Alton Augustus Adams, Sr., was a musician, writer, hotelier, and the first black bandmaster of the United States Navy. Born in the Virgin Islands in 1889, Adams joined the U.S. military in 1917. ...Although naval policy at the time restricted blacks to menial jobs, Adams and his all-black ensemble provided a bridge between the local population and their all-white naval administrators. His memoirs, edited by Mark Clague, with a foreword by Samuel Floyd, Jr., reveal an inspired activist who believed music could change the world, mitigate racism, and bring prosperity to his island home.
Global increases in ultraviolet-B radiation (UVBR) associated with stratospheric ozone depletion are potentially contributing to the decline of numerous amphibian species around the world. Exposure ...to UVBR alone reduces survival and induces a range of sublethal effects in embryonic and larval amphibians. When additional environmental stressors are present, UVBR can have compounding negative effects. Thus, examination of the effects of UVBR in the absence of other stressors may substantially underestimate its potential to affect amphibians in natural habitats. We examined the independent and interactive effects of increased UVBR and high conspecific density would have embryonic and larval striped marsh frogs (Limnodynastes peronii). We exposed individuals to a factorial combination of low and high UVBR levels and low, medium, and high densities of striped marsh frog tadpoles. The response variables were time to hatching, hatching success, posthatch survival, burst-swimming performance of tadpoles (maximum instantaneous swim speed following an escape response), and size and morphology of tadpoles. Consistent with results of previous studies, we found that exposure to UVBR alone increased the time to hatching of embryos and reduced the burst-swimming performance and size of tadpoles. Similarly, increasing conspecific density increased the time to hatching of embryos and reduced the size of tadpoles, but had no effect on burst-swimming performance. The negative effect of UVBR on tadpole size was not apparent at high densities of tadpoles. This result suggests that tadpoles living at higher densities may invest relatively less energy in growth and thus have more energy to repair UVBR-induced damage. Lower densities of conspecifics increased the negative effects of UVBR on developing amphibians. Thus, low-density populations, which may include declining populations, may be particularly susceptible to the detrimental effects of increased UVBR and thus may be driven toward extinction faster than might be expected on the basis of results from single-factor studies. Los incrementos en la radiación ultravioleta-B (RUVB) asociados con la disminución de ozono atmosférico potencialmente están contribuyendo a la declinación de numerosas especies de anfibios en el mundo. La exposición a RUVB por si sola reduce la supervivencia e induce una gama de efectos subletales en embriones y larvas de anfibios. Cuando hay la presencia de estresantes mbientales adicionales, la RUVB puede tener efectos negativos combinados. Por lo tanto, el análisis de los efectos de la RUVB en ausencia de otros estresantes puede subestimar sustancialmente su potencial para afectar anfibios en hábitats naturales. Examinamos los efectos independientes e interactivos del incremento de RUVB y la densidad conespecífica de embriones y larvas de ranas (Limnodynastes peronii). Expusimos a individuos a una combinación factorial de niveles bajos y altos de RUVB y densidades bajas, medianas y altas de renacuajos de L. peronii. Las variables de respuesta fueron el tiempo hasta la eclosión, éxito de eclosión, supervivencia de postlarvas, explosión natatoria de renacuajos (velocidad máxima instantánea de nado después de una respuesta de escape) y tamaño y morfología de renacuajos. Consistente con los resultados de estudios previos, encontramos que la exposición a la RUVB por si sola incrementó el tiempo hasta la eclosión de los embriones y redujo la explosión natatoria y el tamaño de los renacuajos. Similarmente, el incremento de la densidad conespecífica incrementó el tiempo hasta la eclosión de los embriones y redujo el tamaño de los renacuajos, pero no tuvo efecto sobre la explosión natatoria. El efecto negativo de la RUVB sobre el tamaño de los renacuajos no fue aparente en densidades altas de renacuajos. Este resultado sugiere que los renacuajos que viven en densidades altas pueden invertir relativamente menos energía en el crecimiento y por tanto tienen más energía para reparar daños inducidos por la RUVB. Densidades bajas de conespecíficos incrementaron los efectos negativos de la RUVB sobre los anfibios en desarrollo. Por lo tanto, poblaciones con baja densidad, que pueden incluir poblaciones en declinación, pueden ser particularmente susceptibles a los efectos perjudiciales del incremento de RUVB y por lo tanto pueden llegar a extinguirse más rápidamente de lo esperado a partir de los resultados de estudios de un solo factor.
Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron ...adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c^{2} mass dark matter. We present new constraints for sub-GeV/c^{2} dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12 306±184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c^{2}. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below 3.6 GeV/c^{2}.
We present a search for dark matter particles with sub-GeV/c^{2} masses whose interactions have final state electrons using the DarkSide-50 experiment's (12 306±184) kg d low-radioactivity liquid ...argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section σover ¯_{e}, the axioelectric coupling constant g_{Ae}, and the dark photon kinetic mixing parameter κ. We also set the first dark matter direct-detection constraints on the mixing angle |U_{e4}|^{2} for keV/c^{2} sterile neutrinos.
The energetic costs for animals to locomote on land influence many aspects of their ecology. Size accounts for much of the among‐species variation in terrestrial transport costs, but species of ...similar body size can still exhibit severalfold differences in energy expenditure. We compiled measurements of the (mass‐specific) minimum cost of pedestrian transport (COTmin, mL/kg/m) for 201 species – by far the largest sample to date – and used phylogenetically informed comparative analyses to investigate possible eco‐evolutionary differences in COTmin between various groupings of those species. We investigated number of legs, ectothermy and endothermy, waddling, and nocturnality specifically in lizards. Thus, our study primarily revisited previous theories about variations in COTmin between species, testing them with much more robust analyses. Having accounted for mass, while residual COTmin did not differ between bipedal and other species, specifically waddling bipeds were found to have relatively high COTmin. Furthermore, nocturnal lizards have relatively low COTmin although temperature does not appear to affect COTmin in ectotherms. Previous studies examining across‐species variation in COTmin from a biomechanical perspective show that the differences between waddling birds and nonwaddling species, and between nocturnal lizards and other ecotherms, are likely to be attributable to differences in ground reaction forces, posture, and effective limb length.
The energy costs for animals to move can be a considerable proportion of their energy budget and thus a key aspect of their ecology. We collated data on running costs for over 200 species and explored differences between groups within a phylogenetically informed framework. Having accounted for mass, waddling species were confirmed to have high energy costs to run (about double), while nocturnal lizards were found to run at about half the energy cost of other ectotherms.
Temperature has pervasive effects on physiological processes and is critical in setting species distribution limits. Since invading Australia, cane toads have spread rapidly across low latitudes, but ...slowly into higher latitudes. Low temperature is the likely factor limiting high-latitude advancement. Several previous attempts have been made to predict future cane toad distributions in Australia, but understanding the potential contribution of phenotypic plasticity and adaptation to future range expansion remains challenging. Previous research demonstrates the considerable thermal metabolic plasticity of the cane toad, but suggests limited thermal plasticity of locomotor performance. Additionally, the oxygen-limited thermal tolerance hypothesis predicts that reduced aerobic scope sets thermal limits for ectotherm performance. Metabolic plasticity, locomotor performance and aerobic scope are therefore predicted targets of natural selection as cane toads invade colder regions. We measured these traits at temperatures of 10, 15, 22.5 and 30°C in low- and high-latitude toads acclimated to 15 and 30°C, to test the hypothesis that cane toads have adapted to cooler temperatures. High-latitude toads show increased metabolic plasticity and higher resting metabolic rates at lower temperatures. Burst locomotor performance was worse for high-latitude toads. Other traits showed no regional differences. We conclude that increased metabolic plasticity may facilitate invasion into higher latitudes by maintaining critical physiological functions at lower temperatures.
DarkSide-50 has demonstrated the high potential of dual-phase liquid argon time projection chambers in exploring interactions of WIMPs in the GeV/c2 mass range. The technique, based on the detection ...of the ionization signal amplified via electroluminescence in the gas phase, allows us to explore recoil energies down to the sub-keV range. We report here on the DarkSide-50 measurement of the ionization yield of electronic recoils down to ~ 180 eVer, exploiting 37Ar and 39Ar decays, and extrapolated to a few ionization electrons with the Thomas-Imel box model. Moreover, we present a model-dependent determination of the ionization response to nuclear recoils down to ~ 500 eVnr, the lowest ever achieved in liquid argon, using in situ neutron calibration sources and external datasets from neutron beam experiments.
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