Comparisons using optoelectronic modulation spectroscopy of n-type GaAs epitaxial layers formed on buffer layers prepared at normal and low temperatures

Optoelectronic modulation spectroscopy (OEMS) has been used to examine defect-related states in GaAs metal-semiconductor, field-effect transistor (MESFET) structures prepared by molecular-beam epitaxy (MBE) on buffer layers formed at normal and low temperatures. The technique was used to simultaneously observe the spectra of defect states near to the interface with the buffer layer and in the active layer. There were few responses that were common to the structures. The most prominent was an electron trap with a depth of 0.92 eV. This was present throughout both structures and may be from a native defect in GaAs. With few exceptions the states seen in a particular structure were present in the active layer as well as near to the interface with the buffer layer suggesting that, in each case, the defects originated from the active/buffer layer interface or from the buffer layer. The most significant difference was that states in the low-temperature (LT)-based structure generally exhibited replicating responses with specific energy periodicities. A model describes this in terms of optical-absorption transitions to the local vibrational states of defects. Five different replica series were observed. The vibrational characteristics of the defects found in the LT material suggest that they are different in character and extent to those defects found in material formed on a normally prepared buffer layer. Their Frank-Condon energies ranged from 9–332 meV.     

Lipid peroxidation in thyroid tissue of people with diffuse toxic goiter

BACKGROUND: A growing number of dependent elderly people is cared for at home by family members. However, long-term caregiving may become an intolerable strain for some families and lead to failure of family care. The aim of the study was to examine if level of physical and mental disability of the patient influences the extent of perceived caregiver burden representing risk factor for negative outcome. METHODS AND RESULTS: 128 elderly patients with disability and dependency (37 men, 91 women, average age 79.9 +/- 6.9 yrs) and 128 their primary caregivers, mostly family members (28.9% men, 71.1% women) were evaluated. Functional status of care recipient was assessed by means of Barthel ADL Index (mean = 70.9 +/- 26.5), IADL Test (mean = 31.4 +/- 23.5) and Mini-Mental State Exam, MMSE (mean = 20.4 +/- 6.5). Average score of Caregiver Burden Interview (CBI) was 34.7 +/- 18.8. According to CBI, 40.6% of caregivers were found under high or even extremely hig level of stress. Level of perceived burden correlated significantly with physical and mental disability level, in decreasing order for IADL, ADL and MMSE (rs = 0.582-0.708, p < 0.001). CONCLUSIONS: Caregiver burden of family caregivers is significantly related to the level of functioning and cognitive impairment of care recipient, particularly to his/her ability to perform instrumental activities. Functional decline of elderly patient represents a risk factor which contributes to negative caregiving outcome and institutional placement.     

Are Stress Management Programs Indicators of Good Places to Work? Results of a National Survey.

Data from a national survey of organizations were used to examine whether there are differences in the quality of worklife among organizations that offer stress management programs (SMPs) and those that do not. After controlling for size and industry, the authors found organizations with SMPs to be more likely to offer programs that encourage employee well-being, safety, and skill development than those without SMPs. However, there was no difference in the number of accidents, harassment complaints, or discrimination complaints. Organizations that offered SMPs also tended to offer other programs (i.e., substance abuse and mental health services) to facilitate worker health and well-being and, in this respect, the presence of an SMP appeared to be an indicator of a better place to work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scaling of impact damage in fiber composites from laboratory specimens to structures

Impact damage in fiber composite structures remains of much concern, and is often the limiting factor in establishing allowable strain levels. The complexity of impact damage formation usually dictates that experiments are required, but scaling of results from small laboratory scale specimens to large structures is not well understood. The following paper presents the results of an analytical and experimental investigation intended to develop procedures for prediction of damage formation and subsequent strength loss, with particular emphasis on scaling of results with respect to structure size. The experimental investigation involved both drop-weight and airgun impact on carbon/epoxy plates and cylinders. Five sizes of plates ranging from 50 × 50 × 1·072 mm to 250 × 250 × 5·36 mm, and two sizes of cylinders with diameters of 96·5 and 319 mm, were employed in the experimental program. Delamination was observed to increase with specimen size more than would be expected if stresses controlled the delamination extent, as would be predicted by fracture mechanics. Regions of broken fibers were observed in the impacted specimens, that were best correlated with the applied specimen stress or strains, independent of specimen size. It is seen that knowledge of the failure mechanisms involved is required to predict scaling of damage with confidence.     

Immunoblot studies in the differential diagnosis of porcine brucellosis: an immunodominant 62 kDa protein is related to the mycobacterial 65 kDa heat shock protein (HSP-65)

Smooth Brucella spp. share certain lipopolysaccharide antigens with other bacteria, resulting in serological cross-reactions which can prevent the definitive diagnosis of brucellosis. To identify other antigens with serodiagnostic potential, immunoblot studies following sodium dodecyl sulphate-polyacrylamide gel electrophoresis were carried out. Sera from pigs experimentally infected with Brucella suis and naturally infected feral pigs, sera from pigs from a farm with a known history of Yersinia enterocolitica 0:9 infection, Brucella Complement Fixation Test (CFT) reactor pigs (aetiology unknown) and pigs from consistently Brucella CFT negative farms were examined. Although B. suis infected pigs recognized a total of nine B. melitensis antigens, individual pigs rarely recognized more than three antigens in the range. A 62 kDa antigen was recognized by the majority (73%) of the Brucella infected pigs, but only by 10 to 23% of pigs from the other groups. This antigen was shown to be the Brucella homologue of the ubiquitous 65 kDa heat shock protein (HSP-65) family by immunoblot studies with 14 monoclonal antibodies to the Mycobacterium leprae HSP-65. Only four of these monoclones (Y1.2, ML-30, D7C and IIIC8) identified the B. melitensis 62 kDa protein suggesting that unshared, potentially Brucella specific, regions exist. Sera from Y. enterocolitica 0:9 infected pigs, CFT reactor pigs (aetiology unknown), CFT negative pigs and hyperimmune pig serum raised to Y. enterocolitica 0:9 also recognized B. melitensis antigens, most notably a 17 kDa protein. This antigen appears to be a common cross-reactive protein.     

Isolation and characterization of AFP-binding proteins from tumor and fetal human tissues

The AFP receptor (rAFP) was discovered in embryonal and tumor tissues with a high level of proliferation. The AFP-binding protein (AFPbp) possibly containing the AFP-receptor (rAFP) was isolated from human embryos and human breast cancer tissue using affinity chromatography on an AFP-Sepharose column. The similarity of molecular weight, subunit composition, and immunological characteristics was shown for embryonal and tumor AFPbp using immunoblotting, gel-filtration, and PAAG electrophoresis. Judging from Superose-12 gel-filtration data, the protein molecular weight made up to 320-380 kDa. The presence of an IgG-binding site was detected in embryonal and tumor AFPbp by Western blot analysis.     

Structure of a G-protein-coupling domain of a muscarinic receptor predicted by random saturation mutagenesis

The third intracellular loop (i3) plays a critical role in the coupling of many receptors to G-proteins. In muscarinic receptor subtypes, the N- and C-terminal regions (Ni3 and Ci3) of this loop are sufficient to direct appropriate G-protein coupling. The relative functional contributions of all amino acids within Ni3 was evaluated by constructing libraries of m5 muscarinic receptors containing random mutations in Ni3 and screening them using high throughput assays based on ligand-dependent transformation of NIH 3T3 cells. In receptors that retained a wild type phenotype, the pattern of functionally tolerated substitutions is consistent with the presence of three turns of an alpha helix extending from the transmembrane domain. All of the amino acid positions that tolerate radical substitutions face away from a conserved hydrophobic face that ends with an arginine, and helix-disrupting proline substitutions were not observed. All of the mutant receptors with significantly compromised phenotypes had amino acid substitutions in residues predicted to form the hydrophobic face. Similar data from the Ci3 region (Burstein, E. S., Spalding, T. A., Hill-Eubanks, D., and Brann, M. R. (1995) J. Biol. Chem. 270, 3141-3146) are consistent with the presence of a single helical turn extending from the transmembrane domain, with an alanine that defines G-protein affinity. Functionally critical residues of Ni3 and Ci3 are predicted to be in close proximity where they form the G-protein-coupling domain.     

Analysis of lung tumor risks in rats exposed to radon

This article measures the racial disparities in home ownership and home equity among preretirement-aged households. It computes the proportion of the racial gap explained by discrimination in housing and credit markets. Maximum likelihood and nonlinear least squares estimates are obtained for models of home ownership probabilities and home equity, conditional on home ownership, yielding computations for expected home equity for black and white households. The results reveal an average discriminatory gap in expected home equity as a percent of the actual gap of 55%. In the top third of the family income distribution, the measured discriminatory gap is 82%; in the middle third it is 83%; in the lowest third it is 62%.