Evaluation of left ventricular function with cardiac magnetic resonance imaging using Fourier fitting

The aims of this study were to investigate the applicability of Fourier fitting in the magnetic resonance (MR) evaluation of left ventricular (LV) function and to determine the optimal number of harmonics for fitting. Cine cardiac MR imaging was performed in 10 subjects, and an LV time–volume curve was generated. Fourier fitting was applied to the original curve using 1–10 harmonics, and the qualities of the time–volume curve and first-derivative curve were evaluated. LV functional parameters were calculated from curves generated with and without fitting. The quality of the original time–volume curve was good, and Fourier fitting had no substantial effect on functional parameters obtained directly from the time–volume curve such as ejection fraction. The first-derivative curve generated without fitting showed substantial artificial fluctuation. The application of Fourier fitting depressed the fluctuation and tended to decrease estimates of peak ejection rate and peak filling rate. Five or six harmonics appeared to be appropriate for obtaining a high-quality first-derivative curve. In conclusion, Fourier fitting was indicated to aid in reducing the artificial fluctuation of the first-derivative curve generated from cine cardiac MR imaging and to contribute to the evaluation of functional parameters derived from the first-derivative curve.     

平面运动刚体的恢复系数公式的推导

针对平面运动刚体的碰撞,给出了恢复系数公式的一种证明方法.     

Three-dimensional analysis of regional left ventricular endocardial curvature from cardiac magnetic resonance images

Purpose

Left ventricular (LV) remodeling is usually assessed using global changes in LV volume. We hypothesized that three-dimensional analysis of regional endocardial curvature from magnetic resonance images could provide clinically useful information on localized LV remodeling. We tested this approach by investigating regional differences in endocardial curvature in normal and hypokinetic ventricles.

Materials and Methods

Images were obtained in 44 patients with normal LV function (NL, N=14), dilated cardiomyopathy (DCM, N=15) or ischemic heart disease (IHD, N=15). Local surface curvedness, normalized to take into account instantaneous LV size (C_n), was calculated throughout the cardiac cycle and compared between segment groups: NL (N=401), IHD (N=92) and DCM (N=255).

Results

In all normal segments, C_n gradually increased during systole and then decreased during diastole. While both maximum and minimum values of C_n were comparable in the basal and midventricular segments, they were significantly higher in the four apical segments and highest in the apical cap. In addition, percent change in C_n was higher in mid and apical compared to basal segments (P<.05). At all LV levels, C_n values in DCM segments were lower (P<.05) than in NL and IHD segments, which were similar. In contrast, percent change in C_n was significantly lower in both IHD and DCM segments compared to NL.

Conclusion

Three-dimensional analysis of LV endocardial curvature yielded quantitative information on regional ventricular shape consistent with the known pathophysiology, supporting its potential clinical usefulness in the evaluation of LV remodeling.     

Effect of the three-body force on triton asymptotic normalization constants by the hyperspherical harmonics expansion method

We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction significantly.     

A dynamical theory of Brownian motion for the Rayleigh gas

A dynamical theory of the Brownian motion is worked out for the Rayleigh gas and open problems of this theory are surveyed.     

均质椭圆柱面刚体转动惯量的计算

根据转动惯量的定义,运用计算转动惯量的质量投影法,计算了均质椭圆柱面刚体对转轴的转动惯量.     

自由落体和抛体偏离的另一种解法

给出一种落体偏离问题的简洁解法,同时还解决了上抛物体的偏离问题。     

浮体稳定性的研究

指出了《新概念物理教程：力学》中的一处不妥并给出了正确的结论。     

分形物体转动惯量的计算

由分形物体的自相似性、转动惯量的量纲和平行轴定理,分别计算并得到分形三角形、分形正方体、分形四面体和科赫雪花的转动惯量.     

运动物体反射电磁波多普勒效应的一般情况

讨论了电磁波在任意角入射于运动物体反射信号多普勒效应的一般情况,给出了以可测量表达的多普勒效应基本相关的直接推导。     

Effect of heavy quark symmetry on the mass difference ofB-system in minimal left right symmetric model

An estimation of the mass difference of system with heavy quark symmetry formalism is presented. The effective Hamiltonian describing the transition (whereh=b forB _d ⁰ -system) is considered in a manifest left right symmetric (MLRS) model along with contribution from neutral Higgs boson. We use the spin and flavor symmetry for heavy quarks to obtain the transition matrix element 〈B _d ⁰ |ℋ_eff(x)| _d ⁰ 〉 in terms of Isgur-Wise function. Assuming thatB _d ⁰ and states are at rest, we find that Isgur-Wise function turns out to be unity. However using the experimental values of ΔM _K and as input, we find thatM _R=835 GeV andM _H⩾2·9 TeV.     

电磁阻尼落体运动实验仪研究

设计了电磁阻尼落体实验仪,可以定量研究受电磁阻尼的落体运动过程,在不同的阻尼条件下验证速度和路程公式,并计算出阻尼系数.     

A volume‐exclusion normalization procedure for quantitative Raman confocal microspectroscopy of immersed samples applied to human embryonic stem cells

Raman microspectroscopy is a quantitative instrumental method with considerable promise for the nondestructive analysis of living biological samples. Amongst samples of particular interest are human embryonic stem cells because of their therapeutic potential and because examination using Raman microspectroscopy does not appear to adversely affect this potential. However, it can be difficult to compare different spectra obtained with this technique and to quantify the native cellular constituents of such samples because their characteristic dimensions are difficult to establish or may vary from point to point. We present here a method to normalize spectra and estimate sample thicknesses based on a reference component present in the basal cell culture medium when we perform spectroscopy on colonies of living cells. Because more basal medium is displaced from the sampling volume as the cell layer increases in thickness, and because this component is present in the medium but excluded from cells, a concomitant decline therefore occurs in the intensity of the Raman scattering from the reference component. This permits comparisons between samples because their spectra can be scaled in inverse relation to their excluded volumes. Furthermore, estimations of sample thicknesses can also be obtained based on the same concept. Thus, the absolute quantification of cellular components becomes possible because cell sample volumes can be determined. Although applied to human embryonic stem cells, the approach is sufficiently general to be adapted for use with other samples. Copyright © 2011 John Wiley & Sons, Ltd.     

含遮蔽抛射沉积模型的有限尺寸效应

含遮蔽抛射沉积模型是在抛射沉积(BD)模型的基础上考虑了粒子以一定的角度分布倾斜入射的情况.本文应用外推方法确定了大尺寸极限下含遮蔽抛射沉积模型的各标度指数,讨论了该模型的有限尺寸效应及其标度性质.从模拟结果可以看出含遮蔽BD模型的有限尺寸效应与BD模型有所不同,遮蔽这种非局域作用可以显著地改变BD模型的标度性质. 关键词： 遮蔽效应 抛射沉积模型 有限尺寸效应 动力学标度     

Subtleties in data analysis related to the size of critical region

We comment on the analysis of the critical behavior of a layered driven diffusive system recently done by Achahbar and Marro. We discuss why we believe their method of taking the thermodynamic limit and determining the order-parameter exponent leads to unreliable estimates.     

Effect of temporal resolution on the estimation of left ventricular function by cardiac MR imaging

The aim of this study was to investigate the effect of temporal resolution on the estimation of left ventricular (LV) function by cardiac magnetic resonance (MR) imaging using a steady-state free precession (SSFP) sequence. Left ventricular function was assessed by cine MR imaging using a segmented SSFP sequence in 10 healthy volunteers. Views per segment (VPS) were set at 8 and 20, resulting in high and low true temporal resolution, respectively. Irrespective of VPS, images were reconstructed at 40 cardiac phases, providing high apparent temporal resolution. Data were analyzed using 40, 20 and 10 phases to simulate different apparent temporal resolutions. Increasing the cardiac phases used for analysis slightly decreased mean end-systolic volume (ESV) and slightly increased mean ejection fraction (EF). No substantial difference in estimates of end-diastolic volume (EDV) was found between VPSs of 8 and 20. Imaging with a VPS of 20 yielded a larger ESV and smaller EF than imaging with a VPS of 8 when 40 phases were used. In conclusion, low true temporal resolution causes overestimation of ESV and underestimation of EF. Improvement of apparent temporal resolution mildly reduces but does not eliminate the errors caused by low true temporal resolution.     

电磁脉冲作用人体的数值模拟和分析

 建立色散介质3维真实人体模型，用色散介质时域有限差分（（FD）2TD）方法计算了强电磁脉冲（EMP）对人体的作用。结果表明，电磁脉冲对人体的透入主要决定于脉冲前沿，受脉冲宽度的影响较小；透入体内的脉冲，相对辐照脉冲显著变窄；人体吸收的电磁能没有明显受到辐照脉冲能注量的影响；虽然人体从单个脉冲吸收的能量远低于用比吸收能定义的安全标准，但这种剂量的照射在离体培养的人肝细胞（L-02）上却产生了明显的生物学效应，这意味着比吸收能难以作为人员安全评估标准。     

An explanation for deviations from the quark number scaling of elliptic flows in low PT region

We carry out a systematic study of the different contributions to the deviations of the elliptic flows from the quark number scaling in high energy heavy ion collision in a quark combination model.The effects that we considered are:the resonance decay,the flavor dependence of the quark elliptic flow and the combination of quarks/antiquarks with slightly different transverse momenta.Our results show that the deviations observed in experiments can be well reproduced within the combination framework if all the three effects are considered. We make a detailed analysis of the different contributions using a Monte-Carlo program and suggest measuring the quark number scaling in intermediate P_T range more precisely.