28,705 research outputs found

    Space and time from translation symmetry

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    We show that the notions of space and time in algebraic quantum field theory arise from translation symmetry if we assume asymptotic commutativity. We argue that this construction can be applied to string theory.Comment: 10 pages, Essential changes and additions, in particular, in the discussion of string field theor

    Theoretical Predictions of Superconductivity in Alkali Metals under High Pressure

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    We calculated the superconductivity properties of alkali metals under high pressure using the results of band theory and the rigid-muffin-tin theory of Gaspari and Gyorffy. Our results suggest that at high pressures Lithium, Potassium, Rubidium and Cesium would be superconductors with transition temperatures approaching 520K5-20 K. Our calculations also suggest that Sodium would not be a superconductor under high pressure even if compressed to less than half of its equilibrium volume. We found that the compression of the lattice strengthens the electron-phonon coupling through a delicately balanced increase of both the electronic and phononic components of this coupling. This increase of the electron-phonon coupling in Li is due to an enhancement of the ss-pp channel of the interaction, while in the heavier elements the pp-dd channel is the dominant component.Comment: 6 pages, 8 figure

    Suitability of a CMV/EGFP cassette to monitor stable expression from human artificial chromosomes but not transient transfer in the cells forming viable clones

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    Human artificial chromosomes (HACs) were generated by transfer of telomerized PAC constructs containing alpha satellite DNA of various human chromosomes. To monitor which cells took up constructs and subsequently formed stable clones under blasticidin S (BS) selection, a CMV/EGFP expression cassette was inserted into a HAC construct based on chromosome 5 alpha satellite DNA (142 kb). Lipofection into HT1080 cells resulted in a small proportion of cells exhibiting bright green fluorescence on day 1. Areas containing such early green cells were marked, and plates monitored over 2 weeks. In only one out of 41 marked areas, a viable clone developed. In the remaining 40 areas, the green cells ceased division at 1-8 cells. In contrast, outside the marked areas, 16 stable clones formed which did not exhibit green fluorescence during the first cell divisions, but all cells of each became green around day 4 -6. Fluorescence in situ hybridization (FISH) analysis of isolated clonal lines demonstrated low copy HAC formation without integration. We conclude that transient expression of an EGFP marker on HAC DNA is not a suitable means for the identification of the proportion of transfected cells which are capable of forming viable clones. One explanation could be that the high copy number required to consistently detect transient EGFP expression (Schindelhauer and Laner, 2002) impairs viability and clone formation. Copyright (C) 2004 S. Karger AG, Basel

    Effects of weak self-interactions in a relativistic plasma on cosmological perturbations

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    The exact solutions for linear cosmological perturbations which have been obtained for collisionless relativistic matter within thermal field theory are extended to a self-interacting case. The two-loop contributions of scalar λϕ4\lambda\phi^4 theory to the thermal graviton self-energy are evaluated, which give the O(λ)O(\lambda) corrections in the perturbation equations. The changes are found to be perturbative on scales comparable to or larger than the Hubble horizon, but the determination of the large-time damping behavior of subhorizon perturbations requires a resummation of thermally induced masses.Comment: 11 pages, REVTEX, 4 postscript figures included by epsf.sty - expanded version (more details on the resummation of thermal masses which is required for the late-time damping behaviour

    Aminoacyl tRNA synthetase complex interacting multifunctional protein 1 simultaneously binds Glutamyl-Prolyl-tRNA synthetase and scaffold protein aminoacyl tRNA synthetase complex interacting multifunctional protein 3 of the multi-tRNA synthetase complex

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    Higher eukaryotes have developed extensive compartmentalization of amino acid (aa) - tRNA coupling through the formation of a multi-synthetase complex (MSC) that is composed of eight aa-tRNA synthetases (ARS) and three scaffold proteins: aminoacyl tRNA synthetase complex interacting multifunctional proteins (AIMP1, 2 and 3). Lower eukaryotes have a much smaller complex while yeast MSC consists of only two ARS (MetRS and GluRS) and one ARS cofactor 1 protein, Arc1p (Simos et al., 1996), the homolog of the mammalian AIMP1. Arc1p is reported to form a tripartite complex with GluRS and MetRS through association of the N-terminus GST-like domains (GST-L) of the three proteins (Koehler et al., 2013). Mammalian AIMP1 has no GST-L domain corresponding to Arc1p N-terminus. Instead, AIMP3, another scaffold protein of 18 kDa composed entirely of a GST-L domain, interacts with Methionyl-tRNA synthetase (MARS) (Quevillon et al., 1999) and Glutamyl-Prolyl-tRNA Synthetase (EPRS) (Cho et al., 2015). Here we report two new interactions between MSC members: AIMP1 binds to EPRS and AIMP1 binds to AIMP3. Interestingly, the interaction between AIMP1 and AIMP3 complex makes it the functional equivalent of a single Arc1p polypeptide in yeast. This interaction is not mapped to AIMP1 N-terminal coiled-coil domain, but rather requires an intact tertiary structure of the entire protein. Since AIMP1 also interacts with AIMP2, all three proteins appear to compose a core docking structure for the eight ARS in the MSC complex

    Abelian Duality

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    We show that on three-dimensional Riemannian manifolds without boundaries and with trivial first real de Rham cohomology group (and in no other dimensions) scalar field theory and Maxwell theory are equivalent: the ratio of the partition functions is given by the Ray-Singer torsion of the manifold. On the level of interaction with external currents, the equivalence persists provided there is a fixed relation between the charges and the currents.Comment: 11 pages, LaTeX, no figures, a reference added, submitted to Phys. Rev.

    Extreme southern locations for moss sporophytes in Antarctica

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    Abundant immature sporophytes of the moss Pottia heimii are reported from the Lower Taylor Valley, McMurdo Dry Valleys and from Cape Chocolate, Victoria Land. These finds extend the reported southern limit for the occurrence of abundant moss sporophytes to 77° 55′S

    1RXSJ062518.2+733433: A bright, soft intermediate polar

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    We present the results of 50 hours time-resolved R-band photometry of the ROSAT all-sky survey source 1RXSJ062518.2+733433. The source was identified by Wei et al. (1999) as a cataclysmic variable. Our photometry, performed in 10 nights between February 11, 2003, and March 21, 2003, reveals two stable periodicities at 19.7874 and 283.118 min, which are identified as probable spin and orbital periods of the binary. We therefore classify 1RXSJ062518.2+733433 as an intermediate polar. Analysis of the RASS X-ray observations reveal a variability of 100% in the X-ray flux and a likely soft X-ray excess. The new IP thus joins the rare group of soft IPs with only four members so far.Comment: submitted to A&A, 5 pages, 6 figures of reduced qualit
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