to the initial amount of dichloromethane. These findings were verified by experiment. Simulations also showed that radial distribution functions and dihedral angle distributions were insensitive to the amount of dichloromethane present. However, using Dijkstra's algorithm, we observed that the distribution of minimum path lengths between crosslinks shifts appreciably to larger values as the amount of dichloromethane increases. This suggests that solvent-encapsulated curing can allow for control over network topology without changing crosslink density or intermolecular packing, and the properties derived from it, in highly crosslinked polymers.     

Brief coping skills treatment for cocaine abuse: 12-month substance use outcomes.

Patients (N?=?108) in a study of cocaine-specific coping skills training (CST), which was found to reduce cocaine use during a 3-month follow-up, were followed for an additional 9 months. CST involved coping skills training in the context of high-risk situations. Control treatment used meditation-relaxation. Both were added to comprehensive private substance abuse treatment. Patients in CST who relapsed had significantly fewer cocaine use days than did the control group during the first 6 months, then both conditions did equally well. Patients in CST also drank alcohol more frequently in the last 6 months than did contrast patients but did not differ in heavy drinking days. For cocaine use outcomes, no interaction of treatment was found with gender, education, route of administration, drug use severity, sociopathy, or depression. Implications include the need to investigate different lengths and combinations of treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vacuum electronics for the 21st century

This article explores the history and diversity of this remarkable technology, with emphasis on advances in vacuum-electronic amplifiers, including the microwave power module (MPM), that have been enabled by the ongoing development of modeling and simulation tools. These physics-based codes, enabled by rapid advances in computational hardware, allow simulation-based design and optimization of complex vacuum-electronic circuits. The growth of satellite-based digital communications technology over the past decade has opened lucrative commercial opportunities for vacuum-electronic amplifiers. This exciting new area requires the efficient production of high-frequency power and the ability to handle spectrally efficient modulations within stringent packaging constraints at affordable cost     

Ischemic changes in the canine heart as affected by the dimethyl quaternary analog of propranolol, UM-272 (SC-27761)

The effects of the dimethyl quarternary analog of propranolol, UM-272, on myocardial infarct volume were studied in the canine heart. Myocardial infarction was produced by occlusion of the left circumflex coronary artery for 60 minutes followed by reperfusion and quantitation of infarct volume 24 hours later. Groups of dogs were either untreated or pretreated with UM-272 with an initial loading dose of 5.0 mg/kg (group A) or 2.5 mg/kg (group B) 30 minutes before occlusion of the left circumflex coronary artery. Both group A and group B animals received additional doses of 2.5 mg/kg of UM-272 every 90 minutes for a period of 6 hours so that the total respective doses were 15 and 12.5 mg/kg. Control animals received comparable volumes of 0.9% sodium chloride solution. All animals were followed throughout the 6-hour procedure with continuous electrocardiographic recordings which were used to assess the effects of acute myocardial ischemia upon disturbances in cardiac rhythm and the effects of drug treatment. Dogs which survived the procedure were given tetracycline i.v. the next day and sacrificed 1 hour later by an overdose of pentobarbital sodium. The hearts were removed and the left ventricle was sliced and examined first under ultraviolet light to localize the ischemic zone by noting the tetracycline fluorescence. The ventricular slices were next incubated in nitro blue tetrazolium which stains normal myocardial tissue, thus allowing one to quantitate the volume of infarcted myocardium by excising and weighing the nonstained and stained muscle separately. The untreated control group had an infarct volume of 23.8 +/- 3.2 g/100 g of left ventricle. The treated animals in groups A and B had respective infarct volumes of 2.3 +/- 0.8 g/100 g (P less than .001) and 7.0 +/- 3.3 g/100 g (P less than .025) of left ventricle. During the acute phase of ischemia and reperfusion, arrhythmias and alterations in the ST-segment, R-wave amplituted and development of pathologic Q-waves were more prominent in the untreated animals and almost totally absent in the treated animals. UM-272 produced a dose-dependent decrease in heart rate as well as a decrease in developed isometric tension. Pretreatment with UM-272 did not prevent the derangement of function in the ischemic zone nor did it permit a return of function upon reperfusion, even though it reduced the degree of cellular damage resulting from 60 minutes of regional ischemia. A possible mechanism for the protective effect of UM-272 may be through its ability to reduce myocardial contractility and heart rate, both of which would reduce myocardial oxygen consumption and thus produce a more favorable balance between myocardial oxygen supply and myocardial oxygen demand.     

Cytokine production at the site of disease in human tuberculosis

Clinical and immunologic evidence suggests that tuberculous pleuritis provides a model to understand protective immune mechanisms against Mycobacterium tuberculosis. We therefore evaluated the pattern of cytokine mRNA expression and cytokine production in pleural fluid and blood of patients with tuberculous pleuritis. RNA was extracted from mononuclear cells, reverse transcribed to cDNA, and amplified by polymerase chain reaction (PCR). After normalization for T-cell cDNA, cDNA from pleural fluid cells and peripheral blood mononuclear cells (PBMC) was amplified with cytokine-specific primers. PCR product was quantified by Southern blot. For the Th1 cytokines gamma interferon (IFN-gamma) and interleukin-2 (IL-2), PCR product was greater in pleural fluid than in blood, whereas PCR product for the Th2 cytokine IL-4 was decreased in pleural fluid compared with blood. Concentrations of IFN-gamma were elevated in pleural fluid compared with serum, but IL-2, IL-4, and IL-5 were not detectable. Mean concentrations of IFN-gamma and IL-2 in supernatants of M. tuberculosis-stimulated pleural fluid cells were significantly greater than corresponding concentrations in supernatants of stimulated PBMC. In situ hybridization showed that increased IFN-gamma production by pleural fluid cells was associated with a 20- to 60-fold increase in the frequency of antigen-reactive IFN-gamma-mRNA-expressing cells. Because IL-10 can be produced by T cells and macrophages, pleural fluid cells and PBMC were normalized for beta-actin cDNA content and then amplified by PCR with IL-10-specific primers. IL-10 mRNA was greater in pleural fluid cells than in PBMC and was expressed predominantly by macrophages. IL-10 concentrations were elevated in pleural fluid versus serum. These data provide strong evidence for compartmentalization of Th1 cytokines and IL-10 at the site of disease in humans with a resistant immune response to mycobacterial infection.     

Psychosocial stress and coping in smokers who relapse or quit.

Selected responses and coping skills in 23 male and 21 female adult smokers and ex-smokers were evaluated in 4 situational contexts: general social competence, smoking-specific high-risk-for-relapse situations, social anxiety, and relaxation. Results show that quitters coped better than relapsers with intrapersonal (e.g., negative mood) smoking-specific situations. Quitters had lower heart rates than relapsers during relaxation and intrapersonal situations and had lower anxiety scores at the end of the procedures. Women showed more stress and less confidence in their ability to cope than men. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive modification of saccadic eye movements.

Experiments are reported in which the target for a saccadic eye movement was displaced during the saccade. Ss adapted to the displacement by altering the amplitudes of subsequent saccades to compensate for it. Analysis of kinematic details of the saccade trajectories revealed that the adaptation did not arise from a simple remapping of perceived target locations. Instead, the adaptation appeared to be accomplished by a change in the gain of the saccadic system. The gain change arose primarily from a change in the magnitude of the force pulse for the saccade, not a change in the duration of the pulse. These results have implications for the mechanisms that underlie saccades in normal situations. In particular, people can separately adjust the magnitudes and durations of the force pulses used to produce saccades. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odor of the muskox

The behavior of captive male muskoxen was observed closely during their characteristic superiority display, the anatomy of the preputial region was studied in two adults and three calves, and preputial washings and preorbital gland secretion were subjected to gas chromatography and mass spectroscopy. During the superiority display, the prepuce was everted to form a pendulous tube tipped with a fringe of matted hair. Owing to the movement of the animal, the urine that dribbled from the preputial opening was liberally applied to the long guard hairs of the belly. The superiority display was almost exclusively confined to dominant males and apparently accounted for their odor. In the quiescent state, the hair seen around the preputial opening was drawn inside and formed an 8 cm-wide band on the lining of the prepuce. The preputial washings contained large amounts of benzoic acid andp-cresol. The infraorbital gland secretion contained cholesterol, benzaldehyde, and a homologous series of saturated -lactones ranging from 8 to 12 carbons. The latter compounds and the natural secretion smell similar to the human nose.