Advanced impingement/film-cooling schemes for high-temperature gas turbines : numerical study

Ongoing research strives to optimize gas turbine blade film cooling so that it achieves maximum performance while using a minimum amount of coolant. The feasibility of an advanced impingement/film cooling scheme will be numerically investigated in this thesis. This scheme combines both the advantages of traditional film cooling with those of impingement cooling. The hole that transports the coolant fluid from the inside to the outside of the blade in this scheme is designed in such a way that the coolant must go through a bend before exiting into the mainstream, thus impinging onto the blade material. Furthermore, flow turbulators, or pedestals, are located on the path of the coolant before it exits from the hole, minimizing aerodynamic losses. Turbulence was modeled using the standard k-[varepsilon] turbulence model and two of its variants, namely the realizable and Renormalization Group k-[varepsilon] turbulence models with enhanced wall treatment. (Abstract shortened by UMI.

Identification of a micropeptide and multiple secondary cell genes that modulate <i>Drosophila</i> male reproductive success

Even in well-characterized genomes, many transcripts are considered noncoding RNAs (ncRNAs) simply due to the absence of large open reading frames (ORFs). However, it is now becoming clear that many small ORFs (smORFs) produce peptides with important biological functions. In the process of characterizing the ribosome-bound transcriptome of an important cell type of the seminal fluid-producing accessory gland of Drosophila melanogaster, we detected an RNA, previously thought to be noncoding, called male-specific abdominal (msa). Notably, msa is nested in the HOX gene cluster of the Bithorax complex and is known to contain a micro-RNA within one of its introns. We find that this RNA encodes a "micropeptide" (9 or 20 amino acids, MSAmiP) that is expressed exclusively in the secondary cells of the male accessory gland, where it seems to accumulate in nuclei. Importantly, loss of function of this micropeptide causes defects in sperm competition. In addition to bringing insights into the biology of a rare cell type, this work underlines the importance of small peptides, a class of molecules that is now emerging as important actors in complex biological processes

Tooling design and microwave curing technologies for the manufacturing of fiber-reinforced polymer composites in aerospace applications

The increasing demand for high-performance and quality polymer composite materials has led to international research effort on pursuing advanced tooling design and new processing technologies to satisfy the highly specialized requirements of composite components used in the aerospace industry. This paper reports the problems in the fabrication of advanced composite materials identified through literature survey, and an investigation carried out by the authors about the composite manufacturing status in China’s aerospace industry. Current tooling design technologies use tooling materials which cannot match the thermal expansion coefficient of composite parts, and hardly consider the calibration of tooling surface. Current autoclave curing technologies cannot ensure high accuracy of large composite materials because of the wide range of temperature gradients and long curing cycles. It has been identified that microwave curing has the potential to solve those problems. The proposed technologies for the manufacturing of fiber-reinforced polymer composite materials include the design of tooling using anisotropy composite materials with characteristics for compensating part deformation during forming process, and vacuum-pressure microwave curing technology. Those technologies are mainly for ensuring the high accuracy of anisotropic composite parts in aerospace applications with large size (both in length and thickness) and complex shapes. Experiments have been carried out in this on-going research project and the results have been verified with engineering applications in one of the project collaborating companies

Fresh air funds and functional families: The enduring politics of race, family and place in juvenile justice reform

This article examines the enduring ways that racial politics are masked by discourses of place and family in the history of juvenile justice in the USA. The tropes of place and family have been invoked since the inception of the USA’s juvenile justice system and have influenced the processes of policing, removal, and return, even as the latest incarnation of reforms focus on building juvenile justice facilities and alternatives to incarceration within urban areas. By pointing to recent manifestations of this rhetoric in New York, the article identifies the thread that links these claims together: the desire by social control agents for submission by the primarily impoverished and young people of color who defy legal authority

Polyethylene/Polyhydroxyalkanoates-based Biocomposites and Bionanocomposites

The development of advanced polymer composite materials having superior mechanical properties has opened up new horizons in the field of science and engineering. Polyethylene (PE) is considered one of the most widely used thermoplastics in the world due to its excellent properties which have excellent chemical inertness, low coefficient of friction, toughness, near-zero moisture absorption, ease of processing and electrical properties. Polyhydroxyalkanoates (PHAs) are garnering increasing attention in the biodegradable polymer market because of their promising properties such as high biodegradability in different environments. This chapter covers polyethylene/polyhydroxyalkanoates-based biocomposites and bionanocomposites. It summarizes many of the recent research accomplishments in the area of PE/PHAs-based biocomposites and bionanocomposites such as state-of-the-art regarding different methods of their preparation. Also discussed are different characterization techniques and use of PE/PHAs-based biocomposites and bionanocomposites in biomedical, packaging, structural, military, coating, fire retardant, aerospace and optical applications, along with recycling and lifetime studies

Role of mediator complex subunits in transcriptional regulation by GATA and FOG transcription factors during Drosophila development

Un enjeu majeur en Biologie est de comprendre comment les milliers de gènes composant le génome sont contrôlés afin d'être exprimés dans les bonnes cellules au bon moment. Cette régulation a lieu en grande partie à l'étape de pré-initiation de la transcription. Ce processus résulte de l'action concertée de nombreuses protéines, dont le complexe Médiateur (MED, ~30 sous-unités protéiques ou SU, >1,5MDa) qui joue un rôle conservé dans la régulation de la transcription des gènes par l'ARN Polymérase II (PolII), de la levure à l'Homme. Ce complexe se lie simultanément à la PolII et aux facteurs de transcription spécifiques (FT). Les FT reconnaissent et se fixent à des séquences régulatrices d'ADN, et dirigent l'expression de leurs gènes-cibles au cours du développement. Le complexe MED, ubiquitaire dans les cellules eucaryotes, semble intégrer le " code des FT " spécifique à chaque cellule, et réguler en conséquence le recrutement et l'activité de la PolII au promoteur des gènes-cibles des FT. La drosophile est un organisme modèle fournissant des outils génétiques puissants pour répondre à des questions biologiques importantes in vivo, notamment concernant la transcription génique. Une famille de FT, les GATA, est impliquée dans des processus développementaux similaires chez les mammifères et la mouche. Ils activent et répriment la transcription, selon le gène considéré et la présence de certains cofacteurs comme les protéines FOG. Le travail présenté ici vise à comprendre comment les FT GATA utilisent le MED pour réguler la transcription de leurs gènes cibles, positivement et négativement. Au cours de ce travail, nous avons généré les premières lignées mutantes pour le gène Med1, et entrepris la caractérisation des fonctions de la SU Med1, connue pour être un cofacteur des FT GATA chez les vertébrés. Nous avons montré que certaines SU MED (dont Med1, 12, 13, 15 et 19) sont impliquées dans des processus dépendant des GATA, tels que l'hématopoïèse, la morphogénèse du notum et la formation des soies mécanosensorielles dorso-centrales. Les deux derniers dépendent du FT GATA Pannier (Pnr) qui, seul, active la transcription des gènes pro-neuraux ac-sc, ou la réprime en présence de son partenaire FOG U-shaped (Ush). Des analyses clonales in vivo ont révélé que Med1, Med15 et Med19, ainsi que Med12 et Med13 appartenant au module détachable CDK8, sont critiques pour l'activation d'ac-sc de façon cellulaire-autonome, suggérant un lien fonctionnel avec Pnr. De manière intéressante, CycC et Cdk8 du module CDK8 ne sont pas requises pour l'activation d'ac-sc, mais sont requises pour sa répression dans les cellules voisines, soulignant la diversité d'action des SU MED in vivo. Med19 interagit physiquement avec Pnr, et pourrait donc être le point d'ancrage par lequel Pnr recrute le MED pour activer la transcription. De plus, le facteur FOG Ush inhibe l'interaction Med19-Pnr en formant un hétérodimère Pnr-Ush. La compétition pour se fixer à Pnr entre Med19 (co-activateur) et Ush (co-répresseur) pourrait expliquer les actions antagonistes de Pnr sur ses gènes-cibles. Med19 est également requise pour la transactivation par un autre GATA : Serpent (Srp, cf. Gobert et al. 2010). Nous montrons ici que Med19 interagit également avec Srp, suggérant que Med19 pourrait être un cofacteur général des GATA, alors que Med1 ne semble pas avoir d'affinité pour les GATA chez la drosophile (contrairement à la SU Med1 chez les mammifères). Cela soulève des questions quant à la manière par laquelle les interactions entre FT et SU MED apparaissent, puis sont conservées, ou non, au cours l'évolution. Ces résultats mettent en lumière des interactions croisées entre Med19, GATA-Pnr et FOG-Ush qui permettent de comprendre mécanistiquement comment Pnr active et réprime la transcription. Ce travail représente une étape importante pour la compréhension de la façon dont les combinatoires de FT sont intégrées par le MED pour aboutir à une régulation fine de la transcription.A major aim of today's research in Biology is to understand how the thousands of genes composing the genome are regulated in order to be expressed in the right cells at the right time. This regulation occurs in large part before gene transcription, at the pre-initiation step. This process results of the concerted action of many proteins, including the large Mediator complex (MED, ~30 protein subunits, >1.5 MDa), which plays a conserved and crucial role in the regulation of protein-coding genes transcription by RNA polymerase II (PolII), from yeast to humans. This modular complex makes direct core contacts with PolII and general transcription factors, while some subunits can bind to DNA-bound specific transcription factors (TFs). TFs recognize and bind specific regulatory DNA sequences, and drive the tissue-specific expression of their target genes during development. The ubiquitously expressed MED is thought to integrate a cell-specific STF "code" to regulate PolII recruitment and activity at gene promoters. Drosophila melanogaster is a valuable animal model that provides many genetic tools - such as mutant strains and transgenic lines - to address important biological questions in vivo, such as how gene transcription is regulated. A family of TFs, the GATAs, is involved in diverse developmental processes in both Drosophila and vertebrates. They are both activator and repressor TFs, depending on the target gene and the available cofactors, such as Friend Of GATA (FOG) family proteins. The work presented here aimed to understand how GATA TFs use the MED to regulate their target genes both positively and negatively. During the course of this work we generated the first Drosophila mutants for Med1, and investigated the functions of this important subunit in vivo, known as a cofactor of GATAs in vertebrates. We identified a subset of Drosophila MED subunits (including Med1, 12, 13, 15, 19) which are required for proper GATA-dependent processes, such as haematopoiesis, notum morphogenesis and dorso-central (DC) mechanosensory bristle emergence. The last two processes depend on Pannier (Pnr), a GATA-type TF, which directly activates achaete-scute (ac-sc) proneural genes transcription singly, and represses it in presence of its FOG partner U-shaped (Ush). Clonal analysis in vivo showed that Med1, Med15 and Med19, along with Med12/13 subunits of the detachable "CDK8" module of the MED, are critical for ac-sc activation in a cell-autonomous manner, suggesting functional interactions with Pnr. Interestingly, CycC and Cdk8 subunits from CDK8 module are not involved in ac-sc activation, but are required to ensure ac-sc inhibition in surrounding cells, underscoring the diversity of MED subunits functions in vivo. Moreover, we show that Med19 binds physically to Pnr. Thus, Med19 might be the anchor point by which Pnr recruits the MED at Pnr-activated genes. Furthermore, the FOG factor U-shaped inhibits Med19-Pannier interaction by heterodimerizing with Pannier. Thus, the competition for Pnr binding between Med19 (coactivator) and Ush (corepressor) could be responsible for the antagonistic roles of Pnr on the transcription of its target genes. Interestingly, Med19 is also required for transactivation by another GATA factor: Serpent (Srp, cf. Gobert et al., 2010). Here we show that Med19 also interacts physically with Srp, suggesting that Med19 could be a general cofactor of GATAs in drosophila. On the other hand, Med1 showed no affinity for Drosophila GATAs (contrary to vertebrate Med1), raising questions about the way MED-TF interactions are acquired and maintained, or not, during evolution. This work highlights the interplay between Med19, GATA-Pnr and FOG-Ush, allowing a mechanistic understanding of Pnr actions as both an activator and a repressor of gene transcription. This PhD thesis is an important step towards appreciating how combinatorial codes of TFs are integrated by the MED to regulate gene transcription during development