Stratification Patterns Research Articles

Post-wildfire neighborhood change: Evidence from the 2018 Camp Fire

As the number of highly destructive wildfires grows, it is increasingly important to understand the long-term changes that occur to fire-affected places. Integrating approaches from social and biophysical science, we document two forms of neighborhood change following the 2018 Camp Fire in the United States, examining the more than 17,000 residential structures within the burn footprint. We found that mobile or motor homes, lower-value residences, and absentee owner residences had a significantly higher probability of being destroyed, providing evidence that housing stock filtering facilitated socially stratified patterns of physical damage. While the relationship between building value and destruction probability could be explained by measures of building density and distance to nearby roads, building type remained an independent predictor of structure loss that we could not fully explain by adding environmental covariates to our models. Using a geospatial machine learning technique, we then identified buildings that had been reconstructed within the burn footprint 20 months after the fire. We found that reconstructed buildings were more likely to have been owner-occupied prior to the fire and had higher average pre-fire property value, suggesting an emerging pattern of cost-burden gentrification. Our findings illustrate the importance of examining the built environment as a driver of socially uneven disaster impacts. Wildfire mitigation strategies are needed for mobile and motor home residents, renters, low-income residents, and dense neighborhoods.

Vertically stratified interactions of nectarivores and nectar-inhabiting bacteria in a liana flowering across forest strata.

Vertical stratification is a key feature of tropical forests and plant-frugivore interactions. However, it is unclear whether equally strong patterns of vertical stratification exist for plant-nectarivore interactions and, if so, which factors drive these patterns. Further, nectar-inhabiting bacteria, acting as "hidden players" in plant-nectarivore interactions, might be vertically stratified, either in response to differences among strata in microenvironmental conditions or to the nectarivore community serving as vectors. We observed visitations by a diverse nectarivore community to the liana Marcgravia longifolia in a Peruvian rainforest and characterized diversity and community composition of nectar-inhabiting bacteria. Unlike most other plants, M. longifolia produces inflorescences across forest strata, enabling us to study effects of vertical stratification on plant-nectarivore interactions without confounding effects of plant species and stratum. A significantly higher number of visits were by nectarivorous bats and hummingbirds in the midstory than in the understory and canopy, and the visits were strongly correlated to flower availability and nectar quantity and quality. Trochiline hummingbirds foraged across all strata, whereas hermits remained in the lower strata. The Shannon diversity index for nectar-inhabiting bacterial communities was highest in the midstory. Our findings suggest that vertical niche differentiation in plant-nectarivore interactions seems to be partly driven by resource abundance, but other factors such as species-specific preferences of hummingbirds, likely caused by competition, play an important role. We conclude that vertical stratification is an important driver of a species' interaction niche highlighting its role for promoting biodiversity and ecosystem functioning.

Citation Elites in Polytheistic and Umbrella Disciplines: Patterns of Stratification and Concentration in Danish and British Science

The notion of science as a stratified system is clearly manifested in the markedly uneven distribution of productivity, rewards, resources, and recognition. Although previous studies have shown that institutional environments for conducting research differ significantly between national science systems, disciplines, and subfields, it remains to be shown whether any systematic variations and patterns in inequalities exist among researchers in different national and domain specific settings. This study investigates the positioning of citation elites as opposed to ‘ordinary’ researchers by way of examining three dimensions of concentration (accumulation of publications and citations, specialisation, and institutional concentration) in biology, economics and physics in Denmark and the UK. Across all three dimensions, we put Richard Whitley’s bipartite theory to the test, suggesting a nexus between the intellectual structure of a discipline and the configuration of its elite. The study draws on a dataset of researchers who published most of their publications in either physics, biology, or economics over the 1980–2018 period and with at least one publication in 2017–2018 while affiliated to either a British or a Danish university. We find higher degrees of concentration in the UK compared to Denmark, and that physics and biology respectively display the greatest and lowest degree of concentration. Similar patterns in disciplinary differences are observed in both countries, suggesting that concentration patterns are largely rooted in disciplinary cultures and merely amplified by the national context.

A maximum projective stratification criterion for selecting space-filling designs

Space-filling designs are commonly used in computer experiments. In this paper, we propose a maximum projective stratification criterion for classifying and ranking space-filling designs. We first introduce a stratification metric, which is proved to be a variance decomposition of the frequency representation of a design. Based on this metric, we define the new criterion to sequentially minimize a projective stratification pattern, that quantifies the stratification property of a design when projected into one up to full dimensions. Numerical results show that, when the space-filling property in cluster of projections with respect to dimensions is paid attention on, our criterion is more rational than existing criteria. We further study the intimate connections between our criterion and existing criteria. The extension of this criterion for a design with prime power levels to general levels are also discussed.

Changing Patterns of Social Inequality and Stratification in Relation to Migration, Ethnicity, Gender, Class, and Education in South Africa

Purpose: This paper examines the changing patterns of social inequality and stratification in relation to migration, ethnicity, gender, class, and education
 Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries.
 Findings: Changing patterns of social inequality and stratification are influenced by migration, ethnicity, gender, class, and education. Migration can lead to economic disparities for immigrants, either through improved opportunities or exploitation. Ethnicity remains a significant factor, with ethnic minorities facing discrimination and limited access to resources. Gender inequality persists with disparities in pay and leadership roles, while class-based inequality continues through inheritance and income distribution. Access to quality education plays a vital role in social mobility, but disparities in resources and rising tuition costs can limit opportunities.
 Unique Contribution to Theory, Practice and Policy: Intersectionality theory, Human capital theory & Transnationalism theory may be used to anchor future studies on changing patterns of social inequality and stratification in relation to migration, ethnicity, gender, class, and education. Organizations and institutions should implement diversity and inclusion programs that go beyond tokenism. Develop and implement comprehensive immigration reform policies that address the rights and social integration of migrants.

Cooperation between autotrophic and heterotrophic denitrifiers under low C/N ratios revealed by individual-based modelling

Denitrifying biofilms, in which autotrophic denitrifiers (AD) and heterotrophic denitrifiers (HD) coexist, play a crucial role in removing nitrate from water or wastewater. However, it is difficult to elucidate the interactions between HD and AD through sequencing-based experimental methods. Here, we developed an individual-based model to describe the interspecies dynamics and priority effects between sulfur-based AD (Thiobacillus denitrificans) and HD (Thauera phenylcarboxya) under different C/N ratios. In test I (coexistence simulation), AD and HD were initially inoculated at a ratio of 1:1. The simulation results showed excellent denitrification performance and a coaggregation pattern of denitrifiers, indicating that cooperation was the predominant interaction at a C/N ratio of 0.25 to 1.5. In test II (invasion simulation), in which only one type of denitrifier was initially inoculated and the other was added at the invasion time, denitrifiers exhibited a stratification pattern in biofilms. When HD invaded AD, the final HD abundance decreased with increasing invasion time, indicating an enhanced priority effect. When AD invaded HD, insufficient organic carbon sources weakened the priority effect by limiting the growth of HD populations. This study reveals the interaction between autotrophic and heterotrophic denitrifiers, providing guidance for optimizing wastewater treatment process.

Processes of stratification and vertical turbulent mixing in a choked lagoon system

This work concentrates on the processes of stratification and turbulent mixing in a choked shallow lagoon, Xiaohai Lagoon, by using a three-dimensional hydrodynamic model. The model results were processed to derive buoyancy frequency, shear production, gradient Richardson number, and buoyancy flux during the tidal cycles. The parameters regarding stratification and turbulent mixing exhibited significant heterogeneity within the lagoon. Shear production primarily occurred in the downstream region with complex shoreline and bed morphology, whereas stratification was predominantly developed in the flat upstream region by tidal strain and baroclinic strain, especially during the ebb tide. The salinity mixing indicated by buoyancy flux was thus mainly confined during the ebbs in the downstream region and the middle-lower layer of the upstream region. In addition, the distribution of the gradient Richardson number indicated dominances of shear instability and buoyancy effects in the downstream and upstream regions, respectively. By simulating various combinations of river discharges and offshore tidal ranges, we examined the variations of stratification and turbulent mixing within the lagoon's parameter space. The results revealed the influence of the interaction between tidal and runoff forces through a modulation of the salinity interface's moving range. Further investigation of the buoyancy balance underlying the variation in stratification revealed the dominance of straining and mixing, while advection played a secondary role. Straining dominance appeared at locations with sufficient streamwise density gradients in the upstream region during the ebb. The contribution of advection was essential, as straining and mixing largely counteracted each other's effects through their persistent competition. A conceptual model for the stratification and mixing patterns in choked lagoons during the tidal cycle was then proposed. This conceptual model clarifies the process of the interaction between stratification and turbulent mixing in the distinctive hydrological and geomorphic environments of choked lagoons and could serve as a conference for investigating other lagoon systems in the world.

Stratification of Kidney Transplant Recipients Into Five Subgroups Based on Temporal Disease Trajectories.

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Considerable clinical research has focused on improving graft survival and an increasing number of kidney recipients die with a functioning graft. There is a need to improve patient survival and to better understand the individualized risk of comorbidities and complications. Here, we developed a method to stratify recipients into similar subgroups based on previous comorbidities and subsequently identify complications and for a subpopulation, laboratory test values associated with survival. First, we identified significant disease patterns based on all hospital diagnoses from the Danish National Patient Registry for 5752 kidney transplant recipients from 1977 to 2018. Using hierarchical clustering, these longitudinal patterns of diseases segregate into 3 main clusters of glomerulonephritis, hypertension, and diabetes. As some recipients are diagnosed with diseases from >1 cluster, recipients are further stratified into 5 more fine-grained trajectory subgroups for which survival, stratified complication patterns as well as laboratory test values are analyzed. The study replicated known associations indicating that diabetes and low levels of albumin are associated with worse survival when investigating all recipients. However, stratification of recipients by trajectory subgroup showed additional associations. For recipients with glomerulonephritis, higher levels of basophils are significantly associated with poor survival, and these patients are more often diagnosed with bacterial infections. Additional associations were also found. This study demonstrates that disease trajectories can confirm known comorbidities and furthermore stratify kidney transplant recipients into clinical subgroups in which we can characterize stratified risk factors. We hope to motivate future studies to stratify recipients into more fine-grained, homogenous subgroups to better discover associations relevant for the individual patient and thereby enable more personalized disease-management and improve long-term outcomes and survival.

Prediction model of buoyancy-driven flow rate in inclined tunnels with a localized buoyancy source: Emphasis on stratification effects

In inclined narrow and long spaces such as tunnels, the buoyancy-driven flow pattern and the resulting ventilation flow rate are different from those in enclosure-type buildings, because of their large length-to-width aspect ratios. In this paper, the buoyancy-driven flow rate induced by a localized heat source in inclined tunnels was investigated. Theoretical analysis and three series of experiments including non-isothermal or isothermal buoyancy sources, i.e., large-scale fire tests, brine-water tests and helium-air tests were performed. Two typical buoyant flow patterns were identified in the experiments, which are stratified and well-mixed patterns, respectively. Both the stratification pattern and the longitudinal decay rate of temperature rise were proved to be correlated with a dimensionless factor, η=B01/3ΔLsina/(g0′1/2H3/2), which is composed of characteristic parameters referring to both buoyancy source and geometrical configuration. The flow stratification results in stack effect attenuation and consequently ventilation flow rate reduction. A model for predicting the buoyancy-driven flow rate in such spaces was proposed, with special emphasis on the effects of stratification pattern. The predictions were validated with the experimental data, and the necessity for accounting for the stack effect attenuation caused by stratification was proved. The prediction model possesses an explicit expression and can thus provide a convenient tool for design calculations.

Temporary stratification promotes large greenhouse gas emissions in a shallow eutrophic lake

Abstract. Shallow lakes and ponds undergo frequent temporary thermal stratification. How this affects greenhouse gas (GHG) emissions is moot, with both increased and reduced GHG emissions hypothesised. Here, weekly estimations of GHG emissions, over the growing season from May to September, were combined with temperature and oxygen profiles of an 11 ha temperate shallow lake to investigate how thermal stratification shapes GHG emissions. There were three main stratification periods with profound anoxia occurring in the bottom waters upon isolation from the atmosphere. Average diffusive emissions of methane (CH4) and nitrous oxide (N2O) were larger and more variable in the stratified phase, whereas carbon dioxide (CO2) was on average lower, though these differences were not statistically significant. In contrast, there was a significant order of magnitude increase in CH4 ebullition in the stratified phase. Furthermore, at the end of the period of stratification, there was a large efflux of CH4 and CO2 as the lake mixed. Two relatively isolated turnover events were estimated to have released the majority of the CH4 emitted between May and September. These results demonstrate how stratification patterns can shape GHG emissions and highlight the role of turnover emissions and the need for high-frequency measurements of GHG emissions, which are required to accurately characterise emissions, particularly from temporarily stratifying lakes.

Marcadores del discurso de cita directa en corpus españoles del PRESEEA: estratificación social y distribución diatópica

The aim of this paper is to carry out a study on the social behavior and diatopic distribution of direct quotation markers considering data from PRESEEA-Spain oral corpus. On the one hand, from a sociolinguistic perspective, we will focus on the relation of the use of these discursive units with criteria such as sex, age, and educational level; and, on the other hand, we will consider their productivity in the samples of each city studied. As general results, the presence of different discourse markers (pues, o sea, en plan, etc.) that introduce direct quotation has been observed, a function linked to the initial position they occupy in the utterance. Furthermore, the geolectal difference is evidenced not only in quotation markers that are of exclusive use in some urban areas of Spain, but also in the stratification patterns according to social criteria.

Chordal measurement of phase fraction distribution in a static gas-liquid system using collimated gamma-ray densitometer and artificial neural networks

Two-phase flow occurs in various industries, as in the production of oil and gas. A collimated gamma-ray densitometer is applied for the study of a static gas-liquid system that simulates a stratified flow pattern. It stands out for its non-intrusive measurement capacity, its high sensitivity to density variations and its good spatial resolution. Chordal phase fraction distributions are obtained in a tube containing water and air at room conditions, with the water level varied between 25%, 50% and 75%. The results obtained highlight the usefulness of the collimated gamma-ray densitometer to determine phase fraction distributions along the pipe’s cross section. Furthermore, this study suggests the use of an artificial neural network (ANN) model for predicting holdup in pipeline systems using a dataset of 110 experimental data points. The ANN model considers factors such as absorbed intensity, water cut percentage, and dimensionless h/D ratio. The adopted configuration includes the use of the Adam solver, Rectified Linear Unit (ReLU) activation function, a batch size of 3, two hidden layers (60 neurons each), and a learning rate of 0.001. The model achieves good accuracy, with a minimum mean square error (MSE) of 0.3% and a low mean absolute error (MAE) of 0.028.

Vertical explorers: Unraveling vertical and horizontal patterns of vascular epiphyte diversity in a dwarf cloud forest

Vascular epiphytes are plants that grow on phorophytes, and their distribution may vary both horizontally and vertically. Understanding the factors shaping epiphyte distribution and their relationship with alpha and beta diversities is crucial for understanding richness and composition patterns. We investigated alpha and beta diversity variation in the vertical and horizontal stratification of epiphyte communities across different vegetation types in a dwarf cloud forest. Twenty-four 20 × 10 m plots were established in three vegetation types defined by distinct soil characteristics, different phorophyte height and differences in tree species composition in Parque Estadual do Ibitipoca, Minas Gerais, Brazil. Phorophytes were divided into four strata: (A) base of the trunk, (B) lower trunk, (C) inner canopy, and (D) outer canopy. Alpha and beta diversity analyses were performed for each site. We found a reduced stratification in the area, indicating minimal composition differences between the strata. However, the canopy exhibited greater species richness than the trunk. Vegetation types F1 and F2 displayed higher richness compared to F3. Orchidaceae was the richest family overall, while Bromeliaceae and Polypodiaceae were more frequent. Holoepiphytes were highly representative, demonstrating consistent patterns of richness, composition, and dispersion, with anemochorous species being the most abundant. This study highlights the unique patterns of epiphyte stratification, emphasizing the importance of biotic and abiotic characteristics in colonization processes. Despite the low canopy of the forest, the non-uniformity in stratification demonstrates that formation characteristics, such as height, play a significant role in shaping epiphyte richness and composition patterns.

Class-based preschool enrolment - social stratification and quality differences in the Swedish preschool market

ABSTRACT In this article, we analyse overarching patterns of social stratification in, and quality differences between, Swedish preschools. Drawing on a Bourdieusian social classification scheme, we evidence in what type of preschools different social groups enrol their children in, and to what extent Swedish preschool children encounter different levels of quality at municipal, for-profit and non-profit providers in the preschool market. The analysis employs individual register data from Statistics Sweden covering all families in Swedish preschools for the year 2019. This comprises information on approximately 510 000 children and 122 000 unique families. We use descriptive statistics, looking at over- and under-representation in enrolment patterns of 38 social groups along with quality indicators of different providers in terms of preschool size, teacher and staff ratio and the level of teachers with Swedish background. Results from this total population analysis of Swedish preschool enrolment reveal indicators of particular class practices, where upper- and middle-class families are overrepresented in both for-profit and non-profit preschools in contrast to working-class families. Simultaneously, private providers may not always deliver high standards of structural quality, which clouds the image of how quality is viewed by parents in general, and by upper- and middle-class families in particular.

Hydrothermal Conditions in Deep Soil Layer Regulate the Interannual Change in Gross Primary Productivity in the Qilian Mountains Area, China

The variability in soil hydrothermal conditions generally contributes to the diverse distribution of vegetation cover types and growth characteristics. Previous research primarily focused on soil moisture alone or the average values of soil hydrothermal conditions in the crop root zone (0–100 cm). However, it is still unclear whether changes in gross primary productivity (GPP) depend on the hydrothermal conditions at different depths of soil layers within the root zone. In this study, the soil hydrothermal conditions from three different layers, surface layer 0–7 cm (Level 1, L1), shallow layer 7–28 cm (Level 2, L2), and deep layer 28–100 cm (Level 3, L3) in the Qilian Mountains area, northwestern China, are obtained based on ERA5-Land reanalysis data. The Sen-MK trend test, Pearson correlation analysis, and machine learning algorithm were used to explore the influence of these three soil hydrothermal layers on GPP. The results show that soil moisture values increase with soil depth, while the soil temperature values do not exhibit a stratified pattern. Furthermore, the strong correlation between GPP and deep soil hydrothermal conditions was proved, particularly in terms of soil moisture. The Random Forest feature importance extraction revealed that deep soil moisture (SM-L3) and surface soil temperature (ST-L1) are the most influential variables. It suggests that regulations of soil hydrothermal conditions on GPP may involve both linear and nonlinear effects. This study can obtain the temporal and spatial dynamics of soil hydrothermal conditions across different soil layers and explore their regulations on GPP, providing a basis for clarifying the relationship between soil and vegetation in arid mountain systems.

Conditioning grandparent care-labour mobility at the care-migration systems nexus: Australia and the UK

ABSTRACT A ‘transnational turn’ in welfare regime theory has disrupted methodologically nationalist analyses of care regimes generating analytical frameworks that capture the interdependencies between care and migration regimes. Those frameworks share a focus on migration for paid care labour as the vehicle connecting care and migration regimes transnationally. In this paper, we highlight familial care-labour mobility as an additional mechanism connecting care and migration regimes across borders. Drawing on the care circulation framework, we argue that a focus on these informal global care chains helps to bridge macro structural level approaches of the frameworks that focus on paid care labour with the more micro-level transnational family care approach. We focus on grandparent care-labour mobility, arguing that while it is ‘familial’, ‘informal’, ‘private’ and ‘invisible’, its dynamics and the lived experiences of those entwined within it, are mediated at the care-migration systems nexus. Through case-studies on grandparent care-labour mobility between China and Australia and India and the UK, we examine how the care-migration systems nexus is shaped by the prevailing logic of neoliberalism and ensuing patterns of stratification within care and migration systems. We conclude by highlighting the need for a transnational ethics of family care to govern the care-migration systems nexus.

Parallel shifts in flight-height associated with altitude across incipient Heliconius species.

Vertical gradients in microclimate, resource availability, and interspecific interactions are thought to underly stratification patterns in tropical insect communities. However, only a few studies have explored the adaptive significance of vertical space use during the early stages of reproductive isolation. We analysed flight-height variation across speciation events in Heliconius butterflies, representing parallel colonizations of high-altitude forest. We measured flight-height in wild H. erato venus and H. chestertonii, parapatric lowland and mountain specialists, respectively, and found that H. chestertonii consistently flies at a lower height. By comparing our data to previously published results for the ecologically equivalent H. e. cyrbia (lowland) and H. himera (high altitude), we found that the species flying closest to the ground are those that recently colonized high-altitude forests. We show that these repeated trends largely result from shared patterns of ecological selection producing parallel trait-shifts in H. himera and H. chestertonii. Although our results imply a signature of local adaptation, we did not find an association between resource distribution and flight-height in H. e. venus and H. chestertonii. We discuss how this pattern may be explained by variations in forest structure and microclimate. Overall, our findings underscore the importance of behavioural adjustments during early divergence mediated by altitude-shifts.

Reservoir Stratification Modulates the Influence of Impoundments on Fish Mercury Concentrations along an Arid Land River System.

Impoundment is among the most common hydrologic alterations with impacts on aquatic ecosystems that can include effects on mercury (Hg) cycling. However, landscape-scale differences in Hg bioaccumulation between reservoirs and other habitats are not well characterized nor are the processes driving these differences. We examined total Hg (THg) concentrations of Smallmouth Bass (Micropterus dolomieu) collected from reservoir, tailrace, and free-flowing reaches along an 863 km segment of the Snake River, USA, a semiarid river with 22 impoundments along its course. Across three size-classes (putative 1-year-old, first reproductive, and harvestable sized fish), THg concentrations in reservoirs and tailraces averaged 76% higher than those in free-flowing segments. Among reservoirs, THg concentrations were highest in reservoirs with inconsistent stratification patterns, 47% higher than annually stratified, and 144% higher than unstratified reservoirs. Fish THg concentrations in tailraces immediately downstream of stratified reservoirs were higher than those below unstratified (38-130%) or inconsistently stratified (32-79%) reservoirs. Stratification regimes influenced the exceedance of fish and human health benchmarks, with 52-80% of fish from stratifying reservoirs and downstream tailraces exceeding a human consumption benchmark, compared to 6-17% where stratification did not occur. These findings suggest that impoundment and stratification play important roles in determining the patterns of Hg exposure risk across the landscape.

Modular interneuron circuits control motion sensitivity in the mouse retina

Neural computations arise from highly precise connections between specific types of neurons. Retinal ganglion cells (RGCs) with similar stratification patterns are positioned to receive similar inputs but often display different response properties. In this study, we used intersectional mouse genetics to achieve single-cell type labeling and identified an object motion sensitive (OMS) AC type, COMS-AC(counter-OMS AC). Optogenetic stimulation revealed that COMS-AC makes glycinergic synapses with the OMS-insensitive HD2p-RGC, while chemogenetic inactivation showed that COMS-AC provides inhibitory control to HD2p-RGC during local motion. This local inhibition, combined with the inhibitory drive from TH2-AC during global motion, explains the OMS-insensitive feature of HD2p-RGC. In contrast, COMS-AC fails to make synapses with W3(UHD)-RGC, allowing it to exhibit OMS under the control of VGlut3-AC and TH2-AC. These findings reveal modular interneuron circuits that endow structurally similar RGC types with different responses and present a mechanism for redundancy-reduction in the retina to expand coding capacity.

Stratification pattern enumerator and its applications

Abstract Space-filling designs are widely used in computer experiments. A minimum aberration-type space-filling criterion was recently proposed to rank and assess a family of space-filling designs including orthogonal array-based Latin hypercubes and strong orthogonal arrays. However, it is difficult to apply the criterion in practice because it requires intensive computation for determining the space-filling pattern, which measures the stratification properties of designs on various subregions. In this article, we propose a stratification pattern enumerator to characterise the stratification properties. The enumerator is easy to compute and can efficiently rank space-filling designs. We show that the stratification pattern enumerator is a linear combination of the space-filling pattern. Based on the connection, we develop efficient algorithms for calculating the space-filling pattern. In addition, we establish a lower bound for the stratification pattern enumerator and present construction methods for designs that achieve the lower bound using multiplication tables over Galois fields. The constructed designs have good space-filling properties in low-dimensional projections and are robust under various criteria.