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.

Ring-diagram analysis of the structure of solar active regions

Abstract: We measure differences in structure between active and quiet regions of the Sun using the frequencies of high-degree modes determined from ring-diagram analyses. We find that both the speed of sound and the adiabatic index Γ1 differ in active regions as compared with quiet regions. In the immediate subsurface layers, the sound speed is lower in active regions, but below a depth of about 7 Mm the opposite is true. A comparison of sound-speed inversion results with those for Γ1 indicates that at least a part of the differences between active and quiet regions is likely to be due to the structural and thermal perturbations caused by magnetic fields in the active region.

Miro clusters regulate ER-mitochondria contact sites and link cristae organization to the mitochondrial transport machinery.

Abstract: Mitochondrial Rho (Miro) GTPases localize to the outer mitochondrial membrane and are essential machinery for the regulated trafficking of mitochondria to defined subcellular locations. However, their sub-mitochondrial localization and relationship with other critical mitochondrial complexes remains poorly understood. Here, using super-resolution fluorescence microscopy, we report that Miro proteins form nanometer-sized clusters along the mitochondrial outer membrane in association with the Mitochondrial Contact Site and Cristae Organizing System (MICOS). Using knockout mouse embryonic fibroblasts we show that Miro1 and Miro2 are required for normal mitochondrial cristae architecture and Endoplasmic Reticulum-Mitochondria Contacts Sites (ERMCS). Further, we show that Miro couples MICOS to TRAK motor protein adaptors to ensure the concerted transport of the two mitochondrial membranes and the correct distribution of cristae on the mitochondrial membrane. The Miro nanoscale organization, association with MICOS complex and regulation of ERMCS reveal new levels of control of the Miro GTPases on mitochondrial functionality. Mitochondrial cristae organization and ER-mitochondria contact sites are critical structures for cellular function. Here, the authors use super-resolution microscopy to show that Miro GTPases form clusters required for normal ER-mitochondria contact sites formation and to link cristae organization to the mitochondrial transport machinery.

Broadband parametric amplification with impedance engineering: Beyond the gain-bandwidth product

Abstract: We present an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product. We achieve this by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a $\lambda/2$ transformer. Our theoretical model predicts an extremely flat gain profile with a bandwidth enhancement proportional to the square root of amplitude gain. We experimentally demonstrate a nearly flat 20 dB gain over a 640 MHz band, along with a mean 1-dB compression point of -110 dBm and near quantum-limited noise. The results are in good agreement with our theoretical model.

Search for the X(4140) state in B+→J/ψϕK+ decays with the D0 detector

Abstract: We investigate the decay B+ -> J/psi phi K+ in a search for the X(4140) state, a narrow threshold resonance in the J/psi phi system. The data sample corresponds to an integrated luminosity of 10.4 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. We observe a mass peak with a statistical significance of 3.1 standard deviations and measure its invariant mass to be M = 4159.0 +/- 4.3(stat) +/- 6.6(syst) MeV and its width to be Gamma = 19.9 +/- 12.6(stat)(-8.0)(+3.0)(syst) MeV.

Phase diagram of the strongly disordered s -wave superconductor NbN close to the metal-insulator transition

Abstract: We present a phase diagram as a function of disorder in three-dimensional NbN thin films as the system enters the critical disorder for destruction of the superconducting state. The superconducting state is investigated using a combination of magnetotransport and scanning tunneling spectroscopy measurements. Our studies reveal three disorder regimes. At low disorder (${k}_{F}l$ \ensuremath{\sim} 10--4), the system follows the mean field Bardeen-Cooper-Schrieffer behavior, where the superconducting energy gap vanishes at the temperature at which electrical resistance appears. For stronger disorder ($1l{k}_{F}l$ 4), a ``pseudogap'' state emerges, where a gap in the electronic spectrum persists up to temperatures much higher than ${T}_{c}$, suggesting that Cooper pairs continue to exist in the system even after the zero resistance state is destroyed. Finally, at even stronger disorder (${k}_{F}l$ 1), the global superconducting ground state is destroyed even though superconducting correlations continue to survive, as evidenced from a pronounced magnetoresistance peak at low temperatures.