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51.
Supramolecular Control of Spin Exchange in a Spin‐Labelled [2]Rotaxane Incorporating a Tetrathiafulvalene Unit 下载免费PDF全文
Dr. Francesco Romano Roberta Manoni Dr. Paola Franchi Prof. Elisabetta Mezzina Prof. Marco Lucarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2775-2779
The EPR properties of a novel triradical obtained by single‐electron oxidation of a nitroxide‐spin‐labelled rotaxane containing a tetrathiafulvalene unit and cyclobis(paraquat‐p‐phenylene) ring is reported. Rotaxanation is proved to have a dramatic effect on through‐space magnetic interactions between radical fragments. Analysis of the EPR spectra by a three‐jump model, allowed us to obtain structural information on the interlocked structure. 相似文献
52.
A. Baraldi C. Ghezzi A. Parisini
A. Bosacchi
S. Franchi 《Applied Surface Science》1991,50(1-4):405-409The low-temperature Hall mobility of photoexcited electrons has been measured in Si-doped MBE AlGaAs samples and compared with calculated data using the background acceptor density and the alloy scattering potential as free parameters. The possibility of discriminating between negative- or positive-U electron correlation energy for the DX centre has been investigated through a careful analysis of mobility versus temperature curves relating to different photoexcited electron densities. A crucial role of the acceptor density to explain the experimental data within the positive-U model has been evidenced. 相似文献
53.
Zs. J. Horvth P. Frigeri S. Franchi Vo. Van Tuyen E. Gombia R. Mosca L. Dzsa 《Applied Surface Science》2002,190(1-4):222-225
Excess current was obtained in GaAs/InAs quantum dot structures at low temperatures and low current levels. This excess current exhibited instabilities with changing the bias, and over the time. It has been concluded that the excess current is a minority injection current connected with recombination through defects originated from the formation of QDs. The instabilities are connected with unstable occupation of energy levels induced by the above defects, which depend on temperature and on the current level. 相似文献
54.
Stability constants, rates of association and dissociation, and thermodynamic and activation parameters for the formation of inclusion complexes between the radical guest, N-benzyl- tert-butyl- d 9-nitroxide and beta- or 2,6- O-dimethyl-beta-cyclodextrin (CDs), have been determined by EPR spectroscopy in water in the presence of 14 different alcohols, differing in size and lipophilicity. In all cases, it was found that addition of alcohol, depending on its structure and concentration, causes a reduction of the stability of the paramagnetic complex. Global analysis of EPR data allowed us to explain the CDs binding behavior: we discarded the formation of a ternary complex, where alcohol and radical guest are coincluded into CD cavity, while data were found more consistent with the formation of a binary complex alcohol:CD competing with the monitored complex nitroxide:CD. Both kinetic and thermodynamic analysis of the experimental results have revealed that the presence of alcohols affects to a larger extent the dissociation rather then the association of radical probe and CD and that the former process is of greater importance in determining the stability of the complex, this confirming the reliability of the competition model proposed. This competition has been used for the indirect determination of the stability constants of complexes between CD and examined alcohols. By using a similar approach, we showed EPR spectroscopy can be considered a rapid and accurate technique to investigate the CDs binding behavior toward different nonradical guest. 相似文献
55.
Abstract We show global existence and uniqueness for a system of partial differential equations that is a model for chalcopyrite disease within sphalerite. Using direct methods in the calculus of variations, we proof existence of a solution to an implicit time discretisation, derive uniform bounds and pass to the limit. By considering a regularised problem, it is possible to extend the existence results to logarithmic free energies. Furthermore, by an integration in time method we can show uniqueness of the solution. Additionally a free energy inequality affirms thermodynamical correctness of the model. 相似文献
56.
57.
Annalisa?BaldiEmail author Bruno?Franchi Pierre?Pansu 《Mathematische Annalen》2016,365(3-4):1633-1667
The \(L^1\)-Sobolev inequality states that for compactly supported functions u on the Euclidean n-space, the \(L^{n/(n-1)}\)-norm of a compactly supported function is controlled by the \(L^1\)-norm of its gradient. The generalization to differential forms (due to Lanzani and Stein and Bourgain and Brezis) is recent, and states that a the \(L^{n/(n-1)}\)-norm of a compactly supported differential h-form is controlled by the \(L^1\)-norm of its exterior differential du and its exterior codifferential \(\delta u\) (in special cases the \(L^1\)-norm must be replaced by the \(\mathcal H^1\)-Hardy norm). We shall extend this result to Heisenberg groups in the framework of an appropriate complex of differential forms. 相似文献
58.
Franca Franchi Barbara Lazzari Roberta Nibbi 《Mathematical Methods in the Applied Sciences》2015,38(17):4075-4087
We present a nonlinear model for Johnson–Segalman type polymeric fluids in porous media, accounting for thermal effects of Oldroyd‐B type. We provide a thermodynamic development of the Darcy's theory, which is consistent with the interlacement between thermal and viscoelastic relaxation effects and diffusion phenomena. The appropriate invariant convected time derivative for the flux vector and the stress tensor is discussed. This is performed by investigating the local balance laws and entropy inequality in the spatial configuration, within the single‐fluid approach. For constant parameters, our thermomechanical setting is of Jeffreys type with two delay time parameters, and hence, in the linear/linearized version, it is strictly related to phase‐lag theories within first‐order Taylor approximations. A detailed spectral analysis is carried out for the linearized version of the model, with a scrutiny to some significant limit situations, enhancing the stabilizing effects of the dissipative and elastic mechanisms, also for retardation responses. For polymeric liquids, rheological aspects, wave propagation properties and analogies with other theories with lagging are pointed out. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
59.
Continuous dependence on boundary and Soret coefficients in double diffusive bidispersive convection
Franca Franchi Roberta Nibbi Brian Straughan 《Mathematical Methods in the Applied Sciences》2020,43(15):8882-8893
We develop a theory for double diffusive convection in a double porosity material along the Brinkman scheme. The Soret effect is included whereby a temperature gradient may directly influence salt concentration. The boundary conditions on the temperature and salt fields are of general Robin type. A number of a priori estimates are established whereby, through energy arguments, we prove continuous dependence of the solution on the Soret coefficient and on the coefficients in the boundary conditions in the L2- norm. 相似文献
60.
In this paper we prove subelliptic estimates for operators of the form Δx + λ2 (x)S in ?N = ? × ?, where the operator S is an elliptic integro - differential operator in ?N and λ is a nonnegative Lipschitz continuous function. 相似文献