12,241 research outputs found
Cosmic optical activity from an inhomogeneous Kalb-Ramond field
The effects of introducing a harmonic spatial inhomogeneity into the
Kalb-Ramond field, interacting with the Maxwell field according to a
`string-inspired' proposal made in earlier work are investigated. We examine in
particular the effects on the polarization of synchrotron radiation from
cosmologically distant (i.e. of redshift greater than 2) galaxies, as well as
the relation between the electric and magnetic components of the radiation
field. The rotation of the polarization plane of linearly polarized radiation
is seen to acquire an additional contribution proportional to the square of the
frequency of the dual Kalb-Ramond axion wave, assuming that it is far smaller
compared to the frequency of the radiation field.Comment: 9 pages, Revtex, no figure
Synthesis and Characterization of Oxomolybdenum and Oxovanadium Complexes
Synthesis and characterization of two different O-N donor hydrazide ligands and their corresponding dioxomolybdenum(VI) and oxovanadium(V) complexes have been reported. The hydrazides synthesized, are characterized by IR spectroscopy and by C, H, N, analysis. The ligands were directly used for metallation with metal precursors having acetyl acetonate groups. One of the acetyl acetonate groups get separated from the metal precursor and carbonyl group of that acetyl acetonate group undergoes condensation with hydrazide forming insitu hydrazone ligand. The complexes formed are also successfully characterized by IR, UV-Vis, C, H, N analysis and cyclic voltammetry
Agricultural diversification in India and role of urbanization
Indian agriculture is diversifying during the last two decades towards High-Value Commodities (HVCs) i.e., fruits, vegetables, milk, meat, and fish products. The pace has been accelerated during the decade of 1990s. HVCs account for a large share in the total value of agricultural production. Supply and demand side factors coupled with infrastructural development and innovative institutions drive these changes. In this paper, the focus is on diversification towards HVCs in the context of urbanization. Group of urban districts (districts with >1.5 million urban population) have a higher share of HVCs compared to the urban-surrounded (near urban districts) and other districts (districts in the hinterland). Among the HVCs, vegetables and meat products have a higher share in urban districts compared to the other two groups. Milk production is more widespread due to excellent network of co-operatives and infrastructure facilities. Using GIS (geographic Information System) approach it was found that urban-surrounded districts with better road network connection to urban centers have been able to diversify towards HVC's to meet the demand in the urban centers. Model results further confirm these findings. Thus, urbanization is a strong demand side driver promoting HVCs. Since urban population is growing at more than 3% per annum, demand for HVCs will drive their production. The analysis has also brought out regional variations in HVCs across different districts in the country that has implications on regional development and planning, and consequently on public and private sector investment strategies.
Noncommutative brane-world, (Anti) de Sitter vacua and extra dimensions
We investigate a curved brane-world, inspired by a noncommutative D3-brane,
in a type IIB string theory. We obtain, an axially symmetric and a spherically
symmetric, (anti) de Sitter black holes in 4D. The event horizons of these
black holes possess a constant curvature and may be seen to be governed by
different topologies. The extremal geometries are explored, using the
noncommutative scaling in the theory, to reassure the attractor behavior at the
black hole event horizon. The emerging two dimensional, semi-classical, black
hole is analyzed to provide evidence for the extra dimensions in a curved
brane-world. It is argued that the gauge nonlinearity in the theory may be
redefined by a potential in a moduli space. As a result, D=11 and D=12
dimensional geometries may be obtained at the stable extrema of the potential.Comment: 17 pages, 1 figur
Online Optimization Methods for the Quantification Problem
The estimation of class prevalence, i.e., the fraction of a population that
belongs to a certain class, is a very useful tool in data analytics and
learning, and finds applications in many domains such as sentiment analysis,
epidemiology, etc. For example, in sentiment analysis, the objective is often
not to estimate whether a specific text conveys a positive or a negative
sentiment, but rather estimate the overall distribution of positive and
negative sentiments during an event window. A popular way of performing the
above task, often dubbed quantification, is to use supervised learning to train
a prevalence estimator from labeled data.
Contemporary literature cites several performance measures used to measure
the success of such prevalence estimators. In this paper we propose the first
online stochastic algorithms for directly optimizing these
quantification-specific performance measures. We also provide algorithms that
optimize hybrid performance measures that seek to balance quantification and
classification performance. Our algorithms present a significant advancement in
the theory of multivariate optimization and we show, by a rigorous theoretical
analysis, that they exhibit optimal convergence. We also report extensive
experiments on benchmark and real data sets which demonstrate that our methods
significantly outperform existing optimization techniques used for these
performance measures.Comment: 26 pages, 6 figures. A short version of this manuscript will appear
in the proceedings of the 22nd ACM SIGKDD Conference on Knowledge Discovery
and Data Mining, KDD 201
One Relator Quotients of Graph Products
In this paper, we generalise Magnus' Freiheitssatz and solution to the word
problem for one-relator groups by considering one relator quotients of certain
classes of right-angled Artin groups and graph products of locally indicable
polycyclic groups
Null Branes in Curved Backgrounds
We consider null bosonic p-branes in curved space-times. Some exact solutions
of the classical equations of motion and of the constraints for the null
membrane in general stationary, axially symmetrical, four dimensional, gravity
background are found.Comment: 19 pages, LaTeX, no figures. Extended version. To appear in Phys.
Rev.
Preparation of Alginate Gel Beads Containing Metformin Hydrochloride Using Emulsion- Gelation Method
A new emulsion gelation method was used to prepare gel beads for a highly water-soluble drug metformin hydrochloride using sodium alginate as the polymer. The gel beads containing oil was prepared by gently mixing or homogenizing oil and water phase containing sodium alginate which was then extruded into calcium chloride solution to produce gel beads. The effects of factors like type of oil and percentage of oil on the morphology and release characteristics were investigated. A variety of oils were used to study the effect on the sustaining property of the formed beads. The oil entrapped calcium alginate gel beads showed good sustained release. Scanning electron photomicrographs demonstrated minute oil globules on the beads and also through the inner surface of the beads. The beads also showed floating behavior depending on the type of the oil that have been used for the preparation.
Tropical Journal of Pharmaceutical Research Vol. 4 (2) 2005: pp. 489-49
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