Pumping Force Research Articles

Brain motion and volume transmission: Keeping the interstice flowing

Human brain undergoes two different kinds of movements: subtle pulsatile ones associated with the cardiac cycle and others of a greater magnitude related to breathing activity. These motions constitute a pumping force for the circulation of cerebrospinal fluid (CSF). Moreover, brain motion (BM) plays a fundamental role as a driving force for the interstitial and CSF flow of tracers. We hypothesize that BM is more than a mere consequence of cardiac and respiratory activities; that it would be part of a fundamental physiological mechanism by propelling the interstitial flow of messengers, a mechanism also known as ‘non-synaptic transmission’ or ‘volume transmission’ (VT). Intracranial hypertension (ICH), a frequent complication of severe head trauma, is related to brain stiffness. Under this circumstance, not only brain perfusion could be at risk, but BM could be engaged as well. Decompressive craniectomy, presently indicated to reduce ICH refractory to medical treatment, could play a role in helping BM and VT. Once brain swelling is overcome, the closure of the cranial bone defect would ensure the recovery of the spatial and temporal patterns of BM. We discuss evidence supportive of the necessary role of a minimal and sequential BM for an adequate VT.

Forced-flow planar chromatography in the rear view mirror.

Mobile phase progress in planar stationary phase can be evoked by either external or internal forces. An internal force is capillarity, while gravity, electric field, a pump and centrifugal forces belong to external forces. Overpressured layer chromatography gives a widely used special chapter of forced-flow planar chromatography, a special bridge between high-performance liquid column chromatography and thin-layer chromatography (TLC). A simple and special rule characterizes the progress of mobile phase. Optimal efficiency is composed by the doubled effect of flow resulting from the pump-forced mobile phase (convex profile of laminar flow) and capillary forces on the dry stationary phase (concave laminar flow). This review describes the most important aspects of forced-flow TLC, including how the set-ups are developed and also the progress of detection methods used.

Component Analysis of Unsteady Hydrodynamic Force of Closed-Type Centrifugal Pump with Single Blades of Different Blade Outlet Angles

Single-blade centrifugal impellers for sewage systems undergo both unsteady radial and axial thrusts. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces and determine the generation mechanism behind them. In this study, we conducted component analyses of radial and axial thrusts of closed, single-blade centrifugal pumps with different blade outlet angles by numerical analysis while considering leakage flow. The results revealed the effect of the blade outlet angle on the components of radial and axial thrusts. For increased flow rates, the time-averaged values of the pressure component were similar for all impellers, although its fluctuating components were higher for impellers with larger blade outlet angles. Moreover, the fluctuating inertia component of the impeller with a blade outlet angle of 8° decreased as the flow rate increased, whereas those with 16° and 24° angles increased. Therefore, the radial thrust on the hydraulic part was significantly higher for impellers with high blade outlet angles.

Development of new “multivolute casing” geometries for radial force reduction in centrifugal pumps

Large radial force causes several issues in pumps, such as noise, vibration, and extra load on the bearings. To reduce the radial force, the effects of concentric volute and multivolute geometry on the head, efficiency, and radial force of a low speed centrifugal pump at off-design conditions were investigated. Commercial software with the k – ω turbulence model and automatic near wall treatment was employed for the prediction of fluid flow inside the pump. Flow simulations for three casings concentric at 180°, 270°, and 360° from the tongue showed that the 270° concentric volute generates the lowest radial force at throughout the entire range of flow rate. The triple-volute and tetravolute casings are also proposed as new volute geometries. The flow analysis of a double-volute, triple-volute, and tetravolute show that the triple-volute is the most appropriate volute geometry at off-design conditions.

Electomechanical Model for Non-Excitable Cells

Mechanical and electrical properties of cells are crucial in regulating a wide range of cellular processes, such as motility, cancer metastasis, and embryogenesis. Cell size and membrane potential are both highly regulated properties in eukaryotic, non-excitable cells. The proposed model explains the interplay between mechanical, electrical, and biochemical properties of a cell, and can have important implications for pathology and medicine. The combination of osmosis-driven water flow, passive ion flux, ion pumping, signaling, and cytoskeletal forces provide a mechanism for how cells control their volume and membrane potential. For example, the model predicts that cell volume increases during depolarization and decreases slightly during hyperpolarization. Whole cell voltage clamp experiments provide a technique for measuring cell volume while controlling membrane potential. Experiments done on different eukaryotic, non-excitable cancer cell lines validate the model.

A COMPARATIVE STUDY ON THE RESISTANCES OF BUCKET FOUNDATION IN SAND WITH DIFFERENT INSTALLATION METHODS

Model tests have been performed to investigate the vertical, horizontal and cone tip resistances of bucket foundations embedded in sand with different installation methods; suction force by pump and jacking force by actuator. Micro-cone penetrometer was used to evaluate the variation of the effective stress inside pile after model pile installation. As a result, in vertical pull-out test, the pile installed jacking force method shows 3 times larger resistance than installed suction force method. In horizontal pull-out test, the ultimate horizontal capacity and the slope of load-displacement curve for the model pile installed by suction force were decreased by 22% and 40% respectively compared to the pile installed by jacking force. In cone penetration test, inside cone tip resistance of the pile installed by suction force shows about 40% smaller than that installed by jacking force. It is because the effective stress was reduced due to upward seepage of inner pile in sand by suction force. Therefore, we can see that the effect of installation method on bucket foundation has to be considered to investigate the behavior of it experimentally.

Flux controllable pumping of water molecules in a double-walled carbon nanotube

A water pumping system model has been designed based on the double-walled carbon nanotube. In this system, the inner tube is fixed as the water channel, while the exterior one can move, similar to the piston motion along the axial direction, to create a pumping force. Molecular dynamics simulations confirm that both the water flux and the water dipole orientation are sensitive to the velocity of motions of the outer tube so that a controllable unidirectional water flow can be achieved in this system by varying the velocity. Its pumping ability comes mainly from the carbon-water van der Waals driving forces of the exterior tube. The piston motion of the outer tube changes the position of the vdW balance point, which not only leads to the increase of vdW force on the water molecules already residing in the inner tube, but also enlarges their accelerated distance. Meanwhile, the orientation of water molecules inside the inner tube is strongly coupled to the water flux, the probability of +dipole states attains unity at v = 0.05 Å/ps, where the water flux reaches its maximum value (2.02 ns-1). Compared to the pump which is controlled by uniform electric field, the transmission efficiency of our mechanical pump is higher. This design may open a new way for water pumping in the field of nanodevices.

Effect of the volute tongue profile on the performance of a low specific speed centrifugal pump

In this study, we investigated the effects of volute tongue geometry variation on the head, efficiency, and radial force of a centrifugal pump. Numerical simulation modeling based on [Formula: see text] turbulence with automatic near wall treatments was used to simulate the turbulent flow. The effect of blade position with respect to the volute tongue on instantaneous pump characteristics was investigated. The parametric studies were done for cutwater gap, tongue shape, and volute tongue angle. Numerical results showed that the large cutwater gap caused lower radial force, especially at high flow rates. Investigations using various volute tongue shapes indicated that the short tongue volute decreased the radial force at design and low flow rates. Considering all aspects, the most satisfactory volute tongue angle was found to be 5° less than the outlet velocity angle of the impeller; yielding about 40% lower radial force than others at the design point.

Respiratory conservation of energy with dioxygen: cytochrome C oxidase.

Cytochrome c oxidase (CcO) is the terminal oxidase of cell respiration which reduces molecular oxygen (O₂) to H2O coupled with the proton pump. For elucidation of the mechanism of CcO, the three-dimensional location and chemical reactivity of each atom composing the functional sites have been extensively studied by various techniques, such as crystallography, vibrational and time-resolved electronic spectroscopy, since the X-ray structures (2.8 Å resolution) of bovine and bacterial CcO have been published in 1995.X-ray structures of bovine CcO in different oxidation and ligand binding states showed that the O₂reduction site, which is composed of Fe (heme a 3) and Cu (CuB), drives a non-sequential four-electron transfer for reduction of O₂to water without releasing any reactive oxygen species. These data provide the crucial structural basis to solve a long-standing problem, the mechanism of the O₂reduction.Time-resolved resonance Raman and charge translocation analyses revealed the mechanism for coupling between O₂reduction and the proton pump: O₂is received by the O₂reduction site where both metals are in the reduced state (R-intermediate), giving the O₂-bound form (A-intermediate). This is spontaneously converted to the P-intermediate, with the bound O₂fully reduced to 2 O²⁻. Hereafter the P-intermediate receives four electron equivalents from the second Fe site (heme a), one at a time, to form the three intermediates, F, O, and E to regenerate the R-intermediate. Each electron transfer step from heme a to the O₂reduction site is coupled with the proton pump.X-ray structural and mutational analyses of bovine CcO show three possible proton transfer pathways which can transfer pump protons (H) and chemical (water-forming) protons (K and D). The structure of the H-pathway of bovine CcO indicates that the driving force of the proton pump is the electrostatic repulsion between the protons on the H-pathway and positive charges of heme a, created upon oxidation to donate electrons to the O₂reduction site. On the other hand, mutational and time-resolved electrometric findings for the bacterial CcO strongly suggest that the D-pathway transfers both pump and chemical protons. However, the structure for the proton-gating system in the D-pathway has not been experimentally identified. The structural and functional diversities in CcO from various species suggest a basic proton pumping mechanism in which heme a pumps protons while heme a 3 reduces O₂as proposed in 1978.

Giant and flux controllable pumping of water molecules in a double-walled carbon nanotube

We designed a water pumping system based on double-walled carbon nanotube. In this system, the inner tube was fixed as the water channel, while the exterior was moved similarly to the piston motion along the axial direction to induce pumping force. Molecular dynamics simulations confirmed that the water flux is sensitive to the motion velocity of the outer tube so that giant and controllable unidirectional water flow can be achieved in this system by varying the velocity. The enhancement of the pumping ability mainly results from the carbon–water van der Waals driving forces of the exterior tube and the osmosis pressure of the water reservoir. This design may open a new way for water pumping in the field of nanodevices.

Determination of Static and Dynamic Component of Axial Force in Double Suction Centrifugal Pump

This article observes the research results of flow behavior in the impeller chamber of the double suction centrifugal pump. On the basis of the research results we have determine the values of static and dynamic component of axial force.

A direct link between haemodynamic failure and inflammatory activation in heart failure: the simplified approach to heart failure and to creation of life

This editorial refers to ‘Peripheral venous congestion causes inflammation, neurohormonal and endothelial cell activation’[†][1], by P.C. Colombo et al. on page 448 ‘Simplicity does not precede complexity, but follows it’Alan Perlis The classical pathophysiological concept of heart failure (HF) is, of course, the failing pumping force of the myocardium leading to poor tissue perfusion and subsequent functional failure of a range of tissues and organs. The logical consequence, to treat this problem by medically enforced stronger myocardial contractility, failed dramatically, however, as mortality in the long run was even increased with treatment by catecholamines or phosphodiesterase inhibitors. The reasoning from these clinical findings together with further studies formed the basis for the paradigm of neuroendocrine activation as a major underlying principle of HF above and beyond haemodynamic failure. The neurohormonal hypothesis of HF as proposed 20 years ago by Milton Packer1 soon became established as a cornerstone of HF pathophysiology. In fact, all of today's medical treatment concepts in chronic HF with proven benefits on prognosis target neurohormonal activation in some way. This insight was only the first step that opened an era of huge advances in understanding the complexity of the pathophysiology of heart failure. Beyond the haemodynamic failure and neuroendocrine activation, further paradigms were uncovered as contributing to clinical symptoms, to progression, and to mortality of HF. As one prominent feature, inflammatory immune activation was recognized to occur in HF, adding further complexity by linking haemodynamic, endothelial, and metabolic dysfunction ( Figure 1 ). Moreover, it soon became apparent that it is not only the myocardium itself which is the target and promoter of the disease. On the contrary, multiple systemic effects involve peripheral tissues … [1]: #fn-2

Effect of Blade Outlet Angle on Unsteady Hydrodynamic Force of Closed-Type Centrifugal Pump with Single Blade

Geometrically, the single-blade centrifugal impeller, commonly used today as a sewage pump, is not axially symmetric. For this reason, the static pressure around the impeller fluctuates greatly when the impeller is rotating, and not only the radial thrust but also the axial thrust shows large fluctuations. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces. In this study, we investigated the unsteady hydrodynamic forces in a closed-type centrifugal pump with a single blade for different blade outlet angles using a numerical analysis that takes into account both experiment and the leakage flow. The results clearly showed the effect of the blade outlet angle on that act on the impeller. The root-mean-square value of the fluctuating component of the total radial thrust was roughly the same for whichever impeller at low flow rate, but at high flow rates, the value increased for impellers with larger blade outlet angles. Moreover, when the leakage flow rate increased with increasing static pressure around the impeller, such that the rear and front shroud parts were subject to high pressure, the absolute value of the axial thrust on both these parts increased.

High reliability nanosandwiched Pt/Ti multilayer electrode actuators for on-chip biomedical applications

Microactuators provide the main driving force for fluid pumping in microfluidic devices and thus play an important role in on-chip biomedical applications. Interdigitated electrode based electrochemical actuators have provided a viable choice for effective actuation with advantages of flexible controllability, biocompatibility and ease of fabrication. However, the current feature size of a typical electrode structure is around 100 μm, which is relatively large for device miniaturization and integration. Further decrease in the feature size will lead to dramatic decrease in the reliability and lifetime of the actuators, caused by metal delamination. In this work, we propose a novel design of electrodes to fabricate a new type of microactuator with high reliability. To prevent the occurrence of delamination, a nanosandwiched multilayer structure of titanium/platinum is used to construct the conductive metal layer for the interdigitated electrodes. The feature size of the electrodes is greatly reduced to 20 μm where we have reduced the size by 80% of the similar structures reported previously. At the same time, the lifetime of the new electrodes has been dramatically increased to over 400% as compared to the conventional design. With these remarkable improvements in the electrode design, we have fabricated a prototype microfluidic device integrating the new microactuator for drug tests in cancer therapy, demonstrating its usefulness for on-chip biomedical applications.

Research on the effect of wear-ring clearances to the axial and radial force of a centrifugal pump

Varying of the wear-ring clearance not only has a distinct effect on the volumetric loss of the centrifugal pump, but also on the performance of the centrifugal pump including the axial and radial forces. Comparing with the experimental studies, numerical simulation methods have some special advantages, such as the low cost, fast and high efficiency, and convenient to get the detailed structure of the internal flow characteristics, so it has been widely used in the fluid machinery study in recent years. In order to study the effect of wear-ring clearance on the force performance of the centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump with three variable styles of the wear-rings was simulated: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Comparing with the experiment, numerical results show a good agreement. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the axial force of the centrifugal pump, while has tiny effect on the radial force for all the conditions.

Analysis of flow characteristics of a cam rotor pump

Immersed solid model of CFX is a professional method to solve dynamic grid problems of small gaps. In this work, the flow characteristics of a cam pump were calculated by immersed solid model. Results show that the flow rate of the cam pump decreases with the discharge pressure, but increases with the rotor speed; radial force of the cam pump increases with the rotor speed, as well as the discharge pressure. Meanwhile, the values of various parameters present pulsations of different levels. Moreover, the flow pulsation increases with the discharge pressure, but decreases with the rotor speed. In addition, the dominant frequency of various parameters is mainly influenced by integer multiples of the blade passing frequency. This paper may play a certain role for the selection of main parameters, as well as the pulsation reduction of the cam pump.

Numerical research on the effects of impeller pump-out vanes on axial force in a solid-liquid screw centrifugal pump

A commercial CFD code has been used to predict the performance of a screw centrifugal pump with pump-out vanes, especially when changing regularity of impeller axial force based on the solid-liquid two-phase flow. The Unsteady Reynolds Averaged Navier-Stokes (URANS) approach has been applied to solve the unsteady, incompressible, three-dimensional turbulent. The SIMPLEC algorithm, standard wall functions and mix two-phase flow model were applied. The RNG k ε-model was used to account the turbulence effects. By changing the number of impeller pump-out vanes and width, six different screw centrifugal pump numerical simulation projects were given, and each scheme in the different solid volume fraction were calculated respectively. The change rules of axial force, velocity and pressure distribution of flow field were obtained on the different condition and different volume fraction. The results showed that the axial forces values based solid-fluid two-phase greater than based single-phase clear water, but both changing regularity of the axial force were consistent; as same condition, the same solid-phase volume concentration, with the increase of pump-out vanes number or width, the impeller axial force increased as well. Meanwhile the number of the pump-out vanes and the width of pump-out vanes in balancing the impeller axial force, there are the most optimal value.

Detection of Cochlear Amplification and Its Activation

The operation of the mammalian cochlea relies on a mechanical traveling wave that is actively boosted by electromechanical forces in sensory outer hair cells (OHCs). This active cochlear amplifier produces the impressive sensitivity and frequency resolution of mammalian hearing. The cochlear amplifier has inspired scientists since its discovery in the 1970s, and is still not well understood. To explore cochlear electromechanics at the sensory cell/tissue interface, sound-evoked intracochlear pressure and extracellular voltage were measured using a recently developed dual-sensor with a microelectrode attached to a micro-pressure sensor. The resulting coincident in vivo observations of OHC electrical activity, pressure at the basilar membrane and basilar membrane displacement gave direct evidence for power amplification in the cochlea. Moreover, the results showed a phase shift of voltage relative to mechanical responses at frequencies slightly below the peak, near the onset of amplification. Based on the voltage-force relationship of isolated OHCs, the shift would give rise to effective OHC pumping forces within the traveling wave peak. Thus, the shift activates the cochlear amplifier, serving to localize and thus sharpen the frequency region of amplification. These results are the most concrete evidence for cochlear power amplification to date and support OHC somatic forces as its source.

Numerical and Experimental Study of Axial Force and Hydraulic Performance in a Deep-Well Centrifugal Pump With Different Impeller Rear Shroud Radius

A multistage deep-well centrifugal pump (DCP) with different impeller rear shroud radius have been investigated both numerically and experimentally under multiconditons, which aims at studying the influence of impeller rear shroud radius to the axial force and pump hydraulic performance. During this study, a two-stage DCP equipped with three different impellers was simulated employing the commercial computational fluid dynamics (CFD) software ANYSY-Fluent to solve the Navier-Stokes equations for three-dimensional steady flow. High-quality structured grids were meshed on the whole computational domain. Test results were acquired by prototype experiments, and then compared with the predicted pump performance and axial force. The static pressure distribution in the pump passage obtained by numerical simulation was analyzed. The results indicated that the appropriate impeller rear shroud radius could improve the pump performance and lower the axial force significantly.

Comparison between a Heat Pipe and a Thermosyphon Performance with Variable Evaporator Length_ENG

Heat pipes and two phase thermosyphons are heat transfer devices whose operating principles are based on the evaporation/condensation of a working fluid using the capillary pumping forces (in the case of heat pipe) and gravity forces (in the case of two phase thermosyphons) to ensure the fluid circulation. The two systems were designed and constructed to investigate the performance and the affecting parameters, using ethanol as a working fluid. The affecting parameters which were studied are power input (200≤Q≤700) W, working fluid filling ratios (35% and 85%) and aspect ratio, the ratio of evaporator length to inner diameter, (4.0, 7.8 and11.5) . The experimental results showed that the best performance of heat pipe obtained at aspect ratio (7.8) and (85%) filling ratio at (500) W where the maximum heat transfer coefficient was (9950) W/m2.oC, while for the two phase thermosyphon the best performance was obtained at aspect ratio (4.0) for (35%) filling ratio and power input (600) W with maximum heat transfer coefficient equals to(4590) W/m2.oC. The overall comparison between the two systems showed that the performance of the heat pipe is better than that of the two phase thermosyphon. The experimental results of heat pipe was compared with theoretical and empirical correlations showing reasonable agreement especially with immura with percent 70%. KEY WORDS: heat pipe, two phase thermosyphon, aspect ratio, filling ratio