Polar surfaces, growth

Fig. 2.3 The development of polarity and asymmetric division in Saccharomyces cerevisiae. The diagram is reproduced in a slightly simplified form from the work of Lew Reed (1995) with the permission of Current Opinion in Genetics and Development, (a) The F-actin cytoskeleton strands = actin cables ( ) cortical actin patches, (b) The polarity of growth is indicated by the direction of the arrows (arrows in many directions signifies isotropic growth), (c) 10-nm filaments which are assembled to form a ring at the neck between mother and bud. (d) Construction of the cap at the pre-bud site. Notice that the proteins of the cap become dispersed at the apical/isotropic switch, first over the whole surface of the bud, then more widely. Finally, secretion becomes refocussed at the neck in time for cytokinesis, (e) The status and distribution of the nucleus and microtubules of the spindle. Notice how the spindle pole body ( ) plays an important part in orientation of the mitotic spindle.

Tolbert, M. A., and A. M. Middlebrook, Fourier Transform Infrared Studies of Model Polar Stratospheric Cloud Surfaces Growth and... 

Tolbert, M.A., and Middlebrook, A.M. (1990) Fourier Transform infrared studies of model polar stratospheric cold surfaces growth and evaporation of ice and nitric acid/ice, J. Geophys. Res. 95, 22423-22431. 

Y. Shishkin and O. Kordina, Bulk growth of 6H-SiC on non-basal quasi-polar surfaces,/. Cryst. Growth, 291, 317-319 (2006). 

The preference for similar polarities could also be attributed to similar solubilities of co-crystal formers. Most co-crystals in the CSD were prepared as single crystals grown from solution, and similar co-former solubilities make finding the right conditions for single crystal growth easier. However, the lack of correlation in descriptors usually associated with aqueous solubility (Log P, polar surface area) suggests that solubility is not the decisive factor behind the preferred similarity of polarity descriptors. 

Both n-type GaN and highly resistive GaN Mg platelets have been used as seeds for HVPE growth. The (0001) polar surfaces of the seed crystals were prepared for the growth by mechanical and chemical polishing. The n-type GaN needles were used for seeding in their as grown state. 

The ZnO film was of O polarity. The observed surface morphology was explained as follows for growth conducted on the O-polar surface, the surface diffusion length of... 

Wang, Z.L., Kong, X.Y. and Zuo, J.M. (2003) Induced growth of asymmetric nanocantilever arrays of polar surfaces. Physical Review Letters, 91, 185502. 

Calcium carbonate (calcite) scale formation in hard water can be prevented by the addition of a small amount of soluble polyphosphate in a process known as threshold treatment. The polyphosphate sorbs to the face of the calcite nuclei and further growth is blocked. Polyphosphates can also inhibit the corrosion of metals by the sorption of the phosphate onto a thin calcite film that deposits onto the metal surface. When the polyphosphate is present, a protective anodic polarization results. 

RAIRS is a non-destructive infrared technique with special versatility - it does not require the vacuum conditions essential for electron spectroscopic methods and is, therefore, in principle, applicable to the study of growth processes [4.270]. By use of a polarization modulation technique surfaces in a gas phase can be investigated. Higher surface sensitivity is achieved by modulation of the polarization between s and p. This method can also be used to discriminate between anisotropic near-sur-face absorption and isotropic absorption in the gas phase [4.271]. 

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