Wood basic density effect of Eucalyptus grandis in the paper making

The basic density is the main technical property of the wood due to the fact of the easy determination andcorrelation with the others wood properties. In this article, it was evaluated wood chips from a five-years-oldEucalyptus grandis in three different silvicultural treatments for pulp and paper production. First, a conventionalkraft pulping was executed in the same conditions and then submitted to some elemental chlorine free(ECF) bleaching process to achieve the target brightness of 88 ± 1% ISO. The bleached pulps were refined ina Jokro Mill at 0, 2250, 4500 and 6750 revolutions and their physical, mechanical and optical properties wereanalyzed. The statistical analysis indicated a difference in the wood basic density from the different silviculturaltreatments. The yield of the pulping process was not affected by the variation of the wood basic density.The denser wood had the advantage of a lower specific wood consumption while the disadvantage was agreater difficulty in the delignification and a decrease in the selectivity of the pulping process. The denserwood was the one with the best bleachability and the one that most consumed chlorine in the bleaching process.The increase of the wood density caused gains in the fisical and optical properties of the bleached pulpand losses in the mechanical properties.The optical properties of the pulps from denser woods are more resistantthan the negative effects of mechanical properties.Keywords: Kraft pulping; pulp bleaching; paper properties

Correction of Enhanced Na+-H+ Exchange of Rat Small Intestinal Brush-Border Membranes in Streptozotocin-induced Diabetes by Insulin or 1,25-Dihydroxycholecalciferol

Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol [1,25(0H)2D3J for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na+-H+ exchange activity, using 22Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent 22Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced 'Na uptake in diabetes was a result of increased maximal velocity (V.,.) of this exchanger with no change in apparent affinity (K.) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the alterations to control values, without any significant changes in K., concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na+-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(0H)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin. (J. Clin. Invest