Immobilization induces a very rapid increase in osteoclast activity

We studied in a randomized, strictly controlled cross-over design, the effects of 6 days 6 degrees head-down tilt bed rest (HDT) in eight male healthy subjects in our metabolic ward. The study consisted of two periods (phases) of 11 days each in order to allow for the test subjects being their own controls. Both study phases were identical with respect to environmental conditions, study protocol and diet. Two days before arriving in the metabolic ward the subjects started with a diet. The diet was continued in the metabolic ward. The metabolic ward period (1l days) was divided into three parts: 4 ambulatory days, 6 days either HDT or control and 1 recovery day. Continuous urine collection started on the first day in the metabolic ward to analyze calcium excretion and bone resorption markers. On the 2nd ambulatory day in the metabolic ward and on the 5th day in HDT or control blood was drawn to analyze serum calcium, parathyroid hormone, and bone formation markers. Urinary calcium excretion was, as early as the first day in immobilization, increased (p<0.01). CTX- and NTX-excretion stayed unchanged in the first 24 h in HDT compared to the control. But already on the 2nd day of immobilization, both bone resorption markers significantly increased. We conclude from these results--pronounced rise of bone resorption markers--that already 24 h of immobilization induce a significant rise in osteoclast activity in healthy subjects. Thus, it appears possible to use short-term bed rest studies as a first step for the development of countermeasures to immobilization.     

Experimental support for an immunological approach to the search for life on other planets

We propose a three-phase approach to test for evidence of life in extraterrestrial samples. The approach capitalizes on the flexibility, sensitivity, and specificity of antibody-antigen interactions. Data are presented to support the first phase, in which various extraction protocols are compared for efficiency, and in which a preliminary suite of antibodies are tested against various antigens. The antigens and antibodies were chosen on the basis of criteria designed to optimize the detection of extraterrestrial biomarkers unique to living or once-living organisms.     

Recurrent isolation of hydrogen peroxide-resistant spores of Bacillus pumilus from a spacecraft assembly facility

While the microbial diversity of a spacecraft assembly facility at the Jet Propulsion Laboratory (Pasadena, CA) was being monitored, H2O2-resistant bacterial strains were repeatedly isolated from various surface locations. H2O2 is a possible sterilant for spacecraft hardware because it is a low-temperature process and compatible with various modern-day spacecraft materials, electronics, and components. Both conventional biochemical testing and molecular analyses identified these strains as Bacillus pumilus. This Bacillus species was found in both unclassified (entrance floors, anteroom, and air-lock) and classified (floors, cabinet tops, and air) locations. Both vegetative cells and spores of several B. pumilus isolates were exposed to 5% liquid H2O2 for 60 min. Spores of each strain exhibited higher resistance than their respective vegetative cells to liquid H2O2. Results indicate that the H2O2 resistance observed in both vegetative cells and spores is strain-specific, as certain B. pumilus strains were two to three times more resistant than a standard Bacillus subtilis dosimetry strain. An example of this trend was observed when the type strain of B. pumilus, ATCC 7061, proved sensitive, whereas several environmental strains exhibited varying degrees of resistance, to H2O2. Repeated isolation of H2O2-resistant strains of B. pumilus in a clean-room is a concern because their persistence might potentially compromise life-detection missions, which have very strict cleanliness and sterility requirements for spacecraft hardware.     

COSAC onboard Rosetta: a bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko

The COSAC (Cometary Sampling and Composition Experiment) onboard the Rosetta mission is a combined gas chromatograph (GC)-mass spectrometer (MS). It is situated on Philae, the lander of the mission, which is intended to land on the nucleus of comet 67P/Churyumov- Gerasimenko. The purpose of the experiment is to analyze the volatile fraction of soil samples retrieved by a drill. For investigation, the samples will be pyrolysed, and the emanating gases fed into a GC, into an MS, or the combination of both. In the first part of this paper, the bioastronomical relevance of such measurements is outlined. In the second part the details of the hardware and its performance are described.     

半导体式奌火系统

苏联,以乌里扬诺夫(列宁)命名的列宁格勒电工学院,电介质及半导体教研室 航空发动机的点火系统,大都采用了由磁电机来供电的高压火花放电式电咀。这种点水系统的结构复杂,体积笨重,并且在使用上还存在着严重的缺陷。这些缺陷,首     

在高频负荷下钛合金及耐热合金持久强度的研究

1.引言 新型优质材料的制造及其在工艺上的应用与金属疲劳强度问题的研究,关系极为密切。这一问题对于现代航空发动机构造的发展具有特别重要的意义。因为,这种发动机的零件是在高温和高频振动负荷的情况之下工作的。在喷气发动机中,负荷最大的零件     

考古,寻找进化的雕塑——对话罗伯特·巴克（下）

斯：你不仅是知名的古生物学家，而且是一位有造诣的艺术家。你是怎样学习绘画的？ 巴：任何人都能作画。绘画的能力不在你的指尖，而在你的眼睛里。如果你能看见结构，如果你能看见形式，你就能把它记录下来。我上解剖学课，就把学生带到动物园，对他们说：“画那头美洲豹。”“我不会画。”他们说。“你们能看见那头美洲豹吗？”“能看见。”“肘部是直的还是弯的？“‘噢，弯的”“踝关节是弯的吗？”“是的。”“它比狗的踝关节还要弯吧？”“不错。”“把它画下来。”要是你懂得怎样看结构，能在你的头脑中大概画下一系列东西，你就能把它画到纸上。     

考古，寻找进化的雕塑——对话罗伯特·巴克（上）

达林·R．斯蒂尔（以下简称“斯”）：你刚上四年级的时候就决定研究恐龙。是受到什么影响吗？     

用于飞机健康监控的传感器技术不断升级

得益于数据处理和存储技术的进步，从飞机上获取的数据量呈爆发式增长，可对飞机实施预测性维修的机会也越来越多。其中，不断进步的传感器技术是支撑飞机健康监控技术发展的关键因素。     

航空货运市场诱惑力不减

1998年世界许多地区出现的经济和金融动荡对近期世界民航业的旅客运输的前景罩上一层阴影。但是,多方面的发展资料显示出,在今后几年里,货运飞机的市场仍然强劲。其中最为显著的一点是,空中客车工业公司积极参与与波音和麦道的传统强项货机市场的角逐,并获得来自美国联合包裹运送公司的大笔订单。在90年代,为了满足不断增长的需求,每年全球西方制造的货运喷气飞机机队大约增加80架。在今后20年,每年该数字预计增加一倍。货运机队飞机达到1500架下页表是全球1470架西制货机队的构成情况。另外,俄罗斯／独联体的经营者还有大约600架…