Design of higher Chern number two-band structures from topological defect perspective.

In this article, we propose two methods for designing higher Chern number models from the topological defect perspective. Based on the fact that the Chern number is equal to a summation of the charges of meron defects, we show that the higher Chern number structures can be realized by either moving the positions of merons or increasing the amount of them. The combination of the two methods is also verified to be a viable approach. We shall construct several models and investigate their energy spectrum. More than one gapless state can be observed on the edges of these models. Expectedly, our theory promises to provide not only a simple approach to obtain the Chern number without computing any integrals, but also a practical technique for new material design.

Topological defects in Haldane model and higher Chern numbers in monolayer graphene.

We consider the Haldane model, a two-band model in monolayer graphene with non-trivial Chern numbers. Two types of topological defects, monopoles and merons, are derived from the model: (a) the monopole defects occur at the Dirac points, where the system experiences a topological transition and the Chern numberCtakes an indeterminate value. The sign-change of the mass term after this transition indicates different topological states labeled by differentCnumbers; (b) the meron defects occur as per a varying mass term. Summing up the topological charges of the merons leads to theCevaluation for the energy bands of an insulating bulk, and the result we obtain is in full agreement to the past literature. Furthermore, in this paper we propose a high-Cmodel through studying the limitation behavior of the Hamiltonian vector in the neighborhood of the topological defects. It is discovered that two conducting states may arise form the edges, where the lower band of the insulating bulk carries a higher Chern number,C=±2.

In Situ CVD Derived Co-N-C Composite as Highly Efficient Cathode for Flexible Li-O2 Batteries.

To promote the development of high energy Li-O2 batteries, it is important to design and construct a suitable and effective oxygen-breathing cathode. Herein, activated cobalt-nitrogen-doped carbon nanotube/carbon nanofiber composites (Co-N-CNT/CNF) as the effective cathodes for Li-O2 batteries are prepared by in situ chemical vapor deposition (CVD). The unique architecture of these electrodes facilitates the rapid oxygen diffusion and electrolyte penetration. Meanwhile, the nitrogen-doped carbon nanotube/carbon nanofiber (N-CNT/CNF) and Co/CoNx serve as reaction sites to promote the formation/decomposition of discharge product. Li-O2 batteries with Co-N-CNT/CNF cathodes exhibit superior electrochemical performance in terms of a positive discharge plateau (2.81 V) and a low charge overpotential (0.61 V). Besides, Li-O2 batteries also present a high discharge capacity (11512.4 mAh g-1 at 100 mA g-1 ), and a long cycle life (130 cycles). Meanwhile, the Co-N-CNT/CNF cathode also has an excellent flexibility, thus the assembled flexible battery with Co-N-CNT/CNF can work normally and hold a wonderful capacity rate under various bending conditions.

A Water-/Fireproof Flexible Lithium-Oxygen Battery Achieved by Synergy of Novel Architecture and Multifunctional Separator.

To meet the increasing demands for portable and flexible devices in a rapidly developing society, it is urgently required to develop highly safe and flexible electrochemical energy-storage systems. Flexible lithium-oxygen batteries with high theoretical specific energy density are promising candidates; however, the conventional half-open structure design prevents it from working properly under water or fire conditions. Herein, as a proof-of-concept experiment, a highly safe flexible lithium-oxygen battery achieved by the synergy of a vital multifunctional structure design and a unique composite separator is proposed and fabricated. The structure can effectively prevent the invasion of water from the environment and combustion, which is further significantly consolidated with the help of a polyimide and poly(vinylidene fluoride-co-hexafluoropropylene) composite separator, which holds good water resistance, thermal stability, and ionic conductivity. Unexpectedly, the obtained lithium-oxygen battery exhibits superior flexibility, water resistance, thermal resistance, and cycling stability (up to 218 cycles; at a high current of 1 mA and capacity of 4 mA h). This novel water/fireproof, flexible lithium-oxygen battery is a promising candidate to power underwater flexible electronics.

Decorating carbon nanofibers with Mo2C nanoparticles towards hierarchically porous and highly catalytic cathode for high-performance Li-O2 batteries.

A facile synthesis of the hierarchically porous cathode with Mo2C nanoparticles through the electrospinning technique and heat treatment is proposed. The carbonization temperature of the precursors is the key factor for the formation of Mo2C nanoparticles on the carbon nanofibers (MCNFs). Compared with the Mo2N nanoparticles embedded into N-doped carbon nanofibers film (MNNFs) and N-doped carbon nanofibers film (NFs), the battery with MCNFs cathode is capable of operation with a high-capacity (10,509 mAh g-1 at 100 mA g-1), a much reduced discharge-charge voltage gap, and a long-term life (124 cycles at 200 mA g-1 with a specific capacity limit of 500 mAh g-1). These excellent performances are derived from the synergy of the following advantageous factors: (1) the hierarchically self-standing and binder-free structure of MCNFs could ensure the high diffusion flux of Li+ and O2 as well as avoid clogging of the discharge product, bulk Li2O2; (2) the well dispersed Mo2C nanoparticles not only afford rich active sites, but also facilitate the electronic transfer for catalysis.

Nanoengineered Ultralight and Robust All-Metal Cathode for High-Capacity, Stable Lithium-Oxygen Batteries.

The successful development of Li-O2 battery technology depends on resolving the issue of cathode corrosion by the discharge product (Li2O2) and/or by the intermediates (LiO2) generated during cell cycling. As an important step toward this goal, we report for the first time the nanoporous Ni with a nanoengineered AuNi alloy surface directly attached to Ni foam as a new all-metal cathode system. Compared with other noncarbonaceous cathodes, the Li-O2 cell with an all-metal cathode is capable of operation with ultrahigh specific capacity (22,551 mAh g-1 at a current density of 1.0 A g-1) and long-term life (286 cycles). Furthermore, compared with the popularly used carbon cathode, the new all-metal cathode is advantageous because it does not show measurable reactivity toward Li2O2 and/or LiO2. As a result, extensive cyclability (40 cycles) with 87.7% Li2O2 formation and decomposition was obtained. These superior properties are explained by the enhanced solvation-mediated formation of the discharge products as well as the tailored properties of the all-metal cathode, including intrinsic chemical stability, high specific surface area, highly porous structure, high conductivity, and superior mechanical stability.

High-Performance Integrated Self-Package Flexible Li-O2 Battery Based on Stable Composite Anode and Flexible Gas Diffusion Layer.

With the rising development of flexible and wearable electronics, corresponding flexible energy storage devices with high energy density are required to provide a sustainable energy supply. Theoretically, rechargeable flexible Li-O2 batteries can provide high specific energy density; however, there are only a few reports on the construction of flexible Li-O2 batteries. Conventional flexible Li-O2 batteries possess a loose battery structure, which prevents flexibility and stability. The low mechanical strength of the gas diffusion layer and anode also lead to a flexible Li-O2 battery with poor mechanical properties. All these attributes limit their practical applications. Herein, the authors develop an integrated flexible Li-O2 battery based on a high-fatigue-resistance anode and a novel flexible stretchable gas diffusion layer. Owing to the synergistic effect of the stable electrocatalytic activity and hierarchical 3D interconnected network structure of the free-standing cathode, the obtained flexible Li-O2 batteries exhibit superior electrochemical performance, including a high specific capacity, an excellent rate capability, and exceptional cycle stability. Furthermore, benefitting from the above advantages, the as-fabricated flexible batteries can realize excellent mechanical and electrochemical stability. Even after a thousand cycles of the bending process, the flexible Li-O2 battery can still possess a stable open-circuit voltage, a high specific capacity, and a durable cycle performance.

Ultrathin, Lightweight, and Wearable Li-O2 Battery with High Robustness and Gravimetric/Volumetric Energy Density.

An ultrathin, lightweight, and wearable Li-O2 battery with a novel segmented structure is first fabricated by employing a "break up the whole into parts" strategy. Superior battery performance including low overpotential, high specific capacity, good rate capability, excellent cycle stability, and high gravimetric/volumetric energy density (294.68 Wh kg-1 /274.06 Wh L-1 ) is successfully achieved even under repeatedly various deformation.

Cathode Surface-Induced, Solvation-Mediated, Micrometer-Sized Li2 O2 Cycling for Li-O2 Batteries.

The "nonsticky" surface of a highly stable RuO2 /carbon nanotube cathode enhances the formation and decomposition of cathode surface-induced, solvation-mediated, micrometer-sized discharge products Li2 O2 in Li-O2 batteries and thus significantly improves the specific capacity, overpotentials, and cycle life. These findings contribute to a new understanding how the cathode surface controls Li-O2 electrochemistry.

Flexible and Foldable Li-O2 Battery Based on Paper-Ink Cathode.

A flexible freestanding air cathode inspired by traditional Chinese calligraphy art is built. When this novel electrode is employed as both a new concept cathode and current collector, to replace conventional rigid and bulky counterparts, a highly flexible and foldable Li-O2 battery with excellent mechanical strength and superior electrochemical performance is obtained.

Artificial Protection Film on Lithium Metal Anode toward Long-Cycle-Life Lithium-Oxygen Batteries.

An artificial while very stable solid electrolyte interphase film is formed on lithium metal using an electrochemical strategy. When this protected Li anode is first used in a Li-O2 battery, the film formed on the anode can effectively suppress the parasitic reactions on the Li anode/electrolyte interface and significantly enhance the cycling stability of the Li-O2 battery.

Decreased expression of complement regulatory proteins, CD55 and CD59, on peripheral blood leucocytes in patients with type 2 diabetes and macrovascular diseases.

BACKGROUND: Macro- and microvascular diseases are the leading cause of morbidity and mortality in diabetic patients, but their mechanisms remain unclear. Recent reports provide evidence that the levels of CD55 and CD59 are decreased in diabetic microvascular diseases. However, very little is known about the levels of CD55 and CD59, the relationship between them and carotid artery intima-media thickness, and the effects of statins on CD55 and CD59 in diabetic macrovascular diseases. METHODS: The mean fluorescence intensity (MFI) of CD55 and CD59 expression on peripheral blood leucocyte subsets (lymphocytes, monocytes and neutrophils) was studied using flow cytometry, and carotid artery intima-media thickness was measured using B-mode ultrasonography in 23 healthy subjects (controls), 19 patients with type 2 diabetes (T2DM), and 43 patients with type 2 diabetes and macrovascular diseases (T2DM-M). The patients with T2DM-M were assigned to two subgroups based on whether statins were used: group with statins (n = 23) and group without statins (n = 20). RESULTS: Compared with the controls and T2DM, the MFI of CD55 positive neutrophils was significantly lower in T2DM-M (P = 0.049 vs controls and P = 0.033 vs T2DM); similarly, the MFI of CD59 positive monocytes was also lower in T2DM-M (P = 0.038 vs controls and P = 0.043 vs T2DM). The MFI of CD59 positive neutrophils in T2DM-M was lower than in T2DM (P = 0.032). The levels of CD55 and CD59 were negatively associated with age and blood pressure (r = -0.245 - -0.352, P = 0.041 - 0.003), but not acute-phase reactants and carotid artery intima-media thickness. The levels of CD55 and CD59 increased after treatment with statins, but the results were not significantly different (P > 0.05). CONCLUSIONS: CD55 and CD59 expressions on peripheral blood leucocytes are decreased in T2DM patients with macrovascular diseases. The results suggest that the decreased levels of complement regulatory proteins might play an important role in diabetic macrovascular diseases.

[Role of gap junction in ischemic preconditioning].

OBJECTIVE: To investigate the role of gap junction in ischemic preconditioning (IPC). METHODS: Sprague-Dawley rats were subjected to a 30 min coronary artery occlusion followed by 4 h of reperfusion (I/R). Rats were divided into seven groups: I/R, IPC/R, IPC/R + 5-hydroxydecanoic acid (mitochondrial ATP sensitive potassium channel antagonist), I/R + diazoxide (mitochondrial ATP sensitive potassium channel agonist), I/R + 5-hydroxydecanoic acid + diazoxide, I/R + 18beta-glycyrrhetinic acid (gap junction blocker) and I/R + 18beta-glycyrrhetinic acid + 5-hydroxydecanoic acid. Hemodynamics and myocardial infarct size were measured and connexin43 phosphorylation and subcellular distribution were determined by quantitative immunoblotting and confocal immunofluorescence. RESULTS: Infarct size was reduced in IPC/R, I/R + diazoxide and I/R + 18beta-glycyrrhetinic acid group (13.34% +/- 7.87%, 11.02% +/- 2.24%, and 15.03% +/- 11.35%, respectively; P < 0.001 vs. I/R group: 45.81% +/- 7.91%). 5-hydroxydecanoic acid abolished the cardioprotective effects of IPC and diazoxide (46.57% +/- 5.36% and 47.36% +/- 3.17%; P > 0.05 vs. I/R) but not the effects of glycyrrhetinic acid (14.60% +/- 7.36%; P < 0.001 vs. I/R). Phosphorylation of connexin43 was significantly increased, dephosphorylation and connexin43 intracellular redistribution significantly decreased (Cx43 size in the cellular membrane 1.00% +/- 0.35% and 0.83% +/- 0.31%, P < 0.001 vs. I/R: 0.19% +/- 0.06%) by IPC and diazoxide and these effects could be abolished by 5-hydroxydecanoic acid. CONCLUSION: Ischemic preconditioning could reduce myocardial infarction size by activating mitochondrial ATP sensitive potassium channel and modulating connexin43 phosphorylation and internalization.