Development of the 'rich club' in brain connectivity networks from 438 adolescents & adults aged 12 to 30

The 'rich club' coefficient describes a phenomenon where a network's hubs (high-degree nodes) are on average more intensely interconnected than lower-degree nodes. Networks with rich clubs often have an efficient, higher-order organization, but we do not yet know how the rich club emerges in the living brain, or how it changes as our brain networks develop. Here we chart the developmental trajectory of the rich club in anatomical brain networks from 438 subjects aged 12-30. Cortical networks were constructed from 68×68 connectivity matrices of fiber density, using whole-brain tractography in 4-Tesla 105-gradient high angular resolution diffusion images (HARDI). The adult and younger cohorts had rich clubs that included different nodes; the rich club effect intensified with age. Rich-club organization is a sign of a network's efficiency and robustness. These concepts and findings may be advantageous for studying brain maturation and abnormal brain development.

Test-retest reliability of graph theory measures of structural brain connectivity

The human connectome has recently become a popular research topic in neuroscience, and many new algorithms have been applied to analyze brain networks. In particular, network topology measures from graph theory have been adapted to analyze network efficiency and 'small-world' properties. While there has been a surge in the number of papers examining connectivity through graph theory, questions remain about its test-retest reliability (TRT). In particular, the reproducibility of structural connectivity measures has not been assessed. We examined the TRT of global connectivity measures generated from graph theory analyses of 17 young adults who underwent two high-angular resolution diffusion (HARDI) scans approximately 3 months apart. Of the measures assessed, modularity had the highest TRT, and it was stable across a range of sparsities (a thresholding parameter used to define which network edges are retained). These reliability measures underline the need to develop network descriptors that are robust to acquisition parameters.

Serum cholesterol and variant in cholesterol-related gene CETP predict white matter microstructure

Several common genetic variants influence cholesterol levels, which play a key role in overall health. Myelin synthesis and maintenance are highly sensitive to cholesterol concentrations, and abnormal cholesterol levels increase the risk for various brain diseases, including Alzheimer's disease. We report significant associations between higher serum cholesterol (CHOL) and high-density lipoprotein levels and higher fractional anisotropy in 403 young adults (23.8 ± 2.4years) scanned with diffusion imaging and anatomic magnetic resonance imaging at 4Tesla. By fitting a multi-locus genetic model within white matter areas associated with CHOL, we found that a set of 18 cholesterol-related, single-nucleotide polymorphisms implicated in Alzheimer's disease risk predicted fractional anisotropy. We focused on the single-nucleotide polymorphism with the largest individual effects, CETP (rs5882), and found that increased G-allele dosage was associated with higher fractional anisotropy and lower radial and mean diffusivities in voxel-wise analyses of the whole brain. A follow-up analysis detected white matter associations with rs5882 in the opposite direction in 78 older individuals (74.3 ± 7.3years). Cholesterol levels may influence white matter integrity, and cholesterol-related genes may exert age-dependent effects on the brain.

Identifying candidate gene effects by restricting search space in a multivariate genetic analysis of white matter microstructure

Several genetic variants are thought to influence white matter (WM) integrity, measured with diffusion tensor imaging (DTI). Voxel based methods can test genetic associations, but heavy multiple comparisons corrections are required to adjust for searching the whole brain and for all genetic variants analyzed. Thus, genetic associations are hard to detect even in large studies. Using a recently developed multi-SNP analysis, we examined the joint predictive power of a group of 18 cholesterol-related single nucleotide polymorphisms (SNPs) on WM integrity, measured by fractional anisotropy. To boost power, we limited the analysis to brain voxels that showed significant associations with total serum cholesterol levels. From this space, we identified two genes with effects that replicated in individual voxel-wise analyses of the whole brain. Multivariate analyses of genetic variants on a reduced anatomical search space may help to identify SNPs with strongest effects on the brain from a broad panel of genes.

Provisioning a 3.3 MW PhotoVoltaic generation system onto a distribution authority’s 11 kV rural feeder

This paper describes part of an engineering study that was undertaken to demonstrate that a multi-megawatt Photovoltaic (PV) generation system could be connected to a rural 11 kV feeder without creating power quality issues for other consumers. The paper concentrates solely on the voltage regulation aspect of the study as this was the most innovative part of the study. The study was carried out using the time-domain software package, PSCAD/EMTDC. The software model included real time data input of actual measured load and scaled PV generation data, along with real-time substation voltage regulator and PV inverter reactive power control. The outputs from the model plot real-time voltage, current and power variations throughout the daily load and PV generation variations. Other aspects of the study not described in the paper include the analysis of harmonics, voltage flicker, power factor, voltage unbalance and system losses.

Adoption of alternative habitats by a threatened, "obligate" forest-dwelling bat in a fragmented landscape

While they are among the most ecologically important animals within forest ecosystems, little is known about how bats respond to habitat loss and fragmentation. The threatened lesser short-tailed bat (Mystacina tuberculata), considered to be an obligate deep-forest species, is one of only 2 extant land mammals endemic to New Zealand; it plays a number of important roles within native forests, including pollination and seed dispersal, and rarely occurs in modified forests. We used radiotelemetry to study the movements, roosting behavior, and habitat use of M. tuberculata within a fragmented landscape comprised of 3 main habitat types: open space (harvested forest and pastoral land), native forests, and exotic pine plantations. We found that the bats had smaller home-range areas and travelled shorter nightly distances than populations investigated previously from contiguous native forest. Furthermore, M. tuberculata occupied all 3 habitat types, with native forest being preferred overall. However, individual variation in habitat selection was high, with some bats preferring exotic plantation and open space over native forest. Roosting patterns were similar to those previously observed in contiguous forest; individual bats often switched between communal and solitary roosts. Our findings indicate that M. tuberculata exhibit some degree of behavioral plasticity that allows them to adapt to different landscape mosaics and exploit alternative habitats. To our knowledge, this is the first such documentation of plasticity in habitat use for a bat species believed to be an obligate forest-dweller.

Females as mobile resources: communal roosts promote the adoption of lek breeding in a temperate bat

Males of lek-breeding species defend clustered territories from which they display to visiting females. However, the mechanisms leading to the adoption of clustered male display sites are often unknown. In this study, we examined the possibility of a resource-based lek in New Zealand’s lesser short-tailed bat (Mystacina tuberculata) (Mammalia: Chiroptera), by assessing the placement of “singing roosts” used by males in relation to communal roosting sites used by females. The “resource-based lek” model posits that males settle near resources required by females to increase female encounter rates. For most bat species, where females are highly mobile and widely dispersed across landscapes while foraging, communal daytime roosts dominated by females may represent such a resource. Through use of video footage, spatial analyses of singing-roost locations, and passive-integrated transponder tags we confirmed that M. tuberculata employs a lek mating system. We found that male singing roosts were significantly clustered in space, were defended by resident individuals, and were visited by females (who did not receive resources from males) for mating purposes. Transponder records also indicated that some singing roosts were shared between multiple males. Spatial logistic regression indicated that singing-roost locations were associated with communal roosting sites. Communal roosts are selected based on criteria independent of the locations of singing roosts, suggesting that males responded to the location of communal roosts and not the reverse. Mystacina tuberculata thus provides evidence of a resource-based lek, and is only the second bat species worldwide confirmed to use a lek-mating system.

Effect of different surface profile on wear of rail steel (AS1085.1) used in Australian heavy-haul railways

The extreme diversity of conditions acting on railways necessitates a variety of experimental approaches to study the critical wear mechanisms that present themselves at the contact interface. This work investigates the effects of contact pressure and geometry in rolling-contact wear tests by using discs with different radii of curvature to simulate the varying contact conditions that may be typically found in the field. It is commonly adapted to line contact interface as it has constant contact pressure. But practical scenario of the rail wheel interface, the contact area increase and contact pressure change as tracks worn off. The tests were conducted without any significant amount of traction, but micro slip was still observed due to contact deformation. Moreover, variation of contact pressure was observed due to contact patch elongation and diameter reduction. Rolling contact fatigue, adhesive and sliding wear were observed on the curved contact interface. The development of different wear regimes and material removal phenomena were analysed using microscopic images in order to broaden the understanding of the wear mechanisms occurring in the rail-wheel contact.

Projecting excess emergency department visits and associated costs in Brisbane, Australia, under population growth and climate change scenarios

The direct and indirect health effects of increasingly warmer temperatures are likely to further burden the already overcrowded hospital emergency departments (EDs). Using current trends and estimates in conjunction with future population growth and climate change scenarios, we show that the increased number of hot days in the future can have a considerable impact on EDs, adding to their workload and costs. The excess number of visits in 2030 is projected to range between 98–336 and 42–127 for younger and older groups, respectively. The excess costs in 2012–13 prices are estimated to range between AU$51,000–184,000 (0–64) and AU$27,000–84,000 (65+). By 2060, these estimates will increase to 229–2300 and 145–1188 at a cost of between AU$120,000–1,200,000 and AU$96,000–786,000 for the respective age groups. Improvements in climate change mitigation and adaptation measures are likely to generate synergistic health co-benefits and reduce the impact on frontline health services.

Stone baby: An exploration of trembling and its potential for visual art

Informed by Kristeva's formulation of affect and Winnicott's Holding Environment, this practice-led visual art project is an exploration into how sensitivity to the physical sensation of trembling can sustain a creative practice. Building upon this is a further enquiry into what the significance of the affective experience of trembling is for an ethics of affect in contemporary art. I have done this through object and video-based installations informed by my own experience of trembling. This has been further informed by the work of artists like Louise Bourgeois, Dennis Del Favero and Willie Doherty. The creative outcomes contribute to the discourse around ethical responses to affect by extending and developing on the works of these artists.

Why do Queenslanders seek care in emergency departments? A population study

Objective This study aims to identify the main reasons for which first time and multiple users seek medical care through Queensland emergency departments (ED). Methods A cross-sectional survey was conducted at eight public EDs among presenting patients (n = 911). The questions measured the socio-demographic characteristics of patients, their beliefs and attitudes towards EDs services, and perceptions of health status. Bivariate and binary logistic regression analyses were performed to examine the differences between first time and multiple users of EDs. Results First time and multiple users accounted for 55.5% and 44.5%, respectively. Multiple users themselves believed to be sicker, have poorer health status, and additional and/or chronic health conditions. Multiple users more strongly believed that their condition required treatment at an ED and perceived their condition as being very serious. Multiple users reported weekly household incomes below $600, and half of the multiple users were not working as compared to 35% first time users. Multivariate analysis showed that multiple use was significantly associated with the existence of additional health problems, having chronic condition, lower self-efficacy, and need for ED treatment. Conclusions Patients who sought care for multiple times at EDs more often than first time users suffered from additional and chronic conditions. Their opinion of an ED as the most suitable place to address their current health problem was stronger than first time users. Any proposed demand management strategies need to address these beliefs together with the reasoning of patients to provide effective and appropriate care outside or within ED services.

Acute inflammatory response to low-, moderate- and high-load resistance exercise in women with breast cancer-related lymphoedema

Background Resistance exercise is emerging as a potential adjunct therapy to aid in the management of breast cancer-related lymphedema (BCRL). However, the mechanisms underlying the relationships between the acute and long-term benefits of resistance exercise on BCRL are not well understood. Purpose. To examine the acute inflammatory response to upper-body resistance exercise in women with BCRL and to compare these effects between resistance exercises involving low-, moderate- and high-loads. The impact on lymphoedema status and associated symptoms was also compared. Methods Twenty-one women aged 62 ± 10 years with mild to severe BCRL participated in the study. Participants completed a low-load (15-20 repetition maximum), moderate-load (10-12 repetition maximum) and high-load (6-8 repetition maximum) exercise sessions consisting of three sets of six upper-body resistance exercises. Sessions were completed in a randomized order separated by a seven to 10 day wash-out period. Venous blood samples were obtained to assess markers of exercise-induced muscle damage and inflammation (creatine kinase [CK], C-reactive protein [CRP], interleukin-6 [IL-6] and tumour necrosis factor-alpha [TNF-α]). Lymphoedema status was assessed using bioimpedance spectroscopy and arm circumferences, and associated symptoms were assessed using visual analogue scales (VAS) for pain, heaviness and tightness. Measurements were conducted before and 24 hours after the exercise sessions. Results No significant changes in CK, CRP, IL-6 and TNF-α were observed following the low-, moderate- or high-load resistance exercise sessions. There were no significant changes in arm swelling or symptom severity scores across the three resistance exercise conditions. Conclusions The magnitude of acute exercise-induced inflammation following upper-body resistance exercise in women with BCRL does not vary between resistance exercise loads. Given these observations, moderate- to high-load resistance training is recommended for this patient population as these loads prompt superior physiological and functional benefits.

Ratcheting and wear behavior of Australian rail steel: Experimental investigation of material properties and sampling method

To The ratcheting behavior of high-strength rail steel (Australian Standard AS1085.1) is studied in this work for the purpose of predicting wear and damage to the rail surface. Historically, researchers have used circular test coupons obtained from the rail head to conduct cyclic load tests, but according to hardness profile data, considerable variation exists across the rail head section. For example, the induction-hardened rail (AS1085.1) shows high hardness (400-430 HV100) up to four-millimeters into the rail head’s surface, but then drops considerably beyond that. Given that cyclic test coupons five millimeters in diameter at the gauge area are usually taken from the rail sample, there is a high probability that the original surface properties of the rail do not apply across the entire test coupon and, therefore, data representing only average material properties are obtained. In the literature, disks (47 mm in diameter) for a twin-disk rolling contact test machine have been obtained directly from the rail sample and used to validate rolling contact fatigue wear models. The question arises: How accurate are such predictions? In this research paper, the effect of rail sampling position on the ratcheting behavior of AS1085.1 rail steel was investigated using rectangular shaped specimens. Uniaxial stress-controlled tests were conducted with samples obtained at four different depths to observe the ratcheting behaviour of each. Micro-hardness measurements of the test coupons were carried out to obtain a constitutive relationship to predict the effect of depth on the ratcheting behaviour of the rail material. This work ultimately assists the selection of valid material parameters for constitutive models in the study of rail surface ratcheting.

Experimental investigation of wear modes of hardened rail material used in Australian heavy-haul railways

This work investigates the effects of contact pressure and geometry in rolling-contact wear tests by using discs with different radii of curvature to simulate the varying contact conditions that may be typically found in the field. The tests were conducted without any significant amount of traction, but micro slip was still observed due to contact deformation. Moreover, variation of contact pressure was observed due to contact patch elongation and diameter reduction. Rolling contact fatigue, adhesive and sliding wear were observed on the curved contact interface. The development of different wear regimes and material removal phenomena were analyzed using microscopic images in order to broaden the understanding of the wear mechanisms occurring in the rail-wheel contact.

Study of surface evolution in the wheel-rail interface

This paper aims to trace surface evolution in the wheel-rail interface using data obtained from a twin-disc testing machine and the surface replication technique. Changes in the surface profile of the rail testing disc are explicitly analysed according to the wear mechanism, which helps elaborate a better understanding of the attrition of asperities during the wearing-in process of surface modification. The surface profile amplitude was seen to decrease during the initial running-in phase of the experiment cycle, and after reaching a saturation value, the profile amplitude then increased. Ultimately the results show that grinding will roughen the rail surface and the wheel-rail contact conditions will then remove this surface damage to some saturation value of the profile height. The variation in the rail surface profile beyond this point is then only dependant on the contact conditions which exist between the wheel and rail during normal operation.