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Robert Burns Woodward is considered one of the greatest synthetic organic chemists of our time, if not the greatest. This article presents evidence that Woodward was also one of the greatest physical organic chemists as well. Among Woodward and his collaborators' most important accomplishments in the field of physical organic chemistry are: the Woodward–Hoffmann rules; the derivation and use of structure–mechanism–reactivity relationships in his multifold structure determinations and total syntheses; the Woodward ultraviolet rules and the Octant Rule; and his early demonstration that synthetic organic chemistry can contribute to the synthesis of potential superconductors and thus, to material science. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

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During the last decade the term ‘spin glass’ has become prominent in the literature on magnetism. It refers to magnetic alloys where the spins on the impurities become locked or frozen into random orientations below a characteristic temperature T 0. In this article the properties of spin glasses are described with particular reference to the two archetypal examples AuFe and CuMn. Interest in spin glasses was mainly stimulated by some a.c. susceptibility measurements which showed sharp, cusp-like peaks, accurately defining T 0 and suggesting that some type of phase transition was occurring. The Mossbauer effect and the anomalous Hall effect also showed clear features at T 0 supporting this viewpoint. But measurements of the electrical resistivity and ‘specific heat’, here usually meaning the molar heat capacity, also the remanence, magnetic hysteresis and time-dependent effects observed in spin glasses were difficult to reconcile with a phase transition approach. This article discusses the results obtained from the very wide variety of experimental techniques which have been used to investigate spin glasses, and also deals with some of the important theoretical concepts which have arisen out of these studies. Then follows a short account of the many systems which have been found to exhibit spin glass behaviour and which suggest that it is a widespread magnetic state of matter. Lastly, an example is given which shows that some of the ideas of spin glasses are applicable to problems outside the sphere of magnetic alloys.  相似文献   

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This article describes the scientific objectives, the scientific and operational plans and the observational programme of the international Atlantic Tropical Experiment in which some 70 countries pclrticipated during Jun-September 1974. The main aim waa to make, for the first time, an intensive study of the structure, evolution and transport properties of tropical weather systems and their role in the global circulation of the atmosphere as a whole. Some preliminary results are described but it will be two or three years before the vast mass of data is fully processed and analysed and made available in the form of validated data sets for detailed researoh studies and for input to numerical models. However, there is already good reason to believe that the major scientific objectives of the experiment will be achieved and that the knowledge gained will lead to improved weather forecasting both in the tropics, and in middle latitudes where accurate predictions for more than about three days ahead may not be possible without taking into account the import of heat and moiature from the tropical oceans through the large convective clouds of the tropical atmosphere.  相似文献   

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Relativistic electrons undergoing centripetal acceleration in a synchrotron emit a highly collimated forward cone of continuous radiation. The continuum extends from the extreme ultraviolet to the radiofrequency region for electrons of GeV energies and is very suitable for absorption spectroscopy in the region of the ultraviolet extending from a few tens of ågströms to 2000 Å. This paper discusses some properties of synchrotron radiation of interest to spectroscopists and some experimental difficulties associated with ultraviolet spectroscopy. Examples we given of ultraviolet spectra of free atoms and molecules and also of solids obtained recently with synchrotron radiation.  相似文献   

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