595 research outputs found
The effects of TiO2 sol concentration on single- and multiple-scratch damage in electroplated Ni–B-TiO2 sol composite coating
No full textThe electrodeposited sol-enhanced Ni–B–TiO2 composite coatings were elaborated using a novel electroplating process. This coating was assessed in terms of tribological behavior and corrosion resistance. However, the adhesion strength of this coating has not been discussed so far. The aim of this study is to evaluate the adhesion behavior of this coating, considering different TiO2 sol concentration in the plating solution in order to predict its effectiveness and its sustainability when used in mineral crushing process. A progressive load scratch test and multi-pass scratch test were performed on coatings. The morphology of scratched surfaces was analyzed to identify the scratch failure mechanism. The results indicate that the addition of TiO2 sol significantly enhanced the deposit adhesion to the substrate compared to pure Ni–B coating. No spallation failure was observed on the sol-enhanced coatings after progressive load scratch test, contrary to Ni–B coating. Moreover, the multi-pass scratch test demonstrated that the improvement in adhesion strength depends strongly on the quantity of the TiO2 sol added to the plating solution. For the optimal concentration of TiO2 sol (25 ml/L), the sol-enhanced Ni–B–TiO2sol composite coating boasts the best adhesion strength. However, further increase in TiO2 sol concentration results in a deterioration of coating adhesion
KOMBUCHA TEA: A BIORESOURCE FOR ACETICACID BACTERIA
No full textKombucha or Tea fungus is a traditional fermented beverageobtained during sweetened tea fermentation conductedby acetic acid bacteria (AAB) and yeasts. Historically,Kombucha appeared first in Asia and thereafter its usesand consumption spread from Russia, central Europe andthen over the world. It is composed of a cellulose floatingpellicle and a sour slightly and sparkling broth. However,in spite of vinegar, kombucha remained not well exploredmainly as a niche of AAB strains exploitable in biotechnologicalapplications. The aim of this study was to overviewthe occurrence of AAB in kombucha samples fromliquid and pellicle phases. Kombucha from black andgreen tea was obtained by inoculating a previously grownculture into a freshly prepared tea infusion containing10% of sucrose, 3% (w/v) of cellulose pellicle and 10%(v/v) of broth and led to fermentation up to 15 days in abatch system under aerobic condition. Titrable acidity reacheda maximum of 12 g/L at the end of fermentation inblack kombucha and 6 g/L in green one. pH dropped fromapproximately 3.7 until 2.75 for both samples as a resultof acids formation. Maximum ethanol accumulated at theday 15 did not exceed 0.5% (v/v) for both samples.Cellulose layer become thicker during fermentation, startingfrom 2-3 mm until 10 mm. AAB strains were isolatedfrom pellicle and liquid phases by sampling each 3 daysusing GYC and ACBS media. A total of 93 strains werecollecting during 15 days of fermentation of which 50 arecellulose producing. The majority of strains were tolerantto 5% (v/v) of ethanol and to 30% (w/v) of glucose. Thiswork opens an issue to explore the diversity of AAB fromKombucha focusing their ability to produce cellulose andto grow in low-acidic and sugary environment
Morphological, spectroscopic and photocatalytic properties of Eu3+:TiO2 synthesized by solid-state and hydrothermal-assisted sol-gel processes
No full textEu3+ doped TiO2 powders were synthesized by solid-state reaction and hydrothermal-assisted sol-gel process. They were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence techniques. Both synthetic procedures yield the pure anatase phase of titania. The excitation and emission spectra and the decay profiles were measured for different thermal treatments of the samples, in order to investigate the effects of the synthesis conditions on the doping mechanism. The photocatalytic activity was investigated by measuring the degradation of methylene blue under UV light irradiation and a correlation between its efficiency and the luminescence performance has been proposed
Glacial Mediterranean sea surface temperatures based on planktonic foraminiferal assemblages
No full textWe present a new reconstruction of Mediterranean sea surface temperatures (SST) during the last glacial maximum (LGM). A calibration data set based on census counts of 23 species of planktonic foraminifera in 129 North Atlantic and 145 Mediterranean core top samples was used to develop summer, winter and annual average SST reconstructions using artificial neural networks (ANNs) and the revised analogue method (RAM). Prediction errors determined by cross-validation of the calibration data set ranged between 0.5 and 1.1 °C, with both techniques being most successful in predicting winter SSTs. Glacial reconstructions are based on a new, expanded data set of 273 samples in 37 cores with consistent minimum level of age control.The new LGM reconstructions suggest that the east–west temperature gradient during the glacial summer was 9 °C, whereas during the glacial winter, the gradient was 6 °C, both some 4 °C higher than that existing today. In contrast to earlier studies, our results tend to suggest much cooler SST estimates throughout the glacial Mediterranean, particularly in the eastern basin where previous SST reconstructions indicated a decrease of only 1 °C. Our new SST reconstructions will provide the modelling community with a detailed and updated portrayal of the Mediterranean Sea during the LGM, setting new targets on which glacial simulations can be tested
Comparative investigation of scratch resistance and tribological performance of Ni–B–TiO2 composite coatings prepared by conventional and novel processing methods
No full textNi?B?TiO2 composite coatings were elaborated by conventional and novel methods. While the first one was designed using TiO2 powder, the second was prepared by adding TiO2 sol in the bath solution. A comparative study between both coatings was performed in terms of microstructure, adhesion strength and wear resistance. To achieve a systematic study, various characterization tests were carried out, including Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), microhardness test, progressive load scratch test, reciprocating sliding test and multi-pass scratch test. The results showed that the TiO2 structure (crystalline or amorphous) has extensively changed the microstructure of Ni?B matrix. Furthermore, it was proven that the novel process provided superior scratch response and better wear resistance of the Ni?B deposit since it offers a compact structure. Nevertheless, the traditional method yielded to porous one, thus leading to mediocre mechanical properties of the same coating
Quels modèles de développement pour la Tunisie de demain?
No full textJeudi 22 septembre 2011 au Palais des Congrès : « Quels modèles de développement pour la Tunisie de demain ? ». Interview de M. Maher KALLEL Président de Carthage Business Angels et Président de l'Association NOUR. Interview réalisée par Ghazi El Khamsa - ATUGE https://www.youtube.com/watch?v=mkgWl--CSIc M. Maher Kallel nous présente l'association Carthage Business Angels (CBA), première association de Business Angels en Tunisie. Carthage Business Angels regroupe les premiers acteurs du finan..
Synthesis, characterization and optical spectroscopy of GdPO4:Er3+
No full textA series of Er3+-doped GdPO4 phosphors was synthesized using a conventional solid-state reaction. The monazite structure (space group P121/n1) of the obtained materials was confirmed using X-ray diffraction and Fourier transform infrared spectroscopy. Their optical spectra (excitation, emission, absorption, decay curves) were measured at room temperature in the visible and near-infrared (NIR) regions. The UV–visible–NIR optical absorption spectrum of GdPO4:7% Er3+ was analyzed based on Judd–Ofelt (J–O) theory and the J–O intensity parameter (Ω2, Ω4, Ω6) was calculated. J–O intensity parameters were used to evaluate spontaneous emission properties such as branching ratios, transition probabilities, and radiative lifetime. The calculated quantum efficiency of the 1.5 μm emission (4I13/2−4I15/2) was calculated to be 89%. This result proved that GdPO4:Er3+ is suitable for use in optical amplifiers and is a potential host for laser applications. The most interesting transitions, located at about 540 nm, and 1.0 and 1.5 μm were investigated as a function of doping level and of temperature, to assess the conditions needed for the highest emission performance and to explore the range of application, in particular in the fields of lighting, thermal sensing, and of phosphors for bio-imaging
Effect of 17 alpha-Ethinylestradiol Exposure on Phycocyanin Metabolite Production and Antioxydant System of Phormidium Versicolor NCC466
No full textMicro-analysis as a Tool for the Characterization of Historical Masonry Buildings: The Decorative Elements of the Basilica Della Beata Vergine Maria Del Rosario (Polesella, Rovigo)
No full textThe Basilica of the Beata Vergine Maria del Rosario of Polesella, the subject of this study, was built in the mid-eighteenth century in the village of Polesella (in the province of Rovigo, Veneto Region, Italy). Some restoration work on the Basilica has been necessary for recent years; this has allowed sampling of interior plasters on which preliminary microanalyses have been performed to better characterize the building materials used, in support of subsequent repair work. Among the many planned restoration works, interventions on the interior walls were, in addition, also planned. For this, the interior plasters and interior painting of the church were studied through observations with SEM–EDS. The objective of this work is mainly to show how archeometric analyses can be a valuable tool to improve the knowledge and characterization of the materials used, in this case, on some decorative elements of the Basilica. In particular, regarding the frescoes, the research was also aimed at identifying the type of pigments used by the author Luigi Battisti, believed to be the author of some of the works on display
Response of the pelagic enviroment to palaeoclimatic changes in the central Mediterranean Sea during the Late Quaternary.
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