7,740 research outputs found
The child in charge: The case of child-participatory design of an environmental sustainability serious game
In a technology-advanced world, it is known that children are growing up surrounded by electronic devices such as computers, mobile phones, and tablets, and eventually use them in their daily routines. Whereas the accessibility of these powerful tools is a long-standing issue, there is the need to conduct further studies including children during the design process. In this paper we explore a child-centred design approach through a serious game on sustainability. Participatory design, prototyping and evaluation are part of the process where we explore behaviour and feedback regarding the requested tasks. The preliminary results indicate that the children actively engaged with the prototypes, giving feedback and new ideas to make the serious game more engaging and easier for other children.info:eu-repo/semantics/acceptedVersio
BPS black holes, the Hesse potential, and the topological string
The Hesse potential is constructed for a class of four-dimensional N=2
supersymmetric effective actions with S- and T-duality by performing the
relevant Legendre transform by iteration. It is a function of fields that
transform under duality according to an arithmetic subgroup of the classical
dualities reflecting the monodromies of the underlying string compactification.
These transformations are not subject to corrections, unlike the
transformations of the fields that appear in the effective action which are
affected by the presence of higher-derivative couplings. The class of actions
that are considered includes those of the FHSV and the STU model. We also
consider heterotic N=4 supersymmetric compactifications. The Hesse potential,
which is equal to the free energy function for BPS black holes, is manifestly
duality invariant. Generically it can be expanded in terms of powers of the
modulus that represents the inverse topological string coupling constant,
, and its complex conjugate. The terms depending holomorphically on
are expected to correspond to the topological string partition function and
this expectation is explicitly verified in two cases. Terms proportional to
mixed powers of and are in principle present.Comment: 28 pages, LaTeX, added comment
Phase diagram for non-axisymmetric plasma balls
Plasma balls and rings emerge as fluid holographic duals of black holes and
black rings in the hydrodynamic/gravity correspondence for the Scherk-Schwarz
AdS system. Recently, plasma balls spinning above a critical rotation were
found to be unstable against m-lobed perturbations. In the phase diagram of
stationary solutions the threshold of the instability signals a bifurcation to
a new phase of non-axisymmetric configurations. We find explicitly this family
of solutions and represent them in the phase diagram. We discuss the
implications of our results for the gravitational system. Rotating
non-axisymmetric black holes necessarily radiate gravitational waves. We thus
emphasize that it would be important, albeit possibly out of present reach, to
have a better understanding of the hydrodynamic description of gravitational
waves and of the gravitational interaction between two bodies. We also argue
that it might well be that a non-axisymmetric m-lobed instability is also
present in Myers-Perry black holes for rotations below the recently found
ultraspinning instability.Comment: 1+22 pages, 3 figures. v2: minor corrections and improvements,
matches published versio
Electromagnetic radiation from collisions at almost the speed of light: an extremely relativistic charged particle falling into a Schwarzschild black hole
We investigate the electromagnetic radiation released during the high energy
collision of a charged point particle with a four-dimensional Schwarzschild
black hole. We show that the spectra is flat, and well described by a classical
calculation. We also compare the total electromagnetic and gravitational
energies emitted, and find that the former is supressed in relation to the
latter for very high energies. These results could apply to the astrophysical
world in the case charged stars and small charged black holes are out there
colliding into large black holes, and to a very high energy collision
experiment in a four-dimensional world. In this latter scenario the calculation
is to be used for the moments just after the black hole formation, when the
collision of charged debris with the newly formed black hole is certainly
expected. Since the calculation is four-dimensional, it does not directly apply
to Tev-scale gravity black holes, as these inhabit a world of six to eleven
dimensions, although our results should qualitatively hold when extrapolated
with some care to higher dimensions.Comment: 6 pages, 2 figure
Mapping atmospheric pollutant emissions in European countries
WOS:000300110900009 (Nº de Acesso Web of Science)In this paper we present a methodology which enables the graphical representation, in a bi-dimensional Euclidean space, of atmospheric pollutants emissions in European countries. This approach relies on the use of Multidimensional Unfolding (MDU), an exploratory multivariate data analysis technique. This technique illustrates both the relationships between the emitted gases and the gases and their geographical origins. The main contribution of this work concerns the evaluation of MDU solutions. We use simulated data to define thresholds for the model fitting measures, allowing the MDU output quality evaluation. The quality assessment of the model adjustment is thus carried out as a step before interpretation of the gas types and geographical origins results. The MDU maps analysis generates useful insights, with an immediate substantive result and enables the formulation of hypotheses for further analysis and modeling
Fertilidade do solo em sistemas agroflorestais.
Discussão sobre o tema desenvolvimento sustentável ocupa grande espaço na sociedade devido ao declínio na qualidade de vida no meio rural e urbano. A perda de qualidade de vida associa-se à intensa degradação dos recursos naturais atrelada à modernização da agricultura e ao aumento populacional das cidades. A agricultura é função da interação de fatores socioambientais e naturais, englobando dimensões sociais, culturais, políticas e econômicas. O desafio para uma agricultura sustentável passa pelo ajuste das relações socioeconômicas que governam o que é produzido, como é produzido e para quem é produzido. Isto necessita de uma abordagem que integra os princípios agronômicos, ecológicos e socioeconômicos à compreensão e avaliação do efeito das tecnologias sobre os sistemas agrícolas e a sociedade como um todo.Palestra
Radiocarbon and blue optically stimulated luminescence chronologies of the Oitavos consolidated dune (Western Portugal)
The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (~20,000 cal BP) than the OSL age measurement (~15,000 yr), while 14C age measurements on the inorganic component and the gastropods produced ages of ~35,000 yr and ~34,000 yr, respectively. Rare-earth
element analyses provide evidence that the gastropods incorporate geological carbonate, making them an unreliable indicator of the age of the paleosol. We propose that the 14C age of the small organic component of the paleosol is also likely to be unreliable due to incorporation of residual material. The OSL age measurement of the upper paleosol (~15,000 yr) is consistent with the age for the base of the dune (~14,500 yr). The younger OSL age for the top of the dune (~12,000 yr) suggests that it was built up by at least 2 sand pulses or that there was a remobilization of material at the top during its evolution, prior to consolidation
UCP2 and ANT differently modulate proton-leak in brain mitochondria of long-term hyperglycemic and recurrent hypoglycemic rats
A growing body of evidence suggests that mitochondrial
proton-leak functions as a regulator of reactive
oxygen species production and its modulation may limit
oxidative injury to tissues. The main purpose of this work
was to characterize the proton-leak of brain cortical mitochondria
from long-term hyperglycemic and insulininduced
recurrent hypoglycemic rats through the modulation
of the uncoupling protein 2 (UCP2) and adenine nucleotide
translocator (ANT). Streptozotocin-induced diabetic
rats were treated subcutaneously with twice-daily insulin
injections during 2 weeks to induce the hypoglycemic episodes.
No differences in the basal proton-leak, UCP2 and
ANT protein levels were observed between the experimental
groups. Mitochondria from recurrent hypoglycemic rats
presented a decrease in proton-leak in the presence of
GDP, a specific UCP2 inhibitor, while an increase in
proton-leak was observed in the presence of linoleic acid,
a proton-leak activator, this effect being reverted by the
simultaneous addition of GDP. Mitochondria from longterm
hyperglycemic rats showed an enhanced susceptibility
to ANT modulation as demonstrated by the complete inhibition
of basal and linoleic acid-induced proton-leak caused
by the ANT specific inhibitor carboxyatractyloside. Our
results show that recurrent-hypoglycemia renders mitochondria
more susceptible to UCPs modulation while the protonleak
of long-term hyperglycemic rats is mainly modulated
by ANT, which suggest that brain cortical mitochondria
have distinct adaptation mechanisms in face of different
metabolic insults.The authors’ work is supported by the Fundação
para a Ciência e a Tecnologia (FCT) (PTDC/SAU-NEU/103325/2008)
co-funded by Fundo Europeu de Desenvolvimento Regional (FEDER)
via Programa Operacional Factores de Competitividade (COMPETE).
Susana Cardoso has a PhD fellowship from the Portuguese Foundation
for Science and Technology (SFRH/BD/43968/2008)
An effective singular oscillator for Duffin-Kemmer-Petiau particles with a nonminimal vector coupling: a two-fold degeneracy
Scalar and vector bosons in the background of one-dimensional nonminimal
vector linear plus inversely linear potentials are explored in a unified way in
the context of the Duffin-Kemmer-Petiau theory. The problem is mapped into a
Sturm-Liouville problem with an effective singular oscillator. With boundary
conditions emerging from the problem, exact bound-state solutions in the spin-0
sector are found in closed form and it is shown that the spectrum exhibits
degeneracy. It is shown that, depending on the potential parameters, there may
or may not exist bound-state solutions in the spin-1 sector.Comment: 1 figure. arXiv admin note: substantial text overlap with
arXiv:1009.159
Pinning of spiral fluxons by giant screw dislocations in YBa_2Cu_3O_7 single crystals: Josephson analog of the fishtail effect
By using a highly sensitive homemade AC magnetic susceptibility technique,
the magnetic flux penetration has been measured in YBa_2Cu_3O_7 single crystals
with giant screw dislocations (having the structure of the Archimedean spirals)
exhibiting a=3 spiral turnings, the pitch b=18.7 microns and the step height
c=1.2nm (the last parameter is responsible for creation of extended weak-link
structure around the giant defects). The magnetic field applied parallel to the
surface enters winding around the weak-link regions of the screw in the form of
the so-called spiral Josephson fluxons characterized by the temperature
dependent pitch b_f(T). For a given temperature, a stabilization of the fluxon
structure occurs when b_f(T) matches b (meaning an optimal pinning by the screw
dislocations) and manifests itself as a pronounced low-field peak in the
dependence of the susceptibility on magnetic field (applied normally to the
surface) in the form resembling the high-field (Abrikosov) fishtail effect.Comment: see also http://www.jetpletters.ac.ru/ps/1886/article_28701.shtm
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