Valve Movement Research Articles

Asymmetry in the jet opening: underwater jet vectoring mechanism by dragonfly larvae

Aquatic Anisopteran dragonfly larvae achieve respiration and propulsion by repetitive water jets flowing through their anal openings. Previous studies have shown that the tri-leaflet anal valves modulate the emerging jet by varying the opening size. We discovered that the valves are also capable of controlling the opening asymmetry by independent retraction of a leaflet. This study shows the effects of their valve asymmetry control on the respiratory and propulsive flows. Furthermore, the effects of size variation are re-evaluated using fluid momentum and power equations. Synchronized dual cameras recorded the valve movement and the flow generated by Aeshnidae sp. During the respiratory jetting, retraction of a single leaflet positions the opening in an off-centred locale, from which diagonally deflected jets emerge. The resulting flow field, together with the opening size modulation, implicates a reduction in the reinhalation of the exhaled jet and partial powering of the refilling process. Instead, during the propulsive jetting, concurrent partial retraction of the three leaflets results in the centred opening. The resulting jet flows straight, which has an implication for lowering form drag. Additionally, the propulsive aperture size control suggests improved thrust production. Our study highlights the significant influence that an asymmetrically positioned jet opening can have on biological jet flow. The findings inspire a new mechanism for jet vectoring that may prove useful for application in the broader engineering field.

Quantifying salinity and season effects on eastern oyster clearance and oxygen consumption rates

There are few data on Crassostrea virginica physiological rates across the range of salinities and temperatures to which they are regularly exposed, and this limits the applicability of growth and production models using these data. The objectives of this study were to quantify, in winter (17 °C) and summer (27 °C), the clearance and oxygen consumption rates of C. virginica from Louisiana across a range of salinities typical of the region (3, 6, 9, 15 and 25). Salinity and season (temperature and reproduction) affected C. virginica physiology differently; salinity impacted clearance rates with reduced feeding rates at low salinities, while season had a strong effect on respiration rates. Highest clearance rates were found at salinities of 9–25, with reductions ranging from 50 to 80 and 90 to 95% at salinities of 6 and 3, respectively. Oxygen consumption rates in summer were four times higher than in winter. Oxygen consumption rates were within a narrow range and similar among salinities in winter, but varied greatly among individuals and salinities in summer. This likely reflected varying stages of gonad development. Valve movements measured at the five salinities indicated oysters were open 50–60% of the time in the 6–25 salinity range and ~ 30% at a salinity of 3. Reduced opening periods, concomitant with narrower valve gap amplitudes, are in accord with the limited feeding at the lowest salinity (3). These data indicate the need for increased focus on experimental determination of optimal ranges and thresholds to better quantify oyster population responses to environmental changes.

A New 2D Echocardiographic Approach to Evaluate the Membrane and Valve Movement of the Berlin Heart EXCOR VAD Chamber in Pediatric VAD Patients.

The use of Berlin Heart EXCOR VAD (BH) is a validated therapy to bridge pediatric patients to heart transplant. Serial echocardiographic (ECHO) assessment of VAD patients is necessary to support patients' management. This work aims at developing an innovative strategy to evaluate the BH device functioning by ECHO and its interaction with the native heart in a pediatric population. ECHO evaluation of BH membrane movement, and inflow and outflow valves was performed in 2D, 2D-color Doppler, M-mode, and M-mode color Doppler to assess the functioning of the device by direct positioning of the ECHO probe on the BH cannulas and membranes. Forty Berlin Heart EXCOR VAD were analyzed in 18 patients. Seven BH were placed as RVAD and 33 as LVAD. Results evidenced that 14 (21) inflow (outflow) valves presented a mild regurgitation, while 5 inflow (3 outflow) valves presented a moderate regurgitation. In three cases, we observed severe valve regurgitation with back flow in the left ventricle/right atrium. In both cases, the BH chambers were substituted, but we observed that in one case the regurgitation was due to cannulas compression, while in the other case it was due to valve malfunctioning. The M-mode and the ECHO of the membranes and valves permitted to appreciate the beat phenomenon to assess if the native heart and the BH are working in opposite or in the same phase. The membrane ECHO permits evaluation of minimal changes in membrane movement to assure the completely empty-completely fully work modality. Systematic ECHO assessment of BH chamber might support the BH programming and the detection of anomalous VAD-heart interaction.

Actuator stiction compensation via variable amplitude pulses

A novel model free stiction compensation scheme is developed which eliminates the oscillations and also reduces valve movement, allowing good setpoint tracking and disturbance rejection. Pulses with varying amplitude are added to the controller output to overcome stiction and when the error becomes smaller than a specified limit, the compensation ceases and remains in a standby mode. The compensation re-starts as soon as the error exceeds the user specified threshold. The ability to cope with uncertainty in friction is a feature achieved by the use of pulses of varying amplitude. The algorithm has been evaluated via simulation and by application on an industrial DCS system interfaced to a pilot scale process with features identical to those found in industry including a valve positioner.

Effects of intake and exhaust valve timing on the performance of an air‐powered rotary engine

This work is aimed at improving the performance of the air‐powered rotary engine. A dynamic simulation model which includes an eccentric motion and rotary valve movement was established by our particle image velocimetry (PIV) experimental data. Then the power and specific steam consumption (SSC) was evaluated. The pressure distribution in the chamber was obtained which was difficult to obtain through experiment. Simulation results showed that for the work process and pressure distribution, the intake valve timing mainly affected the intake expansion stage (A2) and pure expansion stage (B). Due to this, a relatively low pressure was distributed in the middle of the chamber and this was beneficial to the intake and work processes. The exhaust valve timing mainly affected the exhaust stage (C) and initial intake stage (A1). Therefore, a relatively high pressure which was distributed in the middle‐rear of the chamber was beneficial to the exhaust processes. For the power and SSC, the power increased initially then decreased and the SSC decreased with the increase of intake advance angle respectively. Both the power and the SSC increased with the increase of intake duration angle. The power increased while the SSC decreased with the increase of exhaust advance angle. The power increased and the SSC decreased initially then increased with the increase of exhaust duration angle. The preferred parameters were found to be 30° CA, 240° CA, 30° CA, and 280° CA. These improved parameters had a 2.7% increase in the power and also a 2.4% decrease in the SSC. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1462–1474, 2018

Shell Valve Movement of Pacific Oysters, Crassostrea gigas, in Response to Low Salinity Water

Shell Valve Movement of Pacific Oysters, Crassostrea gigas, in Response to Low Salinity Water

The sense of hearing in the Pacific oyster, Magallana gigas.

There is an increasing concern that anthropogenic noise could have a significant impact on the marine environment, but there is still insufficient data for most invertebrates. What do they perceive? We investigated this question in oysters Magallana gigas (Crassostrea gigas) using pure tone exposures, accelerometer fixed on the oyster shell and hydrophone in the water column. Groups of 16 oysters were exposed to quantifiable waterborne sinusoidal sounds in the range of 10 Hz to 20 kHz at various acoustic energies. The experiment was conducted in running seawater using an experimental flume equipped with suspended loudspeakers. The sensitivity of the oysters was measured by recording their valve movements by high-frequency noninvasive valvometry. The tests were 3 min tone exposures including a 70 sec fade-in period. Three endpoints were analysed: the ratio of responding individuals in the group, the resulting changes of valve opening amplitude and the response latency. At high enough acoustic energy, oysters transiently closed their valves in response to frequencies in the range of 10 to <1000 Hz, with maximum sensitivity from 10 to 200 Hz. The minimum acoustic energy required to elicit a response was 0.02 m∙s-2 at 122 dBrms re 1 μPa for frequencies ranging from 10 to 80 Hz. As a partial valve closure cannot be differentiated from a nociceptive response, it is very likely that oysters detect sounds at lower acoustic energy. The mechanism involved in sound detection and the ecological consequences are discussed.

Sensitivity analysis of the dynamic response of an electronic fuel injector regarding fuel properties and operating conditions

The sensitivity of fuel properties to the dynamic response (needle valve opening/closing delay and needle valve opening/closing time) of a electronic fuel injector was investigated. The fuel properties in different operating conditions were varied individually in bulk modulus, density and viscosity. Firstly, an electronic fuel injector model was built and validated by injection rate and injection mass at three different rail pressures and three different activation times. Secondly, a DOE (design of experiment) model was built and the Uniform Latin Hypercube (ULH) design method was applied to study the influences of the fuel properties on the injector dynamic response from a statistical point of view. The effects of the fuel properties were compared by using a SS-ANOVA (smoothing spline analysis of variance) method at both a low and a high rail pressure. The bulk modulus was found to play a dominant role in influencing the valve opening/closing delay at the low rail pressure. However, at the high rail pressure, the effects of the viscosity are prominent, while the effects of the bulk modulus and the density are negligible. Additionally, how these fuel properties affect the dynamic response were reported by RSM (Response Surface Method) function charts, and the details of the pressure differences and needle valve movements were also disclosed.

Mechanisms of ovipositor insertion and steering of a parasitic wasp

Drilling into solid substrates with slender beam-like structures is a mechanical challenge, but is regularly done by female parasitic wasps. The wasp inserts her ovipositor into solid substrates to deposit eggs in hosts, and even seems capable of steering the ovipositor while drilling. The ovipositor generally consists of three longitudinally connected valves that can slide along each other. Alternative valve movements have been hypothesized to be involved in ovipositor damage avoidance and steering during drilling. However, none of the hypotheses have been tested in vivo. We used 3D and 2D motion analysis to quantify the probing behavior of the fruit-fly parasitoid Diachasmimorpha longicaudata (Braconidae) at the levels of the ovipositor and its individual valves. We show that the wasps can steer and curve their ovipositors in any direction relative to their body axis. In a soft substrate, the ovipositors can be inserted without reciprocal motion of the valves. In a stiff substrate, such motions were always observed. This is in agreement with the damage avoidance hypothesis of insertion, as they presumably limit the overall net pushing force. Steering can be achieved by varying the asymmetry of the distal part of the ovipositor by protracting one valve set with respect to the other. Tip asymmetry is enhanced by curving of ventral elements in the absence of an opposing force, possibly due to pretension. Our findings deepen the knowledge of the functioning and evolution of the ovipositor in hymenopterans and may help to improve man-made steerable probes.

Does sustained tolerance of reduced salinity seawater alter phagocytosis efficiency in haemocytes of the blue mussel Mytilus edulis (L.)?

Climate change driven increases in precipitation and extreme weather events bring with them periodic introductions of large volumes of freshwater to coastal waters and the possibility of extended salinity reductions capable of challenging marine organisms living there. Mytilus edulis is an osmoconformer, with no physiological capacity to maintain its haemolymph osmolarity above that of a dilute seawater medium. These mussels can however tolerate reduced seawater salinity to some degree by using intracellular volume control mechanisms to extend the range of seawater salinity they can tolerate, allowing them to continue to feed, respire and maintain general cellular function in fluctuating salinity conditions. When M. edulis are exposed to a falling salinity gradient, a critical salinity is reached that triggers closure of the valves, isolating their internal tissues from the surrounding environment and protecting them from further osmotic stress. This study investigated whether sustained tolerance of M. edulis to seawater with salinity just higher than the threshold level for valve closure affected haemocyte phagocytosis efficiency. Phagocytosis by haemocytes plays a significant role in the immune system of M. edulis by removing foreign bodies such as invading micro-organisms, together with dead and dying cells from the haemolymph. Valve gaping behaviour was recorded continuously in mussels exposed to a reducing seawater salinity gradient to establish the critical level initiating valve closure. M. edulis were then held for 5d within a flow through seawater system at a salinity of 25, close to the trigger value for valve closure in the population of mussels investigated (Namsenfjord, Norway). The exposed mussels continued to hold their valves open and active throughout, though mean valve gape and movement between valves were generally lower than control mussels held at ambient seawater with salinity of 34.3. Post-exposure total haemocyte counts and haemolymph protein concentrations in exposed mussels were similar to the controls, while phagocytosis performance, measured using flow cytometry, improved in the reduced salinity exposed mussels. These findings support a conclusion that M. edulis have the physiological capacity to continue to irrigate their gills for at least 5days when held continuously at seawater salinity close to their valve closure trigger level without detriment to haemocyte phagocytosis efficiency, a key component of their immune-response system. Such a capability will be important in the event of increasing persistent reduced salinity episodes.

Valve movement of three species of North American freshwater mussels exposed to elevated carbon dioxide.

Freshwater mussels are at-risk taxa and may be exposed to high levels of carbon dioxide (CO2) because of the potential use of CO2 to control the movement of invasive aquatic fish species. One potential behavioral response to a change in the partial pressure of CO2 (pCO2) may be altered valve movement. In this study, three species of mussels were fitted with modified sensors and exposed to two regimes of pCO2 to define thresholds of impaired valve movement. The first experiment demonstrated that Pyganodon grandis were much more tolerant to rising pCO2 relative to Lampsilis siliquoidea (acute closure at ∼200,000μatm in comparison to ∼80,000μatm). The second experiment consisted of monitoring mussels for 6days and exposing them to elevated pCO2 (∼70,000μatm) over a 2-day period. During exposure to high pCO2, Lampsilis cardium were open for nearly the entire high pCO2 period. Conversely, P. grandis were closed for most of the period following exposure to high pCO2. For L. siliquoidea, the number of closures decreased nearly 40-fold during high pCO2. The valve movement responses observed suggest species differences, and exposure to elevated pCO2 requires a reactive response.

Sensitivity to selected contaminants in a biological early warning system using &lt;i&gt;Anodonta woodiana&lt;/i&gt; (Mollusca)

Several early warning systems for the monitoring of water quality are based on the assessment of valve opening/closing in bivalves. Tests were conducted to assess the sensitivity of the mussel Anodonta woodiana , installed on the Mosselmonitor, to seven contaminants and evaluate the usefulness of these sensors for detecting pollution events in the Po River (Italy). Mussels were exposed for 30 min to increasing concentrations of chromium (range 0.01–5 mg/L); arsenic (range 0.05–2.5 mg/L); sodium dodecyl sulphate SDS (range 0.25–50 mg/L); phenol (range 0.1–100 mg/L); oxadiazon (range 0.001–5 mg/L); trichloroethylene (range 0.01–100 mg/L); and crude oil (range 0.5–50 mg/L). Treatment with the highest concentration of SDS elicited two types of alarm response. In a second set of tests, the bivalves were exposed for 6 h to a selected concentration of each chemical. Only SDS led to a dramatic alteration of valve opening, resulting in alarms. This system would have limited applications for monitoring drinking water influent. Keywords: bioindication, mussels, valve movement, toxicity test, toxic substances

19 Tricuspid valve in valve implants in congenital heart disease patients

Patients with congenital tricuspid valve problems or post surgical complications often need biological vale implants quite early on in child hood with risk of size/growth mismatch, valve degeneration and severe stenosis or mixed disease, which expose them to the high risk of multiple redo surgeries. We report 3 cases of transcatheter tricuspid valve in valve implants in the last 18 months, additionally one of them had a percutaneous pulmonary valve implantation (PPVI) at the same procedure after ensuring a widely patent tricuspid valve. Patient ages 19, 11, 26 yrs. The failing valves in all 3 were a perimount valves, sizes 23 to 31mm. The inserted valves were Sapien Edwards valves 20 to 29 mm, we used the ViV surgically oriented app which guides the best size, the wire park in the on of the branch pulmonary artery over which the valve mounted onto a balloon within the IVC then manipulated into position within the old valve. Rapid LV pacing would reduce the cardiac output to ensure minimal valve movements during implantation. The valve is deployed with fluoroscopy and TOE guidance, excellent final result with Drop of the mean PG across the valve from 9 to 1 mmHg with no valvar or paravalvar leak, Conclusion Percutaneous Tricuspid valve implant is a save procedure in patients with failed surgical biological tricuspid valves, and seems to be the logical way forward to avoid redo surgical procedures and more scarring of the right atrium and right ventricle, heart block and arrhythmias.

Characteristics of valve movement pattern of the Japanese scallop Mizuhopecten yessoensis related to environmental changes

Characteristics of valve movement pattern of the Japanese scallop Mizuhopecten yessoensis related to environmental changes

A Study on Bio-Monitoring Systems using Shell Valve Movements of Pacific Oysters (Crassostrea gigas) in response to Abnormal High Water Temperature

A Study on Bio-Monitoring Systems using Shell Valve Movements of Pacific Oysters (Crassostrea gigas) in response to Abnormal High Water Temperature

Behavioral responses of Arctica islandica (Bivalvia: Arcticidae) to simulated leakages of carbon dioxide from sub-sea geological storage

Sub-sea geological storage of carbon dioxide (CO2) provides a viable option for the Carbon Capture and Storage (CCS) approach for reducing atmospheric emissions of this greenhouse gas. Although generally considered to offer a low risk of major leakage, it remains relevant to establish the possible consequences for marine organisms that live in or on sediments overlying these storage areas if such an event may occur. The present study has used a series of laboratory exposures and behavioral bioassays to establish the sensitivity of Arctica islandica to simulated leakages of CO2. This long-lived bivalve mollusc is widely distributed throughout the North Sea, an area where geological storage is currently taking place and where there are plans to expand this operation significantly. A recently published model has predicted a maximum drop of 1.9pH units in seawater at the point source of a substantial escape of CO2 from sub-sea geological storage in this region. Valve movements of A. islandica exposed to reduced pH seawater were recorded continuously using Hall effect proximity sensors. Valve movement regulation is important for optimising the flow of water over the gills, which supplies food and facilitates respiration. A stepwise reduction in seawater pH showed an initial increase in both the rate and extent of valve movements in the majority of individuals tested when pH fell to 6.2 units. Exposing A. islandica to pH 6.2 seawater continuously for seven days resulted in a clear increase in valve movements during the first 40h of exposure, followed by a gradual reduction in activity intensity over the subsequent five days, suggesting acclimation. The ability of both exposed and control bivalves to burrow successfully into sediment on completion of this exposure was very similar. A final exposure trial, testing whether increased valve movements initiated by reduced pH were related to foot extension during attempted burrowing, found no such association. In summary, significant changes in valve behavior did not occur until seawater pH fell to 6.2 units. The response took the form of an increase in valve activity rather than closure. The absence of foot extension coincident with increased valve movements indicates A. islandica were not attempting to burrow, leaving the possibility that valve movements are supporting a respiratory response to hypercapnia. In conclusion, A. islandica appears to be tolerant of reductions in seawater pH equivalent to those predicted for substantial losses of CO2 through leakage from sub-sea geological storage.

Transesophageal echocardiography to assess mitral valve movement and flow during long term cardiopulmonary resuscitation: How cardiac effects fade with time

BackgroundAlthough the cardiac pump and the thoracic pump are the two main theories, the actual mechanisms of blood flow during Cardiopulmonary Resuscitation (CPR) in humans are still unclear. The aim of this study was to explore the relationship between the pump mechanism and time after cardiac arrest. Methods and results20 patients with non-traumatic cardiac arrest were enrolled in this study. Transesophageal two-dimensional and pulse-doppler echocardiography were used during CPR. The duration of CPR was 60–80min if there was no return of spontaneous circulation (ROSC). We found: (1) The mechanisms of blood flow during CPR varied with time: the thoracic pump took the place of the cardiac pump after prolonged CPR in the same patient. (2) Peak transmitral flow (TMF) decreased (p<0.05) after prolonged CPR in patients with mitral valve closure during chest compressions. (3) Longer elapsed time from collapse to CPR and TEE was correlated to lower peak TMF in CPR (Both p<0.05). (4) Peak TMF(p<0.01), mitral valve time-velocity integrals(p<0.05), left ventricular stroke volume (p<0.05) and end-tidal carbon dioxide tension (p<0.05) is higher in the group of patients with mitral valve closure during chest compressions. This group of patients had a shorter time from collapse to CPR (p<0.01), shorter time from collapse to TEE (p<0.01) and had overall better outcomes. ConclusionsThe pump mechanism changes over the course of prolonged CPR. Cardiac effect is an essential part of the pump at the beginning of cardiac arrest, but it faded with time, making the thoracic pump the dominate mechanism after prolonged CPR.

Short-Term Behavioural Responses of the Great Scallop Pecten maximus Exposed to the Toxic Alga Alexandrium minutum Measured by Accelerometry and Passive Acoustics.

Harmful algal blooms produced by toxic dinoflagellates have increased worldwide, impacting human health, the environment, and fisheries. Due to their potential sensitivity (e.g., environmental changes), bivalves through their valve movements can be monitored to detect harmful algal blooms. Methods that measure valve activity require bivalve-attached sensors and usually connected cables to data transfers, leading to stress animals and limit the use to sessile species. As a non-intrusive and continuously deployable tool, passive acoustics could be an effective approach to detecting harmful algal blooms in real time based on animal sound production. This study aimed to detect reaction changes in the valve movements of adult Pecten maximus exposed to the toxic dinoflagellate Alexandrium minutum using both accelerometry and passive acoustic methods. Scallops were experimentally exposed to three ecologically relevant concentrations of A. minutum for 2 hours. The number of each type of valve movement and their sound intensity, opening duration, and valve-opening amplitude were measured. Four behaviours were identified: closures, expulsion, displacement, and swimming. The response of P. maximus to A. minutum occurred rapidly at a high concentration. The valve activity of P. maximus was different when exposed to high concentrations (500 000 cells L-1) of A. minutum compared to the non-toxic dinoflagellate Heterocapsa triquetra; the number of valve movements increased, especially closure and expulsion, which were detected acoustically. Thus, this study demonstrates the potential for acoustics and sound production changes in the detection of harmful algal blooms. However, field trials and longer duration experiments are required to provide further evidence for the use of acoustics as a monitoring tool in the natural environment where several factors may interfere with valve behaviours.

Effect of dissimilar valve lift on a bi-fuel CNG engine operation

The combustion of spark ignition engines converted to bi-fuel CNG is unstable and proper air and fuel mixing strategy is a concern. Also, CNG fuel causes the coefficient of variation for indicated mean effective pressure (COVimep) higher than 10% which is into the region of unstable combustion. In order to create stable combustion more turbulence is required. This paper studies the valve movement with dissimilar valve lift (DVL) to increase swirl in the engine. The intake valve is the last point of airflow entry into an engine and the modification of the movement can contribute to increase turbulence. Three DVL setting simulated via computational fluid dynamics (CFD) gave improvement in peak pressure by 4% and a 32.2% improvement in flame propagation speed compared to baseline CNG. Engine testing shows that, the engine COVimep improves up to 8.7%, while efficiency improves by 5.7% and BSFC is reduced by 5.4% respectively with the 1 mm DVL at 4000 rpm compared to baseline CNG. The rate of heat release (ROHR) also shows early heat release of the fuel. The novelty is better mileage for future CNG engine design.

DOPPLER ECHOCARDIOGRAPHIC FINDINGS IN TISSUE ENGINEERED AORTIC VALVE IN A SHEEP MODEL

Background: Heart valve diseases are considered a common disease in human and animals, and valve replacement is an option for treatment of valvular diseases. Objectives: In this study efficacy of a tissue engineered valve in thoracic aorta was evaluated with transthoracic echocardiography. Methods: This study was undertaken on 6 male sheep. Echocardiography was performed on all sheep 24 hours before surgery and repeated 24 hours (D1), 2 weeks (W2) and 4 weeks (W4) after surgery. Right parasternal long axis view of left ventricular outflow tract (LVOT) was used to assess hemodynamic across new valve. Results: Velocity time integral (VTI) significantly decreased from 18.98±2.88 before surgery to 12.55±2.48 one day after surgery (D1) (p<0.05). Mean Velocity (Vmean) decreased significantly from 52.56±12.01 to 39.72±12.30 at D1 (p<0.05). But maximum velocity (Vmax) was constant during study. There was not any statistical difference between mean Pressure gradient (Pgmean) or maximum pressure gradient (Pgmax) in comparison with pre-surgery and D1, W2 and W4. At D1, W2 and W4, time to peak (TTP) differed significantly from previous time. Conclusions: Our results demonstrated that this tissue engineered aortic valve (TEAV) could change some hemodynamic parameters, but heart could compensate some of them. Valve movement remained normal but the major complication was aneurism which seems to be the result of poor scaffold.