ATOMIC AND NUCLEAR PHYSICS

Author: ABSI ABDESLAM.
Year: 2004.
University: SEVILLA.
Place of defense: FACULTAD DE FÍSICA.
Place of preparation: FACULTAD DE FÍSICA.

Summary: 1. We conducted a follow-up time, from 1999 to 2001, the radioactive environmental impact in the estuary of the rivers and Odiel Red, in Huelva, as a result of the change in the management of discharges of phosphogypsum doing two factories of phosphoric acid and fertilizers from the decade from 1960 until the end of 1997. 2. We have determined the activity concentrations of 226RA and 238U in samples of water and 226RA, 238U and 210PO in sediment samples collected after the change in waste management in late 1997 (sampling 1999.2001 and 2002). 3. We compardo our results with those published for the period immediately preceding or subsequent to the event 1988-1998, constatanto a natural process of restoring the river to its natural levels of radioactivity. 4. We have to point measurement and analysis techniques for the determination of the concentrations of actividd each of the rasionucleidos mentioned. 5. We conducted various exercises quality and intercomparison to verify the soundness of the procedures radioquímicos and measure radioactivity put in place for this work.

Author: LEON BLASCO ASUNCION.
Year: 2004.
University: POLITÉCNICA DE VALENCIA.
Place of defense: Dep. Ingenieria Quimica y Nuclear.
Place of preparation: Universidad Politécnica de Valencia.

Summary: The takeoff that brachytherapy has experienced in recent years through the application of new radioactive isotopes and the use of artificial systems deferred load has increased interest in improving dosimetry of this type of medical treatment. In parallel with this development, the use of Monte Carlo method in this discipline has turned into a simulation technique preferable to calculation procedures deterministic or experimental measurements. In this context, it raises the dosimetry study of surface applicator brachytherapy in Leipzig and source of iridium 192. The fundamental tool that has sustained is the code of Monte Carlo MCNP, chosen by their powerful resources in terms of programming complex geometries, definition of radioactive sources, methods variance reduction and modeling of physical phenomena provide full details. The work presented here begins with the collection of some of the dosimetric parameters of the source of Ir-192 MicroSelectron HDR Classic Nucletron, established by the protocol TG - 43 of the AAPM. It has sought to validate the methodology for use of the program by comparing results with those already accepted as reliable, and thereby lay a solid foundation for subsequent calculations. Here are performed a series of calculations and measurements from one of the six potential applicators Leipzig in combination with the source of 192-Ir to verify the consistency between the two values. Based on this confirmation is in a position to carry out more detailed calculations taking advantage of the possibilities offered by the code MCNP. Therefore obtained curves isodosis amid homogeneous for the six applicators available on the source MicroSelectron 192Ir HDR Classic. The last part of the thesis responds to the concerns about the impact know from the point of view of the presence of dosimetric anatomical heterogeneities in the region for treatment. All procedures for calculating doses used at present are based on data or estimates in half homogeneous comprising water, which is equivalent to the material fabric. However, while they are radiating areas where the thickness of tissue is minimal and are within a few millimeters in depth formations and bone cavities, it seems likely that its impact on the amount of energy imparted to both tumors and organs healthy next is not negligible. Tapping the potential of simulation off the pilot, have been reproduced in a simplified real circumstances and has studied the field of radiation in that case. The results show a significant influence of the different tissues and open the door to new lines of inquiry to a body still unknown.

Author: CAMPAYO ESTEBAN JUAN MANUEL.
Year: 2005.
University: POLITÉCNICA DE VALENCIA.
Place of defense: INGENIERÍA QUÍMICA Y NUCLEAR.
Place of preparation: UNIVERSIDAD POLITÉCNICA DE VALENCIA.

Summary: Assessing the quality of the image of a fantoma radiographic is one of the main routes in a comprehensive quality control program of radiographic equipment. In order to make a proper diagnosis in diagnostic radiology appropriate diagnostic radiology, it is necessary that the objects with low contrast and diameter can be distinguished from the fund. Thus, the evaluation of the image quality obtained in these terms is very useful to characterize the physical properties in the process of the chain of image. This thesis has developed a method for analyzing the quality of the digital image of a fantoma mammography techniques through automatic process. Have been applied to conventional mammography units and systems mamográficos of computed radiography. Using the digital system allows for the acquisition of the image directly, thus avoiding the need for digitization automatic image analysis obtained by a team of traditional revealed. The techniques used for the treatment of the image are technical standards as umbralización the picture to detect objects, the regional growth through depiexeles seed, the use of morphological operators to determine the shape and size of objects, and so on. This study allows to obtain information about the characteristics of the phantoms, very difficult to obtain through direct observation because of its small size and moderate contrast. The ultimate objective of this work is to obtain one or more parameters to characterize the reference in the image quality of fantoma in an objective manner. These parameters used to compare images obtained in various centers mamográficos, as well as to study the temporal evolution of the image quality produced by a plant diagnostic mammography determined.

Author: FERNÁNDEZ SÁNCHEZ EVA MARÍA.
Year: 2005.
University: VALLADOLID.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In order to understand the process of adsorption of O2 and CO on aggregate gold free and supported on aluminum oxide, we have developed the study from first principles of the structural and electronic properties of the different systems of interest. First there has been a comparative study of the properties of noble metals (Cu, Ag and Au) of up to 13 atoms, neutral and charged explaining the similarities and differences between them. We have identified the most stable structures for these metals found that aggregates gold prefer flat structures to larger sizes than those of silver and copper and metal for a given change in geometries 3D occurs at larger sizes for aggregates that anionic cationic neutral. On the other hand, for aggregate gold find that the shift to structures 3D depends heavily on functional exchange and correlation. This trend of lower dimensionality of aggregates Au is favored by relativistic effects, which show a decrease in energy advocacy sd leading to hybridization of Orbital semilleno 6s with the orbital occupied 5dz2. In addition, we found that the flatness of aggregates gold is associated with the location of the electrons des d, because the contribution to the total energy of the kinetic energy is lower at isomers levels in 3D. Also, we found that aggregates small n = 13 silver and to a lesser extent, copper have magic numbers according to the layered model 3D alkali metals (1 electron s), while gold remains a model of layers two dimensions that favors with magic number N = 6. We have also optimized geometries with EMG and LDA hollow aggregates for gold with 18, 20, 32, 50 and 162 atoms built on structures octaedrales, decaedrales and icosaedrales verifying rule Hund widespread 2 (2N +1) 2. Using molecular dynamics to 700 K can see that these geometries are equilibrium structures for both functional xc. But with LDA compact structures are more stable than the hollow, except for Au20. Using the structures of power for smaller aggregates of gold we have studied the adsorption of O2 and CO in aggregate gold free between 5 and 10 atoms. To aggregate 6 and 7 atoms adsorption disociativa O2 is favorable compared to the molecular adsorption. The oxygen molecule prefers placed in top position except for Au5, where they prefer to make a bridge between two Au. Get effect par-impar to the number of atoms for the adsorption energy, the distance liaison OO, transfer load O2 to aggregate, the vibrational frequency of the molecule O2 latter with inverse correlation. On the other hand, for the adsorption of CO to get more stable configuration corresponds to CO in top position except for Au5 and Au7 where CO is in a position to bridge the more stable isomer, which is due to the increase in overhead * donation of eo. This effect also generates increase in the distance liaison CO and the reduction in the frequency of vibrational eo, about setting mole Finally, within the group of noble metals on results we have studied free on noble metal free, the effect of dopar aggregates gold with a cationic atom of a metal transition (Sc, Ti, V, Cr, Fe and Mn). Note that only occurs a gain in energy liaison to dopar adding gold with Sc, while for the other transition metals is unfavorable compared to gold. From the resulting second in the total energy compared to the number of atoms, we found that these aggregates presented magic number n = 6 for Se, n = 5 for Ti and n = 5 and 7 for V, Cr, Mn, Fe and, total acue 8 rdo with 14a9 experiments, without the need to go to a layered model type jellium electron-localized, poorly suited to transition metals with orbital d incomplete. In addition, we found that the multiplicity of different spin isomers AunM + increases when the distance liaison M-Au increases as the coordination of the atom M decreases. Once analyzed aggregates gold, we have studied the adsorption of 02, CO, H20 of aggregates and alumina surface. Finally this oxide (alumina) is used as the substrate in studying reactivity of aggregates Au supported against the OC. First aggregates alumina estequiométricos have a regular little structure, with a few exceptions, with distances liaison and coordination in the range of the amorphous phase and the different stages alotrópicas of phase extensive. A structural feature of these aggregates is the presence of a diamond AI2O2 between two units AI04 sharing two oxígenos. These units tend to adsorb to form an atom of O on amorphous aggregates with geometry, while the ordered structure is the O atom forms a molecule of O2 with an atom aggregate. In the study we found that the structure affects an important role in the electronic properties, finding isomers with a small difference in power who have ordered or amorphous structure respectively, but with very different electronic properties. Since the structures of alumina obtained for the smaller aggregates (n = 7) we have studied the adsorption and dissociation processes of a water molecule on these structures. We found that (AI203) n with n = 2 and 3, the dissociation about Al OH H + and O on the closest is the most favorable, however for n = 4 decoupling takes place that leads the H + O to the second neighbor By fixing of the OH. The analysis of distances between added and the water molecule together with the analysis of excess burden allows us to clearly differentiate the processes of molecular adsorption and dissociation in small aggregates. We have studied peak stability of the aggregates (AI2O3) nAIO through the second resulting in an energy liaison regard, but we have not found any peak for n = 15, contrary to suggest experiments. In addition, we have analyzed the atomic structure (distance Al-O, coordination Al) and electronics (PDOS), (AI2O3) 2O finding that these properties are similar to those of the amorphous alumina. Completing the ultimate goal of this thesis we studied the formation of Still / (AI203) 2O and Au / (OO01) -A203, with n = 1 and 8, as well as the adsorption of CO on each of the previous systems at its configuration more stable except for Au8 / -AI2O3. For n = 1, these configurations have the Au At a coordination 3, forming a different angle with the different substrates. The aggregate (AI2O3) 20 found positions in competitive adsorption energy that do not occur on the surface. For the adsorption of CO on the system Au / (AI2O3) 20 are three situations. CO is adsorbed directly on the Au atom (without substantial changes in the substrate), the interface Au-sustrato or an intermediate configuration. When adsorption occurs on the system Au / -A1203 adsorb at the interface Au-sustrato is not stable, because there are not many oxígenos surface and burden sharing sites are lower. For both substrates the position of adsorption is more favorable position directly on top of the Au atom. The adsorption of CO at the interface Au / (AI2O3) 20 atom C form a bridge between an atom of O Au on the surface. From the results we see the addition (AI2O3) 20 models of the correct sites and energy of adsorption of CO on Au endured an atom on the surface (0001) a-A1203 and also provides other sites, typical of a surface excess oxygen. Comparing the results for the adsorption of CO on Au8 free and supported on (AI203) 20 we see that the difference in the structure in the aggregate Au8 in both systems is due to effects of the substrate. CO is adsorbed on top position on Au little coordinated with a similar distance OC. For Au8 / (AI2O3) 20 CO has also set on gold atoms with coordination 4 and energies similar to the more favorable. This increases the number of sites reaction due to the effect of the substrate, so that the activity toward the Au8 could CO be greater for the added endured.

Author: VILARRASA ANDRÉS AMPARO.
Year: 2005.
University: COMPLUTENSE DE MADRID.
Place of defense: UNIVERSIDAD COMPLUTENSE DE MADRID.
Place of preparation: UNIVERSIDAD COMPLUTENSE DE MADRID.

Summary: Breast cancer is the most common cause of death among women. The most effective method for reducing mortality now is the early detection and diagnosis of lesions of the same. With regard to the detection, the difficulties are related to the small size of the lesions, low-contrast image in some areas of overlap with normal tissue structures suspicious devices in the mammograms, and so on. The diagnosis of lesions found, largely depends on the training, experience and diligence of the radiologist to interpret mammograms. The fundamental objective being pursued is to avoid both false positives and negatives. To reduce the failure rate diagnoses and unnecessary biopsies can be used double reading. Although this method achieves its goal, poses the following disadvantages: increased workload and costs. Therefore, this thesis proposes a system of intelligent design for the detection, diagnosis and prognosis of breast abnormalities using original techniques. This system has been designed for parallel detection of microcalcifications and masses), are used algorithms based on artificial vision and mathematical morphology. For prognosis (benign or malignant), and diagnosis (patológico9 used artificial neuron networks. Prognosis, using networks of neurons fed forward with a supervised training algorithm. Diagnosis using Kohonen networks. System design consists of three modules, a first module, called mass detection subsystem, which is responsible for the segmentation and obtain the characteristics of the masses that might arise in a digital mammogram. The second module, called subistema detection of microcalcifications, charged the segmentation and obtain discriminating characteristics of microcalcifications existing digital mammography, and the third and final module responsible for the diagnosis of injuries encountered by previous subsystems. This system is called SADIMA System (Autoadaptativo Diagnostic Mamográfico).

Author: CALDERON OBALDIA EDUARDO.
Year: 2005.
University: COMPLUTENSE DE MADRID.
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: CENTRO DE INVESTIGACIONES ENERGÉTICAS, MEDIOAMBIENTALES Y TECNOLÓGICAS-CIEMAT.

Summary: 1 - The first item addressed in the work deals with the characterization of the electrical probes (Langmuir and Mach) and the interpretation of the signals obtained. We can summarize the results obtained in the following manner: * The standard level of fluctuations in the flow of ion saturation is proving very similar in areas both inside and outside layer is formed due to disruption to the body of the probe. * The turbulent radial transport measures undertaken within and outside the area of disturbance of the body of the probe, show values very consistent with each other, taking into account the uncertainties caused by the determination of the area collecting actual probes. These results prior investigations into question the recent interpretations on measures electrical probes under the influence of the area of disturbance that causes the body of the probe. 2-On the other hand, experiments on tH-II have shown that the relationship between plasma density standard recycling particles can increase up to a factor two to polarize the limiter without netrada significant impurities, which would imply a improved plasma confinement, these experiments have led to the following observations: * During the transition to this regime of containment towards improved induced polarization has been observed in the different behaviors turbulent transport and reducing fluctuations. This result shows changes in the electric field due to confinement. * Both flows perpendicular as parallels are modified to implement the polarization, which indicates as the polarization experiments can be carried out both the location of the shear layer as to the characteristics of the fluctuations. * The study of the relaxation times of the potential of plasma and electric field shows that the changes are made in two different scales, a scale slow-related properties of confinement and overall comparable with other fast times that develops turbulence . Currently being conducted systematic research on the influence of magnetic configuration and relaxation of the potential plasma and electric fields. 3, has been investigating the connection between the levels of turbulence and electric fields to the structure of the density profiles in the peripheral region of the plasma (SOL) in different scenarios. The experimental results obtained show that: * The structure of the turbulence in the zone more external plasma TH-II has shown a clear reduction of fluctuations when measured on a warming NBI off the measure obtained regime warming ECR . As a result the effective radial velocity inferred from the extent of turbulent flow decreases about a factor 10 in plasma heated by injection neutral, thereby decreasing the events observed rapid Warming ECH. This produces a clear evidence for radial velocity coupling between events rapid transport and the structure of the profiles in the plasma edge. * The results obtained by changing the density plasma surrounding the value necessary for the development of the shear layer on the edge, show the existence of a minimum level of turbulence for the development of this layer in the flow, or what is the same for the appearance of an electric field on the edge of the plasma TJ-II, above which the fluctuations diminish. The flow of particles measured in the external zone decreases when the plasma density is greater than the critical value found. These results may be considered compatible with a state of improved plasma confinement. * One of the most important results that were obtained as a result of inserting an electrode polarized on the edge of the plasma, was the drastic reduction in the levels of transport turbulent ExB 8. The ca d15 mbios in the profile of the electric field that occurs in the edge plasma may explain the dramatic reduction in the turbulent transport, thus leading to an improvement in the confinement of particles and energy, and a reduction in the values of the density in the peripheral region (SOL). The experiments show for the first time a direct link between the structure of turbulence and structure of the profiles in the plasma edge. 4-While most of the results of this paper are based on research obtained in the stellarator TH-II also conducted experiments on the device linear plasma PSI-2. Based on the prototype zone proposed by Chavers / Chang-Díoaz, has designed and manufactured a probe combined CFML for measuring force (and hence temperature ionic) and parallel flow (Mach probes) and measures Langmuir probe . As a result of these experiments came to the following conclusions: * The calibration of the probe has been crucial to the consistency of actions: factors such as thermal strain, vibration by magnetic field or other devices, air currents and fatigue of the material, have been taken into account to develop a calibration curve to consider all these aspects. * Given the stationary conditions of PSI-2 was successfully reproduce various scenarios performing very consistent. It varied currents in the cathode, the type of gas to be injected, the intensity of the magnetic field and on the other side was interrupted voluntarily gas injection to observe the behavior of relaxation of the probe only under the influence of magnetic field. At the same time, the varied lengths of the probe to obtain various calibration curves and thus find the greater sensitivity it could have under the influence plasma once immersed in the column of gas PSI-2. * Forces of the order of several mN and ionic temperatures in the range of 1-2 eV were observed both at the edge and at the center of the plasma column. Using argon plasmas measures provided strong enough to continue using it for our purposes, instead of helium plasma, as the benchmark of the measure was lost when used consistently high currents in the cathode (200) using helium, but not with argon. This new diagnostic system for measuring temperature ionic could provide some very interesting results in the study of the behavior of the temperature at the edge of the plasma fusion devices. Finally, the results in this report are of particular interest for the development of predictive models of transport in the peripheral region of the plasma, as well as to develop control techniques for the improvement of plasma confinement.

Author: BLANCO VILLAREAL EMILIO JOSÉ.
Year: 2005.
University: COMPLUTENSE DE MADRID.
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: CIEMAT.

Summary: That argument is framed in the field of reflectometría microwave applied to nuclear fusion plasmas magnetically confined. In Chapter 1 is an introduction to nuclear fusion showing the objectives to be achieved in line with research by magnetic confinement fusion. It describes the two large groups of experimental devices present setellarators and tokamaks, showing its advantages and disadvantages. In Chapter 2 lays the theoretical foundation on which is based the technique of reflectometría microwave and described the two modes of propagation employees frequent and regular manner so extraordinary. In Chapter 3 describes a code of two-dimensional wave comprehensive based on the technique FDTD (Finite-Difference Time-Domain) solves the Maxwell equations in plasmas magnetizados with fluctuations of density in the time domain. In chapters 4, 5 and 6 applies this code to study various aspects of reflectometría microwave. In Chapter 4 explores an asymmetry that appears in the equations describing the propagation in an extraordinary manner and its effect on the average pilot being undertaken reflectometría. In Chapter 5 describes the reflectometro pilot installed in the TJ-II stellarator located at CIEMAT (Madrid), and shows the experimental measures that have been undertaken. Interpretation of results is validated with the help of full-wave code. In chapter 6, the code is used to study pair's ability reflectometría Doppler to measure the speed of rotation perpendicular plasma. We are studying various scenarios for the curvature of plasma and / or front of waves and shown the conditions under which the rotational speed of the plasma measured reflectometría is reliable.