共查询到20条相似文献，搜索用时 171 毫秒
1.
竹叶有效成分和抗活性氧自由基效能的研究 总被引：43，自引：3，他引：43
在对竹叶有效成分进行定性预试验的基础上，调查了６个属１７种竹叶春、夏、秋３季的总黄酮和总酚含量，用化学发光法检测其醇提物对和ＯＨ的清除能力，同时考察其对亚硝化反应的阻断作用。结果表明，总黄酮和总酚含量均以秋叶为最高，分别占干基含量的１．９７±０．５７％和４．２１±１．０５％；秋叶提取物对和ＯＨ的ＩＣ（５０）分别为４．９３±２．３６μｇ／ｍｌ和１．４８±ｏ．９１μｇ／ｍｌ。竹叶提取物普遍显示了较强的清除活性氧自由基的作用，且是显著的量效关系。体外模拟胃液条件下测得秋叶醇提物对亚硝酸盐的清除率和对Ｎ－亚硝胺合成的阻断率与相同浓度的ＶＣ具有可比性。竹叶可以作为一种潜在的自由基清除剂和天然抗氧化剂的新资源加以研究和开发。 相似文献
2.
南亚热带桉树林和针阔混交林土壤及凋落物持水能力比较 总被引：3，自引：1，他引：2
以桉树林（第2代和第1代）和杉木针阔混交林（10～11 a和5～7 a生）为研究对象,探讨南亚热带4种试验林0～100 cm土层土壤及凋落物持水能力。结果表明,在0～100 cm土层,针阔混交林土壤总孔隙度和毛管孔隙度均高于桉树林,而土壤非毛管孔隙度却显著低于桉树林（P＜0．05）,表明针阔混交林土壤中有效水的贮存容量高于桉树林。受土壤总孔隙度和毛管孔隙度的影响,针阔混交林土壤最大持水量和毛管持水量显著高于桉树林（P＜0．05）。4种试验林田间持水量的差异不显著（P＞0．05）,说明4种试验林土壤保水能力基本一致。4种林分凋落物量表现为桉树林Ⅳ＞桉树林Ⅱ＞针阔混交林Ⅰ＞针阔混交林Ⅲ,桉树林凋落物最大持水量、最大拦蓄量和有效拦蓄量显著高于针阔混交林（P＜0．05）。 相似文献
3.
4.
于2012年10月至2013年9月在云南野生动物园，采用瞬时扫描法和全事件观察法对繁殖期白化孟加拉虎的行为进行了研究。结果表明：在发情交配期雌雄白化孟加拉虎的行为时间分配差异不显著（P〉0．05），均将较多的时间用于休息和运动；在妊娠期雌性白化孟加拉虎将较多的时间用于休息和运动，较少的时间用于摄食、睡眠和其它行为，对比妊娠期4只雌虎的行为，不同个体在同一种行为间差异性极显著（P〈0．01）；产仔期雌虎将更多的时间用于产仔和舔舐幼虎，其次是休息；在哺乳期雌虎将较多的时间用于休息，其次是哺乳和运动。通过单因素方差分析表明，在繁殖期不同阶段休息行为差异性极显著（P〈0．01），睡眠、运动和其它行为差异性不显著（P〉0．05）。 相似文献
5.
以水竹叶为原料，采用水浴和超声波两种提取方法，通过单因素与正交试验确定了水竹叶总黄酮提取的最佳条件，并筛选了不同树脂对总黄酮的吸附和解吸附特性。实验结果表明：水浴提取最佳条件为：温度50℃，提取时间2．0h，乙醇体积分数60％，固液比1：20（g：mL，下同）；总黄酮得率1.65％。影响得率的因素为：固液比〉乙醇体积分数〉提取温度〉提取时间。超声波提取最佳条件为：2．0g水竹叶，超声波作用时间30min，乙醇体积分数60％，固液比1：15；总黄酮得率为1．27％。影响得率的因素为：超声波作用时间〉乙醇体积分数〉固液比。AB-8树脂对总黄酮纯化具有较好效果，体积分数为70％的乙醇是较好的解吸剂。 相似文献
6.
为了研究笼养丹顶鹤在越冬期对寒冷地区的适应性, 2014年11—12月采用瞬时扫描法对沈阳森林动物园鹤基地的8对丹顶鹤（Grus japonensis）进行昼间行为的研究和领域利用情况的调查。结果发现,越冬期雌雄丹顶鹤昼间对采食区、运动场、遮阴棚的利用存在一定差异,雌性丹顶鹤在雪前、雪中和雪后采食行为有极差异显著（P＜001）,雪前和雪中张望和采食行为差异显著（P＜005）。雪中和雪后除张望和采食行为差异极显著（P＜001）外,其他行为均不显著;雄性丹顶鹤雪前和雪中游走、警戒、休息行为差异显著（P＜005）,雪中和雪后理羽、游走和张望差异极显著（P＜001）,雪前和雪后休息行为差异显著（P＜005）。笼养雌雄性丹顶鹤在北方高纬度地区越冬期分别采用不同的行为对策来适应低温环境。 相似文献
7.
本试验旨在研究沙棘提取物对断奶仔猪的免疫调节作用。选用28±2日龄断奶的长×大仔猪24头。随机分成试验组和对照组,每组3个重复,每重复4头猪（公母各半）,试验组饲粮添加0．1％沙棘提取物,测定免疫器官指数、T淋巴细胞亚群、细胞因子、血液和肝、肾、脾的抗氧化能力指标。结果表明,添加0．1％沙棘提取物组脾脏指数、胸腺指数均显著提高（P〈0．05）;T淋巴细胞CD4＋亚群比例显著提高（P〈0．05）,CD8＋比例显著降低（P〈0．05）,CD＋／CD8＋比值极显著提高（P〈0．01）;第1、2周白细胞介素-2（IL-2）显著提高（P〈0．05）;第1、3、4周IFN-1显著提高（P〈0．05）;血清T—AOC显著提高（P〈0．05）。试验证明在断奶仔猪日粮中添加0．1％沙棘提取物可以通过提高血液总抗氧化能力来增强仔猪的免疫功能。 相似文献
8.
以银杏叶为原料，采用皂化反应、溶剂冷冻和Ⅱ级分子蒸馏分离聚戊烯醇不皂化物，精制银杏叶聚戊烯醇（GP），纯度87．3％。通过建立人脑瘤SF763、人肺腺瘤A549和艾氏腹水瘤Ec移植小鼠模型，GP口服给药，研究GP对人脑瘤SF763裸鼠和艾氏腹水瘤Ec小鼠的生命延长率，观察GP对人肺腺瘤A549裸鼠的抑瘤率。结果表明：生药剂量320mg／kgGP联合2mg／kg阿霉素（ADM），其生命延长率为88％（P〈0．01），GP能明显延长荷人脑瘤SF763裸鼠生命；GP在大于40mg／kg时对人肺腺瘤A549裸鼠具有明显的抑制作用（P〈0．05），最佳剂量为GP80mg／kg，接种时间11d，抑瘤率为82．2％（P〈0．01）；GP对艾氏腹水瘤EC小鼠的生存期呈现负量效关系，GP最佳剂量范围在5-10mg／kg，最高生命延长率为32．77％（P〈0．05）。 相似文献
9.
雷竹提早出笋覆盖材料筛选试验初报 总被引：1，自引：0，他引：1
试验表明，松针、竹叶、猪栏、狼衣、菜籽壳５种覆盖材料，对雷竹提早出笋均有作用。其中松针效果最为显著，土温（２０ｃｍ）平均增加１．６℃，提早出笋９～３９ｄ，早期（３月３１日前）产量达１４６７０ｋｇ／ｈｍ２比对照提高３．３倍。 相似文献
10.
采用时间序列分析方法，研究了长白山红松阔叶林鸟类物种多样性的季节变化。结果表明，Shannon-Wiener多样性指数季节变化的格局表现为春秋高、冬夏低的双蜂型特点，并与物种、数量和优势度之间有极显著的相关关系；群落各指数季节间的显著差异主要表现在冬季与其他各季之间；各月前两个优势种的比例在多样性格局构成中具有非常重要的作用；5月前和9月后，气温对Slmnnon-Wiener多样性指数格局的影响极为显著(r=0．9209，P＜0．01)。 相似文献
11.
应用简化生物圈模式（SiB2）模拟通榆地气通量研究 总被引：3，自引：0，他引：3
主要通过对比观测与SiB2模拟的吉林通榆农田和草地样地的感热通量、潜热通量、CO2通量和气温来检测独立版简化生物圈模式的数值模拟能力。在模拟中,农田和草地代表半干旱区2种典型的地表覆盖类型,它们的全年冠层高度和叶面积指数都处于变化当中,在非生长季地表裸露,而在生长季,冠层高度农田可达2m,草地可达0.8m,对应的叶面积指数分别可达4.2和2.4。SiB2模型模拟用观测值为初始场,以半小时气象观测为驱动场。对2003年的模拟和观测的比对研究表明:在生长季模式具有很好的模拟小时时间尺度的潜热、感热和CO2通量及地表气温的能力;(2)模式模拟土壤热通量可能偏大;(3)模拟的逐日潜热、感热和CO2通量及地表气温可用合理地反映全年的季节变化。图11表3参23。 相似文献
12.
Effect of particle shape on linear expansion of particleboard 总被引：2，自引：0，他引：2
Hinoki (Japanese cypress) strand with 0.6mm thickness was hammer-milled to prepare three types of particles that had the same thickness but different lengths and widths. Screen analysis and image analysis were conducted to evaluate the shape and distribution of the particle dimensions. Laboratory-scale particleboards were fabricated at three density levels using these particles. To determine the true effect of particle shape on the linear expansion (LE) of the board, these boards exhibited almost the same temperature behavior during pressing, the same density profile, and the same bending properties at each board density level. LE at 40°C and 90% relative humidity of the board was found to be affected by the particle shape. The board composed of small particles showed a larger LE at the same density level. It was considered that the out-of-plane orientation angle of the particles affected the LE of the boards. Thickness swelling and internal bond strength were also affected by the particle shape.Part of this report was presented at the 50th annual meeting of the Japan Wood Research Society, Kyoto, April 2000 相似文献
13.
Effects of strand length and layer structure on some properties of strandboard made from bamboo 总被引：1，自引：0，他引：1
Strandboard panels were experimentally produced from moso bamboo (Phyllostachys pubescens) using various strand lengths and layer structures to evaluate the effects of manufacturing parameters on panel properties.
The strandboard was fabricated in a laboratory using diphenylmethane diisocyanate (MDI) resin and laboratory-made strands
of four lengths and four different structures. Strand alignment distributions and concentration parameter (k) values were greatly affected by strand length. A linear correlation was found between the value of k and the modulus of rupture (MOR), with correlation coefficients of 0.81 and 0.93 for unidirectional boards and three-layer
boards, respectively. This correlation may be used to predict the strength properties of boards. Bending properties were significantly
affected by both the strand length and the layer structure of the bamboo strandboard tested. Elasticity data from unidirectional
boards and random boards can be used to predict the elastic properties of three-layer boards. The linear expansion (LE) of
the random boards increased with decreasing strand length. The difficulty in mat forming and resin distribution for longer
strands could cause deviation in modulus of elasticity (MOE) and LE, especially in strand lengths around 80 mm. 相似文献
14.
Kohta Miyamoto Shigehiko Suzuki Takayoshi Inagaki Ritsuo Iwata 《Journal of Wood Science》2002,48(4):309-314
Mat consolidation behavior was investigated at various press closing times (PCTs) using hinoki (Japanese cypress) particle mats. The temperature in the core layer of the mat, press pressure, and platen distance were measured. At the plateau stage during hot pressing, the core temperature decreased with increasing PCT. The core temperature did not increase before the platen distance equaled the target board thickness in the PCT range of 4–50 s and rose slightly when the PCT exceeded 100s. There was a linear relation between the logarithm of PCT and the maximum press pressure. The density profile across board thickness was strongly affected by the PCT. As the PCT increased, the position of the peak density (PD) moved toward the core layer as the PD itself decreased. The effect of PCT on the linear expansion (LE) of the board is discussed in relation to the density profile. There was no difference in LE after high relative humidity treatment in the PCT range 4–50s. LE appeared to be related to the low density and the precured region of the board surface. The LE after drying treatment was around –0.1%, and the thickness swelling after high relative humidity and drying treatments increased with increasing PCT.Part of this report was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 1988 相似文献
15.
The objective of this study was to investigate the physical and mechanical performance of flakeboard reinforced with bamboo strips. The study investigated three different bamboo strip alignment patterns and an experimental control. All panels were tested in static bending both along parallel and perpendicular to the lengths of the bamboo strips. Internal bond strength (IB), thickness swelling (TS), linear expansion (LE), and water absorption (WA) were also examined. As expected, modulus of rupture (MOR) and modulus of elasticity (MOE) were substantially greater for all three experimental panel types as compared to the control group. LE was also improved for all three experimental panel groups. The bamboo strip alignment patterns had no significant effect on TS, WA and IB. The sample means for MOR, MOE and LE tested perpendicular to the bamboo strip lengths yielded slightly lower mean values than corresponding samples tested parallel to the bamboo strips lengths. This difference in mechanical properties is largely attributed to low panel density in the failure zones. 相似文献
16.
探讨了松乳菇多糖对机体免疫功能的影响,以高、中、低浓度的松乳菇多糖为材料,分别以免疫器官重量法、碳粒廓清实验法、抗应激能力实验和耐高温实验对小白鼠进行非特异性免疫试验.结果表明:高浓度组与对照组相比较,小白鼠胸腺指数和脾脏指数均有显著增加(p<0.05),与低浓度组相比较,脾脏指数有显著增加(p<0.05);高浓度组与对照组、低浓度组相比较其吞噬系数有显著增加(p<0.05);高浓度组与对照组相比游泳时间上有显著增加(p<0.05);各浓度松乳茹多糖对提高小白鼠耐高温能力不明显.松乳菇多糖能明显提高小白鼠的免疫功能. 相似文献
17.
从雷蘑AS 5.105深层发酵的滤液中分离得到胞外粗多糖CGP,以KM系S180荷瘤小白鼠为实验模型,用免疫器官重量法,进行高、中、低剂量CGP的腹腔注射实验。结果表明,CGP具有较高的抑瘤活性,并与剂量呈显著相关性;高剂量组与对照组相比较,小白鼠胸腺指数和脾脏指数均有显著增加,P<0.05;与低剂量组相比较,脾脏指数有显著增加,P<0.05。表明CGP能明显提高小白鼠的免疫功能。 相似文献
18.
《Southern Forests》2013,75(4):277-285
Field establishment of South Africa’s most important commercial pine species, Pinus patula, is severely hampered by the pitch canker fungus, Fusarium circinatum. Importantly, hybrids between P. patula and other pine species tolerant to the pitch canker fungus, such as P. tecunumanii and P. oocarpa, have been identified as an alternative planting stock. In this study, variation in tree volume and dynamic modulus of elasticity (MOEdym) of the P. patula × P. tecunumanii (low- and high-elevation [LE and HE] ecotypes) hybrid was compared with the P. elliottii × P. caribaea hybrid, and the pure species P. tecunumanii (LE) and P. patula. The MOEdym was assessed using the Fakkop TreeSonic microsecond instrument across three sites. The results of the study showed that P. patula × P. tecunumanii LE performed significantly better than P. patula × P. tecunumanii HE for volume and MOEdym, which in turn was significantly better than P. patula. The MOEdym and tree growth decreased with an increase in elevation. There was significant taxon × site interaction for volume and MOEdym. The results of these trials suggested that P. patula × P. tecunumanii LE is a suitable alternative to P. patula in the Sabie region of Mpumalanga in South Africa on frost-free sites, in terms of the traits that were assessed. 相似文献
19.
We investigated the bending properties of composite boards produced by reinforcing both sides of corrugated particleboard with medium-density fiberboard (MDF). Thickness swelling and linear expansion (LE) were measured to assess the dimensional stabilities of the composite board. Although the apparent density of the composite board was 0.48g/cm3, its strength was found to be equivalent to that of 18-type particleboard as described in JIS A 5908. The boards parallel/perpendicular anisotropy in strength was 0.9. The modulus of rupture (MOR) of the composite board increased with board density only up to a certain density, beyond which the MOR was constant. On the other hand, the thickness swelling of both corrugated particleboard and the composite board was smaller than that of flat-type particleboard, satisfying the JIS A 5908 standard of 12%. Linear expansion (soaking in water of ordinary temperature for 24h) of corrugated particleboard was 0.7%–0.9% in the parallel direction and 2.1%–3.1% in the perpendicular direction; hence, anisotropy in linear expansion existed in the corrugated particleboard. The linear expansion of the composite board was 0.6%–0.9% in the parallel direction and 1.8%–2.5% in the perpendicular direction. Although the LE of the composite board was lower than that of corrugated particleboard, it is necessary to improve the LE of composite board for practical use. 相似文献
20.
Uncertainty in eddy covariance measurements and its application to physiological models 总被引：1，自引：0，他引：1
Flux data are noisy, and this uncertainty is largely due to random measurement error. Knowledge of uncertainty is essential for the statistical evaluation of modeled and measured fluxes, for comparison of parameters derived by fitting models to measured fluxes and in formal data-assimilation efforts. We used the difference between simultaneous measurements from two towers located less than 1 km apart to quantify the distributional characteristics of the measurement error in fluxes of carbon dioxide (CO2) and sensible and latent heat (H and LE, respectively). Flux measurement error more closely follows a double exponential than a normal distribution. The CO2 flux uncertainty is negatively correlated with mean wind speed, whereas uncertainty in H and LE is positively correlated with net radiation flux. Measurements from a single tower made 24 h apart under similar environmental conditions can also be used to characterize flux uncertainty. Uncertainty calculated by this method is somewhat higher than that derived from the two-tower approach. We demonstrate the use of flux uncertainty in maximum likelihood parameter estimates for simple physiological models of daytime net carbon exchange. We show that inferred model parameters are highly correlated, and that hypothesis testing is therefore possible only when the joint distribution of the model parameters is taken into account. 相似文献