Roentgen (unit) this derivative quantity the roentgen equivalent physical (rep) to distinguish it from the ICR roentgen. The introduction of the roentgen measurement unit, which relied upon measuring the ionisation of air, replaced earlier less accurate practices that relied on timed exposure, film exposure, or fluorescence. This led the way to setting exposure limits,and the National Council on Radiation Protection and Measurements of the United States established the first formal dose limit in 1931 as 0.1 roentgen per day. The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection (ICRP) soon followed with a limit of
The Invention of Art of human expression and embellishment. Reviewer Marc Spiegler called the book "a must-read for anyone active in the arts". The Invention of Art The Invention of Art: A Cultural History (2001) is an art history book by Dr. Larry Shiner (1934- ), Emeritus Professor of Philosophy, History, and Visual Arts at the University of Illinois, Springfield Shiner spent over a decade to finish the work of this book. The book sees fine art as a modern invention due to social transformations during the 18th century. David Clowney, writing for "Contemporary Aesthetics" summarizes the central thesis of this book. "In The