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31.
Valber A. Pedrosa Josiane Caetano Sergio A. S. Machado Renato S. Freire Mauro Bertotti 《Electroanalysis》2007,19(13):1415-1420
Studies on the immobilization of acetylcholinesterase onto a SAM gold electrode and the use of the fabricated biosensor for the determination of carbaryl and parathion are presented. The influence of pH, ionic strength, enzyme loading and concentration of glutaraldehyde on the response of the biosensor was investigated . The amperometric biosensor developed in this study provided linearity to parathion and carbaryl in the 2.0 a 30.0×10?6 mol L?1 concentration range. The detection limits under the optimum working conditions were found to be 9.3 μg L?1 for parathion and 9.0 μg L?1 for carbaryl. The enzyme electrode was found to be stable for 7 days. 相似文献
32.
Antonio?S.?AraújoEmail author Marcelo?J.?B.?Souza Antonio?O.?S.?Silva Anne?M.?G.?Pedrosa Joana?M.?F.?B.?Aquino Ana?C.?S.?L.?S.?Coutinho 《Adsorption》2005,11(2):181-186
The variation of surface properties of SiMCM-41 and AlMCM-41 nanoporous materials as function of synthesis time was examined.
The main properties studied were: surface area, pore diameter, pore volume, mesoporous parameter, and wall thickness. Siliceous
MCM-41 molecular sieves were synthesized starting from hydrogels with the following molar compositions: 4.58SiO2:0.435Na2O:1 CTMABr:200 H2O for SiMCM-41, and 4.58SiO2:0.485 Na2O:1 CTMABr:0.038 Al2O3:200 H2O, for AlMCM-41. Cetyltrimethylammonium bromide (CTMABr) was used as the structural template. The crystallographic parameters
were obtained from XRD data and by nitrogen adsorption using the BET and BJH methods. The results obtained showed a significant
variation of the surface properties of the MCM-41 materials as a function of the synthesis time reaching silica wall thickness
of ca. 2 nm on the fourth day. 相似文献
33.
34.
Patrícia Susano Joana Silva Celso Alves Alice Martins Susete Pinteus Helena Gaspar Mrcia Inês Goettert Rui Pedrosa 《Molecules (Basel, Switzerland)》2022,27(19)
The growing knowledge about the harmful effects caused by some synthetic ingredients present in skincare products has led to an extensive search for natural bioactives. Thus, this study aimed to investigate the dermatological potential of five fractions (F1–F5), obtained by a sequential extraction procedure, from the brown seaweed Saccorhiza polyschides. The antioxidant (DPPH, FRAP, ORAC and TPC), anti-enzymatic (collagenase, elastase, hyaluronidase and tyrosinase), antimicrobial (Staphylococcus epidermidis, Cutibacterium acnes and Malassezia furfur), anti-inflammatory (nitric oxide, tumor necrosis factor-α, interleukin-6 and interleukin-10) and photoprotective (reactive oxygen species) properties of all fractions were evaluated. The ethyl acetate fraction (F3) displayed the highest antioxidant and photoprotective capacity, reducing ROS levels in UVA/B-exposed 3T3 fibroblasts, and the highest anti-enzymatic capacity against tyrosinase (IC50 value: 89.1 µg/mL). The solid water-insoluble fraction (F5) revealed the greatest antimicrobial activity against C. acnes growth (IC50 value: 12.4 µg/mL). Furthermore, all fractions demonstrated anti-inflammatory potential, reducing TNF-α and IL-6 levels in RAW 264.7 macrophages induced with lipopolysaccharides. Chemical analysis of the S. polyschides fractions by NMR revealed the presence of different classes of compounds, including lipids, polyphenols and sugars. The results highlight the potential of S. polyschides to be incorporated into new nature-based skincare products. 相似文献
35.
Antonio?S.?AraujoEmail author Antonio?O.?S.?Silva Marcelo?J.?B.?Souza Ana?C.?S.?L.?S.?Coutinho Joana?M.?F.?B.?Aquino José?A.?Moura Anne?M.?G.?Pedrosa 《Adsorption》2005,11(2):159-165
In this work the acid properties of a series of HZSM-12 zeolites with different Si/Al ratio were studied. The ZSM-12 crystals
were synthesized by the hydrothermal method starting from a gel with the following molar composition: 20MTEA:10Na2O:x Al2O3:100SiO2:2000H2O, with x = 0.50, 0.67, 1, 1.25 and 2, respectively. The gels were crystallized at 140∘C for 6 days, then washed, dried and calcined to remove the MTEA template. The samples were ion-exchanged with an ammonium
chloride solution and calcined again to obtain the zeolites in the acid form. The materials thus obtained were characterized
by XRD, SEM, BET, TG and n-butylamine adsorption. The Si/Al ratio in the reaction mixture affects the amount of zeolite produced and the size of the
particles. The XRD analysis indicated that the ZSM-12 zeolite crystallizes in a pure form only with Si/Al ratio above 33.
The SEM analysis showed the presence of crystallites with very well defined prismatic shapes. The removal of the MTEA of the
pores of the ZSM-12 by TG indicated that there are two kinds of internal sites occupied by MTEA inside the structure. The
BET area of the ZSM-12 decreases proportionally with the crystallinity of materials. The desorption of n-butylamine showed
that the acid site density is proportional to aluminum content, but the Si/Al ratio shows little influence on the relative
strengths of these sites. 相似文献
36.
Lucas Vinícius deFaria Thalles Pedrosa Lisboa Gustavo Chevitarese Azevedo Rafael Arromba Sousa Maria Auxiliadora CostaMatos Rodrigo Alejandro Abarza Muoz Renato CamargoMatos 《Electroanalysis》2019,31(4):646-651
Dipyrone (metamizole sodium) is one of the most consumed drugs in the world. In this work a novel analytical method was developed for dipyrone sensing. This method involves the amperometric detection on a chemically‐reduced graphene‐oxide (CRGO)‐modified glassy carbon electrode. Raman spectroscopy and scanning electron microscopy revealed the presence of multilayer graphene layers that contributed to the electrocatalytic oxidation of dipyrone and increase in the electroactive area. Advantages of this sensor include elimination of previous separations, solvent extraction, or sample filtration, low detection limit (0.13 μmol L?1) with a linear range from 48 to 246 μmol L?1 and adequate recovery values (97–103 %). Applied to commercial pharmaceutical samples, this method showed results ranging from 451 to 541 mg of dipyrone per tablet, which agreed with the expected values. The results obtained by amperometry were compared statistically with the official method recommended by the Brazilian Pharmacopoeia (iodometric method), with no significant differences between them at 95 % confidence level. The proposed method is accurate for the monitoring of sodium dipyrone in pharmaceutical formulations, highlighting the lower reagent consumption and interferences in the analytical process. 相似文献
37.
Angel Alberola José M. Andrés Alfonso Gonzãlez Rafael Pedrosa Pedro Prãdanos 《合成通讯》2013,43(16):2537-2547
2-Acylthiophenes and ethyl 2-thiophene-carboxylates are prepared regioselectively by reaction of 3-ctil oroenones and 2-acylenammoni urn chlorides with α-mercapto derivatives in good to moderate yields. 相似文献
38.
M. A. Pedrosa C. Hidalgo A. López-Fraguas B. Ph. Van Milligen R. Balbín J. A. Jiménez E. Sánchez J. Castellano TJ-II Team L. García B. A. Carreras V. E. Lynch 《Czechoslovak Journal of Physics》2000,50(12):1463-1470
It has been shown that transport barriers in toroidal magnetically confined plasmas tend to be linked to regions of unique
magnetic topology such as the location of a minimum in the safety factor, rational surfaces or the boundary between closed
and open flux surfaces. In the absence ofE×B sheared flows, fluctuations are expected to show maximum amplitude near rational surfaces, and plasma confinement might tend
to deteriorate. On the other hand, if the generation ofE×B sheared flows were linked to low order rational surfaces, these would be beneficial for confinement. Experimental evidence
ofE×B sheared flows linked to rational surfaces has been obtained in the plasma edge region of the TJ-II stellarator.
Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000. 相似文献
39.
Valber A. Pedrosa Tony Gnanaprakasa Shankar Balasubramanian Eric V. Olsen Virginia A. Davis Aleksandr L. Simonian 《Electrochemistry communications》2009,11(7):1401-1404
Multifunctional coatings were produced by the layer by layer assembly of single-walled carbon nanotubes (SWNT) dispersed in DNA and lysozyme (LSZ) on an insulating glass substrate. The electrochemical properties of these mechanically robust biocoatings were characterized for the first time using scanning electrochemical microscopy (SECM) and impedance spectroscopy (IS). SECM surface analysis demonstrated an increase in tip current with a corresponding increase in the number of oppositely polarized interlaced layers, indicating that subsequent layers were not electrically insulated from each other and a direct correlation exists between SECM feedback response and the number of layers. The rate of charge transport was also dependent on the chemical composition/polarity of the outermost surface layer. Coatings terminating in SWNT-DNA resulted in more positive feedback than those terminating in SWNT-LSZ. IS analysis demonstrated that the SWNT-DNA had a low charge transfer resistance in comparison with SWNT-LSZ, which is consistent with the results obtained by SECM. These results enable enhanced fundamental understanding and prediction of the electrical properties of SWNT-biopolymer layers with controlled interlaced polarities and orientation. Furthermore, these finding highlight the potential for SWNT-biopolymers in electronic and sensing applications. 相似文献
40.
TMSCF3 adds to chiral 2-acyl-1,3-perhydrobenzoxazines with total diastereoselectivity leading to quaternary trifluoromethyl alcohols. Further transformation of the addition products yields enantiomerically enriched trifluoromethylated 1,2-diols and 1,2-amino alcohols. 相似文献