Isotopic discrimination and turn-over are fundamental to the application of stable isotope ecology in animals. However, detailed information for specific tissues and species are widely lacking, notably for herbivorous species. We provide details on tissue-specific carbon and nitrogen discrimination and turn-over times from food to blood, feathers, claws, egg tissues ...

We report the case of a highly trained endurance athlete (22-year-old) who developed anemia (Hb 9.5 mg/dl) over a period of 6 months. Iron deficient or haemolytic anemia, as well as chronic loss of blood, were excluded. Further, laboratory analyses revealed that this athlete exhibited very low levels of testosterone due ...

BACKGROUND: Peritoneal fibrosis is an essential precursor condition to the development of encapsulating peritoneal sclerosis (EPS). This serious complication leads to a high mortality rate in peritoneal dialysis (PD) patients. Although several factors, including highly concentrated glucose in the dialysis solution, are believed to be potent agents for peritoneal fibrosis, ...

Objective: To describe peritoneal drain fluid volume, fluid cytology, and blood-to-peritoneal fluid lactate and glucose concentration differences after exploratory celiotomy in normal dogs. Study Design: Prospective study. Animals: Healthy Beagle dogs (n=10). Methods: After exploratory celiotomy, a peritoneal drain was placed, and peritoneal fluid was recorded every 6 hours for ...

This review focuses on the role of the venous valves in the genesis of thrombus formation in venous thromboembolic disease (VTE). Clinical VTE and the evidence for the valvular origin of venous thrombosis are reviewed. Virchow's triad is then used as a framework for discussion to approach the question posed ...

OBJECTIVES: We checked the efficiency of a new dialysis device adapted to small volumes to remove glycerol from cryopreserved red blood cells. DESIGN AND METHODS: Dialysis was performed on D-Tube96™ Dialyzer Mini device. In a preliminary trial, we measured the residual glycerol before, and 2, 4 and 24 hours after ...

Introduction: Catheter dysfunction is a concern when using double-lumen catheters in hemodialysis (HD). Reversing the connection mode results in higher blood flows, but also enhanced recirculation. We evaluated total solute removal (TSR) of different uremic retention solutes during a complete HD session, once with reversed (RL) and once with correctly ...

Hemodialysis is a life-saving medical modality that cleanses the blood using an artificial kidney, called a dialyzer. Hemodialysis uses contact between the patient's blood and the semipermeable membrane of the extracorporeal dialyzer to remove compounds such as blood urea nitrogen, creatinine, electrolytes, minerals, anions, cations, certain drugs and toxins, and ...

Aim:  The current recommendation in setting up the Neopuff is to use a gas flow of 5-15 L/min. We investigated if the sensitivity of the positive end expiratory pressure (PEEP) valve varies at different flow rates within this range. Methods:  Five Neopuffs were set up to provide a PEEP of 5 cm ...

The ability of an infusion set to deliver a specific amount of drug to the patient can be directly related to the presence of an antireflux valve and dead-space volume. In this study we quantified separately the impact of these 2 components on drug delivery. Various infusion sets were assessed ...

The objective of this study was to determine the optimum dialyzer jacket structure and hollow-fiber dialysis membrane, both of which are indispensable factors for achieving high dialysis performance, by clarifying the relationship between the dialysis performance and the flow of dialysate and blood in a hollow-fiber dialyzer. We evaluated the ...

The current design of the bileaflet valve, the leaflets of which open outside first, differs significantly from the natural valve whose leaflets open center first. This difference generates a completely different flow field in the bileaflet valve compared to that in the natural heart valve. In a previous study, it ...

Color Doppler jet area (CDJA) is an important measure used to classify mitral regurgitation (MR) severity. The investigators hypothesized that the presence and configuration of multiple regurgitant jets can alter CDJA quantification for fixed regurgitant volumes. This has relevance to MR assessment prior to the treatment of valves with multiple ...

To assess the impact of cannula valve connectors on haemolysis of blood samples drawn from newly inserted cannulae. In a semi-blinded, randomized study paired blood samples, with and without cannula valve connector, were obtained from patients within the ED and tested for haemolysis, defined as haemolysis index of greater than ...

Current designs of bileaflet mechanical heart valves put patients at an increased risk of thromboembolism. In particular, regurgitant flow through the b-datum line is associated with nonphysiologic flow characteristics such as elevated shear stresses, regions of recirculation, and increased mixing, all of which may promote thrombus formation. We have previously ...

Because of the shortage of organs for transplant in pediatric patients with end-stage heart failure, Penn State is developing a pneumatically driven 12 cc pulsatile pediatric ventricular assist device (PVAD). A major concern is the flow field changes related to the volume decrease and its effect on device thrombogenicity. Previous ...

Thromboembolic complications (TECs) of bileaflet mechanical heart valves (BMHVs) are believed to be due to the nonphysiologic mechanical stresses imposed on blood elements by the hinge flows. Relating hinge flow features to design features is, therefore, essential to ultimately design BMHVs with lower TEC rates. This study aims at simulating ...

When studying mechanical heart valve cavitation, a physical model allows direct flow field and pressure measurements that are difficult to perform with actual valves, as well as separate testing of water hammer and squeeze flow effects. Movable rods of 5 and 10 mm diameter impinged same-sized stationary rods to simulate squeeze ...

To use time-resolved three-dimensional phase-contrast magnetic resonance (MR) imaging, also called four-dimensional flow MR imaging, to evaluate systolic blood flow patterns in the ascending aorta that may predispose patients with a bicuspid aortic valve (BAV) to aneurysm. The HIPAA-compliant protocol received institutional review board approval, and informed consent was obtained. ...

BACKGROUND: It has been previously demonstrated that a new index of aortic stenosis (AS) severity derived from dobutamine stress echocardiography (DSE), the projected aortic valve area (AVA) at a normal transvalvular flow rate (AVA(proj)), is superior to traditional Doppler echocardiographic indices to discriminate true severe from pseudosevere low-gradient AS. The ...

OBJECTIVE: Hemodynamics plays a critical role in atherogenesis, but the association between flow pattern and preferential localization of lesion is not fully understood. We developed a mouse model of aortic valve regurgitation (AR) to change the aortic flow pattern and observed the effects on plaque formation. METHODS AND RESULTS: High-frequency ...

Schlieren images of low-speed helium flow from a nozzle of circular cross section reveal instability in the jet occurring approximately 1 cm from the nozzle orifice. Accompanying this instability is a pronounced whistle. In this presentation, both qualitative and quantitative analyses of the observed phenomenon will be discussed.

To clarify the flow pattern from a transventricular apical aortic cannula, hydrodynamic analysis of transventricular apical aortic cannulation (apical cannulation) was performed using particle-image velocimetry in a glass aortic model. Simulated apical cannulation using a 7-mm Sarns Soft-Flow cannula and the newly developed 7-mm apical aortic cannula was compared with ...

Interactions between flow and biological cells and tissues are intrinsic to the circulatory, respiratory, digestive and genitourinary systems. In the circulatory system, an understanding of the complex interaction between the arterial wall (a living multi-component organ with anisotropic, nonlinear material properties) and blood (a shear-thinning fluid with 45% by volume ...

Around 250,000 heart valve replacements are performed every year around the world. Due their higher durability, approximately 2/3 of these replacements use mechanical prosthetic heart valves (mainly bileaflet valves). Although very efficient, these valves can be subject to valve leaflet malfunctions. These malfunctions are usually the consequence of pannus ingrowth ...

Our group has developed an electrohydraulic total artificial heart (EHTAH) with two diaphragm-type blood pumps. Cavitation in a mechanical heart valve (MHV) causes valve surface damage. The objective of this study was to investigate the possibility of estimating the MHV cavitation intensity using the slope of the driving pressure just ...

This paper deals with the design and characterization of an electromagnetic actuation micropump with superimposed dual chambers. An integral part of microfluidic system includes micropumps which have become a critical design focus and have the potential to alter treatment and drug delivery requirements to patients. In this paper, conceptual design ...

Interactions between flow and biological cells and tissues are intrinsic to the circulatory, respiratory, digestive and genitourinary systems. In the circulatory system, an understanding of the complex interaction between the arterial wall (a living multi-component organ with anisotropic, non-linear material properties) and blood (a shear-thinning fluid with 45% by volume ...

Use of patient-specific drain-phase parameters has previously been suggested to improve peritoneal dialysis (PD) adequacy. Improving management of the drain period may also help to minimize intraperitoneal volume (IPV). A typical gravity-based drain profile consists of a relatively constant initial fast-flow period, followed by a transition period and a decaying ...

Proportional strategies for artificial ventilation are the most recent form of synchronized partial ventilatory assistance and intra-breath control techniques available in clinical practice. Currently, the majority of commercial ventilators allowing proportional ventilation uses proportional valves to generate the flow rate pattern. This paper proposes on-off solenoid valves for proportional ventilation ...

Aortic stenosis caused by valve calcification is a major cause of death around the world. Hemodynamic factors have been suggested to be major players in the development of valve calcification, yet a detailed knowledge of the blood flow dynamics as experienced by endothelial cells on valve surfaces is still lacking. ...

Hydrodynamic valve performance is usually evaluated by effective orifice area (EOA), geometric orifice area (GOA) and transvalvular pressure gradients (PG). Magnetic resonance imaging (MRI) is a very efficient tool for assessing these parameters. In this study, we evaluated a silicone rubber trileaflet valve using MRI. EOA, GOA and PG were ...

This study examines a horizontal wall jet impinging onto a forward facing step in a cross-flow. Planar laser induced fluorescence (PLIF) experiments in a water channel indicate that the wall-jet flow after impinging onto the step, becomes a vertical jet with an elliptical cross section. Experiments indicate that the jet ...

Thromboembolic complications of bileaflet mechanical heart valves (BMHV) are believed to be due to detrimental stresses imposed on blood elements by the hinge flows. Characterization of these flows is thus crucial to identify the underlying causes for complications. In this study, we conduct three-dimensional pulsatile flow simulations through the hinge ...

Quantification of aortic regurgitation (AR) using echocardiography is challenging. A newly established echocardiographic method, vector flow mapping (VFM), can directly measure blood flow volume (FV) regardless of rheological characteristics. We intended to assess the accuracy of VFM in the quantification of chronic AR. Twenty-one patients with chronic AR, along with ...

Heart valve anomalies are some of the most common congenital heart defects, yet neither the genetic nor the epigenetic forces guiding heart valve development are well understood. When functioning normally, mature heart valves prevent intracardiac retrograde blood flow; before valves develop, there is considerable regurgitation, resulting in reversing (or oscillatory) ...

Heart valve defects are the most common cardiac defects. Therefore, defining the mechanisms of cardiac valve development is critical to our understanding and treatment of these disorders. At early stages of embryonic cardiac development, the heart begins as a simple tube that then becomes constricted into separate atrial and ventricular ...

We introduce a flow regulating technology that uses trapped air bubbles in a hydrophobic microfluidic channel. We present basic designs for flow regulators and flow valves using trapped air. Experiments have successfully demonstrated the capability of this technique for delivering constant and varying flow rate, and for on-off valving. This ...

We have performed high-resolution fluid-structure interaction simulations of physiologic pulsatile flow through a bi-leaflet mechanical heart valve (BMHV) in an anatomically realistic aorta. The results are compared with numerical simulations of the flow through an identical BMHV implanted in a straight aorta. The comparisons show that although some of the ...

OBJECTIVES: To validate 3-dimensional (3D) 3-directional velocity-encoded (VE) magnetic resonance imaging (MRI) for flow assessment through all 4 heart valves simultaneously with retrospective valve-tracking during off-line analysis in healthy volunteers and in patients with valvular regurgitation. MATERIAL AND METHODS: Three-dimensional 3-directional VE MRI was performed in 22 healthy volunteers and ...

Nonequilibrium Alfvénic flows have been observed in plasma jets during the helicity injection stage of the Caltech spheromak experiment. Density and time of flight measurements of these jets show that the flows convect dense plasma (beta approximately 1) because of the axial gradient in the current channel profile. A simplified ...

BACKGROUND: Cardiovascular magnetic resonance measurements of the volumes of the right and left ventricle and of the flows in the ascending aorta and main pulmonary artery contribute to the assessment of patients with valvular regurgitation or intracardiac or extracardiac shunts. Ventricular volumes are measured by planimetry and summation of end-diastolic ...

According to the valve cusp hypoxia hypothesis (VCHH), deep venous thrombosis is caused by sustained non-pulsatile (streamline) venous blood flow. This leads to hypoxemia in the valve pockets; hypoxic injury to the inner (parietalis) endothelium of the cusp leaflets activates the elk-1/egr-1 pathway, leading to leukocyte and platelet swarming at ...

Surgical intervention for chronic aortic or mitral regurgitation in asymptomatic individuals is recommended on the basis of regurgitant severity and the hemodynamic consequences on the left ventricle (LV). Echocardiography is the standard tool in clinical practice for evaluation of adults with chronic regurgitation. Regurgitant volume (RV) and fraction (RF) can ...

Optical methods for microfluidic flow manipulation offer a flexible, noncontact technique for both fluid actuation and valving. At present, however, such techniques are limited by their high laser power requirements, low achieved flow rates, or poor valve switching times. Here we demonstrate a microfluidic valving technique based on optothermorheological manipulation ...

An orifice flow system has been developed indigenously which is a primary standard for the calibration of high vacuum gauges in the range of 10(-3)-10(-6) mbar. It consists of a constant-volume flow meter, designed to generate a known flow rate of a particular gas to the vacuum chamber. This chamber ...

Brightness-modulated ultrasonography, continuous-wave Doppler, and pulsed-wave Doppler-echocardiography were used to analyze the functional morphology of the undisturbed heart of ball pythons. In particular, the action of the muscular ridge and the atrio-ventricular valves are key features to understand how patterns of blood flow emerge from structures directing blood into the ...

The gluonic contribution to the nuclear modification factor R_{AA} is investigated for central Au + Au collisions at sqrt[s] = 200 AGeV employing a perturbative QCD-based parton cascade including radiative processes. A flat quenching pattern is found up to transverse momenta of 30 GeV, which is slightly smaller compared with ...

Partial left atrial ligation before cardiac septation redistributes intracardiac blood flow and produces left ventricular hypoplasia in the chick. We hypothesized that redistributed intracardiac blood flow adversely alters aortic arch development. We ligated the left atrial appendage with a 10-0 nylon suture at stage 21 chick embryos, then reincubated up ...

Morphogenesis of the "immature symmetric embryonic aortic arches" into the "mature and asymmetric aortic arches" involves a delicate sequence of cell and tissue migration, proliferation, and remodeling within an active biomechanical environment. Both patient-derived and experimental animal model data support a significant role for biomechanical forces during arch development. The ...