Matrix measures and random walks

In this paper we study the connection between matrix measures and random walks with a tridiagonal block transition matrix. We derive sufficient conditions such that the blocks of the n-step transition matrix of the Markov chain can be represented as integrals with respect to a matrix valued spectral measure. Several stochastic properties of the processes are characterized by means of this matrix measure. In many cases this measure is supported in the interval [-1, 1]. The results are illustrated by several examples including random walks on a grid and the embedded chain of a queuing system. --Markov chain,block tridiagonal transition matrix,spectral measure,matrix measure,quasi birth and death processes,canonical moments

Object-guided Spatial Attention in Touch: Holding the Same Object with Both Hands Delays Attentional Selection

Abstract Previous research has shown that attention to a specific location on a uniform visual object spreads throughout the entire object. Here we demonstrate that, similar to the visual system, spatial attention in touch can be object guided. We measured event-related brain potentials to tactile stimuli arising from objects held by observers' hands, when the hands were placed either near each other or far apart, holding two separate objects, or when they were far apart but holding a common object. Observers covertly oriented their attention to the left, to the right, or to both hands, following bilaterally presented tactile cues indicating likely tactile target location(s). Attentional modulations for tactile stimuli at attended compared to unattended locations were present in the time range of early somatosensory components only when the hands were far apart, but not when they were near. This was found to reflect enhanced somatosensory processing at attended locations rather than suppressed processing at unattended locations. Crucially, holding a common object with both hands delayed attentional selection, similar to when the hands were near. This shows that the proprioceptive distance effect on tactile attentional selection arises when distant event locations can be treated as separate and unconnected sources of tactile stimulation, but not when they form part of the same object. These findings suggest that, similar to visual attention, both space- and object-based attentional mechanisms can operate when we select between tactile events on our body surface.</jats:p

Insights on the Process of Using Interpretive Phenomenological Analysis in a Sport Coaching Research Project

Interpretative Phenomenological Analysis (IPA) is a qualitative research methodology used to understand participants’ subjective realities through personal interpretations of their lived experiences and the meanings they attach to these experiences (Smith, 2011). IPA has been used predominantly in health psychology, with rising interest within the field of sport psychology and coaching. This article seeks to describe insights about the processes of IPA by a research team using the methodological approach for the first time. These experiences are shared against the backdrop of research exploring the lived experiences of Masters athletes within the context of coached competitive swim programs. We describe how the multiple facets of IPA influence the refinement of the research question, the planning and implementation of data collection, and data analysis and interpretation. We elaborate on our perceptions of the complexities of IPA and make recommendations for how future research teams might smoothly navigate the rigorous research process to yield rich in-depth data and interpretations

Comparative genome-centric analysis reveals seasonal variation in the function of coral reef microbiomes

Microbially mediated processes contribute to coral reef resilience yet, despite extensive characterisation of microbial community variation following environmental perturbation, the effect on microbiome function is poorly understood. We undertook metagenomic sequencing of sponge, macroalgae and seawater microbiomes from a macroalgae-dominated inshore coral reef to define their functional potential and evaluate seasonal shifts in microbially mediated processes. In total, 125 high-quality metagenome-assembled genomes were reconstructed, spanning 15 bacterial and 3 archaeal phyla. Multivariate analysis of the genomes relative abundance revealed changes in the functional potential of reef microbiomes in relation to seasonal environmental fluctuations (e.g. macroalgae biomass, temperature). For example, a shift from Alphaproteobacteria to Bacteroidota-dominated seawater microbiomes occurred during summer, resulting in an increased genomic potential to degrade macroalgal-derived polysaccharides. An 85% reduction of Chloroflexota was observed in the sponge microbiome during summer, with potential consequences for nutrition, waste product removal, and detoxification in the sponge holobiont. A shift in the Firmicutes:Bacteroidota ratio was detected on macroalgae over summer with potential implications for polysaccharide degradation in macroalgal microbiomes. These results highlight that seasonal shifts in the dominant microbial taxa alter the functional repertoire of host-associated and seawater microbiomes, and highlight how environmental perturbation can affect microbially mediated processes in coral reef ecosystems.Australian Government Department of Industry, Innovation and Science; Advance Queensland PhD Scholarship Great Barrier Reef Marine Park Authority Management Award National Environmental Science Program (NESP)info:eu-repo/semantics/publishedVersio

Exploring the Context of Coached Masters Swim Programs: A Narrative Approach

Knowing the psychosocial themes in a specific sport context allows us to understand athletes’ experiences and informs approaches of coaches (Côté et al., 1995) and sport programmers (Danish et al., 2005). Few qualitative studies focus on psychosocial conditions of adult athletes in coached sport settings. The purpose of this study was to capture important psychosocial themes from the perspective of Masters swimmers involved in day-to-day coached swimming environments. Data were collected using semi-structured open-ended interviews with 10 competitive swimmers (5 male, 5 female; M age = 53 years; range: 45-65 years). Analyses revealed four over-arching themes that represented athletes’ a) motives for swimming, b) perspectives on competition, c) experiences specific to being a Masters swimmer, and d) perspectives on being coached. Using a qualitative narrative approach (Denison, 2011), we developed three narrative profiles to depict how our Masters swimmers had different experiences relating to these themes. Discussion focuses on how swimmers’ understanding of the four over-arching themes depends on their profile

Origins of Metabolic Signals

Diameters of microvessels undergo continuous structural adaptation in response to hemodynamic and metabolic stimuli. To ensure adequate flow distribution, metabolic responses are needed to increase diameters of vessels feeding poorly perfused regions. Possible modes of metabolic control include release of signaling substances from vessel walls, from the supplied tissue and from red blood cells (RBC). Here, a theoretical model was used to compare the abilities of these metabolic control modes to provide adequate tissue oxygenation, and to generate blood flow velocities in agreement with experimental observations. Structural adaptation of vessel diameters was simulated for an observed mesenteric network structure in the rat with 576 vessel segments. For each mode of metabolic control, resulting distributions of oxygen and deviations between simulated and experimentally observed flow velocities were analyzed. It was found that wall-derived and tissue-derived growth signals released in response to low oxygen levels could ensure adequate oxygen supply, but RBC- derived signals caused inefficient oxygenation. Closest agreement between predicted and observed flow velocities was obtained with wall-derived growth signals proportional to vessel length. Adaptation in response to oxygen- independent release of a metabolic signal substance from vessel walls or the supplied tissue was also shown to be effective for ensuring tissue oxygenation due to a dilution effect if growth signal substances are released into the blood. The present results suggest that metabolic signals responsible for structural adaptation of microvessel diameters are derived from vessel walls or from perivascular tissue

What are the Odds? The Neural Correlates of Active Choice during Gambling

Gambling is a widespread recreational activity and requires pitting the values of potential wins and losses against their probability of occurrence. Neuropsychological research showed that betting behavior on laboratory gambling tasks is highly sensitive to focal lesions to the ventromedial prefrontal cortex (vmPFC) and insula. In the current study, we assessed the neural basis of betting choices in healthy participants, using functional magnetic resonance imaging of the Roulette Betting Task. In half of the trials, participants actively chose their bets; in the other half, the computer dictated the bet size. Our results highlight the impact of volitional choice upon gambling-related brain activity: Neural activity in a distributed network – including key structures of the reward circuitry (midbrain, striatum) – was higher during active compared to computer-dictated bet selection. In line with neuropsychological data, the anterior insula and vmPFC were more activated during self-directed bet selection, and responses in these areas were differentially modulated by the odds of winning in the two choice conditions. In addition, responses in the vmPFC and ventral striatum were modulated by the bet size. Convergent with electrophysiological research in macaques, our results further implicate the inferior parietal cortex (IPC) in the processing of the likelihood of potential outcomes: Neural responses in the IPC bilaterally reflected the probability of winning during bet selection. Moreover, the IPC was particularly sensitive to the odds of winning in the active-choice condition, when the processing of this information was required to guide bet selection. Our results indicate an important role of the IPC in human decision-making under risk and help to integrate neuropsychological data of risk-taking following vmPFC and insula damage with models of choice derived from human neuroimaging and monkey electrophysiology

Improved visibility of character conflicts in quasi-median networks with the EMPOP NETWORK software

Aim To provide a valuable tool for graphical representation of mitochondrial DNA (mtDNA) data that enables visual emphasis on complex substructures within the network to highlight possible ambiguities and errors. Method We applied the new NETWORK graphical user interface, available via EMPOP (European DNA Profiling Group Mitochondrial DNA Population Database; www. empop.org) by means of two mtDNA data sets that were submitted for quality control. Results The quasi-median network torsi of the two data sets resulted in complex reticulations, suggesting ambiguous data. To check the corresponding raw data, accountable nodes and connecting branches of the network could be identified by highlighting induced subgraphs with concurrent dimming of their complements. This is achieved by accentuating the relevant substructures in the network: mouse clicking on a node displays a list of all mtDNA haplotypes included in that node; the selection of a branch specifies the mutation(s) connecting two nodes. It is indicated to evaluate these mutations by means of the raw data. Conclusion Inspection of the raw data confirmed the presence of phantom mutations due to suboptimal electrophoresis conditions and data misinterpretation. The network software proved to be a powerful tool to highlight problematic data and guide quality control of mtDNA data tables

UAS Maintenance: A Critical Component in Maintaining Airworthiness

Over the last several decades, the notion of traditional aircraft design has significantly changed. While there are many modern aircraft that resemble earlier models, their components, systems, and overall architecture have evolved, including the introduction of small unmanned aircraft systems (sUAS). Despite the growing consumer attraction to own and operate these aircraft, the subsequent impact on safety is an area of intense concern. The requirement of an established maintenance program for manned aircraft is rooted in ensuring that all aircraft are deemed safe for flight. Preventive maintenance schedules are based on component reliability data, which minimizes unnecessary maintenance while preventing maintenance-related aircraft accidents. This same requirement has not been extended to small unmanned aircraft systems. Current regulations and requirements for sUAS maintenance refer only to maintaining airworthiness, with no specific scheduled or unscheduled maintenance practices required. As the demand for small unmanned aircraft systems continues to grow, the safety threat will rise. The requirement of formal maintenance practices, which are based on component reliability data, would fulfill this need. To further explore the possibility of an established maintenance program for sUAS operators, this paper reviews current maintenance requirements and proposes new accident data collection measures which contribute to the creation of a scheduled maintenance program. A formal certification process which follows a modified MSG-3 process is also proposed