Inference from specimen observation

Alloy systems have been known to man since the Bronze Age. It is, however, only in recent times that they have been the subject of systematic studies, and in these studies no tool has proved more powerful than the technique of crystal structure analysis. Indeed, the extension of our knowledge and understanding of the properties of intermetallic systems to which it has given rise is one of the greatest achievements of crystal chemistry. Prior to the application of X-ray methods, the investigation of the properties of alloy systems was confined principally to observations of their behaviour in the liquid state, and the behaviour of the metal as a solid could be determined only by inference from these observations. Transitions in the solid state and the effect of mechanical or heat treatment could not, of course, be observed in this way, and for information on these properties the microscope and other purely physical methods had to be invoked. Even so, these methods were all more or less indirect, and it is only since the application of X-ray analysis that it has been possible to investigate directly in the solid state, under the precise conditions which are of technical interest and without damage to the specimen, the exact positions of all the atoms in the structure, and so to refer to their ultimate cause the physical and chemical properties of the alloy. 

Rhodium supported on y-ALOs is an important component of 3-way automotive catalysts and has been studied by a wide variety of methods [1-5] including ESR. In the last 15 years Rh-species introduced into zeolites of different types (Y, X, L, A, SAPO) have also been examined by several techniques [6-9]. However, most of these methods were applied after the specimens were removed from actual reaction conditions and transferred into the respective characterization instruments and the state or behavior of the catalyst in-situ was arrived at indirectly by inference. Also the deactivation processes or the effect of modifiers is seldom, if ever, determined by direct in-situ observations. We have previously devised a method for high-temperature measurement of ESR-active ions under flow conditions and applied it to characterize specimens containing Cu [10] or Cr " [11]. We have extended this method now to specimens containing Rh. Here, we summarize the results of a study of the interaction of Rh/y-ALOB and Rh/ZSM-5 with different gases and gas mixtures (NO, NO2, CO, propene, O2, H2O) at 120-573 °K. The amount of Rh present in the samples is evaluated quantitatively. The effect of copper and lanthanide addition on the stabilization of by the zeolitic matrix was also investigated. 

Arctic fungi seem very different from these examples, as patterns of genetic diversity described above were not observed in any of the arctic-alpine species discussed in this paper. Instead, clades inferred within each species contained specimens from distant geographic regions, and geographic population pairs... 

Captming electronic data in the field has had some important spin-off advantages that we had not initially appreciated. The most significant of these is the large volmne of observational records that we are now able to document. Common species, especially dominant trees, are often under-collected and so poorly represented in herbaria. Distribution maps produced from herbarium specimens are, thus, incomplete and do not represent the true picture (Fig 18.2A). Occurrence data can be inferred fi-om the list of associated species sometimes listed on specimen labels, but they will be scattered throughout the collections in a herbarium. Unless a herbarimn has a complete dataset of digitised label data it would be very laborious... 

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