微波体模

用水、盐,聚氯乙烯粉和羧甲基纤维钠四种材料配制成一种适用的微波体模(模拟肌肉组织)。该体模的复介电系数在300～2500MHz范围内与实际人体肌肉组织的误差≤5％。这种体模的优点是材料立足国内,价廉,室温下配制,使用方便。本文也给出这种体模的温度特性,稳定性和热学特性,供电磁场生物效应和微波热疗等研究使用。     

An image-based modeling framework for patient-specific computational hemodynamics

We present a modeling framework designed for patient-specific computational hemodynamics to be performed in the context of large-scale studies. The framework takes advantage of the integration of image processing, geometric analysis and mesh generation techniques, with an accent on full automation and high-level interaction. Image segmentation is performed using implicit deformable models taking advantage of a novel approach for selective initialization of vascular branches, as well as of a strategy for the segmentation of small vessels. A robust definition of centerlines provides objective geometric criteria for the automation of surface editing and mesh generation. The framework is available as part of an open-source effort, the Vascular Modeling Toolkit, a first step towards the sharing of tools and data which will be necessary for computational hemodynamics to play a role in evidence-based medicine.     

Biofluid Aspects of Embryo Transfer

Embryo transfer (ET) is the last stage of extracorporal fertilization during which the embryo is placed in the uterine cavity with a medium-filled catheter 2–3 days after in vitro fertilization. While fertilization in the laboratory occurs at very high rates (>:90%), the overall success of the procedure (i.e., take home baby) is still very low (<25%) and assumed to be mainly due to implantation failure. A computational model was developed to simulate ET within the uterine cavity by a fluid-filled catheter inserted into a two-dimensional channel with oscillating walls. The results showed that the speed at which the embryos are injected from the catheter dominates the procedure and controls the velocity of their transport within the uterine cavity. ET at excessively high injection speeds may lead to ectopic pregnancies, while uterine peristalsis affects transverse dispersion only during injection at low injection speeds. The presence of the catheter within the uterus does not affect flow patterns downstream of its tip. The potential risks to implantation failure due to mechanical factors involved in the ET processes are discussed. © 2003 Biomedical Engineering Society. PAC2003: 8719-j, 8710+e     

A Model for Transport and Dispersion in the Circulatory System Based on the Vascular Fractal Tree

Materials are distributed throughout the body of mammals by fractal networks of branching tubes. Based on the scaling laws of the fractal structure, the vascular tree is reduced to an equivalent one-dimensional, tube model. A dispersion–convection partial differential equation with constant coefficients describes the heterogeneous concentration profile of an intravascular tracer in the vascular tree. A simple model for the mammalian circulatory system is built in entirely physiological terms consisting of a ring shaped, one-dimensional tube which corresponds to the arterial, venular, and pulmonary trees, successively. The model incorporates the blood flow heterogeneity of the mammalian circulatory system. Model predictions are fitted to published concentration-time data of indocyanine green injected in humans and dogs. Close agreement was found with parameter values within the expected physiological range. © 2003 Biomedical Engineering Society. PAC2003: 8710+e, 8719Hh, 8719Uv     

Antisense oligodeoxynucleotides against thrombomodulin suppress the cell growth of lung adenocarcinoma cell line A549

Thrombomodulin (TM), an anticoagulant factor on endothelial cells, is known to be expressed in non-endothelial cells as well. In neoplastic cells of lung adenocarcinomas, TM is expressed but its correlation with growth potential has not been studied. As TM expression has a negative correlation with cell proliferation in lung squamous cell carcinomas, we examined its growth effect on lung adenocarcinoma cells of the A549 cell line by inhibiting TM expression with antisense oligodeoxynucleotides (ODN). In the antisense ODN transfected cells, the expression of TM mRNA was decreased to 49% at 12 h and 47% at 24 h, which was in accordance with TM expression at the protein level. By IdU (5-iodo-2'-deoxyuridine) incorporation assay, the growth of A549 cells was found to have decreased to 36% of the control level at 24 h post-transfection. The suppression of cell growth was maintained in a concentration-dependent manner for 48 h after transfection, when the expression of TM started to rebound. In the transfected cells, the G1 phase cell count was reduced to 60.7%, compared with 68.2% in the control transfectants. These results suggest that TM expression may play a suppressive role in the proliferation activity of A549 lung adenocarcinoma cells.     

红细胞聚集与取向对其悬浮液电阻抗的影响——I.实验研究

本文通过测量具有不同流变特性的红细胞悬浮液电阻抗的动态与静态变化，研究了红细胞聚集与取向对其悬浮液电阻抗的影响。首次得出以下结论：１．红细胞聚集使其悬浮液电阻抗显著减小。２．由于低切变率下红细胞聚集与高切变率下红细胞取向的共同影响，使血液电阻抗随切变率的变化具有双相特性。这增加了对血液电特性的新认识，表明可利用电阻抗测定红细胞聚性。     

单侧多节段后部结构切除对腰椎旋转稳定性影响的生物力学研究

目的：研究多节段脊柱后部结构对腰椎旋转稳定性的影响。方法：选用７具成人新鲜尸体脊柱标本（Ｌ１～Ｓ１），采用单侧多节段逐步切除腰椎后部结构的方法，形成７种状态，从单侧多节段开窗至全椎板及双侧小关节切除等。通过脊柱三维运动试验机施加１０Ｎｍ的扭转载荷，使脊柱产生左、右轴向旋转运动。结果：全椎板加双侧小关节部分切除后，腰椎旋转稳定性受到显著影响。结论：除小关节骨性结构及关节囊外，椎板及后部韧带结构对维持腰椎旋转稳定性亦有重要作用     

蛇毒抗栓酶对氧自由基致血小板变化的影响

次黄嘌呤／黄嘌呤氧化酶体系产生的氧自由基在体外能明显增加血中板膜微粘度，脂质过氧化代射产物丙二醛含量，血小板胞内游离钙浓度和血小板５－羟色胺的释放量。０．０３ｕ／ｍｌ的蛇毒抗栓酶明显抑制前二种效应，但促进血小板释放５－羟色胺，增加血小板胞内游离钙浓度，结果表明蛇毒抗栓酶对血小板膜有保护作用。