Commissioning of a new commercial plastic scintillator system for radiotherapy

Introduction Since 1992 there have been several articles published on research on plastic scintillators for use in radiotherapy. Plastic scintillators are said to be tissue equivalent, temperature independent and dose rate independent [1]. Although their properties were found to be promising for measurements in megavoltage X-ray beams there were some technical difficulties with regards to its commercialisation. Standard Imaging has produced the first commercial system which is now available for use in a clinical setting. The Exradin W1 scintillator device uses a dual fibre system where one fibre is connected to the Plastic Scintillator and the other fibre only measures Cerenkov radiation [2]. This paper presents results obtained during commissioning of this dosimeter system. Methods All tests were performed on a Novalis Tx linear accelerator equipped with a 6 MV SRS photon beam and conventional 6 and 18 MV X-ray beams. The following measurements were performed in a Virtual Water phantom at a depth of dose maximum. Linearity: The dose delivered was varied between 0.2 and 3.0 Gy for the same field conditions. Dose rate dependence: For this test the repetition rate of the linac was varied between 100 and 1,000 MU/min. A nominal dose of 1.0 Gy was delivered for each rate. Reproducibility: A total of five irradiations for the same setup. Results The W1 detector gave a highly linear relationship between dose and the number of Monitor Units delivered for a 10 9 10 cm2 field size at a SSD of 100 cm. The linearity was within 1 % for the high dose end and about 2 % for the very low dose end. For the dose rate dependence, the dose measured as a function of repetition the rate (100–1,000 MU/min) gave a maximum deviation of 0.9 %. The reproducibility was found to be better than 0.5 %. Discussion and conclusions The results for this system look promising so far being a new dosimetry system available for clinical use. However, further investigation is needed to produce a full characterisation prior to use in megavoltage X-ray beams.

Desarrollo de un programa de ciencia-literatura.

Un programa de ciencia-literatura podría proporcionar una atalaya diferente para el estudio de la ciencia. Esto podrá ayudar a los estudiantes a meditar seriamente las cosas y a aceptar lo menos posible de buena fe. Los profesores también deberían darse cuenta de que un programa de ambas ciencias podría mejorar la enseñanza de las ciencias. El asunto de la ciencia como de la literatura se ocupa, a cierto nivel, de postulados y hechos. El enfoque de ciencia-literatura ofrece materia de estudio en la cual los estudiantes pueden aplicar la lógica inductiva y deductiva a la naturaleza del orden y organización en sistemas vivos. Además, estas dos áreas pueden ayudar a que los estudiantes se vuelvan más críticos frente a arbitrariedades y sistemas de creencias preestablecidas. Pueden desarrollarse puntos de referencia científicos y literarios que supongan las condiciones necesarias para la supervivencia de sistemas vivos. Durante el Renacimiento, la filosofía natural o historia natural, de la cual surgió la ciencia, influía en la literatura. Durante el siglo XVII, la nueva ciencia puede haber desempeñado un rol importante en cambiar el estilo de la prosa en Inglaterra. Más tarde, la teoría de la evolución, de Darwin, la teoría de la relatividad, de Einstein, y otras motivaron a novelistas, poetas, dramaturgos y críticos literarios a cambiar su visión del hombre y del mundo. Entre los poetas y novelistas más recientes cuyas obras fueron influidas por acontecimientos, se cuentan: Walt Whitman, James Russel lowell, James Joyce, Virginia Wolf y Marcel Proust. Ciencia y literatura pueden referirse a los mismos fenómenos, pero desde distintos puntos de vista. Las distintas disciplinas se complementan entre sí. Ninguna disciplina aislada agota el tema.

Controle de Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) em instalações para frangos de corte

Searching for a new alternative to A. diaperinus control, it was evaluated the action of Spinosad in two concentrations (250ppm, 400ppm) and two doses (0.05 L/m 2 and 0.1 L/m 2), applied in poultry broiler facilities naturally infested by this coleoptera. Assessments of the infestation were held in weekly intervals, during 49 days after treatment, using traps. The percentage of effectiveness were calculated from the results of the number of adults and/or larval stages in control and treated groups. Spinosad at the concentration of 250ppm, applied at a dose of 0.1L/m2, can be considered ineffective against these beetles, however the application of 400ppm at a dose of 0.1L/m2 showed high efficacy and short residual period. The dose of 0.1L/m 22 of Spinosad at the concentration of 400ppm demonstrated, between treatments, better effectiveness against coleopters, reaching efficacy of 100% against larvae of A. diaperinus, observed after the seventh day post-treatment.