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81.
Mariaelena Ricca Vito Foderà Valeria Vetri Gianpiero Buscarino Maria Montalbano Maurizio Leone 《Journal of food science》2012,77(10):C1084-C1089
Abstract: Extra virgin olive oil (EVOO) is recognized as one of the healthiest foods for its high content of antioxidants, which forestall and slow down radical formation. Free radical‐initiated oxidation is considered one of the main causes of rancidity in fats and oils. As a consequence, reliable protocols for the investigation of oil oxidation based on selective, noninvasive, and fast methods are highly desirable. Here we report an experimental approach based on UV‐Vis absorbance, steady‐state fluorescence, and electron paramagnetic resonance (EPR) spectroscopy for studying oxidation processes induced by temperature for a period up to 35 d on Sicilian EVOO samples. We followed the decrease in β‐carotene content during incubation time and observed changes in polyphenols and tocopherols during the oxidation processes, focusing on the time scale of those changes. Using EPR spectroscopy, the free radical formation in different oil samples is reported, providing a fingerprint for both the antioxidant content and temporal features of the oxidation process at its early stage. Practical Application: We monitor β‐carotene and chlorophyll in an auto‐oxidation process. A protocol based on spectroscopic measurements is presented and can be used for the quality control process of commercial olive oil. 相似文献
82.
Maria Selvaggi Vito Laudadio Cataldo Dario Vincenzo Tufarelli 《Journal of the science of food and agriculture》2014,94(15):3090-3099
Sheep is the second most important dairy species after cow worldwide, and especially in the Mediterranean and Middle East regions. In some countries, the difficult environmental conditions require a peculiar adaptation and, in these contexts, sheep are able to provide higher quality protein than cattle. In the least‐developed countries, the amount of dairy sheep and ovine milk production is progressively increasing. In order to improve dairy productions, in particular those with local connotations, it is necessary to obtain in‐depth information regarding milk quality and rheological properties. The genetic polymorphisms of milk proteins are often associated with quantitative and qualitative parameters in milk and are potential candidate markers that should be included in breeding strategies similar to those already available for cattle. Due to the current and growing interest in this topic and considering the large amount of new information, the aim of this study was to review the literature on sheep milk protein polymorphisms with a particular emphasis on recent findings in order to give scientists useful support. Moreover, the effects of different protein variants on milk yield and composition are discussed. © 2014 Society of Chemical Industry 相似文献
83.
Recently, giant carrier mobility μ (>10(5) cm(2) V(-1) s(-1)) and micrometer electron mean free path (l) have been measured in suspended graphene or in graphene encapsulated between inert and ultraflat BN layers. Much lower μ values (10000-20000 cm(2) V(-1) s(-1)) are typically reported in graphene on common substrates (SiO(2), SiC) used for device fabrication. The debate on the factors limiting graphene electron mean free path is still open with charged impurities (CI) and resonant scatterers (RS) indicated as the most probable candidates. As a matter of fact, the inhomogeneous distribution of such scattering sources in graphene is responsible of nanoscale lateral inhomogeneities in the electronic properties, which could affect the behavior of graphene nanodevices. Hence, high resolution two-dimensional (2D) mapping of their density is very important. Here, we used scanning capacitance microscopy/spectroscopy to obtain 2D maps of l in graphene on substrates with different dielectric permittivities, that is, SiO(2) (κ(SiO2) = 3.9), 4H-SiC (0001) (κ(SiC) = 9.7) and the very-high-κ perovskite strontium titanate, SrTiO(3) (001), briefly STO (κ(STO) = 330). After measuring l versus the gate bias V(g) on an array of points on graphene, maps of the CI density (N(CI)) have been determined by the neutrality point shift from V(g) = 0 V in each curve, whereas maps of the RS density (N(RS)) have been extracted by fitting the dependence of l on the carrier density (n). Laterally inhomogeneous densities of CI and RS have been found. The RS distribution exhibits an average value ~3 × 10(10) cm(-2) independently on the substrate. For the first time, a clear correlation between the minima in the l map and the maxima in the N(CI) map is obtained for graphene on SiO(2) and 4H-SiC, indicating that CI are the main source of the lateral inhomogeneity of l. On the contrary, the l and N(CI) maps are uncorrelated in graphene on STO, while a clear correlation is found between l and N(RS) maps. This demonstrates a very efficient dielectric screening of CI in graphene on STO and the role of RS as limiting factor for electron mean free path. 相似文献
84.
Accardi R Oxelmark E Jauniaux N de Pinto V Marchini A Tommasino M 《Yeast (Chichester, England)》2004,21(7):539-548
Members of the YERO57c/YJGFc/UK114 protein family have been identified in bacteria and eukaryotes. The budding yeast Saccharomyces cerevisiae contains two different proteins of this family, Hmf1p and Mmf1p. We have previously shown that Mmf1p is a mitochondrial protein functionally related to its human homologue and able to influence the maintenance of mitochondrial DNA. Deletion of Mmf1 results in loss of the mitochondrial genome. Using a multicopy suppression approach, we have identified a protein of the mitochondrial large ribosomal subunit, MRPL40, which stabilizes mtDNA in Deltammf1 cells. Overexpression of MRPL40 did not prevent loss of mtDNA in a mutant strain lacking the mitochondrial protein Abf2p. Thus, MRPL40 does not have a general effect on mtDNA stability, but it may be specific for the mmf1-null strain. We also show that the Deltamrpl40 cells present a similar phenotype to the mmf1-null strain, having reduced mtDNA stability and growth rate. Furthermore, we observed that rho(+)Deltamrpl40 haploid cells can be obtained when tetrads are directly dissected on medium containing a non-fermentable carbon source. Thus, replication and segregation of the mtDNA can occur in the absence of MRPL40. We also show that another mitochondrial ribosomal protein, MRPL38, is able to overcome the Deltammf1-associated defect. Together, our results suggest a link between Mmf1p and the two mitochondrial ribosomal proteins. 相似文献
85.
Elixabet Díaz-de-Cerio Urszula Tylewicz Vito Verardo Alberto Fernández-Gutiérrez Antonio Segura-Carretero Santina Romani 《Food Analytical Methods》2017,10(8):2781-2791
Psidium guajava L. has gained a special attention as health plant due to the presence of phenolic compounds. Box-Behnken design (BBD) has been applied for the extraction of target compounds from guava leaves via sonotrode ultrasound-assisted extraction (UAE). Different extraction times (5, 30, and 55 min), ratios of ethanol/water (50, 75, and 100% (v/v)), and ultrasound (US) power (80, 240, and 400 W) were tested to find their effect on the sum of phenolic compound (SPC), flavonols and flavan-3-ols via HPLC-ESI-QqQ-MS, and antioxidant activity (DPPH and TEAC assays). The best process conditions were as follows: 40 min, 60% ethanol/water (v/v), and 200 W. Established method has been used to extract phenolic compounds in two guava leaves varieties (pyrifera and pomifera). Pyrifera var. showed greater values of the SPC via HPLC-ESI-QqQ-MS (49.7 mg/g leaf dry weight (d.w.)), flavonols (12.51 mg/g d.w.), flavan-3-ols (7.20 mg/g d.w.), individual phenolic compounds, and antioxidant activity (8970 ± 5 and 465 ± 6 μmol Trolox/g leaf d.w, respectively) than pomifera var. Conventional extraction showed lower amounts of phenolic compounds (7.81 ± 0.03 and 4.64 ± 0.01 mg/g leaf d.w. for flavonols and flavan-3ols, respectively) in comparison to the ultrasound-assisted ones. 相似文献
86.
Vecchio C Sonde S Bongiorno C Rambach M Yakimova R Raineri V Giannazzo F 《Nanoscale research letters》2011,6(1):269
In this work, we present a nanometer resolution structural characterization of epitaxial graphene (EG) layers grown on 4H-SiC
(0001) 8° off-axis, by annealing in inert gas ambient (Ar) in a wide temperature range (T
gr from 1600 to 2000°C). For all the considered growth temperatures, few layers of graphene (FLG) conformally covering the 100
to 200-nm wide terraces of the SiC surface have been observed by high-resolution cross-sectional transmission electron microscopy
(HR-XTEM). Tapping mode atomic force microscopy (t-AFM) showed the formation of wrinkles with approx. 1 to 2 nm height and
10 to 20 nm width in the FLG film, as a result of the release of the compressive strain, which builds up in FLG during the
sample cooling due to the thermal expansion coefficients mismatch between graphene and SiC. While for EG grown on on-axis
4H-SiC an isotropic mesh-like network of wrinkles interconnected into nodes is commonly reported, in the present case of a
vicinal SiC surface, wrinkles are preferentially oriented in the direction perpendicular to the step edges of the SiC terraces.
For each T
gr, the number of graphene layers was determined on very small sample areas by HR-XTEM and, with high statistics and on several
sample positions, by measuring the depth of selectively etched trenches in FLG by t-AFM. Both the density of wrinkles and
the number of graphene layers are found to increase almost linearly as a function of the growth temperature in the considered
temperature range. 相似文献
87.
Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy of Cr onto n -type silicon and covered with a 50-nm epitaxial silicon cap. Two types of samples were investigated: in one of them, the
NCs were localized near the deposition depth, and in the other they migrated near the surface. The electrical characteristics
were investigated in Schottky junctions by current-voltage and capacitance-voltage measurements. Atomic force microscopy (AFM),
conductive AFM and scanning probe capacitance microscopy (SCM) were applied to reveal morphology and local electrical properties.
The scanning probe methods yielded specific information, and tapping-mode AFM has shown up to 13-nm-high large-area protrusions
not seen in the contact-mode AFM. The electrical interaction of the vibrating scanning tip results in virtual deformation
of the surface. SCM has revealed NCs deep below the surface not seen by AFM. The electrically active probe yielded significantly
better spatial resolution than AFM. The conductive AFM measurements have shown that the Cr-related point defects near the
surface are responsible for the leakage of the macroscopic Schottky junctions, and also that NCs near the surface are sensitive
to the mechanical and electrical stress induced by the scanning probe. 相似文献
88.
In this article, a scanning probe method based on nanoscale capacitance measurements was used to investigate the lateral homogeneity
of the electron mean free path both in pristine and ion-irradiated graphene. The local variations in the electronic transport
properties were explained taking into account the scattering of electrons by charged impurities and point defects (vacancies).
Electron mean free path is mainly limited by charged impurities in unirradiated graphene, whereas an important role is played
by lattice vacancies after irradiation. The local density of the charged impurities and vacancies were determined for different
irradiated ion fluences. 相似文献
89.
Antonio Vita Giuseppe Cristiano Cristina Italiano Stefania Specchia Francesco Cipitì Vito Specchia 《International Journal of Hydrogen Energy》2014
The in situ deposition of 1.5 wt.% Ru/γ-Al2O3 catalytic layers on cordierite monoliths (400 cpsi, diameter 1 cm, length 1.5 cm), combining Solution Combustion Synthesis (SCS) with Wet Impregnation (WI), was addressed. First of all, the physicochemical properties of the catalyst at powder level were investigated by X-ray Diffraction (XRD), N2 adsorption (BET), and H2 chemisorption, while the morphology of final structured catalysts was evaluated by SEM analysis and mechanical strength tests by sonication. The catalytic activity towards methane Oxy-Steam Reforming (OSR) reaction was studied after the choice of the most suitable catalyst load, carrying out tests varying the temperature (500–800 °C), the oxygen-to-carbon ratio (O/C = 0.45–0.75, oxygen as moles), the steam-to-carbon ratio (S/C = 1.0–2.4), and the weight space velocity (WSV = 34,000–400,000 N ml gcat−1 h−1), in order to identify the optimum operative conditions. The results showed that a total catalytic layer load (active metal plus oxide carrier) equal to 6.5 mg cm−2 was enough to achieve excellent performances, while no substantial improvements were obtained at higher catalytic layer loads. Moreover, the coated Ru/γ-Al2O3 monolith exhibited a good catalytic activity towards the studied reaction also at considerably high WSV values (till 400,000 N ml gcat−1 h−1). 相似文献
90.
The paper presents a review of the measurement methods and the technologies for wideband spectrum sensing. Wideband spectrum sensing is a relevant task in RF measurement instruments and telecommunications equipments. The first part of the paper is dedicated to the discussion of methods. They have been classified into five main approaches: (i) signal detection with known sub-band width; (ii) joint sub-band boundaries and level estimation; (iii) spectrum segmentation; (iv) compressed sensing; and (v) cooperative sensing. Methods following approaches (ii) and (iii) are the most suitable for the implementation in measuring instruments, since they allow separation of the signals, sharing the observed band. Therefore, greater attention has been paid to these approaches throughout the paper. A second part of the paper is dedicated to the analysis of main technologies enabling wideband spectrum sensing, dealing with the (i) RF frontend, (ii) A/D conversion, and (iii) waveform processing section of a potential instrument. 相似文献