Photochemical Route to the Production of Fullerene Allotropes

A photochemical route to the formation of two C60 molecules which are bridged by one and up to eighteen carbon atoms to form bucky-dumbbell shaped molecules, i.e., C60 \u3e C \u3c C60 to C60 \u3e C = C = C = C = C = C = C = C = C = C \u3c C60, etc. is described. Irradiation of C60 in solutions of chloroform and iodine (magenta color) with pulsed laser light from the frequency tripled (355 nm) Nd:YAG laser produced a dark crimson color. Matrix assisted laser desorption ionization (MALDI) negative ion mass spectroscopy was used to examine the irradiated fullerenes. Irradiation of solutions under low laser power for short periods of time (∼ 1 hr) gave exclusively C60 \u3e C \u3c C60 as evidenced from the negative ion spectrum. Higher power and longer irradiation times (∼ 3 hrs) produced C60 \u3e Cn \u3c C60 samples yielding negative ions with n = 1 to l8. Ions for even n bucky-dumbells are more abundant than for odd n which may represent the greater electron affinity anticipated for even n species. High performance liquid chromatography was used to separate the bucky-dumbbells from the dominant C60 molecules as well as C60 \u3e C \u3c C60 from the remaining clusters, confirming that the dumbbells were produced in the solution and not in the MALDI process. High Resolution TEM pictures and Raman spectra of the bucky-dumbells are also presented

Spatially Resolved Laser and Thermal Desorption/Ionization Coupled with Mass Spectrometry

The work discussed in this dissertation is aimed at creating novel approaches to chemical imaging that ultimately allow for submicron resolution. This goal has been approached from two direction using laser based desorption and coupling it with an AFM using apertureless tip-enhanced laser ablation/ionization. The second direction was through the development a new approach to thermal desorption based mass spectrometry experiments by using a proximal probe to spatially desorb the surface and ionizing the plume of neutrals using a secondary ionization source at atmospheric pressure. The thermal desorption approach allows for the easy scaling of the technique all the way from the millimeter to the nanometer regime. In the nanometer regime an AFM platform with silicon based heating AFM probes is used to locally desorb material from nanometer sized craters. The final work in this thesis focused on trying to improve laser based desorption through a secondary ionization of the neutrals plume by capturing the laser desorption plume into a liquid and then electrospaying the solution into a MS. The added benefit of being able to capture the desorption plume into a liquid is the ability to carry out post sampling processing of the captured analyte via high performance liquid chromatography. The ability to clean up a sample via HPLC also allow for the detection of isobaric compounds as well as trace level materials which otherwise would be obscured by matrix effects in complicated sample matrixes like tissues. This application of laser desorption with a secondary ionization by capture into a liquid could be envisioned to be applied to AFM based laser desorption techniques where boosting the ionization efficiency is crucial for signal detection

Immune mechanisms behind plaque vulnerability: experimental and clinical studies

Physical disruption of atherosclerotic plaques causes many acute thrombotic complications such as myocardial infarction and stroke. The resistance of the atherosclerotic plaque to disruption depends in part on the integrity of its fibrous cap, which prevents contact between the highly thrombogenic lipid core and the circulating blood. The fibrillar collagens types I and III synthesized by smooth muscle cells (SMCs) largely determine the tensile strength of the cap. Sites of plaque rupture display signs of active inflammation that can impair plaque stability. Macrophages and mast cells release a set of collagen-degrading enzymes. Additional possible mechanisms include inhibited expression of procollagen genes and induction of death or reduced renewal of the collagen-producing SMC population, both phenomena promoted by T cell-derived interferon-? (IFN?). However, little attention has been given to the post-translational modification of collagen fibers in the fibrous caps. It is known that efficient extracellular cross-linking of collagen catalyzed by the enzyme lysyl oxidase (LOX) confers biomechanical properties and proteolytic resistance of the mature collagen fiber. Thus, failure of collagen maturation may lead to a defective extracellular matrix in the fibrous cap. Using atherosclerosis-prone mice and samples of human carotid endarterectomies, we investigated whether pro- and anti-inflammatory mediators can affect the LOX-dependent collagen maturation in atherosclerotic lesions, thus leading to plaque weakening. To study the effect of T cell-driven inflammation, we used genetically modified mice with hypercholesterolemia and disrupted TGFß signaling in T cells (Apoe-/- x CD4dnTßRII). These mice developed larger atherosclerotic lesions with augmented levels of IFN?, increased numbers of activated macrophages and, importantly, impaired maturation of collagen fibers, consistent with a vulnerable phenotype (Paper I). Analysis of mRNA and protein content showed a significant decrease of LOX in aortae of Apoe-/- x CD4dnTßRII mice. T cell-driven inflammation in these mice provoked a limited selective increase in the expression of proteinases that degrade the extracellular matrix, but no increase in collagen fragmentation was detected. Therefore, we concluded that exaggerated T cell-driven inflammation limits the extracellular maturation of collagen in the atherosclerotic plaque. The stability of atherosclerotic lesions was investigated in Apoe-/- mice after treatment with osteoprotegerin (OPG), a cytokine of the TNFR superfamily and a circulating decoy receptor for the receptor activator of nuclear factor ?B ligand (RANKL) (Paper II). Treatment with OPG facilitated accumulation of SMCs and increased formation of mature collagen fibers within the lesions of Apoe-/- mice. Aortic mRNA level of LOX was also upregulated in treated animals. In cell culture studies, OPG promoted proliferation of rat aortic SMCs. Therefore, we suggested that osteoprotegerin may be a possible mediator of lesion stabilization. We further investigated if a similar pattern as that obtained in the animal experiments could also be found in the human disease (Paper III). We were able to detect LOX protein in SMC- and collagen-rich areas of human carotid lesions. A higher LOX mRNA and protein were associated with a more stable phenotype of the plaques. Examination of gene expression in plaques revealed a positive correlation between mRNA expression of LOX and mRNA for OPG, and a negative correlation between LOX mRNA and markers of inflammation. This data suggests that LOX may contribute to the stabilization of human atherosclerotic lesions and that its expression is controlled by inflammation. In paper IV we reported that mRNA and protein content of 5-lipoxygenase activating protein (FLAP) were highly upregulated in aortae of Apoe-/- x CD4dnTßRII mice compared with Apoe-/- littermates. FLAP immunoreactive protein co-localized with CD68+ macrophages. Augmented ex vivo formation of leukotriene B4 in aortae of transgenic mice further supported functional significance of the increased level of FLAP. Treatment with the FLAP-inhibitor MK-886 not only decreased the number of CD3+ cells in lesions and IFN? mRNA levels in aortae of Apoe-/- x CD4dnTßRII mice, but, most importantly, significantly reduced atherosclerotic lesion size. Although FLAP inhibition did not have any significant effect on collagen synthesis, it can be considered as a possible therapeutic tool to stabilize the plaque by reducing the degree of local inflammation. In summary, the findings of this thesis identify extracellular maturation of collagen, catalyzed by LOX, as important in maintaining the stability of the fibrous cap in the atherosclerotic lesion. The process of collagen maturation is regulated by pro- and anti-inflammatory mediators within the plaque, and it may serve as a target for development of new diagnostic and therapeutic tools

INTERNET PARA OS GANHOS DOS ESTUDANTES: LOCAL DE TRABALHO OU ESPAÇO DE COMUNICAÇÃO

La sobrecarga de trabajo de los docentes puede ocasionar desafíos para los docentes que provoquen agotamiento a largo plazo si no se abordan. En consecuencia, el presente estudio tiene como objetivo examinar las fuentes de prevención del agotamiento desde las perspectivas de los supervisores EFL (inglés como lengua extranjera). Los participantes fueron 85 supervisores de EFL iraníes cuyo trabajo consistía en observar y dar retroalimentación a los maestros sobre su desempeño docente en varios niveles de dominio del idioma, desde los niveles de primaria hasta los avanzados. En este estudio se empleó un diseño secuencial de método mixto. Primero, la recopilación de datos cualitativos se realizó mediante entrevistas con 30 participantes para determinar las fuentes de prevención del agotamiento desde la perspectiva de los supervisores. A continuación, se diseñó un cuestionario de prevención de agotamiento utilizando los resultados de las entrevistas, después de lo cual se administró a los participantes restantes. Los datos recopilados fueron analizados por factores para identificar los componentes de la construcción de prevención de agotamiento. Los resultados del análisis de contenido de los datos de la entrevista indicaron que el apoyo de los maestros por parte de sus colegas, la situación menos estresante y la satisfacción laboral fueron las principales fuentes de prevención del agotamiento. El análisis factorial mostró las mismas fuentes de agotamiento que los componentes principales de la construcción de prevención de agotamiento. Los hallazgos de este estudio enfatizan la contribución del apoyo educativo y emocional de los maestros, proporcionando un lugar de trabajo constructivo y saludable, así como ingresos deseables como formas de prevención del agotamiento en los maestros de EFL.Teacher work overload can cause challenges for teachers leading to burnout in the long term if not addressed. Consequently, the present study aims at examining the sources of burnout prevention from EFL (English as a foreign Language) supervisors’ perspectives. The participants were 85 Iranian EFL supervisors whose job was observing and giving feedback to teachers about their teaching performance at various levels of language proficiencies from elementary to advanced levels. A sequential mixed method design was employed in this study. First, collection of qualitative data was performed using interviews with 30 participants in order to determine the sources of burnout prevention from supervisors’ perspectives. Next, a burnout prevention questionnaire was designed using the results of the interviews, after which it was administered to the remaining participants. The collected data were factor analyzed to identify the components of burnout prevention construct. Results of content analysis of the interview data indicated that teachers’ support from their colleagues, less stressful situation, and job satisfaction were the main sources of burnout prevention. Factor analysis showed the same sources of burnout as the main components of the burnout prevention construct. The findings of this study emphasize on the contribution of teachers’ educational and emotional support, providing constructive and healthy working place, as well as desirable income as ways for prevention of burnout in EFL teachers.A sobrecarga de trabalho do professor pode causar desafios para os professores, levando a esgotamento a longo prazo, se não forem abordados. Consequentemente, o presente estudo tem como objetivo examinar as fontes de prevenção de burnout das perspectivas dos supervisores de EFL (inglês como língua estrangeira). Os participantes foram 85 supervisores iranianos de EFL, cujo trabalho era observar e dar feedback aos professores sobre seu desempenho no ensino em vários níveis de proficiência linguística, do nível básico ao avançado. Um método misto sequencial foi empregado neste estudo. Primeiro, a coleta de dados qualitativos foi realizada por meio de entrevistas com 30 participantes, a fim de determinar as fontes de prevenção de burnout na perspectiva dos supervisores. Em seguida, foi elaborado um questionário de prevenção de burnout, utilizando os resultados das entrevistas, após o qual foi aplicado aos demais participantes. Os dados coletados foram analisados por fatores para identificar os componentes do construto de prevenção de burnout. Os resultados da análise de conteúdo dos dados da entrevista indicaram que o apoio dos professores de seus colegas, a situação menos estressante e a satisfação no trabalho foram as principais fontes de prevenção de burnout. A análise fatorial mostrou as mesmas fontes de burnout que os principais componentes do construto de prevenção de burnout. As conclusões deste estudo enfatizam a contribuição do apoio educacional e emocional dos professores, proporcionando um local de trabalho construtivo e saudável, bem como a renda desejável como formas de prevenção do esgotamento nos professores de EFL