5,390 research outputs found
Primordial Magnetic Fields in the Post-recombination Era and Early Reionization
We explore the ways in which primordial magnetic fields influence the thermal
and ionization history of the post-recombination universe. After recombination
the universe becomes mostly neutral resulting also in a sharp drop in the
radiative viscosity. Primordial magnetic fields can then dissipate their energy
into the intergalactic medium (IGM) via ambipolar diffusion and, for small
enough scales, by generating decaying MHD turbulence. These processes can
significantly modify the thermal and ionization history of the
post-recombination universe. We show that the dissipation effects of magnetic
fields which redshifts to a present value Gauss
smoothed on the magnetic Jeans scale and below, can give rise to Thomson
scattering optical depths \tau \ga 0.1, although not in the range of
redshifts needed to explain the recent WMAP polarization observations. We also
study the possibility that primordial fields could induce the formation of
subgalactic structures for z \ga 15. We show that early structure formation
induced by nano-Gauss magnetic fields is potentially capable of producing the
early re-ionization implied by the WMAP data. Future CMB observations will be
very useful to probe the modified ionization histories produced by primordial
magnetic field evolution and constrain their strength.Comment: 19 pages, 7 figures, Minor changes to match version accepted in MNRA
Relation between hyponatremia and alteration in gross metabolic parameters after atypical antipsychotic therapy
Background: Weight gain and hyponatremia which is dilutional in nature, has been well known adverse effects associated with use of atypical antipsychotic medication but the plausible impact of dilutional hyponatremia on weight gain has not been explored.Methods: One hundred and three patients more than 18 years of age of either gender who were prescribed, olanzapine or risperidone, were tested for serum electrolytes (Na+ and K+) and gross metabolic parameters (weight and waist circumference) were measured for baseline and post drug testing.Results: Most common age group was 30-39 years of age in the patient study sample (n=103) with 38 (36.90%) patients were females while rest 63 (63.10%) were males. There was no significant association between serum sodium levels and weight gain was observed (p >0.05). It was observed that in olanzapine group 64% of the studied cases had weight gain whereas in risperidone group only 20.8% reported weight gain (p 0.05).Conclusions: Olanzapine was primarily responsible for weight gain and increase in waist circumference over risperidone. These gross metabolic parameters were not influenced by hyponatremia
Generation of Magnetic Field in the Pre-recombination Era
We study the possibility of generating magnetic fields during the evolution
of electron, proton, and photon plasma in the pre-recombination era. We show
that a small magnetic field can be generated in the second order of
perturbation theory for scalar modes with adiabatic initial conditions. The
amplitude of the field is \la 10^{-30} \rm G at the present epoch for scales
from sub-kpc to \ga 100 \rm Mpc.Comment: 8 page
The bottomside parameters <i>B0</i>, <i>B1</i> obtained from incoherent scatter measurements during a solar maximum and their comparisons with the IRI-2001 model
International audienceHigh resolution electron density profiles (Ne) measured with the Arecibo (18.4 N, 66.7 W), Incoherent Scatter radar (I. S.) are used to obtain the bottomside shape parameters B0, B1 for a solar maximum period (1989?90). Median values of these parameters are compared with those obtained from the IRI-2001 model. It is observed that during summer, the IRI values agree fairly well with the Arecibo values, though the numbers are somewhat larger during the daytime. Discrepancies occur during winter and equinox, when the IRI underestimates B0 for the local times from about 12:00 LT to about 20:00 LT. Furthermore, the IRI model tends to generally overestimate B1 at all local times. At Arecibo, B0 increases by about 50%, and B1 decreases by about 30% from solar minimum to solar maximum
On the Clustering of GRBs on the Sky
The two-point correlation of the 4th (current) BATSE catalog (2494 objects)
is calculated. It is shown to be consistent with zero at nearly all angular
scales of interest. Assuming that GRBs trace the large scale structure in the
universe we calculate the angular correlation function for the standard CDM
(sCDM) model. It is shown to be at if the
BATSE catalog is assumed to be a volume-limited sample up to .
Combined with the error analysis on the BATSE catalog this suggests that nearly
GRBs will be needed to make a positive detection of the two-point
angular correlation function at this angular scale.Comment: 5 pages, Latex with aipproc.sty, incl. 1 ps-Fig., Proc. of the 5th
Huntsville Gamma Ray Burst Symposium, Oct. 1999, ed. R.M. Kippen, AI
Galactic dust polarized emission at high latitudes and CMB polarization
We estimate the dust polarized emission in our galaxy at high galactic
latitudes, which is the dominant foreground for measuring CMB polarization
using the high frequency instrument (HFI) aboard Planck surveyor. We compare it
with the level of CMB polarization and conclude that, for angular scales , the scalar-induced CMB polarization and temperature-polarization
cross-correlation are much larger than the foreground level at . The tensor-induced signals seem to be at best comparable to the
foreground level.}Comment: Latex document, 4 pages, 2 figures, to appear in "Fundamental
parameters in Cosmology", Rencontres de Moriond, 199
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