1,429 research outputs found
Investigation of Nonlinear Pupil Dynamics by Recurrence Quantification Analysis
Pupil is controlled by the autonomous nervous system(ANS). It shows complexmovements and changes of size even in conditions of constant stimulation. The possibility of extracting information on ANS by processing data recorded during a short experiment using a low cost system for pupil investigation is studied. Moreover, the significance of nonlinear information contained in the pupillogram is investigated. We examined 13 healthy subjects in different stationary conditions, considering habitual dental occlusion (HDO) as a weak stimulation of the ANS with respect to the maintenance of the rest position (RP) of the jaw. Images of pupil captured by infrared cameras were processed to estimate position and size on each frame. From such time series, we extracted linear indexes (e.g., average size, average displacement, and spectral parameters) and nonlinear information using recurrence quantification analysis (RQA). Data were classified using multilayer perceptrons and support vector machines trained using different sets of input indexes: the best performance in classification was obtained including nonlinear indexes in the input features. These results indicate that RQA nonlinear indexes provide additional information on pupil dynamics with respect to linear descriptors, allowing the discrimination of even a slight stimulation of the ANS. Their use in the investigation of pathology is suggeste
The Relative Space: Space Measurements on a Rotating Platform
We introduce here the concept of relative space, an extended 3-space which is
recognized as the only space having an operational meaning in the study of the
space geometry of a rotating disk. Accordingly, we illustrate how space
measurements are performed in the relative space, and we show that an old-aged
puzzling problem, that is the Ehrenfest's paradox, is explained in this purely
relativistic context. Furthermore, we illustrate the kinematical origin of the
tangential dilation which is responsible for the solution of the Ehrenfest's
paradox.Comment: 14 pages, 2 EPS figures, LaTeX, to appear in the European Journal of
Physic
A brief journey through collision models for multipartite open quantum dynamics
The quantum collision models are a useful method to describe the dynamics of
an open quantum system by means of repeated interactions between the system and
some particles of the environment, which are usually termed "ancillas". In this
paper, we review the main collision models for the dynamics of multipartite
open quantum systems, which are composed of several subsystems. In particular,
we are interested in models that are based on elementary collisions between the
subsystems and the ancillas, and that simulate global and/or local Markovian
master equations in the limit of infinitesimal timestep. After discussing the
mathematical details of the derivation of a generic collision-based master
equation, we provide the general ideas at the basis of the collision models for
multipartite systems, we discuss their strengths and limitations, and we show
how they may be simulated on a quantum computer. Moreover, we analyze some
properties of a collision model based on entangled ancillas, derive the master
equation it generates for small timesteps, and prove that the coefficients of
this master equation are subject to a constraint that limits their generality.
Finally, we present an example of this collision model with two bosonic
ancillas entangled in a two-mode squeezed thermal state.Comment: Submitted to a special issue of Open Syst. Inf. Dyn. devoted to the
memory of Prof. A. Kossakowski. Comments and suggestions are welcom
Evolution and timing of salt diapirism in the Iranian sector of the Persian Gulf
The Iranian sector of the Persian Gulf is affected by more than 30 large diapiric structures triggered by the mobilization
of the Infracambrian Hormuz Complex, an evaporite-rich unit that overlies Precambrian basement at the
base of the sedimentary succession. Nineteen non-piercing diapirs, without any appreciable salt intrusion into
the upper succession, were studied in detail and retro-deformed by the decompaction and unfolding of 13 seismic
horizons that were identified by the interpretation of a dense grid of 2D seismic lines and calibrated by well
data.
Salt uplift had begun by the Early Palaeozoic and persists to the present day,with major pulses of intensity during
the Middle Triassic, Cenomanian, Late Oligocene, and post-Middle Miocene. The structural reconstructions and
the analysis of the progressive deformation of the study diapirs do not show any link between diapiric uplift
and local tectonic structures, and no clear correlation with the regional geodynamic events acting at the boundary
of the Arabian plate.
On the contrary, the salt uplift seems strongly influenced by the differential rate of sedimentation that affected
the whole study basin (more than 40,000 km2), with a coefficient of correlation between the salt uplift rate
and the differential rate of sedimentation (expressed by the standard deviation of the sedimentation rate calculated
over the entire basin) of 0.95. This downbuilding mechanism of diapiric growth is apparently induced by
differential sedimentation over long distances (several tens of kilometers), showing that the flow of salt affected
the whole basin and not just the areas around the single diapiric structures
Eye and hand movements disrupt attentional control
Voluntary attentional control is the ability to selectively focus on a subset of visual information in the presence of other competing stimuli–a marker of cognitive control enabling flexible, goal-driven behavior. To test its robustness, we contrasted attentional control with the most common source of attentional orienting in daily life: attention shifts prior to goal-directed eye and hand movements. In a multi-tasking paradigm, human participants attended at a location while planning eye or hand movements elsewhere. Voluntary attentional control suffered with every simultaneous action plan, even under reduced task difficulty and memory load–factors known to interfere with attentional control. Furthermore, the performance cost was limited to voluntary attention: We observed simultaneous attention benefits at two movement targets without attentional competition between them. This demonstrates that the visual system allows for the concurrent representation of multiple attentional foci. Since attentional control is extremely fragile and dominated by premotor attention shifts, we propose that action-driven selection plays the superordinate role for visual selection
The Sagnac Effect in curved space-times from an analogy with the Aharonov-Bohm Effect
In the context of the natural splitting, the standard relative dynamics can
be expressed in terms of gravito-electromagnetic fields, which allow to
formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere
that this formal analogy can be used to derive the Sagnac effect in flat
space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize
those results to study the General Relativistic corrections to the Sagnac
effect in some stationary and axially symmetric geometries, such as the
space-time around a weakly gravitating and rotating source, Kerr space-time,
G\"{odel} universe and Schwarzschild space-time.Comment: 14 pages, 1 EPS figure, LaTeX, accepted for publication in General
Relativity and Gravitatio
A Rigorous Approach to the Feynman-Vernon Influence Functional and its Applications. I
A rigorous representation of the Feynman-Vernon influence functional used to describe open quantum systems is given, based on the theory of infinite dimensional oscillatory integrals. An application to the case of the density matrices describing the Caldeira-Leggett model of two quantum systems with a quadratic interaction is treated
Complete phase retrieval of photoelectron wavepackets
Coherent, broadband pulses of extreme ultraviolet (XUV) light provide a new
and exciting tool for exploring attosecond electron dynamics. Using
photoelectron streaking, interferometric spectrograms can be generated that
contain a wealth of information about the phase properties of the
photoionization process. If properly retrieved, this phase information reveals
attosecond dynamics during photoelectron emission such as multielectron
dynamics and resonance processes. However, until now, the full retrieval of the
continuous electron wavepacket phase from isolated attosecond pulses has
remained challenging. Here, after elucidating key approximations and
limitations that hinder one from extracting the coherent electron wavepacket
dynamics using available retrieval algorithms, we present a new method called
Absolute Complex Dipole transmission matrix element reConstruction (ACDC). We
apply the ACDC method to experimental spectrograms to resolve the phase and
group delay difference between photoelectrons emitted from Ne and Ar. Our
results reveal subtle dynamics in this group delay difference of photoelectrons
emitted form Ar. These group delay dynamics were not resolvable with prior
methods that were only able to extract phase information at discrete energy
levels, emphasizing the importance of a complete and continuous phase retrieval
technique such as ACDC. Here we also make this new ACDC retrieval algorithm
available with appropriate citation in return
Community Energy for enhancing the energy transition
In the transition process towards renewable energy systems, the way to involve final users in the energy production is still complex.
Although many steps forward have been made by Community Energy (CE) around the world and especially in the European Uniion
(EU), there are still many entry obstacles that do not allow a revolution in the energy market. After presenting the state of the art on the
development of Community Energy in Europe, the main features of community energy have been explored in this paper. This work
reports a complete overview of the current perception of Community Energy among people, analyzing the vision that a possible end user
could have in approaching this innovative system of energy sharing. To achieve this goal, the paper presents the results of a survey, with
the aim of studying how people can be more involved in the energy market and how they could have access to community energy. The
outcomes show how people needs should be considered, in order to increase awareness and control over the energy that they consume
for better development of future community energy. The current weaknesses and shortcomings in the diffusion of communities are also
analyzed, and some suggestions and discussions are made on how to overcome these limitations
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