1,786 research outputs found
Development of improved thermoelectric mater- ials for spacecraft applications final summary report, 29 jun. 1964 - 29 jun. 1965
Thermoelectric materials for spacecraft applications - optimization of bismuth-antimony alloys and ag-sb-fe-te-se system alloys for thermoelectric cooling in space environmen
Delineating land/forest fire burnt scars with ERS Interferometric Synthetic Aperture Radar
Helicase on DNA: A Phase coexistence based mechanism
We propose a phase coexistence based mechanism for activity of helicases,
ubiquitous enzymes that unwind double stranded DNA. The helicase-DNA complex
constitutes a fixed-stretch ensemble that entails a coexistence of domains of
zipped and unzipped phases of DNA, separated by a domain wall. The motor action
of the helicase leads to a change in the position of the fixed constraint
thereby shifting the domain wall on dsDNA. We associate this off-equilibrium
domain wall motion with the unzipping activity of helicase. We show that this
proposal gives a clear and consistent explanation of the main observed features
of helicases.Comment: Revtex4. 5 pages. 4 figures. Published versio
Are autistic traits measured equivalently in individuals with and without an Autism Spectrum Disorder?:An invariance analysis of the Autism Spectrum Quotient Short Form
It is common to administer measures of autistic traits to those without autism spectrum disorders (ASDs) with, for example, the aim of understanding autistic personality characteristics in non-autistic individuals. Little research has examined the extent to which measures of autistic traits actually measure the same traits in the same way across those with and without an ASD. We addressed this question using a multi-group confirmatory factor invariance analysis of the Autism Quotient Short Form (AQ-S: Hoekstra et al. in J Autism Dev Disord 41(5):589-596, 2011) across those with (n = 148) and without (n = 168) ASD. Metric variance (equality of factor loadings), but not scalar invariance (equality of thresholds), held suggesting that the AQ-S measures the same latent traits in both groups, but with a bias in the manner in which trait levels are estimated. We, therefore, argue that the AQ-S can be used to investigate possible causes and consequences of autistic traits in both groups separately, but caution is due when combining or comparing levels of autistic traits across the two group
The master sex-determination locus in threespine sticklebacks is on a nascent Y chromosome.
BACKGROUND: Many different environmental and genetic sex-determination mechanisms are found in nature. Closely related species can use different master sex-determination switches, suggesting that these developmental pathways can evolve very rapidly. Previous cytological studies suggest that recently diverged species of stickleback fish have different sex chromosome complements. Here, we investigate the genetic and chromosomal mechanisms that underlie sex determination in the threespine stickleback (Gasterosteus aculeatus). RESULTS: Genome-wide linkage mapping identifies a single chromosome region at the distal end of linkage group (LG) 19, which controls male or female sexual development in threespine sticklebacks. Although sex chromosomes are not cytogenetically visible in this species, several lines of evidence suggest that LG 19 is an evolving sex chromosome system, similar to the XX female/XY male system in many other species: (1) males are consistently heterozygous for unique alleles in this region; (2) recombination between loci linked to the sex-determination region is reduced in male meiosis relative to female meiosis; (3) sequence analysis of X- and Y-specific bacterial artificial chromosome (BAC) clones from the sex-determination region reveals many sequence differences between the X- and Y-specific clones; and (4) the Y chromosome has accumulated transposable elements and local duplications. CONCLUSIONS: Taken together, our data suggest that threespine sticklebacks have a simple chromosomal mechanism for sex determination based on a nascent Y chromosome that is less than 10 million years old. Further analysis of the stickleback system will provide an exciting window into the evolution of sex-determination pathways and sex chromosomes in vertebrates
Synthesis of Fluorine-18 Functionalized Nanoparticles for use as in vivo Molecular Imaging Agents
Nanoparticles containing fluorine-18 were prepared from block copolymers made by ring opening metathesis polymerization (ROMP). Using the fast initiating ruthenium metathesis catalyst (H_2IMes)(pyr)_2(Cl)_2Ru=CHPh, low polydispersity amphiphilic block copolymers were prepared from a cinnamoyl-containing hydrophobic norbornene monomer and a mesyl-terminated PEG-containing hydrophilic norbornene monomer. Self-assembly into micelles and subsequent cross-linking of the micelle cores by light-activated dimerization of the cinnamoyl groups yielded stable nanoparticles. Incorporation of fluorine-18 was achieved by nucleophilic displacement of the mesylates by the radioactive fluoride ion with 31% incorporation of radioactivity. The resulting positron-emitting nanoparticles are to be used as in vivo molecular imaging agents for use in tumor imaging
Dendrimers Clicked Together Divergently
ABSTRACT: Dendrimers containing 1,4-triazole linkages between each generation were grown divergently via the Click chemistry inspired Huisgen 1,3-dipolar cycloaddition reaction in the presence of a Cu(I) catalyst. The monomeric unit (1-propargylbenzene-3,5-dimethanol) contained the alkyne functionality, while the core (1,2-bis(2-azidoethoxy)ethane) and growing dendrimers presented the azide groups necessary for this type of Click reaction. The first generation dendrimer was also functionalized with alkyne termini to demonstrate an alternative pathway allowed by this chemistry. Synthesis and characterization, with infrared (IR), 1H and 13C NMR spectroscopies, high-resolution mass spectrometry, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), are reported for these divergently grown dendrimers
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Compact portable electric power sources
This report provides an overview of recent advances in portable electric power source (PEPS) technology and an assessment of emerging PEPS technologies that may meet US Special Operations Command`s (SOCOM) needs in the next 1--2- and 3--5-year time frames. The assessment was performed through a literature search and interviews with experts in various laboratories and companies. Nineteen PEPS technologies were reviewed and characterized as (1) PEPSs that meet SOCOM requirements; (2) PEPSs that could fulfill requirements for special field conditions and locations; (3) potentially high-payoff sources that require additional R and D; and (4) sources unlikely to meet present SOCOM requirements. 6 figs., 10 tabs
The prevalence and incidence of mental ill-health in adults with autism and intellectual disabilities
The prevalence, and incidence, of mental ill-health in adults with intellectual disabilities and autism were compared with the whole population with intellectual disabilities, and with controls, matched individually for age, gender, ability-level, and Down syndrome. Although the adults with autism had a higher point prevalence of problem behaviours compared with the whole adult population with intellectual disabilities, compared with individually matched controls there was no difference in prevalence, or incidence of either problem behaviours or other mental ill-health. Adults with autism who had problem behaviours were less likely to recover over a two-year period than were their matched controls. Apparent differences in rates of mental ill-health are accounted for by factors other than autism, including Down syndrome and ability level
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