Interpretation of proton radiography experiments of hohlraums with three-dimensional simulations.

Proton radiography experiments of laser-irradiated hohlraums performed at the OMEGA laser facility are analyzed using three-dimensional (3D) hydrodynamic simulations coupled to a proton trajectography package. Experiments with three different laser irradiation patterns were performed, and each produced a distinct proton image. By comparing these results with synthetic proton images obtained by sending protons through plasma profiles in the hohlraum obtained from 3D radiation hydrodynamic simulations, it is found that the simulated images agree favorably with the experimental images when electric fields, due to the electron pressure gradients that arise from 3D structures occurring during plasma expansion, are included. These comparisons provide quantitative estimates of the electric field present inside the hohlraums.

Experimental evidence for the enhanced and reduced stopping regimes for protons propagating through hot plasmas.

Our understanding of the dynamics of ion collisional energy loss in a plasma is still not complete, in part due to the difficulty and lack of high-quality experimental measurements. These measurements are crucial to benchmark existing models. Here, we show that such a measurement is possible using high-flux proton beams accelerated by high intensity short pulse lasers, where there is a high number of particles in a picosecond pulse, which is ideal for measurements in quickly expanding plasmas. By reducing the energy bandwidth of the protons using a passive selector, we have made proton stopping measurements in partially ionized Argon and fully ionized Hydrogen plasmas with electron temperatures of hundreds of eV and densities in the range 1020-1021 cm-3. In the first case, we have observed, consistently with previous reports, enhanced stopping of protons when compared to stopping power in non-ionized gas. In the second case, we have observed for the first time the regime of reduced stopping, which is theoretically predicted in such hot and fully ionized plasma. The versatility of these tunable short-pulse laser based ion sources, where the ion type and energy can be changed at will, could open up the possibility for a variety of ion stopping power measurements in plasmas so long as they are well characterized in terms of temperature and density. In turn, these measurements will allow tests of the validity of existing theoretical models.

Enhancement of Quasistationary Shocks and Heating via Temporal Staging in a Magnetized Laser-Plasma Jet.

We investigate the formation of a laser-produced magnetized jet under conditions of a varying mass ejection rate and a varying divergence of the ejected plasma flow. This is done by irradiating a solid target placed in a 20 T magnetic field with, first, a collinear precursor laser pulse (10^{12} W/cm^{2}) and, then, a main pulse (10^{13} W/cm^{2}) arriving 9-19 ns later. Varying the time delay between the two pulses is found to control the divergence of the expanding plasma, which is shown to increase the strength of and heating in the conical shock that is responsible for jet collimation. These results show that plasma collimation due to shocks against a strong magnetic field can lead to stable, astrophysically relevant jets that are sustained over time scales 100 times the laser pulse duration (i.e., >70 ns), even in the case of strong variability at the source.

Absolute dosimetric characterization of Gafchromic EBT3 and HDv2 films using commercial flat-bed scanners and evaluation of the scanner response function variability.

Radiochromic films (RCF) are commonly used in dosimetry for a wide range of radiation sources (electrons, protons, and photons) for medical, industrial, and scientific applications. They are multi-layered, which includes plastic substrate layers and sensitive layers that incorporate a radiation-sensitive dye. Quantitative dose can be retrieved by digitizing the film, provided that a prior calibration exists. Here, to calibrate the newly developed EBT3 and HDv2 RCFs from Gafchromic™, we used the Stanford Medical LINAC to deposit in the films various doses of 10 MeV photons, and by scanning the films using three independent EPSON Precision 2450 scanners, three independent EPSON V750 scanners, and two independent EPSON 11000XL scanners. The films were scanned in separate RGB channels, as well as in black and white, and film orientation was varied. We found that the green channel of the RGB scan and the grayscale channel are in fact quite consistent over the different models of the scanner, although this comes at the cost of a reduction in sensitivity (by a factor ∼2.5 compared to the red channel). To allow any user to extend the absolute calibration reported here to any other scanner, we furthermore provide a calibration curve of the EPSON 2450 scanner based on absolutely calibrated, commercially available, optical density filters.

Topology of megagauss magnetic fields and of heat-carrying electrons produced in a high-power laser-solid interaction.

The intricate spatial and energy distribution of magnetic fields, self-generated during high power laser irradiation (at Iλ^{2}∼10^{13}-10^{14} W.cm^{-2}.µm^{2}) of a solid target, and of the heat-carrying electron currents, is studied in inertial confinement fusion (ICF) relevant conditions. This is done by comparing proton radiography measurements of the fields to an improved magnetohydrodynamic description that fully takes into account the nonlocality of the heat transport. We show that, in these conditions, magnetic fields are rapidly advected radially along the target surface and compressed over long time scales into the dense parts of the target. As a consequence, the electrons are weakly magnetized in most parts of the plasma flow, and we observe a reemergence of nonlocality which is a crucial effect for a correct description of the energetics of ICF experiments.

Laboratory formation of a scaled protostellar jet by coaligned poloidal magnetic field.

Although bipolar jets are seen emerging from a wide variety of astrophysical systems, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of protostellar jets, such as the well-studied jet HH 154.

Monochromatic short pulse laser produced ion beam using a compact passive magnetic device.

High-intensity laser accelerated protons and ions are emerging sources with complementary characteristics to those of conventional sources, namely high charge, high current, and short bunch duration, and therefore can be useful for dedicated applications. However, these beams exhibit a broadband energy spectrum when, for some experiments, monoenergetic beams are required. We present here an adaptation of conventional chicane devices in a compact form (10 cm × 20 cm) which enables selection of a specific energy interval from the broadband spectrum. This is achieved by employing magnetic fields to bend the trajectory of the laser produced proton beam through two slits in order to select the minimum and maximum beam energy. The device enables a production of a high current, short duration source with a reproducible output spectrum from short pulse laser produced charged particle beams.

Panniculitis in a patient on methotrexate for mixed connective tissue disease.

Accelerated nodulosis during methotrexate therapy for rheumatoid arthritis has been well described. There have been recent reports of nodulosis in patients on methotrexate for other inflammatory conditions. Panniculitis is a newly discovered pathological entity in this setting. We describe a case of panniculitis in a woman receiving methotrexate for mixed connective tissue disease.

[Diagnostic and therapeutic management of urinary infections. Survey in the medical services of the hospitals south of the Marseille Hospital Center]. / Prise en charge diagnostique et thérapeutique des infections urinaires. Enquête dans les services de médecine des hôpitaux sud du CHU de Marseille.

OBJECTIVE: The aim of this prospective study was to observe diagnostic and antibiotic prescribing practices in urinary tract infection disease (UTID) in comparison with available guidelines. PATIENTS AND METHODS: We included all patients hospitalized in four medical wards of the Sainte-Marguerite Hospital in Marseille France who suffered from UTID. RESULTS: During the study period, 60 cases of UTID were observed, 29 were community-acquired and 31 were nosocomially-acquired. Management of uncomplicated UTID, the most frequent type (47/60 cases), showed considerable divergence between practices and guidelines. Not in keeping with the guidelines, urinalysis reagent strips were only used for 3 of the 47 cases. Furthermore, broad-spectrum antibiotics were prescribed as the first line treatment in more than 70% of the patients whereas only half of these prescriptions were warranted according to the guidelines. For complicated UTID however (13 cases) diagnostic and antibiotic prescribing practices were globally in accordance with the guidelines. CONCLUSION: This survey points out the divergence between guidelines and real management of UTID in hospitals. Clinical practices should be revisited to be in agreement with guidelines. Drafting antibiotic prescription guides explaining UTID management would be helpful for training future physicians.

[Prescriptions and consumption of hypnotic and anxiolytic drugs in the South University Hospital of Marseille]. / Prescription et consommation des médicaments hypnotiques et anxiolytiques dans les services de médecine des hôpitaux sud du CHU de Marseille.

An investigation of prescription and consumption of hypnotic and anxiolytic drugs in hospital was carried out and has associated a transverse prescription study and a prospective consumption study. The prescription study was undertaken on one day in several medical departments of Sainte-Marguerite Hospital in Marseille in February 1999. Of the 91 hospitalized patients included, 42 (46 per cent) had been prescribed a hypnotic or anxiolytic. Furthermore, the quantities of drugs taken out of the pharmacy during the month of February were 1.54 time more than those prescribed. This discrepancy was even more obvious in the case of certain benzodiazepines such as bromazepam (ratio from 1 to 4) and lorazepam (ratio from 1 to 8). Self-prescription and patients being supplied without a prescription are the hypotheses advanced to explain this phenomenon.

[Fragility of scientifically acquired data. The example of fluoride salts in osteoporosis]. / Fragilité des données acquises de la science. L'exemple du fluor dans l'ostéoporose.

Although there is a pathophysiological rationale for the use of sodium fluoride for the treatment of postmenopausal osteoporosis and a long history of clinical trials, there is no evidence today of its clinical efficacy. The use of sodium fluoride was a long-standing practice for many years which became official policy when strong scientific arguments suggested its efficacy. The lack of methodologically solid evidence however raised some doubts, echoed by the regulatory authorities, and led to a re-evaluation. The unacceptable risk/benefit ratio demonstrated by the new results was a major scientific event giving the scientific community a concrete example of why evidence provided by clinical research must be regularly revisited.

[Disclosure of a fatal pheochromocytoma during general anesthesia]. / Révélation d'un phéochromocytome mortel lors d'une anesthésie générale.

A case is reported of a phaeochromocytoma revealed during a general anaesthesia by a sudden hypertensive crisis associated with acute pulmonary oedema and signs of extreme sympathetic stimulation (bilateral mydriasis, piloerection, peripheral vasoconstriction). Aortic angiography revealed the tumour lying in an ectopic retroperitoneal situation and spasm in the superior mesenteric arterial territory. The patient died at the thirtieth hour from septic shock due to necrotizing colitis.