测量低真空系统压强的U型管油压强计

本文介绍了一种测量范围为１ｍｍＨｇ—２０ｍｍＨｇ，测量精度为０．１ｍｍＨｇ的低真空测量装置及其使用条件和方法。有效地代替了以水银为媒质的旋转式麦氏真空计。     

Vacuum states on compressible Navier-Stokes equations with general density-dependent viscosity and general pressure law

In this paper,we study the one-dimensional motion of viscous gas with a general pres- sure law and a general density-dependent viscosity coefficient when the initial density connects to the vacuum state with a jump.We prove the global existence and the uniqueness of weak solutions to the compressible Navier-Stokes equations by using the line method.For this,some new a priori estimates are obtained to take care of the general viscosity coefficientμ(ρ)instead ofρ~θ.     

Cholera toxin-induced modulation of gene expression: elucidation via cDNA microarray for rational cell-based sensor design

Cell-based biosensors utilize functional changes in cellular response to identify the biological threats in a physiological relevant manner. Cell-based sensors have been used for a wide array of applications including toxicological assessment and drug-screening. In this paper, we utilize DNA arrays to identify differential gene expression events induced by toxin exposure for the purpose of developing a reporter gene assay system compatible with insertion into a cell-based sensor platform. HT29, an intestine epithelial cell line, was used as a cell model to study the cholera toxin (CT)-induced host cell modulation using DNA array analysis. A false positive model was generated from analysis of housekeeping genes in untreated control experiments to characterize our system and to minimize the number of false positives in the data. Threshold probability scores (−3.72), which gives <0.02% false positives for up/down regulation from the false positive model, were used to identify 73 and 25 known genes/expression tag sequences (ESTs) that were up- and down-regulated, respectively, in cells exposed 23 nM of CT. Using quantitative multiplex PCR assay, the gene expression levels for several genes shown to be modulated according to the microarray experiments, such as apolipoprotein D (Apol D), E-cadherin, and cyclin A2, were confirmed. The differential expression of genes encoding cytochrome P450, glutathione transferase (GST), and MGAT2 were noteworthy and consistent with previous studies. Our study provides an approach to analyze cDNA microarray data with defined false positive rates. The utility of cDNA microarray information for the design of cell-based sensor using a reporter gene approach is discussed.     

Effect of vacuum, oxygen and carbon dioxide on the track registration in SR-90 and CR-39

The molecular structure of SR-90 and CR-39 is very similar except that the average length of carbonate linkages in SR-90 is 1.6 times longer than in CR-39. However, the effect of vacuum and carbon dioxide (CO₂) on the track registration of these two detectors is very different: 1) the sensitivity of CR-39 becomes very low in vacuum; the sensitivity of SR-90 does not go down to zero even after storage in vacuum for a long time; 2) the sensitivity of SR-90 decreases both in air and in vacuum but the original sensitivity can be restored by storing it in CO₂ of 13 atm for several days. We also found that the sensitization of latent tracks by oxygen (O₂) is effective only at the time of irradiation but the sensitization by CO₂ is effective after irradiation.     

Elliptical Solutions to the Standard Cosmology Model with Realistic Values of Matter Density

We have examined a solution to the FRW model of the Einstein and de Sitter Universe, often termed the standard model of cosmology, using wide values for the normalized cosmic constant (Ω_∧) and spacetime curvature (Ω _k ) with proposed values of normalized matter density. These solutions were evaluated using a combination of the third type of elliptical equations and were found to display critical points for redshift z, between 1 and 3, when Ω_∧ is positive. These critical points occur at values for normalized cosmic constant higher than those currently thought important, though we find this solution interesting because the Ω_∧ term may increase in dominance as the Universe evolves bringing this discontinuity into importance. We also find positive Ω_∧tends towards attractive at values of z which are commonly observed for distant galaxies.     

Global classical solutions to the compressible micropolar viscous fluids with large oscillations and vacuum

In this paper, we consider the three dimensional Cauchy problem of the compressible micropolar viscous flows. We prove the existence of unique global classical solution for smooth initial data with small initial energy but possibly large oscillations and the initial density may allowed to contain the interior and far field vacuum states. Furthermore, the large time behavior of the solution is obtained as well.     

Vacuum Rabi Splitting and Kerr Effect of a Hybrid Spin–Magnon–Photon System

The vacuum Rabi splitting and Kerr effect are investigated theoretically in a hybrid spin–magnon–photon system, where the nitrogen-vacancy center in diamond driven by two light fields is coupled to a spherical micromagnet embedded in a superconducting coplanar waveguide resonator. The results indicate that the phenomenon of the Mollow triplet and vacuum Rabi splitting can appear by controlling the spin–magnon coupling and magnon–photon coupling. It is shown that the probe absorption spectrum can be adjusted effectively via the pump frequency detuning. Moreover, it is demonstrated that the optical Kerr effect can be tuned by changing the Rabi frequency. This work may provide a possibility for the applications in quantum information processing and quantum sensing of magnetic signal.     

孔底空腔爆炸应力场分布的动光弹试验研究

在保护层开挖中,孔底空腔装药爆破的方法被证明对保护建基面是行之有效的。为了研究炮孔孔底空腔装药结构的爆炸作用机理,运用动光弹试验模拟介质受到爆炸载荷作用下的动态响应,分析了不同装药结构的孔底应力场分布情况及其作用规律;文中介绍了动光弹模型试验设计参数,通过对试验中条纹级数与比例距离曲线的对比分析,得出了合理的孔底空腔能有效地降低爆炸峰值压力和有利于保护建基面的结论。     

Missing value imputation strategies for metabolomics data

The origin of missing values can be caused by different reasons and depending on these origins missing values should be considered differently and dealt with in different ways. In this research, four methods of imputation have been compared with respect to revealing their effects on the normality and variance of data, on statistical significance and on the approximation of a suitable threshold to accept missing data as truly missing. Additionally, the effects of different strategies for controlling familywise error rate or false discovery and how they work with the different strategies for missing value imputation have been evaluated. Missing values were found to affect normality and variance of data and k‐means nearest neighbour imputation was the best method tested for restoring this. Bonferroni correction was the best method for maximizing true positives and minimizing false positives and it was observed that as low as 40% missing data could be truly missing. The range between 40 and 70% missing values was defined as a “gray area” and therefore a strategy has been proposed that provides a balance between the optimal imputation strategy that was k‐means nearest neighbor and the best approximation of positioning real zeros.     

金属蒸气真空弧离子源CO离子注入对不锈钢摩擦磨损性能的影响

采用金属蒸气真空弧离子源对1Cr18Ni9Ti不锈钢进行Co离子注入,考察了注入处理试样的摩擦磨损性能.结果表明:Co注入处理样品的表面硬度比未注入样品的高1.0～1.5倍,且硬度随离子束流密度的增大而增大;Co注入处理试样的摩擦系数显著降低至约0.20,磨损体积损失降低25%～45%;当束流密度为22μA/cm2、注入剂量为5×1017/cm2时,注入处理样品的摩擦系数为0.19,耐磨寿命最长;在所选定的试验参数范围以内,当临界束流密度处于22μA/cm2时,保留剂量最大,改性表面硬度最高,耐磨性能最佳.