A Proposed Dynamic Pressure and Temperature Primary Standard

Diatomic gas molecules have a fundamental vibrational motion whose frequency is affected by pressure in a simple way. In addition, these molecules have well defined rotational energy levels whose populations provide a reliable measure of the thermodynamic temperature. Since information concerning the frequency of vibration and the relative populations can be determined by laser spectroscopy, the gas molecules themselves can serve as sensors of pressure and temperature. Through measurements under static conditions, the pressure and temperature dependence of the spectra of selected molecules is now understood. As the time required for the spectroscopic measurement can be reduced to nanoseconds, the diatomic gas molecule is an excellent candidate for a dynamic pressure/temperature primary standard. The temporal response in this case will be limited by the equilibration time for the molecules to respond to changes in local thermodynamic variables. Preliminary feasibility studies suggest that by using coherent anti-Stokes Raman spectroscopy we will be able to measure dynamic pressure up to 10⁸ Pa and dynamic temperature up to 1500 K with an uncertainty of 5%.     

Pathogen-specific risk factors and protective factors for acute diarrheal disease in urban Brazilian infants

To evaluate potential risk factors and protective factors for acute diarrheal disease in urban infants, 500 infants < or = 12 months old with diarrhea and 500 age-matched control subjects coming to a S?o Paulo emergency room were studied. On multivariate analysis, these apparently sporadic community-acquired cases of diarrhea were significantly associated with hospitalization in the month before onset (odds ratio [OR], 3.4), day care center exposure (OR, 2.0), prior diarrhea in another household member (OR, 4.4), and low family income (OR, 1.8). Breast-feeding infants < 6 months old (OR, 0.3) and boiling household drinking water (OR, 0.4) were protective. Enteropathogenic Escherichia coli (EPEC; OR, 12.0) and Salmonella (OR, 7/0, discordant pairs) infections were associated with prior hospitalization, rotavirus infections were associated with day care (OR, 6/0), and breast-feeding was protective against EPEC infections (OR, 0.1). These results suggest that certain preventive strategies can prevent a substantial proportion of cases of diarrheal disease in Brazilian infants.     

Mibefradil inhibition of T-type calcium channels in cerebellar purkinje neurons

The antihypertensive agent mibefradil completely and reversibly inhibited T-type calcium channels in freshly isolated rat cerebellar Purkinje neurons. The potency of mibefradil was increased at less hyperpolarized holding potentials, and the apparent affinity was correlated with the degree of channel inactivation. At 35 degrees, the apparent dissociation constant Kapp was 1 microM at a holding voltage of -110 mV (corresponding to noninactivated channels) and 83 nM at a holding voltage of -70 mV (corresponding to 65% inactivation). The increased affinity was attributable mainly to a decreased off-rate. Mibefradil also inhibited P-type calcium channels in Purkinje neurons, but inhibition was much less potent. At a holding potential of -70 mV, the Kapp for mibefradil inhibition of P-type channels was approximately 200-fold higher than that for inhibition of T-type channels. Mibefradil should be a useful compound for distinguishing T-type channels from high voltage-activated calcium channels in neurons studied in vitro.     

Space-charge behavior of “Thin-MOS” diodes with MBE-grown silicon films

We present basic theoretical and experimental characteristics of a novel “Thin-MOS” technology, which has promising aspects for integrated high-frequency devices up to several hundred gigahertz. The operation of such devices depends on charge injection into undoped silicon layers of ～ 1000-Å thickness, grown by molecular beam epitaxy on heavily doped substrates, and isolation by thermally grown oxides of ～ 100-Å thickness. Capacitance-voltage characteristics measured at “high” and “low” frequencies agree well with theoretical ones derived from uni- and ambipolar space-charge models. We conclude that after oxidation the residual doping in the epilayer is less than ～ 10¹⁶ cm^?3 and rises by 3 orders of magnitude at the substrate interface within less than 100 Å and that interface states at the oxide interface can be kept low.     

高粱食品:一种古老作物带来新的健康

高粱是一种古老的作物初次被驯化于非洲,并在公元前3000年左右推广到了世界各地.高粱是一种抗旱的谷类作物,生长在其它作物无法生存的半干旱气候条件下,在2002年世界高粱产量达到5450万公吨.美国高粱年产量可达1300～1500万公吨左右,其中30%～50%用于出口,在西方国家中用高粱喂养动物已非常普遍,大约世界高粱产量的40%被用于作为非洲和印度等国家人民的食物.在美国对于患有腹乳糜泻疾病无法适应面筋蛋白的人已经用白色食品级的杂交作物生产出运用于无小麦产品作为食用,不能食用小麦或其它谷类作物比如黑麦,大麦,他们提供了些刺激性小的面粉已成为用于制造无小麦食品的原料.当高粱缺乏面筋时,高粱粉便不能生产有黏性和弹性的生面团,因此蛋奶糊配方被用于制造高粱产品,包括面包威化饼干、面条和比萨饼皮,这些原来都是由面粉制成.研究表明,高粱系生产高质量食物,因此种植高梁将被用于改善提高食物质量,最近一些研究表明由于这种古老作物包括含有二十烷醇(policosanols)的多酚复合物和高粱蜡的高抗氧化水平,可能对健康有独特的益处,对于保护心血管的健康至关重要.尤其在把小麦作为主要食物的西方世界,对于给患有腹乳糜泻疾病的人们提供了健康稳定的主食是一个挑战.因此高粱这种古老的作物作为21世纪的主要谷类作物引来了新的兴趣和前途,这是由于(1)它对于患有腹乳糜泻疾病的人是一种富有潜力的主食.(2)保持食物的营养和健康的高抗氧化水平和蜡含量.(3)由于它的抗干旱性和有限供水量的高生产量,2030年预期人口指数增长明显.