Swimming behavior and energetics of sharks

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution December 1988In a field study of blue shark swimming behavior, acoustic telemetry was used to record depth, swimming speed and tailbeat frequency from free-ranging blue sharks (Prionace glauca) in northwestern Atlantic slope waters. Records obtained from five sharks show a consistent pattern of vertical migration between the surface and depths as great as 450 meters, with the deepest dives occurring during the daytime and shallower dives at night. Mean swimming speed was 44.5 ± 1.6 (X±S.E.) cm.s-1 (0.179 ± 0.014 lengths.s-1) for three sharks, with short bursts up to 180 cm.s-1. Mean tailbeat frequency was 0.335 ± 0.021 beats.s-1. Measurement of swimming speed and rate of vertical movement during dives permits calculation of angles of ascent and descent. For 84 dives deeper than 50 m, the descent angle averaged 8.0 ± 0.7 degrees from the horizontal while the ascent angle was 6.4 ± 0.5 degrees. Tailbeat records indicate that blue sharks actively swam downward during most of the descent, with brief periods of gliding which appear to be associated with the most rapid descent rates. The observed diving behavior does not match that predicted by theory to be energetically optimal for migration, and may instead represent a strategy for encountering and capturing prey. Heart rate, metabolic rate and activity were simultaneously recorded in the laboratory from lemon sharks (Negaprion brevirostris) during rest and spontaneous exercise, and from leopard sharks (Triakis semifasciata) during steady swimming at controlled speeds to evaluate the usefulness of heart rate as a measure of field metabolic rate. Heart rate was monitored by acoustic telemetry using a frequency modulated ECG transmitter, and metabolic rate was measured as oxygen consumption rate. For seven lemon sharks at 25°C, mean resting values for heart rate and oxygen consumption rate were 52.0 + 0.4 (S.E.) beats.min-1 and 162.0 ± 2.0 (S.E.) mg02.kg-1hr-1, respectively. Both parameters increased significantly (p<.001) during swimming, to means of 55.9 ± 0.2 beats.min-1 and 233.6 + 2.3 mg Oz.kg-1hr-1, at a mean swimming speed of 0.400 ± 0.003 body heart rate and oxygen consumption rate were 36.6 + 1.8 beats.min-1 and 105.3 ± 35.6 mg Oz.kg-1.hr-1. While swimming-at the maximum sustained speed (0.84 ± 0.03 lengths.s-1) for 30-60 minutes, these rates were 46.9 + 0.9 beats.min- and 229.3 + 13.2 mg Oz.kg-1.hr-1. The observed elevations in heart rate from rest to exercise account for 20% of the increase in oxygen uptake in the lemon shark and 32% in the leopard shark, leaving the remainder to be brought about by increases in stroke volume and/or arteriovenous oxygen difference. Significant linear regressions of oxygen consumption rate on heart rate were obtained for both lemon sharks and leopard sharks; separate regressions were obtained for individual lemon sharks . Heart rate was approximately as closely correlated to oxygen consumption rate as was swimming speed.Financial support throughout this project was from several sources: the WHO! education office, a grant from the Coastal Research Center to the author, and NSF grants OCE-8311512 to FGC, OCE-8743949 to SHG, and DCB-8416852 to JBG

Cooperative Tutoring: Transforming Collaboration in the Writing Center

Cooperative tutoring in a writing center setting consists of two tutors who work collaboratively with one student. It is a variation of one method of training new tutors, where the novice tutor observes the expert tutor during a tutoring session and eventually participates with the expert tutor. This study focused on the interactions between the tutors. Through cooperative tutoring, tutors learn new or different tutoring approaches from each other, which in turn serves as ongoing professional development. I explain the methodology used in the study, and I analyze the data. From the data analysis, I identify three preliminary categories, which are Equal Partners, New Alliance, and Trainer/Trainee. Equal Partners sessions are characterized by a strong sense of camaraderie between the tutors and a willingness to share both tutoring and academic writing strategies with each other and the student. During an Equal Partners session, tutors acknowledge the other tutor's strategies and incorporate parts of it into their own tutoring style. These sessions are more directive, and the tutors' focus is on teaching specific strategies for academic writing as well as passing on college survival lore. New Alliance sessions occur when both tutors are more actively engaged with the overall topic of the student's paper. Both of the tutors and the student share experiences and ideas on a personal level, working towards understanding how to craft ideas through academic discourse. In this way an alliance is formed with the writing center tutors and the student. During the Trainer/Trainee sessions, the tutors involved attempt to apply cooperative tutoring techniques but were unable to make the shift from the roles they once held as a trainer and a trainee. Finally, I present a summary and interpretation of my findings. I also discuss the limitations of the study and indicate areas for further research

Agile Entwicklung physischer Produkte 2023: Eine Studie zum aktuellen Stand in der industriellen Praxis

In der Entwicklung von mechatronischen Produkten nimmt die agile Entwicklung bereits seit einigen Jahren eine zunehmend wichtigere Rolle ein. Im Rahmen dieser Studienserie wird seit 2018 das Fortschreiten der Agilität in der DACH-Region untersucht. In der vorliegenden Ausgabe des Jahres 2023 liegt der Fokus dem Verständnis und der Anwendung agiler Arbeitsweisen, den Herausforderungen in deren Skalierung und der Bedeutung von Prototyping im genannten Kontext. Die Ergebnisse dieser Studie beruhen, wie auch in den vorangegangenen Jahren, auf den Aussagen von Praktikern aus einem breiten Spektrum an Industrieunternehmen, die an einer Online-Umfrage teilgenommen haben. Die Studie beschreibt sowohl quantitative als auch qualitative Ergebnisse aus der industriellen Praxis