Dual Valve Research Articles

Clinical event rates with the On-X bileaflet mechanical heart valve: A multicenter experience with follow-up to 12 years

The aim of the study was to establish clinical event rates for the On-X bileaflet mechanical heart valve (On-X Life Technologies Inc, Austin, Tex) using an audit of data from the 3 centers within Europe with the longest history of implanting. All patients receiving the On-X valve between March 1, 1998, and June 30, 2009, at 3 European centers were studied. Data were collected using questionnaire and telephone surveys augmented by outpatient visits and examination of clinical records. There were 691 patients, with a mean age of 60.3 years, who received 761 valves in total: 407 mitral valve replacements, 214 aortic valve replacements, and 70 aortic + mitral valve replacements (dual valve replacement). Total follow-up was 3595 patient-years, with a mean of 5.2 years (range, 0-12.6 years). Early (≤ 30 days) mortality was 5.4% (mitral valve replacement), 0.9% (aortic valve replacement), and 4.3% (dual valve replacement). Linearized late (>30 days) mortality expressed per patient-year was 3.6% (mitral valve replacement), 2.2% (aortic valve replacement), and 4.1% (dual valve replacement), of which valve-related mortality was 0.5% (mitral valve replacement), 0.2% (aortic valve replacement), and 1.8% (dual valve replacement). Late linearized thromboembolism rates were 1.0% (mitral valve replacement), 0.6% (aortic valve replacement), 1.8% (dual valve replacement). Bleeding rates were 1.0% (mitral valve replacement), 0.4% (aortic valve replacement), and 0.9% (dual valve replacement). Thrombosis rates were 0.1% (mitral valve replacement), 0% (aortic valve replacement), and 0.3% (dual valve replacement). Reoperation rates were 0.6% (mitral valve replacement), 0.2% (aortic valve replacement), and 1.2% (dual valve replacement). The On-X valve has low adverse clinical event rates in longer-term follow-up (mean 5.2 years and maximum 12.6 years).

Design and Experimental Study a Logging Instrument with Dual Channel and Two-Way Hydraulic Control Valve

The paper introduces the working principle of a logging instrument, and according to the working principle and instrument’s function of two-way hydraulic control valve. Facing to the key problems of process equipment in the actual service and workflow, the structure of value was designed and optimized. At the same time, the logging instrument with a dual-channel and two-way hydraulic control valve is designed and processed. Meanwhile, we build an experimental platform and make the experiment according to principle of the instrument. The results show that the design of this dual-channel and two-way hydraulic control valve logging instrument met the work requirements, and it has high reliability in oil exploration, which could be promoted and used in logging areas.

Improvement of temperature accuracy in oil cooler systems with gas bypass

In keeping with the development of machine tools with higher speed, more axes, and a greater degree of sophistication, thermal deformation is becoming an important factor in the precision of machine tools. It has been found that thermal error accounts for about 70% of the total error in machine tools. As such, oil coolers which absorb heat from heat generating parts with cold oil are being used to reduce the error caused by thermal deformation. The gas bypass type oil coolers used in ultra-precision (temperature accuracy within ±0.1°C) machine tools are simple in structure and precise in terms of their temperature control performance; however, they have a limitation as regards temperature control due to the instability of their performance under light load conditions. In this study, an oil cooler system equipped with dual electronic valves was developed to solve the problems of the single electronic valve system and achieve more precise temperature control. To verify the performance of the developed system, its performance under the operating conditions of rated load, DIN 8602 standard, and ISO/DIS 230-3 operational mode was compared and analyzed. The proposed oil cooler system is applicable to semiconductor equipment, ultra-precision injection molds, and ultra-precision machine tools, and improves the quality of the products.

New valve-mechanical model of urinary tract function: the theory of biological dual valves.

IntroductionUntil now, peristalsis has been the only known method of urine transport. The main objective of this paper was to study urinary tract function – especially the upper urinary tract, the ureter – from a new mechanical point of view. The physical (physical dual valves) and biological basis (biological dual valves) of a new functional model is presented based on previous observations and knowledge.MethodsA review of the literature was performed, with special emphasis on ureter motility.ResultsAfter analyzing the anatomy and physiology of the urinary tract, complemented by basic physical observations, the authors have developed a new valve-mechanical model of urinary tract function. A comprehensive mechanical hypothesis is also presented, integrating the role of peristalsis.ConclusionsThe authors believe that the new theory enhances previous knowledge. From a structural point of view, the urinary tract may be considered to consist of dualvalves. The dual-valve mechanism combined with peristalsis allows better explanation of the function of the upper urinary tract in particular. The main conclusion is that the flow in the urinary tract must be studied integrally within the body. This new theory does not contradict well-known and acknowledged theories, and moreover, it may help solve certain medical problems.

Permanent Pacemaker Implantation Following Aortic Valve Replacement: Current Prevalence and Clinical Predictors

The incidence of conduction disease requiring permanent pacemaker (PPM) implantation following aortic valve replacement (AVR) ranges from 3% to 6%. Data concerning the potential risks for PPM requirement associated with certain valve types have been conflicting and controversial. We sought to evaluate the prevalence, predictors for PPM implantation, and PPM dependency during follow-up in patients undergoing AVR. A total of 214 consecutive patients undergoing AVR were studied retrospectively. A total of 207 patients were included in the statistical analysis. Clinical variables including valve size and types were catalogued and the incidence of PPM evaluated. Cardiac rhythm device clinic records were examined and PPM dependency status was catalogued. Multivariate analyses were performed to determine predictors of PPM implantation and PPM dependency during follow-up. Fifteen patients (7.2%) required PPM postoperatively. After controlling for clinical and surgical characteristics, predictors for PPM included preoperative first-degree atrioventricular block with and without left anterior fascicular block or intraventricular conduction delay [odd ratios (OR) = 12.5, P = 0.001], cardiac arrest postoperatively (OR = 9.4, P = 0.012), and combined aortic and mitral valve surgery (OR = 11.5, P = 0.027). Aortic valve types did not predict complete heart block (CHB) and PPM implantation. Of those patients who underwent PPM implantation, 70% were classified as PPM dependent during long-term follow-up. CHB and PPM implantation continue to be common complications of AVR. Preexisting atrioventricular with intrafascicular or intraventricular conduction disease along with cardiac arrest and dual valve surgery are the most important significant predictors of PPM implantation and PPM dependency during follow-up. The selection of valve types did not predict conduction disease requiring PPM implantation.

INVESTIGATION OF LOW END TORQUE DIP PROBLEM OF CAMPRO 1.6L ENGINE

The main objective of this work is to perform an extensive study on the causes of the torque dip in CAMPRO engine and subsequently to provide the best solution that will improve the performance, reliability as well as production cost. CAMPRO engine is a basic Double Overhead Camshaft (DOHC) which has a capacity of 1597 cc and installed with a total of 16 valves developed by Malaysian car manufacturer PROTON in the year 2000.The CAMPRO engine experiences performance downfall when it reaches at certain rpm. The phenomenon is known as torque dip or torque loss where the output torque is not smooth, consequently formed a dip in the torque curve. The dip which occurs at 2500 – 3500 rpm is mainly influenced by the geometry of the designed intake manifold and valve timing. Analysis is mostly confined on the intake manifold geometry and the valve timing. Two possible solutions viz., dual length intake manifold and variable valve timing are analyzed.

Modeling Fresh Air Charge and Residual Gas Fraction on a Dual Independent Variable Valve Timing SI Engine

Modeling Fresh Air Charge and Residual Gas Fraction on a Dual Independent Variable Valve Timing SI Engine

Dual seal valve

Dual seal valve

Intermediate Results After a Modified Yasui Procedure With the Lecompte Maneuver

Three patients with ventricular septal defect, obstructed aortic arch, and valvular aortic stenosis underwent a modification of the Yasui procedure (the Norwood type aortic reconstruction, intraventricular rerouting from the left ventricle to the dual arterial valves, and reconstruction of the right ventricular outflow tract by the Lecompte maneuver). With a follow-up of up to 60 months, the outcome is excellent without progressive lesions or reoperation.

Surface-Micromachined Parylene Dual Valves for On-Chip Unpowered Microflow Regulation

This paper presents the world's first surface-micromachined parylene dual-valved microfluidic system for on-chip unpowered microflow regulation. Incorporating a normally closed and a normally open passive check valve in a back-to-back configuration inside a microchannel, the dual-valved system has successfully regulated the pressure/flow rate of air and liquid without power consumption or electronic/magnetic/thermal transduction. By exclusively using parylene C (poly-para-xylylene C) as the structural material, the fabricated valves have higher flexibility to shunt flows in comparison to other conventional thin-film valves. A state-of-the-art multilayer polymer surface-micromachining technology is applied here to fabricate parylene microvalves of various designs. The parylene-based devices are completely biocompatible/implantable and provide an economical paradigm for fluidic control in integrated lab-on-a-chip systems. Design, fabrication, and characterization of the parylene dual valves are discussed in this paper. Testing results have successfully demonstrated that the microflow regulation of the on-chip dual-valved system can achieve a bandpass profile in which the pressure control range is 0-50 mmHg with corresponding flow rates up to 2 mL/min for air flow and 1 muL/min flow rate for water flow. This regulation range is suitable for controlling biological conditions in human health care, with potential applications including drug delivery and regulation of elevated intraocular pressure (IOP) in glaucoma patients

Inactivation of Staphylococcus spp. strains in whole milk and orange juice using ultra high pressure homogenisation at inlet temperatures of 6 and 20 °C

The objective of this work was to evaluate the inactivation induced by ultra high pressure homogenisation (UHPH) of Staphylococcus aureus ATCC 13565 and Staphylococcus carnosus CECT 4491 inoculated into milk and orange juice considering the effect of inlet temperature of the sample (6 and 20 °C) on the lethality values and on the production of sublethal injuries. Samples of UHT whole milk and UHT orange juice were inoculated at a concentration of approximately 7.0 log (CFU/ml) and pressurized with a dual valve UHPH machine at 300 MPa at the primary homogenising valve and at 30 MPa on the secondary valve. Viable and injured bacterial counts were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 °C for milk, and after 3, 6, 9, 12, and 15 days of storage at 4 °C for orange juice. The inlet temperature, the food matrix and the kind of strain influenced significantly ( P < 0.05) the lethality level, which was higher for S. aureus in whole milk at an inlet temperature of 20 °C. No sublethal injuries were detected after treatments. The change over time of viable counts for both strains showed a very strong decreasing tendency during the storage at 4 °C for orange juice, while the strain S. carnosus showed a low decreasing tendency and greater resistance when inoculated in milk and pressurized at 6 °C.

병렬구조의 압력측정 시스템 개발

In this paper, we developed a pressure measurement apparatus with the parallel structure to improve the measurement efficiency of pressure sensors by reducing the measurement time of pressure. The developed system has two parallel positions for loading Silicon pressure sensor and has a dual valve structure. The semiconductor pressure sensors prepared by Copal Electronics were used to confirm the performance of the developed measurement system. Two stage differential amplifier circuit was employed to amplify the weak output signal and the amplified output signal was improved utilizing a low-pass filter. New apparatus shows the measurement time of pressure two times shorter than that of conventional one with the serial structure, while both structures show the similar linear output versus pressure characteristics.

FLATNESS BASED CONTROL OF A DUAL COIL SOLENOID VALVE

This paper presents first results in the attempt to control a dual coil solenoid valve by means of a flatness based approach. First the modeling effort is described, then the differential flatness of the system is shown. The modeling results revealed that the system lacks controllability, when considering one coil only for actuating the valve. Therefore a suitable strategy for energizing both coils has been developed. The flatness property then is used to design feasible reference trajectories for the spool motion with the following properties: soft-landing of the spool, minimal driving current, feasible subject to voltage constraints. Simulation results demonstrate the usefulness and robustness of the approach.

Design and characterization of late-mixing flash pyrolytic reactor molecular-beam source

We report on the design and characterization of an intense pulsed beam source for the generation of expansion-cooled radical species. The source combines both dual pulsed valve late mixing for coexpansion of reactive gases with a pyrolytic end nozzle as a flash kinetic reactor. As a demonstration of the source we present evidence of BrO and ClO radical production and subsequent photodissociation studies of these species using velocity map ion imaging. The radicals are characterized by a rotational temperature of 150±40K although substantially lower temperatures should be possible.

417 クリーンルームへの水噴霧加湿の性能評価 : 噴霧ノズルの位置が室内湿度分布に及ぼす影響(環境数値シミュレーションI,環境保全型エネルギー技術)

Direct humidification using compressed air atomizer is one of the conventional methods at printing factory. Atomized water removes heat from air when it evaporates so it contributes to both heating and cooling cost. We have improved the control system that can keep the humidity constant using dual control valves. When the humidification system is being applied to existing factory, the examination of setting-up interval of atomizers is needed to uniformity the humidity in clean room. In this study, we tried to estimate the distribution of humidity using simulation of CFD.

Successful treatment of a lifesite hemodialysis access system pocket infection with large-volume kanamycin solution irrigation

Bridge devices—dialysis catheters and subcutaneous access devices—play a critical role in increasing the placement of arteriovenous (AV) fistulas by providing hemodialysis vascular access while AV fistulas mature. The LifeSite Hemodialysis Access System (Vasca Inc, Tewskburg, MA), a fully implantable, subcutaneous dual valve access system, has been shown to have lower complication rates, higher blood flow rates, and better long-term device survival than conventional tunneled hemodialysis catheters, indicating it may better meet the requirements for optimally bridging to a fistula. This case study of a 48-year-old black man undergoing chronic hemodialysis for renal failure because of insulin-dependent diabetes describes a simple approach for resolving localized pocket infections associated with the LifeSite System by drip irrigation of the valves and tissue pockets with an antibiotic solution. Eight weeks after implantation of the LifeSite System, the patient exhibited symptoms of infection of the lateral LifeSite valve tissue pocket, which on culture was shown to be caused by Staphylococcus aureus. Flushing the LifeSite valve and tissue pocket with a large volume of kanamycin solution, in conjunction with intravenous vancomycin and routine irrigation of the valve with isopropyl alcohol, resolved the infection after 1 treatment. The LifeSite System successfully bridged the patient to a transposed basilic vein fistula created through a 2-stage surgical procedure. The LifeSite System provided uninterrupted access for hemodialysis over a period of 6 months while the fistula matured. The LifeSite System should allow surgeons to attempt fistula construction in more patients, including diabetics, access-challenged patients, and patients with small vessels, who may benefit from a nontraditional surgical approach toward fistula creation.

Development of an automated in-line microfiltration system coupled to an HPLC for the determination of solubility.

An automated in-line microfiltration system coupled to an HPLC was developed for the determination of solubility. Filtrations and subsequent solubility determinations are performed using a standard Gilson dilutor and autosampler and dual Rheodyne valves equipped with a filtration assembly and configured to an HPLC system. The solubility data obtained using the automated in-line microfiltration system are in good agreement with the results obtained using conventional manual preparation techniques. Automating this labor-intensive and often variable portion of the solubility determination provides a reliable means of improving both the consistency and quality of solubility data.

Conformation and stability of the hydrogen-bonded complex 6-oxabicyclo

The hydrogen-bonded complex between 6-oxabicyclo[3.1.0]hexane and hydrogen chloride was investigated by microwave spectroscopy in a supersonic jet. A dual flow pulsed valve was used to preclude chemical reaction between the monomers. Only the equatorial conformer was observed and the spectra of three isotopomers, (C5H8O, H35Cl), (C5H8O, H37Cl) and (C5H8O, D35Cl), were measured. The derived structure of the complex has Cs symmetry with the hydrogen chloride pointing to the domain of the equatorial lone pair of electrons at the oxygen atom. The three atoms involved in the hydrogen bond adopt a bent arrangement with a O...H distance of 1.77(4) A, a (O...H-Cl) angle of 115(4)degrees, and a deviation of 15.4(14)degrees of the hydrogen bond from collinearity. In agreement with the experimental results, ab initio calculations predict the equatorial form to be the most stable one.

Optimization of Solid-Phase Microextraction (SPME) for the Recovery of Explosives from Aqueous and Post-Explosion Debris Followed by Gas and Liquid Chromatographic Analysis

Solid-phase microextraction (SPME) has been evaluated for the recovery of explosives residues from aqueous samples and real post-explosion solid debris samples and optimized using gas chromatography with an electron capture detector (GC-ECD) and high-performance liquid chromatography with ultraviolet detection (HPLC-UV). A modified SPME/HPLC interface utilizing dual six-port valves allowed for independent optimization of SPME desorption and injection variables that provided improved chromatographic resolution and sensitivity. A unique combination of cyano and octadecyl columns resulted in the complete separation of the 14 explosives in EPA method 8330 mixture using HPLC with good quantitative results. At the optimum SPME conditions, the limits of detection (LOD) were found to be of 5 ng/mL to 16 ng/mL of explosives in water and 10 microg/kg to 40 microg/kg of explosives from soil. The technique has been successfully applied to the analysis of real post-explosion debris and can be adapted for use in the field utilizing portable chromatographic instruments.

Temperature-responsive permeability of porous PNIPAAm-g-PE membranes

Grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), onto porous polyethylene (PE) membranes by UV irradiation was investigated. A wide range of graft yields (5–449%) was achieved by varying irradiation time (20–240 min) and monomer concentration (1.2–3.6 wt %). Characterization by XPS and SEM shows that the graft polymers are located both on the external surfaces as well as inside the pores of the membranes. Diffusional permeation experiments show that two distinct types of temperature responses were observed, depending on the graft yield; permeability increases with temperature in low graft yield membranes, while permeability decreases with temperature in high graft yield membranes. A mechanism explaining the dual valve functions of the graft membrane is proposed based on the location of the graft polymers on the membrane. It was also observed the permeability response exhibits a maximum with permeant molecular weight. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2133–2142, 1998