Surface exchange area of the porcine placenta: morphometry of anisotropic interdigitating microvilli

The pig has a diffuse epitheliochorial placenta. The foeto-maternal surface area (S_V(F), S_V(M)) is enlarged at three levels: level I: macroscopic folds of uterine mucosa covered by foetal membranes; level II: light microscopic folds of uterine epithelium covered by trophoblastic epithelium; level III: ultrastructural formation of both maternal and foetal microvilli in an interdigitating pattern. This study presents a morphometric method, using intersection counting, to estimate the surface area of these interdigitating, highly oriented microvilli at level III, i.e. the ‘true’ surface exchange area. The method is applied to different stages in pregnancy. The epithelial surfaces are enlarged by a factor 8–11 due to the formation of microvilli. This factor varies during pregnancy, being lower early in gestation and before delivery, and for the first time it is shown to be significantly different for mother and foetus. At level III the foetal surface of placenta is larger than the maternal indicating that the two opposing surfaces are not congruent at the ultrastructural level and that membrane-linked placental transport may be different in mother and foetus. A three-compartment model is suggested for placental exchange with maternal, intermicrovillous and foetal compartments.     

The effect of six fixatives on the areas of rabbit neurons and rabbit and rat cerebral slices.

Cell bodies of cerebral neurons from rabbits were isolated by hand, transferred to a microscope slide in a ‘199’ medium, and the projected areas of their cytoplasm and nuclei were measured. In sixty-four cells there was a strong correlation between the projected areas of the cytoplasm and the nuclei (r=0.66, P < 0001), and the ratio of the projected areas was 11.6. The medium was then replaced by the following fixatives: formalin (10% v/v), Bouin's, Carnoy's, Susas, glutaraldehyde (5% v/v), and osmium tetroxide (1% w/v). Cerebral slices were obtained from the grey and white matter of rabbit and rat, and were also measured before and after treatment with similar fixatives. Relative to the unfixed areas, glutaraldehyde and osmium tetroxide had no significant effect on the projected areas of isolated cells, Carnoy's fixative shrunk the areas of the cytoplasm by means of 16.26%, Bouin's by a mean of 49%, and Susas by a mean of 65%. The shrinkage of the cytoplasm and the nuclei was not significantly different from that of the nuclei for each of these three fixatives individually, but with formalin the mean shrinkage of the cytoplasm was 46% while the nuclei did not shrink significantly. Using the same fixatives the effect on the areas of the cerebral slides from rabbit and rat were as follows: glutaraldehyde and osmium tetroxide caused no change in area; Carnoy's, formalin and Bouin's fixative diminished the areas by a mean of 10–20%, and Susa's by a mean of 35%. It was concluded that a particular fixative often caused a different degree of shrinkage to the cytoplasm, nuclei and cerebral slice. In general, the lower the osmotic pressure of the fixative, the less shrinkage it induced.     

梯度正则化法在土壤非饱和水分运动参数反演中的应用

基于多孔介质流体动力学理论和参数反演辨识技术,建立了非饱和土壤水分运动反问题的数学模型及最优化模型,并采用梯度正则化方法对非饱和土壤水分运动参数进行反演辨识.数值算例反演结果表明,采用梯度正则化方法对解的先验信息依赖极小,解决了参数初值对反演结果的敏感性问题,且反演结果与测试结果具有很好的一致性.     

Estimation of the optimal regularization parameter of an iterative wavelet algorithm for signal recovery

Two methods of statistical estimation of the optimal regularization parameter of a nonlinear algorithm for signal recovery are proposed, one of which is based on the optimality criterion and the other one on the residual principle. These methods have simple algorithmic implementation and do not need a priori information about the quantitative characteristics of the sought solution. The results of numerical experiments show the effectiveness of the method based on the optimality criterion.     

Numerical experiments on determination of spatially concentrated time-varying loads on a beam: an iterative regularization method

This paper treats a solution for the ill-posed (inverse) load determination problem for a time-varying load on a beam. The ill-posed nature of the problem causes numerical instability. Conventional numerical approach for solutions results in arbitrarily large errors in solution. The Tikhonov regularization method, which is a non-iterative stabilization technique, has been widely adopted for overcoming the ill-posed nature (or numerical instability). However, in this paper, we introduce an “iterative” regularization method, specifically, the iterated Tikhonov regularization method. The iterated method is applied to the present load determination problem. The result of the iterative method is compared with that of the (non-iterative) Tikhonov regularization. The rate of convergence for the introduced iterative method turned out to be very fast. The accuracy and applicability of the introduced method are examined through a numerical experiment.     

Localization of protein in the rabbit yolk sac splanchnopleur by two methods of autoradiography.

The distribution of protein labelled with radioactive iodine or tritium within cells of the yolk sac, after it was injected into the uterine lumen of pregnant rabbits, was studied by means of two autoradiographic techniques, one using the classical loop method of Caro & vanTubergen (1962), and the other using Normandin's direct deposition method (Normandin, 1973). The resolution of the latter method was found to be approximately 10 times more sensitive than that of the former (Hemmings & Williams, 1976); thus rendering the site of labelled protein easier to locate. Both techniques are reproducible, but the direct deposition method is easier to handle. Location of protein was detected within vacuoles, and sometimes free in the cytoplasm.     

Microfibril-microvessel connections in the rabbit eye: Correlative confocal and electron microscopy

The connections between elastic tissue and microvessels (arterioles, capillaries, and venules) in the rabbit eye were examined by light and electron microscopy. In particular, confocal scanning laser microscopy of tissue stained with orcein and examined by fluorescence using a rhodamine filter was correlated with electron microscopic observations. The goal was an analysis of the way in which elastic tissue of the uvea (i.e., choroid, ciliary body, and iris) and the optic nerve of the eye connect to the microvessels in these structures. Confocal microscopy revealed these connections advantageously and showed how they link the elastic tissue meshwork in the perivascular tissue spaces with the wall of the blood vessels. Electron microscopy showed that the connections consist of bundles of 10–12 nm diameter microfilaments that insert into vascular basement membranes. These connections may contribute to the vascular response to changes in blood pressure or intraocular pressure in the eye.     

The influence of the regularization parameter and the first estimate on the performance of Tikhonov regularized non-linear image restoration algorithms

This paper reports studies on the influence of the regularization parameter and the first estimate on the performance of iterative image restoration algorithms. We discuss regularization parameter estimation methods that have been developed for the linear Tikhonov–Miller filter to restore images distorted by additive Gaussian noise. We have performed experiments on synthetic data to show that these methods can be used to determine the regularization parameter of non-linear iterative image restoration algorithms, which we use to restore images contaminated by Poisson noise. We conclude that the generalized cross-validation method is an efficient method to determine a value of the regularization parameter close to the optimal value. We have also derived a method to estimate the regularization parameter of a Tikhonov regularized version of the Richardson–Lucy algorithm.   These iterative image restoration algorithms need a first estimate to start their iteration. An obvious and frequently used choice for the first estimate is the acquired image. However, the restoration algorithm could be sensitive to the noise present in this image, which may hamper the convergence of the algorithm. We have therefore compared various choices of first estimates and tested the convergence of various iterative restoration algorithms. We found that most algorithms converged for most choices, but that smoothed first estimates resulted in a faster convergence.     

An analytical study of the wear pattern of an abraded rubber surface: the interaction model

ABSTRACT

The relationship between the volume loss rate and the wear pattern along an abraded rubber surface has been confirmed. Experimentally, long and short pattern spacings are formed along the abraded direction that, respectively, represent the initial and final pattern spacings. By modelling the abrasion, or the sliding contact, as a vibration system, an analytical study to identify the pattern spacing is carried out. There are two proposed interaction models of the contact between the rubber surface and the abrader, i.e. separation and unification, thus, the interaction along the sliding contact is a combination of both. It is confirmed that the separation model is correlated to the initial pattern spacing. The results are obtained that the final pattern spacing not only depends on the static load of the abrader but also depends on the dynamic load due to the inertia effect of the moving parts of abrasion apparatus.     

In vitro confocal imaging of the rabbit cornea

We were able to observe in vitro the fine structure of the rabbit cornea using a laser scanning confocal microscope, especially in the regions between Descemet's membrane and the epithelial basal lamina. We observed submicrometre filaments throughout the stroma with high concentrations adjacent to Descemet's membrane, and found extensive interconnecting processes between stromal keratocytes. There are numerous regions containing nerve plexuses in the stroma. We found a deeply convoluted basal lamina adjacent to the epithelium, and observed regions containing junctions between endothelial cells in fluorescent images of rabbit corneas stained with the actin-specific compound fluorescein phalloidin.     

Message of the President elected for the term 2016-2019

正Dear all Dear IFToMM officers(Chairs of MOs,Chairs of PCs and TCs,members of EC)It is a great privilege and honour for me to serve again as President of IFToMM for the term 2016–2019.I thank the delegates and the Chairs of Member Organizations(MOs)for having voted my candidature and for promising support of my actions for future development of IFToMM.     

Controlled vascular corrosion casting of the rabbit eye

We have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross-linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.     

模式化大粒度构件的可复用性研究

针对大粒度构件复用度低的问题,为提高企业应用软件的开发效率,基于对大粒度构件的组成及复用效率影响因素的分析,提出模式化大粒度构件的概念.基于大粒度构件的可配置特性,在大粒度构件生命周期的各阶段给出其相应的生产和复用方法.以企业相关领域的大粒度构件为例,验证了提高大粒度构件复用度方法的实用性,增强了对业务需求变化的适应性.     

直面WTO格局的压缩机行业

评说了我国容积式压缩机产业的技术水准、市场热点和发展动向。以及已拥有的WTO格局下的若干优势。     

Strain pattern following surface replacement of the hip

The aim is to compare the strain pattern in intact and resurfaced femurs using validated third-generation composite femurs and rosette strain gauges. The rosette strain gauges were applied to an intact and a resurfaced third-generation composite femur at three sites: the narrowest part of the lateral surface of the neck, the narrowest part of the medial surface of the neck, and the medial surface at the level of the lesser trochanter. The maximum and minimum principal strains were calculated at axial loads of 600, 800, and 1000 N. Further tests were carried out with an additional abductor load. The maximum principal strains in the resurfaced femur were approximately 50 per cent higher in the lateral surface of the neck and about 25 per cent higher in the lesser trochanteric region than in the intact femur. Inclusion of the abductor force decreased the strains in both the intact and the resurfaced femurs, particularly at the lateral surface of the femoral neck. Increased strain at the lateral surface of the femoral neck following hip resurfacing could be a cause of neck fracture, particularly if there are other predisposing factors such as notching of the femoral neck and/or abductor dysfunction. Meticulous repair of the abductors is warranted if a lateral approach is used.     

Lyapunov Redesign of Model Reference Adaptive Control System for long term ventilation of lung.

A lyapunov redesign of Model reference adaptive control system for a long term, automatically regulated, ventilatory system is presented. A fixed resistance-capacitance RC analog lung model is used to generate a desirable (reference response) alveolar pressure. The instantaneous difference in alveolar pressures between the patient and its model is fed to an adaptive controller. The controller is designed to adjust the patient's inflating pressure in such a way as to reduce the instantaneous difference in the alveolar pressures to zero. The adaptive control system described can be implemented provided the patient's alveolar pressure is continuously measurable. Unfortunately, this measurement is impossible to realize; therefore, a method to estimate the continuous alveolar pressure of the patient is to be developed. This estimation is achieved indirectly from the identification process of the patient's respiratory parameter. The same Lyapunov redesign is used in this identification process. Digital simulation of the control of the patient's inflating pressure and the identification process, as well as the simulation of the combined system, were performed. The result has demonstrated the ability of this adaptive system to perform in a fast and stable manner.     

ISO9001:2000标准中7.6条款在生产中的应用

针对ISO9001：2000标准中7．6条款对监视和测量装置的检定、校准要求，阐述了在实际生产过程中为确保监视和测量结果准确、为产品符合性提供有效保证所应该做的工作。     

Tensile and compressive properties of the medial rabbit meniscus

Quantification of the material properties of the meniscus is of paramount importance, creating a 'gold-standard' reference for future tissue engineering research. The purpose of this study was to determine the compressive and circumferential tensile properties in the rabbit meniscus. Creep and recovery indentation experiments were performed on the meniscus using a creep indentation apparatus and analysed via a finite element optimization method to determine the compressive material properties at six topographical locations. Tensile properties of samples taken circumferentially from the rabbit meniscus were also examined. Results show that the femoral side of the anterior portion exhibits the highest aggregate modulus (510 +/- 100 kPa) and shear modulus (240 +/- 40 kPa), while the lowest aggregate modulus (120 +/- 30 kPa) and shear modulus (60 +/- 20 kPa) were found on the femoral side of the posterior location. Values of 156.6 +/- 48.9 MPa for Young's modulus and of 21.6 +/- 7.0 MPa for the ultimate tensile strength of were found from the tensile samples, which are similar to the values found in other animal models. These baseline values of material properties will be of help in future tissue engineering efforts.