9,667 research outputs found
Degeneracy between warm and coupled cold dark matter: A clarifying note
Wei et al [PRD 88, 043510 (2013)] have proposed the existence of a
cosmological degeneracy between warm dark matter (WDM), modified gravity and
coupled cold dark matter (CDM) cosmologies at both the background expansion and
the growth of density perturbation levels, i.e., corresponding cosmological
data would not be able to differentiate such scenarios. Here, we will focus on
the specific indistinguishability between a warm dark matter plus cosmological
constant () and coupled scalar field-CDM scenarios. Although the
statement of Wei et al is true for very specific conditions we present a more
complete discussion on this issue and show in more detail that these models are
indeed distinguishable. We show that the degeneracy breaks down since coupled
models leave a specific signature in the redshift space distortion data which
is absent in the uncoupled warm dark matter cosmologies. Furthermore, we
complement our claim by providing the reasons which suggest that even at
nonlinear level a breaking of such apparent equivalence is also expected.Comment: 6 pages, 1 Figure; revised version, section IV extended and enriched
with further discussion, title altered, typos corrected and new references
added. Version published in PR
Alterations in brain connectivity due to plasticity and synaptic delay
Brain plasticity refers to brain's ability to change neuronal connections, as
a result of environmental stimuli, new experiences, or damage. In this work, we
study the effects of the synaptic delay on both the coupling strengths and
synchronisation in a neuronal network with synaptic plasticity. We build a
network of Hodgkin-Huxley neurons, where the plasticity is given by the Hebbian
rules. We verify that without time delay the excitatory synapses became
stronger from the high frequency to low frequency neurons and the inhibitory
synapses increases in the opposite way, when the delay is increased the network
presents a non-trivial topology. Regarding the synchronisation, only for small
values of the synaptic delay this phenomenon is observed
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Optimized Multimode Interference Fiber Based Refractometer in A Reflective Interrogation Scheme
A fiber based refractometer in a reflective interrogation scheme is investigated and optimized. A thin gold film was deposited on the tip of a coreless fiber section, which is spliced with a single mode fiber. The coreless fiber is a multimode waveguide, and the observed effects are due to multimode interference. To investigate and optimize the structure, the multimode part of the sensor is built with 3 different lengths: 58 mm, 29 mm and 17 mm. We use a broadband light source ranging from 1475 nm to 1650 nm and we test the sensors with liquids of varying refractive indices, from 1.333 to 1.438. Our results show that for a fixed wavelength, the sensor sensitivity is independent of the multimode fiber length, but we observed a sensitivity increase of approximately 0.7 nm/RIU for a one-nanometer increase in wavelength
Free software: A Social, Educational, Collaborative and Open to Human Inventiveness Network.
Technological advances are present in different segments of society and, in education, social transformations are consolidated as an important element for technical, human and political development, for that, it is necessary to dialogue with technologies that converge to the same look, in this sense. , Free Software represents an advance in this perception of collaborative movement, acting as a link to a scenario that represents the sum of all knowledge in the teaching versus learning relationship. This model used in Free Software, which prioritizes the subject in the construction of knowledge, constitutes an important ally for the consolidation of the elements present in the spaces of education, whether due to the cultural diversity resulting from the existing relations between the production communities, whether by the amount of existing technological resources in the different areas of knowledge and for the different levels of education. The graphic representation, supported by the theory of networks, about the existing relationships between the different areas of knowledge and the various levels of education on the quantity of software cataloged in the database of the Blog Software Livre na Educação (BSLE) of the Federal University of Rio Grande do Sul (UFRGS), although not exhausted by the present study, presents itself as an important analysis tool for discussions that dialogue with this theme, and which aims, in addition to bringing the reader closer to the theme, a computational model on the elements present in these relationships, contributing to the analysis of potentialities and specific needs in each area, especially in the educational context
Generation of higher derivatives operators and electromagnetic wave propagation in a Lorentz-violation scenario
We study the perturbative generation of higher-derivative operators as
corrections to the photon effective action, which are originated from a Lorentz
violation background. Such corrections are obtained, at one-loop order, through
the proper-time method, using the zeta function regularization. We focus over
the lowest order corrections and investigate their influence in the propagation
of electromagnetic waves through the vacuum, in the presence of a strong,
constant magnetic field. This is a setting of experimental relevance, since it
bases active efforts to measure non linear electromagnetic effects. After
surprising cancellations of Lorentz violating corrections to the Maxwell's
equation, we show that no effects of the kind of Lorentz violation we consider
can be detected in such a context.Comment: v2: 13 pages, no figures, section IV considerably rewritten, main
results unchanged and are now obtained in a simpler way. To appear in PL
Renal Oncocytoma in Pregnancy. An Unusual Presentation of Secondary Hypertension
Introdução: O oncocitoma renal representa 5-7% das neoplasias primárias do rim, é diagnosticado em doentes assintomáticos e caracteriza-se por um comportamento benigno, sem invasão dos tecidos adjacentes ou metastização. O seu diagnóstico no decurso da gravidez é raro, havendo poucos casos descritos na literatura.
Caso clÃnico: Os autores apresentam o caso de uma nulÃpara de 32 anos com hipertensão arterial de difÃcil controlo diagnosticada à s sete semanas gestacionais com internamento à s 24 semanas por quadro de hipertensão crónica agravada com pré-eclâmpsia sobreposta, edema agudo
do pulmão e instabilidade hemodinâmica com necessidade de suporte ventilatório mecânico,
restrição do crescimento fetal e morte fetal. O estudo etiológico do quadro hipertensivo efectuado no perÃodo pós-parto permitiu demonstrar a existência de um tumor renal-oncocitoma.
Conclusão: O comportamento clÃnico do oncocitoma renal permanece mal caracterizado
durante a gravidez, podendo associar-se, apesar do seu comportamento teoricamente benigno, a um desfecho materno e fetal adverso. É fundamental excluir uma possÃvel causa secundária nos quadros hipertensivos de difÃcil controlo
O extrativismo da castanha-do-brasil na região do Baixo Rio Branco, RR.
bitstream/item/36945/1/39.pd
Coaches’ migration: decisions and perceived importance of international experience
The migration of coaches is a topic that has seen increasing research interest in recent years. Discussions are evolving around the factors driving coaches' migration, their experiences, and perceptions held by other sports stakeholders. This study aimed to explore the decision-making processes of coaches regarding migration and their views on the phenomenon. A total of 68 coaches, both with and without international experience, participated in the study. Data collection involved an online survey comprisingclosed-ended questions. For data analysis, we employed a One-Way ANOVA to draw comparisons across independent variables. Interestingly, coaches with international experience have been more frequently approached with offers than their counterparts without such experience. Nevertheless, the majority of the coaches did not perceive foreign coaches as essential to sports development. Coaches with international backgrounds expressed a belief that native coaches should exclusively coach their national teams. Overall, coaches did not highly value international placements or experience. These unexpected findings have significant implications for coach training programs globally. The results are further explored in the context of the expertise required to work in a globalised sports setting and interact with stakeholders from diverse cultural backgrounds
Electric properties of granitic rocks
The objective of this work is to clarify the role of water content on the charge trans- port mechanisms of different granitic rocks. The mineralogical content of the rocks will also be taken into account. From the electrical point of view these materials are rather insulating porous media where charge injection creates different phenomena like build-up charges, space charge limited currents, surface effects and other behav- iors that resemble much a variety of oxides, like AlO
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