Identification of strontium in the merger of two neutron stars.

Half of all of the elements in the Universe that are heavier than iron were created by rapid neutron capture. The theory underlying this astrophysical r-process was worked out six decades ago, and requires an enormous neutron flux to make the bulk of the elements1. Where this happens is still debated2. A key piece of evidence would be the discovery of freshly synthesized r-process elements in an astrophysical site. Existing models3-5 and circumstantial evidence6 point to neutron-star mergers as a probable r-process site; the optical/infrared transient known as a 'kilonova' that emerges in the days after a merger is a likely place to detect the spectral signatures of newly created neutron-capture elements7-9. The kilonova AT2017gfo-which was found following the discovery of the neutron-star merger GW170817 by gravitational-wave detectors10-was the first kilonova for which detailed spectra were recorded. When these spectra were first reported11,12, it was argued that they were broadly consistent with an outflow of radioactive heavy elements; however, there was no robust identification of any one element. Here we report the identification of the neutron-capture element strontium in a reanalysis of these spectra. The detection of a neutron-capture element associated with the collision of two extreme-density stars establishes the origin of r-process elements in neutron-star mergers, and shows that neutron stars are made of neutron-rich matter13

Mass and metallicity scaling relations of high-redshift star-forming galaxies selected by GRBs

We present a comprehensive study of the relations between gas kinematics, metallicity and stellar mass in a sample of 82 gamma-ray burst (GRB)-selected galaxies using absorption and emission methods. We find the velocity widths of both emission and absorption profiles to be a proxy of stellar mass. We also investigate the velocity–metallicity correlation and its evolution with redshift. Using 33 GRB hosts with measured stellar mass and metallicity, we study the mass–metallicity relation for GRB host galaxies in a stellar mass range of 108.2–1011.1 M⊙ and a redshift range of z ∼ 0.3–3.4. The GRB-selected galaxies appear to track the mass–metallicity relation of star-forming galaxies but with an offset of 0.15 towards lower metallicities. This offset is comparable with the average error bar on the metallicity measurements of the GRB sample and also the scatter on the mass–metallicity relation of the general population. It is hard to decide whether this relatively small offset is due to systematic effects or the intrinsic nature of GRB hosts. We also investigate the possibility of using absorption-line metallicity measurements of GRB hosts to study the mass–metallicity relation at high redshifts. Our analysis shows that the metallicity measurements from absorption methods can significantly differ from emission metallicities and assuming identical measurements from the two methods may result in erroneous conclusions

Mushroom Intake and Risk of Epithelial Ovarian Cancer in Southern Chinese Women

OBJECTIVE: This study aimed to investigate the association between mushroom consumption and risk of epithelial ovarian cancer in southern Chinese women.METHODS: A hospital-based case-control study was undertaken in Guangzhou, Guangdong Province, from 2006 to 2008. Participants were 500 incident patients with epithelial ovarian cancer and 500 controls, with a mean (SD) age of 59 (6) years. Information on habitual mushroom consumption was obtained by face-to-face interview using a validated and reliable food frequency questionnaire. Unconditional logistic regression analyses were performed to assess the association between mushroom intake and the ovarian cancer risk.RESULTS: The patients with ovarian cancer consumed less mushrooms (mean [SD], 28.48 [37.45] g/d) than did controls (mean [SD], 30.75 [41.85] g/d). Apparent reductions in cancer risk were found at high levels of intake, especially for the common white button mushroom with adjusted odds ratios 0.68 (95% confidence interval, 0.52-0.89) for women consuming more than 2 g per day relative to those who consume less than that (P = 0.005). Decreases in risk at high levels of intake were also observed for serous and mucinous subtypes of epithelial ovarian tumors.CONCLUSIONS: Intake of mushrooms, particularly white button mushroom, seemed to be inversely associated with the incidence of epithelial ovarian cancer in southern Chinese women

Methodological considerations in the analysis of fecal glucocorticoid metabolites in tufted capuchins (Cebus apella)

Analysis of fecal glucocorticoid (GC) metabolites has recently become the standard method to monitor adrenocortical activity in primates noninvasively. However, given variation in the production, metabolism, and excretion of GCs across species and even between sexes, there are no standard methods that are universally applicable. In particular, it is important to validate assays intended to measure GC production, test extraction and storage procedures, and consider the time course of GC metabolite excretion relative to the production and circulation of the native hormones. This study examines these four methodological aspects of fecal GC metabolite analysis in tufted capuchins (Cebus apella). Specifically, we conducted an adrenocorticotrophic hormone (ACTH) challenge on one male and one female capuchin to test the validity of four GC enzyme immunoassays (EIAs) and document the time course characterizing GC me- tabolite excretion in this species. In addition, we compare a common field-friendly technique for extracting fecal GC metabolites to an established laboratory extraction methodology and test for effects of storing “field extracts” for up to 1 yr. Results suggest that a corticosterone EIA is most sensitive to changes in GC production, provides reliable measures when extracted according to the field method, and measures GC metabolites which remain highly stable after even 12 mo of storage. Further, the time course of GC metabolite excretion is shorter than that described yet for any primate taxa. These results provide guidelines for studies of GCs in tufted capuchins, and underscore the importance of validating methods for fecal hormone analysis for each species of interest

The 2175 angstrom Extinction Feature in the Optical Afterglow Spectrum of GRB 180325A at z =. 2.25

The ultraviolet (UV) extinction feature at 2175 Å is ubiquitously observed in the Galaxy but is rarely detected at high redshifts. Here we report the spectroscopic detection of the 2175 Å bump on the sightline to the γ-ray burst (GRB) afterglow GRB 180325A at z = 2.2486, the only unambiguous detection over the past 10 years of GRB follow-up, at four different epochs with the Nordic Optical Telescope (NOT) and the Very Large Telescope (VLT)/X-shooter. Additional photometric observations of the afterglow are obtained with the Gamma-Ray burst Optical and Near-Infrared Detector (GROND). We construct the near-infrared to X-ray spectral energy distributions (SEDs) at four spectroscopic epochs. The SEDs are well described by a single power law and an extinction law with R V ≈ 4.4, A V ≈ 1.5, and the 2175 Å extinction feature. The bump strength and extinction curve are shallower than the average Galactic extinction curve. We determine a metallicity of [Zn/H] > −0.98 from the VLT/X-shooter spectrum. We detect strong neutral carbon associated with the GRB with equivalent width of W r(λ 1656) = 0.85 ± 0.05. We also detect optical emission lines from the host galaxy. Based on the Hα emission-line flux, the derived dust-corrected star formation rate is ~46 ± 4 M ⊙ yr−1 and the predicted stellar mass is log M */M ⊙ ~ 9.3 ± 0.4, suggesting that the host galaxy is among the main-sequence star-forming galaxies

GRB 190114C in the nuclear region of an interacting galaxy A detailed host analysis using ALMA, the HST, and the VLT

Context. For the first time, very high energy emission up to the TeV range has been reported for a gamma-ray burst (GRB). It is still unclear whether the environmental properties of GRB 190114C might have contributed to the production of these very high energy photons, or if it is solely related to the released GRB emission. Aims. The relatively low redshift of the GRB (z = 0.425) allows us to study the host galaxy of this event in detail, and to potentially identify idiosyncrasies that could point to progenitor characteristics or environmental properties that might be responsible for this unique event. Methods. We used ultraviolet, optical, infrared, and submillimetre imaging and spectroscopy obtained with the HST, the VLT, and ALMA to obtain an extensive dataset on which the analysis of the host galaxy is based. Results. The host system is composed of a close pair of interacting galaxies (Δv = 50 km s−1), both of which are well detected by ALMA in CO(3-2). The GRB occurred within the nuclear region (∼170 pc from the centre) of the less massive but more star-forming galaxy of the pair. The host is more massive (log(M/M⊙) = 9.3) than average GRB hosts at this redshift, and the location of the GRB is rather unique. The higher star formation rate was probably triggered by tidal interactions between the two galaxies. Our ALMA observations indicate that both host galaxy and companion have a high molecular gas fraction, as has been observed before in interacting galaxy pairs. Conclusions. The location of the GRB within the core of an interacting galaxy with an extinguished line of sight is indicative of a denser environment than typically observed for GRBs and could have been crucial for the generation of the very high energy photons that were observed

The Properties of GRB 120923A at a Spectroscopic Redshift of z approximate to 7.8

Gamma-ray bursts (GRBs) are powerful probes of early stars and galaxies, during and potentially even before the era of reionization. Although the number of GRBs identified at z gsim 6 remains small, they provide a unique window on typical star-forming galaxies at that time, and thus are complementary to deep field observations. We report the identification of the optical drop-out afterglow of Swift GRB 120923A in near-infrared Gemini-North imaging, and derive a redshift of $z={7.84}_{-0.12}^{+0.06}$ from Very Large Telescope/X-shooter spectroscopy. At this redshift the peak 15–150 keV luminosity of the burst was 3.2 × 1052 erg s−1, and in this sense it was a rather typical long-duration GRB in terms of rest frame luminosity. This burst was close to the Swift/Burst Alert Telescope detection threshold, and the X-ray and near-infrared afterglow were also faint. We present ground- and space-based follow-up observations spanning from X-ray to radio, and find that a standard external shock model with a constant-density circumburst environment of density n ≈ 4 × 10−2 cm−3 gives a good fit to the data. The near-infrared light curve exhibits a sharp break at t ≈ 3.4 days in the observer frame which, if interpreted as being due to a jet, corresponds to an opening angle of ${\theta }_{\mathrm{jet}}\approx 5^\circ$. The beaming-corrected γ-ray energy is then ${E}_{\gamma }\approx 2\times {10}^{50}$ erg, while the beaming-corrected kinetic energy is lower, ${E}_{{\rm{K}}}\approx {10}^{49}$ erg, suggesting that GRB 120923A was a comparatively low kinetic energy event. We discuss the implications of this event for our understanding of the high-redshift population of GRBs and their identification

Search for New Physics Using Quaero: A General Interface to D0 Event Data

We describe Quaero, a method that i) enables the automatic optimization of searches for physics beyond the standard model, and ii) provides a mechanism for making high energy collider data generally available. We apply Quaero to searches for standard model WW, ZZ, and ttbar production, and to searches for these objects produced through a new heavy resonance. Through this interface, we make three data sets collected by the D0 experiment at sqrt(s)=1.8 TeV publicly available.Comment: 7 pages, submitted to Physical Review Letter

The ALMA REBELS Survey: The Cosmic H i Gas Mass Density in Galaxies at z ≈ 7

The neutral atomic gas content of individual galaxies at large cosmological distances has until recently been difficult to measure due to the weakness of the hyperfine H i 21 cm transition. Here we estimate the H i gas mass of a sample of main-sequence star-forming galaxies at z ∼ 6.5-7.8 surveyed for [C ii] 158 μm emission as part of the Reionization Era Bright Emission Line Survey (REBELS), using a recent calibration of the [C ii]-to-H i conversion factor. We find that the H i gas mass excess in galaxies increases as a function of redshift, with an average of M Hi /M ⋆ ≈ 10, corresponding to H i gas mass fractions of f Hi = M Hi /(M ⋆ + M Hi ) = 90%, at z ≈ 7. Based on the [C ii] 158 μm luminosity function (LF) derived from the same sample of galaxies, we further place constraints on the cosmic H i gas mass density in galaxies (ρ Hi ) at this redshift, which we measure to be ρ H I = 7.1 − 3.0 + 6.4 × 10 6 M ⊙ Mpc − 3 . This estimate is substantially lower by a factor of ≈10 than that inferred from an extrapolation of damped Lyα absorber (DLA) measurements and largely depends on the exact [C ii] LF adopted. However, we find this decrease in ρ Hi to be consistent with recent simulations and argue that this apparent discrepancy is likely a consequence of the DLA sight lines predominantly probing the substantial fraction of H i gas in high-z galactic halos, whereas [C ii] traces the H i in the ISM associated with star formation. We make predictions for this buildup of neutral gas in galaxies as a function of redshift, showing that at z ≳ 5, only ≈10% of the cosmic H i gas content is confined in galaxies and associated with the star-forming ISM

Identification and Classification of Hubs in Brain Networks

Brain regions in the mammalian cerebral cortex are linked by a complex network of fiber bundles. These inter-regional networks have previously been analyzed in terms of their node degree, structural motif, path length and clustering coefficient distributions. In this paper we focus on the identification and classification of hub regions, which are thought to play pivotal roles in the coordination of information flow. We identify hubs and characterize their network contributions by examining motif fingerprints and centrality indices for all regions within the cerebral cortices of both the cat and the macaque. Motif fingerprints capture the statistics of local connection patterns, while measures of centrality identify regions that lie on many of the shortest paths between parts of the network. Within both cat and macaque networks, we find that a combination of degree, motif participation, betweenness centrality and closeness centrality allows for reliable identification of hub regions, many of which have previously been functionally classified as polysensory or multimodal. We then classify hubs as either provincial (intra-cluster) hubs or connector (inter-cluster) hubs, and proceed to show that lesioning hubs of each type from the network produces opposite effects on the small-world index. Our study presents an approach to the identification and classification of putative hub regions in brain networks on the basis of multiple network attributes and charts potential links between the structural embedding of such regions and their functional roles