Far-field e-beam detection of hybrid cavity-plasmonic modes in gold micro-holes

Manipulation of light-beams with subwavelenth metallic devices has motivated intensive studies, following the discovery of extraordinary transmission of electromagnetic waves through sub-wavelength apertures in thin noble-metal films. The propagation of light in these holes can be investigated at greately improved spatial resolution by means of focused electron-beams. Here we demonstrate direct e-beam excitation of radiative cavity modes well below the surface plasmon (SP) frequency, of isolated rectangular holes in gold films, illuminating the hotly debated phenomenon of the extraordinary optical transmission through subwavelength holes. The exceptionally long range e-beam interaction with the metal through the vacuum, involving electromagnetic excitations within the light cone, is allowed by momentum conservation breakdown along the e-beam axis. Two types of lowlying excited modes are revealed: radiative cavity modes which are nearly unaffected by SPs, and SP polariton modes with waveguide character in the near field region of the slit walls, which in spite of the strong hybridization preserve the waveguide cutoff frequencies and symmetry characteristics.Comment: 16 pages, 4 figures, 1 tabl

Security by Spatial Reference:Using Relative Positioning to Authenticate Devices for Spontaneous Interaction

Spontaneous interaction is a desirable characteristic associated with mobile and ubiquitous computing. The aim is to enable users to connect their personal devices with devices encountered in their environment in order to take advantage of interaction opportunities in accordance with their situation. However, it is difficult to secure spontaneous interaction as this requires authentication of the encountered device, in the absence of any prior knowledge of the device. In this paper we present a method for establishing and securing spontaneous interactions on the basis of emphspatial references that capture the spatial relationship of the involved devices. Spatial references are obtained by accurate sensing of relative device positions, presented to the user for initiation of interactions, and used in a peer authentication protocol that exploits a novel mechanism for message transfer over ultrasound to ensures spatial authenticity of the sender

Metagenomes of Red Sea Subpopulations Challenge the Use of Marker Genes and Morphology to Assess Trichodesmium Diversity

Trichodesmium are filamentous cyanobacteria of key interest due to their ability to fix carbon and nitrogen within an oligotrophic marine environment. Their blooms consist of a dynamic assemblage of subpopulations and colony morphologies that are hypothesized to occupy unique niches. Here, we assessed the poorly studied diversity of Trichodesmium in the Red Sea, based on metagenome-assembled genomes (MAGs) and hetR gene-based phylotyping. We assembled four non-redundant MAGs from morphologically distinct Trichodesmium colonies (tufts, dense and thin puffs). Trichodesmium thiebautii (puffs) and Trichodesmium erythraeum (tufts) were the dominant species within these morphotypes. While subspecies diversity is present for both T. thiebautii and T. erythraeum, a single T. thiebautii genotype comprised both thin and dense puff morphotypes, and we hypothesize that this phenotypic variation is likely attributed to gene regulation. Additionally, we found the rare non-diazotrophic clade IV and V genotypes, related to Trichodesmium nobis and Trichodesmium miru, respectively that likely occurred as single filaments. The hetR gene phylogeny further indicated that the genotype in clade IV could represent the species Trichodesmium contortum. Importantly, we show the presence of hetR paralogs in Trichodesmium, where two copies of the hetR gene were present within T. thiebautii genomes. This may lead to the overestimation of Trichodesmium diversity as one of the copies misidentified T. thiebautii as Trichodesmium aureum. Taken together, our results highlight the importance of re-assessing Trichodesmium taxonomy while showing the ability of genomics to capture the complex diversity and distribution of Trichodesmium populations

Id1 Restrains p21 Expression to Control Endothelial Progenitor Cell Formation

Loss of Id1 in the bone marrow (BM) severely impairs tumor angiogenesis resulting in significant inhibition of tumor growth. This phenotype has been associated with the absence of circulating endothelial progenitor cells (EPCs) in the peripheral blood of Id1 mutant mice. However, the manner in which Id1 loss in the BM controls EPC generation or mobilization is largely unknown. Using genetically modified mouse models we demonstrate here that the generation of EPCs in the BM depends on the ability of Id1 to restrain the expression of its target gene p21. Through a series of cellular and functional studies we show that the increased myeloid commitment of BM stem cells and the absence of EPCs in Id1 knockout mice are associated with elevated p21 expression. Genetic ablation of p21 rescues the EPC population in the Id1 null animals, re-establishing functional BM-derived angiogenesis and restoring normal tumor growth. These results demonstrate that the restraint of p21 expression by Id1 is one key element of its activity in facilitating the generation of EPCs in the BM and highlight the critical role these cells play in tumor angiogenesis

Origins of large critical temperature variations in single layer cuprates

We study the electronic structures of two single layer superconducting cuprates, Tl$_2$Ba$_2$CuO$_{6+\delta}$ (Tl2201) and (Bi$_{1.35}$Pb$_{0.85}$)(Sr$_{1.47}$La$_{0.38}$)CuO$_{6+\delta}$ (Bi2201) which have very different maximum critical temperatures (90K and 35K respectively) using Angular Resolved Photoemission Spectroscopy (ARPES). We are able to identify two main differences in their electronic properties. First, the shadow band that is present in double layer and low T$_{c,max}$ single layer cuprates is absent in Tl2201. Recent studies have linked the shadow band to structural distortions in the lattice and the absence of these in Tl2201 may be a contributing factor in its T$_{c,max}$.Second, Tl2201's Fermi surface (FS) contains long straight parallel regions near the anti-node, while in Bi2201 the anti-nodal region is much more rounded. Since the size of the superconducting gap is largest in the anti-nodal region, differences in the band dispersion at the anti-node may play a significant role in the pairing and therefore affect the maximum transition temperature.Comment: 6 pages, 5 figures,1 tabl

Crystal structure, electronic, and magnetic properties of the bilayered rhodium oxide Sr3Rh2O7

The bilayered rhodium oxide Sr3Rh2O7 was synthesized by high-pressure and high-temperature heating techniques. The single-phase polycrystalline sample of Sr3Rh2O7 was characterized by measurements of magnetic susceptibility, electrical resistivity, specific heat, and thermopower. The structural characteristics were investigated by powder neutron diffraction study. The rhodium oxide Sr3Rh2O7 [Bbcb, a = 5.4744(8) A, b = 5.4716(9) A, c = 20.875(2) A] is isostructural to the metamagnetic metal Sr3Ru2O7, with five 4d electrons per Rh, which is electronically equivalent to the hypothetic bilayered ruthenium oxide, where one electron per Ru is doped into the Ru-327 unit. The present data show the rhodium oxide Sr3Rh2O7 to be metallic with enhanced paramagnetism, similar to Sr3Ru2O7. However, neither manifest contributions from spin fluctuations nor any traces of a metamagnetic transition were found within the studied range from 2 K to 390 K below 70 kOe.Comment: To be published in PR

Uniaxial-Pressure induced Ferromagnetism of Enhanced Paramagnetic Sr3Ru2O7

We report a uniaxial pressure-dependence of magnetism in layered perovskite strontium ruthenate Sr3Ru2O7. By applying a relatively small uniaxial pressure, greater than 0.1 GPa normal to the RuO2 layer, ferromagnetic ordering manifests below 80 K from the enhanced-paramagnet. Magnetization at 1 kOe and 2 K becomes 100 times larger than that under ambient condition. Uniaxial pressure dependence of Curie temperature T_C suggests the first order magnetic transition. Origin of this uniaxial-pressure induced ferromagnetism is discussed in terms of the rotation of RuO6 octahedra within the RuO2 plane.Comment: 8 pages, 3 figures. to be published in Journal of the Physical Society of Japan, vol.73, No.5 (2004

Transformation of in-plane ρ(T)\rho (T) in YBa2Cu3O7−δYBa_{2}Cu_{3}O_{7-\delta} at fixed oxygen content

This paper reveals the origin of variation in the magnitude and temperature dependence of the normal state resistivity frequently observed in different YBCO single crystal or thin film samples with the same $T_{c}$. We investigated temperature dependence of resistivity in $YBa_{2}Cu_{3}O_{7-\delta}$ thin films with 7- $\delta = 6.95$ and 6.90, which were subjected to annealing in argon at 400-420 K ($120-140^{o}C$). Before annealing these films exhibited a non-linear $\rho_{ab}(T)$, with a flattening below 230 K, similar to $\rho_{b}(T)$ and $\rho_{ab}(T)$ observed in untwinned and twinned YBCO crystals, respectively. For all films the annealing causes an increase of resistivity and a transformation of $\rho_{ab}(T)$ from a non-linear dependence towards a more linear one (less flattening). In films with 7- $\delta = 6.90$ the increase of resistivity is also associated with an increase in $T_{c}$. We proposed the model that provides an explanation of these phenomena in terms of thermally activated redistribution of residual O(5) oxygens in the chain-layer of YBCO. Good agreement between the experimental data for $\rho_{ab}(t,T)$, where t is the annealing time, and numerical calculations was obtained.Comment: 8 pages, 9 figures, submitted to PR

Structural and Magnetic Instabilities of La2−x_{2-x}Srx_xCaCu2_2O6_6

A neutron scattering study of nonsuperconducting La$_{2-x}$Sr$_x$CaCu$_2$O$_6$ (x=0 and 0.2), a bilayer copper oxide without CuO chains, has revealed an unexpected tetragonal-to-orthorhombic transition with a doping dependent transition temperature. The predominant structural modification below the transition is an in-plane shift of the apical oxygen. In the doped sample, the orthorhombic superstructure is strongly disordered, and a glassy state involving both magnetic and structural degrees of freedom develops at low temperature. The spin correlations are commensurate.Comment: published versio

The PI3K/Akt pathway upregulates Id1 and integrin α4 to enhance recruitment of human ovarian cancer endothelial progenitor cells

<p>Abstract</p> <p>Background</p> <p>Endothelial progenitor cells (EPCs) contribute to tumor angiogenesis and growth. We aimed to determine whether inhibitors of differentiation 1 (Id1) were expressed in circulating EPCs of patients with ovarian cancer, whether Id1 could mediate EPCs mobilization and recruitment, and, if so, what underlying signaling pathway it used.</p> <p>Methods</p> <p>Circulating EPCs cultures were from 25 patients with ovarian cancer and 20 healthy control subjects. Id1 and integrin α4 expression were analyzed by real-time reverse transcription-polymerase chain reaction and western blot. EPCs proliferation, migration, and adhesion were detected by MTT, transwell chamber, and EPCs-matrigel adhesion assays. Double-stranded DNA containing the interference sequences were synthesized according to the structure of a pGCSIL-GFP viral vector and then inserted into a linearized vector. Positive clones were identified as lentiviral vectors that expressed human Id1 short hairpin RNA (shRNA).</p> <p>Results</p> <p>Id1 and integrin α4 expression were increased in EPCs freshly isolated from ovarian cancer patients compared to those obtained from healthy subjects. siRNA-mediated Id1 downregulation substantially reduced EPCs function and integrin α4 expression. Importantly, Inhibition of PI3K/Akt inhibited Id1 and integrin α4 expression, resulting in the decreasing biological function of EPCs.</p> <p>Conclusions</p> <p>Id1 induced EPCs mobilization and recruitment is mediated chiefly by the PI3K/Akt signaling pathway and is associated with activation of integrin α4.</p