A Dirichlet problem for harmonic forms inC 1-domains

A Dirichlet problem for harmonic forms in openC ¹-domains is here investigated with boundary data of classL ^p .Work partially supported by MURST 60% and 40%.     

Analytic properties of the S-matrix for interactions with Yukawa-potential tails

We give an explicit analytic expression for the S-matrix in the case of an arbitrary central interaction inside a sphere of finite radius with a Yukawa-potential tail at large distances. The method uses the completeness of the wave functions outside the finite sphere and also the unitarity and the symmetry conditions for the S-matrix. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 147, No. 1, pp. 113–128, April, 2006.     

On the interphace between the outer and inner parts of the crust of a neutron star

A critical point determining the interphace between the outer and inner parts of the crust of a neutron star has been found using a previously developed self-consistent semi-microscopic method. The critical density ρ_d thus obtained is only slightly lower than the commonly accepted value. At the same time, the equilibrium structure of the crust near the critical point differs significantly from that obtained in known calculations.     

Occupational exposures to solar ultraviolet radiation of vineyard workers in Tuscany (Italy)

A study to quantify the UV exposure of vineyard workers was carried out using polysulphone dosimetry. The study took place in Tuscany (Italy) involving 32 vineyard workers, covering three different stages of the vine's growth. The level of personal exposure expressed as a function on the available ambient UV radiation was determined. We also assessed skin reflectance parameters, pre and post exposure. It was found that during spring backs received between 53% and 87% of ambient exposure and arms between 30% and 60%. During summer, the workers received on the back between 36% and 77% of ambient exposure and between 19% and 43% of ambient exposure on the arm. The comparison with the occupational UV exposure limit showed that all subjects received UV exposures in excess of the limit. The exposure of back of neck exceeded 10 SED (assumed as a threshold level of sun-adapted skin for Mediterranean subjects) in spring, which means that in the case of non sun-adapted skin and without sun protection, erythema can be induced in this targeted population. The cumulative exposure was also estimated under specific assumptions of UV exposure giving values in some cases higher than previous studies.     

Distortion products and backward-traveling waves in nonlinear active models of the cochlea

This study explores the phenomenology of distortion products in nonlinear cochlear models, predicting their amplitude and phase along the basilar membrane. The existence of a backward-traveling wave at the distortion-product frequency, which has been recently questioned by experiments measuring the phase of basilar-membrane vibration, is discussed. The effect of different modeling choices is analyzed, including feed-forward asymmetry, micromechanical roughness, and breaking of scaling symmetry. The experimentally observed negative slope of basilar-membrane phase is predicted by numerical simulations of nonlinear cochlear models under a wide range of parameters and modeling choices. In active models, positive phase slopes are predicted by the quasi-linear analytical computations and by the fully nonlinear numerical simulations only if the distortion-product sources are localized apical to the observation point and if the stapes reflectivity is unrealistically small. The results of this study predict a negative phase slope whenever the source is distributed over a reasonably wide cochlear region and/or a reasonably high stapes reflectivity is assumed. Therefore, the above-mentioned experiments do not contradict "classical" models of cochlear mechanics and of distortion-product generation.     

Fermi surface reconstruction in strongly correlated Fermi systems as a first-order phase transition

A quantum phase transition in strongly correlated Fermi systems beyond the topological quantum critical point has been studied using the Fermi liquid approach. The transition takes place between topologically equivalent states with three Fermi surface sheets, but one of them is characterized by a quasiparticle halo in the quasiparticle momentum distribution n(p), and the other one is characterized by a hole pocket. It has been found that the transition between these states is a first-order phase transition for the interaction constant g and temperature T. The phase diagram in the vicinity of this transition has been constructed.     

Many-body theory of π electron systems

Many-body perturbation theory is developed within the dielectric function method presented in a preceding paper [15]. We have explicitly considered the local field corrections (which are disregarded in the random phase approximation) to the self consistent field. These corrections are of second order in the density-density correlation function x and are evaluated exactly in the framework of the adopted approximation scheme because all the integrals which appear in the expressions can be evaluated analytically. Here the method is applied to π electron systems within the zero differential overlap approximation ; explicit calculations of the excitation energies of the benzene molecule using different parametrizations are presented. Comparison is made with results obtained in the RPA and other schemes.     

On the detection of early cochlear damage by otoacoustic emission analysis

Theoretical considerations and experimental evidence suggest that otoacoustic emission parameters may be used to reveal early cochlear damage, even before it can be diagnosed by standard audiometric techniques. In this work, the statistical distributions of a set of otoacoustic emission parameters chosen as candidates for the early detection of cochlear damage (global and band reproducibility, response level, signal-to-noise ratio, spectral latency, and long-lasting otoacoustic emission presence) were analyzed in a population of 138 ears. These ears have been divided, according to a standard audiometric test, in three classes: (1) ears of nonexposed bilaterally normal subjects, (2) normal ears of subjects with unilateral noise-induced high-frequency hearing loss, and (3) their hearing impaired ears. For all analyzed parameters, a statistically significant difference was found between classes 1 and 2. This difference largely exceeds the difference observed between classes 2 and 3. This fact suggests that the noise exposure, which was responsible for the unilateral hearing loss, also caused subclinical damage in the contralateral, audiometrically normal, ear. This is a clear indication that otoacoustic emission techniques may be able to early detect subclinical damages.     

Wavelet and matching pursuit estimates of the transient-evoked otoacoustic emission latency

Different time-frequency techniques may be used to investigate the relation between latency and frequency of transient-evoked otoacoustic emissions. In this work, the optimization of these techniques and the interpretation of the experimental result are discussed. Time-frequency analysis of click-evoked otoacoustic emissions of 42 normal-hearing young subjects has been performed, using both wavelet and matching pursuit algorithms. Wavelet techniques are very effective to provide fast and reliable evaluation of the average latency of large samples of subjects. A major advantage of the matching pursuit technique, as observed by Jedrzejczak et al. [J. Acoust. Soc. Am. 115, 2148-2158 (2004)], is to provide detailed information about the time evolution of the response of single ears at selected frequencies. A hybrid matching pursuit algorithm that includes Fourier spectral information was developed, capable of speeding-up computation times and of identifying "spurious" atoms, whose latency-frequency relation is apparently anomalous. These atoms could be associated with several known phenomena, either intrinsic, such as intermodulation distortion, spontaneous emissions and multiple internal reflections, or extrinsic, such as instrumental noise, linear ringing and the acquisition window onset. A correct interpretation of these phenomena is important to get accurate estimates of the otoacoustic emission latency.     

Approximation of the microscopic effective pairing interaction by the off-shell T matrix for free nucleon-nucleon scattering

The effective pairing interaction in the ¹ S ₀ channel as calculated microscopically within the Brueckner method for a planar slab of nuclear matter by using the separable version of the Paris nucleon-nucleon potential is investigated. The effective interaction is determined for the model space including all negative-energy single-particle states. An analysis is performed for two values of the chemical potential, μ=?8 and ?4 MeV. It is shown that, to a high precision, the effective interaction can be approximated by the off-shell T matrix for free nucleon-nucleon interaction, the T matrix in question being taken at a negative value of the total energy of two nucleons E=2μ.