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Spiekermann, Sarah. "Online information search with electronic agents." Doctoral thesis, Humboldt-Universität zu Berlin, Wirtschaftswissenschaftliche Fakultät, 2001. http://dx.doi.org/10.18452/14715.
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Basierend auf einem Onlineexperiment mit 206 Teilnehmern untersucht die Dissertation, wie Konsumenten im Internet nach Informationen zu hochwertigen Produkten suchen und welche Rolle dabei virtuelle Verkaufsberater (elektronische Agenten) spielen. Im Kontext eines online Kamerakaufes mit Hilfe eines virtuellen Agenten wird der Erklärungswert traditioneller Faktoren der Informationssuche für das Onlinemedium untersucht. Dabei werden das wahrgenommene Kaufrisiko, die persönliche Bedeutung des Kaufes sowie das vorhandene Produktwissen als Einflussvariablen getestet. Darüber hinaus wird untersucht, welche Rolle das Datenschutzbewusstsein des Konsumenten in der Interaktion spielt und wie stark ein Zustand des 'Flows' (fließen) die Informationssuchtiefe beeinflussen. Die für Kameras beobachtete Onlinesuche nach Produktinformationen wird in einem zweiten Schritt mit der Onlinesuche nach Jacken verglichen. Eine wesentliche Erkenntnis der empirischen Arbeit ist, dass virtuelle Verkaufsberater bei der Suche nach unterschiedlichen Produkten nicht dieselbe Wichtigkeit haben. So wird deutlich, dass sich Konsumenten auf der Suche nach dem Erfahrungsgut Jacke relativ weniger auf die Empfehlung des Agenten verlassen als dies im Kaufprozess von Kameras der Fall ist. Hinzu kommen einige signifikante Anzeichen dafür, dass Konsumenten den Suchprozess stärker zu kontrollieren wünschen und weniger an Agenten delegieren, desto mehr Kaufrisiko bzw. Kaufunsicherheit sie empfinden. Schließlich zeigt sich analog zu älteren Studien, dass Konsumenten mit mehr Produktwissen weniger mit virtuellen Verkaufsberatern interagieren. Im letzten Kapitel der Dissertation geht es um eine potentiell maßgebliche Barriere für den Einsatz von virtuellen Verkaufsberatern: die Angst von Konsumenten ihre Privatsphäre einzubüßen und zum 'gläsernen Kunden' zu werden. Die empirischen Ergebnisse legen hier jedoch nahe, dass Datenschutzbedenken die Konsumenten nicht davon abhalten, sich online mitzuteilen. Ganz im Gegenteil wird deutlich, dass Konsumenten sogar bereit sind, sehr persönliche Informationen von sich preiszugeben, wenn das System eine entsprechende Gegenleistung bietet (wie beispielsweise eine persönliche Produktempfehlung). Die Ergebnisse suggerieren, dass es einen großen Gestaltungsspielraum für Unternehme gibt, über elektronische Dialogsysteme mit ihren Kunden zu kommunizieren. Würden Unternehmen das potentielle Spektrum an persönlichen Fragen nutzen, die im Rahmen eines Kaufprozesses sinnvoll sind, könnten sie wertvolle Einblicke in das Entscheidungsverhalten ihrer Kunden gewinnen. Hingegen sollte beachtet werden, dass eine mangelhafte Berücksichtigung des Datenschutzes gleichzeitig auch Unbehangen beim Nutzer auslöst, welches sich in signifikant kürzeren Interaktionszeiten wiederspiegelt. Es ist daher im Interesse von Unternehmen, für eine datenschutzfreundliche Interaktionsumgebung zu sorgen.Based on an online experiment with 206 subjects the thesis investigates how consumers search for high-involvement products online and herein rely on the assistance of electronic advisor agents. In the context of a camera purchase traditional constructs relevant in offline information search (including perceived product risk, purchase involvement and product knowledge) are tested for their relevance in an online environment. In addition, new constructs impacting online search, namely privacy concerns and flow, are analyzed. Finally, information search behavior for cameras is compared with the one for jackets. One major finding is that agents do not play the same role in, and are not equally important for, online information search in different product categories. Thus, it appears, that the search process for the experience good 'jacket' involves relatively less reliance on an electronic agent than this is the case in the purchase process for cameras. Moreover, the separate analysis of manually controlled and agent-assisted search shows that, at a significant level, consumers prefer to manually control the search process the more risk they perceive. In line with older studies the data also suggest that the more product knowledge a consumer perceives the less he interacts with an agent for information search purposes. In the last chapter, the thesis focuses on a potentially major impediment for agent interaction, namely consumer privacy concerns. The empirical results show that, against expectations, privacy concerns to not seem to significantly impede consumer disclosure online. In contrast, evidence is produced that if systems offer appropriate returns in the form of personalized recommendations online users seem to be ready to reveal even highly personal information. The findings suggest that there is a lot of room for online marketers to communicate with their clients through dialogue-based electronic agents. If marketers used the spectrum of legitimate personal questions that are related to the product selection process more systematically, they could gain valuable insight into their customers' decision making process as well as on decisive product attributes. However, unfavorable privacy settings do seem to induce a feeling of discomfort among users which then leads to less interaction time. Marketers therefore have to provide for a comforting privacy environment in order to make their customers feel good about the interaction.
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Gopinathan-Leela, Ligon, and n/a. "Personalisation of web information search: an agent based approach." University of Canberra. Information Sciences & Engineering, 2005. http://erl.canberra.edu.au./public/adt-AUC20060728.120849.
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The main purpose of this research is to find an effective way to personalise information
searching on the Internet using middleware search agents, namely, Personalised Search
Agents (PSA). The PSA acts between users and search engines, and applies new and existing
techniques to mine and exploit relevant and personalised information for users.
Much research has already been done in developing personalising filters, as a middleware
technique which can act between user and search engines to deliver more personalised results.
These personalising filters, apply one or more of the popular techniques for search result
personalisation, such as the category concept, learning from user actions and using metasearch
engines. By developing the PSA, these techniques have been investigated and
incorporated to create an effective middleware agent for web search personalisation.
In this thesis, a conceptual model for the Personalised Search Agent is developed,
implemented by developing a prototype and benchmarked the prototype against existing web
search practices. System development methodology which has flexible and iterative
procedures that switch between conceptual design and prototype development was adopted as
the research methodology.
In the conceptual model of the PSA, a multi-layer client server architecture is used by
applying generalisation-specialisation features. The client and the server are structurally the
same, but differ in the level of generalisation and interface. The client handles personalising
information regarding one user whereas the server effectively combines the personalising
information of all the clients (i.e. its users) to generate a global profile. Both client and server
apply the category concept where user selected URLs are mapped against categories. The
PSA learns the user relevant URLs both by requesting explicit feedback and by implicitly
capturing user actions (for instance the active time spent by the user on a URL). The PSA also
employs a keyword-generating algorithm, and tries different combinations of words in a user
search string by effectively combining them with the relevant category values.
The core functionalities of the conceptual model for the PSA, were implemented in a
prototype, used to test the ideas in the real word. The result was benchmarked with the results
from existing search engines to determine the efficiency of the PSA over conventional
searching. A comparison of the test results revealed that the PSA is more effective and
efficient in finding relevant and personalised results for individual users and possesses a
unique user sense rather than the general user sense of traditional search engines.
The PSA, is a novel architecture and contributes to the domain of knowledge web information
searching, by delivering new ideas such as active time based user relevancy calculations,
automatic generation of sensible search keyword combinations and the implementation of a
multi-layer agent architecture. Moreover, the PSA has high potential for future extensions as
well. Because it captures highly personalised data, data mining techniques which employ
case-based reasoning make the PSA a more responsive, more accurate and more effective tool
for personalised information searching.
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Velazquez, Elio. "Mobile agents in distributed search, a comparative study." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57761.pdf.
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Velazquez, Elio Carleton University Dissertation Computer Science. "Mobile agents in distributed search: a comparative study." Ottawa, 2001.
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Mayer, Michael McClanahan. "Persistent search: a bridge between depth-first and breadth-first search for physical agents." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26160.
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Temple, Thomas J. (Thomas John). "A general index heuristic for search with mobile agents." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67175.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 181-187) and index.
This dissertation considers a suite of search problems in which agents are trying to find goals in minimum expected time. Unlike search in data structures in which time is measured by a number operations, search in metric spaces measures time by units of distance and has received much less attention. In particular, search strategies that attempt to minimize expected search time are only available for a handful of relatively simple cases. Nonetheless many relevant search problems take place in metric spaces. This dissertation includes several concrete examples from navigation and surveillance that would have previously only been approachable by much more ad hoc methods. We visit these examples along the way to establishing relevance to a much larger set of problems. We present a policy that is an extension of Whittle's index heuristic and is applicable under the following assumptions. * The location of goals are independent random variables. " The agents and goals are in a length space, i.e., a metric space with continuous paths. * The agents move along continuous paths with bounded speed. " The agents' sensing is noiseless. We demonstrate the performance of our policy by applying it to a diverse set of problems for which solutions are available in the literature. We treat each of the following problems as a special case of a more general search problem: " search in one-dimensional spaces such as the Line Search Problem (LSP) and Cow Path Problem (CPP), " search in two-dimensional spaces such as the Lost in a Forest Problem (LFP) and problems of coverage, " problems in networks such as the Graph Search Problem (GSP) and Minimum Latency Tour Problem (MLTP), and " dynamic problems such as the Persistent Patrol Problem (PPP) and Dynamic Traveling Repairperson Problem (DTRP). On each of these we find that our policy performs comparably to, and occasionally better than, the accepted solutions developed specifically for these problems. As a result, we believe that this dissertation contributes a significant inroad into a large space of search problems that meets our assumptions, but that remains unaddressed.
by Thomas. J. Temple.
Ph.D.
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Gulland, Elizabeth-Kate. "Spatial Semantic Search with Online Agents and Weighted Ontologies." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/59674.
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Information retrieval results can be enhanced by incorporating context from both user and data into a search. This thesis contributes to this aim by automatically building data-specific weighted ontologies for semantic searches, ranking spatial data by proximity to a target location, and encapsulating these abilities into web agents that can return ranked semantic search results in response to a given query input.
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Chryssanthou, Erja. "Studies on laboratory diagnosis of fungal infection and antifungal susceptibility /." Stockholm, 1998. http://diss.kib.ki.se/search/diss.se.cfm?19981016chry.
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Jadhav, Gopal P. "Search for Pseudomonas aeruginosa immune-modulatory but non-inducing agents." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10407/.
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Dysfunctional immunity which is the most common antecedent of immunological diseases is central to the common disorders like rheumatoid arthritis, psoriasis, thyroid disease, type-1 diabetes mellitus, multiple sclerosis and other autoimmune conditions that are leading causes of chronic morbidities and disabilities. The currently employed therapies suffer from serious side effects. For example, steroid therapy, being nonselective is seldom used. Myleotoxicity limits azathioprine while cyclosporine-A (CsA) and FK506 do show myleo-, nephro and neuro-toxicities. Antibody therapies cause immune mediated toxicity. Therefore, the need of developing less toxic and specific immune modulatory agents is a top priority. Recently, Pseudomonas aeruginosa quorum sensing signal molecules (QSSMs), N-(3-oxododecanoyl)-L-homoserine lactone (3O, C12-HSL) and 2-n-heptyl-3-hydroxy-4-(1H)-quinolone (PQS) have been found to modulate eukaryotic immune processes via different targets. The structure activity relationship (SAR) study of 3O, C12-HSL by Chhabra et.al, showed that L-homoserine lactone ring, 3-oxo or hydroxyl group and 12 to14-carbons long acyl chain, apparently conferring optimum lipophilicity and flexibility, are important for immune modulation. However, the new analogues including 3O, C12-HSL negated clinical usefulness as these also participated in bacterial quorum-sensing (QS) activity thus promoting bacterial growth. Also analogues with more than 12-carbons alkyl chain could not be explored by in vitro immune assays due to their limited solubility in the solvents employed. The present study addresses these issues by making further judicial structural changes in the 3O, C12-HSL in order to optimize its immune modulatory activity while losing its intrinsic QS activity. Accordingly, a series of new ring variants, 3-acetoxy, aza, thia, oxa and fluorine substituted analogues were developed. The later were largely confined in the 1, 3-dicarbonyl segment of the 3O, C12-HSL structure in order to modulate the 3-enolic content of the molecule. Also tetramic acid analogue, a non-enzymatic degradative product of 3O, C12-HSL was synthesized. After purity and identity characterization the new analogues were evaluated for their immune modulation (with murine cells proliferation assay), cytotoxicity (with Trypan dye exclusion assay) and auto-inducing or QS activity (with a specifically designed lux bacterial bio-reporter). The splenocyte proliferation assay demonstrated that immune suppression in 4-aza analogues increased with increasing alkyl chain (up to C15) yet without any solubility problems in the standard solvents used. Similar trend was observed when N4 was alkyl substituted (n-propyl, being most potent). At least one of the C2 hydrogens was found to be essential for activity since, difluoro substitution lost activity. Retention of immune suppression by N3-OH and increased potency by N3-NH2 (EC50=0.99 microM) demonstrated that C3=O can be replaced by an appropriate H-bond donor/acceptor groups. Complete loss of activity with 3-thia substitution (3-thia C12-HSL) and then regain of potency by 3-sulfoxide/sulfone derivatives further demonstrated the importance of 3-oxo (suitable H-bond acceptor/donor) in immune suppression. Insertion of oxygen at C4 retained activity but additional oxygen(s) in the side chain yielded analogues that were devoid of immune suppression. Analogue with thiazole ring instead of HSL ring retained activity. In case of hetero ring altered analogues of 3O, 4-aza C12-HSL, almost all retained immune suppressive activities except their oxa analogues. In conclusion, all the above strategies have delivered potent immune modulatory agents yet gratifyingly devoid of QS activity. Some of the most potent and promising non-inducing immune modulatory agents are 3O, 4-aza-C15-HSL (EC50 0.65 microM), 3-NH2-3-aza-C12-HSL (EC50 0.99 microM) and N, N'-dimethyl-2-(3-oxo-4-azadodecanoyl) aminobenzamide (EC50 0.7 microM) and are worthy of further study to be developed as therapeutic agents.
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Heimbürger, Mikael. "Endothelial cell interactions with neutrophils : studies of adhesion and effects of lipoxygenase metabolites and antirheumatic drugs /." Stockholm, 1998. http://diss.kib.ki.se/search/diss.se.cfm?19981023heim.
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Huang, Miao Jun. "Contiguous search by mobile agents in cube networks and chordal rings." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26661.
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In this thesis we consider the problem of searching for an intruder in a network. There is a team of collaborative software agents that are deployed to capture a hostile intruder (e.g., a virus). These agents move along the network links and the intruder has the capability of escaping arbitrarily fast. We propose different strategies for the solution of the problem in some widely used topologies for the local area network and interconnection network: hypercube network, butterfly network and chordal ring network. In each topology, different models are studied depending on the capabilities of agents; i.e., agents' synchronicity, cloning power and visibility. For each model, we analyze the strategies in terms of number of agents employed, number of moves performed by the agents, and time.
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Sundqvist, Jacob, and Jonas Ekskog. "Victim Localization Using RF-signals and Multiple Agents in Search & Rescue." Thesis, Linköpings universitet, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120620.
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A common problem in existing Search And Rescue (SAR) systems is that they must be activated by the missing person in order to work. This requires an awareness of the the risk of becoming distressed, which in many cases is not feasible. Furthermore, most of the localization systems require specialized hardware.In this thesis, the victim is assumed to wear a cellphone that could be located using readily available consumer electronics. A method of estimating the position of a transmitter, given radio signal measurements at different locations, is developed and verified with real and simulated data. A proof-of-concept system is built in which several users can jointly collect received signal strength data at different locations using mobile phones. The system analyzes the data in real-time and guides the users in the search by estimating the origin of the signal.An outdoor field test is conducted in which the searchers using the system are able to locate the hidden target phone without prior knowledge regarding the position. We are able to localize the victim with an accuracy of 10-20 meters in a timely manner using android smartphones. This shows the potential of a similar system in \abbrSAR scenarios. However, more work is needed to make the system viable in real scenarios and to remove some of the delimitations of the current implementation.
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Spiekermann, Sarah [Verfasser], Dan [Gutachter] Ariely, and Oliver [Gutachter] Günther. "Online information search with electronic agents / Sarah Spiekermann ; Gutachter: Dan Ariely, Oliver Günther." Berlin : Humboldt-Universität zu Berlin, 2001. http://d-nb.info/1207621501/34.
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Barbu, Andreea. "Developing mobile agents through a formal approach." Paris 12, 2005. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002282380204611&vid=upec.
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Nous nous intéressons dans cette thèse à la modélisation et à la vérification de systèmes d'agents mobiles. Le développement d'une structure pour les agents mobiles demande le développement de solutions pour un ensemble de problèmes spécifiques dû à la mobilité. Une question dans le développement de logiciel est : le programme proposé est-il vraiment une solution pour le problème considéré. Une façon de répondre à cette question consiste à utiliser les méthodes formelles. Dans notre approche, nous construisons un modèle du problème (la spécification) en uitilisant le Pi calcul d'ordre supérieur. En ayant ce modèle formel comme base, Nous pouvons vérifier que ce modèle possède les propriétés voulues ; valider le modèle à travers es simulations ; être capable de prouver que l'implémentation est cohérente par rapport à la spécification. En profitant de nos résultats, nous avons implémenté un prototype qui permet la validation de systèmes d'agents mobiles conçus avec le Pi-calcul d'ordre supThis thesis deals with the modelling and validation of mobile agent systems. The development of a support structure for mobile agents demans the development of solutions for set of specific problems that appear due to mobility. A basic question in software development is if the proposed program is really a solution for the considered problem. One way to answer this question is through the use of formal methods. In our approach, the first step is to build a model of the solution (specification) using the higher-order Pi-calculus. Having this formal model as a base, we can : validate the model through simulations ; carry out mathematical tests to guarantee that this model possesses the required properties (verification) ; being able to prove that the implementation is correct with respect to the specification. Making use of our results, we have implemented a prototype called HOPiTool which allows the possibility of validation of mobile agent systems conceived with higher-order Pi-calc
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Williams, Philip. "Chemical investigations of marine cyanobacteria : the search for new anticancer agents from the sea /." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6878.
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Trias, Mansilla Albert. "Unstructured P2P social search query routing algorithms for agentified social networks." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/131395.
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The village paradigm presents some benefits compared with the library paradigm; people can adapt the answer content as a function of who is requesting the information, or furthermore, people can perform clarifications of the answer content; at the same time, the explanations in documents remain static and are the same for all of the readers, and no clarifications can be performed. The proliferation of online social networks along with the advances in artificial intelligence allow us to consider village paradigm automation. The contributions of this doctoral dissertation are the following: to analyze the village paradigm, seeking the aspects that might be automated; the Asknext social search protocol, which uses stop messages; to study the effect of social network topologies on the proposed protocol; the algorithm Question Waves, which contributes in improving the relevance of the received answersEl paradigma del poble presenta alguns beneficis enfront al de la biblioteca, com que les persones poden adaptar el contingut de la resposta en funció de qui tenen davant o fins i tot poden fer aclariments sobre el contingut, mentre el contingut dels textos es manté estàtic. La proliferació de les xarxes socials, conjuntament amb els avenços en intel·ligència artificial, permeten considerar l’automatització del paradigma del poble. Les contribucions d’aquesta tesi són: analitzar el paradigma del poble per veure quins aspectes són automatitzables; el protocol de cerca social Asknext, que utilitza missatges d’aturada; estudiar l’efecte de les característiques de les topologies de les xarxes socials en el protocol Asknext; l’algorisme Question Waves, que contribueix en millorar la rellevància de les respostes rebudes en el procés de cerca
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Feng, Chao. "Approaches to the Search of Platinum Anticancer Agents: Derivatizing Current Drugs and Incorporating HDAC Inhibition." Scholarly Commons, 2019. https://scholarlycommons.pacific.edu/uop_etds/3637.
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Platinum-based anticancer drugs, such as cisplatin, carboplatin, and oxaliplatin, have been approved for clinical use worldwide for decades. Despite their enormous success, their widespread application is hindered by either cross-resistance or toxic side effects, including nephrotoxicity and neurotoxicity. The need to overcome these drawbacks has stimulated the search for new platinum-based drugs.
This dissertation will start with the accidental discovery of cisplatin, followed by an introduction of other platinum-based anticancer agents, including the action mechanism, general structures, and development history. Picoplatin is a newer generation of platinum-based anticancer agent. The bulky 2-methylpyridine as a non-leaving group on picoplatin could reduce the detoxification effect caused by thiol-containing species, such as glutathione and metallothionein, thus may grant picoplatin the ability to overcome cisplatin resistance. A convenient synthesis route for picoplatin derivatives has been developed. 11 new picoplatin derivatives have been designed by varying the bulkiness of the non-leaving amine group. All complexes have been characterized by different instrumentations, including MS, 1H NMR, 13C NMR, 195Pt NMR, HMQC, X-ray crystallography, and elemental analysis. Different bioassays, such as DNA binding, cell viability, and cellular accumulation, have been applied to evaluate their efficacy on cisplatin-sensitive ovarian cancer cell line A2780 and cisplatin-resistant ovarian cancer cell line A2780cis. The newly designed picoplatin derivatives show comparable efficacy with that of picoplatin and less resistance compared with cisplatin. The study of picoplatin derivatives laid the foundation toward the research of bifunctional platinum-based anticancer agents by incorporating histone deacetylase (HDAC) inhibition.
Histone acetyltransferase (HAT) and histone deacetylase (HDAC) are a pair of important enzymes in epigenetic regulation. They work in harmony to acetylate and deacetylate histone lysine residues, resulting in a more relaxed or more condensed chromatin structure, respectively. HDAC has been found to be overexpressed in some cancer cells. Since 2006, 5 HDAC inhibitors (HDACi) have entered clinical use for cancer treatment. 19 new HDACi with additional coordination sites on the phenyl cap have been designed, synthesized, and evaluated. A few of the new HDACi show comparable or even better HDAC inhibition than that of Vorinostat (SAHA, the first FDA approved HDACi).
A logical design would involve the installation of HDACi on the platinum center as a non-leaving group ligand. When the bifunctional drug reaches the cancer cell, the synergistic effect could be maintained as the relaxed chromatin structure makes DNA more susceptible to be attacked by the platinum centers, thus increase the anticancer activity and possibly selectivity toward cancer cells. 6 Pt-HADCi conjugates have been designed and synthesized. Dual functions of the new Pt-HDACi have been confirmed by DNA electrophoresis assay and HDAC inhibition assay. One of the Pt-HDACi (CF-101) shows comparable cytotoxicity with cisplatin and less resistance, which could be used as the lead compound for further structural modification and in vivo studies.
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Kang, Shugang. "Multi-agent based beam search for intelligent production planning and scheduling." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38977205.
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Kang, Shugang, and 康書剛. "Multi-agent based beam search for intelligent production planning and scheduling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38977205.
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Stavrunova, Olena. "Labor market policies in an equilibrium matching model with heterogeneous agents and on-the-job search." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/150.
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Tabaza, Yahia Zakaria Abdelqader. "Implementing metabolomics tools in the search for new anti-proliferative agents from the plant-associated endophytes." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29567.
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In the search for new anticancer agents of natural origin against breast and lung cancer (ZR-75 and A549 cancer cell lines, respectively), plant-associated endophytes could be a good source for bioactive secondary metabolites. Twenty six endophytes were obtained from four different Jordanian plants; Anchusa strigosa, Anthemis palestina, Euphorbia peplus and Rumex cyprius. Internal transcribed spacer (ITS) gene sequencing was implemented to identify the obtained endophytes. Based on their biological activity and chemical profile, three endophytes namely Curvularia australiensis, Chaetomium subaffine and Fusarium acuminatum were chosen for the scale-up. These endophytes were cultured in liquid and rice media at different time periods to optimise their growth and production of compounds, employing both NMR and mass spectrometry-based metabolomics. The medium that afforded better yield, more chemical diverse extract and more potent biological activity was chosen for scaling-up purposes. Each of the scaled-up extracts was subjected to liquid-liquid partitioning followed by fractionation using a high-throughput flash-chromatography system. The fractions obtained from the first chromatography step were tested in-vitro against both breast and lung cancer (ZR-75 and A549 cell lines, respectively) and analysed using both proton nuclear magnetic resonance (NMR) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The HRMS data were processed with MZmine then subjected to Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA). The OPLS-DA results pinpointed the biologically active secondary metabolites. Metabolomics-guided isolation work targeted the bioactive secondary metabolites. As a result, five new compounds and ten known compounds were obtained from the three scaled-up endophytes. The isolated compounds were elucidated by employing 1D and 2D NMR then tested against ZR-75 and A549 cell lines. Twelve compounds were found active against ZR-75 cell line, which included five new compounds. Six compounds were found active against A549 cell line that included one of the new natural products isolated.
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Barus, M. M. "Search for antimicrobial agents among functional derivatives of 3-[5-(4-nitrophenyl) -2-furyl] -4-pyrazolecarbaldehydes." Thesis, БДМУ, 2021. http://dspace.bsmu.edu.ua:8080/xmlui/handle/123456789/18517.
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Tu, Jian. "Combinational search for diagnostic agents and application of affinity capillary electrophoresis in high-throughput library screening /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488190109871014.
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Wong, Su Yong. "Aspects of cellular damage induced by physical and chemical (mitochondriotropic) agents." Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020644.
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Various agents such as heat, ultrasound, rhodamine derivatives and carbonylcyanide m-chlorophenylhydrazone are used to induce cellular damage so as to understand certain events leading to cell death using a mammalian cell culture system - HeLa S3 cells. Clonogenic assay is insensitive as it is an end-point technique for determining the effectiveness of cell-killing. A combined approach using protein synthesis, oxygen consumption, time-sequenced morphological study, flow cytometric analysis and others is used instead. Ultrasound is used also because it can produce heat especially when focussing beams are employed. However, with the present experimental set-up system, it is the formation of microbubbles (cavitations) together with microstreaming in a fluid medium and not heat, that produce the 'shattering' damage to the HeLa S3 cells in suspensions. Heating e.g. at 42oC for a brief period can produce 'thermoprotection' to other stimuli, in this case ultrasound. Mitochondria are found to be highly sensitive to heat especially at 45oC and the compounds used in this study. Multivesicular and myelinoid-multivesicular bodies are related to mitochondria. Lysosomes do not appear to play a critical role in the early events leading to cell death. It is suggested that by damaging mitochondria leading to an irreversible state of cellular 'energy crisis' could be the earliest event in cell death.
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Kellett, Matthew. "Black Hole Search in the Network and Subway Models." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20674.
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In this thesis we look at mobile agent solutions to black hole search and related problems. Mobile agents are computational entities that are autonomous, mobile, and can interact with their environment and each other. The black hole search problem is for a team of these agents to work together to map or explore a graph-like network environment where some elements of the network are dangerous to the agents. Most research into black hole search has focussed on finding a single dangerous node: a black hole. We look at the problem of finding multiple black holes and, in the case of dangerous graph exploration, multiple black links as well.
We look at the dangerous graph exploration problem in the network model. The network model is based on a normal static computer network modelled as a simple graph. We give an optimal solution to the dangerous graph exploration problem using agents that start scattered on nodes throughout the network. We then make the problem more difficult by allowing an adversary to delete links during the execution of the algorithm and provide a solution using scattered agents.
In the last decade or two, types of networks have emerged, such as ad hoc wireless networks, that are by their nature dynamic. These networks change quickly over time and can make distributed computations difficult. We look at black hole search in one type of dynamic network described by the subway model, which we base on urban subway systems. The model allows us to look at the cost of opportunistic movement by requiring the agents to move using carriers that follow routes among the network's sites, some of which are black holes. We show that there are basic limitations on any solution to black hole search in the subway model and prove lower bounds on any solution's complexity. We then provide two optimal solutions that differ in the agents' starting locations and how they communicate with one another.
Our results provide a small window into the cost of deterministic distributed computing in networks that have dynamic elements, but which are not fully random.
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Liao, Yan. "Decentralized Decision Making and Information Sharing in a Team of Autonomous Mobile Agents." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353101024.
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Buron, Cédric. "Un système multi-agents pour une place de marché de facture." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS314.
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Dans les entreprises, l’écart entre la date où les entreprises engagent leurs dépenses et la date où elles sont payées entraîne un besoin en fonds de roulement à l’origine de problèmes dont la sévérité va de la perte de contrat au dépôt de bilan. Dans le contexte actuel, le recours à l’emprunt pour éviter ces situations est hélas complexe pour les PME, les banques refusant de prêter lorsqu’elles estiment que le risque est trop important. Une possibilité est alors de recourir au factoring, et de faire financer ses créances. Dans cette thèse, nous proposons une place de marché de factoring intelligente, basée sur des travaux de négociation automatique et de mechanism design: nous proposons d’analyser théoriquement et expérimentalement les problématiques liées aux agents curieux cherchant à inférer les informations privées des autres agents, entraînant des surcoûts de leur point vue comme de celui de la plate-forme. Nous proposons également de concevoir un protocole de négociation qui s’oppose à de tels comportements, donnant aux agents une incitation à ne négocier que lorsqu’ils souhaitent vraiment obtenir un bien. Nous proposons ensuite un agent de négociation automatique. Pour la conception de la stratégie de notre agent, nous proposons d’exploiter les méthodes de Monte Carlo Tree Search, qui ont récemment fait leur preuve dans l’IA pour les jeux. Notre agent est capable d’apprendre de son partenaire bien que ce ne soit pas son objectif premier, afin de trouver un accord qui lui soit favorable. Il s’appuie pour cela sur des technique de modélisation d’adversaire impliquant des méthodes d’apprentissage tels que l’apprentissage bayésien et la régression de processus gaussiensFor most companies, the time gap between the moment when they begin to spend money and the moment when they receive payment from their customer generates a working capital requirement. The latter may create issues such as contract lost or bankruptcy. In the current context, getting credits from banks may be either costly or even impossible for Small and Medium Enterprises. Indeed, many banks refuse to lend money for small companies or when they estimate that there is a risk. It is then possible to rely on other solutions as factoring and get immediate credit from the invoices. In this thesis, we propose a factoring marketplace based on related to curious agents that try to infer private information from their partners. This kind of behavior is harmful both for the agents and for the platform more generally. We thus propose to design a negotiation protocol resistant to such behavior by endowing the agents with an incentive to negotiate only when they really try to get a good. We then propose an automated negotiation agent which relies on Monte Carlo Tree Search techniques. Those techniques have proved to be quite efficient in AI for games. Our agent is able to learn information from its partner, though it is not its main objective in order to get to a beneficial agreement. For this purpose, it relies on opponent modeling techniques and machine learning such as Bayesian Learning and Gaussian Process Regression
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Yap, MunTuck. "An Investigation of a Distributed Search Mechanism Consisting of a Set of Cooperative Agents Implemented With Different Heuristics Schemes." NSUWorks, 2002. http://nsuworks.nova.edu/gscis_etd/936.
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The purpose of this research is to investigate a model for designing distributed search algorithm based on the use of a distributed system of cooperating agents who communicate only through messages. This model does not require any form of synchronization among the agents as required in most models of distributed algorithms. Each message contains both the state of the computation and eventually the solution to the problem. For a solution to be complete, all the agents within the domain must process the message. This form of processing is termed as "assembly-line processing". This model is not dependent on the ordering of messages but the arrival of each message presents a unique solution to the problem. To demonstrate the usefulness of this model, this research had selected the Traveling Salesman Problem (TSP). It is not the intent of this research to find a faster method for solving the TSP. By making use of various known schemes for solving the TSP to be implemented within the framework of this model demonstrates the usefulness of this computational model to build distributed search algorithms fairly easily without having to worry about synchronization issues. The known schemes for solving TSP ranges from the brute-force method to the ant colony scheme. The heuristic schemes use some evaluation functions to remove "not-so-good" solutions fairly early in the processing. This has the advantage of decreasing the number of messages being relayed. The results from these schemes demonstrate the feasibility of this model for solving problems like the TSP. This research also demonstrates that without having to worry about synchronization issues allows changes to be made to schemes more manageable. More work is required to determine the operational characteristics of this model and the type of problems it can handle.
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Sghir, Inès. "A Multi-Agent based Optimization Method for Combinatorial Optimization Problems." Thesis, Angers, 2016. http://www.theses.fr/2016ANGE0009/document.
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Nous élaborons une approche multi-agents pour la résolution des problèmes d’optimisation combinatoire nommée MAOM-COP. Elle combine des métaheuristiques, les systèmes multi-agents et l’apprentissage par renforcement. Les heuristiques manquent d’une vue d’ensemble sur l’évolution de la recherche. Notre objectif consiste à utiliser les systèmes multi-agents pour créer des méthodes de recherche coopératives. Ces méthodes explorent plusieurs métaheuristiques. MAOM-COP est composée de plusieurs agents qui sont l’agent décideur, les agents intensificateurs et les agents diversificateurs (agents croisement et agent perturbation). A l’aide de l’apprentissage, l’agent décideur décide dynamiquement quel agent à activer entre les agents intensificateurs et les agents croisement. Si les agents intensificateurs sont activés, ils appliquent des algorithmes de recherche locale. Durant leurs recherches, ils peuvent s’échanger des informations, comme ils peuvent déclencher l’agent perturbation. Si les agents croisement sont activés, ils exécutent des opérateurs de recombinaison. Nous avons appliqué MAOM-COP sur les problèmes suivants : l’affectation quadratique, la coloration des graphes, la détermination des gagnants et le sac à dos multidimensionnel. MAOM-COP possède des performances compétitives par rapport aux algorithmes de l’état de l’artWe elaborate a multi-agent based optimization method for combinatorial optimization problems named MAOM-COP. It combines metaheuristics, multiagent systems and reinforcement learning. Although the existing heuristics contain several techniques to escape local optimum, they do not have an entire vision of the evolution of optimization search. Our main objective consists in using the multi-agent system to create intelligent cooperative methods of search. These methods explore several existing metaheuristics. MAOMCOP is composed of the following agents: the decisionmaker agent, the intensification agents and the diversification agents which are composed of the perturbation agent and the crossover agents. Based on learning techniques, the decision-maker agent decides dynamically which agent to activate between intensification agents and crossover agents. If the intensifications agents are activated, they apply local search algorithms. During their searches, they can exchange information, as they can trigger the perturbation agent. If the crossover agents are activated, they perform recombination operations. We applied MAOMCOP to the following problems: quadratic assignment, graph coloring, winner determination and multidimensional knapsack. MAOM-COP shows competitive performances compared with the approaches of the literature
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Kaczmarska, Zuzanna. "Search for new antiviral compounds using fragment screening methodology." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285075.
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Picornaviridae are among the most diverse and oldest known viral families that include many important pathogens of humans and animals. They are small, icosahedral (+)ssRNA viruses, causing a variety of diseases, such as encephalitis, and poliomyelitis. Vaccines are available for poliovirus, hepatitis A virus and foot-and mouth disease virus, but no effective prophylaxis is implemented for other picornaviruses. Thus far, anti-viral research has focused on the capsid, whereas inhibitors targeting non-structural proteins (i.e. proteases, helicases, polymerases) have remained largely unaddressed.
The project was focused on structural and biochemical characterization of the enterovirus-B93 (EVB93) 3C protease alone and in complex with several covalent inhibitors. The second objective was to identify the first non-covalent potent inhibitors of the EV-B93 3C protease and their further biochemical, antiviral, and structural evaluation.
This work studied the in-vitro proteolytic activity of the EV-B93 3C protease, alone and in the presence of two known covalent inhibitors - rupintrivir and compound 1, as well as three low molecular weight covalent inhibitors - NZO, NZN and DB5_60. The crystal structures of the EV-B93 3C protease alone and in complex with rupintrivir, compound 1, and NZN molecule were solved at high resolution (1.57, 1.50, 1.32, and 1.73 Å, respectively). The structures revealed that the protein adapts a chymotrypsinlike fold similarly to other picornavirus 3C proteases and possesses His-40, Glu-71 and Cys-147 as a catalytic triad.
The STD NMR-based fragment screening was performed to select non-covalent binders of the EV-B93 3C protease. Validation and profiling of the most promising non-covalent hits were done using thermal shift assay (TSA), surface plasmon resonance (SPR), and proteolytic activity assay. 44 analogs of the most potent molecule were evaluated in the in-vitro proteolytic activity assay. The most active compound displayed IC50 value of 5 flM. Further chemical optimization was performed resulting in more efficient inhibitor with similar IC50 value. Selected analogs were tested in the in-vitro proteolytic assay against analogous 3C proteases from the following viruses: human rhinovirus-A49, enterovirusD68, aichivirus A, porcine sapelovirus, and equine rhinitis B virus. All compounds exhibited good inhibitory activity against three of the tested proteases. Furthermore, in a cell-based proteolytic assay and an antiviral assay the compounds did not exhibit either proteolytic or antiviral activity, which may be explained by several factors such as lack of cell permeability, low solubility and/or high toxicity.
Extensive co-crystallization and soaking trials were performed to obtain crystal structures of noncovalent complexes of the EV-B93 3C protease with the most potent compounds. Regrettably, no additional electron density was identified in the proteolytic active site. Bioinformatics docking simulations suggested potential binding mode of the optimized compound. These pointed to the presumed pockets occupied by the compound that interact with the two conserved residues from the catalytic triad. Since the most potent compound is a relatively large and rigid molecule, it is unable to bind to the protease without its previous rearrangement, which is unfavorable in the crystalline state of the protein. This observation may explain the inability of the non-covalent molecules to co-crystallize with EV-B93 3C protease. The results obtained in this study may aid the design of potent, noncovalent antivirals targeting enteroviral 3C proteases.Los Picornaviridae son una de las familias de virus más diversas y conocidas desde hace más tiempo. Esta familia incluye importantes agentes patógenos que afectan a humanos y a animales. Los Picornaviridae son virus pequeños, icosaédricos, de ARN de cadena sencilla de sentido positivo y causan una gran variedad de enfermedades, tales como encefalitis y poliomielitis. Se dispone de vacunas para el poliovirus, el virus de la hepatitis A y el virus de la fiebre aftosa, pero no se ha implementado ninguna profilaxis efectiva para otros picornavirus. Hasta ahora, la investigación antiviral se ha centrado en la cápside, mientras que los inhibidores dirigidos a proteínas no estructurales (como las proteasas, las helicasas y las polimerasas) están todavía por explorar. Este proyecto se centró en la caracterización estructural y bioquímica de la proteasa 3C de enterovirus B93 (EV-B93) y de los complejos de esta proteasa con varios inhibidores covalentes. El segundo objetivo fue conseguir inhibidores no covalentes de la proteasa EV-B93 3C y realizar una caracterización bioquímica, antiviral y estructural de los complejos de EV-B93 3C con estos inhibidores.
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Au, Manix. "Automatic State Construction using Decision Trees for Reinforcement Learning Agents." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/15965/1/Manix_Au_Thesis.pdf.
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Reinforcement Learning (RL) is a learning framework in which an agent learns a policy from continual interaction with the environment. A policy is a mapping from states to actions. The agent receives rewards as feedback on the actions performed. The objective of RL is to design autonomous agents to search for the policy that maximizes the expectation of the cumulative reward.
When the environment is partially observable, the agent cannot determine the states with certainty. These states are called hidden in the literature. An agent that relies exclusively on the current observations will not always find the optimal policy. For example, a mobile robot needs to remember the number of doors went by in order to reach a specific door, down a corridor of identical doors.
To overcome the problem of partial observability, an agent uses both current and past (memory) observations to construct an internal state representation, which is treated
as an abstraction of the environment.
This research focuses on how features of past events are extracted with variable granularity regarding the internal state construction. The project introduces a new method that applies Information Theory and decision tree technique to derive a tree structure, which represents the state and the policy. The relevance, of a candidate feature, is assessed by the Information Gain Ratio ranking with respect to the cumulative expected reward.
Experiments carried out on three different RL tasks have shown that our variant of the U-Tree (McCallum, 1995) produces a more robust state representation and faster learning. This better performance can be explained by the fact that the Information Gain Ratio exhibits a lower variance in return prediction than the Kolmogorov-Smirnov statistical test used in the original U-Tree algorithm.
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Au, Manix. "Automatic State Construction using Decision Trees for Reinforcement Learning Agents." Queensland University of Technology, 2005. http://eprints.qut.edu.au/15965/.
Full textAbstract:
Reinforcement Learning (RL) is a learning framework in which an agent learns a policy from continual interaction with the environment. A policy is a mapping from states to actions. The agent receives rewards as feedback on the actions performed. The objective of RL is to design autonomous agents to search for the policy that maximizes the expectation of the cumulative reward. When the environment is partially observable, the agent cannot determine the states with certainty. These states are called hidden in the literature. An agent that relies exclusively on the current observations will not always find the optimal policy. For example, a mobile robot needs to remember the number of doors went by in order to reach a specific door, down a corridor of identical doors. To overcome the problem of partial observability, an agent uses both current and past (memory) observations to construct an internal state representation, which is treated as an abstraction of the environment. This research focuses on how features of past events are extracted with variable granularity regarding the internal state construction. The project introduces a new method that applies Information Theory and decision tree technique to derive a tree structure, which represents the state and the policy. The relevance, of a candidate feature, is assessed by the Information Gain Ratio ranking with respect to the cumulative expected reward. Experiments carried out on three different RL tasks have shown that our variant of the U-Tree (McCallum, 1995) produces a more robust state representation and faster learning. This better performance can be explained by the fact that the Information Gain Ratio exhibits a lower variance in return prediction than the Kolmogorov-Smirnov statistical test used in the original U-Tree algorithm.
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Chitkul, Bordin. "Solid phase synthesis of polyamine conjugates in the search for new inhibitors of trypanothione reductase and transfection agents for gene therapy." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393917.
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Waiter, Gordon David. "The NMR proton relaxation effectiveness of paramagnetic metal ions and their potential as MRI contrast agents." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU077829.
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Paramagnetic lanthanide ions have been investigated as possible MIR phantom materials and contrast agents. The aim of this study is to determine if it is possible to apply the well known Solomon-Bloembergen equations to solutions of paramagnetic lanthanide ions that have fast electron spin relaxation times, compared to Gadolinium, the most widely used ion for NMR. Studies of the relaxivity, frequency and temperature dependence, show that there is a considerable difference in those properties over the series. Chelation of the ions to EDTA and DTPA resulted in a decrease in the relaxivity which was directly proportional to the decrease in the number of water molecules in the inner co-ordination sphere. The fit of the Solomon-Bloembergen equations to the variable frequency and temperature relaxation times showed that theory is valid for the fast electron spin ions and allowed the calculation of the electron spin relaxation times. This showed that there is a difference of 5 orders of magnitude between Gadolinium, the ion demonstrated to have a slow electron spin relaxation time, and the remaining ions. The addition of EDTA chelated forms of these ions to agarose gels produced NMR phantom materials with relaxation time characteristics that could be chosen to fulfil a desired application. The biodistribution of Gd-DTPA was investigated using ESR and NMR. The concentration of Gd-DTPA in excised rat tissue, 20 minutes after intraperitoneal injection, was determined, by the change in NMR water proton relaxation time from that of a control tissue, and by ESR from direct measurement of the microwave power absorbed by the sample, which is directly proportional to the number of unpaired electron spins in the sample. The results from these two methods of determining contrast agent concentration agree well with each other both in the order of biodistribution and on the absolute concentrations.
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Rouet, Vincent. "Étude des interactions du VEGF (Vascular Endothelial Growth Factor) et de biomimétiques des héparanes sulfates, les RGTA (ReGeneraTing Agents)." Paris 12, 2004. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002147210204611&vid=upec.
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L'angiogenèse est un processus dynamique par lequel de nouveaux vaisseaux capillaires sanguins se forment. Ce phénomène est dépendant à la fois (les facteurs (le croissance, comme le VEGF (Vascular Endothelial growth Factor) et des composants de la matrice extracellulaire tels que les héparanes sulfates (HS). Les RGTA (ReGeneraTing Agents) sont des mimétiques (les HIS qui agissent in vivo en stimulant la vitesse et la qualité des processus cicatriciels et en particulier la phase d'angiogenèse. Ce travail a permis d'établir que les RGTA, biopolymères mimant sur le plan fonctionnel les HS et dont la définition chimique est maîtrisée et définie par la qualité et le taux de groupement chimiques qui les caractérisent. Interagissent fortement en fonction de leur structure avec le VEGF, Ils augmentent de plus la fixation du VEGF à ses récepteurs de haute affinité. Ces interactions modulent les activités biologiques du VEGF en augmentant la prolifération et la migration des cellules endothéliales in vitro et l'angiogenèse in vivo. Ces interactions ne s'expriment qu'a partir du moment où les RGTA possèdent (les groupements carboxylates et sulfates, ces derniers apparaissant comme les groupements ionisables les plus impliqués. L'activité potentialisatrice d'un RGTA carboxyméthylé et sulfaté appelé Dl20 a également été démontrée dans un modèle d'angiogenèse in vivo au cours de la régénération musculaire. Cette étude a comparé les cinétiques d'expression de certains gènes les plus caractéristiques de l'angiogenèse dans un muscle squelettique soumis à une ischémie totale chez le rat. Les analogies fonctionnelles des RGTA avec les HS naturels dépendent de la fonctionnalisation de ces biomimétiques comme l'illustre la qualité des interactions établies avec le VEGF et les activités biologiques qui en découlent au cours de l 'angiogenèse associée à la régénération du muscle squelettiqueAngiogenesis is a process involved in the growth of new blood vessels capillaries that is dependant on both growth factors like VEGF (Vascular Endothelial growth Factor) and extracellular matrix components like heparan sulfate (HS). RGTA are HS mimetics whose chemical composition is controlled and defined that act in vivo as wound healing and angiogenesis stimulators. This study showed that RGTA bound with high affinity to VEGF. They enhance the fixation of VEGF to its high affinity receptors and are involved in VEGF biological activities potentializatio. Including the proliferation and migration of endothelial cells in vitro and angiogenesis in an in vivo assay. In a structure-function relationship study, ve showed that the carhoxymethylated and sulfated residues were involved in the RGTA effects. A carboxymethylated and sulfated RGTA named D120 is c efficient in potentializating angiogenesis in a model of muscular regeneration, as observed with angiogenesis related-gene expression analyses throughout skeletal muscular ischemia kinetic study. In conclusion, this study has begun to elucidate both structural requirements and functional implications of RGTA and VEGF interaction and its biological impact on physiolocical angiogenesis
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Kanzow, Sebastian. "Approche pour l'ordonnancement distribué de workflows dans le contexte d'entreprises virtuelles : une méthodologie basée multi-agents pour la planification et l'éxécution de processus distribués." Paris 12, 2004. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002137950204611&vid=upec.
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Les workflows inter-organisationnels sont soumis à des contraintes particulières : leur nature distribuée exclut toute gestion centralisée, pour des raisons de confidentialité et déchelle. Nous développons une méthodologie multi-agents, pour l'ordonnancement distribué dynamique de tâches assujetties à des contraintes temporelles et de ressources. L'algorithme d'ordonnancement est basé sur un calcul dynamique de la priorité des tâches. La confidentialité est respectée, en limitant les informations échangées à des valeurs probabilistes. L'architecture s'appuie sur la mobilité d’agents chargés de l'exécution des tâches et sur la gestion réactive des ressources, où des perturbations sont absorbées implicitement. Nous définissons le protocole de négociation entre les agents et deux heuristiques pour l'allocation et l'ordonnancement de tâchesInter-organizational workflows are particularly constrained: their distributed nature excludes centralized management, for confidentiality and scalability reasons. We develop a multi-agent methodology for distributed dynamic scheduling of tasks that are subject to temporal and resource constraints, based on a dynamic priority determination. Confidentiality is respected by limiting information exchange to probabilistic values. The proposed architecture relies on mobile agents for task execution and reactive resource management, where perturbations are absorbed implicitly. We define a negotiation protocol between agents and two heuristics for task assignment and scheduling
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Guo, Yuhan. "Metaheuristics for solving large size long-term car pooling problem and an extension." Thesis, Artois, 2012. http://www.theses.fr/2012ARTO0206/document.
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La dispersion spatiale de l'habitat et des activités de ces dernières décennies a fortement contribué à un allongement des distances et des temps de trajets domicile-travail. Cela a pour conséquence un accroissement de l'utilisation des voitures particulières, notamment au sein et aux abords des grandes agglomérations. Afin de réduire les impacts dus à l'augmentation du trafic routier, des services de covoiturage, où des usagers ayant la même destination se regroupent en équipage pour se déplacer, ont été mis en place partout dans le monde. Nous présentons ici nos travaux sur le problème de covoiturage régulier. Dans cette thèse, le problème de covoiturage régulier a été modélisé et plusieurs métaheuristiques de résolution ont été implémentées, testées et comparées. La thèse est organisée de la façon suivante: tout d'abord, nous commençons par présenter la définition et la description du problème ainsi que le modèle mathématique associé. Ensuite, plusieurs métaheuristiques pour résoudre le problème sont présentées. Ces approches sont au nombre de quatre: un algorithme de recherche locale à voisinage variable, un algorithme à base de colonies de fourmis, un algorithme génétique guidée et un système multi-agents génétiques auto-adaptatif. Des expériences ont été menées pour démontrer l'efficacité de nos approches. Nous continuons ensuite avec la présentation et la résolution d'une extension du problème de covoiturage occasionel comportant plusieurs destinations. Pour terminer, une plate-forme de test et d'analyse pour évaluer nos approches et une plate-forme de covoiturage sont présentées dans l'annexeNowadays, the increased human mobility combined with high use of private cars increases the load on environment and raises issues about quality of life. The extensive use of private cars lends to high levels of air pollution, parking problem, traffic congestion and low transfer velocity. In order to ease these shortcomings, the car pooling program, where sets of car owners having the same travel destination share their vehicles, has emerged all around the world. We present here our research on the long-term car pooling problem. In this thesis, the long-term car pooling problem is modeled and metaheuristics for solving the problem are investigated. The thesis is organized as follows. First, the definition and description of the problem as well as its mathematical model are introduced. Then, several metaheuristics to effectively and efficiently solve the problem are presented. These approaches include a Variable Neighborhood Search Algorithm, a Clustering Ant Colony Algorithm, a Guided Genetic Algorithm and a Multi-agent Self-adaptive Genetic Algorithm. Experiments have been conducted to demonstrate the effectiveness of these approaches on solving the long-term car pooling problem. Afterwards, we extend our research to a multi-destination daily car pooling problem, which is introduced in detail manner along with its resolution method. At last, an algorithm test and analysis platform for evaluating the algorithms and a car pooling platform are presented in the appendix
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Kem, Oudom. "Modélisation et exploitation des connaissances de l’environnement : une approche multi-agents pour la recherche d’itinéraires multi-objectifs dans des environnements ubiquitaires." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEM023.
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L'utilisation des téléphones intelligents, le recours aux assistants personnels intelligents ou encore le développement des maisons intelligentes sont autant d'exemples illustrant le développement toujours plus rapide de l'informatique ubiquitaire, de l'Internet des objets et de l'intelligence artificielle. Le croisement des résultats issus de ces domaines de recherche contribue à changer notre quotidien et constitue un environnement fertile pour de nouveaux travaux. Ainsi, l’intégration des entités cyber-physiques dans des environnements sociaux de différentes échelles allant des maisons aux villes intelligentes amène de très nombreuses perspectives. Ce changement de paradigme met à notre disposition une énorme quantité d'informations et de services utiles, offrant ainsi la possibilité de traiter les problèmes classiques de manière nouvelle, différente et potentiellement plus efficace. Si les solutions à construire bénéficient de ces possibilités, elles doivent également répondre à de nouvelles contraintes et nouveaux défis. La recherche d’itinéraires multi-objectifs est un sous-cas du problème classique de recherche d'un chemin entre un lieu de départ et une destination auquel s'ajoute la contrainte de passage par un ensemble de lieux permettant de satisfaire un ensemble de buts. L'objectif de cette thèse est de proposer une solution pour la résolution de la recherche d'itinéraires multi-objectifs appliqués aux environnements cyber-physiques tels que les Smart Transits. Dans notre solution, nous avons proposé une méthode fondée sur les technologies du web sémantique pour modéliser de manière intégrée un environnement cyber-physique dans toutes ses dimensions, i.e., cybernétiques, physiques et sociales. Pour la recherche de chemin, nous avons proposé une approche multi-agents, exécutant un algorithme de recherche collaborative et incrémentale, qui utilise les connaissances de l'environnement pour trouver le chemin optimal. Cet algorithme adapte aussi le chemin en prenant en compte la dynamique de l'environnementFrom intelligent artificial personal assistants to smart cities, we are experiencing the shifting towards Internet of Things (IoT), ubiquitous computing, and artificial intelligence. Cyber-physical entities are embedded in social environments of various scales from smart homes, to smart airports, to smart cities, and the list continues.This paradigm shift coupled with ceaseless expansion of the Web supplies us with tremendous amount of useful information and services, which creates opportunities for classical problems to be addressed in new, different, and potentially more efficient manners. Along with the new possibilities, we are, at the same time, presented with new constraints, problems, and challenges. Multi-goal pathfinding, a variant of the classical pathfinding, is a problem of finding a path between a start and a destination which also allows a set of goals to be satisfied along the path. The aim of this dissertation is to propose a solution to solve multi-goal pathfinding in ubiquitous environments such as smart transits. In our solution, to provide an abstraction of the environment, we proposed a knowledge model based on the semantic web technologies to describe a ubiquitous environment integrating its cybernetic, physical, and social dimensions. To perform the search, we developed a multi-agent algorithm based on a collaborative and incremental search algorithm that exploits the knowledge of the environment to find the optimal path. The proposed algorithm continuously adapts the path to take into account the dynamics of the environment
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Rossi, Ednilson Geraldo. "Ambiente de apoio ao desenvolvimento de aplicações distribuídas e reconfiguráveis utilizando agentes de busca e classificação inteligentes." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-24092009-154121/.
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A área de engenharia de software passou por muitas alterações desde sua criação. Vista como uma técnica para aumentar a produtividade e baixar os custos, a reutilização de software é um dos principais estudos dos pesquisadores da área de computação. Como a reconfiguração de software é na verdade a reutilização de um software, porém com algumas adaptações, este trabalho tem por objetivo desenvolver uma metodologia e um conjunto de ferramentas que agilizem e facilitem o processo de reutilização/reconfiguração de componentes de software. A associação destas ferramentas constitui um mecanismo de armazenamento, indexação, busca e recuperação de artefatos de software. Este mecanismo trabalha com a estrutura dos projetos de software e também com as relações semânticas existentes entre os termos utilizados no software. Para representar a estrutura interna do software (características e relacionamentos) utiliza-se de um metamodelo. Já as relações semânticas são representadas por meio de um tesauro. Por fim, todas as informações do metamodelo e do tesauro são armazenadas em um repositório de software que é manipulado por agentes de software.Software engineering area suffered many transformations since its creation. Usually seen as a technique to raise productivity and decrease costs, softwares reusing is one of the main studies in computer field. Since softwares reconfiguration is, in essence, a software reuse, although with some adaptations, this work aims to develop a methodology and a set of tools that speed up and facilitate the process of reuse/reconfiguration of software components. These tools association constitute a mechanism of storing, indexing, search and recovering of software artifacts. This mechanism works with the structure of software projects and also with semantic relationships that exist between the software\'s terms. To represent software\'s inner structure (features and relationships) a metamodel is used. Semantic relationships are represented by a thesaurus. Finally, all the informations from metamodel and thesaurus are stored in a software repository, which is manipulated by software agents.
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Cevoli, Alessandro. "Engineering behavioural differentiation in robots controlled by Boolean networks." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19106/.
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The design of control software for robots that are required to face different and unpredictable environmental conditions is of paramount importance in current robotic research. A viable solution to attain such a control software consists in exploiting the rich dynamics of biological cell models; indeed, cells are capable of differentiating into specific types, each characterized by peculiar behavioural traits suited to the particular environmental condition in which the cell acts. Moreover, if properly triggered, cells can also undergo type changes. Inspired by this phenomenon, in this work we have devised a method to support the automatic design of robots controlled by Boolean networks (BNs), which are a notable model of genetic regulatory networks. The initial behaviour of the robot is not specific, i.e. its BN is in an undifferentiated state. When specific environmental conditions appear, the BN changes its dynamics that in turn induces a specific behaviour in the robot. If, subsequently, the environmental signals change, the robot is able to return to the initial, undifferentiated behaviour and then differentiate again into a different behaviour, according to the external signals. This method is shown in detail, along with a thorough experimental analysis, in a case study involving taxis behaviours.
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Alloing, Camille. "Processus de veille par infomédiation sociale pour construire l'e-réputationd'une organisation. Approche par agents-facilitateurs appliquée à la DSIC de La Poste." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT4021/document.
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Cette recherche-action menée au sein de la DSIC de La Poste s’intéresse à la réputation des organisations et à son pendant numérique (l’e-réputation) par le prisme des sciences de l’information-communication. Elle propose le développement d’un processus et d’un dispositif de veille stratégique par infomédiation sociale permettant à une organisation d’évaluer, de gérer et in fine de construire son e-réputation.Dans un premier temps, nous présentons un cadre théorique de la réputation des organisations comme objet info-communicationnel. Puis nous abordons l’e-réputation (ou réputation en ligne) des organisations comme une information stratégique constituée de l’ensemble des indicateurs issus de la commensuration des interactions intentionnelles endogènes ou automatisées des communautés virtuelles avec l’organisation : productions d’opinions, notations ou encore agir des publics.Dans un deuxième temps, nous nous questionnons sur les moyens à disposition du groupe La Poste pour construire cette e-réputation. Par « construction », nous entendons la manière de structurer l’environnement informationnel dans lequel les publics de l’organisation évoluent chaque jour sur le web dit social, et plus spécifiquement sur la plate-forme Twitter. Dans ce cadre, nos observations empiriques nous permettent de mettre en exergue, de questionner et d’analyser des utilisateurs du web dont les pratiques informationnelles nous amènent à les qualifier « d’agents-facilitateurs », et dont la caractéristique principale est de participer à la prescription informationnelle et à la médiation documentaire sur le web.Suite à l’observation de certains de ces agents et à la production d’une typologie, nous proposons un modèle et un processus de veille les intégrant. Processus dont les résultats opérationnels au sein de La Poste mettent en avant la nécessaire prise en compte et analyse des pratiques de recommandation des internautes au sein des réseaux socionumériques afin que l’organisation construise son e-réputation de manière proactiveThis research within La Poste's DSIC is focused on corporate reputation and on e-reputation through the prism of information and communication sciences. It proposes the development of a web monitoring and a social search process enabling to assess, manage and build online reputation.At first, we present a theoretical framework for corporate reputation as an info-communicational object. Then we discuss corporate e-reputation such as a strategic information made up of all commensuration indicators constituted by intentional (endogenous or not) interactions with the virtual communities and the firm : productions of opinions, assessment or public behavior.In a second step, we investigate how La Poste group can build its e-reputation. By "build" we mean the way to structure the informational environment where customers evolve each day on social web, and more specifically on the Twitter platform. In this context, our empirical observations allow us to highlight, question and analyze, web users whose informational practices permit us to qualify of "facilitators-agents", and whose main characteristic is to participate in informational prescription and the documentary mediation on the web.After the observation of some of these agents and the production of a typology, we propose a model and a monitoring process to integrate them. Our process's results in La Poste show the need to take into account and analyse recommendation practices on social networks to build corporate e-reputation proactively
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Chen, Hsinchun, Marshall C. Ramsey, and P. Li. "The Java Search Agent Workshop." Physica-Verlag, 2000. http://hdl.handle.net/10150/105368.
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Artificial Intelligence Lab, Department of MIS, University of ArizonaAs part of the ongoing Illinois Digital Library Initiative project, this paper presents the Java Search Agent Workshop (JSAW), a testbed designed for Java-based information searching. Based on artificial intelligence, neural networks, and G-Search, we implemented several search methods in Java to demonstrate their feasibility in various database, Internet, Intranet, and digital library search tasks. In addition to detailing our design rationale and implementation status, we present several sample Java implementations including a best first search spider and G-Search spider for Internet searching, and a Hopfield neural network based visualizer for database searching. Lessons learned and future directions are also presented.
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Chatzilygeroudis, Konstantinos. "Micro-Data Reinforcement Learning for Adaptive Robots." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0276/document.
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Les robots opèrent dans le monde réel, dans lequel essayer quelque chose prend beaucoup de temps. Pourtant, les methodes d’apprentissage par renforcement actuels (par exemple, deep reinforcement learning) nécessitent de longues périodes d’interaction pour trouver des politiques efficaces. Dans cette thèse, nous avons exploré des algorithmes qui abordent le défi de l’apprentissage par essai-erreur en quelques minutes sur des robots physiques. Nous appelons ce défi “Apprentissage par renforcement micro-data”. Dans la première contribution, nous avons proposé un nouvel algorithme d’apprentissage appelé “Reset-free Trial-and-Error” qui permet aux robots complexes de s’adapter rapidement dans des circonstances inconnues (par exemple, des dommages) tout en accomplissant leurs tâches; en particulier, un robot hexapode endommagé a retrouvé la plupart de ses capacités de marche dans un environnement avec des obstacles, et sans aucune intervention humaine. Dans la deuxième contribution, nous avons proposé un nouvel algorithme de recherche de politique “basé modèle”, appelé Black-DROPS, qui: (1) n’impose aucune contrainte à la fonction de récompense ou à la politique, (2) est aussi efficace que les algorithmes de l’état de l’art, et (3) est aussi rapide que les approches analytiques lorsque plusieurs processeurs sont disponibles. Nous avons aussi proposé Multi-DEX, une extension qui s’inspire de l’algorithme “Novelty Search” et permet de résoudre plusieurs scénarios où les récompenses sont rares. Dans la troisième contribution, nous avons introduit une nouvelle procédure d’apprentissage du modèle dans Black-DROPS qui exploite un simulateur paramétré pour permettre d’apprendre des politiques sur des systèmes avec des espaces d’état de grande taille; par exemple, cette extension a trouvé des politiques performantes pour un robot hexapode (espace d’état 48D et d’action 18D) en moins d’une minute d’interaction. Enfin, nous avons exploré comment intégrer les contraintes de sécurité, améliorer la robustesse et tirer parti des multiple a priori en optimisation bayésienne. L'objectif de la thèse était de concevoir des méthodes qui fonctionnent sur des robots physiques (pas seulement en simulation). Par conséquent, tous nos approches ont été évaluées sur au moins un robot physique. Dans l’ensemble, nous proposons des méthodes qui permettre aux robots d’être plus autonomes et de pouvoir apprendre en poignée d’essaisRobots have to face the real world, in which trying something might take seconds, hours, or even days. Unfortunately, the current state-of-the-art reinforcement learning algorithms (e.g., deep reinforcement learning) require big interaction times to find effective policies. In this thesis, we explored approaches that tackle the challenge of learning by trial-and-error in a few minutes on physical robots. We call this challenge “micro-data reinforcement learning”. In our first contribution, we introduced a novel learning algorithm called “Reset-free Trial-and-Error” that allows complex robots to quickly recover from unknown circumstances (e.g., damages or different terrain) while completing their tasks and taking the environment into account; in particular, a physical damaged hexapod robot recovered most of its locomotion abilities in an environment with obstacles, and without any human intervention. In our second contribution, we introduced a novel model-based reinforcement learning algorithm, called Black-DROPS that: (1) does not impose any constraint on the reward function or the policy (they are treated as black-boxes), (2) is as data-efficient as the state-of-the-art algorithm for data-efficient RL in robotics, and (3) is as fast (or faster) than analytical approaches when several cores are available. We additionally proposed Multi-DEX, a model-based policy search approach, that takes inspiration from novelty-based ideas and effectively solved several sparse reward scenarios. In our third contribution, we introduced a new model learning procedure in Black-DROPS (we call it GP-MI) that leverages parameterized black-box priors to scale up to high-dimensional systems; for instance, it found high-performing walking policies for a physical damaged hexapod robot (48D state and 18D action space) in less than 1 minute of interaction time. Finally, in the last part of the thesis, we explored a few ideas on how to incorporate safety constraints, robustness and leverage multiple priors in Bayesian optimization in order to tackle the micro-data reinforcement learning challenge. Throughout this thesis, our goal was to design algorithms that work on physical robots, and not only in simulation. Consequently, all the proposed approaches have been evaluated on at least one physical robot. Overall, this thesis aimed at providing methods and algorithms that will allow physical robots to be more autonomous and be able to learn in a handful of trials
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Gibbins, Nicholas Miles. "An agent system for query routing search." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247227.
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Dias, Liliana de Almeida. "Search for new lantibiotics." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12175.
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Mestrado em Biotecnologia - Biotecnologia MolecularA procura de microrganismos produtores de novos compostos antimicrobianos é primordial no combate ao fenómeno mundial de resistência microbiana face aos antimicrobianos atualmente disponíveis. A natureza é uma fonte de diversos produtos, entre os quais se podem destacar os antimicrobianos. Os péptidos naturais podem ser sintetizados in vivo, por bactérias, através de vias metabólicas ribossomais ou não ribossomais. De destaque entre os péptidos antimicrobianos ribossomais produzidos por bactérias são as bacteriocinas. As bacteriocinas de classe I incluem os péptidos com modificações pós-traducionais, os lantipéptidos, que são caracterizados pela presença dos aminoácidos lantionina e metil-lantionina. Os lantipéptidos com atividade antimicrobiana designam-se lantibióticos. Estes, são capazes de inibir o crescimento de várias bactérias de Gram-positivo clinicamente relevantes como, por exemplo, Staphylococcus aureus resistente à meticilina. O trabalho desenvolvido teve como objectivo a procura/ pesquisa de novos antibacterianos, produzidos por bactérias isoladas em ambientes pouco comuns, nomeadamente, grutas e locais muito contaminados por metais pesados - minas de urânio e de ferro. Para tal, testou-se a atividade antibacteriana de 76 bactérias isoladas nos diferentes locais contra 12 estirpes indicadoras, de Gram-positivo e de Gram-negativo. Todos os isolados que apresentaram atividade foram classificados por sequenciação do gene 16S rRNA. Dentro deste grupo, foram selecionadas bactérias pertencentes aos filos Firmicutes e Actinobacteria para a realização de ensaios de produção de antimicrobianos em cultura líquida. De seguida, determinou-se a estabilidade proteolítica e térmica dos antimicrobianos produzidos por três estirpes de B. amyloliquefaciens (SL8, Sma1 e MO15). Atualmente, existem e estão depositados nas bases de dados 13 genomas de B. amyloliquefaciens totalmente sequenciados. Assim, e utilizando a plataforma antiSMASH 2.0 procedeu-se à identificação de possíveis clusters de lantibióticos nesses genomas. Os genes biossintéticos de lantibióticos foram identificados apenas em três desses genomas; em dois desses genomas detectou-se o cluster de genes do lantibiótico mersacidina e no outro detectou-se a presença de um cluster ainda não caracterizado. Com base nessa informação, investigou-se a presença de genes característicos de operões biossintéticos de lantipéptidos nas estirpes SL8, Sma1 e MO15. O gene estrutural da mersacidina foi detectado nos três isolados. No entanto, o gene mrsM, que codifica para a enzima de modificação da mersacidina, apenas foi identificado nas estirpes SL8 e Sma1. Por outro lado, a amplificação de outra lanM não foi possível no isolado MO15. Foi ainda pesquisada a presença do péptido mersacidina, nos sobrenadantes das culturas líquidas destas estirpes, por MALDI-TOF/MS. Contudo, este lantibiótico não foi detectado em nenhum dos sobrenadantes. O presente estudo abre perspectivas para a identificação de lantibióticos nas estirpes em estudo. Por outro lado, outros estudos serão realizados envolvendo a pesquisa e caracterização dos compostos produzidos pelas restantes estirpes da coleção e que não foram exploradas nesta tese.
Searching for new antimicrobials is crucial to address the phenomenon of microbial resistance to the most common antibiotics. Nature is a source of several products, namely antimicrobials. Natural peptides can be synthetized in vivo by bacteria through a nonribosomal or a ribosomal pathway. Among the ribosomal antimicrobial peptides produced by bacteria, the so-called bacteriocins are worth attention. Among these, the class I bacteriocins comprise the post-translationally modified peptides, designated lanthipeptides, which are characterized by the uncommon amino acids lanthionine and methyllanthionine. The lanthipeptides with antimicrobial activity are referred as lantibiotics. The lantibiotics are able to inhibit the growth of several clinically relevant Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus. This work aimed to search for new antibacterials produced by microorganisms isolated from uncommon sources, namely, caverns and heavy metal contaminated sites – uranium and iron mines. To that end, the antibacterial potential of 76 bacterial isolates from the different origins was investigated against 12 indicator strains, both Gram positive and Gram negative. All the isolates with antibacterial activity were affiliated by 16S rRNA gene sequence. Among these, bacteria belonging to the phyla Firmicutes and Actinobacteria were selected and included three Bacillus amyloliquefaciens - SL8, Sma1 and MO15. These isolates were investigated for antibacterial production assays in liquid culture. Supernatants with bioactivity were further investigated for proteolytic and temperature stability of the antimicrobial compounds produced. Presently, 13 genomes B. amyloliquefaciens are fully sequenced and assembled. Using the antiSMASH 2.0 platform putative clusters for lanthipeptides were surveyed in all of these genomes and were found on three of the genomes only. Two of these clusters corresponded to the mersacidin and the other was uncharacterized. Thus, the presence of genes involved in the biosynthesis of lantibiotics was investigated in the three strains selected. It was found that SL8, Sma1 and MO15 isolates contain the mersacidin structural gene. However, the mrsM gene, which encodes the mersacidin modification enzyme, was only amplified in SL8 and Sma1 strains. Moreover, no other lanM was identified in the MO15 isolate. Therefore, the presence of the mersacidin peptide in culture supernatants was investigated by MALDI-TOF/MS. However, this lantibiotic was not detected in any of the three supernatants. The present work opens perspectives for the identification of lantibiotics produced by the strains studied. Also, other studies will be carried out to characterize the peptides produced by all the isolates of the bacterial culture collection constructed in the present study.
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Martin, Simon. "Multi-agent based cooperative search in combinatorial optimisation." Thesis, University of Portsmouth, 2013. https://researchportal.port.ac.uk/portal/en/theses/multiagent-based-cooperative-search-in-combinatorial-optimisation(7fcdfce2-57fa-4a03-b6cc-ef6b70979cb8).html.
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Cooperative search provides a class of strategies to design more effective search methodologies by combining (meta-) heuristics for solving combinatorial optimisation problems. This area has been little explored in operational research. This thesis proposes a general agent-based distributed framework where each agent implements a (meta-) heuristic. An agent continuously adapts itself during the search process using a cooperation protocol based on reinforcement learning and pattern matching. Good patterns which make up improving solutions are identified and shared by the agents. A theoretical approach to the understanding of the potential of agent-based systems is also proposed. This agent-based system aims to raise the level of generality by providing a flexible framework to deal with a variety of different problem domains. The proposed framework so far has been tested on Permutation Flow-shop Scheduling, Travelling Salesman Problem and Nurse Rostering. These instances have yielded some promising results. As part of the nurse rostering work a novel approach to modelling fairer nurse rosters is proposed.
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Junghanns, Andreas. "Pushing the limits, new developments in single-agent search." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0033/NQ46861.pdf.
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Sjöö, Kristoffer. "Functional understanding of space : Representing spatial knowledge using concepts grounded in an agent's purpose." Doctoral thesis, KTH, Datorseende och robotik, CVAP, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-48400.
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This thesis examines the role of function in representations of space by robots - that is, dealing directly and explicitly with those aspects of space and objects in space that serve some purpose for the robot. It is suggested that taking function into account helps increase the generality and robustness of solutions in an unpredictable and complex world, and the suggestion is affirmed by several instantiations of functionally conceived spatial models. These include perceptual models for the "on" and "in" relations based on support and containment; context-sensitive segmentation of 2-D maps into regions distinguished by functional criteria; and, learned predictive models of the causal relationships between objects in physics simulation. Practical application of these models is also demonstrated in the context of object search on a mobile robotic platform.QC 20111125
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Caetano, Tânia Isabel Sousa. "Lichenicidin biosynthesis and search for novel antibacterial peptides." Doctoral thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/3836.
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Doutoramento em BiologiaA estirpe Bacillus licheniformis I89 possui a capacidade de produzir alguns compostos com actividade antibacteriana. No presente estudo, a separação desses compostos foi realizada através da aplicação de vários procedimentos, incluindo extracção em fase sólida e cromatografia liquida de alta pressão. Dois destes compostos bioactivos constituem o lantibiótico de classe II lichenicidina e são caracterizados pela massas molecular de 3250 Da (Bliα) e 3020 Da (Bliβ). O cluster responsável pela biossíntese da lichenicidina foi heterologamente expresso em Escherichia coli, constituindo a primeira descrição da produção de um lantibiótico totalmente in vivo num hospedeiro Gram-negativo. Este sistema foi subsequentemente explorado com o objectivo de relacionar cada proteína codificada no cluster genético da lichenicidina na produção dos péptidos Bliα e Bliβ. O desenvolvimento do sistema de trans complementação possibilitou a produção de variantes destes péptidos. A análise das massas moleculares destas variantes assim como a análise dos padrões de fragmentação obtidos por MS/MS permitiu a revisão de algumas das características estruturais previamente proposta para Bliα e Bliβ. A análise dos genes hipoteticamente envolvidos na protecção da estirpe produtora contra a acção antibiótica da lichenicidina revelou, que em E. coli, a sua ausência não resulta no aumento da susceptibilidade a este composto. Verificou-se também que a presença destes genes não é essencial para a produção de lichenicidina em E. coli. Foi também confirmado experimentalmente que a membrana externa da E. coli constitui uma barreira natural para a entrada dos péptidos na célula. De facto, uma das características intrigantes da produção de lichenicidina por uma bactéria de Gram negativo reside no mecanismo de transporte dos dois péptidos através da membrana externa. Neste estudo foi demonstrado que na ausência da proteína de membrana TolC, a massa molecular de Bliα e Bliβ não foi identificada no sobrenadante de E. coli, demonstrando assim que a sua presença no ambiente extra-celular não se devia a um processo de lise bacteriana. Foi ainda avaliada a capacidade da maquinaria biossintética da lichenicidina para produzir o lantibiótico haloduracina, através do processamento de chimeras lichenicidina-haloduracina, contudo, os resultados foram negativos. Verificou-se ainda que em determinadas condições de incubação, a diferenciação da morfologia original da estirpe B. licheniformis I89 pode ocorrer. Esta dissociação implicou a transição da colónia parental e rugosa para uma colónia de aparência mais simples e suave. Desta forma, as diferenças das duas morfologias em termos de taxa de crescimento, esporulação e actividade antibiótica foram investigadas. Considerando especificamente Bliα e Bliβ verificou-se que a abundância destes péptidos nas culturas do fenótipo fino é geralmente inferior aquela identificada nas culturas do fenótipo parental. Por último, a diversidade de elementos genéticos constituintes de péptido sintetases não ribossomais (NRPS) foi investigada em lagoas no centro de Portugal e em solos provenientes de caves do sul de Portugal, revelando a presença de potenciais novas NRPS nestes ambientes.
Bacillus licheniformis I89 has the ability to produce some antibacterial compounds. In the present study, the separation of such compounds was achieved by the application of several procedures, including solid phase extraction and preparative high-pressure liquid chromatography. Two of these compounds constitute the class II lantibiotic lichenicidin and are characterized by the molecular masses of 3250 Da (Bliα) and 3020 Da (Bliβ). The lichenicidin gene cluster was successfully expressed in Escherichia coli, constituting the first report of a complete lantibiotic gene cluster heterologous expression in a Gram-negative host. This system was further exploited to characterize and assign the function of the proteins encoded in the biosynthetic gene cluster. Moreover, a trans complementation system was developed for the expression of Bliα and Bliβ mutants in vivo. The assignment of essential amino acid residues for bioactivity was investigated by generation of Ala-mutants. Also, several features of Bliα and Bliβ structures were revised by analysis of MS/MS fragmentation patterns obtained for wild type and mutated peptides. Regarding the lichenicidin self-protection in E. coli, it was found that immunity genetic determinants are not essential to Bliα and Bliβ production. Furthermore, it was experimentally confirmed that the E. coli outer membrane constitutes a natural barrier to the biological activity of lichenicidin. An intriguing feature of the lichenicidin production by E. coli lies in the export mechanism of Bliα and Bliβ peptides. Herein, it was demonstrated that the presence of these peptides in the E. coli supernatants resulted from their translocation through the bacterial cell wall. In fact, it was found that in the absence of the outer membrane protein TolC none of the lichenicidin peptides could be detected in the bacterial supernatants. The potential of the E. coli lichenicidin expression system to produce the closely related lantibiotic haloduracin through the biosynthetic processing of lichenicidin-haloduracin chimeras was also attempted in the present study, however, without success. It was found that under certain circumstances of incubation, B. licheniformis I89was able to differentiate from its parental rough phenotype to a more simple and smooth morphology. The differences in terms of growth, sporulation and antagonistic activity of both phenotypes were investigated in two different culture media. Regarding the production of lichenicidin peptides, it was found that the abundance of Bliα and Bliβ in extracts from the smooth phenotype cultivated in TSB was lower than that detected in the rough phenotype extracts. Finally, the screening of genetic elements associated with nonribosomal peptide synthetases was performed in Portuguese lagoons and soil from caves using a culture-independent approach. A wide variety of adenylation domains was identified, providing evidence that potentially novel NRPSs are present in these environments.
FCT - SFRH/BDE/15559/2005
Laboratório Medinfar SA
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Smith, Kevin Douglas. "Distributed data search and retrieval in open mobile agent systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60251.pdf.
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