Interfacial Engineering of NiO/NiCo2O4 Porous Nanofibers as Efficient Bifunctional Catalysts for Rechargeable Zinc-Air Batteries.

To meet the crucial demand of regenerative Zn-air (ZA) batteries, low cost, highly efficient, and durable electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are needed to replace the noble metal. Herein, porous NiO/NiCo2O4 nanofibers with superior electrocatalytic performance are synthesized by a facile electrospinning strategy with precursor transition metal salts in nonstoichiometric ratio, which confers the heterostructured NiO/NiCo2O4 with abundant interface-related active sites and electronic transmission channels. Density functional calculation results reveal the chemical bonds easily form between NiO and NiCo2O4 to facilitate the charge transfer, while X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy results demonstrate there are abundant Ni3+ and Co3+ species in NiO/NiCo2O4 due to the interfacial engineering. As a result, the NiO/NiCo2O4 porous nanofibers exhibit highly efficient and durable performances of OER and ORR in KOH solution, including a lower overpotential of 357 mV at 10 mA cm-2 (OER) and half-wave potential of 0.73 V (ORR) than that of the individual. What's more, the NiO/NiCo2O4-based ZA battery displays excellent specific capacities of 814.4 mA h g-1, and good cycling stability of 175 h. Additionally, the flexible ZA battery displays a long cycling life of 14 h and decent flexibility. This work shows that construction of the heterostructure could provide a feasible method to optimize their electrocatalytic performance and make them widely used in power source devices.

Error analysis and new dual-cosine window for estimating the sensor frequency response function from the step response data.

Aiming at reducing the estimation error of the sensor frequency response function (FRF) estimated by the commonly used window-based spectral estimation method, the error models of interpolation and transient errors are derived in the form of non-parameter models. Accordingly, window effects on the errors are analyzed and reveal that the commonly used hanning window leads to smaller interpolation error which can also be significantly eliminated by the cubic spline interpolation method when estimating the FRF from the step response data, and window with smaller front-end value can restrain more transient error. Thus, a new dual-cosine window with its non-zero discrete Fourier transform bins at -3, -1, 0, 1, and 3 is constructed for FRF estimation. Compared with the hanning window, the new dual-cosine window has the equivalent interpolation error suppression capability and better transient error suppression capability when estimating the FRF from the step response; specifically, it reduces the asymptotic property of the transient error from O(N-2) of the hanning window method to O(N-4) while only increases the uncertainty slightly (about 0.4 dB). Then, one direction of a wind tunnel strain gauge balance which is a high order, small damping, and non-minimum phase system is employed as the example for verifying the new dual-cosine window-based spectral estimation method. The model simulation result shows that the new dual-cosine window method is better than the hanning window method for FRF estimation, and compared with the Gans method and LPM method, it has the advantages of simple computation, less time consumption, and short data requirement; the actual data calculation result of the balance FRF is consistent to the simulation result. Thus, the new dual-cosine window is effective and practical for FRF estimation.

Molecular cloning and expression analysis of the gene encoding proline dehydrogenase from Jatropha curcas L.

Proline dehydrogenase (ProDH) (EC 1.5.99.8) is a key enzyme in the catabolism of proline. The enzyme JcProDH and its complementary DNA (cDNA) were isolated from Jatropha curcas L., an important woody oil plant used as a raw material for biodiesels. It has been classified as a member of the Pro_dh superfamily based on multiple sequence alignment, phylogenetic characterization, and its role in proline catabolism. Its cDNA is 1674 bp in length with a complete open reading frame of 1485 bp, which encodes a polypeptide chain of 494 amino acids with a predicted molecular mass of 54 kD and a pI of 8.27. Phylogenetic analysis indicated that JcProDH showed high similarity with ProDH from other plants. Reverse transcription PCR (RT-PCR) analysis revealed that JcProDH was especially abundant in the seeds and flowers but scarcely present in the stems, roots, and leaves. In addition, the expression of JcProDH increased in leaves experiencing environmental stress such as cold (5 °C), heat (42 °C), salt (300 mM), and drought (30 % PEG6000). The JcProDH protein was successfully expressed in the yeast strain INVSc1 and showed high enzyme activity in proline catabolism. This result confirmed that the JcProDH gene negatively participated in the stress response.

Frequency-domain correction of sensor dynamic error for step response.

To obtain accurate results in dynamic measurements it is required that the sensors should have good dynamic performance. In practice, sensors have non-ideal dynamic characteristics due to their small damp ratios and low natural frequencies. In this case some dynamic error correction methods can be adopted for dealing with the sensor responses to eliminate the effect of their dynamic characteristics. The frequency-domain correction of sensor dynamic error is a common method. Using the existing calculation method, however, the correct frequency-domain correction function (FCF) cannot be obtained according to the step response calibration experimental data. This is because of the leakage error and invalid FCF value caused by the cycle extension of the finite length step input-output intercepting data. In order to solve these problems the data splicing preprocessing and FCF interpolation are put forward, and the FCF calculation steps as well as sensor dynamic error correction procedure by the calculated FCF are presented in this paper. The proposed solution is applied to the dynamic error correction of the bar-shaped wind tunnel strain gauge balance so as to verify its effectiveness. The dynamic error correction results show that the adjust time of the balance step response is shortened to 10 ms (shorter than 1/30 before correction) after frequency-domain correction, and the overshoot is fallen within 5% (less than 1/10 before correction) as well. The dynamic measurement accuracy of the balance is improved significantly.

Hydrogen peroxide-induced proline and metabolic pathway of its accumulation in maize seedlings.

Exogenous H(2)O(2) treatment led to a significant accumulation of proline in coleoptiles and radicles of maize seedlings. It also induced an almost immediate and rapid increase of activity of the key enzymes Delta(1)-pyrroline-5-carboxylate synthetase and glutamate dehydrogenase of the glutamate pathway of proline biosynthesis and an up-regulation of Delta(1)-pyrroline-5-carboxylate synthetase gene expression. Activities of the key enzymes arginase and ornithine aminotransferase of the ornithine pathway of proline biosynthesis increased only after 12h of H(2)O(2) treatment. Furthermore, the H(2)O(2) treatment caused an early decrease of the activity of proline dehydrogenase, a key enzyme of proline degradation. These results indicate that H(2)O(2) might be involved in signal transduction events, leading to proline accumulation in maize seedlings, and that the H(2)O(2)-induced proline accumulation is a combined result of the sequential activation of the glutamate and ornithine pathways of proline biosynthesis and the simultaneous inhibition of proline degradation by H(2)O(2).