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Features of the motion of gel particles in a three-phase bubble column under foaming and non-foaming conditions

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Chinese Journal of Chemical Engineering 2018年第6期26卷 1370-1382页

作者： Gabriel Salierno Mauricio Maestri Stella Piovano Miryan Cassanello Maria Angelica Cardona Daniel Hojman Hector Somacal laboratorio de Reactores y Sistemas para la lndustria-LARSl Dep. lndustrias FCEyN Universidad de Buenos Aires Int. GiJiraldes 2620 CI428BGA Buenos Aires Argentina laboratorio de Diagnóstico por Radiaciones-LADiR Dep. de Fisica Experimental. Comision National de Energia Atomica (CNEA) San Martin Buenos Aires Argentina Universidad de San Martin San Martin Buenos Aires Argentina

Features of the motion of gel particles in a three-phase bubble column with non-foaming and foaming gas–liquid systems,determined by using experiments of radioactive particle tracking(RPT),have been *** tracer used is a gel particle which resembles typical immobilized *** tracer trajectory is analyzed to extract relevant information for design *** solid velocity field,turbulence parameters,dispersion coefficients,mixing times and flow transitions are determined and *** presence of foam significantly affects many quantified parameters,especially within the heterogeneous flow *** hydrodynamic stresses are reduced in the presence of foam,especially close to the *** dispersion coefficients also decrease,and the solid mixing time is only slightly affected by the presence of *** holdup,inferred both from RPT experiments and from gamma ray scanning,is higher for foaming systems and leads to a shift in the transition gas velocity towards higher values.

关键词： Bubble columns Solid motion Gel beads Foaming Particle tracking Mixing

Phylogenetic endemism of the orchids of Megamexico reveals complementary areas for conservation

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Plant Diversity 2022年第4期44卷 351-359页

作者： Brandon E.Gutierrez-Rodríguez Marilyn Vasquez-Cruz Victoria Sosa Instituto de Ecología AC Carretera Antigua a Coatepec 351El Haya91073 XalapaVeracruzMexico Unidad de Genomica avanzada Laboratorio Nacional de Genomica para La BiodiversidadCentro de Investigaciony Estudios Avanzados IrapuatoLibramiento Norte Carretera Leon Km.9.636821 IrapuatoGuanajuatoMexico

Orchid diversity provides a unique opportunity to further our understanding of biotic and abiotic factors linked to patterns of richness,endemism,and phylogenetic endemism in many ***,orchid diversity is consistently threatened by illegal trade and habitat ***,we identified areas critical for orchid conservation in the biogeographic province of *** this purpose,we evaluated orchid endemism,phylogenetic diversity,and phylogenetic endemism within Megamexico and characterized orchid life *** results indicate that the majority of the regions with the highest estimates of endemism and phylogenetic endemism are in southern Mexico and northern Central America,mostly located on the Pacific side of *** the most important orchid lineages,several belong to epiphytic lineages such as Pleurothallidinae,Laeliinae and *** also found that species from diverse and distantly related lineages converge in montane forests where suitable substrates for epiphytes ***,the southernmost areas of phylogenetic diversity and endemism of Megamexico are in unprotected ***,we conclude that the most critical areas for orchid conservation in Megamexico are located in southern Mexico and northern Central *** recommend that these areas should be given priority by the Mexican system of natural protected areas as complementary conservation areas.

关键词： Epiphytes Geophytes Orchids Phylogenetic endemism Weighted endemism

Asymmetric hydrogenation and transfer hydrogenation in the enantioselective synthesis of flavonoids

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Organic Chemistry Frontiers 2022年第4期9卷 1165-1194页

作者： Guilherme S.Caleffi Felipe C.demidoff Carmen Najera Paulo R.R.Costa laboratorio de Quimica Bioorganica(LQB) Instituto de Pesquisas de Produtos NaturaisUniversidade Federal do Rio de JaneiroAv.Carlos Chagas Filho 373Bloco HCidade Universitaria21941-902 Rio de Janeiro Centro de Innovacion en Quimica avanzada(ORFEO-CINQA) Universidad de AlicanteApdo.99E-03080 AlicanteSpain

Asymmetric hydrogenation(AH)and asymmetric transfer hydrogenation(ATH)are versatile synthetic methodologies widely employed in the preparation of chiral *** this review,we explore the applications of AH and ATH in the total synthesis of natural flavonoids and their analogues,highlighting the limitations and opportunities in the field.

关键词： compounds field hydrogenation

Non-linear modeling of kinetic and equilibrium data for the adsorption of hexavalent chromium by carbon nanomaterials:Dimension and functionalization

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Chinese Journal of Chemical Engineering 2019年第4期27卷 912-919页

作者： Miguel de la Luz-Asunción Eduardo E.Pérez-Ramírez Ana L.Martínez-Hernández Victor M.Castano Víctor Sánchez-Mendieta Carlos Velasco-Santos Facultad de Quimica Universidad Autonoma del Estado de Mexico Km. 12 de la carretera Toluca-Atlacomulco C.P. 50200 San Cayetano Toluca Estado de Mexico Mexico Tecnologico Nacional de Mexico-Instituto Tecnologico de Queretaro Division de Estudios de Posgrado e Investigacion Av. Tecnologico s/n esq. GraL Mariano Escobedo Col. Centro Historico C.P. 76000 Santiago de Queretaro Queretaro Mexico Centro de fisica Aplicada y Tecnologia avanzada Universidad Nacional Autonoma de Mexico Boulevard Juriquilla 3001 Queretaro 76230 Mexico

The adsorption capacities for the removal of hexavalent chromium from aqueous solutions by six carbon nanomaterials have been evaluated. Single-walled and multi-walled carbon nanotubes as received and after oxidation treatment, graphene oxide and reduced graphene oxide are the materials with different dimension and functionalization compared in this research. Carbon nanotubes have been modified using hydrogen peroxide as oxidizing agent under microwave radiation. The oxidation treatment on carbon nanotubes has a positive effect increasing the adsorbent–adsorbate interaction. Rate-controlling mechanisms and equilibrium data are analyzed using non-linear models. Non-linear method is proposed as the most suitable method for determining the kinetic and equilibrium parameters. The values of adsorption energy(E) obtained from the Dubinin–Radushkevich isotherm,have been found around 0.371 and 0.870 k J·mol-1, indicating physical adsorption. Therefore, the pseudo-second order model represents better the kinetic experimental data. The results show that the Langmuir isotherm provides a slightly better fit to the experimental data compared with the Freundlich isotherm, indicating homogeneous distribution of active sites on carbon nanomaterials and monolayer adsorption. The separation factors RLare found in the range of 0–1, suggesting that the adsorption process is suitable for all adsorbents. The mechanisms for hexavalent chromium removal have been proposed as electrostatic interactions and hydrogen bonding.

关键词： Carbon nanotubes Graphene Adsorption Hexavalent chromium Kinetic

Tailoring thermoelectric properties of Zr(0.43)Hf(0.57)NiSn half-Heusler compound by defect engineering

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Rare Metals 2020年第6期39卷 659-670页

作者： Krzysztof Galazka Wenjie Xie Sascha Populoh Myriam H.Aguirre Songhak Yoon Gesine Büttner Anke Weidenkaff Institute of Plasma Physics and Laser Microfusion Warsaw 01-497Poland department of Materials Science Technische Universitat DarmstadtDarmstadt 64287Germany Laboratory for Solid State Chemistry and Catalysis EmpaDlibendorf 8600Switzerland Instituto de Nanociencia de Aragon Universidad de ZaragozaSaragossa 50018Spain departamento de fisica de la Materia Condensada Universidad de ZaragozaSaragossa 50009Spain laboratorio de Microscopias avanzadas Universidad de ZaragozaSaragossa 50018Spain Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS Hanau 63457Germany

The thermoelectric transport properties of Zr0.43Hf0.57 NiSn half-Heusler compounds were investigated for samples sintered with different spark plasma sintering(SPS)periods:8,32 and 72 *** means of scanning transmission electron microscopy with a highangular annular dark-field detector(STEM-HAADF),it was found that sintering time affected the defect concentration,namely the amount of Ni interstitial atoms,and created locally ordered inclusions of full-Heusler *** structural information,phase composition and electrical transport properties could be consistently explained by the assumption that Ni interstitials give rise to an impurity band situated about 100 meV below the bottom of the conduction band via a self-doping *** impurity band was found to merge with the conduction band for the sample with intermediate SPS *** effect was ascribed to the gradual dissolution of full-Heusler phase inclusions and production of interstitial Ni defects,which eventually vanished for the sample with the longest sintering *** was demonstrated that the modification of the density of states near the edge of the conduction band and enhanced overall charge carrier concentration provided by defect engineering led to overall 26%increase in the thermoelectric figure of merit(ZT)with respect to the other samples.

关键词： Thermoelectric Half-Heusler Interstitial defect engineering

Empirical formulae to describe some physical properties of small groups of protogalaxies with multiplicity

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Research in Astronomy and Astrophysics 2021年第8期21卷 141-158页

作者： Guillermo Arreaga-Garcia departamento de Investigacion en fisica Universidad de Sonora Apdo.Postal 14740C.P.83000HermosilloSonoraMexico

By means of identical cubic elements,we generate a partition of a volume in which a particle-based cosmological simulation is carried *** each cubic element,we determine the gas particles with a normalized density greater than an arbitrarily chosen density *** using a proximity parameter,we calculate the neighboring cubic elements and generate a list of *** imposing dynamic conditions on the gas particles,we identify gas clumps and their neighbors,so that we calculate and fit some properties of the groups so identified,including the mass,size and velocity dispersion,in terms of their multiplicity(here defined simply as the number of member galaxies).Finally,we report the value of the ratio of kinetic energy to gravitational energy of such dense gas clumps,which will be useful as initial conditions in simulations of gravitational collapse of gas clouds and clusters of gas clouds.

关键词： galaxies:kinematics and dynamics hydrodynamics methods:numerical

A Study of the Structural, Optical and Electrical Properties of SnS Thin Films Modified by Plasma

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材料科学与工程（中英文B版） 2013年第6期3卷 352-358页

作者： Aar6n Gomez Horacio Martinez Manuela Calixto-Rodriguez David Avellaneda Pedro Guillermo Reyes Osvaldo Flores laboratorio de fisica avanzada Facultad de Ciencias Universidad Autonoma del Estado de Mexico Estado de Mexico Mexico laboratorio de Espectroscopia Instituto de Ciencias Fisicas Universidad Nacional Aut6noma de Mdxico Cuernavaca MorelosMdxico Intituto de Energia Renovable Universidad Nacional Aut6noma de Mdxico Cuernavaca Morelos M~xico Facultad de Ingenieria Meconica y Electrica Universidad Autonoma de Nuevo Leon Mexico

Spring Theory as an Approach to the Unification of Fields

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Journal of Modern Physics 2016年第15期7卷 2219-2230页

作者： Ling Man Tsang fisica laboratorio TIS Macao University of Science and Technology Macao China

The cosmological constant is necessary to be retained in Einstein’s field equations with value depending on the mass of the source. An overview of the spring theory in astrophysics and cosmology is included in this paper. In short range force, the two interacting particles are point-like vertices connected by a bosonic spring. We also suspect that electron may contain negative sterile neutrino. The self energy of a point charge is not infinite so that renormalisation is not necessary.

关键词： Cosmological Constant Dark Matter Classical Electrostatics Short Range Interaction

Te-seeded growth of few-quintuple layer Bi2Te3 nanoplates

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Nano Research 2014年第9期7卷 1243-1253页

作者： Yanyuan Zhao Maria de la Mata Richard L. J. Qiu Jun Zhang Xinglin wen Cesar Magen Xuan P. A. Gao Jordi Arbiol Qihua Xiong Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological UniversitySingapore 637371 Institut de Ciencia de Materials de Barcelona ICMAB-CSIC E-08193 Bellaterra CAT Spain department of Physics Case Western Reserve University Cleveland Ohio 44106 USA laboratorio de Microscopfas avanzadas (LMA) Instituto de Nanociencia de Aragon (INA) - ARAID and Departamento de Fisica de la Materia Condensada Universidad de Zaragoza 50018 Zaragoza Spain Institucio Catalana de Recerca i Estudis Avancats (ICREA) 08010 Barcelona CAT Spain NOVITAS Nanoelectronics Centre of Excellence School of Electrical and Electronic Engineering Nanyang Technological University Singapore 639798

We report on a Te-seeded epitaxial growth of ultrathin Bi2Te3 nanoplates （down to three quintuple layers （QL）） with large planar sizes （up to tens of micrometers） through vapor transport. Optical contrast has been systematically investigated for the as-grown Bi2Te3 nanoplates on the SiO2/Si substrates, experimentally and computationally. The high and distinct optical contrast provides a fast and convenient method for the thickness determination of few-QL Bi2Te3 nanoplates. By aberration-corrected scanning transmission electron microscopy, a hexagonal crystalline structure has been identified for the Te seeds, which form naturally during the growth process and initiate an epitaxial growth of the rhombohedral- structured Bi2Te3 nanoplates. The epitaxial relationship between Te and Bi2T% is identified to be perfect along both in-plane and out-of-plane directions of the layered nanoplate. Similar growth mechanism might be expected for other bismuth chalcogenide layered materials.

关键词： Te nucleation seed epitaxial growth Bi2Te3 few-quintuple layer TEM cross-section optical contrast