Signature calorimétrique de cohérence de phase quantique dans des anneaux mésoscopiques

We decide to measure calorimetric signature of quantum phase coherence in mesoscopic ringsNous avons décidé de chercher à mesurer la présence des courants permanents dans des anneaux métalliques mésocopiques d'un point de vue thermique, en enregistrant les variations de chaleur spécifique des anneau

Searching for thermal signatures of persistent currents in normal metal rings

We introduce a calorimetric approach to probe persistent currents in normal metal rings. The heat capacity of a large ensemble of silver rings is measured by nanocalorimetry under a varying magnetic field at different temperatures (60 mK, 100 mK and 150 mK). Periodic oscillations versus magnetic field are detected in the phase signal of the temperature oscillations, though not in the amplitude (both of them directly linked to the heat capacity). The period of these oscillations ($\Phi_0/2$, with $\Phi_0 = h/e$ the magnetic flux quantum) and their evolution with temperature are in agreement with theoretical predictions. In contrast, the amplitude of the corresponding heat capacity oscillations (several $k_{\mathrm{B}}$) is two orders of magnitude larger than predicted by theory

Thermodynamics of small systems by nanocalorimetry: from physical to biological nano-objects

Membrane based nanocalorimeters have been developed for ac calorimetry experiments. It has allowed highly sensitive measurements of heat capacity from solid state physics to complex systems like polymers and proteins. In this article we review what has been developed in ac calorimetry toward the measurement of very small systems. Firstly, at low temperature ac calorimetry using silicon membrane permits the measurement of superconducting sample having geometry down to the nanometer scale. New phase transitions have been found in these nanosystems illustrated by heat capacity jumps versus the applied magnetic field. Secondly, a sensor based on ultra-thin polymer membrane will be presented. It has been devoted to thermal measurements of nanomagnetic systems at intermediate temperature (20K to 300K). Thirdly, three specific polyimide membrane based sensors have been designed for room temperature measurements. One is devoted to phase transitions detection in polymer, the second one to protein folding/unfolding studies and the third one will be used for the study of heat release in living cells. The possibility of measuring systems out of equilibrium will be emphasized

Calorimetric signature of quantum phase coherence in mesoscopic rings.

Dans ce manuscrit, nous présentons des mesures haute résolution de chaleur spécifique Cp réalisées sur des anneaux mésoscopiques d'argent à très basses températures. Le but de cette expérience est de mettre en évidence une possible signature thermique due à la présence de courants permanents. Ce phénomène reste encore mal compris malgré de nombreuses expériences. Il existe en effet des contradictions entre les différents modèles théoriques et les résultats expérimentaux. L'approche thermique que nous exposons ici est un angle nouveau qui n'a jamais été exploré. Sous champ magnétique, une oscillation de période égale au quantum de flux Φ0=h/e (ou moitié) de Cp est attendue théoriquement. L'échantillon étudié est composé d'un grand nombre d'anneaux d'argent mésoscopiques déposés sur une membrane en silicium suspendue. Nous avons réalisé, à différentes températures, de multiples balayages en champ de la chaleur spécifique. Un traitement des signaux obtenus a ensuite été réalisé afin de repérer une éventuelle périodicité. Il a révélé la présence sur le signal de phase d'une oscillation de période h/2e n'apparaissant pas sur le module de la chaleur spécifique. Cette signature est maximale à 100mK. La fréquence et l'amplitude obtenues sont en accord avec les prédictions théoriques. La sensibilité atteinte est de ΔC~10^(-14)J/K sur le module (et de Δφ~10^(-2) degrés sur la phase) soit 10^(-21)J/K par anneau. Les résultats présentés ici apportent donc de nouveaux éléments dans l'analyse des courants permanents.In this thesis, we report very high resolution specific heat measurements of normal metal mesoscopic silver rings at very low temperatures. The objective of this experiment is to measure the possible existence of thermal signatures due to the presence of persistent currents. This phenomenon is still misunderstood despite many measurements. Some contradictions exist between experimental results and the different theories. The thermal approach is a new point of view. Under magnetic field, the Cp variation is expected be periodic with the quantum of flux Φ0=h/e or half of the quantum of flux as it has been theoretically predicted. The studied samples is composed by a large number of silver rings with an electronic phase coherence length of few microns at low temperatures. They were deposited on the suspended membrane of a silicon sensor. We have realized, at different temperatures, a large number of identical scans of the heat capacity variation as a function of the applied field. A signal processing work on this data has then been realized to detect signal periodicities. It showed a difference between the module and the phase of the heat capacity. A peak can be observed on the FFT at a frequency corresponding to h/2e on the phase signal. The peak appears particularly at 100mK with a amplitude which is consistent with previous calculations. A sensitivity of ΔC~10^(-14)J/K on the module (Δφ~10^(-2) degrees on the phase) has been reached whether 10^(-21)J/K per ring. Thus, the presented experiences give new elements in the field of persistent currents

Temperature modulation measurements of the thermal properties of nanosystems at low temperatures

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A reappraisal of outcome of elective surgery after successful non-operative management of an intra-abdominal abscess complicating ileocolonic Crohn's disease.A subgroup analysis of a nationwide prospective cohort.

International audienceFew prospective data exist on outcomes of surgery in Crohn's disease (CD) complicated by an intra-abdominal abscess after resolution of this abscess by antibiotics optionally combined with drainage

Associations between the severity of medical and surgical complications and perception of surgeon empathy in esophageal and gastric cancer patients

International audienceObjective: To assess the impact of global physician empathy and its three subdimensions (establishing rapport, emotional and cognitive processes) on the severity of postoperative complications in a sample of cancer patients.Methods: We retrospectively analyzed data on 256 patients with esogastric cancer from the French national FREGAT database. Empathy and its subdimensions were assessed using the patient-reported CARE scale and the severity of medical and surgical complications was reported with the Clavien-Dindo classification system. The usual covariates were included in multinomial logistic regression analyses.Results: Physician empathy predicted the odds of reporting major complications. When patients perceived high empathy, they were less likely to report major complications compared to no complications (OR = .95, 95% CI = [.91-.99], p = .029). Among the three dimensions, only "establishing rapport" (OR = .84, 95% CI = [.73-.98], p = .019) and the "emotional process" (OR = .85, 95% CI = [.74-.98], p = .022) predicted major complications.Conclusions: Physician empathy is essential before surgery. Further research is needed to understand the mechanisms associating empathy with health outcomes in cancer. Physicians should be trained to establish good rapport with patients, especially in the preoperative period