55,266 research outputs found
Scalar mesons above and below 1 GeV
We show that two nonets and a glueball provide a consistent description of
data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional
(q bar q) nonet mixed with the glueball of lattice QCD. Below 1 GeV the states
also form a nonet, as implied by the attractive forces of QCD, but of more
complicated nature. Near the center they are 4 quark states of the Jaffe type
in S-wave, with some (q bar q) in P-wave, but further out they rearrange in
colour to two colourless (q bar q) pairs and finally as meson-meson states. A
simple effective chiral model for such a system with two scalar nonets can be
made involving two coupled linear sigma models. One of these could be looked
upon as the Higgs sector of nonpertubative QCD.Comment: 34 pages in Latex, minor improvements in sec
Fronts and frontogenesis as revealed by high time resolution data
Upper air sounding are used to examine a cold front of average intensity. Vertical cross sections of potential temperature and wind, and horizontal analyses were compared and adjusted for consistency. These analyses were then used to study the evolution of the front, found to consist of a complex system of fronts occurring at all levels of the troposphere. Low level fronts were strongest at the surface and rapidly weakened with height. Fronts in the midddle troposphere were much more intense. The warm air ahead of the fronts was nearly barotropic, while the cold air behind was baroclinic through deep layers. A deep mixed layer was observed to grow in this cold air
A Systematic Experimental and Computational Investigation of a Class of Contoured Wall Fuel Injectors
The performance of a particular class of fuel injectors for
scramjet engine applications is addressed. The contoured
wall injectors were aimed at augmenting mixing through
axial vorticity production arising from interaction of the
fueVair interface with an oblique shock. Helium was used to
simulate hydrogen fuel and was injected at Mach 1.7 into a
Mach 6 airstream. The effects of incoming boundary layer
height. injector spacing, and injectant to freestream pressure and velocity ratios were investigated. Results from threedimensional flow field surveys and Navier-Stokes
simulations are presented. Performance was judged in
terms of mixing, loss generation and jet penetration.
Injector performance was strongly dependent on the
displacement effect of the hypersonic boundary layer which
acted to modify the effective wall geometry. The impact of
the boundary layer varied with injector array spacing.
Widely-spaced arrays were more resilient to the detrimental
effects of large boundary layers. Strong dependence on
injectant to free stream pressure ratio was also displayed.
Pressure ratios near unity were most conducive to losseffective mixing and strong jet penetration. Effects due to variation in mean shear associated with non-unity velocity ratios were found to be secondary within the small range of values tested
Aircraft remote sensing of phytoplankton spatial patterns during the 1989 Joint Global Ocean Flux Study (JGOFS) North Atlantic bloom experiment
Mesoscale phytoplankton chlorophyll variability near the Joint Global Ocean Flux study sites along the 20 W meridian at 34 N, 47 N, and 59 N is discussed. The NASA P-3 aircraft and the Airborne Oceanographic Lidar (AOL) system provides remote sensing support for the North Atlantic Bloom Experiment. The principal instrument of the AOL system is the blue-green laser that stimulates fluorescence from photoplankton chlorophyll, the principal photosynthetic pigment. Other instruments on the NASA P-3 aircraft include up- and down-looking spectrometers, PRT-5 for infrared measurements to determine sea surface temperature, and a system to deploy and record AXBTs to measure subsurface temperature structure
Nongassing NiCd battery cell
Method of constructing nickel cadmium batteries prevents excessive gas buildup and allows hermetic sealing of battery for increased service life and reduced maintenance cost
Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-Row Radial Aircraft Engine
The NACA injection impeller was developed to improve the mixture distribution of aircraft engines by discharging the fuel from a centrifugal supercharger impeller, thus promoting a thorough mixing of fuel and charge air. Tests with a double-row radial aircraft engine indicated that for the normal range of engine power the NACA injection impeller provided marked improvement in mixture distribution over the standard spray-bar injection system used in the same engine. The mixture distribution at cruising conditions was excellent; at 1200, 15OO, and 1700 brake horsepower, the differences between the fuel-air ratios of the richest and the leanest cylinders were reduced to approximately one-third their former values. The maximum cylinder temperatures were reduced about 30 [degrees] F and the temperature distribution was improved by approximately the
degree expected from the improvement in mixture distribution. Because the mixture distribution of the engine tested improves slightly at engine powers exceeding 1500 brake horsepower and because the effectiveness of the particular impeller diminished slightly at high rates of fuel flow, the improvement in mixture distribution at
rated power and rich mixtures was less than that for other conditions.
The difference between the fuel-air ratios of the richest and the leanest cylinders of the engine using the standard spray bar was so great that the fuel-air ratios of several cylinders were well below the chemically correct mixture, whereas other cylinders were operating at rich mixtures. Consequently, enrichment to improve engine cooling actually increascd some of the critical temperatures. The uniform mixture distribution providod by the injection impeller restored the normal response of cylinder temperatures to mixture enrichnent
A serological investigation of caseous lymphadenitis in four flocks of sheep
A double antibody sandwich ELISA developed by ID-DLO, Lelystad to detect Corynebocterium pseudotuberculosis infection was used on 329 sheep from four pedigree Suffolk flocks in which clinical cases of caseous lymphadenitis (CLA) had occurred. At subsequent necropsy, typical CLA lesions were seen in 133 sheep, and the diagnosis was confirmed on culture. Lesions were most commonly seen in lungs (n = 46), parotid lymph nodes (n = 44), prescapular lymph nodes (n = 38) and mediastinal lymph nodes (n = 31). The sensitivity of the ELISA test for detecting culture-positive sheep was 0.88, while the specificity of the test was 0.55. The antibody ELISA detected 87.5 per cent of sheep that had CLA lesions restricted to internal organs only. It was concluded that the ELISA test has a valuable role in detecting sheep with both clinical and subclinical CLA
Import of cytochrome c heme lyase into mitochondria
Cytochrome c heme lyase (CCHL) catalyses the covalent attachment of the heme group to apocytochrome c during its import into mitochondria. The enzyme is membrane-associated and is located within the intermembrane space. The precursor of CCHL synthesized in vitro was efficiently translocated into isolated mitochondria from Neurospora crassa. The imported CCHL, like the native protein, was correctly localized to the intermembrane space, where it was membrane-bound. As with the majority of mitochondrial precursor proteins, CCHL uses the MOM19-GIP receptor complex in the outer membrane for import. In contrast to proteins taking the general import route, CCHL was imported independently of both ATP-hydrolysis and an electrochemical potential as external energy sources. CCHL which lacks a cleavable signal sequence apparently does not traverse the inner membrane to reach the intermembrane space; rather, it translocates through the outer membrane only. Thus, CCHL represents an example of a novel, 'non-conservative' import pathway into the intermembrane space, thereby also showing that the import apparatus in the outer membrane acts separately from the import machinery in the inner membrane
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