2,923 research outputs found
Non-boost-invariant motion of dissipative and highly anisotropic fluid
The recently formulated framework of anisotropic and dissipative
hydrodynamics (ADHYDRO) is used to describe non-boost-invariant motion of the
fluid created at the early stages of heavy-ion collisions. Very strong initial
asymmetries of pressure are reduced by the entropy production processes. By the
appropriate choice of the form of the entropy source we can reproduce realistic
scenarios for the isotropization expected in heavy-ion collisions. Our previous
results are generalized by including the realistic equation of state as the
limit of the isotropization processes.Comment: Version accepted for publication in Journal of Physics G: Nuclear and
Particle Physic
Ultraviolet avalanche in anisotropic non-Abelian plasmas
We present solutions of coupled particle-field evolution in classical U(1)
and SU(2) gauge theories in real time on three-dimensional lattices. For
strongly anisotropic particle momentum distributions, we find qualitatively
different behavior for the two theories when the field strength is high enough
that non-Abelian self-interactions matter for SU(2). It appears that the energy
drained by a Weibel-like plasma instability from the particles does not build
up exponentially in transverse magnetic fields but instead returns,
isotropically, to the hard scale via a rapid avalanche into the ultraviolet.Comment: 22 pages, 10 figures; v3: small textual changes; updated to
correspond with version to appear in publicatio
Features of a Separating Turbulent Boundary Layer as Revealed by Laser and Hot-Film Anemometry
Experiments have been performed to determine the fundamental nature of boundary layer separation produced by an adverse pressure gradient. Measurements upstream and downstream of the separation zone have been made utilizing laser and hot-film anemometry techniques.
A completely mobile backscattering laser anemometer was developed. This alone is a significant development because of the relatively long focal lengths required for measurements in a 36 wide wind tunnel. Signal processing was achieved by a digital signal sampling and storage system. Both mean and fluctuating velocities in both the unseparated and separated flow regions were measured. Experimental results are in fairly good agreement with hot-film measurements, with some recent improvements in data acquisition being noted.
Flush-wall hot-film sensors were used to determine wall shear stresses and fluctuations, both upstream and downstream of separation. These data indicate that the law of the wall apparently is valid up to the location of intermittent separation or the location of intermittent backflow next to the wall. Visual observations indicate that the location of intermittent separation is in agreement with Sandborn\u27s criterion. The outer region flow downstream of the beginning of separation is characterized by a similarity mixing-layer velocity profile
15 Epidemiology of nontuberculous mycobacteria in the USA: Pilot study utilizing closed healthcare systems
Ferromagnetic redshift of the optical gap in GdN
We report measurements of the optical gap in a GdN film at temperatures from
300 to 6K, covering both the paramagnetic and ferromagnetic phases. The gap is
1.31eV in the paramagnetic phase and red-shifts to 0.9eV in the spin-split
bands below the Curie temperature. The paramagnetic gap is larger than was
suggested by very early experiments, and has permitted us to refine a
(LSDA+U)-computed band structure. The band structure was computed in the full
translation symmetry of the ferromagnetic ground state, assigning the
paramagnetic-state gap as the average of the majority- and minority-spin gaps
in the ferromagnetic state. That procedure has been further tested by a band
structure in a 32-atom supercell with randomly-oriented spins. After fitting
only the paramagnetic gap the refined band structure then reproduces our
measured gaps in both phases by direct transitions at the X point.Comment: 5 pages, 4 figure
Locally anisotropic momentum distributions of hadrons at freeze-out in relativistic heavy-ion collisions
A spheroidal anisotropic local momentum distribution is implemented in the
statistical model of hadron production. We show that this form leads to exactly
the same ratios of hadronic abundances as the equilibrium distributions, if the
temperature is identified with a characteristic transverse-momentum scale.
Moreover, to a very good approximation the transverse-momentum spectra of
hadrons are the same for isotropic and anisotropic systems, provided the size
of the system at freeze-out is appropriately adjusted. We further show that
this invariance may be used to improve the agreement between the model and
experimental HBT results.Comment: 7 pages, 4 figure
Early dynamics of transversally thermalized matter
We argue that the idea that the parton system created in relativistic
heavy-ion collisions is formed in a state with transverse momenta close to
thermodynamic equilibrium and its subsequent dynamics at early times is
dominated by pure transverse hydrodynamics of the perfect fluid is compatible
with the data collected at RHIC. This scenario of early parton dynamics may
help to solve the problem of early equilibration.Comment: 4 pages, 2 figures, Talk given by M. Chojnacki at Quark Matter 2008,
Jaipur, Indi
A Pilot Study of Loss Aversion for Drug and Non-Drug Commodities in Cocaine Users
BackgroundâNumerous studies in behavioral economics have demonstrated that individuals are more sensitive to the prospect of a loss than a gain (i.e., loss aversion). Although loss aversion has been well described in âhealthyâ populations, little research exists in individuals with substance use disorders. This gap is notable considering the prominent role that choice and decision-making play in drug use. The purpose of this pilot study was to evaluate loss aversion in active cocaine users.
MethodsâCurrent cocaine users (N = 38; 42% female) participated in this within-subjects laboratory pilot study. Subjects completed a battery of tasks designed to assess loss aversion for drug and non-drug commodities under varying risk conditions. Standardized loss aversion coefficients (λ) were compared to theoretically and empirically relevant normative values (i.e., λ = 2).
ResultsâCompared to normative loss aversion coefficient values, a precise and consistent decrease in loss aversion was observed in cocaine users (sample λ â 1). These values were observed across drug and non-drug commodities as well as under certain and risky conditions.
ConclusionsâThese data represent the first systematic study of loss aversion in cocaine-using populations and provide evidence for equal sensitivity to losses and gains or loss equivalence. Futures studies should evaluate the specificity of these effects to a history of cocaine use as well as the impact of manipulations of loss aversion on drug use to determine how this phenomenon may contribute to intervention development efforts
Buspirone Maintenance Does Not Alter the Reinforcing, Subjective, and Cardiovascular Effects of Intranasal Methamphetamine
BackgroundâMedications development efforts for methamphetamine-use disorder have targeted central monoamines because these systems are directly involved in the effects of methamphetamine. Buspirone is a dopamine autoreceptor and D3 receptor antagonist and partial agonist at serotonin 1A receptors, making it a logical candidate medication for methamphetamine-use disorder. Buspirone effects on abuse-related behaviors of methamphetamine have been mixed in clinical and preclinical studies. Experimental research using maintenance dosing, which models therapeutic use, is limited. This study evaluated the influence of buspirone maintenance on the reinforcing effects of methamphetamine using a self-administration procedure, which has predictive validity for clinical efficacy. The impact of buspirone maintenance on the subjective and cardiovascular response to methamphetamine was also determined.
MethodsâEight research participants (1 female) reporting recent illicit stimulant use completed a placebo-controlled, crossover, double-blind protocol in which the pharmacodynamic effects of intranasal methamphetamine (0, 15, and 30 mg) were assessed after at least 6 days of buspirone (0 and 45 mg/day) maintenance.
ResultsâIntranasal methamphetamine functioned as a reinforcer and produced prototypical stimulant-like subjective (e.g., increased ratings of Good Effects and Like Drug) and cardiovascular (e.g., elevated blood pressure) effects. These effects of methamphetamine were similar under buspirone and placebo maintenance conditions. Maintenance on buspirone was well tolerated and devoid of effects when administered alone.
ConclusionsâThese data suggest that buspirone is unlikely to be an effective pharmacotherapy for methamphetamine-use disorder. Given the central role of monoamines in methamphetamine-use disorder, it is reasonable for future studies to continue to target these systems
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