透过检测中的准直镜精度容限

在干涉检验过程中, 被检元件的面形误差检测精度受到干涉仪系统结构的影响, 从而降低测量结果的可靠性。为了得到较高的检测精度, 必须对检测系统进行分析, 建立测量误差和系统结构的关联度。根据菲涅耳衍射近似理论, 就菲佐干涉仪中的准直镜和标准镜面形误差对透过检测的影响进行了研究。通过对波前相位传递情况的分析, 得出波前误差和系统结构参量的相关性, 去除空腔系统误差, 优化结构参量, 并建立准直镜误差容限表达式。经计算得出, 当被检面形变误差为0.2λ时, 测试误差可以达到0.02λ, 而对准直镜的面形误差要求

Study on eight-pass dual-frequency laser interferometer with nanometer precision

A new dual-frequency laser displacement measurement interferometer with nanometer precision has been developed. An eight-pass optical subdivision technology is proposed to improve resolution based on commercial interferometers. A static positioning error measuring method has been used to examine the precision and repeatability of the laser interferometer. An optical resolution of 1.24 nm and an accuracy of nanometer scale have been achieved.

Modelling and simulation of the second-order Doppler error of a laser dual-frequency interferometer

Only the first- order Doppler frequency shift is considered in current laser dual- frequency interferometers; however; the second- order Doppler frequency shift should be considered when the measurement corner cube ( MCC) moves at high velocity or variable velocity because it can cause considerable error. The influence of the second- order Doppler frequency shift on interferometer error is studied in this paper, and a model of the second- order Doppler error is put forward. Moreover, the model has been simulated with both high velocity and variable velocity motion. The simulated results show that the second- order Doppler error is proportional to the velocity of the MCC when it moves with uniform motion and the measured displacement is certain. When the MCC moves with variable motion, the second- order Doppler error concerns not only velocity but also acceleration. When muzzle velocity is zero the second- order Doppler error caused by an acceleration of 0.6g can be up to 2.5 nm in 0.4 s, which is not negligible in nanometric measurement. Moreover, when the muzzle velocity is nonzero, the accelerated motion may result in a greater error and decelerated motion may result in a smaller error.

A novel optical subdivision method for dual-frequency interferometer

The theory of optical subdivision techniques of dual-frequency laser interferometers is stated. And a novel optical subdivision technique is proposed originally to enhance resolution of a commercial interferometer by adding some corner-cubes. Then the performance of the interferometer is tested. The interferometer resolution of 1.24 nm and the average error of below 2 nm are achieved by using the technique. The most novel of the optical subdivision technique is without lambda/4 plates. It is less sensitive to environmental changes, it has prodigious potential to improve resolution farther and it can reduce polarization mixing error. (C) 2007 Elsevier GmbH. All rights reserved.

CORRELATION OF ZONA-BINDING WITH OOCYTE MATURATION AND SPERM MOTILITY IN RHESUS-MONKEYS BY HEMIZONA ASSAY

The hemizona assay (HZA) in Rhesus monkeys was employed to study the correlation of zona-binding ability with sperm motility or with naturally developing oocytes at various maturational stages. Oocytes from unstimulated ovaries were retrieved within 2 hr from monkeys sacrificed for vaccine production (in reproductive season, but with their menstrual cycles not determined). Oocytes were divided into four groups based on their morphological maturation: 1) Oocytes surrounded by more than one cumulus layer (MC); 2) Oocytes retaining intact germinal vesicle nuclei (GV); 3) Oocytes with germinal vesicle breakdown showing distinct perivitelline space (PVS); and 4) Oocytes extruding the first polar body (PB1). The mean numbers of sperm bound to hemizona for PBI, PVS, GV, and MC groups were 132.9 +/- 12.0, 71.5 +/- 10.1, 36.1 +/- 4.0, and 20.1 +/- 2.9 (Mean +/- SE), respectively. The four groups showed significant differences from each other in sperm/egg binding ability (P < 0.01). The number of bound sperm significantly increased with oocyte maturation. The present study also showed that zona-binding ability was also affected by sperm motility. For sperm with 67.7% motility and sperm with 31.2% motility, the average numbers of bound sperm were 43.5 +/- 2.2 and 25.3 +/- 2.9 (Mean +/- SE), respectively. There was significantly higher binding ability for sperm with higher motility (P < 0.01). The results suggest that: 1)The rhesus monkey model can serve as a very sensitive model for studying sperm/egg interaction by HZA; 2) Sperm motility positively correlated with sperm/egg binding; and 3) Sperm/egg binding ability increases with oocyte maturation. The binding ability is highest when oocytes matured to the PB1 stage, which is also the best opportunity for fertilization. This is strong evidence for the ''zona maturation'' hypothesis. (C) 1994 Wiley-Liss, Inc.

Homologs of eukaryotic Ras superfamily proteins in prokaryotes and their novel phylogenetic correlation with their eukaryotic analogs

Ras superfamily proteins are key regulators in a wide variety of cellular processes. Previously, they were considered to be specific to eukaryotes, and MglA, a group of obviously different prokaryotic proteins, were recognized as their only prokaryotic an

Statistical correlation between protein secondary structure and messenger RNA stem-loop structure

Anew integrated sequence-structure database, called IADE (Integrated ASTRAL-DSSP-EMBL), incorporating matching mRNA sequence, amino acid sequence, and protein secondary structural data, is constructed. It includes 648 protein domains. Based on the IADE database, we studied the relation between RNA stem-loop frequencies and protein secondary structure. It was found that the alpha-helices and beta-strands on proteins tend to be preferably "coded" by mRNA stem region, while the coils on proteins tend to be preferably "coded" by mRNA loop region. These tendencies are more obvious if we observe the structural words (SWs). An SW is defined by a four-amino-acid-fragment that shows the pronounced secondary structural (alpha-helix or beta-strand) propensity. It is demonstrated that the deduced correlation between protein and mRNA structure can hardly be explained as the stochastic fluctuation effect. (C) 2003 Wiley Periodicals, Inc.

Development of a biotic index using the correlation of protozoan communities with chemical water quality

A method of comparing data on protozoan communities with chemical parameters is presented. Using data from an extensive survey of the River Hanjiang in China, each species of protozoa has been given a species pollution value (SPV) related to its occurrence in waters with different degrees of pollution. A comprehensive chemical index is calculated for each site based on water quality standards for eight chemical parameters. The index is calculated from the relationship between the observed levels of each chemical at a site, compared with the limits of the drinking water quality standards of the People's Republic of China. From the distribution of each species at sites with differing chemical index values, a SPV is calculated. The SPV for each species is obtained by summing the logarithmic value of 10 times the chemical pollution divided by the number of chemical parameters, then divided by the stations where the species occurs. The community pollution value (CPV), which is the average SPVs of all protozoa at a site, is used to evaluate water quality. The CPV has been shown to have a close correlation with the degree of water pollution. It is not necessary for all the protozoa in a sample to have SPVs listed in this paper, provided at least 56% of the protozoa in a sample have an SPV value, the CPV will be applicable.