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Proton Precession Magnetometer
A proton magnetometer, also known as a proton precession magnetometer (PPM), uses the principle of Earth's field nuclear magnetic resonance (EFNMR) to measure very small variations in the Earth's magnetic field, allowing ferrous objects on land and at sea to be detected. It is used in land-based archaeology to map the positions of demolished walls and buildings, and at sea to locate wrecked ships, sometimes for recreational diving. PPMs were once widely used in mineral exploration. They have largely been superseded by Overhauser effect magnetometers and alkali vapour (cesium, rubidium, and potassium) or helium magnetometers, which sample faster and are more sensitive. Principles of operation A direct current flowing in a solenoid creates a strong magnetic field around a hydrogen-rich fluid (kerosine and decane are popular; water can also be used), causing some of the protons to align with that field. The current is then interrupted, and as protons realign themselves with t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1967 Proton Magnetometer
Events January * January 1 – Canada begins a year-long celebration of the 100th anniversary of Canadian Confederation, Confederation, featuring the Expo 67 World's Fair. * January 5 ** Spain and Romania sign an agreement in Paris, establishing full consular and commercial relations (not diplomatic ones). ** Charlie Chaplin launches his last film, ''A Countess from Hong Kong'', in the UK. * January 6 – Vietnam War: United States Marine Corps, USMC and Army of the Republic of Vietnam, ARVN troops launch ''Operation Deckhouse Five'' in the Mekong Delta. * January 8 – Vietnam War: Operation Cedar Falls starts. * January 13 – A military coup occurs in Togo under the leadership of Étienne Eyadema. * January 14 – The Human Be-In takes place in Golden Gate Park, San Francisco; the event sets the stage for the Summer of Love. * January 15 ** Louis Leakey announces the discovery of pre-human fossils in Kenya; he names the species ''Proconsul nyanzae, Kenyapithecus africanus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proton–gyromagnetic Ratio
The nucleon magnetic moments are the intrinsic magnetic dipole moments of the proton and neutron, symbols ''μ''p and ''μ''n. Protons and neutrons, both nucleons, comprise the nucleus of atoms, and both nucleons behave as small magnets whose strengths are measured by their magnetic moments. The nucleons interact with normal matter through either the nuclear force or their magnetic moments, with the charged proton also interacting by the Coulomb force. The proton's magnetic moment, surprisingly large, was directly measured in 1933, while the neutron was determined to have a magnetic moment by indirect methods in the mid 1930s. Luis Alvarez and Felix Bloch made the first accurate, direct measurement of the neutron's magnetic moment in 1940. The proton's magnetic moment is exploited to make measurements of molecules by proton nuclear magnetic resonance. The neutron's magnetic moment is exploited to probe the atomic structure of materials using scattering methods and to manipul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diving Support Equipment
Diving support equipment is the equipment used to facilitate a diving operation. It is either not taken into the water during the dive, such as the gas panel and compressor, or is not integral to the actual diving, being there to make the dive easier or safer, such as a surface decompression chamber. Some equipment, like a diving stage, is not easily categorised as diving or support equipment, and may be considered as either. Breathing gas equipment * * * * * * * * * * * * * * * * * * * * * * * * Platforms * ** ** ** * ** * Habitats * ** ** ** ** ** ** ** Decompression equipment * * * * * Deployment systems * * * * * * * – A suspended foot support allowing divers to use a leg to help lift themselves from the water into the boat. * * * * Remotely controlled underwater vehicles * * * * * * * * * * * * * * * * * * * * * * * Dive planning and recording equipment * * * * * * Saf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indiana
Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th state on December 11, 1816. It is bordered by Lake Michigan to the northwest, Michigan to the north, Ohio to the east, the Ohio River and Kentucky to the south and southeast, and the Wabash River and Illinois to the west. Various indigenous peoples inhabited what would become Indiana for thousands of years, some of whom the U.S. government expelled between 1800 and 1836. Indiana received its name because the state was largely possessed by native tribes even after it was granted statehood. Since then, settlement patterns in Indiana have reflected regional cultural segmentation present in the Eastern United States; the state's northernmost tier was settled primarily by people from New England and New York, Central Indiana by migrants fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angel Mounds
Angel Mounds State Historic Site ( 12 VG 1), an expression of the Mississippian culture, is an archaeological site managed by the Indiana State Museum and Historic Sites that includes more than of land about southeast of present-day Evansville, in Vanderburgh and Warrick counties in Indiana. The large residential and agricultural community was constructed and inhabited from AD 1100 to AD 1450, and served as the political, cultural, and economic center of the Angel chiefdom. It extended within of the Ohio River valley to the Green River in present-day Kentucky. The town had as many as 1,000 inhabitants inside the walls at its peak, and included a complex of thirteen earthen mounds, hundreds of home sites, a palisade (stockade), and other structures. Designated a National Historic Landmark in 1964, the property also includes an interpretive center, recreations of Mississippian structures, a replica of a 1939 Works Projects Administration archaeology laboratory, and a area aw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoremanent Magnetization
When an igneous rock cools, it acquires a thermoremanent magnetization (TRM) from the Earth's field. TRM can be much larger than it would be if exposed to the same field at room temperature (see isothermal remanence). This remanence can also be very stable, lasting without significant change for millions of years. TRM is the main reason that paleomagnetists are able to deduce the direction and magnitude of the ancient Earth's field. History As early as the eleventh century, the Chinese were aware that a piece of iron could be magnetized by heating it until it was red hot, then quenching in water. While quenching it was oriented in the Earth's field to get the desired polarity. In 1600, William Gilbert published ''De Magnete'' (1600), a report of a series of meticulous experiments in magnetism. In it, he described the quenching of a steel rod in the direction of the Earth's field, and he may have been aware of the Chinese work. In the early 20th century, a few investigators foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxford University
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the University of Oxford, the oldest university in the English-speaking world; it has buildings in every style of English architecture since late Anglo-Saxon. Oxford's industries include motor manufacturing, education, publishing, information technology and science. History The history of Oxford in England dates back to its original settlement in the Saxon period. Originally of strategic significance due to its controlling location on the upper reaches of the River Thames at its junction with the River Cherwell, the town grew in national importance during the early Norman period, and in the late 12th century became home to the fledgling University of Oxford. The city was besieged during The Anarchy in 1142. The university rose to domina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martin Aitken
Martin Jim Aitken FRS (11 March 1922 – 13 June 2017) was a British archaeometrist. Aitken was born in Stamford, Lincolnshire, and studied physics at Wadham College, Oxford. He was a fellow of Linacre College, Oxford. He was Professor of Archaeometry at the University of Oxford from 1985 until he retired in 1989. Aitken organised annual meetings which became the Symposium on Archaeometry and Archaeological Prospection". He had an interest in absolute dating: radiocarbon dating from 1957, thermoluminescence dating from the 1960s, and later helped develop optically stimulated luminescence In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications: * Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pott ... as a dating method dating. He died in June 2017 at the age of 95. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Banded Iron Formation
Banded iron formations (also known as banded ironstone formations or BIFs) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness and extend laterally for several hundred kilometers. Almost all of these formations are of Precambrian age and are thought to record the Great Oxygenation Event, oxygenation of the Earth's oceans. Some of the Earth's oldest rock formations, which formed about (Year#SI prefix multipliers, Ma), are associated with banded iron formations. Banded iron formations are thought to have formed in sea water as the result of oxygen production by photosynthesis, photosynthetic cyanobacteria. The oxygen combined with dissolved iron in Earth's oceans to form insoluble iron oxides, which precipitated out, forming a thin layer on the ocean floor. Each band is similar to a varve, resulting from cyclic variations in oxygen production. Banded iron formation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Pole
The geomagnetic poles are antipodal points where the axis of a best-fitting dipole intersects the surface of Earth. This ''theoretical'' dipole is equivalent to a powerful bar magnet at the center of Earth, and comes closer than any other point dipole model to describing the magnetic field observed at Earth's surface. In contrast, the magnetic poles of the actual Earth are not antipodal; that is, the line on which they lie does not pass through Earth's center. Owing to motion of fluid in the Earth's outer core, the actual magnetic poles are constantly moving (secular variation). However, over thousands of years, their direction averages to the Earth's rotation axis. On the order of once every half a million years, the poles reverse (i.e., north switches place with south) although the time frame of this switching can be anywhere from every 10 thousand years to every 50 million years. The poles also swing in an oval of around in diameter daily due to solar wind deflecting the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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