Determination of the Primordial Magnetic Field Power Spectrum by Faraday Rotation Correlations

(Abridged) This paper introduces the formalism which connects between rotation measure (\RM) measurements for extragalactic sources and the cosmological magnetic field power spectrum. It is shown that the amplitude and shape of the cosmological magnetic field power spectrum can be constrained by using a few hundred radio sources, for which Faraday \RMs are available. This constraint is of the form B_{rms} \simless 1 \times [2.6\times10^{-7} cm^{-3}/ \bar n_b] h nano-Gauss (nG) on \sim 10-50 \hmpc scales. The constraint is superior to and supersedes any other constraint which come from either CMB fluctuations, Baryonic nucleosyn thesis, or the first two multipoles of the magnetic field expansion. Demonstration of the ability to detect such magnetic fields, using Bayesian statistics, is carried out by constructing simulations of the field and mimicking observations. This procedure also provides error estimates for the derived quantities. The two main noise contributions due to the Galactic RM and the internal RM are treated in a statistical way. For power indices -1\leq n \leq 1 in a flat cosmology (Omega_m=1) we estimate the signal-to-noise ratio, Q, for limits on the magnetic field B_{rms} on ~50 h^{-1}Mpc scale. Employing one patch of a few square degrees on the sky with source number density n_{src}, an approximate estimate yields Q\simeq 3 \times (B_{rms}/1 {nG})(n_{src}/50 {deg}^{-2}) (2.6\times10^{-7} {cm}^{-3}/ \bar n_b) h $. An all sky coverage, with much sparser, but carefully tailored sample of ~500 sources, yields Q \simeq 1 with the same scaling. An ideal combination of small densely sampled patches and sparse all-sky coverage yields Q\simeq 3 with better constraints for the power index. All of these estimates are corroborated by the simulations.Comment: 30 pages, figures included, To appear in the Ap.

Identification of a Proliferation Gene Cluster Associated with HPV E6/E7 Expression Level and Viral DNA Load in Invasive Cervical Carcinoma

Specific HPV DNA sequences are associated with more than 90% of invasive carcinomas of the uterine cervix. Viral E6 and E7 oncogenes are key mediators in cell transformation by disrupting TP53 and RB pathways. To investigate molecular mechanisms involved in the progression of invasive cervical carcinoma, we performed a gene expression study on cases selected according to viral and clinical parameters. Using Coupled Two-Way Clustering and Sorting Points Into Neighbourhoods methods, we identified a Cervical Cancer Proliferation Cluster composed of 163 highly correlated transcripts, many of which corresponded to E2F pathway genes controlling cell proliferation, whereas no primary TP53 targets were present in this cluster. The average expression level of the genes of this cluster was higher in tumours with an early relapse than in tumours with a favourable course (P=0.026). Moreover, we found that E6/E7 mRNA expression level was positively correlated with the expression level of the cluster genes and with viral DNA load. These findings suggest that HPV E6/E7 expression level plays a key role in the progression of invasive carcinoma of the uterine cervix via the deregulation of cellular genes controlling tumour cell proliferation. HPV expression level may thus correspond to a biological marker useful for prognosis assessment and specific therapy of the disease

Dynamic model and stationary shapes of fluid vesicles

A phase-field model that takes into account the bending energy of fluid vesicles is presented. The Canham-Helfrich model is derived in the sharp-interface limit. A dynamic equation for the phase-field has been solved numerically to find stationary shapes of vesicles with different topologies and the dynamic evolution towards them. The results are in agreement with those found by minimization of the Canham-Helfrich free energy. This fact shows that our phase-field model could be applied to more complex problems of instabilities.Comment: Accepted for publication in EPJE. 9 pages, 7 figure

Lensing by Lyman Limit Systems: Determining the Mass to Gas Ratio

We present a new method to determine the total mass-to-neutral gas ratio in Lyman-limits systems. The method exploits the relation between the neutral hydrogen column density and the magnification of background sources due to the weak gravitational lensing that these systems induce. Because weak lensing does not provide a direct measure of mass, one must use this relation in a statistical sense to solve for the average mass-to-gas ratio and its distribution. We use a detailed mock catalog of quasars (sources) and Lyman-limit systems (lenses) to demonstrate the applicability of this approach through our ability to recover the parameter. This mock catalog also allows us to check for systematics in the method and to sketch its limitations. For a universal constant mass-to-gas ratio and a sample of N quasars, we obtain an unbiased estimate of its value with 95% confidence limits (independent of its actual value) of +/- 140 {10^5/N)^0.5.Comment: 20 pages, 11 figures submitted to Ap

A First Step Towards Automatically Building Network Representations

To fully harness Grids, users or middlewares must have some knowledge on the topology of the platform interconnection network. As such knowledge is usually not available, one must uses tools which automatically build a topological network model through some measurements. In this article, we define a methodology to assess the quality of these network model building tools, and we apply this methodology to representatives of the main classes of model builders and to two new algorithms. We show that none of the main existing techniques build models that enable to accurately predict the running time of simple application kernels for actual platforms. However some of the new algorithms we propose give excellent results in a wide range of situations