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Investigation of the degradation rate of electron beam processed and friction stir processed biocompatible ZKX50 magnesium alloy

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Journal of Magnesium and Alloys 2022年第3期10卷 768-781页

作者： Fatemeh Iranshahi Mohammad Bagher Nasiri fernando Gustavo Warchomicka Christof Sommitsch Joining and Forming Institute of Materials ScienceGraz University of TechnologyKopernikusgasse 24/IGraz 8010Austria

Together with the mechanical properties,the degradation rate is an important factor for biodegradable *** ZKX50 Mg alloy is a suitable candidate to be used as a biodegradable implant due to its favorable biocompatibility and mechanical *** research investigates the degradation rate and corrosion behavior of the ZKX50 as a function of the microstructure constituents and their *** grain refinement is the main strengthening mechanism for the ZKX50,the effect of the microstructure refinement on the corrosion rate was studied by applying electron beam processing(EBP)and friction stir processing(FSP)on the ZKX50 cast *** study the effect of the microstructure constituents and their morphology a subsequent solution heat treatment(HT)was applied to the processed *** results show that the EBP and FSP lead to a uniform and remarkably refined microstructure of the ZKX50 alloy and homogeneous distribution of the intermetallic *** results of electrochemical corrosion tests together with the microstructure characterization show that microgalvanic corrosion is the predominant mechanism that occurs between the Ca2Mg6Zn3 intermetallic phase andα-Mg *** to the results attained through the electrochemical tests,the EBPed-HT ZKX50 alloy shows higher corrosion resistance compared to all other conditions immersed in 0.5 wt.%NaCl *** dissolution and spheroidizing of Ca2Mg6Zn3 particles during the solution heat treatment provides higher corrosion resistance mainly by decreasing the microgalvanic *** microstructure of the heat-treated samples does not show a significant grain coarsening which can degrade the enhancement of the mechanical properties achieved by the EBP and FSP.

关键词： Magnesium alloys Electron beam processing Friction stir processing Corrosion Biodegradable metals.

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Modelling of tropospheric delays in geosynchronous synthetic aperture radar

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Science China(Information Sciences) 2017年第6期60卷 85-102页

作者： Dexin LI Marc RODRIGUEZ-CASSOLA Pau PRATS-IRAOLA Zhen DONG Manqing WU Alberto moreira School of Electronic Science and Engineering National University of Defense Technology (NUDT) Department of Electrical and Computer Engineering Technical University of Munich (TUM) German Aerospace Center (DLR)

As a direct consequence of the orbital height, the integration time in geosynchronous synthetic aperture radar(GEO SAR) with metric or decimetric azimuth resolutions is in the order of several hundreds or even thousands of seconds. With such long integration time, the compensation of residual tropospheric propagation terms poses one of the fundamental challenges associated with GEO SAR missions. In order to better characterise the impact of the propagation errors on GEO SAR imaging, we put forward a model for the simulation of the tropospheric delay appropriate for the accurate simulation of GEO SAR surveys. The suggested model, with a deterministic background component and a random turbulent one, incorporates some of the most recent meteorological data for the characterization of the troposphere. To illustrate the relevance of the derivation, the suggested model is used for performance estimation and raw data simulation of GEO SAR raw data. Substantial conclusion on the system impulse response and the associated calibration requirements is also drawn from the analysis.

关键词： geosynchronous SAR missions propagation errors tropospheric hydrostatic delay topospheric wet delay Kolmogorov power law Matérn covariances raw data simulation reverse backprojection

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HPV18 Utilizes Two Alternative Branch Sites for E6*I Splicing to Produce E7 Protein

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Virologica Sinica 2019年第2期34卷 211-221页

作者： Ayslan Castro Brant Vladimir Majerciak Miguel Angelo Martins moreira Zhi-Ming Zheng Tumor Virus RNA Biology Section RNA Biology Laboratory Center for Cancer Research National Cancer Institute NIH Frederick MD 21702 USA Genetics Post-Graduation Program Rio de Janeiro Federal University Rio de Janeiro Brazil Genetics Program Nacional Cancer Institute INCA Rio de Janeiro 20231-050 Brazil

Human papillomavirus 18(HPV18) E6 and E7 oncogenes are transcribed as a single bicistronic E6 E7 pre-mRNA. The E6 ORF region in the bicistronic E6 E7 pre-mRNA contains an intron. Splicing of this intron disrupts the E6 ORF integrity and produces a spliced E6*I RNA for efficient E7 translation. Here we report that the E6 intron has two overlapped branch point sequences(BPS) upstream of its 30 splice site, with an identical heptamer AACUAAC, for E6*I splicing. One heptamer has a branch site adenosine(underlined) at nt 384 and the other at nt 388. E6*I splicing efficiency correlates to the expression level of E6 and E7 proteins and depends on the selection of which branch site. In general, E6*I splicing prefers the 30 ss-proximal branch site at nt 388 over the distal branch site at nt 384. Inactivation of the nt 388 branch site was found to activate a cryptic acceptor site at nt 636 for aberrant RNA splicing. Together, these data suggest that HPV18 modulates its production ratio of E6 and E7 proteins by alternative selection of the two mapped branch sites for the E6*I splicing, which could be beneficial in its productive or oncogenic infection according to the host cell environment.

关键词： Human papillomavirus 18 (HPV18) HPV splicing Branch point E6,E7,E6 intron HPV oncogenes

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A Sylvester-Based IMEXMethod via Differentiation Matrices for Solving Nonlinear Parabolic Equations

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Communications in Computational Physics 2013年第9期14卷 1001-1026页

作者： Francisco de la Hoz fernando Vadillo Department of Applied Mathematics Statistics and Operations ResearchFaculty of Science and TechnologyUniversity of the Basque Country UPV/EHUBarrio Sarriena S/N48940 LeioaSpain

In this paper we describe a new pseudo-spectral method to solve numerically two and three-dimensional nonlinear diffusion equations over unbounded domains,taking Hermite functions,sinc functions,and rational Chebyshev polynomials as basis *** idea is to discretize the equations by means of differentiation matrices and to relate them to Sylvester-type equations by means of a fourth-order implicit-explicit scheme,being of particular interest the treatment of three-dimensional Sylvester equations that we *** resulting method is easy to understand and express,and can be implemented in a transparent way by means of a few lines of *** test numerically the three choices of basis functions,showing the convenience of this new approach,especially when rational Chebyshev polynomials are considered.

关键词： Semi-linear diffusion equations pseudo-spectral methods differentiation matrices Hermite functions sinc functions rational Chebyshev polynomials IMEX methods Sylvester equations blow-up

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Multigear Bubble Propulsion of Transient Micromotors

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Research 2020年第1期2020卷 1384-1392页

作者： Amir Nourhani Emil Karshalev fernando Soto Joseph Wang Department of Nanoengineering University of California San DiegoLa JollaCA 92093USA Department of Mechanical Engineering Department of BiologyBiomimicry Research and Innovation CenterUniversity of AkronAkronOH 44325USA

Transient,chemically powered micromotors are promising biocompatible engines for *** propose a framework to investigate in detail the dynamics and the underlying mechanisms of bubble propulsion for transient chemically powered *** observations on the variations of the micromotor active material and geometry over its lifetime,from initial activation to the final inactive state,indicate different bubble growth and ejection mechanisms that occur stochastically,resulting in time-varying micromotor *** identify three processes of bubble growth and ejection,and in analogy with macroscopic multigear machines,we call each process a *** 1 refers to bubbles that grow on the micromotor surface before detachment while in Gear 2 bubbles hop out of the *** 3 is similar in nature to Gear 2,but the bubbles are too small to contribute to micromotor *** study the characteristics of these gears in terms of bubble size and ejection time,and how they contribute to micromotor *** ability to tailor the shell polarity and hence the bubble growth and ejection and the surrounding fluid flow is *** understanding of the complex multigear bubble propulsion of transient chemical micromotors should guide their future design principles and serve for fine tuning the performance of these micromotors.

关键词： bubble transient chemically

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Understanding the El Nio Costero of 2017: The Definition Problem and Challenges of Climate Forecasting and Disaster Responses

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International Journal of Disaster Risk Science 2017年第4期8卷 489-492页

作者： Ivan J.Ramírez fernando Briones Department of Anthropology Colorado State University Consortium for Capacity Building/INSTAAR University of Colorado Graduate Program in Public Health Colorado State University

This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Nio costero(coastal) of2017, which developed rapidly with no warning and had catastrophic effects in Peru. Such a localized El Nio was not documented since 1925. An initial review suggests that in addition to the characteristics of the event(surprise),government responses may have been inadequate(as media reported) because of conflicting forecast reports(U.S. and Peru), which provoked a hydrometeorological debate and stifled decision making. Partly to blame was the El Nio definition problem, which can cause uncertainty and affect perception of risk, depending on which region of the equatorial Pacific one uses to identify an event. Responses were further complicated by the fact that some regions within Peru were experiencing drought prior to the El Nio costero's onset and impacts from the El Nio 2015–2016 were less than expected. Furthermore, a new government was in place, which may have hindered action. Thus, El Nio costero provides lessons to heed, not only with respect to the forecast information, but also with reference to the context of the forecast and disaster setting, which can influence disaster responses to hydrometeorological threats.

关键词： Disaster risk reduction Ecuador El Nio costero El Nio forecast El Nio-Southern Oscillation Peru Teleconnections

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Communities of saprobic fungi on leaf litter of Vismia guianensis in remnants of the Brazilian Atlantic Forest

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Journal of Forestry Research 2017年第1期28卷 163-172页

作者： Loise Araujo Costa Luís fernando Pascholati Gusmao Laboratorio de Micologia Av Transnordestina Departamentode Ciências BiológicasUniversidade Estadual de Feira deSantanas/nNovo HorizonteFeira de SantanaBA 44031-460Brazil

We examined the mycobiota associated with Vismia guianensis leaf litter in three Atlantic Forest remnants of Brazil＇ s semiarid region. Among the study sites, two remnants were protected forest reserves, whereas the third was influenced by major anthropogenic activities. Eighteen litter samples were collected in wet and dry seasons and were processed by particle filtration technique. A total of 4750 fungal isolates of 142 taxa were identified. Species richness was higher in litter samples collected during wet season. Nonmetric multidimensional scaling multivariate analysis showed differences in the composition of fungal communities among the sampling sites and the seasons. Analysis of similarity showed that the differences were statistically significant （R = 0.85; P = 0.0001）. Our findings revealed that spatial and temporal heterogeneity, and human activities had significant impacts on the saprobic fungi of V. guianensis leaf litter.

关键词： Biodiversity Conservation Seasonality Spatial heterogeneity Tropical fungi

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Stipa tenacissima Does not Affect the Foliar δ^(13)C and δ^(15)N of Introduced Shrub Seedlings in a Mediterranean Semi-arid Steppe

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Journal of Integrative Plant Biology 2006年第8期48卷 897-905页

作者： fernando T.Maestre Susana Bautista Jordi Cortina Departamento de Ecologia Universidad de AlicanteApartado de correos 9903080 AlicanteSpain Department of Biology Duke UniversityPhytotron BuildingScience DriveBox 90340DurhamNorth Carolina 27708-0340USA Centro de Estudios Ambientales del Mediterraneo C/ Charles Darwin 1446980 PaternaSpain

Recent studies have shown that the tussock grass Stipa tenacissima L. facilitates the establishment of late-successional shrubs, in what constitutes the first documented case of facilitation of woody plants by grasses. With the aim of increasing our knowledge of this interaction, in the present study we investigated the effects of S. tenacissima on the foliar δ13C, δ15N, nitrogen concentration, and carbon ： nitrogen ratio of introduced seedlings of Pistacia lentiscus L., Quercus coccifera L., and Medicago arborea L. in a semi-arid Mediterranean steppe. Six months after planting, the values of δ13C ranged between -26.9‰ and -29.6‰, whereas those of δ15N ranged between -1.9‰ and 2.7‰. The foliar C ： N ratio ranged between 10.7 and 53.5, and the nitrogen concentration ranged between 1.0% and 4.4%. We found no significant effect of the microsite provided by S. tenacissima on these variables in any of the species evaluated. The values of δ13C were negatively correlated with predawn water potentials in M. arborea and were positively correlated with relative growth rate in Q. coccifera. The values of δ15N were positively correlated with the biomass allocation to roots in the latter species. The present results suggest that the modification of environmental conditions in the are surrounding S. tenacissima was not strong enough to modify the foliar isotopic and nitrogen concentration of shrubs during the early stages after planting.

关键词： facilitation Medicago arborea Pistacia lentiscus Quercus coccifera stable isotopes steppe Stipa tenacissima.

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Geo-vegetation Mapping and Soil Geochemical Characteristics of the Indikolapelessa Serpentinite Outcrop,Southern Sri Lanka

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Journal of Earth Science 2014年第1期25卷 152-168页

作者： Tilak Hewawasam G W A R fernando Danushka Priyashantha Department of Natural Resources Sabaragamuwa University of Sri Lanka Department of Geography University of Peradeniya Department of Physics Open University of Sri Lanka

The serpentinite blocks of Indikolapelessa, located along an identified litho-tectonic boundary between the Highland Complex （HC） and the Vijayan Complex （VC） of Sri Lanka, have undergone extensive lateralization with metal enrichment. Characteristic serpentinite vegetation with some endemic species was recognized in the soils and supergene deposits develop on serpentinite lithology. This type of geological and ecological relationship forms vegetation covers on serpentinite lithologies which are sharply demarcated from the surrounding metamorphic terrains. The aforesaid ＂geo-ecological phenomenon＂ can be used as a tool for geo-vegetation mapping in ultramafic terrains to trace the geological boundaries in landscapes where rock outcrops are virtually absent. We success- fully applied the concept of geo-vegetation mapping in order to demarcate the boundary of underlain serpentinite rocks from surrounding non-serpentinite metamorphic rocks （e.g. granitic gneiss）. The hypothesis was supported by the geochemical variations of soils/supergene deposits found at serpen- tinite and non-serpentinite sites, especially immobile elements and some trace elements. Based on whole rock chemistry and soil chemical data obtained, we suggest that the Indikolapelessa serpentinite outcrop, together with the other four serpentinite outcrops, is more likely to represent the Mg-rich mantle fragments at the time of overthrusting of the two crustal blocks of HC and VC during the Pan- African event.

关键词： serpentinite serpentinite soil geochemistry geo-vegetation ultramafic rock Sri Lanka.

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Heritage Today: The Art of Transforming What We Received from the Past

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Built Heritage 2017年第3期1卷 60-68页

作者： fernando Perez Oyarzun Faculty of Architecture Design and Urban StudiesPontificia Universidad Católica de ChileSantiagoChile

The paper aims at highlighting the new reality of urban and architectural *** maintains that the current public claim for heritage protection radically diverges from the original endeavour of protecting national *** significant expansion of heritage goods and the involvement of citizen movements in the decisions about them are two of the most visible aspects of this *** paper suggests that a renovated idea of heritage is currently *** should take into consideration aspects such as its economic value and its connection to the quality of daily *** that urban preservation has turned to be part of planning,the paper foregrounds some of the problems of keeping it as a separate legal and cultural *** is exemplified by Latin American reality and some specific cases from *** it highlights the positive role of transformation and adaptation in the preservation of heritage.

关键词： heritage urban heritage heritage challenges heritage transformation Latin American heritage

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