Prediction of unsteady aerodynamic loadings caused by leading edge and trailing edge control surface motions in subsonic compressible flow: Computer program description

A digital computer program has been developed to calculate unsteady loadings caused by motions of lifting surfaces with leading edge or trailing edge controls based on the subsonic kernel function approach. The pressure singularities at hinge line and side edges have been extracted analytically as a preliminary step to solving the integral equation by collocation. The program calculates generalized aerodynamic forces for user supplied deflection modes. Optional intermediate output includes pressure at an array of points, and sectional generalized forces. From one to six controls on the half span can be accommodated

Unified Models of Molecular Emission from Class 0 Protostellar Outflow Sources

Low mass star-forming regions are more complex than the simple spherically symmetric approximation that is often assumed. We apply a more realistic infall/outflow physical model to molecular/continuum observations of three late Class 0 protostellar sources with the aims of (a) proving the applicability of a single physical model for all three sources, and (b) deriving physical parameters for the molecular gas component in each of the sources. We have observed several molecular species in multiple rotational transitions. The observed line profiles were modelled in the context of a dynamical model which incorporates infall and bipolar outflows, using a three dimensional radiative transfer code. This results in constraints on the physical parameters and chemical abundances in each source. Self-consistent fits to each source are obtained. We constrain the characteristics of the molecular gas in the envelopes as well as in the molecular outflows. We find that the molecular gas abundances in the infalling envelope are reduced, presumably due to freeze-out, whilst the abundances in the molecular outflows are enhanced, presumably due to dynamical activity. Despite the fact that the line profiles show significant source-to-source variation, which primarily derives from variations in the outflow viewing angle, the physical parameters of the gas are found to be similar in each core.Comment: MNRAS 12 pages, 16 figure

The origin of the strings in the outer regions of Eta Carinae

The narrow optical filaments (`strings' or `spikes') emerging from the Homunculus of Eta Carinae are modelled as resulting from the passage of ballistic `bullets' of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. An archive HST image and new forbidden line profiles of the most distinct of the strings are presented and discussed in terms of this simple model.Comment: 5 pages, 4 figure

A high-speed bi-polar outflow from the archetypical pulsating star Mira A

Optical images and high-dispersion spectra have been obtained of the ejected material surrounding the pulsating AGB star Mira A. The two streams of knots on either side of the star, found in far ultra-viollet (FUV) GALEX images, have now been imaged clearly in the light of Halpha. Spatially resolved profiles of the same line reveal that the bulk of these knots form a bi-polar outflow with radial velocity extremes of +- 150 km/s with respect to the central star. The South stream is approaching and the North stream receding from the observer. A displacement away from Mira A between the position of one of the South stream knots in the new Halpha image and its position in the previous Palomar Observatory Sky Survey (POSS I) red plate has been noted. If interpreted as a consequence of expansion proper motions the bipolar outflow is tilted at 69deg +- 2deg to the plane of the sky, has an outflow velocity of 160 +- 10 km/s and is ~1000 y old.Comment: 8 pages, 5 figures. Accepted for pubication by A&

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear. Aims. The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object. Methods. VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical Echelle spectra are used to investigate MyCn 18. Morpho-kinematic modelling was used to firmly constrain the structure and kinematics of the source. A timescale analysis was used to determine the kinematical age of the nebula and its main components. Results. A spectroscopic study of MyCn 18's central and offset region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Bracket gamma emission are detected from the central regions of MyCn 18. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. A kinematical age of the nebula and its components were obtained by the P-V arrays and timescale analysis. Conclusions. The structure and kinematics of MyCn 18 are better understood using an interactive 3-D modelling tool called shape. A dimensional and timescale analysis of MyCn 18's major components provides a possible mechanism for the nebula's asymmetry. The putative central star is somewhat offset from the geometric centre of the nebula, which is thought to be the result of a binary system. We speculate that the engulfing and destruction of an exoplanet during the AGB phase may have been a key event in shaping MyCn 18 and generating of its hypersonic knotty outflow.Comment: 15 pages, 3 tables, 13 figures. Accepted for publication by A&

Clumpy Ultracompact HII Regions I: Fully Supersonic Wind-blown Models

We propose that a significant fraction of the ultracompact HII regions found in massive star-forming clouds are the result of the interaction of the wind and ionizing radiation from a young massive star with the clumpy molecular cloud gas in its neighbourhood. Distributed mass loading in the flow allows the compact nebulae to be long-lived. In this paper, we discuss a particularly simple case, in which the flow in the HII region is everywhere supersonic. The line profiles predicted for this model are highly characteristic, for the case of uniform mass loading. We discuss briefly other observational diagnostics of these models.Comment: To appear in Monthly Notices of the Royal Astronomical Society. 5 pages LaTeX (uses mn.sty and epsf.sty macros) + 4 PS figures. Also available via http://axp2.ast.man.ac.uk:8000/Preprints.htm

Baculovirus diversity and its effect on virulence.

The baculovirus, SpexNPV is the biggest mortality agent of natural populations of the African armyworm, Spodoptera exempta and in terms of control has displayed considerable potential as a bioinsecticide in aerial spray trials undertaken by Natural Resources International (NRI). This project was charged with assessing the diversity of natural populations of SpexNPV, a subject of direct relevance for the development of SpexNPV as a bioinsecticde and about which little was known. The genetic composition of a natural SpexNPV population was characterized using in vivo cloning techniques and RFLP analysis. Seventeen individual genotypes were isolated from the wild-type population and phylogenetic analysis was carried out to attempt to assess their potential relatedness, but no single conclusion on their shared histories could be reached. The fitness traits (pathogenicity, speed of kill and viral yield of OBs) of eight genotypes and the wild-type virus were assessed in laboratory bioassays. A nine-fold difference in pathogenicity (estimated in terms of LD50) was witnessed between the different genotypes. Genotypes and wild-type virus also varied in their speed of kill and yield and although there was evidence of a trade-off between speed of kill and yield trade-off, for a number of the genotypes, this study failed to demonstrate any statistical evidence for a general trade-off between these fitness traits. SpexNPV epizootics, from out-breaking populations of armyworm in Northern Tanzania, were sampled in 2002 and 2004. RFLP analysis was conducted on individual virus-infected larvae and revealed a high level of heterogeneity. In addition, forty percentage of all isolates analysed were identified as mixed-genotype infections by the presence of sub-molar bands in RE profiles. This genetic diversity appeared to lack any obvious population structure. Controlled mixed-genotype inoculations were carried out to assess any change in phenotype relative to single-genotype infections. Genotypes, which were found to be equally pathogenic in single-genotype infections, were combined in equal ratio. Thirteen different dual inoculations were carried out across a range of doses. Mixedgenotype infections were found to be more pathogenic, and in general, possess longer speeds of kill relative to single genotype infections. The effect on yield varied considerably between mixtures. The inclusion of more than two genotypes within the mixtures (2-, 4-, 8-, and 16-genotype inoculations) revealed a correlation between level of diversity and pathogenicity and, to a certain extent, between level of diversity and speed of kill. This appears to suggest that mixed-infections possess higher levels of fitness than single genotype infections and that genetic diversity of SpexNPV should be maintained when used as a bioinsecticide

Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68

We present observations of 13CO, C18O, HCO+, H13CO+, DCO+ and N2H+ line emission towards the Barnard 68 starless core. The line profiles are interpreted using a chemical network coupled with a radiative transfer code in order to reconstruct the radial velocity profile of the core. Our observations and modeling indicate the presence of complex radial motions, with the inward motions in the outer layers of the core but outward motions in the inner part, suggesting radial oscillations. The presence of such oscillation would imply that B68 is relatively old, typically one order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the radial velocity profiles of starless cores.Comment: 12 pages, 3 figures, to appear in the Astrophysical Journal Letter