Application of an electron microscope conductive mode of operation for the study of optoelectronic devices

Imperial Users onl

Near threshold kaon-kaon interaction in the reactions e+ e- --> K+ K- gamma and e+ e- --> K0 K0bar gamma

Strong interactions between pairs of the K+ K- and K0 K0bar mesons can be studied in radiative decays of phi(1020) mesons. We present a theoretical model of the reactions e+ e- --> phi --> K+ K- gamma and e+ e- --> phi --> K0 K0bar gamma. The K+ K- and K0 K0bar effective mass dependence of the differential cross sections is derived. The total cross sections and the branching fractions for the two radiative phi decays are calculated.Comment: 4 pages, 3 figures, contribution to 15th International Workshop on Meson Physics, Cracow, Poland, 7th - 12th June 201

Recent Developments in Electrical Microcharacterization Using the Charge Collection Mode of the Scanning Electron Microscope

There are six distinguishable types of charge collection (CC) signal. Consequently specially designed CC detection systems are needed to obtain e.g. true EBIC and EBIV measurements and make quantitative electrical microcharacterization possible. EBIC and EBIV can arise from fields due to barriers such as p-n junctions or due to changes in doping e.g. p to p+. Materials, defect and device parameters are calculable from these signals. Hot-cold stages are important for temperature dependence studies of contrast, for improving signal to noise ratios and reducing leakage currents. Image processing and pattern recognition methods are vital for rapidly locating and evaluating the information in CC micrographs of large scale circuits. Some recent applications of these techniques to junctions and Schottky barriers in devices, to dislocations and grain boundaries, to microplasmas and to the location of defects in large scale intergration (LSI) devices are presented

Palgol: A High-Level DSL for Vertex-Centric Graph Processing with Remote Data Access

Pregel is a popular distributed computing model for dealing with large-scale graphs. However, it can be tricky to implement graph algorithms correctly and efficiently in Pregel's vertex-centric model, especially when the algorithm has multiple computation stages, complicated data dependencies, or even communication over dynamic internal data structures. Some domain-specific languages (DSLs) have been proposed to provide more intuitive ways to implement graph algorithms, but due to the lack of support for remote access --- reading or writing attributes of other vertices through references --- they cannot handle the above mentioned dynamic communication, causing a class of Pregel algorithms with fast convergence impossible to implement. To address this problem, we design and implement Palgol, a more declarative and powerful DSL which supports remote access. In particular, programmers can use a more declarative syntax called chain access to naturally specify dynamic communication as if directly reading data on arbitrary remote vertices. By analyzing the logic patterns of chain access, we provide a novel algorithm for compiling Palgol programs to efficient Pregel code. We demonstrate the power of Palgol by using it to implement several practical Pregel algorithms, and the evaluation result shows that the efficiency of Palgol is comparable with that of hand-written code.Comment: 12 pages, 10 figures, extended version of APLAS 2017 pape

Strong interaction between kaons in the reactions e+ e- --> K+ K- gamma and e+ e- --> K0 K0bar gamma

A theoretical model of the reactions e+ e- --> K+ K- gamma and e+ e- --> K0 K0bar gamma has been derived. The strong interaction between kaons is taken into account using a general form of the K Kbar scattering amplitude. It is shown that some models formulated in the past are particular cases of the present approach. The formulae for the K Kbar effective mass dependence of the differential cross section as well as for the angular kaon and photon distributions and for the branching fractions of the phi(1020)--> K+ K- gamma and phi(1020)--> K0 K0bar gamma decays have been obtained. We present numerical results for the functions entering into transition amplitudes, K Kbar effective mass distributions, total cross sections, and branching fractions. Finally, the model is generalized to treat other reactions with two pseudoscalar mesons accompanying a photon in the final state.Comment: 17 pages, 7 figure

The Impact of a Weighted Warmup on 1 - Mile Run Performance

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Effect of Light Brightness on Cycling Performance

poste

Efficient assembly and secretion of recombinant subviral particles of the four dengue serotypes using native prM and E proteins.

© 2009 Wang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: Flavivirus infected cells produce infectious virions and subviral particles, both of which are formed by the assembly of prM and E envelope proteins and are believed to undergo the same maturation process. Dengue recombinant subviral particles have been produced in cell cultures with either modified or chimeric proteins but not using the native forms of prM and E. Methodology/Principal Findings: We have used a codon optimization strategy to obtain an efficient expression of native viral proteins and production of recombinant subviral particles (RSPs) for all four dengue virus (DV) serotypes. A stable HeLa cell line expressing DV1 prME was established (HeLa-prME) and RSPs were analyzed by immunofluorescence and transmission electron microscopy. We found that E protein is mainly present in the endoplasmic reticulum (ER) where assembly of RSPs could be observed. Biochemical characterization of DV1 RSPs secretion revealed both prM protein cleavage and homodimerization of E proteins before their release into the supernatant, indicating that RSPs undergo a similar maturation process as dengue virus. Pulse chase experiment showed that 8 hours are required for the secretion of DV1 RSPs. We have used HeLa-prME to develop a semi-quantitative assay and screened a human siRNA library targeting genes involved in membrane trafficking. Knockdown of 23 genes resulted in a significant reduction in DV RSP secretion, whereas for 22 others we observed an increase of RSP levels in cell supernatant. Conclusions/Significance: Our data describe the efficient production of RSPs containing native prM and E envelope proteins for all dengue serotypes. Dengue RSPs and corresponding producing cell lines are safe and novel tools that can be used in the study of viral egress as well as in the development of vaccine and drugs against dengue virus.This work was supported by the 6th European Framework programme DENFRAME and by the Research Fund for the Control of Infectious Diseases of Hong Kong (RFCID#08070952)

Polycrystalline texture causes magnetic instability in greigite

Magnetic stability of iron mineral phases is a key for their use as paleomagnetic information carrier and their applications in nanotechnology, and it critically depends on the size of the particles and their texture. Ferrimagnetic greigite (Fe$_{3}$S$_{4}$) in nature and synthesized in the laboratory forms almost exclusively polycrystalline particles. Textural effects of inter-grown, nano-sized crystallites on the macroscopic magnetization remain unresolved because their experimental detection is challenging. Here, we use ferromagnetic resonance (FMR) spectroscopy and static magnetization measurements in concert with micromagnetic simulations to detect and explain textural effects on the magnetic stability in synthetic, polycrystalline greigite flakes. We demonstrate that these effects stem from inter-grown crystallites with mean coherence length (MCL) of about 20 nm in single-domain magnetic state, which generate modifiable coherent magnetization volume (CMV) configurations in the flakes. At room temperature, the instability of the CVM configuration is exhibited by the angular dependence of the FMR spectra in fields of less than 100 mT and its reset by stronger fields. This finding highlights the magnetic manipulation of polycrystalline greigite, which is a novel trait to detect this mineral phase in Earth systems and to assess its fidelity as paleomagnetic information carrier. Additionally, our magneto-spectroscopic approach to analyse instable CMV opens the door for a new more rigorous magnetic assessment and interpretation of polycrystalline nano-materials