YY CMi: contact or near contact system?

New V photoelectric observations of the eclipsing system YY CMi, obtained at La Silla, Chile, and Merate Observatory, Italy, are presented. New times of minima and ephemeris based on our observations are also given. The V light curve was analysed by using the WD code to derive the geometrical and physical parameters of the system. Since no spectroscopic mass ratio is available, the q-search method was applied to yield the preliminary range of the mass ratio in order to search for the final solution. First the unspotted solution was carried out by using the unperturbed parts of the light curve and applying the DC program of the WD code. The solution was performed by assuming contact (mode 3) and semi-detached (mode 4) configuration, since no classification of the system is possible from the shape of the light curve. The solution in mode 4 does not lead to an acceptable model, since the secondary was found to be slightly overcontact. Therefore the contact solution was finally adopted. Moreover the light curve peculiarities (Max II fainter than Max I and excess of light around the phase 0.32) were explained by assuming a cool and a hot spot on the surface of the secondary (cooler) component. The degree of contact is very small (f about 3%) and the thermal contactis poor (T1-T2) about 650 K. These results together with the high photometric mass ratio q about 0.89 indicate that YY CMi is very probably a system at the beginning or the end of the contact phase.Comment: 7 pages, 7 ps figures. Accepted for Astronomy and Astrophysics, Supplement Serie

Close-up of primary and secondary asteroseismic CoRoT targets and the ground-based follow-up observations

To optimise the science results of the asteroseismic part of the CoRoT satellite mission a complementary simultaneous ground-based observational campaign is organised for selected CoRoT targets. The observations include both high-resolution spectroscopic and multi-colour photometric data. We present the preliminary results of the analysis of the ground-based observations of three targets. A line-profile analysis of 216 high-resolution FEROS spectra of the delta Sct star HD 50844 reveals more than ten pulsation frequencies in the frequency range 5-18 c/d, including possibly one radial fundamental mode (6.92 c/d). Based on more than 600 multi-colour photometric datapoints of the beta Cep star HD180642, spanning about three years and obtained with different telescopes and different instruments, we confirm the presence of a dominant radial mode nu1=5.48695 c/d, and detect also its first two harmonics. We find evidence for a second mode nu2=0.3017 c/d, possibly a g-mode, and indications for two more frequencies in the 7-8 c/d domain. From Stromgren photometry we find evidence for the hybrid delta Sct/gamma Dor character of the F0 star HD 44195, as frequencies near 3 c/d and 21 c/d are detected simultaneously in the different filters.Comment: 7 pages, 6 figures, HELAS II International Conference "Helioseismology, Asteroseismology and MHD Connections", 2008, J.Phys.: Conf. Ser. 118, 01207

Spectroscopic Survey of {\gamma} Doradus Stars I. Comprehensive atmospheric parameters and abundance analysis of {\gamma} Doradus stars

We present a spectroscopic survey of known and candidate $\gamma$\,Doradus stars. The high-resolution, high signal-to-noise spectra of 52 objects were collected by five different spectrographs. The spectral classification, atmospheric parameters (\teff, $\log g$, $\xi$), $v\sin i$ and chemical composition of the stars were derived. The stellar spectral and luminosity classes were found between G0-A7 and IV-V, respectively. The initial values for \teff\ and \logg\ were determined from the photometric indices and spectral energy distribution. Those parameters were improved by the analysis of hydrogen lines. The final values of \teff, \logg\ and $\xi$ were derived from the iron lines analysis. The \teff\ values were found between 6000\,K and 7900\,K, while \logg\,values range from 3.8 to 4.5\,dex. Chemical abundances and $v\sin i$ values were derived by the spectrum synthesis method. The $v\sin i$ values were found between 5 and 240\,km\,s$^{-1}$. The chemical abundance pattern of $\gamma$\,Doradus stars were compared with the pattern of non-pulsating stars. It turned out that there is no significant difference in abundance patterns between these two groups. Additionally, the relations between the atmospheric parameters and the pulsation quantities were checked. A strong correlation between the $v\sin i$ and the pulsation periods of $\gamma$\,Doradus variables was obtained. The accurate positions of the analysed stars in the H-R diagram have been shown. Most of our objects are located inside or close to the blue edge of the theoretical instability strip of $\gamma$\,Doradus.Comment: 18 pages, 13 figure

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate their fundamental parameters and the abundances of 16 chemical species in a self-consistent manner. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general abundance trends as a function of the metallicity observed in stars of the Galactic disk. After an allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN cycle. A contamination by NeNa-cycled material in the most massive stars is also discussed. With the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low- and intermediate-mass stars.Comment: Accepted for publication in A&A, 25 pages, 13 colour figures (revised version after language editing

Pretransitional behavior in a water-DDAB-5CB microemulsion close to the demixing transition. Evidence for intermicellar attraction mediated by paranematic fluctuations

We present a study of a water-in-oil microemulsion in which surfactant coated water nanodroplets are dispersed in the isotropic phase of the thermotropic liquid crystal 5CB. As the temperature is lowered below the isotropic to nematic phase transition of pure 5CB, the system displays a demixing transition leading to a coexistence of a droplet rich isotropic phase with a droplet poor nematic. The transition is anticipated, in the high T side, by increasing pretransitional fluctuations in 5CB molecular orientation and in the nanodroplet concentration. The observed phase behavior supports the notion that the nanosized droplets, while large enough for their statistical behavior to be probed via light scattering, are also small enough to act as impurities, disturbing the local orientational ordering of the liquid crystal and thus experiencing pretransitional attractive interaction mediated by paranematic fluctuations. The pretransitional behavior, together with the topology of the phase diagram, can be understood on the basis of a diluted Lebwohl-Lasher model which describes the nanodroplets simply as holes in the liquid crystal.Comment: 64 pages, 16 figures, J. Chem. Phys. in pres

CAPMIX -Deploying Capacitors for Salt Gradient Power Extraction

AbstractThe process of mixing sea and river water can be utilised as a power source. At present, three groups of technology are established for doing so; i) mechanical; Pressure Retarded Osmosis PRO, ii) electrochemical reactions; Reverse ElectroDialysis (RED) and Nano Battery Electrodes (NBE) and iii) ultra capacitors; Capacitive Double Layer Expansion (CDLE) and Capacitors charge by the Donnan Potentials (CDP). The chemical potential for salt gradient power systems is only limited by the feed solution concentrations and is the same for all types of salt power branches, but the electric work to the grid, however, relies on the route of conversion and means chosen therein. The CAPMIX project is a joint project to develop and explore ultra capacitors for doing so.Ultra-capacitor materials can interact with sea and river water in order to be deployed as an electricity source. The author consortium is currently exploring two routes to extract the potential free energy from mixing sea and river water by such means. These two routes are the Capacitive Double Layer Expansion (CDLE) and Capacitors charge by the Donnan Potentials (CDP), which are both recently reported, since 2009. The denominator of the two processes is the porous carbon capacitors constituting the capacitors where the chemical energy is converted into electric energy (current). The CDP differs from the CDLE mainly because it includes the use of membranes in addition to the capacitor materials

A nonhomogeneous boundary value problem in mass transfer theory

We prove a uniqueness result of solutions for a system of PDEs of Monge-Kantorovich type arising in problems of mass transfer theory. The results are obtained under very mild regularity assumptions both on the reference set $\Omega\subset\mathbf{R}^n$, and on the (possibly asymmetric) norm defined in $\Omega$. In the special case when $\Omega$ is endowed with the Euclidean metric, our results provide a complete description of the stationary solutions to the tray table problem in granular matter theory.Comment: 22 pages, 2 figure

Characterization of anisotropic nano-particles by using depolarized dynamic light scattering in the near field

Light scattering techniques are widely used in many fields of condensed and sof t matter physics. Usually these methods are based on the study of the scattered light in the far field. Recently, a new family of near field detection schemes has been developed, mainly for the study of small angle light scattering. These techniques are based on the detection of the light intensity near to the sample, where light scattered at different directions overlaps but can be distinguished by Fourier transform analysis. Here we report for the first time data obtained with a dynamic near field scattering instrument, measuring both polarized and depolarized scattered light. Advantages of this procedure over the traditional far field detection include the immunity to stray light problems and the possibility to obtain a large number of statistical samples for many different wave vectors in a single instantaneous measurement. By using the proposed technique we have measured the translational and rotational diffusion coefficients of rod-like colloidal particles. The obtained data are in very good agreement with the data acquired with a traditional light scattering apparatus.Comment: Published in Optics Express. This version has changes in bibliograph