Effects of Lymphangion Subdivision in a Numerical Model of a Lymphatic Vessel

2011 ◽  
Author(s):  
Christopher D. Bertram ◽  
Charles Macaskill ◽  
James E. Moore
Keyword(s):  
Smooth Muscle ◽  
Numerical Model ◽  
Lymphatic Vessel ◽  
Smooth Muscle Contraction ◽  
Lumped Parameter Model ◽  
Active Tension ◽  
Lumped Parameter ◽  
Pumping Efficiency ◽  
In Series ◽  
Passive Compression

We have recently reported development of a lumped-parameter model for several lymphangions in series [1]. The model provides for both active smooth muscle contraction (intrinsic pumping) and passive compression of the lymphatic by external tissues (extrinsic pumping). The valves which define the lymphangions vary their resistance sigmoidally, having a high (low) resistance for an adverse (favorable) pressure difference. With no refractory period between sinusoidal active tension episodes, maximum pumping efficiency was reached when each lymphangion contracted 135° after that immediately upstream; simultaneous contraction (corresponding to the situation of extrinsic pumping) was especially inefficient.

A Fast and Effective Method for the Optimization of the Valve Plate of Swashplate Axial Piston Pumps

2021 ◽  
Author(s):  
Gianluca Marinaro ◽  
Emma Frosina ◽  
Kim Stelson ◽  
Adolfo Senatore
Keyword(s):  
Numerical Model ◽  
Dynamic Pressure ◽  
Valve Plate ◽  
Lumped Parameter Model ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Flow Ripple ◽  
Lumped Parameter ◽  
Pressure Ripple ◽  
Axial Piston

Abstract This research presents a lumped parameter numerical model aimed at designing and optimizing an axial piston pump. For the first time, it has been shown that a lumped parameter model can accurately model axial piston pump dynamics based on a comparison with CFD models and experimental results. Since the method is much more efficient than CFD, it can optimize the design. Both steady-state and dynamic behaviors have been analyzed. The model results have been compared with experimental data, showing a good capacity in predicting the pump performance, including pressure ripple. The swashplate dynamics have been investigated experimentally, measuring the dynamic pressure which controls the pump displacement; a comparison with the numerical model results confirmed the high accuracy. An optimization process has been conducted on the valve plate geometry to control fluid-born noise by flow ripple reduction. The NLPQL algorithm is used since it is suitable for this study. The objective function to minimize is the well-known function, the Non-Uniformity Grade, a parameter directly correlated with flow ripple. A prototype of the best design has been realized and tested, confirming a reduction in the pressure ripple. An endurance test was also conducted. As predicted from the numerical model, a significant reduction of cavitation erosion was observed.

PAF-induced contraction of canine trachea mediated by 5-hydroxytryptamine in vivo

1989 ◽  
Vol 66 (2) ◽  
pp. 638-643 ◽  
Author(s):  
T. M. Murphy ◽  
N. M. Munoz ◽  
J. Moss ◽  
J. S. Blake ◽  
M. M. Mack ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Dose Response ◽  
Contractile Response ◽  
Platelet Activating Factor ◽  
Smooth Muscle Contraction ◽  
Active Tension ◽  
Response Curves ◽  
Arteriovenous Difference

We studied the secretory correlates of tracheal smooth muscle contraction caused by platelet-activating factor (PAF) in nine mongrel dogs in vivo. In five dogs, dose-response curves were generated by rapid intra-arterial injection of 10(-10) to 10(-6) mol PAF into the isolated tracheal circulation; tracheal contractile response was measured isometrically in situ. To examine the mechanism by which PAF elicits contraction of canine trachealis, concentrations of serotonin (5-HT) and histamine were assayed in the venous effluent as the arteriovenous difference (AVd) in mediator concentration across the airway for each level of contraction. PAF caused dose-related active tracheal tension to a maximum of 37.2 +/- 5.4 g/cm (10(-6) mol PAF). The AVd in 5-HT increased linearly from 0.20 +/- 0.05 (10(-9) mol PAF) to 3.5 +/- 0.3 ng/ml (10(-6) mol PAF) (P less than 0.005). In contrast, the AVd in histamine was insignificant and did not change with increasing doses of PAF. A positive correlation was obtained between the AVd in 5-HT and active tracheal tension (r = 0.92, P less than 0.001); there was no correlation between AVd in histamine and active tension (r = -0.16). PAF-induced parasympathetic activation was not mediated by 5-HT; contraction elicited by exogenous 5-HT was not affected by muscarinic blockade. We conclude that nonparasympathetically mediated contraction elicited acutely by PAF in dogs results at least in part from secondary release of serotonin and is not mediated by histamine.

Highly Reduced Lumped Parameter Models Representing Impedance Functions at the Interface of One-Dimensional Viscoelastic Continua

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Masato Saitoh
Keyword(s):  
Degrees Of Freedom ◽  
Reaction Force ◽  
Lumped Parameter Model ◽  
Computational Time ◽  
Dynamic Problems ◽  
Modal Expansion ◽  
Mass Element ◽  
Lumped Parameter ◽  
In Series ◽  
Impedance Functions

In recent dynamic problems dealing with high-frequency excitations, such as ultrasonic vibrations, a proper representation of rods transmitting kinetic energy from the interface attached to the vibrating system to the other end is strongly demanded for effectively reducing computational time and domain. A highly reduced lumped parameter model that properly simulates the dynamic characteristics of a uniform, isotropic, homogeneous, and viscoelastic rod subjected to excitations at its end is proposed in this paper. The model consists of springs, dashpots, and so called “gyro-mass elements.” The gyro-mass element generates a reaction force proportional to the relative acceleration of the nodes between which it is placed. This model consists of units arranged in series, each unit consisting of a spring, a dashpot, and a gyro-mass element arranged in parallel. A formula is proposed for determining the properties of the elements in the units based on the modal expansion. The results show that a notable reduction of 90% in the degrees of freedom is accomplished with high accuracy by using the proposed model consisting of a set of units associated with modes in a target frequency region and a supplemental unit associated with residual stiffness, which is advantageous for efficient numerical computations in recent dynamic problems.

Parameter Sensitivity Analysis of a Lumped-Parameter Model of Lymphangions in Series

2012 ◽  
Author(s):  
Samira Jamalian ◽  
James E. Moore ◽  
Christopher D. Bertram ◽  
Will Richardson
Keyword(s):  
Sensitivity Analysis ◽  
Interstitial Fluid ◽  
Lymphatic System ◽  
Lumped Parameter Model ◽  
Node Dissection ◽  
Parameter Sensitivity Analysis ◽  
Protein Balance ◽  
Vital Functions ◽  
Lumped Parameter ◽  
In Series

The lymphatic system is responsible for vital functions in the human body. In particular, it plays an important role in the immune system mechanism whereby undesirable elements are destroyed in the lymph nodes. But cancer cells also spread via the lymphatic system. The system maintains fluid and protein balance by gathering approximately 4 L/day of interstitial fluid and returning it to the venous system. Lymphedema, an ailment of the system for which there is no known cure, primarily affects cancer patients who have undergone lymph node dissection [1]. To understand how to treat such pathologies of the lymphatic system, it is first necessary to examine its fluid flow and pumping mechanisms quantitatively.

scholarly journals Preliminary Results on Experimental Modelling of an Adsorption Chiller

2021 ◽  
Vol 6 ◽  
pp. 29
Author(s):  
Nayrana Daborer-Prado ◽  
Alois Resch
Keyword(s):  
Numerical Model ◽  
Water Cycle ◽  
Cooling System ◽  
Numerical Study ◽  
Lumped Parameter Model ◽  
Coefficient Of Performance ◽  
Adsorption Refrigeration ◽  
Experimental Modelling ◽  
Adsorption Chiller ◽  
Lumped Parameter

Adsorption refrigeration, as a renewable cooling method, has received more attention in the last few years. The interest in this technology comes especially from developing and tropical countries, where the demand for cooling increases every year due to economy and population growth. Based on this scenario, this work aims to develop a numerical model of an adsorption chiller driven with solar energy, which can be used to optimize the cooling system operation of the building where the device is situated and compare it with the current cooling methods in use. The numerical study here presented was created using Matlab/Simulink™, it is based on a lumped parameter model that relies on physical properties and represents a cooling system using a pair of silica gel-water in a two-bed chiller. In this study, the authors proposed a simplified version of the system and the numerical model, which aims to reduce the simulation time and provide faster results. Besides the temperatures in the system, which range from 52 °C to 72 °C in the hot cycle and 12 °C to 23 °C in the chilled water cycle, the results also include the variation of water uptake in the two adsorbent beds. In general, the simulated temperature, cooling and heating power and coefficient of performance (COP) are in fair agreement with the literature data, nevertheless, the final results show that improvements still have to be performed.

Initial Steps Toward Development of a Lumped-Parameter Model of the Lymphatic Network

2013 ◽  
Author(s):  
Samira Jamalian ◽  
Christopher D. Bertram ◽  
James E. Moore
Keyword(s):  
Blood Circulation ◽  
Lymphatic Vessel ◽  
Lymphatic System ◽  
Lymphatic Vessels ◽  
The Body ◽  
Lumped Parameter Model ◽  
Circulation System ◽  
Blood Circulation System ◽  
Lumped Parameter ◽  
Lymphatic Network

One of the primary functions of the lymphatic system is maintaining fluid and protein balance in the body. The system holds this balance by collecting about four liters of fluid every day from the interstitial space and returning it back to the subclavian vein. In contrast to the blood circulation system that relies on the heart for pumping, there is no central pump in the lymphatic system. Thus, the transport of viscous fluid against gravity and pressure difference occurs by recruiting extrinsic and intrinsic pumping mechanisms. Extrinsic pumping is the transport of lymph due to the movements outside the lymphatic vessel such as the pulse in blood vessels, whereas the intrinsic pumping is transport of lymph by contraction of lymphatic muscle cells embedded in the walls of lymphatic vessels. Similar to the veins, the bi-leaflet valves throughout the lymphatic network prevent backflow. Lymphatic valves are biased open and allow for small amounts of back flow before they completely shut.

scholarly journals A multiscale sliding filament model of lymphatic muscle pumping

2021 ◽  
Author(s):  
Christopher J. Morris ◽  
David C. Zawieja ◽  
James E. Moore
Keyword(s):  
Smooth Muscle ◽  
Interstitial Fluid ◽  
Cellular Level ◽  
Calcium Oscillations ◽  
Lumped Parameter Model ◽  
Maximum Efficiency ◽  
Lumped Parameter ◽  
Muscle Types ◽  
Lymphatic Pumping ◽  
The Relationship

AbstractThe lymphatics maintain fluid balance by returning interstitial fluid to veins via contraction/compression of vessel segments with check valves. Disruption of lymphatic pumping can result in a condition called lymphedema with interstitial fluid accumulation. Lymphedema treatments are often ineffective, which is partially attributable to insufficient understanding of specialized lymphatic muscle lining the vessels. This muscle exhibits cardiac-like phasic contractions and smooth muscle-like tonic contractions to generate and regulate flow. To understand the relationship between this sub-cellular contractile machinery and organ-level pumping, we have developed a multiscale computational model of phasic and tonic contractions in lymphatic muscle and coupled it to a lymphangion pumping model. Our model uses the sliding filament model (Huxley in Prog Biophys Biophys Chem 7:255–318, 1957) and its adaptation for smooth muscle (Mijailovich in Biophys J 79(5):2667–2681, 2000). Multiple structural arrangements of contractile components and viscoelastic elements were trialed but only one provided physiologic results. We then coupled this model with our previous lumped parameter model of the lymphangion to relate results to experiments. We show that the model produces similar pressure, diameter, and flow tracings to experiments on rat mesenteric lymphatics. This model provides the first estimates of lymphatic muscle contraction energetics and the ability to assess the potential effects of sub-cellular level phenomena such as calcium oscillations on lymphangion outflow. The maximum efficiency value predicted (40%) is at the upper end of estimates for other muscle types. Spontaneous calcium oscillations during diastole were found to increase outflow up to approximately 50% in the range of frequencies and amplitudes tested.

Smooth muscle contraction and viscoelasticity of arterial wall

1970 ◽  
Vol 48 (8) ◽  
pp. 510-523 ◽  
Author(s):  
M. Wurzel ◽  
G. R. Cowper ◽  
James M. McCooK
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Elastic Properties ◽  
Mechanical Model ◽  
Arterial Wall ◽  
Viscoelastic Behavior ◽  
Smooth Muscle Contraction ◽  
Ringer’S Solution ◽  
In Series ◽  
Coefficient Of Viscosity

Elasticity and viscosity, of fully relaxed and gradedly contracted arterial wall, were measured on spirally cut rabbit aortic strips suspended in Ringer's solution. Pre-extended contracted tissue submitted to additional stretch shows an instantaneous and a slow elongation. Only instantaneous elongation was observed on fully relaxed tissue. This behavior can be simulated by a mechanical model consisting of a spring in series with a dashpot, and a second spring in parallel with the first spring–dashpot component. The modulus of the first spring and the coefficient of viscosity both increase steadily with increasing contraction, while the modulus of the second spring decreases. The first spring–dashpot component is believed to represent the viscoelastic behavior of smooth muscle on its non-contractile network. The second spring probably represents the combined elastic properties of arterial elastin and collagen.

Hemodynamics of collapsible vessels with tone: the vascular waterfall

1963 ◽  
Vol 18 (5) ◽  
pp. 924-932 ◽  
Author(s):  
S. Permutt ◽  
R. L. Riley
Keyword(s):  
Smooth Muscle ◽  
Theoretical Analysis ◽  
Slight Modification ◽  
Smooth Muscle Contraction ◽  
Active Tension ◽  
Pressure Flow ◽  
Critical Closing Pressure ◽  
Flow Through ◽  
The Difference ◽  
Closing Pressure

A theoretical analysis is presented of pressure-flow relationships in arterioles based on the assumption that the presence of active tension produced by smooth muscle contraction causes a critical closing pressure which is itself a function of the magnitude of the active tension. This analysis differs from those previously carried out in that it uses the pressure-flow relationships of a waterfall rather than those described by Poiseuille's law to characterize the flow between arterioles and capillaries in the presence of active tension. It is suggested that, under some conditions, the driving pressure for the flow through arterioles is not the difference between the inflow pressure and outflow pressure of the arterioles, but rather the difference between the inflow pressure and the critical closing pressure. This seemingly slight modification causes marked differences in the interpretation of pressure-flow relationships and vascular resistance in the presence of active tone. Submitted on December 10, 1962

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