Development and performance evaluation of detectors in a Compton camera arrangement for ion beam range monitoring in particle therapy

The growing interest in particle beam therapy for cancer treatment is driven by the ability to provide high precision dose delivery. However, this benefit demands a high accuracy on the determination of the well-localized dose deposition (Bragg peak), which has to be located within the tumor volume. Different approaches for the beam range monitoring are worldwide being evaluated. The Compton camera is one of the proposed techniques, which aims at providing real-time, in-vivo proton (or ion) beam range monitoring by means of the detection of secondary prompt gamma rays, resulting from nuclear reactions between the particle beam and the biological tissue. The purpose of our project is to develop and commission an imaging system based on a Compton camera detector arrangement which could monitor in (ultimately) real-time the ion beam range. In the context of this thesis a Compton camera detector prototype was characterized, consolidated and commissioned with both a multi-layer and a mono-layer scatter component. The first detector arrangement belongs to the LMU Compton camera: the detector components were extensively characterized in order to determine the limitations imposed by their internal structure and the required configuration for an optimum performance. The complexity of the signal readout and processing could be reduced in view of facilitating an envisaged clinical applicability of the system. The scatter component (tracker) is formed by a stack of six highly segmented double-sided Si-strip detectors, whereas a monolithic LaBr3(Ce) scintillator (5 x 5 x 3 cm3) acts as the absorber component and is coupled to a segmented position-sensitive multi-anode photomultiplier tube (PMT). The initially applied 256-fold segmented PMT was replaced by a 64-fold segmented PMT, and similar or even superior performance was demonstrated for the latter one. The same trend of an improving spatial resolution, with an increasing energy of the incoming photon, which was observed when using the 256-fold segmented PMT, was also preserved: at 137Cs energy a value of 3.4(1) mm was obtained, while at the 1173 keV and 1332 keV 60Co photopeaks the spatial resolution reached values of 2.9(1) mm, thus below the 3 mm absorber resolution envisaged by the Compton camera design. Moreover, first tests in view of a possible replacement of the LaBr3(Ce) scintillation material with the cost-effective and radio-pure CeBr3 scintillator material were pursued and seem promising (ΔE/E ≃ 4% at 662 keV and comparable timing properties as LaBr3(Ce)). The signal processing and data readout system for the scatter component was upgraded from an ASIC-based electronics to a more flexible and higher performing electronics based on discrete components. Full compliance of the new frontend electronics with the detector signal specifications of our camera prototype was achieved: an acceptance of both signal polarities was introduced as well as a trigger capability for the scatter component, which previously did not exist. Furthermore, the upgrade of the signal processing and data acquisition was extended to the whole Compton camera setup, adapting the new frontend electronics designed initially for replacing the outdated ASIC-based modules of the scatterer also to the signal properties of the absorber scintillator and its segmented readout. This allowed for reducing the complexity of the system and finally achieve a 1 Mcps count rate capability as required in a clinical scenario: the VME-based readout modules were implemented into the new DAQ software and the data streams of scatterer and absorber were merged. The reduced granularity of the PMT signal channels combined with the use of the new signal processing and data acquisition system based on optical fibers makes the Compton camera setup less complex and more flexible. All detectors can be mounted in a newly designed Faraday cage, which includes also an active cooling, capable of reducing the dark current in the silicon detectors. The upgraded system was tested in the laboratory as well as under online conditions with particle beams at the Tandem accelerator in Garching. A validation with high energy prompt-γ rays was performed, bombarding water and PMMA targets with a 20 MeV proton beam and the same detector performance could be demonstrated also with the new signal processing system. The achievable trigger rate was increased by one order of magnitude and due to the efficient selection of Compton scattered events by triggering on the scatter component, the ratio of registered Compton events could be increased by about three orders of magnitude compared to the previous data acquisition system. The camera system was also tested by hitting a water target with a pulsed deuteron beam in order to allow for assessing the timing performance. With an envisaged improved version of the internal implantation structure of the segmented silicon scatter modules, the multi-layer Compton camera system will be ready for a full performance characterization of the imaging system's capabilities. By using the high performing LaBr3(Ce) monolithic scintillator as absorber, a Compton camera setup was also arranged with a mono-layer scattering component consisting of a pixelated 22 x 22 array of GAGG scintillator crystals. A proof of principle study was carried out using 137Cs and 60Co calibration sources: the source position reconstruction was performed with the MEGAlib software and the resulting reconstructed images from experimental data were compared to images reconstructed from simulated data. A source shift of 2 mm could be resolved by the system with sub-millimeter accuracy. A trend of improving angular resolution with the incoming photon energy reflects the detectors' (energy and spatial resolution) performance improvements with increasing energy. The system was characterized in different geometrical configurations, in order to address not only a possible prompt-gamma imaging application, but also a multi-modality detector system able to be applied also in PET- or gamma-PET-like imaging scenarios

Physical Education and teacher education. Passing the craft in the Teaching Practice class. Coversations, demands and analysis in order to reflect

El presente informe comparte algunos de los hallazgos resultantes del ejercicio de investigar en torno a la tarea docente en la formación profesional en Educación Física. El objetivo del estudio realizado pretendió describir y analizar cómo se enseña a enseñar Educación Física, al indagar en los modos de transmitir el oficio en clases de Práctica Docente y Residencia III y IV, dos unidades curriculares que abren a la perspectiva del ejercicio docente, al ofrecer al estudiantado un acercamiento a la realidad educativa y a las condiciones y procesos reales del trabajo docente en Educación Física escolar. Desde un enfoque cualitativo y etnográfico, se observaron y registraron las clases de cuatro docentes durante un período prolongado que, junto a las entrevistas en profundidad realizadas a cada uno/a, conformaron el corpus empírico de referencia. A partir de la información construida se exploran una serie de acciones docentes que expresan los modos de transmitir el oficio. El uso de la pregunta como herramienta que posibilita conversación; la exigencia estudiantil como responsabilidad docente; la necesidad de construir sentidos epistémicos y éticos y la problematización en clase de Práctica de la clase ofrecida en el patio. En clave artesanal, profesores y estudiantes hacen docencia.This report shares some of the findings resulting from the exercise of investigating the teaching task in professional training in Physical Education. The objective of the study carried out describes and analyzes how Physical Education is taught to teach, by investigating the ways of passing the craft in the clases of Teaching Practice III and IV. Two curricular units that open to the perspective of teaching, by offering to the students an approach to the educational reality and the real conditions and processes of the teaching work in school Physical Education. From a qualitative and ethnographic point of view, the classes of four teachers were observed and recorded over a prolonged period that, together with the in-depth interviews carried out with each one, made up the empirical reference corpus. From the data constructed, a series of teaching actions show the ways of passing the craft. The use of the question as a tool that enables conversation; the student's demand as a teaching responsibility; the need to build epistemic and ethical meanings and the problematization in Practice class about the school yard class. Similar to a craftman, teachers and students teach.Facultad de Humanidades y Ciencias de la Educació

Alkyne Selective Hydrogenation with Mono- and Bimetallic- Anchored Catalysts

Partial hydrogenation of alkynes has industrial and academic relevance on a large scale; industries such as petrochemical, pharmacological and agrochemical use these compounds as raw material. Finding an economic, active and selective catalyst for the production of alkenes through partial hydrogenation of alkynes is thus an important challenge. Mono- and bimetallic catalysts (palladium, ruthenium and nickel) were synthetized by the incipient wetness technique using gamma alumina and an activated carbon as supports. The catalysts were characterized by inductively coupled plasma, hydrogen chemisorption, temperature-programmed reduction and X-ray photoelectronic spectroscopy (XPS). The objective of this work is to study 1-heptyne-selective hydrogenation using supported catalysts influenced by different factors: (a) pretreatment reduction temperature, (b) reaction temperature, (c) type of support, (d) metal loading, (e) precursor salt and (f) addition of a second metal to monometallic palladium catalyst. The Lindlar commercial catalyst, commonly used in these types of reactions, was used for comparative purposes. XPS technique allowed verifying that the presence of electron-deficient species on the catalyst surface with high metal loading affects the conversion and selectivity to the desired product. Nevertheless, the influence of geometrical effects and/or mixed active sites in the catalysts, as well as metal-metal and metal-support interactions, cannot be neglected

Enseñar a enseñar Educación Física: conocimiento, investigación y experiencia

Esta investigación nace del interés por hacer visibles las experiencias de profesores experimentados y recién iniciados en la práctica docente, documentando singularidades de su hacer en aquellas mediaciones cotidianas puestas en juego en la tarea de enseñar a enseñar, en búsqueda -por qué no- de indicios para nuevas prácticas y sentidos. Sostiene Achilli “dar existencia teórica a lo obvio, a lo oculto, contradictorio y desconocido de la vida diaria, recuperando al sujeto de las acciones socioeducativas, recuperando su racionalidad subjetiva” (2008, p.52). Las preguntas que guían esta investigación son ¿los docentes recuperan en sus propuestas las preocupaciones que hoy instalan los discursos políticos y teóricos? ¿Desde qué concepciones (de enseñanza, de aprendizaje, específicas del campo de la EF) se ofrecen esos conocimientos? ¿Qué conocimientos privilegian los docentes en sus propuestas? ¿Cuáles son los conocimientos que los docentes de la formación reconocen con imprescindibles para los estudiantes? ¿Son diferentes las propuestas de los docentes recién iniciados y las de aquellos que tienen más experiencia? ¿Cómo enseñan a enseñar los profesores de Práctica docente del PEF?Trabajo publicado en Giordano, Carlos José y Morandi, Glenda (comps.). Memorias de las 2º Jornadas sobre las Prácticas Docentes en la Universidad Pública. La enseñanza universitaria a 100 años de la reforma: legados, transformaciones y compromisos. Universidad Nacional de La Plata: La Plata, 2019.Presidenci

Enseñar a enseñar Educación Física: conocimiento, investigación y experiencia

Esta investigación nace del interés por hacer visibles las experiencias de profesores experimentados y recién iniciados en la práctica docente, documentando singularidades de su hacer en aquellas mediaciones cotidianas puestas en juego en la tarea de enseñar a enseñar, en búsqueda -por qué no- de indicios para nuevas prácticas y sentidos. Sostiene Achilli “dar existencia teórica a lo obvio, a lo oculto, contradictorio y desconocido de la vida diaria, recuperando al sujeto de las acciones socioeducativas, recuperando su racionalidad subjetiva” (2008, p.52). Las preguntas que guían esta investigación son ¿los docentes recuperan en sus propuestas las preocupaciones que hoy instalan los discursos políticos y teóricos? ¿Desde qué concepciones (de enseñanza, de aprendizaje, específicas del campo de la EF) se ofrecen esos conocimientos? ¿Qué conocimientos privilegian los docentes en sus propuestas? ¿Cuáles son los conocimientos que los docentes de la formación reconocen con imprescindibles para los estudiantes? ¿Son diferentes las propuestas de los docentes recién iniciados y las de aquellos que tienen más experiencia? ¿Cómo enseñan a enseñar los profesores de Práctica docente del PEF?Trabajo publicado en Giordano, Carlos José y Morandi, Glenda (comps.). Memorias de las 2º Jornadas sobre las Prácticas Docentes en la Universidad Pública. La enseñanza universitaria a 100 años de la reforma: legados, transformaciones y compromisos. Universidad Nacional de La Plata: La Plata, 2019.Presidenci

Enseñar a enseñar Educación Física: conocimiento, investigación y experiencia

Esta investigación nace del interés por hacer visibles las experiencias de profesores experimentados y recién iniciados en la práctica docente, documentando singularidades de su hacer en aquellas mediaciones cotidianas puestas en juego en la tarea de enseñar a enseñar, en búsqueda -por qué no- de indicios para nuevas prácticas y sentidos. Sostiene Achilli “dar existencia teórica a lo obvio, a lo oculto, contradictorio y desconocido de la vida diaria, recuperando al sujeto de las acciones socioeducativas, recuperando su racionalidad subjetiva” (2008, p.52). Las preguntas que guían esta investigación son ¿los docentes recuperan en sus propuestas las preocupaciones que hoy instalan los discursos políticos y teóricos? ¿Desde qué concepciones (de enseñanza, de aprendizaje, específicas del campo de la EF) se ofrecen esos conocimientos? ¿Qué conocimientos privilegian los docentes en sus propuestas? ¿Cuáles son los conocimientos que los docentes de la formación reconocen con imprescindibles para los estudiantes? ¿Son diferentes las propuestas de los docentes recién iniciados y las de aquellos que tienen más experiencia? ¿Cómo enseñan a enseñar los profesores de Práctica docente del PEF?Trabajo publicado en Giordano, Carlos José y Morandi, Glenda (comps.). Memorias de las 2º Jornadas sobre las Prácticas Docentes en la Universidad Pública. La enseñanza universitaria a 100 años de la reforma: legados, transformaciones y compromisos. Universidad Nacional de La Plata: La Plata, 2019.Presidenci

Clinical Impact of the Polypill for Cardiovascular Prevention in Latin America: A Consensus Statement of the Inter-American Society of Cardiology.

The burden of cardiovascular diseases (CVD) is increasing, particularly in low-middle-income countries such as most of Latin America. This region presents specific socioeconomic characteristics, generating a high incidence of CVD despite efforts to control the problem. A consensus statement has been developed by Inter-American Society of Cardiology with the aim of answering some important questions related to CVD in this region and the role of the polypill in cardiovascular (CV) prevention as an intervention to address these issues. A multidisciplinary team composed of Latin American experts in the prevention of CVD was convened by the Inter-American Society of Cardiology and participated in the process and the formulation of statements. To characterize the prevailing situation in Latin American countries, we describe the most significant CV risk factors in the region. The barriers that impair the use of CV essential medications are also reviewed. The role of therapeutic adherence in CV prevention and how the polypill emerges as an effective strategy for optimizing adherence, accessibility, and affordability in the treatment of CVDs are discussed in detail. Clinical scenarios in which the polypill could represent an effective intervention in primary and secondary CV prevention are described. This initiative is expected to help professionals involved in the management of CVD and public health policymakers develop optimal strategies for the management of CVDs

Activity and sulfur resistance of Rh(I) and Pd(II) complexes

Two complexes of Rh(I) and Pd(II) with chloride and tridecylamine ligands were obtained and characterized by Elementary Analysis and by XPS and FTIR spectroscopies. Complexes anchored on γ-Al2O3 were tested in the styrene semi-hydrogenation reaction carried out in the absence or presence of a sulfur poison. Although both low loaded catalysts were highly selective, the Pd(II) complex was three times more active than the Rh(I) complex. The rhodium complex was more sulfur resistant but less active than the palladium complex. Differences in conversion and sulfur resistance between both complexes could be related to electronic and/or geometric effects