Characterizing heterogeneous forest structure in ponderosa pine forests via UAS-derived structure from motion.

Increasingly, dry conifer forest restoration has focused on reestablishing horizontal and vertical complexity and ecological functions associated with frequent, low-intensity fires that characterize these systems. However, most forest inventory approaches lack the resolution, extent, or spatial explicitness for describing tree-level spatial aggregation and openings that were characteristic of historical forests. Uncrewed aerial system (UAS) structure from motion (SfM) remote sensing has potential for creating spatially explicit forest inventory data. This study evaluates the accuracy of SfM-estimated tree, clump, and stand structural attributes across 11 ponderosa pine-dominated stands treated with four different silvicultural prescriptions. Specifically, UAS-estimated tree height and diameter-at-breast-height (DBH) and stand-level canopy cover, density, and metrics of individual trees, tree clumps, and canopy openings were compared to forest survey data. Overall, tree detection success was high in all stands (F-scores of 0.64 to 0.89), with average F-scores > 0.81 for all size classes except understory trees (< 5.0 m tall). We observed average height and DBH errors of 0.34 m and - 0.04 cm, respectively. The UAS stand density was overestimated by 53 trees ha-1 (27.9%) on average, with most errors associated with understory trees. Focusing on trees > 5.0 m tall, reduced error to an underestimation of 10 trees ha-1 (5.7%). Mean absolute errors of bole basal area, bole quadratic mean diameter, and canopy cover were 11.4%, 16.6%, and 13.8%, respectively. While no differences were found between stem-mapped and UAS-derived metrics of individual trees, clumps of trees, canopy openings, and inter-clump tree characteristics, the UAS method overestimated crown area in two of the five comparisons. Results indicate that in ponderosa pine forests, UAS can reliably describe large- and small-grained forest structures to effectively inform spatially explicit management objectives.

Calibration of confidence and assessed clinical skills competence in undergraduate paediatric OSCE scenarios: a mixed methods study.

BACKGROUND: The relationship between confidence and competence in clinical skills development is complex but important. This study aims to determine undergraduate paediatric student confidence in performing three common paediatric clinical skills framed as Objective Structured Clinical Examination (OSCE) scenarios and to compare this with subsequent assessed performance. The study also aims to explore possible barriers to successful paediatric skills completion. METHODS: A mixed-methods study was conducted on medical students. Cross-sectional questionnaire data relating to confidence in performing a number of paediatric skills were compared with assessed paediatric skills competency. Focus groups were carried out to identify themes in paediatric skills completion to triangulate this data. RESULTS: Eighty-five medical students participated in the study. Students had high levels of pre-test confidence in their ability to perform paediatrics skills. However agreement between pre-test confidence and subsequent task performance was poor and students had significantly greater belief in their skills ability than was subsequently demonstrated. Focus groups identified paediatric skills complexity, conflicting teaching and having limited supervised skills opportunities and as being possible contributory factors to this discrepancy. CONCLUSIONS: Student paediatric skills confidence is not matched by performance. The reasons for this are diverse but mostly modifiable. A major factor is the lack of supervised skills experience with appropriate feedback to support students in learning to calibrate their confidence against their competence. A number of recommendations are made including the introduction of formative assessment opportunities.

Investigation of the Iron-Peroxo Complex in the Fenton Reaction: Kinetic Indication, Decay Kinetics, and Hydroxyl Radical Yields.

The Fenton reaction describes the reaction of Fe(II) with hydrogen peroxide. Several researchers proposed the formation of an intermediate iron-peroxo complex but experimental evidence for its existence is still missing. The present study investigates formation and lifetime of this intermediate at various conditions such as different Fe(II)-concentrations, absence vs presence of a hydroxyl radical scavenger (dimethyl sulfoxide, DMSO), and different pH values. Obtained results indicate that the iron-peroxo complex is formed under all experimental conditions. Based on these data, stability of the iron-peroxo complex could be examined. At pH 3 regardless of [Fe(II)]0 decay rates for the iron-peroxo complex of about 50 s-1 were determined in absence and presence of DMSO. Without DMSO and [Fe(II)]0 = 300 µM variation of pH yielded decay rates of about 70 s-1 for pH 1 and 2 and of about 50 s-1 at pH 3 and 4. Hence, the iron-peroxo complex becomes more stable with increasing pH. Furthermore, pH-dependent hydroxyl radical yields were determined to investigate whether the increasing stability of the intermediate complex may indicate a different reaction of the iron-peroxo complex which might yield Fe(IV) instead of hydroxyl radical formation as suggested in literature. However, it was found that hydroxyl radicals were produced proportionally to the Fe(II)-concentration.

Etica y política del psicoanálisis: el psicoanalista ciudadano

Recopilación de trabajos producidos en el Ateneo