5,916 research outputs found
Spinning particles, axion radiation, and the classical double copy
We extend the perturbative double copy between radiating classical sources in
gauge theory and gravity to the case of spinning particles. We construct, to
linear order in spins, perturbative radiating solutions to the classical
Yang-Mills equations sourced by a set of interacting color charges with
chromomagnetic dipole spin couplings. Using a color-to-kinematics replacement
rule proposed earlier by one of the authors, these solutions map onto radiation
in a theory of interacting particles coupled to massless fields that include
the graviton, a scalar (dilaton) and the Kalb-Ramond axion field
. Consistency of the double copy imposes constraints on the
parameters of the theory on both the gauge and gravity sides of the
correspondence. In particular, the color charges carry a chromomagnetic
interaction which, in , corresponds to a gyromagnetic ratio equal to
Dirac's value . The color-to-kinematics map implies that on the gravity
side, the bulk theory of the fields has
interactions which match those of -dimensional `string gravity,' as is the
case both in the BCJ double copy of pure gauge theory scattering amplitudes and
the KLT relations between the tree-level -matrix elements of open and closed
string theory.Comment: 10+5 pages, LaTeX, 2 figures. v2:Fixed typos and added minor
clarification
Finite-rate water condensation in combustion-heated wind tunnels
A quasi-one-dimensional method for computing finite rate nucleation and droplet growth of water in a supersonic expansion of combustion products is presented. Sample computations are included for the Langley 8 foot High Temperature Tunnel, but the method can also be applied to other combustion heated wind tunnels. The sample results indicate that the free stream static pressure can be in the range of 25 to 60 percent greater than that computed for isentropic nozzle flow without water condensation. The method provides a tool for examining the effects of water condensation on static state properties and velocity of the supersonic stream in combustion heated wind tunnels
A rapid method for the computation of equilibrium chemical composition of air to 15000 K
A rapid computational method has been developed to determine the chemical composition of equilibrium air to 15000 K. Eleven chemically reacting species, i.e., O2, N2, O, NO, N, NO+, e-, N+, O+, Ar, and Ar+ are included. The method involves combining algebraically seven nonlinear equilibrium equations and four linear elemental mass balance and charge neutrality equations. Computational speeds for determining the equilibrium chemical composition are significantly faster than the often used free energy minimization procedure. Data are also included from which the thermodynamic properties of air can be computed. A listing of the computer program together with a set of sample results are included
Glutathione S-Transferase activity and total thiol status in chronic alcohol abusers before and 30 days after alcohol abstinence
Background: Glutathione S Transferase (GST) has been involved in detoxification process in the liver and its activity has been shown to be increased in alcohol abusers. In the current work we measured the GST activity, total thiol status, AST, ALT, and direct bilirubin in chronic alcohol abusers before and 30 days after alcohol abstinence and lifestyle modification. Methods: Serum and urine GST activity and total thiol status were determined using spectrophotometric methods and serum transaminases were determined using clinical chemistry analyzer. Results: We found,significant increase in serum and urine GST (p<0.001), AST (p<0.001), ALT (p<0.001), and decrease in total thiol status (p<0.001) in chronic alcohol abusers. GST activity significantly decreased (p<0.001) and total thiol status were improved significantly (p<0.001) 30 days after alcohol abstinence and lifestyle modification. Conclusion: This study provides preliminary data to suggest the role of GST as prognostic indicator of alcohol abstinence with possible trend towards an improvement in liver function
Mechanically-Deployed Hypersonic Decelerator and Conformal Ablator Technologies for Mars Missions
The concept of a mechanically deployable hypersonic decelerator, developed initially for high mass (approximately 40 MT) human Mars missions, is currently funded by OCT for technology maturation. The ADEPT (Adaptive, Deployable Entry and Placement Technology) project has broad, game-changing applicability to in situ science missions to Venus, Mars, and the Outer Planets. Combined with maturation of conformal ablator technology (another current OCT investment), the two technologies provide unique low-mass mission enabling capabilities otherwise not achievable by current rigid aeroshell or by inflatables. If this abstract is accepted, we will present results that illustrate the mission enabling capabilities of the mechanically deployable architecture for: (1) robotic Mars (Discovery or New Frontiers class) in the near term (2) alternate approaches to landing MSL-class payloads, without the need for supersonic parachute or lifting entry, in the mid-term and (3) Heavy mass and human missions to Mars in the long term
Local Invariants and Pairwise Entanglement in Symmetric Multi-qubit System
Pairwise entanglement properties of a symmetric multi-qubit system are
analyzed through a complete set of two-qubit local invariants. Collective
features of entanglement, such as spin squeezing, are expressed in terms of
invariants and a classifcation scheme for pairwise entanglement is proposed.
The invariant criteria given here are shown to be related to the recently
proposed (Phys. Rev. Lett. 95, 120502 (2005)) generalized spin squeezing
inequalities for pairwise entanglement in symmetric multi-qubit states.Comment: 9 pages, 2 figures, REVTEX, Replaced with a published versio
Highly reddened type Ia supernova SN 2004ab: another case of anomalous extinction
We present optical photometric and spectroscopic results of supernova SN
2004ab, a highly reddened normal type Ia supernova. The total reddening is
estimated as = 1.70 0.05 mag. The intrinsic decline rate
parameter, is 1.27 0.05, and -band
absolute magnitude at maximum is 19.31 0.25 mag.
The host galaxy NGC 5054 is found to exhibit anomalous extinction with very low
value of = 1.41 0.06 in the direction of SN 2004ab. Peak bolometric
luminosity is derived as = 43.10 0.07
erg\,s. The photospheric velocity measured from absorption minimum of
Si\,{\sc ii} 6355 line shows a velocity gradient of = 90
km\,s\,d, indicating that SN 2004ab is a member of the high
velocity gradient (HVG) subgroup. The ratio of strength of Si\,{\sc ii}
5972 and 6355 absorption lines, (Si\,{\sc ii}) is
estimated as 0.37, while their pseudo equivalent widths suggest that SN 2004ab
belongs to broad line (BL) type subgroup.Comment: 13 pages, 5 tables, 16 figures, accepted for publication in MNRA
Ballistic Entries for Saturn, Uranus, and Neptune with HEEET TPS
One important observation from the Ice Giants Study was that the predicted and margined thicknesses of HEEET were greater than could be woven with the currently established loom capabilities. Since the cost of a loom upgrade could be substantial and time consuming, the present work explored the entry trajectory space to determine what combinations of entry parameters would result in HEEET thicknesses that fit within the existing loom infrastructure. Toward this end, the entry trajectory space, parameterized by ballistic coefficient and entry flight path angle, was systematically explored for 45 sphere-cone geometries of 3 different radii 0.2 m, 0.3 m, and 0.4 m which covered the range from Galileo-derived probes considered in the Ice Giants Study, and a follow-on study on the possibility of using a single probe architecture (in terms of size and mass) for various destinations, including Venus, Saturn, Uranus, and Neptune. The entry velocities, latitudes, and azimuths at Uranus and Neptune used in the present work were taken from the Ice Giants Study. For each 3DOF trajectory generated by a NASA Ames in-house code, TRAJ, the material response and thickness were computed using another NASA Ames code, FIAT, along with a margins policy proposed by the HEEET project. In the present work, ballistic coefficients ranging from 200 kg/sq m to 350 kg/sq m were considered along with entry flight path angles ranging from -16 to -36 (primarily to allow deceleration loads to vary between 50 g and 200 g)
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