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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.
191

Effect of B chromosomes on recombination frequency in maize

Khanna, Anupama Q. Weber, David F. January 1998 (has links)
Thesis (Ph. D.)--Illinois State University, 1998. / Title from title page screen, viewed July 5, 2006. Dissertation Committee: David F. Weber (chair), Marjorie A. Jones, Anthony Otsuka, Derek McCracken, Radheshyam Jayaswal. Includes bibliographical references (leaves 85-91) and abstract. Also available in print.
192

Αξιολόγηση των παραμέτρων που επηρεάζουν την απόδοση των BPLC συστημάτων στα ηλεκτρικά δίκτυα / Evaluation of the factors that affect the performance of the BPLC systems at electric networks

Μπακλαγής, Δημοσθένης- Σωτήριος 28 September 2010 (has links)
Στην εργασία αυτή αρχικά θα αναφερθούν οι τρόποι παροχής ευρυζωνικών υπηρεσιών και θα αναλυθεί το δίκτυο BPL, καθώς και τα οφέλη που μπορεί να έχουν χρήστες και επιχειρήσεις από το δίκτυο αυτό. Επίσης θα δειχθεί η αρχιτεκτονική ενός δικτύου BPL και οι απαραίτητες συσκευές ώστε το υπάρχων ηλεκτρικό δίκτυο να παρέχει ευρυζωνικές υπηρεσίες. Στη συνέχεια θα παρουσιαστούν στατιστικά στοιχεία για την παγκόσμια πρόσβαση σε τηλεπικοινωνιακές υπηρεσίες και ηλεκτρισμό και θα προταθεί μια προοπτική επέκτασης της τεχνολογίας BPL στις αναπτυσσόμενες χώρες. Στο επόμενο κεφάλαιο παρουσιάζονται οι παράμετροι που επηρεάζουν την απόδοση των BPL δικτύων Μέσης, Χαμηλής Τάσης και εσωτερικού. Διαπιστώνεται ότι η αύξηση των κλάδων ανάμεσα σε πομπό και δέκτη προκαλεί σημαντική μείωση στην απόδοση, επίσης το επίπεδο της διαμόρφωσης επηρεάζει σημαντικά τη χωρητικότητα των καναλιών. Στη συνέχεια συγκρίνονται τα ασύρματα με τα ενσύρματα οικιακά δίκτυα, αναφέρονται τα διαθέσιμα πρωτόκολλα στην ενσύρματη και ασύρματη δικτύωση και παρατίθεται μία συγκριτική δοκιμή ανάμεσα σε BPL προσαρμογείς διαφόρων κατασκευαστών. Τέλος χρησιμοποιήθηκε ένα ζευγάρι προσαρμογέων της Belkin βασισμένων στο πρόσφατο πρωτόκολλο Homeplug AV για την δημιουργία ενός οικιακού δικτύου BPL ανάμεσα σε δύο υπολογιστές. Κάνοντας χρήση του προγράμματος Jperf μετρήθηκε το διαθέσιμο εύρος ζώνης για το δίκτυο μας με τα πρωτόκολλα TCP και UDP, επίσης διευκρινίστηκαν οι παράγοντες εκείνοι που μπορεί να μειώσουν το εύρος ζώνης. Πιο συγκεκριμένα διαπιστώθηκε μείωση της απόδοσης με αύξηση των κλάδων ανάμεσα στους προσαρμογείς. Ταυτόχρονα διαπιστώθηκε ότι η χρήση πολύπριζου με φίλτρα προστασίας προκαλεί σημαντική πτώση μέχρι και μηδενισμό του διαθέσιμου εύρους ζώνης και πρέπει να αποφεύγεται. Παράλληλα, έγινε σύγκριση του πρωτοκόλλου Homeplug AV με το παλαιότερο Homeplug 1.0 καθώς και με το πρωτόκολλο ασύρματης δικτύωσης IEEE 802.11.g, και διαπιστώθηκε η εξέλιξη που υπάρχει στα πρωτόκολλα μεταφοράς δεδομένων μέσω των ηλεκτρικών καλωδιώσεων. Με την διεξαγωγή πειραμάτων στον χώρο του εργαστηρίου Υψηλών τάσεων, διαπιστώθηκε ότι το δίκτυο μας δεν επηρεάζεται από κρουστικό θόρυβο. Τέλος, διαπιστώσαμε ότι η σύνδεση και αποσύνδεση φορτίου επηρεάζει σημαντικά το εύρος ζώνης όταν παρεμβάλλονται πολλοί κλάδοι. / The way of providing broadband services and the analysis of Broadband over Power Lines (BPL) networks will be initially presented in this thesis˙ Plus the benefits that can be assessed by the users and companies alike. The architecture of a typical bpl network will be presented and the necessary devices to use power lines for broadband communications. Following statistics for the global access to telecommunication services and electricity will be presented plus the prospect of extending the BPL technology is introduced, for the developed countries. In the next chapter parameters that affect outputs’ performance for Low, Medium Voltage as well as indoor BPL networks are referred. It is realized that the increase of branch between transmitter and receiver causes important reduction in the capacity, also the level of modulation influences considerably the capacity of channels. Afterwards, wireless and the wired home networks are compared, the available protocols in the wired and wireless networking are reported and a comparative trial between bpl adaptors by various constructors are mentioned. Finally a pair of Belkin bpl adaptors based on recent Homeplug AV was used for the creation of one home network between two computers. Using the Jperf we measured the available bandwidth for our network with TCP and UDP protocols, we also clarified those factors that can degrade the bandwidth. We also mentioned reduction of bandwidth icreasing the number of branches between the adaptors. It was also realized that the use of surge protector causes important reduction to bandwidth and it should be avoided. We also compared the Homeplug AV protocol with the older Homeplug 1.0 and with the IEEE 802.11.g protocol. Finally , after experiments in the laboratory of High voltages, it was realized that our adaptors are not influenced by impulse noise.
193

Οι στρατηγικές προώθησης των φαρμακευτικών σκευασμάτων και οι σύγχρονες τάσεις της διαφήμισης: η περίπτωση των μη συνταγογραφούμενων φαρμάκων (ΜΗ.ΣΥ.ΦΑ.)

Κοτρωνίας, Νικόλαος 22 November 2011 (has links)
Η παρούσα διπλωματική εργασία, έχει σκοπό να δώσει στον αναγνώστη µια εικόνα των ιδιαίτερων χαρακτηριστικών της αγοράς των Over the Counter (OTC), καθώς και των στρατηγικών προώθησης των φαρμακευτικών σκευασμάτων. Για την επίτευξη του ως άνω σκοπού, διενεργήθηκε έρευνα, η οποία παρουσιάζεται στην εργασία αυτή, μαζί με μελέτες, άρθρα, προτάσεις και απόψεις επιστημόνων του Marketing, των Οικονομικών της Υγείας, και της Πολιτικής στο χώρο του φαρμάκου, από τη σχετική βιβλιογραφία. / The present thesis aims to present to the reader the particular characteristics of the Over the Counter (OTC) drug market as well as strategies for their promotion. For the achievement of the above-mentioned aim, a reasearch was held, which is presented in this work, with studies, articles, proposals and opinions of scientists of Marketing, Finances of Health, and Policy in the space of medicine, from the relative bibliography.
194

Development of alternative pulse width modulation methods for conventional and multilevel voltage source inverters

Paterakis, Fotis Konstantinos January 2016 (has links)
Multilevel inverters have attracted wide interest in both the academic community and the industry for the past decades. Therefore, the investigation and development of modulation strategies in multilevel inverters emerges as a necessity for the industry and researchers. In this doctoral thesis, alternative modulation methods suitable for three-level conventional single-phase inverters and especially for cascade H-bridge multilevel inverters are discussed and proposed. The theory of Equal Areas is reformed and presented and its modifications are proposed. These modifications are compared with other well-known modulation schemes, such as carrier-based modulation schemes and programmed pulse width modulation techniques. The advantage of the modified Equal Areas Pulse Width Modulation (EAPWM) is its algorithmic simplicity due to simple algebraic relationships, which results in less computational effort. A fully mathematical formulation for the Equal Areas modulation is proposed for both conventional and multilevel inverters. The EAPWM is shown to produce well-formed switched output voltages that have low total harmonic distortion at even low switching frequencies. The importance of this thesis is complimented by the results, produced after the implementation of EAPWM in multilevel inverters, which can be used as a more accurate reference when compared with other modulation strategies. Moreover, this direct modulation strategy has been extended to work on higher amplitude modulation ratios, in a linear manner, while entering the over modulation region. In this context, modified algorithms have been developed using different criteria for the calculation of the pulses’ width and their placement inside the time interval. The equal areas method, implemented in conventional single-phase inverters, uses odd pulse numbers per half cycle, holding integer frequency ratios in contrast to its implementation in multilevel inverters, where non-integer frequency ratios occur due to the level-by-level application. The application of the method is verified by simulations together with experimental work using a full-scale prototype inverter.
195

EFFECTS OF CHARACTER VOICE-OVER ON PLAYERS' ENGAGEMENT IN A DIGITAL ROLE-PLAYING GAME ENVIRONMENT

Byun, JaeHwan 01 December 2012 (has links)
Learner engagement has been considered one of the keys that can lead learners to successful learning in a multimedia learning environment such as digital game-based learning. Regarding this point, game-based learning advocates (e.g., Gee, 2003; Prensky, 2001) have asserted that digital games have great potential to engage learners. Nonetheless, there have been only a small number of empirical research studies of players' engagement, and there is little consensus on which elements of digital games critically engage people in play (Garris, Ahlers, & Driskell, 2002). Furthermore, despite the possibility that sensory stimuli can be factors influencing digital game players' engagement, there have been very few attempts to examine empirically the relationship between engagement and sensory stimuli. This study examined the effects of game characters' voice-over in digital games on players' engagement, by using a short digital role-playing game modified from Neverwinter Nights 2. A randomized control-group post-test only design was used to collect data from 74 participants (22 female, 52 male); engagement was measured by a modification of the Game Engagement Questionnaire (Brockmyer et al., 2009). Data analysis revealed that the GEQ mean scores of the participants who played the game with voice-over was much higher than that of the participants who played without voice-over. The difference of the mean scores between the two groups was statistically significant (t = 2.45, df = 72 p = .02), and the effect size, Cohen's d, was .58 (moderately significant). The results of this study will guide educational practitioners to the identification of more effective ways of adopting, developing, and modifying digital games for educational purposes, as well as furthering the research and guiding the practice in instructional multimedia design and development.
196

Regulação de serviços over-the-top (OTT) e pós-convergência tecnológica : uma análise do regime jurídico setorial de serviços OTT de voz nos EUA e no Brasil

Fernandes, Victor Oliveira 26 February 2018 (has links)
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Direito, Programa de Pós-Graduação em Direito, 2018. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-05-15T15:47:01Z No. of bitstreams: 1 2018_VictorOliveiraFernandes.pdf: 2203164 bytes, checksum: 7ad140f25258e6eb1c8529479d6651b8 (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2018-06-05T12:54:35Z (GMT) No. of bitstreams: 1 2018_VictorOliveiraFernandes.pdf: 2203164 bytes, checksum: 7ad140f25258e6eb1c8529479d6651b8 (MD5) / Made available in DSpace on 2018-06-05T12:54:35Z (GMT). No. of bitstreams: 1 2018_VictorOliveiraFernandes.pdf: 2203164 bytes, checksum: 7ad140f25258e6eb1c8529479d6651b8 (MD5) Previous issue date: 2018-06-04 / Esta dissertação trata da regulação de serviços baseados na internet, comumente chamados de serviços over-the-top (OTT). Em especial, o objetivo do estudo é analisar o regime jurídicosetorial aplicável aos serviços OTT de voz definido a partir da atuação das agências reguladoras de telecomunicações norte-americana e brasileira no recorte temporal das últimas duas décadas. Com base em teorias que consubstanciam prescrições normativas sobre como regular serviços de telecomunicações e internet no contexto pós-convergência tecnológica, o trabalho busca responder à seguinte pergunta de pesquisa: as atuações das agências reguladoras nacionais de telecomunicações no período histórico analisado têm resultado na construção de regimes jurídicos estáveis e horizontais em mercados funcionalmente equivalentes? De início, apontase uma hipótese negativa, tendo em vista as assimetrias regulatórias a que estão submetidos os serviços de telecomunicações e de internet potencialmente substitutivos nas jurisdições analisadas. O expediente investigativo se desenvolve em quatro capítulos. No Capítulo 1, é feita uma breve revisão da ainda incipiente literatura sobre serviços OTT, destacando-se os seus principais aspectos regulatórios controversos e a importância da atuação das agências reguladoras de telecomunicações, no limite da sua competência, para a definição do regime jurídico setorial aplicável àqueles serviços. No Capítulo 2, é realizada uma explicação pormenorizada das teorias de regulação utilizadas neste estudo, destacando-se três prescrições que delas derivam e que são fixadas como variáveis de análise do objeto de pesquisa delimitado. No Capítulo 3, são examinados o enquadramento jurídico dos serviços OTT no âmbito do Telecommunications Act de 1996 e o processo histórico de conformação dos direitos e das obrigações regulatórias aplicáveis aos serviços OTT de voz nessa jurisdição pela Federal Communications Commision (FCC). No Capítulo 4, analisa-se o enquadramento dos serviços OTT na Lei Geral de Telecomunicações (LGT), bem como as possibilidades de regulação desses serviços na interface entre a LGT e o Marco Civil da Internet (MCI). Investiga-se de que forma a Agência Nacional de Telecomunicações (ANATEL) tem definido o regime jurídico setorial dos serviços OTT de voz nos últimos anos e quais são os principais desafios atuais envolvidos na superação das assimetrias regulatórias existentes entre serviços de telecomunicações e os Serviços de Valor Adicionado (SVA). Por fim, a conclusão do trabalho consolida os resultados da análise das experiências nacionais comparadas, apontando em relação a elas (i) uma coincidência quanto ao diagnóstico de insuficiência da bipolaridade normativa entre serviços de telecomunicações e serviços de internet; (ii) uma divergência, ainda que parcial, quanto ao manejo de políticas regulatórias incrementais na definição das obrigações econômicas e sociais aplicáveis os serviços OTT de voz; e (iii) uma ausência comum de perspectivas de reformas estruturais voltadas ao estabelecimento de regimes jurídicos estáveis e horizontais em mercados funcionalmente equivalentes. / This dissertation analyses the regulation of internet-based services, commonly known as overthe-top services (OTT). The study examines the regulatory framework applicable to OTT voice services in light of decisions and procedures implemented by the telecommunications regulatory agencies in USA and Brazil over the last two decades. It addresses the following research question: have the decisions and procedures implemented by the telecommunications regulatory agencies constructed a regulatory framework that apply the same rules to substitutes services? The initial hypothesis is negative, due to distinct regulatory rules applicable to telecommunications operators and internet firms in both jurisdictions. The analysis is undertaken in four chapters. In Chapter One, the dissertation engages in a short review of the currently scarce literature related to OTT regulation. In Chapter Two, it explores legal theories that offer normative prescriptions for regulating telecommunications and internet-based services in the so-called post-technological convergence era. In Chapter Three, it analyses the classification of services established by the North American Telecommunications Act of 1996 and the regulatory procedures related to OTT voice services which were implemented by the Federal Communications Commission (FCC) over the last two decades. In Chapter Four, the dissertation analyses the legal framework of OTT in Brazil, under the General Telecommunications Law and the Brazilian Civil Rights Framework for the Internet. It examines how the Brazilian telecommunications agency (Agência Nacional de Telecomunicações – ANATEL) has treated OTT voice services during the analyzed period. It also addresses the current challenges for overcoming regulatory asymmetries between telecommunications services and value-added services in Brazil. In its conclusion, the comparative regulatory analysis indicates (i) an undisputed insufficiency of the legal dichotomy between telecommunications and value-added services; (ii) a partial difference in the implementation of incremental regulatory strategies applicable to OTT voice services and (iii) a common lack of perspective of structural reforms that could establish convergent regulatory policies in functional equivalent markets.
197

Numerical solutions to some inverse problems

Van, Cong Tuan Son January 1900 (has links)
Doctor of Philosophy / Department of Mathematics / Alexander G. Ramm / In this dissertation, the author presents two independent researches on inverse problems: (1) creating materials in which heat propagates a long a line and (2) 3D inverse scattering problem with non-over-determined data. The theories of these methods were developed by Professor Alexander Ramm and are presented in Chapters 1 and 3. The algorithms and numerical results are taken from the papers of Professor Alexander Ramm and the author and are presented in Chapters 2 and 4.
198

Using Pittsburgh Sleep Quality Index Scores to Predict Polysubstance Use Among College Students

January 2014 (has links)
abstract: The effects of over-the-counter drug (OTC) use on college students' health has been debated in the field of psychology with researchers arguing that poor sleep quality among college students is the result of polysubstance use. However, this explanation is not a foregone conclusion. These researchers have not adequately addressed the issue poor sleep quality among college students and its relationship to polysubstance use. This is an important issue because prolonged unsupervised OTC drug use and poor sleep quality can impact long-term health and lessen students' likelihood of being successful in college. This paper addresses the issue of OTC drug use with special attention to sleep quality. Pittsburgh Sleep Quality Index Scores were collected to assess subjective sleep quality and its relationship to OTC drug use. Several other risk factors including binge drinking, marijuana use, and illicit drug use were also accounted for in this model. This study argues that, although the current literature suggests that poor sleep quality is the effect of drug use rather than the cause; the relationships between these factors are still unclear. This study aims to fill a gap in the college drug use literature by establishing a relationship between poor sleep quality and OTC drug use in a college sample. / Dissertation/Thesis / M.S. Psychology 2014
199

Idosos CentenÃrios, a arte de envelhecer / Elderly century, the art of aging

TÃnia de AraÃjo Barboza 23 September 2011 (has links)
INTRODUCTION. Whereas the elderly population is increasing and that centenarians represent an ideal model of longevity, combining quantity with quality of life, the study of this age group it is essential for developing policies and programs to promote successful aging. OBJECTIVES. Understanding the factors that may be associated with living conditions and health of elderly centenarians (aged 98 years or more) in the city of Fortaleza and seek to identify whether the social support networks and family, the power over life, the personality traits and spirituality can contribute to extreme longevity. METHODS. It is an exploratory and descriptive study with qualitative approach, with the locus the city of Fortaleza, Ceara, Brazil, and as six elderly subjects aged over 98 years in a position to respond to the interview in his home. The instruments used for data collection were structured interviews and in depth, recorded and transcribed verbatim, after the participants signed a consent form. The method used for data analysis was recommended by Bardin - Content Analysis. The project followed the ethical guidelines of the National Health Council, which preserved the anonymity of the respondents for their cognominaÃÃo with names of birds. RESULTS. The reports most frequently observed and interviewed were transformed into five categories as follows: Category 1 - It was very good to my life!, Category 2 - I like it when I have to talk to, Category 3 - The friendship I value family a lot; Category 4 - The family sends my money and Category 5 - I was always charitable. CONCLUSION: the personality characteristics of the respondent, namely, extroversion, low neuroticism, kindness and consciensiosidade, the presence of family support and the subjective feeling of autonomy seem to have contributed positively to their quality of life and health. It was also observed that the respondents escaped from aging-related diseases, and maintained their independence until very advanced ages. Further studies are needed in order to understand the extreme longevity and also foster the creation of public policies for a better quality of life and support for this age group. / INTRODUÃÃO. Considerando que a populaÃÃo de idosos està aumentando e que os centenÃrios representam um modelo ideal de longevidade, aliando quantidade com qualidade de vida, o estudo desse grupo etÃrio torna-se fundamental para o desenvolvimento de polÃticas e programas de promoÃÃo do envelhecimento bem-sucedido. OBJETIVOS. Compreender os fatores que podem estar associados à condiÃÃo de vida e saÃde de idosos centenÃrios (com idade igual ou superior a 98 anos) do MunicÃpio de Fortaleza e procurar identificar se as redes de apoio social e familiar, a alimentaÃÃo ao longo da vida, os traÃos da personalidade e espiritualidade podem contribuir para a longevidade extrema. MÃTODOS. à um estudo exploratÃrio e descritivo com abordagem qualitativa, tendo como locus a cidade de Fortaleza-CearÃ-Brasil, e como sujeitos seis idosos com idade acima de 98 anos em condiÃÃes de responder à entrevista realizada em seu domicilio. Os instrumentos utilizados para a coleta de dados foram entrevistas estruturadas e em profundidade, gravadas e transcritas literalmente, apÃs os participantes assinarem o Termo de Consentimento Livre e Esclarecido. O mÃtodo utilizado para a anÃlise de dados foi o preconizado por Bardin â AnÃlise de ConteÃdo. O projeto obedeceu aos preceitos Ãticos do Conselho Nacional de SaÃde, sendo o anonimato dos entrevistados preservado por sua cognominaÃÃo com nomes de pÃssaros. RESULTADOS. As falas mais freqÃentes dos entrevistados foram observadas e transformadas em cinco categorias de anÃlise: Categoria 1 â Foi muito boa a minha vida!; Categoria 2 â Gosto quando tenho com quem conversar; Categoria 3 â A amizade da famÃlia eu prezo muito; Categoria 4 â A famÃlia manda no meu dinheiro e Categoria 5 â Sempre fui caridoso. CONCLUSÃO: as caracterÃsticas da personalidade do entrevistado, a saber, extroversÃo, baixos nÃveis de neuroticismo, amabilidade e consciensiosidade; a presenÃa do suporte familiar e a sensaÃÃo subjetiva de autonomia parecem ter contribuÃdo positivamente para sua qualidade de vida e saÃde. Observou-se tambÃm que os entrevistados escaparam das doenÃas relacionadas ao envelhecimento, tendo sua autonomia mantida atà idades bem avanÃadas. Novos estudos sÃo necessÃrios, visando a compreender a longevidade extrema e tambÃm fomentar a criaÃÃo de polÃticas pÃblicas voltadas para uma melhor qualidade de vida e apoio à esta faixa etÃria.
200

Efeito da temperatura na eletro-oxidação oscilatória de ácido fórmico sobre platina: experimentos e simulações / Temperature effect in the oscillatory electro-oxidation of formic acid on platinum: experiments and simulations

Raphael Nagao de Sousa 09 April 2009 (has links)
Ritmos biológicos são regulados por mecanismos homeostáticos que asseguram a confiabilidade funcional do relógio fisiológico independentemente de mudanças de temperatura no ambiente. Compensação de temperatura, ou a independência do período oscilatório em relação à temperatura, é conhecida por exercer um papel central em muitos ritmos biológicos, mas um fenômeno raro em osciladores químicos. Estudou-se nessa dissertação a influência da temperatura na dinâmica oscilatória durante a oxidação catalítica de ácido fórmico sobre eletrodo de platina policristalina. Os experimentos foram conduzidos em cinco temperaturas diferentes de 5 à 25 ºC, e as oscilações foram estudadas sob controle galvanostático. Resultados experimentais foram comparados a um novo modelo proposto para a eletro-oxidação de ácido fórmico, considerando formato como intermediário ativo e a desidrogenação da água em altos potenciais. Sob condições oscilatórias apenas comportamento anti-Arrhenius foi observado. Sobre-compensação com coeficiente de temperatura (q10, definido como a razão entre a constante de velocidade à temperatura T + 10 ºC e em T) < 1 é achada para a maioria dos casos, exceto em altas correntes aplicadas onde compensação de temperatura, q10 ~ 1 predomina. O comportamento do período e amplitude resulta de uma combinação complexa entre a temperatura e corrente aplicada ou, equivalentemente, a distância do equilíbrio termodinâmico. Altas energias de ativação aparente foram obtidas em condições voltamétricas, não-oscilatórias, as quais implicam que o comportamento anti-Arrhenius observado sob regime oscilatório resulta de um acoplamento entre as rotas reacionais em vez de uma fraca dependência da temperatura nas etapas elementares. Mecanisticamente, os experimentos e o modelo matemático sugerem que o período em regime de (sobre)compensação de temperatura durante a eletro-oxidação de ácido fórmico sobre platina é governado pelo acoplamento entre as taxas reacionais de formação/remoção de monóxido de carbono e formato em condições oscilatórias. / Biological rhythms are regulated by homeostatic mechanisms that assure that physiological clocks function reliably independent of temperature changes in the environment. Temperature compensation, i.e. the independence of the oscillatory period on temperature, is known to play a central role in many biological rhythms, but it is rather rare in chemical oscillators. It was studied in this master thesis the influence of temperature on the oscillatory dynamics during the catalytic oxidation of formic acid on a polycrystalline platinum electrode. The experiments are performed at five temperatures from 5 to 25 ºC, and the oscillations studied under galvanostatic control. Experimental results are compared to a new model proposed for formic acid electro-oxidation, which includes formate as an active intermediate and water dehydrogenation at high potentials. Under oscillatory conditions only non-Arrhenius behavior is observed. Over-compensation with temperature coefficient (q10, defined as the ratio between the rate constants at temperature T + 10 ºC and at T) < 1 is found in most cases, except that temperature compensation with q10 ~ 1 predominates at high applied currents. The behavior of the period and the amplitude result from a complex interplay between temperature and applied current or, equivalently, the distance from thermodynamic equilibrium. High, positive apparent activation energies were obtained under voltammetric, non-oscillatory conditions, which implies that the non-Arrhenius behavior observed under oscillatory conditions results from the interplay among reaction steps rather than from a weak temperature dependence of the individual steps. Mechanistically, the experiments and the mathematical model suggest that the period in temperature (over)compensation regime during electro-oxidation of formic acid at platinum is governed by the coupling among the reaction rates of formation/removal of carbon monoxide and formate coverage in oscillatory conditions.

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