Massive-star supernovae as major dust factories

We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to 678 days after outburst and are accompanied by increasing optical extinction and growing asymmetries in the emission-line profiles. Radiative-transfer models show that up to 0.02 solar masses of dust has formed within the ejecta, beginning as early as 250 days after outburst. These observations show that dust formation in supernova ejecta can be efficient and that massive-star supernovae could have been major dust producers throughout the history of the universe

Production of dust by massive stars at high redshift

The large amounts of dust detected in sub-millimeter galaxies and quasars at high redshift pose a challenge to galaxy formation models and theories of cosmic dust formation. At z > 6 only stars of relatively high mass (> 3 Msun) are sufficiently short-lived to be potential stellar sources of dust. This review is devoted to identifying and quantifying the most important stellar channels of rapid dust formation. We ascertain the dust production efficiency of stars in the mass range 3-40 Msun using both observed and theoretical dust yields of evolved massive stars and supernovae (SNe) and provide analytical expressions for the dust production efficiencies in various scenarios. We also address the strong sensitivity of the total dust productivity to the initial mass function. From simple considerations, we find that, in the early Universe, high-mass (> 3 Msun) asymptotic giant branch stars can only be dominant dust producers if SNe generate <~ 3 x 10^-3 Msun of dust whereas SNe prevail if they are more efficient. We address the challenges in inferring dust masses and star-formation rates from observations of high-redshift galaxies. We conclude that significant SN dust production at high redshift is likely required to reproduce current dust mass estimates, possibly coupled with rapid dust grain growth in the interstellar medium.Comment: 72 pages, 9 figures, 5 tables; to be published in The Astronomy and Astrophysics Revie

Laparoscopic conversion of Roux-en-Y gastric bypass to biliopancreatic diversion

Background This report describes the laparoscopic conversion of a Roux-en-Y gastric bypass (RYGBP) to biliopancreatic diversion (BPD). Case report In January 1995, a 47-year-old woman with a body mass index (BMI) of 54 kg/m 2 benefited from a silicon ring vertical banded gastroplasty (SRVBG) for morbid obesity. She showed significant weight loss and reached a BMI of 30 kg/m2. After 7 years, she experienced weight regain (BMI, 34.5 kg/m2), so a laparoscopic conversion to RYGBP was proposed. The patient again had a successful weight loss (BMI, 26 kg/m2), but 6 years later, she mentioned a weight regain (BMI, 33 kg/m2) with invalidating retrosternal pain. The nutritionist's analysis of the patient showed a certain modification of the alimentary character with frequent meals (grazing/polyphagia), and the psychologist's consultation identified an important binge-eating disorder. A laparoscopic conversion of RYGBP to BPD was proposed. The procedure consisted of (1) adhesiolysis and reduction of a hiatal hernia, (2) sectioning of the gastric pouch proximally to the gastrojejunostomy, (3) resection of the fundus of the gastric remnant excluded by the previous SRVBG, (4) restoration of the continuity of the stomach between the gastric pouch and the gastric remnant, (5) resection of the gastric antrum and pylorus, (6) deconstruction of the previous jejunojejunostomy, (7) restoration of the continuity of the small bowel, (8) measurement of the new common and alimentary limbs and construction of the jejunoileostomy, (9) closure of the mesenteric defect, (10) construction of the gastroileostomy, (11) closure of Petersen's space, and (12) repair of the hiatal hernia followed by a leak test. Results The operative time was 320 min, and the blood loss was 380 ml. The patient had an uneventful recovery and was discharged on postoperative day 5. Her BMI was 30.5 kg/m2 after 3 months and 26 kg/m2 after 6 months. The barium swallow showed good transit through the gastrointestinal tract. Conclusions The laparoscopic conversion of RYGBP to BPD is technically feasible and effective during the short term for cases of repeated weight regain. © Springer Science+Business Media, LLC 2009.SCOPUS: ar.jinfo:eu-repo/semantics/publishe