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81.
Erika Ribechini Manuel Bacchiocchi Thibaut Deviese Maria Perla Colombini 《Journal of Analytical and Applied Pyrolysis》2011,91(1):219-223
An analytical method based on pyrolysis in the presence of hexamethyldisilazane followed by gas chromatographic/mass spectrometric analysis, Py(HMDS)-GC/MS, was used for the first time to study birch bark tar, an adhesive that has been used since the Palaeolithic period. Py(HMDS)-GC/MS enabled us to obtain information simultaneously both on polymerised and solvent soluble fractions of birch bark tar. A very particular chromatographic pattern was obtained, which was mainly characterised by the presence of homologous series of linear saturated and unsaturated monocaboxylic fatty acids, and homologous series of straight-chain alkenes and alkanes. The pattern can be linked to suberin and suberan, which are known to be present in birch barks. In addition, lupane-type triterpenoids were also revealed. Py(HMDS)-GC/MS was initially applied to a reference material, and was then used to study the archaeological adhesives from a wooden spindle recovered in a Gallo-Roman burial (3rd century AD) and from the golden sheath of a Thracian dagger (8th-7th centuries BC) recovered in Belogradets (Bulgaria). 相似文献
82.
PbS quantum dots of average size 10 nm are encapsulated in a matrix (polyvinyl alcohol (PVA)) following chemical route. They are irradiated with 160 MeV Ni12+ ion beam with fluences 1012-1013 ions/cm2. Red shift in the absorption response in the optical absorption spectra reveal size enhancement of the quantum dots after irradiation and was confirmed by transmission electron microscopy (TEM). Photoluminescence (PL) study was carried out with excitation wavelength 325 nm on both unirradiated and irradiated samples at different fluences and fluence-dependent surface states and excitonic emission is observed in the PL study. The Huang-Rhys coupling constant decreases significantly after swift heavy ion (SHI) irradiation and shows a decreasing trend with increase in ion fluence. 相似文献
83.
Quantitative measurements of OH concentration fields by two-dimensional laser-induced fluorescence 总被引:1,自引:0,他引:1
A. Arnold R. Bombach B. Käppeli A. Schlegel 《Applied physics. B, Lasers and optics》1997,64(5):579-583
Received: 7 May 1996/Revised version: 21 October 1996 相似文献
84.
A. Lawitzki I. Plath W. Stricker J. Bittner U. Meier K. Kohse-Höinghaus 《Applied physics. B, Lasers and optics》1990,50(6):513-518
Temperature profiles in several premixed low pressure H2/O2/N2 flames and in an atmospheric pressure CH4/air flame were determined by laser-induced fluorescence (LIF) and by CARS experiments. In the LIF study, temperatures were derived from OH excitation spectra, CARS temperatures were deduced from N2
Q-branch spectra. The present study is the first quantitative comparison of these two methods for temperature determination in flames burning at pressures up to 1 bar. The resulting temperatures showed good agreement. 相似文献
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Vinyl polymerization of norbornene catalyzed by 2‐Py‐amidine Ni(II) complex/methylaluminoxane systems
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Yong‐Ping Niu Xiao‐Wei Wang Zhi‐Wu Zheng Xiao‐Fei Ma Jun‐Qing Cai Jun‐Kai Zhang Jin‐Lian Cheng 《应用有机金属化学》2014,28(9):688-695
Two 2‐Py‐amidine ligands (2‐Py―NH―C(Ph)═N―Ar, Ar = 2,6‐Me2C6H3 and 2,6‐iPr2C6H3) and the corresponding Ni(II) complexes ( 1 and 2 ) were synthesized and characterized using elemental analysis and FT‐IR, UV–visible, 1H NMR and 13C NMR spectroscopies. X‐ray crystal structures indicate that the chelate ring conformation of the less bulky complex 1 is relatively planar compared with that of the bulky complex 2 . Paramagnetic 1H NMR and 13C NMR studies show that, in solution, the time‐average structures of complexes 1 and 2 have mirror symmetry. Both complexes 1 and 2 were used as catalyst precursors for norbornene polymerization with methylaluminoxane as a co‐catalyst. The effects of Al/Ni ratio, temperature and structure of precursors on the catalytic performance were investigated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
88.
Prashant Kumar 《Journal of organometallic chemistry》2009,694(22):3643-3464
Ruthenium complexes [(η5-C5H5)Ru(κ1-P-PPh2Py)(PPh3)Cl] (1) and [(η5-C5H5)Ru(κ2-P-N-PPh2Py)(PPh3)]+ (1a) containing diphenyl-2-pyridylphosphine (PPh2Py) are reported. Coordinated PPh2Py in the complex [(η5-C5H5)Ru(κ1-P-PPh2Py)(PPh3)Cl] (1) exhibits monodentate behavior. In presence of NH4PF6 in methanol at room temperature it afforded chelated complex [(η5-C5H5)Ru(κ2-P,N-PPh2Py)(PPh3)]+ (1a). Further, 1 reacted with various species viz., CH3CN, NaCN, NH4SCN and NaN3 to afford cationic and neutral complexes [(η5-C5H5)Ru(κ1-P-PPh2Py)(PPh3)L]+ and [(η5-C5H5)Ru(κ1-P-PPh2Py)(PPh3)L] [L = CH3CN (1b); CN− (1c); N3− (1d) and SCN− (1e)] and it’s reaction with N,N-donor chelating ligands dimethylglyoxime (H2dmg) and 1,2-phenylenediamine (pda) gave cationic complexes [(η5-C5H5)Ru(κ1-P-PPh2Py)(κ2-N-N)]PF6 [κ2-N-N = dmg (1f) and pda (1g)]. The complexes 1-1g have been characterized by physicochemical techniques and crystal structures of 1, 1a, 1c, 1e and 1f have been determined by single crystal X-ray analyses. Catalytic potential of the complex 1 has been evaluated in water under aerobic conditions. It was observed that the complex 1 selectively catalyzes reduction of aldehyde into alcohol. 相似文献
89.
90.
The m/n = 2/1 neoclassical tearing modes are first observed in HL-2A low density, low beta plasma with central electron cyclotron resonance heating. The neoclassical tearing modes (NTMs) are triggered by a sawtooth crash with m/n = 1/1 precursors, which are toroidal coupled with a small scale m/n = 2/1 mode. The time history of the island width is compared with the prediction of the NTM theory, showing a good agreement between theory and experiment. 相似文献