Massive stars as thermonuclear reactors and their explosions following core collapse

Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are reviewed. How stars manage to burn their fuel so slowly most of the time are also considered. Stellar thermonuclear reactions involving protons in hydrostatic burning are discussed first. Then I discuss triple alpha reactions in the helium burning stage. Carbon and oxygen survive in red giant stars because of the nuclear structure of oxygen and neon. Further nuclear burning of carbon, neon, oxygen and silicon in quiescent conditions are discussed next. In the subsequent core-collapse phase, neutronization due to electron capture from the top of the Fermi sea in a degenerate core takes place. The expected signal of neutrinos from a nearby supernova is calculated. The supernova often explodes inside a dense circumstellar medium, which is established due to the progenitor star losing its outermost envelope in a stellar wind or mass transfer in a binary system. The nature of the circumstellar medium and the ejecta of the supernova and their dynamics are revealed by observations in the optical, IR, radio, and X-ray bands, and I discuss some of these observations and their interpretations.Comment: To be published in " Principles and Perspectives in Cosmochemistry" Lecture Notes on Kodai School on Synthesis of Elements in Stars; ed. by Aruna Goswami & Eswar Reddy, Springer Verlag, 2009. Contains 21 figure

Dietary intervention strategies for ethnic Chinese women with gestational diabetes mellitus:A systematic review and meta-analysis

Aim Ethnic Chinese women are one of the populations at high risk of gestational diabetes mellitus (GDM) internationally. This systematic review aimed to determine which dietary intervention strategies were found to be effective in improving glycaemic control and pregnancy outcomes among ethnic Chinese women with GDM. Methods The review protocol was registered with PROSPERO (CRD42016043585). Eight English and four Chinese language databases were searched for randomised controlled trials and cohort studies of dietary intervention among ethnic Chinese women with GDM. Review Manager 5.3 and GRADE criteria were used in meta-analysis and assessment of quality of evidence. Results Included studies comprised 3944 women in 29 eligible studies. Compared to standard treatment, low glycaemic index (GI) diets, low glycaemic load (GL) diets and fibre-enriched diets were associated with a reduction in fasting plasma glucose, 2-hour plasma glucose and HbA1c, and improved neonatal outcomes. Low GL diets were associated with reduced caesarean section risk. Conclusions In ethnic Chinese women with GDM, low GI diets, low GL diets and fibre-enriched diets were associated with improved glycaemic control and pregnancy outcomes. Given the lack of direct comparison of these three diets, future direct comparison trials are necessary to determine optimal dietary intervention strategies