奥氏和乌氏粘度计测定液体粘滞系数公式推导中的错误

用泊肃叶定律推导奥氏和乌氏粘度计测量液体粘滞系数的计算公式中存在两点错误:1.奥氏和乌氏粘度计测量液体粘滞系数时,其毛细管是处于竖直位置,而洎肃叶定律只适用于水平均匀园管,不适用于非水平管;2.推导过程认为Δp=ρgh是毫无道理的。     

泊肃叶公式的一般推导

一般普通物理教科书中,对泊肃叶公式的推导都是在水平管的特殊条件下进行的,因此将结果运用到非水平管的情况时(如用奥氏或乌氏粘度计测液体粘带系数时)就会产生一些问题,要解决这些问题,最根本的办法是给泊肃叶公式以一般推导,得到在不同情况下都能直接应用的一般形式。这可由求解流体动力学基本方程而得以解决。对于不可压缩的粘性流体,当它的密度ρ及粘滞系数η为常数时,与本文有关的流体动力学基本方程是:     

改进毛细管粘度计的新思路

本文详细分析毛细管粘度计样液中剪变率的分布规律,揭示毛细管粘度计测出血液的粘度是等效粘度,提出以管两端压强差△p为毛细管粘度计测出的血液表观粘度的比较参照条件,从理论上解决了ηa-△p曲线的测绘,提供了改进毛细管粘度计的思路.总之,对毛细管粘度计进行了具体深入、系统的探讨.     

非牛顿流体流量公式的推导及修正因子的物理定义：以卡森流体,滨汉？…

作者依据卡森方程及泊肃叶公式推导出卡森流体的流量公式为：Ｑｃ＝πＲ＾４△Ｐ／８ηｃＬ（１－根号τｃ／τ）＾２。用同样方法导出滨汉氏流体的流量公式为：ＱＢ＝πＲ＾４△Ｐ／８ηＢＬ（１－τＢ／τ）。对于其它非牛顿流体，只要能建立ηα与△Ｐ（τ）之间的定量关系，均可代入泊肃叶公式得到该流体的流量公式。卡森流体修正因子（１－根号τｃ／τ）＾２与冈小天流量公式中的Ｆ（ξ）值不同，经实验验证（１－根号（ιｃ／     

肺内液黏度和表面张力测量的临床意义与测量方法

肺内液主要指由气道黏液和肺泡内表面衬里液所形成的一连续液体薄层,对于维持肺的健康至关重要。介绍肺内液流变学特性在维持气道稳定性、保证肺正常的屏障与清除功能、避免呼吸机相关性肺损伤和新生儿呼吸窘迫综合征表面活性剂替代治疗等方面的临床意义,同时总结Langmuir-Wilhelmy天平法、捕获气泡法、毛细管黏度计和旋转黏度计等液体表面张力和黏度测量的经典方法,以及粒子追踪微流变仪、轴对称液滴边缘形状分析等新技术,比较这些方法的优缺点,为临床研究肺内液流变学特性辅助肺疾病的诊断和治疗提供重要参考。     

非牛顿流体流量公式的推导及修正因子的物理定义(以卡森流体、滨汉氏流体为例)

作者依据卡森方程及泊肃叶公式推导出卡森流体的流量公式为：Ｑｃ＝πＲ４ΔＰ８ηｃＬ（１－τｃτ）２。用同样方法导出滨汉氏流体的流量公式为：ＱＢ＝πＲ４ΔＰ８ηＢＬ（１－τＢτ）。对于其它非牛顿流体，只要能建立ηａ与ΔＰ（τ）之间的定量关系，均可代入泊肃叶公式得到该流体的流量公式。卡森流体修正因子（１－τｃτ）２与冈小天流量公式中的Ｆ（ξ）值不同，经实验验证（１－（τｃτ）２值与实验结果吻合，而Ｆ（ξ）值在γ＜２００ｓ－１时与实验结果有较大差距。修正因子有明确的物理意义，它是定量表示屈服值对流量及表观粘度影响程度的物理量。若以τｃ＝０时的流量（Ｑ０）及粘度（ηｃ）为准，则屈服值为τｃ时的流量（Ｑｃ）及ηａ符合下式：Ｑｃ／Ｑ０＝ηｃ／ηａ＝修正因子。该式为实验验证及获得修正因子提供了实验方法及理论依据。作者建议把修正因子作为血液流变学及血液动力学的定量指标。     

关于“流体的运动”的教学点评

本文从科学的研究方法、流体动力学是血液动力学与血液流变学的基础、伯努利方程的物理意义与特点、牛顿粘性定律的物理意义与特点、泊肃叶定律对讨论血流问题的基础意义、体积流量的数学描述、速度梯度的概念与描述、雷诺数的物理意义与特点、关于流阻的讨论等九个问题提出自己在备课与教学中的思考与点评,也对当前某些教材中的不妥表述提出辨析。本文可为教师钻研教材与深入备课提供借鉴,也可供医学生深人学习和提高作参考。     

利用毛细管测量血液粘度的研究

目前普遍使用的毛细管式血液粘度计一般只能给出两个切变率下的粘度值,而且高切和低切所对应的切变率的具体值又不确切.为此,本文提出了一种解决毛细管粘度计测量非牛顿流体(如血液)的粘度时切变率不可知的问题的方法,提出了一种结构设计模型,并推导出了切变率-粘度-体积流量的关系,并以测量不同切变率下的粘度为例给出了仪器结构设计模型.     

气体栓塞现象中δ值的意义及其测试方法的研究

本文指出气体栓塞现象中δ［１］值的测定，在表面物理学、物理化学等学科中，理论和实践方面的意义：给出δ值的二种定义：提出δ值的一种切实可行的测试方法：液体两端的压强差采用方便可行的“热加压法”来实现，同时还指出实验成败的关键所在。最后对塑料毛细管中一段和数段蒸溜水液柱进行了测量，得出精确可靠的δ值，并证实：推动数段液柱所需的大小压强主与液柱的段数成正比的结论。     

动脉的血流量与血压的空间和时间变化率同步

在生理学等相关书籍中多有关于动脉血流量与血压随时间变化关系曲线,但却未见对它们为何有如此关系做出解释,这正是本文力图解决的问题。研究以实验曲线为依据,借助泊肃叶定律和相关物理、数学知识,通过分析、推理而阐明血流量与血压梯度的关系。研究推断在一次心动周期过程中动脉血管中任一截面的血流量随时间的变化与该处血压的空间变化率和时间变化率大致同步。血流量与血压不同步。     

An Alternative Derivation for Bronnikov’s Reconstruction Algorithm in X-ray Phase Contrast Tomography

In this article, we present an alternative derivation for Bronnikov’s reconstruction algorithm in X-ray phase contrast tomography with holographic measurements. A two-step method was used in the alternative derivation. The phase shift induced by the object was obtained by Fourier transform and the real part of the complex refractive index of the object was retrieved by applying the conventional filtered backprojection method. The alternative derivation provides an easier way to understand the reconstruction formula.     

International community consensus standard for reporting derivation of human embryonic stem cell lines

The development and implementation of new methods in human embryonic stem cell (hESC) research is fraught with difficulties, not least of which is the highly variable reporting of the number and quality of embryos used to derive hESC lines. Without a clear minimum information convention among the derivation teams, understanding and comparing derivation methods and their potential impact on the resulting stem cell line will continue to be extremely difficult. In order to address this issue, we consulted international teams regarding the implementation of a minimum information convention for derivation with the aim of universal use, data collection and central analysis, followed by a multi-author publication. The responses demonstrated overwhelming support for such a system; over 90% of the respondents agreed that a universal standard for reporting the derivation of hESC lines was essential as part of the international effort to advance the field efficiently, and over 87% plan to use this standard and share collected data in Spring 2008 for central analysis and public dissemination. A number of future steps are planned in order to ensure that this standard evolves with the field and remains relevant and up-to-date. Our aim is to incorporate these data within existing international initiatives aimed at improving derivation standards. This article is an open-access publication in order to make the convention freely available to the international community and encourage universal participation.     

Human embryonic stem cell derivation: from the IVF perspective to therapeutic applications

Human embryonic stem cells (hESC) are capable of proliferating indefinitely in an undifferentiated state and are pluripotent, being able to differentiate into most cell types under the correct conditions. Since the establishment of the first hESC line in 1998, the hope has existed that these cells could constitute an unlimited cell source for replacement therapy in the treatment of various diseases and disabilities. However, there is opposition and concern within society towards hESC derivation. The purpose of this article is to introduce the medical and scientific issues surrounding hESC derivation for clinical use concerning the source for this research (human embryos donated from in vitro fertilization procedures), and the methodologies implicated in feeder-free, xeno-free derivation that will allow potential clinical applications.     

Hodgkin's lymphoma of T-cell type: clonal association with a CD30+ cutaneous lymphoma.

The derivation of Reed-Sternberg cells in Hodgkin's lymphoma has been a subject of great interest. In most cases, Reed-Sternberg cells seem to be derived from germinal center B cells. In few sporadic cases, a T-cell origin has been shown. This article supports the concept of a T-cell derivation for rare cases of Hodgkin's lymphoma and provides evidence of a novel mechanism of pathogenesis from chronic inflammation in the skin.     

Treatment of obsessive-compulsive disorder in patients who have comorbid major depression

Many patients who have obsessive-compulsive disorder (OCD) also meet criteria for additional diagnoses such as mood, anxiety, and personality disorders. The presence of severe depression, and major depressive disorder per se, impedes response to treatment for OCD that uses the best available treatments. In this article, the comorbidity data in OCD are reviewed, then the relationship between depression and OCD treatment outcome is reviewed. Next, the derivation and implementation of a treatment program specifically for depressed OCD patients are illustrated with a case example. The article closes with a discussion of implications and directions gleaned from this single case study.     

Efficient derivation of embryonic stem cells by inhibition of glycogen synthase kinase-3

Embryonic stem (ES) cells are derived from the inner cell mass (ICM) of blastocysts. The use of ES cells as a source of differentiated cells holds great promise for cell transplantation therapy. The efficiency of ES cell derivation is affected by genetic variation in mice; that is, some mouse strains, such as C57BL/6, are amenable to ES cell derivation, whereas others, such as BALB/c, are refractory. Developing an efficient method to establish ES cells from strains of various genetic backgrounds should be valuable for derivation of ES cells in various mammalian species, including human. Although it is well-established that various signaling pathways, including phosphoinositide 3-kinase (PI3K)/Akt and Wnt/beta-catenin, regulate the maintenance of ES cell pluripotency, little is known about the signaling pathways involved in the derivation of ES cells from ICMs. In this study, we demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3), one of the crucial molecules in the regulation of the Wnt/beta-catenin, Hedgehog, and Notch signaling pathways, dramatically augmented ES cell derivation from both C57BL/6 and BALB/c mouse strains. In contrast, Akt signaling activation enhanced the growth of ICM but did not increase the efficiency of ES cell derivation. Our study establishes an efficient means for ES cell derivation by pharmacological inhibition of GSK-3.     

Convolution reconstruction techniques for divergent beams

A rigorous derivation of a convolution reconstruction technique for diverging beams which does not require reordering the data is given. It is shown that such techniques allow both rapid data collection and rapid but nevertheless accurate reconstruction. The performance of the method is demonstrated by reconstructions of both a mathematically generated phantom representing cross sections of the human thorax and also cross sections of the intact thorax of a dog from actual X-ray data.     

Whole-blastocyst culture followed by laser drilling technology enhances the efficiency of inner cell mass isolation and embryonic stem cell derivation from good- and poor-quality mouse embryos: new insights for derivation of human embryonic stem cell lines

The optimization of human embryonic stem (hES) cell line derivation methods is challenging because many worldwide laboratories have neither access to spare human embryos nor ethical approval for using supernumerary human embryos for hES cell derivation purposes. Additionally, studies performed directly on human embryos imply a waste of precious human biological material. In this study, we developed a new strategy based on the combination of whole-blastocyst culture followed by laser drilling destruction of the trophoectoderm for improving the efficiency of inner cell mass (ICM) isolation and ES cell derivation using murine embryos. Embryos were divided into good- and poor-quality embryos. We demonstrate that the efficiency of both ICM isolation and ES cell derivation using this strategy is significantly superior to whole-blastocyst culture or laser drilling technology itself. Regardless of the ICM isolation method, the ES cell establishment depends on a feeder cell growth surface. Importantly, this combined methodology can be successfully applied to poor-quality blastocysts that otherwise would not be suitable for laser drilling itself nor immunosurgery in an attempt to derive ES cell lines due to the inability to distinguish the ICM. The ES cell lines derived by this combined method were characterized and shown to maintain a typical morphology, undifferentiated phenotype, and in vitro and in vivo three germ layer differentiation potential. Finally, all ES cell lines established using either technology acquired an aneuploid karyotype after extended culture periods, suggesting that the method used for ES cell derivation does not seem to influence the karyotype of the ES cells after extended culture. This methodology may open up new avenues for further improvements for the derivation of hES cells, the majority of which are derived from frozen, poor-quality human embryos.     

The spectral component of electrogastrography (EGG): factors of variation in normal subjects, and in patients with cancer and ulcers

A study of the spectral analysis of the electrogastrography has been mad in man in a non-invasive condition: normal subjects in two groups: young and old subjects (n = 72) were compared with gastric cancers (n = 42) and ulcerous (n = 22) subjects. Morning recording (10-11 h a.m.), in fasting conditions, were repeated every three successive days. In normal subjects, the mean frequency of the spectral gastric component is very stable (2.8 +/- 0.2 cycles per min), whatever be the sex, the age of the body weight. In normal subjects, the mean spectral amplitude (y) varied with the derivation: in derivation 3-6 (according to the antro-pyloric axis) is the greatest amplitude (y = 52 +/- 22 microV). In the cancerous condition, the range of the frequencies increases, but the mean frequency does not change (2.8 +/- 0.3 cycles per min). However, in 7 cancerous subjects the frequencies (x) fell beyond the limits of the population with an (x) being either less than or equal to 2.4 or greater than or equal to 3.2 cycles per min. In a great proportion (forty-seven per cent) of the cancerous subjects, an important and significant increase of amplitude is recorded (at least in one derivation). In these cases, the location of the cancer is the cardia, the fundus or the pylorus. The amplitudes fall significantly beyond those observed in ulcerous patients. The possible explanations of these variations and the applications to the future monitoring of patients are discussed.     

On calculating the finite centre of rotation for rigid planar motion

In this technical note, a simpler least squares derivation for calculating the angle of rotation and finite centre of rotation of a set of marker points undergoing rigid planar rotation and translation is shown. The major advantage of the approach, other than the simple derivation, is the automatic inclusion of the calculation of a scaling factor between the two point sets - the calculation of which was not obvious in previous approaches [Challis J. Estimation of the finite center of rotation in planar movements. Med Eng Phys 2001;23(3):227-33, Spoor C, Veldpaus F. Rigid body motion calculated from spatial coordinates of markers. J Biomech 1980;13:391-3]. The final numerical calculations are similar to those of [Challis J. Estimation of the finite center of rotation in planar movements. Med Eng Phys 2001;23(3):227-33] and are trivial to implement. A matlab routine for computing the two quantities, and the scaling factor, is included. We demonstrate the method on a clinical example using lateral radiographs of the lumbar spine.