Isotopic historical development

A synopsis of the topics treated in this monograph follows. Chapter 1 is a brief survey of historical developments in the field of isotope effects through the early 1930s. Chapters 2 and 3 give developments of the fundamental quantum mechanical, thermodynamic, and molecular vibration theory required to under-... 

It is possible to obtain NMR spectra of nearly all elements, although not always from observing the isotope with the highest natural abundance, as can be seen from the examples of carbon and oxygen. For reasons connected with the historical development of NMR spectroscopy, nuclei of all species other than H are referred to as heteronuclei. 

There are a number of tracers that have been used to help understand chemical reactions and interactions. Historically, development of modem tracer methods began with the pioneering work of the Hungarian physical chemist, George Charles de Hevesy, in the early 1900s. De Hevesy s work focused on the use of radioactive tracers to study chemical processes, for which he was awarded the Nobel Prize in Chemistry in 1943. Radioactive tracers, also known as radioactive labels, are based on the use of a given radioisotope. However, it is important to note that there are also isotopic tracers (or isotopic labels). Isotopes are forms of a chemical element with different atomic mass, which have nuclei with the same atomic number (i.e. number of protons) but different numbers of neutrons. Examples include H, " C, and which are radioactive forms of stable elements... 

Catalytic reactions of hydrocarbons over zeolites are reviewed. The historical development of various mechanistic proposals, particularly of the carbonium ion type, is traced. In spite of numerous catalytic, spectroscopic, and structural studies which have been reported concerning the possible roles of Bronsted acid, Lewis acid, and cationic sites, it still is not possible to formulate a comprehensive mechanistic picture. New activity and product data for cumene cracking and isotope redistribution in deuterated benzenes over Ca-and La-exchanged Y zeolites is presented. Cracking of the isomeric hexanes over alkali metal-exchanged Y and L zeolites has been studied. This cracking is clearly radical rather than carbonium-ion in nature but certain distinct differences from thermal cracking are described. 

Petit, J.F., Technological Aspects of the Historical Development of Eurodif, in Proceedings of the International Symposium on Isotope Separation and Chemical Exchange Uranium Enrichment, Oct. 29-Nov. 1, 1990, Tokio, Yasuhiko Fuji, Takanobu Ishida, Kazuo Takeuchi, Editors, 103, 1990. 

In the following, the various concepts available for studying human element metabolism in vivo will be briefly explained. Because the field is so wide, the focus of this chapter will be more on underlying principles rather than historical developments and experimental details. An in-depth discussion of the practicalities of how to design and conduct stable isotope studies in humans would go beyond the scope of this chapter and will only be highlighted when considered relevant. For technical details, the interested reader is referred to the references cited, which have been selected as representative examples for the subject matter, or available monographs [17-21]. 

Different combinations of stable xenon isotopes have been sealed into each of the fuel elements in fission reactors as tags so that should one of the elements later develop a leak, it could be identified by analyzing the xenon isotope pattern in the reactor s cover gas (4). Historically, the sensitive helium mass spectrometer devices for leak detection were developed as a cmcial part of building the gas-diffusion plant for uranium isotope separation at Oak Ridge, Tennessee (129), and heHum leak detection equipment is stiU an essential tool ia auclear technology (see Diffusion separation methods). 

Most historical studies do not contain the detailed information needed to develop carbon budgets. They are also confounded by erosional losses, changes in the chemical methods to measure SOC, management-induced differences in bulk density, and different methods to calculate turnover kinetics. The consequences of these problems are that it is difficult to compare studies and calculate carbon turnover rates. To overcome these problems simplifying assumptions are often used (Clay et al. 2006 Johnson et al. 2006 Bolinder et al. 2007). Assumptions can reduce the usefulness of the findings. This chapter reviews non-isotopic and 13C isotopic approaches for determining SOC maintenance and implications of simplifying assumptions on SOC turnover calculations. 

We have alluded above to the fact that dietary reconstruction from bone can be no more than a relatively long-term average, since in life bone is constantly remodelled. In general, a dietary reconstruction based on bone collagen is likely to represent the average diet of that individual over the last few years of life -perhaps up to as much as ten years before death, depending on the particular bone used. An extension of the isotopic dietary method is to use the differential information available within a single skeleton to study human lifetime mobility. This technique has been developed and exploited most clearly on historic material from South Africa (Sealy et al., 1995 Sealy, 2001 Cox et al., 2001). 

Historical Vignette 11.3] W. Wallace Cleland (1930-present) received his A.B. from Oberlin College in 1950 and his M.S. and Ph.D. from the University of Wisconsin-Madison in 1953 and 1955, respectively. After a postdoctoral fellowship spent at the University of Chicago he returned to Madison to join the faculty where he remains and is still actively involved in research. Cleland has devoted a great deal of time to developing and using isotope effect techniques to study enzyme mechanisms, see for example J. Biol. Chem. 278, 51975 (2003). (Photo credit Biochemistry Department, University of Wisconsin, Madison)... 

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