排序方式: 共有102条查询结果,搜索用时 15 毫秒
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52.
Mir Ali Farajzadeh Shirin Ghochi Eskandar Ali Ranji Elham Feyz 《Mikrochimica acta》2007,159(3-4):363-369
A high performance liquid chromatography (HPLC) method is presented for the determination of Chimassorb 944 in polymeric matrix.
A reversed phase column octadecyl silane (ODS) is used as a stationary phase. As a mobile phase, a mixture of THF:methanol:triethanol
amine (90:10:1.5) (v:v:w) is used. The HPLC system was equipped with an UV detector and the absorbance of the analyte was
recorded at 240 nm. In the case of polymers, 0.5 g of them along with 100 mg Irganox 1010 (for preventing oxidation of Chimassorb
944) were dissolved in boiling xylene, and then extracted with sulfuric acid 1 M four times. The extract was neutralized with
sodium hydroxide solution and the analyte was re-extracted into carbon tetrachloride and then injected to the HPLC system.
This method is an accurate and relatively fast technique for determination of Chimassorb 944 in polymers. 相似文献
53.
Addison N. Desnoyer Weiying He Shirin Behyan Weiling Chiu Jennifer A. Love Pierre Kennepohl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5259-5268
The electronic nature of Ni π-complexes is underexplored even though these complexes have been widely postulated as intermediates in organometallic chemistry. Herein, the geometric and electronic structure of a series of nickel π-complexes, Ni(dtbpe)(X) (dtbpe=1,2-bis(di-tert-butyl)phosphinoethane; X=alkene or carbonyl containing π-ligands), is probed using a combination of 31P NMR, Ni K-edge XAS, Ni Kβ XES, and DFT calculations. These complexes are best described as square planar d10 complexes with π-backbonding acting as the dominant contributor to M−L bonding to the π-ligand. The degree of backbonding correlates with 2JPP from NMR and the energy of the Ni 1s→4pz pre-edge in the Ni K-edge XAS data, and is determined by the energy of the π*ip ligand acceptor orbital. Thus, unactivated olefinic ligands tend to be poor π-acids whereas ketones, aldehydes, and esters allow for greater backbonding. However, backbonding is still significant even in cases in which metal contributions are minor. In such cases, backbonding is dominated by charge donation from the diphosphine, which allows for strong backdonation, although the metal centre retains a formal d10 electronic configuration. This ligand-induced backbonding can be formally described as a 3-centre-4-electron (3c-4e) interaction, in which the nickel centre mediates charge transfer from the phosphine σ-donors to the π*ip ligand acceptor orbital. The implications of this bonding motif are described with respect to both structure and reactivity. 相似文献
54.
N. F. Zobov R. I. Ovsyannikov S. V. Shirin O. L. Polyansky 《Optics and Spectroscopy》2007,102(3):348-353
Quantum numbers have been assigned in the theoretical spectra of three isotopologues of the water molecule: H2 16O, H2 17O, and H2 18O. The spectra were calculated by variational methods in the region 0–26000 cm?1 at a temperature of 296 K. For each molecule, the quantum numbers are assigned to more than 28000 levels. The quantum numbers are assigned to 216766, 210679, and 211073 spectral lines of the H2 16O, H2 17O, H2 18O molecules, respectively. The theoretical spectra with the assigned quantum numbers are available in the Internet. 相似文献
55.
Shirin Shayegh Hojjat Amrollahi Bioki Mahmood Borhani Zarandi Narjes Kabiri Samani Alireza Rahnamanic 《Polymer Science Series B》2017,59(5):616-623
Hybrid polyaniline based composites incorporating zinc sulfide nanoparticles have been synthesized by using chemical oxidation technique. Morphological and optical properties of the nanocomposite were characterized by scanning electron microscopy, Fourier transform infrared and UV–Vis spectroscopy measurement. The results were compared with pure polyaniline. The characteristic FTIR peaks of polyaniline were found to shift to lower wave-number in nanocomposite. The band gap of nanocomposites increases and the refractive index of the nanocomposites decreases with increasing content of ZnS nanoparticles. These results showed the interaction between ZnS nanoparticles and polyaniline. 相似文献
56.
Maksyutenko P Muenter JS Zobov NF Shirin SV Polyansky OL Rizzo TR Boyarkin OV 《The Journal of chemical physics》2007,126(24):241101
We report here the measurements of rovibrational levels in the electronic ground state of water molecule at the previously inaccessible energies above 26,000 cm(-1). The use of laser double-resonance overtone excitation extends this limit to 34,200 cm(-1), which corresponds to 83% of the water dissociation energy. We use experimental data to generate a semiempirical potential energy surface that now allows prediction of water levels with sub-cm(-1) accuracy at any energy up to the new limit. 相似文献
57.
Polypropylene (PP)/polyamide6 (PA6)/ethylene propylene diene monomer (EPDM) (70/15/15) ternary polymer blends compatibilized with maleic‐anhydride‐grafted EPDM (EPDM‐g‐MA) were prepared by melt blending using a twin‐screw extruder (TSE) in different processing conditions (barrel temperature profile, screw speed, and mixing sequence). The microstructures of prepared ternary blends were studied and compared to the predictions of spreading coefficient, minimum relative interfacial energy (RIE), and dynamic interfacial energy phenomenological models. The observed morphologies were somehow different from the model predictions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
58.
Shirin Fanaian Nodar Al-Manasir Kaizheng Zhu Anna-Lena Kj?niksen Bo Nystr?m 《Colloid and polymer science》2012,290(16):1609-1616
Effects of some sodium salts (NaCl, NaClO3, and NaSCN) in the Hofmeister series on deswelling and temperature-induced aggregation behavior of microgels of poly(N-isopropylacrylamide) (PNIPAAM) and PNIPAAM-co-PAA with attached poly(acrylic acid) moieties were investigated with the aid of turbidimetry and dynamic light scattering. Addition of salt in the concentration range 0.1–0.5?M generated aggregation of the PNIPAAM microgel particles at elevated temperatures, but it was no distinct difference between chaotropic and kosmotropic anions. In contrast, the flocculation behavior at high temperatures for PNIPAAM-co-PAA revealed a prominent influence of salinity and type of anion on the formation of aggregates. The aggregation transition was shifted to the highest temperature for the most chaotropic anion (SCN?), and the aggregation transition at the same salt concentration is consistent with the typical Hofmeister series. The turbidity results from the PNIPAAM-co-PAA microgels disclosed a two-step transition for the considered anions, and both a low and high temperature change in the turbidity data was observed. The high-temperature transition followed the Hofmeister series. 相似文献
59.
S Safaei I Mohammadpoor-Baltork AR Khosropour M Moghadam S Tangestaninejad V Mirkhani 《Molecular diversity》2012,16(3):591-600
A variety of pyrazolo[3,4-d]pyrimidine-6(7H)-thione derivatives were easily synthesized with a novel, simple, efficient, and regioselective method via three-component condensation reaction of 5-methyl-1H-pyrazol-3-amine, arylisothiocyanates, and aldehydes in the presence of catalytic amount of p-toluenesulfonic acid (p-TSA) in 1-butyl-3-methylimidazolium bromide ionic liquid with excellent yields and short reaction times. 相似文献
60.
Mohammad Hossein Tavakoli Talaye Arjmand Abasi Shirin Omid Ebrahim Mohammadi‐Manesh 《Crystal Research and Technology》2013,48(2):58-68
In this paper, for an inductively heated Czochralski furnace used to grow sapphire single crystal, influence of the inner (wall‐to‐wall) and crystal internal (bulk) radiation on the characteristics of the growth process such as temperature and flow fields, structure of heat transfer and crystal‐melt interface has been studied numerically using the 2D quasi‐steady state finite element method. The obtained results of global analysis demonstrate a strong dependence of thermal field, heat transport structure and crystal‐melt interface on both types of radiative heat transfer within the growth furnace. 相似文献