Characterization of the Exradin W1 scintillator for use in radiotherapy.

PURPOSE: To evaluate the main characteristics of the Exradin W1 scintillator as a dosimeter and to estimate measurement uncertainties when used in radiotherapy. METHODS: We studied the calibration procedure, energy and modality dependence, short-term repeatability, dose-response linearity, angular dependence, temperature dependence, time to reach thermal equilibrium, dose-rate dependence, water-equivalent depth of the effective measurement point, and long-term stability. An uncertainty budget was derived for relative and absolute dose measurements in photon and electron beams. RESULTS: Exradin W1 showed a temperature dependence of -0.225% °C(-1). The loss of sensitivity with accumulated dose decreased with use. The sensitivity of Exradin W1 was energy independent for high-energy photon and electron beams. All remaining dependencies of Exradin W1 were around or below 0.5%, leading to an uncertainty budget of about 1%. When a dual channel electrometer with automatic trigger was not used, timing effects became significant, increasing uncertainties by one order of magnitude. CONCLUSIONS: The Exradin W1 response is energy independent for high energy x-rays and electron beams, and only one calibration coefficient is needed. A temperature correction factor should be applied to keep uncertainties around 2% for absolute dose measurements and around 1% for relative measurements in high-energy photon and electron beams. The Exradin W1 scintillator is an excellent alternative to detectors such as diodes for relative dose measurements.

Spatial and temporal variation in Chaetanaphothrips orchidii Moulton (Thysanoptera: Thripidae) population and its damage on lemon.

Chaetanaphothrips orchidii Moulton has recently been detected in lemon (Citrus limon) orchards in northwest Argentina, causing high levels of damage on fruits. Severe damage results in the rejection of fruit for export, which must then be sold in the industry. However, the restrictions imposed by the citrus industry on insecticide residues sometimes also result in fruit rejection. Here, we studied the ecology and behavior of C. orchidii in order to propose a pest management strategy that could meet both export and industry demands. Seasonal occurrence and canopy distribution of C. orchidii in lemon orchards were evaluated, and field experimental manipulations of thrips populations were performed to analyze how the length (45, 100, 130, and 200 days) and timing (January, February, or March) of C. orchidii activity related with fruit damage. Lemons harvested during summer showed lower infestation levels (∼0.64 individual per fruit) than those harvested in winter (∼1.88 individuals per fruit). Higher proportions of damaged fruits were recorded in the lower part of the tree. Changes in the population levels of C. orchidii were closely associated with fruit phenology. The longer the lemon fruits were exposed to the thrips, the higher was the damage. However, the time of infestations did not affect fruit damage. Our data provide a first step towards understanding the factors that determine the severity of fruit damage caused by C. orchidii in northwest Argentina.

Physicochemical properties of enrofloxacin.

The physicochemical properties of enrofloxacin, a fluoroquinolone that inhibits the activity of bacterial DNA gyrase, are described. Its spectral, solubility and related physicochemical characteristics are discussed. The dissociation behaviour of enrofloxacin was examined by UV spectrophotometry at 25 degrees C in a series of buffers ranging from pH 1 to 10. The corresponding macro- and microscopic dissociation constants were calculated. The apparent n-octanol-water partition coefficients were measured from pH 2 to 10.