720 research outputs found
Imaging a Quasar Accretion Disk with Microlensing
We show how analysis of a quasar high-magnification microlensing event may be
used to construct a map of the frequency-dependent surface brightness of the
quasar accretion disk. The same procedure also allows determination of the disk
inclination angle, the black hole mass (modulo the caustic velocity), and
possibly the black hole spin. This method depends on the validity of one
assumption: that the optical and ultraviolet continuum of the quasar is
produced on the surface of an azimuthally symmetric, flat equatorial disk,
whose gas follows prograde circular orbits in a Kerr spacetime (and plunges
inside the marginally stable orbit). Given this assumption, we advocate using a
variant of first-order linear regularization to invert multi-frequency
microlensing lightcurves to obtain the disk surface brightness as a function of
radius and frequency. The other parameters can be found by minimizing
chi-square in a fashion consistent with the regularized solution for the
surface brightness.
We present simulations for a disk model appropriate to the Einstein Cross
quasar, an object uniquely well-suited to this approach. These simulations
confirm that the surface brightness can be reconstructed quite well near its
peak, and that there are no systematic errors in determining the other model
parameters. We also discuss the observational requirements for successful
implementation of this technique.Comment: accepted to ApJ for publicatio
GnRH removal in the 7-11 CO-Synch for timed insemination of beef heifers
The use of artificial insemination can improve genetics, shorten the calving season,
and increase weaning weights by having more
calves born earlier in the breeding season.
Reasons that this technology has not been
used by many producers may include poor
conception rates, time, and cost. Research has been directed at shortening the synchronization time and controlling time of ovulation to eliminate estrous detection using a timed artificial insemination.
Use of a progestin, like the Eazi-Breed
CIDR or melengestrol acetate (MGA), is desirable because they are effective in synchronizing estrus and they can also induce cyclicity in anestrus or prepubertal females. In addition, gonadotropin releasing hormone (GnRH) is commonly included in a synchronization plan because it induces ovulation and synchronizes follicular development. The most common synchronization protocol for beef heifers consists of feeding MGA for 14 days, a prostaglandin injection 17 to 19 days later followed by five days of heat detection for a total duration of 36 to 38 days. Recent research suggests that acceptable conception
rates can be achieved when shortening the
time of MGA to seven days. One example is
the 7-11 CO-Synch which is comprised of
seven days of MGA feeding followed by the
CO-Synch protocol starting on day 11 (see
Figure 1). We have obtained greater then 60%
conception rates using the 7-11 CO-Synch in
previous years. The feeding of MGA not only
synchronizes the estrous cycle but provides
exposure to a progestin that may induce prepubertal heifers to begin cycling. The GnRH injection at day 11 should synchronize the follicular wave which will tighten the timing of ovulation and improve timed insemination conception rates. The disadvantage to this synchronization protocol is that it requires the heifers to go through the chute four times. It
is also believed that heifers are less responsive to GnRH than cows. Thus we tested this protocol with or without the day 11 GnRH injection on conception rates of beef heifers
Electronic correlations in vanadium chalcogenides: BaVSe3 versus BaVS3
Albeit structurally and electronically very similar, at low temperature the
quasi-one-dimensional vanadium sulfide BaVS3 shows a metal-to-insulator
transition via the appearance of a charge-density-wave state, while BaVSe3
apparently remains metallic down to zero temperature. This different behavior
upon cooling is studied by means of density functional theory and its
combination with the dynamical mean-field theory and the rotationally-invariant
slave-boson method. We reveal several subtle differences between these
chalcogenides that provide indications for the deviant behavior of BaVSe3 at
low temperature. In this regard, a smaller Hubbard U in line with an increased
relevance of the Hund's exchange J plays a vital role.Comment: 16 pages, 11 figures, published versio
Approaching finite-temperature phase diagrams of strongly correlated materials: a case study for V2O3
Examining phase stabilities and phase equilibria in strongly correlated
materials asks for a next level in the many-body extensions to the
local-density approximation (LDA) beyond mainly spectroscopic assessments. Here
we put the charge-self-consistent LDA+dynamical mean-field theory (DMFT)
methodology based on projected local orbitals for the LDA+DMFT interface and a
tailored pseudopotential framework into action in order to address such
thermodynamics of realistic strongly correlated systems. Namely a case study
for the electronic phase diagram of the well-known prototype Mott-phenomena
system VO at higher temperatures is presented. We are able to describe
the first-order metal-to-insulator transitions with negative pressure and
temperature from the self-consistent computation of the correlated total energy
in line with experimental findings.Comment: 12 pages, 15 figures, new data adde
Effect of heifer source on reproductive performance, culling, marketing and profitability for a commercial heifer development program
A commercial heifer development operation
purchased 483 weanling Angus × Hereford
heifers from 11 sources. Heifers were fed a
common silage-based diet through an initial
developmental period and retained or culled
based on average daily gain, pelvic area, and
disposition . The percentage of heifers culled
from each source ranged from 18.1% to 94.7%
and were either sold directly through a local sale
barn or sent to a feedlot with retained
ownership . Estrus was synchronized, and
heifers were artificially inseminated (AI) for 30
days followed by 15 days of natural mating.
First service conception rates for each source
ranged from 0% to 92.3%, whereas overall
pregnancy rates for the 45-day breeding season
ranged from 81.3% to 100%. When expressed
as a percentage of the original heifers purchased
from each source, overall pregnancy rates
ranged from 5.3% to 80%. Heifers that lost
their fetuses were sold for a net loss of 160, 89 per head,
respectively. With accurate records, stringent
culling practices, and evaluation of cost and
performance, producers can optimize profit
potential of replacement heifers. Early culling
and pregnancy diagnosis also will decrease costs
while increasing opportunities to minimize the
financial risks
Production of Recombinant Adeno-associated Virus Vectors Using Suspension HEK293 Cells and Continuous Harvest of Vector From the Culture Media for GMP FIX and FLT1 Clinical Vector
Adeno-associated virus (AAV) has shown great promise as a gene therapy vector in multiple aspects of preclinical and clinical applications. Many developments including new serotypes as well as self-complementary vectors are now entering the clinic. With these ongoing vector developments, continued effort has been focused on scalable manufacturing processes that can efficiently generate high-titer, highly pure, and potent quantities of rAAV vectors. Utilizing the relatively simple and efficient transfection system of HEK293 cells as a starting point, we have successfully adapted an adherent HEK293 cell line from a qualified clinical master cell bank to grow in animal component-free suspension conditions in shaker flasks and WAVE bioreactors that allows for rapid and scalable rAAV production. Using the triple transfection method, the suspension HEK293 cell line generates greater than 1 × 105 vector genome containing particles (vg)/cell or greater than 1 × 1014 vg/l of cell culture when harvested 48 hours post-transfection. To achieve these yields, a number of variables were optimized such as selection of a compatible serum-free suspension media that supports both growth and transfection, selection of a transfection reagent, transfection conditions and cell density. A universal purification strategy, based on ion exchange chromatography methods, was also developed that results in high-purity vector preps of AAV serotypes 1–6, 8, 9 and various chimeric capsids tested. This user-friendly process can be completed within 1 week, results in high full to empty particle ratios (>90% full particles), provides postpurification yields (>1 × 1013 vg/l) and purity suitable for clinical applications and is universal with respect to all serotypes and chimeric particles. To date, this scalable manufacturing technology has been utilized to manufacture GMP phase 1 clinical AAV vectors for retinal neovascularization (AAV2), Hemophilia B (scAAV8), giant axonal neuropathy (scAAV9), and retinitis pigmentosa (AAV2), which have been administered into patients. In addition, we report a minimum of a fivefold increase in overall vector production by implementing a perfusion method that entails harvesting rAAV from the culture media at numerous time-points post-transfection
Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas
In this work, we examine the validity of several common simplifying
assumptions used in numerical neoclassical calculations for nonaxisymmetric
plasmas, both by using a new continuum drift-kinetic code and by considering
analytic properties of the kinetic equation. First, neoclassical phenomena are
computed for the LHD and W7-X stellarators using several versions of the
drift-kinetic equation, including the commonly used incompressible-ExB-drift
approximation and two other variants, corresponding to different effective
particle trajectories. It is found that for electric fields below roughly one
third of the resonant value, the different formulations give nearly identical
results, demonstrating the incompressible ExB-drift approximation is quite
accurate in this regime. However, near the electric field resonance, the models
yield substantially different results. We also compare results for various
collision operators, including the full linearized Fokker-Planck operator. At
low collisionality, the radial transport driven by radial gradients is nearly
identical for the different operators, while in other cases it is found to be
important that collisions conserve momentum
A novel estrus-synchronization program for anestrous and cycling, suckled, beef cows
We used four herds at three Kansas ranches
to evaluate the potential of two new estrus
synchronization strategies to increase estrus
expression and fertility of 911 crossbred suckled
beef cows. The treatments included: 1) 100 μg
of GnRH and a 6-mg norgestomet ear implant
on day -7 and 25 mg of PG F2" and implant
removal on day 0 (GnRH+NORG+PG F2"); 2)
100 μg of GnRH on day - 7 and 25 mg of PGF 2"
on day 0 (GnRH+PG F2"); and 3 ) (control) 25-
mg injections of PG F2" on days -14 and 0;
(2×PGF2" control) . The GnRH+NORG+ PGF 2"
and GnRH+PGF treatments increased (P<.01) 2"
the overall percentages of cows detected in
estrus by 49% and 27% and pregnancy rates by
46% and 37%, respectively, over the control
group, without altering conception rate. Both
treatments increase d the estrus, conception, and
pregnancy rates of noncycling cows, compared
to controls
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