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This contribution is concerned with an adaptive control strategy for the mean temperature of an automotive three-way catalytic converter. Tailored finite-dimensional approximations of the complex infinitedimensional mathematical model of the catalytic converter serve as a basis for the design of an extended Kalman filter for state profile estimation and of an adaptive backstepping controller for the mean temperature. Although the model used for observer design relies on (semi-)discretising the infinite-dimensional model, a simple model for the mean temperature employing a phenomenological approach to describe the reaction heat is used for control design. The observer/controller is tested in simulation scenarios using a validated model of the three-way catalytic converter. [ABSTRACT FROM AUTHOR]

The interest in electrophoretic deposition (EPD) of ceramics has widely increased owing to its versatility to combine different materials in unique shapes and structures interesting for several applications (e.g. solid oxide fuel cells, thermal barrier coatings and biomaterials). In this work, an automated robotic EPD set-up was constructed and used to produce tetragonal and cubic zirconia multilayered specimens, which combine the high conductivity of the cubic layer with the high toughness of the tetragonal layer. This automated EPD set-up allowed us to study in detail the very sensitive EPD process, whose success highly depends on a good control of the EPD parameters (e.g. electrode distance, applied tension, deposition time). Tetragonal layers of 20 (im and cubic layers of 10 (am were obtained with high reproducibility. The in situ measurement of the electric current evolution with the deposition time enabled us to analyse the EPD process for each layer. [ABSTRACT FROM AUTHOR]

Many spatial patterns in biology arise through differentiation of selected cells within a tissue, which is regulated by a genetic network. This is specified by its structure, parameterisation and the noise on its components and reactions. The latter, in particular, is not well examined because it is rather difficult to trace. The authors use suitable local mathematical measures based on the Voronoi diagram of experimentally determined positions of epidermal plant hairs (trichomes) to examine the variability or noise in pattern formation. Although trichome initiation is a highly regulated process, the authors show that the experimentally observed trichome pattern is substantially disturbed by cell-to-cell variations. Using computer simulations, they find that the rates concerning the availability of the protein complex that triggers trichome formation plays a significant role in noise-induced variations of the pattern. The focus on the effects of cell noise yields further insights into pattern formation of trichomes. The authors expect that similar strategies can contribute to the understanding of other differentiation processes by elucidating the role of naturally occurring fluctuations in the concentration of cellular components or their properties. [ABSTRACT FROM AUTHOR]

Auxin interacts with its own polar transport to influence cell polarity and tissue patterning. Research over the past decade has started to deliver new insights into the molecular mechanisms that drive and regulate polar auxin transport. The most prominent auxin efflux protein, PIN1, has subsequently become a crucial component of auxin transport models because it is now known to direct auxin flow and maintain local auxin gradients. Recent molecular and genetic experiments have allowed the formulation of conceptual models that are able to interpret the role of (i) auxin, (ii) its transport, and (iii) the dynamics of PIN1 in generating temporal and spatial patterns. Here we review the current mathematical models of patterning in two specific developmental contexts: lateral shoot and vein formation, focusing on how these models can help to untangle the details of auxin transport-mediated patterning. [ABSTRACT FROM AUTHOR]

The article discusses the efforts to create an animal model of Fanconi syndrome (FS), a disorder in which the proximal tubular function of the kidney is impaired, after ifosfamide (IFO) administration given to rats. It was informed that the IFO was injected for 4 or 5 treatment courses (TCs) to adult female rats, young female rats and male rats. It was claimed that 28% of the rats died, but surviving animals did not show any sign of renal failure after five TCs which could be caused by starving and not by nephrotoxicity. It was found out that IFO induces abnormalities in rat renal function resembling sub-clinical FS which requires too many rats for screening tests.

Objective: The use of cyclosporin A (CSA) and tacrolimus (TAC) in organ transplantation and in the therapy of immune disorders is often hampered by adverse effects, mainly nephro-, hepato- and neurotoxicity. For the development of these side effects, among others, an increased formation of reactive oxygen species, probably generated by the cytochrome P450 (CYP) system, has been accused. Since in this respect literature data are inconsistent, in the present study possible pro- and/or antioxidant effects of CSA and TAC and the involvement of the CYP system were re-evaluated in vitro. Methods: Effects of CSA and TAC were examined on CYP mediated oxidase functions by stimulated lipid peroxidation (LPO), H2O2 production, and lucigenin (LC) or luminol (LM) amplified chemiluminescence (CL) in liver microsomes of either untreated rats or of rats treated with β-naphthoflavone (BNF), phenobarbital (PB) or dexamethasone (DEX) and in human liver microsomes. Results: In rat liver microsomes, CSA displayed pro-oxidant properties (though only very slightly), whereas in human liver microsomes small antioxidant effects were seen. With TAC in both species the antioxidant capacity prevailed. Treatment of rats with BNF or DEX caused an increase in the pro-oxidant effects of CSA with respect to LPO or LM-CL, whereas in liver microsomes of DEX-treated rats H2O2 production and LC-CL were diminished. Conclusions: CSA seems to have both pro-oxidant and antioxidant properties, whereas with TAC mainly an antioxidant capacity was seen. The CYP system seems to be involved in the pro-oxidant influence of CSA. Whether pro-oxidant or antioxidant effects predominate may depend on the antioxidant capacity of a tissue and on the CYP isoforms mainly present. [ABSTRACT FROM AUTHOR]

During the fatigue process of bone, cracks generally initiate from the inherent defects existing in the bone. The fatigue lives of bone specimens at different stress levels as well as at different stress ratios R were evaluated using a computer simulation in which the crack propagation behaviour initiated from the inherent defects in the bone are herein considered. The S-N curves as well as the distributions of fatigue lives obtained by the simulations accurately conform with the experimental results. With the strain threshold epsilon(max) representing fatigue failure of the bone specimen, the values of 1500 microepsilon for R = -1, 2500 microepsilon for R = 0.1 and 4000 microepsilon for R = 10 were extrapolated from the simulations. These values conform with experimental values reported in the literature. Such conformity indicates that the strain threshold for fatigue failure is associated with the threshold value for crack propagation. [ABSTRACT FROM AUTHOR]

Stress-controlled load increase and constant amplitude tests were performed on the cast magnesium alloy AZ91D. Rather small values of the plastic strain amplitude reflect the very localised plastic deformation predominant in the αI-phase. The cyclic deformation and temperature curves of the load increase tests exhibit cyclic yield strength values which allow a good estimation of the endurance limit. Stress amplitudes above the endurance limit lead to cyclic hardening. As compared to the behaviour under monotonic tensile loading, the alloy exhibits cyclic hardening. Microscopic investigations illustrate the different influences of the α- and β-phase in respect to crack initiation. [Copyright &y& Elsevier]

Indwelling vascular catheters are a major cause of nosocomial sepsis. Prevention of colonization of polymeric surfaces by continuous release of bactericidal, highly biocompatible antimicrobials incorporated into polymers has been investigated as a promising new approach. An antimicrobial polyurethane catheter was investigated by HPLC and various antimicrobial assays. Controlled drug delivery governed by the physico-chemical mass transfer from the polyurethane bulk provided long-term release of the antimicrobial substances from the material to the outer surface and catheter lumen. The in vitro activity of catheters coated with miconazole and rifampicin against 158 clinical isolates of catheter-associated infections was evaluated. Incubated in physiological NaCl at 37°C, the half-life of inhibitory activity of catheters coated with miconazole or rifampicin exceeded 3 weeks. In static and dynamic adhesion assays, coated catheters were able to prevent colonization with Staphylococcus aureus, Staphylococcus epidermidis and enterococci. To produce catheters resistant to infection, a potent antimicrobial efficacy combined with an excellent biocompatibility over time is needed. The long lasting efficacy of the antimicrobial polyurethane alloy as well as the increased antifungal activity of miconazole combined with rifampicin may be regarded as a promising improvement for long-term central venous access. [ABSTRACT FROM PUBLISHER]

ABSTRACT- Consequences of bilateral nephrectomy (NX) for liver functions and for hepatic excretion of various endogenous substances were characterized in rats 24 h after NX. Plasma concentrations of urea, creatinine, fibrinogen, and glutathione increased significantly after NX, whereas the concentrations of total protein, albumin, and lipids decreased. The hepatic excretion of urea, creatinine, phospholipids, cholesterol, and aldosterone significantly increased in uremia, and excretions of protein and glutathione diminished. Active biliary transport can be diminished after NX by the effects of uremic toxins on the liver cells or by the competition phenomena between endogenous substances, which are normally excreted in urine, at the hepatocellular level. Reduced glutathione content and increased lipid peroxidation in hepatocytes have been found. Changes in lipid and protein metabolism after NX can be proved. [ABSTRACT FROM AUTHOR]

Objective: Previously we could show that 5/6 nephrectomy (5/6NX) induces mainly glomerular sclerosis and nearly no interstitial fibrosis. However, a single uranyl nitrate (UN) administration was followed by disseminated interstitial fibrosis. The question arose whether or not the combination of 5/6NX and UN results in a more severe damage indicated by histological changes. Methods: Female 60-day-old Wistar rats were used. At days 0 and 3 a two step operation for 5/6NX was done. Three weeks later a single administration of 0.5 mg UN/100 g b. wt. was given. Experimental groups: sham operated controls, 5/6NX, 5/6NX-UN, between weeks 6 and 16 after 5/6NX daily administration of 4 mg/100 g b. wt. perindopril (PERI; = ACE-inhibitor) or 2 mg/100 g b. wt. pirfenidone (PIR) or 4 µg/100 g b. wt. halofuginone (HALO; both inhibitors of collagen synthesis). Parameters measured: urine volume, electrolyte and protein excretion, creatinine clearance, blood pressure; morphology. Results: No difference occurred concerning functional consequences between 5/6NX and 5/6NX-UN without treatment. PERI and PIR decreased blood pressure significantly in sham operated control rats. Blood pressure increased after 5/6NX and 5/6NX-UN was completely prevented by both inhibitors of collagen synthesis, whereas ACE inhibition was effective only in the 5/6NX-model. The substances did not reduce polyuria, neither in 5/6NX nor in 5/6NX-UN. Despite the prevention of blood pressure increase by both inhibitors of collagen synthesis, only HALO reduced proteinuria significantly after 5/6NX, but not in the 5/6NX-UN model. PERI reduced the proteinuria in the 5/6NX model, as known from other ACE-inhibitors, and also after 5/6NX-UN. The functional results will be discussed in detail on the basis of histology. Conclusions: Morphological changes in the kidney which are strongest in 5/6NX-UN are effectively reduced by PIR and HALO. This indicates that a reduction in collagen synthesis is protective against the progression of chronic renal failure after renal mass reduction. [ABSTRACT FROM AUTHOR]