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61.
Treatment of tosylates with aqueous dimethylformamide furnish mainly formates 相似文献
62.
A strategy is described for the synthesis of β-(1,3)-GlcA-GlcNAc dimeric and tetrameric glycoclusters through the conjugation of disaccharide groups onto a diaminodiamide aromatic scaffold by reductive amination. 相似文献
63.
Summary. The use of mixed finite element methods is well-established in the numerical approximation of the problem of nearly incompressible
elasticity, and its limit, Stokes flow. The question of stability over curved elements for such methods is of particular significance
in the p version, where, since the element size remains fixed, exact representation of the curved boundary by (large) elements is
often used. We identify a mixed element which we show to be optimally stable in both p and h refinement over curvilinear meshes. We prove optimal p version (up to ) and h version (p = 2, 3) convergence for our element, and illustrate its optimality through numerical experiments.
Received August 25, 1998 / Revised version received February 16, 1999 / Published online April 20, 2000 –? Springer-Verlag
2000 相似文献
64.
Caputo R Garroni S Olid D Teixidor F Suriñach S Baró MD 《Physical chemistry chemical physics : PCCP》2010,12(45):15093-15100
We synthesized Na(2)[B(12)H(12)] by a solid state procedure and thermal decomposition of Na[B(3)H(8)], and calculated from a first-principles approach the thermodynamic and structural properties. In particular, the calculated enthalpy of formation of the monoclinic structure, at T = 0 K, of -1086.196 kJ mol(-1) showed that it is a very stable compound. Therefore, in case it were formed during the thermal decomposition of NaBH(4), it would be rather considered a product, which, in addition, prevents the subsequent re-hydrogenation process because of its low reactivity to hydrogen. We reported the isotherms of absorption of H(2), O(2), and H(2)O, calculated both theoretically and experimentally. 相似文献
65.
M. L. Shah R. C. Das P. K. Mandal D. R. Rathod Vas Dev K. G. Manohar B. M. Suri 《Pramana》2010,75(6):1141-1144
We report the measurement of photoexcitation cross-sections of three first-step uranium transitions (0 → 16900.38 cm −1, 0 → 17361.89 cm −1 and 620 → 17361.89 cm −1) using saturation method. These measurements were performed on a resonance ionization mass spectrometry (RIMS) set-up consisting
of Nd:YAG-pumped dye lasers, a reflectron time-of-flight mass spectrometer and high-temperature atomic vapour source. The
uranium vapours were excited and photoionized by two-colour, three-photon photoionization scheme using Nd:YAG-pumped dye laser
system. The resultant photoion signal was monitored as a function of dye laser fluence used for first step excitation to measure
the excitation cross-section values. A new approach was adopted to overcome the large uncertainties associated with such measurements.
With this approach the cross-section of transitions whose value is already reported in the literature was measured as a bench
mark. By normalizing the measured value to the reported value, a scaling factor was derived. This scaling factor was used
to scale up the cross-section values of other transitions measured by this method. 相似文献
66.
Puri S Handa G Kalsotra AK Gupta VK Shawl AS Suri OP Qazi GN 《Journal of chromatographic science》2006,44(4):177-180
St. John's Wort (Hypericum perforatum), a perennial flowering plant, has been used medicinally for thousands of years and has most recently been identified as an effective treatment for mild to moderate depression and neuralgic disorders. This work presents a procedure for the isolation of naphthodianthrones from St. John's Wort by an accelerated extraction and separation of marker compounds by preparative high-performance liquid chromatography (HPLC) with photodiode array detection. The accelerated extraction method minimizes the extraction time and increases the yield, and the marker compounds obtained by preparative HPLC are of 98% purity. The compounds are characterized by liquid chromatography-mass spectrometry (electrospray ionization) and NMR spectra. 相似文献
67.
Antonyraj Arockiasamy Randall M. German Paul Wang Mark F. Horstemeyer Pavan Suri S. J. Park 《Journal of Thermal Analysis and Calorimetry》2010,100(1):361-366
Differential scanning calorimetry (DSC) is a powerful technique that measures the heat evolution from a sample under a controlled
condition and studies the phase transformation, precipitation, and dissolution activities. In this work, we investigated the
influence of admixed silicon and silicon carbide and the effect of different atmospheres on the heat flow properties and microstructure
of atomized Al6061 powder using DSC and scanning electron microscopy. The DSC analysis revealed the addition of silicon considerably
decreased the temperature of first endothermic peaks. With an increase in silicon content the enthalpy for the first endothermic
peak increased, whereas the second endothermic peak decreased. An endothermic peak, indicating the formation of AlN, was observed
for powders without the silicon addition, but was noticeably absent in the case of alloys with Si addition. The SiC addition
has no influence on changing the enthalpy of the systems we investigated. The reason for this behavior is analyzed and presented
in this article. 相似文献
68.
Molar excess volumes of mixing VE for binary mixtures of furfuryl alcohol with the aromatic hydrocarbons benzene, toluene, ethylbenzene, and o-, m-, and p-xylene were determined for the entire composition range at 25°C. VE was negative for the mixtures containing benzene, toluene and pxylene but positive for mixtures containing ethylbenzene and o- and m-xylene. The results are discussed in terms of specific interaction present in the binary mixture and are compared with those previously reported for tetrahydrofuran, fur an or furfural binary mixtures with aromatic hydrocarbons. 相似文献
69.
Calorimetric studies of the ferromagnetic Curie temperature Tc, and the crystallization kinetics of the metallic glass Fe78B9Si13 have been performed in an attempt to elucidate the possibility of reversible relaxation processes near Tc and the crystallization mechanisms taking place. From the change of Tc with heating rate and on annealing it appears that ageing irreversibly increases the Curie temperature. Crystallization is thermally activated following an Arrhenius behaviour and proceeds in two stages, the best fit to the experimental data for each stage of crystallization has been obtained by use of a Johnson-Mehl-Avrami-Erofe'ev equation. The effective activation energy and the kinetic exponent are respectively E = (4.7 ± 0.1) eV, n = 2.0 ± 0.2 for the first and E = (4.5 ± 0.1) eV, n = 4.0 ± 0.2 for the second stage of crystallization. From these results it appears that the mechanisms of crystallization are quite different in both stages. 相似文献
70.
Perturbative calculation of the cross section in double ionization by
high-energy Compton scattering
Z. Kaliman K. Pisk T. Surić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):369-372
In this paper we investigate double ionization in high-energy Compton scattering from the He-atom including both the shake-off
mechanism and a perturbative correction to that mechanism.
The correction is calculated in second-order perturbation theory and includes Coulomb electron-electron interaction in addition
to the correlation in the ground state of the He-atom. Our calculations for the ratio of double to single cross section cover
the range from 30 to 300 keV of impact photon energy and explain the slow convergence of the ratio towards the asymptotic
value. 相似文献