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排序方式: 共有195条查询结果,搜索用时 15 毫秒
1.
L Gasparini M Racchi L Benussi D Curti G Binetti A Bianchetti M Trabucchi S Govoni 《Canadian Metallurgical Quarterly》1997,231(2):113-117
The standard method for assessing the carcinogenicity of lubricating oil base stocks is the mouse skin-painting bioassay. This assay has the advantage of directly measuring the endpoint of interest, dermal carcinogenicity, but has the drawback of being time-consuming and expensive. For this reason, a variety of biological and chemical assays have been developed as predictive alternatives to the in vivo assay. This publication describes the application of three such methods to the assessment of carcinogenic potential of hydrotreated, re-refined oils: the modified Ames test, the analytical determination of 3-7-ring polycyclic aromatic compound content and the 32P-postlabeling assay for DNA adduct induction. 相似文献
2.
We report on the synthesis results obtained for some compositions in the Co(GaxIn1-x)2S4 family, whose intermediate member CoGaInS4 is shown to display a layered structure. This result is discussed and compared with the literature. 相似文献
3.
A Aliverti L Piubelli G Zanetti T Lübberstedt RG Herrmann B Curti 《Canadian Metallurgical Quarterly》1993,32(25):6374-6380
To investigate the functional role of the cysteine residues present in the spinach ferredoxin-NADP+ oxidoreductase, we individually replaced each of the five cysteine residues with serine using site-directed mutagenesis. All of the mutant reductases were correctly assembled in Escherichia coli except for the C42S mutant protein. C114S and C137S mutant enzymes apparently showed structural and kinetic properties very similar to those of the wild-type reductase. However, C272S and C132S mutations yielded enzymes with a decreased catalytic activity in the ferredoxin-dependent reaction (14 and 31% of the wild type, respectively). Whereas the C132S was fully competent in the diaphorase reaction, the C272S mutant flavoprotein showed a 35-fold reduction in catalytic efficiency with respect to the wild-type enzyme (0.4 versus 14.28 microM-1 s-1) due to a substantial decrease of kcat. NADP+ binding by the C272S mutant enzyme was apparently quantitatively the same (Kd = 37 microM) but qualitatively different, as shown by the differential spectrum. Stopped-flow experiments showed that the enzyme-FAD reduction rate was considerably decreased in the C272S mutant reductase, along with a much lower yield of the charge-transfer transient species. It is inferred from these data that the charge transfer (FAD-NADPH) between the reductase and NADPH is required for hydride transfer from the pyridine nucleotide to flavin to occur with a rate compatible with catalysis. 相似文献
4.
Marcos R. Guilherme Adriano V. Reis Alexandre T. Paulino André R. Fajardo Edvani C. Muniz Elias B. Tambourgi 《应用聚合物科学杂志》2007,105(5):2903-2909
This contribution describes the absorption percentage of Pb2+ and Cu2+ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal‐absorption tests, upon sequential pH variation, indicated that the SH has pH‐sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (? COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb2+, 81.99% for Cu2+ in water and 63.64% for Pb2+, and 76.67% for Cu2+ in saline water with 0.1 mol kg?1 ionic strength. A replicated 22 full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal‐absorption results demonstrated that the SH is a convenient material for absorption of Pb2+ and Cu2+ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
5.
Gabriela Brunosi Medeiros Paulo Ricardo de Souza Karina Miyuki Retamiro Celso Vataru Nakamura Edvani Curti Muniz Elisângela Corradini 《应用聚合物科学杂志》2021,138(36):50898
The production of polymer fibers from the combination of zein and PEO might have great potential in the field of biomaterial. Zein/PEO fibers were obtained in this work through solution electrospinning. An experimental design, 24-1, was used for evaluating the influences of PEO content in the blend, distance from the needle tip to the collector, applied electric voltage and solution flow for average fiber diameter and relative-yield process. Beyond this, the relationship between PEO content in the blend and the fiber properties were evaluated through FTIR, DSC, TG, tensile tests, and cytotoxic tests. The factor that exerts the greatest effect on the average fiber diameter response was the electrical voltage. The increase in PEO content in the blend decreased the thermal stability and increased the degree of the fibers' crystallinity. The mechanical tests showed that fibers with higher elongation were obtained at richer PEO blends. The fibers presented cytocompatible characteristics. 相似文献
6.
E. P. Muniz J. R. C. Proveti R. D. Pereira B. Segatto P. S. S. Porto V. P. Nascimento M. A. Schettino E. C. Passamani 《Journal of Materials Science》2013,48(4):1543-1554
The kinetics of formation of NiFe2O4 nanoparticles were investigated where the nanoparticles were produced by the proteic-sol–gel method using coconut water followed by annealing in (i) air, (ii) air in the presence of boron nitride (BN), or (iii) nitrogen. The sample dried at 473 K for 5.5 h was composed of small disordered NiFe2O4 nanoparticles in a superparamagnetic state as determined from Mössbauer spectroscopy. In general, heat treatment at high temperature leads to a nanocomposite rich in NiFe2O4. In air, annealing at 1173 K for 8 h favored the formation of the magnetically ordered NiFe2O4 inverse spinel structure, with bulk characteristics and average crystal sizes of approximately 66 nm. In a nitrogen atmosphere and in compacted BN powder under air atmosphere, the NiFe2O4 spinel structure stabilized for temperatures up to 873 and 773 K, respectively, however, decomposition of the NiFe2O4 phase into other undesired structures was observed above 873 K. 相似文献
7.
Viviane Oliveira Soares Francisco Carlos Serbena Gabriel dos Santos Oliveira Crislaine da Cruz Robson Ferrari Muniz Edgar Dutra Zanotto 《Ceramics International》2021,47(4):4707-4714
Transparent and translucent glass-ceramics (GCs) are found in an increasing number of domestic and high-technology applications. In this paper, we evaluated and optimized the effects of two-stage heat treatments on the resulting crystalline phases and microstructure of a glass of the SiO2–Li2O–P2O5–TiO2–CaO–ZnO–Al2O3 system. The objective was to develop a transparent nanostructured glass-ceramic (GC). After numerous heat treatment trials, we found that a long nucleation period of 72 h at 455 °C followed by a crystal growth treatment at 660 °C for 2 h resulted in a highly translucent GC having homogenously distributed nanocrystals. The relatively high amount of P2O5 (2.5 mol%) induced the formation of lithium disilicate as the main crystal phase. We thus developed a GC having crystals under 50 nm, with a high crystallized fraction (52%vol. Li2Si2O5 and 26% vol Li2SiO3), transmittance of approximately 80% in the visible spectrum for 1.2 mm thick specimens, nano hardness of 8.7 ± 0.1 GPa (load of 400 mN), a high elastic modulus of 138 ± 3 GPa as measured by nanoindentation, and good flexural strength (350 ± 40 MPa) as measured by ball-on-3 balls tests. Due to its high content of Li+, this GC has the potential to be chemically strengthened and can be further developed to be used in a number of applications, such as on displays of electronic devices. 相似文献
8.
Sustained release of potassium diclofenac from a pH‐responsive hydrogel based on gum arabic conjugates into simulated intestinal fluid 下载免费PDF全文
Adriano V. Reis Thais A. Moia Danielly L. A. Sitta Marcos R. Mauricio Ernandes T. Tenório‐Neto Marcos R. Guilherme Adley F. Rubira Edvani C. Muniz 《应用聚合物科学杂志》2016,133(16)
This work describes the preparation, the swelling properties and the potassium diclofenac (KDF) release profile of hydrogels of gum arabic (GA), N′,N′‐dimethylacrylamide, and methacrylic acid. In order to convert GA into a hydrogel, the polysaccharide was vinyl‐modified with glycidyl methacrylate. The hydrogels showed pH‐responsive swelling changes, which were more expressive in the basic environment. Release data of KDF were adjusted to a diffusion‐based kinetic model that provides an important insight on affinity of the drug for hydrogel and solvent, which may be the leading parameter for release of guest molecules from polymers. The KDF release from the hydrogels into simulated intestinal fluid decreases when the amount of modified GA increases. This was demonstrated to be due to the higher affinity of KDF for GA‐richer hydrogel, which makes the anti‐inflammatory release less favorable. The analysis of released drug half‐time (t1/2 = 16.10 and 21.51 h) indicated sustained release characteristics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43319. 相似文献
9.
Viviane Muniz da Silva Fragoso Carla Patrícia de Morais Coura Luanda Yanaan Hoppe Marília Amável Gomes Soares Dilson Silva Celia Martins Cortez 《International journal of molecular sciences》2016,17(1)
The aim of this work was to study the interaction of sulpiride with human serum albumin (HSA) and bovine serum albumin (BSA) through the fluorescence quenching technique. As sulpiride molecules emit fluorescence, we have developed a simple mathematical model to discriminate the quencher fluorescence from the albumin fluorescence in the solution where they interact. Sulpiride is an antipsychotic used in the treatment of several psychiatric disorders. We selectively excited the fluorescence of tryptophan residues with 290 nm wavelength and observed the quenching by titrating HSA and BSA solutions with sulpiride. Stern-Volmer graphs were plotted and quenching constants were estimated. Results showed that sulpiride form complexes with both albumins. Estimated association constants for the interaction sulpiride–HSA were 2.20 (±0.08) × 104 M−1, at 37 °C, and 5.46 (±0.20) × 104 M−1, at 25 °C. Those for the interaction sulpiride-BSA are 0.44 (±0.01) × 104 M−1, at 37 °C and 2.17 (±0.04) × 104 M−1, at 25 °C. The quenching intensity of BSA, which contains two tryptophan residues in the peptide chain, was found to be higher than that of HSA, what suggests that the primary binding site for sulpiride in albumin should be located next to the sub domain IB of the protein structure. 相似文献
10.
da Silva Breno Augusto Tabosa Thome Pascoalino Liege Aguiar de Souza Ricardo Luiz Muniz Edvani Curti Curti Priscila Schroeder 《Polymer Bulletin》2020,77(3):1157-1176
Polymer Bulletin - In this work, electrospun fibers of poly(butylene adipate-co-terephthalate) (PBAT) and poly(N-isopropylacrylamide) (PNIPAAm) blends, PBAT/PNIPAAm, with different mass ratios,... 相似文献