Textured VN coatings with Ag3VO4 solid lubricant reservoirs

Silver oxovanadate powders were produced using a low temperature hydrothermal synthesis method. X-ray diffraction (XRD) and Raman microscopy revealed the formation of the α-Ag₃VO₄ phase, and differential scanning calorimetry (DSC) indicated that the powders underwent phase changes with the increase of temperature (formation of Ag-deficient phases). Ag₃VO₄ precipitates were subsequently investigated as potential high temperature solid lubricant (SL) powders that may be burnished onto textured surfaces. Textured coatings were produced by the sputter deposition of vanadium nitride (VN) thin films, followed by the fabrication of a periodic array of micro-scale dimples with reactive ion etching (RIE). The etched patterns acted as reservoirs to replenish the sliding contact with solid lubricants. The effectiveness of this new design of high temperature tribological coating was tested using a pin-on-desk tribotester. A significant decrease in the wear rate and coefficient of friction (CoF) was achieved at high temperatures (750 °C) and was maintained as a result of the storage of the Ag₃VO₄ phase in the dimples. After wear testing, Raman spectroscopy and XRD were used to identify the phase composition developed as a result of tribotesting. It was found that the burnished powders were more effective in enhancing the tribological properties of textured films compared to burnished/un-burnished monolithic VN coatings.     

Embedded phase change material microinclusions for thermal control of surfaces

The performance and lifetime of sensors, microelectronic devices, mini air vehicle components and other systems can benefit from maintenance of a constant temperature profile or a local temperature that does not exceed a pre-selected, critical value during short-term transient loading events. In this work, the utility of surfaces featuring phase change materials (PCMs) encapsulated within micro-reservoirs was evaluated as a passive thermal management system for mitigation of transient temperature spikes. Patterned silicon substrates with 40 μm diameter, 10 μm deep trenches were prepared by reactive ion etching in an Ar/CF₄ plasma. The features were filled with an organic phase change material possessing a high latent heat and known to undergo melting at a target operating temperature of approximately 60 °C. An infrared microscope was used to produce temporally and spatially resolved temperature maps of the surface during heating. When a constant heat flux of approximately 200 W m^− 2 was used for uniform heating of the sample area from 50 to 75 °C the PCM encapsulated materials demonstrated an isothermal plateau period lasting 5–8 s near the PCM melting point. A similar plateau was also observed during cooling below the PCM melting point. From the isothermal time during heating the areal thermal energy storage density was estimated to be approximately 800 J m^− 2, close to that predicted by the calculated volume of PCM contained within the sample. The effects of PCM inclusions on surface temperature gradients during pulsed laser heating were also investigated. An infrared (980 nm) laser at a fixed power and repetition rate was focused into a 1 mm diameter beam on surfaces with and without PCM encapsulation for rapid heating (analogous to heating from resistive contacts in microelectronic circuits) of different duration from 0.5 to 5.0 s. The surface temperature stayed below the desired temperature limit for 100 mW laser pulses lasting up to 2 s in duration. Transient temperature profiles of Si/PCM surfaces showed that micro-scale volumes of embedded phase change material stored sufficient quantities of heat to stabilize and otherwise control surface temperatures for potentially useful periods of time in selected applications.     

Optimal Decay Rate for Unidimensional Thermoelastic Problem within the Green-Lindsay Model

In this article we consider the system of generalized thermoelasticity under Green–Lindsay model in one dimension with Dirichlet–Neumann boundary conditions. First, the roots of the characteristic polynomial are investigated by applying an approach based on the implicit function theorem. Then we prove the exponential decay of the associated energy and describe the optimal decay rate. The numerical calculation of the corresponding characteristic roots is done for different real materials. Then another approach based on Hurwitz criterion is applied to obtain the decay rate analytically. Finally, we present a discussion of the decay rate given by both approaches, as well as a comparison with already-existing results for Lord–Shulman and classical models of thermoelasticity.     

The effect of magnetic treatment on the physico-chemical and microbiological characteristics of hard waters

The main objective of this study was to investigate the effect of magnetic treatment on the physico-chemical and bacteriological characteristics of hard waters. The scaling power of tested waters was evaluated using the rapid controlled precipitation (RCP) method. Results showed that magnetic treatment affects calcium carbonate crystallization. The RCP tests confirmed that the scaling power of the magnetically treated water was inhibited. Experimental results also indicated a significant improvement in the bacteriological quality of the treated water. Average reductions of 2.02 log Total coliforms, 0.95 log Escherichia coli and 1.06 log Faecal streptococci were obtained.     

Long-term water quality monitoring of the Sejnane reservoir in northeast Tunisia

The Sejnane reservoir in northeast Tunisia provides drinking and irrigation water. Long-term water quality monitoring data including precipitation, evaporation, temperature, pH, conductivity, dissolved oxygen, turbidity, total suspended solids, major anions and cations, fluoride, BOD₅, NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, P _tot, fecal coliform bacteria, boron and heavy metals (Fe, Zn, Cu, Ni, Pb, Cr and Cd) are reported. The appropriateness for irrigation was estimated by the SAR and Na percentage and the water quality assessed using the Canadian Water Quality Index as good to excellent, which confirmed its suitability for drinking, aquatic life and irrigation purposes.      

Chemical composition and antioxidant and radical‐scavenging activities of Periploca laevigata root bark extracts

BACKGROUND: The root powder of Periploca laevigata is used for preparing soft drinks and as an aromatic in Tunisia. The infusion or decoction of its root bark has widespread use in folk medicine. The plant is used to treat digestive disorders and hypertensive effects as well as other health problems. RESULTS: The antioxidant activities of extracts of P. laevigata root bark obtained with solvents of different polarity were investigated using assays of 1,1‐diphenyl‐2‐picrylhydrazyl radical‐scavenging activity, ferric‐reducing capacity, β‐carotene‐bleaching ability, hydroxyl radical‐scavenging activity and lipid peroxidation inhibition. The methanol extract, with the highest amount of total phenolics and flavonoids, showed the highest antioxidant activities in all assays, followed by the water extract. Gas chromatography/mass spectrometry was used to determine the composition of the water and methanol extracts. Thirty‐four compounds were identified in the methanol extract, with proflavine (516.2 g kg^?1 dry matter (DM)) and 4‐methoxysalicylaldehyde (198.3 g kg^?1 DM) being the most abundant. Sixteen compounds were identified in the water extract, of which 4‐hydroxy‐3‐methoxyphenethylene glycol (351.2 g kg^?1 DM) was the main component. CONCLUSION: As far as is known, this is the first report on the chemical composition and biological activities of phenolic extracts from P. laevigata. The results of the study indicate that the root bark of this plant might be a good candidate for further investigation in developing new antioxidants. Copyright © 2009 Society of Chemical Industry     

Mid infrared and fluorescence spectroscopies coupled with factorial discriminant analysis technique to identify sheep milk from different feeding systems

Mid infrared spectroscopy (MIR) combined with multivariate data analysis was used to discriminate between ewes milk samples according to their feeding systems (controls, ewes fed scotch bean and ewes fed soybean). The MIR spectra were scanned throughout the first 11 weeks of the lactation stage. When factorial discriminant analysis (FDA) with leave one-out cross-validation was applied, separately, to the three spectral regions in the MIR (i.e. 3000–2800, 1700–1500 and 1500–900 cm⁻¹), the classification rate was not satisfactory. Therefore, the first principal component (PCs) scores (corresponding to 3, 10 and 10 for, respectively, the 3000–2800, 1700–1500 and 1500–900 cm⁻¹) of the principal component analysis (PCA) extracted from each of the data sets were pooled (concatenated) into a single matrix and analysed by FDA. Correct classification amounting to 71.7% was obtained. Finally, the same procedure was applied to the MIR and fluorescence data sets and 98% of milk samples were found to be correctly classified. Milk samples belonging to control and soybean groups were 100% correctly classified. Regarding milk samples originating from the scotch bean group, only 2 out of 33 samples were misclassified. It was concluded that concatenation of the data sets collected from the two spectroscopic techniques is an efficient tool for authenticating milk samples according to their feeding systems, regardless of the lactation stage.     

Isolation and characterisation of trypsin from sardinelle (Sardinella aurita) viscera

BACKGROUND: In Tunisia, sardinelle (Sardinella aurita) catches totalled about 13 300 t in 2002. During processing, solid wastes including heads and viscera are generated, representing about 30% of the original raw material. Viscera, one of the most important by‐products of the fishing industry, are recognised as a potential source of digestive enzymes, especially proteases with high activity over a wide range of pH and temperature conditions. This paper describes the purification procedure and some biochemical characterisation of trypsin from S. aurita viscera. RESULTS: Trypsin from the viscera of sardinelle (S. aurita) was purified by fractionation with ammonium sulphate, Sephadex G‐75 gel filtration, Sepharose mono Q anion exchange chromatography, ultrafiltration and a second Sephadex G‐75 gel filtration, resulting in a 5.42‐fold increase in specific activity and 6.1% recovery. The molecular weight of the purified enzyme was estimated to be 24 kDa using size exclusion chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified enzyme showed esterase‐specific activity on N‐α‐benzoyl‐L ‐arginine ethyl ester (BAEE) that was four times greater than its amidase‐specific activity on N‐α‐benzoyl‐DL ‐arginine‐p‐nitroanilide (BAPNA). The optimal pH and temperature for enzyme activity were pH 8 and 55 °C respectively using BAEE as a substrate. The trypsin kinetic constants K_m and k_cat on BAPNA were 1.67 mmol L^?1 and 3.87 s^?1 respectively, while the catalytic efficiency k_cat/K_m was 2.31 s^?1 L mmol^?1. CONCLUSION: Trypsin was purified from sardinelle (S. aurita) viscera. Biochemical characterisation of S. aurita trypsin showed that this enzyme can be used as a possible biotechnological tool in the fish‐processing and food industries. Copyright © 2008 Society of Chemical Industry     

Design of Level Ground Laterals in Trickle Irrigation Systems

A nonlinear differential equation describing the pressure head grade line along nontapered laterals is derived. For horizontal pipes, the solution of the problem yields the pressure head grade line implicitly in an integral form. The outstanding outcome of this approach is the establishment of an analytical relation between the inlet discharge and the pressure heads at the inlet and at the distal ends of the pipe. The current method is deemed to be very accurate as compared to the stepwise method. It is proven that the discharge within the pipe varies quasilinearly with the distance which corroborates the assumption of constant outflow used in the drop ratio approach. The main feature of this method is that it provides the tools whereby a designer can achieve the crossover from the input to the output data and vice versa.