Canavan disease

Canavan disease (CD) is an autosomal recessive disorder, characterized by spongiform degeneration of the white matter of the brain. Aspartoacylase (ASPA) hydrolyses N-acetylaspartic acid to aspartate and acetate. Mutation of the gene results in enzyme deficiency to result CD. The clinical features seen in the disease are head lag, macrocephaly, hypotonia and mental retardation. More than forty five mutations have been identified in the ASPA gene. Pathophysiological abnormalities seen in CD is likely due to abnormal metabolic levels of NAA, aspartate, acetate, aspartate aminotransferase, glutamate, glutamate dehydrogenase, g-aminobutyric acid, and ketoglutarate dehydrogenase complex. These pathways are useful to understand possible therapeutical targets and pharmacological manipulations in CD

Exactly solvable Kitaev model in three dimensions

We introduce a spin-1/2 model in three dimensions which is a generalization of the well-known Kitaev model on a honeycomb lattice. Following Kitaev, we solve the model exactly by mapping it to a theory of non-interacting fermions in the background of a static Z_2 gauge field. The phase diagram consists of a gapped phase and a gapless one, similar to the two-dimensional case. Interestingly, unlike in the two-dimensional model, in the gapless phase the gap vanishes on a contour in the k space. Furthermore, we show that the flux excitations of the gauge field, due to some local constraints, form loop like structures; such loops exist on a lattice formed by the plaquettes in the original lattice and is topologically equivalent to the pyrochlore lattice. Finally, we derive a low-energy effective Hamiltonian that can be used to study the properties of the excitations in the gapped phase.Comment: 9 pages, 7 figures; published version; a new section and more references adde

Gapless points of dimerized quantum spin chains: analytical and numerical studies

We study the locations of the gapless points which occur for quantum spin chains of finite length (with a twisted boundary condition) at particular values of the nearest neighbor dimerization, as a function of the spin S and the number of sites. For strong dimerization and large values of S, a tunneling calculation reproduces the same results as those obtained from more involved field theoretic methods using the non-linear sigma-model approach. A different analytical calculation of the matrix element between the two Neel states gives a set of gapless points; for strong dimerization, these differ significantly from the tunneling values. Finally, the exact diagonalization method for a finite number of sites yields a set of gapless points which are in good agreement with the Neel state calculations for all values of the dimerization, but the agreement with the tunneling values is not very good even for large S. This raises questions about possible corrections to the tunneling results.Comment: Revtex4, 10 pages including 5 figure

Development of a scalable generic platform for adaptive optics real time control

The main objective of the present project is to explore the viability of an adaptive optics control system based exclusively on Field Programmable Gate Arrays (FPGAs), making strong use of their parallel processing capability. In an Adaptive Optics (AO) system, the generation of the Deformable Mirror (DM) control voltages from the Wavefront Sensor (WFS) measurements is usually through the multiplication of the wavefront slopes with a predetermined reconstructor matrix. The ability to access several hundred hard multipliers and memories concurrently in an FPGA allows performance far beyond that of a modern CPU or GPU for tasks with a well defined structure such as Adaptive Optics control. The target of the current project is to generate a signal for a real time wavefront correction, from the signals coming from a Wavefront Sensor, wherein the system would be flexible to accommodate all the current Wavefront Sensing techniques and also the different methods which are used for wavefront compensation. The system should also accommodate for different data transmission protocols (like Ethernet, USB, IEEE 1394 etc.) for transmitting data to and from the FPGA device, thus providing a more flexible platform for Adaptive Optics control. Preliminary simulation results for the formulation of the platform, and a design of a fully scalable slope computer is presented.Comment: Paper presented as part of SPIE ICOP 2015 Conference Proceeding

Gender and innovation processes in integrated fish agri-food systems in Bangladesh and the Philippines: Insights from the CGIAR Research Program on FISH

This FISH report provides insights on the interactions between gender norms, agency, and innovation in fish agri-food systems