Does knowledge have a half-life? An observational study analyzing the use of older citations in medical and scientific publications.

Objectives: In the process of scientific progress, prior evidence is both relied on and supplanted by new discoveries. We use the term 'knowledge half-life' to refer to the phenomenon in which older knowledge is discounted in favour of newer research. By quantifying the knowledge half-life, we sought to determine whether research published in more recent years is preferentially cited over older research in medical and scientific articles.

Assessments of Perfusion, Blood Flow, and Vascular Structure in Ambulatory Subjects: Guidance for Translational Research Scientists.

Research involving human subjects in ambulatory settings is a critical link in the chain comprising translational research, spanning preclinical research to human subject and patient cohort studies. There are presently a wide array of techniques and approaches available to investigators wishing to study blood flow, perfusion, and vascular structure and function in human subjects. In this multi-sectioned review, we discuss capillaroscopy, carotid intima-media thickness, flow-mediated dilation, laser Doppler flowmetry, near-infrared spectroscopy, peripheral arterial tonometry, pulse wave velocity, retinal fundus imaging, and vascular plethysmography.