Detectability of the First Cosmic Explosions

We present a fully self-consistent simulation of a synthetic survey of the furthermost cosmic explosions. The appearance of the first generation of stars (Population III) in the Universe represents a critical point during cosmic evolution, signaling the end of the dark ages, a period of absence of light sources. Despite their importance, there is no confirmed detection of Population III stars so far. A fraction of these primordial stars are expected to die as pair-instability supernovae (PISNe), and should be bright enough to be observed up to a few hundred million years after the big bang. While the quest for Population III stars continues, detailed theoretical models and computer simulations serve as a testbed for their observability. With the upcoming near-infrared missions, estimates of the feasibility of detecting PISNe are not only timely but imperative. To address this problem, we combine state-of-the-art cosmological and radiative simulations into a complete and self-consistent framework, which includes detailed features of the observational process. We show that a dedicated observational strategy using $\lesssim 8$ per cent of total allocation time of the James Webb Space Telescope mission can provide us up to $\sim 9-15$ detectable PISNe per year.Comment: 9 pages, 8 figures. Minor corrections added to match published versio

Actin polymerization controls the activation of multidrug efflux at fertilization by translocation and fine-scale positioning of ABCB1 on microvilli.

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Molecular Biology of the Cell 23 (2012): 3663-3672, doi:10.1091/mbc.E12-06-0438.Fertilization changes the structure and function of the cell surface. In sea urchins, these changes include polymerization of cortical actin and a coincident, switch-like increase in the activity of the multidrug efflux transporter ABCB1a. However, it is not clear how cortical reorganization leads to changes in membrane transport physiology. In this study, we used three-dimensional superresolution fluorescence microscopy to resolve the fine-scale movements of the transporter along polymerizing actin filaments, and we show that efflux activity is established after ABCB1a translocates to the tips of the microvilli. Inhibition of actin poly­merization or bundle formation prevents tip localization, resulting in the patching of ABCB1a at the cell surface and decreased efflux activity. In contrast, enhanced actin polymerization promotes tip localization. Finally, interference with Rab11, a regulator of apical recycling, inhibits activation of efflux activity in embryos. Together our results show that actin-mediated, short-range traffic and positioning of transporters at the cell surface regulates multidrug efflux activity and highlight the multifaceted roles of microvilli in the spatial distribution of membrane proteins.Funding was provided by the National Institute of Child Health and Human Development (058070), the National Center for Research Resources (P30-NS047101), the Krinsk Research Advancement Initiative to A.H., a Scripps Postdoctoral Scholar Fellowship to K.W., and NICHD award 062178 to A.M.R

Spacelab energetic ion mass spectrometer

Basic design criteria are given for an ion mass spectrometer for use in studying magnetospheric ion populations. The proposed instrument is composed of an electrostatic analyzer followed by a magnetic spectrometer and simultaneously measures the energy per unit and mass per unit charge of the ion species. An electromagnet is used for momentum analysis to extend the operational energy range over a much wider domain than is possible with the permanent magnets used in previous flights. The energetic ion source regions, ion energization mechanisms, field line tracing, coordinated investigations, and orbit considerations are discussed and operations of the momentum analyzer and of the electrostatic energy analyzer are examined

"I'm a bit concerned" - early actions and psychological constructions in a child protection helpline

This article analyzes early actions in 50 calls reporting cases of abuse to a national child protection helpline in the UK (the National Society for the Prevention of Cruelty to Children Helpline, NSPCC). It focuses on the early turns in the caller's reason for call, in particular, a class of constructions in which the caller describes himself or herself as "concerned about x" (or similar). Analysis of the corpus of calls suggests concern constructions are canonical early elements of the reason-for-call sequence. Concern constructions (a) are oriented to a pre-move in the caller's reason for call, (b) project the unpacking of concerns in a way oriented to the NSPCCs institutional role, (c) attend to epistemological asymmetries between caller and call taker and remove the requirement for disaffiliative next actions such as asking for the basis of claims, (d) provide a way for the Child Protection Officer to take abuse claims seriously while not presupposing their truth, and (e) display an appropriate caller stance. These observations are supported by an analysis of deviant cases. The broader implications of this study for the relation between psychology, interaction, and institutions are discussed

Optical Properties of Radio-selected Narrow Line Seyfert 1 Galaxies

We present results from the analysis of the optical spectra of 47 radio-selected narrow-line Seyfert 1 galaxies (NLS1s). These objects are a subset of the First Bright Quasar Survey (FBQS) and were initially detected at 20 cm (flux density limit ~1 mJy) in the VLA FIRST Survey. We run Spearman rank correlation tests on several sets of parameters and conclude that, except for their radio properties, radio-selected NLS1 galaxies do not exhibit significant differences from traditional NLS1 galaxies. Our results are also in agreement with previous studies suggesting that NLS1 galaxies have small black hole masses that are accreting very close to the Eddington rate. We have found 16 new radio-loud NLS1 galaxies, which increases the number of known radio-loud NLS1 galaxies by a factor of ~5.Comment: 18 pages, 20 figures, Accepted for publication in Ap

Location matters: evaluating Greater Prairie-Chicken (Tympanuchus cupido) boom chorus propagation

Anthropogenic disturbances can affect species of conservation concern by influencing their behavior. Of special concern is the possibility that noise from anthropogenic structures in grassland habitats, such as wind turbines and roads, may affect the propagation of the low-frequency boom chorus of lekking male Greater Prairie-Chickens (Tympanuchus cupido). We used sound pressure levels from acoustic recordings taken at 10 leks in the Nebraska Sandhills, USA during 2013 and 2014 in a SPreAD-GIS sound propagation model to make spatial projections of the boom chorus under a variety of conditions including landscape composition, conspecific attendance, and weather. We then used sets of linear mixed models in a model selection process to determine how background noise, female and male lek attendance, time of day, relative humidity, air temperature, and wind speed affected the area of chorus propagation. The predicted area of propagation decreased with increasing background noise (β = -0.09, SE = 0.04) and increased with greater female lek attendance (β = 0.09, SE = 0.03), higher levels of relatively humidity (β = 0.07, SE = 0.03), and higher air temperatures (β = 0.05, SE = 0.03). Our analyses provide new insight on how acoustic, social, and meteorological factors influence an important reproductive behavior in an imperiled prairie grouse

Indoor Inertial Waypoint Navigation for the Blind

Indoor navigation technology is needed to support seamless mobility for the visually impaired. This paper describes the construction and evaluation of an inertial dead reckoning navigation system that provides real-time auditory guidance along mapped routes. Inertial dead reckoning is a navigation technique coupling step counting together with heading estimation to compute changes in position at each step. The research described here outlines the development and evaluation of a novel navigation system that utilizes information from the mapped route to limit the problematic error accumulation inherent in traditional dead reckoning approaches. The prototype system consists of a wireless inertial sensor unit, placed at the users’ hip, which streams readings to a smartphone processing a navigation algorithm. Pilot human trials were conducted assessing system efficacy by studying route-following performance with blind and sighted subjects using the navigation system with real-time guidance, versus offline verbal directions

The Nucleosynthetic Imprint of 15-40 Solar Mass Primordial Supernovae on Metal-Poor Stars

The inclusion of rotationally-induced mixing in stellar evolution can alter the structure and composition of presupernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine spherical explosions in 15, 25 and 40 solar mass stars at Z = 0 and 10^-4 solar metallicity with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants. On the other hand, the Z=10^-4 solar metallicity models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal free stars than the Z = 10^-4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557-4840, with a zero metallicity 15 solar mass, 2.4 x 10^51 erg supernova. A Salpeter IMF averaged integration of our yields for Z=0 models with explosion energies of 2.4x10^51 ergs or less is in good agreement with the abundances observed in larger samples of extremely metal-poor stars, provided 15 solar mass stars are included. Since the abundance patterns of extremely metal-poor stars likely arise from a representative sample of progenitors, our yields suggest that low-mass supernovae contributed the bulk of the metals to the early universe.Comment: 16 pages, 11 figures; submitted to Ap

Turbulent Cold Flows Gave Birth to the First Quasars

How quasars powered by supermassive black holes (SMBHs) formed less than a billion years after the Big Bang is still one of the outstanding problems in astrophysics 20 years after their discovery$^{1-4}$. Cosmological simulations suggest that rare cold flows converging on primordial haloes in low-shear environments could have created these quasars if they were 10$^4$ - 10$^5$ M$_{\odot}$ at birth but could not resolve their formation$^{5-8}$. Semianalytical studies of the progenitor halo of a primordial quasar found that it favours the formation of such seeds but could not verify if one actually appeared$^9$. Here we show that a halo at the rare convergence of strong, cold accretion flows creates massive BH seeds without the need for UV backgrounds, supersonic streaming motions, or even atomic cooling. Cold flows drive violent, supersonic turbulence in the halo that prevents star formation until it reaches a mass that triggers sudden, catastrophic baryon collapse that forms 31,000 and 40,000 M$_{\odot}$ stars. This simple, robust process ensures that haloes capable of forming quasars by z $>$ 6 produce massive seeds. The first quasars were thus a natural consequence of structure formation in cold dark matter cosmologies, not exotic, finely-tuned environments as previously thought$^{10-14}$.Comment: Author's version of a Letter published in Nature on July 6th, 202