Stoichiometry in GaAs grown in outer space measured nondestructively

A semi-insulating (SI) GaAs single crystal ingot was successfully grown in a recoverable satellite. The two-dimensional distribution of stoichiometry in space-grown SI-GaAs single crystal wafer was studied nondestructively based upon x-ray Band diffraction. The avenge stoichiometry in the space-grown crystal is 0.50007 with mean square deviation of 6 x 10(-6), and shows a better stoichiametric property than the ground-grown SI-GaAs. The average etch pit density (EPD) of dislocations in the crystal revealed by molten KOH is 2.0 x 10(4) cm(-2), and the highest EPD is 3.1 x 10(4) cm(-2). This result indicates that the structural properly of the crystal is quite good.

Structural properties of SI-GaAs grown in space

The structural properties of Semi-insulating gallium arsenide (SI-GaAs) crystal grown with power-travelling technique in space have been studied by double-crystal x-ray diffractometry and chemical etching. The quality of the crystal was first evaluated by x-ray rocking-curve method. The full width at half maximum of x-ray rocking curve in space-grown SI-GaAs is 9.4+/-0.08 are seconds. The average density of dislocations revealed by molten KOH is 2.0 X 10(4) cm(-2), and the highest density is 3.1 X 10(4) cm(-2). The stoichiometry in the single crystal grown in space is improved as well. Unfortunately, the rear of the ingot grown in space is polycrystalline owing to being out of control of power. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

Behavior of Pentacene Initial Nucleation on Various Dielectrics and Its Effect on Carrier Transport in Organic Field-Effect Transistor

The influence of dielectric surface energy on the initial nucleation and the growth of pentacene films as well as the electrical properties of the pentacene-based field-effect transistors are investigated. We have examined a range of organic and inorganic dielectrics with different surface energies, such as polycarbonate/SiO2, polystyrene/SiO2, and PMMA/SiO2 bi-layered dielectrics and also the bare SiO2 dielectric. Atomic force microscopy measurements of sub-monolayer and thick pentacene films indicated that the growth of pentacene film was in Stranski-Kranstanow growth mode on all the dielectrics. However, the initial nucleation density and the size of the first-layered pentacene islands deposited on different dielectrics are drastically influenced by the dielectric surface energy. With the increasing of the surface energy, the nucleation density increased and thus the average size of pentacene islands for the first mono-layer deposition decreased. The performance of fabricated pentacene-based thin film transistors was found to be highly related to nucleation density and the island size of deposited Pentacene film, and it had no relationship to the final particle size of the thick pentacene film. The field effect mobility of the thin film transistor could be achieved as high as 1.38 cm(2)/Vs with on/off ratio over 3 x 10(7) on the PS/SiO2 where the lowest surface energy existed among all the dielectrics. For comparison, the values of mobility and on/off ratio were 0.42 cm(2)/Vs and 1 x 10(6) for thin film transistor deposited directly on bare SiO2 having the highest surface energy.

Faraday Glasses with a Large Size and High Performance

A kind of Faraday glass with a size of 40 mm x 14 mm and 100-300 mm x 25 mm, respectively, was prepared by the melting and casting process, which had neither a Pt particulate nor a bubble or striation. The measurement results showed that the surface homogeneity of the samples was up to +/- 1 x 10-6, the laser threshold reached 10 J/cm2 (1 omega, 3 ns), and the Verdet constants of the glasses were -0.273 min/Oe/cm at 632.8 nm and -0.076 min/Oe/cm at 1064 nm, respectively.

Investigation of high cycle and Very-High-Cycle Fatigue behaviors for a structural steel with smooth and notched specimens

The high cycle and Very-High-Cycle Fatigue (VHCF) properties of a structural steel with smooth and notched specimens were studied by employing a rotary bending machine with frequency of 52.5 Hz. For smooth specimens, VHCF failure did occur at fatigue cycles of 7.1 x 10(8) with the related S-N curve of stepwise tendency. Scanning Electron Microscopy (SEM) was used for the observations of the fracture surfaces It shows that for smooth specimens the crack origination is surface mode in the failure regime of less than 10(7) cycles While at VHCF regime, the material failed from the nonmetallic inclusion lies in the interior of material, leading to the formation of fisheye pattern. The dimensions of crack initiation region were measured and discussed with respect to the number of cycles to failure. The mechanism analysis by means of low temperature fracture technique shows that the nonmetallic inclusion in the interior of specimen tends to debond from surrounding matrix and form a crack. The crack propagates and results to the final failure. The stress intensity factor and fatigue strength were calculated to investigate the crack initiation properties. VHCF study on the notched specimens shows that the obtained S-N curve decreases continuously. SEM analysis reveals that multiple crack origins are dominant on specimen surface and that fatigue crack tends to initiate from the surface of the specimen. Based on the fatigue tests and observations, a model of crack initiation was used to describe the transition of fatigue initiation site from subsurface to surface for smooth and notched specimens. The model reveals the influences of load, grain size, inclusion size and surface notch on the crack initiation transition. (C) 2010 Elsevier Ltd. All rights reserved

Applications of Heavy Ion Irradiation in Photonic Crystal Research

Photonic crystals (PC) have received extensive attention for the photonic band gap (PBG). The polystyrene (PS) particles bottom-up approach is a productive method for photonic crystal manufacture, this kind of photonic crystals having an unique PBG that depends on the particle's shape, sizes and defects. Heavy ion irradiation is a very useful method to induce defects in PC and change the shapes of the particles to tune the PBG. MeV heavy ion irradiation leads to an anisotropic deformation of the particles from spherical to ellipsoidal, the aspect ratio of which can be precisely controlled by using the ion energy and flux. Sub-micrometer PS particles were deposited on a Cu substrate and were irradiated at 230 K by using heavy ion energy and fluence in the range from 2 to 10 MeV and 1 x 10(14) cm(-2) to 1 x 10(15) cm(-2); respectively.

Applications of Heavy Ion Irradiation in Photonic Crystal Research

Photonic crystals (PC) have received extensive attention for the photonic band gap (PBG). The polystyrene (PS) particles bottom-up approach is a productive method for photonic crystal manufacture, this kind of photonic crystals having an unique PBG that depends on the particle's shape, sizes and defects. Heavy ion irradiation is a very useful method to induce defects in PC and change the shapes of the particles to tune the PBG. MeV heavy ion irradiation leads to an anisotropic deformation of the particles from spherical to ellipsoidal, the aspect ratio of which can be precisely controlled by using the ion energy and flux. Sub-micrometer PS particles were deposited on a Cu substrate and were irradiated at 230 K by using heavy ion energy and fluence in the range from 2 to 10 MeV and 1 x 10(14) cm(-2) to 1 x 10(15) cm(-2); respectively.

厌氧复合菌系的筛选及含纤维素原料预处理复合菌剂的研究

本文从不同厌氧生境中获得7组(C-2、Y-2、L-2 、NZ、H-3、CZ、L-3)具有纤维素降解能力的复合菌系。经过不断传代、淘汰纤维素降解能力降低的菌系，最后得到一组高效、传代稳定的厌氧纤维素分解复合菌系L-3。该菌系可使滤纸在42 h内溃烂，并能在分解纤维素的同时产氢气。对L-3复合菌系的产酶条件进行了研究，结果表明，在实验范围内该菌系的产酶最适条件为：pH 6.5，温度37 ℃，接种量5 %，最佳碳源为滤纸，最佳氮源为硫酸铵。第10天测得羧甲基纤维素酶(CMCase)、滤纸酶(FPA)、外切葡聚糖酶(C1)、β-葡聚糖苷酶(β-glucodase)的酶活分别为0.216 U/ml、0.101 U/ml、0.132 U/ml、0.002 U/ml，滤纸失重率70.6 %。发酵代谢产物乙醇和丁酸含量分别可达1378 mg/L 、2695 mg/L，发酵产生的气体中氢气含量最高可达70.2 %。DGGE结果表明该菌系主要由14种菌组成，其中有三株菌在发酵前后菌数发生了明显的变化，说明在以滤纸为底物的降解过程中，这三株菌起到了重要作用，对这三株菌进行了分子生物学鉴定，初步定为Clostridium phytofermentans、Clostridium cellulovorans、Desulfovibrio sp。 利用实验室分离得到的纤维素降解菌，最终配制出由10、X-1、X-13、ST-13、L-3组成的好氧-厌氧纤维素降解复合菌剂。以秸秆为发酵底物，菌剂接种量1%，利用复合菌剂预处理后的秸秆，发酵总产气量相对于对照提高了71.62%，甲烷含量最高可达70.08%。 A group of microbial consortia L-3 was isolated from the anaerobic fermentation residue of corn stalk, which could degrade cellulose and produce hydrogen. The CMCase, FPA, C1 and β-glucosidase activity of L-3 could reach to 0.216 U/ml, 0.101 U/ml, 0.132 U/ml and 0.002 U/ml, respectively. In the filter degrading process, the filter paper collapsed in the liquid culture within 42 h and the filter degrading rate could reach to 70.6% in the 13 days, meanwhile, hydrogen was determined and the highest hydrogen content was 70.2%. The optimum cellulase-degrading conditions were filter papaer as the carbon source, (NH4)2SO4 as the nitrogen source, 37 ℃ and pH 6.5 in this experiment. DGGE results showed that the microbial consortia L-3 mainly included 14 strains. The amount of 3 strains were changed during the fermentation. These strains were identified as Clostridium phytofermentans、Clostridium cellulovorans、Desulfovibrio sp by 16S rDNA sequence analysis. The cellulose- degrading microbial agent was composed by 10, X-1, X-13, ST-13, L-3 which were isolated in the laboratory. The straw pretreated by cellulose-degrading microbial agent was used to ferment, the total biogas production increased by 72% comparing to the control. The content of methane could reach to 70.08%。

适合探测较轻粒子的一种多极平行板雪崩计数器

一种高性能多极双维位置灵敏平行板雪崩计数器(multi-plate parallel plate avalanchecounter,MPPAC)在兰州中能重离子加速器放射性次级束流线(radioactive ion beam line in lanzhou,RIBLL)上被应用,由二次雪崩带来的高增益使它很适合探测较高能量的较轻粒子,它主要由1个中心阳极,x,y位置栅极和2个阴极组成,位置信号由x,y位置栅极采用电荷分除法读出,使用异丁烷工作气体,气压650Pa,阳极+400V,阴极-350V时,对于α粒子位置分辨为0.55mm(半高全宽度,fwhm),位置线性色散远好于±0.2mm,探测效率大于99.2％,同时,也研究了位置分辨与阳极、阴极电压的关系,与放大器成形时间常数的依赖,随工作气压变化等。

Microstructural evolution in silicon implanted with chlorine ions

In the present work p-type Si specimens were implanted with Cl ions of 100 keV to successively increasing fluences of 1 x 10(15), 5 x 10(15), 1 x 10(16) and 5 x 10(16) ions cm(-2) and subsequently annealed at 1073 K for 30 min. The microstructure was investigated with the transmission electron microscopy (TEM) in both the plane-view and the cross-sectional view. The implanted layer was amorphized after chlorine implantation even at the lowest ion fluence, while re-crystallization of the implanted layer occurs on subsequent annealing at 1073 K. In the annealed specimens implanted above the lowest fluence three layers along depth with different microstructures were found, which include a shallow polycrystalline porous layer, a deeper single-crystalline layer containing high density of gas bubbles, a well separated deeper layer composed of dislocation loops in low density. With increasing ion fluence the thickness of the porous polycrystalline layer increases. It is indicated that chlorine can suppress the epitaxial re-crystallization of implanted silicon, when the implant fluence of Cl ions exceeds a certain level.

Effects of annealing on the photoluminescence of He ion implanted sapphire after 230-MeV Pb ion irradiation

Single crystal sapphire (Al2O3) samples implanted with 110 keV He and irradiated at 320 K by Pb-208(27), ions with energy of 1.1 MeV/u to the fluences ranging from 1 X 10(12) to 5 X 10(14) ion/cm(2) and subsequently annealed at 600, 900 and 1100 K. The obtained PL spectra showed that emission peaks centred at 375, 390, 413, and 450 nm appeared in irradiated samples. The peak of 390 ran became very intense after 600 K annealing. The peak of 390 nm weakened and 510 nm peak started to build up at 900 K annealing, the peak of 390 nm vanished and 510 nm peak increased with the annealing temperature rising to 1100 K. Infrared spectra showed a broadening of the absorption band between 460 cm(-1), and 510 cm(-1) indicating strongly damaged regions being formed in the Al2O3 samples and position shift of the absorption band at 1000-1300 cm(-1) towards higher wavenumber after Pb irradiation.

Physical property measurement of therapeutic carbon ion beam in the shallow-seated tumor therapy terminal at HIRFL

For the first time the physical properties of therapeutic carbon-ion beam supplied by, the shallow-seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL) are measured. For a 80.55MeV/u C-12 ion beam delivered to the therapy terminal, the homogeneity of irradiation fields is 73.48%, when the beam intensity varied in the range of 0.001-0.1nA (i.e. 1 X 10(6) - 1 X 10(8) particles per second). The stability of the beam intensity within a few minutes is estimated to be 80.87%. The depth-dose distribution of the beam at the isocenter of the therapy facility is measured, and the position of the high-dose Bragg peak is found to be located at the water-equivalent depth of 13.866mm. Based on the relationship between beam energy and Bragg peak position, the corresponding beam energy at the isocenter of the therapy terminal is evaluated to be 71.71MeV/u for the original 80.55MeV/u C-12 ion beam, which consisted basically with calculation. The readout of the previously-used air-free ionization chamber regarding absorbed dose is calibrated as well in this experiment. The results indicate that the performance of the therapy facility should be optimized further to meet the requirements of clinical trial.

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV Fe-56 and 1.755 GeV Xe-136 ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

辐照诱导的人正常肝细胞系HL-7702细胞远后效应

近年来，放射治疗在肿瘤治疗中的作用受到了越来越多的重视，放疗技术和手段的迅速发展为人们选择放疗创造了更多的机会[1]。放疗是利用电离辐射对细胞，特别是细胞中的遗传物质DNA的损伤作用，诱发病灶部位不正常细胞的凋亡和坏死来治疗肿瘤的。即使制定了周密的放疗方案和计划，放疗过程中难免也会对正常组织和细胞造成一定程度的损伤，而且辐射的远后效应和旁效应的发现，也使得放射治疗肿瘤的安全性受到了很大的关注。要想充分发挥放疗的优势，而又使其对人体正常组织的毒副作用尽可能降低，就必须搞清楚电离辐射对细胞造成的各种损伤的类型及其分子机理。自从电离辐射的远后效应和旁效应被发现以来就一直是辐射生物医学领域的研究热点，国内外的科研人员进行了大量的实验试图解释它们的本质，可是几十年来相关领域的研究一直局限于细胞学的水平，在向分子水平前进的道路上遇到了巨大的困难[2,3]。目前对于电离辐射远后效应和旁效应的研究是相对独立进行的，很少有探讨二者相互关系的论文发表。本文试图在总结前人科研成果并结合对自己所取得的实验数据进行分析的基础上对电离辐射的远后效应、旁效应、基因不稳定性与电离辐射所产生的活性氧自由基的关系进行初步的探讨。实验方法与结果： 1.用X射线辐照人正常肝细胞系HL-7702细胞，运用胞质分离阻滞微核实验检测细胞微核率，AnnexinV-FITC细胞凋亡检测试剂盒检测细胞凋亡率，细胞微核率和凋亡率随着辐照剂量的增加而显著增加。X射线照射后细胞继续传代培养，第七代时不同剂量辐照后子代细胞微核率和凋亡率同未辐照细胞的微核率和凋亡率相比已经没有明显区别。对不同剂量辐照后传代七代的细胞再次照射2.5Gy相同的剂量，发现受初次不同剂量辐照的细胞其微核率和凋亡率再次出现明显差异，初次辐照剂量高的细胞再次相同剂量辐照后的微核率和凋亡率也高。 2.对不同剂量X射线辐照后的细胞继续传代到第十五代时用H2O2浓度为1ul/ml的培养基处理15min，发现受初次不同剂量辐照的细胞其微核率再次出现比较明显差异，初次辐照剂量高的细胞H2O2处理后的微核率也高。 3.对受到不同剂量X射线辐照的人正常肝细胞存活后代进行二次辐照，分两组分别给予1.5GyX射线和1Gy碳离子束辐照，并检测二次辐照后细胞的微核率，发现重离子束二次辐照后并不像X射线一样可以诱发初次X射线辐照造成的损伤信息的表达，而只是表现出二次重离子辐照所造成的损伤。结论： 1.X射线辐照导致了HL-7702细胞基因组不稳定性这一辐射远后效应，X射线二次辐照辐照存活细胞的子代细胞可以诱发辐射的远后效应（如基因组不稳定性）明显的表现； 2.X射线辐照导致的HL-7702细胞后代基因组不稳定性，可以通过H2O2处理而得以诱发，揭示电离辐射过程中产生的氧自由基可能与辐射的远后效应存在密切的联系； 3.电离辐射产生的ROS在诱发细胞产生微核中具有重要的作用，但是并非唯一的影响因素。 4.X射线和12C6+重离子束辐照后存活细胞的后代中的细胞损伤类型可能存在着本质上的区别

一氧化氮（NO）对人肝癌细胞的重离子辐射增敏作用

为了探索一氧化氮（nitric oxide，NO）作为重离子治癌的辐射增敏剂的相关机理和应用前景，本课题采用NO与12C6+离子束(或X射线)辐照协同作用人肝癌细胞（SMMC-7721细胞和HepG2细胞），研究了NO与辐照相结合对两种细胞的生物学效应影响，为重离子治癌中放射增敏剂的临床应用提供一定的理论基础和实验依据。现得出结论如下： 1． 重离子辐射与X射线辐射相比，能够更有效地杀死肿瘤细胞。 2． NO能够增加肿瘤细胞的辐射敏感性。 3 NO的放射增敏效果在一定浓度范围内存在浓度效应关系。 4 NO对不同细胞系的辐射增敏作用效果并不完全相同