Newly formed dust within the circumstellar environment of SN Ia-CSM 2018evt.

Dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae play an important role in dust production. We report evidence of dust formation in the cold, dense shell behind the ejecta-circumstellar medium (CSM) interaction in the Type Ia-CSM supernova (SN) 2018evt three years after the explosion, characterized by a rise in mid-infrared emission accompanied by an accelerated decline in the optical radiation of the SN. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Hα emission line. Our model suggests enhanced CSM dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. By the time of the last mid-infrared observations at day +1,041, a total amount of 1.2 ± 0.2 × 10-2 M⊙ of new dust has been formed by SN 2018evt, making SN 2018evt one of the most prolific dust factories among supernovae with evidence of dust formation. The unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history.

The development and implementation of quality assurance programs to support nutritional measurements.

The National Institute of Standards and Technology administers quality assurance programs devoted to improving measurements of nutrients and related metabolites in foods, dietary supplements, and serum and plasma samples. These programs have been developed in collaboration with the National Institutes of Health to assist measurement communities in their efforts to achieve accurate results that are comparable among different laboratories and over time. Targeted analytes include micronutrients, botanical markers, nutritional elements, contaminants, fatty acids, and vitamin D metabolites.

Circumstellar material in type Ia supernovae via sodium absorption features.

Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems.

The afterglow of GRB 050709 and the nature of the short-hard gamma-ray bursts.

The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.

The sub-energetic gamma-ray burst GRB 031203 as a cosmic analogue to the nearby GRB 980425.

Over the six years since the discovery of the gamma-ray burst GRB 980425, which was associated with the nearby (distance approximately 40 Mpc) supernova 1998bw, astronomers have debated fiercely the nature of this event. Relative to bursts located at cosmological distance (redshift z approximately 1), GRB 980425 was under-luminous in gamma-rays by three orders of magnitude. Radio calorimetry showed that the explosion was sub-energetic by a factor of 10. Here we report observations of the radio and X-ray afterglow of the recent GRB 031203 (refs 5-7), which has a redshift of z = 0.105. We demonstrate that it too is sub-energetic which, when taken together with the low gamma-ray luminosity, suggests that GRB 031203 is the first cosmic analogue to GRB 980425. We find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows. We expect intensive follow-up of faint bursts with smooth gamma-ray light curves (common to both GRB 031203 and 980425) to reveal a large population of such events.

An asymptotic-giant-branch star in the progenitor system of a type Ia supernova.

Stars that explode as supernovae come in two main classes. A type Ia supernova is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectrum; this class of supernova is thought to produce the majority of iron-peak elements in the Universe. They are also used as precise 'standard candles' to measure the distances to galaxies. While there is general agreement that a type Ia supernova is produced by an exploding white dwarf star, no progenitor system has ever been directly observed. Significant effort has gone into searching for circumstellar material to help discriminate between the possible kinds of progenitor systems, but no such material has hitherto been found associated with a type Ia supernova. Here we report the presence of strong hydrogen emission associated with the type Ia supernova SN2002ic, indicating the presence of large amounts of circumstellar material. We infer from this that the progenitor system contained a massive asymptotic-giant-branch star that lost several solar masses of hydrogen-rich gas before the supernova explosion.

Essential concepts in clinical epidemiology for pediatric practice.

Providing the best possible health care requires the integration of individual clinical experience with external clinical information, often derived from published research papers. This article reviews several important concepts in clinical epidemiology that should help the pediatric clinician become a more active and critical reader. Among the basic concepts reviewed are measurement of disease occurrence, relative risk, and screening within the context of the pediatric practice.

Supernova 1987A!

Light from the brightest supernova in almost 400 years arrived at Earth on 23 February 1987. Although located 160,000 light years away in a satellite galaxy of our own known as the Large Magellanic Cloud, this supernova's relative proximity compared to all others that have been observed in modern times has allowed observations, which were never possible before, to be made from space, from detectors on the ground and carried by balloons and airplanes, and from neutrino detectors deep underground. What emerges is a greater understanding of one of the most violent events in the universe, the death of a massive star. For the most part, theoretical expectations have been borne out, but some major surprises have made the event all the more fascinating.

Steroid metabolism and binding activity in a murine renal tumor cell line.

The purpose of this study was to partially characterize the steroid binding activity of murine renal tumor cells in continuous culture. The steroid receptor content of a cloned renal tumor cell line (RAG) and a subline RAG-2 was examined by sucrose gradient analysis, hydroxylapatite and dextran-coated charcoal methods. The RAG cells lacked estrogen- and progestin-binding activity, whereas specific 5 alpha-dihydrotestosterone (DHT) and dexamethasone (Dx) binding activities were detected as 8S peaks on low salt gradients. The specificity of DHT binding was examined by sucrose gradient analysis: DHT, R1881 and ORG2058 all completely inhibited [3H]DHT binding whereas diethylstilbestrol and Dx were ineffective. The androgen receptor content of the RAG cells was approx. 15 fmol/mg cytosol protein by the hydroxylapatite-filter assay, with an estimated Kd for methyltrienolone (R1881) of 5 nM at 0 degrees C. Scatchard analysis of [3H]Dx binding by RAG cytosol showed a Kd of 6 nM for Dx and 44 nM for corticosterone at 0 degrees C. Glucocorticoid receptor levels were estimated to be 182 fmol/mg cytosol protein by dextran-coated charcoal assay. Metabolism of [3H]testosterone and [3H]DHT by RAG cells was examined 1, 4 and 6 h after exposure to labeled hormone. Radioactive DHT was the primary intracellular metabolite recovered after exposure to [3H]testosterone. There was little conversion of DHT to androstanediol.

Analysis of androgen-sensitivity in rat prostate X mouse kidney cell hybrids.

Variant androgen-sensitive cell lines were produced by fusing freshly isolated epithelial cells from the rat ventral prostate with a line of murine renal tumor (RAG) cells. The properties of the cloned lines of the prostate X RAG hybrids can be summarized as follows: (1) the modal chromosome number of the hybrid cell lines ranged from 68 to 176; (2) the cells had doubling times of 7.6-49.5 h; and (3) epitheloid, ameboid and intermediate morphologies were observed among the various lines. The proliferative response of various hybrid lines to treatment with 10 nM 5 alpha-dihydrotestosterone was used to classify the hybrids as either very sensitive (greater than 40% reduction in cell doubling time), sensitive (greater than 10% reduction in doubling time) to androgens, or insensitive (less than 10% reduction in doubling time) to androgens. There was no direct relationship between the androgen-sensitivity of the cells and their androgen receptor content, suggesting that these variant cell lines may be useful for the study of the genetic factors involved in cellular responses to androgens.

Binding of the rat liver 7-8 S dexamethasone receptor to deoxyribonucleic acid.

The 7-8 S form of the [3H]dexamethasone (9 alpha-fluoro-11 beta,17,21-trihydroxy-16 alpha-methylpregna-1,4-diene-3, 20-dione) receptor from rat liver cytosol can be converted to the 3-4 S form by RNase treatment or high salt, suggesting a salt-sensitive association between the receptor protein and RNA. In DNA-cellulose column assays, the gradient-purified 3-4 S form bound DNA more efficiently than the 7-8 S form, though the 7-8 S form was also capable of binding to DNA-cellulose to a significant extent. Activated 7-8 S dexamethasone receptor could be released from its association with soluble DNA by treatment with DNase I. Sucrose gradient analysis showed that the released receptor sedimented as the 7-8 S form and was sensitive to RNase treatment, which induced a conversion to the 3-4 S form. Activated RNase-generated 3-4 S receptor again displayed a higher degree of binding to soluble DNA and was recovered in the 3-4 S form following DNase extraction. The fact that the 3-4 S form bound immobilized or soluble DNA more efficiently suggests that the associated RNA of the 7-8 S form interferes directly or indirectly with the receptor association with DNA. The observation that the receptor binds to DNA in its 7-8 S form suggests that the receptor complex is capable of binding RNA and DNA concurrently.

The effects of ribonuclease on rat liver dexamethasone receptor: increased affinity for deoxyribonucleic acid and altered sedimentation profile.

The ability of the dexamethasone (9 alpha-fluoro-11 beta, 17,21-trihydroxy-16 alpha-methylpregna-1,4-diene-3,20-dione)-receptor complex to bind to DNA-cellulose is stimulated by RNase treatment of the activated receptor. Both RNase A and RNase T1 can induce the stimulation. The enhancement of the DNA binding ability occurs concomitantly with an alteration of the sedimentation profile of the dexamethasone-receptor complex from the 7-8S form to the 3-4S form in low salt sucrose gradients. If RNase treatment occurs in the presence of sodium molybdate, both the increase in DNA binding ability and the alteration in sedimentation profile fail to occur. Treatment of the receptor with high salt suggests that the 3-4S form can reversibly combine with a factor in a salt-sensitive association. These experiments indicate that the 7-8S form of the dexamethasone-receptor complex is associated with a RNA molecule(s) that can be removed by RNase treatment or salt dissociation, and that this RNA inhibits the binding of the receptor to DNA.

Adrenocorticosteroid therapy in alcoholic hepatitis. A prospective, double-blind randomized study.

In a prospective, randomized, double-blind study of prednisolone therapy of acute alcoholic hepatitis, 39% of the total group of 28 patients died. Mortality and cumulative survival were similar in steroid- and placebo-treated patients. After 14 days of therapy, the serum albumin concentration and white blood count were significantly higher in the steroid group, but all other parameters were similar. An increased risk of fungal infection appeared to be associated with steroid therapy.

Intraarterial vasopressin in the treatment of upper gastrointestinal hemorrhage: a prospective, controlled clinical trial.

Intraarterial vasopressin has been reported to be effective in the treatment of massive upper gastrointestinal hemorrhage. A prospective, controlled clinical trial comparing conventional treatment with conventional therapy plus intraarterial vasopressin was undertaken. Sixty episodes of upper gastrointestinal hemorrhage were evaluated during a 40-month period; 32 received conventional and 28 conventional plus vasopressin therapy. The two groups of patients were similar in type and severity of their bleeding lesions and in their underlying diseases. Vasopressin was more effective in controlling hemorrhage from nonvariceal lesions (P less than 0.05) and from varices (P less than 0.01) than conventional therapy. Transfusion requirements were significantly reduced in those patients who received vasopressin. Paradoxically, survival was not affected by vasopressin administration. The failure of cessation of hemorrhage to improve survival is thought to be due to the degree of advancement of the underlying disease, to the torrential nature of the hemorrhage, to the frequency of recurrent hemorrhage, and to the use of intraarterial vasopressin in some patients in the conventional treatment group in whom conventional therapy had failed.

Portacaval anastomosis and peptic ulcer: a nonassociation.

The incidence of peptic ulcer is increased in cirrhosis and is widely believed to be even greater in cirrhotic patients with portacaval anastomosis (PCA). Two prospective, controlled investigations of prophylactic PCA were evaluated to compare the frequency of peptic ulcer in two groups of cirrhotic patients with similar clinical and laboratory manifestations of cirrhosis randomly selected to be an unoperated Control Group (60 patients) or to have PCA (Shunt Group, 48 patients). In addition, nonrandomized groups of cirrhotic patients, 77 of whom were excluded from the randomized study and 44 of whom had therapeutic PCA, were studied. A diagnosis of chronic peptic ulcer was based on the demonstration of an ulcer crater by X-ray, endoscopy, surgery, or autopsy. Prior to inclusion in these studies, approximately 10% of patients had had peptic ulcer. After inclusion, during a mean follow-up period of 45 months, 12% of both the Control and Shunt Groups developed peptic ulcers. The frequency of complications of peptic ulcer, of recurrence of peptic ulcer, or of acute or symptomatic (unproved) ulcer were similar in both groups. Ulcers tended to develop later in shunted than in unshunted patients. Similar data were obtained from three of four other controlled investigations of PCA. This investigation does not find an increased occurrence of peptic ulcer after PCA. The frequency of ulcer in cirrhosis appears to increase with the duration of the disease independent of the presence or absence of PCA.