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1.
Furanosesquiterpenes from Commiphora sphaerocarpa and related adulterants of true myrrh 总被引：2，自引：0，他引：2
A new furanosesquiterpene, (1E)-8,12-epoxygermacra-1,7,10,11-tetraen-6-one (3), was isolated from the resin of Commiphora sphaerocarpa together with the known compounds curzerenone (1), furanodienone (2), (1E)-3-methoxy-8,12-epoxygermacra-1,7,10,11-tetraen-6-one (4), (1(10)E,2R*,4R*)-2-methoxy-8,12-epoxygermacra- 1(10),7,11-trien-6-one (5), and dihydropyrocurzerenone (6). Hydrodistillates of the resins of C. sphaerocarpa, C. holtziana, C. kataf and C. myrrha were analysed. The identifications were aided by NMR, GC and GC-MS. 相似文献
2.
为探究预热温度对压缩木材的色饱和度差(ΔC*)、色相差(ΔH*)、总体色差(ΔE*)、吸湿率、厚度变化和回弹率的影响,以毛白杨(Populus tomentosa)为研究对象,将其封端、浸水和放置后置于热压机上进行预热12 min,预热温度分别为90、120、150、180℃和210℃,预热完成后在相同温度下压缩5 mm。结果表明:随着预热温度的升高,ΔC*、ΔH*和ΔE*逐渐增大,温度>150℃,三者急剧增大,说明150℃是材色变化的一个关键温度点。随着预热温度的升高,压缩木材的吸湿率、厚度变化和回弹率逐渐减小,温度>150℃,三者急剧减小,说明150℃也是压缩木材尺寸稳定性变化的一个关键温度点。此外,ΔE*和回弹率呈线性负相关,ΔE*越大,其对应的回弹率越小。 相似文献
3.
Dewar RC 《Tree physiology》1990,6(4):417-428
This paper discusses the general formulation of a model that describes carbon storage in a forest and its timber products as a function of the forest growth curve, the rotation period and the carbon retention curves for the timber products. After a number of rotations, the rotation-averaged quantity of stored carbon approaches an asymptotic value. It is shown that, when forests are managed for maximum sustained yield of biomass, the contribution to asymptotic carbon storage from timber products is about 2.5D/T* times the contribution from living trees, where D is the characteristic decay time for reconversion of timber products to carbon dioxide, and T* is the normal rotation period for maximum sustained yield. For a given value of D/T*, carbon storage can be optimized if the policy of maximizing sustained yield is relaxed. For D/T* < 1, as the rotation period is increased indefinitely, the asymptotic level of carbon storage increases monotonically toward the value of the carbon content of living trees at maturity, g(f). For D/T* > 1, there is a finite, optimal rotation period, T(o), greater than T*, for which asymptotic carbon storage is greater than g(f). As D/T* tends to large values, however, T(o) tends to T*, so that, in this limit, management for maximum sustained yield also ensures maximum carbon storage. From initial planting, the time taken to reach asymptotic carbon storage decreases as the normal rotation period, T*, decreases, but increases almost linearly with increasing decay time of timber products, D. This result qualifies the short-term value of any particular planting strategy. 相似文献
4.
5.
为给观赏海棠果色分类、果色育种及特异果色种质的挖掘提供理论依据与技术参考,采用X-Rite色差计对27份观赏海棠种质在果实的不同生长发育时期的果色进行了观测,并对观赏海棠群体果色的时序动态变化规律进行了研究。结果表明:(1)观赏海棠种质果实色彩参数a*、h°、b*值的变异程度均高于其C*和L*参数值。(2)基于果实不同生长发育时期观赏海棠种质群体果色a*、h°、b*等参数值的聚类分析结果表明,海棠种质群体果实生长初期其果色为红绿色,随着果实的日益成熟,其果色呈现出黄色、橙色及红橙色等种色彩。(3)从基于观赏海棠种质群体在果实不同生长发育时期的果色L*、C*、h°等参数值而构建的CIELCH色空间动态分布格局图中可以发现,所有种质在其L*维度方向呈整体上移趋势;在C*维度方向呈整体右移趋势;在h°维度方向上,红色果皮(h°值为0~35)的种质所占比例呈"下降—升高—下降"的变化趋势,橙色果皮(h°值为35~55)的种质所占比例呈"升高—下降—升高—下降"的变化趋势,黄色果皮(h°值为55~90)的种质所占比例呈"升高—下降—升高"的变化趋势,绿色果皮(h°值为90~110)的种质所占比例呈先升高后下降的变化趋势。(4)对其果色稳定性(色差值△E)的分析结果表明,‘火鸟’‘金丰收’‘冬金’‘冬红’全年果皮颜色的变化均明显,且其果期均长,而‘完美紫色’和‘紫王子’海棠果皮的颜色从幼果期至成熟期均呈紫色。 相似文献
6.
红木类木材表面材色和光泽度的分布特征 总被引：9，自引：0，他引：9
采用X-rite SP60积分球式分光光度仪对19种红木类木材表面材色参数进行测量，讨论了这些参数的色空间分布特征，其结果为：L^＊为26—47，a^＊为1—17，b^＊为1～21；V为1～4，C为1～13，H为9R～4Y。大部分分布在YR色调系内，分布在低明度范围（L^＊，V值较低）的偏黑色、暗红褐色等深材色树种。ward聚类分析结果：紫檀木类、乌木类、条纹乌木类、黑酸枝木类和鸡翅木类归为第一大类；花梨木类、香枝木类、红酸枝类归为第二大类。两大类之间色度学参数欧式距离为30．8004。对19种红木类木材表面光泽度的测量结果为：红木素材与一般木材相比表面光泽度较高，GZL数值变化范围为5．77％-15．02％，GZT数值变化范围为4．07％～7.7％。 相似文献
7.
3种棕榈藤藤材防变色的研究 总被引：5，自引：0，他引：5
目前,棕榈藤(rattan)主要用作家具、工艺品,其产品具有很高的商品价值.藤制品在使用过程中色调逐渐加深(变色),尽管变色对材质材性影响不大,但对色调有损伤,直接影响制品的外观,降低商品价值.因此,抑制藤材的变色对保持产品外观和商品价值具有重要意义. 相似文献
8.
通过对樟子松木材变色部位的化学处理及分析认为,樟子松蓝变类型属于微生物变色;室温下,自然和湿润两种状态放置的樟子松木材,随着时间的变化(以2个月为1个时间单位),L*(明度)、a*(变红度)、TW(白度)都有所下降,DE*(总色差)呈上升趋势,而b*(变黄度)分别呈现增强和减弱两种相反方向的变化趋势. 相似文献
9.
Cycloartane saponins from Astragalus peregrinus as modulators of lymphocyte proliferation. 总被引：1，自引：0，他引：1
L Verotta M Guerrini N A El-Sebakhy A M Asaad S M Toaima M E Abou-Sheer Y D Luo J M Pezzuto 《Fitoterapia》2001,72(8):894-905
From Astragalus peregrinus, four cycloartane-type saponins have been isolated and their structures elucidated by spectral means as 20(R),24(S)-epoxy-9 beta,19-cyclolanostane-3 beta,6 alpha,16 beta,25-tetrol 3-O-beta-D-glucopyranoside (1), 20(R),24(S)-epoxy-9 beta,19-cyclolanostane-3 beta,6 alpha,16 beta,25-tetrol 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranoside (2), 20(R),24(S)-epoxy-9 beta,19-cyclolanostane-3 beta,6 alpha,16 beta,25-tetrol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside (3) and 20(R),25-epoxy-9 beta,19-cyclolanostane-3 beta,6 alpha,16 beta,24(S)-tetrol (24-O-acetyl)- 3-O-alpha-L-rhamnopyranosyl-(1-->2)-(6'-O-acetyl)-beta-D-glucopyranoside (4). Compounds 2 and 3 showed to stimulate the proliferation of mouse splenocytes and were not significantly cytotoxic. 相似文献
10.
探讨了近红外光谱(NIRs)技术对实现热处理毛竹分选和性能在线检测的可能性。采集了3种不同温度(150,180和210℃)热处理及未处理毛竹的径切面近红外光谱信息,应用主成分分析方法与偏最小二乘法对竹材进行分类,并建立了热处理竹材的材色、密度以及力学性能预测模型。结果表明:1)近红外光谱二阶导数谱图在7 004和6 452 cm-1等吸收带处很好地反映了竹材热处理对应化学成分的变化,表明了近红外光谱变化与化学成分变化的一致性,也说明了NIRs用于快速分析热处理竹材材性的可能性; 2)热处理竹材在主成分得分图中呈明显的聚类分布特征,说明了NIRs技术对于热处理竹材良好的分类能力; 3)材色预测模型的模型参数R2≥0.93、RPD均大于3.90,表现出了非常好的材色预测性能。气干密度、绝干密度以及抗弯强度预测模型的R2分别为0.83,0.85和0.82,RPD分别为2.42,2.59和2.34,能够满足竹材性能的评估精度要求。 相似文献
11.
《中国林业科技(英文版)》2012,(Z1):29-38
Bamboo deterioration caused by light becomes a significant problem as application of bamboo extends from indoor to outdoor.The color and roughness of bamboo are two important exterior performances.This study focused on UV resistant nano composites coatings for exterior use and what aimed to find a formulation which could enhance the durability of bamboo.Four kinds of film-forming materials and four kinds of nano particles were used to improve bamboo exterior performance.The color and roughness of nano composites coatings were measured during accelerated weathering.Artificial aging time was 174 h at the temperature of 50 ℃.The experiment showed nanocomposites coatings had significant improvement in UV-shielding and nearly all the samples presented a darkening tendency in ΔL* and increasing tendency in Δa*,ΔE* and ΔRa.The orthogonal experiment obtained the least change in color and Ra which could be achieved with nano composites coating made by melamine resin and TiO2 when a* was considered as an important index.Film-forming material was the only factor which had significant influence on color and roughness when a* was not considered as important index,then melamine resin was the best choice. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(2):179-191
The effects of felling season, log storage and kiln drying on stemwood discoloration of sixty mature silver birches ( Betula pendula ) were studied and provided with CIEL*a*b* colour coordinates. The colour differences were expressed as j E* including split up of j L*, j a* and j b*. The results showed that fresh wood colour depends on the felling season: light and pale colours were recorded for samples taken from autumn- and winter-felled trees, whereas the colour of fresh wood was considerably darker if the felling took place in the spring or summer. After storage, notable changes in colour were observed. After drying, all samples showed low lightness, moderate redness and relatively high yellowness under the drying conditions used in the study regardless of the felling season or duration of storage. The main colour component responsible for the discoloration was lightness, while chroma values redness and yellowness played a minor role. 相似文献
13.
The effect of heat treatment on the surface colour and hygroscopic properties of pine wood were investigated in this study. Boards of Scots pine wood (Pinus sylvestris L.) were subjected to thermal treatment at 200°C, for 4, 6, and 8 h. The change of equilibrium moisture content and density values of the specimens in order to facilitate the understanding of the treated material behavior. The colour parameters L*, a* and b*, used to depict the total colour change (Δ E) of wood surface, were shown to change proportionally to the treatment intensity. Moreover, swelling in the tangential and radial directions and absorption of the specimens appeared to be enhanced in great extent by the thermal treatment process. The mean value of swelling percentage in the tangential direction decreased 10.26%, 17.22%, and 19.60% for specimens treated for 4, 6, and 8 h, respectively, referring to the final measurement after 72 h of immersion. In radial direction, mean value of swelling percentage decreased 19.56%, 32.75%, and 34.65% for treated for 4, 6 and 8 h, respectively, after 72 h immersion, which attests the decrease in swelling and improvement in the hygroscopic behavior of Scots pine wood. 相似文献
14.
A new phytosterone, (20R, 22R)-2beta, 3beta, 20, 22, 26-pentahydroxy-cholestan-7,12-dien-6-one (1), was isolated from the roots of Achyranthes bidentata. The structure was elucidated on the basis of spectral data. 相似文献
15.
Manabendra Deka Miha Humar Gregor Rep Borut Kričej Marjeta Šentjurc Marko Petrič 《Wood Science and Technology》2008,42(1):5-20
A series of experiments were carried out to investigate the colour stability of chemically treated and thermally modified
wood compared to non-modified wood during long term artificial UV light irradiation. One set of wood samples was vacuum-pressure
impregnated with alkaline (pH 9.8) copper (II) ethanolamine aqueous solution, while another set of samples from the same wood
block was thermally modified at 210°C and −0.90 bar for 2 h. The treated and modified wood samples along with the non-modified
ones were exposed to artificial UV light with the wave length in the region of UVA (315–400 nm) and UVB (280–315 nm) intermittently
for 500 h. Colour measurements were carried out throughout the irradiation period at an interval of 100 h according to CIEL*a*b*
system, where the results are presented in terms of ΔE, ΔL*, Δa* and Δb* values. Better photo-stability in terms of colour changes was recorded for both treated and modified woods compared to the
non-modified one. By means of EPR and DRIFT spectroscopic study it was shown that some degree of colour stability of treated
and modified woods, achieved during artificial UV light irradiation, resulted from lignin modifications and monomers of phenolic
compounds. 相似文献
16.
I. Kadzere C. B. Watkins I. A. Merwin F. K. Akinnifesi J. D. K. Saka 《Agroforestry Systems》2007,69(2):167-173
Uapaca kirkiana (Muell. Arg.) is a woodland fruit tree that is native to parts of eastern, central and southern Africa. Unripe fruits are
harvested from wild and semi-wild sources by dislodging them from trees. Ripe fruits are gathered from the ground after abscission.
Utilization of the fruits is affected by problems such as variability of fruit quality and high perishability. Quality attributes
of fruits harvested on 1 and 17 November, and 3 December 2003 and kept at 25–30°C, have been evaluated. On the second and
third harvests, fruits were also stored in polythene bags to investigate a common incubation method to hasten ripening. Fruit
weight and colour before and after ripening, and the soluble solids concentrations (SSC) of ripe fruits were measured. The
redness (a*) values at harvest increased from 3.5 to 5.3 units from 1 November to 3 December. Over this period there was a
significant decline in both lightness (L*; 63.8 to 58.9 units) and yellowness (b*, 39.6 to 36.4 units). Skin colour became
darker during storage as reflected by the decreasing lightness (L* values from 63.8 to 44.5 units), yellowness (b* values
from 36.6 to 20.1 units) and increasing redness (a* values from 3.5 to 8.8 units). Fruits harvested on 17 November and 3 December
did not darken during storage as much as fruits harvested on 1 November. Fruits harvested on 3 December lost less weight (13.7%)
during storage than those harvested on 1 November (34.0%), while the respective SSC measured 6 days after harvest were 18.1%
and 9.9%. Fruits kept in polythene bags had 5.3% lower SSC than those kept on plates. The results demonstrate the benefits
of delaying fruit harvest to improve quality attributes such as fruit skin colour at harvest and during storage, to reduce
weight loss and to obtain higher SSC during storage. 相似文献
17.
近红外光谱法测定毛竹综纤维素的含量研究 总被引：5，自引：0，他引：5
研究了用近红外光谱(NIR)结合多变量统计分析技术对毛竹综纤维素含量的快速测定。用常规实验室方法测定了54个竹材样品的综纤维素含量,用近红外光谱仪采集相应样品的光谱,对原始光谱进行二阶导数和25点平滑预处理后,从54个竹材样品中挑选41个代表性的样品建模,选择1011~1675nm和1930~2488nm波段区间,用偏最小二乘法(PLS1)和完全交互验证方式建立毛竹综纤维素含量的预测模型。结果表明,毛竹综纤维素含量和近红外光谱之间存在非常好的相关性,预测模型的相关系数(RP)为0.95,预测模型的标准偏差(SEP)为0.76%。 相似文献
18.
对相同立地条件下的10、20、30、40年生樟子松人工固沙林进行胸径、边材厚度测定,分析不同年龄边材厚度与胸径相关关系及不同年龄边材生长特征。结果表明:10年生时平均边材宽度为6cm;20~30年生平均边材增幅小;30~40年生时边材增幅大。10年、20年生樟子松边材厚度与胸径关系模型符合抛物线模型,拟合方程分别为y=0.146 2 x~2-1.554 6 x+6.401 7(R~2=0.975 3)、y=-0.057 6 x~2+1.456 1 x-4.761 9(R~2=0.669 7);30年生樟子松东、南两个方位边材厚度与胸径关系可用曲线拟合,东方位符合指数模型,方程为y=0.980 1e0.081 1 x(R~2=0.733 7),南方位符合抛物线方程y=0.009 x~2-0.07 x+1.940 4(R~2=0.518 7)或指数方程y=1.082 7 e~(0.065 4 x)(R~2=0.516 4);40年生樟子松的东方位和北方位可用幂指数模型拟合,分别为y=0.196 5 x~(1.077 2)(R~2=0.476 8)和y=0.029 1 x~(1.748 8)(R~2=0.785 5),南、西方位的相关关系可用指数模型拟合,表达式分别为y=0.673 e~(0.104 7 x)(R~2=0.750 4)和y=0.455 8 e ~(0.123 84 x)(R~2=0.934 6)。不同年龄边材宽度显著差异,可以反映其生长状况、水分利用对策、物质生产等方面的特征。 相似文献
19.
Three new dammarane-type triterpene saponins ginsenosides Rh(18) (1), Rh(19) (3) and Rh(20) (4), along with two new triterpene sapogenins 12β,23(R)-epoxydammara-24-ene-3β,6α,20(S)-triol (2) and dammara-(20E)22,25-diene-3β,6α,12β,24S-tetrol (5) were isolated from the stems and leaves of Panax ginseng C. A. Mey. Their structures were elucidated on the basis of spectral evidence and comparisons with literature data. 相似文献
20.
对日本冲绳岛北部相同土壤条件下的琉球松纯林及其混交林的土壤氮素及有机碳素、地表凋落物量、枯枝落叶量以及土壤氮素矿化速率进行了比较研究。结果表明 ,琉球松纯林的地表凋落物层氮、碳平均贮量分别为133kg·hm- 2 和 7199kg·hm- 2 ,混交林则分别为 10 5kg·hm- 2 和 6 14 3kg·hm- 2 。然而 ,混交林地表 10cm矿质土层的氮、碳贮量则显著高于纯林 ,氮素比纯林多 4 93kg·hm- 2 ,碳素多 5 5 5 4kg·hm- 2 。在 30d的实验室培养实验中 ,混交林表层土壤的氮素矿化速率高于纯林 18% ;而且 ,混交林的落叶和土壤的碳氮比值亦明显低于松纯林。混交林土壤的年平均矿化氮素 (NH4 NO3- )浓度高于纯林 2 2 %。与松纯林相比 ,混交林通过枯枝落叶年平均氮素归还量多 4 3 7kg·hm- 2 ,碳素归还量多 16 5 5kg·hm- 2 。混交林具有较高的氮素归还量 ,主要是混交林的针叶含氮含量较高以及大量的高含氮量的阔叶落叶所致。上述结果充分说明针阔混交导致了林分氮素循环的变化。 相似文献