Roentgen (unit) One roentgen deposits of absorbed dose in dry air, or in soft tissue. One roentgen of X-rays may deposit anywhere from in bone depending on the beam energy. This tissue-dependent conversion from kerma to absorbed dose is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a reference medium, which is ambiguous in the latest NIST definition. The roentgen has its roots in the Villard unit defined in 1908 by the American Roentgen Ray Society as "the quantity of radiation which liberates by ionisation one esu of electricity per cm of air under normal conditions
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