Search results for "script"
showing 10 items of 5143 documents
Physical and Chemical Inhomogeneities Inside the Vela SNR Shell: Indications of Ejecta Shrapnels
2007
We present the results of the combined analysis of three XMM-Newton EPIC observations of the northern rim of the Vela SNR. The three pointings cover an area of ~10 pc^2 (at 250 pc) behind the main shock front and we aim at studying with high resolution the spatial distribution of the physical and chemical properties of the X-ray emitting plasma on this large scale. We produce count-rate images and equivalent width maps of the Ne IX and Mg XI emission blends. We also perform a spatially resolved spectral analysis of a set of physically homogeneous regions. We reveal physical and chemical inhomogeneities in the X-ray emitting plasma. In particular, we find large variations of the O, Ne, Mg, a…
Computational Chromosome Conformation Capture by Correlation of ChIP-seq at CTCF motifs
2018
Background: Transcription factors (TFs) bind to gene promoters or distal regulatory elements that interact with the promoter via chromatin looping. While the TF binding sites themselves are detected genome-wide by ChIP-seq experiments, it is difficult to associate them regulated genes without information of chromatin looping. Recent experimental techniques such as Hi-C or ChIA-PET measure long-range interactions genome-wide but are experimentally elaborate and have limited resolution. Here, we present Computational Chromosome Conformation Capture by Correlation of ChIP-seq at CTCF motifs (7C). Results: While ChIP-seq was not designed to detect contacts, the formaldehyde treatment in the ChI…
A weakly random Universe?
2010
The cosmic microwave background (CMB) radiation is characterized by well-established scales, the 2.7 K temperature of the Planckian spectrum and the $10^{-5}$ amplitude of the temperature anisotropy. These features were instrumental in indicating the hot and equilibrium phases of the early history of the Universe and its large scale isotropy, respectively. We now reveal one more intrinsic scale in CMB properties. We introduce a method developed originally by Kolmogorov, that quantifies a degree of randomness (chaos) in a set of numbers, such as measurements of the CMB temperature in some region. Considering CMB as a composition of random and regular signals, we solve the inverse problem of …
Bounding effective operators at the one-loop level: the case of four-fermion neutrino interactions
1994
The contributions of non-standard four-neutrino contact interactions to electroweak observables are considered at the one-loop level by using the effective quantum field theory. The analysis is done in terms of three unknown parameters: the strength of the non-standard neutrino interactions, $\tilde{F}$, an additional derivative coupling needed to renormalize the divergent contributions that appear when the four-neutrino interactions are used at the loop level and a non-standard non-derivative $Z$-${\bar\nu} \nu$ coupling. Then, the precise measurements of the invisible width of the $Z$-boson at LEP and the data on the neutrino deep-inelastic scattering yield the result $\tilde{F} = (-100 \…
Nucleon-to-Delta transition form factors in chiral effective field theory using the complex-mass scheme
2018
We calculate the form factors of the electromagnetic nucleon-to-$\Delta$-resonance transition to third chiral order in manifestly Lorentz-invariant chiral effective field theory. For the purpose of generating a systematic power counting, the complex-mass scheme is applied in combination with the small-scale expansion. We fit the results to available empirical data.
Comparing estimators of the galaxy correlation function
1999
We present a systematic comparison of some usual estimators of the 2--point correlation function, some of them currently used in Cosmology, others extensively employed in the field of the statistical analysis of point processes. At small scales, it is known that the correlation function follows reasonably well a power--law expression $\xi(r) \propto r^{-\gamma}$. The accurate determination of the exponent $\gamma$ (the order of the pole) depends on the estimator used for $\xi(r)$; on the other hand, its behavior at large scale gives information on a possible trend to homogeneity. We study the concept, the possible bias, the dependence on random samples and the errors of each estimator. Erro…
Relaxation of periodic and nonstandard growth integrals by means of two-scale convergence
2019
An integral representation result is obtained for the variational limit of the family functionals $\int_{\Omega}f\left(\frac{x}{\varepsilon}, Du\right)dx$, as $\varepsilon \to 0$, when the integrand $f = f (x,v)$ is a Carath\'eodory function, periodic in $x$, convex in $v$ and with nonstandard growth.
On the observability of Bell's inequality violation in the two-atoms optical Stern-Gerlach model
2005
Using the optical Stern-Gerlach model, we have recently shown that the non-local correlations between the internal variables of two atoms that successively interact with the field of an ideal cavity in proximity of a nodal region are affected by the atomic translational dynamics. As a consequence, there can be some difficulties in observing violation of the Bell's inequality for the atomic internal variables. These difficulties persist even if the atoms travel an antinodal region, except when the spatial wave packets are exactly centered in an antinodal point.
Microscopic description of α-like resonances
2000
A description of $\ensuremath{\alpha}$-like resonances is given in terms of single-particle states including narrow Gamow resonances in continuum. The equations of motion are derived within the multistep shell-model approach; the lowest collective two-particle eigenmodes are used as building blocks for the four-particle states. A good agreement with the low-lying states in ${}^{212}\mathrm{Po}$ is obtained. A new technique to estimate the $\ensuremath{\alpha}$-particle formation amplitude for any multipolarity is proposed. The spectroscopic factor of the $\ensuremath{\alpha}$-decay between ground states is reproduced, but the total width is by two orders of magnitude less than the experimen…
Cosmological perturbations in extended electromagnetism. General gauge invariant approach
2013
A certain vector-tensor (VT) theory is revisited. It was proposed and analyzed as a theory of electromagnetism without the standard gauge invariance. Our attention is first focused on a detailed variational formulation of the theory, which leads to both a modified Lorentz force and the true energy momentum tensor of the vector field. The theory is then applied to cosmology. A complete gauge invariant treatment of the scalar perturbations is presented. For appropriate gauge invariant variables describing the scalar modes of the vector field (A-modes), it is proved that the evolution equations of these modes do not involve the scalar modes appearing in General Relativity (GR-modes), which are…