Reverse Hawking-Page Phase Transition in de Sitter Black Holes

In the context of black hole chemistry, we study the thermodynamics of asymptotically de Sitter black holes with conformal scalar hair in Einstein gravity. The hair parameter allows us to attain thermodynamic equilibrium between the event horizon and the cosmological horizon. We find that the system of the black hole and the de Sitter space surrounding it undergo a Reverse Hawking-Page phase transition provided we consider the grand-canonical ensemble.Comment: 17 pages, 6 figures; typos fixed, some added discussion, no changes in physics conclusion

Thermalon mediated phase transitions in Gauss-Bonnet gravity

Thermalons can mediate phase transitions between different vacua in higher curvature gravity, potentially changing the asymptotic structure of the spacetime. Treating the cosmological constant as a dynamical parameter, we study these phase transitions in the context of extended thermodynamic phase space. We find that in addition to the AdS to dS phase transitions previously studied, thermal AdS space can undergo a phase transition to an asymptotically flat black hole geometry. In the context of AdS to AdS transitions, we comment on the similarities and differences between thermalon transitions and the Hawking-Page transition.Comment: 20 pages, 11 figures; reference added, corrected to match published versio

An unusual appearance of giant Meckel’s diverticulum

Meckel's diverticulum (MD) results from incomplete involution of the proximal portion of the vitelline duct. Although MD is the most commonly diagnosed congenital gastrointestinal anomaly, it is estimated to affect only 2% of the population worldwide. Most cases are asymptomatic, and diagnosis is often made following investigation of unexplained gastrointestinal bleeding, perforation, inflammation or obstruction that prompt clinic presentation. While MD range in size from 1-10 cm, cases of giant MD (B5 cm) are relatively rare and associated with more severe forms of the complications. Herein, we report a 43-year-old male patient presented at the Emergency Department with a complaint of abdominal pain, associated with fever (38,5C), nausea and anorexia. The clinical examination revealed pain in the right lower quadrant, as well as abdominal guarding and rebound tenderness. The leucocyte count was elevated at 18 × 109/L. Plain abdominal xray depicted multiple air-fluid levels. An abdominal and pelvic CT scan revealed a fluid-filled structure in the pelvis adjacent to the distal small bowel. The surgical method of exploration can be either by laparoscopy or through an open incision. Exploratory laparotomy was performed and revealed oedema throughout the entire small bowel, dilation of small bowel segments, and a giant Meckel's diverticulum (10 cm long) with mushroom appearance on the antimesenteric border of the small bowel at 70 cm proximal to the ileocaecal valve . Resection of the small bowel was performed with a linear stapler and an ileoileal anastomosis was generated using a 80 mm endo-GIA stapler. Patient was discharged on post-operative day 4 without any complications. Histopathologic examination indicated Meckel's diverticulitis without gastric or pancreatic metaplasia.Pan African Medical Journal 2015; 2

Contribution to the study of the dynamic behavior of planetary gears in nonstationary regimes in presence of defects

ABSTRACT: The present PhD study is focused on analyzing the dynamic behavior of planetary gear transmissions in non-stationary conditions in presence of defects. The strategy of this thesis is based on building a numerical model which is referred to a test bench composed of a test planetary gear set mounted back to back with reaction gear set which allow the power recirculation. First of all, modal analysis techniques were studied to characterize the dynamic behavior of the system. a comparative study between three modal analysis techniques was carried out in order to determine the modal properties in different running condition. Stabilization diagram and Modal assurance criterion were used to estimate the obtained modes. Experimental and numerical modes of each technique were compared and discussed. In addition, the effect of load and meshing stiffness variation on the modal parameters were highlighted. The study of the dynamic behavior of the model corresponding to the test bench was performed initially in stationary conditions where the speed and the torque are constant. Modulation sidebands are highlighted through numerical simulations issued from a three-dimensional model and experimental measurements. Influence of the gravity of carrier on the dynamic response were also investigated taking into account the interaction between meshing gears, the weight of the planet carrier systems. Then, the dynamic behavior under non-stationary excitations such as the variable load, variable speed and run up regimes was investigated. Time frequency analysis was developed to characterize frequency of vibration signals issued from non-stationary operating conditions. Numerical results obtained by the Short Time Fourier Transform are validated through vibration measurements on test bench during operation under these conditions. However, a non linear model of the model taking into account the Hertzian stiffness was developed and studied in non stationary regime presented by the variable load and run up regime. Finally, the dynamic response of the system in presence of two kinds of defect was analyzed and discussed in stationary and non stationary regimes. Order tracking method was used to identify the defects in run up and variable loading condition for the simulated and experimental determined signals