774 research outputs found
Preheating after multifield inflation with nonminimal couplings, II: Resonance Structure
This is the second in a series of papers on preheating in inflationary models
comprised of multiple scalar fields coupled nonminimally to gravity. In this
paper, we work in the rigid-spacetime approximation and consider field
trajectories within the single-field attractor, which is a generic feature of
these models. We construct the Floquet charts to find regions of parameter
space in which particle production is efficient for both the adiabatic and
isocurvature modes, and analyze the resonance structure using analytic and
semi-analytic techniques. Particle production in the adiabatic direction is
characterized by the existence of an asymptotic scaling solution at large
values of the nonminimal couplings, , in which the dominant
instability band arises in the long-wavelength limit, for comoving wavenumbers
. However, the large- regime is not reached until
. In the intermediate regime, with , the resonance structure depends strongly on wavenumber and
couplings. The resonance structure for isocurvature perturbations is distinct
and more complicated than its adiabatic counterpart. An intermediate regime,
for , is again evident. For large values of
, the Floquet chart consists of densely spaced, nearly parallel
instability bands, suggesting a very efficient preheating behavior. The
increased efficiency arises from features of the nontrivial field-space
manifold in the Einstein frame, which itself arises from the fields' nonminimal
couplings in the Jordan frame, and has no analogue in models with minimal
couplings. Quantitatively, the approach to the large- asymptotic
solution for isocurvature modes is slower than in the case of the adiabatic
modes.Comment: 46 pages, 23 figures. References added and minor edits made to match
published versio
Preheating after multifield inflation with nonminimal couplings, III: Dynamical spacetime results
This paper concludes our semi-analytic study of preheating in inflationary
models comprised of multiple scalar fields coupled nonminimally to gravity.
Using the covariant framework of paper I in this series, we extend the
rigid-spacetime results of paper II by considering both the expansion of the
universe during preheating, as well as the effect of the coupled metric
perturbations on particle production. The adiabatic and isocurvature
perturbations are governed by different effective masses that scale differently
with the nonminimal couplings and evolve differently in time. The effective
mass for the adiabatic modes is dominated by contributions from the coupled
metric perturbations immediately after inflation. The metric perturbations
contribute an oscillating tachyonic term that enhances an early period of
significant particle production for the adiabatic modes, which ceases on a
time-scale governed by the nonminimal couplings . The effective mass of
the isocurvature perturbations, on the other hand, is dominated by
contributions from the fields' potential and from the curvature of the
field-space manifold (in the Einstein frame), the balance between which shifts
on a time-scale governed by . As in papers I and II, we identify
distinct behavior depending on whether the nonminimal couplings are small
(), intermediate (),
or large ().Comment: 34 pages, 11 figures. References added and minor edits made to match
published versio
A Protease Isolated from the Latex of Plumeria rubra Linn (Apocynaceae) 1: Purification and Characterization
Purpose: To isolate, purify and characterize protease from the latex of the plant.Methods: Protease was isolated from the latex of Plumeria rubra Linn using acetone precipitation method and purified by a sequence of DEAE cellulose column chromatography, followed by two successive column purification in Sephadex G-50 and Sephadex G-200. The molecular weight of the purified protease was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDSPAGE). The protease was given a trivial name, Plumerin-R.Results: Plumerin-R showed a single protein band on SDS-PAGE and molecular weight was approximately 81.85 kDa. It remained active over a broad range of temperature but had optimum activity at 55 °C and pH 7.0 when casein was used as substrate. Activation of the protease by a thiol-activating agent indicated the presence of sulfhydryl as an essential group for its activity.Conclusion: A protease from the latex of Plumeria rubra Linn was purified to homogeneity by a simple purification procedure and then characterized.Keywords: Protease, Plumerin-R, Sulfhydryl, Purification; Characterizatio
A fluorophore attached to nicotinic acetylcholine receptor beta M2 detects productive binding of agonist to the alpha delta site
To study conformational transitions at the muscle nicotinic acetylcholine (ACh) receptor (nAChR), a rhodamine fluorophore was tethered to a Cys side chain introduced at the beta-19' position in the M2 region of the nAChR expressed in Xenopus oocytes. This procedure led to only minor changes in receptor function. During agonist application, fluorescence increased by (Delta-F/F) approximate to 10%, and the emission peak shifted to lower wavelengths, indicating a more hydrophobic environment for the fluorophore. The dose-response relations for Delta-F agreed well with those for epibatidine-induced currents, but were shifted approximate to 100-fold to the left of those for ACh-induced currents. Because (i) epibatidine binds more tightly to the alpha-gamma-binding site than to the alpha-delta site and (ii) ACh binds with reverse-site selectivity, these data suggest that Delta-F monitors an event linked to binding specifically at the alpha-delta-subunit interface. In experiments with flash-applied agonists, the earliest detectable Delta-F occurs within milliseconds, i.e., during activation. At low [ACh] (less than or equal to 10 muM), a phase of Delta-F occurs with the same time constant as desensitization, presumably monitoring an increased population of agonist-bound receptors. However, recovery from Delta-F is complete before the slowest phase of recovery from desensitization (time constant approximate to 250 s), showing that one or more desensitized states have fluorescence like that of the resting channel. That conformational transitions at the alpha-delta-binding site are not tightly coupled to channel activation suggests that sequential rather than fully concerted transitions occur during receptor gating. Thus, time-resolved fluorescence changes provide a powerful probe of nAChR conformational changes
A Protease Isolated from the Latex of Plumeria rubra Linn (Apocynaceae) 2: Anti-inflammatory and Wound- Healing Activities
Purpose: The aim of this study was to investigate the anti-inflammatory and wound-healing activities of the protease isolated from the latex of Plumeria rubra Linn.Methods: The protease was isolated from the latex of the plant by acetone precipitation method and given a trivial name, Plumerin-R. The anti-inflammatory activity of the protease was based on its effects on carrageenan-induced paw oedema in rats. Its wound healing effect was investigated using an excision wound rat model.Results: Four hours after treatment, the reduction in carrageenan-induced rat paw oedema by 20, 40 and 80 mg/kg body weight of plumerin-R was 21.6, 33.8 and 48.8 %, respectively, while oedema reduction by indomethacin (10 mg/kg) was 58.0 %. Plumerin-R showed significant (p < 0.05) wound closure and epithelialization time compared with control.Conclusion: This study demonstrates that the protease, Plumerin-R, has significant anti-inflammatory and wound-healing properties.Keywords: Protease, Plumerin-R, Anti-inflammatory, Excision wound, Healing
A new species of Philautus (Anura: Rhacophoridae) from the Eastern Ghats, south-eastern India
A new species of Philautus is described from the vicinity of Vishakhapatnam, Andhra
Pradesh in south-eastern India. The new species is compared with congeners from
peninsular India and Sri Lanka. Since the members of the genus are restricted to wet
evergreen forests of the region, remnant patches of wet forests within a now largely
degraded and arid Eastern Ghats are apparently refugia, supporting species that are
tolerant of mesic conditions
Leptobrachium smithi Matsui, Nabitabhata, and Panha, 1999 (Anura: Megophryidae), an Addition to the Fauna of Myanmar (Burma)
Three specimens of Leptobrachium from the collections of the Zoological Survey of India are identified
as Leptobrachium smithi. These specimens were collected by Limborg in 1877. These are the first confirmed records
of Leptobrachium smithi for Myanmar
Microbial transformation of xenobiotics for environmental bioremediation
The accumulation of recalcitrant xenobiotic compounds is due to continuous efflux from population and industrial inputs that have created a serious impact on the pristine nature of our environment. Apart from this, these compounds are mostly carcinogenic, posing health hazards which persist over a long period of time. Metabolic pathways and specific operon systems have been found in diverse but limited groups of microbes that are responsible for the transformation of xenobiotic compounds.Distinct catabolic genes are either present on mobile genetic elements, such as transposons and plasmids, or the chromosome itself that facilitates horizontal gene transfer and enhances the rapid microbial transformation of toxic xenobiotic compounds. Biotransformation of xenobiotic compounds in natural environment has been studied to understand the microbial ecology, physiology and evolution for their potential in bioremediation. Recent advance in the molecular techniques including DNA fingerprinting, microarrays and metagenomics is being used to augment the transformation of xenobiotic compounds. The present day understandings of aerobic, anaerobic and reductive biotransformation by co-metabolic processes and an overview of latest developments in monitoring the catabolic genes of xenobiotic-degrading bacteria are discussed elaborately in this work. Till date, several reviews have come up, highlighting the problem of xenobiotic pollution, yet a comprehensiveunderstanding of the microbial biodegradation of xenobiotics and its application is in nascent stage. Therefore, this is an attempt to understand the microbial role in biotransformation of xenobiotic compounds in context to the modern day biotechnology
Catalogue of amphibian types in the collection of the Zoological Survey of India
The amphibian types in the collection of the National Zoological Collection,
maintained by the Zoological Survey of India (ZSI), Kolkata (Calcutta), as well as those
held by the regional stations at Dehra Dun and Chennai, are listed, up to 1 September
2000. The list includes many historical specimens collected and/or described by
pioneering European naturalists, including Edward Blyth, Thomas Jerdon, William
Blanford, William Theobald, Ferdinand Stoliczka, Nelson Annandale, and John
Anderson, as well as those more recently described from expeditions to the Nicobar
Islands, Arunachal Pradesh and Kerala, by the staff of the ZSI during the present
century. The annotated list includes original citations, registration numbers, nature of
types, and present status of every taxon. Additional remarks are provided where
necessary. A total of 346 type specimens of amphibians are represented, including those
representing 105 anuran species, one caudate species and nine apodan species, from
Pakistan, India, Sri Lanka, Myanmar, China, Malaysia, and Indonesia. Syntypes from
the original type series of two name-bearing taxa have lost their type status through the
designation of lectotypes. In addition, the types of 39 name-bearing taxa described by the
staff and members of the Asiatic Society of Bengal cannot be located in the ZSI collection
Statistics of leading digits leads to unification of quantum correlations
We show that the frequency distribution of the first significant digits of
the numbers in the data sets generated from a large class of measures of
quantum correlations, which are either entanglement measures, or belong to the
information-theoretic paradigm, exhibit a universal behaviour. In particular,
for Haar uniformly simulated arbitrary two-qubit states, we find that the
first-digit distribution corresponding to a collection of chosen computable
quantum correlation quantifiers tend to follow the first-digit law, known as
the Benford's law, when the rank of the states increases. Considering a
two-qubit state which is obtained from a system governed by paradigmatic spin
Hamiltonians, namely, the XY model in a transverse field, and the XXZ model, we
show that entanglement as well as information theoretic measures violate the
Benford's law. We quantitatively discuss the violation of the Benford's law by
using a violation parameter, and demonstrate that the violation parameter can
signal quantum phase transitions occurring in these models. We also comment on
the universality of the statistics of first significant digits corresponding to
appropriate measures of quantum correlations in the case of multipartite
systems as well as systems in higher dimensions.Comment: v1: 11 pages, 5 figures, 2 tables; v2: 11 pages, 6 figures, 2 tables,
new results added, extended version of the published pape
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