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The 4f-electron delocalization plays a key role in the low-temperature properties of rare-earth metals and intermetallics, and it is normally realized by the Kondo coupling between 4f and conduction electrons. Due to the large Coulomb repulsion of 4f electrons, the bandwidth-control Mott-type delocalization, commonly observed in d-electron systems, is difficult in 4f-electron systems and remains elusive in spectroscopic experiments. Here we demonstrate that the bandwidth-control orbital-selective delocalization of 4f electrons can be realized in epitaxial Ce films by thermal annealing, which results in a metastable surface phase with reduced layer spacing. The quasiparticle bands exhibit large dispersion with exclusive 4f character near \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{{{\Gamma }}}$$\end{document}Γ¯ and extend reasonably far below the Fermi energy, which can be explained from the Mott physics. The experimental quasiparticle dispersion agrees well with density-functional theory calculation and also exhibits unusual temperature dependence, which could arise from the delicate interplay between the bandwidth-control Mott physics and the coexisting Kondo hybridization. Our work opens up the opportunity to study the interaction between two well-known localization-delocalization mechanisms in correlation physics, i.e., Kondo vs Mott, which can be important for a fundamental understanding of 4f-electron systems., The mechanism of the delocalization transition of 4f electrons in closely-packed Ce metal has been debated. Here, the authors present photoemission evidence for bandwidth-controlled Mott delocalization in a previously unreported structural phase of thin epitaxial Ce films obtained by thermal annealing.

To study the effects of La on the microstructure and mechanical properties of refractory high entropy alloys, NbMoTiVSi0.2 alloys with different La contents were prepared. Phase constitution, microstructure evolution, compressive properties and related mechanisms were systematically studied. Results show that the alloys with La addition are composed of BCC solid solution, eutectic structure, MSi2 disilicide phase and La-containing precipitates. Eutectic structure and most of La precipitates are formed at the grain boundaries. Disilicide phase is formed in the grains. La can change the grain morphologies from dendritic structure to near-equiaxed structure, and the average grain size decreases from 180 to 20 μm with the increase of La content from 0 to 0.5 at.%. Compressive testing shows that the ultimate strength and the yield strength increase with the increase of La content, which is resulted from the grain boundary strengthening. However, they cannot be greatly improved because of the formation of MSi2 disilicide phase with low strength. The ductility decreases with the increase of La content, which is due to the La precipitates and brittle MSi2 disilicide phase.

Plenty of nonlinear optical (NLO) crystals containing VO4 and AsO4 tetrahedra as NLO-active units have been found. Among them, Li3MO4 (M = V, As) and LiA2MO4 (A = Rb, Cs; M = V, As) are isostructur...

Apocarotenoids, which play important roles in the growth and development of horticultural plants, are produced by the action of carotenoid cleavage oxygenase (CCO) family members or nonenzymatic cleavage actions. Apocarotenoids are commonly found in leaves, flowers, and fruits of many horticultural plants and participate in the formation of pigments, flavors, hormones, and signaling compounds. Some of them are recognized as important aroma components of fruit and flower with aromatic odor, such as βß-ionone, β-damascenone, and 6-methyl-5-hepten-2-one in tomato fruit, and have low odor thresholds with β-ionone having odor threshold of only 0.007 ppb. In this review, the main apocarotenoid aroma components in horticultural plants were listed, and factors influencing their production were discussed at first. Then, the biosynthetic pathway of apocarotenoid aromas was briefly introduced, and the CCDs gene family was highlighted, and the nonenzymatic production of apocarotenoid aromas was also mentioned. Next, chemical and molecular regulations of apocarotenoid aromas and their biological activities were summarized. Finally, further exploration aspects needed were suggested. We anticipate that this review can afford some crucial information for comprehensive application of apocarotenoid volatile compounds in horticultural plants.

In the travel process of urban residents, travelers will take a series of activities such as imitation and exclusion by observing other people’s travel modes, which affects their following trips. This process can be seen as a repeated game between members of the travelers. Based on the analysis of this game and its evolution trend, a multi-dimensional game model of low-carbon travel for residents is established. The two dimensional game strategies include whether to accept the low-carbon concept and whether to choose low-carbon travel. Combined with evolutionary game theory, the low-carbon travel choices of residents in different cities are simulated, and the evolutionary stability strategies are obtained. Finally, the influences of the main parameters of the model on the evolution process and stability strategies are discussed. The results show that travelers would develop towards two trends. Cities with more developed public traffic system have a higher proportion of receiving low-carbon concept and choosing low-carbon travel. Cities with underdeveloped public transport system could increase this proportion by some measures such as encouraging residents to choose slow transport and increasing the propaganda of low-carbon travel, but the positive effects of the measures like propaganda have a limited impact on the proportion.

This paper studies the structural, electronic and optical properties of a new group IV-V two-dimensional (2D) material GeP under the influence of different strains by using the first-principles calculations. The strains discussed in this paper include both the uniaxial strain along the different lattice vector directions, as well as the biaxial strain. The results show that monolayer GeP is a 2D dynamically stable semiconductor with low structural symmetry. In terms of the electronic property, regardless of the compressive strain or tensile strain applied in any direction, the band-gap of the monolayer GeP exhibits a decreasing tendency, and it remains semiconductivity in the range of −10% compressive strain to 10% tensile strain. As for the optical property, it is anisotropic. When GeP is subjected to a strain, regardless of the directions, the optical property of monolayer GeP is significantly affected more by tensile strain than by compressive strain. When the monolayer GeP is subjected to a tensile strain, its optical absorption and reflectivity in the visible light region to some extent increase, while its transmittance reduces. When it is subjected to a compressive strain, the main change in optical properties such as absorption and reflectivity occurs in the deep ultraviolet region. In particular, the monolayer GeP is most susceptible to deformation by the strain in a direction, and only compressive strain in a direction will cause GeP to undergo a transition from an indirect band-gap semiconductor to a direct band-gap semiconductor, which results in the improvements of absorption efficiency and reflectivity efficiency in the low energy region. Our calculated results indicate that the electronic and optical properties of monolayer GeP can be efficiently and regularly regulated by strain. In the future, it can be a suitable 2D materials used in optically polarized devices, blue light-emitting diode devices, and strain-tunable photoelectric nanodevices .

By using first-principles calculations, we characterized the structural stability, electronic and optical properties of novel two-dimensional (2D) monolayer transition-metal dichalcogenide (TMDC) HfX2 (X = S, Se). In our study, the PBE method is mainly used to calculate the electronic and optical properties, and the HSE06 method is used to further modify the band gap and optical absorption edge. It is indicated that monolayer 1-T HfS2 and HfSe2 present a stable indirect band gap semiconductor when the strain is 0%. The band gap of all monolayer 1-T HfX2 decreases significantly and the optical absorption edge shows an obvious red-shift trend with an increasing in-layer biaxial compressive strain. When the compressive strain is greater than −8% in HfS2 and -6% in HfSe2 respectively, the band gap decreases to zero, and so the semiconductor-metal transition was produced. Conversely, the band gap increases insignificantly with the increasing in-layer biaxial tensile strain from 0% to +10% while the absorption edge reveals an inconspicuous blue-shift trend. The general rule for the change of the band gap and the absorption edge tuned by strain of monolayer HfX2 could be explained well according to the different changes of near-band-edge states. Moreover, with the vertical electric field (E-field) increases, there is the band gap decreases and the absorption edge red shifts in all monolayer HfX2 under different in-layer biaxial strains. Our study suggests that the strain and electric field (E-field) engineering are effective tunable approaches to alter the electronic and optical properties of monolayer HfX2. Namely, we suggest that the functions of TMD could be changed by setting up suitable strain and E-field on few-layer materials in the future.

Nitrogen (N) addition is an important nutrient strategy for alpine grassland in northwestern China to improve productivity for livestock needs. A field experiment was conducted in a semi-arid alpine grassland in northwestern China to investigate the effect of N addition rates on soil N2O emissions over the growing seasons of 2017 and 2018. Treatments included six N addition rates (0, 10, 30, 60, 120, 240 kg N ha−1 y−1), which were applied before each growing season. The N2O fluxes increased with N addition rates and showed different episodic changes between the two growing seasons. In 2017, the maximum N2O flux rate occurred within 2 weeks following N addition. In 2018, however, the maximum N2O flux rate occurred later in the growing season due to a heavy rainfall event. Growing season cumulative N2O emissions ranged between 0.32 and 1.11 kg N ha−1, and increased linearly with N addition rates. Increasing N addition rates over 60 kg N ha−1 yr−1 did not further increase plant above-ground biomass. The inter-annual variability of N2O flux suggests the importance of soil moisture in affecting N2O emissions. It is particularly important to avoid over-applying N nutrients beyond plant needs to reduce its negative effect on the environment while maintaining livestock productivity. The N2O flux rate increased with soil dissolved organic carbon (DOC) and soil pH. These results suggest the optimal N addition rate to the livestock grassland in this region should be 60 kg N ha−1 yr−1.

Heavy fermion compounds exhibiting a ferromagnetic quantum critical point have attracted considerable interest. Common to two known cases, i.e., CeRh_{6}Ge_{4} and YbNi_{4}P_{2}, is that the 4f moments reside along chains with a large interchain distance, exhibiting strong magnetic anisotropy that was proposed to be vital for the ferromagnetic quantum criticality. Here, we report an angle-resolved photoemission study on CeRh_{6}Ge_{4} in which we observe sharp momentum-dependent 4f bands and clear bending of the conduction bands near the Fermi level, indicating considerable hybridization between conduction and 4f electrons. The extracted hybridization strength is anisotropic in momentum space and is obviously stronger along the Ce chain direction.The hybridized 4f bands persist up to high temperatures, and the evolution of their intensity shows clear band dependence. Our results provide spectroscopic evidence for anisotropic hybridization between conduction and 4f electrons in CeRh_{6}Ge_{4}, which could be important for understanding the electronic origin of the ferromagnetic quantum criticality.

We investigated the coexistence of superconductivity and antiferromagnetic order in the compound Er$_{2}$O$_{2}$Bi with anti-ThCr$_{2}$Si$_{2}$-type structure through resistivity, magnetization, specific heat measurements and first-principle calculations. The superconducting transition temperature $T_{\rm c}$ of 1.23 K and antiferromagnetic transition temperature $T_{\rm N}$ of 3 K are observed in the sample with the best nominal composition. The superconducting upper critical field $H_{\rm c2}$(0) and electron-phonon coupling constant $\lambda$$_{e-ph}$ in Er$_{2}$O$_{2}$Bi are similar to those in the previously reported non-magnetic superconductor Y$_{2}$O$_{2}$Bi with the same structure, indicating that the superconductivity in Er$_{2}$O$_{2}$Bi may have the same origin as in Y$_{2}$O$_{2}$Bi. The first-principle calculations of Er$_{2}$O$_{2}$Bi show that the Fermi surface is mainly composed of the Bi 6$p$ orbitals both in the paramagnetic and antiferromagnetic state, implying minor effect of the 4$f$ electrons on the Fermi surface. Besides, upon increasing the oxygen incorporation in Er$_{2}$O$_{x}$Bi, $T_{\rm c}$ increases from 1 to 1.23 K and $T_{\rm N}$ decreases slightly from 3 to 2.96 K, revealing that superconductivity and antiferromagnetic order may compete with each other. The Hall effect measurements indicate that hole-type carrier density indeed increases with increasing oxygen content, which may account for the variations of $T_{\rm c}$ and $T_{\rm N}$ with different oxygen content.

Beach scarps are commonly associated with nourishment. Large and persistent beach scarps not only affect the performance of beach nourishment, but also are safety hazards to tourists. In this study, the morphological evolution of beach scarps was examined at a nourished beach in a low-energy and micro-tidal environment. Topographic surveys of nine beach profiles were carried out every 3–6 months after nourishment, lasting for nearly 4.5 years, combined with observed and simulated hydrodynamic data. The results showed that beach scarps were extensively developed after nourishment and migrated landward gradually. The formation of beach scarps was attributed to the higher designed berm, while the migration was possibly initiated by the subsequent higher total water level connected with the irregular tides. However, scarps were completely removed by the first post-nourishment severe storm and had been long absent ever since although two other energetic storms approached. This was different from the result of previous studies, which could be attributed to the much gentler upper beach slope. These results highlighted that the first post-nourishment storm played a key role in the evolution of beach scarps at low-energy and micro-tidal nourished beaches. This study also proposed two methods of determining berm elevation in beach nourishment according to China’s experiences, which would be helpful for other countries’ beach nourishment projects.

We predict, through first-principles calculations, a different class of Janus two-dimensional (2D) materials $X{\mathrm{Sn}}_{2}Y$ ($X, Y=\mathrm{P}$, As, Sb, and Bi; $X\ensuremath{\ne}Y$). It has found that these 2D monolayers have intrinsic polarization effect owing to presence of mirror-symmetry breaking. $\mathrm{Sb}{\mathrm{Sn}}_{2}\mathrm{Bi}, \mathrm{As}{\mathrm{Sn}}_{2}\mathrm{Sb}$, and $\mathrm{P}{\mathrm{Sn}}_{2}\mathrm{As}$ have a semiconducting feature, however $\mathrm{As}{\mathrm{Sn}}_{2}\mathrm{Bi}, \mathrm{P}{\mathrm{Sn}}_{2}\mathrm{Bi}$, and $\mathrm{P}{\mathrm{Sn}}_{2}\mathrm{Sb}$ have a metallic feature with inverted band structure. When the spin-orbit coupling (SOC) is considered, the double Rashba effects are found in $\mathrm{Sb}{\mathrm{Sn}}_{2}\mathrm{Bi}$. Band inversion coupling with SOC leads to unexpected spin-valley splitting characteristics in $\mathrm{As}{\mathrm{Sn}}_{2}\mathrm{Bi}, \mathrm{P}{\mathrm{Sn}}_{2}\mathrm{Bi}$, and $\mathrm{P}{\mathrm{Sn}}_{2}\mathrm{Sb}$, showing a circle-type Berry curvature. The electronic and spin properties of Janus $X{\mathrm{Sn}}_{2}Y$ monolayers are tunable via applying external strain and electric field, resulting in Rashba-type spin-splitting, ${p}_{z}/{p}_{xy}$ band inversion, and a Dirac cone. In particular, the sombrero band dispersion and Van Hove singularity are revealed in $\mathrm{P}{\mathrm{Sn}}_{2}\mathrm{As}$ by exerting tensile strain. We therefore investigate the Lifshitz transition and inverse Edelstein effect (also referred as spin-charge conversion) of the strained $\mathrm{P}{\mathrm{Sn}}_{2}\mathrm{As}$. On the basis of the k\ifmmode\cdot\else\textperiodcentered\fi{}p model in the clean limit, the Drude coefficient for spin-charge conversion is estimated to be about 0.086 $e$/\AA{} as tensile strain of +3%. Finally, the synergic effect of tensile strain and electric field is considered to manipulate the spin-charge conversion. Our results provide a class of 2D materials to investigate the Rashba effect, Lifshitz transition, and spin-charge conversion.

Using angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED), together with density-functional theory (DFT) calculation, we report the formation of charge density wave (CDW) and its interplay with the Kondo effect and topological states in CeSbTe. The observed Fermi surface (FS) exhibits parallel segments that can be well connected by the observed CDW ordering vector, indicating that the CDW order is driven by the electron-phonon coupling (EPC) as a result of the nested FS. The CDW gap is large (∼0.3 eV) and momentum-dependent, which naturally explains the robust CDW order up to high temperatures. The gap opening leads to a reduced density of states (DOS) near the Fermi level (EF), which correspondingly suppresses the many-body Kondo effect, leading to very localized 4f electrons at 20 K and above. The topological Dirac cone at the X point is found to remain gapless inside the CDW phase. Our results provide evidence for the competition between CDW and the Kondo effect in a Kondo lattice system. The robust CDW order in CeSbTe and related compounds provide an opportunity to search for the long-sought-after axionic insulator.

Evidence for broken time reversal symmetry (TRS) has been found in the superconducting states of the ${R}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ ($R=\text{Sc}$, Y, Lu) compounds with a centrosymmetric caged crystal structure, but the origin of this phenomenon is unresolved. Here, we report neutron diffraction measurements of single crystals with $R=\text{Lu}$, as well as measurements of the temperature dependence of the magnetic penetration depth using a self-induced tunnel-diode-oscillator (TDO)-based technique, together with band structure calculations using density functional theory. Neutron diffraction measurements reveal that the system crystallizes in a tetragonal caged structure, and that one of the nominal Lu sites in the ${\mathrm{Lu}}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ structure is occupied by Sn, yielding a composition ${\mathrm{Lu}}_{5\ensuremath{-}x}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18+x}$ ($x=1$). The low temperature penetration depth shift $\mathrm{\ensuremath{\Delta}}\ensuremath{\lambda}(T)$ exhibits an exponential temperature dependence below around $0.3{T}_{c}$, giving clear evidence for fully gapped superconductivity. The derived superfluid density is reasonably well accounted for by a single-gap $s$-wave model, whereas agreement cannot be found for models of TRS breaking states with two-component order parameters. Moreover, band structure calculations reveal multiple bands crossing the Fermi level, and indicate that the aforementioned TRS breaking states would be expected to have nodes on the Fermi surface, in contrast to the observations.

Ferromagnetic quantum critical points were predicted to be prohibited in clean itinerant ferromagnetic systems, yet such a phenomenon was recently revealed in CeRh$_6$Ge$_4$, where the Curie temperature can be continuously suppressed to zero under a moderate hydrostatic pressure. Here we report the observation of quantum oscillations in CeRh$_6$Ge$_4$ from measurements using the cantilever and tunnel-diode oscillator methods in fields up to 45 T, clearly demonstrating that the ferromagnetic quantum criticality occurs in a clean system. In order to map the Fermi surface of CeRh$_6$Ge$_4$, we performed angle-dependent measurements of quantum oscillations at ambient pressure, and compared the results to density functional theory calculations. The results are consistent with the Ce 4f electrons remaining localized, and not contributing to the Fermi surface, suggesting that localized ferromagnetism is a key factor for the occurrence of a ferromagnetic quantum critical point in CeRh$_6$Ge$_4$., Comment: 12 pages, 3 figures

Coexistence of topological bands and charge density wave (CDW) in topological materials has attracted immense attentions because of their fantastic properties, such as axionic-CDW, three-dimensional quantum Hall effect, etc. In this work, a nodal-line semimetal InxTaS2 characterized by CDW and superconductivity is successfully synthesized, whose structure and topological bands (two separated Wely rings) are similar to In0.58TaSe2. A 2 x 2 commensurate CDW is observed at low temperature in InxTaS2, identified by transport properties and STM measurements. Moreover, superconductivity emerges below 0.69 K, and the anisotropy ratio of upper critical field [Gamma = H||ab c2(0)=H||c c2(0)] is significantly enhanced compared to 2H-TaS2, which shares the same essential layer unit. According to the Lawrence-Doniach model, the enhanced Gamma may be explained by the reduced effective mass in kx-ky plane, where Weyl rings locate. Therefore, this type of layered topological systems may offer a platform to investigate highly anisotropic superconductivity and to understand the extremely large upper critical field in the bulk or in the two-dimensional limit., Comment: Accepted for publication in PRB

Carbon and nitrogen contents and their isotopic components, and AMS (Accelerator Mass Spectrometry) radiocarbon dating ages, were measured for 57 coastal sediments from Weizhou Island to analyze the distribution of total inorganic carbon (TIC) and its carbon and oxygen isotopic components (&delta, 13Ccarb and &delta, 18Ocarb), total organic carbon (TOC) and total nitrogen (TN) contents and their stable isotopic components (&delta, 13CTOC and &delta, 15NTN), and their environmental significance. The results showed that the oldest age of coastal sediments on Weizhou Island was 2750 cal. a BP (before present), and the average TIC contents of cores A1, A2, B1, C1, and D1 in the intertidal zone were all greater than 5%, where &delta, 18Ocarb were enriched, whereas the TIC contents in cores A3, C2, and D2 of the supra-tidal zone were low, where &delta, 18Ocarb were depleted. Moreover, TIC decreased sharply, 4.95% on average, to close to zero from the estuary to the upstream region in the C1-C2 section. The average C/N ratio was 7.02, and &delta, 15NTN were between &minus, 14.96&permil, and &minus, 27.26&permil, 14.38&permil, and 4.12&permil, respectively. These measurements indicate that the TIC in coastal sediments mainly came from seawater. Cores A1, A2, and B1 in the northern intertidal zone exhibited organic terrestrial signals because of C3 and C4 plant inputs, which indicates that the important source on the northern coast of Weizhou Island came from island land but followed the decrease in C3 plants. The lacustrine facies deposits were mainly distributed in the upper reaches of the river, the northern coastline was advancing toward the sea, and part of the southwestern coastal sediments rapidly accumulated on the shore under the influence of a storm surge. The relative sea level of the Weizhou Island area has continuously declined at a rate of approximately 2.07 mm/a, using beach rock as a marker, since the Holocene.

Different types of pockmarks, including single pockmarks, circular pockmarks, elongated pockmarks, chain-type pockmarks, and compound pockmarks, were identified in coastal areas around Fujian, China. The sediments associated with pockmarks were mainly silty clay to clay, with a small quantity of silt with fine sand. The sulfate content in the pore water in the sedimentary layers associated with pockmarks decreased with depth from the surface, whereas the free methane content increased with depth. The interaction between sulfate and methane is well known, but differences in the sulfate&ndash, methane transitional zone (SMTZ) were observed in different areas with different hydrologic characteristics. The sedimentary SMTZ of the offshore Zhe-Min mud wedge was shallow, at 50&ndash, 70 cm below the seafloor. The sedimentary SMTZ was moderately deep (90&ndash, 115 cm) in the central bay area and deep (180&ndash, 200 cm) in the sandy area offshore. This variability in SMTZ depth reflects different amounts of free methane gas in the underlying formations, with a shallower SMTZ indicating a higher free methane content. The free methane had &delta, 13C values of &minus, 26.47&permil, to &minus, 8.20&permil, and a biogenic hybrid genetic type. The flux of sedimentary gas from the pockmark surfaces, calculated according to Fick&rsquo, s formula, was 2.89 to 18.85 L/m2&middot, a. The shape, size, and scale of the pockmarks are directly related to the substrate type and the gas production of the underlying strata and thus vary with the sedimentary environment and development stage. Therefore, different types of pockmarks, in various phases of development, are associated with different sedimentary and dynamical conditions. A single circular pockmark is formed by a strong methane flux. As the intensity of methane flux weakens, the pockmark becomes elongated in the direction of the water flow because of long-term erosion induced by regular hydrodynamic forces. Finally, under a weak intensity of methane flux and the influence of complex hydrodynamic conditions, pockmarks merge to form large-scale compound pockmarks.

There are complex nonlinear behaviors and mechanisms in the bolted joint interface. Thus, the bolted joint is crucial to the complex nonlinear dynamic response of the structure. However, in the traditional structural dynamic analysis, the screw connection is usually neglected, which makes it challenging to analyze and study the nonlinear dynamic behavior of bolted structures. Hence, based on the Timoshenko beam theory and finite element method, this paper introduces a model considering thread connection to analyze the dynamic response under different excitation. Eventually, the results indicate that owing to the local nonlinearity of bolts, the whole bolted cantilever beam shows hardening-type characteristics. In addition, the frequency response curve also depicts the typical nonlinear phenomenon of instability and uncertainty, namely bifurcation, which preliminarily verifies the correctness and accuracy of the bolted cantilever beam model.

We predict that CeBi in the ferromagnetic state is a Weyl semimetal. Our calculations within density functional theory show the existence of two pairs of Weyl nodes on the momentum path $(0, 0, k_z)$ at $15$ meV} above and $100$ meV below the Fermi level. Two corresponding Fermi arcs are obtained on surfaces of mirror-symmetric (010)-oriented slabs at $E=15$ meV and both arcs are interrupted into three segments due to hybridization with a set of trivial surface bands. By studying the spin texture of surface states, we find the two Fermi arcs are strongly spin-polarized but in opposite directions, which can be detected by spin-polarized ARPES measurements. Our theoretical study of quasiparticle interference (QPI) for a nonmagnetic impurity at the Bi site also reveals several features related to the Fermi arcs. Specifically, we predict that the spin polarization of the Fermi arcs leads to a bifurcation-shaped feature only in the spin-dependent QPI spectrum, serving as a fingerprint of the Weyl nodes., 9 pages with 9 embedded figures. Supplemental material shortened

The electronic structure and phonon properties of LaNiSi, LaPtSi, and LaPtGe have been studied using the first-principles density functional calculations. The electronic density of states near Fermi level of these compounds are dominated by the transition metal $d$ orbitals and Si/Ge $p$ orbitals, forming six sheets of Fermi surfaces. The asymmetric spin-orbit coupling lifts the spin degeneracies and creates four topological Weyl nodal rings around $X$ points, protected by the nonsymmorphic symmetry and time-reversal symmetry. The bare-electron susceptibility does not show a prominent feature, and electron-phonon coupling is sufficient to explain the observed superconductivity.

The emerging thermal metamaterials and metadevices demonstrate significant potential to transform thermal conduction. However, the thermal conductivities of existing devices are all restricted at fixed values if the configuration or constituent materials are static. Thermal convection provides an additional tool to boost and flexibly modify the heat transfer in moving matter, but it is essentially distinct from thermal conduction since the Onsager reciprocity is generally broken in the former but preserved in the latter. Therefore, it is difficult to use convective components for sophisticated control of conductive heat. Here, it is shown that a convective system can be made undistinguishable from a conductive one in principle, by discovering and operating on the reciprocal line of mechanically rotating systems. The realized thermal metadevice can thus mimic a solid-like material whose thermal conductivity dynamically covers a wide range. It offers great possibilities of real-time smooth control over heat transfer for broad applications.

The optical properties, structural properties and electronic properties of a new two-dimensional (2D) monolayer C3N under different strains are studied in this paper by using first-principles calculations. The applied strain includes in-layer biaxial strain and uniaxial strain. The monolayer C3N is composed of a number of hexagonal C rings with N atoms connecting them. It is a stable indirect band gap 2D semiconductor when the strain is 0%. It could maintain indirect semiconductive character under different biaxial and uniaxial strains from e = −10% to e = 10%. As for its optical properties, when the uniaxial strain is applied, the absorption and reflectivity along the armchair and zigzag directions exhibit an anisotropic property. However, an isotropic property is presented when the biaxial strain is applied. Most importantly, both uniaxial tensile strain and biaxial tensile strain could cause the high absorption coefficient of monolayer C3N to be in the deep ultraviolet region. This study implies that strain engineering is an effective approach to alter the electronic and optical properties of monolayer C3N. We suggest that monolayer C3N could be suitable for applications in optoelectronics and nanoelectronics.

Bismuth based (Bi-based) materials exhibit promising potential for the study of two-dimensional (2D) topological insulators or quantum spin Hall (QSH) insulators due to their intrinsic strong spin-orbit coupling (SOC). Herein, we theoretically propose a new inversion-asymmetry topological phase with tunable Rashba effect in a 2D bismuthene monolayer, which is driven by the sublattices half-oxidation (SHO). The nontrivial topology is identified by the SHO induced p-p band inversion at the Γ point, the Z2 topological number, and the metallic edge states. Interestingly, the SOC opens a band gap as large as 0.26 eV at Γ, which is twice as large as that of the freestanding bismuthene monolayer, revealing a predominant contribution of the orbital filtering effect. Inversion-symmetry breaking leads to a substantial Rashba constant of 11.5 eV Å near the valence band top, which is about twice as large as that of the freestanding bismuthene monolayer due to the SHO effect. In particular, the topological insulator-to-topological semimetal phase-transition and the tunable Rashba effect were achieved by exerting a moderate strain. We demonstrate that 3% stretching is the most desirable strain to obtain superior properties. Hexagonal boron nitrogen (h-BN) is proposed to serve as a suitable substrate for SHO-Bi in practical applications. Our findings not only provide a new route to engineering a 2D inversion-asymmetry topological insulator but also represent a significant advance in the exploration of 2D Bi-based topological materials.

Superconductivity in crystals without inversion symmetry has received extensive attention due to its unconventional pairing and possible nontrivial topological properties. Using first-principles calculations, we systemically study the electronic structure of noncentrosymmetric superconductors A2Cr3As3 (A = Na, K, Rb, and Cs). Topologically protected triply degenerate points connected by one-dimensional arcs appear along the C3 axis, coexisting with strong ferromagnetic (FM) fluctuations in the non-superconducting state. Within random phase approximation, our calculations show that strong enhancements of spin fluctuations are present in K2Cr3As3 and Rb2Cr3As3 and are substantially reduced in Na2Cr3As3 and Cs2Cr3As3. Symmetry analysis of pairing gap Δ(k) and spin–orbit coupling gk suggest that the arc surface states may also exist in the superconducting state, giving rise to possible nontrivial topological properties.

Significance The 3D nodal points in Dirac and/or Weyl semimetals are in the vanguard of quantum materials research. A hallmark of these systems is the linear band dispersion. This latter electronic stricture gives rise to unconventional transport and optical phenomena. Here, we demonstrate that solids with dispersive nodal lines in the electronic structure share many common aspects with the response of 3D nodal-points systems. We investigated N b A s 2 using a combination of optical and magneto-optical techniques and have identified electromagnetic signature of dispersive nodal lines. This particular compound has allowed us to inquire the impact of spin-orbit coupling on the universal characteristic of nodal metals.

We have performed systematic first principles study of the electronic structure and band topology properties of $LnPn$ compounds ($Ln$=Ce, Pr, Gd, Sm, Yb; $Pn$=Sb, Bi). Assuming the $f$-electrons are well localized in these materials, both hybrid functional and modified Becke-Johnson calculations yield electronic structure in good agreement with experimental observations, while generalized gradient approximation calculations severely overestimate the band inversions. From Ce to Yb, a systematic reduction of band inversion with respect to the increasing $Ln$ atomic number is observed, and $\mathcal{Z}_2$ for Ce$Pn$ and Yb$Pn$ are [1;000] and [0;000], respectively. In both hybrid functional and modified Becke-Johns calculations, a topologically nontrivial to trivial transition is expected around SmSb for the antimonides and around DyBi for the bismuthides. Such variation is related with lanthanide contraction, but is different from simple pressure effect., Updated version

Topological metals, including Dirac and Weyl semimetals, represent a wide class of quantum materials with non-trivial electronic band structures. The essential properties of Dirac or Weyl fermions, including light effective mass and high mobility, have been observed in a number of semimetal compounds, which in turn exhibit large positive magnetoresistances. Here, we report an unexpected observation of all these properties in α-gallium (α-Ga) single crystals, a pure metal that is in the liquid phase at room temperature and ambient pressure. Based on systematical transport measurements, α-Ga single crystal is found to exhibit large magnetoresistance, reaching about 1.66 × 106 per cent at 2 K in a magnetic field of 9 T. At low temperatures the de Haas–van Alphen and Shubinikov de Hass quantum oscillations show ultrahigh mobility and very small cyclotron effective mass for charge carriers, together with a non-trivial Berry phase. Combined with first-principle band structure calculations, these properties demonstrate α-Ga as a rare topological pure metal. Furthermore, superconductivity with Tc of ~0.9 K is confirmed by both specific heat and resistivity measurements. These findings suggest that α-Ga is a unique pure metal displaying both non-trivial topological and superconducting properties. A comprehensive investigation of bulk properties of α-Ga single crystals grown using a super cooled method—Ga is a metal that is liquid at room temperature—revealed that at very low temperatures this material exhibits a number of interesting properties; in particular, topology and superconductivity coexist. Bin Chen and colleagues measured a very large magnetoresistance, accompanied by a light effective mass and high mobility for the charge carriers, properties that suggest that the material is a topological metal. This conclusion is supported by first-principle calculations. Moreover, previous measurements indicating that the material is superconducting at very low temperature were experimentally confirmed. Materials exhibiting both topological properties and superconductivity provide a useful testing ground for understanding the interplay between superconducting pairing mechanisms and topology of the electronic band structure.

Design of functional materials with targeted properties is a challenge because of the diversity of their potential structures. The functional performances of materials are mainly determined by the chemistry and electronic structure of modules consisting of local atomic groups with special arrangements. Tetrahedral modules are excellent modules for designing deep-ultraviolet/ultraviolet (UV) nonlinear optical (NLO) materials, but they are rarely favored due to their unpredictable optical anisotropy and second harmonic generation (SHG) response. In this work, we have developed a module-guided ab initio approach for evaluating the optical anisotropy of tetrahedral modules. The application of this method indicates that the tetrahedral modules with a specific arrangement will enhance the optical anisotropy of materials. With the functional modules consisting of tetrahedral modules and rare-earth cations, new high-performance rare-earth phosphates were assembled. These materials are promising deep-UV NLO materials because of their appropriate birefringences, large band gaps, moderate SHG responses, and easy to obtain large size crystals.

Transition-metal chalcogenides host various phases of matter, such as charge-density wave (CDW), superconductors, and topological insulators or semimetals. Superconductivity and its competition with CDW in low-dimensional compounds have attracted much interest and stimulated considerable research. Here we report pressure induced superconductivity in a strong spin-orbit (SO) coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe$_4$, which is a CDW material under ambient pressure. With increasing pressure, the CDW transition temperature is gradually suppressed, and superconducting transition, which is fingerprinted by a steep resistivity drop, emerges at pressures above 12.4 GPa. Under pressure $p$ = 69 GPa, zero resistance is detected with a transition temperature $T_c$ = 2.2 K and an upper critical field $H_{c2}$= 2 T. We also find large magnetoresistance (MR) up to 102\% at low temperatures, which is a distinct feature differentiating NbTe$_4$ from other conventional CDW materials., https://rdcu.be/LX8w

The first successful catalytic borylation of unactivated aromatic C-N bonds of tertiary anilines without the preactivation or any directing groups is demonstrated. The reactivity of both N,N-dialkylarylamines and N-arylpyrroles were investigated systematically, and the targeted products were furnished in moderate to good yields. The DFT calculation results indicated that the catalytic cycle is furnished via a five-membered cyclic transition-state due to the steric hindrance of the Ni/NHC catalytic system.

As the isoelectronic counterpart of phosphorene, monolayer group IV-VI binary MX (M = Ge, Sn; X = Se, S) compounds have drawn considerable attention in recent years. In this paper, we construct four high-symmetry stacking models for bilayer MX to tune their electronic properties. We systematically explore the dynamical and thermal stabilities of all bilayer MX. It is found that five of them are possible at room temperature. Then, we perform first-principles calculations to study how the bilayer structure affects their electronic properties. The results demonstrate that the electronic properties of MX materials can be modulated by forming bilayer structures. Their bandgap can be tuned over a wide range from 0.789 to 1.617 eV, and an indirect-to-direct transition occurs in three cases. Considering the flexibility of bilayer MX, we utilize in-plane uniaxial tensile strain to adjust their band structures and achieve much more indirect-to-direct bandgap transitions. The realization of direct bandgaps will be helpful for their application in next-generation high-efficiency modern nano-optoelectronic and photovoltaic devices. We also study the responses of different bilayer MX to an external vertical electric field. It is found that their bandgaps decrease rapidly with the increase of the electric field.

As one of the most potentially ideal carriers of single-atom catalysts (SACs), two-dimensional materials have been widely concerned by researchers. In this work, the electronic properties and electrocatalytic activity of precious metals (PM) adsorbed silicene are studied based on density functional theory (DFT). The results show that Ru-, Rh-, Pd-, Os-, Ir-, and Pt-adsorbed silicene at the H-site are more stable. Secondly, From the comparative analysis of the adsorption energy and free energy of the hydrogen evolution reaction (HER) intermediates and oxygen evolution reaction (OER) intermediates of the stable adsorption systems, it can be concluded that the Ru, Rh, and Ir adsorption systems can promote the hydrogen evolution reaction (HER) process, while the Rh adsorption system has good oxygen evolution reaction (OER) activity. Besides, the electronic properties of precious metals (PM) adsorbed silicene are also discussed. Our theoretical studies indicated that silicene supported precious metals (PM) have good electrocatalytic performance, which could contribute to the application of silicene in electrocatalysis in the future.

We investigate the electronic structure of group VI-B transition metal di-arsenides (TAs2, T = Mo, W). By comparing the formation energies, the centrosymmetric di-arsenides compounds are energetically more stable, in contrast to the di-phosphorides (MoP2/WP2). Both compounds can be well described by a two-band model with a pair of well-separated electron/hole bands. The electron/hole carrier density is nearly compensated in MoAs2 (|n e − n h |/n h $${{\mathscr{Z}}}_{2}$$ Z 2 classification for all partially occupied bands are topologically strong (1;001), and therefore robust surface states are expected in these materials. Using the adaptive K-mesh method, no energy degenerate state could be found except the spin degeneracy in the whole Brillouin zone, excluding the possibility of intrinsic Dirac or Weyl points near the Fermi level in the system.

As a member of the binary group-Ⅳ monochalcogenide monolayer materials, GeSe monolayer possesses better property than most others due to its direct band-gap and small carrier effective mass. Hence, we chose GeSe monolayer as the object to embellish and modify. Using density functional theory calculations, we have investigated its tunable electronic and magnetic properties via absorbing light non-metallic atom (H, F, Cl). From our study, we can see that, in H adatom-decorated system, the electronic property of GeSe monolayer can be effectively manipulated, and keeps the direct band-gap in most situations. H adatom-decorated structures have dilute magnetic states. Most of them cause a bipolar semiconducting behavior, while the rest owns a spin-gapless-semiconducting feature. For most of the F and Cl adatom-decorated systems, they own p-type semiconducting feature. Meanwhile, the magnetism appears only in F adatom-decorated D-Se structure. These results demonstrate that the decoration for GeSe is an available approach to tune its electronic and magnetic properties. After the modification, the GeSe monolayer shows desirable potential in the application of spintronics and optoelectronic devices.

Based on first-principles calculations including spin-orbit coupling, we investigated the stability and electronic structure of unexplored double-side decorated arsenenes. It has been found that these new double-side decorated arsenenes, which we call “hydrogen-arsenene-halogen (H-As-X, X is halogen)”, are dynamically stable via the phonon dispersion calculations except H-As-F sheets. In particular, all of H-As-X nanosheets are direct band gap semiconductors with a strong dispersion near the Fermi level, which is substantially different from the previous works of double-side decorated arsenenes with zero band gaps. Our results reveal a new route to change the band gap of arsenene from indirect to direct. Furthermore, we also studied bilayer, trilayer, and multilayer H-As-Cl sheets to explore the effects of the layer number. The results indicate that bilayer, trilayer, and multilayer H-As-Cl sheets display novel electronic structure, namely multi-Dirac cones character, and the Dirac character depends sensitively on the layer number. It is noted that the frontier states near the Fermi level are dominantly controlled by the top and bottom layers in trilayer and multilayer H-As-Cl sheets. Our findings may provide the valuable information about the new double-side decorated arsenene sheets in various practical applications in the future.

Materials where the electronic bands have unusual topologies allow for the realization of novel physics and have a wide range of potential applications. When two electronic bands with linear dispersions intersect at a point, the excitations could be described as Weyl fermions which are massless particles with a particular chirality. Here we report evidence for the presence of Weyl fermions in the ferromagnetic state of the low-carrier density, strongly correlated Kondo lattice system CeSb, from electronic structure calculations and angle-dependent magnetoresistance measurements. When the applied magnetic field is parallel to the electric current, a pronounced negative magnetoresistance is observed within the ferromagnetic state, which is destroyed upon slightly rotating the field away. These results give evidence for CeSb belonging to a new class of Kondo lattice materials with Weyl fermions in the ferromagnetic state., Comment: 18 pages, 4 figures, Supplementary Information available from journal link (open access)

In this article a successful protocol was developed to construct carbon–carbon bonds by the extrusion of the O atom of ethers via nickel catalysis in the presence of reductants. This methodology is featured as a highly economic route to construct sp3–sp3 C–C bonds through dual C–O activation of ethers with good functional group tolerance.

A moveable multi-use neutron imaging facility was constructed based on a compact accelerator D-T neutron source, for use in thermal and fast neutron radiography and tomography. Experiments were carried out to investigate the imaging quality for different standard samples. The smallest width of a slit that can be tested by digitized thermal neutron radiography was found to be 0.06 mm, while the smallest diameter of holes tested by digitized fast neutron radiography was 0.5 mm. A gadolinium wire of 0.2 mm in diameter within a multi-material structure was reconstructed clearly with thermal neutron tomography, and holes in a light material were reconstructed with fast neutron tomography.

Author(s): Xie, W; Wu, Y; Du, F; Wang, A; Su, H; Chen, Y; Nie, ZY; Mo, SK; Smidman, M; Cao, C; Liu, Y; Takabatake, T; Yuan, HQ | Abstract: A number of rare-earth monopnictides have topologically nontrivial band structures together with magnetism and strong electronic correlations. In order to examine whether the antiferromagnetic (AFM) semimetal YbAs (TN=0.5 K) exhibits such a scenario, we have grown high-quality single crystals using a flux method, and characterized the magnetic properties and electronic structure using specific heat, magnetotransport, and angle-resolved photoemission spectroscopy (ARPES) measurements, together with density functional theory (DFT) calculations. Both ARPES and DFT calculations find no evidence for band inversions in YbAs, indicating a topologically trivial electronic structure. From low-temperature magnetotransport measurements, we map the field-temperature phase diagram, where we find the presence of a field stabilized phase distinct from the AFM phase at low temperatures. An extremely large magnetoresistance (XMR) for both YbAs and the nonmagnetic counterpart LuAs is also observed, which can consistently be accounted for by the presence of electron-hole compensation. Moreover, an angle-dependent study of the Shubnikov-de Haas effect oscillations reveals very similar Fermi surfaces between YbAs and LuAs, with light effective masses down to at least 0.5 K, indicating that the Yb-4f electrons are well localized, and do not contribute to the Fermi surface. However, the influence of the localized Yb-4f electrons on the magnetotransport of YbAs can be discerned from the distinct temperature dependence of the XMR compared to that of LuAs, which we attribute to the influence of short-ranged spin correlations that appear well above TN.

Logistics activities are an important source of energy consumption and environmental issues. Research conclusions and practical experience show that promoting the development of container multimodal transport is an effective way to reduce the level of carbon footprint. The key to influencing the development of container multimodal transport lies in the cooperation of all participants and links (modes of transport, transport businesses). Evaluating the synergy degree is a key step in this development process. This paper takes the whole process of container multimodal transportation as the research perspective, analyzes the operation process, and treats the process as a production system composed of four subsystems: facilities and equipment, organizational management, business operations, and information interactions. Through in-depth interviews and an analysis of the academic literature and policy documents, we establish a synergy degree evaluation index system and measurement model of container multimodal transport based on synergy theory and case studies. The research results are consistent with the actual situation. From 2015 to 2018, the synergy of container multimodal transport system of China&rsquo, s G port developed slowly, but generally moved in a more orderly direction.

In ferromagnetic solids, a transverse voltage can be generated by a longitudinal temperature gradient even in the absence of a magnetic field. This thermoelectric counterpart of the anomalous Hall effect is dubbed the anomalous Nernst effect (ANE), and both of these effects are expected to scale with spontaneous magnetization. Here, we report the observation of a giant ANE in a newly discovered magnetic Weyl semimetal ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ crystal. The Hall effect and the Nernst effect show sharp jumps at a threshold field and exhibit a clear hysteresis loop below the Curie temperature ${T}_{C}$. The anomalous Nernst signal, ${S}_{yx}^{A}$, peaks at a maximum value of $\ensuremath{\sim}5$ $\ensuremath{\mu}\mathrm{V}/\mathrm{K}$, which is comparable to the largest seen in previous magnetic materials and seriously violates the conventional scale relation in conventional ferromagnets. Moreover, the anomalous transverse thermoelectric conductivity ${\ensuremath{\alpha}}_{yx}^{A}$ reaches about $\ensuremath{\sim}10$ A/K m at 70 K, the largest in known semimetals. These results together with first-principles calculation provide strong evidence that the giant ANE originated from the nontrivial Berry curvature near the chiral Weyl points, which are very close to the Fermi level in this compound.

We report the discovery of a new noncentrosymmetric superconductor CaPtAs. It crystallizes in a tetragonal structure (space group $I4_1md$, No.109), featuring three dimensional honeycomb networks of Pt-As and a much elongated $c$-axis ($a = b = 4.18 $ \AA, and $c = 43.70 $ \AA). The superconductivity of CaPtAs with $T_c$ = 1.47 K was characterized by means of electrical resistivity, specific heat, and ac magnetic susceptibility. The electronic specific heat $C_\mathrm{e}(T)/T$ shows evidence for a deviation from the behavior of a conventional BCS superconductor, and can be reasonably fitted by a $p$-wave model. The upper critical field $\mu_0H_{c2}$ of CaPtAs exhibits a relatively large anisotropy, with an in-plane value of around 204 mT and an out-of-plane value of 148 mT. Density functional theory calculations indicate that the Pt-5$d$ and As-4$p$ orbitals mainly contribute to the density of states near the Fermi level, showing that the Pt-As honeycomb networks may significantly influence the superconducting properties., Comment: 9 pages, 8 figures. Accepted for publication in Science China Physics, Mechanics & Astronomy

We investigate the electronic structure of nickelate superconductor NdNiO2 upon hole doping, by means of density-functional theory and dynamical mean-field theory. We demonstrate the strong intrinsic hybridization between strongly correlated states formed by Ni-3dx2-y2 orbital and itinerant electrons due to Nd-5d and Ni-3dz2 orbitals, producing a valence-fluctuating correlated metal as the normal state of hole-doped NdNiO2. The Hund's rule appears to play a dominating role on multi-orbital physics in the lightly doped compound, while its effect is gradually reduced by increasing the doping level. Crucially, the hole-doping leads to intricate effects on Ni-3d orbitals, such as a non-monotonic change of electron occupation in lightly doped level, and a flipping orbital configuration in the overdoped regime. Additionaly, we also map out the topology of Fermi surface at different doping levels. These findings render a preferred window to peek into electron pairing and superconductivity., Comment: 6 pages, 4 figures. 4 supply pages

Lifshitz transition represents a sudden reconstruction of Fermi surface structure, giving rise to anomalies in electronic properties of materials. Such a transition does not necessarily rely on symmetry-breaking and thus is topological. It holds a key to understand the origin of many exotic quantum phenomena, for example the mechanism of extremely large magnetoresistance (MR) in topological Dirac/Weyl semimetals. Here, we report studies of the angle-dependent MR (ADMR) and the thermoelectric effect in W2As3 single crystal. The compound shows a large unsaturated MR (of about 70000% at 4.2 K and 53 T). The most striking finding is that the ADMR significantly deforms from the horizontal dumbbell-like shape above 40 K to the vertical lotus-like pattern below 30 K. The window of 30-40 K also corresponds substantial changes in Hall effect, thermopower and Nernst coefficient, implying an abrupt change of Fermi surface topology. Such a temperature-induced Lifshitz transition results in a compensation of electron-hole transport and the large MR as well. We thus suggest that the similar method can be applicable in detecting a Fermi-surface change of a variety of quantum states when a direct Fermi-surface measurement is not possible., Comment: 19 pages, 5 figures

Elucidating the orbital level origin of second harmonic generation (SHG) in materials and identifying the local contributions is a long-standing challenge. We report a first principles approach for the SHG where the contributions from individual orbitals or atoms can be evaluated via symmetry adapted Wannier functions without semiempirical parameters. We apply this method to the common SHG materials KBe_{2}BO_{3}F_{2}, KCaCO_{3}F, and β-BaB_{2}O_{4}, and show that the orbitals on noncentrosymmetric sublattices are responsible for SHG effect and the energies of these orbitals control the magnitude.

Using angle-resolved photoemission spectroscopy (ARPES) and resonant ARPES, we report evidence of strong anisotropic conduction-$f$ electron mixing ($c\text{\ensuremath{-}}f$ mixing) in CeBi by observing a largely expanded Ce $5d$ pocket at low temperature, with no change in the Bi $6p$ bands. The anisotropic Fermi surface (FS) expansion is accompanied by a pronounced spectral weight transfer from the local $4{f}^{0}$ peak of Ce (corresponding to $\mathrm{C}{\mathrm{e}}^{3+}$) to the itinerant conduction bands near the Fermi level. Careful analysis suggests that the observed large FS change (with a volume expansion of the electron pocket up to 40%) can most naturally be explained by a small valence change $(\ensuremath{\sim}1%)$ of Ce, which coexists with a very weak Kondo screening. Our work therefore provides evidence for a FS change driven by real charge fluctuations deep in the Kondo limit, which is highly dependent on the orbital character and momentum and is made possible by the low carrier density.

We report the first-principles study on the H-intercalated Cr-based superconductor ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}{\mathrm{H}}_{x}$. Our results show a paramagnetic ground state for ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}\mathrm{H}$. The electronic structure consists of two quasi-one-dimensional (Q1D) Fermi surfaces and one three-dimensional Fermi surface which are mainly contributed by Cr-${d}_{{z}^{2}}, {d}_{{x}^{2}\ensuremath{-}{y}^{2}}$, and ${d}_{xy}$ orbitals. The bare electron susceptibility shows a $\mathrm{\ensuremath{\Gamma}}$-centered imaginary peak, indicating possible ferromagnetic spin fluctuations. Upon moderate hole doping, the system undergoes a Lifshitz transition, which may enhance the Q1D feature of the system. The Bader charge analysis and electron localization functions reveal a strong bonding nature of hydrogen in ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}\mathrm{H}$, which results in a nontrivial electron doping in ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}\mathrm{H}$.

IMPORTANCE: Prolonged sitting, particularly watching television or videos, has been associated with increased risk of multiple diseases and mortality. However, changes in sedentary behaviors over time have not been well described in the United States. OBJECTIVE: To evaluate patterns and temporal trends in sedentary behaviors and sociodemographic and lifestyle correlates in the US population. DESIGN, SETTING, AND PARTICIPANTS: A serial, cross-sectional analysis of the US nationally representative data from the National Health and Nutrition Examination Survey (NHANES) among children aged 5 through 11 years (2001-2016); adolescents, 12 through 19 years (2003-2016); and adults, 20 years or older (2003-2016). EXPOSURES: Survey cycle. MAIN OUTCOMES AND MEASURES: Prevalence of sitting watching television or videos for 2 h/d or more, computer use outside work or school for 1 h/d or more, and total sitting time (h/d in those aged ≥12 years). RESULTS: Data on 51 896 individuals (mean, 37.2 years [SE, 0.19]; 25 968 [50%] female) were analyzed from 2001-2016 NHANES data, including 10 359 children, 9639 adolescents, and 31 898 adults. The estimated prevalence of sitting watching television or videos for 2 h/d or more was high among all ages (children, 62% [95% CI, 57% to 67%]; adolescents, 59% [95% CI, 54% to 65%]; adults, 65% [95% CI, 61% to 69%]; adults aged 20-64 years, 62% [95% CI, 58% to 66%]; and ≥65 years, 84% [95% CI, 81% to 88%] in the 2015-2016 cycle). From 2001 through 2016, the trends decreased among children over time (difference, −3.4% [95% CI, −11% to 4.5%]; P for trend =.004), driven by non-Hispanic white children; were stable among adolescents (−4.8% [95% CI, −12% to 2.3%]; P for trend =.60) and among adults aged 20 through 64 years (−0.7% [95% CI, −5.6% to 4.1%]; P for trend =.82); but increased among adults aged 65 years or older (difference, 3.5% [95% CI, −1.2% to 8.1%]; P for trend =.03). The estimated prevalence of computer use outside school or work for 1 h/d or more increased in all ages (children, 43% [95% CI, 40% to 46%] to 56% [95% CI, 49% to 63%] from 2001 to 2016; difference, 13% [95% CI, 5.6% to 21%]; P for trend

Human activities for exploitation and utilization of coastal zones have transformed coastline morphology and severely changed regional flow fields, underwater topography, and sediment distribution in the sea. In this study, single-beam bathymetry coupled with sediment sampling and analysis was carried out to ascertain submarine topography, geomorphology and sediment distribution patterns, and explore sediment provenance in Qinzhou Bay, China. The results show the following: (1) the underwater topography in Qinzhou Bay is complex and variable, with water depths in the range of 0–20 m. It can be divided into four underwater topographic zones (the central (outer Qinzhou Bay), eastern (Sanniang Bay), western (east of Fangcheng Port), and southern (outside of the bay) parts), (2) based on geomorphological features, the study area comprises four major submarine geomorphological units (i.e., tide-dominated delta, tidal sand ridge group, tidal scour troughs, and underwater slope) and two intertidal geomorphological units (i.e., tidal flat and abrasion platforms), (3) sandy sediments are widely present in Qinzhou Bay, accounting for 70% of the total sediments. From the mouth of the Maowei Sea to the central and northern part of Qinzhou Bay, the sediments gradually become coarser, shifting from sandy mud to muddy sand, and then to fine sand and medium–coarse sand, especially inside the trench. The detrital minerals contained in the sediments mainly consist of quartz, feldspar, ilmenite, leucosphenite, tourmaline, and detrital minerals, whereas the clay minerals are dominated by kaolinite, followed by illite and smectite. The sediment provenance is mainly terrigenous input from near-source river. With sea reclamation and dam construction, outer Qinzhou Bay has experienced enormous morphological variation of its coastline. Human activities for exploitation and utilization of coastal zones have transformed coastline morphology and severely changed regional flow fields, underwater topography, and sediment distribution in the sea. Together with the channel effect where the velocity of ebb tide is greater than that of flood tide, the underwater topography is characterized by increased scale and height difference of troughs and ridges as well as enhanced offshore deposition.