壳聚糖在荔枝果酒澄清中的应用研究

研究了壳聚糖对荔枝果酒的澄清作用,比较了荔枝果酒用壳聚糖处理前后的主要成分的变化.结果表明,经壳聚糖处理后可溶性固形物、酚类物质、可溶性蛋白质、果胶、酒精度、色度等均有不同程度的下降,透光率提高.当壳聚糖用量为0.6 g.L-1时对荔枝果酒的澄清效果最好,且具有很好的生物稳定性,说明壳聚糖是一种有效的荔枝果酒澄清剂.     

Anatomical variations in wood among four native species of Leguminosae grown in arid areas of China

Morphological features and anatomical variations are described and illustrated in detail for four native species of Legumi-nosae grown in arid sandy regions in China, which are Hedysarum scoparium Fisch.et Mey., Caragana korshiskii Kom., Lespedeza bicolor Turcz. and Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. All species showed similar morphological features: distinct growth ring boundaries, ring to semi-ring-porosity, simple perforation plates, alternate intervessel pitting, nonseptate fibers, para...     

竹材表面润湿性研究

从竹材表面润湿性的原理推导入手,采用测定竹材表面接触角的方法,对竹材表面的自由能、路易丝-范得华力和酸碱力关系进行研究,并分析不同部位和不同处理方法对竹材表面湿润性的影响.结果表明:表面粗糙度,抽提物的含量和分布是影响竹材表面润湿性的主要原因;竹材的表面自由能是以路易丝-范得华力为主体;竹材表面的自由能差异主要由竹材表面的酸碱力引起;竹材表面具有稳定的路易丝-范得华力,其数值大小不受竹材表面的化学成分的影响.     

杉木间伐小径材材性试验研究

杉木间伐小径材材性试验结果与成材杉木比较:密度小,晚材率较低,生长较快,吸水性较强;材质为未成熟幼林材种,物理性质较差,力学强度有所降低,作为建筑结构用材时,在设计与施工中必须注意到其强度的降低,采取必要的措施。杉木间伐小径材纤维长度与成材相似,纤维宽度略宽、纤维长宽比值略小,但尚为良好的纤维原料。     

酸催化下苯酚液化木材的制备与表征

在硫酸作用下用苯酚对人工林杨木和杉木进行液化,考察反应时间、反应温度等对液化反应的影响,并对液化产物进行表征分析.结果表明:1)在硫酸催化下,杨木和杉木被苯酚液化的历程相似,但残渣含量稍有不同.酸性催化剂不仅对纤维素和半纤维素起作用,对木质素也起作用.2)反应温度比反应时间对液化效率的影响大,二者均能影响液化产物的分子量和分子量分布.通常杉木液化产物的重均分子量高于杨木.3)液化过程中,木质素和半纤维素首先被液化,最后是纤维素.木材组分的分解、酚化和再缩聚反应主宰整个液化动力学过程及液化产物的结构特征.     

Dielectric properties of copper-ethanolamine treated Chinese fir (Cunninghamia lanceolata Hook.)

In order to clarify the interaction between copper and wood substances in wood treated with copper containing water-borne wood preservatives, the dielectric constant ε′ and dielectric loss factor ε″ of untreated wood and wood treated with four concentration levels of copper-ethanolamine (Cu-EA) solutions were determined within a temperature range from –100 to 40°C and a frequency range from 100 to 1 MHz. Three dielectric relaxation processes were observed in the ε″ spectrum; among them R-I is based on the reorientation of methylol groups in the amorphous region of wood cell walls and R-II is related to wood extractives. R-III appeared in Cu-EA treated wood, and its magnitude decreases with the concentration of Cu-EA solutions used in this experiment. This relaxation process was considered to be based on the reorientation of copper-ethanolamine-wood complexes in wood cell walls. At low copper retention, the hydrogen in the complex can form hydrogen bonding with adjacent hydroxyl groups, which results in a strong bonding state between copper and wood; at high copper retention, the numerous copper-ethanolamine complexes not only hinder them from forming hydrogen bonding with adjacent wood molecules due to steric hindrance, but also weaken the interaction between wood molecules themselves, which corresponds to reducing ε″ values of both R-I and R-III processes. The results explain the fact of in-creasing copper leaching in wood treated with high concentration copper-based water-borne preservatives.     

游离甲醛和人造板释放甲醛

甲醛是室内空气污染源，它常与甲醛系统粘接连在一起，本文根据国内外资料评述人造板甲醛释放量，分析了脲醛树脂的水解和人造板释放甲醛的机理，还介绍了甲醛的毒害，各国政府的有关法规以各种降低甲醛释放量的方法。     

气干材导热系数的温度特性

本文依据气体分子运动论与传热学的基本理论，在２０～１００℃温度范围内，讨论了气干材传热过程中，木材内部水分的蒸发与水蒸汽扩散的行为，研究了温度变化对气手材导热系数发生影响的规律．在理论分析与实验数据分析的基础上，推广和扩充以往关于气干材导热系数的讨论，提出了一个描述气干材导热系数温度特性的公式，计算结果与实验值比较符合     

Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol

Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly). For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania. The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena. The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height. IITA Journal paper number 335     

低温胁迫下暖季型草坪草质膜透性比较研究

以狗牙根、中华结缕草、假俭草、百喜草4个草种为试验材料,用电导率测定其分别在5℃、0℃、-5℃、-10℃不同低温下12h、24h、36h、48h的电解质外渗率的变化,并对4个草种抗寒过程进行方差分析。结果表明,低温处理后各草种叶片电解质的外渗率呈S型曲线增加。中华结缕草电解质透出率变化缓慢,具有较强的抗寒性。假俭草抗寒性最弱。4种试材抗寒强弱顺序为:中华结缕草>狗牙根>百喜草>假俭草。