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

The Gulf of Cádiz: thrusting or strike-slip motion?

In the Gulf of Cádiz (SW Iberian Peninsula) the boundary between Eurasia and Nubia plates corresponds to a narrow band well defined by the seismicity, where large earthquakes (M>7.0) may be associated to N-S to NNW-SSE horizontal compression due to the convergence between the two plates. Most of these earthquakes are at shallow depth (less than 40 km), with some foci at intermediate-depth, showing E-W distribution and limited by a narrow band less than 20 km wide that broadens as we move to the Strait of Gibraltar. In this area the lithospheric material is relatively rigid and the stresses are released by larger earthquakes. General tectonic models proposed for the Azores-Tunisia plate boundary explain fairly well the nature of its seismicity and tectonic motions; however, details of some of its aspects are still poorly understood and controversial. Zittelini et al. (2009) has recently proposed for the Gulf of Cádiz, transcurrent-transpressional motion along a long strike slip fault based on multichannel seismic reflection surveys. However, this contradicts the compressional motion and reverse faulting of large 1755 Lisbon earthquake (~Mw9), which generate a large tsunami and the recent moderate (Mw>6.0) in 1964, 2007 and 2009 and large (Mw= 8.0) in 1969 earthquakes occurred in the region. These earthquakes show thrusting motion along E-W faults with the southern block going under, corresponding to horizontal NW-SE compression, and they can be related directly to the plate convergence between Nubia and Iberia. References Zitellini et al., 2009. The quest for the Africa–Eurasia plate boundary west of the Strait of Gibraltar. Earth and Planetary Science Letters 280 (2009) 13–50

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

Detection of new eruptions in the Magellanic Clouds LBVs R 40 and R 110

We performed a spectroscopic and photometric analysis to study new eruptions in two luminous blue variables (LBVs) in the Magellanic Clouds. We detected a strong new eruption in the LBV R40 that reached $V \sim 9.2$ in 2016, which is around $1.3$ mag brighter than the minimum registered in 1985. During this new eruption, the star changed from an A-type to a late F-type spectrum. Based on photometric and spectroscopic empirical calibrations and synthetic spectral modeling, we determine that R\,40 reached $T_{\mathrm{eff}} = 5800-6300$~K during this new eruption. This object is thereby probably one of the coolest identified LBVs. We could also identify an enrichment of nitrogen and r- and s-process elements. We detected a weak eruption in the LBV R 110 with a maximum of $V \sim 9.9$ mag in 2011, that is, around $1.0$ mag brighter than in the quiescent phase. On the other hand, this new eruption is about $0.2$ mag fainter than the first eruption detected in 1990, but the temperature did not decrease below 8500 K. Spitzer spectra show indications of cool dust in the circumstellar environment of both stars, but no hot or warm dust was present, except by the probable presence of PAHs in R\,110. We also discuss a possible post-red supergiant nature for both stars

TRANSIENT KNICKPOINTS” NO LEITO DOS RIOS, SIGNIFICADO NA EVOLUÇÃO DA PAISAGEM

Neste trabalho apresenta-se uma síntese sobre a relevância dos knickpoints na estruturação do perfil longitudinal dos rios e indirectamente, na evolução da paisagem. Aborda-se o significado dos knickpoints relativamente aos conceitos de equilíbrio e desequilíbrio do perfil longitudinal, difundidos na literatura. Leis que regem a incisão fluvial, testadas em modelos físico-matemáticos, estabelecidos nas duas últimas décadas, são também referidas. Salientam-se as potencialidades que decorrem deste tipo de análise quantitativa dos perfis longitudinais dos rios, nomeadamente: a identificação de troços relíquia e troços ajustados a novas condições de equilíbrio; a reconstituição de antigos leitos (erodidos) a jusante de knickpoints transitórios e a correlação com outras unidades geomorfológicas, como sejam os terraços fluviais. A relação entre o comportamento das vagas de erosão com a morfologia dos knickpoints e com certos modelos de evolução da paisagem é salientada neste trabalho

Compostagem laminar em sistema orgânico de banana.

A utilização de práticas agrícolas não convencionais capazes de melhorar os atributos físicos, químicos e biológicos do solo é fundamental no sistema orgânico. A compostagem laminar, com o aproveitamento de resíduos orgânicos de baixo custo e fácil disponibilidade, é uma alternativa que pode ser viável.PDF. 139_11

Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes

Numerical Cherenkov radiation (NCR) or instability is a detrimental effect frequently found in electromagnetic particle-in-cell (EM-PIC) simulations involving relativistic plasma beams. NCR is caused by spurious coupling between electromagnetic-field modes and multiple beam resonances. This coupling may result from the slow down of poorly-resolved waves due to numerical (grid) dispersion and from aliasing mechanisms. NCR has been studied in the past for finite-difference-based EM-PIC algorithms on regular (structured) meshes with rectangular elements. In this work, we extend the analysis of NCR to finite-element-based EM-PIC algorithms implemented on unstructured meshes. The influence of different mesh element shapes and mesh layouts on NCR is studied. Analytic predictions are compared against results from finite-element-based EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure

Scattering and Bound State Green's Functions on a Plane via so(2,1) Lie Algebra

We calculate the Green's functions for the particle-vortex system, for two anyons on a plane with and without a harmonic regulator and in a uniform magnetic field. These Green's functions which describe scattering or bound states (depending on the specific potential in each case) are obtained exactly using an algebraic method related to the SO(2,1) Lie group. From these Green's functions we obtain the corresponding wave functions and for the bound states we also find the energy spectra.Comment: 21 Latex pages. Typos corrected. Results unchanged. Version to appear in JM