Various Types Of Pores Research Articles

Porous carriers for controlled/modulated drug delivery.

Considerable research efforts have been directed in recent years towards the development of porous carriers as controlled drug delivery matrices because of possessing several features such as stable uniform porous structure, high surface area, tunable pore size and well-defined surface properties. Owing to wide range of useful properties porous carriers have been used in pharmaceuticals for many purposes including development of floating drug delivery systems, sustained drug delivery systems. Various types of pores like open, closed, transport and blind pores in the porous solid allow them to adsorb drugs and release them in a more reproducible and predictable manner. Pharmaceutically exploited porous adsorbents includes, silica (mesoporous), ethylene vinyl acetate (macroporous), polypropylene foam powder (microporous), titanium dioxide (nanoporous). When porous polymeric drug delivery system is placed in contact with appropriate dissolution medium, release of drug to medium must be preceded by the drug dissolution in the water filled pores or from surface and by diffusion through the water filled channels. The porous carriers are used to improve the oral bioavailability of poorly water soluble drugs, to increase the dissolution of relatively insoluble powders and conversion of crystalline state to amorphous state.

Macroscopic Properties of Inhomogeneous Material with Randomly Distributed Pores

Porous materials such as engineering ceramics and metal foams have a specific feature such that internal structure has a significant influence on the mechanical properties from the viewpoint of porosity and morphology. This paper discusses the relationship between microscopic morphology and macroscopic properties of the porous materials based on the homogenization technique, in which pores are randomly distributed over the domain. Various types of pores are examined and the conjunction between different elemental types is discussed. A wide range of porosity is covered from a low porosity of 5% such as engineering ceramics to 80% of foam-like materials within the same numerical strategy. It is found that the macroscopic property with low porosity shows good agreement with both experimental curve and micromechanics prediction, in which the elasticity coefficient is affected by morphology of internal structure. In contrast with the low porosity, the morphology effect diminishes and is hardly observed in high porosity region where the macroscopic stiffness is almost linear on the porosity.

Mechanism of Beautifulness of Hair and the Structure Factors

The mechanisms of beautifulness of Japanese black and brown hairs, the structure factors influencing on appearance, and technologies to develop hair shine and vividness of color are reviewed. Various types of pores in each part of the fiber generated by hair damage cause light scattering, which leads to loosing hair shine. Pore fixation technology using aqueous malic acid solution was found effective to reduce light scattering due to swelling ability of the organic acid. Furthermore, the novel chroma enhancement technology with using only shampoo and conditioner is reviewed. Fibers with surface structures having fine concaves and convexes show developing vividness in color. The mechanism of the color enhancement was explained by approximation theory of effective media, by which the refractive index of the treated fiber surfaces was estimated to be less than 1.3.

Methanol steam reforming over paper-like composites of Cu/ZnO catalyst and ceramic fiber

Copper–zinc oxide catalyst powders were successfully prepared into paper-like composites, called catalyst paper in this study, using ceramic fibers as the carrier matrix of the catalyst. A papermaking technique with a dual polyelectrolyte retention system was used. Catalyst particles were supported on the ceramic fiber networks tailored in the catalyst paper having various types of pores. Pieces of catalyst paper were subjected to methanol steam reforming (MSR) to produce hydrogen gas for fuel cell applications. They demonstrated a higher performance for methanol conversion and hydrogen production in the MSR reaction than commercial Cu/ZnO catalyst pellets, exhibiting an efficacy equivalent to that of the original catalyst powders. The concentration of carbon monoxide, which acts as a catalytic poison for fuel electrode catalysts, decreased remarkably, without any carbon monoxide reduction system. Moreover, the porous structure of catalyst paper influenced the MSR efficiency. It was assumed that the macropores ca. 20 μm in diameter greatly contributed to the MSR performance, rather than the mesopores on the catalyst surfaces. Thus, the porous, flexible and easy-to-handle catalyst paper is a promising material for practical MSR applications.

Characterization of Microporosity in Ordered Mesoporous Material MAS-7 by 129Xe NMR Spectroscopy

A new kind of ordered mesoporous aluminosilicate material MAS-7, containing micropores inside its pore walls, has been investigated by 129Xe NMR spectroscopy as a function of xenon pressure over a wide range of temperatures. 129Xe NMR results reveal that two different independent micropore systems are present in the mesoporous walls of MAS-7. Two signals are observed in the 129Xe NMR spectra, which can be attributed to two kinds of fast exchange of xenon atoms in the two different types of micropores (micropores I and II) with those in the mesopores and in the interparticle space of MAS-7. Coadsorption experiments of xenon and guest molecules with different sizes provide an estimation of the sizes of micropores in MAS-7. Micropore I has a diameter of ca. 0.74 nm, which is most likely formed by the primary structure units of zeolite beta. Micropore II possesses a relatively small pore diameter of 0.44−0.49 nm, which may be generated from partial occlusion of triblock polymer (template used in the synthesis of MAS-7) chains into the mesoporous walls of MAS-7. The details of xenon adsorption and motion are also thoroughly studied by variable-temperature (VT) 129Xe NMR experiments. The VT 129Xe NMR experiments suggest that even bulk (solid or liquid) xenon atoms probably formed on the mesoporous wall still undergo fast exchange with xenon in the other adsorption states (such as xenon in the micropores) at 124 K, indicating there is a good communication among the various types of pores in MAS-7.

Occurrence of Pore-Filling Halite in Carbonate Rocks, Nesson Anticline, Williston Basin, North Dakota: ABSTRACT

Clear, colorless pore-filling halite of late diagenetic origin occurs locally in the Devonian Dawson Bay, Winnipegosis, and Ashern Formations, the Silurian Interlake Formation, and the Ordovician Red River Formation. The halite occludes a variety of pore types and individual pores are filled with single crystals or aggregates of only a few crystals. This halite is present in quantities ranging from a trace to approximately 12%. Cores from McGregor field, Williams County, show the Winnipegosis Formation consists of mixed-skeletal lime wackestones and mudstones. These contain vugs up to 4 in. (10 cm) in size, intraparticle pores, and shelter porosity within pelecypod shells, up to 4 in. (10 cm) in size, which are occluded with halite. Halite also fills common small discontinuous vertical fractures. The upper 200 ft (61 m) of the Interlake Formation locally exhibits the most striking occurrences of pore-filling halite. These dolostones consist predominantly of intraclast-peloid mudstones, wackestones, packstones, occasional grainstones, algal boundstones, and solution-collapse breccias containing vug, fenestral, interparticle, shelter, intercrystalline, moldic, channel, breccia, and fracture porosity types. All porosity types, except intercrystalline, can be halite filled. A rare occurrence of pore-filling halite exists in Red River cores from Blue Buttes field, McKenzie County, where a dolomitic, mixed-skeletal, more » lime mudstone and wackestone lithofacies contains vugs, discontinuous vertical fractures, and intraparticle porosity types occluded with halite. In most occurrences, the pore systems were noneffective prior to halite infilling and had no potential as hydrocarbon reservoirs. However, it has been demonstrated that halite plugging in the Interlake Formation has locally formed updip seals to hydrocarbon migration. « less

Carbonate Pore Systems: Porosity/Permeability Relationships and Geologic Analysis: ABSTRACT

The porosity/permeability relationships of the common carbonate rock types have been studied, with emphasis on the variety of pore types in upward-shoaling grainstone sequences including: Smackover, Lansing, Salem, and San Andres Formations. A result of these studies is an improved conceptual understanding of permeability gained from the cross-plotting of porosity and permeability data from plugs and whole cores accompanied by textural and fabric analyses of rock samples, thin-sections, serial sections, and pore casts. Importantly, many depositional rock types cross-plot as distinctly different populations, commonly yielding linear trends on semi-log paper. These trends indicate a degree of order in the seemingly chaotic pore systems of carbonate rocks which have undergon cementation and/or compaction. For grainstone samples, there appears to be a change in the slope of this trend between the compaction and cementation phases of diagenesis. Once the depositional texture and fabric of the rock are defined in terms of porosity and permeability, the evaluation of fractures and secondary porosity can be addressed. The secondary porosity is observed to be as high as 14% of the rock volume in the Smackover example and 21% of an oolitic sample from the Lansing Formation. Pore casts and serial sections reveal that the grain-moldic porosity is poorly connected to the intragranular pore system and contributes little to the permeability of the rock. This insight allows quantitative estimates of this type of secondary End_Page 513------------------------------ porosity using standard porosity and permeability data. The geologic and quantitative analysis of the various pore types and porosity/permeability relationships also aided in the interpretation of the log data from the reservoirs studied. End_of_Article - Last_Page 514------------

A Strength–Porosity Relation Involving Different Pore Geometry and Orientation

A number of empirical and semiempirical expressions which relate the strength of brittle polycrystalline materials to the total porosity have been proposed by various investigators. The present study demonstrates from a purely theoretical point of view that not only the total porosity but the pore shape and orientation are important factors affecting the strength. A strength‐porosity relation is derived that takes pore shape and orientation into account. Examples of how various types of pores should affect the strength are presented.