基于SIM900A远程语音预警系统的硬件设计

本设计是利用GSM/GPRS公共网络平台,不受恶劣地形、天气的影响,只要公网覆盖的区域即可实现其远程语音和短信预警,也可使用本地麦克风预警。本设计可广泛应用于水利、气象、地质灾害等的防治工程,也适用于学校、矿山、广场等公共场所的安全预警。     

Scrolls and nested tubes in multiwall carbon nanotubes

Recent high-resolution transmission electron microscopy (HREM) studies of multiwalled carbon nanotubes (MWCNTs) reveal a class of defects analogous to edge dislocations in a crystal. These defects are believed to mark the transition from scrolls on one side to nested tubes on the other. On the tube side, layer spacing becomes irregular. Analysis of the helicity of the tubes shows a strong correlation between diameter and helicity. This suggests that the organizing principle for the tubes is not Van der Waals forces, as in the case of graphite or turbostratic carbon, but preservation of helicity. Based on these observations and total energy calculations, the authors speculate that graphene monolayers initially form scrolls and subsequently transform into multiwall nanotubes through the progression of defects. Scrolls and nested tubes thus coexist within a single MWNT.     

Aqueous electrochemical intercalation of bromine into graphite fibers

For the first time, graphite fibers have been electrochemically intercalated with Br⁻ that have the same structure and properties as those intercalated from vapor phase Br₂. This was accomplished by intercalating pitch-based Thornel^® K-1100 graphite fibers at low temperature (near 0 °C) and high currents (2 A) for long times (6 h). The mechanism appears to be that Br⁻ is oxidized to aqueous Br₂ which, when sufficient local concentration builds up, intercalates the fiber. This was confirmed by intercalating K-1100 fiber in a saturated aqueous Br₂ solution without passing an electrical current. The applied voltage does apparently lower the activation energy of the reaction as evidenced by the observation that P-120 and P-100 fibers will not intercalate in aqueous Br₂ unless a voltage is applied.     

改性5A分子筛对水中As(Ⅴ)的吸附作用研究

改性5A分子筛是一种高效吸附材料。实验用5A分子筛作为载体,制备了该吸附剂,并表征了其基本性质。结果表明,改性5A分子筛对As(Ⅴ)具有很高的吸附率和选择性;室温下,pH=7时,改性5A分子筛吸附As(Ⅴ)的吸附等温线符合Langmuir型和Freundlich型。     

Evolution of chemistry and morphology during the carbonization and combustion of rice husk

Both fine carbon/silica and pure silica powders can be obtained by carbonization and combustion of rice husk under non-isothermal conditions, and the products can be used for preparation of high-quality ceramic materials. Studies on the morphology, chemical and physical characteristics of products were carried out by N₂-adsorptionmeter, SEM, XRD, FTIR, ICP-MS and EA. Results indicate that decreasing the heating rate increased the specific surface area, pore volume and pore diameter. At a heating rate of 5 °C/min, the specific surface areas of both the carbon/silica and pure silica powders were 261 and 235 m²/g, and the average pore diameters were 2.2 and 5.4 nm, respectively. The products obtained from various heating rates were all amorphous. Thermogravimetric analysis was employed to study the reaction characteristics during carbonization or combustion, indicating that decomposition process of rice husk could be divided into three temperature zones. This results of the study can also provide the important information on the recovery of biomass material from rice husk.     

Important issues in a molecular dynamics simulation for characterising the mechanical properties of carbon nanotubes

This paper discusses several important issues in a molecular dynamics simulation for analysing carbon nanotubes and their mechanical properties. In particular, the paper addresses the problems in selecting appropriate inter-atomic potentials, number of thermostat atoms, thermostat techniques, time and displacement steps and number of relaxation steps to reach the dynamic equilibrium. Based on these, the structural changes of armchair and zigzag nanotubes and their mechanical properties are investigated. The Young's modulus and Poisson's ratio of the armchair tube are 3.96 and 0.15 TPa, respectively, and those of the zigzag tube are 4.88 and 0.19 TPa, respectively. The best simulation technique identified in this study predicts that the ultimate tensile strain of a carbon nanotube is around 40% before atomic bond breakage.     

不同剂量A群脑膜炎球菌多糖菌苗的反应

应用30和50μg A 群脑膜炎球菌多糖菌苗,接种不同年龄组儿童和青少年、观察其全身和局部反应及大面积普种的异常反应。结果表明:接种30和50μg 菌苗后全身和局部反应轻微,两种剂量的接种反应无差别,仅有两个点接种两个不同年龄组时出现50μg 的全身及局部反应高于30μg。普种50多万人均未发生异常反应。     

Preparation of highly crystalline nanofibers on Fe and Fe-Ni catalysts with a variety of graphene plane alignments

The present study confirmed that highly crystalline nanofibers with controlled structure may be prepared over Fe and Fe-Ni alloy catalysts. The degree of graphitization of various carbon nanofibers (CNFs) was analyzed by using C(0 0 2) peaks from the XRD profiles. The C(0 0 2) peaks of CNFs over Fe catalyst shifted to higher angle and became narrower as the preparation temperature increased from 560 to 620 °C. Tubular CNFs prepared at temperature higher than 630 °C showed lower 2θ angles compared to those of platelet fibers. CNFs prepared over Fe-Ni catalysts tended to resemble those prepared over Fe catalysts. The degree of graphitization of platelet CNFs resembled natural graphite, while d_{0 0 2} of the tubular CNFs showed values below the 3.39 Å reported as a theoretical minimum for a cylindrical alignment. Lc_{0 0 2} of platelet and tubular CNFs increased by heat treatment at 2000 and 2800 °C though d_{0 0 2} changed little. A transverse section of platelet and tubular CNFs had a hexagonal shape, not a round shape. The hexagonal column allows AB stacking of hexagonal planes that can give perfect hexagonal alignment.     

An EGF-pseudomonas exotoxin A recombinant protein with a deletion in toxin binding domain specifically kills EGF receptor bearing cells

We constructed two chimeric toxins; one composed of epidermalgrowth factor (EGF) and pseudomonas exotoxin A (PE), designatedEGF-PE and the other composed of EGF and PE with a deletionof the Ia domain (cell-binding domain), designated EGF-PE (ALT="{delta}" BORDER="0">Ia).Both chimeric toxins reacted with anti-EGF and anti-PE antibodies.The cell-killing experiments showed that EGF-PE, but not EGF-PE(ALT="{delta}" BORDER="0">Ia),was cytotoxic to the murine fibroblast cell line NR6, whichcarried the PE receptor, but not the EGF receptor. However,after NR6 was transfected with DNA for the expression of humanEGF receptor, the transfected cell line, designated NRHER5,overexpressed human EGF receptors and became sensitive to EGF-PE(ALT="{delta}" BORDER="0">IA).The cytotoxicity of EGF-PE(ALT="{delta}" BORDER="0">Ia), but not EGF-PE, to NRHER5 canbe completely blocked by an excess amount of EGF. To completelyreverse the cytotoxicity of EGF-PE on NRHER5, both the EGF receptorpathway and the PE receptor pathway need to be blocked. Theseresults suggest that EGF-PE exhibits both EGF and PE bindingactivities, while EGF-PE(ALT="{delta}" BORDER="0">IA) possesses only EGF binding activity.Thus, EGF-PE(ALT="{delta}" BORDER="0">Ia) may be a better chimeric toxin than EGF-PEin terms of target specificity to EGF receptor bearing cells.We, therefore, examined the cytotoxicity of EGF-PE(ALT="{delta}" BORDER="0">Ia) to varioushuman cancer cell lines. We find that human cancer cells containingmore EGF receptors are more sensitive to EGF-PE(ALT="{delta}" BORDER="0">Ia).