Blood Flow and Transport in the Human Placenta

2019 ◽  
Vol 51 (1) ◽  
pp. 25-47 ◽  
Author(s):  
Oliver E. Jensen ◽  
Igor L. Chernyavsky
Keyword(s):  
Three Dimensional ◽  
Blood Gases ◽  
Maternal Blood ◽  
Transport Processes ◽  
Fetal Blood ◽  
Flow And Transport ◽  
Blood Flows ◽  
Capillary Networks ◽  
Solute Uptake ◽  
Recent Developments

The placenta is a multifunctional organ that exchanges blood gases and nutrients between a mother and her developing fetus. In humans, fetal blood flows through intricate networks of vessels confined within villous trees, the branches of which are bathed in pools of maternal blood. Fluid mechanics and transport processes play a central role in understanding how these elaborate structures contribute to the function of the placenta and how their disorganization may lead to disease. Recent advances in imaging and computation have spurred significant advances in simulations of fetal and maternal flows within the placenta across a range of length scales. Models describe jets of maternal blood emerging from spiral arteries into a disordered and deformable porous medium, as well as solute uptake by fetal blood flowing through elaborate three-dimensional capillary networks. We survey recent developments and emerging challenges in modeling flow and transport in this complex organ.

scholarly journals Quantifying the impact of tissue metabolism on solute transport in feto-placental microvascular networks

2019 ◽  
Vol 9 (5) ◽  
pp. 20190021 ◽  
Author(s):  
Alexander Erlich ◽  
Gareth A. Nye ◽  
Paul Brownbill ◽  
Oliver E. Jensen ◽  
Igor L. Chernyavsky
Keyword(s):  
Maternal Blood ◽  
Physiological Parameter ◽  
Nonlinear Kinetics ◽  
Tissue Metabolism ◽  
Capillary Networks ◽  
Solute Uptake ◽  
Terminal Villi ◽  
Parameter Values ◽  
The Impact ◽  
Villous Tissue

The primary exchange units in the human placenta are terminal villi, in which fetal capillary networks are surrounded by a thin layer of villous tissue, separating fetal from maternal blood. To understand how the complex spatial structure of villi influences their function, we use an image-based theoretical model to study the effect of tissue metabolism on the transport of solutes from maternal blood into the fetal circulation. For solute that is taken up under first-order kinetics, we show that the transition between flow-limited and diffusion-limited transport depends on two new dimensionless parameters defined in terms of key geometric quantities, with strong solute uptake promoting flow-limited transport conditions. We present a simple algebraic approximation for solute uptake rate as a function of flow conditions, metabolic rate and villous geometry. For oxygen, accounting for nonlinear kinetics using physiological parameter values, our model predicts that villous metabolism does not significantly impact oxygen transfer to fetal blood, although the partitioning of fluxes between the villous tissue and the capillary network depends strongly on the flow regime.

Effects of fetal-maternal exchange transfusion on fetal oxygenation and blood flow distribution

1984 ◽  
Vol 247 (4) ◽  
pp. H655-H660 ◽  
Author(s):  
J. Itskovitz ◽  
B. W. Goetzman ◽  
C. Roman ◽  
A. M. Rudolph
Keyword(s):  
Blood Flow ◽  
Exchange Transfusion ◽  
Venous Blood ◽  
Flow Distribution ◽  
Blood Gases ◽  
Maternal Blood ◽  
Organ Blood Flow ◽  
Fetal Life ◽  
Fetal Blood ◽  
Fetal Oxygenation

The effect of reducing hemoglobin affinity for O2 on fetal oxygenation was assessed in seven fetal lambs in which fetal blood was almost completely replaced by maternal blood 2-3 days postoperatively. Measurements of fetal blood gases and organ blood flow (radionuclide-labeled microsphere technique) were obtained before and 1 h after the exchange transfusion. Umbilical venous blood PO2 increased from 29 +/- 5 to 35 +/- 6 (SD) Torr (P less than 0.001) but hemoglobin O2 saturation decreased from 78.2 +/- 10.3 to 39.8 +/- 8.8% (P less than 0.001), resulting in a 46% decrease in umbilical venous blood O2 content. Since umbilical-placental blood flow also decreased (P less than 0.002), O2 delivery to the fetus decreased by 64% (P less than 0.002). Although O2 extraction increased from 32.5 +/- 6.8 to 50.9 +/- 9.0% (P less than 0.002), fetal O2 consumption fell from 7.28 +/- 1.97 to 4.10 +/- 1.20 ml X min-1 X kg-1 (P less than 0.02), and metabolic acidemia developed. No significant change in fetal cardiac output was observed. Blood flow increased significantly to the myocardium and adrenals but fell in the placenta, carcass, and lungs and was maintained in other organs. This resulted in a significant decrease in the amount of O2 delivered to all fetal organs except to the myocardium in which it was maintained. In the sheep the higher affinity of fetal blood hemoglobin for O2 helps maintain normal oxygenation during fetal life by facilitating O2 uptake at the placenta and unloading O2 in the tissues.

Mathematical Model Investigation of Far-Field Transport of Ocean-Dumped Sewage Sludge Related to Remote Sensing

1982 ◽  
Vol 14 (3) ◽  
pp. 33-39
Author(s):  
C Y Kuo
Keyword(s):  
New York ◽  
Sewage Sludge ◽  
Laboratory Data ◽  
Three Dimensional ◽  
Approximate Model ◽  
Transport Processes ◽  
Far Field ◽  
New York Bight ◽  
Mean Current

An existing, three-dimensional, Eulerian-Lagrangian finite-difference model was modified and used to examine the far-field transport processes of dumped sewage sludge in the New York Bight. Both in situ and laboratory data were utilized in an attempt to approximate model inputs such as mean current speed, vertical and horizontal diffusion coefficients, particle size distributions, and specific gravities. Concentrations of the sludge near the sea surface predicted from the computer model were compared qualitatively with those remotely sensed.

scholarly journals Three-dimensional 𝒩 = 2 supersymmetric gauge theories and partition functions on Seifert manifolds: A review

2019 ◽  
Vol 34 (23) ◽  
pp. 1930011 ◽  
Author(s):  
Cyril Closset ◽  
Heeyeon Kim
Keyword(s):  
Correlation Functions ◽  
Gauge Theories ◽  
Three Dimensional ◽  
Partition Functions ◽  
Exact Results ◽  
Strongly Coupled ◽  
Seifert Manifolds ◽  
Recent Developments ◽  
Supersymmetric Gauge ◽  
Chern Simons

We give a pedagogical introduction to the study of supersymmetric partition functions of 3D [Formula: see text] supersymmetric Chern–Simons-matter theories (with an [Formula: see text]-symmetry) on half-BPS closed three-manifolds — including [Formula: see text], [Formula: see text], and any Seifert three-manifold. Three-dimensional gauge theories can flow to nontrivial fixed points in the infrared. In the presence of 3D [Formula: see text] supersymmetry, many exact results are known about the strongly-coupled infrared, due in good part to powerful localization techniques. We review some of these techniques and emphasize some more recent developments, which provide a simple and comprehensive formalism for the exact computation of half-BPS observables on closed three-manifolds (partition functions and correlation functions of line operators). Along the way, we also review simple examples of 3D infrared dualities. The computation of supersymmetric partition functions provides exceedingly precise tests of these dualities.

Recent Developments In Monochromatic Microprobe X-Ray Fluorescence (MMXRF)

1998 ◽  
Vol 4 (S2) ◽  
pp. 378-379
Author(s):  
Z. W. Chen ◽  
D. B. Wittry
Keyword(s):  
Materials Science ◽  
High Vacuum ◽  
Three Dimensional ◽  
High Sensitivity ◽  
X Rays ◽  
Fluorescence Excitation ◽  
X Ray ◽  
Quantitative Microanalysis ◽  
Recent Developments ◽  
Fifth Order

A monochromatic x-ray microprobe based on a laboratory source has recently been developed in our laboratory and used for fluorescence excitation. This technique provides high sensitivity (ppm to ppb), nondestructive, quantitative microanalysis with minimum sample preparation and does not require a high vacuum specimen chamber. It is expected that this technique (MMXRF) will have important applications in materials science, geological sciences and biological science.Three-dimensional focusing of x-rays can be obtained by using diffraction from doubly curved crystals. In our MMXRF setup, a small x-ray source was produced by the bombardment of a selected target with a focused electron beam and a toroidal mica diffractor with Johann pointfocusing geometry was used to focus characteristic x-rays from the source. In the previous work ∼ 108 photons/s were obtained in a Cu Kα probe of 75 μm × 43 μm in the specimen plane using the fifth order reflection of the (002) planes of mica.

Recent Developments in the Evolution of Morphologies and Controllers for Physically Simulated Creatures

2001 ◽  
Vol 7 (1) ◽  
pp. 77-87 ◽  
Author(s):  
Tim Taylor ◽  
Colm Massey
Keyword(s):  
Recent Work ◽  
Original Work ◽  
Three Dimensional ◽  
Parallel Computer ◽  
Connection Machine ◽  
Recent Developments ◽  
Body Shapes

Karl Sims' work [25, 26] on evolving body shapes and controllers for three-dimensional, physically simulated creatures generated wide interest on its publication in 1994. The purpose of this article is threefold: (a) to highlight a spate of recent work by a number of researchers in replicating, and in some cases extending, Sims' results using standard PCs (Sims' original work was done on a Connection Machine CM-5 parallel computer). In particular, a re-implementation of Sims' work by the authors will be described and discussed; (b) to illustrate how off-the-shelf physics engines can be used in this sort of work, and also to highlight some deficiencies of these engines and pitfalls when using them; and (c) to indicate how these recent studies stand in respect to Sims' original work.

Recent developments in fabricating drag reduction surfaces covering biological sharkskin morphology

2016 ◽  
Vol 32 (1) ◽  
Author(s):  
Yuehao Luo ◽  
Xia Xu ◽  
Dong Li ◽  
Wen Song
Keyword(s):  
Global Warming ◽  
Drag Reduction ◽  
Rapid Development ◽  
Three Dimensional ◽  
Viscous Drag ◽  
Environment Protection ◽  
Uv Curable ◽  
Recent Developments ◽  
Potential Benefits ◽  
Energy Shortage

AbstractWith the rapid development of science and technology, increasing research interests have been focused on environment protection, global warming, and energy shortage. At present, reducing friction force as much as possible has developed into an urgent issue. Sharkskin effect has the potential ability to lower viscous drag on the fluid-solid interface in turbulence, and therefore, how to fabricate bio-inspired sharkskin surfaces is progressively becoming the hot topic. In this review, various methods of fabricating drag reduction surfaces covering biological sharkskin morphology are illustrated and discussed systematically, mainly involving direct bio-replicated, synthetic fabricating, bio/micro-rolling, enlarged solvent-swelling, drag reduction additive low-releasing, trans-scale enlarged three-dimensional fabricating, flexible printing, large-proportional shrunken bio-replicating, ultraviolet (UV) curable painting, and stretching deformed methods. The overview has the potential benefits in better acquainting with the recent research status of fabricating sharkskin surfaces covering the biological morphology.

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