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David Collins

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Papers by David Collins

Does increasing the number of channels during neuromuscular electrical stimulation reduce fatigability and produce larger contractions with less discomfort?

Purpose: Neuromuscular electrical stimulation (NMES) recruits motor units (MUs) at unphysiologica... more Purpose: Neuromuscular electrical stimulation (NMES) recruits motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits different MUs from each site, reducing MU firing rates and fatigability. This study aimed to determine whether rotating pulses between an increasing number of stimulation channels (cathodes) reduces contraction fatigability and increases the ability to generate torque during NMES. A secondary outcome was perceived discomfort. Methods: Fifteen neurologically-intact volunteers completed 4 sessions. NMES was delivered over the quadriceps through 1 (NMES1), 2 (NMES2), 4 (NMES4) or 8 (NMES8) channels. Fatigability was assessed over 100 contractions (1s on/1s off) at an initial contraction amplitude that was 20% of a maximal voluntary contraction (MVC). Torque-frequency relationships were characterized over 6 frequencies from 20-120Hz. Results: NMES4 and NMES8 resulted in less decline...

A qualitative investigation of elite golf coaches knowledge and the epistemological chain

The aim of the study was to explore the existence and application of the epistemological chain (E... more The aim of the study was to explore the existence and application of the epistemological chain (EC) construct in the decision making of elite golf coaches. Eight male expert golf coaches were recruited for the study. Employing a qualitative methodology, semi-structured interviews were conducted to gain understanding of the participants‟ perceptions and application of the EC and to determine its overall effect on their knowledge development. Data were analysed to identify themes using interpretive phenomenological analysis (IPA). Results indicate the EC is indeed present in the coaching of elite golfers and implemented in a structured and coherent form. This raises a number of interesting issues regarding coach and player development that may impact upon future pedagogical provision.

Microfluidic acoustic sawtooth metasurfaces for patterning and separation using traveling surface acoustic waves

Lab on a Chip, 2021

We demonstrate microfluidic acoustic sawtooth-like metasurfaces that create steerable acoustoflui... more

Unconventional acoustic approaches for localized and designed micromanipulation

Lab on a Chip, 2021

We highlight recent acoustofluidic advances that demonstrate versatility for activities beyond pe... more

The epistemological chain in action: coaching in high level golf

An epistemological chain, as it relates to sport, may be understood as the sequencing of tacit co... more An epistemological chain, as it relates to sport, may be understood as the sequencing of tacit coaching knowledge that a coach may adopt or impart to a given performer in a given sport. It is a make-up of beliefs and actions that constitutes how they go about coaching. The aim of the study was to explore the nature and application of the epistemological chain (EC) construct in the decision making of high level golf coaches. In particular we were interested in determining whether the EC was evident and operationalized in a coherent manner. Five male high level golf coaches interviewed in an earlier study were observed delivering a coaching session. These observations provided the basis of subsequent semi-structured interviews which explored general behaviours in order to determine the overall implementation of the EC. Data were analysed to identify themes aligned to the core elements of the EC. Results indicate that the EC is indeed present in a coherent fashion and highlights its ut...

$Research paper thumbnail of Periodic Rayleigh streaming vortices and Eckart flow arising from traveling-wave-based diffractive acoustic fields$

Periodic Rayleigh streaming vortices and Eckart flow arising from traveling-wave-based diffractive acoustic fields

Physical Review E, 2021

Recent studies have demonstrated that periodic time-averaged acoustic fields can be produced from... more Recent studies have demonstrated that periodic time-averaged acoustic fields can be produced from traveling surface acoustic waves (SAWs) in microfluidic devices. This is caused by diffractive effects arising from a spatially limited transducer. This permits the generation of acoustic patterns evocative of those produced from standing waves, but instead with the application of a traveling wave. While acoustic pressure fields in such systems have been investigated, acoustic streaming from diffractive fields has not. In this work we examine this phenomenon and demonstrate the appearance of geometry-dependent acoustic vortices, and demonstrate that periodic, identically rotating Rayleigh streaming vortices result from the imposition of a traveling SAW. This is also characterized by a channel-spanning flow that bridges between adjacent vortices along the channel top and bottom. We find that the channel dimensions determine the types of streaming that develops; while Eckart streaming has been previously presumed to be a distinguishing feature of traveling-wave actuation, we show that Rayleigh streaming vortices also results. This has implications for microfluidic actuation, where traveling acoustic waves have applications in microscale mixing, separation, and patterning.

The critical importance of mask seals on respirator performance: An analytical and simulation approach

PLOS ONE, 2021

Filtering facepiece respirators (FFRs) and medical masks are widely used to reduce the inhalation... more Filtering facepiece respirators (FFRs) and medical masks are widely used to reduce the inhalation exposure of airborne particulates and biohazardous aerosols. Their protective capacity largely depends on the fraction of these that are filtered from the incoming air volume. While the performance and physics of different filter materials have been the topic of intensive study, less well understood are the effects of mask sealing. To address this, we introduce an approach to calculate the influence of face-seal leakage on filtration ratio and fit factor based on an analytical model and a finite element method (FEM) model, both of which take into account time-dependent human respiration velocities. Using these, we calculate the filtration ratio and fit factor for a range of ventilation resistance values relevant to filter materials, 500–2500 Pa∙s∙m−1, where the filtration ratio and fit factor are calculated as a function of the mask gap dimensions, with good agreement between analytical...

format_quoteGood mask edges seal enhances filtration ratio significantly, especially for higher pressure drop materials, aiding manufacturers and users in mask fit importance.format_quote

Respiration mask waveguide optimisation for maximised speech intelligibility

The Journal of the Acoustical Society of America, 2021

Both the scarcity and environmental impact of disposable face masks, as in the COVID-19 pandemic,... more Both the scarcity and environmental impact of disposable face masks, as in the COVID-19 pandemic, have instigated the recent development of reusable masks. Such face masks reduce transmission of infectious agents and particulates, but often impact a user's ability to be understood when materials, such as silicone or hard polymers, are used. In this work, we present a numerical optimisation approach to optimise waveguide topology, where a waveguide is used to transmit and direct sound from the interior of the mask volume to the outside air. This approach allows acoustic energy to be maximised according to specific frequency bands, including those most relevant to human speech. We employ this method to convert a resuscitator mask, made of silicone, into respiration personal protective equipment (PPE) that maximises the speech intelligibility index (SII). We validate this approach experimentally as well, showing improved SII when using the fabricated device. Together, this design represents a unique and effective approach to utilize and adapt available apparatus to filter air while improving the ability to communicate effectively, including in healthcare settings.

format_quoteProposed a numerical optimization approach focusing on mask shape modification to enhance sound transmission without active components.format_quote

$Research paper thumbnail of Diffraction-based acoustic manipulation in microchannels enables continuous particle and bacteria focusing$

Diffraction-based acoustic manipulation in microchannels enables continuous particle and bacteria focusing

Lab on a Chip, 2020

We explore a unique diffractive acoustic phenomenon arising from a surface acoustic wave and chan... more

Identification of Mycoplasma fermentans in Synovial Fluid Samples from Arthritis Patients with Inflammatory Disease

Journal of Clinical Microbiology, 2000

Since 1970 Mycoplasma fermentans has been suspected of being associated with rheumatoid arthritis... more Since 1970 Mycoplasma fermentans has been suspected of being associated with rheumatoid arthritis. However, this association has been difficult to prove, and this has been our goal. The distribution of M. fermentans was studied in the synovial fluid of patients suffering from different arthritides. Samples of synovial fluid were taken from patients with well-defined disease and a clear diagnosis. After removal of the inflammatory cells and hyaluran, they were treated with proteinase K and tested by a single or fully nested PCR with primers directed against part of the two 16S rRNA genes of M. fermentans . The product was sequenced automatically, by using an ALF Express automatic sequencer, to confirm the mycoplasma species and to identify the strain since the two genes were usually found to be polymorphic. This was also true of the type strain, strain PG18. M. fermentans was detected in 23 of 26 (88%) rheumatoid arthritis patients, and four different strains were found. It was also ...

Dialogues among Books in Medieval Western Magic and Divination

Aestimatio: Critical Reviews in the History of Science, 2018

Dialogues among Books in Medieval Western Magic and Divination is a volume of collected scholarsh... more Dialogues among Books in Medieval Western Magic and Divination is a volume of collected scholarship-a preface and seven chapters-that emerged from a conference on divination in Erlangen in 2012. It offers a competent and thought-provoking introduction to the ways that magical texts can be historically interpreted in relation to one another and to other kinds of literature. The quality of the individual chapters and the coherence of the whole are excellent.

Jesuit Prison Ministry in the Witch Trials of the Holy Roman Empire: Friedrich Spee SJ and His Cautio criminalis (1631), written by Frank Sobiech

Journal of Jesuit Studies, 2020

Massively Multiplexed Submicron Particle Patterning in Acoustically Driven Oscillating Nanocavities

Small, 2020

This article is protected by copyright. All rights reserved. 2 Nanoacoustic fields are a promisin... more This article is protected by copyright. All rights reserved. 2 Nanoacoustic fields are a promising method for particle actuation at the nanoscale, though THz frequencies are typically required to create nanoscale wavelengths. In this work we demonstrate the generation of robust nanoscale force gradients using MHz driving frequencies via acoustic-structure interactions. A structured elastic layer at the interface between a microfluidic channel and a travelling surface acoustic wave (SAW) device results in sub-micron acoustic traps, each of which can trap individual sub-micron particles. The acoustically-driven deformation of nanocavities gives rise to time-averaged acoustic fields which direct suspended particles towards, and trap them within, the nanocavities. The use of SAWs permits massively multiplexed particle manipulation with deterministic patterning at the single-particle level. In this work, 300-nm-diameter particles are acoustically trapped in 500-nm-diameter cavities using travelling SAWs with wavelengths in the range of 20-80 μm with one particle per cavity. On-demand generation of nanoscale acoustic force gradients has wide application for nanoparticle manipulation, including bioparticle enrichment and enhanced catalytic reactions for industrial applications.

format_quoteDeveloped a novel method to manipulate millions of sub-micron particles into single traps, decoupling acoustic wavelength and force gradient length scale.format_quote

Acoustic fields and microfluidic patterning around embedded micro-structures subject to surface acoustic waves

Soft Matter, 2019

Recent research has shown that interactions between acoustic waves and microfluidic channels can ... more

Accelerated Test Methods for Reliability Prediction

Journal of Quality Technology, 2013

Traditional testing methods are costly and inefficient for predicting the lifetimes of materials ... more Traditional testing methods are costly and inefficient for predicting the lifetimes of materials that are expected to function reliably over many years, such as components in the nuclear stockpile. Alternatives to traditional tests accelerate the aging of components by subjecting them to conditions outside normal service or storage ranges, which, in principle, provides test data within a compressed time frame. Alternatives include accelerated life testing (ALT), accelerated degradation testing (ADT), highly accelerated life testing (HALT), highly accelerated stress screening (HASS), and variants on these methods. Use of accelerated methods is often hindered by organizational conflicts between testing as part of an iterative process of finding and removing defects and testing as a means of estimating or predicting reliable life. We are developing a taxonomy for classifying types of accelerated tests and a statistical framework for reconciling conflicting objectives and optimizing the use of testing resources.

Research and Practice in Talent Identification and Development—Some Thoughts on the State of Play

Journal of Applied Sport Psychology, 2018

Although there has been considerable growth in talent identification and development research, th... more Although there has been considerable growth in talent identification and development research, the mixed quality and lack of applied focus means little has changed in the field. We propose the Performance-Outcome-Process continuum, a structure which examines ideas based on what and how they contribute to the talent development process. Reflecting a pracademic focus we highlight the importance of understanding the processes and mechanisms of development-focused constructs to best bridge the research-practice divide. We suggest a pragmatic approach that prioritises the quality of research and the importance of applied impact; at least in research which claims to be for sport. To bridge the research-practice divide in Talent Identification and Development, it is important that translational and pragmatic research becomes the norm, with progression from the retrospective studies which have been typical in this domain. Focusing on the processes and mechanisms that generate comprehensive development would seem a logical step especially for investigations that want to make a difference in applied settings.

The effect of active immunization against adrenocorticotropic hormone on cortisol, β-endorphin, vocalization, and growth in pigs1

Journal of Animal Science, 2005

Because the poor growth performance of intensively housed pigs is associated with increased circu... more Because the poor growth performance of intensively housed pigs is associated with increased circulating glucocorticoid concentrations, we investigated the effects of glucocorticoid suppression by inducing a humoral immune response to ACTH on physiological and production variables in growing pigs. Grower pigs (28.6 ± 0.9 kg) were immunized with amino acids 1 through 24 of ACTH conjugated to ovalbumin and suspended in diethylaminoethyl (DEAE) dextran-adjuvant or adjuvant alone (control) on d 1, 28, and 56. The ACTH-specific antibody titers generated suppressed increases in cortisol concentrations on d 63 in response to an acute stressor

format_quoteACTH immunization did not affect weight gain or feed intake but increased β-endorphin levels, suggesting potential for improved pig production efficiency.format_quote

Reproducibility of the lung anatomy under Active Breathing Coordinator control: dosimetric consequences for scanned proton treatments

Medical physics, Jan 19, 2018

The treatment of moving targets with scanned proton beams is challenging. For motion mitigation, ... more The treatment of moving targets with scanned proton beams is challenging. For motion mitigation, an Active Breathing Coordinator (ABC) can be used to assist breath-holding. The delivery of pencil beam scanning fields often exceeds feasible breath-hold durations, requiring high breath-hold reproducibility. We evaluated the robustness of scanned proton therapy against anatomical uncertainties when treating non-small-cell lung cancer (NSCLC) patients during ABC controlled breath-hold. Four subsequent MRIs of five healthy volunteers (3 male, 2 female, age: 25-58, BMI:19-29) were acquired under ABC controlled breath-hold during two simulated treatment fractions, providing both intra- and inter-fractional information about breath-hold reproducibility. Deformation vector fields between these MRIs were used to deform CTs of five NSCLC patients. Per patient, four or five cases with different tumor locations were modeled, simulating a total of 23 NSCLC patients. Robustly optimized (3 and 5 mm...

Periodization and Self-Regulation in Action Sports: Coping With the Emotional Load

Frontiers in psychology, 2018

Action sports usually include some danger and personal challenge. The levels of both are often fu... more Action sports usually include some danger and personal challenge. The levels of both are often further increased when the sport is placed in a competitive environment. In this paper, we consider the Olympic disciplines of freeskiing and snowboarding in park and pipe. We consider some pertinent theoretical perspectives, then offer some insights on their operation using a range of data from ongoing research and support work. Finally, we offer a number of practical steps which can be taken to optimize performance, both in learning and practicing new tricks and in executing them under the pressures of competition.

Perceived Behavioral Control as a Key to Integrative Medicine

Journal of evidence-based integrative medicine

The purpose of the present study was to identify the factors that are the strongest predictors of... more The purpose of the present study was to identify the factors that are the strongest predictors of intentions and use of integrative medicine approaches in clinical practice. Ajzen's theory of planned behavior was used to guide our examination of these questions. Health care professionals exposed to a Veterans Health Administration program (N = 288) who completed survey instruments prior to and immediately after the program and 3 months later were the participants for this study. Findings suggest that the theory of planned behavior performs reasonably well in explaining our data showing the integration of integrative medicine approaches into clinical practice. We found that self-efficacy to use integrative health approaches and perceived preparedness to discuss nonpharmaceutical approaches with patients were the strongest predictors of intentions to use integrative health approaches and self-reported change in clinical practice. The implications of these findings are discussed.