Deconvoluting the Competing Effects of Zeolite Framework Topology and Diffusion Path Length on Methanol to Hydrocarbons Reaction

Neurotransmitter homeostasis in and around a synapse involves complex random processes such as diffusion, molecular binding, and uptake by glial transporters. A three-dimensional stochastic diffusion model of a synapse was developed to provide molecular-level details of neurotransmitter homeostasis not predicted by alternative models based on continuum approaches. The development was illustrated through an example case cortico-accumbens synapse that successfully integrated neuroadaptations observed after chronic cocaine. By incorporating cystine-glutamate exchanger as a nonsynaptic release site for glutamate, the stochastic model was used to quantify the relative contributions of synaptic and nonsynaptic sources to extracellular concentration and to estimate molecular influx rates into the perisynapse. A perturbation analysis showed that among the parameters considered, variation in surface density of glial transporters had the largest effect on glutamate concentrations. The stochastic diffusion model of the example synapse was further generalized to characterize glial morphology by studying the role of diffusion path length in supporting neurotransmitter gradients and isolating the synapse. For the same set of parameters, diffusion path length was found to be proportional to the gradient supported.

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Changes in diffusion path length with old age in diffuse optical tomography

Journal of Biomedical Optics ◽

10.1117/1.jbo.17.5.056002 ◽

2012 ◽

Vol 17 (5) ◽

pp. 056002 ◽

Cited By ~ 14

Author(s):

Clément Bonnéry ◽

Paul-Olivier Leclerc ◽

Michèle Desjardins ◽

Rick Hoge ◽

Louis Bherer ◽

...

Keyword(s):

Old Age ◽

Path Length ◽

Optical Tomography ◽

Diffuse Optical Tomography ◽

Diffusion Path ◽

Diffusion Path Length

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Relating model parameters to basic soil properties

Soil Research ◽

10.1071/sr03098 ◽

2004 ◽

Vol 42 (7) ◽

pp. 841 ◽

Cited By ~ 7

Author(s):

Hasan Merdun ◽

Virgil L. Quisenberry

Keyword(s):

Soil Properties ◽

Path Length ◽

Water Pressure ◽

Effective Diffusion ◽

Diffusion Path ◽

Model Parameters ◽

Mixing Depth ◽

Flow And Transport ◽

Diffusion Path Length ◽

Parameter Values

Relating model parameters to basic soil characteristics can help to differentiate and classify soils based on their flow and transport characteristics and ultimately helps to develop a sound management tool to protect groundwater from industrial and agricultural contaminants. In this study, the model parameters (effective diffusion path-length or aggregate half-width, boundary soil water pressure, boundary hydraulic conductivity, saturated hydraulic conductivity, tortuosity in macropores, dispersivity, mixing depth) obtained from simulation of water flow and solute transport for 3 soils (Maury, Cecil, Lakeland) with contrasting properties were related to see whether these derived parameters can be related to variation in fundamental soil properties such as texture and structure and thus the flow and transport characteristics of the soils. The boundary is a division point in which the soil porosity is divided into macropores and micropores. The ANOVA test showed that the parameter values of effective diffusion path-length and tortuosity in macropores for 3 soils were not different from each other, but the parameter values of saturated and boundary hydraulic conductivities including the texture (clay content) were statistically different. Moreover, the means of boundary soil water pressure, dispersivity, and mixing depth for 3 soils were significantly different. These results suggest that relating model parameters to basic soil properties in order to differentiate and classify soils based on their flow and transport characteristics is promising and needs further study.

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The role of intraparticle diffusion path length during electro-assisted regeneration of ion exchange resins: Implications for selective adsorbent design and reverse osmosis pretreatment

Chemical Engineering Journal ◽

10.1016/j.cej.2020.127821 ◽

2021 ◽

Vol 407 ◽

pp. 127821

Author(s):

Hang Dong ◽

Ziyan Wu ◽

Matthew J. Liu ◽

William A. Tarpeh

Keyword(s):

Ion Exchange ◽

Reverse Osmosis ◽

Path Length ◽

Diffusion Path ◽

Intraparticle Diffusion ◽

Ion Exchange Resins ◽

Diffusion Path Length ◽

Selective Adsorbent ◽

Exchange Resins

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Microstructure and Magnetic Properties of NdFeB Sintered Magnets Diffusion-Treated with Cu/Al Mixed Dyco Alloy-Powder

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0189 ◽

2017 ◽

Vol 62 (2) ◽

pp. 1263-1266 ◽

Cited By ~ 7

Author(s):

M.-W. Lee ◽

K.-H. Bae ◽

S.-R. Lee ◽

H.-J. Kim ◽

T.-S. Jang

Keyword(s):

Grain Boundary ◽

Diffusion Path ◽

Boundary Phase ◽

Core Shell ◽

Phase Layer ◽

Sintered Magnets ◽

The Core ◽

Shell Type ◽

Property Changes ◽

And Diffusion

AbstractWe investigated the microstructural and magnetic property changes of DyCo, Cu + DyCo, and Al + DyCo diffusion-treated NdFeB sintered magnets. The coercivity of all diffusion treated magnet was increased at 880ºC of 1stpost annealing(PA), by 6.1 kOe in Cu and 7.0 kOe in Al mixed DyCo coated magnets, whereas this increment was found to be relatively low (3.9 kOe) in the magnet coated with DyCo only. The diffusivity and diffusion depth of Dy were increased in those magnets which were treated with Cu or Al mixed DyCo, mainly due to comparatively easy diffusion path provided by Cu and Al because of their solubility with Ndrich grain boundary phase. The formation of Cu/Al-rich grain boundary phase might have enhanced the diffusivity of Dy-atoms. Moreover, relatively a large number of Dy atoms reached into the magnet and mostly segregated at the interface of Nd2Fe14B and grain boundary phases covering Nd2Fe14B grains so that the core-shell type structures were developed. The formation of highly anisotropic (Nd, Dy)2Fe14B phase layer, which acted as the shell in the core-shell type structure so as to prevent the reverse domain movement, was the cause of enhancing the coercivity of diffusion treated NdFeB magnets. Segregation of cobalt in Nd-rich TJP followed by the formation of Co-rich phase was beneficial for the coercivity enhancement, resulting in the stabilization of the metastable c-Nd2O3phase.

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Evaluation of MACRO model by short-term water and solute transport simulation in Maury silt loam soil

Plant Soil and Environment ◽

10.17221/3563-pse ◽

2011 ◽

Vol 51 (No. 3) ◽

pp. 110-123 ◽

Cited By ~ 1

Author(s):

H. Merdun ◽

V.L. Quisenberry

Keyword(s):

Solute Transport ◽

Water Flow ◽

Chloride Transport ◽

Effective Diffusion ◽

Diffusion Path ◽

Silt Loam ◽

Short Term ◽

Silt Loam Soil ◽

Diffusion Path Length ◽

Loam Soil

Modeling preferential flow has been a concern of many academic fields in the past 30 years all over the world and helps to prevent groundwater contamination. A dual-porosity model, MACRO, was evaluated for short-term (less than 2 days) simulation of water flow and non-reactive solute (chloride) transport through the profile of six plots in well-structured Maury silt loam soil. Water flow in micropores is calculated by the Richards’ equation while simple gravity flow is assumed in the macropores. Solute transport in the micropores is calculated by the convection-dispersion equation (CDE) while the dispersion and diffusion in the CDE is neglected for the solute transport in the macropores. The applied water and chloride reached the bottom of the profile during the 2 and 1-hour(s) application periods in studies 2 and 3, respectively. There is a strong indication of macropore flow in this soil. Based on the statistical criteria, the model accurately simulated water flow and solute transport with depth and time in all plots. The mean values of three statistical parameters (coefficient of residual mass, model efficiency, and correlation coefficient) for water and chloride transport were –0.0014, 0.791, 0.903 and 0.0333, 0.923, 0.956, respectively. Preliminary studies showed that the model could not simulate flow and transport well enough with the one-domain flow concept. In the two-domain flow, effective diffusion path-length, boundary hydraulic conductivity, and boundary soil water pressure were the three most important parameters that control flow and transport between the two domains. The effective diffusion path-length represented the structural development with depth in the Maury silt loam soil.

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First-Principles Investigation of Atomic Hydrogen Adsorption and Diffusion on/into Mo-doped Nb (100) Surface

Applied Sciences ◽

10.3390/app8122466 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2466 ◽

Cited By ~ 7

Author(s):

Yang Wu ◽

Zhongmin Wang ◽

Dianhui Wang ◽

Jiayao Qin ◽

Zhenzhen Wan ◽

...

Keyword(s):

First Principles ◽

Atomic Hydrogen ◽

Energy Barrier ◽

Hydrogen Adsorption ◽

Hydrogen Permeation ◽

Diffusion Path ◽

Interstitial Site ◽

Octahedral Interstitial Site ◽

Tetrahedral Interstitial Site ◽

And Diffusion

To investigate Mo doping effects on the hydrogen permeation performance of Nb membranes, we study the most likely process of atomic hydrogen adsorption and diffusion on/into Mo-doped Nb (100) surface/subsurface (in the Nb12Mo4 case) via first-principles calculations. Our results reveal that the (100) surface is the most stable Mo-doped Nb surface with the smallest surface energy (2.75 J/m2). Hollow sites (HSs) in the Mo-doped Nb (100) surface are H-adsorption-favorable mainly due to their large adsorption energy (−4.27 eV), and the H-diffusion path should preferentially be HS→TIS (tetrahedral interstitial site) over HS→OIS (octahedral interstitial site) because of the correspondingly lower H-diffusion energy barrier. With respect to a pure Nb (100) surface, the Mo-doped Nb (100) surface has a smaller energy barrier along the HS→TIS pathway (0.31 eV).

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