6,718 research outputs found
Economic Liberalization - A Stumbling Block in the Commercialization of Indigenous Calcium Silicide Technology
Indian ferro alloy industry is passing through one of its worst periods by the process of economic liberalization. Its production in our country is coming down mainly due to inadequate indigenous demand, non-availability of exports and high power cost as compared to other competing countries. The indigenous calcium silicide technology developed at National Metallurgical Laboratory; Jamshedpur could not be commercialized on account of thenew economic liberalization policy of Government of India
Shape-invariant quantum Hamiltonian with position-dependent effective mass through second order supersymmetry
Second order supersymmetric approach is taken to the system describing motion
of a quantum particle in a potential endowed with position-dependent effective
mass. It is shown that the intertwining relations between second order partner
Hamiltonians may be exploited to obtain a simple shape-invariant condition.
Indeed a novel relation between potential and mass functions is derived, which
leads to a class of exactly solvable model. As an illustration of our
procedure, two examples are given for which one obtains whole spectra
algebraically. Both shape-invariant potentials exhibit harmonic-oscillator-like
or singular-oscillator-like spectra depending on the values of the
shape-invariant parameter.Comment: 16 pages, 5 figs; Present e-mail of AG: [email protected]
Phosphorylation of pRb: mechanism for RB pathway inactivation in MYCN-amplified retinoblastoma.
A small, but unique subgroup of retinoblastoma has been identified with no detectable mutation in the retinoblastoma gene (RB1) and with high levels of MYCN gene amplification. This manuscript investigated alternate pathways of inactivating pRb, the encoded protein in these tumors. We analyzed the mutation status of the RB1 gene and MYCN copy number in a series of 245 unilateral retinoblastomas, and the phosphorylation status of pRb in a subset of five tumors using immunohistochemistry. There were 203 tumors with two mutations in RB1 (RB1(-/-) , 83%), 29 with one (RB1(+/-) , 12%) and 13 with no detectable mutations (RB1(+/+) , 5%). Eighteen tumors carried MYCN amplification between 29 and 110 copies: 12 had two (RB1(-/-) ) or one RB1 (RB1(+/-) ) mutations, while six had no mutations (RB1(+/+) ). Immunohistochemical staining of tumor sections with antibodies against pRb and phosphorylated Rb (ppRb) displayed high levels of pRb and ppRb in both RB1(+/+) and RB1(+/-) tumors with MYCN amplification compared to no expression of these proteins in a classic RB1(-/-) , MYCN-low tumor. These results establish that high MYCN amplification can be present in retinoblastoma with or without coding sequence mutations in the RB1 gene. The functional state of pRb is inferred to be inactive due to phosphorylation of pRb in the MYCN-amplified retinoblastoma without coding sequence mutations. This makes inactivation of RB1 by gene mutation or its protein product, pRb, by protein phosphorylation, a necessary condition for initiating retinoblastoma tumorigenesis, independent of MYCN amplification
Explainable deep learning for insights in El Ni\~no and river flows
The El Ni\~no Southern Oscillation (ENSO) is a semi-periodic fluctuation in
sea surface temperature (SST) over the tropical central and eastern Pacific
Ocean that influences interannual variability in regional hydrology across the
world through long-range dependence or teleconnections. Recent research has
demonstrated the value of Deep Learning (DL) methods for improving ENSO
prediction as well as Complex Networks (CN) for understanding teleconnections.
However, gaps in predictive understanding of ENSO-driven river flows include
the black box nature of DL, the use of simple ENSO indices to describe a
complex phenomenon and translating DL-based ENSO predictions to river flow
predictions. Here we show that eXplainable DL (XDL) methods, based on saliency
maps, can extract interpretable predictive information contained in global SST
and discover SST information regions and dependence structures relevant for
river flows which, in tandem with climate network constructions, enable
improved predictive understanding. Our results reveal additional information
content in global SST beyond ENSO indices, develop understanding of how SSTs
influence river flows, and generate improved river flow prediction, including
uncertainty estimation. Observations, reanalysis data, and earth system model
simulations are used to demonstrate the value of the XDL-CN based methods for
future interannual and decadal scale climate projections
On Deterministic Sketching and Streaming for Sparse Recovery and Norm Estimation
We study classic streaming and sparse recovery problems using deterministic
linear sketches, including l1/l1 and linf/l1 sparse recovery problems (the
latter also being known as l1-heavy hitters), norm estimation, and approximate
inner product. We focus on devising a fixed matrix A in R^{m x n} and a
deterministic recovery/estimation procedure which work for all possible input
vectors simultaneously. Our results improve upon existing work, the following
being our main contributions:
* A proof that linf/l1 sparse recovery and inner product estimation are
equivalent, and that incoherent matrices can be used to solve both problems.
Our upper bound for the number of measurements is m=O(eps^{-2}*min{log n, (log
n / log(1/eps))^2}). We can also obtain fast sketching and recovery algorithms
by making use of the Fast Johnson-Lindenstrauss transform. Both our running
times and number of measurements improve upon previous work. We can also obtain
better error guarantees than previous work in terms of a smaller tail of the
input vector.
* A new lower bound for the number of linear measurements required to solve
l1/l1 sparse recovery. We show Omega(k/eps^2 + klog(n/k)/eps) measurements are
required to recover an x' with |x - x'|_1 <= (1+eps)|x_{tail(k)}|_1, where
x_{tail(k)} is x projected onto all but its largest k coordinates in magnitude.
* A tight bound of m = Theta(eps^{-2}log(eps^2 n)) on the number of
measurements required to solve deterministic norm estimation, i.e., to recover
|x|_2 +/- eps|x|_1.
For all the problems we study, tight bounds are already known for the
randomized complexity from previous work, except in the case of l1/l1 sparse
recovery, where a nearly tight bound is known. Our work thus aims to study the
deterministic complexities of these problems
Nonsingular potentials from excited state factorization of a quantum system with position dependent mass
The modified factorization technique of a quantum system characterized by
position-dependent mass Hamiltonian is presented. It has been shown that the
singular superpotential defined in terms of a mass function and a excited state
wave function of a given position-dependent mass Hamiltonian can be used to
construct non-singular isospectral Hamiltonians. The method has been
illustrated with the help of a few examples.Comment: Improved version accepted in J. Phys.
Absorption of Electro-magnetic Waves in a Magnetized Medium
In continuation to our earlier work, in which the structure of the vacuum
polarisation tensor in a medium was analysed in presence of a background
electro-magnetic field, we discuss the absorptive part of the vacuum
polarization tensor. Using the real time formalism of finite temperature field
theory we calculate the absorptive part of 1-loop vacuum polarisation tensor in
the weak field limit (). Estimates of the absorption probability are
also made for different physical conditions of the background medium.Comment: 9 Pages. One figure. LaTe
Optical Activity From Extra Dimension
Optical activity, like Faraday effect, is a rotation of the plane of
polarization of propagating light in a medium and can be attributed to
different sources with distinct signatures. In this note we discuss the effect
of optical activity {\it{in vacuum}} due to Kaluza-Klein scalar field ,
in the presence of an external electro-magnetic field. The astrophysical
implication of this effect is indicated. We also point out the possibility of
observing the same in laboratory conditions.Comment: Four Page
Transport and Magnetic Properties of R1-xAxCoO3 (R=La, Pr and Nd; A=Ba, Sr and Ca)
Transport and magnetic measurements have been carried out on perovskite
Co-oxides R1-xAxCoO3 (R=La, Pr, and Nd; A=Ba, Sr and Ca; 0<x<0.5: All sets of
the R and A species except Nd1-xBaxCoO3 have been studied.). With increasing
the Sr- or Ba-concentration x, the system becomes metallic ferromagnet with
rather large magnetic moments. For R=Pr and Nd and A=Ca, the system approaches
the metal- insulator phase boundary but does not become metallic. The magnetic
moments of the Ca-doped systems measured with the magnetic field H=0.1 T are
much smaller than those of the Ba- and Sr-doped systems. The thermoelectric
powers of the Ba- and Sr-doped systems decrease from large positive values of
lightly doped samples to negative ones with increasing doping level, while
those of Ca-doped systems remain positive. These results can be understood by
considering the relationship between the average ionic radius of R1-xAx and the
energy difference between the low spin and intermediate spin states. We have
found the resistivity-anomaly in the measurements of Pr1-xCaxCoO3 under
pressure in the wide region of x, which indicates the existence of a phase
transition different from the one reported in the very restricted region of
x~0.5 at ambient pressure [Tsubouchi et al. Phys. Rev. B 66 (2002) 052418.]. No
indication of this kind of transition has been observed in other species of R.Comment: 9 pages, 8 figures. J. Phys. Soc. Jpn. 72 (2003) No.
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