Forced Convection Past a Rotating Sphere: Modeling Oxygen Transport to a Pond Snail Embryo

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
D. A. Nield ◽  
A. V. Kuznetsov
Keyword(s):  
Forced Convection ◽  
Quantitative Study ◽  
Oxygen Transport ◽  
Oxygen Transfer ◽  
Pond Snail ◽  
Gaseous Exchange ◽  
Helisoma Trivolvis ◽  
Rotating Sphere

Helisoma trivolvis pond snail embryos are known for their rotation, which is induced by beating of cilia at the embryo's surface. A common hypothesis links this behavior to enhancing oxygen transfer to the embryo's surface. In this paper, this hypothesis is quantified, and the effect of the rotation on the supply of oxygen to an embryo, which is approximately spherical in shape, is studied. To the best of our knowledge, this is the first research presenting a quantitative study on the effect of an embryo's rotation on facilitating gaseous exchange between the embryo and the environment.

Regulation of early embryonic behavior by nitric oxide in the pond snail Helisoma trivolvis

2002 ◽  
Vol 205 (20) ◽  
pp. 3143-3152 ◽  
Author(s):  
Alison G. Cole ◽  
Aniseh Mashkournia ◽  
Shawn C. Parries ◽  
Jeffrey I. Goldberg
Keyword(s):  
Nitric Oxide ◽  
Rotation Rate ◽  
Apical Dendrite ◽  
Rotational Behavior ◽  
Pond Snail ◽  
Ciliary Activity ◽  
No Donors ◽  
Helisoma Trivolvis ◽  
Fourfold Increase ◽  
Nos Inhibitors

SUMMARY Helisoma trivolvis embryos display a cilia-driven rotational behavior that is regulated by a pair of serotonergic neurons named ENC1s. As these cilio-excitatory motor neurons contain an apical dendrite ending in a chemosensory dendritic knob at the embryonic surface, they probably function as sensorimotor neurons. Given that nitric oxide (NO) is often associated with sensory neurons in invertebrates, and has also been implicated in the control of ciliary activity, we examined the expression of NO synthase (NOS) activity and possible function of NO in regulating the rotational behavior in H. trivolvis embryos. NADPH diaphorase histochemistry on stage E25-E30 embryos revealed NOS expression in the protonephridia, buccal mass,dorsolateral ciliary cells and the sensory dendritic knobs of ENC1. At stages E35-40, the pedal ciliary cells and ENC1's soma, apical dendrite and proximal descending axon were also stained. In stage E25 embryos, optimal doses of the NO donors SNAP and SNP increased the rate of embryonic rotation by twofold, in contrast to the fourfold increase caused by 100 μmol l-1serotonin. The NOS inhibitors L-NAME (10 mmol l-1) and 7-NI (100μmol l-1) decreased the rotation rate by approximately 50%,whereas co-addition of L-NAME and SNAP caused a twofold increase. In an analysis of the surge and inter-surge subcomponents of the rotational behavior, the NO donors increased the inter-surge rotation rate and the surge amplitude. In contrast, the NO inhibitors decreased the inter-surge rotation rate and the frequency of surges. These data suggest that the embryonic rotational behavior depends in part on the constitutive excitatory actions of NO on ENC1 and ciliary cells.

scholarly journals Identification, molecular structure and expression of two cloned serotonin receptors from the pond snail, Helisoma trivolvis

2008 ◽  
Vol 211 (6) ◽  
pp. 900-910 ◽  
Author(s):  
S. Mapara ◽  
S. Parries ◽  
C. Quarrington ◽  
K.-C. Ahn ◽  
W. J. Gallin ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Serotonin Receptors ◽  
Pond Snail ◽  
Helisoma Trivolvis

Oxygen transfer across composite oxygen transport membranes

2004 ◽  
Vol 174 (1-4) ◽  
pp. 253-260 ◽  
Author(s):  
B VANHASSEL
Keyword(s):  
Oxygen Transport ◽  
Oxygen Transfer

Computational Analysis of O2 Separating Membrane for a CO2-Emission-Free Power Process

2004 ◽  
Author(s):  
Faruk Selimovic ◽  
Bengt Sunde´n ◽  
Mohsen Assadi ◽  
Azra Selimovic
Keyword(s):  
Co2 Capture ◽  
Oxygen Transport ◽  
Oxygen Transfer ◽  
Operating Conditions ◽  
Oxide Surface ◽  
Oxygen Separation ◽  
Supporting Layer ◽  
Considerable Impact ◽  
Steady State Heat ◽  
And Performance

The increased demand for clean power in recent years has led to the development of various processes that include different types of CO2 capture. Several options are possible: pre-combustion concepts (fuel de-carbonization and subsequent combustion of H2), post-combustion concepts (tail-end CO2 capture solutions, such as amine scrubbing), and integrated concepts in which combustion is carried out in pure a O2 or oxygen-enriched environment instead of air. The integrated concepts involve the use of oxygen-, hydrogen-, or CO2-separating membranes resulting in exhaust gas containing CO2 and water, from which CO2 can easily be separated. In contrast to traditional oxygen pumps, where a solid oxide electrolyte is sandwiched between two gas-permeable electrodes, a dense, mixed ionic-electronic conducting membrane (MIECM) shows high potential for oxygen separation without external electrodes attached to the oxide surface. Models for oxygen transport through dense membranes have been reported in numerous recent studies. In this study, an equation for oxygen separation has been integrated into a steady-state heat and mass transfer membrane model. Oxygen transfer through a porous supporting layer of membrane is also taken into account. The developed FORTRAN code has been used for numerical investigation and performance analysis of the MIECM and the oxygen transport potential over a range of operating conditions. Preliminary results indicate that a non-uniform temperature distribution, for a given set of oxygen inlet boundary conditions has considerable impact on the oxygen flux and membrane efficiency. Since the implementation of detailed membrane models in heat and mass balance calculations for system studies would result in excessive calculation time, results from this study will be utilized for the generation of correlations describing the oxygen transfer as a function of operating parameters such as temperature and partial pressure. This modeling approach is expected to improve the accuracy of system studies.

Methodology for Predicting Oxygen Transport on an Intravenous Membrane Oxygenator Combining Computational and Analytical Models

2005 ◽  
Vol 127 (7) ◽  
pp. 1127-1140 ◽  
Author(s):  
Amador M. Guzmán ◽  
Rodrigo A. Escobar ◽  
Cristina H. Amon
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Oxygen Transport ◽  
Oxygen Transfer ◽  
Analytical Models ◽  
Pulsation Frequency ◽  
Membrane Oxygenator ◽  
Transfer Rates ◽  
Numerical Predictions ◽  
Flow Mixing

A computational methodology for accurately predicting flow and oxygen-transport characteristics and performance of an intravenous membrane oxygenator (IMO) device is developed, tested, and validated. This methodology uses extensive numerical simulations of three-dimensional computational models to determine flow-mixing characteristics and oxygen-transfer performance, and analytical models to indirectly validate numerical predictions with experimental data, using both blood and water as working fluids. Direct numerical simulations for IMO stationary and pulsating balloons predict flow field and oxygen transport performance in response to changes in the device length, number of fibers, and balloon pulsation frequency. Multifiber models are used to investigate interfiber interference and length effects for a stationary balloon whereas a single fiber model is used to analyze the effect of balloon pulsations on velocity and oxygen concentration fields and to evaluate oxygen transfer rates. An analytical lumped model is developed and validated by comparing its numerical predictions with experimental data. Numerical results demonstrate that oxygen transfer rates for a stationary balloon regime decrease with increasing number of fibers, independent of the fluid type. The oxygen transfer rate ratio obtained with blood and water is approximately two. Balloon pulsations show an effective and enhanced flow mixing, with time-dependent recirculating flows around the fibers regions which induce higher oxygen transfer rates. The mass transfer rates increase approximately 100% and 80%, with water and blood, respectively, compared with stationary balloon operation. Calculations with combinations of frequency, number of fibers, fiber length and diameter, and inlet volumetric flow rates, agree well with the reported experimental results, and provide a solid comparative base for analysis, predictions, and comparisons with numerical and experimental data.

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