用纸浆代棉花合成CMC

羧甲基纤维素(CMC)系天然纤维素的衍生物。它是由天然纤维素分子上引入强极性羧甲基钠而得到的。我们采用纸浆为原料替代棉花生产CMC,测试了其性能,并讨论了反应温度、反应时间和碱用量对粘度的影响。结果表明:此法简化了工艺,原料来源广泛,产品性能优良,成本低,能满足使用要求。     

抗寒性不同的油橄榄品种和单株叶片扫描电镜观察

抗寒性强的油橄榄——克里302、尼基特371的叶片,扫描电镜下的特征是:(1) 近轴表皮角质膜厚,蜡质结晶致密。(2) 远轴表皮内陷气孔,密被鳞毛。(3) 叶两面栅栏组织发达,为旱生形态阳叶结构。     

The development of the human spleen

Summary Splenic tissue of human fetuses from the 14^th to the 24^th week of gestation (menstrual age) were investigated by light- and electron microscopy to describe the development of the red and white pulp in close relationship to the differentiation of the vascular tree. Special interest is focussed on the differentiation of the T-cell- and the B-cell regions and their specific stationary cells.The preliminary stage, here called the primary vascular reticulum, lasts up to the 14^th gestational week (gw). Numerous erythrocytes, normoblasts and macrophages are seen among a network of mesenchymal cells and argyrophilic fibers. Hematopoiesis, especially erythropoiesis, can be recognized.The characteristic organ structure becomes established during the subsequent transformation stage of the fetal spleen, beginning with the 15^th gw. Splenic lobules begin to form during the 15^th to 17^th gw. They consist of a central artery, surrounded by a sheath of lightly stained stationary cells which resemble myofibroblasts. At the periphery of these lobules the red pulp forms. Initially mobile cells are distributed throughout the reticulum. Soon they begin to accumulate in the venous sinuses, which develop from lacunae among the reticular network and come into contact with the venous system. The endothelial wall of these sinuses remains discontinuous, confirming the theory of the open vascularization of the spleen. The development of the larger veins is correlated with the differentiation of the splenic trabeculae.The development of the white pulp is correlated with the stage of lymphoid colonization within the spleen, beginning around the 18^th gw. An accumulation of lymphocytes around the central arteries can be recognized during the 19^th and 20^th gw. These lymphoid cells show morphological and immunohistochemical characteristics of T-precursor cells. Within the now assembling periarterial lymphoid sheath (PALS) a few precursors of interdigitating cells (IDC) are recognizable, giving evidence for the differentiation of the T-cell region.Around the 23^rd gw the assemblage of primary follicles is discernible at the periphery of the PALS. Precursors of the follicular dendritic reticulum cell (FDRC), the specific stationary cell of the B-cell region, have been recognized. This observation leads to the conclusion that the small primary follicles represent the beginning formation of the B-cell region.The significance of the vascular system for the differentiation of the specific splenic organization is discussed.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 111)The authors appreciate the contribution of human fetal material from Dr. von Hollweg and Dr. Körner from the Hospital Heidberg, Hamburg, and the excellent technical assistance of Mrs. H. Hansen, Mrs. I. Knauer, Mrs. M.v. Kolszynski, Mrs. J. Quitzau, Mrs. H. Siebke and Mrs. H. Waluk     

Immune-complex-trapping cells in the spleen of the oriental fire-bellied toad,Bombina orientalis

Summary The spleen of the oriental fire-bellied toad, Bombina orientalis, consists of well-developed white pulp, separated from the lymphocytic marginal zone by the connective tissue boundary layer. Injection of peroxidase-conjugated rabbit anti-peroxidase revealed that these immune complexes were localized on the surface of acid-phosphatase-positive and non-specific-esterasepositive cells in the white pulp. The majority of immunecomplex-trapping cells were present around the blood vessels. Cell processes of some of these cells penetrated into the wall of blood vessels. The significance of the present findings is discussed with respect to the evolution of immune-complex-trapping cells in the spleen.     

Effect of Organic Acids on Reactions Catalyzed by Manganese Peroxidase from Phanerochaete chrysosporium

The effect of several organic acids on the oxidation of Mn(II) catalyzed by manganese peroxidase was studied. Reactivities of manganese peroxidase and chemically prepared Mn(III) organic acid complexes towards phenolic compounds were compared. If lactate appears to be the best complexant for manganese peroxidase activity, chemically prepared Mn(III)—lactate complex is a less effective oxidant towards phenolic compounds than other Mn(III)—complexes. Our results agree with the hypothesis that certain organic acids are involved in the catalytic cycle of manganese peroxidase. Malonate and lactate seem to be the most attractive complexants for practical applications of manganese peroxidase and were used in enzymatic treatment of hardwood kraft pulp. Bleaching of kraft pulp was studied and after alkaline extraction, a significant decrease of kappa number was measured. The bleaching was enhanced in lactate buffer.     

Histological Techniques to Improve Testing of Pulpal Response of Teeth to Filling Material

Two fixation fluids, two fixation techniques and two embedding methods were investigated for their effects on the quality of sections of teeth for pulpal response to filling materials to improve evaluation of pulpal responses. Sections from 32 baboon teeth were prepared, half with experimental cavities and half without, using either 10% formaldehyde or 4% glutaraldehyde, longitudinal tooth splitting or removal of the tooth apex, and paraffin or K plast resin embedding; decalcification in a formic acid mixture was a constant throughout. Histometric analysis showed that paraffin embedding produced less shrinkage than the K Plast resin embedding although the difference was not statistically significant. Six parameters of separation at the pu1p:dentine interface were studied: embedding, fixative, presence or absence of a cavity, cutting technique and individual animal tooth type. Statistical investigation revealed that fixative, cutting technique, and fixative and cutting technique combined had significant influences on the separation artifact. Of the combinations tested the choice of embedding method depends on which of the two artifacts, shrinkage or separation, is more adverse in the opinion of the investigator. Four percent glutaraldehyde together with the longitudinal split technique of fixation. processed by either K Plast resin embedding or paraffin embedding produced satisfactory pulpal sections.     

Utility of field-based artificial streams for assessing effluent effects on riverine ecosystems

Experimentation using field-based artificial streams provides a promising, complimentary approach to biomonitoring assessments because artificial streams provide control over relevant environmental variables and true replication of treatments. We have used large and small artificial stream systems, based in the field, to examine the effect of treated bleached kraft pulp mill effluent (BKME) on the benthos of three large rivers in western Canada. Under natural regimes of temperature, water chemistry, and insolation, these artificial streams provide current velocities and substrata to food chains or food webs that are representative of those in the study river. With these tools we have shown that BKME stimulated mayfly growth in the Thompson River above that which could be accounted for by fertilization of their algal food supply. In contrast, moulting frequency was inhibited at high BKME concentrations. Results from artificial streams also indicate that increased algal biomass and abundances of benthic communities downstream of BKME outfalls were induced by nutrient enrichment from the effluent. BKME treatments did not change diatom species richness in the Fraser River, or diatom species diversity in either the Athabasca or Fraser Rivers. Artificial streams provide a means of understanding the mechanisms of stressor effects over a continuum ranging from single stressor effects on specific taxa to the effects of multiple stressors on communities and ecosystems. Because riverside deployment provides environmental realism within a replicated experimental design, this approach can (i) address questions that cannot be examined using laboratory tests or field observations, (ii) improve our mechanistic understanding of stressor effects on riverine ecosystems, and (iii) can contribute directly to the development, parameterization, and testing of models for predicting ecosystem-level responses.     

Lignin genetic engineering

Although lignins play important roles in plants, they often represent an obstacle to the utilization of plant biomass in different areas: pulp industry, forage digestibility. The recent characterization of different lignification genes has stimulated research programmes aimed at modifying the lignin profiles of plants through genetic engineering (antisense and sense suppression of gene expression). The first transgenic plants with a modification of monomeric composition of lignins and lignin content have been recently obtained. Down regulation of the OMT gene induces dramatic reduction of syringyl units. CAD down regulated plants exhibit a unusual red phenotype associated with the developing xylem and several chemical modifications of their lignins including an increase in cinnamaldehydes in the polymer structure. Interestingly this novel lignin is removed more easily during the pulping process. In both OMT and CAD down regulated plants no changes in phenotypic characteristics such as growth architecture and morphology were observed. More recent experiments have shown that a reduction of CCR activity determines specific changes in the coloration of the xylem area suggesting significant chemical modifications which are currently being studied.These different results show that it is possible to manipulate lignins through targeted genetic transformation of plants and that lignins exhibit a relative flexibility of their chemical structure. Future developments should probe the impact of down regulating the expression of other recently characterized lignification genes such as F5H and CCoAOMT and also of a combination of genes in order to tailor lignins more adapted to specific purposes. In addition to biotechnological applications which should provide important economical benefits for utilization of wood in the pulp industry, genetic engineering of lignins offer very promising perspectives for the understanding of lignin synthesis, structure and properties.     

Assessment of various commercial enzymes in the bleaching of radiata pine kraft pulps

Four xylanase preparations that are commercially available, namely Cartazyme from Sandoz, Ecopulp from Alko-ICI, Irgazyme from Ciba-Genencor and Pulpzyme HB from Novo Nordisk, were tested in bleaching experiments of kraft pulps from Pinus radiata. The main objective of this study was to optimize a reduction in the consumption of chlorine dioxide in the bleaching sequences C₉₀/D₁₀E_oDED, C₇₀/D₃₀E_oDED and D₁₀₀EDED. Enzymatic treatments led to savings of ClO₂ between 3.5 and 3.9 kg per air-dried tons (ADT) in the three bleaching sequences, without affecting the target brightness of the pulps. In these assays, some minor although reproducible differences in the performance of the enzymes were observed. In most cases, xylanase treatment partially affected the beatability of the pulps, measured as the number of revolutions in the PFI mill required to reach the same tensile index as the respective controls.     

Organosolv pulping of wheat straw by use of phenol

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and phenol concentration) for wheat straw with phenol-water mixtures on the properties of the pulp obtained (yield and holocellulose, -cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, -cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the wastewater with multiple-R, R² and adjusted-R² high values. The process variables must be set at low variables in order to ensure a high yield and pH. Conversely, if high holocellulose and -cellulose contents, and low lignin and ethanol-benzene extractable contents are desired, then a high temperature (200°C), long cooking time (120 min), and intermediate phenol concentration (65%) must be used.