Universal stage

Figure 48.2 shows that a compares the ratio of atom or ion abundances for two isotopes in each of two samples. If a is not equal to 1, then the isotopes in one sample must have a different ratio from those in the other. If isotopes behave chemically almost identically on a universal stage,... 

Spindle stages and universal stages allow a sample to be placed in any orientation relative to the microscope s optical axis. 

Investigations of the interference figures may be performed with a polarizing microscope equipped with a four-axis universal stage. Normally, for polarizing microscope measurements, transparent crystal thin sections... 

C. J. Langway, Lee fabrics and the universal stage, Technical Report 62, U. S. Army snow ice and permafrost research establishment, Wilmette, II, 1958. Special thanks for assistance with the Rigsby stage from Rachel Obbard, Dartmouth College. 

Deformation by intracrystalline slip and dynamic reaystallization. These are important mechanisms for the development of crystallographic preferred orientation (CPO) and property anisotropy. Slip bands associated with intracrystalline flow may easily be seen in optical reflection microscopy of previously flattened and polished surfaces of specimens that are subsequently deformed as described above. CPO developments are less easily demonstrated, because it required the making of thin sections of deformed ice and the use of a simple universal stage to determine the orientation of the crystallographic c axis. 

Confocal laser scanning microscopy. A laser scanning confocal microscope system was used to analyze the microstructure of the fdm components and films A model IRBE (inverted) microscope (Leica Microsystems, Bannockburn, IL) with a universal stage and 20X objective lens was coupled to a TCS NT/SP scanner head (Leica Microsystems, Exton, PA). Sheets of samples or powders in MatTek dishes (MatTek Corp., Ashland, MA) were illuminated with the 488 nm line of an Argon laser and fluorescence was collected in one channel (520-580 nm) and reflection at 488 nm was collected in another. Fluorescence emission spectra for the sample powders of SFP and Pectin were collected in the range of 500-680 nm. 

Conodont elements were extracted from the host rock using standard acid dissolution techniques (see Stone, 1987, for a review). The elements were placed in 10-well black-field slides, one element to a well. This ensured that each element could be easily relocated. Elements were photographed on the slide. The measurements taken were insensitive to orientation within the x-y plane of the slide. Orientation of this plane with respect to the z-axis did, however, have an effect on the measurements and so was kept as constant as possible through use of a universal stage, which allows independent tilting of the x-y plane. This stage is more sophisticated than Barnett s (1970) design and allows finer control of specimen orientation. 

This suffices to show, for the purpose of the present chapter, that the optics of feldspars can yield information of considerable importance, provided the investigator has a substantial degree of experience and is skillful with the petrological microscope, including the use of universal stage techniques. For a detailed account of the considerable volume of recent work in this field, the reader should consult Deer et al. [1963, vol. IV] or similar books. As a final warning for the soils investigator, it should be noted... 

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