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101.
Nicolás E. Tenaglia Roberto E. Boeri Alejandro D. Basso Juan M. Massone 《International Journal of Cast Metals Research》2017,30(2):103-111
In this study the as-cast macro and microstructures of medium C – high Si cast steels of three different levels of alloying are characterised. The application of a colour-etching reagent sensitive to Si segregation effectively revealed the solidification macrostructure, showing that the patterns of macrostructure and microsegregation are governed by the initial precipitation of δ-ferrite dendrites. A study of microsegregation carried out using advanced EDS techniques showed that, for the studied chemical compositions, Si, Mn, Cr, Ni, Mo and Al tend to concentrate at the last liquid to solidify. Accordingly, effective partition coefficients of values below unity were calculated for all alloying elements tested. It was verified that the minimum local Si contents measured on the steels investigated were greater than 1.7%, value above the minimum value (1.5%) necessary to obtain carbide-free bainite after austempering. 相似文献
102.
Chemical and enzymatic interesterification are used to create spreadable fats. However, a comparison between the two processes
in terms of their acute metabolic effects has not yet been investigated. A randomised crossover study in obese (plasma TAG > 1.69 mmol/L,
and BMI > 30 (BMI = kg/m2) or waist circumference > 102 cm, n = 11, age = 59.3 ± 1.8 years) and non-obese (plasma triacylglycerol (TAG) < 1.69 mmol/L, and BMI < 30 or waist circumference < 102 cm,
n = 10, age = 55.8 ± 2.2 years) men was undertaken to compare the effects of chemical versus enzymatic interesterification
on postprandial risk factors for type 2 diabetes (T2D) and cardiovascular disease (CVD). TAG, cholesterol, glucose, insulin
and free fatty acid concentrations were measured for 6 h following consumption of 1 g fat/kg body mass of non-interesterified
(NIE), chemically interesterified (CIE), enzymatically interesterified (EIE) stearic acid-rich fat spread or no fat, each
with 50 g available carbohydrate from white bread. Interesterification did not affect postprandial glucose, insulin, free
fatty acids or cholesterol (P > 0.05). Following ingestion of NIE, increases in serum oleic acid were observed, whereas both oleic and stearic acids were
increased with CIE and EIE (P < 0.05). While postprandial TAG concentrations in non-obese subjects were not affected by fat treatment (P > 0.05), obese subjects had an 85% increase in TAGs with CIE versus NIE (P < 0.05). The differences in TAG response between non-obese and obese subjects suggest that interesterification may affect
healthy individuals differently compared to those already at risk for T2D and/or CVD. 相似文献
103.
Silvana?Martini Constantin?Bertoli Maria?Lidia?Herrera Ian?Neeson Alejandro?MarangoniEmail author 《Journal of the American Oil Chemists' Society》2005,82(5):305-312
An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead
of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in
concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples
were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was
followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships
were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC.
TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r
2>0.9) in a linear fashion (v=2.601 SFC+1433.0). 相似文献
104.
Alejandro Moncayo-Lasso Ricardo A. Torres-Palma John Kiwi Norberto Benítez Csar Pulgarin 《Applied catalysis. B, Environmental》2008,84(3-4):577-583
A woven inorganic silica fabric loaded with Fe-ions (EGF-Fe) was tested under simulated solar light during hydroquinone degradation. The abatement of hydroquinone was observed to attain about 80% within 3 h. The photo-catalyst was also tested to inactive Escherichia coli K12 at “natural” pH and in the presence of a low concentration of H2O2. Addition of H2O2 (10 mg L−1) did not by itself to bacterial inactivation. Total bacterial inactivation was mediated by EGF-Fe fabrics in the presence of H2O2 (10 mg L−1) under solar light irradiation. A sample containing active (culturable) bacteria (105 CFU mL−1) decreased to values <1 CFU mL−1 within 3 h reaction. Fe-mediated homogeneous process decreased the bacterial CFU content by about two orders of magnitude within 4 h. During the degradation of hydroquinone only a small amount of iron ions were found in solution of about 1.2 mg L−1, within 90 min decreasing to values ≤0.5 mg L−1 after 180 min. The leaching of Fe-ions did not affect the photo-catalyst performance since EGF-Fe fabric did not deactivate after five or more cycles. The Fe-ions founds in solution mineralized hydroquinone to levels below 37% of its initial content. The present study presents the first report on the beneficial role of a heterogeneous iron supported catalyst leading to efficient bacterial inactivation in aqueous solution with iron leaching <0.1 mg L−1, the detection limit for Fe-analysis in solution. No bacterial re-growth was observed during a post-irradiation period up to 24 h in the dark. 相似文献
105.
Mireia Casanovas Irene Reyes-Resina Alejandro Lillo Jaume Lillo Raul Lpez-Arnau Jorge Camarasa Elena Escubedo Gemma Navarro Rafael Franco 《International journal of molecular sciences》2021,22(5)
Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A2A receptor (A2AR). First, we noticed that methamphetamine does not affect A2A functionality if the receptor is expressed in a heterologous system. However, A2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB1 receptor (CB1R) and the sigma 1 receptor (σ1R). Signaling via both adenosine A2AR and cannabinoid CB1R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A2AR–CB1R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A2AR- and the CB1R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ1R, alters the expression and function of two interacting receptors, A2AR, which is a therapeutic target for neuroprotection, and CB1R, which is the most abundant G protein-coupled receptor (GPCR) in the brain. 相似文献
106.
Flexible and hydrophobic biobased films were obtained using zein esterified with methanol and para-toluene (p-toluene) sulfonic acid, cutin from tomato peels and ethanol. Esterification was confirmed by proton nuclear magnetic resonance and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). Non-modified zein films were brittle and hydrophilic. ATR-FTIR demonstrated that zein esterification increased zein hydrophobicity. Without cutin, esterified zein films were hydrophobic but brittle. Addition of cutin yielded films that were flexible and hydrophobic, as demonstrated by contact angle measurements. Principal component analysis (PCA) of ATR-FTIR data showed that intensities at 3195 cm−1 and 3490 cm−1 were correlated to the relative hydrophobicity of zein films. PCA also showed that films of esterified zein and cutin were more hydrophobic than their counterparts (non-modified zein without cutin). Optical and scanning electron microscopy demonstrated that esterified zein was compatible with cutin and yielded cohesive films, which did not fracture upon bending. 相似文献
107.
Flor R. Siperstein Carlos Avendaño Jordan J. Ortiz Alejandro Gil-Villegas 《American Institute of Chemical Engineers》2021,67(3):e17186
The isosteric heat of adsorption is an important thermodynamic property used to characterize and optimize adsorption processes. In this work, analytic expressions for isosteric heats of adsorption are derived for a collection of commonly used isotherm models and a two-dimensional molecular equation of state based on the SAFT-VR approach. The use of these expressions is presented with an example of adsorption of nitrous oxide, N2O, on biochar, which is a waste biomass charcoal that exhibits high adsorption potential. The results show that accurate fitting of the adsorption isotherms leads to consistent results obtained with different approaches; however, the predicted isosteric heat of adsorption exhibits strong variations in the regions where experimental data is insufficient such in the region of low pressure/low coverage. Convergence on the prediction of the isosteric heat of adsorption by the different models is only observed in the region where no extrapolation of experimental data is needed. 相似文献
108.
Alejandro García Rodríguez Jorge V. Miguel Oria Alexis Delgado Gómez 《Welding International》2016,30(7):527-534
The present work is based on an assessment of experimentally obtained results from the application of different methods of evaluation, reported in the specialised literature, of the electrical charge transference stability in the arc. A simple factorial design, taking the welding current as independent variable, was applied to the process with an AWS A5.1 E6013 electrode. The welds were carried out in the flat position by a gravity device. It was possible to obtain criteria to classify the electrical charge transference stability of the process by digital signal processing and a statistical technique. The outcome was based on visual inspection and morphologic studies. It was concluded that amongst the considered parameters, the average value of the arc conductivity during reignition peaks and the quantity of reignition peaks are the more representative indices, both from statistics and from phenomenological points of view. This finding is validated by the fact that the bead morphology and the stability analysis of the electrical charge transference process coincides with the fact that the 160 A (for 4 mm-diameter electrodes) is the most stable regime. 相似文献
109.
Wojciech Polkowski Natalia Sobczak Rafał Nowak Artur Kudyba Grzegorz Bruzda Adelajda Polkowska Marta Homa Patrycja Turalska Merete Tangstad Jafar Safarian Elmira Moosavi-Khoonsari Alejandro Datas 《Journal of Materials Engineering and Performance》2018,27(10):5040-5053
For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism. 相似文献
110.
Ana M. Díez-Pascual Mohammed Naffakh Alejandro Ansón M. Teresa Martínez Marián A. Gómez 《Carbon》2010,48(12):3485-3499
Poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT) composites incorporating polysulfones as compatibilizers were fabricated by melt-blending, after pre-processing based on ball milling and mechanical treatments in an organic solvent. Their structure, morphology and thermal properties have been investigated. Microscopic observations showed a uniform distribution of the CNTs and good miscibility between the compatibilizer and matrix phases. The incorporation of wrapped SWCNTs leads to a remarkable increase in the degradation temperatures of the matrix in comparison with non-compatibilized samples, attributed to the high thermal stability of the polysulfones and the compatibilizing effect. The addition of very small CNT loadings raises the crystallization temperature and the degree of crystallinity of PEEK. At higher concentrations, the inactive nucleating activity of the nanofillers, the confinement of the polymer chains within the CNT network and the presence of an amorphous compatibilizer moderately hinder PEEK crystallization. Synchrotron X-ray diffraction experiments indicate the existence of reorganization phenomena of the matrix crystals during the heating of the composites. Improved thermal properties are found for composites incorporating arc-purified SWCNTs, attributed to the higher degree of debundling and lower metal content of these CNTs. These compatibilized composites are new materials for potential high-temperature structural applications. 相似文献