Shape aggregation

Many industrial semi-crystalline polymer materials like polypropylene, polyamides, or polyesters contain nucleating agents or clarifiers which form needle-shaped aggregates already in the polymer melt. "For this purpose the pattern is desmeared using the measured primary beam. For a less involved treatment it may be sufficient to know the integral width of the primary beam profile in fiber direction. 

In infected cells, fungal prion proteins are aggregated. This property has been demonstrated in experiments in which the prion protein was fused with green fluorescent protein (GFP). In wild-type cells, fluorescence was homogeneously distributed throughout the cytoplasm while in cells exhibiting the prion phenotype, it was concentrated in discrete spots and/or variably shaped aggregates (Fig. 4 Coustou-Linares et al, 2001 ... 

Pharmacological strategy of CNTs generally relies on four main critical issues (1) preparation of nanovectors, (2) uptake, (3) function, and (4) elimination (Fig. 12.4). The physicochemical characteristics of CNTs including size, shape, aggregation, chemical composition, surface functionalization, and solubility play an important role in the biodistribution and pharmacokinetics of nanomaterials (Champion et al., 2007 Kostarelos, 2003 Lacerda et al., 2006 Nishiyama, 2007 Oberdorster et al., 2005 Radomski et al., 2005)... 

Pressure cycling high hydrostatic pressure (e.g., 500 Mpa) induces disintegration of casein micelles and reassociation on pressure reduction Hydrophobic casein particles, formed under pressure, reassociate into smaller and more irregularly shaped aggregates Dickinson 2006a... 

Ion-pairing between the paramagnetic [Co(tdt)2] monoanion and nine different cations was examined by Tsao and Lim.105 The cations belong to either of two classes, quaternary ammonium or substituted V-octylpyridinium ions. By recording the H NMR spectra as a function of concentration (nitrobenzene, 307 K), the concentration association constants (Kas) were obtained. Substituent effects were found to influence the ion-pair geometry, as deduced from the isotropic shifts of the cationic protons and their shift ratios. In low dielectric constant solvents, speculation consistent with the magnetic anisotropy and the relation between the cationic proton shifts and concentration was tendered for cylindrically shaped aggregates. 

The rod-shaped aggregates, 2 E, also have inner, lipophilic and outer, polar regions with the polar groups directed outwards. Usually the lattices are hexagonally arranged, but more complicated configurations have been encountered. 

In two-component systems of association of colloid and water the sequence of phases, as the water content decreases, is micellar solution - hexagonally packed polar rods complex phases with rod-shaped aggregates lamellar mesophase D - crystalline surfactant. Some of these steps may be absent, depending, for example, on the temperature. 

It should also be noted that the viscometric technique can detect the presence of star-shaped aggregates, having the ionic active centers. The addition of ethylene oxide to hydrocarbon solutions of poly(isoprenyl)lithium leads to a nearly two-fold increase in viscosity144). Conversely, this results in an approximately twenty-fold decrease in solution viscosity, after termination by the addition of trimethylchloro-silane. This change in solution viscosity is reflected in the gelation which occurs when difunctional chains are converted to the ionic alkoxy active centers 140,145,146). Branched structures have also been detected 147> by viscometry for the thiolate-lithium active center of polypropylene sulfide) in tetrahydrofuran. 

Fig. 12 Neat melamine Hekates 40, their 1 1 host-guest complexes 41,42 and the 1 3 aggregates of a melamine core with three arms 43 and 44. The disk-shaped aggregates 41 stack in a Colrd phase [99]. The Janus-type Hekate 42 arrange in a Colh phase with hexagonal superstructure of the nanosegregated semi-perfluorinated chains [105]. The supramolecular Hekate discs 43-45 self-assemble by hydrogen bonding of the three arms around a melamine core...

The analysis of the first effect can be made by comparing a spherical and an infinite rod-shaped aggregate with the same radius, surface charge density and amphiphile concentration. The infinite rod really corresponds to the condition in thenor-... 

Symbol Aggregate shape Aggregate - cement ratio water cement ratio Fines content % Fines ione... 

The primary particles are solid, smooth surfaced spheres which are clustered into irregular shaped aggregates with a typical mean particle size of 40-50 pm with a range of 0.1-100 pm. 

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