Decrease Of Internal Surface Area Research Articles

Lignin enrichment and enzyme deactivation as the root cause of enzymatic hydrolysis slowdown of steam pretreated sugarcane bagasse

The enzymatic hydrolysis (EH) rate normally decreases during the hydrolysis, leaving unhydrolyzed material as residue. This phenomenon occurs during the hydrolysis of both cellulose (avicel) and lignocellulosic material, in nature or even pretreated. The progression of EH of steam pretreated sugarcane bagasse was associated with an initial (fast), intermediate (slower) and recalcitrant (slowest) phases, at glucan to glucose conversion yields of 61.7, 81.6 and 86%, respectively. Even though the EH of avicel as a simpler material than steam pretreated sugarcane bagasse, EH slowdown was present. The less thermo-stable endo-xylanase lost 58% of initial enzyme activity, followed by β-glucosidase that lost 16%, culminating in FPase activity loss of 30% in the first 24hours. After 72hours of EH the total loss of FPase activity was 40% compared to the initial activity. Analysis of the solid residue from EH showed that lignin content, phenolic compounds and ash increased while glucan decreased as hydrolysis progressed. During the initial fast phase of EH, the total solid residue surface area consisted predominantly of internal surface area. Thereafter, in the intermediate and recalcitrant phases of EH, the ratio of external:internal surface area increased. The proposed fiber damage and decrease in internal surface area, probably by EH action, was visualized by scanning electron microscopy imagery. The higher lignin/glucan ratio as EH progressed and enzyme deactivation by thermo instability were the main effects observed, respectively to substrate and enzyme.

Highly porous activated glassy carbon film sandwich structure for electrochemical energy storage in ultracapacitor applications: Study of the porous film structure and gradient

Glassy carbon plates were thermochemically gas phase oxidized to obtain monolithic sandwichlike electrode assemblies with high surface area porous films for electrochemical energy storage applications. Film thicknesses were varied by variation of oxidation parameters time, temperature, and oxygen concentration and measured with electron microscopy. The mass density of the porous carbon film material was estimated by fitting a geometrical model to experimental gravimetric data. Optical Raman spectroscopy line scans suggest that the porosity has a gradient between the surface and the film/bulk interface, which is supported by pore-size distribution data obtained from small-angle x-ray scattering (SAXS) on slightly oxidized and fully oxidized samples. Detailed inspection of the power law behavior of SAXS data suggests that the internal surface area of well-oxidized glassy carbon (GC) is compact and extends over the entire probed volume and thus has optimal pore connectivity. This effect goes along with pore enlargement and a relative decrease of internal surface area per volume. Slightly oxidized carbon has no pore space with a compact, high connectivity internal surface area. The corresponding SAXS power law and the x-ray density suggest that this high volumetric surface area must be interpreted as a result of surface roughness, rather than true geometric or volumetric surface area. In consequence, is this surface area of limited use for electrochemical energy storage?

Compaction of microporous amorphous solid water by ion irradiation

We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface area of the pores, signaled by infrared absorption by dangling bonds, precedes the decrease in the pore volume during irradiation. Our results imply that impacts from cosmic rays can cause compaction in the icy mantles of the interstellar grains, which can explain the absence of dangling bond features in the infrared spectrum of molecular clouds.

Small-angle neutron scattering and cyclic voltammetry study on electrochemically oxidized and reduced pyrolytic carbon

The electrochemical double layer capacitance and internal surface area of a pyrolytic carbon material after electrochemical oxidation and subsequent reduction was studied with cyclic voltammetry and small-angle neutron scattering. Oxidation yields an enhanced internal surface area (activation), and subsequent reduction causes a decrease of this internal surface area. The change of the Porod constant, as obtained from small-angle neutron scattering, reveals that the decrease in internal surface area is not caused merely by a closing or narrowing of the pores, but by a partial collapse of the pore network.

Effect of intensive drying of viscose fibres on their properties

Experimental data are given on the effect of moisture evaporation rate in drying viscose yarns on the strength and elongation, sorptive capacity for water vapor from the air, swelling, shrinkage, and wear resistance of yarns. It has been found that, by regulating the drying temperature, it is possible to affect the capillary-porous structure of a yarn to a considerable degree. Raising the temperature and the drying rate leads to an improvement in wear resistance and yarn elasticity. However, due to the decrease in internal surface area, one may expect a decrease in the sorptive capacity of the yarn in dyeing. A decrease in drying temperature helps increase the degree of swelling, and helps improve the absorption of dye by the yarn.

Morphologic and phenotypic analysis of an outcross line of blotchy mouse.

Blotchy is an X-linked recessive mutation at the "Mottled" locus in the mouse. The affected blotchy male (Blo/Y) mouse from an inbred genetic background demonstrates morphologic and physiologic abnormalities consistent with emphysema in adult life. Breeding of Blo/Y mice has been difficult because the inbred Blo/Y males are sterile. We report the successful development of a line of outbred Blo/Y male and Blo/Blo female nice by the controlled outcross mating of the inbred heterozygous Blo/+ female with the Argonne hybrid B6CF1 male mouse. The subsequent outcross Blo/Y progeny breed vigorously with the outcrossed Blo/+ female. The lungs of the outbred Blo/Blo female and inbred Blo/Y male mice demonstrate mild to moderate panacinar emphysema with a significant decrease in internal surface area (p less than 0.005) and an increase in mean linear intercept (p less than 0.005). In contrast, the lungs of the outbred Blo/Y is structurally normal. Despite the absence of emphysema-like changes in the outbred Blo/Y males, there were phenotypic features that suggest inherited abnormalities in connective tissue proteins including 1) high incidence of aortitis leading to premature death from aneurysmal rupture, and 2) significant decrease in the morphometrically determined parenchymal elastic fiber length in the lung (p less than 0.01). The outbred blotchy strain may be a useful experimental animal model in determining the pathogenesis of emphysema.

Emphysema-like changes in the lungs of starved rats.

We examined the effects of starvation on lung structure in rats allowed only one fifth of their measured daily food consumption until they lost 40% of their initial body weight, and evaluated volume-pressure relationships in saline-filled lungs, lung morphometric and connective tissue morphologic features and lung ultrastructure by scanning electron microscopy. Compared with rats fed full rations, the volume-pressure curve was shifted upward and to the left and the chord compliance was significantly increased. In the starved rats, enlargement of air spaces and alveolar wall destruction was associated with a significant increase in mean linear intercept and a decrease in internal surface area. Elastic fibers appeared short, irregular, and fewer in number in starved lungs. Scanning electron microscopy showed enlarged air spaces, thin, irregular, and effaced alveolar walls, and an increased number and size of interalveolar pores in the starved group. We concluded that starvation results in mechanical and morphologic changes in the lung similar to those seen in emphysema, and that starved lung may be a useful experimental model for the study of emphysema.

The pathology of elastase-induced panacinar emphysema in hamsters.

A single dose of crystalline, porcine pancreatic elastase injected intratracheally into hamsters induces widespread alveolar enlargement with subpleural bullae. A uniformly severe lesion is consistently induced by 0-2 mg elastase per 100 g body weight and with negligible mortality. Compared with controls, which showed no lesion, elastase-damaged lungs show a highly significant (P less than or equal to 0-001) increase in alveolar size and a decrease in internal surface area. Taken with the associated physiological abnormalities, these findings closely simulate human emphysema of the panlobular (panacinar) type. Histologically it appears that elastase converts the fine elastic fibres in alveolar walls and pleura into thickened, nodular fibres which may also be broken along their length. With higher doses of elastase, i.e., 0-5 mg/100 g body weight, many pulmonary arteries showed segmental loss of inner and outer elastic laminae, usually with thrombosis on the overlying endothelium. The mechanism of this thrombosis is unclear. These experiments suggest that damage to elastic fibres may be an important element in the development of human panacinar emphysema, and that the damage could be one pathogenetic mechanism which produces damage of elastic fibres.