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71.
通过采集乌鲁木齐大泉湖火区土壤样及实验室测定,研究了火区土壤理化性质与重金属Hg,As,Cu,Pb,Cr,Zn,Ni空间分布特征。结果表明:温度正常区土壤温度随采样深度增加的幅度较温度异常区小;温度正常、温度异常区土壤有机质含量随深度的增加均减少,温度正常区I,II,III,IV层土壤有机质含量大于温度异常区相应土层有机质含量;温度异常区土壤层I重金属Cu,Pb,Cr,Zn,Ni含量均小于温度正常区土壤层I相应重金属含量,II层则有增加的趋势并大于温度正常区相应土层重金属含量;温度正常区、温度异常区土壤Hg,As,Cu,Ni重金属含量随深度变化幅度及波动幅度较小,而温度异常区土壤Pb,Cr,Zn重金属含量随深度变化波动幅度较温度正常区大;火区热效应、地形、土壤及气象因子是影响土壤重金属分布的主要原因。土壤典型重金属砷形态分析表明:残留态砷含量最高,水溶态砷含量最低;水溶态砷在火区取样区域内I,II,III,IV土壤层区域富集特征与各层土壤碳酸钙富集特征趋于一致;温度正常区土壤残留态砷、铁形砷含量随深度变化的趋势与土壤碳酸钙含量随深度变化趋势一致;温度异常区残留态砷含量随深度增加波动趋势与土壤有机质含量波动趋势有较强关联性;温度正常区、温度异常区均值水溶态砷含量基本稳定,表明其与温度、土壤特性等无明显相关性。 相似文献
72.
目的观察沙利度胺(TLD)和三氧化二砷(As2O3)对急性髓系白血病(AML)细胞分泌血管内皮生长因子(VEGF)和P-糖蛋白(P-gp)的影响。方法收集22例AML患者[完全缓解(CR)患者15例(CR组)和未缓解患者7例(非CR组)]的骨髓液,用Ficoll淋巴细胞分离液分离出骨髓单个核细胞(BMMNC),按实验设计分为a、d、f、h组:a组加BMMNC 800μL;d组加BMMNC 800μL+TLD 100μL(TLD终质量浓度300μg.mL-1);f组加BMMNC 800μL+As2O3100μL(As2O3终浓度25μmol.L-1);h组加BMMNC 800μL+TLD 100μL+As2O3100μL(TLD终质量浓度300μg.mL-1,As2O3终浓度25μmol.L-1)。均于37℃、5%CO2、饱和湿度条件下传代培养,取对数生长期细胞,各组均培养72 h。用双抗体夹心酶联免疫法(ELISA)法检测细胞培养上清液中VEGF的含量,用流式细胞术(FCM)检测细胞膜上MDR1/P-gp的表达率。结果非CR组细胞培养上清中的VEGF含量、细胞膜上P-gp的表达水平均显著高于CR组(P〈0.01);非CR患者P-gp表达率与VEGF含量具有一定的正相关性[r=0.646(a组),r=0.695(d组),r=0.645(f组),r=0.650(h组);均P〈0.05]。结论对于初治AML患者,化疗前后VEGF的含量与细胞膜表面P-gp表达的联合检测可作为监测病情和判断预后的指标。 相似文献
73.
Barringer JL Bonin JL Deluca MJ Romagna T Cenno K Alebus M Kratzer T Hirst B 《The Science of the total environment》2007,379(1):56-74
We examined potential sources and the temporal dynamics of arsenic (As) in the slightly alkaline waters of the Wallkill River, northwestern New Jersey, where violations of water-quality standards have occurred. The study design included synoptic sampling of stream water and bed sediments in tributaries and the mainstem, hyporheic-zone/ground water on the mainstem, and seasonal and diurnal sampling of water at selected mainstem sites. The river valley is bordered by gneiss and granite highlands and shale lowlands and underlain by glacial deposits over faulted dolomites and the Franklin Marble. Ore bodies in the Marble, which have been mined for rare Zn ore minerals, also contain As minerals. Tributaries, which drain predominantly forested and agricultural land, contributed relatively little As to the river. The highest concentrations of As (up to 34 mug/L) emanated from the outlet of man-made Lake Mohawk at the river's headwaters; these inputs varied substantially with season--high during warm months, low during cold months, apparently because of biological activity in the lake. Dissolved As concentrations were lower (3.3 microg/L) in river water than those in ground water discharging into the riverbed (22 microg/L) near the now-closed Franklin Mine. High total As concentrations (100-190 mg/kg) on the <0.63 microm fraction of bed sediments near the mine apparently result from sorption of the As in the ground-water discharge as well as from the As minerals in the streambed. As concentrations in river water were diluted during high stream flow in fall, winter and spring, and concentrated during low flow in summer. In unfiltered samples from a wetlands site, diurnal cycles in trace-element concentrations occurred; As concentrations appeared to peak during late afternoon as pH increased, but Fe, Mn, and Zn concentrations peaked shortly after midnight. The temporal variability of As and its presence at elevated concentrations in ground water and sediments as well as streamwater demonstrate the importance of (1) sampling a variety of media and (2) determining the time scales of As variability to fully characterize its passage through a river system. 相似文献
74.
The martensite start temperature (Ms), the martensite austenite re‐transformation start temperature (As) and the re‐transformation finish temperature (Af) of six high alloyed Cr‐Mn‐Ni steels with varying Ni and Mn contents in the wrought and as‐cast state were studied. The aim of this investigation is the development of the relationships between the Ms, As, Af, T0 temperatures and the chemical composition of a new type of Cr‐Mn‐Ni steels. The investigations show that the Ms, As and Af temperatures decrease with increasing nickel and manganese contents. The Af temperature depends on the amount of martensite. Regression equations for the transformation temperatures are given. The experimental results are based on dilatometer tests and microstructure investigations. 相似文献
75.
K. L. Fry C. P. Kuo C. A. Larsen R. M. Cohen G. B. Stringfellow A. Melas 《Journal of Electronic Materials》1986,15(2):91-96
We report the organometallic vapor phase epitaxial (OMVPE) growth of InP and Ga0.47In0.53As using a new organometallic indium source, ethyldimethylindium (EDMIn), rather than the traditional sources triethylindium
(TEIn) or trimethylindium (TMIn). EDMIn is a liquid at room temperature and its vapor pressure at 17° C was found to be 0.85
Torr using thermal decomposition experiments. The growth results using EDMIn were compared to those using TMIn in the same
atmospheric pressure reactor. For InP, use of EDMIn resulted in a high growth efficiency of 1.3 × 104 μm/ mole, which was independent of the growth temperature and comparable to the growth efficiency obtained with TMIn. The
high growth efficiency is consistent with the observation of no visible parasitic gas phase reactions upstream of the substrate.
The 4K photoluminescence (PL) spectra consist of a peak due to bound excitons and an impurity related peak 38 meV lower in
energy. This impurity peak is ascribed to conduction band to acceptor transitions from carbon, due to the decreasing relative
intensity of this peak with increasing V/III ratio. The relative intensity of the C impurity peak decreases by five times
when the growth temperature is increased from 575 to 675° C, with a corresponding increase in the room temperature electron
mobility from 725 to 3875 cm2/ Vs. For GalnAs lattice-matched to InP, use of EDMIn also resulted in a temperatureindependent high growth efficiency of
1.0 x 104 μm/mole, indicating negligible parasitic reactions with AsH3. The In distribution coefficient was nearly constant at a value of 0.9, however the run to run composition variation was
slightly higher for EDMIn than for TMIn. The 4K PL showed donor-acceptor pair transitions due to C and Zn. The C impurity
peak intensity decreased dramatically with increasing growth temperature, accompanied by an increase in the room temperature
electron mobility to 5200 cm2/Vs. Overall, the growth of both InP and GalnAs using EDMIn was qualitatively similar to that using TMIn, although the room
temperature electron mobilities were lower for the new source than for our highest purity bottle of TMIn. 相似文献
76.
77.
D. Chandra M. W. Goodwin M. C. Chen J. A. Dodge 《Journal of Electronic Materials》1993,22(8):1033-1037
Arsenic diffusion coefficients were measured in HgCdTe at 350°C within the single phase field. The diffusion coefficients
displayed a strong dependence on Hg pressure, increasing by more than 1×103 with decreasing Hg pressure. These measurements were performed by growing As doped HgCdTe films by Hg-rich liquid phase epitaxy
on undoped or In-doped base layers, where the growth temperature ranged between 330 and 350°C. Use of these low growth temperatures
under Hg-rich conditions permitted attainment of virtual step profiles in As, with negligible diffusion into the base layers.
These provided ideal starting points for subsequent diffusion anneals. Diffusion of arsenic under selected low Hg pressures
was then employed to tune the positioning of the p/n junction for double layer heterojunction films, by locating it ahead
of the heterointerface. Formation of valence band barriers to the photogenerated minority carriers across the junction could
thus be avoided. When on the other hand, diffusion experiments were performed under Hg saturated conditions, the heterointerface
moved at a faster rate than the p/n junction, leading to the formation of valence band barriers. 相似文献
78.
79.
M. Jaime-Vasquez M. Martinka R. N. Jacobs M. Groenert 《Journal of Electronic Materials》2006,35(6):1455-1460
A detailed analysis of the As-exposed Si (112) and subsequent Te exposure was performed. X-ray photoelectron spectroscopy
shows that the Te- and As-exposed Si (112) surface had 70% As and 27% Te coverage, respectively. Direct surface coverage measurement
with ion scattering spectroscopy (ISS) shows that the Si (111) surface is completely covered by As, and that of the Si (112)
had about 78% and 20% coverage of As and Te, respectively. Finally, using ISS shadowing effects, it was found that the Te
atoms were positioned mainly on the step edges. 相似文献
80.
Oxygen has always been considered to be a major contaminant in the organo-metallic vapor phase epitaxy (OMVPE) of Al
x
Ga1−x
As. Oxygen incorporation has been invoked as a contributor to low luminescence efficiency, dopant compensation and degradation
of surface morphology among other deleterious effects. This study presents quantitative measurements of oxygen concentration
in nominally high purity Al
x
Ga1−x
As. The oxygen concentration was measured as a function of alloy composition, growth temperature, andV/III ratio. Quantitative secondary ion mass spectroscopy (SIMS) measurements were used to determine the oxygen content as well
as the carbon concentration in the film. The oxygen concentration increases with decreased growth temperature and V/III ratio
while increasing superlinearly with Al content in the epitaxial layer. 相似文献