Mechanical stages

Microchemical or ultramicrochemical techniques are used extensively ia chemical studies of actinide elements (16). If extremely small volumes are used, microgram or lesser quantities of material can give relatively high concentrations in solution. Balances of sufficient sensitivity have been developed for quantitative measurements with these minute quantities of material. Since the amounts of material involved are too small to be seen with the unaided eye, the actual chemical work is usually done on the mechanical stage of a microscope, where all of the essential apparatus is in view. Compounds prepared on such a small scale are often identified by x-ray crystallographic methods. 

Kreuz-stein, m. cross-stone (chiastolite, harmo-tome, staurolite). -attick,n. crosspiece fourway cross(piece). -tisch, m. (Micros.) mechanical stage. 

Figure 13.8. Images of an automated mechanical stage used for transfer printing.

Figure 13.14. Bending tests on three-layer stacks of Si, GaN, and SWNT devices supported by a plastic substrate, (a) Images of the automated mechanical stages used to bend the system, (b) Normalized transconductances (gm/gom) of devices in each layer after bending (to a 3.7-mm radius) and unbending (to a flat state) the devices several thousand times, (squares ps-Si MOSFETs circles SWNT TFTs triangles ps-GaN HEMTs.) (Reprinted with permission from Ref. 42. Copyright 2006 American Association for the Advancement of Science.)...

It is impossible to deflect an electron beam to cover an entire 3-to-4 inch diameter silicon wafer or mask substrate hence mechanical stages are required to move the substrate through the deflection field of the electron... 

Place the sample on a clean, dust-free microscope slide mounted on the mechanical stage of the microscope, aligned so that the ink marks are parallel to one axis of the stage. 

Shift the mechanical stage until each of the ink marks coincides with the ocular cross hair. 

Record both positions by reading the mechanical stage scale and vernier. 

The gas-pressure tuning interferometer was used in the experiments described in Section 7.3.2. The mechanical stage type was used in the experiment described in Sections 7.3.3 and 7.4.2. The piezo type was used in the experiment described in Section 7.4.1. It should be noted that the mechanical stage and the piezo types are not installed in a vacuum chamber. 

The second stage is the formation of a new enolate on the other side of the ketone from the first. Note that the original enolate, the intermediate in the conjugate addition, can cyclize to give only an unstable four-membered ring so this cyclization would be reversible, The next intermediate, the aldol product, is often isolated from Robinson annelations, the Robinson annelation mechanism—stage 2 the intramolecular aldol reaction... 

The find stage is dehydration of the aldol and an ElcB reaction that involves the carbonyi group sa in a standard aldol reaction (Chapter 27). Another enolate must form In the same position as the last, the Robinson anneletlon mechanism—stage 3t the ElcB dehydration... 

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