668 research outputs found
Quasinormal modes of a black hole with a cloud of strings in Einstein-Gauss-Bonnet gravity
The quasinormal modes for a scalar field in the background spacetime
corresponding to a black hole, with a cloud of strings, in
Einstein-Gauss-Bonnet gravity, and the tensor quasinormal modes corresponding
to perturbations in such spacetime, were both calculated using the WKB
approximation. In the obtained results we emphasize the role played by the
parameter associated with the string cloud, comparing them with the results
already obtained for the Boulware-Deser metric. We also study how the
Gauss-Bonnet correction to general relativity affects the results for the
quasinormal modes, comparing them with the same background in general
relativity.Comment: 15 pages, 7 figures; To appear in IJMP
Cloud of strings in f(R) gravity
We derive the solution for a spherically symmetric string cloud configuration
in a d-dimensional spacetime in the framework of f(R) theories of gravity. We
also analyze some thermodynamic properties of the joint black hole - cloud of
strings solution. For its Hawking temperature, we found that the dependence of
the mass with the horizon is significantly different in both theories. For the
interaction of a black hole with thermal radiation, we found that the shapes of
the curves are similar, but shifted. Our analysis generalizes some known
results in the literature.Comment: Version accepted for CP
Helminth parasites of Madeiran rockpool fishes, with a redescription of Schikhobalotrema longivesiculatum Orecchia & Paggi, 1975 (Digenea: Haplosplanchnidae), and some comments on their zoogeographical relationships
Seven species of Madeiran rockpool fishes were examined for their helminth parasites. Only two of these harboured
helminth parasites. The most frequently encountered parasite was the digenean Schikhobalotrema longivesiculatum
Orecchia & Paggi, 1975 from Parablennius parvicornis; this species is redescribed and discussed. The paucity
of the parasite fauna of Madeiran rockpool fishes and the zoogeographical relationships of the digenean fauna of
Madeiran marine fishes are commented upon.info:eu-repo/semantics/publishedVersio
The implementation of mobile location based-games and Qr codes : the case of MobiGeo
Education is being revolutionized by the introduction, of mobile technologies in the teaching and learning process. However, studies that focus in the application of mobile technologies to informal
learning environments is scarce and not systematized [1]. This is the reason for conducting a research
project that involved a urban game MobiGeo, designed in to take better advantage of the flexibility and
ubiquity offered by the Mobile Learning (ML) but also taking into account the importance of motivation
and interaction to enhance students learning.
The definition of ML has been a complicated task for researchers, but there are assumptions that can
not be neglected: the mobility, portability and ubiquity [2], these are features that will drive new learning spaces and thus motivate students. This idea is supported by [2] that introduces the concepts
of "just in time", "just enough" and "just-for-me" and [4] that speaks of the triad "location
independenceā, "independence time" and "meaningful contentā.
These principles of "anytime" and "anywhere" consolidated by mobile technologies came to renew the
variety of educational activities available to teachers and in this context arises the concept of mobile
location-based games. According to [5] "these games are played in physical space, but at the same
time, they are supported by actions and events in an interconnected virtual space", which can be
classified into three categories: ludic, pedagogic and hybrid. By being in direct contact with the
contents to assimilate and move in a real context, students will have a more significant learning [6]
and this will result in the mobilization of knowledge in different contexts. To make the connection
between the physical and the virtual world, our research has made use of Qr codes as these devices provide information in real time and in a dynamically way.
For this research was idealized an urban game called āMobiGeoā, that respect the principles
suggested by [7] and that has as common thread the history of the European Union. To measure
results the researchers developed a questionnaire that was adapted from a proposal of [8] which
created a "Model to evaluate Educational Gamesā, so our proposal was built taking into account the
motivational model of Kirkpatrick (level1) and encompassing three major dimensions:
Motivation/Interest, Interaction and Perceived Learning. To assess the Motivation/Interest was used
the Model ARCS (Relevance, Confidence and Satisfaction) and items of Fun, Immersion and
Challenge of āGame User Experienceā. On the other hand the interaction was evaluated by items of
the Social Interaction dimension of the āGame of User Experienceā, the Learning Perceptions were
evaluated by Bloom's Taxonomy (Knowledge category).
In this paper we present the design and implementation of the MobiGeo outdoor learning activity with
a group of 173 students from the 7th grade of a basic school in the north of Portugal. Initial results
show that this urban game with Qr codes was an adequate activity to use in informal learning
environments that could engage students in gaming with high degrees of motivation and interaction in order to solve the tasks presented to them and so consolidate and acquired new knowledge about the European Union.CIEC ā Research Centre on Child Studies, UM (FCT R&D 317
Tsallis holographic dark energy in the Brans-Dicke cosmology
Using the Tsallis generalized entropy, holographic hypothesis and also
considering the Hubble horizon as the IR cutoff, we build a holographic model
for dark energy and study its cosmological consequences in the Brans-Dicke
framework. At first, we focus on a non-interacting universe, and thereinafter,
we study the results of considering a sign-changeable interaction between the
dark sectors of the cosmos. Our investigations show that, compared with the
flat case, the power and freedom of the model in describing the cosmic
evolution is significantly increased in the presence of the curvature. The
stability analysis also indicates that, independent of the universe curvature,
both the interacting and non-interacting cases are classically unstable. In
fact, both the classical stability criterion and an acceptable behavior for the
cosmos quantities, including the deceleration and density parameters as well as
the equation of state, are not simultaneously obtainable.Comment: Accepted version, Eur. Phys. J. C (2018
Monitoring aggregation processes in multiphase systems: a review
Particle aggregation is essential in many industrial processes, spanning the pharmaceutical and food industries, polymer production, and the environment, among others. However, aggregation can also occur, in some processes, as a non-desired side effect. Thus, to be able to monitor aggregation in industrial processes is of high importance to guarantee that the final, required product characteristics are obtained. In this paper, we present an extensive review of the different techniques available for monitoring particle characteristics in industrial processes involving particulate materials, with special emphasis on aggregation processes. These methods include both off-line and on-line techniques, based either on image acquisition techniques or different radiation scattering techniques (light-scattering and ultrasound spectroscopy). The principles behind each technique are addressed, together with their relevant applications, advantages, and disadvantages
- ā¦