Fingering instability in wildfire fronts

A two-dimensional model for the evolution of the fire line – the interface between burned and unburned regions of a wildfire – is formulated. The fire line normal velocity has three contributions: (i) a constant rate of spread representing convection and radiation effects; (ii) a curvature term that smooths the fire line; and (iii) a Stefan-like term in the direction of the oxygen gradient. While the first two effects are geometrical, (iii) is dynamical and requires the solution of the steady advection–diffusion equation for oxygen, with advection owing to a self-induced ‘fire wind’, modelled by the gradient of a harmonic potential field. The conformal invariance of this coupled pair of partial differential equations, which has the Péclet number Pe as its only parameter, is exploited to compute numerically the evolution of both radial and infinitely long periodic fire lines. A linear stability analysis shows that fire line instability is possible, dependent on the ratio of curvature to oxygen effects. Unstable fire lines develop finger-like protrusions into the unburned region; the geometry of these fingers is varied and depends on the relative magnitudes of (i)–(iii). It is argued that for radial fires, the fire wind strength scales with the fire's effective radius, meaning that Pe increases in time, so all fire lines eventually become unstable. For periodic fire lines, Pe remains constant, so fire line stability is possible. The results of this study provide a possible explanation for the formation of fire fingers observed in wildfires

Analysis of 180 genetic variants in a new interactive FX variant database reveals novel insights into FX deficiency

Coagulation Factor X (FX), often termed Stuart-Prower Factor, is a plasma glycoprotein composed of the γ-carboxyglutamic acid (Gla) domain, two epidermal growth factor domains (EGF-1, EGF-2) and the serine protease (SP) domain. FX plays a pivotal role in the coagulation cascade, activating thrombin to promote platelet plug formation and prevent excess blood loss. Genetic variants in FX disrupt coagulation and lead to FX or Stuart-Prower Factor deficiency. To better understand the relationship between FX deficiency and disease severity, an interactive FX variant database has been set up at https://www.factorx-db.org, based on earlier websites for the Factor XI and IX coagulation proteins. To date (April 2021), we report 427 case reports on FX deficiency corresponding to 180 distinct F10 genetic variants. Of these, 149 are point variants (of which 128 are missense), 22 are deletions, three are insertions and six are polymorphisms. FX variants are phenotypically classified as being Type I or Type II. Type I variants involve the simultaneous reduction of FX coagulant activity (FX:C) and FX antigen levels (FX:Ag), whereas Type II variants involve a reduction in FX:C with normal FX:Ag plasma levels. Both types of variants were distributed throughout the FXa protein structure. Analyses based on residue surface accessibilities showed the most damaging variants to occur at residues with low accessibilities. The interactive FX web database provides a novel easy-to-use resource for clinicians and scientists to improve the understanding of FX deficiency. Guidelines are provided for clinicians who wish to use the database for diagnostic purposes

A systematic review of commercial cognitive training devices: Implications for use in sport

 This is the final version. Available from Frontiers Media via the DOI in this record.Background: Cognitive training (CT) aims to develop a range of skills, like attention and decision-making, through targeted training of core cognitive functions. While CT can target context specific skills, like movement anticipation, much CT is domain general, focusing on core abilities (e.g., selective attention) for transfer to a range of real-world tasks, such as spotting opponents. Commercial CT (CCT) devices are highly appealing for athletes and coaches due to their ease of use and eye-catching marketing claims. The extent to which this training transfers to performance in the sporting arena is, however, unclear. Therefore, this paper sought to provide a systematic review of evidence for beneficial training effects of CCT devices and evaluate their application to sport. Methods: An extensive search of electronic databases (PubMed, PsychInfo, GoogleScholar, and SportDiscus) was conducted to identify peer-reviewed evidence of training interventions with commercially available CT devices. Forty-three studies met the inclusion criteria and were retained for quality assessment and synthesis of results. Seventeen studies assessed transfer effects beyond laboratory cognitive tests, but only 1 directly assessed transfer to a sporting task. Results: The review of evidence showed limited support for far transfer benefits from CCT devices to sporting tasks, mainly because studies did not target the sporting environment. Additionally, a number of methodological issues with the CCT literature were identified, including small sample sizes, lack of retention tests, and limited replication of findings by researchers independent of the commercial product. Therefore, evidence for sporting benefits is currently limited by the paucity of representative transfer tests and a focus on populations with health conditions. Conclusions: Currently there is little direct evidence that the use of CCT devices can transfer to benefits for sporting performance. This conclusion, however, stems more from a lack of experimental studies in the sporting field and a lack of experimental rigor, rather than convincing null effects. Subsequently, there is an opportunity for researchers to develop more reliable findings in this area through systematic assessment in athletic populations and major methodological improvements.Defence Human Capability Science and Technology Centre, U

An external focus of attention promotes flow experience during simulated driving

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.Achieving a state of flow is associated with positive experiences and improved sporting performance (Jackson & Csikszentmihalyi, 1999). Focused attention is a fundamental component of the flow experience, but to date there has been little investigation of whether attention plays a causal role in creating flow, or is a product of it. Consequently, this study aimed to test the effect of an attentional focus manipulation on flow and performance in a simulated driving task. It was predicted that an external focus would lead to improved visuomotor control, greater flow experience and improved performance. Thirty-three participants from a student population completed the driving task under both internal and external focus instructions. Eye movements and steering wheel movements were recorded during each race. Participants reported greater flow experience (p 0.28). These findings suggest that adopting an external focus of attention may contribute to positive performance states such as flow

Revisiting the t 0.5 Dependence of SEI Growth

SEI growth in lithium-ion batteries is commonly assumed to scale with t 0.5, in line with simple models of diffusion-limited surface layer growth. As a result, this model is widely used for empirical predictions of capacity fade in lithium-ion batteries. However, the t 0.5 model is generally not theoretically sufficient to describe all of the various SEI growth modes. Furthermore, previous literature has not convincingly demonstrated that this model provides the best fit to measurements of SEI growth. In this work, we discuss the theoretical assumptions of the t 0.5 model, evaluate claims of t 0.5 dependence in six previously published datasets and one new dataset, and compare the performance of this model to that of other models. We find that few of the purported t 0.5 fits in literature are statistically justified, although t 0.5 generally describes SEI growth during storage better than SEI growth during cycling. Finally, we evaluate how the fitted exponents in the power-law models vary as a function of time, and we illustrate the limitations of using t 0.5 for prediction without validating its applicability to a particular dataset. This work illustrates the theoretical and empirical limitations of the t 0.5 model and highlights alternatives for more accurate estimates and predictions of SEI growth

Analysis of 272 genetic variants in the upgraded interactive FXI web database reveals new insights on FXI deficiency

Coagulation Factor XI (FXI) is a plasma glycoprotein composed of four apple (Ap) domains and a serine protease (SP) domain. FXI circulates as a dimer and activates Factor IX (FIX), promoting thrombin production and preventing excess blood loss. Genetic variants that degrade FXI structure and function often lead to bleeding diatheses, commonly termed FXI deficiency. The first interactive FXI variant database underwent initial development in 2003 at https://www.factorxi.org. Here, based on a much improved FXI crystal structure, the upgraded FXI database contains information regarding 272 FXI variants (including 154 missense variants) found in 657 patients, this being a significant increase from the 183 variants identified in the 2009 update. Type I variants involve the simultaneous reduction of FXI coagulant activity (FXI:C) and FXI antigen levels (FXI:Ag), whereas Type II variants result in decreased FXI:C yet normal FXI:Ag. The database updates now highlight the predominance of Type I variants in FXI. Analysis in terms of a consensus Ap domain revealed the near-uniform distribution of 81 missense variants across the Ap domains. A further 66 missense variants were identified in the SP domain, showing that all regions of the FXI protein were important for function. The variants clarified the critical importance of changes in surface solvent accessibility, as well as those of cysteine residues and the dimer interface. Guidelines are provided below for clinicians who wish to use the database for diagnostic purposes. In conclusion, the updated database provides an easy-to-use web resource on FXI deficiency for clinicians

Women recovering from social rejection: The effect of the person and the situation on a hormonal mechanism of affiliation

Rejection can motivate either affiliation or withdrawal. In order to study how personality and situational variables influence whether women will be motivated to affiliate versus withdraw, we manipulate social feedback (rejection vs. acceptance) and opportunity for face-to-face interaction (blocked vs. face-to-face) and measure the individual difference variables rejection sensitivity and social anxiety. We test how these variables affect endogenous progesterone and cortisol concentrations, which are presumed to signal motivational responses to rejection. We find that three-way interactions involving social feedback, opportunity for face-to-face interactions, and either social anxiety or rejection sensitivity significantly predict progesterone change, but not cortisol change. Both interactions are driven by sharp progesterone decreases for women high in social anxiety/rejection sensitivity who have been rejected and who have no opportunity to reaffiliate in a face-to-face interaction. This progesterone change may be a physiological marker of motivation for social avoidance following rejection for women who cannot reaffiliate and who are particularly socially anxious or sensitive to rejection

Virtually the same? How impaired sensory information in virtual reality may disrupt vision for action

This is the final version. Available on open access from Springer via the DOI in this recordVirtual reality (VR) is a promising tool for expanding the possibilities of psychological experimentation and implementing immersive training applications. Despite a recent surge in interest, there remains an inadequate understanding of how VR impacts basic cognitive processes. Due to the artificial presentation of egocentric distance cues in virtual environments, a number of cues to depth in the optic array are impaired or placed in conflict with each other. Moreover, realistic haptic information is all but absent from current VR systems. The resulting conflicts could impact not only the execution of motor skills in VR but also raise deeper concerns about basic visual processing, and the extent to which virtual objects elicit neural and behavioural responses representative of real objects. In this brief review, we outline how the novel perceptual environment of VR may affect vision for action, by shifting users away from a dorsal mode of control. Fewer binocular cues to depth, conflicting depth information and limited haptic feedback may all impair the specialised, efficient, online control of action characteristic of the dorsal stream. A shift from dorsal to ventral control of action may create a fundamental disparity between virtual and real-world skills that has important consequences for how we understand perception and action in the virtual world.Royal Academy of Engineering (RAE