9,881 research outputs found
GM crops and gender issues
Correspondence in the December issue by Jonathan Gressel not only states that gender issues in rural settings have not been adequately addressed with respect to weed control biotech but also asserts that such technology can increase the quality of life of rural women in developing countries. Improved weed control is a labor-saving technology that can result in less employment in a labor surplus rural economy. Often in rural areas, wage income is the main source of income and an important determinant of the quality of life, particularly where employment opportunities are generally limited. Apart from soil preparation, planting and weeding, harvesting is also 'femanual' work that can generate more employment if yields are higher. Biotech can enhance the quality of life of women but only if the technology is associated with overall generation of rural employment
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
The structure of dark matter halos in hierarchical clustering theories
During hierarchical clustering, smaller masses generally collapse earlier
than larger masses and so are denser on the average. The core of a small mass
halo could be dense enough to resist disruption and survive undigested, when it
is incorporated into a bigger object. We explore the possibility that a nested
sequence of undigested cores in the center of the halo, which have survived the
hierarchical, inhomogeneous collapse to form larger and larger objects,
determines the halo structure in the inner regions. For a flat universe with
, scaling arguments then suggest that the core density
profile is, with . But
whether such behaviour obtains depends on detailed dynamics. We first examine
the dynamics using a fluid approach to the self-similar collapse solutions for
the dark matter phase space density, including the effect of velocity
dispersions. We highlight the importance of tangential velocity dispersions to
obtain density profiles shallower than in the core regions. If
tangential velocity dispersions in the core are constrained to be less than the
radial dispersion, a cuspy core density profile shallower than 1/r cannot
obtain, in self-similar collapse. We then briefly look at the profiles of the
outer halos in low density cosmological models where the total halo mass is
convergent. Finally, we analyze a suite of dark halo density and velocity
dispersion profiles obtained in cosmological N-body simulations of models with
n= 0, -1 and -2. We find that the core-density profiles of dark halos, show
considerable scatter in their properties, but nevertheless do appear to reflect
a memory of the initial power spectrum, with steeper initial spectra producing
flatter core profiles. (Abridged)Comment: 31 pages, 7 figures, submitted to Ap
Giant Meterwave Radio Telescope observations of an M2.8 flare: insights into the initiation of a flare-coronal mass ejection event
We present the first observations of a solar flare with the GMRT. An M2.8
flare observed at 1060 MHz with the GMRT on Nov 17 2001 was associated with a
prominence eruption observed at 17 GHz by the Nobeyama radioheliograph and the
initiation of a fast partial halo CME observed with the LASCO C2 coronograph.
Towards the start of the eruption, we find evidence for reconnection above the
prominence. Subsequently, we find evidence for rapid growth of a vertical
current sheet below the erupting arcade, which is accompanied by the flare and
prominence eruption.Comment: Accepted for publication in Solar Physic
Hibiscus sabdariffa Affects Ammonium Chloride-Induced Hyperammonemic Rats
Hibiscus sabdariffa (HS) is an edible medicinal plant, indigenous to India, China and Thailand and is used in Ayurveda and traditional medicine. Alcoholic extract of HS leaves (HSEt) was studied for its anti-hyperammonemic and antioxidant effects in brain tissues of ammonium chloride-induced hyperammonemic rats. Oral administration of HSEt (250 mg kg−1 body weight) significantly normalizes the levels of ammonia, urea, uric acid, creatinine and non-protein nitrogen in the blood. HSEt significantly reduced brain levels of lipid peroxidation products such as thiobarbituric acid and reactive substances (TBARS) and hydroperoxides (HP). However, the administered extract significantly increased the levels of antioxidants such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH) in brain tissues of hyperammonemic rats. This investigation demonstrates significant anti-hyperammonemic and antioxidant activity of HS
Ion viscosity mediated by tangled magnetic fields: an application to black hole accretion disks
We derive expressions for a ``hybrid'' viscosity arising from Coulomb collisions between ions in the presence of tangled magnetic fields. Such magnetic fields are expected to be embedded in accretion flows onto black holes and other compact objects. Ion viscosity in the absence of magnetic fields has been shown to appreciable in hot accretion disks, but it was thought that the presence of the smallest of magnetic fields would effectively quench it. We show that the hybrid viscosity in hot (ion temperatures around 10^11-10^12 K) accretion disks results in values of the Shakura Sunyaev \alpha parameter around 0.01 to 0.1-0.5. We do not model the generation of the tangled magnetic fields; we merely assume its presence and assume it to be arbitrarily strong
A Unified treatment of small and large- scale dynamos in helical turbulence
Helical turbulence is thought to provide the key to the generation of
large-scale magnetic fields. Turbulence also generically leads to rapidly
growing small-scale magnetic fields correlated on the turbulence scales. These
two processes are usually studied separately. We give here a unified treatment
of both processes, in the case of random fields, incorporating also a simple
model non-linear drift. In the process we uncover an interesting plausible
saturated state of the small-scale dynamo and a novel analogy between quantum
mechanical (QM) tunneling and the generation of large scale fields. The steady
state problem of the combined small/large scale dynamo, is mapped to a
zero-energy, QM potential problem; but a potential which, for non-zero mean
helicity, allows tunneling of bound states. A field generated by the
small-scale dynamo, can 'tunnel' to produce large-scale correlations, which in
steady state, correspond to a force-free 'mean' field.Comment: 4 pages, 1 figure, Physical Review Letters, in pres
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