3,806 research outputs found

    The non-continuous direction vector I test

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    On the Alexandrov Topology of sub-Lorentzian Manifolds

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    It is commonly known that in Riemannian and sub-Riemannian Geometry, the metric tensor on a manifold defines a distance function. In Lorentzian Geometry, instead of a distance function it provides causal relations and the Lorentzian time-separation function. Both lead to the definition of the Alexandrov topology, which is linked to the property of strong causality of a space-time. We studied three possible ways to define the Alexandrov topology on sub-Lorentzian manifolds, which usually give different topologies, but agree in the Lorentzian case. We investigated their relationships to each other and the manifold's original topology and their link to causality.Comment: 20 page

    Cooperative coupling of ultracold atoms and surface plasmons

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    Cooperative coupling between optical emitters and light fields is one of the outstanding goals in quantum technology. It is both fundamentally interesting for the extraordinary radiation properties of the participating emitters and has many potential applications in photonics. While this goal has been achieved using high-finesse optical cavities, cavity-free approaches that are broadband and easy to build have attracted much attention recently. Here we demonstrate cooperative coupling of ultracold atoms with surface plasmons propagating on a plane gold surface. While the atoms are moving towards the surface they are excited by an external laser pulse. Excited surface plasmons are detected via leakage radiation into the substrate of the gold layer. A maximum Purcell factor of ηP=4.9\eta_\mathrm{P}=4.9 is reached at an optimum distance of z=250 nmz=250~\mathrm{nm} from the surface. The coupling leads to the observation of a Fano-like resonance in the spectrum.Comment: 9 pages, 4 figure

    Down-regulated CK8 expression in human intervertebral disc degeneration

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    As an intermediate filament protein, cytokeratin 8 (CK8) exerts multiple cellular functions. Moreover, it has been identified as a marker of notochord cells, which play essential roles in human nucleus pulposus (NP). However, the distribution of CK8 positive cells in human NP and their relationship with intervertebral disc degeneration (IDD) have not been clarified until now. Here, we found the percentage of CK8 positive cells in IDD (25.7+/-4.14%) was significantly lower than that in normal and scoliosis NP (51.9+/-9.73% and 47.8+/-5.51%, respectively, p<0.05). Western blotting and qRT-PCR results confirmed the down-regulation of CK8 expression in IDD on both of protein and mRNA levels. Furthermore, approximately 37.4% of cell clusters were CK8 positive in IDD. Taken together, this is the first study to show a down-regulated CK8 expression and the percentage of CK8 positive cell clusters in IDD based upon multiple lines of evidence. Consequently, CK8 positive cells might be considered as a potential option in the development of cellular treatment strategies for NP repair.published_or_final_versio

    Efficient unidirectional nanoslit couplers for surface plasmons

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    Plasmonics is based on surface plasmon polariton (SPP) modes which can be laterally confined below the diffraction limit, thereby enabling ultracompact optical components. In order to exploit this potential, the fundamental bottleneck of poor light-SPP coupling must be overcome. In established SPP sources (using prism, grating} or nanodefect coupling) incident light is a source of noise for the SPP, unless the illumination occurs away from the region of interest, increasing the system size and weakening the SPP intensity. Back-side illumination of subwavelength apertures in optically thick metal films eliminates this problem but does not ensure a unique propagation direction for the SPP. We propose a novel back-side slit-illumination method based on drilling a periodic array of indentations at one side of the slit. We demonstrate that the SPP running in the array direction can be suppressed, and the one propagating in the opposite direction enhanced, providing localized unidirectional SPP launching.Comment: 13 pages, 4 figure

    Trayectorias laborales de jóvenes trabajadores de la actividad vitivinícola : departamento Maipú, Mendoza

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    La presente investigación tuvo como eje los vínculos entre educación y trabajo en la vitivinicultura mendocina desde 1990 . El objetivo general fue comprender los procesos de incorporación de jóvenes de ambos sexos al mundo del trabajo y su vínculo con las estrategias de formación y los esquemas de percepción en el mercado vitivinícola mendocino desde los 90. Se analizaron e identificaron los tipos de trayectorias educativas, laborales y transiciones existentes en los jóvenes. También los condicionantes de género que operan desde la perspectiva de las mujeres jóvenes. Se buscó comprender las formas que adquieren, cómo se manifiestan y varían las perspectivas acerca del trabajo, de las exigencias laborales y las condiciones del mercado de trabajo a lo largo de las trayectorias educativas y laborales y cuáles son los principales elementos constitutivos de las trayectorias de inserción, qué factores están asociados a sus variaciones y cómo se vinculan con las expectativas y estrategias de formación de inserción laboral.Fil: Martín, María Eugenia. CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) - Universidad Nacional de CuyoFil: Zamarbide, Gabriela. Universidad Nacional de Cuy

    Characteristics of transposable element exonization within human and mouse

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    Insertion of transposed elements within mammalian genes is thought to be an important contributor to mammalian evolution and speciation. Insertion of transposed elements into introns can lead to their activation as alternatively spliced cassette exons, an event called exonization. Elucidation of the evolutionary constraints that have shaped fixation of transposed elements within human and mouse protein coding genes and subsequent exonization is important for understanding of how the exonization process has affected transcriptome and proteome complexities. Here we show that exonization of transposed elements is biased towards the beginning of the coding sequence in both human and mouse genes. Analysis of single nucleotide polymorphisms (SNPs) revealed that exonization of transposed elements can be population-specific, implying that exonizations may enhance divergence and lead to speciation. SNP density analysis revealed differences between Alu and other transposed elements. Finally, we identified cases of primate-specific Alu elements that depend on RNA editing for their exonization. These results shed light on TE fixation and the exonization process within human and mouse genes.Comment: 11 pages, 4 figure

    QCD corrections to J/ψJ/\psi plus Z0Z^0-boson production at the LHC

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    The J/ψ+Z0J/\psi+Z^0 associated production at the LHC is an important process in investigating the color-octet mechanism of non-relativistic QCD in describing the processes involving heavy quarkonium. We calculate the next-to-leading order (NLO) QCD corrections to the J/ψ+Z0J/\psi +Z^0 associated production at the LHC within the factorization formalism of nonrelativistic QCD, and provide the theoretical predictions for the distribution of the J/ψJ/\psi transverse momentum. Our results show that the differential cross section at the leading-order is significantly enhanced by the NLO QCD corrections. We conclude that the LHC has the potential to verify the color-octet mechanism by measuring the J/ψ+Z0J/\psi+Z^0 production events.Comment: 14 page revtex, 5 eps figures, to appear in JHEP. fig5 and the corresponding analysis are correcte
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