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111.
L. S. de C. Oliveira M. T. X. Silva A. Vasquez J. A. H. da Jornada 《Hyperfine Interactions》1991,66(1-4):267-270
An exploratory Mössbauer spectroscopy study of the Fe-C system in the C rich region, prepared by high pressure-high temperature treatment near the graphite-diamond stability line, was made. The results obtained for the different processing conditions give no evidence of Fe intercalation in graphite. The presence of some water in the cell produced hydrated Fe complexes, which can explain the deleterious effect of water or hydrogen in the high pressure diamond synthesis. 相似文献
112.
Miloslav Duchoň Anatolij Dvurečenskij Paolo de Lucia 《International Journal of Theoretical Physics》1997,36(9):1941-1958
We present a solution to the moment problem for effect algebras, concerning mean values of all powers of an observable concentrated
on the interval [0, 1] for states from a convex set. We give a solution for particular examples, e.g., for the set of all
effect operators. We examine how this problem is related to a socalled E-property. Finally, we give a solution for observables
studied in the operational approach to physical theories. 相似文献
113.
J.-J. Sauvain L. F. de Alencastro J. Tarradellas R. Camenzind G. Karlaganis C. Vuilleumier 《Fresenius' Journal of Analytical Chemistry》1994,350(7-9):555-562
The analysis of PCB in transformer oils has been achieved with three HRGC/ECD based methods, proposed by the International Electrotechnical Commission (IEC/TC 10), by the Comité Européen de Normalisation (CEN/TC 19/WG 22) and by the Deutsches Institut für Normung (DIN 51 527). The same clean-up, described in the CEN/TC 19/WG 22, has been used for all the samples, allowing a comparison of the quantification procedure only. The total chlorine content has also been determined with X-ray fluorescence. These different methods of quantification are compared and their application for legislative purposes is discussed.Dedicated to Professor Dr Dieter Klockow on the occasion of his 60th birthday 相似文献
114.
Patricia Smichowski María Beatriz de la Calle Guntiñas Carmen Cámara 《Fresenius' Journal of Analytical Chemistry》1994,348(5-6):380-384
Summary A method is described for antimony preconcentration based on retention on a column of activated alumina. Recovery is 80% when no pH-control and 4 mol/l HCl as eluent are used. The preconcentration factor is 400. The method was applied to the determination of antimony in spiked tap and sea water. The analytical performance of the method is discussed. 相似文献
115.
J.C. Góes S.D. FigueiróJ.A.C. de Paiva I.F. de VasconcelosA.S.B. Sombra 《Journal of Physics and Chemistry of Solids》2002,63(3):465-470
In this paper, we report results of a study of the physicochemical, dielectric and piezoelectric properties of anionic and native collagen films, considering the development of new biomaterials which have potential applications in coating of cardiovascular prostheses, support for cellular growth and in systems for controlled drug delivery. The piezoelectric strain tensor element d14, the elastic constant s55, and the dielectric permittivity ?11 were measured for the anionic and native collagen films. It was observed that the collagen samples submitted to the alkaline treatment present lower thermal stability than those made from native collagen. However, the treated samples present a higher piezoelectricity compared with the native collagen. The frequency constant fL and the piezoelectric strain element d14, obtained for the alkaline-treated sample (72 h), present the highest values for the samples under study (444.1 kHz m and 0.079 pC/N, respectively). We believe that the alkaline treatment led to an increase of the organization of the microscopic fiber structure of the sample, which could result in an increase of the piezoelectricity. 相似文献
116.
117.
118.
The existing classification of homogeneous quaternionic spaces is not complete. We study these spaces in the context of certainN=2 supergravity theories, where dimensional reduction induces a mapping betweenspecial real, Kähler and quaternionic spaces. The geometry of the real spaces is encoded in cubic polynomials, those of the Kähler and quaternionic manifolds in homogeneous holomorphic functions of second degree. We classify all cubic polynomials that have an invariance group that acts transitively on the real manifold. The corresponding Kähler and quaternionic manifolds are then homogeneous. We find that they lead to a well-defined subset of the normal quaternionic spaces classified by Alekseevskiî (and the corresponding special Kähler spaces given by Cecotti), but there is a new class of rank-3 spaces of quaternionic dimension larger than 3. We also point out that some of the rank-4 Alekseevskiî spaces were not fully specified and correspond to a finite variety of inequivalent spaces. A simpler version of the equation that underlies the classification of this paper also emerges in the context ofW
3 algebras.Communicated by K. Gawedzki 相似文献
119.
Katalytische Epoxidierung und 1,2‐Dihydroxylierung von Olefinen mit Bispidin‐Eisen(II)/H2O2‐Systemen
120.
Principles and recent developments in ultrasound contrast agents 总被引:6,自引:1,他引:5
The behaviour of gas bubbles and gas encapsulated spheres as echographic contrast agents is reviewed. Compared with rigid spheres, gas bubbles are superior scattering agents and they offer a number of useful properties which can be exploited in a variety of ways. The analysis of their velocity of sound, back-scatter intensity, second harmonic emission and resonant frequency opens up new perspectives in the development of contrast agents for echocardiographic research with potential clinical applications. 相似文献