PECVD of diamond-like carbon (a-C:H) from the decomposition of methane in a high-density inductively coupled discharge

The paper describes an experimental investigation of the diamond-like carbon deposition process from methane precursor with an innovative high-density inductively coupled plasma source. It appears that a high plasma density allows a fast growth of diamond-like carbon coatings exhibiting a high hardness. In contrast to what is usually found in the literature, it seems that the ion species participate significantly to the growth of the carbon film when exposed to a high ion flux.     

Spatial and seasonal variations and ecotoxicological significance of sediment trace metal concentrations in Kebir-Rhumel basin (Northeast of Algeria)

This study sought to assess sediment contamination by trace metals (cadmium, chromium, cobalt, copper, manganese, nickel, lead and zinc), to localize contaminated sites and to identify environmental risk for aquatic organisms in Wadis of Kebir Rhumel basin in the Northeast of Algeria. Water and surficial sediments (0-5 cm) were sampled in winter, spring, summer and autumn from 37 sites along permanent Wadis of the Kebir Rhumel basin. Sediment trace metal contents were measured by Flame Atomic Absorption Spectroscopy. Trace metals median concentrations in sediments followed a decreasing order: Mn > Zn > Pb > Cr > Cu > Ni > Co > Cd. Extreme values (dry weights) of the trace metals are as follows: 0.6-3.4 microg/g for Cd, 10-216 microg/g for Cr, 9-446 microg/g for Cu, 3-20 microg/g for Co, 105-576 microg/g for Mn, 10-46 microg/g for Ni, 11-167 microg/g for Pb, and 38-641 microg/g for Zn. According to world natural concentrations, all sediments collected were considered as contaminated by one or more elements. Comparing measured concentrations with American guidelines (Threshold Effect Level: TEL and Probable Effect Level: PEL) showed that biological effects could be occasionally observed for cadmium, chromium, lead and nickel levels but frequently observed for copper and zinc levels. Sediment quality was shown to be excellent for cobalt and manganese but medium to bad for cadmium, chromium, copper, lead, nickel and zinc regardless of sites.     

Assessment of sediment quality and pore water ecotoxicity in Kebir Rhumel basin (NE-Algeria): a combined approach

The objectives of this study are to use different approaches to assess the current pollution status in the wadis of the Kebir Rhumel basin. First, sediment trace metal contents were measured by flame atomic absorption spectroscopy. Then, sediment quality was assessed on the basis of contamination assessment indexes such as: Geoaccumulation Index (Igeo), Contamination factor (C(f)), Contamination degree (C(d)), Sediment Pollution Index (SPI) and SEQ guidelines (Consensus Sediment Quality Guidelines). In addition, several toxicity tests (Daphnia magna mobility inhibition acute test-48 h, Aliivibrio fischeri luminescence inhibition acute test - 15/30 mn and Pseudokirchneriella subcapitata growth inhibition chronic test - 72 h) were conducted to assess sediment pore water ecotoxicity. Trace metal concentrations followed the order: Mn > Zn > Pb > Cr > Cu > Ni > Co > Cd. Indexes used indicate varying degrees of sediment quality. Igeo, C(f), C(d) and SPI reveal a polymetallic contamination dominated by two or more elements in which Cd, Cu and Pb are of greatest concern. SEQ guidelines showed that biological effects on fauna would likely be observed occasionally and/or frequently for Cd, Cr, Cu, Pb and Zn contents. Test organisms exposed to sediment pore water showed that the algal P. subcapitata test was more sensitive than the D. magna and A. fischeri tests. Hence, algal growth inhibition proved to be the most sensitive response to contaminants present in sediment extracts but a significant relationship with trace metal contents was not demonstrated.     

Advances in Bioapplications of Carbon Nanotubes

This progress report provides an overview on recent advances in bioapplications of carbon nanotubes including the chemical modification of carbon nanotubes, targeting specifically their covalent and noncovalent conjugations with a variety of biological and bioactive species (proteins and peptides, DNAs/RNAs, and carbohydrates). Furthermore, the significant recent development and progress in the use of carbon nanotubes for biosensors, drug and other delivery systems, bioimaging, etc. and in the understanding of in vivo biodistribution and toxicity of carbon nanotubes are reported.     

Physicochemical Characterization and Antioxidant Activity of Commercial Portuguese Honeys

The present study evaluated the physicochemical characteristics and antioxidant activity of 13 commercial honeys from diverse floral origin, produced in Portugal. The values of electrical conductivity of cardoon and pennyroyal honeys were superior to the maximum limits defined by European legislation. Citrus, strawberry tree, and 1 sample of lavender honeys had values of diastase activity below those determined by European legislation. Strawberry tree, pennyroyal, and cardoon honeys had the highest amounts of potassium that coincided with the highest electrical conductivity. Strawberry tree honey was the most effective as antioxidant along with cardoon and heather honeys. This ability was strongly correlated with the amounts of phenols and flavonoids and not with the levels of vitamin C or proline.     

The dark side of galaxy formation

I discuss the discovery of a population of extremely luminous, but very dusty and very distant, galaxies in the submillimetre (submm) waveband. Almost all the light emitted by the stars in these galaxies is absorbed by interstellar dust (which is produced by the same stars) and re-radiated in the far-infrared. This leaves little to be detected at optical wavelengths and results in most of these galaxies being effectively invisible in even the deepest optical images obtainable with the Hubble space telescope. Yet this population contributes most of the light emitted by galaxies at wavelengths of lambda > or approximately equal 100 microm over the lifetime of the Universe. Together with other observations, this suggests that perhaps up to half of all the stars seen in galaxies today were formed in very dusty regions in the early Universe. Hence, studying the galaxies detected in the submm wavebands is critical for developing and testing models of galaxy formation and evolution. Individually, these luminous submm galaxies are forming stars a thousand times faster than our Galaxy is at the present-day, sufficiently fast to form all the stars in the most luminous galaxy in the local Universe within a short period, up to ca. 0.1-1 Gyr. Detailed study of a handful of examples of this population confirm these estimates and unequivocally identify the bulk of this submm-selected population with dusty, star-burst galaxies in the very distant Universe. The extreme faintness of this population in the optical and near-infrared wavebands, resulting from their obscuration by dust, means that our understanding of the detailed nature of these galaxies is only slowly growing. I give a brief summary of the properties of these highly obscured systems and describe the wide range of facilities currently being developed that will greatly aid in their study.     

A comparative study of recent relay autotuning methods for multivariable systems

A typical procedure for designing multivariable controllers is the following: build a model for the multivariable process, choose the control structure, calculate the control parameters, test the controller (possibly with simulation) and then retune controller parameters as necessary. This procedure is complex and time consuming even for scalar control loops. For multivariable controllers, the procedure is even more daunting. Automation of the design method is and has been a concern of many researchers. There has been a large number of papers on relay autotuning of control systems. The choice of relay feedback to solve the design problem is justified by the possible integration of system identification and control into the same design strategy, giving birth to relay autotuning. In this paper, nine different relay autotuning methods for multivariable systems are compared. Most of these methods have common basics but they may differ in the tuning procedure, convergence, identification method, control structure and performance achievement. The paper summarizes these methods and investigates the advantages and drawback of each algorithm.     

Kinetics and Thermodynamics of Oil Extraction from Olive Cake

The kinetics of oil extraction from olive cake by using ethanol 96% was studied for different solvent-to-solids ratios and temperatures. The thermodynamic aspect of the extraction process was also examined. In the kinetic study, the results produced by the model of So and Macdonald (a model involving two main mechanisms of oil extraction: a washing process and a diffusion process with two stages) were found to be in good agreement with the experimental data. The yield of oil in the extract increased with increasing contact time, solvent-to-solids ratio and extraction temperature. The calculated values of the mass transfer coefficients of various stages of the extraction were found to increase linearly with solvent-to-solids ratio and temperature. In all cases, the predominant mechanism in the extraction was the washing of the oil occurring on the particle surface. The values of the activation energy were 8.56 kJ mol⁻¹ for the washing stage, 9.88 kJ mol⁻¹ for the first stage of diffusion and 17.55 kJ mol⁻¹ for the second stage of diffusion by changing temperature from 20 to 50 °C. Further, the results obtained from thermodynamic study of extraction process gave positive values of enthalpy and entropy changes and negative values of change in free energy. Under the equilibrium conditions, the temperature coefficient was found to be 1.02.     

The role of the experimental data base used to identify material parameters in predicting the cyclic plastic response of an austenitic steel

The first objective of this paper investigates the influence of the previous strain history on ratcheting. New tests were performed where different strain-controlled histories have been applied prior to ratcheting tests. It is demonstrated that under the same conditions, one can observe ratcheting, plastic shakedown or elasticity according to the prior strain-controlled history. The second objective points out the correlation between the experimental data base devoted to the identification of the material parameters and the quality of the predictions in cyclic plasticity. The results suggest that the choice of the tests should be closely linked to the capabilities of the model. In particular, the presence of non proportional strain-controlled tests in the data base may be not a good choice if the model itself is not able to represent explicitly such a character. All tests considered here were performed on 304L SS at room temperature.     

Effect of freezing treatments and yeast amount on sensory and physical properties of sweet bakery products

The frozen bakery market has grown significantly in developed countries over the past decade.