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1.
Angel L. Ortiz Camila S. Rodrigues Fernando Guiberteau Yu Zhang 《Journal of the European Ceramic Society》2021,41(11):5728-5739
The microstructural development during crystallization firing of a commercially-available dental-grade nanostructured lithia-zirconia glass-ceramic (Vita Suprinity® PC) was unraveled using a wide battery of ex-situ and in-situ characterization techniques. It was found that the milling blocks are slightly crystallized glass-ceramics, with a complex chemical composition and consisting of partially de-polymerized glass plus lithium silicate (Li2SiO3) nanocrystals. It was also found that during crystallization firing the glassy matrix first reacts with part of the Li2SiO3 to form lithium disilicate (Li2Si2O5) at ~810?820 °C, and then lithium orthophosphate (Li3PO4) precipitates from the glass. This results in glass-ceramics with abundant nanocrystals embedded in a sparse zirconosilicate glass matrix (containing many other cations subsumed) that, due to its high viscosity, inhibited crystal growth. Therefore, these dental glass-ceramics are not reinforced with zirconia (ZrO2) crystals unless over-fired above ~890 °C and at the expense of its singular nanostructure. Finally, this study opens doors for optimizing the clinical performance of these dental glass-ceramics via microstructural tailoring. 相似文献
2.
Cindy Joanna Caballero-Prado Jose Angel Merino-Mascorro Norma Heredia Jorge Dvila-Avia Santos García 《Food science and biotechnology》2021,30(4):599
Shiga-toxin-producing Escherichia coli strains are pathogenic for humans and cause mild to severe illnesses. In this study, the antimicrobial effect of citral, eugenol, and hexanal in combination with heat shock (HS) was evaluated in terms of the growth, biofilm formation, swarming, and expression of virulence genes of STEC serotypes (O157:H7, O103, O111, and O26). Eugenol was the most effective compound against the growth of E. coli strains (MBC = 0.58 to 0.73 mg/mL), followed by citral (MBC = 0.86 to 1.26 mg/mL) and hexanal (MBC = 2.24 to 2.52 mg/mL). Biofilm formation and swarming motility have great variability between STEC strains. Natural compounds—alone or combined with HS—inhibited biofilm formation; however, swarming motility was induced by most treatments. The expression of the studied genes during biofilm formation and swarming under natural antimicrobials was affected but not in a uniform pattern. These treatments could be used to control contamination of STEC and inhibit biofilm formation. 相似文献
3.
Quoc Ahn Tran Bastien Chevalier Miguel Angel Benz-Navarrete Pierre Breul Roland Gourvès 《Soils and Foundations》2019,59(6):2348-2355
This paper presents a calculation method for obtaining the continuous variation in stress between the tip and the soil during dynamic penetration tests, particularly in the case of using the Panda 3® penetration testing device. The originality of the method is that the tip stress can be computed continuously throughout the driving process. For each impact of the hammer on the penetrometer, data are recorded by sensors located at the top of the apparatus. Then, the stress at the tip and the displacement of the apparatus are calculated with a method based on the propagation of waves in the device. A three-dimensional numerical model of the penetration test, based on the Panda 3® specifications and using the discrete element method (DEM), is proposed in this paper. The purpose of the simulations is to validate the calculation method by comparing the curves of the tip stress versus the penetration distance obtained in two different ways, the first being the distance directly observed at the tip and the second being the distance calculated from the data recorded at the top of the penetrometer, as with the experimental device. The entire apparatus is represented, including the hammer, the rod, and the tip, and is driven into the model soil. The calculation method is applied, and the results are compared to the actual response of the soil to the driving of the penetrometer directly at the tip, which can be obtained with the numerical model. The responses are found to be very similar, confirming the theoretical framework and its underlying assumptions. This method is applied to dynamic penetration tests and provides the opportunity to obtain mechanical parameters other than the tip resistance from the tests. 相似文献
4.
María T. Colomer Lidia Zur Maurizio Ferrari Angel L. Ortiz 《Ceramics International》2018,44(11):11993-12001
Rhabdophane-type Eu3+,Tb3+-codoped LaPO4·nH2O single-crystal nanorods with the compositions La0.99999-xEuxTb0.00001PO4·nH2O (x?=?0–0.03), La0.99999-yTbyEu0.00001PO4·n′H2O (y?=?0–0.010), and La0.99999-zTbzEu0.000007PO4·n′′H2O (z?=?0–0.012) were hydrothermally synthesized with microwaves. It is shown that the Eu3+,Tb3+ codoping does not affect the thermal stability of these nanorods, which is due to the formation of substitutional solid solutions with both Eu3+ and Tb3+ replacing La3+ in the crystal lattice. Moreover, it is also shown that monazite-type Eu3+,Tb3+-codoped LaPO4 single-crystal nanorods can be obtained by calcining their rhabdophane-type Eu3+,Tb3+-codoped LaPO4·(n,n′ or n′′)H2O counterparts at moderate temperature in air, and that they are thermally stable. It is also observed that, for the same Eu3+,Tb3+-codoping content, the monazite-type Eu3+,Tb3+-codoped LaPO4 nanorods exhibit higher photoluminescent efficiency than the rhabdophane-type Eu3+,Tb3+-codoped LaPO4· (n,n′ or n′′)H2O nanorods. Moreover, it is found that the highest photoluminescence emission corresponds to the monazite-type La0.96999Eu0.02Tb0.00001PO4 nanorods for the La0.99999-xEuxTb0.00001PO4 system. However, for those compositions energy transfer from Tb3+ to Eu3+ does not occur. In addition, for an efficient energy transfer to occur, a content of at least 1?mol% Tb3+ is needed in all the studied materials. 相似文献
5.
Alberto Ballesteros Ester Laguna-Gutierrez Paula Cimavilla-Roman Maria Luisa Puertas Antonio Esteban-Cubillo Julio Santaren Miguel Angel Rodriguez-Perez 《应用聚合物科学杂志》2021,138(46):51373
In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear rheology and X-ray micro-computed tomography. Sepiolites treated with quaternary ammonium salts (O-QASEP) are better dispersed in the PS matrix than natural sepiolites (N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A percolated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEP and 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O-QASEP present the lowest cell size and the most homogeneous cellular structures. 相似文献
6.
7.
Angel L. Ortiz Victor M. Candelario Oscar Borrero-López Fernando Guiberteau 《Journal of the European Ceramic Society》2018,38(4):1158-1163
The sliding-wear resistance of pure near fully-dense B4C is investigated, and the wear mode/mechanisms identified, under lubrication with water, diesel fuel, and paraffin oil. It is found that the wear is mild in the three cases, with specific wear rates (SWRs) of 10?16–10?17 m3/N m. Nonetheless, the wear resistance of the B4C ceramic is one order of magnitude greater under oil lubrication (1016 N m/m3) than under water lubrication (1015 N m/m3), and twice as great for the specific case of paraffin oil than diesel fuel, attributable to the lubricant’s viscosity. It is also found that the wear mode is always abrasion, and that the wear mechanisms are plastic deformation and localized fracture with grain pullout. However, in agreement with the macro-wear data, the severity of the wear damage is lower under lubrication with paraffin oil, followed by diesel fuel, and lastly water. Finally, microstructural considerations are discussed with a view to enhancing the sliding-wear resistance of B4C triboceramics. 相似文献
8.
Griselda Castruita-de León Claudia Y. Yeverino-Miranda Angel de J. Montes-Luna Hector Iván Meléndez-Ortiz German Alvarado-Tenorio Luis Alfonso García-Cerda 《应用聚合物科学杂志》2020,137(3):48286
Flat mixed matrix membranes (MMMs) comprising polysulfone and clinoptilolite-type natural zeolite were prepared by casting. Zeolite was modified with three alkylamines: ethanolamine (EA), bis(2-hydroxypropyl)amine (BHPA), and polyethylenimine (PEI) by the impregnation method. Impregnated zeolite samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and N2 adsorption–desorption. The alkylamine loading extent determined by thermogravimetric analysis was 5.2, 4.8, and 8.5% for EA, BHPA, and PEI, respectively. Analyses of MMMs showed that the incorporation of impregnated zeolite affected the glass-transition temperature (Tg) and mixed-gas transport properties. In this regard, a decreasing trend of the Tg values from 185.5 °C for the polymeric membrane up to 176.6 °C for Clino-EA-based MMM was recorded. In addition, the gas separation performance was evaluated at two different feed pressures. At 50 psi, MMMs showed an enhancement up to 30% on the CO2 permeability (22.79 Barrer) and 55% on the CO2/CH4 selectivity (45.78) in comparison with the polymeric membrane (CO2 permeability 17.34 Barrer; CO2/CH4 selectivity 29.38). These values varied depending on the alkylamine, BHPA being the most selective. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48286. 相似文献
9.
James G. Kohl Andrew G. Kohl Angel Licea-Claverie Arturo Zizumbo-Lopez Randika Jayasinghe Mascareneous Ashokcline 《Polymer-Plastics Technology and Engineering》2020,59(13):1463-1472
ABSTRACT Waste can be considered a crisis across the world, especially in the Global South where landfills are collapsing and vector-borne illnesses are increasing. Due to the increase in the amount of waste plastic in the environment, different uses of recycled plastics are being investigated. One such use is roofing tiles. This has been put in place in Sri Lanka through the Waste for Life organization. Here, recycled polyethylene is filled with rice husk particles. Due to the hydrophilic nature of the rice husk, the strength of the polyethylene composites decreased with increasing rice husk filler. Since the roofing tiles do not need to support a large load, the loss in strength should not be too detrimental. However, the creep behavior was improved with 10% and 20% filler. This is important in that the temperature on the roof can reach high temperatures. 相似文献
10.
Raquel Herrero-Labrador Angel Trueba-Saiz Laura Martinez-Rachadell M
Estrella Fernandez de Sevilla Jonathan A. Zegarra-Valdivia Jaime Pignatelli Sonia Diaz-Pacheco Ana M. Fernandez Ignacio Torres Aleman 《International journal of molecular sciences》2020,21(24)
Obesity is a risk factor for Alzheimer’s disease (AD), but underlying mechanisms are not clear. We analyzed peripheral clearance of amyloid β (Aβ) in overweight mice because its systemic elimination may impact brain Aβ load, a major landmark of AD pathology. We also analyzed whether circulating insulin-like growth factor I (IGF-I) intervenes in the effects of overweight as this growth factor modulates brain Aβ clearance and is increased in the serum of overweight mice. Overweight mice showed increased Aβ accumulation by the liver, the major site of elimination of systemic Aβ, but unaltered brain Aβ levels. We also found that Aβ accumulation by hepatocytes is stimulated by IGF-I, and that mice with low serum IGF-I levels show reduced liver Aβ accumulation—ameliorated by IGF-I administration, and unchanged brain Aβ levels. In the brain, IGF-I favored the association of its receptor (IGF-IR) with the Aβ precursor protein (APP), and at the same time, stimulated non-amyloidogenic processing of APP in astrocytes, as indicated by an increased sAPPα/sAPPβ ratio after IGF-I treatment. Since serum IGF-I enters into the brain in an activity-dependent manner, we analyzed in overweight mice the effect of brain activation by environmental enrichment (EE) on brain IGF-IR phosphorylation and its association to APP, as a readout of IGF-I activity. After EE, significantly reduced brain IGF-IR phosphorylation and APP/IGF-IR association were found in overweight mice as compared to lean controls. Collectively, these results indicate that a high-fat diet influences peripheral clearance of Aβ without affecting brain Aβ load. Increased serum IGF-I likely contributes to enhanced peripheral Aβ clearance in overweight mice, without affecting brain Aβ load probably because its brain entrance is reduced. 相似文献