Surface Disorder of GaN Irradiated by Highly Charged Arq+-Ions

Surface damage of gallium nitride films irradiated by Arq+ (6 ≤ q ≤ 16) ions at room temperature is studied by the atomic force microscopy. It is found that when charge state exceeds a threshold value, significant swelling was turned into obvious erosion in the irradiated region. The surface change of the irradiated region strongly depends on the charge state and ion fluence. On the other hand, surface change is less dependent on the kinetic energy nearly in the present experimental range (120 keV≤ Ek ≤ 220 keV). For q ≤ 14, surface of the irradiated region iscovered with an amorphous layer, rough and bulgy. A step-up appears between the irradiated and un-irradiated region. Moreover, the step height and the surface roughness are functions of the ion dose and charge state...

Surface erosion of GaN bombarded by highly charged Pb-208(q+)-Ions

Surface change of gallium nitride specimens after bombardment by highly charged Pbq+-ions (q = 25, 35) at room temperature is studied by means of atomic force microscopy. The experimental results reveal that the surface of GaN specimens is significantly etched and erased. An unambiguous step-up is observed. The erosion depth not only strongly depends on the charge state of ions, but also is related to the incident angle of Pbq+-ions and the ion dose. The erosion depth of the specimens in 60 incidence (tilted incidence) is significantly deeper than that of the normal incidence. The erosion behaviour of specimens has little dependence on the kinetic energy of ion (E-k = 360, 700 keV). On the other hand, surface roughness of the irradiated area is obviously decreased due to erosion compared with the un-irradiated area. A fiat terrace is formed.

基于JUPITER的uClinux移植及其应用实例；uClinux Porting Based on JUPITER and example of Application

介绍了嵌入式处理器JUPITER,详细分析了uClinux嵌入式操作系统的特点。给出了基于JUPITER和uClinux的嵌入式网关。通过嵌入式网关实例详细说明了在JUPITER上的移植uClinux的方法,以及uClinux下应用程序的开发。

富铬酵母对实验性糖尿病小鼠模型的治疗

目的：三价铬作为葡萄糖耐量因子的有效活性成分，具有改善糖尿病人的糖代谢和脂代谢的作用，因此补充三价铬是糖尿病治疗中的有效的营养措施，富铬酵母是目前向人体提供三价铬的有效途径，并且葡萄糖耐量因子可以提高靶组织对胰岛素的敏感性而不促进胰腺的胰岛素分泌，为治疗糖尿病提供了一种新方法。 方法：（1）取昆明种小鼠，分对照与实验组，适应性喂养后实验组小鼠按40mg/kg体重注射STZ，对照组注射相应体积柠檬酸缓冲液,连续注射5天，3天后测血糖值，取血糖值≥11.1mmol/L为成功模型。成模小鼠分为两组，一组灌胃富铬酵母悬液4周，另一组灌胃蒸馏水4周，测血糖值。（2）取昆明种小鼠，分对照与实验组，适应性喂养后实验组小鼠按200mg/kg体重注射STZ，对照组注射相应体积柠檬酸缓冲液，3d后测血糖，取血糖值≥11.1mmol/L为成功模型。成模小鼠分为两组，一组灌胃富铬酵母悬液4周，另一组灌胃蒸馏水4周，测血糖值。（3）取C57BL/6J断乳小鼠，随机分为正常饲料组和高脂饲料组，分别用相应饲料喂养3 周。高脂饲料组又分为高脂饲料对照组和高脂饲料实验组。第3 周末, 高脂饲料实验组腹腔内按100mg/kg体重一次性腹腔注射STZ；正常饲料组和高脂饲料对照组腹腔注射相应体积的无菌柠檬酸缓冲液。继续喂养4 周。小鼠以第7周末血糖为准，≥11.1mmol/L为成功模型。成模小鼠分为2组，1组每日灌胃富铬酵母悬液，另一组灌服相应体积的去离子水，4周后，测血糖值。 结果：对Ⅰ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖明显低于对照组血糖（p<0.05），4周后显著低于(p<0.01)；对Ⅱ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖明显低于对照组血糖（p<0.05），3周后显著低于(p<0.01)；对肥胖引起的Ⅱ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖显 著低于对照组血糖(p<0.01)，且血清胰岛素浓度之间没有明显差异。 结论：富铬酵母具有明显的降血糖作用，且不刺激胰岛素分泌

The Early Diagenetic Formation of Organic Sulfur in the Sediments of Mangrove Lake, Bermuda

Due to a low mineral content, the sapropelic sediments depositing in Mangrove Lake, Bermuda, provide an excellent opportunity to explore for possible additions of sulfur to organic matter during the early stages of diagenesis. We evaluated early diagenetic organic sulfur transformations by monitoring the concentrations and stable isotopic compositions of a number of inorganic and organic sulfur pools, thereby accounting for all of the sulfur in the sediments. We have identified and quantified the following sulfur pools: porewater sulfate, porewater sulfide, elemental sulfur, pyrite sulfur, hydrolyzable organic sulfur (HYOS), chromium-reducible organic sulfur (CROS), and nonchromium-reducible organic sulfur (Non-CROS). Of the organic sulfur pools, the Non-CROS pool is by far the largest, followed by CROS, and finally HYOS. By 60 cm depth these pools contribute, respectively, to 85, 7.9, and 3.6% of the total solid phase sulfur. The HYOS pool is probably of biological origin and shows no interaction with the sulfur compounds produced during diagenesis. By contrast, CROS is produced, most likely, from the diagenetic addition of polysulfides to functionalized lipids in the upper, H2S-poor, elemental sulfur-rich, region of the sediment. A portion of this sulfur pool is unstable and decomposes on contact with the H2S-rich porewaters. The portion of CROS that remains in the sulfidic waters appears to readily exchange sulfur isotopes with H2S. While some of the Non-CROS pool is of biological origin, some is also formed by the diagenetic addition of sulfur to organic compounds in the upper H2S-poor region of the sediment. By contrast with CROS, Non-CROS is not diagenetically active in the H2S-rich porewaters. Overall, somewhere between 27 and 53 % of the organic sulfur buried in Mangrove Lake sediments is of diagenetic origin, with the remaining organic sulfur derived from biosynthesis. We extrapolate our Mangrove Lake results and calculate that in typical coastal marine sediments between 11 and 29 μmol g−1 of organic sulfur will form during early diagenesis, of which 2–5 μmol g−1 will be chromium reducible.

Automated voltammetric system for shipboard determination of metal speciation in sea water

An automated and semi-intelligent voltammetric system is described for trace metal analysis. The system consists of a voltammeter interfaced with a personal computer, a sample changer, 2 peristaltic pumps, a motor burette and a hanging mercury drop electrode. The system carries out fully automatically approximately 5 metal determinations per hour (including at least 3 repetitive scans and calibration by standard addition) at trace levels encountered in clean sea water. The computer program decides what level of standard addition to use and evaluates the data prior to switching to the next sample. Alternatively, the system can be used to carry out complexing ligand titration with copper whilst recording the labile copper concentration; in this mode up to 8 full titrations are carried out per day. Depth profiles for chromium speciation in the Mediterranean Sea and a profile for copper complexing ligand concentrations in the North Atlantic Ocean measured on board-ship with the system are presented. The chromium speciation was determined using a new method to differentiate between Cr(III) and Cr(VI) utilizing adsorption of Cr(III) on silica particles.

不同土壤对Cr吸附的动力学特征

该文采用振荡平衡法比较了来自中国15个省区16种土壤对Cr(VI)的吸附及其动力学特性,并探讨了土壤pH值、阳离子交换量、黏粒含量和有机质对Cr(VI)吸附及其动力学参数的影响。结果表明:具有较低土壤pH值和较高物理黏粒含量的土壤对Cr(VI)具有较大的表观吸附量,而土壤阳离子交换量和有机质因素对土壤Cr(VI)的表观吸附量影响较小。酸性土壤对Cr(VI)吸附能力较强,可以采用一级动力学方程和抛物线方程描述Cr(VI)在酸性土壤中的动力学行为,且土壤的表观吸附速率和平衡时的吸附量与土壤的pH值呈显著(p<0.05)负相关关系,而与物理黏粒含量呈显著(p<0.01)正相关关系;而碱性土壤对Cr(VI)吸附能力较小,很难用动力学方程描述其吸附动力学特性。可见,土壤pH值不仅影响土壤对Cr(VI)的表观吸附量,并且对Cr(VI)表观吸附动力学特征产生了较大影响。

重金属对小麦根干重和在不同培肥条件下对土壤铵态氮的影响

笔者的研究目的在于了解土壤重金属污染对小麦根部生长发育的影响以及在不同培肥条件下土壤重金属的生物活性的变化情况。通过盆栽试验研究了重金属铬、镉和铅三种重金属对小麦根重的影响,利用室内培养试验研究了氮磷化肥、氮磷化肥+低秸、氮磷化肥+中秸、氮磷化肥+高秸、氮磷肥+厩肥、氮磷肥+低秸(休闲田)以及无肥对照区等7种不同培肥条件下重金属铬、镉和铅对土壤铵态氮含量的影响。研究结果表明,重金属铬对小麦的根重影响较大,这3种重金属的复合污染对小麦根重的影响要比单因素条件下的影响要明显;在不同肥料条件下重金属对土壤环境内的铵态氮的影响作用存在差异,氮磷肥料条件下,重金属对土壤铵态氮的抑制作用明显增强;氮磷+低秸(休闲田)条件下,重金属铬、镉与铅对土壤铵态氮的抑制性显著降低,铵态氮总量基本影响较小。通过研究表明,不同培肥条件能够影响土壤重金属的生物活性,可以通过控制土壤培肥条件达到降低土壤重金属生物活性,减轻对重金属污染土壤的程度。

Rectangular AgIn(WO4)(2) nanotubes: A promising photoelectric material

Rectangular AgIn(WO4)(2) nanotubes with a diameter range of 80 to 120 nm and length up to 2 mu m have been synthesized by a hydrothermal method. These nanotubes exhibit interesting white light emissions when using 320 nm as the excitation wavelength. A photocatalytic reaction for water decomposition to evolve K, was performed under UV irradiation, and the rate of H, evolution is nearly seven times that of the sample prepared by a solid-state reaction, which shows much higher photocatalytic activities compared with their bulk counterparts.

Electronic and mechanical properties of 5d transition metal mononitrides via first principles

The electronic and mechanical properties of 5d transition metal mononitrides from LaN to AuN are systematically investigated by use of the density-functional theory. For each nitride, Six Structures are considered, i.e., rocksalt, zinc blende, CsCl, wurtzite, NiAs and WC structures. Among the considered structures, rocksalt structure is the most stable for LaN, HfN and ALIN, WC structure for TaN, NiAs structure for WN, wurtzite structure for ReN, OsN, IrN and PtN. The most stable Structure for each nitride is mechanically stable. The formation enthalpy increases from LaN to AuN.

Ab initio study on the physical properties of CoN3 and RhN3 with skutterudite structure

The elastic and electronic properties of hypothetical CoN3 and RhN3 with cubic skutterudite structure were studied by first principles calculations based on density functional theory. By choosing different initial geometries, two local minima or modifications were located on the potential energy surface, termed as modifications I and II. Both compounds are mechanically stable. For each compound, modification I is lower in energy than II. Thermodynamically stable phases can be achieved by applying pressures. Modification II is lower in energy than I at above 50 GPa for both compounds.

Structural stability and electronic properties of Co2N, Rh2N and Ir2N

The structural stability and electronic properties of Co2N, Rh2N and Ir2N were Studied by using the first principles based on the density functional theory. Two Structures were considered for each nitride, orthorhombic Pnnm phase and cubic Pa (3) over bar phase. The results show that they are all mechanically stable. Co2N in both phases are thermodynamically stable due to the negative formation energy, while the remaining two compounds are thermodynamically unstable.