Analytical electron tomography mapping of the SiC pore oxidation at the nanoscale

Silicon carbide is a ceramic material that has been widely studied because of its potential applications, ranging from electronics to heterogeneous catalysis. Recently, a new type of SiC materials with a medium specific surface area and thermal conductivity, called β-SiC, has attracted overgrowing interest as a new class of catalyst support in several catalytic reactions. A primary electron tomography study, performed in usual mode, has revealed a dual surface structure defined by two types of porosities made of networks of connected channels with sizes larger than 50 nm and ink-bottled pores with sizes spanning from 4 to 50 nm. Depending on the solvent nature, metal nanoparticles could be selectively deposited inside one of the two porosities, a fact that illustrates a selective wetting titration of the two types of surfaces by different liquids. The explaining hypothesis that has been put forward was that this selectivity against solvents is related to the pore surface oxidation degree of the two types of pores. A new technique of analytical electron tomography, where the series of projections used to reconstruct the volume of an object is recorded in energy filtered mode (EFTEM), has been implemented to map the pore oxidation state and to correlate it with the morphology and the accessibility of the porous network. Applied, for the first time, at a nanoscale resolution, this technique allowed us to obtain 3D elemental maps of different elements present in the analysed porous grains, in particular oxygen; we found thus that the interconnected channel pores are more rapidly oxidized than the ink-bottled ones. Alternatively, our study highlights the great interest of this method that opens the way for obtaining precise information on the chemical composition of a 3D surface at a nanometer scale.     

A fully automatic CAD-CTC system based on curvature analysis for standard and low-dose CT data

Computed tomography colonography (CTC) is a rapidly evolving noninvasive medical investigation that is viewed by radiologists as a potential screening technique for the detection of colorectal polyps. Due to the technical advances in CT system design, the volume of data required to be processed by radiologists has increased significantly, and as a consequence the manual analysis of this information has become an increasingly time consuming process whose results can be affected by inter- and intrauser variability. The aim of this paper is to detail the implementation of a fully integrated CAD-CTC system that is able to robustly identify the clinically significant polyps in the CT data. The CAD-CTC system described in this paper is a multistage implementation whose main system components are: 1) automatic colon segmentation; 2) candidate surface extraction; 3) feature extraction; and 4) classification. Our CAD-CTC system performs at 100% sensitivity for polyps larger than 10 mm, 92% sensitivity for polyps in the range 5 to 10 mm, and 57.14% sensitivity for polyps smaller than 5 mm with an average of 3.38 false positives per dataset. The developed system has been evaluated on synthetic and real patient CT data acquired with standard and low-dose radiation levels.     

Impedimetric detection of dopamine on poly(3-aminophenylboronic acid) modified skeleton nickel electrodes

Detection of biologic compounds in particular dopamine is usually based on the complexation between boronic acid groups and diols. For this reason the development of new sensors based on direct monitoring of boronic acid–diol complexation is attractive. A measurable electric response due to a change in the dopamine concentration can be achieved on electrodes modified with boronic groups. In this work a modified electrode has been obtained by electropolymerization of 3-aminophenylboronic acid in aqueous solutions on a preformed polyaniline layer electrochemically deposited on smooth and skeleton nickel electrodes. The modified electrodes have been tested as impedimetric sensors for the detection of dopamine in aqueous phosphate buffer at pH = 7.4. Both sensors gave a linear response for dopamine concentrations between 10^?5 and 10^?10 mol L^?1. Poly(3-aminophenylboronic acid) modified skeleton nickel electrode has the advantage of an increased specific surface area, that lead to a high density of boronic acid groups and hence to a better sensitivity.     

New Results on Path Approximation

In this paper we give bounds on the complexity of some algorithms for approximating 2-D and 3-D polygonal paths with the infinite beam measure of error. While the time/space complexities of the algorithms known for other error measures are well understood, path approximation with infinite beam measure seems to be harder due to the complexity of some geometric structures that arise in the known approaches. Our results answer some open problems left in previous work. We also present a more careful analysis of the time complexity of the general iterative algorithm for infinite beam measure and show that it could perform much better in practice than in the worst case. We then propose a new approach for path approximation that consists of a breadth first traversal of the path approximation graph, without constructing the graph. This approach can be applied to any error criterion in any constant dimension. The running time of the new algorithm depends on the size of the output: if the optimal approximating path has m vertices, the algorithm performs F(m) iterations rather than n–1 in the previous approaches, where F(m) \le n–1 is the number of vertices of the path approximation graph that can be reached with at most m–2 edges. This is the first output sensitive path approximation algorithm.     

Critical stresses in rolling contact fatigue

An analysis of the main hypotheses concerning the critical stresses in rolling contact fatigue is presented. It is considered that none of these hypotheses correlates adequately with all the experimental aspects of the phenomenon of rolling contact fatigue. A new hypothesis is proposed; this hypothesis states that the equivalent stress is the critical stress in rolling contact fatigue. By considering the influence of the residual stresses it is shown how the optimum fatigue life in rolling contact can be achieved.     

Achieving a sustainable interoperability of standards

Agile enterprises and networks are required to continuously evolve so as to adequately respond to a dynamic, global and very competitive business environment. Unfortunately, this continuous change requirement affects the capacity of the enterprise to effectively interoperate internally and externally. Adding to this problem, the standards typically used as pillars for enterprise and network management and (inter)operation are themselves subject to continuous change and often bring their own interoperability, inconsistency and overlap problems. It is essential that such concerns are identified and addressed in a sustainable manner, i.e. taking into account the life cycles of all entities involved as their interoperability capabilities and requirements change along their lives. This paper focuses on interoperability issues specific to standards and proposes a novel and original way forward based on principles tested in previous case studies combining elements from the Enterprise Interoperability, Architecture and Integration, Collaborative Networks and Artificial Intelligence bodies of knowledge.     

Urchin-like self-supported carbon nanotubes with macroscopic shaping and fully accessible surface

A self-supported carbon nanotubes (SSCNTs) with nanoscopic properties and controlled macroscopic shape were synthesized by a Chemical Vapour Deposition (CVD) method using a mixture of ethane/hydrogen and a Fe/Al₂O₃ growth catalyst. The SSCTs were obtained in the form of beads of 6–8 mm in diameter, with a hollow core structure and a high and fully accessible specific surface area, i.e. 140–180 m².g^? 1. In addition, the macroscopic shape and open structure of these SSCNTs allow them to be efficiently used as catalyst support either in a gas-phase or in a liquid-phase configuration.     

New Two-Frequency Method and Devices for Electromagnetic Levitation Drip- and Leakage-Free Melting of Metals

A new method and devices for the electromagnetic levitation melting of metallic samples with greater weights and axisymmetrically stabilized positions is presented in this paper.The new method is applying two homogeneous magnetic fields of different frequencies,whose field lines are in absence of a charge horizontally and reciprocally normal in order to exert electromagnetic lift forces also on the axis of the levitated sample.Therefore the weight of the charge can be increased and the charge can be drip-and leakage-free melted.The method can be used in a melting furnace with or without a cold protective wall,as well as for the coreless induction valves applied for flow rate control,e.g.in the continuous casting of molten metals.The applicability of the method was experimentally examined and proved by tests conducted with three types of laboratory setups.