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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.
321

Remoção de substâncias húmicas por meio da oxidação com ozônio e peróxido de hidrogênio e filtração lenta / not available

Edson Pereira Tangerino 30 May 2003 (has links)
A presença de substâncias húmicas na água de abastecimento tem recebido a atenção de diversos pesquisadores nas últimas décadas, pois pode gerar subprodutos ao ser exposta a agentes oxidantes e desinfetantes. A filtração em múltiplas etapas (FiME) se apresenta como uma alternativa para realizar o tratamento de água de comunidades de pequeno porte, entretanto, a eficiência quanto à remoção de cor verdadeira associada ao carbono orgânico dissolvido ou às substâncias húmicas, tem sido questionada ou relatada como baixa. A filtração lenta com pré-ozonização vem sendo utilizada, pois o ozônio atua nas moléculas da matéria orgânica, aumentando sua biodegradabilidade e seus subprodutos desaparecem logo após a aplicação. A aplicação conjunta do ozônio e peróxido de hidrogênio, tem o objetivo de produzir espécies com radicais livres, de vida curta, que sejam altamente reativos e possam oxidar a maior parte das substâncias presentes na água natural. A presente pesquisa avaliou a remoção de substâncias húmicas na filtração lenta, utilizando para essa avaliação parâmetros indiretos como cor verdadeira, absorvância 254 nm e carbono orgânico dissolvido. Foram realizados cinco ensaios utilizando quatro filtros lentos, sendo dois com camada de carvão ativado granular (CAG), em que foram ensaiadas várias alternativas de pré-oxidação com ozônio e peróxido de hidrogênio. Obteve-se, como principal conclusão, que os filtros lentos com CAG, precedidos de oxidação com ozônio e depois peróxido de hidrogênio, em dosagens adequadas, apresentaram remoção média de cor verdadeira de 64% da cor inicial. Concluiu-se, também, que o peróxido de hidrogênio afeta o desenvolvimento da camada biológica, interferindo no desenvolvimento da perda de carga, na remoção de turbidez e na remoção de substâncias húmicas. / The presence of humic substances in the water of supply has been received attention of several researchers in the last decades, because it can generate by-products when being exposed to oxidants and disinfectant. The multistage filtration (FiME) is an alternative considered to achieve water treatment for small size rural communities, however, the efficiency with relationship to the removal of true color associated to the dissolved organic carbon or to the humic substances, it has been questioned or reported as low. The slow filtration with pre-ozonation is being used, since the ozone acted in the molecules of the organic matter of high molecular weight, increasing its biodegradability and by-products disappear soon after the application. The combined application of the ozone and hydrogen peroxide have the objective of producing species with free radicals, of short-lived, that are highly reagents and can oxidize most of the present substances in the natural water. The present research it evaluated the removal of humic substances in the slow sand filtration, using for that evaluation indirect parameters as true color, absorbance 254 nm and dissolved organic carbon. Five experiments were realized using four slow filters, being two with layer of activated carbon to granulate (CAG), in that several pre-oxidation alternatives were rehearsed with ozone and peróxido of hydrogen. It was obtained, as main conclusion that the slow filters with CAG preceded ofoxidation with ozone and hydrogen peroxide, in appropriate dosagens, presented medium removal of true color of 64% of the initial color. It was also concludes that the hydrogen peroxide interferes the development of the biological layer, interfering in the development of the loss of head, in the turbidity removal and in the removal of humic substances.
322

The Slow Movements of Anton Bruckner's Symphonies: Dialogical Perspectives

Venegas Carro, Gabriel Ignacio, Venegas Carro, Gabriel Ignacio January 2017 (has links)
This study presents a detailed analytical examination of formal organization in Anton Bruckner’s early instrumental slow movements: from the String Quartet, WAB 111, to the Third Symphony, WAB 103. It proposes an analytical methodology and conception of the formative process of musical works that seeks to 1) reappraise the development and idiosyncrasies of his slow movements’ form, and 2) turn the textual multiplicity often associated with Bruckner’s large-scale works (a scholarly issue often referred to as the “Bruckner Problem”) into a Bruckner Potential. In addressing traditional and innovative formal aspects of Bruckner’s music, critics have tended to overemphasize one side or the other, consequentially portraying his handling of form as either whimsical or excessively schematic. By way of a reconstruction of Bruckner’s early experiments with slow-movement form (1862–1873), this study argues that influential lines of criticism in the reception history of Bruckner’s large-scale forms find little substantiation in the acoustical surface of Bruckner’s music and its dialogic engagement with mid- and late-19th-century generic expectations. Because the textual multiplicity often associated with Bruckner’s works does not sit comfortably with traditional notions of authenticity and authorship, Bruckner scholarship has operated under aesthetic premises that fail to acknowledge textual multiplicity as a basic trait of his oeuvre. The present study circumvents this shortcoming by conceiving formal-expressive meaning in Bruckner’s symphonies as growing out of a dual-dimensional dialogue comprising 1) an outward dialogue, characterized by the interplay between a given version of a Bruckner symphony and its implied genre (in this case, sonata form); and 2) an inward dialogue, characterized by the interplay among the various individualized realizations of a single Bruckner symphony. The analytical method is exemplified through a detailed consideration of each of the surviving realizations of the slow movement of Bruckner’s Third Symphony, WAB 103.
323

Cultivating a Food Movement : Slow Food USA’s Role in Moving Society Towards Sustainability

Feldman, Maja, Kingfisher, Alli, Sundborg, Cindy January 2011 (has links)
With society’s growing population and the earth’s limited resources, the current world food system is unsustainable. Slow Food USA (SFUSA) is an existing food-related Non-Governmental Organization (NGO) focusing on the expansion of Good, Clean, and Fair food. This research aims to help SFUSA to strategically support society’s move towards sustainability. To do this, the authors used the Framework for Strategic Sustainable Development (FSSD) to examine the current reality of SFUSA, where the opportunities and challenges for the organization to strategically plan toward sustainability were identified. The authors then used Leverage Points (LPs) to identify opportunities for how SFUSA can strategically intervene in the world food system to create change and the challenges that exist in doing so. The results of this research allowed the team to create a list of recommendations. Of these results, five were picked as the most strategic recommendations for SFUSA: 1) Co-create a shared common vision of sustainable food for society 2) Define a common language and branding among chapters that are in alignment with SFUSA 3) Implement a strategic planning process founded in a principle-based definition of sustainability 4) Expand educational outreach to specific targeted groups at the chapter level 5) Advocate for policy changes to remove barriers to widely available and affordable, sustainably produced agriculture.
324

The Effects of a Classroom Social Skills Training Program on Socially Maladaptive Learning Disabled Elementary Students

Williams, Victoria R. (Victoria Riggs) 05 1900 (has links)
This study examined the effectiveness of the Human Resource Development model of classroom social skills with intermediate elementary learning disabled children. A pretest posttest control group design was employed. The sample consisted of 40 fourth-, fifth-, and sixth-grade LD pupils who scored in the bottom fourth of their classes in peer acceptance. The subjects were randomly assigned to the treatment or control group. Treatment consisted of six daily one hour training sessions covering the five skills of physically attending, psychologically attending, greeting, making polite requests and complying with requests. Subjects met in groups of six to eight in lieu of learning assistance and were instructed through methods including modeling, demonstration, role playing, didactic instruction, feedback and self-monitoring. The control group received no treatment but went to learning assistance as usual.
325

Evaluation of biosand filter as a water treatment method in Ghana : An experimental study under local conditions in Ghana / Utvärdering av biosandfilter som vattenreningsmetod i Ghana : En experimentell studie under lokala förhållanden i Ghana

Andersson, Linn January 2017 (has links)
The availability to clean drinking water is something a lot of people take for granted today. Daily, there are about 1.8 billion people around the world that drinks water from a contaminated water source. Unfortunately, the deficiency is a fact, and about 361 000 children under the age of five die each year because of diarrheal disease (WHO, 2016a).  Earlier studies show that a biosand filter is an easy and efficient water purification method that cleans the water both physically, biologically and chemically. A biosand filter is often built using local material and is filled with sand, which makes the construction cheap and easy to repair is needed. Earlier studies have shown that this purification method can reduce waterborne disease by 99,9% with the help of a biofilm layer which develop in the top layer of the sand if the conditions are meet (CAWST, 2009). The purpose with this study was to build and evaluate a biosand filter as a water treatment method in Ghana. In total, three biosand filters was built with local material, each with different sand heights. The evaluation was done by studying the waters physical, biological and chemical properties before and after the filtration, which then was compared to the water quality standards from the World Health Organization (WHO) and Sweden. The results show that none of the three filters could produce water which met the standards for drinking water, which might be caused by the high flow of water through the filter which prevented the biofilm to grow. With the help from the results in Ghana, a new design of a water filter has been made to reduce the flow of water through the filter. Which gave a new biosand filter design with a diameter of 42 cm that, sand height of 80 cm and gravel height of 15 cm. / Tillgången till rent dricksvatten är idag något som många tar som en självklarhet. I dagsläget är det omkring 1.8 miljarder människor i världen som dagligen dricker vatten från en kontaminerad vattenkälla. Dessvärre är bristen på rent dricksvatten ett faktum, vilket gör att det årligen dör cirka 361 000 barn under fem års ålder på grund av diarrésjukdomar världen över (WHO, 2016a).  Tidigare studier har visat på att biosandfilter är en enkel och effektiv vattenreningsmetod för att rena vatten både fysiskt, biologiskt och kemiskt. Ett biosandfilter är ofta byggt med lokala material och fylld med sand, vilket gör konstruktionen billig och enkel att reparera vid behov. Tidigare studier har visat på att vattenreningsmetoden kan reducera vattenburna sjukdomar med upp till 99.9% med hjälp av ett biofilmslager som utvecklas i sandlagrets övre skikt om förhållandena är gynnsamma (CAWST, 2009).  Syftet med denna studie var att bygga och utvärdera biosandfilter som vattenreningsmetod i Ghana. Totalt byggdes tre biosandfilter av lokala material med olika sandhöjder. Utvärderingen gjordes utifrån att studera vattnets fysiska, kemiska och biologiska egenskaper före och efter filtrationen, som sedan jämfördes med vattenkvalitetsstandarder från World Health Organization (WHO) och Sverige. Resultaten visade på att ingen av de tre sandfiltret kunde producera vatten med en drickvattenstandard, detta tros bero på det höga flödet genom filtret som hindrat biofilmstillväxten. Med hjälp av resultat från Ghana har en ny design av ett biosandfilter tagits fram för att minska flödet genom filtret. Vilket gav en filterdiameter som är ungefär 42 cm som sedan är fylld med 80 cm sand och 15 cm grus.
326

The social participation of children identified as having moderate learning difficulties/slow learning and the different ways of assessing such children in Kuwait and England (a comparative study)

Alqallaf, Bader January 2015 (has links)
This study addressed two main areas in the field of special education needs. First, it considered the concepts of MLD\Slow learning and the different ways to understand and recognise such terms in England and Kuwait. Second, it considered the stability of the social participation of children identified as having MLD\Slow learning in mainstream primary schools in both countries. The study utilized a cross-cultural design, which relies heavily on longitudinal and ethnographic approaches. In each country, two mainstream primary schools agreed to participate (i.e., four schools in total), comprising 22 children with MLD in England and 31 with slow learning in Kuwait. The results indicated that the concept of MLD was unclear to the participants, and that there was no procedurally objective way that could be followed to assess or recognise children with MLD in England. On one hand, this could lead to different assessment results for one child; on the other hand, it could also provide a flexible system through which MLD can be assessed in multiple ways. In contrast, slow learning in Kuwait is assessed objectively based solely on the IQ test as a main method, which could question the validity of the assessment. The results indicated that children with MLD in England were not found to be a homogenous group in terms of their social participation. Nonetheless, most of them displayed positive social participation with their typically developing children, as they were accepted to some extent by their peers and showed a good extent of friendship with their peers. Their social interactions were no different compared to that of their non-SEN peers. In contrast, the children with slow learning displayed no social interaction or friendship with their non-SEN peers who showed little acceptance of slow learning children. The results also indicated that the dimensions of friendship and peers’ acceptance levels were inter-related to some extent and could predict each other, albeit weakly with the dimension of social-self-concept.
327

Biolayer development in a slow sand filter in Ghana : Designing a filter that is benefiting the biolayer development under local conditions / Biofilmstillväxten i ett långsamsandfilter i Ghana : Utveckla ett filter som är gynnsamt för biofilmens tillväxt under lokala förhållanden

Hummerhielm, Linda January 2017 (has links)
In 2015, the United nations presented the 17 Global Goals that would put an end to extreme poverty, inequality and climate change by 2030. One of these goals was clean water and sanitation. In 2015 1.8 billion people did not have access to clean water. Because of the contaminated water, one million people die every year worldwide. Africa, and especially Ghana, has had a high development in the recent years. The population has grown and more resources are needed. Clean water in Ghana is not a given matter, three million people live without access to clean water. To work towards the Global Goal water can be clean locally. A simple and cheap way is to build slow sand filters, which also are the purpose of this project. These filters purify the water mechanically, chemically and biologically. The biologically purification takes place in the biolayer that grows on the sand inside the filter and it consumes contaminants in the water. It takes about a month for the biolayer to be fully developed and clean the water to its full potential. The positive aspects with sand filters are that people get healthier and can save money that can be invested in education or business. It can also reduce the need for water in plastic bags or bottles and would reduce littering. The companies that produce this water could end their business and air pollutions would be reduced as well.   During this project, slow sand filters have been tested and evaluated in Sweden and Ghana with the purpose to develop a theoretical filter that benefits the biolayer under local conditions in Ghana, this was of the one aims. Experiments in Sweden showed that the flow decreased with increased sand height and decreased hydraulic head. In Ghana three filters were built with the sand heights 30, 50 and 80 cm to clean 7 litres of drinking water for a family of four. None of these produced drinkable water by WHO’s and EU’s standards.   The next aim was to understand which chemical and physical factors that effected the development of the biolayer. The detected relations were absolute conductivity, total alkalinity, coliform bacteria and oxidantial reduction potential which were between the biolayer in the 30 and 50 filters.   The flow rate in Ghana was too high and to lower it, a new diffuser with smaller holes would be built to get the recommended flow of 0,4 m3/m2/h. A too high flow broke the bound between the biolayer and made an uncomfortable environment. A sedimentation should be installed before the sand filter to reduce the variations of the incoming water such as turbidity, suspended solids etc., so the biolayer would flourish. It was not enough dissolved oxygen in the water so the pause period would be decreased to 12 hours to get more oxygen in the filter each day. For a sand filter to work as planned a lot of attention should be given to the filter. It is a system that should be used all the time for the best purification. To build a filter takes a lot of time and it also takes time for the biolayer to develop. If it is not going to be used much, another treatment method should be used.   The last aim was to evaluate the cost of the materials that could be bought locally to the filter. One filter cost about 130 GHS. / 2015 tog Förenta nationerna fram de 17 globala målen för att få ett slut på extrem fattigdom, ojämlikhet och klimatförändringen till år 2030. Ett av dessa mål handlar om rent vatten och sanitet. 2015 var det 1,8 miljarder människor som inte hade tillgång till rent vatten. På grund av det förorenade vattnet dör en miljon människor i hela världen varje år. Afrika, och speciellt Ghana, har haft en snabb utveckling de senaste åren. Folkmängden har ökat och mer naturresurser behövs. Rent vatten i Ghana är inte en självklarhet, tre miljoner människor lever idag utan tillgång till rent vatten i Ghana. Ett sätt för att jobba mot det globala målet är rening av vatten lokalt. Ett enkelt och billigt sätt är att bygga långsamsandfilter, vilket även var syftet med denna studien. Dessa filter renar vattnet mekaniskt, kemiskt och biologiskt. Den biologiska reningen sker av en biofilm som växer på sanden inuti filtret som konsumerar föroreningar i vattnet. Det tar ungefär en månad för biofilmen att bli färdigutvecklad och rena vattnet till sin fulla potential. Det positiva med sandfilter är att människorna skulle bli friskare och spara pengar som kan investeras på utbildning eller företag. Ur miljöpunkt skulle reduktionen av köpt vatten i plastpåsar och flaskor minska nedskräpningen och företagen som producerar dessa kan avsluta produktionen och därmed minska luftföroreningar.    Under detta projekt har långsamsandfilter utvärderats både i Sverige och Ghana för att utveckla ett nytt teoretiskt filter som gynnar tillväxten av biofilm under lokala förhållanden i Ghana, vilket var ett mål. Experimenten i Sverige visade att flödet sjönk med ökad sandhöjd, men även med minskat hydrauliskt tryck. I Ghana byggdes tre filter med sand höjderna 30, 50 och 80 cm för att rena 7 liter dricksvatten till en familj på fyra. Ingen av dessa lyckades producera drickbart vatten enligt WHO:s och EU:s standarder.   Nästa mål var att förstå vilka av de kemiska och fysiska faktorer som påverkade biofilmstillväxten. Det förhållanden som upptäcktes var absolut konduktivitet, total alkalinitet, coliform bacteria och oxidential reduction potential vilket fanns i 30 och 50 filtret.   Flödet i Ghana var för högt, så för att minska det skulle en diffusör med mindre hål byggas för att få det rekommenderade flödet 0,4 m3/m2/h. Ett för högt flöde gjorde sönder bindingen mellan biofilmen och skapade en otrivsam miljö. En sedimentation skulle installeras innan sandfiltret för att minska variationer på ingående vatten i filtret för att få biofilmen att trivas bättre. Det fanns för lite löst syre i vattnet och om pausperioden minskas till 12 timmar skulle mer syre i filtret varje dag. För att ett sandfilter ska fungera som planerat måste mycket tid läggas på filtret. Sandfilter är ett system som bör används ofta för bästa rening. Att bygga ett filter kräver mycket tid, samt att det tar tid innan biofilmen har utvecklats. Om sandfiltret inte kommer används mycket föreslås att en annan metod används istället.   Det sista målet var att utvärdera kostnaden av materialen som kunde köpas lokalt till filtret. Ett filter kostade runt 130 GHS.
328

Slow delivery of low-income housing at munipal level with special reference to the Nelson Mandela Bay Munipality

Scheepers, Mario Jacques January 2011 (has links)
The provision of adequate housing is an important part of government's commitment towards providing a better quality of life to the people of South Africa. Housing delivery is, however, not taking place to the extent and speed that will eliminate the backlog in housing delivery. The researcher aims to (i) evaluate and investigate the reasons why housing delivery at municipal level is slow, (ii) discuss the effect of inefficient implementation on delivery, (iii) examine the influence of the lack of infrastructure and the lack of skilled municipal officials and employees of construction organisations and the processes followed to make a success of housing delivery. Chapter 2, Section 26(1), Act 108 0f 1996 of the Constitution of South Africa states that everyone has the right to have access to adequate housing. This places an obligation on government to provide adequate housing to all citizens, within the restriction of available resources. The lack of land hampers the speed at which municipalities can deliver low-income housing. Housing and basic infrastructure (water, sewer and roads) form an integral part of the governments commitment to reduce poverty and improve the quality of life of South Africans. The fact that municipalities do not have capacity to address housing delivery and the fact that most artisans are near retirement age also influence the rate that houses can be delivered. Adequate housing processes are needed for housing delivery to take place, without it government will not succeed in delivering adequate housing. The results of the survey and the literature review confirm that housing delivery at municipality level is slow, that municipal officials need training and more employees to insure that housing delivery improves. The results also show the importance of infrastructure and land, the importance of implementing housing policies and processes adequately.
329

Identifying children at risk : the predictive validity of kindergarten screening measures

Jacobsen, S. Suzanne January 1990 (has links)
The early identification of children who are "at risk" of experiencing learning problems is of interest to educators and policymakers. Conflicting evidence exists regarding the efficacy of screening measures for identifying children "at risk". The rationale for screening programs is that early identification of problems allows for treatment which may eliminate more severe problems from developing. If a student is identified as "at risk", school personnel may intervene with remedial programs. Subsequently, if the student succeeds, the earlier prediction is no longer valid. The identification of "at risk" would appear inaccurate because the intervention was successful in improving skills. Researchers often measure the prediction of "at risk" with a correlation coefficient. To the extent that the intervention is successful, the correlation of the identification of "at risk" with later measures of achievement is lowered. One of the problems with research on early prediction has been failure to control for the effects of the interventions which were implemented as a consequence of screening. An evaluation of "at risk" prediction is important because results of screening procedures are used to make decisions about retentions and the allocation of special services. The purpose of this study is to investigate the relationship between kindergarten screening measures and grade three achievement for two entire cohorts enrolled in 30 schools in one school district. The analysis employs a two-level hierarchical linear regression model to estimate the average within-school relationship between kindergarten screening measures and grade three achievement in basic skills, and determine whether this relationship varies significantly across schools. The model allows for the estimation of the relationship with control for individual pupil characteristics such as age, gender and physical problems. The study examines the extent to which the relationship between kindergarten screening and grade three achievement is mediated by children receiving learning assistance or attending extended (4-year) primary schooling. The study also examines differences among schools in the kindergarten screen/achievement relationships and the achievement of "at risk" pupils by including school characteristics in the analysis. The results of this study indicate positive relationships between kindergarten screening measures and achievement outcomes, even after controlling for age, gender and physical conditions. The kindergarten screen/achievement relationship did not vary among schools. The study failed to demonstrate that controlling for interventions would improve the kindergarten screen/achievement relationship; in fact the effects were in the opposite direction. Levels of adjusted achievement of pupils who obtained scores at the cut-off point for risk status varied significantly among schools. The "at risk" pupils performed better on all four achievement measures in schools with high school mean-ability than similar pupils in schools with low school mean-ability. These results show that progress in the study of the predictive validity of screening measures can be made through the use of hierarchical regression techniques. Researchers need to give consideration to the effects of educational interventions and the contextual effects of schools. / Education, Faculty of / Educational and Counselling Psychology, and Special Education (ECPS), Department of / Graduate
330

Etude du rôle des proteines QkiA et QkiC dans la myofibrillogénèse précoce et la maturation des fibres musculaires lentes chez le Poisson Zèbre / Role of proteins Quaking A and C in early myofibrillogenesis and maturation of slow muscle fibers in zebrafish embryos

Dutrieux, Francois Xavier 17 January 2014 (has links)
Chez le poisson zèbre, le muscle squelettique axial est composé de deux types de fibres musculaires différentes, les fibres lentes et les fibres rapides, organisées le long de l’axe antéro-postérieur et délimités par des frontières somitiques. Les cellules cuboïdes adaxiales, précurseurs des fibres lentes, sont les premières cellules musculaires à se différencier. En cours de somitogenèse elles s’allongent et migrent à partir de la notochorde radialement vers l’extérieur du somite formant une couche monocellulaire de fibres lentes mononuclées. Au sein de ces précurseurs en cours de réarrangement, se déroule l’initiation de la myofibrillogénèse. Ces premières étapes de formation des myofibrilles sont peu connues et nous aimerions comprendre les mécanismes sous-jacents liés à cette initiation. La structure et la composition du sarcomère sont conservées au cours de l’évolution, offrant la possibilité d’utiliser le poisson zèbre comme model afin de mieux comprendre les processus de myofibrillogénèse chez les Vertébrés et potentiellement d’expliquer l’origine des Myopathies Myofibrillaires qui affectent le développement des myofibrilles chez l’Homme. Récemment, nous avons montré que la perte de fonction la protéine Quaking A chez le poisson zèbre perturbait, entre autre, la maturation finale des fibres musculaires lentes. Cette protéine de liaison aux ARN fait partie de la famille des protéines à domaine STAR, elle possède généralement d’autres isoformes chez les Vertébrés. Au cours de ma thèse, j’ai identifié chez le poisson zèbre, par comparaison de séquence in silico, un homologue du gène qkiA que nous avons nommé qkiC. L’expression des gènes qkiA et qkiC est recouvrante sur le territoire des cellules adaxiales. Bien que la perte de fonction de QkiC n’ait aucuns effets sur développement des fibres lentes, la perte de fonction conjointe de QkiA et QkiC induit un phénotype cellulaire autonome sévère et ce, dès les stades précoce de myofibrillogénèse. Ensemble nos données suggèrent une interaction fonctionnelle des deux homologues dans les cellules adaxiales que nous avons cherché à comprendre et à décrire. Un phénotype similaire est induit par la perte de fonction des protéines Mef2C/D, Nous avons montré que ces deux voies agissent en parallèle afin d’initier et d’accompagner le programme de myofibrillogénèse. A 24hpf, une accumulation des protéines de Myosine et une dissection/désolidarisation des filaments épais sont observées dans les fibres lentes, fortement lié à une destruction importante de la bande-Z. Ces phénotypes sont similaires à ceux utilisés par les pathologistes pour décrire les Myopathies Myofibrillaires. Ainsi, notre étude montre un nouveau type de régulation précoce de la myofibrillogénèse et offre un model potentiel pour étudier chez le poisson zèbre les myopathies myofibrillaire. / In zebrafish, myotomes are organized along the antero-posterior axis within repeated units called somites. Contractile fibers are subdivided into two muscle cell types, the slow muscle fibers and the fast muscle fibers. The slow muscle cells are located on the surface of the embryo body while the fast muscle cells are located deeper in the somite, underneath the slow muscle cells. Myogenesis correspond to transitions from unspecified mesodermal cells to mature and functional muscle fibers. These cellular transitions have been extensively studied. However relatively little is known about early developmental mechanisms that are required to form premyofibrils, neither about maturation processes, during which premyofibrils evolved in contractile myofibers. This process called myofibrillogenesis involved a dynamic assembly of the elementary components of the sarcomere that occurred first in adaxial cells, the muscle precursors of slow muscle fibers. Here we show that QkiA and QkiC, two RNA-binding proteins with STAR domain, are required during the early step of myofibrillogenesis where Moysin proteins are not correctly assembled. This early phenotype leads to a strong and specific alteration in the maturation of thick Myosin filaments at 24hpf. The combined QkiA/QkiC loss of function induced a dissection of thick filaments followed by the accumulation of Myosin proteins at the tip of slow muscle cells in a cell autonomous manner. Interestingly, the loss of function of Mef2C/D, two myogenic enhancers from the same family, induced a similar phenotype. However we have shown that Quaking and Mef2 proteins act in parallel ways to control and regulate myofibrillogenesis. Remarkably, we have seen that the accumulation of Myosin, the dissection of thick filaments and the alteration of the Z-disk, induced by QkiA/C loss of function, are the pathologic phenotypes found in Human Myofibrillar Myopathies (MFM). This subgroup of myopathies has been created recently and very few is known about mechanisms involved in those diseases. We propose that QkiA and QkiC is another regulated system that is required to initiated and maintained myofibrillogenesis.

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