Preferred growth direction of III-V nanowires on differently oriented Si substrates

One of the nanowire (NW) characteristics is its preferred elongation direction. Here, we investigated the impact of Si substrate crystal orientation on the growth direction of GaAs NWs. We first studied the self-catalyzed GaAs NW growth on Si (111) and Si (001) substrates. SEM observations show GaAs NWs on Si (001) are grown along four directions without preference on one or some of them. This non-preferential NW growth on Si (001) is morphologically in contrast to the extensively reported vertical preferred GaAs NW growth on Si (111) substrates. We propose a model based on the initial condition of an ideal Ga droplet formation on Si substrates and the surface free energy calculation which takes into account the dangling bond surface density for different facets. This model provides further understanding of the different preferences in the growth of GaAs NWs along selected directions depending on the Si substrate orientation. To verify the prevalence of the model, NWs were grown on Si (311) substrates. The results are in good agreement with the three-dimensional mapping of surface free energy by our model. This general model can also be applied to predictions of NW preferred growth directions by the vapor-liquid-solid growth mode on other group IV and III–V substrates

Modeling of Polymer Clay Nanocomposite for a Multiscale Approach

The mechanical property enhancement of polymer reinforced with nano-thin clay platelets (of high aspect ratio) is associated with a high polymer-filler interfacial area per unit volume. The ideal case of fully separated (exfoliated) platelets is generally difficult to achieve in practice: a typical nanocomposite also contains multilayer stacks of intercalated platelets. Here we use numerical modelling to investigate how the platelet properties affect the overall mechanical properties. The configuration of platelets is modelled using a statistical interpretation of the Representative Volume Element (RVE) approach, in which an ensemble of "sample" heterogeneous material is generated (with periodic boundary conditions). A simple Monte Carlo algorithm is used to place non-intersecting platelets in the RVE according to a specified set of statistical distributions. The effective stiffness of the platelet-matrix system is determined by measuring the stress (using standard Finite Element analysis) produced as a result of applying a small deformation to the boundaries, and averaging over the entire statistical ensemble. In this work we determine the way in which the platelet properties (curvature, filling fraction, stiffness, aspect ratio) and the number of layers in the stack affect the overall stiffness enhancement of the nanocomposite. Thus, we bridge the gap between behaviour on the macroscopic scale with that on the scale of the nano-reinforcement, forming part of a multi-scale modelling framework.Comment: 39 pages, 19 figure

Mutations in FKBP10 Cause Recessive Osteogenesis Imperfecta and Bruck Syndrome

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue characterized by bone fragility and alteration in synthesis and posttranslational modification of type I collagen. Autosomal dominant OI is caused by mutations in the genes (COL1A1 or COL1A2) encoding the chains of type I collagen. Bruck syndrome is a recessive disorder featuring congenital contractures in addition to bone fragility; Bruck syndrome type 2 is caused by mutations in PLOD2 encoding collagen lysyl hydroxylase, whereas Bruck syndrome type 1 has been mapped to chromosome 17, with evidence suggesting region 17p12, but the gene has remained elusive so far. Recently, the molecular spectrum of OI has been expanded with the description of the basis of a unique posttranslational modification of type I procollagen, that is, 3-prolyl-hydroxylation. Three proteins, cartilage-associated protein (CRTAP), prolyl-3-hydroxylase-1 (P3H1, encoded by the LEPRE1 gene), and the prolyl cis-trans isomerase cyclophilin-B (PPIB), form a complex that is required for fibrillar collagen 3-prolyl-hydroxylation, and mutations in each gene have been shown to cause recessive forms of OI. Since then, an additional putative collagen chaperone complex, composed of FKBP10 (also known as FKBP65) and SERPINH1 (also known as HSP47), also has been shown to be mutated in recessive OI. Here we describe five families with OI-like bone fragility in association with congenital contractures who all had FKBP10 mutations. Therefore, we conclude that FKBP10 mutations are a cause of recessive osteogenesis imperfecta and Bruck syndrome, possibly Bruck syndrome Type 1 since the location on chromosome 17 has not been definitely localized. © 2011 American Society for Bone and Mineral Research

Synthesis of anthraquinone based electroactive polymers: A critical review

Conducting polymers or synthetic monomers have revolutionized the world and are at the heart of scientific research having a scope of vast diverse applications in many technological fields. The conducting and redox polymers have been investigated as energy storage systems because of their better sustainability, ease of synthesis, and environmental compatibility. Owing to the conducting properties of quinones, they gain too much importance among the researchers. Keeping in view the importance and sustainability of conducting polymers, for the first time, this study compiles a detailed overview of synthetic approaches followed by investigations on electrochemical properties and future directions. This study critically examines the synthetic process of simple monomers, substituted monomers, and polymers of anthraquinone (AQ) under the classification of low- and high-molecular-weight AQ–based derivatives, their working principles, and their electrochemical applications, which enable us to explore their novel possible application in automotive, solar cell devices, aircraft aileron, and biomedical equipment. Irrefutably, we confirm that high-molecular-weight polymeric AQ compounds are best in comparison with low-molecular-weight AQ monomers because they have pre-eminent properties over monomeric systems. Because of the significant properties of AQ, polymeric systems are high demanding and have emerged as a hot topic among the researchers these days. In the current scenario, this study is of immense importance because it identifies and discusses the right and sustainable combination and paves the way to utilize these novel materials in different technologies

Flow batteries for energy management : novel algebraic modelling approaches to properly assess their value

Redox Flow Battery (RFB) systems are promising technologies for the multi-hour electrical energy storage that will be necessary for on-demand electricity supply based on wind and solar power. Deriving maximum value from a RFB requires optimisation of both the system design and its operation. In this work three novel algebraic modelling approaches are introduced to represent RFB operation more accurately while maintaining quick optimisation times. First the typical linear programming (LP) optimisation problem is re-posed in terms of current-density rather than power, allowing voltaic losses to be expressed as a quadratic function (QP). Secondly, it is then shown that the current-density framework supports a novel constraint for the avoidance of high cell voltage that may damage the stack. Thirdly, for the first time a binary variable (MIQP) to describe active/idle states is introduced. This allows coulombic leakage and pumping losses to be modelled as fixed terms without constantly draining the RFB, and it allows for the optimisation of pump rating in a VRFB. In a day-ahead energy management case study, it is found that the QP optimisation predicts an additional 19 % annual revenue when compared to the LP optimisation. This capture of the true flexibility of the RFB operation allows its full value to be assessed, and therefore advances the case for their deployment within the energy system. Furthermore, the formulations developed are not only applicable to RFBs but to the scheduling of other battery systems, particularly Li-ion, and balance of plant optimisation, such as the sizing of inverters and climate control systems in the context of parasitic losses

Майер Василий (Вильгельм) Евгеньевич : к 85-летию со дня рождения : биоблиогр. указ.

To explore the effect of neodymium (Nd) on the deformation mechanisms of Mg–Zn alloys,texture and lattice strain developments of hot‐rolled Mg–Zn (Z1) and Mg–Zn–Nd (ZN10) alloyswere investigated using in situ synchrotron diffraction and compared with elasto‐viscoplastic selfconsistentsimulation under tensile loading. The Nd‐containing ZN10 alloys show much weakertexture after hot rolling than the Nd‐free Z1 alloy. To investigate the influence of the initial textureon the texture and lattice strain evolution, the tensile tests were carried out in the rolling andtransverse direction. During tension, the {002} texture components develop fast in Z1, whichwas not seen for ZN10. On the other hand, fiber // loading direction (LD) developed in bothalloys, although it was faster in ZN10 than in Z1. Lattice strain investigation showed that //LD‐oriented grains experienced plastic deformation first during tension, which can be related tobasal slip activity. This was more apparent for ZN10 than for Z1. The simulation results show that theprismatic slip plays a vital role in the plastic deformation of Z1 directly from the beginning. In contrast,ZN10 plastic deformation starts with dominant basal slip but during deformation prismatic slipbecomes increasingly important

Variable structure control with chattering reduction of a generalized T-S model

In this paper, a fuzzy logic controller (FLC) based variable structure control (VSC) is presented. The main objective is to obtain an improved performance of highly non-linear unstable systems. New functions for chattering reduction and error convergence without sacrificing invariant properties are proposed. The main feature of the proposed method is that the switching function is added as an additional fuzzy variable and will be introduced in the premise part of the fuzzy rules; together with the state variables. In this work, a tuning of the well known weighting parameters approach is proposed to optimize local and global approximation and modelling capability of the Takagi-Sugeno (T-S) fuzzy model to improve the choice of the performance index and minimize it. The main problem encountered is that the T-S identification method can not be applied when the membership functions are overlapped by pairs. This in turn restricts the application of the T-S method because this type of membership function has been widely used in control applications. The approach developed here can be considered as a generalized version of the T-S method. An inverted pendulum mounted on a cart is chosen to evaluate the robustness, effectiveness, accuracy and remarkable performance of the proposed estimation approach in comparison with the original T-S model. Simulation results indicate the potential, simplicity and generality of the estimation method and the robustness of the chattering reduction algorithm. In this paper, we prove that the proposed estimation algorithm converge the very fast, thereby making it very practical to use. The application of the proposed FLC-VSC shows that both alleviation of chattering and robust performance are achieved

The Development and Application of a Dot-ELISA Assay for Diagnosis of Southern Rice Black-Streaked Dwarf Disease in the Field

Outbreaks of the southern rice black-streaked dwarf virus (SRBSDV) have caused significant crop losses in southern China in recent years, especially in 2010. There are no effective, quick and practicable methods for the diagnosis of rice dwarf disease that can be used in the field. Traditional reverse transcription-polymerase chain reaction (RT-PCR) methodology is accurate but requires expensive reagents and instruments, as well as complex procedures that limit its applicability for field tests. To develop a sensitive and reliable assay for routine laboratory diagnosis, a rapid dot enzyme-linked immunosorbent assay (dot-ELISA) method was developed for testing rice plants infected by SRBSDV. Based on anti-SRBSDV rabbit antiserum, this new dot-ELISA was highly reliable, sensitive and specific toward SRBSDV. The accuracy of two blotting media, polyvinylidene fluoride membrane (PVDF membrane) and nitrocellulose filter membrane (NC membrane), was compared. In order to facilitate the on-site diagnosis, three county laboratories were established in Shidian (Yunnan province), Jianghua (Hunan Province) and Libo (Guizhou province). Suspected rice cases from Shidian, Yuanjiang and Malipo in Yunnan province were tested and some determined to be positive for SRBSDV by the dot-ELISA and confirmed by the One Step RT-PCR method. To date, hundreds of suspected rice samples collected from 61 districts in southwestern China have been tested, among which 55 districts were found to have rice crops infected by SRBSDV. Furthermore, the test results in the county laboratories showed that Libo, Dehong (suspected samples were sent to Shidian) and Jianghua were experiencing a current SRBSDV outbreak