Modèle Monte Carlo du transport dans l'atmosphère des électrons relativistes et des photons gamma en relation avec les TGF

Les orages sont des sources de phénomènes transitoires intenses, notamment lumineux, dans le domaine visible, mais également dans le domaine des rayons X et gamma. Ces phénomènes sont détectés sous la forme de flash de photons X et gamma appelés "Terrestrial Gamma Ray Flashes" (TGF). L'objet de cette thèse est le développement d'un modèle numérique pour étudier et comprendre les mécanismes associés aux TGF. L'étude des TGF est donc importante pour comprendre la physique des éclairs et des orages (qui sont des phénomènes très communs mais dont la microphysique reste encore très mal comprise) ainsi que le couplage entre l'atmosphère et l'ionosphère de la Terre. Cette thèse s'inscrit plus particulièrement dans le cadre de la préparation de la mission TARANIS du CNES, qui sera lancée en 2017. TARANIS disposera en particulier des instruments XGRE et IDEE, capables de caractériser les photons X/gamma et les électrons relativistes associés. Après son émission, vers 15 km d'altitude, le flux de rayons gamma du TGF est filtré et altéré par l'atmosphère, et une petite partie peut être détectée par un satellite en orbite basse. Cette dernière est constituée de photons primaires diffusés, ainsi que d'électrons, de positrons et de photons produits de manière secondaire. Une partie des leptons secondaires va pouvoir sortir de l'atmosphère et sera ensuite confinée par les lignes de champ géomagnétique. Ainsi, pouvoir établir des contraintes sur le mécanisme source des TGF à partir des observations est un problème inverse très complexe, qui ne peut être traité que par le développement d'un modèle de transport des particules énergétiques impliquées. Dans cette thèse, nous faisons dans un premier temps une synthèse des principaux travaux ayant été effectués concernant les observations et la modélisation associées aux TGF, depuis leur découverte, il y a environ 20 ans, jusqu'à nos jours. Dans un deuxième temps, nous présentons et justifions la validité du modèle MC-PEPTITA de transport des particules énergétiques concernées. Ce dernier utilise des méthodes Monte-Carlo, les jeux de sections efficaces EPDL et EEDL, des méthodes d'interaction similaires à celles présentées dans le code PENELOPE. De plus, des modèles extérieurs pour l'atmosphère (NRLMSISE-00) et pour le champ magnétique terrestre (IGRF-11) y sont intégrés. Le modèle collisionnel de MC-PEPTITA est ensuite validé par comparaison avec le code de référence GEANT4 du CERN. Une fois le modèle construit et validé, nous présentons et décomposons en détail la simulation d'un événement TGF typique pour en faire ressortir toute sa complexité. Finalement, nous procédons à des comparaisons directes entre le modèle et les données mesurées par le télescope spatial Fermi pour établir ou vérifier des propriétés importantes concernant les TGF et les faisceaux d'électrons et de positrons associés.Thunderstorms are sources of intense transient phenomena, including light in the visible range and also in X and gamma rays. These phenomena are detected in the form of photon flashes called "Terrestrial Gamma Ray Flashes" (TGF). The purpose of this thesis is the development of a numerical model to study and understand the mechanisms associated with TGF. Studying TGF is then important to understand the physics of lightning and thunderstorms (which are very common phenomena, but the micro-physics is still poorly understood), together with the coupling between the atmosphere and the ionosphere of the Earth. This thesis is also part of the preparation for the TARANIS mission from the CNES, which will be launched in 2017. Among others, TARANIS will have the XGRE and IDEE instruments, able to characterize X/gamma photons and the associated relativistic electrons. After its emission, at around 15 km altitude, this flux of gamma-rays are filtered and altered by the atmosphere and a small part of it may be detected by a satellite in low earth orbit. This last is made of scattered primary photons, together with secondary produced electrons and positrons. A part of these secondary can escape the atmosphere and will then be confined by geomagnetic field lines. Thus, trying to get information on the initial flux from the measurement is a very complex inverse problem, which can only be tackled by the use of a model solving the transport the involved high energy particles. In this thesis, we firstly make a synthesis of the main work that has been done concerning observations and modeling associated with TGF, since their discovery, around 20 years ago, until today. Secondly, we present and validate the MC-PEPTITA model for the transport of the involved energetic particles. It uses Monte-Carlo methods, the EPDL and EEDL cross-section sets, and the methods of simulation of the interactions are similar to what is presented for the PENELOPE code. Moreover, exterior models for the atmosphere (NRLMSISE-00) and the magnetic field of the Earth (IGRF-11) are also integrated. The collision model of MC-PEPTITA is then validated by comparison with the reference code GEANT4 from the CERN. Furthermore, its ability to reproduce precisely some real lightcurves observed by the Fermi space telescope helps to strengthen even more its validation. Once the model is built and validated, we present and decompose in detail the simulation of a typical TGF event, in order to bring out all its complexity. Finally, we conduct direct comparisons between the model and the data measured by the Fermi space telescope to establish or verify important properties concerning the TGF and the associated beams of electrons and positrons

Los kloppers en su rueca : no mezclar lino con lana, una experiencia bogotana 1918-1938

El principal objetivo del presente trabajo es describir la historia de los Kloppers, un oficio que se repitió en todas las capitales de Colombia y Latinoamérica y que consistió en vender ropa puerta a puerta a crédito. Fue el primer oficio de muchos judíos askenazis con el cual lograron acceder a un capital mayor y convertirse en futuros industriales. Viajar a través del telar que compone de la historia de los Kloppers en Bogotá y ver cómo se van cruzando las hebras permite identificar las tensiones entre los judíos ambulantes y la resistencia externa de los comerciantes colombianos, que reaccionaron cuando hubo una notable presencia del comercio judío en Bogotá y sintieron que empezaban a romperse ciertas jerarquías establecidas en el comercio y en el vestir de los ciudadanos. Esta investigación marcha siempre en busca responder esta pregunta: ¿a qué se debe el éxito comercial de los Kloppers? Y se apoya en las respuestas de otras preguntas: ¿en qué condiciones llegaban a Bogotá?, ¿cómo estaban Colombia y Bogotá para favorecer el éxito comercial? ¿Quiénes eran los Kloppers? y ¿cómo fue el proceso de compra y venta?PregradoLICENCIADO(A) EN HISTORI

Pro-social behavior in rats is modulated by social experience

In mammals, helping is preferentially provided to members of one's own group. Yet, it remains unclear how social experience shapes pro-social motivation. We found that rats helped trapped strangers by releasing them from a restrainer, just as they did cagemates. However, rats did not help strangers of a different strain, unless previously housed with the trapped rat. Moreover, pair-housing with one rat of a different strain prompted rats to help strangers of that strain, evidence that rats expand pro-social motivation from one individual to phenotypically similar others. To test if genetic relatedness alone can motivate helping, rats were fostered from birth with another strain and were not exposed to their own strain. As adults, fostered rats helped strangers of the fostering strain but not rats of their own strain. Thus, strain familiarity, even to one's own strain, is required for the expression of pro-social behavior

History of Richmond as a port city

The purpose of this study has been to trace the evolution and course of Richmond as a port city from its beginning date, its period of gradual growth, the years of peak activity in the nineteenth century, the beginning of its decline in world trade, the subsequent renaissance of the port, followed by a recent decline at the present time, pointing out factors which brought it about and contributed to each of these stages

Longitudinal Remote SBRT/SRS Training in Latin America: A Prospective Cohort Study

BACKGROUND: Continuing medical education in stereotactic technology are scarcely accessible in developing countries. We report the results of upscaling a longitudinal telehealth training course on stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS), after successfully developing a pilot course in Latin America. METHODS: Longitudinal training on SBRT and SRS was provided to radiation oncology practitioners in Peru and Colombia at no cost. The program included sixteen weekly 1-hour live conferencing sessions with interactive didactics and a cloud-based platform for case-based learning. Participant-reported confidence was measured in 16 SBRT/SRS practical domains, based on a 1-to-5 Likert scale. Pre- and post-curriculum exams were required for participation credit. Knowledge-baseline, pre- and post-curriculum surveys, overall and single professional-group confidence changes, and exam results were assessed. RESULTS: One hundred and seventy-three radiotherapy professionals participated. An average of 56 (SD ±18) attendees per session were registered. Fifty (29.7%) participants completed the pre- and post-curriculum surveys, of which 30% were radiation oncologists (RO), 26% radiation therapists (RTT), 20% residents, 18% medical physicists and 6% neurosurgeons. Significant improvements were found across all 16 domains with overall mean +0.55 (SD ±0.17, p\u3c0.001) Likert-scale points. Significant improvements in individual competences were most common among medical physicists, RTT and residents. Pre- and post-curriculum exams yielded a mean 16.15/30 (53.8 ± 20.3%) and 23.6/30 (78.7 ± 19.3%) correct answers (p\u3c0.001). CONCLUSION: Longitudinal telehealth training is an effective method for improving confidence and knowledge on SBRT/SRS amongst professionals. Remote continuing medical education should be widely adopted in lower-middle income countries

Propuesta de diseño de una Red Móvil basada en la tecnología TD- SDMA en la región Autónoma del atlántico sur de Nicaragua

En este trabajo monográfico se realizó un diseño de una red móvil usando el modelo de propagación estándar (Stardard Propagation Model- SPM) en la Región Autónoma del Atlántico Sur (RAAS) en Bluefields, Nueva guinea y el rama, realizando estudios de cobertura, datos de terreno y predicciones para determinar la cantidad de estaciones base que requiere el diseño de una red óptima

Una búsqueda de alteraciones metabólicas que acompañen a las hiperhomocisteinemias causadas por errores genéticos del metabolismo de la metionina. Una revisión bibliográfica.

En 1969 McCully hipotetizó que la hiperhomocisteinemia (H-Hcy) está asociada al desarrollo de enfermedades cardiovasculares tras observar el desarrollo temprano de arteriosclerosis en pacientes con deficiencias de Cbl-C y cistationina β-sintasa, que afectan al metabolismo de la metionina y que -como única anomalía bioquímica común- compartían elevados niveles sanguíneos de homocisteína (Hcy). Esta hipótesis se consolidó cuando otros investigadores descubrieron que defectos en la enzima Metilentetrahidrofolato reductasa (MTHFR), implicada también en el metabolismo de la metionina, cursaba igualmente con H-Hcy e importantes daños vasculares.Consecuentemente, el tratamiento de estas enfermedades se ha dirigido a controlar y reducir los niveles de Hcy, para limitar las patologías asociadas.En esta revisión, se ha recopilado información de las concentraciones plasmáticas de metabolitos relacionados con el metabolismo de la Metionina de 234 pacientes con deficiencia de CBS, 47 con defectos de cbl, 203 con deficiencia de MTHFR, 50 con defectos de remetilación y 87 con presentaciones clínicas asociadas a deficiencia de las vitaminas B12 y B9, obtenidos de los datos presentes en 9 publicaciones. Los datos obtenidos muestran que todas las situaciones anteriores se presentan con H-Hcy, pero también parecen hacerlo con hipocisteinemia (h-Cys).Aunque sabemos que la observación anterior es incompleta, hemos contemplado la posibilidad de que algunas patologías descritas en las hiperhomocisteinemias pudiesen tener su origen, no en las elevaciones de Hcy, sino en una escasez de Cys. Utilizando ese punto de partida, hemos identificado dianas potenciales de una escasez de Cys, y considerado como una disfuncionalidad de estas pudiera dar origen a presentaciones clínicas (PCs) compartidas en las homocistinurias. Sorprendentemente, algunas de las dianas moleculares aquí identificadas podrían explicar razonablemente relevantes presentaciones clínicas de estas enfermedades.Finalmente, se sugieren estrategias nutricionales considerando la posibilidad de que algunas patologías de las homocistinurias pudiesen tener su origen en una escasez de Cys. <br /

Bacterial genome adaptation to niches: Divergence of the potential virulence genes in three Burkholderia species of different survival strategies

BACKGROUND: Two closely related species Burkholderia mallei (Bm) and Burkholderia pseudomallei (Bp) are serious human health hazards and are potential bio-warfare agents, whereas another closely related species Burkholderia thailandensis (Bt) is a non-pathogenic saprophyte. To investigate the genomic factors resulting in such a dramatic difference, we first identified the Bm genes responsive to the mouse environment, and then examined the divergence of these genes in Bp and Bt. RESULTS: The genes down-expressed, which largely encode cell growth-related proteins, are conserved well in all three species, whereas those up-expressed, which include potential virulence genes, are less well conserved or absent notably in Bt. However, a substantial number of up-expressed genes is still conserved in Bt. Bm and Bp further diverged from each other in a small number of genes resulting from unit number changes in simple sequence repeats (ssr) in the homologs. CONCLUSION: Our data suggest that divergent evolution of a small set of genes, rather than acquisition or loss of pathogenic islands, is associated with the development of different life styles in these bacteria of similar genomic contents. Further divergence between Bm and Bp mediated by ssr changes may reflect different adaptive processes of Bm and Bp fine-tuning into their host environments

Constraints on Recoil Leader Properties Estimated from X-ray Emissions in Aircraft-Triggered Discharges

During Airbus aircraft campaigns flying into thunderstorms in 2014–2016, X-rays were observed during two stages of aircraft-triggered lightning: nanosecond pulses of X-rays associated with negative leader steps and bursts of X-rays during recoil events. This work will focus on the observations of X-ray bursts associated with recoils. Recoils are observed as microsecond-fast changes in the local electric field, associated with large currents passing through the aircraft, and are found to sometimes be associated with bursts of X-rays. From over 200 aircraft-triggered lightning strikes, 54 recoil events were found to be associated with microsecond bursts of X-rays. The majority of the bursts consist of 1–3 X-ray pulses, with some bursts containing as many as 29 X-ray pulses. We compare the observed superposed X-ray spectrum with modeled spectra using a GEANT4 model of the detector and aircraft, to determine the source potential needed to accelerate the electrons that produce the observed X-rays. A model of the recoil leader was made to determine the gap distance and gap potential between the recoil leader and the aircraft. From the modeling, we determine a solution space for the gap and leader lengths where the gap length is constrained by the observed minimum and maximum times between the onset of the X-ray pulses and the onset of the current pulses detected at the aircraft (1 to 93 m). We also find two constraints from the fitting of the modeled spectra to the superposed spectrum, limiting the leader length to between 1 and ∼240 m.publishedVersio

In‐Flight Observation of Positron Annihilation by ILDAS

We report a 511‐keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In‐flight Lightning Damage Assessment System (ILDAS) on board of an A340 test aircraft. The aircraft was intentionally flying through a thunderstorm at 12‐km altitude over Northern Australia in January 2016. Two gamma ray detectors showed a significant count rate increase synchronously with fast electromagnetic field variations registered by an on‐board antenna. A sequence of 10 gamma ray enhancements was detected, each lasted for about 1 s. Their spectrum mainly consists of 511‐keV photons and their Compton component. The local electric activity during the emission was identified as a series of static discharges of the aircraft. A full‐scale Geant4 model of the aircraft was created to estimate the emission area. Monte Carlo simulation indicated that the positrons annihilated in direct vicinity or in the aircraft body.publishedVersio