1,671 research outputs found
Sling Complications
https://digitalscholarship.unlv.edu/wrin_briefs/1003/thumbnail.jp
Surgeon Volume
https://digitalscholarship.unlv.edu/wrin_briefs/1002/thumbnail.jp
Cellular location and activity of Escherichia coli RecG proteins shed light on the function of its structurally unresolved C-terminus
RecG is a DNA translocase encoded by most species of bacteria. The Escherichia coli protein targets branched DNA substrates and drives the unwinding and rewinding of DNA strands. Its ability to remodel replication forks and to genetically interact with PriA protein have led to the idea that it plays an important role in securing faithful genome duplication. Here we report that RecG co-localises with sites of DNA replication and identify conserved arginine and tryptophan residues near its C-terminus that are needed for this localisation. We establish that the extreme C-terminus, which is not resolved in the crystal structure, is vital for DNA unwinding but not for DNA binding. Substituting an alanine for a highly conserved tyrosine near the very end results in a substantial reduction in the ability to unwind replication fork and Holliday junction structures but has no effect on substrate affinity. Deleting or substituting the terminal alanine causes an even greater reduction in unwinding activity, which is somewhat surprising as this residue is not uniformly present in closely related RecG proteins. More significantly, the extreme C-terminal mutations have little effect on localisation. Mutations that do prevent localisation result in only a slight reduction in the capacity for DNA repair. © 2014 The Author(s)
Nested Scales of Spatial and Temporal Variability of Soil Water Content Across a Semiarid Montane Catchment
Topographic redistribution of water has been represented by various terrain metrics (e.g., topographic wetness index, slope, and upslope accumulated area). This type of landscape characterization has promoted the use of terrain metrics to inform how spatial patterns of soil volumetric water content (VWC) influence streamflow, ecological processes, and associated nutrient fluxes. However, evaluation of what these static terrain metrics reflect has only been accomplished in a few catchments. Additionally, previous research suggests that relationships between topographic metrics and VWC could be different across catchments through time. Here we measured VWC from snowmelt through summer drydown across a semiarid montane catchment. Using a spatially nested sampling design, we assessed the spatiotemporal variability of VWC from plot (tens of meters) to landscape scales (hundreds of meters). Variance of riparian area VWC increased as the catchment dried, while upland variance decreased, highlighting the utility of delineating distinct landscape units when considering spatial variability of moisture, rather than calculating statistics across the landscape as a whole. In contrast to previous research, we found that the relationship between VWC and topographic metrics persisted through the dry catchment state, suggesting that patterns of topographic redistribution of water during snowmelt continued to influence dry season VWC despite variability in plot scale vertical processes (e.g., evapotranspiration). Future research should focus on resolving the relationship between catchment moisture state and VWC variability as a function of wetness state, seasonality, and magnitude of precipitation, topography, and soil depth
OMCat: Catalogue of Serendipitous Sources Detected with the XMM-Newton Optical Monitor
The Optical Monitor Catalogue of serendipitous sources (OMCat) contains
entries for every source detected in the publicly available XMM-Newton Optical
Monitor (OM) images taken in either the imaging or ``fast'' modes. Since the OM
is coaligned and records data simultaneously with the X-ray telescopes on
XMM-Newton, it typically produces images in one or more near-UV/optical bands
for every pointing of the observatory. As of the beginning of 2006, the public
archive had covered roughly 0.5% of the sky in 2950 fields.
The OMCat is not dominated by sources previously undetected at other
wavelengths; the bulk of objects have optical counterparts. However, the OMCat
can be used to extend optical or X-ray spectral energy distributions for known
objects into the ultraviolet, to study at higher angular resolution objects
detected with GALEX, or to find high-Galactic-latitude objects of interest for
UV spectroscopy.Comment: 25 pages, 22 figures, submitted to PAS
Theoretical Study of Spin-dependent Electron Transport in Atomic Fe Nanocontacts
We present theoretical predictions of spintronic transport phenomena that
should be observable in ferromagnetic Fe nanocontacts bridged by chains of Fe
atoms. We develop appropriate model Hamiltonians based on semi-empirical
considerations and the known electronic structure of bulk Fe derived from ab
initio density functional calculations. Our model is shown to provide a
satisfactory description of the surface properties of Fe nano-clusters as well
as bulk properties. Lippmann-Schwinger and Green's function techniques are used
together with Landauer theory to predict the current, magneto-resistance, and
spin polarization of the current in Fe nanocontacts bridged by atomic chains
under applied bias. Unusual device characteristics are predicted including
negative magneto-resistance and spin polarization of the current, as well as
spin polarization of the current for anti-parallel magnetization of the Fe
nanocontacts under moderate applied bias. We explore the effects that
stretching the atomic chain has on the magneto-resistance and spin polarization
and predict a cross-over regime in which the spin polarization of the current
for parallel magnetization of the contacts switches from negative to positive.
We find resonant transmission due to dangling bond formation on tip atoms as
the chain is stretched through its breaking point to play an important role in
spin-dependent transport in this regime. The physical mechanisms underlying the
predicted phenomena are discussed.Comment: 13 pages, 6 figures, Accepted for publication in Physical Review
Optical Transitions in Highly Excited States: RF LOG Spectrum of XeI
Pulsed laser optogalvanic spectroscopy of diluted gases in a
32MHz radio frequency discharge (RF LOG) was applied to xenon
in a pressure range from 0.01to several Torr. The optical transitions
caused by exciting the products of the discharge with laser energies from 14,000to 17,000cm? have been recorded and assigned. At low pressures, most transitions originate in the 5d states, whereas at higher pressures those from the 6p and 6s\u27 states become dominant. Results indicate that (il) coupling and selection rules /),J. = O, ± 1 and /),K. = O, ± 1 provide the most appropriate description of the observed transitions to the lower n-states. However, some transitions with /),K. = ± 2 also possess considerable intensity for some higher angular momentum transitions (p-d, d-f). The low pressure spectra are dominated by the d-f transitions for which all series have been observed. An important feature of these series is that at high n values (n> 20) the oscillatory potential of the RF field starts to populate high angular momentum states and causes a substantial broadening of the transitions to these states. In addition, close to the ionization limit, field induced ionization can take place and, under certain conditions,
this may cause certain high series members to disappear. The
corresponding results are presented and discussed
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