Secondary composite structure

The development of composite micro/mesoporous materials opens new perspectives for the improvement of zeolytic catalysts. These materials combine the advantages of both zeolites and mesoporous molecular sieves, in particular, strong acidity, high thermal and hydrothermal stability and improved diffusivity of bulky molecules due to reduction of the intracrystalline diffusion path length, resulting from creation of secondary mesoporous structure. It can be expected that the creation of secondary mesoporous structure in zeolitic crystals, on the one hand, will result in the improvement of the effectiveness factor in hydroisomerization process and, on the other hand, will lead to the decrease of the residence time of products and minimization of secondary reactions, such as cracking. This will result in an increase of both the conversion and the selectivity to isomerization products. 

Mesostructured materials are granules containing individual platelets (crystals) associated in a fairly random manner. This type of configuration is always associated with a bi-porous structure, in which small particles (platelets) have pores, usually mesopores, different from the composite particle (secondary mesopores and macropores). The secondary pore structure controls access to the individual crystal mesoporosity. As a result, different mass transfer resistances to diffusion through bi-porous structures could be present. In order to evaluate the relative significance of both primary and secondary pore diffusion, usually two different particle sizes are employed in diffusion measurements. 

In this study the ratio of the particle sizes was set to two based on the average value for the two samples. As a result, if the diffusion is entirely controlled by secondary pore structure (interparticle diffusion) the ratio of the effective diffusion time constants (Defl/R2) will be four. In contrast, if the mass transport process is entirely controlled by intraparticle (platelet) diffusion, the ratio will become equal to unity (diffusion independent of the composite particle size). For transient situations (in which both resistances are important) the values of the ratio will be in the one to four range. Diffusional time constants for different sorbates in the Si-MCM-41 sample were obtained from experimental ZLC response curves according to the analysis discussed in the experimental section. Experiments using different purge flow rates, as well as different purge gases... 

Figure 28-20 Composite structure representing several tRNA precursors arranged in a similar secondary structure (see also Fig. 5-30). The arrows indicate splice points. Variable positions are designated (O) for the mature tRNA and (X) for the intervening sequence and also in loops where insertions or deletions occur. From Ogden et al.603...

From the viewpoint of zootaxa, the silkworm and the spider belong to insect and arachnid of arthropod, respectively. Their silk proteins (fibroin for silkworm silk and spidroin for spider major ampullate silk) do not have any genetic heritage in common and their amino acids sequence compositions are different too. However, the silkworm and spider employ a similar spinning process to produce silk. Furthermore, the silkworm silk and the major ampullate silk have a number of similar structural characteristics, both at the level of the secondary protein structure and the condensed silk morphology. Therefore, for the sake of convenience, they are discussed together in some parts of this text. 

Catalyst activity is related to the nature, the number, the strength, and the spatial arrangement of the chemical bonds that are momentarily created between the reactants and the surface, which relies on the composition, structure, and morphology of the solid catalyst [9], In this regard, catalyst activity greatly depends on the active component, or components included in the catalyst composition. A catalyst is composed of a major active component, the proportion of which surpasses that of other components, and secondary components, which are included to improve catalyst activity, and which are called additives or, sometimes, promoters or modifiers [2,9],... 

In the early stages of bone formation, the osteons dominate the bone structure to make an overall structure of fiber-matrix composite. While the primary bone has a dense structure, the secondary bone structure is this composite. As a result, the cortical bone structure becomes very complex. It is microscopically porous, has a lamellar structure, and is also a fiber-matrix composite. Size and packing of osteons and canals, and their orientation, determine the mechanical properties of these bones. 

It was necessary to establish a methodology to predict secondary fragment hazards and fragment suppression characteristics of the composite structural steel walls of a suppressive shield (] ). 

The subject of the secondary protein structure as a means of defining the performance characteristics ofwheat endosperm-known as hardness-been explored over a seven year period [39, 40]. Another approach, taken by Baron et al., involves the IMS imaging of the endosperm cell walls rather than of the protein found in the endosperm itself [61]. All of these authors performed the imaging in situ, following removal of the protein and starch, in order to study the compositional and architectural heterogeneity and, in relation to this, wheat hardness. In this case, the research was focused on kernel hardness rather than on endosperm hardness, as was the case with our studies. A further study of carbohydrate polymers by the same group involved the investigation of cereal arabinoxylans in relation to their structure and physico-chemical properties. 

In other words, the sum of functional properties depends on the physicochemical characteristics of the whole system containing the working protein. The determinant properties of the protein itself are the amino acid composition, structure (primary, secondary, tertiary, quaternary), and conformational stability the charge of the molecule and its dimensions, shape, and topography the extent of polarity and hydrophobicity, and the nature of protein-protein interactions. 

The secondary wall found in wood cells is composed of two or three layers, known as SI, S2, and S3, respectively. In each of these layers, the cellulose microfibrils are "spirally-wound" at a different angle to the major axis of the tracheid. This variation in microfibril angle imparts strength to the fiber structure in a variety of directions. Within the bast or schlerenchyma cells found in flax, hemp, jute, and kenaf, the secondary wall is less thick than that of wood, but contains layers of similarly spirally-wound microfibrils embedded in a hemicellulose and pectin-rich matrix. This "composite structure" imparts potentially high strength to regions of the cell wall. Figures 9.1 and 9.2 show a schematic representation of flax fiber and a section of an elementary fiber with its fibrillar structure in its secondary cell wall [31]. 

Polymer composite structures used in aerospace applications require NDT at various levels depending on their designation as a primary or secondary structure. A primary structure is a structure where the failure could result in loss of the air vehicle or life and therefore usually requires 100% instrumented NDT. A secondary structure... 

The assembly of composite structural elements into a complete integrated structure will often involve bonding processes. These may be co-bonds or secondary bonds. In co-bonds, a cured composite is assembled with a film adhesive to an uncured laminate layup. The assembly is cured in an oven or autoclave. Secondary bonds are bonds between two cured laminates. The adhesive may be film or paste, and the cure may be in an oven or at room temperature. Composite repair following a damage event usually involves a co-bond by scarfing out the damage area, laying... 

Extensive usage of advanced composites has been committed to production on the Boeing aircraft family of the 757, 767, and 737. The history of Boeing s use of RPs is well documented. Applications include secondary exterior structure with functional and decorative internal... 

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