Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation

BackgroundCrocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known.Methodology/Principal FindingsWe measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research.Conclusions/SignificanceCritical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination

Web-assisted assessment of professional behaviour in problem-based learning: more feedback, yet no qualitative improvement?

Although other web-based approaches to assessment of professional behaviour have been studied, no publications studying the potential advantages of a web-based instrument versus a classic, paper-based method have been published to date. This study has two research goals: it focuses on the quantity and quality of comments provided by students and their peers (two researchers independently scoring comments as correct and incorrect in relation to five commonly used feedback rules (and resulting in an aggregated score of the five scores) on the one, and on the feasibility, acceptability and perceived usefulness of the two approaches on the other hand (using a survey). The amount of feedback was significantly higher in the web-based group than in the paper based group for all three categories (dealing with work, others and oneself). Regarding the quality of feedback, the aggregated score for each of the three categories was not significantly different between the two groups, neither for the interim, nor for the final assessment. Some, not statistically significant, but nevertheless noteworthy trends were nevertheless noted. Feedback in the web-based group was more often unrelated to observed behaviour for several categories for both the interim and final assessment. Furthermore, most comments relating to the category ‘Dealing with oneself’ consisted of descriptions of a student’s attendance, thereby neglecting other aspects of personal functioning. The survey identified significant differences between the groups for all questionnaire items regarding feasibility, acceptability and perceived usefulness in favour of the paper-based form. The use of a web-based instrument for professional behaviour assessment yielded a significantly higher number of comments compared to the traditional paper-based assessment. Unfortunately, the quality of the feedback obtained by the web-based instrument as measured by several generally accepted feedback criteria did not parallel this increase

Medical Professionalism: Conflicting Values for Tomorrow's Doctors

BACKGROUND: New values and practices associated with medical professionalism have created an increased interest in the concept. In the United Kingdom, it is a current concern in medical education and in the development of doctor appraisal and revalidation. OBJECTIVE: To investigate how final year medical students experience and interpret new values of professionalism as they emerge in relation to confronting dying patients and as they potentially conflict with older values that emerge through hidden dimensions of the curriculum. METHODS: Qualitative study using interpretative discourse analysis of anonymized student reflective portfolios. One hundred twenty-three final year undergraduate medical students (64 male and 59 female) from the University of Cambridge School of Clinical Medicine supplied 116 portfolios from general practice and 118 from hospital settings about patients receiving palliative or end of life care. RESULTS: Professional values were prevalent in all the portfolios. Students emphasised patient-centered, holistic care, synonymous with a more contemporary idea of professionalism, in conjunction with values associated with the 'old' model of professionalism that had not be directly taught to them. Integrating 'new' professional values was at times problematic. Three main areas of potential conflict were identified: ethical considerations, doctor-patient interaction and subjective boundaries. Students explicitly and implicitly discussed several tensions and described strategies to resolve them. CONCLUSIONS: The conflicts outlined arise from the mix of values associated with different models of professionalism. Analysis indicates that 'new' models are not simply replacing existing elements. Whilst this analysis is of accounts from students within one UK medical school, the experience of conflict between different notions of professionalism and the three broad domains in which this conflict arises are relevant in other areas of medicine and in different national contexts

The applicability of evaluable wastes for the adsorption of Reactive Black 5

In this study, it is proposed that pumpkin seed hulls and eggshells that are household wastes are low-cost materials to remove the Reactive Black 5 from water media. Through a number of experiments, the influences of the contact time, adsorption quantity, temperature, and pH of the solution were studied. Characterization of pumpkin seed hulls and eggshells was done by using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Adsorption of the experimental data well fitted with both the models called Langmuir and Freundlich isotherm. The maximum experimental capacities of adsorption related to pumpkin seed hulls and eggshells were 9.18 and 18.46 mg g -1 , respectively. The optimum conditions were determined as adsorbent amount = 0.5 g L -1 , pH = 6, and contact time = 15 min for the eggshells adsorption process and adsorbent dosage = 1 g L -1 , pH = 2, and contact time = 30 min for the pumpkin seed hulls adsorption system. In addition, pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics were used to study the adsorbing dynamics of Reactive Black 5 onto pumpkin seed hulls and eggshells. In this study, it was observed that the pseudo-second-order kinetic was appropriate. Calculation of the thermodynamic parameters, such as changes in the free energy, enthalpy, and entropy of adsorption, was performed. According to the thermodynamic parameters, these processes were less spontaneous, practicable, and exothermic. To remove the dye from aqueous solutions, the pumpkin seed hulls and eggshells can be used as an alternative cheap adsorbent. © 2018, Islamic Azad University (IAU)