Strain to alter the covalency and superconductivity in transition metal diborides

Among layered metal diborides, MB2, only MgB2 is a superconductor. However, a strategically applied mechanical stress that removes metal–boron covalency can turn ScB2 into a superconductor with the same mechanism

Lepton masses and mixings in orbifold models with three Higgs families

We analyse the phenomenological viability of heterotic Z(3) orbifolds with two Wilson lines, which naturally predict three supersymmetric families of matter and Higgs fields. Given that these models can accommodate realistic scenarios for the quark sector avoiding potentially dangerous flavour-changing neutral currents, we now address the leptonic sector, finding that viable orbifold configurations can in principle be obtained. In particular,it is possible to accomodate present data on charged lepton masses, while avoiding conflict with lepton flavour-violating decays. Concerning the generation of neutrino masses and mixings, we find that Z(3) orbifolds offer several interesting possibilities.Comment: 28 pages, 11 figures. References adde

A new species of Prosorhynchoides (Trematoda, Bucephalidae) from the intertidal rocky zone of central Chile

A new bucephalid species, Prosorhynchoides carvajali sp. nov. is described. This parasite was found in three marine fish, Auchenionchus microcirrhis (type-host), A. variolosus and Sicyases sanguineus (other-hosts), collected from the intertidal rocky zones of central Chile. P. carvajali sp. nov. is characterized by a pharynx in a post-equatorial position, a large cirrus sac length (half of the total worm length) and rounded caecum extending dorsally and anteriorly from pharynx. Although Prosorhynchoides carvajali sp. nov. closely resembles P. labiata; the latter has an elongated, narrow and inverted-U-shape caecum, contrasting to P. carvajali sp. nov. which has a larger rounded caecum, directed anteriorly. To our knowledge this is the first known report of Prosorhynchoides on the South American Pacific coast

Geometric Hamilton-Jacobi Theory

The Hamilton-Jacobi problem is revisited bearing in mind the consequences arising from a possible bi-Hamiltonian structure. The problem is formulated on the tangent bundle for Lagrangian systems in order to avoid the bias of the existence of a natural symplectic structure on the cotangent bundle. First it is developed for systems described by regular Lagrangians and then extended to systems described by singular Lagrangians with no secondary constraints. We also consider the example of the free relativistic particle, the rigid body and the electron-monopole system.Comment: 40 page

The high-pressure behavior of CaMoO4

We report a high-pressure study of tetragonal scheelite-type CaMoO4 up to 29 GPa. In order to characterize its high-pressure behavior, we have combined Raman and optical-absorption measurements with density-functional theory calculations. We have found evidence of a pressure-induced phase transition near 15 GPa. Experiments and calculations agree in assigning the high-pressure phase to a monoclinic fergusonite-type structure. The reported results are consistent with previous powder x-ray-diffraction experiments, but are in contradiction with the conclusions obtained from earlier Raman measurements, which support the existence of more than one phase transition in the pressure range covered by our studies. The observed scheelite-fergusonite transition induces significant changes in the electronic band gap and phonon spectrum of CaMoO4. We have determined the pressure evolution of the band gap for the low- and high-pressure phases as well as the frequencies and pressure dependences of the Raman-active and infrared-active modes. In addition, based upon calculations of the phonon dispersion of the scheelite phase, carried out at a pressure higher than the transition pressure, we propose a possible mechanism for the reported phase transition. Furthermore, from the calculations we determined the pressure dependence of the unit-cell parameters and atomic positions of the different phases and their room-temperature equations of state. These results are compared with previous experiments showing a very good agreement. Finally, information on bond compressibility is reported and correlated with the macroscopic compressibility of CaMoO4. The reported results are of interest for the many technological applications of this oxide.Comment: 36 pages, 10 figures, 8 table

1RXS J180408.9-342058: an ultra compact X-ray binary candidate with a transient jet

We present a detailed NIR/optical/UV study of the transient low mass X-ray binary 1RXS J180408.9-342058 performed during its 2015 outburst, aimed at determining the nature of its companion star. We obtained three optical spectra at the 2.1 m San Pedro Martir Observatory telescope (Mexico). We performed optical and NIR photometric observations with both the REM telescope and the New Technology Telescope (NTT) in La Silla. We obtained optical and UV observations from the Swift archive. Finally, we performed optical polarimetry of the source by using the EFOSC2 instrument mounted on the NTT. The optical spectrum of the source is almost featureless since the hydrogen and He I emissions lines, typically observed in LMXBs, are not detected. Similarly, carbon and oxygen lines are neither observed. We marginally detect the He II 4686 AA emission line, suggesting the presence of helium in the accretion disc. No significant optical polarisation level was observed. The lack of hydrogen and He I emission lines in the spectrum implies that the companion is likely not a main sequence star. Driven by the tentative detection of the He II 4686 AA emission line, we suggest that the system could harbour a helium white dwarf. If this is the case, 1RXS J180408.9-342058 would be an ultra-compact X-ray binary. By combining an estimate of the mass accretion rate together with evolutionary tracks for a He white dwarf, we obtain a tentative orbital period of ~ 40 min. On the other hand, we also built the NIR-optical-UV spectral energy distribution (SED) of the source at two different epochs. One SED was gathered when the source was in the soft X-ray state, and it is consistent with the presence of a single thermal component. The second SED, obtained when the source was in the hard X-ray state, shows a thermal component together with a tail in the NIR, likely indicating the presence of a (transient) jet.Comment: 8 pages, 5 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics (Section 7

Analysis of a MEMS-based ring oscillator

International audienceThis work introduces a MEMS oscillator composed exclusively of mechanical switches as logic components. The electromechanical model of the system is developed and the conditions for a periodic response are established

Finger Pinch Loosening and Tightening Torques on Small Cylindrical Handles Among Industrial Workers

An experiment was conducted with 23 assembly line workers in a manufacturing plant to study to the variation in finger torque strengths on small handles. Subjects exerted MVC torques on small cylindrical handles with different finger contact surface finishes (smooth and knurled) and different diameters (3.3, 5.0, 6.4, 9.5, and 19.0 mm). Three similar handles with flanged finger contact were also tested to simulate torqueing on a specific medical device. The flange widths were 6.4, 9.5, and 19.0 cm. Both loosening and tightening peak torques were measured.  Ten males and 13 females between the ages of 22 and 55 years were tested. Each performed 26 different torque exertions while standing (20 on cylinders and 6 on flanges). The results indicated that finger torque strength decreased steadily as diameter of the cylindrical handle, or length of the flange, decreased. It was also stronger for tightening compared to loosening, and for knurled cylinders compared with smooth cylinders. Of greater interest was the 2-factor interaction effects on torque – surface*direction, surface*diameter and diameter*direction for the cylinders; and direction*width for the flanges. These interactions indicate that the change in torque over one torqueing factor is not independent of other factors.  These results have implications for the design of small device parts, as in some types of medical products.