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51.
C. De Brauer M. P. Merlin P. Germain T. Guerandel 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):75-82
Heat capacities of anhydrous -and -cyclodextrin were measured by adiabaticcalorimetry between 10 K and 300 K. The thermalbehaviour of the two compounds exhibits significantdifferences. -Cyclodextrin shows an anomalousexcess heat capacity in the entire region between 70 Kand 210 K. In the case of -cyclodextrin, anendothermic effect is observed at 240K. This effect isanalysed through the study of the correspondingentropy change and discussed in terms ofintramolecular organization.Using the known heat capacity values of anhydrous-CD, a comparative analysis has been developed.For each cyclodextrin, the average behaviour of abound -D-glucopyranose has been calculated andcompared. From a thermodynamic point of view, thedegree of organization of the dehydrated macrocycliccompounds could be expressed as-CD -CD -CD. 相似文献
52.
53.
P. Michel M. ODonnell R. Biname A.M. Hesbain-Frisque L. Ghosez J.P. Declercq G. Germain E. Arte M. Van Meerssche 《Tetrahedron letters》1980,21(26):2577-2580
Adducts of alkyl(phenylthio)ketenes to cyclopentadiene are cleaved with KOH-t-BuOK with retention of configuration at three centers. This observation broadens the synthetic potential of the method of vicinal alkylation of olefins. This method has been used for the vicinal addition of [Cm + Cn] units to cyclopentadiene. 相似文献
54.
Christophe Viglianti Khalil Hanna Christine De Brauer Patrick Germain 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):275-280
The removal of Polycyclic Aromatic Hydrocarbons (PAHs) from soil using pure water is quite ineffective due to␣their low aqueous solubility. Most of present processes are based on organic cosolvents or surfactants, leading to potential environmental hazard. Addition of cyclodextrin (CD) in aqueous washing solutions has been shown to␣increase the removal efficiency several times, while being non-toxic agents. Herein are investigated the effectiveness of cyclodextrins to remove PAHs occurring in industrially aged-contaminated soil. β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPCD) and methyl-β-cyclodextrin (MCD) solutions were used for soil flushing in column test or batch experiments to evaluate some influent parameters that can significantly increase the removal efficiency. The process parameters chosen were CD concentration, ratio of washing solution volume to soil weight, and temperature of washing solution. These parameters were found to have a significant and almost linear effect on PAHs removal from the contaminated soil, except the temperature where no significant enhancement in PAHs extraction was observed for temperature range from 5 to 35 °C. Removal capacity of HPCD and MCD was higher than BCD one. The PAHs extraction enhancement factor compared to water was about 200. 相似文献
55.
D. Canet C. Malveau D. Grandclaude P. Tekely F. Beaume Y. Germain 《Macromolecular Symposia》2005,220(1):33-44
Two different samples of high-density polyethylene (HDPE) have been studied. One (isotropic) is extracted from the material core whereas the other (anisotropic) involves two sides which have been in contact with the injection mold. It is observed by NMR microscopy (using radiofrequency field gradients) that these two sides favor toluene penetration into the material. The distribution of toluene nuclear spin relaxation times (extracted from proton T1 and T2 images) exhibits likewise important differences between the two samples. These differences can be accounted for by partial molecular ordering at the vicinity of the “mold sides”. Finally, in investigating the anisotropic sample (without solvent), three different phases (two amorphous and one crystalline) are revealed by 13C chemical shift imaging experiments (performed with radiofrequency field gradients under CP/MAS conditions). Each amorphous component is preferentially present at one of the two “mold sides”. 相似文献
56.
57.
An experimental exploratory study of laminar, transitional and turbulent boundary layers on a slender, sharp cone at zero
incidence in hypervelocity flow was conducted in the shock tunnel T5, whose high operating pressure permits achieving the
necessary high Reynolds numbers at high total enthalpy. Surface heat transfer rate and resonantly enhanced flow visualization
were used to determine transition location and flow structure. Results suggest that the transition mechanism at the conditions
tested is via the Tollmien–Schlichting instability, but since no detailed information about the noise spectrum in the facility
is available, a definite conclusion is not possible. A strong, gas-dependent increase of the transition Reynolds number evaluated
at the reference temperature on specific total enthalpy was observed. This effect increases monotonically with decreasing
the dissociation energy of the gas.
Received: 1 February 1996/Accepted: 28 June 1996 相似文献
58.
P. Germain M. Laguës 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):497-505
We study the electronic and magnetic structure of the undoped ideal two and three-leg ladder cuprates by assuming a moderate
on site coulombic repulsion. This analysis is an extension of the Fermi liquids studies proposed for the CuO2 plane in view to explain the high Tc superconductivity and the competition with the antiferromagnetic phase. At zero doping, the quasi-one-dimensionality of the
structure results in SDW correlations with different (commensurate) vectors according to the number of legs, which contrasts
with the predictions made from the Heisenberg model. At mean field, and for n = 3 (Sr2Cu3O5), we predict a magnetic ordered state, detected by μSr and NMR measurements with critical temperatures consistent with our
assumptions on the physical parameters, the modulation vector being .The presence of several bands at the Fermi level explains why there is no observable gap in the static susceptibility measurements.
For n = 2, we predict a gap consistent with experimental Curie susceptibility. But the expected magnetic instability is detected
only in La2Cu2O5, where the interladder coupling is stronger. In every case the one-dimensional van Hove singularities are far from the Fermi
level, making difficult the obtaining of high Tc superconductivity.
Received 3 June 1998 相似文献
59.
60.
Pereira R Furst A Iglesias B Germain P Gronemeyer H de Lera AR 《Organic & biomolecular chemistry》2006,4(24):4514-4525
A reactivity study, aided by NMR spectroscopy, allowed a mechanistic rationale to be postulated for the palladium-catalyzed regioselective coupling of arylboronic acid (and arylstannane where feasible) at the position next to the sulfur atom in functionalized dibromothiophenes and dibromothiazoles. The analysis of the NMR spectra (using 19F from the boronic acid CF3 group and 31P from the phosphine of the catalyst as probes) of the entire reaction starting from the dibromoheterocycles allowed the qualitative proposal that the transmetalation is the rate-limiting step for both sequential substitution processes. The extremely facile oxidative addition at the C-Br bond next to the sulfur atom of the heterocycle instead determines the positional selectivity. An additional Stille reaction then replaced the second halogen, providing the trisubstituted heterocyclic scaffolds of PPAR ligands, which displayed PPARbeta/delta agonist activity, as revealed by reporter assays in living cells. 相似文献