Periodic Firing Research Articles

Spatial structure of natural landscapes within the Chornobyl Exclusion Zone

The article demonstrates the results of a study of the landscape structure of the Chornobyl Radiation and Ecological Biosphere Reserve (Ukr.: Chornobylskyi radiatsiino-ekolohichnyi biosfernyi zapovidnyk – ChREBR). Because of radioactive pollution, a sharp drop in human activity, and the granting of the territory the status of a protected object, the process of area rewilding took on certain characteristics and led to the return of ecosystems’ natural processes. The studies cover a 7-year period from 2016 to 2022, i.e., from the moment this territory was granted protected status. That territory was abandoned by people more than 37 years ago and the former rural and urban landscapes have either already been transformed or are in the process of being transformed into natural ones. The scale of forest massifs has changed during the previous seven years, which has caused increased pasture overgrowth. huge forest massifs have been lost because of enormous forest fires and floods, particularly along the Pripet and Uzh rivers. Semi-natural successions occur in the gardens, and wooden homes are almost extinct. From orbit, a number of communities no longer resemble settlements. They are cloaked in bushes and trees instead. For places that have been ploughed, the same holds true. The last seven years show that change is happening more slowly than in the decades before. The pattern of natural processes in ecosystems, including periodic fires, the blocking of reclamation channels, and other factors, is the primary driver of changes in the composition of the land cover.

Periodic firing evolution of a Hindmarsh–Rose neuron model and FPGA circuit implementation

Periodic firing evolution of a Hindmarsh–Rose neuron model and FPGA circuit implementation

The effect of fire on tree-ring width and tracheid dimensions of Pinus nigra

Summary Forest fires play a significant role in the growth and development of trees because they can damage the phloem and cambium. Fire injury induces the formation of fire scars that can cause xylem dysfunction. The study area is located in Taşköprü, Kastamonu (Western Black Sea of Turkiye), where two forest fires occurred in 1957 and 2020. In this study, the effect of the 1957 fire on the tree-ring widths and tracheid dimensions of Pinus nigra trees was investigated. We measured tree-ring widths and tracheid dimensions of fire-scarred (FS) and unscarred (UF) trees during four different periods: the pre-fire period (1947–1956), fire event year (1957), and post–fire periods (1958–1967 and 2011–2020). In this study, UF trees showed almost 2.5–3 times wider tree–ring widths (TRWs) than FS trees. FS and UF trees also showed great variation in tracheid dimensions in the four different periods; the average tracheid diameter (TD), lumen area (TLA), and wall thickness (TWT) values increased significantly in UF trees compared to FS trees during the fire event and post-fire periods. The average TD, TLA, and average tracheid lumen diameter (TLD) decreased during the fire and post-fire years in the FS trees. In this study, we suggest that fire injury significantly affects the tracheid dimensional traits of FS Pinus nigra trees. Our results also suggest that although Pinus nigra trees experienced serious fire damage, they continued to grow but with a decrease in tracheid size.

Investigation of 2021 wildfire impacts on air quality in southwestern Turkey

In the summer of 2021, unusually intense wildfires happened in southwestern Turkey, especially in Antalya and Mugla with destroying effects on forests, wildlife, and communities residing there. This study aims to understand the air quality impacts of these wildfires. A time period (June–September 2021) covering pre-, fire, and post-periods was investigated using NO2 ground-based observations and TROPOMI CO, HCHO, and NO2 satellite retrievals along with VIIRS FRP. Eight fire regions were selected for detailed analysis in Antalya (An-1-2), Mugla (Mu-1-4), and Mersin (Me-1-2). The highest fire intensity was found in An-1 and followed by Mu-1. CO also showed strongest signals over An-1 (6.73 × 1018 molecules/cm2) with highest levels (1.44 × 1019 molecules/cm2) in the downwind of the wildfires. NO2 showed fire signals in or in very close proximity to the fire regions with strongest signal and largest impact area in An-1 (>8.75 × 1016 molecules/cm2). HCHO showed a different pattern due to HCHO undergoing chemical production and loss in the wildfire plume. HCHO highest levels were not observed over the fire regions, but inside the transported plume with maximum levels for An-1 (3.60 × 1016 molecules/cm2) and for An-2 (3.23 × 1016 molecules/cm2). CO and NO2 increase continued not only in fire, but also in post-fire period, whereas HCHO levels indicated decreases in post-fire compared to pre-fire period. The increases in column concentrations in fire period ranges from 17.6 to 123.1% for CO, 40.6–116.5% for HCHO and 34.4–294.5% for NO2. Higher increases were observed over the Mediterranean Sea especially for CO. Correlations with FRP indicated highest correlations with CO and NO2 and low correlations with HCHO. This study showed that the capability of sparse, ground-level air quality monitoring stations to capture wildfire impacts are limited in the region, because the plume transport was driven by wind direction and wildfire smoke plumes are elevated due to buoyancy. Satellite retrievals are better for capturing the wildfire plume transport and estimating the overall air quality impacts of wildfires.

Predicting dynamics of wildfire regimes in Yunnan, China

In recent years, the rise in global warming has significantly increased forest fires, affecting the environment and economy. Predicting forest fire dynamics under climate change is now a crucial research field. To address this need, this study focuses on the impact of climate change on forest fires, with a particular focus on the fire dynamics in Yunnan Province. This study utilizes the RegCM regional climate model and the Canadian Fire Weather Index (FWI) to simulate and analyze forest fire dynamics in Yunnan Province from 2019 to 2033 under three climate scenarios: RCP2.6, RCP4.5, and RCP8.5. Findings indicate climate change will increase temperatures, alter humidity and wind speed, and reduce precipitation in Yunnan, extending the fire danger period, especially under RCP8.5 scenarios. The FWI values rise across Yunnan, particularly in the west under RCP2.6 and RCP8.5. The study concludes that future carbon emissions correlate with these changes, leading to more frequent, longer, and severe forest fires. This research is vital for managing and preventing forest fires in Yunnan, a region prone to such disasters.

Psychotropic Medication Prescriptions and Large California Wildfires

Wildfires, intensified by climate change, have known effects on physical health but their effects on mental health are less well characterized. It has been hypothesized that the residential proximity to a large wildfire can exacerbate underlying mental health conditions as evidenced by increased prescriptions of psychotropic medications. To evaluate the association between the occurrence of large wildfires and the prescription rates of psychotropic medications immediately following the start of the fire. This cohortstudy used an interrupted time-series analysis to compare psychotropic medication prescriptions in the 6 weeks before and after each of 25 wildfires. The setting was California counties within metropolitan statistical areas (MSAs) experiencing large wildfires from 2011 through 2018. Participants included individuals residing in California MSAs with prescriptions of psychotropic medications recorded in the Merative MarketScan Research Database (MarketScan) during the study period. Statistical analysis was performed for these 25 large wildfires occurring between September 2011 and November 2018. Residential proximity to large wildfires that burned more than 25 000 acres occurring in a California county within an MSA. Prescriptions of psychotropic medications, including antidepressants, antipsychotics, anxiolytics, hypnotics, and mood-stabilizers, with statins as a negative control outcome. For the study period, prescription data and patient-level attributes were extracted for 7 115 690 unique individuals (annual mean [range]: 889 461 [455 705-1 426 928] individuals) enrolled in MarketScan and residing in fire-affected MSAs. This study found a statistically significant increase in prescriptions of antidepressants (rate ratio [RR], 1.04 [95% CI, 1.01-1.07]), anxiolytics (RR, 1.05 [95% CI, 1.02-1.09]), and mood-stabilizing medications (RR, 1.06 [95% CI, 1.01-1.13]) in the fire period compared with the prefire baseline. However, the prescriptions of antipsychotics, hypnotics, and the negative control outcome, statins, showed no significant association. In this cohort study of large California wildfires, the occurrence of wildfire was associated with increased mental health burden as reflected in increased prescription rates of certain psychotropic medications. The findings underscore the need for further scientific examination into the mental health effects of wildfires and the allocation of mental health resources in disaster responses. California experienced a substantial burden of wildfires from 2011 to 2018, and as wildfires become more intense and frequent in the context of anthropogenic climate change, it is increasingly important to understand and address their mental health effects.

Fire dynamics and driving mechanisms on the Eastern Coast of China since the Late Pleistocene: evidence from charcoal records on Shengshan Island

Fires play a significant role in ecosystems, exerting a profound influence on climate, vegetation, and geochemical cycles, while being reciprocally affected by these factors. The reconstruction of past fire events serves as a valuable window into understanding environmental changes over time. To investigate the history of ancient fires on the Eastern Coast of China, we conducted the first charcoal analysis on a loess profile of Shengshan Island (East China Sea). Along with other biological and geochemical proxies, we successfully reconstructed the ancient fire dynamics and elucidated their driving mechanisms in this region since the Late Pleistocene. Our initial findings revealed a peak in charcoal concentration during the 60-50 ka period, but after calibrating for sedimentation rate, the concentration significantly decreased. Fire activities remained weak during 50-30 ka, likely due to the scarcity of combustible materials. Between 30-12 ka, fires were frequent in the early period, while gradually diminishing during the later stage. Dry climate and dense vegetation likely attributed to frequent fires in early period, while some extreme events (e.g., sudden change in temperature) may have decreased the fire frequency in later period. The Holocene (began ~12 ka) evidenced the most frequent fire events as a high charcoal concentration was recorded, likely caused by human activities. After comparing our findings with other paleoecological records from surrounding areas, we confirmed the accuracy of our reconstruction of ancient fires. This reconstruction captures not only local shifts but also broader regional changes. Overall, our study highlights the importance of calibrating sedimentation rate in charcoal profiles, while also contributing to an enhanced understanding of environmental changes along the Eastern Coast of China since the Late Pleistocene.

Sustaining eastern oak forests: Synergistic effects of fire and topography on vegetation and fuels.

Across much of the eastern United States, oak forests are undergoing mesophication as shade-tolerant competitors become more abundant and suppress oak regeneration. Given the historical role of anthropogenic surface fires in promoting oak dominance, prescribed fire has become important in efforts to reverse mesophication and sustain oaks. In 2000 we established the Ohio Hills Fire and Fire Surrogate (FFS) study to examine whether repeated prescribed fire (Fire), mechanical partial harvest (Mech), and their combined application (Mech + Fire) reduced the dominance of subcanopy mesophytic competitors, increased the abundance of large oak-hickory advance regeneration, created a more diverse and productive ground-layer flora, and produced fuel beds more conducive to prescribed fire, reducing the risk of high-severity wildfire. Here we report on the ~20-year effects of treatments on vegetation and fuels and examine the support for interactive effects across a topographic-moisture and energy gradient. In general, we found that Fire and Mech + Fire treatments tended to reverse mesophication while the Mech-only treatment did not. The moderate and occasionally high-intensity fires resulted in effects that were ultimately very similar between the two fire treatments but were modulated by topography with increasing fire severity on drier sites. In particular, we found support for an interaction effect between treatment and topography on forest structure and tree regeneration responses. Fire generally reduced mesophytic tree density in the midstory and sapling strata across all site conditions, while leading to substantial gains in the abundance of large oak-hickory advance regeneration on dry and intermediate landscape positions. Fire also promoted ground-layer diversity and created compositionally distinct communities across all site conditions, primarily through the increased richness of native perennial herbs. However, the fire had limited effects on fine surface fuel loading and increased the loading of large woody fuels, potentially increasing the risk of high-severity wildfire during drought conditions. We conclude that two decades of repeated fires, with and without mechanical density reduction, significantly shifted the trajectory of mesophication across most of the landscape, particularly on dry and intermediate sites, highlighting the capacity of a periodic fire regime to sustain eastern oak forests and promote plant diversity but modulated by topography.

Fly Ash Geopolymer Paste for NSM CFRP Application Under Elevated Temperatures: Material Development

Strengthening of reinforced concrete (RC) structures using near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) technique is exhibited as effective and promising technology. However, having epoxy adhesive as the binding agent between the CFRP laminate and concrete substrate presents a serious drawback due to its low glass transition temperature (GT), which when exceeded, the epoxy adhesive loses its mechanical strength. This study focuses on optimizing a fly ash (FA) geopolymer adhesive as an alternative to epoxy. Several mixes with different constituent proportions have been investigated for their residual compressive strength and volume change at different firing periods. One mix was quenched in water to introduce and evaluate thermal shock impacts. The results demonstrate that the highest compressive strength at ambient temperature and the lowest volume change at elevated temperatures were recorded by the mix with the lowest SiO2/K2O. Mixes with higher activator alkali content achieved the highest residual compressive strength and exhibited expansion at elevated temperatures. Furthermore, the geopolymer exposed to water quenching recorded a slight decrease in both residual compressive strength and volume in comparison with samples cooled naturally. Overall, the findings suggest that employing potassium-based geopolymers in NSM CFRP applications could offer significant improvements in terms of advancing thermomechanical performance.

A Study to Assess the Knowledge on Fire Safety at Work Place among the Health Care Workers at a Tertiary Care Hospital

Fire safety is a crucial set of precautions and practices designed to prevent the outbreak of fires, minimise their destructive potential, and ensure the safety of individuals and property. It also helps early detection, and effective response strategy in the event of a fire emergency. This study employed a descriptive cross-sectional analytical design, with 384 participants selected using a proportional quota sampling technique. A self-structured questionnaire was used to assess the knowledge of fire safety. This questionnaire covered various aspects of fire safety, including fire prevention strategies, early detection methods, and effective response strategies. The primary objective was represented by frequency and percentage, while the secondary objective was analysed using a chi-square test. This rigorous methodology ensures the reliability and validity of the study's findings. The results showed that most participants (77.1%) had good to very good knowledge, with 48.2 percent having good knowledge and 28.9 percent having average knowledge. Only 13.3 percent needed improvement. The study also found a statistically significant association between the level of understanding of fire safety and certain demographic variables. The fire safety interventions implemented at JIPMER, including periodic fire drills and comprehensive training, have been proved highly effective. Additionally, the annual fire safety training for healthcare workers, which covers fire safety regulations, evacuation procedures, and fire extinguishers, has contributed to the high level of knowledge among most healthcare workers at JIPMER, Puducherry.

Microelectrode Arrays for Detection of Neural Activity in Depressed Rats: Enhanced Theta Activity in the Basolateral Amygdala.

Depression is a common and severely debilitating neuropsychiatric disorder. Multiple studies indicate a strong correlation between the occurrence of immunological inflammation and the presence of depression. The basolateral amygdala (BLA) is crucial in the cognitive and physiological processing and control of emotion. However, due to the lack of detection tools, the neural activity of the BLA during depression is not well understood. In this study, a microelectrode array (MEA) based on the shape and anatomical location of the BLA in the brain was designed and manufactured. Rats were injected with lipopolysaccharide (LPS) for 7 consecutive days to induce depressive behavior. We used the MEA to detect neural activity in the BLA before modeling, during modeling, and after LPS administration on 7 consecutive days. The results showed that after LPS treatment, the spike firing of neurons in the BLA region of rats gradually became more intense, and the local field potential power also increased progressively. Further analysis revealed that after LPS administration, the spike firing of BLA neurons was predominantly in the theta rhythm, with obvious periodic firing characteristics appearing after the 7 d of LPS administration, and the relative power of the local field potential in the theta band also significantly increased. In summary, our results suggest that the enhanced activity of BLA neurons in the theta band is related to the depressive state of rats, providing valuable guidance for research into the neural mechanisms of depression.

Long-term fire and grazing regimes modify soil physical properties and root traits in North American tallgrass prairie

The native Konza tallgrass prairie is maintained by two key natural processes, periodic fire and ungulate grazing. As a potential crucial feedback mechanism, how fire and grazing influence plant root traits and soil properties in the tallgrass prairie ecosystem remains less known. Here, we investigated the effects of long-term fire and grazing regimes on soil physical properties and root traits at the Konza Prairie Biological Station, near Manhattan, KS, USA. Soil cores were collected under control (unburned and ungrazed), fire (annually burned), grazing (annually grazed), and fire + grazing (annually burned and grazed) treatments. Soil water retention, total root volume, specific root length, specific root area, and root biomass were measured. We found that both fire and grazing significantly reduced soil water retention, increased soil bulk density and soil microporosity (<50 μm), and reduced macroporosity (>50 μm) compared to the unburned and ungrazed treatment. Fire and grazing also significantly reduced litter accumulation by 79 % (burned), 57 % (grazed), and 77 % (burned and grazed). Fire increased specific root area by 15 %. Grazing and fire + grazing significantly decreased specific root length by 40 % and 29 %, and specific root area by 33 % and 24 %, respectively. Litter production was positively related to soil volumetric water content and soil pore volume of 300–50 μm, but negatively related to soil bulk density and soil pore volume of less 50 μm. Soil volumetric water content was positively correlated to specific root lengths, and soil bulk density was negatively related to specific root length and specific root area. There was a significant negative relationship between root diameter and soil volumetric water content under burned and grazed treatment. The SEM model showed that fire, grazing, and fire + grazing regimes were associated with dead root biomass (R2 = 0.38) and root length density (R2 = 0.40) indirectly through soil bulk density and litter accumulation. Our findings suggested that the annual fire + grazing regime seriously leads to the degradation of tallgrass prairie by influencing soil physical properties, reducing root trait functions and root biomass, and altering the relationship between root diameter and soil volumetric water content.

Hubungan Masa Kerja Dan Keikutsertaan Pelatihan Dengan Keterampilan Penggunaan Alat Pemadam Api Ringan (Apar) Pada Karyawan Rumah Sakit Mandalika Nusa Tenggara Barat Tahun 2023

Sytem by humans as managers or occupants of the building. Many of us encounter discrepancies regarding Light Fire Extinguishers (APAR) both in how to use, place, inspect and how to maintain APAR. This had an impact on the failure of the fire extinguishing process at the start of the incident, causing a fire. The purpose of this study is to describe and analyze the relationship between working period, training participation and skills in using Light Fire Extinguishers (APAR) for Mandalika Hospital employees in 2023. This study used analytic observation with a cross-sectional method and usus an observational approach. This study uses univariate analysis and bivariate analysis. The result of the study showed that 33.8% of respondents with long working period were skilled in suing Light Fire Extinguishers while 66.2% were unskilled. Respondents with new working period were 18.4% unskilled, while 81.6% new working period were unskilled with a chi-square P = 0.087 &gt; 0.05. It meant that there was not any relationship between working period and Light Fire Extinguishers use skills. As many as 41.3% of skilled respondents had participated in training on the use of Light Fire Extinguishers, while 58.7% were unskilled. Respondents who had never participated in training but were skilled in using APAR were 20.3% and respondents who had never participated in training were 79.7% unskilled with a chi-square value P = 0.015 &lt; 0.05 indicating that there was a relationship between participation in training and Light Fire Extinguishers use skills.

Subthalamic nucleus neuronal activity entropy in the effective stimulation area in patients with Parkinson’s disease

One of the most successful and promising treatments for Parkinson’s disease today is deep brain stimulation (DBS). Accurate localization of the stimulation area is critical for the outcome of surgical DBS electrode implantation in the subthalamic nucleus (STN). To achieve this, microelectrode recording is used during surgery to precisely locate the STN borders [1], while test stimulations with a macroelectrode are widely employed to enhance DBS electrode placement accuracy. Thus, through testing multiple trajectories, the most clinically effective one can be selected. However, a comprehensive and reliable description of the specific single neuron activity associated with successful DBS electrode implantation is currently lacking. A study was conducted using microelectrode recordings (MER) of single neuron activity in the STN of 21 Parkinson’s disease patients (UPDRS III off/on=46.9/12.8) to identify the neuronal activity features associated with the most favorable clinical outcome of test stimulation. A comparative analysis of 29 activity parameters, such as firing rate, oscillatory activity intensity in different frequency ranges (Oscores), coefficient of variation, burst, pause index, among others [2], was conducted for 618 identified neurons. In addition, the approach of computing the entropy of the change in interspike intervals (ISI) of the pulse sequence [3] and the process of identifying patterns of neural activity using hierarchical clustering [4] were implemented. A comparative analysis of single neuron activity indicated notable (p 0.05) variations between disregarded and selected paths for the ultimate implantation of DBS electrode, solely relying on entropy parameters. Trajectories that delivered optimal test stimulation outcomes demonstrated reduced entropy of interspike intervals. Only the patterns of neuronal activity characterized by extended periods of steady firing and brief pauses, referred to as tonic and pause activity, respectively, were found to contribute to the difference in entropy between trajectories. In contrast, there were no statistically significant differences detected in entropy values associated with neurons demonstrating burst activity. Furthermore, we observed a positive and significant correlation between entropy values and the degree of improvement in disease presentation before and after administration of medication. A comparative analysis was conducted on the activity of single neurons along different trajectories with varied test stimulation responses. The results showed a weak effectiveness of linear parameters in determining the optimal electrode insertion path for improved clinical outcomes. However, the use of non-linear activity parameters, specifically entropy, in single neurons effectively differentiated trajectories with significant versus absent/insignificant test stimulation results. Furthermore, the significance of entropy in establishing the basal ganglia functions and describing information transfer processes in movement control is emphasized by interpreting this parameter as a measure of uncertainty or unpredictability of the information system in relation to the findings of other studies [5].

Investigation of the post-blast fire performance of RC members

An explosion or blast can trigger a subsequent fire in the building structure. In the case of reinforced concrete (RC) structures, blast loading can result in relatively large residual deformations and locked-in stresses in the affected members prior to fire exposure. Such residual deformations and locked-in stresses can have a detrimental effect on the subsequent fire performance of RC members. Accordingly, this paper presents results from a numerical study investigating the post-blast fire (PBF) performance of isolated RC columns. A simplified numerical model was developed to implement the integrated environment for modeling the interaction between blast and PBF scenarios without employing complex user-defined subroutines in ABAQUS. The developed FE model was validated against the experimental blast and fire tests. The RC column was subjected to blast loads of distinct scaled distances (Z) simulating the far-field and near-field scenarios. Further, the blast-damaged columns were exposed to a standard fire and evaluated the PBF performance. Results indicated that the fire resistance period (FRP) of RC columns is significantly reduced by prior blast damage, with reductions ranging from 0.8 % to 72 % as Z decreases from 2 to 0.8 m/kg1/3. Consequently, to mitigate these detrimental blast effects and ensure adequate PBF resistance, a transverse reinforcement with a diamond configuration in the plastified region of the RC column is recommended. Furthermore, the study explores the impact of axial load levels on RC column performance under PBF scenarios. It's observed that an increase in axial load levels beyond 25 % of the critical axial load-bearing capacity results in a 100 % reduction in the post-blast FRP of the RC columns. Additionally, Pressure-Impulse (P-I) diagrams are developed examining the blast cases that yield specific post-blast FRP for the RC columns. Notably, the diamond configuration demonstrates superior blast resistance for the same post-blast FRP, as evidenced by the P-I diagrams.

A neuron model with nonlinear membranes.

One-layer membrane separates the gradient field in and out of the cell, while some two-layer membranes filled with excitable media/material are important to regulate the energy flow when ions are propagated and diffused. The intracellular and extracellular media can be effectively separated by the membrane. It is important to clarify and describe the biophysical function and then the capacitive property can be reproduced in equivalent neural circuit. Here, we suggest the cell membrane has certain thickness and becomes flexible under external stimuli, therefore, it is considered as a kind of nonlinear media. To mimic the physical property of the two-layer cell membrane, a nonlinear resistor is used to connect two linear circuits, which is used to describe the electrical characteristic of two sides of the cell membrane, respectively. The combination of two linear circuits via a nonlinear resistor can describe the energy characteristic and firing mode in the flexible membrane of biophysical neurons. Circuit equations are defined and converted into equivalent nonlinear oscillator like a neuron. The voltage difference for the two capacitors can be consistent with the membrane potential for the neuron. The Hamilton energy function for this neuron can be mapped from the field energy in the electronic components, and it is also derived by using Helmholtz's theorem. The neuron can show similar spiking and bursting firing patterns, and uncertain diversity in membrane potentials is effective to support continuous firing patterns and mode transition under external stimulus. Furthermore, noisy disturbance is applied to induce coherence resonance. The results indicate that the lower coefficient variability and higher average energy level supports periodic firing in the neuron under coherence resonance. Therefore, this neuron model with nonlinear membranes (or two-layer form) is more suitable for identifying the biophysical property of biological neuron.

Minute-scale periodicity of neuronal firing in the human entorhinal cortex

Grid cells in the entorhinal cortex demonstrate spatially periodic firing, thought to provide a spatial map on behaviorally relevant length scales. Whether such periodicity exists for behaviorally relevant time scales in the human brain remains unclear. We investigate neuronal firing during a temporally continuous experience by presenting 14 neurosurgical patients with a video while recording neuronal activity from multiple brain regions. We report on neurons that modulate their activity in a periodic manner across different time scales-from seconds to many minutes, most prevalently in the entorhinal cortex. These neurons remap their dominant periodicity to shorter time scales during a subsequent recognition memory task. When the video is presented at two different speeds, a significant percentage of these temporally periodic cells (TPCs) maintain their time scales, suggesting a degree of invariance. The TPCs' temporal periodicity might complement the spatial periodicity of grid cells and together provide scalable spatiotemporal metrics for human experience.

Spatio-Temporal Characteristics of Ice–Snow Freezing and Its Impact on Subtropical Forest Fires in China

Ice–snow freezing may disrupt the growth condition and structure of forest vegetation, increasing combustible loads and thus triggering forest fires. China’s subtropical regions are rich in forest resources, but are often disturbed by ice–snow freezing, especially due to climate change. Clarifying the responsive areas and times of forest fires to ice-snow freezing in this region is of vital importance for local forest fire management. In this study, meteorological data from 2001 to 2019 were used to extract the precipitation and its duration during the freezing period in order to analyze the freezing condition of forest vegetation in subtropical China. To improve the accuracy of identifying forest fires, we extracted forest fire information year-by-year and month-by-month based on the moderate resolution imaging spectroradiometer (MODIS) active fire data (MOD14A2) using the enhanced vegetation index (EVI), and analyzed the forest fire clustering characteristics in the region using the Moran’s Index. Then, correlation analysis between forest fires and freezing precipitation was utilized to explore the responsive areas and periods of forest fires caused by ice–snow freezing. Our analysis shows the following: (1) during the period of 2001–2019, the ice–snow freezing of forest vegetation was more serious in Hunan, Jiangxi, Hubei, and Anhui provinces; (2) forest fires in subtropical China have shown a significant downward trend since 2008 and their degree of clustering has been reduced from 0.44 to 0.29; (3) forest fires in Hunan, Jiangxi, and Fujian provinces are greatly affected by ice–snow freezing, and their correlation coefficients are as high as 0.25, 0.25, and 0.32, respectively; and (4) heavy ice–snow freezing can increase forest combustibles and affect forest fire behavior in February and March. This research is valuable for forest fire management in subtropical China and could also provide a reference for other regions.

Dynamics and synchronization in a memristor-coupled discrete heterogeneous neuron network considering noise

Research on discrete memristor-based neural networks has received much attention. However, current research mainly focuses on memristor–based discrete homogeneous neuron networks, while memristor-coupled discrete heterogeneous neuron networks are rarely reported. In this study, a new four-stable discrete locally active memristor is proposed and its nonvolatile and locally active properties are verified by its power-off plot and DC V–I diagram. Based on two-dimensional (2D) discrete Izhikevich neuron and 2D discrete Chialvo neuron, a heterogeneous discrete neuron network is constructed by using the proposed discrete memristor as a coupling synapse connecting the two heterogeneous neurons. Considering the coupling strength as the control parameter, chaotic firing, periodic firing, and hyperchaotic firing patterns are revealed. In particular, multiple coexisting firing patterns are observed, which are induced by different initial values of the memristor. Phase synchronization between the two heterogeneous neurons is discussed and it is found that they can achieve perfect synchronous at large coupling strength. Furthermore, the effect of Gaussian white noise on synchronization behaviors is also explored. We demonstrate that the presence of noise not only leads to the transition of firing patterns, but also achieves the phase synchronization between two heterogeneous neurons under low coupling strength.

Numerical simulation and experiment of double chamber brake based on CFD

The artillery firing process will instantly produce high-temperature and high-pressure gunpowder gas, this process will produce shock waves. The gunpowder gas has a limited effect on the projectile during the firing and ballistic after-effects period, however, it has a very obvious effect on the stability of the gun body, and the reduction of the stability of the gun body directly affects the firing accuracy and the safety of the firing personnel. Based on the method of Computational Fluid Dynamics (CFD), numerical simulation is carried out, and the structure and flow parameters of the muzzle flow field are obtained by using three-dimensional Euler's control equation, gas equation of state, and k-epsilon model, as well as dynamic mesh technology. By comparing the flow parameters of the brake before and after optimization, and analyzing the results obtained from the 8-round firing experiments, the efficiency of the optimized brake is increased by 8.2%, and the deviation between the experimental data and the simulation results is only 10.5%, which not only verifies the accuracy of the numerical simulation calculations but also verifies the optimized brake's good retracting effect. The results of the study can provide a reference for the optimization and design of the double-chamber brake.