Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger.

The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process). Such transients, named 'macronovae' or 'kilonovae', are believed to be centres of production of rare elements such as gold and platinum. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst at redshift z = 0.356, although findings indicating bluer events have been reported. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source GW170817 and γ-ray burst GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides.

Advances on human milk hormones and protection against obesity.

Extensive research shows that breast milk could have positive health effects not limited to infancy, but extend into childhood and adulthood. Recently many studies have provided new evidence on the long—term positive effects of breastfeeding, in particular protection against obesity and type 2 diabetes, suggesting that breast milk may have a role in the programming of later metabolic diseases. The mechanism throughout breastfeeding that exerts these effects has been a major focus of interest for researchers and it is still not completely known. There are some hints for biological plausibility of beneficial effects of breastfeeding including macronutrient intake, hormonal and behavioural mechanisms related to breast milk composition. Breast milk biochemical components, such as protein quantity and quality, polyunsaturated fatty acids, oligosaccharides, cytokines and hormones, in particular leptin, adiponectin and resistin together with the breastfeeding practice itself can influence infants feeding behaviour and regulation of growth and appetite control later in life. Further research is needed to confirm the possibility that hormones present in breast milk exert a metabolic and beneficial effects.

Slowly fading super-luminous supernovae that are not pair-instability explosions.

Super-luminous supernovae that radiate more than 10(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of (56)Ni are synthesized; this isotope decays to (56)Fe via (56)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10(-6) times that of the core-collapse rate.

High serum leptin levels in infancy can potentially predict obesity in childhood, especially in formula-fed infants.

AIM: To investigate serum leptin levels in breast-fed and formula-fed infants in infancy and their possible relationship to body mass index (BMI) in childhood. METHODS: We enrolled 237 healthy term infants between September 2000 and April 2004 and tested their serum leptin levels, took anthropometric measurements and calculated BMI. A follow-up study was carried out to evaluate the BMI of 89 of these infants in childhood, in relation to their serum leptin levels in infancy, at a median (interquartile range) age of 8.8 years (7.8-10.2). The statistical significance of this multivariate analysis was set at p < 0.05. RESULTS: Breast-fed infants had significantly higher serum leptin levels than formula-fed ones (p < 0.05). Children who were formula-fed in infancy had a significantly higher BMI, at follow-up, than those who were breast-fed (p < 0.001). Furthermore, we identified a leptin cut-off value of 2.7 ng/mL, below which infants had a higher BMI in childhood. CONCLUSION: A higher leptin level in infancy may be inversely associated with BMI in childhood, suggesting that this hormone in infancy is a potential predictor of obesity in later life. Further investigation is required to be conclusive and to confirm our empirical evidence.

Using genetic, cognitive and multi-modal neuroimaging data to identify ultra-high-risk and first-episode psychosis at the individual level.

BACKGROUND: Group-level results suggest that relative to healthy controls (HCs), ultra-high-risk (UHR) and first-episode psychosis (FEP) subjects show alterations in neuroanatomy, neurofunction and cognition that may be mediated genetically. It is unclear, however, whether these groups can be differentiated at single-subject level, for instance using the machine learning analysis support vector machine (SVM). Here, we used a multimodal approach to examine the ability of structural magnetic resonance imaging (sMRI), functional MRI (fMRI), diffusion tensor neuroimaging (DTI), genetic and cognitive data to differentiate between UHR, FEP and HC subjects at the single-subject level using SVM. METHOD: Three age- and gender-matched SVM paired comparison groups were created comprising 19, 19 and 15 subject pairs for FEP versus HC, UHR versus HC and FEP versus UHR, respectively. Genetic, sMRI, DTI, fMRI and cognitive data were obtained for each participant and the ability of each to discriminate subjects at the individual level in conjunction with SVM was tested. RESULTS: Successful classification accuracies (p < 0.05) comprised FEP versus HC (genotype, 67.86%; DTI, 65.79%; fMRI, 65.79% and 68.42%; cognitive data, 73.69%), UHR versus HC (sMRI, 68.42%; DTI, 65.79%), and FEP versus UHR (sMRI, 76.67%; fMRI, 73.33%; cognitive data, 66.67%). CONCLUSIONS: The results suggest that FEP subjects are identifiable at the individual level using a range of biological and cognitive measures. Comparatively, only sMRI and DTI allowed discrimination of UHR from HC subjects. For the first time FEP and UHR subjects have been shown to be directly differentiable at the single-subject level using cognitive, sMRI and fMRI data. Preliminarily, the results support clinical development of SVM to help inform identification of FEP and UHR subjects, though future work is needed to provide enhanced levels of accuracy.

Ghrelin and obestatin in infants, lactating mothers and breast milk.

AIM: To investigate the role of ghrelin and obestatin in infancy. METHODS: We measured ghrelin and obestatin concentrations in blood samples of infants, lactating mothers, and in breast milk. RESULTS: The median (interquartile range) serum ghrelin concentrations were 922.11 (868.44) pg/ml in infants, 667.88 (942.78) pg/ml in lactating mothers, and 526.4 (439.86) pg/ml in breast milk. The serum obestatin levels were 844.87 (805.14) pg/ml in infants, 759.105 (855.55) pg/ml in lactating mothers, and 846.6 (472.07) pg/ml in breast milk. A positive correlation was found for serum ghrelin concentrations in breastfed infants and lactating mothers (p < 0.001, r = 0.789), serum ghrelin concentrations in breastfed infants and in breast milk (p < 0.001, r = 0.581), serum ghrelin concentrations in lactating mothers and in breast milk (p = 0.021, r = 0.450), and serum obestatin concentrations in breastfed infants and in lactating mothers (p = 0.047, r = 0.609). CONCLUSION: We report for the first time the serum obestatin concentrations in infants and confirm the presence of correlations between ghrelin and obestatin in lactating mothers and breast milk. The correlations found early in infants' life, when hormones begin to exert their effects on feeding behavior, suggest that they may be involved in these processes.

Adiponectin in breast milk: relation to serum adiponectin concentration in lactating mothers and their infants.

AIMS: The aims of the study were to determine human breast milk adiponectin concentration and to investigate its relationship with serum adiponectin concentration in lactating mothers and their infants and also to evaluate the relationship between serum adiponectin concentration and anthropometric parameters in nurses and infants. METHODS: We enrolled 60 healthy term breastfed (BF) infants and their lactating mothers. Adiponectin was determined by radioimmunoassay test in serum and by enzyme-linked immunosorbent assay test in human milk (HM). Infants' and mothers' anthropometric parameters were measured. RESULTS: Median (25‰, 75‰) adiponectin concentration in HM was 9.99 (3.59, 20.52) ng/mL. Serum adiponectin concentration in infants was 60.49 (45.76, 74.24) µg/mL and in lactating mothers 21.14 (12.61, 29.66) µg/mL. Adiponectin concentration in HM correlated positively with adiponectin in mothers' serum; r = 0.60 (p < 0.001) and in infants' serum r = 0.37 (p = 0.015). Adiponectin in HM correlated negatively with infants' age r = -0.3 (p = 0.04). Infants' serum adiponectin correlated negatively with their weight r = -0.35 (p = 0.005), length r = -0.35 (p = 0.006) and age r = -0.46 (p < 0.001) and mothers' serum adiponectin with their weight r = -0.37 (p = 0.02) and body mass index r = -0.45 (p = 0.004). CONCLUSIONS: The observed correlations between adiponectin in mothers, HM and BF infants may be suggestive for a metabolic link between nurses and infants through milk.

Long-term monitoring drug resistance by ultra-deep pyrosequencing in a chronic hepatitis B virus (HBV)-infected patient exposed to several unsuccessful therapy schemes.

The aim of this study was to analyze the spectrum and dynamics of low-prevalent HBV mutations in the reverse transcriptase (rt) and S antigen by ultra-deep pyrosequencing (UDPS). Samples were obtained from a chronically infected patient who was followed throughout a thirteen-year period. This technology enabled simultaneous analysis of 4084 clonally amplified fragments from the patient allowing detecting low prevalent (<1%) mutations during the follow-up. At baseline, HBV sequences were predominately wild-type. Under sequential HBV monotherapies including lamivudine, adefovir and entecavir, a high frequency of rtM204I mutation was detected initially as unique and then coexisting with rtM204V. Both mutations were statistically associated with rtA200V and rtV207I, respectively. Once the entecavir and tenofovir combined therapy was started, polymerase and consequently envelope gene mutations appeared at several positions at a higher frequency than before, including the entecavir resistance-associated mutation rtT184L.

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.

A low-energy core-collapse supernova without a hydrogen envelope.

The final fate of massive stars depends on many factors. Theory suggests that some with initial masses greater than 25 to 30 solar masses end up as Wolf-Rayet stars, which are deficient in hydrogen in their outer layers because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion of some of them produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel. An alternative origin for low-energy supernovae is the collapse of the oxygen-neon core of a star of 7-9 solar masses. No weak, hydrogen-deficient, core-collapse supernovae have hitherto been seen. Here we report that SN 2008ha is a faint hydrogen-poor supernova. We propose that other similar events have been observed but have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN 2002cx-like events). This discovery could link these faint supernovae to some long-duration gamma-ray bursts, because extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce such long gamma-ray bursts, the afterglows of which do not show evidence of associated supernovae.

Onset of submarine debris flow deposition far from original giant landslide.

Submarine landslides can generate sediment-laden flows whose scale is impressive. Individual flow deposits have been mapped that extend for 1,500 km offshore from northwest Africa. These are the longest run-out sediment density flow deposits yet documented on Earth. This contribution analyses one of these deposits, which contains ten times the mass of sediment transported annually by all of the world's rivers. Understanding how this type of submarine flow evolves is a significant problem, because they are extremely difficult to monitor directly. Previous work has shown how progressive disintegration of landslide blocks can generate debris flow, the deposit of which extends downslope from the original landslide. We provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide, encased within deposits of a more dilute flow type called turbidity current. Very little sediment was deposited across the intervening large expanse of sea floor, where the flow was locally very erosive. Sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea-floor gradient from 0.05 degrees to 0.01 degrees. This debris flow was probably generated by flow transformation from the decelerating turbidity current. The alternative is that non-channelized debris flow left almost no trace of its passage across one hundred kilometres of flat (0.2 degrees to 0.05 degrees) sea floor. Our work shows that initially well-mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean.

A very faint core-collapse supernova in M85.

An anomalous transient in the early Hubble-type (S0) galaxy Messier 85 (M85) in the Virgo cluster was discovered by Kulkarni et al. on 7 January 2006 that had very low luminosity (peak absolute R-band magnitude M(R) of about -12) that was constant over more than 80 days, red colour and narrow spectral lines, which seem inconsistent with those observed in any known class of transient events. Kulkarni et al. suggest an exotic stellar merger as the possible origin. An alternative explanation is that the transient in M85 was a type II-plateau supernova of extremely low luminosity, exploding in a lenticular galaxy with residual star-forming activity. This intriguing transient might be the faintest supernova that has ever been discovered.

Detection of circumstellar material in a normal type Ia supernova.

Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. Here we report the spectroscopic detection of circumstellar material in a normal type Ia supernova explosion. The expansion velocities, densities, and dimensions of the circumstellar envelope indicate that this material was ejected from the progenitor system. In particular, the relatively low expansion velocities suggest that the white dwarf was accreting material from a companion star that was in the red-giant phase at the time of the explosion.

A giant outburst two years before the core-collapse of a massive star.

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.

Solid-phase synthesis of indolizidine and quinolizidine derivatives.

An efficient method for the construction of simple indolizidine and quinolizidine derivatives on solid support has been developed. An intramolecular tandem Michael reaction initiated by the nucleophilic attack of a suitably placed amino group on the tethered Wittig condensation products between 4- or 5-aminoaldehydes attached to a trityl chloride resin and 4-[(4-methylphenyl)sulfonyl]-1-(triphenylphosphoranylidene)-2-b utanon e is the key step.

The Properties of Supernova 1997cy Associated with GRB 970514.

The extraordinary SN 1997cy associated with GRB 970514 has been observed photometrically and spectroscopically for nearly 2 yr. At the time of discovery, SN 1997cy was the brightest supernova (SN) ever observed (MV