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91.
Summary By using the boson transformation method, the electromagnetic properties of a ferromagnetic superconducting film have been
studied. The magnetic field, the induction field and the magnetization have been calculated analytically in the London limit.
Particularly, we have studied the dependence of the various fields on the phenomenological parameter μ, on the temperature
and on the film thickness and the dependence oft
s
, a critical temperature below which a spontaneous magnetization appears, on the parameter μ and on the film thickness. Finally,
the magnetic properties of the film are analysed in the linear and nonlinear approximation as functions of temperature and
thickness.
Riassunto Utilizzando il metodo della trasformazione bosonica le proprietà elettromagnetiche di un film superconducente ferromagnetico sono state studiate. Il campo magnetico, il camp di induzione magnetica e la magnetizzazione sono stati calcolati analiticamente nel limite di London. In particolare, abbiamo studiato la dipendenza dei vari campi dal parametro fenomenologico μ, dalla temperatura e dallo spessore del film e la dipendenza dit s , temperatura critica al di sotto della quale appare la magnetizzazione spontanea, dal parametro μ e dallo spessore del film. Infine le proprietà magnetiche del film sono analizzate in approssimazione lineare e non lineare in funzione della temperatura e dello spessore.
Резюме Исследуются электромагнитные свойства ферромагнитной сверхпро водящей пленки с помощъю метода бозонного нреобразования. В пределе Лондона аналитически вычисляются магнитное поле, индуцированное поле и намагниченность. В частности, рассматривается зависимость вышеуказанных полей от феноменологического параметра μ, от температуры и от толщины пленки, а также зависимостьt s критической температуры, ниже которой возникает спонтанная намагниченность, от параметра μ и толщины пленки. В заключение, анализируются свойства пленки в зависимости от температуры и толщины в линейном и нелинейном приближениях.相似文献
92.
G. Kozlowski H. Matsumoto H. Umezawa J.P. Whitehead F. Mancini C.Y. Huang C.E. Olsen M.B. Maple H.C. Hamaker M.S. Torikachvili F.E. Wang 《Solid State Communications》1985,54(3):221-225
We have investigated the surface impedance penetration depth, Λ, of ErRh4B4 and Er0.5Ho0.5Rh4B4 both experimentally and theoretically. For ErRh4B4, owing to the critical spin fluctuations just above Ts ( > Tc2), the critical temperature at which surface ferromagnetism appears, Λ?1 decreases smoothly as T decreases toward Ts. For Er0.5Ho0.5Rh4B4, the decrease in Λ?1 owing to spin fluctuations for T ? Tc2 is very small, and Λ?1 decreases abruptly at Tc2. Theoretical values of Λ?1 are in good agreement with the data. 相似文献
93.
94.
95.
The raspailynes (novel long-chain enol ethers of glycerol having the enol ethers double bond conjugated in sequence, to an acetylenic and an olefinic bond, isolated from the North-East-Atlantic sponges Raspailia pumila and R. ramosa) are stable under normal hydrolytic conditions for enol ethers. In contrast, when their solutions are evaporated, these lipids such as raspailyne Bl (=(?))-3-[(1Z,5Z)-(tetradeca-1,5-dien-3-ynyl)oxy]-1,2-propanediol;(?- 2 ) rapidly react with aerial O2 under normal laboratory-daylight conditions, with rupture of the C=C enol ether bond to give 1-O-formylglycerol ( 3 ) and an aldehyde (such as tridec-4-en-2ynal( 4 ) from (?)- 2 ). This reaction must be caused by triplet O2, since thermally generated singlet O2 has no effect on (?)- 2 in solution. That the mere presence of an enol-ether moiety conjugated to an acetylenic group is responsible for such a behaviour is demonstrated with the model compounds 1-methoxypentadec-1-en-3-yn-5-ol ( 6a ) and its 5-O-acetyl or 5-O-tetra-hydropyranyl derivatives 6b and 6c , respectively. Resistance to both hydroytic conditions and singlet O2 of these compounds is thought to arise from electron depletion at the enol-ether C(beta;) atom by the acetylenic group. Plausible reaction pathways for enol-ether bond rupture in these compounds by aerial O2 are outlined. 相似文献
96.
Chillemi G Barone V D'Angelo P Mancini G Persson I Sanna N 《The journal of physical chemistry. B》2005,109(18):9186-9193
In this paper, we present a state-of-the-art 100 ns molecular dynamics simulation of a cadmium(II) aqueous solution that highlights a very flexible ion first coordination shell which transits between hexa- and heptahydrated complexes. From this investigation, a dynamical picture of the water exchange process emerges that takes place through an associative mechanism for the solvent substitution reaction. Our procedure starts from the generation of an effective two-body potential from quantum mechanical ab initio calculations in which the many-body ion-water terms are accounted for by the polarizable continuum method (PCM). This approach is computationally very efficient and has allowed us to carry out extremely long molecular dynamics simulations, indispensable to reproduce the dynamic properties of the cadmium(II) aqueous solution. Quantum mechanical ab initio calculations of the hexa- and heptahydrated complexes extracted from MD configurations have revealed stable minima for both clusters with the water molecules arranged in T(h)() and C(2) symmetries in the hexa- and heptahydrated complexes, respectively, with a slight energetic preference for the heptahydrated one. Finally, a comparison of the calculated hexa- and heptahydrated cluster IR and Raman spectra with the experimental data in the literature, has demonstrated that the IR spectroscopy is not able to distinguish between the two species, whereas the Raman spectrum of the Cd(2+)-(H(2)O)(7) cluster provides a better agreement with the experimental data. 相似文献
97.
Jay D. Mancini Yu Zhou Peter F. Meier 《International journal of quantum chemistry》1994,50(2):101-107
The derivation of the connected moments expansion (CMX ) is examined as well as the singularities that arise in the series expansion for the ground-state energy. Explicit analytic results are presented that show a canceling of these singularities. Also, an alternate moments expansion (AMX ) is derived that closely models the CMX but displays a varied computational range. © 1994 John Wiley & Sons, Inc. 相似文献
98.
Valensin D Mancini FM Łuczkowski M Janicka A Wisniewska K Gaggelli E Valensin G Łankiewicz L Kozlowski H 《Dalton transactions (Cambridge, England : 2003)》2004,(1):16-22
The copper(II) binding features of the APP(145-155) and APP(145-157) fragments of the amyloid precursor protein, Ac-Glu-Thr-His-Leu-His-Trp-His-Thr-Val-Ala-Lys-NH2 and Ac-Glu-Thr-His-Leu-His-Trp-His-Thr-Val-Ala-Lys-Glu-Thr-NH2 were studied by NMR spectroscopy and NMR findings were supported by UV-vis, CD and EPR spectra. Potentiometric measurements were performed only for the more soluble Ac-Glu-Thr-His-Leu-His-Trp-His-Thr-Val-Ala-Lys-Glu-Thr-NH2 peptide fragment. The following was shown: (i) the imidazole rings of all the three His residues are involved in metal coordination; (ii) metal binding induces ionisation of Leu-148 and His-149 amide nitrogens that complete the donor set to copper(II) in the species dominant at neutral pH; (iii) the unusual coordination scheme of the His-Xxx-His-Xxx-His consensus sequence justifies the high specificity for Cu(II) when compared to SOD-like or albumin-like peptides or even in amyloid Abeta fragments. The present findings may represent the key for interpreting the observed requirement of His residues conservation for the redox cycling between Cu(II) and Cu(I) by soluble APP. 相似文献
99.
Amenitsch H Bombelli C Borocci S Ceccacci F Mancini G Rappolt M 《Journal of colloid and interface science》2004,280(1):212-218
Investigations aimed at clarifying the nature of geometrical domains of amidic sodium N-dodecanoyl-l-prolinate are reported. NMR investigations on the association of aromatic solutes with the aggregates formed by the amidic surfactant in water show the selective binding of some solutes to the Z domains. Fluorescence quenching experiments allowed us to measure the aggregation number of the aggregates. SAXS experiments gave the average size and structural features of the aggregates. A NMR ROESY experiment evidenced the mosaic-like nature of the domains inside the same aggregate. 相似文献
100.
Frassanito R Cantonati M Tardìo M Mancini I Guella G 《Journal of chromatography. A》2005,1082(1):33-42
The analysis and identification of a wide range of secondary metabolites biosynthesized by different algal taxa and cyanobacteria has been performed through a selective and sensitive methodology, mainly based on reversed-phase HPLC coupled both to UV photodiode array detection and to atmospheric pressure mass spectrometric techniques (HPLC-DAD-APIMS). Results are reported here with special attention to the analyses carried out both on the natural phytoplankton (mixed populations) of Lake Tovel (Northern Italy, Brenta Dolomites) and on enclosure-produced biomass of the dinoflagellate Glenodinium sanguineum Marchesoni (1941). This analytical procedure might represent a powerful tool for the fast screening of the taxonomic composition (broad groups, e.g. divisions) of natural mixed populations of phytoplankton, by providing a reliable distribution of accessory pigments extracted from microalgae, such as carotenoids and chlorophyll derivatives. Furthermore, we showed that in the same chromatographic analysis other classes of natural products, such as galactolipids, alkaloids, sterols and mycosporine-like amino acids, can be detected by using combined optical and mass spectrometric techniques. These metabolites represent distinctive biochemical signatures, sometimes even at the species level. 相似文献