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Caorsi V Ronzitti E Vicidomini G Krol S McConnell G Diaspro A 《Microscopy research and technique》2007,70(5):452-458
In the last decade, fluorescence resonance energy transfer (FRET) has become a useful technique for studying intermolecular interactions applied to the analysis of biological systems. Although FRET measurements may be very helpful in the comprehension of different cellular processes, it can be difficult to obtain quantitative results, hence the necessity of studying FRET on controllable systems. Here, a fuzzy nanostructured system called a nanocapsule is presented as a nanometric-device allowing distance modulation, thus preserving photophysical properties of fluorescent dyes and exhibiting good potential features for improving quantitative FRET analysis. We evaluated the behavior of such a sample using four FRET methods (three of them based on steady-state fluorescence and one using lifetime measurements). Within some limitations that can be overcome, these nanodevices have the potential to serve as a benchmark system for characterizing new FRET couples and to develop quantitative approaches for FRET analysis. 相似文献
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Pastorino M. Massa A. Caorsi S. 《IEEE transactions on instrumentation and measurement》2000,49(3):573-578
The problem of reconstructing locations, shapes, and dielectric permittivity distributions of two-dimensional dielectric objects from measurements of the scattered electric field is addressed. A numerical approach is proposed which is based on a multi-illumination multiview processing. In particular, the inverse problem is recast as a global nonlinear optimization problem, which is solved by a genetic algorithm. The final objective of the approach is the image reconstruction of highly contrasted bodies 相似文献
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This paper deals with the problem of the calculation of surface integrals for electromagnetic scattering in the case of the widely popular double-triangular basis functions first introduced by Rao, Wilton, and Glisson (1982). An entire set of formulas is obtained which overrides the difficulties inherent to the singularity of the integrands, and results showing the stability, accuracy, and efficiency of the methods developed are reported in an application of the method of moments to the case of perfectly conducting surfaces and computation of near field in domains including the surface itself. Furthermore, the authors provide insight as regards the capability of triangular basis functions to model near field patterns 相似文献
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An overconstrained version of the moment method is presented that is based on a redundant number of testing functions and the use of a pseudoinversion transformation to solve the related overdetermined system of equations. Preliminary results prove that numerical solutions to electromagnetic scattering problems involved in SAR calculation can also be reached by using limited computer resources.<> 相似文献
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An overconstrained version of the method of moments (MoM) for SAR (specific absorption rate) evaluation in biological bodies is presented. A number of testing functions larger than the number of basis functions is used in order to better constrain the solution near corners and edges. A rectangular system is obtained and solved by means of a pseudoinversion algorithm. Comparisons with results reported in the literature show an enhancement of MoM capabilities in SAR calculations, without a consistent increase in computational requirements 相似文献
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Renzo Azaro Salvatore Caorsi Matteo Pastorino 《International journal of imaging systems and technology》1998,9(5):395-403
This article deals with short-range active microwave imaging. In particular, a 3-GHz imaging system based on a modulated scattering technique is described. By using a probe made of an array of (passive) dipoles rotating around a test area, it is possible to measure the field scattered by a long cylinder under approximately transverse-magnetic illumination conditions. Moreover, some considerations are made concerning the relationship for the modulated scattering techniques. Finally, some preliminary experimental results are presented. They were obtained by using a numerical approach to the electromagnetic inverse scattering problem which is developed in the spatial domain, and by making use of a modified Born approximation. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 395–403, 1998 相似文献
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In this paper, a new version of the iterative multiscaling method (IMM) is proposed for reconstructing multiple scatterers in two-dimensional microwave imaging problems. This paper describes the new procedure evaluating the effectiveness of the IMM previously assessed for single object detection. Starting from inverse scattering integral equations, the problem is recast in a minimization one by defining iteratively (at each level of the scaling procedure) a suitable cost function, firstly allowing a detection of the unknown objects, successively a location of the scatterers, and finally, a quantitative reconstruction of the scenario under test. Thanks to its properties, the approach allows an effective use of the information achievable from inverse scattering data. Moreover, the adopted kind of expansion is able to deal with all possible multiresolution combinations in an easy and computationally inexpensive way. Selected numerical examples concerning dielectric, as well as dissipative objects in noisy environments or starting from experimentally acquired data are reported in order to confirm the usefulness of the introduced tool and of the effectiveness of the proposed procedure. 相似文献
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Caorsi S. Ciaramella S. Gragnani G.L. Pastorino M. 《Microwave Theory and Techniques》1995,43(3):632-640
This paper deals with integral-equation-based numerical methods for microwave imaging using regularization procedures to overcome ill-conditioning problems. The strong dependence of reconstruction quality on “a priori” information is discussed. Such information is required to select a suitable number of independent columns when using truncated pseudoinversions (or other regularization parameters, in different cases) for accurate dielectric reconstructions. Moreover, a criterion for the choice of the optimal number of independent columns is proposed, and the possibility of making this choice less critical by using a multiview version of the method is explored. Finally, a modified procedure is presented that further increases the range from which to choose the number of independent columns that allows one to achieve acceptable reconstructions 相似文献
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This paper deals with electromagnetic scattering by nonlinear dielectric objects. In particular, a numerical approach is developed that is aimed at determining the distributions of the electromagnetic field vector inside a three-dimensional nonlinear, inhomogeneous, isotropic scatterer illuminated by a time-periodic incident electric field vector. An integral-equation formulation for the full-vector scattering problem is considered, and the nonlinear effect is taken into account by introducing equivalent sources and a Fourier-series representation. A system of integral equations (for each harmonic vector component and for the static term) is obtained that includes the internal electric field distribution as the unknown. After discretization, the solution is reduced to solving an algebraic system of nonlinear equations. Some preliminary numerical results are reported concerning scatterers that exhibit a specific (quadratic) dependence of the dielectric permittivity on the total electric field. The harmonic components of the scattered electric field outside the objects are also computed 相似文献