Constant strain rate compression of bovine cortical bone on the Split-Hopkinson Pressure Bar

Cortical bone is a visco-elastic material which implies that strain rate will affect its response. Although the Split-Hopkinson Pressure Bar is an accepted technique for determining the dynamic compressive properties of cortical bone it has been shown that the strain rate of compression does not remain constant throughout the duration of a classical experiment with a uniform striker. This raises concerns as to the measurement of smeared responses. This paper presents a shaped striker technique whereby the incident pulse can be shaped to attain a constant strain rate experiment for bovine bone. Shaped strikers offer benefits such as reusability and increased test repeatability. A comparison of the stress–strain–strain rate responses attained through classical and constant strain rate experiments shows that the shape of the stress–strain curves from conventional experiments is adversely affected in the portion where the strain rate varies. The dynamic response corridors for the two tests are similar, however the ultimate properties are affected. It is concluded that the strain rate history should be presented with dynamic stress–strain responses since the instantaneous strain rate is a likely contributor to potential constitutive models.http://www.elsevier.com/locate/msechb2016Mechanical and Aeronautical Engineerin

Exploring South Africa’s southern frontier : a 20-year vision for polar research through the South African National Antarctic Programme

Abstract: Please refer to full text to view abstrac

Exploring South Africa’s southern frontier: A 20-year vision for polar research through the South African National Antarctic Programme

Antarctica, the sub-Antarctic islands and surrounding Southern Ocean are regarded as one of the planet’s last remaining wildernesses, ‘insulated from threat by [their] remoteness and protection under the Antarctic Treaty System’1 . Antarctica encompasses some of the coldest, windiest and driest habitats on earth. Within the Southern Ocean, sub-Antarctic islands are found between the Sub-Antarctic Front to the north and the Polar Front to the south. Lying in a transition zone between warmer subtropical and cooler Antarctic waters, these islands are important sentinels from which to study climate change.2 A growing body of evidence3,4 now suggests that climatically driven changes in the latitudinal boundaries of these two fronts define the islands’ short- and long-term atmospheric and oceanic circulation patterns. Consequently, sub-Antarctic islands and their associated terrestrial and marine ecosystems offer ideal natural laboratories for studying ecosystem response to change.5 For example, a recent study6 indicates that the shift in the geographical position of the oceanic fronts has disrupted inshore marine ecosystems, with a possible impact on top predators. Importantly, biotic responses are variable as indicated by different population trends of these top predators.7,8 When studied collectively, these variations in species’ demographic patterns point to complex spatial and temporal changes within the broader sub-Antarctic ecosystem, and invite further examination of the interplay between extrinsic and intrinsic drivers

Exploring South Africa's southern frontier : a 20-year vision for polar research through the South African National Antarctic Programme

Antarctica, the sub-Antarctic islands and surrounding Southern Ocean are regarded as one of the planet’s last remaining wildernesses, ‘insulated from threat by [their] remoteness and protection under the Antarctic Treaty System’. Antarctica encompasses some of the coldest, windiest and driest habitats on earth. Within the Southern Ocean, sub-Antarctic islands are found between the Sub-Antarctic Front to the north and the Polar Front to the south. Lying in a transition zone between warmer subtropical and cooler Antarctic waters, these islands are important sentinels from which to study climate change. A growing body of evidence now suggests that climatically driven changes in the latitudinal boundaries of these two fronts define the islands’ short- and long-term atmospheric and oceanic circulation patterns. Consequently, sub-Antarctic islands and their associated terrestrial and marine ecosystems offer ideal natural laboratories for studying ecosystem response to change. For example, a recent study indicates that the shift in the geographical position of the oceanic fronts has disrupted inshore marine ecosystems, with a possible impact on top predators. Importantly, biotic responses are variable as indicated by different population trends of these top predators. When studied collectively, these variations in species’ demographic patterns point to complex spatial and temporal changes within the broader sub-Antarctic ecosystem, and invite further examination of the interplay between extrinsic and intrinsic drivers.http://www.sajs.co.zaam2017GeneticsMammal Research InstituteZoology and Entomolog

The use of operational modal analysis and mode tracking for insight into polar vessel operations

Accurate dynamic models of flexible ship structures are required to predict structural vibration caused by environmental loads. Knowledge of dynamic or modal properties are important, for example, to study fatigue damage. In this paper, operational modal analysis (OMA) is used to identify the vibration characteristics of a polar vessel from full-scale acceleration measurements. Five modes are tracked over a range of different operating and environmental conditions, including calm, open water, two ice cases and an open water storm. Compared to the calm, open water conditions, vertical bending modes were generally affected the most by the operating environment, with natural frequency and damping increasing up to 3.7 and 349 %, respectively, in ice. Severity of two-node and three-node vertical bending responses, quantified using a root-mean-square value, were found to be especially large during the open water storm case. Temporal behaviour of two-node and three-node vertical bending due to wave-slamming further contained multiple whipping responses, pointing towards possible cumulative damage over a large number of stress cycles occurring at the midship. Higher damping in ice resulted in responses with lower magnitudes and shorter durations

Exploring South Africa’s southern frontier : a 20-year vision for polar research through the South African National Antarctic Programme

Abstract: Please refer to full text to view abstrac

Decisional Conflict Scale Findings among Patients and Surrogates Making Health Decisions: Part II of an Anniversary Review

Background. We explored decisional conflict as measured with the 16-item Decisional Conflict Scale (DCS) and how it varies across clinical situations, decision types, and exposure to decision support interventions (DESIs). Methods. An exhaustive scoping review was conducted using backward citation searches and keyword searches. Eligible studies were published between 1995 and March 2015, used an original experimental/observational research design, concerned a health-related decision, and provided DCS data. Dyads independently screened titles/abstracts and full texts, and extracted data. We performed narrative syntheses and calculated average or median DCS scores. Results. We included 246 articles reporting on 253 studies. DCS scores ranged from 2.4 to 89.6 out of 100. Highest baseline DCS scores were for care planning (30.5 ± 12.8, median = 30.9) and treatment decisions (30.5 ± 14.6, median = 28.0), in contexts of primary care (33.8 ± 19.8), obstetrics/gynecology (28.8 ± 10.4), and geriatrics (32.6 ± 10.7). Baseline scores were high among decision makers who were ill (29.5 ± 13.8, median = 27.2) or making decisions for themselves (29.7 ± 14.8, median = 26.9). Total DCS scores 37.4). After DESI use, DCS scores decreased short-term but increased or remained the same long-term (>6 months). Conclusions. DCS scores were highest at baseline and decreased after decision making. DESIs decreased decisional conflict immediately after decision making. The largest improvements after DESIs were in decision makers who were ill, male, or made decisions for themselves. Meta-analyses focusing on decision types, contexts, and interventions could inform hypotheses about the expected effects of DESIs, the best timing for measurement, and interpretation of DCS scores

Decisional Conflict Scale Use over 20 Years: The Anniversary Review

Background. The Decisional Conflict Scale (DCS) measures 5 dimensions of decision making (feeling: uncertain, uninformed, unclear about values, unsupported; ineffective decision making). We examined the use of the DCS over its initial 20 years (1995 to 2015). Methods. We conducted a scoping review with backward citation search in Google Analytics/Web of Science/PubMed, followed by keyword searches in Cochrane Library, PubMed, Ovid MEDLINE, EMBASE, CINAHL, AMED, PsycINFO, PRO-Quest, and Web of Science. Eligible studies were published between 1995 and March 2015, used an original experimental/observational research design, concerned a health-related decision, and provided DCS data (total/subscales). Author dyads independently screened titles, abstracts, full texts, and extracted data. We performed narrative data synthesis. Results. We included 394 articles. DCS use appeared to increase over time. Three hundred nine studies (76%) used the original DCS, and 29 (7%) used subscales only. Most studies used the DCS to evaluate the impact of decision support interventions (n = 238, 59%). The DCS was translated into 13 languages. Most decisions were made by people for themselves (n = 353, 87%), about treatment (n = 225, 55%), or testing (n = 91, 23%). The most common decision contexts were oncology (n = 113, 28%) and primary care (n = 82, 20%). Conclusions. This is the first study to descriptively synthesize characteristics of DCS data. Use of the DCS as an outcome measure for health decision interventions has increased over its 20-year existence, demonstrating its relevance as a decision-making evaluation measure. Most studies failed to report when decisional conflict was measured during the decision-making process, making scores difficult to interpret. Findings from this study will be used to update the DCS user manual

T cell responses to SARS-1 CoV-2 spike cross-recognize Omicron

The SARS-CoV-2 Omicron variant has multiple Spike (S) protein mutations1,2 that contribute to escape from antibody neutralization3–6 and reduce vaccine protection from infection7,8. The extent to which other components of the adaptive response such as T cells may still target Omicron and contribute to protection from severe outcomes is unknown. We assessed the ability of T cells to react with Omicron spike in participants who were vaccinated with Ad26.CoV2.S, BNT162b2, or unvaccinated convalescent COVID-19 patients (n=70). We found that 70-80% of the CD4+ and CD8+ T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar to Beta and Delta variants, despite Omicron harboring considerably more mutations. In Omicron-infected hospitalized patients (n=19), there were comparable T cell responses to ancestral spike, nucleocapsid and membrane proteins to those patients hospitalized in previous waves dominated by the ancestral, Beta or Delta variants (n=49). Thus, despite Omicron’s extensive mutations and reduced susceptibility to neutralizing antibodies, the majority of T cell responses, induced by vaccination or infection, cross-recognize the variant. It remains to be determined whether well-preserved T cell immunity to Omicron contributes to protection from severe COVID-19, and is linked to early clinical observations from South Africa and elsewhere9–12