Studies on elemental tellurium under high pressure

A non-linear behaviour in the resistance of tellurium as a function of pressure has been observed. At each pressure the resistance shows a time variation. At lower pressures, the normalized resistance increases with time, and at higher pressures, the normalized resistance decreases exponentially as a function of time. This change in behaviour with respect to time occurs in the region of the steepest descent in the resistance versus pressure plot. However, the magnitude of the change in the resistance with time is small compared to a change in the resistance with pressure. The origin of this behaviour is suggested to be linked with the generation and annealing of localized charged defects. This revised version was published online in November 2006 with corrections to the Cover Date.     

Oxidation of TiAl based intermetallics

The high temperature oxidation behaviour of the binary and ternary alloys of the Ti–48Al system was studied at different temperatures. The primary objectives of this work were the establishment of the activation energies, the migration tendencies of the alloy species, mechanism of oxidation and chemistry of the oxide scales. The ternary additions were Cr (1.5 at 19%), V (2.2 at%), W (0.2 at%) and Mn (1.4 at%). The addition of ternary additions did not play a significant role in the oxidation behaviour at 704°C. At 815°C the alloys with Cr and V exhibited linear oxidation behaviour with large weight gains while the base Ti–48Al alloys exhibited the best behaviour. At 982°C the Mn-containing alloy was the worst, exhibiting a linear oxidation behaviour while the alloy with V and W and the base alloy with 400 p.p.m. oxygen exhibited the best oxidation behaviour. At 982°C the outermost oxide layer in contact with air is always near stoichiometric TiO₂. In all the alloys a layer of porosity is created just below the outer TiO₂ layer by the Kirkendall mechanism due to the rapid outward diffusion of Ti atoms. The addition of trivalent atoms like Cr in small amounts appear to be detrimental to the oxidation process as they can generate additional oxygen vacancies while the addition of atoms with valence of 5, such as V, and 6, such as W, appear to have beneficial effect on the oxidation behaviour at 982°C by tying up oxygen vacancies. This revised version was published online in November 2006 with corrections to the Cover Date.     

Bioceramics

Ceramics, glasses, and glass-ceramics are increasingly being tested for use in the human body. These materials often have excellent chemical properties for biomedical use, but they are brittle and show fatigue. Careful analysis of their mechanical properties is needed to determine appropriate applications. Hydroxylapatite is emerging as the most promising bioceramic because it shows no foreign body reactions and bonds strongly to bone; if properly made without pores or second phases it has excellent fatigue resistance. Glass-ceramics containing hydroxylapatite crystals also show good promise for many applications. Different forms of these materials, such as dense, granular, mixed granular with plaster of Paris, and coatings on metals are being tested and have very good potential as bioceramics.     

Substrate uptake by Gordonia amarae in activated sludge foams by FISH-MAR.

Gordonia amarae is a right-angled branching filament belonging to the mycolic acid-containing Actinobacteria which is commonly found in many foaming activated sludge wastewater treatment plants. Although studies on different substrates as sole carbon sources by pure cultures of G. amarae have been carried out, none have examined substrate uptake by this organism in situ. Uptake of several hydrophilic and hydrophobic substrates by G. amarae was evaluated in situ using a combination of fluorescence in situ hybridization and microautoradiography. G. amarae could assimilate a range of both hydrophilic and hydrophobic substrates. From the data, G. amarae appears to be physiologically active under aerobic, anaerobic and anoxic condition (NO2 and NO3) for some substrates. This might explain why attempts to control foaming caused by G. amarae using anoxic and anaerobic selectors have been unsuccessful. This study emphasizes that bacteria can behave differently in situ to pure cultures and that it is important to evaluate the in situ physiology of these bacteria if we are to better understand their role in the wastewater treatment process.     

A new approach to the decomposition of Boolean functions by the method of <Emphasis Type="Italic">q</Emphasis>-partitions. III. Joint decomposition of a function system

The paper considers the set-theoretical approach to the joint decomposition of systems of Boolean functions of variables specified in different representation forms. The approach is based on the method of q-partitions of conjuncterms and concept of decomposition clones. Theorems on joint decomposition of a system of full and partial functions are formulated. The approach is illustrated by examples. Parts I and II of this article are published in No. 5 (2001) and No. 1 (2002). __________ Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 39–58, March–April 2007.     

Synchronization properties of two coupled multisection semiconductor lasers emitting chaotic light

We present numerical simulations describing the dynamics of two multisection semiconductor lasers emitting in a chaotic regime coupled in a master-slave configuration. By changing the current of the passive section of the master laser, we observe a change in the maximum correlation between the outputs of the two systems. These devices are promising candidates for on-off phase-shift keying encryption.     

Statistical analysis of uniform-sampling phase-locked loops based on Volterra functional expansions

With the use of Volterra functional expansions in the domain of the multidimensional z transform, discrete uniform-sampling analogues of digital phase-locked loops of the first, second, and (N + 2)th orders with a delay of N sampling periods are analyzed.     

A new general equivalence transformation for mixed lumped and nonuniform distributed networks with synthesis applications

Contents A new general equivalence transformation for cascades of lossless nonuniform transmission lines (NTL's) and lumped reactance two-ports (LRT's) is presented. Based on this transformation a new synthesis method for NTL's and NTL-LRT cascades is established, by means of which microwave filters and matching sections can be constructed on the basis of a rational function of the complex frequency. Thus, given specifications can practically be met arbitrarily well. In contrast to others the new method is at the same time exact and easy to handle. A synthesis example is given at the end.

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Eine neue allgemeine Äquivalenztransformation für gemischt-kon-zentriert-ungleichförmig-verteilte Netzwerke mit Syntheseanwendungen

Übersicht Es wird eine neue allgemeine Äquivalenztrans-formation für Kettenschaltungen aus (verlustlosen inhomogenen) Leitungen und (konzentrierten) Reaktanzzweitoren vorgestellt. Auf der Grundlage dieser Transformation wird ein neues Syntheseverfahren für Leitungen und Leitungs-Reaktanzzweitor-Kettenschaltungen begründet, mit Hilfe dessen Mikrowellenfilter und-anpassungsglieder auf der Grundlage einer rationalen Funktion der komplexen Frequenz konstruiert werden können. Somit können vorgegebene Spezifikationen praktisch beliebig genau realisiert werden. Im Gegensatz zu anderen ist das neue Verfahren gleichzeitig exakt und leicht zu handhaben. Am Schluß ist ein Synthesebeispiel angegeben.