OSTIblog Articles in the OSTIblog Topic

Amazing Aerogels

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Amazing Aerogels

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Aerogels are some of the most fascinating materials on the planet. They were discovered in the 1930s by Stanford University’s Samuel Kistler who proved that he could successfully replace a gel’s liquid with a gas by drying it, thereby creating a substance that was structurally a gel, but without liquid. Since their invention aerogels have primarily been made of silica but can be made of a growing variety of substances including transition metal oxides, organic polymers, biological polymers, semiconductor nanostructures, graphene, carbon, carbon nanotubes and metals as well as aerogel composite materials and the list is growing.

A brief glimpse of beautiful aerogels shows us they are in a class by themselves with combinations of materials properties that no other material possesses. And, these properties can be adjusted by tailoring the production process. Among other characteristics, aerogels are solid, rigid, and dry despite being named gels. They are the lightest known solids in existence and made of almost nothing. Silica aerogels, for example, typically consist of more than 96% air and the remaining 4% is a wispy web of silica. Their looks are also deceiving. You might think you could pass your hand right through a transparent silica aerogel, sometimes nicknamed ‘frozen smoke,’ but think again—it is very solid to the touch. Extraordinarily strong, aerogels are able to support over 2000 times their own weight. They are also very fragile-- at first cushiony to the touch, they shatter with a bit more pressure. They are good thermal insulators and are capable of withstanding temperatures in excess of 1000 degrees Fahrenheit. They can be mixed, formed, spread, sprayed or fabricated into slabs, pellets, or most any shape desirable. Because aerogels have these incredible characteristics, they are outstanding materials for...

Related Topics: Aerogels, biological, carbon, graphene, metals, OSTIBLOG, oxides, planet, polymers, semiconductor, silica

The Reverend Thomas Bayes

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The Reverend Thomas Bayes

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During the 1700’s, the Reverend Thomas Bayes was a nonconformist minister at the Mount Sion Chapel in Tunbridge Wells, UK, about 40 miles southeast of central London.  Having studied both theology and logic at the University of Edinburgh, he was also a mathematician and developed a strong interest in probability late in life. He was known to have published only one book on theology and one book on mathematics in his lifetime. A third manuscript he never published about the probability of cause made him famous. After his death, a good friend Richard Price recognized the importance of the paper and, after extensive editing, submitted it for publication. More than 20 years later, the great French mathematician, Pierre-Simon Laplace devised the formula for Bayes’ probability of causes and acknowledged Bayes as the discoverer of what we now know as Bayesian inference.  

This year is the 250^th anniversary of Bayesian inference. During its history, the Bayes theory has been doubted, disproven, defended, and challenged again and again and again.  It has consistently been an important tool in understanding what we really know, given the evidence and other information we have. It helps incorporate "conditional probabilities" into our conclusions. 

Bayesian inference has recently become prominent in many scientific fields due to the availability of simulation-based computational tools for implementation. Researchers at Los Alamos National Laboratory are using Bayes’ theorem to deduce structures of crystals and determine macromolecular structures. The Lawrence Livermore National Laboratory describes how a sequential Bayesian processor would be used to assess...

Related Topics: Bayesian Inference, Oak Ridge National Laboratory, OSTIBLOG, Thomas Bayes