Academic literature on the topic 'Environmenal gradient'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Environmenal gradient.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Environmenal gradient":
1
Jacobucci, G. B., A. Z. Güth, A. Turra, and F. P. P. Leite. "Influence of a narrow depth gradient and season on the morphology, phenology, and epibiosis of the brown alga Sargassum cymosum." Journal of the Marine Biological Association of the United Kingdom 91, no. 4 (December 9, 2010): 761–70. http://dx.doi.org/10.1017/s0025315410001633.
Abstract:
Temporal and spatial fluctuations of environmental parameters are normally assigned as causes of variations in morpho-phenological characters of seaweeds and in their epibionts, but formal tests of such hypotheses are lacking, especially in narrow gradients. The present study evaluated the influence of a very small depth gradient (1 to 3 m) and of subtle seasonality characteristic of tropical areas on morpho-phenological traits and on the occurrence of sessile epiphytic organisms using a controlled orthogonal sampling design in a sublittoral population of the tropical brown alga Sargassum cymosum. Four temporal samples were obtained over a one-year period at three depths using nine replicates. The wet weight, maximum length, number of primary and secondary branches, and proportion of secondary branches with receptacles were recorded. Epibiosis was estimated by visual evaluation of percentage cover on secondary branches. Algal morphology varied as a function of the period of the year (weaker effect) and depth (stronger effect) but in different ways for each variable analysed. In general, fronds tended to be shorter, heavier, and more ramified in shallower areas. In relation to time, the morphological characters tended mostly to present higher values in January (summer) and/or April (autumn). Frequency of receptacles did not depend on algal morphology and depth at all but varied in time, although only in the deepest area. Epibiosis also did not depend on algal morphology but varied in relation to time (stronger effect) and, to a lesser extent, depth (weaker effect). The effect of time upon epibiosis also depended on the biological group analysed. These data support the hypothesis that algal morphology varies in relation to period of the year and depth, even under small temporal and spatial environmenal gradients.
2
Catling, PC, and RJ Burt. "Studies of the Ground-Dwelling Mammals of Eucalypt Forests in South-Eastern New South Wales: the Effect of Environmental Variables on Distribution and Abundance." Wildlife Research 22, no. 6 (1995): 669. http://dx.doi.org/10.1071/wr9950669.
Abstract:
The distribution and abundance of ground-dwelling mammals was examined in 13 areas within 500 000 ha of eucalypt (Eucalyptus) forest in SE New South Wales. Data are presented on the distribution and abundance of species in relation to 3 environmental gradient types involving 9 variables: 2 direct gradients (temperature, rainfall); 6 indirect gradients (aspect, steepness of slope, position on slope, landform profile around the site, altitude, season) and a resource gradient (lithology). Many species of ground-dwelling mammal of the forests of SE New South Wales were present along all gradients examined, although wide variation in abundance occurred for some species. Eight species were correlated with direct gradients and all species were correlated with at least one indirect gradient. There was wide variation and species diversity with lithology, but the variation was not related to nutrient status. Although variations in abundance occurred along environmental gradients, the composition of the ground-dwelling mammal fauna in SE New South Wales forests changed little. A fourth gradient type, the substrate gradient (biomass of plants), had the greatest effect, because in the short-term disturbances such as logging and fire play an important role. Disturbance can have a profound influence on the substrate gradient, but no influence on environmental gradients. The results are discussed in relation to the arboreal mammals and avifauna in the region and Environmental and Fauna Impact studies and forest management.
3
Stine, Caleb A., and Jennifer M. Munson. "Autologous Gradient Formation under Differential Interstitial Fluid Flow Environments." Biophysica 2, no. 1 (January 4, 2022): 16–33. http://dx.doi.org/10.3390/biophysica2010003.
Abstract:
Fluid flow and chemokine gradients play a large part in not only regulating homeostatic processes in the brain, but also in pathologic conditions by directing cell migration. Tumor cells in particular are superior at invading into the brain resulting in tumor recurrence. One mechanism that governs cellular invasion is autologous chemotaxis, whereby pericellular chemokine gradients form due to interstitial fluid flow (IFF) leading cells to migrate up the gradient. Glioma cells have been shown to specifically use CXCL12 to increase their invasion under heightened interstitial flow. Computational modeling of this gradient offers better insight into the extent of its development around single cells, yet very few conditions have been modelled. In this paper, a computational model is developed to investigate how a CXCL12 gradient may form around a tumor cell and what conditions are necessary to affect its formation. Through finite element analysis using COMSOL and coupled convection-diffusion/mass transport equations, we show that velocity (IFF magnitude) has the largest parametric effect on gradient formation, multidirectional fluid flow causes gradient formation in the direction of the resultant which is governed by IFF magnitude, common treatments and flow patterns have a spatiotemporal effect on pericellular gradients, exogenous background concentrations can abrogate the autologous effect depending on how close the cell is to the source, that there is a minimum distance away from the tumor border required for a single cell to establish an autologous gradient, and finally that the development of a gradient formation is highly dependent on specific cell morphology.
4
He, W. M., and R. M. Callaway. "The potential for misleading correlations in single-factor analysis of complex gradients." Web Ecology 9, no. 1 (December 21, 2009): 77–81. http://dx.doi.org/10.5194/we-9-77-2009.
Abstract:
Abstract. Gradient analysis is an important tool for describing patterns in ecology. Natural environmental gradients are complex combinations of factors, suggesting that gradientsshould, when possible, be analyzed in multi-factorial ways. We searched papers published in Ecology, Global Change Biology, Journal of Ecology, Oecologia, Oikos, and Journal of Vegetation Science from January 2001 to December 2005, and found 133 papers matching two keywords: “gradient analysis” and “environmental gradient”. Of these, 86 utilized single-factor correlation analyses between ecological entities and natural environmental gradients. Thus the use of single-factor correlations in studies of natural environmental gradients is widespread despite the potential of this approach to overemphasize the importance of the particular factor chosen. We reanalyzed a data set from the literature, provided a example of contrasting analyses, and analyzed our own data with both single- and multiple-factor analyses to demonstrate how single-factor correlation can result in correlations that provide incomplete analysis. Integrated multi-factor approaches to studying natural environmental gradients cannot solve all analytical problems when two or more important variables are correlated, but are likely to better test the relative importance of factors driving ecological patterns.
5
Souza, Fernanda M., Eliandro R. Gilbert, Kalina M. Brauko, Luciano Lorenzi, Eunice Machado, and Mauricio G. Camargo. "Macrobenthic community responses to multiple environmental stressors in a subtropical estuary." PeerJ 9 (December 7, 2021): e12427. http://dx.doi.org/10.7717/peerj.12427.
Abstract:
We assessed how multi- and univariate models reflect marine environmental health based on macrobenthic community responses to three environmental stressor categories: hydrodynamics, organic enrichment and metal contamination. We then compared the models with the benthic index AMBI (AZTI Marine Biotic Index). Macrobenthic community and physicochemical variables were sampled at 35 sites along Babitonga Bay, a subtropical estuary in Southern Brazil. Distance-based linear modelling identified depth, grain size and organic matter as well as Cu and Zn as key stressors affecting the macrobenthos. Using canonical analysis of principal coordinates (CAP), we developed three multivariate models based on the variability in community composition, creating stress gradients. The metal gradient showed better correlation with the benthic community. Sediment quality indices (Geoaccumulation Index and Contamination Factor) showed a low to moderate contamination status, with higher concentrations for Cr, Ni and Zn at the inner areas of the bay. According to AMBI, Babitonga Bay has a “good” environmental health status, and the AMBI values show stronger correlations with the hydrodynamic and organic enrichment gradients (r = 0.50 and r = 0.47) rather than the metal gradient (r = 0.29). Lumbrineridae polychaetes (not included in the AMBI list) and Scoloplos sp. were negatively related to the metal contamination gradient and were considered sensitive, while Sigambra sp., Magelona papillicornis, the gastropod Heleobia australis and species of the crustacean order Mysida were positively related to the gradient and considered tolerant to higher concentrations of metals in the sediment. Despite the inconsistency in the ecological classification provided by AMBI and its relationship with the metal gradient, our results suggest that the environmental quality was satisfactory for the studied gradients. The metal gradient showed the weakest correlation to AMBI. In such cases, the ecological classification of taxa by the index should be evaluated under the perspective of the action of inorganic genotoxic contaminants represented by metals.
6
Connor, Stephanie J., Alexa C. Alexander-Trusiak, and Donald J. Baird. "Vulnerability of diatom communities in the Peace–Athabasca Delta to environmental change." PeerJ 6 (August 9, 2018): e5447. http://dx.doi.org/10.7717/peerj.5447.
Abstract:
Habitat degradation associated with resource development is a major ecological concern, particularly in Canada’s boreal zone where limited information on biodiversity is available. Habitat degradation can lead to reductions in biodiversity and ecosystem function, especially when drivers of variability and diversity patterns have not been identified for a region of interest. In this study, the distribution of diatom genera in the Peace–Athabasca Delta in northeastern Alberta was examined in relation to seasonal, geographic, and alkalinity gradients. Grab samples of six abiotic variables (total dissolved nitrogen, total dissolved phosphorus, dissolved iron, turbidity, pH, and specific conductance (SPC)) were taken from 12 remote wetlands over three sampling periods, and regressed against an ordination of diatom community composition to identify key environmental drivers of diatom community variation. Indirect gradient analysis identified two major gradients among sites. First, separation of sites among sampling periods showed successional seasonal changes in diatom community composition. Second, separation of sites from the Peace sub-delta and Birch sub-delta showed a gradient of geographic separation. Direct gradient analysis failed to explain the underlying drivers of these two gradients, but did show that alkalinity is a key driver of diatom community composition in the Embarras sub-delta, and that these sites could be particularly vulnerable to community changes associated with acidification.
7
Campos-Cerqueira, Marconi, and T. Mitchell Aide. "Changes in the acoustic structure and composition along a tropical elevational gradient." Journal of Ecoacoustics 1, no. 1 (December 6, 2017): 1. http://dx.doi.org/10.22261/jea.pnco7i.
Abstract:
Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales.
8
Bogale Worku, Belachew, Melese Genete Muluneh, and Tesfaye Molla. "Influence of Elevation and Anthropogenic Disturbance on Woody Species Composition, Diversity, and Stand Structure in Harego Mountain Forest, Northeastern Ethiopia." International Journal of Forestry Research 2023 (November 17, 2023): 1–17. http://dx.doi.org/10.1155/2023/8842408.
Abstract:
Environmental variables like elevation affect species composition, diversity, distribution, density, and horizontal and upward growth. Ecologists are constantly working to better understand how species diversity varies along elevational gradients, particularly in mountainous ecosystems. Therefore, the purpose of this research was to examine the species’ horizontal and vertical structural diversity along the Harego Mountain Forest’s elevational gradient. The area was categorized into lower, middle, and upper elevations. A total of 67 (20 m × 20 m) plots were created along gradients of elevation 2,079–2,516 meters above sea level (m a.s.l.). Information for floristic composition, diversity, stand structure, and environmental variables were measured and recorded for each plot over the three elevational gradients. Data on anthropogenic disturbances were visually evaluated for every plot in every gradient of elevation. For the diversity analysis, Hill’s diversity statistics were employed. To find significant variations between the three elevational gradients in terms of Hill’s diversity number, stand structure, and environmental variables, the one-way analysis of variance with SPSS version 26 at the 0.05 level of significance was carried out. The finding revealed that 50 woody plants that belonged to 35 families and 44 genera in the 67 sample plots with an elevation of 2,079 to 2,516 were identified. Shrubs were dominant in each elevational gradient. Species richness, abundance, and Hill’s diversity number were all significantly ( p < 0.05 ) greater in the upper elevational gradient of the forest. On the other hand, all stand structures were significantly ( p < 0.05 ) higher in the middle elevational gradient. The effect of anthropogenic disturbances and environmental variables were clearly observed in the lower and upper elevational gradients than in the middle elevation. As a result, there were fewer seedlings, saplings, trees, and shrubs in the gradients of lower and higher elevations. For the conservation of the forest, it is crucial to pay special attention to biotic elements at lower elevations and abiotic factors at higher elevations. Accordingly, involving the local community in forest management, reducing anthropogenic pressure in and around the Harego Mountain Forest through tree planting in farmlands and woodlots and implementing physical soil and water conservation structures are recommended.
9
Allen, Robert B., and Robert K. Peet. "Gradient analysis of forests of the Sangre de Cristo Range, Colorado." Canadian Journal of Botany 68, no. 1 (January 1, 1990): 193–201. http://dx.doi.org/10.1139/b90-026.
Abstract:
Interrelationships between dominant compositional and environmental gradients were studied using 186 forest stands sampled on the east slope of the Sangre de Cristo Range, Colorado. Detrended correspondence analysis and detrended canonical correspondence analysis were used to analyze indirect and direct gradients, respectively. The dominant compositional gradient was strongly correlated with elevation. Increasing elevation was associated with decreasing soil pH and percent base saturation, and increasing total soil N. Ordination of stands stratified by elevation showed the major compositional gradient within each elevation class was strongly correlated with a topographic moisture index. Most soil variables correlated with this gradient in low and high elevation classes. In mid-elevation forests, a third compositional gradient correlated with soil pH, percent base saturation, and potential solar radiation. In these forests, Pinus contorta and Pseudotsuga menziesii were associated with acidic soils on north-facing slopes, whereas Populus tremuloides and Abies concolor were associated with base-rich soils on south-facing slopes. Ordination axes accounted for least variation in comparatively young mid-elevation forests. A plausible explanation is that the mid-elevation forests represent an unpredictable stage in forest development where competition has not yet had sufficient time to sort species along environmental gradients.
10
Olthoff, Adriana E., Carolina Martínez-Ruiz, and Josu G. Alday. "Niche Characterization of Shrub Functional Groups along an Atlantic-Mediterranean Gradient." Forests 12, no. 8 (July 24, 2021): 982. http://dx.doi.org/10.3390/f12080982.
Abstract:
The identification of the factors controlling the understory species distribution and abundance is essential to understand the ecology and dynamics of natural forests and their management response. We assess the relationships between environmental gradients and shrub functional groups distribution patterns and niche characteristics in a transitional area between the Eurosiberian and Mediterranean biogeographic regions in Northern Spain. Here, 772 plots from the 3rd Spanish National Forest Inventory were used. Shrub functional groups respond to the same complex environmental gradients as trees, i.e., the north-south climatic gradient and a slope gradient. Unimodal response curves of shrub functional groups and families dominate along both gradients, providing evidence of successful functional turnover. Similar to tree species, the niche location of functionally related shrubs is close. Functional groups occupying environments with sharp contrast or transitional environments have the broadest niches, whereas those specialized functional groups occupying localized habitats showed the narrowest niches. The knowledge of shrub species distributions and niche characteristics along complex environmental gradients will improve our ability to discuss potential conservation management goals or threats due to land-use changes and future climate change.
Dissertations / Theses on the topic "Environmenal gradient":
1
Delalandre, Léo. "Relations traits-environnement chez les végétaux : du cycle de vie des organismes au cycle de vie des données." Electronic Thesis or Diss., Université de Montpellier (2022-....), 2024. http://www.theses.fr/2024UMONG001.
Abstract:
L’écologie comparative a mis en évidence des associations récurrentes entre les traits fonctionnels des plantes et leur environnement. Ces relations peuvent varier selon le niveau d’organisation considéré – au sein des espèces, entre les espèces, et entre groupes d’espèces –, mais cette dépendance demeure peu étudiée. Une distinction fondamentale dans les théories de l’histoire de vie est effectuée entre espèces annuelles (réalisant leur cycle de vie en une année) et pérennes (cycle de vie sur plus d’une année, avec généralement plusieurs événements de reproduction). Les annuelles et les pérennes herbacées diffèrent quant à leur fonctionnement (vitesse de croissance, investissement dans la production de graines, allocation aux racines, etc.). Cependant, bien qu’elles coexistent fréquemment, peu d’études considèrent les potentielles différences dans les relations traits-environnements entre ces deux groupes. L’objectif de cette thèse est de comprendre les spécificités des variations des traits des plantes annuelles en fonction de la disponibilité en ressources du milieu, à partir de mesures in situ et en jardin commun.Nous avons étudié des communautés de parcours ovins des Grands Causses, où annuelles et pérennes coexistent dans deux conditions environnementales contrastées : i) fertilisation et forte perturbation, et ii) sol pauvre et perturbation mois intense. Nous montrons que les variations des traits liés à la vitesse de croissance et à la densité des tissus foliaires sont plus faibles chez les annuelles que chez les pérennes. Ceci s’explique par (a) un remplacement d’espèces plus élevé chez les pérennes, et (b) la présence d’espèces présentant de plus grandes différences de valeurs de traits entre environnements chez les pérennes. Les variations intraspécifiques sont identiques entre les deux groupes d’espèces. Les mesures effectuées au cours de de ce premier volet ont permis de compléter une base de données de traits en cours de développement. A cette occasion, j’ai contribué à la structuration de cette base par un travail de gestion des données, visant à proposer des modalités de partage des données de traits fonctionnels et des variables environnementales associées ; une synthèse de ce travail est proposée. Dans un second temps, nous avons analysé la variabilité intraspécifique chez les annuelles de ces communautés, afin de tester son origine (génétique ou plastique), d’identifier les traits les plus variables en réponse à la fertilisation, et de comparer cette variabilité entre espèces. Trente populations ont été cultivées en jardin commun, avec une fertilisation faible ou élevée. Les résultats indiquent que i) les variations de traits observées in situ sont vraisemblablement d’origine plastique ; ii) la plasticité est faible sur les traits morphologiques des feuilles et des racines, mais forte sur l’allocation de la biomasse et la teneur en azote ; iii) les espèces préférentes pour des milieux riches en nutriments sont plus plastiques sur leur teneur en azote.Enfin, un travail de revue de la littérature a été engagé de manière à déterminer quels traits sont déterminants pour les herbacées annuelles et pérennes, en raisonnant sur les composantes de la démographie (reproduction, croissance, survie), dont l’importance diffère selon le cycle de vie. Nous proposons un article d’opinion visant à proposer comment mieux intégrer le cycle de vie et les trait morpho-physio-phénologiques communément mesurés.Cette thèse propose une étude des relations entre traits fonctionnels et environnement à différents niveaux d’organisation : entre cycles de vie, entre espèces, et au sein des espèces. Elle met en évidence que les relations trait-environnement peuvent varier entre ces niveaux, s’inscrivant dans un regain d’intérêt pour la prise en compte de la dépendance au contexte en écologie comparativeComparative ecology has highlighted recurring associations between plant functional traits and their environment. These relationships may vary depending on the level of organization considered – within species, between species, and among groups of species – but this dependency remains poorly studied. A fundamental distinction in life history theories is made between annual species (completing their life cycle in one year) and perennial species (life cycle over more than one year, usually with multiple reproductive events). Annual and perennial herbaceous plants differ in their functioning (growth rate, investment in seed production, allocation to roots, etc.). However, despite their frequent coexistence, few studies have considered potential differences in trait-environment relationships between these two groups. The objective of this thesis is to understand the specific variations in the traits of annual plants depending on resource availability, based on in situ measurements and in a common garden setting.We studied herbaceous communities in the Grands Causses, where annuals and perennials coexist in two contrasting environmental conditions: i) fertilization and high disturbance, and ii) poor soil and less intense disturbance. We show that variations in traits related to growth rate and leaf tissue density are lower in annuals than in perennials. This is explained by (a) a higher species turnover in perennials, and (b) the presence of species with larger differences in trait values between environments in perennials. Intraspecific variations are identical between the two groups of species. Measurements made during this first part were used to complete a trait database under development. On this occasion, I contributed to the structuring of this database through data management work, aiming to propose modalities for sharing functional trait data and associated environmental variables; a synthesis of this work is proposed.Secondly, we analyzed intraspecific variability in annuals from these communities, in order to test its origin (genetic or plastic), to identify the most variable traits in response to fertilization, and to compare this variability between species. Thirty populations were grown in a common garden, with low or high fertilization. The results indicate that i) the observed trait variations in situ are likely of plastic origin; ii) plasticity is low in morphological leaf and root traits but high in biomass allocation and nitrogen content; iii) species preferring nutrient-rich environments are more plastic in their nitrogen content.Finally, a literature review was undertaken to determine which traits are determinant for annual and perennial herbaceous plants, reasoning on demographic components (reproduction, growth, survival), the importance of which differs according to the life cycle. We propose an opinion article aiming to better integrate life cycle and commonly measured morpho-physio-phenological traits.This thesis proposes a study of the relationships between functional traits and the environment at different levels of organization: between life cycles, between species, and within species. It highlights that trait-environment relationships can vary between these levels, fitting into a renewed interest in context dependency in comparative ecology
2
Heilmayer, Olaf. "Environment, adaptation and evolution: scallop ecology across the latitudinal gradient = Umwelt, Anpassung und Evolution: Ökologie der Jakobsmuscheln im latitudinalen Gradienten /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2004. http://www.gbv.de/dms/bs/toc/385417098.pdf.
3
Danczak, Robert E. "Dynamics in Microbial Ecology Across an Environmental Stability Gradient." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1530878203337741.
4
Leandro, Sérgio Miguel Franco Martins. "Environmental forcing of an estuarine gradient of zooplankton abundance and production." Doctoral thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/936.
Abstract:
Doutoramento em BiologiaOs copépodes são pequenos e frágeis crustáceos que constituem um dos grupos de organismos metazoários mais abundantes do mundo. Em ambientes marinhos e estuarinos, os copépodes assumem um papel de extrema relevância ao nível das cadeias tróficas, nomeadamente na transferência de matéria e energia de níveis tróficos inferiores (fitoplâncton) para níveis tróficos superiores (ex. larvas de peixe). A importância ecológica dos copépodes reflecte-se no elevado número de citações constantes no ISI Web of Knowledge (7716 citações entre 1969 e 2006) e no destaque que os mesmos continuam a possuir em estudos recentes de planctologia marinha e estuarina. Esta dissertação teve como objectivos principais (1) descrever variações espacio-temporais em termos de abundância e biomassa de populações estuarinas de copépodes da Ria de Aveiro (Portugal) e a sua relação com parâmetros hidrológicos (salinidade, temperatura, clorofila a e precipitação; (2) comparar as taxas de crescimento e desenvolvimento de populações alopátricas de copépodes; (3) definir modelos de crescimento dependentes da temperatura para as formas juvenis (nauplius e copepoditos) de Acartia tonsa; (4) avaliar o forçamento ambiental na distribuição e abundância de populações de Acartia e (5) calcular taxas de produção secundária potenciais para as populações de Acartia. Numa primeira fase, foi objecto de estudo a comunidade de copépodes estuarinos, para a qual foram descritos os padrões temporais de abundância e biomassa e obtidas estimativas de produção secundária. Os resultados obtidos neste estudo permitiram concluir que, entre outros aspectos, a abundância e biomassa da comunidade de copépodes da Ria de Aveiro se encontra significativamente correlacionada de modo positivo com a salinidade e com a temperatura da água. As estimativas das taxas de produção secundária derivadas da aplicação de modelos gerais de crescimento mostraram ser algo diferentes, sendo a estimativa dada pelo modelo de Hunthey & Lopez (1992) mais elevada do que a obtida pelo modelo de Hirst & Bunker (2003). O crescimento e desenvolvimento de espécies de Acartia foram estudados sob condições controladas em termos de alimento e temperatura, de forma a serem definidos modelos de crescimento dependentes da temperatura. A partir destes estudos concluiu-se que as populações alopátricas possuem diferentes respostas à temperatura. Além deste aspecto, também se observou que, pelo menos no caso da A.tonsa, as taxas de crescimento das formas juvenis (nauplius e copepoditos) estimadas in situ ou sob condições saturantes de alimento são similares. resumo O forçamento ambiental das populações de Acartia no Canal de Mira foi avaliado através de uma análise de componentes principais (ACP), que permitiu a análise simultânea das alterações espaciais e temporais das diferentes populações. Esta análise identificou três zonas distintas no estuário com base na abundância de Acartia spp.. Para cada zona, análises de correlação com diferentes desfasamentos temporais entre as variáveis ambientais e a abundância de copépodes, permitiram detectar a existência de forçamentos ambientais específicos, assim como um efeito positivo da biomassa fitoplanctónica na abundância do zooplâncton verificada meses mais tarde. Esta tese demonstrou igualmente a grande importância que as populações de Acartia, especialmente a mais abundante – A. tonsa – assumem na transferência de matéria e energia no ambiente planctónico da Ria de Aveiro (Portugal).
Copepods are small fragile and tiny crustaceans that form one of the world’s most abundant groups of metazoan organisms. In estuarine and marine environments copepods assume a key role in what trophic chains are concerned, namely in the transfer of matter and energy from lower trophic levels (phytoplankton) to higher trophic levels (ex. fish larvae). Copepods ecological importance is proven by the high number of quotations in ISI Web of Knowledge (7716 quotations between 1969 and 2006) and in the significance that they still have concerning current studies on estuarine and marine planktonic studies. The main goals of the present thesis were (1) to characterize and to describe the spatialtemporal patterns of abundance, biomass and production of the estuarine copepod community from Ria de Aveiro (Portugal) and its relationship with hydrological data (salinity, temperature, chlorophyll a and rainfall regime); (2) to compare growth and developmental rates of allopatric copepod populations; (3) to define temperature dependent growth models for nauplii and copepodites of Acartia tonsa; (4) to evaluate environmental forcing on the distribution and abundance of Acartia populations; and (5) to estimate potential secondary production rates of Acartia populations. In a first stage estuarine copepods community was studied, time patterns of abundance and biomass having been described and estimates of secondary production having been obtained. Results achieved by this study have led us to the conclusion that, among other aspects, abundance and biomass of the copepods community in Ria de Aveiro is positively correlated with water salinity and temperature. Estimates of secondary production rates deriving from the use of general growth models were different, the estimate obtained by Hunthey & Lopez (1992) model being higher than the one resulting from the Hirst & Bunker (2003) one. In order to define specific temperature-dependent copepod growth models, the growth and development of Acartia species were studied under controlled conditions of food and temperature. From those studies it was concluded that allopatric populations have different temperature responses. Additionally, it was also observed that, at least for A.tonsa, the growth rates of nauplii and copepodites at saturated food conditions and in situ conditions of food are similar. Environmental forcing of Acartia populations in Canal de Mira was evaluated by means of 3-mode PCA, which analyses simultaneously spatial and temporal changes of multispecies assemblages. This analysis identified three distinct zones along the estuary based on Acartia spp. abundance. For each zone time-lagged correlations between environmental variables and copepods abundance indicated that different zones were forced by different combinations of variables and the existence of delayed effects of phytoplanktonic biomass on the abundance of A.tonsa. This thesis also demonstrated the high importance that Acartia populations, in particular the most abundant A.tonsa, assume on the transfer of matter and energy in the planktonic realm of Ria de Aveiro (Portugal).
5
Hall, David. "Tracing selection and adaptation along an environmental gradient in Populus tremula." Doctoral thesis, Umeå : Institutionen för Ekologi, miljö och geovetenskap, Umeå universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30123.
6
Choboter, Paul F. "Forced Rossby waves in a zero absolute vorticity gradient environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ37107.pdf.
7
Öhlund, Gunnar. "Ecological and evolutionary effects of predation in environmental gradients." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-59465.
Abstract:
Understanding species interactions and how they affect densities and distributions of organisms is a central theme in ecological research. Studying such interactions in an ecosystem context is challenging as they often depend on species-specific characteristics and rates that not only change during the ontogeny of an organism, but also are affected by the surrounding environment. This thesis focuses on two separate questions and study systems that highlight different aspects of how effects of predation can depend on environmental conditions. In the first part of the thesis, we studied how temperature affects attack rate and handling time, two ecological rates with profound importance for predator-prey dynamics. Using a metaanalysis, we first show that the currently dominating model for temperature dependence in predator-prey interactions, i.e. the Arrhenius equation, has weak support in available empirical literature. This suggests that we need new rules for how and when we can generalize on the temperature-dependence of intake rates. We then use a simple model and a series of experiments to demonstrate that differences in the relative physiological capacity between predator and prey can impose strong non-linear effects on temperature-response curves of attack rate. In the second part of the thesis, we study the role of predation along a benthic-pelagic habitat gradient in promoting divergence and resource polymorphism among prey. We show that presence of a large piscivorous predator, the northern pike (Esox lucius), induces dwarfs, giants or divergence into both ecotypes in populations of European whitefish (Coregonus lavaretus) depending on lake characteristics. Using dated introductions of whitefish as controlled natural experiments, we show that pike presence induces rapid life history divergence between pelagic and littoral habitat use strategies, and that this divergence can translate into partial reproductive isolation in a matter of decades. Our results demonstrate the potential for thresholds in a crucial ecological rate, setting the stage for tipping points with potentially far reaching implications for effects of warming on predator prey dynamics and ecosystem stability. Moreover, they illustrate the potentially drastic consequences of such tipping points by demonstrating the importance of a single predator species as a driving force behind the creation and maintenance of biodiversity in a natural system.
8
Ghisbain, Pierre. "Application of a gradient-based algorithm to structural optimization." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/47758.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 175-180).
Optimization methods have shown to be efficient at improving structural design, but their use is limited in the engineering practice by the difficulty of adapting state-of-the-art algorithms to particular engineering problems. This study proposes the use of a robust gradient-based algorithm, whose adaptation to a variety of design problems is more straightforward. The algorithm was first applied to truss geometry and beam shape optimization, both forming part of the increasingly popular class of structural form-finding problems. The results showed that the gradient-based method is an appropriate tool for defining shapes in structures. The robustness of the algorithm was verified, as a series of structural configurations were treated with similar efficiency. The gradient-based method was also applied to a more traditional structural design problem through the optimization of a steel girder, resulting in a hybrid scheme featuring a truss stiffener. Throughout the study, emphasis was laid on the practical computer implementation of the gradient-based algorithm in interaction with structural analysis tools.
by Pierre Ghisbain.
S.M.
9
ASSISI, Mario Benedetto. "Wall(les)s, liminal environments between inside and outside." Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488264.
Abstract:
Wall(les)s is a research on architectural unconventional boundaries. Starting from the wall system, the thesis investigates solutions where its thickness becomes a place of relationship between the parts, generating hybrid territories and contents.
The technological development and the obsession for security, comfort and energy performance of buildings, has further extended the contents of the limit, marking a shift from monolithic wall to a more layered and complex configuration. Moreover a huge amount of devices takes part of it and manages the exchange between the inside and the outside: natural and artificial thermal insulation, double and triple air chambers, heat exchangers, controlled mechanical ventilation, biometric and electronic access devices. The evolution and progress behind the constituent components of our buildings did not have the same impact in terms of typology and space organisations.
To rethink the limit as a spatial threshold is to realise that inside and outside are not separable by just one wall or frame, and as such, numerous territorialities, scales, continuity and discontinuity, transparency and opacity in between can be integrated.
An overall reflection on it, as a unifying element can call for a new integration between the parts unveiling unconventional relations between interior and exterior spaces, architecture and technology.Wall(les)s è una ricerca sui limiti architettonici non convenzionali. Attraverso una lettura per sottosistemi, l’obiettivo è di indagare potenzialità nascoste negli intervalli di spazio tra i vari strati che compongono il sistema parete. Essa nel tempo ha assunto vari significati legati alla protezione, la sicurezza e il comfort segnando un passaggio dalla parete monolitica ad una configurazione sempre più stratificata e complessa, dove ogni elemento svolge una funzione specifica pur mantenendo compatto l’insieme. Il paradigma della sostenibilità e dei cambiamenti climatici impone strategie di riduzione dei consumi energetici, spesso esplicitati attraverso miglioramenti della componentistica degli edifici ma senza nessuna conseguenza in termini architettonici e spaziali. Isolamenti termici naturali ed artificiali, doppie e triple camere d’aria, impianti meccani ed elettrici e ventilazione meccanica controllata sono solamente alcuni dei dispositivi che regolano lo scambio tra interno ed esterno. Interrogandosi sulla profondità e la composizione della parete, la ricerca mette in luce idee e interventi capaci di dare spessore agli intervalli di spazio nascosti facendoli diventare luoghi dell’abitare intermedio, ambiguo e indeterminato. La parete intesa come elemento di organizzazione architettonica e spaziale ma allo stesso tempo come dispositivo di gestione climatica potrebbe richiamare a una nuova unione tra architettura e tecnologia, tra spazio e impianto.
10
Owings, Paul C. "High Gradient Magnetic Separation of nanoscale magnetite." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/12020.
Abstract:
Master of ScienceDepartment of Civil Engineering
Alexander P. Mathews
Nanoscale magnetite is being examined for possible uses as an adsorbent of heavy metals and for the enhancement of water treatment processes such as stripping of trichloroethylene (TCE) from contaminated water supplies and wastewaters. Methods for recovering nanoscale magnetite must be developed before the particles can be used in water treatment processes. This is necessary because expelling high amounts of particles into the environment will be unacceptable and costly; if captured they can be reused; additionally, they could potentially cause environmental impacts due to their stability in an aqueous environment and possible toxicity. Nanoscale magnetite is superparamagnetic, so it has a high magnetic susceptibility, and hence it is very attracted to magnetized materials. Utilizing the magnetic properties of magnetite may be one possible means of separating the particles from a treatment process. High Gradient Magnetic Separation (HGMS) has been studied for the separation of micron and even tenths of a micron size particles, but there is little experimental data for HGMS of nanoscale magnetite. This research looks to filter nanoscale magnetite through a HGMS and determine the capture efficiency of the filter. Subsequently, the filter was backwashed to determine particle recover efficiencies. The flow rate was adjusted to determine the dependency of particle capture efficiency on cross sectional velocity through the filter. Additionally, particle loading was changed to better understand the correlation of particle loading with capture efficiency. Filtrations for nanoscale magnetite dispersed with sodium tripolyphosphate were also completed as well as filtrations of nanoscale magnetite coated with silica and magnetite silica composites. Experimental data in this research indicates that magnetite nanoparticles can be captured at 99.8% efficiency or higher in a well-designed filtration system. Capture efficiencies around 99.8% have been found for magnetite. The silica coated magnetite and magnetite silica composites were captured at efficiencies as high as 96.7% and 97.9%, respectively. The capture efficiency of the dispersed magnetite is lower than non-dispersed magnetite and most promising at relatively low fluid flow velocities and particle loadings. The maximum capture efficiency for dispersed magnetite particles was 90.3%. Both magnetite and dispersed magnetite were successfully recovered using backwash at pH of 10 to 11.
Books on the topic "Environmenal gradient":
1
George, Mulamoottil, Warner Barry G, McBean Edward A, and University of Waterloo. Wetlands Research Centre., eds. Wetlands: Environmental gradients, boundaries, and buffers. Boca Raton: CRC, Lewis Publishers, 1996.
2
Heilmayer, Olaf. Environment, adaptation, and evolution: Scallop ecology across the latitudinal gradient = Umwelt, Anpassung und Evolution : Ökologie der Jakobsmuscheln im latitudinalen Gradienten. Bremerhaven: Alfred-Wegener-Institut für Polar- und Meeresforschung, 2004.
3
Davison, William, and Hao Zhang, eds. Diffusive Gradients in Thin-Films for Environmental Measurements. Cambridge: Cambridge University Press, 2016. http://dx.doi.org/10.1017/cbo9781316442654.
4
Zajdlik, B. A. Report on biological toxicity tests using pollution gradient studies - Sydney Harbor. [Ottawa]: Environment Canada, Marine Environment Division, 2000.
5
Mascarenhas, A. C. Poverty, environment, and livelihood along the gradients of the Usambaras in Tanzania. Dar es Salaam: Research on Poverty Alleviation, 2000.
6
Erwin, Beck, ed. Gradients in a tropical mountain ecosystem of Ecuador. Berlin: Springer, 2008.
7
Walker, Larry L. Environmental gradients of potential rangeland vegetation in the interior Pacific Northwest: A chart book. Portland, OR: Bureau of Land Management, Oregon State Office, 1996.
8
Law, R. D. Strain-gauge balance performance and internal temperature gradients measured in a cryogenic environment. London: HMSO, 1992.
9
Monahan, Patricia. Pollution report card: Grading America's school bus fleets. Cambridge, MA: Union of Concerned Scientists, 2002.
10
Edelman-Furstenberg, Yael. Ecological trends across a human-impact organic load gradient along the Mediterranean shore: Benthic macrofaunal evidence. Jerusalem: Geological survey of Israel, 2008.
Book chapters on the topic "Environmenal gradient":
1
Barletta, Mario, and David Valença Dantas. "Environmental Gradients." In Encyclopedia of Estuaries, 237–42. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-8801-4_136.
2
Terlizzi, Antonio, and David R. Schiel. "Patterns Along Environmental Gradients." In Ecological Studies, 101–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/b76710_7.
3
Cirpka, Olaf A. "Intrinsic Remediation in Natural-Gradient Systems." In SERDP/ESTCP Environmental Remediation Technology, 217–38. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-2239-6_9.
4
Takeda, Hiroshi. "Decomposition Processes of Litter Along a Latitudinal Gradient." In Environmental Forest Science, 197–206. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5324-9_20.
5
Raffaelli, David, and Stephen Hawkins. "The shore environment: major gradients." In Intertidal Ecology, 1–35. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-009-1489-6_1.
6
Palmer, Michael W. "Gradient Analysis of Ecological Communities (Ordination)." In Handbook of Environmental and Ecological Statistics, 241–74. Boca Raton : Taylor & Francis, 2018.: Chapman and Hall/CRC, 2019. http://dx.doi.org/10.1201/9781315152509-11.
7
Zoltai, S. C., and D. H. Vitt. "Canadian wetlands: Environmental gradients and classification." In Classification and Inventory of the World’s Wetlands, 131–37. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0427-2_11.
8
New, Tim R. "Insects Along Urban-Rural Gradients." In Insect Conservation and Urban Environments, 33–64. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-21224-1_3.
9
Prenger, F. C., W. F. Stewart, D. D. Hill, L. R. Avens, L. A. Worl, A. Schake, K. J. Aguero, D. D. Padilla, and T. L. Tolt. "High Gradient Magnetic Separation Applied to Environmental Remediation." In Advances in Cryogenic Engineering, 485–91. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2522-6_58.
10
Avens, Larry R., Laura A. Worl, Dennis D. Padilla, F. Coyne Prenger, and Dallas D. Hill. "Use of High Gradient Magnetic Separation for Actinide Applications." In Actinides and the Environment, 467–71. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-0615-5_29.
Conference papers on the topic "Environmenal gradient":
1
Sundararaghavan, Harini G., Gary A. Monteiro, and David I. Shreiber. "Guided Axon Growth by Gradients of Adhesion in Collagen Gels." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-69124.
Abstract:
During development, neurites are directed by gradients of attractive and repulsive soluble (chemotactic) cues and substrate-bound adhesive (haptotactic) cues. Many of these cues have been extensively researched in vitro, and incorporated into strategies for nerve and spinal cord regeneration, primarily to improve the regenerative environment. To enhance and direct growth, we have developed a system to create 1D gradients of adhesion through a 3D collagen gel using microfluidics. We test our system using collagen grafted with bioactive peptide sequences, IKVAV and YIGSR, from laminin — an extra-cellular matrix (ECM) protein known to strongly influence neurite outgrowth. Gradients are established from ∼0.37mg peptide/mg collagen – 0, and ∼0.18 mg peptide/mg collagen – 0 of each peptide and tested using chick dorsal root ganglia (DRG). Neurite growth is evaluated 5 days after gradient formation. Neurites show increased growth in the gradient system when compared to control and biased growth up the gradient of peptides. Growth in YIGSR-grafted collagen increased with steeper gradients, whereas growth in IKVAV-grafted collagen decreased with steeper gradients. These results demonstrate that neurite growth can be enhanced and directed by controlled, immobilized, haptotactic gradients through 3D scaffolds, and suggest that including these gradients in regenerative therapies may accelerate nerve and spinal cord regeneration.
2
Sundararaghavan, Harini G., Gary A. Monteiro, and David I. Shreiber. "Microfluidic Generation of Adhesion Gradients Through 3D Collagen Gels: Implications for Neural Tissue Engineering." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192987.
Abstract:
During development, neurites are directed by gradients of attractive and repulsive soluble (chemotactic) cues and substrate-bound adhesive (haptotactic) cues. Many of these cues have been extensively researched in vitro, and incorporated into strategies for nerve and spinal cord regeneration, primarily to improve the regenerative environment. To enhance and direct growth, we have developed a system to create 1D gradients of adhesion through a 3D collagen gel using microfluidics. We test our system using collagen grafted with bioactive peptide sequences, IKVAV and YIGSR, from laminin — an extra-cellular matrix (ECM) protein known to strongly influence neurite outgrowth [1, 2]. Gradients are established from 0.14 mg/ml–0, and 0.07 mg/ml–0 of each peptide and tested using chick dorsal root ganglia (DRG). Neurite growth is evaluated 5 days after gradient formation. Neurites show increased growth in the gradient system when compared to control and biased growth up the gradient of peptides. These results demonstrate that neurite growth can be enhanced and directed by controlled, immobilized, haptotactic gradients through 3D scaffolds, and suggest that including these gradients in regenerative therapies may accelerate nerve and spinal cord regeneration.
3
Geng, Wenguang, Baoming Chen, Kai Sun, Li Wang, and Fang Liu. "Experimental Study of Natural Convective Heat and Mass Transfer With Cross Diffusion Effects in Closed Cavity." In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18504.
Abstract:
Natural convective heat and mass transfer with Soret effect and Dufour effect is experimental studied in this paper to investigate the diffusion characteristic of volatile organic compounds (VOCs) in multi-physical fields. Firstly, Soret effect (thermal diffusion effect) experiment is conducted. The transfer process of isobutane and nitrogen in two close container connected by a small-diameter pipe is experimental studied. The results show that temperature difference between the two containers would conduct a solute concentration difference. Furthermore, multi-component convective diffusion experiment in a closed cavity which simulate indoor environment is developed under temperature gradient, humidity and propane gas concentration gradients. In this experiment, Temperature, humidity and concentration of propane could be surveyed real-time and do not interfere the natural convection in the closed cavity. The experiment results show that that the temperature gradient and the water vapor concentration gradient have effects on the convective diffusion of VOCs indoor environment. The cross diffusion effects would be taken into consideration for the problem of simultaneous heat and mass transfer especially in the presence of large temperature and concentration gradients.
4
Chen, Baoming, Wenguang Geng, Maocheng Tian, and Fang Liu. "Numerical Study of Natural Convective Diffusion of VOCs With Soret and Dufour Effects in Ternary-Component System." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68679.
Abstract:
The effect of cross diffusion namely Soret effect and Dufour effect on the convective diffusion of volatile organic compounds (VOCs) indoor environment is investigated in this paper. Based on the principle of thermodynamics of irreversible processes, a mathematical model is developed for the ternary component system (VOCs, dry air and water vapor) with compensating thermal and solute gradients, and this mathematical model is solved numerically by commercial CFD (Fluent) code. Profiles of the dimensionless velocity, temperature and concentration are shown graphically with Soret and Dufour coefficients. Furthermore, the cross diffusion effects on the mass transfer induced by two different solute (VOCs and water vapor) concentration gradients is numerical studied. Finally, numerical values of physical quantities, such as the average Nusselt number and Sherwood number are presented. The numerical results show that the temperature gradient and the water vapor concentration gradient have an effect on the convective diffusion of VOCs indoor environment, and the cross diffusion effects would be taken into consideration for the problem of simultaneous heat and mass transfer especially in the presence of large temperature and concentration gradients.
5
Zhu, Dongming, Kang N. Lee, and Robert A. Miller. "Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30632.
Abstract:
Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protections of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.
6
Kim, J. G., C. M. Chun, J. H. Lee, Y. C. Cho, and I. H. Nam. "Remediation of arsenic contaminated soil with high gradient magnetic separation." In ENVIRONMENTAL IMPACT 2016. Southampton UK: WIT Press, 2016. http://dx.doi.org/10.2495/eid160081.
7
Berardi, L., O. Giustolisi, and E. Todini. "Enhanced Global Gradient Algorithm: A General Formulation." In World Environmental and Water Resources Congress 2009. Reston, VA: American Society of Civil Engineers, 2009. http://dx.doi.org/10.1061/41036(342)21.
8
Zhang, Yuandong, Fengxue Gu, and Xiaoling Pan. "Gradient analysis and environmental interpretation of desert-oasis ecotone vegetation in Fukang, Xinjiang." In Third International Asia-Pacific Environmental Remote Sensing Remote Sensing of the Atmosphere, Ocean, Environment, and Space, edited by Xiaoling Pan, Wei Gao, Michael H. Glantz, and Yoshiaki Honda. SPIE, 2003. http://dx.doi.org/10.1117/12.466214.
9
Proctor, Fred, Nashat Ahmad, and George Switzer. "Crosswind Shear Gradient Affect on Wake Vortices." In 3rd AIAA Atmospheric Space Environments Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-3038.
10
Wang, D. X., and L. He. "Adjoint Aerodynamic Design Optimization for Blades in Multi-Stage Turbomachines: Part I—Methodology and Verification." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50208.
Abstract:
The adjoint method for blade design optimization will be described in this two-part paper. The main objective is to develop the capability of carrying out aerodynamic blading shape design optimization in a multi-stage turbomachinery environment. To this end, an adjoint mixing-plane treatment has been proposed. In the first part, the numerical elements pertinent to the present approach will be described. The gradients of a single objective function of a weighted sum of objectives and constraints with respect to detailed blade shape perturbations are obtained very efficiently by the continuous adjoint method. The steepest descent method is used to drive the design to an optimum. The adjoint mixing-plane treatment enables the adjoint equations to be solved in a multi-stage environment. The adjoint solver is verified by comparing gradient results with a direct finite difference method and through a 2D inverse design. The adjoint mixing-plane treatment is verified by comparing gradient results against those by the finite difference method for a 2D compressor stage. The redesign of the 2D compressor stage further demonstrates the validity of the adjoint mixing-plane treatment and the benefit of using it in a multi-bladerow environment.
Reports on the topic "Environmenal gradient":
1
Montalvo-Bartolomei, Axel, Bryant Robbins, Erica Medley, and Benjamin Breland. Backward erosion testing : Magnolia Levee. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/42140.
Abstract:
Using a confined flume device, an experimental study investigated the critical horizontal gradient of soils obtained from a site identified as potentially vulnerable to backward erosion piping (BEP). Tests were conducted on glacial outwash material obtained from a sand and gravel quarry in the vicinity of Magnolia Levee in the community of Magnolia, OH. The two bulk samples collected from the quarry had similar grain-size distributions, grain roundness, and depositional environments as the foundation materials beneath the levee. Samples were prepared at various densities and subjected to gradual increases of flow in a wooden flume with an acrylic top until BEP was observed. The critical average horizontal gradient ranged from 0.21 to 0.30 for a bulk sample with a coefficient of uniformity of 1.6, while tests conducted on a bulk sample with a coefficient of uniformity of 2.5 yielded critical average horizontal gradients of 0.31 to 0.36. The critical average gradients measured during these tests compared favorably to values in the literature after applying adjustments according to Schmertmann’s method.
2
Samach, Alon, Douglas Cook, and Jaime Kigel. Molecular mechanisms of plant reproductive adaptation to aridity gradients. United States Department of Agriculture, January 2008. http://dx.doi.org/10.32747/2008.7696513.bard.
Abstract:
Annual plants have developed a range of different mechanisms to avoid flowering (exposure of reproductive organs to the environment) under adverse environmental conditions. Seasonal environmental events such as gradual changes in day length and temperature affect the timing of transition to flowering in many annual and perennial plants. Research in Arabidopsis and additional species suggest that some environmental signals converge on transcriptional regulation of common floral integrators such as FLOWERING LOCUS T (FT). Here we studied environmental induction of flowering in the model legume Medicago truncatula. Similarly to Arabidopsis, the transition to flowering in M. truncatula is hastened by long photoperiods and long periods of vernalization (4°C for 2-3 weeks). Ecotypes collected in Israel retain a vernalization response even though winter temperatures are way above 4°C. Here we show that this species is also highly responsive (flowers earlier) to mild ambient temperatures up to 19°C simulating winter conditions in its natural habitat. Physiological experiments allowed us to time the transition to flowering due to low temperatures, and to compare it to vernalization. We have made use of natural variation, and induced mutants to identify key genes involved in this process, and we provide here data suggesting that an FT gene in M.truncatula is transcriptionally regulated by different environmental cues. Flowering time was found to be correlated with MtFTA and MtFTB expression levels. Mutation in the MtFTA gene showed a late flowering phenotype, while over-expressing MtFTA in Arabidopsis complemented the ft- phenotype. We found that combination of 4°C and 12°C resulted in a synergistic increase in MtFTB expression, while combining 4°C and long photoperiods caused a synergistic increase in MtFTA expression. These results suggest that the two vernalization temperatures work through distinct mechanisms. The early flowering kalil mutant expressed higher levels of MtFTA and not MtFTB suggesting that the KALIL protein represses MtFTA specifically. The desert ecotype Sde Boker flowers earlier in response to short treatments of 8-12oc vernalization and expresses higher levels of MtFTA. This suggests a possible mechanism this desert ecotype developed to flower as fast as possible and finish its growth cycle before the dry period. MtFTA and FT expression are induced by common environmental cues in each species, and expression is repressed under short days. Replacing FT with the MtFTA gene (including regulatory elements) caused high MtFTA expression and early flowering under short days suggesting that the mechanism used to repress flowering under short days has diversified between the two species.The circadian regulated gene, GIGANTEA (GI) encodes a unique protein in Arabidopsis that is involved in flowering mechanism. In this research we characterized how the expression of the M.truncatula GI ortholog is regulated by light and temperature in comparison to its regulation in Arabidopsis. In Arabidopsis GI was found to be involved in temperature compensation to the clock. In addition, GI was found to be involved in mediating the effect of temperature on flowering time. We tested the influence of cold temperature on the MtGI gene in M.truncatula and found correlation between MtGI levels and extended periods of 12°C treatment. MtGI elevation that was found mostly after plants were removed from the cold influence preceded the induction of MtFT expression. This data suggests that MtGI might be involved in 12°C cold perception with respect to flowering in M.truncatula. GI seems to integrate diverse environmental inputs and translates them to the proper physiological and developmental outputs, acting through several different pathways. These research enabled to correlate between temperature and circadian clock in M.truncatula and achieved a better understanding of the flowering mechanism of this species.
3
Tolman, Deborah. Environmental Gradients, Community Boundaries, and Disturbance the Darlingtonia Fens of Southwestern Oregon. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.3008.
4
Hudson, Austin, Hans Moritz, and Jarod Norton. Sediment mobility, closure depth, and the littoral system – Oregon and Washington coast. Engineer Research and Development Center (U.S.), September 2022. http://dx.doi.org/10.21079/11681/45346.
Abstract:
Forty years ago, the depth of closure concept was introduced to provide a systematic, process-based approach to evaluate seasonal changes in cross-shore profiles and sediment mobility in the nearshore. This study aims to extend that theory by directly considering wave-asymmetry in the nearshore environment. This technical note introduces a methodology to calculate wave induced dispersal of dredged material placed in nearshore sites and summarizes analyses validating the approach using data from the South Jetty Site at the Mouth of the Columbia River. This investigation highlights the notion of a cross-shore gradient in nearshore placement effectiveness of dredged material that can assist project managers plan and execute sustainable sediment management practices at coastal inlets.
5
Aaron Hogan, Aaron Hogan. How do roots vary? An exploration of root functional traits across an environmental gradient in Hainan, China. Experiment, June 2017. http://dx.doi.org/10.18258/9485.
6
Sommer, Stefan, Sascha Flögel, Michael Walter, and Frank Wenzhöfer. Autonomous Robotic Network to Resolve Coastal Oxygen Dynamics : Cruise No. AL547, 20.10. – 31.10.2020, Kiel – Kiel, ARCODYN. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2022. http://dx.doi.org/10.3289/cr_al547.
Abstract:
The ALKOR cruise AL547 represents a concluding milestone of the Helmholtz innovation project ARCHES (Autonomous Robotic Networks to Help Modern Societies). The aim was to implement a heterogeneous robotic sensing network to simultaneously monitor changes in the water column and at the seafloor. The network has been developed by a consortium of partners from AWI, DLR, GEOMAR and the University of Kiel. The participating sensing platforms allow for real-time data transfer and the entire network shall be able to autonomously respond to environmental changes in the ocean. The network comprised seven different mobile and stationary platforms. Tests were conducted at the Mittelgrund working area in the entrance of the Eckernförde Bay (western Baltic Sea). During 47 stations the various sensing platforms were deployed and recovered for maintenance. A total of 87853 messages were sent using hydro-acoustics, of which 71734 messages contained O 2 data, 15177 were status messages, 926 messages were commands to trigger a change of the measurement behavior of a platform and 16 messages represented broadcasts about the environmental status. We synoptically recorded short-term O 2 time series on the different platforms, which were placed along a depth gradient in the working area. As the Eckernförde Bay is known for sporadic fish kills by anoxia we hope to contribute to a better understanding of the O 2 dynamics in coastal areas. - (ALKOR-Berichte ; AL547)
7
Wells, Aaron, Tracy Christopherson, Gerald Frost, Matthew Macander, Susan Ives, Robert McNown, and Erin Johnson. Ecological land survey and soils inventory for Katmai National Park and Preserve, 2016–2017. National Park Service, September 2021. http://dx.doi.org/10.36967/nrr-2287466.
Abstract:
This study was conducted to inventory, classify, and map soils and vegetation within the ecosystems of Katmai National Park and Preserve (KATM) using an ecological land survey (ELS) approach. The ecosystem classes identified in the ELS effort were mapped across the park, using an archive of Geo-graphic Information System (GIS) and Remote Sensing (RS) datasets pertaining to land cover, topography, surficial geology, and glacial history. The description and mapping of the landform-vegetation-soil relationships identified in the ELS work provides tools to support the design and implementation of future field- and RS-based studies, facilitates further analysis and contextualization of existing data, and will help inform natural resource management decisions. We collected information on the geomorphic, topographic, hydrologic, pedologic, and vegetation characteristics of ecosystems using a dataset of 724 field plots, of which 407 were sampled by ABR, Inc.—Environmental Research and Services (ABR) staff in 2016–2017, and 317 were from existing, ancillary datasets. ABR field plots were located along transects that were selected using a gradient-direct sampling scheme (Austin and Heligers 1989) to collect data for the range of ecological conditions present within KATM, and to provide the data needed to interpret ecosystem and soils development. The field plot dataset encompassed all of the major environmental gradients and landscape histories present in KATM. Individual state-factors (e.g., soil pH, slope aspect) and other ecosystem components (e.g., geomorphic unit, vegetation species composition and structure) were measured or categorized using standard classification systems developed for Alaska. We described and analyzed the hierarchical relationships among the ecosystem components to classify 92 Plot Ecotypes (local-scale ecosystems) that best partitioned the variation in soils, vegetation, and disturbance properties observed at the field plots. From the 92 Plot Ecotypes, we developed classifications of Map Ecotypes and Disturbance Landscapes that could be mapped across the park. Additionally, using an existing surficial geology map for KATM, we developed a map of Generalized Soil Texture by aggregating similar surficial geology classes into a reduced set of classes representing the predominant soil textures in each. We then intersected the Ecotype map with the General-ized Soil Texture Map in a GIS and aggregated combinations of Map Ecotypes with similar soils to derive and map Soil Landscapes and Soil Great Groups. The classification of Great Groups captures information on the soil as a whole, as opposed to the subgroup classification which focuses on the properties of specific horizons (Soil Survey Staff 1999). Of the 724 plots included in the Ecotype analysis, sufficient soils data for classifying soil subgroups was available for 467 plots. Soils from 8 orders of soil taxonomy were encountered during the field sampling: Alfisols (<1% of the mapped area), Andisols (3%), Entisols (45%), Gelisols (<1%), Histosols (12%), Inceptisols (22%), Mollisols (<1%), and Spodosols (16%). Within these 8 Soil Orders, field plots corresponded to a total of 74 Soil Subgroups, the most common of which were Typic Cryaquents, Typic Cryorthents, Histic Cryaquepts, Vitrandic Cryorthents, and Typic Cryofluvents.
8
Meghir, Costas, Orazio P. Attanasio, Natalia Varela, Sally Grantham-McGregor, and Marta Rubio-Codina. The Socio-Economic Gradient of Child Development: Cross-Sectional Evidence from Children 6-42 Months In Bogota. Inter-American Development Bank, January 2013. http://dx.doi.org/10.18235/0011641.
Abstract:
We study the socio-economic gradient of child development on a representative sample of low- and middle-income children aged 6-42 months in Bogota, using the Bayley Scales of Infant Development, a high quality test based on direct observation of the child's abilities. We find a statistically significant difference between children in the 90th and 10th percentile of the wealth distribution in our sample of 0.33 standard deviations (SD) in cognition, 0.29 SD in receptive language and 0.38 SD in expressive language at 14 months. The socio-economic gap increases substantially with age to 1 SD (cognition), 0.80 SD (receptive language) and 0.69 SD (expressivelanguage) by 42 months. While the gap persists after controlling for mediating factors such as parental and biomedical characteristics, the level of stimulation in the home, and the quality of the institutional care setting; its size is significantly reduced by variables related to the home environment i.e. parental investments in care quantity and quality. These findings have important implications for the design of well-targeted, effective and timely interventions that promote early childhood development.
9
Schmit, Steve. Cut and capture system technology for demilitarization of underwater munitions. Engineer Research and Development Center (U.S.), April 2024. http://dx.doi.org/10.21079/11681/48376.
Abstract:
Munitions are encountered in a variety of underwater environments as unexploded ordnance (UXO) or munitions and explosives of concern (MEC). These items can cause unacceptable explosive risks to critical infrastructure, recreational divers, and fishermen. The primary goal of the demonstrations was to validate an underwater suite of tools that can be used to render underwater UXO and MEC safe in shallow water (i.e., up to 100 ft). US Navy underwater ranges in the Gulf of Mexico, south of the Naval Support Activity–Panama City, were selected for the first two demonstrations to fully display the integrated system by processing inert munitions, such as the Navy 5 in./38 cal and the Army 105 mm High Explosive (HE) M1 projectile. The third demonstration, however, occurred at the Naval Surface Warfare Center (NSWC), Crane, Lake Glendora Test Facility, in Sullivan, Indiana. Twenty US Army 105 mm HE M1 projectiles filled with TNT were successfully processed. Overall, this project showed that Gradient Technology’s high-pressure waterjet demilitarization technology can be reliably operated underwater at depths less than 100 ft of seawater when the supporting equipment is located on the deck of a vessel or floating pier system.
10
López Bóo, Florencia, Mayaris Cubides Mateus, Rita Sorio, Giorgina Garibotto, and Christian Beron. Measuring the Quality of the Home Environment of Young Children in Uruguay: Socioeconomic Gradients in the HOME inventory. Inter-American Development Bank, October 2018. http://dx.doi.org/10.18235/0001368.