Selenium content of feeds and effect of dietary selenium on hair and blood serum.

A selenium depletion diet (.025 ppm selenium) was fed to two male Holstein calves for its effect on concentrations of selenium in serum. By 90 days, selenium in serum was depressed from .022 ppm to .013 ppm, and one of two calves had died of "possible white muscle disease." Repletion was rapid in that a diet containing .200 ppm selenium increased selenium in serum to .028 ppm within 2 wk. Dietary .280 ppm selenium increased it to .051 ppm in 1 wk. Eleven cows and eleven calves showed averages of .030 ppm in serum (range of .013 to .051 ppm) fed a diet of corn silage (.039 ppm) and supplement (.090 ppm). A sampling of feedstuffs showed a wide range of selenium among feedstuffs (.023 for corn cobs to 2.663 ppm for dried egg albumin) and a wide range within one type feedstuff (shelled corn, .017 to .219 ppm).     

Thermal Annealing and Propagation of Shockley Stacking Faults in 4H-SiC PiN Diodes

Stacking faults within 4H-SiC PiN diodes are known to be detrimental to device operation. Here, we present electroluminescence (EL) images of 4H-SiC PiN diodes providing evidence that electrically and optically stimulated Shockley stacking fault (SSF) propagation is a reversible process at temperatures as low as 210°C. Optical beam induced current (OBIC) images taken following complete optical stressing of a PiN diode and that lead to a small number of completely propagated SSFs provide evidence that such defects propagate across the n–/p+ interface and continue to grow throughout the p+ layer. These observations bring about questions regarding the validity of the currently accepted driving force mechanism for SSF propagation.     

Effects of the application of fertilisers and trace elements on the cobalt content of herbage cut for conservation

The effects of the application of fertilisers, especially N and trace elements, on the content of Co in mixed grassland herbage and its main constituent species, have been studied. Data have been obtained from field experiments on three mineral soils and on a deep acid peat. The herbage was cut at the silage stage of growth three or four times a year for at least three successive years. Without added Co, N applications increased Co content in herbage on peat but reduced it on mineral soils mainly by eliminating clover which had a higher Co content than grasses. Applying 0.5 kg ha^?1 Co as cobalt sulphate increased herbage Co content, the increase being greater on peat than on mineral soils. These increased levels were unaffected by N applications on mineral soils but were further increased by applied N on peat. The number of years during which the Co additions were effective in producing herbage containing at least 0.1 mg Co kg^?1 dry matter varied on the different soils, ranging from barely three years on one mineral soil to over five years on peat. Without added Co the last cuts in October usually had the highest Co content and the first cuts in June the lowest. With added Co, the seasonal effects were more variable, but the Co content in the herbage frequently decreased from the first to the last cuts.     

Large S-section-ring-cavity diode lasers: directional switching, electrical diagnostics, and mode beating spectra

Semiconductor lasers with monolithically integrated ring cavities exceeding 1 cm in perimeter were fabricated and characterized optically and electrically. Directional switching was observed, influenced by S-section seeding of unidirectional operation. The lasing threshold was identified by differential current-voltage measurements, which are also shown to be useful in monitoring directional switching. Mode beating was observed at three radio-frequency bands: 7.6, 15.2, and 22.9 GHz.     

Influence of Temperature on Shockley Stacking Fault Expansion and Contraction in SiC PiN Diodes

While Shockley stacking fault (SSF) creation and expansion within 4H-SiC bipolar devices is well known, only recently was it observed that this expansion and the associated increase in the forward voltage drop (V _f) could be completely reversed via low-temperature annealing. Here we report the temperature dependence of the recovery rate of the V _f drift via annealing, reporting an activation energy of 1.3 ± 0.3 eV. The V _f drift was observed to saturate following extended electrical stressing, and it was observed that the value of V _f at this saturation was inversely proportional to the stressing temperature. We also observed that SSF and V _f drift recovery could occur in highly stressed diodes at elevated temperatures even under high current injection conditions (14 A/cm²).     

弥补模拟控制器缺点的数字控制器

新兴的电源控制数字IC缺乏模拟IC中一些很常见的基本特性,如内建栅极驱动和限流特性。数字电源控制器通常只有PWM（脉宽调制）逻辑输出,而离散栅极驱动器很少包括限流功能。此外,多数带保护的FET只能在低频、低端应用中工作。     

Pantothenic acid, coenzyme A, and human chronic ulcerative and granulomatous colitis

To investigate further an apparent relationship between chronic ulcerative and granulomatous colitis and pantothenic acid deficiency, colonic tissues obtained at the time of colectomy in 29 patients with these disorders were assayed for pantothenic acid and for coenzyme A (CoA) activity. For comparison, normal colonic tissues free of pathological lesions were obtained from 31 patients having colectomy for carcinoma or diverticulitis. Plasma, red blood cells, and colonic mucosa were assayed microbiologically for free and total pantothenic acid. The activity of CoA in colonic mucosa was determined by assaying the acetylation of sulfanilamide. Concentrations of free, bound, and total pantothenic acid in blood and in colonic mucosa did not differ between the two groups of patients. Bound pantothenic acid increased linearly with total pantothenic acid. Colonic mucosa concentrated free pantothenic acid to about 50 times the level of blood, and pantothenic acid in red cells was similar to the concentration in plasma. Compared to normal gut mucosa, CoA activity was markedly low in mucosa from patients with chronic ulcerative or granulomatous disease despite the presence of normal amounts of free and bound pantothenic acid. A block in the conversion of bound pantothenic acid to CoA in diseased mucosa is suggested.     

Evidence for the presence of components of the alternative (properdin) pathway of complement activation in respiratory secretions

Activation of the alternative complement pathway by respiratory secretory IgA was demonstrated by incubating purified, aggregated preparations of serum and secretory IgA with neat human serum. No depletion of the early components (C1-4) was observed, but 63 and 70% of C3-9, respectively, were consumed. The C3-9-consuming capacity of heat-aggregated nasal secretions from an IgA-deficient volunteer was compared with heat-aggregated nasal secretions from a normal volunteer known to have secretory IgA. The deficient secretions consumed C3-9, whereas the IgA deficient secretions did not. Reconstitution of the nasal secretions from the IgA-deficient volunteer with purified secretory IgA produced alternative pathway activation. Factor B of the alternative complement pathway was found to be present in 16 of 18 bronchoalveolar lavage samples (BALF) from normal volunteers. Simultaneous measurement of lavage and serum albumin and Factor B concentrations rendered it unlikely that Factor B was merely a transudative product from serum in half the samples but rather suggested that it may be a component of lower respiratory tract secretions. The presence of an intact alternative complement pathway in BALF was indicated by showing that cobra venom factor and endotoxin cleaved functionally pure human C3 when mixed with BALF, but had no effect on C3 in the absence of BALF.