The principal economic sources of rare earths are the minerals bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. The rare earths are a relatively abundant group of 17 elements composed of scandium, yttrium, and the lanthanides. The elements range in crustal abundance from cerium, the 25th most abundant element of the 78 common elements in the Earth's crust at 60 parts per million, to thulium and lutetium, the least abundant rare-earth elements at about 0.5 part per million. The elemental forms of rare earths are iron gray to silvery lustrous metals that are typically soft, malleable, and ductile and usually reactive, especially at elevated temperatures or when finely divided. The rare earths' unique properties are used in a wide variety of applications.
Applications And Investigations In Earth Science Answer Key.rar
Today, Chad brings his wealth of experience to his role as a consultant, where he specializes in incident response, corporate espionage, and computer forensics. Here at SANS, Chad is a senior instructor and co-author for two six-day courses: FOR500: Windows Forensic Analysis, which focuses on the core skills required to become a certified forensic practitioner, and FOR508: Advanced Digital Forensics, Incident Response, and Threat Hunting, which teaches sophisticated computer intrusion analysis and advanced threat hunting techniques.Chad\'s experience brings immeasurable depth to his classes. He focuses not only on tools and techniques but also on understanding how those artifacts can be used to prove or disprove questions students are asked to investigate in their daily jobs. As Chad says, "Forensics is both an art and a science, and I find hearing about real-world applications provides new perspectives and can help unlock a student\'s ability to think unconventionally." Chad keeps his class goals simple: teach and lead discussions on the most important topics and make sure students have as much time as possible to work on the exercises. "I\'m a big believer in hands-on learning," he says, "and we work hard to ensure the exercises in our classes are as realistic as possible. When students put all the pieces of a forensic investigation together themselves, it leads to those \'aha\' moments that are so valuable."The methodologies Chad teaches in his courses are the same ones he has used successfully on countless examinations. "Our exercises are months in the making and provide realistic, real-world evidence samples on which to practice," says Chad. "I have had numerous students report going back to their teams, blowing them away with a new technique, and promptly becoming the trainer themselves."One of Chad\'s most memorable experiences in the classroom brought that immediacy of techniques to a whole new level."I was teaching some of my latest research on browser artifacts, recently added to the FOR500 class. Research showed that a specific browser database could be missing a day or more of information if not properly handled. There happened to be a law enforcement officer in class who was investigating a murder, and in his examination of the suspect\'s computer he had noted missing data during a critical 24-hour period. From our class discussion, the officer now had a tool and technique to recover the missing data in his case. Not surprisingly, he left class early!"In addition to being a graduate of the U.S. Air Force Academy, Chad holds B.S. and M.S. degrees in computer science, as well as GCFA, GCIH, GREM, and ENCE certifications.In his free time, Chad loves to travel and takes full advantage of the unique destinations his career takes him. He spends much of his time at home mountain biking, skiing, snowboarding, and mountaineering. Chad recently took a ski mountaineering trip to Antarctica, about as far away from a Wi-Fi signal as you can get!
W.C. Röntgen reported the discovery of X-rays in December 1895 after seven weeks of assiduous work during which he had studied the properties of this new type of radiation able to go through screens of notable thickness. He named them X-rays to underline the fact that their nature was unknown. The news of this discovery immediately aroused an immense interest in the public and also initiated intense research in several directions. Physicians and physicists began as early as January 1896 to use X-rays on patients to investigate the skeleton and subsequently the lung and other organs. This was the birth or radiology. Rapidly they observed skin erythema, which led to the idea of using X-rays against a variety of lesions. In June 1896 the first patient was treated by radiotherapy. J.J. Thomson (Cambridge, U.K.) showed that X-rays were able to ionize gaz and the study of this phenomenon led to the discovery of electrons in 1897. In order to understand the emission of X-rays, H. Becquerel (Paris) investigated the role of the phosphorescence of the glass of the tube and while doing so discovered radioactivity in March 1896. X-rays and radioactivity were at the origin of the scientific revolution at the end of the 19th and the beginning of the 20th centuries. Research on radioactive materials demonstrated the existence of atoms which had been till then only a convenient hypothesis for explaining chemical reactions, but whose reality was considered as dubious by most physicists. Moreover, interaction of particles emitted by radionuclides and atoms enabled first the study of the structure of the atom and subsequently its nucleus. Matter, elements which were thought to be immutable were found to be transmutable, and eventually to disintegrate. The origin of the energy transferred to the radiation which was emitted appeared as a mystery and in order to explain it the physicist had to accept that matter could convert energy. In 1903 Einstein established the equivalence between matter and energy. Matter, energy, electricity, light which were formerly considered as continuous quantities were found to be discrete: there are particles of matter (elementary particles), energy (quanta, Planck 1905), electricity (electron), light (photons). Radioactive decay, particle interactions imposed a probabilistic physics which progressively replaced classic deterministic physics. Radioactivity can be used as a clock to measure time in the universe. Datations were made for fossils, art masterpieces and also for the earth, the solar system and universe. X-rays diffraction proved to be a powerful tool for studying crystals and molecules, in particular protein, and in 1953 enabled to demonstrate the DNA double helix. Hence X-rays and radioactivity originated a revolution in physics and science and in the vision of nature. The imperceptible and yet so powerful rays demonstrated the deficiencies of our senses. Mathematical entities and instrumentation must complement our sensations. The huge increment in our knowledge is accompanied by a divorce between the scientist and the layman who now often has great difficulties understanding new concepts not only in physics but also in biology. 2ff7e9595c
Comments