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51.
J. Ihringer J. K. Maichle W. Prandl A. W. Hewat Th. Wroblewski 《Zeitschrift für Physik B Condensed Matter》1991,82(2):171-176
The ceramic superconductor BaPb0.75Bi0.25O3 is monoclinic atT<430 K with space groupI2/m. Lattice constants and the atomic coordinates result from 20 reflection groups (12<2<120°, =1.1267 Å) collected with a high resolution powder diffractometer using a synchrotron radiation source and a full neutron powder pattern (6<2<140, =1.909 Å). Synchrotron and neutron data were simtultaneously refined with SIMREF, a new profile refinement program, based on the Rietveld method. Group theoretical analysis of the distortion field leading from the ideal perovskite structure toI2/m exhibitsR
4
+
symmetry. A comparison is made with the corresponding distortions in nonsuperconducting BaBiO3 where three different symmetry types are identified. The space groupI2/m found for BaPb0.75Bi0.25O3 allows only one type of averaged (Pb/Bi)O6 octahedron in the structure: this may support valence fluctuations and hence contribute to the mechanism of superconductivity in this particular compound. 相似文献
52.
Ohne Zusammenfassung
On the local zeta function of Shimura varieties. Monodromy filtration and vanishing cycles in unequal characteristic相似文献
53.
Th. Freudenberg W. Radloff H. -H. Ritze V. Stert K. Weyers F. Noack I. V. Hertel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,36(3-4):349-364
The formation of protonated and unprotonated ammonia cluster ions is studied by femtosecond two colour two photon pump-probe techniques applied to (NH3) n and (ND3) n clusters withn up to 8. The fourth harmonic (~ 200 nm, 6.2 eV, 160 fs) of a Ti: Sapphire laser pulse is used to excite the clusters in a state corresponding to theà state of NH3 while the third harmonic (267 nm, 4.65 eV) is used for the subsequent ionisation step. Employing a combination of the optical Bloch equations for the excitation process and rate equations for the cluster dynamics we calibrate the zero time delay and carefully analyse the time dependence of the pump-probe signal. Several distinct intermediate steps in the time evolution can be distinguished, having characteristic time constants ranging from 40 fs to over 100 ps. They are discussed in a consistent scheme for the excitation, ionisation and protonation dynamics, accounting also for characteristic differences observed between deuterated and undeuterated species. A particularly remarkable time dependence of the homogeneous (NH3) 2 + cluster ion signal is interpreted as a fingerprint of internally protonated neutral precursors of the type NH3NH2NH4. 相似文献
54.
The barrier to internal rotation in thioacetaldehyde was investigated within the PCILO and CNDO/2 framework using standard and optimized geometries. The optimized geometries give for the barrier of PCILO a value closer to the experimental one (1.06 kcal mol?1) whereas the CNDO/2 results yield a qualitatively wrong conformational behavior. 相似文献
55.
Zusammenfassung Die Reaktion von 2-Pyridylessigsäurederivaten (1a, 1b) mit Diketen (2) in sied. Eisessig liefert in 1-Stellung substit. 4-Methyl-2-chinolizinone.
Syntheses of heterocycles, CXXI: Quinolizines and indolizines. A synthesis of 4-methyl-2-quinolizinones
The reaction of 2-pyridylacetic acid derivatives (1a, 1b) with diketene (2), gives 4-methyl-2-quinolizinones.相似文献
56.
Zusammenfassung Salicylsäurechlorid (1) reagiert mit Campherimin ·HCl bzw. Campheranil oder mit Aldazinen zu Derivaten des 1,3-Benzoxazin-4-ons.
Salicoyl chloride reacts with camphorimine hydrochloride and camphoranile or with aldazines to give derivatives of 1.3-benzoxazin-4-ones.相似文献
57.
Hexanethiolate monolayer-protected gold nanoclusters (MPCs) were used as redox quenchers at the polarizable water/1,2-dichloroethane (DCE) interface. Photocurrent responses originating from the heterogeneous quenching of photoexcited water soluble porphyrin complexes by MPCs dissolved in the DCE phase were observed. As MPCs can function as both electron acceptors and donors, the photocurrent results from the superposition of two simultaneous processes, which correspond to the oxidation and reduction of MPCs. The magnitude of the net photocurrent is essentially determined by the balance of the kinetics of these two processes, which can be controlled by tuning the Galvani potential difference between the two phases. We show that, within the available potential window, the apparent electron-transfer rate constants follow classical Butler-Volmer dependence on the applied potential difference. 相似文献
58.
A. H. F. van Vliet Th. de Graauw 《International Journal of Infrared and Millimeter Waves》1981,2(3):465-477
A review is given of different types of quarter wave plates as presently used in the optical and microwave spectral range, with a view to their application in the sub-mm wave-length range. Two types of quarter wave plates have been constructed and results of measurements at 640m are given. 相似文献
59.
Paul Kirren Lucile Barka Saher Rahmani Nicolas Bondon Nicolas Donzel Philippe Trens Aurlie Bessire Laurence Raehm Clarence Charnay Jean-Olivier Durand 《Molecules (Basel, Switzerland)》2022,27(13)
(1) Background: Due to human activities, greenhouse gas (GHG) concentrations in the atmosphere are constantly rising, causing the greenhouse effect. Among GHGs, carbon dioxide (CO2) is responsible for about two-thirds of the total energy imbalance which is the origin of the increase in the Earth’s temperature. (2) Methods: In this field, we describe the development of periodic mesoporous organosilica nanoparticles (PMO NPs) used to capture and store CO2 present in the atmosphere. Several types of PMO NP (bis(triethoxysilyl)ethane (BTEE) as matrix, co-condensed with trialkoxysilylated aminopyridine (py) and trialkoxysilylated bipyridine (Etbipy and iPrbipy)) were synthesized by means of the sol-gel procedure, then characterized with different techniques (DLS, TEM, FTIR, BET). A systematic evaluation of CO2 adsorption was carried out at 298 K and 273 K, at low pressure. (3) Results: The best values of CO2 adsorption were obtained with 6% bipyridine: 1.045 mmol·g−1 at 298 K and 2.26 mmol·g−1 at 273 K. (4) Conclusions: The synthetized BTEE/aminopyridine or bipyridine PMO NPs showed significant results and could be promising for carbon capture and storage (CCS) application. 相似文献
60.
Dielectric relaxation experiments were carried out on mixed alkali metaphosphate glasses between room temperature and about 300°C (f = 103 s?1). The observed relaxations appeared to be connected with the movement of the alkali ions from site to site. By using stainless steel electrodes it was possible to reveal a relaxation peak free from conduction losses and due only to the migration from site to site of the cations. When two cations of dissimilar sizes are simultaneously present a mixed alkali effect was observed, i.e. an unproportionally large reduction in the alkali ion mobilities. It is shown that this effect can be at least partly explained by considering the changes in the potential energy states upon mixing dissimilar cations due to polarizing forces and coulombic interactions. 相似文献