Evaluation of the BACTEC radiometric method in the early diagnosis of tuberculosis

A comparison of the BACTEC radiometric method with the conventional culture and drug susceptibility testing methods on isolates from clinical specimens in pulmonary and extrapulmonary tuberculosis, childhood TB and TB in HIV-infected individuals was undertaken. In the case of pulmonary TB, the rate of isolation of positive cultures was significantly faster with the BACTEC method, with 87 per cent of the positives being obtained by 7 days, and 96 per cent by 14 days. However, while there was no difference in the total number of positive cultures by the two methods in smear positive pulmonary tuberculosis, in smear negative pulmonary TB, the BACTEC method yielded more number of positive cultures. In extrapulmonary TB, HIV-TB and childhood TB, although the BACTEC method did not yield additional positives, the detection of positives was considerably faster than by the conventional methods, in which the degree of growth was also scanty. The agreement in drug susceptibility tests was 94 per cent for streptomycin and isoniazid, 99 per cent for rifampicin and 91 per cent for ethambutol. Further, most of the drug susceptibility test results became available within 8 days by the BACTEC method. By facilitating early diagnosis, the BACTEC method may prove to be cost effective in a population with a high prevalence of tuberculosis, particularly in the extrapulmonary and paucibacillary forms of the disease

A Generative-Discriminative Basis Learning Framework to Predict Clinical Severity from Resting State Functional MRI Data

We propose a matrix factorization technique that decomposes the resting state fMRI (rs-fMRI) correlation matrices for a patient population into a sparse set of representative subnetworks, as modeled by rank one outer products. The subnetworks are combined using patient specific non-negative coefficients; these coefficients are also used to model, and subsequently predict the clinical severity of a given patient via a linear regression. Our generative-discriminative framework is able to exploit the structure of rs-fMRI correlation matrices to capture group level effects, while simultaneously accounting for patient variability. We employ ten fold cross validation to demonstrate the predictive power of our model on a cohort of fifty eight patients diagnosed with Autism Spectrum Disorder. Our method outperforms classical semi-supervised frameworks, which perform dimensionality reduction on the correlation features followed by non-linear regression to predict the clinical scores

Quasi-equilibrium optical nonlinearities in spin-polarized GaAs

Semiconductor Bloch equations, which microscopically describe the dynamics of a Coulomb interacting, spin-unpolarized electron-hole plasma, can be solved in two limits: the coherent and the quasi-equilibrium regime. These equations have been recently extended to include the spin degree of freedom, and used to explain spin dynamics in the coherent regime. In the quasi-equilibrium limit, one solves the Bethe-Salpeter equation in a two-band model to describe how optical absorption is affected by Coulomb interactions within a spin-unpolarized plasma of arbitrary density. In this work, we modified the solution of the Bethe-Salpeter equation to include spin-polarization and light holes in a three-band model, which allowed us to account for spin-polarized versions of many-body effects in absorption. The calculated absorption reproduced the spin-dependent, density-dependent and spectral trends observed in bulk GaAs at room temperature, in a recent pump-probe experiment with circularly polarized light. Hence our results may be useful in the microscopic modelling of density-dependent optical nonlinearities in spin-polarized semiconductors.Comment: 7 pages, 6 figure

Near-IR studies of recurrent nova V745 Scorpii during its 2014 outburst

The recurrent nova (RN) V745 Scorpii underwent its third known outburst on 2014 February 6. Infrared monitoring of the eruption on an almost daily basis, starting from 1.3d after discovery, shows the emergence of a powerful blast wave generated by the high velocity nova ejecta exceeding 4000 kms$^{-1}$ plowing into its surrounding environment. The temperature of the shocked gas is raised to a high value exceeding 10$^{8}$K immediately after outburst commencement. The energetics of the outburst clearly surpass those of similar symbiotic systems like RS Oph and V407 Cyg which have giant secondaries. The shock does not show a free-expansion stage but rather shows a decelerative Sedov-Taylor phase from the beginning. Such strong shockfronts are known to be sites for $\gamma$ ray generation. V745 Sco is the latest nova, apart from five other known novae, to show $\gamma$ ray emission. It may be an important testbed to resolve the crucial question whether all novae are generically $\gamma$ ray emitters by virtue of having a circumbinary reservoir of material that is shocked by the ejecta rather than $\gamma$ ray generation being restricted to only symbiotic systems with a shocked red giant (RG) wind. The lack of a free-expansion stage favors V745 Sco to have a density enhancement around the white dwarf (WD), above that contributed by a RG wind. Our analysis also suggests that the WD in V745 Sco is very massive and a potential progenitor for a future SN Ia explosion.Comment: To appear in ApJ (Letters