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排序方式: 共有155条查询结果,搜索用时 31 毫秒
1.
In this paper, by using elementary analysis, we establish some new Lyapunov-type inequalities for nonlinear systems of differential equations, special cases of which contain the well-known equations such as Emden-Fowler-type and half-linear equations. The inequalities obtained here can be used as handy tools in the study of qualitative behaviour of solutions of the associated equations. 相似文献
2.
The Manganese(III)-based regioselective α′-keto radical generation of unsaturated ketones is a versatile synthetic procedure with broad applicability. The generated α′-keto radical slowly creates a metal enolate in a solvent at reflux. The resultant metal enolate affords the corresponding α′-allylated α,β-unsaturated ketones in good yields. This method is the first example of the metal mediated regioselective α′-allylation of α,β-unsaturated ketones. The ketones that have α or β-alkoxy groups also work efficiently. 相似文献
3.
A new Schiff base, N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane, has been synthesized for the very sensitive
determination of iron(III) and iron(II) in natural water samples. It enabled a very selective and rapid method for iron determination
to be developed. The method has also been applied to total iron determination in sediment samples. In the preconcentration
system, the Schiff base reagent is mixed with the samples and chelates containing iron(III). The complexes are then adsorbed
on silica gel within a column system. Elution of the adsorbed chelate from the silica gel was performed with a small volume
of acetone containing 2.5% nitric acid. The iron is measured off-line by flame atomic absorption spectrometry. The method
can be applied to the preconcentration, separation and speciation of iron. The effects of parameters such as pH, sample flow
rate, eluent flow rate, foreign ions and ligand concentration have been investigated. The effect of humic acid that can produce
complexes with metal ions in natural systems has also been investigated. The results obtained indicate that the method is
not affected by the presence of up to 10 ppm humic acid, which would be a very high concentration to be present in natural
systems. The solid phase extraction method developed has been applied to the determination of iron in both natural water samples
and sediment samples. The LOD was found to be 0.17 mg L−1 when no preconcentration was used, although preconcentration factors of 100 could be achieved. The recovery values for spiked
samples were between 100 and 104%. The results were compared statistically with those from the standard 1,10 phenanthroline
method used for iron speciation in water systems. A Student’s t-test indicated no significant difference between the two methods. In addition, this method was applied to the analysis of
a certified sediment sample, LGC 6156. Generally, a 10-fold preconcentration factor was required for the analysis of natural
water samples. 相似文献
4.
Emel Önal Cheng Zhang Derya Davarcı Ümit İşci Guillaume Pilet Andrew K. Whittaker Fabienne Dumoulin 《Tetrahedron letters》2018,59(6):521-523
A cyclotriphosphazene substituted with six 3,5-bis(trifluoromethyl) benzyloxy units was designed as a novel 19F MRI contrast agent. The resulting molecule has 36 magnetically equivalent fluorine atoms and exhibited suitable MRI properties with high imaging sensitivity, confirming the proof-of-concept as a convenient scaffold for the production of new 19F MRI contrasts agents. 相似文献
5.
6.
7.
We construct a representation of the infinite dimensional complex Clifford algebra on the Hilbert space of square-integrable
complex-valued functions on the Cantor set, which we show to be equivalent to the classical Fock representation. 相似文献
8.
Nazl Turan Yücel Ümmühan Kandemir Ümide Demir
zkay
zgür Devrim Can 《Molecules (Basel, Switzerland)》2021,26(11)
Vortioxetine is a multimodal antidepressant drug that affects several brain neurochemicals and has the potential to induce various pharmacological effects on the central nervous system. Therefore, we investigated the centrally mediated analgesic efficacy of this drug and the mechanisms underlying this effect. Analgesic activity of vortioxetine (5, 10 and 20 mg/kg, p.o.) was examined by tail-clip, tail-immersion and hot-plate tests. Motor performance of animals was evaluated using Rota-rod device. Time course measurements (30–180 min) showed that vortioxetine (10 and 20 mg/kg) administrations significantly increased the response latency, percent maximum possible effect and area under the curve values in all of the nociceptive tests. These data pointed out the analgesic effect of vortioxetine on central pathways carrying acute thermal and mechanical nociceptive stimuli. Vortioxetine did not alter the motor coordination of mice indicating that the analgesic activity of this drug was specific. In mechanistic studies, pre-treatments with p-chlorophenylalanine (serotonin-synthesis inhibitor), NAN-190 (serotonin 5-HT1A receptor antagonist), α-methyl-para-tyrosine (catecholamine-synthesis inhibitor), phentolamine (non-selective α-adrenoceptor blocker), and naloxone (non-selective opioid receptor blocker) antagonised the vortioxetine-induced analgesia. Obtained findings indicated that vortioxetine-induced analgesia is mediated by 5-HT1A serotonergic, α-adrenergic and opioidergic receptors, and contributions of central serotonergic and catecholaminergic neurotransmissions are critical for this effect. 相似文献
9.
Avcıbaşı Uğur Türkyarar Taner Karadağ Ayşegül Bakan Buket Yavaşoğlu Nefise Ülkü Karabay Kuşat Kevser Akgöl Sinan Gülcemal Derya Tekin Volkan Müftüler Fazilet Zümrüt Biber Topal Gökcen Parlak Yasemin Gümüşer Fikriye Gül 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):511-525
Journal of Radioanalytical and Nuclear Chemistry - The aim of this study is the synthesis of a novel 99mTc-labeld graft polymer and the biological evaluation of its in vitro and in vivo properties.... 相似文献
10.
Derya Tarinc Burcu Dogan-Topal Aysegul Golcu Sibel A. Ozkan 《Journal of Analytical Chemistry》2014,69(9):899-908
A voltammetric study of the oxidation of Ceftazidime (CEFT) has been carried out at the glassy carbon electrode by cyclic, differential pulse (DPV) and square wave (SWV) voltammetry. The oxidation of CEFT was irreversible and exhibited diffusion controlled process depending on pH. The oxidation mechanism was proposed and discussed. According to the linear relationship between the peak current and concentration, DPV and SWV voltammetric methods for CEFT assay in pharmaceutical dosage forms and human urine were developed. For analytical purposes, a well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H2SO4 at 1.00 and 1.02 V for differential pulse and square wave voltammetric techniques, respectively. The linear response was obtained within the range of 4 × 10?6?8 × 10?5 M with a detection limit of 6 × 10?7 M for differential pulse and 4 × 10?6–2 × 10?4 M with a detection limit of 1 × 10?6 M for square wave voltammetric technique. The determination of CEFT in 0.1 M H2SO4 was possible over the 2 × 10?6–1 × 10?4 M range in urine sample for both techniques. The standard addition method was used for the recovery studies. 相似文献