Статті в журналах з теми "Strongly annular function"
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1
Monahan, Adam H., and John C. Fyfe. "On Annular Modes and Zonal Jets." Journal of Climate 21, no. 9 (May 1, 2008): 1963–78. http://dx.doi.org/10.1175/2007jcli1841.1.
Повний текст джерелаАнотація:
Abstract This study considers the relation of the annular mode to the kinematics of a fluctuating jet in zonal-mean zonal wind and to the zonal index, using an idealized model of fluctuations in the eddy-driven jet. When the sphericity of the domain is accounted for, observed and numerically simulated annular modes for the Southern Hemisphere summertime are found to be in excellent agreement. In particular, the annular mode and zonal index mode are shown to be related but distinct. Although the annular mode is strongly (but not identically) related to fluctuations in jet position, fluctuations in jet strength and width are shown to also be important for its simulation. When the sphericity of the domain is neglected, analytic expressions for the leading empirical orthogonal function (EOF) modes of zonal-mean geopotential for the cases of individual fluctuations in jet strength, position, and width can be obtained. None of these EOF modes have the characteristics of the annular mode. In the presence of simultaneous fluctuations in jet strength and position, the leading zonal-mean geopotential EOF mode (strongly resembling the annular mode) is shown to mix the zonal index mode of zonal-mean zonal wind with other EOF modes, demonstrating why the annular mode and zonal index mode are related but distinct. The greater sensitivity to domain size of EOF modes of geopotential relative to the EOF modes of zonal-mean zonal wind is also discussed. This study focuses on the Southern Hemisphere summertime, which is characterized by a single, eddy-driven jet; the generality of the results presented suggest that the conclusions should be qualitatively unchanged in the presence of both subtropical and eddy-driven jets.
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Jalali, Mohammad Hadi, and Behrooz Shahriari. "Elastic Stress Analysis of Rotating Functionally Graded Annular Disk of Variable Thickness Using Finite Difference Method." Mathematical Problems in Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/1871674.
Повний текст джерелаАнотація:
Elastic stress analysis of rotating variable thickness annular disk made of functionally graded material (FGM) is presented. Elasticity modulus, density, and thickness of the disk are assumed to vary radially according to a power-law function. Radial stress, circumferential stress, and radial deformation of the rotating FG annular disk of variable thickness with clamped-clamped (C-C), clamped-free (C-F), and free-free (F-F) boundary conditions are obtained using the numerical finite difference method, and the effects of the graded index, thickness variation, and rotating speed on the stresses and deformation are evaluated. It is shown that using FG material could decrease the value of radial stress and increase the radial displacement in a rotating thin disk. It is also demonstrated that increasing the rotating speed can strongly increase the stress in the FG annular disk.
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MATHAI, STEPHEN C., CHRISTOPHER T. SIBLEY, PAUL R. FORFIA, JAMES O. MUDD, MICAH R. FISHER, RYAN J. TEDFORD, NOAH LECHTZIN, et al. "Tricuspid Annular Plane Systolic Excursion Is a Robust Outcome Measure in Systemic Sclerosis-associated Pulmonary Arterial Hypertension." Journal of Rheumatology 38, no. 11 (October 1, 2011): 2410–18. http://dx.doi.org/10.3899/jrheum.110512.
Повний текст джерелаАнотація:
Objective.The tricuspid annular plane systolic excursion (TAPSE) strongly reflects right ventricular (RV) function and predicts survival in idiopathic pulmonary arterial hypertension (PAH). But its role in systemic sclerosis (SSc)-associated PAH has not been established. Our objective was to validate the TAPSE in the assessment of RV function and prediction of survival in SSc-PAH.Methods.Fifty consecutive patients with SSc-PAH who underwent echocardiography with TAPSE measurement within 1 h of clinically indicated right heart catheterization were followed prospectively. The relationship between TAPSE and measures of RV function and measures of survival was assessed.Results.The majority of the cohort were women in New York Heart Association class III/IV with severe PAH (mean cardiac index 2.4 ± 0.8 l/min/m2). RV function was significantly impaired (mean cardiac index 2.1 ± 0.7 vs 2.9 ± 0.8 l/min/m2; p < 0.01) and RV afterload was significantly greater (mean pulmonary vascular resistance 11.1 ± 5.1 vs 5.8 ± 2.5 Wood units; p < 0.01) in subjects with a TAPSE ≤ 1.7 cm. The proportion surviving in the low TAPSE group was significantly lower [0.56 (95% CI 0.37–0.71) and 0.46 (95% CI 0.28–0.62) vs 0.87 (95% CI 0.55–0.96) and 0.79 (95% CI 0.49–0.93), 1- and 2-year survival, respectively]. TAPSE ≤ 1.7 cm conferred a nearly 4-fold increased risk of death (HR 3.81, 95% CI 1.31–11.1, p < 0.01).Conclusion.TAPSE is a robust measure of RV function and strongly predicts survival in patients with PAH-SSc. Future studies are needed to identify the responsiveness of TAPSE to PAH-specific therapy and to assess its diagnostic utility in PAH-SSc.
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Posson, H., and N. Peake. "The acoustic analogy in an annular duct with swirling mean flow." Journal of Fluid Mechanics 726 (June 10, 2013): 439–75. http://dx.doi.org/10.1017/jfm.2013.210.
Повний текст джерелаАнотація:
AbstractThis paper is concerned with modelling the effects of swirling flow on turbomachinery noise. We develop an acoustic analogy to predict sound generation in a swirling and sheared base flow in an annular duct, including the presence of moving solid surfaces to account for blade rows. In so doing we have extended a number of classical earlier results, including Ffowcs Williams & Hawkings’ equation in a medium at rest with moving surfaces, and Lilley’s equation for a sheared but non-swirling jet. By rearranging the Navier–Stokes equations we find a single equation, in the form of a sixth-order differential operator acting on the fluctuating pressure field on the left-hand side and a series of volume and surface source terms on the right-hand side; the form of these source terms depends strongly on the presence of swirl and radial shear. The integral form of this equation is then derived, using the Green’s function tailored to the base flow in the (rigid) duct. As is often the case in duct acoustics, it is then convenient to move into temporal, axial and azimuthal Fourier space, where the Green’s function is computed numerically. This formulation can then be applied to a number of turbomachinery noise sources. For definiteness here we consider the noise produced downstream when a steady distortion flow is incident on the fan from upstream, and compare our results with those obtained using a simplistic but commonly used Doppler correction method. We show that in all but the simplest case the full inclusion of swirl within an acoustic analogy, as described in this paper, is required.
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Carlhäll, C., L. Wigström, E. Heiberg, M. Karlsson, A. F. Bolger, and E. Nylander. "Contribution of mitral annular excursion and shape dynamics to total left ventricular volume change." American Journal of Physiology-Heart and Circulatory Physiology 287, no. 4 (October 2004): H1836—H1841. http://dx.doi.org/10.1152/ajpheart.00103.2004.
Повний текст джерелаАнотація:
The mitral annulus (MA) has a complex shape and motion, and its excursion has been correlated to left ventricular (LV) function. During the cardiac cycle the annulus’ excursion encompasses a volume that is part of the total LV volume change during both filling and emptying. Our objective was to evaluate the contribution of MA excursion and shape variation to total LV volume change. Nine healthy subjects aged 56 ± 11 (means ± SD) years underwent transesophageal echocardiography (TEE). The MA was outlined in all time frames, and a four-dimensional (4-D) Fourier series was fitted to the MA coordinates (3-D+time) and divided into segments. The annular excursion volume (AEV) was calculated based on the temporally integrated product of the segments’ area and their incremental excursion. The 3-D LV volumes were calculated by tracing the endocardial border in six coaxial planes. The AEV (10 ± 2 ml) represented 19 ± 3% of the total LV stroke volume (52 ± 12 ml). The AEV correlated strongly with LV stroke volume ( r = 0.73; P < 0.05). Peak MA area occurred during middiastole, and 91 ± 7% of reduction in area from peak to minimum occurred before the onset of LV systole. The excursion of the MA accounts for an important portion of the total LV filling and emptying in humans. These data suggest an atriogenic influence on MA physiology and also a sphincter-like action of the MA that may facilitate ventricular filling and aid competent valve closure. This 4-D TEE method is the first to allow noninvasive measurement of AEV and may be used to investigate the impact of physiological and pathological conditions on this important aspect of LV performance.
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Hassanzadeh, Pedram, and Zhiming Kuang. "The Linear Response Function of an Idealized Atmosphere. Part I: Construction Using Green’s Functions and Applications." Journal of the Atmospheric Sciences 73, no. 9 (August 10, 2016): 3423–39. http://dx.doi.org/10.1175/jas-d-15-0338.1.
Повний текст джерелаАнотація:
Abstract A linear response function (LRF) determines the mean response of a nonlinear climate system to weak imposed forcings, and an eddy flux matrix (EFM) determines the eddy momentum and heat flux responses to mean-flow changes. Neither LRF nor EFM can be calculated from first principles owing to the lack of a complete theory for turbulent eddies. Here the LRF and EFM for an idealized dry atmosphere are computed by applying numerous localized weak forcings, one at a time, to a GCM with Held–Suarez physics and calculating the mean responses. The LRF and EFM for zonally averaged responses are then constructed using these forcings and responses through matrix inversion. Tests demonstrate that LRF and EFM are fairly accurate. Spectral analysis of the LRF shows that the most excitable dynamical mode, the neutral vector, strongly resembles the model’s annular mode. The framework described here can be employed to compute the LRF and EFM for zonally asymmetric responses and more complex GCMs. The potential applications of the LRF and EFM constructed here are (i) forcing a specified mean flow for hypothesis testing, (ii) isolating/quantifying the eddy feedbacks in complex eddy–mean flow interaction problems, and (iii) evaluating/improving more generally applicable methods currently used to construct LRFs or diagnose eddy feedbacks in comprehensive GCMs or observations. As an example for (iii), in Part II, the LRF is also computed using the fluctuation–dissipation theorem (FDT), and the previously calculated LRF is exploited to investigate why FDT performs poorly in some cases. It is shown that dimension reduction using leading EOFs, which is commonly used to construct LRFs from the FDT, can significantly degrade the accuracy owing to the nonnormality of the operator.
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Massey, Richard John, Phoi Phoi Diep, Marta Maria Burman, Anette Borger Kvaslerud, Lorentz Brinch, Svend Aakhus, Lars Gullestad, Ellen Ruud, and Jan Otto Beitnes. "Impaired right ventricular function in long-term survivors of allogeneic haematopoietic stem-cell transplantation." Open Heart 8, no. 2 (December 2021): e001768. http://dx.doi.org/10.1136/openhrt-2021-001768.
Повний текст джерелаАнотація:
AimsSurvivors of allogeneic haematopoietic stem-cell transplantation (allo-HSCT) are at higher risk of cardiovascular disease. We aimed to describe right ventricular (RV) systolic function and risk factors for RV dysfunction in long-term survivors of allo-HSCT performed in their youth.Methods and resultsThis cohort included 103 survivors (53% female), aged (mean±SD) 17.6±9.5 years at allo-HSCT, with a follow-up time of 17.2±5.5 years. Anthracyclines were used as first-line therapy for 44.7% of the survivors. The RV was evaluated with echocardiography, and found survivors to have reduced RV function in comparison to a group of healthy control subjects: Tricuspid annular plane systolic excursion, (TAPSE, 20.8±3.7 mm vs 24.6±3.8 mm, p<0.001), RV peak systolic velocity (RV-s’, 11.2±2.3 cm/s vs 12.3±2.3 cm/s, p=0.001), fractional area change (FAC, 41.0±5.2% vs 42.2±5.1%, p=0.047) and RV free-wall strain (RVFWS, −27.1±4.2% vs −28.5±3.3%, p=0.043). RV systolic dysfunction (RVSD) was diagnosed in 14 (13.6%), and was strongly associated with progressive left ventricular systolic dysfunction (LVSD). High dosages of anthracyclines were associated with greater reductions in RV and LV function. Multivariable linear regressions confirmed global longitudinal strain to be a significant independent predictor for reduced RV function.ConclusionImpaired RV function was found in long-term survivors of allo-HSCT who were treated in their youth. This was associated with progressive left ventricle dysfunction, and pretransplant therapies with anthracyclines. The occurrence of RVSD was less frequent and was milder than coexisting LVSD in this cohort.
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de Beurs, K. M., and G. M. Henebry. "Northern Annular Mode Effects on the Land Surface Phenologies of Northern Eurasia." Journal of Climate 21, no. 17 (September 1, 2008): 4257–79. http://dx.doi.org/10.1175/2008jcli2074.1.
Повний текст джерелаАнотація:
Abstract Land surface phenology (LSP) is the spatiotemporal development of the vegetated land surface as revealed by synoptic sensors. Modeling LSP across northern Eurasia reveals the magnitude, significance, and spatial pattern of the influence of the northern annular mode. Here the authors fit simple LSP models to two normalized difference vegetation index (NDVI) datasets and calculate the Spearman rank correlations to link the start of the observed growing season (SOS) and the timing of the peak NDVI with the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices. The relationships between the northern annular mode and weather station data, accumulated precipitation derived from the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) dataset, accumulated growing degree-days (AGDDs) derived from the NCEP–Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) reanalysis, and the number of snow days from the National Snow and Ice Data Center are investigated. The analyses confirm strong relationships between the temporal behavior of temperature and precipitation and large-scale climatic variability across Eurasia. The authors find widespread influence of the northern annular mode (NAM) on the land surface phenologies across northern Eurasia affecting 200–300 Mha. The tundra ecoregions were especially impacted with significant results for about a quarter of the biome. The influence of the AO was also extensive (>130 Mha) for the boreal forests. The AO appears to affect the Asian part of northern Eurasia more strongly than the NAO, especially for the NDVI peak position as a function of AGDD. Significant responses of vegetation timing to NAO and AO in northeastern Russia have not been as well documented as the seasonal advancement in Europe. The two Advanced Very High Resolution Radiometer NDVI datasets yield fields of LSP model parameter estimates that are more similar in dates of peak position than in dates for SOS and more similar for AO than for NAO. As a result, the authors conclude that peak position appears to be a more robust characteristic of land surface phenology than SOS to link vegetation dynamics to variability and change in regional and global climates.
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Pfaff, Marina, Michael F. G. Klein, Erich Müller, Philipp Müller, Alexander Colsmann, Uli Lemmer, and Dagmar Gerthsen. "Nanomorphology of P3HT:PCBM-Based Absorber Layers of Organic Solar Cells after Different Processing Conditions Analyzed by Low-Energy Scanning Transmission Electron Microscopy." Microscopy and Microanalysis 18, no. 6 (November 20, 2012): 1380–88. http://dx.doi.org/10.1017/s143192761201344x.
Повний текст джерелаАнотація:
AbstractIn this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.
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Gold, Jonathan, Yohei Akazawa, Mei Sun, Kendall S. Hunter, and Mark K. Friedberg. "Relation between right ventricular wall stress, fibrosis, and function in right ventricular pressure loading." American Journal of Physiology-Heart and Circulatory Physiology 318, no. 2 (February 1, 2020): H366—H377. http://dx.doi.org/10.1152/ajpheart.00343.2019.
Повний текст джерелаАнотація:
Right ventricle (RV) pressure loading can lead to RV fibrosis and dysfunction. We previously found increased RV, septal hinge-point and left ventricle (LV) fibrosis in experimental RV pressure loading. However, the relation of RV wall stress to biventricular fibrosis and dysfunction is incompletely defined. Rabbits underwent progressive pulmonary artery banding (PAB) over 3 wk with hemodynamics, echocardiography, and myocardial samples obtained at a terminal experiment at 6 wk. An additional group received PAB and treatment with an endothelin receptor antagonist. The endocardial and epicardial borders of short-axis echo images were traced and analyzed with invasive pressures to yield regional end-diastolic (ED) and end-systolic (ES) wall stress. To increase clinical translation, computer model-derived wall stress was compared with Laplace wall stress. The relation of wall stress with fibrosis (picrosirius red staining) and ventricular function was analyzed. ED wall stress in all regions and RV and LV free-wall ES wall stress were increased in PAB rabbits versus sham animals. Laplace wall stress correlated well with computational models. In PAB, fibrosis was highest in the RV free wall, then septal hinge regions, and lowest in the septum and LV free wall. Fibrosis was moderately related to ED ( r = 0.47, P = 0.0011), but not ES wall stress. RV ED wall stress was strongly related to echo indexes of function (strain rate: r = 0.71, P = 0.048; E′, r = −0.75, P = 0.0077; tricuspid annular plane systolic excursion: r = 0.85, P = 0.0038) and RV fractional area change ( r = 0.77, P = 0.027). ED, more than ES, wall stress is related moderately to fibrosis and strongly to function in experimental RV pressure loading, especially at the septal hinge-point regions, where fibrosis is prominent. This suggests that wall stress partially links RV pressure loading, fibrosis, and dysfunction and may be useful to follow clinically. NEW & NOTEWORTHY Biventricular fibrosis and dysfunction impact outcomes in RV pressure loading, but their relation to wall stress is poorly defined. Using a pulmonary artery band rabbit model, we entered echocardiography and catheter data into a computer model to yield regional end-diastolic (EDWS) and end-systolic (ESWS) wall stress. EDWS, more than ESWS, correlated with fibrosis and dysfunction, especially at the fibrosis-intense septal hinge-point regions. Thus, wall stress may be clinically useful in linking RV pressure loading to regional fibrosis and dysfunction.
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Redett, David A. "Strongly Annular Functions in Bergman Space." Computational Methods and Function Theory 7, no. 2 (June 22, 2007): 429–32. http://dx.doi.org/10.1007/bf03321655.
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Pui, Alexander, Ashish Sharma, Agus Santoso, and Seth Westra. "Impact of the El Niño–Southern Oscillation, Indian Ocean Dipole, and Southern Annular Mode on Daily to Subdaily Rainfall Characteristics in East Australia." Monthly Weather Review 140, no. 5 (May 1, 2012): 1665–82. http://dx.doi.org/10.1175/mwr-d-11-00238.1.
Повний текст джерелаАнотація:
Abstract The relationship between seasonal aggregate rainfall and large-scale climate modes, particularly the El Niño–Southern Oscillation (ENSO), has been the subject of a significant and ongoing research effort. However, relatively little is known about how the character of individual rainfall events varies as a function of each of these climate modes. This study investigates the change in rainfall occurrence, intensity, and storm interevent time at both daily and subdaily time scales in east Australia, as a function of indices for ENSO, the Indian Ocean dipole (IOD), and the southern annular mode (SAM), with a focus on the cool season months. Long-record datasets have been used to sample a large variety of climate events for better statistical significance. Results using both the daily and subdaily rainfall datasets consistently show that it is the occurrence of rainfall events, rather than the average intensity of rainfall during the events, which is most strongly influenced by each of the climate modes. This is shown to be most likely associated with changes to the time between wet spells. Furthermore, it is found that despite the recent attention in the research literature on other climate modes, ENSO remains the leading driver of rainfall variability over east Australia, particularly farther inland during the winter and spring seasons. These results have important implications for how water resources are managed, as well as how the implications of large-scale climate modes are included in rainfall models to best capture interannual and longer-scale variability.
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Vledouts, A., J. Quinard, N. Vandenberghe, and E. Villermaux. "Explosive fragmentation of liquid shells." Journal of Fluid Mechanics 788 (January 5, 2016): 246–73. http://dx.doi.org/10.1017/jfm.2015.716.
Повний текст джерелаАнотація:
The forced radial expansion of a spherical liquid shell by an exothermic chemical reaction is a prototypical configuration for the explosion of cohesive materials in three dimensions. The shell is formed by the capillary pinch off of a thin liquid annular jet surrounding a jet of reactive gaseous mixture at ambient pressure. The encapsulated gas in the resulting liquid bubble is a mixture of hydrogen and oxygen in controlled relative proportions, which is ignited by a laser plasma aimed at the centre of the bubble. The strongly exothermic combustion of the mixture induces the expansion of the hot burnt gas, pushing the shell radially outwards in a violently accelerated motion. That motion triggers the instability of the shell, developing thickness modulations ultimately piercing it in a number of places. The capillary retraction of the holes concentrates the liquid constituting the shell into a web of ligaments, whose breakup leads to stable drops. We offer a comprehensive description of the overall process, from the kinematics of the shell initial expansion, to the final drop size distribution as a function of the composition of the gas mixture, the initial shell radius and thickness.
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Tournadre, Jean, Bertrand Chapron, and Nicolas Reul. "High-Resolution Imaging of the Ocean Surface Backscatter by Inversion of Altimeter Waveforms." Journal of Atmospheric and Oceanic Technology 28, no. 8 (August 1, 2011): 1050–62. http://dx.doi.org/10.1175/2011jtecho820.1.
Повний текст джерелаАнотація:
Abstract This paper presents a new method to analyze high-resolution altimeter waveforms in terms of surface backscatter. Over the ocean, a basic assumption of modeling altimeter echo waveforms is to consider a homogeneous sea surface within the altimeter footprint that can be described by a mean backscatter coefficient. When the surface backscatter varies strongly at scales smaller than the altimeter footprint size, such as in the presence of surface slicks, rain, small islands, and altimeter echoes can be interpreted as high-resolution images of the surface whose geometry is annular and not rectangular. A method based on the computation of the imaging matrix and its pseudoinverse to infer the surface backscatter at high resolution (~300 m) from the measured waveforms is presented. The method is tested using synthetic waveforms for different surface backscatter fields and is shown to be unbiased and accurate. Several applications can be foreseen to refine the analysis of rain patterns, surface slicks, and lake surfaces. The authors choose here to focus on the small-scale variability of backscatter induced by a submerged reef smaller than the altimeter footprint as the function of tide, significant wave height, and wind.
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Zhang, Ning, Yunfei Zhang, Denghui Dai, Yu Zhang, Baoyin Sun, and Xin Chen. "Propagation of Nonplanar SH Waves Emanating from a Fault Source around a Lined Tunnel." Sustainability 14, no. 16 (August 15, 2022): 10127. http://dx.doi.org/10.3390/su141610127.
Повний текст джерелаАнотація:
An analytical solution is presented for scattering nonplanar SH waves emanating from a fault source using a lined tunnel. The lined tunnel is assumed to be an annular elastic solid in half-space. A simplified circular arc fault model is employed to represent the wave source. By means of the separation of variables method, all wave fields are given in terms of the wave function series with unknown coefficients. Taking advantage of the method of images, the zero-stress boundary condition on the horizontal ground surface is satisfied automatically. By applying Graf’s addition formula, a system of equations for seeking the unknowns is derived by taking advantage of the boundary conditions. The problem of wave scattering is finally solved after seeking solutions for the system of equations through standard matrix techniques. The effects of fault distance, fault curvature, and fault orientation are revealed with numerical results. It is found that the plane waves provide a good approximation to the fault-induced cylindrical waves when the source-receiver distance or fault radius of curvature is larger enough. Fault-induced topographic effects are strongly affected by source orientation.
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Bernal-González, Luis, and Antonio Bonilla. "Families of strongly annular functions: linear structure." Revista Matemática Complutense 26, no. 1 (September 1, 2011): 283–97. http://dx.doi.org/10.1007/s13163-011-0080-9.
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Fogt, Ryan L., and David H. Bromwich. "Decadal Variability of the ENSO Teleconnection to the High-Latitude South Pacific Governed by Coupling with the Southern Annular Mode*." Journal of Climate 19, no. 6 (March 15, 2006): 979–97. http://dx.doi.org/10.1175/jcli3671.1.
Повний текст джерелаАнотація:
Abstract Decadal variability of the El Niño–Southern Oscillation (ENSO) teleconnection to the high-latitude South Pacific is examined by correlating the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-yr Re-Analysis (ERA-40) and observations with the Southern Oscillation index (SOI) over the last two decades. There is a distinct annual contrast between the 1980s and the 1990s, with the strong teleconnection in the 1990s being explained by an enhanced response during austral spring. Geopotential height anomaly composites constructed during the peak ENSO seasons also demonstrate the decadal variability. Empirical orthogonal function (EOF) analysis reveals that the 1980s September–November (SON) teleconnection is weak due to the interference between the Pacific–South American (PSA) pattern associated with ENSO and the Southern Annular Mode (SAM). An in-phase relationship between these two modes during SON in the 1990s amplifies the height and pressure anomalies in the South Pacific, producing the strong teleconnections seen in the correlation and composite analyses. The in-phase relationship between the tropical and high-latitude forcing also exists in December–February (DJF) during the 1980s and 1990s. These results suggest that natural climate variability plays an important role in the variability of SAM, in agreement with a growing body of literature. Additionally, the significantly positive correlation between ENSO and SAM only during times of strong teleconnection suggests that both the Tropics and the high latitudes need to work together in order for ENSO to strongly influence Antarctic climate.
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Petkanych, Myroslav M., Sergiy V. Potashev, Nataliia V. Bankovska, and Vasil V. Lazoryshynets. "Ventricular Myocardial Function and Central Hemodynamics in Patients with Secondary Atrial Septal Defect and Persistent or Paroxysmal Atrial Fibrillation." Ukrainian Journal of Cardiovascular Surgery 30, no. 1 (46) (March 23, 2022): 49–58. http://dx.doi.org/10.30702/ujcvs/22.30(01)/pp005-4958.
Повний текст джерелаАнотація:
Background. Atrial fibrillation (AF) is the world’s most frequent arrhythmia associated with significant morbidity and mortality. Non-invasive multimodal imaging provides all necessary information for tactical decisions about radiofrequency catheter ablation and other methods of pharmacological and invasive AF treatment. Survival of patients with congenital heart diseases (CHDs) has grown over the past years. Still, there is a significant gap in evidence-based data regarding management of such patients with AF. Previously in Ukraine there were no studies of echocardiography parameters in patients with CHDs with paroxysmal or persistent AF, namely, those to find predictors for successful AF treatment before atrial septal defect (ASD) surgical or percutaneous closure.
The aim. To evaluate ventricular myocardial function and central hemodynamics in patients with secondary ASD and paroxysmal or persistent AF compared to patients with paroxysmal or persistent AF without CHD.
Methods. Weexamined54patients(36[66.7%]menand18[33.3%]women)aged61.4±9.8yearswithsecondaryASDand paroxysmal or persistent AF. Control group included 56 patients (38 [67.9%] men and 18 [32.1%] women) without CHD with non-valvular paroxysmal or persistent AF. All the patients underwent transthoracic and transesophageal echocardiography with tissue Doppler imaging and speckle-tracking echocardiography for longitudinal myocardial strain evaluation.
Results. The patients in the study and control groups were comparable in terms of age and gender as well as comorbidities and cardiovascular risk factors. There were significant differences in the left heart remodeling indices and central hemodynamics alteration grades, for instance, the patients of the study group had significantly higher grade of left ventricular (LV) hypertrophy. Patients with ASD also had significantly more dilated LV and left atrium (LA) cavities and higher combined indices of LV filling pressure – E/E’ (14.9±4.2 vs. 9.6±5.3, p<0.0001) and E/Vp (2.84±0.44 vs. 2.25±0.61, p<0.0001), explaining more frequent AF in patients with ASD. The study group patients also had significantly higher systolic (sPAP) (52.4±2.8 vs. 44.6±3.2, p<0.0001) and mean (mPAP) (38.6±4.3 vs. 31.7±1.9, p<0.0001) pulmonary artery pressure compared to control group, as well as significantly worse all known indices of right ventricle (RV) myocardial function and right chambers overload. Global RV longitudinal strain strongly correlated with RV fractional area change (r = 0.75; p<0.0001), and especially highly with tricuspid annular plane systolic excursion (r = 0.97; p<0.0001) and tricuspid annular peak systolic velocity S’ (r = 0.98; p<0.0001) during tissue Doppler imaging, making it trustworthy and valuable predictor of RV myocardial dysfunction and its potential restoration after defect correction. Patients with ASD much more often had significant moderate-to-severe functional tricuspid regurgitation (92.6% vs. 53.4%, p<0.0001) with significantly higher central venous pressure indices (16.4±2.4 vs. 10.2±2.5, p<0.0001) as per significantly wider inferior vena cava (IVC) (1.89±0.31 vs. 1.43±0.42, p<0.0001) and it’s higher inspiratory collapse. IVC diameter strongly correlated with integral RV filling pressure (that is, right atrial pressure) index E/E’ (r = 0.98; p<0.0001). Also, study group demonstrated significantly more frequent LA appendage thrombosis (40.7% vs. 21.4%, p=0.029) along with much more marked spontaneous contrast phenomenon and lower LA appendage expulsion rate (26.7±5.1 vs. 34.3±7.2, p<0.0001).
Conclusions. Stratification of patients with ASD complicated by paroxysmal or persistent AF for radiofrequency catheter ablation requires thorough echocardiographic examination with targeted certain indices evaluation aiming at earlier intervention in order to earlier diagnosis and invasive or surgical treatment in this specific patient group, namely LV hypertrophy grade, left chambers dilation with LV global systolic function evaluation, pulmonary hypertension grade as per sPAP and mPAP evaluation, as well as combined right chambers overload grade indices, including RV myocardial function by all methods including speckle-tracking echocardiography.
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Gietzelt, Thomas, Volker Toth, Manfred Kraut, Uta Gerhards, and Robin Dürrschnabel. "Comprehensive Study of the Deformation Behavior during Diffusion Bonding of 1.4301 (AISI 304) as a Function of Material Width and Aspect Ratio." Metals 10, no. 9 (August 19, 2020): 1116. http://dx.doi.org/10.3390/met10091116.
Повний текст джерелаАнотація:
In this paper, the impact of material width as well as aspect ratio on deformation during diffusion bonding of layered samples were investigated. For this, six annular samples with a constant cross-sectional area but an increasing diameter and thus decreasing material width were designed. In a first set of experiments, specimens of a constant height of h = 20 mm were examined. Each sample consisted of 10 sheets, 2 mm in thickness each. Diffusion bonding was performed at T = 1075 °C, t = 4 h and p = 15 MPa. Subsequently, additional samples with a constant aspect ratio of about three but different material width were diffusion bonded. For this, additional layers were added. It was expected that the deformation should be nearly constant for a constant aspect ratio. However, comparing the deformation to a sample possessing an aspect ratio of about three from the first batch, a much higher deformation was obtained now. Bonding a third sample, a deformation in the same range as for the other two samples of the second batch was obtained. It was found that due to the evaporation of metals, the thermocouples were subjected to aging, which was proven indirectly by the evaluation of heating power. Since the diffusion coefficient of the metals follows an exponential law, deformation changes considerably with temperature. This emphasizes that exact temperature measurement is very important, especially for bonding microprocessor devices at constant contact pressure. The experiments showed that the deformation depends strongly on geometry. Bonding parameters cannot be generalized. For layered setups, the contribution that thickness tolerances from manufacturing and leveling of surface roughnesses of sheets add to the overall deformation cannot be reliably separated. After diffusion bonding, thickness tolerances increase with a lateral dimension. Obviously, the stiffness of the pressure dies is crucial.
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Bauer-Marschallinger, Bernhard, Wouter A. Dorigo, Wolfgang Wagner, and Albert I. J. M. van Dijk. "How Oceanic Oscillation Drives Soil Moisture Variations over Mainland Australia: An Analysis of 32 Years of Satellite Observations*." Journal of Climate 26, no. 24 (December 2, 2013): 10159–73. http://dx.doi.org/10.1175/jcli-d-13-00149.1.
Повний текст джерелаАнотація:
Abstract Australia is frequently subject to droughts and floods. Its hydrology is strongly connected to oceanic and atmospheric oscillations (climate modes) such as the El Niño–Southern Oscillation (ENSO), Indian Ocean dipole (IOD), and southern annular mode (SAM). A global 32-yr dataset of remotely sensed surface soil moisture (SSM) was used to examine hydrological variations in mainland Australia for the period 1978–2010. Complex empirical orthogonal function (CEOF) analysis was applied to extract independent signals and to investigate their relationships to climate modes. The annual cycle signal represented 46.3% of the total variance and a low but highly significant connection with SAM was found. Two multiannual signals with a lesser share in total variance (6.3% and 4.2%) were identified. The first one had an unstable period of 2–5 yr and reflected an east–west pattern that can be associated with ENSO and SAM but not with IOD. The second one, a 1- to 5-yr oscillation, formed a dipole pattern between the west and north and can be linked to ENSO and IOD. As expected, relationships with ENSO were found throughout the year and are especially strong during southern spring and summer in the east and north. Somewhat unexpectedly, SAM impacts strongest in the north and east during summer and is proposed as the key driver of the annual SSM signal. The IOD explains SSM variations in the north, east, and southeast during spring and also in the west during winter.
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Ilyas, Aneeqa, Muhammad Hassan Zafar, and Sana Amin. "HEART FAILURE." Professional Medical Journal 25, no. 02 (February 10, 2018): 282–86. http://dx.doi.org/10.29309/tpmj/2018.25.02.457.
Повний текст джерелаАнотація:
Objectives: To observe the function of left ventricular contractile and its pairingwith failure preserved ejection fraction. Study Design: Observational longitudinal study.Setting: Punjab institute of Cardiology. Period: Jan 2017 to June 2017. Methods: Four Hundredtwenty one Heart failure patients (mean age 51 ± 7 years, 56% females, left ventricular ejectionfraction 55±5%) undergo Left ventricular investigation through echocardiography and left heartcatheterization of 191 patients. Through tricuspid annular plane systolic excursion (TAPSE),Patients were sorting out and data collect. Mean TAPSE score were 15.03±4.06 cm without anygender differences. Body surface presents strong relation with TAPSE values (r=0.74). Manydifferent pattern consistently found within same patients leading to heart failure, but patientswith HFpEFin which each component is operative behave differently. Results: Transformationof different evidences in clinical practice needs proper level of proofs regarding evidences. Outof four hundred twenty one heart failure patients, patients with prolonged heart failure symptomsand high rate of ejection fraction due to adaptive changes by the human body, whereas patientswith aggressive mode of work have high mortality ratio. Out of all physiological derangementswere strongly link with the TAPSE. Different biomarker-based strategies are much required toimplement for excellent patient outcome in heart diseases. Conclusion: Using most commonclinical features, we listed four major features with mark differences acts in remodeling andmaintain in heart failure. Patients with decreases ejection fraction have more advanced heartfailure. Therapeutic treatment specifically targeting main components of heart failure havebetter pathophysiological changes in less time. HFpEF patients are more chances to developadaptive cardiac changes.
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Mettu, Anilkumar, Ninad Loke, Vilas Patil, Rahul Panday, and Sreenivasarao Gajula. "Hydrocracking of Di-and Triaromatic Hydrocarbons to Monoaromatics over Mixed Bi-functional Catalysts." Catalysis Research 2, no. 3 (January 10, 2022): 1. http://dx.doi.org/10.21926/cr.2203021.
Повний текст джерелаАнотація:
In this study, we present selective hydrocracking of poly (di and tri) aromatic compounds to monoaromatics, such as benzene, toluene, and xylenes (BTX), over a mixture of Pt/Al2O3 and Y zeolites. The polyaromatic compounds feed is a combined simulated model feed, which is similar to light cycle oil (LCO) in composition. The feed is processed in a fixed bed reactor over a catalyst mixture: in the first step, selective hydrogenation of di and tri-aromatic compounds occurs in the presence of Pt/Al2O3 catalyst, followed by conversion of selective hydrocracking of partial hydrogenated polyaromatic hydrocarbons into BTX-rich stream over Y zeolite. The structural properties and Pt dispersion of Pt/Al2O3 were studied by X-ray powder diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The acidity of Y zeolite with different SiO2/Al2O3 ratios (SAR) was studied by temperature-programmed desorption of NH3 (NH3-TPD). In addition, the textural properties of catalysts were determined using the N2 adsorption and desorption method. Different parameters such as the effect of temperature, effect of weight hourly space velocity (WHSV), different SAR of Y zeolite, Pt/Al2O3, and Y zeolite wt% ratios, and paraffin concentration were investigated. The maximum BTX yield of ~28 wt.% was obtained at 450°C, WHSV-0.7 h-1, H2 pressure 60 bar, Pt/Al2O3, and Y zeolite ratios of 1:2 (wt%) at Y zeolite SAR of 80. These results suggest that the yield of BTX strongly depends on the hydrogenation function (Pt/Al2O3) and acidity function of Y zeolite. Furthermore, the concentration of paraffin plays a key role in the conversion of diaromatics and triaromatics and desired products of BTX formation.
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Song, Xiangzhou, and Lisan Yu. "High-Latitude Contribution to Global Variability of Air–Sea Sensible Heat Flux." Journal of Climate 25, no. 10 (May 14, 2012): 3515–31. http://dx.doi.org/10.1175/jcli-d-11-00028.1.
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Abstract The study examined global variability of air–sea sensible heat flux (SHF) from 1980 to 2009 and the large-scale atmospheric and ocean circulations that gave rise to this variability. The contribution of high-latitude wintertime SHF was identified, and the relative importance of the effect of the sea–air temperature difference versus the effect of wind on decadal SHF variability was analyzed using an empirical orthogonal function (EOF) approach. The study showed that global SHF anomalies are strongly modulated by SHF at high latitudes (poleward of 45°) during winter seasons. Decadal variability of global wintertime SHF can be reasonably represented by the sum of two leading EOF modes, namely, the boreal wintertime SHF in the northern oceans and the austral wintertime SHF in the southern oceans. The study also showed that global wintertime SHF is modulated by the prominent modes of the large-scale atmospheric circulation at high latitudes. The increase of global SHF in the 1990s is attributable to the strengthening of the Southern Hemisphere annular mode index, while the decrease of global SHF after 2000 is due primarily to the downward trend of the Arctic Oscillation index. This study identified the important effects of wind direction and speed on SHF variability. Changes in winds modify the sea–air temperature gradient by advecting cold and dry air from continents and by imposing changes in wind-driven oceanic processes that affect sea surface temperature (SST). The pattern of air temperature anomalies dominates over the pattern of SST anomalies and dictates the pattern of decadal SHF variability.
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Pi, Hongyang, Samuel G. Rayner, David D. Ralph, Stephanie Nolley, Lia M. Barros, Zachary L. Steinberg, and Peter J. Leary. "Thyroid-stimulating hormone and mortality in pulmonary arterial hypertension." BMJ Open Respiratory Research 9, no. 1 (July 2022): e001348. http://dx.doi.org/10.1136/bmjresp-2022-001348.
Повний текст джерелаАнотація:
IntroductionPulmonary arterial hypertension (PAH) remains a serious and life-threatening illness. Thyroid dysfunction is relatively understudied in individuals with PAH but is known to affect cardiac function and vascular tone in other diseases. The aim of this observational study was to evaluate the association between thyroid-stimulating hormone (TSH), mortal and non-mortal outcomes in individuals with PAH.MethodsThe Seattle Right Ventricle Translational Science (Servetus) Study is an observational cohort that enrolled participants with PAH between 2014 and 2016 and then followed them for 3 years. TSH was measured irrespective of a clinical suspicion of thyroid disease for all participants in the cohort. Linear regression was used to estimate the relationships between TSH and right ventricular basal diameter, tricuspid annular plane systolic excursion and 6-minute walk distance. Logistic regression was used to estimate the relationship with New York Heart Association Functional Class, and Cox proportional hazards were used to estimate the relationship with mortality. Staged models included unadjusted models and models accounting for age, sex at birth and aetiology of pulmonary hypertension with or without further adjustment for N-terminal-pro hormone brain natriuretic peptide.ResultsAmong 112 participants with PAH, TSH was strongly associated with mortality irrespective of adjustment. There was no clear consistent association between TSH and other markers of severity in a cohort with PAH.DiscussionThis report reinforces the important observation that TSH is associated with survival in patients with PAH, and future study of thyroid dysfunction as a potential remediable contributor to mortality in PAH is warranted.
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Guo, Sian Wun, and Jik Chang Leong. "MHD Couette Flow in Cylindrical Porous Annulus with Perfectly Conducting Walls." Applied Mechanics and Materials 284-287 (January 2013): 829–33. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.829.
Повний текст джерелаАнотація:
This work obtained an analytical solution for a steady cylindrical MHD Couette flow in a porous medium between two perfectly conducting rotating cylinders under the influence of a non-uniform radial magnetic field. Since part of the analytical solution is expressed in terms of the integral of the Modified Bessel function of the first and second kinds of variable order, numerical integration was performed. Current results indicate that the flow may become more uniform when the strength of the external magnetic field is increased. The magnetic fluid tends to slow down if the permeability of the porous medium decreases. If the porous annulus is thick, the momentum of the flow is more difficult to propagate from the outer cylinder into the inner part of the annulus. If both the inner and outer cylinders rotate, the shear effect the inner cylinder imposes is only relatively influential in the region close to it. A decrease in Da no less than 10-2 may increase the amount of magnetic field induced. The transfer of momentum across the annular space is easier in a thin porous annulus than a thick one and hence induces a stronger magnetic field. If the inner cylinder rotates in the direction opposite of the outer one, the magnetic field in the clockwise direction will be induced in some region.
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Lucero, Jacob E., Taylor Noble, Stephanie Haas, Michael Westphal, H. Scott Butterfield, and Christopher J. Lortie. "The dark side of facilitation: native shrubs facilitate exotic annuals more strongly than native annuals." NeoBiota 44 (April 5, 2019): 75–93. http://dx.doi.org/10.3897/neobiota.44.33771.
Повний текст джерелаАнотація:
Positive interactions enhance biodiversity and ecosystem function, but can also exacerbate biological invasions. Facilitation of exotic invaders by exotic foundation species (invasional meltdown) has been studied extensively, but facilitation of exotic invaders by native foundation species has attracted less attention. Specifically, very few studies have examined the extent that native foundation species facilitate native and exotic competitors. Understanding the processes that mediate interactions between native and exotic species can help explain, predict, and improve management of biological invasions. Here, we examined the effects of native foundation shrubs on the relative abundance of the annual plant community – including native and exotic taxa – from 2015–2018 in a desert ecosystem at Carrizo Plain National Monument, California, USA (elevation: 723 m). Shrub effects varied by year and by the identity of annual species, but shrubs consistently enhanced the abundance of the annual plant community and facilitated both native (n=17 species) and exotic (n=4 species) taxa. However, at the provenance level, exotic annuals were facilitated 2.75 times stronger in abundance than native annuals, and exotic annuals were always more abundant than natives both near and away from shrubs. Our study reaffirms facilitation as an important process in the organisation of plant communities and confirms that both native and exotic species can form positive associations with native foundation species. However, facilitation by native foundation species can exacerbate biological invasions by increasing the local abundance of exotic invaders. Thus, the force of facilitation can have a dark side relevant to ecosystem function and management.
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Li, W., M. Yuan, C. D. Carter, and C. Tong. "Experimental investigation of the effects of mean shear and scalar initial length scale on three-scalar mixing in turbulent coaxial jets." Journal of Fluid Mechanics 817 (March 16, 2017): 183–216. http://dx.doi.org/10.1017/jfm.2017.101.
Повний текст джерелаАнотація:
In a previous study we investigated three-scalar mixing in a turbulent coaxial jet (Caiet al.J. Fluid Mech., vol. 685, 2011, pp. 495–531). In this flow a centre jet and a co-flow are separated by an annular flow; therefore, the resulting mixing process approximates that in a turbulent non-premixed flame. In the present study, we investigate the effects of the velocity and length scale ratios of the annular flow to the centre jet, which determine the relative mean shear rates between the streams and the degree of separation between the centre jet and the co-flow, respectively. Simultaneous planar laser-induced fluorescence and Rayleigh scattering are employed to obtain the mass fractions of the centre jet scalar (acetone-doped air) and the annular flow scalar (ethylene). The results show that varying the velocity ratio and the annulus width modifies the scalar fields through mean-flow advection, turbulent transport and small-scale mixing. While the evolution of the mean scalar profiles is dominated by the mean-flow advection, the shape of the joint probability density function (JPDF) was found to be largely determined by the turbulent transport and molecular diffusion. Increasing the velocity ratio results in stronger turbulent transport, making the initial scalar evolution faster. However, further downstream the evolution is delayed due to slower small-scale mixing. The JPDF for the higher velocity ratio cases is bimodal at some locations while it is always unimodal for the lower velocity ratio cases. Increasing the annulus width delays the progression of mixing, and makes the effects of the velocity ratio more pronounced. For all cases the diffusion velocity streamlines in the scalar space representing the effects of molecular diffusion generally converge quickly to a curved manifold, whose curvature is reduced as mixing progresses. The curvature of the manifold increases significantly with the velocity and length scale ratios. Predicting the observed mixing path along the manifold as well as its dependence on the velocity and length scale ratios presents a challenge for mixing models. The results in the present study have implications for understanding and modelling multiscalar mixing in turbulent reactive flows.
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Hanumantha Reddy, M., George Cherian, and Bagirath Raghuraman. "Evaluation of the Results of Balloon Pulmonary Angioplasty in Patients with Chronic Distal Pulmonary Thromboembolic Disease and Pulmonary Hypertension." Indian Journal of Cardiovascular Disease in Women - WINCARS 06, no. 03 (July 2021): 157–64. http://dx.doi.org/10.1055/s-0041-1736257.
Повний текст джерелаАнотація:
Introduction The gold standard curative treatment for chronic pulmonary thromboembolic disease and pulmonary hypertension (CTEPH) is pulmonary thromboendarterectomy (PTE). Balloon pulmonary angioplasty (BPA) is emerging for distal CTEPH patients, where lesion is inaccessible for surgery. This is the first study conducted in Indian patients for evaluating the impact of BPA in patients with distal CTEPH. Aims and Objectives To evaluate the effect of BPA in patients with distal CTEPH with the help of New York Heart Association (NYHA) functional class and 6-minute walk distance (6MWD). To study decrease in pulmonary artery pressure and improvement in right atrial and right ventricular function with the help of echocardiography. Material and Methods Study population—CTEPH patients presenting to the hospital during the study interval of 16 months from January 2017 to April 2018. A. Method: This was an observational retrospective and prospective follow-up study. All distal CTEPH patients after meeting inclusion and exclusion criteria were taken for study. B. Detailed case records containing information on demographics, clinical features and necessary blood and imaging investigations, ventilation/perfusion (V/Q) scan, computed tomography pulmonary angiography (CTPA), right heart catheterization (RHC) study, pulmonary angiogram, and BPA procedure details were obtained for all participants. C. After 8 weeks of last BPA session, patients were assessed clinically and then 6-minute walk test, blood investigations and echocardiography were done. Data Analysis Statistical analysis was performed by using the software SPSS 22.0 version. We used paired t-test to test the significant difference in the mean pre- and post-BPA. p-value < 0.05 will be considered as statistically significant. Results In our study, mean age of presentation was 39.81 ± 12 years. Out of 11 patients, 5 were females and 6 were males. Mean duration of symptoms was 40.5 months. The total number of BPA sessions performed were 30. The minimum number of BPA sessions undergone was 1 and maximum number of BPA sessions undergone by one patient was 5, with 45% of patients undergoing 2 BPA sessions. The total number of segmental arteries dilated was 104. Segmental vessels dilated per each session was 3.46. There was statistically significant improvement in NYHA class and 6MWD after BPA. 6MWD increased from 299 m to 421 m (p-value < 0.001). This improvement in functional capacity is strongly associated with the improvement in right ventricular (RV) function (tricuspid annular plane systolic excursion [TAPSE] from 15.3 mm to 18.9 mm) and with the reduction in pulmonary artery systemic pressure (PASP) (from 92 mm Hg to 60 mm Hg). Conclusion In patients with distal CTEPH who undergo BPA, there was statistically significant improvement in 6MWD. These changes correspond to a treatment-induced reduction in pulmonary artery pressure and lend support to use of BPA in patients with distal CTEPH. ECHO and 6MWD can be used for evaluating BPA efficacy and monitoring disease progression.
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Lubis, Sandro W., and Pedram Hassanzadeh. "An Eddy–Zonal Flow Feedback Model for Propagating Annular Modes." Journal of the Atmospheric Sciences 78, no. 1 (January 2021): 249–67. http://dx.doi.org/10.1175/jas-d-20-0214.1.
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AbstractThe variability of the zonal-mean large-scale extratropical circulation is often studied using individual modes obtained from empirical orthogonal function (EOF) analyses. The prevailing reduced-order model of the leading EOF (EOF1) of zonal-mean zonal wind, called the annular mode, consists of an eddy–mean flow interaction mechanism that results in a positive feedback of EOF1 onto itself. However, a few studies have pointed out that under some circumstances in observations and GCMs, strong couplings exist between EOF1 and EOF2 at some lag times, resulting in decaying-oscillatory, or propagating, annular modes. Here, we introduce a reduced-order model for coupled EOF1 and EOF2 that accounts for potential cross-EOF eddy–zonal flow feedbacks. Using the analytical solution of this model, we derive conditions for the existence of the propagating regime based on the feedback strengths. Using this model, and idealized GCMs and stochastic prototypes, we show that cross-EOF feedbacks play an important role in controlling the persistence of the annular modes by setting the frequency of the oscillation. We find that stronger cross-EOF feedbacks lead to less persistent annular modes. Applying the coupled-EOF model to the Southern Hemisphere reanalysis data shows the existence of strong cross-EOF feedbacks. The results highlight the importance of considering the coupling of EOFs and cross-EOF feedbacks to fully understand the natural and forced variability of the zonal-mean large-scale circulation.
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Belabid, Jabrane, and Soufiane Belhouideg. "Hydromagnetic natural convection from a horizontal porous annulus with heat generation or absorption." MATEC Web of Conferences 307 (2020): 01005. http://dx.doi.org/10.1051/matecconf/202030701005.
Повний текст джерелаАнотація:
The problem of unsteady laminar, two-dimensional hydromagnetic natural convection heat transfer in a concentric horizontal cylindrical annulus filled with a fluid-saturated porous medium in the presence of a transverse magnetic field and fluid heal generation effects is studied numerically. It is assumed that the inner and outer walls of the cylindrical annulus are maintained at uniform and constant temperatures Ti and To respectively. The model consists of the heat equation and the equations of motion under the Darcy law. The derived problem with the stream function-temperature formulation is solved numerically using the alternating direction implicit method. This investigation concerns the effect of magnetic field inclination angle, Hartmann number and heat generation on the heat transfer and the flow pattern. The obtained numerical results are presented graphically in terms of streamlines and isotherms. It was found that the heat transfer mechanisms and the flow characteristics depend strongly on the magnetic field inclination angle, Hartmann number and heat generation..
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Evin, Morgane, Alban Redheuil, Gilles Soulat, Ludivine Perdrix, Golmehr Ashrafpoor, Alain Giron, Jérôme Lamy, et al. "Left atrial aging: a cardiac magnetic resonance feature-tracking study." American Journal of Physiology-Heart and Circulatory Physiology 310, no. 5 (March 1, 2016): H542—H549. http://dx.doi.org/10.1152/ajpheart.00504.2015.
Повний текст джерелаАнотація:
Importance of left atrial (LA) phasic function evaluation is increasingly recognized for its incremental value in terms of prognosis and risk stratification. LA phasic deformation in the pathway of normal aging has been characterized using echocardiographic speckle tracking. However, no data are available regarding age-related variations using feature-racking (FT) techniques from standard cine magnetic resonance imaging (MRI). We studied 94 healthy adults (41 ± 14 yr, 47 women), who underwent MRI and Doppler echocardiography on the same day for left ventricular (LV) diastolic function evaluation. From cine MRI, longitudinal strain and strain rate, radial motion fraction, and radial relative velocity, respectively, corresponding to the reservoir, conduit, and LA contraction phases, were measured using dedicated FT software. Longitudinal strain and radial motion fraction decreased gradually and significantly with aging for both reservoir ( r > 0.31, P < 0.003) and conduit ( r > 0.54, P < 0.001) phases, whereas they remained unchanged during the LA contraction phase. Subsequently, the LA contraction-to-reservoir ratio increased significantly with age ( r > 0.44, P < 0.001). Longitudinal strain rate and radial relative velocity significantly decreased with age (reservoir: r = 0.39, P < 0.001, conduit: r > 0.54, P < 0.001), and these associations tended to be stronger in women than in men. Finally, associations of LA functional indexes with age were stronger in individuals with lower transmitral early-to-atrial maximal velocity ratio and mitral annulus maximal longitudinal velocity, as well as higher transmitral early maximal-to-mitral annulus maximal longitudinal velocity ratio, highlighting the LV-LA interplay. Age-related changes in LA phasic function indexes were quantified by cine MRI images using a FT technique and were significantly related to age and LV diastolic function.
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Ye, Zi, Patricia A. Pellikka, and Iftikhar J. Kullo. "Sex differences in associations of cardio-ankle vascular index with left ventricular function and geometry." Vascular Medicine 22, no. 6 (September 20, 2017): 465–72. http://dx.doi.org/10.1177/1358863x17725810.
Повний текст джерелаАнотація:
The cardio-ankle vascular index (CAVI) is a measure of global arterial stiffness. We hypothesized that CAVI is associated with left ventricular (LV) function and geometry in individuals without structural heart disease. We measured CAVI in 600 participants (mean age 60.3±14.6 years, 54% men) without history of atherosclerotic cardiovascular disease who were referred for transthoracic echocardiography. Linear regression analysis was used to assess the association of CAVI with LV function (peak mitral annular systolic s’ and early diastolic velocity e’) and structure (LV mass index (LVMI) and relative wall thickness (RWT)). Older age, male sex, lower body mass index, history of hypertension, diabetes and chronic kidney disease were each associated with a higher CAVI (adjusted R2 = 0.56, all p < 0.01). A higher CAVI was associated with lower s’ and e’, and greater RWT, independent of age, sex, systolic BP and other conventional cardiovascular risk factors (all p < 0.05); a borderline association of higher CAVI with greater LVMI ( p = 0.05) was present. Associations with e’, s’ and RWT were similar in women and men but the association with LVMI was stronger in women than in men ( p for interaction = 0.02, multivariable-adjusted β = 6.92, p < 0.001 in women; p > 0.1 in men). In conclusion, a higher CAVI, a measure of global arterial stiffness, is associated with worse LV systolic function, worse diastolic relaxation, and greater LV RWT in both men and women, and with LVMI in women.
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de Sousa, José Renato M., Fernando J. M. de Sousa, Marcos Q. de Siqueira, Luís V. S. Sagrilo, and Carlos Alberto D. de Lemos. "A Theoretical Approach to Predict the Fatigue Life of Flexible Pipes." Journal of Applied Mathematics 2012 (2012): 1–29. http://dx.doi.org/10.1155/2012/983819.
Повний текст джерелаАнотація:
This paper focuses on a theoretical approach to access the fatigue life of flexible pipes. This methodology employs functions that convert forces and moments obtained in time-domain global analyses into stresses in their tensile armors. The stresses are then processed by well-known cycle counting methods, andS-Ncurves are used to evaluate the fatigue damage at several points in the pipe’s cross-section. Finally, Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers, the effect of the annulus conditions, the importance of evaluating the fatigue life in various points of the pipe’s cross-section, and the effect of mean stresses. The results obtained suggest that the friction between layers and the annulus conditions strongly influences the fatigue life of flexible pipes. Moreover, mean stress effects are also significant, and at least half of the wires in each analyzed section of the pipe must be considered in a typical fatigue analysis.
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McDaniel, Robert Ray, Asoke Kumar Deysarkar, Michael Joseph Callanan, and Charles A. Kohlhaas. "An Improved Method for Measuring Fluid Loss at Simulated Fracture Conditions." Society of Petroleum Engineers Journal 25, no. 04 (August 1, 1985): 482–90. http://dx.doi.org/10.2118/10259-pa.
Повний текст джерелаАнотація:
Abstract A test apparatus is designed to carry out dynamic and static fluid-loss tests of fracturing fluids. This test apparatus simulates the pressure difference, temperature, rate of shear, duration of shear, and fluid-flow pattern expected under fracture conditions. For a typical crosslinked fracturing fluid, experimental results indicate that fluid loss values can be a function of temperature, pressure differential, rate of shear, and degree of non-Newtonian behavior of the fracturing fluid. A mathematical development demonstrates that the fracturing-fluid coefficient and filter-cake coefficient can be obtained only if the individual pressure drops can be measured during a typical fluid-loss test. Introduction In a hydraulic fracturing treatment, the development of fracture length and width is strongly dependent on a number of key fluid and formation parameters. One of the most important of these parameters is the rate at which the fracturing fluid leaks, off into the created fracture faces. This parameter, identified as fluid loss, also influences the time required for the fracture to heal after the stimulation treatment has been terminated. This in turn will influence the final distribution of proppant in the fracture and will dictate when the well can be reopened and the cleanup process started. Historically, tests to measure fluid loss have been carried out primarily under what is characterized as static conditions. In such tests, the fracturing fluid is forced through filter paper or through a thin core wafer under a pressure gradient, and the flow rate at the effluent side is determined. Of course, the use of filter paper cannot account for reservoir formation permeability and porosity; therefore, the fluid-loss characteristics derived from such tests should be viewed as only gross approximations. The static core-wafer test on the other hand, reflects to some extent the interaction of the formation and fracturing-fluid properties. However, one important fluid property is altogether ignored in such static core-wafer tests. This is the effect of shear rate in the fracture on the rheology (viscosity) of fracturing fluid and subsequent effects of viscosity on the fluid loss through the formation rock. In the past, several attempts were made to overcome the drawbacks of static core-wafer tests by adopting dynamic fluid-loss tests. Although these dynamic tests were a definite improvement over the static versions, each had drawbacks or limitations that could influence test results. In some of the studies, the shearing area was annular rather than planar as encountered in the fracture. In other cases, the fluid being tested did not experience a representative shear rate for a sufficiently long period of time. An additional problem arose because most studies were performed at moderate differential pressures and temperatures. The final drawback in several of the studies was that the fluid flow and leakoff patterns did not realistically simulate those occurring in the field. In the first part of this paper, we emphasize the design of a dynamic fluid-loss test apparatus that possesses none of these drawbacks. In the second part of the paper, test results with this apparatus are presented for three different fluid systems. These systems areglycerol, a non-wall-building Newtonian fluid,a polymer gel solution that is slightly wall-building and non-Newtonian, anda crosslinked fracturing system that is highly non-Newtonian in nature and possesses the ability to build a wall (filter cake) on the fracture face (see Table 1). The fluids were subjected to both static and dynamic test procedures. In the third part of the paper, results of experiments carried out with crosslinked fracturing fluid for different core lengths, pressure differences, temperatures, and shear rates are compared and the significance of the difference of fluid loss is emphasized. Experimental Equipment and Procedure The major components of the experimental apparatus shown in Fig. 1 are a fluid-loss cell, circulation pump, heat exchanger, system pressurization accumulators, and a fluid-loss recording device. The construction material throughout most of the system is 316 stainless steel. The fluid loss is measured through a cylindrical core sample, 1.5 in. [3.81 cm] in diameter, mounted in the fluid-loss cell. Heat-shrink tubing is fitted around the circumference of the core and a confining pressure is maintained to prevent channeling. Fracturing fluid is circulated through a rectangular channel across one end of the core. SPEJ P. 482^
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Cesario, M. M., and J. R. Bartles. "Compartmentalization, processing and redistribution of the plasma membrane protein CE9 on rodent spermatozoa. Relationship of the annulus to domain boundaries in the plasma membrane of the tail." Journal of Cell Science 107, no. 2 (February 1, 1994): 561–70. http://dx.doi.org/10.1242/jcs.107.2.561.
Повний текст джерелаАнотація:
Western blotting, immunofluorescence and immunogold electron microscopy were used to examine the compartmentalization, processing and redistribution of the integral plasma membrane protein CE9 on the spermatozoa of rats, mice and hamsters. In each species examined, spermatozoal CE9 was found to undergo endoproteolytic processing followed by a net redistribution from the posterior-tail domain into the anterior-tail domain of the plasma membrane during epididymal maturation. Compared to spermatozoa of the rat and mouse, those of the hamster were found to express a greater proportion of their CE9 within the anterior-tail plasma membrane domain at all stages of maturation. As a consequence, CE9 was judged to be a suitable marker for two different spermatozoal plasma membrane domains: the posterior-tail plasma membrane domain (spermatozoa from the testis and caput epididymidis of the rat and mouse) and the anterior-tail domain (spermatozoa from the cauda epididymidis of the hamster). Immunogold electron microscopy was used to pinpoint the positions of the boundaries of these CE9-containing plasma membrane domains at a high level of resolution. In each case, the position of the CE9 domain boundary was found to be strongly correlated with that of the subplasmalemmal electron-dense ring known as the annulus. The precise spatial relationship between the CE9 domain boundary and the annulus was, however, found to differ significantly among species and/or as a function of maturation.
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Sinclair, Kate E., Nancy A. N. Bertler, and Tas D. van Ommen. "Twentieth-Century Surface Temperature Trends in the Western Ross Sea, Antarctica: Evidence from a High-Resolution Ice Core." Journal of Climate 25, no. 10 (May 14, 2012): 3629–36. http://dx.doi.org/10.1175/jcli-d-11-00496.1.
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Abstract A 125-yr ice core record of climate from the Whitehall Glacier ice divide provides exceptionally high-resolution stable isotope data from the northwest margin of the Ross Sea, Antarctica. This is the only proxy data available to extend the instrumental record of temperature in this region, where little is known about climate variability over the past two centuries. Using ECMWF Interim Re-Analysis (ERA-Interim) data, this study develops a precipitation-weighted δ18O-temperature transfer function of 0.62‰ °C−1, which is comparable to other proximal ice cores, such as Taylor, Talos, and Law Domes. Reconstructed mean annual temperatures show no significant change between 1882 and 2006. However, a decrease in cold season [April–September (AMJJAS)] temperatures of −1.59° ± 0.84°C decade−1 (at 90% confidence) is observed since 1979. This cooling trend is in contrast to a surface temperature record from Ross Island (Scott Base) where significant spring warming is observed. It is also coincident with a positive trend in the southern annular mode, which is linked to stronger southerly winds and increased sea ice extent and duration in the western Ross Sea.
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Shamsah, Alyah, Sarah Cartmell, Stephen Richardson, and Lucy Bosworth. "Mimicking the Annulus Fibrosus Using Electrospun Polyester Blended Scaffolds." Nanomaterials 9, no. 4 (April 3, 2019): 537. http://dx.doi.org/10.3390/nano9040537.
Повний текст джерелаАнотація:
Treatments to alleviate chronic lower back pain, caused by intervertebral disc herniation as a consequence of degenerate annulus fibrosus (AF) tissue, fail to provide long-term relief and do not restore tissue structure or function. This study aims to mimic the architecture and mechanical environment of AF tissue using electrospun fiber scaffolds made from synthetic biopolymers-poly(ε-caprolactone) (PCL) and poly(L-lactic) acid (PLLA). Pure polymer and their blends (PCL%:PLLA%; 80:20, 50:50, and 20:80) are studied and material properties-fiber diameter, alignment, % crystallinity, tensile strength, and water contact angle-characterized. Tensile properties of fibers angled at 0°, 30°, and 60° (single layer scaffolds), and ±0°, ±30°, and ±60° (bilayer scaffolds) yield significant differences, with PCL being significantly stiffer with the addition of PLLA, and bilayer scaffolds considerably stronger. Findings suggest PCL:PLLA 50:50 fibers are similar to human AF properties. Furthermore, in vitro culture of AF cells on 50:50 fibers demonstrates attachment and proliferation over seven days. The optimal polymer composition for production of scaffolds that closely mimic AF tissue both structurally, mechanically, and which also support and guide favorable cell phenotype is identified. This study takes a step closer towards successful AF tissue engineering and a long-term treatment for sufferers of chronic back pain.
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Früh, W. G. "Low-order models of wave interactions in the transition to baroclinic chaos." Nonlinear Processes in Geophysics 3, no. 3 (September 30, 1996): 150–65. http://dx.doi.org/10.5194/npg-3-150-1996.
Повний текст джерелаАнотація:
Abstract. A hierarchy of low-order models, based on the quasi-geostrophic two-layer model, is used to investigate complex multi-mode flows. The different models were used to study distinct types of nonlinear interactions, namely wave- wave interactions through resonant triads, and zonal flow-wave interactions. The coupling strength of individual triads is estimated using a phase locking probability density function. The flow of primary interest is a strongly modulated amplitude vacillation, whose modulation is coupled to intermittent bursts of weaker wave modes. This flow was found to emerge in a discontinuous bifurcation directly from a steady wave solution. Two mechanism were found to result in this flow, one involving resonant triads, and the other involving zonal flow-wave interactions together with a strong β-effect. The results will be compared with recent laboratory experiments of multi-mode baroclinic waves in a rotating annulus of fluid subjected to a horizontal temperature gradient.
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Friedberg, Mark K., Renee Margossian, Minmin Lu, Laura Mercer-Rosa, Heather T. Henderson, Arni Nutting, Kevin Friedman, et al. "Systolic-diastolic functional coupling in healthy children and in those with dilated cardiomyopathy." Journal of Applied Physiology 120, no. 11 (June 1, 2016): 1301–18. http://dx.doi.org/10.1152/japplphysiol.00635.2015.
Повний текст джерелаАнотація:
Systolic and diastolic function affect dilated cardiomyopathy (DCM) outcomes. However, systolic-diastolic coupling, as a distinct characteristic, may itself affect function but is poorly characterized. We hypothesized that echocardiographic left ventricular (LV) longitudinal systolic tissue velocities (S') correlate with diastolic longitudinal velocities (E') and that their relationship is associated with ventricular function and that this relationship is impaired in pediatric DCM. We analyzed data from the Pediatric Heart Network Ventricular Volume Variability study, using linear regression and generalized additive modeling to assess relationships between S' and E' at the lateral and septal mitral annulus. We explored relationships between the systolic:diastolic (S:D) coupling ratio (S':E' relative to age) and ventricular function. Up to 4 echocardiograms from 130 DCM patients (mean age: 9.3 ± 6.1 yr) and 1 echocardiogram from each of 591 healthy controls were analyzed. S' and E' were linearly related in controls ( r = 0.64, P < 0.001) and DCM ( r = 0.83, P < 0.001). In DCM, the magnitude of association between S' and E' was reduced with progressive ventricular remodeling. The S:D ratio was more strongly associated with LV function in controls vs. DCM. The septal S:D ratio was higher (presumed worse) in DCM vs. controls (0.69 ± 0.13 vs. 0.62 ± 0.12, P = 0.001). A higher septal S:D ratio was associated with worse LV dimensions (parameter estimate: 0.0061, P = 0.004), mass (parameter estimate: 0.0074, P = 0.002), ejection fraction (parameter estimate: −0.0303, P = 0.024), and inflow propagation (parameter estimate: −0.3538, P < .001). S:D coupling becomes weaker in DCM with LV remodeling and dysfunction. The S:D coupling ratio may be useful to assess coupling, warranting study in relation to patient outcomes.
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Hio, Yasuko, and Shigeo Yoden. "Interannual Variations of the Seasonal March in the Southern Hemisphere Stratosphere for 1979–2002 and Characterization of the Unprecedented Year 2002." Journal of the Atmospheric Sciences 62, no. 3 (March 1, 2005): 567–80. http://dx.doi.org/10.1175/jas-3333.1.
Повний текст джерелаАнотація:
Abstract Dynamical features of the interannual variations of the seasonal march in the Southern Hemisphere stratosphere are investigated with the NCEP–NCAR reanalysis dataset from 1979 to 2002, and the unprecedented year 2002, in which a major stratosphere sudden warming occurred, is characterized by comparing it with the other 23 yr. A multiple empirical orthogonal function analysis of the stratospheric mean zonal wind and a composite analysis based on the principal component of the leading mode show that the interannual variations are characterized by early or late deceleration of the polar-night jet, which is well correlated with the variation of a time-averaged upward Eliassen–Palm (EP) flux in the lower stratosphere. The stronger wave activity in the lower stratosphere is associated with the earlier “shift down” of the jet. The composite difference of the stratospheric mean zonal wind can be traced down to the lower troposphere in September and October. These features are consistent with the variations of the Southern Hemisphere annular mode, although the main disturbance to maintain the variations is different between the stratosphere and troposphere. Some scatter diagrams show the extreme situation of the year 2002. It is far from the cluster of the other 23 yr, but the large deviation in 2002 is consistent with the tendency of the fluctuations in the other years except for its extreme nature.
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Matar, Maher, Ala’aldeen Al-Halhouli, Andreas Dietzel, and Stephanus Büttgenbach. "Performance enhancement of the synchronous micropump based on experimental and numerical investigations of the magnetic field flux density in planar microcoils." Transactions of the Institute of Measurement and Control 40, no. 2 (August 25, 2016): 469–76. http://dx.doi.org/10.1177/0142331216661757.
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This study presents numerical and experimental investigations targeting enhancing the magnetic field flux magnitudes in electroplated copper microcoils. Improved designs are used in the development of a new generation of the electromagnetic-based synchronous micropump in order to enhance its performance (i.e. the maximum achievable output pressure and flow rate). The synchronous micropump concept is based on managing the movement of two magnets in an annular fluidic channel. The magnets’ rotation is achieved by sequentially activating a set of three-dimensional microcoils to repel or attract one magnet (travelling piston) through the channel, whereas the second one is anchored between the inlet and the outlet ports (valve piston). At the end of each pumping cycle, the magnets exchange their functions. To achieve the maximum achievable output pressure and flow rate, higher magnetic fields without exceeding the material temperature limitation are required. The stronger the magnetic fields that can be generated, the higher the hydraulic power that the pump can deliver. The microcoil conductor width and height were optimized to generate higher magnetic field flux intensity within the pump limitation parameters (i.e. pump footprint and coils’ maximum heat dissipation limit). The new generation of the synchronous pump was run at a rotational speed of up to 800 rpm and provided a maximum flow rate of 3.56 ml/min and a maximum pressure head of 687 Pa.
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Zhao, Ming. "Simulations of Atmospheric Rivers, Their Variability, and Response to Global Warming Using GFDL’s New High-Resolution General Circulation Model." Journal of Climate 33, no. 23 (December 2020): 10287–303. http://dx.doi.org/10.1175/jcli-d-20-0241.1.
Повний текст джерелаАнотація:
AbstractA 50-km-resolution GFDL AM4 well captures many aspects of observed atmospheric river (AR) characteristics including the probability density functions of AR length, width, length–width ratio, geographical location, and the magnitude and direction of AR mean vertically integrated vapor transport (IVT), with the model typically producing stronger and narrower ARs than the ERA-Interim results. Despite significant regional biases, the model well reproduces the observed spatial distribution of AR frequency and AR variability in response to large-scale circulation patterns such as El Niño–Southern Oscillation (ENSO), the Northern and Southern Hemisphere annular modes (NAM and SAM), and the Pacific–North American (PNA) teleconnection pattern. For global warming scenarios, in contrast to most previous studies that show a large increase in AR length and width and therefore the occurrence frequency of AR conditions at a given location, this study shows only a modest increase in these quantities. However, the model produces a large increase in strong ARs with the frequency of category 3–5 ARs rising by roughly 100%–300% K−1. The global mean AR intensity as well as AR intensity percentiles at most percent ranks increases by 5%–8% K−1, roughly consistent with the Clausius–Clapeyron scaling of water vapor. Finally, the results point out the importance of AR IVT thresholds in quantifying modeled AR response to global warming.
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Cimino, Sara, Luciano Agati, Domenico Filomena, Viviana Maestrini, Sara Monosilio, Lucia Ilaria Birtolo, Michele Mocci, et al. "3D Echo Characterization of Proportionate and Disproportionate Functional Mitral Regurgitation before and after Percutaneous Mitral Valve Repair." Journal of Clinical Medicine 11, no. 3 (January 27, 2022): 645. http://dx.doi.org/10.3390/jcm11030645.
Повний текст джерелаАнотація:
Background: The impact of percutaneous mitral valve repair (PMVr) on long-term prognosis in patients with functional mitral regurgitation (FMR) is still unclear. Recently, a new conceptual framework classifying FMR as proportionate (P-MR) and disproportionate (D-MR) was proposed, according to the effective regurgitant orifice area/left ventricular end-diastolic volume (EROA/LVEDV) ratio. The aim was to assess its possible influence on PMVr efficacy. Methods: A total of 56 patients were enrolled. MV annulus, LV volumes and function were assessed. Global longitudinal strain (GLS) was also calculated. Patients were divided into two groups, according to the EROA/LVEDV ratio. Echocardiographic follow-up was performed after 6 months, and adverse events were collected after 12 months. Results: D-MR patients (n = 28, 50%) had a significantly more elliptical MV annulus (p = 0.048), lower tenting volume (p = 0.01), higher LV ejection fraction (LVEF: 32 ± 7 vs. 26 ± 5%, p = 0.003), lower LVEDV, LV end-systolic volume (LVESV) and mass (LVEDV/i: 80 ± 20 vs. 126 ± 27 mL, p = 0.001; LVESV/i: 60 ± 20 vs. 94 ± 23 mL, p < 0.001; LV mass: 249 ± 63 vs. 301 ± 69 gr, p = 0.035). GLS was more impaired in P-MR (p = 0.048). After 6 months, P-MR patients showed a higher rate of MR recurrence. After 12 months, the rate of CV death and rehospitalization due to HF was significantly higher in P-MR patients (46% vs. 7%, p < 0.001). P-MR status was strongly associated with CV death/rehospitalization (HR = 3.4, CI 95% = 1.3–8.6, p = 0.009). Conclusions: Patients with P-MR seem to have worse outcomes after PVMr than D-MR patients. Our study confirms the importance of the EROA/LVEDV ratio in defining different subsets of FMR based on the anatomical characteristic of MV and LV.
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Liu, Jun, Dongyou Wu, Guangjing Liu, Rui Mao, Siyu Chen, Mingxia Ji, Pingqing Fu, et al. "Impact of Arctic amplification on declining spring dust events in East Asia." Climate Dynamics 54, no. 3-4 (December 26, 2019): 1913–35. http://dx.doi.org/10.1007/s00382-019-05094-4.
Повний текст джерелаАнотація:
AbstractDust aerosols play key roles in affecting regional and global climate through their direct, indirect, and semi-direct effects. Dust events have decreased rapidly since the 1980s in East Asia, particularly over northern China, primarily because of changes in meteorological parameters (e.g. surface wind speed and precipitation). In this study, we found that winter (December–January–February) Arctic amplification associated with weakened temperature gradients along with decreased zonal winds is primarily responsible for the large decline in following spring (March–April–May) dust event occurrences over northern China since the mid-1980s. A dust index was developed for northern China by combining the daily frequency of three types of dust event (dust storm, blowing dust, and floating dust). Using the empirical orthogonal function (EOF) analysis, the first pattern of dust events was obtained for spring dust index anomalies, which accounts for 56.2% of the variability during 1961–2014. Moreover, the enhanced Arctic amplification and stronger Northern Hemisphere annular mode (NAM) in winter can result in the anticyclonic anomalies over Siberia and Mongolia, while cyclonic anomalies over East Europe in spring. These results are significantly correlated with the weakened temperature gradients, increased precipitation and soil moisture, and decreased snow cover extent in the mid-latitude over Northern Hemisphere. Based on the future predictions obtained from the Fifth Climate Models Intercomparison Project (CMIP5), we found that the dust event occurrences may continually decrease over northern China due to the enhanced Arctic amplification in future climate.
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Gardner, David R., Rod W. Douglass, and Steven A. Trogdon. "Linear stability of natural convection in spherical annuli." Journal of Fluid Mechanics 221 (December 1990): 105–29. http://dx.doi.org/10.1017/s0022112090003500.
Повний текст джерелаАнотація:
Natural convection in a Boussinesq fluid filling the narrow gap between two isothermal, concentric spheres at different temperatures depends strongly on radius ratio, Prandtl number, and Grashof number. When the inner sphere has a higher temperature than the outer sphere, and for fixed values of radius ratio and Prandtl number, experiments show the flow to be steady and axisymmetric for sufficiently small Grashof number and quasi-periodic and axisymmetric for Grashof numbers greater than a critical value. It is our hypothesis that the observed transition is a flow bifurcation. This hypothesis is examined by solving an appropriate eigenvalue problem. The critical Grashof number, critical eigenvalues, and corresponding eigenvectors are obtained as functions of the radius ratio, Prandtl number, and longitudinal wavenumber. Critical Grashof numbers range from 1.18 × 104 to 2.63 × 103 as Prandtl number Pr increases from zero to 0.7, for radius ratios of 0.900 and 0.950. A transitional Prandtl number Prt exists such that for Pr < Prt the bifurcation is time-periodic and axisymmetric. For Pr > Prt the bifurcation is steady and non-axisymmetric with wavenumber twoA first approximation to the bifurcated flow is obtained using the critical eigenvectors. For Pr < Prt the bifurcation sets in as a cluster of relatively strong cells with alternating directions of rotation. The cells remain fixed in location, but pulsate with time. The cluster moves toward the top of the annulus as Pr increases toward Prt. An important feature of the non-axisymmetric bifurcation for Pr > Prt is a set of four cells located at each pole of the annulus in which the radial velocity alternates direction in moving from any one cell to an adjacent one. For fixed radius ratio, the average Nusselt number at criticality varies only slightly with Prandtl number.
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Liess, Stefan, Arjun Kumar, Peter K. Snyder, Jaya Kawale, Karsten Steinhaeuser, Frederick H. M. Semazzi, Auroop R. Ganguly, Nagiza F. Samatova, and Vipin Kumar. "Different Modes of Variability over the Tasman Sea: Implications for Regional Climate*." Journal of Climate 27, no. 22 (November 4, 2014): 8466–86. http://dx.doi.org/10.1175/jcli-d-13-00713.1.
Повний текст джерелаАнотація:
Abstract A new approach is used to detect atmospheric teleconnections without being bound by orthogonality (such as empirical orthogonal functions). This method employs negative correlations in a global dataset to detect potential teleconnections. One teleconnection occurs between the Tasman Sea and the Southern Ocean. It is related to El Niño–Southern Oscillation (ENSO), the Indian Ocean dipole (IOD), and the southern annular mode (SAM). This teleconnection is significantly correlated with SAM during austral summer, fall, and winter, with IOD during spring, and with ENSO in summer. It can thus be described as a hybrid between these modes. Given previously found relationships between IOD and ENSO, and IOD’s proximity to the teleconnection centers, correlations to IOD are generally stronger than to ENSO. Increasing pressure over the Tasman Sea leads to higher (lower) surface temperature over eastern Australia (the southwestern Pacific) in all seasons and is related to reduced surface temperature over Wilkes Land and Adélie Land in Antarctica during fall and winter. Precipitation responses are generally negative over New Zealand. For one standard deviation of the teleconnection index, precipitation anomalies are positive over Australia in fall, negative over southern Australia in winter and spring, and negative over eastern Australia in summer. When doubling the threshold, the size of the anomalous high-pressure center increases and annual precipitation anomalies are negative over southeastern Australia and northern New Zealand. Eliassen–Palm fluxes quantify the seasonal dependence of SAM, ENSO, and IOD influences. Analysis of the dynamical interactions between these teleconnection patterns can improve prediction of seasonal temperature and precipitation patterns in Australia and New Zealand.
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Gollan, Gereon, and Richard J. Greatbatch. "On the Extratropical Influence of Variations of the Upper-Tropospheric Equatorial Zonal-Mean Zonal Wind during Boreal Winter." Journal of Climate 28, no. 1 (December 31, 2014): 168–85. http://dx.doi.org/10.1175/jcli-d-14-00185.1.
Повний текст джерелаАнотація:
Abstract Variations in the global tropospheric zonal-mean zonal wind [U] during boreal winter are investigated using rotated empirical orthogonal functions applied to monthly means. The first two modes correspond to the northern and southern annular mode and modes 3 and 4 represent variability in the tropics. One is related to El Niño–Southern Oscillation and the other has variability that is highly correlated with the time series of [U] at 150 hPa between 5°N and 5°S [U150]E and is related to activity of the Madden–Julian oscillation. The extratropical response to [U150]E is investigated using linear regressions of 500-hPa geopotential height onto the [U150]E time series. Use is made of reanalysis data and of the ensemble mean output from a relaxation experiment using the European Centre for Medium-Range Weather Forecasts model in which the tropical atmosphere is relaxed toward reanalysis data. The regression analysis reveals that a shift of the Aleutian low and a wave train across the North Atlantic are associated with [U150]E. It is found that the subtropical waveguides and the link between the North Pacific and North Atlantic are stronger during the easterly phase of [U150]E. The wave train over the North Atlantic is associated with Rossby wave sources over the subtropical North Pacific and North America. Finally, it is shown that a linear combination of both [U150]E and the quasi-biennial oscillation in the lower stratosphere can explain the circulation anomalies of the anomalously cold European winter of 1962/63 when both were in an extreme easterly phase.
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van Zalen, Jet, Nikhil R. Patel, Steven J Podd, Prashanth Raju, Rob McIntosh, Gary Brickley, Louisa Beale, Lydia P. Sturridge, and Guy W. L. Lloyd. "Prognostic importance of tissue velocity imaging during exercise echocardiography in patients with systolic heart failure." Echo Research and Practice 2, no. 1 (March 2015): 19–27. http://dx.doi.org/10.1530/erp-14-0074.
Повний текст джерелаАнотація:
Resting echocardiography measurements are poor predictors of exercise capacity and symptoms in patients with heart failure (HF). Stress echocardiography may provide additional information and can be expressed using left ventricular ejection fraction (LVEF), or diastolic parameters (E/E′), but LVEF has some major limitations. Systolic annular velocity (S′) provides a measure of longitudinal systolic function, which is relatively easy to obtain and shows a good relationship with exercise capacity. The objective of this study was to investigate the relationship among S′, E/E′ and LVEF obtained during stress echocardiography and both mortality and hospitalisation. A secondary objective was to compare S′ measured using a simplified two-wall model. A total of 80 patients with stable HF underwent exercise stress echocardiography and simultaneous cardiopulmonary exercise testing. Volumetric and tissue velocity imaging (TVI) measurements were obtained, as was peak oxygen uptake (VO2 peak). Of the total number of patients, 11 died and 22 required cardiac hospitalisation. S′ at peak exertion was a powerful predictor for death and hospitalisation. Cut-off points of 5.3 cm/s for death and 5.7 cm/s for hospitalisation provided optimum sensitivity and specificity. This study suggests that, in patients with systolic HF, S′ at peak exertion calculated from the averaged spectral TVI systolic velocity of six myocardial segments, or using a simplified measure of two myocardial segments, is a powerful predictor of future events and stronger than LVEF, diastolic velocities at rest or exercise and VO2 peak. Results indicate that measuring S′ during exercise echocardiography might play an important role in understanding the likelihood of adverse clinical outcomes in patients with HF.
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Mac-Thiong, Jean-Marc, Jahangir Asghar, Stefan Parent, Harry L. Shufflebarger, Amer Samdani, and Hubert Labelle. "Posterior convex release and interbody fusion for thoracic scoliosis: technical note." Journal of Neurosurgery: Spine 25, no. 3 (September 2016): 357–65. http://dx.doi.org/10.3171/2016.2.spine15557.
Повний текст джерелаАнотація:
Anterior release and fusion is sometimes required in pediatric patients with thoracic scoliosis. Typically, a formal anterior approach is performed through open thoracotomy or video-assisted thoracoscopic surgery. The authors recently developed a technique for anterior release and fusion in thoracic scoliosis referred to as “posterior convex release and interbody fusion” (PCRIF). This technique is performed via the posterior-only approach typically used for posterior instrumentation and fusion and thus avoids a formal anterior approach. In this article the authors describe the technique and its use in 9 patients—to prevent a crankshaft phenomenon in 3 patients and to optimize the correction in 6 patients with a severe thoracic curve showing poor reducibility. After Ponte osteotomies at the levels requiring anterior release and fusion, intervertebral discs are approached from the convex side of the scoliosis. The annulus on the convex side of the scoliosis is incised from the lateral border of the pedicle to the lateral annulus while visualizing and protecting the pleura and spinal cord. The annulus in contact with the pleura and the anterior longitudinal ligament are removed before completing the discectomies and preparing the endplates. The PCRIF was performed at 3 levels in 4 patients and at 4 levels in 5 patients. Mean correction of the main thoracic curve, blood loss, and length of stay were 74.9%, 1290 ml, and 7.6 days, respectively. No neurological deficit, implant failure, or pseudarthrosis was observed at the last follow-up. Two patients had pleural effusion postoperatively, with 1 of them requiring placement of a chest tube. One patient had pulmonary edema secondary to fluid overload, while another patient underwent reoperation for a deep wound infection 3 weeks after the initial surgery. The technique is primarily indicated in skeletally immature patients with open triradiate cartilage and/or severe scoliosis. It can be particularly useful if there is significant vertebral rotation because access to the disc and anterior longitudinal ligament from the convex side will become safer. The PCRIF is an alternative to the formal anterior approach and does not require repositioning between the anterior and posterior stages, which prolongs the surgery and can be associated with an increased complication rate. The procedure can be done in the presence of preexisting pulmonary morbidity such as pleural adhesions and decreased pulmonary function because it does not require mobilization of the lung or single-lung ventilation. However, PCRIF can still be associated with pulmonary complications such as a pleural effusion, and care should be taken to avoid iatrogenic injury to the pleura. Placement of a deep wound drain at the level of the PCRIF is strongly recommended if postoperative bleeding is anticipated, to decrease the risk of pleural effusion.
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FELISBERTI, FATIMA, and ANDREW M. DERRINGTON. "Long-range interactions modulate the contrast gain in the lateral geniculate nucleus of cats." Visual Neuroscience 16, no. 5 (September 1999): 943–56. http://dx.doi.org/10.1017/s0952523899165143.
Повний текст джерелаАнотація:
In previous work, we have shown that sudden image displacements well outside the classical receptive field modulate the visual sensitivity of LGN relay cells. Here we report the effect of image displacements on the response versus contrast function. The stimuli consisted of a central spot of optimal size and polarity (contrast range: 3–98%), flashed alone or in the presence of a peripheral annulus (radii: 5–15 deg) containing a low spatial-frequency grating displaced at saccade-like velocities (shift). The most consistent effect of the shift on the response to a central spot was to reduce the responsiveness of Y relay cells and, to a lesser extent, of X relay cells. The reduction in responsiveness was primarily a divisive rather than a subtractive effect and could be modelled by assuming that a greater contrast was required to produce a given excitatory response. In the absence of a central spot, remote motion had inhibitory effects on the firing rates of the majority of relay cells, but its effect on retinal ganglion cells was mainly excitatory. When the shifting grating covered the classical receptive field and its periphery, facilitatory effects or suppressive effects, depending on the spatial phase of the pattern, were observed in both retinal and geniculate cells. Remote motion strongly suppresses the responsiveness of relay cells to stimuli within the classical receptive field. This suppressive effect involves intrageniculate processing and is primarily associated with a reduction in contrast gain. It is likely that shift suppression contributes to the loss of visual sensitivity observed in saccadic suppression.