Southwest University

About: Southwest University is a education organization based out in Chongqing, China. It is known for research contribution in the topics: Gene & Population. The organization has 29772 authors who have published 27755 publications receiving 409441 citations. The organization is also known as: Southwest University in Chongqing & SWU.

Secrecy Capacity Analysis Over $\alpha - \mu $ Fading Channels

Abstract: In this letter, we study the secrecy capacity of the classic Wyner’s model over the $\alpha - \mu $ fading channels, where $\alpha $ and $\mu $ specify the nonlinearity and clustering of fading channels, respectively. The average secrecy capacity (ASC) is derived in closed-form by using the extended generalized bivariate Fox’s H-function. Moreover, the asymptotic analysis of ASC in high signal-to-noise ratio (SNR) regime is conducted. The asymptotic results unveil that the ASC follows the scaling law of $\Theta \left ({ {\ln \rho } }\right )$ , where $\rho $ stands for the ratio between the average powers of main channels and eavesdropping channels. Moreover, the ASC can be enhanced by increasing the transmit SNR, while there exists a ceiling of ASC as the SNRs at both sides are improved simultaneously. The accuracy of the analytical results is validated by Monte-Carlo simulations. The numerical results show that rigorous fading channels are beneficial to the secrecy performance, that is, serious nonlinearity (small $\alpha $ ) and sparse clustering (small $\mu $ ) will lead to the improvement of ASC.

One-Step Electrodeposition of Co/CoP Film on Ni Foam for Efficient Hydrogen Evolution in Alkaline Solution

Abstract: The development of high-efficiency catalysts for hydrogen evolution via water splitting has been an effective strategy to solve the energy environmental problems and energy crisis. The abundant-reserving transition metals and their phosphides are becoming attractive Pt alternatives for hydrogen evolution reaction (HER). Herein, a crystalline/amorphous Co/CoP film was facilely prepared on nickel foam (NF) by a one-step electrodeposition technique at room temperature, named Co/CoP-NF. The as-prepared Co/CoP-NF electrocatalyst exhibits excellent electrocatalytic activity for HER, on par with Pt/C, showing a low overpotential of 35 mV at a current density of 10 mA·cm–2 and small Tafel slope of 71 mV·dec–1 in 1.0 M NaOH solution. More importantly, the Co/CoP-NF catalyst presents good long-term durability at an overpotential of 60 mV. Moreover, the influence of the electrodeposition parameters on the catalytic performance of the catalyst was discussed. This study offers an effective strategy to develop a non-no...

A Novel Type of P450c17 Lacking the Lyase Activity Is Responsible for C21-Steroid Biosynthesis in the Fish Ovary and Head Kidney

Abstract: Cytochrome P450c17 is the single enzyme that mediates the 17 alpha-hydroxylase and 17, 20 lyase activities during the biosynthesis of steroid hormones in the gonads and adrenal gland. However, the mechanism underlying its dual action continues to be a controversy in the field of steroidogenesis in fish. In an attempt to resolve this issue, we identified a novel type of P450c17 (P450c17-II) by an in silico analysis from the genomes of six fish species. We cloned P450c17-II from tilapia and medaka, and comparison with the conventional P450c17-I revealed that they differ in gene structure and enzymatic activity. Enzymatic assays by thin-layer chromatography revealed that P450c17-II possesses only the 17 alpha-hydroxylase activity without any 17, 20 lyase activity, unlike P450c17-I, which has both these activities. In testis, both P450c17-I and -II express in the interstitial cells. Remarkable differences, revealed by in situ hybridization, in the expression patterns of the P450c17-I and -II in the ovary and head kidney of tilapia during various stages of development strongly suggest that P450c17-I is responsible for the synthesis of estradiol-17beta in the ovary, whereas P450c17-II is required for the production of C21 steroids such as cortisol in the head kidney. More interestingly, a temporally controlled switching is observable in the expression of these two genes during the steroidogenic shift from estradiol-17beta to the C21 steroid, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (maturation-inducing hormone of fish oocytes) in the fish ovary, revealing a role for P450c17-II in the production of hormones that induce oocyte maturation in fish.