The function of astrorhizae in stromatoporoids: quantitative tests

Paleobiology ◽  
1991 ◽  
Vol 17 (2) ◽  
pp. 121-132 ◽  
Author(s):  
Michael LaBarbera ◽  
George E. Boyajian
Keyword(s):  
Cost Function ◽  
Transport System ◽  
Fluid Transport ◽  
Soft Tissues ◽  
Flow System ◽  
Bulk Flow ◽  
Suspension Feeding ◽  
Branch Points ◽  
Related Cost ◽  
Branching Hierarchy

Using the diameters of the channels at branch points, we quantitatively test three alternative models of the function of astrorhizae in stromatoporoids. The distribution of diameters at branch points is significantly different from the distribution that would be predicted from models of either a diffusive function or a bulk-flow system in which resistance to flow was constant at all levels of the branching hierarchy. The distribution of channel diameters is virtually identical to that predicted by a model (Murray's law) that simultaneously minimizes resistance to flow and some volume-related cost function. Astrorhizae thus carried a bulk flow of fluid and can be inferred to have been lined with cellular elements; the exchange sites associated with the fluid-transport system were distributed throughout the soft tissues of the stromatoporoid animal. The most parsimonious hypothesis of function, that the fluid-transport system was associated with suspension feeding, implies strong similarities between the structure of the stromatoporoid animal and living sponges.

Assessment of the energy-related cost function over a range of walking speeds

2019 ◽  
Vol 18 (6) ◽  
pp. 1837-1846
Author(s):  
Emiliano Pablo Ravera ◽  
Marcos José Crespo ◽  
Paola Andrea Catalfamo Formento
Keyword(s):  
Cost Function ◽  
Related Cost ◽  
Walking Speeds

scholarly journals An extravascular fluid transport system based on structural framework of fibrous connective tissues in human body

2019 ◽  
Vol 52 (5) ◽  
Author(s):  
Hongyi Li ◽  
Chongqing Yang ◽  
Yajun Yin ◽  
Fang Wang ◽  
Min Chen ◽  
...  
Keyword(s):  
Transport System ◽  
Human Body ◽  
Fluid Transport ◽  
Connective Tissues ◽  
Structural Framework ◽  
Extravascular Fluid

scholarly journals The Effects of the Emission Cost on Route Choices of International Container Ships

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
Hyangsook Lee ◽  
Kang-Dae Lee ◽  
Sangho Choo
Keyword(s):  
Air Pollution ◽  
Cost Function ◽  
Network Model ◽  
Transport System ◽  
Environmental Effects ◽  
Transportation Cost ◽  
The World ◽  
Route Choices ◽  
Ocean Carriers

Maritime freight shipping has increased significantly and air pollution from international ships has grown accordingly, having serious environmental effects all over the world. This paper analyzes the effects of the emission cost on ocean route choices, focusing on international container ships. First, the paper formulates a freight network model that captures decisions and interactions of ocean carriers and port terminal operators in the maritime freight transport system. Then, the emission cost is calculated based on an activity-based approach as a component of the ocean transportation cost function. A case study is examined to find if the emission cost affects ocean route choices. The results indicate that the optimal ocean route and transportation cost are changed distinctively due to the emission cost. The research discusses how the emission cost plays a role in route changes and why ocean carriers have to consider these costs in their routing decisions.

scholarly journals The Lobster Optic Lamina

1966 ◽  
Vol 1 (3) ◽  
pp. 275-280
Author(s):  
J. HÁMORI ◽  
G. A. HORRIDGE
Keyword(s):  
Glial Cells ◽  
Transport System ◽  
Fluid Transport ◽  
Dark Light ◽  
Dark Cells ◽  
Extensive System ◽  
Structural Support ◽  
Synaptic Region ◽  
Extracellular Transport ◽  
Light Cells

There are 3 distinct types of glial cells in the optic lamina of the lobster: dark, light, and sheet cells, all distinguished from the neurons by being multipolar and not having dictyosomes. Dark cells are surrounded by intercellular material and together with light cells constitute a structural support for the groups of nerve cells. Light cells are also sheath cells for the neuron somata. The sheet cells have numerous flat processes which together form the 2 glial layers in which the synaptic region is sandwiched. An extensive system of extracellular cisterns between the sheet processes may serve for fluid transport towards the fibres and synapses, and the numerous vesicles in the sheet cells may represent an extension of the extracellular transport system.

Model studies on distributions of blood cells at microvascular bifurcations

1985 ◽  
Vol 248 (4) ◽  
pp. H568-H576 ◽  
Author(s):  
S. Chien ◽  
C. D. Tvetenstrand ◽  
M. A. Epstein ◽  
G. W. Schmid-Schonbein
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Particle Flux ◽  
Flow Behavior ◽  
Bulk Flow ◽  
Spherical Particles ◽  
Branch Points ◽  
Particle Distributions ◽  
Model Studies ◽  
Neutrally Buoyant

To model the flow behavior of white and red blood cells at microvascular branch points, the distribution of neutrally buoyant spherical and disk-shaped particles at a symmetric T bifurcation was investigated for low Reynolds number flows (0.01-0.1). The particle distribution was represented by the fractional particle flux to a daughter branch as a function of the fractional volumetric bulk flow to the same branch. Particle-to-tube diameter ratios of 0.32-0.79 were studied for the spherical particles and 0.4-0.8 for the disks. As the particle dimensions approach that of the tube, the relation between the fractional particle flux and fractional bulk flow changes from a linear relation of unity slope to a nonlinear S-shaped curve. Measurements of the flow divider at the entrance to the bifurcation and the eccentricity distributions for the spheres and disks were used to develop a model that permits prediction of the observed particle distributions. These results can be used to interpret the distribution of white and red blood cells in microvascular bifurcations with dimensions close to the cell size.

A Triangle Based Finite Volume Method for the Integration of Lubrication’s Incompressible Bulk Flow Equations

2000 ◽  
Vol 123 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Mihai Arghir ◽  
Jean Fre^ne
Keyword(s):  
Flow System ◽  
A Priori ◽  
Simple Algorithm ◽  
Bulk Flow ◽  
System Of Equations ◽  
Flow Equations ◽  
Application Range ◽  
Lubrication Equation ◽  
Laminar And Turbulent Flow ◽  
Control Volumes

It is well known that for a reduced Reynolds number Re*=ρVH/μs˙H/L greater than unity, inertia forces have a dominant effect in the transport equations, thus rendering the classical lubrication equation inapplicable. The so called “bulk flow” system of equations is then the appropriate mathematical model for describing the flow in bearing and seals operating at Re*⩾1. The difficulty in integrating this system of equations is that one has to deal with coupled pressure and velocity fields. Analytic methods have a very narrow application range so a numerical method has been proposed by Launder and Leschziner in 1978. It represents a natural extrapolation of the successful SIMPLE algorithm applied to the bulk flow system of equations. The algorithm used rectangular, staggered control volumes and represented the state of the art at that moment. In the present work we introduced a method using triangular control volumes. The basic advantage of triangles versus rectangles is that non rectangular domains can be dealt without any a priori limitation. The present paper is focused on the description of the discretized equations and of the solution algorithm. Validations for bearings and seals operating in incompressible, laminar and turbulent flow regime are finally proving the accuracy of the method.

Sign in / Sign up

Export Citation Format

Share Document