A Model for the Color Glass Condensate Versus Jet Quenching

A model for the Color Glass Condensate as opposed to jet quenching is proposed for the explanation of the presently available RHIC data. Good fits to these data are presented. A clear way to distinguish between the two possible explanations is also given.Comment: 3 pages, 1 figur

Nonperiodic delay mechanism in time-dependent chaotic scattering

We study the occurence of delay mechanisms other than periodic orbits in systems with time dependent potentials that exhibit chaotic scattering. By using as model system two harmonically oscillating disks on a plane, we have found the existence of a mechanism not related to the periodic orbits of the system, that delays trajectories in the scattering region. This mechanism creates a fractal-like structure in the scattering functions and can possibly occur in several time-dependent scattering systems.Comment: 12 pages, 9 figure

A nonlinear classical model for the decay widths of Isoscalar Giant Monopole Resonances

The decay of the Isoscalar Giant Monopole Resonance (ISGMR) in nuclei is studied by means of a nonlinear classical model consisting of several noninteracting nucleons (particles) moving in a potential well with an oscillating nuclear surface (wall). The motion of the nuclear surface is described by means of a collective variable which appears explicitly in the Hamiltonian as an additional degree of freedom. The total energy of the system is therefore conserved. Although the particles do not directly interact with each other, their motions are indirectly coupled by means of their interaction with the moving nuclear surface. We consider as free parameters in this model the degree of collectivity and the fraction of nucleons that participate to the decay of the collective excitation. Specifically, we have calculated the decay width of the ISGMR in the spherical nuclei $^{208}\rm{Pb}$, $^{144}\rm{Sm}$, $^{116}\rm{Sn}$ and $^{90}\rm{Zr}$. Despite its simplicity and its purely classical nature, the model reproduces the trend of the experimental data which show that with increasing mass number the decay width decreases. Moreover the experimental results (with the exception of $^{90}\rm{Zr}$) can be well fitted using appropriate values for the free parameters mentioned above. It is also found that these values allow for a good description of the experimentally measured $^{112}\rm{Sn}$ and $^{124}\rm{Sn}$ decay widths. In addition, we give a prediction for the decay width of the exotic isotope $^{132}Sn$ for which there is experimental interest. The agreement of our results with the corresponding experimental data for medium-heavy nuclei is dictated by the underlying classical mechanics i.e. the behaviour of the maximum Lyapunov exponent as a function of the system size

Quantum versus Classical Dynamics in a driven barrier: the role of kinematic effects

We study the dynamics of the classical and quantum mechanical scattering of a wave packet from an oscillating barrier. Our main focus is on the dependence of the transmission coefficient on the initial energy of the wave packet for a wide range of oscillation frequencies. The behavior of the quantum transmission coefficient is affected by tunneling phenomena, resonances and kinematic effects emanating from the time dependence of the potential. We show that when kinematic effects dominate (mainly in intermediate frequencies), classical mechanics provides very good approximation of quantum results. Moreover, in the frequency region of optimal agreement between classical and quantum transmission coefficient, the transmission threshold, i.e. the energy above which the transmission coefficient becomes larger than a specific small threshold value, is found to exhibit a minimum. We also consider the form of the transmitted wave packet and we find that for low values of the frequency the incoming classical and quantum wave packet can be split into a train of well separated coherent pulses, a phenomenon which can admit purely classical kinematic interpretation

Hyperacceleration in a stochastic Fermi-Ulam model

Fermi acceleration in a Fermi-Ulam model, consisting of an ensemble of particles bouncing between two, infinitely heavy, stochastically oscillating hard walls, is investigated. It is shown that the widely used approximation, neglecting the displacement of the walls (static wall approximation), leads to a systematic underestimation of particle acceleration. An improved approximative map is introduced, which takes into account the effect of the wall displacement, and in addition allows the analytical estimation of the long term behavior of the particle mean velocity as well as the corresponding probability distribution, in complete agreement with the numerical results of the exact dynamics. This effect accounting for the increased particle acceleration -Fermi hyperacceleration- is also present in higher dimensional systems, such as the driven Lorentz gas.Comment: 4 pages, 3 figures. To be published in Phys. Rev. Let

The ELPAT Living Organ Donor Psychosocial Assessment Tool (EPAT): from 'What' to 'How' of Psychosocial Screening - a Pilot Study

Thorough psychosocial screening of donor candidates is required in order to minimize potential negative consequences and to strive for optimal safety within living donation programmes. We aimed to develop an evidence-based tool to standardize the psychosocial screening process. Key concepts of psychosocial screening were used to structure our tool: motivation and decision-making, personal resources, psychopathology, social resources, ethical and legal factors and information and risk processing. We (i) discussed how each item per concept could be measured, (ii) reviewed and rated available validated tools, (iii) where necessary developed new items, (iv) assessed content validity and (v) pilot-tested the new items. The resulting ELPAT living organ donor Psychosocial Assessment Tool (EPAT) consists of a selection of validated questionnaires (28 items in total), a semi-structured interview (43 questions) and a Red Flag Checklist. We outline optimal procedures and conditions for implementing this tool. The EPAT and user manual are available from the authors. Use of this tool will standardize the psychosocial screening procedure ensuring that no psychosocial issues are overlooked and ensure that comparable selection criteria are used and facilitate generation of comparable psychosocial data on living donor candidates.info:eu-repo/semantics/publishedVersio

An ELPAT definition of the concept ‘Psychosocial’ in the context of Screening Living Organ Donors in Europe: A Concept Mapping approach

Introduction: Across Europe, transplant centers vary in the set of psychosocial screening criteria/guidelines used for the selection of eligible living donors. Our aim was to explore whether a common framework underlies this variation in screening criteria and, based on this framework, to develop a consensus on the essential elements of psychosocial screening of living liver and kidney donors. In order to do so, a research question was set out to define a conceptual framework of the concept ‘Psychosocial’ in the context of screening living organ donors in Europe. We formulated the following research question: Which psychosocial screening criteria are most commonly reported and considered as most important or effective in selecting eligible kidney and liver donors? Method: Concept mapping methodology was used to create a visual representation of the complex topic ‘Psychosocial’ in the context of screening living organ donors in Europe, in which underlying concepts, the relative importance of these concepts and the interplay between different concepts are organized. Initial psychosocial screening criteria (N=83) were derived from an extensive systematic literature review on guidelines, protocols and consensus statements on psychosocial screening practices, complemented by group brainstorm sessions. These criteria were then sorted and rated for their importance and effectiveness by 26 project participants. The data were analyzed using the Concept System Core© Software, which provided us with graphical depictions (concept maps) illustrating the view of project participants on these screening criteria. Pattern Matches and Go-Zones showed us the highlycommon, important and effective criteria. Results: The concept map procedure resulted in six clusters of psychosocial screening criteria: (1) Motivation and decision making (2) Personal resources (3) Psychopathology (4) Social resources (5) Ethical and Legal factors (6) Information and risk processing. Bivariate rating of these criteria revealed which important criteria are already frequently used for screening and which require more attention. Based on the cluster map and bivariate ratings we constructed a conceptual framework for non-medical risk factors that need to be considered when screening potential living organ donors. Conclusion: We provided a conceptual framework of psychosocial screening criteria which can serve as a practical recommendation for the psychosocial screening of potential living organ donors