2,539 research outputs found
Outer-Sphere Effects on Reduction Potentials of Copper Sites in Proteins: The Curious Case of High Potential Type 2 C112D/M121E Pseudomonas aeruginosa Azurin
Redox and spectroscopic (electronic absorption, multifrequency electron paramagnetic resonance (EPR), and X-ray absorption) properties together with X-ray crystal structures are reported for the type 2 Cu^(II) C112D/M121E variant of Pseudomonas aeruginosa azurin. The results suggest that Cu^(II) is constrained from interaction with the proximal glutamate; this structural frustration implies a “rack” mechanism for the 290 mV (vs NHE) reduction potential measured at neutral pH. At high pH (~9), hydrogen bonding in the outer coordination sphere is perturbed to allow axial glutamate ligation to Cu^(II), with a decrease in potential to 119 mV. These results highlight the role played by outer-sphere interactions, and the structural constraints they impose, in determining the redox behavior of transition metal protein cofactors
Optimal Time-Series Selection of Quasars
We present a novel method for the optimal selection of quasars using
time-series observations in a single photometric bandpass. Utilizing the damped
random walk model of Kelly et al. (2009), we parameterize the ensemble quasar
structure function in Sloan Stripe 82 as a function of observed brightness. The
ensemble model fit can then be evaluated rigorously for and calibrated with
individual light curves with no parameter fitting. This yields a classification
in two statistics --- one describing the fit confidence and one describing the
probability of a false alarm --- which can be tuned, a priori, to achieve high
quasar detection fractions (99% completeness with default cuts), given an
acceptable rate of false alarms. We establish the typical rate of false alarms
due to known variable stars as <3% (high purity). Applying the classification,
we increase the sample of potential quasars relative to those known in Stripe
82 by as much as 29%, and by nearly a factor of two in the redshift range
2.5<z<3, where selection by color is extremeley inefficient. This represents
1875 new quasars in a 290 deg^2 field. The observed rates of both quasars and
stars agree well with the model predictions, with >99% of quasars exhibiting
the expected variability profile. We discus the utility of the method at
high-redshift and in the regime of noisy and sparse data. Our time series
selection complements well independent selection based on quasar colors and has
strong potential for identifying high redshift quasars for BAO and other
cosmology studies in the LSST era.Comment: 28 pages, 8 figures, 3 tables; Accepted to A
Effects of Material Mapping Agnostic Partial Volume Correction for Subject Specific Finite Elements Simulations
Partial Volume effects are present at the boundary between any two types of
material in a CT image due to the scanner's Point Spread Function, finite voxel
resolution, and importantly, the discrepancy in radiodensity between the two
materials. In this study a new algorithm is developed and validated that builds
on previously published work to enable the correction of partial volume effects
at cortical bone boundaries. Unlike past methods, this algorithm does not
require pre-processing or user input to achieve the correction, and the
correction is applied directly onto a set of CT images, which enables it to be
used in existing computational modelling workflows. The algorithm was validated
by performing experimental three point bending tests on porcine fibulae
specimen and comparing the experimental results to finite element results for
models created using either the original, uncorrected CT images or the partial
volume corrected images. Results demonstrated that the models created using the
partial volume corrected images did improved the accuracy of the surface strain
predictions. Given this initial validation, this algorithm is a viable method
for overcoming the challenge of partial volume effects in CT images. Thus,
future work should be undertaken to further validate the algorithm with human
tissues and through coupling it with a range of different finite element
creation workflows to verify that it is robust and agnostic to the chosen
material mapping strategy
Evaluation of Barrier Sprays in Eastern North Carolina
Presented for World Environmental Health Day, September 26, 2016 in Greenville, North Carolina.Suspend® Polyzone® (deltamethrin) and Bifen
Insecticide/Termiticide (bifenthrin) were evaluated
in two eastern North Carolina neighborhoods from
May 18 – Oct 19, 2015 (23 weeks). Lots were sprayed
every 21 days. At 17 fixed locations (13 treatment,
four control), Centers for Disease Control and
Prevention (CDC) CO2-baited traps were deployed
overnight, once/week. Oviposition traps were also
deployed weekly and remained for seven days to
measure Aedes albopictus abundance. Mosquitoes were
identified to species and tabulated by location and
week. Adult and egg abundance was generally
significantly higher in control versus treatment traps.
The abundance of Psorophora columbiae and Ae. vexans
was significantly higher in control versus treatment
traps. Bifenthrin and deltamethrin showed
differences in efficacy (e.g. Ae. vexans, An. punctipennis,
and Ps. ferox abundance was higher in bifenthrin
traps compared to deltamethrin and control traps),
but this varied across neighborhoods and species.This study was funded by Bayer Crop Science and The Mosquito Authorit
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