Evolution of InAs branches in InAs/GaAs nanowire heterostructures

Branched nanowireheterostructures of InAs∕GaAs were observed during Au-assisted growth of InAs on GaAsnanowires. The evolution of these branches has been determined through detailed electron microscopy characterization with the following sequence: (1) in the initial stage of InAsgrowth, the Au droplet is observed to slide down the side of the GaAsnanowire, (2) the downward movement of Aunanoparticle later terminates when the nanoparticle encounters InAsgrowing radially on the GaAsnanowire sidewalls, and (3) with further supply of In and As vapor reactants, the Aunanoparticles assist the formation of InAs branches with a well-defined orientation relationship with GaAs∕InAs core/shell stems. We anticipate that these observations advance the understanding of the kink formation in axial nanowireheterostructures.The Australian Research Council is acknowledged for the financial support of this project. One of the authors M.P. acknowledges the support of an International Postgraduate Research Scholarship

Multiscale boundary element method for Laplace equation

In this paper, the multiscale boundary element method is applied to solve the Laplace equation numerically. The new technique is the coupling of the multiscale technique and the boundary element method in order to speed up the computation. A numerical example is given to illustrate the efficiency of the proposed method. The computed numerical solutions by the proposed method will be compared with the solutions obtained by the conventional boundary element method with the help of Fortran compiler. By comparison, results show that the new technique use less iterations to arrive at the solutions

Política de álgebra universal I, acesso, e desigualdade: Resultados de uma pesquisa nacional

Many in the US view algebra as a gatekeeper to advanced study of mathematics, and increasing enrollment in algebra courses as a strategy to address unequal access to educational opportunity. As a result, universal enrollment policies, which require all students to complete Algebra I by grade 8 or 9, have garnered attention in school districts or states. Based on a view that school districts are the primary implementers of state and national policy in the US, this study surveyed a nationally representative sample of districts to investigate the prevalence of such policies and their relationship to algebra enrollment. Districts reported substantial increases in Algebra I enrollments in eighth grade, although ninth grade remains the most common year students enroll. Only 26% of districts reported having universal enrollment policies; in these districts, linear regression indicated that an association with higher eighth grade Algebra I enrollment was moderated by poverty level (measured by FRL). As a result, universal policies, while decreasing within-district disparities, may increase disparities between districts. These disparities may be explained by maximally maintained inequality (Raftery Hout, 1993) and effectively maintained inequality theories (Lucas, 2001), which posit that more affluent groups take deliberate action to perpetuate inequalities.Muchas personas en EEUU ven la álgebra como un portero para el estudio de matemáticas avanzadas y más inscripciones en cursos de álgebra como una estrategia para abordar el acceso desigual a las oportunidades educativas. La álgebra I en le nivel 8 o 9 se ha prestado atención a los distritos o estados escolares. En base a una visión de que los distritos escolares son los principales implementadores de la política estadual y nacional en los Estados Unidos, este estudio investigó una muestra de distritos para investigar la prevalencia de dichas políticas y su relación con la matrícula de álgebra. Los distritos reportaron aumentos sustanciales en las inscripciones de Álgebra I en le nivel 8, aunque la matrícula de le nivel 9 es más común. Sólo el 26% de los distritos relataron tener políticas universales de matrícula y regresión lineal indicaron que una asociación con inscripción superior en álgebra I de le nivel 8 fue moderada por el nivel de pobreza en esos distritos. Como resultado, al disminuir las disparidades dentro del distrito, las políticas universales pueden aumentar las disparidades entre los distritos. Esas disparidades pueden ser explicadas por la desigualdad máxima mantenida (Raftery Hout, 1993) y teorías de desigualdad efectivamente mantenidas (Lucas, 2001), que argumentan que grupos más afluentes toman acciones deliberadas para perpetuar las desigualdades.Muchas pessoas em EUA ven a álgebra como um portero para o estudo de matemáticas avançadas e mais inscrições em cursos de álgebra como uma estratégia para abordar o acesso desigual às oportunidades educativas. A álgebra I en le nivel 8 o 9 se ha prestado atenção a distritos ou estados escolares. Na base de uma visão de que os distritos escolares são os principais implementadores da política estadual e nacional nos Estados Unidos, este estudo investigou uma amostra de distritos para investigar a prevalência de políticas e sua relação com a matrícula de álgebra. Os distritos reportaram aumentos substanciales em inscrições de Álgebra I en le nivel 8, embora a matrícula do nível 9 es más común. Apenas os 26% dos distritos relataram ter políticas universais de matrícula e regresso lineal indicando que é uma associação com inscrição superior em álgebra I do nível 8 foi moderada pelo nível de propriedade de seus imigrantes. Como resultado, al disminuir as disparidades dentro do distrito, as políticas universais podem aumentar as disparidades entre os distritos. Estudo das expectativas para a desigualdade máxima da manutenção (Raftery Hout, 1993) e teorias de desigualdad efetivamente mantenidas (Lucas, 2001), que argumentan que grupos mais afluentes toman acciones deliberadas para perpetuar las desigualdades

Floral biology of Schismatoglottis baangongensis (Araceae) in West Sarawak, Borneo

The flowering mechanism, visiting insect activities, reproductive system, and floral scent composition of Schismatoglottis baangongensis a Northwest Bornean locally endemic limestone-restricted protogynous mesophyte were investigated. Anthesis started at dawn and lasted ca 29 h. Fruit set for open pollination (93 %) and restricted access pollination (88 %) were high. Colocasiomyia (Diptera, Drosophilidae) and Cycreon (Coleoptera, Hydrophilidae) were the main pollinators. Colocasiomyia flies present in much higher numbers than Cycreon beetles individually carried significantly less pollen load. Chaloenus (Chrysomelidae, Galerucinae) was inadvertent pollinators, and Atheta (Coleoptera, Staphylinidae) passive visitors. Pollen transferal between dissimilar insect genera (Colocasiomyia and Chaloenus) is reported for the first time. Low pollen/ovule ratio of S. baangongensis indicated an efficient pollination mechanism. Ester compound class floral odours, especially the dominant compounds 3-butenoic acid, 3-methyl-, methyl ester, were decisive in attracting pollinators. The spadix appendix of S. baangongensis was the main olfactory body although the spathe was detected to release an additional N-containing compound, an indole. An increase in the total amount of floral scent from the pistillate flower zone during pistillate phase of anthesis from Period I (06:00–08:00 h) to Period II (08:00–10:00 h) was postulated to detain insects in the lower chamber of the inflorescence

Structural characteristics of GaSb∕GaAs nanowire heterostructures grown by metal-organic chemical vapor deposition

Highly lattice mismatched (7.8%) GaAs∕GaSbnanowireheterostructures were grown by metal-organic chemical vapor deposition and their detailed structural characteristics were determined by electron microscopy. The facts that (i) no defects have been found in GaSb and its interfaces with GaAs and (ii) the lattice mismatch between GaSb∕GaAs was fully relaxed suggest that the growth of GaSbnanowires is purely governed by the thermodynamics. The authors believe that the low growth rate of GaSbnanowires leads to the equilibrium growth

ApoE Receptor 2 Regulates Synapse and Dendritic Spine Formation

Apolipoprotein E receptor 2 (ApoEr2) is a postsynaptic protein involved in long-term potentiation (LTP), learning, and memory through unknown mechanisms. We examined the biological effects of ApoEr2 on synapse and dendritic spine formation-processes critical for learning and memory.In a heterologous co-culture synapse assay, overexpression of ApoEr2 in COS7 cells significantly increased colocalization with synaptophysin in primary hippocampal neurons, suggesting that ApoEr2 promotes interaction with presynaptic structures. In primary neuronal cultures, overexpression of ApoEr2 increased dendritic spine density. Consistent with our in vitro findings, ApoEr2 knockout mice had decreased dendritic spine density in cortical layers II/III at 1 month of age. We also tested whether the interaction between ApoEr2 and its cytoplasmic adaptor proteins, specifically X11α and PSD-95, affected synapse and dendritic spine formation. X11α decreased cell surface levels of ApoEr2 along with synapse and dendritic spine density. In contrast, PSD-95 increased cell surface levels of ApoEr2 as well as synapse and dendritic spine density.These results suggest that ApoEr2 plays important roles in structure and function of CNS synapses and dendritic spines, and that these roles are modulated by cytoplasmic adaptor proteins X11α and PSD-95

First order polarization tensor approximation using multivariate polynomial interpolation method via least square minimization technique

This paper proposes a new numerical approach useful in dealing with nearly singular integrals, specifically, the integral of the first order polarization tensor (PT). Polarization tensor represents the integral equations in an asymptotic series, and it can also define the boundary value problem of a partial differential equation (PDE). Since PT has been widely used and implemented in many engineering areas, particularly electric and magnetic field areas, it is crucial to estimate the first order PT solutions accurately. In this regard, the computation of PT for different geometry types is basically from the quadratic interpolation and the multivariate polynomial fitting using the least square method. The numerical calculation of the integral of the singular integral operator, ∗ which is one of the primary integral processes before we obtained the solution of PT uses the multivariate polynomial fitting. This paper aims to provide an accurate numerical solution for first order PT for different geometry types, particularly sphere and ellipsoid geometry. The numerical results of the proposed method are shown together with the comparison of its analytical solutions. From the results obtained, the numerical solution of first order PT shows higher accuracy and higher convergence as the number of surface elements increases. The numerical and the analytical solution of first order PT for a sphere is discussed and represented in graphical form. The utilization of two different software types throughout this study is Netgen Mesh Generator and MATLAB to aid the numerical computation process. The simulation and the numerical examples verify the effectiveness and efficiency of the proposed method

Evidence of blocking effect on carrier trapping process by necking region in very narrow AlGaAs/GaAs V-grooved quantum wire structure

Transient band-gaprenormalization (BGR) effects are investigated in AlGaAs/GaAs V-grooved quantum structures. The temperature-dependent transient BGR effects in the sidewall quantum well (SQWL) provide direct evidence of the existence of the blocking effect by the necking region barrier on the carrier trapping process. These effects provide a useful method to show the existence of the necking region, particularly for very thin SQWL structures. The temperature-dependent lifetimes of the SQWL and quantum wire (QWR) provide further proof of the carrier trapping process from the SQWL to the QWR.This work was supported in part by a grant from the Academic Frontier Promotion Project of Monbusho, Shanghai ‘‘QiMingXing’’ Fund No. 98QA14004, the State Key Program for Basic Research of China, and the AusAID through IDP Education Australia under Australia-China Institutional Links Program

Temperature dependence of photoluminescence from single core-shell GaAs–AlGaAs nanowires

Temperature-dependent polarized microphotoluminescencemeasurements of single GaAs∕AlGaAs core-shell nanowires are used to probe their electronic states. The low-temperature emission from these wires is strongly enhanced compared with that observed in bare GaAsnanowires and is strongly polarized, reflecting the dielectric mismatch between the nanowire and the surrounding air. The temperature-dependentband gap of the nanowires is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 120K, with an activation energy of 17meV reflecting the presence of nonradiative defects.This work was supported by the University of Cincinnati. Australian authors gratefully acknowledge the financial support from the Australian Research Council

High Affinity Human Antibody Fragments to Dengue Virus Non-Structural Protein 3

Dengue virus is the most prevalent mosquito transmitted infectious disease in humans and is responsible for febrile disease such as dengue fever, dengue hemorrhagic fever and dengue shock syndrome. Dengue non-structural protein 3 (NS3) is an essential, multifunctional, viral enzyme with two distinct domains; a protease domain required for processing of the viral polyprotein, and a helicase domain required for replication of the viral genome. In this study ten unique human antibody fragments (Fab) that specifically bind dengue NS3 were isolated from a diverse library of Fab clones using phage display technology. The binding site of one of these antibodies, Fab 3F8, has been precisely mapped to the third α-helix within subdomain III of the helicase domain (amino acids 526–531). The antibody inhibits the helicase activity of NS3 in biochemical assays and reduces DENV replication in human embryonic kidney cells. The antibody is a valuable tool for studying dengue replication mechanisms