Southern Africa is good place to research role of fetal malnutrition in chronic diseases

Editor — We are interested in Scrimshaw\u27s allusion to populations in Latin America in his editorial on the relation between fetal malnutrition and chronic disease in later life. There, in the 1960s, despite a high prevalence of low birth weight, the preva­ lence of atherosclerosis and of myocardial infarction was low

The Revealing Dust: Mid-Infrared Activity in Hickson Compact Group Galaxy Nuclei

We present a sample of 46 galaxy nuclei from 12 nearby (z<4500 km/s) Hickson Compact Groups (HCGs) with a complete suite of 1-24 micron 2MASS+Spitzer nuclear photometry. For all objects in the sample, blue emission from stellar photospheres dominates in the near-IR through the 3.6 micron IRAC band. Twenty-five of 46 (54%) galaxy nuclei show red, mid-IR continua characteristic of hot dust powered by ongoing star formation and/or accretion onto a central black hole. We introduce alpha_{IRAC}, the spectral index of a power-law fit to the 4.5-8.0 micron IRAC data, and demonstrate that it cleanly separates the mid-IR active and non-active HCG nuclei. This parameter is more powerful for identifying low to moderate-luminosity mid-IR activity than other measures which include data at rest-frame lambda<3.6 micron that may be dominated by stellar photospheric emission. While the HCG galaxies clearly have a bimodal distribution in this parameter space, a comparison sample from the Spitzer Nearby Galaxy Survey (SINGS) matched in J-band total galaxy luminosity is continuously distributed. A second diagnostic, the fraction of 24 micron emission in excess of that expected from quiescent galaxies, f_{24D}, reveals an additional 3 nuclei to be active at 24 micron. Comparing these two mid-IR diagnostics of nuclear activity to optical spectroscopic identifications from the literature reveals some discrepancies, and we discuss the challenges of distinguishing the source of ionizing radiation in these and other lower luminosity systems. We find a significant correlation between the fraction of mid-IR active galaxies and the total HI mass in a group, and investigate possible interpretations of these results in light of galaxy evolution in the highly interactive system of a compact group environment.Comment: 20 pages, 17 figures (1 color), uses emulateapj. Accepted for publication by Ap

The Distribution of High Redshift Galaxy Colors: Line of Sight Variations in Neutral Hydrogen Absorption

We model, via Monte Carlo simulations, the distribution of observed U-B, B-V, V-I galaxy colors in the range 1.75<z<5 caused by variations in the line-of-sight opacity due to neutral hydrogen (HI). We also include HI internal to the source galaxies. Even without internal HI absorption, comparison of the distribution of simulated colors to the analytic approximations of Madau (1995) and Madau et al (1996) reveals systematically different mean colors and scatter. Differences arise in part because we use more realistic distributions of column densities and Doppler parameters. However, there are also mathematical problems of applying mean and standard deviation opacities, and such application yields unphysical results. These problems are corrected using our Monte Carlo approach. Including HI absorption internal to the galaxies generaly diminishes the scatter in the observed colors at a given redshift, but for redshifts of interest this diminution only occurs in the colors using the bluest band-pass. Internal column densities < 10^17 cm^2 do not effect the observed colors, while column densities > 10^18 cm^2 yield a limiting distribution of high redshift galaxy colors. As one application of our analysis, we consider the sample completeness as a function of redshift for a single spectral energy distribution (SED) given the multi-color selection boundaries for the Hubble Deep Field proposed by Madau et al (1996). We argue that the only correct procedure for estimating the z>3 galaxy luminosity function from color-selected samples is to measure the (observed) distribution of redshifts and intrinsic SED types, and then consider the variation in color for each SED and redshift. A similar argument applies to the estimation of the luminosity function of color-selected, high redshift QSOs.Comment: accepted for publication in ApJ; 25 pages text, 14 embedded figure

Neutron reflection from the liquid helium surface.

The reflection of neutrons from a helium surface has been observed for the first time. The 4He surface is smoother in the superfluid state at 1.54 K than in the case of the normal liquid at 2.3 K. In the superfluid state we also observe a surface layer ~200 Å thick which has a subtly different neutron scattering cross-section, which may be explained by an enhanced Bose-Einstein condensate fraction close to the helium surface. The application of neutron reflectometry described in this paper creates new and exciting opportunities for the surface and interfacial study of quantum fluids

A Chandra−SwiftChandra-Swift View of Point Sources in Hickson Compact Groups: High AGN fraction but a dearth of strong AGNs

We present $Chandra$ X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances $34 - 89$ Mpc. We perform detailed X-ray point source detection and photometry, and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities ($L_X$) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices ($\Gamma$), hardness ratios, and $L_X$, in the full ($0.5-8.0$ keV), soft ($0.5-2.0$ keV) and hard ($2.0-8.0$ keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions (LINERs). Two-thirds of our galaxies have nuclear X-ray sources with $Swift$/UVOT counterparts. Two nuclei have $L_{X,{\rm 0.5-8.0 keV}}$~$> 10^{42}$ erg s$^{-1}$, are strong multi-wavelength AGNs and follow the known $\alpha_{\rm OX}-\nu L_{\nu,\rm near UV}$ correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in $\alpha_{\rm OX}-\nu L_{\nu,\rm near UV}$ space, which also hosts other, normal, galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with $M_R \le -20$ and $L_{X,{\rm 0.5-8.0 keV}} \ge 10^{41}$ erg s$^{-1}$ is $0.08^{+0.35}_{-0.01}$, somewhat higher than the $\sim 5$ fraction in galaxy clusters.Comment: 77 pages (emulateapj), 28 tables, 11 figures. Accepted by ApJS on March 5, 201

The RNA Helicase DDX6 Controls Cellular Plasticity by Modulating P-Body Homeostasis

Post-transcriptional mechanisms have the potential to influence complex changes in gene expression, yet their role in cell fate transitions remains largely unexplored. Here, we show that suppression of the RNA helicase DDX6 endows human and mouse primed embryonic stem cells (ESCs) with a differentiation-resistant, “hyper-pluripotent” state, which readily reprograms to a naive state resembling the preimplantation embryo. We further demonstrate that DDX6 plays a key role in adult progenitors where it controls the balance between self-renewal and differentiation in a context-dependent manner. Mechanistically, DDX6 mediates the translational suppression of target mRNAs in P-bodies. Upon loss of DDX6 activity, P-bodies dissolve and release mRNAs encoding fate-instructive transcription and chromatin factors that re-enter the ribosome pool. Increased translation of these targets impacts cell fate by rewiring the enhancer, heterochromatin, and DNA methylation landscapes of undifferentiated cell types. Collectively, our data establish a link between P-body homeostasis, chromatin organization, and stem cell potency

Barriers to correct child restraint use: A qualitative study of child restraint users and their needs

© 2018 Motor vehicle crashes are a major cause of death and injury to children worldwide. Although risk of injury to child passengers can be reduced by using a child restraint, most restraints are incorrectly used. This greatly reduces the restraints’ protective potential; however there is limited research on drivers of correct child restraint use. The aim of this study was to explore perceived barriers and motivators of correct child restraint use in experienced child restraint users, to inform interventions to promote correct use. Motivations and risk perceptions concerning incorrect child restraint use among high and low socioeconomic populations and culturally and linguistically diverse (CALD) child restraint users in Sydney, Australia were qualitatively examined. Six focus groups (N = 44 participants) were facilitated using a semi-structured discussion guide. Transcriptions were deductively analysed using QSR NVivo11 software and the COM-B model of behaviour. Common perceived barriers to correct restraint use were: (a) difficulty interpreting instructions and labels, particularly among CALD participants; (b) remembering and attending to correct use information; (c) lack of information and behavioural feedback on how to correctly install and use a child restraint; and (d) low confidence in ability to install and use a child restraint correctly. The results indicate current child restraint product information is poorly understood, particularly among those whose first language is not English. Interventions to increase correct child restraint use should address access to correct use information, capability to understand and use these, and the influence of motivation, memory and attention in the process

Gradient elasto-plasticity with the generalised interpolation material point method.

The modelling of geomechanics problems can require a method that allows large deformations and non-linear material behaviour, in this respect the Generalised Material Point Method (GIMPM) is ideal. A fully implicit version of GIMPM has recently been developed for geomechanics problems and some aspects of its implementation are described here. An area that has received less attention in material point methods is that conventional analysis techniques constructed in terms of stress and strain are unable to resolve structural instabilities such as shear banding. This is because they do not contain any measure of the length of the microstructure of the material analysed, such as molecule size or grain structure. Gradient theories provide extensions of the classical equations with additional higher-order terms. The use of length scales makes it possible to model a finite thickness shear band which is not possible with traditional methods. Much work has been done on using gradient theories to include the effect of microstructure in the finite element method (and other numerical analysis techniques) however this yet to be combined with material point methods. In this paper the key equations that are required to extend the implicit GIMPM method to include gradient elasto-plasticity are detailed