550 research outputs found
RNA polymerase III interferes with Ty3 integration
AbstractTy3, a gypsylike retrotransposon of budding yeast, integrates at the transcription initiation site of genes transcribed by RNA polymerase III (pol III). It was previously shown that integration in vitro requires intact promoter elements and the pol III transcription factors TFIIIB and TFIIIC. In order to test the effect of pol III on integration, increasing amounts of a pol III-containing fraction were added to Ty3 in vitro integration reactions. The pol III-containing fraction was inhibitory to integration. These results are consistent with a model where the Ty3 integration complex and pol III recognize similar features of the stable transcription complex and compete with each other for access to the transcription initiation site
Large spin relaxation rates in trapped submerged-shell atoms
Spin relaxation due to atom-atom collisions is measured for magnetically
trapped erbium and thulium atoms at a temperature near 500 mK. The rate
constants for Er-Er and Tm-Tm collisions are 3.0 times 10^-10 cm^3 s^-1 and 1.1
times 10^-10 cm^3 s^-1, respectively, 2-3 orders of magnitude larger than those
observed for highly magnetic S-state atoms. This is strong evidence for an
additional, dominant, spin relaxation mechanism, electrostatic anisotropy, in
collisions between these "submerged-shell" L > 0 atoms. These large spin
relaxation rates imply that evaporative cooling of these atoms in a magnetic
trap will be highly inefficient.Comment: 10 pages, 3 figure
Superconducting Gatemon Qubit based on a Proximitized Two-Dimensional Electron Gas
The coherent tunnelling of Cooper pairs across Josephson junctions (JJs)
generates a nonlinear inductance that is used extensively in quantum
information processors based on superconducting circuits, from setting qubit
transition frequencies and interqubit coupling strengths, to the gain of
parametric amplifiers for quantum-limited readout. The inductance is either set
by tailoring the metal-oxide dimensions of single JJs, or magnetically tuned by
parallelizing multiple JJs in superconducting quantum interference devices
(SQUIDs) with local current-biased flux lines. JJs based on
superconductor-semiconductor hybrids represent a tantalizing all-electric
alternative. The gatemon is a recently developed transmon variant which employs
locally gated nanowire (NW) superconductor-semiconductor JJs for qubit control.
Here, we go beyond proof-of-concept and demonstrate that semiconducting
channels etched from a wafer-scale two-dimensional electron gas (2DEG) are a
suitable platform for building a scalable gatemon-based quantum computer. We
show 2DEG gatemons meet the requirements by performing voltage-controlled
single qubit rotations and two-qubit swap operations. We measure qubit
coherence times up to ~2 us, limited by dielectric loss in the 2DEG host
substrate
The DEEP2 Galaxy Redshift Survey: Spectral classification of galaxies at z~1
We present a Principal Component Analysis (PCA)-based spectral
classification, eta, for the first 5600 galaxies observed in the DEEP2 Redshift
Survey. This parameter provides a very pronounced separation between absorption
and emission dominated galaxy spectra - corresponding to passively evolving and
actively star-forming galaxies in the survey respectively. In addition it is
shown that despite the high resolution of the observed spectra, this parameter
alone can be used to quite accurately reconstruct any given galaxy spectrum,
suggesting there are not many `degrees of freedom' in the observed spectra of
this galaxy population. It is argued that this form of classification, eta,
will be particularly valuable in making future comparisons between high and
low-redshift galaxy surveys for which very large spectroscopic samples are now
readily available, particularly when used in conjunction with high-resolution
spectral synthesis models which will be made public in the near future. We also
discuss the relative advantages of this approach to distant galaxy
classification compared to other methods such as colors and morphologies.
Finally, we compare the classification derived here with that adopted for the
2dF Galaxy Redshift Survey and in so doing show that the two systems are very
similar. This will be particularly useful in subsequent analyses when making
comparisons between results from each of these surveys to study evolution in
the galaxy populations and large-scale structure.Comment: 10 pages, 9 figures, Accepted for publication in Ap
Geographic Variation in Salt Marsh Structure and Function for Nekton: a Guide to Finding Commonality Across Multiple Scales
Coastal salt marshes are distributed widely across the globe and are considered essential habitat for many fish and crustacean species. Yet, the literature on fishery support by salt marshes has largely been based on a few geographically distinct model systems, and as a result, inadequately captures the hierarchical nature of salt marsh pattern, process, and variation across space and time. A better understanding of geographic variation and drivers of commonalities and differences across salt marsh systems is essential to informing future management practices. Here, we address the key drivers of geographic variation in salt marshes: hydroperiod, seascape configuration, geomorphology, climatic region, sediment supply and riverine input, salinity, vegetation composition, and human activities. Future efforts to manage, conserve, and restore these habitats will require consideration of how environmental drivers within marshes affect the overall structure and subsequent function for fisheries species. We propose a future research agenda that provides both the consistent collection and reporting of sources of variation in small-scale studies and collaborative networks running parallel studies across large scales and geographically distinct locations to provide analogous information for data poor locations. These comparisons are needed to identify and prioritize restoration or conservation efforts, identify sources of variation among regions, and best manage fisheries and food resources across the globe
Were Fertile Crescent crop progenitors higher yielding than other wild species that were never domesticated?
During the origin of agriculture in the Fertile Crescent, the broad spectrum of wild plant species exploited by hunter-gatherers narrowed dramatically. The mechanisms responsible for this specialization and the associated domestication of plants are intensely debated. We investigated why some species were domesticated rather than others, and which traits they shared.
We tested whether the progenitors of cereal and pulse crops, grown individually, produced a higher yield and less chaff than other wild grasses and legumes, thereby maximizing the return per seed planted and minimizing processing time. We compared harvest traits of species originating from the Fertile Crescent, including those for which there is archaeological evidence of deliberate collection.
Unexpectedly, wild crop progenitors in both families had neither higher grain yield nor, in grasses, less chaff, although they did have larger seeds. Moreover, small-seeded grasses actually returned a higher yield relative to the mass of seeds sown. However, cereal progenitors had threefold fewer seeds per plant, representing a major difference in how seeds are packaged on plants.
These data suggest that there was no intrinsic yield advantage to adopting large-seeded progenitor species as crops. Explaining why Neolithic agriculture was founded on these species, therefore, remains an important unresolved challenge
Etiology of Severe Non-malaria Febrile Illness in Northern Tanzania: A Prospective Cohort Study.
The syndrome of fever is a commonly presenting complaint among persons seeking healthcare in low-resource areas, yet the public health community has not approached fever in a comprehensive manner. In many areas, malaria is over-diagnosed, and patients without malaria have poor outcomes. We prospectively studied a cohort of 870 pediatric and adult febrile admissions to two hospitals in northern Tanzania over the period of one year using conventional standard diagnostic tests to establish fever etiology. Malaria was the clinical diagnosis for 528 (60.7%), but was the actual cause of fever in only 14 (1.6%). By contrast, bacterial, mycobacterial, and fungal bloodstream infections accounted for 85 (9.8%), 14 (1.6%), and 25 (2.9%) febrile admissions, respectively. Acute bacterial zoonoses were identified among 118 (26.2%) of febrile admissions; 16 (13.6%) had brucellosis, 40 (33.9%) leptospirosis, 24 (20.3%) had Q fever, 36 (30.5%) had spotted fever group rickettsioses, and 2 (1.8%) had typhus group rickettsioses. In addition, 55 (7.9%) participants had a confirmed acute arbovirus infection, all due to chikungunya. No patient had a bacterial zoonosis or an arbovirus infection included in the admission differential diagnosis. Malaria was uncommon and over-diagnosed, whereas invasive infections were underappreciated. Bacterial zoonoses and arbovirus infections were highly prevalent yet overlooked. An integrated approach to the syndrome of fever in resource-limited areas is needed to improve patient outcomes and to rationally target disease control efforts
Weak Lensing with SDSS Commissioning Data: The Galaxy-Mass Correlation Function To 1/h Mpc
(abridged) We present measurements of galaxy-galaxy lensing from early
commissioning imaging data from the Sloan Digital Sky Survey (SDSS). We measure
a mean tangential shear around a stacked sample of foreground galaxies in three
bandpasses out to angular radii of 600'', detecting the shear signal at very
high statistical significance. The shear profile is well described by a
power-law. A variety of rigorous tests demonstrate the reality of the
gravitational lensing signal and confirm the uncertainty estimates. We
interpret our results by modeling the mass distributions of the foreground
galaxies as approximately isothermal spheres characterized by a velocity
dispersion and a truncation radius. The velocity dispersion is constrained to
be 150-190 km/s at 95% confidence (145-195 km/s including systematic
uncertainties), consistent with previous determinations but with smaller error
bars. Our detection of shear at large angular radii sets a 95% confidence lower
limit , corresponding to a physical radius of
kpc, implying that galaxy halos extend to very large radii. However, it is
likely that this is being biased high by diffuse matter in the halos of groups
and clusters. We also present a preliminary determination of the galaxy-mass
correlation function finding a correlation length similar to the galaxy
autocorrelation function and consistency with a low matter density universe
with modest bias. The full SDSS will cover an area 44 times larger and provide
spectroscopic redshifts for the foreground galaxies, making it possible to
greatly improve the precision of these constraints, measure additional
parameters such as halo shape, and measure the properties of dark matter halos
separately for many different classes of galaxies.Comment: 28 pages, 11 figures, submitted to A
Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240
We present deep VERITAS observations of the blazar PKS 1424+240, along with
contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and Swift UV
Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar
resides at a redshift of , displaying a significantly attenuated
gamma-ray flux above 100 GeV due to photon absorption via pair-production with
the extragalactic background light. We present more than 100 hours of VERITAS
observations from three years, a multiwavelength light curve and the
contemporaneous spectral energy distributions. The source shows a higher flux
of (2.1) ph ms above 120 GeV in 2009 and
2011 as compared to the flux measured in 2013, corresponding to
(1.02) ph ms above 120 GeV. The measured
differential very high energy (VHE; GeV) spectral indices are
3.80.3, 4.30.6 and 4.50.2 in 2009, 2011 and 2013,
respectively. No significant spectral change across the observation epochs is
detected. We find no evidence for variability at gamma-ray opacities of greater
than , where it is postulated that any variability would be small and
occur on longer than year timescales if hadronic cosmic-ray interactions with
extragalactic photon fields provide a secondary VHE photon flux. The data
cannot rule out such variability due to low statistics.Comment: ApJL accepted March 17, 201
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