纤维素纳米晶体膜及胆甾型液晶图案的制备

以微晶纤维素为原料,采用硫酸水解法制备了纤维素纳米晶体悬浮液,再通过室温下自然干燥的方法制备了纤维素纳米晶体薄膜。通过扫描电子显微镜、紫外可见分光光度计和偏光显微镜,分别研究了纤维素纳米晶体薄膜的光学性能、内部微观结构以及纤维素纳米晶体悬浮液的光学织构变化。研究结果表明,在质量分数64%硫酸、45℃条件下,水解微晶纤维素2 h后可制得稳定的纤维素纳米晶体悬浮液;超声处理后的悬浮液可形成胆甾型液晶相,随着悬浮液浓度的变化,通过偏光显微镜可以观察到胆甾型液晶的圆盘织构、条纹织构以及特征指纹织构;超声处理后悬浮液制备的纤维素纳米晶体彩色薄膜具有胆甾型液晶结构;利用偏光显微镜观察到的胆甾型液晶纹理和色彩图案具有防伪性能,可将它们制成具有唯一性的防伪标签。     

芦苇浆纳米纤维素的制备工艺条件优化及形貌分析

采用硫酸水解芦苇浆制备纳米纤维素,并用正交试验优化了工艺参数,分析了硫酸质量分数、反应温度和水解时间对芦苇浆制备纳米纤维素得率的影响.用透射电镜表征了芦苇浆制备的纳米纤维素的形貌.结果表明硫酸水解芦苇浆制备纳米纤维素的3个工艺参数对其得率的影响为硫酸质量分数的影响最大,反应温度的影响次之,而水解时间的影响较小;硫酸水解芦苇浆制备纳米纤维素的优化工艺条件为硫酸质量分数52％,反应温度47℃,水解时间4h,此条件下纳米纤维素得率最高(82.81％).芦苇浆制备的纳米纤维素经透射电镜观察呈棒状,纤维素长度达到纳米级.     

MCC接枝PVA/可溶性淀粉保鲜膜的制备

为开发全生物降解聚乙烯醇/可溶性淀粉复合膜,以聚乙烯醇和可溶性淀粉为基材,D-山梨醇为增塑剂,柠檬酸为交联剂,硅烷化接枝后的微晶纤维素为增强相,制备得到高性能全生物降解复合膜。通过对复合膜的机械性能、结构形态等进行表征,探究微晶纤维素接枝率对复合膜吸水率、溶解度、透光率、水蒸气透过率以及保鲜等性能的影响规律。结果表明：当调制的主体膜液中聚乙烯醇与可溶性淀粉质量比为82.83∶17.17、D-山梨醇质量分数为12.39%、柠檬酸质量分数为8.95%,制备得到的复合膜水蒸气透过率未符合标准且耐水性较差,而接枝2%微晶纤维素的复合膜水蒸气透过率降低了27.38%,吸水率与溶解度分别降低了11.69%和7.99%,且透光率能达到90.5%;微晶纤维素与正硅酸乙酯配比为2∶4时接枝效果最佳;当微晶纤维素质量分数为2%时复合膜热稳定性最佳,在香蕉保鲜性上提高42.1%。综上,经过一定量的微晶纤维素接枝改性的复合膜满足保鲜膜相关标准,并且保鲜性能提升明显,可作为一种可靠的全生物降解保鲜膜。     

液氮冷冻干燥法制备纳米纤维素气凝胶

纤维素气凝胶被誉为继有机气凝胶和无机气凝胶之后的新一代气凝胶,是新生的第三代材料,在吸附材料等领域具有广阔的应用前景。笔者先以微晶纤维素(MCC)为原料经硫酸水解法制得纳米纤维素(NCC),再通过无机盐溶液物理凝胶成型法、叔丁醇置换和液氮冷冻干燥制备球形纤维素气凝胶。利用场发射扫描电子显微镜(SEM)、万能力学试验机、热重分析仪、全自动比表面积及孔隙分析仪对所制备的纳米纤维素气凝胶的力学性能、微观形貌、比表面积、孔径分布及热稳定性进行表征分析。结果表明,液氮冷冻干燥法制备的球形纳米纤维素气凝胶主要为疏松多孔的三维层状结构同时存在少量三维网络结构,其比表面积在104.07~164.97 cm~2/g之间,孔径主要分布在10~25 nm内;纳米纤维素气凝胶的力学性能、压缩强度、密度随着纳米纤维素质量分数的增加而变大;纳米纤维素气凝胶的热稳定性与微晶纤维素和纳米纤维素相似。     

高温高压制备微晶纤维素新工艺的研究

探讨处理温度、处理时间和盐酸浓度对高温高压制备微晶纤维素的影响,结果表明:从微晶纤维素得率角度,高温高压制备微晶纤维素的最佳工艺为:盐酸质量分数为2.5%、处理时间为180 min、水解温度为130℃;从表面膨胀体积角度,高温高压制备微晶纤维素的最佳工艺为:盐酸质量分数为1.0%、处理时间为120 min、水解温度为150℃。     

聚乙烯醇/纳米纤维素/石墨烯复合薄膜的制备与性能

利用生物质纳米纤维素纤维的高强度和高长径比,向聚乙烯醇中引入纳米纤维素,可改善薄膜的拉伸性能。针对聚乙烯醇阻隔性能的改善问题,选用片层的还原氧化石墨烯作为增强相,将自制的纳米纤维素和氧化石墨烯加入聚乙烯醇溶液中,以D-果糖为绿色还原剂,分别添加质量分数0.2%,0.4%,0.6%,0.8%的还原氧化石墨烯,采用浇涂法制备聚乙烯醇/纳米纤维素/石墨烯复合薄膜。通过纳米纤维素与石墨烯的协同增强作用,研制了兼具优良阻隔性能和拉伸性能的生物降解薄膜。结果表明,当纳米纤维素和石墨烯质量分数分别为0.8%和0.6%时,聚乙烯醇/纳米纤维素/石墨烯复合薄膜的拉伸强度、氧气透过系数、对水的接触角和吸水率分别为88.76 MPa、0.592×10-15cm~3·cm/(cm~2·s·Pa)、90.5°和72.9%。但石墨烯的用量存在一个阈值,当质量分数高于0.6%时,复合薄膜的力学和阻隔性能反而下降。     

K-卡拉胶与纳米微晶纤维素凝胶化的研究

K-卡拉胶和纳米微晶纤维素(CNC)共混时可以得到凝胶多糖。多糖总质量分数为1%,K-卡拉胶与纳米微晶纤维素的比例为9∶1时,可达到协同相互作用的最大值。研究了pH值和体系盐离子浓度对凝胶强度的影响,并通过FT-IR光谱和Raman光谱对这两种多糖之间的相互作用机理进行了初步的探讨。     

叔丁醇冷冻干燥法制备纳米纤维素气凝胶

以纳米纤维素为原料,采用"CaCl_2溶液促进物理凝胶法"制备水凝胶,选用叔丁醇溶液为置换溶剂并采用"多步法"完成溶剂置换,最后通过冷冻干燥法制备纳米纤维素气凝胶。通过扫描电子显微镜(SEM)、全自动比表面积与孔隙度分析仪和热重分析仪(TG)对所制备的纳米纤维素气凝胶进行微观形貌、比表面积、孔径分布及热稳定性进行表征分析。结果表明:叔丁醇冷冻干燥法制备的纳米纤维素气凝胶是具有层状的以中孔和大孔为主的多孔材料,其比表面积可达174.3 m2/g,收缩率仅为7.86%,平均孔径约为18.4 nm。随着纤维素质量分数的增加,纳米纤维素气凝胶的吸附量和比表面积增大,孔隙度增加,收缩率逐渐减小;纳米纤维素气凝胶具有与微晶纤维素和纳米纤维素相似的热稳定特性。CaCl_2溶液通过改变原始溶胶体系的电荷分布而使粒子更易相互靠近聚集形成凝胶,落入其中的纳米纤维素颗粒会保持其落入瞬间的完整状态。     

纳米纤维素制备优化及其形貌表征

通过硫酸水解微晶纤维素制备纳米纤维素,分析硫酸浓度、反应温度和水解时间对纳米纤维素得率的影响,采用正交实验优化了实验参数。用场发射环境扫描电镜(ESEM-FEG)和透射电镜(HR-TEM)表征了微晶纤维素与纳米纤维素的形貌,并对其尺寸分布进行了分析。结果表明,当硫酸浓度为56%,反应温度40℃,水解时间90min时,纳米纤维素得率最高,达55.40%;电镜观察纳米纤维素呈棒状,其尺寸较微晶纤维素明显减小,直径2-24nm,长度为50-450nm。     

微晶纤维素丙烯酸酯复合微球的制备及性能研究与运用

采用反相悬浮聚合法制备微晶纤维素丙烯酸酯复合微球,在油水比(O/W,质量比)为2.4:1.烷基酚聚氧乙烯醚(OP)与十二烷基硫酸钠(SLS)质量比为4:1,甲基丙烯酸甲酯(MMA)、丙烯酸正丁酯(BA)与N-羟甲基丙烯酰胺(NMA)为35:15:3和搅拌速率为200-400 r/min条件下,可以得到微晶纤维素丙烯酸酯复合微球.而且对微球的内部结构、性能和微晶纤维素反应前后结晶度进行了分析.结果表明,微晶纤维素参与了交联并被包埋在聚丙烯酸酯内部.将粒径为85 nm左右的复合微球与聚甲基丙烯酸甲酯(PMMA)共混制备膜塑料,可以得到弯曲性能优异、吸水率低的黄色半透明的模塑料.     

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.     

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。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.