233 research outputs found
A study of density modulation index in the inner heliospheric solar wind during solar cycle 23
The ratio of the rms electron density fluctuations to the background density
in the solar wind (density modulation index, )
is of vital importance in understanding several problems in heliospheric
physics related to solar wind turbulence. In this paper, we have investigated
the behavior of in the inner-heliosphere from 0.26 to 0.82 AU.
The density fluctuations have been deduced using extensive
ground-based observations of interplanetary scintillation (IPS) at 327 MHz,
which probe spatial scales of a few hundred km. The background densities ()
have been derived using near-Earth observations from the Advanced Composition
Explorer (). Our analysis reveals that and does not vary appreciably with heliocentric distance. We
also find that declines by 8% from 1998 to 2008. We discuss the
impact of these findings on problems ranging from our understanding of Forbush
decreases to the behavior of the solar wind dynamic pressure over the recent
peculiar solar minimum at the end of cycle 23..Comment: 13 Pages, 8 Figures, Accepted for publication in Ap
Caging dynamics in a granular fluid
We report an experimental investigation of the caging motion in a uniformly
heated granular fluid, for a wide range of filling fractions, . At low
the classic diffusive behavior of a fluid is observed. However, as
is increased, temporary cages develop and particles become increasingly
trapped by their neighbors. We statistically analyze particle trajectories and
observe a number of robust features typically associated with dense molecular
liquids and colloids. Even though our monodisperse and quasi-2D system is known
to not exhibit a glass transition, we still observe many of the precursors
usually associated with glassy dynamics. We speculate that this is due to a
process of structural arrest provided, in our case, by the presence of
crystallization.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Universal velocity distributions in an experimental granular fluid
We present experimental results on the velocity statistics of a uniformly
heated granular fluid, in a quasi-2D configuration. We find the base state, as
measured by the single particle velocity distribution , to be universal
over a wide range of filling fractions and only weakly dependent on all other
system parameters. There is a consistent overpopulation in the distribution's
tails, which scale as . More
importantly, the high probability central region of , at low velocities,
deviates from a Maxwell-Boltzmann by a second order Sonine polynomial with a
single adjustable parameter, in agreement with recent theoretical analysis of
inelastic hard spheres driven by a stochastic thermostat. To our knowledge,
this is the first time that Sonine deviations have been measured in an
experimental system.Comment: 13 pages, 15 figures, with minor corrections, submitted to Phys. Rev.
Experimental evaluation of the anti-ulcer activity of the ethanolic extract of grape (Vitis vinifera) seed in wistar albino rats against aspirin plus pylorus ligation induced gastric ulcer model
Background: There is an increased demand for newer safer drugs for the treatment of peptic ulcer disease as its incidence is increasing gradually in view of changing lifestyle and stress. The objective of this study was to evaluate the anti-ulcer activity of ethanol extract of seeds of Vitis vinifera.Methods: The ethanol extract of Vitis vinifera was investigated for its anti-ulcer activity in rats against Aspirin plus Pylorus ligation induced gastric ulcer.The antiulcer activity was assessed by determining and comparing gastric volume, pH, free and total acidity; ulcer number and its inhibition, ulcer severity and ulcer index.Results: A significant antiulcer activity was observed. Pylorus ligation model showed significant (p<0.01) reduction in gastric volume, free acidity and ulcer index as compared to control.Conclusions: This present study indicates that Vitis vinifera seed extract have potential anti-ulcer activity in the model tested
- …