Superpixels are the results of an image oversegmentation. They are an established intermediate level image representation and used for various applications including object detection, 3d reconstruction and semantic segmentation. While there are various approaches to create such segmentations, there is a lack of knowledge about their properties. In particular, there are contradicting results published in the literature. This thesis identifies segmentation quality, stability, compactness and runtime to be important properties of superpixel segmentation algorithms. While for some of these properties there are established evaluation methodologies available, this is not the case for segmentation stability and compactness. Therefore, this thesis presents two novel metrics for their evaluation based on ground truth optical flow. These two metrics are used together with other novel and existing measures to create a standardized benchmark for superpixel algorithms. This benchmark is used for extensive comparison of available algorithms. The evaluation results motivate two novel segmentation algorithms that better balance trade-offs of existing algorithms: The proposed Preemptive SLIC algorithm incorporates a local preemption criterion in the established SLIC algorithm and saves about 80 % of the runtime. The proposed Compact Watershed algorithm combines Seeded Watershed segmentation with compactness constraints to create regularly shaped, compact superpixels at the even higher speed of the plain watershed transformation. Operating autonomous systems over the course of days, weeks or months, based on visual navigation, requires repeated recognition of places despite severe appearance changes as they are for example induced by illumination changes, day-night cycles, changing weather or seasons - a severe problem for existing methods. Therefore, the second part of this thesis presents two novel approaches that incorporate superpixel segmentations in place recognition in changing environments. The first novel approach is the learning of systematic appearance changes. Instead of matching images between, for example, summer and winter directly, an additional prediction step is proposed. Based on superpixel vocabularies, a predicted image is generated that shows, how the summer scene could look like in winter or vice versa. The presented results show that, if certain assumptions on the appearance changes and the available training data are met, existing holistic place recognition approaches can benefit from this additional prediction step. Holistic approaches to place recognition are known to fail in presence of viewpoint changes. Therefore, this thesis presents a new place recognition system based on local landmarks and Star-Hough. Star-Hough is a novel approach to incorporate the spatial arrangement of local image features in the computation of image similarities. It is based on star graph models and Hough voting and particularly suited for local features with low spatial precision and high outlier rates as they are expected in the presence of appearance changes. The novel landmarks are a combination of local region detectors and descriptors based on convolutional neural networks. This thesis presents and evaluates several new approaches to incorporate superpixel segmentations in local region detection. While the proposed system can be used with different types of local regions, in particular the combination with regions obtained from the novel multiscale superpixel grid shows to perform superior to the state of the art methods - a promising basis for practical applications.

Denna studie jämför berättande elevtexter som är skrivna med penna och på tangentbord i årskurs 4 och 6. Jämförelsen görs både mellan redskapen inom årskurserna och mellan årskurserna. Studien omfattar 29 texter från årskurs 4 och 27 texter från årskurs 6. Antalet deltagare var 15 elever i årskurs 4 och 15 elever i årskurs 6. Elevtexterna analyserades utifrån fyra olika aspekter: textlängd, narrativ kvalitet, lexikal variation och stavning. Resultatet inom årskurs 6 visade att eleverna skrev signifikant längre texter på tangentbord. Eleverna i årskurs 4 presterade bättre med penna gällande narrativ kvalitet och lexikal variation, men presterade däremot bättre på tangentbord gällande textlängd och stavning. Dessa skillnader var dock inte statistisk signifikanta. Resultatet diskuteras utifrån simple view of writing.

[ES] Los pilares tubulares de acero rellenos de hormigón (CFST) son un tipo de elementos estructurales mixtos que han ganado popularidad recientemente debido a su excelente comportamiento estructural y al uso racional de los materiales en su fabricación. Con la introducción de un perfil de acero dentro de una sección CFST, surge un nuevo tipo de sección mixta: los pilares tubulares de acero rellenos de hormigón con perfil de acero interior (SR-CFST), en los cuáles se centra esta tesis. Esta tipología incrementa la capacidad portante a temperatura ambiente de los pilares CFST y mejora su comportamiento a fuego, ya que el perfil interior está protegido térmicamente por el hormigón que lo rodea. Las investigaciones disponibles en la bibliografía sobre pilares SR-CFST aún son escasas, pese a sus significativas capacidades mecánicas tanto a temperatura ambiente como a elevada. En esta tesis se revisa el estado del arte sobre pilares SR-CFST, llegando a la conclusión de que son necesarias más investigaciones para comprender el comportamiento de estas secciones a temperatura elevada. La presente tesis analizará el comportamiento frente al fuego de pilares SR-CFST mediante ensayos experimentales y simulaciones numéricas. Inicialmente, se lleva a cabo una campaña experimental para analizar el comportamiento de los pilares bajo dos escenarios: una primera fase que estudia el comportamiento de los pilares tras su exposición al fuego, y una segunda en la que se analizará el comportamiento termo-mecánico de pilares cortos SR-CFST bajo carga constante e incremento progresivo de la temperatura. Tras ello, se desarrolla un modelo de elementos finitos para extender los resultados obtenidos experimentalmente y estudiar en profundidad el comportamiento de los pilares SR-CFST en fuego. El modelo numérico se valida con los ensayos termo-mecánicos realizados anteriormente, así como comparando sus predicciones con los resultados experimentales extraídos de la bibliografía. Con el modelo desarrollado se realizan una serie de estudios paramétricos para examinar la influencia de los parámetros geométricos más relevantes, así como para analizar el efecto del uso de materiales de alta resistencia en el comportamiento a fuego de los pilares. En base a los resultados obtenidos de los estudios paramétricos, se lleva a cabo una propuesta para determinar de forma sencilla la distribución de temperaturas seccional en un tiempo de exposición al fuego dado. Empleando las temperaturas equivalentes obtenidas y en línea con las directrices del Eurocódigo 4 Parte 1.2, se propone una nueva expresión para evaluar la resistencia plástica seccional de los pilares SR-CFST bajo la acción del fuego. Esta propuesta cubre un campo de aplicación que actualmente no está contemplado en la normativa europea. / [CA] Els pilars tubulars d'acer plens de formigó (CFST) són un tipus de membres estructurals mixtes que han guanyat popularitat recentment degut al seu excel·lent comportament estructural y a l'ús moderat de materials en la seua construcció. Amb la introducció d'un perfil d'acer dins d'una secció CFST, s'obté un nou tipus de secció mixta: els pilars tubulars d'acer plens de formigó amb perfil d'acer interior (SR-CFST), al voltant dels quals se centra esta tesi. Esta tipologia incrementa la capacitat a temperatura ambient dels pilars CFST i millora el seu comportament a foc, ja que el perfil interior està protegit tèrmicament pel formigó que l'envolta. Les investigacions disponibles a la bibliografia sobre pilars SR-CFST encara són escasses, malgrat les seues significatives capacitats mecàniques tant a temperatura ambient com a elevada. En esta tesi es revisa l'estat de l'art sobre pilars SR-CFST, concloent que són necessàries més investigacions per tal de comprendre el comportament d'estes seccions a alta temperatura. En la present tesi s'analitzarà el comportament a foc dels pilars SR-CFST per mitjà d'assajos experimentals i simulacions numèriques. Inicialment es desenvolupa una campanya experimental per tal d'analitzar el comportament dels pilars en dos situacions: una primesa fase estudia el comportament dels pilars després de la seua exposició al foc i una segona en què s'analitza el comportament termo-mecànic de pilars curts SR-CFST subjectes a una càrrega constant i a un increment progressiu de la temperatura. Seguidament es desenvolupa un model d'elements finits realista per tal d'estendre els resultats obtinguts experimentalment i estudiar en profunditat el comportament dels pilars SR-CFST en foc. El model numèric es valida amb els assajos termo-mecànics realitzats anteriorment, així com comparant les seues prediccions amb els resultats disponibles a la bibliografia. Amb ajuda del model desenvolupat es realitzen una sèrie d'estudis paramètrics per tal d'examinar la influència dels paràmetres geomètrics més rellevants així com l'efecte de l'ús de materials d'alta resistència en el comportament a foc dels pilars. Basat en els resultats obtinguts dels estudis paramètrics, es desenvolupa una proposta per determinar, de forma senzilla, la distribució de temperatures seccional en un temps d'exposició al foc concret. Amb les temperatures equivalents obtingudes i en línia en les indicacions de l'Eurocódi 4 Part 1.2, es proposa un nou mètode per avaluar la resistència plàstica seccional de pilars SR-CFST baix l'acció del foc. Esta proposta cobreix un camp d'aplicació que actualment no està contemplat en la normativa europea. / [EN] Concrete-filled steel tubular (CFST) columns are a type of composite structural members that have gained popularity in recent years owing to their excellent structural performance and rational use of the materials. By embedding a steel profile inside a CFST section, a new and innovative type of composite section is generated: the so-called steel-reinforced concrete-filled steel tubular (SR-CFST) column, which is the focus of this thesis. This typology improves the room temperature capacity of CFST columns, while enhancing their fire performance, as the inner steel profile is thermally protected by the surrounding concrete. Despite their remarkable load-bearing capacity at both room and elevated temperature, investigations on SR-CFST columns under fire are still scarce. The state of the art on the fire behaviour of SR-CFST columns is reviewed in this thesis, proving that further research is needed to completely understand the performance of this type of columns under elevated temperature. The fire performance of SR-CFST columns is analysed in this thesis by means of experimental tests and numerical simulations. First, an experimental investigation is conducted to study the behaviour of these composite columns under two scenarios: the first phase of the experimental campaign is focused on the post-fire performance, while the second phase is conducted to determine the thermo-mechanical performance of SR-CFST stub columns under constant load and increasing temperature. Subsequently, a realistic finite element model is developed to extend the experimental results and analyse in depth the behaviour of SR-CFST columns in fire. The numerical model is validated against the previously performed thermo-mechanical tests, as well as by comparing its predictions with the available experimental results from the literature. A series of parametric studies are conducted to analyse the influence of the relevant geometrical parameters and to study the effect of the use of high-strength materials on the fire performance of the columns. Based on the results of the parametric studies, a simplified proposal is developed to easily determine the cross-sectional temperature distribution at a given fire exposure time. Using the obtained equivalent temperatures and in line with the current provisions in Eurocode 4 Part 1.2, a new design equation is proposed to evaluate the cross-sectional plastic resistance of SR-CFST columns under fire conditions, filling an existing gap in the European design code. / The authors would like to express their sincere gratitude for the help provided through the Grant PID2019-105908RB-I00 and for the first author’s pre-doctoral contract through the Grant PRE2020-093106 funded by MCIN/AEI/10.13039/501100011033 and by ‘‘ESF Investing in your future’’. Finally, the authors would like to acknowledge the funding for open access charge from CRUE-Universitat Politècnica de València. / Medall Martos, D. (2024). Numerical and experimental research on the fire resistance of composite columns with steel sections embedded in concrete and high strength materials [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/207130

This study is a two part research project that describes and evaluates the efforts of the researcher to bring change in Cyprus' educational system, in the field of simple electric circuits. The objective of the first part was the assessment and evaluation of Cypriot STVE students' perceptions about simple electric circuits. The objective of the second part was to measure the effectiveness that conceptual change model-based instructional activities designed by the researcher had on changing students' misconceptions about simple electric circuits towards scientifically accepted ideas. Transformative mixed methods research design was used consisting mainly from an one-group pre-test post-test design with Determining and Interpreting Resistive Electric Circuits Concepts Test 1.2 as a research instrument, while interviews and field notes were used for triangulation. The findings showed that there was a significant improvement in students' understanding of simple electric circuit concepts that were taught using conceptual change model-based instructional activities. / Science and Technology Education / M. Sc. (Mathematics, Science and Technology Education)

Wards occupy significant proportions of hospital floor areas and due to their constant use, represent a worthwhile focus of study. Single-bed wards are specifically of interest owing to the isolation aspect they bring to infection control, including airborne pathogens, but threats posed by airborne pandemics and family-involvement in hospital care means cross-infection is still a potential problem. In its natural mode, ventilation driven by combined wind and buoyancy forces can lead to energy savings and achieve thermal comfort and high air change rates through secure openings. These are advantageous for controlling indoor airborne pathogens and external air and noise pollution. However, there is lack of detailed evidence and guidance is needed to gain optimum performance from available natural ventilation systems. This research is a proof of concept investigation into the feasibility and impact of natural ventilation systems targeting airflow rates, thermal comfort, heating energy and control of pathogenic bio-aerosols in hospital wards. In particular, it provides insights into the optimal areas of vent openings which could satisfy the complex three-pronged criteria of contaminant dilution, low heating energy and acceptable thermal comfort for occupants in a naturally ventilated single bed ward. The main aim of this thesis is the structured study of four systems categorised into three groups: Simple Natural Ventilation (SNV) in which single and dual-openings are used on the same external wall; Advanced Natural Ventilation (ANV) which is an emerging concept; and finally Natural Personalised Ventilation (NPV) which is an entirely new concept borne out of the limitations of previous systems and gaps in literature. The focus of this research is in the exploratory study of the weaknesses and potentials of the four systems, based on multi-criteria performances metrics within three architecturally distinct single-bed ward designs. In contributing to the body of existing knowledge, this thesis provides a better understanding of the performances of three existing systems while presenting the new NPV system. The analysis is based on dynamic thermal modelling and computational fluid dynamics and in the case of the NPV system, salt-bath experiments for validation and visualisation of transient flows. In all cases, wards were assumed to be free of mechanical ventilation systems that might influence the natural flow of air. The thesis meets three major objectives which have resulted in the following contributions to current knowledge: An understanding of the limitations and potentials of same-side openings, especially why and how dual-openings can be useful when retrofitted into existing wards. Detailed analysis of bulk airflow, thermal comfort, heating energy and room air distribution achievable from existing SNV and ANV systems, including insights to acceptable trickle ventilation rates, which will be particular useful in meeting minimum dilution and energy requirements in winter. This also includes qualitative predictions of the airflow pattern and direction obtainable from both systems. The innovation and study of a new natural ventilation system called Natural Personalised Ventilation (NPV) which provides fresh air directly over a patient s bed, creating a mixing regime in the space and evaluation of its comfort and energy performances. A low-energy solution for airborne infection control in clinical spaces is demonstrated by achieving buoyancy-driven mixing ventilation via the NPV system, and a derivative called ceiling-based natural ventilation (CBNV) is shown. A comparative analysis of four unique natural ventilation strategies including their performance rankings for airflow rates, thermal comfort, energy consumption and contaminant dilution or removal using an existing single-bed ward design as case study. Development of design and operational recommendations for future guidelines on utilising natural ventilation in single-bed wards either for refurbishment or for proposed designs. These contributions can be extended to other clinical and non-clinical spaces which are suitable to be naturally ventilated including treatment rooms, office spaces and waiting areas. The findings signify that natural ventilation is not only feasible for ward spaces but that there is opportunity for innovation in its application through further research. Future work could focus on related aspects like: impacts of fan-assisted ventilation for a hybrid flow regime; pre-heating of supply air; integration with passive heat recovery systems as well the use of full-scale experiments to fine-tune and validate findings.

Le virus de l’hépatite C (VHC) est un virus à ARN simple brin positif (ssARN) qui se replique dans le foie. Deux cents millions de personnes sont infectées par le virus dans le monde et environ 80% d’entre elles progresseront vers un stade chronique de l’infection. Les thérapies anti-virales actuelles comme l’interféron (IFN) ou la ribavirin sont de plus en plus utilisées mais ne sont efficaces que dans la moitié des individus traités et sont souvent accompagnées d’une toxicité ou d’effets secondaires indésirables. Le système immunitaire inné est essentiel au contrôle des infections virales. Les réponses immunitaires innées sont activées suite à la reconnaissance par les Pathogen Recognition Receptors (PRRs), de motifs macromoléculaires dérivés du virus appelés Pathogen-Associated Molecular Patterns (PAMPs). Bien que l'activation du système immunitaire par l'ARN ou les protéines du VHC ait été largement étudiée, très peu de choses sont actuellement connues concernant la détection du virus par le système immunitaire inné. Et même si l’on peut très rapidement déceler des réponses immunes in vivo après infection par le VHC, l’augmentation progressive et continue de la charge virale met en évidence une incapacité du système immunitaire à contrôler l’infection virale. Une meilleure compréhension des mécanismes d’activation du système immunitaire par le VHC semble, par conséquent, essentielle au développement de stratégies antivirales plus efficaces. Dans le présent travail nous montrons, dans un modèle de cellule primaire, que le génome ARN du VHC contient des séquences riches en GU capables de stimuler spécifiquement les récepteurs de type Toll (TLR) 7 et 8. Cette stimulation a pour conséquence la maturation des cellules dendritiques plasmacytoïdes (pDCs), le production d’interféron de type I (IFN) ainsi que l’induction de chémokines et cytokines inflammatoires par les différentes types de cellules présentatrices d’antigènes (APCs). Les cytokines produites après stimulation de monocytes ou de pDCs par ces séquences ssARN virales, inhibent la production du virus de façon dépendante de l’IFN. En revanche, les cytokines produites après stimulation de cellules dendritiques myéloïdes (mDCs) ou de macrophages par ces mêmes séquences n’ont pas d’effet inhibiteur sur la production virale car les séquences ssARN virales n’induisent pas la production d’IFN par ces cellules. Les cytokines produites après stimulation des TLR 7/8 ont également pour effet de diminuer, de façon indépendante de l’IFN, l’expression du récepteur au VHC (CD81) sur la lignée cellulaire Huh7.5, ce qui pourrait avoir pour conséquence de restreindre l’infection par le VHC. Quoiqu’il en soit, même si les récepteurs au VHC comme le CD81 sont largement exprimés à la surface de différentes sous populations lymphocytaires, les DCs et les monocytes ne répondent pas aux VHC, Nos résultats indiquent que seuls les macrophages sont capables de reconnaître le VHC et de produire des cytokines inflammatoires en réponse à ce dernier. La reconnaissance du VHC par les macrophages est liée à l’expression membranaire de DC-SIGN et l’engagement des TLR 7/8 qui en résulte. Comme d’autres agonistes du TLR 7/8, le VHC stimule la production de cytokines inflammatoires (TNF-α, IL-8, IL-6 et IL-1b) mais n’induit pas la production d’interféron-beta par les macrophages. De manière attendue, la production de cytokines par des macrophages stimulés par les ligands du TLR 7/8 ou les séquences ssARN virales n’inhibent pas la réplication virale. Nos résultats mettent en évidence la capacité des séquences ssARN dérivées du VHC à stimuler les TLR 7/8 dans différentes populations de DC et à initier une réponse immunitaire innée qui aboutit à la suppression de la réplication virale de façon dépendante de l’IFN. Quoiqu’il en soit, le VHC est capable d’échapper à sa reconnaissance par les monocytes et les DCs qui ont le potentiel pour produire de l’IFN et inhiber la réplication virale après engagement des TLR 7/8. Les macrophages possèdent quant à eux la capacité de reconnaître le VHC grâce en partie à l’expression de DC-SIGN à leur surface, mais n’inhibent pas la réplication du virus car ils ne produisent pas d’IFN. L’échappement du VHC aux défenses antivirales pourrait ainsi expliquer l’échec du système immunitaire inné à contrôler l’infection par le VHC. De plus, la production de cytokines inflammatoires observée après stimulation in vitro des macrophages par le VHC suggère leur potentielle contribution dans l’inflammation que l’on retrouve chez les individus infectés par le VHC. / Hepatitis C virus (HCV), a positive single stranded RNA (ssRNA) virus that replicates in the liver, infects 200 million people worldwide, with approximately 80% of infected individuals ultimately suffering from chronic HCV infection. Antiviral therapies, including interferon and ribavirin, have improved considerably in recent years, but are effective in only about one-half of those treated, and are associated with significant side effects and toxicity. Innate immune defenses are essential to control viral infection; the innate response is activated through recognition of viral macromolecular motifs known as pathogen-associated molecular patterns (PAMPs) that are recognized by a multitude of Pathogen recognition receptors (PRRs). Although immune activation induced by HCV RNA or proteins has been extensively studied, the detection of HCV by the innate immune system remains poorly understood. Despite activation of the immune response early after HCV infection in vivo, the persistent increase inpatient HCV viral load suggests the failure of the immune response to control HCV infection. A better understanding of the mechanisms of immune activation induced by HCV is crucial for development of effective strategies for HCV treatment. Here we demonstrate in primary cell models that the HCV genome contained GU-rich RNA sequences that specifically trigger Toll-like receptors (TLR) 7/8, resulting in maturation of plasmacytoid dendritic cells (pDCs) and production of type I interferon (IFN), induction of inflammatory cytokines and chemokines in different antigen presenting cells (APCs). Cytokines produced by monocytes and pDCs upon stimulation of HCV-derived ssRNA inhibited HCV production in an IFN-dependent manner, whereas cytokines produced by myeloid DCs (mDCs) and macrophages had no inhibitory effect on virus production, due to a defect in IFN induction by HCV ssRNA in these cells. TLR7/8 stimulated cytokines also down-regulated the expression of the HCV receptor CD81 on Huh7.5 in an IFN-independent manner that may restrict HCV infection. However, although HCV receptors like CD81 were widely expressed on different subsets of lymphocytes, DCs and monocytes did not respond to HCV particles, and our data indicates that only macrophages sense HCV and produce inflammatory cytokines. The recognition of HCV by macrophages is related to the expression of DC-SIGN on macrophages, and results in TLR7/8 engagement. Similar to a TLR7/8 agonist, HCV stimulation induces inflammatory cytokine production (TNF-α, IL-8, IL-6 and IL-1b) by macrophages but does not stimulate interferon-beta production in macrophages, Congruously, TLR7/8 and HCV RNA mediated cytokine production in macrophages did not inhibit HCV replication. Our results reveal that HCV RNA has the potential to trigger TLR7/8 in DC populations, and initiate an innate immune response against HCV infection that leads to an IFN-dependent suppression of viral replication. However, HCV is able to escape detection by monocytes and DCs, which produce type I IFN and suppress HCV replication when TLR7/8 is engaged. Macrophages possess the capacity to detect HCV, in part because of surface expression of DC-SIGN. In turn, macrophages produce inflammatory cytokines that nevertheless fail to inhibit HCV replication due to lack of IFN-beta production. Evasion of antiviral defense by HCV may explain the failure of innate immunity in control of HCV infection. Moreover, inflammatory cytokine production by macrophages upon HCV stimulation in vitro suggests that activation of macrophages may contribute to inflammation in HCV infected individuals.

Approved for public release, distribution is unlimited / The performance of network management tools for SONET/SDH networks subject to the load conditions is studied and discussed in this thesis. Specifically, a SONET network which consists of four CISCO ONS 15454s, managed by a CISCO Transport Manager, is set up in the Advanced Network Laboratory of the Naval Postgraduate School. To simulate a realistic data transfer environment for the analysis, Smartbits Avalanche software is deployed to simulate multiple client-server scenarios in the SONET network. Traffic from the management channel is then captured using a packet sniffer. Queuing analysis on the captured data is performed with particular emphasis on properties of self-similarity. In particular, the Hurst parameter which determines the captured traffic's degree of self-similarity is estimated using the Variance-Index plot technique. Link utilization is also derived from the computation of first-order statistics of the captured traffic distribution. The study shows that less management data was exchanged when the SONET network was fully loaded. In addition, it is recommended that CTM 4.6 be used to manage not more than 1552 NEs for safe operation. The results presented in this thesis will aid network planners to optimize the management of their SONET/SDH networks. / Civilian, Ministry of Defense, Singapore

Haemophilus parainfluenzae (Hp) and H. influenzae (Hi) are closely related members of the Pasteurellaceae family and are common commensal bacteria of the human nasopharynx. Whilst Hi is frequently implicated in meningitis, otitis media and respiratory tract infections, reports of pathogenic behaviour by Hp are very rare. Lipopolysaccharide (LPS) is a key component of the Gram negative cell wall, and its structure influences the ability of Haemophilus to interact with the host and evade immune clearance. A better understanding of the differences in LPS structure between Hi and Hp could help to ascertain which parts of the molecule are important for commensal and pathogenic behaviour. Hi LPS comprises lipid A, a conserved oligosaccharide inner core, and an oligosaccharide outer core that differs between strains. The latter is partly phase variable by the slipped strand mispairing during replication of DNA repeat tracts within several LPS biosynthesis genes. Very little was known about LPS in Hp so we investigated its biosynthesis and structure in a panel of 20 Hp carriage isolates. Using PCR, DNA sequencing and Southern analysis we demonstrated that Hp possesses homologues of the Hi lipid A and inner core LPS synthesis genes and a few of the genes for outer core synthesis; however, homologues of the Hi phase variable outer core genes were largely absent and did not contain repeat tracts. The results of immunoblotting and collaborative structural analysis were consistent with this data. Phosphocholine, a phase variable Hi LPS epitope that has been implicated in otitis media, was found to be absent in Hp LPS due to the lack of four genes required for its biosynthesis and incorporation. The introduction of these genes into Hp led to the phase variable addition of phosphocholine to the LPS, indicating that there is no fundamental reason why Hp could not use a similar mechanism of variation to Hi if it was advantageous to do so. SDS-PAGE data suggested the presence of O-antigens (repeated chains of sugars) in many of the Hp strains, an unusual feature for Haemophilus, and all of the strains were found to contain a potential O-antigen synthesis locus. Each locus encodes homologues of several glycosyltransferases in addition to either the Wzy polymerase- or ABC transporter-dependent mechanisms of O-antigen synthesis and transport. Comparisons of wild type and isogenic mutant strains showed that the O-antigen enhances resistance to complement-mediated killing and appears to affect adhesion to epithelial cells in vitro. Hp is a successful commensal organism but lacks the flexibility of adapting its LPS using repeat-mediated phase variation, potentially limiting its range of host niches.

Le maintien de la stabilité du génome est essentiel pour la propagation de l’information génétique et pour la croissance et la survie des cellules. Tous les organismes possèdent des systèmes de prévention des dommages et des réarrangements de l’ADN et nos connaissances sur ces processus découlent principalement de l’étude des génomes bactériens et nucléaires. Comparativement peu de choses sont connues sur les systèmes de protection des génomes d’organelles. Cette étude révèle l’importance des protéines liant l’ADN simple-brin de la famille Whirly dans le maintien de la stabilité du génome des organelles de plantes. Nous rapportons que les Whirlies sont requis pour la stabilité du génome plastidique chez Arabidopsis thaliana et Zea mays. L’absence des Whirlies plastidiques favorise une accumulation de molécules rearrangées produites par recombinaison non-homologue médiée par des régions de microhomologie. Ce mécanisme est similaire au “microhomology-mediated break-induced replication” (MMBIR) retrouvé chez les bactéries, la levure et l’humain. Nous montrons également que les organelles de plantes peuvent réparer les bris double-brin en utilisant une voie semblable au MMBIR. La délétion de différents membres de la famille Whirly entraîne une accumulation importante de réarrangements dans le génome des organelles suite à l’induction de bris double-brin. Ces résultats indiquent que les Whirlies sont aussi importants pour la réparation fidèle des génomes d’organelles. En se basant sur des données biologiques et structurales, nous proposons un modèle où les Whirlies modulent la disponibilité de l’ADN simple-brin, régulant ainsi le choix des voies de réparation et permettant le maintien de la stabilité du génome des organelles. Les divers aspects de ce modèle seront testés au cours d’expériences futures ce qui mènera à une meilleure compréhension du maintien de la stabilité du génome des organelles. / Maintenance of genome stability is essential for the accurate propagation of genetic information and for cell growth and survival. Organisms have therefore developed efficient strategies to prevent DNA lesions and rearrangements. Much of the information concerning these strategies has been obtained through the study of bacterial and nuclear genomes. Comparatively little is known about how organelle genomes maintain a stable structure. This study implicates the single-stranded nucleic acid-binding proteins of the Whirly family in the maintenance of plant organelle genome stability. Here we report that the plastid-localized single-stranded DNA binding proteins of the Whirly family are required for plastid genome stability in Arabidopsis thaliana and Zea mays. Absence of plastidial Whirlies favors the accumulation of rearranged molecules that arise through a non-homologous recombination mechanism mediated by regions of microhomology. This mechanism is similar to the microhomology-mediated break-induced replication (MMBIR) described in bacteria, yeast and humans. Additionally we show that plant organelles can repair double-strand breaks using a MMBIR-like pathway. Plants lacking Whirly proteins accumulate elevated levels of microhomology-mediated DNA rearrangements upon double-strand break induction, indicating that Whirlies also contribute to the accurate repair of plant organelle genomes. Using biological and structural data, we propose a working model in which Whirlies modulate the access of repair proteins and complementary DNA to single-stranded regions, thereby regulating the choice of repair pathways and maintaining plant organelle genome stability. The various aspects of this model will be tested in future experiments which should allow a better understanding of the mechanisms underlying genome stability in plant organelles.

This study aimed at evaluating and demonstrating the feasibility of using Concentrated Solar Thermal technology combined with biomass energy technology as a hybrid renewable energy system to supply the process heat requirements in small scale industries in Sri Lanka. Particularly, the focus was to apply the concept to the expanding hotel industry, for covering the thermal energy demand of a medium scale hotel. Solar modules utilize the rooftop area of the building to a valuable application. Linear Fresnel type of solar concentrator is selected considering the requirement of the application and the simplicity of fabrication and installation compared to other technologies. Subsequently, a wood-fired boiler is deployed as the steam generator as well as the balancing power source to recover the effects due to the seasonal variations in solar energy. Bioenergy, so far being the largest primary energy supply in the country, has a good potential for further growth in industrial applications like small hotels.  When a hotel with about 200-guests capacity and annual average occupancy of 65% is considered, the total annual CO2 saving is accounted as 207 tons compared with an entirely fossil fuel (diesel) fired boiler system. The annual operational cost saving is around $ 40,000 and the simple payback period is within 3-4 years. The proposed hybrid system can generate additional 26 employment opportunities in the proximity of the site location area.   This solar-biomass hybrid concept mitigates the weaknesses associated with these renewable technologies when employed separately. The system has been designed in such a way that the total heat demand of hot water and process steam supply is managed by renewable energy alone. It is thus a self-sustainable, non-conventional, renewable energy system. This concept can be stretched to other critical medium temperature applications like for example absorption refrigeration. The system is applicable to many other industries in the country where space requirement is available, solar irradiance is rich and a solid biomass supply is assured.