Application of photon Doppler velocimetry to direct impact Hopkinson pressure bars.

Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion, and faster achievement of force equilibrium. Currently, these advantages are gained at the expense of all information about the striker impacted specimen face, preventing the experimental determination of force equilibrium, and requiring approximations to be made on the sample deformation history. In this paper, we discuss an experimental method and complementary data analysis for using photon Doppler velocimetry to measure surface velocities of the striker and output bars in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system. We discuss extracting velocity and force measurements, and the precision of measurements. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains in fully dense metals, and improvement for all strains in slow and non-equilibrating materials.This research was supported by grants from QinetiQ and the Engineering and Physical Sciences Research Council.This is the author accepted manuscript. The final version is available from AIP Publishing via http://dx.doi.org/10.1063/1.494093

Plastic pollution: why is it a public health problem?

Derived from petrochemicals,1 plastics are composed of monomers that are sequenced into polymer chains. Since their commercial development in the 1930s and 1940s, the modern world has become hugely reliant on plastics. They have extensively replaced wood, metal, ceramics and glass in manufacture and construction. They are embedded in the economic system and our daily lives. There are many different types of plastic with different potentials to be reused or recycled (Box 1).

On the Production of High-Purity Docosahexaenoic Acid from Heterotrophic Microalgae

Omega-3 fatty acids provide significant health benefits and are a popular nutritional supplement in the nutraceuticals industry. Omega-3 fatty acids such as docosahexaenoic Acid (DHA) and eicosapentaenoic Acid (EPA) have been reported to improve heart health and mental health. In addition, DHA consumption has been tied to improvements in infant cognitive development. Therefore, high-purity DHA is a desired ingredient in the production of infant formula. The omega-3 oils originating from fish tend to have carcinogenic risks in addition to a bad odor. In recent years, the industry trend has shifted to producing these omega-3 fatty acids via microalgae species– making it a profitable time to enter the DHA production market. The proposed design is for a plant to cultivate the Schizochytrium cells in the upstream process, and then extract and purify the desired omega-3 fatty acid oils in the downstream process. The project proposal called for production of 881,800 lb DHA per year, but our plant has the capacity to produce 1,148,000 lb DHA per year at a competitive price of $362.90 per lb of DHA. Clinton, Iowa was chosen as the plant location due to its proximity to the Mississippi River and the Archer Daniels Midland (ADM) plant, allowing for direct access to water and waste disposal. Our process is estimated to have an IRR of 153.8$775,600,000 and a ROI of 206.5%. The process itself begins with fermentation of the microalgae cells, starting with lab-scale fermentors, increasing in size to seed fermentors, and finally scaling up to production fermentor size. Schizochytrium sp. is the strain of heterotrophic microalgae, chosen for its ability to accumulate lipids in high concentration, and its ability to produce DHA triglyceride in high selectivity with respect to other omega-3 fatty acids. Following fermentation, extraction operations are carried out with a hexane solvent and bead mill to extract the crude oils. The hexane is then evaporated and recycled back to the bead mill. The purification process of the crude oil involves saponification of the triglycerides into fatty acid salts. Acetic acid is then added to convert the salts into the final docosahexaenoic acid product. The saponification and protonation reactions take place in Scheibel columns. The final DHA product is 98% pure by mass, and will be sent to a pack out station to be packaged into pharmaceutical grade drums for customers

Evidence-Based Medicine: Feminist Criticisms and Implications for Women's Health

Evidence-based medicine (EBM) dates back to 19th-century Paris and started out as a new paradigm for practicing medicine, with the aim of replacing anecdote with high-quality evidence from positivist-style research. Despite the clear logic underpinning EBM, there have been numerous criticisms, including maintenance of an archaic view of evidence as "facts," failure to acknowledge that all research is underpinned by the beliefs of the researcher, and the simple fact that medical research has historically been androcentric and results generalized to female patients. In this essay, we discuss the criticisms of EBM, with a focus on feminist critiques based on three central feminist epistemologies: feminist empiricism, standpoint theory, and social constructivism. We argue that EBM potentially perpetuates gaps in women's health and advocate for incorporating feminist epistemologies into future medical research to garner further understanding of social influences on women's health. In addition, we argue that EBM may degrade the clinical acumen and that critical thinking should become a key component of medical school curricula. "To question the foundations of a discipline or practice is not necessarily to deny its value, but rather to stimulate a judicious and balanced appraisal of its merits."1 Evidence-based medicine (EBM) started out as a new paradigm for practicing medicine, replacing theoretical reasoning and anecdote with evidence from high-quality studies.2 From the outset, critics have expressed concerns that methods for gathering evidence are flawed and questioned the external validity of studies gathering information from groups of people and applying them to the individual.3 In this study, we will review the conceptual background of EBM, discuss some of the general criticisms of EBM, and finally critique EBM from a feminist perspective

Self-Reported Time to Diagnosis and Proportions of Re-diagnosis in Female Patients with Chronic Conditions in Australia: A Cross-sectional Survey

Background: The diagnosis of chronic conditions in women is complicated by the historical androcentricity in medical research. Sex and gender gaps in health research may translate to unequal healthcare for women. This cross-sectional survey study aimed to ascertain the median time to diagnosis, proportions of rediagnosis and time to rediagnosis for Australian women with chronic conditions. Methods: An online survey collected anonymous data from voluntary participants. Data were analyzed using Stata14. Cox Proportional Hazards model was used to analyze time to diagnosis and rediagnosis. Logistic regression analysis was used to assess the significance of rediagnosis rates by diagnosis, age at diagnosis, income, employment, state of residence, disability status, and Indigenous status. Results: The median time from first appointment to initial diagnosis was 6 months (range 1 day–50 years) (interquartile range [IQR] 3.74 years). The median time to rediagnosis was 4 years (IQR 9) with a range of 1 day–43 years. Almost half of the women (n = 161/343, 47%) reported their primary condition being rediagnosed. From the complete responses, 40% were rediagnosed from one organic condition to another organic condition, however, 32% of women originally diagnosed with psychological, medically unexplained syndromes, or chronic pain were later rediagnosed with organic conditions. Conclusion: Median wait times for a diagnosis for women in Australia, when factoring in high rates of rediagnosis and time to rediagnosis, was 4 years. It is important that clinicians are aware of the high rediagnosis rates in female patients with chronic conditions and understand the potential impact of systemic biases on the diagnostic process for women under their care

Seasonal and diel patterns in singing activity of humpback whales migrating through Bermuda

Humpback whales (Megaptera novaeangliae) produce song and non-song vocalisations, which allows their presence to be detected through passive acoustic monitoring. To determine the seasonal and diel acoustic presence and acoustic behaviour of humpback whales at the migratory stopover site off Bermuda, three hydrophones were deployed between March 2018 and April 2019 on Challenger Bank and the Bermuda platform. Song was the predominant vocalisation type encountered, with 65% of song recordings containing whale chorus and a clear seasonal trend of humpback whale occurrence in the spring and winter months from late December to mid-May. A strong diel pattern in singing activity was detected. Singing activity significantly increased at night relative to the daytime (p<0.01), whilst twilight periods were characterised by intermediate levels of singing. The song structure encountered in spring 2018 consisted of 18 units, 6 themes and 5 transitional phrases. The high occurrence of whale chorus and the strong seasonal and diel patterns of male humpback whale singing activity highlights the importance of Bermuda not just on their northward migration during spring, as described historically, but also on their southward migration during winter. Bermuda therefore constitutes a two-way migratory stopover site for humpback whales. The present study also provides Bermuda’s planning authorities with better constraints on the duration and intensity of anthropogenic activities in these waters