10,116 research outputs found
Operating experiences of retardant bombers during firefighting operations
Data are presented on operational practices and maneuver accelerations experienced by two Douglas DC-6B airplanes converted to retardant bombers and used in firefighting operations. The data cover two fire seasons in the mountainous regions of the northwestern United States
Development of a high capacity toroidal Ni/Cd cell
A nickel cadmium battery design which can offer better thermal management, higher energy density and much lower cost than the state-of-the-art is emphasized. A toroidal Ni/Cd cell concept is described. It was critically reviewed and used to develop two cell designs for practical implementation. One is a double swaged and the other a swaged welded configuration
Family Businesses: Can the Family and the Business Finances Be Separated? Preliminary Results
Small businesses had nearly $1.25 trillion in loans outstanding from commercial lenders, business finance companies, other businesses in the form of trade credit, and friends and relatives in the early 1990s (Ou, 1991). Based on recent information derived from the National Survey on Small Business Finance (NSSBF), loans held by commercial banks and family members or owners of the firm were significant sources of credit, comprising 54 and 18 percent of all loans, respectively (Haynes, 1996). The relative importance of these types of loans suggests that the finances of the business and the family are often intertwined. This study utilizes the recently released Survey of Consumer Finances to examine the impact of small business ownership on the household’s debt structure
Modeling the ballistic-to-diffusive transition in nematode motility reveals variation in exploratory behavior across species
A quantitative understanding of organism-level behavior requires predictive
models that can capture the richness of behavioral phenotypes, yet are simple
enough to connect with underlying mechanistic processes. Here we investigate
the motile behavior of nematodes at the level of their translational motion on
surfaces driven by undulatory propulsion. We broadly sample the nematode
behavioral repertoire by measuring motile trajectories of the canonical lab
strain N2 as well as wild strains and distant species. We focus on
trajectory dynamics over timescales spanning the transition from ballistic
(straight) to diffusive (random) movement and find that salient features of the
motility statistics are captured by a random walk model with independent
dynamics in the speed, bearing and reversal events. We show that the model
parameters vary among species in a correlated, low-dimensional manner
suggestive of a common mode of behavioral control and a trade-off between
exploration and exploitation. The distribution of phenotypes along this primary
mode of variation reveals that not only the mean but also the variance varies
considerably across strains, suggesting that these nematode lineages employ
contrasting ``bet-hedging'' strategies for foraging.Comment: 46 pages, 18 figures, 6 table
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Submillimetre CO observations of the Cepheus A outflow
The authors have carried out spectral mapping of the Cep A region in the J = 3-2 transition of CO. The high velocity wings symptomatic of outflowing gas are evident over a region ~6×6 arc min in extent (~1.3×1.3 pc). There appear to be 2 outflows, as found also for HCO+ by Loren et al. (1985). The CO J = 3-2 red wing intensity is enhanced relative both to lower transition CO data and to HCO+ J = 1-0, particularly to the south and east of Cep A, a result which suggests the presence of hot, optically thin gas in the flow. No such significant enhancement is seen, however, in the blue wing. The data are discussed in terms of a 2 component outflow in which the HCO+ emission originates mainly from dense clumps in the flow while a less dense (but >4×104cm-3) interclump medium is responsible for most of the 12CO emission
Impact of multiscale dynamical processes and mixing on the chemical composition of the upper troposphere and lower stratosphere during the Intercontinental Chemical Transport Experiment–North America
We use high-frequency in situ observations made from the DC8 to examine fine-scale tracer structure and correlations observed in the upper troposphere and lower stratosphere during INTEX-NA. Two flights of the NASA DC-8 are compared and contrasted. Chemical data from the DC-8 flight on 18 July show evidence for interleaving and mixing of polluted and stratospheric air masses in the vicinity of the subtropical jet in the upper troposphere, while on 2 August the DC-8 flew through a polluted upper troposphere and a lowermost stratosphere that showed evidence of an intrusion of polluted air. We compare data from both flights with RAQMS 3-D global meteorological and chemical model fields to establish dynamical context and to diagnose processes regulating the degree of mixing on each day. We also use trajectory mapping of the model fields to show that filamentary structure due to upstream strain deformation contributes to tracer variability observed in the upper troposphere. An Eulerian measure of strain versus rotation in the large-scale flow is found useful in predicting filamentary structure in the vicinity of the jet. Higher-frequency (6–24 km) tracer variability is attributed to buoyancy wave oscillations in the vicinity of the jet, whose turbulent dissipation leads to efficient mixing across tracer gradients
TAB interconnects for space concentrator solar cell arrays
The Boeing Company has evaluated the use of Tape Automated Bonding (TAB) and Surface Mount Technology (SMT) for a highly reliable, low cost interconnect for concentrator solar cell arrays. TAB and SMT are currently used in the electronics industry for chip interconnects and printed circuit board assembly. TAB tape consists of sixty-four 3-mil/1-oz tin-plated copper leads on 8-mil centers. The leads are thermocompression gang bonded to GaAs concentrator solar cell with silver contacts. This bond, known as an Inner Lead Bond (ILB), allows for pretesting and sorting capability via nondestruct wire bond pull and flash testing. Destructive wire pull tests resulted in preferred mid-span failures. Improvements in fill factor were attributed to decreased contact resistance on TAB bonded cells. Preliminary thermal cycling and aging tests were shown excellent bond strength and metallurgical results. Auger scans of bond sites reveals an Ag-Cu-Tin composition. Improper bonds are identified through flash testing as a performance degradation. On going testing of cells are underway at Lewis Research Center. SMT techniques are utilized to excise and form TAB leads post ILB. The formed leads' shape isolates thermal mismatches between the cells and the flex circuit they are mounted on. TABed cells are picked and placed with a gantry x-y-z positioning system with pattern recognition. Adhesives are selected to avoid thermal expansion mismatch and promote thermal transfer to the flex circuit. TAB outer lead bonds are parallel gap welded (PGW) to the flex circuit to finish the concentrator solar cell subassembly
Limits on the Position Wander of Sgr A*
We present measurements with the VLBA of the variability in the centroid
position of Sgr A* relative to a background quasar at 7-mm wavelength. We find
an average centroid wander of 71 +/- 45 micro-arcsec for time scales between 50
and 100 min and 113 +/- 50 micro-arcsec for timescales between 100 and 200 min,
with no secular trend. These are sufficient to begin constraining the viability
of the hot-spot model for the radio variability of Sgr A*. It is possible to
rule out hot spots with orbital radii above 15GM_SgrA*/c^2 that contribute more
than 30% of the total 7-mm flux. However, closer or less luminous hot spots
remain unconstrained. Since the fractional variability of Sgr A* during our
observations was ~20% on time scales of hours, the hot-spot model for Sgr A*'s
radio variability remains consistent with these limits. Improved monitoring of
Sgr A*'s centroid position has the potential to place significant constraints
upon the existence and morphology of inhomogeneities in a supermassive black
hole accretion flow.Comment: 14 pages, 3 figures submitted to Ap
Species Identification of Golden and Bald Eagle Talons Using Morphometrics
The Golden Eagle (Aquila chrysaetos) and Bald Eagle (Haliaeetus leucocephalus) are the largest avian predators in North America, and are thus species of great ecological importance and cultural significance. There is a long history of human use of eagle body parts, and this use continues today: Bald and Golden eagles are among the North American birds most affected by the illegal wildlife trade. Detached eagle talons are often recovered in both law enforcement and archaeological contexts, but data to allow morphological identification of these talons have been lacking. This study documents measureable differences in the morphology of Bald Eagle and North American Golden Eagle talons, which can be used to identify the detached talons of these two species. We measured talon samples of both species from the U.S. Fish and Wildlife Service’s National Fish and Wildlife Forensics Laboratory and other collections and categorized them according to species, sex, age, and digit number (Digits I–IV). We then conducted ANOVA and principal components analysis to test for statistical differences in the talon measurements of these two species. Although species identification was not always possible, due to overlap in the morphology of the talons of the two eagles, our results demonstrated that measurements allow identification of many talons, especially the large talons of Digits I and II, which are most commonly recovered in law enforcement cases. These results will be valuable for researchers studying North American eagle remains in the contexts of law enforcement, archaeology, and anthropology
Submillimeter wavelength molecular spectroscopy of the Orion molecular cloud
A submillimeter wavelength spectroscopic study of the Orion molecular cloud has been made in the J = 4-3 HCN, H13CN, HCO+, H13CO+, and J = 7-6 CS molecular transitions. Densities of up to a few times 106 cm-3 are found coupled with high inferred brightness temperatures, indicating kinetic temperatures of 120 K. Evidence for lower densities in the surrounding ambient molecular cloud is presented along with maps of HCN and HCO+ emission. The maps indicate different spatial distributions in the two lines. The abundances of HCN and HCO+ in the plateau source are found to be enhanced relative to those in the surrounding molecular cloud, and there is a suggestion that a number of small-angular-diameter clumps may be present. The present observations do not confirm the previously reported detection of CO+ in the interstellar medium
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