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91.
Crude oil analysis has long been an inspiration for the development of analytical techniques. Especially mass spectrometry
has flourished as a result of the challenge these extremely complex problems offer. Here an overview of different analytical
methods is presented that shows different ways to analyze volatile and nonvolatile crude oil components. Focus has been placed
on the use of mass spectrometry and especially the new developments that have been introduced using the emerging technique
of Fourier transform ion cyclotron resonance mass spectrometry. These studies are examples of how far the development of analytical
methods has come for the task of studying such complex problems. 相似文献
92.
Kuno Schwrzer Saroj K. Rout Derya Bessinger Fabio Lima Cara E. Brocklehurst Konstantin Karaghiosoff Thomas Bein Paul Knochel 《Chemical science》2021,12(39):12993
We report the selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold using a Br/Mg-exchange, as well as regioselective magnesiations and zincations with TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl), followed by trapping reactions with various electrophiles. In addition, we report a fragmentation of the pyrazole ring, giving access to push–pull dyes with a proaromatic (1,3-dihydro-2H-imidazol-2-ylidene)malononitrile core. These functionalization methods were used in the synthesis of an isostere of the indolyl drug pruvanserin. Comparative assays between the original drug and the isostere showed that a substitution of the indole ring with a 1H-imidazo[1,2-b]pyrazole results in a significantly improved solubility in aqueous media.A methodology for the selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold has been developed and used in the synthesis of novel push–pull dyes and a non-classical isostere of the indolyl drug pruvanserin. 相似文献
93.
94.
Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy 总被引:1,自引:0,他引:1
P. Bala Srinivasan J. Liang C. Blawert M. Störmer W. Dietzel 《Applied Surface Science》2009,255(7):4212-4218
Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15 mA cm−2, 75 mA cm−2, and 150 mA cm−2 and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15 min treated coatings produced at higher current density levels were thicker, they showed poor corrosion resistance when compared to that of the coatings obtained at 15 mA cm−2. Short-term treatments (2 min and 5 min) at 150 mA cm−2 yielded coatings of thickness and corrosion resistance comparable to that of the low current density coatings. The superior corrosion resistance of the low thickness coatings is attributed to the better pore morphology and compactness of the layer. 相似文献
95.
We report theoretical results on the magnetic behavior of free standing nanowires of Ti. Four different structures of Ti nanowires-linear, ladder, dimerized, and zigzag-with nonmagnetic, ferromagnetic, and anti-ferromagnetic configurations were considered. Exploration of magnetism in these atomic chains leads to ferromagnetic behavior for all the structures: zigzag structure shows almost degenerate ferromagnetic and anti-ferromagnetic states though. The zigzag structure of Ti nanowires is favored of all for low values of nearest neighbor distances, whereas the dimerized structure is favored at larger atomic separations. Our work helps to resolve the controversy in the predicted ground state magnetic nature of zigzag chains of Ti as reported in recent previous works. The maximum value of magnetic moment (0.93 μB/atom) occurs in the ladder chains while the zigzag chains show the minimum value (0.17 μB/atom). Interestingly, all the structures in the magnetic configuration show metastable state except the dimerized structure. Ferromagnetic dimerized nanowires seem to be a potential candidate for use in spintronics. The projected density of states shows that dx2−y2 and dxy bands play a leading role in magnetism of linear and ladder structures, whereas there is no outstanding contribution from a particular d-orbital for zigzag and dimerized nanowires. The charge density plots suggest that linear and zigzag structures have metallic bonding whereas covalent bonding is predominant in the dimerized and ladder structures. The estimated diameters for the favored ferromagnetic configuration of these ultrathin nanowires lie in the range 1.9-3.4 Å and indicate the instability of the ladder structure, as also projected by the relative cohesive energy and relative break force values. 相似文献
96.
Vishnu Shanker Saroj L. Samal Gopal K. Pradhan Chandrabhas Narayana Ashok K. Ganguli 《Solid State Sciences》2009,11(2):562-569
Nanocrystalline NaNbO3 and NaTaO3 have been synthesized by the reverse micellar technique for the first time. The particle size of NaNbO3 was found to be 18 nm while that of NaTaO3 was found to be 40 nm (much smaller size than most of the earlier reports on NaTaO3). Rietveld refinement of X-ray diffraction data and Raman spectroscopy confirm that the nanoparticles of NaNbO3 and NaTaO3 have orthorhombically distorted structures with Pmc21 and Pbnm space groups, respectively. The dielectric constant at 25 °C of NaNbO3 and NaTaO3 was found to be 209 and 147 at 1 kHz, respectively. The antiferroelectric transition in NaNbO3 shifts to lower temperature (325 °C) in the nanocrystalline solid. 相似文献
97.
Manimaran B Lai LJ Thanasekaran P Wu JY Liao RT Tseng TW Liu YH Lee GH Peng SM Lu KL 《Inorganic chemistry》2006,45(20):8070-8077
Alkoxy- and thiolato-bridged Re(I) molecular rectangles [{(CO)3Re(mu-ER)2Re(CO)3}2(mu-bpy)2] (ER = SC4H9, 1a; SC8H17, 1b; OC4H9, 2a; OC12H25, 2b; bpy = 4,4'-bipyridine) exhibit strong interactions with several planar aromatic molecules. The nature of their binding was studied by spectral techniques and verified by X-ray diffraction analysis. Standard absorption and fluorescence titrations showed that a relatively strong 1:1 interaction occurs between aromatic guests such as pyrene and these rectangles. The results of a single-crystal X-ray diffraction analysis show that the recognition of 1 with a pyrene molecule is mainly due to CH...pi interactions and the face of the guest pyrene is located over the edges of the bpy linkers of 1. This is a fairly novel example of an interaction that is rarely designed into a host-guest pair. Furthermore, the interaction of 1 with Ag+ results in the self-organization of supramolecular arrays, as revealed by solid-state data. 相似文献
98.
Yun J. Lee Jason R. King Bala Chandra Chenna Samuel B. OwensJr. Jason L. Freeman Gary M. Gray Sadanandan E. Velu 《Journal of chemical crystallography》2009,39(12):902-907
Abstract
Details of the synthesis and crystal structure determination of (E)-2-(7-(3-(thiophen-2-yl)acrylamido)-2,3-dihydro-5-oxobenzo[e][1,4]oxazepin-1(5H)-yl)ethyl acetate are presented. The compound crystallizes in the triclinic P−1 space group (a = 8.3377(17), b = 9.792(2), c = 12.469(3) ?, α = 96.39(3)°, β = 108.50(3)°, γ = 97.68(3)°, V = 943.9(3) ?3, Z = 2). Interesting features of the structure include intermolecular hydrogen bonding between the amide proton on one molecule and the carbonyl oxygen of the dihydrooxazepinone ring on an adjacent molecule, the boat conformation of the dihydrooxazepinone ring, and π-π stacking between thiophene and phenyl rings on adjacent molecules with a distance between centroids of 3.79(2) ?. 相似文献99.
Hashmi S. A. Bhat Md Yasir Singh Manoj K. Sundaram N. T. Kalyana Raghupathy Bala P. C. Tanaka Hideaki 《Journal of Solid State Electrochemistry》2016,20(10):2817-2826
Journal of Solid State Electrochemistry - We report the studies on composite gel polymer electrolytes (GPEs) comprising 0.5 M solution of sodium trifluoromethane sulfonate (Na-triflate or... 相似文献
100.
Thomas S Paul SK Shandilya S Agarwal A Saxena N Awasthi AK Matta Hb Vir D Mathela CS 《The Analyst》2012,137(15):3571-3582
The present study describes the identification and characterization of two process impurities and major stress degradants in darifenacin hydrobromide using high performance liquid chromatography (HPLC) analysis. Forced degradation studies confirmed that the drug substance was stable under acidic, alkaline, aqueous hydrolysis, thermal and photolytic conditions and susceptible only to oxidative degradation. Impurities were identified using liquid chromatography coupled with ion trap mass spectrometry (LC-MS/MS(n)). Proposed structures were unambiguously confirmed by synthesis followed by characterization using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and elemental analysis (EA). Based on the spectroscopic, spectrometric and elemental analysis data, the unknown impurities were characterized as 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-2-oxo-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-A), 2-[1-(2-benzofuran-5-yl-ethyl)-pyrrolidin-3-yl]-2,2-diphenylacetamide (Imp-B), 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-ethyl]-1-oxy-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-C) and 2-{1-[2-(7-bromo-2,3-dihydrobenzofuran-5-yl)-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-D). Plausible mechanisms for the formation and control of these impurities have also been proposed. The method was validated as per regulatory guidelines to demonstrate specificity, sensitivity, linearity, precision, accuracy and the stability-indicating nature. Regression analysis showed a correlation coefficient value greater than 0.99 for darifenacin hydrobromide and its impurities. The accuracy of the method was established based on the recovery obtained between 86.6 and 106.7% for all impurities. 相似文献