Production of Low Concentration Particulate Aerosols by a Sonic Disseminator Technique

Ultrasonic vibrator for producing stable, low concentration, bacterial spore aeroso

A preliminary analysis of the radiation burden of a typical Mars lander mission

Predicted radiation dosage for Mars lander missio

A mathematical model for the thermoradiation inactivation of dry Bacillus subtilis var. Niger spores

Empirically based kinetic model describing synergistic inactivation of dry Bacillus subtilis by combined heat and gamma radiation environmen

Electrical Characterization of Crystalline UO\u3csub\u3e2\u3c/sub\u3e, ThO\u3csub\u3e2\u3c/sub\u3e AND U\u3csub\u3e0.71\u3c/sub\u3eTh\u3csub\u3e0.29\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e

Uranium dioxide (UO2), thorium dioxide (ThO2), and UxTh1-xO2 alloys are characterized for suitability in uranium-based neutron detectors. ThO2 was studied for an envisioned UO2/ThO2 heterojunction. A U0.71Th0.29O2 alloy was studied because of its resistance to oxidation and potential use in surface passivation. The U0.71Th0.29O2 effective Debye temperature of 217± 24 K was measured using temperature-dependent x-ray photoemission spectroscopy (XPS). The specific heat capacity for the U0.71Th0.29O2 alloy was calculated from the Debye temperature and compared to the heat capacity obtained from modulated-temperature differential scanning calorimetry (MDSC). The XPS derived Debye temperature specific heat capacity was lower than with MDSC due to effects of a vacuum reduced crystal surface. Angle resolved XPS provides depth profiling of a UO2 surface. The U 4f7/2 peaks are evident of U4+ and U6+ oxidation states with an increase in the U4+ oxidation state further from the surface. The presence of U 5f peaks in the valence band spectra provided evidence of U4+ but does not preclude the presence of U6+, while the electronic band-gap energy remained at 2.2 eV, confirming the presence of UO2. These surface characteristics indicated a vacuum reduced UO2 surface and excess oxygen incorporated into the lattice forming a UO2+x selvedge region

Cathodoluminescence and Photoemission of Doped Lithium Tetraborate

Lithium tetraborate (Li2B4O7) crystals are being developed for possible use in solid state neutron detectors. The 6Li(n,α)3H and 10B(n,α)7Li reactions are the basis for neutron detection, and a Li2B4O7 crystal enriched with Mn should show improved efficiency for neutron detection. There is a lack of fundamental characterization information regarding this useful material, particularly with regard to its electronic configuration. Photoemission spectroscopy was used to determine the energy level structure of the Mn doped Li2B4O7 crystals. Measurements were made using ultraviolet photoemission spectroscopy (UPS) using synchrotron radiation on two different beamlines. The first was the 3 m toroidal grating monochromator (TGM) beam line confirming the presence of Mn. Secondly, the normal incident monochromator (NIM) beamline studied the band gap states. Measurements were made at elevated sample temperatures to reduce charging effects. Photoemission studies provided evidence of Mn in the bulk crystal at 47.2 eV. Valence band analysis provided the presence of surface states but no acceptor sites. Cathodoluminescence studies were performed on undoped and Mn doped at beam energies from 5 to 10 KeV and at room temperature. Self trapped exciton emission states are evident in the undoped and Mn doped Li2B4O7 sample ranging in energies from 3.1 to 4.1 eV

Reduction of leukocyte microvascular adherence and preservation of blood-brain barrier function by superoxide-lowering therapies in a piglet model of neonatal asphyxia

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical (O2⋅_) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removing O2⋅_ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical.Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously.Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition of O2⋅_ production by oxypurinol, or elimination of O2⋅_ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels.Conclusion: Using three different strategies to either prevent formation or enhance elimination of O2⋅_ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lower O2⋅_ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia

Helical automatic approaches of helicopters with microwave landing systems

A program is under way to develop a data base for establishing navigation and guidance concepts for all-weather operation of rotorcraft. One of the objectives is to examine the feasibility of conducting simultaneous rotorcraft and conventional fixed-wing, noninterfering, landing operations in instrument meteorological conditions at airports equipped with microwave landing systems (MLSs) for fixed-wing traffic. An initial test program to investigate the feasibility of conducting automatic helical approaches was completed, using the MLS at Crows Landing near Ames. These tests were flown on board a UH-1H helicopter equipped with a digital automatic landing system. A total of 48 automatic approaches and landings were flown along a two-turn helical descent, tangent to the centerline of the MLS-equipped runway to determine helical light performance and to provide a data base for comparison with future flights for which the helical approach path will be located near the edge of the MLS coverage. In addition, 13 straight-in approaches were conducted. The performance with varying levels of state-estimation system sophistication was evaluated as part of the flight tests. The results indicate that helical approaches to MLS-equipped runways are feasible for rotorcraft and that the best position accuracy was obtained using the Kalman-filter state-estimation with inertial navigation systems sensors

Advanced turboprop technology development

The efficiency of high-speed turboprop propulsion systems is considered with emphasis on fuel savings. Specific topics discussed include: (1) high efficiency and low noise of propeller design; (2) fuselage noise attenuation; (3) propeller and gear box maintenance; and (4) engine-airframe integration

The XV-15 tilt rotor research aircraft

The design characteristics of the XV-15 Tilt rotor research aircraft are presented. Particular attention is given to the following: control system; conversion system; and propulsion system. Flight test results are also reported

Engaging Assessment in English Language Arts

Assessment is key to effective instruction. In the English classroom, engaging assessment can appear difficult because of the emphasis on the development of core reading skills. However, learning how students decipher information reveals that each individual learns according to their own unique connections. Examining and understanding the impact of Dr. Howard Gardner’s Multiple Intelligence Theory is the key to engaging assessments. This thesis dissects Dr. Gardner’s M.I. Theory and provides insight on how students learn. Furthermore, the research focuses on how Gardner’s Theory can be used to develop strategies and assessments in order to accurately and diversely assess student learning