Imaging applications from a laser wakefield accelerator

Laser-plasma wakefield acceleration (LWFA) is a promising technology that is attracting the attention of the scientific community. It is a new acceleration concept where electrons can be accelerated to very high energy (~150 MeV) in a very short distance (mm scale). Electrons "surf" plasma waves excited by the passage of a high power laser (~1018 Wcm-2) through plasma. Electrons in the LWFA can undergo transverse oscillation and emit synchrotron-like X-ray radiation, commonly known as betatron radiation, in a narrow cone along the laser propagation axis. The properties of both the electrons and the X-rays produced by the LWFA make them excellent candidates for a wide range of applications. In this thesis, both betatron X-ray and bremsstrahlung sources from the ALPHA-X laboratory are used to carry out both conventional imaging and X-ray phase-contrast imaging experiments to explore the feasibility of real-world applications. The characterisation of the betatron X-ray radiation produced by the LWFA in the ALPHA-X laboratory is presented. In the last Chapter, a brief discussion of the potential of LWFA technology for clinical applications is presented.Laser-plasma wakefield acceleration (LWFA) is a promising technology that is attracting the attention of the scientific community. It is a new acceleration concept where electrons can be accelerated to very high energy (~150 MeV) in a very short distance (mm scale). Electrons "surf" plasma waves excited by the passage of a high power laser (~1018 Wcm-2) through plasma. Electrons in the LWFA can undergo transverse oscillation and emit synchrotron-like X-ray radiation, commonly known as betatron radiation, in a narrow cone along the laser propagation axis. The properties of both the electrons and the X-rays produced by the LWFA make them excellent candidates for a wide range of applications. In this thesis, both betatron X-ray and bremsstrahlung sources from the ALPHA-X laboratory are used to carry out both conventional imaging and X-ray phase-contrast imaging experiments to explore the feasibility of real-world applications. The characterisation of the betatron X-ray radiation produced by the LWFA in the ALPHA-X laboratory is presented. In the last Chapter, a brief discussion of the potential of LWFA technology for clinical applications is presented

La economía de los argentinos: reglas de juego para una sociedad próspera y justa. Federico Sturzenegger. Bos Aires: Planeta. 2003 [288 páginas]

Texto dispoñible en galego e españolNO

Challenges of dosimetry of ultra-short pulsed very high energy electron beams

Very high energy electrons (VHEE) in the range from 100–250 MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetric properties compared with 6-20 MV photons generated by clinical linear accelerators (LINACs). VHEE beams have characteristics unlike any other beams currently used for radiotherapy: femtosecond to picosecond duration electron bunches, which leads to very high dose per pulse, and energies that exceed that currently used in clinical applications. Dosimetry with conventional online detectors, such as ionization chambers or diodes, is a challenge due to non-negligible ion recombination effects taking place in the sensitive volumes of these detectors. FLUKA and Geant4 Monet Carlo (MC) codes have been employed to study the temporal and spectral evolution of ultrashort VHEE beams in a water phantom. These results are complemented by ion recombination measurements employing an IBA CC04 ionization chamber for a 165 MeV VHEE beam. For comparison, ion recombination has also been measured using the same chamber with a conventional 20 MeV electron beam. This work demonstrates that the IBA CC04 ionization chamber exhibits significant ion recombination and is therefore not suitable for dosimetry of ultrashort pulsed VHEE beams applying conventional correction factors. Further study is required to investigate the applicability of ion chambers in VHEE dosimetry

An enhanced algorithm for semantic-based feature reduction in spam filtering

With the advent and improvement of ontological dictionaries (WordNet, Babelnet), the use of synsets-based text representations is gaining popularity in classification tasks. More recently, ontological dictionaries were used for reducing dimensionality in this kind of representation ( e.g. , Semantic Dimensionality Reduction System (SDRS) (Vélez de Mendizabal et al., 2020)). These approaches are based on the combination of semantically related columns by taking advantage of semantic information extracted from ontological dictionaries. Their main advantage is that they not only eliminate features but can also combine them, minimizing (low-loss) or avoiding (lossless) the loss of information. The most recent (and accurate) techniques included in this group are based on using evolutionary algorithms to find how many features can be grouped to reduce false positive (FP) and false negative (FN) errors obtained. The main limitation of these evolutionary-based schemes is the computational requirements derived from the use of optimization algorithms. The contribution of this study is a new lossless feature reduction scheme exploiting information from ontological dictionaries, which achieves slightly better accuracy (specially in FP errors) than optimization-based approaches but using far fewer computational resources. Instead of using computationally expensive evolutionary algorithms, our proposal determines whether two columns (synsets) can be combined by observing whether the instances included in a dataset ( e.g. , training dataset) containing these synsets are mostly of the same class. The study includes experiments using three datasets and a detailed comparison with two previous optimization-based approaches.Xunta de Galicia | Ref. ED431C 2022/03-GRCAgencia Estatal de Investigación | Ref. Ref. TIN2017-84658-C2-1-

Improving pipelining tools for pre-processing data

The last several years have seen the emergence of data mining and its transformation into a powerful tool that adds value to business and research. Data mining makes it possible to explore and find unseen connections between variables and facts observed in different domains, helping us to better understand reality. The programming methods and frameworks used to analyse data have evolved over time. Currently, the use of pipelining schemes is the most reliable way of analysing data and due to this, several important companies are currently offering this kind of services. Moreover, several frameworks compatible with different programming languages are available for the development of computational pipelines and many research studies have addressed the optimization of data processing speed. However, as this study shows, the presence of early error detection techniques and developer support mechanisms is very limited in these frameworks. In this context, this study introduces different improvements, such as the design of different types of constraints for the early detection of errors, the creation of functions to facilitate debugging of concrete tasks included in a pipeline, the invalidation of erroneous instances and/or the introduction of the burst-processing scheme. Adding these functionalities, we developed Big Data Pipelining for Java (BDP4J, https://github.com/sing-group/bdp4j), a fully functional new pipelining framework that shows the potential of these features.Agencia Estatal de Investigación | Ref. TIN2017-84658-C2-1-RXunta de Galicia | Ref. ED481D-2021/024Xunta de Galicia | Ref. ED431C2018/55-GR

A multiple classifier system identifies novel cannabinoid CB2 receptor ligands

Abstract Drugs have become an essential part of our lives due to their ability to improve people’s health and quality of life. However, for many diseases, approved drugs are not yet available or existing drugs have undesirable side effects, making the pharmaceutical industry strive to discover new drugs and active compounds. The development of drugs is an expensive process, which typically starts with the detection of candidate molecules (screening) after a protein target has been identified. To this end, the use of high-performance screening techniques has become a critical issue in order to palliate the high costs. Therefore, the popularity of computer-based screening (often called virtual screening or in silico screening) has rapidly increased during the last decade. A wide variety of Machine Learning (ML) techniques has been used in conjunction with chemical structure and physicochemical properties for screening purposes including (i) simple classifiers, (ii) ensemble methods, and more recently (iii) Multiple Classifier Systems (MCS). Here, we apply an MCS for virtual screening (D2-MCS) using circular fingerprints. We applied our technique to a dataset of cannabinoid CB2 ligands obtained from the ChEMBL database. The HTS collection of Enamine (1,834,362 compounds), was virtually screened to identify 48,232 potential active molecules using D2-MCS. Identified molecules were ranked to select 21 promising novel compounds for in vitro evaluation. Experimental validation confirmed six highly active hits (> 50% displacement at 10 µM and subsequent Ki determination) and an additional five medium active hits (> 25% displacement at 10 µM). Hence, D2-MCS provided a hit rate of 29% for highly active compounds and an overall hit rate of 52%.Dutch Scientific Council | Ref. VENI 14410Xunta de Galicia | Ref. ED431C2018/55-GR

Toxoplasmosis: epidemiologic study of hospitalizated cases in Spain (2000-2021)

Artículo[ES] Introducción: La toxoplasmosis es una zoonosis de distribución mundial causada por Toxoplasma gondii. El ser humano actúa como huésped intermediario dentro de un ciclo multiespecie en el que los hospedadores definitivos son los félidos. La importancia de la infección humana se centra, principalmente, en personas inmunocomprometidas y en los casos congénitos (mujeres gestantes que han transmitido la enfermedad al feto). El objetivo fue describir la epidemiología de la hospitalización con diagnóstico toxoplasmosis en España durante el período 2000-2021.Método: Se plantea un análisis descriptivo de las hospitalizaciones en España con diagnóstico de toxoplasmosis entre los años 2000-2021, a partir de datos del Registro de Atención Sanitaria Especializada. Las variables analizadas fueron: sexo, edad y Comunidades y Ciudades Autónomas (CCAA).Resultados: durante el período 2000-2021 se produjeron 8.102 altas hospitalarias con diagnóstico toxoplasmosis, (tasa de hospitalización acumulada por 100.000 hab. TH=0,81). Esta TH ha ido disminuyendo a lo largo del período, pasando de 1,55 en 2000 hasta 0,48 en 2021. El número de ingresos fue mayor en hombres y en éstos, se ha ido produciendo un descenso más acusado. El grupo de edad con la mayor TH acumulada fue el de 35-39 años (TH=1,96). Las CCAA con mayores TH totales fueron, Ceuta, Melilla, Islas Baleares y Cataluña. Conclusiones: Las TH por toxoplasmosis han descendido progresivamente a lo largo del período 2000-2021. Este descenso es más acusado en hombres y se debe, sobre todo, a la disminución de la TH en el grupo de edad de 35-39 años. [EN] Introduction: Toxoplasmosis is a worldwide zoonotic disease caused by Toxoplasma gondii. Humans are intermediate hosts within a multispecies cycle in which felids are definitive hosts. The importance of the human infection is restricted to immunocompromised individuals and pregnant women who can transmit the disease to the fetus. The purpose was to describe toxoplasmosis hospitalization epi-demiology in Spain during 2000-2021.Methods: A descriptive analysis of hospitalization in Spain with a diagnosis of toxoplasmosis from 2000 to 2021 was performed using data from the Specialized Health Care Registry (RAE-CMBD). The variables analyzed were sex, age and Autonomous Communities (CCAA).Results: During the period 2000-2021 there were 8,102 hospital admissions with a diagnosis of to-xoplasmosis (hospitalization rate HT = 0.81). This HT decreased throughout the period, from 1.55 (2000) to 0.48 in 2021. The number of admissions was higher in men and in these, there has been a steeper decline over the period. The age group with the highest accumulated HT was 35-39 years old (HT=1.96). The CCAA with the highest total HT were Ceuta, Melilla, Balearic Islands and Catalonia. Conclusions: HT toxoplasmosis have progressively decresed throughout 2000-2021. This decrease is more pronounced in men and is due, above all, to the decrease in HT in 35-39 age group.N

Alterações climáticas nas Bacias do Sado e Tejo e seus efeitos na produtividade de arroz

SFRH/BD/121892/2016A agricultura é fortemente dependente das condições meteorológicas. As alterações climáticas podem modificar padrões de precipitação levando à ocorrência de fenómenos extremos como secas e cheias. As culturas irrigadas, como é o caso do arroz, podem ser afectadas por escassez de água devido à ocorrência de extensos períodos de secas ou até mesmo cheias. Em Portugal, importantes áreas de produção orizícola estão localizadas nas bacias do Tejo e do Sado. A análise da precipitação de estações meteorológicas desde 1931/32 até 2016/17 na bacia do Sado e 1909/10 até 2016/17 na bacia do Tejo evidenciam variações similares na distribuição anual da precipitação. Desde o início dos registos até 1949/50 foi observado um período seco, seguido de um húmido desde 1950/51 até 1994/95. Um período instável e seco foi observado desde 1995/96 até à actualidade com um decréscimo no padrão de precipitação e uma maior oscilação relativamente à tendência que se vinha verificando. Em contrapartida, em períodos húmidos, o regime de precipitações é mais regular e com menos episódios muito húmidos e muito secos. Para avaliar os efeitos do regime de distribuição anual da precipitação foi estudada a produtividade de dois canteiros de arroz no intervalo de 10 e 11 anos, não tendo sido observada qualquer correlação com a precipitação porque esta depende de muitos outros factores, tais como as técnicas agrícolas utilizadas ou variedades cultivadas.publishersversionpublishe

Gamma-ray production from resonant betatron oscillations of accelerated electrons in a plasma wake

The laser-plasma wakefield accelerator is a novel ultra-compact particle accelerator. A very intense laser pulse focused onto plasma can excites plasma density waves. Electrons surfing these waves can be accelerated to very high energies with unprecedented accelerating gradients in excess of 1 GV/cm. While accelerating, electrons undergo transverse betatron oscillations and emit synchrotron-like x-ray radiation into a narrow on-axis cone, which is enhanced when electrons interact with the electromagnetic field of the laser. In this case, the laser can resonantly drive the electron motion, lading to direct laser acceleration. This occurs when the betatron frequency matches the Doppler down-shifted frequency of the laser. As a consequence, the number of photons emitted is strongly enhanced and the critical photon energy is increases to 100’s of ke

Defining robustness protocols: a method to include and evaluate robustness in clinical plans.

This is the final version of the article. It first appeared from IOP Publishing via http://dx.doi.org/10.1088/0031-9155/60/7/2671We aim to define a site-specific robustness protocol to be used during the clinical plan evaluation process. Plan robustness of 16 skull base IMPT plans to systematic range and random set-up errors have been retrospectively and systematically analysed. This was determined by calculating the error-bar dose distribution (ebDD) for all the plans and by defining some metrics used to define protocols aiding the plan assessment. Additionally, an example of how to clinically use the defined robustness database is given whereby a plan with sub-optimal brainstem robustness was identified. The advantage of using different beam arrangements to improve the plan robustness was analysed. Using the ebDD it was found range errors had a smaller effect on dose distribution than the corresponding set-up error in a single fraction, and that organs at risk were most robust to the range errors, whereas the target was more robust to set-up errors. A database was created to aid planners in terms of plan robustness aims in these volumes. This resulted in the definition of site-specific robustness protocols. The use of robustness constraints allowed for the identification of a specific patient that may have benefited from a treatment of greater individuality. A new beam arrangement showed to be preferential when balancing conformality and robustness for this case. The ebDD and error-bar volume histogram proved effective in analysing plan robustness. The process of retrospective analysis could be used to establish site-specific robustness planning protocols in proton therapy. These protocols allow the planner to determine plans that, although delivering a dosimetrically adequate dose distribution, have resulted in sub-optimal robustness to these uncertainties. For these cases the use of different beam start conditions may improve the plan robustness to set-up and range uncertainties.This work was partly funded by an MRC Doctoral Training Grant