Characterization of silicon carbide thin films and their use in colour sensor

A series of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films were prepared by plasma-enhanced chemical vapour deposition (PECVD) using a gas mixture of silane, methane, and hydrogen as the reactive source. The previous results show that a high excitation frequency, together with a high hydrogen dilution ratio of the reactive gases, allow an easier incorporation of the carbon atoms into the silicon-rich a-Si1-xCx:H film, widen the valence controllability. The data show that films with optical gaps ranging from about 1.9 to 3.6 eV could be produced. In this work the influence of the hydrogen dilution ratio of the reactive gases on the a-Si1-xCx:H film properties was investigated. The microstuctural and photoelectronic properties of the silicon carbide films were characterized by Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA), and FT-IR spectrometry. The results show that a higher hydrogen dilution ratio enhances the incorporation of silicon atoms in the amorphous carbon matrix for carbon-rich a-Si1-xCx:H films. One pin structure was prepared by using the a-Si1-xCx:H film as the intrinsic layer. The light spectral response shows that this structure fits the requirement for the top junction of colour sensor. (c) 2004 Elsevier B.V. All rights reserved.

Experimental investigation on TBAB clathrate hydrate slurry flows in a horizontal tube: Forced convective heat transfer behaviors

Tetra-n-butyl-ammonium bromide (TBAB) clathrate hydrate slurry (CHS) is one kind of secondary refrigerants, which is promising to be applied into air-conditioning or latent-heat transportation systems as a thermal storage or cold carrying medium for energy saving. It is a solid-liquid two phase mixture which is easy to produce and has high latent heat and good fluidity. In this paper, the heat transfer characteristics of TBAB slurry were investigated in a horizontal stainless steel tube under different solid mass fractions and flow velocities with constant heat flux. One velocity region of weakened heat transfer was found. Moreover, TBAB CHS was treated as a kind of Bingham fluids, and the influences of the solid particles, flow velocity and types of flow on the forced convective heat transfer coefficients of TBAB CHS were investigated. At last, criterial correlations of Nusselt number for laminar and turbulent flows in the form of power function were summarized, and the error with experimental results was within 20%.

气体喷嘴反冲传输技术及在核科学中的应用

The gas-jet recoil transport technique is developed and improved as a new rapid and effective on-line and off beam method following "rabbit" apparatus in the study of short lives nuclei. It can transport the short half-life nuclear reaction products far from high radioactive area for collection and measurement at low background area. This technique has been widely used in the researches with accelerator and reactor. It is indispensable basic experimental technology and tool applied to nuclear reaction, spec...中文摘要：气体喷嘴反冲传输技术是继"跑兔"装置之后发展和完善起来的适合于短寿命核素研究的一种快速而有效的在线脱束方法。它能够将短寿命核反应产物传输至远离高辐射区的低本底场所进行收集和测量。该技术已在加速器和反应堆上得到了广泛的应用,是一种研究核反应、核谱学和合成与鉴别新元素、新核素的一种不可缺少的基本实验技术和工具。描述了气嘴系统的结构、基本原理、设计要求以及它的主要特性,特别是对系统的气体动力学机制以及各种参数对系统特性的影响等进行了讨论。最后,综述了它在核物理、核化学以及质谱学等领域的应用情况,并且给出了几个应用的典型例子。

八单元一维位置灵敏雪崩室

In the experiment of nuclear reaction, it is important to measure the mass, charge, energy and emitted direction of particles. For multiparameter measurement, we must use a detector or a group of detectors which can give the time, energy, and position information. The Large Area position sensitive Ionization Chamber(LAIC) is one of the eight experiment terminals of HIRFL. It is built for researching nuclear reactions from low energy to intermediate energy. It is an excellent equipment for energy measurements and atomic number identification of emitted fragments in this energy region. It is also designed to give the time and position information of the emitted fragments by itself. Obviously, an IC can not supply a good timing signal. Moreover, the mechanical installation is different from the original design by some other reasons. In this case, it is not enough to obtain the correct direction information of the emitted fragments. To obtain good timing signals and the correct direction information, some modifications must be made. It is well known that a PPAC can give us excellent timing signals. It also can be easily built as a position sensitive detector. For this reason, a specially designed PPAC is installed in the entrance of the LAIC. For the different purposes, two types of PPACs were designed and tested. Both are OCTPSACs (OCTunit one dimension Position Sensitive Avalanche Counter). In this paper, both OCTPSACs will be introduced. Based on the requirements of the LAIC, the OCTPSACs consist of eight position sensitive PPACs. Each PPAC has an anode and a cathode. In both cases, the sizes are same. But different type of cathodes are used. In one type of OCTPSAC, its cathode is made of wire plane. It consists of gold-plated tungsten wires with the diameter of 20μm, spaced 0.5 mm apart from each other. The anode is a mylar foil which was evaporated by gold layer with the thickness of 50μg/cm~2 mounted on a printed plate in the shape of rectangle. the thickness of mylar foil is 1.5μm. The gap between anode and cathode is 3mm. The performance of the OCTPSAC has been tested by using a ~(252)Cf source in flowing isobutylene gas at the pressure of 3.4mb. The intrinsic time resolution of 289ps and position resolution of 2 mm have been obtained. In another type of OCTPSAC, the cathode is made of mylar foil, which is composed of gold strip by vacuume evaporation method with a special mask on the mylar foil. The thickness and the width of the gold strip is 50μg/cm~2 and 1.7mm. The strips are spaced 0.3 mm apart from each other. The anode is the same as the former type. We have obtained the time resolution of 296ps and position resolution of 2mm by using ~(241)Am-a source when the gas pressure is 6 mb and high voltage is 600V. The working gas is heptane

Determination of urinary oxidative DNA damage marker 8-hydroxy-2 '-deoxyguanosine and the association with cigarette smoking

8-hydroxy-2'-deoxyguanosine (8OHdG) has been widely used as a biomarker of oxidative DNA damage in both animal models and human studies. To evaluate the effect of cigarette smoking on oxidative stress, we studied the levels of urinary 8OHdG from smokers and non-smokers and investigated the association with cigarette smoking. The urinary 8OHdG concentrations were determinated by capillary electrophoresis with end-column amprometric detection (CE-AD) after a single-step solid phase extraction (SPE), and then quantitatively expressed as a function of creatinine excretion. To increase the concentration sensitivity, a dynamic pH junction was used and the focusing effect was obvious when using 30 mM phosphate (pH 6.50) as sample matrix. The limit of detection is 4.3 nM (signal-to-noise ratio S/N = 3). The relative standard deviation (R.S.D.) was 1.1% for peak current, and 2.3% for migration time. Based on the selected CE-AD method, it was found that the mean value of urinary 8OHdG levels in the smokers significantly higher than that in non-smokers (31.4 +/- 18.9 nM versus 14.4 +/- 7.6 nM, P = 0.0004; 23.5 +/- 21.3 mug g(-1) creatinine versus 12.6 +/- 13.2 mug g(-1) creatinine, P = 0.028). (C) 2004 Elsevier B.V. All rights reserved.

On the propagation rate of the chemical waves observed during the course of CO oxidation on a Ag/Pt(110) composite surface

We have analyzed the propagation rate of the chemical waves observed during the course of CO oxidation on a Ag/Pt(I 10) composite surface that were reported in our previous papers [Surf Interface Anal. 2001, 32, 179; J. Phys. Chem. B 2002, 106, 5645]. In all cases, the propagation rate v can be adequately fitted as v = v(0) + D-0/d, in which v(0) and D-0 are constants, and d is the distance between the reaction front of the chemical wave and the boundary from which the chemical wave originates. We propose that the surface species responsible for the formation of the chemical wave comes from two paths: the adsorption of molecules in the gas phase on the surface and the migration from the adjacent surface with different catalytic activity. v(0) corresponds to the contribution from the surface species due to the adsorption, and D-0/d to that of the surface species that migrates from the adjacent surface. The rate equation clearly suggests that the observed chemical wave results from the coupling between adjacent surfaces with different catalytic activities during the course of heterogeneous catalysis. These results, together with our previous reports, provide a good fundamental understanding of spillover, an important phenomenon in heterogeneous catalysis.

Activated carbon supported bimetallic CoMo carbides synthesized by carbothermal hydrogen reduction

A carbothermal hydrogen reduction method was employed for the preparation of activated carbon supported bimetallic carbide. The resultant samples were characterized by BET surface area measurement, X-ray diffraction, and temperature-programmed reduction-mass spectroscopy. The results showed that nanostructured beta-Mo2C can be formed on the activated carbon by carbothermal hydrogen reduction above 700 degreesC. The particle sizes of beta-Mo2C increase with increasing reaction temperatures and Mo loading. The bimetallic CoMo carbide can be synthesized by the carbothermal hydrogen reduction even around 600 degreesC. The bimetallic CoMo carbide is from carbothermal hydrogen reduction of CoMoO4 precursor and is easily formed when the Co/Mo molar ratio is 1.0. Separation of the bimetallic CoMo carbide phase into Mo carbide and Co metal occurs when the temperature of the reduction is above 700 degreesC. The addition of a second metal such as Co and Ni, decreases the formation temperature of carbide because the second metal promotes formation of CHx species from reactive carbon atoms or groups on carbon material and hydrogen, which further carburizes oxide precursors. (C) 2003 Elsevier Science Ltd. All rights reserved.

黄土高原半干旱区集流灌草立体配置与水分调控

该区干旱与水土流失并存 ,降雨量时空分配不均 ,且水热并不同步 (在春夏 ,植物常因缺水而枯死 ) ,致使生态环境建设中恢复植被的难度大。为此 ,采用工程整地措施与灌草立体配置模式 ,发展集流灌草植被 ,调蓄土壤水分 ,促进灌草植被的快速恢复。结果表明 ,在水平阶营造柠条和披碱草 ,在生长初期 0～ 50 0 cm土层含水量可分为 3个明显的层次 ;在生长的第 4年随着灌草根系深扎 ,土壤水分过耗 ,出现明显的干土层 ,分布深度在 1 2 0～ 2 0 0 cm,厚度为 1 0 0 cm。在第 8年干土层扩大到 1 0 0～ 30 0 cm,厚度为 2 0 0 cm。第 1 4年土壤含水量有所回升 ,但幅度不大 ,同第 8年相比 ,仅提高 1 .5～ 2 .0个百分点。水平阶的柠条灌木林随着生长时间的延续 ,其水分贮量变化是否增加 ,仍有待继续研究。该区 0～ 50 0 cm多年土壤贮水量 ,在生长初期 ( 4月份 ) ,1 5年生柠条480 .1 5mm,1 2年生沙棘、山桃分别为 41 4.6mm和 385.4mm,在生长末期 ( 1 0月 ) ,柠条 498.31mm,沙棘 42 3.31 mm,山桃 ...

Synthesis and characterization of the titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands and their behavior in ethylene polymerization

A series of new titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands (3a-h and 6a-h), [PhN=CRCHC(CF3)O](2)TiCl2 (3a, R = Me; 3b, R = n-C5H11; 3c, R = i-Pr; 3d, R = Cy; 3e, R = t-Bu; 3f, R = CH=CHPh; 3g, R = Et; 3h, R = n-C11H23) and [PhN=C(CF3)CHC(R)O](2)TiCl2 (6a, R = Ph; 6b, R = n-C5H11; 6c, R = i-Pr; 6d, R = Cy; 6e, R = t-Bu; 6f, R = CH=CHPh; 6g, R = CHPh2; 6h, R = CF3) have been synthesized and characterized. X-ray crystal structures analyses suggest that complexes 3c-e and 6c-d all adopt a distorted octahedral geometry around the titanium center. Complexes 3c, 3d and 6c display a cis-configuration of the two chlorine atoms around the titanium center, while complex 6d shows a trans-configuration of the two chlorine atoms. Especially, the configurational isomers (cis and trans) of complex 3e were identified both in solution and in the solid state by NMR and X-ray analyses. With modified methylaluminoxane as a cocatalyst, all the complexes are active towards ethylene polymerization, and produce high molecular weight polymers.

Structure and electrochemical characteristics of TiV1.1Mn0.9Nix (x=0.1-0.7) alloys

The structure and electrochemical properties of TiV1.1Mn0.9Nix (x = 0.1-0.7) solid solution electrode alloys have been investigated. It is found that these alloys mainly consist of a solid solution phase with body centered cubic (bcc) structure and a C14 Laves secondary phase. The solid solution alloys show easy activation behavior, high temperature dischargeability, high discharge capacity and favorable high-rate dischargeability as a negative electrode material in Ni-MH battery. The maximum discharge capacity is 502 mAh g(-1) at 303 K when x = 0.4. Electrochemical impedance spectroscopy (EIS) test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with increasing Ni content.

Impedance study of (PEO)(10)LiClO4-Al2O3 composite polymer electrolyte with blocking electrodes

A composite solid polymer electrolyte (SPE) of (PEO)(10)LiClO4-Al2O3 was prepared and Pt and stainless steel(SS) blocking electrodes were used for an impedance study. It was found that the semicircle in the high frequency range and the straight line in the low frequency range depend upon different blocking electrodes and polarization potentials applied in the experiments. In the equivalent circuit. two constant phase elements (CPE) have been used instead of the pure geometrical and double layer capacitances. respectively. A theoretical line calculated from their estimated values has a good correlation with the experiment data. Moreover. the equivalent circuit also can be used to explain the impedance properties of Pt and stainless steel (SS) blocking electrodes both in the high and the low frequency ranges. (C) 2001 Elsevier Science Ltd. All rights reserved.

Chlorination and oxidation of aromatic polyamides .1. Synthesis and characterization of some aromatic polyamides

The synthesis is described of some aromatic polyamides based on unsubstituted, and methyl-, carboxy-, and sulfo-substituted diamines by interfacial polycondensation. Some of them are crosslinked and some of them contain heterocyclic aromatic rings. Their chemical structures are characterized by IR and C-13 solid-state NMR spectra and the spectra are interpreted. (C) 1996 John Wiley & Sons, Inc.

Epoxidation of styrene on Si/Ti/SiO2 catalysts prepared by chemical grafting

Titania-silica (Ti/SiO2) and silica-titania-silica (Si/Ti/SiO2) catalysts were:prepared by chemical grafting using TiCl4 and tetraethyl orthosilicate (TEOS) as precursors and SiO2 as support. The prepared catalysts were characterized by UV Raman and visible Raman spectroscopies, XRD and the epoxidation of styrene; Ti/SiO2: catalyst grafted with only titanium species is not very active for epoxidation using H2O2 (30%), but is active and-selective when one uses tert-butyl hydroperoxide (TBHP). The catalyst grafted at high temperatures shows better epoxide selectivity. Si/Ti/SiO2 catalyst, the titanium-silica grafted further with TEOS, is active and selective for the epoxidation of styrene using either dilute H2O2 or TBHP, possibly due to the fact that the grafting of Ti/SiO2 with TEOS modifies the coordination structure of titanium and makes the titanium sites of Si-O-Ti-O-Si species less hydrophilic. A characteristic band at 1085cm(-1) due to Ti-O-Si species is detected for the grafted catalysts by UV resonance Raman spectroscopy. Reaction between TiCl4 and SiO2 at high temperatures favors the formation of Ti-O-Si species. Better activity and selectivity to epoxide,is found for the catalysts with more Ti-O-Si species. It is assumed that the active sites are the highly isolated Ti-O-Si species. For Si/Ti/SiO2 catalyst, the gas phase O-2 can participate in the catalytic oxidation of styrene when H2O2 is present ana:ii causes the formation of benzaldehyde. (C) 2000 Elsevier Science B.V. All rights reserved.

Simulation chamber studies of the atmospheric degradation of naphthalene, 1-nitronaphthalene and phthaldialdehyde

A detailed series of simulation chamber experiments has been performed on the atmospheric degradation pathways of the primary air pollutant naphthalene and two of its photooxidation products, phthaldialdehyde and 1-nitronaphthalene. The measured yields of secondary organic aerosol (SOA) arising from the photooxidation of naphthalene varied from 6-20%, depending on the concentrations of naphthalene and nitrogen oxides as well as relative humidity. A range of carbonyls, nitro-compounds, phenols and carboxylic acids were identified among the gas- and particle-phase products. On-line analysis of the chemical composition of naphthalene SOA was performed using aerosol time-of-flight mass spectrometry (ATOFMS) for the first time. The results indicate that enhanced formation of carboxylic acids may contribute to the observed increase in SOA yields at higher relative humidity. The photolysis of phthaldialdehyde and 1-nitronaphthalene was investigated using natural light at the European Photoreactor (EUPHORE) in Valencia, Spain. The photolysis rate coefficients were measured directly and used to confirm that photolysis is the major atmospheric loss process for these compounds. For phthaldialdehyde, the main gas-phase products were phthalide and phthalic anhydride. SOA yields in the range 2-11% were observed, with phthalic acid and dihydroxyphthalic acid identified among the particle phase products. The photolysis of 1-nitronaphthalene yielded nitric oxide and a naphthoxy radical which reacted to form several products. SOA yields in the range 57-71% were observed, with 1,4-naphthoquinone, 1-naphthol and 1,4-naphthalenediol identified in the particle phase. On-line analysis of the SOA generated in an indoor chamber using ATOFMS provided evidence for the formation of high-molecular-weight products. Further investigations revealed that these products are oxygenated polycyclic compounds most likely produced from the dimerization of naphthoxy radicals. These results of this work indicate that naphthalene is a potentially large source of SOA in urban areas and should be included in atmospheric models. The kinetic and mechanistic information could be combined with existing literature data to produce an overall degradation mechanism for naphthalene suitable for inclusion in photochemical models that are used to predict the effect of emissions on air quality.

D-Amino acid peptide residualizing agents bearing N-hydroxysuccinimido- and maleimido-functional groups and their application for trastuzumab radioiodination.

INTRODUCTION: Proteins that undergo receptor-mediated endocytosis are subject to lysosomal degradation, requiring radioiodination methods that minimize loss of radioactivity from tumor cells after this process occurs. To accomplish this, we developed the residualizing radioiodination agent N(ϵ)-(3-[(*)I]iodobenzoyl)-Lys(5)-N(α)-maleimido-Gly(1)-D-GEEEK (Mal-D-GEEEK-[(*)I]IB), which enhanced tumor uptake but also increased kidney activity and necessitates generation of sulfhydryl moieties on the protein. The purpose of the current study was to synthesize and evaluate a new D-amino acid based agent that might avoid these potential problems. METHODS: N(α)-(3-iodobenzoyl)-(5-succinimidyloxycarbonyl)-D-EEEG (NHS-IB-D-EEEG), which contains 3 D-glutamates to provide negative charge and a N-hydroxysuccinimide function to permit conjugation to unmodified proteins, and the corresponding tin precursor were produced by solid phase peptide synthesis and subsequent conjugation with appropriate reagents. Radioiodination of the anti-HER2 antibody trastuzumab using NHS-IB-D-EEEG and Mal-D-GEEEK-IB was compared. Paired-label internalization assays on BT474 breast carcinoma cells and biodistribution studies in athymic mice bearing BT474M1 xenografts were performed to evaluate the two radioiodinated D-peptide trastuzumab conjugates. RESULTS: NHS-[(131)I]IB-D-EEEG was produced in 53.8%±13.4% and conjugated to trastuzumab in 39.5%±7.6% yield. Paired-label internalization assays with trastuzumab-NHS-[(131)I]IB-D-EEEG and trastuzumab-Mal-D-GEEEK-[(125)I]IB demonstrated similar intracellular trapping for both conjugates at 1h ((131)I, 84.4%±6.1%; (125)I, 88.6%±5.2%) through 24h ((131)I, 60.7%±6.8%; (125)I, 64.9%±6.9%). In the biodistribution experiment, tumor uptake peaked at 48 h (trastuzumab-NHS-[(131)I]IB-D-EEEG, 29.8%±3.6%ID/g; trastuzumab-Mal-D-GEEEK-[(125)I]IB, 45.3%±5.3%ID/g) and was significantly higher for (125)I at all time points. In general, normal tissue levels were lower for trastuzumab-NHS-[(131)I]IB-D-EEEG, with the differences being greatest in kidneys ((131)I, 2.2%±0.4%ID/g; (125)I, 16.9%±2.8%ID/g at 144 h). CONCLUSION: NHS-[(131)I]IB-D-EEEG warrants further evaluation as a residualizing radioiodination agent for labeling internalizing antibodies/fragments, particularly for applications where excessive renal accumulation could be problematic.