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1.
Food Chem ; : 128236, 2020 Oct 10.
Artículo en Inglés | MEDLINE | ID: mdl-33092913

RESUMEN

Impact of the "Intensification of Vaporization by Decompression to the Vacuum" (IVDV) on extraction of polyphenols from olive leaves was investigated. Using Response Surface Methodology, the effect of three variables were studied: initial water content of leaves, processing time and steam pressure on total phenolic content (TPC). Extractions of TPC from leaves were achieved either using 100% water as a solvent (w100), or 50% (v/v) aqueous ethanol (w50). Following IVDV pretreatment, TPC yields were enhanced with both solvents by approximately 3 times compared to the negative controls. Furthermore, oleuropein and hydroxytyrosol were intensified by up to 600% and 238% respectively. Antioxidant-antiradical assays revealed higher activities, up to 3.5 times, in extracts from IVDV-treated leaves. Calculation of the extraction indices Zp, reflecting cellular damage, confirmed the beneficial effect of IVDV on the extraction yield. Finally, Scanning Electron Microscopy (SEM) permitted the morphological observation of IVDV-treated as compared to untreated leaves.

2.
Biomed Res Int ; 2018: 1803425, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29992135

RESUMEN

This study evaluated the effect of air abrasion before and after sintering with different particle type, shape, and size on the surface morphology, monoclinic phase transformation, and bond strength between resin cement and zirconia surface using primer containing silane and MDP. Airborne particle abrasion (APA) was performed on zirconia before and after sintering with different particle shape and size (50 µm Al2O3 and 25 µm silica powder). 120 square shaped presintered zirconia samples (Amann Girrbach) were prepared (3 mm height × 10 mm width × 10 mm length) and polished with grit papers #800, 1000, 1200, 1500, and 2000. Samples were divided into 6 groups according to surface treatment-group A: (control) no surface treatment; group B: APA 50 µm Al2O3 before sintering (BS); group C: APA 50 µm Al2O3 after sintering (AS); group D: APA25 µm silica powder (BS); group E: APA25 µm silica powder (AS) at a pressure of 3.5 bar; and group F: APA 25 µm silica powder (AS) at a pressure of 4 bar. Samples were analyzed using XRD, AFM, and SEM. The samples were submitted to shear bond strength (SBS) test. A dual cure resin cement (RelyX Ultimate) and primer (Scotchbond Universal) were used. Data were analyzed with ANOVA and Tukey test (α ≥ 0.05). APA in group B significantly increased the surface roughness when compared to all other groups. A significant monoclinic phase transformation (t-m) value was observed in groups C and F and a reverse transformation occurred in presintered groups. The SBS value of group A was 11.58 ± 1.43 and the highest significant shear bond strength value was for groups B (15.86 ± 1.92) and C (17.59 ± 2.21 MPa) with no significant difference between them. Conclusions. The use of APA 50 µm Al2O3 before sintering and the application of primer containing MDP seem to be valuable methods for durable bonding with zirconia. The use of APA 50 µm Al2O3 after sintering induced the highest (t-m) phase transformation.


Asunto(s)
Recubrimiento Dental Adhesivo , Cementos de Resina , Circonio , Óxido de Aluminio , Materiales Dentales , Análisis del Estrés Dental , Ensayo de Materiales , Resistencia al Corte , Propiedades de Superficie
3.
ChemSusChem ; 11(18): 3023-3047, 2018 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-29984904

RESUMEN

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO2 under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO2 and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO2 to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO2 -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO2 -based materials further.

4.
J Contemp Dent Pract ; 19(2): 156-165, 2018 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-29422464

RESUMEN

AIM: The aim of this study was to evaluate the effect of different surface treatments on roughness, grain size, and phase transformation of presintered zirconia. MATERIALS AND METHODS: Surface treatments included airborne particle abrasion (APA) before and after sintering with different particles shape, size, and pressure (50 µm Al2O3, 50 µm glass beads, and ceramic powder). Thirty-five square-shaped presin-tered yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic slabs (Zenostar ZR bridge, Wieland) were prepared (4 mm height × 10 mm width × 10 mm length) and polished with silicon carbide grit papers #800, 1000, 1200, 1500, and 2000 to ensure identical initial roughness. Specimens were divided into five groups according to surface treatment: group I (control): no surface treatment; group II: APA 50 µm Al2O3 after sintering; group III: APA 50 µm Al2O3 particles before sintering; group IV: APA 50 µm glass bead particles before sintering; and group V: APA ceramic powder before sintering. Specimens were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) analyses, and tested for shear bond strength (SBS). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by post hoc tests for multiple comparisons Tukey's test (a > 0.05). RESULTS: Air abrasion before sintering significantly increased the surface roughness when compared with groups I and III. The highest tetragonal to monoclinic (t-m) phase transformation (0.07%) was observed in group III, and a reverse transformation was observed in presintered groups (0.01%). Regarding bond strength, there was a significant difference between APA procedures pre- and postsintering. CONCLUSION: Air abrasion before sintering is a valuable method for increasing surface roughness and SBS. The abrasive particles' size and type used before sintering had a little effect on phase transformation. CLINICAL SIGNIFICANCE: Air abrasion before sintering could be supposed to be an alternative surface treatment method to air abrasion after sintering.


Asunto(s)
Abrasión Dental por Aire/métodos , Circonio/química , Óxido de Aluminio/química , Compuestos Inorgánicos de Carbono/química , Cerámica/química , Materiales Dentales/química , Vidrio/química , Ensayo de Materiales , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Transición de Fase , Presión , Resistencia al Corte , Compuestos de Silicona/química , Propiedades de Superficie , Difracción de Rayos X
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