异步电动机球轴承的状态维修与剩余寿命预估

本文通过在计算机上用作图的方法，对大量轴承故障等级发展现场数据的分析，建立了球轴承等级ＡｄＢ发展的随机过程数学模型；研究该随机过程的均值函数和均方差函数，提出了电动机球轴承剩余寿命预估的方差曲线的近拟折一法；以及均值曲线趋势外法，实际应用证明，这两种方法均可用于预估球轴承利余使用寿命。这种剩余寿命预估的技术用于工厂设备维护，具有较大的经济价值。     

Lymphotoxin beta receptor-dependent control of lipid homeostasis

Hyperlipidemia, one of the most important risk factors for coronary heart disease, is often associated with inflammation. We identified lymphotoxin (LT) and LIGHT, tumor necrosis factor cytokine family members that are primarily expressed on lymphocytes, as critical regulators of key enzymes that control lipid metabolism. Dysregulation of LIGHT expression on T cells resulted in hypertriglyceridemia and hypercholesterolemia. In low-density lipoprotein receptor-deficient mice, which lack the ability to control lipid levels in the blood, inhibition of LT and LIGHT signaling with a soluble lymphotoxin beta receptor decoy protein attenuated the dyslipidemia. These results suggest that the immune system directly influences lipid metabolism and that LT modulating agents may represent a novel therapeutic route for the treatment of dyslipidemia.     

Norepinephrine pools in rat brain: differences in turnover rates and pathways of metabolism

The rate of disappearance of intracisternally administered [(3)H]norepinephrine from rat brain gradually declines as a multiphasic exponential function of time. Conversion to [(3)H]normetanephrine accounts for a larger fraction of the [(3)H]norepinephrine released in the brain shortly after its intracisternal injection than that released at later times. Pools of norepinephrine in the brain thus appear to differ in their turnover rates and pathways of metabolism. The pool of norepinephrine with a rapid rate of turnover and an appreciable conversion to normetanephrine, identified by the techniques reported here, may correspond to a pool of newly synthesized norepinephrine in the brain.     

Failure to confirm XMRV/MLVs in the blood of patients with chronic fatigue syndrome: a multi-laboratory study

Murine leukemia viruses (MLVs), including xenotropic-MLV-related virus (XMRV), have been controversially linked to chronic fatigue syndrome (CFS). To explore this issue in greater depth, we compiled coded replicate samples of blood from 15 subjects previously reported to be XMRV/MLV-positive (14 with CFS) and from 15 healthy donors previously determined to be negative for the viruses. These samples were distributed in a blinded fashion to nine laboratories, which performed assays designed to detect XMRV/MLV nucleic acid, virus replication, and antibody. Only two laboratories reported evidence of XMRV/MLVs; however, replicate sample results showed disagreement, and reactivity was similar among CFS subjects and negative controls. These results indicate that current assays do not reproducibly detect XMRV/MLV in blood samples and that blood donor screening is not warranted.     

Morphological disparity of ammonoids and the mark of Permian mass extinctions

The taxonomic diversity of ammonoids, in terms of the number of taxa preserved, provides an incomplete picture of the extinction pattern during the Permian because of a strongly biased fossil record. The analysis of morphological disparity (the variety of shell shapes) is a powerful complementary tool for testing hypotheses about the selectivity of extinction and permits the recognition of three distinct patterns. First, a trend of decreasing disparity, ranging for about 30 million years, led to a minimum disparity immediately before the Permian-Triassic boundary. Second, the strongly selective Capitanian crisis fits a model of background extinction driven by standard environmental changes. Third, the end-Permian mass extinction operated as a random, nonselective sorting of morphologies, which is consistent with a catastrophic cause.     

GRK2-dependent S1PR1 desensitization is required for lymphocytes to overcome their attraction to blood

Lymphocytes egress from lymphoid organs in response to sphingosine-1-phosphate (S1P); minutes later they migrate from blood into tissue against the S1P gradient. The mechanisms facilitating cell movement against the gradient have not been defined. Here, we show that heterotrimeric guanine nucleotide-binding protein-coupled receptor kinase-2 (GRK2) functions in down-regulation of S1P receptor-1 (S1PR1) on blood-exposed lymphocytes. T and B cell movement from blood into lymph nodes is reduced in the absence of GRK2 but is restored in S1P-deficient mice. In the spleen, B cell movement between the blood-rich marginal zone and follicles is disrupted by GRK2 deficiency and by mutation of an S1PR1 desensitization motif. Moreover, delivery of systemic antigen into follicles is impaired. Thus, GRK2-dependent S1PR1 desensitization allows lymphocytes to escape circulatory fluids and migrate into lymphoid tissues.     

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.     

苎麻疫霉对几种杀菌剂的离体敏感性测定

在实验室条件下,研究了苎麻疫霉(PhytophthoraboehmeriaeSawada)对甲霜灵、地茂散、代森锰锌和杀毒矾的离体敏感性。结果显示,甲霜灵、地茂散、代森锰锌和杀毒矾对苎麻疫霉的菌丝生长抑制EC50平均值分别为0.0295mg/L、2.0283mg/L、25.1452mg/L和2882.8708mg/L,表明供试苎麻疫霉菌株对甲霜灵表现极为敏感,最低达0.0194mg/L;而对杀毒矾抗药性极强,最高达10158.7122mg/L,且各菌株间的最大差异达49.9倍。利用SPSS软件分析表明,各供试杀菌剂对苎麻疫霉菌株的质量浓度EC50值之间均不存在显著相关性,表明苎麻疫霉对上述杀菌剂的抗性或敏感性间不存在交互作用。     

Cloning of a gene fragment encoding bovine complement component C3d with expression and characterization of derived fusion proteins

The gene fragment coding for bovine C3d gene (boC3d) was cloned and expressed as a component of fusion proteins destined for use in vaccine studies in cattle, and for in vitro experiments. This fragment of complement protein C3 (C3d) has been shown to enhance B cell responses when complexed with antigen. Three potential vaccine constructs were engineered to contain one, two or three boC3d units linked to a fragment of the leukotoxin of Mannheimia haemolytica A1, an economically important pathogen of cattle that causes a fibrinous pneumonia in calves. A recombinant biotinylated boC3d protein (for use in in vitro studies) was generated by endogenous biotinylation in Escherichia coli by means of the BirA holoenzyme synthetase. All recombinant proteins incorporated polyhistidine tags and were purified by nickel-agarose chromatography, then analyzed by SDS-PAGE and Western immunoblot. The identity of boC3d was confirmed by mass spectrometry, since monoclonal antibodies to boC3d were not available. To date, published research into the adjuvant activities of C3d has been limited to experiments in mice and rabbits, using antigens unrelated to diseases occurring naturally in these species. The boC3d fusion proteins expressed in this study will provide the basis for immunization trials in cattle and studies of receptor binding and cell activation of bovine lymphocytes.