The sinister steeples of Alexander North

Alexander North (1858–1945), who practised chiefly in Tasmania, was an outstandingly original architect during the stylistic period in Australia now commonly called Federation. His work includes features that represent an extreme expression of established forms, and draws attention to some inadequately explained characteristics of the period. Prominent among these is a series of church spires that North designed in Tasmania between 1893 and 1927, which evoke peculiar associations in the minds of many who notice them. Those associations, which depend mainly on graphic works published during the same era, were unlikely to have been intended by the architect. They provide evidence in support of an associationist theory of aesthetic response that has gone out of fashion, and a salutary reminder that architectural historians must seek to see through the eyes of their period and not the projections of hindsight

A rock in a hard place : European use of dolerite in Tasmania

Despite being more prevalent in Tasmania than elsewhere, dolerite found relatively limited use by early European settlers. Dolerite was used in foundations, basements and retaining walls, but was difficult to shape and at least in the first half of the colonial century, highly unfashionable both in colour and texture, although acceptable for industrial buildings and rural outbuildings. Later in the nineteenth century, quarried stones of uniform colour were used to build some notable churches as well as basements for buildings of other materials. There was a progression during the three decades before the First World War from use of stones of varied size to a preference for stones of regular appearance; after which dolerite was largely replaced by concrete. For much of the twentieth century, dolerite was chiefly crushed for road metal, concrete aggregate or railway ballast, with occasional use in formal building. Towards the end of that period, it returned to building in decorative features, and to engineering practice as filling for gabions and in massive assemblies of boulders. This overview traces the use of dolerite in Tasmania from early colonial times to present-day practices in fashionable architecture and as a structural building material

Averaged electron collision cross sections for thermal mixtures of beta-alanine conformers in the gas phase

A theoretical study of elastic electron scattering by gas-phase amino acid molecule β-alanine (NH2–CH2–CH2–COOH) is presented. R-matrix calculations are performed for each of the ten lowest-lying, thermally-accessible conformers of β-alanine. Eigenphase sums, resonance features, differential and integral cross sections are computed for each conformer. The positions of the low-energy shape resonance associated with the unoccupied ${\pi }^{* }$ orbital of the −COOH group are found to vary from 2.5 to 3.3 eV and the resonance widths from 0.2 to 0.5 eV depending on the conformation. The temperature-dependent population ratios are derived, based on temperature-corrected Gibbs free energies. Averaged cross sections for thermal mixtures of the 10 conformers are presented. A comparison with previous results for the α-alanine isomer is also presented

Variability of myocardial perfusion dark rim Gibbs artifacts due to sub-pixel shifts

<p>Abstract</p> <p>Background</p> <p>Gibbs ringing has been shown as a possible source of dark rim artifacts in myocardial perfusion studies. This type of artifact is usually described as transient, lasting a few heart beats, and localised in random segments of the myocardial wall. Dark rim artifacts are known to be unpredictably variable. This article aims to illustrate that a sub-pixel shift, i.e. a small displacement of the pixels with respect to the endocardial border, can result in different Gibbs ringing and hence different artifacts. Therefore a hypothesis for one cause of dark rim artifact variability is given based on the sub-pixel position of the endocardial border. This article also demonstrates the consequences for Gibbs artifacts when two different methods of image interpolation are applied (post-FFT interpolation, and pre-FFT zero-filling).</p> <p>Results</p> <p>Sub-pixel shifting of <it>in vivo </it>perfusion studies was shown to change the appearance of Gibbs artifacts. This effect was visible in the original uninterpolated images, and in the post-FFT interpolated images. The same shifted data interpolated by pre-FFT zero-filling exhibited much less variability in the Gibbs artifact. The <it>in vivo </it>findings were confirmed by phantom imaging and numerical simulations.</p> <p>Conclusion</p> <p>Unless pre-FFT zero-filling interpolation is performed, Gibbs artifacts are very dependent on the position of the subendocardial wall within the pixel. By introducing sub-pixel shifts relative to the endocardial border, some of the variability of the dark rim artifacts in different myocardial segments, in different patients and from frame to frame during first-pass perfusion due to cardiac and respiratory motion can be explained. Image interpolation by zero-filling can be used to minimize this dependency.</p

Three dimensional first-pass myocardial perfusion imaging at 3T: feasibility study

<p>Abstract</p> <p>Background</p> <p>In patients with ischemic heart disease, accurate assessment of the extent of myocardial perfusion deficit may be important in predicting prognosis of clinical cardiac outcomes. The aim of this study was to compare the ability of three dimensional (3D) and of two dimensional (2D) multi-slice myocardial perfusion imaging (MPI) using cardiovascular magnetic resonance (CMR) in determining the size of defects, and to demonstrate the feasibility of 3D MPI in healthy volunteers at 3 Tesla.</p> <p>Methods</p> <p>A heart phantom was used to compare the accuracy of 3D and 2D multi-slice MPI in estimating the volume fraction of seven rubber insets which simulated transmural myocardial perfusion defects. Three sets of cross-sectional planes were acquired for 2D multi-slice imaging, where each set was shifted along the partition encoding direction by ± 10 mm. 3D first-pass contrast-enhanced (0.1 mmol/kg Gd-DTPA) MPI was performed in three volunteers with sensitivity encoding for six-fold acceleration. The upslope of the myocardial time-intensity-curve and peak SNR/CNR values were calculated.</p> <p>Results</p> <p>Mean/standard deviation of errors in estimating the volume fraction across the seven defects were -0.44/1.49%, 2.23/2.97%, and 2.59/3.18% in 3D, 2D 4-slice, and 2D 3-slice imaging, respectively. 3D MPI performed in healthy volunteers produced excellent quality images with whole left ventricular (LV) coverage. Peak SNR/CNR was 57.6 ± 22.0/37.5 ± 19.7 over all segments in the first eight slices.</p> <p>Conclusion</p> <p>3D performed better than 2D multi-slice MPI in estimating the size of perfusion defects in phantoms. Highly accelerated 3D MPI at 3T was feasible in volunteers, allowing whole LV coverage with excellent image quality and high SNR/CNR.</p

Meta-analysis of the diagnostic performance of stress perfusion cardiovascular magnetic resonance for detection of coronary artery disease

<p>Abstract</p> <p>Aim</p> <p>Evaluation of the diagnostic accuracy of stress perfusion cardiovascular magnetic resonance for the diagnosis of significant obstructive coronary artery disease (CAD) through meta-analysis of the available data.</p> <p>Methodology</p> <p>Original articles in any language published before July 2009 were selected from available databases (MEDLINE, Cochrane Library and BioMedCentral) using the combined search terms of magnetic resonance, perfusion, and coronary angiography; with the exploded term coronary artery disease. Statistical analysis was only performed on studies that: (1) used a [greater than or equal to] 1.5 Tesla MR scanner; (2) employed invasive coronary angiography as the reference standard for diagnosing significant obstructive CAD, defined as a [greater than or equal to] 50% diameter stenosis; and (3) provided sufficient data to permit analysis.</p> <p>Results</p> <p>From the 263 citations identified, 55 relevant original articles were selected. Only 35 fulfilled all of the inclusion criteria, and of these 26 presented data on patient-based analysis. The overall patient-based analysis demonstrated a sensitivity of 89% (95% CI: 88-91%), and a specificity of 80% (95% CI: 78-83%). Adenosine stress perfusion CMR had better sensitivity than with dipyridamole (90% (88-92%) versus 86% (80-90%), P = 0.022), and a tendency to a better specificity (81% (78-84%) versus 77% (71-82%), P = 0.065).</p> <p>Conclusion</p> <p>Stress perfusion CMR is highly sensitive for detection of CAD but its specificity remains moderate.</p

Genome-wide analyses identify a role for SLC17A4 and AADAT in thyroid hormone regulation

Thyroid dysfunction is an important public health problem, which affects 10% of the general population and increases the risk of cardiovascular morbidity and mortality. Many aspects of thyroid hormone regulation have only partly been elucidated, including its transport, metabolism, and genetic determinants. Here we report a large meta-analysis of genome-wide association studies for thyroid function and dysfunction, testing 8 million genetic variants in up to 72,167 individuals. One-hundred-and-nine independent genetic variants are associated with these traits. A genetic risk score, calculated to assess their combined effects on clinical end points, shows significant associations with increased risk of both overt (Graves' disease) and subclinical thyroid disease, as well as clinical complications. By functional follow-up on selected signals, we identify a novel thyroid hormone transporter (SLC17A4) and a metabolizing enzyme (AADAT). Together, these results provide new knowledge about thyroid hormone physiology and disease, opening new possibilities for therapeutic targets

The trans-ancestral genomic architecture of glycemic traits

Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 × 10−8), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution