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Zecca A.,University of Trento | Chiari L.,University of Trento | Chiari L.,Flinders University | Garcia G.,Institute Matematicas Y Fisica Fundamental | And 4 more authors.
New Journal of Physics | Year: 2011

In this paper, we report original measurements of total crosssections (TCSs) for positron scattering from an important biomolecule, α-tetrahydrofurfuryl alcohol (THFA). The energy range of these measurements was 0.15-50.15 eV, whereas the energy resolution was ∼260 meV. In addition, we report theoretical results, calculated within the independent-screened additivity rule (IAM-SCAR) formalism, on the corresponding electron impact total crosssections. In this case, the energy range is 1-10 000 eV. With the advent of new particle track simulation codes, which incorporate accurate atomic and molecular data in order to provide interaction details at the nanoscale, interest in positron and electron TCSs has enjoyed something of a recent renaissance as they specify the mean free path between collisions in such codes. Because the present data are, to the best of our knowledge, the first TCSs to be reported for positron scattering from THFA, they fill an important void in the knowledge available to us from the literature. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source


Gonzalez-Diaz P.F.,Institute Matematicas Y Fisica Fundamental | Moruno P.M.,Institute Matematicas Y Fisica Fundamental | Yurov A.V.,Kant Russian State University
Gravitation and Cosmology | Year: 2010

We work out a multiverse scenario whose physical characteristics enable us to advance the following conjecture: whereas the physics of particles and fields is confined to live in the realm of the whole multiverse formed by finite-time single universes, the physics of our observable universe must be confined to just one of the infinite number of universes where such a universe is consistently referred to an infinite cosmic time. If this conjecture is adopted, then some current fundamental problems that appear when one tries to make compatible particle physics and cosmology-such as the cosmological constant, the arrow of time and the existence of a finite proper size of the horizon-can be solved. © 2010 Pleiades Publishing, Ltd. Source


Zecca A.,University of Trento | Chiari L.,University of Trento | Garcia G.,Institute Matematicas Y Fisica Fundamental | Blanco F.,Complutense University of Madrid | And 2 more authors.
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2010

In this paper we report original measurements of total cross sections for positron scattering from the important biomolecule pyrimidine. The energy range of these measurements was 0.3-45 eV, while the energy resolution was ∼260 meV. In addition, we report theoretical results, calculated within the independent atom-screened additivity rule (IAM-SCAR) formalism, for the corresponding electron impact total cross sections. In that case the energy range is 1-10 000 eV. Total cross sections are very important input data for codes that seek to simulate charged-particle tracks in matter, as they define the mean-free path between collisions. As the present data and computations are to the best of our knowledge the first total cross sections to be reported for either positron or electron scattering from pyrimidine, they fill an important void in our available knowledge in the literature. © 2010 IOP Publishing Ltd. Source


Maljkovic J.B.,University of Belgrade | Blanco F.,Complutense University of Madrid | Garcia G.,Institute Matematicas Y Fisica Fundamental | Marinkovic B.P.,University of Belgrade | Milosavljevic A.R.,University of Belgrade
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2012

Elastic electron scattering from gaseous formamide (H 2NCHO) has been investigated. Absolute elastic differential cross sections (DCSs) were determined both experimentally and theoretically. The measurements were performed using a cross beam technique, for the incident energies of 100, 150 and 300 eV and scattering angles from 20°to 110°. Relative elastic DCSs were measured as a function of the angle and the absolute DCSs were determined using the relative flow method. The calculations of electron interaction cross sections are based on a corrected form of the independent-atom method, known as the SCAR (screen corrected additivity rule) procedure and using an improved quasifree absorption model. Calculated results agree very well with the experiment. © 2011 Elsevier B.V. All rights reserved. Source


Ranada A.F.,Complutense University of Madrid | Tiemblo A.,Institute Matematicas Y Fisica Fundamental
Canadian Journal of Physics | Year: 2012

It is usually assumed that the t parameter in the equations of dynamics can be identified with the indication of the pointer of a clock. Things are not so simple, however. In fact, because the equations of motion can be written in terms of t but also in terms of t′ = f(t), f being any well-behaved function, any one of those infinite parametric times t′ is as good as the newtonian one to study classical dynamics in hamiltonian form. Here we show that, as a consequence of parametric invariance, one of the foundations of classical dynamics, the relation between the mathematical parametric time t in the equations of dynamics and the physical dynamical time σ that is measured with a particular clock (which is itself a dynamical system) requires the characterization of the clock that is used to achieve a complete treatment of dynamical systems. These two kinds of time, therefore, must be carefully distinguished. Furthermore, we show that not all the dynamical clock-times are necessarily equivalent and that the observational fingerprint of this nonequivalence has, curiously, the same form as that of the Pioneer anomaly. This suggests, therefore, that an acceleration to one another of the astronomical and the atomic times, t astr and t atom, can contribute to the total amount of the anomaly. © 2012 Published by NRC Research Press. Source

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