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排序方式: 共有2434条查询结果,搜索用时 31 毫秒
831.
Estrella Espada-Bellido Marta Ferreiro-González Gerardo F. Barbero Ceferino Carrera Miguel Palma Carmelo G. Barroso 《Food Analytical Methods》2018,11(9):2384-2395
Black mulberry (Morus nigra L.) is one of the most important species of the genus Morus as its fruit contains substantial levels of anthocyanins and phenolic compounds which show a potentially positive effect on the human health. Nowadays, PLE is becoming a promising extraction technology. Therefore, the development of fast extraction methods of anthocyanins and phenolic compounds from mulberry pulp using pressurized-liquid extraction (PLE) has been studied in this paper. The operating conditions (solvent, temperature, pressure, purge time, pH, and flushing) were investigated by a Box–Behnken design. Analysis of the model clearly showed that the most influential factors were temperature and solvent composition. The optimum extraction conditions for anthocyanins were 47.2% methanol in water, a temperature of 75.5 °C, pressure of 200 atm, a purge time of 90 s, pH 3.01, and 50.2% for flushing. The best conditions for the extraction of phenolics were 74.6% methanol, 99.4 °C, 100 atm, 90 s purge, pH 7, and 100% flushing. The optimum extraction time was 10 min. The precision values of the methods were also evaluated and excellent results (RSD?<?5%) were obtained. The developed methods were successfully applied to several mulberry marmalade samples. The results using PLE were compared to those achieved by UAE methods. Similar extraction yields were obtained for anthocyanins by PLE and UAE under optimized conditions; however, PLE required less methanol consumption. Besides, PLE showed higher extraction efficiency for total phenolic compounds. From the results, it can be concluded that pressurized-liquid extraction can be considered as an efficient alternative and powerful tool for the extraction of bioactive compounds from mulberries. 相似文献
832.
Miguel Teixeira Marta C. Campo David A. Pacheco Tanaka Margot A. Llosa Tanco César Magen Adélio Mendes 《Carbon》2011,49(13):4348-4358
Composite carbon molecular sieve membranes (c-CMSM) were prepared from phenolic resin loaded with boehmite by a single dipping–drying–pyrolysis step. The composite membrane was analyzed by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, mercury porosimetry, CO2 adsorption and permeation experiments. It was produced a 2 μm thick composite uniform layer on top of a α-Al2O3 support. The composite top layer exhibited nanowires of Al2O3 1–2 nm thick and 10–30 nm long well dispersed in a microporous carbon matrix. The micropores network accounted for 63% of the total pore volume (DR isotherm). The c-CMSM exhibited ideal O2/N2 and C3H6/C3H8 permselectivities of 5 and 15, respectively. The performance of the c-CMSM for pair C3H6/C3H8 was above the upper bound curve for polymeric membranes, making it a promising vehicle for olefin purification. 相似文献
833.
Pedro Cañamero‐Martínez José Luis de la Fuente Marta Fernández‐García 《应用聚合物科学杂志》2011,120(4):2166-2172
The curing reaction of a well‐defined glycidyl methacrylate‐co‐butyl acrylate statistical copolymer, prepared by atom transfer radical polymerization, and a commercial linear diamine (Jeffamine D‐230) was studied with the objectives of constructing and discussing a time–temperature–transformation isothermal curing for this system. Thermal and rheological analyses were used to obtain the gelation and vitrification times. Differential scanning calorimetry data showed a one‐to‐one relationship between the glass‐transition temperature (Tg) and fractional conversion independent of the cure temperature. As a result, Tg was used as a measurement of conversion. We obtained a kinetically controlled master curve for isothermal curing temperatures from 50 to 100°C by shifting Tg versus the natural logarithm time data to a reference temperature of 80°C. We calculated the apparent activation energy by applying two different methods, gel time measurements versus shift factors, suggesting a good agreement between them. Isoconversion contours were calculated by the numerical integration of the kinetic model. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
834.
H‐Shaped Oligofluorenes for Highly Air‐Stable and Low‐Threshold Non‐Doped Deep Blue Lasing
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835.
In this paper we deal with the minimum label spanning tree problem. This is a relevant problem with applications such as telecommunication networks or electric networks, where each edge is assigned with a label (such as a color) and it is intended to determine a spanning tree with the minimum number of different labels. We introduce some mixed integer formulations for this problem and prove that one of their relaxations always gives the optimal value. Finally we present and discuss the results of computational experiments. 相似文献
836.
Katarzyna Mitura Grzegorz Bartosz Bogdan Walkowiak Zofia Paw?owska Marta Kie?-?wierczyńska 《Surface & coatings technology》2006,201(6):2117-2123
The unique properties of thin diamond layers make them perspective candidates for producing advanced micro-electronic devices, coatings for cutting tools and optics. However, due to the highest biocompatibility of carbon resulting from the presence of this element in the human body, it appears to be a potential biomaterial.Carbon, especially in the form of the nanocrystalline diamond film, have found industrial applications in the area of medical implants.The studies of carbon films as coatings for implants in surgery were aimed at the investigations of biological resistance of implants, histopathological investigations on laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrode's solution.Different medical implants are covered by Nanocrystalline Diamond Coatings (NCD). NCD forms the barrier diffusion between implant and human environment. The research on NCD proved that diamond layers are biocompatible with living organisms.Diamond Powder Particles (DPP) is an extended surface of NCD. Biological research with diamond powder can answer the basic question: what is the influence of DPP on cells, tissues and organs in human organism? 相似文献
837.
Anna Kubacka Manuel Ferrer María L. Cerrada Cristina Serrano Manuel Snchez-Chaves Marta Fernndez-García Alicia de Andrs Rafael J. Jimnez Riobo Fernando Fernndez-Martín Marcos Fernndez-García 《Applied catalysis. B, Environmental》2009,89(3-4):441-447
TiO2 incorporation into an isotactic polypropylene (iPP) polymeric matrix was achieved via a straightforward and cost-effective melting process using laboratory-made nanometric anatase-TiO2 and an industrial polymer. The structural characteristics of the resulting nanocomposite thin films as a function of the inorganic component content were examined using wide and small angle X-ray scattering (WAXS/SAXS) and vibrational Raman spectroscopy. Electron scanning and transmission microscopy (SEM/TEM) studies were also performed to provide evidence of the nanometric dispersion of the oxide within the polymer matrix, showing the presence of average aggregates of ca. 80 nm. TiO2 incorporation into the iPP renders self-sterilized nanocomposite films upon light excitation, the activity of which was tested against Gram negative (P. aeruginosa) and positive (E. faecalis) bacteria. TiO2 displays maximum activity for a sample containing a 2 wt.% of anatase-TiO2 irrespective of the microorganism nature. The antimicrobial activity of the nanocomposite films is significantly enhanced with respect to that of the oxide alone. This key fact is interpreted on physical basis with the help of a complete optical (UV–vis and photoluminescence) and electron paramagnetic resonance (EPR) characterization. 相似文献
838.
Computer simulations are increasingly used in biological fields. The amazing power, storage ability, and processing speeds available nowadays have enabled the implementation of computer individual-based models (IbMs) to simulate really complex biological populations. Computers can easily keep track of thousands of individuals (often called ’agents’), whose complex behaviours and large amounts of associated data were daunting only 20 years ago. As such, computer modelling has just entered a field where traditional PDE models used to reign alone. A study of the exchange and non-trivial relationship between these two fields, computer IbMs versus classic partial differential equations (PDEs), is appropriate. The aim of this paper is to compare both approaches through a relevant example, namely the evolution of a yeast population in a batch culture. Thus, this paper deals with the utilization of both classical mathematics and computer science in the solution of problems arising in microbiology. First, an IbM approach to study the evolution of a yeast batch culture is presented. Second, an equivalent PDE model is derived by using some techniques from the interacting particle systems field. Third, a comparison and discussion on the advantages and drawbacks of both modelling tools is given. 相似文献
839.
Ultrasonic studies of outburst-prone coals 总被引:1,自引:0,他引:1
840.
The effect of Nb and Cr dopants as well as Sn4+ additions on the electronic structure of rf-sputtered TiO2 thin films and its subsequent influence on gas sensor performance is reported. The changes in the electrical conductivities of TiO2 thin films doped with up to 10 at.% Nb, 4 at.% Cr and TiO2-SnO2 in the full range of compositions upon exposure to hydrogen and oxygen are demonstrated. The spectral dependence of the absorption coefficient in the vicinity of the band gap transition of TiO2 is shown to be affected by doping. 相似文献