Amorphous process selection

Availability and utilization of various analytical techniques are essential to ensure the quality of the drug product throughout the development of ASD including process selection to effectively micro-embed the amorphous dmg into the polymer matrix, downstream processing, and physical stability upon storage. 

We provide background information on past solubilization technologies and describe the attributes of HPMCAS that make it ideal for use as a dispersion polymer for SDD platform technology. Speciation theory, formulation and process selection methodology, and performance of amorphous HPMCAS-based SDDs are then described. 

The writing process, that is, the transition crystalline — amorphous, is caused by briefly (<50 100 ns) heating up the selected storage area (diameter (( )) ca 0.5—1 Hm) by a laser pulse to a temperature above the melting point of the memory layer (Eig. 15, Record), such that the film locally melts. When cooled faster than a critical quench rate (10 -10 ° K/s), the formation of crystalline nuclei is suppressed and the melted area sohdifies into the amorphous (glass-like) state. 

The laser spray process uses a high power carbon dioxide laser focused onto the surface of the part to be metallized. A carrier gas such as belium blows metal particles into the path of the laser and onto the part. The laser melted particles may fuse to the surface, or may be incorporated into an aHoy in a molten surface up to 1-mm thick. The laser can be used for selective aHoying of the surface, for production of amorphous coatings, or for laser hardening. 

Activated carbon is an amorphous solid with a large internal surface area/pore strucmre that adsorbs molecules from both the liquid and gas phase [11]. It has been manufactured from a number of raw materials mcluding wood, coconut shell, and coal [11,12]. Specific processes have been developed to produce activated carbon in powdered, granular, and specially shaped (pellet) forms. The key to development of activated carbon products has been the selection of the manufacturing process, raw material, and an understanding of the basic adsorption process to tailor the product to a specific adsorption application. 

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by synthetic amorphous silica-alumina, which is more active and stable. Incorporating zeolites (crystalline alumina-silica) with the silica/alumina catalyst improves selectivity towards aromatics. These catalysts have both Fewis and Bronsted acid sites that promote carbonium ion formation. An important structural feature of zeolites is the presence of holes in the crystal lattice, which are formed by the silica-alumina tetrahedra. Each tetrahedron is made of four oxygen anions with either an aluminum or a silicon cation in the center. Each oxygen anion with a -2 oxidation state is shared between either two silicon, two aluminum, or an aluminum and a silicon cation. 

Fig. 4 shows the SEM images of SWNTs purified by the thermal oxidation and acid-treated. Fig. 4(a) shows a SEM image of the raw soot. In addition to the bundle of SWNTs, carbonaceous particles are shown in the figure. These stractural features mi t be causal by various in the arcing process because of an inhomogeneous distribution of catalysts in the anodes [7]. It can be seen that the appearance of SWNTs was curled and quite different fiom that of MWNTs. Fig. 4(b) shows a decrease of amorphous carbons after oxidation. The basic idea of the selective etching is that amorphous carbons can be etched away more easily than SWNTs due to the faster oxidation reaction rate [2]. Since the CNTs are etched away at the same time, the yield is usually low. The transition metals can be etched away by an add treatment. Fig. 4(c) shows the SEM image of the acid-treated sample, where the annealed sample was immersed in 10 % HCl. 

Although cracking also occurs on chlorine-treated clays and amorphous silica-aluminas, the application of zeolites has resulted in a significant improvement in gasoline yield. The finite size of the zeolite micropores prohibits the formation of large condensed aromatic molecules. This beneficial shape-selectivity improves the carbon efficiency of the process and also the lifetime of the catalyst. 

Biomineralization. The processes controlling biomineralization are summarized in Fig. 6.1c. Organized biopolymers at the sites of mineralization are essential to these processes. In unicellular organisms these macromolecules act primarily as spatial boundaries through which ions are selectively transported to produce localized supersaturation within discrete cellular compartments. In many instances, particularity in organisms such as the diatoms that deposit shells of amorphous silica, the final shape of the mineral appears to be dictated by the ultrastrucure of the membrane-bound compartment. Thus, a diversity of mineral shapes can be biologi-... 

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