scholarly journals An intravascular bioartificial pancreas device (iBAP) with silicon nanopore membranes (SNM) for islet encapsulation under convective mass transport

Lab on a Chip ◽  
2017 ◽  
Vol 17 (10) ◽  
pp. 1778-1792 ◽  
Author(s):  
Shang Song ◽  
Charles Blaha ◽  
Willieford Moses ◽  
Jaehyun Park ◽  
Nathan Wright ◽  
...  
Keyword(s):  
Mass Transport ◽  
Cell Density ◽  
Porcine Model ◽  
Convective Transport ◽  
Bioartificial Pancreas ◽  
Islet Encapsulation ◽  
Nanopore Membranes

The SNM-based iBAP demonstrates viability and functionality at clinically relevant cell density and hemocompatibility under convective transport in a porcine model.

scholarly journals Correction: An intravascular bioartificial pancreas device (iBAP) with silicon nanopore membranes (SNM) for islet encapsulation under convective mass transport

Lab on a Chip ◽  
2017 ◽  
Vol 17 (13) ◽  
pp. 2334-2334
Author(s):  
Shang Song ◽  
Charles Blaha ◽  
Willieford Moses ◽  
Jaehyun Park ◽  
Nathan Wright ◽  
...  
Keyword(s):  
Mass Transport ◽  
Bioartificial Pancreas ◽  
Islet Encapsulation ◽  
Nanopore Membranes

Correction for ‘An intravascular bioartificial pancreas device (iBAP) with silicon nanopore membranes (SNM) for islet encapsulation under convective mass transport’ by Shang Song et al., Lab Chip, 2017, 17, 1778–1792.

Mass Transport Modelling in Porous Media Using Delay Differential Equations

2006 ◽  
Vol 258-260 ◽  
pp. 586-591
Author(s):  
António Martins ◽  
Paulo Laranjeira ◽  
Madalena Dias ◽  
José Lopes
Keyword(s):  
Porous Media ◽  
Differential Equations ◽  
Mass Transport ◽  
Delay Differential Equations ◽  
Dispersion Model ◽  
Flow Characteristics ◽  
Convective Transport ◽  
Transport Modelling ◽  
Flow Field Characteristics ◽  
Delay Differential

In this work the application of delay differential equations to the modelling of mass transport in porous media, where the convective transport of mass, is presented and discussed. The differences and advantages when compared with the Dispersion Model are highlighted. Using simplified models of the local structure of a porous media, in particular a network model made up by combining two different types of network elements, channels and chambers, the mass transport under transient conditions is described and related to the local geometrical characteristics. The delay differential equations system that describe the flow, arise from the combination of the mass balance equations for both the network elements, and after taking into account their flow characteristics. The solution is obtained using a time marching method, and the results show that the model is capable of describing the qualitative behaviour observed experimentally, allowing the analysis of the influence of the local geometrical and flow field characteristics on the mass transport.

Coupled Porohyperelastic Mass Transport (PHEXPT) Finite Element Models for Soft Tissues Using ABAQUS

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Jonathan P. Vande Geest ◽  
B. R. Simon ◽  
Paul H. Rigby ◽  
Tyler P. Newberg
Keyword(s):  
Finite Element ◽  
Mass Transport ◽  
Soft Tissues ◽  
Convective Transport ◽  
Finite Deformations ◽  
Nonlinear Material ◽  
Finite Element Models ◽  
Finite Element Software ◽  
Mobile Species ◽  
Highly Nonlinear

Finite element models (FEMs) including characteristic large deformations in highly nonlinear materials (hyperelasticity and coupled diffusive/convective transport of neutral mobile species) will allow quantitative study of in vivo tissues. Such FEMs will provide basic understanding of normal and pathological tissue responses and lead to optimization of local drug delivery strategies. We present a coupled porohyperelastic mass transport (PHEXPT) finite element approach developed using a commercially available ABAQUS finite element software. The PHEXPT transient simulations are based on sequential solution of the porohyperelastic (PHE) and mass transport (XPT) problems where an Eulerian PHE FEM is coupled to a Lagrangian XPT FEM using a custom-written FORTRAN program. The PHEXPT theoretical background is derived in the context of porous media transport theory and extended to ABAQUS finite element formulations. The essential assumptions needed in order to use ABAQUS are clearly identified in the derivation. Representative benchmark finite element simulations are provided along with analytical solutions (when appropriate). These simulations demonstrate the differences in transient and steady state responses including finite deformations, total stress, fluid pressure, relative fluid, and mobile species flux. A detailed description of important model considerations (e.g., material property functions and jump discontinuities at material interfaces) is also presented in the context of finite deformations. The ABAQUS-based PHEXPT approach enables the use of the available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries, nonlinear material laws, pre- and postprocessing, etc.). PHEXPT FEMs can be used to simulate the transport of a relatively large neutral species (negligible osmotic fluid flux) in highly deformable hydrated soft tissues and tissue-engineered materials.

Bidirectional Solute Transport in Peritoneal Dialysis

1994 ◽  
Vol 14 (4) ◽  
pp. 327-337 ◽  
Author(s):  
Jacek Waniewski ◽  
Olof Heimbürger ◽  
Min Sun Park ◽  
Andrzej Werynski ◽  
Bengt Lindholm
Keyword(s):  
Peritoneal Dialysis ◽  
Mass Transport ◽  
Solute Transport ◽  
Experimental Studies ◽  
Convective Transport ◽  
Sieving Coefficient ◽  
Middle Molecules ◽  
Bidirectional Transport ◽  
Transport Of Macromolecules ◽  
Reabsorption Rate

Objective Three transport components are involved in solute transport in peritoneal dialysis: diffusion, convective transport, and peritoneal reabsorption of dialysate (fluid and solutes). The relative impact of these components on measurable transport characteristics (dialysateto-plasma concentration ratio, diffusive mass transport coefficient, unidirectional clearances) may depend on the direction of solute transport, that is, from blood to dialysate or vice versa. The application of the bidirectional characteristics for the assessment of fluid and solute transport in peritoneal dialysis is reviewed and evaluated. Data Sources Theoretical analysis as well as computer simulations were applied to discuss available data from our own studies on peritoneal transport as well as from published clinical, experimental, and theoretical studies in the same field. Study Selection Thirty-three relevant clinical and experimental studies as well as theoretical analyses derived from the literature were reviewed. Data Extraction Data were extracted to highlight current controversies in the literature concerning the assessment of peritoneal reabsorption rate based on transport of macromolecules, middle molecules, and small solutes. Results Peritoneal reabsorption is the main component of the transport of macromolecules infused into the peritoneal cavity, and these solutes are currently being used for the assessment of the rate of reabsorption. In contrast, diffusive transport and peritoneal reabsorption cannot be experimentally discriminated for small solutes which exhibit negligible sieving through the membrane in convective transport (i.e., solutes with sieving coefficient equal to 1). For middle molecules each transport component may be of importance and may have an independent impact on bidirectional transport characteristics. Conclusions Middle molecules, with sieving coefficients substantially less than 1, may be applied for estimation of peritoneal reabsorption rate using bidirectional transport characteristics, as apparent diffusive mass transport coefficients or unidirectional clearances. However, an independent measurement of sieving coefficient is necessary for this method.

scholarly journals Silicon nanopore membrane (SNM) for islet encapsulation and immunoisolation under convective transport

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Shang Song ◽  
Gaetano Faleo ◽  
Raymond Yeung ◽  
Rishi Kant ◽  
Andrew M Posselt ◽  
...  
Keyword(s):  
Convective Transport ◽  
Islet Encapsulation

scholarly journals Cell density modulates intracellular mass transport in neural networks

2017 ◽  
Vol 91 (5) ◽  
pp. 503-509 ◽  
Author(s):  
Patricia Cintora ◽  
Jyothi Arikkath ◽  
Mikhail Kandel ◽  
Gabriel Popescu ◽  
Catherine Best-Popescu
Keyword(s):  
Neural Networks ◽  
Mass Transport ◽  
Cell Density

scholarly journals Shear stress mediates metabolism and growth in electroactive biofilms

2018 ◽  
Author(s):  
A-Andrew D Jones ◽  
Cullen R Buie
Keyword(s):  
Shear Stress ◽  
Mass Transport ◽  
Development Time ◽  
Convective Transport ◽  
Geobacter Sulfurreducens ◽  
Bioelectrochemical Systems ◽  
Corrosion Resistant ◽  
Ph Stress ◽  
Small Pore ◽  
Biofilm Development

Electroactive bacteria such asGeobacter sulfurreducensandShewanella onedensisproduce electrical current during their respiration; this has been exploited in bioelectrochemical systems. These bacteria form thicker biofilms and stay more active than soluble-respiring bacteria biofilms because their electron acceptor is always accessible. In bioelectrochemical systems such as microbial fuel cells, corrosion-resistant metals uptake current from the bacteria, producing power. While beneficial for engineering applications, collecting current using corrosion resistant metals induces pH stress in the biofilm, unlike the naturally occurring process where a reduced metal combines with protons released during respiration. To reduce pH stress, some bioelectrochemical systems use forced convection to enhance mass transport of both nutrients and byproducts; however, biofilms’ small pore size limits convective transport, thus, reducing pH stress in these systems remains a challenge. Understanding how convection is necessary but not sufficient for maintaining biofilm health requires decoupling mass transport from momentum transport (i.e. fluidic shear stress). In this study we use a rotating disc electrode to emulate a practical bioelectrochemical system, while decoupling mass transport from shear stress. This is the first study to isolate the metabolic and structural changes in electroactive biofilms due to shear stress. We find that increased shear stress reduces biofilm development time while increasing its metabolic rate. Furthermore, we find biofilm health is negatively affected by higher metabolic rates over long-term growth due to the biofilm’s memory of the fluid flow conditions during the initial biofilm development phases. These results not only provide guidelines for improving performance of bioelectrochemical systems, but also reveal features of biofilm behavior. Results of this study suggest that optimized reactors may initiate operation at high shear to decrease development time before decreasing shear for steady-state operation. Furthermore, this biofilm memory discovered will help explain the presence of channels within biofilms observed in other studies.

Oxygen Distribution in Packed Bed Membrane Reactors For Partial Oxidation Systems and its Effect On Product Selectivity

2004 ◽  
Vol 2 (1) ◽  
Author(s):  
U. Kuerten ◽  
Martin van Sint Annaland ◽  
J.A.M. Kuipers
Keyword(s):  
Mass Transport ◽  
Oxygen Concentration ◽  
Partial Oxidation ◽  
Waste Product ◽  
Packed Bed ◽  
Product Formation ◽  
Convective Transport ◽  
Membrane Reactors ◽  
Concentration Profiles ◽  
Concentration Gradients

Packed bed membrane reactors (PBMRs) are currently considered for the distributive addition of oxygen in partial oxidation systems. Among other advantages the decreased oxygen concentrations in the PBMR can result in improved product selectivities for reaction systems in which the oxygen dependency of the target product formation is less pronounced than that of the waste product formation. Oxidative dehydrogenation (ODH) of methanol to formaldehyde (Diakov et al., 2002) and ethylbenzene to styrene (Shakhnovich et al., 1984) are industrially relevant examples of such a kinetic system.To achieve considerable selectivity improvements the oxygen concentration should be kept small compared to hydrocarbon concentrations. However, a decrease of the oxygen concentration is accompanied with a decrease in the effectiveness of the catalyst particles since the intraparticle oxygen concentration gradients (and not the hydrocarbon concentration gradients) predominantly determine the actual activity and product selectivities of the catalyst, rendering the common effectiveness factors inapplicable for the modeling of a PBMR.Furthermore, concentration profiles over the radius of the packed bed can emerge, if the radial mass transport rate of oxygen from the membrane wall to the center of the bed is insufficient compared to the local oxygen consumption rate. If the transmembrane flux is dominated by convective transport as typical with porous membranes, the radial oxygen concentration profiles result in increased product losses, and the use of a one-dimensional reactor model may result in an overestimation of the product selectivity.In this paper the effect of limitations of the oxygen mass transport in a PBMR – i.e. intraparticle and from the membrane to the centerline of the packed bed – have been discussed for the ODH of methanol and ethylbenzene.

A Model of Dopant Transport During Bridgman Crystal Growth With Magnetically Damped Buoyant Convection

1999 ◽  
Vol 122 (1) ◽  
pp. 159-164 ◽  
Author(s):  
N. Ma ◽  
J. S. Walker
Keyword(s):  
Magnetic Field ◽  
Crystal Growth ◽  
Mass Transport ◽  
Axial Magnetic Field ◽  
Convective Transport ◽  
Transient Model ◽  
Buoyant Convection ◽  
Electromagnetic Damping ◽  
Vertical Bridgman ◽  
Bridgman Crystal Growth

This paper presents a model for the unsteady transport of a dopant during the vertical Bridgman crystal growth process with a planar crystal-melt interface and with an externally applied axial magnetic field. This dilute mass transport depends on the convective and diffusive mass transport of the dopant. The convective mass transport is driven by buoyant convection in the melt, which produces nonuniformities in the concentration in both the melt and the crystal. This convective transport is significant even for a strong magnetic field Bo=2 T. However, the electromagnetic damping of the melt motion produces a local region adjacent to the crystal-melt interface which is dominated by diffusion. Thus, this melt solidifies with a relatively radially uniform concentration, so that the radial distribution of dopants in the crystal is also relatively radially uniform. The transient model predicts the dopant distribution in the entire crystal. [S0022-1481(00)02301-X]

scholarly journals Determination of Best Tropopause Definition for Convective Transport Studies

2018 ◽  
Vol 75 (10) ◽  
pp. 3433-3446 ◽  
Author(s):  
Emily M. Maddox ◽  
Gretchen L. Mullendore
Keyword(s):  
Mass Transport ◽  
Potential Vorticity ◽  
Deep Convection ◽  
Three Dimensional ◽  
Static Stability ◽  
Convective Transport ◽  
Lapse Rate ◽  
Tracer Concentration ◽  
Temperature Lapse Rate ◽  
Cloud Resolving Model

An idealized three-dimensional cloud-resolving model is used to investigate the sensitivity of cross-tropopause convective mass transport to tropopause definition. A simulation is conducted to encompass the growth and decay cycle of a supercell thunderstorm, with a focus on irreversible transport above the tropopause. Five previously published tropopause definitions are evaluated: World Meteorological Organization (WMO) temperature lapse rate, potential vorticity, static stability, vertical curvature of the Brunt–Väisälä frequency, and stratospheric tracer concentration. By analyzing the behavior of different definitions both during and after active convection, we are able to define “best” choices for tropopause definitions as those that return to states most closely matching the preconvective environment. Potential vorticity and stratospheric tracer concentration are shown to perform poorly when analyzing deep convection. The WMO thermal tropopause and static stability definitions are found to perform the best, providing similar tropopause placement and quantities of irreversible mass transport. This investigation highlights the challenges of defining a tropopause in the vicinity of deep convection and demonstrates the need to clearly communicate calculation methods and threshold choices in the literature.

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