Using X-ray spectroscopy of relativistic laser plasma interaction to reveal parametric decay instabilities: a modeling tool for astrophysics.

By analyzing profiles of experimental x-ray spectral lines of Si XIV and Al XIII, we found that both Langmuir and ion acoustic waves developed in plasmas produced via irradiation of thin Si foils by relativistic laser pulses (intensities ~1021 W/cm2). We prove that these waves are due to the parametric decay instability (PDI). This is the first time that the PDI-induced ion acoustic turbulence was discovered by the x-ray spectroscopy in laser-produced plasmas. These conclusions are also supported by PIC simulations. Our results can be used for laboratory modeling of physical processes in astrophysical objects and a better understanding of intense laser-plasma interactions.

[Full field optical coherence tomography of prostate biopsies: a step towards pre-histological diagnosis?]. / Tomographie par cohérence optique plein champ des biopsies de la prostate: un pas vers le diagnostic pré-histologique?

OBJECTIVES: To evaluate the value of full field optical coherence tomography (FFOCT) for cancer detection on prostate biopsies PATIENTS AND METHODS: Eight consecutive patients who underwent prostate biopsies for an elevated PSA or suspicious DRE findings were included in the study. For each patient, one to three biopsy cores were imaged with FFOCT immediately after sampling. Images obtained were analyzed by a pathologist blinded to the pathological results, and classified into three categories: non-cancerous tissue, suspicion of malignancy and prostate carcinoma. A pathological correlation analysis was further performed. RESULTS: Sixteen biopsy cores were analyzed. The median FFOCT procedure time was of 4 (3-5) minutes. No artifact was noted in subsequent pathological analysis. Six cores were involved with cancer and eight cores showed no evidence of cancer. On two cores, diagnosis was uncertain, and immuno-histochemical analysis confirmed cancer involvement in one of them. The agreement rate between standard histological analysis and FFOCT evaluation was of 81% (13/16). The three cases of disagreement were due to one false positive and two false negatives of FFOCT analysis. CONCLUSIONS: FFOCT of prostate biopsy cores seemed to be feasible and to allow concordant results with those of pathological analysis in the majority of the cases.

Floquet-Liouville approach for calculating Stark profiles in plasmas in the presence of a strong oscillating field.

The formalism for the calculation of Stark line profiles in hot dense plasmas submitted to a strong oscillating field is extensively developed. The Liouville space, usually used to deal with the calculation of Stark profiles in dense plasmas, and the Floquet theory, developed to solve time-periodic problems, have been joined together to solve the time-dependent Liouville equation in the so-called Floquet-Liouville formalism. The strong-oscillating-field spectroscopic signatures and their error estimations are discussed for hydrogen- and heliumlike aluminum lines.

Experimental discovery of charge-exchange-caused dips in spectral lines from laser-produced plasmas.

We report the first experimental observation of charge-exchange-caused dips (also called x dips) in spectral lines of multicharged ions in laser-produced plasmas. Specifically, in the process of a laser irradiation of targets made out of aluminum carbide, we observed two x dips in the Ly(gamma) line of Al XIII perturbed by fully stripped carbon. From the practical point of view, this opens up a way to experimentally produce not-yet-available fundamental data on charge exchange between multicharged ions, virtually inaccessible by other experimental methods. From the theoretical viewpoint, the results are important because the x dips are the only one signature of charge exchange in profiles of spectral lines emitted by plasmas and they are the only one quasimolecular phenomenon that could be observed at relatively "low" densities of laser-produced plasmas.

Extrema in transition energies resulting not in satellites but in dips within spectral lines

The paper deals with a frequently encountered situation where the energy difference between the terms involved in a radiative transition, being plotted versus the radiator-perturber separation, shows extrema. The paradigm, based on 30 years of theoretical and experimental studies, is that the extrema in the transition energy result in satellites in spectral line profiles. In this Rapid Communication we show that this paradigm breaks down: the extrema in the transition energy can also result in dips in spectral line profiles. Moreover, we demonstrate that if the extremum in the transition energy is due to the charge exchange, its spectral signature most probably should be a dip rather than a satellite.

Hydrogen Balmer-alpha broadening in dense plasmas.

This work presents a theoretical analysis of experimental results for the hydrogen Balmer-alpha line in dense plasmas, with electron densities between 2x10(18) and 9x10(18) e/cm(3) A simulation of both electrons and ions is employed to produce reliable theoretical widths. These results are essentially in agreement with standard theory results and, for the most part, disagree with the experimental results. Consequently, either mechanisms not accounted for in the theoretical results (such as quadrupoles) are more important than previously thought at these densities, or else there is a problem in the experimental data (such as a possible reabsorption, which is not ruled out by the experimental data).