The Effect of Repeated Low Temperature on Eggs of the Alfalfa Weevil (Coleoptera: Curculionidae)

Three ages of alfalfa weevil, Hypera postica (Gyllenhal) eggs were exposed to repeated exposures of -15 and -20°C. Fresh-laid eggs were quite susceptible and 3- and 5day old eggs were relatively resistant to -15\u27C, but all ages of eggs showed considerable susceptibility to -20°C, with an average LT50 of 2.2 days. Comparison of this data with similar studies utilizing constant low temperature exposures showed the effect to be independent of temporal interruptions

Use with Caution: Interpreting Consumer Expenditure Income Group Data

Economic well-being has been an issue relevant to American public discourse for some time and has become a topic of particular interest among journalists, policymakers, and ordinary American families. The Consumer Expenditure Survey (CE) is often used as a tool to analyze the effects of economic well-being. Though the Census Bureau independently collects and processes income data—the CE is the only Federal survey that collects information on income, expenditures, and associated demographic characteristics from U.S. consumers. As a result, CE data are useful for answering many salient questions related to economic well-being. However, CE data are also complex and should be used with an understanding of the limitations of these data. This Beyond the Numbers article examines assumptions users often make regarding how the CE measures household wealth, by providing examples of the nuances in the data and composition of five household groupings. The examples provide a clearer snapshot of economic well-being found in the income quintiles. The article uses tabulations of households by quintiles of income before taxes that many researchers use to identify the “poor” and the “rich” in the CE data. These terms are subjective and potentially pejorative. Another common set of terms for these types of analyses are “low-income” and “high-income.” These are also subjective terms, and they are imprecise for communicating the concept of economic well-being, which involves other measures of wealth (e.g. stocks, bonds, cash assets, etc.). Misunderstandings arise potentially when researchers use terms like “rich” and “poor” to describe households rather than focus solely on income measures. So, what are the common assumptions made about the economic well-being of the “poor” and “rich” when using CE data to compare income groups

Effect of Cluster Formation on Isospin Asymmetry in the Liquid-Gas Phase Transition Region

Nuclear matter within the liquid-gas phase transition region is investigated in a mean-field two-component Fermi-gas model. Following largely analytic considerations, it is shown that: (1) Due to density dependence of asymmetry energy, some of the neutron excess from the high-density phase could be expelled into the low-density region. (2) Formation of clusters in the gas phase tends to counteract this trend, making the gas phase more liquid-like and reducing the asymmetry in the gas phase. Flow of asymmetry between the spectator and midrapidity region in reactions is discussed and a possible inversion of the flow direction is indicated.Comment: 9 pages,3 figures, RevTe

Calibrated, cosmological hydrodynamical simulations with variable IMFs I: Method and effect on global galaxy scaling relations

The recently inferred variations in the stellar initial mass function (IMF) among local highmass early-type galaxies may require a reinterpretation of observations of galaxy populations and may have important consequences for the predictions of models of galaxy formation and evolution. We present a new pair of cosmological, hydrodynamical simulations based on the EAGLE model that self-consistently adopts an IMF that, respectively, becomes bottomor top-heavy in high-pressure environments for individual star-forming gas particles. In such models, the excess stellarmass-to-light (M/L) ratio with respect to a reference IMF is increased due to an overabundance of low-mass dwarf stars or stellar remnants, respectively. Crucially, both pressure-dependent IMFs have been calibrated to reproduce the observed trends of increasing excessM/L with central stellar velocity dispersion (σe) in early-type galaxies, while maintaining agreement with the observables used to calibrate the EAGLE model, namely the galaxy luminosity function, half-light radii of late-type galaxies, and black holemasses.We find that while theM/L excess is a good measure of the IMF for low-mass slope variations, it depends strongly on the age of the stellar population for high-mass slope variations. The normalization of the [Mg/Fe]-σerelation is decreased (increased) for bottom- (top-)heavy IMF variations, while the slope is not strongly affected. Bottom-heavy variations have little impact on galaxy metallicities, half-light radii of early-type galaxies, or star formation rates, while top-heavy variations significantly increase these quantities for high-mass galaxies, leading to tension with observations. © 2018 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society

New measurements of total ionizing dose in the lunar environment

[1] We report new measurements of solar minimum ionizing radiation dose at the Moon onboard the Lunar Reconnaissance Orbiter (LRO) from June 2009 through May 2010. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on LRO houses a compact and highly precise microdosimeter whose design allows measurements of dose rates below 1 micro-Rad per second in silicon achieved with minimal resources (20 g, ∼250 milliwatts, and ∼3 bits/second). We envision the use of such a small yet accurate dosimeter in many future spaceflight applications where volume, mass, and power are highly constrained. As this was the first operation of the microdosimeter in a space environment, the goal of this study is to verify its response by using simultaneous measurements of the galactic cosmic ray ionizing environment at LRO, at L1, and with other concurrent dosimeter measurements and model predictions. The microdosimeter measured the same short timescale modulations in the galactic cosmic rays as the other independent measurements, thus verifying its response to a known source of minimum-ionizing particles. The total dose for the LRO mission over the first 333 days was only 12.2 Rads behind ∼130 mils of aluminum because of the delayed rise of solar activity in solar cycle 24 and the corresponding lack of intense solar energetic particle events. The dose rate in a 50 km lunar orbit was about 30 percent lower than the interplanetary rate, as one would expect from lunar obstruction of the visible sky

Galaxy mergers can initiate quenching by unlocking an AGN-driven transformation of the baryon cycle

We use zoom simulations to show how merger-driven disruption of the gas disc in a galaxy provides its central active galactic nucleus (AGN) with fuel to drive outflows that entrain and expel a significant fraction of the circumgalactic medium (CGM). This in turn suppresses replenishment of the interstellar medium, causing the galaxy to quench up to several Gyr after the merger. We start by performing a zoom simulation of a present-day star-forming disc galaxy with the EAGLE galaxy formation model. Then, we re-simulate the galaxy with controlled changes to its initial conditions, using the genetic modification technique. These modifications either increase or decrease the stellar mass ratio of the galaxy’s last significant merger, which occurs at z ≈ 0.74. The halo reaches the same present-day mass in all cases, but changing the mass ratio of the merger yields markedly different galaxy and CGM properties. We find that a merger can unlock rapid growth of the central supermassive black hole if it disrupts the co-rotational motion of gas in the black hole’s vicinity. Conversely, if a less disruptive merger occurs and gas close to the black hole is not disturbed, the AGN does not strongly affect the CGM, and consequently the galaxy continues to form stars. Our result illustrates how a unified view of AGN feedback, the baryon cycle and the interstellar medium is required to understand how mergers and quenching are connected over long timescales