内切纤维素酶Ι在混合办公废纸酶法脱墨中的作用

对内切纤维素酶Ⅰ(EGⅠ)在混合办公废纸酶法脱墨中的作用进行了研究。结果表明：EGⅠ在混合办公废纸脱墨中起着明显作用，浆料经EGⅠ处理后浮选有比较高的油墨脱出率。EGⅠ脱墨的最佳工艺条件为：温度60℃，pH值7．5，时间40min，每克浆酶用量0．5IU；酶处理过程中随着酶用量的增加，纸浆平均聚合度呈下降趋势，当每克浆酶用量为0．5IU时，纸浆聚合度下降的幅度不大。含有碳酸钙填料和(或)涂料的废纸其灰分的存在影响酶脱墨效果；酸处理可提高油墨脱出率，浆料经酸处理后可进一步提高EGI的脱墨效果。     

内切木聚糖酶与木糖苷酶预处理对麦草浆漂白性能的影响

研究了内切木聚糖酶与木糖苷酶预处理对麦草浆漂白性能的影响。结果表明，无论是内切木聚糖酶还是木糖苷酶预处理漂白浆的白度均比对照浆高，分别高出对照浆的2．5和1．9个百分点，同时漂白浆的强度也好于对照浆的强度。内切木聚糖酶和木糖苷酶混合预处理漂白浆的白度分别比内切木聚糖酶和木糖苷酶高出0．9和1．5个百分点，这表明内切木聚糖酶和木糖苷酶在纸浆预处理过程中具有协同作用。通过电镜观察发现经内切木聚糖酶和木糖苷酶预处理后纸浆的表面和横断面有许多孔隙，其中经内切木聚糖酶预处理后纸浆的孔隙比木糖苷酶要多而且大。通过X-射线衍射分析发现内切木聚糖酶和木糖苷酶均不能破坏纸浆的结晶度。     

中性脱墨剂起泡性与脱墨效果间关系的研究

在中性条件下对混合办公废纸(MOW)进行脱墨,研究了脱墨效果和脱墨剂起泡性之间的关系。结果表明,在单一组分脱墨剂中,阴离子表面活性剂起泡性越强脱墨效果越差,起泡性最好的AEC-7-Na脱墨浆白度仅为80.51%(ISO),泡沫越稳定脱墨效果越好,泡沫稳定性最强的ABS脱墨浆白度达到83.04%(ISO)。非离子表面活性剂的脱墨效果与起泡性强弱无明显关系,泡沫的稳定性对脱墨效果没有影响。在非/阴离子表面活性剂复配实验中证明,其脱墨效果与脱墨剂泡沫之间的关系不确定,非离子表面活性剂的搜集能力和两种活性剂的复配性是决定脱墨效果的主要因素。得到了几组脱墨效果较为理想的中性脱墨组合(质量比均为1∶1):T-80+SAS、AEO20+AES、AEO12+AEC-7-Na、S-80+AES。     

酶处理对混合杨木P-RC APMP浆打浆性能的影响

探讨了纤维素酶、木聚糖酶处理对混合杨木温和预处理和盘磨化学处理的碱性过氧化氢机械浆(P-RC APMP)的打浆性能和打浆能耗的影响。结果表明:与未经过酶处理浆相比,纤维素酶和木聚糖酶处理可明显改善纸浆的打浆性能和降低打浆能耗,纸浆打浆度提高1.0～6.5°SR,或在相同打浆度下打浆能耗降低10%～25%。纤维素酶处理浆裂断长提高18%,撕裂指数提高14%,耐破指数提高16%,耐折度提高100%。木聚糖酶处理纸浆白度提高1.7度(ISO),纸浆物理强度略有上升。纤维素酶在改善纸浆打浆性能、降低打浆能耗和提高物理强度方面好于木聚糖酶,木聚糖酶在改善纸浆光学性能方面优于纤维素酶。酶处理可以使纸浆纤维结构变得疏松柔软,从而增强纤维间的交织能力。     

碱性纤维素酶发酵条件的研究

采用芽孢杆菌Bacillus sp.AC-2作为碱性纤维素酶的生产菌株，对其发酵条件进行了研究。适宜的种子茵龄为24h；适于产酶的培养温度为37℃，培养基初始pH值10．5；在碳源和氮源分别为1％的淀粉和2％的豆饼粉时，碱性纤维素酶活力可达到76．04U／mL。该酶反应的最适温度为60℃；酶液在70℃以下、pH值6．0～10．0范围内稳定。该酶制剂在棉织物洗涤和纸浆脱墨方面具有良好的应用前景。     

纤维素酶系组成对二次纤维形态与表面结构的影响

用不同滤纸酶活力和羧甲基纤维素酶活力比(F／C)值的纤维素酶系处理轻量涂布纸二次纤维，研究了纤维素酶系组成对二次纤维性能的影响。随着F／C值从0增到2．5，长度小于0．2mm的纤维分布密度由23．55％降低到17．50％。纤维加权平均长度由1．067mm增加到1．168mm，纤维的卷曲系数由0．103下降到0．087；纤维的扭结强度由0．78个／mm增加到0．84个／mm。随着F／C值的增加，纤维素酶系外切酶的酶解作用增强，细小组分逐渐减少，二次纤维平均长度呈上升趋势，卷曲程度下降，有利于浆料滤水性能的改善，但纤维扭结强度上升对单根纤维强度和纸张强度产生不利影响。     

酶在木材制浆造纸工业中的应用

评述了酶在木材制浆造纸工业中的应用，包括：酶的应用迅速发展；酶－－机械制前途；酶漂白纸浆更值得重视；酶对废纸脱墨效果好；酶能改善纸张的性质和酶可以降低废水毒性。     

酶在木材制浆造纸工业中的应用

评述了酶在木材制浆造纸工业中的应用，包括：酶的应用迅速发展；酶一机械制浆很有前途；酶漂白纸浆更值得重视；酶对废纸脱墨效果好；酶能改善纸张的性质和酶可以降低废水毒性。     

二次纤维酶水解生成葡萄糖的研究

将回收的废纸脱墨、洗净即为二次纤维。脱去其中的木质素和半纤维素，得纤维素，用纤维素酶水解生成葡萄糖。对温度、pH值、酶用量、时间分别进行单因素试验，通过测定水解液葡萄糖含量，找出水解的适宜条件：温度45℃，pH值4．8，酶用量8IU／g(对绝干原料)，产率可达60％以上。     

黄胸散白蚁纤维素酶的研究

对黄胸散白蚁体内纤维素酶所做的研究结果表明，37℃时，C1酶与pNPC底物反应的最佳时间为1h，Cx酶与CMC-Na和β-葡糖苷酶与Salicin反应的最佳时间均为0．25h。黄胸散白蚁工蚁头部纤维素酶主要是Cx酶和β-葡糖苷酶。肠道组织中，3种纤维素酶主要分布于前肠和后肠组织。Cx酶在前肠的酶量占肠道组织该酶总量的52．9％；C1和β-葡糖苷酶绝大部分在后肠，在该部位所含酶量分别占整个肠道组织酶总量的83．3％和80．2％。说明3种纤维素酶的活性在不同组织中有较大差异。     

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.