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41.
Mirosław Dors Helena Nowakowska Mariusz Jasiński Jerzy Mizeraczyk 《Plasma Chemistry and Plasma Processing》2014,34(2):313-326
Results of chemical kinetics modeling in methane subjected to the microwave plasma at atmospheric pressure are presented in this paper. The reaction mechanism is based on the methane oxidation model without reactions involving nitrogen and oxygen. For the numerical calculations 0D and 1D models were created. 0D model uses Calorimetric Bomb Reactor whereas 1D model is constructed either as Plug Flow Reactor or as a chain of Plug Flow Reactor and Calorimetric Bomb Reactor. Both models explain experimental results and show the most important reactions responsible for the methane conversion and production of H2, C2H2, C2H4 and C2H6 detected in the experiment. Main conclusion is that the chemical reactions in our experiment proceed by a thermal process and the products can be defined by considering thermodynamic equilibrium. Temperature characterizing the methane pyrolysis is 1,500–2,000 K, but plasma temperature is in the range of 4,000–5,700 K, which means that methane pyrolysis process is occurring outside the plasma region in the swirl gas flowing around the plasma. 相似文献
42.
Gonzalo Abellán Jose A. Carrasco Eugenio Coronado Helena Prima-García 《Journal of Sol-Gel Science and Technology》2014,70(2):292-299
Pure and highly crystalline FeNi3 alloy nanoparticles (NPs) were synthesized via sol–gel route with benzyl alcohol, using hydrazine as a reduction reagent without the usage of additional surfactant molecules nor further annealing processes. The structural studies revealed that the particle size is of ca. 200 nm, whose structure consisted on aggregation of small crystallites of about 13 nm. The magnetic properties of the as-synthesized NPs were similar to the bulk with a saturation magnetization of 95 emu g?1. Moreover, the coercive field was ca. 50 G, exhibiting a M r /M s ratio of 0.03, indicative of soft ferromagnetism. The electrical transport in the temperature range 2–300 K exhibits a typical ferromagnetic metallic behaviour. Finally, similar FeNi3 NPs were synthesized in EtOH/H2O mixtures in the presence of sodium dodecyl sulphate molecules as surfactant for comparative purposes, exhibiting a typical half hard magnetic behaviour, highlighting the interest of the reported benzylic route. 相似文献
43.
Herein we present co-crystallisation as a strategy for materials discovery in the field of switchable spin crossover (SCO) systems. Using [Fe(3-bpp)2]·2A (where 3-bpp = 2,6-bis(pyrazol-3-yl)pyridine, A = BF4−/PF6−) as a starting point, a total of 11 new cocrystals have been synthesised with five different dipyridyl coformers. Eight of these systems show spin crossover behaviour, and all show dramatically different switching properties from the parent complex. The cocrystals have been studied by variable temperature single-crystal X-ray diffraction and SQUID magnetometry to develop structure–property relationships. The supramolecular architecture of the cocrystals depends on the properties of the coformer. With linear, rigid coformer molecules leading to 1D supramolecular hydrogen-bonded chains, while flexible coformers form 2D sheets and bent coformers yield 3D network structures. The SCO behaviour of the cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials. The wider applicability of this strategy to the design of hybrid multifunctional materials is also discussed.The switching behaviour of spin crossover cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials. 相似文献
44.
Brandon Aguiar Helena Carmo Jorge Garrido Jos M. Sousa Lobo Isabel F. Almeida 《Molecules (Basel, Switzerland)》2022,27(1)
Polyphenols are a large family of natural compounds widely used in cosmetic products due to their antioxidant and anti-inflammatory beneficial properties and their ability to prevent UV radiation-induced oxidative stress. Since these compounds present chromophores and are applied directly to the skin, they can react with sunlight and exert phototoxic effects. The available scientific information on the phototoxic potential of these natural compounds is scarce, and thus the aim of this study was to evaluate the photoreactivity and phototoxicity of five phenolic antioxidants with documented use in cosmetic products. A standard ROS assay was validated and applied to screen the photoreactivity of the natural phenolic antioxidants caffeic acid, ferulic acid, p-coumaric acid, 3,4-dihydroxyphenylacetic acid (DOPAC), and rutin. The phototoxicity potential was determined by using a human keratinocyte cell line (HaCaT), based on the 3T3 Neutral Red Uptake phototoxicity test. Although all studied phenolic antioxidants absorbed UV/Vis radiation in the range of 290 to 700 nm, only DOPAC was able to generate singlet oxygen. The generation of reactive oxygen species is an early-stage chemical reaction as part of the phototoxicity mechanism. Yet, none of the studied compounds decreased the viability of keratinocytes after irradiation, leading to the conclusion that they do not have phototoxic potential. The data obtained with this work suggests that these compounds are safe when incorporated in cosmetic products. 相似文献
45.
Dr. Tran Quang Hung Dr. Ferial Terki Dr. Souleymane Kamara Mourad Dehbaoui Prof. Salam Charar Brajalal Sinha Prof. CheolGi Kim Dr. Philippe Gandit Il'ya A. Gural'skiy Dr. Gabor Molnar Dr. Lionel Salmon Dr. Helena J. Shepherd Dr. Azzedine Bousseksou 《Angewandte Chemie (International ed. in English)》2013,52(4):1185-1188
46.
Luiz Pereira Ramos Helena Maria Wilhelm 《Applied biochemistry and biotechnology》2005,123(1-3):807-819
In recent years, the concept of producing biodiesel from renewable lipid sources has regained international attention. In
Brazil, a national program was launched in 2002 to evaluate the technical, economic, and environmental competitiveness of
biodiesel in relation to the commercially available diesel oil. Several research projects were initiated nationwide to investigate
and/or optimize biodiesel production from renewable lipid sources and ethanol derived from sugarcane (ethyl esters). Once
implemented, this program will not only decrease our dependence on petroleum derivatives but also create new market opportunities
for agribusiness, opening new jobs in the countryside, improving the sustainability of our energy matrix, and helping the
Brazilian government to support important actions against poverty. This article discusses the efforts to develop the Brazilian
biodiesel program in the context of technical specifications as well as potential oilseed sources. 相似文献
47.
Semiconducting Carbon Nanotubes for Improved Efficiency and Thermal Stability of Polymer–Fullerene Solar Cells 下载免费PDF全文
Teddy Salim Hang‐Woo Lee Lydia Helena Wong Zhenan Bao Yeng Ming Lam 《Advanced functional materials》2016,26(1):51-65
The effects of the incorporation of semiconducting single‐walled nanotubes (sc‐SWNTs) with high purity on the bulk heterojunction (BHJ) organic solar cell (OSC) based on regioregular poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61‐butyric acid methyl ester (rr‐P3HT:PCBM) are reported for the first time. The sc‐SWNTs induce the organization of the polymer phase, which is evident from the increase in crystallite size, the red‐shifted absorption characteristics and the enhanced hole mobility. By incorporating sc‐SWNTs, OSC with a power conversion efficiency (PCE) as high as 4% can be achieved, which is ≈8% higher than our best control device. A novel application of sc‐SWNTs in improving the thermal stability of BHJ OSCs is also demonstrated. After heating at 150 °C for 9 h, it is observed that the thermal stability of rr‐P3HT:PCBM devices improves by more than fivefold with inclusion of sc‐SWNTs. The thermal stability enhancement is attributed to a more suppressed phase separation, as shown by the remarkable decrease in the formation of sizeable crystals, which in turn can be the outcome of a more controlled crystallization of the blend materials on the nanotubes. 相似文献
48.
49.
Vivian?Regina?Trist?o Fernando?Felippe?de?Carvalho Cinthia?Zanini?Gomes Adriana?Regina?Miranda Cíntia?C.?Vequi-Suplicy Maria?Teresa?Lamy Nestor?Schor Maria?Helena?Bellini 《Journal of fluorescence》2010,20(3):665-669
The progression to end-stage renal failure is independent of the initial pathogenic mechanism. Metabolic acidosis is a common
consequence of chronic renal failure that results from inadequate ammonium excretion and decreased tubular bicarbonate reabsorption.
Protoporphyrin IX (PpIX) is the immediate metabolic precursor of the heme molecule. The purpose of this study was to evaluate
the levels of erythrocytes protoporphyrin IX at an animal model during progressive renal disease. A total of 36 eight-week-old
male Wistar rats were divided into six groups: Normal, 4 and 8 weeks after 5/6 nephrectomy (NX). Renal function was evaluated
by creatinine clearance and plasma creatinine levels. The autofluorescence of erythrocytes porphyrin of healthy and NX rats
was analyzed using fluorescence spectroscopy. Emission spectra were obtained by exciting the samples at 405 nm. Significant
differences between normal and NX rats autofluorescence shape occurred in the 600–700 nm spectral region. A correlation was
observed between emission band intensity at 635 nm and progression of renal disease. 相似文献
50.