Natural variants of crops are generated from wild progenitor plants under both natural and human selection. Diverse crops that are able to adapt to various environmental conditions are valuable ...resources for crop improvements to meet the food demands of the increasing human population. With the completion of reference genome sequences, the advent of high-throughput sequencing technology now enables rapid and accurate resequencing of a large number of crop genomes to detect the genetic basis of phenotypic variations in crops. Comprehensive maps of genome variations facilitate genome-wide association studies of complex traits and functional investigations of evolutionary changes in crops. These advances will greatly accelerate studies on crop designs via genomics-assisted breeding. Here, we first discuss crop genome studies and describe the development of sequencing-based genotyping and genome-wide association studies in crops. We then review sequencing-based crop domestication studies and offer a perspective on genomics-driven crop designs.
Continuing the lines developed in Han (2010) 20, in this paper we study nonhomogeneous wavelet systems in high dimensions. It is of interest to study a wavelet system with a minimum number of ...generators. It has been shown in Dai et al. (1997) 9 that for any d×d real-valued expansive matrix M, a homogeneous orthonormal M-wavelet basis can be generated by a single wavelet function. On the other hand, it has been demonstrated in Han (2010) 20 that nonhomogeneous wavelet systems, though much less studied in the literature, play a fundamental role in wavelet analysis and naturally link many aspects of wavelet analysis together. In this paper, we are interested in nonhomogeneous wavelet systems in high dimensions with a minimum number of generators. As we shall see in this paper, a nonhomogeneous wavelet system naturally leads to a homogeneous wavelet system with almost all properties preserved. We also show that a nonredundant nonhomogeneous wavelet system is naturally connected to refinable structures and has a fixed number of wavelet generators. Consequently, it is often impossible for a nonhomogeneous orthonormal wavelet basis to have a single wavelet generator. However, for redundant nonhomogeneous wavelet systems, we show that for any d×d real-valued expansive matrix M, we can always construct a nonhomogeneous smooth tight M-wavelet frame in L2(Rd) with a single wavelet generator whose Fourier transform is a compactly supported C∞ function. Moreover, such nonhomogeneous tight wavelet frames are associated with filter banks and can be easily modified to achieve directionality in high dimensions. As an illustration, we present a bivariate directional tight 2I2-wavelet frame, which has an underlying tight framelet filter bank and can be efficiently implemented. Our analysis of nonhomogeneous wavelet systems employs a notion of frequency-based nonhomogeneous (or more generally, nonstationary) dual wavelet frames in the distribution space. Such a notion allows us to completely separate the perfect reconstruction property of a wavelet system from its stability in various function spaces. We provide a complete characterization of frequency-based nonstationary dual wavelet frames in the distribution space.
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•MPs impacts on Cd adsorption and desorption in a farmland soil were first studied.•Adding MPs decreased soil adsorption capacity for Cd, but increased Cd desorption.•MPs impacts ...depended on MPs dose and particle size, and solution pH.•Addition of MPs may increase the mobility of Cd in soil, resulting in additional risks.
Microplastics (MPs) in terrestrial ecosystems particularly agroecosystem are attracting increasing attention worldwide. However, the influences of MPs on adsorption and desorption of contaminants in agricultural soils remain unknown. Here, batch experiments were conducted to study the effects of polyethylene MPs on Cd adsorption and desorption in a farmland soil under varying conditions. Both Cd adsorption and desorption in soils with or without MPs reached equilibrium within 120 min. Cd adsorption kinetics followed the pseudo-second order model, and the adsorption isotherm fitted to the Langmuir model more precisely than the Freundlich model. Overall, addition of MPs decreased Cd adsorption but increased desorption, and the effects varied with MPs dose and particle size, and solution pH. MPs-induced decrease in Cd adsorption and increase in Cd desorption were more pronounced at higher MPs dose and larger particle size, but varied differently from solution pH. EDS analysis confirmed Cd adsorption on MPs surface. Both MPs before and after Cd adsorption showed similar XRD patterns, indicating MPs maintained a high crystallinity and no new crystalline phases formed. In conclusion, the input of MPs into soil might enhance the mobility of Cd via mitigating soil adsorbing capacity, thereby posing additional risks of Cd to agroecosystem.
•Recent research on dielectric transition and ferroelectricity is overviewed.•Basic concepts and fundamentals of the two properties are introduced.•Structural changes during the phase transitions are ...discussed.
Structural phase transition in solid-state materials is an underlying factor for emergence and evolution of a number of important physical/chemical properties. In this review, we summarize recent achievements on two types of structural phase transition-associated properties, i.e., dielectric transition and ferroelectricity, in coordination compounds. The basic concepts and fundamentals of structural phase transition and the two properties are briefly introduced. This review aims to reveal the role of the structural phase transitions on bulk properties and afford a perspective on the connections among multiple topics of coordination chemistry from the structural phase transition viewpoint. It would be appealing to researchers in multidisciplinary fields such as coordination chemistry, crystal engineering, supramolecular chemistry, condensed matter physics, responsive materials and molecular machines.
The Road Towards 6G: A Comprehensive Survey Jiang, Wei; Han, Bin; Habibi, Mohammad Asif ...
IEEE open journal of the Communications Society,
2021, Letnik:
2
Journal Article
Recenzirano
Odprti dostop
As of today, the fifth generation (5G) mobile communication system has been rolled out in many countries and the number of 5G subscribers already reaches a very large scale. It is time for academia ...and industry to shift their attention towards the next generation. At this crossroad, an overview of the current state of the art and a vision of future communications are definitely of interest. This article thus aims to provide a comprehensive survey to draw a picture of the sixth generation (6G) system in terms of drivers, use cases, usage scenarios, requirements, key performance indicators (KPIs), architecture, and enabling technologies. First, we attempt to answer the question of "Is there any need for 6G?" by shedding light on its key driving factors, in which we predict the explosive growth of mobile traffic until 2030, and envision potential use cases and usage scenarios. Second, the technical requirements of 6G are discussed and compared with those of 5G with respect to a set of KPIs in a quantitative manner. Third, the state-of-the-art 6G research efforts and activities from representative institutions and countries are summarized, and a tentative roadmap of definition, specification, standardization, and regulation is projected. Then, we identify a dozen of potential technologies and introduce their principles, advantages, challenges, and open research issues. Finally, the conclusions are drawn to paint a picture of "What 6G may look like?." This survey is intended to serve as an enlightening guideline to spur interests and further investigations for subsequent research and development of 6G communications systems.
Two crustal cross sections through the eastern margin of the Tibetan Plateau are jointly determined from deep seismic sounding. The E–W trending line AA’ passes through the western Sichuan plateau ...(including the Songpan‐Garze terrane and the Longmenshan fault belt) and ends in the Sichuan basin (a part of the Yangtze craton). Line BB’ has a trend of NNE and crosses the Songpan‐Garze terrane. Two‐dimensional crustal structures along the profiles were jointly determined by the additional use of existing deep seismic sounding data. Our seismic velocity models indicate that the western Sichuan plateau and the Sichuan basin have crustal thicknesses of 62 and 43 km, average crustal P wave velocities of 6.27 and 6.45 km/s and lower crustal (Vp > 6.5 km/s) thicknesses of 27 and 15 km, respectively. Density models constructed from the seismic velocity models are consistent with observed Bouguer gravity anomalies. We infer that collision between the Tibetan Plateau and the Yangtze craton has caused thickening of the lower crust and uplift of the western Sichuan plateau. We detect a low‐velocity layer in the upper crust of the western Sichuan plateau but observe no equivalence in the Sichuan basin; west dipping thrusts may detach into this low‐velocity layer. The seismic phase PmP in the western Sichuan plateau has low amplitude, suggesting high attenuation in the lower crust (Qp of 100–300). We suggest that the high attenuation is a consequence of lower crustal flow caused by the large lower crustal thickness beneath the western Sichuan plateau.
Abstract
Artificially performing chemical reactions in living biosystems to attain various physiological aims remains an intriguing but very challenging task. In this study, the Schiff base reaction ...was conducted in cells using Sc(OTf)
3
as a catalyst, enabling the in situ synthesis of a hollow covalent organic polymer (HCOP) without external stimuli. The reversible Schiff base reaction mediated intracellular Oswald ripening endows the HCOP with a spherical, hollow porous structure and a large specific surface area. The intracellularly generated HCOP reduced cellular motility by restraining actin polymerization, which consequently induced mitochondrial deactivation, apoptosis, and necroptosis. The presented intracellular synthesis system inspired by the Schiff base reaction has strong potential to regulate cell fate and biological functions, opening up a new strategic possibility for intervening in cellular behavior.
Flexible hydroelectric generators (HEGs) are promising self‐powered devices that spontaneously derive electrical power from moisture. However, achieving the desired compatibility between a continuous ...operating voltage and superior current density remains a significant challenge. Herein, a textile‐based van der Waals heterostructure is rationally designed between conductive 1T phase tungsten disulfide@carbonized silk (1T‐WS2@CSilk) and carbon black@cotton (CB@Cotton) fabrics with an asymmetric distribution of oxygen‐containing functional groups, which enhances the proton concentration gradients toward high‐performance wearable HEGs. The vertically staggered 1T‐WS2 nanosheet arrays on the CSilk fabric provide abundant hydrophilic nanochannels for rapid carrier transport. Furthermore, the moisture‐induced primary battery formed between the active aluminum (Al) electrode and the conductive textiles introduces the desired electric field to facilitate charge separation and compensate for the decreased streaming potential. These devices exhibit a power density of 21.6 µW cm−2, an open‐circuit voltage (Voc) of 0.65 V sustained for over 10 000 s, and a current density of 0.17 mA cm−2. This performance makes them capable of supplying power to commercial electronics and human respiratory monitoring. This study presents a promising strategy for the refined design of wearable electronics.
Through constructing 2D nanosheet arrays and moisture‐induced primary battery system, a high‐performance and flexible hydroelectric generator is developed with a sustained open‐circuit voltage of 0.65 V, and an excellent short‐circuitcurrent of 0.51 mA. Moreover, these prepared flexible hydroelectric generators can be used in the wearable self‐powered field.
Homogeneous wavelets and framelets have been extensively investigated in the classical theory of wavelets and they are often constructed from refinable functions via the multiresolution analysis. On ...the other hand, nonhomogeneous wavelets and framelets enjoy many desirable theoretical properties and are often intrinsically linked to the refinable structure and multiresolution analysis. In this paper, we provide a comprehensive study on connecting homogeneous wavelets and framelets to nonhomogeneous ones with the refinable structure. This allows us to understand better the structure of homogeneous wavelets and framelets as well as their connections to the refinable structure and multiresolution analysis.
Textile‐based generators that can convert low‐grade energy from the human body or environment into sustainable electricity have generated immense scientific interest in self‐powered wearable ...applications. However, their low power density and environmental suitability have extremely restricted their portable applications in complex and mutable environments. Herein, an asymmetric sandwich structure between molybdenum disulfide (MoS2)‐carbonized silks (MCs) and MoS2/MXene–Cottons (MMCs) to construct efficient thermo–hydroelectric generators (THEGs) that synergistically harvest heat‐moisture energy to generate considerable electricity is rationally designed. Notably, the large surface area of MoS2/MXene van der Waals heterojunctions (vdWhs) enables efficient charge collection, and the vertical MoS2 nanosheet arrays supply abundant nanochannels for a highly efficient hydration effect, generating an output power density of 32.26 µW cm−2 after wetting with deionized water. Combined with the sensitive temperature recognition ability with a Seebeck coefficient of 23.5 µV K−1, the application possibilities of these prepared THEGs in the mutual conversion of fingertip temperature/language, and the monitoring of the human physiological state is foresee.
Thermo–hydroelectric generators (THEGs) are successfully constructed based on a sandwich structure between p‐type MoS2‐carbonized silks (MCs) with vertical MoS2 nanosheet arrays and n‐type MoS2/MXene–Cottons (MMCs) with van der Waals heterojunctions, demonstrating a Seebeck coefficient of 23.5 µV K−1 and a high output power density of 32.26 µW cm−2, which are favorable acting as self‐powered sensors for health monitoring.
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