2,578 research outputs found
Hypercube technology
The JPL designed MARKIII hypercube supercomputer has been in application service since June 1988 and has had successful application to a broad problem set including electromagnetic scattering, discrete event simulation, plasma transport, matrix algorithms, neural network simulation, image processing, and graphics. Currently, problems that are not homogeneous are being attempted, and, through this involvement with real world applications, the software is evolving to handle the heterogeneous class problems efficiently
Radio Galaxy Zoo: The Distortion of Radio Galaxies by Galaxy Clusters
We study the impact of cluster environment on the morphology of a sample of
4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the
sample lies within a projected 15 Mpc of an optically identified cluster.
Brightest cluster galaxies (BCGs) are more likely than other cluster members to
be radio sources, and are also moderately bent. The surface density as a
function of separation from cluster center of non-BCG radio galaxies follows a
power law with index out to (Mpc), which
is steeper than the corresponding distribution for optically selected galaxies.
Non-BCG radio galaxies are statistically more bent the closer they are to the
cluster center. Within the inner (Mpc) of a cluster,
non-BCG radio galaxies are statistically more bent in high-mass clusters than
in low-mass clusters. Together, we find that non-BCG sources are statistically
more bent in environments that exert greater ram pressure. We use the
orientation of bent radio galaxies as an indicator of galaxy orbits and find
that they are preferentially in radial orbits. Away from clusters, there is a
large population of bent radio galaxies, limiting their use as cluster
locators; however, they are still located within statistically overdense
regions. We investigate the asymmetry in the tail length of sources that have
their tails aligned along the radius vector from the cluster center, and find
that the length of the inward-pointing tail is weakly suppressed for sources
close to the center of the cluster.Comment: 23 pages, 17 figures, 2 tables. Supplemental data files available in
The Astronomical Journal or contact autho
Results of the 2016 Indianapolis Biodiversity Survey, Marion County, Indiana
Surprising biodiversity can be found in cities, but urban habitats are understudied. We report on a bioblitz conducted primarily within a 24-hr period on September 16 and 17, 2016 in Indianapolis, Indiana, USA. The event focused on stretches of three waterways and their associated riparian habitat: Fall Creek (20.6 ha; 51 acres), Pleasant Run (23.5 ha; 58 acres), and Pogue’s Run (27.1 ha; 67 acres). Over 75 scientists, naturalists, students, and citizen volunteers comprised 14 different taxonomic teams. Five hundred ninety taxa were documented despite the rainy conditions. A brief summary of the methods and findings are presented here. Detailed maps of survey locations and inventory results are available on the Indiana Academy of Science website (https://www.indianaacademyofscience.org/)
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Structure of the SecY channel during initiation of protein translocation
Many secretory proteins are targeted by signal sequences to a protein-conducting channel, formed by prokaryotic SecY- or eukaryotic Sec61-complexes, and are translocated across the membrane during their synthesis1,2. Crystal structures of the inactive channel show that the SecY subunit of the heterotrimeric complex consists of two halves that form an hourglass-shaped pore with a constriction in the middle of the membrane and a lateral gate that faces the lipid phase3-5. The closed channel has an empty cytoplasmic funnel and an extracellular funnel that is filled with a small helical domain, called the plug. During initiation of translocation, a ribosome–nascent chain complex binds to the SecY/Sec61 complex, resulting in insertion of the nascent chain. However, the mechanism of channel opening during translocation is unclear. Here, we have addressed this question by determining structures of inactive and active ribosome–channel complexes with cryo-electron microscopy. Non-translating ribosome–SecY channel complexes derived from Methanococcus jannaschii or Escherichia coli show the channel in its closed state, and indicate that ribosome binding per se causes only minor changes. The structure of an active E. coli ribosome–channel complex demonstrates that the nascent chain opens the channel, causing mostly rigid body movements of the N- and C-terminal halves of SecY. In this early translocation intermediate, the polypeptide inserts as a loop into the SecY channel with the hydrophobic signal sequence intercalated into the open lateral gate. The nascent chain also forms a loop on the cytoplasmic surface of SecY rather than directly entering the channel
Step-Indexed Normalization for a Language with General Recursion
The Trellys project has produced several designs for practical dependently
typed languages. These languages are broken into two
fragments-a_logical_fragment where every term normalizes and which is
consistent when interpreted as a logic, and a_programmatic_fragment with
general recursion and other convenient but unsound features. In this paper, we
present a small example language in this style. Our design allows the
programmer to explicitly mention and pass information between the two
fragments. We show that this feature substantially complicates the metatheory
and present a new technique, combining the traditional Girard-Tait method with
step-indexed logical relations, which we use to show normalization for the
logical fragment.Comment: In Proceedings MSFP 2012, arXiv:1202.240
Enhancing the Competitiveness of the Arab SMEs
Statistics show that SMEs represent 90% of total companies in the vast majority of economies worldwide and provide 40-80% of total job opportunities in addition to contributing largely to GDPs of many countries. For example, SMEs constitute more than 99%1 of all non-agricultural private enterprises in Egypt and account for nearly three-quarters of new employment generation. for Kuwait, this sector constitutes approximately 90% of the private workforce, including labor and imported an estimated 45% of the labor force, employment and national rates of less than 1%, in Lebanon, more than 95% of the total enterprises, contribute about 90% of the jobs. In the UAE , small and medium enterprises accounted about 94.3% of the economic projects in the country, and employs about 62% of the workforce and contributes around 75% of the GDP of the state. In addition, they account for 96% of the GDP in Yemen in 2005, and about 77%, 59%, 25% in Algeria, Palestine and Saudi Arabia, respectively, during the same year.It is often argued that the Governments should promote SMEs because of their greater economic benefits compared to the large firms in terms of job creation, efficiency and growth.Following are the major driving force to strengthen SMEs in the Arab countries:
(1) SMEs are the important vehicle in terms of employments and poverty alleviation. SME employs a large share of the labour force in many Arab countries.
(2) SMEs make significant contributions to the national economy of the country;
and Can be a tool to accelerate the growth of exports.
(3) SMEs foster an entrepreneurial culture and make the economy more resilient
to the global fluctuations.
The aim of this research is to study enhancing the competitiveness of Arab small and medium enterprises
Maternal vitamin D during pregnancy and offspring autism and autism-associated traits:a prospective cohort study
Background
There has been a growing interest in the association between maternal levels of vitamin D during pregnancy and offspring autism. However, whether any associations reflect causal effects is still inconclusive.
Methods
We used data from a UK-based pregnancy cohort study (Avon Longitudinal Study of Parents and Children) comprising 7689 births between 1991 and 1992 with maternal blood vitamin D levels recorded during pregnancy and at least one recorded outcome measure, including autism diagnosis and autism-associated traits. The association between each outcome with seasonal and gestational age-adjusted maternal serum 25-hydroxyvitamin D during pregnancy was estimated using confounder-adjusted regression models. Multiple imputation was used to account for missing data, and restricted cubic splines were used to investigate nonlinear associations. Mendelian randomization was used to strengthen causal inference.
Results
No strong evidence of an association between maternal serum 25-hydroxyvitamin D during pregnancy and any offspring autism-associated outcome was found using multivariable regression analysis (autism diagnosis: adjusted OR = 0.98, 95% CI = 0.90–1.06), including with multiple imputation (autism diagnosis: adjusted OR = 0.99, 95% CI = 0.93–1.06), and no evidence of a causal effect was suggested by Mendelian randomization (autism diagnosis: causal OR = 1.08, 95% CI = 0.46–2.55). Some evidence of increased odds of autism-associated traits at lower levels of maternal serum 25-hydroxyvitamin D was found using spline analysis.
Limitations
Our study was potentially limited by low power, particularly for diagnosed autism cases as an outcome. The cohort may not have captured the extreme lows of the distribution of serum 25-hydroxyvitamin D, and our analyses may have been biased by residual confounding and missing data.
Conclusions
The present study found no strong evidence of a causal link between maternal vitamin D levels in pregnancy and offspring diagnosis or traits of autism
GALEX UV Color Relations for Nearby Early-Type Galaxies
We use GALEX/optical photometry to construct color-color relationships for
early-type galaxies sorted by morphological type. We have matched objects in
the GALEX GR1 public release and the first IR1.1 internal release, with the RC3
early-type galaxies having a morphological type -5.5<T<-1.5 with mean error in
T<1.5, and mean error on (B-V)T<0.05. After visual inspection of each match, we
are left with 130 galaxies with a reliable GALEX pipeline photometry in the
far-UV and near-UV bands. This sample is divided into Ellipticals (-5.5<T<-3.5)
and Lenticulars (-3.5<T<-1.5). After correction for the Galactic extinction,
the color-color diagrams FUV-NUV vs. (B-V)_{Tc} are plotted for the two
subsamples. We find a tight anti-correlation between the FUV-NUV and (B-V)_{Tc}
colors for Ellipticals, the UV color getting bluer when the (B-V)_{Tc} get
redder. This relationship very likely is an extension of the color-metallicity
relationship into the GALEX NUV band. We suspect that the main source of the
correlation is metal line blanketing in the NUV band. The FUV-NUV vs B-V
correlation has larger scatter for lenticular galaxies; we speculate this
reflects the presence of low level star formation. If the latter objects (i.e.
those that are blue both in FUV-NUV and B-V) are interpreted as harboring
recent star formation activity, this would be the case for a few percent (~4%)
of Ellipticals and ~15% of Lenticulars; this would make about 10% of early-type
galaxies with residual star formation in our full sample of 130 early-type
galaxies. We also plot FUV-NUV vs. the Mg_2 index and central velocity
dispersion. We find a tight anti-correlation between FUV-NUV and the Mg_2
index(...).Comment: 25 pages, 5 figures, accepted for publication in ApJS (abstract
abridged), typos corrected in section 2.
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