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排序方式: 共有241条查询结果,搜索用时 46 毫秒
191.
Mustafa İlhan Mete Kaan Ekmekçi Abdullah Demir Halil Demirer 《Journal of fluorescence》2016,26(5):1637-1643
Undoped and PbNb2O6:Eu3+ (1.0 ≤ x ≤ 6.0 mol%) phosphors were synthesized at 1100 °C for 3.5 h by the conventional solid state reaction method. Synthesized PbNb2O6:Eu3+ phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed series of excitation peaks between 350 and 430 nm due to the 4f–4f transitions of Eu3+. For 395.0 nm excitation, emission spectra of Eu3+ doped samples were observed at 591 nm (orange) and 614 nm (red) due to the 5D0 → 7F1 transitions and 5D0 → 7F2 transitions, respectively. PL analysis results also showed that the emission intensity increased by increasing Eu3+ ion content. No concentration quenching effect was observed. The CIE chromaticity color coordinates (x,y) of the PbNb2O6:Eu3+ phosphors were found to be in the red region of the chromaticity diagram. 相似文献
192.
Volkan Eyupoglu Halil Ibrahim Turgut Recep Ali Kumbasar 《Journal of Dispersion Science and Technology》2018,39(6):802-813
The study was to determine selective removal and recovery of Cr(VI) from acidic media by solvent extraction (SX) using asymmetric imidazolium-based room temperature imidazolium bromide salts (ARTILs) as the extractants. The relevant parameters on the extraction and the stripping of Cr(VI) were investigated to identify optimum conditions. The optimum conditions were determined as equilibration time 5 minutes, acid concentration and type 0.5?mol/L H2SO4, stirring speed 1200?rpm, extractant concentration and type 0.5?mol/L ARTIL5, phase ratio 2.0 and stripping reagent type, and concentration 2.0?mol/L NH3. In optimum conditions, decyl substituted ARTIL was best in extraction process about 99.7% of extraction rate, whereas moderately hydrophobic pentyl substituted ARTIL was best in stripping process about 70.0% of stripping rate. Also, the optimized process was found as so selective toward Cr(VI) in the presence of the other metal ions with an environmental-friendly liquid–liquid–based SX method. 相似文献
193.
Cetin Bayrak Halil Senol Sedef Sirtbasi Ertan Sahin Abdullah Menzek 《Tetrahedron》2018,74(40):5839-5849
Reactions of benzyne with ester derivatives of spiro[2.4]hepta-4,6-dien-1-ylmethanol were performed. By rearrangement reaction of cyclopropyl methanol units of ((1s*,1′R*,2R*,4′S*)-1′,4′-dihydrospiro[cyclopropane-1,9'-[1,4]methanonaphthalen]-2-yl) methyl 3,5-dinitrobenzoate (13) and its isomer (14), corresponding allyl chlorides were obtained. Two rearrangement products were obtained from bromination of compound 13 with an equivalent amount of Br2. A naphthalene derivative including allyl and CHO moiety was formed for reactions from compounds with epoxide of 13 and 14 with NaN3 by sequential rearrangements. Formations of products are discussed. 相似文献
194.
The [2 + 2] cycloadditions of cyclopentyne and benzyne to ethylene are explored at the B3LYP and CASSCF levels, supplemented by CCSD(T) and CAS-MP2 calculations at the stationary points. The biradical path in the benzyne system is computed to be about 4.1 kcal/mol lower than the concerted path, consistent with the experimentally observed loss of original stereochemistry in this cycloaddition. However, computations fail to confirm the 99% stereoretention in the corresponding reaction of cyclopentyne. The concerted and biradical paths in the latter reaction are found to involve nearly isoenergetic barriers, thus predicting only about 75% stereoretention. More sophisticated theoretical methods seem to be needed to resolve the issue in the cyclopentyne system. 相似文献
195.
A new, simple and rapid spectrophotometric FI method for the accurate and precise determination of Hg(II) in pharmaceutical preparations has been developed. The method is based on the measuring the decrease of absorbance intensity of p-nitrobenzoxosulfamate (NBS) due to the complexation with Hg(II). The absorption peak of the NBS, which is decreased linearly by addition of Hg(II), occurs at 430 nm in 2×10−4 mol l−1 HNO3 as a carrier solution. Optimization of chemical and FI variables has been made. A micro column consisting of several packing materials applied instead of reaction coil was also investigated. A background level of Fe(III) maintained in reagent carrier solution with NBS was found useful for sensitivity and selectivity. Under the optimized conditions, the sampling rate was over 100 h−1, the calibration curve obtained were linear over the range 1-10 μg ml−1, the detection limit was lower than 0.2 μg ml−1 for a 20 μl injection volume, and the precision [Sr=1% at 2 μg ml−1 Hg(II) (n=10)] was found quite satisfactory. Application of the method to the analysis of Hg(II) in pharmaceutical preparations resulted a good agreement between the expected and found values. 相似文献
196.
Süheyla Özbey Engin Kendi Halil Hoşgören Mahmut Toğrul 《Journal of inclusion phenomena and macrocyclic chemistry》1998,30(1):79-87
The crystal structure of a new complex of a diaza-crown ether having two side arms has been determined from X-ray diffraction data. The compound crystallizes in space group P1 with cell dimensions a = 9.982(1), b = 10.685(1), c = 20.376(2)Å, = 81.09(1), = 80.92(1), = 88.43(1)0, Z = 2. The structure has been solved by direct methods and refined to the final R value of 0.053 for 3458 observed reflections and 424 parameters. The diaza-18-crown-6 ligand adopts an approximate D3d conformation. The Na+ ion is held inside the molecular cavity of this macroring ligand and a ClO-4 oxygen coordinates with Na+. The average Na–-O (18-crown-6) and Na–-N bond lengths are 2.426(4) and 2.786(5)Å, respectively; the Na–-O (ClO-4) bond length is 2.472(4)Å. The mean cavity radius is 1.10 Å and the NN nonbonding distance is 4.605(6)Å. 相似文献
197.
The Photolyase/Cryptochrome Family of Proteins as DNA Repair Enzymes and Transcriptional Repressors
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198.
Dilhan?M.?KalyonEmail author Halil?Gevgilili Rahmi?Yazici Albert?J.?Post Gregory?J.?McFann 《Rheologica Acta》2004,43(4):396-405
Many bar soaps are processed using continuous processing technologies, including single and twin screw extrusion. However, in spite of the industrial importance of the extrusion-based processing of bar soaps the rheological behavior of bar soaps is poorly understood. Here, the shear viscosity and the formation of gross surface irregularities upon extrusion of the bar soap were investigated using steady torsional, rectangular slit, and capillary flows. Furthermore, the structure development aspects were investigated using wide-angle X-ray diffraction and scanning electron microscopy. It is revealed that the flow and deformation behavior of bar soaps is complicated by the ubiquitous presence of wall slip, viscoplasticity, gross surface irregularities, and various structuring aspects. The orientation of crystallites and the shear stress dependent fracture of a crystalline component of the formulation at the wall during flow were identified as some of the contributing effects to the development of the structure of the bar soap during flow and deformation. 相似文献
199.
200.
Esmanur lhan Pelin Poan Danuta Kruk Miosz Wojciechowski Maciej Osuch Roksana Markiewicz Stefan Jurga Mecit Halil Oztop 《Molecules (Basel, Switzerland)》2022,27(7)
Starch-based confectionery products were prepared using different types of sugar. In addition to using different sugar, starch was replaced with soy protein isolate (SPI) in some of the products. 1H NMR spin-lattice relaxation experiments were performed for the collection of products in a broad frequency range from 4 KHz to 30 MHz to get insight into the influence of different sugar types and SPI on the dynamics of water in composite gel systems. The relaxation data have been decomposed into relaxation contributions associated with two different pools of water molecules characterized by different mobility. The translation dynamics of water molecules has been quantitatively described in terms of a dedicated relaxation model. The influence of the sample composition (the type of sugar and/or the presence of SPI) on the water mobility was thoroughly discussed. The results indicate that the addition of soy protein does not affect water dynamics for samples including sucrose. In addition, as the complementary measurements, physical properties of the products, such as the moisture content, water activity and texture, were investigated in terms of X-ray diffraction and thermogravimetric analysis. 相似文献