Biomedical subjects

Mark Denny

Publications and source records attributed to Mark Denny.

3 recordsLinked to original sources

PubMed2003

Ectopic pregnancy.

Ectopic pregnancy is a high-risk diagnosis that is increasing in frequency and is still commonly missed in the emergency department. The emergency physician needs a high index of suspicion and must understand that the history, physical examination, and a single quantitative beta-hCG level cannot reliably rule out an ectopic pregnancy. Most pregnant patients who present to the emergency department during the first trimester with abdominal or pelvic pain, regardless of the presence of vaginal bleeding, should undergo further evaluation with ultrasonography. Ultrasound findings in conjunction with quantitative beta-hCG levels guide the management of the patient.

Abortifacient Agents, Nonsteroidal↗

PubMed2002

The mechanics of wave-swept algae.

Wave-swept marine algae must contend with the hydrodynamic forces imposed by extreme water velocities. Nonetheless, they seldom have a shape that appears streamlined and they are constructed of weak, compliant materials. How do they survive? The answer is complex, but a coherent story is beginning to emerge. The combined effect of frond shape and material properties ensures that algae are flexible. In small individuals, flexibility allows the plant to reorient and reconfigure in flow, thereby assuming a streamlined shape and reducing the applied hydrodynamic force. In large individuals, flexibility allows fronds to 'go with the flow', a strategy that can at times allow the plant to avoid hydrodynamic forces but may at other times impose inertial loads. Our understanding of algal mechanics is such that we can begin to predict the survivorship of algae as a function of size, spatial distribution and wave climate.

Biomechanical Phenomena↗

PubMed2002

Blade motion and nutrient flux to the kelp, Eisenia arborea.

Marine algae rely on currents and waves to replenish the nutrients required for photosynthesis. The interaction of algal blades with flow often involves dynamic reorientations of the blade surface (pitching and flapping) that may in turn affect nutrient flux. As a first step toward understanding the consequences of blade motion, we explore the effect of oscillatory pitching on the flux to a flat plate and to two morphologies of the kelp Eisenia arborea. In slow flow (equivalent to a water velocity of 2.7 cm s(-1)), pitching increases the time-averaged flux to both kelp morphologies, but not to the plate. In fast flow (equivalent to 20 cm s(-1) in water), pitching has negligible effect on flux regardless of shape. For many aspects of flux, the flat plate is a reliable model for the flow-protected algal blade, but predictions made from the plate would substantially underestimate the flux to the flow-exposed blade. These measurements highlight the complexities of flow-related nutrient transport and the need to understand better the dynamic interactions among nutrient flux, blade motion, blade morphology, and water flow.

Animals↗