X-ray Fluorescence and Neutron Activation Analysis of Obsidian from the Red Sea Coast of Eritrea

The strategic location of Eritrea along the Red Sea coast and the Horn of Africa makes it an important place to study human prehistory over a long span of time. However, recurrent political instability and the environmental adversity in the region have hindered comprehensive archaeological investigation. Paleolithic research in Eritrea began after the country obtained independence from Ethiopia in 1991. Geological survey in the Abdur area, along the Gulf of Zula coast (Figure 1), identified Paleolithic artifacts embedded in reef limestone dating to ~ 125 Ka BP (Walter et al., 2000). Based on this evidence, human coastal adaptation during the Late Pleistocene has been proposed. To explore the archaeological potential of the region, surveys and excavations were recently initiated along the Gulf of Zula and Buri Peninsula portions of the Red Sea coast. The survey documented a series of prehistoric sites from coastal and inland contexts featuring Acheulian, Middle Stone Age (MSA) and Later Stone Age (LSA) artifacts (Beyin and Shea, 2007). The Acheulian and MSA Lithic assemblages include highly deflated surface scatters of handaxes, prepared core products and retouched points made on locally available materials such as basalt, shale, and rhyolite. These assemblages however, lack secured stratigraphic contexts and obtaining radiometric dating is problematical. Excavations at three sites, Asfet, Misse East and Gelalo NW (Figure 1) in 2006 produced archaeological deposits of LSA affinity with mollusk shell association. A large quantity of debitage, blades, bladelets, backed tools and microliths characterize the lithic artifacts. A few of the artifacts are shown in Figure 2. The LSA bearing archaeological strata have been dated to the Early Holocene by 14C (AMS)

Reduction of thermal conductivity in ferroelectric SrTiO3 thin films

Bulk SrTiO3 is a quantum paraelectric in which an antiferrodistortive distortion below approximate to 105 K and quantum fluctuations at low temperature preclude the stabilization of a long-range ferroelectric state. However, biaxial mechanical stress, impurity doping, and Sr nonstoichiometry, among other mechanisms, are able to stabilize a ferroelectric or relaxor ferroelectric state at room temperature, which develops into a longer-range ferroelectric state below 250 K. In this paper, we show that epitaxial SrTiO3 thin films grown under tensile strain on DyScO3 exhibit a large reduction of thermal conductivity, approximate to 60% of at room temperature, with respect to identical strain-free or compressed films. The thermal conductivity shows a further reduction below 250 K, a temperature concurrent with the peak in the dielectric constant [J. H. Haeni et al., Nature (London) 430, 758 (2004)]. These results suggest that strain gradients in the relaxor and ferroelectric phase of SrTiO3 are very effective phonon scatterers, limiting the thermal transport in this material

Tetherin restricts direct cell-to-cell infection of HIV-1

<p>Abstract</p> <p>Background</p> <p>Tetherin (BST-2/CD317/HM1.24) is an interferon (IFN)-inducible factor of the innate immune system, recently shown to exert antiviral activity against HIV-1 and other enveloped viruses by tethering nascent viral particles to the cell surface, thereby inhibiting viral release. In HIV-1 infection, the viral protein U (Vpu) counteracts this antiviral action by down-modulating tetherin from the cell surface. Viral dissemination between T-cells can occur <it>via </it>cell-free transmission or the more efficient direct cell-to-cell route through lipid raft-rich virological synapses, to which tetherin localizes.</p> <p>Results</p> <p>We established a flow cytometry-based co-culture assay to distinguish viral transfer from viral transmission and investigated the influence of tetherin on cell-to-cell spread of HIV-1. Sup-T1 cells inducible for tetherin expression were used to examine the impact of effector and target cell tetherin expression on virus transfer and transmission. Using this assay, we showed that tetherin inhibits direct cell-to-cell virus transfer and transmission. Viral Vpu promoted viral transmission from tetherin-expressing cells by down-modulating tetherin from the effector cell surface. Further, we showed that tetherin on the target cell promotes viral transfer and transmission. Viral infectivity in itself was not affected by tetherin.</p> <p>Conclusion</p> <p>In addition to inhibiting viral release, tetherin also inhibits direct cell-to-cell spread. Viral protein Vpu counteracts this restriction, outweighing its possible cost of fitness in cell-to-cell transmission. The differential role of tetherin in effector and target cells suggest a role for tetherin in cell-cell contacts and virological synapses.</p

Efficient Triangle Counting in Large Graphs via Degree-based Vertex Partitioning

The number of triangles is a computationally expensive graph statistic which is frequently used in complex network analysis (e.g., transitivity ratio), in various random graph models (e.g., exponential random graph model) and in important real world applications such as spam detection, uncovering of the hidden thematic structure of the Web and link recommendation. Counting triangles in graphs with millions and billions of edges requires algorithms which run fast, use small amount of space, provide accurate estimates of the number of triangles and preferably are parallelizable. In this paper we present an efficient triangle counting algorithm which can be adapted to the semistreaming model. The key idea of our algorithm is to combine the sampling algorithm of Tsourakakis et al. and the partitioning of the set of vertices into a high degree and a low degree subset respectively as in the Alon, Yuster and Zwick work treating each set appropriately. We obtain a running time $O \left(m + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right)$ and an $\epsilon$ approximation (multiplicative error), where $n$ is the number of vertices, $m$ the number of edges and $\Delta$ the maximum number of triangles an edge is contained. Furthermore, we show how this algorithm can be adapted to the semistreaming model with space usage $O\left(m^{1/2}\log{n} + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right)$ and a constant number of passes (three) over the graph stream. We apply our methods in various networks with several millions of edges and we obtain excellent results. Finally, we propose a random projection based method for triangle counting and provide a sufficient condition to obtain an estimate with low variance.Comment: 1) 12 pages 2) To appear in the 7th Workshop on Algorithms and Models for the Web Graph (WAW 2010

Comparative biochemical analysis of HIV-1 subtype B and C integrase enzymes

<p>Abstract</p> <p>Background</p> <p>Integrase inhibitors are currently being incorporated into highly active antiretroviral therapy (HAART). Due to high HIV variability, integrase inhibitor efficacy must be evaluated against a range of integrase enzymes from different subtypes.</p> <p>Methods</p> <p>This study compares the enzymatic activities of HIV-1 integrase from subtypes B and C as well as susceptibility to various integrase inhibitors <it>in vitro</it>. The catalytic activities of both enzymes were analyzed in regard to each of 3' processing and strand transfer activities both in the presence and absence of the integrase inhibitors raltegravir (RAL), elvitegravir (EVG), and MK-2048.</p> <p>Results</p> <p>Our results show that integrase function is similar with enzymes of either subtype and that the various integrase strand transfer inhibitors (INSTIs) that were employed possessed similar inhibitory activity against both enzymes.</p> <p>Conclusion</p> <p>This suggests that the use of integrase inhibitors against HIV-1 subtype C will result in comparable outcomes to those obtained against subtype B infections.</p

Report on a Retroperitoneal Teratoma (Foetus in foetu)

Successful removal of a retroperitoneal teratoma from an infant is described. Various theories dealing with the origin of such tumors are discussed. Blood supply, hemopoiesis and circulation of the tumor have been investigated

Field-Induced Magnetization Steps in Intermetallic Compounds and Manganese Oxides: The Martensitic Scenario

Field-induced magnetization jumps with similar characteristics are observed at low temperature for the intermetallic germanide Gd5Ge4and the mixed-valent manganite Pr0.6Ca0.4Mn0.96Ga0.04O3. We report that the field location -and even the existence- of these jumps depends critically on the magnetic field sweep rate used to record the data. It is proposed that, for both compounds, the martensitic character of their antiferromagnetic-to-ferromagnetic transitions is at the origin of the magnetization steps.Comment: 4 pages,4 figure