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排序方式: 共有515条查询结果,搜索用时 15 毫秒
21.
Laura E. Muresan Adrian I. Cadis Ioana Perhaita Emil Indrea 《Central European Journal of Chemistry》2014,12(10):1023-1031
Yttrium silicate doped with cerium (Y2SiO5:Ce) was obtained from Y-Ce-Si based precursors prepared by the simultaneous addition of reagents (SimAdd) technique. The synthesis of the precursors was done in well controlled conditions using ammonium oxalate, ammonium carbonate or urea as precipitating agents. Results regarding the influence of precipitating agents on the morpho structural and photoluminescent characteristics of Y2SiO5:Ce are reported. The TG analysis in correlation with EGA, FT-IR and XRD investigations reveals the formation of oxalate, hydroxy-carbonate or hydroxy-nitrate based compounds, the same as the conversion of the precursors to well crystallized yttrium silicate. XRD patterns show that the precursors are amorphous except for the sample prepared with ammonium oxalate. Depending on the precipitation conditions, the phosphors phase composition varies from single phase (X2-Y2SiO5) to a mixture of phases (X2-Y2SiO5, X1-Y2SiO5, Y2O3). Under UV excitation, phosphors exhibit the specific blue emission of cerium with an intensity that varies from 175.8% (urea) to 96.0% (ammonium carbonate) and to 78.5% (ammonium oxalate). The emission intensity depends on the phase purity and order degree of the phosphors. PACS Classification codes:78.55 Hx, 81.20Fw 相似文献
22.
George Cosmin Nad Cristiana tefania Novac Ioana Adriana Matei Cosmina Maria Bouari Zoltan Miklos Gal Octavia Maria Tamas-Krumpe Adrian Maximilian Macri Nicodim Iosif Fi 《Molecules (Basel, Switzerland)》2021,26(8)
The conjunctival bacterial resident and opportunistic flora of dogs may represent a major source of dissemination of pathogens throughout the environment or to other animals and humans. Nevertheless, contamination with bacteria from external sources is common. In this context, the study of the antimicrobial resistance (AMR) pattern may represent an indicator of multidrug resistant (MDR) strains exchange. The present study was focused on a single predisposed breed—Saint Bernard. The evaluated animals were healthy, but about half had a history of ocular disease/treatment. The swabs collected from conjunctival sacs were evaluated by conventional microbiological cultivation and antimicrobial susceptibility testing (AST). The most prevalent Gram-positive was Staphylococcus spp.; regardless of the history, while Gram-negative was Pseudomonas spp.; exclusively from dogs with a history of ocular disease/treatment. Other identified genera were represented by Bacillus, Streptococcus, Trueperella, Aeromonas and Neisseria. The obtained results suggest a possible association between the presence of mixed flora and a history of ocular disease/treatment. A high AMR was generally observed (90%) in all isolates, especially for kanamycin, doxycycline, chloramphenicol and penicillin. MDR was recorded in Staphylococcus spp. and Pseudomonas spp. This result together with a well-known zoonotic potential may suggest an exchange of these strains within animal human populations and the environment. 相似文献
23.
Nicola Y. Edwards David M. Schnable Ioana R. Gearba-Dolocan Jenna L. Strubhar 《Molecules (Basel, Switzerland)》2021,26(1)
Lanthanide complexes have been developed and are reported herein. These complexes were derived from a terpyridine-functionalized calix[4]arene ligand, chelated with Tb3+ and Eu3+. Synthesis of these complexes was achieved in two steps from a calix[4]arene derivative: (1) amide coupling of a calix[4]arene bearing carboxylic acid functionalities and (2) metallation with a lanthanide triflate salt. The ligand and its complexes were characterized by NMR (1H and 13C), fluorescence and UV-vis spectroscopy as well as MS. The photophysical properties of these complexes were studied; high molar absorptivity values, modest quantum yields and luminescence lifetimes on the ms timescale were obtained. Anion binding results in a change in the photophysical properties of the complexes. The anion sensing ability of the Tb(III) complex was evaluated via visual detection, UV-vis and fluorescence studies. The sensor was found to be responsive towards a variety of anions, and large binding constants were obtained for the coordination of anions to the sensor. 相似文献
24.
JPC – Journal of Planar Chromatography – Modern TLC - Given the large applicability in both pharmaceutical and cosmetic field, this work was aimed at analytical (high-performance... 相似文献
25.
Raluca‐Ioana Stefan‐van Staden Alexandrina Moscalu‐Lungu Jacobus Frederick van Staden 《Electroanalysis》2020,32(1):178-184
Three stochastic sensors based on nanodiamond (nDP) paste modified with α, β, and γ‐cyclodextrin were designed and characterized for pattern recognition of aspartame, acesulfame K and sodium cyclamate in beverages, ketchup, and biological fluids. The linear concentration ranges obtained for acesulfame K (between 1.00×10?10 mol L?1and 1.00×10?3 mol L?1), for aspartame (between 1.00×10?12 mol L?1 and 1.00×10?3 mol L?1) and for sodium cyclamate (between 4.97×10?12 mol L?1 and 4.97×10?3 mol L?1) allow their assay in biological fluids, beverages and ketchup. The lowest limits of quantification were obtained using the stochastic sensor based on γ‐CD/nDP: for acesulfame K 1.00×10?10 mol L?1, for aspartame 1.00×10?12 mol L?1 and for sodium cyclamate 4.97×10?12 mol L?1. All three stochastic sensors revealed very high values of sensitivities. The proposed method was reliable for qualitative and quantitative assay of aspartame, acesulfame K and sodium cyclamate in beverages, ketchup, and in biological fluids such as urine. 相似文献
26.
Raluca Pele Gabriel Marc Anca Stana Ioana Ionu Cristina Nastas Brîndua Tiperciuc Ilioara Oniga Adrian Pîrnu Laurian Vlase Ovidiu Oniga 《Molecules (Basel, Switzerland)》2022,27(8)
Considering the important damage caused by the reactive oxygen (ROS) and nitrogen (RNS) species in the human organism, the need for new therapeutic agents, with superior efficacy to the known natural and synthetic antioxidants, is crucial. Quinazolin-4-ones are known for their wide range of biological activities, and phenolic compounds display an important antioxidant effect. Linking the two active pharmacophores may lead to an increase of the antioxidant activity. Therefore, we synthesized four series of new hybrid molecules bearing the quinazolin-4-one and phenol scaffolds. Their antioxidant potential was evaluated in vitro, considering different possible mechanisms of action: hydrogen atom transfer, ability to donate electrons and metal ions chelation. Theoretical quantum and thermodynamical calculations were also performed. Some compounds, especially the ortho diphenolic ones, exerted a stronger antioxidant effect than ascorbic acid and Trolox. 相似文献
27.
N. F. Bunkin N. V. Suyazov A. V. Shkirin P. S. Ignat’ev K. V. Indukaev 《Journal of Experimental and Theoretical Physics》2009,108(5):800-816
Experiments using phase-modulation interference microscopy and Mueller-matrix polarimetry show that double-distilled water free of foreign solid matter contains macroscopic light scatterers. Numerical calculations suggest that these scatterers can be represented as micrometer-size clusters of polydisperse air bubbles with effective radii between 70 and 90 nm. The fractal dimension of the clusters varies from 2.4 to 2.8, and their concentration is on the order of 106 cm?3. 相似文献
28.
A self-consistent set of equations describing the evolution of linear spherically symmetrical perturbations in the Friedmann
world is derived for an arbitrary equation of state. A singular part of perturbations corresponding to a massive particle-like
source is separated, an evolution equation for calculating the source mass is obtained and solved exactly. An exact solution
to evolution equations for perturbations at an arbitrary equation of state is constructed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–76, January, 2008. 相似文献
29.
N. F. Bunkin N. V. Suyazov A. V. Shkirin P. S. Ignat’ev K. V. Indukaev 《Physics of Wave Phenomena》2008,16(4):243-260
Experiments on modulation interference microscopy and measurement of light scattering matrix elements showed that double distilled
water purified from solid impurities contains macroscopic scatterers of optical radiation. It follows from numerical calculation
that these scatterers can be micrometer-scale clusters formed by polydisperse air bubbles with effective radii of 70 to 90
nm. The fractal dimension of such clusters is within 2.4–2.8 and their concentration is ∼ 106 cm−3. 相似文献
30.
When a single DNA molecule is stretched beyond its normal contour length, a force-induced melting transition is observed. Ethidium binding increases the DNA contour length, decreases the elongation upon melting, and increases the DNA melting force in a manner that is consistent with the ethidium-induced changes in duplex DNA stability known from thermal melting studies. The DNA stretching curves map out a phase diagram and critical point in the force-extension-ethidium concentration space. Intercalation occurs between alternate base pairs at low forces and between every base pair at high forces. 相似文献