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Acid Pretreatment (acid + pretreatment)
Selected AbstractsFour-year water degradation of a resin-modified glass-ionomer adhesive bonded to dentinEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2004Jan De Munck Glass-ionomers are auto-adhesive to tooth tissue through combined micro-mechanical and chemical bonding. How much each of the two bonding components contributes to the actual bonding effectiveness is, however, not known and there is not much information available on long-term stability. The objective of this study was to assess the bonding effectiveness of a resin-modified glass-ionomer adhesive to dentin after 4 yr of water storage. Fuji Bond LC (GC) was applied without (i) and with pretreatment using (ii) a polyalkenoic acid conditioner and (iii) a 37.5% phosphoric acid etchant. The etchant was used to exclude any chemical interaction with hydroxyapatite. The micro-tensile bond strength (µTBS) to dentin decreased significantly over the 4 yr period in all three experimental groups. After 24 h and 4 yr, the lowest µTBS was recorded when dentin was not pretreated. The highest µTBS was obtained following polyalkenoic acid pretreatment, although this was not significantly different from specimens that were pretreated using phosphoric acid. Pretreating dentin with phosphoric acid intensified micromechanical interlocking at the expense of chemical bonding potential to hydroxyapatite. Nevertheless, correlating the µTBS data with failure analysis through scanning electron microscopy and transmission electron microscopy indicated that combined micro-mechanical and chemical bonding involving pretreatment with the polyalkenoic acid conditioner yielded the most durable bond. [source] Impact of dilute acid pretreatment on the structure of bagasse for bioethanol productionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010Wei-Hsin Chen Abstract Dilute acid pretreatment is a commonly used pretreatment method in the course of producing bioethanol from lignocellulosics and the structure variation of the lignocellulosics is highly related to the pretreatment process. To understand the impact of dilute acid pretreatment on the structure of bagasse, four different pretreatment conditions by varying heating time are considered where the bagasse and the pretreated materials are examined using a variety of analysis methods. The obtained results indicate that the thermogravimetric analysis (TGA) is able to provide a useful insight into the recognition of lignocellulosic structure. Specifically, the peak of the TGA of the pretreated materials moves toward the low temperature region, revealing that the lignocellulosic structure is loosened. However, the characteristic of crystal structure of cellulose remains in the pretreated materials. Increasing heating time enhances the pretreatment procedure; as a result, the average particle size of the investigated materials increases with heating time. This swelling behavior may be attributed to the enlarged holes inside the particles in that the surface area decreases with increasing heating time. In addition, when the heating time is increased to a certain extent (e.g. 15,min), some fragments are found at the surface and they tend to peel off from the surface. It follows that the dilute acid pretreatments have a significant effect on the bagasse structure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Immunohistochemical studies of the PrPCJD deposition in Creutzfeldt-Jakob diseaseNEUROPATHOLOGY, Issue 2 2000Shinichiro Tanaka The PrPCJD deposition in eight brains of sporadic Creutzfeldt-Jakob disease (CJD) was examined immunohistochemically using both hydrolytic autoclaving and formic acid pretreatment in order to understand the pathogenesis of CJD. Synaptic-type PrP immunoreactivity was revealed in the gray matter in all cases and had a tendency to be weaker in devastated areas in cases with a longer duration of illness. However, in one particular case with numerous prion plaques, the degeneration was relatively mild while PrPCJD immunoreactivity was intense despite the longest duration of illness among the examined cases. Deep layer accentuation of PrPCJD immunoreactivity was observed in the cerebral cortices in most cases. This staining pattern, however, disappeared in a burnt-out lesion exhibiting status spongiosus. The granular layer was damaged mostly in the cerebellum of the advanced cases. PrPCJD and synaptophysin immunoreactivities decreased as the tissue degeneration progressed. Interestingly, the Purkinje cells had no positivity for PrPCJD in all cases, although the neurons in relatively preserved cerebellum showed apparent positivity for synaptophysin. In the Ammon's horn and subiculum the neurons were well preserved despite the marked immunoreactivity for PrPCJD in all cases, although some cases demonstrated severe spongiform change. Approximately half of the cases showed intracytoplasmic inclusion body-like immunoreactivity for PrPCJD in neurons of the dentate nucleus. These findings suggest that PrPCJD deposition may be an event that precedes neuronal degeneration evolving from deeper layers of the cerebral cortex. Although the Ammon's horn and subiculum showed striking PrPCJD deposition and spongiform change, neuronal loss did not take place, suggesting that deposited PrPCJD itself seems not to be directly harmful to the neurons. Some investigators have assumed that microglia activated by PrPCJD plays an important role in neuronal degeneration. Considering this, we speculate that microglia in the Ammon's horn and subiculum may have a unique characteristic of not responding to PrPCJD. [source] Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologiesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Rajeev Kumar Abstract Moderate loadings of cellulase enzyme supplemented with ,-glucosidase were applied to solids produced by ammonia fiber expansion (AFEX), ammonia recycle (ARP), controlled pH, dilute sulfuric acid, lime, and sulfur dioxide pretreatments to better understand factors that control glucose and xylose release following 24, 48, and 72 h of hydrolysis and define promising routes to reducing enzyme demands. Glucose removal was higher from all pretreatments than from Avicel cellulose at lower enzyme loadings, but sugar release was a bit lower for solids prepared by dilute sulfuric acid in the Sunds system and by controlled pH pretreatment than from Avicel at higher protein loadings. Inhibition by cellobiose was observed to depend on the type of substrate and pretreatment and hydrolysis times, with a corresponding impact of ,-glucosidase supplementation. Furthermore, for the first time, xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover, and xylose, xylobiose, and xylotriose were shown to have progressively greater effects on hydrolysis rates. Consistent with this, addition of xylanase and ,-xylosidase improved performance significantly. For a combined mass loading of cellulase and ,-glucosidase of 16.1 mg/g original glucan (about 7.5 FPU/g), glucose release from pretreated solids ranged from 50% to75% of the theoretical maximum and was greater for all pretreatments at all protein loadings compared to pure Avicel cellulose except for solids from controlled pH pretreatment and from dilute acid pretreatment by the Sunds pilot unit. The fraction of xylose released from pretreated solids was always less than for glucose, with the upper limit being about 60% of the maximum for ARP and the Sunds dilute acid pretreatments at a very high protein mass loading of 116 mg/g glucan (about 60 FPU). Biotechnol. Bioeng. 2009;102: 457,467. © 2008 Wiley Periodicals, Inc. [source] Impact of dilute acid pretreatment on the structure of bagasse for bioethanol productionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010Wei-Hsin Chen Abstract Dilute acid pretreatment is a commonly used pretreatment method in the course of producing bioethanol from lignocellulosics and the structure variation of the lignocellulosics is highly related to the pretreatment process. To understand the impact of dilute acid pretreatment on the structure of bagasse, four different pretreatment conditions by varying heating time are considered where the bagasse and the pretreated materials are examined using a variety of analysis methods. The obtained results indicate that the thermogravimetric analysis (TGA) is able to provide a useful insight into the recognition of lignocellulosic structure. Specifically, the peak of the TGA of the pretreated materials moves toward the low temperature region, revealing that the lignocellulosic structure is loosened. However, the characteristic of crystal structure of cellulose remains in the pretreated materials. Increasing heating time enhances the pretreatment procedure; as a result, the average particle size of the investigated materials increases with heating time. This swelling behavior may be attributed to the enlarged holes inside the particles in that the surface area decreases with increasing heating time. In addition, when the heating time is increased to a certain extent (e.g. 15,min), some fragments are found at the surface and they tend to peel off from the surface. It follows that the dilute acid pretreatments have a significant effect on the bagasse structure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologiesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Rajeev Kumar Abstract Moderate loadings of cellulase enzyme supplemented with ,-glucosidase were applied to solids produced by ammonia fiber expansion (AFEX), ammonia recycle (ARP), controlled pH, dilute sulfuric acid, lime, and sulfur dioxide pretreatments to better understand factors that control glucose and xylose release following 24, 48, and 72 h of hydrolysis and define promising routes to reducing enzyme demands. Glucose removal was higher from all pretreatments than from Avicel cellulose at lower enzyme loadings, but sugar release was a bit lower for solids prepared by dilute sulfuric acid in the Sunds system and by controlled pH pretreatment than from Avicel at higher protein loadings. Inhibition by cellobiose was observed to depend on the type of substrate and pretreatment and hydrolysis times, with a corresponding impact of ,-glucosidase supplementation. Furthermore, for the first time, xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover, and xylose, xylobiose, and xylotriose were shown to have progressively greater effects on hydrolysis rates. Consistent with this, addition of xylanase and ,-xylosidase improved performance significantly. For a combined mass loading of cellulase and ,-glucosidase of 16.1 mg/g original glucan (about 7.5 FPU/g), glucose release from pretreated solids ranged from 50% to75% of the theoretical maximum and was greater for all pretreatments at all protein loadings compared to pure Avicel cellulose except for solids from controlled pH pretreatment and from dilute acid pretreatment by the Sunds pilot unit. The fraction of xylose released from pretreated solids was always less than for glucose, with the upper limit being about 60% of the maximum for ARP and the Sunds dilute acid pretreatments at a very high protein mass loading of 116 mg/g glucan (about 60 FPU). Biotechnol. Bioeng. 2009;102: 457,467. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||