3,701 research outputs found
The Mean Ultraviolet Spectrum of a Representative Sample of Faint z~3 Lyman Alpha Emitters
We discuss the rest-frame ultraviolet emission line spectra of a large (~100)
sample of low luminosity redshift z~3.1 Lyman alpha emitters (LAEs) drawn from
a Subaru imaging survey in the SSA22 survey field. Our earlier work based on
smaller samples indicated that such sources have high [OIII]/[OII] line ratios
possibly arising from a hard ionising spectrum that may be typical of similar
sources in the reionisation era. With optical spectra secured from VLT/VIMOS,
we re-examine the nature of the ionising radiation in a larger sample using the
strength of the high ionisation diagnostic emission lines of CIII]1909,
CIV1549, HeII1640, and OIII]1661,1666 in various stacked subsets. Our analysis
confirms earlier suggestions of a correlation between the strength of Ly-alpha
and CIII] emission and we find similar trends with broad band UV luminosity and
rest-frame UV colour. Using various diagnostic line ratios and our stellar
photoionisation models, we determine both the gas phase metallicity and
hardness of the ionisation spectrum characterised by xi_ion - the number of
Lyman continuum photons per UV luminosity. We confirm our earlier suggestion
that xi_ion is significantly larger for LAEs than for continuum-selected Lyman
break galaxies, particularly for those LAEs with the faintest UV luminosities.
We briefly discuss the implications for cosmic reionisation if the metal-poor
intensely star-forming systems studied here are representative examples of
those at much higher redshift.Comment: 15 pages, 9 figures. Accepted for publication in MNRA
Eighth Amendment Challenges to the Length of a Criminal Sentence: Following the Supreme Court “From Precedent to Precedent”
Defendant A was convicted twice previously of felonies and sentenced to prison for fraudulent use of a credit card (28.36). Upon his third felony conviction for obtaining money by false pretenses ($120.75), he received a mandatory life sentence under a state recidivist statute
The Lyman Continuum Escape Survey: Ionizing Radiation from [O III]-Strong Sources at a Redshift of 3.1
We present results from the LymAn Continuum Escape Survey (LACES), a Hubble
Space Telescope (HST) program designed to characterize the ionizing radiation
emerging from a sample of Lyman alpha emitting galaxies at redshift . As many show intense [O III] emission characteristic of
star-forming galaxies, they may represent valuable low redshift analogs of
galaxies in the reionization era. Using HST Wide Field Camera 3 / UVIS
to image Lyman continuum emission, we investigate the escape fraction of
ionizing photons in this sample. For 61 sources, of which 77% are
spectroscopically confirmed and 53 have measures of [O III] emission, we detect
Lyman continuum leakage in 20%, a rate significantly higher than is seen in
individual continuum-selected Lyman break galaxies. We estimate there is a 98%
probability that of our detections could be affected by foreground
contamination. Fitting multi-band spectral energy distributions (SEDs) to take
account of the varying stellar populations, dust extinctions and metallicities,
we derive individual Lyman continuum escape fractions corrected for foreground
intergalactic absorption. We find escape fractions of 15 to 60% for individual
objects, and infer an average 20% escape fraction by fitting composite SEDs for
our detected samples. Surprisingly however, even a deep stack of those sources
with no individual detections provides a stringent upper limit on the
average escape fraction of less than 0.5%. We examine various correlations with
source properties and discuss the implications in the context of the popular
picture that cosmic reionization is driven by such compact, low metallicity
star-forming galaxies.Comment: 26 pages, 16 figures, accepted for publication in Ap
Development of a Next-Generation NIL Library in Arabidopsis Thaliana for Dissecting Complex Traits
The identification of the loci and specific alleles underlying variation in quantitative traits is an important goal for evolutionary biologists and breeders. Despite major advancements in genomics technology, moving from QTL to causal alleles remains a major challenge in genetics research. Near-isogenic lines are the ideal raw material for QTL validation, refinement of QTL location and, ultimately, gene discovery. Results: In this study, a population of 75 Arabidopsis thaliana near-isogenic lines was developed from an existing recombinant inbred line (RIL) population derived from a cross between physiologically divergent accessions Kas-1 and Tsu-1. First, a novel algorithm was developed to utilize genome-wide marker data in selecting RILs fully isogenic to Kas-1 for a single chromosome. Seven such RILs were used in 2 generations of crossing to Tsu-1 to create BC1 seed. BC1 plants were genotyped with SSR markers so that lines could be selected that carried Kas-1 introgressions, resulting in a population carrying chromosomal introgressions spanning the genome. BC1 lines were genotyped with 48 genome-wide SSRs to identify lines with a targeted Kas-1 introgression and the fewest genomic introgressions elsewhere. 75 such lines were selected and genotyped at an additional 41 SNP loci and another 930 tags using 2b-RAD genotyping by sequencing. The final population carried an average of 1.35 homozygous and 2.49 heterozygous introgressions per line with average introgression sizes of 5.32 and 5.16 Mb, respectively. In a simple case study, we demonstrate the advantage of maintaining heterozygotes in our library whereby fine-mapping efforts are conducted simply by self-pollination. Crossovers in the heterozygous interval during this single selfing generation break the introgression into smaller, homozygous fragments (sub-NILs). Additionally, we utilize a homozygous NIL for validation of a QTL underlying stomatal conductance, a low heritability trait. Conclusions: The present results introduce a new and valuable resource to the Brassicaceae research community that enables rapid fine-mapping of candidate loci in parallel with QTL validation. These attributes along with dense marker coverage and genome-wide chromosomal introgressions make this population an ideal starting point for discovery of genes underlying important complex traits of agricultural and ecological significance.NSF DEB-1022196, DEB-0618302, DEB-0618347, IOS-09221457Integrative Biolog
The thermal contact conductance of hard and soft coat anodized aluminium
An experimental investigation of the thermal contact conductance of anodized coatings Introduction The thermal performance of microelectronic components has become increasingly important as systems are miniaturized. The dense packaging on standard electronic modules (SEM), widely used in military applications, often leads to thermally induced failures because of the thermal resistance occurring between the module guide fibs and the chassis card rails. This thermal resistance results from the limited contact area at the interface, the uneven contact pressure, surface characteristics, and the bulk resistance of the coatings on the card rails and guide ribs. As circuit densities have increased, cooling schemes have been developed to maintain device temperatures within their optimum design specification. However, other techniques that help reduce the temperature change across component interfaces must also be investigated. Many electronic systems incorporate anodized surfaces, which contribute to the thermal resistance at component interfaces. This paper reports the results of an experimental investigation of anodized films grown at different temperatures and in different electrolyte solutions, and compares these results with previously published information
Recommended from our members
ASSESSMENT OF STREAM FISH MORTALITY FROM SHORT-TERM EXPOSURE TO ILLITE CLAYS USED AS AN IN SITU METHOD FOR REMEDIATING 137CS CONTAMINATED WETLANDS
Due to their physical properties, illite clays can sorb cesium-137 almost irreversibly, and therefore sequester contamination from the environment. However, applying large amounts of clay to natural aquatic habitats for in situ remediation purposes may create conditions of high turbidity and sedimentation. To evaluate potential effects of turbidity from illite application on survivorship of stream fish, yellowfin shiners (Notropis lutipinnis) and tessellated darters (Etheostoma olmstedi) were subjected to treatment with two different types of clay in flow-through simulated stream raceways. Turbidity and fish mortality were subsequently monitored for seven days. At 2-m downstream from the application point, mean turbidity peaked during clay application at 525 and 72 nephelometric turbidity units (NTU) in the air-floated illite and semi-dry illite treatments, respectively. Turbidity returned to levels similar to that of the controls (4-6 NTU) after four hours in the air-floated illite raceways and one hour in the semi-dry illite raceways. Although the majority of the suspended clay was quickly flushed from the system and the remaining settled to the bottom, turbidity did continue to fluctuate because of fish movements and sediment resuspension. Fish mortality did not significantly differ among control and illite treated raceways
The role of the Niemann-Pick disease, type C1 protein in adipocyte insulin action.
The Niemann-Pick disease, type C1 (NPC1) gene encodes a transmembrane protein involved in cholesterol efflux from the lysosome. SNPs within NPC1 have been associated with obesity and type 2 diabetes, and mice heterozygous or null for NPC1 are insulin resistant. However, the molecular mechanism underpinning this association is currently undefined. This study aimed to investigate the effects of inhibiting NPC1 function on insulin action in adipocytes. Both pharmacological and genetic inhibition of NPC1 impaired insulin action. This impairment was evident at the level of insulin signalling and insulin-mediated glucose transport in the short term and decreased GLUT4 expression due to reduced liver X receptor (LXR) transcriptional activity in the long-term. These data show that cholesterol homeostasis through NPC1 plays a crucial role in maintaining insulin action at multiple levels in adipocytes
Recommended from our members
Abnormal lateralization of functional connectivity between language and default mode regions in autism
Background: Lateralization of brain structure and function occurs in typical development, and abnormal lateralization is present in various neuropsychiatric disorders. Autism is characterized by a lack of left lateralization in structure and function of regions involved in language, such as Broca and Wernicke areas. Methods: Using functional connectivity magnetic resonance imaging from a large publicly available sample (n = 964), we tested whether abnormal functional lateralization in autism exists preferentially in language regions or in a more diffuse pattern across networks of lateralized brain regions. Results: The autism group exhibited significantly reduced left lateralization in a few connections involving language regions and regions from the default mode network, but results were not significant throughout left- and right-lateralized networks. There is a trend that suggests the lack of left lateralization in a connection involving Wernicke area and the posterior cingulate cortex associates with more severe autism. Conclusions: Abnormal language lateralization in autism may be due to abnormal language development rather than to a deficit in hemispheric specialization of the entire brain
Multisite functional connectivity MRI classification of autism: ABIDE results
Background:: Systematic differences in functional connectivity MRI metrics have been consistently observed in autism, with predominantly decreased cortico-cortical connectivity. Previous attempts at single subject classification in high-functioning autism using whole brain point-to-point functional connectivity have yielded about 80% accurate classification of autism vs. control subjects across a wide age range. We attempted to replicate the method and results using the Autism Brain Imaging Data Exchange (ABIDE) including resting state fMRI data obtained from 964 subjects and 16 separate international sites. Methods:: For each of 964 subjects, we obtained pairwise functional connectivity measurements from a lattice of 7266 regions of interest covering the gray matter (26.4 million “connections”) after preprocessing that included motion and slice timing correction, coregistration to an anatomic image, normalization to standard space, and voxelwise removal by regression of motion parameters, soft tissue, CSF, and white matter signals. Connections were grouped into multiple bins, and a leave-one-out classifier was evaluated on connections comprising each set of bins. Age, age-squared, gender, handedness, and site were included as covariates for the classifier. Results:: Classification accuracy significantly outperformed chance but was much lower for multisite prediction than for previous single site results. As high as 60% accuracy was obtained for whole brain classification, with the best accuracy from connections involving regions of the default mode network, parahippocampaland fusiform gyri, insula, Wernicke Area, and intraparietal sulcus. The classifier score was related to symptom severity, social function, daily living skills, and verbal IQ. Classification accuracy was significantly higher for sites with longer BOLD imaging times. Conclusions:: Multisite functional connectivity classification of autism outperformed chance using a simple leave-one-out classifier, but exhibited poorer accuracy than for single site results. Attempts to use multisite classifiers will likely require improved classification algorithms, longer BOLD imaging times, and standardized acquisition parameters for possible future clinical utility
Αξιοβίωτη Ολοκληρωμένη Ανάπτυξη. Από την Θεωρία στην Πράξη: Η περίπτωση των αστέγων της Αθήνας
Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Περιβάλλον και Ανάπτυξη
- …