High temperature mechanical deformation of an additive manufactured nickel based superalloy using small scale test methods

Nickel based superalloys have been utilised within numerous industrial sectors from power generation to chemical processing plants for over four decades as a result of their ability to retain mechanical properties at arduous temperatures alongside excellent oxidation and corrosion resistance. Within the aerospace industry, they have been primarily used within regions of the gas turbine engine where metal temperatures can often exceed 1000°C and high temperature deformation mechanics are prominent. Although typically manufactured using traditional wrought and casting methodologies, the aerospace industry has become increasingly interested in the use of Additive Layer Manufacturing (ALM) as a means of fabrication to take advantage of the numerous benefits that ALM has to offer. Detailed characterisation of the structural integrity of components processed via additive processes is a key requirement of the understanding. In this paper, the small punch creep (SPC) test has been applied to samples of a high gamma prime containing nickel-based superalloy manufactured using the laser powder bed fusion (LPBF) process. Several different builds are investigated and ranked, with ALM builds provided in different epitaxial orientations and with contrasting process parameters to help determine the optimal process parameters

Reductions in External Divalent Cations Evoke Novel Voltage-Gated Currents in Sensory Neurons

It has long been recognized that divalent cations modulate cell excitability. Sensory nerve excitability is of critical importance to peripheral diseases associated with pain, sensory dysfunction and evoked reflexes. Thus we have studied the role these cations play on dissociated sensory nerve activity. Withdrawal of both Mg2+ and Ca2+ from external solutions activates over 90% of dissociated mouse sensory neurons. Imaging studies demonstrate a Na+ influx that then causes depolarization-mediated activation of voltage-gated Ca2+ channels (CaV), which allows Ca2+ influx upon divalent re-introduction. Inhibition of CaV (ω-conotoxin, nifedipine) or NaV (tetrodotoxin, lidocaine) fails to reduce the Na+ influx. The Ca2+ influx is inhibited by CaV inhibitors but not by TRPM7 inhibition (spermine) or store-operated channel inhibition (SKF96365). Withdrawal of either Mg2+ or Ca2+ alone fails to evoke cation influxes in vagal sensory neurons. In electrophysiological studies of dissociated mouse vagal sensory neurons, withdrawal of both Mg2+ and Ca2+ from external solutions evokes a large slowly-inactivating voltage-gated current (IDF) that cannot be accounted for by an increased negative surface potential. Withdrawal of Ca2+ alone fails to evoke IDF. Evidence suggests IDF is a non-selective cation current. The IDF is not reduced by inhibition of NaV (lidocaine, riluzole), CaV (cilnidipine, nifedipine), KV (tetraethylammonium, 4-aminopyridine) or TRPM7 channels (spermine). In summary, sensory neurons express a novel voltage-gated cation channel that is inhibited by external Ca2+ (IC50∼0.5 µM) or Mg2+ (IC50∼3 µM). Activation of this putative channel evokes substantial cation fluxes in sensory neurons

Comparative Antianaerobic Activities of Doripenem Determined by MIC and Time-Kill Analysis▿

Against 447 anaerobe strains, the investigational carbapenem doripenem had an MIC50 of 0.125 μg/ml and an MIC90 of 1 μg/ml. Results were similar to those for imipenem, meropenem, and ertapenem. Time-kill studies showed that doripenem had very good bactericidal activity compared to other carbapenems, with 99.9% killing of 11 strains at 2× MIC after 48 h