4,293 research outputs found
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 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) have been extended to dipolar ordered states. The
experimental results for the component of the spin diffusion parallel with the
external field are cm/s for the
[001] direction and cm/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
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