Green's function probe of a static granular piling

We present an experiment which aim is to investigate the mechanical properties of a static granular assembly. The piling is an horizontal 3D granular layer confined in a box, we apply a localized extra force at the surface and the spatial distribution of stresses at the bottom is obtained (the mechanical Green's function). For different types of granular media, we observe a linear pressure response which profile shows one peak centered at the vertical of the point of application. The peak's width increases linearly when increasing the depth. This green function seems to be in -at least- qualitative agreement with predictions of elastic theory.Comment: 9 pages, 3 .eps figures, submitted to PR

Mesure expérimentale de la fonction réponse d'un matériau granulaire

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Jamming Patterns and Blockade Statistics in Model Granular Flows

International audienc

The white test for intraoperative screening of bile leakage: a potential trigger factor for acute pancreatitis after liver resection—a case series

International audienceAcute pancreatitis after liver resection is a rare but serious complication, and few cases have been described in the literature. Extended lymphadenectomy, and long ischemia due to the Pringle maneuver could be responsible of post-liver resection acute pancreatitis, but the exact causes of AP after hepatectomy remain unclear. Cases presentation We report here three cases of AP after hepatectomy and we strongly hypothesize that this is due to the bile leakage white test. 502 hepatectomy were performed at our center and 3 patients (0.6%) experienced acute pancreatitis after LR and all of these three patients underwent the white test at the end of the liver resection. None underwent additionally lymphadenectomy to the liver resection. All patient had a white-test during the liver surgery. We identified distal implantation of the cystic duct in these three patients as a potential cause for acute pancreatitis. Conclusion The white test is useful for detection of bile leakage after liver resection, but we do not recommend a systematic use after LR, because severe acute pancreatitis can be lethal for the patient, especially in case of distal cystic implantation which may facilitate reflux in the main pancreatic duct

Science in the sandbox: Fluctuations, friction and instabilities

The study of granular materials is a novel and rapidly growing field. These materials are interest for a number of reasons, both practical and theoretical. They exhibit a rich of novel dyanamical states, and they exhibit 'phases'-solid, liquid, and gas-that resemble conventional thermodynamic phases. However, the presence of strong dissipation through friction and inelasticity places these systems well outside the usual class of systems that can be explained by equilibrium thermodynamics. Thus, there are important challenges to create new kinds of statistical physics and new analytical descriptions for the mean and fluctuating behavior of these materials. We explore recent work that focuses on several important issues. These include force propagation and fluctuations in static and driven systems. It is well known that forces propagate through granular structures along networks-force chains, whose structure is a function of history. It is much less clear how to describe this process, and even what kind of structures evolve in physical experiments. After a brief overview of the field, we consider models of force propagation and recent experiments to test these models. Among the latter are experiments that probe force profiles at the base of sandpiles and experiments that determine the Green's function response to point perturbations in granular systems. We also explore the nature of force fluctuations in slowly evolving systems, particulary sheared granular systems. These can be very strong-with rms fluctuations in the force that are as strong as the mean force. Finally, we pursue the analogy between conventional phases of matter, where we particularly focus on the transition between fluid and solid granular states in the presence of sustained horizontal shaking