Recursos de colección

E-Prints Complutense (109.028 recursos)

En este archivo los docentes e investigadores de la UCM depositan sus documentos en acceso abierto (open access)

Tipo = Artículo

Mostrando recursos 1 - 20 de 2.006

  1. Abduction, Bayesianism and Best Explanations in Physics

    Rivadulla Rodríguez, Andrés
    This article claims the validity of abductive reasoning, or inference to the best explanation, as a practice of discovery of explanatory scientific hypotheses. Along the way to achieve this objective I present here a series of arguments that question the feasibililty of Bayesianism as a theory of scientific confirmation. Having solved this issue, I resort to an episode of contemporary astrocosmology that I interpret as an eloquent example of the effectiveness of abductive methodology in contemporary theoretical physics.

  2. Estimation of interaction energy and contact stiffness in atomic-scale sliding on a model sodium chloride surface in ethanol

    Agmon, Liron; Shahar, Itai; Yosufov, Danny; Pimentel Guerra, Carlos; Pina Martínez, Carlos Manuel; Gnecco, Enrico; Berkovich, Ronen
    Friction force microscopy (FFM) in aqueous environments has recently proven to be a very effective method for lattice-resolution imaging of crystal surfaces. Here we demonstrate the use of ethanol for similar measurements on water-soluble materials. Lattice resolved frictional stick-slip traces of a cleaved NaCl(100) surface submerged in ethanol are compared with previous obtained FFM results in ultrahigh vacuum (UHV). We use the Prandtl-Tomlinson framework to estimate the amplitude of the corrugation potential and the contact stiffness. The surface potential amplitude scales with the applied normal loads are in good agreement with data obtained for NaCl measured under UHV conditions, but...

  3. Electrodeposition of Bi thin films on n-GaAs(111)B. II. Correlation between the nucleation process and the structural and electrical properties

    Prados Díaz, Alicia; Ranchal Sánchez, Rocío
    The surface morphology and the crystal structure of 40 nm thin Bi films electrodeposited on GaAs(111)B at different growth overpotentials have been studied by means of atomic force microscopy and X-ray diffraction, respectively. The Bi/GaAs interface has also been electrically characterized by means of current-voltage curves that have been analyzed with the thermionic-field emission theory. Taking into account the results presented in Part I, we can conclude that the structural and electrical properties of the Bi layers are correlated with the nucleation process and, therefore, with the energy band diagram of the semiconductor-electrolyte interface. We have found that surface morphology...

  4. Electrodeposition of Bi thin films on n-GaAs(111)B. I. Correlation between the overpotential and the nucleation process

    Prados Díaz, Alicia; Ranchal Sánchez, Rocío
    Bismuth thin films constitute a promising nanostructure for the fabrication of spin-based devices. To achieve this goal, it is necessary to obtain high-quality Bi layers with controlled and reproducible properties. Therefore, studies focused on the understanding of the nucleation process and the correlation between the growth conditions and the film properties are of great interest. In this work, we have studied the electrodeposition of Bi thin films onto GaAs(111)B substrates at different overpotentials. In Part I, we have analyzed the nucleation of the films by means of potentiostatic curves. The current density transients have been deconvoluted into individual processes taking...

  5. Wilson fermions and axion electrodynamics in optical lattices

    Bermúdez, A.; Mazza, L.; Rizzi, M.; Goldman, N.; Lewenstein, M.; Martin-Delgado Alcántara, Miguel Ángel
    We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3 þ 1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

  6. Realistic time-reversal invariant topological insulators with neutral atoms

    Goldman, N.; Satija, I.; Nikolic, P.; Bermúdez, A.; Martin-Delgado Alcántara, Miguel Ángel; Lewenstein, M.; Spielman, I.B.
    We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states.We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and...

  7. The U(1) lattice gauge theory universally connects all classical models with continuous variables, including background gravity

    Xu, Ying; De las Cuevas, Gemma; Dür, Wolfgang; Briegel, Hans J.; Martin-Delgado Alcántara, Miguel Ángel
    We show that the partition function of many classical models with continuous degrees of freedom, e.g. abelian lattice gauge theories and statistical mechanical models, can be written as the partition function of an (enlarged) four–dimensional lattice gauge theory (LGT) with gauge group U(1). This result is very general that it includes models in different dimensions with different symmetries. In particular, we show that a U(1) LGT defined in a curved spacetime can be mapped to a U(1) LGT with a flat background metric. The result is achieved by expressing the U(1) LGT partition function as an inner product between two...

  8. Sedimentology, clay mineralogy and palaeosols of the Mid-Carnian Pluvial Episode in E Spain: insights into humidity and sea-level variations

    Barrenechea, José F.; López Gómez, José; Horra del Barco, Raúl de la
    This study examines rainfall variations of the Mid-Carnian Pluvial Episode (CPE) based on the continental fluvial sedimentology, palaeosol and clay mineralogy records of the Stable Meseta (E Spain). In the formation examined, Manuel Fm or K2 Fm, the CPE is represented by three regressive-transgressive sequences (R-T), or subunits K2.1, K2.2 and K2.3, from base to top. Each subunit broadly consists of a genetic stratigraphic sequence bearing well-developed highstand, lowstand and transgressive system tracts (HST, LST and TST). Hydromorphic features in the palaeosols suggest changes in the activity of both ground and surface waters. The clay mineral assemblage is dominated by...

  9. Mg-rich carbonates mediated by a bacterium isolated from an extreme alkaline lake in Central Spain

    Sanz Montero, Esther; Cabestrero Aranda, Óscar; Sánchez-Román, Mónica

  10. Interregional mobility of talent in Spain: The role of job opportunities and qualities of places during the recent economic crisis

    Sánchez Moral, S.; Arellano, A.; Diez Pisonero, R.

  11. Late glacial and post-glacial deposits of the Navamuño peatbog (Iberian Central System): Chronology and paleoenvironmental implications

    Turu, Valenti; Carrasco González, Rosa María; Pedraza Gilsanz, Javier de; Ros, Xavier; Ruiz-Zapata, María Blanca; Soriano-López, Joan Manuel; Mur-Cacuho, Elena; Pélachs-Mañosa, Albert; Muñoz Martín, Alfonso; Sánchez, Jesús; Echeverria-Moreno, Anna
    The Navamuño peatbog (Sierra de Béjar, western Spain) is a ∼14 ha pseudo-endorheic depression with boundaries defined by a lateral moraine of the Cuerpo de Hombre paleoglacier and fault-line scarps on granite bedrock. The stratigraphy of the Navamuño peatbog system is characterized here using borehole data to a depth of 20 m. An integrated interpretation from direct-push coring, dynamic probing boreholes and handheld auger drillings advances our knowledge of the Navamuño polygenetic infill. Correlating this data with those obtained in other studies of the chronology and evolutionary sequence of the Cuerpo de Hombre paleoglacier has enabled us to establish the...

  12. Metric and morphological comparison between the Arago (France) and Atapuerca-Sima de los Huesos (Spain) dental samples, and the origin of Neanderthals

    Bermúdez de Castro, José María; Martinón-Torres, María; Martínez de Pinillos, Marina; García Campos, Cecilia; Modesto Mata, Mario; Martín-Francés, Laura; Arsuaga, Juan Luis
    The variability observed in the growing Middle Pleistocene hominin fossil record of Europe continues to trigger much debate on taxonomic issues and the biological processes that gave rise to Neanderthals. Here we present a metric and morphological comparative study of the dental samples recovered from the sites of Arago (southeast France) and Sima de los Huesos (SH) in the Sierra de Atapuerca (northern Spain). These sites are key to providing answers to these questions since they have yielded the largest hominin samples so far recovered for this time period. Despite the geographical proximity of the two sites and the contemporaneity...

  13. Synthesis of full Poincare beams by means of uniaxial crystals

    Piquero Sanz, Gemma María; Monroy, L.; Santarsiero, M.; Alonzo, M.; Gonzalez de Sande, Juan Carlos
    A simple optical system is proposed to generate full-Poincare beams (FPBs), i.e. beams presenting all possible states of (total) polarization across their transverse section. The method consists in focusing a uniformly polarized laser beam onto a uniaxial crystal having its optic axis parallel to the propagation axis of the impinging beam. A simple approximated model is used to obtain the analytical expression of the beam polarization at the output of the crystal. The output beam is then proved to be a FPB. By changing the polarization state of the input field, full-Poincare beams are still obtained, but presenting different distributions...

  14. Memory effect and magnetocrystalline anisotropy impact on the surface magnetic domains of magnetite(001)

    Martín García, Laura; Chen, Gong; Montaña, Yaiza; Mascaraque Susunaga, Arantzazu; Pabón, Beatriz M.; Schmid, Andreas K.; Figuera, Juan de la
    The structure of magnetic domains, i.e. regions of uniform magnetization separated by domain walls, depends on the balance of competing interactions present in ferromagnetic (or ferrimagnetic) materials. When these interactions change then domain configurations also change as a result. Magnetite provides a good test bench to study these effects, as its magnetocrystalline anisotropy varies significantly with temperature. Using spin-polarized electron microscopy to map the micromagnetic domain structure in the (001) surface of a macroscopic magnetite crystal (similar to 1 cm size) shows complex domain patterns with characteristic length-scales in the micrometer range and highly temperature dependent domain geometries. Although heating...

  15. Nanomotors for Nucleic Acid, Proteins, Pollutants and Cells Detection

    Baeza, Alejandro; Vallet Regí, María
    The development of nanomachines able to operate at the nanoscale, performing complex tasks such as drug delivery, precision surgery, or cell detection, constitutes one of the most important challenges in nanotechnology. The principles that rule the nanoscale are completely different from the ones which govern the macroscopic world and, therefore, the collaboration of scientists with expertise in different fields is required for the effective fabrication of these tiny machines. In this review, the most recent advances carried out in the synthesis and application of nanomachines for diagnosis applications will be presented in order to provide a picture of their potential...

  16. Hexahidrita-epsomita en el deterioro de piedra dolomítica del patrimonio arquitectónico

    Fort González, Rafael; Varas Muriel, María José; Pérez-Monserrat, Elena Mercedes; Vázquez Calvo, María del Carmen

  17. Caracterización y procedencia de la sillería granítica del convento de la Encarnación (Madrid)

    Pérez-Monserrat, Elena Mercedes; Fort González, Rafael
    This work faces the study of the granitic masonry of external façades of the Convent of the Incarnation (Madrid). The aim is to characterize the employed granites in the temple in order to locate its provenance, both of the original granite utilized in the two constructive stages of the Convent (17th and 18th centuries) as well as the replacement one used in latter restorations (20th century). Their petrographical properties and their geochemistry trend, allow to establish the granitic material provenance in the Valdemorillo-Zarzalejo (Madrid) granites outcrops, corresponding to medium grained biotitic monzogranites. The quarries of that area have supplied granitic...

  18. Active fault databases and seismic hazard calculations: a compromise between science and practice. Review of case studies from Spain

    Garcia Mayordomo, Julián; Martín Banda, Raquel; Insua Arévalo, Juan Miguel; Alvarez Gómez, José Antonio; Martínez Diaz, José Jesús
    Since the Quaternary Active Faults Database of Iberia (QAFI) was released in February 2012 a number of studies aimed at producing seismic hazard assessments have made use of it. We will present a summary of the shortcomings and advantages that were faced when QAFI was considered in different seismic hazard studies. These include the production of the new official seismic hazard map of Spain, performed in the view of the foreseen adoption of Eurocode-8 throughout 2017. The QAFI database was considered as a complementary source of information for designing the seismogenic source-zone models used in the calculations, and particularly for...

  19. Comprehensive phenological description of essential-oil chemotypes of Salvia lavandulifolia Vahl Grown under the same environmental conditions

    Usano Alemany, Jaime; Palá Paúl, Jesús; Herráiz Peñalver, David
    A comprehensive description of diverse essential-oil chemical profiles was conducted with twelve individual plants of Salvia lavandulifolia Vahl (Spanish sage) gathered from wild populations and grown under identical culture conditions. Whereas the chemical polymorphism within species of aromatic plants is well known, both the statistical significance of the differences in the chemical composition and the setting of chemical profiles have been scarcely studied. Remarkably different essential-oil chemical profiles were described for the wild-growing plants, which remained different during the three years of cultivation, even when acute situations of water stress occurred. Different patterns of representative compounds throughout the phenological cycle...

  20. Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems

    Ochoa-Hueso, Raúl; Arróniz-Crespo, María; Bowker, Matthew A.; Maestre, Fernando T.; Pérez Corona, Esther; Theobald, Mark R.; Vivanco, Marta G.; Manrique, Esteban
    Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found...

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