Quantum Antiferromagnetism in Quasicrystals

The antiferromagnetic Heisenberg model is studied on a two-dimensional bipartite quasiperiodic lattice. The distribution of local staggered magnetic moments is determined on finite square approximants with up to 1393 sites, using the Stochastic Series Expansion Quantum Monte Carlo method. A non-trivial inhomogeneous ground state is found. For a given local coordination number, the values of the magnetic moments are spread out, reflecting the fact that no two sites in a quasicrystal are identical. A hierarchical structure in the values of the moments is observed which arises from the self-similarity of the quasiperiodic lattice. Furthermore, the computed spin structure factor shows antiferromagnetic modulations that can be measured in neutron scattering and nuclear magnetic resonance experiments. This generic model is a first step towards understanding magnetic quasicrystals such as the recently discovered Zn-Mg-Ho icosahedral structure.Comment: RevTex, 4 pages with 5 figure

Penrose Quantum Antiferromagnet

The Penrose tiling is a perfectly ordered two dimensional structure with fivefold symmetry and scale invariance under site decimation. Quantum spin models on such a system can be expected to differ significantly from more conventional structures as a result of its special symmetries. In one dimension, for example, aperiodicity can result in distinctive quantum entanglement properties. In this work, we study ground state properties of the spin-1/2 Heisenberg antiferromagnet on the Penrose tiling, a model that could also be pertinent for certain three dimensional antiferromagnetic quasicrystals. We show, using spin wave theory and quantum Monte Carlo simulation, that the local staggered magnetizations strongly depend on the local coordination number z and are minimized on some sites of five-fold symmetry. We present a simple explanation for this behavior in terms of Heisenberg stars. Finally we show how best to represent this complex inhomogeneous ground state, using the "perpendicular space" representation of the tiling.Comment: 4 pages, 5 figure

In vitro drug screening system using membrane alteration in macrophages by Mycobacterium leprae

The observation that live Mycobacterium leprae on entry into macrophages from lepromatous leprosy patients reduced the number of EA rosetting macrophages, was extended to macrophages from Swiss white mice also. Further, the fact that dead Mycobacterium leprae do not bring about such a change in macrophages from mice, allowed us to develop this into a bacterial viability testing system. Thus drug treated macrophages in the presence of Mycobacterium leprae showed normal rosetting ability if Mycobacterium leprae are inactivated by the drug, but showed reduced level of rosetting when bacteria were not susceptible to the drug. It was shown that a drug like dapsone, does act on Mycobacterium leprae based on its permeability, quantity available inside the macrophages and inhibition of its action by Para amino benzoic acid. The inactivation of Mycobacterium leprae by sulphone and rifampicin was also proved by the flourescence diacetate method, which showed poorly viable bacteria after exposure to drugs. Thus it has been possible to develop a rapid drug screening method for testing the activity of unknown compound against Mycobacterium leprae

A single base deletion in the SLC45A2 gene in a Bullmastiff with oculocutaneous albinism.

Oculocutaneous albinism type 4 (OCA4) in humans and similar phenotypes in many animal species are caused by variants in the SLC45A2 gene, encoding a putative sugar transporter. In dog, two independent SLC45A2 variants are known that cause oculocutaneous albinism in Doberman Pinschers and several small dog breeds respectively. For the present study, we investigated a Bullmastiff with oculocutaneous albinism. The affected dog was highly inbred and resulted from the mating of a sire to its own grandmother. We obtained whole genome sequence data from the affected dog and searched specifically for variants in candidate genes known to cause albinism. We detected a single base deletion in exon 6 of the SLC45A2 gene (NM_001037947.1:c.1287delC) that has not been reported thus far. This deletion is predicted to result in an early premature stop codon. It was confirmed by Sanger sequencing and perfectly co-segregated with the phenotype in the available family members. We genotyped 174 unrelated dogs from diverse breeds, all of which were homozygous wildtype. We therefore suggest that SLC45A2:c.1287delC causes the observed oculocutaneous albinism in the affected Bullmastiff

A renormalisation approach to excitable reaction-diffusion waves in fractal media

Of fundamental importance to wave propagation in a wide range of physical phenomena is the structural geometry of the supporting medium. Recently, there have been several investigations on wave propagation in fractal media. We present here a renormalization approach to the study of reaction-diffusion (RD) wave propagation on finitely ramified fractal structures. In particular we will study a Rinzel-Keller (RK) type model, supporting travelling waves on a Sierpinski gasket (SG), lattice

LITERATURE IN THE FIELD OF SPINAL CORD INJURY: AN ANALYSIS

ABSTRACT: Presents an analysis of the literature in the field of Spinal Cord Injury as indexed the MEDLINE database in the Pubmed for the period 2008 to the 2017. It is noticed that the total of 28303 records on the literature of Spinal Cord Injury is covered. It is also noticed that the maximum number of records was published during year 2017. It was observed that the Journal Article consists of 41.73% and other publication types with different percentages. English language forming 95.07% of the total and other languages follows with minimum records. The United States has contributed the highest number of records in the study. 29 primary journals grouped in zone-1 published 3941 journal articles, the second zone comprises of 238 journals published 4031 journal articles and 1790 journals grouped in the third zone published 3840 journal articles. Of the 29 Journals in zone-1, twelve journals are published in the United States and followed by other countries. In zone-1 & 2; out of 267 journals, 37.45% frequently cited journals are the United States and India contributed eight journals

Quantum Spins and Quasiperiodicity: a real space renormalization group approach

We study the antiferromagnetic spin-1/2 Heisenberg model on a two-dimensional bipartite quasiperiodic structure, the octagonal tiling -- the aperiodic equivalent of the square lattice for periodic systems. An approximate block spin renormalization scheme is described for this problem. The ground state energy and local staggered magnetizations for this system are calculated, and compared with the results of a recent Quantum Monte Carlo calculation for the tiling. It is conjectured that the ground state energy is exactly equal to that of the quantum antiferromagnet on the square lattice.Comment: To appear in Physical Review Letter