The effect of shear rate on the viscosity of solutions of sodium carboxymethylcellulose and k-carrageenan

The apparent viscosities of aqueous solutions of sodium carboxymethylcellulose (NaCMC) and k-carrageenan have been measured over a range of shear rates from 14 to 1142 s^?1. Comparable measurements were also made on gum solutions to which glucose, sucrose, or glucose syrup had been added. For all the solutions the variation of relative viscosity with shear rate fits a power law equation. Addition of sugars to the most concentrated solutions of NaCMC has no effect on the non-Newtonian behaviour but addition of glucose syrup to the most dilute solutions of NaCMC decreased the non-Newtonian behaviour. However, the general pattern of behaviour showed close similarity with that of guar gum and locust bean gum. In the more concentrated glucose and sucrose solutions the non-Newtonian behaviour of k-carrageenan was increased appreciably. There was no comparable effect on k-carrageenan in glucose syrup solutions. This different behaviour of k-carrageenan is attributed to the development of solute-solute interactions.     

Cytotoxicity of Newly Synthesized Quinazoline–Sulfonamide Derivatives in Human Leukemia Cell Lines and Their Effect on Hematopoiesis in Zebrafish Embryos

Many quinazoline derivatives with pharmacological properties, such as anticancer activity, have been synthesized. Fourteen quinazoline derivatives bearing a substituted sulfonamide moiety (4a–n) were previously synthesized and fully characterized. These compounds exerted antiproliferative activity against cell lines derived from solid tumors. Herein, the antileukemic activities of these compounds (4a–n) against two different leukemia cell lines (Jurkat acute T cell and THP-1 acute monocytic) were investigated. Our investigation included examining their activity in vivo in a zebrafish embryo model. Remarkably, compounds 4a and 4d were the most potent in suppressing cell proliferation, with an IC₅₀ value range of 4–6.5 µM. Flow cytometry analysis indicated that both compounds halted cell progression at the G2/M phase and induced apoptosis in a dose-dependent manner. RT-PCR and Western blot analyses also showed that both compounds effectively induced apoptosis by upregulating the expression of proapoptotic factors while downregulating that of antiapoptotic factors. In vivo animal toxicity assays performed in zebrafish embryos indicated that compound 4d was more toxic than compound 4a, with compound 4d inducing multiple levels of teratogenic phenotypes in zebrafish embryos at a sublethal concentration. Moreover, both compounds perturbed the hematopoiesis process in developing zebrafish embryos. Collectively, our data suggest that compounds 4a and 4d have the potential to be used as antileukemic agents.     

On the fretting wear mechanism of Zr-alloys

Zirconium alloys are highly desirable in nuclear applications due to their transparency to thermal energy neutrons and for their high corrosion resistance. The main objective of this study is to investigate the fretting wear mechanism of Zr–2.5%Nb alloy. The experimental work was carried out in air at 265 °C, using a specially designed fretting wear tribometer. The transfer of material, the change in the wear volume and the maximum wear depth with the number of cycles were measured through 3D mapping of the topography of the fretted surface. SEM and Fourier Transform Infrared Interferometry methods were used to examine the microspall pits and to measure the distribution of the thickness of oxide layer in the fretting region. For relatively small slip amplitude, the results showed that the fretting wear mechanism is initially dominated by adhesion and abrasion actions and then by delamination and surface fatigue. The time variation of the wear losses was shown to be cyclic until a steady state value is reached. At high slip amplitudes, however, abrasion and delamination are the only dominant wear mechanisms. The volumetric wear losses were found to decrease monotonically with the number of cycles. A novel approach was introduced, whereby the thermal and electrical contact resistances of the fretting interface are simultaneously measured. The results demonstrated the potential use of this non-intrusive approach for real-time monitoring of the fretting wear mechanism.     

Dempster–Shafer theory-based human activity recognition in smart home environments

Context awareness and activity recognition are becoming a hot research topic in ambient intelligence (AmI) and ubiquitous robotics, due to the latest advances in wireless sensor network research which provides a richer set of context data and allows a wide coverage of AmI environments. However, using raw sensor data for activity recognition is subject to different constraints and makes activity recognition inaccurate and uncertain. The Dempster–Shafer evidence theory, known as belief functions, gives a convenient mathematical framework to handle uncertainty issues in sensor information fusion and facilitates decision making for the activity recognition process. Dempster–Shafer theory is more and more applied to represent and manipulate contextual information under uncertainty in a wide range of activity-aware systems. However, using this theory needs to solve the mapping issue of sensor data into high-level activity knowledge. The present paper contributes new ways to apply the Dempster–Shafer theory using binary discrete sensor information for activity recognition under uncertainty. We propose an efficient mapping technique that allows converting and aggregating the raw data captured, using a wireless senor network, into high-level activity knowledge. In addition, we propose a conflict resolution technique to optimize decision making in the presence of conflicting activities. For the validation of our approach, we have used a real dataset captured using sensors deployed in a smart home. Our results demonstrate that the improvement of activity recognition provided by our approaches is up to of 79 %. These results demonstrate also that the accuracy of activity recognition using the Dempster–Shafer theory with the proposed mappings outperforms both naïve Bayes classifier and J48 decision tree.     

Policosanol characterization and accumulation during ripening of Tunisian Olea europaea L. fruits

Policosanol is a mixture of bioactive molecules shown to have beneficial effects in treating hypercholesterolemia. Food products enriched in policosanol are currently available in the US market. In the present study, eight policosanol components were identified by GC‐MS during the ripening of Meski olives. The quantitative characterization of these compounds was performed using GC‐FID. The results showed that the maximum level of total policosanol components (947.20 mg/100 g oil) was reached at the 26^th week after the flowering date of Meski olives. Hexacosanol and tetracosanol were the predominant policosanol components at Meski olive maturity. However pentacosanol, heptacosanol and tricosanol were less present in the olives and they accounted for 14% of the total policosanol at complete maturity of the fruit. The total policosanol content of Meski olives was higher than that of beeswax and whole sugar cane, which belong to the sources of dietary supplements containing policosanol. These findings indicate that olive is a potential source of these health‐enhancing compounds for functional foods and nutraceutical applications.     

Changes in the Content of Phenolic Compounds in Flaxseed Oil During Development

The phenolic fraction of flaxseed oil was quantified during the development of three varieties (H52, O116 and P129). Seed samples were collected at regular intervals from 7 to 56 days after flowering (DAF). During oilseed processing, less polar compounds are co-extracted with oil. The methanolic extracts were obtained by solid phase extraction. Separation of phenolic compounds was conducted by high-performance liquid chromatography-mass spectrometry. The main phenolic compounds detected during maturation were: diphyllin, pinoresinol, matairesinol, secoisolariciresinol, vanillic acid, ferulic acid and vanillin. The highest amount of lignans (6.74 mg of analyte/kg of flaxseed oil) was detected at 7 DAF in P129 variety. The maximum level of phenolic acids (2.57 mg of analyte/kg of flaxseed oil) was reached at 7 DAF in P129 which had also the highest content of simple phenols (1.37 mg of analyte/kg of flaxseed oil) at the same date after flowering. At full maturity, the content of phenolic compounds in three varieties ranged from 0.26 to 0.36 mg of analyte/kg of flaxseed oil. The highest content of total phenolic compounds using the Folin–Ciocalteu method was detected in P129 variety (196.42 mg CAEs/kg of flaxseed oil) at 7 DAF. Results of this study indicate that flaxseed oils contain different amounts of phenolic compounds using different methods.     

Electrical Transport Properties of Carbon Aerogels

Carbon aerogels are prepared by sol-gel polymerization and supercriticle drying. By controlling the mass ratio of reactants and the molar ratio of resorcinol to catalyst (R/C), carbon aerogels with different microstructure can be developed. Hall effect is measured by Van der Bow method. The results show that the electrical conductivity increases with increasing density of carbon aerogel, and Hall mobility at high temperature is nearly constant, while at low temperature the absolute value of Hall mobility increases linearly with decreasing temperature. The abnormal sign of Hall mobility is probably related to the microstructure of carbon aerogels, which influence the transport path of carriers.     

Studies of reaction of tetramethylthiourea with hydrogen peroxide: evidence of formation of tetramethylthiourea monoxide as a key intermediate of the reaction

The reaction between tetramethylthiourea (TMTU) and hydrogen peroxide was studied by UV–VIS spectroscopy, ESI mass spectrometry, ¹H NMR, cyclic voltammetry and surface-enhanced Raman scattering. We found that the reaction includes two consecutive steps, that is, (i) an oxidation of TMTU to TMTU monoxide (TMTMO) and (ii) further oxidation of TMTU monoxide to tetramethylurea (TMU) and sulfate. The second step is complex and seems to include extrusion of sulfur monoxide (SO). Density functional theory calculations were employed on tetramethylthiourea oxide models in order to underline differences between monoxide and di- and trioxides. Calculations predict that the TMTMO structure can be best explained as an adduct of thiourea with an oxygen atom (═S–>O).     

LaFeO3 ceramics as selective oxygen sensors at mild temperature

In this study, an investigation about the oxygen sensing properties of lanthanum orthoferrite (LaFeO₃) ceramics is reported. LaFeO₃ nanoparticles were synthesized by using tartaric sol-gel route and annealed in air at different temperatures (500, 700 and 900 °C). The samples have been characterized by using thermal analysis (TA), BET surface area and porosity, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results of sensing tests indicate that LaFeO₃ nanoparticles exhibit good response to oxygen at mild temperatures (300–450 °C). The effect of annealing temperature on gas sensing performance was investigated, demonstrating that LaFeO₃ ceramics obtained after annealing at 500 °C display better characteristics with respect to others. The oxygen sensor developed shows also high stability in humid environment and excellent selectivity to oxygen over other interfering gases such as CO, NO₂, CO₂, H₂ and ethanol.     

Studies on the Combined Action of Amylases and Glucose Isomerase on Starch and its Hydrolysates. Part III. Conversion of Starch to Glucose-Fructose Syrup

Glucose syrup was produced by liquefaction of starch using acid, acid-enzyme, one-step enzyme and two-steps enzyme process followed by saccharification by free and immobilized glucoamylase. The effect of D-glucose concentration and temperature on conversion of glucose syrup by glucose isomerase was studied. 50% glucose concentration and temperature range of 65 – 70°C gave the maximum conversion value to fructose. The isomerization was applied as a pilot plant process. The relative sweetness of glucose-fructose syrup was calculated and found that the syrup with fructose content of 26% has the same sweetness as sucrose.