Microstructure and properties of aluminum alloy2090 weldments

ABSTRACT. The effects of welding on aluminum alloy 2090 are examined along with the metallurgical changes associated with welding and aging. The results of the study show that the gas tungsten arc (GTA) and electron beam (EB) weldment properties are controlled by the precipitate size and distribution. There is a tradeoff between strength and elongation. In the as-welded condition, solid solution strengthening is the primary strengthening mechanism present. As a result, the weldment strengths are less than 200 MPa (29 ksi), but the elongations are greater than 4%. In the postweld aged condition, an inhomogeneous distribution of solutes results in an inhomogeneous distribution of precipitates, causing strain localization. Although the weldment strengths increase, the weldment elongations decrease precipitously. The peak strengths of EB and GTA weldments are obtained aging at 160°C (320°F) for 32 h with 75% joint efficiency and at 190°C (374°F) for 16 h with 65% joint efficiency, respectively. Aging at 230 C C (446°F) leads to coarsening of precipitates as well as the intermetallic constituents; the weldment strengths deteriorate rapidly, but the elongations improve. The best overall weldment properties are obtained in the solution heat treated and aged conditions, and are associated with a homogeneous distribution of strengthening precipitates

Explosively driven facture and fragmentation of metal cylinders and rings

Cylinders and rings fabricated from AerMet{reg_sign} 100 alloy and AISI 1018 steel have been explosively driven to fragmentation in order to determine the fracture strains for these materials under plane strain and uniaxial stress conditions. The phenomena associated with the dynamic expansion and subsequent break up of the cylinders are monitored with high-speed diagnostics. In addition, complementary experiments are performed in which fragments from the explosively driven cylinder are recovered and analyzed to determine the statistical distribution associated with the fragmentation process as well as to determine failure mechanisms. The data are used to determine relevant coefficients for the Johnson-Cook (Hancock-McKenzie) fracture model. Metallurgical analysis of the fragments provides information on damage and failure mechanisms

Adiabatic shear band formation in explosively driven AerMet-100 alloy cylinders

Two differently heat-treated AerMet-100 alloy cylinders were explosively driven to fragmentation. Soft-captured fragments were studied to characterize the deformation and damage induced by high explosive loading. The characterization of the fragments reveals that the dominant failure mechanism appears to be dynamic fracture along adiabatic shear bands. These shear bands differ in size and morphology depending on the heat-treated conditions. Nanoindentation measurements of the adiabatic shear bands in either material condition indicate higher hardness in the bands compared to the matrix regions of the fragments

Evidence of Strong Stabilizing Effects on the Evolution of Boreoeutherian (Mammalia) Dental Proportions

The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar–molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammal

First mirror test in JET for ITER : Complete overview after three ILW campaigns

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011-2016, 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified layer on surface has very small amount of impurities such as D, Be, C, N, O and Ni. All mirrors from the divertor (inner, outer, base under the bulk W tile) lost reflectivity by 20-80% due to the beryllium-rich deposition also containing D, C, N, O, Ni and W. In the inner divertor N reaches 5 x 10(17) cm(-2), W is up to 4.3 x 10(17) cm(-2), while the content of Ni is the greatest in the outer divertor: 3.8 x 10(17) cm(-2). Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 x 10(16) cm(-2). The thickness of deposited layer is in the range of 90 nm to 900 nm. The layer growth rate in the base (2.7 pm s(-1)) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrors located at the cassette mouth, flaking of deposits and erosion occurred.Peer reviewe

Serial selection for invasiveness increases expression of miR-143/miR-145 in glioblastoma cell lines

<p>Abstract</p> <p>Background</p> <p>Glioblastoma multiforme (GBM) is the most common primary central nervous system malignancy and its unique invasiveness renders it difficult to treat. This invasive phenotype, like other cellular processes, may be controlled in part by microRNAs - a class of small non-coding RNAs that act by altering the expression of targeted messenger RNAs. In this report, we demonstrate a straightforward method for creating invasive subpopulations of glioblastoma cells (IM3 cells). To understand the correlation between the expression of miRNAs and the invasion, we fully profiled 1263 miRNAs on six different cell lines and two miRNAs, miR-143 and miR-145, were selected for validation of their biological properties contributing to invasion. Further, we investigated an ensemble effect of both miR-143 and miR-145 in promoting invasion.</p> <p>Methods</p> <p>By repeated serial invasion through Matrigel^®-coated membranes, we isolated highly invasive subpopulations of glioma cell lines. Phenotypic characterization of these cells included <it>in vitro </it>assays for proliferation, attachment, and invasion. Micro-RNA expression was compared using miRCURY arrays (Exiqon). In situ hybridization allowed visualization of the regional expression of miR-143 and miR-145 in tumor samples, and antisense probes were used investigate <it>in vitro </it>phenotypic changes seen with knockdown in their expression.</p> <p>Results</p> <p>The phenotype we created in these selected cells proved stable over multiple passages, and their microRNA expression profiles were measurably different. We found that two specific microRNAs expressed from the same genetic locus, miR-143 and miR-145, were over-expressed in our invasive subpopulations. Further, we also found that combinatorial treatment of these cells with both antisense-miRNAs (antimiR-143 and -145) will abrogated their invasion without decreasing cell attachment or proliferation.</p> <p>Conclusions</p> <p>To best of our knowledge, these data demonstrate for the first time that miR-143 and miR-145 regulate the invasion of glioblastoma and that miR-143 and -145 could be potential therapeutic target for anti-invasion therapies of glioblastoma patients.</p