Laser-controlled fluorescence in two-level systems

The ability to modify the character of fluorescent emission by a laser-controlled, optically nonlinear process has recently been shown theoretically feasible, and several possible applications have already been identified. In operation, a pulse of off-resonant probe laser beam, of sufficient intensity, is applied to a system exhibiting fluorescence, during the interval of excited- state decay following the initial excitation. The result is a rate of decay that can be controllably modified, the associated changes in fluorescence behavior affording new, chemically specific information. In this paper, a two-level emission model is employed in the further analysis of this all-optical process; the results should prove especially relevant to the analysis and imaging of physical systems employing fluorescent markers, these ranging from quantum dots to green fluorescence protein. Expressions are presented for the laser-controlled fluorescence anisotropy exhibited by samples in which the fluorophores are randomly oriented. It is also shown that, in systems with suitably configured electronic levels and symmetry properties, fluorescence emission can be produced from energy levels that would normally decay nonradiatively. © 2010 American Chemical Society

Functional intercomparison of intraoperative radiotherapy equipment – Photon Radiosurgery System

BACKGROUND: Intraoperative Radiotherapy (IORT) is a method by which a critical radiation dose is delivered to the tumour bed immediately after surgical excision. It is being investigated whether a single high dose of radiation will impart the same clinical benefit as a standard course of external beam therapy. Our centre has four Photon Radiosurgery Systems (PRS) currently used to irradiate breast and neurological sites. MATERIALS AND METHODS: The PRS comprises an x-ray generator, control console, quality assurance tools and a mobile gantry. We investigated the dosimetric characteristics of each source and its performance stability over a period of time. We investigated half value layer, output diminution factor, internal radiation monitor (IRM) reproducibility and depth-doses in water. The half value layer was determined in air by the broad beam method, using high purity aluminium attenuators. To quantify beam hardening at clinical depths, solid water attenuators of 5 and 10 mm were placed between the x-ray probe and attenuators. The ion chamber current was monitored over 30 minutes to deduce an output diminution factor. IRM reproducibility was investigated under various exposures. Depth-dose curves in water were obtained at distances up to 35 mm from the probe. RESULTS: The mean energies for the beam attenuated by 5 and 10 mm of solid water were derived from ICRU Report 17 and found to be 18 and 24 keV. The average output level over a period of 30 minutes was found to be 99.12%. The average difference between the preset IRM limit and the total IRM count was less than 0.5%. For three x-ray sources, the average difference between the calculated and actual treatment times was found to be 0.62% (n = 30). The beam attenuation in water varied by approximately 1/r(3). CONCLUSION: The x-ray sources are stable over time. Most measurements were found to lie within the manufacturer's tolerances and an intercomparison of these checks suggests that the four x-ray sources have similar performance characteristics

Developments in the Photonic Theory of Fluorescence

Conventional fluorescence commonly arises when excited molecules relax to their ground electronic state, and most of the surplus energy dissipates in the form of photon emission. The consolidation and full development of theory based on this concept has paved the way for the discovery of several mechanistic variants that can come into play with the involvement of laser input – most notably the phenomenon of multiphoton-induced fluorescence. However, other effects can become apparent when off-resonant laser input is applied during the lifetime of the initial excited state. Examples include a recently identified scheme for laser-controlled fluorescence. Other systems of interest are those in which fluorescence is emitted from a set of two or more coupled nanoemitters. This chapter develops a quantum theoretical outlook to identify and describe these processes, leading to a discussion of potential applications ranging from all-optical switching to the generation of optical vortices

Mise en perspective des Enquêtes Nationales Transports 1973/74 - 1981/82 - 1993/94 - 2007/08 : Correction de certaines erreurs de mesure dans l'Enquête Nationale sur les Transports et les Déplacements 2007-08

Subvention Ministère - DRI : N°07 MT S018°Rapport de rechercheLorsque dans une enquête rétrospective par sondage nous voulons mesurer un événement rare avec une "assez grande" précision, nous avons 3 possibilités : augmenter la taille de l'échantillon, le stratifier et/ou étendre la période d'observation. Le budget d'une enquête étant connu nous pouvons facilement définir la taille de notre échantillon. Nous pouvons aussi estimer la taille de chaque strate, en utilisant, par exemple, une allocation proportionnelle. Le responsable d'enquête a par contre plus de liberté pour définir la longueur de la période d'observation, mais dans cette dimension il peut être contraint par des problèmes de mémorisation des événements observés. Dans l'enquête Nationale sur les Transports et les Déplacements de 2007-08, une personne du ménage (l'individu « Kish ») devait décrire ses déplacements à longue distance (plus de 80 km à vol d'oiseau) des trois derniers mois précédant l'interview, en faisant appel à sa mémoire. Nous suspectons donc des erreurs de mémorisation de ces voyage

A survey of the supportive care needs of informal caregivers of adult bone marrow transplant patients

Purpose This study aims to describe the supportive care needs of informal caregivers (ICG) of adult bone marrow transplant (BMT) patients. In addition, we explored relationships between levels of unmet need, psychological morbidity and patient and ICG characteristics. Methods and sample We invited patients within 24 months of BMT to participate in a cross-sectional survey. Consenting patients asked their ICG to complete and return the questionnaire booklet. Measures included the Supportive Care Needs Survey Partners and Carers and General Health Questionnaire. Key results Two hundred patients were approached, and 98 completed questionnaires were received (response rate = 49 %). We found high unmet need and psychological morbidity among ICGs and an association between ICG unmet need and psychological morbidity. Patient functioning, particularly anxiety and depression, sexual dysfunction and resumption of usual activities impacted on ICG unmet need and psychological morbidity. No associations were found between ICG unmet need and psychological morbidity and the following variables: type of BMT, time from BMT, ICG gender, number of dependents and patient age. Conclusion ICG of BMT patients have high levels of unmet need and psychological morbidity in the months that follow a BMT. This highlights the importance of thorough needs assessment to ensure limited resources are targeted to those most in need.</p