An Elastomeric Micrometering System for the Controlled Administration of Drugs

1977 ◽  
Vol 50 (5) ◽  
pp. 959-968 ◽  
Author(s):  
J. C. Wright ◽  
R. G. Buckles ◽  
J. T. Dunn ◽  
H. M. Leeper ◽  
S. I. Yum
Keyword(s):  
Silicone Rubber ◽  
Hoop Stress ◽  
Control Flow ◽  
Low Flow ◽  
Rubber Tubing ◽  
Flow Rates ◽  
Fluid Delivery ◽  
Elastomeric Materials ◽  
Stable Flow

Abstract When drugs are infused, it is often necessary to minimize the volume of fluid delivered. Fluid delivery rates of 1 cm3/h or less are frequently desirable; however, the accurate metering of fluids at such low flow rates to the human body has been difficult to accomplish. The metering devices most commonly used to control flow rate from a constant-pressure source have been micrometer valves, clamped tubes, capillaries, and porous plugs. Each of these devices has specific disadvantages : micrometer valves are expensive and bulky, clamped tubes are not stable for long-term infusion and present a hazard of greatly fluctuating flow rates, capillary tubes are subject to particle blockage and are not adjustable, and porous plugs suffer from lack of adjustability. Recently a valve made of extruded silicone rubber rod with axial holes was reported to yield stable flow rates; it was adjusted by placement in a plastic clamp. A new low-infusion-rate metering system has been developed to overcome the above deficiencies. This system consists of axially aligned polyurethane fibers contained within the lumen of a length of silicone rubber tubing. The fibers fill the lumen to the extent that they are subjected to a compressive hoop stress by the tubing. The assembly represents two elastomeric materials in states of strain, exerting equal and opposite stresses on each other. The elastomeric tubular assembly is contained in a rigid, adjustable, U-shaped enclosure that controls the deformation of the assembly. While other elastomeric materials would be suitable for the elastomeric valving system, we report here on our experience with polyurethane fibers and silicone rubber tubing. These materials were selected for their expected compatibility with most aqueous drugs and their availability.

scholarly journals A new instrument to measure plot-scale runoff

2014 ◽  
Vol 4 (2) ◽  
pp. 589-608 ◽  
Author(s):  
R. D. Stewart ◽  
Z. Liu ◽  
D. E. Rupp ◽  
C. W. Higgins ◽  
J. S. Selker
Keyword(s):  
Water Level ◽  
Surface Runoff ◽  
Large Scale ◽  
Multiple Scales ◽  
Low Cost ◽  
Low Flow ◽  
Flow Rates ◽  
New Instrument ◽  
Water Level Measurements

Abstract. Accurate measurement of the amount and timing of surface runoff at multiple scales is needed to understand fundamental hydrological processes. At the plot-scale (i.e., length scales on the order of 1 to 10 m) current methods for direct measurement of runoff either store the water in a collection vessel, which is unconducive to long-term monitoring studies, or utilize expensive installations such as large-scale tipping buckets or flume/weir systems. We developed an alternative low-cost, robust and reliable instrument to measure runoff that we call the "Upwelling Bernoulli Tube" (UBeTube). The UBeTube instrument is a pipe with a slot machined in its side that is installed vertically at the base of a runoff collection system. The flow rate through the slot is inferred by measuring the water height within the pipe. The geometry of the slot can be modified to suit the range of flow rates expected for a given site; we demonstrate a slot geometry which is capable of measuring flow rates across more than three orders of magnitude (up to 300 L min−1) while requiring only 30 cm of hydraulic head. System accuracy is dependent on both the geometry of the slot and the accuracy of the water level measurements. With an off-the-shelf pressure transducer sensor, the mean theoretical error for the demonstrated slot geometry was ~17% (ranging from errors of more than 50% at low flow rates to less than 2% at high flow rates), while the observed error during validation was 1–25%. A simple correction factor reduced this mean error to −14%, and further reductions in error could be achieved through the use of taller, narrower slot dimensions (which requires greater head gradients to drive flow) or through more accurate water level measurements. The UBeTube device has been successfully employed in a long-term rainfall-runoff study, demonstrating the ability of the instrument to measure surface runoff across a range of flows and conditions.

Optimizing the Design of Unbonded Flexible Pipelines With More Realistic Predictions of pH and H2S Content in the Annulus

2017 ◽  
Author(s):  
Li Ke ◽  
Carol Taravel-Condat ◽  
Jean Kittel ◽  
Rémy Mingant ◽  
Claude Duret-Thual ◽  
...  
Keyword(s):  
Ph Monitoring ◽  
Stationary Phases ◽  
Oil Field ◽  
Low Flow ◽  
Small Scale ◽  
Flow Rates ◽  
Dissolved Iron ◽  
Flexible Pipes ◽  
Steel Grades

Due to its high metallic confinement, the annulus of unbonded flexible pipelines is a specific and mild corrosive medium for carbon steel armour wires. This environment presents high supersaturation levels of dissolved iron, leading to pH values far above thermodynamic equilibrium. Furthermore, the permeation of acidic gases (such as CO2 and H2S) through the polymer pressure sheath occurs at very low flow rates. Since the annulus is supersaturated with dissolved iron, part of the H2S is consumed as it slowly arrives into the annulus. Therefore, the annular medium contains low levels of gas far below those predicted by standard thermodynamic models, and less H2S is available to trigger sour cracking. The recent development of harsher oil field conditions (higher water depths, increased CO2 content, presence of H2S...) induced the need to refine the design of flexible pipes to propose more cost effective solutions. As pH and H2S content are key parameters for the selection of steel grades, taking into account the supersaturation and the H2S consumption in the annulus allows major optimization of flexible pipes by using for instance steel grades with higher strength. Therefore, extensive experimental work was conducted over the past years to better characterize the annulus and predict more realistic pH and H2S levels. In this paper, the following developments are presented: – A kinetic corrosion model named FlexCor was derived from numerous corrosion tests done at various CO2 pressures in confined configuration, with in-situ pH monitoring. These tests were performed over long durations (3 months) in order to capture the effective long term supersaturated pH. The kinetic model is able to simulate the transient and stationary phases of the supersaturated pH evolution up to 45 bara of CO2, providing a good fit with the experimental data. The tests also demonstrated that the annulus environment remains supersaturated even at high CO2 partial pressures. – A methodology taking into account the H2S consumption was developed based on extensive long-term small scale and full scale testing (> 2 years), where low flow rates of H2S were imposed. The experimental results show that H2S consumption is far from negligible, even when the annulus is not fully flooded. This H2S consumption methodology was certified by an Independent Verification Agency and is now being applied on commercial projects.

Design and Application of Low Flow Steam Siphon Jet Pumps

2016 ◽  
Author(s):  
Robert A. Leishear ◽  
William M. Bennett ◽  
Jackie Cooper
Keyword(s):  
Experimental Data ◽  
Specific Gravity ◽  
Closed Form ◽  
Steam Pressure ◽  
Control Flow ◽  
Low Flow ◽  
Jet Pump ◽  
Pump Design ◽  
Flow Rates ◽  
Jet Pumps

Low flow steam siphon jet pumps are referred to as rate jets, since these pumps have the ability to control flow rates by varying the steam pressure applied to the jet. The jet pump design consists of several components. Steam inlet piping is connected to a steam nozzle that directs steam into the jet body to provide energy to lift a liquid, or feed. Feed is lifted up through the suction lift piping, where the condensing steam forces the liquid into a diffuser and out of the jet discharge piping. Closed form equations cannot model these jets, and commercial computer models to describe jet performance are still in a state of development. In general, experimental data is required to determine the performance characteristics of this type of jet design. Numerous tests were performed on different jet designs to evaluate the effects of motive steam pressures, suction lift, discharge head, jet dimensions, and the specific gravity of the fluid that is lifted and pumped by the jet. Additionally, the system installation significantly affects the performance of siphon jets, and one such installation was studied.

scholarly journals A new instrument to measure plot-scale runoff

2015 ◽  
Vol 4 (1) ◽  
pp. 57-64 ◽  
Author(s):  
R. D. Stewart ◽  
Z. Liu ◽  
D. E. Rupp ◽  
C. W. Higgins ◽  
J. S. Selker
Keyword(s):  
Water Level ◽  
Surface Runoff ◽  
Large Scale ◽  
Multiple Scales ◽  
Low Cost ◽  
Low Flow ◽  
Flow Rates ◽  
New Instrument ◽  
Water Level Measurements

Abstract. Accurate measurement of the amount and timing of surface runoff at multiple scales is needed to understand fundamental hydrological processes. At the plot scale (i.e., length scales on the order of 1–10 m) current methods for direct measurement of runoff either store the water in a collection vessel, which is not conducive to long-term monitoring studies, or utilize expensive installations such as large-scale tipping buckets or flume/weir systems. We developed an alternative low-cost, robust and reliable instrument to measure runoff that we call the "Upwelling Bernoulli Tube" (UBeTube). The UBeTube instrument is a pipe with a slot machined in its side that is installed vertically at the base of a runoff collection system. The flow rate through the slot is inferred by measuring the water height within the pipe. The geometry of the slot can be modified to suit the range of flow rates expected for a given site; we demonstrate a slot geometry that is capable of measuring flow rates across more than 3 orders of magnitude (up to 300 L min−1) while requiring only 30 cm of hydraulic head. System accuracy is dependent on both the geometry of the slot and the accuracy of the water level measurements. Using a pressure sensor with ±7 mm accuracy, the mean theoretical error for the demonstrated slot geometry was ~17% (ranging from errors of more than 50% at low flow rates to less than 2% at high flow rates), while the observed error during validation was 1–25%. A simple correction factor reduced this mean error to 0–14%, and further reductions in error could be achieved through the use of taller, narrower slot dimensions (which requires greater head gradients to drive flow) or through more accurate water level measurements. The UBeTube device has been successfully employed in a long-term rainfall-runoff study, demonstrating the ability of the instrument to measure surface runoff across a range of flows and conditions.

Modelling of Waste Form Performance and System Release

1984 ◽  
Vol 44 ◽  
Author(s):  
Aaron Barkatt ◽  
Pedro B. Macedo ◽  
Barbara C. Gibson ◽  
Charles J. Montrose
Keyword(s):  
Aqueous Medium ◽  
High Flow ◽  
Waste Glass ◽  
Waste Form ◽  
Low Flow ◽  
Matrix Elements ◽  
Release Rates ◽  
Flow Rates ◽  
Quantitative Calculations

AbstractKinetic and thermodynamic approaches to the derivation of long-term release rates of species from defense waste glass are reviewed. It is concluded that at high flow rates kinetic factors are pre-dominant, while at low flow rates saturation of the aqueous medium with respect to major matrix elements, particularly with respect to silica present in the glass and in its alteration products, becomes a controlling factor. Quantitative calculations indicate that under likely repository conditions the release rates can be expected, in general, to fall below the NRC criterion of 10−5 yr−1.

951: “Experience in the Treatment of Low Flow Priapism”; A Novel, Easy and Effective Technique: A Long-Term, Binational, Multi-Institutional Study in 18 Patients Over 8 Years

2007 ◽  
Vol 177 (4S) ◽  
pp. 314-315
Author(s):  
Jose A. Medina Machuca ◽  
Jose A. Medina Coello ◽  
Hugo Manzanilla ◽  
Francisco A. Gutierrez
Keyword(s):  
Low Flow ◽  
Effective Technique

Biomedical Materials to Repair Retinal Detachments

1985 ◽  
Vol 55 ◽  
Author(s):  
Miguel F. Refojo
Keyword(s):  
Retinal Detachment ◽  
Silicone Rubber ◽  
Methyl Acrylate ◽  
Silicone Oil ◽  
Vitreous Body ◽  
Light Sensitivity ◽  
Scleral Buckling ◽  
Intraocular Injection ◽  
Other Substances

ABSTRACTImplants are essential for the repair of retinal detachments. The implant buckles the wall of the eye and apposes the detached retina with the choroid, thus restoring light sensitivity to the retina. The scleral buckling also relieves traction on the retina from a shrinking vitreous body. The implant materials most commonly used are solid silicone rubber and silicone sponges, but both types have some disadvantages. A poly(hydroxyethyl acrylate-co-methyl acrylate) hydrogel implant with improved properties of softness and antibiotic absorption is also available for retinal detachment surgery. Proliferative vitreoretinopathy involves various conditions of retinal detachment complicated by vitreous fibrosis, which, after vitrectomy, may be treated with intraocular injection of fluids that support the retina against the choroid. For conditions requiring a long-term implant, silicone oil although controversial is the material of choice. Many other substances have been investigated but none better has yet been found.

Monitoring Effects of Catchment Management Practices on Phosphorus Loads into the Eutrophic Peel-Harvey Estuary, Western Australia

1986 ◽  
Vol 18 (4-5) ◽  
pp. 53-61 ◽  
Author(s):  
P. B. Birch ◽  
G. G. Forbes ◽  
N. J. Schofield
Keyword(s):  
Management Practices ◽  
Major Change ◽  
High Flow ◽  
Catchment Management ◽  
Flow Rates ◽  
Early Results ◽  
Phosphorus Loads ◽  
Time Of Year ◽  
High Runoff

Early results from monitoring runoff suggest that the programme to reduce application of superphosphate to farmlands in surrounding catchments has been successful in reducing input of phosphorus to the eutrophic Peel-Harvey estuary. In the estuary this phosphorus fertilizes algae which grow in abundance and accumulate and pollute once clean beaches. The success of the programme has been judged from application of an empirical statistical model, which was derived from 6 years of data from the Harvey Estuary catchment prior to a major change in fertilizer practices in 1984. The model relates concentration of phosphorus with rate of flow and time of year. High phosphorus concentrations were associated with high flow rates and with flows early in the high runoff season (May-July). The model predicted that the distribution of flows in 1984 should have resulted in a flow-weighted concentration of phosphorus near the long-term average; the observed concentration was 25% below the long-term average. This means that the amount of phosphorus discharged into the Harvey Estuary could have been about 2 5% less than expected from the volume of runoff which occurred. However several more years of data are required to confirm this trend.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

Sign in / Sign up

Export Citation Format

Share Document