Synthesis and TL Characterization of Li2B4O7 Doped with Cooper and Manganese

Copper (Cu) and manganese (Mn) doped tissue equivalent Li2B4O7 were prepared by solid state sintering. The glow curves shows a high temperature peak at 222 °C for Li2B4O7:Cu and for Li2B4O7:Mn at 218 °C. Linear dose response is observed up to 140 Gy. With a thermal treatment at 125 °C, the first peak of the phosphors doped with copper (95 °C) and manganese (90 °C) disappears and the main TL peaks remain isolated. The dose rate dependence was studied by exposing the samples at doses of 25 Gy and 250 Gy. At low dose it was observed that the Li2B4O7:Cu TL response has non-dependence on dose rate, and at higher dose was observed that there is a dependence of the TL response with the different dose rateFil: Guarneros Aguilar, C.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; MéxicoFil: Cruz Zaragoza, E.. Universidad Nacional Autónoma de México. Instituto de Ciencias Nucleares. Unidad de Irradiación y Seguridad Radiológica; MicronesiaFil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Bs.as.. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; ArgentinaFil: Palomino Merino, R.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; MéxicoFil: Espinosa, J.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; Méxic

TES-8: Advanced Exo-Brake, VR and COM Experiments

The TES-8 was jettisoned from the International Space Station on January 31, 2019. As an orbital laboratory and 8th in on-going series, the design makes use of a standard set of interfaces and safety features that permit rapid re-flight. On this flight, an advanced Exo-Brake is flown with de-orbit targeting capability that will engender sample return capability from LEO platforms. A Virtual Reality data recording system uses stereo imaging and efficient data-compression with an NVIDIA GPU (Graphics Processing Unit) to permit compression and transmission of very large data files. An SDR (Software Defined Radio) will download data to the NEN (Near Earth Network) for the first time - demonstrating potential use in cis-lunar space using S-band. For the first time, a comparison will be made regarding the functionality of the Iridium and Globalstar short burst data modems - as essential communication tools for future nano-sat projects. Lastly, the 7 micro-processors and 4 cameras provide an excellent learning platform for university students and NASA young professionals

Modulated Exo-Brake Flight Testing - Modeling and Test Results - Successes with Exo-Brake Development and Targeting for Future Sample Return Capability: TES-6,7,8 Flight Experiments

No abstract availabl

Modeling the Exo-Brake and the Development of Strategies for De-Orbit Drag Modulation

The Exo-Brake is a simple, non-propulsive means of de-orbiting small payloads from orbital platforms such as the International Space Station (ISS). Two de-orbiting experiments with fixed surface area Exo-Brakes have been successfully conducted in the last two years on the TechEdSat-3 and -4 nano-satellite missions. The development of the free molecular flow aerodynamic data-base is presented in terms of angle of attack, projected front surface area variation, and altitude. Altitudes are considered ranging from the 400km ISS jettison altitude to 90km. Trajectory tools are then used to predict de-orbit/entry corridors with the inclusion of the key atmospheric and geomagnetic uncertainties. Control system strategies are discussed which will be applied to the next two planned TechEdSat-5 and -6 nano-satellite missions - thus increasing the targeting accuracy at the Von Karman altitude through the proposed drag modulation technique

TechEdSat-N and ETC Series

This presentation address the issues and how to involve students in the process of develping, building and certifying flight hardware for ISS and development of Mars missions

Influence of laser pulse regime on the structure and optical properties of TiO2 nanolayers

TiO2 films were deposited onto glass substrates by pulsed laser deposition (PLD) in high vacuum under monopulse and multipulse excitation. After deposition, a thermal treatment on air atmosphere was done to promote crystallization. Films were studied by x-ray diffraction, energy dispersive spectroscopy, scanning electron, atomic force microscopy, UV-vis spectroscopy, and ellipsometry. After air annealing, films gain a different amount of oxygen: TiO1.9 in multipulse regime versus TiO1.7 in the monopulse one. Splashing is observed in both regimes although in the multipulse mode greater particles are found, that derived in a less compact film after annealing which could be the cause of the better oxygen diffusion. The optical band gap of the film prepared with monopulse excitation is 3.09 eV. This value increased to 3.34 eV with annealing, corresponding to that of anatase. The film made with multipulses has an Eg = 3.12 eV which was invariant upon annealing. The difference in the properties of the films grown in the different regimes was attributed to the re-excitation of the plasma during the ablation process in the multipulse ablation that leads to an increased splashing density and thereafter a less compact film and the presence of off-stoichiometry inclusions within the film bulk.Fil: Peñaloza Mendoza, Y.. Instituto Politécnico Nacional; MéxicoFil: Alvira, Fernando Carlos. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Biomembranas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Caballero Briones, F.. Instituto Politécnico Nacional; MéxicoFil: Guarneros Aguilar, C.. Instituto Politécnico Nacional; MéxicoFil: Ponce, L.. Instituto Politécnico Nacional; Méxic

lambda bar minigene-mediated inhibition of protein synthesis involves accumulation of peptidyl-tRNA and starvation for tRNA.

Expression of the bacteriophage lambda two-codon, AUG AUA, barI minigene (bar+) leads to the arrest of protein synthesis in cells defective in peptidyl-tRNA hydrolase (Pth). It has been hypothesized that translation of the bar+ transcript provokes premature release and accumulation of peptidyl-tRNA (p-tRNA). Inhibition of protein synthesis would then result from either starvation of sequestered tRNA or from toxicity of accumulated p-tRNA. To test this hypothesis and to investigate the cause of arrest, we used a coupled in vitro transcription-translation system primed with DNA containing bar+ and the beta-lactamase-encoding gene of the vector as a reporter. The results show that expression of bar+ minigene severely inhibits beta-lactamase polypeptide synthesis by Pth-defective extracts and partially inhibits synthesis by wild-type extracts. Fractions enriched for Pth, or a homogeneous preparation of Pth, prevented and reversed bar+-mediated inhibition. A mutant minigene, barA702, which changes the second codon AUA (Ile) to AAA (Lys), was also toxic for Pth-defective cells. Expression of barA702 inhibited in vitro polypeptide synthesis by Pth-defective extracts and, as with bar+, exogenous Pth prevented inhibition. Addition of pure tRNALys prevented inhibition by barA702 but not by bar+. Expression of bar+ and barA702 led to release and accumulation of p-tRNAIle and p-tRNALys respectively but bar+ also induced accumulation of p-tRNALys. Finally, bar+ stimulated association of methionine with ribosomes probably as fMet-tRNAfMet and the accumulation of methionine and isoleucine in solution as peptidyl-tRNA (p-tRNA). These results indicate that minigene-mediated inhibition of protein synthesis involves premature release of p-tRNA, misincorporation of amino acyl-tRNA, accumulation of p-tRNAs and possibly sequestration of tRNAs