Air structure

The effects of dispersion and birefringence on stellar interferometry will be discussed in Sections 17.2.3 and 17.2.4. New kind of fibres has been design to manage the dispersion properties using a silica / air structure. These fibres, so called Photonic Crystal Fibres, are very promising for many applications (Peyrilloux et al., 2002). 

The compounds of these ligands,89 especially those of imidazole, have been more effectively studied than those of the more classical ligands, i.e. pyridine and ammonia. The biological role of imidazole moieties as donors has given impetus to these studies in the 1970s, and the compounds are generally more robust in the air and at ambient temperature, although some are still unstable, especially with respect to oxidation in moist air. Structural data are more complete more full X-ray determinations are available, and nearly maximum use has been made of X-ray powder data, especially by Reedijk and co-workers,90 for comparison with other species of known structure. 

Figure 6.2 Thin section transmission electron micrograph of the structure of ice cream at high magnification, showmg fat droplets (marked f) and casein micelles (c) (Reprinted from A Study of Fat and Air Structures in Ice cream , Copyright 1999, with permission from Elsevier (the scale bar is 1 pm))...

The bisraethano[16]annulene forms golden brown needles which are stable in air. Structure (A) is probably favoured thermodynamically. Its n.m.r. spectrum implies that it is the sj/w-isomer and that it is paratropic [197]. It can be reduced to a dianion [197]. 

Another new low temperature method for the synthesis of PbTe has been reported. In this method NaOH dissolved in distilled water and heated to 80 °C to which tellurium and Na2HP04 was added. On turning purple-black the solution was added with lead acetate trihydrate aqueous solution in drops and heated at 110 °C. The obtained black precipitate was cooled to room temperature, washed with distilled water, acetone and ethanol and dried in air. Structural analyses indicate that sharp microneedle like crystals of the size 2 pm with 90-130 nm diameter. 

Jes Broeng, Stig E. Barkou, Anders Bjarklev, Jonathan C. Knight, Tim A. Birks, and Philip St. J. Russell Highly increased photonic band gaps in silica/air structures. Opt. Commn., 156(4-6), (1998) 240-244... 

---