High Temperature Treatment (high + temperature_treatment)

Distribution by Scientific Domains

Selected Abstracts

High temperature arsenic doping of CdHgTe epitaxial layers

A. Vlasov
Abstract Experimental results on solid-state arsenic doping of the n-type bulk and ISOVPE epitaxial CdXHg1- XTe (X = 0.19 0.3) alloys are presented. The arsenic doped thin epitaxial CdxHg1- xTe films (nAs , 5 1016 1 1020 cm -3; d = 2 5 ,m) obtained by RF sputtering in a mercury glow discharge were used as As diffusion sources. The arsenic diffusion and activation were carried out at temperatures T = 500 600 C under Hg vapour pressure. Immediately after the high temperature treatment all samples were annealed to annihilate point defects. The SIMS analysis was used for determination of the quantitative admixture distribution of As in the diffusion area. The arsenic electrical activity has been evaluated by means of differential Hall, resistivity and thermoemf measurements. The analysis of experimental data obtained as well as their comparison with previously obtained results has been performed. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Energy allocation in juvenile sablefish: effects of temperature, ration and body size

S. M. Sogard
The lipid deposition of juvenile sablefish Anoplopoma fimbria was examined, in particular, the changes in allocation over time. Growth rates of early juveniles (initial size 36,50 mm total length, LT) were manipulated using two temperatures (10 and 20 C) and two rations (ad libitum and 3,4% body mass day,1). Fish LT, mass and lipid content were measured every 3 weeks for 15 weeks. Irrespective of treatment, the relationship of total lipid content with body size was clearly hyperallometric; small juveniles allocated relatively more energy to growth and less to lipid storage than large juveniles. After adjusting for the influence of body size, temperature and ration significantly influenced body composition but these effects varied over the course of the experiment. In the first 3 week time period, fish on the high ration, high temperature treatment had reduced lipid storage relative to other treatments, but in all subsequent time periods their lipid concentrations were similar to or higher than those of fish on other treatments. In contrast, fish held at low rations and low temperatures initially had average levels of lipid concentration, but after 6 weeks their levels were lower than other treatments. Estimation of allocation to lipid storage over time (proportion of dry mass increase comprised of lipid) suggested that fish in all of the treatments were approaching an asymptotic level of lipid concentration (c. 50,60% of dry mass) but with different rates of lipid increase. Within a treatment, it was predicted that individual differences in allocation would result in trade-offs between somatic growth and storage. This trade-off was evident only for fish held on low rations at low temperatures. In contrast, fish held on high rations at high temperatures exhibited the opposite pattern of a positive correlation between somatic growth and storage. These results suggest that lipostatic regulation of appetite is unlikely in juvenile sablefish. When resources are unlimited, this species appears to adopt a maximizing strategy for both somatic growth and lipid accumulation. [source]

Fabrication and optical properties of nano-structured semipolar InGaN/GaN quantum wells on c-plane GaN template

Hongbo Yu
Abstract High density self-assembled nanostructured semipolar (NSSP) GaN pyramids are fabricated based on c-plane GaN template by in situ silane treatment followed by high temperature treatment. Semipolar InGaN/GaN multiple quantum wells (MQWs) were subsequently grown on the NSSP GaN. Optical properties of the MQWs were studied by temperature- dependent and excitation density varied photoluminescence. It was found that the internal electric field in the NSSP MQWs were remarkably reduced in comparison with planar c-plane MQWs. The internal quantum efficiency of the NSSP MQWs was measured to be > 30% which showed potential applications in III-nitride light emitters. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

DNA endoreduplication in maize endosperm cells: the effect of exposure to short-term high temperature

G. Engelen-Eigles
ABSTRACT DNA endoreduplication in Zea mays L. (cv. A619 W64A) endosperm peaks between 16 and 18 d after pollination (DAP). The physiological function of DNA endoreduplication is not known but it is believed to be important in maize kernel development. In the present study, we investigated how 2, 4 or 6 d of high temperature (35 C) affected DNA endoreduplication and maize kernel development in comparison with control kernels grown at 25 C. Data were collected on fresh weight (FW), nuclei number, mitotic index, and DNA endoreduplication. Maize endosperm FW and nuclei number were reduced by exposure to 4 or 6 d of high temperature. At 18 DAP, the 2 d high temperature treatment (HTT) caused a reduction in FW and nuclei number, but had no effect on DNA endoreduplication and average DNA content per endosperm. However, when the exposure to high temperature was increased to 4 or 6 d, FW, nuclei number and the magnitude of DNA endoreduplication were progressively reduced, and the peak mitotic index was delayed compared with the control endosperm. At 18 DAP, the 4 d treatment showed 547% of the cells were 3 or 6 C, whereas only 412% were 12 C or higher. Six days of high temperature also resulted in a reduction in endosperm FW, nuclei number and a delay in the peak of mitotic index. DNA endoreduplication occurred in the kernels exposed to this treatment, although the magnitude was severely reduced compared with the control kernels. Nuclear DNA content was highly correlated (r= 093) with kernel FW, suggesting an important role of DNA endoreduplication in determining endosperm FW. The data suggest that high temperature during endosperm cell division exerted negative effects on DNA endoreduplication by dramatically reducing the nuclei number, leaving fewer nuclei available for DNA endoreduplication. However, the data also suggest that prolonged exposure to high temperature restricts entry of mitotic cells into the endoreduplication phase of the cell cycle. [source]