Binding between endohedral Na atoms in Si clathrate I; a first principles study

We investigate the binding nature of the endohedral sodium atoms with the ensity functional theory methods, presuming that the clathrate I consists of a sheaf of one-dimensional connections of Na@Si$_{24}$ cages interleaved in three perpendicular directions. Each sodium atom loses 30% of the 3s$^1$ charge to the frame, forming an ionic bond with the cage atoms; the rest of the electron contributes to the covalent bond between the nearest Na atoms. The presumption is proved to be valid; the configuration of the two Na atoms in the nearest Si$_{24}$ cages is more stable by 0.189 eV than that in the Si$_{20}$ and Si$_{24}$ cages. The energy of the beads of the two distorted Na atoms is more stable by 0.104 eV than that of the two infinitely separated Na atoms. The covalent bond explains both the preferential occupancies in the Si$_{24}$ cages and the low anisotropic displacement parameters of the endohedral atoms in the Si$_{24}$ cages in the [100] directions of the clathrate I.Comment: First page: Affiliation added to PDF and PS versio

Mechanisms Underlying Robustness and Tunability in a Plant Immune Signaling Network

SummaryThe plant immune signaling network needs to be robust against attack from fast-evolving pathogens and tunable to optimize immune responses. We investigated the basis of robustness and tunability in the signaling network controlling pattern-triggered immunity (PTI) in Arabidopsis. A dynamic network model containing four major signaling sectors, the jasmonate, ethylene, phytoalexin-deficient 4, and salicylate sectors, which together govern up to 80% of the PTI levels, was built using data for dynamic sector activities and PTI levels under exhaustive combinatorial sector perturbations. Our regularized multiple regression model had a high level of predictive power and captured known and unexpected signal flows in the network. The sole inhibitory sector in the model, the ethylene sector, contributed centrally to network robustness via its inhibition of the jasmonate sector. The model’s multiple input sites linked specific signal input patterns varying in strength and timing to different network response patterns, indicating a mechanism enabling tunability

Construction and characterization of a BAC library from a gynogenetic channel catfish Ictalurus punctatus

A bacterial artificial chromosome (BAC) library was constructed by cloning HindIII-digested high molecular weight DNA from a gynogenetic channel catfish, Ictalurus punctatus, into the vector pBeloBAC11. Approximately 53 500 clones were arrayed in 384-well plates and stored at -80°C (CCBL1), while clones from a smaller insert size fraction were stored at -80°C without arraying (CCBL2). Pulsed-field gel electrophoresis of 100 clones after NotI digestion revealed an average insert size of 165 kb for CCBL1 and 113 kb for CCBL2. Further characterization of CCBL1 demonstrated that 10% of the clones did not contain an insert. CCBL1 provides a 7.2-fold coverage of the channel catfish haploid genome. PCR-based screening demonstrated that 68 out of 74 unique loci were present in the library. This represents a 92% chance to find a unique sequence. These libraries will be useful for physical mapping of the channel catfish genome, and identification of genes controlling major traits in this economically important species

An intrinsic B cell defect is required for the production of autoantibodies in the lpr model of murine systemic autoimmunity

Mice homozygous for the gene lpr develop marked lymphadenopathy and a spectrum of autoantibodies closely resembling that of human systemic lupus erythematosus. The unusual T cell phenotype of the expanded lymphocyte population and the T-dependence of several antibodies in this strain have suggested that primary T cell abnormalities underlie the autoimmune syndrome. Using double chimeras, we now show that expression of the lpr gene in B cells is absolutely necessary for autoantibody production. Combinations of anti-Thy 1.2 + C' treated bone marrow from congenic strains of C57BL/6 mice, differing only at the immunoglobulin heavy chain (Igh) and lpr loci, were transferred into lethally irradiated B6/lpr mice. Double chimerism was documented by allotype-specific surface IgD and IgM immunofluorescence assay of peripheral blood and by allotype-specific enzyme-linked immunosorbent assay for total IgM in serum. Despite the presence of both +/+ and lpr B cells, IgM and IgG2a anti-chromatin as well as IgM anti-IgG were entirely the products of lpr B cells. Total serum IgG2a and IgG1 were also dominated by the lpr phenotype but not to the same extent. A similar experiment using B6/lpr-Igha recipients confirmed these findings. Additional experiments in which B6/lpr recipients were infused with ratios of donor bone marrow favoring B6.C20 +/+ over B6/lpr showed that even though +/+ B cells were overrepresented, autoantibodies were only of the lpr allotype. In addition, in the presence of lpr B cells, normal B cells showed little response to an exogenous, T cell-dependent antigen. The data thus indicate that lpr B cells manifest an intrinsic abnormality which is essential for autoantibody production in the lpr model

The Optical System for the Large Size Telescope of the Cherenkov Telescope Array

The Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) is designed to achieve a threshold energy of 20 GeV. The LST optics is composed of one parabolic primary mirror 23 m in diameter and 28 m focal length. The reflector dish is segmented in 198 hexagonal, 1.51 m flat to flat mirrors. The total effective reflective area, taking into account the shadow of the mechanical structure, is about 368 m$^2$. The mirrors have a sandwich structure consisting of a glass sheet of 2.7 mm thickness, aluminum honeycomb of 60 mm thickness, and another glass sheet on the rear, and have a total weight about 47 kg. The mirror surface is produced using a sputtering deposition technique to apply a 5-layer coating, and the mirrors reach a reflectivity of $\sim$94% at peak. The mirror facets are actively aligned during operations by an active mirror control system, using actuators, CMOS cameras and a reference laser. Each mirror facet carries a CMOS camera, which measures the position of the light spot of the optical axis reference laser on the target of the telescope camera. The two actuators and the universal joint of each mirror facet are respectively fixed to three neighboring joints of the dish space frame, via specially designed interface plate.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Grain Size and Texture of Cu2ZnSnS4 Thin Films Synthesized by Cosputtering Binary Sulfides and Annealing: Effects of Processing Conditions and Sodium

We investigate the synthesis of kesterite Cu2ZnSnS4 (CZTS) polycrystalline thin films using cosputtering from binary sulfide targets followed by annealing in sulfur vapor at 500 {\deg}C to 650 {\deg}C. The films are the kesterite CZTS phase as indicated by x-ray diffraction, Raman scattering, and optical absorption measurements. The films exhibit (112) fiber texture and preferred low-angle and Sigma3 grain boundary populations which have been demonstrated to reduce recombination in Cu(In,Ga)Se2 and CdTe films. The grain growth kinetics are investigated as functions of temperature and the addition of Na. Significantly, lateral grain sizes above 1 um are demonstrated for samples grown on Na-free glass,demonstrating the feasibility for CZTS growth on substrates other than soda lime glass

Fermi-LAT Observations and A Broadband Study of Supernova Remnant CTB 109

CTB 109 (G109.1-1.0) is a Galactic supernova remnant (SNR) with a hemispherical shell morphology in X-rays and in the radio band. In this work we report the detection of {\gamma}-ray emission coincident with CTB 109, using 37 months of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. We study the broadband characteristics of the remnant using a model that includes hydrodynamics, efficient cosmic ray acceleration, nonthermal emission and a self-consistent calculation of the X-ray thermal emission. We find that the observations can be successfully fit with two distinct parameter sets, one where the {\gamma}-ray emission is produced primarily by leptons accelerated at the SNR forward shock and the other where {\gamma}-rays produced by forward shock accelerated cosmic-ray ions dominate the high-energy emission. Consideration of thermal X-ray emission introduces a novel element to the broadband fitting process, and while it does not rule out either the leptonic or the hadronic scenarios, it constrains the parameter sets required by the model to fit the observations. Moreover, the model which best fits the thermal and nonthermal emission observations is an intermediate case, where both radiation from accelerated electrons and hadrons contribute almost equally to the {\gamma}-ray flux observed.Comment: 10 pages, 6 figures. Accepted for publication in Ap

Performance Limiting Factors of Cu2ZnSn(SxSe1-x)4 Solar Cells Prepared by Thermal Evaporation

Cu2ZnSn(SxSe1−x)4 (CZTSSe) thin film solar cells have been prepared by vacuum-based thermal evaporation of metal and binary sulfide precursors followed by annealing in a mixed chalcogen vapor at 550 °C for one hour. The Zn/Sn ratio in the precursor was varied from 0.75 to 1.50 keeping the Cu/(Zn+Sn) ratio constant at 0.7. The best performing solar cell was obtained with a final film composition of Cu/(Zn+Sn)=0.77 and Zn/Sn=1.13 corresponding to a Zn/Sn ratio of 0.9 in the precursor. The champion cell exhibited an open-circuit voltage (VOC) of 506 mV, short-circuit current density (JSC) of 22.92 mA/cm2, and a fill factor (FF) of 35% resulting in a total area efficiency (η) of 4.06% without any antireflection coating. Cell performance was found to be limited by high series resistance (RS)=31.1 Ω and a low shunt resistance (Rsh)=125.2 Ω. No detrimental secondary phases, such as Cu2−xS(Se) or ZnS were detected in the absorber film. Microstructural investigation suggested that small multigrain structure of the CZTSSe absorber layer, presence of an interfacial Mo(S,Se)x blocking barrier, and micro-air-voids at the Mo back contact are the major contributors to the origin of high Rs. Morphological study of the CZTSSe film surface by atomic force microscopy revealed micro-pores that act as low resistance shunt paths and explains the source of such low Rsh. The performance limiting factors of the vacuum based thermally evaporated CZTSSe thin film solar cells are reported

Coupled-Cluster Approach to Electron Correlations in the Two-Dimensional Hubbard Model

We have studied electron correlations in the doped two-dimensional (2D) Hubbard model by using the coupled-cluster method (CCM) to investigate whether or not the method can be applied to correct the independent particle approximations actually used in ab-initio band calculations. The double excitation version of the CCM, implemented using the approximate coupled pair (ACP) method, account for most of the correlation energies of the 2D Hubbard model in the weak ($U/t \simeq 1$) and the intermediate $U/t$ regions ($U/t \simeq 4$). The error is always less than 1% there. The ACP approximation gets less accurate for large $U/t$ ($U/t \simeq 8$) and/or near half-filling. Further incorporation of electron correlation effects is necessary in this region. The accuracy does not depend on the system size and the gap between the lowest unoccupied level and the highest occupied level due to the finite size effect. Hence, the CCM may be favorably applied to ab-initio band calculations on metals as well as semiconductors and insulators.Comment: RevTeX3.0, 4 pages, 4 figure

Peluang Peningkatan Tipe Terminal di Kecamatan Banyumaik (Analisis Demand dan Supply)

Kecamatan Banyumanik merupakan kecamatan yang terus mengalami perkembangan baik dari jumlah penduduk maupun pelayanan kotanya. Kecamatan ini juga berbatasan langsung dengan kabupaten Semarang dan menjadi gerbang koridor semarang atas atau semarang bagian Selatan sehingga memiliki pergerakan yang tinggi sebagai jalur keluar masuknya kota Semarang. Pergerakan yang tinggi tersebut tidak diimbangi dengan ketersediaan fasilitas transportasi pendukung yaitu terminal. Terminal merupakan salah satu fasilitas utama yang memiliki peran penting dalam sistem transportasi. Menurut keputusan menteri nomor 35 tahun 2003 pengertian terminal adalah prasarana transportasi jalan untuk keperluan memuat dan menurunkan orang dan/atau barang serta mengatur kedatangan dan pemberangkatan kendaraan umum, yang merupakan salah satu wujud simpul jaringan transportasi. Terminal juga memiliki peran yang penting sebagai unsur tata ruang dalam kaitannya untuk meningkatkan mobilitas dan efisiensi kehidupan kota. Terminal merupakan tempat untuk mengurangi kemacetan dimana dapat mengatur lokasi pergantian moda transportasi menjadi lebih teratur. Lokasi sebuah terminal harus sesuai dengan rencana tata ruang wilayah (RTRW) dan sesuai dengan kebutuhan masyarakat Di kecamatan Banyumanik hanya memiliki sub terminal atau terminal bantu yang berfungsi sebagai tempat transit dan pergantian moda. Demand yang tinggi terhadap fasilitas transportasi tersebut tidak sebanding dengan supply fasilitas terminal yang tersedia sehingga mengakibatkan timbulnya titik-titik baru yang digunakan masyarakat untuk menunggu angkutan yaitu terminal bayangan. Terminal bayangan ini muncul karena adanya demand yang tinggi dari mayarakat banyumanik terhadap kebutuhan sarana transportasi dan efisiensi waktu. Ketidakseimbangan antara demand dan supply ini mengakibatkan berbagai dampak makro maupun mikro terhadap lalu lintas maupun jaringan angkutan di Kecamatan Banyumanik dan kota Semarang