Motivated by an increasing demand for functionality and reliability of systems operating in harsh, ionizing-radiation environments, the core of the present research is an investigation of the response of rare-earth-doped, aluminosilicate fibers to ionizing radiation. These rare-earth-doped fibers, consisting of fibers doped with ions of erbium (Er³⁺) and ytterbium (Yb³⁺) designed for use in amplifier systems, reveal average specific losses in response to ⁶⁰Co gamma radiation to be in the range of 0.0285 - 0.193 dB/(m•krad(Si)) at wavelengths from 1300 nm to 1400 nm. An ionizing dose rate dependence was identified in which high dose rates of approximately 40 rad(Si)/s invariably lead to higher induced losses than lower dose rates of approximately 14 rad(Si)/s, indicating the possibility of complex radiation-related phenomena underlying the observed absorption. Data clearly show that Er³⁺-doped fibers are more sensitive to ionizing-radiation in comparison to Yb³⁺-doped fibers, while Er³⁺/Yb³⁺ co-doped fibers are found to be the least sensitive to radiation of all the fibers examined. Evidence of color center formation associated with the dopant aluminum is found in results of visible spectroscopy conducted on gamma-irradiated preform samples and on fibers flown in low-Earth orbit. Near infrared spectroscopic data is consistent with absorption derived from this dopant as well, with the interpretation of band-tailing from the visible portion of the spectrum. Evidence of the formation of a defect intrinsic to the silicate host matrix, the Non-Bridging Oxygen Hole Center (NBOHC), is also found following ionizing radiation of the optical fiber preforms. Since the observed ionizing-radiation-induced absorption is concentrated in the visible portion of the spectrum, the performance of actively operated rare-earth-doped amplifiers is largely impacted by the pump wavelength, which is located at higher energies within the near-infrared portion of the spectrum and therefore closer to the visible portion of the spectrum than the lasing wavelength. Experimental results stemming from rare-earth-doped amplifiers operated under ionizing radiation substantiate the importance of the pumping wavelength, and suggest the presence of cascaded pump photon absorption processes. Based on these results, pumping at longer wavelengths is advised to reduce the effect of color center absorption on this crucial aspect of active fiber amplifier operation.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

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Neste trabalho realizamos uma série de medidas de correntes elétricas através de amostras de polímeros isolantes submetidos a radiação por feixe eletrônico, amostras essas inserida em um circuito em modo de corrente. A energia do feixe incidente foi sempre tal que não atravessava totalmente a amostra, depositando em seu interior excesso de carga negativa. A polaridade dessa carga foi determinada pela curva de emissão secundária. Como a energia do feixe foi sempre muito superior à energia EII (abaixo dessa energia o número de elétrons injetados pelo feixe é menor que os arrancados para fora da amostra, e acima desse valor o contrário ocorre), as amostras usadas (polifluoretileno-propileno, polietileno de alta densidade e polietileno de baixa densidade) foram carregadas negativamente. Devido à radiação parcialmente penetrante, cada amostra foi dividida em duas regiões distintas: irradiada e não-irradiada. Na região não-irradiada permanece a condutividade intrínseca do material, enquanto na irradiada a condutividade foi muito aumentada devido à geração de portadores secundários pela radiação. As curvas de corrente foram medidas durante e após a irradiação sob diferentes campos elétricos aplicados externamente. Vários modelos teóricos foram aplicados para explicar os resultados de correntes medidas. O mais simples foi o Modelo Caixa, onde a penetração dos primários era um valor fixo r, dividindo a amostra em condutividade induzida g1 de 0 a r, e condutividade intrínseca gi, de r a L, sendo g1 gi (L é a espessura da amostra). O modelo mais sofisticado levou em conta uma região &#916r em torno de r pois considera que o freamento dos elétrons não ocorre todos no mesmo ponto, mas tem uma dispersão em tomo de um ponto r. Por esse motivo a condutividade induzida é dependente da posição, e num caso mais geral depende também do tempo. Durante a irradiação da amostra inserida no circuito de medida, pode ocorrer injeção pelos eletrodos alterando, em determinadas circunstâncias, a polaridade do excesso de carga. Como resultado dos ajustes teórico-experimentais vários parâmetros elétricos dos materiais foram obtidos. / This work presents several electric current measurements in dieletric polymers under irradiation by electron beam. The samples were irradiated in a current mode circuit. The energy of the beam provided a negative charge profile charge in the bulk o the sample. The polarity of the deposited charge was determined by a secundary emission curve. Since the energy of the beam was always bigger tham EII (which defines the balance between the injected electrons and the emitted ones; below EII the sample became positively charged, while above it is negatively charged) the samples (polyethylene propylene, high density polyethylene and low density polyethylene) were always negatively charged. Each irradiated sample was divided in two regions: the irradiated region and the non-irradiated one. Due to the secondary generated carries, the condutivity of the irradiated region gi was orders of magnitude higher than the intrinsic condutivity g1. The eletric currents were measured during and after the irradiation, under different external electric fields. Several theoretical models were used to explain the experimental results. The simplest one, the box models, considers the induced condutivity gb from 0 to r, and the intrinsic condutivity gi from r to L (L being the sample thickeness). The more sophisticated model, on the other hand, considers a range value &#916r around the point r. It means that the stopping power is not abruptly but rather is distributed in a region &#916r around the point r. For this reason the induced conductivity depends on the position, and in a more general framework, also in time. During the irradiation, carriers are injected to the sample by the electrodes, and in certain conditions the excess of charge has its polarity inverted. From the theoretical-experimental fittings important electrical parametes of the materials were obtained.

<p>Radiation-induced lung injury (RILI) is a common condition in the setting of lung and breast cancer. Often, patients who suffer from RILI experience pneumonitis and pulmonary fibrosis months after treatment. These pathologies have commonly been modeled using mice and observing their deterioration until mortality and quantifying pathology on histological sections.<b> </b></p> <p>With this study, we used a longitudinal microCT and a 7T MRI to characterize male C57Bl/6 mice irradiated with a single dose of 20 Gy to the whole thoracic area delivered by an X-Rad cabinent irradiator. CT was performed with a respiratory gating sequence at 2 week timepoints to construct an RIPF model. The fraction of RIPF to total lung volume was calculated at each time point from images, and the data was anaylzed using one-way ANOVA Welch and Dunnett’s T3 multiple comparisons tests. Tidal lung volumes were also calculated and anlyazed in a simlar manner. Mice were then imaged using MRI and CT at 0, 5, and 8 week timepoints to compare results. These results were analyzed for comparison (ANOVA and Dunnett’s T3) and correlation (Pearson’s r) with each other. Histology was later performed using H&E and Trichrome stains to provide ex-vivo verification of pathology.<b> </b>At the 10-12 week time point ( ) significant RIPF formed. Weeks proceeding showed increased significance until the 22+ week timepoint, which showed less statistical significance ( ) due to increased variance at this timepoint. Dunnett’s T3 test showed no significant differences between tidal lung volumes over time. Tests also showed no significant differences between CT and MRI results with a correlation coefficient of .<b> </b>Early in the study, problems arose when pre-marture mortality was occurring to a significant portion of our subjects. Analysis later showed issues during irradiation that resulted in significant dose being absorbed by the stomach. Adjusting our shiedling lead to increased early survival of our subjects enabling us to contine our study. Significant RIPF development was not significant until 10-12 weeks post-irradiation, then RIPF became more severe at proceeding timepoints. Tidal lung volume showed no significant deviation over the development of RIPF. This result is most likely affected by the variation of results at later timepoints, since several mice with severe RIPF were significantly hindered in their ability to breathe during the study. MRI results showed close correlation with CT results and prodcued similar values at early timepoints. However, noticeable differences were seen at later timepoints when significant RIPF developed ( ). <b></b></p>

Introduction First described in 2002, osteonecrosis of the jaw (ONJ, or avascular necrosis of the jaw) is an uncommon but potentially serious side effect of treatment with bisphosphonates. Although typically identified in patients with multiple myeloma and other malignancies, a few cases have been reported in patients taking bisphosphonates - a potent drug class used in the treatment of osteoclast-mediated bone resorption issues, including postmenopausal osteoporosis, Paget's disease, multiple myeloma, and malignant hypercalcemia. The clinical diagnosis of ONJ can be obscured by jaw pain, abscess, swelling, and fistulas, but exposed bone is a distinctive sign. This reports a case of ONJ secondary to bisphosphonate use in a 65-year-old woman and clinical management complications. Case Presentation A 65-year-old lady with history of age-related osteoporosis and compression fractures on alendronate for 4 years, squamous cell carcinoma of neck status post excision and radiotherapy 11-years prior, Sjogren's syndrome and discoid lupus on hydroxychloroquine, diabetes, hypertension, stroke and multiple dental abscesses presents with persistent neck pain. Initial CT neck with contrast showed diffuse fat stranding. Subsequently, alendronate was discontinued due to jaw necrosis suspicion. Eight months later, repeat CT scan showed new non-mass-like soft tissue thickening in the subcutaneous fat abutting the right anterior mandible with mandibular teeth cavities and periapical lucencies, likely to be periodontal cellulitis versus radiation osteonecrosis. Later, patient complained of a piece of bone penetrating the skin of her chin and presented with continuous drainage from sinus tract in her mandible, which was diagnosed as osteonecrosis attributed to bisphosphonates, previous radiation therapy, and dental abscesses. Patient was started on abaloparatide, an osteo-anabolic medication for osteoporosis and enrolled in hyperbaric oxygen therapy which immensely helped in controlling sinus drainage. Patient is currently awaiting mandibular reconstruction surgery. Discussion ONJ, often associated with pain, swelling, exposed bone, local infection, and pathologic fracture of the jaw, is a rare complication of bisphosphonate therapy. Currently, no prospective data exists to advise the benefits of therapy discontinuation however most clinical practices tend to discontinue at least temporarily. The incidence increases with longer treatment duration, particularly when therapy exceeds four years. Risk factors for developing ONJ while taking bisphosphonates include IV administration, anticancer therapy, dose and duration of exposure, dental extractions/implants, glucocorticoids, smoking, diabetes, and preexisting dental disease. Case reports and series suggest benefit from hyperbaric oxygen therapy in wound healing, pain, and quality of life at three months, however no significant differences exist with outcomes beyond three months. Patients being considered for therapy with a bisphosphonate should be thoroughly evaluated for dental issues, prior to initiating therapy. Conservative management with limited debridement, antibiotic therapy as needed, and topical mouth rinses rather than aggressive surgical resection are recommended. Conservative therapy may result in healing in a significant proportion of patients. Surgical resection of necrotic bone should be reserved for refractory or advanced cases. Providers should remain cautious while prescribing high doses of bisphosphonates in patients with increased risk factors to prevent, timely diagnose and treat this condition. References Edwards BJ, Gounder M, McKoy JM, et al. Pharmacovigilance and reporting oversight in US FDA fast-track process: bisphosphonates and osteonecrosis of the jaw. Lancet Oncol 2008; 9:1166. Khosla S, Burr D, Cauley J, et al. Bisphosphonate-associated osteonecrosis of the jaw: report of a task force of the American Society for Bone and Mineral Research. J Bone Miner Res 2007; 22:1479. Hoff AO, Toth BB, Altundag K, et al. Frequency and risk factors associated with osteonecrosis of the jaw in cancer patients treated with intravenous bisphosphonates. J Bone Miner Res 2008; 23:826.

Cette thèse est le résultat d'un travail sur l'effet d'irradiation de cellules solaires à triple jonction (TJ) GaInP/GaAs /Ge en forme de réseau dans des conditions LILT. Initié par les besoins de la compréhension des performances EOL des cellules solaires dans la mission JUICE, nous avons trouvé des phénomènes très particuliers qui ne sont pas supposés se produire si celle-ci a été irradiée à température ambiante. Tout d'abord, une cellule de composante inférieure montrait une plus grande chute d'Isc à une température plus basse, ce qui suggère potentiellement une limitation de courant par la sous-cellule inférieure dans la structure TJ. Une dépendance en température de la récupération RF(Isc) par un recuit isochrone et, la dépendance d'orientation de la dégradation Isc de la cellule composante inférieure impliquaient que son mécanisme de dégradation pourrait être lié à des grappes de défauts formées comme des zones isolantes (non actives) pour les transporteurs minoritaires. Par ailleurs, nous avons observé en général une plus grande dégradation de FF et Pmax des cellules TJ irradiées par les électrons, par rapport aux cellules irradiées aux protons. Cette nette différence provient surtout des sous-cellules supérieure et inférieure en raison de l'apparition d'un courant d'obscurité excessif. Ce courant supplémentaire dans l'obscurité semble être lié à l'effet tunnel indirect par des défauts induits par l'irradiation électronique. En outre, EOL FF et Pmax semblaient se propager de plus en plus d'une cellule à l'autre à mesure que la fluence des électrons augmentait. Une approche de dose d'endommagement par déplacement (DDD) a été appliquée à des cellules TJ irradiées par des électrons et des protons de 1 et 2 MeV et à ses cellules composantes. Il s'est avéré que les électrons de 2 MeV induisaient une plus grande dégradation que les autres pour tous les paramètres (Isc, Voc, FF, Pmax). La cellule du milieu a montré une correspondance parfaite de DDD entre les cellules irradiées par électrons et protons en condition LILT, indiquant que les défauts finaux produits par les irradiations par électrons et protons sont peut-être les mêmes. La TJ et sa cellule de composant supérieur présentaient moins de dégradation sur les Voc sous irradiation électronique que l'irradiation protonique. Pour la cellule du composant de Ge, l'irradiation électronique a induit une dégradation beaucoup plus importante des Voc, FF et Pmax par rapport à l'irradiation protonique. Pour améliorer la dureté de rayonnement des cellules en réduisant le courant d'obscurité en excès, il serait intéressant de diminuer la concentration en dopage des jonctions pour réduire la création de défauts secondaires liés aux impuretés. / This thesis is the result of work on the irradiation effect of lattice matched GaInP/GaAs/Ge triple junction (TJ) solar cells in LILT conditions. Initiated by needs of the understanding of EOL performances of the solar cells in JUICE mission, we have found very peculiar phenomena which are not supposed to occur if it was irradiated at room temperature. First, a bottom component cell exhibited a larger drop of Isc at a lower temperature, which potentially proposes a current limiting by the bottom sub-cell in the TJ structure. A temperature dependence of RF(Isc) recovery by an isochronal annealing and the orientation dependence of Isc degradation of the bottom component cell have implied that its degradation mechanism could be related to defect clusters formed along proton tracks, acting like insulating (non active) area for minority carriers. Second, we have observed in general larger degradation of FF and Pmax from electron irradiated TJ cells compared to proton irradiated ones. This distinct difference has originated especially from the top and bottom sub-cells due to the occurrence of excess dark current. This additional current in dark seems to be related to the indirect tunneling effect by defects induced by electron irradiation. Furthermore, EOL FF and Pmax appeared to be more and more spread from cell to cell as the electron fluence increased. A displacement damage dose (DDD) approach was applied to 1 and 2 MeV electron and proton irradiated TJ cells and its component cells. It turned out that 2 MeV electrons induced greater degradation than others for all parameters (Isc, Voc, FF, Pmax). The middle component cell showed almost a perfect match of DDD between electron and proton irradiated cells in LILT condition, indicating that the final defects produced by electron and proton irradiations are perhaps the same. TJ and its top component cell showed less degradation on Voc under the electron irradiation compared to the proton irradiation. For the Ge bottom component cell, the electron irradiation induced much larger downgrading of Voc, FF and Pmax compared to the proton irradiation. To improve the radiation hardness of the cells by reducing the excess dark current, it would be worth to decrease the doping concentration of junctions to reduce the creation of secondary defects related to impurities.

Medical radiation is estimated to contribute to over 200,000 deaths annually. Recent increases in the use of radiation-producing medical imaging examinations have led to increasing cumulative radiation dose to the general public. Multiple measures have been taken to address this alarming trend, including physician education, technologist education on dose reduction, and equipment-facilitated dose reduction techniques. Shield use can reduce the primary beam by up to 95%. Medical imaging technologists are the primary individuals responsible for applying shielding during an examination. Currently, literature shows that technologists are not shielding individuals as often as they should. After pilot testing, medical imaging technologists were recruited via email to participate in a national cross-sectional survey in September 2017. The survey contained items related to technologists’ demographics, shielding behaviors, and attitudes and beliefs measured at four social-ecological levels – intrapersonal, interpersonal, organizational, and community. The American Registry of Radiologic Technologists (ARRT) provided a list of technologists’ email addresses from their directory. One thousand six-hundred and sixty-one email notifications were sent out in the summer of 2017. Of those, 218 technologists (13%) completed the survey. Among technologists who considered their primary modality to be computed tomography (CT), organizational level factors were a positive significant predictor of shielding behavior. None of the four levels were significant in predicting shielding behavior among diagnostic radiological technologists (x-ray). Individual factors were significantly correlated to shielding behavior among radiologic technologists in the intrapersonal, organizational, and community levels. Study results indicated that interventions implemented at the organizational level may be most effective in increasing shield use among CT technologists. Additional research is needed to better understand factors affecting shield use among medical imaging technologists.

<p>An investigation of the influence of three alloying elements Chromium, Phosphorus, and Nitrogen with the solute types of oversized substitutional, undersized substitutional, and interstitial on the irradiation induced microstructural evolution and hardening</p>