Quantum well intermixing for the fabrication of InGaAsN/GaAs lasers with pulsed anodic oxidation

Quantum well (QW) intermixing was carried out by post-growth rapid thermal annealing in InGaAsN/GaAs QW laser structures grown by solid-source molecular-beam epitaxy. The intensity and width of the photoluminescence peak showed a dependence on annealing temperature and time, and the maximum intensity and minimum linewidth were obtained after the wafer was annealed at 670 °C for 60 s. The peak luminescence energy blueshifted with increasing annealing time, although it plateaued at an annealing time that corresponded to that yielding the maximum luminescence intensity. The diffusion coefficient for indium was determined from a comparison between experimental data and modeling, but showed that QW intermixing alone was not sufficient to account for the relatively large blueshift after annealing. Defects related to the incorporation of nitrogen in the QW layer were responsible for the low photoluminescence efficiency in the as-grown samples and were annealed out during rapid thermal annealing. During annealing, nitrogen interstitials moved to vacancy sites within the QW and thus suppressed QW intermixing. After annealing wafers under conditions giving the maximum luminescence intensity, lasers were fabricated with pulsed anodic oxidation. © 2004 American Institute of Physics.published_or_final_versio

阿爾泰哈巴河群的沉積時代及其構造背景

Habahe Group mainly consists of elastic sediments, which widely distribute in the Chinese Altai and can provide important constraints on the tectonic evolution of the Central Asian Orogenic Belt (CAOB). However, there are different opinions about its deposition time and tectonic background. Previous studies suggested that the Habahe Group formed in Sinian to Mid-Ordovician or Mid- to Late Ordovician in a passive continental margin. On the other hand, recent geological investigations reveal a long lasting subduction-related setting in the Chinese Altai at least since Cambrian. The current geochronological study for detrital zircons from the Habahe Group reveals that the detrital zircons of individual samples, irrespective of their lithological and metamorphic differences, all show similar age patterns, with the early Paleozoic ( 206Pb/ 238U age = 463 ± 542Ma) grains predominating. The youngest detrital zircons from different samples display similar ages (ca. 470Ma), which may reflect the maximum deposition time of the Habahe Group. Dating of growth rim of detrital zircons from migmatite yielded a Mid-Devonian age (384 ± 6Ma), which was coeval with intrusion of Early to Mid-Devonian granitic plutons in the area and clearly indicates the minimum deposition time of the Hababe Group. Therefore, the deposition time of the Habahe Group can be constrained to be Mid-Ordovician to Early Devonian. Zircon U Pb dating results indicate that the detrital zircons of the Habahe Group are dominated by early Paleozoic grains, with small proportion formed in Precambrian. The early Paleozoic detrital zircons are mostly magmatic in origin, and their less rounded shapes indicate a limited transportation. The age and morphological characteristics of the detrital zircons are consistent with those of detrital zircons in active tectonic settings and indicate that the Chinese Altai was under an active continental margin environment during the Early Paleozoic. 北疆阿爾泰造山帶的哈巴河群變質碎屑巖分布廣泛,其沉積時代和構造環境對于認識中亞造山帶的演化歷史有重要意義。早期研究認為哈巴河群沉積于震旦紀—中奧陶世時期,形成于被動大陸邊緣構造環境。而最近有學者根據中亞造山帶的地質演化背景提出,阿爾泰形成于活動陸緣構造環境。對哈巴河群中碎屑鋯石的年代學研究表明,不同巖性或變質程度不同的樣品碎屑鋯石主要類群具有相似的年齡分布特征,其206Pb/238U 年齡主要介于463～542Ma 之間。在這些樣品中, 最年輕的碎屑鋯石年齡均集中于470Ma 左右,代表了碎屑沉積的時代下限。而哈巴河群混合巖樣品中碎屑鋯石增生邊形成于中泥盆世晚期（384±6Ma）,與侵入該群的早古生代花崗巖的年齡十分接近,大致反映了哈巴河群碎屑巖沉積時代的上限,因此哈巴河群的沉積時代應在早泥盆世—中奧陶世之間。鋯石的形態和內部結構特征顯示哈巴河群的年輕碎屑鋯石類群（463～542Ma）主要為巖漿鋯石,其磨圓度較差,而且在比例上遠高于前寒武紀碎屑鋯石。上述特點與活動大陸邊緣碎屑鋯石類群分布特征完全一致,反映阿爾泰在中奧陶世至早泥盆世可能處于活動大陸邊緣構造環境。postprin

Unique Carboniferous-Permian tectonic-metallogenic framework of Northern Xinjiang (NW China): Constraints for the tectonics of the southern Paleoasian Domain

The late Paleozoic tectonic-metallogenic framework of North Xinjiang of the southern Paleoasian Domain was characterized by a serious of Carboniferous-Permian events, including: (1) late Carboniferous-Permian Chinese Altay island arc and its metamorphism, granulite in the Chinese Altay, radiolarian chert and high-pressure/ultra-high-pressure metamorphism; (2) late Carboniferous-early Permian adakites, Alaskan-type mafic-ultramafic complexes, and calc-alkaline magmatism, together with porphyry copper deposits, which occurred in the North Xinjiang; and (3) late Carboniferous ophiolite and island arc volcanic rocks located in the Tian Shan. Combined with the facts that there was no typical foreland basin, no typical collisional-type granitoid, and there were large amount of strike-slip faulting, it is suggested that in the Carboniferous-early Permian North Xinjiang was characterized by the coexistence of compression-extension-strike-slip structures with active magmatism and metallogeny. These phenomena all indicate that there were active margins during the late Carboniferous-early Permian, leading to the notion that the complicated accretionary orogeny along the southern Paleoasian Domain may have lasted to the latest Carboniferous-Permian.新疆北部晚古生代独特的构造一成矿作用以发育大量石炭纪一二叠纪构造一成矿事件为特征, 其中包括: (l) 发育于晚石炭世一二叠世的阿尔泰岛弧及其变质事件、阿尔泰麻粒岩与基性杂岩、西南天山放射虫硅质岩和高压一超高压一低压麻拉岩相变质事件; (2 )北疆发育的石炭纪(一二叠世)埃达克岩一高镁安山岩一富N d 玄武质岩组合、阿拉斯加型基性一超基性杂岩和大量的与俯冲相关的钙碱性岩浆活动与斑岩型铜矿床成矿作用; (3) 天山晚石炭世晚期蛇绿岩与岛弧火山岩等。结合北疆地区相关的前陆盆地发育不明显、碰撞型花岗岩欠发育与大量发育平行造山带大型走滑构造等现象, 可以认为新疆北部在石炭纪一二叠纪挤压一伸展一走滑并存, 岩浆活动与成矿作用活跃。这些新进展表明新疆北部在晚石炭世一二叠纪可能仍存在活动陆缘, 因此, 古亚洲洋构造域南部复杂增生造山作用最后延至晚石炭世晚期一二叠纪。published_or_final_versio

Supersymmetric Decays of the Z' Boson

The decay of the Z' boson into supersymmetric particles is studied. We investigate how these supersymmetric modes affect the current limits from the Tevatron and project the expected sensitivities at the LHC. Employing three representative supersymmetric Z' models, namely, E_6, U(1)_{B-L}, and the sequential model, we show that the current limits of the Z' mass from the Tevatron could be reduced substantially due to the weakening of the branching ratio into leptonic pairs. The mass reach for the E_6 Z' bosons is about 1.3-1.5 TeV at the LHC-7 (1 fb^{-1}), about 2.5 - 2.6 TeV at the LHC-10 (10 fb^{-1}), and about 4.2 - 4.3 TeV at the LHC-14 (100 fb^{-1}). A similar mass reach for the U(1)_{B-L} Z' is also obtained. We also examine the potential of identifying various supersymmetric decay modes of the Z' boson because it may play a crucial role in the detailed dynamics of supersymmetry breaking.Comment: 30 pages, including 13 figures. improvements to the presentation and references adde

Cross-species gene expression analysis of species specific differences in the preclinical assessment of pharmaceutical compounds

Animals are frequently used as model systems for determination of safety and efficacy in pharmaceutical research and development. However, significant quantitative and qualitative differences exist between humans and the animal models used in research. This is as a result of genetic variation between human and the laboratory animal. Therefore the development of a system that would allow the assessment of all molecular differences between species after drug exposure would have a significant impact on drug evaluation for toxicity and efficacy. Here we describe a cross-species microarray methodology that identifies and selects orthologous probes after cross-species sequence comparison to develop an orthologous cross-species gene expression analysis tool. The assumptions made by the use of this orthologous gene expression strategy for cross-species extrapolation is that; conserved changes in gene expression equate to conserved pharmacodynamic endpoints. This assumption is supported by the fact that evolution and selection have maintained the structure and function of many biochemical pathways over time, resulting in the conservation of many important processes. We demonstrate this cross-species methodology by investigating species specific differences of the peroxisome proliferatoractivator receptor (PPAR) a response in rat and human

A seasonal cycle in the export of bottom water from the Weddell Sea

Dense water formed over the Antarctic continental shelf rapidly descends into the deep ocean where it spreads throughout the global ocean as Antarctic Bottom Water1, 2. The coldest and most voluminous component of this water mass is Weddell Sea bottom water1, 3, 4, 5, 6, 7. Here we present observations over eight years of the temperature and salinity stratification in the lowermost ocean southeast of the South Orkney Islands, marking the export of Weddell Sea bottom water. We observe a pronounced seasonal cycle in bottom temperatures, with a cold pulse in May/June and a warm one in October/November, but the timing of these phases varies each year. We detect the coldest bottom water in 1999 and 2002, whereas there was no cold phase in 2000. On the basis of current velocities and water mass characteristics, we infer that the pulses originate from the southwest Weddell Sea. We propose that the seasonal fluctuations of Weddell Sea bottom-water properties are governed by the seasonal cycle of the winds over the western margin of the Weddell Sea. Interannual fluctuations are linked to the variability of the wind-driven Weddell Sea gyre and hence to large-scale climate phenomena such as the Southern Annular Mode and El Niño/Southern Oscillation

CrossHybDetector: detection of cross-hybridization events in DNA microarray experiments

Background\ud DNA microarrays contain thousands of different probe sequences represented on their surface. These are designed in such a way that potential cross-hybridization reactions with non-target sequences are minimized. However, given the large number of probes, the occurrence of cross hybridization events cannot be excluded. This problem can dramatically affect the data quality and cause false positive/false negative results.\ud \ud Results\ud CrossHybDetector is a software package aimed at the identification of cross-hybridization events occurred during individual array hybridization, by using the probe sequences and the array intensity values. As output, the software provides the user with a list of array spots potentially 'corrupted' and their associated p-values calculated by Monte Carlo simulations. Graphical plots are also generated, which provide a visual and global overview of the quality of the microarray experiment with respect to cross-hybridization issues.\ud \ud Conclusion\ud CrossHybDetector is implemented as a package for the statistical computing environment R and is freely available under the LGPL license within the CRAN project

Light hadron, Charmonium(-like) and Bottomonium(-like) states

Hadron physics represents the study of strongly interacting matter in all its manifestations and the understanding of its properties and interactions. The interest on this field has been revitalized by the discovery of new light hadrons, charmonium- and bottomonium-like states. I review the most recent experimental results from different experiments.Comment: Presented at Lepton-Photon 2011, Mumbai, India; 21 pages, 18 figures; add more references; some correctio

Linearly polarized photoluminescence of InGaN quantum disks embedded in GaN nanorods

We have investigated the emission from InGaN/GaN quantum disks grown on the tip of GaN nanorods. The emission at 3.21 eV from the InGaN quantum disk doesn't show a Stark shift, and it is linearly polarized when excited perpendicular to the growth direction. The degree of linear polarization is about 39.3% due to the anisotropy of the nanostructures. In order to characterize a single nanostructure, the quantum disks were dispersed on a SiO2 substrate patterned with a metal reference grid. By rotating the excitation polarization angle from parallel to perpendicular relative to the nanorods, the variation of overall PL for the 3.21 eV peak was recorded and it clearly showed the degree of linear polarization (DLP) of 51.5%