Fast Stochastic Hierarchical Bayesian MAP for Tomographic Imaging

Any image recovery algorithm attempts to achieve the highest quality reconstruction in a timely manner. The former can be achieved in several ways, among which are by incorporating Bayesian priors that exploit natural image tendencies to cue in on relevant phenomena. The Hierarchical Bayesian MAP (HB-MAP) is one such approach which is known to produce compelling results albeit at a substantial computational cost. We look to provide further analysis and insights into what makes the HB-MAP work. While retaining the proficient nature of HB-MAP's Type-I estimation, we propose a stochastic approximation-based approach to Type-II estimation. The resulting algorithm, fast stochastic HB-MAP (fsHBMAP), takes dramatically fewer operations while retaining high reconstruction quality. We employ our fsHBMAP scheme towards the problem of tomographic imaging and demonstrate that fsHBMAP furnishes promising results when compared to many competing methods.Comment: 5 Pages, 4 Figures, Conference (Accepted to Asilomar 2017

Topological density wave states of non-zero angular momentum

The pseudogap state of high temperature superconductors is a profound mystery. It has tantalizing evidence of a number of broken symmetry states, not necessarily conventional charge and spin density waves. Here we explore a class of more exotic density wave states characterized by topological properties observed in recently discovered topological insulators. We suggest that these rich topological density wave states deserve closer attention in not only high temperature superconductors but in other correlated electron states, as in heavy fermions.Comment: Expanded version, 7 pages, 6 figure

Charge and spin collective modes in a quasi-1D model of Sr2RuO4

Given that Sr2RuO4 is a two-component p-wave superconductor, there exists the possibility of well defined collective modes corresponding to fluctuations of the relative phase and spin-orientation of the two components of the order parameter. We demonstrate that at temperatures much below Tc, these modes have energies small compared to the pairing gap scale if the superconductivity arises primarily from the quasi 1D (dxz and dyz) bands, while it is known that their energies become comparable to the pairing gap scale if there is a substantial involvement of the quasi 2D (dxy) band. Therefore, the orbital origin of the superconductivity can be determined by measuring the energies of these collective modes.Comment: 11 pages (6 pages for main text), 2 figure

The Sensitivity of the Southwest Monsoon Phytoplankton Bloom to Variations in Aeolian Iron Deposition over the Arabian Sea

[1] A coupled, 3-D biophysical ocean general circulation model is used to investigate how aeolian iron deposition affects the Arabian Sea ecosystem. Two separate aeolian iron deposition fields, derived from the GISS and GOCART atmospheric transport models, have been applied as surface boundary conditions. The model results exhibit widespread biogeochemical sensitivity to the choice of deposition field. With GOCART deposition, SW Monsoon phytoplankton blooms in the western and central Arabian Sea are enhanced and exhibit greater realism. The central Arabian Sea bloom is supported by supplemental input of horizontally advected iron from a pool that undergoes a yearlong progression that begins in the Gulf of Oman, where the difference in aeolian iron enrichment between the two deposition fields is most prevalent. The GOCART-enhanced blooms result in a more pronounced shift toward netplankton, an increase in euphotic zone export flux of up to a 20% during the SW Monsoon and an additional annual biogenic export of 3.5 TgC. The potential ramifications of regional N-cycle alteration through stimulation of N2-fixation that is promoted by significant aeolian mineral flux needs to be explored. The canonical thinking that the northern Arabian Sea is invariably iron replete is now being challenged by both our model results and recent observational studies. As well, our results indicate that Arabian Sea iron concentrations are strongly modulated by the specific nature of aeolian mineral deposition. Thus climate or land use influences on dust mobilization could exercise leading-order controls on regional biogeochemical variability, metabolic status and air-sea exchanges of CO2

Effect of iron on the growth and siderophore production of mycobacteria

To gain a better understanding of the role of iron in the pathogenesis of tuberculosis, the growth and production of siderophores were studied in the presence of different concentrations of free iron in vitro with M. smegmatis and virulent, avirulent and low virulent strains of M. tuberculosis. Increase in the concentrations of iron caused an appreciable increase in the growth (as assessed by cell dry-weight and log viable counts) of all 4 strains. This was, however accompanied by a significant decrease in the production of both exochelins and mycobactins, suggesting that these siderophores are necessary only under iron-deficient conditions. The growth and production of siderophores were significantly higher with the virulent strain of M.tuberculosis than with the avirulent (or) the low virulent strains

Effect of haemoglobin on the growth of mycobacteria and production of siderophores

Hemoglobin is known to support the growth of several bacterial species. The growth and the production of siderophores by 4 strains of mycobacteria in the presence of hemoglobin was studied in vitro. The findings were compared with those obtained in the presence of equivalent concentrations of iron in the medium. Increase in the concentrations of hemoglobin caused an appreciable increase in the growth of all 4 strains. This was however, accompanied by a significant decrease in the production of both exochelins and mycobactins. It was also observed that hemoglobin supported the growth of all strains as well as that with free iron and the concentrations of both siderophores was significantly higher in the presence of hemoglobin than in that of free iron

Effect of Anti-tuberculosis Drugs on the Iron- Sequestration Mechanisms of Mycobacteria

The effect of sub-lethal concent-rations of isoniazid, ethambutol, rifampicin and pyrazinamide on the growth in vitro and the production of both exochelins and mycobactins by the high virulent and the South Indian low virulent strains of M. tuberculosis was examined under iron-deficient and iron-rich conditions. There was a marked decrease in the growth of both strains in the presence of increasing concentrations of all four drugs, the inhibition being total in the presence of minimal inhibitory concentrations of the drugs. It was also observed that the growthinhibitory effect of all four drugs was slightly reversed in the presence of high concentration of iron in the medium. A significant increase was observed in the concentrations of both siderophores in the presence of all four drugs, under both iron-deficient (or) iron-rich conditions