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Visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using in-situ environmental(scanning) transmission electron microscopy

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Journal of Energy Chemistry 2021年第6期30卷 281-290,I0007页

作者： Michael R.Ward robert W.Mitchell Edward D.Boyes Pratibha l.Gai The York Nanocentre University of YorkYork YO105DDUK Department of Physics University of YorkYork YO105DDUK Department of Electronic Engineering University of YorkYork YO105DDUK Department of Chemistry University of YorkYork YO105DDUK

Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst *** noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia *** and graphitic carbons are of interest as supports for the *** considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well *** we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom *** recording snapshots of the reaction dynamics,the behaviour of the catalysts is *** images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support *** all play key roles in the mobility,sintering and growth of the *** experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts.

关键词： In-situ visualization Atomic scale reaction dynamics In-situ environmental scanning transmission electron microscopy with single atom resolution Supported nanoparticles Ammonia synthesis Oxidation reactions

Testing allometric scaling relationships in plant roots

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Forest Ecosystems 2020年第4期7卷 770-780页

作者： Qiang Deng Zhiyou Yuan Xinrong Shi T.Ryan lock robert l.Kallenbach State Key laboratory of Soil Erosion and Dryland Farming on the loess Plateau Institute of Soil and Water ConservationChinese Academy of Sciences and Ministry of Water ResourcesYangling 712100ShaanxiChina. University of Chinese Academy of Sciences Beijing 100049China. Institute of Soil and Water Conservation Northwest A&F UniversityYangling 712100ShaanxiChina Division of Plant Sciences College of AgricultureFoodand Natural ResourcesUniversity of Missouri108 Waters HallColumbiaMO 65211USA.

Background:Metabolic scaling theory predicts that plant productivity and biomass are both ***,this theory has not yet been tested in plant ***:In this study,we tested how metabolic scaling occurs in plants using a comprehensive plant root dataset made up of 1016 observations from natural *** generated metabolic scaling exponents by logtransformation of root productivity versus ***:Results showed that the metabolic scaling exponents of fine root(lose to 1.0 for all ecosystem types and functional *** exponents decreased in coarse roots(>2mm in diameter).Conclusions:We found isometric metabolic scaling in fine roots,a metabolically active organ similar to seedlings or *** findings also indicate a shift in metabolic scaling during plant ***,our study supports the absence of any unified single constant scaling exponent for metabolism-biomass relationships in terrestrial plants,especially for forests with woody species.

关键词： Allometry Biomass Metabolic scaling Plant roots Productivity

Nickel oxide thin films grown by chemical deposition techniques: Potential and challenges in next-generation rigid and flexible device applications

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InfoMat 2021年第5期3卷 536-576页

作者： Mari Napari Tahmida N.Huq robert l.Z.Hoye Judith l.MacManus-Driscoll Department of Materials Science and Metallurgy University of CambridgeCambridgeUK Centre for Electronics Frontiers Zepler Institute for Photonics and NanoelectronicsUniversity of SouthamptonSouthamptonUK Department of Materials Imperial College LondonLondonUK

Nickel oxide(NiOx),a p-type oxide semiconductor,has gained significant attention due to its versatile and tunable *** has become one of the critical materials in wide range of electronics applications,including resistive switching random access memory devices and highly sensitive and selective sensor *** addition,the wide band gap and high work function,coupled with the low electron affinity,have made NiOx widely used in emerging optoelectronics and p-n *** properties of NiOx thin films depend strongly on the deposition method and *** implementation of NiOx in next-generation devices will require controllable growth and processing methods that can tailor the morphological and electronic properties of the material,but which are also compatible with flexible *** this review,we link together the fundamental properties of NiOx with the chemical processing methods that have been developed to grow the material as thin films,and with its application in electronic *** focus solely on thin films,rather than NiOx incorporated with one-dimensional or two-dimensional *** review starts by discussing how the p-type nature of NiOx arises and how its stoichiometry affects its electronic and magnetic *** discuss the chemical deposition techniques for growing NiOx thin films,including chemical vapor deposition,atomic layer deposition,and a selection of solution processing approaches,and present examples of recent progress made in the implementation of NiOx thin films in devices,both on rigid and flexible ***,we discuss the remaining challenges and limitations in the deposition of device-quality NiOx thin films with chemical growth methods.

关键词： atomic layer deposition chemical vapor deposition electronics nickel oxide solution processing thin films

Changes in free amino acids and polyamine levels in Satsuma leaves in response to Asian citrus psyllid infestation and water stress

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Insect Science 2014年第6期21卷 707-716页

作者： Nasir S. A. Malik Jose l. Perez Madhurababu Kunta Joseph M. Patt robert l. Mangan USDA-ARS ERRC 600 E Mermaid lane Wyndmoor PA 19038-8598 USDA-ARS SPARC 2881 F&B Road College Station TX 77845 Texas A&M University-Kingsville Citrus Center 312 North International Blvd Weslaeo TX 78596 U. S. Horticultural Research laboratory 2001 South Rock Road Fort Pierce FL 34945 Subtropical Horticultural Research Station 13601 Old Coulter Road Miami FL 33158 USDA-ARS 2413 E. Hwy 83 Weslaco TX 78596 USA

The effects of biotic and abiotic stresses on changes in amino acids and polyamine levels in Satsuma orange （Citrus unshiu; cultivar Owari） leaves were inves- tigated. Asian citrus psyllids Diaphorina citri （Kuwayama）（ACP） infestation was used to induce biotic stress while a water deficit was imposed to induce abiotic stress. Potted trees were infested by placing 50 psyllids on 3 citrus leaves enclosed in nylon mesh bags for 5 d. A parallel set of plants were kept water stressed by maintaining the soil at 20% water holding capacity for 5 d. levels of total free amino acids were higher in water stressed and ACP infested leaves. Polyamine putrescine increased in infested leaves but not in water stressed leaves. Proline was the most abundant amino acid and its levels significantly increased by both biotic and abiotic stresses. Proline levels in infested leaves were significantly higher than the water stressed leaves. Histidine, methionine, asparagine, arginine, serine, and leucine levels also increased significantly in infested leaves, but in water stressed leaves only leucine, methionine, and threonine increased. levels of amino acids, such as tyrosine, isoleucine, phenylalanine, glutamic acid, and alanine, declined in infested leaves. Under water stress asparagine, phenylalanine, serine, and histidine also declined compared to controls. This indicates that while proteolysis occurred under both stresses, metabolic conversion of amino acids was different under the two stresses. In ACP infested leaves some amino acids may be used as feeding material and/or converted into secondary metabolites for defense.

关键词： amino acids citrus Diaphorina citri polyamines

Towards real-time detection of wastewater in surface waters using fluorescence spectroscopy

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Journal of Environmental Sciences 2019年第12期31卷 195-202页

作者： Ye Z.Yang Nicolas M.Peleato Raymond l.legge robert C.Andrews Department of Ciuil and Mineral Engineering University of Toronto35 St.George St.TorontoOntario M5S 1A4Canada School of Engineering Uniuersity of British Columbia Okanagan1137 Alwmni AueKeloiunaBritish Columbia V1V 1V7Canada Department of Chemical Engineering University of Waterloo200 University Ave.WWaterlooOntario N2L 3G1Canada

The presence of municipal wastewater at the intake of a major drinking water treatment facility located on lake Ontario was examined using fluorescence data collected during a period of continuous *** addition,controlled mixing of lake water and wastewater sampled from a local treatment facility were conducted using a bench-scale fluorescence system to quantify observed changes in natural organic *** linear regression was applied to components derived from parallel factors *** resulting mean absolute error for predicted wastewater level was 0.22%(V/V,wastewater/lake water),indicating that wastewater detection at below 1.0%(V/V)was *** of sucralose,a wastewater indicator,were conducted for treated wastewater as well as surface water collected at two intake locations on lake *** suggested minimal wastewater contribution at the drinking water intake.A wastewater detection model using a moving baseline was developed and applied to continuous fluorescence data collected at one of the drinking water intakes,which agreed well with sucralose ***,the simulated addition of 1.0%(V/V)of wastewater/wastewater was detectable in 89%of samples analyzed,demonstrating the utility of fluorescence-based wastewater monitoring.

关键词： Excitation emission matrices Parallel factors analysis Natural organic matter Source water monitoring Wastewater impact Water quality assessment

Hurricane disturbances, tree diversity, and succession in North Carolina Piedmont forests, USA

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Journal of Forestry Research 2019年第1期30卷 219-231页

作者： Weimin Xi robert K.Peet Michael T.lee Dean l.Urban Department of Biology University of North Carolina at Chapel Hill Department of Biological and Health Sciences Texas A & M University-Kingsville The Nicholas School of the Environment Duke University

Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events(i.e., tropical cyclones, including hurricanes,typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes(tropical cyclones that occurs in the Atlantic Ocean and northeastern Pacific Ocean) lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA. Species richness(S) and Shannon–Wiener's diversity index(H') were used to evaluate the changes in tree diversity. The changes in composition were assessed with Nonmetric Multidimensional Scaling. The pre-hurricane successional phase can strongly influence both the damage severity and subsequent responses. Although there is often an immediate drop in diversity following a hurricane, understory tree diversity quickly increases to levels that exceed those prior to the disturbance. This leads to an increase in diversity in stands that were substantially damaged. Hurricanes significantly decrease the dominance of shade-intolerant canopy species while increasing preestablished, more shade-tolerant species. We conclude that large, and infrequent hurricanes help to maintain local tree diversity, but also accelerate the increase in dominance of understory species such as red maple and beech.

关键词： Wind disturbance Tree species diversity Plant succession Disturbance-diversity relationship Piedmont forests

Soil resource availability and its effect on the ecophysiology and establishment of Stipa pulchra

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Journal of Plant Ecology 2019年第4期12卷 603-614页

作者： robert l.Fitch Erin J.Questad Edward G.Bobich Department of Biological Sciences California State Polytechnic UniversityPomona3801 West Temple Avenue PomonaCA 91768USA

Aims The objectives of this study were to(i)determine the importance of soil moisture and soil nitrogen availability as resource requirements for the establishment of Stipa pulchra,(ii)to examine how changes in slope within a local habitat can affect the accumulation of soil moisture and soil nitrogen and(iii)to measure the physiological re-sponses of *** among such slope *** The field experiment occurred in the San JoséHills of Southern California on the California State Polytechnic University,Pomona *** were established within three different slope loca-tions(shallow,moderate and steep)within four separate *** nitrogen treatments(ambient,addition and removal)were replicated within each slope location for all four canyons,and five *** plants were planted in each *** nitrogen accumula-tion and soil moisture,as well as other abiotic variables,were meas-ured across the varied slope locations and nitrogen *** measured the cover,stress,and reproduction of *** plants for 2 years and used a mesocosm experiment to determine how ***-chra responds to varying water and nitrogen *** Findings Stipa pulchra had a strong positive response to the wettest watering treatment and a weak response to nitrogen addition in the meso-cosm *** the field experiment,*** responded positively in moderate slope locations and did not respond to ni-trogen treatments,possibly due to *** patterns of soil moisture were driven by slope,soil compaction and solar *** nitrogen accumulation did not vary among slope *** restoration of ***,priority should be placed on managing soil moisture availability and determining suitable edaphic factors.

关键词： establishment ecophysiology slope soil moisture soil properties nitrogen deposition

Characteristics of Anthropogenic Sulfate and Carbonaceous Aerosols over East Asia: Regional Modeling and Observation

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Advances in Atmospheric Sciences 2008年第6期25卷 946-959页

作者： Yan HUANG William l. CHAMEIDES Qian TAN robert E. DICKINSON School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta GA 30332 Nicholas School of the Environment and Earth Sciences Duke University Durham NC 27708 Goddard Earth Sciences and Technology Center University of Maryland Baltimore MD 21228

The authors present spatial and temporal characteristics of anthropogenic sulfate and carbonaceous aerosols over East Asia using a 3-D coupled regional climate-chemistry-aerosol model, and compare the simulation with the limited aerosol observations over the region. The aerosol module consists of SO2, SO4^2-, hydrophobic and hydrophilic black carbon （BC） and organic carbon compounds （OC）, including emission, advections, dry and wet deposition, and chemical production and conversion. The simulated patterns of SO2 are closely tied to its emission rate, with sharp gradients between the highly polluted regions and more rural areas. Chemical conversion （especially in the aqueous phase） and dry deposition remove 60% and 30% of the total SO2 emission, respectively. The SO4^2- shows less horizontal gradient and seasonality than SO2, with wet deposition （60%） and export （27%） being two major sinks. Carbonaceous aerosols are spatially smoother than sulfur species. The aging process transforms more than 80% of hydrophobic BC and OC to hydrophilic components, which are removed by wet deposition （60%） and export （30%）. The simulated spatial and seasonal SO4^2-, BC and OC aerosol concentrations and total aerosol optical depth are generally consistent with the observations in rural areas over East Asia, with lower bias in simulated OC aerosols, likely due to the underestimation of anthropogenic OC emissions and missing treatment of secondary organic carbon. The results suggest that our model is a useful tool for characterizing the anthropogenic aerosol cycle and for assessing its potential climatic and environmental effects in future studies.

关键词： regional climate modeling anthropogenic emission sulfate aerosol black carbon and organic carbon East Asia

Bone morphogenetic protein signaling：a promising target for white matter protection in perinatal brain injury

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Neural Regeneration Research 2018年第7期13卷 1183-1184页

作者： Jill Chang robert W.Dettman Maria l.V.Dizon Department of Pediatrics Feinberg School of Medicine Northwestern University Chicago IL USA Stanley Manne Research Institute Chicago IL USA

Prematurely born newborns,as well as those born at term,may suffer from several types of brain injury including hypoxic-ischemic injury,intracranial hemorrhage,both intraventricular and parenchymal,and injury that is the consequence of intrauterine growth restriction（IUGR）.Injury of all types can impact the motor and cognitive abilities of *** mechanisms leading to disability are not completely understood.

关键词： In Bone morphogenetic protein signaling:a promising target for white matter protection in perinatal brain injury