12,059 research outputs found
The Distribution of Household Wealth in India
assets, liabilities, vertical inequality, horizontal inequality, land, real estate
Small-scale microwave background anisotropies due to tangled primordial magnetic fields
An inhomogeneous cosmological magnetic field creates vortical perturbations
that survive Silk damping on much smaller scales than compressional modes. This
ensures that there is no sharp cut-off in anisotropy on arc-minute scales. As
we had pointed out earlier, tangled magnetic fields, if they exist, will then
be a potentially important contributor to small-angular scale CMBR
anisotropies. Several ongoing and new experiments, are expected to probe the
very small angular scales, corresponding to multipoles with l>1000. In view of
this observational focus, we revisit the predicted signals due to primordial
tangled magnetic fields, for different spectra and different cosmological
parameters. We also identify a new regime, where the photon mean-free path
exceeds the scale of the perturbation, which dominates the predicted signal at
very high l. A scale-invariant spectrum of tangled fields which redshifts to a
present value B_{0}=3\times 10^{-9} Gauss, produces temperature anisotropies at
the 10 micro Kelvin level between l ~ 1000-3000. Larger signals result if the
univese is lambda dominated, if the baryon density is larger, or if the
spectral index of magnetic tangles is steeper, n > -3. The signal will also
have non-Gaussian statistics. We predict the distinctive form of the increased
power expected in the microwave background at high l in the presence of
significant tangled magnetic fields. We may be on the verge of detecting or
ruling out the presence of tangled magnetic fields which are strong enough to
influence the formation of large-scale structure in the Universe.Comment: 5 pages, 2 figures, submitted to MNRAS Letter
Nucleophilicity/Electrophilicity Excess in Analyzing Molecular Electronics
Intramolecular electron transfer capability of all metal aromatic and
anti-aromatic aluminum cluster compounds is studied in terms of density
functional theory based global and local reactivity descriptors. This study
will provide important inputs towards the fabrication of the material required
for molecular electronics.Comment: 21 pages, 6 figures, 13 table
The role of wind gusts in upper ocean diurnal variability
Upper ocean processes play a key role in air-sea coupling, with variability on both short and long time scales. The diurnal cycle associated with diurnal solar insolation and nighttime cooling, may act, along with stochastic wind variability, on upper ocean temperatures and stratification resulting in a diurnal warm layer and a nonlinear rectified effect on longer time scales. This study describes diurnal changes in upper ocean temperature for a location in the equatorial Indian Ocean, using observations from the Dynamics of the Madden-Julian Oscillation field campaign, a high vertical resolution 1-D process model, and a diurnal cycling scheme. Solar forcing is the main driver of diurnal variability in upper ocean temperature and stratification. Yet except during nighttime convection, winds with variability on the order of hours (here referred to as “wind gusts”) regulate how fast surface water is mixed to greater depths when daily mean winds are weak. Wind gusts are much stronger than diurnal winds. Even using stochastic wind gusts but no diurnal winds as input in a 1-D process model yields an estimate of diurnal temperature that compares well with observations. A new version of the Large and Caron (2015) scheme (LC2015) provides an estimate of upper ocean diurnal temperature that is consistent with observations. LC2015 has the advantage of being suitable for implementation in a climate model, with the goal to improve SST estimates, hence the simulated heat flux at the air-sea interface. Yet LC2015 is not very sensitive to the inclusion or omission of the high-frequency component of the wind
The Prospects for Sustained Growth in Africa: Benchmarking the Constraints
A dozen countries had weak institutions in 1960 and yet sustained high rates of growth subsequently. We use data on their characteristics early in the growth process to create benchmarks with which to evaluate potential constraints on sustained growth for sub-Saharan Africa. This analysis suggests that what are usually regarded as first-order problems -- broad institutions, macroeconomic stability, trade openness, education, and inequality -- may not nowbe binding constraints in Africa, although the extent of ill-health, internal conflict, and societal fractionalization do stand out as problems in contemporary Africa. A key question is to what extent Africa can rely on manufactured exports as a mode of "escape from underdevelopment," a strategy successfully deployed by almost all the benchmark countries. The benchmarking comparison specifically raises two key concerns as far as a development strategy based on expanding exports of manufactures is concerned: micro-level institutions that affect the costs of exporting, and the level of the real exchange rate -- especially the need to avoid overvaluation.
Valence-electron transfer and a metal-insulator transition in a strongly correlated perovskite oxide
We present transport and thermal data for the quadruple-perovskites
MCu3(Ti1-xRux)4O12 where 0 < x < 1. A metal-insulator transition (MIT) occurs
for Ru concentrations x~0.75. At the same time, the Cu2+ antiferromagnetic
state is destroyed and it's magnetic entropy suppressed by Ru on a 1:1 basis.
This implies that each Ru transfers an electron to a Cu ion and thus the MIT
correlates with filling the Cu 3d shell. The Cu spin entropy in this strongly
correlated electron material provides a unique probe among MIT systems.Comment: 15 pages, 4 figures, 1 tabl
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
Recent applications of the transonic wing analysis computer code, TWING
An evaluation of the transonic-wing-analysis computer code TWING is given. TWING utilizes a fully implicit approximate factorization iteration scheme to solve the full potential equation in conservative form. A numerical elliptic-solver grid-generation scheme is used to generate the required finite-difference mesh. Several wing configurations were analyzed, and the limits of applicability of this code was evaluated. Comparisons of computed results were made with available experimental data. Results indicate that the code is robust, accurate (when significant viscous effects are not present), and efficient. TWING generally produces solutions an order of magnitude faster than other conservative full potential codes using successive-line overrelaxation. The present method is applicable to a wide range of isolated wing configurations including high-aspect-ratio transport wings and low-aspect-ratio, high-sweep, fighter configurations
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