Through-hole membranes of nanoporous alumina formed by anodizing in oxalic acid and their applications in fabrication of nanowire arrays

The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried out in 0.3 M oxalic acid at the temperature of 20 °C. This relatively high temperature shortens significantly the anodizing time and allows to fabricate quickly thick through-hole membranes without the additional operating cost of a cooling circuit. The structural features of anodic porous alumina such as pore diameter, interpore distance, porosity, pore density and pore circularity were investigated at various durations of pore opening/widening process carried out in 5% H₃PO₄. An excellent agreement of AAO structural features measured in FE-SEM images of the studied samples with results from software calculations was observed. The pore shape can be monitored qualitatively by fast Fourier transforms (FFTs) and quantitatively by calculation the percentage of pore circularity. Additionally, the regularity of the hexagonal arrangement of nanopores in through-hole AAO membranes was compared for various opening/widening time ranging from 40 to 100 min. It was shown that three-dimensional (3D) representations of FE-SEM images and their surface-height distribution diagrams provide interesting information about the surface roughness evolution during the pore opening/widening process. A template-assisted fabrication of Ag and Sn nanowire arrays by electrochemical deposition into the pores of the prepared AAO templates was also successfully demonstrated.     

Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane

Multifunctional new material—polyurethane shape memory polymer (PU-SMP)—was subjected to tension carried out at room temperature at various strain rates. The influence of effects of thermomechanical couplings on the SMP mechanical properties was studied, based on the sample temperature changes, measured by a fast and sensitive infrared camera. It was found that the polymer deformation process strongly depends on the strain rate applied. The initial reversible strain is accompanied by a small drop in temperature, called thermoelastic effect. Its maximal value is related to the SMP yield point and increases upon increase of the strain rate. At higher strains, the stress and temperature significantly increase, caused by reorientation of the polymer molecular chains, followed by the stress drop and its subsequent increase accompanying the sample rupture. The higher strain rate, the higher stress, and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. The constitutive model of SMP valid in finite strain regime was developed. In the proposed approach, SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature.     

Mechanised welding of tubes to tubeplates

Abstract

With the introduction of the Ministerial Decree of 24 November 1984, which allows the use of polyethylene in the construction of underground pipelines for gas transportation, the said material and the relevant tvelding techniques have undergone considerable development in Italy.

This paper describes the main characteristics of this unusual plastic and indicates the welding processes normally used for joining P E pipes and fittings.

The accent is placed on the present possibilities of destructive and non-destructive testing of the welded joints, and an outline is given of the new Italian plan for the qualification of welders of polyethylene, prepared by UNIPLAST in conjunction with the Italian Welding Institute.     

Brain Glucose Transporters: Role in Pathogenesis and Potential Targets for the Treatment of Alzheimer’s Disease

The most common cause of dementia, especially in elderly people, is Alzheimer’s disease (AD), with aging as its main risk factor. AD is a multifactorial neurodegenerative disease. There are several factors increasing the risk of AD development. One of the main features of Alzheimer’s disease is impairment of brain energy. Hypometabolism caused by decreased glucose uptake is observed in specific areas of the AD-affected brain. Therefore, glucose hypometabolism and energy deficit are hallmarks of AD. There are several hypotheses that explain the role of glucose hypometabolism in AD, but data available on this subject are poor. Reduced transport of glucose into neurons may be related to decreased expression of glucose transporters in neurons and glia. On the other hand, glucose transporters may play a role as potential targets for the treatment of AD. Compounds such as antidiabetic drugs, agonists of SGLT1, insulin, siRNA and liposomes are suggested as therapeutics. Nevertheless, the suggested targets of therapy need further investigations.     

Phase equilibria in the cobalt oxide-copper oxide system

Thermodynamic properties were determined for the system cobalt oxide-copper oxide by means of an electromotive force (EMF) measurement techniques using galvanic cells with calciastabilized zirconia (CSZ) as the solid electrolyte and with air as the reference electrode according to the following schemes: CuO, Cu₂O | CSZ | air and CoO-CuO, Cu₂O CSZ | air for composition variables y=X_Cu/(X_Co+X_cu equal to 0.05, 0.15, 0.25, 0.35, 0.45, 0.667, and 0.8; and within the temperature interval 1200–1350 K. Thermodynamic properties calculated directly from EMF values were combined with the available literature data on phase equilibria, and thermodynamic properties of solid phases in the Co-Cu-O system were assessed. Both terminal solid solutions, (Co,Cu)O and (Cu,Co)O, were described by a sublattice model with Redlich-Kister excess term. The interaction parameters for both (Co,Cu)O and (Cu,Co)O solid solutions and the Gibbs energy of formation for the intermediate phase Cu₂CoO₃ were obtained. The Gibbs energies of fictive end-members: monoclinic “CoO” and “CuO” with rock salt structure were derived as well. The phase diagrams were calculated using the assessed thermodynamic parameters. The (T, y) phase diagram was calculated for existence under ambient air. The property diagrams log₁₀P(O₂) versus composition and activity of CuO versus composition were calculated at 1273 K. The results of our calculations were in a good agreement with available experimental data. This paper was presented at CALPHAD XXX International Conference on Phase Diagram Calculations in York, UK, May 27–June 1, 2001, and appeared in the Conference Abstracts on Page 75.     

The phase stability of solid LiAlO2 used for the electrolyte matrix of molten carbonate fuel cells

LiAlO₂ is used as a solid matrix for molten carbonate fuel cell (MCFC) electrolyte tiles. These devices operate within the temperature range of 870–970 K. The -crystallographic form of this compound is commonly used for fabrication of these matrix tiles. The thermodynamic stability of this phase within the above temperature range is not clear and it is reasonable to consider the transformation to take place in solid LiAlO₂ in presence of molten alkali carbonates. In order to establish the crystallographic form of the compound that forms as a product of reaction between the liquid Li₂CO₃ and solid Al₂O₃, the kinetics of LiAlO₂ formation has been investigated. Values of conversion factor as a function of the reaction time have been determined both for a stoichiometric reaction mixture and for mixtures with an excess of the liquid 0.53 Li₂CO₃ + 0.47 Na₂CO₃ eutectic. The simultaneous determination of the reaction conversion factor and the relative intensity of the characteristic x-ray peak for the – LiAlO₂ form in the reaction mixture have shown that, within 843–973 K, in experiments of ca 100–10 hours, respectively, only this phasev of LiAlO₂ is formed. These results may explain the presence of some – LiAlO₂ amount in the MCFC electrolyte tiles after long run tests of these devices.     

Fuzzy histograms, weak fuzzification and accumulation of periodic quantities

The influence of the scale of a fuzzy membership function used to fuzzify a histogram is analysed. It is shown that for a class of fuzzifying functions it is possible to indicate the limit for fuzzification, at which the mode of the histogram equals the mean of the data accumulated in it. The fuzzification functions for which this appears are: the quadratic function for aperiodic histograms and the cosine square function for periodic ones. The scaled and clipped versions of these functions can be used to control the degree of fuzzification belonging to the interval [0,1]. While the quadratic function is related to the widely known Huber-type clipped mean or the kernel function derived from the Epanechnikov kernel, the clipped cosine square seems to be less known. The indications for using strong or weak fuzzification, according to the value of the fuzzification degree, are justified by examples in two applications: classic Hough transform-based image registration and novel accumulation-based line detection. Typically, the weak fuzzification is recommended. The images used are related to simulation images from teleradiotherapy and to mammographic images.     

Grinding of coal in the presence of vapours of organic compounds

The effect exerted by the sorption of vapour of several chemical compounds on the crushing of bituminous coal was investigated. Air-dry samples of a low-rank coal (82.7 wt%C) a coking coal (87.0 wt%C) and a high-rank coal (91.7 wt%C) were saturated with methanol, ammonia and benzene vapour for 100 h, crushed in a ball-mill, and subjected to sieve analysis. Sorption of methanol causes a marked increase of the crushability of all coals tested. Coal crushability increasing with increase of rank. The results have been interpreted according to the polymeric model of coal structure.     

Einfluß des Erweichungsprozesses auf die Geschwindigkeit der Reduktion von Sinter mit Wasserstoff

Im vorliegenden Beitrag wurde der Einfluß des Erweichungsprozesses auf die Reduktionsgeschwindigkeit von Sinter untersucht. Dabei wurde die Reduktionsgeschwindigkeit von Hochofensinter in einem Temperaturbereich um den Erweichungspunkt bestimmt. Es wurde ein rapider, mit dem Erweichungseffekt wie auch mit dem Porositätsschwund verknüpfter Geschwindigkeitsrückgang festgestellt. Diese Erscheinung findet in einem Temperaturbereich statt, der den Temperaturen des Erweichungsbeginns beim untersuchten Sintermaterial im vorreduzierten Zustand entspricht. Somit ist der Erweichungsvorgang als grundlegende Ursache für die festgestellte Abnahme der Reduktionsgeschwindigkeit zu betrachten. Mikroskopische Direktbeobachtungen der Reduktion von Sinter im Erweichungszustand zeigten Erscheinungen, die zu einem Porositätsschwund führen. Messungen des Porenvolumens und der spezifischen Porenoberfläche an Sinter – vor wie nach abgeschlossener Erweichung und Reduktion – bestätigten die Porositätsabnahme. Diese erschwert den Reduktionsgaszufluß zu den Eisenoxiden und verlangsamt so die Reduktionsgeschwindigkeit.