In vitro activities of small peptides from snake venom against clinical isolates of drug-resistant Mycobacterium tuberculosis

The recent re-emergence of tuberculosis, especially the multidrug-resistant cases, has highlighted the importance of screening effective novel drugs against Mycobacterium tuberculosis. In this study, the in vitro activities of small peptides isolated from snake venom were investigated against multidrug-resistant M. tuberculosis. Minimum inhibitory concentrations (MICs) were determined by the Bactec TB-460 radiometric method. A small peptide with the amino acid sequence ECYRKSDIVTCEPWQKFCYREVTFFPNHPVYLSGCASECTETNSKWCCTTDKCNRARGG (designated as vgf-1) from Naja atra (isolated from Yunnan province of China) venom had in vitro activity against clinically isolated multidrug-resistant strains of M. tuberculosis. The MIC was 8.5 mg/l. The antimycobacterial domain of this 60aa peptide is under investigation. (C) 2003 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved.

Graphene-passivated nickel as an oxidation-resistant electrode for spintronics.

We report on graphene-passivated ferromagnetic electrodes (GPFE) for spin devices. GPFE are shown to act as spin-polarized oxidation-resistant electrodes. The direct coating of nickel with few layer graphene through a readily scalable chemical vapor deposition (CVD) process allows the preservation of an unoxidized nickel surface upon air exposure. Fabrication and measurement of complete reference tunneling spin valve structures demonstrate that the GPFE is maintained as a spin polarizer and also that the presence of the graphene coating leads to a specific sign reversal of the magneto-resistance. Hence, this work highlights a novel oxidation-resistant spin source which further unlocks low cost wet chemistry processes for spintronics devices.

Light absorption and electrical transport in Si:O alloys for photovoltaics

Thin films (100-500 nm) of the Si:O alloy have been systematically characterized in the optical absorption and electrical transport behavior, by varying the Si content from 43 up to 100 at. %. Magnetron sputtering or plasma enhanced chemical vapor deposition have been used for the Si:O alloy deposition, followed by annealing up to 1250 °C. Boron implantation (30 keV, 3-30× 1014 B/cm2) on selected samples was performed to vary the electrical sheet resistance measured by the four-point collinear probe method. Transmittance and reflectance spectra have been extracted and combined to estimate the absorption spectra and the optical band gap, by means of the Tauc analysis. Raman spectroscopy was also employed to follow the amorphous-crystalline (a-c) transition of the Si domains contained in the Si:O films. The optical absorption and the electrical transport of Si:O films can be continuously and independently modulated by acting on different parameters. The light absorption increases (by one decade) with the Si content in the 43-100 at. % range, determining an optical band gap which can be continuously modulated into the 2.6-1.6 eV range, respectively. The a-c phase transition in Si:O films, causing a significant reduction in the absorption coefficient, occurs at increasing temperatures (from 600 to 1100 °C) as the Si content decreases. The electrical resistivity of Si:O films can be varied among five decades, being essentially dominated by the number of Si grains and by the doping. Si:O alloys with Si content in the 60-90 at. % range (named oxygen rich silicon films), are proved to join an appealing optical gap with a viable conductivity, being a good candidate for increasing the conversion efficiency of thin-film photovoltaic cell. © 2010 American Institute of Physics.

The potential use of 241Am as proliferation resistant burnable poison in PWRs

This paper discusses the use of 241Am as proliferation resistant burnable poison for light water reactors. Homogeneous addition of small (as little as 0.12%) amounts of 241Am to the conventional light water reactor fuel results in significant increase in 238Pu/Pu ratio in the discharged fuel improving its proliferation resistance. Moreover, 241Am, admixed to the fuel, acts as burnable absorber allowing for substantial reduction in conventional reactivity control means without a notable fuel cycle length penalty. This is possible due to favorable characteristics of 241Am transmutation chain. The fuel cycle length penalty of introducing 241Am into the core is evaluated and discussed, as well as the impact of He production in the fuel pins and degradation of reactivity feedback coefficients. Proliferation resistance and reactivity control features related to the use of 241Am are compared to those of using 237Np, which has also been suggested as an additive to the conventional fuel in order to improve its proliferation resistance. It was found that 241Am admixture is more favorable than 237Np admixture because of the smaller fuel cycle length penalty and higher burnable poison savings. Addition of either 237Np or 241Am would provide substantial but not ultimate protection from misuse of Pu originating in the spent fuel from the commercial power reactors. Therefore, the benefits from application of the concept would have to be carefully evaluated against the additional costs and proliferation risks associated with manufacturing of 237Np or 241Am doped fuel. Although this work concerns specifically with PWRs, the conclusions could also be applied to BWRs and, to some extent, to other thermal spectrum reactor types. © 2009 Elsevier Ltd. All rights reserved.

The potential use of 241Am as proliferation resistant burnable poison

This paper discusses the use of 141Am as proliferation resistant burnable poison for light water reactors. Homogeneous addition of small (less than 1 %) amounts of 241Am to the conventional LWR fuel results in significant increase in 238Pu/Pu ratio in the discharged fuel improving its proliferation resistance. Moreover, 241Am, admixed to the fuel, acts as burnable absorber allowing for substantial reduction in conventional reactivity control means without notable fuel cycle length penalty. This is possible due to favourable characteristics of 241Am transmutation chain. The fuel cycle length penalty of introducing 241Am into the core is evaluated and discussed, as well as the impact of He production in the fuel pins and degradation of reactivity feedback coefficients. Proliferation resistance and reactivity control features related to the use of 241Am are compared to those of using 237Np, which has also been suggested as an additive to the conventional fuel in order to improve its proliferation resistance. It was found that 241Am admixture is more favourable than 237Np admixture because of the smaller fuel cycle length penalty and higher burnable poison savings.