As a promising substitute for fossil fuels, hydrogen has emerged as a clean and renewable energy. A key challenge is the efficient production of hydrogen to meet the commercial-scale demand of ...hydrogen. Water splitting electrolysis is a promising pathway to achieve the efficient hydrogen production in terms of energy conversion and storage in which catalysis or electrocatalysis plays a critical role. The development of active, stable, and low-cost catalysts or electrocatalysts is an essential prerequisite for achieving the desired electrocatalytic hydrogen production from water splitting for practical use, which constitutes the central focus of this review. It will start with an introduction of the water splitting performance evaluation of various electrocatalysts in terms of activity, stability, and efficiency. This will be followed by outlining current knowledge on the two half-cell reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), in terms of reaction mechanisms in alkaline and acidic media. Recent advances in the design and preparation of nanostructured noble-metal and non-noble metal-based electrocatalysts will be discussed. New strategies and insights in exploring the synergistic structure, morphology, composition, and active sites of the nanostructured electrocatalysts for increasing the electrocatalytic activity and stability in HER and OER will be highlighted. Finally, future challenges and perspectives in the design of active and robust electrocatalysts for HER and OER towards efficient production of hydrogen from water splitting electrolysis will also be outlined.
In postmitotic neurons, the activation of RAS family small GTPases regulates survival, growth and differentiation. Dysregulation of RAS or its major effector pathway, the cascade of RAF-, ...mitogen-activated and extracellular-signal regulated kinase kinases (MEK), and extracellular-signal regulated kinases (ERK) causes the RASopathies, a group of neurodevelopmental disorders whose pathogenic mechanisms are the subject of intense research. I here summarize the functions of RAS-RAF-MEK-ERK signaling in neurons
, and discuss perspectives for harnessing this pathway to enable novel treatments for nervous system injury, the RASopathies, and possibly other neurological conditions.
Liquid‐metal (LM)‐based flexible and stretchable electronics have attracted widespread interest in wearable computing, human–machine interaction, and soft robotics. However, many current examples are ...one‐off prototypes, whereas future implementation requires mass production. To address this critical challenge, an integrated multimaterial 3D printing process composed of direct ink writing (DIW) of sealing silicone elastomer and special LM‐silicone (LMS) inks for manufacturing high‐performance LM‐based flexible and stretchable electronics is presented. The LMS ink is a concentrated mixture of LM microdroplets and silicone elastomer and exhibits excellent printability for DIW printing. Guided by a verified theoretical model, a printing process with high resolution and high speed can be easily implemented. Although LMS is not initially conductive, it can be activated by pressing or freezing. Activated LMS possesses good conductivity and significant electrical response to strain. Owing to LMS's unique structure, LMS‐embedded flexible electronics exhibit great damage mitigation, in that no leaking occurs even when damaged. To demonstrate the flexibility of this process in fabricating LM‐based flexible electronics, multilayer soft circuits, strain sensors, and data gloves are printed and investigated. Notably, utilizing LMS's unique activating property, some functional circuits such as one‐time pressing/freezing‐on switch can be printed without any structural design.
A special liquid‐metal–silicone (LMS) ink and corresponding multimaterial printing process are developed for fabricating all‐printed flexible and stretchable electronics. It exhibits excellent printability and good conductivity, significant electrical response to deformation, and great reliability. Thanks to these, all‐printed flexible electronics with high throughput, resolution, and device reliability can be easily fabricated.
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•Existence of MPs was observed in guppy gut.•Exposure to MPs decreased the gut digestive enzymes activities.•Exposure to MPs stimulated the expression of gut immune response.•Exposure to MPs induced ...gut microbiota dysbiosis.
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Microplastics (MPs) are widely distributing in aquatic environment. They are easily ingested by aquatic organisms and accumulate in digestive tract especially of intestine. To explore the potential effects of MPs on intestine, here we, using juvenile guppy (Poecilia reticulata) as experimental animal, investigated the response characteristics of digestion, immunity and gut microbiota. After exposure to 100 and 1000 μg/L concentrations of MPs (polystyrene; 32–40 μm diameters) for 28 days, we observed that MPs could exist in guppy gut and induce enlargement of goblet cells. Activities of digestive enzymes (trypsin, chymotrypsin, amylase and lipase) in guppy gut generally reduced. MPs stimulated the expression of immune cytokines (TNF-α, IFN-γ, TLR4 and IL-6). Through high throughput sequencing of 16S rRNA gene, decreases in diversity and evenness and changed composition of microbiota were found in guppy gut. PICRUSt analysis revealed that MPs might have effects on intestinal microbiota functions, such as inhibition of metabolism and repair pathway. Our findings suggested that MPs could retain in the gut of juvenile guppy, impair digestive performance, stimulate immune response and induce microbiota dysbiosis in guppy gut. The results obtained here provide new insights into the potential risks of MPs to aquatic animals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Massive emissions of CO2 have caused environmental problems all over the world. The fixation of CO2 into cyclic carbonates is regarded as an effective way of capturing and utilizing CO2. Ionic liquid ...catalysts (ILCs) have received great attention and been employed for catalyzing the above reaction in recent years due to their unique properties. However, there are still a few problems requiring solutions in order to finally find the “ideal catalyst”. Herein, we reviewed a number of recent related literature. The progresses of both homogeneous and heterogeneous ILCs were discussed to find out where we are and which directions to work on. The effects of cations and anions of ionic liquids (ILs), functional groups, reaction phase states, structures of supports, preparation methods of supported ionic liquids (SILs), and interactions between the ILs and supports were investigated systematically. Accordingly, basic principles of designing ILCs for the title reaction are summarized and directions of future investigations are highlighted.
Designing ILs: Homogeneous and heterogeneous ionic liquid catalysts for the cycloaddition reaction of CO2 and epoxides to synthesize cyclic carbonates were reviewed. The effects of cations and anions of ionic liquids, functional groups, reaction phase states, structures of supports, preparation methods of supported ionic liquids, and interactions between the ILs and supports were investigated. Accordingly, basic principles of designing ionic liquid catalysts for the reaction were summarized.
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•Three “M-glasses” alloys and one B2-containing Mg-based glassy composites have been classified.•Microstructure, GFA and mechanical behaviours have been discussed and compared.•Both as-cast and ...annealed “M-glasses” BMG composites are categorized and discussed.•The possible future work on “M-glasses” composites has been proposed.
The brittleness and work-softening of Bulk Metallic Glasses (BMGs) prevent their wide applications as structural engineering materials. In order to settle this problem, the BMG composites containing B2 phase with lower shear modulus and body-centred cubic structure (BCC) via in-situ or ex-situ modes were developed. Although a lot of attempts have been proposed to enhance the plastic deformation, the work-softening remained unsettled before the concept of transformation-induced plasticity (TRIP) in steels was introduced about ten years ago. The BMG composites incorporating the B2 phase possess the macroscopically plastic deformability and work-hardening induced by the martensitic transformation (MT) from B2 to B19′ or B33 upon uniaxial loading. Since then, many studies focus on formation of the B2 phase in Zr- and Ti-based BMG composites and the effect of B2 phase on tensile plasticity and strain-hardening. Although the enhanced plastic strain and work-hardening under compression have been extensively obtained, the improved tensile ductility and work-hardening of BMG composites have been scarcely achieved. To get a thorough understanding about formation of the B2 phase and its effect on mechanical properties, a comprehensive review is critically important and necessary, which is the aim of the present work.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells. However, under fuel cell operating conditions, state-of-the-art oxygen ...reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells.
The rapid progress of proton exchange membrane fuel cells (PEMFCs) and alkaline exchange membrane fuel cells (AMFCs) has boosted the hydrogen economy concept via diverse energy applications in the ...past decades. For a holistic understanding of the development status of PEMFCs and AMFCs, recent advancements in electrocatalyst design and catalyst layer optimization, along with cell performance in terms of activity and durability in PEMFCs and AMFCs, are summarized here. The activity, stability, and fuel cell performance of different types of electrocatalysts for both oxygen reduction reaction and hydrogen oxidation reaction are discussed and compared. Research directions on the further development of active, stable, and low‐cost electrocatalysts to meet the ultimate commercialization of PEMFCs and AMFCs are also discussed.
The development of fuel cells is of great significance for achieving a sustainable society. Recent progress in cathodic electrocatalysts for proton exchange membrane fuel cells and anodic and cathodic electrocatalysts for alkaline exchange membrane fuel cells is summarized. The rational design strategies, structure evolution, activities, fuel cell performance, and durability of noble‐metal‐ and non‐noble‐metal‐based electrocatalysts are discussed.
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Orchidaceae (with >28,000 orchid species) are one of the two largest plant families, with economically and ecologically important species, and occupy global and diverse niches with primary ...distribution in rainforests. Among orchids, 70% grow on other plants as epiphytes; epiphytes contribute up to ~50% of the plant diversity in rainforests and provide food and shelter for diverse animals and microbes, thereby contributing to the health of these ecosystems. Orchids account for over two‐thirds of vascular epiphytes and provide an excellent model for studying evolution of epiphytism. Extensive phylogenetic studies of Orchidaceae and subgroups have ;been crucial for understanding relationships among many orchid lineages, although some uncertainties remain. For example, in the largest subfamily Epidendroideae with nearly all epiphytic orchids, relationships among some tribes and many subtribes are still controversial, hampering evolutionary analyses of epiphytism. Here we obtained 1,450 low‐copy nuclear genes from 610 orchid species, including 431 with newly generated transcriptomes, and used them for the reconstruction of robust Orchidaceae phylogenetic trees with highly supported placements of tribes and subtribes. We also provide generally well‐supported phylogenetic placements of 131 genera and 437 species that were not sampled by previous plastid and nuclear phylogenomic studies. Molecular clock analyses estimated the Orchidaceae origin at ~132 million years ago (Ma) and divergences of most subtribes from 52 to 29 Ma. Character reconstruction supports at least 14 parallel origins of epiphytism; one such origin was placed at the most recent common ancestor of ~95% of epiphytic orchids and linked to modern rainforests. Ten occurrences of rapid increase in the diversification rate were detected within Epidendroideae near and after the K‐Pg boundary, contributing to ~80% of the Orchidaceae diversity. This study provides a robust and the largest family‐wide Orchidaceae nuclear phylogenetic tree thus far and new insights into the evolution of epiphytism in vascular plants.
Orchidaceae are one of two largest angiosperm families with ~28,000 species and mainly grow as epiphytes on trees in rainforests. Evolutionary analyses of 610 orchids with 431 new transcriptomes provides a robust Orchidaceae phylogeny and suggests that the expansion of rainforests probably promoted the origin and diversification of epiphytic orchids.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract This study offers a novel 3D bioprinting method based on hollow calcium alginate filaments by using a coaxial nozzle, in which high strength cell-laden hydrogel 3D structures with built-in ...microchannels can be fabricated by controlling the crosslinking time to realize fusion of adjacent hollow filaments. A 3D bioprinting system with a Z-shape platform was used to realize layer-by-layer fabrication of cell-laden hydrogel structures. Curving, straight, stretched or fractured filaments can be formed by changes to the filament extrusion speed or the platform movement speed. To print a 3D structure, we first adjusted the concentration and flow rate of the sodium alginate and calcium chloride solution in the crosslinking process to get partially crosslinked filaments. Next, a motorized XY stages with the coaxial nozzle attached was used to control adjacent hollow filament deposition in the precise location for fusion. Then the Z stage attached with a Z-shape platform moved down sequentially to print layers of structure. And the printing process always kept the top two layers fusing and the below layers solidifying. Finally, the Z stage moved down to keep the printed structure immersed in the CaCl2 solution for complete crosslinking. The mechanical properties of the resulting fused structures were investigated. High-strength structures can be formed using higher concentrations of sodium alginate solution with smaller distance between adjacent hollow filaments. In addition, cell viability of this method was investigated, and the findings show that the viability of L929 mouse fibroblasts in the hollow constructs was higher than that in alginate structures without built-in microchannels. Compared with other bioprinting methods, this study is an important technique to allow easy fabrication of lager-scale organs with built-in microchannels.
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