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1.
The fluorescence lifetime of Nile Red (NR) is not sensitive to dielectric solvent–solute interactions but markedly decreases with the increase of the hydrogen bond donating ability in alcohols because vibrations associated with hydrogen bonding are involved in the deactivation process. The negligible viscosity effect indicates that twisting of the diethylamino moiety of NR does not play significant role in the dissipation of the excitation energy. 相似文献
2.
Szöllosi G Bucsi I Cserényi S Bartók M 《Rapid communications in mass spectrometry : RCM》2005,19(24):3743-3748
We have studied the adsorption on a platinum (Pt) catalyst of two compounds utilizable as a chiral basic catalyst and a chiral modifier, dihydrocinchonidine (DHCD), and a new cinchona alkaloid derivative containing a bulky group, the Ph3SiO-DHCD molecule. The method of choice was the detection by electrospray ionization (ESI) ion-trap tandem mass spectrometry (MS/MS) of hydrogen/deuterium (H/D) exchange at room temperature, in tetrahydrofuran, at a D2 pressure of 1 bar. Based on the ESI-MS/MS spectrum of the new compound, we propose a mechanism for the formation of the silatropylium cation containing a Si-O bond. From the fragmentation pattern of Ph3SiO-DHCD it was confirmed that ESI-ion-trap MS/MS can be used to study the adsorption processes of complicated carbon compounds by investigating their H/D exchange reactions. In the case of Ph3SiO-DHCD, the results demonstrate that H/D exchange takes place mainly on the quinoline skeleton. However, the strong pi-bonded adsorption of the quinoline skeleton parallel with the imaginary plane of Pt is not preferred because the bulky Ph3Si group inhibits the multiple pi-bonded adsorption of the Ph3SiO-DHCD. Because of this hindrance the molecule was adsorbed tilted via the nonbonding electron pair of the N atom and C2' atom of the quinoline skeleton; consequently, mainly alkaloid-d1 and alkaloid-d2 are formed. 相似文献
3.
J.?MajumdarEmail author F.?Cser M.?C.?Jollands R.?A.?Shanks 《Journal of Thermal Analysis and Calorimetry》2004,78(3):849-863
Differential scanning calorimetry has been used to study the heat flow during melting and crystallisation of a range of polypropylene post-consumer waste (PP PCW) grades and blends. The heat flow curves and the heat capacity curves indicated that the PP PCW grades and blends contained contaminants even after manual sorting and a cleaning process. The enthalpies of the PP PCW grades were lower than that for the virgin grades, as a result of degradation. Small amounts of polymeric contaminants (up to 10%) did not affect the enthalpies of PP PCW although other contaminants may have had some effect. The enthalpies of the PCW blends could in general be predicted by a linear additive rule, which is of importance for recycling a variety of PP PCW products.The authors would like to thank Dr. M. Killen (Basell Australia Pty. Ltd.), Mr. P. Slaven (Citiwide MRF), Dasma Valley Waste Prop. Ltd. and Mr. I. Janetzki (Huhtamaki Australia Ltd.) for supplying materials for this project. Financial support for the project was provided by Basell Australia and Ecorecycle Victoria, Australia. 相似文献
4.
Annealing experiments have been carried out at a few degrees below the melting point of different polyethylenes (LDPE, LLDPE,
HDPE), of polypropylene (PP) and of Nylon-6. The heat capacities decrease during the annealing, within a 2-4 min time scale,
to a lower value which corresponds to the extrapolated heat capacity values obtained for the cooling cycle when the polymer
is cooled from the melt. Heat capacities in the heating cycle following the cooling cycle of PP, Nylon-6 and HDPE have the
same value as during the cooling section. This is not the case for LDPE and LLDPE.
Exothermic total heat flow in the cooling section following the annealing indicates that the crystallisation takes place during
the cooling rather than during the annealing period. The total melting enthalpy measured before and after the annealing cycle
is the same.
The reversing heat flow shows an excellent fit to the change of the crystallinity measured by small angle scattering of synchrotron
radiation during a heating cycle at temperatures below the melting peak.
A coupled thermodynamic interaction of the crystalline and the amorphous phases is concluded from this study. This kind of
interaction is possible at the lateral end of polymeric chains incorporated into the crystalline phase. This is an indication
of the portion of tie molecules in the system, i.e. the portion of fringed micelle type of crystalline morphology with respect
to that of folded chain lamellae.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Annealing experiments have been carried out just below the melting temperature of both polyethylene (LLDPE) and polypropylene
(PP) and their blends. The total melting enthalpy measured after the annealing cycle was greater by 10-15% with respect to
the value having been measured before it. During the annealing period the heat capacity decreases to a lower value within
the first 2-3 min. Heat capacities of PP (either in pure form or in the blends) measured during the heating cycle following
the annealing cycle have the same value as during the cooling section. The heat capacities of the LLDPE in the heating cycle
following the annealing were those of the preceding heating cycle. The total heat flows in the cooling section following the
annealing cycle were greater than those in another cooling cycle at the same temperatures indicating that the crystallisation
takes place during the cooling rather than during the annealing periods.
The presence of LLDPE decreases the crystallisation temperature of PP. The presence of SEBS in the blend results in a greater
crystallisation temperature than that of pure PP. The crystallisation temperature of LLDPE increases with increasing levels
of PP.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Szabolcs Cserényi Imre Bucsi Károly Felf?ldi 《Reaction Kinetics and Catalysis Letters》2006,87(2):395-403
Summary The enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied on Pt-alumina catalysts modified by C3-substituted
cinchonidines (NC, A, B, C1, C2in Fig. 1) and for comparison by DHCDand MeO-DHCDin AcOH. The effect of the C3-substituent on the reaction rate and the enantioselectivity were examined. Using the Engelhard
4759 catalyst under mild experimental conditions (room temperature, hydrogen pressure 1 bar) such as DHCDthe (R)-ethyl lactate formed in excess (e.e.max: 79-91%)</o:p> 相似文献
7.
Different grades of linear low density polyethylenes (LLDPEs) have been quenched cooled step-wise and crystallised isothermally
at (a series of increasing) temperatures in a DSC (thermal fractionated samples). These samples have been investigated by
temperature modulated DSC (MDSC). The heat flow curves of the thermal fractionated materials were compared with those obtained
from samples crystallised at a relatively slow cooling rate of 2 K min-1(standard samples).
The melting enthalpy obtained from the total heat flow of the thermal fractionated samples was 0-10 J g-1higher than those of standard samples. The melting enthalpy obtained from the reversing heat flows was 13-31 J g-1lower in the thermal fractionated samples than in the standard samples. The ratio of the reversing melting enthalpy to the
total melting enthalpy increased with decreasing density of the PE. The melting temperature of the endotherms formed by the
step-wise cooling was 9 K higher than the crystallisation temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Imre Bucsi Szabolcs Cserényi Károly Felf?ldi Mihály Bartók 《Reaction Kinetics and Catalysis Letters》2006,87(2):281-289
Summary We synthesized C9-O-silyl ethers of cinchonidine and dihydrocinchonidine (1-8), seven of which have not been known before. The structures of the compounds were verified by ESI-ion-trap MS and 1H-NMR. Fragmentation of silyl ethers containing Si-phenyl bonds was studied for the first time. The compounds obtained will
be utilized as chiral catalysts of certain asymmetric syntheses.</o:p> 相似文献
9.
N-acryloyl piperidine (AP) was copolymerized with mesogenic monomers [such as cholesteryl acrylate (CA) and phenyl-p-acryloyloxy benzoate (PAB)] in isotropic solution using radical initiation (AAP = 1.1, rCA = 0.16, and rAP = 0.81, rPAB = 0.16. The copolymers are anisotropic having minimum values of transition and clearing points with composition. The composition corresponding to the minimum is a boundary between two structures as indicated by wide-angle X-ray scattering. Distribution of the gyration radii determined by GPC in tetrahydrofuran is identical to that of solid polymers measured by small-angle X-ray scattering, except that the average value of the latter is about 10?6 cm less than that of the former. It was established that AP as a non-mesogenic comonomer did not suppress the mesomorphism of the copolymer and in fact formed mesomorphic homopolymers. In the solid polymer, the macromolecule which is anisotropic in geometry was found to form the structural unit having a minimum of the melting and clearing point with composition, as for a eutectic system. 相似文献
10.
We demonstrate that neutron holography permits us to extend the determination of atomic positions beyond nearest neighbors at least up to the fourth neighboring shell around cadmium probe atoms alloyed into a lead crystal. The accuracy achieved is sufficient to allow quantitative determination of displacements of atoms due to elastic distortions induced by impurity atoms. The atomic positions derived from the holographic data are in good agreement with those expected theoretically due to Friedel oscillations in this system. In addition, the atomic positions are in qualitative agreement with results obtained in an independent experiment studying the diffuse distortion scattering around Bragg peaks. 相似文献