ScAlMgO_4晶体的生长缺陷

采用提拉法生长出φ30 mm×55 mm的ScAlMgO4晶体。在晶体生长过程中有轻微的挥发,粉末X射线衍射分析表明:挥发物质为MgO单相。运用扫描电镜、光学显微镜以及高分辨X射线衍射仪对晶体中的包裹物、开裂、生长条纹和小角晶界缺陷进行了研究。结果表明:温度梯度和热应力是形成晶体中缺陷的主要原因。通过合理设计温场,控制固-液界面的形状及冷却过程的降温速率,可以提高晶体的完整性。

导模法和温度梯度法生长r面蓝宝石(英文)

r面(0112)蓝宝石晶体可用作制备非极性GaN薄膜的衬底。采用温度梯度法(temperature gradient technique,TGT)和导模法(edge-defined film-fed crystal growth,EFG)生长了质量良好的r面蓝宝石晶体。利用双晶衍射、光学显微镜、光谱仪观察和分析了晶体的结构和缺陷。结果表明:TGT法生长的r蓝宝石晶体的双晶摇摆曲线对称性好,半高宽值仅为18 rad.s,位错密度为4×103 cm-2,透过率达83%,晶体质量好。与TGT法相比,EFG法生长的r面蓝宝石晶体的结构完整性较差,位错密度为5×105 cm-2,透过率仅为75%。但是EFG法具有晶体生长速度快,后期加工成本低的优点。

Influence of carbon on the thermoluminescence and optically stimulated luminescence of α -Al2O3:C crystals

alpha-Al2O3:C crystal shows excellent thermoluminescence (TL) and optically stimulated luminescence (OSL) properties but the real role carbon plays in this crystal is still not clearly understood so far. In this work, alpha-Al2O3:C crystal doping with different amounts of carbon were grown by the temperature gradient technique, and TL and OSL properties of as-grown crystals were investigated. Additionally, a mechanism was proposed to explain the role of carbon in forming the TL and OSL properties of alpha-Al2O3:C. TL and OSL intensities of as-grown crystals increase with the increasing amount of carbon doping in the crystal, but no shift is found in the glow peak location at 465 K. As the amount of carbon doping in the crystals decreases, OSL decay rate becomes faster. With the increase in heating rate, the integral TL response of as-grown crystals decreases and glow peak shifts to higher temperatures. TL response decrease rate increases with the increasing amount of carbon doping in the crystals. All the TL and OSL response curves of as-grown crystals show linear-sublinear-saturation characteristic, and OSL dose response exhibits higher sensitivity and wider linear dose range than that of TL. The crystal doping with 5000 ppm carbon shows the best dosimetric properties. Carbon plays the role of a dopant in alpha-Al2O3:C crystal and four-valent carbon anions replace the two-valent anions of oxygen during the crystal growth process, and large amounts of oxygen vacancies were formed, which corresponds to the high absorption coefficient of F and F+ centers in the crystals.

α-Al_2O_3:C晶体的热释光和光释光特性

以高纯α-Al2O3和石墨为原料,采用温梯法生长了α-Al2O3:C晶体,使用RisΦTL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al2O3:C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al2O3:C晶体的光释光衰减曲线由快衰减和慢衰减两个部分组成,随着辐照剂量的增加,快衰减部分衰减速率变化不大,而慢衰减部分衰减速率加快.在5×10-6—10Gy剂量范围内,α-Al2O3:C晶体的热释光剂量响应呈现良好的线性关系,30Gy时达到饱和;光释光剂量响应在5×10-6—60Gy剂量范围内呈现良好的线性关系,100Gy时达到饱和.与热释光相比,光释光剂量响应具有更高的灵敏度和更宽的线性剂量响应范围.

Growth of alpha-Al2O3:C crystal with highly sensitive optically stimulated luminescence

In this work. an alpha-Al2O3:C crystal was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as the raw materials. The optical, optically stimulated luminescence (OSL) properties and dosimetric characteristics of as-grown crystal were investigated. As-grown alpha-Al2O3:C crystal shows strong absorption band at 205, 230 and 256 nm. Three-dimensional thermoluminescence (TL) emission spectrum of the crystal shows a single emission peak at similar to 415 nm. The OSL decay curve can be fitted to two exponentials, the faster component and the slower component. The OSL response of the crystal shows a linear-sublinear-saturation characteristic. As-grown alpha-Al2O3:C crystal shows excellent linearity in the dose range from 5 x 10(-6) to 50 Gy. For doses higher than the saturation dose (100 Gy). the OSL sensitivity decreases as the dose increases. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Study of Al2O3/MgF2 HR coatings at 355 nm

With the present work we tried to study the effective methods to improve the laser-induced damage threshold (LIDT) and reflectance of HR coatings at 355 nm. The work presented in this paper wits part of an ongoing study about vacuum annealing. It was dedicated to study the effects Of Vacuum annealing with different temperature gradients on the structure, optical properties and laser-induced damage threshold (LIDT) of 355nm Al2O3/MgF2HR coatings. A number of samples were prepared by electron beam evaporation using the same deposition process with an optimal deposition temperature of 280 degrees C. After deposition, samples were annealed in the coating chamber for 3 h with different temperature gradients. Morphologies of the samples were observed by Leica-DMRXE. Microscope, Structure of the samples had been characterized by X-ray diffraction (XRD). Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer, The LIDT of the samples was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. It was found that the temperature gradient of vacuum annealing had significant effects on the morphology, structure, absorption, and LIDT of the samples, (c) 2005 Elsevier Ltd. All rights reserved.

Thermodynamic damage mechanism of transparent films caused by a low-power laser

A new model for analyzing the laser-induced damage process is provided. In many damage pits, the melted residue can been found. This is evidence of the phase change of materials. Therefore the phase change of materials is incorporated into the mechanical damage mechanism of films. Three sequential stages are discussed: no phase change, liquid phase change, and gas phase change. To study the damage mechanism and process, two kinds of stress have been considered: thermal stress and deformation stress. The former is caused by the temperature gradient and the latter is caused by high-pressure drive deformation. The theory described can determine the size of the damage pit. (c) 2006 Optical Society of America.

黑龙江嘉荫地区古新世孢粉植物群及古植被、古气候研究

植物是环境变化的重要指示物之一。晚白垩至早第三纪时期，全球生态系统发生了剧烈变化，研究这一时期植物对了解地质历史时期环境变化趋势, 认识和保护当今环境有重要意义。我国黑龙江省嘉荫县有这一时期的地层发育，其中乌云煤矿和白山头是主要的露头剖面。前人曾从地质时代、孢粉及植物化石角度对这两个剖面进行过研究，但是仍有部分问题尚存争议。在本项工作中，我们对两个剖面的孢粉样品进行了系统采样，部分孢粉类型同时在光镜和电镜下进行了拍照。我们还对存在争议的这两个剖面的地质时代进行了讨论。同时，首次用共存分析法对这两个剖面的在沉积时期的气候进行了整体及分段的定量重建。另外，我们结合中其它地点的气候重建工作对不同时期的纬度温度梯度进行了研究。 乌云煤矿和白山头两个乌云组剖面的古新世孢粉植物群的研究结果表明：乌云煤矿孢粉植物群主要是与榛属（Corylus），桤木属（Alnus），桦木属（Betula），榆属（Ulmus）及松属（Pinus）有亲缘关系的植物；白山头剖面的孢粉植物类型与乌云煤矿基本一致，但是其中针叶类植物的花粉所占比重较大。 根据乌云煤矿与白山头剖面的孢粉类型在地层中的分布，以及与其它古新世地层的对比，我们认为乌云煤矿与白山头含孢粉段的地质时代为古新世。 用共存分析法得到乌云组古新世气候参数有两组。孢粉类型的共存结果为：年均温14.8-14.9℃，年降水量816-1389mm；植物化石类型的共存结果为：年均温16.3-16.8℃, 年降水：1124-1623mm。对乌云煤矿与白山头两个剖面孢粉带中的孢粉类型的气候参数分别进行共存，结果表明，除乌云煤矿孢粉第三带到第四带外，乌云地区的年均温在整个沉积时期均呈上升趋势；年均降水量的变化趋势与年均温基本一致。 根据从古新世到现代不同地点气候定量重建的年均温参数，我们计算得到了不同时期纬度温度梯度变化的值：<0.1℃/古纬度（古新世）、 0.1℃/古纬度（始新世）、0.45℃/纬度（中新世）、0.55℃/纬度（上新世）。结合当今全球的平均温度梯度值（0.7℃/纬度），我们得出纬度温度梯度的值从古新世以来呈不断上升的趋势。这一结果显示65Ma 以来赤道与极地间的温度差异逐渐增大，同时也提示了全球温度可能呈下降趋势。

Plankton Community Succession in Artificial Systems Subjected to Cyanobacterial Blooms Removal using Chitosan-Modified Soils

Using artificial systems to simulate natural lake environments with cyanobacterial blooms, we investigated plankton community succession by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting and morphological method. With this approach, we explored potential ecological effects of a newly developed cyanobacterial blooms removal method using chitosan-modified soils. Results of PCR-DGGE and morphological identification showed that plankton communities in the four test systems were nearly identical at the beginning of the experiment. After applying the newly developed and standard removal methods, there was a shift in community composition, but neither chemical conditions nor plankton succession were significantly affected by the cyanobacteria removal process. The planted Vallisneria natans successfully recovered after cyanobacteria removal, whereas that in the box without removal process did not. Additionally, canonical correspondence analysis indicated that other than for zooplankton abundance, total phosphorus was the most important environmental predictor of planktonic composition. The present study and others suggest that dealing with cyanobacteria removal using chitosan-modified soils can play an important role in controlling cyanobacterial blooms in eutrophicated freshwater systems.

Genetic diversity of plankton community as depicted by PCR-DGGE fingerprinting and its relation to morphological composition and environmental factors in lake donghu

To collect information about the genetic diversity of the plankton community and to study how plankton respond to environmental conditions, plankton samples were collected from five stations representing different trophic levels in a shallow, eutrophic lake (Lake Donghu), and investigated by PCR-DGGE fingerprinting. A total of 100 bands (61 of 16S rDNA bands and 39 of 18S rDNA bands) were detected. The DGGE bands unique to any single station accounted for 38% of the total bands, whereas common bands detected at all five stations accounted for only 11%. Using UPGMA clustering and MDS ordination of DGGE fingerprints, stations I and II were found to initially group together into one cluster, which was later joined by station V. Stations III and IV were isolated into two separate groups of one station each. Some differences in grouping relationships were found when analysis was completed on the basis of chemical characteristics and morphological composition, with zooplankton composition showing the greatest variability. However, the most similar stations (I and II) were always initially grouped into one cluster. Moreover, stations that exhibited the same or similar trophic level (stations III and IV), but different concentrations of heavy metals, were further differentiated by the DGGE method. Results of the present study indicated that PCR-DGGE fingerprinting was more sensitive than the traditional methods, as other studies suggested. Additionally, PCR-DGGE appears to be more appropriate for diversity characterization of the plankton community, as it is more canonical, systematic, and effective. Most importantly, fingerprinting results are more convenient for the comparative analyses between different studies. Therefore, the use of the described fingerprinting analysis may provide an operable and sensitive biomonitoring approach to identify critical, and potentially negative, stress within an aquatic ecosystem.

Operational Optimization of GaN Thin Film Growth Employing Numerical Simulation in a Showerhead MOCVD Reactor

A detailed reaction-tran sport model was studied in a showerhead reactor for metal organic chemical vapor deposition of GaN film by using computational fluid dynamics simulation. It was found that flat flow lines without swirl are crucial to improve the uniformity of the film growth, and thin temperature gradient above the suscptor can increase the film deposition rate. By above-mentioned research, we can employ higher h (the distance from the susceptor to the inlet), P (operational pressure) and the rate of susceptor rotation to improve the film growth.

Thermal induced facet destructive feature of quantum cascade lasers

We present a study on the facet damage profile of quantum cascade lasers (QCLs). Conspicuous cascade half-loop damage strips on front facet are observed when QCLs catastrophically failed. Due to the large difference on thermal conductivities between active region and the substrate, dominant heat is compulsively driven to the substrate. Abundant heat accumulation and dissipation on substrate build large temperature gradient and thermal lattice mismatch. Thermal-induced stress due to sequential mismatch leads to the occurrence of the multistep damages on front facet. Good agreement is achieved between the observed locations of damaged strips and the calculated results.

毛细管电泳电化学检测联用的应用研究

本论文探讨了毛细管电泳电化学检测器的应用。主要包括以下六个方面的内容：1．毛细管电泳与电化学检测联用测定别嗓呤醇及其代谢产物氧化镖吟醇。该方法简单、快速、灵敏。并且应用于加标尿样的分析时也取得了令人满意的结果。2．采用毛细管电泳一安培检测来定量测定中草药中的活性组分姜黄素，用自制的磷酸三丁酷树脂萃取柱来预处理样品，同时实现对姜黄素的浓缩。经毛细管电泳分离后，姜黄素可以用碳纤维电极检测。3．毛细管电泳电化学发光对尿液中的丙环定的检测。用离子交换柱尽可能除去尿中的离子的干扰，电化学发光试剂印比淀钉采用柱后加入的方式，具有三级胺结构的丙环定可被定量检测到。4．溶胶一凝胶一碳复合材料电极作为毛细管电泳安培检测器的表征。我们报道了这种电极的制作，探讨了不同尺寸的电极在毛细管电泳中的应用。当电极直径100μm，一些分析指标如：检测限、线性范围以及重现性都较好，可以做为安培检测器与毛细管电泳联用。5，毛细管电泳脉冲安培检测生物胺。分离并定量检测了四种生物胺，腐胺、尸胺、亚精胺及精胺。并用该方法测定了牛奶中的生物胺。该方法比已报道的毛细管电泳间接紫外检测的检测限低，比气相色谱及液相色谱需样品体积小，不需要烦琐的衍生步骤。6．溶胶一凝胶一碳复合材料电极作为电泳芯片的安培检测器。我们报道了一种简单，重现性好的芯片上的盘电极的制作方法。由于该安培检测器最大的特点就是稳定性好，重现性高所以我们在其上又沉积了一层铜，以扩大该芯片的应用范围。用集成了该安培检测器的芯片，我们分别测定了肾上腺素和葡萄糖。

ITO导电玻璃和PDMS微芯片毛细管电泳电化学发光检测的研究

微全分析系统是目前很前沿的研究领域，尽管现在还没有真正意义的微全分析系统出现，但它代表了分析科学的发展趋势。本文主要研究了ITO导电玻璃和PDMS微芯片毛细管电泳和电化学发光检测方法。微芯片毛细管电泳对与其联用的检测器有相当高的要求，一些传统的检测方法很难适应于微芯片毛细管电泳。电化学发光检测是一种新兴的检测技术，在化学、生物、医学诊断以及免疫分析中展现出良好的应用前景。如何实现和完善微芯片毛细管电泳与电化学发光检测联用技术是本论文的重点。我们采用聚二甲基硅氧烷（poly（dimethylsiloxone），简称PDMS）和玻璃作为芯片材料，以锢锡氧化物（indium桩n oXide，简称工T0）导电玻璃为工作电极设计了一种集成化的微芯片毛细管电泳电化学发光检测器。其中，芯片的底片由工TO导电玻璃经光刻、化学腐蚀等方法处理后得到。ITO是一种透明的导电材料，作为工作电极集成到芯片的底片上，PDMS层与芯片底片采用可逆键合的方式键合，大大简化了操作并提高了电化学发光信号的采集效率。我们采用脯氨酸作为被测物对检测器进行了表征。在实验过程中，微芯片毛细管电泳及工T0工作电极都表现出良好的稳定性。我们还提出了电化学和电化学发光同时检测技术，应用于微芯片毛细管电泳和常规毛细管电泳。在这种电化学和电化学发光双检测模式中，三联吡陡钉（Ru（bpy）32+既作为电化学发光检测所需的发光试剂与被分析物反应生成激发态的Ru（bpy）32+＊产生电化学发光信号，又在电极表面平行催化电化学反应得到增强的电流响应，提高电化学检测的灵敏度。电化学信号与电化学发光信号同时产生并分别记录，从而实现了电化学和电化学发光同时检测。我们将这种检测技术与芯片或常规毛细管电泳结合，以多巴胺及三种药物分子山蓖若碱、氧氟沙星和利多卡因作为被测物对其进行了表征。这种同时检测方法与其它多检测模式相比更为简单、方便，比单一的电化学或电化学发光检测可以获得更多的被分析物信息，扩大单一检测方式的应用范围。