Tunable Interband Transitions in Twisted h-BN/Graphene Heterostructures

In twisted h-BN/graphene heterostructures, the complex electronic properties of the fast-traveling electron gas in graphene are usually considered to be fully revealed. However, the randomly twisted heterostructures may also have unexpected transition behaviors, which may influence the device performance. Here, we study the twist angle-dependent coupling effects of h-BN/graphene heterostructures using monochromatic electron energy loss spectroscopy. We find that the moir\'e potentials alter the band structure of graphene, resulting in a redshift of the intralayer transition at the M-point, which becomes more pronounced up to 0.25 eV with increasing twist angle. Furthermore, the twisting of the Brillouin zone of h-BN relative to the graphene M-point leads to tunable vertical transition energies in the range of 5.1-5.6 eV. Our findings indicate that twist-coupling effects of van der Waals heterostructures should be carefully considered in device fabrications, and the continuously tunable interband transitions through the twist angle can serve as a new degree of freedom to design optoelectrical devices

A numerical method for the inverse stochastic spectrum problem

Abstract. Inverse stochastic spectrum problem involves the construction of a stochastic matrix with a prescribed spectrum. A di erential equation aimed to bring forth the steepest descent ow in reducing the distance between isospectral matrices and nonnegative matrices, represented in terms of some general coordinates, is described. The ow is further characterized by an analytic singular value decomposition to maintain the numerical stability and to monitor the proximity to singularity. This ow approach canbe used to design Markov chains with speci ed structure. Applications are demonstrated by numerical examples

ON THE INVERSE EIGENVALUE PROBLEM FOR REAL CIRCULANT MATRICES

Abstract. The necessary condition for eigenvalue values of a circulant matrix is studied. It is then proved that the necessary condition also su ces the existence of a circulant matrix with the prescribed eigenvalue values. 1. Introduction

On the least squares approximation of symmetric-definite pencils subject to generalized spectral constraints

Abstract. A general framework for the least squares approximation of symmetric-de nite pencils subject to generalized eigenvalues constraints is developed in this paper. This approach can be adapted to di erent applications, including the inverse eigenvalue problem. The idea is based on the observation that a natural parameterization for the set of symmetric-de nite pencils with the same generalized eigenvalues is readily available. In terms of these parameters, descent ows on the isospectral surface aimed at reducing the distance to matrices of the desired structure can be derived. These ows can be designed to carry certain other interesting properties and may beintegrated numerically

A coupled thermal–hydrological–mechanical model for geothermal energy extraction in fractured reservoirs

Abstract Understanding fluid flow in fractured porous media under coupled thermal–hydrological–mechanical (THM) conditions is a fundamental aspect of geothermal energy extraction. In this study, we developed a fully coupled THM model, incorporating porosity and permeability variations, to scrutinize the process of geothermal energy extraction within fractured porous reservoirs. Moreover, we accentuated the significance of natural fracture orientation and hydraulic fracture permeability on fluid trajectories and heat extraction efficiency. Simulation results revealed that hydraulic fractures predominantly govern fluid channels and thermal exchange between injected water and the reservoir. Interconnected natural fractures bolster water migration into the reservoir, while detached fractures exert minimal influence on fluid dynamics, underscoring the crucial role of fracture connectivity in optimizing heat extraction efficiency. The sensitivity analysis indicated that larger fracture angles marginally hinder pressure and cool-water dispersion into the fractured reservoir, resulting in subtle enhancements in heat extraction rates and average production temperatures. An upsurge in hydraulic fracture permeability augments fluid velocity and thermal exchange, thereby fostering heat extraction efficiency. The THM model developed in this study offers a comprehensive insight into fluid flow within fractured porous media and its implications on geothermal energy extraction

Table_1_Unraveling the spatial–temporal distribution patterns of soil abundant and rare bacterial communities in China’s subtropical mountain forest.XLS

IntroductionThe pivotal roles of both abundant and rare bacteria in ecosystem function are widely acknowledged. Despite this, the diversity elevational patterns of these two bacterial taxa in different seasons and influencing factors remains underexplored, especially in the case of rare bacteria.MethodsHere, a metabarcoding approach was employed to investigate elevational patterns of these two bacterial communities in different seasons and tested the roles of soil physico-chemical properties in structuring these abundant and rare bacterial community.Results and discussionOur findings revealed that variation in elevation and season exerted notably effects on the rare bacterial diversity. Despite the reactions of abundant and rare communities to the elevational gradient exhibited similarities during both summer and winter, distinct elevational patterns were observed in their respective diversity. Specifically, abundant bacterial diversity exhibited a roughly U-shaped pattern along the elevation gradient, while rare bacterial diversity increased with the elevational gradient. Soil moisture and N:P were the dominant factor leading to the pronounced divergence in elevational distributions in summer. Soil temperature and pH were the key factors in winter. The network analysis revealed the bacteria are better able to adapt to environmental fluctuations during the summer season. Additionally, compared to abundant bacteria, the taxonomy of rare bacteria displayed a higher degree of complexity. Our discovery contributes to advancing our comprehension of intricate dynamic diversity patterns in abundant and rare bacteria in the context of environmental gradients and seasonal fluctuations.</p

Data_Sheet_1_Unraveling the spatial–temporal distribution patterns of soil abundant and rare bacterial communities in China’s subtropical mountain forest.docx

IntroductionThe pivotal roles of both abundant and rare bacteria in ecosystem function are widely acknowledged. Despite this, the diversity elevational patterns of these two bacterial taxa in different seasons and influencing factors remains underexplored, especially in the case of rare bacteria.MethodsHere, a metabarcoding approach was employed to investigate elevational patterns of these two bacterial communities in different seasons and tested the roles of soil physico-chemical properties in structuring these abundant and rare bacterial community.Results and discussionOur findings revealed that variation in elevation and season exerted notably effects on the rare bacterial diversity. Despite the reactions of abundant and rare communities to the elevational gradient exhibited similarities during both summer and winter, distinct elevational patterns were observed in their respective diversity. Specifically, abundant bacterial diversity exhibited a roughly U-shaped pattern along the elevation gradient, while rare bacterial diversity increased with the elevational gradient. Soil moisture and N:P were the dominant factor leading to the pronounced divergence in elevational distributions in summer. Soil temperature and pH were the key factors in winter. The network analysis revealed the bacteria are better able to adapt to environmental fluctuations during the summer season. Additionally, compared to abundant bacteria, the taxonomy of rare bacteria displayed a higher degree of complexity. Our discovery contributes to advancing our comprehension of intricate dynamic diversity patterns in abundant and rare bacteria in the context of environmental gradients and seasonal fluctuations.</p