Optical Properties of GaSb Nanofibers

Amorphous GaSb nanofibers were obtained by ion beam irradiation of bulk GaSb single-crystal wafers, resulting in fibers with diameters of ~20 nm. The Raman spectra and photoluminescence (PL) of the ion irradiation-induced nanofibers before and after annealing were studied. Results show that the Raman intensity of the GaSb LO phonon mode decreased after ion beam irradiation as a result of the formation of the amorphous nanofibers. A new mode is observed at ~155 cm-1 both from the unannealed and annealed GaSb nanofiber samples related to the A1g mode of Sb–Sb bond vibration. Room temperature PL measurements of the annealed nanofibers present a wide feature band at ~1.4–1.6 eV. The room temperature PL properties of the irradiated samples presents a large blue shift compared to bulk GaSb. Annealed nanofibers and annealed nanofibers with Au nanodots present two different PL peaks (400 and 540 nm), both of which may originate from Ga or O vacancies in GaO. The enhanced PL and new band characteristics in nanostructured GaSb suggest that the nanostructured fibers may have unique applications in optoelectronic devices

Rapid Diagnosis of Tuberculosis with the Xpert MTB/RIF Assay in High Burden Countries: A Cost-Effectiveness Analysis

A cost-effectiveness study by Frank Cobelens and colleagues reveals that Xpert MTB/RIF is a cost-effective method of tuberculosis diagnosis that is suitable for use in low- and middle-income settings

Effect of Standard Tuberculosis Treatment on Plasma Cytokine Levels in Patients with Active Pulmonary Tuberculosis

CITATION: Riou, C. et al. 2012. Effect of standard tuberculosis treatment on plasma cytokine levels in patients with active pulmonary tuberculosis. PLoS ONE, 7(5): e36886, doi:10.1371/journal.pone.0036886.The original publication is available at http://journals.plos.org/plosoneBackground: Sputum Mycobacterium tuberculosis (Mtb) culture is commonly used to assess response to antibiotic treatment in individuals with pulmonary tuberculosis (TB). Such techniques are constrained by the slow growth rate of Mtb, and more sensitive methods to monitor Mtb clearance are needed. The goal of this study was to evaluate changes in plasma cytokines in patients undergoing treatment for TB as a means of identifying candidate host markers associated with microbiologic response to therapy. Methods: Twenty-four plasma cytokines/chemokines were measured in 42 individuals diagnosed with active pulmonary TB, 52% were HIV co-infected. Individuals, undergoing a 26-week standard TB treatment, were followed longitudinally over 18 months and measurements were associated with HIV status and rates of sputum culture conversion. Results: Plasma concentrations of interferon-inducible protein-10 (IP-10) and vascular endothelial growth factor (VEGF) were significantly reduced upon TB treatment, regardless of HIV status. By the end of treatment, IP-10 concentrations were significantly lower in HIV negative individuals when compared to HIV-positive individuals (p = 0.02). Moreover, in HIV negative patients, plasma VEGF concentrations, measured as early as 2-weeks post TB treatment initiation, positively correlated with the time of sputum conversion (p = 0.0017). No significant changes were observed in other studied immune mediators. Conclusions: These data suggest that VEGF plasma concentration, measured during early TB treatment, could represent a surrogate marker to monitor sputum culture conversion in HIV uninfected individuals.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036886Publisher's versio

The effect of carbohydrate availability following exercise on whole-body insulin action

One bout of exercise enhances insulin-stimulated glucose uptake (insulin action), but the effect is blunted by consumption of carbohydrate-containing food after exercise. The independent roles of energy and carbohydrate in mediating post-exercise insulin action have not been systematically evaluated in humans. The purpose of this study was to determine if varying carbohydrate availability, with energy intake held constant, mediates post-exercise insulin action. Ten young (21 +/- 2 y, overweight (body fat 37% +/- 3%) men and women completed 3 conditions in random order: (i) no-exercise (BASE), (ii) exercise with energy balance but carbohydrate deficit (C-DEF), and (iii) exercise with energy and carbohydrate balance (C-BAL). In the exercise conditions, subjects expended 30% of total daily energy expenditure on a cycle ergometer at 70% VO2 peak. Following exercise, subjects consumed a meal that replaced expended energy (~3000 kJ) and was either balanced (intake = expenditure) or deficient (-100 g) in carbohydrate. Twelve hours later, insulin action was measured by continuous infusion of glucose with stable isotope tracer (CIG-SIT). Changes in insulin action were evaluated using a one-way ANOVA with repeated measures. During CIG-SIT, non-oxidative glucose disposal (i.e., glucose storage) was higher in C-DEF than in BASE (27.2 +/- 3.2 vs. 16.9 +/- 3.5 micromol.L-1.kg-1.min-1, p \u3c 0.05). Conversely, glucose oxidation was lower in C-DEF (8.6 +/- 1.3 micromol.L-1.kg-1.min-1) compared with C-BAL (12.2 +/- 1.2 micromol.L-1.kg-1.min-1), and BASE (17.1 +/- 2.2 micromol.L-1.kg-1.min-1), p \u3c 0.05). Fasting fat oxidation was higher in C-DEF than in BASE (109.8 +/- 10.5 vs. 80.7 +/- 9.6 mg.min-1, p \u3c 0.05). In C-DEF, enhanced insulin action was correlated with the magnitude of the carbohydrate deficit (r = 0.82, p \u3c 0.01). Following exercise, re-feeding expended energy, but not carbohydrate, increased fasting fat oxidation, and shifted insulin-mediated glucose disposal toward increased storage and away from oxidation

Effect of timing of energy and carbohydrate replacement on post-exercise insulin action

The nutritional environment surrounding an exercise bout modulates post-exercise insulin action. The purpose of this study was to determine how timing energy and carbohydrate replacement proximate to an exercise bout influences exercise-enhanced insulin action. To create an appropriate baseline, sensitivity to insulin was reduced in 9 healthy young men (n=6) and women (n=3) by 2 days of energy surplus and detraining. Then, insulin action (glucose uptake per unit plasma insulin) was assessed by stable isotope dilution during a continuous glucose infusion 12 h after a standardized meal under 4 conditions. In 3 conditions, the meal replaced the energy and carbohydrate expended during an exercise bout (62.9+/-2.8 min cycle ergometry at 65% VO2 peak followed by ten 30 s sprints). The meal was given before (Pre), immediately after (ImmPost), or 3 h after exercise (Delay). The 4th condition was a no-exercise control (Control). Data were analyzed using linear mixed-effects models with planned contrasts. Relative to Control, insulin action increased by 22% in Pre (p=0.05), 44% in ImmPost (p\u3c0.01), and 19% in Delay (p=0.09). Non-oxidative disposal was higher, and oxidative disposal was lower in ImmPost relative to Control and Pre (p\u3c0.05). Hepatic glucose production was suppressed by the infusion to a greater extent in Pre and Delay (76.9%+/-8.8% and 81.2%+/-4.7%) compared with ImmPost (64.7%+/-10.0%). A bout of exercise enhances insulin action even when expended energy and carbohydrate are replaced. Further, timing of energy and carbohydrate consumption subtly modulates the effectiveness of exercise to enhance insulin action