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To expand the selection range of materials for blades in gas turbines, new single crystal superalloys with different Re contents were developed and the microstructures, high temperature tensile properties and fracture behaviors were investigated. The dendrites and γ+γ′ eutectic are observed in the as-cast superalloys. After heat treatment, the γ+γ′ eutectic in the interdendritic regions is completely eliminated and cubic γ′ phase with regular morphology maintains a coherent relationship with γ matrix. The size of γ′ phase decreases with the increasing Re due to its inhibition effect on the growth of γ′ phase. The three alloys have little differences in strength below 850 °C and possess the maximum tensile strength at 760 °C. However, the strength of 3Re and 0Re alloys is obviously higher than that of 1.5Re alloy at 980 °C due to the higher content of refractory elements. In addition, all alloys have a very obvious work hardening peak below 760 °C before fracture. With the increasing temperature, the characteristics of plastic fracture become more obvious due to the changes of dislocation motion. At 650 °C, the alloys show quasi-cleavage fracture. At 980 °C, numerous dimples can be clearly seen while no slip deformation trace is found, showing obvious dimple aggregation fracture. The γ′ phase elongates along the direction of stress loading, and the γ channel perpendicular to the direction of the stress axis widens. The rafting phenomenon of γ′ phase in the all three single crystal superalloys does not appear, indicating the alloys have good microstructure stability.

Vacuum brazing of TC4 titanium alloy and 316L stainless steel was conducted using Ag70.5Cu27.5Ti2filler metal, the effects of microstructure and mechanical properties of brazing temperature on interface were investigated, and the bonding mechanism of brazed joint was also established. The results show that the filler metal and the base metal on both sides were completely diffused and bonded well. The microstructure of brazed joint interface is as follows: TC4 titanium alloy/diffusion layer(α-Ti + Ti2Cu)/reaction layer (including TiCu and Ti2Cu)/joint center area/TiFe layer/316L stainless steel. When the holding time lasted for 15 min, the shear strength of brazed joint first increased and then decreased as the brazing temperature rose. When the brazing temperature upped to 870 °C, the maximum of shear strength reached 190 MPa, and then the fracture occurred in the center of the brazed joint. The hardness of the joints gradually increased as the temperature rose, and the mean value reached maximum of 323 HV at 930 °C.

To obtain higher comprehensive mechanical properties while avoid the adverse effects of Re element on the microstructure and economy of the alloy, a Re-free nickel-based single crystal superalloy is developed based on the Rene N5 single crystal superalloy. The microstructure evolution, compression properties, tensile properties, deformation mechanism and fracture behaviour of the self-designed alloy are investigated. The experimental results show that after the complete heat treatment, cuboidal γ′ precipitates with high degree of regular morphology are formed. The size of γ′ precipitates is about 0.49μm, and the volume fraction is approximately 61%, which are better than those for a conventional second generation single crystal superalloy. The alloy reaches its maximum compressive and tensile strength at 760°C and shows excellent microstructure thermal stability and improved mechanical properties. The alloy has an obvious strain hardening stage when the temperature is lower than 760°C, while the softening stage is not obvious. When the temperature reaches 850°C, the stress–strain curve of the sample mainly shows that the variable stress increases abruptly at the beginning and then decreases immediately. The tensile fracture of a single crystal at medium and low temperature is characterized by a slip fracture with a certain plastic deformation. A high temperature tensile fracture is characterized by typical plastic deformation, and its mechanism is a creep fracture with a uniform deformation.

This article provides an update on the current progress in identification of KCNQ4mutations responsible for DFNA2, a subtype of autosomal dominant nonsyndromic progressive hearing loss.

The simplest cellular model for classical conditioning in the nudibranch mollusk,Hermissenda crassicornis, involves the presynaptic hair cells and postsynaptic photoreceptors. Whereas the cellular mechanisms for postsynaptic photoreceptors have been studied extensively, the presynaptic mechanisms remain uncertain. Here, we determined the phenotype of the voltage-dependent Ca2+current in the presynaptic hair cells that may be directly involved in changes in synaptic efficacy during classical conditioning. The Ca2+current can be classified as a P-type current because its activation voltage under seawater recording conditions is approximately −30 mV, it showed slow inactivation, and it is reversibly blocked by ω-agatoxin-IVA. The steady-state activation and inactivation curves revealed a window current, and the single-channel conductance is approximately 20 pS. The P-type current was enhanced by cAMP analogs (approximately 1.3-fold), and by forskolin, an activator of adenylyl cyclase (approximately 1.25-fold). In addition, the P-type current showed voltage-dependent facilitation, which is mediated by protein kinase A (PKA). Specifically, the PKA inhibitor peptide [PKI(6–22)amide] blocked the enhancement of the Ca2+current produced by conditioning depolarization prepulses. Because neurotransmitter release is mediated by Ca2+influx via voltage-gated Ca2+channels, and because of the nonlinear relationship between the Ca2+influx and neurotransmitter release, we propose that voltage-dependent facilitation of the P-type current in hair cells would produce a robust change in synaptic efficacy.

We assessed the functional determinants of the properties of L-type Ca2+currents in hair cells by co-expressing the pore-forming CaV1.3α1subunit with the auxiliary subunits β1Aand/or α2δ. Because Ca2+channels in hair cells are poised to interact with synaptic proteins, we also co-expressed the CaV1.3α1subunit with syntaxin, vesicle-associated membrane protein (VAMP), and synaptosome associated protein of 25 kDa (SNAP25). Expression of the CaV1.3α1subunit in human embryonic kidney cells (HEK 293) produced a dihydropyridine (DHP)-sensitive Ca2+current (peak current density −2.0 ± 0.2 pA/pF; n= 11). Co-expression with β1Aand α2δsubunits enhanced the magnitude of the current (peak current density: CaV1.3α1+ β1A= −4.3 ± 0.8 pA/pF,n= 10; CaV1.3α1+ β1A+ α2δ= −4.1 ± 0.6 pA/pF, n= 9) and produced a leftward shift of approximately 9 mV in the voltage-dependent activation of the currents. Furthermore, co-expression of CaV1.3α1with syntaxin/VAMP/SNAP resulted in at least a twofold increase in the peak current density (−4.7 ± 0.2 pA/pF; n= 11) and reduced the extent of inactivation of the Ca2+currents. Botulinum toxin, an inhibitor of syntaxin, accelerated the inactivation profile of Ca2+currents in hair cells. Immunocytochemical data also indicated that the Ca2+channels and syntaxin are co-localized in hair cells, suggesting there is functional interaction of the CaV1.3α1with auxiliary subunits and synaptic proteins, that may contribute to the distinct properties of the DHP-sensitive channels in hair cells.