1,499 research outputs found
THE CAUSES AND CONSEQUENCES OF INDIVIDUAL VARIATION IN PARENTAL CARE BEHAVIOR
Behavioral traits can be remarkably flexible depending on the conditions in which they are expressed, yet, in spite of this flexibility, persistent differences between individuals appear to limit the potential expression of behaviors. For example, despite evidence that parents provide variable amounts of parental care in response to changing environmental conditions, they also differ in the overall level of care they provide. I used a behavioral reaction norm approach to study individual variation in parental care behavior in free-living house sparrows (Passer domesticus). I investigated the nature of this variation by studying the relationship between different forms of parental care, the biological basis of individual variation in care, and the effect of this variation in care on offspring. First, I found a positive covariance between nestling provisioning and nest defense. Parents that provided high levels of care in one context provided high levels of care in the other context, even after accounting for measures of offspring value. Second, I sought to identify the biological sources that create and maintain consistent individual differences in the level of care a parent provides. I found that the likelihood of feeding nestlings large food items was positively associated with genetic heterozygosity, but did not find evidence that nestling provisioning was influenced by additive genetic variation in this population. Parents hatched from larger eggs provisioned offspring at a higher rate than parents hatched from smaller eggs, but there was no effect of other conditions experienced in the nest on the level of care expressed as an adult. I also tested if differences in problem-solving ability were related to differences in parental care behavior. Although I found that problem-solving parents fledged more offspring than parents that could not solve the problem, parental care was not associated with any measure of problem-solving ability. Finally, I found that individual variation in parental care reaction norms predicted the growth rate, size, and immune response of nestlings, which in turn positively affected offspring survival and recruitment. My findings reveal factors maintaining individual differences in parental care behavior and offer new insights into the causes and consequences of individual variation
Endothelial Restoration of Receptor Activity-Modifying Protein 2 Is Sufficient to Rescue Lethality, but Survivors Develop Dilated Cardiomyopathy.
RAMPs (receptor activity-modifying proteins) serve as oligomeric modulators for numerous G-protein-coupled receptors, yet elucidating the physiological relevance of these interactions remains complex. Ramp2 null mice are embryonic lethal, with cardiovascular developmental defects similar to those observed in mice null for canonical adrenomedullin/calcitonin receptor-like receptor signaling. We aimed to genetically rescue the Ramp2(-/-) lethality in order to further delineate the spatiotemporal requirements for RAMP2 function during development and thereby enable the elucidation of an expanded repertoire of RAMP2 functions with family B G-protein-coupled receptors in adult homeostasis. Endothelial-specific expression of Ramp2 under the VE-cadherin promoter resulted in the partial rescue of Ramp2(-/-) mice, demonstrating that endothelial expression of Ramp2 is necessary and sufficient for survival. The surviving Ramp2(-/-) Tg animals lived to adulthood and developed spontaneous hypotension and dilated cardiomyopathy, which was not observed in adult mice lacking calcitonin receptor-like receptor. Yet, the hearts of Ramp2(-/-) Tg animals displayed dysregulation of family B G-protein-coupled receptors, including parathyroid hormone and glucagon receptors, as well as their downstream signaling pathways. These data suggest a functional requirement for RAMP2 in the modulation of additional G-protein-coupled receptor pathways in vivo, which is critical for sustained cardiovascular homeostasis. The cardiovascular importance of RAMP2 extends beyond the endothelium and canonical adrenomedullin/calcitonin receptor-like receptor signaling, in which future studies could elucidate novel and pharmacologically tractable pathways for treating cardiovascular diseases
Quantitative chemical mapping of InGaN quantum wells from calibrated high-angle annular dark field micrographs
We present a simple and robust method to acquire quantitative maps of compositional fluctuations in nanostructures from low magnification high-angle annular dark field (HAADF) micrographs calibrated by energy-dispersive X-ray (EDX) spectroscopy in scanning transmission electron microscopy (STEM) mode. We show that a nonuniform background in HAADF-STEM micrographs can be eliminated, to a first approximation, by use of a suitable analytic function. The uncertainty in probe position when collecting an EDX spectrum renders the calibration of HAADF-STEM micrographs indirect, and a statistical approach has been developed to determine the position with confidence. Our analysis procedure, presented in a flowchart to facilitate the successful implementation of the method by users, was applied to discontinuous InGaN/GaN quantum wells in order to obtain quantitative determinations of compositional fluctuations on the nanoscale
Formation of proto-globular cluster candidates in cosmological simulations of dwarf galaxies at
We perform cosmological hydrodynamical simulations to study the formation of
proto-globular cluster candidates in progenitors of present-day dwarf galaxies
at ) as part of the
"Feedback in Realistic Environment" (FIRE) project. Compact ( pc),
relatively massive (), self-bound stellar clusters form at in
progenitors with . Cluster formation
is triggered when at least of dense, turbulent gas
reaches as a
result of the compressive effects of supernova feedback or from cloud-cloud
collisions. The clusters can survive for ; absent numerical
effects, they would likely survive substantially longer, perhaps to . The
longest-lived clusters are those that form at significant distance -- several
hundreds of pc -- from their host galaxy. We therefore predict that globular
clusters forming in progenitors of present-day dwarf galaxies will be offset
from any pre-existing stars within their host dark matter halos as opposed to
deeply embedded within a well-defined galaxy. Properties of the nascent
clusters are consistent with observations of some of the faintest and most
compact high-redshift sources in \textit{Hubble Space Telescope} lensing fields
and are at the edge of what will be detectable as point sources in deep imaging
of non-lensed fields with the \textit{James Webb Space Telescope}. By contrast,
the star clusters' host galaxies will remain undetectable.Comment: 14 pages, 5 figures, submitted to MNRA
Quasar Clustering from SDSS DR5: Dependences on Physical Properties
Using a homogenous sample of 38,208 quasars with a sky coverage of drawn from the SDSS Data Release Five quasar catalog, we study the
dependence of quasar clustering on luminosity, virial black hole mass, quasar
color, and radio loudness. At , quasar clustering depends weakly on
luminosity and virial black hole mass, with typical uncertainty levels for the measured correlation lengths. These weak dependences are
consistent with models in which substantial scatter between quasar luminosity,
virial black hole mass and the host dark matter halo mass has diluted any
clustering difference, where halo mass is assumed to be the relevant quantity
that best correlates with clustering strength. However, the most luminous and
most massive quasars are more strongly clustered (at the level)
than the remainder of the sample, which we attribute to the rapid increase of
the bias factor at the high-mass end of host halos. We do not observe a strong
dependence of clustering strength on quasar colors within our sample. On the
other hand, radio-loud quasars are more strongly clustered than are radio-quiet
quasars matched in redshift and optical luminosity (or virial black hole mass),
consistent with local observations of radio galaxies and radio-loud type 2 AGN.
Thus radio-loud quasars reside in more massive and denser environments in the
biased halo clustering picture. Using the Sheth et al.(2001) formula for the
linear halo bias, the estimated host halo mass for radio-loud quasars is , compared to for
radio-quiet quasar hosts at .Comment: Updated version; accepted for publication in Ap
The clustering of galaxies at z~0.5 in the SDSS-III Data Release 9 BOSS-CMASS sample: a test for the LCDM cosmology
We present results on the clustering of 282,068 galaxies in the Baryon
Oscillation Spectroscopic Survey (BOSS) sample of massive galaxies with
redshifts 0.4<z<0.7 which is part of the Sloan Digital Sky Survey III project.
Our results cover a large range of scales from ~0.5 to ~90 Mpc/h. We compare
these estimates with the expectations of the flat LCDM cosmological model with
parameters compatible with WMAP7 data. We use the MultiDark cosmological
simulation together with a simple halo abundance matching technique, to
estimate galaxy correlation functions, power spectra, abundance of subhaloes
and galaxy biases. We find that the LCDM model gives a reasonable description
to the observed correlation functions at z~0.5, which is a remarkably good
agreement considering that the model, once matched to the observed abundance of
BOSS galaxies, does not have any free parameters. However, we find a deviation
(>~10%) in the correlation functions for scales less than ~1 Mpc/h and ~10-40
Mpc/h. A more realistic abundance matching model and better statistics from
upcoming observations are needed to clarify the situation. We also estimate
that about 12% of the "galaxies" in the abundance-matched sample are satellites
inhabiting central haloes with mass M>~1e14 M_sun/h. Using the MultiDark
simulation we also study the real space halo bias b(r) of the matched catalogue
finding that b=2.00+/-0.07 at large scales, consistent with the one obtained
using the measured BOSS projected correlation function. Furthermore, the linear
large-scale bias depends on the number density n of the abundance-matched
sample as b=-0.048-(0.594+/-0.02)*log(n/(h/Mpc)^3). Extrapolating these results
to BAO scales we measure a scale-dependent damping of the acoustic signal
produced by non-linear evolution that leads to ~2-4% dips at ~3 sigma level for
wavenumbers k>~0.1 h/Mpc in the linear large-scale bias.Comment: Replaced to match published version. Typos corrected; 25 pages, 17
figures, 9 tables. To appear in MNRAS. Correlation functions (projected and
redshift-space) and correlation matrices of CMASS presented in Appendix B.
Correlation and covariance data for the combined CMASS sample can be
downloaded from http://www.sdss3.org/science/boss_publications.ph
Effect of continuous nutrient enrichment on microalgae colonizing hard substrates
In order to understand the effect of changing nutrient conditions on benthic microalgae on hard substrates, in-situ experiments with artificial substrates were conducted in Kiel Fjord, Western Baltic Sea. As an extension of previous investigations, we used artificial substrates without silicate and thus were able to supply nutrient media with different Si:N ratios to porous substrates, from where they trickled out continuously. The biofilm developing on these substrates showed a significant increase in biovolume due to N + P enrichment, while Si alone had only minor effects. The stoichiometric composition of the biomass indicated nitrogen limitation during most of the year. The C:N ratios were lowered by the N + P addition. The algae were dominated by diatoms in most cases, but rhodophytes and chlorophytes also became important. The nutrient treatment affected the taxonomic composition mostly at the species level. The significance of the results with regard to coastal eutrophication is discussed
Thermal stabilization of thymidylate synthase by engineering two disulfide bridges across the dimer interface
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: the low-redshift sample
We report on the small-scale (0.5 r h−1 Mpc) clustering of 78 895 massive (M* ~ 1011.3 M⊙) galaxies at 0.2 z 13 h−1 M⊙, a large-scale bias of ~2.0 and a satellite fraction of 12 ± 2 per cent. Thus, these galaxies occupy haloes with average masses in between those of the higher redshift BOSS CMASS sample and the original SDSS I/II luminous red galaxy sample
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