Oriental pearls

Natural or oriental pearls are produced naturally by bivalves, such as oysters and clams, and by a few gastropods, such as abalone. Cultured pearls are induced by the introduction of foreign objects into the mantle cavity. Modem cultured pearls are usually seeded with a sphere made from the shell of Mississippi River mussels (family Unionidae). The culturing process involves prying open the shell and inserting both the seed or nucleus that will become the core of the new pearl, and a piece of donated mande tissue from another oyster. 

Dirix, Y., Bastiaansen, C., Caseri, W., and Smith, R, Oriented pearl-necklace arrays of metallic nanoparticles in polymers a new route toward polarization-dependent color filters, Adv. Mater, 11, 223-227 (1999a). 

Different topologies can result in the preparation of polymer-embedded metal clusters. To prepare materials characterized by the properties of surface atoms or with characteristics coming from the confinement effect, a contact-free dispersion of clusters must result in the polymer matrix, since only in this case the large amount of surface atoms present allows the surface properties of matter to prevail on that of bulk. Both regular (eg, imiaxially oriented pearl-necklace type of arrays of nanoparticles) and irregular metal cluster distributions are used in technological applications. 

The liquid drops of tears that you have shed Shall come again, transformed to orient pearl,... 

Y. Dirix, C. Bastiaansen, W. Caseri and P. Smith, Oriented pearl-necklace arrays of metallic nanoparticles... 

Pearlescent pigments give rise to a white pearl effect often accompanied by a coloured iridescence. The most important pearlescent pigments consist of thin platelets of mica coated with titanium dioxide which partly reflect and partly transmit incident light. Simultaneous reflection from many layers of oriented platelets creates the sense of depth which is characteristic of pearlescent lustre and, where the particles are of an appropriate thickness, colours are produced by interference phenomena. Pearlescent pigments are used in automotive finishes, plastics and cosmetics. 

Figure 71. Optical principles of conventional and luster pigments A) Conventional pigment that absorbs and scatters light B) Metal effect pigment with complete regular reflection C) Natural pearl composed of alternating layers of protein and CaC03 D) Nacreous pigment the pearl is simulated by parallel orientation of the pigment platelets...

Natural pearl essence (Essence d Oriente, Fish Silver) is a pigment suspension derived from fish scales, skin, or bladder. It is the oldest commercial pearl luster pigment, consisting mainly of a mixture of the purines guanine [73-40-5] (75-97%) and hypoxanthine [68-94-0] (25-3%). 

Table VI summarizes observed manifestations of field-generated forces- The field effects may manifest themselves as an orientation of particles in the direction of the field or perpendicular to it or, "pearl chain" formation, i.e., the alignment of particles in the field direction may occur. This has long been considered a mysterious demonstration of microwave induced biological effects. Deformation or destruction of cells can be achieved with fields. The movement of cells in inhomogeneous electrical fields can be affected.

It is this ability to secrete the organic and inorganic compounds that make up the shell, which gives the mollusc the ability to secrete the same substances to produce pearls. All pearls consist of approximately 90 per cent calcium carbonate, plus water, and an organic matrix. As with the nacreous inner layer of the shell, the calcium carbonate in pearls fbnns as aragonite platelets and gives the pearl its nacreous lustre (sometimes called orient ). 

By, A., Ethier, J.C., Lauriault, G., LeBelle, M., Lodge, B.A., Savard, C., Sy, W.-W. and Wilson, W.L. (1989) Traditional oriental medicines I. Black Pearl identification and chromatographic determination of some undeclared medicinal ingredients. J. Chromatogr. 469, 406-411. 

When a DC pulse is applied to a couple of fluid-phase vesicles, which are in contact and oriented in the direction of the field, electrofusion can be observed. Vesicle orientation (and even alignment into pearl chains) can be achieved by application of an AC field to a vesicle suspension. This phenomenon is also observed with cells [164, 165] and is due to dielectric screening of the field. When the suspension is dilute, two vesicles can be brought together via the AC field and aligned. A subsequent application of a DC pulse to such a vesicle couple can lead to fusion. The necessary condition is that poration is induced in the contact area between the two vesicles. The possible steps of the electrofusion of two membranes are schematically illustrated in Figure 7.8a. In Sections 7.5.2.1 and 7.5.2.2, consideration will be given to the fusion of vesicles with different membrane composition or different composition of the enclosed solutions. 

The mixture was subjected to B = 400 mT uniform magnetic field. The imposed field orients the magnetic dipoles and if the particles are spaced closely enough, mutual particle interactions occur. Due to the attractive forces, a pearl chain structure develops as shown in Fig. 5. This phenomenon is called the magneto-rheological effect [53,55,57]. 

Pearls from the Golden Cabinet, Subhuti Dharmananda, Oriental Healing Arts Institute, Long Beach, CA, 1988... 

When a very narrow X-ray beam (with a spread of wavelengths) is directed on the center of a genuine pearl, all the crystallites are irradiated parallel to a trigonal axis and the result is a Laue photograph with 6-fold symmetry. In a cultured pearl the narrow beam will have an arbitrary orientation with respect to the crystallite axes (of the central core) and an unsymmetrical Laue photograph will result. (See J. Bijvoet et al., X-ray Analysis of Crystals. Butterworth (1951).)... 

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