Project of a superfluid He3 detector for direct detection of non-baryonic dark matter : MACHe3

MACHe3 (MAtrix of Cells of superfluid Helium 3) is a project of non-baryonic Dark Matter search using superfluid He3 as sensitive medium. Simulations on a high granularity matrix show very good rejection against background events. First results on a prototype cell are very encouraging. Neutron detection has been highlighted as well as cosmic muon detection. A phenomenological study has been done with the DarkSUSY code to investigate complementarity of MACHe3 with existing Dark Matter detectors.Comment: 5 pages, 5 figures, to appear in Proceedings of the 4th Marseille International Cosmology Conferenc

Electromagnetic surface states in structured perfect-conductor surfaces

Surface-bound modes in metamaterials forged by drilling periodic hole arrays in perfect-conductor surfaces are investigated by means of both analytical techniques and rigorous numerical solution of Maxwell's equations. It is shown that these metamaterials cannot be described in general by local, frequency-dependent permittivities and permeabilities for small periods compared to the wavelength, except in certain limiting cases that are discussed in detail. New related metamaterials are shown to exhibit exciting optical properties that are elucidated in the light of our simple analytical approach.Comment: 5 figure

Multiboost: a multi-purpose boosting package

http://jmlr.csail.mit.edu/papers/v13/benbouzid12a.htmlThe MultiBoost package provides a fast C++ implementation of multi-class/multi-label/multi-task boosting algorithms. It is based on AdaBoost.MH but it also implements popular cascade classifiers and FilterBoost. The package contains common multi-class base learners (stumps, trees, products, Haar filters). Further base learners and strong learners following the boosting paradigm can be easily implemented in a flexible framework

Spin-orbit coupled Bose-Einstein condensate in a tilted optical lattice

Bloch oscillations appear for a particle in a weakly tilted periodic potential. The intrinsic spin Hall effect is an outcome of a spin-orbit coupling. We demonstrate that both these phenomena can be realized simultaneously in a gas of weakly interacting ultracold atoms exposed to a tilted optical lattice and to a set of spatially dependent light fields inducing an effective spin-orbit coupling. It is found that both the spin Hall as well as the Bloch oscillation effects may coexist, showing, however, a strong correlation between the two. These correlations are manifested as a transverse spin current oscillating in-phase with the Bloch oscillations.Comment: 12 pages, 7 figure

Energy-dependent effective interactions for dilute many-body systems

We address the issue of determining an effective two-body interaction for mean-field calculations of energies of many-body systems. We show that the effective interaction is proportional to the phase shift, and demonstrate this result in the quasiclassical approximation when there is a trapping potential in addition to the short-range interaction between a pair of particles. We calculate numerically energy levels for the case of an interaction with a short-range square-well and a harmonic trapping potential and show that the numerical results agree well with the analytical expression. We derive a generalized Gross--Pitaevskii equation which includes effective range corrections and discuss the form of the electron--atom effective interaction to be used in calculations of Rydberg atoms and molecules.Comment: 6 pages, 2 figure

Force dependent fragility in RNA hairpins

We apply Kramers theory to investigate the dissociation of multiple bonds under mechanical force and interpret experimental results for the unfolding/refolding force distributions of an RNA hairpin pulled at different loading rates using laser tweezers. We identify two different kinetic regimes depending on the range of forces explored during the unfolding and refolding process. The present approach extends the range of validity of the two-states approximation by providing a theoretical framework to reconstruct free-energy landscapes and identify force-induced structural changes in molecular transition states using single molecule pulling experiments. The method should be applicable to RNA hairpins with multiple kinetic barriers.Comment: Latex file, 4 pages+3 figure

Microstructure Effects for Casimir Forces in Chiral Metamaterials

We examine a recent prediction for the chirality-dependence of the Casimir force in chiral metamaterials by numerical computation of the forces between the exact microstructures, rather than homogeneous approximations. We compute the exact force for a chiral bent-cross pattern, as well as forces for an idealized "omega"-particle medium in the dilute approximation and identify the effects of structural inhomogeneity (i.e. proximity forces and anisotropy). We find that these microstructure effects dominate the force for separations where chirality was predicted to have a strong influence. To get observations of chirality free from microstructure effects, one must go to large separations where the effect of chirality is at most $\sim10^{-4}$ of the total force.Comment: 5 pages, 4 figure

Expression levels of HMGA2 in adipocytic tumors correlate with morphologic and cytogenetic subgroups

Background: The HMGA2 gene encodes a protein that alters chromatin structure. Deregulation, typically through chromosomal rearrangements, of HMGA2 has an important role in the development of several mesenchymal neoplasms. These rearrangements result in the expression of a truncated protein lacking the acidic C-terminus, a fusion protein consisting of the AT-hook domains encoded by exons 1-3 and parts from another gene, or a full-length protein; loss of binding sites for regulatory microRNA molecules from the 3' untranslated region (UTR) of HMGA2 has been suggested to be a common denominator.Methods: Seventy adipocytic tumors, representing different morphologic and cytogenetic subgroups, were analyzed by qRT-PCR to study the expression status of HMGA2; 18 of these tumors were further examined by PCR to search for mutations or deletions in the 3'UTR.Results: Type (full-length or truncated) and level of expression varied with morphology and karyotype, with the highest levels in atypical lipomatous tumors and lipomas with rearrangements of 12q13-15 and the lowest in lipomas with 6p- or 13q-rearrangements, hibernomas, spindle cell lipomas and myxoid liposarcomas. All 18 examined tumors showed reduced or absent expression of the entire, or parts of, the 3'UTR, which was not due to mutations at the DNA level.Conclusion: In adipocytic tumors with deregulated HMGA2 expression, the 3'UTR is consistently lost, either due to physical disruption of HMGA2 or a shift to production of shorter 3'UTR