VV Pup in a low state: secondary-star irradiation or stellar activity?

Aims. Emission lines in polars show complex profiles with multiple components that are typically ascribed to the accretion stream, threading region, accretion spot, and the irradiated secondary-star. In low-state polars the fractional contribution by the accretion stream, and the accretion spot is greatly reduced offering an opportunity to study the effect of the secondary-star irradiation or stellar activity. We observed VV Pup during an exceptional low-state to study and constrain the properties of the line-forming regions and to search for evidence of chromospheric activity and/or irradiation. Methods. We obtained phase-resolved optical spectra at the ESO VLT+FORS1 with the aim of analyzing the emission line profile and radial velocity as a function of the orbital period. We also tailored irradiated secondary-star models to compare the predicted and the observed emission lines and to establish the nature of the line-forming regions. Results. Our observations and data analysis, when combined with models of the irradiated secondary-star, show that, while the weak low ionization metal lines (FeI and MgI) may be consistent with irradiation processes, the dominant Balmer H emission lines, as well as NaI and HeI, cannot be reproduced by the irradiated secondary-star models. We favor the secondary-star chromospheric activity as the main forming region and cause of the observed H, NaI, and He emission lines, though a threading region very close to the L1 point cannot be excluded.Comment: 10 pages, 9 figures, in press on A&

Emerging giant resonant exciton induced by Ta-substitution in anatase TiO2_{2}: a tunable correlation effect

Titanium dioxide (TiO$_2$) has rich physical properties with potential implications in both fundamental physics and new applications. Up-to-date, the main focus of applied research is to tune its optical properties, which is usually done via doping and/or nano-engineering. However, understanding the role of $d$-electrons in materials and possible functionalization of $d$-electron properties are still major challenges. Herewith, within a combination of an innovative experimental technique, high energy optical conductivity, and of the state-of-the-art {\it ab initio} electronic structure calculations, we report an emerging, novel resonant exciton in the deep ultraviolet region of the optical response. The resonant exciton evolves upon low concentration Ta-substitution in anatase TiO$_{2}$ films. It is surprisingly robust and related to strong electron-electron and electron-hole interactions. The $d$- and $f$- orbitals localization, due to Ta-substitution, plays an unexpected role, activating strong electronic correlations and dominating the optical response under photoexcitation. Our results shed light on a new optical phenomenon in anatase TiO$_{2}$ films and on the possibility of tuning electronic properties by Ta substitution

Variation in Stemmatal Morphology of Larvae of Liodessus noviaffinis Miller (Dytiscidae: Hydroporinae: Bidessini)

Second and third instars tentatively identified as Liodessus noviaffinis Miller have six dorsolateral stemmata near the origin of each antenna. However, each stemma lacks a corneal (cuticular) lens on the surface exterior to its internal sensory pigmented components

TW Hydrae: evidence of stellar spots instead of a Hot Jupiter

TW Hydrae shows significant radial-velocity variations in the optical regime. They have been attributed to a 10 Jupiter Mass planet orbiting the star at 0.04 AU. In this work, we have tested whether the observed RV variations can be caused by stellar spots. We have also analyzed new optical and infrared data to confirm the signal of the planet companion. We fitted the RV variations of TW Hya using a cool spot model. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation <10 m/s, which is less than the errors of the RV measurements discussed in an earlier publication. The analysis of new optical RV data, with typical errors of 10 m/s, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed, although not at a very significant level. The infrared H-band RV curve is almost flat, showing a small variation (<35 m/s) that is not consistent with the optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter around TW Hya.Comment: accepted for publication in A&

Rotational Velocities of Very Low Mass Binaries

We present rotational velocities for individual components of eleven very low mass (VLM) binaries with spectral types between M7.5 and L4. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics (LGS AO) system. The binaries were targeted as part of a dynamical mass program, and their orbital inclinations are used to translate vsini into a rotational velocity for each component. We find that the observed sources tend to be rapid rotators (vsini > 10 km s^(-1)), consistent with previous measurements for ultracool objects. Five systems have component vsini's that are statistically different, with three binaries having velocity differences greater than 25 km s^(-1). To bring these discrepant rotational velocities into agreement would require their rotational axes to be inclined between 10 to 40° with respect to each other, and that at least one component has a significant inclination with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have interesting implications for binary star formation. Two of the binaries with large differences in rotational velocity are also known radio sources, LP 349-25AB and 2MASS 0746+20AB. LP 349-25B is rotating at ∼95 km s^(-1), within a factor of ∼3 of the break up speed, and is one of the most rapidly rotating VLM objects known

Privacy threats and practical solutions for genetic risk tests

Recently, several solutions have been proposed to address the complex challenge of protecting individuals' genetic data during personalized medicine tests. In this short paper, we analyze different privacy threats and propose simple countermeasures for the generic architecture mainly used in the literature. In particular, we present and evaluate a new practical solution against a critical attack of a malicious medical center trying to actively infer raw genetic information of patients. © 2015 IEEE

Electronic structure of the MO oxides (M=Mg, Ca, Ti, V) in the GW approximation

The quasiparticle band structures of nonmagnetic monoxides, MO (M=Mg, Ca, Ti, and V), are calculated by the GW approximation. The band gap and the width of occupied oxygen 2p states in insulating MgO and CaO agree with experimental observation. In metallic TiO and VO, conduction bands originated from metal 3d states become narrower. Then the partial densities of transition metal e_g and t_2g states show an enhanced dip between the two. The effects of static screening and dynamical correlation are discussed in detail in comparison with the results of the Hartree-Fock approximation and the static Coulomb hole plus screened exchange approximation. The d-d Coulomb interaction is shown to be very much reduced by on-site and off-site d-electron screening in TiO and VO. The dielectric function and the energy loss spectrum are also presented and discussed in detail.Comment: 10 pages, 5 figure