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The effects of free radicals and hypotaurine on the development of bovine embryos produced by in vitro fertilization of in vitro-matured oocytes were examined. Embryos that developed to the 4- to 6-cell stage after in vitro fertilization were cultured without feeder cells in TCM199 medium supplemented with 1% calf serum (CS) under either 5% C[O.sub.2] in air or 5% [O.sub.2], 5% C[O.sub.2] and 90% [N.sub.2]. The percentages of blastocysts (including early, expanding, and hatched stages) that developed under 5% [O.sub.2] was higher (P < .01) than the percentage of those that developed under 20% [O.sub.2]. The respective percentages in 5% vs 20% [O.sub.2] concentration were as follows: blastocysts (d 8), 49% vs 17%; expanded blastocysts (d 8), 19% vs 6%; hatched blastocysts (d 10), 16% vs 0%. The development of embryos to blastocysts was suppressed (P < .05) when oxygen radicals were generated in culture medium by 2,2[inches]-azobis(2-amidinopropane) dihydrochloride (AAPH) under both 5% and 20% [O.sub.2]. The addition of hypotaurine permitted the development of embryos to blastocyst stage in medium with AAPH only under 5% [O.sub.2] (P < .05), but superoxide dismutase (SOD) did not permit the development of embryos to blastocysts. Alternatively, when embryos were cultured in medium without AAPH, the rates of development into blastocysts under 20% [O.sub.2] increased (P [less than] .05) by the addition of hypotaurine and SOD. However, under 5% [O.sub.2], the rates of blastocyst formation were not improved by addition of hypotaurine and SOD. Moreover, the cell numbers of blastocysts cultured in medium containing hypotaurine were greater (P < .01) than those of blastocysts cultured in medium without hypotaurine. It is concluded that hypotaurine may exert beneficial effects on in vitro development of bovine embryos under both 20% [O.sub.2] and 5% [O.sub.2] of gaseous conditions. Key Words: Bovine, Embryos, Oxygen Concentration, In Vitro Development, Hypotaurine

Electron emission properties of Spindt-type platinum field emission cathodes were investigated. The current–voltage characteristics together with the current fluctuation during long term operation were evaluated in ultrahigh vacuum. The changes of the emission properties in hydrogen, oxygen or carbon monoxide gas ambient were also investigated. Significant improvement of the emission properties was found when the cathode was operated in carbon monoxide ambient under a certain condition. It was found that the effect of the improvement lasted at least 200 h, and resistance against the oxygen exposure was also improved. The changes of the electron emission properties during long term operation in ultrahigh vacuum and in gas ambient were analyzed with the Seppen–Katamuki chart, of which ordinate and abscissa are slope and intercept of Fowler–Nordheim plot. The electron emission properties were distributed along a straight line in the Seppen–Katamuki chart, and those of the cathode improved by carbon monoxide exposure were distributed along another line. The deviation of the electron emission property in ultrahigh vacuum was considered to be due to change in the geometry of the emitting surface. The major reason for the modification of electron emission properties in carbon monoxide ambient was considered to be deposition of carbon onto the emitting surface, resulting in reduction of the work function. From the deviation of the Fowler–Nordheim characteristics in the Seppen–Katamuki chart, we presented an empirical equation for field emission. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Research is done on strained Si (e-Si) grown on Si-rich relaxed Si1-xGex buffers (single-channel heterostructures0 which can be used to fabricate n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) with enhanced performance over bulk Si. In conclusion, it is speculated that the low extracted mobility in such heterostructures results from the difference in conduction band minima between Ge and Si.