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Validation of a discrete element model using magnetic resonance measurements

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Particuology 2009年第4期7卷 297-306页

作者： Christoph R.Müller stuart A.Scott Daniel j.Holland Belinda C.Clarke Andrew j.Sederman john S.Dennis Lynn F.Gladden Department of Chemical Engineering and Biotechnology University of CambridgePembroke StreetCambridge CB2 3RAUnited Kingdom

The discrete element model （DEM） is a very promising modelling strategy for two-phase granular systems. However, owing to a lack of experimental measurements, validation of numerical simulations of two-phase granular systems is still an important issue. In this study, a small two-dimensional gas- fluidized bed was simulated using a discrete element model. The dimensions of the simulated bed were 44mm × 10mm × 120 mm and the fluidized particles had a diameter dp = 1.2 mm and density ρp = 1000 kg/m^3. The comparison between DEM simulations and experiments are performed on the basis of time-averaged voidage maps. The drag-law of Beetstra et al. [Beetstra, R., van der Hoef, M.A., ＆ Kuipers,j. A. M. （2007b）. Drag force of intermediate Reynolds number flow past mono- and bidispersed arrays of spheres. AIChE journal, 53,489-501 ] seems to give the best results. The simulations are fairly insensitive to the coefficient of restitution and the coefficient of friction as long as some route of energy dissipation during particle-particle and particle-wall contact is provided. Changing the boundary condition of the gas phase at the side-walls from zero-slip to full-slip does not affect the simulation results. Care is to be taken that the cell sizes are chosen so that a reasonable number of particles can be found in a fluid cell.

关键词： Discrete element modelling Magnetic resonance imaging Voidage Gas-fluidized beds

Using a 3-D multicellular simulation of spinal cord injury with live cell imaging to study the neural immune barrier to nanoparticle uptake

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Nano Research 2016年第8期9卷 2384-2397页

作者： Alan P. Weightman stuart I. jenkins Divya M. Chari Cellular and Neural Engineering Group Institute for Science and Technology in Medicine Huxley Building Keele University Keele ST55BG UK

Development of nanoparticle （NP） based therapies to promote regeneration in sites of central nervous system （CNS; i.e, brain and spinal cord） pathology relies critically on the availability of experimental models that offer biologically valid predictions of NP fate in vivo. However, there is a major lack of biological models that mimic the pathological complexity of target neural sites in vivo, particularly the responses of resident neural immune cells to NPs. Here, we have utilised a previously developed in vitro model of traumatic spinal cord injury （based on 3-D organotypic slice arrays） with dynamic time lapse imaging to reveal in real-time the acute cellular fate of NPs within injury foci. We demonstrate the utility of our model in revealing the well documented phenomenon of avid NP sequestration by the intrinsic immune cells of the CNS （the microglia）. Such immune sequestration is a known translational barrier to the use of NP-based therapeutics for neurological injury. Accordingly, we suggest that the utility of our model in mimicking microglial sequestration behaviours offers a valuable investigative tool to evaluate strategies to overcome this cellular response within a simple and biologically relevant experimental system, whilst reducing the use of live animal neurological injury models for such studies.

关键词： organotypic slice culture microglia immune barrier corticosteroid dexamethasone time lapse microscopy

Effects of endophyte infection on the competitive ability of Achnatherum sibiricum depend on endophyte species and nitrogen availability

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journal of Plant Ecology 2019年第5期12卷 815-824页

作者： Yong Zhou Xia Li Hui Liu Yubao Gao Wade j.Mace stuart D.Card Anzhi Ren Department of Plant Biology and Ecology College of Life SciencesNankai University94 Weijin RoadTianjin 300071China College of Landscape and Travel Hebei Agricultural UniversityBaoding 071001China Department of Plant Biology College of Life SciencesHebei UniversityBaoding 071001China AgResearch Ltd Grasslands Research CentrePrivate Bag 11008Palmerston North 4442New Zealand

Aims the leaves of almost all terrestrial plant species are colonized by endophytic *** to agronomic grasses,which usually harbor few endophytes,native grasses generally possess greater endophyte species *** studies examining endophyte effects on natural grasses under competition normally considered the infection status(infected or uninfected),and rarely considered endophyte *** We examined the effects of endophyte infection and of endophyte species on the interspecific competitive ability of a subdominant species,Achnatherum sibiricum,at two nitrogen levels(high ni-trogen and low nitrogen).Achnatherum sibiricum plants infected by two different species of endophyte(Epichloësibirica and ***)and uninfected plants were grown in monoculture and binary mixtures with a dominant species,Stipa grandis(six individuals per species for monocultures and three+three in-dividuals of each species in mixtures).Shoot and root biomass,tiller number and total phenolic concentration were measured after 3 ***,the aggressivity index was calculated to compare the competitive ability of *** relative to *** Findings Both ***(Eg)-and ***(Es)-infected *** plants showed a greater competitive ability than the uninfected plants under high nitrogen supply,while the opposite result oc-curred under low nitrogen *** high nitrogen levels,Eg plants had a higher tiller number and a greater shoot biomass in-hibitory effect on *** than Es plants had when growing in mixture,while Es plants showed better root growth performance than Eg and uninfected plants under mixture conditions at all ni-trogen levels.A higher concentration of phenolic compounds in Eg plants than in Es plants might contribute to the higher inhibi-tory effect of Eg plants on competing *** study indicates that the interaction between endophyte infection and nitrogen availability can alter the competitive ability o

关键词： Achnatherum sibiricum Epichloëendophytes interspecific competition native grass nutrient supply

INSTABILITY OF HAGEN-POISEUILLE FLOW FOR NON-AXISYMMETRIC MODE

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Applied Mathematics and Mechanics(English Edition) 1989年第5期10卷 407-417页

作者：王发民 j. T. stuart (F. R. S.) Institute of Mech. Academia Sinica Beijing Imperial College U. K.

An investigation is described for instability problem of flow through a pipe of circular cross section. As a disturbance motion, we consider a general non-axisym-metric mode. An associated amplitude or modulation equation has been derived for this disturbance motion. This equation belongs to a diffusion *** coefficient of it can be negative while Reynolds number increases, because of the complex interaction between molecular diffusion and convection. The negative diffusivity, when it occurs, causes a concentration and focussing of energy within decaying slugs, acting as a role of reversing natural decays.

关键词： INSTABILITY OF HAGEN-POISEUILLE FLOW FOR NON-AXISYMMETRIC MODE

Vegetation productivity responses to drought on tribal lands in the four corners region of the Southwest USA

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Frontiers of Earth Science 2018年第1期12卷 37-51页

作者： Mohamed Abd Salam EL-VILALY Kamel DIDAN stuart E. MARSH Willem j.D. VAN LEEUWEN Michael A. CRIMMINS Armando Barreto MUNOZ The Intemational Food Policy Research Institute Washington DC 20006-1002 USA Vegetation Index and Phenology Lab Department of Agricultural and Biosystems Engineering The University of Arizona Tucson AZ 85721-0036 USA Arizona Remote Sensing Center School of Natural Resources and the Environment The University of Arizona Tucson AZ 85721-0043 USA Department of Soils Water and Environmental Science The University of Arizona Tucson AZ 85721-0038 USA

For more than a decade, the Four Comers Region has faced extensive and persistent drought conditions that have impacted vegetation communities and local water resources while exacerbating soil erosion. These persistent droughts threaten ecosystem services, agriculture, and livestock activities, and expose the hypersensitivity of this region to inter-annual climate variability and change. Much of the intermountain Western United States has sparse climate and vegetation monitoring stations, making fine-scale drought assessments difficult. Remote sensing data offers the opportunity to assess the impacts of the recent droughts on vegetation productivity across these areas. Here, we propose a drought assessment approach that integrates climate and topographical data with remote sensing vegetation index time series. Multisensor Normalized Difference Vegetation Index （NDVI） time series data from 1989 to 2010 at 5.6 km were analyzed to characterize the vegetation productivity changes and responses to the ongoing drought. A multi-linear regression was applied to metrics of vegetation productivity derived from the NDVI time series to detect vegetation productivity, an ecosystem service proxy, and changes. The results show that around 60.13% of the study area is observing a general decline of greenness （p 〈 0.05）, while 3.87% show an unexpected green up, with the remaining areas showing no consistent change. Vegetation in the area show a significant positive correlation with elevation and precipitation gradients. These results, while, confirming the region＇s vegetation decline due to drought, shed further light on the future directions and challenges to the region＇s already stressed ecosystems. Whereas the results provide additional insights into this isolated and vulnerable region, the drought assessment approach used in this study may be adapted for application in other regions where surfacebased climate and vegetation monitoring record is spatially and temporally limited.

关键词： drought remote sensing Hopi Navajo Nation

Electrophysiological assessment of primary cortical neurons genetically engineered using iron oxide nanoparticles

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Nano Research 2017年第8期10卷 2881-2890页

作者： Michael G. Evans Arwa Al-Shakli stuart I. jenkins Divya M. Chari School of Life Sciences Keele University Keele Staffordshire ST5 5BG UK Institute for Science and Technology in Medicine Keele University Keele Staffordshire ST5 5BG UK

The development of safe technologies to genetically modify neurons is of great interest in regenerative neurology, for both translational and basic science applications. Such approaches have conventionally been heavily reliant on viral transduction methods, which have safety and production limitations. Magnetofection （magnet-assisted gene transfer using iron oxide nanoparticles as vectors） has emerged as a highly promising non-viral alternative for safe and reproducible genetic modification of neurons. Despite the high potential of this technology, there is an important gap in our knowledge of the safety of this approach, namely, whether it alters neuronal function in adverse ways, such as by altering neuronal excitability and signaling. We have investigated the effects of magnetofection in primary cortical neurons by examining neuronal excitability using the whole cell patch clamp technique. We found no evidence that magnetofection alters the voltage-dependent sodium and potassium ionic currents that underpin excitability. Our study provides important new data supporting magnetofection as a safe technology for bioengineering of neuronal cell populations.

关键词： transfection magnetic nanoparticle green fluorescent protein (GFP) whole-cell patch clamp fluorescence microscopy

Independent and complementary bio-functional effects of CuO andGa_(2)O_(3) incorporated as therapeutic agents in silica-and phosphate-based bioactive glasses

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journal of Materiomics 2022年第4期8卷 893-905页

作者： T.Tite A.C.Popa B.W.stuart H.R.Fernandes I.M.Chirica G.A.Lungu D.Macovei C.Bartha L.Albulescu C.Tanase S.Nita N.Rusu D.M.Grant j.M.F.Ferreira G.E.Stan National Institute of Materials Physics MagureleRO-077125Romania Advanced Materials Research Group Faculty of EngineeringUniversity of NottinghamNG72RDUK CICECOdAveiro Institute of Materials Department of Materials and Ceramics EngineeringUniversity of Aveiro3810-193AveiroPortugal “Victor Babes”National Institute of Research and Development in Pathology and Biomedical Sciences BucharestRO-050096Romania National Institute for Chemical Pharmaceutical Research and Development BucharestRO-031299Romania

The incorporation of therapeutic-capable ions into bioactive glasses(BGs),either based on silica(SBGs)or phosphate(PBGs),is currently envisaged as a proficient path for facilitating bone *** with this view,the single and complementary structural and bio-functional roles of CuO andGa_(2)O_(3)(in the 2e5 mol%range)were assessed,by deriving a series of SBG and PBG formulations startingfrom the parent glass systems,FastOs®BG e 38.5SiO2d36.1CaOd5.6P2O5d19.2MgOd0.6CaF2,and50.0P2O5d35.0CaOd10.0Na_(2)Od5.0 Fe2O_(3)(mol%),respectively,using the process of *** inter-linked physico-chemistry e biological response of BGs was assessed in search of bio-functional *** light was shed on the structural role e as network former or modifier e ofCu and Ga,immersed in SBG and PBG *** preliminary biological performance was surveyedin vitro by quantification of Cu and Ga ion release under homeostatic conditions,cytocompatibility assays(in fibroblast cell cultures)and antibacterial tests(against Staphylococcus aureus).The similar(Cu)anddissimilar(Ga)structural roles in the SBG and PBG vitreous networks governed their ***,Cuions were leached in similar concentrations(ranging from 10e35 ppm and 50e110 ppm at BG doses of 5and 50 mg/mL,respectively)for both type of BGs,while the release of Ga ions was 1e2 orders ofmagnitude lower in the case of SBGs(i.e.,0.2e6 ppm)compared to PBGs(i.e.,9e135 ppm).This wasattributed to the network modifier role of Cu in both types of BGs,and conversely,to the network former(SBGs)and network modifier(PBGs)roles of *** glasses were cytocompatible at a dose of 5 mg/mL,while at the same concentration the antimicrobial efficiency was found to be accentuated by the coupledrelease of Cu and Ga ions from *** collective assessment,the most prominent candidate material forthe further development of implant coatings and bone graft substitutes was delineated as the38.5SiO2d34.1CaOd5.6P2O5d16.2MgOd

关键词： Bioactive glass Copper Gallium Structure Ion release Antibacterial

Using accelerometry to compare costs of extended migration in an arctic herbivore

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Current Zoology 2017年第6期63卷 667-674页

作者： Mitch D. WEEGMAN stuart BEARHOP Geoff M. HILTON Alyn j. WALSH Larry GRIFFIN Yehezkel S. RESHEFF Ran NATHAN Anthony DAVID Fox Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Cornwall Campus Penryn TR109EZ UK Wildfowl & Wetlands Trust Slimbridge Gloucester GL2 7BT UK National Parks and Wildlife Service Wexford Wildfowl Reserve North Slob Wexford Ireland Wildfowl & Wetlands Trust Caerlaverock Wetland Centre Eastpark Farm Caerlaverock Durnfriesshire DG1 4RS UK Department of Ecology Evolution and Behavior The Hebrew University of Jerusalem Givat Ram Jerusalem 91904 Israel Department of Bioscience Aarhus University Kale Grenavej 14 RФnde DK-8410 Denmark Present address: School of Natural Resources University of Missouri Columbia MO 65211 USA.

Understanding how individuals manage costs during the migration period is challenging because individuals are difficult to follow between sites; the advent of hybrid Global Positioning System-acceleration (ACC) tracking devices enables researchers to link spatial and temporal attributes of avian migration with behavior for the first time ever. We fitted these devices on male Greenland white-fronted geese wintering at 2 sites (Loch Ken, Scotland and Wexford, Ireland) to understand whether birds migrating further during spring fed more on wintering and staging areas in advance of migration episodes. Although Irish birds flew significantly further (ca. 300 km) than Scottish birds during spring, their cumulative hours of migratory flight, flight speed during migration, and overall dynamic body ACC (i.e., a proxy for energy expenditure) were not significantly different. Further, Irish birds did not feed significantly more or expend significantly more energy in advance of migration episodes. These results suggest broad individual plasticity in this species, although Scottish birds arriving on breeding areas in Greenland with greater energy stores (because they migrated less) may be better prepared for food scarcity, which might increase their reproductive success.

关键词： Greenland white-fronted geese avian migration cost energy expenditure global positioning system–acceleration tracking devices individual decision-making proportion of time feeding

Regional scientific research benefits threatened-species conservation

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National Science Review 2019年第6期6卷 1076-1079页

作者： Yisi Hu Zhenhua Luo Colin A.Chapman stuart L.Pimm Samuel T.Turvey Michael j.Lawes Carlos A.Peres Tien Ming Lee Pengfei Fan School of Life Sciences Sun Yat-Sen University School of Life Sciences Central China Normal University Department of Anthropology and School of Environment Mc Gill University School of Life Sciences University of Kwa Zulu-Natal The College of Life Sciences Northwest University Nicholas School of the Environment Duke University

Although conventional wisdom considers knowledge of threatened species’ ecology and status essential for conservation, few studies demonstrate this in a quantitative way across many species and within the same political entity. Here,we evaluated the impacts of scientific research against conservation interventions(including funding) and specieslevel correlates, accounting for phylogenetic relatedness, on the conservation

关键词： China Regional scientific research benefits threatened-species conservation