Fluorescent tetraruthenated porphyrins embedded in monolithic SiO2 gels by the sol-gel process

In this work silica gels have been prepared by a sol-gel method using tetraethylorthosilicate as gel precursor. The tetraruthenated porphyrins H2(3-TRPyP), Co(3-TRPyP), and H2(4-TRPyP) were incorporated into the systems during gel formation without problems commonly found in the process, such as aggregation. Spectroscopic studies of the resulting silica gels revealed the presence of absorption bands in the range 200-400 nm associated with the transitions of the groups ruthenium-bipyridine, along with the Soret band at the same wavelengths observed in solution. The porphyrins were found to preserve fluorescence emission properties in the range 650-700 nm even after the aging period. Study of the thermal behavior and decomposition kinetics evidenced that the porphyrin H2(4-TRPyP) is the least stable of the group and that all compounds decompose according to first-order kinetics.     

Association of bound states of the coulomb potential with resonances of the coulomb potential perturbed by a barrier

In the present article we show how the bound states of the Coulomb potential may be associated with resonances that occur when this potential is perturbed by a barrier potential. The main idea is to trace the bound states on successive switching on of the barrier perturbation. It is found that those bound states that are localized inside the barrier are highly sensitive to variation with respect to the barrier height, whereas those that are localized outside are less sensitive. However, there are certain intervals for the barrier height when the role of being “a state localized inside the barrier” is shifted from one bound state to another. The result can be pictured as a “relay race,” where the “deliveries of the baton” are carried out over corresponding avoided crossings. The baton is ultimately handed over to a shape-type resonance state.     

Analytical chemistry in controlled thermonuclear fusion

The analytical problems arising in the fuel cycle of a fusion reactor have to be discussed separately for the various subsystems of such a reactor. Thus, in the case of plasma exhaust purification, concentration assays of the tritiated impurities must be carried out quickly and, whenever possible, under flow conditions. Conventional methods may be employed for this purpose, such as mass spectrometry, FT-IR spectrometry and laser Raman spectrometry, but they will all have to be adapted to special conditions, especially for online operation.     

Zur Realisierbarkeit der Darstellungen der 3-dimensionalen Drehgruppe

Ohne Zusammenfassung     

Utilisation des accelerateurs en analyse par activation,notamment pour la caracterisation des materiaux purs

The principal means of activation, their potential performances and their special fields of application are reviewed briefly. The possibilities offered by charged particles and gammaphotons regarding the determination of light elements or other impurities in pure materials are surveyed. Examples relatives to the evaluation of boron, carbon, nitrogen, oxygen or fluorine contents in metals (Na, Al, Ti, Ni, Cu, Zr, Mo, Ta, W, Pb, etc.), alloys (PbCuTe, PbSnCd) and semiconductors (Si, AsGa, InP, etc.) are given. For some of these products, the results obtained by nuclear methods are compared with values supplied by other analytical techniques. Once the concentration levels of these impurities fall below 1 μg·g⁻¹, the superiority of the former methods appears clearly.      

Analytical application of the direct observation of nuclear reactions induced by low-energy protons and leading to the emission of γ-photons,which are measured

The yields of the most characteristic photon emissions of the elements Li, Be, B, C, N, O and F were plotted for incident proton energies ranging from 400 keV to 1500 keV. The possibilities offered by the use of this direct observation method to measure the superficial concentrations of these elements are deduced. The sensitivities intrinsically obtainable with our experimental device are given and the practical possibilities of the method are discussed, allowance being made for the simultaneous presence of several of the above elements.