Inlet spillage drag tests and numerical flow-field analysis at subsonic and transonic speeds of a 1/8-scale, two-dimensional, external-compression, variable-geometry, supersonic inlet configuration

Accurate spillage drag and pressure data are presented for a realistic supersonic inlet configuration. Results are compared with predictions from a finite-differencing, inviscid analysis computer procedure. The analytical technique shows good promise for the evaluation of inlet drag, but necessary refinements were identified. A detailed description of the analytical procedure is contained in the Appendix

An Obstruction to Quantization of the Sphere

In the standard example of strict deformation quantization of the symplectic sphere $S^2$, the set of allowed values of the quantization parameter $\hbar$ is not connected; indeed, it is almost discrete. Li recently constructed a class of examples (including $S^2$) in which $\hbar$ can take any value in an interval, but these examples are badly behaved. Here, I identify a natural additional axiom for strict deformation quantization and prove that it implies that the parameter set for quantizing $S^2$ is never connected.Comment: 23 page. v2: changed sign conventio

Preliminary Canopy Removal Experiments in Algal Dominated Communities Low on the Shore and in the Shallow Subtidal on the Isle of Man

The algal dominated communities immediately above and below the low-water spring level on a moderately exposed Manx shore were investigated by canopy removal experiments. Fucus serratus, Laminaria digitata and L. hyperborea were removed. Competition was shown to be important in determining the zonation of L. digitata and the distribution along the wave exposure gradient of other species such as Alaria esculenta, Desmarestia aculeata and D. viridis, and L. saccharina. Many species of algal epiphytes were early colonizers of canopy removal areas suggesting that competition from canopy algae usually restricts them to an epiphytic habit. The results indicate that interactions between macrophytes are much more important than grazing in structuring these communities

The Double Quasar Q2138-431: Lensing by a Dark Galaxy?

We report the discovery of a new gravitational lens candidate Q2138-431AB, comprising two quasar images at a redshift of 1.641 separated by 4.5 arcsecs. The spectra of the two images are very similar, and the redshifts agree to better than 115 km.sec$^{-1}$. The two images have magnitudes $B_J = 19.8$ and $B_J = 21.0$, and in spite of a deep search and image subtraction procedure, no lensing galaxy has been found with $R < 23.8$. Modelling of the system configuration implies that the mass-to-light ratio of any lensing galaxy is likely to be around $1000 M_{\odot}/L_{\odot}$, with an absolute lower limit of $200 M_{\odot}/L_{\odot}$ for an Einstein-de Sitter universe. We conclude that the most likely explanation of the observations is gravitational lensing by a dark galaxy, although it is possible we are seeing a binary quasar.Comment: 17 pages (Latex), 8 postscript figures included, accepted by MNRA

A Technique for the Nondestructive Detection of Voids and Composition Anomalies in Metal Matrix Composite Wires Using X or γ Rays

An initial study of a technique proposed for the nondestructive testing of metal matrix composites is the subject of this paper. These composites are manufactured in the form of approximately 1/2-mm-diameter “precursor” wires. Larger structures are fabricated by diffusion bonding of lay-ups. Reliable nondestructive quality control indicators of wire integrity have not yet been developed although a number of possibilities are being examined.1 Testing of the precursor wires is difficult because current manufacturing processes produce wires that may be entirely satisfactory but that vary in cross-sectional geometry, in surface properties, and sometimes in the amount of matrix material that is present. Techniques based on observations of wire resistance, surface emissivity, and sound emission signatures are difficult to interpret because of these characteristics. Wire imaging using x-ray or neutron techniques is also difficult because large lengths of wire must be examined with a resolution in the plane of the wire exceeding 50 line pairs per millimeter

On the relationship between sigma models and spin chains

We consider the two-dimensional $\rm O(3)$ non-linear sigma model with topological term using a lattice regularization introduced by Shankar and Read [Nucl.Phys. B336 (1990), 457], that is suitable for studying the strong coupling regime. When this lattice model is quantized, the coefficient $\theta$ of the topological term is quantized as $\theta=2\pi s$, with $s$ integer or half-integer. We study in detail the relationship between the low energy behaviour of this theory and the one-dimensional spin-$s$ Heisenberg model. We generalize the analysis to sigma models with other symmetries.Comment: To appear in Int. J. MOd. Phys.

In-Seasno Nitrogen Management for Corn Production

Water quality impairment related to nitrogen (N) continues to be a concern in Iowa, including the nitrate drinking water standard, USEPA proposed surface water quality nutrient criteria, and Gulf of Mexico hypoxia. Addressing these issues could include strict guidance for N input to corn and resultant N use practices that require very high level of management and risk, with unknown economic consequences. Rate of N application is an important management factor in corn production related to nitrate reaching surface water systems. Rate is also important in regard to economic return. While applying only the needed fertilizer N rate in a given year will not stop nitrate from leaving corn fields, nor necessarily achieve proposed water quality goals, it can result in reduced residual soil nitrate and help lessen corn production\u27s impact on water quality Therefore, it is possible that being able to assess corn N fertilization need differentially each season would improve corn N use efficiency and reduce nitrate susceptible to loss compared to application of an average agronomic rate each year

Traffic noise alters individual social connectivity, but not space-use, of Red-backed Fairywrens

The prevalence of human-generated noise is posing novel challenges to birds, by changing how they communicate or causing them to disperse away from the source of noise. We sought to understand how noise affected space-use and social connectivity in a small passerine bird, the Red-backed Fairywren (Malurus melanocephalus). As the displaced birds would likely be forced to occupy a smaller area that may already have resident individuals, we predicted that noise-affected birds would show increased social connectivity that may include new individuals. To test this, we introduced an experimental point-source of traffic noise to groups of fairywrens in an otherwise quiet habitat and compared the change in social connectivity of birds in groups exposed to noise to the changes in social connectivity in neighbouring groups unaffected by noise. Contrary to our prediction, noise-affected birds had reduced social connectivity during experimental noise treatments, as measured by weighted-degree, which was driven by a reduction of interactions with birds of neighbouring groups outside the noise zone. Additionally, we did not discern a change in space-use in response to our noise treatment. Therefore, we suggest that noise reduces the efficacy of signal transmission and detection in this species, resulting in the reduction of social connectivity between groups of this otherwise highly social songbird