A Dark Hydrogen Cloud in the Virgo Cluster

VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies et al. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocity width of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy with this velocity width would be expected to be 12th magnitude or brighter; however deep CCD imaging has failed to turn up a counterpart down to a surface-brightness level of 27.5 B mag/sq. arcsec. The HI observations show that it is extended over at least 16 kpc which, if the system is bound, gives it a minimum dynamical mass of ~10^11 M_solar and a mass to light ratio of M_dyn/L_B > 500 M_solar/L_solar. If it is tidal debris then the putative parents have vanished; the remaining viable explanation is that VIRGOHI21 is a dark halo that does not contain the expected bright galaxy. This object was found because of the low column density limit of our survey, a limit much lower than that achieved by all-sky surveys such as HIPASS. Further such sensitive surveys might turn up a significant number of the dark matter halos predicted by Dark Matter models.Comment: Accepted by ApJ

Reduction of claustrophobia during magnetic resonance imaging: methods and design of the "CLAUSTRO" randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Magnetic resonance (MR) imaging has been described as the most important medical innovation in the last 25 years. Over 80 million MR procedures are now performed each year and on average 2.3% (95% confidence interval: 2.0 to 2.5%) of all patients scheduled for MR imaging suffer from claustrophobia. Thus, prevention of MR imaging by claustrophobia is a common problem and approximately 2,000,000 MR procedures worldwide cannot be completed due to this situation. Patients with claustrophobic anxiety are more likely to be frightened and experience a feeling of confinement or being closed in during MR imaging. In these patients, conscious sedation and additional sequences (after sedation) may be necessary to complete the examinations. Further improvements in MR design appear to be essential to alleviate this situation and broaden the applicability of MR imaging. A more open scanner configuration might help reduce claustrophobic reactions while maintaining image quality and diagnostic accuracy.</p> <p>Methods/Design</p> <p>We propose to analyze the rate of claustrophobic reactions, clinical utility, image quality, patient acceptance, and cost-effectiveness of an open MR scanner in a randomized comparison with a recently designed short-bore but closed scanner with 97% noise reduction. The primary aim of this study is thus to determine whether an open MR scanner can reduce claustrophobic reactions, thereby enabling more examinations of claustrophobic patients without incurring the safety issues associated with conscious sedation. In this manuscript we detail the methods and design of the prospective "CLAUSTRO" trial.</p> <p>Discussion</p> <p>This randomized controlled trial will be the first direct comparison of open vertical and closed short-bore MR systems in regards to claustrophobia and image quality as well as diagnostic utility.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00715806">NCT00715806</a></p

A case-based approach to UTI imaging – making sense of the guidelines

Urinary tract infections (UTIs) are common amongst children and invariably result in imaging tests to look for correctable causes that may predispose the child to infection. The objective of imaging is to identify those children at risk of long-term renal damage. The ideal imaging algorithm is extensively debated in the literature owing to the lack of evidence-based data, evolving theories on the pathophysiology of UTI and vesicoureteric reflux (VUR). The present article provides a case-based approach to the imaging of UTIs and proposes guidelines relevant to the South African setting

Lecture - Distinguished Professor Peter Hannaford AC: Crystallizing Time with Lasers

To celebrate his appointment as a Companion of the Order of Australia (AC) for eminent service to science, please join Swinburne Distinguished Professor Peter Hannaford as he discusses the fascinating realm of 'Time Crystals'. The discovery of the laser by Ted Maiman in 1960 was greeted as a gift from the gods, to be able to pour watts of tuneable coherent light into just a few kilohertz along a line almost as straight as a geodesic. The laser has since revolutionised our daily lives, but it has also revolutionised scientific research. For instance, lasers now allow us to chill a cloud of atoms down to within just a few nanokelvin of absolute zero and to enter the strange quantum world of the Bose-Einstein condensate, predicted by Einstein in 1925 and realised in the laboratory some 70 years later. More recently, it has been predicted, by Krzysztof Sacha in Krakow, that a Bose-Einstein condensate, when periodically driven, can spontaneously reorganise its motion so that it evolves with a period some tens of times longer than the period of the drive, to form a new state of quantum matter – a ‘time crystal’. In this lecture, Professor Hannaford will describe an experiment currently in progress at Swinburne to create such a big time crystal, which promises to allow us to extend condensed matter science to the fourth dimension – time

Spatial ecology and resource selection of a high elevation American marten population in the northeastern United States

High elevation forests that contain mature, closed canopy stands are considered important habitat for American martens (Martes americana, (Turton, 1806)) in the northeastern United States. To investigate this hypothesis, we monitored 15 radio-collared martens over a 2-year period and measured spatial use, and second- and third-order resource selection from 33 seasonal home ranges and 889 telemetry locations. The population was comprised primarily of adults that had small home range size with average seasonal fidelity. During leaf-off seasons, martens selected against regenerating forest at both scales and selected for mixedwood and softwood forest and areas with rugged terrain within home ranges. Second order selection was less pronounced during leaf-on seasons, yet martens exhibited greater selection for hardwood forest and areas with rugged terrain within home ranges. Home range size was correlated positively with amount of regenerating forest, and body condition index scores were lower during winter indicating that these spatial and temporal attributes were influential. Although martens utilized low elevation forest with extensive timber harvesting, contiguous, mature and rugged high elevation forest was used preferentially during winter. Land managers should minimize disturbance of montane ecosystems to ensure population viability for martens and other boreal forest species along distributional edges.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author