KARYOTYPE EVOLUTION OF SHREW MOLES (SORICOMORPHA: TALPIDAE)

The Chinese long-tailed mole (Scaptonyx fusicaudus) closely resembles American (Neurotrichus gibbsii) and Japanese (Dymecodon pilirostris and Urotrichus talpoides) shrew moles in size, appearance, and ecological habits, yet it has traditionally been classified either together with (viz subfamily Urotrichinae) or separately (tribe Scaptonychini) from the latter genera (tribe Urotrichini sensu lato). We explored the merit of these competing hypotheses by comparing the differentially stained karyotypes of S.fusicaudus and N. gibbsii with those previously reported for both Japanese taxa. With few exceptions, diploid chromosome number (2n = 34), fundamental autosomal number (FNa = 64), relative size, and G-banding pattern of S. fusicaudus were indistinguishable from those of D. pilirostris and U. talpoides. In fact, only chromosome 15 differed significantly between these species, being acrocentric in D. pilirostris, subtelocentric in U. talpoides, and metacentric in S. fusicaudus. This striking similarity is difficult to envisage except in light of a shared common ancestry, and is indicative of an exceptionally low rate of chromosomal evolution among these genera. Conversely, the karyotype of N. gibbsii deviates markedly in diploid chromosome and fundamental autosomal number (2n = 38 and FNa = 72, respectively), morphology, and G-banding pattern from those of Scaptonyx and the Japanese shrew moles. These differences cannot be explained by simple chromosomal rearrangements, and Suggest that rapid chromosomal reorganization Occurred ill the karyotype evolution of this species, possibly due to founder or bottleneck events.

陕西省汉台区粮食供需平衡及其对策研究

笔者对汉台区粮食生产的现状、粮食消费与需求进行分析,研究结果表明:汉台区人均粮食为229kg,远低于全国人均粮食380kg拥有量的水平。粮作比、粮食总产量和人均粮食产量总体上呈现下降的趋势;汉台区近30年粮食缺口较大,粮食自给率低,粮食供给难以满足当地粮食需求;按90%自给率计算,要实现2010年小康的总产目标,必须保证34575hm2种植面积。

黄土高原植被建设中的有关问题

针对黄土高原植被建设中存在的覆被率低 ,造林成活率、保存率低和效益低等问题 ,提出了只有在生态效益、树种选择等方面转变观念 ,才能切实搞好植被建设 ,并提出了植被建设中值得注意的若干重大问题

工业无线网络WIA标准体系与关键技术

工业无线技术是一种本世纪初新兴的、面向设备间信息交互的无线网络技术,适合在恶劣的工业现场环境下使用,具有强抗扰、低功耗、实时通信等技术特征,是对现有无线技术在工业应用方向上的功能扩展和技术创新,并将最终转化为新的无线技术标准。本文介绍我国在工业无线技术方面的研究进展,重点介绍具有自主知识产权的工业无线网络核心技术以及相关国家标准体系的建设情况。

Effects of disk rotation rate on the growth of ZnO films by low-pressure metal-organic chemical vapor deposition

ZnO films were grown at low pressure in a vertical metal-organic vapor deposition (MOCVD) reactor with a rotating disk. The structural and morphological properties of the ZnO films grown at different disk rotation rate (DRR) were investigated. The growth rate increases with the increase of DRR. The ZnO film grown at the DRR of 450 revolutions per minute (rpm) has the lowest X-ray rocking curve full width at half maximum and shows the best crystalline quality and morphology. In addition, the crystalline quality and morphology are improved as the DRR increased but both are degraded when the DRR is higher than 450 rpm. These results can help improve in understanding the rotation effects on the ZnO films grown by MOCVD. (C) 2007 Elsevier B.V. All rights reserved.

Low-timing-jitter, stretched-pulse passively mode-locked fiber laser with tunable repetition rate and high operation stability

We design a low-timing-jitter, repetition-rate-tunable, stretched-pulse passively mode-locked fiber laser by using a nonlinear amplifying loop mirror (NALM), a semiconductor saturable absorber mirror (SESAM), and a tunable optical delay line in the laser configuration. Low-timing-jitter optical pulses are stably produced when a SESAM and a 0.16 m dispersion compensation fiber are employed in the laser cavity. By inserting a tunable optical delay line between NALM and SESAM, the variable repetition-rate operation of a self-starting, passively mode-locked fiber laser is successfully demonstrated over a range from 49.65 to 50.47 MHz. The experimental results show that the newly designed fiber laser can maintain the mode locking at the pumping power of 160 mW to stably generate periodic optical pulses with width less than 170 fs and timing jitter lower than 75 fs in the 1.55 mu m wavelength region, when the fundamental repetition rate of the laser is continuously tuned between 49.65 and 50.47 MHz. Moreover, this fiber laser has a feature of turn-key operation with high repeatability of its fundamental repetition rate in practice.

Graft chain propagation rate coefficients of acrylic acid in melt graft copolymerization with linear low density polyethylene

Graft chain propagation rate coefficients (k(p.g)) for grafting AA onto linear low density polyethylene (LLDPE) in the melt in ESR tubes have been measured via Fourier transform infrared (FTIR) spectroscopy and electron spin resonance (ESR) spectroscopy in the temperature range from 130 to 170 degrees C. To exclude the effect of homopolymerization on the grafting. the LLDPE was pre-irradiated in the air by electron beam to generate the peroxides and then treated with iodide solution to eliminating one kind of peroxides, hydroperoxide. The monomer conversion is determined by FTIR and the chain propagation free-radical concentration is deduced from the double integration of the well-resolved ESR spectra, consisting nine lines in the melt. The temperature dependence of k(p.g) is expressed:The magnitude of k(p.g) from FTIR and ESR analysis is in good agreement with the theoretical data deduced from ethylene-AA copolymerization, suggesting this method could reliably and directly provide the propagation rate coefficient. The comparison of k(p.g) with the data extrapolated from solution polymerization at modest temperature indicates that the extrapolated data might not be entirely fitting to discuss the kinetics behavior in the melt.

Modified Simplified Rate Equation Model of Flowing Chemical Oxygen-Iodine Laser and its Application

A modified simplified rate equation (RE) model of flowing chemical oxygen-iodine laser (COIL), which is adapted to both the condition of homogeneous broadening and inhomogeneous broadening being of importance and the condition of inhomogeneous broadening being predominant, is presented for performance analyses of a COIL. By using the Voigt profile function and the gain-equal-loss approximation, a gain expression has been deduced from the rate equations of upper and lower level laser species. This gain expression is adapted to the conditions of very low gas pressure up to quite high pressure and can deal with the condition of lasing frequency being not equal to the central one of spectral profile. The expressions of output power and extraction efficiency in a flowing COIL can be obtained by solving the coupling equations of the deduced gain expression and the energy equation which expresses the complete transformation of the energy stored in singlet delta state oxygen into laser energy. By using these expressions, the RotoCOIL experiment is simulated, and obtained results agree well with experiment data. Effects of various adjustable parameters on the performances of COIL are also presented.

Carbon transition efficiency and process cost in high-rate, large-area deposition of diamond films by DC arc plasma jet

A new DC plasma torch in which are jet states and deposition parameters can be regulated over a wide range has been built. It showed advantages in producing stable plasma conditions at a small gas flow rate. Plasma jets with and without magnetically rotated arcs could be generated. With straight are jet deposition, diamond films could be formed at a rate of 39 mu m/h on Mo substrates of Phi 25 mm, and the conversion rate of carbon in CH4 to diamond was less than 3%. Under magnetically rotated conditions, diamond films could be deposited uniformly in a range of Phi 40 mm at 30 mu m/h, with a quite low total gas flow rate and high carbon conversion rate of over 11%. Mechanisms of rapid and uniform deposition of diamond films with low gas consumption and high carbon transition efficiency are discussed.

Ice induced low temperature fatigue crack propagation in offshore structural steel A131

To investigate the low temperature fatigue crack propagation behavior of offshore structural steel A131 under random ice loading, three ice failure modes that are commonly present in the Bohai Gulf are simulated according to the vibration stress responses induced by real ice loading. The test data are processed by a universal software FCPUSL developed on the basis of the theory of fatigue crack propagation and statistics. The fundamental parameter controlling the fatigue crack propagation induced by random ice loading is determined to be the amplitude root mean square stress intensity factor K-arm. The test results are presented on the crack propagation diagram where the crack growth rate da/dN is described as the function of K-arm. It is evident that the ice failure modes have great influence on the fatigue crack propagation behavior of the steel in ice-induced vibration. However, some of the experimental phenomena and test results are hard to be physically explained at present. The work in this paper is an initial attempt to investigate the cause of collapse of offshore structures due to ice loading.

Low Spring Constant Regulates P-Selectin-Psgl-1 Bond Rupture

Forced dissociation of selectin-ligand bonds is crucial to such biological processes as leukocyte recruitment, thrombosis formation, and tumor metastasis. Although the bond rupture has been well known at high loading rate r(f) (>= 10(2) pN/s), defined as the product of spring constant k and retract velocity v, how the low r(f) (< 10(2) pN/s) or the low k regulates the bond dissociation remains unclear. Here an optical trap assay was used to quantify the bond rupture at r(f) <= 20 pN/s with low k (similar to 10(-3)-10(-2) pN/nm) when P-selectin and P-selectin glycoprotein ligand 1 (PSGL-1) were respectively coupled onto two glass microbeads. Our data indicated that the bond rupture force f retained the similar values when r(f) increased up to 20 pN/s. It was also found that f varied with different combinations of k and v even at the same r(f). The most probable force, f

Self-consistent kinetic modeling of low-pressure inductively coupled radio-frequency discharges

An efficient method for solving the spatially inhomogeneous Boltzmann equation in a two-term approximation for low-pressure inductively coupled plasmas has been developed. The electron distribution function (EDF), a function of total electron energy and two spatial coordinates, is found self-consistently with the static space-charge potential which is computed from a 2D fluid model, and the rf electric field profile which is calculated from the Maxwell equations. The EDF and the spatial distributions of the electron density, potential, temperature, ionization rate, and the inductive electric field are calculated and discussed. (C) 1996 American Institute of Physics.

Self-consistent kinetic modeling of electron distribution function in a low-pressure inductively coupled plasma

Based upon the spatially inhomogeneous Boltzmann equation in two-term approximation coupled with electromagnetic and fluid model analysis for the recently developed inductively coupled plasma sources, a self-consistent electron kinetic model is developed. The electron distribution function, spatial distributions of the electron density and ionization rate are calculated and discussed.