Complete suspension of particles in mechanically agitated vessels

A new model is proposed to explain the mechanism of complete suspension of solid particles in cylindrical flat-bottomed stirred tanks. According to this model the suspension of the particles at rest on certain zones of the tank bottom is mainly due to turbulent eddies of a scale of the order of the particles size. The development of this hypothesis has led, with some other assumptions, to an expression which has been experimentally verified and compared with analogous expressions available in literature.     

Colour performance of ceramic nano-pigments

Ceramic nano-pigments have been recently developed for ink-jet decoration of ceramic tiles using quadrichromic technology (cyan, magenta, yellow, and black colours). The colouring mechanisms and performance of CoAl₂O₄, Au, (Ti,Cr,Sb)O₂ and CoFe₂O₄ nano-pigments were investigated by DRS, XRD and colorimetry. The nano-pigments were dispersed in several ceramic glazes and glassy coatings and their colour performance was compared with that of conventional micro-pigments. Each nano-pigment was characterized in terms of its colour mechanism and chemico-physical stability. Although the micro-pigments provided more saturated hues, intense colours were achievable in nano-pigments despite their very small particle size (<50 nm). Limitations to the use of nano-pigments arose for very high firing temperatures (>1200 °C) due to particle growth (e.g. Au) or dissolution in the glassy phase (e.g. titania).     

Coded transmissions for space links affected by solar scintillation: Baseband analysis

A thorough analysis of the behavior of error‐correcting codes over space links affected by solar scintillation is presented. The relevant channel parameters are fixed through the development of a model based on real missions' data. Both telecommand and telemetry links are considered in fast and slow fading conditions. Besides classical coherent modulation schemes, the possibility to use noncoherent modulation schemes is considered, to eliminate the problem of phase tracking. For the case of channels with very slow fading, the use of external interleavers or erasure coding is proposed to cope with error bursts.     

Fas-induced changes in cdc2 and cdk2 kinase activity are not sufficient for triggering apoptosis in HUT-78 cells

Telomerase activity is frequently associated with the malignant phenotype, and it can be considered an almost ubiquitous tumor marker. In this study, we evaluated telomerase activity in telomerase-positive human tumor cell lines exposed in vitro to antineoplastic agents. The results show that drug-induced cell killing of tumor cells is associated with a decline in detectable telomerase activity. The decrease of telomerase activity levels paralleled cell growth impairment evaluated by cell count or by measurement of cell ability to convert tetrazolium salt to colored formazan [3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide assay]. The observed telomerase activity remaining after treatment with antineoplastic agents is most likely to reflect activity from the remaining viable cells. When tumor cell lines resistant to the chemotherapeutic agents temozolomide or doxorubicin were treated with these compounds, no decline of telomerase activity or cell growth was observed. The results of the present study indicate that resistance of neoplastic cells to chemotherapeutic agents can be monitored by following telomerase activity. Moreover, the test can be performed with a limited number of neoplastic cells, such as those frequently obtained from tumor biopsies. These findings provide a rationale for developing new in vitro chemosensitivity assays, and detection of telomerase activity may be a novel marker of chemotherapy failure.     

An adaptive design for quantized feedback control of uncertain switched linear systems

This paper addresses the problem of asymptotic tracking for switched linear systems with parametric uncertainties and dwell‐time switching, when input measurements are quantized due to the presence of a communication network closing the control loop. The problem is solved via a dynamic quantizer with dynamic offset that, embedded in a model reference adaptive control framework, allows the design of the adaptive adjustments for the control parameters and for the dynamic range and dynamic offset of the quantizer. The overall design is carried out via a Lyapunov‐based zooming procedure, whose main feature is overcoming the need for zooming out at every switching instant, in order to compensate for the possible increment of the Lyapunov function at the switching instants. It is proven analytically that the resulting adjustments guarantee asymptotic state tracking. The proposed quantized adaptive control is applied to the piecewise linear model of the NASA Generic Transport Model aircraft linearized at multiple operating points.     

Physicochemical characteristics and bronchial epithelial cell cytotoxicity of Folpan 80 WG® and Myco 500®, two commercial forms of folpet

Background

Pesticides, in particular folpet, have been found in rural and urban air in France in the past few years. Folpet is a contact fungicide and has been widely used for the past 50 years in vineyards in France. Slightly water-soluble and mostly present as particles in the environment, it has been measured at average concentration of 40.1 μg/m³ during its spraying, 0.16–1.2 μg/m³ in rural air and around 0.01 μg/m³ in urban air, potentially exposing both the workers and the general population. However, no study on its penetration by inhalation and on its respiratory toxicity has been published. The objective of this study was to determine the physicochemical characteristics of folpet particles (morphology, granulometry, stability) in its commercial forms under their typical application conditions. Moreover, the cytotoxic effect of these particles and the generation of reactive oxygen species were assessed in vitro on respiratory cells.

Results

Granulometry of two commercial forms of folpet (Folpan 80WG^® and Myco 500^®) under their typical application conditions showed that the majority of the particles (>75%) had a size under 5 μm, and therefore could be inhaled by humans. These particles were relatively stable over time: more than 75% of folpet remained in the particle suspension after 30 days under the typical application conditions. The inhibitory concentration (IC₅₀) on human bronchial epithelial cells (16HBE14o-) was found to be between 2.89 and 5.11 μg/cm² for folpet commercial products after 24 h of exposure. Folpet degradation products and vehicles of Folpan 80 WG^® did not show any cytotoxicity at tested concentrations. At non-cytotoxic and subtoxic concentrations, Folpan 80 WG^® was found to increase DCFH-DA fluorescence.

Conclusion

These results show that the particles of commercial forms of folpet are relatively stable over time. Particles could be easily inhaled by humans, could reach the conducting airways and are cytotoxic to respiratory cells in vitro. Folpet particles may mediate its toxicity directly or indirectly through ROS-mediated alterations. These data constitute the first step towards the risk assessment of folpet particles by inhalation for human health. This work confirms the need for further studies on the effect of environmental pesticides on the respiratory system.     

CLIMAX: CelL‐Interleaved Merged ATM conneXions

The realization of multiway group communications and scaleable IP switching over ATM networks requires merging of virtual connections to be possible. This capability, known as VC merging, cannot be provided by ATM networks which use a standard ATM protocol stack. This paper describes CLIMAX, a simple and efficient solution that allows for VC merging while keeping the typical advantages of cell‐switching. This revised version was published online in June 2006 with corrections to the Cover Date.