205 research outputs found
Study of the microstructure resulting from brazed aluminium materials used in heat exchangers
Re-solidification of AA4343 cladding after brazing as well as the related precipitation in the modified AA3003 core material have been investigated. Analysis of the re-solidified material showed that partial dissolution of the core alloy occurs in both the brazing joints and away of them. Far from the brazing joints, the dissolution is, however, limited and diffusion of silicon from the liquid into the core material leads to solid-state precipitation in the so-called “band of dense precipitates” (BDP). On the contrary, the dissolution is enhanced in the brazing joint to such an extent that no BDP could be observed. The intermetallic phases present in the resolidified areas as well as in the core material have been analyzed and found to be mainly cubic alpha-Al(Mn,Fe)Si. These results were then compared to predictions made with available phase diagram information
Etablissement de la texture au cours du soudage TIG d’alliages austénitiques : soudures réelles et numériques
The structure prediction of metallic alloys during a welding or additive manufacturing process is the key point for the joining’s properties. In addition to the welding parameters (or additive manufacturing), the base metal microstructure, chemical homogeneity and crystallographic structure are numerous factors playing an important role on the final microstructure and texture development. Few studies are available in this way. This work purposes a focus on the microstructure establishment during the welded zone solidification during Gas Tungsten Arc Welding. The materials investigated are nickel – chromium – iron austenitic alloys. The grain selection is tracked in a real weld and a texturation criteria is proposed. The following data’s are compared to the properties of the numerical weld experience. The conclusion suggests that is necessary to improve the knowledges in the grain selection mechanism in order to produce numerical welding microstructure in good accordance with real microstructure welding.La prédiction de la structure des alliages métalliques durant une étape de soudage ou de fabrication additive est un point clef du développement de ces procédés et des propriétés des assemblages. En plus des paramètres de soudage (ou de fabrication additive), la microstructure du métal de base, son homogénéité chimique et sa nature cristallographique sont autant de facteur jouant un rôle sur l’établissement final des microstructures et des textures pour lesquels peu d’études détaillées sont disponibles. Une description précise de l’établissement des microstructures de solidification lors du soudage TIG d’alliage austénitique nickel-chrome-fer est réalisée dans ce travail. La sélection des grains dans la soudure est suivie dans une soudure réelle. Un critère de texturation est proposé et les données sont comparées aux textures simulées d’où il ressort l’importance d’augmenter la connaissance des mécanismes de sélection de grains pour espérer modéliser encore plus fidèlement les propriétés microstructurales et de texture générées par le soudage
Effect of Ce and Sb on Primary Graphite Growth in Cast Irons
It is well-known that if certain trace elements are present in cast iron melts the morphology of the graphite precipitates can be altered. In order to understand the effect of doping elements on primary growth of graphite, pure Fe–Sb alloys were prepared by induction melting. They were then placed in graphite crucibles and heated to a temperature above the Fe–C eutectic so that the charge became saturated in carbon and melted. To obtain Fe–Ce alloys, metallic Ce was added at the bottom of a graphite crucible and covered with iron, and then heated as for the Fe–Sb charge. In both cases, the melt was then cooled and held slightly above the eutectic temperature so that primary graphite crystals, which had nucleated on the crucible walls and then detached from it, could grow freely in the melt. The influence of the added elements on graphite growth was revealed by the change in the shape and distribution of the crystals compared to those obtained in similar experiments carried out with pure Fe. The experiments were made in air and vacuum so as to point out possible interactions between the elements present in the melt and oxygen
Cell arrest and cell death in mammalian preimplantation development
The causes, modes, biological role and prospective significance of cell death in preimplantation development in humans and other mammals are still poorly understood. Early bovine embryos represent a very attractive experimental model for the investigation of this fundamental and important issue.
To obtain reference data on the temporal and spatial occurrence of cell death in early bovine embryogenesis, three-dimensionally preserved embryos of different ages and stages of development up to hatched blastocysts were examined in toto by confocal laser scanning microscopy. In parallel, transcript abundance profiles for selected apoptosis-related genes were analyzed by real-time reverse transcriptase-polymerase chain reaction. Our study documents that in vitro as well as in vivo, the first four cleavage cycles are prone to a high failure rate including different types of permanent cell cycle arrest and subsequent non-apoptotic blastomere death. In vitro produced and in vivo derived blastocysts showed a significant incidence of cell death in the inner cell mass (ICM), but only in part with morphological features of apoptosis. Importantly, transcripts for CASP3, CASP9, CASP8 and FAS/FASLG were not detectable or found at very low abundances.
In vitro and in vivo, errors and failures of the first and the next three cleavage divisions frequently cause immediate embryo death or lead to aberrant subsequent development, and are the main source of developmental heterogeneity. A substantial occurrence of cell death in the ICM even in fast developing blastocysts strongly suggests a regular developmentally controlled elimination of cells, while the nature and mechanisms of ICM cell death are unclear. Morphological findings as well as transcript levels measured for important apoptosis-related genes are in conflict with the view that classical caspase-mediated apoptosis is the major cause of cell death in early bovine development
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Cluster analysis of downscaled and explicitly simulated North Atlantic tropical cyclone tracks
A realistic representation of the North Atlantic tropical cyclone tracks is crucial as it allows, for example, explaining potential changes in US landfalling systems. Here we present a tentative study, which examines the ability of recent climate models to represent North Atlantic tropical cyclone tracks. Tracks from two types of climate models are evaluated: explicit tracks are obtained from tropical cyclones simulated in regional or global climate models with moderate to high horizontal resolution (1° to 0.25°), and downscaled tracks are obtained using a downscaling technique with large-scale environmental fields from a subset of these models. For both configurations, tracks are objectively separated into four groups using a cluster technique, leading to a zonal and a meridional separation of the tracks. The meridional separation largely captures the separation between deep tropical and sub-tropical, hybrid or baroclinic cyclones, while the zonal separation segregates Gulf of Mexico and Cape Verde storms. The properties of the tracks’ seasonality, intensity and power dissipation index in each cluster are documented for both configurations. Our results show that except for the seasonality, the downscaled tracks better capture the observed characteristics of the clusters. We also use three different idealized scenarios to examine the possible future changes of tropical cyclone tracks under 1) warming sea surface temperature, 2) increasing carbon dioxide, and 3) a combination of the two. The response to each scenario is highly variable depending on the simulation considered. Finally, we examine the role of each cluster in these future changes and find no preponderant contribution of any single cluster over the others
Cross-European challenges for multi-risk assessment and management: insights from the first two years of MYRIAD-EU
Challenges in assessing and managing multi-hazard risks: A European stakeholders perspective
The latest evidence suggests that multi-hazards and their interrelationships (e.g., triggering, compound, and consecutive hazards) are becoming more frequent across Europe, underlying a need for resilience building by moving from single-hazard-focused to multi-hazard risk assessment and management. Although significant advancements were made in our understanding of these events, mainstream practice is still focused on risks due to single hazards (e.g., flooding, earthquakes, droughts), with a limited understanding of the stakeholder needs on the ground. To overcome this limitation, this paper sets out to understand the challenges for moving towards multi-hazard risk management through the perspective of European stakeholders. Based on five workshops across different European pilots (Danube Region, Veneto Region, Scandinavia, North Sea, and Canary Islands) and an expert workshop, we identify five prime challenges: i) governance, ii) knowledge of multi-hazards and multi-risks, iii) existing approaches to disaster risk management, iv) translation of science to policy and practice, and v) lack of data. These challenges are inherently linked and cannot be tackled in isolation with path dependency posing a significant hurdle in transitioning from single- to multi-hazard risk management. Going forward, we identify promising approaches for overcoming some of the challenges, including emerging approaches for multi-hazard characterisation, a common understanding of terminology, and a comprehensive framework for guiding multi-hazard risk assessment and management. We argue for a need to think beyond natural hazards and include other threats in creating a comprehensive overview of multi-hazard risks, as well as promoting thinking of multi-hazard risk reduction in the context of larger development goals
Inhibitor of apoptosis proteins, NAIP, cIAP1 and cIAP2 expression during macrophage differentiation and M1/M2 polarization
Monocytes and macrophages constitute the first line of defense of the immune system
against external pathogens. Macrophages have a highly plastic phenotype depending on
environmental conditions; the extremes of this phenotypic spectrum are a pro-inflammatory
defensive role (M1 phenotype) and an anti-inflammatory tissue-repair one (M2 phenotype).
The Inhibitor of Apoptosis (IAP) proteins have important roles in the regulation of several cellular
processes, including innate and adaptive immunity. In this study we have analyzed the
differential expression of the IAPs, NAIP, cIAP1 and cIAP2, during macrophage differentiation
and polarization into M1 or M2. In polarized THP-1 cells and primary human macrophages,
NAIP is abundantly expressed in M2 macrophages, while cIAP1 and cIAP2 show
an inverse pattern of expression in polarized macrophages, with elevated expression levels
of cIAP1 in M2 and cIAP2 preferentially expressed in M1. Interestingly, treatment with the
IAP antagonist SMC-LCL161, induced the upregulation of NAIP in M2, the downregulation
of cIAP1 in M1 and M2 and an induction of cIAP2 in M1 macrophages.This work was supported by Universidad
de Granada, Plan Propio 2015;#P3B: FAM, VMC
(http://investigacion.ugr.es/pages/planpropio/2015/
resoluciones/p3b_def_28072015); Universidad
de Granada CEI BioTic;#CAEP2-84: VMC (http://
biotic.ugr.es/pages/resolucionprovisional
enseaanzapractica22demayo/!); and Canadian nstitutes of Health Research;#231421, #318176,
#361847: STB, ECL, RK (http://www.cihr-irsc.gc.
ca/e/193.html). The funders had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript
Achieving Education for Sustainable Development (ESD) in Early Childhood Education Through Critical Reflection in Transformative Learning
The central role of education in creating a more sustainable future has been already recognized by educators and policy-makers alike. This chapter argues that this can only be truly achieved through the efforts of teachers in implementing an “education of a different kind,” a general educational shift that seeks to encompass a converging transformation of the priorities and mindsets of education professionals. In this regard, the professional preparation of teachers, as the leading actors in shaping children’s learning processes, and their continuous professional development are vital considerations for Education for Sustainable Development (ESD) to be successfully achieved. Linking transformative learning and ESD has emerged as a distinct and useful pedagogy because they both support the process of critically examining habits of mind, then revising these habits and acting upon the revised point of view. This study aims to describe and evaluate the potential of transformative learning in innovating mainstream education toward sustainability by focusing on the role of critical reflection in a capacity building research project realized in Turkey. The data was gathered from 24 early childhood educators using a mixed-method research design involving learning diaries, a learning activities survey, and follow-up interviews. This chapter identified content, context, and application method of the in-service training as factors that have contributed to the reflective practices of the participants. In addition, presenting the implications regarding the individual differences in how learners engage in critical reflection practices, this research offers a framework for a content- and process-based approach derived from Mezirow’s conception of critical reflection
Fosmid library end sequencing reveals a rarely known genome structure of marine shrimp Penaeus monodon
<p>Abstract</p> <p>Background</p> <p>The black tiger shrimp (<it>Penaeus monodon</it>) is one of the most important aquaculture species in the world, representing the crustacean lineage which possesses the greatest species diversity among marine invertebrates. Yet, we barely know anything about their genomic structure. To understand the organization and evolution of the <it>P. monodon </it>genome, a fosmid library consisting of 288,000 colonies and was constructed, equivalent to 5.3-fold coverage of the 2.17 Gb genome. Approximately 11.1 Mb of fosmid end sequences (FESs) from 20,926 non-redundant reads representing 0.45% of the <it>P. monodon </it>genome were obtained for repetitive and protein-coding sequence analyses.</p> <p>Results</p> <p>We found that microsatellite sequences were highly abundant in the <it>P. monodon </it>genome, comprising 8.3% of the total length. The density and the average length of microsatellites were evidently higher in comparison to those of other taxa. AT-rich microsatellite motifs, especially poly (AT) and poly (AAT), were the most abundant. High abundance of microsatellite sequences were also found in the transcribed regions. Furthermore, <it>via </it>self-BlastN analysis we identified 103 novel repetitive element families which were categorized into four groups, <it>i.e</it>., 33 WSSV-like repeats, 14 retrotransposons, 5 gene-like repeats, and 51 unannotated repeats. Overall, various types of repeats comprise 51.18% of the <it>P. monodon </it>genome in length. Approximately 7.4% of the FESs contained protein-coding sequences, and the Inhibitor of Apoptosis Protein (IAP) gene and the Innexin 3 gene homologues appear to be present in high abundance in the <it>P. monodon </it>genome.</p> <p>Conclusions</p> <p>The redundancy of various repeat types in the <it>P. monodon </it>genome illustrates its highly repetitive nature. In particular, long and dense microsatellite sequences as well as abundant WSSV-like sequences highlight the uniqueness of genome organization of penaeid shrimp from those of other taxa. These results provide substantial improvement to our current knowledge not only for shrimp but also for marine crustaceans of large genome size.</p
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