Increase In Pressure Gradient Research Articles

Flow regime transition of multicomponent oil in shale nanopores

Understanding the shale oil flow mechanism in nanopores is crucial for optimizing development strategies and enhancing recovery in shale oil reservoirs. Despite the widespread use of molecular dynamics simulations in studying shale oil flow, oversimplified shale oil and shale nanopore models compromise result reliability, and a definitive shale oil flow regime has yet to be established. This study, employing validated molecular models, investigated 26-component oil flow in authentic shale kerogen and quartz nanopores. For the first time, we elucidated the nonlinear flux increase due to flow regime transition with pressure gradient. At low pressure gradients, shale oil flux gradually increased with a parabolic velocity profile. With the increasing pressure gradient, the velocity profile shifted from parabolic to piston-like, especially in quartz nanopores, indicating a positive slip velocity. Consequently, the shale oil flux increased significantly. At high pressure gradients, the growth of shale oil flux decelerated while maintaining a piston-like velocity profile. Through analysis of density distribution and oil-wall interactions, we revealed that oil desorption and redistribution triggered the flow regime transition. The flow regime transition occurred with the widening of quartz nanopores. Increased nanopore width and temperature notably enhanced shale oil flow. This study underscored the importance of accounting for shale oil’s multicomponent properties and roughness and composition of shale nanopores. It determined shale oil flow regimes under various conditions, advancing our comprehension of shale oil flow mechanisms in realistic settings and furnishing a theoretical foundation for enhancing shale oil recovery.

Pressure gradient and an upstream cylinder on nanofluid flow around a heated cylinder: Heat transfer and entropy analysis

This study numerically investigates the nanofluid flow around a long heated cylinder of square cross-section (DSC) with height placed parallel to a cold wall at a fixed gap height The incident flow is Couette–Poiseuille (C–P) flow. Another cylinder of rectangular cross section (UREP) is placed on the upstream side in an inline arrangement with different gap spacings between the cylinders. The base fluid is chosen as the water and ethylene glycol–water mixture. Numerical experiments are made using staggered grid arrangement on non–uniform grid, finite volume methods, and Semi–Implicit Method for Pressure Linked Equations algorithm. Impact of pressure gradient at the inlet (due to C–P flow), position and shape (square/rectangular) of the UREP, nanoparticle concentration, and base fluid on the crowding of isotherms around edges of the DSC and hence to the heat transfer characteristics (Nusselt number and entropy generation rate density) is investigated. Bejan number is used to ratify that the irreversibility due to heat transfer is the major constituent of the total system irreversibility here. A reduction of heat transfer and entropy generation from the values of an isolated DSC is natural here due to the inline arrangement. An effort is made to improve the heat transfer by reducing the height of the UREP or/and by generating unsteadiness in the incoming flow to the DSC using a bluffer UREP or/and an increased pressure gradient. Finally, some scenarios are reported where the heat transfer decrement is less in comparison to that of the total system irreversibility.

Porcine or Bovine Tissue Valves: Which are Better for Surgical Aortic Valve Replacement?

Summary The choice between mechanical and bioprosthetic aortic valve implants is affected by relatively clear criteria. However, the choice between porcine or pericardial valve is more complex regarding bioprosthetic devices. We aimed to elucidate any hemodynamic and clinical difference between two widely used bioprosthetic valves: the Sorin Mitroflow bovine pericardial valve and the St. Jude Medical Epic Supra porcine valve. We retrospectively studied 71 consecutive patients separated into two groups based on the valve they received. Clinical outcomes included patient survival and hemodynamic performance of the implanted prostheses. Patients were assessed at one and five years postoperatively. Mean transprosthetic pressure gradients were used as a marker of hemodynamic performance. The Mitroflow valve exhibited lesser mean transvalvular gradients than the Epic valve for all labelled sizes at one and five years postoperatively. The 5-year survival was equal between groups. Both prostheses demonstrated a small but significant increase in mean pressure gradients in the fifth year. Most patients enjoyed significant clinical improvement as assessed by NYHA functional class. Both bioprostheses performed very well with excellent hemodynamic parameters. The pericardial valves are a safe and appropriate choice for surgical bioprosthetic aortic valve replacement.

Stratospherically induced circulation changes under the extreme conditions of the no-Montreal-Protocol scenario

Abstract. The Montreal Protocol and its amendments (MPA) have been a huge success in preserving the stratospheric ozone layer from being destroyed by unabated chlorofluorocarbon (CFC) emissions. The phaseout of CFCs has not only prevented serious impacts on our health and climate, but also avoided strong alterations of atmospheric circulation patterns. With the Earth system model SOCOLv4, we study the dynamical and climatic impacts of a scenario with unabated CFC emissions by 2100, disentangling radiative and chemical (ozone-mediated) effects of CFCs. In the stratosphere, chemical effects of CFCs (i.e., the resulting ozone loss) are the main drivers of circulation changes, weakening wintertime polar vortices and speeding up the Brewer–Dobson circulation. These dynamical impacts during wintertime are due to low-latitude ozone depletion and the resulting reduction in the Equator-to-pole temperature gradient. Westerly winds in the lower stratosphere strengthen, which is for the Southern Hemisphere (SH) similar to the effects of the Antarctic ozone hole over the second half of the 20th century. Furthermore, the winter and spring stratospheric wind variability increases in the SH, whereas it decreases in summer and fall. This seasonal variation in wind speed in the stratosphere has substantial implications for the major modes of variability in the tropospheric circulation in the scenario without the MPA (No-MPA). We find coherent changes in the troposphere, such as patterns that are reminiscent of negative Southern and Northern Annular modes (SAM and NAM) and North Atlantic Oscillation (NAO) anomalies during seasons with a weakened vortex (winter and spring); the opposite occurs during seasons with strengthened westerlies in the lower stratosphere and troposphere (summer). In the troposphere, radiative heating by CFCs prevails throughout the year, shifting the SAM into a positive phase and canceling out the ozone-induced effects on the NAO, whereas the North Pacific sector shows an increase in the meridional sea-level pressure gradient as both CFC heating and ozone-induced effects reinforce each other there. Furthermore, global warming is amplified by 1.7 K with regionally up to a 12 K increase over eastern Canada and the western Arctic. Our study sheds light on the adverse effects of a non-adherence to the MPA on the global atmospheric circulation, uncovering the roles of the underlying physical mechanisms. In so doing, our study emphasizes the importance of the MPA for Earth's climate to avoid regional amplifications of negative climate impacts.

Effects of Variable Pressure Outlets for Array Jet Impingement Cooling With a Bidirectional Exit Air Scheme

Abstract Array jet impingement in conjunction with other cooling methods such as effusion cooling is used in gas turbine combustion zones to provide optimized cooling in the form of double wall cooling around a combustion chamber. Utilizing a transient liquid crystal (TLC) technique an experimental investigation into the effects of pressure gradients and single versus multiple exits for array jet impingement crossflow is evaluated in the form of a detailed heat transfer analysis. In this study, four pressure gradients to bias mass flow ratios as (1:1), (2:1), (3:1), and (1:0), two jet array configurations either inline or staggered with jet to jet spacings (x/D = y/D) of 1.4, 1.9, and 2.2, three jet to target distances (z/D) ranging from 2 to 4, and three Reynolds number from 5000 to 15,000 are considered. In total, a test matrix of 72 different performance conditions was evaluated. Results are presented as local and area averaged Nusselt number plots along with local heat transfer coefficient contours. Overall, Nusselt number decreases with increased (z/D) and increased pressure gradient bias toward a single exit from (1:1) to (1:0). There is also slightly better performance from inline jet array configurations compared to staggered configurations.

Transient of flow regimes and slip boundary analysis of water and gas in nano clay pores

ABSTRACT Nanoscale two-phase flow is important during shale gas production. In this work, molecular dynamics simulations are employed to investigate fluid flow regimes of water and methane under different pressure gradients inside the nanoscale slit pores. The illite mineral is selected to model the clay pores based on the Small-Angle X-ray Diffraction (SAXD) experiment. The different flow regimes of gas-water two-phase are visualised and the structures are analysed. As the driving pressure gradient increases, it is observed that the two-phase flow in the slit undergoes transitions from intermittent flow to a transition stage between intermittent flow and annular flow, and finally fully converts to annular flow. The slip conditions during the two-phase flow on the hydrophilic illite surface are investigated. We found that the negative slip length stays around 0.25 nm within the range of practical production pressure gradients, which can be used for accurate production prediction. This work provides detailed insights into the nanoscale water and gas two-flow inside the clay nanopores during shale gas exploration.

Effect of fractal surface roughness and pressure gradient on the hydraulic behavior of fluid flow through a 3D single rough fracture

This study mainly aimed to numerically investigate the influence of fractal roughness and pressure gradient on the fluid flow through a three-dimensional (3D) single rough fracture with a constant mechanical aperture. To avoid confusion created by the Reynolds number caused by different definitions of characteristic length, the critical pressure gradient was utilized to characterize the onset of non-linear flow in rough fractures. Further, the effect of fractal dimension on the critical pressure gradient was also investigated. The rough fracture surfaces with different fractal dimensions are generated by an open source code SynFrac, and the COMSOL Multiphysics software package based on the finite element method was used to simulate the fluid flow through the generated 3D rough fracture model by solving the Navier-Stokes equations. For each case, Forchheimer’s law was used to describe nonlinear flow and the numerical results show that the critical pressure gradient, ranging from 15.68 kPa/m to 1.50 kPa/m, decreases exponentially with the increase in fractal dimension. The results also show that the relationship between relative effective fracture aperture and pressure gradient can be fitted well by a power function. These results suggest that the non-linear flow appears earlier as the fractal dimension and pressure gradient increase.

Transcatheter Pulmonary Artery Banding in High-Risk Neonates: In-Vitro Study Provoked by Initial Clinical Experience.

Very high-risk, ductal-dependent or complex two-ventricle patients with associated comorbidities often require pulmonary blood flow restriction as bridge to a more definitive procedure, but current surgical options may not be well-tolerated. An evolving alternative utilizes a fenestrated Micro Vascular Plug (MVP) as a transcatheter, internal pulmonary artery band. In this study, we report a case series and an in-vitro evaluation of the MVP to elicit understanding of the challenges faced with device implantation. Following single-center, retrospective review of eight patients who underwent device placement, an in-vitro flow study was conducted on MVP devices to assess impact of device and fenestration sizing on pulmonary blood flow. A mathematical model was developed to relate migration risk to vessel size. Results of the engineering analysis were compared to the clinical series for validation. At median follow-up of 8months (range 1-15), survival was 63% (5/8), and 6 (75%) patients underwent subsequent target surgical intervention with relatively low mortality (1/6). Occluder-related challenges included migration (63%) and peri-device flow, which were evaluated in-vitro. The device demonstrated durability over normal and supraphysiologic conditions with minimal change in fenestration size. Smaller vessel size significantly increased pressure gradient due to reduced peri-device flow and smaller effective fenestration size. Device oversizing, with appropriate adjustment to fenestration size, may reduce migration risk and provide a clinically appropriate balance between resulting pressure gradient and Qp:Qs. Our results can guide the interventionalist in appropriately selecting the device and fenestrations based on patient-specific anatomy and desired post-implantation flow characteristics.

Physical and Numerical Simulation of Tight Gas Flow at the Microscale

The porous media in tight reservoirs are mainly composed of micro- and nanopores, gas seepage through which is complex, making it difficult to study. Physical simulation using micron tubes is an intuitive and effective method to study the seepage mechanism of tight gas. The lattice Boltzmann method (LBM) is the most effective method for the tight gas seepage simulation, and it has been widely used. Microscale gas seepage simulation experiments and LBM simulations of micron tubes with different inner diameters were performed. The results showed that in micron tubes, the gas flow increases nonlinearly with an increasing pressure gradient. Influenced by compression and rarefaction effects, the degree of the nonlinearity of pressure distribution in series micron tubes increases with inlet pressure. The existence of a connecting channel between parallel micron tubes breaks the linear distribution of pressure in the original micron tubes, and the gas forms a raised relative high-pressure area at the connection of the two micron tubes; the wider the channel, the greater the bulge. The average gas flow rate in the whole micron tube increases with the channel width, and the seepage capacity increases instead of decreases. The diameter change of one micron tube has no effect on the gas flow in the other micron tube. Although the two micron tubes are connected, they are still relatively independent individuals. These research results lay a foundation for the correct understanding of the characteristics and laws of tight gas seepage in the pores of reservoirs at the micro- and nanoscales, and they have important theoretical significance for the study of seepage mechanisms in tight gas reservoirs.

A mathematical model for pre-Darcy flow in low permeability porous media with stress sensitivity and the boundary-layer effect

Pre-Darcy flow is widely found in many naturally porous media, such as low-permeability clay. Nonflowing liquid boundary layers strongly influence fluid flow in low-permeability porous media. There is evidence in the literature that the porosity and permeability of low-permeability porous media change with variations in the effective stress, which is called stress sensitivity. In this paper, a new mathematical model for pre-Darcy flow in low-permeability porous media is developed and validated with experimental data from the literature. The nonflowing boundary layer thickness can be obtained from the proposed model instead of the empirical equation. First, an equation for calculating the pore radius with stress sensitivity is derived. Two parameters εp and εr are defined to calculate the nonflowing boundary layer thickness. Second, based on the capillary bundle model, the apparent flow velocity and apparent liquid permeability of the porous media are determined. Finally, the stress sensitivity and boundary-layer effects on the apparent flow velocity and apparent liquid permeability are analyzed. The research results show that the effect of stress sensitivity on apparent flow velocity increases with increasing pore compressibility. When the pore compressibility Cp>0 MPa−1, the apparent liquid permeability increases continuously with increasing pressure gradient. When the pore compressibility Cp=0 MPa−1, the apparent liquid permeability continues to increase with increasing pressure gradient. The apparent liquid permeability eventually tends to a constant value. The apparent flow velocity decreases with εp, and εr decreases at a given pressure gradient. The larger εp and εr are, the faster the rate of increase in the apparent liquid permeability with increasing pressure gradient. The proposed model can estimate the apparent flow velocity at different pressure gradients with a high accuracy. This work is important for understanding flow phenomena in low permeability porous media, such as landslides caused by seepage of water in clay.

Aortic valve calcification is promoted by interleukin-8 and restricted through antagonizing CXCR2.

Inflammatory cytokines play a critical role in the progression of calcific aortic valve disease (CAVD), for which there is currently no pharmacological treatment. The aim of this study was to test the hypothesis that interleukin-8 (IL-8), known to be involved in arterial calcification, also promotes aortic valve calcification (AVC) and to evaluate whether pharmacologically blocking the IL-8 receptor, CXC motif chemokine receptor 2 (CXCR2), could be effective in preventing AVC progression. A cohort of 195 patients (median age 73, 74% men) diagnosed with aortic valve stenosis (severe in 16.9% of cases) were prospectively followed by CT for a median time of 2.6 years. A Cox proportional hazards regression analysis indicated that baseline IL-8 serum concentrations were associated with rapid progression of AVC, defined as an annualized change in the calcification score by CT ≥ 110 AU/year, after adjustment for age, gender, bicuspid anatomy and baseline disease severity. In vitro, exposure of primary human aortic valvular interstitial cells (hVICs) to 15 pg/ml IL-8 induced a two-fold increase in inorganic phosphate (Pi)-induced calcification. IL-8 promoted NFκB pathway activation, MMP-12 expression, and elastin degradation in hVICs exposed to Pi. These effects were prevented by SCH527123, an antagonist of CXCR2. The expression of CXCR2 was confirmed in hVICs and samples of aortic valves isolated from patients with CAVD, in which the receptor was mainly found in calcified areas, along with MMP-12 and a degraded form of elastin. Finally, in a rat model of chronic kidney disease-associated CAVD, SCH527123 treatment (1 mg/kg/day given orally for 11 weeks) limited the decrease in aortic cusp separation, the increase in maximal velocity of the transaortic jet, and the increase in aortic mean pressure gradient measured by echocardiography, effects that were associated with a reduction in hydroxyapatite deposition and MMP-12 expression in the aortic valves. Overall, these results highlight, for the first time, a significant role for IL-8 in the progression of CAVD by promoting calcification via a CXCR2-- and MMP-12-dependent mechanism that leads to elastin degradation, and identify CXCR2 as a promising therapeutic target for the treatment of CAVD.

TIME DEPENDENT PRESSURE GRADIENT EFFECTS ON UNSTEADY MHD COUETTE FLOW THROUGH A PARALLEL POROUS PLATE

In this paper, the unsteady MHD Couette flow through a porous medium of a viscous incompressible fluid bounded by two parallel porous plates under the influence of thermal radiation and chemical reaction is investigated. A uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to time dependent pressure gradient. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using perturbation and Eigenfunction expansion techniques. The effects of some non-dimensional parameters are graphically represented and interpreted. It is observed that primary velocity is maximum when pressure gradient is time dependent as compared to when it is independent on time. Also, increase in temperature dependent pressure gradient leads to oscillation in primary velocity along distance y.

Pitfalls and Tips in the Assessment of Aortic Stenosis by Transthoracic Echocardiography.

Aortic stenosis (AS) is a valvular heart disease that significantly contributes to cardiovascular morbidity and mortality worldwide. The condition is characterized by calcification and thickening of the aortic valve leaflets, resulting in a narrowed orifice and increased pressure gradient across the valve. AS typically progresses from a subclinical phase known as aortic sclerosis, where valve calcification occurs without a transvalvular gradient, to a more advanced stage marked by a triad of symptoms: heart failure, syncope, and angina. Echocardiography plays a crucial role in the diagnosis and evaluation of AS, serving as the primary non-invasive imaging modality. However, to minimize misdiagnoses, it is crucial to adhere to a standardized protocol for acquiring echocardiographic images. This is because, despite continuous advances in echocardiographic technology, diagnostic errors still occur during the evaluation of AS, particularly in classifying its severity and hemodynamic characteristics. This review focuses on providing guidance for the imager during the echocardiographic assessment of AS. Firstly, the review will report on how the echo machine should be set to improve image quality and reduce noise and artifacts. Thereafter, the review will report specific emphasis on accurate measurements of left ventricular outflow tract diameter, aortic valve morphology and movement, as well as aortic and left ventricular outflow tract velocities. By considering these key factors, clinicians can ensure consistency and accuracy in the evaluation of AS using echocardiography.

Computational analysis and biomechanical study of Oldroyd-B fluid with homogeneous and heterogeneous reactions through a vertical non-uniform channel

Abstract Homogeneous and heterogeneous reactions play a decisive role in biological procedures such as burning, polymer creation, ceramic construction, distillation, and catalysis. The magnetic properties of hemoglobin molecules are organic. Magnetic resonance imaging (MRI) and electronic components with an electromagnetic field are now readily available, allowing for the explanation of fundamental biological processes. These ideas form the foundation of an ongoing study that attempts to look into the impact of both homogeneous and heterogeneous reactivity on the peristaltic transport of magnetohydrodynamics Oldroyd-B fluid. When convective and partial sliding conditions are present, the configuration changes to a non-uniform vertical channel. The fundamental partial differential equations are resolved utilizing the Homotopy Analysis Method. Entropy optimization has been carried out. The primary limits entering the problem are investigated, and then a graph is used to show the influences of temperature, velocity, skin fraction, Nusselt number, and pressure increase against mean circulation, trapping phenomena, homogeneous reactions, and heterogeneous way to respond. When magnetic parameter rises, the velocity of Oldroyd-B fluid and Bejan number decrease, while temperature, entropy generation, and pressure gradient increase. The tables show that the skin friction coefficient rises for accumulative values of the Grashof number and magnetic parameter, while the skin friction coefficient drops for rising values of the velocity slip parameter and Reynolds number. The Nusselt number increases for large values of Eckert, Grashof numbers, and magnetic parameters.

Coronary embolism due to probable clinical bioprosthetic aortic valve thrombosis: a case report

BackgroundCoronary embolism is a relatively rare but important non-atherosclerotic cause of acute coronary syndrome, mainly caused by atrial fibrillation and mechanical heart valve thrombosis due to subtherapeutic anticoagulation. There have been increasing reports of bioprosthetic valve thrombosis (BPVT), but thromboembolic events are rare and mainly affect the cerebrovascular system. Coronary embolism is an extremely rare complication of BPVT.Case presentationA 64-year-old male presented with non-ST-Elevation myocardial infarction (NSTEMI) to an Australian regional health service. Three years ago, he had undergone Bentall procedure with bioprosthetic aortic valve replacement for severe aortic regurgitation and significant aortic root dilatation. Diagnostic coronary angiography revealed embolic occlusion of first diagonal branch in the absence of underlying atherosclerosis. Prior to NSTEMI presentation, the patient was clinically asymptomatic apart from the progressive increase in transaortic mean pressure gradient on transthoracic echocardiography which was first detected seven months after surgical aortic valve replacement. Transoesophageal echocardiography showed restrictions of the aortic leaflet opening but no evidence of mass or vegetation. After eight weeks of warfarin therapy, the raised aortic valve gradient returned to normal. Lifelong warfarin was prescribed, and patient remained clinically well at 39-month follow-up.ConclusionWe experienced a case of coronary embolism in a patient with probable BPVT. Reversible bioprosthetic valve hemodynamic deterioration after anticoagulation strongly supports the diagnosis in the absence of histopathology. Early moderate-to-severe hemodynamic valve deterioration warrants further investigations, including cardiac computed tomography and sequential echocardiography, to investigate for probable BPVT and consideration of timely anticoagulation initiation to prevent thromboembolic events.

Left atrial function assessed by speckle tracking echocardiography as a marker of atrial reverse remodeling in patients with mitral regurgitation treated with transcatheter edge-to-edge repair

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial reverse remodeling has been defined relying on changes in left atrial volume following specific procedures. Little is known about functional assessment of the left atrium by left atrial strain and left atrial emptying fraction (LAEF) following edge-to-edge mitral repair. Purpose The aim of this study is to assess left atrial function by speckle tracking echocardiography and changes in LAEF, as markers of atrial reverse remodeling, in patient with mitral regurgitation treated with edge-to-edge repair technique. Methods A total of 35 patients diagnosed with severe functional or organic mitral regurgitation who underwent trans-catheter edge-to-edge mitral valve repair were selected. Demographic, clinical and echocardiographic data were collected at the time of enrollment and after a minimum follow-up of six months. The primary endpoint was to assess if left atrial speckle tracking echocardiographic parameters (LASr, LAScd, LASct) and changes in LAEF were reliable indicators of left atrial reverse remodeling, defined as a reduction in indexed left atrial volume ≥ 15% with respect to basal assessment. Collaterally, we tried to identify clinical and standard echocardiographic parameters significantly related to atrial reverse remodeling. Changes between baseline and follow-up parameters were assessed using paired t-test. Results LASr, LASct and LAEF improved significantly in patients with left atrial remodeling during follow-up (LASr: 15,8%±8,43 vs 19,7%±12,22 - P 0,047; LASct: −6,4%±6,21 vs − 9,9%±8,52 - P 0,036; LAEF: 35,5%±14,17 vs 44,1%±15,17 - P 0,003). Collaterally, among all demographics, clinical and echocardiographic data, the absence of coronary artery disease, a systolic dominant pulmonary vein flow, as assessed with pulse-wave-Doppler after the repair, therapy with ACEi/ARB, lower increases in mitral valve pressure gradient after the procedure and lower pulmonary artery systolic pressure at discharge significantly correlated with reverse atrial remodeling. Conclusions In patients with mitral regurgitation treated with edge-to-edge repair, the assessment of left atrial function by speckle tracking echocardiography and left atrial emptying fraction correlates with atrial reverse remodeling, after a minimum follow-up of six months from the procedure. Further studies are needed to better clarify the impact of left atrial remodeling on strong clinical outcomes in patient with mitral regurgitation treated with edge-to-edge repair technique and the role of functional parameters in the definition of the optimal candidate and timing for the repair.

Early and mid-term outcomes of double-chambered right ventricle repair: An 8-year experience.

Double-chambered right ventricle is a rare and progressive condition that is characterised by obstruction of the right ventricular tract. Double-chambered right ventricle is usually associated with ventricular septal defect. Early surgical intervention is recommended in patients with these defects. Based on this background, the present study aimed to review early and midterm outcomes of primary repair after double-chambered right ventricle. Between January 2014 and June 2021, 64 patients with a mean age of 13.42 ± 12.31 years underwent surgical repair for double-chambered right ventricle. The clinical outcomes of these patients were reviewed and assessed retrospectively. An associated ventricular septal defect was present in all the recruited patients; 48 (75%) patients of sub-arterial type, 15 (23.4%) of perimembranous, and 1 (1.6%) patient of muscular type. The patients were followed up for a mean period of 46.73 ± 27.37 months. During their follow-up, a significant decrease in the mean pressure gradient from 62.33 ± 5.52 mmHg preoperatively to 15.73 ± 2.94 mmHg postoperatively was observed (p < 0.001). Notably, there were no hospital deaths. The development of double-chambered right ventricle in association with ventricular septal defect results in an increased pressure gradient within the right ventricle. The defect needs correction in a timely manner. In our experience, the surgical correction of double-chambered right ventricle is safe and shows excellent early and mid-term results.

Capillary rheometry as a model methodology for obtaining insight in feed mash behaviour at conditions approximating pellet manufacturing

Pellet manufacturing is a useful tool for improving the handling of livestock feed. Pellet manufacturing consists, among others, of a compaction step, which is strongly affected by feed formulation. The role of feed formulation is thought to result from the fact that feed mash physicochemical properties change depending on ingredient composition. This variation in physicochemical properties subsequently affects mash behaviour during compaction, leading to variation in both physical pellet quality and energy costs during pellet manufacturing. Methodologies that allow for the study of material behaviour at pellet manufacturing conditions are needed to investigate the effect of feed formulation on mash flow behaviour. Such methodologies, however, are currently not generally available in the field of feed manufacturing. In this short communication we aim to discuss the application of capillary rheometry as a potential method for studying feed behaviour in the die, at conditions comparable to those during pellet manufacturing. The similarity between the design of the capillary rheometer and the geometry of a ring-die compactor allows for the simulation of some of the conditions experienced by feed mash during compaction, using smaller quantities of sample materials. The observed relation between flux and pressure gradient, for feed mashes evaluated in this short communication, resembles a Herschel-Bulkley relation, indicating that the increase in pressure gradient depends non-linearly on flow rate. While individual pressure gradients provide insight in the relative energy costs of compaction, a modelling approach is recommended to simulate the behaviour of feed mash at conditions more closely approximating those during pellet manufacturing. In summary, capillary rheometry provides an option for studying feed mash behaviour at conditions approximating those in the pellet press during pellet manufacturing.

P81: Development Of A Pre-Operative Planning Tool For Patients With Mitral Regurgitation

Mitral regurgitation is the most frequent valve disease in patients over the age of 65 years. In patients with high surgical risk, transcatheter mitral valve intervention (TMVI) is the preferred therapy. However, patient selection for this therapy remains a challenge. This study aims at developing a simulation tool to assist surgeons pre-operatively to choose the treatment based on the patient’s characteristics. In this study, a clinical data (echocardiography and CT scans) of a TMV recipient with a history of severe mitral calcification was considered. Left ventricular (LV) and mitral valve (MV) models were obtained from pre-TMVI CT scans. Pre- and post-TMVI hemodynamics were generated by a lumped-parameter model which were then applied as boundary conditions for two fluid–structure interaction (FSI) simulations with contractile LV and dynamic MV; first, a pre-TMVI simulation with the anatomical MV model and second, a post-TMVI simulation with a Tendyne transcatheter mitral valve model. Mitral pressure gradients (MPG) and effective orifice area (EOA) were calculated. The predictions of the pre-TMVI simulations closely resembled Echo data. Calcified mitral leaflets led to a narrowing of the diastolic opening area resulting in an increased pressure gradient over the MV; EOA (FSI: 2.1 cm2, ECHO: 1.9 cm2), MPG (FSI: 3.8 mmHg, ECHO: 3.4mmHg). These values improved significantly for the post-TMVI simulation (EOA: 4.5 cm2, MPG: 1.1 mmHg), Figure 1. By combining medical imaging and computer modeling, we established a validated tool that can be used pre-TMVI to assist clinicians to select the optimal therapy based on patients’ characteristics.Figure 1. Pre-, and post-TMVI simulation of a patient with severely calcified mitral valve; TMVI: transcatheter mitral valve intervention

Portal Hypertension in Nonalcoholic Fatty Liver Disease: Challenges and Paradigms.

Portal hypertension in cirrhosis is defined as an increase in the portal pressure gradient (PPG) between the portal and hepatic veins and is traditionally estimated by the hepatic venous pressure gradient (HVPG), which is the difference in pressure between the free-floating and wedged positions of a balloon catheter in the hepatic vein. By convention, HVPG≥10 mmHg indicates clinically significant portal hypertension, which is associated with adverse clinical outcomes. Nonalcoholic fatty liver disease (NAFLD) is a common disorder with a heterogeneous clinical course, which includes the development of portal hypertension. There is increasing evidence that portal hypertension in NAFLD deserves special considerations. First, elevated PPG often precedes fibrosis in NAFLD, suggesting a bidirectional relationship between these pathological processes. Second, HVPG underestimates PPG in NAFLD, suggesting that portal hypertension is more prevalent in this condition than currently believed. Third, cellular mechanoresponses generated early in the pathogenesis of NAFLD provide a mechanistic explanation for the pressure-fibrosis paradigm. Finally, a better understanding of liver mechanobiology in NAFLD may aid in the development of novel pharmaceutical targets for prevention and management of this disease.