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981.
Cesar A. Sanchez Jose A. Rodríguez M. Elena Paez‐Hernandez Eva M. Santos Yolanda Castrillejo 《Electroanalysis》2019,31(2):329-334
A zero‐valent iron nanoparticles modified electrode was employed as an amperometric detector in flow conditions to determine metronidazole and 2‐methyl‐5‐nitroimidazole in pharmaceutical formulations. Flow injection analysis at ?0.6 V (vs. Ag) achieved limits of detection of 2 and 6 μM for metronidazole and 2‐methyl‐5‐nitroimidazole, respectively, but the analysis was not discriminative between the two compounds. When reverse phase high performance liquid chromatography was applied previous to the electrochemical detection both analytes could be analysed simultaneously. However, the limits of detection slightly increased (10 μM) as a consequence of the use of an organic solvent and a lower sample volume. The relative standard deviation of analytical repeatability was <4.0 % in both techniques. The methods were validated by comparing the results obtained from the analysis of commercial samples with those provided by HPLC‐DAD and no significant differences were detected. Results probed that the modified electrode was a successful tool in the FIA and HPLC analysis of nitro compounds. 相似文献
982.
dos Reis Lima Fernanda Maria Silva Saimon Moraes da Silva Freires André Goulart Marília Oliveira Fonseca Damos Flavio Santos de Cassia Silva Luz Rita 《Journal of Solid State Electrochemistry》2019,23(3):725-734
Journal of Solid State Electrochemistry - This paper reports the development of a photoelectrochemical platform based on indium tin oxide (ITO) electrode modified with carboxyl-functionalized... 相似文献
983.
Preparation of Polyfunctional Arylzinc Organometallics in Toluene by Halogen/Zinc Exchange Reactions
Moritz Balkenhohl Dorothe S. Ziegler Alexandre Desaintjean Leonie J. Bole Alan R. Kennedy Eva Hevia Paul Knochel 《Angewandte Chemie (International ed. in English)》2019,58(37):12898-12902
A wide range of polyfunctional diaryl‐ and diheteroarylzinc species were prepared in toluene within 10 min to 5 h through an I/Zn or Br/Zn exchange reaction using bimetallic reagents of the general formula R′2Zn?2 LiOR (R′=sBu, tBu, pTol). Highly sensitive functional groups, such as a triazine, a ketone, an aldehyde, or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of a plethora of functionalized (hetero)arenes after quenching with various electrophiles. Insight into the constitution and reactivity of these bimetallic mixtures revealed the formation of highly active lithium diorganodialkoxyzincates of type [R′2Zn(OR)2Li2]. 相似文献
984.
Anaí L. dos Santos Allan dos S. Polidoro Cláudia A. L. Cardoso Margareth Batistote Maria do Carmo Vieira Rosângela A. Jacques 《Natural product research》2019,33(4):593-597
The present study investigated the essential oil obtained from Campomanesia guazumifolia (Cambess.) O. Berg, an aromatic plant used in Brazilian folk medicine. The chemical composition was performed by GC×GC/qMS. The antioxidant and antimicrobial activities were evaluated by DPPH and BCB and, MIC assays, respectively. Sixty-eight compounds were identified in the oil, where the major compounds were bicyclogermacrene (15%), globulol (5%) and spathulenol (5%). Sesquiterpene hydrocarbons (29 compounds) and oxygenated sesquiterpenes (20 compounds) were the most representative classes of terpenes. DPPH (IC50 value 26.1 ± 0.5 μg/mL) and BCB (68.3 ± 1.5%) values indicated a significant antioxidant activity. The essential oil strongly inhibited Staphylococcus aureus (MIC 15 ± 0.1 μg/mL), Escherichia coli (MIC 25 ± 0.2 μg/mL) and Candida albicans (MIC 5 ± 0.1 μg/mL). The results give a deeper understanding of the chemical composition and report for the first time the antioxidant and antimicrobial potential of the C. guazumifolia essential oil. 相似文献
985.
Ana Santos‐Coquillat Enrique Martínez‐Campos Nelson Vargas‐Alfredo Raúl Arrabal Juan Rodríguez‐Hernndez Endzhe Matykina 《Macromolecular bioscience》2019,19(10)
Magnesium‐based implants present several advantages for clinical applications, in particular due to their biocompatibility and degradability. However, degradation products can affect negatively the cell activity. In this work, a combined coating strategy to control the implant degradation and cell regulation processes is evaluated, including plasma electrolytic oxidation (PEO) that produces a 13 µm‐thick Ca, P, and Si containing ceramic coating with surface porosity, and breath figures (BF) approach that produces a porous polymeric poly(ε‐caprolactone) surface. The degradation of PCL‐PEO‐coated Mg hierarchical scaffold can be tailored to promote cell adhesion and proliferation into the porous structure. As a result, cell culture can colonize the inner PEO‐ceramic coating structure where higher amount of bioelements are present. The Mg/PEO/PCL/BF scaffolds exhibit equally good or better premyoblast cell adhesion and proliferation compared with Ti CP control. The biological behavior of this new hierarchical functionalized scaffold can improve the implantation success in bone and cardiovascular clinical applications. 相似文献
986.
Vanessa Brito Adriana O. Santos Paulo Almeida Samuel Silvestre 《Comptes Rendus Chimie》2019,22(1):73-83
In this study, synthesis, structural characterization, molecular docking studies, and antiproliferative effects in four different cell lines of several novel 16-arylidene-4-azaandrost-5-ene compounds are reported. These compounds were prepared by oxidative cleavage of the enone system of androstenedione followed by an azacyclization reaction and an aldol condensation with various aldehydes at C16. In the androgen-dependent LNCaP cells, the most relevant antiproliferative effects were observed with the 16-phenyl, 16-p-tolyl, and 16-p-nitrophenyl derivatives. Compound 16E-[(4-methylphenyl)methylidene]-4-azaandrost-5-ene-3,17-dione was the most potent in these cells (IC50 = 28.28 μM), having lower antiproliferative effects in the androgen-independent PC-3 cells (IC50 = 45.31 μM). In addition, an interesting selectivity toward cancer cell lines was found for all compounds because a generally low cytotoxicity was detected in healthy human fibroblasts. Furthermore, the 16-p-tolylazaandrostene steroid induced a reduction of viability in LNCaP cells similar to that observed with finasteride, a clinically used 5α-reductase inhibitor. Moreover, molecular docking studies predicted that these 4-azaandrostene derivatives can interact with 5β-reductase, which has a high level of similarity to 5α-reductase enzyme, and with other common targets of steroidal drugs, particularly the enzyme 17α-hydroxylase/17,20-lyase. 相似文献
987.
Abouzaid E Arenton M Barker AR Bellantoni L Bellavance A Blucher E Bock GJ Cheu E Coleman R Corcoran MD Cox B Erwin AR Escobar CO Glazov A Golossanov A Gomes RA Gouffon P Hsiung YB Jensen DA Kessler R Kotera K Ledovskoy A McBride PL Monnier E Nguyen H Niclasen R Ii DG Ping H Ramberg EJ Ray RE Ronquest M Santos E Slater W Smith D Solomey N Swallow EC Toale PA Tschirhart R Wah YW Wang J White HB Whitmore J Wilking MJ Winstein B Winston R Wolfe C Worcester ET Worcester M Yamanaka T Zimmerman ED 《Physical review letters》2008,100(13):131803
The Fermilab KTeV experiment has searched for lepton-flavor-violating decays of the K(L) meson in three decay modes. We observe no events in the signal region for any of the modes studied, and we set the following upper limits for their branching ratios at the 90% C.L.: BR(K(L) --> pi(0) micro(+/-) e(-/+)) <7.6 x 10(-11); BR(K(L) --> pi(0)pi(0) micro(+/-) e(-/+)) <1.7 x 10(-10); BR(pi(0) --> micro(+/-) e(-/+)) <3.6 x 10(-10). This result represents a factor of 82 improvement in the branching ratio limit for K(L) --> pi(0) micro(+/-) e(-/+) and is the first reported limit for K(L) --> pi(0)pi(0) micro(+/-) e(-/+). 相似文献
988.
Fernando Silveira Denise Santos de Sá Zênis Novais da Rocha Maria do Carmo Martins Alves João Henrique Zimnoch dos Santos 《X射线光谱测定》2008,37(6):615-624
A series of metallocenes, namely, [Cp2ZrCl2], [(MeCp)2ZrCl2], [(nBuCp)2ZrCl2], [(iBuCp)2ZrCl2], [(tBuCp)2ZrCl2], [Et(Ind)2ZrCl2], [Et(IndH4)2ZrCl2], and [MeSi2(Ind)2ZrCl2)] were analyzed by extended x‐ray absorption fine structure (EXAFS) and x‐ray photoelectron spectroscopy (XPS). Complementary techniques, UV–vis spectroscopy and cyclic and differential pulse voltammetry, were employed to characterize the organometallic complexes. The catalysts were evaluated in ethylene polymerization, having methylaluminoxane (MAO) as the cocatalyst, and the resulting polymers were characterized by gel permeation chromatography. The structural and electronic effects caused by the coordination sphere around the metal center and their effects on the catalytic activity and polymer characteristics are discussed. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
989.
Fluidic lenses allow for varifocal optical elements, but current approaches are limited by the speed at which focal length can be changed. Here we demonstrate the use of a tunable acoustic gradient (TAG) index of refraction lens as a fast varifocal element. The optical power of the TAG lens varies continuously, allowing for rapid selection and modification of the effective focal length at time scales of 1 mus and shorter. The wavefront curvature applied to the incident light is experimentally quantified as a function of time, and single-frame imaging is demonstrated. Results indicate that the TAG lens can successfully be employed to perform high-rate imaging at multiple locations. 相似文献
990.
Alexandre A. Martins Mario J. Pinheiro 《International Journal of Theoretical Physics》2008,47(10):2706-2715
We address the problem of inertial property of matter through analysis of the motion of an extended charged particle. Our
approach is based on the continuity equation for momentum (Newton’s second law) taking due account of the vector potential
and its convective derivative. We obtain a development in terms of retarded potentials allowing an intuitive physical interpretation
of its main terms. The inertial property of matter is then discussed in terms of a kind of induction law related to the extended
charged particle’s own vector potential. Moreover, it is obtained a force term that represents a drag force acting on the
charged particle when in motion relatively to its own vector potential field lines. The time rate of variation of the particle’s
vector potential leads to the acceleration inertia reaction force, equivalent to the Schott term responsible for the source
of the radiation field. We also show that the velocity dependent term of the particle’s vector potential is connected with
the relativistic increase of mass with velocity and generates a longitudinal stress force that is the source of electric field
lines deformation. In the framework of classical electrodynamics, we have shown that the electron mass has possibly a complete
electromagnetic origin and the obtained covariant equation solves the “4/3 mass paradox” for a spherical charge distribution. 相似文献