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491.
Andrzej Wawer Iwona Wawer Boguslawa Piekarska-Bartoszewicz Andrzej Temeriusz 《光谱学快报》2013,46(6):1079-1090
Abstract The acidic properties of ureido NH protons in two new derivatives of methyl 3,4,6-triacetyl-2-deoxy-β-D-glucopyranoside and i-butylamine (1) and L-leucine (2) were studied by 1H NMR. Stronger influence of polar aprotic solvents, more effective interaction with nitroxyl radical and faster H/D exchange indicate that N1'-H proton which is proximate to the glucopyranose ring is more acidic than N3'-H one in both ureido sugars, this conclusion was supported by semi-empirical AM1 calculation. Hydrogen to deuterium exchange rates are 1.2 x 10?2 to 5.5x 10?3 M?1 min?l. Significantly slower exchange of N3'-H proton standing by Leu residue in 2 can be explained by the existence of internal H-bonds. 相似文献
492.
Grażyna Janowska Agnieszka Kucharska-Jastrząbek Przemysław Rybiński Dorota Wesołek Iwona Wójcik 《Journal of Thermal Analysis and Calorimetry》2010,102(3):1043-1049
This paper presents the results of testing the flammability and fire hazard of butadiene (BR), butadiene-acrylonitrile (NBR)
and butadiene- styrene (SBR) rubbers with the use of oxygen index test, ignition temperature measurement, cone calorimetry
and inverse liquid chromatography. Toxicometric indices, RTFH CO/CO2, WLC50SM and the concentration of polycyclic aromatic hydrocarbons (PAH) have been determined. The results obtained have been interpreted
from the point of view of the chemical constitution of the polymers tested. 相似文献
493.
Tin(II/IV) phosphate was prepared by various synthetic methods. The different methods resulted in tin phosphate with different
properties, i.e., different crystalline form and behaviour during thermal treatment. The prepared materials have 3 mol water
of crystallisation, which they lose in different ways. Total mass loss was between 20 and 30%. This could be connected with
water loss, going generally in two steps in parallel with endothermic processes. At the end of thermal treatment, tin pyrophosphate
is obtained, irrespective of the method of preparation used. 相似文献
494.
Iwona Binkowska Włodzimierz Gałęzowski Arnold Jarczewski 《Central European Journal of Chemistry》2010,8(3):582-586
Proton transfer reactions rates between carbon acids 1-nitro-1-(4-nitrophenyl)ethane (NPNE), 2-methyl-1-nitro-1-(4-nitrophenyl)propane
(MNPNP)) and phosphazenes (BEMP, BTPP, P1-t-Oct) in tetrahydrofuran have been measured, and the activation parameters were determined. The results are compared with
those previously obtained for P1-t-Bu phosphazene, guanidines and amidines.
相似文献
495.
Weak convergence of products of sums of independent and non-identically distributed random variables
Przemys?aw Matu?a Iwona St?pień 《Journal of Mathematical Analysis and Applications》2009,353(1):49-54
We study limit properties in the sense of weak convergence in the space D[0,1] of certain processes based on products of sums of independent and non-identically distributed random variables. The obtained results extend and generalize results known in the i.i.d. case. 相似文献
496.
Magdalena Śliwka‐Kaszyńska Katarzyna Jaszcołt Iwona Anusiewicz 《Journal of separation science》2009,32(18):3107-3115
Four novel 1,3‐alternate calix[4]arene‐bonded silica gel stationary phases possessing different aromatic and aliphatic substituents at the upper rim (CalixNph, CalixBph, CalixHex, and CalixDdc) were prepared and structurally characterized. The comparison and selectivity of these phases were done by using alkylbenzenes, fatty acid p‐bromophenacyl esters, aromatic positional isomers, and polynuclear aromatic hydrocarbons as analytes. Quantum chemistry calculations have also been performed (using an ab initio method) to support the experimental findings. The effect of the type and content of organic modifier on the retention and selectivity of the alkylbenzenes was studied. The retention mechanism is also discussed. The results indicate that the stationary phases behave like RP packings. However, inclusion complex formation and hydrophobic and π–π interactions seem to be involved in the separation process. 相似文献
497.
Phase equilibria established in the PbO - BiVO4 system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed
using DTA and XRD.
相似文献
498.
Marta Bobrowska Janusz Typek Grzegorz Zolnierkiewicz Kamil Wardal Niko Guskos Iwona Pelech Marcin Podsiadly Urszula Narkiewicz 《Central European Journal of Chemistry》2012,10(6):1963-1968
Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of nanocrystalline nickel by ethylene (C2H4) and methane (CH4). Hydrocarbons decomposition on nickel nanoparticles was done at temperatures 500, 600 and 700°C. Magnetic resonance spectra of samples designated as CH4/500, CH4/600, CH4/700, C2H4/500, C2H4/600 and C2H4/700 were obtained by Bruker E 500 spectrometer. The integrated intensities of the resonance spectra were correlated with the carburization conditions (temperature, type of hydrocarbon) during samples preparation. A core-shell model of the investigated samples allowed rough estimation of appropriate shell sizes. 相似文献
499.
Joanna Kowalska Iwona Giska Łukasz Jedynak Beata Krasnodębska‐Ostręga Joanna Pałdyna Monika Sadowska Jerzy Golimowski 《Electroanalysis》2012,24(5):1109-1113
Voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices after thorough mineralization. In the presented work, voltammetric methods were used as reference methods in the preparation process of control plant material. Determination of As, Pt, Tl and other elements (Cd, Cu, Pb, Zn) in plant material prepared in our laboratory is described. For quantitative determination of the elements two independent analytical methods were applied. To obtain plant material containing As, Pt and Tl white mustard (Sinapis alba L.) was hydroponically cultivated under controlled conditions in a nutrient solution with addition of As, Pt and Tl salts. 相似文献
500.
Prochowicz D Justyniak I Kornowicz A Kaczorowski T Kaszkur Z Lewiński J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(24):7367-7371
The polymer network: The reaction of quinine (QN) with CuI under solvothermal, as well as liquid-assisted grinding, conditions afforded a unique 1D homochiral coordination polymer {[Cu(4)(μ(3)-I)(4)(QN)(2)][Cu(3)(μ(3)-I)(2)(μ(2)-I)(QN)(2)](2)}(n), containing both triangular Cu(3)I(3) and cubane Cu(4)I(4) clusters as connecting nodes (see scheme). Van der Waals interactions between the adjacent 1D polymer chains lead to an extended quasi-honeycomb homochiral pillared 3D network with solvent-free 1D channels. 相似文献