Continuum Concept Research Articles

Test of some ecological concepts on the longitudinal distribution of zooplankton along a lowland water course

The distribution of zooplankton communities from the source to the mouth of a lowland water course, the Scheldt, was used to test some concepts on the longitudinal distribution of organisms along both estuarine (Remane’s diversity concept) and riverine reaches (River Continuum Concept (RCC), Riverine Ecosystem Synthesis (RES)). Substantial zooplankton densities were found in both April and June samples all along the water course, and not only in the lower reaches as suggested by the RCC. Based on the zooplankton communities, and using hierarchical classifications and Generalized Linear Model, several successive zones influenced by different physical and chemical variables and trophic conditions could be distinguished along the Scheldt, in agreement with the RES model: the non-tidal riverine, the tidal freshwater, the tidal salinity gradient, and the marine zones. Over the entire freshwater reach, rotifers were numerically dominant during both samplings; crustaceans became more abundant in June than in April, specifically in the downstream reaches. Highest total zooplankton abundance and diversity were found in the tidal freshwater reach, lowest in the brackish water reach, in accordance with Remane’s concept. An influence of the tributaries on zooplankton communities is suggested, directly by import or dilution of zooplankton communities or through changing environmental conditions.

Allochthonous and autochthonous carbon flows in food webs of tropical forest streams

Abstract The River Continuum Concept (RCC) assumes that autochthonous primary production in forest streams is limited by light and is insufficient to sustain secondary production by consumers; they must therefore depend on allochthonous carbon from the surrounding forest. Recent studies have, however, questioned the importance of allochthonous carbon in stream food webs. There is a growing body of evidence using stable‐isotope techniques that demonstrate the importance of algae (autochthonous production) in the food webs of tropical streams. The actual contributions of autochthonous and allochthonous resources are rarely evaluated accurately because few studies consider the diet and the trophic efficiencies of the components of the food web or measure primary and secondary production to estimate the energy flow. We estimated the annual net primary productivity of periphytic microalgae (NPP) and the secondary production of macroinvertebrates (SP) from empirical models and we used stable isotopes of carbon and nitrogen to quantify the flow of material in food webs of five forest streams in the Guapi‐Macacu catchment, Rio de Janeiro, Brazil. NPP ranged from 46 g to 173 g dry mass (DM) m−2, whereas SP ranged from 0.90 g DM m−2 to 2.58 g DM m−2. The contribution of allochthonous carbon to the SP was more important than autochthonous sources and varied from 56% to 74% of all basal energy flow assimilated by primary consumers. The annual ingestion rate of basal sources varied from 8.08 g DM m−2 to 26.57 g DM m−2, with the allochthonous material contributing 76% and 87% of this. The annual ingestion rate of autochthonous material varied from 1.2% to 5.5% of the NPP. The present work suggests that the principal energy source for macroinvertebrates in streams of the Guapi‐Macacu catchment came from the riparian forest, as predicted by the RCC. However, this dependence appeared not to be driven by an absolute lack of autochthonous NPP, which seemed more than sufficient to sustain the entirety of macroinvertebrate SP.

M52. Predictive Influences of Cognitive-Perceptual Experiences in Schizotypy: A Structural Equation Modeling (SEM) Approach

Abstract Background: Schizotypy is a construct that captures quantitative dimensions of the psychosis continuum from normative to clinical expressions. The purpose of this study was to determine the factor structure and criterion validity of a newly revised self-report measure instrument, the Schizotypal Personality Questionnaire–Brief Revised Updated (SPQ-BRU; Davidson, Hoffman, & Spaulding, 2016) for predicting later cognitive-perceptual experiences in college undergraduates. Methods: The study sample was comprised of 2474 undergraduate students (female = 71%) attending a university in the Midwest. First, we aimed to identify the model of best fit between latent measurement models of schizotypy discussed in the prior literature using confirmatory factor analysis (CFA). A series of sequential model comparisons was used to determine the best fitting model of latent schizotypy. Second, we estimated a latent cognitive-perceptual factor from multiple measures collected at a second time point in a subsample of participants (n = 253). Using structural equation modeling (SEM), we tested the impact of latent schizotypy on participants’ subsequent self-reported cognitive-perceptual experiences at time 2. Results: Overall, CFA findings support a 4-factor model of schizotypy described by Callaway and colleagues (2013), (χ2 (108) = 2875.21, P < .001, CFI = 0.929, TLI = 0.922, RMSEA = 0.047, CI (RMSEA) =0.045–0.048, SRMR = 0.057). Proportion of variance explained in this 4-factor model included 45.0% for social anxiety, 67.3% for interpersonal, 61.2% for cognitive-perceptual, and 65.7% for disorganization (all P < .001). Consistent with our hypothesis for aim 2, the hypothesized latent cognitive-perceptual model yielded excellent fit of the data (χ2 (2) = 2.09, P < .352, CFI = 0.999, TLI = 0.998, RMSEA = 0.013, CI (RMSEA) = 0.000–0.127, SRMR = 0.018). Lastly, SEM results for aim 3 indicate specific dimensions of the path model explain 48.9% proportion of variance in cognitive-perceptual experiences at time 2 (χ2 (14) = 13.842, P = .46, CFI = 1.00, TLI = 1.00, RMSEA = 0.00, CI (RMSEA) = 0.00–0.60, SRMR = 0.024). Conclusion: This investigation bolsters a growing body of evidence for the predictive power of schizotypy for cognitive-perceptual phenomena in college students. In addition, this work further advances the concept of the neurodevelopmental continuum of psychosis.

Cross Border Migration and HIV Vulnerability in South Asian Countries

The present study aims to explore two prominent international mobility routes between Bangladesh-India and Nepal-India with a holistic approach capturing the range of HIV-related vulnerabilities faced by the key mobile populations at the origin, transit, and the destination. The study also aims to look at the gradual perpetuation of these vulnerabilities at the place of origin from the destination and finally present issues and challenges for making the cross border migration safe within the concept of continuum of care from a macro perspective. The basic data used for the study have been taken from the issues and concerns emerged during EMPHASIS (Enhancing Mobile Populations’ Access to HIV & AIDS Services, Information and Support) Mid Term Review, 2012. It has been collected using a combination of qualitative and quantitative research methods along with field observations. Findings reveal that, the vulnerabilities associated with the Bangladeshi and Nepali migrants are slightly different in occurrence but as a whole, they both are at high risk of acquiring HIV.

Weaving the Threads of a Continuum: Teacher Education in Hungary from the Perspective of European Developments

This paper aims to examine to what extent and how teacher education in Hungary reflects contemporary European policy and research developments with regard to the continuum of teacher education, meaning the overarching unity of initial teacher education, induction, and continuing professional development. First, the paper examines European policy documents to identify patterns and themes related to the continuum concept. Based on the specific analysis, a framework was developed to explore the continuum of teacher education and this was employed in the case of Hungary. Drawing from a content analysis of official documents and in-depth interviews with national policy experts and teacher educators as well as focus groups with teachers, the paper continues by analysing the development of teacher education in Hungary from the introduction of the Bologna reforms in 2005 to the restoration of undivided initial teacher education in 2012 and the implementation of a new system for the teacher career path in 2013. The findings indicate that while Hungary has adopted several structural elements related to the continuum which reflect European thinking, a lack of interconnections among the different phases of teacher education is apparent.

Longitudinal patterns in an Arkansas River Valley stream: an Application of the River Continuum Concept

Longitudinal patterns in an Arkansas River Valley stream: an Application of the River Continuum Concept

AN APPROACH TO STUDY ELASTIC VIBRATIONS OF FRACTAL CYLINDERS

This paper presents our study of dynamics of fractal solids. Concepts of fractal continuum and time had been used in definitions of a fractal body deformation and motion, formulation of conservation of mass, balance of momentum, and constitutive relationships. A linearized model, which was written in terms of fractal time and spatial derivatives, has been employed to study the elastic vibrations of fractal circular cylinders. Fractal differential equations of torsional, longitudinal and transverse fractal wave equations have been obtained and solution properties such as size and time dependence have been revealed.

Ictiofauna en el Arroyo Grande de Corozal; primer registro de 12 especies de peces para el departamento de Sucre, Colombia

Con el propósito de ampliar el conocimiento de la riqueza íctica del departamento de Sucre, durante los meses de Febrero y Junio de 2013, se hicieron recolectas de la fauna íctica en el tramo bajo del Arroyo Grande de Corozal. Se establecieron 10 estaciones de muestreo distribuidas a lo largo de 20 Km, cuatro muestreos en cada una de ellas, con atarraya y red tipo colador. Se registraron 43 especies de peces distribuidas en 7 Órdenes y 23 familias. Las especies con mayor abundancia relativa fueron Cyphocharax magdalenae (41,69%), Astyanax magdalenae (13,39%), Trachelyopterus insignis (4,91%), Nanocheirodon insignis (4,86%) y Triportheus magdalenae (4,74%). De las 43 especies reportadas, 12 son nuevos registros para el departamento de Sucre. Al agrupar las estaciones en dos zonas con cinco estaciones cada una, se encontraron 43 y 28 especies en las zonas cercana y lejana de la ciénaga respectivamente, con 28 especies en común y 15 exclusivas de la zona baja, distribución que sugiere dos interpretaciones básicas: un comportamiento acorde con lo sugerido en el concepto del río continuo y otra, la caracterización de las ciénagas como áreas de dispersión de especies. Una integración de estas dos hipótesis está definida por la menor disponibilidad de recursos y presencia de corriente en la zona alta y una desembocadura más rica en recursos y con un ambiente más estable para especies no migratorias.

P53 Proteoforms and Intrinsic Disorder: An Illustration of the Protein Structure-Function Continuum Concept.

Although it is one of the most studied proteins, p53 continues to be an enigma. This protein has numerous biological functions, possesses intrinsically disordered regions crucial for its functionality, can form both homo-tetramers and isoform-based hetero-tetramers, and is able to interact with many binding partners. It contains numerous posttranslational modifications, has several isoforms generated by alternative splicing, alternative promoter usage or alternative initiation of translation, and is commonly mutated in different cancers. Therefore, p53 serves as an important illustration of the protein structure–function continuum concept, where the generation of multiple proteoforms by various mechanisms defines the ability of this protein to have a multitude of structurally and functionally different states. Considering p53 in the light of a proteoform-based structure–function continuum represents a non-canonical and conceptually new contemplation of structure, regulation, and functionality of this important protein.

Modeling Allochthonous Dissolved Organic Carbon Mineralization Under Variable Hydrologic Regimes in Boreal Lakes

Here, we explore the interaction between hydrology and the reactivity of allochthonous dissolved organic carbon (DOCalloch) in determining the potential of DOCalloch to generate CO2 through biological and photo-chemical mineralization in boreal lakes. We developed a mechanistic model that integrates the reactivity continuum (RC) concept to reconstruct in-lake mineralization of DOCalloch under variable hydrologic conditions using empirical measurements of DOCalloch concentrations and reactivity as model inputs. The model predicts lake DOCalloch concentration (L-DOCalloch) and its average overall reactivity $$ \left( {\bar{K}_{\text{alloch}} } \right) $$ , which integrates the distribution of DOCalloch ages within the lake as a function of the DOC loading (DOCin), the initial reactivity of this DOCin (k 0), and the lake water residence time (WRT). The modeled DOCalloch mineralization rates and concentrations were in agreement with expectations based on observed and published values of ambient lake DOC concentrations and reactivity. Results from this modeling exercise reveal that the interaction between WRT and k 0 is a key determinant of the ambient concentration and reactivity of lake DOCalloch, which represents the bulk of DOC in most of these lakes. The steady-state $$ \left( {\bar{K}_{\text{alloch}} } \right) $$ also represents the proportion of CO2 that can be extracted from DOCalloch during its transit through lakes, and partly explains the patterns in surface water pCO2 oversaturation that have been observed across gradients of lake size and volume. We estimate that in-lake DOCalloch mineralization could potentially contribute on average 30–40% of the observed surface carbon dioxide partial pressure (pCO2) across northern lakes. Applying the RC framework to in-lake DOCalloch dynamics improves our understanding of DOCalloch transformation and fate along the aquatic network, and results in a predictable mosaic of DOC reactivity and potential CO2 emissions across lakes within a landscape.

河川生態系の中の付着性細菌群集 : 河川連続体仮説の視点から( ミクロな世界からの新展開)

河川生態系の中の付着性細菌群集 : 河川連続体仮説の視点から( ミクロな世界からの新展開)

Critical dimensional limit of continuum fracture mechanics for dislocation emission

One major elementary process in ductile failure is the emission of a dislocation from the crack tip, the criterion for which is well established within the framework of fracture mechanics and involves the intensity of the stress singularity appearing near the crack tip. The continuum-media postulate of fracture mechanics, however, might prevent us from predicting the failure of nanoscale materials, such as ultrathin films and nanowires, because the continuum concept becomes less plausible as the size of the region of interest approaches the atomic scale. Here, we examine the applicability and lower size limit of continuum fracture mechanics at the nanoscale in the case of dislocation emission, by conducting computational simulations that were modeling nanometer-scale Cu specimens. We find that fracture mechanics works successfully for singular fields larger than a few nanometers, but fails for singular fields smaller than 1.5–2.0nm, i.e., the lower size limit of fracture mechanics for dislocation emission. We further demonstrate that this lower size limit is determined by the atomistic nature of the structural instability, suggesting that the limit depends on atomic-level phenomena at the crack tip.

Abstract SY09-01: The tumor immunity continuum as a framework for rational combinations

Abstract The PD-L1/PD-1 pathway is emerging as a central axis for immune-based therapeutic strategies in the treatment of multiple cancers. While these therapies are defined by durable responses extending to impressive overall survival improvement, this clinical benefit is limited to a few. We utilized gene signature analysis of cell subsets associated with the TME and molecular classification of disease using whole transcriptome analysis, PD-L1 IHC, CD8 IHC and tumor mutational load to identify signatures associated with immune response to atezolizumab (ati-PDL1) therapy from large Phase II trials and describe signatures associated with immune escape. Namely, we demonstrate that a preexisting immune response associated with inflamed tumors is highly predictive of clinical benefit to checkpoint inhibition. In addition, we describe both histological and molecular phenotypes associated with immune escape. The biological drivers of PD-L1 expression on tumor cells and tumor infiltrating immune cells will be presented. Using the lessons learned from human tumor immunology, we propose the concept of the tumor immunity continuum as a framework to expand the patient pool that derive long-term clinical benefit by harnessing their immune system. Citation Format: Priti S. Hegde. The tumor immunity continuum as a framework for rational combinations. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr SY09-01.

Biotic fluxes of matter and energy between aquatic and terrestrial ecosystems

This paper is an introduction to a special issue of the journal. A brief historical delineation of the question of studying interfaces between adjacent ecosystems (ecotones) is presented. High biodiversity of ecotones and their vulnerability to natural and anthropogenic impacts, including invasions of alien species, are noted. It is supposed that there is no contradiction between the ecotone and river continuum concepts. The important ecological role of amphibiotic animals and plants in interactions and functioning of the adjacent ecosystems is emphasized. The issue of studying the quantitative parameters of fluxes of matter and energy between ecosystems in conjunction with their qualitative parameters (chemical elemental and biochemical compositions) is considered in the present paper.

Сельско-городской континуум: судьба представления и его связь с пространственной мобильностью населения

Статья посвящена эволюции, схемам и сферам приложения идеи сельско-городского континуума, разнообразию его пространственных и отчасти исторических форм, их типам и свойствам. Эту идею часто определяют от противного, противопоставляя ее антиномии города и села, их резкому разделу, территориальному и социальному. Автору представляется, что сельско-городской континуум (континуумы) служит синонимом расселения, понимаемого как сплошное поле, которое можно исследовать в разном масштабе, при разной пропорции города и села. Из обзора графических схем вытекает вывод, что разные версии комплементарны, отражая эволюционную, полимасштабную и градуальную природу континуума. Анализ избранного западного и российского опыта завершен попыткой типизации континуумов по основным регионам России. Cложность и неоднородность нарастают от локального полусельского типа к межрегиональному мегагородскому с интерференцией разных континуальных полей. Мобильность населения в континуумах иллюстрируют примерные расчеты ее параметров по Москве и России. Эта мобильность делает расселение не только континуальным, но и пульсирующим. В заключении кратко изложены проблемы управления, которому по ряду причин трудно усвоить саму идею континуума.

Evidence for limited trophic transfer of allochthonous energy in temperate river food webs

The River Continuum Concept (RCC) predicts that riverine food webs shift from a reliance on allochthonous energy in headwaters to autochthonous production in lower reaches. However, estimates of resource reliance often fail to account for resource segregation within the food web. Stable-isotope biomarkers can be used to estimate the relative importance of allochthonous and autochthonous material to specific groups and within the food web. δ13C and δ15N isotope ratios were calculated for allochthonous (conditioned leaf litter) and autochthonous (biofilm and bryophytes) basal energy sources, macroinvertebrate functional feeding groups (shredder, grazer, collector–filterer, collector–gatherer, predator), and resident fish species at 17 locations spanning the headwaters to lower reaches of 2 river systems in eastern Canada. Stable-isotope mixing models and correlations were used to identify longitudinal trends in the food webs of both rivers. In headwater streams, allochthonous material was the predominant resource for shredders, whereas all other primary, secondary, and tertiary consumers predominantly used autochthonous basal resources. Stable-isotope ratios of allochthonous material varied minimally between sites. Both autochthonous basal sources were significantly 13C-enriched and 15N-depleted in lower-reach relative to headwater sites. Shredders displayed minimal variation across sites, whereas longitudinal variation in all other primary consumers, macroinvertebrate predators, and fishes was closely correlated with autochthonous basal sources. These results highlight the role of resource segregation within river food webs and indicate that the RCC may not predict energy pathways in all temperate river systems.

Retesting a prediction of the River Continuum Concept: autochthonous versus allochthonous resources in the diets of invertebrates

The River Continuum Concept (RCC) predicts that food webs (and, in particular, invertebrates) of rivers in temperate, forested drainages should exhibit a longitudinal gradient from reliance on terrestrially derived organic matter (e.g., seasonally shed leaves) in the headwaters to autochthonous sources (e.g., algae) in the mid-orders, to suspended material in larger rivers. This prediction has been evaluated by longitudinal comparisons of macroinvertebrate communities in terms of functional feeding groups (FFGs), but such an approach yields only indirect evidence regarding actual food use. To retest this prediction, we investigated invertebrate diets from the Salmon River, Idaho, by examining the gut contents of archived specimens from the longitudinal set of sites sampled in the original 1976 RCC study and by collecting invertebrates from these same sites in 2009. We detected no apparent shifts in diets over the ∼30-y time span. The importance of allochthonous materials in invertebrate diets differed significantly among sites along the longitudinal gradient. As predicted, it was greatest at the 2nd-order headwater site (30–42% of gut contents, on average) and decreased longitudinally to 10 to 20% at the most downstream site. However, invertebrates at the 2nd-order site also consumed large percentages of autochthonous materials (35–45%), and diets contained from 35 to 75% autochthonous resources across all sites. The shredder (Yoraperla) with the highest density at the most upstream 2nd-order site had gut contents composed of 52 to 81% diatoms depending on season, illustrating the importance of autochthonous resources in the headwaters. Our findings show that measuring shifts in FFG alone without examining actual food resources present in macroinvertebrate diets may lead to erroneous inferences regarding patterns of resource use by macroinvertebrates in food webs.

Longitudinal distribution of periphyton algae in the Moskva river under eutrophication

Variations of the species structure of periphyton algae community on submerged plants have been studied along the longitudinal profile of the Moskva R. with the use of multivariate statistical methods. The results of principal-coordinates analysis show the flow velocity and biogenic load to be the major factors governing the spatial variations of periphyton structure. Mantel test shows the difference in the species structure to be correlated more closely with local variations in the environmental factors than with the distance along river channel. Therefore, the spatial distribution of periphyton in the Moskva R. agrees better with the concept of patch dynamics than the concept of river continuum. Estimation of the indicator potential of three ecological guilds of diatoms (low profile, high profile, and motile) has shown a positive response of motile diatoms to an increase in the concentration of biogenic compounds. The effect of other factors, such as light intensity in macrophyte stands and the microdistribution of diatoms in periphyton layer, can disturb the relationship between biogenic substance concentrations and the abundance of low profile and high profile diatoms.

The Where, the When, and the How of Immune Monitoring for Cancer Immunotherapies in the Era of Checkpoint Inhibition.

Clinical trials with immune checkpoint inhibitors have provided important insights into the mode of action of anticancer immune therapies and potential mechanisms of immune escape. Development of the next wave of rational clinical combination strategies will require a deep understanding of the mechanisms by which combination partners influence the battle between the immune system's capabilities to fight cancer and the immune-suppressive processes that promote tumor growth. This review focuses on our current understanding of tumor and circulating pharmacodynamic correlates of immune modulation and elaborates on lessons learned from human translational research with checkpoint inhibitors. Actionable tumor markers of immune activation including CD8(+)T cells, PD-L1 IHC as a pharmacodynamic marker of T-cell function, T-cell clonality, and challenges with conduct of trials that ask scientific questions from serial biopsies are addressed. Proposals for clinical trial design, as well as future applications of peripheral pharmacodynamic endpoints as potential surrogates of early clinical activity, are discussed. On the basis of emerging mechanisms of response and immune escape, we propose the concept of the tumor immunity continuum as a framework for developing rational combination strategies.

Unsociable juvenile male three-spined sticklebacks grow more attractive

An animal’s personality may be an adaptive behavioral response of individuals to consistent differences in physiology and life-history. Studying the relationship between behavior and other fitness-related traits within the pace-of-life syndrome (POLS) framework, which explains the integration of different traits using the concept of a fast-slow life-history continuum, may thus be a useful approach to understanding the evolution and maintenance of animal personality. According to the POLS hypothesis, for example, fast individuals should be behaviorally more active, bolder or less sociable, and potentially invest more in reproduction than slow individuals. Here, we examined whether the sociability of juvenile sticklebacks (Gasterosteus aculeatus) is linked with their key reproductive traits, carotenoid-based nuptial coloration of males and egg production of females. We also tested whether experimental manipulation of environmental conditions (control vs. warm winter) can change pace-of-life and the link between behavioral and reproductive traits. Male sticklebacks prone to shoaling expressed lower peak red coloration at the reproductive stage, during which they were solitary and territorial. In females, fecundity was not correlated with early social behavior. Experimental sticklebacks reared in warm winter conditions decreased their investment in reproduction, but the negative relationship between sociability and sexual signal of males was maintained. Our results suggest that the POLS could partly explain the maintenance of personality under predation pressure or severe mating competition. In natural environments, any benefit to sociable male sticklebacks may be counterbalanced by the cost of growing less attractive. Why do animals vary in personality, and how is such variation maintained within a population? An interesting approach for understanding this is studying how personality traits are correlated with other fitness-related traits within the pace-of-life framework. For the first time, our results show the link between sociability at the juvenile stage and the expression of sexual ornament during reproduction in male three-spined sticklebacks. Sociable juveniles may benefit from reduced predation risk, but they grow less attractive and this may reduce their mating success during reproduction. Thus, the trade-off between survival and reproduction may contribute to the maintenance of among-individual variation in behavior.