Decrease In Pressure Gradient Research Articles

The influence of body position on cerebrospinal fluid circulation

Background. Cerebrospinal fluid (CSF) circulation consists of two components, a net flow and a pulsatile flow. CSF is generally believed to be produced through the ventricular choroid plexuses and absorbed in sites such as the subarachnoid granulations and nerve roots, contributing to the net flow. The pulsatile driving forces include cardiac vascular pulsation, respiration and muscular contraction.1 Measuring CSF flow in the upright posture is important because we spend most of our lifetime upright.
 Methods. Thirty asymptomatic volunteers (age: 22-72; 9 males, 21 females) were scanned in the upright seated and supine position on a 0.6 T multi-position MRI scanner (Fonar, New York, USA). CSF flow and spinal cord pulsation were imaged and quantified at the axial mid-C2 level with cine phase-contrast MRI.
 Results. In the upright posture, heart rate increased by 10%, and peak CSF diastolic flow decreased by 43% compared to the supine posture.2 In addition, the oscillatory volume of CSF exchanged between the spine and cranium decreased by 37% when going from supine to upright posture, consistent with a previous study.3 This could mean that the amount of time spent in different postures as we age may affect the efficiency of glymphatic brain waste clearance and development of neurodegenerative diseases. A less studied but diagnostically important aspect of CSF flow is the concomitant pulsation of spinal cord and central nervous system (CNS) tissue. For example, it is found that in Alzheimer’s Disease patients, the spinal cord at mid-C2 is pulsating much more in the mid to high frequency range (4 to 8 Hz) compared to normal older people in the supine posture. In the normal population, the mid-C2 spinal cord pulsates much less in the upright posture, with a 40% reduction of peak systolic velocity compared to the supine posture. Other postural differences include the more prominent appearance of nerve roots in the supine posture, shift of venous outflow from jugular veins to epidural/smaller veins, and the slimming of the neck when upright. It is also found that CSF flow is much more sensitive to aging in the upright than in the supine position. More specifically, as we age, heart rate change between postures diminishes and the upright peak systolic/peak-to-peak pressure gradient decreases. Since studies have shown that meditation can slow down brain aging, it would be beneficial to study its effect on CSF flow and the process of brain waste production and clearance.
 Conclusions. Besides delineating the many significant postural differences in CSF circulation, multi-position CSF imaging is also valuable in diagnosing various diseases such as Chiari malformation,4 Ehlers-Danlos syndrome and tethered cord syndrome in the lumbar spine. Often pathology that is not evident in the traditional supine imaging position can be visualized in other patient positions. Finally, a seminal study5 in rodents found that glymphatic transport is most efficient in the lateral recumbent position compared to supine or prone position, which concluded that posture must be considered in future diagnostic imaging procedures to assess CSF – interstitial fluid (ISF) transport in humans.

Analysis of the Effectiveness of Arytenoidectomy and Posterior Cordectomy with the Use of CFD Airflow Measurements in Patients with BVFP: A Retrospective Study.

Bilateral vocal fold paralysis (BVFP) is a rare larynx disease manifested by dyspnea, which often requires surgical treatment. The aim of the study is to determine the effectiveness of unilateral arytenoidectomy with posterior cordectomy in the treatment of BVFP using the computational fluid dynamics (CFD) method. This study included 33 patients with BVFP who underwent unilateral laser arytenoidectomy with posterior cordectomy. Glottis area measurements and spirometry, as well as a self-assessment of respiratory efficiency were performed before the surgery and after the recovery period. Using the CFD method, computer models of the glottis were made. Then, changes in air pressure gradient and maximum air velocity at the level of glottis were calculated, and local fields of pressure and air velocities were obtained. The values of glottal surface area (S), spirometry parameters (forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF)), inlet air velocity at the glottal level as well as patients self-assessment of respiratory efficiency turned out to be significantly higher after the operation. The values of maximum velocity at the glottal level, pressure gradient at the glottal level turned out to be significantly lower after the surgery. We observed that the greater the increase in glottal surface area, the greater the decrease in self-assessment scales (visual analogue scale (VAS) and Medical Research Council (MRC)). Increased levels of spirometry parameters after the surgery correlated with smaller decrease of PEF-dependent pressure gradient at the glottal level (PEFΔP CFD). Unilateral laser arytenoidectomy with posterior cordectomy is an effective method for the treatment of BVFP. CFD is a useful tool to determine and visualize the effectiveness of surgical treatment in BVFP.

CLINICAL RESULTS OF BALLOON PLASTY OF PULMONARY ARTERY VALVE IN BULLDOG DOGS

The paper presents the results of a clinical and experimental study to determine the clinical efficacy of surgical treatment of animals with pulmonary artery valve stenosis using balloon plasty. The study was retrospective, animals were evaluated from 2018 to 2020, and the morphofunctional state of the cardiovascular system was assessed before and after surgery. The total sample consisted of 15 animals. Diagnosis of this defect was performed auscultatively and by echocardiography [ultrasound]. On auscultation systolic murmur was heard in all animals. Echocardiography evaluated the geometry and function of the right heart, as well as velocity and gradient on the pulmonary artery valve. All animals were diagnosed with congenital heart defect: pulmonary artery valve stenosis. After diagnosis, each dog underwent balloon plasty of the pulmonary artery valve. No animal died during and after surgical intervention. All animals were discharged on the day of surgery for outpatient treatment. There were no postoperative complications. Maintenance and feeding remained unchanged at all times. All animals became more active after the operation, clinical signs of the disease, if any, were resolved or reduced markedly. One month later, repeated echocardiography was performed to evaluate the pulmonary artery valve velocity and gradient. In one animal we observed increased flow velocity on the pulmonary artery valve, which was associated with increased systolic function after surgery. In the remaining dogs, a decrease in velocity and pressure gradient at the pulmonary artery valve was noted. -

Enhanced thermal effectiveness for electroosmosis modulated peristaltic flow of modified hybrid nanofluid with chemical reactions

In this analysis, the thermal and flow properties of modified hybrid nanofluids (MNFs) have been investigated under the effects of electroosmosis and homogeneous-heterogeneous chemical reactions. Three types of nanoparticles of Cu, CuO, and Al2O3 are utilized to monitor the performance of the MNFs with water as a working liquid. The determination of the heating phenomenon is explored by incorporating the effects of NPs shape, temperature reliant viscosity, Joule heating, heat generation/absorption and viscous dissipation. In this exploration, equal diffusion factors for the auto catalyst and reactants are assumed. The model formulation contains a highly non-linear PDE system, which is converted to ODEs under physical assumptions with lubrication and Debye–Huckel. The solution treatment involves the Homotopy perturbation method for solving the governing differential equations is used. A major outcome discloses that an addition in heterogeneous reaction parameter aids in enhancing the concentration profile. In a result, the temperature curve decreases at increasing volume fraction of the NPs. Modified hybrid NFs have higher heat transfer rate as compared to base H20, or ordinary Al2O3–H20 and hybrid Cu + Al2O3–H20 NFs. Pressure gradient decreases by improving electroosmotic parameter. Further a comparison between analytically (HPM) and numerical results (NDSolve) show that both results are in good agreement.

The coupling effects of pore structure and rock mineralogy on the pre-Darcy behaviors in tight sandstone and shale

The pore structure and mineral composition play a crucial role in controlling the water flow behaviors of low-permeability media, which is characterized by threshold pressure gradient (TPG) and nonlinear flow curve. To figure out the coupling effects of these two factors on pre-Darcy flow regimes, water flow experiments were conducted on four tight sandstones, three shales and one fractured shale. The results indicate that both the TPG and pseudo threshold pressure gradient (PTPG) decrease with an increase in total porosity and macropores porosity. The variation of the nonlinear exponent (n) with total porosity and macropore porosity can be described by an exponential function with three parameters. The clay minerals and brittle minerals exert completely opposite influence on the variation of pre-Darcy flow parameters (PTPG, TPG and n). Both TPG/PTPG and n increase with increasing clay content while reduce with increase in the brittle minerals content. Theoretical analyses based on the disjoining pressure demonstrate that immovable water and electro-viscous effect are mainly responsible for water flow deviating from Darcy's law in tight sandstone and shale. Calculation results show that the proportion of immovable water of intact samples ranges from 23.46% to 89.73%, the movable water content ranges from 10.27%–76.54%. The pre-Darcy flow parameters exponentially increase with increase in immovable water content while exponentially decrease with increasing proportion of movable water. For the shale sample used in this work, the immovable water and electro-viscous effect contributing to the pre-Darcy flow account for 81.11%–90.35% and 9.58%–18.51%, respectively. The different flow regimes are controlled by the pore diameter and the thickness of water with shear fluidity. If the diameter of interconnected pores is larger than 10 μm, the Darcy flow regime dominates. When the diameter of minor pore throat of the flow channels are less than 33.82 nm for sandstones and 37.68 nm for shales, the movement of water in this flow channel would generate the TPG.

Effects of inclined squealer rims on tip leakage vortex and loss in a transonic axial turbine

In this paper, to investigate the effects of inclined squealer rims on tip leakage flow and loss, numerical simulations have been performed on a transonic high-pressure turbine. Based on the geometry of prototype with conventional cavity tip, six modifications with different inclined rims are constructed. The effects of inclined suction side squealer rim (SSSR) on tip leakage flow (TLF) is analyzed emphatically. The results show that it is advantageous to control the TLF and loss if the internal and external surface of SSSR are inclined in a proper direction. When the internal surface of SSSR is inclined toward the cavity, the scraping vortex and its pneumatic labyrinth sealing effect are enhanced, which is beneficial to blocking the TLF and reducing the mixing loss. As the external surface of SSSR is inclined toward the passage, the pressure gradient near the tip changes and the intensity of adverse pressure gradient decreases, which is conducive to suppressing the breakdown of tip leakage vortex (TLV). In addition, the inclined external surface could make the TLV away from the blade and reduce the viscous dissipation. Regarding the aerodynamic performance of the turbine, the inclined pressure side squealer rim (PSSR) could improve the stage efficiency of the turbine by 0.08% relative to the prototype, while the proper inclined SSSR could further improve that by 0.18%.

Carvedilol Achieves Higher Hemodynamic Response and Lower Rebleeding Rates Than Propranolol in Secondary Prophylaxis

Carvedilol induces stronger decreases in hepatic venous pressure gradient (HVPG) than conventional nonselective β-blockers (ie, propranolol). Limited data exist on the efficacy of carvedilol in secondary prophylaxis of variceal bleeding. Patients undergoing paired HVPG measurements for guiding secondary prophylaxis with either carvedilol or propranolol were included in this retrospective analysis. All patients also underwent band ligation. Changes in HVPG and systemic hemodynamics were compared between the 2 groups. Long-term follow-up data on rebleeding, acute kidney injury, nonbleeding decompensation, and liver-related death were analyzed applying competing risk regression. Eighty-seven patients (carvedilol/propranolol, n= 45/42) were included in our study. The median baseline HVPG was 21 mm Hg (interquartile range, 18-24 mm Hg), and 39.1%/48.3%/12.6% had Child-Turcotte-Pugh A/B/C cirrhosis, respectively. Upon nonselective β-blocker initiation, HVPG decreased more strongly in carvedilol users (median relative decrease, -20% [interquartile range: -29% to -10%] vs -11% [-22% to -5%] for propranolol; P= .027), who also achieved chronic HVPG response more often (53.3% vs 28.6%; P= .034). Cumulative incidences for rebleeding (Gray test, P= .027) and liver-related death (P= .036) were significantly lower in patients taking carvedilol compared with propranolol. Notably, ascites development/worsening also was observed less commonly in carvedilol patients (P= .012). Meanwhile, acute kidney injury rates did not differ between the 2 groups (P= .255). Stratifying patients by HVPG response status yielded similar results. The prognostic value of carvedilol intake was confirmed in competing risk regression models. Carvedilol induces more marked reductions in HVPG than propranolol in secondary prophylaxis of variceal bleeding, and thus is associated with lower rates of rebleeding, liver-related death, and further nonbleeding decompensation.

Investigation into boundary layer transition using wall-resolved large-eddy simulations and modeled inflow turbulence

Abstract. The objective of the present paper is to investigate the transition scenario of the flow around a typical section of a wind turbine blade exposed to different levels of inflow turbulence. A rather low Reynolds number of Rec=105 is studied at a fixed angle of attack but under five different turbulence intensities (TIs) up to TI = 11.2 %. Using wall-resolved large-eddy simulations combined with an inflow procedure relying on synthetically generated turbulence and a source-term formulation for its injection within the computational domain, relevant flow features such as the separation bubble, inflectional instabilities and streaks can be investigated. The study shows that the transition scenario significantly changes with rising TI, where the influence of inflectional instabilities due to an adverse pressure gradient decreases, while the influence of streaks increases, resulting in a shift from the classical scenario of natural transition to bypass transition. The primary instability mechanism in the separation bubble is found to be inflectional, and its origin is traced back to the region upstream of the separation. Thus, the inviscid inflectional instability of the separated shear layer is an extension of the instability of the attached adverse pressure gradient boundary layer observed upstream. The boundary layer is evaluated to be receptive to external disturbances such that the initial energy within the boundary layer is proportional to the square of the turbulence intensity. Boundary layer streaks were found to influence the instantaneous separation location depending on their orientation. A varicose mode of instability is observed on the overlap of the leading edge of a high-speed streak with the trailing edge of a low-speed streak. The critical amplitude of this instability was analyzed to be about 32 % of the free-stream velocity.

Evolving Solutions in the Surgical Treatment of Isolated Pulmonary Valve Stenosis

Background: Surgical treatment of isolated pulmonary valve stenosis in infants and children has evolved over the years, shifting from the original exclusive aim at lowering right ventricle pressure to the current concomitant focus on preserving pulmonary valve function. In our study, we sought to analyze the effect of such evolving philosophy on long-term results. Methods: All consecutive patients treated in our center between July 1983 and March 2019 were included. Patients were categorized into 2 groups based on the introduction into treatment practice of sparing valve techniques (1995). Actuarial survival, freedom from reintervention on the right outflow tract, transvalvular mean pressure gradient decrease, and pulmonary valve function at follow-up were analyzed. Results: One hundred twenty-three patients operated before (Group I, n=81) or since (Group II, n=42) 1995 were enrolled in the study. Mean age and weight were 3.0 ± 0.36 years and 16.6 ± 1.7kg, respectively. Early mortality occurred exclusively in 3 patients of Group 1. Transvalvular mean pressure gradient decreased in the entire patient population (from 63.28 ± 12.9mmHg to 16.46 ± 7.9mmHg). At a mean follow-up interval of 4.9 ± 33 years, freedom from death was comparable, but freedom from right ventricular outflow tract reintervention was significantly greater in Group II. Although the transvalvular gradient remained stable over time in non-reoperated survivors (mean value of 16.46 ± 7.9mmHg), pulmonary valve function on 2D-Echo showed severe incompetence in 2 patients of Group I and just mild to moderate incompetence in 20 patients of Group II, with a significantly negative effect of unsuccessful preoperative pulmonary balloon valvuloplasty (14/20 vs 6/20, p=0.025) in the latter. Conclusion: Current pulmonary valve sparing techniques are associated with better results, particularly in terms of freedom from re-interventions and pulmonary valve function at follow-up. Balloon valvuloplasty prior to surgery may worsen operative results, promoting pulmonary insufficiency and therefore should probably be avoided in all patients in whom anatomical characteristics predict failure of percutaneous therapy.

Blood microbiome is associated with changes in portal hypertension after successful direct-acting antiviral therapy in patients with HCV-related cirrhosis

Patients with a significant decrease in hepatic venous pressure gradient (HVPG) have a considerable reduction of liver complications and higher survival after HCV eradication. To evaluate the association between the baseline blood microbiome and the changes in HVPG after successful direct-acting antiviral (DAA) therapy in patients with HCV-related cirrhosis. We performed a prospective study in 32 cirrhotic patients (21 HIV positive) with clinically significant portal hypertension (HVPG ≥10 mmHg). Patients were assessed at baseline and 48 weeks after HCV treatment completion. The clinical endpoint was a decrease in HVPG of ≥20% or HVPG <12 mmHg at the end of follow-up. Bacterial 16S ribosomal DNA was sequenced using MiSeq Illumina technology, inflammatory plasma biomarkers were investigated using ProcartaPlex immunoassays and the metabolome was investigated using GC-MS. During the follow-up, 47% of patients reached the clinical endpoint. At baseline, those patients had a higher relative abundance of Corynebacteriales and Diplorickettsiales order, Diplorickettsiaceae family, Corynebacterium and Aquicella genus and Undibacterium parvum species organisms and a lower relative abundance of Oceanospirillales and Rhodospirillales order, Halomonadaceae family and Massilia genus organisms compared with those who did not achieve the clinical endpoint according to the LEfSe algorithm. Corynebacteriales and Massilia were consistently found within the 10 bacterial taxa with the highest differential abundance between groups. Additionally, the relative abundance of the Corynebacteriales order was inversely correlated with IFN-γ, IL-17A and TNF-α levels and the Massilia genus with glycerol and lauric acid. Baseline-specific bacterial taxa are related to an HVPG decrease in patients with HCV-related cirrhosis after successful DAA therapy.

Relationship Between Procedural Right Bundle Branch Block and 1-Year Outcome After Alcohol Septal Ablation for Hypertrophic Obstructive Cardiomyopathy - A Retrospective Study.

Alcohol septal ablation (ASA) is a treatment option in patients with drug-refractory symptomatic hypertrophic obstructive cardiomyopathy (HOCM). In many patients, right bundle branch block (RBBB) develops during ASA because septal branches supply the right bundle branch. However, the clinical significance of procedural RBBB is uncertain. We retrospectively reviewed 184 consecutive patients with HOCM who underwent ASA. We excluded 40 patients with pre-existing RBBB (n=10), prior pacemaker implantation (n=15), mid-ventricular obstruction type (n=10), and those lost to follow-up (n=5), leaving 144 patients for analysis. Patients were divided into 2 groups according to the development (n=95) or not (n=49) of procedural RBBB. ASA conferred significant decreases in the left ventricular pressure gradient (LVPG) in both the RBBB and no-RBBB group (from 74±48 to 27±27 mmHg [P<0.001] and from 75±45 to 31±33 mmHg [P<0.001], respectively). None of the RBBB patients developed further conduction system disturbances. The percentage reduction in LVPG at 1 year after the procedure was significantly greater in the RBBB than no-RBBB group (66±24% vs. 49±45%; P=0.035). Procedural RBBB was not associated with pacemaker implantation after ASA, but was associated with reduction in repeat ASA (odds ratio 0.34; 95% confidence interval 0.13-0.92; P=0.045). Although RBBB frequently occurs during the ASA procedure, it does not adversely affect clinical outcomes.

An exact solution for blade coating of a second-grade fluid on a porous substrate

This study explores the blade coating process with a simple fixed blade for a second-grade fluid over a moving porous substrate. The article investigates both plane and exponential blade coating. The analysis simplifies the governing equations via lubrication approximation theory by assuming that blade length is much larger than the coating layer thickness. Suitable scales normalize the governing equations. The expressions for pressure gradient and velocity are analytically obtained whereas pressure is attained using a so-called “shooting method” numerical technique. How the Reynolds number [Formula: see text], suction velocity [Formula: see text] and non-Newtonian second-grade parameter [Formula: see text] affect the velocity, pressure gradient, pressure, coating layer thickness and load on the blade are observed and displayed graphically and as tables. Interesting engineering quantities like velocity, pressure gradient and pressure are highlighted in graphical form whereas load and thickness are presented as tables. It is observed that the pressure gradient, pressure, velocity, load and thickness decrease as the parameters [Formula: see text] and [Formula: see text] and [Formula: see text] icrease for the cases of both plane and exponential coaters while all these physical quantities are observed to increase when the parameter [Formula: see text] increases. The most important physical quantity is the load for it is responsible in maintaining the coating quality and thickness. Moreover, it is perceived that the load decreases as the Reynolds number [Formula: see text] and [Formula: see text] increases get accelerated and it increases when parameter [Formula: see text] is increased.

Uneven Warming Likely Contributed to Declining Near‐Surface Wind Speeds in Northern China Between 1961 and 2016

AbstractA decline in mean near‐surface (10 m) wind speed has been widely reported for many land regions over recent decades, yet the underlying cause(s) remains uncertain. This study investigates changes in near‐surface wind speed over northern China from 1961 to 2016, and analyzes the associated physical mechanisms using station observations, reanalysis products and model simulations from the Community Atmosphere Model version 5.1 (CAM5). The homogenized near‐surface wind speed shows a significantly (p &lt; 0.05) decline trend of −0.103 m s−1 decade−1, which stabilized from the 1990s onwards. Similar negative trends are observed for all seasons, with the strongest trends occurring in the central and eastern parts of northern China. Fast warming has occurred at high‐latitudes (i.e., &gt;50°N) in recent decades, which has weakened the annual and seasonal meridional air temperature gradient (−0.33°C to −0.12°C dec−1, p &lt; 0.05, except autumn) between these regions (50°–60°N, 75°–135°E) and the northern China zone (35°–45°N, 75°–135°E). This caused a significant (p &lt; 0.05) decrease in annual and seasonal pressure gradient (−0.43 to −0.20 hPa dec−1) between the two zones, which contributed to the slowdown of winds. CAM5 simulations demonstrate that spatially uneven air temperature increases and near‐surface wind speed decreases over northern China can be realistically reproduced using the so‐called “all forcing” simulation, while the “natural only forcing” simulation fails to realistically simulate the uneven warming patterns and declines in near‐surface wind speed over most of northern China, except for summer.

Effect of lithological rhythm of a confined hydrate reservoir on gas production performance using water flooding in five-spot vertical well system

The lithological features of sediments control the heterogeneity in permeability. This study numerically investigates the effect of lithological rhythm of a confined hydrate reservoir on gas production for warm water injection scenarios. The investigated lithological rhythm structures range from simple rhythms to complex composite rhythms. The depressurization in multiple wells causes significant gas production. However, the decrease in pressure gradient constrained the production of gas and water. The warm water injection enhances the production of gas and water with various lag times, though it results in a low energy efficiency. The positive and reverse rhythms have similar energy efficiencies. The gas and water production rate slightly decrease with the increase in the permeability contrast. The maximum gas production rate increases with the increase in number of composite rhythmic layers. However, the water production changes only slightly. The rhythm structures significantly affect the gas and water production rates. A high permeability region in the bottom part of the reservoir is conducive to warm water breakthrough. However, it is unfavorable for the dissociation of remnant hydrate in low permeability regions. Moreover, the results show that the rhythm structures also affect the gas productivity of each rhythmic layer. The results presented in this study help us understand the effect of complex and real rhythm structures on the gas production performance and the dynamic evolution of hydrate dissociation zone.

A decrease in tricuspid regurgitation pressure gradient associates with favorable outcome in patients with heart failure.

AimsAlthough the prognostic impact of the high tricuspid regurgitation pressure gradient (TRPG) has been investigated, the association of the decrease in TRPG during follow‐up with clinical outcomes in heart failure (HF) has not been previously studied. The aim of this study was to investigate the association of a decrease in TRPG between hospitalization and 6 month visit with subsequent clinical outcomes in patients with acute decompensated HF (ADHF).Methods and resultsAmong 721 patients with available TRPG data both during hospitalization and a subsequent 6 month visit, the study population was divided into two groups: a decrease in TRPG group (>10 mmHg decrease at 6 month visit) (N = 179) and no decrease in TRPG group (N = 542). The primary outcome measure was a composite of all‐cause death or HF hospitalization. The cumulative 6 month incidence of primary outcome measure was significantly lower in the decrease in TRPG group than in the no decrease in TRPG group (12.2% vs. 18.7%, P = 0.02). After adjusting for confounders, there was a significantly lower risk in decrease in TRPG group than in the no decrease in TRPG group for the measured primary outcome (hazard ratio: 0.56, 95% confidence interval 0.32–0.93, P = 0.02). The lower risk in decrease in TRPG group was not different among the basal TRPG values.ConclusionsHeart failure patients with a decrease in TRPG at 6 months after discharge from ADHF hospitalization had lower subsequent risk of all‐cause death and HF hospitalization than those without a decrease in TRPG, regardless of TRPG values.

Properties of the pressure field in highly nonlinear free surface flows with critical jet

In this note we examine fluid violent kinematics in a plunging breaker. The fluid motion is computed in the frame of the potential flow theory. The fluid kinematics is basically generated by forcing the motion of a rectangular tank, starting from rest. When a sufficient level of energy is injected in the fluid, the free surface has highly nonlinear behavior, here a plunging breaker. In the vicinity of the main tip crest, a sharp corner (cusp) appears along the surface of the barrel. The appearance of this critical jet is described and discussed in terms of the spatial and temporal variations of the pressure field. In the present case a local pressure maximum is captured that follows a continuous decreasing pressure gradient in a region of positive Gaussian curvature of the pressure. It is also shown that, at the free surface before the appearance of the critical jet, there is a strong correlation between the change of sign of the Gaussian curvature of the pressure on the one hand and the radius of curvature of the free surface profile on the other hand.

Characteristics and causes of surface wind speed variations in Northwest China from 1979 to 2019

New characteristics of surface wind speed variations in Northwest China and the possible explanations for them have remained undetermined over the recent decades. This study presents the characteristics and possible mechanisms of surface wind speed variations in Northwest China from 1979 to 2019. The results show that the surface wind speed in Northwest China underwent a two-stage change rather than a persistent decline from 1979 to 2019; specifically, it declined significantly before the early 2000s and then increased gradually thereafter. The meridional pressure gradient decrease caused by the meridional temperature gradient reduction corresponded to a decrease in the winter surface wind speed in Northwest China during 1979–2002. The meridional pressure gradient increase caused by the meridional temperature gradient increase was consistent with an increase in the winter surface wind speed in Northwest China during 2003–2019. This suggests that the spatially inhomogeneous variations in surface air temperature in Eurasia's mid-high latitudes may be the main reason for the surface wind speed variations in Northwest China. Furthermore, the decadal strengthening of the East Asian winter monsoon (EAWM) may have resulted in an upward trend of the surface wind speed in Northwest China after the early 2000s by strengthening the Siberian High (SH). Although the variations in the surface wind speed in Northwest China are inconsistent with those in the winter Arctic Oscillation (AO) index, there is a significant negative correlation between them on the interannual timescale. With a negative (positive) AO phase, the surface wind speed in Northwest China increases (decreases) in winter.

Thoughts on Future Trends in Cardiology

Thoughts on Future Trends in Cardiology

Echocardiography in the Assessment of Intraventricular Flows and Pressure Gradients in Obstructive Hypertrophic Cardiomyopathy

Aim To evaluate results of myomectomy by intraventricular pressure gradients (IVPG) and blood flows in patients with obstructive hypertrophic cardiomyopathy (OHCMP).Material and methods The study included a total of 76 subjects, 42 patients with OHCMP (mean age, 39±7 years) and 34 healthy volunteers (mean age, 41±3 years). Prior to and after myomectomy, transthoracic echocardiography was performed and followed by digital image processing and calculation of IVPG and left ventricular (LV) vortex flows. Vector analysis was used to estimate the myocardial displacement rate (V), vortex flows, and LV apex-to-base pressure gradients.Results The study showed a dynamic decrease in the LV apex-to-outflow IVPG by more than 50% and recovery of myocardial contraction velocity in the septal area (р&lt;0.001). The decrease in LV cavity pressure gradient serves as an index for evaluating the effectiveness of OHCMP correction. Myomectomy reduces the load on the myocardium and abolishes mitral valve regurgitation with improvement of LV blood flows as also evidenced by the dynamics of long axis velocity change during the cardiac cycle (dL / dt) and the myocardial contraction velocity (V).Conclusion Effectiveness of the surgical correction of OHCMP is based on the dynamics of myocardial contraction velocities, vortex blood flows, and a decrease in LV apex-to-base IVPG.

Abstract 17142: Long Term Results of Non-Invasive Ultrasound Therapy (NIUT) in Severe Symptomatic Aortic Valve Stenosis - First-in-Man

Background: Not all patients with severe aortic valve stenosis are eligible for open-heart surgery or TAVR. CARDIAWAVE (Paris, France) has developed Valvosoft, a unique non-invasive ultrasound therapy device to treat aortic stenosis. The therapy aims to improve the opening of severely calcified aortic valves by cracking the calcium and reducing the stiffness in the aortic valve tissue by delivering transthoracically local shock waves on the valve leaflets. This study assesses the safety, feasibility and performance of this novel technique. Methods: This is a multi-center, prospective, first-in-man study designed to evaluate the safety and feasibility of the Valvosoft device. Ten patients with severe symptomatic calcific aortic stenosis and not eligible for SAVR/TAVR underwent a Valvosoft ultrasound therapy. Echocardiographic evaluation was performed by an independent core lab at baseline, discharge, and at 1, 3, 6 and 12 months along with clinical follow up. Results: Enrolled patients were advanced in age (84.1±6.5 yrs) with severe comorbidities (8 with heart failure, 5 with coronary heart disease and 5 with kidney failure). All had extensive aortic valve calcification with mean AVA of 0.61±0.17 cm2 and mean pressure gradient of 37.5±10.5 mmHg. At one-month follow-up, six patients had significantly improved their AVA with increase of 27.5% (p=0.03) and mean pressure gradient decrease of 23.2 % (p=0.025). These patients also received the highest dose and longest treatment duration. During one year follow up, 4 patients died due to progression of end stage heart failure not linked to the procedure and one patient had undergone a TAVR procedure. At 12 months, the five remaining patients has no device or procedure related major adverse events nor deterioration of neurological status. Echo, brain-MRI and clinical follow up will be presented. Conclusions: Non-invasive ultrasound therapy is feasible and safe in patients with severe aortic valve stenosis and can improve AVA and hemodynamic parameters. NIUT can be an important tool complementary to TAVI in treating patients with aortic valve stenosis.