共查询到20条相似文献，搜索用时 234 毫秒
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在现已优化出的马比木喜树碱提取工艺基础上,采用同一产地样品,分别以7个浓度梯度(40%～100%)的甲醇、乙醇为提取液,实验筛选出提取率最高的提取液为70%的甲醇;进一步比较了目前马比木喜树碱提取的4几种方法,提取效率值显示浸泡超声热回流提取法最优。在此基础上,利用响应面法对提取工艺进行了进一步优化,获得了最佳提取工艺为:浸泡时间14.80 h,超声时间30.70,液料比为60.00,70℃水浴中回流1.5 h。在此工艺条件下,喜树碱含量为2.29%,回归得到的模型预测效果较好。将优化工艺用于提取12个产地的马比木喜树碱含量,将其与文献报道的相同区域样品所测得最高含量比较,优化出的工艺测得含量是其他工艺的2.4至10倍,大幅度提高了喜树碱提取率,具有明显优越性。 相似文献
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超声辅助提取对竹纤维结构和机械性能的影响 总被引：1，自引：1，他引：0
文章以超声波辅助提取竹纤维,研究超声波处理以及超声波处理方式（前超声和后超声）对低试剂量条件下提取竹纤维结构和热性能的影响。结果表明：超声波处理应用于低试剂量竹纤维提取,可降低竹纤维胶质含量,改善竹纤维细度和细度均匀性。用后超声辅助提取竹纤维,竹纤维胶质含量可降低13.2%,纤维直径由489±247 μm降至224±52 μm,平均直径降低率达54.2%。超声辅助提取对竹纤维机械性能有一定程度的影响,对竹纤维拉伸强度略有降低,拉伸模量下降明显,断裂伸长率略有提高,机械强度均匀性增加;后超声辅助提取较前超声辅助提取对竹纤维的机械性能降低程度小。经提取工艺,竹纤维结晶度增加,但超声辅助提取竹纤维结晶度又略有下降,未超声竹纤维结晶度为56.50%,后超声竹纤维结晶度为55.89%,前超声竹纤维结晶度为56.25%;傅里叶红外光谱分析表明,竹纤维化学结构变化主要由纤维提取工艺引起,超声处理对纤维结构影响不明显;通过电镜观察,经纤维提取工艺,原竹材结构中被胶质包覆的单纤维形态暴露,单丝状明显,超声辅助提取增加了纤维表面粗糙度,后超声辅助提取单丝分散性增强;总体上,超声辅助提取可促进低试剂量条件下的长竹纤维提取,对纤维细度有明显改善效果,但对纤维结构和机械性能影响不大。 相似文献
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《竹子研究汇刊》2017,(3)
采用超声波辅助提取法,对淡竹叶总黄酮和固形物得率的工艺条件进行研究。以水为提取溶剂,通过单因素试验研究提取温度、提取时间、超声功率、料液比以及提取次数等对淡竹叶黄酮得率和固形物得率的影响。在单因素的基础上,通过正交试验对超声波辅助提取淡竹叶黄酮和固形物的工艺进行优化。结果表明:超声波辅助提取淡竹叶总黄酮的最佳工艺条件为提取时间40 min,料液比1∶20,超声温度70℃,超声频率40 k Hz。在此最佳工艺条件下总黄酮得率为1.23%。超声波辅助提取固形物的最佳工艺条件为提取时间50 min,料液比1∶40,超声温度70℃,超声频率50 k Hz。在此最佳工艺条件下固形物得率为13.15%。 相似文献
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通过超声波辅助法提取乌苏里瓦韦总黄酮；NaNO2-Al(NO3)3-NaOH法显色以及紫外分光光度法检测总黄酮含量；单因素法考察超声温度、超声功率、超声时间和料液比；Box-Behnken法优化最佳提取工艺；Design-Expert 10.0.7软件进行数据分析。结果显示：单因素实验考查最佳超声功率为364.41 W,超声温度为58.47℃,超声时间为50 min,液料比为19.99∶1(mL/g)。最佳工艺为超声温度58℃,超声功率360 W,液料比20∶1(mL/g)。乌苏里瓦韦总黄酮的提取率为17.944%。表明该方法可以有效提取乌苏里瓦韦中的总黄酮。 相似文献
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以勃氏甜龙竹竹叶为原料,对其中竹叶黄酮的超声提取工艺进行研究,同时采用高效液相色谱法(HPLC)对勃氏甜龙竹、箬竹、浦竹仔及椅子竹中总黄酮及牡荆苷、异牡荆苷、荭草苷、异荭草苷的含量进行测定。结果表明,勃氏甜龙竹超声提取最佳的工艺为:甲醇作为提取溶剂、浓度为70%、料液比为1︰10(w︰v)、超声时间60min、温度40℃。在最佳提取条件下,勃氏甜龙竹中总黄酮得率能达到4.63%。采用高效液相色谱-外标法测定4种丛生竹中总黄酮,含量分别为0.795 2%、1.166 9%、0.092 6%、0.897 2%。勃氏甜龙竹、箬竹和椅子竹中均含有牡荆苷、异牡荆苷、荭草苷及异荭草苷,浦竹仔中仅含有牡荆苷和异牡荆苷。分析方法的建立,为丛生竹化学资源的利用奠定基础。 相似文献
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《中南林业科技大学学报(自然科学版)》2016,(11)
以湘西产的香桂叶为原料,采用超声-微波协同萃取法对香桂叶油的提取工艺进行了研究。以水为萃取溶剂,对提取次数、微波功率、提取时间、液固比、氯化钠浓度等影响萃取的因素进行了单因素实验。在单因素实验结果的基础上,提取1次,对各因素进行正交实验优化,得出了香桂叶油的萃取优化工艺条件:微波功率75W,提取时间30 min,液固比10(m L/g),氯化钠浓度为4%。与传统的水蒸气蒸馏法相比,超声-微波协同萃取不仅大大缩短了蒸馏时间,而且香桂叶油的提取率从2.411%提高到3.288%。通过GC-MS检测,该工艺下香桂叶油中黄樟油素的含量可高达98.09%。 相似文献
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用层次分析法多指标评价优选金花茶超声提取工艺 总被引：1，自引：0，他引：1
为了探寻以超声波法提取金花茶多种生物活性成分的最佳工艺条件,以金花茶花为研究对象,采用均匀试验设计,就不同乙醇浓度、提取时间、料液比、提取温度对金花茶花中各种活性成分提取效率的影响情况进行了试验,并以总黄酮、多酚、总皂苷提取率为评价指标,采用层次分析法和综合评分法对其提取工艺条件进行了分析与评价。试验结果表明,不同提取工艺条件下金花茶花活性成分的提取率存在明显差异,试验确定的最佳提取工艺条件为:超声提取温度为50℃,乙醇浓度为50%,料液比为1︰40,提取时间为50min。按此工艺条件超声提取,总黄酮的平均得率为15.88%,多酚得率为4.83%,总皂苷得率为12.28%。对金花茶提取工艺条件的综合评价平均分值为13.69,说明所选提取工艺稳定可行。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):427-435
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. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(3):206-217
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. 相似文献
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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. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(2):118-130
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. 相似文献
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Steven Maranz Amadou Niang Antoine Kalinganire Djeneba Konaté Bocary Kaya 《Agroforestry Systems》2008,72(3):231-239
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. 相似文献
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《Wood material science & engineering》2013,8(2):76-84
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. 相似文献
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Astra Zaluma Lauma Bruna Darta Klavina Natalija Burnevica Kristine Kenigsvalde Andis Lazdins Talis Gaitnieks 《Forest Pathology》2019,49(6)
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. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):53-61
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. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):15-27
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. 相似文献
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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。 相似文献