Prevention of excess weight gain in paediatric primary care: beverages only or multiple lifestyle factors. The Smart Step Study, a cluster-randomized clinical trial: Obesity prevention in paediatric primary care

Insufficient evidence exists to support obesity prevention in pediatric primary care

Submicrometer Zeolite A Crystals Formation: Low-Temperature Crystallization Versus Vapor Phase Gel Transformation

International audienceIn the present Study, low-temperature hydrothermal crystallization and vapor phase gel transformation have been employed to synthesis LTA-type zeolite Crystals of submicrometer size. The crystal growth curves under hydrothermal conditions at 35, 50, and 65 degrees C were obtained. From these curves, the induction periods and the times for reaching maximum crystallinity for respective temperatures were determined. A set of characterization methods, including XRD, FTIR, SEM, TEM, and DLS, was employed to obtain complementary information. The inspection of the crystalline solids obtained under hydrothermal conditions showed that the size of the crystals is a function of the crystallization temperature. The largest crystals (300 x 300 nm) were obtained at 65 degrees C, while much smaller particles were synthesized at lower temperatures. Second approach involved vapor-phase transformation of the solid part of initial gel. This approach has also yielded submicrometer-sized zeolite crystallites. The characteristics of crystalline particles synthesized by two methods were compared Both synthetic methods showed relatively high conversion (70-80%) of the initial gel into LTA type zeolite, which is substantial advantage in respect to nanozeolite synthesis from clear solutions

Submicrometer Zeolite A Crystals Formation: Low-Temperature Crystallization Versus Vapor Phase Gel Transformation

International audienceIn the present Study, low-temperature hydrothermal crystallization and vapor phase gel transformation have been employed to synthesis LTA-type zeolite Crystals of submicrometer size. The crystal growth curves under hydrothermal conditions at 35, 50, and 65 degrees C were obtained. From these curves, the induction periods and the times for reaching maximum crystallinity for respective temperatures were determined. A set of characterization methods, including XRD, FTIR, SEM, TEM, and DLS, was employed to obtain complementary information. The inspection of the crystalline solids obtained under hydrothermal conditions showed that the size of the crystals is a function of the crystallization temperature. The largest crystals (300 x 300 nm) were obtained at 65 degrees C, while much smaller particles were synthesized at lower temperatures. Second approach involved vapor-phase transformation of the solid part of initial gel. This approach has also yielded submicrometer-sized zeolite crystallites. The characteristics of crystalline particles synthesized by two methods were compared Both synthetic methods showed relatively high conversion (70-80%) of the initial gel into LTA type zeolite, which is substantial advantage in respect to nanozeolite synthesis from clear solutions

Submicrometer Zeolite A Crystals Formation: Low-Temperature Crystallization Versus Vapor Phase Gel Transformation

International audienc

Phase transitions in excimer laser irradiated zirconia thin films

In the present work, excimer laser irradiation below the ablation threshold is successfully applied as a tool for surface modification of vapor grown amorphous zirconia (ZrO2) thin films. Characterization of virgin and laser processed areas was performed by optical spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), low angle X-ray diffraction (LAXRD) and reflection high energy electron diffraction (RHEED). The occurrence of phase transitions to orthorhombic or monoclinic modification of amorphous zirconia on laser parameters dependency is established. Separation of a new Zr phase is detected in parallel to the formation of crystalline zirconia phases. The observed structure transformations strikingly coincide with some polymorphic transitions in zirconia powders and sintered ceramics. The results obtained demonstrate the necessity for applying both surface and in-depth analytical techniques in characterizing excimer laser induced changes in thin ZrO2 films. (C) 2001 Elsevier Science B.V. All rights reserved

Seeds-induced fluoride media synthesis of nanosized zeolite Beta crystals

International audienceThis study reports on the seeded synthesis of zeolite Beta in fluoride media. Crystal growth kinetics of the material as a function of seed content, crystallization temperature and Si/Al ratio of the initial gel is studied. After the optimization of crystallization conditions a highly crystalline material with crystal size 100-300 nm is synthesized. A counterpart zeolite Beta sample with similar characteristics is obtained in hydroxyl media. The physicochemical properties of fluoride and hydroxyl media syntheiszed zeolites are compared as particular attention is paid to the nature, number and distribution of their active sites. Zeolite Beta sample synthesized in fluoride media exhibits larger number of Broensted acid sites, while the concentration of Lewis acid sites is higher in the zeolite synthesized in hydroxyl media. The two materials are tested in m-xylene transformation, where zeolite Beta synthesized in fluoride medium shows superior performance. The set of experimental data unambiguously proves that seeded synthesis of zeolites in fluoride medium is a promising alternative of the conventional zeolite synthesis in hydroxyl medium. (C) 2013 Elsevier Inc. All rights reserved

Seeds-induced fluoride media synthesis of nanosized zeolite Beta crystals

International audienceThis study reports on the seeded synthesis of zeolite Beta in fluoride media. Crystal growth kinetics of the material as a function of seed content, crystallization temperature and Si/Al ratio of the initial gel is studied. After the optimization of crystallization conditions a highly crystalline material with crystal size 100-300 nm is synthesized. A counterpart zeolite Beta sample with similar characteristics is obtained in hydroxyl media. The physicochemical properties of fluoride and hydroxyl media syntheiszed zeolites are compared as particular attention is paid to the nature, number and distribution of their active sites. Zeolite Beta sample synthesized in fluoride media exhibits larger number of Broensted acid sites, while the concentration of Lewis acid sites is higher in the zeolite synthesized in hydroxyl media. The two materials are tested in m-xylene transformation, where zeolite Beta synthesized in fluoride medium shows superior performance. The set of experimental data unambiguously proves that seeded synthesis of zeolites in fluoride medium is a promising alternative of the conventional zeolite synthesis in hydroxyl medium. (C) 2013 Elsevier Inc. All rights reserved