Sextants

Stamey, T. A. 1995. Making the most out of six systematic sextant biopsies. Urology 45 2-12. 

We made a crude but adequate sextant out of two mirrors and I bought a book about navigation. Using these and a World Almanac we can tell from the sun or the stars exactly where we are on the sea. It s fascinating business and makes the trip more interesting. 

Prior to the development of electronic instruments such as radio, radar, and Global Positioning System (GPS), the determination of one s position was accomplished using a sextant. The sextant was able to pinpoint one s location accurately by measuring the angular distance between the horizon and a celestial object. Repeated sightings were plotted on a nautical chart. This method was suitable for ships and propeller aircraft. 

Nautical sextant (John Campbell) When used with celestial tables, Campbell s sextant allows ships to navigate to within sight of their destinations. 

Octahedral interstices (holes or gaps) are formed in between the center of the base, two vertices and two inner particles, in the unfilled sextants with inner particles, see Figure 4.21 (Chiriac-Putz-Chiriac, 2005). 

Worth remarking how, although none of octahedral holes formed do not completely belong to compact cell, since closing outside of the elementary cell, yet, due to the fact that the same effect appears to all elementary cells, in the global network, what a cell lose from a hole to a neighboring cell wins from another on the distance of the opposite sextant. 

Stoumbakis, N., Cookson, M.S., Reuter, V.E. and Fair, W.R. (1997) Clinical significance of repeat sextant biopsies in prostate cancer patients. Urology, 49 (3A Suppl), 113-8. 

Fig. 8.3. Benzene ring carbon-carbon vibrations. The 1588, 1486, 608, and 404 cm" modes are doubly degenerate in benzene. For descriptive purposes the stretching vibrations are described as whole ring stretching, semicircle stretching, quadrant stretching, and sextant stretching. The in-plane and out-of-plane bendings are described as quadrant and sextant bending.

The 700 cm band involves out-of-plane ring bending by sextants. In mono, meta, and 1,3,5 trisubstitution a prominent IR band appears at 710-665 cm" which is absent or weak in the Raman spectrum. This mode is illustrated in Fig. 8.5 where it can be seen that the 1,3, and 5 ring carbons move oppositely from the 2,4, and 6 ring carbons, out of the ring plane. 

Fig. 8.5. The out-of-plane sextant ring bend vibration in mono, ortho, meta, and para-substituted benzenes. The 1,3,5 ring carbons and the 2,4,6 ring carbons move oppositely out of the plane (+ and —). In mono, meta, and 1,3,5 trisubstituted benzenes, the vibration is IR active at 710-665 cm . When the substituents are identical in ortho and para isomers, this band is infrared inactive.

In-Phase, Out-of-Plane Hydrogen Wagging and Out-of-Plane Sextant Ring Bending Frequencies (in cm )... 

The spectra of 1,3,5-5-triazines show absorption in three main regions, 1550 cm ( quadrant stretching ), 1420 cm ( semicircle stretching ), and 800 cm (out-of-plane ring bending by sextants... 

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