Negative Specific Heat of a Magnetically Self-Confined Plasma Torus

It is shown that the thermodynamic maximum entropy principle predicts negative specific heat for a stationary magnetically self-confined current-carrying plasma torus. Implications for the magnetic self-confinement of fusion plasma are considered.Comment: 10p., LaTeX, 2 eps figure file

Efficient dust ring formation in misaligned circumbinary discs

Binary systems exert a gravitational torque on misaligned discs orbiting them, causing differential precession which may produce disc warping and tearing. While this is well understood for gas-only discs, misaligned cirumbinary discs of gas and dust have not been thoroughly investigated. We perform SKI simulations of misaligned gas and dust discs around binaries to investigate the different evolution of these two components. We choose two different disc aspect ratios: A thin case for which the gas disc always breaks, and a thick one where a smooth warp develops throughout the disc. For each case, we run simulations of five different dust species with different degrees of coupling with the gas component, varying in Stokes number from. 0.002 (strongly coupled dust) to 1000 (effectively decoupled dust). We report two new phenomena: First, large dust grains in thick discs pile up at the warp location, forming narrow dust rings, due to a difference in precession between the gas and dust components. These pile ups do not form at gas pressure maxima, and hence are different.from conventional dust traps. This effect is most evident for St <^> 10-100. Secondly, thin discs tear and break only in the gas, while dust particles with St > 10 form a dense dust trap due to the steep pressure gradient caused by the break in the gas. We find that dust with St < 0.02 closely follow the gas particles, for both thin and thick discs, with radial drift becoming noticeable only for the largest grains in this range

Management of cystic lymphangioma: experience of two referral centers

Introduction/aim Cystic lymphangioma is a benign rare malformation of the lymphatic system consisting of masses of abnormal lymphatic channels, occurring in one out of 2000–4000 live births. Conventional surgical excision remains the most popular method of treatment in many developing countries. Recent advances in sclerotherapy have expanded contemporary management options, particularly when complete surgical resection is difficult because of the presence of multiple loculi and extensive lesions. This study aims to present our experience in the management of these cases.Material and methods Records of all cases of lymphangioma seen at the Pediatric Surgical Unit from Mansoura and Tanta University hospitals in the period from January 2007 to November 2010 were reviewed. Special charts were designed to retrieve the following data from records: age at presentation, sex, site of the pathology, clinical presentation, investigations, management modality, and outcome of treatment.Results There were 93 children; 40 (43%) were males and 53 (57%) were females. Surgery was the line of treatment in 89 cases (one stage in 56 cases and two stages in 33 cases). Four patients underwent injection sclerotherapy as the primary treatment. Recurrence occurred in 16 cases. Other complications included a disfiguring scar in nine patients, seroma in seven patients, skin disruption, hematoma, and hypoglossal nerve palsy in two patients, facial nerve palsy in one patient, and cellulitis following a sclerosant injection in one case.Conclusion A staged operative procedure may be necessary in order to reduce mortality, and sclerotherapy has almost the same efficacy as the first line of management as surgery, although it is not widely practiced in developing countries. There is a high postoperative complication associated with surgical excision, especially with head and neck cystic lymphangiomas. Anesthesia in these patients requires careful monitoring. Long-term follow-up is desirable after excision because of the possibility of recurrence. Keywords: cystic lymphangioma, management, sclerotherap