continuity equation

  • 文章类型: Journal Article
    目的:分析二维(2D)和三维(3D)经食管超声心动图(TEE)估算的人工二尖瓣有效孔口面积(EOA)的一致性。
    目的:本研究选取了2019年3-6月在南京市第一医院行二尖瓣置换术的34例患者。通过2D-TEE测量的左心室流出道(LVOT)的直径用于计算LVOT(CSALVOT)的横截面积。在3D-TEE方法中,LVOT面积是通过表面视图上的平面测量法直接测量的。使用连续性方程计算两种方法的假体二尖瓣的EOA。用Bland-Altman图一致性检验分析两组EOA结果的一致性,线性回归分析两者的相关性。
    目的:在2D和3D方法中,人工二尖瓣的EOA存在显著差异(2.22±0.71cm2vs2.35±0.70cm2,P<0.001),平均差异为-0.14±0.20cm2,95%相干边界为(-0.53,0.25cm2)。EOA-3D和EOA-2D的回归方程为y=0.27+0.94x,这两种方法之间有很好的相关性。
    目的:使用2D和3DTEE评估人工二尖瓣的EOA具有良好的一致性,二维方法估计的结果比三维方法略低约6%。
    OBJECTIVE: To analyze the consistency of effective orifice area (EOA) of prosthetic mitral valve estimated using 2- dimensional (2D) and 3-dimensional (3D) transesophageal echocardiography (TEE).
    OBJECTIVE: This study was conducted among 34 patients undergoing mitral valve replacement surgery in Nanjing First Hospital between March and June in 2019. The diameter of the left ventricular outflow tract (LVOT) measured by 2D-TEE was used to calculate the cross sectional area of LVOT (CSALVOT). In 3D-TEE method, LVOT area was measured directly by planimetry on an enface view. The EOAs of the prosthetic mitral valve were calculated for both methods using the continuity equation. Bland-Altman plot consistency test was used to analyze the consistency between the two sets of EOA results, and linear regression analysis was used to analyze their correlation.
    OBJECTIVE: The EOA of the prosthetic mitral valve differed significantly between 2D method and 3D method (2.22±0.71 cm2 vs 2.35±0.70 cm2, P < 0.001) with a mean difference of -0.14±0.20 cm2 and 95% coherence boundaries of (-0.53, 0.25 cm2). The regression equation for EOA-3D and EOA-2D is y=0.27 + 0.94x, showing a good correlation between the two methods.
    OBJECTIVE: EOA estimation of the prosthetic mitral valve using 2D and 3D TEE has a good consistency, and the results estimated by the 2D method are slightly lower by about 6% than those by the 3D method.
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  • 文章类型: Journal Article
    UNASSIGNED: Anemia caused by left ventricular outflow tract obstruction in patients with hypertrophic obstructive cardiomyopathy (HOCM) has been reported, however, large clinical studies confirming this association are lacking. The objective of the present study was to investigate the relationship between left ventricular outflow tract (LVOT) pressure gradient and hemoglobin in patients with hypertrophic cardiomyopathy (HCM).
    UNASSIGNED: Patient demographics, laboratory and echocardiography data from 310 patients diagnosed with HCM from our hospital who had undergone echocardiography from July 2014 to March 2019 were collected from medical records. Patients were classified into HOCM and non-HOCM groups.
    UNASSIGNED: Compared to the non-HOCM group, patients in the HOCM group had a lower hemoglobin level (112.2 ± 16.7 vs. 132.9 ± 22.2 g/L, p < 0.001). In addition, significant negative correlations between hemoglobin and LVOT pressure gradient were found in males (r = -0.568, p < 0.001) and females (r = -0.589, p < 0.001). Receiver operating characteristic curve analysis revealed that the best cut-off value for hemoglobin to predict HOCM in male patients was 128 g/L with 74.19% sensitivity and 75.51% specificity (area under the curve: 0.763, p < 0.001). For female patients, the cut-off value was 125 g/L, with a sensitivity and specificity of 89.39% and 48.48%, respectively (area under the curve: 0.718, p < 0.001).
    UNASSIGNED: Our results indicate that hemoglobin level is inversely proportional to the LVOT gradient pressure and has value for predicting outflow tract obstruction in patients with HCM.
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  • 文章类型: Journal Article
    分数阶热传导模型与玻尔兹曼输运方程(BTE)之间的关系缺乏详细的研究。在本文中,连续性,基于分数阶声子BTE推导了热传导的本构方程和控制方程。此后,给出了广义Cattaneo方程的基本微观机制。有效热导率κeff在亚扩散状态下收敛,在超扩散状态下发散。建立了散度和均方位移〈|Δx|2〉^tγ之间的联系,即,κeff~tγ-1,与线性响应理论一致。熵概念,包括熵密度,熵通量和熵生产率,同样被研究。观察到两种不平凡的行为,包括熵通量的分数阶表达式和对熵产生率的初始影响。与连续时间随机游走模型相比,结果涉及非经典连续性方程和熵概念。本文是“通过分数微积分进行高级材料建模:挑战和观点”主题的一部分。
    The relationship between fractional-order heat conduction models and Boltzmann transport equations (BTEs) lacks a detailed investigation. In this paper, the continuity, constitutive and governing equations of heat conduction are derived based on fractional-order phonon BTEs. The underlying microscopic regimes of the generalized Cattaneo equation are thereafter presented. The effective thermal conductivity κeff converges in the subdiffusive regime and diverges in the superdiffusive regime. A connection between the divergence and mean-square displacement 〈|Δx|2〉 ∼ tγ is established, namely, κeff ∼ tγ-1, which coincides with the linear response theory. Entropic concepts, including the entropy density, entropy flux and entropy production rate, are studied likewise. Two non-trivial behaviours are observed, including the fractional-order expression of entropy flux and initial effects on the entropy production rate. In contrast with the continuous time random walk model, the results involve the non-classical continuity equations and entropic concepts. This article is part of the theme issue \'Advanced materials modelling via fractional calculus: challenges and perspectives\'.
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  • 文章类型: Journal Article
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