Omnidirectional propulsion in a metachronal swimmer.

Aquatic organisms often employ maneuverable and agile swimming behavior to escape from predators, find prey, or navigate through complex environments. Many of these organisms use metachronally coordinated appendages to execute complex maneuvers. However, though metachrony is used across body sizes ranging from microns to tens of centimeters, it is understudied compared to the swimming of fish, cetaceans, and other groups. In particular, metachronal coordination and control of multiple appendages for three-dimensional maneuvering is not fully understood. To explore the maneuvering capabilities of metachronal swimming, we combine 3D high-speed videography of freely swimming ctenophores (Bolinopsis vitrea) with reduced-order mathematical modeling. Experimental results show that ctenophores can quickly reorient, and perform tight turns while maintaining forward swimming speeds close to 70% of their observed maximum-performance comparable to or exceeding that of many vertebrates with more complex locomotor systems. We use a reduced-order model to investigate turning performance across a range of beat frequencies and appendage control strategies, and reveal that ctenophores are capable of near-omnidirectional turning. Based on both recorded and modeled swimming trajectories, we conclude that the ctenophore body plan enables a high degree of maneuverability and agility, and may be a useful starting point for future bioinspired aquatic vehicles.

Health Communication and Inequalities in Primary Care Access during the COVID-19 Pandemic among Ethnic Minorities in the United Kingdom: Lived Experiences and Recommendations.

Health Communication is critical in the context of public health and this was highlighted during the COVID-19 pandemic. Ethnic minority groups were significantly impacted during the pandemic; however, communication and information available to them were reported to be insufficient. This study explored the health information communication amongst ethnic communities in relation to their experiences with primary health care services during the COVID-19 pandemic. The research used qualitative methodology using focus groups and semi-structured interviews with community members and leaders from three ethnic minority communities (African-Caribbean, Somali and South Asian) in Leicester, United Kingdom. The interviews were audio recorded, transcribed, and open-coded. Rigour was determined through methodological coherence, appropriate and sufficient sampling, and iterative data collection and analysis. Six focus groups and interviews were conducted with 42 participants. Four overarching themes were identified related to health communication, experiences, services and community recommendations to improve primary care communication. To address primary care inequalities effectively and improve future health communication strategies, experiences from the pandemic should be reflected upon, and positive initiatives infused into the healthcare strategies, especially for ethnic minority communities.

Spatiotemporal Asymmetry in Metachronal Rowing at Intermediate Reynolds Numbers.

In drag-based swimming, individual propulsors operating at low Reynolds numbers (where viscous forces dominate over inertial forces) must execute a spatially asymmetric stroke to produce net fluid displacement. Temporal asymmetry (that is, differing duration between the power vs. recovery stroke) does not affect the overall generated thrust in this time-reversible regime. Metachronal rowing, in which multiple appendages beat sequentially, is used by a wide variety of organisms from low to intermediate Reynolds numbers. At the upper end of this range, inertia becomes important, and increasing temporal asymmetry can be an effective way to increase thrust. However, the combined effects of spatial and temporal asymmetry are not fully understood in the context of metachronal rowing. To explore the role of spatiotemporal asymmetry in metachronal rowing, we combine laboratory experiments and reduced-order analytical modeling. We measure beat kinematics and generated flows in two species of lobate ctenophores across a range of body sizes, from 7 to 40 mm in length. We observe characteristically different flows in ctenophores of differing body size and Reynolds number, and a general decrease in spatial asymmetry and increase in temporal asymmetry with increasing Reynolds number. We also construct a one-dimensional mathematical model consisting of a row of oscillating flat plates whose flow-normal areas change with time, and use it to explore the propulsive forces generated across a range of Reynolds numbers and kinematic parameters. The model results show that while both types of asymmetry increase force production, they have different effects in different regions of the parameter space. These results may have strong biological implications, as temporal asymmetry can be actively controlled while spatial asymmetry is likely to be partially or entirely driven by passive fluid-structure interaction.

Metachronal Coordination of Multiple Appendages for Swimming and Pumping.

As a strategy for creating fluid flow, metachronal motion is widespread across sizes and species, including a broad array of morphologies, length scales, and coordination patterns. Because of this great diversity, it has not generally been viewed holistically: The study of metachrony for swimming and pumping has historically been taxonomically siloed, in spite of many commonalities between seemingly disparate organisms. The goal of the present symposium was to bring together individuals from different backgrounds, all of whom have made substantial individual contributions to our understanding of the fluid dynamics of metachronal motion. Because these problems share a common physical-mathematical basis, intentionally connecting this community is likely to yield future collaborations and significant scientific discovery. Here, we briefly introduce the concept of metachronal motion, present the benefits of creating a research network based on the common aspects of metachrony across biological systems, and outline the contributions to the symposium.

Metachronal Motion across Scales: Current Challenges and Future Directions.

Metachronal motion is used across a wide range of organisms for a diverse set of functions. However, despite its ubiquity, analysis of this behavior has been difficult to generalize across systems. Here we provide an overview of known commonalities and differences between systems that use metachrony to generate fluid flow. We also discuss strategies for standardizing terminology and defining future investigative directions that are analogous to other established subfields of biomechanics. Finally, we outline key challenges that are common to many metachronal systems, opportunities that have arisen due to the advent of new technology (both experimental and computational), and next steps for community development and collaboration across the nascent network of metachronal researchers.

Canal neuromasts enhance foraging in zebrafish (Danio rerio).

Aquatic animals commonly sense flow using superficial neuromasts (SNs), which are receptors that extend from the body's surface. The lateral line of fishes is unique among these systems because it additionally possesses receptors, the canal neuromasts (CNs), that are recessed within a channel. The lateral line has inspired the development of engineered sensors and concepts in the analysis of flow fields for submersible navigation. The biophysics of CNs are known to be different from the SNs and thereby offer a distinct submodality. However, it is generally unclear whether CNs play a distinct role in behavior. We therefore tested whether CNs enhance foraging in the dark by zebrafish (Danio rerio), a behavior that we elicited with a vibrating rod. We found that juvenile fish, which have only SNs, bite at this rod at about one-third the rate and from as little as one-third the distance of adults for a high-frequency stimulus (50 < f  < 100 Hz). We used novel techniques for manipulating the lateral line in adults to find that CNs offered only a modest benefit at a lower frequency (20 Hz) and that foraging was mediated entirely by cranial neuromasts. Consistent with our behavioral results, biophysical models predicted CNs to be more than an order of magnitude more sensitive than SNs at high frequencies. This enhancement helps to overcome the rapid spatial decay in high-frequency components in the flow around the stimulus. These findings contrast what has been previously established for fishes that are at least ten-times the length of zebrafish, which use trunk CNs to localize prey. Therefore, CNs generally enhance foraging, but in a manner that varies with the size of the fish and its prey. These results have the potential to improve our understanding of flow sensing in aquatic animals and engineered systems.

Turbulent flow reduces oxygen consumption in the labriform swimming shiner perch, Cymatogaster aggregata.

Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch, Cymatogaster aggregata (a labriform swimmer), were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with particle image velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rate of the swimming fish increased with swimming speed and pectoral fin beat frequency in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (versus low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high-turbulence compared with low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behaviour and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.

Patients' perceptions of fatigue in rheumatoid arthritis: overwhelming, uncontrollable, ignored.

OBJECTIVE: Fatigue is commonly reported by patients with rheumatoid arthritis (RA) but is rarely a treatment target. The aim of this study was to explore the concept of fatigue as experienced by patients with RA. METHODS: Fifteen patients with RA and fatigue (> or =7 on a 10-cm visual analog scale) were individually interviewed and asked about the description, cause, consequence, and management of fatigue. Transcripts were systematically analyzed by 2 researchers independently, relevant phrases were coded, and earlier transcripts were checked for the emerging codes. A random sample of analyses were independently reviewed. A total of 191 codes arising from the data were grouped into 46 categories and overarching themes. RESULTS: Vivid descriptions reflect 2 types of fatigue: severe weariness and dramatic overwhelming fatigue. RA fatigue is different from normal tiredness because it is extreme, often not earned, and unresolving. Participants described physical, cognitive, and emotional components and attributed fatigue to inflammation, working the joints harder, and unrefreshing sleep. Participants described far-reaching effects on physical activities, emotions, relationships, and social and family roles. Participants used self-management strategies but with limited success. Most did not discuss fatigue with clinicians but when they did, they felt it was dismissed. Participants held negative views on the management of fatigue. CONCLUSION: The data show that RA fatigue is important, intrusive, and overwhelming, and patients struggle to manage it alone. These data on the complexity of fatigue experiences will help clinicians design measures, interventions, and self-managment guidance.

What does "disability" mean for medical students? An exploration of the words medical students associate with the term "disability".

CONTEXT: Disability teaching is a core theme in undergraduate medical education. Medical students bring a range of experiences of disability to their medical training. AIM: The principal aim of this study was to explore the words that medical students associate with the term "disability" and to consider how the resulting information could inform teaching. A secondary aim was to see if a short disability course changed the word associations. METHODS: Students were asked to write down 2 words that came to mind when they heard the word "disability", before and after a 4-day course in disability. Words from 4 cohorts were analysed by frequency and the following word dichotomies: visual icons/personal attributes; loss/enabling, and medical model/social model. A random sample of students took part in focus groups at the beginning and end of the course. RESULTS: A total of 381 students provided 667 before-course words and 189 students provided 336 after-course words. Before the course, words denoting visual icons of disability, and loss were prominent, accounting for 85% of the words, and 74% of the words describing personal attributes were negative. Focus group responses at this stage reflected an eagerness to help but patronising terms were prominent, along with concern about political correctness. Students also expressed nervousness about encountering disabled people. In response, teaching was adapted to make it more learner-focused, to offer a safe environment in which students can test out their language, to build on the positive associations and to develop a range of pre-course creative activities with disabled people. After the course a considerable and significant shift in emphasis was observed, with a reduction in the use of visual icon words, an increase in words denoting enablement, and an increase in words relating to the social model of disability and to positive personal attributes (P < 0.001). Focus group participants at this stage reported greater confidence in approaching disabled people but continued to question political correctness. CONCLUSIONS: Medical students associate disability predominantly with depersonalised or negative words. A short disability course appears to change these associations. Reasons for this and implications for teaching are discussed.

Effects of emotional disclosure on psychological and physiological outcomes in patients with rheumatoid arthritis: an exploratory home-based study.

The effects of an exploratory, home-based emotional disclosure intervention on psychological and physiological outcomes were assessed in patients with rheumatoid arthritis. Patients were randomly assigned to a disclosure group (n = 19) in which they wrote/talked about traumatic personal experiences, or to a control group (n = 15) in which they wrote/talked about the events of a particular day. Participants undertook these tasks for periods of 20 minutes on 4 consecutive days. The disclosure group demonstrated increases in negative mood and objective markers of disease activity at 1 week post-intervention. However, there were significant trends for the disclosure group to demonstrate minor improvements in mood and stability in disease activity, compared with the control group. These group differences appeared to be due to deteriorations in the control group more than improvements in the disclosure group.