Numerical study of the initial dynamics in tormac

Using a single fluid magnetohydrodynamic (MHD) code, we study the initial plasma dynamics in Tormac, an experimental device which attempts to confine plasma in a toroidal, two-pole cusp field. The code is in two dimensions and includes classical electrical conductivity and a constant heat conductivity. The full set of nonlinear MHD equations for the mass density, fluid velocity, temperature, the poloidal flux function, and the poloidal current function are solved using a predictor-corrector method

Dynamics of an n=1 explosive instability and its role in high-beta disruptions

Some low-n kink-ballooning modes not far from marginal stability are shown to exhibit a bifurcation between two very distinct nonlinear paths that depends sensitively on the background transport levels and linear perturbation amplitudes. The particular instability studied in this work is an n = 1 mode dominated by an m/n = 2/1 component. It is driven by a large pressure gradient in weak magnetic shear and can appear in various high-beta, hybrid/advanced scenarios. Here it is investigated in reversed shear equilibria where the region around the safety-factor minimum provides the low-shear conditions necessary for instability. For a certain range of parameters, a relatively benign path results in a saturated 'long-lived mode' (LLM) that causes little confinement degradation. At the other extreme, the quadrupole geometry of the 2/1 perturbed pressure field evolves into a ballooning finger that subsequently transitions from exponential to explosive growth. The finger eventually leads to a fast disruption with precursors too short for any mitigation effort. Interestingly, the saturated LLM state is found to be metastable; it also can be driven explosively unstable by finiteamplitude perturbations. Similarities to some high-beta disruptions in reversed-shear discharges are discussed

Incidence and severity of retinopathy of prematurity in Turkey

Background: The purpose of this study was to estimate the current incidence of retinopathy of prematurity (ROP) and the need for treatment in preterm infants in Turkey. Methods: The study included preterm infants who had been screened for ROP between 2011 and 2013 in 49 neonatal intensive care units. Infants with birth weight (BW) ≤1500 g or ≤32 weeks' gestational age and those with BW >1500 g or >32 weeks' GA with an unstable clinical course were included. The incidence of any ROP or severe ROP and treatment modalities were determined. Results: The study population included 15 745 preterm infants: 11 803 (75%) with GA ≤32 weeks, and 3942 (25%) with GA >32 weeks. Overall, 30% were found to have any stage of ROP, and 5% had severe ROP. Severe ROP was diagnosed in 8.2% of infants with BW ≤1500 g and 0.6% of infants with BW >1500 g. Of all infants diagnosed with ROP, 16.5% needed laser photocoagulation, and 20 patients born at >32 weeks' GA required this treatment modality. Vitroretinal surgery was performed in 28 infants with severe ROP: 23 with GA ≤28 weeks and 5 with GA 29-32 weeks. Conclusions: The findings of our study have the important implication that more mature babies are at risk of severe ROP requiring treatment. An effective programme for detecting and treating ROP should be established in Turkey

Incidence and severity of retinopathy of prematurity in Turkey

PubMed ID: 25868788Background: The purpose of this study was to estimate the current incidence of retinopathy of prematurity (ROP) and the need for treatment in preterm infants in Turkey. Methods: The study included preterm infants who had been screened for ROP between 2011 and 2013 in 49 neonatal intensive care units. Infants with birth weight (BW) ?1500 g or ?32 weeks' gestational age and those with BW >1500 g or >32 weeks' GA with an unstable clinical course were included. The incidence of any ROP or severe ROP and treatment modalities were determined. Results: The study population included 15 745 preterm infants: 11 803 (75%) with GA ?32 weeks, and 3942 (25%) with GA >32 weeks. Overall, 30% were found to have any stage of ROP, and 5% had severe ROP. Severe ROP was diagnosed in 8.2% of infants with BW ?1500 g and 0.6% of infants with BW >1500 g. Of all infants diagnosed with ROP, 16.5% needed laser photocoagulation, and 20 patients born at >32 weeks' GA required this treatment modality. Vitroretinal surgery was performed in 28 infants with severe ROP: 23 with GA ?28 weeks and 5 with GA 29-32 weeks. Conclusions: The findings of our study have the important implication that more mature babies are at risk of severe ROP requiring treatment. An effective programme for detecting and treating ROP should be established in Turkey