1,170 research outputs found

    Bio-imaging the entry process of an emerging pathogenic virus: The West Nile virus

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    10.1017/S1431927605500382Microscopy and Microanalysis11suppl 2958-95

    Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator Bi2Se3 with scanning tunneling spectroscopy

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    Scanning tunneling spectroscopic studies of Bi2Se3 epitaxial films on Si (111) substrates reveal highly localized unitary impurity resonances associated with non-magnetic quantum impurities. The strength of the resonances depends on the energy difference between the Fermi level ({E_F}) and the Dirac point ({E_D}) and diverges as {E_F} approaches {E_D}. The Dirac-cone surface state of the host recovers within ~ 2{\AA} spatial distance from impurities, suggesting robust topological protection of the surface state of topological insulators against high-density impurities that preserve time reversal symmetry.Comment: 6 pages, 6 figures. Accepted for fast-track publication in Solid State Communications (2012

    Quantum Mirrors and Crossing Symmetry as Heart of Ghost Imaging

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    In this paper it is proved that the key to understanding the ghost imaging mystery are the crossing symmetric photon reactions in the nonlinear media. Hence, the laws of the plane quantum mirror (QM) and that of spherical quantum mirror, observed in the ghost imaging experiments, are obtained as natural consequences of the energy-momentum conservation laws. So, it is shown that the ghost imaging laws depend only on the energy-momentum conservation and not on the photons entanglement. The extension of these results to the ghost imaging with other kind of light is discussed. Some fundamental experiments for a decisive tests of the [SPDC-DFG]-quantum mirror are suggested.Comment: 11 pages, 9 figure

    Isolation and partial characterization of infectious molecular clones of feline immunodeficiency virus obtained directly from bone marrow DNA of a naturally infected cat.

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    Replication-competent molecular clones of feline immunodeficiency virus (FIV) were isolated directly from the DNA of bone marrow cells of a naturally FIV-infected cat. After transfection in a feline kidney cell line (CrFK) and subsequent cocultivation with peripheral blood mononuclear cells (PBMC), the viral progeny of the clones was infectious for PBMC but not for CrFK cells. PBMC infected with these clones showed syncytium formation, a decrease in cell viability, and gradual loss of CD4+ cells. The restriction maps of these clones differed from those obtained for previously described molecular clones of FIV derived from cats in the United States. The predicted amino acid sequence similarity of the envelope genes of the two clones was 99.3%, whereas the similarities of the sequences of the clones to those of two molecular clones from the United States, Petaluma and PPR, were 86 and 88%, respectively. Most of the differences between the amino acid sequences of the two clones and those of the clones from the United States were found in five different hypervariable (HV) regions, HV-1 through HV-5. The viral progeny of one of these clones was inoculated into two specific-pathogen-free cats. The animals seroconverted, and the virus could be reisolated from their PBMC

    Special symplectic Lie groups and hypersymplectic Lie groups

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    A special symplectic Lie group is a triple (G,ω,)(G,\omega,\nabla) such that GG is a finite-dimensional real Lie group and ω\omega is a left invariant symplectic form on GG which is parallel with respect to a left invariant affine structure \nabla. In this paper starting from a special symplectic Lie group we show how to ``deform" the standard Lie group structure on the (co)tangent bundle through the left invariant affine structure \nabla such that the resulting Lie group admits families of left invariant hypersymplectic structures and thus becomes a hypersymplectic Lie group. We consider the affine cotangent extension problem and then introduce notions of post-affine structure and post-left-symmetric algebra which is the underlying algebraic structure of a special symplectic Lie algebra. Furthermore, we give a kind of double extensions of special symplectic Lie groups in terms of post-left-symmetric algebras.Comment: 32 page

    Observation of Two New N* Peaks in J/psi -> ppinˉp pi^- \bar n and pˉπ+n\bar p\pi^+n Decays

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    The πN\pi N system in decays of J/ψNˉNπJ/\psi\to\bar NN\pi is limited to be isospin 1/2 by isospin conservation. This provides a big advantage in studying NπNN^*\to \pi N compared with πN\pi N and γN\gamma N experiments which mix isospin 1/2 and 3/2 for the πN\pi N system. Using 58 million J/ψJ/\psi decays collected with the Beijing Electron Positron Collider, more than 100 thousand J/ψpπnˉ+c.c.J/\psi \to p \pi^- \bar n + c.c. events are obtained. Besides two well known NN^* peaks at 1500 MeV and 1670 MeV, there are two new, clear NN^* peaks in the pπp\pi invariant mass spectrum around 1360 MeV and 2030 MeV. They are the first direct observation of the N(1440)N^*(1440) peak and a long-sought "missing" NN^* peak above 2 GeV in the πN\pi N invariant mass spectrum. A simple Breit-Wigner fit gives the mass and width for the N(1440)N^*(1440) peak as 1358±6±161358\pm 6 \pm 16 MeV and 179±26±50179\pm 26\pm 50 MeV, and for the new NN^* peak above 2 GeV as 2068±340+152068\pm 3^{+15}_{-40} MeV and 165±14±40165\pm 14\pm 40 MeV, respectively

    Investigating the electronic properties of multi-junction ZnS/CdS/CdTe graded bandgap solar cells

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    The fabrication of multi-junction graded bandgap solar cells have been successfully implemented by electroplating three binary compound semiconductors from II-VI family. The three semiconductor materials grown by electroplating techniques are ZnS, CdS and CdTe thin films. The electrical conductivity type and energy bandgap of each of the three semiconductors were determined using photoelectrochemical (PEC) cell measurement and UV-Vis spectrophotometry techniques respectively. The PEC cell results show that all the three semiconductor materials have n-type electrical conductivity. These two material characterisation techniques were considered in this paper in order to establish the relevant energy band diagram for device results, analysis and interpretation. Solar cells with the device structure glass/FTO/n-ZnS/n-CdS/n-CdTe/Au were then fabricated and characterised using current-voltage (I-V) and capacitance-voltage (C-V) techniques. From the I-V characteristics measurement, the fabricated device structures yielded an open circuit voltage (Voc) of 670 mV, short circuit current density (Jsc) of 41.5 mAcm-2 and fill-factor (FF) of 0.46 resulting in ∼12.8% efficiency when measured at room temperature under AM1.5 illumination conditions. The device structure showed an excellent rectification factor (RF) of 104.3 and ideality factor (n) of 1.88. The results obtained from the C-V measurement also showed that the device structures have a moderate doping level of 5.2×1015 cm-3
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