Precise Flow Rate Research Articles

A new antihistamine levocetirizine inhibits eosinophil adhesion to vascular cell adhesion molecule‐1 under flow conditions

We previously demonstrated that low concentrations of a new antihistamine levocetirizine inhibited eosinophil transmigration through human microvascular endothelial cells. Here, the inhibitory effect of levocetirizine on eosinophil adhesion to recombinant human vascular cell adhesion molecule-1 (rhVCAM)-1 was examined under conditions of shear stress using an in vitro model of the post-capillary venules. Eosinophils isolated from normal subjects were pre-incubated with a concentration range of levocetirizine (10(-6)-10(-10) m) or negative dilution control. Resting or granulocyte macrophage-colony stimulating factor (GM-CSF)-stimulated cells were pumped through rhVCAM-1 (10 microg/mL) coated capillary tubes using a microfluidic syringe pump at a precise and constant flow rate (1 dyn/cm(2)). Images of rolling and firmly adherent eosinophils were captured using real-time video microscopy. Levocetirizine significantly inhibited resting eosinophil adhesion to rhVCAM-1 with maximal effect at 10(-8) M with an EC(50) of 10(-9) m. Levocetirizine almost abolished resting eosinophil adhesion by the 15 min time-point. GM-CSF significantly enhanced eosinophil adhesion and their ability to flatten on rhVCAM-1. Both phenomena were inhibited by levocetirizine in a dose-dependent manner, at both 5 and 15 min (optimal concentration of 10(-8) m with an EC(50) of 10(-9) m). Real-time imaging revealed that the effect of levocetirizine on post-adhesion behaviour (detachment, flatness) contributed to its inhibitory action on eosinophil adhesion to rhVCAM-1. In contrast, very late antigen (VLA)-4 mAb inhibited eosinophil adhesion to rhVCAM-1 from the earliest time-points. Physiologically relevant concentrations of levocetirizine inhibit resting and GM-CSF-stimulated firm eosinophil adhesion to rhVCAM-1 under flow conditions.

Construction of a pulmonary artery pump for unifocalization and repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals

Single-stage repair has been presented as the treatment of choice for pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals. This surgical approach may result in the difficult decision of whether to close the ventricular septal defect. This decision may significantly affect the postoperative course of the patient. There are several diagnostic techniques clinicians may use to help them decide if closure is indicated. One technique is to modify an extracorporeal circuit to deliver precise flow rates of blood into the newly created pulmonary arterial system, at the same time supporting the patient during the operative procedure. While this technique is not novel, there is only a single published description of the circuit. This report is brief and does not discuss potential complications that these modifications may cause. Therefore, it is the purpose of this paper to describe a circuit modification to perform this diagnostic measurement as well as elucidating potential risks of this technique.

Multi-phase ceramics by computer-controlled pressure filtration

A novel apparatus for computer controlled pressure filtration has been constructed. With it, the precise flow rate of multiple ceramic suspensions of different compositions can be controlled. Suspensions are mixed before entering the filtration chamber. By dynamically adjusting the different flow rates, mixed compositions anywhere between 100% composition A to 100% composition B can be realised as a function of the filter cake height. This is suitable for producing e.g. functionally graded materials or layered structures. This has been demonstrated for alumina–zirconia composites. The process is suitable for all materials that can be handled by slip casting.

Determination of the optimal region for interaliasing distance measurement for flow regurgitant rate calculation: a fluid simulation study

Background Color Doppler imaging of the convergent region is promising for quantifying valvular regurgitation. Nevertheless, proximal isovelocity surface area method has limitations. We sought to determine the optimal localization to measure the most precise flow rate using a new approach: the interaliasing distance. Methods A finite volume-based program was used to perform simulations in unsteady flow conditions. Different instantaneous flow rates, leaflet angles, and orifice sizes were tested reproducing physiologic conditions. Relative difference between actual and interaliasing distance flow rate was calculated for each configuration. Results The relationship between the relative error and the aliasing velocity location was described by a third-order polynomial equation. The magnitude of relative error is a function of the flow rate, orifice size, and leaflet angle. Conclusion The optimal distance from the orifice to measure the interaliasing distance was when the closer aliasing was between 4 and 8 mm from the orifice.

A digital miniature pump for medical applications

This paper describes the principle, design, control and performance of a novel miniature linear peristaltic pump. Exhibiting dual and bi-directional feed capabilities that allow the simultaneous pumping of two distinct fluids at measured and precise flow rate, the pump consists of two resilient tubes and two directly actuated pumping units. Both of the two flexible tubes are placed in the pumping units in such a way that when a pumping element reciprocates in any direction to collapse one adjacent segment of the tubing, it will release the other adjacent segment of the same tubing at the same time. The two pumping elements reciprocate in a sequence so that fluid in the flexible tubing is continuously pumped in preset direction. For each pumping element, two reflective optical sensors are used to detect its position. Based on the output of the four position sensors, a digital logical control circuit is built for the pump. Experimental results show that this kind of miniature pump has potential applications in portable infusion/suction systems.

Achieving high time-resolution with a new flow-through type analyzer for total inorganic carbon in seawater.

A fully automated, continuous-flow-through type analyzer was developed to observe rapid changes in the concentration of total inorganic carbon (CT) in coastal zones. Seawater and an H3PO4 solution were fed into the analyzer's mixing coil by two high-precision valveless piston pumps. The CO2 was stripped from the seawater and moved into a carrier gas, using a newly developed continuous-flow-through CO2 extractor. A mass flow controller was used to assure a precise flow rate of the carrier gas. The CO2 concentration was then determined with a nondispersive infrared gas analyzer. This analyzer achieved a time-resolution of as good as 1 min. In field experiments on a shallow reef flat of Shiraho (Ishigaki Island, Southwest Japan), the analyzer detected short-term, yet extreme, variations in CT which manual sampling missed. Analytical values obtained by the analyzer on the boat were compared with those determined by potentiometric titration with a closed cell in a laboratory: CT(flow-through) = 0.980 x CT(titration) + 38.8 with r2 = 0.995 (n = 34; September 1998).

Vélocimétrie Doppler : mise au point d'un protocole d'essai en laboratoire et observations in situ

The acoustic Doppler flowmeters give a global data supposed to be representative of the velocity of the flow. In order to better understand the relation between this data and the velocity, and to obtain precise flow rate measurements, it is necessary to know precisely the working characteristics of the sensors: measurements volume, balance of the acoustic echoes coming from various parts of this volume. A testing procedure has been developped to measure those parameters in a laboratory. The main goal of the interpretation of those results is to lead to a global optimisation of the setup sensor + measuring area + positionning of the sensor in the measurement area.

A simple handheld push-button device for in situ calibration of pneumotachographs

A simple and compact flow calibrator has been devised for generating precise predetermined constant flow rates for checking the calibration of laboratory and clinical flow transducers used in respiratory measurements. The standard version delivers preset flows of 0.5 and 1 l/s, whereas a tuned-up version can produce preset flows of 2.5 and 5 l/s, with an accuracy of +/- 2%. The pressure generated is sufficient to cope with most commonly used respiratory flowmeters. The flow calibrator is built from inexpensive components that are readily obtainable: a fan, a turbine flowmeter, and a feedback circuit in a compact housing. The device is easy to connect to other equipment and to operate. Three flow calibrators have been built and are in regular use in a lung function laboratory and on intensive care wards.

Effectiveness of ultra-violet radiation units in the bactericidal treatment of seawater

Four commercially available ultra-violet (u.v.) radiation units (A, B, C, D) and a specially designed u.v. radiation unit (Kelly-Purdy) were tested for their effectiveness in the bactericidal treatment of seawater to be used in controlled shellfish purification systems. The bactericidal effectiveness of a unit was based on its absolute ability to produce a seawater equivalent to coliform bacterial standards for potable water and its relative ability to reduce the bacterial content of the seawater, as measured by reduction in fecal coliform bacteria and bacteria enumerated by the 35°C and 20°C plate count methods. Units A, B, C and D were the immersed lamp type in which the water to be treated was in direct contact with u.v. radiation lamps; A and C were equipped with “hot” cathode, high intensity lamps (135 μW cm −2 at 1 m) and B and D with “cold” cathode, low intensity lamps (73 μW cm −2 at 1 m). The Kelly-Purdy unit, built specifically for seawater treatment, was equipped with u.v. lamps of intermediate intensity (85 μW cm −2 at 1 m) suspended above the water. Results of the study demonstrated that although units A, B, C and D could be used to treat seawater, all four were affected adversely by turbidity. Units A and C were least affected by turbidity and thus most readily adaptable for seawater treatment. Under most turbidity conditions units B and D would require an efficient filtration system. Tests indicated that the four commercial units would require installation of flow regulation devices, and changes in the lamp compartment to permit rapid disassembly for lamp cleansing and metering of u.v. radiation intensity. The Kelly-Purdy unit produced a bacterially acceptable seawater under most turbidity conditions, but was affected adversely by the higher turbidities (> 80 Jackson Turbidity Units), indicating the need for a filtration system or the establishment of precise flow rate curves for turbidities above the critical level.

Micropump-An Apparatus for Steady State Synthesis of Gas Mixtures at Very Dilute Concentrations

An 8 cm3 positive displacement plunger pump and its associated control systems are described. A choice of 224 precise flow rates from 0.36 cm3/min to 8×10−8 cm3/min is possible. Calibration flow mixtures of paraffin hydrocarbons in helium were prepared in the range 10−7–10−11 mole/sec.