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In this study, various results are presented for laser ablation experiments on aluminum and silicon, made in ambient air by means of subpicosecond laser pulses. These results include threshold fluences for plasma formation and for the appearance of various spectral lines, and the single shot fluence required to remove aluminum layers of various specific thicknesses (ranging from 10 to 500 nm) deposited on a silicon substrate. The threshold fluence for plasma formation is of the order of 0.1 J/cm2. Threshold fluences for the appearance of the spectral lines considered vary from 0.1 to about 5 J/cm2. Finally, our results suggest that for high fluences, even for ultrashort laser pulses, the ablation depth is essentially determined by a long-range process, such as thermal conduction in the solid, rather than by the short range optical depth. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Copyright of Néphrologie & Thérapeutique is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Néphrologie & Thérapeutique is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the expansion in ambient air of a plasma produced by laser ablation from an aluminum target is studied with the help of a one-dimensional fluid code that includes a consistent description of ablation and of the subsequent plasma expansion. Two limiting cases for the expansion geometry have been considered: Cartesian and hemispheric. The plasma temperature and electron density as a function of the space coordinate and time have been obtained for laser pulse durations of 100 fs, 200 ps, and 5 ns, and laser fluences up to a few tens of J/cm². Simulation results are in good agreement with experiments. The code shows that for times typically longer than 1 μs, the plasma space-averaged temperature and electron density are nearly independent of the laser parameters and of the chosen expansion geometry. For a given pulse duration the plasma temperature first increases with the fluence and then reaches a saturation value. It is shown that most of the observed plasma behavior can he explained by radiative cooling. [ABSTRACT FROM AUTHOR]

Time-resolved x-ray spectroscopy has been used to investigate ionization dynamics of a micrometer-sized nanosecond laser-plasma during the plasma start-up phase. Experimental results are modeled using two-dimensional hydrodynamic simulations and time-dependent collisional-radiative calculations. The study clearly shows that, due to the rapid expansion cooling, x-ray emission originates predominantly from a well-localized plasma region characterized by rapidly evolving hydrodynamic conditions. In this region, ionization dynamics is found to depart substantially from the steady-state regime. The measurements provide clear evidence of this transient ionization regime showing good agreement with the time-dependent calculations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Introduction Adapter les doses de médicaments au débit de filtration glomérulaire estimé (DFGe) par équation est difficile, notamment chez les personnes obèses. Nous avons évalué la prévalence de prescriptions non adaptées chez des patients atteints de maladie rénale chronique (MRC), en estimant le DFG par l’équation CKD-EPI, indexée ou non à la surface corporelle (SC). Patients/Matériels et méthodes Dans une cohorte incluant 3033 patients suivis en néphrologie pour une MRC avec un DFGe entre 15 et 60 mL/min/1,73 m2, nous avons examiné les doses journalières de principe actif prescrites dans les 3 mois précédant l’inclusion dans l’étude. Une prescription non adaptée à la fonction rénale (fondée sur les recommandations des résumés des caractéristiques des produits) a été définie comme la prescription déclarée d’un médicament contre-indiqué ou à une dose trop élevée pour le DFGe du patient. Observation/Résultats L’âge médian [écart interquartile] des patients était de 69 [61–76] ans ; 66 % étaient des hommes, 43 % avaient un diabète et 36 %, un indice de masse corporelle ≥ 30 kg/m2. La SC moyenne était de 1,90 ± 0,22 m2. Le DFGe moyen était respectivement de 33 mL/min/1,73 m2 et 36 mL/min, selon que l’équation était indexée ou non à la SC. Le nombre médian de médicaments prescrits était de 8 [5–10] par jour. La proportion de patients avec au moins une prescription non adaptée au DFGe était de 52 % avec, et de 47 % sans indexation à la SC. Les hypouricémiants, les antidiabétiques et les médicaments à visée cardiovasculaire étaient les principales classes de médicaments incriminées. Les patients diabétiques avaient avec une SC moyenne de 1,97 ± 0,21 m2 et un DFGe moyen, respectivement, de 33 mL/min/1,73 m2 et 37 mL/min avec et sans indexation à la SC. En conséquence, chez les 273 patients sous metformine (seule ou en association), la prescription était apparemment contre-indiquée chez 53 patients (19 %) avec un DFGe indexé à la SC < 30 mL/min/1,73 m2, mais chez seulement 29 (11 %) en utilisant l’équation désindexée. Discussion/Conclusion La prévalence globale des prescriptions non adaptées à la fonction rénale touche près d’un patient sur deux avec une MRC modérée ou avancée. La prise en compte de la SC pour estimer le DFG induit des variations dans l’évaluation de cette prévalence qui sont d’autant plus importantes que la SC moyenne s’écarte de la valeur standard de 1,73 m2. Il reste cependant à déterminer si la désindexation de l’équation CKD-EPI modifie l’estimation de l’effet de ces prescriptions apparemment non adaptées sur les risques d’événements iatrogènes, d’hospitalisations et de mortalité. [ABSTRACT FROM AUTHOR]

Abstract: In this work, an aluminum laser plasma produced in ambient air at atmospheric pressure by laser pulses at a fluence of 10 J/cm2 is characterized by time- and space-resolved measurements of electron density and temperature. Varying the laser pulse duration from 6 ns to 80 fs and the laser wavelength from ultraviolet to infrared only slightly influences the plasma properties. The temperature exhibits a slight decrease both at the plasma edge and close to the target surface. The electron density is found to be spatially homogeneous in the ablation plume during the first microsecond. Finally, the plasma expansion is in good agreement with the Sedov''s model during the first 500 ns and it becomes subsonic, with respect to the velocity of sound in air, typically 1 μs after the plasma creation. The physical interpretation of the experimental results is also discussed to the light of a one-dimensional fluid model which provides a good qualitative agreement with measurements. [Copyright &y& Elsevier]