GreenCare for Children -- Measuring Environmental Hazards in the Childcare Industry

Presents findings from a two-year survey administered to a random sampling of childcare providers. Developed and interpreted by a diverse team of industry, technical, and educational experts

Dark Before Light: Testing the Cosmic Expansion History through the Cosmic Microwave Background

The cosmic expansion history proceeds in broad terms from a radiation dominated epoch to matter domination to an accelerated, dark energy dominated epoch. We investigate whether intermittent periods of acceleration are possible in the early universe -- between Big Bang nucleosynthesis (BBN) and recombination and beyond. We establish that the standard picture is remarkably robust: observations of anisotropies in the cosmic microwave background exclude any extra period of accelerated expansion between 1 \leq z \lesssim 10^5 (corresponding to 5\times10^{-4}\ {\rm eV} \leq T \lesssim 25\ {\rm eV}).Comment: 7 pages, 5 figure

Molecular systematics of the Middle American genus Hypopachus (Anura: Microhylidae)

We present the first phylogenetic study on the widespread Middle American microhylid frog genus Hypopachus. Partial sequences of mitochondrial (12S and 16S ribosomal RNA) and nuclear (rhodopsin) genes (1275 bp total) were analyzed from 43 samples of Hypopachus, three currently recognized species of Gastrophryne, and seven arthroleptid, brevicipitid and microhylid outgroup taxa. Maximum parsimony (PAUP), maximum likelihood (RAxML) and Bayesian inference (MrBayes) optimality criteria were used for phylogenetic analyses, and BEAST was used to estimate divergence dates of major clades. Population-level analyses were conducted with the programs NETWORK and Arlequin. Results confirm the placement of Hypopachus and Gastrophryne as sister taxa, but the latter genus was strongly supported as paraphyletic. The African phrynomerine genus Phrynomantis was recovered as the sister taxon to a monophyletic Chiasmocleis, rendering our well-supported clade of gastrophrynines paraphyletic. Hypopachus barberi was supported as a disjunctly distributed highland species, and we recovered a basal split in lowland populations of Hypopachus variolosus from the Pacific versant of Mexico and elsewhere in the Mesoamerican lowlands. Dating analyses from BEAST estimate speciation within the genus Hypopachusoccurred in the late Miocene/early Pliocene for most clades. Previous studies have not found bioacoustic or morphological differences among these lowland clades, and our molecular data support the continued recognition of two species in the genus Hypopachus

Group effects of a non-native plant invasion on rodent abundance

Cheatgrass (Bromus tectorum) is the most prolific invading plant in western North America. Investigations determining the impact of this invasion on population state variables and community dynamics of rodents have largely occurred at the community or species level, creating a knowledge gap as to whether rodents affiliated by a shared taxonomy or other grouping are differentially affected by cheatgrass invasion. We examined rodent abundance along a gradient of cheatgrass cover using various groupings of two nocturnal rodent taxa comprising the majority of the rodent community in the Great Basin Desert. In the summers of 2010–2013, rodents were sampled and vegetation was measured on the U.S. Army Dugway Proving Ground in the Great Basin Desert of Utah, USA. We separately examined estimates of rodent abundance for all combined species within the Cricetidae and Heteromyidae families, the most numerically dominant species, and uncommon species pooled in relation to cheatgrass invasion severity. We detected an expected negative linear relationship between invasion severity and abundance for all cricetid groupings, including the most numerically dominant species, the deer mouse (Peromyscus maniculatus). Unexpectedly, heteromyid abundance exhibited an initial positive relationship, reached a threshold, and then exhibited a negative relationship, a phenomenon driven by Ord’s kangaroo rats (Dipodomys ordii), the most numerically dominant species. We speculate this non-linear finding was caused by a combination of trophic and nontrophic pathways. Our findings provide new insight as to the potential for differential effects of cheatgrass on rodents in arid portions of the western United States. We suggest that future investigations on cheatgrass, and plant invader effects in general, consider parsing animal communities of interest by various taxonomic and/or ecological groupings rather than focusing exclusively on individual species or entire communities

Evaluating the Impact of An Exotic Plant Invasion on Rodent Community Richness and Abundance

Cheatgrass (Bromus tectorum), Russian thistle (Salsola kali), and tall tumblemustard (Sisymbrium altissimum) are nonnative plants widely distributed throughout the desert and shrubsteppe communities of the western United States. The impact of these invaders on plant community structure, form, and function has been well documented, but investigations determining the impacts of this cumulative invasion on terrestrial vertebrates have not been undertaken. Our objective was to assess community-level rodent responses to changes in plant community features, with an emphasis on dominance of invasive plant species. We sampled rodent and plant communities in the Great Basin Desert (Utah) over 4 years. Using estimates of rodent species richness and average nightly captures (relative abundance) as our response variables, we developed generalized linear mixed models (GLMMs) to determine the effects of invasive species cover. We found that rodent richness decreased with increasing abundance of invasive plant cover. Contrary to other studies, there was a nonlinear relationship between invasive species cover and rodent abundance, where rodent captures increased with invasive plant cover, reached a threshold, and then exhibited a negative response. This nonlinear relationship provides support for the intermediate disturbance hypothesis and suggests that moderate levels of plant invasions, by way of bolstering rodent abundance and rodent biomass, could have bottom-up effects (i.e., positively influencing species that predominantly prey upon rodents). Our findings contradict previous findings on plant invasions in arid portions of the western United States and suggest that the species comprising or dominating a given rodent community may determine the impact of plant invasions

Group Effects of a Non-Native Plant Invasion on Rodent Abundance

Cheatgrass (Bromus tectorum) is the most prolific invading plant in western North America. Investigations determining the impact of this invasion on population state variables and community dynamics of rodents have largely occurred at the community or species level, creating a knowledge gap as to whether rodents affiliated by a shared taxonomy or other grouping are differentially affected by cheatgrass invasion. We examined rodent abundance along a gradient of cheatgrass cover using various groupings of two nocturnal rodent taxa comprising the majority of the rodent community in the Great Basin Desert. In the summers of 2010–2013, rodents were sampled and vegetation was measured on the U.S. Army Dugway Proving Ground in the Great Basin Desert of Utah, USA. We separately examined estimates of rodent abundance for all combined species within the Cricetidae and Heteromyidae families, the most numerically dominant species, and uncommon species pooled in relation to cheatgrass invasion severity. We detected an expected negative linear relationship between invasion severity and abundance for all cricetid groupings, including the most numerically dominant species, the deer mouse (Peromyscus maniculatus). Unexpectedly, heteromyid abundance exhibited an initial positive relationship, reached a threshold, and then exhibited a negative relationship, a phenomenon driven by Ord’s kangaroo rats (Dipodomys ordii), the most numerically dominant species. We speculate this non-linear finding was caused by a combination of trophic and nontrophic pathways. Our findings provide new insight as to the potential for differential effects of cheatgrass on rodents in arid portions of the western United States. We suggest that future investigations on cheatgrass, and plant invader effects in general, consider parsing animal communities of interest by various taxonomic and/or ecological groupings rather than focusing exclusively on individual species or entire communities

The Unique Frequency Spectrum of the Blazhko RRc Star LS Her

The Blazhko effect in RR Lyrae stars is still poorly understood theoretically. Stars with multiple Blazhko periods or in which the Blazhko effect itself varies are particularly challenging. This study investigates the Blazhko effect in the RRc star LS Her. Detailed VRI CCD photometry has been performed on 63 nights during six months. LS Her is confirmed to have a Blazhko period of 12.75+/-0.02 days. However, where normally the side frequencies of the Blazhko triplet are expected, an equidistant group of three frequencies is found on both sides of the main pulsation frequency. As a consequence the period and amplitude of the Blazhko effect itself vary in a cycle of 109+/-4 days. LS Her is a unique object turning out to be very important in the verification of the theories for the Blazhko effect.Comment: Accepted for publication in MNRA