Effect of quantum confinement on exciton-phonon interactions

We investigate the homogeneous linewidth of localized type-I excitons in type-II GaAs/AlAs superlattices. These localizing centers represent the intermediate case between quasi-two-dimensional (Q2D) and quasi-zero-dimensional localizations. The temperature dependence of the homogeneous linewidth is obtained with high precision from micro-photoluminescence spectra. We confirm the reduced interaction of the excitons with their environment with decreasing dimensionality except for the coupling to LO-phonons. The low-temperature limit for the linewidth of these localized excitons is five times smaller than that of Q2D excitons. The coefficient of exciton-acoustic-phonon interaction is 5 ~ 6 times smaller than that of Q2D excitons. An enhancement of the average exciton-LO-phonon interaction by localization is found in our sample. But this interaction is very sensitive to the detailed structure of the localizing centers.Comment: 6 pages, 4 figure

Euclid preparation. XV. Forecasting cosmological constraints for the Euclid and CMB joint analysis

Galaxie

Pre-harvest curing: Effects on skin adhesion, chemical composition and shelf-life of sweetpotato roots under tropical conditions

Excoriation (skinning injury) is a serious post-harvest problem for sweetpotato roots. In industrialized countries, sweetpotatoes are exposed to post-harvest curing to facilitate skin toughening and wound healing. However, in developing regions, such a practice is barely undertaken. Pre-harvest curing (PHC), where sweetpotatoes are subjected to defoliation before harvest, is a potential alternative to post-harvest curing. A field trial was conducted in southern Ethiopia. Roots underwent PHC treatment for 3, 7, 10, and 14 days, with 0 days as a control sample. Skin adhesion and chemical composition (ash, crude fibre, crude protein, dry matter, and starch) of the parenchyma and the periderm were measured. Storage testing at ambient conditions for 30 days was conducted. Skin adhesion among all the treatments was significantly increased. The maximum skin adhesion was observed after 14 days (358.92 mN.m); however after 7 days of PHC, no significant change occurred. Root dry matter and ash content remained unaffected by the treatments. An increase in periderm crude fibre was observed for treatment samples, indicating lignification. Parenchyma crude protein concentration demonstrated a sudden drop in value from the control to 3 days of PHC (5.19 to 2.32%). For successive durations, crude protein started to increase from 3 days, demonstrating an active protein metabolism. Starch, the most important constituent affecting palatability and processing of sweetpotato, was not affected by PHC. Roots subjected to PHC for 10 and 14 days presented a potential for enhancing shelf life by having a significantly lower weight loss after 30 days of storage

Eye Movements Reflect Reasoning with Mental Images but Not with Mental Models in Orientation Knowledge Tasks

Abstract. This paper presents results showing that eye movements reflect spa-tial relations in mental images but not in mental models during nearly similar reasoning tasks with directions. These results contribute to the distinction between mental models and mental images based on eye movements. This dif-ferentiation may be applied in the field of human-computer interaction and in-telligent assistance systems. We conducted two experiments about reasoning with cardinal directions employing three-term series problems in the form of: “X is southwest of Z; Y is east of X; as seen from Z, where is Y? ” The results replicate, to some extent, previous findings about preferred mental models. Ad-ditionally, the results indicate that these preferences are susceptible to details of the instructions of the experiment.