Bang-bang Controls and Piecewise Constant ones for Continuous Roesser Systems

In the paper, we prove the bang-bang principle for a continuous linear nonautonomous Roesser system and some approximation result (with respect to piecewise constant controls) for a continuous nonautonomous Roesser system which is linear in the state and nonlinear in the control. Published online: April 2006 The preparation of this paper was supported by the State Committee for Scientific Research, Poland, under Grant 7 T11A 004 21     

Electrical Conduction Behavior of La1+xSr1−xGa3O7–δ Melilite-Type Ceramics

Ceramics of the melilite-type compound La_{1+ x} Sr_{1− x} Ga₃O_7−δ were prepared by conventional ceramic processing. Samples prepared represented the entire homogeneity region of the phase (i.e., x =−0.15 to 0.60). Electrochemical characterization under variable temperature and atmospheric conditions in the vicinity of air entailed four-point direct-current conductivity measurements and electromotive force measurements. La_{1+ x} Sr_{1− x} Ga₃O_7−δ samples exhibited a p -type behavior with generally increased conductivity with increased substitution of lanthanum for strontium, which reached a saturation value of ∼10⁻¹ S·cm⁻¹ at 950°C.     

Cover Image,Volume 66, Issue 10

The cover image, by Bruna A. Bregadiolli et al., is based on the Research Article Towards the synthesis of poly(azafulleroid)s: main chain fullerene oligomers for organic photovoltaic devices, DOI: 10.1002/pi.5419 .

     

Formulation and technology research of new silver solder with flux covering

In their eutectic compositions, Au–Si alloys have a melting point of 369°C, and a colour similar to that of high-grade gold. Results of the manufacture of gold alloys with 2.5%, 2.8% and 3.0% silicon, by means of melting in a plasma furnace with an inert argon atmosphere, are presented in this study. Chemical composition characterisation was carried out by energy dispersion spectroscopy and wave dispersion spectrometry, and metallographic and microstructural analysis by optical microscopy, SEM and DRX, Vickers hardness and mircohardness testing, melting point evaluation by DSC and determination of the SCIELab colorimetric coordinates. The results of the hardness and micro-hardness testing gave values around 110HV, presenting an important increase in the mechanical properties with respect to the traditional high purity gold alloys. The melting temperature for the alloys was around 374°C as well as being a heat very close to the values of pure gold.     

The application of dynamic insulation in buildings

Dynamic insulation, a form of ‘Breathing Wall’ construction which allows the movement of air and moisture through the external walls of a building, was seen as one possible method for reducing building envelope heat losses and achieving high indoor air quality. A research investigation was conducted to provide a firm scientific understanding of dynamic insulation. An important outcome of the work will be the development of building envelope designs which effectively and economically employ dynamic insulation in cold climates. This paper presents some general conclusions, confirming that the energy saving produced by dynamic insulation alone is small relative to that obtained in conjunction with conventional air heat recovery methods.     

Existence of optimal solutions of two-directionally continuous linear repetitive processes

In the paper, an existence theorem for a Lagrange optimal control problem connected with a two-directionally continuous variant of a linear autonomous repetitive process is derived. As a corollary, existence of an optimal solution in the case of cost functional depending on a fixed ??end-function?? is obtained.     

Biomimetic hydroxyapatite coating on glass coverslips for the assay of osteoclast activity in vitro

The osteoclast (OC) is the cell type responsible for the resorption of bone. The activity of this cell is important in the aetiology of a large number of skeletal pathologies, and also for the biocompatibility and osseointegration of orthopaedic implant materials. OC mediated acid hydrolysis of calcium phosphate from the bone matrix offers a prime means of studying the biology and activity of this cell type. We have developed a method of coating glass coverslips with a hydroxyapatite (HA)-like mineral, using a biomimetic approach. Hydroxylation followed by formation of a self assembled monolayer (SAM) using the surfactant triethoxysilylpropyl succinic anhydride (TESPSA), allowed biomimetic deposition of HA-like mineral from a simulated body fluid (SBF). The biocompatibility of the TESPSA SAM-HA coated glass coverslips was tested by culturing human mature OC present in samples of giant cell tumour of bone (GCT). Parameters of OC activity were assayed, including F-actin ring formation, release of calcium and formation of osteoclastic resorption pits, confirming that OC were able to attach to and resorb the coated surface. This approach for the preparation of HA coatings on glass coverslips could have wide applicability for the study of osteoclast behaviour in vitro. Gerald J. Atkins and Peter Majewski share senior author status.