Novel SMA Dowel Connections for Seismically Resilient Timber Buildings

The trend towards sustainable construction practices has led to a growing demand for mid- to high-rise mass timber structures and a growing interest in their behaviour during earthquakes. Due to the brittle nature of wood, timber-based seismic force resisting systems (SFRSs) rely on connections to dissipate energy; these connections effectively act as a ductile energy-dissipative fuse in extreme loading events. Ductile timber connections traditionally fail from a combination of yielding of fasteners and the crushing of wood below the fasteners. While this ensures ductile behaviour, seismic resilience is an increasingly desired trait in SFRSs. Seismically resilient systems seek to reduce or eliminate all disruptions to occupants caused by an earthquake, which can be achieved by designing easily replaceable fuses that absorb permanent damage, or through the design of self-centering systems. Recently, superelastic shape memory alloys (SMAs) have garnered interest in the construction industry for their potential use in resilient self-centering structural systems. Superelasticity is a property which enables a material to recover large strains with no permanent damage. The overarching aim of the current study is to investigate the effectiveness of using superelastic nickel-titanium (NiTi) SMA bars as slender fasteners in timber dowel-type connections to create a self-centering connection for braced timber frames (BTFs). Initially, the self-centering ability of the SMA bars in bending was evaluated by performing cyclic three-point bending tests on the SMA bars. The performance of SMA bars used as straight dowels in a single fastener wood-steel-wood connection was investigated and compared to the behaviour of a traditional steel dowel using the same connection detail. These single dowel tests were modelled in Abaqus, and modelling results showed good agreement with experimental results. Then, the SMA bars were threaded and used in a four-bolt wood-steel-wood connection that was tested in monotonic and cyclic loading. These tests were also performed with traditional ASTM A307 bolts to compare connection behaviour to the current industry standard. The SMA dowel and bolted connections both showed great self-centering abilities and increased strength when compared to connections with traditional steel fasteners. However, the NiTi alloys used in this study showed a tendency to shear suddenly at the wood-steel interface. Additionally, the higher bending strength of the NiTi alloys led to slightly greater wood crushing compared to connections with traditional steel fasteners. While the great self-centering effect of the SMA fasteners show promise for the use of SMAs in connections, it is recommended that further research be conducted on the fatigue behaviour of NiTi dowels in cyclic shear. Additionally, dowel-type fasteners employing a different superelstic alloy, such as iron-based SMAs, should be investigated as they become available. While these alloys are currently still in development, they could be an inexpensive alternative to NiTi with cyclic shear behaviour that is better suited for dowel-type fasteners

Undressing Consent –Preliminary Evaluation of a Campus Sexual Violence Prevention Program

The current study is a preliminary evaluation of the impact of the Undressing Consent post-secondary sexual violence prevention program on student attitudes and beliefs related to consent, understanding of desires and boundaries, societal gendered sexual scripts, and responding to rejection. A primary goal of the study was to create a reliable measure to be used for future evaluation of changes in student attitudes and beliefs related to core program content. In addition, we evaluated student responses to our newly created scales before and after participation in the intervention and between gendered groups. A total sample of 570 students (women and non-binary students pre-intervention, n =208; post-intervention n = 167) participated. Analysis of newly designed scales showed promising results, with the Sexual Scripts scale having good model fit and reliability for the WNB group. An integrated scale including the Sexual Scripts and Response to Rejection scales for men\u27s data also demonstrated good model fit and adequate reliability. However, scale improvement is required for the measurement of the constructs of Consent and Desires & Boundaries. A small but significant change in beliefs was observed among women and non-binary students but such changes were not observed for men. In scale creation, we experienced issues with restricted range for change, independent and unequal gendered sample sizes, and attrition which limit our ability to make inferences regarding program effectivity. Further work on measurement is required to capture student attitudes and behaviours in preparation for a repeated measures randomized control trial of program efficacy

Selected plasma fatty acid levels in subsistence fed sled dogs along the Yukon River: a pilot study for biomonitoring

The introduction of the ‘western diet' marked a decline in omega-3 fatty acids rich foods and a concurrent increase in saturated and omega-6 fatty acids that persists today. Historically, circumpolar people have had a low incidence of obesity, diabetes and cardiovascular disease and this has been largely attributed to polyphenolic compounds and omega-3 fatty acids offered from subsistence foods. In this report, we studied sled dogs as an Arctic sentinel species for monitoring the effect of a changing diet on lipid profiles along the Yukon River. Subsistence fed village sled dogs along the Yukon River, maintained largely on salmon were compared with a control kennel maintained on commercial food. Profiles showed higher levels for long chain omega-3 fatty acids in village subsistence fed dogs compared to control dogs and an opposite trend for omega-6 fatty acids, establishing baseline levels for follow up studies. A comparison with data for previously published mercury levels from the same cohort of dogs revealed a positive correlation with alpha-linolenic fatty acid and a negative correlation with linoleic fatty acid. Food and nutritional security is a concern in the Arctic as the impacts of climate change and transport of contaminants become obvious. This study supports not only the nutritional value of a subsistence diet but also the utility of sled dogs as a sentinel for human dietary chang

A unified treatment of single component replacement models

In this paper we discuss a general framework for single component replacement models. This framework is based on the regenerative structure of these models and by using results from renewal theory a unified presentation of the discounted and average finite and infinite horizon cost models is given. Finally, some well-known replacement models are discussed, and making use of the previous results an easy derivation of their cost functions is presented

Southwest Atlantic water mass evolution during the last deglaciation

The rise in atmospheric CO2 during Heinrich Stadial 1 (HS1; 14.5–17.5 kyr B.P.) may have been driven by the release of carbon from the abyssal ocean. Model simulations suggest that wind‐driven upwelling in the Southern Ocean can liberate 13C‐depleted carbon from the abyss, causing atmospheric CO2 to increase and the δ13C of CO2 to decrease. One prediction of the Southern Ocean hypothesis is that water mass tracers in the deep South Atlantic should register a circulation response early in the deglaciation. Here we test this idea using a depth transect of 12 cores from the Brazil Margin. We show that records below 2300 m remained 13C‐depleted until 15 kyr B.P. or later, indicating that the abyssal South Atlantic was an unlikely source of light carbon to the atmosphere during HS1. Benthic δ18O results are consistent with abyssal South Atlantic isolation until 15 kyr B.P., in contrast to shallower sites. The depth dependent timing of the δ18O signal suggests that correcting δ18O for ice volume is problematic on glacial terminations. New data from 2700 to 3000 m show that the deep SW Atlantic was isotopically distinct from the abyss during HS1. As a result, we find that mid‐depth δ13C minima were most likely driven by an abrupt drop in δ13C of northern component water. Low δ13C at the Brazil Margin also coincided with an ~80‰ decrease in Δ14C. Our results are consistent with a weakening of the Atlantic meridional overturning circulation and point toward a northern hemisphere trigger for the initial rise in atmospheric CO2 during HS1.Key PointsDeep SW Atlantic was unlikely source of light carbon to atmosphere during HS1Mid‐depth isotopic anomalies due to change in northern component waterNorthern component water had robust influence in South Atlantic during HS1Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111970/1/palo20190.pd

Impact of sympathetic nervous system activity on post-exercise flow-mediated dilatation in humans

Transient reduction in vascular function following systemic large muscle group exercise has previously been reported in humans. The mechanisms responsible are currently unknown. We hypothesised that sympathetic nervous system activation, induced by cycle ergometer exercise, would contribute to post-exercise reductions in flow-mediated dilatation (FMD). Ten healthy male subjects (28 ± 5 years) undertook two 30 min sessions of cycle exercise at 75% HRmax. Prior to exercise, individuals ingested either a placebo or an α1-adrenoreceptor blocker (prazosin; 0.05 mg kg−1). Central haemodynamics, brachial artery shear rate (SR) and blood flow profiles were assessed throughout each exercise bout and in response to brachial artery FMD, measured prior to, immediately after and 60 min after exercise. Cycle exercise increased both mean and antegrade SR (P < 0.001) with retrograde SR also elevated under both conditions (P < 0.001). Pre-exercise FMD was similar on both occasions, and was significantly reduced (27%) immediately following exercise in the placebo condition (t-test, P = 0.03). In contrast, FMD increased (37%) immediately following exercise in the prazosin condition (t-test, P = 0.004, interaction effect P = 0.01). Post-exercise FMD remained different between conditions after correction for baseline diameters preceding cuff deflation and also post-deflation SR. No differences in FMD or other variables were evident 60 min following recovery. Our results indicate that sympathetic vasoconstriction competes with endothelium-dependent dilator activity to determine post-exercise arterial function. These findings have implications for understanding the chronic impacts of interventions, such as exercise training, which affect both sympathetic activity and arterial shear stress

Integrated Approach Reveals Role of Mitochondrial Germ-Line Mutation F18L in Respiratory Chain, Oxidative Alterations, Drug Sensitivity, and Patient Prognosis in Glioblastoma

Glioblastoma is the most common and malignant primary brain tumour in adults, with a dismal prognosis. This is partly due to considerable inter- and intra-tumour heterogeneity. Changes in the cellular energy-producing mitochondrial respiratory chain complex (MRC) activities are a hallmark of glioblastoma relative to the normal brain, and associate with differential survival outcomes. Targeting MRC complexes with drugs can also facilitate anti-glioblastoma activity. Whether mutations in the mitochondrial DNA (mtDNA) that encode several components of the MRC contribute to these phenomena remains underexplored. We identified a germ-line mtDNA mutation (m. 14798T &gt; C), enriched in glioblastoma relative to healthy controls, that causes an amino acid substitution F18L within the core mtDNA-encoded cytochrome b subunit of MRC complex III. F18L is predicted to alter corresponding complex III activity, and sensitivity to complex III-targeting drugs. This could in turn alter reactive oxygen species (ROS) production, cell behaviour and, consequently, patient outcomes. Here we show that, despite a heterogeneous mitochondrial background in adult glioblastoma patient biopsy-derived cell cultures, the F18L substitution associates with alterations in individual MRC complex activities, in particular a 75% increase in MRC complex II_III activity, and a 34% reduction in CoQ10, the natural substrate for MRC complex III, levels. Downstream characterisation of an F18L-carrier revealed an 87% increase in intra-cellular ROS, an altered cellular distribution of mitochondrial-specific ROS, and a 64% increased sensitivity to clomipramine, a repurposed MRC complex III-targeting drug. In patients, F18L-carriers that received the current standard of care treatment had a poorer prognosis than non-carriers (373 days vs. 415 days, respectively). Single germ-line mitochondrial mutations could predispose individuals to differential prognoses, and sensitivity to mitochondrial targeted drugs. Thus, F18L, which is present in blood could serve as a useful non-invasive biomarker for the stratification of patients into prognostically relevant groups, one of which requires a lower dose of clomipramine to achieve clinical effect, thus minimising side-effects