•The flapper with curved edge develops a significant cavitation in pilot stage.•The rectangular shape flapper significantly reduces cavitation in pilot stage.•The innovative flapper eliminates ...undesired transverse lateral force.•The innovative flapper maintains the same flow control capability and construction.
The flapper-nozzle pilot stage, whose performance can be deteriorated by the generated flow cavitation phenomenon, is a vital segment in achieving precise control of electrohydraulic servo-valves. Aiming to find out a reasonable flapper shape to reduce cavitation, this paper presents a numerical study of cavitation phenomenon in a flapper-nozzle pilot stage with different flapper shapes. A simple rectangular shape, carefully designed without disturbing the flow control characteristics of the pilot stage, is set as an innovative flapper shape in this work. Cavitation phenomena in the pilot stage are simulated for both of the traditionally used flapper shape and the innovative flapper shape at flow conditions with various nozzle inlet pressures, 1MPa to 7MPa. Then, systematic comparison of resulted cavitation phenomena for the two different flapper shapes is carried out. The results confirm that, for both flapper shapes, cavitation commonly occurs along the nozzle tip wall beyond stagnation region. The curved edge in traditionally used flapper shape is a massive contributor of cavitation in the pilot stage and the selected innovative shape shows a significant reduction of cavitation on its surface. From the flow structure, it is also noticeable that undesired transverse lateral force of sheded vortices is eliminated by using the innovative flapper shape. Meanwhile, the innovative flapper shape highlights the same effectiveness on the performance of flow control as the traditionally used flapper shape. Thus, a simple and effective flapper shape is proposed for cavitation reduction in the flapper-nozzle pilot stage of an electrohydraulic servo-valve.
•Optimum inclination for maximum heat flux changes with latitude of location.•Optimum inclination for maximum heat flux also changes local solar time.•Maximum flow rate increases with increasing of ...riser tube size.•Maximum mass flow rate is obtained at different inclinations for different risers.•Length of two-phase region depends on inclination angles but not riser tube size.
In this work, the effect of riser diameter and its inclination angle on system parameters in a two-phase closed loop thermosyphon solar water heater has been numerically investigated. Here, receivable heat flux by the collector, circulating mass flow rate, driving pressure, total pressure drop, heat transfer coefficient in risers and collector efficiency are defined as system parameters. For this aim, a model of two-phase thermosyphon solar water heater that is acceptable for various inclinations is presented and variations of riser diameter and inclination are considered. The riser tube size is varied from 1.25cm to 2.5cm with inclination range 2–75°. The system absolute pressure is set as 3567Pa and water is chosen as working fluid. The results show that higher inclination angle is required for higher latitude location to obtain maximum solar heat flux. At local solar noon of 21.996 north latitude, the optimum inclination angle increases in the range of 24–44° with increasing of riser diameter giving maximum circulating mass flow rate from 0.02288kg/s to 0.03876kg/s. The longer two-phase heat transfer characteristics can be obtained at smaller inclination angles and mass flow rate for all riser tube sizes. Therefore, it is observed that the optimum inclination angles and diameters for solar heat flux, circulating mass flow rate and heat transfer coefficient in two-phase thermosyphon systemdo not coincide. From this work, better understanding and useful information are provided for constructing two-phase thermosyphon solar heaters.
Cardiovascular resonance (CMR) imaging is a standard imaging modality for assessing cardiovascular diseases (CVDs), the leading cause of death globally. CMR enables accurate quantification of the ...cardiac chamber volume, ejection fraction and myocardial mass, providing information for diagnosis and monitoring of CVDs. However, for years, clinicians have been relying on manual approaches for CMR image analysis, which is time consuming and prone to subjective errors. It is a major clinical challenge to automatically derive quantitative and clinically relevant information from CMR images.
Deep neural networks have shown a great potential in image pattern recognition and segmentation for a variety of tasks. Here we demonstrate an automated analysis method for CMR images, which is based on a fully convolutional network (FCN). The network is trained and evaluated on a large-scale dataset from the UK Biobank, consisting of 4,875 subjects with 93,500 pixelwise annotated images. The performance of the method has been evaluated using a number of technical metrics, including the Dice metric, mean contour distance and Hausdorff distance, as well as clinically relevant measures, including left ventricle (LV) end-diastolic volume (LVEDV) and end-systolic volume (LVESV), LV mass (LVM); right ventricle (RV) end-diastolic volume (RVEDV) and end-systolic volume (RVESV).
By combining FCN with a large-scale annotated dataset, the proposed automated method achieves a high performance in segmenting the LV and RV on short-axis CMR images and the left atrium (LA) and right atrium (RA) on long-axis CMR images. On a short-axis image test set of 600 subjects, it achieves an average Dice metric of 0.94 for the LV cavity, 0.88 for the LV myocardium and 0.90 for the RV cavity. The mean absolute difference between automated measurement and manual measurement is 6.1 mL for LVEDV, 5.3 mL for LVESV, 6.9 gram for LVM, 8.5 mL for RVEDV and 7.2 mL for RVESV. On long-axis image test sets, the average Dice metric is 0.93 for the LA cavity (2-chamber view), 0.95 for the LA cavity (4-chamber view) and 0.96 for the RA cavity (4-chamber view). The performance is comparable to human inter-observer variability.
We show that an automated method achieves a performance on par with human experts in analysing CMR images and deriving clinically relevant measures.
Cardiovascular magnetic resonance (CMR) is the gold standard method for the assessment of cardiac structure and function. Reference ranges permit differentiation between normal and pathological ...states. To date, this study is the largest to provide CMR specific reference ranges for left ventricular, right ventricular, left atrial and right atrial structure and function derived from truly healthy Caucasian adults aged 45-74.
Five thousand sixty-five UK Biobank participants underwent CMR using steady-state free precession imaging at 1.5 Tesla. Manual analysis was performed for all four cardiac chambers. Participants with non-Caucasian ethnicity, known cardiovascular disease and other conditions known to affect cardiac chamber size and function were excluded. Remaining participants formed the healthy reference cohort; reference ranges were calculated and were stratified by gender and age (45-54, 55-64, 65-74).
After applying exclusion criteria, 804 (16.2%) participants were available for analysis. Left ventricular (LV) volumes were larger in males compared to females for absolute and indexed values. With advancing age, LV volumes were mostly smaller in both sexes. LV ejection fraction was significantly greater in females compared to males (mean ± standard deviation SD of 61 ± 5% vs 58 ± 5%) and remained static with age for both genders. In older age groups, LV mass was lower in men, but remained virtually unchanged in women. LV mass was significantly higher in males compared to females (mean ± SD of 53 ± 9 g/m
vs 42 ± 7 g/m
). Right ventricular (RV) volumes were significantly larger in males compared to females for absolute and indexed values and were smaller with advancing age. RV ejection fraction was higher with increasing age in females only. Left atrial (LA) maximal volume and stroke volume were significantly larger in males compared to females for absolute values but not for indexed values. LA ejection fraction was similar for both sexes. Right atrial (RA) maximal volume was significantly larger in males for both absolute and indexed values, while RA ejection fraction was significantly higher in females.
We describe age- and sex-specific reference ranges for the left ventricle, right ventricle and atria in the largest validated normal Caucasian population.
Differences in cardiac and aortic structure and function are associated with cardiovascular diseases and a wide range of other types of disease. Here we analyzed cardiovascular magnetic resonance ...images from a population-based study, the UK Biobank, using an automated machine-learning-based analysis pipeline. We report a comprehensive range of structural and functional phenotypes for the heart and aorta across 26,893 participants, and explore how these phenotypes vary according to sex, age and major cardiovascular risk factors. We extended this analysis with a phenome-wide association study, in which we tested for correlations of a wide range of non-imaging phenotypes of the participants with imaging phenotypes. We further explored the associations of imaging phenotypes with early-life factors, mental health and cognitive function using both observational analysis and Mendelian randomization. Our study illustrates how population-based cardiac and aortic imaging phenotypes can be used to better define cardiovascular disease risks as well as heart-brain health interactions, highlighting new opportunities for studying disease mechanisms and developing image-based biomarkers.
Orthostatic hypotension (OH) has been linked with higher incidence of cardiovascular disease, but little is known about the mechanisms behind this association. We aimed to identify cardiovascular ...disease biomarkers associated with OH through a proteomic profiling approach. Seven hundred seventy-eight patients with unexplained syncope or orthostatic intolerance underwent head-up tilt test and supine blood samples. Of these, 220 met diagnostic criteria of OH, and 179 demonstrated normal hemodynamic response during head-up tilt test. Blood samples were analyzed by antibody-based Proximity Extension Assay technique simultaneously measuring 92 cardiovascular disease-related human protein biomarkers. The discovery algorithm was a sequential 2-step process of biomarker signature identification by supervised, multivariate, principal component analysis and verification by univariate ANOVA with Bonferroni correction. Patients with OH were older (67 versus 60 years;
<0.001) and more likely to be women (48% versus 41%;
>0.001) but did not differ from OH-negative patients in medical history. Principal component analysis identified MMP-7 (matrix metalloproteinase-7), TM (thrombomodulin), MB (myoglobin), TIM-1 (T-cell immunoglobulin and mucin domain-1), CASP-8 (caspase-8), CXCL-1 (C-X-C motif chemokine-1), Dkk-1 (dickkopf-related protein-1), lectin-like LOX-1 (oxidized low-density lipoprotein receptor-1), PlGF (placenta growth factor), PAR-1 (proteinase-activated receptor-1), and MCP-1 (monocyte chemotactic protein-1) as the most robust proteomic signature for OH. From this proteomic feature selection, MMP-7 and TIM-1 met Bonferroni-adjusted significance criteria in univariate and multivariate regression analyses. Proteomic profiling in OH reveals a biomarker signature of atherothrombosis and inflammation. Circulating levels of MMP-7 and TIM-1 are independently associated with OH and may be involved in cardiovascular disease promotion.
Cardiovascular disease (CVD) is the principal cause of mortality and morbidity globally. With the pressures for improved care and translation of the latest medical advances and knowledge to an ...actionable plan, clinical decision-making for cardiologists is challenging. Artificial Intelligence (AI) is a field in computer science that studies the design of intelligent agents which take the best feasible action in a situation. It incorporates the use of computational algorithms which simulate and perform tasks that traditionally require human intelligence such as problem solving and learning. Whilst medicine is arguably the last to apply AI in its everyday routine, cardiology is at the forefront of AI revolution in the medical field. The development of AI methods for accurate prediction of CVD outcomes, non-invasive diagnosis of coronary artery disease (CAD), detection of malignant arrythmias through wearables, and diagnosis, treatment strategies and prediction of outcomes for heart failure (HF) patients, demonstrates the potential of AI in future cardiology. With the advancements of AI, Internet of Things (IoT) and the promotion of precision medicine, the future of cardiology will be heavily based on these innovative digital technologies. Despite this, ethical dilemmas regarding the implementation of AI technologies in real-world are still unaddressed.
To investigate the inflammatory biomarker signature associated with classical orthostatic hypotension (OH).
A cross-sectional study including 778 patients with unexplained syncope and/or orthostatic ...intolerance undergoing head-up tilt test (HUT) and supine blood sampling. Of these, 98 met diagnostic criteria of classical OH and 181 demonstrated normal haemodynamic response during HUT. Blood plasma samples were analysed by antibody-based Proximity Extension Assay technique simultaneously measuring 57 inflammatory and cancer-related human protein biomarkers. The discovery algorithm was a sequential two-step process of biomarker signature identification by multivariate principal component analysis (PCA), and verification by univariate ANOVA with Bonferroni correction.
Patients with classical OH were older (68 vs. 60years; p<0.001) and more likely to be men (58 vs. 41%; p<0.001). PCA and Bonferroni-adjusted ANOVA identified midkine (MK), immunoglobulin-like transcript 3 (ILT-3), regenerating islet-derived protein 4 (REG-4), and tartrate-resistant acid phosphatase type 5 (TR-AP) as the most robust targeted biomarker signature for OH. In multivariate regression analysis adjusting for age, sex, cardiovascular disease and risk factors, the results remained significant for ILT-3 (p=0.036), MK (p=0.008) and REG-4 (p=0.024), but not for TR-AP.
Targeted protein profiling in classical orthostatic hypotension reveals a biomarker signature associated with immunoregulatory functions and vascular inflammation. Circulating levels of midkine, immunoglobulin-like transcript-3, regenerating islet-derived protein-4 are elevated in orthostatic hypotension, suggesting a complex interplay among inflammation, autonomic dysfunction and atherothrombosis.
•Dysautonomia and inflammation have multifaceted and reciprocal interactions.•OH revealed a proteomic signature of inflammation and immunoregulatory functions.•Inflammation and autonomic dysfunction are likely intertwined in atherothrombosis.
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