An insight into the behaviour of aspen CTMP in peroxide bleaching

The objective in the bleaching of mechanical pulps is to selectively remove colour-contributing components (chromophores) while simultaneously preserving pulp yield. In current practice, this involves mainly the use of hydrogen peroxide, especially when high brightness is targeted. The reactions of hydrogen peroxide bleaching, usually performed in alkaline medium, result in chromophore removal through lignin modification and/or solubilization, accompanying an inevitable removal of carbohydrates. The dissolution of lignin and carbohydrates occurs to varying extents that are determined by bleaching parameters, such as peroxide charge and alkalinity. Generally, high peroxide charge coupled with high alkalinity is essential to attaining high pulp brightness. However, this common bleaching practice causes the loss of a considerable amount of organic substances from pulp fibres, which effects the bleaching operation in many respects. For instance, removal of the materials is directly reflected in pulp yield and, in turn, becomes the source of a bleach plant\u27s production of COD (i.e., chemical oxygen demand). Aspen is an important wood species, especially in Western Canada, in the production of market BCTMP. This manufacturing industry contributes, to a great extent, to the regional economy. Technological advances in mechanical pulping and bleaching allow the production of aspen BCTMP products of flexible properties that meet the end use requirements for a broad range of paper products [1]. One advantage of aspen CTMP is its good bleachability. The pulp is currently bleached by peroxide to a brightness of over 85 ISO, which can be used as a furnish for high brightness paper grades. Our earlier studies have shown that in bleaching brightness response is rapid, then slows down, and finally reaches a plateau from which further increasing peroxide charge only slightly increases brightness [2]. It is the final brightness increase of several units that consumes the majority of an applied bleaching chemical and causes a pronounced loss of pulp yield [3]. This high susceptibility of yield loss in the alkaline peroxide bleaching of aspen pulp could be attributed to its high content of hemicelluloses, an alkali-labile pulp component [4]. Quite naturally, one would pose a question on the likelihood of bleaching aspen pulp to high brightness by peroxide while reducing yield loss

Relationship between ambient fine particles and ventricular repolarization changes and heart rate variability of elderly people with heart disease in Beijing, China.

OBJECTIVE: To explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter (PM2.5) on heart repolarization/depolarization and heart rate variability (HRV). METHODS: We conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram (ECG) indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PM2.5 and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology. RESULTS: Significant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.5 on HRV was on lag 1 day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension. CONCLUSION: This study showed ambient PM2.5 could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5

The synthesis of L-(+)-homophenylalanine hydrochloride

L-(+)-Homophenylalanine hydrochloride was synthesized from N-phthaloyl-L-(-)-aspartic anhydride 2 in three steps in 55% overall yield with 99% ee. (C) 2000 Elsevier Science Ltd. All rights reserved

STEREOSELECTIVE HYDROGENATION OF DIBENZO-18-CROWN-6 CATALYZED BY CARBON NANOTUBE-SUPPORTED RHODIUM NANOPARTICLES

Multiwalled carbon nanotube-supported Rh nanoparticles prepared by a simple sonochemical method are highly active for catalytic hydrogenation of dibenzo-18-crown-6 to dicyclohexyl-18-crown-6. The catalytic hydrogenation reaction shows a selectivity favoring the cis-syn-cis isomer over cis-anti-cis isomer of the product by a factor of >= 6. Conventional Rh catalysts supported by activated wood carbon, SiO(2), or Al(2)O(3) can only convert dibenzo-18-crown-6 to dicyclohexyl-18- crown-6 with an cis-syn-cis/cis-anti-cis ratio of <1.7. The Rh nanoparticle catalyst can be reused at least six times without losing its catalytic activity

Changes in the Gut Microbiome Contribute to the Development of Behcet's Disease via Adjuvant Effects

Behcet’s disease (BD) is associated with considerable gut microbiome changes. However, it still remains unknown how the composition of the gut microbiome exactly affects the development of this disease. In this study, transplantation of stool samples from patients with active ocular BD to mice via oral gavage was performed. This resulted in decreases of three short chain fatty acids (SCFAs) including butyric acid, propionic acid and valeric acid in the feces of the BD-recipient group. Intestinal barrier integrity of mice receiving BD feces was damaged as shown by a decreased expression of tight junction proteins and was associated with the release of Lipopolysaccharides (LPS) in the circulation. The mice also showed a higher frequency of splenic neutrophils as well as an enrichment of genes associated with innate immune responses in the neutrophils and CD4 + T cells as identified by single cell RNA sequencing. Analysis of neutrophils and T cells functions in these mice showed an enhanced mesenteric lymph node and splenic Th1 and Th17 cell differentiation in association with activation of neutrophils. Transplantation of BD feces to mice and subsequent induction of experimental uveitis (EAU) or encephalomyelitis (EAE) led to an exacerbation of disease in both models, suggesting a microbial adjuvant effect. These findings suggest that the gut microbiome may regulate an autoimmune response via adjuvant effects including increased gut permeability and enhancement of innate immunity