49 research outputs found
Shock impedance matching experiments in foam-solid targets and implications for "foam buffered ICF"
We studied the influence of foams on laser produced
shocks. Experiments were performed at LULI using a Nd laser
converted to second harmonic, and at MPQ (Max Planck Institut
fĂŒr Quantenoptik) using the iodine Asterix laser converted
to third harmonic. In both cases, sub-ns lasers with pulse
energies of several tens of joules were focused on large
focal spots (hundreds of microns) to reduce 2D effects.
The laser beams were optically smoothed with phase zone
plates (PZP) and directly focused on layered targets made
of a foam layer on the laser side and a stepped Al layer
on the other side. A visible streak camera was used to
detect shock breakthrough at the base and at the step of
the Al target, allowing shock velocity to be determined.
Using the well known SESAME Al equation of state, we determined
shock pressure. A stronger pressure increase was measured
when foam was present, compared to what was obtained by
focusing the laser beam directly on the Al target. This
was due to the impedance mismatch effect at the Al-foam
interface
Shock impedance matching experiments in foam-solid targets : Implications for 'foam-buffered ICF'
The influence of foams on laser-produced shocks has been studied experimentally using sub-ns laser pulses smoothed with phase zone plates and focused on layered foam - aluminium targets. A strong pressure increase was measured when the foam was present in comparison with that obtained by focusing the beam directly onto the aluminium target, due to impedance mismatch at the aluminium - foam interface. Results are compared with computer simulations. The impact of these measurements on the possible use of `foam-buffered targets' for direct-drive inertial confinement fusion is briefly discussed
How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons
COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; pâ<â0.0001) and diagnostic evaluations (16.4% vs. 42.2%; pâ<â0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; pâ<â0.0001) or urgent (20.4% vs. 38.5%; pâ<â0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; pâ<â0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice
Infected pancreatic necrosis: outcomes and clinical predictors of mortality. A post hoc analysis of the MANCTRA-1 international study
: The identification of high-risk patients in the early stages of infected pancreatic necrosis (IPN) is critical, because it could help the clinicians to adopt more effective management strategies. We conducted a post hoc analysis of the MANCTRA-1 international study to assess the association between clinical risk factors and mortality among adult patients with IPN. Univariable and multivariable logistic regression models were used to identify prognostic factors of mortality. We identified 247 consecutive patients with IPN hospitalised between January 2019 and December 2020. History of uncontrolled arterial hypertension (pâ=â0.032; 95% CI 1.135-15.882; aOR 4.245), qSOFA (pâ=â0.005; 95% CI 1.359-5.879; aOR 2.828), renal failure (pâ=â0.022; 95% CI 1.138-5.442; aOR 2.489), and haemodynamic failure (pâ=â0.018; 95% CI 1.184-5.978; aOR 2.661), were identified as independent predictors of mortality in IPN patients. Cholangitis (pâ=â0.003; 95% CI 1.598-9.930; aOR 3.983), abdominal compartment syndrome (pâ=â0.032; 95% CI 1.090-6.967; aOR 2.735), and gastrointestinal/intra-abdominal bleeding (pâ=â0.009; 95% CI 1.286-5.712; aOR 2.710) were independently associated with the risk of mortality. Upfront open surgical necrosectomy was strongly associated with the risk of mortality (pâ<â0.001; 95% CI 1.912-7.442; aOR 3.772), whereas endoscopic drainage of pancreatic necrosis (pâ=â0.018; 95% CI 0.138-0.834; aOR 0.339) and enteral nutrition (pâ=â0.003; 95% CI 0.143-0.716; aOR 0.320) were found as protective factors. Organ failure, acute cholangitis, and upfront open surgical necrosectomy were the most significant predictors of mortality. Our study confirmed that, even in a subgroup of particularly ill patients such as those with IPN, upfront open surgery should be avoided as much as possible. Study protocol registered in ClinicalTrials.Gov (I.D. Number NCT04747990)
Génération de hautes pressions par choc laser : application à la mesure d'équations d'état.
Résumé non disponibl
Recognition of emotions from visual and prosodic cues in Parkinson's disease
OBJECTIVE: To assess whether Parkinson Disease (PD) patients are impaired at perceiving emotions from facial and prosodic cues and whether any putative defective performance concerns recognition of a particular emotion. BACKGROUND: Braak et al. [1] demonstrated that in different stages PD pathology involves the nigrostriatal system, the amygdala, and the insular cortex. Discrete brain lesions to these structures can cause selective deficits in recognising facial and prosodic stimuli expressing particular emotions. However, the investigation of facial and prosodic emotional processing in PD patients has lead to conflicting results. MATERIALS AND METHODS: We compared 27 cognitively unimpaired PD patients with control subjects by means of the Facial Emotion Recognition Battery and the Emotional Prosody Recognition Battery. RESULTS: PD patients were impaired in recognising, selecting, and matching facial affects. In particular, the Facial Emotion Recognition Battery demonstrated a severe impairment in recognising sad and fearful faces. In the Emotional Prosody Recognition Battery PD patients demonstrated a diffuse impairment, including the recognition of emotional and propositional prosody. CONCLUSIONS: Face emotion processing is impaired in PD patients, with a disproportionate deficit involving fear and sadness. The pattern of face expression processing impairment in PD patients might depend on the regional distribution of the pathology. The widespread involvement of both emotional and propositional prosodic processing parallels the aprosodic characteristics of Parkinsonian speech production
Etude expĂ©rimentale et thĂ©orique de la structure Ă©lectronique de l'aluminium en conditions extrĂȘmes par spectroscopie d'absorption X
La matiĂšre en conditions extrĂȘmes appartient au rĂ©gime de la Warm Dense Matter qui se situe Ă la frontiĂšre entre le rĂ©gime plasma dense et le rĂ©gime de la matiĂšre condensĂ©e. Son comportement est encore mal connu et mal dĂ©crit. En effet, sa description thĂ©orique est trĂšs complexe et il est difficile de gĂ©nĂ©rer cet Ă©tat de matiĂšre en laboratoire pour obtenir des donnĂ©es expĂ©rimentales pouvant valider les modĂšles. Ce travail de thĂšse a pour objectif d'Ă©tudier la structure Ă©lectronique de l'aluminium en conditions extrĂȘmes par le diagnostic de la spectroscopie d'absorption X. ExpĂ©rimentalement l'aluminium a Ă©tĂ© portĂ© dans des conditions de fortes densitĂ©s et fortes tempĂ©ratures jusque-lĂ inexplorĂ©es. Par ailleurs, une source X capable de sonder l'aluminium sous choc a Ă©tĂ© gĂ©nĂ©rĂ©e. Deux spectromĂštres X ont permis l'acquisition des spectres d'absorption de l'aluminium dans ces conditions et des diagnostics optiques ont permis de dĂ©duire les conditions de densitĂ© et de tempĂ©rature de l'aluminium de façon indĂ©pendante. En parallĂšle, des calculs ab initio ont Ă©tĂ© rĂ©alisĂ©s pour obtenir des spectres d'absorption dans les mĂȘmes conditions afin de les comparer aux spectres expĂ©rimentaux. Du point de vue thĂ©orique, l'objectif Ă©tait de valider les mĂ©thodes de calcul des spectres d'absorption X dans ce rĂ©gime de fortes densitĂ©s et fortes tempĂ©ratures en analysant les modifications du flanc d'absorption. Le diagnostic de l'absorption X a Ă©galement Ă©tĂ© utilisĂ© pour Ă©tudier le phĂ©nomĂšne physique de la transition mĂ©tal-non mĂ©tal qui a lieu Ă basse densitĂ© (densitĂ© < densitĂ© du solide). Cette transition peut alors ĂȘtre Ă©tudiĂ©e par les changements de la structure Ă©lectronique du systĂšme Ă©tudiĂ©.Matter in extreme conditions belongs to Warm Dense Matter regime which lays between dense plasma regime and condensed matter. This regime is still not well known, indeed it is very complex to generate such plasma in the laboratory to get experimental data and validate models. The goal of this thesis is to study electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy. Experimentally aluminum has reached high densities and high temperatures, up to now unexplored. An X-ray source has also been generated to probe highly compressed aluminum. Two spectrometers have recorded aluminum absorption spectra and aluminum density and temperature conditions have been deduced thanks to optical diagnostics. Experimental spectra have been compared to ab initio spectra, calculated in the same conditions. The theoretical goal was to validate the calculation method in high densities and high temperatures regime with the study of K-edge absorption modifications. We also used absorption spectra to study the metal-non metal transition which takes place at low density (density < solid density). This transition could be study with electronic structure modifications of the system.PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF
Laser shock experiments on metallic glasses: From the Newton's pendulum to spallation process
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Courbes d'Hugoniot de verres métalliques ZrCuAl sous choc laser et évolution de la limite à rupture avec la vitesse de déformation
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Courbes d'Hugoniot de verres métalliques ZrCuAl sous choc laser et évolution de la limite à rupture avec la vitesse de déformation
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