On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

Abstract The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.This work was supported by the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1, EP/H500375/1 and EP/ M005607/1

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.This study was carried out under a MNT ERA-Net Project named NANOMED. The authors gratefully thank the Midi-Pyrénées region (MNT ERA Net Midi-Pyrénées Région, NANOMED2 project) and the Institute National Polytechnique de Toulouse (BQR INPT 2011, BIOREVE project) for supporting this research work, especially the financial support for research carried out in the CIRIMAT and the LGP laboratories (France), and the Basque government and Tratamientos Superficiales Iontech, S.A. for their financial and technical support under the IG-2007/0000381 grant for the development of the LEPS device and deposition of the coatings carried out in Inasmet-Tecnalia. The French industrial collaborators (TEKNIMED SA and 2PS SA) were financed by the OSEO programs

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Structure-Guided Design of Cell Wall Biosynthesis Inhibitors That Overcome beta-Lactam Resistance in Staphylococcus aureus (MRSA).

beta-Lactam antibiotics have long been a treatment of choice for bacterial infections since they bind irreversibly to Penicillin-Binding Proteins (PBPs), enzymes that are vital for cell wall biosynthesis. Many pathogens express drug-insensitive PBPs rendering beta-lactams ineffective, revealing a need for new types of PBP inhibitors active against resistant strains. We have identified alkyl boronic acids that are active against pathogens including methicillin-resistant S. aureus (MRSA). The crystal structures of PBP1b complexed to 11 different alkyl boronates demonstrate that in vivo efficacy correlates with the mode of inhibitor side chain binding. Staphylococcal membrane analyses reveal that the most potent alkyl boronate targets PBP1, an autolysis system regulator, and PBP2a, a low beta-lactam affinity enzyme. This work demonstrates the potential of boronate-based PBP inhibitors for circumventing beta-lactam resistance and opens avenues for the development of novel antibiotics that target Gram-positive pathogens.Eur-Intafa

Phosphatidylinositol-5-Phosphate 4-Kinases Regulate Cellular Lipid Metabolism By Facilitating Autophagy

While the majority of phosphatidylinositol-4, 5-bisphosphate (PI-4, 5-P2) in mammalian cells is generated by the conversion of phosphatidylinositol-4-phosphate (PI-4-P) to PI-4, 5-P2, a small fraction can be made by phosphorylating phosphatidylinositol-5-phosphate (PI-5-P). The physiological relevance of this second pathway is not clear. Here, we show that deletion of the genes encoding the two most active enzymes in this pathway, Pip4k2a and Pip4k2b, in the liver of mice causes a large enrichment in lipid droplets and in autophagic vesicles during fasting. These changes are due to a defect in the clearance of autophagosomes that halts autophagy and reduces the supply of nutrients salvaged through this pathway. Similar defects in autophagy are seen in nutrient-starved Pip4k2a−/−Pip4k2b−/− mouse embryonic fibroblasts and in C. elegans lacking the PI5P4K ortholog. These results suggest that this alternative pathway for PI-4, 5-P2 synthesis evolved, in part, to enhance the ability of multicellular organisms to survive starvation

Preoperative biliary drainage for cancer of the head of the pancreas

BACKGROUND: The benefits of preoperative biliary drainage, which was introduced to improve the postoperative outcome in patients with obstructive jaundice caused by a tumor of the pancreatic head, are unclear. METHODS: In this multicenter, randomized trial, we compared preoperative biliary drainage with surgery alone for patients with cancer of the pancreatic head. Patients with obstructive jaundice and a bilirubin level of 40 to 250 μmol per liter (2.3 to 14.6 mg per deciliter) were randomly assigned to undergo either preoperative biliary drainage for 4 to 6 weeks, followed by surgery, or surgery alone within 1 week after diagnosis. Preoperative biliary drainage was attempted primarily with the placement of an endoprosthesis by means of endoscopic retrograde cholangiopancreatography. The primary outcome was the rate of serious complications within 120 days after randomization. RESULTS: We enrolled 202 patients; 96 were assigned to undergo early surgery and 106 to undergo preoperative biliary drainage; 6 patients were excluded from the analysis. The rates of serious complications were 39% (37 patients) in the early-surgery group and 74% (75 patients) in the biliary-drainage group (relative risk in the early-surgery group, 0.54; 95% confidence interval [CI], 0.41 to 0.71; P<0.001). Preoperative biliary drainage was successful in 96 patients (94%) after one or more attempts, with complications in 47 patients (46%). Surgery-related complications occurred in 35 patients (37%) in the early-surgery group and in 48 patients (47%) in the biliary-drainage group (relative risk, 0.79; 95% CI, 0.57 to 1.11; P = 0.14). Mortality and the length of hospital stay did not differ significantly between the two groups. CONCLUSIONS: Routine preoperative biliary drainage in patients undergoing surgery for cancer of the pancreatic head increases the rate of complications. (Current Controlled Trials number, ISRCTN31939699.) Copyrigh

A hybrid bondline concept for bonded composite joints

Based on the experience in the past and the occurrence of in-service damages, the authorities restrict today the application of adhesive bonding of composite structures for aircraft applications. However, certification limitations can be overcome if occurring disbonds within a bond are stopped by implemented design features, so called disbond stopping features. Consequently, a novel bondline architecture for bonded composite joints is proposed. By implementing a distinct rather ductile thermoplastic phase, a physical barrier for growing disbonds is obtained and thus a fail-safe design, respectively. Moreover, the joint is established by using two different joining technologies, namely adhesive bonding and thermoset composite welding. A sophisticated manufacturing technique is developed for the hybrid bondline concept to achieve a high strength joint. The joint's quality is examined by means of several analytical methods like microsections, scanning electron microscopy (SEM), and energy-dispersive X-Ray (EDX) analysis. Additionally, the mechanical performance is evaluated by static Double Cantilever Beam (DCB) and Single Lap Shear (SLS) tests