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Influence of metal support in-plane symmetry on the corrugation of hexagonal boron nitride and graphene monolayers

Nano Research 2018年第9期11卷 4643-4653页

作者： Antonio d. Martinez-Galera Jose M. gomez-Rodriguez departamento de Fisica de la Matefia Condensada Universidad Autonoma de Madrid Madrid E-28049 Spain Condensed Matter Physics Center (IFIMAC) UniversidadAutdnoma de Madrid Madrid E-28049 Spain Instituto Nicolds Cabrera Universidad Autonoma de Madrid Madrid E-28049 Spain

Predicting the properties of two-dimensional （2d） materials as graphene and hexagonal boron nitride （h-BN） monolayers after their growth on any given substrate is a major challenge. While the influence of the electron configuration of the atoms of the underlying surface is well-understood, the effect of substrate geometry still remains unclear. The structural properties of h-BN monolayers grown on a rectangularly packed Rh（110） surface were characterized in situ by ultrahigh vacuum scanning tunneling microscopy and were compared to those that this material exhibits when grown on substrates showing different crystallographic orientations. Although the h-BN monolayer grown on Rh（110） was dominated by a unique quasiunidimensional moir6 pattern, suggesting considerable interface interaction, the moir6 corrugation was unexpectedly smaller than those reported for strongly interacting interfaces with hexagonal-terminated substrates, owing to differences in the possible binding landscapes at interfaces with differently oriented substrates. Moreover, a rule was derived for predicting how interface corrugation and the existence and extent of subregions within moir6 supercells containing favorable sites for orbital mixing between h-BN monolayers and their supports depend on substrate symmetry. These general symmetry considerations can be applied to numerous 2d materials, including graphene, thereby enabling the prediction of how substrate choice determines the properties of these materials. Furthermore, they could also provide new routes for tuning 2d material properties and for developing nanotemplates showing different geometries for Krowing adsorbate superlattices.

关键词： hexagonal boron nitride graphene two-dimensional materials scanning tunneling microscopy moire superstructures nanotemplates

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The effect of rippling on the mechanical properties of graphene

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Nano Materials Science 2022年第1期4卷 18-26页

作者： Guillermo Lopez-Polin Cristina gomez-Navarro Julio gomez-Herrero Instituto de Ciencia de Materiales de Madrid CSICMadrid E 28049Spain departamento de Física de La Materia Condensada Universidad Autónoma de MadridMadridE-28049Spain IFIMAC Condensed Matter Physics Center(IFIMAC).Universidad Autónoma de Madrid MadridE-28049Spain

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very ***, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient(TEC) of free-standing *** also observed an increase of the Young's modulus with global applied strain and with the introduction of small density defects that we attributed to the decrease of rippling. Here, we will focus on a surprising feature observed in the data: the experiments consistently indicate that only the rippling with wavelengths between 5 and 10 nm influences the mechanics of graphene. The rippling responsible of the negative TEC and anomalous elasticity is thought to be dynamic, i.e. flexural phonons. However, flexural phonons with these wavelengths should have minor effects on the mechanics of graphene, therefore other mechanisms must be considered to address our observations. We propose static ripples as one of the key elements to correctly understand the thermomechanics of graphene and suggest that rippling arises naturally due to a competition of symmetry breaking and anharmonic fluctuations.

关键词： Graphene Mechanical properties Atomic force microscopy defects Ripples Stmain

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Biaxial versus uniaxial strain tuning of single-layer MoS_(2)

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Nano Materials Science 2022年第1期4卷 44-51页

作者： Felix Carrascoso Riccardo Frisenda Andres Castellanos-gomez Materials Science Factory Instituto de Ciencia de Materiales de Madrid(ICMM-CSIC)28049Madrid Spain

Strain engineering has arisen as a powerful technique to tune the electronic and optical properties of twod imensional semiconductors like molybdenum disulfide(MoS_(2)).Although several theoretical works predicted that biaxial strain would be more effective than uniaxial strain to tune the band structure of MoS_(2),a direct experimental verification is still missing in the *** we implemented a simple experimental setup that allows to apply biaxial strain through the bending of a cruciform polymer *** used the setup to study the effect of biaxial strain on the differential reflectance spectra of 12 single-layer MoS_(2)flakes finding a redshift of the excitonic features at a rate between-40 meV/%and-110 meV/%of biaxial *** also directly compare the effect of biaxi al and uniaxial strain on the same single-layer MoS_(2)finding that the biaxial strain gauge factor is 2.3 times larger than the uniaxial strain one.

关键词： finding layer gauge

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A CFd study of the transport and fate of airborne droplets in a ventilated office:The role of droplet−droplet interactions

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Frontiers of Environmental Science & Engineering 2022年第3期16卷 49-62页

作者： Allan gomez-Flores Gukhwa Hwang Sadia Ilyas Hyunjung Kim department of Environment and Energy Jeonbuk National UniversityJeonju Jeonbuk 54896Republic of Korea department of Mineral Resources and Energy Engineering Jeonbuk National UniversityJeonju Jeonbuk 54896Republic of Korea

Previous studies reported that specially designed ventilation systems provide good air quality and safe environment by removing airborne droplets that contain viruses expelled by infected *** water droplets can be stable in the environment and remain suspended in air for prolonged *** between droplets may occur and droplet interactions should be ***,the previous studies focused on other physical phenomena(air flow,drag force,evaporation)for droplet transport and neglected droplet *** this work,we used computational fluid dynamics(CFd)to simulate the transport and fate of airborne droplets expelled by an asymptomatic person and considered droplet *** drag with turbulence for prediction of transport and fate of droplets indicated that the turbulence increased the transport of 1μm droplets,whereas it decreased the transport of 50μm *** contrast to only considering drag and turbulence,consideration of droplet interactions tended to increase both the transport and *** the length scale of the office is much larger than the droplet sizes,the droplet interactions,which occurred at the initial stages of release when droplet separation distances were shorter,had a significant effect in droplet fate by considerably manipulating the final locations on surfaces where droplets ***,it is proposed that when an exact prediction of transport and fate is required,especially for high droplet concentrations,the effects of droplet interactions should not be ignored.

关键词： droplet interactions Aerosols Colloids CFd Transport Fate

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Strain engineering in single-,bi-and tri-layer MoS_(2),MoSe_(2),WS_(2)and WSe_(2)

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Nano Research 2021年第6期14卷 1698-1703页

作者： Felix Carrascoso Hao Li Riccardo Frisenda Andres Castellanos-gomez Materials Science Factory Instituto de Ciencia de Materiales de MadridConsejo Superior de Investigaciones Cientificas28049MadridSpain

Strain is a powerful tool to modify the optical properties of semiconducting transition metal dichalcogenides like MoS_(2),MoSe_(2),WS_(2) and WSe_(2).In this work we provide a thorough description of the technical details to perform uniaxial strain measurements on these two-dimensional semiconductors and we provide a straightforward calibration method to determine the amount of applied strain with high *** then employ reflectance spectroscopy to analyze the strain tunability of the electronic properties of single-,bi-and tri-layer MoS_(2),MoSe_(2),WS_(2) and WSe_(2).Finally,we quantify the flake-to-flake variability by analyzing 15 different single-layer MoS_(2) flakes.

关键词： two-dimensional(2d)materials transition metal dichalcogenides strain engineering band gap differential reflectance

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Orientation effect on ground motion measurement for Mexican subduction earthquakes

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 1-16页

作者： H.P. Hong A. Pozos-Estrada R. gomez department of Civil and Environmental Engineering University of Western Ontario Canada N6A 5B9 Institute of Engineering National Autonomous University of Mexico Mexico D.F.

The existence of the principal directions of the ground motion based on Arias intensity is well-known. These principal directions do not necessarily coincide with the orientations of recording sensors or with the orientations along which the ground motion parameters such as the peak ground acceleration and the pseudo-spectral acceleration （PSA） are maximum. This is evidenced by the fact that the maximum PSA at different natural vibration periods for horizontal excitations do not correspond to the same orientation. A recent analysis carried out for California earthquake records suggests that an orientation-dependent ground motion measurement for horizontal excitations can be developed. The main objective of this study is to investigate and provide seismic ground motion measurements in the horizontal plane, including bidirectional horizontal ground motions, for Mexican interplate and inslab earthquake records. Extensive statistical analyses of PSA are conducted for the assessment. The analysis results suggest that similar to the case of California records, the average behavior of the ratio of the PSA to the maximum resulting PSA can be approximated by a quarter of an ellipse in one quadrant; and that the ratio can be considered to be independent of the value of the maximum resulting PSA, earthquake magnitude, earthquake distance and the focal depth. Sets of response ratios and attenuation relationships that can be used to represent a bidirectional horizontal ground motion measurement for Mexican interplate and inslab earthquakes were also developed.

关键词： orthogonal horizontal excitations bidirectional ground motion measure attenuation relationship pseudospectral acceleration (PSA) response ratio Mexican earthquake

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Effect of Wavelength on Metrological Characteristics of Non-Holographic Fiber Specklegram Sensor

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Photonic Sensors 2015年第1期5卷 1-5页

作者： Victor H. ARISTIZABAL Alejandro HOYOS Edgar RUEdA Nelson d. gomez Jorge A. gomez Grupo de Sistemas en Operaciones y desarrollo Aplicado -SOdA- Universidad Cooperativa de Colombia Cll 50A#41-40 Medellin Colombia Grupo de Fisica Basica y Aplicada Politecnico Colombiano Jaime Isaza Cadavid Cra 48 #7-151 Medellin Colombia Grupo de Optica y Fotonica Instituto de Fisica Universidad de Antioquia Cll 70No. 52-21 Medellin Colombia Grupo de lnvestigacion en Automatica Electronica y Ciencias Computacionales-AE&CC- Instituto Tecnologico Metropolitano - lnstitucion Universitaria Cll 54A #30-01 Medellin Colombia

In this paper, we report some results about the effects of varying the wavelength in a structure of a non-holographic fiber specklegram sensor. In these arrangements, the speckle pattern produced by a multi-mode optical fiber is coupled to the asingle-mode optical fiber with lower numerical aperture, which produces a filtering effect that can be used as an optical transduction mechanism. The influence of the wavelength on the sensor performance is evaluated by changing the laser wavelength, and a strong effect on the linearity and reproducibility of its response is found. Lasers emitting at 1310nm, 1550nm, and 1625nm are used.

关键词： Optical sensing speckle sensor optical fiber sensor mechanical perturbation sensor

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Roles of Polycomb complexes in regulating gene expression and chromatin structure in plants

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Plant Communications 2022年第1期3卷 135-151页

作者： Fernando Baile Angeles gomez-Zambrano Myriam Calonje Institute of Plant Biochemistry and Photosynthesis(IBVF-CSIC-US) Avenida Americo Vespucio 4941092 SevilleSpain

The evolutionary conserved Polycomb Group(PcG)repressive system comprises two central protein complexes,PcG repressive complex 1(PRC1)and *** complexes,through the incorporation of histone modifications on chromatin,have an essential role in the normal development of *** recent years,a significant effort has been made to characterize these complexes in the different kingdoms,and despite there being remarkable functional and mechanistic conservation,some key molecular principles have *** this review,we discuss current views on the function of plant PcG *** compare the composition of PcG complexes between animals and plants,highlight the role of recently identified plant PcG accessory proteins,and discuss newly revealed roles of known PcG *** also examine the mechanisms by which the repression is achieved and how these complexes are recruited to target ***,we consider the possible role of some plant PcG proteins in mediating local and long-range chromatin interactions and,thus,shaping chromatin 3d architecture.

关键词： Polycomb Group PRC1 PRC2 histone modifications gene repression chromatin organization

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The long-term stability of calcium arsenates:Implications for phase transformation and arsenic mobilization

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Journal of Environmental Sciences 2019年第10期31卷 29-41页

作者： danni Zhang Shaofeng Wang Ying Wang Mario A.gomez Yongfeng Jia Key Laboratory of Pollution Ecology and Environmental Engineering Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Institute of Environmental Protection Shenyang University of Chemical Technology Shenyang 110142 China

It is well known that calcium arsenates may not be a good choice for arsenic removal and immobilization in hydrometallurgical ***,they are still produced at some plants in the world due to various ***,calcium arsenates can also naturally precipitate under some specific ***,the transformation process of poorly crystalline calcium arsenates(PCCA)and the stability of these samples under atmospheric CO2 are not yet well *** work investigated the transformation process of PCCA produced by using different neutralization reagents(CaO ***)with various Ca/As molar ratios at pH 7-12 in the presence of atmospheric *** aging at room temperature for a period of time,for samples neutralized with NaOH and precipitated at pH 10 and 12,release of arsenic back into the liquid phase *** contrast,for the samples precipitated at pH 8,the aqueous concentration of arsenic was observed to ***,Raman,and SEM results suggested that the formation of various types of crystalline calcium carbonates and/or calcium arsenates controls the arsenic ***,the application of lime may enhance the stability of the generated ***,no matter what neutralization reagent is used,the stability of the generated PCCA is still of concern.

关键词： Arsenic Precipitate Calcium Stability CO2

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High-throughput study of the anomalous Hall effect

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npj Computational Materials 2023年第1期9卷 767-774页

作者： JakubŽelezný Yuta Yahagi Carles gomez-Olivella Yang Zhang Yan Sun Institute of Physics Czech Academy of SciencesCukrovarnická1016200 Praha 6Czech Republic department of Applied Physics Tohoku UniversitySendaiMiyagiJapan department of Physics and Astronomy University of Tennessee KnoxvilleKnoxvilleTN 37996USA Min H.Kao department of Electrical Engineering and Computer Science University of TennesseeKnoxvilleTN 37996USA Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

despite its long history,the anomalous Hall continues to attract attention due to its complex origins,its connection to topology,and its use as a probe of magnetic *** this work we investigate the anomalous Hall effect in 2871 ferromagnetic materials using an automatic high-throughput calculation *** analyze general properties of the effect,such as its reliance on spin-orbit coupling strength and *** materials with the largest anomalous Hall effect,we find that symmetry-protected band degeneracies in the non-relativistic electronic structure,such as mirror symmetry-protected nodal lines,are typically responsible for the large ***,we examine the dependence of the anomalous Hall effect on magnetization direction and demonstrate deviations from the commonly assumed expression j^(AHE)~M×E.

关键词： effect symmetry protected

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