功能性纤维素基水凝胶材料及其应用研究进展

水凝胶是一类经物理或化学交联形成具有独特三维网络结构的软物质材料,具有良好的生物相容性、优异的柔韧性、结构可设计性和功能可调性,在多功能材料领域备受关注.纤维素是自然界中含量最丰富的天然高分子材料,除了生物相容性好、可生物降解和可再生等优点,纤维素大分子链上的多羟基结构具有形成多重氢键作用的特点,易与水凝胶基体形成良好...     

聚乳酸开发应用方兴未艾

聚乳酸是以乳酸为单体经化学合成的新型生物降解性高分子材料,其无毒、无刺激性,具有优良的生物相容性,可生物分解、吸收,强度高,可塑性好,易加工成型。聚乳酸在生物体内经过酶分解,最终形成二氧化碳和水,不污染环境,因而被认为是最有发展前途的可生物降解高分子材料,备受国内外关注。聚乳酸在医药领域应用极为广泛。目前,聚乳酸的生     

木质素的高附加值应用研究进展

木质素是由3种苯丙烷单元通过醚键和碳碳键相互连接形成的具有三维网状结构的生物高分子,含有丰富的芳环结构、脂肪族和芳香族羟基以及醌基等活性基团。利用木质素的芳香基、酚羟基、醇羟基、羰基和甲氧基等官能团,能制备出具有紫外吸收、生物可分解性、抗菌性、抗氧化、电子传递和吸附性等特性的高分子材料。笔者结合木质素和改性木质素的结构特点,阐述其在胶黏剂与聚氨酯等聚合材料、纳米复合材料、超级电容器电极材料、碳纤维、复合薄膜材料、金属离子吸附材料等领域研究现状,并对其在应用过程中存在的问题进行了分析。最后,阐述了木质素在未来木质素材料化制备高附价值产品应用研究的重点和方向,木质素在电磁波吸收材料、发光材料等新领域具有广阔的应用前景。     

火生态学的发展与未来展望

一、前言1869年,德国生物学家赫克尔(ErnstHackel)首次提出了“生态学”概念。历经一个多世纪的发展和完善,现已成为一个独立的、具有众多分支的、在自然科学中起举足轻重作用的母体学科。最初的生态学概念和原理与政治经济学、社会科学、生物科学、自然地理、环境科学等学科相互渗透和交叉,现已成为包含上百个分支的大学科。各国生态学家(E.P.Odum,王业遽,沈善敏等人)对生态学分支早已做过归纳和论述。因此,可以说生态学发展至今已完全超越了其     

研究我国林业科技论文探讨森林经理学科的发展

森林经理学是林业科学的一个分支,在学科分类上属二级学科。它是研究实现森林永续利用的理论和技术学科。森林经理学是一门涉及生物、技术、经济的综合性学科。建国42年来,林业科技工作者在这一领域进行一定的研究,并发表了大量的论文。本文对这些论文采取文献计量学的方法,进行分析与研究,以判断森林经理学科的发展趋势,探讨该学科在1949年以来42年间的特点和出现的问题,并且为森林经理学科今后的发展提供了信息。     

新技术 新产品

生物电子计算机是用生物分子代替硅片的计算机,它具有当代硅片计算机所无法比拟的优点:体积小、容量大、速度快;具有自我复制和自我改善能力;具有可思维性及复杂的处理功能,而且可直接接受人脑的指挥,如植入人体后可成为人的一个器官,并和大脑和神     

高强度耐侯性的改性聚氯乙烯材料

高强度耐侯性的改性聚氯乙烯材料聚氯乙烯（ＰＶＣ）由于存在光、热稳定性和耐寒性差、弹性低、综合强度不高，低分子增塑剂易迁移等缺陷，限制了它在高技术领域中的应用，随着高分子材料加工技术的发展。尤其是填充、共混、增强等手段的出现，国内外已能够制备出性能范围...     

全息生物学及其在林业上的应用前景

<正> 全息生物学Holographic Biology是中国人创建的生物学的一个新的分支学科。山东大学张颖清同志在提出生物全息律(1980,1981)之后,又进一步提出了全息生物学的概念和理论(1984)。一、全息生物学的基本概念1.生物全息律生物全息律揭示了生物体部分与部分,部分与整体之间的全息对应性。在一个生物体,功能或结构与其周围的部分有相对明显的边界的相对独立的部分被称为全息元。一个全息元上的各个部位,都分别在整体或其它全息元上其所对应的部位生物学特性相似     

性诱剂防治白杨透翅蛾

白杨透翅蛾是杨树的一大害虫,幼虫为害顶芽,形成秃梢;蛀入树干造成组织增生,长成瘤瘿,易被风折。尤其对苗木的为害,损失更大。并可随苗木传播到新区。所以,在调运杨苗时,常被列为重点检疫对象。推广使用“性诱剂防治白杨翅蛾新技术”可解除白杨透翅蛾的为害,减轻杨苗检疫工作量。 1.诱捕材料 白杨透翅蛾性诱剂,代号EZODDOH,纯度为98％-99.5％和84％-94.8％,     

基于时间维度儿童户外活动空间景观设计探析

儿童时期是一个人最易接受新鲜事物、感知自然最敏感的阶段。户外的活动空间是儿童在成长过程中一个接触外界的重要场所。本文基于时间维度探析儿童户外空间景观设计,设法通过时间和空间这样的四维空间来引导儿童在成长的过程中能够更多感受自然、释放天性、获取知识,享受纯真的童年时光。     

秸秆轻质墙体保温性能的研究

采用准稳态法,对不同密度规格的秸秆轻质墙体材料进行热性能测试。通过测试材料的导热系数,计算不同组合墙体的热阻。结果证明秸秆轻质墙体材料具有良好的保温性能,可以作为墙体内衬保温材料,以及非承重墙的墙体材料。     

Three-dimensional light structure of an upland Quercus stand post-tornado disturbance

Light is the most common limiting factor in forest plant communities,influencing species composition,stand structure,and stand productivity in closed canopy stands.Stand vertical light structure is relatively simple under a closed canopy because most light is captured by overstory trees.However,wind disturbance events create canopy openings from local to landscape scales that increase understory light intensity and vertical light structural complexity.We studied the effects of an EF-1 tornado on horizontal and vertical(i.e.three-dimensional)light structure within a Quercus stand to determine how light structure changed with increasing disturbance severity.We used a two-tiered method to collect photosynthetic photon flux density at 4.67 m and 1.37 m above the forest floor to construct three-dimensional light structure across a canopy disturbance severity gradient to see if light intensity varied with increasing tornado damage.Results indicate that increased canopy disturbance closer to the tornado track increased light penetration and light structure heterogeneity at lower forest strata.Increased light intensity correlated with increased sapling density that was more randomly distributed across the plot and had shifted light capture higher in the stand structure.Light penetration through the overstory was most strongly correlated with decreased stem density in the two most important tree species(based on relative dominance and relative density)in the stand,Quercus alba L.(r=-0.31)and Ostrya virginiana(Mill.)K.Koch(r=-0.27,p<.01),and indicated that understory light penetration was most affected by these two species.As managers are increasingly interested in patterning silvicultural entries on natural disturbances,they must understand residual stand and light structures that occur after natural disturbance events.By providing spatial light data that quantifies light structure post-disturbance,managers can use these results to improve planning required for long-term management.The study also provides comparisons with anthropogenic disturbances to the midstory that may offer useful comparisons to natural analogs for future silvicultural consideration.     

Micromechanical properties of common yew (Taxus baccata) and Norway spruce (Picea abies) transition wood fibers subjected to longitudinal tension

The longitudinal modulus of elasticity of common yew is astonishingly low in light of its high raw density. At least this was found for specimens examined at the solid wood level and at the tissue level. However, to reveal if this low axial stiffness is also present at the cellular level, tensile tests were performed on individual yew fibers and on spruce fibers for reference. The results revealed a low stiffness and a high strain to fracture for yew when compared with spruce. This compliant behavior was ascribed to a relatively high microfibril angle of yew measured by X-ray scattering. It can be concluded that the high compliance of yew observed at higher hierarchical levels is obviously controlled by a structural feature present at the cell wall level. In future studies, the biomechanical function of this compliant behavior for the living yew tree would be of particular interest.     

Shoot growth patterns in saplings of Cleyera japonica in relation to light and architectural position

To gain further insight into crown development, the influences of shoot architectural position (branch order) and light environment on patterns of shoot growth of Cleyera japonica Thunberg (Theaceae) were investigated. Annual shoot length and light environment were positively correlated within same-order branches. Shoot length differed significantly among branch orders: shoot length was greater for the lower-order branches when light environments were comparable. Lower-order branches lengthened to a certain extent even if light availability was relatively low, whereas higher-order branches did not grow vigorously even when light availability was relatively high. Within same-order branches, branching was independent of the light environment of the shoot. Sylleptic shoot production differed significantly among branch orders, with most sylleptic shoots being produced on second-order branches. It is concluded that both light condition and architectural position of shoots must be considered when examining the mechanisms underlying crown development.     

鄂西南地区五倍子资源现状调查与利用对策研究

五倍子是重要化工原料。用五倍子加工而成的单宁酸及其系列产品广泛应用于医药、卫生、轻工、食品、电子、国防等行业领域 ,市场前景广阔。以五峰为核心的鄂西南地区五倍子野生资源丰富 ,自然分布面积达 3 3万hm2 ,通过深入调查研究 ,制定发展规划 ,争取项目和资金 ,重点扶持五倍子产业发展 ,是天保新时期促进农民增收、财政增长的新途径 ,也是湖北建设林业产业强省的现实需要。     

Simulating the dynamic behavior of Douglas-fir trees under applied loads by the finite element method

The finite element method of structural analysis was used to model the dynamic behavior of three 20-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees subjected to applied loading. Detailed measurements of stem and branch geometry were made for each tree, enabling the first-order branches of each tree to be represented as individual cantilever beams attached to the stem. Three values for branch modulus of elasticity (E) were assumed: 4, 5 and 6 GPa. For two trees with relatively large crown masses (175 and 250 kg), significantly improved estimates of natural frequency were obtained when the branches were modeled as separate cantilever beams rather than as a series of discrete masses attached to the stem. Closest agreement with the results from field sway tests was found when branch E was 4 GPa. Oscillations of individual branches contributed to the damping of tree oscillations--a phenomenon known as structural damping--with the contribution increasing as branch E decreased. When branch E was 4 GPa, the phase difference between the oscillation of the stem and that of some branches was almost 180 degrees. We applied a series of forces separately to the stem and branches of each tree and determined the mechanical transfer function for each loading case. These transfer functions were similar to the theoretical transfer function for a damped harmonic oscillator, but showed a smaller tree response at higher loading frequencies, particularly when branch E was 4 GPa. Branch structural properties, particularly modulus of elasticity, appear to be important in defining overall tree behavior under applied loading.     

生物柴油植物麻疯树群体构型对资源性环境因素的反应

本文研究了生物柴油植物麻疯树的群体构型与环境的关系,探讨了分支率、分支角度、分支密度和枝长对资源性因素的反应。把乔木林遮盖、土壤厚度和微地形分别作为光照、养分和水分梯度的样地选择标准。结果表明,在林外强光、土层厚度较大与水分含量较高时分支率明显较高,枝长明显较大,分支角度无变化。分支密度是群体构型的一个重要特征,与分支率和枝条密度呈现直线相关。在水分含量较高的样地分支密度显著较高。表明,麻疯树群体构型对资源性环境因素存在明显的反应,具有资源环境依赖性。在生产上,需要从群体构型特征优化上考虑高产和经营问题。     

不同造林密度对米老排人工林枝条发育的影响

目的 探究不同造林密度对米老排枝条发育的影响规律,为米老排修枝培育无节良材提供理论依据。 方法 本研究以8年生米老排密度试验林为研究对象,通过调查一级枝条的数量、基径、长度、分枝角、分枝高和方位角等观测数据,分析5种造林密度对米老排林分9 m以下枝条发育以及空间分布的影响。 结果 表明：米老排枯枝层的高度随密度的增大而增高,枝条总量和枯枝数量受密度影响不显著,林分枯枝率随密度的增大而增大,活枝量与密度呈负相关;米老排树干9 m以下枝条基径、枝长和分枝角均随密度的增大而减小;水平方向上,同一密度,不同方位的枝条基径、枝长、分枝角和数量均随方位角的增大先减小后增大,在光照条件较好的方位区间（0~90°或316~360°）内达到最大值;垂直方向上,枝条基径、长度、数量随相对位置的升高先逐渐增大,之后无显著变化。 结论 造林密度对米老排枝条大小的影响显著,高密度（2 500株·hm-2）可以抑制枝条的生长;建议根据培育目的选择合适的造林密度,并采用目标材种培育技术,在幼龄期对优势木及亚优势木进行人工修枝,提高木材质量。     

异质光环境下云南红豆杉的构型与叶构件水分特征

对全光照、林隙、林冠3种光照环境下6年生云南红豆杉的构型和叶水分特征研究结果表明:云南红豆杉的构型在不同光照条件下存在显著的可塑性变化,叶构件的水分特征也有不同程度的差异。全光环境下的云南红豆杉树体高大、树冠开阔,圆满度为0.97(约为林冠下的两倍);全光下的总体分枝率为8.57,显著大于林隙的6.40和林冠下的4.81;全光中的1级枝长度、枝倾角、叶倾角等构型指标都显著大于林隙和林冠下的;3种光环境下各枝级的叶片分配存在明显的差异,全光下枝条的叶片数量是林隙的2.77倍,是林冠下的6.88倍,但它们都是1级枝的叶最多;叶构件的水分饱和亏缺有随着光照强度减弱而增大的趋势,组织密度、相对含水量、干鲜比则随着光照减弱而减小,表明叶片的抗旱保水和抵御水分胁迫的能力随着光照强度的增强而变大。云南红豆杉为适应不同光环境,在形态和生理方面都做出适应性调整。     

小波分析在中密度纤维板无损检测中的应用

以中密度纤维板为试件,通过纵向共振和弯曲振动试验讨论小波分析方法用于无损检测的可行性.结果表明:小波分析得到的中密度纤维板试件动弹性模量与常规弯曲静弹性模量在0.01水平下相关性非常显著,可以用小波分析方法测得的动弹性模量来表征常规弯曲静弹性模量;可以用小波分析的方法判断出试件是否有缺陷,小波分析在试件缺陷无损检测方面具有优越性.