Chemical vapor deposition and characterization of nitrogen doped TiO2 thin films on glass substrates

Photocatalytically active, N-doped TiO2 thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH3 as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R=[NH3]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R=2200, the N-doped TiO2 layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375–400 °C). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO2 films of comparable thickness

Chemical vapor infiltration of photocatalytically active TiO2 thin films on glass microfibers

Due to the high diffusivity of the chemical species, chemical vapor infiltration (CVI) is a suitable process for the conformal coverage of objects with large dimensions and complex shape geometry. Its large scale capacity and high reproducibility have made the technique favorable for the deposition of non-oxide ceramics. There are few works on other materials and metal-organic compounds are rarely used as molecular precursors. In this study we focus on the deposition of anatase thin films on substrates with large surface area (microfibers) for photocatalytic air treatment systems. Titanium tetra-isopropoxide (TTIP) was used as precursor without additional oxygen source. Using low mole fractions (26–124×10−5) and low deposition temperatures (300–400 °C), a relatively good thickness uniformity was obtained along the reactor axis. Infiltration experiments were achieved in this temperature range and under 1 Torr for high TTIP diffusivity (110–146 cm2 s−1) and low initial Thiele modulus (0.11–0.13) values. Photocatalytic activity of TiO2 coated glass microfiber samples depends on the film morphology, average thickness and infiltration efficiency. It is shown that this later parameter plays a major role due to the increase of active surface area

Les espaces de l'halieutique

L'objet de l'article est la présentation d'un modèle spatialisé forcé par l'environnement de la population de thons albacore de l'Atlantique. Le modèle s'appuie sur des relations non linéaires estimées par modélisation additive généralisée (GAM) caractérisant, d'une part les préférences environnementales des albacores et d'autre part leur capturabilité à différents engins. Formulées analytiquement, les relations caratéristiques des préférences environnementales des albacores sont utilisées pour forcer un modèle d'advection-diffusion-réaction des albacores. Egalement formulées analytiquement, les relations caractérisant la capturabilité à différents engins permettent d'envisager l'ajustement du modèle aux captures observées. Le modèle permet de simuler la répartition des animaux en fonction de l'environnement océanique et des captures réelles. A travers différentes simulations, on s'intéresse au phénomène de surexploitation locale des thons adultes dans le Golfe de Guinée. La très grande ampleur du phénomène observée dans les simulations est discutée. (Résumé d'auteur

Microfibrous TiO2 supported photocatalysts prepared by metal-organic chemical vapor infiltration for indoor air and waste water purification

The photocatalytic degradation of gaseous (toluene) and aqueous (imazapyr, malic acid, orange G) pollutants over TiO2 supported photocatalysts is investigated using a batch reactor. A strong influence of the microstructural characteristics of TiO2 on the decomposition kinetics of the pollutants is found. Well crystallized, porous TiO2-anatase films grown under low pressure at 400–500 8C by MOCVD on glass plates and by MOCVI on glass micro-fibers are the best heterogeneous photocatalysts, showing the highest activity. We demonstrate a good control of these characteristics by choosing the deposition parameters. Achieving conformal coverage (i.e. good infiltration) of glass micro-fibers by the TiO2 thin films has also a strong influence on the photocatalytic activity. A correlation between optimal infiltration, film microstructure and photocatalytic activity is established. Strong similarities between optimal photocatalytic decomposition rate in gas and liquid phase were found with respect to the film microstructure and the photocatalyst mass. The total mineralization of the toluene was prevented because of the deactivation of the photocatalyst surface. However the reactivation of the photocatalyst was achieved by UV irradiation under oxygen stream. This allows a long-term use of the photocatalyst

Effet d'un apport de chaux sur un triticale cultivé sur un vertisol magnésien : enquête agrologique effectuée le 11 septembre 1981 sur la propriété Magnin-Pierson à Tontouta

Les résultats de cette enquête agrologique effectuée sur 2 parcelles contigues d'un vertisol magnésien sous triticale, la première amendée par 1,5 t/ha de CaO sous forme de chaux éteinte, semblent indiquer un effet favorable du chaulage sur ce type de sol et pour cette culture : lamasse des parties aériennes de triticale était de 9% plus élevée sur la parcelle chaulée et les immobilisations correspondantes en Ca de 5%. L'enquête a confirmé par ailleurs la très forte carence naturelle en phosphore de ce type de sol, le stock sol-plante (P assimilable Olsen de l'arumite -0 à 20 cm- plus le P des parties aériennes) étant de l'ordre de grandeur des apports de P par les engrais la même année

Long-Lived Two-Photon Excited Luminescence of Water-Soluble Europium Complex: Applications in Biological Imaging Using Two-Photon Scanning Microscopy.

International audienceA new europium complex presenting good solubility and stability in water, intense emission in the red (616 nm), long luminescence lifetime, and significant two-photon absorption cross-section in the biological window has been designed and successfully used for two-photon scanning microscopy bioimaging experiments on fixed cancer cells

Statut minéral d'un maïs à mi-cycle sur vertisol magnésien : enquête agrologique effectuée le 4 septembre 81 sur la propriété Magnin-Pierson à Tontouta.

Cette étude précise le statut minéral d'un maïs à mi-cycle cultivé sur un vertisol magnésien de la région de Tontouta. Sont mis en relief notamment : une teneur en Ca des plants de ce champ beaucoup plus faible que celle des plants arrivés au même stade de développement sur un sol peu évolué dérivé d'alluvions récentes, mais avec un rapport Ca/Mg équilibré ; des variations de cette teneur en sens inverse de celles du Mg échangeable du sol ; l'insuffisance des fertilisations apportées pour une production élevée. Les deux premiers résultats constituent des indices d'une déficience calcique sur ce type de sol

Uloga enzima u metabolizmu ugljikohidrata pri diferencijaciji staničnih linija šećerne repe

Plant development is influenced by changes in the levels and types of sugars produced metabolically. The normal (N), habituated organogenic (HO) and habituated nonorganogenic (HNO) sugar beet cell lines originate from the same mother plant but exhibit distinct levels of morphogenesis and differentiation, and contain different levels of simple carbohydrates. We aim to elucidate whether differences in the abundance and activity of enzymes involved in carbohydrate metabolism and sugar sensing/signalling help explain the different carbohydrate profiles and differentiation states of the cell lines. Using 13C NMR spectroscopy to analyze cultures of the cell lines over 28 days, we found that N cells accumulated sucrose; HO cells sucrose, glucose and fructose; and HNO cells glucose and fructose. Of three invertase isoforms, the activity of cell wall invertase (CWI) was highest in all the cell lines, and CWI activity was greatest in HNO line. The specific accumulation of intracellular carbohydrates during subculture correlated strongly with CWI activity but less so with the vacuolar and cytoplasmic invertase isoforms, or with sucrose synthase activity. Cell lines showed differences in how sugars regulated invertase and sucrose synthase activity. The role of sugar sensing in the regulation of CWI activity was investigated in the cell lines using glucose and sucrose, as well as carbohydrate analogues such as mannitol, 2-O-deoxyglucose and 3-O-methylglucose. Differences in the regulation of CWI activity by carbohydrates across the three cell lines suggest that CWI can be fine-tuned according to the specific carbohydrate requirements of each line during growth. Differences in sugar signalling pathways across the cell lines were explored using glucose and sucrose in the presence of inhibitors of protein kinases or phosphatases. Taken together, our findings suggest that specific regulation of CWI activity plays an important role in determining the intracellular carbohydrate levels of sugar beet cell lines, and possibly their differentiation state as well.Na razvoj biljke utječu promjene razine i tipa proizvedenog šećera. Iako sve stanične linije šećerne repe, i to normalna, prilagođena organogena i prilagođena neorganogena potječu od iste biljke, na različitim su stupnjevima diferencijacije i morfogeneze te sadrže različitu količinu jednostavnih ugljikohidrata. Svrha je rada bila utvrditi može li se razlikama u količini i aktivnosti enzima, koji sudjeluju u metabolizmu šećera te onih u detekciji i prijenosu signala šećera, objasniti razlika u stupnju diferencijacije staničnih linija te u udjelu ugljikohidrata u njima. Primjenom 13C NMR spektroskopije analizirane su stanične linije tijekom 28 dana kultivacije i ustanovljeno je da normalne stanične linije akumuliraju saharozu, prilagođena organogena stanična linija saharozu, glukozu i fruktozu, a prilagođena neorganogena stanična linija šećerne repe glukozu i fruktozu. Od 3 izoformna oblika invertaze najveća je aktivnost invertaze stanične stijenke u sve 3 stanične linije, osobito u prilagođenih neorganogenih stanica. Specifičnost akumulacije ugljikohidrata u stanici tijekom kultivacije uvelike je ovisila o aktivnosti invertaze stanične stijenke, a manje o onoj vakuolarne i citoplazmatske invertaze te saharoza sintetaze. Šećeri su različito regulirali aktivnost invertaze stanične stijenke i saharoza sintetaze, ovisno o tipu stanične linije. Njihova je uloga istražena pomoću glukoze i saharoze te njihovih analoga, kao što su manitol, 2-O-deoksiglukoza i 3-O-metilglukoza. Utvrđeno je da se aktivnost invertaze stanične stijenke može fino regulirati pomoću ugljikohidrata, ovisno o potrebi staničnih linija za izvorom šećera tijekom rasta. Razlike u putovima prijenosa signala šećera u staničnih linija istražene su pomoću glukoze i saharoze u prisutnosti inhibitora protein kinaza i fosfataza. Na kraju, rezultati autora potvrđuju da specifična regulacija aktivnosti invertaze stanične stijenke ima važnu ulogu u određivanju razine ugljikohidrata u staničnim linijama šećerne repe, a možda i stupnju diferencijacije stanica