![]() Its long-term frequency performance is also exceptional (about 10-15 after one day of averaging). The Sapphire Clock has a short-term fractional frequency stability of around 1x10-15, which is equivalent to only losing or gaining one second every 40 million years. ![]() However, in the sapphire crystal the resonant frequency is so high-10 billion cycles per second-that the electromagnetic signal rings only for a hundred milliseconds. The losses in sapphire are so low that if it were a conventional bell then it would keep ringing for millions of years. A good analogy might be to imagine hitting a bell and using its regular oscillations to count time. There is one particular frequency that will excite the natural resonance of the sapphire crystal – this corresponds to the signal that reinforces itself after one round trip around the crystal surface. Lord Rayleigh first discovered this concept in 1878 when he could hear someone whispering far away on the other side of the church dome at St Paul’s Cathedral. The way the microwave radiation moves around the crystal is called a “Whispering Gallery”. Microwave radiation is injected into the sapphire crystal and propagates around the circumference of the crystal (just inside the surface). At this temperature, the microwave energy lost in the sapphire crystal is the lowest of any substance on Earth. HFS clients enjoy state-of-the-art warehousing, real-time access to critical business data, accounts receivable management and collection, and unparalleled customer service.The Cryogenic Sapphire Oscillator has a 5 cm cylinder-shaped sapphire crystal that is cooled to about -267 ☌, or about 5 or 6 degrees above absolute zero. HFS provides print and digital distribution for a distinguished list of university presses and nonprofit institutions. MUSE delivers outstanding results to the scholarly community by maximizing revenues for publishers, providing value to libraries, and enabling access for scholars worldwide. Project MUSE is a leading provider of digital humanities and social sciences content, providing access to journal and book content from nearly 300 publishers. With warehouses on three continents, worldwide sales representation, and a robust digital publishing program, the Books Division connects Hopkins authors to scholars, experts, and educational and research institutions around the world. With critically acclaimed titles in history, science, higher education, consumer health, humanities, classics, and public health, the Books Division publishes 150 new books each year and maintains a backlist in excess of 3,000 titles. The division also manages membership services for more than 50 scholarly and professional associations and societies. The Journals Division publishes 85 journals in the arts and humanities, technology and medicine, higher education, history, political science, and library science. The Press is home to the largest journal publication program of any U.S.-based university press. One of the largest publishers in the United States, the Johns Hopkins University Press combines traditional books and journals publishing units with cutting-edge service divisions that sustain diversity and independence among nonprofit, scholarly publishers, societies, and associations.
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