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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.
1

Pushing the Limits of the Lithium Indicator Carbon Acidity Scale Using Cyclopentadiene Chemistry and 19F NMR Spectrometry

Ramsey, Harley Andrew 06 June 2022 (has links)
C-H bonds are easily the most common type of ordinary chemical bond and studying carbon acidity will help us understand and predict the reactivity of organic compounds. Carbon acidities are ranked using acidity scales. One of the most prominent is the Streitwieser Lithium Indicator (SLI) scale. The term "indicator scale" implies that acids have been measured against one another in sequential fashion. The SLI scale uses lithium ion as the conjugate-base counterion and THF as the solvent. Historically, the SLI scale has emphasized the characterization of weakly-acidic hydrocarbons. Prior to the work of our group, the strongest acid on the SLI scale has a pK value of about 10. Deck and Thornberry extended the scale to ca. pK = 0 by evaluating 23 perfluoroaryl-substituted cyclopentadiene and indene derivatives, using 19F NMR spectroscopy to determine the equilibrium constants of sequential acid-base reactions. This thesis describes the further extension of the SLI scale to ca. pK = −6. To achieve this result, a set of 11 tetrasubstituted cyclopentadienes were synthesized and their acidities evaluated sequentially with the goal of reaching a low pK value while minimizing the acidity ratio at each incremental step. The four ring substituents were combinations of pentafluorophenyl, perfluoro-4-tolyl, and perfluoro-4-pyridyl, electronegative groups listed in order of increasing electron-withdrawing power. The most acidic compound in the set was 1-pentafluorophenyl-2,3,4-tetrakis(tetrafluoro-4-pyridyl)cyclopentadiene, having pK = −5.99. Trends in the acidities of tetraarylcyclopentadienes are discussed including relative electron-withdrawing power of the three selected substituents, and conformational effects among pairs of regioisomeric cyclopentadiene derivatives. / Master of Science / Carbon acidity refers to the willingness of a carbon-hydrogen bond to release a hydrogen ion. C-H bonds are easily the most common type of ordinary chemical bond, so it makes sense that studying carbon acidity will help us understand and predict the reactivity of organic compounds. For the past several decades, emphasis in this area of research has focused on weak carbon acids, especially the simplest hydrocarbons like benzene and methane. This thesis aims in the opposite direction of synthesizing and measuring stronger and stronger carbon acids until we reach the theoretical limit for a given solvent. Because our research strategy is inherently incremental, compounds were synthesized and their acidities were measured, drawing close to the theoretical limit using tetrahydrofuran as the solvent.
2

Studenters upplevelse av aktivitetsbalans i relation till upplevd hälsa efter covid-19 pandemin / Students’ experience of occupational balance in relation to perceived health after the covid-19 pandemic.

Nilsson, Matilda, Emelie, Olsson January 2023 (has links)
Abstrakt  Introduktion: Covid-19 pandemin påverkade många människors aktivitetsmönster, befintliga vanor och levnadssätt, däribland studenter som fick studera befintliga campusförlagda utbildningar på distans. Restriktioner medförde att studenter besökte färre platser och ägnade mindre tid åt sociala aktiviteter och fysiska aktiviteter. Samtidigt ägnades mer tid åt stillasittande aktiviteter, mediekonsumtion och vila. Studier visar att studenter under pandemin upplevde minskad livskvalitet, ökade stressnivåer och sämre psykisk hälsa. Syfte: Syftet med studien var att beskriva studenters upplevelse av aktivitetsbalans i relation till upplevd hälsa efter covid-19 pandemin. Metod: Studien använde en kvantitativ metod, enkätundersökning med 38 deltagare som rekryterades genom ett bekvämlighetsurval. Enkäten bestod av instrumenten the Occupational Balance Questionnarie (OBQ) och the Salutogenic Health Indicator Scale (SHIS) samt egenkonstruerade frågor. Insamlad data analyserades genom en icke-parametrisk metod. Resultat: Resultatet visar att studenterna upplevde relativt god hälsa, men att aktivitetsbalansen skattades lägre efter pandemin. Positiva samband med högre nivåer av aktivitetsbalans och salutogen hälsa återfanns i stöd från studiekamrater och campusbaserade studier. Studenter som bodde tillsammans med någon skattade högre nivåer av aktivitetsbalans och hälsa, jämfört med ensamboende.  Slutsats: Pandemin har påverkat studenternas aktivitetsbalans och hälsa. Studien fann samband mellan aktivitetsbalans och hälsa i förhållande till studieform, boendeform och upplevt stöd från klasskamrater. / Abstract  Introduction: The covid-19 pandemic affected people’s occupational patterns, habits, and lifestyles, including students who had to study existing campus-based studies online. Restrictions meant that students visited fewer places and spent less time on social and physical activity. More time was spent on sedentary activities, media consumption and rest. Studies have shown that students experienced a reduced quality of life, increased stress levels and poorer mental health during the pandemic.  Aim: The aim of the study was to describe students’ experience of occupational balance in relation to perceived health after the covid-19 pandemic. Method: A quantitative and a non-parametric method was used. 38 participants were included. The questionnaire consisted of the Occupational Balance Questionnaire and The Salutogenic Health Indicator Scale, as well as self-constructed questions.  Results: Students experienced relatively good health, but the occupational balance was possibly lower. Positive associations with higher levels of occupational balance and salutogenic health were found in support from classmates, campus-based studies and living together. Conclusions: Students' occupational balance and health was possibly affected after the pandemic. The study found relationships between occupational balance and health in relation to education form, living situation and their sense of support from classmates.
3

Aligning cognitive processes with the design process in a University-based digital fabrication laboratory (Ub-Fablab) / Harmoniser les processus cognitifs avec le processus de conception dans un laboratoire de fabrication numérique universitaire (Ub-Fablab).

Botleng, Vomaranda Joy 08 October 2018 (has links)
Le concept de Laboratoire de Fabrication Digitale (Fablabs) est au départ, une plateforme de prototypage industriel pour les entrepreneurs locaux. Elle est introduit rapidement dans le domaine de l'éducation et sert de plus en plus souvent de plate-forme pour l'apprentissage et l'innovation.Avec l'impact actuel des technologies numériques au sein des sociétés, des organisations telles que le Conseil national de recherches (CNR) appellent le secteur de l'éducation à se tourner vers les compétences du 21ème siècle, tandis que le secteur industriel repense la conception et la production afin d’assurer la durabilité (y compris l'éco-conception et l'économie circulaire) et adopter les dernières technologies intégrées dans l’entreprise 4.0.Les plateformes « Fablab » implantées dans les universités (Ub-Fablabs) pourraient donc jouer un rôle essentiel en tant que «plateforme de support» pour répondre à ces demandes.Etant donné qu’il y a eu très peu ou pas de recherche sur les capacités de Ub-Fablabs pour répondre à ces demandes, cette recherche a adopté une double approche :1) étudier et aligner les compétences cognitives, affectives et psychomotrices y compris les compétences opérationnelles (en matière de logiciels, de notion de mécanique, d’électricité et de systèmes embarqués, …) intégrées dans le processus de conception d'Ub-Fablabs.2) Évaluer la capacité d'Ub-Fablabs à préparer les citoyens aux futures évolutions dans la conception et la production.Dans la partie 1 de la recherche, le chercheur a observé de près la conception et la production d'une machine servant à écraser des roches (RMM) pour laquelle l'utilisation d'une gamme de technologies (bois, pierre et matériaux synthétiques) ont été requises.Les activités de conception et de production ont été enregistrées à l'aide de notes de terrain, d'enregistrements vidéo et de photographies. Pour garder la trace des activités de conception et de production, un modèle de processus de conception itératif, le «modèle de conception de Nawita» (NDPM) a été développé et utilisé.Les données ont été analysées à l'aide d'une analyse de protocole adaptée et les résultats ont été représentés graphiquement.Les résultats ont montré que matérialiser les idées créatives incubées dans la phase 1 du NDPM a déclenché un pic étonnant de compétences cognitives, affectives et psychomotrices dans les étapes 2, 3 et 4 du NDPM. Ces processus et compétences ont sans aucun doute constitués des compétences requises au 21ème siècle.Dans la partie 2 de la recherche, une analyse adaptée des contenus en ligne a été utilisée pour collecter des données provenant de 90% des Ub-Fablabs dans le monde.Une échelle d'indicateurs de capacité Ub-Fablab (Ub-Fablab CIS) a été développée et utilisée pour évaluer quatre aspects potentiels d'Ub-Fablab. Cette échelle est une aide à la compréhension du processus de création. La plate-forme support incite les esprits proactifs à une meilleure intégration des processus de conception et de production.Ces composants sont: i) Infrastructure technologique; ii) Approche pédagogique constructiviste; iii) Collaboration à travers le réseautage numérique et iv) durabilité (y compris l'éco-conception et l'économie circulaire).Les résultats ont révélé que tous les Ub-Fablabs ont une position forte dans la fourniture d'infrastructures technologiques et une forte approche pédagogique constructiviste, mais peuvent avoir besoin d'améliorer leur capacité de collaboration à travers le réseautage et la restauration de la durabilité.Les résultats de cette recherche fournissent une solide réputation pour les Ub-Fablabs à être utilisés pour augmenter les efforts afin d’équiper les citoyens avec des compétences du 21ème siècle et inciter les esprits proactifs à une meilleure intégration et employabilité. / The concept of Digital Fabrication Laboratories (Fablabs), initially an industrial prototyping platform for local entrepreneurships is rapidly finding its way into the education arena and used as a platform for learning and innovation. With the current impact of digital technology on the societies, there are calls from organizations like the National Research Council (NRC) for the education sector to cater for the so-called 21st Century Skills, while the industrial sector to rethink design and production in order to cater for sustainability (inclusive of eco-design and circular economy) and to embrace the latest technologies in preparation for the Industries 4.0. Fablab platforms established in universities (Ub-Fablabs) could therefore play a vital role as a ‘support platform’ to meet these demands.Since there has been very little or no research into the capacities of Ub-Fablabs to meet these demands, this research took a two-fold approach toi) investigate and align cognitive, affective and psychomotor skills (inclusive of mechanical, electrical and embedded software operational skills) embedded in the design process in Ub-Fablabs.ii) assess the capacity of Ub-Fablabs to prepare citizens for the future design and production industries.In part 1 of the research, the researcher closely observed the design and production of a rock milling machine (RMM) where utilisation of a range of wood, stone and synthetic materials technologies were displayed. The design and production activities were recorded using field notes, video-recording and still photography. To keep trace of the design and production activities, an iterative design process model, the ‘Nawita Design Process Model (NDPM) was developed and utilised. Data was analysed using an adapted protocol analysis and results were graphed using pie and bubble-chart graphing. Results showed that materialising the creative ideas incubated in stage 1 of the NDPM unleashed a stunning peak of cognitive, affective and psychomotor skills in stages 2, 3 and 4 of NDPM. These processes and skills are undoubtedly constituted of the 21st Century Skills.In part 2 of the research, an adapted online content analysis was used to collect data from 90% of the Ub-Fablabs worldwide. An Ub-Fablab Capacity Indicator Scale (Ub-Fablab CIS) was developed and used to score on four potential aspects of Ub-Fablab if it has to be used as a support platform to incubate proactive minds for the future integration of design and production industries. These components are i) Technological infrastructure; ii) Constructionist pedagogical approach; iii) Collaboration through digital networking and iv) sustainability (inclusive of eco-design and circular economy). Results revealed that all Ub-Fablabs have a strong stand in providing technological infrastructures and a strong constructionist pedagogical approach, but may need to improve on its capacity for collaboration through networking and catering for sustainability.The findings of this research provides a strong standing for Ub-Fablabs to be utilised to augment efforts to equip citizens with 21st Century skills and incubate proactive minds for the future integration of design and production industries

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