Rodlike particles

My original plan had been to develop theories for mixtures of liquid crystals with other materials, such as semiflexible polymers, spherical particles, rodlike polymers, nanotubes, surfactant molecules, or membranes. Currently, in 2011, the theoretical studies of the liquid crystal composites are almost completed up to nanotubes. Of course, there are various problems unresolved and it is likely to take about ten more years. 

FIG. 12 A colloidal suspension of rodlike particles. The orientations of the rods are uniformly distributed. 

Separation of colloids by GPC is an important technical advance that may help in the characterization of novel materials. One such separation was the shape separation of gold particles of nanometer size by GPC on a Nucleogel GFC 1000-8 column using sodium dodecyl sulfate and Brij-35 [polyoxyethylene (23) dodecanol] to modulate the adsorption properties of the colloidal gold.42 Rodlike and spherical particles were separated using UV-VIS detection. 

Completely different mechanisms are involved in the self-assembly of the tobacco mosaic virus (TMV). This virus consists of single-strand RNA, which is surrounded by 2,130 identical protein units, each of which consists of 158 amino acid residues. A virus particle, which requires the tobacco plant as a host, has a rodlike structure with helical symmetry ( Stanley needles ). It is 300 nm long, with a diameter of 18nm. The protein and RNA fractions can be separated, and the viral... 

Columnar Rodlike particle, having a width and thickness exceeding that of a needle-type particle. The term prismatic may also be used. 

Nevertheless, the oxalate coprecipitation method has some problems. For example, this method usually results in rodlike doped ceria particles, which are agglomerations of smaller particles with irregular shapes. Hence, the green density of the compact body is relatively low, so it is difficult to fabricate a dense electrolyte film or membrane. In addition, the poor flow of the rodlike powder makes forming difficult. 

We have used the procedure of Marcelja et al (22) to compute r for spherical molecules with the same charge and volume as 200 bp rodlike DNA. Each molecule is at the center of a Wigner-Seitz cell of volume (4/3)with bulk salt concentrations spanning the experimental range (2). The nonlinear Poisson-Boltzmann e( uation is solved numerically with appropriate boundary conditions at the particle surface and the cell boundary. The results are that F = 155 at about 3 mg/mL DNA (twice the experimental concentration) with no added salt, but F is always < 155 for added salt in the experimental range. For NaPSS, with dp 3800 at 1-4 X 10 mg/mL, F > 300, consistent with the observation of a structure factor maximum. 

Hsu et al. (12) prepared rodlike basic cerium(lV) sulfate particles of 1-3 p,m in length from dilute solutions of Ce(S04)2 in acidic media at 90°C (see Fig. 5.1.4). When the concentration of SO42- is lowered, monodispersed polycrystalline spherical particles of Ce02 are obtained under similar conditions. Figure 5.1.5 shows the precipitation domains of the respective species at 90°C for 12 h. Even for the forma-... 

Fig. 5.1.4 (A) TEM and (B) SEM of rodlike particles of basic cerium sulfate prepared by...

Fig. 9.23 SEM images of monodisperse silver powders obtained by reduction of AgNOj in ethylene glycol in the presence of PVP (a) quasi-spherical particles obtained by spontaneous nucleation (dm = 0.64 pun, cr = 0.13 p.m) (b) rodlike particles obtained by heterogeneous nucleation using H2PtCl6 as nucleating agent (particle dimensions 3 xm long and 0.3 xm thick). (From Ref. 13.)...

In the second half of this article, we discuss dynamic properties of stiff-chain liquid-crystalline polymers in solution. If the position and orientation of a stiff or semiflexible chain in a solution is specified by its center of mass and end-to-end vector, respectively, the translational and rotational motions of the whole chain can be described in terms of the time-dependent single-particle distribution function f(r, a t), where r and a are the position vector of the center of mass and the unit vector parallel to the end-to-end vector of the chain, respectively, and t is time, (a should be distinguished from the unit tangent vector to the chain contour appearing in the previous sections, except for rodlike polymers.) Since this distribution function cannot describe internal motions of the chain, our discussion below is restricted to such global chain dynamics as translational and rotational diffusion and zero-shear viscosity. 

FIG. 1.14 Model particles of different shapes with the same or different chemical compositions (a) rodlike particles of akageneite (/3-FeOOH) (b) ellipsoidal particles of hematite (a-Fe203) (c) cubic particles of hematite and (d) rodlike particles of mixed chemical composition (a-Fe203 and /3-FeOOH). All are TEM pictures. (Reprinted with permission of Matijevic 1993.)... 

Green sulfur and nonsulfur bacteria. In these organisms chlorophylls are present in rodlike particles... 

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