The preparation and characterization of chitosan/poly (vinyl alcohol) blended films : mechanical, thermal and surface investigations

In this study, blends of chitosan (CS) and polyvinyl alcohol (PVA) (CS/PVA) having various proportions were prepared and characterized by universal mechanical tester, the differential scanning calorimetry (DSC) and contact angle measurements. Studying the mechanical properties of the films showed that blending improved the tensile strength, which increased with increasing PVA content up to 40% while the elongation% at break of the blends was decreased compared to that of the pure components. The obtained results of DSC suggested that some interaction between chitosan and PVA mostly took place. Static water contact angle measurements showed an improvement in the wettability of the obtained films

MV-TMM: Une approche multi vues pour la gestion de la traçabilité des exigences

The approach MV-TMM (Multi View Traceability Management Method) presented in this thesis aims to guide the companies in their design of requirements traceability models adapted to the context of their projects. This is achieved by allowing the construction of a model based on trace fragments adapted to each phase of the development process or to a specific situation. Furthermore, the approach guides the users to use the traceability model in a requirement management tool. They help them capture and mange the evolution of the traceability data.Après une étude de l‘état de l‘art dans le domaine de la traçabilité des exigences, nous avons constaté que la gestion de la traçabilité a fait l‘objet de plusieurs travaux de recherche. Malgré ces travaux, nous avons constaté que les entreprises rencontrent encore des difficultés à intégrer la traçabilité dans leurs processus de développement. Cela est dû au manque de mécanisme de représentation des différents types d‘informations de traçabilité ainsi qu‘à la méconnaissance du processus de traçabilité des exigences dans un projet.Le travail de cette thèse propose une solution dénommée MV-TMM (un démarche multi vues pour la gestion de la traçabilité) composée de deux éléments principaux : (i) un méta modèle multi vues permettant la représentation des différents types d‘informations de traçabilité et (ii) un processus intentionnel décrivant les étapes nécessaires pour la construction et l‘usage des informations de traçabilité

Human exposure to Anaplasma phagocytophilum in two cities of Northwestern Morocco

Anaplasma phagocytophilum is an emerging tick-borne zoonosis with extensive increased interest. Epidemiological data are available in several regions of the USA, Europe and Asia in contrast to other parts of the world such as North Africa. Blood samples of 261 healthy individuals divided in two groups i.e., dog handlers and blood donors were analysed. Indirect immunofluorescent assay using a commercial kit was performed to detect specific A. phagocytophilum IgG. Two dilutions were used to assess the prevalence of seroreactive samples. Demographic variables were assessed as potential risk factors using exact logistic regression. Seropositivity rates reached 37% and 27% in dog handlers and 36% and 22% in blood donors. No statistically significant differences were found in the prevalence rates between the two groups. Analysis of risk factors such as gender, age groups, outdoor activities, self-reported previous exposure to ticks, or contact with domestic animals (dogs, cats, ruminants and horses) did not shown any significant difference. A. phagocytophilum exposure was common in both high-risk population and blood donors in Morocco

Síntesis y modificación de la estructura de una copoliamida aromática fluorescente: estudio de su aplicación como sensor de cianuro

Los polímeros forman parte de una amplia gama de materiales de gran relevancia a nivel científico, tecnológico e industrial. Esto se debe a que poseen una gran variedad de propiedades físicas y mecánicas, que se encuentran relacionadas intrínsecamente con su estructura, que deriva de la naturaleza del monómero y del tipo de enlace que forman a lo largo de la cadena polimérica, además de los grupos laterales del tipo mono o poli funcional que puedan presentar. Las distintas fuerzas de interacción entre sus cadenas juegan un rol importante en las propiedades finales de estos materiales. El objetivo fundamental del trabajo que constituye el Practicum y el Complemento al Practicum que aquí se presenta ha sido la síntesis de una copoliamida, preparada por copolimerización de la m-fenilendiamina con dos diácidos, el ácido isoftálico y un derivado de éste, que porta en la posición cinco del anillo un grupo urea conectado a un anillo de fluoreno. La elección de estos grupos se basa en los requerimientos que debe cumplir un sensor químico en la detección de aniones: debe presentar un centro de coordinación para el anión (grupo urea) que se encuentra conectado al centro capaz de traducir la coordinación del anión en una señal detectable como puede ser un cambio de color o de fluorescencia. El grupo fluoreno unido a la urea en nuestro caso actúa como unidad indicadora. La modificación química sobre el anillo de fluoreno de esta poliamida ha permitido la preparación de un material que presenta cambios de color en presencia de iones cianuro, lo que constituye un ejemplo de un sistema macromolecular con aplicaciones tecnológicas en el campo de los sensores químico

Turbulent boundary layer on a rough surface with pressure gradient and surface heating

Imperial Users onl

Climate change and agriculture in Burkina Faso

The impacts of climate change (CC) are expected to be higher in developing countries (e.g. Sub-Saharan Africa). However, these impacts will depend on agriculture development and resilience. Therefore, this paper provides a comprehensive analysis of the multifaceted relationships between CC and agriculture in Burkina Faso (BF). A search performed in March 2020 on the Web of Science yielded 1,820 documents and 217 of them were included in the systematic review. The paper provides an overview on both bibliometrics (e.g. journals, authors, institutions) and topics addressed in the literature viz. agriculture subsectors, climate trends in BF, agriculture and CC mitigation (e.g. agriculture-related emissions, soil carbon sequestration), impacts of CC on agriculture (e.g. natural resources, crop suitability, yields, food security) as well as adaptation strategies. BF is experiencing CC as evidenced by warming and an increase in the occurrence of climate extremes. The literature focuses on crops, while animal husbandry and, especially, fisheries are often overlooked. Moreover, most of the documents deal with CC adaptation by the Burkinabe farmers, pastoralists and rural populations. Analysed adaptation options include conservation agriculture and climate-smart agriculture, irrigation, crop diversification, intensification, livelihoods diversification and migration. However, the focus is mainly on agricultural and individual responses, while livelihoods strategies such as diversification and migration are less frequently addressed. Further research is needed on the dual relation between agriculture and CC to contribute to the achievement of the Sustainable Development Goals. Research results are crucial to inform policies aimed at CC mitigation and/or adaptation in rural BF

Temperature dependence of lattice dynamics in quasicrystals

The work presented in this thesis was motivated by the large amount of experimental investigations of the phonons in quasicrystals. The generalized vibrational density of states (GVDOS) was measured for many quasicrystalline phases and in some cases at different temperatures [suck et al (1997), Dugain et al (1997)]. The progress achieved in the structure determination of approximants to some quasicrystals was a legitimate motivation for numerical investigations of lattice dynamics in these structures. Two different types of interatomic interactions were used: the spring model and the ab-initio pair potentials. The investigations explained the shape of some experimentally measured GVDOS (d-AlNiCo, o-Al13Co4 and i-ZnMgY) via the calculation of the partial vibrational densities of states. Both calculated and measured GVDOS of the d-AlNiCo phase showed an intensity excess at low energies relatively to the ideal Debye behaviour. This excess was found to be a consequence of the existence of special modes at theses energies which are called ``quasi-localized modes''. These modes seem to be characteristic of the lattice dynamics in the complex Al-TM structures. To calculate the frequency shift due to the shift of the GVDOS through low energies observed experimentally at high temperatures, a new method based on a Monte-Carlo simulation was developed. It was shown that the quasi-localized modes introduce large frequency shifts at low energies. Finally, the vibrational entropy was also investigated, and it was found that it contributes to the stabilization of the complex structures over the relatively simple structures at high temperatures.Die Arbeit, die in dieser Dissertation präsentiert wird, wurde durch eine Vielzahl von experimentellen Beobachtungen von Phononen in Quasikristallen motiviert. Die verallgemeinerte vibrationelle Zustandsdichte (GVDOS, generalized vibrational density of states) wurde für viele quasikristalline Phasen gemessen und für einige auch bei verschiedener Temperatur [Suck et al. (1997), Dugain et al. (1997)]. Der Fortschritt, der in der Bestimmung von Näherungen für einige Quasikristalle erreicht wurde war eine legitime Motivation für numerische Untersuchungen der Gitterdynamik auf diesen Strukturen. Es wurden zwei unterschiedliche interatomare Wechselwirkungen verwendet: Das Federmodell und die ab-initio Paar Potentiale. Die Untersuchungen erklärten die Form einiger experimenteller GVDOS-Messungen (d-AlNiCo, o-Al13Co4 und i-ZnMgY) mittels der Berechnung der partiellen vibrationellen Zustandsdichte. Beide, berechnete und gemessene, GVDOS der d-AlNiCo Phase zeigten einen Intensitätsanstieg bei kleinen Energien relativ zum idealen Debye Verhalten. Dieser Anstieg stellte sich als Konsequenz der Existenz von besonderen Moden bei diesen Energien heraus, die quasi-lokalisierte Moden genannt werden. Diese Moden scheinen charakteristisch für die Gitterdynamik in den komplexen Al-TM Strukturen zu sein. Um die experimentell beobachtete Frequenzverschiebung aufgrund der Verschiebung der GVDOS durch niedrige Energien zu berechnen, wurde eine neue, auf Monte-Carlo Simulation beruhende, Methode entwickelt. Es wurde gezeigt, daß die quasi-lokalisierten Moden große Frequenzverschiebungen bei kleinen Energien hervorrufen. Letzt-lich wurde auch die vibrationelle Entropie untersucht und es stellte sich heraus, daß sie bei hohen Temperaturen dazu beiträgt die komplexen Strukturen gegenüber den relativ einfachen zu stabilisieren