Concurrent processing for nonlinear analysis of hollow rectangular structural sections

A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow square and rectangular structural sections and implemented on a special purpose multiprocessor computer at NASA Langley Research Center referred to as the Finite Element Machine (FEM). The cross-sectional thrust-moment-curvature relations are generated concurrently using a tangent stiffness approach, and yield surfaces are obtained that represent the interaction between axial load and biaxial moments. For the study, a maximum speed-up factor of 7.69 is achieved on eight processors.     

Theoretical Study of Half-Heusler CsXAs (X = Ca,Sr, and Ba) from First Principle Calculations

Journal of Superconductivity and Novel Magnetism - The structural, electronic, optical, and thermoelectric properties of Cs-based CsXAs (X?=?Ca, Sr, Ba) cubic compounds have been...     

Thermomechanical studies of aluminum nitride filled shape memory polymer composites

High thermal conductivity polyurethane shape memory polymer (SMP) composites filled with aluminum nitride (AlN) were fabricated, and their thermal and thermomechanical properties were studied. The purpose of this microstructure is to improve the thermal properties of the SMPs at low filler content. Morphology of AlN filler in polyurethane SMP matrix and the resulting thermal conductivity was also investigated. Thermal studies have shown that AlN is an effective filler for reinforcement of the polyurethane SMP and that it does not deteriorate the stable physical crosslink structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory material. The thermal conductivities of these SMP composites in relation to filler concentration and temperature were investigated, and it was found that the thermal conductivity can increase up to 50 times in comparison with that of the pure SMP. Furthermore, differential scanning calorimetry tests have shown a significant decrease in the glass transition temperature of the switching segment. Dynamic mechanical studies have shown that the storage modulus of the composites increase with higher AlN content in both glassy and rubbery state. Damping peak decreases and also the curve of damping becomes broader with increasing filler content. Strain fixity rate which expresses the ability of the specimens to fix their strain has been improved slightly in the presence of AlN filler but the final recovery rate of the shape memory measurement has decreased evidently. POLYM. COMPOS., 28:287–293, 2007. © 2007 Society of Plastics Engineers     

Radionuclide concentrations in sand samples from riverbanks of Muzaffarabad,Azad Kashmir

This paper presents the results of a radiological risk assessment arising from the presence of naturally occurring radionuclides in sand samples from three riverbanks in Muzaffarabad.The mean values obtained for 232 Th,226 Ra,and 40 K were found to be 44.58 ± 3.34,48.25 ± 1.77,and 239.92 ± 22.73 Bq kg~(-1),respectively.To assess the uniformity of exposure,the radium equivalent activity(Raeq) was calculated and was found to be130.47 ± 8.29 Bqkg~(-1).The current reported value for Raeqis lower than the maximum permissible value,that is,370 Bq kg~(-1),and equivalent to a gamma dose of1.5 m Svy~(-1).To investigate the possible contribution to health risks of alpha particle exposure,the radon exhalation rate(RER) from the sand samples was determined.The mean RER for all the samples was found to be335 m Bq m-~(2) h~(-1).About 43% of the samples were found to have an indoor excess lifetime cancer risk value slightly higher than recommended safety limit of 1,as proposed by the ICRP.A normalized parameter,the equivalent multiplicative factor,was defined and used to compare the current results with the findings of studies performed in other countries.Our findings are relevant to both human health and future environmental radiation monitoring.     

Fabrication and characterization of matrix type transdermal patches loaded with tizanidine hydrochloride: potential sustained release delivery system

Abstract

Objective: This study was designed to optimize and develop matrix type transdermal drug delivery system (TDDS) containing tizanidine hydrochloride (TZH) using different polymers by solvent evaporation method.

Significance: A strong need exists for the development of transdermal patch having improved bioavailability at the site of action with fewer side effects at off-target organs.

Methods: The patches were physically characterized by texture analysis (color, flexibility, smoothness, transparency, and homogeneity), in vitro dissolution test and FTIR analysis. Furthermore, functional properties essential for TDDS, in vitro percentage of moisture content, percentage of water uptake, in vitro permeation by following different kinetic models, in vivo drug content estimation and skin irritation were determined using rabbit skin.

Results: The optimized patches were soft, of uniform texture and thickness as well as pliable in nature. Novel transdermal patch showed ideal characteristics in terms of moisture content and water uptake. FTIR analysis confirmed no interaction between TZH and cellulose acetate phthalate (CAP). The patch showed sustained release of the drug which increased the availability of short acting TZH at the site of action. The patch also showed its biocompatibility to the in vivo model of rabbit skin.

Conclusions: The results demonstrated that topically applied transdermal patch will be a potential medicated sustain release patch for muscle pain which will improve patient compliance.     

Mechanism of Oxytocin-Induced Contraction in Rat Gastric Circular Smooth Muscle

Oxytocin produces an excitatory effect on gastric muscle through the activation of receptors present on stomach smooth muscle cells. However, the intracellular mechanisms that mediate oxytocin excitatory effects are still largely unknown. Therefore, we aimed to investigate the signaling pathways involved in oxytocin-induced contractions in gastric smooth muscle, shedding light on phospholipase C (PLC)-β1 signaling and its downstream molecules, including inositol 1,4,5- trisphosphate (IP₃) and myosin light chain kinase (MLCK). The contractions of gastric smooth muscle from male rats were measured in an organ bath set up in response to exogenous oxytocin 10⁻⁷ M, in the presence and absence of inhibitors of the indicated signaling molecules. Oxytocin (10⁻⁹–10⁻⁵ M) induced dose-dependent stomach smooth muscle contraction. Pre-incubation with atosiban, an oxytocin receptor inhibitor, abolished the oxytocin-induced contraction. Moreover, PLC β1 inhibitor (U73122) and IP₃ inhibitor Xestospongin C inhibited oxytocin-induced muscle contraction to various degrees. Verapamil, a calcium channel blocker, inhibited oxytocin-induced contraction, and pre-incubation of the strips, with both verapamil and Xestospongin C, further inhibited the excitatory effect of oxytocin. Chelation of intracellular calcium with BAPT-AM (1,2-bis-(o-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid) significantly inhibited the effect of oxytocin on muscle contraction. Finally, pre-incubation of the strips with the Ca²⁺/calmodulin-dependent protein kinase selective inhibitor STO-609 significantly inhibited the contraction induced by oxytocin. These results suggest that oxytocin directly stimulates its cell surface receptor to activate PLC β1, which in turn liberates IP₃, which eventually elevates intracellular calcium, the prerequisite for smooth muscle contraction.     

Determinants of 30-day mortality of spontaneous intracerebral hemorrhage in Pakistan

BACKGROUND: The present study was undertaken to evaluate the determinants of acute (30-day) mortality after spontaneous intracerebral hemorrhage (ICH) in a developing country setting, and to compare these findings with those available from studies conducted in the West. METHODS: Medical records of 146 patients admitted to a major tertiary hospital in Karachi, Pakistan between 1990 and 1991 with a diagnosis of spontaneous ICH were reviewed. The level and intensity of care provided to these patients was similar to that available at modern neurosurgical centers. The salient prognostic indicators that were studied included hypertension, pulse pressure, GCS score, neurologic deficits, and CT-scan predictors including site, size, and intraventricular spread of hemorrhage. These data were used to determine independent predictors of 30-day mortality by univariate and multivariate analysis. Additionally, 30-day survival probabilities for these outcome predictors were also computed. RESULTS: The 30-day mortality after spontaneous ICH was 39.7%. Two-thirds of the patients had a history of hypertension. The important clinical predictors at the multivariate level included GCS score < or =8 and progressive increase in pulse pressure. The CT scan predictors included intraventricular spread of hemorrhage, ventricular enlargement, and size of the bleed. Location of the lesion did not appear to significantly influence mortality. Survival analysis showed a large clustering of deaths within the first 72 hours of hospitalization. CONCLUSIONS: The 30-day mortality rate and prognostic predictors for spontaneous intracerebral hemorrhage were found to be similar to those reported in the Western hemisphere. However, the correlation of incremental increase in pulse pressure with deteriorating prognosis was a new and significant finding.