Industrias paleolíticas eolizadas en la región del Cabo de Peñas (Asturias)

[Resumen] En el borde costero de la región del Cabo Peñas ( Asturias ), se encuentran numerosos registros sedimentarios y prehist6ricos, particularmente del Paleolítico Inferior, que permiten una caracterización precisa entre la evolución litoral y los asentamientos humanos. En este trabajo, se estudian dos localizaciones prehistóricas de indudable interés: la punta de Cabo Peñas y El Otero ( Xagó ), donde vienen apareciendo útiles con signos evidentes de haber sido trabajados por el viento y que se encuentran asociados claramente al ambiente sedimentario. Se han sometido a análisis tipológicos y sedimentológicos, intentandose una aproximación cronológica.[Abstract] In the central and western coastal zone of the Cabo Peñas Asturias), there are several sedimentary and prehistoric records mainly from the Lower Palaeolithic allowing an accurate characterization between the littoral evolution and human establishment. In this work two interesting prehistoric sites are studied Cabo Peñas and El Otero ( Xagó ) where we met sorne eolized prehistoric industries associated to the sedimentary environment. Typologic and sedimentologic analysis were made and a chronology of the process was trie

How different Fermi surface maps emerge in photoemission from Bi2212

We report angle-resolved photoemission spectra (ARPES) from the Fermi energy ($E_F$) over a large area of the ($k_x,k_y$) plane using 21.2 eV and 32 eV photons in two distinct polarizations from an optimally doped single crystal of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212), together with extensive first-principles simulations of the ARPES intensities. The results display a wide-ranging level of accord between theory and experiment and clarify how myriad Fermi surface (FS) maps emerge in ARPES under various experimental conditions. The energy and polarization dependences of the ARPES matrix element help disentangle primary contributions to the spectrum due to the pristine lattice from those arising from modulations of the underlying tetragonal symmetry and provide a route for separating closely placed FS sheets in low dimensional materials.Comment: submitted to PR

FarNet-II: An improved solar far-side active region detection method

Context. Activity on the far side of the Sun is routinely studied through the analysis of the seismic oscillations detected on the near side using helioseismic techniques such as phase shift sensitive holography. Recently, the neural network FarNet was developed to improve these detections. Aims. We aim to create a new machine learning tool, FarNet II, which further increases the scope of FarNet, and to evaluate its performance in comparison to FarNet and the standard helioseismic method for detecting far side activity. Methods. We developed FarNet II, a neural network that retains some of the general characteristics of FarNet but improves the detections in general, as well as the temporal coherence among successive predictions. The main novelties are the implementation of attention and convolutional long short term memory (ConvLSTM) modules. A cross validation approach, training the network 37 times with a different validation set for each run, was employed to leverage the limited amount of data available. We evaluate the performance of FarNet II using three years of extreme ultraviolet observations of the far side of the Sun acquired with the Solar Terrestrial Relations Observatory (STEREO) as a proxy of activity. The results from FarNet II were compared with those obtained from FarNet and the standard helioseismic method using the Dice coefficient as a metric. Results. FarNet II achieves a Dice coefficient that improves that of FarNet by over 0.2 points for every output position on the sequences from the evaluation dates. Its improvement over FarNet is higher than that of FarNet over the standard method. Conclusions. The new network is a very promising tool for improving the detection of activity on the far side of the Sun given by pure helioseismic techniques. Space weather forecasts can potentially benefit from the higher sensitivity provided by this novel method.Comment: Accepted for publication in Astronomy and Astrophysics. Abridged abstrac

Application of intelligent instruments for the monitoring of thrust reverse noise at airports

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Fermi surface and electronic structure of Pb/Ge(111)

The electronic structure of Pb/Ge(111) has been probed along the temperature-induced phase transition ct -root 3X root 3R30 degrees double right arrow 3 X 3 using angle-resolved photoemission. The alpha-root 3X root 3R30 degrees phase is metallic due to the existence of a half-filled, dispersing surface band. The 3 X 3 phase is characterized by the appearance of an additional surface band with 3 X 3 periodicity, whose role in the phase transition is discussed. The Fermi-surface topology of the alpha-root 3X root 3R30 degrees phase has been probed using angle-resolved photoemission. Its shape is undulated, and it resembles strongly the theoretical prediction, with a Fermi momentum of 0.31 Angstrom(-1) along directions and 0.40 Angstrom(-1) along directions. These values were determined from different experimental methods, and agree with the values needed for a perfect 3 X 3 nesting. However, the Fermi surface exhibits no large flat areas suitable for electronic nesting

The Zeeman effect in the G band

We investigate the possibility of measuring magnetic field strength in G-band bright points through the analysis of Zeeman polarization in molecular CH lines. To this end we solve the equations of polarized radiative transfer in the G band through a standard plane-parallel model of the solar atmosphere with an imposed magnetic field, and through a more realistic snapshot from a simulation of solar magneto-convection. This region of the spectrum is crowded with many atomic and molecular lines. Nevertheless, we find several instances of isolated groups of CH lines that are predicted to produce a measurable Stokes V signal in the presence of magnetic fields. In part this is possible because the effective Land\'{e} factors of lines in the stronger main branch of the CH A$^{2}\Delta$--X$^{2}\Pi$ transition tend to zero rather quickly for increasing total angular momentum $J$, resulting in a Stokes $V$ spectrum of the G band that is less crowded than the corresponding Stokes $I$ spectrum. We indicate that, by contrast, the effective Land\'{e} factors of the $R$ and $P$ satellite sub-branches of this transition tend to $\pm 1$ for increasing $J$. However, these lines are in general considerably weaker, and do not contribute significantly to the polarization signal. In one wavelength location near 430.4 nm the overlap of several magnetically sensitive and non-sensitive CH lines is predicted to result in a single-lobed Stokes $V$ profile, raising the possibility of high spatial-resolution narrow-band polarimetric imaging. In the magneto-convection snapshot we find circular polarization signals of the order of 1% prompting us to conclude that measuring magnetic field strength in small-scale elements through the Zeeman effect in CH lines is a realistic prospect.Comment: 22 pages, 6 figures. To be published in the Astrophysical Journa

Lightning climatology of exoplanets and brown dwarfs guided by Solar system data

We highlight financial support of the European Community under the FP7 by an ERC starting grant number 257431. RAT thanks the Royal Astronomical Society (RAS) and the Physics Trust of the University of St Andrews for supporting his summer placement at the University of St Andrews.Clouds form on extrasolar planets and brown dwarfs where lightning could occur. Lightning is a tracer of atmospheric convection, cloud formation and ionization processes as known from the Solar system, and may be significant for the formation of prebiotic molecules. We study lightning climatology for the different atmospheric environments of Earth, Venus, Jupiter and Saturn. We present lightning distribution maps for Earth, Jupiter and Saturn, and flash densities for these planets and Venus, based on optical and/or radio measurements from the World Wide Lightning Location Network and Sferics Timing and Ranging Network radio networks, the Lightning Imaging Sensor/Optical Transient Detector satellite instruments, the Galileo, Cassini, New Horizons and Venus Express spacecraft. We also present flash densities calculated for several phases of two volcano eruptions, Eyjafjallajökull's (2010) and Mt Redoubt's (2009). We estimate lightning rates for sample, transiting and directly imaged extrasolar planets and brown dwarfs. Based on the large variety of exoplanets, six categories are suggested for which we use the lightning occurrence information from the Solar system. We examine lightning energy distributions for Earth, Jupiter and Saturn. We discuss how strong stellar activity may support lightning activity. We provide a lower limit of the total number of flashes that might occur on transiting planets during their full transit as input for future studies. We find that volcanically very active planets might show the largest lightning flash densities. When applying flash densities of the large Saturnian storm from 2010/11, we find that the exoplanet HD 189733b would produce high lightning occurrence even during its short transit.Publisher PDFPeer reviewe