Local Regime Research Articles

Temporal Irreversibility of Large-Scale Brain Dynamics in Alzheimer's Disease.

Healthy brain dynamics can be understood as the emergence of a complex system far from thermodynamic equilibrium. Brain dynamics are temporally irreversible and thus establish a preferred direction in time (i.e., arrow of time). However, little is known about how the time-reversal symmetry of spontaneous brain activity is affected by Alzheimer's disease (AD). We hypothesized that the level of irreversibility would be compromised in AD, signaling a fundamental shift in the collective properties of brain activity toward equilibrium dynamics. We investigated the irreversibility from resting-state fMRI and EEG data in male and female human patients with AD and elderly healthy control subjects (HCs). We quantified the level of irreversibility and, thus, proximity to nonequilibrium dynamics by comparing forward and backward time series through time-shifted correlations. AD was associated with a breakdown of temporal irreversibility at the global, local, and network levels, and at multiple oscillatory frequency bands. At the local level, temporoparietal and frontal regions were affected by AD. The limbic, frontoparietal, default mode, and salience networks were the most compromised at the network level. The temporal reversibility was associated with cognitive decline in AD and gray matter volume in HCs. The irreversibility of brain dynamics provided higher accuracy and more distinctive information than classical neurocognitive measures when differentiating AD from control subjects. Findings were validated using an out-of-sample cohort. Present results offer new evidence regarding pathophysiological links between the entropy generation rate of brain dynamics and the clinical presentation of AD, opening new avenues for dementia characterization at different levels.SIGNIFICANCE STATEMENT By assessing the irreversibility of large-scale dynamics across multiple brain signals, we provide a precise signature capable of distinguishing Alzheimer's disease (AD) at the global, local, and network levels and different oscillatory regimes. Irreversibility of limbic, frontoparietal, default-mode, and salience networks was the most compromised by AD compared with more sensory-motor networks. Moreover, the time-irreversibility properties associated with cognitive decline and atrophy outperformed and complemented classical neurocognitive markers of AD in predictive classification performance. Findings were generalized and replicated with an out-of-sample validation procedure. We provide novel multilevel evidence of reduced irreversibility in AD brain dynamics that has the potential to open new avenues for understating neurodegeneration in terms of the temporal asymmetry of brain dynamics.

Asymptotic analysis for 1D compressible Navier–Stokes–Vlasov equations with local alignment force

We consider the initial-boundary value problem of compressible Navier–Stokes–Vlasov equations under a local alignment regime in a one-dimensional bounded domain. Based on the relative entropy method and compactness argument, we prove that a weak solution of the initial-boundary value problem converges to a strong solution of the limiting two-phase fluid system. This work extends in some sense the previous work of Choi and Jung [Math. Models Methods Appl. Sci. 31(11), 2213–2295 (2021)], which considered the diffusive term ∂ξξfɛ in the kinetic equation. Note that the diffusion term was not considered in this paper.

Convection and intermittency noise in water temperature near a deep Mediterranean seafloor

Turbulent and internal wave motions are important for the exchange of momentum, heat, and suspended matter in the deep sea, which is generally stably stratified in density. Turbulence-generation models involve shear of vertical current differences that deforms stratified waters and convection that is driven by (unstable) buoyancy. In general, shear generation is found more in the interior of the well-stratified ocean, while convection is known to occur near the sea surface, e.g., via nighttime cooling. Far below the surface, the Western Mediterranean Sea is very weakly stratified and offers opportunity to observationally study the deep-sea convection. An opportunistic small set of high-resolution temperature sensors demonstrate not only classic internal-wave-induced turbulence but also convection attributed to geothermal heating and spectral properties that relate to various chaos-theory models, such as 1/σ pink noise (σ denoting frequency), mainly found lying at (0.01 m above) the seafloor, and 1/σ2 Brownian noise, mainly found on a moored line at about 100 m above the seafloor. Near-inertial temperature variations are observed to occur down to the seafloor, thereby disturbing the local convective turbulence regime to shear-dominated one temporarily. The integral turbulence timescale is generally smaller (with dominant higher frequency motions) at the seafloor than about 100 m above it.

Staying in situ or shifting range under ongoing climate change: A case of an endemic herb in theHimalaya‐HengduanMountains across elevational gradients

AbstractAimHow species respond to ongoing climate change has been a hot research topic, especially with the controversy in shifting range (movement) or persisting in local habitat (in situ) as the primary response. Assessing the relative roles of range shifts, phenotypic plasticity and genetic adaptation helps us predict the evolutionary fate of species. We aim to explore the evolutionary strategies of plants under climate change from a keystone herb in alpine ecosystems,Mirabilis himalaica, along its elevational gradient.LocationHimalaya‐Hengduan Mountains, China.MethodsWe combined evidence from population genomics and ecological data in both space and time to investigate the state of “staying” or “moving”. We identified migration events by assessing historical and contemporary gene flow and changes in species distribution. Morphological variation was compared by measuring five traits using specimen data. Moreover, we explored climate‐driven genetic variation and local selection regimes acting on populations in the alpine landscape along an elevational gradient.ResultsOur results argue that staying in situ by morphological variation and local genetic evolution rather than range shifting plays an important role inM. himalaicaresponse to climate change. We first found trace evidence of upward or climatic‐driven shifting along an elevational gradient, although asymmetric gene flow was restricted within microenvironments of mid‐elevational populations. Furthermore, morphological variation comparisons revealed clinal variation, as resource allocation showed a declining pattern in vegetative growth but increased reproductive growth with increasing elevation. Outlier tests and environment association analyses indicated adaptative loci primarily related to thermal‐driven selection and continuous adaptations to high elevation in the Himalaya‐Hengduan Mountains.Main ConclusionsOur findings showM. himalaicamay persist in local habitats rather than shifting range under climate change, exhibiting a low risk of genomic vulnerability in current habitats. This study has important implications in improving our understanding of the evolutionary response in alpine plants to climate change.

Determining the spatial contributions of land use changes on the streamflow and sediment transport regimes: a case study of the Gorganroud watershed in Iran.

Human activities and climate change are recognized as two of the most important drivers of hydrologic variability and have attracted the interest of researchers over the past decade. Changes in land use, dam construction, agricultural development, and global warming are forces that directly or indirectly impact the global and local hydrologic regime. This study examines the effects of these drivers on streamflow and sediment transport in the Gorganroud watershed, located in the north of Iran. In addition, the most sensitive land use patterns are detected using statistical approaches and a hydrologic model. The current study's principal argument is based on the variability of land use patterns during the modeling procedure (2007-2019). The Soil and Water Assessment Tool (SWAT) model is used to consider the land use dynamics during the simulation period based on the hydrological regime of the reference period. The Simple Differential Method (SDM) and Climate Elasticity Method (CEM) are utilized to estimate the contribution rates of land use and climate change in streamflow and sediment transport changes. The results indicate that changes in land use have contributed more than 60% to streamflow and sediment regime changes in all subbasins. A sensitivity analysis of land uses and the spatial distribution of the Human Contribution Rate (HCR) over the study area reveal that an increase in orchard land use (8.7% during the computational period) is primarily responsible for these significant changes.

Entanglement transition through Hilbert-space localization

We study Hilbert-space localization of the many-body dynamics due to ergodicity breaking and analyze this effect in terms of the entanglement entropy and the entanglement spectrum. We find a transition from a regime driven by quantum tunneling to a regime that is dominated by boson-boson interaction, where the latter exhibits ergodicity breaking. Properties of this transition are captured by observation time averaging, which effectively suppresses the large dynamical entanglement fluctuations near the critical point. We employ this approach to the experimentally available bosonic Josephson junction. In this example, the transition from a tunneling regime to Hilbert-space localization reveals clear signatures in the entanglement entropy and entanglement spectrum. Interestingly, the transition point is reduced by quantum effects in comparison to the well-known result of the mean-field approximation in the form of self-trapping. This indicates that quantum fluctuations reduce the classical self-trapping. Different scaling with respect to the number of bosons, $N$, is found in the tunneling and the localization regime: While the entanglement entropy grows logarithmically with $N$ in the tunneling regime, it increases linearly in the localized regime. Our results indicate that entanglement provides a concept for a sensitive diagnosis for the transition from a quantum tunneling regime to Hilbert-space localization.

Environmental and geographical factors structure cauliflower coral's algal symbioses across the Indo‐Pacific

AbstractAimThe symbioses between corals and endosymbiotic dinoflagellates have been described as a flexible relationship whose dynamics could serve as a source of resilience for coral reef ecosystems. However, the factors that drive the establishment and maintenance of this co‐evolutionary relationship remain unclear. We examined the environmental and geographical factors structuring dinoflagellate communities in a wide‐ranging Indo‐Pacific coral to begin to address this gap.LocationDjibouti, Oman, Taiwan and French Polynesia.TaxonCauliflower corals (Pocillopora spp.), dinoflagellates (family Symbiodiniaceae).MethodsWe analysed publicly available amplicon sequence data from the nuclear ribosomal DNA internal transcribed spacer 2, originating from Pocillopora spp. We also compiled environmental data such as sea surface temperature (SST) and time since the last local mass bleaching event. We ran generalized least squares models, PERMANOVAs and indicator species analyses, to understand how thermal regimes and geographical distances impacted Pocillopora spp.'s Symbiodiniaceae community composition.ResultsSea surface temperature was the most important factor driving Symbiodiniaceae community differences, with the largest effect size of the statistically significant factors. When focusing on individual Symbiodiniaceae genera, SST was likewise the most important factor. Our indicator species analyses revealed that specimens that had recently bleached were characterized by roughly equal proportions of Cladocopium spp. and Durusdinium spp., while specimens that had not recently bleached had a similar proportion of Durusdinium spp. as those that had recently bleached, but also showed a reduction in Cladocopium spp., with this deficiency made up by the presence of Symbiodinium spp.Main ConclusionsWe provide further support for the hypothesis that coral's Symbiodiniaceae communities could facilitate host resilience to thermal stress. Our work is in direct conversation with a larger body of biogeography literature that highlights how local environmental regimes can impact contemporary population structure, even in marine taxa with widespread distributions.

Widespread Torpor Use in Hummingbirds from the Thermally Stable Lowland Tropics.

AbstractTorpor, the temporary reduction of metabolic rate and body temperature, is a common energy-saving strategy in endotherms. Because of their small body size and energetically demanding life histories, hummingbirds have proven useful for understanding when and why endotherms use torpor. Previous studies of torpor in hummingbirds have been largely limited to tropical montane species or long-distance migrants that regularly experience challenging thermal conditions. Comparatively little is known, however, about the use of torpor in hummingbirds of the lowland tropics, where relatively high and stable year-round temperatures may at least partially negate the need for torpor. To fill this knowledge gap, we tested for the occurrence of torpor in tropical lowland hummingbirds ( individuals of six species) from central Panama. In controlled experimental conditions simulating the local temperature regime, all six species used torpor to varying degrees and entered torpor at high ambient temperatures (i.e., ≥28°C), indicating that hummingbirds from the thermally stable lowland tropics regularly use torpor. Torpor reduced overnight mass loss, with individuals that spent more time in torpor losing less body mass during temperature experiments. Body mass was the best predictor of torpor depth and duration among and within species-smaller species and individuals tended to use torpor more frequently and enter deeper torpor. Average mass loss in our experiments (∼8%-10%) was greater than that reported in studies of hummingbirds from higher elevation sites (∼4%). We therefore posit that the energetic benefits accrued from torpor may be limited by relatively high nighttime temperatures in the lowland tropics, although further studies are needed to test this hypothesis.

Phase randomization in disordered layered systems

The propagation of light through a disordered layered system in the Anderson localization regime is studied. The light propagation is accompanied by Anderson localization and phase randomization, which are generally related processes. This research is aimed at a detailed study of phase randomization. Particularly, the phase randomization approximation is tested numerically. It is shown that the distribution function of the transmission coefficient phase tends to stationary distribution as the number of layers increases. However, the stationary distribution is generally a non-uniform one contrary to the widely used assumption. The exponential convergence to the stationary distribution allows an unambiguous definition of the length scale of phase randomization.

Harvesting State Support: Institutional Change and Local Agency in Japanese Agriculture by Hanno Jentzsch

Reviewed by: Harvesting State Support: Institutional Change and Local Agency in Japanese Agriculture by Hanno Jentzsch Kae Sekine (bio) Harvesting State Support: Institutional Change and Local Agency in Japanese Agriculture . By Hanno Jentzsch. University of Toronto Press, 2021. xiv, 268 pages. CAD $70.00. Drawing from his exhaustive fieldwork in rural and semiurban Japan for several years, Hanno Jentzsch argues that local agency negotiated and translated national institutional change in the agricultural sector into local practice based on neoinstitutionalist theory and political economy. The backdrop to his book Harvesting State Support is the process of national agricultural reform since the mid-1990s—including market liberalization, the government's withdrawal from market interventionist policies, deregulation, and structural reform—induced by Japan joining the World Trade Organization (WTO). Employing the case of the municipality of Hikawa in Shimane Prefecture, as well as a number of others, Jentzsch invites the reader to discover the processes of farmland consolidation led by national regulatory change and how local actors, such as farmers, local agricultural cooperatives called JA (Japan Agricultural Cooperatives), local administrations, and emerging agribusinesses responded to the change by mobilizing local institutions. The farm consolidation policy was designed to let small-scale [End Page 154] family farmers, often part-time and aging, release their farmlands and to allow emerging, large professional corporate farms, the so-called "bearer farms" which were expected to become more competitive in the international market, to acquire and accumulate these farmlands. However, the author reveals that the results of this policy were heterogeneous among different agricultural localities; while municipalities such as Hikawa achieved a high rate of farmland consolidation, other municipalities had lower levels of consolidation. Based on his case studies, the author points out that village institutions, such as local social ties, norms, and practices in agricultural production and farmland use, significantly influenced farmland exchange and the establishment of hamlet-based collective farms, and therefore the interpretation of national regulatory framework in local practices. Jentzsch found that in some localities where the geographical boundaries of the local JA and local administration correspond with each other, village institutions successfully contributed to consolidating farmland under new macroagricultural reform while protecting the vested interests of local actors. But in localities where these boundaries had been disrupted—by the merger of local JAs from the 1990s induced by financial liberalization and of local municipalities caused by fiscal decentralization from the 2000s—village institutions could not be successfully mobilized in response to national agricultural reform. This book consists of five parts that include 13 chapters. Part 1, "Institutional Change in Japan's Agricultural Sector" (chapters 1–3), is the introduction while part 2, "Japan's Agricultural Support and Protection over Time" (chapters 4–5), illustrates the evolution of Japan's agricultural policies from the postwar period to the second administration of Abe Shinzō that ended in 2020. Part 3, "Local Agricultural Regimes and Village Institutions" (chapters 6–7), explains the significance of local agricultural regimes, local institutional actors, and village institutions that implemented and translated national agricultural reform into local processes in more or less organized ways from the mid-1990s. Part 4, "Village Institutions as Dynamic Resources: Local Renegotiation of Agricultural Support and Protection" (chapters 8–11), provides fine-grained analyses on how the integration of village institutions into local agricultural regimes brought local variations in farmland consolidation, in the roles of entrepreneurial farms and hamlet-based collective farms in local agricultural regimes, and in the impact of boundary changes of JAs and municipalities on the ability of village institutions to effectively respond to the liberalization of the national agricultural regime. Part 5, "Conclusions" (chapters 12–13), summarizes the findings of the study. Jentzsch outlines the implications for the trajectory of Japan's agricultural support and its protection regime. Further, he sketches his own theoretical contribution that emphasizes the effectiveness of local perspectives and insights regarding informal institutions to uncover [End Page 155] the dynamics of local institutional actors in translating macroinstitutional arrangements and to refine the meso-theory of institutional change. The significance of this book is threefold. First, Jentzsch makes Japanese agricultural and rural politics and local realities available to international scholars who can neither access the Japanese literature nor conduct...

Urban regimes and socially significant projects of the urban environment transformation in the Russian Federation

The authors of the article aim to identify the principles and patterns of mutual influence of socially significant projects of transformation of the urban environment and urban regimes in the Russian Federation. Clarence Stone's concept of urban regimes is used as a theoretical framework. Based on the author's system of criteria of social significance, 6 projects of urban environment transformation in 4 cities were selected and analyzed: Okhta Center and Tuchkov Buyan in St. Petersburg, Zaryadye Park and the development of fields of the Timiryazev Academy in Moscow, St. Catherine's Church in Yekaterinburg and concreting of the embankments of the river Vologda in Vologda. If the initial phase of all projects took place in the realities of local urban growth regimes, with the predominance of the interests of the established coalitions of business and government, then the subsequent increase in the role of public activism in all projects and the change of goal-setting under its influence led to a change in the local urban regime during their implementation. It is shown that in five studied cases, during the implementation of projects, there was a transition of local urban regimes from “growth” to “progressive”, and in one – from “growth” to a greater extent towards the “status quo” regime. The general principles and patterns of mutual influence of socially significant transformation projects and urban regimes in the Russian Federation are identified and described: competitive public interaction of all types of actors; change or relocation of the project as a spatial way of conflict resolution; the prevailing shift from the realization of the interests of government and business in favor of society; involvement of paternalistic tools as a way to achieve consensus. Such conditions of mutual influence of socially significant projects and urban regimes can develop in a certain period in any major Russian city, then we can expect in it similar to the described results of space transformation. The results of the study clearly demonstrate the beginning of the process of local transformation of the dominant urban regimes in the Russian Federation.

Anthropogenic activity, hydrological regime, and light level jointly influence temporal patterns in biosonar activity of the Yangtze finless porpoise at the junction of the Yangtze River and Poyang Lake, China.

Under increasing anthropogenic pressure, species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations. The critically endangered Yangtze finless porpoise ( Neophocaena asiaeorientalis asiaeorientalis), once commonly observed in the Yangtze River-Poyang Lake junction, is now rarely seen in the river-lake corridor. In this study, static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor. Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation, as well as environmental variables, including hydrological conditions and light levels. Over approximately three consecutive years of monitoring (2020-2022), porpoise biosonar was detected during 93% of logged days, indicating the key role of the corridor for finless porpoise conservation. In addition, porpoise clicks were recorded in 3.80% of minutes, while feeding correlated buzzes were detected in 1.23% of minutes, suggesting the potential existence of localized, small-scale migration. Furthermore, both anthropogenic and environmental variables were significantly correlated with the diel, lunar, monthly, seasonal, and annual variations in porpoise biosonar activities. During the pandemic lockdown period, porpoise sonar detection showed a significant increase. Furthermore, a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity. In addition to water level and flux, daylight and moonlight exhibited significant correlations with porpoise biosonar activities, with markedly higher detections at night and quarter moon periods. Ensuring the spatiotemporal reduction of anthropogenic activities, implementing vessel speed restrictions (e.g., during porpoise migration and feeding), and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.

Terahertz charge transport dynamics in 3D graphene networks with localization and band regimes.

Terahertz steady-state and time-resolved conductivity and permittivity spectra were measured in 3D graphene networks assembled in free-standing covalently cross-linked graphene aerogels. Investigation of a transition between reduced-graphene oxide and graphene controlled by means of high-temperature annealing allowed us to elucidate the role of defects in the charge carrier transport in the materials. The THz spectra reveal increasing conductivity and decreasing permittivity with frequency. This contrasts with the Drude- or Lorentz-like conductivity typically observed in various 2D graphene samples, suggesting a significant contribution of a relaxational mechanism to the conductivity in 3D graphene percolated networks. The charge transport in the graphene aerogels exhibits an interplay between the carrier hopping among localized states and a Drude contribution of conduction-band carriers. Upon photoexcitation, carriers are injected into the conduction band and their dynamics reveals picosecond lifetime and femtosecond dephasing time. Our findings provide important insight into the charge transport in complex graphene structures.

Temporal dynamics of the superdominant bracken fern Pteridium arachnoideum in Neotropical savanna-riparian forest transitions

Abstract Clonal growth can be especially advantageous in spatially heterogeneous environments and some clonal plants are highly invasive or superdominant, especially in disturbed environments. However, their temporal dynamics in the absence of large disturbances are not well known. We assessed whether patches dominated by the native bracken fern Pteridium arachnoideum expanded or retracted in area over six years. We mapped the contour of eight patches occupied by P. arachnoideum in a savanna-forest transition every two years from 2009 to 2015. The area occupied by most patches was overall stable, indicating that forested patch boundaries may be unsuitable for an effective vegetative spread of P. arachnoideum. One patch fully retracted during the study period, possibly due to extensive herbivory by leafcutter ants. Thus, although clonal foraging may enable the spread of the species to more suitable sites from these patches, these results indicate that P. arachnoideum does not represent a threat to the biodiversity of savanna-riparian forest transitions in the absence of extensive disturbances, as the area of the largest patches remained stable or decreased during our study. These findings highlight that specific characteristics of the local disturbance regime may be key to the cost-effective management of some superdominant native species.

Determination of the maximum flow of the river with anthropogenic factors

This study was aimed to determine the anthropogenic and natural factors affecting hydrological regime of rivers, reliability and safety of hydroelectric facilities. The work of the Uchkurgan hydroelectric complex before and after the commissioning of the Toktogul reservoir with a hydroelectric power station is considered. The observations were conducted over a period of 92 years. A significant decrease in the unevenness of the average long-term water flow has been established for various periods. A homogeneity graph was built, which showed the periods of influence of anthropogenic factors in 1975 and 1990. The following scenarios for determining the maximum water discharges were considered: local water consumption regime, commissioning of the Toktogul reservoir, and energy mode. The estimated verification flow of 0.01% security satisfies the design capacity of the hydroelectric complex of 2720 m3/s..

The local political regime: aspects of Moscow polity

The article discusses the theoretical and methodological foundations of modern political regimes. The evolution of political and regime issues is reflected from the standpoint of the views of researchers reflecting in the 21st century. The crisis of the transit approach is shown, which inevitably led to a rethinking of democracy. The analysis focuses on local modes, which have two basic forms of expression: regional and urban, in relation to large urbanized spaces (megacities). As a result of the application of regional transformation criteria to the political sphere, it is concluded that since 2010, Moscow polity has experienced power-political restructuring in the format of a «pact of elites» and not scenarios of «struggle according to the rules», «war of all against all», «winner gets everything». The use of the methodology of B. Ferman, in relation to the city (Moscow) political regime of 2010, allows us to conclude that the «control regime» explains more the specifics of metropolitan polity than the features of the «coordination regime».

“Stretched” Postsecular Rapprochement: Evangelical Solidarities in a Local Flemish Welfare Regime

“Stretched” Postsecular Rapprochement: Evangelical Solidarities in a Local Flemish Welfare Regime

The assessment of the hydrological regime of the Torysa River by the flashlines index

Climate change has a significant impact on the local and regional hydrological regime. In this study, the hydrological regime and variability of flows in the Torysa river basin were investigated for the period 1973-2020. The flows were evaluated by the RBI index. The results showed that the Torysa river has a large flow variability.

Analysis of Regional Scenarios of New Epidemic Waves of SARS-CoV-2 Coronavirus Based on Equations with a Deviating Argument and Damping Functions

The methods we develop within the framework of transient technical process modeling are adaptable to the tasks of biophysics—both to the prediction of invasions of aggressive species and to the analysis of the dynamics of epidemics. The practical application of modeling results to predict the development of the modern pandemic in 2020 has shown the fundamental limitations of the basic methods of model building. Based on an analysis of the properties of the deterministic SIRS model, it has not been possible to present the variety of forms that the regional dynamics of coronavirus spread has taken. The characteristics of the epidemic process do not remain constant, as a variable pathogen evolves competitively. The phenomena since the outbreak of COVID-19 have proven to be much more complex than the naturally fading waves of pandemic influenza strains as immunity accumulates. The development of a scenario approach to the analysis of individual epidemic situations is promising, taking into account the logic of the evolution of the pathogen and adaptation to the peculiarities of its spread in local populations. We performed an analysis of the available data in terms of oscillation forms to get an idea of the real qualitative diversity of local wavelike dynamics of the epidemic of coronavirus strains and identify some special development scenarios described as a catastrophic cycle breakdown on the basis of the known phase-portrait transformations. Applying a bifurcation approach to the epidemic data, we were able to identify features of local forms of oscillatory epidemic processes. We classified the observed phenomena of outbreaks and attenuation of coronavirus infection waves by correlating the dynamics of epidemics with nonlinear effects. We derived scenarios for a number of epidemic situations (in Brazil, New York, and Japan) using lagged equations. It is shown on the basis of comparison of specific situations that the dynamics of epidemics evolve diversely and variably at the current stage according to the internal unpredictable logic of the confrontation process, which is determined by the rate of change in the joint evolution of the virus and population immunity, including the previously formed T-cell immunity. We were able to analyze variants of COVID-wave transformations in lagged equations using the idea of distinguishing bifurcation-inducing parameters. It is substantiated that all nonlinear effects and transformations of oscillatory modes, isolated by epidemic plots, cannot in principle be obtained within a single model. Comparative scenario analysis supports the hypothesis that epidemic processes are primarily influenced by population immunity and contact density. Vaccination has failed to complete the emergence of new waves of infections, but clearly affects the properties of local oscillatory regimes of disease incidence. Experience with new outbreaks of COVID-19 in 2023 in Sweden, New Zealand, Japan, and South India with fundamentally different coping strategies showed that sustained population immunity blocking coronavirus transmission could not be achieved over the long term. Our assumed scenario for the end of the pandemic is the formation of four stable strains whose sporadic circulation in the regions is controlled by CD8+ T-cell immunity.

The impact of N2 micro-jets on the V-to-M flame shape transition in a premixed swirl burner

Injection of N2 through micro-jets located on the dump plane of a lean premixed swirl stabilized combustor is investigated as a new method for mitigating combustion instabilities. This study focuses on the chemical and fluid dynamic processes by which the N2 micro-jets impact the flame dynamics. An experimental and numerical investigation is performed to characterize the combustion instability during the V-to-M flame shape transition in a swirl burner fueled with premixed CH4/air, at an equivalence ratio of 0.62. Reasonable agreements have been found between the experimental measurements and simulation results. Both of them present that the flame changes from V-shape to M-shape periodically, and a low-frequency instability around 10 Hz is observed accordingly. It is confirmed that intermittent flame extinction in the outer recirculation zone (ORZ) is the source of the combustion instability. Furthermore, injection of N2 through micro-jets located on the combustor dump plane, into the outer recirculation zone, results in a stable V shape flame. It is clearly seen that the ORZ dilution can eliminate the combustion instability without inhibiting the combustion efficiency. A special focus is placed on the impact of the diluent injection on the local flame-flow interaction. The nitrogen micro-jets increase the local nitrogen concentration by 7% on average, lowering the flame speed and extinction strain rates by 27% and 17% respectively. Moreover, the micro-jets increase the turbulence intensity in the ORZ, leading to a significant increase in the Karlovitz number and transferring the local combustion regime from the thin reaction zone regime to the broken reaction zone regime. Hence, the nitrogen micro-jets impact on both the turbulence and the chemical reaction rates prevents flame propagation into the ORZ and results in a stable flame.