PHYSICS, 2

Author: SUAREZ GONZALEZ MARCOS.
Year: 2005.
University: OVIEDO.
Place of defense: FACULTAD CIENCIAS DE LA EDUCACION.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In this Doctoral Thesis is a study perturbativo of the theories of quantum fields supersymmetric gauge (super Yang-Mills, now SYM) in 4 dimensions to finite temperature. To do so, it calculates its free energy as a series in powers of g, the constant acoplo gauge until order g5 using an approach based on the construction of theories effective temperature and finite dimensional reduction as a regulator. Theory No. 4 SYM group to gauge U (N) is related to String Theory through the duality AdS / CFT. This duality makes it possible to calculate the free energy of No. 4 SYM on the edge of acoplo strong and N large, using GDI supergravity in a background AdS5xS5 which is its dual theory in this limit. Until now, the limit of acoplo weak had only been explored in order g3. One of the findings presented in this thesis is calculating the free energy of N 4SYM with gauge group U (N), on the edge of acoplo weak and N large, to order g5. This is the highest order that can be reached with methods exclusively perturbativos. The result obtained is consistent with the hypothesis of an interpolation between soft limits acoplo weak and strong, and improves previous results. In addition, an analysis based on the construction of aproximantes of Padé shows that it is possible to build aproximantes that interpolen between the two regimes. It also performs an analysis of the convergence of the series perturbativa for energy self gained in each of these cases, motivated by what happens to the series similar in QCD: the series converges but not for extremely high values of temperature. It has been shown that increasing the number of supersimetrías seems to carry an associated improvement in the convergence of the series, as the radio apparent convergence grows increasingly to include terms in the series perturbativa. Theories No. 1 SYM and N 2 SYM have a behavior similar to QCD: requires that the ratio T / L (L defined in a manner similar to QCD in each case) is very large for the respective series showing signs of convergence.

Author: SUAREZ DIEZ MARIA.
Year: 2005.
University: OVIEDO.
Place of defense: FACULTAD DE CIENCIAS DE LA EDUCACION.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The first part examines the role of canonical partition of a single particle in a time space of eleven dimensions, with a spatial dimension compactificada in a circle of radius R. An estimated first for a generic observer, when Ra brings infinite recovers Lorentz covariance in 11 dimensions and then an observer at the IMF. The purpose of this analysis is to study how this observer regains the covariance in 11 dimensions and clarify the relationship between action Dirac-Born-Infeld and action Super-Yang-Mills, which is corresponding to the description of the theory matrix in this referral system so particular: the IMF. In the second part of the thesis discusses the effects of temperature on gas ideals of ropes, paying particular attention to the effect of the topology of the space in which the cords spread and the importance of choosing either collective statistical in the conclusions drawn. Ropes-open in an open space or with the dimensions compactificadas circled whose rays tend to infinity, energy and fixed temperature and chemical potential zero. Both descriptions are equivalent despite breaking equipartición. Ropes closed-moving into an area of such size that toroidal cord can be wrapped them. Here our results differ from those set forth in the classical work of Brandenberger and Vafa.

Author: VALBUENA MARTÍNEZ MIGUEL ANGEL.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: Low dimensionality oxides come under study extends for more than two decades. These compounds, but show structures volume 3D, are composed of fundamental units of layers 2D, or chains 1D, which confers these materials your call low dimensionality. One can imagine that as disminuimos dimension of the system, the interactions that initially may be negligible in 3D, are beginning to gain importance. In this way, both the interactions of electrons with the vibrations of the network (fonones), as well as interactions electrón-electrón (electronic correlations), comes increasingly important and lead to the formation of key states at low temperature density waves load (ODC), due to acoplo electrón-fonón, spin density wave (ODE), the effect of interactions electrón-electrón or superconducting phases. In its metallic state at room temperature these materials are interesting from the point of view of the diversions that they have with respect to a model usual cuasi-partículas fluid Fermi (LF). In particular, for systems strictly 1D model LF not still valid, when the system described by the so-called model fluid Luttinger (LL), where its main feature is the so-called separation carga-espín and no cuasi-partículas . The technique of spectroscopy fotoemisión resolved at an angle (ARPES) has emerged as the most powerful in the study of these systems, since they give us access to the electronic structure near the Fermi level, and the Fermi surface ( SF) system. In this way we can study the electrons responsible for the effects of correlations eléctronicas or inestablidades low temperature. On the other hand allows us to measure directly the spectral function giving us very valuable information about the interactions dominate these compounds. This thesis has been studied two of these oxides low dimensionality using ARPES, belonging to the so-called bronzes of Molybdenum. Phase Magneli monoclínica cuasi-2D eta-Mo4O11 presents behavior cash 2D at room temperature and two transitions to ODC to 109 K and 30 K, respectively. Among the main findings is a thorough appraisal of its electronic structure and its SF at room temperature. The experimental results show an excellent agreement with previous theoretical calculations, showing the model fit "hidden" from the SF explaining the instabilities of ODC appeared in this compound. It is also a very particular to the spectra of fotoemisión hardly explicable on the basis of a model LF usual. The possible origin of these spectral forms can be related to effects of separation carga-espín according to a model LL, the dispersion due to surface defects, etc.. With regard to bronze purple cuasi-2D potassium KMo6O17 has given its electronic structure both at room temperature and low temperature in the state of ODC presented. Among the major findings are distinctive signs of a weak coupling of Peierls leading to the ground state of ODC, among which we can mention the opening of a gap at the Fermi level in the expected zones (estimated between 35 and 45 meV) or modification of the dispersion of the band that crosses the Fermi level and the appearance of a band called virtual indicates the new schedule for the actual network in the state of ODC. Again some are abnormally wide spectrum or to 8 usencia 4e5 a Fermi edge in the spectra of fotoemisión integrated angle characteristics can be explained from phenomena separation carga-espín according to a model of LL. Moreover, the spectral shapes may have to do with a strong interaction electrón-fonón leading to the formation of small polarones as seems to happen in the blue bronze quasi 1D potassium K0.3MoO3. Both effects were found in similar materials and remains the development of a model that can include such effects to give a valid explanation to the spectral shapes obtained in this class of materials.

Author: PASCUAL MAROTO LAURA.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: INSTITUTO DE CIENCIA DE MATERIALES (CSIC).
Place of preparation: INSITUTO DE CIENCIA DE MATERIALES DE MADRID (CSIC).

Summary: We knew that the material composition LiCrYMn2-YO4 (0 & 1) with spinel structure could have application as a cathode material for rechargeable lithium batteries. These materials were synthesized by solid state reaction and had a particle size of the order in the micron, making it difficult to use when the battery is loaded / unloading at high currents (short time). In order to achieve high capacities at high currents, in this work we have proposed to the preparation of materials with particle size cathode nano, this will have prepared materials LiCrYMn2-YO4 (0 & 1) by amending Combustion synthesis method to our particular case. We have replaced conventional fuels sugar trade and have optimizing the reaction conditions (sugar) for the best rendimientos.También has studied how varied the average size of particles with subsequent treatments at temperatures rising, and ultimately has studied and understood how the particle size affects the ability of the material to different currents. In this thesis work, the materials have been characterized by thermal analysis (ATD-TG), X-ray Diffraction (XRD), transmission electron microscopy (TEM). The electrical properties are measured using the impedance spectroscopy. The electrochemical characterization has been done through galvanostáticas. It has been shown that you can use sugar (sucrose) as a fuel for combustion in the synthesis of materials LiCrYMn2-YO4 with (0 & 1). The synthesis method developed has enabled us to obtain materials with particle size of the nano (5-10 nm) and spinel structure. A list of sucrose / reagents = 1.5 ago that the reaction proceeds via spontaneous and controlled. These materials are impurificados with residual sugar and a small amount of Mn3O4. The purification of materials is achieved through a heat treatment 400Â ° C. To achieve estequiométrica composition of the materials is necessary to 700Â ° C treat for 1 hour. Compared with the synthesis by solid state reaction, the synthesis Combustion is faster (1 hour versus 48 hours) and the product estequiométrico has an average particle size smaller (50 nm compared to 180 nm). The particle size of materials LiCrYMn2-YO4 increases with increasing temperature treatment in the range 400Â º C-1100Â ° C. Among 400Â ° C and 700Â ° C particle size increased only slightly, from 9 nm to 46 nm. Among 700Â ° C and 1100Â ° C particle size increased significantly from 46 nm to 1560 nm. The content of Cr does not improve the electrical conductivity of materials LiCrYMn2-YO4 which are semiconductor tipo-n. The ions are involved in conducting the Mn3 + and Mn4 +. The curves galvanostática present a plateau at 4V due to Mn and another to 4.8V due to Cr. The capabilities of these potential measures unloading has been analyzed as a function of particle size. In both cases the capacity decreases linearly with the size of the particle being pending the higher the greater the flow that occurs to the insertion of Li + ions in the cathode material. It has been determined the diffusion coefficient of Li + ions in the material content in chromium Y = 0.2. The diffusion coefficient varies with the degree of insertion of Li + in the material (1 10-9 and 5 10-11 cm2 / s), but the change is not gradual. The diffusion coefficient is the same in two samples of different particle size (88nm and 1134nm). The ability to download decreases with cycling, the loss of capacity is higher in the cathode materials that have smaller grains. The cathode materials have been tested in batteries in Li-ion batteries which was used as anode graphite or carbon nanofibres. The 8 capacid 463 ad decreases with the flow and with the cycling and the decline was larger than in the lithium battery that has cash. With materials LiCr0.1Mn1.9O4 have prepared a button type battery (CR2032) 13 mAh capacity and voltage working 4V. This battery has been used as a feed source of a transmitter. The fact that the rechargeable battery is opening up new possibilities for application in front of the (non-rechargeable) batteries that are currently used to feed the transmitter.

Author: RIVIÈRE HERRERA PAULA.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: FACULTAD DE CIENCIAS, U.A.M..
Place of preparation: DEPARTAMENTO DE QUÍMICA, U.A.M..

Summary: When a molecule interacts with a surface can occur several things: its internal links can break to train others, or it may be reflected, in which case there may be changes in the direction (diffraction) or internal energy (rotation or vibration). These changes can be studied to extract information both on the surface and on the interaction molécula-superficie. The H2 is the simplest molecule, and thus the study of their interaction with surfaces periodicals is the first step towards understanding the mechanisms involved in atomic interactions molécula-superficie. In such systems, one can despise overall vibration of the surface (fonones) and the excitation electrón-hueco (working within the approximation of Born-Oppenheimer). With both approaches, the system molécula-superficie consists of six dimensions. The surface of NiAl (110) is of particular interest within the ordered alloys for several reasons: first, exhibit a relaxed structure in which atoms of Ni and Al are at different heights, which has attracted substantial interest both theoretical and experimental in recent years. Secondly, it combines a transition metal reagent, Ni, with a noble metal, not reactive, Al. This causes a great selectivity for disociativa adsorption of H2 depending on the site on the surface. This thesis presents a comprehensive study of the system H2/NiAl (110). First has calculated the potential energy surface for H systems / NiAl (110) (three-dimensional) and H2/NiAl (110) (in six dimensions), using the Functional Theory of Gravity. The structure of the surface of NiAl (110) obtained were compared with experimental results and theoretical available. There were interpolated data obtained with the procedure Reduction of roughness, and then compared the characteristics of the potential energy surface for both systems with earlier work. Likewise, it has studied the case of NiAl (110) H adsorbed on the surface. Several studies have been conducted using both a dynamic method of classical trajectories as a method of quantum wave packets time-dependent, TDWP. Both methods have been studied both decoupling and its dependence with the initial conditions as reflection and diffraction. In the latter case, it has been used for the calculations classic method for discretization giving diffraction peak intensities. The mechanisms involved in the dissociation dynamics have been studied in detail using conventional calculations at 2, 3 and 4 dimensions, as well as small areas of the surface potential energy. Finally, it has conducted a detailed study of the diffraction of hydrogen atoms metal surface model by comparing the results obtained with a method of classical trajectories with those obtained with a method quantum, the Multiconfiguration Time-Dependent Hartree or MCTDH. It has made itself an analysis of the origin of the differences between the results obtained with both methods for different conditions of incidence.

Author: González Pascual César.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: Facultad de Ciencias, U.A.M..
Place of preparation: Física Teórica de la Materia Condensada.

Summary: During the argument have combined two methods based on DFT (theory of functional density) for the search of the minimum energy structures of the systems studied: a fast (FIREBALL) to explore phase space and a more accurate (CASTEP ) to refine. This evidence is not sufficient to establish the desired structure, which will perform simulations STM (tunneling microscope) to compare with the experiment. This will use the model developed by our group, based on the formalism of Green-Keldysh for systems outside the balance. These theoretical calculations are combined with experiments (STM, STS, fotoemisión, LEED, RBS) to reach a perfect understanding of the complex systems studied along the thesis: / GaAs (001) -2x1. Passivation is studied chemistry and electronics surface GaAs (001) with are (the first was successful and second only to the substrate type doped n). Based on data fotoemisión arrived at ending type Ga2Se3. Comparing the energy calculations have 3 structures competing. The high corrugación seen in the STM image is only achieved is for structures with a superficial (which rules out models with dimers), which leads us to propose the model 3B. Ga / Si (112) -6x1. We studied the formation of metal chains on semiconductor surfaces. The theoretical calculations and experimental STM discarded the model originally proposed, so we are looking for a new one. The best reproduced the new STM images (and has less energy) is a model with 2 channels (instead of one) of 5 Ga with a hole. These vacancies form a zigzag that reproduces what obsevado in STM. The system has fluctuations in the top of the chain of Ga highest, this explains the formation of a dímero Ga-Si which allows such fluctuations without the full picture of states change. Lastly, the new model is semiconductor (with a "gap" similar to that observed with STS) and possesses all its "dangling-bonds" saturated, so the surface is chemically passivated. In / Si (111) -4x1 => 4x2 (8x2). We study the structural phase transition and metal-semiconductor this system with temperature. The structure 4x1 high T was well marked: In owns two chains in the form of zigzag on the surface. We arrived at the structure 4x2 semiconductor low T (not found until then), which is derived from the 4x1 combining 2 effects: shear (rigid movement between the two chains) and dimerización of In external. Combine the 4 configurations 4x2 equivalent to get reconstruction 8x2. Using molecular dynamics we understand what happened at all temperatures: low, the system does not have enough energy to cross the barrier being frozen in a 8x2; high, the system fluctuates between configurations equivalent, which is observed on average a reconstruction 4x1 (STM), which is metal and, at its fluctuation, the system found large quantities of metal structures; for T intermediates, there is a third structure: 4x1 semiconductor (the system fluctuates more slowly bringing metal structures located less ). The fluctuaciónes dynamic behind the three structures.

Author: IRISO ARIZ UBALDO.
Year: 2005.
University: BARCELONA.
Place of defense: UNIVERSIDAD DE BARCELONA.
Place of preparation: UNIVERSITAT DE BARCELONA.

Summary: This thesis has studied the phenomenon of electronic clouds (electron cloud) in the Relativistic Heavy Ion Collider (RHIC), the heavy ion accelerator of Brookhaven National Laboratory in New York. When this phenomenon occurs, is a limitation on benefits accelerator in the form of increased pressure inside the cavity, instabilities in the beam of particles, or heat loads in the cavity. The electron cloud depends on the properties superfíciales the wall of the cavity and the properties of the beam particles. It has installed an electron detector which operates regularly to analyze the cases of electron clouds in RHIC. This allows reliable diagnostics on the reasons for the increases pressure inside the cavity empty. Different codes simulation has been compared to the experimental results, and that has helped set the theoretical models on the formation of electron Cloud. These simulation codes are used worldwide to study the electron cloud in different accelerators, and its CPU time can last from hours to days. However, in this thesis has developed a model that describes the formation of the electron cloud through "maps" based forms iterative "bunch-to-bunch." These maps allow describe the formation of the electron cloud from which CPU time does not exceed millisecond. Furthermore, theoretical models based on these maps are predicting chaotic movements in the eclectron cloud.

Author: Fleta Corral María Celeste.
Year: 2005.
University: AUTÓNOMA DE BARCELONA.
Place of defense: Instituto de Microelectrónica.
Place of preparation: Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC).

Summary: This dissertation is devoted to the development of a technology of silicon radiation detectors resistant to high doses of radiation. It first presents a comparative study of Float Zone silicon substrates standard and oxygenated and Czochralski magnetic (MCZ) N-type, indicating that the silicon is the most resistant to high radiation doses and more stable for long times annealing. Next is a comparative study of operational and technological difficulties of the different structures detectors micropistas: p-sobre-n, n-sobre-py n-sobre-n. From the point of view of the collection of load detectors n-sobre-p are presenting an improved performance compared to radiation. Furthermore, it has been found that the silicon N is extremely resistant to changing doping cash caused by radiation.

Author: Colominas Fuster Sergi.
Year: 2005.
University: RAMÓN LLULL.
Place of defense: Escuela Técnica Superior IQS.
Place of preparation: Escuela Técnica Superior IQS.

Summary: One of the possible alternatives to reduce inventory readiotóxico of spent nuclear fuel is the use of type reactors ADS (Accelerator Driven System). These reactors require the development of new technologies, for example, designing cooling systems with molten metal and the use of Pb or 44.5% Pb-55.5% Bi (LBE) as a target of estalación. The use of liquid metals in this type of reactors requires a strict control of its oxygen content. In order to study the chemistry of oxygen in LBE cast, it is proposed the use of potentiometric sensors of oxígenos based in solid electrolytes. It has studied the response of these sensors using different systems regency (In/In2O3, Sn / are and Pt / air), use of different materials such as working electrode (wire molybdenum steel P22, stainless steel 304 and 316L and platinum), the influence of temperature on the response of the sensors and the use of gas in the LBE coverage with a different oxygen content. The presence of metallic impurities can modify the properties químico-físicas of LBE, especially the chemistry of oxygen in the molten metal. For this reason, has studied the response of oxygen sensors using In and Sn as metallic impurities in the LBE cast. The potential difference provided by the sensor can be associated with the partial pressure of oxygen in the LBE through equation Nerst. However, it is not possible to establish a direct relationship between oxygen concentration and potential difference measured in the sensor. Using a sensor potenciométrico oxygen and an electrochemical cell developed, was obtained by columbimétrica an equation that relates the two preliminary variable above.

Author: Megías Fernández Eugenio.
Year: 2005.
University: GRANADA.
Place of defense: Facultad de Ciencias.
Place of preparation: Facultad de Ciencias, Universidad de Granada.

Summary: It develops the method of heat kernel in the context of Quantum Field Theory at finite temperature. It is seen as a gauge general and in the presence of scalar fields that can be not abelianos and not stationary. The loop Polyakov surge a finite temperature as a new entrant gauge covariant. For QCD applies this method to calculate the effective action in the high temperature regime. The result is gauge invariant. It also gets the action of the theory dimensionally reduced. For chiral quark model, specifically Nambu -- Jona-Lasinio and Quark Model Spectral, applies the method to obtain the Lagrangian Theory Quiral Disturbances of finite temperature. The coupling of Polyakov loop with these models can resolve some inconsistencies in presenting their treatment standard finite temperature: generating states multiquarks, counting on Na, etc..

Author: ROMAGUERA ALBENTOSA MIREIA.
Year: 2005.
University: VALENCIA.
Place of defense: FACULTAT DE FÍSICA.
Place of preparation: FACULTAT DE FÍSICA.

Author: ÁLVAREZ SÁNCHEZ MARIA DEL MAR.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS. UNIVERSIDAD AUTONOMA DE MADRID.

Summary: The main aim of this thesis has been the development, characterization and application of a biosensor nanomecánico based micropalancas. The main advantages of this type of sensors embedded in its high sensitivity theory, the small size of the area sensor (1000 m2), the direct reading without markers, its compatibility with microelectronic technology that allows the manufacture of matrices micropalancas and integration capability to get microsystems laptops. The work can be divided into two parts: The first section has developed a biosensor nanomecánico based on a micropalanca and their response has been studied mechanics before two different types of biomolecular recognition, the interaction between an antibody and an antigen and the hybridization between chains DNA. In order to optimize the device has done a characterization of micropalancas depending on their size. The second part has developed a platform for simultaneous reading of several micropalancas and has demonstrated its functioning both static and dynamic mode, subsequently applied to the characterization of matrices micropalancas. The first application done with this biosensor is detection with high sensitivity of molecular recognition of monoclonal antibodies specific to the pesticide DDT. This has been controlled in real time funcionalización of a surface of the micropalanca with hapteno of pesticide. This activation has been accomplished through technical topcoat self assembled, including the formation of multiple layers in order to obtain the proper configuration for immobilizing the receiver. It has demonstrated the ability of the device to detect lower concentrations of antibody to 5g/ml, and the possibility of regeneration of its surface without loss of effectiveness in subsequent surveys. It has also demonstrated the applicability of the competitive tests for the detection of DDT in solution with various concentrations. This paper shows the potential of this new type of sensors for environmental monitoring. Secondly, given the great interest aroused by the genómia in the development of new techniques, studies were conducted immobilization and hybridization of DNA chains simple. To do so, have been measured in real time immobilization of DNA chains modified with a thiol group. Two protocols have been followed coating of different surfaces: formation of a pure single chain DNA tiolado and formation of a mixed monolayer of strings of DNA tiolado and MCH. The hybridization reaction that occurs in both coatings does not produce a signal deflection distinguishable nor reproducible, in contrast to the reaction between antigen and antibody. It has demonstrated the need (for the detection of the reaction of hybridization) micropalancas more sensitive than commercial use (k = 0.1 N / m), as well as the desirability of allowing differential measures eliminate the effects outside their own reaction , as slight changes in temperature or pH which may lead to changes in surface tension at the same level or higher than expected in the hybridization (mN / m). In order to increase the sensitivity of the micropalancas (as demanded measures hybridization of DNA), has done a characterization of the mechanical properties (elastic constant, resonance frequency and quality factor) of micropalancas manufactured in the clean room NJC Barcelona, depending on its size. The elastic constant has been determined by three different methods: one static (using AFM) and two dynamic (method Sader and method Cleveland). It has been shown that the decrease of the constant elasticity of micropalancas (for a fixed thickness of 0,334 m) produces an amplification of the response of deflection generated by a change of tension. Finally, it has developed a platform reading of the response nanomecánica (static and dynamic) matrices micropalancas, based on the detection or 8 ptica of 4f5 deflection of the beam and the automated scanning of a laser diode. The motion control system of diode laser is performed through a magnetic actuator, which is controlled by software ( "Voice-coil") and allows focus sequentially different micropalancas, with a resolution in the position of 100 nm. The reading system developed presents a number of advantages over other existing techniques, such as versatility (as it is independent of the size of micropalancas and the spacing between them), the ability to read up to 100 micropalancas per second reducing the number of elements (diodes and fotodectores) with a consequent simplification in aligning them. It has been demonstrated operation of the platform, both in the detection of the signal deflection and the resonance frequency.

Author: VEGA GONZALEZ JOSE LUIS.
Year: 2005.
University: COMPLUTENSE DE MADRID.
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS (UNIVERSIDAD COMPLUTENSE DE MADRID).

Summary: This research analyzes the memory of diffusion processes and vibration of atoms and molecules on metal surfaces absorbed. There has been a classic treatment and quantum pair analyze the properties of transport taking place in the interaction adsorbato-superficie. The use of a theoretical formalism classical stochastic processes and making use of knowledge in statistical mechanics and non-linear dynamics has helped us to analyze this kind of phenomena and comaprarlos with the experiment. In terms of quantum, we have taken into account the energy exchange adsorbato surface, and we have made use of a second quantization to analyze this problem, considering the system adsorbato-superficie as a problem of open system in which an oscillator harmonico it is coupled to a set of oscillators harmonicos representing the surface. For the first time in memory has been used this theory to analyze surfaces Kramers of this process of dissemination, and has developed a theoretical formalism which takes into account the process of diffusion assisted by vibrating in unison.

Author: DA ROLD LEANDRO.
Year: 2005.
University: AUTÓNOMA DE BARCELONA.
Place of defense: UNIVERSITAT AUTÒNOMA DE BARCELONA.
Place of preparation: UNIVERSITAT AUTÓNOMA DE BARCELONA.

Summary: This thesis explores the breakdown of symmetries in theories with extra dimensions. The main motivation is that the physics of extra dimensions provides new mechanisms for breaking symmetries. In particular explores the breakdown of the chiral symmetry of QCD and the breakdown of asymmetry electro weak (EW) of the Standard Model (SM). The first part is proposing an effective model 5D describing the breakdown in the field of chiral inns. It describes sectors climb, psudoescalar, and axial vector Inns with a model in space curved 5D. The model is weakly coupled and therefore it is possible performs analytical calculations. We predict the masses, constant decay and couplings between inns in terms of the parameters 5D. Condensates were also calculated and the parameters of chiral Lagrangian of piones of QCD. All prediciones agree with the experimental results within the range of validity of the model. Predictions are robust and some relationships are a consequence of asymmetry gauge 5D. Secondly explores the breakdown of symmetry EW in a model with a Higgs compound in the context of a theory 5D in AdS. The model is realistic. Breaking EW is a dynamic effect due mainly to contributions from the top. In a large region of parameter space of observable precision EW are consistent with experimental bounds. The interaction Zbb is protected by a symmetry. The model predicts a light Higgs whose mass is correlated with the mass of resonance fermiónica lighter. The top Right is essentially a composite particle, which are expected deviations with respect to the SM in this sector. Finally presents a method to calculate radiative corrections on theories with extra dimensions. The method is very useful for separating contributions and finite diverge.

Author: ORTEGA CEJAS VICENTE.
Year: 2005.
University: AUTÓNOMA DE BARCELONA.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS DE LA UNIVERSIDAD AUTÓNOMA DE BARCELONA.

Summary: In this thesis explores the effect of delays and temporary memory space in the formation and propagation of wave fronts in reaction systems. La inclusión de estos retrasos y memorias implica cambios cualitativos y cuantitativos respecto a situaciones donde éstas son despreciadas, lo que nos permite la elaboración de modelos que reproducen con bastante fidelidad los datos observados en proceso biológicos como la colonización de un territorio por una especie, la extinction of a species native as a result of calving of an invasive species or viral attack suffered by a colony of bacteria. In the first instance discusses in detail the case of the existence of a single delay in the system, which means that the mathematical description of the phenomenon will be made through an equation in partial derivatives of hyperbolic type instead of the classical equation of reaction - diffusion type which is parabolic. The equation hieprbólica highlights to preserve causality in our system, avoiding the existence of signals that spread with infinite velocity. At the same time, it retains a certain equation mathematical simplicity which makes it a very good candidate to bring physics to other disciplines such as biology, ecology and sociology. Secondly proposed alternative ways of introducing the temporary delay and take into account the existence of memories (both spatial and temporal) in the system. The study of the change in the behavior of fronts depending on the characteristics of memories including delays and makes us see that the differences regarding the classical case, can be very relevant and even, at times, surprising.

Author: RUBI DIEGO.
Year: 2005.
University: AUTÓNOMA DE BARCELONA.
Place of defense: INSTITUTO DE CIENCIA DE MATERIALES DE BARCELONA.
Place of preparation: ESCUELA DE POSTGRADO UAB.

Summary: Since the invention of the transistor in the decade of 40 ', electronic devices have based their operation in the handling of cargo electron to store or process information. However, long has been conducting intensive research work for the implementation of a new generation of devices, known as electronic spin or espintrónica, plus take the burden of the electron can use their degree of freedom spin. Among the materials with potential application in devices espintrónica needs to be improved: 1-ferromagnetic materials with a band of driving completely polarized in spin (such as manganitas, double perovskitas, or some alloys Heussler, among others. 2, - diluted magnetic semiconductor (DMS), obtained in dilute magnetic cations such as Co or Mn in semiconductor standards as ZnO, SnO2, TiO2. The overall framework of the work carried out in this thesis has been the synthesis and study of the structural properties, magnetic Electrical and spectroscopic both ferromagnetic materials in spin polarized (double perovskitas of Fe-Mo, in particular) and DMS systems (ZnO doped with Co and Mn). In the first instance, describes the synthesis and characterization of double perovskitas ceramics type A2FeMoO6 (A = Ca and Sr). Specifically, the work is focused on developing methods that allow raising the Curie temperature of these materials -ampliando thus the range of potential applications of operability. subsequently deals with the study samples of polycrystalline nanomagnetismo, and the exploration of the role played by isolated defects in the stabilization of that interaction. In all cases, there has been an adequate understanding of the physics of these materials have been developed in parallel with different methods of control over their magnetic interaction, opening new avenues that could eventually allow its functionality in devices.

Author: GARCIA GARCIA DANIEL.
Year: 2005.
University: SALAMANCA.
Place of defense: SALA MENOR DE LA HOSPEDERIA DEL COLEGIO FONSECA.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This paper presents the studies carried out in the Department of Applied Physics at the University of Salamanca in the years 2002-2006 on the magnetoimpedancia threading amorphous focusing our attention on the frequency dependence in the range between 0.1 and 30 MHz. The goals have been designing a system for measuring magnetoimpedancia need to tens of MHz, the collection, analysis and subsequent modeling of the experimental results in different compositions. In Chapter 1 is an introduction about the general concepts related to the amorphous wires and magnetoimpedancia. In Chapter 2 explains the manufacturing process of amorphous wires as well as the characterization tests conducted once obtained. At the end of this section we describe the assembly of the system of measurement and data acquisition magnetoimpedancia. Because the frequencies of operation, this step has been studied in detail. In the results section (Chapter 3) the study of magnetoimpedancia in each composition is divided into three parts, where a first mentioned their characteristics, which gave the second and analyze data from the magnetoimpedancia depending on the frequency, putting special interest in the maximum percentages magnetoimpedancia achieved. This section will show the effect on magnetoimpedancia of the composition through the constant magnetostriction. Thirdly, we use two simple theoretical models based on the classic skin effect allowing understand and adequately reproduce the experimental results. Once the results shown in all threads, it was comment and compare summary form indicating the findings. In chapter 4 show the influence of heat treatments on current showing its importance in the amorphous wires to improve magnetoimpedancia.

Author: CUESTA LÓPEZ SANTIAGO.
Year: 2005.
University: ZARAGOZA.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The study of the dynamics, structure and function of macromolecules like proteins, known as proteomics, has gained a recent currently following the establishment of the necessary foundations for deciphering of the human genome. In recent decades, much progress as computer prior knowledge of various computational simulation techniques applied successfully in other branches of science, have provided the necessary tools to deal with problems as complex as the dynamics inherent in the formation of the tertiary structure the proteins: "The protein folding problem". The function of the protein is directly related to its three-dimensional structure (structure native). The folding defects caused failures in its role that can cause disease and degenerative processes. In our work we have focused on a number of cases of clinical and biological interest, which analyzed the dynamics of the process of folding, and characterized the various factors that influence the stability conformacional whole molecular level. One of our most notable work has been the analysis of the structural stability of a small modular protein that is an important part of biological receptor responsible for controlling the level of cholesterol in the blood: The recipient of low-density lipoprotein (LDL-r). The genetic defects in this protein membrane resulting in the disease known as Family Hypercholesterolemia. Our results obtained using molecular simulation, have helped to characterize the impact structural / functional caused by mutations detected clinically in patients. This study has allowed us to lay the groundwork for a computational method of diagnosis with a high predictive value on mutations not yet clinically detected and could easily be extended to other diseases with a similar molecular origin. Moreover, the understanding of the mechanism of gene transcription of the DNA is a real challenge that spans many fields and scientific disciplines. An important part of this doctoral thesis has been devoted to trying to deepen the various theoretical models and improve existing combining both experimental and computational work. Our results have helped explain part of the role of thermal fluctuations of the sequence dependent on the interaction of the double helix with all the complex "molecular machine" that governs the process of gene expression. Additionally, we have succeeded in designing a series of non-linear models that describe the dynamics of distortion of conformations of DNA in the form of fork, "DNA-hairpins." These structures are very important intermediate states in the processes of recombination, replication or transcription, but also are used for designing molecular evidence ( "Molecular beacons") that focus on the identification of specific gene sequences, which can be applied in the detection early cancers. Our results of Molecular Dynamics have characterized the role their characteristics and structural design on the thermodynamic properties displaying experimentally.

Author: CHROBAK FEDERICI RICARDO.
Year: 2005.
University: VIGO.
Place of defense: FACULTAD DE CIENCIAS DE ORENSE.
Place of preparation: FACULTAD DE CIENCIAS DE ORENSE.

Author: PEÑA HIDALGO M. VANESSA.
Year: 2005.
University: COMPLUTENSE DE MADRID.
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS.

Summary: The objective of this thesis is to study the properties of magnetotransporte in different structures epitaxiales where interfaces are particularly complex and several factors such as interfacial disorder, roughness, interdifusión, tension epitaxial, etc.. They can change the physical properties. On the one hand is characterized the behavior of thin films of manganitas lanthanum, and calcium (rust magnetorresistencia colossal) on varying degrees of tension epitaxial. Growth presents different states depending on the strain imposed by the substrate is traction or understanding at the baseline by modifying the properties of the films. So it is that in terms of traction is not observed segregation or chemical separation of phases electronic atomic scale, but the transport and magnetic properties are reduced, while in terms of compression no segregation chemistry, but if separation of electronic phase while the properties of these films related to the material in volume. On the other hand have been studied heterostructures ferromagnetico / superconducting oxides (LCMO / YBCO) with complex interfaces for new spin-dependent effects on the transport properties. La superconductividad en las interfases esta deprimida pro varios factores como la transferencia de carga, la inyección de espines o el efecto de proximidad F/S. Experiments are presented to discuss these mechanisms that suppress super conductivity. In particular, it discusses how the temperature of superconducting criticizes depends on the relative orientation of the imanaciones of layers F ando rise to a new effect magnetorresistencia giant of interest for potential applications espintronica.