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Mechanistic insight into cr(Ⅵ)retention by Si-containing ferrihydrite

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Journal of Environmental Sciences 2024年第5期139卷 217-225页

作者： Ying Hu Qiang Xue Honghan chen Huaming Guo kenneth c.c.rroll Song Wang MOE Key Laboratory of Groundwater circulation and Environmental Evolution School of Water Resources and EnvironmentChina University of Geosciences(Beijing)Beijing 100083China Beijing Key Laboratory of Water Resources and Environmental Engineering School of Water Resources and EnvironmentChina University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China Plant&Environmental Science New Mexico State UniversityNM 88003USA Institute of Theoretical chemistry College of ChemistryJilin UniversityChangchun 130023China

Hexavalent chromium[cr(Ⅵ)]causes serious harm to the environment due to its high toxicity,solubility,and ***(Fh)are the main adsorbent and trapping agent of cr(Ⅵ)in soils and aquifers,and they usually coexist with silicate(Si),forming Si-containing ferrihydrite(Si-Fh)***,the mechanism of cr(Ⅵ)retention by Si-Fh mixtures is poorly *** this study,the behaviors and mechanisms of cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe molar ratios was *** electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and other techniques were used to characterize Si-Fh and cr(Ⅵ)-loading of *** results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios,but cr(Ⅵ)adsorption on Si-Fh decreases with increasing Si/Fe *** is because with an increase in Si/Fe molar ratio,the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and cr(Ⅵ)***,the complexation of cr(Ⅵ)is enhanced due to the increase in adsorbed hydroxyl(A-OH-)on Si-Fh with increasing Si/Fe molar ratio,which partly counteracts the effect of the electrostatic ***,the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with *** functional theory calculation further supports this observation,showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

关键词： Hexavalent chromium Ferrihydrite Si/Fe ratio cr(Ⅵ)Adsorption

Individual and geospatial factors associated with receipt of colorectal cancer screening:a state-wide mixed-level analysis

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Family Medicine and community Health 2024年第S2期12卷 18-25页

作者： Jennifer E Bayly Mara A Schonberg Marcia c castro kenneth J Mukamal Beth Israel Deaconess Medical center BostonMassachusettsUSA Harvard Medical School BostonMassachusettsUSA Department of Global Health and Population Harvard T H Chan School of Public HealthBostonMassachusettsUSA

Background colorectal cancer(cRc)is the second leading cause of cancer death in US adults but can be reduced by *** roles of individual and contextual factors,and especially physician supply,in attaining universal cRc screening remains *** We used data from adults 50-75 years old participating in the 2018 New York(NY)Behavioural Risk Factor Surveillance System linked to county-level covariates,including primary care physician(PcP)density and gastroenterologist(GI)*** were analysed in *** analyses included(1)ecological and geospatial analyses of county-level cRc screening prevalence and(2)individual-level Poisson regression models of receipt of screening,adjusted for socioeconomic and county-level contextual *** Mean prevalence of up-to-date cRc screening was 71%(95%cI 70%to 73%)across NY’s 62 ***-level cRc screening demonstrated significant spatial patterning(Global Moran’s I=0.14,p=0.04),consistent with the existence of county-level contextual *** both county-level and individual-level analyses,lack of health insurance was associated with lower likelihood of up-to-date screening(?−1.09(95%cI−2.00 to-0.19);adjusted prevalence ratio 0.68(95%cI 0.60 to 0.77)),even accounting for age,race/ethnicity and *** contrast,county-level densities of both PcPs and GIs were completely unassociated with screening at either the county or individual *** expected,other determinants at the individual level included education status and *** In this state-wide representative analysis,physician density was completely unassociated with cRc screening,although health insurance status remains strongly *** similar screening environments,broadened insurance coverage for cRc screening is likely to improve screening far more effectively than increased physician supply.

关键词： state screening county

Tigris, Euphrates, and Shatt Al-Arab River System: Historic and Modern Attempts to Manage and Restore Iraq’s Lifeline

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Open Journal of Soil Science 2024年第1期14卷 28-63页

作者： kenneth Ray Olson David R. Speidel college of Agricultural Consumer and Environmental Sciences University of Illinois Urbana USA US Army Iraq Mosul Iraq Foreign Agricultural Service Mahmudiyah Iraq Foreign Agricultural Service Washington D.C. USA

In Iraq, the principal rivers are the Tigris, Shatt Al-Arab and Euphrates. From their headwater sources in the mountains of eastern Türkiye, these rivers descend through valleys and gorges and flow into the uplands of Syria and northern and central alluvial plain of Iraq. The Euphrates and Tigris Rivers confluence to form the Shatt Al-Arab river at Al-Qurnah which flows into the Persian Gulf. From sources in the Zagros Mountains other tributaries join the Tigris from the east. The Tigris and Euphrates rivers flow in a southeastern direction through the central plain and discharge into the Mesopotamian Marshes, which include permanent marshes, lakes, and riparian habitat. The rivers and their tributaries drain an area of 879,790 km2 which includes almost the entire area of Iraq as well as land in Syria, Türkiye, Kuwait and Iran. The region has historical importance as part of the Fertile crescent region and where Mesopotamian civilization first emerged. The post war reconstruction efforts in the Yusifiyah township, an important food production region for Baghdad, illustrate the importance of these water resources. In addition, the advent of soil tunnels by Iraqi insurgents within the riverine corridors will make reconstruction of this resource more complex. The primary objectives of this study are to assess lessons learned, manage, and restore the Tigris, Euphrates, and Shatt Al-Arab river system lifeline in Iraq.

关键词： Mesopotamian Shatt Al-Arab Iraq Tigris Euphrates Baghdad Soil Tunnels Yusifiyah

Predicting the mode of flow in pneumatic conveying systems—A review

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Particuology 2008年第5期6卷 289-300页

作者： Mark G.Jones kenneth c.Williams centre for Bulk Solids and Particulate Technologies School of EngineeringUniversity of NewcastleNewcastle 2308Australia

An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows： fluidised dense phase and plug flow, and dilute phase oniy. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined： basic particle parameter based （e.g. particle size and density） and air-particle parameter based （e.g. permeability and de-aeration）. The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment.

关键词： Pneumatic conveying Mode of flow Dense phase Permeability De-aeration

The Roles of Different cLE Domains in Arabidopsis cLE Polypeptide Activity and Functional Specificity

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Molecular Plant 2010年第4期3卷 760-772页

作者： Ling Meng kenneth c. Ruth Jennifer c. Fletcher Lewis Feldman Department of Plant and Microbial Biology 111 Koshland Hall University of California Berkeley CA 94720-3102 USA Plant Gene Expression center USDA-UC Berkeley 800 Buchanan Street Albany CA 94710 USA

The cLE （cLVATA3/ESR-related） family of plant polypeptide signaling molecules shares a conserved 14-aminoacid （aa） motif, designated the cLE motif, which recent studies suggest is sufficient for cLE function in vitro. In this study, we report that Arabidopsis cLE proteins can function in a tissue-specific manner and confirm some cLE factors can act through different receptors. Using domain swapping, we show for the first time that the cLE motif likely determines much of the functional tissue-specificity of the proteins in planta. However, we also provide evidence in support of the new view that sequences outside the cLE motif （14 aa） contribute to cLE function and functional specificity in vivo. Additionally, we report that deletion of the putative signal peptide from different cLE proteins completely inactivates cLE function in vivo, whereas exchanging the cLE signal peptides with a conventional signal peptide from a rice glycine-rich cell wall protein also influences cLE function. We thus propose that the cLE motif itself determines its functional tissue-specificity by dic- tating the direct recognition and interaction of each cLE peptide with its optimal receptor（s）, whereas the receptor（s） may be available in a tissue-specific manner. On the other hand, the sequences outside the cLE motif may influence cLE function by affecting the processing of cLE peptides, resulting in a change in the availability and/or abundance of cLE peptides in specific tissues and/or cells.

关键词： Arabidopsis cell signaling cLE meristem polypeptide protein domain.

Determination of slug permeability factor for pressure drop prediction of slug flow pneumatic conveying

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Particuology 2008年第5期6卷 307-315页

作者： kenneth c.Williams Mark G.Jones Tobias Krull centre for Bulk Solids and Particulate Technology The University of NewcastleCallaghanNSW 2308Australia

current models for pressure drop prediction of slug flow pneumatic conveying in a horizontal pipeline system assume some type of steady state conditions for prediction, which limits their capability for increased predictive accuracy relative to experimental data. This is partly because of the nature of slug flow pneumatic conveying system, which, as a dynamic system, never becomes stable. By utilising conservation of mass （airflow）, a dynamic pressure analysis model is proposed on the basis of the derivative of the upstream pressure behaviour. The rate of air permeation through slug, one of the important factors in the conservation model, is expressed as a function of a slug permeability factor. Other factors such as slug velocity, slug length and the fraction of stationary layer were also considered. Several test materials were conveyed in single-slug tests to verify the proposed pressure drop model, showing good agreement between the model and experimental results.

关键词： Slug flow pneumatic conveying Pressure drop Air mass conversation Slug permeability factor

characterization of the gas pulse frequency,amplitude and velocity in non-steady dense phase pneumatic conveying of powders

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Particuology 2008年第5期6卷 301-306页

作者： kenneth c.Williams Mark G.Jones Ahmed A.cenna centre for Bulk Solids and Particulate Technologies School of EngineeringUniversity of Newcastle

current modelling techniques for the prediction of conveying line pressure drop in low velocity dense phase pneumatic conveying are largely based on steady state analyses. Work in this area has been on-going for many years with only marginal improvements in the accuracy of prediction being achieved. Experimental and theoretical investigations undertaken by the authors suggest that the flow mechanisms involved in dense phase conveying are dominated by transient effects rather than those of steady state and are possibly the principal reasons for the limited improvement in accuracy. This paper reports on investigations on the pressure fluctuation behaviour in dense phase pneumatic conveying of powders. The pressure behaviour of the gas flow in the top section of the pipeline was found to exhibit pulsatile oscillations. In particular, the pulse velocity showed variation in magnitude while the frequency of the oscillations rarely exceeded 5 Hz. A wavelet analysis using the Daubechie 4 wavelet found that the amplitude of the oscillations increased along the pipeline. Furthermore, there was significant variation in gas pulse amplitude for different types of particulate material.

关键词： Pneumatic conveying Powders Dense phase Pulsatile flow Transient flow

Particle shape characterisation and its application to discrete element modelling

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Particuology 2014年第1期12卷 80-89页

作者： kenneth c.Williams Wei chen Sebastian Weeger Timothy J.Donohue centre for Bulk Solids and Particulate Technologies Newcastle Institute for Energy and Resources The University of Newcastle Georg-Simon-Ohm University Nuremberg TUNRA Bulk Solids Newcastle Institute for Energy and Resources The University of Newcastle

Increasing importance has been placed on particle shape implementation within discrete element mod elling （DEM） in order to more accurately reflect the nonspherical behaviour of the bulk material being handled. As computational resources grow, complex particle shapes are increasingly being modelled as the associated simulation times become more realistic to provide timely solutions. The objective of this research is to assess particle shape descriptors through a digital image segmentation technique, and to further implement particle shape parameters into generation of corresponding irregular shaped DEM particles. Separated and lumped particle images were analysed and reconstructed through the devel opment of two distinct methodologies. Subsequently, various particle shape descriptors were obtained using combinations of image segmentation algorithms, including mathematical morphology processing, thresholding, edge detection, region growing, region splitting and region merging. DEM particles were subsequently created using particle shape results obtained above. Shape parameters of DEM particles were then examined and validated against the real particle shape parameters.

关键词： Particle shapesParticle morphologyImage segmentationDiscrete element modelling

A qualitative study on the pulsatile flow phenomenon in a dense fly ash pneumatic conveyor

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Particuology 2014年第6期12卷 81-91页

作者： Wei chen kenneth c.Williams Isabel Jabs Mark G.Jones centre for Bulk Solids and Particulate Technologies Newcastle Institute for Energy and ResourcesThe University of Newcastle Faculty of Mechanical Engineering Leibniz University of Hanover

Understanding of the dynamic particulate flow structures within a dense gas-fly ash pneumatic conveyor must be improved in order to better aid its design *** complex pulsatile movement of the gas-fly ash mixture dominates the flow performance within the pipeline,and historically,non-invasive measurement devices such as the electrical capacitance tomography（EcT） were often used to sufficiently capture the flow ***,inadequate studies have been conducted on the pulsatile flow phenomenon,which directly relate to the gas-fly ash two-phase flow *** paper aims to investigate the pulsatile flows using an EcT ***,pulsatile flow patterns under various experimental conditions were obtained through *** within a flow were then characterised into pulse growth and decay segments,which represent the superficial fluidisation and deaeration processes during ***,structural and statistical analyses were performed on the pulse growth and decay *** suggested that the increasing air mass flow rate led to the decrease of the superficial fluidisation/deaeration magnitude,however,the increase of the superficial fluidisation/deaeration ***,the air mass flow rate was indicated as the dominant factor in determining the pulsing statistical *** research provides fundamental insights for further modelling the dense fly ash pneumatic flows.

关键词： Pneumatic conveying Electrical capacitance tomography Fly ash Pulsatile flows Flow pattern analysis