433 research outputs found
Longitude : a privacy-preserving location sharing protocol for mobile applications
Location sharing services are becoming increasingly popular. Although many location sharing services allow users to set up privacy policies to control who can access their location, the use made by service providers remains a source of concern. Ideally, location sharing providers and middleware should not be able to access users’ location data without their consent. In this paper, we propose a new location sharing protocol called Longitude that eases privacy concerns by making it possible to share a user’s location data blindly and allowing the user to control who can access her location, when and to what degree of precision. The underlying cryptographic algorithms are designed for GPS-enabled mobile phones. We describe and evaluate our implementation for the Nexus One Android mobile phone
Land cover analysis in wildland-urban interfaces according to wildfire risk: a case study in the South of France
Each year, forest fires destroy about 500,000 ha of vegetation in Europe, predominantly in the Mediterranean region. Many large fires are linked to the land transformations that have taken place in the Mediterranean region in recent decades that have increased the risk of forest fires. On the one hand, agricultural fallows and orchards are slowly being colonized by vegetation, and on the other hand, the forest is not sufficiently used, both of which result in increased accumulation of fuel. In addition, urbanization combined with forest extension results in new spatial configurations called wildland-urban interfaces (WUI). WUI are commonly defined as areas where urban areas meet and interact with rural lands, wildland vegetation and forests. Spatial analyses were performed using a WUI typology based on two intertwined elements, the spatial organization of homes and the structure of fuel vegetation. The organisation of the land cover in terms of representativeness, complexity or road density was evaluated for each type of WUI. Results showed that there were significant differences between the types of WUI in the study area. Three indicators (i) fire ignition density, derived from the distribution of fire ignition points, (ii) wildfire density, derived from the distribution of wildfire area and (iii) burned area ratio, derived from the proportion of the burned area to the total study area were then compared with each type of WUI. Assuming that the three indicators correspond to important aspects of fire risk, we showed that, at least in the south of France, WUI are at high risk of wildfire, and that of the different types of wildland-urban interfaces, isolated and scattered WUI were the most at risk. Their main land cover characteristics, i.e. low housing and road densities but a high density of country roads, and the availability of burnable vegetation such as forested stands and shrubland (garrigue) explain the high fire risk. Improving our knowledge of relationships between WUI environments and fire risk should increase the efficiency of wildfire prevention: to this end, suitable prevention actions and communication campaigns targeting the types of WUI at the highest risk are recommended
Dzyaloshinskii-Moriya interaction in transport through single molecule transistors
The Dzyaloshinskii-Moriya interaction is shown to result in a canting of
spins in a single molecule transistor. We predict non-linear transport
signatures of this effect induced by spin-orbit coupling for the generic case
of a molecular dimer. The conductance is calculated using a master equation and
is found to exhibit a non-trivial dependence on the magnitude and direction of
an external magnetic field. We show how three-terminal transport measurements
allow for a determination of the coupling-vector characterizing the
Dzyaloshinskii-Moriya interaction. In particular, we show how its orientation,
defining the intramolecular spin chirality, can be probed with ferromagnetic
electrodes
Optical investigation of the charge-density-wave phase transitions in
We have measured the optical reflectivity of the quasi
one-dimensional conductor from the far infrared up to the
ultraviolet between 10 and 300 using light polarized along and normal to
the chain axis. We find a depletion of the optical conductivity with decreasing
temperature for both polarizations in the mid to far-infrared region. This
leads to a redistribution of spectral weight from low to high energies due to
partial gapping of the Fermi surface below the charge-density-wave transitions
at 145 K and 59 K. We deduce the bulk magnitudes of the CDW gaps and discuss
the scattering of ungapped free charge carriers and the role of fluctuations
effects
Manufacturing and Installation of the Compound Cryogenic Distribution Line for the Large Hadron Collider
The Large Hadron Collider (LHC) [1] currently under construction at CERN will make use of superconducting magnets operating in superfluid helium below 2 K. A compound cryogenic distribution line (QRL) will feed with helium at different temperatures and pressures the local elementary cooling loops in the cryomagnet strings. Low heat inleak to all temperature levels is essential for the overall LHC cryogenic performance. Following a competitive tendering, CERN adjudicated in 2001 the contract for the series line to Air Liquide (France). This paper recalls the main features of the technical specification and shows the project status. The basic choices and achievements for the industrialization phase of the series production are also presented, as well as the installation issues and status
On the origin of the A and B electronic Raman scattering peaks in the superconducting state of YBaCuO
The electronic Raman scattering has been investigated in optimally oxygen
doped YBaCuO single crystals as well as in crystals
with non-magnetic, Zn, and magnetic, Ni, impurities. We found that the
intensity of the A peak is impurity independent and their energy to
ratio is almost constant (). Moreover, the
signal at the B channel is completely smeared out when non-magnetic Zn
impurities are present. These results are qualitatively interpreted in terms of
the Zeyher and Greco's theory that relates the electronic Raman scattering in
the A and B channels to \textit{d}-CDW and superconducting order
parameters fluctuations, respectively.Comment: Submited to Phys. Rev. Let
Temporally ordered collective creep and dynamic transition in the charge-density-wave conductor NbSe3
We have observed an unusual form of creep at low temperatures in the
charge-density-wave (CDW) conductor NbSe. This creep develops when CDW
motion becomes limited by thermally-activated phase advance past individual
impurities, demonstrating the importance of local pinning and related
short-length-scale dynamics. Unlike in vortex lattices, elastic collective
dynamics on longer length scales results in temporally ordered motion and a
finite threshold field. A first-order dynamic phase transition from creep to
high-velocity sliding produces "switching" in the velocity-field
characteristic.Comment: 4 pages, 4 eps figures; minor clarifications To be published in Phys.
Rev. Let
The "Strange Metal" is a Projected Fermi Liquid with Edge Singularities
The puzzling "strange metal" phase of the high Tc cuprate phase diagram
reveals itself as closer to a Fermi liquid than previously supposed: it is a
consequence of Gutzwiller projection and does not necessarily require exotica
such as an RVB or mysterious quantum critical points. There is a Fermi
liquid-like excitation spectrum but the excitations are asymmetric between
electrons and holes, show anomalous forward scattering and have Z equal to 0.
We explain the power law dependence of conductivity on frequency and predict
anomalies in the tunneling and photoemission spectra.Comment: replaced tocorrect a math error in a later section, to clarify
exposition, and to add references to more experiment
The heparan sulfate sulfotransferase 3-OST3A (HS3ST3A) is a novel tumor regulator and a prognostic marker in breast cancer
International audienceHeparan sulfate (HS) proteoglycan chains are key components of the breast tumor microenvironment that critically influence the behavior of cancer cells. It is established that abnormal synthesis and processing of HS play a prominent role in tumorigenesis, albeit mechanisms remain mostly obscure. HS function is mainly controlled by sulfotransferases, and here we report a novel cellular and pathophysiological significance for the 3-O-sulfotransferase 3-OST3A (HS3ST3A), catalyzing the final maturation step of HS, in breast cancer. We show that 3-OST3A is epigenetically repressed in all breast cancer cell lines of a panel representative of distinct molecular subgroups, except in human epidermal growth factor receptor 2-positive (HER2+) sloan-kettering breast cancer (SKBR3) cells. Epigenetic mechanisms involved both DNA methylation and histone modifications, producing different repressive chromatin environments depending on the cell molecular signature. Gain and loss of function experiments by cDNA and siRNA transfection revealed profound effects of 3-OST3A expression on cell behavior including apoptosis, proliferation, response to trastuzumab in vitro and tumor growth in xenografted mice. 3-OST3A exerted dual activities acting as tumor-suppressor in lumA-michigan cancer foundation (MCF)-7 and triple negative-MD Anderson (MDA) metastatic breast (MB)-231 cells, or as an oncogenic factor in HER2+-SKBR3 cells. Mechanistically, fluorescence-resonance energy transfer-fluorescence-lifetime imaging microscopy experiments indicated that the effects of 3-OST3A in MCF-7 cells were mediated by altered interactions between HS and fibroblast growth factor-7 (FGF-7). Further, this interplay between HS and FGF-7 modulated downstream ERK, AKT and p38 cascades, suggesting that altering 3-O-sulfation affects FGFR2IIIb-mediated signaling. Corroborating our cellular data, a clinical study conducted in a cohort of breast cancer patients uncovered that, in HER2+ patients, high level expression of 3-OST3A in tumors was associated with reduced relapse-free survival. Our findings define 3-OST3A as a novel regulator of breast cancer pathogenicity, displaying tumor-suppressive or oncogenic activities in a cell-and tumor-dependent context, and demonstrate the clinical value of the HS-O-sulfotransferase 3-OST3A as a prognostic marker in HER2+ patients
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