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The 2015/16 El Nino-related glacier changes in the tropical Andes

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Frontiers of Earth Science 2019年第2期13卷 422-429页

作者： Bijeesh Kozhikkodan VEETTiL jefferson Cardia SiMOES Department for Management of Science and Technology Development Ton Due Thang UniversityHo Chi Minh CityVietnam Faculty of Environment and Labour Safety Ton Due Thang UniversityHo Chi Minh CityVietnam Centro Polar e Climatico Universidade Federal do Rio Grande do Sul (UFRGS)CEP91501-970 Porto AlegreBrazil

Significant changes in the area and snowline altitude of two glacierized mountains - Nevado Champara (Cordillera Blanca,Peru) and Cerro Tilata (Cordillera Real,Bolivia)- in the tropical Andes,before and after the recent El Nino in 2015/16 period,have been analysed using Sentinel 2A and Landsat *** is seen that the recent El Nino has been accompanied by higher fluctuation in glacier coverage on Nevado Champara and the loss of glacier coverage on Cerro Tilata was very high during the past 16 *** in snowline altitude of selected glaciers was very high after the 2015/16 El *** in the area covered by snow and ice during the La Nina periods were not enough to cover the ice loss occurred during the previous El Nino events and the strongest El Nino in 2015/ 16 was followed by a significant loss of ice-covered areas in the tropical *** resources in this region will be affected in the near future if the current trends in glacier decline *** strategies needs to be implemented to reduce the impacts of the continuing loss of glacierized on regional communities in the tropical Andean region.

关键词： ENSO tropical Andes glacier loss snowline altitude Sentinel 2A

QUASiLiNEAR EQUATiONS USiNG A LiNKiNG STRUCTURE WiTH CRiTiCAL NONLiNEARiTiES

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Acta Mathematica Scientia 2022年第3期42卷 975-1002页

作者： Edcarlos D.SiLVA jefferson S.SiLVA Federal University of Goi′as Zip code 74001-970Goi′as-GOBrazil

it is to establish existence of a weak solution for quasilinear elliptic problems assuming that the nonlinear term is *** potential V is bounded from below and above by positive *** we are considering a critical term which interacts with higher eigenvalues for the linear problem,we need to apply a linking *** that the lack of compactness,which comes from critical problems and the fact that we are working in the whole space,are some obstacles for us to ensure existence of solutions for quasilinear elliptic *** main feature in this article is to restore some compact results which are essential in variational *** that compactness conditions such as the Palais-Smale condition for the associated energy functional is not available in our *** difficulty is overcame by taking into account some fine estimates on the critical level for an auxiliary energy functional.

关键词： Quasilinear Schrödinger equations linking theorems superlinear elliptic equations critical nonlinearities Bounded potentials

Mechanical buckling induced periodic kinking/stripe microstructures in mechanically peeled graphite fla es from HOPG

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Acta Mechanica Sinica 2015年第4期31卷 494-499页

作者： Manrui Ren Ze Liu Quan-shui Zheng jefferson Zhe Liu Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University

Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. in our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. in this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation：（1） peeling of a graphite flake and （2） mechanical buckling of the flake being sub- jected to bending. in this model, the width of the stripes L is determined by thickness h of the flakes, surface energy Y, and critical buckling strain ecr. Using some appropriate values of y and ecr that are within the ranges determined by other inde- pendent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reason- ably well with our experimental measurements. Conversely, measuring the L-h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechan- ical buckling strain εcr and the interface energy γ.

关键词： HOPG Mechanical exfoliation Periodic microstructures Kinking Mechanical buckling

Refractory Black Carbon Results and a Method Comparison between Solid-state Cutting and Continuous Melting Sampling of a West Antarctic Snow and Firn Core

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Advances in Atmospheric Sciences 2020年第5期37卷 545-554页

作者： Luciano MARQUETTO Susan KASPARi.jefferson Cardia SiMOES Emil BABiK Department of Geological Sciences Central Washington UniversityEllensburgWashington 98926USA Polar and Climatic Center Federal University of Rio Grande do SulPorto AlegreRio Grande do Sul91509-900Brazil

This work presents the refractory black carbon(rBC)results of a snow and firn core drilled in West Antarctica(79°55'34.6"S,94°21'13.3"W)during the 2014?15 austral summer,collected by Brazilian researchers as part of the First Brazilian West Antarctic ice Sheet *** core was drilled to a depth of 20 m,and we present the results of the first 8 m by comparing two subsampling methods—solid-state cutting and continuous melting—both with discrete *** core was analyzed at the Department of Geological Sciences,Central Washington University(CWU),WA,USA,using a single particle soot photometer(SP2)coupled to a CETAC Marin-5 *** continuous melting system was recently assembled at CWU and these are its first *** also present experimental results regarding SP2 reproducibility,indicating that sample concentration has a greater influence than the analysis time on the reproducibility for low rBC concentrations,like those found in the Antarctic *** was carried out using mainly the rBC variation and sulfur,sodium and strontium as secondary parameters,giving the core 17 years(1998?2014).The data show a well-defined seasonality of rBC concentrations for these first meters,with geometric mean summer/fall concentrations of 0.016μg L^?1 and geometric mean winter/spring concentrations of 0.063μg L^?*** annual rBC concentration geometric mean was 0.029μg L^?1(the lowest of all rBC cores in Antarctica referenced in this work),while the annual rBC flux was 6.1μg m^?2 yr^?1(the lowest flux in West Antarctica records so far).

关键词： black carbon West Antarctica ice core single particle soot photometer

Molecular dynamics simulations of the electric double layer capacitance of graphene electrodes in mono-valent aqueous electrolytes

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Nano Research 2016年第1期9卷 174-186页

作者： Gengping Jiang Chi Cheng Dan Li.jefferson Zhe Liu Department of Mechanical and Aerospace Engineering Monash University VIC 3800 Australia Department of Materials Science and Engineering Monash University VIC 3800 Australia Monash Center forAtomically Thin Materials Monash University VIC 3800 Australia

Electrical double layer （EDL） capacitors based on recently emergent graphene materials have shown several folds performance improvement compared to conventional porous carbon materials, driving a wave of technology breakthrough in portable and renewable energy storage. Accordingly, much interest has been generated to pursue a comprehensive understanding of the fundamental yet elusive double layer structure at file electrode^electrolyte interface. in this paper, we carried out comprehensive molecular dynamics simulations to obtain a com- prehensive picture of how ion type, solvent properties, and charging conditions affect the EDL structure at the graphene electrode surface, and thereby its contribution to capacitance. We show that different symmetrical monovalent aqueous electrolytes M^X- （M~ = Na~, K~, Rb＋, and Cs＋; X- = F-, Ci-, and i ） indeed have distinctive EDL structures. Larger ions, such as, Rb＊, Cs＊, C1, and i, undergo partial dehydration and penetrate through the first water layer next to the graphene electrode surfaces under charging. As such, the electrical potential distribution through the EDL strongly depends on the ion type. interestingly, we further reveal that the water can play a critical role in determining the capacitance value. The change of dielectric constant of water in different electrolytes largely cancels out the variance in electric potential drop across the EDL of different ion type. Our simulation sheds new lights on how the interplay between solvent molecules and EDL structure cooperatively contributes to capacitance, which agrees with our experimental results well.

关键词： graphene supercapacitor molecular dynamicssimulations electric double layerstructures aqueous electrolyte monovalent ions

Antimony oxidation and adsorption by in-situ formed biogenic Mn oxide and Fe–Mn oxides

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Journal of Environmental Sciences 2017年第4期29卷 126-134页

作者： Yaohui Bai William A.jefferson Jinsong Liang Tingting Yang Jiuhui Qu Key Laboratory of Drinking Water Science and Technology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China University of Chinese Academy of Sciences Beijing 100049 China

Antimony（Sb）, which can be toxic at relatively low concentrations, may co-exist with Mn（Ⅱ）and/or Fe（Ⅱ） in some groundwater and surface water bodies. Here we investigated the potential oxidation and adsorption pathways of Sb（Ⅲ and V） species in the presence of Mn（Ⅱ） and Mn-oxidizing bacteria, with or without Fe（Ⅱ）. Batch experiments were conducted to determine the oxidation and adsorption characteristics of Sb species in the presence of biogenic Mn oxides（BMOs）, which were formed in-situ via the oxidation of Mn（Ⅱ） by a Mn-oxidizing bacterium（Pseudomonas sp. QJX-1）. Results indicated that Sb（Ⅲ） ions could be oxidized to Sb（V） ions by BMO, but only Sb（V） originating from Sb（Ⅲ） oxidation was adsorbed effectively by BMO. introduced Fe（Ⅱ） was chemically oxidized to Fe OOH, the precipitates of which mixed with BMO to form a new compound, biogenic Fe–Mn oxides（BFMO）. The BMO part of the BFMO mainly oxidized and the Fe OOH of the BFMO mainly adsorbed the Sb species. in aquatic solutions containing both As（Ⅲ） and Sb（Ⅲ）, the BFMO that formed in-situ preferentially oxidized Sb over As but adsorbed As more efficiently. Chemical analysis and reverse transcription real-time polymerase chain reaction revealed that the presence of Fe（Ⅱ）, As（Ⅲ） and Sb（Ⅲ） accelerated the oxidation of Mn（Ⅱ） but inhibited the activity of Mn-oxidizing bacteria. These results provide significant insights into the biogeochemical pathways of Sb, Mn（Ⅱ） in aquatic ecosystems, with or without Fe（Ⅱ）.

关键词： Biogenic Mn oxide Biogenic Fe–Mn oxides Oxidation and adsorption Antimony Arsenic

Van der Waals force-induced intralayer ferroelectric-to-antiferroelectric transition via interlayer sliding in bilayer group-Ⅳmonochalcogenides

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npj Computational Materials 2022年第1期8卷 446-454页

作者： Bo Xu Junkai Deng Xiangdong Ding Jun Sun jefferson Zhe Liu State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University710049Xi’anChina Department of Mechanical Engineering The University of MelbourneParkvilleVIC3010Australia

Two-dimensional materials with ferroelectric properties break the size effect of conventional ferroelectric materials and unlock unprecedented potentials of ferroelectric-related application at small length *** first-principles calculations,a sliding-induced ferroelectric-to-antiferroelectric behavior in bilayer group-iV monochalcogenides(MX,with M=Ge,Sn and X=S,Se)is *** this mechanism,the top layer exhibits a reversible intralayer ferroelectric switching,leading to a reversible transition between the ferroelectric and antiferroelectric states in the bilayer *** results show that the interlayer van der Waals interaction,which is usually considered to be weak,can actually generate an in-plane lattice distortion and thus cause the breaking/forming of intralayer covalent bonds in the top layer,leading to the observed anomalous *** unique property has advantages for energy harvesting over existing piezoelectric and triboelectric *** interlayer sliding-induced big polarization change(40μC cm^(−2))and ultrahigh polarization changing rate generate an open-circuit voltage two orders of magnitude higher than that of MoS_(2)-based *** theoretical prediction of power output for this bilayer MXs at a moderate sliding speed 1 m s^(−1)is four orders of magnitude higher than the MoS_(2)nanogenerator,indicating great potentials in energy harvesting applications.

关键词： ferroelectric interlayer layer

instaGraminoid,a Novel Colorimetric Method to Assess Herbicide Resistance,identifies Patterns of Cross-Resistance in Annual Ryegrass

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Plant Phenomics 2019年第1期1卷 185-197页

作者： jefferson F.Paril Alexandre J.Fournier-Level School of Biosciences University of MelbourneParkvilleVICAustralia

Herbicide resistance in agricultural weeds is a global problem with an increasing understanding that it is caused by multiple genes leading to quantitative *** quantitative patterns of resistance are not easy to decipher withmortality assays alone,and there is a need for straightforward and unbiased protocols to accurately assess quantitative herbicide ***—a computer vision and statistical analysis package—was developed as an automated and scalable method for quantifying herbicide *** package was tested in rigid ryegrass(Lolium rigidum),the most noxious and highly resistant weed in Australia and theMediterranean *** method provides quantitative measures of the degree of chlorosis and necrosis of individual plants which was shown to accurately reflect herbicide *** were able to reliably characterise resistance to four herbicides with different sites of action(glyphosate,sulfometuron,terbuthylazine,and trifluralin)in two *** populations from Southeast ***-validation of themethod across populations and herbicide treatments showed high repeatability and *** positive correlations in resistance of individual plants were observed across herbicides,which suggest either the accumulation of herbicide-specific resistance alleles in single genotypes(multiple stacked resistance)or the presence of general broad-effects resistance alleles(cross-resistance).We used these quantitative estimates of cross-resistance to simulate howresistance development under an herbicide rotation strategy is likely to be higher than expected.

关键词： straight likely Australia

Control of surface wettability via strain engineering

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Acta Mechanica Sinica 2013年第4期29卷 543-549页

作者： Wei Xiong jefferson Zhe Liu Zhi-Liang Zhang Quan-Shui Zheng Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University Department of Structural Engineering Norwegian University of Science and Technology (NTNU)

Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. in light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.

关键词： Wettability ~ Strain engineering ~ Molecular dy-namics simulation