17,909 research outputs found
Cold atom confinement in an all-optical dark ring trap
We demonstrate confinement of Rb atoms in a dark, toroidal optical
trap. We use a spatial light modulator to convert a single blue-detuned
Gaussian laser beam to a superposition of Laguerre-Gaussian modes that forms a
ring-shaped intensity null bounded harmonically in all directions. We measure a
1/e spin-relaxation lifetime of ~1.5 seconds for a trap detuning of 4.0 nm. For
smaller detunings, a time-dependent relaxation rate is observed. We use these
relaxation rate measurements and imaging diagnostics to optimize trap alignment
in a programmable manner with the modulator. The results are compared with
numerical simulations.Comment: 5 pages, 4 figure
Magnetically-controlled velocity selection in a cold atom sample using stimulated Raman transitions
We observe velocity-selective two-photon resonances in a cold atom cloud in
the presence of a magnetic field. We use these resonances to demonstrate a
simple magnetometer with sub-mG resolution. The technique is particularly
useful for zeroing the magnetic field and does not require any additional laser
frequencies than are already used for standard magneto-optical traps. We verify
the effects using Faraday rotation spectroscopy.Comment: 5 pages, 6 figure
Presynchronizing PGF2α and GnRH injections before timed artificial insemination CO-Synch + CIDR program
Fixed-time artificial insemination is an effective management tool that reduces the
labor associated with more conventional artificial insemination programs requiring
detection of estrus. The 7-day CO-Synch + controlled internal drug release (CIDR)
insert protocol has been shown to effectively initiate estrus and ovulation in cycling
and non-cycling suckled beef cows, producing pregnancy rates at or greater than 50%
in beef cows. The gonadotropin-releasing hormone (GnRH) injection that begins the
CO-Synch + CIDR program initiates ovulation in a large proportion of cows, particularly
anestrous cows. The CIDR, which releases progesterone intravaginally, prevents
short estrous cycles that usually follow the first postpartum ovulation in beef cows. Our
hypothesis was that inducing estrus with a prostaglandin injection followed 3 days later
with a GnRH injection, 7 days before applying the 7-day CO-Synch + CIDR protocol,
might increase the percentage of cycling cows that would exhibit synchronous follicular
waves after the onset of the CO-Synch + CIDR protocol. We also hypothesized that
the additional GnRH injection would increase the percentage of anestrous cows that
would ovulate, thereby increasing pregnancy outcomes
The bloodstream differentiation - division of Trypanosoma brucei studied using mitochondrial markers
In the bloodstream of its mammalian host, the African trypanosome Trypanosoma brucei undergoes a life cycle stage differentiation from a long, slender form to a short, stumpy form. This involves three known major events: exit from a proliferative cell cycle, morphological change and mitochondrial biogenesis. Previously, models have been proposed accounting for these events (Matthews & Gull 1994a). Refinement of, and discrimination between, these models has been hindered by a lack of stage-regulated antigens useful as markers at the single-cell level. We have now evaluated a variety of cytological markers and applied them to investigate the coordination of phenotypic differentiation and cell cycle arrest. Our studies have focused on the differential expression of the mitochondrial enzyme dihydrolipoamide dehydrogenase relative to the differentiation-division of bloodstream trypanosomes. The results implicate a temporal order of events: commitment, division, phenotypic differentiation
Time-averaged aerodynamic loads on the vane sets of the 40- by 80-foot and 80- by 120-foot wind tunnel complex
Time-averaged aerodynamic loads are estimated for each of the vane sets in the National Full-Scale Aerodynamic Complex (NFAC). The methods used to compute global and local loads are presented. Experimental inputs used to calculate these loads are based primarily on data obtained from tests conducted in the NFAC 1/10-Scale Vane-Set Test Facility and from tests conducted in the NFAC 1/50-Scale Facility. For those vane sets located directly downstream of either the 40- by 80-ft test section or the 80- by 120-ft test section, aerodynamic loads caused by the impingement of model-generated wake vortices and model-generated jet and propeller wakes are also estimated
Vertical Transmission of Herpes Simplex Virus Acquired After Primary Outbreak in Second Trimester of a Dichorionic Twin Gestation
Background: The incidence of genital herpes simplex virus (HSV) has increased in recent years, particularly among women of reproductive age. This places more neonates at risk for severe morbidity and mortality. Treatment recommendations for primary disease in pregnancy are lacking, particularly for those who acquire. HSV remote from term
An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star
We describe optical photometric and spectroscopic observations of the bright
variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal
variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a
period of 91.645 days. A deep primary eclipse is visible for wavelengths <
4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse
timings and the radial velocity curve of the K0 secondary star indicate an
interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers
material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The
primary star is either an early B-type star or a black hole. If it did contain
a black hole, BG Gem would be the longest period black hole binary known by a
factor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A
Fossil vertebrates from Antigua, Lesser Antilles: Evidence for late Holocene human-caused extinctions in the West Indies
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