http://hdl.handle.net/2117/3983 Thu, 20 Jun 2013 11:05:33 GMT 2013-06-20T11:05:33Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/19550 Title: Second layer of H2 and D2 adsorbed on graphene Authors: Gordillo Bargueño, Maria Carmen; Boronat Medico, Jordi Abstract: We report diffusion Monte Carlo calculations on the phase diagrams of para-H2 and ortho-D2 adsorbed on top of a first layer of the same substances on graphene. We found that the ground state of the second layer is a triangular incommensurate solid for both isotopes. The densities for promotion to a second layer and for the onset of a two-dimensional solid on that second layer compare favorably with available experimental data in both cases. Thu, 13 Jun 2013 15:12:58 GMT http://hdl.handle.net/2117/19550 2013-06-13T15:12:58Z Gordillo Bargueño, Maria Carmen; Boronat Medico, Jordi no We report diffusion Monte Carlo calculations on the phase diagrams of para-H2 and ortho-D2 adsorbed on top of a first layer of the same substances on graphene. We found that the ground state of the second layer is a triangular incommensurate solid for both isotopes. The densities for promotion to a second layer and for the onset of a two-dimensional solid on that second layer compare favorably with available experimental data in both cases. http://hdl.handle.net/2117/19503 Title: Size effects on water adsorbed on hydrophobic probes at the nanometric scale Authors: Calero Borrallo, Carles; Gordillo, Carmen; Martí Rabassa, Jordi Abstract: Molecular dynamics simulations of liquid water at ambient conditions, adsorbed at the external walls of (n,n) single-walled armchair carbon nanotubes have been performed for n = 5, 9, 12. The comparison with the case of water adsorbed on graphene has also been included. The analysis of Helmholtz free energies reveals qualitatively different ranges of thermodynamical stability, eventually starting at a given threshold surface density. We observed that, in the framework of the force field considered here, water does not wet graphene nor (12,12) tubes, but it can coat thinner tubes such as (9,9) and (5,5), which indicates that the width of the carbon nanotube plays a role on wetting. On the other hand, density profiles, orientational distributions of water, and hydrogen-bond populations indicate significant changes of structure of water for the different surfaces. Further, we computed self-diffusion of water and spectral densities of water and carbon molecules, which again revealed different qualitative behavior of interfacial water depending on the size of the nanotube. The crossover size corresponds to tube diameters of around 1 nm. Tue, 04 Jun 2013 13:59:08 GMT http://hdl.handle.net/2117/19503 2013-06-04T13:59:08Z Calero Borrallo, Carles; Gordillo, Carmen; Martí Rabassa, Jordi no Molecular dynamics simulations of liquid water at ambient conditions, adsorbed at the external walls of (n,n) single-walled armchair carbon nanotubes have been performed for n = 5, 9, 12. The comparison with the case of water adsorbed on graphene has also been included. The analysis of Helmholtz free energies reveals qualitatively different ranges of thermodynamical stability, eventually starting at a given threshold surface density. We observed that, in the framework of the force field considered here, water does not wet graphene nor (12,12) tubes, but it can coat thinner tubes such as (9,9) and (5,5), which indicates that the width of the carbon nanotube plays a role on wetting. On the other hand, density profiles, orientational distributions of water, and hydrogen-bond populations indicate significant changes of structure of water for the different surfaces. Further, we computed self-diffusion of water and spectral densities of water and carbon molecules, which again revealed different qualitative behavior of interfacial water depending on the size of the nanotube. The crossover size corresponds to tube diameters of around 1 nm. http://hdl.handle.net/2117/19480 Title: Atomic data mining numerical methods, source code SQlite with Python Authors: Khwaldeh, Ali; Tahat, Amani; Martí Rabassa, Jordi; Tahat, Mofleh Abstract: This paper introduces a recently published Python data mining book (chapters, topics, samples of Python source code written by its authors) to be used in data mining via world wide web and any specific database in several disciplines (economic, physics, education, marketing. etc). The book started with an introduction to data mining by explaining some of the data mining tasks involved classification, dependence modelling, clustering and discovery of association rules. The book addressed that using Python in data mining has been gaining some interest from data miner community due to its open source, general purpose programming and web scripting language; furthermore, it is a cross platform and it can be run on a wide variety of operating systens such as Linux, Windows, FreeBSD, Macintosh, Solaris, OS/2, Amiga, AROS, AS/400, BeOS, OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS, VxWorks, PlayStation, Sharp Zaurus, Windows CE and even PocketPC. Finally this book can be considered as a teaching textbook for data mining in which several methods such as machine learning and statistics are used to extract high-level knowledge from real-world datasets. Fri, 31 May 2013 15:58:19 GMT http://hdl.handle.net/2117/19480 2013-05-31T15:58:19Z Khwaldeh, Ali; Tahat, Amani; Martí Rabassa, Jordi; Tahat, Mofleh no This paper introduces a recently published Python data mining book (chapters, topics, samples of Python source code written by its authors) to be used in data mining via world wide web and any specific database in several disciplines (economic, physics, education, marketing. etc). The book started with an introduction to data mining by explaining some of the data mining tasks involved classification, dependence modelling, clustering and discovery of association rules. The book addressed that using Python in data mining has been gaining some interest from data miner community due to its open source, general purpose programming and web scripting language; furthermore, it is a cross platform and it can be run on a wide variety of operating systens such as Linux, Windows, FreeBSD, Macintosh, Solaris, OS/2, Amiga, AROS, AS/400, BeOS, OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS, VxWorks, PlayStation, Sharp Zaurus, Windows CE and even PocketPC. Finally this book can be considered as a teaching textbook for data mining in which several methods such as machine learning and statistics are used to extract high-level knowledge from real-world datasets. http://hdl.handle.net/2117/19439 Title: High-temperature combustion: Approaching equilibrium using nuclear networks Authors: Cabezón Gómez, Rubén Martín; García Senz, Domingo; Bravo Guil, Eduardo Wed, 29 May 2013 08:18:06 GMT http://hdl.handle.net/2117/19439 2013-05-29T08:18:06Z Cabezón Gómez, Rubén Martín; García Senz, Domingo; Bravo Guil, Eduardo no http://hdl.handle.net/2117/19407 Title: Tricritical behavior of the nematic to smectic-A phase transition in the binary mixture of liquid crystal Authors: Mukherjee, Prabir; Tamarit Mur, José Luis Abstract: We propose a phenomenological model to describe the tricritical behavior of the nematic to smectic- A (N-SmA) phase transition in liquid crystal mixture. To describe the mesophase transitions in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that a tricritical point on the N-SmA phase transition line can be achieved under certain conditions. The predictive capability of the present model for determining the tricritical point of a binary mixture displaying the N-SmA transition has been demonstrated by testing with reported phase diagrams sharing both phases Mon, 27 May 2013 12:17:42 GMT http://hdl.handle.net/2117/19407 2013-05-27T12:17:42Z Mukherjee, Prabir; Tamarit Mur, José Luis no We propose a phenomenological model to describe the tricritical behavior of the nematic to smectic- A (N-SmA) phase transition in liquid crystal mixture. To describe the mesophase transitions in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that a tricritical point on the N-SmA phase transition line can be achieved under certain conditions. The predictive capability of the present model for determining the tricritical point of a binary mixture displaying the N-SmA transition has been demonstrated by testing with reported phase diagrams sharing both phases http://hdl.handle.net/2117/19359 Title: A dynamics analysis of antigen specific T cells during brain autoimmunity supports the role of regulatory T cells in disease outcome Authors: Martinez Pasamar, Sara; Abad Adán, Elena; Moreno, Beatriz; Velez de Mendizabal, Nieves; Martinez Forero, Ivan; García Ojalvo, Jordi; Villoslada, Pablo Tue, 21 May 2013 10:37:45 GMT http://hdl.handle.net/2117/19359 2013-05-21T10:37:45Z Martinez Pasamar, Sara; Abad Adán, Elena; Moreno, Beatriz; Velez de Mendizabal, Nieves; Martinez Forero, Ivan; García Ojalvo, Jordi; Villoslada, Pablo no http://hdl.handle.net/2117/19358 Title: Detecting long-range teleconnections in the climate network via ordinal pattern time-series analysis Authors: Deza, Juan Ignacio; Barreiro, Marcelo; Masoller Alonso, Cristina Tue, 21 May 2013 10:17:14 GMT http://hdl.handle.net/2117/19358 2013-05-21T10:17:14Z Deza, Juan Ignacio; Barreiro, Marcelo; Masoller Alonso, Cristina no http://hdl.handle.net/2117/19335 Title: Focalization of evanescent beams Authors: Botey Cumella, Muriel; Cheng, Yu Chieh; Herrero Simon, Ramon; Romero García, V.; Pico, R.; Sánchez Morcillo, V. J.; Staliunas, Kestutis Abstract: We predict and show the existence of unlocked evanescent waves in two dimensional periodic structures. In a one dimensional periodic structure an evanescent mode are located either at the center or at the boundary of the Brillouin Zone, and the real part of wave-vectors is locked either to zero or to the modulation vector of the periodicity. However, we report an unexpected observation that this is not the case in 2D or 3D PhCs where "unlocked" complex modes can be predicted. As an interesting consequence, due to their “complex” character, or, equivalently, due to their phase freedom, beams constructed from such evanescent waves can show focalization effects. Indeed, we numerically simulate the propagation of such beams in the bandgap of PhC slabs, and we find significant focalization. Fri, 17 May 2013 12:44:37 GMT http://hdl.handle.net/2117/19335 2013-05-17T12:44:37Z Botey Cumella, Muriel; Cheng, Yu Chieh; Herrero Simon, Ramon; Romero García, V.; Pico, R.; Sánchez Morcillo, V. J.; Staliunas, Kestutis no Evanescent waves, nanomaterials, Photonic bandgap materials We predict and show the existence of unlocked evanescent waves in two dimensional periodic structures. In a one dimensional periodic structure an evanescent mode are located either at the center or at the boundary of the Brillouin Zone, and the real part of wave-vectors is locked either to zero or to the modulation vector of the periodicity. However, we report an unexpected observation that this is not the case in 2D or 3D PhCs where "unlocked" complex modes can be predicted. As an interesting consequence, due to their “complex” character, or, equivalently, due to their phase freedom, beams constructed from such evanescent waves can show focalization effects. Indeed, we numerically simulate the propagation of such beams in the bandgap of PhC slabs, and we find significant focalization. http://hdl.handle.net/2117/19289 Title: White dwarf mergers and the origin of R coronae borealis stars Authors: Lorén Aguilar, Pablo; Longland, Richard Leigh; José Pont, Jordi; García-Berro Montilla, Enrique; Althaus, Leandro G.; Isern-Fontanet, J. Abstract: We present a nucleosynthesis study of the merger of a 0.4 M⊙ helium white dwarf with a 0.8 M⊙ carbon-oxygen white dwarf, coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code. The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in qualitative agreement with the observed abundances in R Coronae Borealis stars. Thu, 16 May 2013 11:56:45 GMT http://hdl.handle.net/2117/19289 2013-05-16T11:56:45Z Lorén Aguilar, Pablo; Longland, Richard Leigh; José Pont, Jordi; García-Berro Montilla, Enrique; Althaus, Leandro G.; Isern-Fontanet, J. no We present a nucleosynthesis study of the merger of a 0.4 M⊙ helium white dwarf with a 0.8 M⊙ carbon-oxygen white dwarf, coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code. The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in qualitative agreement with the observed abundances in R Coronae Borealis stars. http://hdl.handle.net/2117/19286 Title: Interaction of Supernovae remnants: From the circumstellar medium to the terrestrial laboratory Authors: Velarde, P; García Senz, Domingo; Bravo Guil, Eduardo; Ogando, F; Relaño, A; Oliva, E Abstract: The evolution of supernova remnants (SNRs) represents a useful and natural laboratory for gasdynamics studies. In this paper the results of several hydrodynamical simulations of the propagation and early phases of interaction of two SNRs embedded in a homogeneous interstellar environment are shown. In particular, the hydrodynamic evolution and collision of twin SNRs during their self-similar stage has been simulated using a two-dimensional Lagrangian hydrocode. In addition, the results of a detailed simulation that attempts to set the adequate conditions to reproduce the same phenomenon through laser ablation of two plastic plugs at the laboratory scale are presented. These results indicate that both large-scale and small-scale simulations display several common features that can be used to design an experiment aimed to validate the hydrodynamical codes. Of particular interest are the structures found around the juncture of the two colliding shells produced by the interaction of the remnants. Thu, 16 May 2013 10:41:34 GMT http://hdl.handle.net/2117/19286 2013-05-16T10:41:34Z Velarde, P; García Senz, Domingo; Bravo Guil, Eduardo; Ogando, F; Relaño, A; Oliva, E no The evolution of supernova remnants (SNRs) represents a useful and natural laboratory for gasdynamics studies. In this paper the results of several hydrodynamical simulations of the propagation and early phases of interaction of two SNRs embedded in a homogeneous interstellar environment are shown. In particular, the hydrodynamic evolution and collision of twin SNRs during their self-similar stage has been simulated using a two-dimensional Lagrangian hydrocode. In addition, the results of a detailed simulation that attempts to set the adequate conditions to reproduce the same phenomenon through laser ablation of two plastic plugs at the laboratory scale are presented. These results indicate that both large-scale and small-scale simulations display several common features that can be used to design an experiment aimed to validate the hydrodynamical codes. Of particular interest are the structures found around the juncture of the two colliding shells produced by the interaction of the remnants. http://hdl.handle.net/2117/19284 Title: Production of intermediate-mass and heavy nuclei Authors: Thielemann, F. K.; Frölich, Carla; Hirschi, R.; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, t.; Martínez Pinedo, Gabriel; Langanke, K; Farouqi, K; Kratz, K.L.; Pfeiffer, B.; Panov, I.; Nadyozhin, D.K.; Blinnikov, S.; Bravo Guil, Eduardo; Hix, W.R.; Höflich, P.; Zinner, Ernst Abstract: Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions — SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae — SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing “hypernovae” after the formation of a central black hole via core collapse. Thu, 16 May 2013 10:33:12 GMT http://hdl.handle.net/2117/19284 2013-05-16T10:33:12Z Thielemann, F. K.; Frölich, Carla; Hirschi, R.; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, t.; Martínez Pinedo, Gabriel; Langanke, K; Farouqi, K; Kratz, K.L.; Pfeiffer, B.; Panov, I.; Nadyozhin, D.K.; Blinnikov, S.; Bravo Guil, Eduardo; Hix, W.R.; Höflich, P.; Zinner, Ernst no Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions — SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae — SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing “hypernovae” after the formation of a central black hole via core collapse. http://hdl.handle.net/2117/19257 Title: Spatial noise reduction in broad area semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Pradeep Kumar, Nikhil; Staliunas, Kestutis Wed, 15 May 2013 14:13:50 GMT http://hdl.handle.net/2117/19257 2013-05-15T14:13:50Z Herrero Simon, Ramon; Botey Cumella, Muriel; Pradeep Kumar, Nikhil; Staliunas, Kestutis no broad emission area semiconductor laser, gain-loss modulation, photonic crystals http://hdl.handle.net/2117/19253 Title: Dispersion management in spatially modulated broad band semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Khumar, N.P.; Staliunas, Kestutis Wed, 15 May 2013 13:44:05 GMT http://hdl.handle.net/2117/19253 2013-05-15T13:44:05Z Herrero Simon, Ramon; Botey Cumella, Muriel; Khumar, N.P.; Staliunas, Kestutis no http://hdl.handle.net/2117/19248 Title: Phase transitions with infinitely many absorbing states in complex networks Authors: Sander, Renan; Ferreira, Silvio C.; Pastor Satorras, Romualdo Abstract: We investigate the properties of the threshold contact process (TCP), a process showing an absorbing-state phase transition with infinitely many absorbing states, on random complex networks. The finite-size scaling exponents characterizing the transition are obtained in a heterogeneous mean-field (HMF) approximation and compared with extensive simulations, particularly in the case of heterogeneous scale-free networks. We observe that the TCP exhibits the same critical properties as the contact process, which undergoes an absorbing-state phase transition to a single absorbing state. The accordance among the critical exponents of different models and networks leads to conjecture that the critical behavior of the contact process in a HMF theory is a universal feature of absorbing-state phase transitions in complex networks, depending only on the locality of the interactions and independent of the number of absorbing states. The conditions for the applicability of the conjecture are discussed considering a parallel with the susceptible-infected-susceptible epidemic spreading model, which in fact belongs to a different universality class in complex networks. Wed, 15 May 2013 12:52:57 GMT http://hdl.handle.net/2117/19248 2013-05-15T12:52:57Z Sander, Renan; Ferreira, Silvio C.; Pastor Satorras, Romualdo no SCALE-FREE NETWORKS, SYSTEMS, LATTICE, MODEL We investigate the properties of the threshold contact process (TCP), a process showing an absorbing-state phase transition with infinitely many absorbing states, on random complex networks. The finite-size scaling exponents characterizing the transition are obtained in a heterogeneous mean-field (HMF) approximation and compared with extensive simulations, particularly in the case of heterogeneous scale-free networks. We observe that the TCP exhibits the same critical properties as the contact process, which undergoes an absorbing-state phase transition to a single absorbing state. The accordance among the critical exponents of different models and networks leads to conjecture that the critical behavior of the contact process in a HMF theory is a universal feature of absorbing-state phase transitions in complex networks, depending only on the locality of the interactions and independent of the number of absorbing states. The conditions for the applicability of the conjecture are discussed considering a parallel with the susceptible-infected-susceptible epidemic spreading model, which in fact belongs to a different universality class in complex networks. http://hdl.handle.net/2117/19244 Title: Consequences of the Collision Between the Gas Ejected in the Collapse of a White Dwarf and a Low-Mass Star Authors: Serichol Augué, Núria; García Senz, Domingo; Bravo Guil, Eduardo Wed, 15 May 2013 11:07:44 GMT http://hdl.handle.net/2117/19244 2013-05-15T11:07:44Z Serichol Augué, Núria; García Senz, Domingo; Bravo Guil, Eduardo no