High-strength large-diameter carbon-base fibers

Material is applicable as reinforcement for metal matrix composites. Composites with large diameter, carbon base monofilaments offer advantages of superior strength at high temperatures and low density and for high temperature equipment where component weight must be minimized

Improvement of chemical vapor deposition process for production of large diameter carbon base monofilaments

Research was conducted to develop large diameter carbon monofilament, containing 25 to 35 mole % element boron, in the 2.0 to 10.0 mil diameter range using the chemical vapor deposition process. The objective of the program was to gain an understanding of the critical process variables and their effect on fiber properties. Synthesis equipment was modified to allow these variables to be studied. Improved control of synthesis variables permitted reduction in scatter of properties of the monofilaments. Monofilaments have been synthesized in the 3.0 to nearly 6.0 mil diameter range having measured values up to 552,000 psi for ultimate tensile strength and up to 30 million psi for elastic modulus

Further development of chemical vapor deposition process for production of large diameter carbon-base monofilaments

The development of large diameter carbon-base monofilament in the 50 micron to 250 micron diameter range using the chemical vapor deposition process is described. The object of this program was to determine the critical process variables which control monofilament strength, monofilament modulus, and monofilament diameter. It was confirmed that wide scatter in the carbon substrate strength is primarily responsible for the scatter in the monofilament strength. It was also shown through etching experiments that defective substrate surface conditions which can induce low strength modular growth in the monofilament layers are best controlled by processing improvements during the synthesis of the substrate. Modulus was found to be linearily proportional to monofilament boron content. Filament modulus was increased to above 27.8MN/sq cm but only by a considerable increase in monofilament boron content to 60 wt. % or more. Monofilament diameter depended upon dwell time in the synthesis apparatus. A monofilament was prepared using these findings which had the combined properties of a mean U.T.S. of 398,000 N/sq cm, a modulus of 18.9 MN/sq cm (24,000,000 psi), and a diameter of 145 microns. Highest measured strength for this fiber was 451,000 N/sq cm (645,000 psi)

Computer vision in microstructural analysis

The following is a laboratory experiment designed to be performed by advanced-high school and beginning-college students. It is hoped that this experiment will create an interest in and further understanding of materials science. The objective of this experiment is to demonstrate that the microstructure of engineered materials is affected by the processing conditions in manufacture, and that it is possible to characterize the microstructure using image analysis with a computer. The principle of computer vision will first be introduced followed by the description of the system developed at Texas A&M University. This in turn will be followed by the description of the experiment to obtain differences in microstructure and the characterization of the microstructure using computer vision

Untangling the Recombination Line Emission from HII Regions with Multiple Velocity Components

HII regions are the ionized spheres surrounding high-mass stars. They are ideal targets for tracing Galactic structure because they are predominantly found in spiral arms and have high luminosities at infrared and radio wavelengths. In the Green Bank Telescope HII Region Discovery Survey (GBT HRDS) we found that >30% of first Galactic quadrant HII regions have multiple hydrogen radio recombination line (RRL) velocities, which makes determining their Galactic locations and physical properties impossible. Here we make additional GBT RRL observations to determine the discrete HII region velocity for all 117 multiple-velocity sources within 18deg. < l < 65deg. The multiple-velocity sources are concentrated in the zone 22deg. < l < 32deg., coinciding with the largest regions of massive star formation, which implies that the diffuse emission is caused by leaked ionizing photons. We combine our observations with analyses of the electron temperature, molecular gas, and carbon recombination lines to determine the source velocities for 103 discrete H II regions (88% of the sample). With the source velocities known, we resolve the kinematic distance ambiguity for 47 regions, and thus determine their heliocentric distances.Comment: 44 pages, 5 figures, 16 pages of tables; Accepted by ApJ

Biology and control of currant lettuce aphid nasonovia ribisnigri

There is a consensus that the development of successful Integrated Pest Management strategies requires a detailed understanding of pest biology. In the case of the currant lettuce aphid (Nasonovia ribisnigri), an economically important pest aphid of lettuce, sources of such information are limited. This study considers key aspects of N. ribisnigri biology which influence its control. In particular, it makes comparisons between biotypes which succumb to (wild-type) or overcome (resistance-breaking), the host plant resistance (Nr-gene) in commercial lettuce cultivars. Experiments on the effects of temperature and photoperiod on the development of N. ribisnigri showed no differences between wild-type and resistance-breaking biotypes. At low temperatures (5, 10 and 15ºC), wild-type biotypes developed to adulthood on resistant cultivars, indicating that the Nr-gene is temperature sensitive. A linear regression between development rate and temperature estimated a lower developmental threshold of around 4.7ºC. Nasonovia ribisnigri usually overwinters as a diapausing egg but overwintering nymphs/adults have been observed. In the laboratory eggs were obtained at 12ºC 13L:11D. Sequential sampling of eggs from the field suggested that diapause ended between late January and early February. Post-diapause development was estimated to take <50 day-degrees using a LDT of 4.7°C. Nasonovia ribisnigri survived the winter as nymphs/adults on Veronica arvensis in the Midlands. Other weed species were suitable hosts in the labratory: Chichorium intybus, Crepis capillaris, Lapsana communis, Hieracium aurantiacum, Hieracium pilosella, Veronica spicata and Veronica officinalis. Field trials, using sequentially planted plots of lettuce, and applying 'exclusion' and pesticidal treatments indicated that natural enemies and emigration regulate aphid populations in the summer and contribute to the mid-summer crash. A large-scale screen of 96 cultivars and wild relatives of lettuce identified new sources of resistance against wild-type and resistance-breaking biotypes. Results from this study can be used to inform further development of an Integrated Pest Management strategy for this pest

Development of manufacturing process for large diameter carbon-base monofilaments by chemical vapor deposition Final report

Manufacturing process for large diameter carbon base monofilaments by chemical vapor depositio

Tele-methylhistamine 1 distribution in rat brain

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65997/1/j.1471-4159.1979.tb02303.x.pd