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Various Defects (various + defect)
Selected AbstractsThe influence of porosity on the fatigue strength of high-pressure die cast aluminiumFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2006J. LINDER ABSTRACT Aluminium is a lightweight material with high strength and good corrosion resistance among other beneficial properties. Thanks to these properties, aluminium is more extensively used in the vehicle industry. High-pressure die casting of aluminium is a manufacturing process that makes it possible to attain complex, multi-functional components with near-net shape. However, there is one disadvantage of such castings, that is, the presence of various defects such as porosity and its effect on mechanical properties. The aim of this work was to investigate the influence of porosity on the fatigue strength of high-pressure die cast aluminium. The objective was to derive the influence of defect size with respect to the fatigue load, and to generate a model for fatigue life in terms of a Kitagawa diagram. The aluminium alloy used in this study is comparable to AlSi9Cu3. Specimens were examined in X-ray prior to fatigue loading and classified with respect to porosity level and eventually fatigue tested in bending at the load ratio, R, equal to ,1. Two different specimen types with a stress concentration factor of 1.05 and 2.25 have been tested. It has been shown that the fatigue strength decreases by up to 25% as the amount of porosity of the specimen is increased. The results further showed that the influence of defects was less for the specimen type with the higher stress concentration. This is believed to be an effect of a smaller volume being exposed to the maximum stress for this specimen type. A Kitagawa diagram was constructed on the basis of the test results and fracture mechanics calculations. A value of 1.4 Mpa m1/2 was used for the so-called stress intensity threshold range. This analysis predicts that defects larger than 0.06 mm2 will reduce the fatigue strength at 5 × 106 cycles for the aluminium AlSi9Cu3 material tested. [source] oleed, a medaka Polycomb group gene, regulates ciliogenesis and left,right patterningGENES TO CELLS, Issue 12 2009Daisuke Arai Left-right (LR) patterning is an essential part of the animal body plan. Primary cilia are known to play a pivotal role in this process. In humans, genetic disorders of ciliogenesis cause serious congenital diseases. A comprehensive mechanism that regulates ciliogenesis has not been proposed so far. Here, we show that EED, a core member of the Polycomb group (PcG) genes and a presumed player in many epigenetic processes, is required for ciliogenesis and subsequent LR patterning in the medaka fish, Oryzias latipes. Moderate knockdown of oleed, a medaka homolog of EED, preferentially caused situs inversus. In the affected embryo, the cilia in Kupffer's vesicle showed various defects in their structure, position and motility. Furthermore, we demonstrated that oleed maintains the expression of Noto, which, in mice, regulates ciliogenesis and LR patterning. This study provides the first evidence for the involvement of epigenetic plasticity in LR patterning through ciliogenesis. [source] Magnetoresistivity model and ionization-energy approximation for ferromagnetsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009Andrew Das Arulsamy Abstract The evolution of resistivity versus temperature (, (T)) curve for different doping elements, and in the presence of various defects and clustering are explained for both diluted magnetic semiconductors (DMS) and manganites. Here, we provide unambiguous evidence that the concept of ionization energy (EI) which is explicitly associated with the atomic energy levels, can be related quantitatively to transport measurements. The proposed ionization energy model is used to understand how the valence states of ions affect the evolution of , (T) curves for different doping elements. We also explain how the , (T) curves evolve in the presence of, and in the absence of defects and clustering. The model also complements the results obtained from first-principles calculations. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] CD34+ stem cell top-ups without conditioning after initial haematopoietic stem cell transplantation for correction of incomplete haematopoietic and immunological recovery in severe congenital immunodeficienciesBRITISH JOURNAL OF HAEMATOLOGY, Issue 4 2006Claire Booth Summary Haematopoietic stem cell transplantation can be limited by ineffective haematopoiesis and poor immune recovery. A CD34+ cell infusion without conditioning has the potential to improve stem cell function with limited toxicity. Eighteen patients with congenital immunodeficiencies received CD34+ boosts for various defects. When given <1 year after the original graft, six of seven cytopenic patients achieved transfusion independence. A second cohort (n = 11) received boosts >1 year after the original graft; only minimal changes in immune function or chimaerism were noted. Unconditioned stem cell boosts have limited toxicity but should be given early after the original graft to be effective. [source] Towards a new classification of ectodermal dysplasiasCLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 4 2003J. Lamartine Summary Ectodermal dysplasias (EDs) constitute a large and complex group of diseases characterized by various defects in hair, nails, teeth and sweat glands. Of the 170 EDs described so far, fewer than 30 have been explained at the molecular level with identification of the causative gene. This review proposes a new classification of EDs based on the function of the protein encoded by the mutated gene. The EDs are reviewed in light of the recent molecular and biochemical findings and an attempt is made to classify ED causative genes into four major functional subgroups: cell,cell communication and signalling; adhesion; transcription regulation; and development. [source] | ||||||||||