1,023 research outputs found
Seasonal variability in ichthyoplankton abundance and assemblage composition in the northern Gulf of Mexico off Alabama
Multiyear ichthyoplankton surveys used to monitor larval fish seasonality, abundance, and assemblage structure can provide early indicators of regional ecosystem changes.
Numerous ichthyoplankton surveys have been conducted in the northern Gulf of Mexico, but few have had high levels of temporal resolution and sample replication. In this study, ichthyoplankton samples were collected monthly (October 2004âOctober 2006) at a single station off the coast of
Alabama as part of a long-term biological survey. Four seasonal periods were identified from observed and
historic water temperatures, including a relatively long (JuneâOctober) âsummerâ period (water temperature >26°C). Fish egg abundance, total larval abundance, and larval
taxonomic diversity were significantly related to water temperature (but not salinity), with peaks in the spring,
springâsummer, and summer periods, respectively. Larvae collected during the survey represented 58 different
families, of which engraulids, sciaenids, carangids, and clupeids were the most prominent. The most abundant taxa collected were unidentified engraulids (50%), sand seatrout
(Cynoscion arenarius, 7.5%), Atlantic bumper (Chloroscombrus chrysurus, 5.4%), Atlantic croaker (Micropogonias undulatus, 4.4%), Gulf menhaden (Brevoortia patronus, 3.8%), and unidentified gobiids (3.6%). Larval
concentrations for dominant taxa were highly variable between years, but the timing of seasonal occurrence for
these taxa was relatively consistent. Documented increases in sea surface temperature on the Alabama shelf may have various implications for larval fish dynamics, as indicated by the presence of tropical larval forms (e.g., fistularids, labrids, scarids, and acanthurids) in our ichthyoplankton collections and in recent juvenile surveys
of Alabama and northern Gulf of Mexico seagrass habitats
Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(â)-myrtenol nitrate
Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a âhalide for nitrateâ substitution. Employing readily available starting materials, reagents and HornerâWadsworthâEmmons chemistry the synthesis of easily separable, synthetically versatile âkey building blocksâ (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, âoff the shelfâ materials. Exploiting their reactivity we have studied their ability to undergo an âallylic halide for allylic nitrateâ substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates (âisoprene nitratesâ) in 66â80% overall yields. Using NOESY experiments the elucidation of the carbonâcarbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our âhalide for nitrateâ substitution chemistry we outline the straightforward transformation of (1R,2S)-(â)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(â)-myrtenol nitrate
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Optimising the analysis of transcript data using high density oligonucleotide arrays and genomic DNA-based probe selection
Background: Affymetrix GeneChip arrays are widely used for transcriptomic studies in a diverse range of species. Each gene is represented on a GeneChip array by a probe-set, consisting of up to 16 probe-pairs. Signal intensities across probe-pairs within a probe-set vary in part due to different physical hybridisation characteristics of individual probes with their target labelled transcripts. We
have previously developed a technique to study the transcriptomes of heterologous species based
on hybridising genomic DNA (gDNA) to a GeneChip array designed for a different species, and subsequently using only those probes with good homology.
Results: Here we have investigated the effects of hybridising homologous species gDNA to study the transcriptomes of species for which the arrays have been designed. Genomic DNA from Arabidopsis thaliana and rice (Oryza sativa) were hybridised to the Affymetrix Arabidopsis ATH1 and Rice Genome GeneChip arrays respectively. Probe selection based on gDNA hybridisation
intensity increased the number of genes identified as significantly differentially expressed in two
published studies of Arabidopsis development, and optimised the analysis of technical replicates obtained from pooled samples of RNA from rice.
Conclusion: This mixed physical and bioinformatics approach can be used to optimise estimates of gene expression when using GeneChip arrays
Seasonal Variability in Ichthyoplankton Abundance and Assemblage Composition in the Northern Gulf of Mexico off Alabama
Multiyear ichthyoplankton surveys used to monitor larval fish seasonality, abundance, and assemblage structure can provide early indicators of regional ecosystem changes. Numerous ichthyoplankton surveys have been conducted in the northern Gulf of Mexico, but few have had high levels of temporal resolution and sample replication. In this study, ichthyoplankton samples were collected monthly (October 2004âOctober 2006) at a single station off the coast of Alabama as part of a long-term biological survey. Four seasonal periods were identified from observed and historic water temperatures, including a relatively long (JuneâOctober) âsummerâ period (water temperature \u3e26°C). Fish egg abundance, total larval abundance, and larval taxonomic diversity were significantly related to water temperature (but not salinity), with peaks in the spring, springâsummer, and summer periods, respectively. Larvae collected during the survey represented 58 different families, of which engraulids, sciaenids, carangids, and clupeids were the most prominent. The most abundant taxa collected were unidentified engraulids (50%), sand seatrout (Cynoscion arenarius, 7.5%), Atlantic bumper (Chloroscombrus chrysurus, 5.4%), Atlantic croaker (Micropogonias undulatus, 4.4%), Gulf menhaden (Brevoortia patronus, 3.8%), and unidentified gobiids (3.6%). Larval concentrations for dominant taxa were highly variable between years, but the timing of seasonal occurrence for these taxa was relatively consistent. Documented increases in sea surface temperature on the Alabama shelf may have various implications for larval fish dynamics, as indicated by the presence of tropical larval forms (e.g., fistularids, labrids, scarids, and acanthurids) in our ichthyoplankton collections and in recent juvenile surveys of Alabama and northern Gulf of Mexico seagrass habitats
Reflections of Cluster Assembly in the Stellar Populations and Dynamics of Member Galaxies
We combine optical (HST) and UV (GALEX) imaging of two intermediate redshift galaxy clusters with spectroscopy of member galaxies, to study the relation between the formation history of cluster galaxies and the assembly history of the cluster structure itself. We identify key differences in the large-scale structure and intracluster medium properties of each cluster. In order to assess the importance of cluster substructure and the ICM in the evolution of cluster galaxies, we examine several key indicators of the recent star-formation and assembly history of cluster galaxies. We find that galaxies in cluster MS 0451 (z = 0.54) exhibit a markedly lower incidence of recent star formation activity than galaxies in cluster Cl 0024 (z = 0.39), likely the result of starvation by the ICM. In addition, Cl 0024 members show evidence for kinematic disturbances that can be linked to the assembly of substructure
Measurement of isoprene nitrates by GCMS
According to atmospheric chemistry models, isoprene nitrates play an important role in determining the ozone production efficiency of isoprene; however this is very poorly constrained through observations as isoprene nitrates have not been widely measured. Measurements have been severely restricted largely due to a limited ability to measure individual isoprene nitrate isomers. An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods are described for the speciated measurements of individual isoprene nitrate isomers. Five of the primary isoprene nitrates which formed in the presence of NOx by reaction of isoprene with the hydroxyl radical (OH) in the Master Chemical Mechanism are identified using known isomers on two column phases and are fully separated on the Rtx-200 column. Three primary isoprene nitrates from the reaction of isoprene with the nitrate radical (NO3) are identified after synthesis from the already identified analogous hydroxy nitrate. A Tenax adsorbent-based trapping system allows the analysis of the majority of the known hydroxy and carbonyl primary isoprene nitrates, although not the (1,2)-IN isomer, under field-like levels of humidity and showed no impact from typical ambient concentrations of NOx and ozone
Notes on Reproduction in the Brownback Salamander (Eurycea aquatica)
Life history data often are lacking for species with an uncertain taxonomic status. As phylogenetic analyses improve and our understanding of species boundaries become more refined, ecological information should likewise keep pace. Here, we report information on the timing of reproduction, clutch size, and nest attendance for the Brownback Salamander (Eurycea aquatica), a species recently documented to be a separate lineage after a long, controversial systematic history. We confirm that this species has the largest clutch size of any lineage within the Eurycea bislineata complex, and suggest that male and male-female nest attendance is not uncommon in this species. We suggest that, in addition to the genetic divergence documented between E. aquatica and other members of the E. bislineata complex, ecological differences also are present and possibly are influenced by the unique springs inhabited by Brownback Salamanders
Notes on Reproduction in the Brownback Salamander (Eurycea aquatica)
Life history data often are lacking for species with an uncertain taxonomic status. As phylogenetic analyses improve and our understanding of species boundaries become more refined, ecological information should likewise keep pace. Here, we report information on the timing of reproduction, clutch size, and nest attendance for the Brownback Salamander (Eurycea aquatica), a species recently documented to be a separate lineage after a long, controversial systematic history. We confirm that this species has the largest clutch size of any lineage within the Eurycea bislineata complex, and suggest that male and male-female nest attendance is not uncommon in this species. We suggest that, in addition to the genetic divergence documented between E. aquatica and other members of the E. bislineata complex, ecological differences also are present and possibly are influenced by the unique springs inhabited by Brownback Salamanders
The high-cost, type 2 diabetes mellitus patient: an analysis of managed care administrative data
BACKGROUND: Type 2 diabetes mellitus (T2DM) affects 25.8 million individuals in the United States and exerts a substantial economic burden on patients, health care systems, and society. Few studies have categorized costs and resource use at the patient level. The goals of this study were to assess predictors of being a high-cost (HC) patient and compare HC T2DM patients with not high-cost (NHC) T2DM patients. METHODS: Using managed care administrative claims data, patients with two or more T2DM diagnoses between 2005 and 2010 were selected. Patients were followed for 1Â year after their first observed T2DM diagnosis; patients not continuously enrolled during this period were excluded from the study. Study measures included annual health care expenditures by component (i.e., inpatient, outpatient, pharmacy, total). Patients accruing total costs in the top 10% of the overall cost distribution (i.e., patients with costsâ>â56,468 (56,778-4,674 (4,695-52,000 more in total annual health care costs than not high-cost T2DM patients. Patients were significantly more likely to be high-cost if they had comorbid conditions, a diagnosis of obesity, or used insulin
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