Metal-insulator transition and electrically-driven memristive characteristics of SmNiO3 thin films

The correlated oxide SmNiO3 (SNO) exhibits an insulator to metal transition (MIT) at 130 {\deg}C in bulk form. We report on synthesis and electron transport in SNO films deposited on LaAlO3 (LAO) and Si single crystals. X-ray diffraction studies show that compressively strained single-phase SNO grows epitaxially on LAO while on Si, mixed oxide phases are observed. MIT is observed in resistance-temperature measurements in films grown on both substrates, with charge transport in-plane for LAO/SNO films and out-of-plane for Si/SNO films. Electrically-driven memristive behavior is realized in LAO/SNO films, suggesting that SNO may be relevant for neuromorphic devices

Simulations of Information Transport in Spin Chains

Transport of quantum information in linear spin chains has been the subject of much theoretical work. Experimental studies by nuclear spin systems in solid-state by NMR (a natural implementation of such models) is complicated since the dipolar Hamiltonian is not solely comprised of nearest-neighbor XY-Heisenberg couplings. We present here a similarity transformation between the XY-Heisenberg Hamiltonian and the grade raising Hamiltonian, an interaction which is achievable with the collective control provided by radio-frequency pulses in NMR. Not only does this second Hamiltonian allows us to simulate the information transport in a spin chain, but it also provides a means to observe its signature experimentally

Conductivity noise study of the insulator-metal transition and phase co-existence in epitaxial samarium nickelate thin films

Interaction between the lattice and the orbital degrees of freedom not only makes rare-earth nickelates unusually "bad metal", but also introduces a temperature driven insulator-metal phase transition. Here we investigate this insulator-metal phase transition in thin films of $\mathrm{SmNiO_3}$ using the slow time dependent fluctuations (noise) in resistivity. The normalized magnitude of noise is found to be extremely large, being nearly eight orders of magnitude higher than thin films of common disordered metallic systems, and indicates electrical conduction via classical percolation in a spatially inhomogeneous medium. The higher order statistics of the fluctuations indicate a strong non-Gaussian component of noise close to the transition, attributing the inhomogeneity to co-existence of the metallic and insulating phases. Our experiment offers a new insight on the impact of lattice-orbital coupling on the microscopic mechanism of electron transport in the rare-earth nickelates.Comment: 5 pages, 4 figure

Spin diffusion of correlated two-spin states in a dielectric crystal

Reciprocal space measurements of spin diffusion in a single crystal of calcium fluoride (CaF$_2$) have been extended to dipolar ordered states. The experimental results for the component of the spin diffusion parallel with the external field are $D_{D}^{||}=29 \pm 3 \times 10^{-12}$ cm$^{2}$/s for the [001] direction and $D_{D}^{||}=33 \pm 4 \times 10^{-12}$ cm$^{2}$/s for the [111] direction. The diffusion rates for dipolar order are significantly faster than those for Zeeman order and are considerably faster than predicted by simple theoretical models. It is suggested that constructive interference in the transport of the two spin state is responsible for this enhancement. As expected the anisotropy in the diffusion rates is observed to be significantly less for dipolar order compared to the Zeeman case.Comment: 4 pages, 2 figures. Resubmitted to PRL - new figure added / discussion expande

Studies on the immunopathology of tuberculosis

In this presentation, two aspects concerning the immunopathology of tuberculosis at the microanatomical level will be considered. The material for this presentation is drawn from our studies on tuberculous lymphadenitis (450 cases) and skin tuberculosis (270 cases). The first question to be considered is ‘when is it necessary to demonstrate the components of M.tuberculosis in the tissues?’ The second is the question of the involvement of humoral immune factors associated with some of the histological manifestations of tuberculosis

The pathophysiology of the complement system in leprosy

The complement system, which consists of a group of proteins and glycoproteins, generally serves to amplify the effects of the interaction of antigen with antibody. In addition, this system, independent of immune mechanisms, can initiate inflammatory responses and function as an important first line of defence. Furthermore, complement plays a cardinal role in metabolising antigen-antibody complexes. More recently, the immunomodulatory effects of several of its components are also being studied. It is currently held that the elimination of Mycobacterium leprae from the human host is mainly through the T-lymphocytes and macrophages and that the complement system is not involved in this process. Nevertheless, in view of the active interaction of M. leprae with the complement system and the form&on of large amounts of immune complexes(IC) in leprosy, the importance of this system in modulating certain immunopathogenetic phenomena is being recognized now. In this communication, the current state knowledge in this field will be reviewed and an attempt will be made to identify possible areas of future research where lacunae exist

Entropic Test of Quantum Contextuality

We study the contextuality of a three-level quantum system using classical conditional entropy of measurement outcomes. First, we analytically construct the minimal configuration of measurements required to reveal contextuality. Next, an entropic contextual inequality is formulated, analogous to the entropic Bell inequalities derived by Braunstein and Caves in [Phys. Rev. Lett. {\bf 61}, 662 (1988)], that must be satisfied by all non-contextual theories. We find optimal measurements for violation of this inequality. The approach is easily extendable to higher dimensional quantum systems and more measurements. Our theoretical findings can be verified in the laboratory with current technology.Comment: 4 pages, 4 figure