64 research outputs found
Quantum phase transition in few-layer NbSe probed through quantized conductance fluctuations
We present the first observation of dynamically modulated quantum phase
transition (QPT) between two distinct charge density wave (CDW) phases in
2-dimensional 2H-NbSe. There is recent spectroscopic evidence for the
presence of these two quantum phases, but its evidence in bulk measurements
remained elusive. We studied suspended, ultra-thin \nbse devices fabricated on
piezoelectric substrates - with tunable flakes thickness, disorder level and
strain. We find a surprising evolution of the conductance fluctuation spectra
across the CDW temperature: the conductance fluctuates between two precise
values, separated by a quantum of conductance. These quantized fluctuations
disappear for disordered and on-substrate devices. With the help of mean-field
calculations, these observations can be explained as to arise from dynamical
phase transition between the two CDW states. To affirm this idea, we vary the
lateral strain across the device via piezoelectric medium and map out the phase
diagram near the quantum critical point (QCP). The results resolve a
long-standing mystery of the anomalously large spectroscopic gap in NbSe
Radiative Corrections to \zbb from Colored Scalars in a Model with Dynamical Symmetry Breaking
Isodoublet color-octet scalar bosons appear in the low-energy limit of a
natural extension of the Standard Model in which the electroweak symmetry is
broken by a condensate. We briefly discuss the model and show that
radiative corrections (involving these scalars) to the branching ratio
are
negative and thus place a stringent lower bound on the masses of the colored
scalars. This turns out to be GeV with GeV and increases
quadratically with . It is emphasized that is a parameter that is
well-determined experimentally and that theoretical estimates are relatively
free from uncertainties emanating from hadronic corrections and are
comparatively insensitive to the value of the top mass.Comment: 9 pages + 3 figures (available upon request), TeX file. Saha
Institute Preprint no. SINP-TNP/93-22 (December 1993
Taming the Scalar Mass Problem with a Singlet Higgs Boson
We investigate the fine-tuning problem in the Standard Model and show that
Higgs boson and top quark masses consistent with current experimental bounds
cannot be obtained unless one extends the particle spectrum. A minimal
extension which achieves this involves addition of a singlet real scalar and
one generation of vectorlike fermions. We show that this leads to a
phenomenologically viable prediction for the mass of the Standard Model Higgs
boson.Comment: (LaTeX file), 13 pages, preprint no. SINP-TNP/94-1
Novel Role of Phosphorylation-Dependent Interaction between FtsZ and FipA in Mycobacterial Cell Division
The bacterial divisome is a multiprotein complex. Specific protein-protein interactions specify whether cell division occurs optimally, or whether division is arrested. Little is known about these protein-protein interactions and their regulation in mycobacteria. We have investigated the interrelationship between the products of the Mycobacterium tuberculosis gene cluster Rv0014c-Rv0019c, namely PknA (encoded by Rv0014c) and FtsZ-interacting protein A, FipA (encoded by Rv0019c) and the products of the division cell wall (dcw) cluster, namely FtsZ and FtsQ. M. smegmatis strains depleted in components of the two gene clusters have been complemented with orthologs of the respective genes of M. tuberculosis. Here we identify FipA as an interacting partner of FtsZ and FtsQ and establish that PknA-dependent phosphorylation of FipA on T77 and FtsZ on T343 is required for cell division under oxidative stress. A fipA knockout strain of M. smegmatis is less capable of withstanding oxidative stress than the wild type and showed elongation of cells due to a defect in septum formation. Localization of FtsQ, FtsZ and FipA at mid-cell was also compromised. Growth and survival defects under oxidative stress could be functionally complemented by fipA of M. tuberculosis but not its T77A mutant. Merodiploid strains of M. smegmatis expressing the FtsZ(T343A) showed inhibition of FtsZ-FipA interaction and Z ring formation under oxidative stress. Knockdown of FipA led to elongation of M. tuberculosis cells grown in macrophages and reduced intramacrophage growth. These data reveal a novel role of phosphorylation-dependent protein-protein interactions involving FipA, in the sustenance of mycobacterial cell division under oxidative stress
Georeferenced soil information system: assessment of database
Land-use planning is a decision-making process that
facilitates the allocation of land to different uses that
provide optimal and sustainable benefit. As land-use
is shaped by society–nature interaction, in land-use
planning different components/facets play a significant
role involving soil, water, climate, animal (ruminant/
non-ruminant) and others, including forestry
and the environment needed for survival of mankind.
At times these components are moderated by human
interference. Thus land-use planning being a dynamic
phenomenon is not guided by a single factor, but by a
complex system working simultaneously,which largely
affects the sustainability. To address such issues a
National Agricultural Innovation Project (NAIP) on
‘Georeferenced soil information system for land-use
planning and monitoring soil and land quality for
agriculture’ was undertaken to develop threshold
values of land quality parameters for land-use planning
through quantitative land evaluation and crop
modelling for dominant cropping systems in major
agro-ecological sub-regions (AESRs) representing
rice–wheat cropping system in the Indo-Gangetic
Plains (IGP) and deep-rooted crops in the black
soil regions (BSR). To assess the impact of landuse
change, threshold land quality indicator values
are used. A modified AESR map for agricultural landuse
planning is generated for effective land-use planning
Soil information system: use and potentials in humid and semi-arid tropics
The articles presented in this special section emanated from the researches of consortium members of the National Agricultural Innovative Project (NAIP, Component 4) of the Indian Council of Agricultural Research (ICAR), New Delhi. These researches have helped develop a soil information system (SIS). In view of the changing scenario all over the world, the need of the hour is to get assistance from a host of researchers specialized in soils, crops, geology, geography and information technology to make proper use of the datasets. Equipped with the essential knowledge of data storage and retrieval for management recommendations, these experts should be able to address the issues of land degradation, biodiversity, food security, climate change and ultimately arrive at an appropriate agricultural land-use planning. Moreover, as the natural resource information is an essential prerequisite for monitoring and predicting global environmental change with special reference to climate and land use options, the SIS needs to be a dynamic exercise to accommodate temporal datasets, so that subsequently it should result in the evolution of the soil information technology. The database developed through this NAIP would serve as an example of the usefulness of the Consortium and the research initiative of ICAR involving experts from different fields to find out the potentials of the soils of humid and semi-arid bioclimatic systems of the country
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Kv1.3 in psoriatic disease: PAP-1, a small molecule inhibitor of Kv1.3 is effective in the SCID mouse psoriasis - Xenograft model
Kv1.3 channels regulate the activation/proliferation of effector memory T cells and thus play a critical role in the pathogenesis of autoimmune diseases. Using a combination of immunohistochemistry, confocal microscopy, flow cytometry and electrophysiology methods we observed a significant enrichment of activated Kv1.3 + memory T cells in psoriasis plaques and synovial fluid from patients with psoriasis/psoriatic arthritis (PsA) compared to non-lesional psoriatic skin, normal skin or peripheral blood lympho-mononuclear cells. In in vitro studies performed with lesional mononuclear cells or T cells derived from skin and joints of psoriatic disease, the small molecule Kv1.3 blocker PAP-1 dose-dependently inhibited proliferation and suppressed IL-2 and IFN-γ production. To further substantiate the pathologic role of Kv1.3 high T EM cells in psoriatic disease we tested whether PAP-1 is able to improve psoriatic disease pathology in the SCID mouse-psoriasis skin xenograft model. Following four weeks of daily treatment with 2% PAP-1 ointment we noticed about 50% reduction in the epidermal thickness (rete peg length) and the number of CD3 + lymphocytes/mm 2 of dermis decreased by 85%. Vehicle treated and untreated plaques in contrast remained unchanged and showed no reduction in epidermis thickness and infiltrating CD3 + T cells and HLA-DR + T cells. Based on these results we propose the development of Kv1.3 targeted topical immunotherapy for psoriasis and possibly for other inflammatory skin conditions, where effector memory T cells are involved in the pathogenesis
Not Available
Not AvailableUnderstanding the physical quality of soil that influences ts hydraulic behaviour helps in formulating
appropriate water management strategies for sustainable crop production. Saturated hydraulic conductivity
(Ks) is a key factor governing the hydraulic properties of soils. Ks can be estimated through various techniques. In the present article we have developed and validated the regression models to predict Ks of the soils of the Indo-Gangetic Plains (IGP) and the black soil regions (BSR) under different bioclimatic systems. While particle size distribution was found to be a key factor to predict Ks of the BSR soils, organic carbon was found useful for the IGP soils. Moreover, the models for Ks of both soils were strengthened by putting in CaCO3 and
exchangeable sodium percentage content. It seems there is ample scope to study the interaction process
for revising Ks to desired levels through management practices in these two important food-growing zones.
An index of soil physical quality, derived from the inflection points of the soil moisture characteristic
curves could well explain the impact of management practices on soil physical quality.Not Availabl
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