A surge of light at the birth of a supernova.

It is difficult to establish the properties of massive stars that explode as supernovae. The electromagnetic emission during the first minutes to hours after the emergence of the shock from the stellar surface conveys important information about the final evolution and structure of the exploding star. However, the unpredictable nature of supernova events hinders the detection of this brief initial phase. Here we report the serendipitous discovery of a newly born, normal type IIb supernova (SN 2016gkg), which reveals a rapid brightening at optical wavelengths of about 40 magnitudes per day. The very frequent sampling of the observations allowed us to study in detail the outermost structure of the progenitor of the supernova and the physics of the emergence of the shock. We develop hydrodynamical models of the explosion that naturally account for the complete evolution of the supernova over distinct phases regulated by different physical processes. This result suggests that it is appropriate to decouple the treatment of the shock propagation from the unknown mechanism that triggers the explosion.

Distributed-feedback blue laser diode utilizing a tunnel junction grown by plasma-assisted molecular beam epitaxy.

In this paper, we demonstrate a novel approach utilizing tunnel junction (TJ) to realize GaN-based distributed feedback (DFB) laser diodes (LDs). Thanks to the use of the TJ the top metal contact is moved to the side of the ridge and the DFB grating is placed directly on top of the ridge. The high refractive index contrast between air and GaN, together with the high overlap of optical mode with the grating, provides a high coupling coefficient. The demonstrated DFB LD operates at λ=450.15 nm with a side mode suppression ratio higher than 35dB. The results are compared to a standard Fabry-Perot LD.

A massive star origin for an unusual helium-rich supernova in an elliptical galaxy.

The unusual helium-rich (type Ib) supernova SN 2005E is distinguished from all supernovae hitherto observed by its faint and rapidly fading light curve, prominent calcium lines in late-phase spectra and lack of any mark of recent star formation near the supernova location. These properties are claimed to be explained by a helium detonation in a thin surface layer of an accreting white dwarf. Here we report that the observed properties of SN 2005cz, which appeared in an elliptical galaxy, resemble those of SN 2005E. We argue that these properties are best explained by a core-collapse supernova at the low-mass end (8-12 solar masses) of the range of massive stars that explode. Such a low-mass progenitor lost its hydrogen-rich envelope through binary interaction, had very thin oxygen-rich and silicon-rich layers above the collapsing core, and accordingly ejected a very small amount of radioactive (56)Ni and oxygen. Although the host galaxy NGC 4589 is an elliptical, some studies have revealed evidence of recent star-formation activity, consistent with the core-collapse model.

An asymmetric explosion as the origin of spectral evolution diversity in type Ia supernovae.

Type Ia supernovae form an observationally uniform class of stellar explosions, in that more luminous objects have smaller decline-rates. This one-parameter behaviour allows type Ia supernovae to be calibrated as cosmological 'standard candles', and led to the discovery of an accelerating Universe. Recent investigations, however, have revealed that the true nature of type Ia supernovae is more complicated. Theoretically, it has been suggested that the initial thermonuclear sparks are ignited at an offset from the centre of the white-dwarf progenitor, possibly as a result of convection before the explosion. Observationally, the diversity seen in the spectral evolution of type Ia supernovae beyond the luminosity-decline-rate relation is an unresolved issue. Here we report that the spectral diversity is a consequence of random directions from which an asymmetric explosion is viewed. Our findings suggest that the spectral evolution diversity is no longer a concern when using type Ia supernovae as cosmological standard candles. Furthermore, this indicates that ignition at an offset from the centre is a generic feature of type Ia supernovae.

Randomized clinical trial of the effect of perioperative synbiotics versus no synbiotics on bacterial translocation after oesophagectomy.

BACKGROUND: The impact of perioperative synbiotics on bacterial translocation and subsequent bacteraemia after oesophagectomy is unclear. This study investigated the effect of perioperative synbiotic administration on the incidence of bacterial translocation to mesenteric lymph nodes (MLNs) and the occurrence of postoperative bacteraemia. METHODS: Patients with oesophageal cancer were randomized to receive perioperative synbiotics or no synbiotics (control group). MLNs were harvested from the jejunal mesentery before dissection (MLN-1) and after the restoration of digestive tract continuity (MLN-2). Blood and faeces samples were taken before and after operation. Microorganisms in each sample were detected using a bacterium-specific ribosomal RNA-targeted reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) method. RESULTS: Some 42 patients were included. There was a significant difference between the two groups in detection levels of microorganisms in the MLN-1 samples. Microorganisms were more frequently detected in MLN-2 samples in the control group than in the synbiotics group (10 of 18 versus 3 of 18; P = 0·035). In addition, bacteraemia detected using RT-qPCR 1 day after surgery was more prevalent in the control group than in the synbiotics group (12 of 21 versus 4 of 21; P = 0·025). Neutrophil counts on postoperative days 1, 2 and 7 after surgery were all significantly higher in the control group than in the synbiotics group. CONCLUSION: Perioperative use of synbiotics reduces the incidence of bacteria in the MLNs and blood. These beneficial effects probably contribute to a reduction in the inflammatory response after oesophagectomy. REGISTRATION NUMBER: ID 000003262 (University Hospital Medical Information Network, http://www.umin.ac.jp).

An optical spectrum of the afterglow of a gamma-ray burst at a redshift of z = 6.295.

The prompt gamma-ray emission from gamma-ray bursts (GRBs) should be detectable out to distances of z > 10 (ref. 1), and should therefore provide an excellent probe of the evolution of cosmic star formation, reionization of the intergalactic medium, and the metal enrichment history of the Universe. Hitherto, the highest measured redshift for a GRB has been z = 4.50 (ref. 5). Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst; the spectrum shows a clear continuum at the long-wavelength end of the spectrum with a sharp cut-off at around 9,000 A due to Lyman alpha absorption at z approximately 6.3 (with a damping wing). A system of absorption lines of heavy elements at z = 6.295 +/- 0.002 was also detected, yielding the precise measurement of the redshift. The Si ii fine-structure lines suggest a dense, metal-enriched environment around the progenitor of the GRB.

An optical supernova associated with the X-ray flash XRF 060218.

Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes--analogues of GRBs, but with lower luminosities and fewer gamma-rays--can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae.

Role of probiotic in preventing acute diarrhoea in children: a community-based, randomized, double-blind placebo-controlled field trial in an urban slum.

Acute diarrhoea remains a major public health challenge in developing countries. We examined the role of a probiotic in the prevention of acute diarrhoea to discover if there was an effect directed towards a specific aetiology. A double-blind, randomized, controlled field trial involving 3758 children aged 1-5 years was conducted in an urban slum community in Kolkata, India. Participants were given either a probiotic drink containing Lactobacillus casei strain Shirota or a nutrient drink daily for 12 weeks. They were followed up for another 12 weeks. The primary outcome of this study was the occurrence of first episodes of diarrhoea. We assessed this during 12 weeks of intake of study agent and also for 12 weeks of follow-up. There were 608 subjects with diarrhoea in the probiotic group and 674 subjects in the nutrient group during the study period of 24 weeks. The level of protective efficacy for the probiotic was 14% (95% confidence interval 4-23, P<0·01 in adjusted model). The reduced occurrence of acute diarrhoea in the probiotic group compared to nutrient group was not associated with any specific aetiology. No adverse event was observed in children of either probiotic or nutrient groups. The study suggests that daily intake of a probiotic drink can play a role in prevention of acute diarrhoea in young children in a community setting of a developing country.

Protective effect of Lactobacillus casei strain Shirota against lethal infection with multi-drug resistant Salmonella enterica serovar Typhimurium DT104 in mice.

AIMS: The anti-infectious activity of lactobacilli against multi-drug resistant Salmonella enterica serovar Typhimurium DT104 (DT104) was examined in a murine model of an opportunistic antibiotic-induced infection. METHODS AND RESULTS: Explosive intestinal growth and subsequent lethal extra-intestinal translocation after oral infection with DT104 during fosfomycin (FOM) administration was significantly inhibited by continuous oral administration of Lactobacillus casei strain Shirota (LcS), which is naturally resistant to FOM, at a dose of 10(8) colony-forming units per mouse daily to mice. Comparison of the anti-Salmonella activity of several Lactobacillus type strains with natural resistance to FOM revealed that Lactobacillus brevis ATCC 14869(T) , Lactobacillus plantarum ATCC 14917(T) , Lactobacillus reuteri JCM 1112(T) , Lactobacillus rhamnosus ATCC 7469(T) and Lactobacillus salivarius ATCC 11741(T) conferred no activity even when they obtained the high population levels almost similar to those of the effective strains such as LcS, Lact. casei ATCC 334(T) and Lactobacillus zeae ATCC 15820(T) . The increase in concentration of organic acids and maintenance of the lower pH in the intestine because of Lactobacillus colonization were correlated with the anti-infectious activity. Moreover, heat-killed LcS was not protective against the infection, suggesting that the metabolic activity of lactobacilli is important for the anti-infectious activity. CONCLUSION: These results suggest that certain lactobacilli in combination with antibiotics may be useful for prophylaxis against opportunistic intestinal infections by multi-drug resistant pathogens, such as DT104. SIGNIFICANCE AND IMPACT OF THE STUDY: Antibiotics such as FOM disrupt the metabolic activity of the intestinal microbiota that produce organic acids, and that only probiotic strains that are metabolically active in vivo should be selected to prevent intestinal infection when used clinically in combination with certain antibiotics.

Intrathymic clonal deletion of V beta 6+ T cells in cyclophosphamide-induced tolerance to H-2-compatible, Mls-disparate antigens.

When C3H (H-2k, Mls-1b) mice were primed intravenously with 10(8) viable spleen cells from AKR (H-2k, Mls-1a) and treated intraperitoneally with 200 mg/kg of cyclophosphamide (CP) 2 d later, not only a long-lasting skin allograft tolerance but also a tolerance in mixed lymphocyte reaction to Mls-1a-encoded antigens was established. The cellular mechanisms of CP-induced tolerance were examined by assessing the V beta 6-bearing T cells that are strongly correlated with reactivity to Mls-1a-encoded antigens bound to MHC class II molecules. At the relatively early stage (2 or 5 wk) after the CP treatment, CD4+-V beta 6+ T cells of C3H origin were preferentially eliminated in the lymph nodes of the tolerant mice, whereas CD8+-V beta 6+ T cells remained. On the other hand, neither CD4+CD8- nor CD4-CD8+ thymocytes bearing a high density of V beta 6 was detected in the chimeric thymus. Namely, in the thymus of the tolerant C3H mice, neither mixed chimerism nor the clonal deletion of the V beta 6-bearing T cells was observed on day 14, whereas both of them were observed on day 35. The clonal deletion and mixed chimerism in the thymus were lasting for greater than 10 wk after the CP treatment. Expression of V beta 6 on the peripheral T cells in the tolerant C3H mice gradually reduced in the process of time. These results strongly suggested that the clonal deletion in the thymus was one of the essential mechanisms in the CP-induced tolerance system.