Dynamic relaxation is an intrinsic and universal feature of glasses and enables fluctuation and dissipation to occur, which induces plentiful behaviour, maintains equilibrium, and achieves evolution ...in glass systems. Relaxation covers a broad time, frequency, and temperature ranges and determines the functions, behaviour, properties and applications of glassy system. Investigations of dynamic relaxation are significant for understanding the nature of glasses, liquids, and the critical issues of glass formation and transition, dynamic and structural heterogeneities, flow behaviour and flow units, various crossover temperatures, deformations, aging and rejuvenation, stability, crystallization, and the mechanical and physical properties of glasses. Metallic glasses (MGs) with unique microstructure and mechanical and functional properties, offer a simple but effective system for study of relaxation and related issues in glass science. In this review, a panoramic view of the state of the art of various aspects of dynamic relaxation in metallic glassy system, as well as a comparison with other glassy systems, is presented. The features and mechanisms of each known relaxation mode including primary α-relaxation, slow and fast 7 -relaxations, nearly constant loss, and boson peak, as well as their coupling in MGs, are reviewed and summarized. Emphasis is presented to the microstructural origin of these dynamic relaxation modes and their connection with the dynamic and structural heterogeneities in MGs. The factors which determine and affect the relaxation modes and behaviour in low-dimensional MGs are also introduced. It is shown that the relaxation in MGs is connected with their structural characteristics, heterogeneity, formation, glass transition, flow behaviour, physical and mechanical properties, crystallization, stability, and the localized atomic diffusion. The roles and the importance of dynamic relaxation in understanding many crucial issues in glassy physics are demonstrated. The correlations between dynamic relaxation and various properties of MGs are established and summarized. With this review on dynamic relaxation in metallic glasses, relaxation in MG can provide an effective perspective for understanding nearly all issues in metallic glasses. It is demonstrated that the relationship of relaxation to various properties, similar to the relationship of structure–property of crystalline materials, can be applied to control and design of new glassy materials with multiple functionalities, superior mechanical performance, and other extraordinary physical and chemical properties. Finally, the key unsolved questions regarding dynamic relaxation in metallic glasses are listed, and several emerging research directions in this still-evolving field are highlighted for future investigations.
Heterostructured metal—organic framework (MOF)‐on‐MOF thin films have the potential to cascade the various properties of different MOF layers in a sequence to produce functions that cannot be ...achieved by single MOF layers. An integration method that relies on van der Waals interactions, and which overcomes the lattice‐matching limits of reported methods, has been developed. The method deposits molecular sieving Cu‐TCPP (TCPP=5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin) layers onto semiconductive Cu‐HHTP (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene) layers to obtain highly oriented MOF‐on‐MOF thin films. For the first time, the properties in different MOF layers were cascaded in sequence to synergistically produce an enhanced device function. Cu‐TCPP‐on‐Cu‐HHTP demonstrated excellent selectivity and the highest response to benzene of the reported recoverable chemiresistive sensing materials that are active at room temperature. This method allows integration of MOFs with cascading properties into advanced functional materials.
MOF‐on‐MOF thin films were prepared from Cu‐HHTP (HHTP=hexahydrotriphenylene) and Cu‐TCPP (TCPP=tetrakis(4‐carboxyphenyl)porphyrin frameworks). The properties of the MOF layers cascade to produce functionality not achieved by a single layer. The MOF‐on‐MOF films demonstrate excellent selectivity and the highest response to benzene among reported recoverable chemiresistive sensing materials active at room temperature.
Bulk metallic glass (BMG) provides plentiful precise knowledge of fundamental parameters of elastic moduli, which offer a benchmark reference point for understanding and applications of the glassy ...materials. This paper comprehensively reviews the current state of the art of the study of elastic properties, the establishments of correlations between elastic moduli and properties/features, and the elastic models and elastic perspectives of metallic glasses. The goal is to show the key roles of elastic moduli in study, formation, and understanding of metallic glasses, and to present a comprehensive elastic perspectives on the major fundamental issues from processing to structure to properties in the rapidly moving field. A plentiful of data and results involving in acoustic velocities, elastic constants and their response to aging, relaxation, applied press, pressure and temperature of the metallic glasses have been compiled. The thermodynamic and kinetic parameters, stability, mechanical and physical properties of various available metallic glasses especially BMGs have also been collected. A survey based on the plentiful experimental data reveals that the linear elastic constants have striking systematic correlations with the microstructural features, glass transition temperature, melting temperature, relaxation behavior, boson peak, strength, hardness, plastic yielding of the glass, and even rheological properties of the glass forming liquids. The elastic constants of BMGs also show a correlation with a weighted average of the elastic constants of the constituent elements. We show that the elastic moduli correlations can assist in selecting alloying components with suitable elastic moduli for controlling the elastic properties and glass-forming ability of the metallic glasses, and thus the results would enable the design, control and tuning of the formation and properties of metallic glasses. We demonstrate that the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to understand flow in metallic glass and glass-forming supercooled liquid, and the model presents a simple and quantitative mathematic expression for flow activation energy of various glasses. The elastic perspectives, which consider all metallic glasses exhibit universal behavior based on a small number of readily measurable parameters of elastic moduli, are presented for understanding the nature and diverse properties of the metallic glasses.
Both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial to water splitting, but require alternative active sites. Now, a general π‐electron‐assisted strategy to ...anchor single‐atom sites (M=Ir, Pt, Ru, Pd, Fe, Ni) on a heterogeneous support is reported. The M atoms can simultaneously anchor on two distinct domains of the hybrid support, four‐fold N/C atoms (M@NC), and centers of Co octahedra (M@Co), which are expected to serve as bifunctional electrocatalysts towards the HER and the OER. The Ir catalyst exhibits the best water‐splitting performance, showing a low applied potential of 1.603 V to achieve 10 mA cm−2 in 1.0 m KOH solution with cycling over 5 h. DFT calculations indicate that the Ir@Co (Ir) sites can accelerate the OER, while the Ir@NC3 sites are responsible for the enhanced HER, clarifying the unprecedented performance of this bifunctional catalyst towards full water splitting.
HER and OER! The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial to water splitting, but require alternative active sites. Now, a general π‐electron‐assisted strategy to anchor single‐atom sites (M=Ir, Pt, Ru, Pd, Fe, Ni) on a heterogeneous support is reported. The M atoms can simultaneously anchor on two distinct domains of the hybrid support, four‐fold N/C atoms, and centers of Co octahedra.
The application of conventional metal–organic frameworks (MOFs) as electrode materials in supercapacitors is largely hindered by their conventionally poor electrical conductivity. This study reports ...the fabrication of conductive MOF nanowire arrays (NWAs) and the application of them as the sole electrode material for solid‐state supercapacitors. By taking advantage of the nanostructure and making full use of the high porosity and excellent conductivity, the MOF NWAs in solid‐state supercapacitor show the highest areal capacitance and best rate performance of all reported MOF materials for supercapacitors, which is even comparable to most carbon materials.
Conductive metal–organic framework (MOF) nanowire arrays (NWAs) are prepared as the sole electrode material for solid‐state supercapacitors. By taking advantage of their nanostructure and making full use of the high porosity and excellent conductivity, the MOF NWAs in the solid‐state supercapacitor show the highest areal capacitance and best rate performance of all reported MOF materials.
Nitrogen (N), potassium (K), and phosphorus (P) are essential macronutrients for plant growth and development, and their availability affects crop yield. Compared with N, the relatively low ...availability of K and P in soils limits crop production and thus threatens food security and agricultural sustainability. Improvement of plant nutrient utilization efficiency provides a potential route to overcome the effects of K and P deficiencies. Investigation of the molecular mechanisms underlying how plants sense, absorb, transport, and use K and P is an important prerequisite to improve crop nutrient utilization efficiency. In this review, we summarize current understanding of K and P transport and signaling in plants, mainly taking Arabidopsis thaliana and rice (Oryza sativa) as examples. We also discuss the mechanisms coordinating transport of N and K, as well as P and N.
Potassium (K) and phosphorus (P) are essential macronutrients for plant growth, development, and crop yield. This review summarizes the current understanding of K and P transport and signaling in plants and discusses the mechanisms coordinating N (nitrogen), K, and P.
The dynamics of glass-forming systems shows a multitude of features that are absent in normal liquids, such as non-exponential relaxation and a strong temperature-dependence of the relaxation time. ...Connecting these dynamic properties to the microscopic structure of the system is challenging because of the presence of the structural disorder. Here we use computer simulations of a metallic glass-former to establish such a connection. By probing the temperature and wave-vector dependence of the intermediate scattering function we find that the relaxation dynamics of the glassy melt is directly related to the local arrangement of icosahedral structures: Isolated icosahedra give rise to a liquid-like stretched exponential relaxation whereas clusters of icosahedra lead to a compressed exponential relaxation that is reminiscent to the one found in a solid. Our results show that in metallic glass-formers these two types of relaxation processes can coexist and give rise to a dynamics that is surprisingly complex.
As one of the most important mineral nutrient elements, potassium (K(+)) participates in many plant physiological processes and determines the yield and quality of crop production. In this review, we ...summarize K(+) signaling processes and K(+) transport regulation in higher plants, especially in plant responses to K(+)-deficiency stress. Plants perceive external K(+) fluctuations and generate the initial K(+) signal in root cells. This signal is transduced into the cytoplasm and encoded as Ca(2+) and reactive oxygen species signaling. K(+)-deficiency-induced signals are subsequently decoded by cytoplasmic sensors, which regulate the downstream transcriptional and posttranslational responses. Eventually, plants produce a series of adaptive events in both physiological and morphological alterations that help them survive K(+) deficiency.
•K+ channels and transporters are involved in diverse physiological processes.•Plants can sense external K+ deficiency and generate low-K+ signals in plant cells.•The transcription of many K+ ...transporter genes are induced by low-K+ stress.•Phosphorylation is crucial for the regulation of both K+ channels and transporters.•Coordination of K+/NO3− absorption and translocation is necessary for plants.
As an essential macronutrient, potassium (K+) plays crucial roles in diverse physiological processes during plant growth and development. The K+ concentration in soils is relatively low and fluctuating. Plants are able to perceive external K+ changes and generate chemical and physical signals in plant cells. The signals can be transducted across the plasma membrane and into the cytosol, and eventually regulates the downstream targets, particularly K+ channels and transporters. As a result, K+ homeostasis in plant cells is modulated, which facilitates plant adaptation to K+ deficient conditions. This minireview focuses on the latest research progress in the diverse functions of K+ channels and transporters as well as their regulatory mechanisms in plant response to low-K+ stress.
A low fasting blood glucose level is a common symptom in diabetes patients and can be induced by high-fat diet (HFD) feeding at an early stage, which may play important roles in the development of ...diabetes, but has received little attention. In this study, five polysaccharides were prepared from
and their effects on HFD-induced fasting hypoglycemia and gut microbiota dysbiosis were investigated. The results indicated that C57BL/6J male mice fed an HFD for 4 weeks developed severe hypoglycemia and four
polysaccharides (SFPs), consisting of Sf-2, Sf-3, Sf-3-1, and Sf-A, significantly prevented early fasting hypoglycemia without inducing hyperglycemia. Sf-1 and Sf-A could also significantly prevent HFD-induced weight gain. Sf-2, Sf-3, Sf-3-1, and Sf-A mainly attenuated the HFD-induced decrease in Bacteroidetes, and all five SFPs had a considerable influence on the relative abundance of
,
, and
. Correlation analysis revealed that the fasting blood glucose level was associated with the relative abundance of
and
. Receiver operating characteristic analysis indicated that
and
exhibited good discriminatory power (AUC = 0.745-0.833) in the prediction of fasting hypoglycemia. Our findings highlight the novel application of SFPs (especially Sf-A) in glucose homeostasis and the potential roles of
and
in the biological activity of SFPs.
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