Pulsar extinction

Radio emission from pulsars, attributed to an instability associated with the creation of electron-positron pairs from gamma rays was investigated. The condition for pair creation therefore lead to an extinction condition. The relevant physical processes were analyzed in the context of a mathematical model, according to which radiation originated at the polar caps and magnetic field lines changed from a closed configuration to an open configuration at the force balance or corotation radius

User-profile-based analytics for detecting cloud security breaches

While the growth of cloud-based technologies has benefited the society tremendously, it has also increased the surface area for cyber attacks. Given that cloud services are prevalent today, it is critical to devise systems that detect intrusions. One form of security breach in the cloud is when cyber-criminals compromise Virtual Machines (VMs) of unwitting users and, then, utilize user resources to run time-consuming, malicious, or illegal applications for their own benefit. This work proposes a method to detect unusual resource usage trends and alert the user and the administrator in real time. We experiment with three categories of methods: simple statistical techniques, unsupervised classification, and regression. So far, our approach successfully detects anomalous resource usage when experimenting with typical trends synthesized from published real-world web server logs and cluster traces. We observe the best results with unsupervised classification, which gives an average F1-score of 0.83 for web server logs and 0.95 for the cluster traces

Small Engine Component Technology (SECT)

A study of small gas turbine engines was conducted to identify high payoff technologies for year-2000 engines and to define companion technology plans. The study addressed engines in the 186 to 746 KW (250 to 1000 shp) or equivalent thrust range for rotorcraft, commuter (turboprop), cruise missile (turbojet), and APU applications. The results show that aggressive advancement of high payoff technologies can produce significant benefits, including reduced SFC, weight, and cost for year-2000 engines. Mission studies for these engines show potential fuel burn reductions of 22 to 71 percent. These engine benefits translate into reductions in rotorcraft and commuter aircraft direct operating costs (DOC) of 7 to 11 percent, and in APU-related DOCs of 37 to 47 percent. The study further shows that cruise missile range can be increased by as much as 200 percent (320 percent with slurry fuels) for a year-2000 missile-turbojet system compared to a current rocket-powered system. The high payoff technologies were identified and the benefits quantified. Based on this, technology plans were defined for each of the four engine applications as recommended guidelines for further NASA research and technology efforts to establish technological readiness for the year 2000

Appearance of the Single Gyroid Network Phase in Nuclear Pasta Matter

Nuclear matter under the conditions of a supernova explosion unfolds into a rich variety of spatially structured phases, called nuclear pasta. We investigate the role of periodic network-like structures with negatively curved interfaces in nuclear pasta structures, by static and dynamic Hartree-Fock simulations in periodic lattices. As the most prominent result, we identify for the first time the {\it single gyroid} network structure of cubic chiral $I4_123$ symmetry, a well known configuration in nanostructured soft-matter systems, both as a dynamical state and as a cooled static solution. Single gyroid structures form spontaneously in the course of the dynamical simulations. Most of them are isomeric states. The very small energy differences to the ground state indicate its relevance for structures in nuclear pasta.Comment: 7 pages, 4 figure

Contaminant removal from enclosed atmospheres by regenerable adsorbents

A system for removing contaminants from spacecraft atmospheres was studied, which utilizes catalyst-impregnated activated carbon followed by in-situ regeneration by low-temperature catalytic oxidation of the adsorbed contaminants. Platinum was deposited on activated carbon by liquid phase impregnation with chloroplatinic acid, followed by drying and high-temperature reduction. Results were obtained for the seven selected spacecraft contaminants by means of three experimental test systems. The results indicate that the contaminants could be removed by oxidation with very little loss in adsorptive capacity. The advantages of a catalyst-impregnated carbon for oxidative regeneration are found to be significant enough to warrent its use

Distribution and Properties of Vesicular Horizons in the Western United States

Vesicular horizons are thin (usuallycm) surface or near-surface horizons characterized by the predominance of vesicular porosity. Th ey are widespread in arid and semiarid lands, occurring on every continent and covering 156,000 km2 of the western United States. Vesicular horizons have critical implications for management due to their role in controlling surface hydrology and dust mobilization. Th is study evaluates the distribution and varia-tion in expression of vesicular horizons across the western United States using the soil databases available from the USDA. A vesicular horizon index (VHI) that incorporates vesicular horizon thickness and the size and quantity of vesicular pores was developed using soil descriptions from a published chronosequence study. Th e VHI was applied to descriptions from the soil survey databases to evaluate vesicular horizon expression across the western United States. Vesicular horizons were better expressed (higher VHI) in the Central and Northern Basin and Range com-pared to the Mojave and Sonoran Basin and Range. Th is may be due to diff erences in temperature regime or to larger areas of playas in the Central and Northern Basin and Range that serve as sources of dust that forms the par-ent material for vesicular horizons. Th e median VHI was highest in the Aridisols and Mollisols compared to other soil orders. No signifi cant relationship was found between VHI and soil textures. Vesicular horizons are widely distributed in western United States and occur across a wide range of soil types and soil-forming environments

Analysis of vesicular porosity in soils using high-resolution X-ray computed tomograpy

Vesicular horizons are common at the surface of arid and semiarid soils and play a critical role in regulating infiltration. Most methods for examining pore morphology in the vesicular horizon involve physical sectioning of the sample and individual measurement of pores, which is time-consuming and provides an incomplete view of the pores. The objectives of this study were to (i) develop methods for the classification and characterization of pores in the vesicular horizon using high resolution X-ray computed tomography (HRXCT) and (ii) use these methods to examine the distribution of pores within vesic-ular peds. Three intact peds were scanned by HRXCT and examined using Blob3D software. A subset of pores from the first scan were observed and used to develop a classification tree model based on quantitative parameters of pore shape. Five major pore classes were found: equant vesicles, non-equant vesicles, individual vughs, connected vughs, and planar voids. All pore types decreased in size with increasing depth in the samples; however, the trend in quantity of pores with depth varied between pore types. In the ped with the least vesicular porosity, there was an increase in size and decrease in number of all pore types between the ped interior and exterior, a pattern which was reduced in the peds that were more dominantly vesicular. The application of HRXCT in this study shows how pore shape and size can be quantified within the vesicular horizon and reveals considerable variation of these characteristics within and between peds

Distribution and Properties of Vesicular Horizons in the Western United States

Vesicular horizons are thin (usuallycm) surface or near-surface horizons characterized by the predominance of vesicular porosity. Th ey are widespread in arid and semiarid lands, occurring on every continent and covering 156,000 km2 of the western United States. Vesicular horizons have critical implications for management due to their role in controlling surface hydrology and dust mobilization. Th is study evaluates the distribution and varia-tion in expression of vesicular horizons across the western United States using the soil databases available from the USDA. A vesicular horizon index (VHI) that incorporates vesicular horizon thickness and the size and quantity of vesicular pores was developed using soil descriptions from a published chronosequence study. Th e VHI was applied to descriptions from the soil survey databases to evaluate vesicular horizon expression across the western United States. Vesicular horizons were better expressed (higher VHI) in the Central and Northern Basin and Range com-pared to the Mojave and Sonoran Basin and Range. Th is may be due to diff erences in temperature regime or to larger areas of playas in the Central and Northern Basin and Range that serve as sources of dust that forms the par-ent material for vesicular horizons. Th e median VHI was highest in the Aridisols and Mollisols compared to other soil orders. No signifi cant relationship was found between VHI and soil textures. Vesicular horizons are widely distributed in western United States and occur across a wide range of soil types and soil-forming environments

Analysis of vesicular porosity in soils using high-resolution X-ray computed tomograpy

Vesicular horizons are common at the surface of arid and semiarid soils and play a critical role in regulating infiltration. Most methods for examining pore morphology in the vesicular horizon involve physical sectioning of the sample and individual measurement of pores, which is time-consuming and provides an incomplete view of the pores. The objectives of this study were to (i) develop methods for the classification and characterization of pores in the vesicular horizon using high resolution X-ray computed tomography (HRXCT) and (ii) use these methods to examine the distribution of pores within vesic-ular peds. Three intact peds were scanned by HRXCT and examined using Blob3D software. A subset of pores from the first scan were observed and used to develop a classification tree model based on quantitative parameters of pore shape. Five major pore classes were found: equant vesicles, non-equant vesicles, individual vughs, connected vughs, and planar voids. All pore types decreased in size with increasing depth in the samples; however, the trend in quantity of pores with depth varied between pore types. In the ped with the least vesicular porosity, there was an increase in size and decrease in number of all pore types between the ped interior and exterior, a pattern which was reduced in the peds that were more dominantly vesicular. The application of HRXCT in this study shows how pore shape and size can be quantified within the vesicular horizon and reveals considerable variation of these characteristics within and between peds

Swanee Sue

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