17,417 research outputs found
Infrared spectroscopic variability of Cygnus X-3 in outburst and quiescence
We present four epochs of high-resolution infrared spectroscopy of the
peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small
flaring and outburst states of the system as defined by radio and X-ray
monitoring. The underlying infrared spectrum of the source, as observed during
radio and X-ray quiescence and small flaring states, is one of broad, weak HeII
and NV emission. Spectral variability in this state is dominated by modulation
at the 4.8 hr orbital period of the system. H-band spectra confirm the
significant hydrogen depletion of the mass donor. The closest spectral match to
the quiescent infrared spectrum of Cyg X-3 is an early-type WN Wolf-Rayet star.
In outburst, the infrared spectrum is dramatically different, with the
appearance of very strong twin-peaked HeI emission displaying both day-to-day
variability and V(iolet)/R(ed) variations with orbital phase. The most likely
explanation appears to be an enhanced stellar wind from the companion. Thus
X-ray and radio outbursts in this system are likely to originate in
mass-transfer, and not disc, instabilities, and the lengthening of the orbital
period will not be smooth but will be accelerated during these outbursts.
Furthermore, the appearance of these lines is suggestive of an asymmetric
emitting region. We propose that the wind in Cyg X-3 is significantly flattened
in the plane of the binary orbit. This may explain the observed twin-peaked HeI
features as well as reconciling a massive Wolf-Rayet secondary with the
relatively small optical depth to X-rays, if the disc wind is inclined at some
angle to the line of sight.Comment: 13 pages, 7 figures. Accepted for publication in MNRA
Single-spin magnetometry with multi-pulse sensing sequences
We experimentally demonstrate single-spin magnetometry with multi-pulse
sensing sequences. The use of multi-pulse sequences can greatly increase the
sensing time per measurement shot, resulting in enhanced ac magnetic field
sensitivity. We theoretically derive and experimentally verify the optimal
number of sensing cycles, for which the effects of decoherence and increased
sensing time are balanced. We perform these experiments for oscillating
magnetic fields with fixed phase as well as for fields with random phase.
Finally, by varying the phase and frequency of the ac magnetic field, we
measure the full frequency-filtering characteristics of different multi-pulse
schemes and discuss their use in magnetometry applications.Comment: 4 pages, 4 figures. Final versio
Universal dynamical decoupling of a single solid-state spin from a spin bath
Controlling the interaction of a single quantum system with its environment
is a fundamental challenge in quantum science and technology. We dramatically
suppress the coupling of a single spin in diamond with the surrounding spin
bath by using double-axis dynamical decoupling. The coherence is preserved for
arbitrary quantum states, as verified by quantum process tomography. The
resulting coherence time enhancement is found to follow a general scaling with
the number of decoupling pulses. No limit is observed for the decoupling action
up to 136 pulses, for which the coherence time is enhanced more than 25 times
compared to spin echo. These results uncover a new regime for experimental
quantum science and allow to overcome a major hurdle for implementing quantum
information protocols.Comment: submitted 24 May 2010; published online 9 September 201
Polarization and readout of coupled single spins in diamond
We study the coupling of a single nitrogen-vacancy center in diamond to a
nearby single nitrogen defect at room temperature. The magnetic dipolar
coupling leads to a splitting in the electron spin resonance frequency of the
nitrogen-vacancy center, allowing readout of the state of a single nitrogen
electron spin. At magnetic fields where the spin splitting of the two centers
is the same we observe a strong polarization of the nitrogen electron spin. The
amount of polarization can be controlled by the optical excitation power. We
combine the polarization and the readout in time-resolved pump-probe
measurements to determine the spin relaxation time of a single nitrogen
electron spin. Finally, we discuss indications for hyperfine-induced
polarization of the nitrogen nuclear spin
Next-to-leading order Calculation of a Fragmentation Function in a Light-Cone Gauge
The short-distance coefficients for the color-octet ^3S_1 term in the
fragmentation function for a gluon to split into polarized heavy quarkonium
states are re-calculated to order alpha_s^2. The light-cone gauge remarkably
simplifies the calculation by eliminating many Feynman diagrams at the expense
of introducing spurious poles in loop integrals. We do not use any conventional
prescriptions for spurious pole. Instead, we only use gauge invariance with the
aid of Collins-Soper definition of the fragmentation function. Our result
agrees with a previous calculation of Braaten and Lee in the Feynman gauge, but
disagrees with another previous calculation.Comment: 16 pages, 4 figures, version published in Physical Review
Analysis of pilot control strategy
Methods for nonintrusive identification of pilot control strategy and task execution dynamics are presented along with examples based on flight data. The specific analysis technique is Nonintrusive Parameter Identification Procedure (NIPIP), which is described in a companion user's guide (NASA CR-170398). Quantification of pilot control strategy and task execution dynamics is discussed in general terms followed by a more detailed description of how NIPIP can be applied. The examples are based on flight data obtained from the NASA F-8 digital fly by wire airplane. These examples involve various piloting tasks and control axes as well as a demonstration of how the dynamics of the aircraft itself are identified using NIPIP. Application of NIPIP to the AFTI/F-16 flight test program is discussed. Recommendations are made for flight test applications in general and refinement of NIPIP to include interactive computer graphics
Effect of time and rate of application of anhydrous ammonia and urea with or without a nitrification inhibitor on the yield and quality of a barley-wheat-canola rotation
Non-Peer ReviewedA project was initiated in the fall of 2006 to compare the effect of early (mid-September) and late (mid to late October) fall, and spring application of anhydrous ammonia and urea on the yield of barley, wheat and canola in barley-wheat-canola-wheat rotation. The experiment now in its third year is being carried out in two locations (Watrous and Lake Lenore) and involves four rates of N (0, 30, 80 and 120 kg N ha-1) with or without treatment with a nitrification inhibitor (N-Serve) annually applied on the same plots and four replicates for a total of 39 treatments. Consistent significant differences in all six-site years were responses to N and anhydrous vs. urea, the latter being a result of the inefficiency of the low N rate (40 kg ha-1) when applied as anhydrous ammonia. Overall, there were no differences due to time of application
The Effect of Sarsaponin on Performance of Finishing Pigs Housed in Crowded Conditions
Sarsaponin, a naturally occurring plant steroid derived from the yucca plant is available as a feed additive. Claims are made of increased pig performance during the finishing period of growth, particularly when the pigs are in crowded, stressed conditions. The study reported herein was designed to evaluate MicroAid, a commercial sarsaponin product, as a feed additive under these conditions
Barley in Swine Finishing Diets
Barley has long been used as a principle energy source in diets for growing finishing swine. Associated with the use of barley instead of corn is poorer feed efficiency due to the higher fiber content of barley. Barley contains more total protein than corn. However, reduction of soybean meal in the diet is limited because of the deficient lysine level in barley. The study reported herein was designed to evaluate diets balanced to be equal in lysine content and ranging in barley content from 0 to 100% of the grain
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