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The electrical conductivity of mineral aggregates depends both on the properties of the constitutive minerals and the ways those minerals are assembled. Mixing, or average models combine the conductivity of single phases to give bulk conductivity of rocks, thereby linking experimental measurements to geophysical observations. In order to compare these mixing models and allow an informed choice, several popular approaches, including bounds and average models, have been used to estimate the conductivity of a typical dry upper mantle and transition zone with a pyrolite composition. All the estimations calculated using the various average models lie between the rigorous constraint that is given by the HS bounds. The average models in this study are found to give similar bulk conductivities with the difference of less than 0.5 orders of magnitude, except the geometric mean, implying that the choice of the average models is insignificant. The effective electrical conductivity of pyrolite mantle has been derived from the conductivity of dry mantle minerals using the effective medium theory, and was found consistent with observed conductivity values for some subsurface regions of the Earth which we expect to be relatively dry. This provides us with baseline conductivity for a dry mantle, which is helpful to understand the water distribution in the deep earth.

Engineering nanoheterostructures (NHs) plays a key role in exploring novel or enhanced physicochemical properties of nanocrystals. Despite previously reported synthetic methodologies, selective synthesis of NHs to achieve the anticipated composition and interface is still challenging. Herein, we presented a colloidal strategy for the regioselective construction of typical Ag-Co2P NHs with precisely controlled location of Ag nanoparticles (NPs) on unique chemically transformed Co2P nanorods (NRs) by simply changing the ratio of different surfactants. As a proof-of-concept study, the constructed heterointerface-dependent hydrogen evolution reaction (HER) catalysis was demonstrated. The multiple Ag NP-tipped Co2P NRs exhibited the best HER performance, due to their more exposed active sites and the synergistic effect at the interfaces. Our results open up new avenues in rational design and fabrication of NHs with delicate control over the spatial distribution and interfaces between different components.

A central issue in the study of fault evolution is to identify shear weakening and its mechanism; currently, studies of fault weakening in narrow slip deformation zones, including those of various slipping planes such as schistosity, foliation, cleavage, joints and faults in rocks, are ongoing. To verify the nanoweakening in shear slipping, we carried out experiments: triaxial compression experiments on sandstones and uniaxial compression experiments on granites. Furthermore, on the basis of scanning electron microscopy (SEM) observations and experimental data analyses, we suggested three kinds of nanoweakening in terms of the corresponding strain stages: (1) The slip nanoweakening caused by the strain hardening deformation stage of the shear slip, which creates nanograins with dense coatings that may be due to the nanocoating on the shear planes, can result in rolling friction rather than with sliding friction, and the former is a principal mechanism of sliding nanoweakening. (2) The rheological nanoweakening caused by the strain softening deformation stage; in view of developing weakened deformation due to grain boundary migration (GBM), the flow of synkinematic minerals and melt coating phenomena lead to rheological nanoweakening. (3) The dynamic nanoweakening caused by thermal pressurization and fluid pressurization during the strain softening stage and strain degenerating stage. Thus, when these aspects are considered in defining the relationship between the nanoweakening at the slipping planes and the strain stages, the representative mechanism and its behavior rules can be obtained.

ConspectusProgramming nanoscale functional objects into complex, sophisticated heterostructures that tremendously outperform their solo objects and even bring about exotic chemical/physical propert...

In this paper, we propose a polarization insensitive metasurface to generate broadband vortex beams with narrow divergence angle. The metasurface is composed of $\mathrm {30\times 30 }$ I-shaped metal elements printed on the F4B substrate with metal ground plane. The wideband is realized by optimizing the parameters of I-shaped unit cell to adjust the resonant frequency. A 360° phase range is achieved by rotating the element along the central axis. The phase superposition method is used to design the metasurface to generate vortex beams with narrow divergence angle. The proposed metasurface can generate broadband vortex beams under circular polarization (CP) and linear polarization (LP) wave excitation. The far-field radiation patterns and near-field characteristics of the metasurface are simulated to verify the proposed design. The gain of vortex beams is better than 15 dBi within 12–20 GHz (relative bandwidth of 50%), and the maximum gains are 23.2 dBi, 25.3 dBi for CP and LP cases, respectively. The broadband metasurface is fabricated and measured, and the measured results agreed well with the simulated ones. The proposed design provides a convenient and flexible way to realize broadband vortex beams with narrow divergence angle.

Interpretation of deep earth structures from electromagnetic data requires the constraint from the electrical conductivity of various minerals experimentally measured at high temperature and high pressure. However, the combination of these measured conductivities of different minerals always fails to match the conductivities of the multiphase rocks under in-situ conditions. To investigate the effect of ion segregation at grain boundaries on bulk conductivity, we measured the electrical conductivities of quartz, albite, and orthoclase single-phase aggregates, as well as those of two multiphase aggregates made up of the three minerals at both ambient pressure and 1 GPa over a range of temperatures. The electrical conductivities of the multiphase aggregates were an order of magnitude higher and the activation enthalpies were lower than those of the three single-phase aggregates. A significant dependence of conductivity on grain size was identified in the multiphase aggregates but not in the single-phase aggregates. The interdiffusion of alkali ions between orthoclase and albite initiated grain boundary ionic conduction, which enhanced the bulk conductivity of the multiphase aggregates to 20 S/m at 1073 K. This conduction mechanism might explain the electrical conductivity anomalies of the active shear zone in the crust.

A nonconformal twofold domain decomposition method (TDDM) based on the hybrid finite element method-boundary element method (FEM-BEM) is proposed for analyzing 3-D multiscale composite structures. The proposed TDDM starts by partitioning the composite object into a closed exterior boundary domain and an interior volume domain. The interior and exterior boundary value problems are coupled to each other through the Robin transmission conditions (RTCs). Both domains are then independently decomposed into subregions to facilitate computation. Specifically, FEM-DDM with the second order transmission conditions (SOTCs) is employed for the interior domain, and BEM-discontinuous Galerkin (BEM-DG) based on the combined field integral equation (CFIE) is applied for the exterior boundary domain. The proposed TDDM allows for nonconformal discretization between any touching subdomains. Without the introduction of a stabilization term that relies on a line integral over intersection of nonmatching meshes and relevant terms involving surface-line integrals, the proposed TDDM provides an effective domain decomposition (DD) preconditioner for the global system. Numerical examples are presented, and the comparisons of the simulation results with FEM-BEM confirm the validity and accuracy of TDDM. Moreover, its ability to model practical large-scale and multiscale targets is also demonstrated.

The second-order nonlinear optical (NLO) effects are usually forbidden in materials with inversion symmetry, which restricts the application of graphene in NLO technologies such as phase-only modul...

We present a theoretical model that can be implemented to study the electromagnetic scattering problem in graphene structure arrays efficiently. The graphene structure arrays are treated as a uniform two-dimensional sheet, and accordingly the optical response is characterized by an equivalent surface conductivity. In the homogenization procedure, the surface conductivity of an infinite graphene sheet are used to depict the local resonances, and the interaction between structures is described by the depolarization factor. The method can be easily extended to investigate the optical properties of multilayer graphene structures by combining the transfer matrix method (TMM), in which the full wave simulations (such as finite element method) are very time- and resource-consuming. Our work provides an alternative solution to optoelectronic devices design based on layered graphene structures.

Pore types and pore size vary systematically across structural deformation in the shale gas reservoirs but lack a comprehensive study. Twelve Longmaxi Shale samples spanning a tectonism range from undeformed to deformed were formed in the structural deformation zone located in a field section of the Chuandong Thrust-Fold Belt, South China. Herein, pore structure investigations are performed using three types of organic-rich shale (undeformed shale, fault-related shale, and fold-related shale) with vitrinite reflectance (Ro value) ranging between 1.90 and 2.57% and total organic carbon (TOC) content ranging between 2.25 and 4.40%. Compared to the undeformed shales, deformed samples are quartz rich and carbonate poor. Total porosity from mercury intrusion porosimetry (MIP) ranges between 3.74 and 5.62% in undeformed shales, 2.66–6.83% in fold-related shales, and 2.55–13.92% in fault-related shales. Scanning electron microscopy (SEM) study of the pore type evolution reveals organic matter (OM) pores are dominant in undeformed shales whereas the interparticle (interP) pores, intraparticle (intraP) pores, micro-channels, and micro-fractures are more developed in both fold- and fault-related shales. A combination of low-pressure gas (N2 and CO2) adsorption and MIP techniques suggests that with increasing structural deformation, micropore volumes relatively increase in fold-related samples, while macropore volumes significantly increase in fault-related shales. These observations and experiments confirm that tectonism produces an open and interconnected pore network within organic-rich shale, which is not related to OM pores. The role of structural deformation during ductile folding and brittle sliding, both in changing the mineral composition and in the producing process of the new pore networks, may be critical to understanding tectonism on organic-rich shales. These data could provide important theoretical guidance and scientific basis for the exploration and development of shale gas and resources assessment in the complex tectonic area of South China.

Cephalopods have remarkable ability to change their body color across a wide range of wavelengths, yet the structural basis remains largely unknown. Reflectin, a protein family assumed to be responsible for structural color in cephalopods, has unique features of higher-order assembly that are tightly regulated by aromatic molecules. Here, we reconstructed the dynamic and reversible color change using purified reflectin protein and demonstrated how the conformational change and the status of assembly led to the change in optical properties. In addition, optical spectral and structural analyses indicated that the “cephalopod-blue” primarily resulted from wavelength-dependent light scattering rather than reflection. Our results suggest a possible role of reflectin in color dynamics. The in vitro reconstruction system we present here may serve as an initial step for designing bio-inspired optical materials based on reflectin protein.

Organic rich shales in coal-bearing strata deposited from marine to lacustrine environments are well developed in China. The Paleozoic coal-bearing shales have been significantly altered by a series of tectonic movements. Based on XRD, SEM, MICP, and a nitrogen adsorption experiment and in combination with other parameters in this paper, the mineral composition and pore structure characterization and deformation mechanism of coal-bearing shales were surveyed. The coal-bearing shales in eastern China undergo various types of deformation, including brittle, ductile, and brittle-ductile deformation. In eastern China, the macro pore size of shales grew with increasing quartz content under different types of structural deformation, while the specific surface area decreases as the quartz content increases in different types of structural deformation; With the increasing of clay mineral content, the average pore size and the specific surface area of BET became larger in the various types deformation shale, while the pore volume decreased in the brittle and brittle -ductile deformation shale and increased in the ductile deformation shale. The ductile and brittle-ductile deformation increase the specific surface area, the total pore volume of nano-pores, and the adsorption capacity of liquid nitrogen, and decrease the nano pore diameter. The micropores in the brittle-ductile and ductile shearing of clay minerals may the main factors affecting pore volume and total specific surface area. And it is the mesoporous structure that undergoes evolution in brittle-ductile-deformed shales, leading them to have the maximum pore volume and pore-specific surface area for pore-fracture systems. Brittle shear results in micro-fractures or large pores and thus has an impact on the desorption and percolation capability of shale gas, Ductile deformation increases the specific surface area of shales and enhances their shale adsorption capacity.

Graphene magnetoplasmons, collective excitations of massless Dirac fermions, can be actively tuned by an external magnetic field in addition to electrostatic gating. Their magneto-optic properties are highly determined by the edges of the structure and their interaction. Here, we focus on the fundamental dipolar magnetoplasmon, which has strong optical activity, and report its extinction spectra in graphene circular rings, eccentric rings, and split rings. We find that, as compared to traditional graphene disks, circular rings still sustain symmetrical mode splitting (${\ensuremath{\omega}}_{+}$ and ${\ensuremath{\omega}}_{\ensuremath{-}}$) but with less energy difference $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}={\ensuremath{\omega}}_{+}\ensuremath{-}{\ensuremath{\omega}}_{\ensuremath{-}}$. Increasing the ratio of inner radius to outer radius, $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}$ will decrease further and eventually vanish at a critical ratio, which can be well described as a function of the only product of cyclotron frequency and relaxation time. In eccentric rings, a small translation of the inner hole will not change the mode splitting and thus the value of $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}$, but for a larger translation, $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}$ increases dramatically, with one magnetoplasmonic mode (polarization dependent) getting dark gradually. In split rings, due to symmetry breaking abruptly, even a very tiny split will cause the disappearance of mode splitting. Our findings contribute to a basic understanding of graphene magnetoplasmons which, in turn, can boost the application of graphene magneto-optic devices at terahertz and infrared frequencies.

The fixed bed gasifier has simple structure, convenient operation and maintenance, and is suitable for use in rural areas. In this paper, a downdraft fixed bed gasifier was designed for biomass gasification using corn cob as raw material. COMSOL Multiphysics software was used to simulate the reduction zone of biomass gasifier. The temperature field and concentration distribution of the reduction zone were studied. The influence of structural parameters of the reduction zone on the composition of syngas was analyzed. The rates of major chemical reactions in the reduction zone were also compared in detail.

Plasmonics in two-dimensional (2D) materials, an emerging direction of nano-optics, has attracted great attention recently, which exhibits unique properties than that in noble metals. Extending its advanced features by different manipulations is very beneficial for its promotion. In this paper, we study plasmonic excitations in graphene and black phosphorus (BP) nanostructures, where the effects of structural symmetry and material anisotropy are discussed. We show that the two factors are crucial to mode excitations, e.g. the extinction can be dominated by higher order modes rather than dipole resonance. The behavior occurs only in the direction hosting larger resonance frequencies, e.g. armchair (AC) direction of BP and shorter side of graphene rectangles. In BP rectangles along AC direction, the two factors are competing, and thus can be applied cooperatively to tune plasmonic resonance, from dipole to higher order excitations. Besides, the manipulation can also be achieved by designing BP square rings, in which the interaction between outer and inner edges show great impact on mode excitations. Our studies further promote the understanding of plasmonics in 2D materials, and will pave the way for particular plasmonic applications.

In mammals, it is believed that the intercellular coupling mechanism between neurons in the suprachiasmatic nucleus (SCN) confers robustness and distinguishes the central clock from peripheral circadian oscillators. Current in vitro culturing methods used in Petri dishes to study intercellular coupling by exogenous factors invariably cause perturbations, such as simple media changes. Here, we design a microfluidic device to quantitatively study the intercellular coupling mechanism of circadian clock at the single cell level, and demonstrate that vasoactive intestinal peptide (VIP) induced coupling in clock mutant Cry1-/- mouse adult fibroblasts engineered to express the VIP receptor, VPAC2, is sufficient to synchronize and maintain robust circadian oscillations. Our study provides a proof-of-concept platform to reconstitute the intercellular coupling system of the central clock using uncoupled, single fibroblast cells in vitro, to mimic SCN slice cultures ex vivo and mouse behavior in vivo phenotypically. Such a versatile microfluidic platform may greatly facilitate the studies of intercellular regulation networks, and provide new insights into the coupling mechanisms of the circadian clock.

Spin angular momentum (SAM), a fundamental property of light, is associated with the right-hand and left-hand circular polarizations. It has never been trivial to engineer a light beam with desired SAM, and especially at the frequency regime other than the visible region. A widely used approach is to build periodic arrays of plasmonic nanostructures that host two orthogonal dipole resonances. As the unit cell, its structure design is crucial, but the design principle remains obscure. We present a model of two orthogonal resonant Lorentz dipoles to quantitatively describe the creation of SAM in such plasmonic quarter-wave plates. The equal amplitude and $\ensuremath{\pi}/2$ phase difference are essential. The requirements can be achieved by structure modulation and, in addition, the amplitude can be manipulated by varying the polarization angle of incident waves. In practice, the resonant frequency difference of two dipoles $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}=|{\ensuremath{\omega}}_{A}\ensuremath{-}{\ensuremath{\omega}}_{B}|$, and their damping rate ${\ensuremath{\kappa}}_{A}$ and ${\ensuremath{\kappa}}_{B}$, should meet a basic criterion, such as $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}\ensuremath{\geqslant}\sqrt{{\ensuremath{\kappa}}_{A}{\ensuremath{\kappa}}_{B}}$. As an illustration, we design a cross-shaped circular polarization convertor, and show its structure and incident angle optimization. We find the optimal working frequency ${\ensuremath{\omega}}_{\mathrm{opt}}$ is roughly equal to $\sqrt{{\ensuremath{\omega}}_{A}{\ensuremath{\omega}}_{B}}$ at the critical condition $\mathrm{\ensuremath{\Delta}}\ensuremath{\omega}=\sqrt{{\ensuremath{\kappa}}_{A}{\ensuremath{\kappa}}_{B}}$. Our results provide good guidance on the design of SAM-enabled plasmonic devices for versatile applications.

Bipolar electrochemistry is an unconventional but powerful technique in the fields of materials science and analytical chemistry. We report here the one-step cathodic deposition of NixCu1–x alloys with a composition gradient and a morphology evolution on a copper substrate, based on an in-plane potential gradient over the interface of a bipolar electrode (BPE) and an electrolytic solution. The alloy gradient was characterized using scanning and transmission electron microscopy techniques. As a result, the deposited alloy layer exhibits a composition gradient from 0 to ca. 89% Ni atoms corresponding to an abundant morphology evolution from pyramids to dendrites and to nano/microballs along the surface of the BPE. Electrochemical screenings were performed for the dissected alloy specimens as the electrocatalyst of hydrogen evolution reaction. The present work shows that bipolar electrochemistry can give access to the fabrication of alloys with abundant architectures as high throughput screening candidates.

To compare the differences in dietary status and knowledge of esophageal cancer (EC) between residents of high- and low-incidence areas. We investigated dietary conditions and EC knowledge among residents in high- and low-EC incidence areas (Yanting and Qingzhen counties). Residents in Yanting consumed more pickled vegetables, salted meat and barbecued food (P

A nonconformal and nonoverlapping domain decomposition (DD) scheme for surface integral equations is presented to analyze electromagnetic scattering from electrically large and complex perfect electric conducting objects. In this work, a discontinuous Galerkin approach is employed to avoid the introduction of artificial touching faces between adjacent subdomains. To weakly enforce the current continuity at the cutting contours of these subdomains, a novel interior penalty term is defined so that the error energy associated with the error charges can be minimized. Consequently, without the introduction of a stabilization term that relies on the line integral over interactions of nonmatching meshes, the proposed method provides an effective DD preconditioner and requires no effort to be extended to curvilinear elements for higher modeling accuracy. To show this, curvilinear Rao–Wilton–Glisson basis functions defined over curvilinear elements are employed in this work to demonstrate the accuracy and efficiency of the proposed DD scheme.

In theory, the macroscopic fracture of materials should correspond with the thermodynamic limit of the fiber bundle model. However, the simulation of a fiber bundle model with an infinite size is unrealistic. To study the finite size effects of the fiber bundle model, fiber bundle models of various size are simulated in detail. The effects of system size on the constitutive behavior, critical stress, maximum avalanche size, avalanche size distribution, and increased step number of external load are explored. The simulation results imply that there is no feature size or cut size for macroscopic mechanical and statistical properties of the model. The constitutive curves near the macroscopic failure for various system size can collapse well with a simple scaling relationship. Simultaneously, the introduction of a simple extrapolation method facilitates the acquisition of more accurate simulation results in a large-limit system, which is better for comparison with theoretical results.

A novel implementation of the integral equation discontinuous Galerkin (IEDG)-based domain decomposition method (DDM), named as the IEDG-DDM, is developed for the efficient analysis of electromagne...

In this work, we propose broadband and switchable terahertz (THz) polarization converters based on either graphene patch metasurface (GPMS) or its complementary structure (graphene hole metasurface, GHMS). The patch and hole are simply cross-shaped, composed of two orthogonal arms, along which plasmonic resonances mediated by Fabry-Perot cavity play a key role in polarization conversion (PC). An incidence of linear polarization will be converted to its cross-polarization (LTL) or circular polarization (LTC), as the reflected wave in the direction of two arms owning the same amplitude and π phase difference (LTL), or ±π/2 phase difference (LTC). Such requirements can be met by optimizing the width and length of two arms, thickness of dielectric layer, and Fermi level EF of graphene. By using GPMS, LTL PC of polarization conversion ratio (PCR) over 90% is achieved in the frequency range of 2.92 THz to 6.26 THz, and by using GHMS, LTC PC of ellipticity χ ≤ −0.9 at the frequencies from 4.45 THz to 6.47 THz. By varying the Fermi level, the operating frequency can be actively tuned, and the functionality can be switched without structural modulation; for instance, GPMS supports LTL PC as EF = 0.6 eV and LTC PC of χ ≥ 0.9 as EF = 1.0 eV, in the frequency range of 2.69 THz to 4.19 THz. Moreover, GHMS can be optimized to sustain LTL PC and LTC PC of |χ| ≥ 0.9, in the frequency range of 4.96 THz to 6.52 THz, which indicates that the handedness of circular polarization can be further specified. The proposed polarization converters of broad bandwidth, active tunability, and switchable functionality will essentially make a significant progress in THz technology and device applications, and can be widely utilized in THz communications, sensing and spectroscopy.

Graphene quantum dots (GQDs) are nanosized fragments of graphene containing a bandgap caused by edge effects and quantum confinement. These features enable GQDs to have attractive photonics applications. During the preparation of graphene nanostructures, defects are unavoidable as they influence the behavior of π-electron transfer, which in turn impact the nonlinear optical (NLO) response. Herein, density functional theory was used to determine the electronic and three-order NLO properties of hexagonal GQDs with structural defects. The size of GQDs and the edge effects on their NLO properties were also investigated. Results showed with increased molecule size, the second hyperpolarizability increased for zigzag- and armchair-edged GQDs. This finding was due to the decrease in their frontier molecular-orbital energy gaps. Moreover, the introduction of point vacancy limited the π-electron transport in the zigzag-edged GQD, thereby widening the frontier molecular-orbital energy gap compared with the perfect zigzag-edged GQDs. However, in the presence of zigzag-edged GQDs having Stone–Wales defects, the energy gap decreased; consequently, the NLO response improved. All these findings provided new insights into the design of novel graphene-based NLO materials that may help expand the applications of GQDs in optoelectronic nanodevices.

Graphene quantum dots (GQDs) with unique and tunable physical properties have been the focus of considerable attention because of their potential for electronic and photonic applications. In this work, the electronic polarizability and second hyperpolarizability of hexagonal GQDs were investigated using density functional theory. The effects of size, substituent, and incident frequency of hexagonal GQDs on their electronic polarizability and second hyperpolarizability were comprehensively examined. Increasing the size of hexagonal GQDs enhanced the electronic polarizability and static second hyperpolarizability. The (hyper)polarizability of hexagonal GQDs was remarkably tuned by introducing electron donor/acceptor groups and incident frequency. This study provides new possibilities for practical applications of graphene materials in the nonlinear optical field.

In this paper, density functional theory method was employed to study the electronic absorption spectrum and electronic static second hyperpolarisability of X-shaped pyrazine derivatives with two-dimensional charge-transfer structures. Computational results show that the push–pull electron abilities of the substituent groups and the length of the conjugated chains affect the electronic spectrum and static second hyperpolarisability of the pyrazine derivatives. As the push–pull electron abilities of the substituent groups or the length of the conjugated chains increases, the frontier molecular orbital energy gap decreases, resulting in increased second hyperpolarisability and redshift of the electronic absorption bands. The electronic absorption spectra of the pyrazine derivatives maintain good transparency in the blue light band. The electronic static second hyperpolarisability exhibits a linear relationship to the frontier molecular orbital energy gap. Particularly, increasing/decreasing the push...