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The Taipan galaxy survey (hereafter simply ‘Taipan’) is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z < 0.4. Taipan will use the newly refurbished 1.2-m UK Schmidt Telescope at Siding Spring Observatory with the new TAIPAN instrument, which includes an innovative ‘Starbugs’ positioning system capable of rapidly and simultaneously deploying up to 150 spectroscopic fibres (and up to 300 with a proposed upgrade) over the 6° diameter focal plane, and a purpose-built spectrograph operating in the range from 370 to 870 nm with resolving power R ≳ 2000. The main scientific goals of Taipan are (i) to measure the distance scale of the Universe (primarily governed by the local expansion rate, H0) to 1% precision, and the growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated ‘virtual observer’ software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.
In arid and semiarid winter crop growing regions of southern Australia, low rainfall, high evaporation, and low soil moisture storage are the limiting factors for crop production. In this region canola (Brassica napus L.) is principally grown in rotation with wheat and pasture species. Some field studies have indicated Indian mustard (Brassica juncea L.) to be more drought tolerant than canola and therefore considered to be better adapted than canola to short season environments. A field experiment was conducted at Wagga Wagga in NSW to determine the effect of two soil moisture regimes on water use efficiency, harvest index, seed and oil quality of cv. Oasis of Indian mustard and cv. Skipton of canola. Significant year × stress and species × stress interaction effects were observed for grain yield, harvest index, seed weight, biomass water productivity, and grain water productivity. Irrigation during the post flowering period resulted in 50% and 200% increases in canola grain yield in the first year (year with higher in-crop water) and the second year (year with low in-crop water), respectively. For mustard, these values were 7% and 45%, respectively. Stressed mustard resulted in higher grain yield than stressed canola while irrigated canola performed better than irrigated mustard. High mustard biomass production resulted in lowering its harvest index. Generally, the biomass water productivity of mustard was higher than that of canola. Grain yield-based water productivity of stressed mustard was higher than that of stressed canola while irrigated canola had higher water productivity than irrigated mustard. When rainfall and actual evapotranspiration drop below some thresholds, mustard becomes a favourable crop. Generally, effects due to the water treatments (stressed v irrigated) were much larger than the differences due to species.
National and international policies have encouraged the establishment of a representative network of marine protected areas (MPAs) in South Africa, with the aim of protecting marine biodiversity. The extent to which these marine and estuarine protected areas (EPAs) represent marine fish species and communities was assessed by comparing their species compositions with those of exploited areas, as sampled using four fishing techniques. Seven hundred fish species were sampled, representing one-third of South Africa's marine fishes. MPAs in coastal habitats scored c. 40% on the Bray-Curtis measure of similarity for species representativeness, but this score declined markedly for offshore ‘trawlable’ fishing grounds. The combined effects of sampling error, temporal variation and the effects of fishing on relative abundance suggest that 80% similarity would be the maximum achieveable. Forty-nine per cent of all fish species that were recorded were found in the 14 MPAs sampled. Redundancy in the MPA network was low, with fish species most commonly being represented in only one MPA or absent. There was greater redundancy in the 33 EPAs, with 40% of species being found in two or more EPAs, but many of these estuaries were adjacent to each other and embedded in large MPAs. Deep water fish communities (>80 m deep) and communities located on the west and south-east coasts of South Africa were most poorly represented by MPAs. Routine fishery surveys provide a robust and repeatable opportunity to assess species representativeness in MPAs, and the method used could form the basis of an operational definition of ‘representative’. In contrast to an assessment based on presence-absence data, this analysis of quantitative data presents a more pessimistic assessment of protection.
Ionizing shocks for plane flows with the magnetic field lying in the flow plane are considered. The gas is assumed to be electrically conducting downstream, but non-conducting upstream. Shocks whose downstream state has a normal velocity component less than the slow magneto-acoustic-wave speed and whose upstream state is supersonic are found to be non-evolutionary in the face of plane magneto-acoustic disturbances, unless the upstream electric field in a frame of reference where the gas is at rest is arbitrary. Velocity conditions are also determined for shock stability with the electric field not arbitrary.
Shock structures are found for the case of large ohmic diffusion, the initial temperature rise and ionization of the gas being caused by a thin transition having the properties of an ordinary gasdynamic shock. For the case where shocks are evolutionary when the upstream electric field is arbitrary, the shock structure requirements only restrict the electric field by limiting the range of possible values. When shocks are evolutionary with the electric field not arbitrary, they can only have a structure for a particular value of the electric field. Limits to the current carried by ionizing shocks and the effects of precursor ionization are discussed qualitatively.
Dasyatis chrysonota is perhaps the most common of the 14 whiptail stingray (Chondrichthyes: Dasyatidae) species known to frequent the temperate coastal waters of southern Africa and like other stingrays they possess life history characteristics that make them vulnerable to over-exploitation. First and 50% maturity (Dw50) were determined for 153 males and 204 females from the Eastern Cape Province of South Africa. Disc width (Dw) for first and Dw50 maturity was estimated at 392 mm and 395 mm Dw, respectively for males and at 500 mm and 505 mm Dw, respectively for females. The reproductive cycle of males, based on gonadosomatic (GSI) and hepatosomoatic (HSI) indices indicates that they are most active during the spring. Females appear to have an annual reproductive cycle with a maximum HSI occurring during the summer and autumn, but it declines steadily through the birthing season reaching a low in the late spring. Fecundity, following a nine month gestation period, averages 2.8 with a range of 1–7. Embryos at six different development stages are described. Dasyatis chrysonota, like other dasyatids, exhibit life history characteristics that make them vulnerable to overexploitation, therefore a precautionary management strategy is advised for this species.
At the 2003 Sydney IAU meeting, Marion Schmitz (Caltech, USA) took over the chair of the Commission 5 Working Group Designations, succeeding Helene Dickel. The Working Group Designations of IAU Commission 5 clarifies existing astronomical nomenclature and helps astronomers avoid potential problems when designating their sources. The most important function of WG Designations during the period 2003-2005 was overseeing the IAU REGISTRY FOR ACRONYMS (for newly discovered astronomical sources of radiation: see the website <http://cdsweb.u-strasbg.fr/cgi-bin/DicForm>) which is sponsored by the WG and operated by the Centre de Données de Strasbourg (CDS). The Clearing House, a subgroup of the WG, screens the submissions for accuracy and conformity to the IAU Recommendations for Nomenclature (<http://cdsweb.u-strasbg.fr/iau-spec.html>). From its beginning in 1997 through August 2006, there have been 132 submissions and 111 acceptances. Attempts to register asterisms, common star names, and suspected variable stars were rejected. The past three years saw 61 acronyms submitted with 50 of them being accepted. (GIRL - yes; WOMEN - no).
The antimicrobial resistance profiles of Campylobacter isolates recovered from a range of retail food samples (n=374) and humans (n=314) to eight antimicrobial compounds were investigated. High levels of resistance in food C. jejuni isolates were observed for ceftiofur (58%), ampicillin (25%) and nalidixic acid (17%) with lower levels observed for streptomycin (7·9%) and chloramphenicol (8·3%). A total of 80% of human C. jejuni isolates were resistant to ceftiofur, while 17% showed resistance to ampicillin and nalidixic acid, 8·6% to streptomycin and 4·1% to chloramphenicol. Resistance to clinically relevant antimicrobials such as erythromycin, ciprofloxacin and tetracycline was 6·7, 12, and 15% respectively for all food isolates and was similar to corresponding resistance prevalences observed for human isolates, where 6·4, 12 and 13% respectively were found to be resistant. Comparisons of C. jejuni isolates in each location showed a high degree of similarity although some regional variations did exist. Comparison of total C. jejuni and C. coli populations showed minor differences, with C. jejuni isolates more resistant to ampicillin and ceftiofur. Multidrug resistance patterns showed some profiles common to human and clinical isolates.
In this paper, an experimental study of laminar magnetohydrodynamic (MHD)
buoyancy-driven flow in a cylindrical cell with axis horizontal is described. A steady
uniform magnetic field is applied vertically to the mercury-filled cell, which is also
subjected to a horizontal temperature gradient. The main features of this internal
MHD thermogravitational flow are made experimentally evident from temperature
and electric potential measurements. Whatever the level of convection, raising the
Hartmann number Ha to a value of the order of 10 is sufficient to stabilize an
initially turbulent flow. At much higher values of the Hartmann number (Ha∼100)
the MHD effects cause a change of regime from boundary-layer driven to core
driven. In this latter regime an inviscid inertialess MHD core flow is bounded by a
Hartmann layer on the horizontal cylindrical wall and viscous layers on the endwalls.
Since the Hartmann layer is found to stay electrically inactive along the cell, the
relevant asymptotic (Ha[Gt ]1) laws for velocity and heat transfer are found from the
balance between the curl of buoyancy and Lorentz forces in the core, together with
the condition that the flow of electric current between core and Hartmann layer is
negligible. A modified Rayleigh number RaG/Ha2,
which is a measure of the ratio of thermal convection to diffusion when there is a balance
between buoyancy and Lorentz forces, is the determining parameter for the flow.
The supersoft X-ray sources are a distinct class of X-ray sources identified by ROSAT. They are characterized by very high luminosities (Lbol ~ 1038 ergs s−1) and black body temperatures of kT~ 30–60 eV. These sources are easily detected in the LMC and SMC because of the low column density of absorbing H gas. Thus, the samples found there are complete. They are much more difficult to find in the Galaxy due to soft X-ray absorption in the galactic plane.
In this study we compare the global populations of stellar X-ray sources in the LMC, SMC, and the Galaxy. After removing foreground stars and background AGN from the samples, the relative numbers of the various types of X-ray point sources within the LMC and SMC are similar, but differ markedly from those in the Galaxy. The Magellanic Clouds are rich in high-mass X-ray binaries (HMXB), especially those containing rapidly rotating Be stars. However, the LMC and SMC both lack the large number of low-mass X-ray binaries (LMXB) found in the Milky Way, which are known to represent a very old stellar population based on their kinematics, chemical composition, and spatial distribution.
Data obtained with ROSAT have established the “supersoft” X-ray sources (SSS) as a separate class of objects. Their unique features include temperatures of ∼30 eV and luminosities of ∼1038 erg s−1. Hasinger (1994) has recently summarized the properties of the SSS presently known in the Galaxy and the Magellanic Clouds (cf., Kahabka & Trümper 1995). The six which are thought to be LMC members are listed in Table 1 and discussed individually, based primarily on optical data we have obtained at CTIO.
Inviscid, adiabatic, one-dimensional flow of a conducting gas in the presence of crossed electric and magnetic fields is investigated for the case where the magnetic field is generated by the current being supplied to the gas. The electrode geometry and the connections to the electrical power supply are such that the magnetic field falls to zero at the downstream end of the MHD duct. The analysis allows for magnetic Reynolds number rm to be anywhere in the range 0 to ∞ The main part of the investigation is restricted to consideration of ducts with constant spacing between electrodes.
The way in which the density of the gas varies along the duct with the changing magnetic field is analysed generally and the results are then applied to the case where gas is fed to the MHD duct from high pressure in a plenum chamber and where the duct exhausts to a region of negligible pressure. If the flow is choked by the converging entry to the duct and the magnetic Reynolds number is moderate to high, the main electromagnetic effect is for the j × B forces to accelerate the gas to supersonic speeds. As rm is reduced, ohmic heating becomes more important, and it may cause the flow to be choked at exit from the duct, giving rise to a reduction in mass flow. For certain ranges of rm and ratio of initial magnetic pressure to plenum-chamber pressure the flow may choke at a sonic point within the duct itself, while accelerating from subsonic to supersonic through the point.
Some illustrative examples of how properties vary with distance along the duct have been computed and the consequences of the analysis for MHD thrusters are explored. The magnetic forces will augment thrust per unit cross-sectional area, the essential measure of this being the drop in magnetic pressure along the duct, but there is an upper limit on the ratio of magnetic pressure to plenum-chamber pressure for flows to be possible. Flow at low magnetic Reynolds number is favoured if the object is to increase specific thrust by reducing mass flow through the duct.
The instability of hypersonic boundary-layer flow over a flat plate is considered. The viscosity of the fluid is taken to be governed by Sutherland's formula, which gives a more accurate representation of the temperature dependence of fluid viscosity at hypersonic speeds than Chapman's approximate linear law. A Prandtl number of unity is assumed. Attention is focused on inviscid instability modes of viscous hypersonic boundary layers. One such mode, the ‘vorticity’ mode, is thought to be the fastest growing disturbance at high Mach numbers, M [Gt ] 1; in particular it is believed to have an asymptotically larger growth rate than any viscous instability. As a starting point we investigate the instability of the hypersonic boundary layer which exists far downstream from the leading edge of the plate. In this regime the shock that is attached to the leading edge of the plate plays no role, so that the basic boundary layer is non-interactive. It is shown that the vorticity mode of instability operates on a different lengthscale from that obtained if a Chapman viscosity law is assumed. In particular, we find that the growth rate predicted by a linear viscosity law overestimates the size of the growth rate by O((log M)½). Next, the development of the vorticity mode as the wavenumber decreases is described. It is shown, inter alia, that when the wavenumber is reduced to O(M-3/2) from the O(1) initial, ‘vorticity-mode’ scaling, ‘acoustic’ modes emerge.
Finally, the inviscid instability of the boundary layer near the leading-edge interaction zone is discussed. Particular attention is focused on the strong-interaction zone which occurs sufficiently close to the leading edge. We find that the vorticity mode in this regime is again unstable. The fastest growing mode is centred in the adjustment layer at the edge of the boundary layer where the temperature changes from its large, O(M2). value in the viscous boundary layer, to its O(1) free-stream value. The existence of the shock indirectly, but significantly, influences the instability problem by modifying the basic flow structure in this layer.
The space distribution of quasars discovered in our CFHT blue grens survey is discussed in detail. Redshifts for about 200 of the quasar candidates show that the sample is relatively complete for 0.2 < z < 3.4 and m < 20.5. Two-thirds of the quasars have z < 1.8 and only 5% have z > 2.5, indicating that high redshift quasars are rare. The surface density of quasars brighter than m = 20.5 is 30 deg−2. Seven quasars with z = 1.165 ± 0.007 discovered in one of the fields have typical separations of ≈20 Mpc and may belong to a very large structure. Statistical tests on our data indicate that clustering among quasars is not common, however. The luminosity dependent density evolution models proposed by Schmidt and Green (1983) combined with a redshift cutoff at high redshift are consistent with our data and that of Schmidt and Green (1983), Marshall et al. (1984), Koo, Kron and Cudworth (1986), and Schmidt, Schneider and Gunn (1986). The model indicates that there was a broad maximum in the comoving density of quasars near z = 1.7. The results will be reported in detail in the March 1987 issue of The Astrophysical Journal.
The best X-ray position (Einstein Observatory HRI - Giacconi et al 1979) for LMC X-3 confirms its identification with the early type star first suggested by Warren and Penfold (1975). Our spectroscopic observations obtained with the CTIO 4–m telescope show the WP star is a slightly reddened B3 V star with mV ≈ 16.9. Large radial velocity variations (Δv ≈ 500 km s−1) reveal an orbital period of 1.7049 days. From the orbital elements (Table 1) one can determine the mass function f(M) = (Mx sin i)3/(Mopt + Mx)2 = 2.3 M⊙, which shows without any assumptions about the mass of the optical star, the orbital inclination, or the mass ratio the unseen X-ray object has a mass >2.3 M⊙. Detailed analysis of the HEAO–1 scanning modulation collimator X-ray data shows that the system does not eclipse, implying that the orbital inclination is ≤ 65°. Assuming the B star mass lies between 4 and 8 M⊙ (an average mass for a normal B3 V star would be about 6–7 M⊙), the mass of the unseen companion must lie between 7 and 13 M⊙ (see Fig. 4a - Hutchings, this volume). Smaller inclinations of course give even higher masses. An important point is that the unseen star must have a mass larger than that of the B star, and thus if it were any kind of normal star it should be easily seen in the spectrum. Thus the X-ray emitting object is a very good candidate for a black hole.
The recent revival of techniques for the imaging of crystal surfaces, using electrons forward-scattered in the RHEED mode and employing modern electron microscopes, has lead to the introduction of valuable new methods for the study of surface structure. Either fixed beam or scanning transmission electron microscopy (STEM) instruments may be used and in each case a lateral resolution of 10Å or better is possible. Simple theoretical treatments suggest that the contrast from surface steps may be attributed to a combination of phase-contrast, diffraction contrast and geometric effects. With a STEM instrument the image information can be combined with information on the local composition and crystal structure by use of microanalysis and microdiffraction techniques. Examples of applications include studies of the surface structure of metals, semiconductors and oxides, and the surface reactions.