44 research outputs found
Thulium and ytterbium-doped titania thin films deposited by MOCVD
In this study we synthesized thin films of titanium oxide doped with thulium
and/or ytterbium to modify the incident spectrum on the solar cells. This could
be achieved either by photoluminescence up-converting devices, or
down-converting devices. As down-converter thin films our work deals with
thulium and ytterbium-doped titanium dioxide. Thulium and ytterbium will act as
sensitizer and emitter, respectively. The rare-earth doped thin films are
deposited by aerosol-assisted MOCVD using organo-metallic precursors such as
titanium dioxide acetylacetonate, thulium and ytterbium
tetramethylheptanedionate solved in different solvents. These films have been
deposited on silicon substrates under different deposition conditions
(temperature and dopant concentrations for example). Adherent films have been
obtained for deposition temperatures ranging from 300{\deg}C to 600{\deg}C. The
deposition rate varies from 0.1 to 1 \mu m/h. The anatase phase is obtained at
substrate temperature above 400{\deg}C. Further annealing is required to
exhibit luminescence and eliminate organic remnants of the precursors. The
physicochemical and luminescent properties of the deposited films were analyzed
versus the different deposition parameters and annealing conditions. We showed
that absorbed light in the near-UV blue range is re-emitted by the ytterbium at
980 nm and by a thulium band around 800 nm.Comment: 4 pages, 6 figures, proceedin
First result of tartaric stabilization by adding mannoproteins (Mannostab™)
Some mannoproteins which are extracted by enzymatic hydrolysis of yeast's cell wall with the aid of commercial preparation composed with beta-glucanases (Glucanexâą) inhihits the tartaric acid's salt breakdown in model solution as well as in wines for an addition between 10 and 25 g/hl. On the other hand, heat extracted mannoproteins arc inactive on the tartaric precipitation stabilization. Furthermore, the crystallization inhibitor activity of the enzymatic extracted mannoproteins is due to the presence of sharply glycosylated mannoproteins of mediummolecular weight (30 to 50 kda) which are not heat extracted. That is why the heat extracted mannoproteins are inactive. The enzymatic extracted mannoproteins are produced at a pilot plan. This preparation (Mannostabâą), soluble in wines, colourless and without any flavour, stabilize with the same efficiency than a freeze treatment and this effective live is superior to the metatartric acid. Moreover, the necessary steps were been taked to permit experimentally this new product : Mannostab
Evaluation of the astringency of commercial tannins by means of the SDSâPAGE-based method.
Optical properties of zinc phthalocyanine thin films prepared by pulsed laser deposition
Effect of free and immobilised stem bromelain on protein haze in white wine
Background and Aims: Several studies have investigated the effectiveness of several proteolytic enzymes in free form as a treatment alternative to bentonite fining for wine stabilisation. This work tested the feasibility of stem bromelain, free or immobilised on a chitosan support, to reduce white wine protein haze potential. Methods and Results: The kinetic behaviour of stem bromelain, in free form and covalently immobilised on chitosan beads, was studied in 12 unfined white table wines fortified with a tripeptide chromogenic substrate. The effectiveness of the protease on wine hazing potential was determined by treating the wines in a laboratory-scale stirred reactor, and the heat test was applied to evaluate the decrease in nephelometric turbidity units. Immobilised protease was active towards the synthetic substrate and in reducing hazing potential of the wine. The effect of wine components on bromelain proteolytic behaviour, as investigated by principal component analysis, was much more noticeable for the free enzyme (in decreasing order of importance: pH, total phenolic substances, free and total sulfur dioxide) than for the immobilised form. Conclusions: An amount of 10 g/L biocatalyst (bromelain immobilised on chitosan beads), after a 24-h treatment in a laboratory-scale stirred reactor, revealed a high capacity to reduce wine haze potential (approximately 70%), which was unaffected by wine composition. Significance of the Study: Immobilised bromelain appears a suitable treatment alternative to bentonite fining for white wine haze stabilisation
Use of Fourier transform infrared spectroscopy to create models forecasting the tartaric stability of wines
Tartaric instability of wines still represents a serious problem in terms of the commercial value of bottled wines, particularly whites, leading consumers to be suspicious as regards the effective healthiness or wholesomeness of products. The study, carried out on 536 Italian wines, investigated the potential of using Fourier Transform Infrared Spectroscopy, distinguishing between white and red/rosĂ© wines, to create models predicting the instability of wines, assessed in comparison to two of the most widespread methods of reference: the âmini-contact testâ (10 min, 0 °C, KHT) and the âcooling testâ (5 days, â4 °C). The models proposed, constructed using 80% of the samples and based on Partial Least Squares-Regression and Artificial Neural Networks, were shown to work well in terms of correct classification (from 89% to 97%) of the external validation subset (20%). As regards the more problematical question of technical management of wines before bottling, in the worst cases only 4â6% of unstable samples were erroneously classified as stabl