Data analysis and navigation in high-dimensional chemical and biological spaces

The goal of this master thesis is to develop and validate a visual data-mining approach suitable for the screening of chemicals in the context of REACH [Registration, Evaluation, Authorization and Restriction of Chemicals]. The proposed approach will facilitate the development and validation of non-testing methods via the exploration of environmental endpoints and their relationship with the chemical structure and physicochemical properties of chemicals. The use of an interactive chemical space data exploration tool using 3D visualization and navigation will enrich the information available with additional variables like size, texture and color of the objects of the scene (compounds). The features that distinguish this approach and make it unique are (i) the integration of multiple data sources allowing the recovery in real time of complementary information of the studied compounds, (ii) the integration of several algorithms for the data analysis (dimensional reduction, generation of composite variables and clustering) and (iii) direct user interaction with the data through the virtual navigation mechanism. All this is achieved without the need for specialized hardware or the use of specific devices and high-cost virtual reality and mixed reality

Mesoscopic approach to progressive breakdown in ultrathin SiO2 layers

The opening of a breakdown path across the ultrathin oxide layer in a metal-oxide-semiconductor structure caused by the application of electrical stress can be analyzed within the framework of the physics of mesoscopic conductors. Using the Landauer formula for a quantum point contact, the author is able to show that the saturation of the gate leakage current is linked to the progressive evolution of the constriction's conductance toward the ballistic transport regime. The possible physical mechanisms responsible for energy dissipation inside the breakdown path as well as the limitations of the proposed approach are discussed

Prospects for detecting an ηc′\eta_c' in two photon processes

We argue that an experimental search for an $\eta_c'$, the first radial excitation of the $\eta_c(2980)$, may be carried out using the two photon process e^+e^- \to e^+e^- \gamma \gamma \ra e^+e^-\eta_c'. We estimate the partial width $\Gamma_{\gamma \gamma}(\eta_c')$ and the branching fraction $B(\eta_c' \to h)$, where $h$ is an exclusive hadronic channel, and find that for $h = K^o_s K^\pm \pi^\mp$ it may be possible to observe this state in two photon collisions at CLEO-II.Comment: 9 pages, LATEX forma

Heavy Quarkonia - A Review of the Experimental Status

A review of the present status of the spectroscopy of heavy quarkonia (b-bbar, c-cbar) is presented.Comment: 6 pages, 4 figures, Presented at the 11th International Conference In Quantum ChromoDynamics (QCD 04), Montpellier, France, 5-9 July 200

Eclipsing Binaries with Possible Light-Time Effect

The period changes of six eclipsing binaries have been studied with focus on the light-time effect. With the least squares method we also calculated parameters of such an effect and properties of the unresolved body in these systems. With these results we discussed the probability of presence of such bodies in the systems with respect to possible confirmation by another method. In two systems we also suggested the hypothesis of fourth body or magnetic activity for explanation of the "second-order variability" after subtraction of the light-time effect of the third body.Comment: 4 pages, 1 figure, 2 tables, conference proceeding

On the equilibrium rotation of Earth-like extra-solar planets

The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets is often assumed to be synchronous with their orbital mean motion. The same assumption persisted for Mercury and Venus until radar observations revealed their true spin rates. As many of these planets follow eccentric orbits and are believed to host dense atmospheres, we expect the equilibrium rotation to differ from the synchronous motion. Here we provide a general description of the allowed final equilibrium rotation states of these planets, and apply this to already discovered cases in which the mass is lower than twelve Earth-masses. At low obliquity and moderate eccentricity, it is shown that there are at most four distinct equilibrium possibilities, one of which can be retrograde. Because most presently known "Earth-like" planets present eccentric orbits, their equilibrium rotation is unlikely to be synchronous.Comment: 4 pages, 2 figures. accepted for publication in Astronomy and Astrophysics. to be published in Astronomy and Astrophysic

New Observations and Analysis of the Bright Semi-Detached Eclipsing Binary mu1 Sco

Using new and published photometric observations of mu1 Sco (HR 6247), spanning 70 years, a period of 1.4462700(5) days was determined. It was found that the epoch of primary minimum suggested by Shobbrook at HJD 2449534.178 requires an adjustment to HJD 2449534.17700(9) to align all the available photometric datasets. Using the resulting combined-data light-curve, radial velocities derived from IUE data and the modelling software PHOEBE, a new system solution for this binary was obtained. It appears that the secondary is close to, or just filling, its Roche-lobe.Comment: 4 figures, 6 tables, 9 pages, uses mn2e.sty, to be published in MNRA

The Empirical Mass-Luminosity Relation for Low Mass Stars

This work is devoted to improving empirical mass-luminosity relations and mass-metallicity-luminosity relation for low mass stars. For these stars, observational data in the mass-luminosity plane or the mass-metallicity-luminosity space subject to non-negligible errors in all coordinates with different dimensions. Thus a reasonable weight assigning scheme is needed for obtaining more reliable results. Such a scheme is developed, with which each data point can have its own due contribution. Previous studies have shown that there exists a plateau feature in the mass-luminosity relation. Taking into account the constraints from the observational luminosity function, we find by fitting the observational data using our weight assigning scheme that the plateau spans from 0.28 to 0.50 solar mass. Three-piecewise continuous improved mass-luminosity relations in K, J, H and V bands, respectively, are obtained. The visual mass-metallicity-luminosity relation is also improved based on our K band mass-luminosity relation and the available observational metallicity data.Comment: 8 pages, 2 figures. Accepted for publication in Astrophysics & Space Scienc

Close Binary System GO Cyg

In this study, we present long term photometric variations of the close binary system \astrobj{GO Cyg}. Modelling of the system shows that the primary is filling Roche lobe and the secondary of the system is almost filling its Roche lobe. The physical parameters of the system are $M_1 = 3.0\pm0.2 M_{\odot}$, $M_2 = 1.3 \pm 0.1 M_{\odot}$, $R_1 = 2.50\pm 0.12 R_{\odot}$, $R_2 = 1.75 \pm 0.09 R_{\odot}$, $L_1 = 64\pm 9 L_{\odot}$, $L_2 = 4.9 \pm 0.7 L_{\odot}$, and $a = 5.5 \pm 0.3 R_{\odot}$. Our results show that \astrobj{GO Cyg} is the most massive system near contact binary (NCB). Analysis of times of the minima shows a sinusoidal variation with a period of $92.3\pm0.5$ years due to a third body whose mass is less than 2.3$M_{\odot}$. Finally a period variation rate of $-1.4\times10^{-9}$ d/yr has been determined using all available light curves.Comment: Accepted for publication in New Astronomy, 18 pages, 4 figures, 7 table