Growth and characterization of GaAs films deposited on Ge/Si composite substrates by metalorganic chemical vapor deposition

We report the results of studies which have been made on heteroepitaxial layers of GaAs and AlGaAs grown by metalorganic chemical vapor deposition on composite substrates that consist of four different types of heteroepitaxial layered structures of Ge and Ge-Si grown by molecular beam epitaxy on (100)-oriented Si substrates. It is found that of the four structures studied, the preferred composite substrate is a single layer of Ge ∼1 μm thick grown directly on a Si buffer layer. The double-crystal X-ray rocking curves of 2 μm thick GaAs films grown on such substrates have FWHM values as small as 168 arc sec. Transmission electron micrographs of these Ge/Si composite substrates has shown that the number of dislocations in the Ge heteroepitaxial layer can be greatly reduced by an anneal at about 750° C for 30 min which is simultaneously carried out during the growth of the GaAs layer. The quality of the GaAs layers grown on these composite substrates can be greatly improved by the use of a five-period GaAs-GaAsP strained-layer superlattice (SLS). Using the results of these studies, low-threshold optically pumped AlGaAs-GaAs DH laser structures have been grown by MOCVD on MBE Ge/Si composite substrates.     

Spinal injuries in New Zealand rugby and rugby league--a twenty year survey

AIMS: To establish trends in frequency of serious spinal cord injuries in rugby and rugby league over a 20 year period and to elucidate patterns of injury from retrospective analysis of cases admitted to New Zealand's two spinal injuries units. METHODS: A detailed survey of unit records with follow-up of selected patients; statistical analysis of data. RESULTS: During the 20 years 1976 to 1995, 119 rugby and 22 rugby league players (total 141) were admitted to New Zealand's two spinal injuries units suffering serious spinal injuries and 47 of these became permanently confined to wheelchairs. There was a steady increase in frequency throughout the period studied. Of the injuries 83% occurred in forwards and 17% in backs. In rugby it was the scrum which produced most injuries, and in rugby league it was the tackle. The early season month of April produced most spinal injuries. In the eighteen months since intense compulsory educational programmes on safety were introduced by the New Zealand Rugby Union there have been no serious spinal cord injuries from rugby scrums. CONCLUSION: Contrary to widespread belief, there has not been a decrease in spinal cord injuries in rugby following rule changes in the mid 1980s. The information produced by this retrospective study has been an effective educational platform to make rugby and rugby league safer.     

Psychosocial and health consequences of adolescent depression in Black and White young adult women.

Depression in adolescent girls may result in negative consequences in young adulthood. The Center for Epidemiologic Studies Depression Scale (CES-D) was administered to 1,727 Black and White girls ages 16 to 18 years who participated in the National Heart, Lung, and Blood Institute's Growth and Health Study. Three years later, women in the depressed groups were more likely to be current smokers, had attained a lower level of education, and reported lower self-worth relative to the nondepressed group. Body dissatisfaction, eating concerns, and loneliness were greater in the depressed groups. Relative to Black women, White women who were moderately depressed during adolescence reported more health care services utilization in young adulthood. Prevention efforts for depressed adolescents should be broadly focused to improve young adult outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of conformational specificity at GPIIb/IIIa: evaluation of conformationally constrained RGD peptides

RGD-containing proteins and peptides are known to bind to the platelet GPIIb/IIIa receptor and inhibit platelet aggregation. That a conformational component to the specificity exists is suggested by significantly lower activity of linear RGD analogs relative to closely related cyclic peptides and small proteins containing the RGD sequence. Recently, conformations for a suite of RGD containing cyclic peptides have been defined by NMR-based methods and, for one molecule, by X-ray diffraction. We report here the NMR-based conformational analysis of an additional cyclic peptide, cyclo(Pro-Arg-Gly-Asp-D-Pro-Gly), and compare the conformational variations in the suite of peptides and related analogs. Biological activity data for these peptides shows a preference of the platelet GPIIb/IIIa receptor for one conformation of the RGD sequence, but suggests its ability to bind a second, distinct conformation.     

Systematic environmental, direct, and service sire effects on conception rate in artificially inseminated Holstein cows

Result of insemination was verified for 329,314 artificial inseminations by 882 service sires to 97,245 Holstein cows in 1,075 herds between May 1970 and December 1983. Estimates of systematic environmental and genetic components of cow and service sire components of conception rate were obtained preliminary to development of a fertility monitoring system. Conception rate was 2.9% higher in stanchion than loose housed herds and 2.3% higher in grade than registered cows. Fall months were superior to winter months, the greatest difference being 6.1% between October and January. Conception rate increased with herd milk production, decreased with both increased cow age, and increased herd size in mature and old cows. Regions and inseminators within regions were highly variable. Conception may be influenced by semen price; however, week day of insemination and duration of semen storage had no effect. Conception rate decreased for semen by bulls 8 yr and older, was lowest for semen harvested in June, but no season of collection effect was detected. No genetic trends for cow and service sire conception rate were found; heritability and repeatability were .08 and .06, respectively. Genetic correlations between cow and service sire conception rate and these components with first lactation production and semen output measures were all near zero. Therefore, the relationship between sire fertility and daughter fertility is near zero.     

Production of aflatoxins on amaranth seeds by Aspergillus spp.

Five varieties of amaranth seeds, cooked and uncooked, were inoculated with toxigenic strains of Aspergillus spp. and the levels of aflatoxins were quantitated. Cooking seeds prior to inoculation increased the level of aflatoxins; aflatoxin levels were the same in all the amaranth varieties inoculated. Aflatoxin level was much lower on amaranth than on rice, corn or winged bean.     

Room temperature electroabsorption in a GexSi1-x PIN photodiode

We present room temperature electroabsorption measurements in a Ge _0.2Si_0.8 pin photodiode. The results appear to be very similar to those reported earlier on Ge_xSi_1-x/Si multiple quantum wells     

Plasma somatotropin and prolactin concentrations in young dairy sires before and after a 24-hour fast

To examine the efficacy of plasma concentrations of bST or prolactin as predictors of expected daughter performance, blood samples were collected from young Holstein sires. Blood samples were collected at 15-min intervals via jugular cannulas from 1000 until 1600 h (d 1), beginning 4 h after morning hay feeding. Bulls were not fed again until after collection of blood samples on d 2. Samples were collected at 15-min intervals from 1000 until 1300 h on d 2. Peak values and frequency of hormonal secretory patterns of each bull were characterized by an iterative process in which values greater than 2 SD from the mean were flagged as peaks and excluded from the subsequent calculation of SD and mean. The process continued until an iteration in which no new peaks were flagged. Imposition of a 24-h fast did not alter mean basal bST or prolactin concentrations, but reduced mean peak and overall concentrations of both hormones. The number of bST peaks on d 1 was inversely related to both USDA and Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and both USDA and Northeast Artificial Insemination Sire Comparison sire PD for milk yield, but was positively correlated on d 2 with USDA Pedigree Index for milk yield. Mean peak bST on d 2 was correlated with Northeast Artificial Insemination Sire Comparison Estimated Breeding Value for fat yield and sire USDA PD for fat yield. Prolactin peak frequency on d 1 was negatively related to Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and sire PD for fat yield. Difference between mean prolactin on d 1 and 2 was negatively related to Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and Estimated Breeding Value for fat yield. Endocrine parameters in young sires may be related to genetic merit for production parameters.     

Field Testing of Moving Short‐baseline Navigation for Autonomous Underwater Vehicles using Synchronized Acoustic Messaging

This paper presents the results from field testing of a unique approach to the navigation of a fleet of autonomous underwater vehicles (AUVs) using only onboard sensors and information provided by a moving surface ship. The approach, considered moving short‐baseline (MSBL) navigation, uses two transponders mounted on a single surface ship that alternately broadcast acoustic messages containing one of the parameters of the kinematic state of the surface ship. The broadcasts are initiated according to a predefined schedule so that the one‐way travel time (OWTT) of the acoustic messages may be used to determine the range to the transponder. Each AUV in the fleet uses the surface ship state measurements and ranges provided by the acoustic messages in two extended Kalman filters (EKFs) for state estimation. The first EKF merges the intermittent surface ship state measurements with a kinematic model to estimate the state of the surface ship. This is necessary because the presented approach uses 13‐bit acoustic messages as opposed to the more commonly used 32‐byte messages, which allow the full state to be encoded in a single broadcast. The second EKF uses the current surface ship state estimate to properly interpret the acoustic ranges, combining them with a kinematic model to estimate the state of the AUV itself. Numerous MSBL navigation experiments were compared against a more traditional approach using a long‐baseline (LBL) array of transponders and OWTT acoustic ranging. The results of all tests were verified by independent LBL measures of position.