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Ren Q.,Peking University | Ren Q.,Max Planck Institute for Mathematics in the Sciences | Kolwankar K.M.,Max Planck Institute for Mathematics in the Sciences | Kolwankar K.M.,Ramniranjan Jhunjhunwala College | And 4 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

We study the interplay of topology and dynamics in a neural network connected with spike-timing-dependent plasticity (STDP) synapses. Stimulated with periodic spike trains, the STDP-driven network undergoes a synaptic pruning process and evolves to a residual network. We examine the variation of topological and dynamical properties of the residual network by varying two key parameters of STDP: synaptic delay and the ratio between potentiation and depression. Our extensive numerical simulations of the leaky integrate-and-fire model show that there exists two regions in the parameter space. The first corresponds to fixed-point configurations, where the distribution of peak synaptic conductances and the firing rate of neurons remain constant over time. The second corresponds to oscillating configurations, where both topological and dynamical properties vary periodically, which is a result of a fixed point becoming a limit cycle via a Hopf bifurcation. This leads to interesting questions regarding the implications of these rhythms in the topology and dynamics of the network for learning and cognitive processing. © 2012 American Physical Society.

Ren Q.,Max Planck Institute for Mathematics in the Sciences | Kolwankar K.M.,Max Planck Institute for Mathematics in the Sciences | Kolwankar K.M.,Ramniranjan Jhunjhunwala College | Samal A.,Max Planck Institute for Mathematics in the Sciences | And 3 more authors.
Physica A: Statistical Mechanics and its Applications | Year: 2010

We study the dynamics of the structure of a formal neural network wherein the strengths of the synapses are governed by spike-timing-dependent plasticity (STDP). For properly chosen input signals, there exists a steady state with a residual network. We compare the motif profile of such a network with that of a real neural network of C. elegans and identify robust qualitative similarities. In particular, our extensive numerical simulations show that this STDP-driven resulting network is robust under variations of the model parameters. © 2010 Elsevier B.V.

Basu H.,Tata Institute of Fundamental Research | Kolwankar K.M.,Ramniranjan Jhunjhunwala College | Dharmadhikari A.K.,Tata Institute of Fundamental Research | Dharmadhikari J.A.,Tata Institute of Fundamental Research | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

We report a scheme for very significantly accelerated growth of dendritic patterns in organic, inorganic, polymeric, and biological liquids, using laser power as low as a few hundred microwatts in the presence of an efficient absorber such as carbon nanotubes (CNTs). The CNTs act as a heat source that drives dendritic growth; their anisotropy ensures a rich diversity of branched patterns. We have studied the time evolution of the accelerated growth patterns; growth patterns are seen on millisecond time scales. We rationalize such unprecedented speed of dendritic growth using a diffusion equation for the temperature field with an additional source term. The predictions of the well-established microscopic solvability theory (MST) are seen to hold on time scales in excess of 100 ms even with the introduction of an additional source term to account for our laser beam. On the other hand, on time scales shorter than 100 ms, MST is seen to break down. Our method opens new vistas for studies on the dynamics of dendritic patterns and crystal growth. © 2012 American Chemical Society.

Gavahne Rahul C.,Ramniranjan Jhunjhunwala College | Usha M.,Ramniranjan Jhunjhunwala College
Research Journal of Biotechnology | Year: 2010

This study investigates factors affecting the production of somatic embryos in Tinospora cordifolia. Fully expanded leaves taken from in-vitro grown plants were used as explants. The explants were cultured on Murashige and Skoog medium supplemented with different concentrations of NAA or 2, 4-D. Explants grown on medium supplemented with 21.48uM NAA gave callus with organized globular protuberances. Somatic embryos when cultured on media containing ABA matured and gave rise to a number of secondary somatic embryos. These somatic embryos germinated when transferred to half strength MS medium supplemented with 5.77uM GA3 and 2.32uM Kinetin.

Shivmurat Y.S.,Ramniranjan Jhunjhunwala College | Usha M.,Ramniranjan Jhunjhunwala College
Research Journal of Biotechnology | Year: 2011

In view of the free radical theory of ageing, antioxidant property is an important characteristic of herbs species. The intake of antioxidants present in food is an important health-protecting factor. In the present study, Ocimum basilicum and Salvia officinalis belonging to the family Lamiaceae were screened for their in vitro antioxidant activity. By employing DPPH (2, 2-diphenyl-1- picrylhydrazyl) and Superoxide radical scavenging assays, it was shown that the methanolic as well as aqueous extracts of leaves of both the herbs were endowed with antioxidant activity, though, as expected, their potency varied. In particular, methanolic extracts of Ocimum basilicum displayed the highest activity. The IC50 value of the extracts tested ranged from 5.38 mg/ml-7.61 mg/ml. It is generally accepted that a diet rich in plants is associated with a reduced incidence of degenerative diseases such as atherosclerosis and cancer. This study suggests that these Lamiaceae plants could be pharmaceutically exploited for their antioxidant properties.

Munoz-Darias T.,National institute for astrophysics | Motta S.,National institute for astrophysics | Motta S.,University dettInsubria | Pawar D.,Ramniranjan Jhunjhunwala College | And 3 more authors.
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2010

We present a 2-day long Rossi X-ray Timing Explorer observation and simultaneous Swift data of the bright X-ray transient XTE J1752-223. Spectral and timing properties were stable during the observation. The energy spectrum is well described by a broken power law with a high-energy cut-off. A cold disc (~0.3 keV) is observed when Swift/X-Rsy Telescope data are considered. The fractional root mean square amplitude of the aperiodic variability (0.002-128 Hz) is 48.2 ± 0.1 per cent, and it is not energy dependent. The continuum of the power density spectrum can be fitted by using four broad-band Lorentzians. A high-frequency (~21 Hz) component and two weak quasi-periodic oscillation-like features are also present. Time lags between soft and hard X-rays roughly follow the relation Δt ∝ ν-0.7, with delays dropping from ~0.5 (0.003 Hz) to ~0.0015 (≥10 Hz) s. Our results are consistent with XTE J1752-223 being a black hole candidate, with all timing and spectral components very similar to those of Cyg X-l during its canonical hard state. © 2010 The Authors. Journal compilation © 2010 RAS.

Pawar D.D.,Ramniranjan Jhunjhunwala College | Kalamkar M.,University of Amsterdam | Altamirano D.,University of Amsterdam | Linares M.,Institute Astmfisica Of Canarias | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We report the discovery of kHz quasi-periodic oscillations (QPOs) in three Rossi X-ray Timing Explorer observations of the low-mass X-ray binary XTE J1701-407. In one of the observations we detect a kHz QPO with a characteristic frequency of 1153 ± 5 Hz, while in the other two observations we detect twin QPOs at characteristic frequencies of 740 ± 5, 1112 ± 17 Hz and 740 ± 11,1098 ± 5 Hz. All detections happen when XTE J1701-407 was in its high-intensity soft state, and their single-trial significance is in the 3.1-7.5σ range. The frequency difference in the centroid frequencies of the twin kHz QPOs (385 ± 13 Hz) is one of the largest seen till date. The 3-30 keV fractional rms amplitude of the upper kHz QPO varies between ∼18 and ∼30 per cent. XTE J1701-407, with a persistent luminosity close to 1 per cent of the Eddington limit, is among the small group of low-luminosity kHz QPO sources and has the highest rms for the upper kHz QPO detected in any source. The X-ray spectral and variability characteristics of this source indicate its atoll source nature. © 2013 The Authors.

Thombare S.,Ramniranjan Jhunjhunwala College | Mukundan U.,Ramniranjan Jhunjhunwala College
Journal of Pure and Applied Microbiology | Year: 2012

Plants have traditionally provided a source of hope for novel drug compounds. The spread of drug resistant pathogens is one of the most serious threats to successful treatment of microbial diseases. Seborrheic dermatitis is a common papulosquamous disorder of the skin. Dandruff, a less severe form of Seborrheic dermatitis, affects a greater proportion of the population. The exact pathogenesis of Seborrheic dermatitis is unknown, however colonization of the lipophilic yeast, Malassezia furfur and an inflammatory reaction to this yeast each seem to play a role in disease etiology. Essential oils have been shown to possess antimicrobial properties. The effect of plant essential oils on the growth of M. furfur was evaluated and reported. Among the 19 different plant essential oil tested, Salvia sclarea, Cinnamomum verum, Cymbopogon flexuosus, Eucalyptus globulus, Thymus vulgaris, Melaleuca alternifolia, Syzygium aromaticum, Rosmarinus officinalis, Matricaria recutita, Cymbopogon martinii, Pogostemon cablin, Cedrus atlantica and Vitus vinifera oil were found to be effective. Antidandruff shampoo was formulated using the lead extracts.

Prasade A.,Bombay Natural History Society | Apte D.,Bombay Natural History Society | Kale P.,Ramniranjan Jhunjhunwala College | Oliveira O.M.P.,Federal University of ABC
Check List | Year: 2015

The benthic ctenophore Vallicula multiformis Rankin, 1956 is recorded for the first time in the Arabian Sea, from the Gulf of Kutch, west coast of India in March 2013. This occurrence represents a remarkable extension of its geographic distribution that until now included only known the Pacific and Atlantic oceans. © 2015 Check List and Authors.

Sesuvium portulacastrum L. (Aizoaceae) is a pioneer, psammophytic associate halophyte of subtropical, Mediterranean regions. It dominates coastal and warmer zones of the world. Apart from being utilized as a vegetable and forage by local people, it is also utilized for bioreclamation of saline soil in the arid and semiarid regions. Coastal soils has poor nitrogen content whereas halophytes which inhabit these areas have high protein content due to the ability to conserve nitrogen and recycle it through their body metabolism. In present investigation, Sesuvium portulacastrum (L.) is used as a model system representing an associate halophyte with efficacy in Nitrogen utilization in saline conditions. The plant has adapted to nitrogen stress by evolving efficient nitrogen assimilating isoenzymes. Isoenzymes of glutamate dehydrogenase (GDH) and Aspartate aminotransferase (AspAT) are separated electrophoretically from the leaves and roots of Sesuvium portulacastrum L. Presence of Isozymes for nitrogen assimilating and distributing enzymes like GDH and AspAT indicates the physiological adaptation of plants growing in saline nitrogen deficient conditions. The same study would be extended to other important enzymes of Nitrogen metabolism to get an insight in efficacy of such halophytes to conserve available Nitrogen from saline soils and help in phytoremediation of saline soils. © 2015 Society for Plant Research. All rights reserved.

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