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41.
Louis L'Hôte 《Fresenius' Journal of Analytical Chemistry》1905,44(8-9):555
Ohne Zusammenfassung 相似文献
42.
43.
Alina Wildenberg Yann Fenard Maxime Carbonnier Alan Kéromnès Benoîte Lefort Zeynep Serinyel Guillaume Dayma Luis Le Moyne Philippe Dagaut Karl Alexander Heufer 《Proceedings of the Combustion Institute》2021,38(1):543-553
The modern catalytic or enzymatic advances allow the production of novel biofuel. Among them, 1,3-dioxolane can be produced from formaldehyde and ethylene glycol, both can be obtained from biomass. In this study, the oxidation of 1,3-dioxolane is studied at stoichiometric conditions. The ignition delay times of 1,3-dioxolane/O2/inert mixtures were measured in a shock tube and in a rapid compression machine at pressures of 20 to 40 bar and temperatures ranging from 630 to 1300 K. The pressure profiles recorded in the rapid compression machine show a first stage of ignition enlightening the influence of the low temperature chemistry of combustion. Furthermore, mole fraction profiles of the stable intermediates produced during the oxidation of 1,3-dioxolane were measured in a jet-stirred reactor at 10 bar. Following these observations, a detailed kinetic model was developed with reaction rate coefficients and thermochemical data calculated by theoretical calculations or estimated by analogies to suitable molecules. In order to get an insight into the most important reaction pathways brute force sensitivity analysis and reaction pathway analysis were performed with the proposed model and discussed. It became clear that in the fuel-in-air case for the alkylhydroperoxide of 1,3-dioxolane the ring opening beta-scission pathway is favored against the further alkane-like second addition to molecular oxygen, which leads to a limited negative temperature coefficient. 相似文献
44.
We present a detailed study of the heating effects in dielectric measurements carried out on a liquid. Such effects come from the dissipation of the electric power in the liquid and give contribution to the nonlinear third harmonics susceptibility χ(3), which depends on the frequency and temperature. This study is used to evaluate a possible "spurious" contribution to the recently measured nonlinear susceptibility of an archetypical glassforming liquid (glycerol). Those measurements have been shown to give a direct evaluation of the number of dynamically correlated molecules temperature dependence close to the glass transition temperature T(g) ≈ 190 K [Crauste-Thibierge et al., Phys. Rev. Lett. 104, 165703 (2010)]. We show that the heating contribution is totally negligible (i) below 204 K at any frequency; (ii) for any temperature at the frequency where the third harmonics response χ(3) is maximum. Besides, this heating contribution does not scale as a function of f/f(α), with f(α)(T) the relaxation frequency of the liquid. In the high frequency range, when f/f(α) ≥ 1, we find that the heating contribution is damped because the dipoles cannot follow instantaneously the temperature modulation due to the heating phenomenon. An estimate of the magnitude of this damping is given. 相似文献
45.
Nathalie Dupré Pauline Rémy Dr. Kévin Micoine Dr. Cécile Boglio Dr. Serge Thorimbert Dr. Emmanuel Lacôte Dr. Bernold Hasenknopf Prof. Max Malacria Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(24):7256-7264
The preparation of new organosoluble Lewis acidic polyoxometalates (POMs) is reported. These complexes were prepared by the incorporation of Zr, Sc, and Y atoms into the corresponding monolacunary Dawson [P2W17O61]10? and Keggin [PW11O39]7? polyoxotungstates. The catalytic activity of these compounds was evaluated for C? C bond formation in the Diels–Alder, Mannich, and Mukaiyama‐type reactions. Comparisons with previously described Lewis acidic POMs are reported. Competitive reactions between imines and aldehydes or between various imines demonstrated that fine tuning of the reactivity could be reached by varying the metal atom incorporated into the polyanionic framework. A series of experiments that employed pyridine derivatives allowed us to distinguish between the Lewis and induced Brønsted acidity of the POMs. These catalysts activate imines in a Lewis acidic way, whereas aldehydes are activated by indirect Brønsted catalysis. 相似文献
46.
Santos TS Kirby BJ Kumar S May SJ Borchers JA Maranville BB Zarestky J te Velthuis SG van den Brink J Bhattacharya A 《Physical review letters》2011,107(16):167202
We demonstrate that delta doping can be used to create a dimensionally confined region of metallic ferromagnetism in an antiferromagnetic (AFM) manganite host, without introducing any explicit disorder due to dopants or frustration of spins. Theoretical consideration of these additional carriers shows that they cause a local enhancement of ferromagnetic double exchange with respect to AFM superexchange, resulting in local canting of the AFM spins. This leads to a highly modulated magnetization, as measured by polarized neutron reflectometry. The spatial modulation of the canting is related to the spreading of charge from the doped layer and establishes a fundamental length scale for charge transfer, transformation of orbital occupancy, and magnetic order in these manganites. Furthermore, we confirm the existence of the canted, AFM state as was predicted by de Gennes [Phys. Rev. 118, 141 (1960)] but had remained elusive. 相似文献
47.
48.
We demonstrate a controlled phase change of π in a degenerate superposition by altering a laser frequency by only 10 MHz. The method relies on the preparation of an adiabatic state involving the M = ±2 and M = 0 states of the 3P2 (J = 2) level of metastable neon. Dependent on the frequency, the preparation proceeds either by stimulated Raman adiabatic passage (STIRAP) or by coherent population trapping (CPT). In the former case the superposition is prepared by adiabatic transfer induced in an extended tripod linkage scheme. In the latter case population is optically pumped into the Zeeman manifold of the level 3P2. The population which does not reach a dark state decays to the ground state of neon. The amplitudes and relative phases of the dark states differ for the two cases. The phase change is monitored using the method of phase-to-population mapping. 相似文献
49.
The gel formation of various 10% molar-mass polyvinyl-chloride (PVC) sample solutions and polymerization temperatures in di-(2-ethylhexyl)phthalate (DOP) was studied by measuring dynamic moduli as functions of gelation (or ageing) time and frequency. The propensity to form gels increases with increasing molar mass and decreasing polymerization temperature. Extraction of a commercial PVC with acetone separates it into a relatively highly crystalline and a nearly non-crystalline polyvinyl chloride. 相似文献
50.
In this experimental study a thorough analysis of the steady and unsteady flow field in a realistic transparent silicone lung
model of the first bifurcation of the upper human airways will be presented. To determine the temporal evolution of the flow
time-resolved particle-image velocimetry recordings were performed for a Womersley number range 3.3 ≤ α ≤ 5.8 and Reynolds
numbers of Re
D
= 1,050, 1,400, and 2,100. The results evidence a highly three-dimensional and asymmetric character of the velocity field
in the upper human airways, in which the influence of the asymmetric geometry of the realistic lung model plays a significant
role for the development of the flow field in the respiratory system. At steady inspiration, the flow shows independent of
the Reynolds number a large zone with embedded counter-rotating vortices in the left bronchia ensuring a continuous streamwise
transport into the lung. At unsteady flow the critical Reynolds number, which describes the onset of vortices in the first
bifurcation, is increased at higher Womersley number and decreased at higher Reynolds number. At expiration the unsteady and
steady flows are almost alike. 相似文献