4,827 research outputs found
Symmetry Breaking in d-Dimensional Self-gravitating Systems
Systems with long-range interactions, such as self-gravitating clusters and
magnetically confined plasmas, do not relax to the usual Boltzmann-Gibbs
thermodynamic equilibrium, but become trapped in quasi-stationary states (QSS)
the life time of which diverges with the number of particles. The QSS are
characterized by the lack of ergodicity which can result in a symmetry broken
QSS starting from a spherically symmetric particle distribution. We will
present a theory which allows us to quantitatively predict the instability
threshold for spontaneous symmetry breaking for a class of d-dimensional
self-gravitating systems.Comment: 5 pages, 4 figures. Accepted for publication in Physical Review
Letter
Arianna: towards a new paradigm for assistive technology at home
Providing elderly and people with special needs to retain their independence
as long as possible is one of the biggest challenges of the society of
tomorrow. Teseo, a startup company spinoff from the University of Genoa, aims
at accelerating the transition towards a sustainable healthcare system. Teseo's
first concept and product, Arianna, allows for the automated recognition of
activities of daily living at home and acts as a wellbeing and healthcare
personalized assistant. This abstract outlines the main concepts underlying its
features and capabilities.Comment: Paper accepted at the Eight Italian Forum on Ambient Assisted Living
(ForItAAL 2017
Water in a Polymeric Electrolyte Membrane: Sorption/Desorption and Freezing phenomena
Nafion is a perfluorosulfonated polymer, widely used in Proton Exchange
Membrane Fuel Cells. This polymer adopts a complex structural organisation
resulting from the microsegregation between hydrophobic backbones and
hydrophilic sulfonic acid groups. Upon hydration appear water-filled channels
and cavities, in which are released the acidic protons to form a solution of
hydronium ions in water embedded in the polymer matrix. Below 273 K, a
phenomenon of water sorption/desorption occurs, whose origin is still an open
question. Performing neutron diffraction, we monitored the quantity of ice
formed during the sorption/desorption as a function of temperature down to 180
K. Upon cooling, we observe that ice forms outside of the membrane and
crystallises in the hexagonal Ih form. Simultaneously, the membrane shrinks and
dehydrate, leading to an increase of the hydronium ions concentration inside
the matrix. Reversibly, the ice melts and the membrane re-hydrate upon heating.
A model of solution, whose freezing point varies with the hydronium
concentration, is proposed to calculate the quantity of ice formed as a
function of temperature. The quantitative agreement between the model and
experimental data explains the smooth and reversible behavior observed during
the sorption or desorption of water, pointing out the origin of the phenomena.
The proposed picture reconciles both confinement and entropic effects. Other
examples of water filled electrolyte nano-structures are eventually discussed,
in the context of clarifying the conditions for water transport at low
temperature
Laws of nature: metaphysics and epistemology
The debate on the metaphysics of laws of nature is one of the many disputes in the metaphysics of science that emerged in the lasts decades of the 20th century. It is historically rooted in the discussions on the role of Divine will in the governance of natural phenomena, held during the 16th to 18th centuries. However, its most immediate antecedent is a pressing point in the agenda of the Received View: the task of settling a distinction between authentic scientific laws and mere accidentally true generalizations. In this context the discussion was mainly about the logical, semantic and syntactic properties of lawlike statements that could underpin the distinction. Conversely, the current debate on the metaphysics of laws presupposes that mere linguistic or logical considerations are insufficient to draw that distinction and something else is needed. That something else is frequently a feature of the world that falls under the domain of metaphysics, a law of nature, as opposed to a scientific lawlike statement. Not every position in the debate would happily admit that laws are something in the world, but all of them agree on the fact that some metaphysical theorization about the world's structure is needed in order to settle the distinction between laws and non-laws.Fil: Borge, Bruno JosĂ©. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad de Buenos Aires. Facultad de FilosofĂa y Letras; ArgentinaFil: Cani, Renato. Universidade Federal de Santa Catarina; Brasi
Potencial expressivo nos jogos indie e gamearte : Breve análise dos jogos Flower e Journey
Digital games have been shown to be a powerful expressive and
communicative medium, struggling against the traditional view of games as
shallow media. It’s especially at indie games space that there has been a
greater experimentation, shifting this paradigm. Flower and Journey are in this
indie universe, and these games have reached a great success in many
spheres, helping this paradigm shift and favoring a new way to face digital
games. The objective of this work is to reflect about the gameplay experience
of both games, showing how these games innovated and helping to understand
why these games have reached an important position on last years
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