Correlating the interstellar magnetic field with protostellar jets and its sources

This article combines new CCD polarimetric data with previous information about protostellar objects in a search for correlations involving the interstellar magnetic field. Specifically, we carried out an optical polarimetric study of a sample of 28 fields of 10 X 10 arcmin^2 located in the neighborhood of protostellar jets and randomly spread over the Galaxy. The polarimetry of a large number of field stars is used to estimate both the average and dispersion of the interstellar magnetic field (ISMF) direction in each region. The results of the applied statistical tests are as follows. Concerning the alignment between the jet direction and the interstellar magnetic field, the whole sample does not show alignment. There is, however, a statistically significant alignment for objects of Classes 0 and I. Regarding the interstellar magnetic field dispersion, our sample presents values slightly larger for regions containing T Tauri objects than for those harboring younger protostars. Moreover the ISMF dispersion in regions containing high-mass objects tends to be larger than in those including only low-mass protostars. In our sample, the mean interstellar polarization as a function of the average interstellar extinction in a region reaches a maximum value around 3% for A(V) = 5, after which it decreases. Our data also show a clear correlation of the mean value of the interstellar polarization with the dispersion of the interstellar magnetic field: the larger the dispersion, the smaller the polarization. Based on a comparison of our and previous results, we suggest that the dispersion in regions forming stars is larger than in quiescent regions.Comment: ApJ accepte

Empiricism and stochastics in cellular automaton modeling of urban land use dynamics

An increasing number of models for predicting land use change in regions of rapidurbanization are being proposed and built using ideas from cellular automata (CA)theory. Calibrating such models to real situations is highly problematic and to date,serious attention has not been focused on the estimation problem. In this paper, wepropose a structure for simulating urban change based on estimating land usetransitions using elementary probabilistic methods which draw their inspiration fromBayes' theory and the related ?weights of evidence? approach. These land use changeprobabilities drive a CA model ? DINAMICA ? conceived at the Center for RemoteSensing of the Federal University of Minas Gerais (CSR-UFMG). This is based on aneight cell Moore neighborhood approach implemented through empirical land useallocation algorithms. The model framework has been applied to a medium-size townin the west of São Paulo State, Bauru. We show how various socio-economic andinfrastructural factors can be combined using the weights of evidence approach whichenables us to predict the probability of changes between land use types in differentcells of the system. Different predictions for the town during the period 1979-1988were generated, and statistical validation was then conducted using a multipleresolution fitting procedure. These modeling experiments support the essential logicof adopting Bayesian empirical methods which synthesize various information aboutspatial infrastructure as the driver of urban land use change. This indicates therelevance of the approach for generating forecasts of growth for Brazilian citiesparticularly and for world-wide cities in general

Structural studies and influence of the structure on the electrical and optical properties of microcrystalline silicon thin films produced by RF sputtering

Microcrystalline silicon thin films were produced by reactive magnetron sputtering on glass substrates under several different conditions (RF power and gas mixture composition). The film structure was studied by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and Raman spectroscopy, allowing the determination of crystal sizes, crystallinity and mechanical strain. These parameters were evaluated by fitting a pseudo-Voigt function to the X-ray data, and by the application of the strong phonon confinement model to the Raman spectra. The degree of crystallinity and the presence of single crystals or crystal agglomerates, which was confirmed by TEM, depends on the preparation conditions, and strongly affects the optical spectra and the electrical transport properties.Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XX

Crystal size and crystalline volume fraction effects on the Erbium emission of nc-Si:Er grown by r.f. sputtering

Erbium-doped low-dimensional Si films with different microstructures were grown by reactive magnetron sputtering on glass substrates by varying the deposition parameters. Their structure and chemical composition were studied by micro-Raman and Rutherford backscattering spectrometry, respectively. In this contribution the Erbium emission is studied as a function of nanocrystalline fraction and average crystal sizes and also as a function of the matrix chemical composition. We discuss the temperature dependence of the Er3+ emission as well as the possible explanations of the low Er active fraction.FCT (POCTI/CTM/39395) and INTAS Project #03-51-6486

Wafer scale fabrication of graphene microelectrode arrays for the detection of DNA hybridization

Since the discovery of graphene, and due to its unique properties, we have witnessed a growing interest in the use of graphene-based devices for applications in the most diverse areas, namely in biosensing, particularly in the detection of genetic material. DNA can bind directly to graphene without the need of a linker and that makes this platform highly interesting for biosensor development. Here, electrochemical chips consisting of 6 independent gold microelectrode arrays as working electrode, and platinum reference and counter electrodes were fabricated at the wafer scale and, after graphene transfer and patterning, were used in the detection of DNA hybridization. Combining the sensitivity of electrochemical impedance spectroscopy and the selectivity of DNA beacons, we were able to detect DNA hybridization in a linear range between 5 pM and 5 nM, which is in the relevant clinical range for many diseases, with sensitivity to single nucleotide polymorphism.Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013info:eu-repo/semantics/acceptedVersio

Optical modulation spectroscopy of hydrogenated microcrystalline silicon

The properties of microcrystalline silicon thin films prepared by RF sputtering were investigated by optical modulation spectroscopy at room temperature and the results were correlated with Raman and conductivity measurements. For comparative purposes, a number of good quality PECVD microc-Si:H samples were also investigated. For PECVD samples the OMS signal is very weak, and only measurable for probe beam energies comparable to the gap of amorphous silicon. This indicates the absence of gap states and therefore a very high crystalline fraction, as confirmed by Raman and TEM measurements. In what concerns RF-sputtered samples, different behaviors can be distinguished: Some samples show a low OMS signal which can be attributed either to a high crystallinity (low density of gap states) or to high recombination rates. These two cases can be distinguished by electrical conductivity values and analysis of the Raman spectra. Other samples exhibit a OMS signal similar to a-Si:H and have low conductivity values, consistent with a Raman spectrum typical of a-Si:H.FCT-grant from PRAXIS XX

Time-Dependent MHD Shocks and Line Emission: The Case of the DG Tau Jet

The line emission from a growing number of Herbig-Haro jets can be observed and resolved at angular distances smaller than a few arcseconds from the central source. The interpretation of this emission is problematic, since the simplest model of a cooling jet cannot sustain it. It has been suggested that what one actually observes are shocked regions with a filling factor of $\sim 1$. In this framework, up to now, comparisons with observations have been based on stationary shock models. Here we introduce for the first time the self-consistent dynamics of such shocks and we show that considering their properties at different times, i.e. locations, we can reproduce observational data of the DG Tau microjet. In particular, we can interpret the spatial behavior of the [SII]6716/6731 and [NII]/[OI]6583/6300 line intensity ratios adopting a set of physical parameters that yield values of mass loss rates and magnetic fields consistent with previous estimates. We also obtain the values of the mean ionization fraction and electron density along the jet, compare these values with the ones derived from observations using the sulfur doublet to constrain the electron density (e.g. Bacciotti et al. 1995).Comment: 6 pages, 3 figure

O organum de Tona, Catalunha

In a document from Tona, Catalonia, dated 888 A. D., we find the word organum among other objects donated to the church of Saint Andrew's monastery. This word has been understood as a clerical or write error, a book of polyphonic music and a musical instrument. However, by comparison with a similar document from Guimarães, in the north-west of the Iberian Peninsula, dated 959 A. D., we can deduce that it is in fact a archaic way to designate the Book of Psalms, that has survived in the Northern Peninsula until the Xth century.[pt] A palavra organum, que encontramos no documento de fundaçao da igreja do mosteiro de Tona, na Catalunha, datado de 888 d. C, foi interpretada como erro de copia ou escrita, livro de polifonía e instrumento musical. Contudo, através da comparação com um documento similar de Guimarães, no Noroeste da Península, datado de 959 d. C, concluímos que se trata de uma forma primitiva de designar o Salterio, que sobreviven na Península até ao séc. X