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== '''[[NMR spectroscopy]]''' ==
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'''NMR spectroscopy''' (MR spectroscopy, NMR or Nuclear Magnetic Resonance Spectroscopy) measures the energy differences between the spin states of nuclei in the presence of a magnetic field by using radio frequency electromagnetic radiation.<ref> I. I. Rabi.(1937) Phys. Rev., 51  652</ref><ref>N. Bloembergen, E. Purcell and R.V.Pound. (1948). Phys. Rev.  73, 679.</ref> <ref>F. Bloch, W. Hansen, and M.E. Packard, (1946) Phys. Rev. 69, 127.</ref> The energy differences between the spin states of the nuclei depend upon the nature of the atom and are influenced by its environment. However, NMR spectroscopy is not limited to measurement of the energy differences between the spin states. NMR signals are also influenced by the motion of the nucleus and the rotational motion of the molecule within which the observed nucleus resides. Therefore, NMR spectroscopy provides  static (structure and composition) as well as dynamic information regarding the system of interest, e.g.,  [[protein]]s, [[DNA]] and other natural products.
==Footnotes==
 
Pulses of radio-frequency electromagnetic radiation can be used to perturb the nuclear spin systems in a variety of ways; the time dependent response of the system of interest can be recorded and analyzed:  
* to correlate different spectral properties of nuclei and/or
* to extract information regarding interactions between nuclear spins within the same molecule and/or
* to obtain information regarding intermolecular interactions. 
The amplitude, frequency, phase and duration of pulses of radio-frequency electromagnetic radiation, as well as static and dynamic position dependent magnetic fields, can be varied in many  combinations giving rise to a wide variety of NMR spectroscopic experiments.
 
NMR spectroscopic techniques are used extensively for structural elucidation of natural products and for quantitative analysis of components of complex mixtures such as body fluids.  However, its applications are not limited to these systems; and
NMR spectroscopy has been used for the study of matter in disordered, ordered and partially ordered systems such as gases, liquids, [[quantum fluids]]
<ref>D.D.Osheroff, W.J.Gully, R.C.Richardson and D.M.Lee, Phys. Rev. Lett. (1972) 29, 920 </ref> <ref>http://nobelprize.org/nobel_prizes/physics/laureates/1996/lee-lecture.pdf </ref>, 
superconductors, solutions, amorphous solids, crystalline solids, [[liquid crystals]], membranes and living organisms. NMR spectroscopic methods have also found use in  [[quantum computing]].
 
''[[NMR spectroscopy|.... (read more)]]''
 
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Latest revision as of 10:19, 11 September 2020

The Irvin pin. The eyes have always been red, but there are urban legends about the meanings of other colors.
A pin from another company, possibly Switlik or Standard Parachute. This style is common in catalogs and auctions of military memorabilia.

The Caterpillar Club is an informal association of people who have successfully used a parachute to bail out of a disabled aircraft. After authentication by the parachute maker, applicants receive a membership certificate and a distinctive lapel pin.

History

Before April 28, 1919 there was no way for a pilot to jump out of a plane and then to deploy a parachute. Parachutes were stored in a canister attached to the aircraft, and if the plane was spinning, the parachute could not deploy. Film industry stuntman Leslie Irvin developed a parachute that the pilot could deploy at will from a back pack using a ripcord. He joined the Army Air Corps parachute research team, and in April 1919 he successfully tested his design, though he broke his ankle during the test. Irvin was the first person to make a premeditated free fall jump from an airplane. He went on to form the Irving Airchute Company, which became a large supplier of parachutes. (A clerical error resulted in the addition of the "g" to Irvin and this was left in place until 1970, when the company was unified under the title Irvin Industries Incorporated.) The Irvin brand is now a part of Airborne Systems, a company with operations in Canada, the U.S. and the U.K.[1].

An early brochure [2] of the Irvin Parachute Company credits William O'Connor 24 August 1920 at McCook Field near Dayton, Ohio as the first person to be saved by an Irvin parachute, but this feat was unrecognised. On 20 October 1922 Lieutenant Harold R. Harris, chief of the McCook Field Flying Station, jumped from a disabled Loening W-2A monoplane fighter. Shortly after, two reporters from the Dayton Herald, realising that there would be more jumps in future, suggested that a club should be formed. 'Caterpillar Club' was suggested because the parachute canopy was made of silk, and because caterpillars have to climb out of their cocoons and fly away. Harris became the first member, and from that time forward any person who jumped from a disabled aircraft with a parachute became a member of the Caterpillar Club. Other famous members include General James Doolittle, Charles Lindbergh and (retired) astronaut John Glenn.

In 1922 Leslie Irvin agreed to give a gold pin to every person whose life was saved by one of his parachutes. By 1945 the number of members with the Irvin pins had grown to over 34,000. In addition to the Irvin Air Chute Company and its successors, other parachute manufacturers have also issued caterpillar pins for successful jumps. Irvin/Irving's successor, Airborne Systems Canada, still provides pins to people who made their jump long ago and are just now applying for membership. Another of these is Switlik Parachute Company, which though it no longer makes parachutes, still issues pins.

Footnotes