Academic literature on the topic 'Knowledge partitioning and distribution'
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Journal articles on the topic "Knowledge partitioning and distribution"
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Rota, Jadranka, Tobias Malm, Nicolas Chazot, Carlos Peña, and Niklas Wahlberg. "A simple method for data partitioning based on relative evolutionary rates." PeerJ 6 (August 28, 2018): e5498. http://dx.doi.org/10.7717/peerj.5498.
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Background Multiple studies have demonstrated that partitioning of molecular datasets is important in model-based phylogenetic analyses. Commonly, partitioning is done a priori based on some known properties of sequence evolution, e.g. differences in rate of evolution among codon positions of a protein-coding gene. Here we propose a new method for data partitioning based on relative evolutionary rates of the sites in the alignment of the dataset being analysed. The rates are inferred using the previously published Tree Independent Generation of Evolutionary Rates (TIGER), and the partitioning is conducted using our novel python script RatePartitions. We conducted simulations to assess the performance of our new method, and we applied it to eight published multi-locus phylogenetic datasets, representing different taxonomic ranks within the insect order Lepidoptera (butterflies and moths) and one phylogenomic dataset, which included ultra-conserved elements as well as introns. Methods We used TIGER-rates to generate relative evolutionary rates for all sites in the alignments. Then, using RatePartitions, we partitioned the data into partitions based on their relative evolutionary rate. RatePartitions applies a simple formula that ensures a distribution of sites into partitions following the distribution of rates of the characters from the full dataset. This ensures that the invariable sites are placed in a partition with slowly evolving sites, avoiding the pitfalls of previously used methods, such as k-means. Different partitioning strategies were evaluated using BIC scores as calculated by PartitionFinder. Results Simulations did not highlight any misbehaviour of our partitioning approach, even under difficult parameter conditions or missing data. In all eight phylogenetic datasets, partitioning using TIGER-rates and RatePartitions was significantly better as measured by the BIC scores than other partitioning strategies, such as the commonly used partitioning by gene and codon position. We compared the resulting topologies and node support for these eight datasets as well as for the phylogenomic dataset. Discussion We developed a new method of partitioning phylogenetic datasets without using any prior knowledge (e.g. DNA sequence evolution). This method is entirely based on the properties of the data being analysed and can be applied to DNA sequences (protein-coding, introns, ultra-conserved elements), protein sequences, as well as morphological characters. A likely explanation for why our method performs better than other tested partitioning strategies is that it accounts for the heterogeneity in the data to a much greater extent than when data are simply subdivided based on prior knowledge.
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Tahmoresnezhad, Jafar, and Sattar Hashemi. "An Efficient yet Effective Random Partitioning and Feature Weighting Approach for Transfer Learning." International Journal of Pattern Recognition and Artificial Intelligence 30, no. 02 (February 2016): 1651003. http://dx.doi.org/10.1142/s0218001416510034.
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One of the serious challenges in machine learning and pattern recognition is to transfer knowledge from related but different domains to a new unlabeled domain. Feature selection with maximum mean discrepancy (f-MMD) is a novel and effective approach to transfer knowledge from source domain (training set) into target domain (test set) where training and test sets are drawn from different distributions. However, f-MMD has serious challenges in facing datasets with large number of samples and features. Moreover, f-MMD ignores the feature-label relation in finding the reduced representation of dataset. In this paper, we exploit jointly transfer learning and class discrimination to cope with domain shift problem on which the distribution difference is considerably large. We therefore put forward a novel transfer learning and class discrimination approach, referred to as RandOm k-samplesets feature Weighting Approach (ROWA). Specifically, ROWA reduces the distribution difference across domains in an unsupervised manner where no label is available in the test set. Moreover, ROWA exploits feature-label relation to separate various classes alongside the domain transfer, and augments the relation of selected features and source domain labels. In this work, we employ disjoint/overlapping small-sized samplesets to iteratively converge to final solution. Employment of local sets along with a novel optimization problem constructs a robust and effective reduced representation for adaptation across domains. Extensive experiments on real and synthetic datasets verify that ROWA can significantly outperform state-of-the-art transfer learning approaches.
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Irles, Claudine, Joel Arias-Martinez, José Guzmán-Bárcenas, and Alicia Ortega. "Plasma membrane subdomain partitioning of Lck in primary human T lymphocytes." Canadian Journal of Physiology and Pharmacology 88, no. 4 (April 2010): 487–96. http://dx.doi.org/10.1139/y09-125.
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Uncovering the plasma membrane distribution of tyrosine kinase Lck is crucial to understanding T lymphocyte triggering. Several studies of Lck species partitioning have given contradictory results. We decided to re-address this point by using phospho-specific antibodies to characterize active and inactive Lck partitioning in raft and non-raft membranes from primary human peripheral blood T lymphocytes. We show that most inactive Lck was localized in rafts and was associated with nearly all CD4 coreceptors and its negative regulator Csk in resting cells, while T cell receptor (TCR) engagement promoted a sustained dephosphorylation of inactive Lck. In contrast, active Lck had a more discrete distribution interacting with only a small number of CD4 coreceptors, and the kinase showed a rapid and short phosphorylation after TCR triggering. The differences in distribution and kinetics may be related to T lymphocyte signalling threshold modulation by Lck species and suggest how TCR triggering is first initiated. This study furthers our knowledge of the TCR activation model in primary human T lymphocytes.
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Shaikh, M. Bilal, M. Abdul Rehman, and Attaullah Sahito. "Optimizing Distributed Machine Learning for Large Scale EEG Data Set." Sukkur IBA Journal of Computing and Mathematical Sciences 1, no. 1 (June 30, 2017): 114. http://dx.doi.org/10.30537/sjcms.v1i1.14.
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Distributed Machine Learning (DML) has gained its importance more than ever in this era of Big Data. There are a lot of challenges to scale machine learning techniques on distributed platforms. When it comes to scalability, improving the processor technology for high level computation of data is at its limit, however increasing machine nodes and distributing data along with computation looks as a viable solution. Different frameworks and platforms are available to solve DML problems. These platforms provide automated random data distribution of datasets which miss the power of user defined intelligent data partitioning based on domain knowledge. We have conducted an empirical study which uses an EEG Data Set collected through P300 Speller component of an ERP (Event Related Potential) which is widely used in BCI problems; it helps in translating the intention of subject w h i l e performing any cognitive task. EEG data contains noise due to waves generated by other activities in the brain which contaminates true P300Speller. Use of Machine Learning techniques could help in detecting errors made by P300 Speller. We are solving this classification problem by partitioning data into different chunks and preparing distributed models using Elastic CV Classifier. To present a case of optimizing distributed machine learning, we propose an intelligent user defined data partitioning approach that could impact on the accuracy of distributed machine learners on average. Our results show better average AUC as compared to average AUC obtained after applying random data partitioning which gives no control to user over data partitioning. It improves the average accuracy of distributed learner due to the domain specific intelligent partitioning by the user. Our customized approach achieves 0.66 AUC on individual sessions and 0.75 AUC on mixed sessions, whereas random / uncontrolled data distribution records 0.63 AUC.
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Schapendonk, Ad H. C. M., Oijen, Sander C. Pot, Riki Van den Boogaard, and Jeremy Harbinson. "Nitrogen Shortage in a Tomato Crop; Scaling up from Effects on Electron-Transport Rate to Plant Productivity." Zeitschrift für Naturforschung C 54, no. 9-10 (October 1, 1999): 840–48. http://dx.doi.org/10.1515/znc-1999-9-1034.
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Optimization of nitrogen supply in a tomato plant is stepwise assessed, from chloroplast characteristics to whole crop performance. Experiments are reported in which important key processes are quantified in relation to the nitrogen content of leaves. Interactions of N effects with leaf aging and canopy light distribution are analyzed. A simulation model that integrates this knowledge is constructed. The results of three nitrogen partitioning scenarios for Rubisco suggest that optimization of the distribution of Rubisco between leaf layers is less important for plant productivity than within-leaf optimization of the photosynthetic apparatus
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Sirbiladze, Gia, Bidzina Matsaberidze, Bezhan Ghvaberidze, Bidzina Midodashvili, and David Mikadze. "Fuzzy TOPSIS based selection index in the planning of emergency service facilities locations and goods transportation." Journal of Intelligent & Fuzzy Systems 41, no. 1 (August 11, 2021): 1949–62. http://dx.doi.org/10.3233/jifs-210636.
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The attributes influencing the decision-making process in planning transportation of goods from selected facilities locations in disaster zones are considered. Experts evaluate each candidate for humanitarian aid distribution centers (HADCs) (service centers) against each uncertainty factor in q-rung orthopair fuzzy sets (q-ROFS). For representation of experts’ knowledge in the input data for planning emergency service facilities locations a q-rung orthopair fuzzy TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) approach is developed. Based on the offered fuzzy TOPSIS aggregation a new innovative objective function is introduced which maximizes a candidate HADC’s selection index and reduces HADCs opening risks in disaster zones. The HADCs location and goods transportation problem is reduced to the bi-criteria problem of partitioning the set of customers by the set of service centers: 1) Minimization of opened HADCs and goods transportation total costs; 2) Maximization of HADCs selection index. Partitioning type transportation constraints are also constructed. Our approach for solving the constructed bi-criteria partitioning problem consists of two phases. In the first phase, based on the covering’s matrix, we generate a new matrix with columns allowing to find all possible partitioning of the demand points with the opened HADCs. In the second phase, using the generated matrix and our exact algorithm we find the partitioning –allocations of the HADCs to the centers corresponded to the Pareto-optimal solutions. The constructed model is illustrated with a numerical example.
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Hu, Jingcheng, Zhongming Chen, Xuan Qin, and Ping Dong. "Reversible and irreversible gas–particle partitioning of dicarbonyl compounds observed in the real atmosphere." Atmospheric Chemistry and Physics 22, no. 10 (May 31, 2022): 6971–87. http://dx.doi.org/10.5194/acp-22-6971-2022.
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Abstract. Glyoxal and methylglyoxal are vital carbonyl compounds in the atmosphere and play substantial roles in radical cycling and ozone formation. The partitioning process of glyoxal and methylglyoxal between the gas and particle phases via reversible and irreversible pathways could efficiently contribute to secondary organic aerosol (SOA) formation. However, the relative importance of two partitioning pathways still remains elusive, especially in the real atmosphere. In this study, we launched five field observations in different seasons and simultaneously measured glyoxal and methylglyoxal in the gas and particle phases. The field-measured gas–particle partitioning coefficients were 5–7 magnitudes higher than the theoretical ones, indicating the significant roles of reversible and irreversible pathways in the partitioning process. The particulate concentration of dicarbonyls and product distribution via the two pathways were further investigated using a box model coupled with the corresponding kinetic mechanisms. We recommended the irreversible reactive uptake coefficient γ for glyoxal and methylglyoxal in different seasons in the real atmosphere, and the average value of 8.0×10-3 for glyoxal and 2.0×10-3 for methylglyoxal best represented the loss of gaseous dicarbonyls by irreversible gas–particle partitioning processes. Compared to the reversible pathways, the irreversible pathways played a dominant role, with a proportion of more than 90 % in the gas–particle partitioning process in the real atmosphere, and the proportion was significantly influenced by relative humidity and inorganic components in aerosols. However, the reversible pathways were also substantial, especially in winter, with a proportion of more than 10 %. The partitioning processes of dicarbonyls in reversible and irreversible pathways jointly contributed to more than 25 % of SOA formation in the real atmosphere. To our knowledge, this study is the first to systemically examine both reversible and irreversible pathways in the ambient atmosphere, strives to narrow the gap between model simulations and field-measured gas–particle partitioning coefficients, and reveals the importance of gas–particle processes for dicarbonyls in SOA formation.
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Grard, Aline, and Jean-François Deliège. "Characterizing Trace Metal Contamination and Partitioning in the Rivers and Sediments of Western Europe Watersheds." Hydrology 10, no. 2 (February 16, 2023): 51. http://dx.doi.org/10.3390/hydrology10020051.
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Adsorption and desorption processes occurring on suspended and bed sediments were studied in two datasets from western Europe watersheds (Meuse and Mosel). Copper and zinc dissolved and total concentrations, total suspended sediment concentrations, mass concentrations, and grain sizes were analyzed. Four classes of mineral particle size were determined. Grain size distribution had to be considered in order to assess the trace metal particulate phase in the water column. The partitioning coefficients of trace metals between the dissolved and particulate phases were calculated. The objective of this study was to improve the description of the processes involved in the transportation and fate of trace metals in river aquatic ecosystems. Useful data for future modelling, management and contamination assessment of river sediments were provided. As it is confirmed by a literature review, the copper and zinc partitioning coefficients calculated in this study are reliable. The knowledge related to copper and zinc (e.g., partitioning coefficients) will allow us to begin investigations into environmental modelling. This modelling will allow us to consider new sorption processes and better describe trace metal and sediment fates as well as pressure–impact relationships.
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Zhu, Zichen, Xiao Hu, and Manos Athanassoulis. "NOCAP: Near-Optimal Correlation-Aware Partitioning Joins." Proceedings of the ACM on Management of Data 1, no. 4 (December 8, 2023): 1–27. http://dx.doi.org/10.1145/3626739.
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Storage-based joins are still commonly used today because the memory budget does not always scale with the data size. One of the many join algorithms developed that has been widely deployed and proven to be efficient is the Hybrid Hash Join (HHJ), which is designed to exploit any available memory to maximize the data that is joined directly in memory. However, HHJ cannot fully exploit detailed knowledge of the join attribute correlation distribution. In this paper, we show that given a correlation skew in the join attributes, HHJ partitions data in a suboptimal way. To do that, we derive the optimal partitioning using a new cost-based analysis of partitioning-based joins that is tailored for primary key - foreign key (PK-FK) joins, one of the most common join types. This optimal partitioning strategy has a high memory cost, thus, we further derive an approximate algorithm that has tunable memory cost and leads to near-optimal results. Our algorithm, termed NOCAP (Near-Optimal Correlation-Aware Partitioning) join, outperforms the state of the art for skewed correlations by up to 30%, and the textbook Grace Hash Join by up to 4×. Further, for a limited memory budget, NOCAP outperforms HHJ by up to 10%, even for uniform correlation. Overall, NOCAP dominates state-of-the-art algorithms and mimics the best algorithm for a memory budget varying from below √||relation|| to more than ||relation||.
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Calliari, Danilo, Guillermo Cervetto, Rafael Castiglioni, and Laura Rodríguez. "Salinity preferences and habitat partitioning between dominant mysids at the Río de la Plata estuary (Uruguay)." Journal of the Marine Biological Association of the United Kingdom 87, no. 2 (April 2007): 501–6. http://dx.doi.org/10.1017/s0025315407055038.
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Mysids are common and abundant organisms in estuaries and coastal waters, where they have a central role in the functioning of food webs. The Río de la Plata (RdlP) is a major estuary that affects biogeographic patterns of marine coastal organisms in the south-west Atlantic, but studies of the plankton in the RdlP are scarce. Knowledge of the mysid fauna in particular is very limited with a single species (likely alien, Neomysis americana), traditionally known to inhabit this 38,000 km2 estuary, and a second one, Mysidopsis tortonesei, only recently reported. The purpose of this paper is to contribute with the knowledge of the mysid fauna of this ecosystem by exploring the spatial distribution and in situ salinity preferences of N. americana and M. tortonesei in the mixohaline region of the RdlP during austral autumn, 2001. Both species showed clear and contrasting haline affinities that resulted in an almost perfect spatial segregation within the study area. Neomysis americana occurred preferentially in oligo- and meso-haline conditions (range <1 to 33.37, but most abundant at salinities <28), while M. tortonesei occurred at salinities >28. Temperature range was quite narrow and it was unlikely that it affected mysid distribution in the estuary. Temporal variability in observed patterns, as well as the role of biological interactions in shaping spatial distribution of N. americana and M. tortonesei within the estuary are subjects that deserve further attention in future studies.
Dissertations / Theses on the topic "Knowledge partitioning and distribution"
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De, Oliveira Joffrey. "Gestion de graphes de connaissances dans l'informatique en périphérie : gestion de flux, autonomie et adaptabilité." Electronic Thesis or Diss., Université Gustave Eiffel, 2023. http://www.theses.fr/2023UEFL2069.
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Les travaux de recherche menés dans le cadre de cette thèse de doctorat se situent à l'interface du Web sémantique, des bases de données et de l'informatique en périphérie (généralement dénotée Edge computing). En effet, notre objectif est de concevoir, développer et évaluer un système de gestion de bases de données (SGBD) basé sur le modèle de données Resource Description Framework (RDF) du W3C, qui doit être adapté aux terminaux que l'on trouve dans l'informatique périphérique. Les applications possibles d'un tel système sont nombreuses et couvrent un large éventail de secteurs tels que l'industrie, la finance et la médecine, pour n'en citer que quelques-uns. Pour preuve, le sujet de cette thèse a été défini avec l'équipe du laboratoire d'informatique et d'intelligence artificielle (CSAI) du ENGIE Lab CRIGEN. Ce dernier est le centre de recherche et de développement d'ENGIE dédié aux gaz verts (hydrogène, biogaz et gaz liquéfiés), aux nouveaux usages de l'énergie dans les villes et les bâtiments, à l'industrie et aux technologies émergentes (numérique et intelligence artificielle, drones et robots, nanotechnologies et capteurs). Le CSAI a financé cette thèse dans le cadre d'une collaboration de type CIFRE. Les fonctionnalités d'un système satisfaisant ces caractéristiques doivent permettre de détecter de manière pertinente et efficace des anomalies et des situations exceptionnelles depuis des mesures provenant de capteurs et/ou actuateurs. Dans un contexte industriel, cela peut correspondre à la détection de mesures, par exemple de pression ou de débit sur un réseau de distribution de gaz, trop élevées qui pourraient potentiellement compromettre des infrastructures ou même la sécurité des individus. Le mode opératoire de cette détection doit se faire au travers d'une approche conviviale pour permettre au plus grand nombre d'utilisateurs, y compris les non-programmeurs, de décrire les situations à risque. L'approche doit donc être déclarative, et non procédurale, et doit donc s'appuyer sur un langage de requêtes, par exemple SPARQL. Nous estimons que l'apport des technologies du Web sémantique peut être prépondérant dans un tel contexte. En effet, la capacité à inférer des conséquences implicites depuis des données et connaissances explicites constitue un moyen de créer de nouveaux services qui se distinguent par leur aptitude à s'ajuster aux circonstances rencontrées et à prendre des décisions de manière autonome. Cela peut se traduire par la génération de nouvelles requêtes dans certaines situations alarmantes ou bien en définissant un sous-graphe minimal de connaissances dont une instance de notre SGBD a besoin pour répondre à l'ensemble de ses requêtes. La conception d'un tel SGBD doit également prendre en compte les contraintes inhérentes de l'informatique en périphérie, c'est-à-dire les limites en terme de capacité de calcul, de stockage, de bande passante et parfois énergétique (lorsque le terminal est alimenté par un panneau solaire ou bien une batterie). Il convient donc de faire des choix architecturaux et technologiques satisfaisant ces limitations. Concernant la représentation des données et connaissances, notre choix de conception s'est porté sur les structures de données succinctes (SDS) qui offrent, entre autres, les avantages d'être très compactes et ne nécessitant pas de décompression lors du requêtage. De même, il a été nécessaire d'intégrer la gestion de flux de données au sein de notre SGBD, par exemple avec le support du fenêtrage dans des requêtes SPARQL continues, et des différents services supportés par notre système. Enfin, la détection d'anomalies étant un domaine où les connaissances peuvent évoluer, nous avons intégré le support des modifications au niveau des graphes de connaissances stockés sur les instances des clients de notre SGBD. Ce support se traduit par une extension de certaines structures SDS utilisées dans notre prototypeThe research work carried out as part of this PhD thesis lies at the interface between the Semantic Web, databases and edge computing. Indeed, our objective is to design, develop and evaluate a database management system (DBMS) based on the W3C Resource Description Framework (RDF) data model, which must be adapted to the terminals found in Edge computing.The possible applications of such a system are numerous and cover a wide range of sectors such as industry, finance and medicine, to name but a few. As proof of this, the subject of this thesis was defined with the team from the Computer Science and Artificial Intelligence Laboratory (CSAI) at ENGIE Lab CRIGEN. The latter is ENGIE's research and development centre dedicated to green gases (hydrogen, biogas and liquefied gases), new uses of energy in cities and buildings, industry and emerging technologies (digital and artificial intelligence, drones and robots, nanotechnologies and sensors). CSAI financed this thesis as part of a CIFRE-type collaboration.The functionalities of a system satisfying these characteristics must enable anomalies and exceptional situations to be detected in a relevant and effective way from measurements taken by sensors and/or actuators. In an industrial context, this could mean detecting excessively high measurements, for example of pressure or flow rate in a gas distribution network, which could potentially compromise infrastructure or even the safety of individuals. This detection must be carried out using a user-friendly approach to enable as many users as possible, including non-programmers, to describe risk situations. The approach must therefore be declarative, not procedural, and must be based on a query language, such as SPARQL.We believe that Semantic Web technologies can make a major contribution in this context. Indeed, the ability to infer implicit consequences from explicit data and knowledge is a means of creating new services that are distinguished by their ability to adjust to the circumstances encountered and to make autonomous decisions. This can be achieved by generating new queries in certain alarming situations, or by defining a minimal sub-graph of knowledge that an instance of our DBMS needs in order to respond to all of its queries.The design of such a DBMS must also take into account the inherent constraints of Edge computing, i.e. the limits in terms of computing capacity, storage, bandwidth and sometimes energy (when the terminal is powered by a solar panel or a battery). Architectural and technological choices must therefore be made to meet these limitations. With regard to the representation of data and knowledge, our design choice fell on succinct data structures (SDS), which offer, among other advantages, the fact that they are very compact and do not require decompression during querying. Similarly, it was necessary to integrate data flow management within our DBMS, for example with support for windowing in continuous SPARQL queries, and for the various services supported by our system. Finally, as anomaly detection is an area where knowledge can evolve, we have integrated support for modifications to the knowledge graphs stored on the client instances of our DBMS. This support translates into an extension of certain SDS structures used in our prototype
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Yang, Lee-Xieng. "Knowledge partitioning in categorization." University of Western Australia. School of Psychology, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0016.
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Schilhard, Petra. "Distribution of IMUNES System graph partitioning." Saarbrücken VDM Verlag Dr. Müller, 2008. http://d-nb.info/98890893X/04.
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Kaviani, Nima. "Partitioning and distribution of web applications to the hybrid cloud." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50017.
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Hybrid cloud deployment is an effective strategy in deploying software services
across public cloud and private infrastructure. It allows deployed software
systems to benefit from cost savings and scalability offerings of the
cloud while keeping control over privacy- or security-sensitive code and data
entities. However, the complexity of determining which code and data entities
should reside on-premises, and which can be migrated to the cloud
is daunting. Researchers have attempted to address this complexity by using
partitioning algorithms to optimize distribution and deployment of code
entities across public cloud and private infrastructure. However, we have
identified the following shortfalls with the existing research work:
Current research does not provide enough flexibility in placement of
software function execution and data entities between public/private
hosts. In particular it does not allow for replication or optimized
separation of code and data entities in relation to one another.
Current research on partitioning of software systems does not explicitly
consider the dynamics of a hybrid cloud deployment when making
decisions about public cloud and private infrastructure. Particularly,
current research lacks support for making explicit tradeoff s between
monetary cost and improved performance in hybrid cloud software
systems. The dynamics of the cloud require partitioning algorithms to be tailored towards features inherent to a hybrid cloud deployment. This includes
encoding data dependency models and component dependency
models of a software system collectively into one unique mathematical
optimization model. There is no existing algorithm that allows
for combined code and data dependency requirements to be modelled
under one optimization formula. This thesis presents my work on implementing algorithms and tools that address the shortcomings of the previous research as discussed above. These algorithms and tools are put together under a partitioning and distribution framework named Manticore. Manticore has been used to drive partitioning and deployment decisions on several open source software systems. The experiment results show an estimate of up to 54% reduction in monetary costs compared to a premises only deployment and 56% improvement in performance compared to a na ive separation of code entities from data entities in a hybrid cloud deployment.Science, Faculty of
Computer Science, Department of
Graduate
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MacLeod, Colin D. "Niche partitioning, distribution and competition in North Atlantic beaked whales." Thesis, Aberdeen : University of Aberdeen, 2005. http://www.marineconnection.org/docs/MacLeod_PhD_Thesis.pdf.
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Vicente, de Bobes Joana. "Distribution and partitioning of organic pollutants and effects in coastal birds." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134824.
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Coastal areas are very susceptible to contamination due to the interaction of marine and anthropogenic processes.
Persistent Organic Pollutants (POPs) are organic compounds very resistent to photolysis and chemical and biological degradation. According to its physicochemical characteristics, POPs are worldwide distributed. These contaminants tend to bioaccumulate through the food webs, so that predators are more sensitive to this contamination. Seabirds are highly exposed to organic pollutants due to their feeding habits and its relatively long life.
In this thesis, it has been studied the accumulation of various families of organic pollutants in two species of gulls breeding in the Iberian Peninsula, the yellow-legged gull (Larus michahellis) and Audouin's gull (L. audouinii). Yellow-legged gull is a large gull very common in the Iberian Peninsula. It is an omnivorous and opportunistic species. Audouin's gull is endemic of the Mediterranean region. Few years ago it was endangered but the great population growth made to be considered now as "nearly threatened" species. It is a piscivorous species but it is increasingly exploiting more fishery discards and continental preys.
In the first study there are determined 6 families of organic pollutants considered by the Stockholm Convention (PCDD/Fs, PBDEs, PCBs, OCs, PFASs and SCCP) in eggs of the two gull species from the Ebro Delta Natural Park. In the following studies, the analyses are based on the study of PFASs in eggs and blood of both gull species and from different colonies of the Iberian Peninsula (Ebro Delta, Medes Islands, Columbretes Islands, Dragonera Island, Grosa Island, Chafarinas Islands, Atlantic Islands of Galicia and Berlengas Islands).
From PFASs levels found in the different matrices the effect of these pollutants on physical (biometric parameters of egg, shell thickness and desiccation index) and hormonal level (through the analysis of the steroid hormones: testosterone and 17ß-estradiol) is studied. It is also assessed the accumulation of these pollutants from the diet of both species (analyzing their own food and through the study of the stable isotopes d13C and d15N, as dietary tracers) and it is estimated the PFASs depuration in blood and its transfer from females to eggs.
The results indicate that organic pollutants are present in the populations of yellow-legged and Audouin's gull breeding in the Iberian Peninsula colonies, being OCs and PCBs the families of compounds with higher concentrations. Among PFASs, the main compound detected in all samples was PFOS. The transfer of organic contaminants from mother to offspring is demonstrated with the levels found in eggs of both species. Analysis of PFASs in blood of males and females shows that females discharge a fraction of the compounds accumulated to the eggs, thus females had lower blood PFASs levels than males. However, the study of hormonal level allows the comparison between the levels in both gull species and with other
studies and to discuss the influence of the different diet. The analysis of PFASs in albumen and egg suggests that these compounds have more affinity for egg-yolk lipids because they are not detected in albumen. The decreasing concentration of PFOS along the egg sequence shows that females PFOS transfer is higher in the first egg but there is also a good correlation between the levels of PFOS among the 3 eggs from the same clutch. The higher concentrations of some PFASs in 3rd eggs (c), comparing with 1st (a) and 2nd (b), and the differences in d13C values between the a-b and b-c eggs are attributed to the "mother effect".
This thesis permits increase the knowledge about the accumulation of POPs in yellow-legged and Audouin's gull from the Iberian Peninsula, to evaluate the differences between the two species and determine the geographical distribution of POPs using eggs as a biomarker of environmental contamination and to study the processes of accumulation and transfer of PFASLes zones costaneres són unes àrees molt sensibles a la contaminació degut a la interacció entre els processos marins i antropogènics. Els emissaris submarins, les desembocadures dels rius, les activitats portuàries, l’abocament de residus, l’aqüicultura, etc. Són algunes de les activitats que poden produir la contaminació de les zones costaneres. Entre d’altres tipus de contaminants, es troben els contaminants orgànics persistents (COPs), aquells compostos orgànics que, en diferent grau, presenten resistència a la fotòlisis, la degradació química i la biològica. Degut a les seves característiques fisico-químiques, els COPs estan distribuïts per tot el món, podent trobar-se fins i tot en zones prístines molt allunyades de la seva font d’emissió original. Aquests contaminants tendeixen a bioacumular-se al llarg de les cadenes tròfiques, de manera que els grans depredadors són més sensibles a aquesta contaminació. Les aus marines estan molt exposades als contaminants orgànics degut als seus hàbits alimentaris i a la seva esperança de vida relativament llarga. En aquesta tesi s’ha estudiat l’acumulació de vàries famílies de contaminants orgànics en dues espècies de gavina de la Península Ibèrica, el gavià argentat (Larus michahellis) i la gavina corsa (L. audouinii). El gavià argentat és una gavina de grans dimensions molt comuna a la Península Ibèrica. És una espècie omnívora i oportunista. S’alimenta tant de recursos marins, com terrestres, com depredant sobre altres aus i també freqüenta abocadors i descarts pesquers. La gavina corsa és una gavina de dimensions mitjanes, endèmica de la regió mediterrània. Fa uns anys estava en situació de risc però el fort creixement poblacional de les últimes dècades l’ha deixat fora de perill sent considerada actualment a nivell internacional com a “quasi amenaçada”. És una espècie piscívora però cada vegada explota més descarts pesquers. En el primer estudi s’analitzen 6 famílies de contaminants orgànics inclosos o sota consideració pel Conveni d’Estocolm (els PCDD/Fs, PBDEs, PCBs, OCs, PFASs i SCCPs) en els ous de les dues espècies de gavina de les respectives colònies del Parc Natural del Delta de l’Ebre. A partir d’aquí els següents treballs es basen en l’estudi de la família dels PFASs en sang i ous d’ambdues espècies i pertanyents a diferents colònies de la Península Ibèrica (Delta de l’Ebre, Illes Medes, Illes Columbretes, Illa de Sa Dragonera, Illa Grosa, Illes Chafarinas, Illes Atlàntiques de Galicia i Ilhas Berlengas), totes en zones d’alt interès ecològic i sota alguna protecció ambiental (parcs naturals, nacionals, reserves marines, reserva de la biosfera, etc.). A partir dels nivells de PFASs trobats en les diferents matrius (primers ous de la posta, clara i rovell d’ou dels 3 ous de la posta i sang d’exemplars adults) s’estudia l’efecte d’aquests contaminants a nivell físic (paràmetres biomètrics de l’ou, gruix de la closca i índex de dessecació) i hormonal (via l’anàlisi de les hormones esteroidees 17β-estadiol i testosterona). S’estudia també l’acumulació d’aquests contaminants a partir de la dieta (analitzant el seu propi aliment i a partir de l’estudi dels isòtops estables de carboni i nitrogen (δ13C i δ15N), indicadors del règim alimentari) i es fa una estima de la depuració dels PFASs en sang i de la seva transferència de femelles a ous. Els resultats indiquen que els contaminants orgànics són presents en les poblacions de gavià argentat i gavina corsa de la Península Ibèrica, sent els OCs i els PCBs les famílies de compostos amb concentracions més elevades. Entre els PFASs, el compost majoritari és el PFOS. La transferència de contaminants orgànics de mares a cries queda demostrada amb els nivells trobats en els ous d’ambdues espècies. De l’anàlisi de PFASs en sang de mascles i femelles de les dues espècies de gavina s’observa que les femelles descarreguen part dels compostos acumulats als ous presentant així nivells en sang inferior que els mascles. No es troba cap relació entre els nivells de PFASs i els paràmetres biomètrics, com tampoc amb els nivells d’esteroides. Tanmateix, l’estudi de les hormones permet comparar els nivells en ambdues espècies amb altres estudis i discutir la influència de la dieta. L’anàlisi de PFASs en clara i rovell d’ou per separat dels 3 ous de les postes de gavina corsa demostren que aquests compostos tenen més afinitat pels lípids del rovell ja que no es detecten en les clares. La concentració decreixent de PFOS al llarg de la seqüència de posta demostra que les femelles descarreguen la majoria de contaminant en el primer ou però que existeix una bona correlació dels nivells de PFOS entre els 3 ous d’un mateix niu. L’augment de les concentracions d’alguns PFASs en el 3r ou i les diferències en els valors de δ13C entre el 1r-3r i 2n-3r ou s’atribueixen a l’anomenat “efecte mare” (possible ús de reserves endògenes per a la formació de l’últim ou enlloc de l’energia aportada per la dieta prèvia a la posta). Aquesta tesi permet augmentar el coneixement sobre l’acumulació de COPs en el gavià argentat i la gavina corsa de la Península Ibèrica, avaluar les diferències entre ambdues espècies i associar-ho a la seva biologia, determinar la distribució geogràfica de COPs utilitzant els ous com a bioindicador de contaminació ambiental i estudiar els processos d’acumulació i transferència de PFASs.
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Sundström, Maria. "Radiosynthesis of Perfluoroalkyl Substances : Chemical analysis, uptake, distribution, and partitioning studies." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-81061.
Full textAbstract:
Perfluoroalkyl substances (PFASs) are widely utilized manmade chemicals. Their properties have made them highly appreciated in a variety of industrial and consumer product applications, including fire-fighting foams, hydraulic fluids, as well as in cookware and food contact papers. However, some of the PFASs are highly persistent in the environment and their toxicological profiles are of concern. Voluntary and regulatory efforts have been taken to reduce the environmental levels of PFASs. These actions have resulted in a reduction of PFASs in human milk from Stockholm as presented in this thesis. The radiosyntheses of 35S-PFOS, 35S-PFBS, and 14C-PFOA presented herein were applied for distribution studies in mice but also for solubility and adhesion experiments of common laboratory solvents and buffers. The radiosynthesis employed reactive Grignard reagents, perfluoroalkyliodides, and 35S-sulfur dioxide or 14C-carbon dioxide. The distribution studies were performed with 35S-PFOS on both pregnant mice and their offspring as well as on male mice. The mice were subjected to whole-body autoradiography and the tissues were analyzed by liquid scintillation counting. Liver and lungs were the target organs for 35S-PFOS in the dams. The fetuses and pups had remarkable high levels of 35S-PFOS in their lungs as well as in the brain. The male mice were given a high dose and a more environmental relevant dose of 35S-PFOS. PFOS was transferred from the blood to the tissues as the dose increased. In another study the distribution pattern of the shorter homologue PFBS was compared to PFOS. 35S-PFBS was utilized and demonstrated a 5-40 fold lower tissue levels in comparison to PFOS. The pharmacokinetic parameters determined for PFHxS in mice, rats, and monkeys will provide valuable insight in establishing a proper risk assessment for this compound. The study confirms the common species differences in serum elimination half-life that are associated with PFASs.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Manuscript.
8
Burton, Edward D., and n/a. "Distribution and Partitioning of Trace Metals and Tributyltin in Estuarine Sediments." Griffith University. School of Environmental Engineering, 2005. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050830.161359.
Full textAbstract:
An improved understanding of the geochemical partitioning of trace metals and tributyltin (TBT) in sediments is of great importance in risk assessment and remedial investigation. The aim of this thesis was to examine the distribution and partitioning behaviour of trace metals and TBT in benthic, estuarine sediments. This was achieved by a series of field- and laboratory-based studies investigating factors controlling the geochemical behaviour of trace metals and TBT in sediments from south-east Queensland, Australia. The distribution and enrichment of selected trace metals in benthic sediments of the Southport Broadwater (a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia) was studied. Sediment contamination for Cd, Cr, Cu, Ni, Pb, Sn and Zn was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical noi-malisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, several sites were found to be strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The geochemical partitioning of Cu, Pb and Zn was examined in sediments collected from three of these sites of sediment contamination. Total Cu, Pb and Zn concentrations in coarse-textured (65 to 90 % sand sized particles), sub-oxic sediments (Eh + 120 to +260 mV) ranged from 8.3 to 194 mg/kg for Cu, 16.3 to 74.8 mg/kg for Pb and 30.1 to 220 mg/kg for Zn, and were related to vertical trends in sediment texture. The association of Cu, Pb and Zn with amorphous oxides, crystalline oxides and organic matter was linearly dependent on the abundance of each phase. For retention by amorphous oxide minerals, the trace metal retention ranged from 5.2 to 23.7 mgcjgFe oxide as Fe for Cu, 1 2.8 to 21 .5 mgpb/gFe oxide as Fe for Pb, and 23. I to 85.7 mgm/gFe oxide as Fe for Zn. Corresponding values for association with crystalline oxides were an order of magnitude less than those for amorphous oxides, indicating a weaker affinity of trace metals for crystalline oxides. The relationships describing association with organic matter ranged from 17.6 to 54.0 mgcu/gorg c for Cu, 6.1 to 9.6 mgpb/gorg c for Pb and 6.4 to 16.4 mgzn/gorg c for Zn. The in-situ solid/pore-water partitioning of TBT and the degradation products, dibutyltin (DBT) and monobutyltin (MBT), was determined for an estuarine sediment profile with previously identified elevated Sn concentrations. Total butyltin levels were (depending on depth) 220 to 8750 jig/kg for TBT, 150 to 5450 jig/kg for DBT and 130 to 4250 jig/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 jig/L for TBT, 0.07 to 3.25 jiglL for DBT, and 0.05 to 0.53 J.tgIL for MBT. The organic carbon normalised distribution ratios (Doc) were similar for TBT, DBT and MBT, and were io to 106 L/kg. Values for the Butyltin Degradation Index (BDI) were larger than I at depths greater than 10 cm below the sediment/water-column interface, indicating that substantial TBT degradation has occurred in the sediments. This suggests that natural attenuation may be a viable sediment remediation strategy. Factors controlling the partitioning behaviour of Cu, Pb and Zn in nonsulfidic, estuarine sediments were examined in controlled laboratory-based studies with the use of combined sorption curve - sequential extraction analysis. This allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behaviour in sulfidic sediments was also determined by sequentially extracting Cu, Pb and Zn from synthetic sulfide minerals, and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the 'carbonate' fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the 'Fe-oxide' (NH2OH.HCI extraction) and 'organic' (H202 extraction) fractions in non-sulfidic sediments. Freundlich isotherm parameters describing sorption to the 'Fe-oxide' and 'organic' fractions were dependent on the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the 'organic' fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH.HCI step (which has been previously interpreted as 'Fe-oxide' bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments. Tributyltin (TBT) sorption to four natural sediment samples in artificial seawater was also examined under a range of modified pH and salinity conditions in controlled laboratory-based studies. Three of the sediment samples were relatively pristine with regard to TBT contamination, but the fourth was a TBT-contaminated sediment from a commercial marina. Sorption of TBT was described well by linear sorption isotherms, with distribution coefficients ranging from 6.1 to 5210 L/kg depending on pH and salinity. Sediment organic C content and particle size distribution were important determinants of sorption behaviour. The presence of resident TBT in the contaminated marina sediment caused a substantial reduction in TBT sorption due to satuaration of high selectivity sites. Desorption of TBT from the marina sediment was described by relatively large observed distribution coefficients ranging from 5100 to 9400 L/kg, suggesting that aging effects may reduce sorption reversibility. Increased artificial seawater salinity generally reduced TBT sorption at pH 4 and pH 6, but enhanced TBT sorption at pH 8. Regardless of salinity, maximum sorption of TBT was observed at pH 6, which is attributed to an optimal balance between abundance of the cationic TBT species and deprotonated surface ligands. Consideration of aqueous TBT speciation along with octanol-water partitioning behaviour suggest that hydrophobic partitioning of TBTCI to non-polar organic matter was important for pH (up to) 6, whilst partitioning of TBTOH was important at higher pH. The effect of aging on the solid/pore-water partitioning and desorption behaviour of TBT in sediments was examined. Three sediment samples with contrasting physical and chemical properties were spiked with 10 mg/kg TBT and aged under sterile conditions for periods of time ranging from I to 84 days. Aging had a negligible effect in a sandy sample with very low organic carbon content (0.2 % w/w). In contrast, for samples with larger amounts of organic carbon (2.6 and 4.8 % w/w), the effect of aging on the solid/pore-water partitioning behaviour was significant. For these samples, the apparent distribution coefficients (Ks) obtained from sequential two hour desorption experiments exhibited a two-fold increase between spiked sediments subjected to aging for 1 day and 84 days. This study demonstrates that aging effects may be an important aspect of TBT fate in contaminated sediments. Overall, the results described in this thesis demonstrate that environmental factors (i.e. pH, salinity, Eh, aging) and sediment composition (i.e. abundance of fine alumino-silicate minerals, organic matter, Fe-oxides, reactive sulfides) exert substantial effects on trace metal and TBT partitioning. The current reliance on measurement of total trace metal and TBT concentrations in contaminated sediment management may consequently lead to inaccurate estimates of environmental risk and inappropriate remediation measures if other factors regulating contaminant distribution and partitioning are ignored.
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Burton, Edward. "Distribution and Partitioning of Trace Metals and Tributyltin in Estuarine Sediments." Thesis, Griffith University, 2005. http://hdl.handle.net/10072/366133.
Full textAbstract:
An improved understanding of the geochemical partitioning of trace metals and tributyltin (TBT) in sediments is of great importance in risk assessment and remedial investigation. The aim of this thesis was to examine the distribution and partitioning behaviour of trace metals and TBT in benthic, estuarine sediments. This was achieved by a series of field- and laboratory-based studies investigating factors controlling the geochemical behaviour of trace metals and TBT in sediments from south-east Queensland, Australia. The distribution and enrichment of selected trace metals in benthic sediments of the Southport Broadwater (a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia) was studied. Sediment contamination for Cd, Cr, Cu, Ni, Pb, Sn and Zn was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical noi-malisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, several sites were found to be strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The geochemical partitioning of Cu, Pb and Zn was examined in sediments collected from three of these sites of sediment contamination. Total Cu, Pb and Zn concentrations in coarse-textured (65 to 90 % sand sized particles), sub-oxic sediments (Eh + 120 to +260 mV) ranged from 8.3 to 194 mg/kg for Cu, 16.3 to 74.8 mg/kg for Pb and 30.1 to 220 mg/kg for Zn, and were related to vertical trends in sediment texture. The association of Cu, Pb and Zn with amorphous oxides, crystalline oxides and organic matter was linearly dependent on the abundance of each phase. For retention by amorphous oxide minerals, the trace metal retention ranged from 5.2 to 23.7 mgcjgFe oxide as Fe for Cu, 1 2.8 to 21 .5 mgpb/gFe oxide as Fe for Pb, and 23. I to 85.7 mgm/gFe oxide as Fe for Zn. Corresponding values for association with crystalline oxides were an order of magnitude less than those for amorphous oxides, indicating a weaker affinity of trace metals for crystalline oxides. The relationships describing association with organic matter ranged from 17.6 to 54.0 mgcu/gorg c for Cu, 6.1 to 9.6 mgpb/gorg c for Pb and 6.4 to 16.4 mgzn/gorg c for Zn. The in-situ solid/pore-water partitioning of TBT and the degradation products, dibutyltin (DBT) and monobutyltin (MBT), was determined for an estuarine sediment profile with previously identified elevated Sn concentrations. Total butyltin levels were (depending on depth) 220 to 8750 jig/kg for TBT, 150 to 5450 jig/kg for DBT and 130 to 4250 jig/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 jig/L for TBT, 0.07 to 3.25 jiglL for DBT, and 0.05 to 0.53 J.tgIL for MBT. The organic carbon normalised distribution ratios (Doc) were similar for TBT, DBT and MBT, and were io to 106 L/kg. Values for the Butyltin Degradation Index (BDI) were larger than I at depths greater than 10 cm below the sediment/water-column interface, indicating that substantial TBT degradation has occurred in the sediments. This suggests that natural attenuation may be a viable sediment remediation strategy. Factors controlling the partitioning behaviour of Cu, Pb and Zn in nonsulfidic, estuarine sediments were examined in controlled laboratory-based studies with the use of combined sorption curve - sequential extraction analysis. This allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behaviour in sulfidic sediments was also determined by sequentially extracting Cu, Pb and Zn from synthetic sulfide minerals, and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the 'carbonate' fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the 'Fe-oxide' (NH2OH.HCI extraction) and 'organic' (H202 extraction) fractions in non-sulfidic sediments. Freundlich isotherm parameters describing sorption to the 'Fe-oxide' and 'organic' fractions were dependent on the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the 'organic' fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH.HCI step (which has been previously interpreted as 'Fe-oxide' bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments. Tributyltin (TBT) sorption to four natural sediment samples in artificial seawater was also examined under a range of modified pH and salinity conditions in controlled laboratory-based studies. Three of the sediment samples were relatively pristine with regard to TBT contamination, but the fourth was a TBT-contaminated sediment from a commercial marina. Sorption of TBT was described well by linear sorption isotherms, with distribution coefficients ranging from 6.1 to 5210 L/kg depending on pH and salinity. Sediment organic C content and particle size distribution were important determinants of sorption behaviour. The presence of resident TBT in the contaminated marina sediment caused a substantial reduction in TBT sorption due to satuaration of high selectivity sites. Desorption of TBT from the marina sediment was described by relatively large observed distribution coefficients ranging from 5100 to 9400 L/kg, suggesting that aging effects may reduce sorption reversibility. Increased artificial seawater salinity generally reduced TBT sorption at pH 4 and pH 6, but enhanced TBT sorption at pH 8. Regardless of salinity, maximum sorption of TBT was observed at pH 6, which is attributed to an optimal balance between abundance of the cationic TBT species and deprotonated surface ligands. Consideration of aqueous TBT speciation along with octanol-water partitioning behaviour suggest that hydrophobic partitioning of TBTCI to non-polar organic matter was important for pH (up to) 6, whilst partitioning of TBTOH was important at higher pH. The effect of aging on the solid/pore-water partitioning and desorption behaviour of TBT in sediments was examined. Three sediment samples with contrasting physical and chemical properties were spiked with 10 mg/kg TBT and aged under sterile conditions for periods of time ranging from I to 84 days. Aging had a negligible effect in a sandy sample with very low organic carbon content (0.2 % w/w). In contrast, for samples with larger amounts of organic carbon (2.6 and 4.8 % w/w), the effect of aging on the solid/pore-water partitioning behaviour was significant. For these samples, the apparent distribution coefficients (Ks) obtained from sequential two hour desorption experiments exhibited a two-fold increase between spiked sediments subjected to aging for 1 day and 84 days. This study demonstrates that aging effects may be an important aspect of TBT fate in contaminated sediments. Overall, the results described in this thesis demonstrate that environmental factors (i.e. pH, salinity, Eh, aging) and sediment composition (i.e. abundance of fine alumino-silicate minerals, organic matter, Fe-oxides, reactive sulfides) exert substantial effects on trace metal and TBT partitioning. The current reliance on measurement of total trace metal and TBT concentrations in contaminated sediment management may consequently lead to inaccurate estimates of environmental risk and inappropriate remediation measures if other factors regulating contaminant distribution and partitioning are ignored.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental Engineering
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HE, AIJING. "UNSUPERVISED DATA MINING BY RECURSIVE PARTITIONING." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1026406153.
Full textBooks on the topic "Knowledge partitioning and distribution"
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G, Altbach Philip. The knowledge context: Comparative perspectives on the distribution of knowledge. Albany, N.Y: State University of New York Press, 1987.
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Woolnough, Andrew P. Distribution and abundance of pest animals in Western Australia: A survey of institutional knowledge. [Forrestfield, W.A.]: Dept. of Agriculture, 2005.
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G, Ainsworth R., and International Water Association, eds. Microbiological water quality in piped distribution systems: A review of knowledge and practices. London: IWA, 2003.
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1965-, Paquin Pierre, and Buckle Donald J. 1947-, eds. Contributions à la connaissance des araignées (Araneae) d'Amérique du Nord =: Contributions to the knowledge of spiders (Araneae) of North America. Varennes, Québec: Association des entomologistes amateurs du Québec, 2001.
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1963-, Bryson J. R., ed. Knowledge, space, economy. London: Routledge, 2000.
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United Nations. Economic Commission for Latin America and the Caribbean. and Unesco. Regional Office for Education in Latin America and the Caribbean., eds. Education and knowledge: Basic pillars of changing production patterns with social equity. Santiago, Chile: Economic Commission for Latin America and the Caribbean, 1992.
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Mallory, M. L. Community knowledge on the distribution and abundance of endangered species in southern Baffin Island, Nunavut, Canada. Ottawa: Minister of Public Works and Government Services Canada, 2001.
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Seattle-King County Bar Association. Continuing Legal Education Committee., ed. The Law of distribution: Essential knowledge for representing manufacturers, suppliers an distributors of goods and services. [Seattle, Wash.]: SKCBA, 1990.
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Kruse, Rudolf. Uncertainty and Vagueness in Knowledge Based Systems: Numerical Methods. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991.
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Falmagne, Jean-Claude, David Eppstein, Christopher Doble, Dietrich Albert, and Xiangen Hu. Knowledge spaces: Applications in education. Heidelberg: Springer, 2013.
Find full textBook chapters on the topic "Knowledge partitioning and distribution"
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Wernhard, Christoph. "Semantic Knowledge Partitioning." In Logics in Artificial Intelligence, 552–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-30227-8_46.
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Steffe, Leslie P. "The Partitioning and Fraction Schemes." In Children's Fractional Knowledge, 315–40. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-0591-8_10.
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Tsai, Kao-Tai. "Recursive Partitioning Modeling." In Machine Learning for Knowledge Discovery with R, 59–100. Boca Raton: Chapman and Hall/CRC, 2021. http://dx.doi.org/10.1201/9781003205685-4.
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Reading, Chris, and Dan Canada. "Teachers’ Knowledge of Distribution." In Teaching Statistics in School Mathematics-Challenges for Teaching and Teacher Education, 223–34. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1131-0_23.
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Priyadarshi, Amitabh, and Krzysztof J. Kochut. "WawPart: Workload-Aware Partitioning of Knowledge Graphs." In Advances and Trends in Artificial Intelligence. Artificial Intelligence Practices, 383–95. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-79457-6_33.
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Zhang, Wei-Bin. "Knowledge, Growth and Wealth Distribution." In Capital and Knowledge, 182–238. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-58254-7_5.
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Hamdi, Fayçal, Brigitte Safar, Chantal Reynaud, and Haïfa Zargayouna. "Alignment-Based Partitioning of Large-Scale Ontologies." In Advances in Knowledge Discovery and Management, 251–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-00580-0_15.
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Galicia, Jorge, Amin Mesmoudi, and Ladjel Bellatreche. "RDFPartSuite: Bridging Physical and Logical RDF Partitioning." In Big Data Analytics and Knowledge Discovery, 136–50. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27520-4_10.
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Aslam, Adeel, Giovanni Simonini, Luca Gagliardelli, Angelo Mozzillo, and Sonia Bergamaschi. "HKS: Efficient Data Partitioning for Stateful Streaming." In Big Data Analytics and Knowledge Discovery, 386–91. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-39831-5_35.
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Sun, Ding, Zhen Huang, Dongsheng Li, Xiangyu Ye, and Yilin Wang. "Improved Partitioning Graph Embedding Framework for Small Cluster." In Knowledge Science, Engineering and Management, 203–15. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-82136-4_17.
Full textConference papers on the topic "Knowledge partitioning and distribution"
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Jiang, Wei, Kadda Yahiaoui, Chang J. Wang, Frank R. Hall, and Tahar Laoui. "FE Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction." In ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-2283.
Full textAbstract:
This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of 3D temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.
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Magalhães, W. F., H. M. Gomes, L. B. Marinho, G. S. Aguiar, and P. Silveira. "Investigating Mobile Edge-Cloud Trade-Offs of Object Detection with YOLO." In VII Symposium on Knowledge Discovery, Mining and Learning. Sociedade Brasileira de Computação - SBC, 2019. http://dx.doi.org/10.5753/kdmile.2019.8788.
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With the advent of smart IoT applications empowered with AI, together with the democratization of mobile devices, moving the computation from cloud to edge is a natural trend in both academia and industry. A major challenge in this direction is enabling the deployment of Deep Neural Networks (DNNs), which usually demand lots of computational resources (i.e. memory, disk, CPU/GPU, and power), in resource limited edge devices. Among the possible strategies to tackle this challenge are: (i) running the entire DNN on the edge device (sometimes not feasible), (ii) distributing the computation between edge and cloud or (iii) running the entire DNN on the cloud. All these strategies involve trade-offs in terms of latency, communication, and financial costs. In this article we investigate such trade-offs in a real-world scenario involving object detection from video surveillance feeds. We conduct several experiments on two different versions of YOLO (You Only Look Once), a state-of-the-art DNN designed for fast and accurate object detection and location. Our experimental setup for DNN model partitioning includes a Raspberry PI 3 B+ and a cloud server equipped with a GPU. Experiments using different network bandwidths are performed. Our results provide useful insights about the aforementioned trade-offs.
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Shi, Hai, and Linda Schmidt. "Partitioning Knowledge for Generative Configuration Design." In ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/dtm-48686.
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Designers and design researchers both agree that developing many feasible alternatives at the conceptual design stage is useful. In this paper we introduce generative configuration design (GCD) for conceptual design. We provide a partition of knowledge accessed during GCD and use the partitioned knowledge foundation to compare design tool architectures so that computational improvements can be made. We present an improved architecture for a GCD algorithm and implement it as a tool for office chair design. Subsequent examples show tradeoffs between computational load and design variety when applying constraints for behavior testing.
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Pujara, Jay, Hui Miao, Lise Getoor, and William W. Cohen. "Ontology-aware partitioning for knowledge graph identification." In the 2013 workshop. New York, New York, USA: ACM Press, 2013. http://dx.doi.org/10.1145/2509558.2509562.
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Priya, Sambhawa, Yuanbo Guo, Michael Spear, and Jeff Heflin. "Partitioning OWL Knowledge Bases for Parallel Reasoning." In 2014 IEEE International Conference on Semantic Computing (ICSC). IEEE, 2014. http://dx.doi.org/10.1109/icsc.2014.34.
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Nishimura, Joel, and Johan Ugander. "Restreaming graph partitioning." In KDD' 13: The 19th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining. New York, NY, USA: ACM, 2013. http://dx.doi.org/10.1145/2487575.2487696.
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Wu, Xindong, Shaojing Sheng, and Peng Zhou. "Balanced Tree Partitioning with Succinct Logic." In 2020 IEEE International Conference on Knowledge Graph (ICKG). IEEE, 2020. http://dx.doi.org/10.1109/icbk50248.2020.00083.
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Akhter, Adnan, Muhammad Saleem, Alexander Bigerl, and Axel-Cyrille Ngonga Ngomo. "Efficient RDF Knowledge Graph Partitioning Using Querying Workload." In K-CAP '21: Knowledge Capture Conference. New York, NY, USA: ACM, 2021. http://dx.doi.org/10.1145/3460210.3493577.
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Muthukaruppan, Muthukumaran, Francis Chiew, and Tony Wong. "Size Distribution and Partitioning of Urban Pollutants." In Ninth International Conference on Urban Drainage (9ICUD). Reston, VA: American Society of Civil Engineers, 2002. http://dx.doi.org/10.1061/40644(2002)202.
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Dai, Zhuyun, Chenyan Xiong, and Jamie Callan. "Query-Biased Partitioning for Selective Search." In CIKM'16: ACM Conference on Information and Knowledge Management. New York, NY, USA: ACM, 2016. http://dx.doi.org/10.1145/2983323.2983706.
Full textReports on the topic "Knowledge partitioning and distribution"
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Nentwich, Michael, ed. (Re-)De-Commodification in Academic Knowledge Distribution? Vienna: self, 2012. http://dx.doi.org/10.1553/ita-pa-mn-01-2.
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Frandsen, Brigham, and Lars Lefgren. Partial Identification of the Distribution of Treatment Effects with an Application to the Knowledge Is Power Program (KIPP). Cambridge, MA: National Bureau of Economic Research, May 2018. http://dx.doi.org/10.3386/w24616.
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Wolf, Shmuel, and William J. Lucas. Involvement of the TMV-MP in the Control of Carbon Metabolism and Partitioning in Transgenic Plants. United States Department of Agriculture, October 1999. http://dx.doi.org/10.32747/1999.7570560.bard.
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The function of the 30-kilodalton movement protein (MP) of tobacco mosaic virus (TMV) is to facilitate cell-to-cell movement of viral progeny in infected plants. Our earlier findings have indicated that this protein has a direct effect on plasmodesmal function. In addition, these studies demonstrated that constitutive expression of the TMV MP gene (under the control of the CaMV 35S promoter) in transgenic tobacco plants significantly affects carbon metabolism in source leaves and alters the biomass distribution between the various plant organs. The long-term goal of the proposed research was to better understand the factors controlling carbon translocation in plants. The specific objectives were: A) To introduce into tobacco and potato plants a virally-encoded (TMV-MP) gene that affects plasmodesmal functioning and photosynthate partitioning under tissue-specific promoters. B) To introduce into tobacco and potato plants the TMV-MP gene under the control of promoters which are tightly repressed by the Tn10-encoded Tet repressor, to enable the expression of the protein by external application of tetracycline. C) To explore the mechanism by which the TMV-MP interacts with the endogenous control o~ carbon allocation. Data obtained in our previous project together with the results of this current study established that the TMV-MP has pleiotropic effects when expressed in transgenic tobacco plants. In addition to its ability to increase the plasmodesmal size exclusion limit, it alters carbohydrate metabolism in source leaves and dry matter partitioning between the various plant organs, Expression of the TMV-MP in various tissues of transgenic potato plants indicated that sugars and starch levels in source leaves are reduced below those of control plants when the TMV-MP is expressed in green tissue only. However, when the TMV-MP was expressed predominantly in PP and CC, sugar and starch levels were raised above those of control plants. Perhaps the most significant result obtained from experiments performed on transgenic potato plants was the discovery that the influence of the TMV-MP on carbohydrate allocation within source leaves was under developmental control and was exerted only during tuber development. The complexity of the mode by which the TMV-MP exerts its effect on the process of carbohydrate allocation was further demonstrated when transgenic tobacco plants were subjected to environmental stresses such as drought stress and nutrients deficiencies, Collectively, these studies indicated that the influence of the TMV-MP on carbon allocation L the result of protein-protein interaction within the source tissue. Based on these results, together with the findings that plasmodesmata potentiate the cell-to-cell trafficking of viral and endogenous proteins and nucleoproteins complexes, we developed the theme that at the whole plant level, the phloem serves as an information superhighway. Such a long-distance communication system may utilize a new class of signaling molecules (proteins and/or RNA) to co-ordinate photosynthesis and carbon/nitrogen metabolism in source leaves with the complex growth requirements of the plant under the prevailing environmental conditions. The discovery that expression of viral MP in plants can induce precise changes in carbon metabolism and photoassimilate allocation, now provide a conceptual foundation for future studies aimed at elucidating the communication network responsible for integrating photosynthetic productivity with resource allocation at the whole-plant level. Such information will surely provide an understanding of how plants coordinate the essential physiological functions performed by distantly-separated organs. Identification of the proteins involved in mediating and controlling cell-to-cell transport, especially at the companion cell-sieve element boundary, will provide an important first step towards achieving this goal.
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Schoen, Robert, Xiaotong Yang, and Gizem Solmaz. Psychometric Report for the 2019 Knowledge for Teaching Early Elementary Mathematics (K-TEEM) Test. Florida State University Libraries, May 2021. http://dx.doi.org/10.33009/lsi.1620243057.
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The 2019 Knowledge for Teaching Early Elementary Mathematics (2019 K-TEEM) test measures teachers’ mathematical knowledge for teaching early elementary mathematics. This report presents information about a large-scale field test of the 2019 K-TEEM test with 649 practicing educators. The report contains information about the development process used for the test; a description of the sample; descriptions of the procedures used for data entry, scoring of responses, and analysis of data; recommended scoring procedures; and findings regarding the distribution of test scores, standard error of measurement, and marginal reliability. The intended use of the data from the 2019 K-TEEM test is to serve as a measure of teacher knowledge that will be used in a randomized controlled trial to investigate the impact—and variation in impact—of a teacher professional-development program for early elementary teachers.
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Mudge, Christopher, Glenn Suir, and Benjamin Sperry. Unmanned aircraft systems and tracer dyes : potential for monitoring herbicide spray distribution. Engineer Research and Development Center (U.S.), October 2023. http://dx.doi.org/10.21079/11681/47705.
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Chemical control of nuisance aquatic vegetation has long been the most widely utilized management tool due to its high level of efficacy, limited environmental impacts, and relatively low cost. However, unprecise application of herbicides can lead to uncontrolled invasive plants and unintended management costs. Therefore, precision herbicide delivery techniques are being developed to improve invasive plant control and minimize impacts to non-target plants. These technological advancements have the potential to enhance aquatic ecosystem protection from invasive species while reducing associated management costs. Despite the benefits of using registered herbicides for aquatic plant control in efforts to restore aquatic habitats, their use is often misunderstood and opposed by public stakeholders. This can lead to significant challenges related to chemical control of nuisance aquatic vegetation. Thus, US Army Corps of Engineers (USACE) Districts seek improved methods to monitor and quantify the distribution (i.e., amount of herbicide retained on plant foliage compared to those deposited into the water column) of herbicides applied in aquatic systems. Monitoring herbicide movement in aquatic systems can be tedious and costly using standard analytical methods. However, since the inert fluorescent tracer dye Rhodamine WT (RWT) closely mimics product movement in the aquatic environment it has been used as a cost-effective surrogate for herbicides tracing. The use of RWT (or other inert tracer dyes) can be an efficient way to quantify herbicide retention and deposition following foliar treatments. However, the collection of operational spray deposition data in large populations of invasive floating and emergent plant stands is labor intensive and costly. One proposed solution is the use of remote sensing methods as an alternative to traditional in situ samples. Specifically, using unmanned aircraft systems (UAS) in conjunction with RWT could provide more efficient monitoring and quantification of herbicide spray distribution and in-water concentrations when using RWT in combination with herbicides. A better understanding of UAS capabilities and limitations is key as this technology is being explored for improved and integrated management of aquatic plants in the U.S. This technical note (TN) provides a review of literature to assess the state of knowledge and technologies that can assist USACE Districts and partners with tracking herbicide movement (using RWT as a surrogate or additive), which could improve operational monitoring, thus reducing the level of uncertainty related to chemical applications and non-target impacts, and thus improve management in aquatic systems.
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Ruiz de Gauna, Itziar, Anil Markandya, Laura Onofri, Francisco (Patxi) Greño, Javier Warman, Norma Arce, Alejandra Navarrete, et al. Economic Valuation of the Ecosystem Services of the Mesoamerican Reef, and the Allocation and Distribution of these Values. Inter-American Development Bank, May 2021. http://dx.doi.org/10.18235/0003289.
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Coral reefs are one of the most diverse and valuable ecosystems on Earth. The Mesoamerican Reef contains the largest barrier reef in the Western Hemisphere. However, its health is threatened, so there is a need for a management and sustainable conservation. Key to this is knowing the economic value of the ecosystem. “Mainstreaming the value of natural capital into policy decision-making is vital” The value of environmental and natural resources reflects what society is willing to pay for a good or service or to conserve natural resources. Conventional economic approaches tended to view value only in terms of the willingness to pay for raw materials and physical products generated for human production and consumption (e.g. fish, mining materials, pharmaceutical products, etc.). As recognition of the potential negative impacts of human activity on the environment became more widespread, economists began to understand that people might also be willing to pay for other reasons beyond the own current use of the service (e.g. to protect coral reefs from degradation or to know that coral reefs will remain intact in the future). As a result of this debate, Total Economic Value (TEV) became the most widely used and commonly accepted framework for classifying economic benefits of ecosystems and for trying to integrate them into decision-making. This report estimates the economic value of the following goods and services provided by the MAR's coral reefs: Tourism & Recreation, Fisheries, Shoreline protection. To our knowledge, the inclusion of non-use values in the economic valuation of the Mesoamerican Barrier Reef System is novel, which makes the study more comprehensive.
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Bédard, K., A. Marsh, M. Hillier, and Y. Music. 3D geological model of the Western Canadian Sedimentary Basin in Saskatchewan, Canada. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331747.
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The Western Canadian Sedimentary Basin (WCSB) covers a large part of southern Saskatchewan and hosts many resources such as critical mineral deposits (i.e. potash, helium and lithium) as well as oil and gas reservoirs and is also targeted for deep CO2 storage projects. There is also growing interest in the groundwater resources, the geothermal potential and hydrogen recovery potential. These applications require knowledge of the subsurface geology such as formation thickness and depth, relationships with adjacent formations or unconformities and ultimately, distribution of physical properties within the basin. 3D geological models can provide this knowledge since they characterize the geometry of subsurface geological features. In addition, they can be used as a framework for fluid flow simulation and estimating the distribution a variety of properties. The 3D geological model presented in this report consists of 51 geological units of which, 49 are stratigraphic units spanning from Cambrian Deadwood Formation at the base of the sequence to Upper Cretaceous Belly River Formation at the top, plus the undivided Precambrian and a preliminary Quaternary unit. The model is cut by 7 major regional unconformities, including the base of the Quaternary sediments. The regional model was constrained using oil and gas well data interpretations, provincial scale bedrock geology maps and knowledge from the previously interpreted areal extent of the Phanerozoic strata. A hybrid explicit-implicit modelling approach was employed to produce the 3D geological model of the WCSB in Saskatchewan using Gocad/SKUATM geomodelling software.
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Idakwo, Gabriel, Sundar Thangapandian, Joseph Luttrell, Zhaoxian Zhou, Chaoyang Zhang, and Ping Gong. Deep learning-based structure-activity relationship modeling for multi-category toxicity classification : a case study of 10K Tox21 chemicals with high-throughput cell-based androgen receptor bioassay data. Engineer Research and Development Center (U.S.), July 2021. http://dx.doi.org/10.21079/11681/41302.
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Deep learning (DL) has attracted the attention of computational toxicologists as it offers a potentially greater power for in silico predictive toxicology than existing shallow learning algorithms. However, contradicting reports have been documented. To further explore the advantages of DL over shallow learning, we conducted this case study using two cell-based androgen receptor (AR) activity datasets with 10K chemicals generated from the Tox21 program. A nested double-loop cross-validation approach was adopted along with a stratified sampling strategy for partitioning chemicals of multiple AR activity classes (i.e., agonist, antagonist, inactive, and inconclusive) at the same distribution rates amongst the training, validation and test subsets. Deep neural networks (DNN) and random forest (RF), representing deep and shallow learning algorithms, respectively, were chosen to carry out structure-activity relationship-based chemical toxicity prediction. Results suggest that DNN significantly outperformed RF (p < 0.001, ANOVA) by 22–27% for four metrics (precision, recall, F-measure, and AUPRC) and by 11% for another (AUROC). Further in-depth analyses of chemical scaffolding shed insights on structural alerts for AR agonists/antagonists and inactive/inconclusive compounds, which may aid in future drug discovery and improvement of toxicity prediction modeling.
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Baker, Michael. DTRS56-02-D-70036-16 Mechanical Damage. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), April 2009. http://dx.doi.org/10.55274/r0011844.
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This report reviews and summarizes the current state of knowledge and practice related to mechanical damage in natural gas and hazardous liquid steel pipelines, with a particular focus on transmission pipelines. Comprehensive voluntary interviews were conducted with 10 pipeline operators who represent a diverse cross-section of industry professionals in the United States, Canada, and Europe. The interviews, which focused on operator practices for detection, characterization, and mitigation of mechanical damage on both gas and liquid transmission and gas distribution pipelines (the latter examined for comparison purposes), provided an invaluable source of data for the development of this report. Operator practices associated with the prevention of mechanical damage primarily resulting from excavation damage were also extensively covered in the interviews. The inquiry primarily included pipelines that comprise transmission systems, but gas distribution companies also reported on their experience with distribution systems consisting of both steel and plastic pipe, the latter reviewed for a comprehensive discussion of the operator's damage prevention programs and issues. Pipeline geographic locations included remote and rugged terrain, rural areas, and constrained urban environments.
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McMartin, I., D. E. Kerr, M. B. McClenaghan, A. Duk-Rodkin, T. Tremblay, M. Parent, and J. M. Rice. Introduction and Summary. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331419.
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This bulletin summarizes surficial geology knowledge and data produced by the Geo-mappingfor Energy and Minerals (GEM) program in the last decade and provides an updated understanding of the nature, distribution, and history of surficial deposits in various glacial terrain types of Canada's North. The advancement in various aspects of surficial geology and the evolution of certain concepts and methods form the subject of the papers that make up this bulletin. Specifically, the papers discuss the status of surficial geology mapping in northern Canada and the development of standards to facilitate map release; highlights from selected GEM surficial geochemical and indicator mineral surveys and the establishment of protocols for drift prospecting; and the revised glacial histories and surficial geology in various regions, from the Mackenzie Mountains to the Labrador coast. This introductory paper to Bulletin 611 describes the scope of the publication and provides a summary of major surficial geology contributions to the GEM program in northern Canada. Remaining knowledge gaps and outstanding issues suggest ideas for future research topics and regions of interest that could inform decisions on mineral exploration and land-use management.