Super-Closeness Between the Ritz Projection and the Finite Element Solution for Some Elliptic Problems

We prove the super-closeness between the finite element solution and the Ritz projection for some second order and fourth order elliptic equations in both the $H^1$and the $L^2$norms. For the fourth order problem, a Ciarlet-Raviart type mixed formulation is used in the analysis. The main tool in the proof is a negative norm estimate of the Ritz projection, which requires $H^{q+1}$ regularity for second order elliptic equations. Therefore, the analysis is done on a domain Ω with smooth boundary, and hence we only consider the pure Neumann boundary problems which can be discretized naturally on such domains, if ignoring the effect of numerical integrals. For the fourth order problem, our results amend the gap between the theoretical estimates and the numerical examples in a previous work [22].     

Simulation of Three-Dimensional Free-Surface Flows Using Two-Dimensional Multilayer Shallow Water Equations

We present an efficient and conservative Eulerian-Lagrangian method for solving two-dimensional hydrostatic multilayer shallow water flows with mass exchange between the vertical layers. The method consists of a projection finite volume method for the Eulerian stage and a method of characteristics to approximate the numerical fluxes for the Lagrangian stage. The proposed method is simple to implement, satisfies the conservation property and it can be used for multilayer shallow water equations on non-flat bathymetry including eddy viscosity and Coriolis forces. It offers a novel method of calculating stratified vertical velocities without the use of the Navier-Stokes equations. Numerical results are presented for several examples and the obtained results for a free-surface flow problem are in close agreement with the analytical solutions. We also test the performance of the proposed method for a test example of wind-driven flows with recirculation     

An actuarial analysis of long-term care demand in Hong Kong

Hong Kong is a fast-aging society. More than 775 000 citizens (around 11% of the total population) in Hong Kong were aged 65 or above in 2002, and it is expected the figure will increase to 2.2 million (or 24% of the total) in 2031. In this paper, an actuarial projection of the demand of long-term care (LTC) services in Hong Kong using the US National Long-Term Care Surveys (NLTCS) data, is provided. The need for LTC in Hong Kong will be growing drastically for older ages in the next few years; around 10% for elderly aged between 65 and 74 and the proportion would mount to 60% for the elderly at age 85 or above. Using a Markov Chain model, an individual's (age–gender specific) future LTC expenditures in Hong Kong have been projected. The net actuarial present values of total future LTC costs are expected to be HK$83 000 and HK$160 000 for males aged 65 and females aged 65, respectively. Alternative funding strategies for these liabilities are discussed. A simple private insurance scheme is chosen to illustrate the actuarial calculations. The results could be useful for funding and planning LTC services in Hong Kong.     

Non-targeted metabolomic biomarkers and metabotypes of type 2 diabetes: A cross-sectional study of PREDIMED trial participants

Aim

To characterize the urinary metabolomic fingerprint and multi-metabolite signature associated with type 2 diabetes (T2D), and to classify the population into metabotypes related to T2D.

双荧光逆向追踪法研究大鼠视网膜节细胞的中枢投射

目的：观察向上丘投射的大鼠视网膜神经节细胞(RGCs)在视网膜内的分布、密度及细胞类型上的差异。方法：将 DiI 与荧光金(FG)注射入 SD 大鼠的同侧和(或)对侧上丘,不同时相荧光显微镜下观察两种荧光标记 RGCs 的分布情况。结果：视网膜与视神经内均可见荧光标记;视网膜内标记 RGCs 的数目随时间延长略有增加。DiI 与 FG 的标记效率无明显差异;RGCs 大多数为对侧投射;视网膜颞背侧区域可见双侧投射细胞;视网膜颞腹侧周边区集中存在同侧投射细胞,多数胞体较大;视网膜其它区域可见零星同侧投射细胞。结论：DiI 与 FG 可高效率逆行标记 RGCs 及部分突起;SD 大鼠视网膜内并存着向对侧、双侧及同侧脑区投射的 RGCs,后二者数量较少,分布局限;同侧投射以大胞体细胞为多。     

大鼠缰核的传出投射—WGA--HRP法研究

向40只大鼠缰核的不同部位(外侧缰核外侧部和内侧部及内侧缰核)微电泳WGA-HRP后,观察顺行标记纤维和终支在脑内的走行和分布。缰核的传出投射经吻侧、对侧及尾侧三条通路。吻侧通路起自外侧缰核,经髓纹向吻侧走行至丘脑背内侧核、带旁核及外侧视前区。对侧通路经缰连合至对侧外侧缰核。尾侧通路主要起自内侧缰核和外侧缰核内侧部,投射到脚间核,并有背腹局部定位,部分纤维向尾侧走行终止于中缝核群及网状结构等处。     

节点反投影方法在三维EIT模型中的仿真与实验研究

电阻抗成像(EIT)技术中逆问题的病态特性是造成重建图像分辨率较低的主要原因之一,增加先验信息是改善成像效果的可行方法.建立三维圆柱体仿真模型,对边界电压数据进行多项式曲面拟合,增加先验信息,采用节点反投影方法进行图像重建.对两种目标模型进行仿真实验,并利用本实验室设计的128通道EIT系统进行水槽物理模型重建实验.仿真实验结果表明,较之传统的反投影方法,两种目标模型采用节点反投影方法重建的总体误差分别降低了8.87％和6.85％;在物理模型中,重建图像可清晰显示目标物体.所提出的方法有望用于提高临床检测与监护的成像质量.     

迭代重建技术在CT腹部低剂量扫描应用的可行性研究

目的 探讨256层螺旋CT应用低管电流联合迭代重建技术在腹部低剂量增强扫描的可行性.方法 对160例拟行腹部CT扫描患者随机分成8组(A～H组),每组20例.A组采用120 kV、250 mAs条件进行腹部常规剂量扫描,图像应用滤波反投影重建.B～H组采用固定管电压120 kV,管电流于250 ～70 mAs之间每次间隔30mAs减低扫描条件行上腹部低剂量扫描,图像采用迭代重建.采用方差分析比较各组图像噪声、对比噪声比、CT剂量指数、CT剂量长度乘积及有效辐射剂量的差异.并对各组图像分别进行质量评分,确定等同于A组图像质量并满足临床诊断要求最低剂量组.图像噪声与体重指数、腹围相关性采用Pearson相关分析.结果 采用迭代算法重建图像的低剂量B～H组主动脉、肝脏、脾脏、胰腺噪声为10.7 ～23.0 HU,B～F组均较常规剂量组A组图像噪声[(13.8～16.8)HU]低,而G、H组图像噪声均明显高于A组.B～E组图像平均噪声与A组比较,差异无统计学意义(P＞0.05),F～H组图像噪声与A组比较,差异有统计学意义(P＜0.05).低剂量组对比噪声比为3.1～14.7,B～E组对比噪声比均高于A组(3.4 ～7.6),但差异无统计学意义(P＞0.05).F～H组对比噪声比出现不同程度下降,部分低剂量组对比噪声比已低于常规剂量A组.低剂量组B～E组图像质量评分均≥3分,并与常规剂量组A组比较差异无统计学意义.F～H组主观图像质量随管电流减低而明显降低,与常规剂量组A组比较差异有统计学意义(P＜0.05).B～H组辐射剂量差异有统计学意义(P＜0.01),A组与B组比较,辐射剂量无统计学意义(P＞0.05).E组为图像质量等同于常规剂量扫描最适低剂量组,辐射剂量降低约35％.图像噪声与体重指数低度相关(r2 =0.316),与腹围高度相关(r2 =0.817)结论 迭代重建可以显著降低图像噪声、辐射剂量,提高图像质量,辐射剂量降低35％仍可得到与常规剂量滤波反投影重建相当的图像质量.