scholarly journals Effects of Arterial Pco2 and Cerebrospinal Fluid Volume Flow Rate Changes on Choroid Plexus and Cerebral Blood Flow in Normal and Experimental Hydrocephalic Cats

1983 ◽  
Vol 3 (3) ◽  
pp. 369-375 ◽  
Author(s):  
S. Nakamura ◽  
G. M. Hochwald
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Cerebral Cortex ◽  
Choroid Plexus ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Brain Blood Flow ◽  
Choroidal Blood Flow ◽  
Flow Rates

The effect of changes in brain blood flow on cerebrospinal fluid (CSF) volume flow rates, and that of changes in CSF volume flow rates on brain blood flow were determined in both normal and kaolin-induced hydrocephalic cats. In both groups of cats, blood flow in grey and white matter, cerebral cortex, and choroid plexus was measured with 105Ru microspheres during normocapnia, and again with 141Ce microspheres after arterial Pco2 was either increased by 300% or decreased by 50%. Blood flow measurements were also made during perfusion of the ventricular system with mock CSF and repeated during perfusion with anisosmotic mannitol solutions to alter CSF volume flow rate. In 30 normal and 26 hydrocephalic cats, blood flow to the cerebral cortex, white matter, and choroid plexus was similar; only blood flow to the caudate nucleus was greater in normal cats. The weight of the choroid plexus from hydrocephalic cats decreased by 17%. Blood flow in the choroid plexus of all cats decreased by almost 50% following hypercapnia or hypocapnia, without a change in the CSF volume flow rate. There was no change in cerebral or choroidal blood flow when CSF volume flow rate was either increased by 170% or decreased by 80%. These results suggest that choroid plexus blood flow does not limit or affect the volume flow rate of CSF from the choroid plexus. CSF volume flow rate can be altered without corresponding blood flow changes of the brain or choroid plexus. Choroid plexus blood flow and the reactivity of both brain and choroidal blood flow to changes in arterial Pco2 were not affected by the hydrocephalus. The lower CSF formation rate of hydrocephalic cats can be attributed in part to the decrease in the mass of choroid plexus tissue.

Postnatal developmental changes in blood flow to choroid plexuses and cerebral cortex of the rat

1994 ◽  
Vol 266 (5) ◽  
pp. R1488-R1492
Author(s):  
J. Szmydynger-Chodobska ◽  
A. Chodobski ◽  
C. E. Johanson
Keyword(s):  
Blood Flow ◽  
Cerebral Cortex ◽  
Vascular System ◽  
Developmental Changes ◽  
Choroidal Blood Flow ◽  
Flow Rates ◽  
Cortical Blood Flow ◽  
Choroid Plexuses ◽  
Choroidal Epithelium ◽  
Cerebral Cortical Blood Flow

Postnatal developmental changes in blood flow to choroid plexuses of the lateral (LVCP) and fourth (4VCP) ventricles and cerebral cortex were studied in pentobarbital-anesthetized rats at 2, 3, 5, and 7-8 wk. Blood flow was measured by indicator fractionation with N-isopropyl-p-[125I]iodoamphetamine as the marker. Blood flow to the LVCP and 4VCP was 2.5 +/- 0.1 and 2.7 +/- 0.1 ml.g-1.min-1, respectively, and did not change between the 2nd and 3rd wk. However, it increased by 34% between the 3rd and 5th wk. From the age of 5 wk on, 4VCP was characterized by higher blood flow rates than LVCP. Cerebral cortical blood flow gradually increased between the 2nd and 5th wk. There was no difference in cortical blood flow between 5-wk-old and adult animals. The changes in choroidal blood flow likely represent a continuing adjustment of the choroidal vascular system to steadily increasing secretory capabilities of the maturing choroidal epithelium.

Abstract W P76: Parent Artery Curvature May Help Determine the Effectiveness of Flow Diverter Treatment

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Brando Dimapasoc ◽  
Aichi Chien
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Simulation Analysis ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Parent Artery ◽  
Flow Volume ◽  
Aneurysm Neck ◽  
Flow Reduction ◽  
Before And After

Introduction: Flow diverters (FDs) aim to treat intracranial aneurysms by altering intra-aneurysmal hemodynamics. Reports have suggested aneurysm and parent artery shape may affect flow reduction in FD-treatment. The purpose of this study is to gain insight into the way in which aneurysm shape and parent artery curvature influence the ability of FDs to redirect flow. Hypothesis: Aneurysm dome size and parent artery curvature affect FD-induced flow reduction within an aneurysm. Methods: FD models constructed based on the Pipeline Embolization Device with 35% area coverage, 30 um strand diameter, and 4 mm nominal diameter were implemented for hemodynamic simulation analysis. The flow reduction effects were tested using aneurysm models featuring different dome sizes and parent artery curvatures. Aneurysm blood flow was analyzed before and after FD stenting in regions of the aneurysm neck, body, and dome. Results: We found that aneurysms with higher parent artery curvature had increased systole flow volume entering aneurysms before and after stenting, regardless of aneurysm size, with pre-FD volume flow rates for curvatures of 20 and 30 degrees, respectively, 1.54 and 2.40 times those for 10 degree curvature. Furthermore, FD reduced flow less in aneurysms with higher curvature. For parent artery curvatures of 10, 20, and 30 degrees, overall reductions of flow volume entering the aneurysm were 91.1±0.56%, 88.2±1.2%, and 85.5±0.28%, respectively. 97.2% of models had more flow reduction at the aneurysm dome than neck. Figure 1 shows representative, post-FD flow in 10 and 30 degree parent arteries, with a greater volume flow rate in (b) depicted by denser streamlines. Aneurysm dome size was not found to have a significant effect on volume flow rate. Conclusions: We found that artery curvature may have a large influence on FD flow reduction, indicating that FD may be less effective at reducing blood flow entering aneurysms located within higher curvature arteries.

Influence of two-phase suction injection on performances of the scroll refrigeration compressor with a high-temperature shell

2021 ◽  
pp. 095440892110302
Author(s):  
Shuaihui Sun ◽  
Wang Zhe ◽  
Li Liansheng ◽  
Bu Gaoxuan
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Coefficient Of Performance ◽  
Two Phase ◽  
Flow Rates ◽  
Injection Volume ◽  
Discharge Temperature

The two-phase suction injection can reduce the discharge temperature of scroll refrigeration compressors, which work under a high-pressure ratio. The heat transfer along the pipe axis from the shell affects the two-phase suction injection significantly for the compressor with a high-temperature shell. In this paper, the suction mixing and heat transfer model was developed to calculate the heat transfer along the pipe axis from the high-temperature compressor shell. Then the model was coupled with the two-phase compressor model to obtain the compressor performance under different suction injection volume flow rates. The compressor with two-phase suction injection was tested under different injection volume flow rates to validate the model. The results indicated that the discharge temperature decreased by 2 °C when the mass injection ratio increased by 1%. As the injection volume flow rates increased, the total mass flow rate increased due to the reduction of the specific volume of the suction fluid; the input work decreased because of the reduction of specific work and the improvement of the motor's electric efficiency. The cooling capacity decreased since the cooling capacity of the injection refrigerant was wasted for cooling the suction process and the compressor shell, especially at high injection volume flow rates. The coefficient of performance reached the maximum value at the injection volume flow rate of 0.015 m3·h−1 and became lower than the coefficient of performance without injection when the injection volume flow rate raised to 0.035 m3·h−1. Hence, the two-phase suction injection can reduce the discharge temperature efficiently at low injection volume flow rates with a slight improvement of coefficient of performance.

Three-dimensional multiphase flow modeling of membrane humidifier for PEM fuel cell application

2019 ◽  
Vol 30 (1) ◽  
pp. 54-74
Author(s):  
Seyed Ali Atyabi ◽  
Ebrahim Afshari ◽  
Mohammad Yaghoub Abdollahzadeh Jamalabadi
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Three Dimensional ◽  
Cross Flow ◽  
High Volume ◽  
Volume Flow ◽  
Dew Point ◽  
Multiphase Model ◽  
Flow Rates ◽  
Content Type

Purpose In this paper, a single module of cross-flow membrane humidifier is evaluated as a three-dimensional multiphase model. The purpose of this paper is to analyze the effect of volume flow rate, dry temperature, dew point wet temperature and porosity of gas diffusion layer on the humidifier performance. Design/methodology/approach In this study, one set of coupled equations are continuity, momentum, species and energy conservation is considered. The numerical code is benchmarked by the comparison of numerical results with experimental data of Hwang et al. Findings The results reveal that the transfer rate of water vapor and dew point approach temperature (DPAT) increase by increasing the volume flow rate. Also, it is found that the water recovery ratio (WRR) and relative humidity (RH) decrease with increasing volume flow rate. In addition, all mixed results decrease with increasing dry side temperature especially at high volume flow rates and this trend in high volume flow rates is more sensible. Although the transfer rate of water vapor and DPAT increases with increasing the wet inlet temperature, WRR and RH reduce. Increasing dew point temperature effect is more sensible at the wet side is compared with the dry side. The humidification performance will be enhanced with increasing diffusion layer porosity by increasing the wet inlet dew point temperature, but has no meaningful effect on other operating parameters. The pressure drop along humidifier gas channels increases with rising flow rate, consequently, the required power of membrane humidifier will enhance. Originality/value According to previous studies, the three-dimensional numerical multiphase model of cross-flow membrane humidifier has not been developed.

scholarly journals A Novel Non-Intrusive Vibration Energy Harvesting Method for Air Conditioning Compressor Unit

2021 ◽  
Vol 13 (18) ◽  
pp. 10300
Author(s):  
Chuan Choong Yang ◽  
Noor Fiqri Razqi Bin Noor Hanafi ◽  
Noor Hazrin Hany Bt Mohamad Hanif ◽  
Ahmad Faris Ismail ◽  
Hsueh-Hsien Chang
Keyword(s):  
Flow Rate ◽  
Air Conditioning ◽  
Volume Flow Rate ◽  
Piezoelectric Sensor ◽  
Volume Flow ◽  
Vibration Energy ◽  
Compressor Unit ◽  
Flow Rates ◽  
Air Volume ◽  
Custom Made

The purpose of harvesting vibration energy is to obtain clean and sustainable energy by converting vibration energy from ambient sources into a voltage output. In this work, a piezoelectric sensor, PZT-5H is attached to a 3D printed and custom-made mounting to be placed at an air conditioning condenser unit, to harvest vibration energy. The configuration of the harvester is non-intrusive, in which the harvester did not intrude into compressor unit operation. Temperature (20 °C, 22 °C, and 24 °C) and air volume flow rates (3 levels of air volume flow rate at 245 L/second, 274 L/second, and 297 L/second) were taken into consideration in this investigation. An accelerometer was first used to investigate the optimum vibration frequency in Hertz, and six locations were identified. Next, the piezoelectric sensor was mounted at these six locations, and the output root-mean-square (RMS) voltage from the piezoelectric sensor was obtained. The analysis of variance (ANOVA) indicated that temperature and air volume flow rates factors were significant. It was found that the location identified with the highest amount of vibration at 830.2 Hz from accelerometer measurement, was also the highest amount of RMS voltage, at 510.82 mV, harvested by the piezoelectric, from the temperature of 20 °C and air volume flow rates at high level (air flow volume flow rate at 297 L/second). From this work, it is feasible to utilize this novel method of harvesting waste vibration energy from the air conditioning compressor unit.

P2427The development of a computational fluid dynamics pipeline for the study of tetralogy of Fallot and coarctation of the aorta in a developing world context

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
L Swanson ◽  
B Owen ◽  
A Revell ◽  
M Ngoepe ◽  
A Keshmiri ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Tetralogy Of Fallot ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Coarctation Of The Aorta ◽  
Volume Flow ◽  
Patient Specific ◽  
Data Set

Abstract Background Tetralogy of Fallot (ToF) and coarctation of the aorta (CoA) each constitute approximately 7% of congenital heart disease (CHD) births worldwide. Compared to developed countries, developing countries have a disparate level of access to prompt diagnosis and treatment for these diseases. Computational fluid dynamics (CFD) approaches implemented on routinely available non-invasive imaging data may yield low-cost improvements to the management of these patients. Purpose The purpose of this research is to develop a patient-specific computational pipeline that allows the modelling of blood flow in diseased arteries of patients suffering from ToF and CoA. The project aims to prove the feasible use of broadly available imaging techniques - CT angiograms (CTA) and echocardiographs (echo) - for achieving this in low-to-middle income countries. The capability of the pipeline will be demonstrated through a qualitative study of the effects of different systemic to pulmonary shunt configurations used in the palliative treatment of ToF. In addition, the effects of idealised stent configurations on the blood flow through the aorta of a patient with CoA will be studied. Methods A retrospective search through the hospital database was conducted to select suitable CTA data for a CoA and ToF case. Data for patient A, a five-month-old child with typical CoA, and patient B, a twelve-month-old child with typical ToF who had a central shunt in place, was found. Echo data was obtained for patient A through an investigation protocol which focused on CFD application whereas there was no echo data available for patient B. As a result, idealised volume flow rate data was implemented for patient B. Geometries for patient A and patient B were extracted and volume discretisation was implemented for grid independence testing. The Navier-Stokes governing equations for fluid flow were solved using the open source software, OpenFOAM, for the transient case where inlet volume flow rate was defined for four cardiac cycles. Figure 1 shows key features of the flow in the shunt and pulmonary branches (A), the aortic arch (B), the inlet at the ascending aorta (C) and the descending aorta (D) for the geometry extracted from the data set of patient B. Figure 1. Key flow features of patient B Results and discussion We have implemented CFD models which are able to qualitatively assess the favourable or unfavourable impact of different approaches to ToF and CoA repairs on the characteristics of blood flow in the aorta and pulmonary arteries. An echo investigation protocol has been developed and successfully applied. CTA studies have been shown as feasible sources of geometry data in spite of the restriction on quality by the important requirement for low doses of radiation in paediatric patients. This project represents progress towards an advanced tool that may be broadly implemented in both well-resourced and minimally-resourced hospitals. Acknowledgement/Funding National Research Fund, British Heart Foundation, Newton Fund (UK MRC, South African Medical Research Council), University of Cape Town

scholarly journals Experimental Studies of Ethyl Acetate Saponification Using Different Reactor Systems: The Effect of Volume Flow Rate on Reactor Performance and Pressure Drop

2019 ◽  
Vol 9 (3) ◽  
pp. 532
Author(s):  
Ekaterina Borovinskaya ◽  
Valentin Khaydarov ◽  
Nicole Strehle ◽  
Alexander Musaev ◽  
Wladimir Reschetilowski
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Experimental Studies ◽  
Chemical Processes ◽  
Volume Flow ◽  
Reactor Performance ◽  
Flow Rates ◽  
Flow Energy ◽  
Mass And Heat Transfer

Microreactors intensify chemical processes due to improved flow regimes, mass and heat transfer. In the present study, the effect of the volume flow rate on reactor performance in different reactors (the T-shaped reactor, the interdigital microreactor and the chicane microreactor) was investigated. For this purpose, the saponification reaction in these reactor systems was considered. Experimental results were verified using the obtained kinetic model. The reactor system with a T-shaped reactor shows good performance only at high flow rates, while the experimental setups with the interdigital and the chicane microreactors yield good performance throughout the whole range of volume flow rates. However, microreactors exhibit a higher pressure drop, indicating higher mechanical flow energy consumption than seen using a T-shaped reactor.

Thermal Analysis of Micro Capillary Pumped Loop System

2009 ◽  
Author(s):  
Chin-Tsan Wang ◽  
Tzong-Shyng Leu ◽  
Jui-Ming Yu ◽  
Yuh-Chung Hu
Keyword(s):  
Thermal Analysis ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Capillary Pumped Loop ◽  
Two Phase ◽  
Flow Rates ◽  
Injection Volume ◽  
Micro Channels ◽  
System Temperature

A Capillary Pumped Loop is a sort of “two-phase heat transport device”. In this study, the micro capillary pumped loop (MCPL) and temperature sensors embedded in the micro-channels were fabricated using MEMS technology. An open type of MCPL was applied to determine the thermal analysis of MCPL corresponding to different injection volume flow rates under the condition of constant heating power 20W. A series of experiments yielded numerous results and are as follows: first, a larger injection volume flow rate results in a lower system temperature. Second, the thermal bubbles begin to degenerate into smaller bubbles at Q volume = 2 μl/min. In addition, the phenomenon of slug flow is observed with increasing injection volume flow rates, especially for the case of Q volume = 15 μl/min. Although the temperature of MCPL was reduced with the injection volume rate, the MCPL possessed an almost constant temperature difference regardless of injection volume flow rate. These findings will be useful in determining the optimal design of MCPL.

Importance of freezing time when iodoantipyrine is used for measurement of cerebral blood flow

1991 ◽  
Vol 261 (1) ◽  
pp. H252-H256
Author(s):  
J. L. Williams ◽  
M. Shea ◽  
A. J. Furlan ◽  
J. R. Little ◽  
S. C. Jones
Keyword(s):  
Blood Flow ◽  
Cerebral Cortex ◽  
Cerebral Blood Flow ◽  
Choroid Plexus ◽  
Quantitative Autoradiography ◽  
Brain Blood Flow ◽  
Freezing Time ◽  
Lower Blood ◽  
The Brain

The goal of the present study was to determine effects of delay of freezing of the brain on distribution of [14C]iodoantipyrine in the brain. Blood flow to parietal cerebral cortex (CBF) and choroid plexus was measured with the indicator fractionation technique and quantitative autoradiography. After injection of iodoantipyrine, each rat was decapitated, and the head was immersed in chlorodifluoromethane (-40 degrees C). The brain was removed from the skull after it was frozen. In some rats, heads were immersed immediately after decapitation, and CBF was markedly heterogeneous. In another group, heads were frozen 3 min after decapitation. In this case, CBF was uniform in its distribution. Average CBF was similar in groups with immediate and delayed freezing (90-104 ml.min-1 x 100 g-1). In contrast, delays in freezing decreased blood flow to choroid plexus from 551 +/- 115 to 261 +/- 48 ml.min-1 x 100 g-1. Our findings indicate that immediate freezing of the brain after decapitation is necessary to prevent diffusion of iodoantipyrine from regions of high blood flow to regions of lower blood flow and underestimations of blood flow in regions with high blood flow.

Suprarenal Fixation: Effect on Blood Flow of an Endoluminal Stent Wire across an Arterial Orifice

2003 ◽  
Vol 10 (2) ◽  
pp. 260-274 ◽  
Author(s):  
Kurt Liffman ◽  
Michael M.D. Lawrence-Brown ◽  
James B. Semmens ◽  
Ilija D. Šutalo ◽  
Anh Bui ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Artery ◽  
Flow Rate ◽  
Analytical Methods ◽  
Volume Flow Rate ◽  
Blood Flow Rate ◽  
Flow Rates ◽  
Fixation Effect ◽  
The Wire ◽  
Numerical And Analytical Methods

Purpose: To investigate what effect, if any, the presence of a stent wire in front of a renal artery has on the volume flow rate of blood through the renal artery. Methods: Experimental, numerical, and analytical modeling methods were used to test 4 separate stent wire configurations: a stent wire across the center of an artery orifice, an off-center wire placed at one-quarter the arterial diameter, a V-shaped wire with its vertex at the center, and 2 stent wires at one-third-diameter spacing. Results: For all the configurations studied, the presence of stent wires has a minimal effect on the blood flow rate into an artery of ≥3-mm diameter, with most flow rates decreasing by around 1%. This is true provided that there is no buildup of material on the wire. When material buildup was “encouraged” to occur, then decreases in flow rate of up to 40% were observed. The numerical and analytical methods indicated that the flow rates would, in most cases, decrease by around 3% to 10%. Conclusions: A bare stent wire in front of a >3-mm-diameter artery decreases the flow rate minimally, providing there is no material on the wire. Although the numerical and analytical methods indicated a greater effect on flow, the approximations required for these 2 methods to obtain meaningful solutions suggest that the experimental results are the most accurate. Nonetheless, the analytical equations provided a useful approximation for determining the effect on blood flow due to the presence of a stent wire.

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