1,721,388 research outputs found
Enhanced electromagnetic wave propagation in lossy media
Full text linkLa profondità di penetrazione di onde elettromagnetiche in mezzi con perdita è un parametro fondamentale in molte applicazioni: dall’interazione con tessuti biologici, al GeoRadar (GPR), dalla comunicazione con mezzi sottomarini, all’analisi dei materiali. Questa dissertazione propone un metodo per raggiungere penetrazione profonda in mezzi con perdite attraverso l’uso di una particolare categoria di onde elettromagnetiche, dette inomogenee o non-uniformi. In particolare, viene studiato il comportamento di onde non omogenee all’interfaccia tra due mezzi, il primo, in cui è presente l’onda incidente, privo di perdite, e il secondo, in cui è presente l’onda trasmessa, con perdite. Le “consuete” onde elettromagnetiche omogenee, in questa situazione, provocano un’onda trasmessa che si attenua esponenzialmente nella direzione normale all’interfaccia tra i due mezzi, minimizzando la penetrazione. Al contrario, onde non omogenee possono provocare onde trasmesse che attenuano esponenzialmente, ma in direzioni diverse da quella normale all’interfaccia tra
i due mezzi, per esempio tale direzione può essere parallela all’interfaccia con il mezzo con perdite oppure, il vettore di attenuazione può addirittura presentare un angolo superiore ai novanta gradi con la normale a tale superficie di separazione,
risultando in un’amplificazione del segnale piuttosto che attenuazione nel mezzo con perdite. Si parte con un approccio analitico al problema, seguito poi un approccio numerico di design di antenna
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abnormal hepatic uptake of low doses of sulfobromophthalein in Gilbert's syndrome: the role of reduced affinity of the plasma membrane carrier of organic anions
No full textSurface Hopping Dynamics with the Frenkel Exciton Model in a Semiempirical Framework
Full text linkWe present an implementation of the Frenkel exciton model in the framework of the semiempirical floating occupation molecular orbitals-configuration interaction (FOMO-CI) electronic structure method, aimed at simulating the dynamics of multichromophoric systems, in which excitation energy transfer can occur, by a very efficient approach. The nonadiabatic molecular dynamics is here dealt with by the surface hopping method, but the implementation we proposed is compatible with other dynamical approaches. The exciton coupling is computed either exactly, within the semiempirical approximation considered, or by resorting to transition atomic charges. The validation of our implementation is carried out on the trans-azobenzeno-2S-phane (2S-TTABP), formed by two azobenzene units held together by sulfur bridges, taken as a minimal model of multichromophoric systems, in which both strong and weak exciton couplings are present
Quasi-diabatic and adiabatic states and potential energy curves for Na-Cd collisions and excimer formation.
No full textWe present the ab initio calculation of potential energy curves for the ground and excited electronic states of the NaCd system. Both quasi-diabatic and adiabatic wavefunctions and energies have been determined, by means of Quasi Degenerate Perturbation Theory (CIPSI algorithm). The spin-orbit coupling has been evaluated with two approximate methods: one is based on effective nuclear charges, the other one exploits the quasi-invariance of the diabatic states with respect to changes in the nuclear coordinate. The present results are relevant as to the interpretation of the emission spectra of the excimer NaCd*, and to the collisional dynamics of excited Na and Cd atoms
Multireference perturbation CI II: selection of the zero-order space.
No full textIn this paper, the second of a series devoted to multi-reference perturbation CI, we tackle the problem of the appropriate selection of the zero-order space in CIPSI calculations. We propose a new selection procedure, explicitly devised in order to obtain a balanced description for different electronic states and nuclear geometries. To this aim, we define numerically the quality of the zero-order space by means of a suitable parameter σ, which is the square norm of the perturbative correction of the wavefunction. The zero-order space is expanded stepwise so as to obtain the same target σ for all states and geometries. This strategy is applied to the calculation of dissociation, activation and transition energies. It yields a much better convergence of perturbative and zero-order results, when compared with the selection procedure previously used
Steatosis as a co-factor in chronic liver diseases
No full textThe finding of lipid accumulation in the liver, so-called hepatic steatosis or non-alcoholic fatty liver disease, is a common condition frequently found in healthy subjects. Its prevalence, in fact, has been estimated by magnetic resonance studies to be about 35% in the general population and 75% in obese persons. Nevertheless, its presence generates liver damage only in a small percentage of subjects not affected by other liver diseases. It should be defined as a “co-factor” capable of affecting severity and progression, and also therapeutic perspectives, of liver diseases to which it is associated. Herein we will evaluate the impact of hepatic steatosis and obesity on the most common liver diseases: chronic viral hepatitis C and B, and alcoholic liver disease
ASPECTS OF ELECTROPHILIC BROMINATION OF ALKENES IN SOLUTION - THEORETICAL CALCULATION OF ATOMIC CHARGES IN BROMONIUM IONS
No full textMultireference perturbation C.I. III. Fast evaluation of the one-particle density matrix
No full textWithin the frame of multireference perturbation configuration interaction we have developed a fast algorithm, based on diagrammatic techniques, for the calculation of the first-order correction to the one-particle density matrix. As an example of an application we have chosen the evaluation of the dipole moment of the CO molecule, where utilization of the first-order density is shown to corroborate the variational calculation
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