Supernova remnants: the X-ray perspective

Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray observations are an important means to study these objects.And in particular the advances made in X-ray imaging spectroscopy over the last two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the products of fresh nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. In this text all the relevant aspects of X-ray emission from supernova remnants are reviewed and put into the context of supernova explosion properties and the physics and evolution of supernova remnants. The first half of this review has a more tutorial style and discusses the basics of supernova remnant physics and thermal and non-thermal X-ray emission. The second half offers a review of the recent advances.The topics addressed there are core collapse and thermonuclear supernova remnants, SN 1987A, mature supernova remnants, mixed-morphology remnants, including a discussion of the recent finding of overionization in some of them, and finally X-ray synchrotron radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2 column-layout. 78 pages, 42 figures. This replaced version has some minor language edits and several references have been correcte

The effects of whole milk compared to skim milk and apple juice consumption in breakfast on appetite and energy intake in obese children: a three-way randomized crossover clinical trial

Abstract Background A limited number of studies have examined the effect of dairy on satiety and short-term energy intake among children; furthermore we are not aware of any study comparing high and low-fat dairy products regarding their effect on appetite and short-term energy intake. Our objective was to assess the effect skim milk (SM) compared to whole milk (WM) and apple juice (AJ) on satiety and energy intake at lunch among 10–12 y children with obesity. Methods Fifty children with obesity who aged 10–12 y were randomized to consume a fixed content breakfast with 240 ml of SM, AJ, or WM for two consecutive days. The study was a three-way randomized crossover study; therefore each participant served as his/her own control. The total appetite, hunger, fullness, desire to eat and prospective consumption were measured using a visual analogue scale (VAS) before breakfast and every one hour after breakfast until a freely consumed lunch. VAS scores and energy intakes were compared using repeated measures procedure. Results Forty-eight participants (24 girls and 24 boys) completed the study. The energy intake was not different between SM, AJ and WM periods (adjusted mean ± standard error (SE) of energy intake: SM = 831.27 ± 30.64 Kcal, AJ = 794.92 ± 28.72 Kcal, WM = 798.87 ± 24.09 Kcal; P = 0.56). The effect was the same for either gender. Children reported higher satiety score 4 h after drinking WM with breakfast compared with SM (P < 0.05). The same association was found only in girls. Furthermore, SM significantly reduced appetite compared to AJ, 2 h after preloads in girls (P < 0.05). Conclusions Full-fat milk may have favorable effects on satiety but not energy intake in subsequent meal compared to skim milk among the children with obesity. Future studies with longer follow-up periods are needed to confirm these results. Trial registration The study protocol was registered with the Iranian registry of clinical trials on 9th October 2016 (registration ID: IRCT2016072012571N5)

Cobalt-56 gamma-ray emission lines from the type Ia supernova 2014J

A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon–oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive 56Ni. After the explosion, the decay chain from 56Ni to 56Co to 56Fe generates gamma-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of 56Co lines at energies of 847 and 1,238 kiloelectronvolts and a gamma-ray continuum in the 200–400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 ± 0.1 solar masses of radioactive 56Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometres per second. The observed gamma-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of 56Ni.Peer ReviewedPostprint (author's final draft

A 12-week double-blind randomized clinical trial of vitamin D₃ supplementation on body fat mass in healthy overweight and obese women

<p>Abstract</p> <p>Background</p> <p>Vitamin D concentrations are linked to body composition indices, particularly body fat mass. Relationships between hypovitaminosis D and obesity, described by both BMI and waist circumference, have been mentioned. We have investigated the effect of a 12-week vitamin D3 supplementation on anthropometric indices in healthy overweight and obese women.</p> <p>Methods</p> <p>In a double-blind, randomized, placebo-controlled, parallel-group trial, seventy-seven participants (age 38±8.1 years, BMI 29.8±4.1 kg/m²) were randomly allocated into two groups: vitamin D (25 μg per day as cholecalciferol) and placebo (25 μg per day as lactose) for 12 weeks. Body weight, height, waist, hip, fat mass, 25(OH) D, iPTH, and dietary intakes were measured before and after the intervention.</p> <p>Results</p> <p>Serum 25(OH)D significantly increased in the vitamin D group compared to the placebo group (38.2±32.7 nmol/L vs. 4.6±14.8 nmol/L; P<0.001) and serum iPTH concentrations were decreased by vitamin D3 supplementation (-0.26±0.57 pmol/L vs. 0.27±0.56 pmol/L; P<0.001). Supplementation with vitamin D3 caused a statistically significant decrease in body fat mass in the vitamin D group compared to the placebo group (-2.7±2.1 kg vs. -0.47±2.1 kg; P<0.001). However, body weight and waist circumference did not change significantly in both groups. A significant reverse correlation between changes in serum 25(OH) D concentrations and body fat mass was observed (r = -0.319, P = 0.005).</p> <p>Conclusion</p> <p>Among healthy overweight and obese women, increasing 25(OH) D concentrations by vitamin D3 supplementation led to body fat mass reduction.</p> <p>This trial is registered at clinicaltrials.gov as NCT01344161.</p