An integrative approach based on probabilistic modelling and statistical inference for morpho-statistical characterization of astronomical data

This paper describes several applications in astronomy and cosmology that are addressed using probabilistic modelling and statistical inference

Broad-area diode-pumped 1W femtosecond fiber system

Summary form only given. High-average-power 310-fs pulses were obtained with an all-fiber chirped pulse amplification (CPA) system. Both the oscillator and the power amplifier are based on Er/Yb-doped fiber for cladding-pumping with broad-area laser diodes. A single 10-cm-long fiber grating is employed in the CPA system as a compact femtosecond-pulse stretcher/compressor

Astrometry via Close Approach Events: Applications to Main-Belt Asteroid (702) Alauda

The release of Gaia catalog is revolutionary to the astronomy of solar system objects. After some effects such as atmospheric refraction and CCD geometric distortion have been taken into account, the astrometric precision for ground-based telescopes can reach the level of tens of milli-arcseconds. If an object approaches a reference star in a small relative angular distance (less than 100 arcseconds), which is called close approach event in this work, the relative positional precision between the object and reference star will be further improved since the systematic effects of atmospheric turbulence and local telescope optics can be reduced. To obtain the precise position of a main-belt asteroid in an close approach event, a second-order angular velocity model with time is supposed in the sky plane. By fitting the relationship between the relative angular distance and observed time, we can derive the time of maximum approximation and calculate the corresponding position of the asteroid. In practice, 5 nights' CCD observations including 15 close approach events of main-belt asteroid (702) Alauda are taken for testing by the 1m telescope at Yunnan Observatory, China. Compared with conventional solutions, our results show that the positional precision significantly improves, which reaches better than 4 milli-arcseconds, and 1 milli-arcsecond in the best case when referenced for JPL ephemeris in both right ascension and declination.Comment: 11 pages, 22 figure

Ultra-large bandwidth hollow-core guiding in all-silica Bragg fibers with nano-supports

We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m.Comment: 9 pages including 5 figure

New insights about the evaluation of human sperm quality: the aromatase example.

Male contribution to the couple's infertility is at first evaluated by the routine examination of semen parameters upon optical microscopy providing valuable information for a rational initial diagnosis and for a clinical management of infertility. But the different forms of infertility defined according to the WHO criteria especially teratozoospermia are not always related to the chromatin structure or to the fertilization capacity. New investigations at the molecular level (transcript and protein) could be developed in order to understand the nature of sperm malformation responsible of human infertility and thus to evaluate the sperm quality. The profile analysis of spermatozoal transcripts could be considered as a fingerprint of the past spermatogenic events. The selection of representative transcripts of normal spermatozoa remains complex because a differential expression (increased, decreased or not modified levels) of specific transcripts has been revealed between immotile and motile sperm fractions issued from normozoospermic donors. Microarrays tests or real-time quantitative PCR could be helpful for the identification of factors involved in the male infertility. Differences in the expression of specific transcripts have been reported between normal and abnormal semen samples. With the aromatase example, we have noted a negative strong correlation between the amount of transcript and the percentage of abnormal forms especially in presence of head defects. Immunocytochemical procedures using fluorescent probes associated with either confocal microscopy or flow cytometry can be also helpful to proceed with further investigations about the localization of proteins in the compartmentalized spermatozoa or the acrosome reaction. The dual location of aromatase both in the equatorial segment, the mid-piece and the tail could explain the double role of this enzyme in acrosome reaction and motility

Order statistics and heavy-tail distributions for planetary perturbations on Oort cloud comets

This paper tackles important aspects of comets dynamics from a statistical point of view. Existing methodology uses numerical integration for computing planetary perturbations for simulating such dynamics. This operation is highly computational. It is reasonable to wonder whenever statistical simulation of the perturbations can be much more easy to handle. The first step for answering such a question is to provide a statistical study of these perturbations in order to catch their main features. The statistical tools used are order statistics and heavy tail distributions. The study carried out indicated a general pattern exhibited by the perturbations around the orbits of the important planet. These characteristics were validated through statistical testing and a theoretical study based on Opik theory.Comment: 9 pages, 12 figures, submitted for publication in Astronomy and Astrophysic

Solving the Klein-Gordon equation using Fourier spectral methods: A benchmark test for computer performance

The cubic Klein-Gordon equation is a simple but non-trivial partial differential equation whose numerical solution has the main building blocks required for the solution of many other partial differential equations. In this study, the library 2DECOMP&FFT is used in a Fourier spectral scheme to solve the Klein-Gordon equation and strong scaling of the code is examined on thirteen different machines for a problem size of 512^3. The results are useful in assessing likely performance of other parallel fast Fourier transform based programs for solving partial differential equations. The problem is chosen to be large enough to solve on a workstation, yet also of interest to solve quickly on a supercomputer, in particular for parametric studies. Unlike other high performance computing benchmarks, for this problem size, the time to solution will not be improved by simply building a bigger supercomputer.Comment: 10 page