高性能紫外写入光纤Bragg光栅的研制

采用未经任何特殊处理的B/Ge双掺光纤，以248nm的KrF准分子激光为光源用相位掩模技术研制出反射率大于98.5%的光纤Bragg光栅，并且使光栅反射谱的边瓣抑制达-20dB以下，其3dB带宽小于0.4nm，具有良好的滤波特性。

Coupled AlxGa1-xAs-AlAs distributed Bragg reflectors for high brightness AlGaInP light emitting diodes

A novel coupled distributed Bragg reflector (DBR) with double thickness periods was theoretically analyzed based on the spontaneous radiation properties of high brightness AlGaInP light emitting diodes(LED). Several important factors were considered including spontaneous radiation angle distribution, absorption and FTR of DBR. Calculation results showed that the optimum optical thickness of single layer of the DBR deviates from 1/4 lambda. AIGaInP high brightness light emitting diodes both with Al0.5Ga0.5As/AlAs coupled DBR and with conventional DBR were fabricated by metalorganic chemical vapor deposition(MOCVD). X-ray double crystal diffraction and reflection spectrum were employed to determine the thickness and reflectivity of the DBR. It was found that reflectivity of coupled DBR is less sensitive to incident angle than conventional DBR, higher external quantum efficiency of light emitting diodes with coupled DBR was obtained than that with conventional DBR.

etl workflow analysis and verification using backwards constraint propagation

University of Twente; Centre for Telematics and Information Technology; Netherlands Organisation for Scientific Research; Jacquard; Capgemini

Nanoadhesion of a Power-Law Graded Elastic Material

The Dugdale-Barenblatt model is used to analyze the adhesion of graded elastic materials at the nanoscale with Young's modulus E varying with depth z according to a power law E = E-0(z/c(0))(k) (0 < k < 1) while Poisson's ratio v remains a constant, where E-0 is a referenced Young's modulus, k is the gradient exponent and c(0) is a characteristic length describing the variation rate of Young's modulus. We show that, when the size of a rigid punch becomes smaller than a critical length, the adhesive interface between the punch and the graded material detaches due to rupture with uniform stresses, rather than by crack propagation with stress concentration. The critical length can be reduced to the one for isotropic elastic materials only if the gradient exponent k vanishes.

Intercellular calcium wave propagation in linear and circuit-like bone cell networks

In the present study, the mechanism of intercellular calcium wave propagation in bone cell networks was identified. By using micro-contact printing and self-assembled monolayer technologies, two types of in vitro bone cell networks were constructed: open-ended linear chains and looped hexagonal networks with precisely controlled intercellular distances. Intracellular calcium responses of the cells were recorded and analysed when a single cell in the network was mechanically stimulated by nano-indentation. The looped cell network was shown to be more efficient than the linear pattern in transferring calcium signals from cell to cell. This phenomenon was further examined by pathway-inhibition studies. Intercellular calcium wave propagation was significantly impeded when extracellular adenosine triphosphate (ATP) in the medium was hydrolysed. Chemical uncoupling of gap junctions, however, did not significantly decrease the transferred distance of the calcium wave in the cell networks. Thus, it is extracellular ATP diffusion, rather than molecular transport through gap junctions, that dominantly mediates the transmission of mechanically elicited intercellular calcium waves in bone cells. The inhibition studies also demonstrated that the mechanical stimulation-induced calcium responses required extracellular calcium influx, whereas the ATP-elicited calcium wave relied on calcium release from the calcium store of the endoplasmic reticulum.

Experimental Setup for Assessing the Energetic Materials Deflagration Propagation under High Temperature and High Pressure Conditions

The technology of "explosion in fractures" is one of new synthetic engineering methods used in low permeability reservoirs. The most important problem arose from the technology is to assess the deflagration propagation capability of milky explosives in rock fractures. In order to investigate detailed this problem in the laboratory, an experimental setup was designed and developed in which different conditions can be simulated. The experimental setup mainly includes two parts. One is the experimental part and the other is the measurement part. In the experimental setup, the narrow slots with different width can be simulated; meanwhile, different initial pressures and initial temperatures can be loaded on the explosives inside the narrow slots. The initial pressure range is from 0-60 MPa, and the initial temperatures range is from room temperature to 100 V. The temperature and the velocity of deflagration wave can be measured; meanwhile the corresponding pressure in the narrow slot is also measured. In the end, some typical measurement results are briefly presented and discussed.

Study on peak overpressure and flame propagation speed of gas deflagration in the tube with obstacles

The on-way peak overpressure and flame propagation speed of gas deflagration in the tube with obstacles are important data for process safety. Based on carbon monoxide deflagration experiments, the paper presents a multi-zone integration model for calculation of on-way peak overpressure, in which the tube with obstacles is considered as a series of venting explosion enclosures which link each others. The analysis of experimental data indicates that the on-way peak overpressure of gas deflagration can be correlated as an empirical formula with equivalence ratio of carbon monoxide oxidation, expansion ratio, flame path length, etc., and that the on-way peak overpressure exhibits a linear relationship with turbulence factor and flame propagation speed. An empirical formula of flame propagation speed is given.

双重辐射源~9C束流在其Bragg峰区对细胞致死效应增强的生物物理机制

相对12C束流而言,β缓发粒子衰变放射性9C束流在其Bragg峰区附近深度对细胞的致死效应明显增强,这已经在我们先前的研究中证实.9C束流的相对生物学效应(RBE)较12C束流要大1倍以上.本研究旨在探讨造成这一重要实验现象的生物物理机理.首先,建立模型计算了用于实验时产生的9C束流的阻止沉积几率密度分布,模型考虑了初始束流的动量分布,束流随贯穿深度增加由核反应导致的离子通量衰减和能量损失岐离等效应.发现9C束流对细胞致死效应增强的区域出现在入射9C离子的阻止沉积区域.其次,以9C束流入射处剂量为1Gy为例,根据计算得到的入射9C离子阻止分布几率密度推导了9C束流在不同贯穿深度上的沉积离子密度,进而得到了不同深度上每细胞内平均沉积9C离子数;同时,由相近剂量平均传能线密度(LET)深度上9C和12C束流实验上测得的细胞存活率推导出了9C及12C束流在这些深度上导致的每细胞平均致死事件数.研究结果表明,在照射剂量相同时每细胞平均沉积9C离子数与9C及12C束流每细胞平均致死事件数之差竟相吻合.由此推测,一个沉积9C离子将造成该细胞死亡.考虑到由9C衰变而发射低能粒子的性质,9C离子细胞中沉积可能会在该细胞中造成团簇损伤,因而本研究结果可作为辐射团簇损伤高效细胞致死的间接证据.

Four-dimensional Newton's constant in brane world with a sloping extra dimension

We show the four-dimensional Newton's constant obtained naturally from five-dimensional brane world with a tinily sloping extra dimension, which is independent of the bulk Weyl tensor. The corresponding universe is stiff fluid dominated when the slope of extra dimension is very small. Otherwise, the universe may be undergoing a self-acceleration at present epoch and have a decelerated phase in very recent past.

An efficient in vitro method for mass propagation of Potentilla potaninii wolf

This study reports a method for high-frequency shoot organogenesis and plant establishment of Potentilla potaninii Wolf. Hypocotyl and cotyledon explants of P. potaninii were cultured on Murashige and Skoog (MS) medium supplemented with various concentrations of benzyladenine (BA) and alpha-naphthaleneacetic acid (NAA) to induce adventitious shoot formation for micropropagation. The highest frequency of adventitious shoot regeneration was achieved from hypocotyl and cotyledon explants grown on MS medium supplemented with 5.0 mg l(-1) BA and 1.0 mg l(-1) NAA. The regenerated shoots rooted most efficiently on half-strength MS medium supplemented with 1.0 mg l(-1) NAA and 0.5 mg l(-1) indole-3-acetic acid or indole-3-butyric acid. The acclimatized plants with normal morphology and growth characters flowered and set seeds in the following year.