2,219 research outputs found
On Dwass' method for deriving the distribution of rank order statistics
summary:This note presents a critical examination of Dwass' method for obtaining the distribution of rank order statistics defined on random samples obtained from the same continuous population. New situations are discussed for the usefulness of the method
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The cardiomyocyte "redox rheostat": Redox signalling via the AMPK-mTOR axis and regulation of gene and protein expression balancing survival and death.
Reactive oxygen species (ROS) play a key role in development of heart failure but, at a cellular level, their effects range from cytoprotection to induction of cell death. Understanding how this is regulated is crucial to develop novel strategies to ameliorate only the detrimental effects. Here, we revisited the fundamental hypothesis that the level of ROS per se is a key factor in the cellular response by applying different concentrations of H2O2 to cardiomyocytes. High concentrations rapidly reduced intracellular ATP and inhibited protein synthesis. This was associated with activation of AMPK which phosphorylated and inhibited Raptor, a crucial component of mTOR complex-1 that regulates protein synthesis. Inhibition of protein synthesis by high concentrations of H2O2 prevents synthesis of immediate early gene products required for downstream gene expression, and such mRNAs (many encoding proteins required to deal with oxidant stress) were only induced by lower concentrations. Lower concentrations of H2O2 promoted mTOR phosphorylation, associated with differential recruitment of some mRNAs to the polysomes for translation. Some of the upregulated genes induced by low H2O2 levels are cytoprotective. We identified p21Cip1/WAF1 as one such protein, and preventing its upregulation enhanced the rate of cardiomyocyte apoptosis. The data support the concept of a "redox rheostat" in which different degrees of ROS influence cell energetics and intracellular signalling pathways to regulate mRNA and protein expression. This sliding scale determines cell fate, modulating survival vs death
Radio and gamma-ray constraints on dark matter annihilation in the Galactic center
We determine upper limits on the dark matter (DM) self-annihilation cross
section for scenarios in which annihilation leads to the production of
electron--positron pairs. In the Galactic centre (GC), relativistic electrons
and positrons produce a radio flux via synchroton emission, and a gamma ray
flux via bremsstrahlung and inverse Compton scattering. On the basis of
archival, interferometric and single-dish radio data, we have determined the
radio spectrum of an elliptical region around the Galactic centre of extent 3
degrees semi-major axis (along the Galactic plane) and 1 degree semi-minor axis
and a second, rectangular region, also centered on the GC, of extent 1.6
degrees x 0.6 degrees. The radio spectra of both regions are non-thermal over
the range of frequencies for which we have data: 74 MHz -- 10 GHz. We also
consider gamma-ray data covering the same region from the EGRET instrument
(about GeV) and from HESS (around TeV). We show how the combination of these
data can be used to place robust constraints on DM annihilation scenarios, in a
way which is relatively insensitive to assumptions about the magnetic field
amplitude in this region. Our results are approximately an order of magnitude
more constraining than existing Galactic centre radio and gamma ray limits. For
a DM mass of m_\chi =10 GeV, and an NFW profile, we find that the
velocity-averaged cross-section must be less than a few times 10^-25 cm^3 s^-1.Comment: 14 pages, 9 figures. Version accepted for publication in PRD.
Reference section updated/extended
Automated System for Detection of Apple Purity and Its Grading
It is always a common problem for all the people to identify the purity of all the fruits that has been purchased from the �fruit mandi� or local fruit stores. In this paper we would like to propose an idea for identifying the purity of apples. At present, among all the apples that are being sold in a shop, only few samples are collected and tested for purity in the laboratories by food Corporation of INDIA (FOI), which might not ensure that all the apples being sold in that respective shop/market are pure. In this paper we are proposing a device which can sense if the chosen apple is pure or not and which can be used by all the common people who are purchasing fruits from the market. Through this infections and disorders caused by fruits consumption can be eradicated to some extent
Geotechnical Investigations for Foundation Design for Multi-storeyed Building
Oil and Natural Gas Commission of India plans to construct a multi-storeyed building in Dehradun city at the foothills of Himalayas. The geotechnical investigations were carried out at site to determine soil parameters for foundation design. It was found that it was not possible to provide a raft foundation for the building and hence alternatively the pile foundation was suggested. The pile load capacity was predicted on the basis of soil parameters determined and a comparison was then made with the results obtained by carrying out load tests on constructed piles
Parker Instability in a Self-Gravitating Magnetized Gas Disk: I. Linear Stability Analysis
To be a formation mechanism of such large-scale structures as giant molecular
clouds (GMCs) and HI superclouds, the classical Parker instability driven by
external gravity has to overcome three major obstacles: The convective motion
accompanying the instability generates thin sheets than large condensations.
The degree of density enhancement achieved by the instability is too low to
make dense interstellar clouds. The time and the length scales of the
instability are significantly longer and larger than the estimated formation
time and the observed mean separation of the GMCs, respectively. This paper
examines whether a replacement of the driving agent from the external to the
self gravity might remove these obstacles by activating the gravitational
instability in the Galactic ISM disk. The self gravity can suppress the
convective motions, and a cooperative action of the Jeans and the Parker
instabilities can remove all the obstacles confronting the classical version of
the Parker instability. The mass and mean separation of the structures
resulting from the odd-parity undular mode solution are shown to agree better
with the HI superclouds than with the GMCs. We briefly discuss how inclusions
of the external gravity and cosmic rays would modify behaviors of the
odd-parity undular mode solution.Comment: 53 pages, 21 figure
Gas Dynamics in the LINER Galaxy NGC 5005: Episodic Fueling of a Nuclear Disk
We report high-resolution CO(1-0) observations in the central 6 kpc of the
LINER galaxy NGC 5005 with the Owens Valley Radio Observatory millimeter array.
Molecular gas is distributed in three components - a ring at a radius of about
3 kpc, a strong central condensation, and a stream to the northwest of the
nucleus but inside the 3 kpc ring. The central condensation is a disk of about
1 kpc radius with a molecular gas mass of 2 x 10^9 M_sun. The stream between
the 3 kpc ring and the nuclear disk lies on a straight dust lane seen in the
optical. If this material moves in the plane of the galaxy, it has a velocity
offset by up to ~ 150 km/s from galactic rotation. We suggest that an optically
inconspicuous stellar bar lying within the 3 kpc ring can explain the observed
gas dynamics. This bar is expected to connect the nuclear disk and the ring
along the position angle of the northwest stream. A position-velocity cut in
this direction reveals features which match the characteristic motions of gas
in a barred potential. Our model indicates that gas in the northwest stream is
on an x_1 orbit at the bar's leading edge; it is falling into the nucleus with
a large noncircular velocity, and will eventually contribute about 2 x 10^8
M_sun to the nuclear disk. If most of this material merges with the disk on its
first passage of pericenter, the gas accretion rate during the collision will
be 50 M_sun/yr. We associate the nuclear disk with an inner 2:1 Lindblad
resonance, and the 3 kpc ring with an inner 4:1 Lindblad resonance. The high
rate of bar-driven inflow and the irregular appearance of the northwest stream
suggest that a major fueling event is in progress in NGC 5005. Such episodic
(rather than continuous) gas supply can regulate the triggering of starburst
and accretion activity in galactic nuclei. (abridged)Comment: 26 pages, 12 figures, AASTeX, ApJ in press (Feb. 10, 2000). For
full-resolution figures, see
http://www.ovro.caltech.edu/mm/science/science.htm
Genetic Evaluation of Leucaena Genotypes in Bundelkhand Region of Central India
During the 1970s and 1980s, Leucaena was known as the “miracle tree” native to Central America and Mexico, because of its worldwide success as a long-lived and highly nutritious forage tree. It is estimated to cover 2-5 million ha area worldwide. The genus Leucaena is one of the most widely grown tropical fodder trees and is the subject of extensive research. This is mainly due to its long life span; high productivity even under regular defoliation; its adaptation to wide climatic and edaphic tolerances; excellent palatability and digestibility and many uses including wood for timber and fuel wood. The species possesses enormous wealth of variability and great potential for economic yield which attract the breeders in utilizing the species in hybridization. A logical way to start any breeding programme is to survey the variations present in the germplasm. Precise information on the nature and degree of genetic divergence in respect of important traits is a prerequisite for undertaking meaningful breeding programme towards the improvement and conservation of a species.
Further an investigation into the nature and degree of divergence among populations will be useful in understanding the course of evolution and for classifying the tree population into groups based on the diversity, particularly when they are overlapping in one more characters. Therefore, the present study was conducted to estimate genetic divergence among different germplasm of genus Leucaena
Anomalous Microwave Emission from the HII region RCW175
We present evidence for anomalous microwave emission in the RCW175 \hii
region. Motivated by 33 GHz 13\arcmin resolution data from the Very Small
Array (VSA), we observed RCW175 at 31 GHz with the Cosmic Background Imager
(CBI) at a resolution of 4\arcmin. The region consists of two distinct
components, G29.0-0.6 and G29.1-0.7, which are detected at high signal-to-noise
ratio. The integrated flux density is Jy at 31 GHz, in good
agreement with the VSA. The 31 GHz flux density is Jy
() above the expected value from optically thin free-free emission
based on lower frequency radio data and thermal dust constrained by IRAS and
WMAP data. Conventional emission mechanisms such as optically thick emission
from ultracompact \hii regions cannot easily account for this excess. We
interpret the excess as evidence for electric dipole emission from small
spinning dust grains, which does provide an adequate fit to the data.Comment: 5 pages, 2 figures, submmited to ApJ Letter
Dense Molecular Gas Associated with the Circumnuclear Star Forming Ring in the Barred Spiral Galaxy NGC 6951
We present high resolution (3" - 5") observations of CO(1-0) and HCN(1-0)
emission from the circumnuclear star forming ring in the barred spiral galaxy
NGC 6951, a host of a type-2 Seyfert, using the Nobeyama Millimeter Array and
45 m telescope. We find that most of the HCN emission is associated with the
circumnuclear ring, where vigorous star formation occurs. The HCN to CO
integrated intensity ratio is also enhanced in the star forming ring; the peak
value of HCN/CO ratio is 0.18, which is comparable to the ratio in the
starbursts NGC 253 and M82. The formation mechanism of dense molecular gas has
been investigated. We find that the shocks along the orbit crowding do not
promote the formation of the dense molecular gas effectively but enhance the
presence of low density GMCs. Instead, gravitational instabilities of the gas
can account for the dense molecular gas formation. The HCN/CO ratio toward the
Seyfert nucleus of NGC 6951 is a rather normal value (0.086), in contrast with
other Seyferts NGC 1068 and M51 where extremely high HCN/CO value of ~ 0.5 have
been reported.Comment: 33 pages, 17 figures, to appear in the Astrophysical Journa
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