Sparse Population Research Articles

Platypus fyke-netting methods: a review of recommended field protocols and options for assessing population abundance

Fyke nets are the preferred type of equipment used for platypus (Ornithorhynchus anatinus) live-trapping surveys in shallow watercourses. However, numerous factors other than abundance may affect the frequency of platypus captures, including when, where and how nets are set, stream discharge and entry into nets by rakali (Hydromys chrysogaster), which create exit holes that are then also available to a platypus. A threefold difference in the mean monthly frequency of platypus captures in fyke nets is also evident across the year. To limit net evasion, it makes sense to reduce net visibility and minimise opportunities for animals to squeeze under, climb over or walk around nets. Time-lapse cameras can also be deployed at fyke-netting sites to estimate how many individuals evade capture. To protect platypus welfare and the welfare of non-target species held in fyke nets, it is important to ensure that captured animals have access to air, to check nets frequently throughout the time they are set and to release bycatch when first encountered. Fyke-netting studies typically generate sparse platypus population data, so care is needed when selecting and interpreting platypus abundance metrics generated through mark–recapture modelling or use of indices.

Soft matter mechanics of baseball’s Rubbing Mud

Researchers looking for sustainable materials with optimal mechanical properties may draw inspiration from a baseball tradition. For nearly 100 y, a mysterious mud harvested from an undisclosed river site in New Jersey (USA) has been the agent of choice in the USA's Major League Baseball for "de-glossing" new baseballs. It is unclear, however, what makes this "Rubbing Mud" work. Here, we perform a multiscale investigation of the rheology and tribology of this mud material under baseball-relevant conditions and identify three mechanisms by which the mud alters the surface properties of the baseball. First, the mud creates a more uniform baseball surface by filling in pores in the leather; this is possible because of its relatively high cohesion (clays and organics) making the material remarkably shear thinning. Second, the residue of cohesive particles coating the baseball effectively doubles contact adhesion. Third, a sparse population of angular sand grains are bonded to the baseball by clay-sized particles, leaving a studded surface that enhances friction. The proportions of cohesive, frictional, and viscous elements in Rubbing Mud conspire to create a soft material with an unusual mix of properties, that could find other applications in the development of sustainable geomaterials. Our improved understanding of the flow and friction of natural muds may also find use in modeling natural hazards such as mudslides and for locomotion in muddy environments.

Resilience of Interurban Public Transport and Impact of COVID-19 on Rural Connectivity in Sparsely Populated Regions

The aim of this research consisted of assessing the effects of the COVID-19 pandemic on the interurban public transport system in a rural region with a sparse population density, considering the number of tickets sold and passengers in each locality, as well as the different connecting lines. From a methodological point of view and with the intention of identifying patterns to explain the behaviour of both the routes and passengers, a series of variables were selected, becoming determining factors that sought to offer a solution to the search for a common trend. Additionally, data processing by the means of statistical analysis and the application of Geographic Information Systems (GIS) tools complemented the procedure. The results obtained in the investigation were provided both by municipality and by interurban routes. An interesting finding of this research was the uneven recovery of the municipalities. The localities closest to the attractor nucleus have recovered more quickly to pre-pandemic mobility levels due to their geographical proximity, larger populations, higher incomes per household, and need to access certain public services. In terms of routes, all the lines showed significant decreases in ticket sales, although with variations. Although passenger numbers have shown a gradual recovery, the initial loss was considerable, and pre-pandemic normality has not been completely achieved. This research provides a comprehensive overview of the changes in interurban mobility over a four-year period. The incorporation of critical variables and the segmentation by municipality and route provide a way to identify discernible patterns of mobility. However, the lack of previous research focusing on the impact of the pandemic in rural areas of low population density restricts the possibility of establishing a comparison and to generalise the findings. The authors consider that future research should include other alternative means of transport in these interurban areas and incorporate variables to characterise passengers, such as age, gender, etc.

An Evaluation of Education Policy in England since 2010 and the Policy Consequences for Small Primary Schools

The fate of small primary schools (pupils aged five–eleven years old) in England is linked to education policy reforms. This paper presents an evaluation of selected education policy reforms in England since 2010 with suggested consequences for small primary schools. The research was undertaken using a qualitative research methodology that employed a document analysis method to create a Policy Document Analysis Frame (PDAF) for the policy evaluation. The implications of the policy reforms for small primary schools were examined through the conceptual lens of Educational Isolation. Educational Isolation identifies the limiting factors of place for a school’s access to the resources required for school improvement. Education policy reform is focused on school improvement. Small primary schools in England are typically located in rural neighbourhoods with sparse populations, resulting in an average of just over 100 pupils per school. The findings suggest that the contextual factors of place and size for small primary schools in England present disadvantages in relation to the selected national education policy reforms. The national funding formula, Multi Academy Trusts (groups of schools independently regulated but centrally funded by the state), and National Standards are the key policy reforms, driven by a neo-liberal ideology, that are suggested to have implications for the future of small schools. Recommendations are offered to the new 2024 Labour government that would support the re-instatement of small primary schools as an integral part of the education landscape in England.

Imaging the large-scale and cellular response to focal traumatic brain injury in mouse neocortex.

Traumatic brain injury (TBI) affects neural function at the local injury site and also at distant, connected brain areas. However, the real-time neural dynamics in response to injury and subsequent effects on sensory processing and behavior are not fully resolved, especially across a range of spatial scales. We used in vivo calcium imaging in awake, head-restrained male and female mice to measure large-scale and cellular resolution neuronal activation, respectively, in response to a mild/moderate TBI induced by focal controlled cortical impact (CCI) injury of the motor cortex (M1). Widefield imaging revealed an immediate CCI-induced activation at the injury site, followed by a massive slow wave of calcium signal activation that traveled across the majority of the dorsal cortex within approximately 30 s. Correspondingly, two-photon calcium imaging in primary somatosensory cortex (S1) found strong activation of neuropil and neuronal populations during the CCI-induced traveling wave. A depression of calcium signals followed the wave, during which we observed atypical activity of a sparse population of S1 neurons. Longitudinal imaging in the hours and days after CCI revealed increases in the area of whisker-evoked sensory maps at early time points, in parallel to decreases in cortical functional connectivity and behavioral measures. Neural and behavioral changes mostly recovered over hours to days in our M1-TBI model, with a more lasting decrease in the number of active S1 neurons. Our results in unanesthetized mice describe novel spatial and temporal neural adaptations that occur at cortical sites remote to a focal brain injury.

Characterization of the cellular components of mouse collecting lymphatic vessels reveals that lymphatic muscle cells are the innate pacemaker cells regulating lymphatic contractions.

Collecting lymphatic vessels (cLVs) exhibit spontaneous contractions with a pressure-dependent frequency, but the identity of the lymphatic pacemaker cell is still debated. By analogy to pacemakers in the GI and lower urinary tracts, proposed cLV pacemaker cells include interstitial cells of Cajal like cells (ICLC) or the lymphatic muscle (LMCs) cells themselves. Here we combined immunofluorescence and scRNAseq analyses with electrophysiological methods to examine the cellular constituents of the mouse cLV wall and assess whether any cell type exhibited morphological and functional processes characteristic of pacemaker cells: a continuous if not contiguous network integrated into the electrical syncytium; spontaneous Ca2+ transients; and depolarization-induced propagated contractions. We employed inducible Cre (iCre) mouse models routinely used to target these specific cell populations including: c-kitCreER T2 to target ICLC; PdgfrβCreER T2 to target pericyte-like cells; PdgfrαCreER ™ to target CD34+ adventitial cells and ICLC; and Myh11CreER T2 to target LMCs directly. These specific inducible Cre lines were crossed to the fluorescent reporter ROSA26mT/mG, the genetically encoded Ca2+ sensor GCaMP6f, and the light-activated cation channel rhodopsin2 (ChR2). c-KitCreER T2 labeled both a sparse population of LECs and round adventitial cells that responded to the mast cell activator compound 48-80. PdgfrβCreER T2 drove recombination in both adventitial cells and LMCs, limiting its power to discriminate a pericyte-specific population. PdgfrαCreER ™ labeled a large population of interconnected, oak leaf-shaped cells primarily along the adventitial surface of the vessel. Of these cells, only LMCs consistently, but heterogeneously, displayed spontaneous Ca2+ events during the diastolic period of the contraction cycle, and whose frequency was modulated in a pressure-dependent manner. Optogenetic depolarization through the expression of ChR2 under control of Myh11CreER T2 , but not PdgfrαCreER ™ or c-KitCreER T2 , resulted in propagated contractions upon photo-stimulation. Membrane potential recordings in LMCs demonstrated that the rate of diastolic depolarization significantly correlated with contraction frequency. These findings support the conclusion that LMCs, or a subset of LMCs, are responsible for mouse cLV pacemaking.

Distributed enhanced multi-objective evolutionary algorithm based on decomposition for cluster analysis in wireless sensor network

Conventional clustering algorithms do not recognize patterns and structures with contradicting objectives in large, distributed datasets. Distributed clustering leverages rapid processing capabilities to allow multiple nodes to work together. This paper proposes a Distributed clustering based on Multiobjective Evolutionary Algorithm by Decomposition (D-MOEA/d) to solve various multiobjective optimization problems in wireless sensor networks (WSNs). In MOEA/d, a multiobjective optimization problem decomposes into several scalar optimization subproblems, each focusing on a distinct objective. Each subproblem is expressed as a clustering problem that uses local data to perform distributed clustering. The proposed method has been extended to achieve improved accuracy in less time by using a smaller feature subset with less redundancy. The Distributed Enhanced MOEA/d (DE-MOEA/d) avoids local optima by achieving diversity in the population using fuzzy-based nearest neighbor selection, sparse population initialization, and evolved mutation operator. This integration improves the accuracy of the clustering process at WSN nodes, ensuring the attainment of well-balanced solutions across multiple optimization criteria in the distributed environment. Average Euclidean and total symmetrical deviations are the two cost functions used to minimize while clustering on the MOEA/d framework. Six real-life WSN datasets are used to assess the performance of the proposed technique: (1) the Delhi air pollution dataset, (2) the Canada weather station dataset, (3) the Thames River water quality dataset, (4) the Narragansett Bay water quality dataset, (5) the Cook Agricultural land dataset and 6) Gordon Soil dataset. The simulation results of both proposed algorithms are compared with Multiobjective distributed particle swarm optimization (DMOPSO) and Distributed K-means (DK-Means). The proposed algorithm DE-MOEA/d performs better in terms of the Silhouette index (SI), Dunn index (DI), Davies–Bouldin index (DBI), and Kruskal–Wallis (KW) statistical test.

Genetic differentiation and diversity do not explain variation in heterosis or inbreeding depression: empirical evidence from a long-lived iteroparous plant

AbstractAssisted gene flow can restore genetic diversity when genetic drift has driven deleterious alleles to high frequencies in small, isolated populations. Previous crosses among 20 populations of Gymnadenia conopsea documented the strongest heterosis and the weakest inbreeding depression in sparse and small populations, consistent with fixation of mildly deleterious alleles by genetic drift. We genotyped the populations used for crosses, and used 1200–1728 SNPs to test the following predictions: (1) heterosis increases with genetic differentiation (FST) to donor populations and decreases with genetic diversity in the recipient population, (2) inbreeding depression increases with genetic diversity, and (3) genetic diversity increases, and mean FST to other populations decreases, with population size and density. Pairwise FST ranged from very low to moderate (0.005–0.20) and genetic diversity varied moderately among populations (proportion of polymorphic loci = 0.52–0.75). However, neither FST between populations, nor genetic diversity in the recipient population, were related to the strength of heterosis. There was also no association between genetic diversity and the strength of inbreeding depression. Genetic diversity increased and mean FST decreased with population size, consistent with reduced diversity and increased differentiation of small populations by genetic drift. The results indicate that the loci conferring heterosis are not mirrored by overall population differentiation, and limited additional information on potential source populations for genetic rescue is gained by the genetic data. Instead, the use of controlled crosses can directly reveal positive effects of introducing new genetic material, and is a simple method with high potential in conservation.

Assessing puma habitat suitability in Uruguay’s Grasslands: exploring source-sink dynamics and conservation implications

ABSTRACT Pumas (Puma concolor) have a broad geographic range across the Americas and are globally listed as Least Concern. However, in Uruguay’s Pampas Grasslands, they are considered Data Deficient and regionally endangered in Argentina and Brazil. Understanding the distribution and population status of pumas is crucial for their conservation. This study examines puma occurrence in Uruguay’s Grasslands within a regional context, assessing habitat suitability and recent land use changes. Using a Species Distribution Model (SDM) in MaxEnt with 224 occurrence records (1999–2011) and bioclimatic and topographic predictors, we found intermediate habitat suitability in the Pampas Grasslands, indicating a naturally sparse puma population. The highest suitability was along riverbanks and riparian areas. Recent land use changes have transformed suitable habitats into areas less likely to support pumas, affecting a significant portion of Uruguay’s land. Our results suggest source-sink dynamics, where Uruguayan puma records likely represent dispersing individuals from established subpopulations in Eastern Argentina and Southern Brazil.

Brain-wide dynamics linking sensation to action during decision-making.

Perceptual decisions rely on learned associations between sensory evidence and appropriate actions, involving the filtering and integration of relevant inputs to prepare and execute timely responses1,2. Despite the distributed nature of task-relevant representations3-10, it remains unclear how transformations between sensory input, evidence integration, motor planning and execution are orchestrated across brain areas and dimensions of neural activity. Here we addressed this question by recording brain-wide neural activity in mice learning to report changes in ambiguous visual input. After learning, evidence integration emerged across most brain areas in sparse neural populations that drive movement-preparatory activity. Visual responses evolved from transient activations in sensory areas to sustained representations in frontal-motor cortex, thalamus, basal ganglia, midbrain and cerebellum, enabling parallel evidence accumulation. In areas that accumulate evidence, shared population activity patterns encode visual evidence and movement preparation, distinct from movement-execution dynamics. Activity in movement-preparatory subspace is driven by neurons integrating evidence, which collapses at movement onset, allowing the integration process to reset. Across premotor regions, evidence-integration timescales were independent of intrinsic regional dynamics, and thus depended on task experience. In summary, learning aligns evidence accumulation to action preparation in activity dynamics across dozens of brain regions. This leads to highly distributed and parallelized sensorimotor transformations during decision-making. Our work unifies concepts from decision-making and motor control fields into a brain-wide framework for understanding how sensory evidence controls actions.

The reality of rurality: Understanding the impact of remoteness on out-of-hospital cardiac arrest in Western Australia - A retrospective cohort study.

Western Australia (WA) spans a large, sparsely-populated area of Australia, presenting a challenge for the provision of Emergency Medical Service (EMS), particularly for time-critical emergencies such as out-of-hospital cardiac arrest (OHCA). To assess the impact of rurality on the epidemiology, incidence and survival of OHCA in WA. We conducted a retrospective cohort study of EMS-attended OHCA in WA from 2015 to 2022. Incidence was calculated on all OHCAs, but the study cohort for the multivariable regression analysis of rurality on survival outcomes consisted of OHCAs of medical aetiology with EMS resuscitation attempted. Rurality was categorised into four categories, derived from the Australian Standard Geographic Classification - Remoteness Areas. The age-standardised incidence of EMS-attended OHCA per 100 000 population increased with increasing remoteness: Major Cities = 104.9, Inner Regional = 123.3, Outer Regional = 138.0 and Remote = 103.9. Compared to Major Cities, the adjusted odds for return of spontaneous circulation (ROSC) at hospital were lower in Inner Regional (aOR = 0.71, 95%CI 0.53-0.95), Outer Regional (aOR = 0.62, 95%CI 0.45-0.86) and Remote areas (aOR = 0.52, 95%CI 0.35-0.77) but there was no statistically significant difference for 30-day survival. Relative to Major Cities, Regional and Remote areas had longer response times, shorter transport-to-hospital times, and higher rates of bystander CPR and automated external defibrillator use. Out-of-hospital cardiac arrest in rural areas had lower odds of ROSC at hospital compared to metropolitan areas, despite adjustment for known prognostic covariates. Despite WA's highly sparse regional population, these differences in ROSC are consistent with those reported in other international studies.

A comparison of the proto-dolomite induced by cyanobacteria and halophilic bacteria: implications for dolomite-inducing microbe identification

This study investigates the morphological and mineralogical characteristics of proto-dolomite induced by two specific microorganisms with varying lifestyles: the extremely halophilic bacterium Vibrio harveyi QPL2 and the cyanobacterium Leptolyngbya boryana. Halophilic bacterially-induced proto-dolomite (HBD) and cyanobacterially-induced proto-dolomite (CBD) were subjected to comprehensive characterization techniques, including X-ray diffraction, scanning electron microscopy, Focused Ion Beam, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The results indicate that both HBD and CBD exhibit a low degree of crystallinity and possess comparable molar ratios of MgCO3 to CaCO3. Moreover, neither of them exhibits the ordered structure of ideal dolomite. HBD and CBD exhibit notable distinctions in external morphology and internal structure. HBD forms a subunit aggregate with a less dense surface and numerous pinhole structures resulting from bacterial survival. In contrast, CBD adopts a bispherical shape with a relatively dense surface and minimal indications of cyanobacterial survival. Both HBD and CBD have an internal hollow structure. However, HBD is characterized by sparse population and loosely arranged subunits, while CBD features only a central cavity. Additionally, HBD particles are smaller compared to CBD particles. These morphological differences suggest that HBD primarily grows through bacterial surface-dependent processes, whereas the growth of CBD is not directly reliant on the surface of cyanobacteria. Compositionally, the weight percentage of crystalline water in CBD exceeded that of HBD with a value of 29.42 % compared to 5.9 %. This increase in internal crystalline water enables a faster conversion of CBD to the ordered ideal dolomite in a specific diagenetic environment. This study implies that the morphology and composition of microbial proto-dolomite may aid in identifying the type of dolomite-inducing microbes.

Circumstances and Pathological Findings in Civilian Helicopter-Related Fatalities.

Helicopters are used worldwide in a range of commercial and private industries and are particularly useful in northern Australia due to the sparse population scattered over large distances with remote regions difficult to access by any other means of transport. Nine civilian helicopter-related fatalities were reported to the Northern Territory coroner between January 2004 and December 2023. The victims were all male (age range, 34-74 years; mean, 52 years). All fatal crashes occurred in remote areas, the majority on cattle stations. Pilots were the sole occupants in 5/9 incidents; in 4 incidents, there were injured survivors. All fatal incidents involved Robinson piston engine helicopters (Robinson R44 models in 2 incidents and Robinson R22 models in the remaining 7). Scene investigations, postmortem examinations, and ancillary investigations were frequently hampered by decomposition of the remains, resulting from difficult search operations and delayed location, retrieval, and storage. Head injuries were present in all cases with chest and spinal injuries in more than half. Integrated assessment of injuries with toxicological and aviation investigations facilitated understanding of the crash dynamics.

One Health in two countries: The politics of transdisciplinary healthcare collaboration in Canada and the United States.

The One Health perspective highlights the potential synergies between the human, animal, and environmental health sciences, especially in an era of budget shortfalls, climate change, and emerging infectious diseases of zoonotic origin. Canadian physicians and veterinarians arguably lay the foundation of One Health in the late 19th century, when they pioneered the study of "comparative medicine" in Montreal, but they fell into disciplinary silos before World War I to the lasting detriment of the Canadian population. This article explores both the advantages and impediments to cross-disciplinary healthcare collaboration in Canada, highlighting the country's vast size, sparse population, and political decentralization in particular, and offers a number of policy recommendations that would allow the country to reclaim its rightful role as a leader in the One Health movement.

Magma storage conditions beneath a peralkaline caldera in the Main Ethiopian Rift

The numerous volcanic centres in the Main Ethiopian Rift (MER) present significant but poorly understood hazards to local populations. The MER is also an important site to gain insights into tectonic processes as it captures the transition from continental rifting (to the south) to incipient seafloor spreading (to the north). Peralkaline magmas account for around 90% of the volcanic products found in the MER. Determining the conditions under which these magmas evolve is critical to understanding rift-related volcanism and its associated hazards. Corbetti Caldera has an extensive record of large-scale, predominantly aphyric, peralkaline rhyolite eruptions. However, little is known about the mafic magmas from which these highly differentiated melts have evolved. Here we present data from the only basaltic deposit found within the caldera, coupled with whole rock, glass and mineral analysis of the peralkaline products, to investigate magma storage conditions at Corbetti. We demonstrate that magma mixing played a role in the evolution of the basaltic magmas and use RhyoliteMELTS modelling to show Corbetti's peralkaline magmas likely evolved at pressures between 100 and 250 MPa, from a magma with an initial water content of 0.5–1 wt%, at or below the QFM buffer. Mineral hygrometry on the sparse crystal populations corroborates the RhyoliteMELTS modelling, suggesting that the basaltic magma had 0.1–1.2 ± 0.32 wt% H2O, and the peralkaline magmas an average of ∼5.5 ± 1.25 wt% H2O. These results also match melt inclusion data for Corbetti and other peralkaline systems. We also provide new 40Ar/39Ar ages for two eruptions, a pre-caldera rhyolitic lava flow (206.7 ± 0.9 ka) and a post-caldera peralkaline ignimbrite (160 ± 0.8 ka). These results add to our understanding of the history of Corbetti and the storage conditions of peralkaline magmas within a continental rift setting and highlight the hydrous nature of Corbetti's magmas and the role that H2O plays during explosive eruptions.

Corticotropin-Releasing Factor Release From a Unique Subpopulation of Accumbal Neurons Constrains Action-Outcome Acquisition in Reward Learning

BackgroundThe nucleus accumbens (NAc) mediates reward learning and motivation. Despite an abundance of neuropeptides, peptidergic neurotransmission from the NAc has not been integrated into current models of reward learning. The existence of a sparse population of neurons containing corticotropin-releasing factor (CRF) has been previously documented. Here, we provide a comprehensive analysis of their identity and functional role in shaping reward learning. MethodsOur multidisciplinary approach included fluorescent in situ hybridization (n = ≥3 mice), tract tracing (n = 5 mice), ex vivo electrophysiology (n = ≥30 cells), in vivo calcium imaging with fiber photometry (n = ≥4 mice), and use of viral strategies in transgenic lines to selectively delete CRF peptide from NAc neurons (n = ≥4 mice). Behaviors used were instrumental learning, sucrose preference, and spontaneous exploration in an open field. ResultsWe showed that the vast majority of NAc CRF-containing neurons are spiny projection neurons (SPNs) comprising dopamine D1-, D2-, or D1/D2-containing SPNs that primarily project and connect to the ventral pallidum and to a lesser extent the ventral midbrain. As a population, they display mature and immature SPN firing properties. We demonstrated that NAc CRF-containing neurons track reward outcomes during operant reward learning and that CRF release from these neurons acts to constrain initial acquisition of action-outcome learning and at the same time facilitates flexibility in the face of changing contingencies. ConclusionsCRF release from this sparse population of SPNs is critical for reward learning under normal conditions.

Chromatin plasticity predetermines neuronal eligibility for memory trace formation.

Memories are encoded by sparse populations of neurons but how such sparsity arises remains largely unknown. We found that a neuron's eligibility to be recruited into the memory trace depends on its epigenetic state prior to encoding. Principal neurons in the mouse lateral amygdala display intrinsic chromatin plasticity, which when experimentally elevated favors neuronal allocation into the encoding ensemble. Such chromatin plasticity occurred at genomic regions underlying synaptic plasticity and was accompanied by increased neuronal excitability in single neurons in real time. Lastly, optogenetic silencing of the epigenetically altered neurons prevented memory expression, revealing a cell-autonomous relationship between chromatin plasticity and memory trace formation. These results identify the epigenetic state of a neuron as a key factor enabling information encoding.

Estimation of Near-surface Ozone Concentration in the Beijing-Tianjin-Hebei Region Based on XGBoost-LME Model

High spatiotemporal resolution data on near-surface ozone concentration distribution is of great significance for monitoring and controlling atmospheric ozone pollution and improving the living environment. Using TROPOMI-L3 NO2, HCHO products, and ERA5-land high-resolution data as estimation variables, an XGBoost-LME model was constructed to estimate the near-surface ozone concentration in the Beijing-Tianjin-Hebei Region. The results showed that： ① Through correlation analysis, surface 2 m temperature （T2M）, 2 m dewpoint temperature （D2M）, surface solar radiation downwards （SSRD）, tropospheric formaldehyde （HCHO）, and tropospheric nitrogen dioxide （NO2） were important factors affecting the near-surface ozone concentration in the Beijing-Tianjin-Hebei Region. Among them, T2M, SSRD, and D2M had strong correlations, with correlation coefficients of 0.82, 0.75, and 0.71, respectively. ② Compared with that of other models, the XGBoost-LME model had the best performance in terms of various indicators. The ten-fold cross-validation evaluation indicators R2, MAE, and RMSE were 0.951, 9.27 μg·m-3, and 13.49 μg·m-3, respectively. At the same time, the model performed well at different time scales. ③ In terms of time, there was a significant seasonal difference in near-surface ozone concentration in the Beijing-Tianjin-Hebei Region in 2019, with the concentration changing in the order of summer > spring > autumn > winter. The monthly average ozone concentration in the region showed an inverted "V" trend, with a slight increase in September. The highest value occurred in July, whereas the lowest value occurred in December. In terms of spatial distribution, the near-surface ozone concentrations in the Beijing-Tianjin-Hebei Region during the months of February and March were generally at the same levels. In January, November, and December, there was a relatively insignificant trend of higher concentrations in the north and lower concentrations in the south. For the remaining months, the spatial distribution of near-surface ozone concentrations in this area predominantly exhibited a pattern of higher concentrations in the south and lower concentrations in the north. High-value areas were predominantly found in the plain regions of the southern part with lower altitudes, dense population, and higher industrial emissions； low-value areas, on the other hand, were primarily located in mountainous areas of the northern part with higher altitudes, sparse population, higher vegetation coverage, and lower industrial emissions.

CRF release from a unique subpopulation of accumbal neurons constrains action-outcome acquisition in reward learning.

The nucleus accumbens (NAc) mediates reward learning and motivation. Despite an abundance of neuropeptides, peptidergic neurotransmission from the NAc has not been integrated into current models of reward learning. The existence of a sparse population of neurons containing corticotropin releasing factor (CRF) has been previously documented. Here we provide a comprehensive analysis of their identity and functional role in shaping reward learning. To do this, we took a multidisciplinary approach that included florescent in situ hybridization (N mice ≥ 3), tract tracing (N mice = 5), ex vivo electrophysiology (N cells ≥ 30), in vivo calcium imaging with fiber photometry (N mice ≥ 4) and use of viral strategies in transgenic lines to selectively delete CRF peptide from NAc neurons (N mice ≥ 4). Behaviors used were instrumental learning, sucrose preference and spontaneous exploration in an open field. Here we show that the vast majority of NAc CRF-containing (NAc CRF ) neurons are spiny projection neurons (SPNs) comprised of dopamine D1-, D2- or D1/D2-containing SPNs that primarily project and connect to the ventral pallidum and to a lesser extent the ventral midbrain. As a population, they display mature and immature SPN firing properties. We demonstrate that NAc CRF neurons track reward outcomes during operant reward learning and that CRF release from these neurons acts to constrain initial acquisition of action-outcome learning, and at the same time facilitates flexibility in the face of changing contingencies. We conclude that CRF release from this sparse population of SPNs is critical for reward learning under normal conditions.

Effects of acute hypoxia exposure and acclimation on the thermal tolerance of an imperiled Canadian minnow.

Elevated water temperatures and low dissolved oxygen (hypoxia) are pervasive stressors in aquatic systems that can be exacerbated by climate change and anthropogenic activities, and there is growing interest in their interactive effects. To explore this interaction, we quantified the effects of acute and long-term hypoxia exposure on the critical thermal maximum (CTmax) of Redside Dace (Clinostomus elongatus), a small-bodied freshwater minnow with sparse populations in the Great Lakes Basin of Canada and designated as Endangered under Canada's Species at Risk Act. Fish were held at 18°C and acclimated to four levels of dissolved oxygen (>90%, 60%, 40%, and 20% air saturation). CTmax was measured after 2 and 10 weeks of acclimation and after 3.5 weeks of reoxygenation, and agitation behavior was quantified during CTmax trials. Aquatic surface respiration behavior was also quantified at 14 weeks of acclimation to oxygen treatments. Acute hypoxia exposure decreased CTmax in fish acclimated to normoxia (>90% air saturation), but acclimation to hypoxia reduced this effect. There was no effect of acclimation oxygen level on CTmax when measured in normoxia, and there was no effect of exposure time to hypoxia on CTmax. Residual effects of hypoxia acclimation on CTmax were not seen after reoxygenation. Agitation behavior varied greatly among individuals and was not affected by oxygen conditions. Fish performed aquatic surface respiration with low frequency, but performed it earlier when acclimated to higher levels of oxygen. Overall, this work sheds light on the vulnerability of fish experiencing acute hypoxia and heat waves concurrently.