91 research outputs found
Potential For Stable Flies And House Flies (Diptera: Muscidae) To Transmit Rift Valley Fever Virus1
Rift Valley fever (RVF), a disease of ruminants and humans, has been responsible for large outbreaks in Africa that have resulted in hundreds of thousands of human infections and major economic disruption due to loss of livestock and to trade restrictions. As indicated by the rapid spread of West Nile viral activity across North America since its discovery in 1999 and the rapid and widespread movement of chikungunya virus from Africa throughout the Indian Ocean Islands to Asia and Europe, an introduced exotic arbovirus can be rapidly and widely established across wide geographical regions. Although RVF virus (RVFV) is normally transmitted by mosquitoes, we wanted to determine the potential for this virus to replicate in 2 of the most globally distributed and common higher flies: house flies, Musca domestica, and stable flies, Stomoxys calcitrans. Neither species supported the replication of RVFV, even after intrathoracic inoculation. However, S. calcitrans was able to mechanically transmit RVFV to susceptible hamsters (Mesocricetus auratus) after probing on infected hamsters with high viral titers. Therefore, S. calcitrans, because of its close association with domestic animals that serve as amplifying hosts of RVFV, should be considered a possible mechanical vector of RVFV, and it may contribute to the rapid spread of a RVF outbreak. Other Stomoxys species present in Africa and elsewhere may also play similar roles
The ACS Nearby Galaxy Survey Treasury. X. Quantifying the Star Cluster Formation Efficiency of Nearby Dwarf Galaxies
We study the relationship between the field star formation and cluster
formation properties in a large sample of nearby dwarf galaxies. We use optical
data from the Hubble Space Telescope and from ground-based telescopes to derive
the ages and masses of the young (t_age < 100Myr) cluster sample. Our data
provides the first constraints on two proposed relationships between the star
formation rate of galaxies and the properties of their cluster systems in the
low star formation rate regime. The data show broad agreement with these
relationships, but significant galaxy-to-galaxy scatter exists. In part, this
scatter can be accounted for by simulating the small number of clusters
detected from stochastically sampling the cluster mass function. However, this
stochasticity does not fully account for the observed scatter in our data
suggesting there may be true variations in the fraction of stars formed in
clusters in dwarf galaxies. Comparison of the cluster formation and the
brightest cluster in our sample galaxies also provide constraints on cluster
destruction models.Comment: 16 pages, 9 figures, Accepted to Ap
Criticality and Superfluidity in liquid He-4 under Nonequilibrium Conditions
We review a striking array of recent experiments, and their theoretical
interpretations, on the superfluid transition in He in the presence of a
heat flux, . We define and evaluate a new set of critical point exponents.
The statics and dynamics of the superfluid-normal interface are discussed, with
special attention to the role of gravity. If is in the same direction as
gravity, a self-organized state can arise, in which the entire sample has a
uniform reduced temperature, on either the normal or superfluid side of the
transition. Finally, we review recent theory and experiment regarding the heat
capacity at constant . The excitement that surrounds this field arises from
the fact that advanced thermometry and the future availability of a
microgravity experimental platform aboard the International Space Station will
soon open to experimental exploration decades of reduced temperature that were
previously inaccessible.Comment: 16 pages, 9 figures, plus harvard.sty style file for references
Accepted for publication in Colloquia section of Reviews of Modern Physic
A novel and well-defined benchmarking method for second generation read mapping
Background Second generation sequencing technologies yield DNA sequence data
at ultra high-throughput. Common to most biological applications is a mapping
of the reads to an almost identical or highly similar reference genome. The
assessment of the quality of read mapping results is not straightforward and
has not been formalized so far. Hence, it has not been easy to compare
different read mapping approaches in a unified way and to determine which
program is the best for what task. Results We present a new benchmark method,
called Rabema (Read Alignment BEnchMArk), for read mappers. It consists of a
strict definition of the read mapping problem and of tools to evaluate the
result of arbitrary read mappers supporting the SAM output format. Conclusions
We show the usefulness of the benchmark program by performing a comparison of
popular read mappers. The tools supporting the benchmark are licensed under
the GPL and available from http://www.seqan.de/projects/rabema.html
Evaluation of Methods for De Novo Genome Assembly from High-Throughput Sequencing Reads Reveals Dependencies That Affect the Quality of the Results
Recent developments in high-throughput sequencing technology have made low-cost sequencing an attractive approach for many genome analysis tasks. Increasing read lengths, improving quality and the production of increasingly larger numbers of usable sequences per instrument-run continue to make whole-genome assembly an appealing target application. In this paper we evaluate the feasibility of de novo genome assembly from short reads (β€100 nucleotides) through a detailed study involving genomic sequences of various lengths and origin, in conjunction with several of the currently popular assembly programs. Our extensive analysis demonstrates that, in addition to sequencing coverage, attributes such as the architecture of the target genome, the identity of the used assembly program, the average read length and the observed sequencing error rates are powerful variables that affect the best achievable assembly of the target sequence in terms of size and correctness
The True Durations of Starbursts: HST Observations of Three Nearby Dwarf Starburst Galaxies
The duration of a starburst is a fundamental parameter affecting the
evolution of galaxies yet, to date, observational constraints on the durations
of starbursts are not well established. Here we study the recent star formation
histories (SFHs) of three nearby dwarf galaxies to rigorously quantify the
duration of their starburst events using a uniform and consistent approach. We
find that the bursts range from ~200 - ~400 Myr in duration resolving the
tension between the shorter timescales often derived observationally with the
longer timescales derived from dynamical arguments. If these three starbursts
are typical of starbursts in dwarf galaxies, then the short timescales (3 - 10
Myr) associated with starbursts in previous studies are best understood as
"flickering" events which are simply small components of the larger starburst.
In this sample of three nearby dwarfs, the bursts are not localized events. All
three systems show bursting levels of star formation in regions of both high
and low stellar density. The enhanced star formation moves around the galaxy
during the bursts and covers a large fraction of the area of the galaxy. These
massive, long duration bursts can significantly affect the structure, dynamics,
and chemical evolution of the host galaxy and can be the progenitors of
"superwinds" that drive much of the recently chemically enriched material from
the galaxy into the intergalactic medium.Comment: 41 pages, 14 figures, ApJ, Accepte
Endemic Venezuelan Equine Encephalitis in Northern Peru
Since Venezuelan equine encephalitis virus (VEEV) was isolated in Peru in 1942, >70 isolates have been obtained from mosquitoes, humans, and sylvatic mammals primarily in the Amazon region. To investigate genetic relationships among the Peru VEEV isolates and between the Peru isolates and other VEEV strains, a fragment of the PE2 gene was amplified and analyzed by single-stranded conformation polymorphism. Representatives of seven genotypes underwent sequencing and phylogenetic analysis. The results identified four VEE complex lineages that cocirculate in the Amazon region: subtypes ID (Panama and Colombia/Venezuela genotypes), IIIC, and a new, proposed subtype IIID, which was isolated from a febrile human, mosquitoes, and spiny rats. Both ID lineages and the IIID subtype are associated with febrile human illness. Most of the subtype ID isolates belonged to the Panama genotype, but the Colombia/Venezuela genotype, which is phylogenetically related to epizootic strains, also continues to circulate in the Amazon basin
A Fragment of the LG3 Peptide of Endorepellin Is Present in the Urine of Physically Active Mining Workers: A Potential Marker of Physical Activity
Biomarker analysis has been implemented in sports research in an attempt to monitor the effects of exertion and fatigue in athletes. This study proposed that while such biomarkers may be useful for monitoring injury risk in workers, proteomic approaches might also be utilised to identify novel exertion or injury markers. We found that urinary urea and cortisol levels were significantly elevated in mining workers following a 12 hour overnight shift. These levels failed to return to baseline over 24 h in the more active maintenance crew compared to truck drivers (operators) suggesting a lack of recovery between shifts. Use of a SELDI-TOF MS approach to detect novel exertion or injury markers revealed a spectral feature which was associated with workers in both work categories who were engaged in higher levels of physical activity. This feature was identified as the LG3 peptide, a C-terminal fragment of the anti-angiogenic/anti-tumourigenic protein endorepellin. This finding suggests that urinary LG3 peptide may be a biomarker of physical activity. It is also possible that the activity mediated release of LG3/endorepellin into the circulation may represent a biological mechanism for the known inverse association between physical activity and cancer risk/survival
Analysis of Biological Features Associated with Meiotic Recombination Hot and Cold Spots in Saccharomyces cerevisiae
Meiotic recombination is not distributed uniformly throughout the genome. There are regions of high and low recombination rates called hot and cold spots, respectively. The recombination rate parallels the frequency of DNA double-strand breaks (DSBs) that initiate meiotic recombination. The aim is to identify biological features associated with DSB frequency. We constructed vectors representing various chromatin and sequence-based features for 1179 DSB hot spots and 1028 DSB cold spots. Using a feature selection approach, we have identified five features that distinguish hot from cold spots in Saccharomyces cerevisiae with high accuracy, namely the histone marks H3K4me3, H3K14ac, H3K36me3, and H3K79me3; and GC content. Previous studies have associated H3K4me3, H3K36me3, and GC content with areas of mitotic recombination. H3K14ac and H3K79me3 are novel predictions and thus represent good candidates for further experimental study. We also show nucleosome occupancy maps produced using next generation sequencing exhibit a bias at DSB hot spots and this bias is strong enough to obscure biologically relevant information. A computational approach using feature selection can productively be used to identify promising biological associations. H3K14ac and H3K79me3 are novel predictions of chromatin marks associated with meiotic DSBs. Next generation sequencing can exhibit a bias that is strong enough to lead to incorrect conclusions. Care must be taken when interpreting high throughput sequencing data where systematic biases have been documented
Kinematics and Chemistry of Stars Along the Sagittarius Trailing Tidal Tail and Constraints on the Milky Way Mass Distribution
We present three-dimensional kinematics of Sagittarius (Sgr) trailing tidal
debris in six fields located 70-130 degrees along the stream from the Sgr dwarf
galaxy core. The data are from our proper-motion (PM) survey of Kapteyn's
Selected Areas, in which we have measured accurate PMs to faint magnitudes in
40x40 arcmin fields evenly spaced across the sky. The radial velocity (RV)
signature of Sgr has been identified among our follow-up spectroscopic data in
four of the six fields and combined with mean PMs of
spectroscopically-confirmed members to derive space motions of Sgr debris based
on 15-64 confirmed stream members per field. These kinematics are compared to
predictions of the Law & Majewski (2010) model of Sgr disruption; we find
reasonable agreement with model predictions in RVs and PMs along Galactic
latitude. However, an upward adjustment of the Local Standard of Rest velocity
Theta_LSR from its standard 220 km/s to at least km/s (and possibly
as high as km/s) is necessary to bring 3-D model debris kinematics
and our measurements into agreement. Satisfactory model fits that
simultaneously reproduce known position, distance, and radial velocity trends
of the Sgr tidal streams, while significantly increasing Theta_LSR}, could only
be achieved by increasing the Galactic bulge and disk mass while leaving the
dark matter halo fixed to the best-fit values from Law & Majewski (2010). We
derive low-resolution spectroscopic abundances along this stretch of the Sgr
stream and find a constant [Fe/H] = -1.15 (with ~0.5 dex scatter in each field
-- typical for dwarf galaxy populations) among the four fields with reliable
measurements. A constant metallicity suggests that debris along the ~60-degree
span of this study was all stripped from Sgr on the same orbital passage.Comment: 26 pages, 24 figures (some with degraded resolution), accepted to
ApJ; full-resolution version available at
http://www.rpi.edu/~carlij/sgr_paper/ms.apjformat.ps.g
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