Design Principle on Carbon Nanomaterials Electrocatalysts for Energy Storage and Conversion

We are facing an energy crisis because of the limitation of the fossil fuel and the pollution caused by burning it. Clean energy technologies, such as fuel cells and metal-air batteries, are studied extensively because of this high efficiency and less pollution. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential in the process of energy storage and conversion, and noble metals (e.g. Pt) are needed to catalyze the critical chemical reactions in these devices. Functionalized carbon nanomaterials such as heteroatom-doped and molecule-adsorbed graphene can be used as metal-free catalysts to replace the expensive and scarce platinum-based catalysts for the energy storage and conversion. Traditionally, experimental studies on the catalytic performance of carbon nanomaterials have been conducted extensively, however, there is a lack of computational studies to guide the experiments for rapid search for the best catalysts. In addition, theoretical mechanism and the rational design principle towards ORR and OER also need to be fully understood. In this dissertation, density functional theory calculations are performed to calculate the thermodynamic and electrochemical properties of heteroatom-doped graphene and molecule-adsorbed graphene for ORR and OER. Gibb's free energy, overpotential, charge transfer and edge effect are evaluated. The charge transfer analysis show the positive charges on the graphene surface caused by the heteroatom, hetero-edges and the adsorbed organic molecules play an essential role in improving the electrochemical properties of the carbon nanomaterials. Based on the calculations, design principles are introduced to rationally design and predict the electrochemical properties of doped graphene and molecule-adsorbed graphene as metal-free catalysts for ORR and OER. An intrinsic descriptor is discovered for the first time, which can be used as a materials parameter for rational design of the metal-free catalysts with carbon nanomaterials for energy storage and conversion. The success of the design principle provides a better understanding of the mechanism behind ORR and OER and a screening approach for the best catalyst for energy storage and conversion

Potential Arrhythmogenic Role of TRPC Channels and Store-Operated Calcium Entry Mechanism in Mouse Ventricular Myocytes

Background and Purpose: Store-operated calcium entry (SOCE) is an important physiological phenomenon that extensively mediates intracellular calcium ion (Ca2+) load. It has been previously found in myocytes isolated from neonatal or diseased hearts. We aimed to determine its existence, molecular nature in undiseased hearts and its potential arrhythmogenic implications under hyperactive conditions.Experimental Approach: Ventricular myocytes isolated from adult FVB mice were studied by using Ca2+ imaging and whole-cell perforated patch-clamp recording. In addition, lead II ECGs were recorded in isolated Langendorff-perfused mice hearts. Functional TRPC channel antibodies and inhibitors, and TRPC6 activator hyperforin were used.Key Results: In this study, we demonstrate the existence and contribution of SOCE in normal adult mouse cardiac myocytes. For an apparent SOCE activation, complete depletion of sarcoplasmic reticulum (SR) Ca2+ by employing both caffeine (10 mM) and thapsigargin (1 μM) or cyclopiazonic acid (10 μM) was required. Consistent with the notion that SOCE may be mediated by heteromultimeric TRPC channels, SOCEs observed from those myocytes were significantly reduced by the pretreatment with anti-TRPC1, 3, and 6 antibodies as well as by gadolinium, a non-selective TRPC channel blocker. In addition, we showed that SOCE may regulate spontaneous SR Ca2+ release, Ca2+ waves, and triggered activities which may manifest cardiac arrhythmias. Since the spontaneous depolarization in membrane potential preceded the elevation of intracellular Ca2+, an inward membrane current presumably via TRPC channels was considered as the predominant cause of cellular arrhythmias. The selective TRPC6 activator hyperforin (0.1–10 μM) significantly facilitated the SOCE, SOCE-mediated inward current, and calcium load in the ventricular myocytes. ECG recording further demonstrated the proarrhythmic effects of hyperforin in ex vivo mouse hearts.Conclusion and Implications: We suggest that SOCE, which is at least partially mediated by TRPC channels, exists in adult mouse ventricular myocytes. TRPC channels and SOCE mechanism may be involved in cardiac arrhythmogenesis via promotion of spontaneous Ca2+ waves and triggered activities under hyperactivated conditions

Design Principles for Dual-Element-Doped Carbon Nanomaterials as Efficient Bifunctional Catalysts for Oxygen Reduction and Evolution Reactions

Dual-element-doped carbon nanomaterials are demonstrated to be more efficient bifunctional catalysts than noble metals to catalyze two key chemical reactions: oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in regenerative fuel cells and metal–air batteries. Moreover, to accelerate the search for the best metal-free catalysts, an activity descriptor is identified for the codoped carbon nanomaterials, which correlates doping structures to their catalytic activities. These predictions are supported by experimental data. Our work also predicts that the synergistic effect of codoping occurs within a certain distance between the codopants. The descriptor enables rational design of new bifunctional catalysts

A Video Security Verification Method Based on Blockchain

This paper proposes a blockchain-based video se- curity verification method. In order to ensure the security of the video, we use data hiding technology to embed message that can ensure the security of the video into the video, at the same time, in order to improve the non-tamperability and non-forgery of data hiding. We construct the hash value of the message embedded in the original video, the hash value of the carrier video (video with embedded message) and the attribute message of the video as video metadata, and upload the video metadata to the blockchain network. Comparing the message extracted from the carrier video with the video metadata stored on the blockchain can achieve double verification of the video. At the same time, distributed storage of carrier video through IPFS can effectively store and manage large-scale video data, ensuring the security and high availability of videos

Petrogenesis and tectonic setting of the Middle Permian A-type granites in Altay, northwestern China: Evidences from geochronological, geochemical, and Hf isotopic studies

The Jiangjunshan and Dakalasu alkali-feldspar granites are located in the central part of the Chinese Altay orogen. In this paper, we present detailed geochemical, zircon U-Pb, and Hf isotopic data of these granites. The Jiangjunshan and Dakalasu alkali-feldspar granites show a high content of SiO2 (72.05-73.27 and 69.55-71.04wt%, respectively), total alkalis (Na2O+K2O=8.41-8.71 and 7.24-8.66wt%, respectively), and high-field strength elements (Zr+Nb+Ce+Y=400.3-482.9 and 156.7-339.3ppm, respectively), as well as high Ga/Al ratios (10,000xGa/Al=3.46-4.19 and 2.62-3.28, respectively) and depletion in Ba, Nb, Sr, and Ti, showing geochemical characteristics similar to those of A-type granites. Zircon U-Pb dating of the Jiangjunshan and Dakalasu alkali-feldspar granites yielded weighted mean dating Pb-206/U-238 ages of 268.3 +/- 1.9 and 270.4 +/- 1.9Ma, respectively, indicating that these granites intruded during the Permian. The Jiangjunshan and Dakalasu alkali-feldspar granites show highly variable zircon epsilon(Hf)(t) values ranging from -7.0 to +5.6, implying that these granites originated from a mixing of mantle-derived magma with crustal materials. Our data on the Jiangjunshan and Dakalasu alkali-feldspar granites, coupled with previous studies of Permian magmatism and metamorphism, suggest that the tectonic regime was in a postcollisional extensional environment in the Chinese Altay orogen during the Permian. Therefore, the change in stress from compression to extension and asthenospheric upwelling triggered by slab break-off plays a significant role in the generation of Jiangjunshan and Dakalasu alkali-feldspar granites