Fault tolerant data transmission reduction method for wireless sensor networks

World Wide Web - Several theoretical studies have clearly demonstrated that the Dual Prediction Mechanism (DPM) remains the most efficient technique for data reduction in Wireless Sensor Networks...     

Large deflection inelastic analysis of space trusses using generalized displacement control method

This paper presents the large deflection inelastic analysis of space truss structures including both geometric and material nonlinearities. The geometric nonlinearity is considered, based on an updated Lagrangian formulation, while the material nonlinearity is accounted for by tracing a complete stress–strain relationship in the elastoplastic range. The nonlinear equilibrium equations are solved using an incremental-iterative scheme based on the generalized displacement control method. This algorithm can accurately trace the equilibrium path of nonlinear problems with multiple limit points and snap-back points. A computer program is developed to predict the inelastic post-buckling behavior of space trusses. Numerical results obtained from the developed program are compared with those reported in the literature to demonstrate the accuracy of the proposed procedure.     

Flame propagation across a flexible obstacle in a square cross-section channel

Flame propagation across a single flexible fence-type obstacle was studied experimentally in a square cross-section channel, and compared to results obtained using similar blockage ratio (BR) rigid obstacles. The experiments were carried out with different BRs in premixed stoichiometric hydrogen-air mixtures, at initial conditions of 101 kPa and 298 K. High-speed Schlieren photography was employed to gain insight into the flame front structure and the flame tip velocity. Pressure transducers were used to measure the pressure at different axial positions near the obstacle. Flame propagation was found to be strongly influenced by the flow contraction of the unburned gas upstream of the obstacle, and the separated flow downstream of the obstacle. The most significant effect of the flexible obstacle, compared to the rigid obstacle, was observed for BRs above 0.71. The flame front evolution was dominated by the shear layer coming off the obstacle leading-edge and the vortex downstream from the obstacle. For the rigid obstacle BRs tested, the shear layer coming off the obstacle leading-edge reattached to the top of the obstacle, resulting in a vortex (i.e., recirculation-zone) downstream of the obstacle. For the high BR flexible obstacles (BR > 0.43), significant obstacle deformation (downstream tilt and vertical compression), and an associated decrease in BR, resulted in slightly lower flame tip velocities past the obstacle. The downstream obstacle tilt resulted in a different type of separated flow, compared to that observed in the rigid obstacle, where the shear layer didn't reattach to the top of the obstacle. The resulting vortex and strong shear layer confined the flame tip to the top part of the channel, delaying the consumption of the unburned gas immediately downstream of the obstacle. The deformation of the flexible obstacle reduced the peak pressure and the rate of pressure rise compared to that obtained with the rigid obstacles.     

LWIR HgCdTe Detectors Grown on Ge Substrates

Long-wavelength infrared (LWIR) HgCdTe p-on-n double-layer heterojunctions (DLHJs) for infrared detector applications have been grown on 100 mm Ge (112) substrates by molecular beam epitaxy (MBE). The objective of this current work was to grow our baseline p-on-n DLHJ detector structure (used earlier on Si substrates) on 100 mm Ge substrates in the 10 μm to 11 μm LWIR spectral region, evaluate the material properties, and obtain some preliminary detector performance data. Material characterization techniques included are X-ray rocking curves, etch pit density (EPD) measurements, compositional uniformity determined from Fourier-transform infrared (FTIR) transmission, and doping concentrations determined from secondary-ion mass spectroscopy (SIMS). Detector properties include resistance-area product (RoA), spectral response, and quantum efficiency. Results of LWIR HgCdTe detectors and test structure arrays (TSA) fabricated on both Ge and silicon (Si) substrates are presented and compared. Material properties demonstrated include X-ray full-width of half-maximum (FWHM) as low as 77 arcsec, typical etch pit densities in mid 10⁶ cm⁻² and wavelength cutoff maximum/minimum variation <2% across the full wafer. Detector characteristics were found to be nearly identical for HgCdTe grown on either Ge or Si substrates.     

Substance use among Asian American adolescents: Influence of race, ethnicity, and acculturation in the context of key risk and protective factors.

This study examines the relative influence of race/ethnicity, acculturation, peer substance use, and academic achievement on adolescent substance use among different Asian American ethnic groups and U.S. racial/ethnic groups. Data from the Wave 1 in-home sample of the National Longitudinal Study of Adolescent Health was used to examine lifetime use of alcohol, tobacco, and marijuana in a full adolescent sample of all racial/ethnic groups (N = 20,745) and a subsample of Asian American adolescents (N = 1,248). Path analysis examined the hypothesized relationships of peer substance use and acculturation as risk factors and academic achievement as a protective factor for racial/ethnic groups. The results indicated that when Asian American adolescents were compared to other major U.S. racial/ethnic groups, peer use and acculturation were both significant mediators of smoking, drinking, and marijuana use, and academic achievement mediated each type of use at a trend level. For Asian American ethnic groups, peer use is a risk factor and, to a lesser extent, academic achievement is a protective factor for substance use. Also, although acculturation is a predictor of substance use, when peer use and academic achievement are taken into account, acculturation—like ethnicity—no longer predicts use. Mediation analyses indicated that peer substance use mediates smoking, drinking, and marijuana use; academic achievement does not; and acculturation mediates substance use for some substances and some Asian American ethnic groups. The results are discussed in terms of their implications for understanding how culturally specific approaches can inform preventive interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The regulation of hippocampal dynorphin by neural/neuroendocrine pathways: models for effects of aging on an opioid peptide system

Previous research has demonstrated increased messenger RNA expression and peptide content in an opioid system localized to hippocampal dentate granule cells in aged rats. This altered regulation of dynorphin was correlated with the emergence of an age-related impairment in spatial learning. Considerable evidence exists for additional effects of aging on systems that provide input to the dynorphin-containing dentate granule cells. Such changes have been well documented for loss of perforant path innervation from entorhinal cortex, deterioration in septohippocampal cholinergic neurons, and high amounts of glucocorticoids that have, among their targets, receptors located in the dentate gyrus. Similar to the effects of aging on hippocampal dynorphin, age-related changes in each of these systems correlate with the severity of spatial learning impairment in aged rats. This raises the possibility that dysregulation of dynorphin in the aged brain is a reactive response to antecedant change(s) in this circuitry, a hypothesis that was examined by separately manipulating in young rats the three neural/neuroendocrine systems identified above. Of the three models examined only removal of the perforant path reproduced the effect of aging on dynorphin in the hippocampal formation. An immunotoxin was used in Experiment 1 to selectively remove septo-hippocampal cholinergic neurons in young rats. No alteration in hippocampal opioid peptides was produced by this treatment. Experiment 2 examined effects of exposure to excess corticosterone. Adrenalectomized rats exhibited a significant decrease in hippocampal dynorphin-A (1-8) content, which was reversed by corticosterone replacement at a concentration approximating normal basal levels. Dynorphin-A (1-8) content, however, was not reliably increased by exposure to excess corticosterone. In contrast, perforant path removal was found to reproduce the effect of aging on dynorphin content; either aspiration of the entorhinal cortex or knife-cut transections of the perforant path reliably increased hippocampal dynorphin content. These results support the conclusion that age-related deterioration in the septohippocampal cholinergic system and evaluated exposure to corticosterone are not sufficient to induce an elevation in hippocampal dynorphin content. Only removal of the perforant path innervation was found to reproduce the elevation in hippocampal dynorphin content observed in aged rats with hippocampal-dependent learning impairment.     

Maleylated-BSA induces hydrolysis of PIP2, fluxes of Ca2+, NF-kappaB binding, and transcription of the TNF-alpha gene in murine macrophages

Magnetic resonance imaging brain scans and neuropsychological assessments of 17 children who met the NIH consensus diagnostic criteria for neurofibromatosis Type 1 were carried out in order to determine if there is a relationship between presence of high intensity signal abnormalities on MRI scans and nonverbal cognitive deficits. Cranial MRI scans in 10 patients (58.8%) demonstrated high intensity signal abnormalities, most frequently in the cerebral peduncles. Fifteen patients had nonverbal cognitive deficits (88.2%), including difficulty judging the orientation of lines, matching complex visual stimulus configurations, recalling pictures of faces, as well as copying and drawing from memory a complex geometric figure. There was not a significant association between nonverbal neuropsychological deficits and presence of high intensity signal abnormalities on MRI scans, possibly because the location of these hyperintense abnormalities was typically below the level of the basal ganglia. These findings suggest that the high intensity signal lesions seen on the MRI scans of children with neurofibromatosis Type 1 do not predict or explain their nonverbal cognitive deficits.     

High-Performance LWIR MBE-Grown HgCdTe/Si Focal Plane Arrays

We have been actively pursuing the development of long-wavelength infrared (LWIR) HgCdTe grown by molecular beam epitaxy (MBE) on large-area silicon substrates. The current effort is focused on extending HgCdTe/Si technology to longer wavelengths and lower temperatures. The use of Si versus bulk CdZnTe substrates is being pursued due to the inherent advantages of Si, which include available wafer sizes (as large as 300 mm), lower cost (both for the substrates and number of die per wafer), compatibility with semiconductor processing equipment, and the match of the coefficient of thermal expansion with silicon read-out integrated circuit (ROIC). Raytheon has already demonstrated low-defect, high-quality MBE-grown HgCdTe/Si as large as 150 mm in diameter. The focal plane arrays (FPAs) presented in this paper were grown on 100 mm diameter (211)Si substrates in a Riber Epineat system. The basic device structure is an MBE-grown p-on-n heterojunction device. Growth begins with a CdTe/ZnTe buffer layer followed by the HgCdTe active device layers; the entire growth process is performed in␣situ to maintain clean interfaces between the various layers. In this experiment the cutoff wavelengths were varied from 10.0 μm to 10.7 μm at 78 K. Detectors with >50% quantum efficiency and R ₀ A ∼1000 Ohms cm² were obtained, with 256 × 256, 30 μm focal plane arrays from these detectors demonstrating response operabilities >99%. Work supported by the Missile Defense Agency (MDA) through CACI Technologies, Inc. subcontract no. 601-05-0088, NVESD technical task order no. TTO-01, prime contract no. DAAB07-03-D-C214, (delivery order no. 0016)     

Localization and quantification of carbon-centered radicals on any amino acid of a protein

A general strategy to localize and quantify carbon-centered radicals within proteins is described. The methodology was first exemplified on amino acids and then on a peptide. This method is applicable to any protein system regardless of size, and the site of hydrogen abstraction by *OH on all residues within proteins is easily and accurately detected.