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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Contributions à l'évaluation de systèmes biométriques embarqués / Contributions to the evaluation of embedded biometric systems

Vibert, Benoît 04 May 2017 (has links)
La biométrie suscite de plus en plus d’intérêt de la part des industriels car nous avons besoin de nouvelles méthodes d’authentification d’un individu : pour du contrôle d’accès physique, du contrôle aux frontières ou pour du paiement. Ces données non révocables et sensibles sont très souvent stockées sur des systèmes embarqués de type élément sécurisé (SE), comme par exemple une carte à puce. Ces SE embarquent aussi un module de comparaison nommé On-Card-Comparison (OCC), permettant de déterminer si le template présenté correspond bien à celui stocké sur l’élément sécurisé. Dans cette thèse, nous nous intéressons particulièrement aux empreintes digitales car c’est une modalité biométrique bien perçue par les usagers. Nous proposons dans cette thèse différentes contributions permettant d’évaluer des systèmes biométriques embarqués. La première est une plateforme d’évaluation de systèmes biométriques nommée EVABIO. La seconde contribution, permet d’évaluer l’incidence sur les performances lors de la réduction de templates biométriques lorsqu’ils doivent être stockés sur un SE. Nous proposons des méthodes permettant de réduire la taille du template biométrique tout en gardant un taux de reconnaissance élevé, garantissant ainsi un bon niveau de performance du système biométrique complet. La dernière contribution étudie les attaques d’un système biométrique embarqué sur SE. Nous regardons quels a priori sont importants pour un imposteur : nous avons montré que le type de l’empreinte digitale est une information importante pour un attaquant. Nous avons également proposé une contre-mesure pour les systèmes embarqués. / Biometrics is sparking the interest of manufacturers and industrial compagniesbecause we are in need of new methods of authenticating individuals: for physicalaccess control, border control or for payments. Non-revocable and sensitive data isvery often stored on embedded systems of the secure element type (SE), such as asmart card. SEs include a comparison module called On-Card-Comparison (OCC),which determines whether the template presented corresponds to the template storedwithin it. In this thesis, we are particularly interested in fingerprints because it is abiometric modality that is very well perceived by the population.We propose in this thesis different contributions to evaluate embedded biometricsystems. The first is a biometric evaluation platform called EVABIO. The secondcontribution evaluates the impact on performance when reducing biometric templatesthat are to be stored on an SE. We propose methods to reduce the size of biometrictemplates while maintaining a high recognition rate thus, guaranteeing a good level ofperformance of the global biometric system. The last contribution studies attacks ona biometric system that is embedded on a SE. We look at what a priori are importantfor an impostor: we have shown that the type of fingerprint is an important a prioriand the reason why we have also proposed a countermeasure for embedded systems.
142

ON GEOMETRIC AND ALGEBRAIC PROPERTIES OF HUMAN BRAIN FUNCTIONAL NETWORKS

Duy Duong-Tran (12337325) 19 April 2022 (has links)
<p>It was only in the last decade that Magnetic Resonance Imaging (MRI) technologies have achieved high-quality levels that enabled comprehensive assessments of individual human brain structure and functions. One of the most important advancements put forth by Thomas Yeo and colleagues in 2011 was the intrinsic functional connectivity MRI (fcMRI) networks which are highly reproducible and feature consistently across different individual brains. This dissertation aims to unravel different characteristics of human brain fcMRI networks, separately through network morphospace and collectively through stochastic block models.</p><p><br></p><p>The quantification of human brain functional (re-)configurations across varying cognitive demands remains an unresolved topic. Such functional reconfigurations are rather subtle at the whole-brain level. Hence, we propose a mesoscopic framework focused on functional networks (FNs) or communities to quantify functional (re-)configurations. To do so, we introduce a 2D network morphospace that relies on two novel mesoscopic metrics, Trapping Efficiency (TE) and Exit Entropy (EE). We use this framework to quantify the Network Configural Breadth across different tasks. Network configural breadth is shown to significantly predict behavioral measures, such as episodic memory, verbal episodic memory, fluid intelligence and general intelligence.</p><p><br></p><p>To properly estimate and assess whole-brain functional connectomes (FCs) is among one of the most challenging tasks in computational neuroscience. Among the steps in constructing large-scale brain networks, thresholding of statistically spurious edge(s) in FCs is the most critical. State-of-the-art thresholding methods are largely ad hoc. Meanwhile, a dominant proportion of the brain connectomics research relies heavily on using a priori set of highly-reproducible human brain functional sub-circuits (functional networks (FNs)) without properly considering whether a given FN is information-theoretically relevant with respect to a given FC. Leveraging recent theoretical developments in Stochastic block model (SBM), we first formally defined and subsequently quantified the level of information-theoretical prominence of a priori set of FNs across different subjects and fMRI task conditions for any given input FC. The main contribution of this work is to provide an automated thresholding method of individuals’ FCs based on prior knowledge of human brain functional sub-circuitry.</p>
143

Empreintes audio et stratégies d'indexation associées pour l'identification audio à grande échelle / Audio-fingerprints and associated indexing strategies for the purpose of large-scale audio-identification

Fenet, Sébastien 23 September 2013 (has links)
Dans cet ouvrage, nous définissons précisément ce qu’est l’identification audio à grande échelle. En particulier, nous faisons une distinction entre l’identification exacte, destinée à rapprocher deux extraits sonores provenant d’un même enregistrement, et l’identification approchée, qui gère également la similarité musicale entre les signaux. A la lumière de ces définitions, nous concevons et examinons plusieurs modèles d’empreinte audio et évaluons leurs performances, tant en identification exacte qu’en identificationapprochée. / N this work we give a precise definition of large scale audio identification. In particular, we make a distinction between exact and approximate matching. In the first case, the goal is to match two signals coming from one same recording with different post-processings. In the second case, the goal is to match two signals that are musically similar. In light of these definitions, we conceive and evaluate different audio-fingerprint models.
144

Privatpersoners användning av biometriteknik : Användbarhet, säkerhet och integritet / Usage of biometrics by regular people

Kjellén, Oliver, Pang, Jillian January 2020 (has links)
Bakgrund Biometriteknik är paraplybegrepp för olika automatiserade tekniker som används vid identifikation av individer. Biometriska identifikationsmetoder såsom fingeravtrycksläsning och ansiktsigenkänning har sedan länge varit reserverade för specifika syften. Idag är situationen förändrad, biometriteknik finns tillgänglig för allmänheten och används i allt större utsträckning. Biometriska metoder för identifikation kan erbjuda säkrare identifiering gentemot vanliga lösenord. Detta är av stor vikt då privatpersoner lagrar allt mer känslig information på sina mobiltelefoner, surfplattor och datorer.  Syfte   Syftet med den här studien är att undersöka hur stor inverkan faktorerna användbarhet, säkerhet och integritet har på privatpersoners användning av biometriska metoder för identifiering på mobiltelefoner, surfplattor och datorer. Efter granskning av tidigare forskning gavs dessa tre faktorer extra fokus. Den första faktorn, säkerhet, identifierades i och med att biometriteknik erbjuder förbättrad säkerhet om tekniken används korrekt. Samt att tidigare forskning pekade på säkerhet som en aspekt privatpersoner må ha i åtanke. Den andra faktorn, användbarhet, återfinns i att forskning visar på att individer värderar användbarhet och enkelhet högt. En tredje faktor, integritet, valdes i och med att viss forsking här hade nått motsägande resultat  Metod Rapporten genomfördes främst med hjälp av en kvantitativ enkätundersökning, svar (n=121) från denna undersökning användes senare för att besvara och reflektera kring forskningsfrågan: Hur stor inverkan har faktorerna användbarhet, säkerhet och integritet på privatpersoners användning av biometriteknik? Ett kapitel som namngavs forskningsöversikt inkluderas också, här har litteratur sållats kvalitativt för att finna relevanta artiklar.  Resultat Den enkätundersökning som genomfördes påvisade att en majoritet av privatpersoner använder sig av biometriska identifieringsmetoder på sina mobiltelefoner, surfplattor samt datorer. Vidare visade det sig att faktorn användbarhet värderades högt, vissa fysiologiska egenskaper som används vid biometrisk identifiering ansågs även som mer eller mindre accepterade. Svar som gavs av respondenter visade också på att privatpersoner ej resonerar speciellt mycket kring integritet och personliga data som lagras vid användning av biometriteknik.  Slutsats Efter genomförd diskussion angående tidigare forskning och de resultat som nåddes utifrån enkätundersökningen konstaterades det att faktorn användbarhet hade stor inverkan på privatpersoners användning av biometriteknik. Säkerhet tas även i åtanke av en mindre del. Faktorn integritet ges ingen eller väldigt liten uppmärksamhet gällande användning av biometriska identifieringsmetoder hos privatpersoner. / Background Biometrics is a field including different automated technologies used for thepurpose of identify individuals. Biometric identification methods such asfingerprint scanning and facial recognition used to be a field reserved forspecific application purposes. Nowadays biometrics are used more frequently,and it is available for the public to use in their everyday life. Biometrics canprovide more secure solutions compared to normal passwords, but to achievethis adoption of said methods is key, especially seeing as users store moresensitive and personal data on their smart devices compared to yesterday’s nonsmartphones. Purpose The purpose of this study is to explore how the factors usability, security andprivacy affect people’s use of biometric solutions on their smartphones,tablets, and computers. After thoroughly reviewing previous literature thesethree main factors gained extra focus. The first factor, security, biometrics dooffer greater security advantages when used the right way. Also, previousresearch points towards security as an aspect people should have in mindwhile using biometrics. The second factor, usability, this aspect is based onprevious research showing that people tend to value functions and features thatare usable. A third factor, privacy, was chosen because research showedconflicting results regarding the importance of this factor.  Method This study was conducted primarily through a quantitative survey, answers(n=121) from this survey was later used to reflect upon the research question:How much of an impact does the factors usability, security and privacy haveover peoples use of biometrics? A chapter providing an overview of previousresearch is also included, for this chapter literature has been reviewed in aqualitative matter to sort out relevant research articles.  Results Results from the survey that was conducted showed that most individuals doindeed use biometrics on their mobile phones, tablets, and computers. Datacollected also indicates that the factor usability had a big impact on peoples useof biometrics. People also responded that they saw some physiological traitsused for biometrics as more, or less accepted to be stored and collected. Otheranswers to the survey showed that individuals generally do not care too muchabout their privacy when using biometrics. Conclusion After concluded discussions regarding previous research and the resultscollected from individuals through the survey a conclusion is reached. Thefactor usability had a big impact on individuals use biometrics. A small part ofindividuals does also consider security to be important. However, the factorprivacy was mostly ignored when it comes to using biometrics on smartphones,tablets and computers.
145

Biometric authentication systems for secured e-transactions in Saudi Arabia. An empirical investigation of the factors affecting users' acceptance of fingerprint authentication systems to improve online security for e-commerce and e-government websites in Saudi Arabia.

Al-Harby, Fahad M. January 2010 (has links)
Security is becoming an increasingly important issue for business, and with it comes the need for appropriate authentication; consequently, it is becoming gradually more important to develop secure e-commerce systems. Fraud via the web, identity theft, and phishing are raising concerns for users and financial organisations. In addition, current authentication methods, like passwords, have many problems (e.g. some users write them down, they forget them, or they make them easy to hack). We can overcome these drawbacks by using biometric authentication systems. Biometric systems are being used for personal authentication in response to the rising issue of authentication and security. Biometrics provide much promise, in terms of preserving our identities without the inconvenience of carrying ID cards and/or remembering passwords. This research is important because the securing of e-commerce transactions is becoming increasingly important. Identity theft, hacking and viruses are growing threats to Internet users. As more people use the Internet, more identity theft cases are being reported. This could harm not only the users, but also the reputation of the organisations whose names are used in these illegal acts. For example, in the UK, online banking fraud doubled in 2008 compared to 2007. More users took to e-shopping and online banking, but failed to take necessary protection. For non-western cultures, the figures for web security, in 2008, illustrated that Saudi Arabia was ranked ninth worldwide for users who had been attacked over the web. The above statistics reflect the significance of information security with e-commerce systems. As with any new technology, user acceptance of the new technology is often hard to measure. In this thesis, a study of user acceptance of biometric authentication systems in e-transactions, such as online banking, within Saudi society was conducted. It examined whether Saudis are practically willing to accept this technology. This thesis focuses upon Saudi Arabia, which has developing economy. It has achieved a rapid rate of growth, and therefore makes an interesting and unique case study. From an economist¿s point of view, Saudi Arabia is the powerhouse of the Middle East. It has the leading regional economy, and, even though it is still relatively young. It has a young and rapid growing population; therefore, this makes Saudi Arabia an attractive potential market for all kinds of e-commerce applications. Having said that, with more than half of population under the age of 30 are more to be expected to take the risk of accepting new technology. For this work, 306 Saudi participants were involved in the experiments. A laboratory experiment was created that actively tested a biometric authentication system in combination with a survey. The Technology Acceptance Model (TAM) was adopted in the first experimental phase as the theoretical basis on which to develop the iv research framework, the model has proven its efficiency as a good predictor for the biometric authentication system. Furthermore, in a second experimental phase, the Unified Theory of Acceptance and Use of Technology (UTAUT) with moderating variables such as age, gender and education level was examined as a proposed conceptual framework to overcome the limitations of TAM. The aim of the study was to explore factors affecting users¿ acceptance of biometric authentication systems. The findings from Structural Equation Modelling (SEM) analysis indicate that education level is a significant moderating factor, while gender and age do not record as significant. This thesis added new knowledge to this field and highlighted the importance of the perceptions of users regarding biometric security technologies. It helps determine the factors affecting the acceptance of biometric technology. To our knowledge, this is the first systematic study of this issue carried out by academic and non-biased researchers in Saudi Arabia. Furthermore, the thesis presents security technology companies and developers of information security products with information to help in the determination of what is significant to their user base when taking into account the introduction of new secure systems and products.
146

Composition of Intracellular and Cell Wall-Bound Phlorotannin Fractions in Fucoid Algae Indicates Specific Functions of These Metabolites Dependent on the Chemical Structure

Birkemeyer, Claudia, Lemesheva, Valeriya, Billig, Susan, Tarakhovskaya, Elena 20 April 2023 (has links)
Accumulation of biologically active metabolites is a specific feature of plant biochemistry, directing the use of plants in numerous applications in the pharmaceutical and food industries. Among these substances, the plethora of phenolic compounds has attracted particular interest among researchers. Here, we report on new findings in phlorotannin research, a large group of multifunctional phenolic substances, produced in brown algae. Comprehensive LC-MS profiling of three algal species allowed us to depict the complex pattern of this structurally diverse compound group across different tissues and subcellular compartments. We compiled more than 30 different phlorotannin series in one sample and used accurate mass spectrometry to assign tentative structures to the observed ions based on the confirmed sum formulas. From that, we found that acetylation, hydroxylation, and oxidation are likely to be the most common in vivo modifications to phlorotannins. Using an alternative data mining strategy to cope with extensive coelution and structural isomers, we quantitatively compared the intensity of different phlorotannin series in species, tissues, and subcellular compartments to learn more about their physiological functions. The structure and intra-thallus profiles of cell wall-bound phlorotannins were studied here for the first time. We suggest that one of the major dibenzodioxin-type phlorotannin series may exclusively target integration into the cell wall of fucoid algae.
147

DEVELOPMENT OF A CHEMICAL FINGERPRINT FOR DETECTING UNTREATED HUMAN SEWAGE POLLUTION IN SURFACE WATER

Pais Goyache, Irene January 2015 (has links)
Untreated human sewage pollution in surface water is of concern because it contributes to the degradation of aquatic ecosystems and it could be a potential hazard to human health. Also, any pollution of surface water, which ultimately supplies drinking water, may affect the drinking water quality. Improper operation and maintenance of separate storm sewer systems are prominent contributors of untreated sewage to source waters, resulting from illicit connections, leakage of sewers, or cross-connections. This thesis studied anthropogenic markers to track untreated sewage in an urban watershed with separate storm sewer system, under dry weather conditions. The main feature of these chemical markers is their degradation behavior at municipal wastewater treatment plants: some markers are completely removed (labile markers), whereas others show only partial or no removal at all (conservative markers). A set of ubiquitous chemical markers with practical analytical detection limits was selected to exploit the labile vs conservative distinction, and determine if untreated human sewage was discharged from stormwater outfalls. The presence of labile markers alone was not enough to confirm the occurrence of untreated sewage in stormwater outfalls. The concentration ratios between labile and conservative markers from several chemical groups (pharmaceuticals and personal care products, over-the-counter medications, artificial sweeteners, and human metabolites) created a chemical fingerprint of untreated sewage, and it was statistically demonstrated to track untreated human sewage in local stormwater outfalls. / Civil Engineering
148

Optimisation of intact cell MALDI method for fingerprinting of methicillin-resistant Staphylococcus aureus

Jackson, K.A., Edwards-Jones, V., Sutton, Chris W., Fox, A.J. January 2005 (has links)
No / The use of matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry on intact cell microorganisms, Intact Cell MALDI (ICM), has been shown by numerous workers to yield effective species level identification. Early work highlighted the significant effect that variation in culture media, incubation conditions and length of incubation had on the spectra produced. Therefore, in order to achieve reliable and reproducible species level identification and sub-typing of microorganisms from ICM fingerprints, it has been essential to develop standardised methods. For methicillin-resistant Staphylococcus aureus (MRSA), a major nosocomial pathogen, we have developed such a standardised method. In this paper we present the experimental parameters, namely, the incubation period, the number of passages required from lyophilised or stored isolates, the method of deposition of the bacterial cells, the concentration of matrix solution, the drying time of bacterial cells prior to the addition of the matrix solution, the time between preparation of the bacterial/matrix sample and analysis and the MALDI pulsed extraction setting, which were considered during the development of defined methods.
149

Herramientas de cribado virtual aplicadas a inhibidores de entrada del VIH. Diseño de nuevos compuestos anti-VIH

Pérez Nueno, Violeta Isabel 25 May 2009 (has links)
Els inhibidors d'entrada del VIH han sorgit recentment com una nova generació de fàrmacs antiretrovirals, els quals bloquegen la unió del virus als co-receptors de membrana CXCR4 i CCR5. S'han desenvolupat diverses molècules petites antagonistes d'aquests co-receptors, algunes de les quals estan actualment en fase d'assaig clínic. No obstant això, donat que no existeixen estructures cristal·logràfiques per aquests co-receptors proteics, és necessari analitzar els modes d'unió d'inhibidors coneguts a la cavitat d'unió extracel·lular dels co-receptors mitjançant experiments de mutagènesi dirigida i estudis computacionals. En general, l'objectiu d'aquestes aproximacions computacionals és cribar un gran nombre de compostos candidats a fàrmacs ràpidament. El cribatge virtual s'ha convertit recentment en un complement útil dels mètodes de cribatge experimentals high-throughput screening per a grans llibreries de compostos. Per tant, en aquesta tesi s'ha portat a terme un protocol de cribatge virtual, mitjançant aproximacions basades en el receptor i en lligands actius coneguts, amb la finalitat de trobar antagonistes de CXCR4 i CCR5 que puguin servir com a potencials inhibidors d'entrada del VIH.Per al cribatge virtual basat en el receptor, s'han millorat els models dels co-receptors CXCR4 i CCR5 construïts a la secció de disseny molecular de l'IQS, i s'han portat a terme assajos preliminars de mode d'unió utilitzant aquests models i lligands coneguts d'elevada afinitat. Així mateix, s'ha analitzat el comportament en el cribatge virtual i en el post-processat de resultats de docking de diferents fingerprints d'interacció en comparació amb els resultats obtinguts per un nou fingerprint d'interacció (APIF) desenvolupat a la secció de disseny molecular de l'IQS.Per al cribatge virtual basat en lligands, s'han comparat models farmacofòrics i diverses aproximacions basades en la forma i propietats moleculars utilitzant lligands d'elevada afinitat com a molècules de referència. A més, s'ha desenvolupat una nova aproximació basada en la forma molecular, la qual s'ha utilitzat per a estudiar en profunditat la hipòtesi de la multi-regió d'unió de la cavitat d'unió extracel·lular del co-receptor CCR5.Tots els mètodes, ja siguin basats en el receptor o en lligands coneguts, s'han aplicat en primer lloc de manera retrospectiva utilitzant una extensa base de dades d'inhibidors de CXCR4/CCR5 i suposats inactius, similars en propietats als actius, recopilada en aquesta tesi. Per a cada receptor, la quimioteca ha estat cribada utilitzat inhibidors coneguts, S'han analitzat els factors d'enriquiment i la diversitat a les llistes finals de hits. A més, s'han portat a terme anàlisis ROC per a ambdós inhibidors de CXCR4 i CCR5 amb la finalitat de comparar l'habilitat del nou algoritme basat en la igualtat de formes de lligands amb la resta d'aproximacions de cribatge utilitzades.Una vegada validades les diferents aproximacions de cribatge i seleccionats els millors paràmetres per a cadascuna d'elles, s'han aplicat les eines de cribatge virtual de manera prospectiva sobre una quimioteca combinatòria dissenyada a la secció de disseny molecular de l'IQS, així com tècniques de disseny de novo de lligands per tal d'identificar nous bloquejadors de l'entrada del VIH a les cèl·lules. / Los inhibidores de entrada del VIH han surgido recientemente como una nueva generación de fármacos antiretrovirales, los cuales bloquean la unión del virus con los co-receptores de membrana CXCR4 y CCR5. Se han desarrollado diversas moléculas pequeñas antagonistas de estos co-receptores, algunas de las cuales están actualmente en fase de ensayo clínico. Sin embargo, dado que no existen estructuras cristalográficas para estos co-receptores proteicos, es necesario analizar los modos de unión de inhibidores conocidos a la cavidad de unión extracelular de los co-receptores mediante experimentos de mutagénesis dirigida y estudios computacionales. En general, el objetivo de estas aproximaciones computacionales es cribar un gran número de compuestos candidatos a fármacos rápidamente. El cribado virtual se ha convertido recientemente en un complemento útil de los métodos de cribado experimentales high-throughput screening para grandes librerías de compuestos. Por lo tanto, en esta tesis se ha llevado a cabo un protocolo de cribado virtual, mediante aproximaciones basadas en el receptor y en ligandos activos conocidos, con el fin de encontrar antagonistas de CXCR4 y CCR5 que puedan servir como potenciales inhibidores de entrada del VIH.Para el cribado virtual basado en el receptor, se han mejorado los modelos de los co-receptores CXCR4 y CCR5 construidos en la sección de diseño molecular del IQS, y se han llevado a cabo ensayos preliminares de modo de unión utilizando estos modelos y ligandos conocidos de elevada afinidad. Asimismo, se ha analizado el comportamiento en el cribado virtual y en el post-procesado de resultados de docking de diferentes fingerprints de interacción en comparación con los resultados obtenidos por un nuevo fingerprint de interacción (APIF) desarrollado en la sección de diseño molecular del IQS.Para el cribado virtual basado en ligandos, se han comparado modelos farmacofóricos y diversas aproximaciones basadas en la forma y propiedades moleculares utilizando ligandos de elevada afinidad como moléculas de referencia. Además, se ha desarrollado una nueva aproximación basada en la forma molecular, la cual se ha utilizado para estudiar en profundidad la hipótesis de la multi-región de unión de la cavidad de unión extracelular del co-receptor CCR5.Todos los métodos, ya sean basados en el receptor o en ligandos conocidos, se han aplicado en primer lugar de manera retrospectiva utilizando una extensa base de datos de inhibidores de CXCR4/CCR5 y supuestos inactivos, similares en propiedades a los activos, recopilada en esta tesis. Para cada receptor, la quimioteca ha sido cribada utilizando inhibidores conocidos, Se han analizado los factores de enriquecimiento y la diversidad en las listas finales de hits. Además, se han llevado a cabo análisis ROC para ambos inhibidores de CXCR4 y CCR5 con el fin de comparar la habilidad del nuevo algoritmo basado en la igualdad de formas de ligandos con el resto de aproximaciones de cribado utilizadas.Una vez validadas las diferentes aproximaciones de cribado y seleccionados los mejores parámetros para cada una de ellas, se han aplicado las herramientas de cribado virtual de manera prospectiva sobre una quimioteca combinatoria diseñada en la sección de diseño molecular del IQS, así como técnicas de diseño de novo de ligandos para identificar nuevos bloqueadores de la entrada del VIH a las células. / HIV entry inhibitors have emerged as a new generation of antiretroviral drugs that block viral fusion with the CXCR4 and CCR5 membrane co-receptors. Several small molecule antagonists for these co-receptors have been developed, some of which are currently in clinical trials. However, because no crystal structures for the co-receptor proteins are available, the binding modes of the known inhibitors within the co-receptor extracellular pockets need to be analyzed by means of site-directed mutagenesis and computational experiments. Generally, the objective of these computational approaches is to screen large numbers of candidate drug compounds rapidly. Virtual screening has recently become a useful complement to laboratory-based high-throughput screening methods for large libraries of compounds. Hence, in this thesis, a virtual screening protocol, using several receptor-based and ligand-based approaches, has been performed to find CXCR4 and CCR5 antagonists that could potentially serve as HIV entry inhibitors.For receptor-based virtual screening, homology models of CXCR4 and CCR5 co-receptors built in our research group have been improved, and preliminary binding mode analyses using these models and high affinity known ligands have been carried out. Also, the performance in virtual screening and docking post-processing of different interaction fingerprints, compared to the results obtained with a new interaction fingerprint (APIF) developed in our research group, has been analysed.For ligand-based virtual screening, pharmacophore modelling and several shape-based and property-based molecular comparison approaches have been compared, using high-affinity ligands as query molecules. Also, a novel consensus shape-based virtual screening approach has been developed and used to investigate and add further evidence for multiple binding sites within the CCR5 extracellular pocket hypothesis.All the receptor-based and ligand-based methods have been firstly applied in a retrospective virtual screening, using a large database of known CXCR4/CCR5 inhibitors and similar presumed inactive molecules assembled in this thesis. For each receptor, the library has been queried using known binders, and the enrichment factors and diversity of the resulting virtual hit lists have been analyzed. Moreover, receiver-operator-characteristic analyses for both CXCR4 and CCR5 inhibitors have been carried out in order to compare the performance of the new consensus shape matching algorithm with the other screening approaches used. Once the different virtual screening approaches have been validated and the best parameters for each one have been selected, prospective virtual screening of a combinatorial library designed by our research group and de novo design methods have been applied to identify new HIV entry blockers.
150

Biometric encryption system for increased security

Jayapal, Ranjith 01 January 2017 (has links)
Security is very important in present day life. In this highly-interconnected world, most of our daily activities are computer based, and the data transactions are protected by passwords. These passwords identify various entities such as bank accounts, mobile phones, etc. People might reuse the same password, or passwords related to an individual that can lead to attacks. Indeed, remembering several passwords can become a tedious task. Biometrics is a science that measures an individual’s physical characteristics in a unique way. Thus, biometrics serves as a method to replace the cumbersome use of complex passwords. Our research uses the features of biometrics to efficiently implement a biometric encryption system with a high level of security.

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