Density of hair

Hairy particles can be also prepared by several methods other than graft polymerization, as shown in Figure 12.2.6. This method has advantages in that it can offer a series of hairy particles having the same size core but different lengths and densities of hairs. 

Or, if a proper solvent is chosen, particulate assemblies of block copolymer can be obtained in it. They will be directly cross-linked. The length and density of hairs of particles were adjusted by postreactions. For example, long hairy particles could be converted to crew-cut particles. 

To date, Monteiro-Riviere and co-workers [60] have published the only studies using electron microscopy to examine the mechanism of iontophoretic transport. They applied mercuric chloride (7.4%) in vivo in pigs for 1 hr (current density 200 p,A/cm ) and subsequently exposed the biopsies to ammonium sulfide vapor to precipitate and localize the mercury, similar to earlier passive transport studies [28]. The micrographs revealed that mercuric chloride traverses intracellularly through the first few layers and intercellularly through the remainder of the stratum comeum. The authors concluded that the intercellular pathway is the predominant route for passive and iontophoretic drug delivery systems. However, it is difficult to eliminate follicular transport as a possible pathway, since only small areas can be examined at a time ( 1 mm ) and the low density of hair follicles (11/cm ) makes it difficult to study them with the electron microscope. 

Table 5-14 describes the describes the influence of cross-link density in different keratin fibers on diffusion rate. These data clearly show that the rate of diffusion into keratin fibers decreases with increasing cystine content and therefore with increasing cross-hnk density. One may conclude that reactions that decrease the cross-link density of hair (e.g., bleaching) will lead to hair that is more rapidly penetrated, and its penetrability will increase with increased bleaching. Decreasing cross-link density obviously increases the rate of transcellular diffusion. 

We have determined the density of human hair in solutions of benzene-carbon tetrachloride by the method of Abbott and Goodings [86]. The density of chemically unaltered hair at 60% RH varied from 1.320 to 1.327, depending on lot (dark brown European hair from DeMeo Bros., New York, and three samples taken from heads of volunteers). The density of our wool control was 1.320, identical with one lot of hair. Permanent waving did not change the density of hair. Bleaching (approximately 25% disulfide rupture) increased it, but only by 0.45%). 

Faraday s constant = /= 23,062cal (volt equivalent) Avogadro s constant = N 6.0238 x 10 molecules mole Density of hair = 1.32 gcm ... 

Testing Using Animal Skin. Human skin is unique in the thickness of its stratum corneum, density of hair follicles, and the nature of its sweat glands [77]. Pieces of skin from animals such as pigs are frequently used in testing the activity of topicals against bacteria [78], but only limited published information is available on the application of this model to viruses [26]. 

Species genotype Color of flesh Density of hairs Average fruit weight (g)... 

An attempt to forecast the further shrinkage of integrated circuits has been made by Gleason (2000). He starts out with some up-to-date statistics during the past 25 years, the number of transistors per unit area of silicon has increased by a factor of 250, and the density of circuits is now such that 20,000 cells (each with a transistor and capacitor) would fit within the cross-section of a human hair. This kind of relentless shrinkage of circuits, following an exponential time law, is known as Moore s law (Moore was one of the early captains of this industry). The question is whether the operation of Moore s Law will continue for some years yet Gleason says that attempts to forecast an end to the validity of Moore s Law have failed dismally it has continued to hold well beyond expectations . The problems at... 

Cilia are thin cylindrical hair-like structures with a cross-sectional radius of 0.1 gm projecting from the apical epithelial surface of ciliated columnar cells. Ciliary length is thought to correspond to periciliary fluid depth and range from approximately 7 gm in proximal airways to roughly 5 gm in more distal airways.- Each ciliated epithelial cell supports approximately 200 cilia at a density of eight cilia/gm. Short microvilli, possibly associated with secretory functions, are interspersed among the cilia. 

Polyvinyl chloride cylinders -1- nylon gauze -1- device for continuous water supply Soil slices at measurable distance from soil-root interface. High bulk density of soil sampled. Nutrient uptake through an induced root hairs surface. Study of rhizosphere effect over a time and distance gradient from the soil-root interface. 47, 67, 127-129... 

Mucus is cleared continuously by cilia, which extend through the periciliary fluid to hook the mucus layer. The claw-like tips of the cilia engage with the mucus layer and transport the latter toward the nasopharynx [8,9]. Cilia are complex motile structures that extend from the surface of columnar ciliated cells the number of cilia per cell is approximately 200 with a cell density of 6-8 cilia per pm2. These hair-like protrusions range in length between 5 and 10 pm and width from 0.1 to 0.3 pm. 

Also, Schmidt et al. (2005) found a significant increase in root hair density by working with Arabidopsis thaliana, which were treated with water extractable humic substances (WEHS), suggesting that these substances induce a nutrient acquisition response that favors the uptake of nutrients via an increase in the absorptive surface area. Furthermore, a phenotypical analysis of an array of mutants harbouring defects in root epidermal patterning revealed that root hair density of the ttg and gl2 mutants, defective in cell specification, was significantly modified, indicating an effect at/or downstream of the determination of the cells. 

Fig. 12.7. Scanning electron microscopy reveals details of hair fibers. Normal hairs from an adult C57BL/6J examined as a whole mount (A) illustrates density of mouse hairs and the nature of the normal skin surface. Manually plucked hairs illustrate the structural differences between some of the hair fiber types (B). Higher magnification of boxed area in B reveals the regular cuticular scale patterns on these hair fibers (C). These approaches illustrate details of hair fiber structure and density (80).

Melanin compounds may appear brown, black, or red. The type of melanin determines hair color, and the density of melanin granules determines the shade. Dark shades of dyed hair contain higher concentrations of dyes. Most hair colors are combinations of organic compounds chosen to produce particular shades. Resorcinol produces a yellow color aminohydroxy-toluene produces a redder hair, and nitrophenylenediamine dye results in very red hair. Graded dyes favored by men often contain lead acetate. The lead ions penetrate into hair and form lead sulfide (PbS), a dark-colored compound. 

The face is the most common site for cosmetic reactions, particularly in the eyelid area.4 5 9 Facial skin is highly permeable, due to a thinner stratum corneum and a greater density of appendages (e.g., sweat glands, hair follicles). Moreover, facial skin contains an elaborate network of sensory nerves. The frequency of cosmetic application is also increased at this body site. Although mild inflammatory changes are often masked on the face, in the event that eruptions do occur, they are readily noticed by the consumer. 

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