Elliptical Annulus Research Articles

Evaluation of the Inner Macula Layers, Circumpapillary Retinal Nerve Fiber Layer, and Minimum Rim Width Thickness in Patients With Pseudoexfoliation Syndrome Without Glaucoma Compared With Controls.

Minimum rim width (MRW) is thinner in patients with non-glaucomatous pseudoexfoliation syndrome (XFS) and may be the first parameter affected in these patients due to the vascular nature of this disease. To evaluate the macular inner layers, circumpapillary retinal nerve fiber layer (cp-RNFL), and MRW in non-glaucomatous XFS compared with healthy patients. In this prospective study, using Heidelberg Spectralis optical coherence tomography with Glaucoma Module Premium Edition, 8×8 grids of macular inner layers were exported, and the global, superior, and inferior thicknesses were used. Also, on the deviation map, the elliptical annulus around the fovea, which was 4.8×4mm in size, was analyzed. Moreover, both groups calculated cp-RNFL and MRW values in 3 superior and 3 inferior sectors. Thirty-two eyes of 32 patients with clinically detected non-glaucomatous XFS and 30 right eyes of age-sex-matched healthy controls were included. No significant difference was found between the case and control groups concerning the intraocular pressure (14.94 ± 2.09 vs 15.27 ± 2.27 mm Hg, respectively, P = 0.556). The MRW of the superotemporal segment (MRW-temporal superior) was significantly thinner in the XFS group compared with the control ones (303.69 ± 60.49 vs 341.43 ± 56.19µm, P = 0.014). No significant differences were found in the other sectors of MRW, macular inner layers, and cp-RNFL thickness between the groups. These findings indicate that the MRW, especially in the superotemporal sector, may show early eye damage in patients with non-glaucomatous XFS, and it may be used to detect the early stage of glaucoma in XFS.

Alterations of the Ganglion Cell Complex in Age-Related Macular Degeneration: An Amish Eye Study Analysis

To compare the ganglion cell complex (GCC) thickness in eyes with age-related macular degeneration (AMD) vs healthy controls in an elderly Amish population. Prospective cross-sectional study. This is a post hoc analysis of the family-based prospective study of Amish subjects. Study subjects underwent imaging with the Cirrus HD-OCT (Carl Zeiss Meditec Inc) using a macular cube protocol of 512 × 128 scans (128 horizontal B-scans, each comprising 512 A-scans) over a 6 mm × 6 mm region centered on the fovea. The ganglion cell analysis algorithm calculated the GCC thickness by segmenting the outer boundaries of the retinal nerve fiber layer (RNFL) and inner plexiform layer (IPL) in all B-scans of the volume, with the region between these boundaries representing the combined thickness of the ganglion cell layer (GCL) and the IPL. A number of parameters were used to evaluate the GCC thickness: the average GCC thickness, minimum (lowest GCC thickness at a single meridian crossing the elliptical annulus), and sectoral (within each of 6 sectoral areas: superior, superotemporal, superonasal, inferior, inferonasal, and inferotemporal). The stage of AMD was graded on color fundus photographs in accordance with the Beckman Initiative for Macular Research classification system. Of 1339 subjects enrolled in the Amish eye study, a total of 1294 eyes of 1294 subjects had all required imaging studies of sufficient quality and were included in the final analysis. Of these, 798 (62%) were female. Following age adjustment, the average GCC thickness was significantly (P < .001) thinner in AMD subjects (73.71 ± SD; 13.77 µm) compared to normals (77.97 ± 10.42 µm). An independent t test showed that the early AMD (75.03 ± 12.45 µm) and late AMD (61.64 ± 21.18 µm) groups (among which eyes with geographic atrophy [GA] had the lowest thickness, of 58.10 ± 20.27 µm) had a statistically significant lower GCC thickness compared to eyes without AMD. There was no significant differences in average GCC thickness between early AMD and intermediate AMD (76.36 ± 9.25 µm) eyes. The GCC thickness in AMD eyes is reduced compared to normal eyes; however, the relationship is complex, with the greatest reduction in late AMD eyes (particularly eyes with GA) but no difference between early and intermediate AMD eyes.

Gnuastro: Measuring Radial Profiles from Images

Radial profiles play a crucial role in the analysis and interpretation of astronomical data, facilitating the extraction of spatial information. However, highly customizable (for different scenarios) measurements over each elliptical annulus can be challenging. In response, we present astscript-radial-profile, which is part of Gnuastro from version 0.15 and has an extensive documentation. A convenient feature of this program is its capability to make the measurements with different operators (mean, median, sigma-clipping, and many more) over ellipses, very quickly and directly on the command-line with minimal dependencies. This research note is reproducible with Maneage, on the Git commit f3ec942.

Compliant Aortic Annulus Sizing With Different Elliptical Ratios Through a Valvuloplasty Balloon Catheter.

Aortic stenos (AS) is a heart valve disease that commonly affects the elderly. Transcatheter aortic valve implantation is a minimally invasive treatment that allows to replace the function of the diseased native valve with a prosthetic device, relying on catheters for device implantation. According to the current clinical guidelines, the choice of the implanted device is based on preoperative sizing determined by image-based technology. However, this assessment faces inherent limitations that can lead to sub-optimal sizing of the prosthesis; in turn, this can cause major post-operative complications like aortic regurgitation or cardiac electrical signal disruption. By utilizing balloon pressure and volume data, this article proposes an intra-operative method for determining the dimension of the aortic annulus which takes into account its compliance and geometric irregularity. The intra-balloon pressure-volume curves were obtained using an Automated Balloon Inflation Device operating a commercially available valvuloplasty balloon catheter. A sizing algorithm to estimate the dimensions of the annulus was integrated via a validated analytical model and a numerical model for balloon free-inflation. Tests were performed on circular and elliptical idealised aortic phantoms. Experimental results confirm that the pressure-volume data processed with the sizing algorithm can be used to determine the circular annular diameter for all tissue rigidities. The measurement of stiffer elliptical annulus phantoms shows good accuracy and high repeatability. This work represents substantial progress toward improving the selection of TAVI devices by using balloon catheters to improve the sizing of compliant aortic annuli with complex geometry.

Risk evaluation of adverse aortic events in patients with non-circular aortic annulus after transcatheter aortic valve implantation: a numerical study.

Transcatheter aortic valve implantation (TAVI) is a micro-invasive surgery used to treat patients with aortic stenosis (AS) efficiently. However, the uneven valve expansion can cause a non-circular annulus, which is one of the main factors leading to complications after TAVI. As a preliminary work, the main purpose of this study was to evaluate the risk of adverse aortic events in patients with a non-circular aortic annulus after TAVI. This study numerically investigated the distribution of four wall shear stress (WSS)-based indicators and three helicity-based indicators in eight patient-specific aortas with different annulus including circular, type I elliptical and type II elliptical shapes. Both elliptical annulus features can significantly enhance the intensity of the helicity (h2) in the ascending aorta (p < 0.001). However, for the type I elliptical annulus, the spiral flow structure was changed into low-velocity and disturbed flow pattern close to the inner side of the aortic arch. For the type II elliptical annulus, the spiral flow remained but became skewed in distribution. The elliptical annulus feature could increase the general level WSS-based indicators, especially in the ascending aorta. However, due to the disturbance of spiral flow or second helical flow in ascending aortas, areas with low TAWSS accompanied by high oscillatory shear index (OSI) and cross flow index (CFI) were observed in all the ascending aortas with non-circular annulus. The elliptical annulus feature can change the hemodynamic environment in the aortic arch, especially in the ascending aorta. Although both elliptical annulus features enhanced the strength of helicity, the uniform distribution of the helical flow was disturbed, especially in the ascending aorta, indicating the potential risk of adverse aortic events may increase. Therefore, for the patients without paravalvular leak but elliptical annulus shape after TAVI treatment, surgeons may be needed to consider further dilatation to make the non-circular annulus become circular.

Double diffusive Buoyancy‐driven flow in a fluid‐saturated elliptical annulus with a neural network‐based prediction of heat and mass transfer

AbstractThis paper presents a numerical study of buoyancy‐driven double‐diffusive convection within an elliptical annulus enclosure filled with a saturated porous medium. An in‐house built FORTRAN code has been developed, and computations are carried out in a range of values of Darcy–Rayleigh number Ram (10 ≤ Ram ≤ 500), Lewis number Le (0.1 ≤ Le ≤ 10), and the ratio of buoyancy forces N (−5 ≤ N ≤ 5). In addition, three methods are used, namely the multi‐variable polynomial regression, the group method of data handling (GMDH), and the artificial neural network (ANN) for the predictions of heat and mass transfer rates. First, results are successfully validated with existing numerical and experimental data. Then, the results indicated that temperature and concentration distributions are sensitive to the Lewis number and thermal and mass plumes are developing in proportion to the Lewis number. Two particular values of Lewis number Le = 2.735 and Le = 2.75 captured the flow's transition toward an asymmetric structure with a bifurcation of convective cells. The average Nusselt number tends to have an almost asymptotic value for Le » 5. For the case of aiding buoyancies N &gt; 1, the average Nusselt Number decreased by 33% when the Lewis number increased to its maximum value. Then, it increased by 10% when the Lewis number increased to Le = 1 for the case of opposing buoyancies N &lt; 1 and then decreased by 33% when the Lewis number increased to its maximum value., contrary to the behavior of the average Sherwood number that increased by 700% for both cases N &gt; 1 and N &lt; 1. New correlations of , and as a function of Ram, Le, and N are derived and compared with GMDH and ANN methods, and the ANN method showed higher performance for the prediction of and with R2 exceeding 0.99.

Tricuspid valve anatomy of massive to torrential tricuspid regurgitation: Computed tomography analysis

BackgroundWe aimed to comprehensively assess tricuspid valve anatomy and to determine factors associated with the more advanced stages beyond severe TR (i.e., massive to torrential). MethodsWe retrospectively analyzed the pre-procedural cardiac CT images in patients with ≥severe TR using 3mensio software. The tricuspid valve annulus size, right-atrial and right-ventricular dimensions, tenting height, and leaflet angles were measured. ResultsA total of 103 patients were analyzed. The mean effective regurgitant orifice area was 61.7 ​± ​31.5 ​mm2, vena contracta was 13.1 ​± ​4.6 ​mm, and massive/torrential TR was observed in 62 patients. Compared to patients with severe TR, patients with massive/torrential TR had a larger tricuspid annulus area (18.6 ​± ​3.4 ​cm2 vs. 20.6 ​± ​5.3 ​cm2, p ​= ​0.037), right atrial short-axis diameter (66.1 ​± ​9.1 ​mm vs. 70.6 ​± ​9.9 ​mm, p ​= ​0.022), increased tenting height (8.8 ​± ​3.6 ​mm vs. 10.7 ​± ​3.7 ​mm, p ​= ​0.014), and greater leaflet angles (anterior leaflet: 22 ​± ​9° vs. 32 ​± ​13°, p ​< ​0.001; posterior leaflet: 22 ​± ​11° vs. 30 ​± ​11°, p ​= ​0.003). In the multivariable logistic regression model, the angle of anterior leaflet (OR 1.08, 95%CI 1.03–1.14, p ​= ​0.004) and posterior leaflet (OR 1.07, 95%CI 1.02–1.13, p ​= ​0.007) were associated with massive/torrential TR. Additionally, patients with massive/torrential TR more often had TR jets from non-central/non-anteroseptal commissure (34% vs. 76%, p ​< ​0.001). In the multivariable model, a greater angle of the leaflets and a more elliptical annulus were associated with non-central/non-anteroseptal TR jets. ConclusionsAnterior and posterior leaflet angles are significant factors associated with massive/torrential TR. Furthermore, leaflet angles and ellipticity of the tricuspid valve are associated with the location of TR jets.

Regression modeling for laminar flow of herschel–barkley fluids in the concentric elliptical annulus

Deep fractured formations have poor pressure-bearing capacity and a narrow safety drilling fluids density window, leading to high risk of well control. Accurate prediction of annulus pressure drop is great significance to the safe drilling of deep fractured formations. Conventional annulus pressure drop predictions are mostly based on regular circular annulus but elliptical annulus are easily formed due to the rock structure, mechanical properties and heterogeneity of ground stress. In order to accurately and conveniently predict the pressure drop of the Herschel–Barkley (H–B) fluids laminar flow in the concentric annulus of elliptical wellbore (CAEW), an analytical model based on the assumption of narrow-slot flow was established and solved by considering the flow core in this paper. We found that the flow pattern index, the proportion of inner and outer diameter and the proportion of the major and minor axes were the main influencing factors through analysis. On this basis, a new method for predicting pressure drop of the H-B fluids in the CAEW was established. It was found that the new regression model was in excellent agreement with the analytical and numerical models, with most of the error bars within ± 10%, indicating that the regression model could accurately predict the dimensionless pressure gradient in the CAEW without complex mathematic method.

3D Echo Characterization of Proportionate and Disproportionate Functional Mitral Regurgitation before and after Percutaneous Mitral Valve Repair.

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.

Mitochondrial Dysfunction in Primary Open-Angle Glaucoma Characterized by Flavoprotein Fluorescence at the Optic Nerve Head

To investigate the presence of flavoprotein fluorescence (FPF) at the optic nerve head (ONH) rim as a marker of mitochondrial dysfunction in primary open-angle glaucoma (POAG) and control eyes. Retrospective cross-sectional study of patients recruited from the New York Eye and Ear Infirmary of Mount Sinai. A total of 86 eyes (50 eyes of 30 patients with POAG and 36 eyes of 20 control participants) were enrolled. The presence of POAG was defined by circumpapillary retinal nerve fiber layer thickness (cpRNFLT) of less than the bottom fifth percentile of the normative database, glaucomatous ONH changes, and visual field defects on 24-2 tests. Primary open-angle glaucoma and control eyes were imaged using the OcuMet Beacon. A 23°× 23° infrared scan was obtained, and an FPF scan was performed within a capture field spanning 13° in diameter. The ONH margins on the infrared image were identified by software algorithms. Then, FPF was measured within an elliptical annulus around the ONH rim, with the inner and outer boundaries corresponding to 0.5 to 1.1 times the ONH rim size. Flavoprotein fluorescence at the OHN rim in POAG and control eyes. Differences in FPF between POAG and control eyes were characterized through mixed-effects logistic regression, adjusted for age and interocular pressure. Flavoprotein fluorescence was significantly higher in POAG versus control eyes, with a mean ± SD of 46.4 ± 27.9 versus 28.0 ± 11.7 (P < 0.001), respectively. Among POAG eyes, FPF showed correlation to visual field mean deviation (P < 0.001), visual field pattern standard deviation (P= 0.003), and cpRNFLT (P= 0.001) on linear mixed-effects models. Higher FPF in POAG versus control eyes suggests the presence of mitochondrial dysfunction at the ONH rim in eyes with glaucomatous damage. The degree of FPF corresponds to disease severity, as measured by visual field and nerve fiber layer thickness metrics. Thus, FPF may represent a metabolic indicator of disease status that reveals the extent of injury in glaucoma.

Changes in Peripapillary and Macular Vessel Densities and Their Relationship with Visual Field Progression after Trabeculectomy.

The aim of this study was to determine the factors associated with visual field (VF) deterioration after trabeculectomy, including the peripapillary vessel density (pVD) and macular vessel density (mVD) changes assessed by optical coherence tomography angiography (OCT-A). Primary open-angle glaucoma patients with more than two years of follow-up after trabeculectomy were included. pVD was calculated in a region defined as a 750 μm-wide elliptical annulus extending from the optic disc boundary. mVD was calculated in the parafoveal (1–3 mm) and perifoveal (3–6 mm) regions. VF deterioration was defined as the rate of mean deviation (MD) worse than −1.5 dB/year. The change rates of pVD and mVD were compared between the deteriorated VF and non-deteriorated VF groups. The factors associated with the rate of MD were determined by linear regression analyses. VF deterioration was noted in 14 (21.5%) of the 65 eyes that underwent trabeculectomy. The pVD (−2.26 ± 2.67 vs. −0.02 ± 1.74%/year, p ≤ 0.001) reduction rate was significantly greater in the deteriorated VF group than in the non-deteriorated VF group, while that of parafoveal (p = 0.267) and perifoveal (p = 0.350) VD did not show a significant difference. The linear regression analysis showed that the postoperative MD reduction rate was significantly associated with the rate of pVD reduction (p = 0.016), while other clinical parameters and preoperative vascular parameters did not show any association. Eyes with greater loss of peripapillary retinal circulation after trabeculectomy tended to exhibit VF deterioration. The assessment of peripapillary vascular status can be an adjunctive strategy to predict visual function after trabeculectomy.

Local thermal non-equilibrium (LTNE) effects on thermal-free convection in a nanofluid-saturated horizontal elliptical non-Darcian porous annulus

In this investigation, a comprehensive and accurate numerical analysis of the local thermal non-equilibrium effects on the natural convection characteristics in a horizontal elliptical porous annulus saturated with nanofluid has been carried out using finite volume technique. The internal surface is isothermally heated while the external one is fixed at uniform lower temperature. The nanofluid phase and the solid phase of the porous structure are out of local thermal equilibrium situation. The heat and the hydrodynamics equations in their dimensionless form under Darcy–Brinkman Forchheimer model were solved computationally by the finite volume technique using the standard SIMPLER algorithm. The results have been examined for various porous medium properties under the LTNE condition. The standard 0.05 significance level was used to identify the local thermal equilibrium within the system. According to the obtained results, the higher the Darcy number and the smaller the non-dimensional heat transfer coefficient for the solid/nanofluid interface, the modified thermal conductivity ratio and the media’s porosity, the higher are the LTNE effects. In addition, the spatial distribution contours of the LTNE sources within the porous annulus were schematized.

Analysis of the effects of local thermal non-equilibrium (LTNE) on thermo-natural convection in an elliptical annular space separated by a nanofluid-saturated porous sleeve

Local thermal non-equilibrium effects on heat natural convection features in a horizontal confocal elliptical annulus with the inner cylinder covered with a nanofluid-saturated porous sleeve is investigated in this study. The steady and laminar natural convective flow is incited by the thermal buoyancy resulting from the differential heating between the inner and outer annulus' surfaces. The nanofluid phase and the solid phase of the porous sleeve are hors local thermal equilibrium situation. The heat and the hydrodynamics equations in their dimensionless form under Darcy-Brinkman Forchheimer model for the porous region were computationally solved by the finite volume technique using the standard SIMPLER algorithm. The results were analyzed according to different porous materials characteristics under LTNE condition. The standard 0.05 significance level was employed to determine the local thermal equilibrium situation in the porous sleeve. For the first time, contours of the spatial distribution of the LTNE sources within the porous sleeve region were represented.

Transcatheter Aortic Valve Replacement in Pure Native Aortic Valve Regurgitation: Challenging Pathology Awaiting Specialized Devices.

Patients with aortic incompetence frequently present with anatomical and pathological challenges such as elliptical dilated annulus, dilated aortic root, dilated ascending aorta, and with no calcification in the aortic cusps or annulus. Patients are commonly in graver clinical condition as a result of a long silent clinical course before overt congestive heart failure. All of the above make transcatheter therapies for native aortic valve regurgitation more challenging with poorer outcomes, escalating the risk of insufficient anchoring, prosthesis migration, and residual paravalvular leak compared with current transcatheter aortic valve replacement (TAVR) outcomes for aortic stenosis. There is a need for specialized TAVR devices to address this complex pathology. Surgical aortic valve replacement is the current treatment option and the gold standard for patients with aortic incompetence (AR). Currently, the specific off-label indication for TAVR in pure native AR could be a feasible and reasonable option, as a compassionate treatment is limited to inoperable patients and agreed on by the heart team.

A Comparative Study on Thermal-Hydraulic Performance of Different Non-Newtonian Nanofluids Through an Elliptical Annulus

Abstract This paper presents a numerical investigation on heat transfer and flow behavior for non-Newtonian nanofluids with different nanoparticles (Al2O3 and CuO) and carboxymethyl cellulose (CMC) with water as a base fluid. The analysis has been carried out in an elliptical tube. Power-law model is adopted to depict the non-Newtonian nature of nanofluid. The present study has been done with a range of nanosized particles 0–4% by volume, and the variation of Reynolds number is kept under the laminar condition. The physical model covers two concentric tubes used to create an annular space. The effects of volume fraction, particle type, and base fluid have been investigated at different Reynolds numbers numerically. Also, the effect of pressure and heat transfer coefficient on the flow behavior of non-Newtonian nanofluids is analyzed. The results concluded that Al2O3 particles showed 219% and CuO particles give 195% higher heat transfer coefficient as compared with pure water.

Natural Convection between A Pair of Elliptical Cylinders in Blunt and Slender Situations (Dept.M)

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Study of Ostwald-de Waele fluid flow in an elliptical annulus using the slot model and the CFD approach

Among consequences that can be induced by a non-uniform distribution of the stress and other causes during the drilling process is the elliptical shape of the well and consideration of this effect would improve the accuracy of the drilling fluid hydrodynamics prediction. In the present work, the elliptical shape of the annular space is simplified to apply the slot model taking into account the rotation of the inner cylinder. Moreover, the Slot model results are compared with the experimental data, as well as, with the CFD outcomes where a reasonable concordance is observed, especially for low ratios of the major and minor semi-axis. Also, the CFD results are validated with the experimental data from the flow loop setup. We concluded that the increase of the major and minor semi-axis ratio of the elliptical annulus results in a linear increase of the Ostwald-de Waele frictional pressure loss in the laminar regime for all considered rotation speeds of the inner cylinder. In addition, the increase of the eccentricity from 0 to 0.75 has a positive effect where the frictional pressure loss is decreased by almost 28% for all rotation speeds for the elliptical annulus ().

The enthalpy-based lattice Boltzmann method (LBM) for simulation of NePCM melting in inclined elliptical annulus

Constrained melting of ice as a PCM11Phase Change Material. in inclined elliptical annulus should be studied. Efficiency of heat transfer enhancement methods such as insertion of Cu nanoparticles and metallic porous matrix in this heat storage system must be determined. Porous material is made of alloys of Nickel and Steel. The enthalpy-based LBM22Lattice Boltzmann Method. with a D2Q9-DDF33Double Distribution Function. model at the REV44Representative Elementary Volume. scale is implemented. There is thermal equilibrium condition between porous media and PCM. Also, for NEPCM55Nanoparticles-Enhanced PCM. melting, the single phase flow model is adopted. Particle diameter in nanofluid is equal to 100 nm. The sub-cooling of solid PCM is ignored. Prandtl number, Stefan number, Rayleigh number and Darcy number are 6.2, 1, 2×105 and 10−3, respectively. The volumetric concentric of the nanoparticles is between 0 and 0.02. Porosity is between 1 and 0.9. It is found that inclination of the elliptical annulus does not engender any change in the liquid fraction. Inserting nanoparticles is best effective technique to enhance liquid fraction in oblate annulus due to enhanced conduction heat transfer. Use of porous matrix is recommended for prolate and inclined configurations. It obviates considerably stable stratification at bottom of elliptical annulus as a thermal storage unit.

P.410 Searching for predictive validity in animal tests for mania-like behaviour

The precise and convenient calculation of bottom hole pressure can provide a guarantee for safe drilling. Most of the existing models for determining the downhole pressure or annular pressure gradient (PG) are applied only to the circular wellbore. Due to the nonuniform in situ stress and the anisotropism of formation rock, the borehole formed by rotary drilling is the closest to the ellipse, that is, the irregular circular borehole. Therefore, it is of importance to research YPL fluid flow through the eccentric elliptical annulus (EEA) for the accurate prediction of bottom hole pressure. In this paper, a numerical model for determining the PG of YPL fluid flow in the EEA is developed on the basis of fluid mechanics. Then, through parameter studies, a new regression model (RM) of the pressure ratio in the EEA is established. The commercial software ANSYS was used to research the laminar flow of yield-power-law fluids through the EEA, and the simulation results are used to verify the numerical model and new regression model. The main conclusions are as follows. (1) The PG increases quasi-linearly or linearly with the mean velocity, fluid consistency index and yield stress and hardly changes with the azimuth of the inner pipe center. The PG decreases with a/b (η) and eccentricity (ε) when the mean velocity is constant. (2) The new regression model is valid for the ranges 0.2≤Kd ≤ 0.8, 0≤ε ≤ 0.95, 0.2 ≤ n ≤ 1.0, and 1.0≤η ≤ 1.2 and shows excellent agreement with existing model and computational fluid dynamics (CFD) simulations, within ±5% error bars. (3) The maximum velocity first increases and then decreases with ε. The results of axial velocity and PG using CFD software are found to be in excellent agreement with the numerical model solutions. (4) Predicting the PG in the EEA using the new regression model has high precision and without complicated numerical computation.

Quantitative Analysis of Microvasculature in Macular and Peripapillary Regions in Early Primary Open-Angle Glaucoma

ABSTRACTPurpose: To evaluate macular and radial peripapillary capillary vessel densities (RPC VD) across normal, pre-perimetric (PPG), and early perimetric primary open-angle glaucoma (EG) using optical coherence tomography angiography (OCTA).Materials and Methods: Forty-four PPG eyes, 42 EG eyes, and 41 normal eyes were consecutively enrolled. All subjects underwent visual field, OCT, and OCTA examinations. Macular vessel densities were measured in the superficial layer. RPC VD was measured within a 750-μm-wide elliptical annulus extending outward from disc boundary. Diagnostic ability was evaluated with area under the receiver operating curve.Results: Parafoveal vessel densities (ParaVDs) in the PPG group were comparable to the normal group (p > .05), except for temporal quadrant (p = .044), while perifoveal vessel densities (PeriVD) were lower in the PPG group (p < .05). ParaVD and PeriVD were lower in the EG group compared with the normal group (p < .001). Superior-temporal and inferior-temporal retinal nerve fiber layers (RNFLs) were significantly decreased in the EG group compared with the PPG group (p < .05), while only inferior-temporal RPC VD was lower in the EG group (p < .05). RPC VD was comparable to RNFL and ganglion cell complex (GCC) in the diagnosis of PPG (p > .05). Macular whole image vessel density and PeriVD were comparable to RPC VD, RNFL, and GCC in diagnosing EG (p > .05).Conclusions: In early primary open-angle glaucoma, significant microvascular damage was present in both macular and peripapillary areas. The damage of macular microvasculature was more prominent in the peripheral area. Vessel density parameters showed promising diagnostic ability in early glaucoma.Abbreviations: POAG = primary open-angle glaucoma; RGC = retinal ganglion cell; OCTA = optical coherence tomography angiography; RNFL = retinal nerve fiber layer; PPG = pre-perimetric primary open-angle glaucoma; EG = early perimetric primary open-angle glaucoma; IOP = intraocular pressure; PSD = pattern standard deviation; MD = mean deviation; GCC = ganglion cell complex; SBP = systolic blood pressure; DBP = diastolic blood pressure; MAP = mean arterial pressure; MOPP = mean ocular perfusion pressure; wiVD = whole image vessel density; ParaVD = parafoveal vessel density; PeriVD = perifoveal vessel density; RPC VD = radial peripapillary capillary vessel density; AUC = area under the receiver operating curve