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The nature of the frictional force at the macro-, micro-, and nano-scales

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Friction 2014年第1期2卷 40-46页

作者： esteban BROITMAN IFM Linköping UniversitySE 58183Sweden

Nowadays it is accepted that the friction force is a combined effect arising from various phenomena:adhesive forces,capillary forces,contact elasticity,topography,surface chemistry,and generation of a third body,*** of them can dominate depending on the experimental force and length scales of the *** forces in macro-tribology are in the Newtons,while are reduced to milli-/micro-Newtons,and nano-Newtons in micro-and nano-tribology,*** this paper,experimental friction results from fullerene like CNx films and single-crystal Si at the three scales will be *** complex and broad variety of processes and phenomena connected with the dry friction coefficient at the macro-,micro-,and nano-scale point of view will be highlighted.

关键词： macrotribology microtribology nanotribology carbon nitride silicon

Induced pluripotent stem cell (iPS) technology:promises and challenges

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Chinese Science Bulletin 2009年第1期54卷 2-8页

作者： MIGUEL A esteban Laboratory of Regenerative Biology South China Institute for Stem Cell Biology and Regenerative MedicineGuangzhou Institute of Biomedicine and HealthChinese Academy of Sciences

In 2006,an article published in Cell by Shinya Yamanaka took by surprise the stem cell research community. By performing systematic retroviral transduction of factors enriched in embryonic stem (ES) cells,the authors demonstrated the reprogramming of mouse fibroblasts into an ES cell-like state. These cells,baptized iPS (induced pluripotent stem) cells,were immediately recognized as a ground-breaking discovery. Subsequently,the same authors and other groups reported a similar achievement with human fibroblasts. Two years later,the number of top quality papers on iPS is astonishing,and interest in the scientific community has risen to a fever pitch. But although iPS has the potential to revolutionize Regenerative Medicine,important questions still remain unanswered. Work from multiple laboratories worldwide including ours is focused on deciphering the molecular mechanisms of iPS,and trying to improve the technique to make it suitable for the clinic. In this review article we briefly discuss the past,present and future of iPS,with emphasis on urgent issues to be solved.

关键词：自身更新多能性胚胎干细胞多能干细胞

Short-term effects of post-fire mulching with straw or wood chips on soil properties of semi-arid forests

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Journal of Forestry Research 2023年第6期34卷 1777-1790页

作者： Manuel esteban Lucas Borja Demetrio Antonio Zema Department of Agroforestry Technology Science and GeneticsSchool of Advanced Agricultural and Forestry EngineeringCampus Universitario s/nCastilla La Mancha UniversityE-02071 Castilla La ManchaAlbaceteSpain Department AGRARIA “Mediterranea”University of Reggio CalabriaLocalitàFeo di VitoI-89122 Reggio CalabriaItaly

Few studies have compared the variability of soil properties using different types of mulches in semi-arid *** study evaluated the changes in physico-chemical soil properties in a semi-arid forest of Central Eastern Spain,where straw and pine wood chips were distributed as mulch three months after a *** were sampled under burned and unmulched and burned and mulched plots three and nine months after the *** data was processed using Principal Component Analysis(PCA)and Analytical Hierarchical Cluster Analysis(AHCA).Mulching with straw or wood chips did not have any significant effects on the texture and chemical properties of burned sites few months after the *** contrast,significant changes are expected over time in organic matter,nutrients and many *** were no significant differences in soil properties between the two *** low changes were confirmed by PCA coupled with AHCA,which did not show a clear distinction among the three soil ***,a noticeable and significant variability of many of these properties over time was *** study shows that mulching does not degrade of soil properties in the short-term after a wildfire and after post-fire treatments,and thus helps protect semi-arid forest ecosystems against the negative impacts of high-severity fires.

关键词： Post-fire management High-severity fire Aridisols Erosion Vegetal residues incorporation Soil degradation

Origin of light emission and enhanced Eu^(3+) photoluminescence in tin-containing glass

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Journal of Rare Earths 2015年第1期33卷 27-32页

作者： José A.Jiménez esteban Rosim Fachini Department of Chemistry University of North FloridaJacksonville FL 32224 USA Department of Physical Sciences General Studies Faculty University of Puerto RicoRío Piedras PR 00931 USA

A barium-phosphate glass matrix was co-doped with Sn O and Eu2O3 for investigating on material luminescent properties. Optical absorption and X-ray photoelectron spectroscopy（XPS） were employed in the characterization of tin species. The prevalence of divalent tin was indicated by the XPS data in accord with a conspicuous absorption band detected around 285 nm ascribed to twofold-coordinated Sn centers（isoelectronic with Sn^2＋）. Photoluminescence（PL） excitation spectra obtained by monitoring Eu^3＋ emission from the 5D0 state revealed a broad excitation band from about 250 to 340 nm, characteristic of donor/acceptor energy transfer. Under excitation of such at 290 nm, the co-doped material exhibited a bright whitish luminescence, and a four-fold enhanced Eu3＋ emission relative to a purely Eu-doped reference. Time-resolved PL spectra recorded under the excitation at 290 nm exposed a broad band characteristic of the twofold-coordinated Sn centers and emission bands of Eu^3＋ ions, which appeared well separated in time in accord with their emission decay dynamics. The data suggested that light absorption took place at the Sn centers（donors） followed by energy transfer to Eu^3＋ ions（acceptors） which resulted in populating the 5D0 emitting state. Energy transfer pathways likely resulting in the enhanced Eu3＋ photoluminescence and the consequential light emission were discussed.

关键词： energy transfer glasses luminescence optical materials rare earths

Numerical modeling of cracking pattern's influence on the dynamic response of thickened tailings disposals: a periodic approach

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Earthquake Engineering and Engineering Vibration 2018年第1期17卷 179-190页

作者： Gabriel Ferrer esteban Sáez Christian Ledezma School of Engineering Pontificia Universidad Católica de Chile National Research Center for Integrated Natural Disaster Management

Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials（tailings） are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal（TTD） is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with ＂fresh＂ tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings＇ behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.

关键词： Thickened tailings Liquefaction Periodic modeling

The impact of cultural assumptions on simulated energy, comfort, and investment returns of design decisions in two desert climates

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Building Simulation 2021年第4期14卷 931-944页

作者： esteban Estrella Guillen Holly W.Samuelson Christine Vohringer Harvard Graduate School of Design 48 Quincy St.CambridgeMAUSA Universidad de Monterrey Av.Ignacio Morones Prieto 4500San Pedro Garza GarcíaNLMexico

In Latin America, default assumptions and borrowed templates and methodologies are often used in energy modeling, resulting in models that might not represent their cultural context and leading to policies awkwardly fit to local practices. Policy-driving low-income housing studies in Mexico, for example, activated both heating and cooling in energy models even though less than 5% of the homes in the country have heating systems. This paper illustrates the importance of modeling local sociocultural habits and practices, and how this can affect design outcomes. Here, we modeled low-income housing representative of typical residences in two desert climates-Hermosillo, Mexico, and Copiapo, Chile-using EnergyPlus. Settings representing local practices in each region were tested against default values, including occupancy settings, regional construction systems, and importantly, HVAC settings related to partial conditioning. Their impacts were measured via variation in energy use, comfort conditions, and the payback period of design upgrades. Results demonstrated how certain assumptions can have a high “design significance”, a term we propose for inputs that completely change optimal design decisions, as well as the importance of considering thermal comfort in such decisions. Including partial conditioning, for example, resulted in at least double the payback period and discomfort degrees for design upgrades in 16 of 24 instances.

关键词： performance simulation energy model low-cost housing housing policy thermal comfort culture

Effective parameter study for the facile and controlled growth of silver molybdate nano/micro rods

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Frontiers of Materials Science 2016年第4期10卷 375-384页

作者： Javier esteban Enriquez MONTENEGRO Dinesh Pratap SINGH Department of Physics University of Santiago Chile Avenida Ecuador 3493 Estacion Central Santiago 9170124 Chile

Controlled growth of nano/micro structures by controlling the effective parameters is the basic requirement for the application point of view in various areas. Here we report the facile growth of silver molybdate nanolmicro rods by mixing the solution of silver nitrate and ammonium molybdate at ambient condition followed by hydrothermal treatment at various temperatures for 12 h. To achieve the goal for the synthesis of long, high yield and homogeneous nanorods various effective parameters have been studied to set the most effective conditions for the growth. Among possible effective parameters first the temperature of the furnace was set by warring the temperature and then at the set temperature the concentration of reactants （NH4）6Mo7O24 and silver nitrate are varied respect to each other. The pH and temperature values were monitored during the mixing of the reactants. Structurallmicrostructural characterization revealed the optimum condition of 150℃ of the furnace and the concentration of （NH4）sMo7O24 and silver nitrate as described in various tables.

关键词： silver molybdate nanorod Ag6Mo10O33 controlled growth silver nitrate

Perception of Disasters and Land Reclamation in an Informal Settlement on Reclaimed Land:Case of the BASECO Compound,Manila,the Philippines

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International Journal of Disaster Risk Science 2020年第5期11卷 640-654页

作者： Ven Paolo Bruno Valenzuela Miguel esteban Onuki Motoharu Graduate Program in Sustainability Science-Global Leadership Initiative The University of TokyoKashiwaChiba 277-8563Japan Department of Civil and Environmental Engineering Waseda UniversityTokyo 169-8555Japan

Southeast Asia's coastal urban areas continue to grow,with land reclamation fast becoming an important option for megacities to address issues of economic growth and increasing population *** are divided over the advantages and disadvantages of land reclamation,though this process continues unabated,exposing settlements to coastal *** Bataan Shipping and Engineering Company(BASECO)compound is an informal settlement on reclaimed land in Manila,the *** informal coastal settlements view disaster risk and their more pressing socioeconomic needs is crucial to understanding the potentials and repercussions of land *** a topographic survey,a questionnaire survey,and the protective action decision model,this study explored the perception of disasters and land reclamation of informal settlers who are living on reclaimed *** study found that people are aware of disaster risks,but are more concerned with everyday *** are divided on the issue of further land *** on the original non-reclaimed land view it as a coastal defense,while those on reclaimed land fear potential *** this,all locations in the community are concerned with the loss of jobs,economic opportunities,and eviction,rather than potential disasters.

关键词： Coastal hazards Flooding Informal settlements Land reclamation Philippines Risk perception Urbanization

Recent advances in wheel–rail RCF and wear testing

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Friction 2023年第12期11卷 2181-2203页

作者： Sundar SHRESTHA Maksym SPIRYAGIN esteban BERNAL Qing WU Colin COLE Centre for Railway Engineering Central Queensland UniversityRockhampton 4701Australia Australasian Centre for Rail Innovation Canberra 2601Australia

The wear and rolling contact fatigue (RCF) testing approaches for wheels and rails have been reviewedand evaluated in this study. The study points out the advantages and limitations of the existing approaches. Thebroad analysis revealed that scaled laboratory-based wear testing is widely applied. However, it is necessary topredetermine the input parameters and observing parameters for scaled wear testing for three reasons: first, toemulate the real-world scenarios as closely as possible;second, to postprocess the results received from the scaledtesting and transfer them into real practice at full scale;third, to present the results in a legible/appropriate ***, most of the important parameters required for wear testing have been discussed with fundamental andsystematic explanations provided. Additionally, the transition of the parameters from the real-world into the testdomain is explained. This study also elaborates on the challenges of the RCF and wear testing processes andconcludes by providing major considerations toward successful testing.

关键词： wear testing rolling contact fatigue(RCF)testing wheel-rail