Electron beam welding of dissimilar metals

Using electron beam welding and braze welding techniques, thirty-five dissimilar metal joints were made and rated on the basis of visual, metallographic, tensile and bend testing BY G. METZGER AND R. LISON ABSTRACT. At the outset of this study on the weldability of dissimilar metal joints, some preliminary information on the weld metal properties of various joint combinations was obtained from arc melted buttons. When the information proved to be of minimum value in predicting the weldability of the electron beam welds under study, this approach was discontinued. Thirty-three two-member combinations of dissimilar metals were electron beam welded as squaregroove butt joints in 0.08 and 0.12 in. sheet material. Many joints were "braze welded" by offsetting the electron beam about 0.02 in. from the butt joint to achieve fusion of the lower melting point metal, but no significant fusion of the other member of the pair. The welds were evaluated by visual and metallographic examination, transverse tensile tests, and bend tests. The welds Ag/AI, Ag/Ni15Cr7Fe, Cu/NM5Cr7Fe, Cu/V, Cu20Ni/Ni15Cr7Fe, Fe18Cr8Ni/Ni, Fe18Cr8Ni/NM5Cr7Fe, Cb/Ti, Cb/V, Ni/NM5Cr7Fe and Cb/V10Ti were readily welded and weld properties were excellent. Others which had only minor defects included the Ag/Cu20Ni, Ag/Ti

Improved Thermodynamic Descriptions of Carbides in Ni-Based Superalloys

The Ni-based superalloy René 41 has sparked recent interest for applications in next-generation aircraft engines due to its high-temperature strength that is superior to all similar grades. These desirable properties are achieved by careful control of the microstructure evolution during thermomechanical processing, and this is commonly informed by simulations. In particular, the grain boundary carbides M6C and M23C6 play an essential role in controlling the grain size and strength of the final product. Therefore, a solid understanding of the thermodynamic stability and thermokinetic evolution of these carbides is essential. However, thermokinetic simulations using existing thermodynamic databases have been demonstrated to have discrepancies between thermodynamic stabilities and experimental observations. Here, we collected a new experimental time–temperature–precipitation diagram. In conjunction with improved crystallographic descriptions, these experimental results are used to modify a CALPHAD database for M6C and M23C6. The modified database correctly identifies temperature regions with rapid carbide precipitation kinetics. Further, kinetic simulations and strengthening models successfully predict the hardness increase due to γ′ precipitation. The modified database has been applied to Udimet 700, Waspaloy, and Haynes 282, demonstrating improved results. These updates will facilitate more accurate simulations of the microstructure evolution during thermomechanical processing of advanced Ni-based superalloys for aerospace and other applications

Deregulation of cancer-stem-cell-associated miRNAs in tissues and sera of colorectal cancer patients

Colorectal cancer (CRC) is a deadly tumour in Western countries characterized by high cellular/molecular heterogeneity. Cancer stem cells (CSC) act in cancer recurrence, drug-resistance and in metastatic epithelial-to-mesenchymal transition. microRNAs (miRNAs) contribute to cancer is increasing, and miRNA roles in CSC phenotype and fate and their utility as CRC biomarkers have also been reported. Here, we investigated miR-21, miR-221, miR-18a, miR-210, miR-31, miR-34a, miR-10b and miR-16 expression in experimental ALDH+ and CD44+/CD326+ colorectal CSCs obtained from the human CRC cell lines HCT-116, HT-29 and T-84. Then, we moved our analysis in cancer tissue (CT), healthy tissue (HT) and serum (S) of adult CRC patients (n=12), determining relationships with clinical parameters (age, sex, metastasis, biochemical serum markers). Specific miRNA patterns were evident in vitro (normal, monolayers and CSCs) and in patients' samples stratified by TNM stage (LOW vs HIGH) or metastasis (Met vs no-Met). miR-21, miR-210, miR-34a upregulation ad miR-16 dowregulation associated with the CSCs phenotype. miR-31b robustly overexpressed in monolayers and CSCs, and in CT ad S of HIGH grade and Met patients, suggesting a role as marker of CRC progression and metastasis. miR-18a upregulated in all cancer models and associated to CSC phenotype, and to metastasis and age in patients. miR-10b downregulated in CT and S of LOW/HIGH grade and no-Met patients. Our results identify miRNAs useful as colorectal CSC biomarker and that miR-21, miR-210, miR-10b and miR-31b are promising markers of CRC. A specific role of miR-18a as metastatic CRC serum biomarker in adult patients was also highlighted

Opto-mechanical measurement of micro-trap via nonlinear cavity enhanced Raman scattering spectrum

High-gain resonant nonlinear Raman scattering on trapped cold atoms within a high-fineness ring optical cavity is simply explained under a nonlinear opto-mechanical mechanism, and a proposal using it to detect frequency of micro-trap on atom chip is presented. The enhancement of scattering spectrum is due to a coherent Raman conversion between two different cavity modes mediated by collective vibrations of atoms through nonlinear opto-mechanical couplings. The physical conditions of this technique are roughly estimated on Rubidium atoms, and a simple quantum analysis as well as a multi-body semiclassical simulation on this nonlinear Raman process is conducted.Comment: 7 pages, 2 figure

Discovery of a Wide Planetary-mass Companion to the Young M3 Star GU Psc

We present the discovery of a comoving planetary-mass companion ~42" (~2000 AU) from a young M3 star, GU Psc, a likely member of the young AB Doradus Moving Group (ABDMG). The companion was first identified via its distinctively red i − z color (>3.5) through a survey made with Gemini-S/GMOS. Follow-up Canada–France–Hawaii Telescope/WIRCam near-infrared (NIR) imaging, Gemini-N/GNIRS NIR spectroscopy and Wide-field Infrared Survey Explorer photometry indicate a spectral type of T3.5 ± 1 and reveal signs of low gravity which we attribute to youth. Keck/Adaptive Optics NIR observations did not resolve the companion as a binary. A comparison with atmosphere models indicates T_eff = 1000–1100 K and log g = 4.5–5.0. Based on evolution models, this temperature corresponds to a mass of 9–13  M_Jup for the age of ABDMG (70–130 Myr). The relatively well-constrained age of this companion and its very large angular separation to its host star will allow its thorough characterization and will make it a valuable comparison for planetary-mass companions that will be uncovered by forthcoming planet-finder instruments such as Gemini Planet Imager and SPHERE

The puzzling issue of silica toxicity: are silanols bridging the gaps between surface states and pathogenicity?

Background: Silica continues to represent an intriguing topic of fundamental and applied research across various scientific fields, from geology to physics, chemistry, cell biology, and particle toxicology. The pathogenic activity of silica is variable, depending on the physico-chemical features of the particles. In the last 50 years, crystallinity and capacity to generate free radicals have been recognized as relevant features for silica toxicity. The ‘surface’ also plays an important role in silica toxicity, but this term has often been used in a very general way, without defining which properties of the surface are actually driving toxicity. How the chemical features (e.g., silanols and siloxanes) and configuration of the silica surface can trigger toxic responses remains incompletely understood. Main body: Recent developments in surface chemistry, cell biology and toxicology provide new avenues to improve our understanding of the molecular mechanisms of the adverse responses to silica particles. New physicochemical methods can finely characterize and quantify silanols at the surface of silica particles. Advanced computational modelling and atomic force microscopy offer unique opportunities to explore the intimate interactions between silica surface and membrane models or cells. In recent years, interdisciplinary research, using these tools, has built increasing evidence that surface silanols are critical determinants of the interaction between silica particles and biomolecules, membranes, cell systems, or animal models. It also has become clear that silanol configuration, and eventually biological responses, can be affected by impurities within the crystal structure, or coatings covering the particle surface. The discovery of new molecular targets of crystalline as well as amorphous silica particles in the immune system and in epithelial lung cells represents new possible toxicity pathways. Cellular recognition systems that detect specific features of the surface of silica particles have been identified. Conclusions: Interdisciplinary research bridging surface chemistry to toxicology is progressively solving the puzzling issue of the variable toxicity of silica. Further interdisciplinary research is ongoing to elucidate the intimate mechanisms of silica pathogenicity, to possibly mitigate or reduce surface reactivity. Keywords: Silica, Silicosis, Lung cancer, Auto-immune diseases, Surface reactivity, Silanol, Coating, Modelling, Spectroscopy, Atomic force microscop