Tata Institute of Fundamental Research

About: Tata Institute of Fundamental Research is a education organization based out in Mumbai, Maharashtra, India. It is known for research contribution in the topics: Magnetization & Large Hadron Collider. The organization has 7786 authors who have published 21742 publications receiving 622368 citations. The organization is also known as: TIFR.

pn Heterojunctions in NiO:TiO2 composites with type-II band alignment assisting sunlight driven photocatalytic H2 generation

Abstract: To accentuate the role of pn heterojunctions in composites, the photocatalytic properties of two composites NTC11 (NiO and TiO 2 in 1:1 molar ratio) and NTC36 (0.35:0.65) were investigated in detail for H 2 evolution reaction and compared with the component pure oxides, NiO, TiO 2 and NiTiO 3 prepared by sol-gel route. Among all samples, NTC11 was distinctly most active (greater than pure TiO 2 by ∼22 times, NiO has negligible activity) and yielded reproducible H 2 yields for 60 h under repetititive cycles in sunlight confirming its photostability. Maximum photocatalytic Hydrogen yield @ 0.6 l/h/m 2 with apparent quantum efficiency (AQE) of 5.4% and solar fuel efficiency (SFE) of 0.8% under sunlight and 1.4 l/h/m 2 with AQE of 7.8% under UV–vis irradiation along with evolution of bubbles was observed over Pt(1 wt%)/NTC11. Synthesis conditions, calcination temperature and phase compositions were very critical and played an essential role in determining the overall hydrogen yield. Presence of NiTiO 3 was found to be derogatory for the photocatalytic activity of NTC36. The key factors responsible for enhanced rate of sunlight assisted hydrogen generation over NTC11 were 1. Formation of pn nanojunctions in NTC11 evident by enhanced life times of charge carriers monitored by time resolved photoluminescence, uniform distribution of NiO and TiO 2 nanoparticles with Ni/Ti in ratio of 0.99 and 0.95 at bulk and surface, respectively. 2. Favourable morphological characteristics: monodisperse, nanosized faceted particles, higher surface area, better porosity and pore volume. 3. Coformation of minimal NiTiO 3 phase. 4. First principles calculations by density functional theory (DFT) over pure NiO revealed it’s electronic and band structure that helped in understanding its behavior as PL quencher and its contribution in visible light absorption of composites, 5. Valence band offset (ΔE v ) and conduction band offset (ΔE c ) at NiO and TiO 2 heterojunction was calculated to be 0.53 eV and 0.93 eV, respectively. 6. Type-II band alignment was derived at the interface and mechanism was proposed, 7. The effective forbidden gap was deduced to be 3.2(E g,TiO2 ) − ΔE v = 3.6(E g NiO ) − ΔE c = 2.67 eV. Thus, a composite of pn oxides offers lower band gap energy of 2.67 eV as compared to both pure oxides TiO 2 and NiO with effectiveness in charge separation across the pn junction leading to efficient improved photocatalyst.

A World-Wide Net of Solar Radio Spectrometers: e-CALLISTO

Abstract: Radio spectrometers of the CALLISTO type to observe solar flares have been distributed to nine locations around the globe. The instruments observe automatically, their data is collected every day via internet and stored in a central data base. A public web-interface exists through which data can be browsed and retrieved. The nine instruments form a network called e-CALLISTO. It is still growing in the number of stations, as redundancy is desirable for full 24 h coverage of the solar radio emission in the meter and low decimeter band. The e-CALLISTO system has already proven to be a valuable new tool for monitoring solar activity and for space weather research.

Characterization and reversal of synaptic defects in the amygdala in a mouse model of fragile X syndrome.

Abstract: Fragile X syndrome (FXS), a common inherited form of mental impairment and autism, is caused by transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene. Earlier studies have identified a role for aberrant synaptic plasticity mediated by the metabotropic glutamate receptors (mGluRs) in FXS. However, many of these observations are derived primarily from studies in the hippocampus. The strong emotional symptoms of FXS, on the other hand, are likely to involve the amygdala. Unfortunately, little is known about how exactly FXS affects synaptic function in the amygdala. Here, using whole-cell recordings in brain slices from adult Fmr1 knockout mice, we find mGluR-dependent long-term potentiation to be impaired at thalamic inputs to principal neurons in the lateral amygdala. Consistent with this long-term potentiation deficit, surface expression of the AMPA receptor subunit, GluR1, is reduced in the lateral amygdala of knockout mice. In addition to these postsynaptic deficits, lower presynaptic release was manifested by a decrease in the frequency of spontaneous miniature excitatory postsynaptic currents (mEPSCs), increased paired-pulse ratio, and slower use-dependent block of NMDA receptor currents. Strikingly, pharmacological inactivation of mGluR5 with 2-methyl-6-phenylethynyl-pyridine (MPEP) fails to rescue either the deficit in long-term potentiation or surface GluR1. However, the same acute MPEP treatment reverses the decrease in mEPSC frequency, a finding of potential therapeutic relevance. Therefore, our results suggest that synaptic defects in the amygdala of knockout mice are still amenable to pharmacological interventions against mGluR5, albeit in a manner not envisioned in the original hippocampal framework.

Effect of cessation of tobacco use on the incidence of oral mucosal lesions in a 10-yr follow-up study of 12,212 users.

Abstract: OBJECTIVE: To study the effect of cessation of tobacco use on the incidence of lichen planus, leukoplakia and other oral mucosal lesions. DESIGN: A 10–yr cohort study in a rural population of Ernakulam district, Kerala, India. MATERIAL AND METHODS: Some 12 212 tobacco users were interviewed and examined in a basetine survey and re-examined annually for 10 years. At each examination they were exposed to health educational programs to encourage them to quit their tobacco use. The incidence rates were calculated using person-years method among those who stopped their tobacco use and all others. RESULTS: A total of 77 681 person-years of observation accrued among men and 32 544 among women. Among men 6.5% of these and among women 14.4% were in the stopped category. The incidence of oral lichen planus did not show any consistent association with cessation of tobacco habits (incidence ratio I.35) but for leukoplakia there was a substantial drop in the incidence after cessation (incidence ratio 0.3I). Several other tobacco-associated oral mucosal lesions such as oral lichen planus-like lesion, smoker's palate, preteukoplakia, central papillary atrophy of the tongue and leukoedema showed either zero, or very small incidence, after cessation. CONCLUSION: The reported association between tobacco use and lichen planus appears to be indirect but for all other lesions it is direct. The cessation of tobacco use led to a substantial fall in the incidence of leukoplakia and other lesions implying a reduced risk for oral cancer after cessation of tobacco use.

Phases of large N vector Chern-Simons theories on S 2 × S 1

Abstract: We study the thermal partition function of level k U(N) Chern-Simons theories on S 2 interacting with matter in the fundamental representation. We work in the ’t Hooft limit, $ N,k\to \infty $ , with $ \lambda ={N \left/ {k} \right.} $ and $ \frac{{{T^2}{V_2}}}{N} $ held fixed where T is the temperature and V 2 the volume of the sphere. An effective action proposed in arXiv:1211.4843 relates the partition function to the expectation value of a ‘potential’ function of the S1 holonomy in pure Chern-Simons theory; in several examples we compute the holonomy potential as a function of λ. We use level-rank duality of pure Chern-Simons theory to demonstrate the equality of thermal partition functions of previously conjectured dual pairs of theories as a function of the temperature. We reduce the partition function to a matrix integral over holonomies. The summation over flux sectors quantizes the eigenvalues of this matrix in units of $ \frac{{2\pi }}{k} $ and the eigenvalue density of the holonomy matrix is bounded from above by $ \frac{1}{{2\pi \lambda }} $ . The corresponding matrix integrals generically undergo two phase transitions as a function of temperature. For several Chern-Simons matter theories we are able to exactly solve the relevant matrix models in the low temperature phase, and determine the phase transition temperature as a function of λ. At low temperatures our partition function smoothly matches onto the N and λ independent free energy of a gas of non renormalized multi trace operators. We also find an exact solution to a simple toy matrix model; the large N Gross-Witten-Wadia matrix integral subject to an upper bound on eigenvalue density.