845 research outputs found
Gauging the spectator equations
We show how to derive relativistic, unitary, gauge invariant, and charge
conserving three-dimensional scattering equations for a system of hadrons
interacting with an electromagnetic field. In the method proposed, the
spectator equations describing the strong interactions of the hadrons are
gauged using our recently introduced gauging of equations method. A key
ingredient in our model is the on-mass-shell particle propagator. We discuss
how to gauge this on-mass-shell propagator so that both the Ward-Takahashi and
Ward identities are satisfied. We then demonstrate our gauging procedure by
deriving the gauge-invariant three-dimensional expression for the deuteron
photodisintegration amplitude within the spectator approach.Comment: 17 pages, REVTeX, epsf, 1 Postscript figur
Neutrino-Oxygen CC0 scattering in the SuSAv2-MEC model
We present the predictions of the SuSAv2-MEC model for the double
differential charged-current muonic neutrino (antineutrino) cross section on
water for the T2K neutrino (antineutrino) beam. We validate our model by
comparing with the available inclusive electron scattering data on oxygen and
compare our predictions with the recent T2K -O data, finding
good agreement at all kinematics. We show that the results are very similar to
those obtained for C scattering, except at low energies, and we
comment on the origin of this difference. A factorized spectral function model
of O is also included for purposes of comparison.Comment: 28 pages, 10 figures, JLAB-THY-17-2586. Version 2 accepted for
publication in Journal of Physics G: Nucl. Part. Phy
Evaluación de la función adrenal en perros
En 30 perros sanos, hemos estudiado los niveles de cortisol plasmático antes y después de la administración de hormona adrenocórticotropa (ACTH sintético, vía i.m.) y de dexametasona (dosis de 0,01 y 0,02 mg/Kg p.v., vía i.v.), Las pruebas se iniciaron siempre antes de las 10 horas de la mañana y las determinaciones de cortisol plasmático se evaluaron mediante técnicas de RIA. En nuestras condiciones de trabajo, hemos encontrado unos niveles basales de cortisol cuyo rango va de 0,17 a 7,95 ug/ dl. Se ha observado que, en perros sin sintomatología adrenal y con perfiles hematológicos y bioquímicos normales, la prueba de estimulación con ACTH exógeno, a las dos horas de su administración, es capaz de discriminar como animales sanos el 76,7% de los individuos (23 animales), dando falsos resultados positivos en el 10% (3 animales) y una estimulación baja en el U)% (4 animales). La prueba con dexametasona (0,01 mg/Kg p.v.), a las 8 horas de su aplicación, sólo es capaz de ejercer efecto inhibitorio en el 40% de los casos (12 individuos); pero cuando se incrementa la dosis al doble (dexametasona 0,02 mg/Kg p.v.) se 49 obtienen los mejores resultados de toda la experiencia porque se produce el efecto supresor esperado en el 96,7% de los individuos (29 animales).Thirty healty dogs uiere evaluated for plasma cortisol values before and after adrenocorticotrophic hormone (ACm, administered i.m.) and low dose dexamethasone (0.01 and 0.02 mglKgp.v. administered i.u.). The assays started always before 10 hour A.M.} and cortisol plasma concentrations were determined by RIA. In our laboratory we have obserued the normal baseline morning cortisol concentration was between 0.17 and 7.95 ¡..tgldl. ACTH-estimulation test wasfound abnormal bypereponse in 10% (J animals), anormallow stimulation in 11.1% (a dogs) and a expected byperreponse in 76.7% (23) ofthe normal dogs.Dexamethasone-screening test (0.01 mg/Kgp.v.) bring us supressed effect in 40% (12 animals). But wefound the best reliable results when screening test was applied with 0.02 mg/Kgp.v. dexamethasone dose. the suppressed especting effect wasfound in 06. 7% (29 dogs)
THE ROLE OF PRODUCT ATTRIBUTES IN THE AGRICULTURAL NEGOTIATIONS
Marketing, International Relations/Trade,
RPA quasi-elastic responses in infinite and finite nuclear systems
Quasi-elastic responses in nuclear matter and in C and Ca
nuclei are calculated in ring approximation to investigate the finite size
effects on the electromagnetic quasi-elastic responses. A method to simulate
these effects in infinite systems calculations is proposed. The sensitivity of
the results to the various terms of the residual interaction is studied. The
results of nuclear matter RPA calculations are compared with those obtained in
ring approximation to evidence the importance of the exchange terms.Comment: 14 pages, 8 figure
On the Structure of Measurement Noise in Eye-Tracking
Past research has discovered fractal structure in eye movement variability and interpreted this result as having theoretical ramifications. No research has, however, investigated how properties of the eye-tracking instrument might affect the structure of measurement varia-bility. The current experiment employed fractal and multifractal methods to investigate whether an eye-tracker produced intrinsic random variation and how features of the data recording procedure affected the structure measurement variability. The results of this experiment revealed that the structure of variation from a fake eye was indeed random and uncorrelated in contrast to the fractal structure from a fixated, real human eye. Moreover, the results demonstrated that data-averaging generally changes the structure of variation, introducing spurious structure into eye movement variability
Origin of Relativistic Effects in the Reaction D(e,e'p)n at GeV Energies
In a series of recent publications, a new approach to the non-relativistic
reduction of the electromagnetic current operator in calculations of
electro-nuclear reactions has been introduced. In one of these papers, the
conjecture that at energies of a few GeV, the bulk of the relativistic effects
comes from the current and not from the nuclear dynamics was made, based on the
large relativistic effects in the transverse-longitudinal response. Here, we
explicitly compare a fully relativistic, manifestly covariant calculation
performed with the Gross equation, with a calculation that uses a
non-relativistic wave function and a fully relativistic current operator. We
find very good agreement up to missing momenta of 400 MeV/c, thus confirming
the previous conjecture. We discuss slight deviations in cross sections for
higher missing momenta and their possible origin, namely p-wave contributions
and off-shell effects.Comment: 25 pages, 11 figure
Herding model and 1/f noise
We provide evidence that for some values of the parameters a simple agent
based model, describing herding behavior, yields signals with 1/f power
spectral density. We derive a non-linear stochastic differential equation for
the ratio of number of agents and show, that it has the form proposed earlier
for modeling of 1/f^beta noise with different exponents beta. The non-linear
terms in the transition probabilities, quantifying the herding behavior, are
crucial to the appearance of 1/f noise. Thus, the herding dynamics can be seen
as a microscopic explanation of the proposed non-linear stochastic differential
equations generating signals with 1/f^beta spectrum. We also consider the
possible feedback of macroscopic state on microscopic transition probabilities
strengthening the non-linearity of equations and providing more opportunities
in the modeling of processes exhibiting power-law statistics
First-principles investigation of spin polarized conductance in atomic carbon wire
We analyze spin-dependent energetics and conductance for one dimensional (1D)
atomic carbon wires consisting of terminal magnetic (Co) and interior
nonmagnetic (C) atoms sandwiched between gold electrodes, obtained employing
first-principles gradient corrected density functional theory and Landauer's
formalism for conductance. Wires containing an even number of interior carbon
atoms are found to be acetylenic with sigma-pi bonding patterns, while cumulene
structures are seen in wires containing odd number of interior carbon atoms, as
a result of strong pi-conjugation. Ground states of carbon wires containing up
to 13 C atoms are found to have anti-parallel spin configurations of the two
terminal Co atoms, while the 14 C wire has a parallel Co spin configuration in
the ground state. The stability of the anti-ferromagnetic state in the wires is
ascribed to a super-exchange effect. For the cumulenic wires this effect is
constant for all wire lengths. For the acetylenic wires, the super-exchange
effect diminishes as the wire length increases, going to zero for the atomic
wire containing 14 carbon atoms. Conductance calculations at the zero bias
limit show spin-valve behavior, with the parallel Co spin configuration state
giving higher conductance than the corresponding anti-parallel state, and a
non-monotonic variation of conductance with the length of the wires for both
spin configurations.Comment: revtex, 6 pages, 5 figure
Modeling quark-hadron duality in polarization observables
We apply a model for the study of quark-hadron duality in inclusive electron
scattering to the calculation of spin observables. The model is based on
solving the Dirac equation numerically for a scalar confining linear potential
and a vector color Coulomb potential. We qualitatively reproduce the features
of quark-hadron duality for all potentials considered, and discuss the onset of
scaling and duality for the responses, spin structure functions, and
polarization asymmetries. Duality may be applied to gain access to kinematic
regions which are hard to access in deep inelastic scattering, namely for
, and we discuss which observables are most suitable for this
application of duality
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