1,804 research outputs found
Cosmic Chronometers: Constraining the Equation of State of Dark Energy. II. A Spectroscopic Catalog of Red Galaxies in Galaxy Clusters
We present a spectroscopic catalog of (mostly) red galaxies in 24 galaxy
clusters in the redshift range 0.17 < z < 0.92 obtained with the LRIS
instrument on the Keck I telescope. Here we describe the observations and the
galaxy spectra, including the discovery of three cD galaxies with LINER
emission spectra, and the spectroscopic discovery of four new galaxy-galaxy
lenses in cluster environments.Comment: Submitted to ApJ
Neutral Evolution as Diffusion in phenotype space: reproduction with mutation but without selection
The process of `Evolutionary Diffusion', i.e. reproduction with local
mutation but without selection in a biological population, resembles standard
Diffusion in many ways. However, Evolutionary Diffusion allows the formation of
local peaks with a characteristic width that undergo drift, even in the
infinite population limit. We analytically calculate the mean peak width and
the effective random walk step size, and obtain the distribution of the peak
width which has a power law tail. We find that independent local mutations act
as a diffusion of interacting particles with increased stepsize.Comment: 4 pages, 2 figures. Paper now representative of published articl
Kallikrein-1 blockade inhibits aortic expansion in a mouse model and reduces prostaglandin E2 secretion from human aortic aneurysm explants
Background: Abdominal aortic aneurysm (AAA) is an important cause of mortality in older adults. The kinin B2 receptor agonist, bradykinin, has been implicated in AAA pathogenesis through promoting inflammation. Bradykinin is generated from high- and low-molecular-weight kininogen by the serine protease kallikrein-1. The aims of this study were first to examine the effect of neutralizing kallikrein-1 on AAA development in a mouse model and second to test how blocking kallikrein-1 affected cyclooxygenase-2 and prostaglandin E2 in human AAA explants.
Methods and Results: Neutralization of kallikrein-1 in apolipoprotein E-deficient (ApoE-/-) mice via administration of a blocking antibody inhibited suprarenal aorta expansion in response to angiotensin (Ang) II infusion. Kallikrein-1 neutralization decreased suprarenal aorta concentrations of bradykinin and prostaglandin E2 and reduced cyclooxygenase-2 activity. Kallikrein-1 neutralization also decreased protein kinase B and extracellular signal-regulated kinase 1/2 phosphorylation and reduced levels of active matrix metalloproteinase 2 and matrix metalloproteinase 9. Kallikrein-1 blocking antibody reduced levels of cyclooxygenase-2 and secretion of prostaglandin E2 and active matrix metalloproteinase 2 and matrix metalloproteinase 9 from human AAA explants and vascular smooth muscle cells exposed to activated neutrophils.
Conclusions: These findings suggest that kallikrein-1 neutralization could be a treatment target for AAA
Direct Analysis of Aerosolized Chemical Warfare Simulants Captured on a Modified Glass-Based Substrate by “Paper-Spray” Ionization
Paper spray ionization mass spectrometry offers a rapid alternative platform requiring no sample preparation. Aerosolized chemical warfare agent (CWA) simulants trimethyl phosphate, dimethyl methylphosphonate, and diisopropyl methylphosphonate were captured by passing air through a glass fiber filter disk within a disposable paper spray cartridge. CWA simulants were aerosolized at varying concentrations using an in-house built aerosol chamber. A custom 3D-printed holder was designed and built to facilitate the aerosol capture onto the paper spray cartridges. The air flow through each of the collection devices was maintained equally to ensure the same volume of air sampled across methods. Each approach yielded linear calibration curves with R2 values between 0.98–0.99 for each compound and similar limits of detection in terms of disbursed aerosol concentration. While the glass fiber filter disk has a higher capture efficiency (≈40%), the paper spray method produces analogous results even with a lower capture efficiency (≈1%). Improvements were made to include glass fiber filters as the substrate within the paper spray cartridge consumable. Glass fiber filters were then treated with ammonium sulfate to decrease chemical interaction with the simulants. This allowed for improved direct aerosol capture efficiency (>40%). Ultimately, the limits of detection were reduced to levels comparable to current worker population limits of 1 × 10–6 mg/m3
Variation in tibial functionality and fracture susceptibility among healthy, young adults arises from the acquisition of biologically distinct sets of traits
Physiological systems like bone respond to many genetic and environmental factors by adjusting traits in a highly coordinated, compensatory manner to establish organ‐level function. To be mechanically functional, a bone should be sufficiently stiff and strong to support physiological loads. Factors impairing this process are expected to compromise strength and increase fracture risk. We tested the hypotheses that individuals with reduced stiffness relative to body size will show an increased risk of fracturing and that reduced strength arises from the acquisition of biologically distinct sets of traits (ie, different combinations of morphological and tissue‐level mechanical properties). We assessed tibial functionality retrospectively for 336 young adult women and men engaged in military training, and calculated robustness (total area/bone length), cortical area (Ct.Ar), and tissue‐mineral density (TMD). These three traits explained 69% to 72% of the variation in tibial stiffness ( p < 0.0001). Having reduced stiffness relative to body size (body weight × bone length) was associated with odds ratios of 1.5 (95% confidence interval [CI], 0.5–4.3) and 7.0 (95% CI, 2.0–25.1) for women and men, respectively, for developing a stress fracture based on radiography and scintigraphy. K‐means cluster analysis was used to segregate men and women into subgroups based on robustness, Ct.Ar, and TMD adjusted for body size. Stiffness varied 37% to 42% among the clusters ( p < 0.0001, ANOVA). For men, 78% of stress fracture cases segregated to three clusters ( p < 0.03, chi‐square). Clusters showing reduced function exhibited either slender tibias with the expected Ct.Ar and TMD relative to body size and robustness (ie, well‐adapted bones) or robust tibias with reduced residuals for Ct.Ar or TMD relative to body size and robustness (ie, poorly adapted bones). Thus, we show there are multiple biomechanical and thus biological pathways leading to reduced function and increased fracture risk. Our results have important implications for developing personalized preventative diagnostics and treatments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98270/1/jbmr1879.pd
Phase distribution, composition and disorder in Y2(Hf,Sn)2O7 ceramics : insights from solid-state NMR spectroscopy and first-principles calculations
The authors would like to thank the ERC (EU FP7 Consolidator Grant 614290 “‘EXONMR’”), and EPSRC for support for SS and ASG (EP/L005581/1). SEA would like to thank the Royal Society and Wolfson Foundation for a merit award. We acknowledge support from the Collaborative Computational Project on NMR Crystallography CCP-NC funded by EPSRC (EP/M022501/1).A NMR crystallographic approach, combining 89Y, 119Sn and 17O NMR spectroscopy with X-ray diffraction and first-principles calculations has been used investigate the number and type of phases present, and the local structure and disorder in Y2Hf2–xSnxO7 ceramics. Although a phase change is predicted with increasing Hf content, NMR spectra clearly show the presence of a significant two-phase region, with a Sn-rich pyrochlore and relatively Hf-rich defect fluorite phase co-existing for much of the compositional series. A single-phase pyrochlore is found only for the Sn end member, and a single defect fluorite phase only for x = 0 to 0.2. A solid-solution limit of ~10% is seen for the substitution of Hf into Y2Sn2O7, although no evidence is seen for any cation ordering or antisite disorder in this phase. In the defect fluorite phase there is preferential ordering of oxygen vacancies around Sn, which is only ever seen in a six-coordinate environment. The remaining vacancies are more likely to be associated with Hf than with Y, although this distinction is less apparent at higher Sn concentrations. To acquire 17O NMR spectra samples were post-synthetically exchanged with 17O2(g), although high temperatures (> 900 ºC) were required to ensure uniform enrichment of different chemical species. although these 17O NMR spectra confirm the formation of mixed-metal materials and the presence of two phases, more quantitative analysis is hindered by the overlap of signals from pyrochlore and defect fluorite phases. In all cases, DFT calculations play a vital role in the interpretation and assignment of the NMR spectra, and in understanding the local structure and disorder in these complex multi-phase materials.PostprintPostprintPeer reviewe
Both unmedicated and medicated individuals with schizophrenia show impairments across a wide array of cognitive and reinforcement learning tasks
BACKGROUND: Schizophrenia is a disorder characterized by pervasive deficits in cognitive functioning. However, few well-powered studies have examined the degree to which cognitive performance is impaired even among individuals with schizophrenia not currently on antipsychotic medications using a wide range of cognitive and reinforcement learning measures derived from cognitive neuroscience. Such research is particularly needed in the domain of reinforcement learning, given the central role of dopamine in reinforcement learning, and the potential impact of antipsychotic medications on dopamine function.
METHODS: The present study sought to fill this gap by examining healthy controls (N = 75), unmedicated (N = 48) and medicated (N = 148) individuals with schizophrenia. Participants were recruited across five sites as part of the CNTRaCS Consortium to complete tasks assessing processing speed, cognitive control, working memory, verbal learning, relational encoding and retrieval, visual integration and reinforcement learning.
RESULTS: Individuals with schizophrenia who were not taking antipsychotic medications, as well as those taking antipsychotic medications, showed pervasive deficits across cognitive domains including reinforcement learning, processing speed, cognitive control, working memory, verbal learning and relational encoding and retrieval. Further, we found that chlorpromazine equivalency rates were significantly related to processing speed and working memory, while there were no significant relationships between anticholinergic load and performance on other tasks.
CONCLUSIONS: These findings add to a body of literature suggesting that cognitive deficits are an enduring aspect of schizophrenia, present in those off antipsychotic medications as well as those taking antipsychotic medications
1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
Sagittarius A*, the ~4 x 10^6 solar mass black hole candidate at the Galactic
Center, can be studied on Schwarzschild radius scales with (sub)millimeter
wavelength Very Long Baseline Interferometry (VLBI). We report on 1.3 mm
wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on
Mauna Kea, the ARO/SMT on Mt. Graham in Arizona, and two telescopes of the
CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator
1924-292 were observed over three consecutive nights, and both sources were
clearly detected on all baselines. For the first time, we are able to extract
1.3 mm VLBI interferometer phase information on Sgr A* through measurement of
closure phase on the triangle of baselines. On the third night of observing,
the correlated flux density of Sgr A* on all VLBI baselines increased relative
to the first two nights, providing strong evidence for time-variable change on
scales of a few Schwarzschild radii. These results suggest that future VLBI
observations with greater sensitivity and additional baselines will play a
valuable role in determining the structure of emission near the event horizon
of Sgr A*.Comment: 8 pages, submitted to ApJ
Resolving the inner jet structure of 1924-292 with the EVENT HORIZON TELESCOPE
We present the first 1.3 mm (230 GHz) very long baseline interferometry model
image of an AGN jet using closure phase techniques with a four-element array.
The model image of the quasar 1924-292 was obtained with four telescopes at
three observatories: the James Clerk Maxwell Telescope (JCMT) on Mauna Kea in
Hawaii, the Arizona Radio Observatory's Submillimeter Telescope (SMT) in
Arizona, and two telescopes of the Combined Array for Research in
Millimeterwave Astronomy (CARMA) in California in April 2009. With the greatly
improved resolution compared with previous observations and robust closure
phase measurement, the inner jet structure of 1924-292 was spatially resolved.
The inner jet extends to the northwest along a position angle of at
a distance of 0.38\,mas from the tentatively identified core, in agreement with
the inner jet structure inferred from lower frequencies, and making a position
angle difference of with respect to the cm-jet. The size of
the compact core is 0.15\,pc with a brightness temperature of
\,K. Compared with those measured at lower frequencies, the
low brightness temperature may argue in favor of the decelerating jet model or
particle-cascade models. The successful measurement of closure phase paves the
way for imaging and time resolving Sgr A* and nearby AGN with the Event Horizon
Telescope.Comment: 6 pages, 4 figures, accepted for publication in ApJ
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