Ultrathin compound semiconductor on insulator layers for high-performance nanoscale transistors

Over the past several years, the inherent scaling limitations of silicon (Si) electron devices have fuelled the exploration of alternative semiconductors, with high carrier mobility, to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been actively studied: such devices combine the high mobility of III-V semiconductors and the well established, low-cost processing of Si technology. This integration, however, presents significant challenges. Conventionally, heteroepitaxial growth of complex multilayers on Si has been explored-but besides complexity, high defect densities and junction leakage currents present limitations in this approach. Motivated by this challenge, here we use an epitaxial transfer method for the integration of ultrathin layers of single-crystal InAs on Si/SiO(2) substrates. As a parallel with silicon-on-insulator (SOI) technology, we use 'XOI' to represent our compound semiconductor-on-insulator platform. Through experiments and simulation, the electrical properties of InAs XOI transistors are explored, elucidating the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Importantly, a high-quality InAs/dielectric interface is obtained by the use of a novel thermally grown interfacial InAsO(x) layer (~1?nm thick). The fabricated field-effect transistors exhibit a peak transconductance of ~1.6?mS?μm(-1) at a drain-source voltage of 0.5?V, with an on/off current ratio of greater than 10,000.     

薄膜充气梁模态分析方法及特性研究

薄膜结构模态特性是研究其动力性能的基础,本文首先根据柔性薄膜结构受力特点,考虑大变形、初始预应力刚化几何非线性效应,通过小杨氏模量法找形分析得到平衡形态,继承其位形与初始平衡应力,然后采用分块兰索斯法对薄膜充气梁模态进行数值计算分析,考察了影响薄膜充气梁模态特性的主要因素：压力、薄膜厚度、管径（长细比）。提出薄膜结构湿模态概念,考虑外流场对薄膜充气梁的耦合作用,分别采用拟密度法和流固耦合法计算了薄膜充气梁的湿模态,通过与干模态的比较验证了外流场对薄膜充气梁的耦合效应。     

Functional characterisation of naturally occurring mutations in human melanopsin

Melanopsin is a blue light-sensitive opsin photopigment involved in a range of non-image forming behaviours, including circadian photoentrainment and the pupil light response. Many naturally occurring genetic variants exist within the human melanopsin gene (OPN4), yet it remains unclear how these variants affect melanopsin protein function and downstream physiological responses to light. Here, we have used bioinformatic analysis and in vitro expression systems to determine the functional phenotypes of missense human OPN4 variants. From 1242 human OPN4 variants collated in the NCBI Short Genetic Variation database (dbSNP), we identified 96 that lead to non-synonymous amino acid substitutions. These 96 missense mutations were screened using sequence alignment and comparative approaches to select 16 potentially deleterious variants for functional characterisation using calcium imaging of melanopsin-driven light responses in HEK293T cells. We identify several previously uncharacterised OPN4 mutations with altered functional properties, including attenuated or abolished light responses, as well as variants demonstrating abnormal response kinetics. These data provide valuable insight into the structure–function relationships of human melanopsin, including several key functional residues of the melanopsin protein. The identification of melanopsin variants with significantly altered function may serve to detect individuals with disrupted melanopsin-based light perception, and potentially highlight those at increased risk of sleep disturbance, circadian dysfunction, and visual abnormalities.     

Integrated genotype calling and association analysis of SNPs, common copy number polymorphisms and rare CNVs

Accurate and complete measurement of single nucleotide (SNP) and copy number (CNV) variants, both common and rare, will be required to understand the role of genetic variation in disease. We present Birdsuite, a four-stage analytical framework instantiated in software for deriving integrated and mutually consistent copy number and SNP genotypes. The method sequentially assigns copy number across regions of common copy number polymorphisms (CNPs), calls genotypes of SNPs, identifies rare CNVs via a hidden Markov model (HMM), and generates an integrated sequence and copy number genotype at every locus (for example, including genotypes such as A-null, AAB and BBB in addition to AA, AB and BB calls). Such genotypes more accurately depict the underlying sequence of each individual, reducing the rate of apparent mendelian inconsistencies. The Birdsuite software is applied here to data from the Affymetrix SNP 6.0 array. Additionally, we describe a method, implemented in PLINK, to utilize these combined SNP and CNV genotypes for association testing with a phenotype.     

TULA-2, a novel histidine phosphatase, regulates bone remodeling by modulating osteoclast function

Bone is a dynamic tissue that depends on the intricate relationship between protein tyrosine kinases (PTK) and protein tyrosine phosphatases (PTP) for maintaining homeostasis. PTKs and PTPs act like molecular on and off switches and help modulate differentiation and the attachment of osteoclasts to bone matrix regulating bone resorption. The protein T cell ubiquitin ligand-2 (TULA-2), which is abundantly expressed in osteoclasts, is a novel histidine phosphatase. Our results show that of the two family members, only TULA-2 is expressed in osteoclasts and that its expression is sustained throughout the course of osteoclast differentiation, suggesting that TULA-2 may play a role during early as well late stages of osteoclast differentiation. Skeletal analysis of mice that do not express TULA or TULA-2 proteins (DKO mice) revealed that there was a decrease in bone volume due to increased osteoclast numbers and function. Furthermore, in vitro experiments indicated that bone marrow precursor cells from DKO mice have an increased potential to form osteoclasts. At the molecular level, the absence of TULA-2 in osteoclasts results in increased Syk phosphorylation at the Y352 and Y525/526 residues and activation of phospholipase C gamma 2 (PLCγ2) upon engagement of immune-receptor-tyrosine-based-activation-motif (ITAM)—mediated signaling. Furthermore, expression of a phosphatase-dead TULA-2 leads to increased osteoclast function. Taken together, these results suggest that TULA-2 negatively regulates osteoclast differentiation and function.     

A preliminary survey of the insect fauna of the Hajar Mountain Range,Oman

The Hajar Mountain Range of Northern Oman is an important centre of species endemism, and of biogeographical interest as a crossroads between the Afrotropical and Palaearctic regions. Despite this, the invertebrate fauna of the region is largely unknown, with very little dedicated research or surveys having been undertaken until now. Here we present the invertebrate species collected and identified from five different survey locations within the Hajar Mountains. This preliminary checklist contains 296 records, of which 36 are new records for Oman. Our surveys also discovered two new species of ant: Lepisiota omanensis collected from Jebel Qahwan Reserve and at the base of Jebel Akhdar, and Anochetus annetteae from Hibra Village in the Nakhl Region.     

Effects of exotic grasses on soil seed banks in southeastern Arizona grasslands

Species richness in Madrean mixed-grass prairies dominated by native or exotic species in southeastern Arizona was characterized at the community and point scales using ten 1-m 2 quadrats nested within each of eight 1000-m 2 plots. In the 1000-m 2 plots average richness was significantly higher in oak savanna (OS, 121.0 species) than in exotic grassland on mesa tops (EMT, 52.0 species), whereas native grassland on mesa slopes (NMS, 92.5 species) and native grassland on mesa tops (NMT, 77.0 species) did not differ significantly in richness from OS or EMT. When richness was partitioned by life form, EMT was notably poorer than other community types in species of perennial grasses, perennial herbs, and summer annuals. In the 1-m 2 quadrats, OS (21.2 species), NMS (20.9 species), and NMT (20.7 species) were significantly richer than EMT (5.9 species). Cover in 1-m 2 plots was significantly higher in EMT than in NMT, NMS, or OS. Species richness at the point scale showed a unimodal relation to canopy cover, with cover accounting for 30% of the variation in number of species in 1-m2 quadrats. Competitive exclusion and allelopathy have perhaps limited species richness at the point scale in exotic grassland. There was no evidence of a species-pool effect between point and community scales, but such an effect between community and landscape scales was supported. Madrean mixed-grass prairies are landscapes with high species richness in comparison to other grassland types in North America, providing a large pool of potential colonizing species at the community scale. Beta-diversity (between communities) within the landscape of the Appleton-Whittell Research Ranch was consequently high despite a relative lack of habitat diversity.     

Comparison of desert valvata snail growth at three densities of the invasive New Zealand mudsnail

Invasive species are of concern to natural resource managers and conservation biologists. The New Zealand mudsnail ( Potamopyrgus antipodarum ) has invaded many freshwaters of the western United States with unknown consequences on the native benthic invertebrate fauna. We conducted a laboratory investigation to determine if mudsnails affected the growth of the desert valvata snail ( Valvata utahensis ), a species native to the Snake River in southern Idaho. Results indicated that increasing densities of mudsnails limited the growth rate and absolute growth of the desert valvata. We suggest that absolute growth is a better metric than growth rate for comparing snail species and assessing interactions between them.     

Life history of the cui-ui, Chasmistes cujus Cope, in Pyramid Lake, Nevada: a review

The cui - ui, Chasmistes cujus Cope, a member of the sucker family and endemic to Pyramid Lake, Nevada, is listed as endangered by the U.S. Fish and Wildlife Service. Cui - ui was once a major source of sustenance for native Americans, who have inhabited the Lahontan region for at least 11,000 years. The Northern Paiutes developed sophisticated fishing technology to harvest this resource. The original distribution of cui - ui was the ancient Lake Lahontan complex, but as a result of climatic changes it was restricted to the Pyramid – Winnemucca – Truckee system by the turn of the 20th century. Transbasin water diversions (1905 to present) have resulted in further restrictions of habitat. The species is now limited to Pyramid Lake and the lower Truckee River. Reproduction is from hatcheries as well as limited natural reproduction. Females produce more than 40,000 2 - mm eggs per year. The normal development is described from the unfertilized egg through 912 hours post - hatching, when the fry are actively feeding and approaching adult body form. The unusual feature of adult cui - ui morphology is the relatively large ventro - terminal mouth, with thin and obscurely papillose lips. Cui - ui grow slowly and may live 18 years or possibly much longer; females generally live longer and attain a greater size than males. The highest adult mortality probably occurs during spawning runs. At this time they are vulnerable to predation, stress, and sometimes environmental degradation. The highest larval mortality probably occurs from predation when they are planted or migrate into the lake. The trophic ecology of the species is poorly understood, but they are known to ingest algae and zooplankton. Spawning behavior is documented. At present, natural reproduction is probably still the limiting factor for the cui - ui population. Cui - ui composed less than one percent of the total fish in Pyramid Lake during 1975–1977. During 1982 the largest cui - ui spawning run (13,000) in recent years occurred. The activity of cui - ui in the lake closely resembles that of the Tahoe sucker being most active during the spawning season each spring. Cui - ui inhabit the inshore - benthic zone and the pelagic waters of Pyramid Lake (