Strong symmetry breaking rhythms created by folded nodes in a pair of symmetrically coupled, identical Koper oscillators.

The Koper model is a prototype system with two slow variables and one fast variable that possesses small-amplitude oscillations (SAOs), large-amplitude oscillations (LAOs), and mixed-mode oscillations (MMOs). In this article, we study a pair of identical Koper oscillators that are symmetrically coupled. Strong symmetry breaking rhythms are presented of the types SAO-LAO, SAO-MMO, LAO-MMO, and MMO-MMO, in which the oscillators simultaneously exhibit rhythms of different types. We identify the key folded nodes that serve as the primary mechanisms responsible for the strong nature of the symmetry breaking. The maximal canards of these folded nodes guide the orbits through the neighborhoods of these key points. For all of the strong symmetry breaking rhythms we present, the rhythms exhibited by the two oscillators are separated by maximal canards in the phase space of the oscillator.

Neuromorphic Engineering in Wetware: Discriminating Acoustic Frequencies through Their Effects on Chemical Waves.

Some features of the human nervous system can be mimicked not only through software or hardware but also through liquid solutions of chemical systems maintained under out-of-equilibrium conditions. We describe the possibility of exploiting a thin layer of the Belousov-Zhabotinsky (BZ) reaction as a surrogate for the cochlea for sensing acoustic frequencies. Experiments and simulations demonstrate that, as in the human ear where the cochlea transduces the mechanical energy of the acoustic frequencies into the electrochemical energy of neural action potentials and the basilar membrane originates topographic representations of sounds, our bioinspired chemoacoustic system, based on the BZ reaction, gives rise to spatiotemporal patterns as the representation of distinct acoustic bands through transduction of mechanical energy into chemical energy. Acoustic frequencies in the range 10-2000 Hz are partitioned into seven distinct bands based on three attributes of the emerging spatiotemporal patterns: (1) the types and frequencies of the chemical waves, (2) their velocities, and (3) the Faraday waves' wavelengths.

Role of Fast and Slow Inhibitors in Oscillatory Rhythm Design.

In biological or abiotic systems, rhythms occur, owing to the coupling between positive and negative feedback loops in a reaction network. Using the Semenov-Whitesides oscillatory network for thioester hydrolysis as a prototype, we experimentally and theoretically analyzed the role of fast and slow inhibitors in oscillatory reaction networks. In the presence of positive feedback, a single fast inhibitor generates a time delay, resulting in two saddle-node bifurcations and bistability in a continuously stirred tank reactor. A slow inhibitor produces a node-focus bifurcation, resulting in damped oscillations. With both fast and slow inhibitors present, the node-focus bifurcation repeatedly modulates the saddle-node bifurcations, producing stable periodic oscillations. These fast and slow inhibitions result in a pair of time delays between steeply ascending and descending dynamics, which originate from the positive and negative feedbacks, respectively. This pattern can be identified in many chemical relaxation oscillators and oscillatory models, e.g., the bromate-sulfite pH oscillatory system, the Belousov-Zhabotinsky reaction, the trypsin oscillatory system, and the Boissonade-De Kepper model. This study provides a novel understanding of chemical and biochemical rhythms and suggests an approach to designing such behavior.

Transitions of Collective Motions Driven by Phase Resetting.

The front cover artwork is provided by Prof. Gao's group. The image shows the motion patterns transition of the active gel group under the step light intensity, which describes the mechanism of a new collective emergence structure. Read the full text of the Research Article at 10.1002/cphc.202300054.

Optimized Modulation and Coding for Dual Modulated QR Codes.

We present optimized modulation and coding for the recently introduced dual modulated QR (DMQR) codes that extend traditional QR codes to carry additional secondary data in the orientation of elliptical dots that replace black modules in the barcode images. By dynamically adjusting the dot size, we realize gains in embedding strength for both the intensity modulation and the orientation modulation that carry the primary and secondary data, respectively. Furthermore, we develop a model for the coding channel for the secondary data that enables soft-decoding via 5G NR (new radio) codes already supported by mobile devices. The performance gains for the proposed optimized designs are characterized via theoretical analysis, simulations, and actual experiments using smartphone devices. The theoretical analysis and simulations inform our design choices for the modulation and coding, and the experiments characterize the overall improvement in performance for the optimized design over the prior unoptimized designs. Importantly, the optimized designs significantly increase usability of DMQR codes with commonly used QR code beautification that cannibalizes a portion of the barcode image area for the insertion of a logo or image. In experiments with a capture distance of 15 inches, the optimized designs increase the decoding success rates between 10% and 32% for the secondary data while also providing gains for primary data decoding at larger capture distances. When used with beautification in typical settings, the secondary message is decoded with a high success rate for the proposed optimized designs, whereas it invariably fails for the prior unoptimized designs.

Transitions of Collective Motions Driven by Phase Resetting.

Abrupt (i. e. step) environmental changes, such as natural disasters or the intervention of predators, can alter the internal dynamics of groups with active units, leading to the rapid destruction and/or restructuring of the group, with the emergence of new collective structures that endow the system with adaptability. Few studies, to date, have considered the influence of abrupt environmental changes on emergent behavior. Here, we use a model of active matter, the Belousov-Zhabotinsky (BZ) self-oscillating gel, to study the mechanism of formation and transition between modes of collective locomotion caused by changes of illumination intensity in arrays of interacting photosensitive active units. New forms of collective motion can be generated by step changes of illumination intensity. These transformations arise from the phase resetting and wave-signal regeneration induced by the abrupt parameter variation, while gradual change results in different evolution of collective motion. Our results not only suggest a novel mechanism for emergence, but also imply that new collective behaviors could be accessible via discontinuous parameter changes.

Symmetry-breaking rhythms in coupled, identical fast-slow oscillators.

Symmetry-breaking in coupled, identical, fast-slow systems produces a rich, dramatic variety of dynamical behavior-such as amplitudes and frequencies differing by an order of magnitude or more and qualitatively different rhythms between oscillators, corresponding to different functional states. We present a novel method for analyzing these systems. It identifies the key geometric structures responsible for this new symmetry-breaking, and it shows that many different types of symmetry-breaking rhythms arise robustly. We find symmetry-breaking rhythms in which one oscillator exhibits small-amplitude oscillations, while the other exhibits phase-shifted small-amplitude oscillations, large-amplitude oscillations, mixed-mode oscillations, or even undergoes an explosion of limit cycle canards. Two prototypical fast-slow systems illustrate the method: the van der Pol equation that describes electrical circuits and the Lengyel-Epstein model of chemical oscillators.

A report on quality-of-life outcomes following transmastoid plugging of superior semicircular canal dehiscence in a newly established service in a UK hospital.

OBJECTIVE: This study aimed to evaluate the quality-of-life outcomes following transmastoid plugging of semicircular canal dehiscence in a newly established service in a UK hospital. METHOD: Quality-of-life outcomes were measured using the Glasgow benefit Inventory score in three patients who underwent transmastoid plugging for superior semicircular canal dehiscence between September 2019 and March 2020. Patients also completed pre- and post-operative symptomatic questionnaires and vestibular-evoked myogenic potential testing. RESULTS: All three patients reported an improvement in overall quality-of-life outcomes with a mean overall Glasgow Benefit Inventory score of +37 (range, +22.2-66.6). There were no immediate post-operative complications and hearing was preserved in all patients. CONCLUSION: This study reported an initial successful experience with transmastoid plugging of superior semicircular canal dehiscence. In all patients, improvement in quality-of-life measures and symptoms was reported.

Balance testing: does it make a difference?

OBJECTIVE: This study aimed to analyse whether referral for specialist balance testing influences diagnosis and management of patients with dizziness. METHOD: This was a retrospective study examining patients referred for vestibular function testing between 1 January 2018 and 30 June 2018. RESULTS: A total of 101 patients were referred, with 69 patients (68.3 per cent) receiving a preliminary 'pre-vestibular function testing balance diagnosis', which included benign paroxysmal positional vertigo (32.7 per cent), Ménière's disease (13.8 per cent) and migraine (14.9 per cent). Following vestibular function testing, revised diagnoses were achieved for 54 patients (53.5 per cent), including benign paroxysmal positional vertigo (14.9 per cent), Ménière's disease (3.0 per cent) and migraine (10.9 per cent). Pre-vestibular function testing balance diagnoses were confirmed for 32.4 per cent of patients. If no pre-vestibular function testing suspected diagnosis was provided, vestibular function testing was significantly more likely to be inconclusive. Following vestibular function testing, 38.6 per cent were discharged, 21.7 per cent were referred to another specialty and treatment was commenced for 17.8 per cent of patients. CONCLUSION: Referral for vestibular function testing has a role when attempting to answer a clear clinical question. Diagnosing the underlying aetiology of complex imbalance is challenging, but diagnosis can be assisted by judicious use of vestibular function testing.

Ehrlichia canis rapid spread and possible enzooty in northern South Australia and distribution of its vector Rhipicephalus linnaei.

Recent concerns have arisen in Australia regarding detections of the exotic bacterium Ehrlichia canis which has resulted in ehrlichiosis outbreaks. In Australia, it is spread by the tropical brown dog tick Rhipicephalus linnaei, formerly Rhipicephalus sanguineus sensu lato tropical lineage. Previously, the tick has been recorded in South Australia in the Coober Pedy and the Oodnadatta areas. This study, which includes historical specimens data held in historical Australian arthropod collections, along with 10 sampled remote communities, confirms the wide distribution range of this species within the State. E. canis was detected by PCR in the ticks. The percentage of dogs hosting PCR-positive ticks increased from 2.8% (95% confidence interval [CI]: 0.3 to 9.7) in November-December 2020 to 62.9% (95% CI: 44.9 to 78.5) end of February 2021, initially in two then in seven Anangu Pitjantjatjara Yankunytjatjara lands communities in the far northern regions of South Australia. Our results suggest a rapid spread of the pathogen. No evidence of E. canis was found in nine regional communities. The extended tropical brown dog tick distribution indicates a greater area where E. canis may occur and may require management to minimise the impacts of ehrlichiosis outbreaks. Without the implementation of effective detection and control programs, this extended distribution of R. linnaei is likely to result in the spread of the bacterium to other regions.

Effect of obstructions on growing Turing patterns.

We study how Turing pattern formation on a growing domain is affected by discrete domain discontinuities. We use the Lengyel-Epstein reaction-diffusion model to numerically simulate Turing pattern formation on radially expanding circular domains containing a variety of obstruction geometries, including obstructions spanning the length of the domain, such as walls and slits, and local obstructions, such as small blocks. The pattern formation is significantly affected by the obstructions, leading to novel pattern morphologies. We show that obstructions can induce growth mode switching and disrupt local pattern formation and that these effects depend on the shape and placement of the objects as well as the domain growth rate. This work provides a customizable framework to perform numerical simulations on different types of obstructions and other heterogeneous domains, which may guide future numerical and experimental studies. These results may also provide new insights into biological pattern growth and formation, especially in non-idealized domains containing noise or discontinuities.

Peptide-Modulated pH Rhythms.

Many drugs adjust and/or control the spatiotemporal dynamics of periodic processes such as heartbeat, neuronal signaling and metabolism, often by interacting with proteins or oligopeptides. Here we use a quasi-biocompatible, non-equilibrium pH oscillatory system as a biomimetic biological clock to study the effect of pH-responsive peptides on rhythm dynamics. The added peptides generate feedback that can lengthen or shorten the oscillatory period during which the peptides alternate between random coil and coiled-coil conformations. This modulation of a chemical clock supports the notion that short peptide reagents may have utility as drugs to regulate human body clocks.

Nanogel Crosslinking-Based Belousov-Zhabotinsky Self-Oscillating Polyacrylamide Gel with Improved Mechanical Properties and Fast Oscillatory Response.

The Belousov-Zhabotinsky (BZ) self-oscillating gel is a unique actuator suited for studying the behavior of intelligent soft robots. However, the traditional BZ self-oscillating polyacrylamide (PAAm) gel is easily broken and is slow to response to stimuli, which limits its practical application. Therefore, the preparation of BZ gels with sensitive responses to external stimuli and desirable, robust mechanical properties remains a challenge. In this work, PAAm-activated nanogels with unpolymerized double bonds are used as nanocrosslinkers to synthesize a nanogel crosslinking-based BZ (NCBZ) self-oscillating PAAm gel, whose mechanical properties, for example, antipuncture, cutting, and tensile properties, are superior to those of traditional PAAm BZ-self-oscillating gels. The oscillatory period of the traditional gel is much longer than that of the corresponding homogeneous BZ system, resulting from the slow response of the gel to changes in redox potential, whereas large, interconnected pores inside the NCBZ gel provide efficient channels for rapid species transport, supporting fast response of the gel, which results in almost the same period of chemomechanical oscillations as the homogeneous system under the same conditions. Scanning electron microscopy results show that the NCBZ gel is more stable than the traditional BZ PAAm gel after 7 h of oscillation. Our results make it possible to prepare robust gel motors and provide promising application prospects for smart soft robots, actuators, sensors, tissue engineering, and other applications.

Mesoscopic Pitting Oscillation-Induced Periodic Anodic Layer Electrodissolution of Au(111).

The electrodissolution of Au(111) in anaerobic cupric/ammonia/thiosulfate solutions, typical of a non-equilibrium dissipative system, was investigated via in situ electrochemical atomic force microscopy. At a specific initial concentration ratio of aqueous ammonia to cupric ions, the pit number and average pit area increase autocatalytically, while the pit depth increases monotonically during dissolution. A further increase in this initial concentration ratio leads to oscillatory dynamics in the pit number and average pit area while the pit depth fluctuates between one and two atoms. Mechanistic analysis indicates that alternation between formation and dissolution of a sulfur film results in periodic pitting, which produces gold dissolution layer by layer. This work presents a new dissolution mode, i.e., periodic layer dissolution generated by oscillatory pitting processes in addition to a pitting mode with a continually increasing depth, and the use of high initial concentration ratios of ammonia to cupric ion to accelerate the elimination of passivating sulfur film for Au dissolution.

Rotational Locomotion of an Active Gel Driven by Internal Chemical Signals.

Chemical waves arising from coupled reaction and transport can serve as biomimetic "nerve signals" to study the underlying origin and regulation of active locomotion. During wave propagation in more than one spatial dimension, the propagation direction of spiral and pulse waves in a nanogel-based PAAm self-oscillating gel, i.e., the orientation of the driving force, may deviate from the normal direction to the wave fronts. Alternating forward and backward retrograde wave locomotion along the normal and tangential kinematic vectors with a phase difference leads to a curved path, i.e., rotational locomotion. This work indicates that appendages in an organism are not required for this type of locomotion. This locomotion mechanism reveals a general principle underlying the dynamical origin of biological helical locomotion and also suggests design approaches for complex locomotion of soft robots and smart materials.

Fighting Against Stroke in Latin America: A Joint Effort of Medical Professional Societies and Governments.

Introduction: Stroke is one of the leading causes of death in Latin America, a region with countless gaps to be addressed to decrease its burden. In 2018, at the first Latin American Stroke Ministerial Meeting, stroke physician and healthcare manager representatives from 13 countries signed the Declaration of Gramado with the priorities to improve the region, with the commitment to implement all evidence-based strategies for stroke care. The second meeting in March 2020 reviewed the achievements in 2 years and discussed new objectives. This paper will review the 2-year advances and future plans of the Latin American alliance for stroke. Method: In March 2020, a survey based on the Declaration of Gramado items was sent to the neurologists participants of the Stroke Ministerial Meetings. The results were confirmed with representatives of the Ministries of Health and leaders from the countries at the second Latin American Stroke Ministerial Meeting. Results: In 2 years, public stroke awareness initiatives increased from 25 to 75% of countries. All countries have started programs to encourage physical activity, and there has been an increase in the number of countries that implement, at least partially, strategies to identify and treat hypertension, diabetes, and lifestyle risk factors. Programs to identify and treat dyslipidemia and atrial fibrillation still remained poor. The number of stroke centers increased from 322 to 448, all of them providing intravenous thrombolysis, with an increase in countries with stroke units. All countries have mechanical thrombectomy, but mostly restricted to a few private hospitals. Pre-hospital organization remains limited. The utilization of telemedicine has increased but is restricted to a few hospitals and is not widely available throughout the country. Patients have late, if any, access to rehabilitation after hospital discharge. Conclusion: The initiative to collaborate, exchange experiences, and unite societies and governments to improve stroke care in Latin America has yielded good results. Important advances have been made in the region in terms of increasing the number of acute stroke care services, implementing reperfusion treatments and creating programs for the detection and treatment of risk factors. We hope that this approach can reduce inequalities in stroke care in Latin America and serves as a model for other under-resourced environments.

Period-doubling route to mixed-mode chaos.

Mixed-mode oscillations (MMOs) are a complex dynamical behavior in which each cycle of oscillation consists of one or more large amplitude spikes followed by one or more small amplitude peaks. MMOs typically undergo period-adding bifurcations under parameter variation. We demonstrate here, in a set of three identical, linearly coupled van der Pol oscillators, a scenario in which MMOs exhibit a period-doubling sequence to chaos that preserves the MMO structure, as well as period-adding bifurcations. We characterize the chaotic nature of the MMOs and attribute their existence to a master-slave-like forcing of the inner oscillator by the outer two with a sufficient phase difference between them. Simulations of a single nonautonomous oscillator forced by two sine functions support this interpretation and suggest that the MMO period-doubling scenario may be more general.

Influence of survival, promotion, and growth on pattern formation in zebrafish skin.

The coloring of zebrafish skin is often used as a model system to study biological pattern formation. However, the small number and lack of movement of chromatophores defies traditional Turing-type pattern generating mechanisms. Recent models invoke discrete short-range competition and long-range promotion between different pigment cells as an alternative to a reaction-diffusion scheme. In this work, we propose a lattice-based "Survival model," which is inspired by recent experimental findings on the nature of long-range chromatophore interactions. The Survival model produces stationary patterns with diffuse stripes and undergoes a Turing instability. We also examine the effect that domain growth, ubiquitous in biological systems, has on the patterns in both the Survival model and an earlier "Promotion" model. In both cases, domain growth alone is capable of orienting Turing patterns above a threshold wavelength and can reorient the stripes in ablated cells, though the wavelength for which the patterns orient is much larger for the Survival model. While the Survival model is a simplified representation of the multifaceted interactions between pigment cells, it reveals complex organizational behavior and may help to guide future studies.

Chemomechanical origin of directed locomotion driven by internal chemical signals.

Asymmetry in the interaction between an individual and its environment is generally considered essential for the directional properties of active matter, but can directional locomotions and their transitions be generated only from intrinsic chemical dynamics and its modulation? Here, we examine this question by simulating the locomotion of a bioinspired active gel in a homogeneous environment. We find that autonomous directional locomotion emerges in the absence of asymmetric interaction with the environment and that a transition between modes of gel locomotion can be induced by adjusting the spatially uniform intensity of illumination or certain kinetic and mechanical system parameters. The internal wave dynamics and its structural modulation act as the impetus for signal-driven active locomotion in a manner similar to the way in which an animal's locomotion is generated via driving by nerve pulses. Our results may have implications for the development of soft robots and biomimetic materials.