15,448 research outputs found
Experimental Observation of Coherence and Stochastic Resonances in an Electronic Chua Circuit
Stochastic and coherence resonances appear in nonlinear systems subjected to
an external source of noise and are characterized by a maximum response at the
optimal value of the noise intensity. This paper shows experimentally that it
is possible to observe them in a chaotic system. To this end we have analysed
an electronic Chua circuit running in the chaotic regime and added noise to its
dynamics. In the case of coherence resonance, we observe an optimal periodicity
for the jumps between chaotic attractors, whereas in the case of stochastic
resonance we observe a maximum in the signal-to-noise ratio at the frequency of
an external sinusoidal perturbation.Comment: 6 page
Flora das Culturas Agrícolas da Ilha de Santiago (cabo Verde)
Com o objectivo de caracterizar as comunidades vegetais que acompanham as culturas
agrícolas de sequeiro e de regadio praticadas em Santiago e, particularmente, no vale da ribeira
Seca, efectuaram-se 16 levantamentos titoecológicos ao longo deste curso de água e encostas
sobranceiras. A inventaria@0 floristica revelou a presenta de 118 taro pertencenteas 3 3 familias.
Analisaram-sea, inda,6 2 levantamentorse alizadose m diversosp ontosd a ilha, tendo sido
identificados1 72t axa pertencenteas 42 familiasG. ramineae. Leguminosae e Compositue sao as
famílias melhor representadasA. flora inventariadaC comparadac om a referida em trabalhos
precedentesr,e alizadosp or outrosa utores,r evelandolao correnciad e, pelo menos,1 82t axa na
flora infestante.
Os levantamentos da ribeira Seca foram analisadosa travt5sd o programad e análise
numérica TWINSPAN, que indicou a presentad e 4 agrupamentosv egetais distintos, cuja
interpretacao,a tendendoà s característicase dáticas,c limáticase topográticasd os locais onde
ocorrem,s ugeriua disponibilidadeh idrica comoo factorm aisd eterminantde as uac omposicáo.
Palavras-chavefl:o ra, adventiciasd asc ulturasT, WINSPAN, ilhasd eC aboV erde, Santiago.
In order to identify and to characterizeth e plant communitiesp resenat t the irrigated and
dry cropso f ribeira Secav alley, it were established16 s amplep lots. The tloristic inventory has revealedt he presenteo f 118 tara belongingt o 33 families.I n addition,m ore 62 samplep lots,were establishedth roughoutt he island,w hich permittedt he identifkation of 172t ara from 42 families.G ramineae, CompQsitae &ndL eguminosae weret he mostr epresentativeosn es.T his flora
is comparedw ith that referred in precedingw orksf rom othersa uthors,r evealingt he occurrence
of, at least, 182 tma in the weed flora.
The application of the TWINSPAN numerical analysis, to the plots in the ribeira Seca
vallcy. has revealed the presente of 4 distinct plant communities, which were related with
edaphic,c limatic and topographicf actors.T his analysiss uggestetdh at the water availability wa.s the mainf actor affecting the speciesc ompositionof the communities.
Key-words:f lora weedsT, WINSPAN, CapeV erdei slandsS, antiago
On the long-term correlation between the flux in the Ca II H & K and Halpha lines for FGK stars
The re-emission in the cores of the Ca II H & K and H lines, are well
known proxies of stellar activity. However, these activity indices probe
different activity phenomena, the first being more sensitive to plage
variation, while the other one being more sensitive to filaments. In this paper
we study the long-term correlation between and , two indices based on the Ca II H & K and H lines
respectively, for a sample of 271 FGK stars using measurements obtained over a
9 year time span. Because stellar activity is one of the main obstacles
to the detection of low-mass and long-period planets, understanding further
this activity index correlation can give us some hints about the optimal target
to focus on, and ways to correct for these activity effects. We found a great
variety of long-term correlations between and . Around 20% of our sample has strong positive correlation between
the indices while about 3% show strong negative correlation. These fractions
are compatible with those found for the case of early-M dwarfs. Stars
exhibiting a positive correlation have a tendency to be more active when
compared to the median of the sample, while stars showing a negative
correlation are more present among higher metallicity stars. There is also a
tendency for the positively correlated stars to be more present among the
coolest stars, a result which is probably due to the activity level effect on
the correlation. Activity level and metallicity seem therefore to be playing a
role on the correlation between and . Possible
explanations based on the influence of filaments for the diversity in the
correlations between these indices are discussed in this paper.Comment: 18 pages, 13 figures, 4 tables, accepted for publication in Astronomy
and Astrophysic
Second Generation of 'Miranda Procedure' for CP Violation in Dalitz Studies of B (\& D \& \tau) Decays
The `Miranda Procedure' proposed for analyzing Dalitz plots for CP
asymmetries in charged B and D decays in a model-independent manner is extended
and refined. The complexity of CKM CP phenomenology through order
is needed in searches for New Dynamics (ND). Detailed analyses of three-body
final states other great advantages: (i) They give us more powerful tools for
deciding whether an observed CP asymmetry rep- resents the manifestation of ND
and its features. (ii) Many advantages can already be obtained by the `Miranda
Procedure' without construction of a detailed Dalitz plot de- scription. (iii)
One studies CP asymmetries independent of production asymmetries. We illustrate
the power of a second generation Miranda Procedure with examples with time
integrated rates for decays to final states as
trial runs with comments on .Comment: 29 pages, 7 figure
Ilha de santiago (Cabo Verde) - Notas Florísticas e Fitogeográficas
Dez taya (Achyranthes aspera var.pubescens, Andropogon/astigiatus, Anthephora cristata, Cenchrus
bgorus, Chamaecrista mimosoides, Commelina d~@sa subsp. d$iia, Forsskaolea viridis, Tephrosia
linearis, Tolpis/arinulosa e Stylosanthes humilis) sãom encionadopse lap rimeirav ez paraS antiagoE. stacitacáo constitui também,p ara4 deles,a suap rimeirar eferencia para o arquipélagod e CaboV erde.
A ~orrkcia de espéciese ndémicasc,u ja presentan estai lha não era verificada desdeh á longa data, é ylientada. Pelo valor dasc omunidadevse getaisq uen eleso correm, sãor eferidosa lgunslo caisp articti+nente importantes.biJorus, Chamaecrista mimosoides, Commelina dl@ia subsp. d@úsa, Forsskaolea viridis, Tephrosia
finearis, To~pisfürinulosa and Stylosanthes humilis) are quoted for the first time to Santiago, being ‘four of them unknown in the Cape Verde archipelago. It is remarked the observation of endemic species which :presente, although known in this island, where not seen for a long time. In reasori of its interesting plant communities,it is referred somei mportants ites
Durabilidade natural de quatro madeiras amazônicas em contato com o solo.
bitstream/item/27931/1/com.tec.66.pd
Hanbury Brown Twiss effect for ultracold quantum gases
We have studied 2-body correlations of atoms in an expanding cloud above and
below the Bose-Einstein condensation threshold. The observed correlation
function for a thermal cloud shows a bunching behavior, while the correlation
is flat for a coherent sample. These quantum correlations are the atomic
analogue of the Hanbury Brown Twiss effect. We observe the effect in three
dimensions and study its dependence on cloud size.Comment: Figure 1 availabl
The Territorial Agenda 2030: Towards a common language? A review of a conceptual framework
The Territorial Agenda 2030 aims to provide multi-level strategic orientation to increase cohesion and overcome the 21st century pressing challenges. In multilingual contexts, the ideas and concepts
communicated in such agendas must be clear and well-defined. In our study, we conducted a content
analysis of the concepts of environment, inequality, justice, sustainability, territory and transition in contrast with former versions of this agenda. We found that, since 1983, the Territorial Agenda conceptual
framework changed significantly in its meaning and semantic universe of reference.info:eu-repo/semantics/publishedVersio
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