The structural, gaseous phase hydrogen storage, and electrochemical properties of a series of Mn-modified misch-metal based superlattice metal hydride alloys were investigated in part one of this ...two-part series of papers. X-ray diffraction analysis showed that these alloys are all multi-phased compositions with different abundances of AB2, AB3, A2B7, AB4, and AB5 phases. Substitution of Ni in the B-site by Mn promotes AB5 phase formation and decreases both gaseous phase and electrochemical capacities due to the reduction in the abundance of main hexagonal A2B7 phase. AC impedance and magnetic susceptibility measurement were employed to characterize the surface of Mn-free and Mn-modified alloys and show deterioration in surface catalytic ability as the Mn-content increases. Mn-modification adversely affected misch-metal based superlattice metal hydride alloy properties such as phase homogeneity, capacity, cycle stability, high-rate performance, and surface reaction.
•The various properties of misch-metal superlattice alloys were studied.•Mn partially substituting Ni promotes formation of AB5 phase.•Mn decreases hydrogen storage capacities and degrade the surface catalytic ability.•Mn adversely affects the cycle stability and high rate dischargeability.•Magnetic susceptibility confirmed the Ni in the surface oxide as catalyst.
Chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each ...constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 phases, the TiNi phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.
•We synthesized a series of Laves-BCC metal hydride alloys by arc melting.•Influences of chemical composition to capacity and rate capability were studied.•Removal of Fe and reduction in Mn improve the high-rate performance of the alloy.•Removal of Zr eliminates C14 phase and deteriorates storage properties.•TiNi secondary phase is found to improve the capacity and rate capability.
Aurora-A/STK15/BTAK, which encodes a centrosome-associated kinase, is amplified and overexpressed in multiple types of human tumors, including breast cancer. However, the causal relationship between ...overexpression of Aurora-A and tumorigenesis has not been fully established due to contradictory data obtained from different experimental systems. To investigate this, we generated a mouse strain that carries an MMTV-Aurora-A transgene. We showed that all the MMTV-Aurora-A mice displayed enhanced branch morphogenesis in the mammary gland and about 40% developed mammary tumors at 20 months of age. The tumor incidence was significantly increased in a p53(+/-) mutation background with about 70% MMTV-Aurora-A;p53(+/-) animals developed tumors at 18 months of age. Of note, overexpression of Aurora-A led to genetic instability, characterized by centrosome amplification, chromosome tetraploidization and premature sister chromatid segregation, at stages prior to tumor formation. Most notably, the severe chromosomal abnormality did not cause cell death owing to the activation of AKT pathway, including elevated levels of phosphorylated AKT and mammalian target of rapamycin, and nuclear accumulation of cyclin D1, which enabled continuous proliferation of the tetraploid cells. These data establish Aurora-A as an oncogene that causes malignant transformation through inducing genetic instability and activating oncogenic pathways such as AKT and its downstream signaling.
A series of Ti12Zr21.5V10Cr7.5Mn8.1Co8.0Ni32.2−xSn0.3Al0.4Znx, x = 0, 1, 2, and 3 alloys made by an arc melting process was studied. As the Zn-content increases, the TiNi phase abundance increases, ...which reduces the Ni-content in the main C14 phase causing an isotropic expansion of the unit cell. Both the equilibrium pressure and heat of hydride formation are reduced via a synergetic effect between the main phase and secondary phases, which causes small increases in both gaseous phase maximum H-storage capacity and full discharge capacity measured electrochemically. The C15 phase abundance shows a peak value for improvement in activation and high-rate performance in the alloy containing 1 at% Zn and a passivated surface is formed to hinder the activation and high-rate performance. Despite of the passivated surface at room temperature, the −40 °C charge-transfer resistance of a 3 at% Zn-addition was much improved by increase of both surface area and surface catalytic ability. In a sealed cell, the addition of 1 at% Zn in the AB2 metal hydride alloy improves the −10 °C capacity and cycle stability at the expense of power reduction. The effects of Zn-substitution were also compared with those obtained from Si, Fe, Cu, Y, and Mo.
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•Partial replacement of Ni by Zn in AB2 metal hydride alloy was studied.•With increase in Zn, TiNi phase increases, unit cell expands, and ΔH decreases.•C15 phase is crucial for the high-rate performance and activation behavior.•1 at% of Zn can improve the storage capacity, activation, and cycle stability.•High Zn-content (>1 at%) passivates the surface and impedes high-rate capability.
The structures, gaseous phase hydrogen storage, and electrochemical properties of a series of (Nd0.83Mg0.16Zr0.01)(Ni0.953Al0.046Co0.001)α alloys, where α = 3.3, 3.4, 3.5, 3.6, and 3.7, before and ...after annealing (900 °C and 5 h in argon) were studied. Besides the main Nd2Ni7 phase, other secondary phases, such as MgNdNi4, NdNi5, NdNi3, NdNi, and CeNi3, were present in most of the samples and influenced the hydrogen storage properties. After annealing, several changes happened: the stoichiometry of the main Nd2Ni7 phase remained constant at B/A = 3.3 and its abundance increased; the abundances of the major secondary phases decreased but were not totally eliminated (which helped preserve the catalytic effects); both the gaseous phase hydrogen storage and electrochemical capacity increased; the high-rate dischargeability decreased slightly; and the activation became more difficult. A stoichiometry of AB3.5 showed the best compromise among electrochemical capacity, high-rate dischargeability, and ease of activation.
► The influences of stoichiometry and annealing to Nd-A2B7 alloys were studied. ► Secondary phases are critical as catalyst for hydrogen storage. ► Annealing improves capacity and high-rate dischargeability. ► Annealed AB3.5 has the best electrochemical properties.
The DNA damage response (DDR) cascade and ROS (reactive oxygen species) signaling are both involved in the induction of cell death after DNA damage, but a mechanistic link between these two pathways ...has not been clearly elucidated. This study demonstrates that ROS induction after treatment of cells with neocarzinostatin (NCS), an ionizing radiation mimetic, is at least partly mediated by increasing histone H2AX. Increased levels of ROS and cell death induced by H2AX overexpression alone or DNA damage leading to H2AX accumulation are reduced by treating cells with the antioxidant N-Acetyl-L-Cysteine (NAC), the NADP(H) oxidase (Nox) inhibitor DPI, expression of Rac1N17, and knockdown of Nox1, but not Nox4, indicating that induction of ROS by H2AX is mediated through Nox1 and Rac1 GTPase. H2AX increases Nox1 activity partly by reducing the interaction between a Nox1 activator NOXA1 and its inhibitor 14-3-3zeta. These results point to a novel role of histone H2AX that regulates Nox1-mediated ROS generation after DNA damage.
Effects of thermal annealing (between 800 and 1100 °C) on the structural, gaseous phase and electrochemical hydrogen storage properties of a Laves phase-related body-centered-cubic (BCC) alloy, ...Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, were studied. Only BCC, TiNi, and C14 phases appeared in the as-cast sample. Annealing at 800 and 900 °C increased the main hydrogen storage BCC phase abundance and reduced C14 and TiNi catalytic phases. Annealing at 1000 °C promoted the formation of Ti2Ni phase. A σ-VNi phase appeared after annealing at 1100 °C. In addition, the annealed samples also contained Zr and TiO2 debris. Electrochemical results suggested optimized annealing conditions of 900 °C for 12-h to optimize the storage capacity, high-rate performance, and activation due to a favorable balance in abundance between storage phase (BCC) and catalytic phases (C14 and TiNi).
•Effects of annealing to a Laves phase-related BCC metal hydride alloy are reported.•900 °C for 12 h is found to be optimal for electrochemical properties.•Annealing at 1000 °C promotes formation of Ti2Ni phase.•Annealing at 1100 °C, a σ-VNi phase is formed.•The open-circuit voltage decreases with the increase in plateau pressure.
Annealing Nd-only AB3.74 metal hydride alloy was found to effectively increase composition homogeneity, main A2B7 phase abundance, and both gaseous phase and electrochemical hydrogen storage ...capacities, as well as to facilitate activation, and improve battery high-rate performance, charge retention, and cycle life. As the phase abundance of the main A2B7 phase increases in the alloy with higher annealing temperatures, the general electrochemical performance improves. Extending the annealing period from 5 to 16 h further increases the A2B7 phase abundance, but deteriorates the high-rate dischargeability due to the reduction of AB5 catalytic phase.
•La addition to AB2 alloys promotes formation of LaNi phase.•LaNi phase facilitates formation and high-rate operation by increasing surface area.•LaNi phase causes pulverization and degrades the ...cycle stability.•-40°C low temperature was much improved with La-addition.
The structure of a series AB2 metal hydride alloys, in which La substitutes for Zr (Ti12Zr22.8−xV10Cr7.5Mn8.1Co7.0Ni32.2LaxAl0.4, x=0 to 5), is studied and correlated to various hydrogen storage properties in both gaseous phase and electrochemical systems. La, instead of entering the main Laves phase, forms a LaNi secondary phase which has very limited solubility with other elements. This phase improves activation of both capacity and high-rate dischargeability through a dramatic increase in surface area due to pulverization. The presence of LaNi phase also improves the high-rate dischargeability, facilitating the bulk diffusion of protons through synergetic effects with the main Laves phase. La-content in the alloys also suppresses the TiNi secondary phase due to competition of Ni with the LaNi phase. The lattice constants and unit cell volume of the main C14 phase decreases as more Zr (relatively large) is substituted out, which leads to a less stable hydride with higher equilibrium plateau pressure, higher ΔH, and lower hydrogen storage capacity. With the addition of La in the alloy samples, C14 and LaNi phase abundances increase while C15 and TiNi phase abundances decrease. At −40°C, the charge-transfer resistance of the La-containing alloys decreases as a result of increased catalytic ability in the main phase. The lowest overall charge-transfer resistance obtained from electrochemical impedance spectroscopy analysis measured at −40°C is 11Ω g.
•Substantial improvement in −40°C performance of Si-doped AB2 alloys.•Improvement through increases in both surface area and catalytic ability.•1% of Si is recommended for capacity, high-rate, and ...catalytic consideration.•A method of measuring Si-content using conventional ICP is introduced.
The ultra-low temperature (−40°C) charge transferred resistance of a Laves phase based-AB2 metal hydride alloy was reduced by a factor of 5 by a partial substitution of Ni with Si in Ti12Zr21.5V10Cr7.5Mn8.1Co8.0Ni32.2−xSixSn0.3Al0.4, where x=0–4. This improvement was due to the increases in surface area from the higher leaching-rate of the oxidation product of Si and to the surface catalytic effect with the incorporation of Si. The microstructure, gaseous phase hydrogen storage, and electrochemical properties of these alloys were investigated and reported. With the addition of Si in the formula, the abundances of both C15 and TiNi minor phases increased, which resulted in decreases in both maximum gaseous phase hydrogen storage and electrochemical capacities. Some changes on the chemical compositions of the minor phases from the Si-incorporation were observed but cannot be correlated to the improvement in low-temperature performance. These changes are the transition from Zr to ZrO2, the decrease in Ti/Zr ratio in the TiNi phase, and the higher Sn-content in the TiNi phase. An amount of 1at.% of Si is recommended from the balance among capacity, bulk diffusion, surface area, and catalytic properties of the alloys. In addition, a special sample preparation method for using inductively coupled plasma analysis to determine the Si-content in the sample was developed and presented.
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