Type Ia supernovae (SNe Ia) play a prominent role in understanding the evolution of the Universe. They are thought to be thermonuclear explosions of mass-accreting carbon-oxygen white dwarfs (CO WDs) ...in binaries, although the mass donors of the accreting WDs are still not well determined. In this article, I review recent studies on mass-accreting WDs, including H- and He-accreting WDs. I also review currently most studied progenitor models of SNe Ia, i.e., the single-degenerate model (including the WD+MS channel, the WD+RG channel and the WD+He star channel), the double-degenerate model (including the violent merger scenario) and the sub-Chandrasekhar mass model. Recent progress on these progenitor models is discussed, including the initial parameter space for producing SNe Ia, the binary evolutionary paths to SNe Ia, the progenitor candidates for SNe Ia, the possible surviving companion stars of SNe Ia, some observational constraints, etc. Some other potential progenitor models of SNe Ia are also summarized, including the hybrid CONe WD model, the core-degenerate model, the double WD collision model, the spin-up/spin-down model and the model of WDs near black holes. To date, it seems that two or more progenitor models are needed to explain the observed diversity among SNe Ia.
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bstract
We utilize a novel method for the partial-wave unitarity recently suggested in 1 to analyse the hypergeometric Coon amplitude. In this approach we use a new type of harmonic numbers as a ...basis. Owing to the properties of the harmonic numbers this method bypasses lots of difficulties and can be used to derive a clear and unified form for the partial-wave coefficients. This new approach further streamlines the partial-wave unitarity analysis. As an instance, we re-derive the unitarity bounds from Regge trajectory analysis and find the new critical condition of the hypergeometric Coon amplitude. Our new method also benefits the discussion on the various limits of this amplitude. Specifically, we demonstrate the manifest positivity of super string below
d ≤
10 from our new perspective.
The introduction of oxygen vacancies (Ov) has been regarded as an effective method to enhance the catalytic performance of photoanodes in oxygen evolution reaction (OER). However, their stability ...under highly oxidizing environment is questionable but was rarely studied. Herein, NiFe‐metal–organic framework (NiFe‐MOFs) was conformally coated on oxygen‐vacancy‐rich BiVO4 (Ov‐BiVO4) as the protective layer and cocatalyst, forming a core–shell structure with caffeic acid as bridging agent. The as‐synthesized Ov‐BiVO4@NiFe‐MOFs exhibits enhanced stability and a remarkable photocurrent density of 5.3±0.15 mA cm−2 at 1.23 V (vs. RHE). The reduced coordination number of Ni(Fe)‐O and elevated valence state of Ni(Fe) in NiFe‐MOFs layer greatly bolster OER, and the shifting of oxygen evolution sites from Ov‐BiVO4 to NiFe‐MOFs promotes Ov stabilization. Ovs can be effectively preserved by the coating of a thin NiFe‐MOFs layer, leading to a photoanode of enhanced photocurrent and stability.
A core–shell Ov‐BiVO4@NiFe‐MOFs photoanode was constructed via a coordination‐assisted self‐assembly method. A NiFe‐MOFs thin layer acts as protective layer and cocatalyst to shift active sites from oxygen vacancies to NiFe‐MOFs, leading to improved stability and activity for OER. This molecular‐based approach tailors the coordination and electronic structure of active sites and provides mechanistic insights for rational design of photocatalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) are two emerging and explosively growing families of crystalline porous materials (CPMs). These robust frameworks are ...characterized by their extraordinary porosity, tremendous structural diversity, and versatile functional tunability with precision at the molecular level. In this review, we present recent milestones of MOFs and COFs in the fields of batteries and supercapacitors, two important technologies in electrochemical energy storage (EES), and highlight the functions that a CPM can offer in EES devices, including the storage of electrochemical energy, stabilization of electrode materials, pathways for charge transport, manipulation on mass transport, and promotion of electrochemical reactions. Key requirements for each function are discussed, with future directions provided for further development.
This review highlights the functions of metal-organic frameworks and covalent-organic frameworks in batteries and supercapacitors.
Phospholipids are major constituents of biological membranes. The fatty acyl chain composition of phospholipids determines the biophysical properties of membranes and thereby affects their impact on ...biological processes. The composition of fatty acyl chains is also actively regulated through a deacylation and reacylation pathway called Lands' cycle. Recent studies of mouse genetic models have demonstrated that lysophosphatidylcholine acyltransferases (LPCATs), which catalyze the incorporation of fatty acyl chains into the
sn
-2 site of phosphatidylcholine, play important roles in pathophysiology. Two LPCAT family members, LPCAT1 and LPCAT3, have been particularly well studied. LPCAT1 is crucial for proper lung function due to its role in pulmonary surfactant biosynthesis. LPCAT3 maintains systemic lipid homeostasis by regulating lipid absorption in intestine, lipoprotein secretion, and de novo lipogenesis in liver. Mounting evidence also suggests that changes in LPCAT activity may be potentially involved in pathological conditions, including nonalcoholic fatty liver disease, atherosclerosis, viral infections, and cancer. Pharmacological manipulation of LPCAT activity and membrane phospholipid composition may provide new therapeutic options for these conditions.
Several studies have investigated the determinants of CO2 emission; however, prior research has been neglected to examine the emission of CO2 due to the trade of goods and services and royalty and ...licensing fees. To do so, the present work contributes to research stream by investigating the relationship between imported technology and environmental degradation within the time span of 1980–2011 in the case of China. Based on the Auto Regressive Distributive Lag (ARDL) model and Vector Error Correction (VECM) Granger causality approach we draw an inference that imported technologies mainly contributes to CO2 emission in the long run path for China. The long run causality results originates bi-directional causality between imported technology and CO2 emission. Moreover, in the long run, feedback hypothesis is also detected between energy consumption and CO2 emission. To ensure the stability of model and reliability of results for policy implication numerous significant tests are carried out. This study suggests that Government of China needs to expand input in R&D for higher technological strength and intellectual property rights management capacity, which will be favorable for the protection of the environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
As a promising two‐dimensional conjugated polymer, graphitic carbon nitride (g‐C3N4) has been utilized as a low‐cost, robust, metal‐free, and visible‐light‐active photocatalyst in the field of solar ...energy conversion. This Review mainly describes the latest advances in g‐C3N4 photocatalysts for water splitting. Their application in CO2 conversion, organosynthesis, and environmental purification is also briefly discussed. The methods to modify the electronic structure, nanostructure, crystal structure, and heterostructure of g‐C3N4, together with correlations between its structure and performance are illustrated. Perspectives on the challenges and opportunities for the future exploration of g‐C3N4 photocatalysts are provided. This Review will promote the utilization of g‐C3N4 materials in the fields of photocatalysis, energy conversion, environmental remediation, and sensors.
Metal‐free photocatalysis: Recent progress in g‐C3N4 photocatalysis is highlighted. The four fundamental approaches for modification of g‐C3N4 photocatalysts are discussed: electronic structure modulation, nanostructure design, crystal‐structure engineering, and heterostructure construction. The application of g‐C3N4 photocatalysts are briefly summarized and the opportunities and challenges in this field are discussed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
An optical fiber biosensor based on gold nanoparticles and protein A co-modified Au film coated photonic crystal fiber (Au-PCF) is proposed and demonstrated for human IgG detection. For the electric ...field coupling effect between surface plasmon resonance (SPR) of Au film and localized surface plasmon resonance (LSPR) of gold nanoparticles, the refractive index sensitivity can be enhanced significantly. Besides, goat anti-human IgG is immobilized by protein A modified on the gold nanoparticles surface to interact with human IgG. Protein A can specifically bind the Fc region of the antibodies and has a high degree of orientation for capturing antibodies. Experimental results indicate that the refractive index sensitivity of Au-PCF sensor modified gold nanoparticles reaches 3915 nm/RIU, which is about 1.6 times higher than the Au-PCF sensor without gold nanoparticles modified. The lowest detection limit of human IgG based on gold nanoparticles and protein A co-modified Au-PCF sensor is 37 ng/mL, which is about 2.4 times and 6.3 times lower than gold nanoparticles-Au-PCF sensor and Au-PCF sensor, respectively. Such a sensitivity enhanced optical fiber biosensor based on SPR-LSPR coupling effect has potential application in clinical disease diagnosis and immunoassays.
In this paper, we propose a joint optimization design for a non-orthogonal multiple access (NOMA)-based satellite-terrestrial integrated network (STIN), where a satellite multicast communication ...network shares the millimeter wave spectrum with a cellular network employing NOMA technology. By assuming that the satellite uses multibeam antenna array and the base station employs uniform planar array, we first formulate a constrained optimization problem to maximize the sum rate of the STIN while satisfying the constraint of per-antenna transmit power and quality-of-service requirements of both satellite and cellular users. Since the formulated optimization problem is NP-hard and mathematically intractable, we develop a novel user pairing scheme so that more than two users can be grouped in a cluster to exploit the NOMA technique. Based on the user clustering, we further propose to transform the non-convex problem into an equivalent convex one, and present an iterative penalty function-based beamforming (BF) scheme to obtain the BF weight vectors and power coefficients with fast convergence. Simulation results confirm the effectiveness and superiority of the proposed approach in comparison with the existing works.
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