Positive Feedback Process Research Articles

Right to Vote and Electoral Judiciary in Brazil

Abstract This paper aims to demonstrate how the constitutional guarantees of the right to vote and the constitutional design of the Electoral Judiciary have protected electoral integrity in Brazil during the Bolsonaro administration. The 1988 Constitution entrenched voting rights, expanded suffrage, and adopted compulsory voting, creating inclusive voting practices that facilitate voter turnout. The constitutional system also provided for an independent Electoral Judiciary that operates on all levels of electoral governance, including rulemaking. As the sole electoral management body in the country, the Electoral Judiciary generated a process of positive feedback that reinforced its authority. This process has also been guaranteed by the institutional linkage of the Superior Electoral Court with the Federal Supreme Court, where the latter acts as a self-referencing veto point, upholding the decisions of the Electoral Judiciary. Keywords: voting rights, electoral management, electoral justice, Brazilian election law.

Depressive symptoms and the processing of unexpected social feedback: Differences in surprise levels, feedback acceptance, and "immunizing" cognition.

Negative social expectations are a key symptom of depression. It has been suggested that individuals with depressive symptoms tend to maintain these expectations by devaluing new experiences that do not fit prior expectations. However, our understanding of the role of such "immunizing" cognition in response to unexpected social feedback in depression, as well as the cognitive mechanisms involved, remains limited. This study investigated the association between depressive symptoms and the cognitive processing of unexpected positive or negative social feedback using a novel, video-based approach featuring naturalistic social stimuli in a subclinical online sample (N = 155). We also examined how surprise levels, feedback acceptance and immunizing cognition relate to other cognitive processes, such as attributional style and rumination, using cross-sectional network analyses. Robust multiple linear regression analyses revealed that depressive symptoms were associated with higher surprise levels (R2adj. = .27), lower feedback acceptance (R2adj. = .19), and higher levels of immunizing cognition (R2adj. = .09) in response to unexpected positive social feedback, but only partially to unexpected negative social feedback. The network analysis suggested that self-efficacy expectations for coping with negative feelings and acceptance of positive social feedback had the strongest expected influence on the different cognitive processes. Our study highlights the challenges that individuals with depressive symptoms face in utilizing positive social feedback to modify negative expectations. For clinicians, our findings suggest the importance of promoting acceptance of positive social feedback, while simultaneously inhibiting immunizing cognition and avoiding the use of overly positive feedback.

Research on the sub-millisecond underwater electrical wire explosion process

Abstract Underwater electric wire explosion (UEWE) has great potential as a shockwave source for medical and industrial applications. This paper focuses on the process of the sub-millisecond underwater electrical wire explosion (smUEWE). The study compared the smUEWE and the microsecond underwater electrical wire explosion, which revealed the occurrence of partial vaporization under smUEWE, leading to the formation of bamboo-shaped cavities and frontal shock waves. The experiments of smUEWE were carried out under different stored energy, the results indicated the plasma shrinkage and cavity separation during the overall ionization process. Additionally, the study observed secondary breakdown caused by the uneven distribution of ionization products. An analysis was conducted on smUEWE considering partial vaporization, which divided the electrical explosion into a positive feedback process which promoted the axial instability and a negative feedback process which formed the uniform plasma channel. The analysis results was consistent with the experimental results.

My choice, my actions: self-determination, not instrumental value of outcomes enhances outcome monitoring during learning.

Freedom of choice enhances our sense of agency. During goal-directed behavior, the freedom to choose between different response options increases the neural processing of positive and negative feedback, indicating enhanced outcome monitoring under conditions of high agency experience. However, it is unclear whether this enhancement is predominantly driven by an increased salience of self- compared to externally determined action outcomes or whether differences in the perceived instrumental value of outcomes contribute to outcome monitoring in goal-directed tasks. To test this, we recorded electroencephalography while participants performed a reinforcement learning task involving free choices, action-relevant forced choices, and action-irrelevant forced choices. We observed larger midfrontal theta power and N100 amplitudes for feedback following free choices compared with action-relevant and action-irrelevant forced choices. In addition, a Reward Positivity was only present for free but not forced choice outcomes. Crucially, our results indicate that enhanced outcome processing is not driven by the relevance of outcomes for future actions but rather stems from the association of outcomes with recent self-determined choice. Our findings highlight the pivotal role of self-determination in tracking the consequences of our actions and contribute to an understanding of the cognitive processes underlying the choice-induced facilitation in outcome monitoring.

Mechanism for compound daytime-nighttime heatwaves in the Barents–Kara Sea during the boreal autumn and their relationship with sea ice variability

The frequency of heatwaves in the Arctic is on the rise under global warming. These occurrences not only profoundly impact the local ecological environment but also exert remote effects on East Asia and even the global climate. Yet, there exists a noticeable dearth of research focus on Arctic compound daytime-nighttime heatwaves, limiting our comprehension of Arctic climate dynamics. We investigated the occurrence and extinction mechanism for compound daytime-nighttime heatwaves in the Barents–Kara Sea (BKS) during the boreal autumn and explored their association with the sea ice variability. Our results show that a significant dipole pattern appears in the geopotential height two days before the occurrence of compound daytime-nighttime heatwaves in the BKS during autumn, characterized by a negative anomaly centered over Greenland and a positive anomaly centered over the BKS. A robust southerly anomaly in the middle of this dipole pattern facilitates the continuous inflow of warm, moist air from the Atlantic Ocean to the BKS. Both the strong intrusion of moisture and the transport of heat (positive temperature advection) driven by the large-scale atmospheric circulation increase downward latent heat flux, sensible heat flux and net longwave radiation. These factors collectively increase the near-surface temperature over the BKS, ultimately leading to the occurrence of compound daytime-nighttime heatwaves in this region of the Arctic. The extinction of compound daytime-nighttime heatwaves in the BKS is a result of the weakening of the transport of heat and intrusion of water vapor caused by changes in the large-scale circulation. The intrusion of water vapor and the transport of heat significantly reduce the sea ice concentration in most of the BKS. This reduction in sea ice persists for an additional day after the termination of compound daytime-nighttime heatwaves in the BKS. A process of positive atmospheric temperature feedback on a sub-monthly scale may potentially influence the maintenance of compound daytime-nighttime heatwaves in the BKS during the boreal autumn.

Subjective cognitive decline in healthy older adults is associated with altered processing of negative versus positive feedback in a probabilistic learning task.

Older adults who worry about their own cognitive capabilities declining, but who do not show evidence of actual cognitive decline in neuropsychological tests, are at an increased risk of being diagnosed with dementia at a later time. Since neural markers may be more sensitive to early stages of cognitive decline, in the present study we examined whether event-related potential responses of feedback processing, elicited in a probabilistic learning task, differ between healthy older adults recruited from the community, who either did (subjective cognitive decline/SCD-group) or did not report (No-SCD group) worry about their own cognition declining beyond the normal age-related development. In the absence of group differences in learning from emotionally charged feedback in the probabilistic learning task, the amplitude of the feedback-related negativity (FRN) varied with feedback valence differently in the two groups: In the No-SCD group, the FRN was larger for positive than negative feedback, while in the SCD group, FRN amplitude did not differ between positive and negative feedback. The P3b was enhanced for negative feedback in both groups, and group differences in P3b amplitude were not significant. Altered sensitivity in neural processing of negative versus positive feedback may be a marker of SCD.

Biodegradable Cascade-Amplified Nanotheranostics for Photoacoustic-Guided Synergistic PTT/CDT/Starvation Antitumor in the NIR-II Window.

The development of nanoassemblies, activated by the tumor microenvironment, capable of generating photothermal therapy (PTT) and amplifying the "ROS (·OH) storm," is essential for precise and effective synergistic tumor treatment. Herein, an innovative cascade-amplified nanotheranostics based on biodegradable Pd-BSA-GOx nanocomposite for NIR-II photoacoustic imaging (PAI) guides self-enhanced NIR-II PTT/chemodynamic therapy (CDT)/starvation synergistic therapy. The Pd-BSA-GOx demonstrates the ability to selectively convert overexpressed H2O2 into strongly toxic ·OH by a Pd/Pd2+-mediated Fenton-like reaction at a lower pH level. Simultaneously, the GOx generates H2O2 and gluconic acid, effectively disrupting nutrient supply and instigating tumor starvation therapy. More importantly, the heightened levels of H2O2 and increased acidity greatly enhance the Fenton-like reactivity, generating a significant "·OH storm," thereby achieving Pd2+-mediated cascade-amplifying CDT. The specific PTT facilitated by undegraded Pd accelerates the Fenton-like reaction, establishing a positive feedback process for self-enhancing synergetic PTT/CDT/starvation therapy via the NIR-II guided-PAI. Therefore, the multifunctional nanotheranostics presents a simple and versatile strategy for the precision diagnosis and treatment of tumors.

Selfish Grower Behavior Can Group-optimally Eradicate Plant Diseases Caused by Coinfection

Game-theoretic behavioral and epidemiological models suggest that it is impossible to eradicate a disease through voluntary control actions when individuals behave according to their own interests. The simple reason is that free-riding behavior, which is best for self-interest, leads to a control coverage on the group level that is insufficient to eradicate the disease. Here we show that, for diseases that are caused by coinfection, self-interest can actually result in the socially optimal outcome of disease eradication. Our result challenges the conventional wisdom that selfish behavior undermines the group interest; it resolves a social dilemma in the absence of any cooperation, institutional arrangements, or social norms. Our model is motivated by coinfecting plant viruses, common among agricultural crops and natural plants, and the behavioral dynamics of growers to adopt protective action (biological or chemical control). The epidemiological scenario, in which the disease is eradicated by self-interest, is characterized by a positive feedback process in which coinfection enhances infectivity. Similar feedback structures exist for a range of typical epidemiological processes that facilitate disease persistence if prevalence is sufficiently large. The underlying mechanism may therefore be applicable to other diseases.

Spatial migration of temporal earthquake clusters driven by the transfer of differential stress between neighbouring fault/shear-zone structures

Uncertainty concerning the processes responsible for slip-rate fluctuations associated with temporal clustering of surface faulting earthquakes is a fundamental, unresolved issue in tectonics, because strain-rates accommodated by fault/shear-zone structures are the key to understanding the viscosity structure of the crust and seismic hazard. We constrain the timing and amplitude of slip-rate fluctuations that occurred on three active normal faults in central Italy over a time period of 20–30 kyrs, using in situ36Cl cosmogenic dating of fault planes. We identify five periods of rapid slip on individual faults lasting a few millennia, separated time periods of up to 10 millennia with low or zero slip-rate. The rapid slip pulses migrated across the strike between the faults in two waves from SW to NE. We replicate this migration with a model where rapid slip induces changes in differential stress that drive changes in strain-rate on viscous shear zones that drive slip-rate variability on overlying brittle faults. Earthquakes increase the differential stress and strain-rate on underlying shear zones, which in turn accumulate strain, re-loading stress onto the overlying brittle fault. This positive feedback produces high strain-rate episodes containing several large magnitude surface faulting earthquakes (earthquake clusters), but also reduce the differential stress on the viscous portions of neighbouring fault/shear-zones slowing the occurrence of large-magnitude surface faulting earthquakes (earthquake anticlusters). Shear-zones on faults experiencing anticlusters continue to accumulate viscous strain at a lowered rate, and eventually this loads the overlying brittle fault to failure, initiating a period of rapid slip through the positive feedback process described above, and inducing lowered strain-rates onto neighbouring fault/shear-zones. We show that these patterns of differential stress change can replicate the measured earthquake clustering implied by the 36Cl data. The stress changes are related to the fault geometry in terms of distance and azimuth from the slipping structure, implying that (a) strain-rate and viscosity fluctuations for studies of continental rheology, and (b) slip-rates for seismic hazard purposes are to an extent predictable given knowledge of the fault system geometry.

Selenium-SelK-GPX4 axis protects nucleus pulposus cells against mechanical overloading-induced ferroptosis and attenuates senescence of intervertebral disc

Intervertebral disc degeneration (IVDD) is one of the most prevalent spinal degenerative disorders and imposes places heavy medical and economic burdens on individuals and society. Mechanical overloading applied to the intervertebral disc (IVD) has been widely recognized as an important cause of IVDD. Mechanical overloading-induced chondrocyte ferroptosis was reported, but the potential association between ferroptosis and mechanical overloading remains to be illustrated in nucleus pulposus (NP) cells. In this study, we discovered that excessive mechanical loading induced ferroptosis and endoplasmic reticulum (ER) stress, which were detected by mitochondria and associated markers, by increasing the intracellular free Ca2+ level through the Piezo1 ion channel localized on the plasma membrane and ER membrane in NP cells. Besides, we proposed that intracellular free Ca2+ level elevation and the activation of ER stress are positive feedback processes that promote each other, consistent with the results that the level of ER stress in coccygeal discs of aged Piezo1-CKO mice were significantly lower than that of aged WT mice. Then, we confirmed that selenium supplementation decreased intracellular free Ca2+ level by mitigating ER stress through upregulating Selenoprotein K (SelK) expression. Besides, ferroptosis caused by the impaired production and function of Glutathione peroxidase 4 (GPX4) due to mechanical overloading-induced calcium overload could be improved by selenium supplementation through Se-GPX4 axis and Se-SelK axis in vivo and in vitro, eventually presenting the stabilization of the extracellular matrix (ECM). Our findings reveal the important role of ferroptosis in mechanical overloading-induced IVDD, and selenium supplementation promotes significance to attenuate ferroptosis and thus alleviates IVDD, which might provide insights into potential therapeutic interventions for IVDD.

Evaluation of the mechanisms acting on the Atlantic Meridional Overturning Circulation in CESM2 for the 1pctCO2 experiment

The Atlantic Meridional Overturning Circulation (AMOC) is a crucial component of the Earth's climate system due to its fundamental role in heat distribution, carbon and oxygen transport, and the weather. Other climate components, such as the atmosphere and sea ice, influence the AMOC. Evaluating the physical mechanisms of those interactions is paramount to increasing knowledge about AMOC's functioning. In this study, the authors used outputs from the Community Earth System Model version 2 and observational data to investigate changes in the AMOC and the associated physical processes. Two DECK experiments were evaluated: piControl and 1pctCO2 , with an annual increase of 1% of atmospheric CO2 . The analysis revealed a significant decrease in the AMOC, associated with changes in mixed layer depth and buoyancy in high latitudes of the North Atlantic, resulting in the shutdown of deep convection and potentially affecting the formation of North Atlantic Deep Water and Antarctic Bottom Water. A vital aspect observed in this study is the association between increased runoff and reduced water evaporation, giving rise to a positive feedback process. Consequently, the rates of freshwater spreading have intensified during this period, which could lead to an accelerated disruption of the AMOC beyond the projections of existing models.

Young people on social media in a globalized world: self-optimization in highly competitive and achievement-oriented forms of life.

Research investigating young people's social media use has been criticized for its limited theoretical foundations and scope. This paper elaborates young people's social media activity from a socio-ecological evolutionary perspective (SEE), where young people's online exchanges cannot be divorced from the highly competitive and achievement-oriented modern market cultures in which they live. In highly competitive and achievement-oriented forms of life, young people's social media environments are often constituted as dynamic and evolving extrinsically oriented ecological niches that afford for status and identity enhancement while also affording for peer approval, belongingness, and self-worth nested within, and subordinate to, these higher-order affordances. The extrinsic value organization of social media platforms that serve young people's status and identity-enhancement are embodied by a community of mutually interdependent criteria that are evolutionary-based, developmentally salient, and market-driven: physical attractiveness, high (educational and extracurricular) achievements, and material success. Young people's online signaling of these interdependent extrinsic criteria affords for status-allocation and self-enhancement, where each criteria becomes an arena for social competition and identity formation, enabling young people to build personal and optimal models of social success congruent with their own interests and abilities. Young people's status and identity enhancing signaling of these extrinsic criteria is moving toward increasingly idealized or perfect embodiments, informed by accelerating, short-term positive feedback processes that benefit from the technological affordances and densely rewarding peer environments instantiated on social media.

Extreme heat waves in June 2021 over Europe regulated by shrinking Eurasian snow cover in mid–high latitudes

Europe has experienced many extreme heat waves over the past few decades. In this study, the physical processes underlying these long-lasting and wide-ranging heat wave events are investigated based on a case study in Europe in June 2021. Heat waves are associated with barotropic anticyclonic anomalies accompanied by positive geopotential height anomalies locally. These anomalies persist under the conditions of increased meridional air temperature gradients of the mid–upper troposphere in the high latitudes of Eurasia and the formation of the Arctic front jet. The shrinking high-latitude snow cover in April–May favors higher surface temperatures and larger meridional temperature gradients in June in the mid–upper troposphere due to the soil moisture–evaporation–temperature positive feedback process. The summer Arctic front jet is then strengthened, and the mid-latitude westerly winds are weakened. This atmospheric circulation background favors waveguide formation and wave resonance that produces high-amplitude atmospheric waves and the stagnation of ridges in the mid-latitudes. Numerical experiments using the Community Atmosphere Model version 5 verify the proposed physical mechanisms, with the climatic responses in sensitivity experiments to anomalous snowfall rates closely resembling the observational results. Therefore, in June 2021, under the identified atmospheric circulation background and the perturbation of the upstream positive phase of the North Atlantic Oscillation, the large-scale barotropic high pressure and barotropic anticyclonic circulation in the study region tended to be stable and persistent, which is favorable for the production of long-lasting and wide-ranging heat wave events.

Freedom of choice boosts midfrontal theta power during affective feedback processing of goal-directed actions

Sense of agency, the feeling of being in control of one’s actions and their effects, is particularly relevant during goal-directed actions. During feedback learning, action effects provide information about the best course of action to reinforce positive and prevent negative outcomes. However, it is unclear whether agency experience selectively affects the processing of negative or positive feedback during the performance of goal-directed actions. As an important marker of feedback processing, we examined agency-related changes in midfrontal oscillatory activity in response to performance feedback using electroencephalography. Thirty-three participants completed a reinforcement learning task during which they received positive (monetary gain) or negative (monetary loss) feedback following item choices made either by themselves (free-choice) or by the computer (forced-choice). Independent of choice context, midfrontal theta activity was more enhanced for negative than positive feedback. In addition, free, compared to forced choices increased midfrontal theta power for both gain and loss feedback. These results indicate that freedom of choice in a motivationally salient learning task leads to a general enhancement in the processing of affective action outcomes. Our findings contribute to an understanding of the neuronal mechanisms underlying agency-related changes during action regulation and indicate midfrontal theta activity as a neurophysiological marker important for the monitoring of affective action outcomes, irrespective of feedback valence.

The positive atmospheric-ocean feedback process causing the equatorial Pacific SST bias in CAS-ESM2-0

The positive atmospheric-ocean feedback process causing the equatorial Pacific SST bias in CAS-ESM2-0

Studies on the Light-Induced Phase Transition of CsPbBr3 Metal Halide Perovskite Materials.

We investigate the internal mechanism of the light-induced phase transition of CsPbBr3 perovskite materials via density functional theory simulations. Although CsPbBr3 tends to appear in the orthorhombic structure, it can be changed easily by external stimulus. We find that the transition of photogenerated carriers plays the decisive role in this process. When the photogenerated carriers transit from the valence band maximum to conduction band minimum in the reciprocal space, they actually transit from Br ions to Pb ions in the real space, which are taken away by the Br atoms with higher electronegativity from Pb atoms during the initial formation of the CsPbBr3 lattice. The reverse transition of valence electrons leads to the weakening of bond strength, which is proved by our calculated Bader charge, electron localization function, and integral value of COHP results. This charge transition releases the distortion of the Pb-Br octahedral framework and expands the CsPbBr3 lattice, providing possibilities to the phase transition from the orthorhombic structure to tetragonal structure. This phase transition is a self-accelerating positive feedback process, increasing the light absorption efficiency of the CsPbBr3 material, which is of great significance for the widespread promotion and application of the photostriction effect. Our results are helpful to understand the performance of CsPbBr3 perovskite under a light irradiation environment.

The contribution of theta and delta to feedback processing in children with developmental language disorder

PurposeThe study aimed at evaluating feedback processing at the electrophysiological level and its relation to learning in children with developmental language disorder (DLD) to further advance our understanding of the underlying neural mechanisms of feedback-based learning in children with this disorder.MethodA feedback-based probabilistic learning task required children to classify novel cartoon animals into two categories that differ on five binary features, the probabilistic combination of which determined classification. The learning outcomes’ variance in relation to time- and time–frequency measures of feedback processing were examined and compared between 20 children with developmental language disorder and 25 age-matched children with typical language development.ResultsChildren with developmental language disorder (DLD) performed poorer on the task when compared with their age-matched peers with typical language development (TD). The electrophysiological data in the time domain indicated no differences in the processing of positive and negative feedback among children with DLD. However, the time–frequency analysis revealed a strong theta activity in response to negative feedback in this group, suggesting an initial distinction between positive and negative feedback that was not captured by the ERP data. In the TD group, delta activity played a major role in shaping the FRN and P3a and was found to predict test performance. Delta did not contribute to the FRN and P3a in the DLD group. Additionally, theta and delta activities were not associated with the learning outcomes of children with DLD.ConclusionTheta activity, which is associated with the initial processing of feedback at the level of the anterior cingulate cortex, was detected in children with developmental language disorder (DLD) but was not associated with their learning outcomes. Delta activity, which is assumed to be generated by the striatum and to be linked to elaborate processing of outcomes and adjustment of future actions, contributed to processing and learning outcomes of children with typical language development but not of children with DLD. The results provide evidence for atypical striatum-based feedback processing in children with DLD.

Perspectives of the Fritz‐Scheffer Awardee 2021: Profile‐ to ecosystem‐scale perspectives on soil organic matter formation as demonstrated by woody debris in forest dynamics

AbstractSoil organic matter (SOM) forms along a continuum from individual particles, pores, and aggregates to litter–soil profiles and larger ecosystems such as forests. However, forest management of SOM stocks and the carbon therein requires knowledge on which processes and factors at which scales determine SOM formation from forest biomass. As evident from woody debris at the profile scale, SOM forms through additions, transformations, translocations, and removals of litter by soil organisms and environmental components. Yet SOM stocks only increase if litter additions‐to‐removals are out of steady state or enter a new steady state that ignores older litter. Both happen through disturbance and self‐selecting feedback processes in ecosystems consisting of autotrophs, heterotrophs, and their physical environment. One such positive feedback process is litter‐SOM transformation by heterotrophs that releases nutrients that promote plant productivity and thus litter input. Stocks of litter‐SOM, heterotrophs, nutrients, and plants thus exhibit Lotka–Volterra dynamics (i.e., predator–prey interactions) and only increase when attractor states (i.e., steady series or sets of states) change due to disturbance. Evidence of evolving feedback processes and disturbance in SOM would help identify limits, potentials, and precariousness of ecosystems in light of global change, but remains to be found.

Development of associations between elementary school students' mindsets and attentional neural processing of feedback in an arithmetic task.

The aim of this study was to examine the development of the associations between elementary school students' mindsets and the attentional neural processing of positive and negative feedback in math. For this, we analyzed data collected twice from 100 Finnish elementary school students. During the autumn semesters of their 3rd and 4th grade, the participants' general intelligence mindset and math ability mindset were measured with a questionnaire, and their brain responses elicited by performance-relevant feedback were recorded during an arithmetic task. We found that students' fixed mindsets about general intelligence and math ability were associated with greater attention allocated to positive feedback as indicated by a larger P300. These associations were driven by the effects of mindsets on attention allocation to positive feedback in grade 4. Additionally, 4th graders' more fixed general intelligence mindset was marginally associated with greater attention allocated to negative feedback. In addition, the effects of both mindsets on attention allocation to feedback were marginally stronger when the children were older. The present results, although marginal in the case of negative feedback and mainly driven by effects in grade 4, are possibly a reflection of the greater self-relevance of feedback stimuli for students with a more fixed mindset. It is also possible that these findings reflect the fact that, in evaluative situations, mindset could influence stimulus processing in general. The marginal increase in the effects of mindsets as children mature may reflect the development of coherent mindset meaning systems during elementary school years.

Experimental and numerical study of flame acceleration and DDT in a channel with continuous obstacles

Flame acceleration and deflagration-to-detonation transition (DDT) in obstructed channels is an important subject of research for propulsion and explosion safety. Experiment and numerical simulation of DDT in a stoichiometric hydrogen–oxygen mixture in a channel equipped with continuous triangular obstacles were conducted in this work. In the experiment, high-speed schlieren photography was used to record the evolution of reaction front and strong pressure waves. A pressure transducer was used to record the pressure build-up. In the numerical simulation, a high-order numerical method was used to solve the fully compressible reactive Navier–Stokes equations coupled with a calibrated chemical-diffusive model. The calculations are in good agreement with experimental observations. The result shows that the triangular obstacles can significantly promote flame acceleration and provide conditions for the occurrence of DDT. In the early stages of flame acceleration, the main cause for flame roll-up and distortion is the effect of vortices generated in the gaps between neighbouring triangular obstacles. The scales and velocities of vortices are determined by the positive feedback process between combustion-generated flow and flame propagation. The continuous triangular obstacles create an intricate flow field and increase the complexity of shock reflections. This complicated flow leads to local detonation initiation through different mechanisms, i.e. flame-flame collisions and flame-shock interactions. Successive local detonation ignitions and failures are produced in the obstacle gaps due to the continuous layout of the triangular obstacles. It was found that successive local detonation ignitions are critical for the eventual success of DDT formation because the shock waves generated by them continually strengthen the leading shock. The detonation failure or survival due to diffraction depends on the height of the narrow space (h*) between the bulk flame and obstacle vertex, and can be quantitatively characterised by the ratio of the space height to detonation cell size (), h*/.