Light-yield response of liquid scintillators using 2–6 MeV tagged neutrons

Knowledge of the neutron light-yield response is crucial to the understanding of scintillator-based neutron detectors. In this work, neutrons from 2–6MeV have been used to study the scintillation light-yield response of the liquid scintillators NE 213A, EJ 305, EJ 331 and EJ 321P using event-by-event waveform digitization. Energy calibration was performed using a GEANT4 model to locate the edge positions of the Compton distributions produced by gamma-ray sources. The simulated light yield for neutrons from a PuBe source was compared to measured recoil proton distributions, where neutron energy was selected by time-of-flight. This resulted in an energy-dependent Birks parameterization to characterize the non-linear response to the lower energy neutrons. The NE 213A and EJ 305 results agree very well with existing data and are reproduced nicely by the simulation. New results for EJ 331 and EJ 321P, where the simulation also reproduces the data well, are presented

Quenched phosphorescence as alternative detection mode in the chiral separation of methotrexate by electrokinetic chromatography

Quenched phosphorescence was used, for the first time, as detection mode in the chiral separation of methotrexate (MTX) enantiomers by electrokinetic chromatography. The detection is based on dynamic quenching of the strong emission of the phosphorophore 1-bromo-4-naphthalene sulfonic acid (BrNS) by MTX under deoxygenated conditions. The use of a background electrolyte with 3 mg/mL 2-hydroxypropyl-β-cyclodextrin and 20% MeOH in 25 mM phosphate buffer (pH 7.0) and an applied voltage of 30 kV allowed the separation of l-MTX and its enantiomeric impurity d-MTX with sufficient resolution. In the presence of 1 mM BrNS, a detection limit of 3.2 × 10−7 M was achieved, about an order of magnitude better than published techniques based on UV absorption. The potential of the method was demonstrated with a degradation study and an enantiomeric purity assessment of l-MTX. Furthermore, l-MTX was determined in a cell culture extract as a proof-of-principle experiment to show the applicability of the method to biological samples

Women’s prospects to adopt enhanced freshness formulation (EFF) technologies for banana in Morogoro rural district, Tanzania

The Journal of the Faculty of Food and Agriculture Volume 95 Special Issue 1This paper draws lessons from a study based on forecasts rather than actual results. The study was conducted to identify factors that could potentially affect women’s decisions to adopt enhanced freshness formulation (EFF) technologies among banana growers in Morogoro, Tanzania. The study tested whether men and women were equally likely to adopt EFF technologies. The authors also explored whether women who are willing and able to influence adoption decisions and women who are willing but unable to influence adoption decisions face similar adoption challenges. The results from logit model suggest that the adoption prospect is lower among female adopters than male adopters (p < .05). The study predicted a higher probability of female growers to be willing and able to influence adoption decisions among younger female growers compared to those over 35 years old (p < .1) although the overall impact on the adoption rate was low, owing to limited participation of young farmers (11 %) in banana production. The findings reveal less willingness and ability to adopt the technologies among female growers who perceived EFF applications as labour-insensitive technologies (p < .05). Likewise, the study identified higher willingness and ability to influence the adoption among growers whose bananas were not about to be harvested (p < .05). The authors recommend continued efforts to address a priori challenges that can potentially undermine adoption with easy-to-use preparation and application methods, and by targeting growers whose fruits are at early stages of maturation. Future studies could focus on the potential impacts of specific types of EFF technologies on the adoption prospect

Women’s prospects to adopt enhanced freshness formulation (EFF) technologies for banana in Morogoro rural district, Tanzania

The Journal of the Faculty of Food and Agriculture Volume 95 Special Issue 1This paper draws lessons from a study based on forecasts rather than actual results. The study was conducted to identify factors that could potentially affect women’s decisions to adopt enhanced freshness formulation (EFF) technologies among banana growers in Morogoro, Tanzania. The study tested whether men and women were equally likely to adopt EFF technologies. The authors also explored whether women who are willing and able to influence adoption decisions and women who are willing but unable to influence adoption decisions face similar adoption challenges. The results from logit model suggest that the adoption prospect is lower among female adopters than male adopters (p < .05). The study predicted a higher probability of female growers to be willing and able to influence adoption decisions among younger female growers compared to those over 35 years old (p < .1) although the overall impact on the adoption rate was low, owing to limited participation of young farmers (11 %) in banana production. The findings reveal less willingness and ability to adopt the technologies among female growers who perceived EFF applications as labour-insensitive technologies (p < .05). Likewise, the study identified higher willingness and ability to influence the adoption among growers whose bananas were not about to be harvested (p < .05). The authors recommend continued efforts to address a priori challenges that can potentially undermine adoption with easy-to-use preparation and application methods, and by targeting growers whose fruits are at early stages of maturation. Future studies could focus on the potential impacts of specific types of EFF technologies on the adoption prospect

GEANT4-based calibration of an organic liquid scintillator

A light-yield calibration of an NE 213A organic liquid scintillator detector has been performed using both monoenergetic and polyenergetic gamma-ray sources. Scintillation light was detected in a photomultiplier tube, and the corresponding pulses were subjected to waveform digitization on an event-by-event basis. The resulting Compton edges have been analyzed using a GEANT4 simulation of the detector which models both the interactions of the ionizing radiation as well as the transport of scintillation photons. The simulation is calibrated and also compared to well-established prescriptions used to determine the Compton edges, resulting ultimately in light-yield calibration functions. In the process, the simulation-based method produced information on the gain and intrinsic pulse-height resolution of the detector. It also facilitated a previously inaccessible understanding of the systematic uncertainties associated with the calibration of the scintillation-light yield. The simulation-based method was also compared to well-established numerical prescriptions for locating the Compton edges. Ultimately, the simulation predicted as much as 17% lower light-yield calibrations than the prescriptions. These calibrations indicate that approximately 35% of the scintillation light associated with a given gamma-ray reaches the photocathode. It is remarkable how well two 50 year old prescriptions for calibrating scintillation-light yield in organic scintillators have stood the test of time

GEANT4-based calibration of an organic liquid scintillator

A light-yield calibration of an NE 213A organic liquid scintillator detector has been performed using both monoenergetic and polyenergetic gamma-ray sources. Scintillation light was detected in a photomultiplier tube, and the corresponding pulses were subjected to waveform digitization on an event-by-event basis. The resulting Compton edges have been analyzed using a GEANT4 simulation of the detector which models both the interactions of the ionizing radiation as well as the transport of scintillation photons. The simulation is calibrated and also compared to well-established prescriptions used to determine the Compton edges, resulting ultimately in light-yield calibration functions. In the process, the simulation-based method produced information on the gain and intrinsic pulse-height resolution of the detector. It also facilitated a previously inaccessible understanding of the systematic uncertainties associated with the calibration of the scintillation-light yield. The simulation-based method was also compared to well-established numerical prescriptions for locating the Compton edges. Ultimately, the simulation predicted as much as 17% lower light-yield calibrations than the prescriptions. These calibrations indicate that approximately 35% of the scintillation light associated with a given gamma-ray reaches the photocathode. It is remarkable how well two 50 year old prescriptions for calibrating scintillation-light yield in organic scintillators have stood the test of time

Technique for the measurement of intrinsic pulse-shape discrimination for organic scintillators using tagged neutrons

Fast-neutron/gamma-ray pulse-shape discrimination has been performed for the organic liquid scintillators NE 213A and EJ 305 using a time-of-flight based neutron-tagging technique and waveform digitization on an event-by-event basis. Gamma-ray sources and a Geant4-based simulation were used to calibrate the scintillation-light yield. The difference in pulse shape for the neutron and gamma-ray events was analyzed by integrating selected portions of the digitized waveform to produce a figure-of-merit for neutron/gamma-ray separation. This figure-of-merit has been mapped as a function of detector threshold and also of neutron energy determined from time-of-flight. It shows clearly that the well-established pulse-shape discrimination capabilities of NE 213A are superior to those of EJ 305. The extra information provided by the neutron-tagging technique has resulted in a far more detailed assessment of the pulse-shape-discrimination capabilities of these organic scintillators