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排序方式: 共有148条查询结果,搜索用时 15 毫秒
81.
Marcos V. dos S. Rezende Paulo J. R. Montes Felipe M. dos S. Soares Claudiane dos Santos Mário E. G. Valerio 《Journal of synchrotron radiation》2014,21(1):143-148
Xerogels of strontium chlorate and aluminium chlorate doped with europium (un‐co‐doped) and co‐doped with rare earth ions (Ln = Gd, Dy, Er and Y) were prepared using the proteic sol–gel route. Synchrotron radiation was used to investigate the effect of different co‐dopants on the Eu3+→ Eu2+ reduction process during the synthesis of the samples. Samples were excited at the Eu LIII‐edge and the XANES regions were analyzed. The results suggest that some of the Eu ions can be stabilized in the divalent state and that it is difficult to completely reduce Eu3+ to Eu2+ during thermal treatment. The mechanisms of the Eu reduction processes are explained by a proposed model based on the incorporation of charge‐compensation defects. 相似文献
82.
83.
Leonardo S. Teixeira Iram M. Mundim Weidson C. Souza Douglas R. Ramos Karine B. Bellorio Fernanda G. Marques Kênnia R. Rezende 《Chromatographia》2009,69(Z2):149-156
A fast, sensitive and specific liquid chromatography-mass spectrometry method has been developed for quantification of digoxin
in human plasma. The method was optimized to bioequivalence studies aiming higher sensitivity and selectivity than previously
published methods, in addition to shorter run time allowing high-throughput sample analyses from volunteers. Chromatographic
separation was achieved by an RP-18e column hyphenated to an API 5000 mass spectrometer system set at negative electrospray
ionization and operating in the MRM mode. Calibration curve was linear over a wide range of concentration (50.0–6000.0 pg mL−1), with the lower limit of quantification at 50.0 pg mL−1 and without interfering peaks at the retention time of digoxin (2.09 min). Dexamethasone was used as internal standard and
samples were cleaned up by liquid-liquid extraction obtaining a mean recovery of 73.8%. Validation results confirmed inter-batch
accuracy (−8.66 to 5.78%), precision (4.1–10.6%) and stability, in accordance with the U.S. Food and Drug Administration and
the Brazilian National Health Surveillance Agency guidelines. The developed analytical method could be successfully applied
to a single oral dose (0.25 mg), one-way, randomized, two-sequence, crossover bioequivalence study validating, up to date,
the fastest analysis and the most sensitive and specific method already published for digoxin quantification. 相似文献
84.
A new dual (fluorescent and spin) probe is described, where a N-aryl-2,4,6-triphenylpyridinium fluorophore is attached to a TEMPO fragment through an amide link. The resulting sensor 4 was evaluated as a hydrogen-abstracting agent in acetonitrile and in an aqueous solution of reduced Triton-X 100, being as resistant to hydrolysis as quinoline-TEMPO 1, but more hydrophobic than this probe. 相似文献
85.
The technique of Brillouin light scattering is used to observe strong excitation of magnons in antiferromagnetically coupled trilayers of Fe/Cr/Fe at room temperature. The magnons are driven out of equilibrium by a microwave current applied in the trilayer through point contacts. The magnitude of the scattering intensity is investigated as a function of the magnon wave number and applied magnetic field. Confirming recent theoretical predictions, the observations provide strong evidence of electronic spin injection in the rf driving field. 相似文献
86.
Thais Biondino Sardella Giorno Fernanda Alves Lima Ana Laura Macedo Brand Camila Martins de Oliveira Claudia Moraes Rezende Patricia Dias Fernandes 《Molecules (Basel, Switzerland)》2021,26(12)
Background: N-octadecanoyl-5-hydroxytryptamide (C18-5HT) is an amide that can be obtained by the coupling of serotonin and octadecanoic acid. This study aims to characterize the in vivo and in vitro anti-inflammatory activity of C18-5HT. Methods: A subcutaneous air pouch model (SAP) was used. The exudates were collected from SAP after carrageenan injection to assess cell migration and inflammatory mediators production. RAW 264.7 cells were used for in vitro assays. Results: C18-5HT significantly inhibited leukocyte migration into the SAP as well as nitric oxide (NO) and cytokines production and protein extravasation. We also observed an reduction in some cytokines and an increase in IL-10 production. Assays conducted with RAW 264.7 cells indicated that C18-5HT inhibited NO and cytokine produced. Conclusions: Taken together, our data suggest that C18-5HT presents a significant effect in different cell types (leukocytes collected from exudate, mainly polumorphonuclear leukocytes and cell culture macrophages) and is a promising compound for further studies for the development of a new anti-inflammatory drug. 相似文献
87.
88.
Coffee samples were analyzed by GC/MS in order to determine the most important peaks for the discrimination of the varieties Arabica and Robusta. The resulting peak tables from chromatographic analysis were aligned and pretreated before being submitted to multivariate analysis. A rapid and easy-to-perform peak alignment procedure, which does not require advanced programming skills to use, was compared with the tedious manual alignment procedure. The influence of three types of data pretreatment, normalization, logarithmic and square root transformations and their combinations, on the variables selected as most important by the regression coefficients of partial least squares-discriminant analysis (PLS-DA), are shown. Test samples different from those used in the calibration and comparison with the substances already known as being responsible for Arabica and Robusta coffees discrimination were used to determine the best pretreatments for both datasets. The data pretreatment consisting of square root transformation followed by normalization (RN) was chosen as being the most appropriate. The results obtained showed that the much quicker automated aligned method could be used as a substitute for the manually aligned method, allowing all the peaks in the chromatogram to be used for multivariate analysis. 相似文献
89.
In this Letter we study the behavior of the eigenvalues of an operator defined by the action associated to a generic quadratic time-dependent Hamiltonian. This is done using a polar representation of the solutions of the corresponding linear Hamiltonian system. A proof of the Morse index theorem is given. 相似文献
90.
Pedro J. de Rezende Flávio K. Miyazawa Anderson T. Sasaki 《Operations Research Letters》2013,41(5):552-555
We present PTASs for the disk cover problem: given geometric objects and a finite set of disk centers, minimize the total cost for covering those objects with disks under a polynomial cost function on the disks’ radii. We describe the first FPTAS for covering a line segment when the disk centers form a discrete set, and a PTAS for when a set of geometric objects, described by polynomial algebraic inequalities, must be covered. The latter result holds for any dimension. 相似文献