New methodology to measure the dynamics of ocular wave front aberrations during small amplitude changes of accommodation

We present a methodology to measure the systematic changes of aberrations induced by small changes in amplitude of accommodation. We use a method similar the one used in electrophysiology, where a periodic stimulus is presented to the eye and many periods (epochs) of the stimulus are averaged. Using this technique we have measured changes in higher order aberrations from 0.006μm to 0.02μm and correlated them with amplitude changes of accommodation as small as 0.14D. These small changes would have been undetectable without epoch averaging. The correlation coefficients of Zernike terms with defocus were calculated, demonstrating higher values of correlation for epoch averaging. The accurate monitoring of defocus at the start of the accommodation response has shown some interesting trends that may be related with the mechanisms behind accommodation

Dipolar glass polymers containing polarizable groups as dielectric materials for energy storage applications. A minireview

Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R−S(=O)2−R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and β relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as “dipolar glass polymers”. Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed

Cluster Model for Near-barrier Fusion Induced by Weakly Bound and Halo Nuclei

The influence on the fusion process of coupling transfer/breakup channels is investigated for the medium weight $^{6,7}$Li+$^{59}$Co systems in the vicinity of the Coulomb barrier. Coupling effects are discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model. Applications to $^{6}$He+$^{59}$Co induced by the borromean halo nucleus $^{6}$He are also proposed.Comment: 5 pages, 3 figures, FINUSTAR2 Conference, Aghios Nikolaus, Crete, Greece. 10-14 September 200

A study of Schwinger-Dyson Equations for Yukawa and Wess-Zumino Models

We study Schwinger-Dyson equation for fermions in Yukawa and Wess-Zumino models, in terms of dynamical mass generation and the wavefunction renormalization function. In the Yukawa model with $\gamma_5$-type interaction between scalars and fermions, we find a critical coupling in the quenched approximation above which fermions acquire dynamical mass. This is shown to be true beyond the bare 3-point vertex approximation. In the Wess-Zumino model, there is a neat cancellation of terms leading to no dynamical mass for fermions. We comment on the conditions under which these results are general beyond the rainbow approximation and also on the ones under which supersymmetry is preserved and the scalars as well do not acquire mass. The results are in accordance with the non-renormalization theorem at least to order $\alpha$ in perturbation theory. In both the models, we also evaluate the wavefunction renormalization function, analytically in the neighbourhood of the critical coupling and numerically, away from it.Comment: 12 pages and 7 Postscript figures, accepted for publication in Journal of Physics G: Nuclear and Particle Physic

Solving the two-center nuclear shell-model problem with arbitrarily-orientated deformed potentials

A general new technique to solve the two-center problem with arbitrarily-orientated deformed realistic potentials is demonstrated, which is based on the powerful potential separable expansion method. As an example, molecular single-particle spectra for $^{12}$C + $^{12}$C $\to$ $^{24}$Mg are calculated using deformed Woods-Saxon potentials. These clearly show that non-axial symmetric configurations play a crucial role in molecular resonances observed in reaction processes for this system at low energy

Solar System experiments do not yet veto modified gravity models

The dynamical equivalence between modified and scalar-tensor gravity theories is revisited and it is concluded that it breaks down in the limit to general relativity. A gauge-independent analysis of cosmological perturbations in both classes of theories lends independent support to this conclusion. As a consequence, the PPN formalism of scalar-tensor gravity and Solar System experiments do not veto modified gravity, as previously thought.Comment: 7 pages, latex, submitted to Phys. Rev.