4,039 research outputs found
Supernovae as Probes of Extra Dimensions
Since the dawn of the new millennium, there has been a revived interest in
the concept of extra dimensions.In this scenario all the standard model matter
and gauge fields are confined to the 4 dimensions and only gravity can escape
to higher dimensions of the universe.This idea can be tested using table-top
experiments, collider experiments, astrophysical or cosmological observations.
The main astrophysical constraints come from the cooling rate of supernovae,
neutron stars, red giants and the sun. In this article, we consider the energy
loss mechanism of SN1987A and study the constraints it places on the number and
size of extra dimensions and the higher dimensional Planck scale.Comment: 5 pages, no figures, new references are adde
Development of ductile claddings for dispersion-strengthened nickel-base alloys Final report
Development of ductile oxidation-resistant cladding alloys for thoria dispersion, strengthened nickel and nickel-chromiu
Spatiotemporal chaos and the dynamics of coupled Langmuir and ion-acoustic waves in plasmas
A simulation study is performed to investigate the dynamics of coupled
Langmuir waves (LWs) and ion-acoustic waves (IAWs) in an unmagnetized plasma.
The effects of dispersion due to charge separation and the density nonlinearity
associated with the IAWs, are considered to modify the properties of Langmuir
solitons, as well as to model the dynamics of relatively large amplitude wave
envelopes. It is found that the Langmuir wave electric field, indeed, increases
by the effect of ion-wave nonlinearity (IWN). Use of a low-dimensional model,
based on three Fourier modes shows that a transition to temporal chaos is
possible, when the length scale of the linearly excited modes is larger than
that of the most unstable ones. The chaotic behaviors of the unstable modes are
identified by the analysis of Lyapunov exponent spectra. The space-time
evolution of the coupled LWs and IAWs shows that the IWN can cause the
excitation of many unstable harmonic modes, and can lead to strong IAW
emission. This occurs when the initial wave field is relatively large or the
length scale of IAWs is larger than the soliton characteristic size. Numerical
simulation also reveals that many solitary patterns can be excited and
generated through the modulational instability (MI) of unstable harmonic modes.
As time goes on, these solitons are seen to appear in the spatially partial
coherence (SPC) state due to the free ion-acoustic radiation as well as in the
state of spatiotemporal chaos (STC) due to collision and fusion in the
stochastic motion. The latter results the redistribution of initial wave energy
into a few modes with small length scales, which may lead to the onset of
Langmuir turbulence in laboratory as well as space plasmas.Comment: 10 Pages, 14 Figures; to appear in Physical Review
Prevalence of HPV in Oesophageal Biopsies and its Correlation with Expression Of P16INK4A
Background: The association of Human papillomavirus (HPV ) and p16INK4a is well established with cervical malignancies and has been studied in oral mucosa also. Koilocytosis, that is considered to be a hallmark of HPV infection is also seen in oesophageal mucosa. Aims: This study was designed to determine the prevalence of HPV in biopsies from inflammatory and neoplastic lesions of oesophagus and correlate it with expression of p16INK4a. Materials and Methods: The study included 102 oesophageal biopsies. Haematoxylin & Eosin stained sections were examined for morphological details including koilocytosis. Immunohistochemistry for HPV and p16INK4a were done on 50 biopsies. HPV positivity was graded and scoring for p16INK4a was done. Results: Various grades of koilocytosis was noted in 68.75%, 94.73% and 72.91% controls, inflammatory and neoplastic lesions respectively. IHC for HPV was positive in 80% control, 75% inflammatory and 100% cases of neoplastic lesion. Complete score for p16INK4a was 0.60, 0.59 and 3.63 in control, inflammatory and neoplastic lesion. The difference in expression of p16INK4a between neoplastic and inflammatory lesion was statistically significant. Conclusion: Expression of p16INK4a protein showed good correlation with HPV infection in inflammatory and neoplastic lesions. Thus IHC for p16INK4a which is easily available can be used as an indirect evidence of HPV infection in neoplastic lesion where expensive molecular technique for HPV DNA measurement is not feasibl
Effect of Plant Growth Regulators on Corm Production in Gladiolus
Experiments (spraying and dipping) were carried out to study the effect of different plant growth regulators with two methods of application on gladiolus cv. Pusa Jyotsna for various parameters of corm production. Spraying TIBA at 500 ppm produced maximum number of corms. Maximum number of cormels was produced by dipping corms in kinetin at 500 ppm concentration. Corm weight was maximum by dipping with 200 ppm of GA3. Spraying GA3 at 500 ppm resulted in maximum weight of cormels per plant and maximum diameter of corms. Dipping in 500 ppm of GA3 produced maximum volume of corms. Propagation co-efficient was maximum in BA at 100 ppm as spray treatment, whereas it was minimum in the case of TIBA at 1500 ppm. This may be due to growth retardation
The dependence of the estimated luminosities of ULX on spectral models
Data from {\it Chandra} observations of thirty nearby galaxies were analyzed
and 365 X-ray point sources were chosen whose spectra were not contaminated by
excessive diffuse emission and not affected by photon pile up. The spectra of
these sources were fitted using two spectral models (an absorbed power-law and
a disk blackbody) to ascertain the dependence of estimated parameters on the
spectral model used. It was found that the cumulative luminosity function
depends on the choice of the spectral model, especially for luminosities ergs/s. In accordance with previous results, a large number () of the sources have luminosities ergs/s (Ultra-Luminous X-ray
sources) with indistinguishable average spectral parameters (inner disk
temperature keV and/or photon index ) with those of the
lower luminosities ones. After considering foreground stars and known
background AGN,we identify four sources whose minimum luminosity exceed
ergs/s, and call them Extremely Luminous X-ray sources (ELX). The
spectra of these sources are in general better represented by the disk black
body model than the power-law one. These ELX can be grouped into two distinct
spectral classes. Two of them have an inner disk temperature of keV and
hence are called ``supersoft'' ELX, while the other two have temperatures
keV and are called ``hard'' ELX. The estimated inner disk
temperatures of the supersoft ELX are compatible with the hypothesis that they
harbor intermediate size black holes, which are accreting at times
their Eddington Luminosity. The radiative mechanism for hard ELX, seems to be
Inverse Comptonization, which in contrast to standard black holes systems, is
probably saturated.Comment: Accepted for publication in Astrophysical Journal. 9 pages. Complete
long Tables 4 and 5 are given as tab4.tex and tab5.tex separatel
Localized whistlers in magnetized spin quantum plasmas
The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves
(whistlers) along an external magnetic field, and their modulation by
electrostatic small but finite amplitude ion-acoustic density perturbations are
investigated in a uniform quantum plasma with intrinsic spin of electrons. The
effects of the quantum force associated with the Bohm potential and the
combined effects of the classical as well as the spin-induced ponderomotive
forces (CPF and SPF respectively) are taken into consideration. The latter
modify the local plasma density in a self-consistent manner. The coupled modes
of wave propagation is shown to be governed by a modified set of nonlinear
Schr\"{o}dinger-Boussinesq-like equations which admit exact solutions in form
of stationary localized envelopes. Numerical simulation reveals the existence
of large-scale density fluctuations that are self-consistently created by the
localized whistlers in a strongly magnetized high density plasma. The
conditions for the modulational instability (MI) and the value of its growth
rate are obtained. Possible applications of our results, e.g., in strongly
magnetized dense plasmas and in the next generation laser-solid density plasma
interaction experiments are discussed.Comment: 9 pages, 4 figures; To appear in Physical Review E (2010
Flexible copper-indium-diselenide films and devices for space applications
With the ever increasing demands on space power systems, it is imperative that low cost, lightweight, reliable photovoltaics be developed. One avenue of pursuit for future space power applications is the use of low cost, lightweight flexible PV cells and arrays. Most work in this area assumes the use of flexible amorphous silicon (a-Si), despite its inherent instability and low efficiencies. However, polycrystalline thin film PV such as copper-indium-diselenide (CIS) are inherently more stable and exhibit better performance than a-Si. Furthermore, preliminary data indicate that CIS also offers exciting properties with respect to space applications. However, CIS has only heretofore only produced on rigid substrates. The implications of flexible CIS upon present and future space power platforms was explored. Results indicate that space qualified CIS can dramatically reduce the cost of PV, and in most cases, can be substituted for silicon (Si) based on end-of-life (EOL) estimations. Furthermore, where cost is a prime consideration, CIS can become cost effective than gallium arsenide (GaAs) in some applications. Second, investigations into thin film deposition on flexible substrates were made, and data from these tests indicate that fabrication of flexible CIS devices is feasible. Finally, data is also presented on preliminary TCO/CdS/CuInSe2/Mo devices
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