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Multi-fin systems, like fish or fish-inspired vehicles, are governed by unsteady three-dimensional interactions between their multiple fins. In particular, dorsal/anal fins have received much attention because they are just upstream of the main thrust-producing fin: the caudal (tail) fin. We used a tuna-inspired fish model with variable fin sharpness to study the interaction between elongated dorsal/anal fins and caudal fins. We found that the performance enhancement is stronger than previously thought (15 % increase in swimming speed and 50 % increase in swimming economy) and is governed by a three-dimensional dorsal-fin-induced cross-flow that lowers the angle of attack on the caudal fin and promotes spanwise flow. Both simulations and multi-layer particle image velocimetry reveal that the cross-flow stabilizes the leading edge vortex on the caudal fin, similar to how wing strakes prevent stall during fixed-wing aircraft manoeuvres. Unlike other fin–fin interactions, this mechanism is phase-insensitive and offers a simple, passive solution for flow control over oscillating propulsors. Our results therefore improve our understanding of multi-fin flow interactions and suggest new insights into dorsal/anal fin shape and placement in fish and fish-inspired vehicles.
Experiments and computations are presented for a foil pitching about its leading edge near a planar, solid boundary. The foil is examined when it is constrained in space and when it is unconstrained or freely swimming in the cross-stream direction. It was found that the foil has stable equilibrium altitudes: the time-averaged lift is zero at certain altitudes and acts to return the foil to these equilibria. These stable equilibrium altitudes exist for both constrained and freely swimming foils and are independent of the initial conditions of the foil. In all cases, the equilibrium altitudes move farther from the ground when the Strouhal number is increased or the reduced frequency is decreased. Potential flow simulations predict the equilibrium altitudes to within 3 %–11 %, indicating that the equilibrium altitudes are primarily due to inviscid mechanisms. In fact, it is determined that stable equilibrium altitudes arise from an interplay among three time-averaged forces: a negative jet deflection circulatory force, a positive quasistatic circulatory force and a negative added mass force. At equilibrium, the foil exhibits a deflected wake and experiences a thrust enhancement of 4 %–17 % with no penalty in efficiency as compared to a pitching foil far from the ground. These newfound lateral stability characteristics suggest that unsteady ground effect may play a role in the control strategies of near-boundary fish and fish-inspired robots.
Scaling laws for the thrust production and energetics of self-propelled or fixed-velocity three-dimensional rigid propulsors undergoing pitching motions are presented. The scaling relations extend the two-dimensional scaling laws presented in Moored & Quinn (AIAA J., 2018, pp. 1–15) by accounting for the added mass of a finite-span propulsor, the downwash/upwash effects from the trailing vortex system of a propulsor and the elliptical topology of shedding trailing-edge vortices. The novel three-dimensional scaling laws are validated with self-propelled inviscid simulations and fixed-velocity experiments over a range of reduced frequencies, Strouhal numbers and aspect ratios relevant to bio-inspired propulsion. The scaling laws elucidate the dominant flow physics behind the thrust production and energetics of pitching bio-propulsors, and they provide guidance for the design of bio-inspired propulsive systems.
Blood samples from normal and Plasmodium berghei infected mice are being analyzed for trace elements by charged particle induced x-rays. Approximately 0.25 ml of the sample (whole blood, washed red cells, or plasma) is dry ashed. The ashes are mounted on a 0.003 inch Kapton foil. The analysis is performed by bombardment of the samples by a beam of 2.0 MeV protons and detection of the characteristic x-rays by a 175-eV-resolution lithium-drifted silicon detector. The data are analyzed by an on-line PDP-9 computer-based data acquisition system. Results indicate an increase in the K, Ca, Cu, and Zn per unit volume of the red cells of the malaria infected mice relative to the amounts measured for uninfected blood, and a decrease in the K, Ca, and Fe and an increase in the Cu per unit volume in the plasma of the infected mice.
We describe the motivation and design details of the ‘Phase II’ upgrade of the Murchison Widefield Array radio telescope. The expansion doubles to 256 the number of antenna tiles deployed in the array. The new antenna tiles enhance the capabilities of the Murchison Widefield Array in several key science areas. Seventy-two of the new tiles are deployed in a regular configuration near the existing array core. These new tiles enhance the surface brightness sensitivity of the array and will improve the ability of the Murchison Widefield Array to estimate the slope of the Epoch of Reionisation power spectrum by a factor of ∼3.5. The remaining 56 tiles are deployed on long baselines, doubling the maximum baseline of the array and improving the array u, v coverage. The improved imaging capabilities will provide an order of magnitude improvement in the noise floor of Murchison Widefield Array continuum images. The upgrade retains all of the features that have underpinned the Murchison Widefield Array’s success (large field of view, snapshot image quality, and pointing agility) and boosts the scientific potential with enhanced imaging capabilities and by enabling new calibration strategies.
Sometime about 1603, Thomas Hariot (1560-1621) reflected on fame and reputation and on references and allusions that had been made to him personally by contemporary authors. On the back of the final folio of his nearly finished work ‘The Doctrine of Nauticall Triangles Compendious,’ Hariot jotted down a series of references to books which, on examination, seem surely to refer to Hariot or his beliefs. Such a list could have been compiled from curiosity or vanity or for use in conversations with his friends. But it may have had a more specific purpose, since Hariot was a controversial figure frequently called on to account for his ideas or his associations. The making of such a list could therefore have been to forearm himself against the kind of evidence which might be adduced against him from printed sources.
Few studies have examined the challenges faced by emergency medicine (EM) physicians in conducting goals of care discussions. This study is the first to describe the perceived barriers and facilitators to these discussions as reported by Canadian EM physicians and residents.
A team of EM, palliative care, and internal medicine physicians developed a survey comprising multiple choice, Likert-scale and open-ended questions to explore four domains of goals-of-care discussions: training; communication; environment; and patient beliefs.
Surveys were sent to 273 EM staff and residents in six sites, and 130 (48%) responded. Staff physicians conducted goals-of-care discussions several times per month or more, 74.1% (80/108) of the time versus 35% (8/23) of residents. Most agreed that goals-of-care discussions are within their scope of practice (92%), they felt comfortable having these discussions (96%), and they are adequately trained (73%). However, 66% reported difficulty initiating goals-of-care discussions, and 54% believed that admitting services should conduct them. Main barriers were time (46%), lack of a relationship with the patient (25%), patient expectations (23%), no prior discussions (21%), and the inability to reach substitute decision-makers (17%). Fifty-four percent of respondents indicated that the availability of 24-hour palliative care consults would facilitate discussions in the emergency department (ED).
Important barriers to discussing goals of care in the ED were identified by respondents, including acuity and lack of prior relationship, highlighting the need for system and environmental interventions, including improved availability of palliative care services in the ED.
We report seven cases of probable endotoxin poisoning linked to contaminated compounded glutathione. Five of the cases were using the infusions for treatment of Lyme disease highlighting the risks of using compounded sterile preparations for unapproved indications, especially if the quality of source products cannot be assured.
Innovative evidence-based interventions are needed to equip research mentors with skills to address cultural diversity within research mentoring relationships. A pilot study assessed initial outcomes of a culturally tailored effort to create and disseminate a novel intervention titled Culturally Aware Mentoring (CAM) for research mentors.
Intervention development resulted in 4 products: a 6 hour CAM training curriculum, a facilitator guide, an online pretraining module, and metrics to evaluate the effectiveness of CAM training.
Participants were 64 research mentors from 3 US research-intensive universities. Quantitative pretraining and posttraining evaluation survey data were collected.
Participants found high value and satisfaction with the CAM training, reported gains in personal cultural awareness and cultural skills, and increased intentions and confidence to address cultural diversity in their mentoring.
Study findings indicate that the CAM training holds promise to build research mentors’ capacity and confidence to engage directly with racial/ethnic topics in research mentoring relationships.
Big bale silage has become increasingly popular on many livestock farms in Ireland yet there is limited information on its use for sheep. The objective of this experiment was to compare the effects of feeding chopped or unchopped big bale silage, pit silage and hay when supplemented with either a barley or a molassed sugar beet pulp based concentrate when fed to ewes in late pregnancy on feed intake, ewe weight and body condition score changes, gestation length, lamb birth weight and colostrum yield.
Sixty four mature lowland cross ewes (8/treatment) were oestrus synchronised in October and mated to terminal sire breeds (Suffolk, Texel or Charollais). The ewes were housed, winter shorn and pregnancy scanned in December, following which twin bearing animals were allocated to a 4 x 2 factorial experiment and individually fed either un-chopped or chopped big bale silage which had been wilted for 36-48 hours as is usual for this type of forage, pit silage, which had been wilted for 18-24 hours or hay.