DMD的活化预处理及其全无氯漂序的研究

研究了桉木硫酸盐浆对氧脱木质素段和过氧化氢漂段的活化作用以及ＤＭＤ用量对氧段和过氧化氢段浆性能的影响,使经ＭＯＱＭＰ多段漂白的纸浆最终白度达８０％以上,纸浆粘度满足要求,可以实现桉木硫酸盐浆的全无氯漂白。     

木聚糖酶预处理对麦草化学机械浆可漂性及白度的改善

探讨了以玉米芯片为碳源制备木聚糖酶及麦草化学机械浆经该木聚糖酶预处理后可漂性和白度的改善效果。结果表明，直接以玉米芯为底物、里氏木霉为菌种产酶效果较好，当底物浓度为18g/L时，木聚糖酶活力可达38．34IU／mL。木聚糖酶预处理有利于改善麦草化机浆的可漂性，促进其过氧化氢漂白，有提高漂白浆白度，降低漂剂消耗。研究表明，当经单段H2O2漂至相同白度时，木聚糖酶预处理后可节约50％的H2O2用量。若麦草CMP酶处理后采用高浓度两段过氧化氢漂白，即XP3P3漂序（H2O2总量为6％0时，白度可达60％（ISO）以上。     

麦草氧碱法纸浆压力/温度过氧化氢漂白

麦草氧碱法纸浆经压力/温度H2O2(Ppt)漂白时,纸浆的卡伯值随H2O2用量和氧压的提高而下降,卡伯值从17.3下降至2.38,下降幅度达86.2 %,表明Ppt漂白时,脱木质素效果明显.若采用氧脱木质素 -鳌合处理 -压力温度H2O2漂白(OQPpt)和氧脱木质素 -酸处理 -压力温度H2O2(OAPpt)漂程,当H2O2用量为原料质量的3 %～4 %时,均可将麦草氧碱纸浆漂至白度80 %(SBD,以下同)左右,而采用OAPpt漂白比OQPpt漂白的纸浆的白度高2.0 %左右,且聚合度达到1 038左右.     

新疆杨幼龄材带皮硫酸盐法化学浆漂白性能的研究

研究了新疆杨木１～３年生带皮硫酸盐法化学浆的漂白规律。结果表明：采用单段和二段次氯酸盐漂白，漂后浆白度较低，分别为６３．１％和６６．７％（ＳＢＤ）；采用常规次氯酸盐三段漂白（ＣＥＨ），漂白度可达７５％（ＳＢＤ）以上；采用少量过氧化氢结合常规次氯酸盐多段漂白，漂后浆白度达８０％（ＳＢＤ）以上。     

E－An－76在桦木KP浆及麦草Soda－AQ浆CEH三段漂中的应用

研究了半纤维素酶Ｅ－Ａｎ－７６作为漂白助剂对桦木硫酸盐浆及麦草烧碱蒽醌浆ＣＥＨ三段漂的影响。结果表明：桦木ＫＰ浆用Ｅ－Ａｎ－７６预处理后再经ＣＥＨ三段漂，其白度明显高于相同用氯量下未用酶预处理的漂白浆。另一方面在保持白度不变的情况下酶处理浆的漂白可节省近５０％的用氯量。麦草Ｓｏｄａ－ＡＱ浆经Ｅ－Ａｎ－７６预处理后再经ＣＥＨ三段漂与酶未处理浆的ＣＥＨ三段漂比较亦可明显提高白度，但得率下降严重。通过对桦木ＫＰ浆酶解液中还原糖以及单糖组成分析，发现浆中再沉积或回吸的木聚糖在Ｅ－Ａｎ－７６助剂漂白中起着重要作用。     

氧脱木质素技术的应用前景

氧脱木质素技术应用到多段漂白高白度浆生产工艺流程中，可以提高细浆得率，降低纸浆的粘度损失，提高白度，减少氯化段有效氯用量３０％～５０／，减少漂白段的ＣＯＤ和ＡＯＸ的排放量。     

三倍体毛白杨低硬度NaOH-AQ浆全无氯漂白的研究

通过实验探讨了三倍体毛白杨低硬度NaOH-AQ浆（卡伯值13．5，粘度851mL／g。白度37％，ISO）H2O2强化氧脱木质素（QOP）的工艺务件，在此基础上提出了QOP、QP全无氯漂白的漂序，此漂序可以把该纸浆漂至82．0％（ISO），粘度保持在716mL／g，漂后纸浆得率91．78％，而且该漂序可操作性强，是一种适合低硬度NaOH-AQ浆的全无氯漂白新工艺。     

硫酸盐竹浆氧脱木质素和全无氯漂白的研究

通过比较不同条件下氧脱木质素后浆料的卡伯值、黏度、得率、白度和脱木质素选择性等指标,研究了硫酸盐竹浆卡伯值25.6氧脱木质素工艺参数,发现用碱量和温度是决定氧脱木质素效果的主要因素.最佳工艺条件为:用碱量3.5%,温度85℃,氧气压力0.6MPa,保温时间80min.两段氧脱木质素(中间不洗涤)可以提高木质素脱除率和选择性.研究还发现,在氧碱脱木质素过程中加入醌类混合物助剂(表示为Oq),可使浆料的黏度和氧脱木质素的选择性大大提高.采用OQ(PO)、(O1O2)Q(PO)、OQ(PO)1(PO)2和OqQ(PO) 4种短漂序都可使竹浆白度达到80%(ISO) 以上,且具有很好的白度稳定性.OQ(PO)、(O1O2)Q(PO)和OQ(PO)1(PO)2 3种漂序漂后浆纸页强度性能相近,OqQ(PO)漂后浆的抗张指数、撕裂指数和耐破指数明显高于其它3种漂序.     

相思木EMCC硫酸盐浆氧脱木质素前后酶处理的影响研究

研究了酶处理对相思木EMCC(延伸改良连续蒸煮)硫酸盐浆(KP浆)氧脱木质素效果的影响。结果表明,由白腐菌直接合成的漆酶/木聚糖酶体系(LXS)预处理相思木EMCC硫酸盐浆的的适宜酶用量为7 IU/g;LXS预处理后浆料氧脱木质素的适宜反应时间、最高反应温度及用碱量分别为60 min、100℃和2.5%;利用LXS进行氧脱木质素后处理的适宜反应时间及酶用量分别为2 h和5 IU/g。SEM观察到经过酶处理后纤维表面及横切面出现大量的裂隙及孔隙,其中以酶后处理最为明显,为后续漂白中化学药品的渗透和漂白降解产物的溶出创造条件。     

E—An—76在桦木KP浆及麦草Soda—AQ浆CEM三段漂中的应用

研究了半纤维素酶Ｅ－Ａｎ－７６作为漂白助剂对桦木硫酸盐浆及麦草烧碱蒽醌浆ＣＥＨ三段漂的影响。结果表明，桦木ＫＰ浆用Ｅ－Ａｎ－７６处理后再经ＣＥＨ三段漂，其白度明显高于相同用氯量下未用酶预处理的漂白浆。另一方面在保持白主东变的情况下酶处理浆的漂白节省近５０％的用氯量。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.