Effects of beta radiation on nanostructured semiconductor devices for low energy radiation sensing

Beta radiation detection currently relies primarily on scintillation detectors. However, the construction of these detectors tends to be large which significantly limits their applicability for field-use. A nanostructured Pt/TiO2/Ti Schottky device was constructed for use as a compact, low energy radiation detector by making use of surface plasmon resonance which has been shown to enhance energy coupling in similar technologies. The fabrication of the device was done by first electrochemically anodizing a titanium substrate to create a nanoporous surface, followed by annealing to produce a crystalline, semiconducting TiO2 layer and finally the deposition of the Pt Schottky metal through atomic layer deposition. Modeling of the device using COMSOL software showed the formation of strong electric fields when nanostructures were present. Exposure of the device to low energy 63Ni beta radiation showed a 2-to-3-fold increase to the forward current during radiation exposure without any additional signal amplification. This increase in the current is a consequence of a 2 to 4 percent lowering of the Schottky barrier height during radiation exposure as well as the production of hot and secondary electrons in the semiconductor. Subsequent improvements to the device using rapid thermal annealing resulted in a nearly 6 percent decrease of the Schottky barrier height during radiation exposure and a consequent 5-fold increase to the forward bias current in the presence of radiation. Thus, in its current construction the device is capable of being used as a qualitative low energy beta radiation detector.Includes bibliographical references

Cover crops and compost influence soil enzymes during 6 years of tillage-intensive, organic vegetable production

Soil enzymes are considered sensitive indicators of soil health but are not well understood in tillage-intensive vegetable systems. The activities of soil enzymes involved in nutrient cycling (β-glucosidase, β-glucosaminidase, alkaline phosphatase, dehydrogenase, aspartase, and L-asparaginase) were evaluated during 6 yr of commercial-scale production in five organic vegetable systems in Salinas, CA. The systems differed in yard-waste compost inputs (none or 15.2 Mg ha–1 yr–1), winter cover crop frequency (annually or every fourth year), and cover crop type (legume-rye, mustard, or rye). Large differences in cumulative organic matter input (7.4 to 136.8 Mg ha–1) from compost and cover crop shoots affected soil enzyme activities. With exception of aspartase, all enzyme activities were on average lowest without compost, intermediate with compost and infrequent cover cropping, and highest with compost and annual cover cropping. After 6 yr of vegetable production there was a positive relationship between microbial biomass and activities of all enzymes except aspartase. Despite lower inputs of cover crop shoot biomass from mustard compared with rye and the legume-rye, and differences in shoots residue quality, cover crop type had relatively little influence on enzyme activities. We conclude that soil enzyme activities were influenced primarily by annual cover cropping. These results and other attributes of soil health in this long-term study illustrate the importance of frequent cover cropping in tillage-intensive vegetable production. This raises questions about the sustainability of organic and conventional vegetable systems if cover crops are seldom used, and highlights the need for innovative strategies to increase cover cropping

Investigation of the Performance of Different Types of Zirconium Microstructures under Extreme Irradiation Conditions

The safe and continued operation of the US nuclear power plants requires improvement of the radiation resistant properties of materials used in nuclear reactors. Zirconium is a material of particular interest due to its use in fuel cladding. Studies performed on other materials have shown that grain boundaries can play a significant role on the radiation resistant properties of a material. Thus, the focus of our research is to investigate the performance of different zirconium microstructures under irradiation conditions similar to those in commercial nuclear reactors. Analysis of the surface morphology of zirconium both pre- and post-irradiation was conducted with Scanning Electron Microscopy (SEM). Cold-rolled (small-grain microstructure) and annealed (large-grained microstructure) zirconium samples were mechanically polished in order to be irradiated. Room temperature irradiation of zirconium samples was conducted at energies of 100 eV and 1 keV with He+ ions at a flux of 1 x1020 m-2 using a gridded ion source. High temperature (350°C and 700⁰C) He+ irradiations were performed at an energy of 100 eV using a gridless end-hall ion source at the same flux. Transmission Electron Microscopy (TEM) was conducted to determine the grain size of the zirconium samples. Preliminary results show greater surface damage on the rolled zirconium samples than on the annealed samples for all irradiation cases. The difference in damage was most evident in high temperature irradiations. These findings suggest that large-grained zirconium may be more suitable for fuel cladding applications. Further testing will be performed using higher fluxes, temperatures and energies

Diagnostic Decays of the X(3872)

The unusual properties of the X(3872) have led to speculation that it is a weakly bound state of mesons, chiefly $D^0\bar D^{0*}$. Tests of this hypothesis are investigated and it is proposed that measuring the $3\pi J/\psi$, $\gamma J/\psi$, $\gamma \psi'$, $\bar K K^*$, and $\pi\rho$ decay modes of the $X$ will serve as a definitive diagnostic of the molecule hypothesis.Comment: 6 pages revtex4, 3 eps figure

Search for plant biomagnetism with a sensitive atomic magnetometer

We report what we believe is the first experimental limit placed on plant biomagnetism. Measurements with a sensitive atomic magnetometer were performed on the Titan arum (Amorphophallus titanum) inflorescence, known for its fast bio-chemical processes while blooming. We find that the surface magnetic field from these processes, projected along the Earth's magnetic field, and measured at the surface of the plant, is less then ~0.6uG.Comment: 5 pages, 5 figures, to be published - modified one sentence in abstract + reformatted fi

Estudio hidrológico e hidráulico para el diseño de un puente vehicular sobre el Río Moyocc – Cangallo – Ayacucho, 2020

Desempeña un estudio hidrológico e hidráulico para el estudio definitivo del diseño del puente vehicular sobre el río Moyocc del distrito de Cangallo. Para ello se determinó las propiedades del río en la sección del puente con el fin de conocer la luz hidráulica del puente, el nivel de aguas máximas extraordinarias (NAME), el borde libre recomendado y las cotas máximas de socavación. Para lograr dichos resultados se planteó cuatro capítulos. El primer capítulo presenta la introducción relacionada al tema, la importancia del proyecto, objetivos de la investigación, la identificación de problemas, la propuesta de solución, los alcances y delimitaciones del tema. El segundo capítulo detalla los antecedentes de estudios referentes al análisis hidrológico e hidráulico de puentes, las bases teóricas fundamentales y las de ingeniería que se utilizará para elaboración de los cálculos. El tercer capítulo aborda las características de la zona de investigación, la recolección de datos, que incluye la información meteorológica, cartográfica y fisiográfica de la cuenca, evaluación del estudio de suelos y cobertura vegetal. Además, detalla las consideraciones de diseño y cálculos de ingeniería ejecutados tanto para la hidrología como la hidráulica como: El análisis de precipitaciones, estimación de los caudales máximos, calibración del modelo, las características hidráulicas y el cálculo de las socavaciones. El cuarto capítulo presenta el resultado final que son los parámetros geomorfológicos de la cuenca de estudio, los resultados de los caudales de diseño, el NAME y la profundidad de socavación local, por contracción y general, el cual se expone en las conclusiones

A Survey of 10-Micron Silicate Emission from Dust around Young Sun-Like Stars

We obtained low resolution (R = 100) mid-infrared (8-13 micron wavelengths) spectra of 8 nearby young main sequence stars with the Keck 1 telescope and Long-Wavelength Spectrometer (LWS) to search for 10 micron silicate (Si-O stretch) emission from circumstellar dust. No stars exhibited readily apparent emission: Spectra were then analyzed by least-squares fitting of a template based on a spectrum of Comet Hale-Bopp. Using this technique, we were able to constrain the level of silicate emission to a threshold ten times below what was previously possible from space. We found one star, HD 17925, with a spectrum statistically different from its calibrator and consistent with a silicate emission peak of 7% of the photosphere at a wavelength of 10 microns. Excess emission at 60 microns from this star has already been reported.Comment: 19 total pages, 5 Postscript figures, 2 tables, Late