Flow instabilities in transonic small disturbance theory

The dynamics of unsteady transonic small disturbance flows about two-dimensional airfoils is examined, with emphasis on the behavior in the region where the steady state flow is nonunique. It is shown that nonuniqueness results from an extremely long time scale instability which occurs in a finite Mach number and angle of attack range. The similarity scaling rules for the instability are presented and the possibility of similar behavior in the Euler equations is discussed

Astrochemistry and Astrophotonics for an Antarctic Observatory

Due to its location and climate, Antarctica offers unique conditions for long-period observations across a broad wavelength regime, where important diagnostic lines for molecules and ions can be found, that are essential to understand the chemical properties of the interstellar medium. In addition to the natural benefits of the site, new technologies, resulting from astrophotonics, may allow miniaturised instruments, that are easier to winterise and advanced filters to further reduce the background in the infrared.Comment: 4 pages, to be published in EAS Publications Series, Vol. 40, Proc. of 3rd ARENA conferenc

Free serum cortisol during the postoperative acute phase response determined by equilibrium dialysis liquid chromatography-tandem mass spectrometry

In severely ill patients low concentrations of the corticosteroid binding globulin are typically found; the aim of this study was to quantify directly free bioactive cortisol concentrations in the sera of postoperative cardiosurgical patients. Serum samples of 12 consecutive patients undergoing aortocoronary bypass surgery taken preoperatively and on the postoperative days 1 to 4 were analyzed. Total serum cortisol was quantified using liquid chromatographytandem mass spectrometry with an online sample extraction system and trideuterated cortisol as the internal standard, and free serum cortisol was measured after overnight equilibrium dialysis. Whereas on the first postoperative day, the median total serum cortisol concentration was approximately twofold increased compared to preoperative samples (preoperatively, 245 nmol/l (interquartile range (IQR) 203293 nmol/l); first postoperative day, 512 nmol/l (IQR 410611 nmol/l)), median dialyzable free cortisol concentration was almost sevenfold increased (preoperatively, 14.2 nmol/l (IQR 10.920.7 nmol/l); first postoperative day, 98.3 nmol/l (IQR 81.3134 nmol/l)). On the fourth postoperative day, median free cortisol was still significantly increased compared to baseline sampling (p < 0.05), whereas median total cortisol was not. A median of 5.7% (IQR 5.47.0%) of total cortisol was found as free cortisol on the preoperative day, 21.2% (IQR 18.9 23.5%) on the first postoperative day and 10.5% (IQR 9.814.0%) on the fourth postoperative day. It is concluded that during the postoperative period the freeto bound ratio of cortisol is highly variable and that during the acute phase response direct quantification of free bioactive cortisol concentrations seems to be biologically more appropriate than the measurement of total cortisol concentrations

Statistical analysis of the primary outcome in acute stroke trials

Common outcome scales in acute stroke trials are ordered categorical or pseudocontinuous in structure but most have been analyzed as binary measures. The use of fixed dichotomous analysis of ordered categorical outcomes after stroke (such as the modified Rankin Scale) is rarely the most statistically efficient approach and usually requires a larger sample size to demonstrate efficacy than other approaches. Preferred statistical approaches include sliding dichotomous, ordinal, or continuous analyses. Because there is no best approach that will work for all acute stroke trials, it is vital that studies are designed with a full understanding of the type of patients to be enrolled (in particular their case mix, which will be critically dependent on their age and severity), the potential mechanism by which the intervention works (ie, will it tend to move all patients somewhat, or some patients a lot, and is a common hazard present), a realistic assessment of the likely effect size, and therefore the necessary sample size, and an understanding of what the intervention will cost if implemented in clinical practice. If these approaches are followed, then the risk of missing useful treatment effects for acute stroke will diminish

The Taurus Tunable Filter Field Galaxy Survey: Sample Selection and Narrowband Number-Counts

Recent evidence suggests a falling volume-averaged star-formation rate (SFR) over z ~ 1. It is not clear, however, the extent to which the selection of such samples influences the measurement of this quantity. Using the Taurus Tunable Filter (TTF) we have obtained an emission-line sample of faint star-forming galaxies over comparable lookback times: the TTF Field Galaxy Survey. By selecting through emission-lines, we are screening galaxies through a quantity that scales directly with star-formation activity for a given choice of initial mass function. The scanning narrowband technique furnishes a galaxy sample that differs from traditional broadband-selected surveys in both its volume-limited nature and selection of galaxies through emission-line flux. Three discrete wavelength intervals are covered, centered at H-alpha redshifts z = 0.08, 0.24 and 0.39. Galaxy characteristics are presented and comparisons made with existing surveys of both broadband and emission-line selection. When the number-counts of emission-line objects are compared with those expected on the basis of existing H-alpha surveys, we find an excess of ~ 3 times at the faintest limits. While these detections are yet to be independently confirmed, inspection of the stronger subsample of galaxies detected in both the line and continuum (line-on-continuum subsample; 13 %) is sufficient to support an excess population. This increase in the emission-line field population implies higher star-formation densities over z ~ 0.4. However, further study in the form of multi-object spectroscopic follow-up is necessary to quantify this and confirm the faintest detections in the sample.Comment: 48 pages, 12 figures. To appear in the Astrophysical Journal. An abridged version of the Abstract is shown her

Cohort Profile: Mamanengane or the Africa Centre Vertical Transmission Study

How did the study come about? From the mid-1990s, the success of antiretroviral prophylaxis to reduce HIV RNA viral load in plasma and avoidance of breastfeeding provided the real possibility that mother-to-child transmission (MTCT) of HIV-1 could be markedly reduced, 1 with an implicit understanding that these measures could be effectively applied to all HIV-infected women in developing countries. 2,3 The latter constitute the overwhelming majority of HIV-positive pregnancies resulting in approximately half a million new infant infections annually. 4 However, the inappropriate use of formula milks amongst impoverished populations resulted in major adverse effects; without the nutritiona

Spin-Orbit Coupling in LaAlO3_3/SrTiO3_3 interfaces: Magnetism and Orbital Ordering

The combination of Rashba spin-orbit coupling and electron correlations can induce unusual phenomena in the metallic interface between SrTiO$_3$ and LaAlO$_3$. We consider effects of Rashba spin-orbit coupling at this interface in the context of the recent observation of anisotropic magnetism. Firstly, we show how Rashba spin-orbit coupling in a system near a band-edge can account for the observed magnetic anisotropy. Secondly, we investigate the coupling between in-plane magnetic-moment anisotropy and nematicity in the form of an orbital imbalance between d$_{xz}$ / d$_{yz}$ orbitals. We estimate this coupling to be substantial in the low electron density regime. Such an orbital ordering can affect magneto transport

NGC 300: an extremely faint, outer stellar disk observed to 10 scale lengths

We have used the Gemini Multi-object Spectrograph (GMOS) on the Gemini South 8m telescope in exceptional conditions (0.6" FWHM seeing) to observe the outer stellar disk of the Sculptor group galaxy NGC 300 at two locations. At our point source detection threshold of r' = 27.0 (3-sigma) mag, we trace the stellar disk out to a radius of 24', or 2.2 R_25 where R_25 is the 25 mag/arcsec**2 isophotal radius. This corresponds to about 10 scale lengths in this low-luminosity spiral (M_B = -18.6), or about 14.4 kpc at a cepheid distance of 2.0 +/- 0.07 Mpc. The background galaxy counts are derived in the outermost field, and these are within 10% of the mean survey counts from both Hubble Deep Fields. The luminosity profile is well described by a nucleus plus a simple exponential profile out to 10 optical scale lengths. We reach an effective surface brightness of 30.5 mag/arcsec**2 (2-sigma) at 55% completeness which doubles the known radial extent of the optical disk. These levels are exceedingly faint in the sense that the equivalent surface brightness in B or V is about 32 mag/arcsec**2. We find no evidence for truncation of the stellar disk. Only star counts can be used to reliably trace the disk to such faint levels, since surface photometry is ultimately limited by nonstellar sources of radiation. In the Appendix, we derive the expected surface brightness of one such source: dust scattering of starlight in the outer disk.Comment: ApJ accepted -- 30 pages, 13 figures -- see ftp://www.aao.gov.au/pub/local/jbh/astro-ph/N300 for full resolution figures and preprin