text: In the end, though, we will need to accommodate to an era of permanently higher fuel costs. Even as a dedicated opponent of sprawl, I enter this new era with real concern.
  
  Diffusive motion — displacement due to the cumulative effect of irregular fluctuations — has been a fundamental concept in mathematics and physics since Einstein’s work on Brownian motion. It is also relevant to understanding various aspects of quantum theory. This book explains diffusive motion and its relation to both nonrelativistic quantum theory and quantum field theory. It shows how diffusive motion concepts lead to a radical reexamination of the structure of mathematical analysis. The book’s inspiration is Princeton University mathematics professor Edward Nelson’s influential work in probability, functional analysis, nonstandard analysis, stochastic mechanics, and logic. The book can be used as a tutorial or reference, or read for pleasure by anyone interested in the role of mathematics in science. Because of the application of diffusive motion to quantum theory, it will interest physicists as well as mathematicians.
  The introductory chapter describes the interrelationships between the various themes, many of which were first brought to light by Edward Nelson. In his writing and conversation, Nelson has always emphasized and relished the human aspect of mathematical endeavor. In his intellectual world, there is no sharp boundary between the mathematical, the cultural, and the spiritual. It is fitting that the final chapter provides a mathematical perspective on musical theory, one that reveals an unexpected connection with some of the book’s main themes.
  
  Morphine has been used for centuries to relieve severe pain. However, its pain-relief properties are coupled with considerable side effects. Morphine imitates the action of molecules produced naturally by the brain (endorphins). So why does it have such harmful side effects? This question has recently been elucidated by Sébastien Granier, researcher at the Institute of Functional Genomics (Inserm/CNRS/Universités de Montpellier 1 and 2) and his team, in conjunction with collaborators in the US. The 3D structure of brain receptors is likely to differ, depending on the type of molecule bound upon it (morphine or endorphin): the body’s response will be completely and accordingly modified. Thanks to this discovery, the researchers have now set their sights on retaining the benefits of morphine while eliminating any undesired side effects.
  Opium is a natural poppy (papaver somniferum) extract and is one of the oldest drugs known to man, used for its psychotropic, sedative and analgesic properties. These effects are caused by its major component: morphine. Today morphine has widespread clinical pain-relief applications.
  Morphine’s action is relayed by μ-opioid receptors expressed at the surface of cells in the central nervous system. These receptors are part of a superfamily of proteins, G protein-coupled receptors (GPCR), which are the target of around 30% of drugs currently on the market.