Development of the avian lymphatic system

Recently, highly specific markers of the lymphatic endothelium have been found enabling us to reinvestigate the embryonic origin of the lymphatics. Here we present a review of our studies on the development of the lymphatic system in chick and quail embryos. We show that the lymphatic endothelium is derived from two sources: the embryonic lymph sacs and mesenchymal lymphangioblasts. Proliferation studies reveal a BrdU-labeling index of 11.5% of lymph sac endothelial cells by day 6.25, which drops to 3.5% by day 7. Lymphangioblasts are able to integrate into the lining of lymph sacs. Lymphatic endothelial cells express the vascular endothelial growth factor (VEGF) receptors-2 and -3. Their ligand, VEGF-C, is expressed almost ubiquitously in embryonic and fetal tissues. Elevated expression levels are found in the tunica media of large blood vessels, which usually serve as major routes for growing lymphatics. The homeobox gene, Prox1, is expressed in lymphatic but not in blood vascular endothelial cells throughout all stages examined, namely, in developing lymph sacs of day 6 embryos and in lymphatics at day 16. Experimental studies show the existence of lymphangioblasts in the mesoderm, a considerable time before the development of the lymph sacs. Lymphangioblasts migrate from the somites into the somatopleure and contribute to the lymphatics of the limbs. Our studies indicate that these lymphangioblasts already express Prox1.     

Convex Digital Polygons,Maximal Digital Straight Segments and Convergence of Discrete Geometric Estimators

Discrete geometric estimators approach geometric quantities on digitized shapes without any knowledge of the continuous shape. A classical yet difficult problem is to show that an estimator asymptotically converges toward the true geometric quantity as the resolution increases. For estimators of local geometric quantities based on Digital Straight Segment (DSS) recognition this problem is closely linked to the asymptotic growth of maximal DSS for which we show bounds both about their number and sizes on Convex Digital Polygons. These results not only give better insights about digitized curves but indicate that curvature estimators based on local DSS recognition are not likely to converge. We indeed invalidate a conjecture which was essential in the only known convergence theorem of a discrete curvature estimator. The proof involves results from arithmetic properties of digital lines, digital convexity, combinatorics and continued fractions.     

Application of time resolved emission techniques within the failure analysis flow

As the number of transistors and metal layers increases, traditional fault isolation techniques are less successful in exactly isolating the failing net or transistor to allow physical failure analysis. One tool to minimize the gap between global fault isolation – by means of emission microscopy or laser based techniques (TIVA, OBIRCH) – and physical root cause analysis is Time Resolved Emission (TRE). This paper presents two case studies illustrating the application of TRE within the failure analysis flow to generate a reasonable physical failure hypothesis.     

Mining association rules for the quality improvement of the production process

Academics and practitioners have a common interest in the continuing development of methods and computer applications that support or perform knowledge-intensive engineering tasks. Operations management dysfunctions and lost production time are problems of enormous magnitude that impact the performance and quality of industrial systems as well as their cost of production. Association rule mining is a data mining technique used to find out useful and invaluable information from huge databases. This work develops a better conceptual base for improving the application of association rule mining methods to extract knowledge on operations and information management. The emphasis of the paper is on the improvement of the operations processes. The application example details an industrial experiment in which association rule mining is used to analyze the manufacturing process of a fully integrated provider of drilling products. The study reports some new interesting results with data mining and knowledge discovery techniques applied to a drill production process. Experiment’s results on real-life data sets show that the proposed approach is useful in finding effective knowledge associated to dysfunctions causes.     

Large Bolometer Arrays with Superconducting NbSi Sensors for Future Space Experiments

New techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described.      

Performance characteristics of a new structured packing

A new structured packing using carbon fibres, called Sepcarb^® 4D, is presented. This packing has several attractive properties, such as high voidage (ε=94%) and high effective area (a=420 m² m^?3). These properties are advantageous for packing used as a gas–liquid contactor for separation units. To determine the internal characteristics of this packing, we performed several experiments using a 150-mm-internal-diameter column. Firstly, hydrodynamics experiments were conducted using an air–water counter current flow to determine the pressure drop (for both dry and wet packing) and flooding point. Secondly, the mass transfer efficiency was determined in terms of HETP (height equivalent to theoretical plate) by total reflux experiments with an n-heptane/cyclohexane mixture at atmospheric pressure. Hydrodynamic performance and mass transfer efficiency were compared with those of packings generally used in distillation and absorption.