Extrusion-rotomolding of plasticized PVC formulations

In this work, we present a novel process to produce plasticized PVC articles. Plasticized PVC dispersion resin (dry blend) was extruded and poured into a hot mold. The mold was transferred to a rotomolding machine, where the final geometry was obtained. Formulations using commercial PVC suspension resin and three different types of plasticizers were prepared under different processing conditions. The physical appearance of the articles and the tensile properties of the materials were evaluated.     

Probabilistic linear models for multiresolution estimation in gray-level images

A multiresolution analysis of digital gray-level images is presented. A gray-level multi-scale framework is determined from two main assumptions: the gray scale is binary at the finest spatial resolution, and the gray levels of composed regions are obtained additively. In order to interrelate the gray-level histograms of the same image at different resolutions, probabilistic linear models are developed, which are then applied for estimation. Linear-optimization theory is used as a way of constructing such models. A general procedure for image processing is sketched, based on gray-level estimation. A versatile algorithm for nonlinear filtering is derived. Some examples of prospective applications are given.This work was partially supported by grant TIC91-646 from the DGYCIT of the Spanish Government.     

A genetic model for undifferentiated cell tumor formation: similar tumors formed by different cell lines transformed by the E1A oncogene

The activation of oncogenes and the mutation/deletion of suppressor genes may be involved in tumor heterogeneity. In an attempt to study tumor heterogeneity, we transformed cell lines from epithelial (PAM 212), mesenchymal (NIH-3T3), or melanocytic origin (L-BIOBR) with the wild type E1a oncogene. To make the cell lines tumorigenic, cells were infected with Harvey sarcoma virus carrying the v-H-ras oncogene. The transformed cells were injected into nude mice and the tumors studied by optical and electron microscopy. The tumors formed by v-H-ras-transformed cells consisted of epitheliod melanomas, spindle cells sarcomas and poorly-differentiated carcinomas, depending on the cell of origin. In contrast, the tumors obtained from cells also carrying the E1a oncogene showed a predominant small and undifferentiated cell pattern regardless of the cell of origin. We conclude that the E1a oncogene products induce a negative control of differentiation, independent of the cell type, and that tumors formed by cells carrying the E1a oncogene display an undifferentiated cell pattern.     

The analysis of arbitrarily shaped aperture-coupled patch antennasvia a mixed-potential integral equation

A mixed-potential integral equation (MPIE) is formulated for the electric and magnetic currents on a multilayered aperture-coupled patch antenna. The integral equation is solved via the method of moments (MoM) using subsectional basis functions that allow the analysis of nonrectangular aperture and patch shapes. The input impedance and radiation efficiency of various aperture-coupled elements are calculated using the proposed technique and compared to measured results. The advantages and disadvantages of several aperture and patch configurations are discussed, and six methods of numerically de-embedding the element's input impedance are compared     

液体低温热导率的测试

介绍了非稳态法测试液体在低温下（－１００～５０℃）的热导率的测试原理、方法，测试了全氟三乙胺的低温热导率。为了提高测试的重复性，采用了相对比较法，并给出了测试装置及测试结果和误差分析。     

保安矿柱回采地压监测数据分析

通过现场在马头门附近设立监测站进行长期监测井筒地压，分析了井筒附近地压活动规律，并与数值模拟分析值进行对比验证，从而为安全、高效地提前回收保安矿柱提供有力的保障。     

疏松砂岩地层出砂对套管损坏的研究

以东濮凹陷文明寨油田历年井况调查的套管损坏资料为依据，在对出砂油井套管损坏形态、层位与射孔状况、岩石性质等因素进行综合分析基础上，对疏松砂岩出砂、上覆岩层坍塌等主要方面导致的套管受力变形进行研究，为探讨防治措施提供依据。     

节理岩体的代表单元集合体模型及弹性参数预测

本文明确提出了节理岩体“代表单元集合体”的概念和模型，通过对节理岩体的“代表单元集合体”进行数值模拟，研究了节理岩体的“代表单元集合体”的变形特性，建立了节理岩体的弹性模型，提出了预测节理岩体宏观等效弹性参数的计算机模拟方法，并将其应用于岩体工程稳定性分析中。     

Cyclic variations in the permeability of the cell wall of Saccharomyces cerevisiae.

To study cell-cycle-related variations in wall permeability of Saccharomyces cerevisiae, two approaches were used. First, an asynchronous culture was fractionated by centrifugal elutriation into subpopulations containing cells of increasing size. The subpopulations represented different stages of the cell cycle as judged by light microscopy. Cell wall porosity increased when these subpopulations became enriched with budded cells. Secondly, synchronous cultures were obtained by releasing MATa cells from alpha-factor induced G1-arrest. These cultures grew synchronously for at least two generations. The cell wall porosity increased sharply in these cultures, shortly before buds became visible and was maximal during the initial stages of bud growth. It decreased in cells which had completed nuclear migration and before abscission of the bud had occurred. The porosity reached its lowest value during abscission and in unbudded cells. We examined the incorporation of mannoproteins into the wall during the cell cycle. SDS-extractable mannoproteins were incorporated continuously. However, the incorporation of glucanase-extractable mannoproteins, which are known to affect cell wall porosity, showed cyclic oscillations and reached its maximum after nuclear migration. This coincided with a rapid decrease in cell wall porosity, indicating that glucanase-extractable mannoproteins might contribute to this decrease.