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11.
Summary. Ponderosa pine, Pinus ponderosa Laws. (Pinaceae), forests in Arizona have suffered from a nine-year period of drought and bark beetle, Ips lecontei Swaine (Coleoptera: Scolytidae), outbreaks. Abiotic and biotic stress in ponderosa pine results in the induced synthesis
of certain monoterpenes that may in turn affect bark beetle behavior and survival. In this study, we investigate whether induced
monoterpene production could result in a different monoterpene composition that remains stored in the needles or the trunk
resin of the tree. Needle and resin samples in addition to trunk cores were collected from ponderosa pines at three locations
in Arizona. Ungulate browsing induced a significant increase in limonene (P=0.010) and in chemodiversity (P=0.009), a measure
of the evenness of distribution among the monoterpenes present in needles. We compared the level of ‘stress’ of the trees
by measuring the thickness of annual rings in living trees and those that were killed by bark beetles. Where drought occurred,
the spacing of annual rings from the last 10 years of trees killed by bark beetles was significantly smaller (P=0.020) compared
to living trees. There was no difference in the monoterpene composition between the core sections of closest spacing of annual
rings (stressed years) compared to the sections of widest spacing, which indicates that monoterpenes are distributed evenly
throughout the extended resin system. In the area where the degree of drought was less overall, none of the individual monoterpenes
present in the resin was related to bark beetle killed trees. However, about half the living pines had resin in which one
of the major monoterpenes (α-pinene, Δ3-carene, and limonene) was absent, and these trees had a lower monoterpene chemodiversity compared to trees killed by bark
beetles. Trees with these three major monoterpenes, corresponding to the average relative proportion in living pines at that
location, may sustain higher selection and colonization by bark beetles. 相似文献
12.
环境样品采集于湖北省鸭儿湖地区。每一样品分作两份,一份用于高分辨色质联用多离子检测法测定,另一份样品的提取液经多层色谱净化后再用7-乙氧基-异吩 唑酮-脱乙基酶(EROD)活力诱导法进行生物测试。PCDDs/PCDF_s和PCB_s总的TCDD毒性等价指数(TEQ_s)最高,分别为1090ng/kg和996ng/kg。说明湖中二 类化合物来源于附近化工厂有机氯生产排放的污水。同时,周围农田中发现的二 类化合物数量少得多。这些化合物可能是来自于污水灌溉或大气尘降。在本研究中,EROD生物测试法具有良好的剂量效应关系,适合于对环境样品中的二 类化合物进行快速定量筛选,而HRGC/HRMS-MID对生物测试所获得的数据作了进一步确认。 相似文献
13.
Land conflicts in developing countries are costly both directly and through increased land degradation. An important policy goal is to create respect for borders. This often involves mandatory, expensive interventions. We propose a new policy design, which in theory promotes neighborly relations at low cost. A salient feature is the option to by-pass regulation through consensus. The key idea combines the insight that social preferences transform social dilemmas into coordination problems with the logic of forward induction. As a first, low-cost pass at empirical evaluation, we conduct an experiment among farmers in the Ethiopian highlands, a region exhibiting features typical of countries where borders are often disputed. 相似文献
14.
This study examined the adverse effects of TiO2 nanoparticle (nano-TiO2) on the kidney and liver of Wistar rats. Changes of serum biochemical parameters and pathological lesions indicated that liver and kidney were significantly affected in animals treated with 50?mg?kg?1 of nano-TiO2. The inverse relationship between the level of reactive oxygen species and the activities of superoxide dismutase, catalase, and glutathione peroxidase indicates that nano-TiO2 induces oxidative stress. A significant increase in the apoptosis of liver and kidney in a dose-dependent manner was also observed. The ultrastructural observations confirmed the internalization of nano-TiO2 and their direct involvement in the mitochondria-mediated cytotoxicity. Data indicated that nano-TiO2 induce oxidative stress which produces genotoxicity such as oxidative DNA damage, micronuclei (MN) induction, and cell apoptosis in liver and kidney. 相似文献
15.
投入产出分析中重要的影响力系数和感应度系数被引入到我国的产业环境关联研究中,但采用的计算方法却多是存在缺陷的传统公式,对指标的政策意义解读也有待深入.在梳理2项指标前沿发展的基础上,以部门最终产品构成系数为权数,改进了表征产业碳关联的碳影响力系数和碳影响诱导系数(代替原碳感应度系数)的计算公式,并指出前者主要对应产业政策,对部门划分水平较不敏感,而后者主要对应节能减排政策,对部门划分水平较敏感.将改进的指标应用于2010年上海市,结果表明,其产业政策应扶植服务业和先进制造业,鼓励重化工业和专用设备制造业转型,逐步淘汰多数传统中低端制造业,节能减排政策的重点实施部门则应扩大到部分高能耗服务业. 相似文献
16.
Lerchl A 《Die Naturwissenschaften》2008,95(2):165-170
A previous study has shown a marked and continuing decline in weekend births in Germany between 1988 and 2003 (Lerchl, Naturwissenschaften 92:592-594, 2005). The present study was performed to investigate the possible influence of caesarean sections (CS) on weekend birth number and on the involvement of midwives in births for all 16 German states for the year 2003. In total, data from 706,721 births were sorted according to weekday of births and state, respectively, and the weekend births avoidance rates were calculated. Weekend births were consistently less frequent than births during the week, with an average of -15.3% for all states and due to fewer births on Saturdays (-13.6%) and Sundays (-16.7%). Between the states, weekend births avoidance rates ranged from -11.6% (Bremen) to -24.2% (Saarland). The proportion of CS was 25.5% for all states, ranging from 19.2% (Sachsen and Sachsen-Anhalt) to 30.5% (Saarland). CS and weekend births avoidance rates were significantly correlated, consistent with the hypothesis that primary (planned) CS are regularly scheduled on weekdays. The number of births per midwife (BPM) was calculated according to the number of active members in the states' professional midwives' organizations. The mean number of BPM was 59.5, ranging from 45.2 (Bremen) to 82.4 (Sachsen-Anhalt). CS and BPM were significantly correlated, consistent with the hypothesis that higher CS ratios are associated with lower midwife involvement in births. It is concluded that the decline in weekend births and lower involvement of midwives are caused, at least in part, by an increased number of caesarean sections. 相似文献
17.
18.
目的 解决LKJ主机的超高斯振动试验问题。方法 基于LKJ主机的实测振动环境数据,提出一种超高斯振动数据归纳方法,并应用该方法归纳出LKJ主机x、y、z向的实测PSD,同时按5.66的加速因子构建出超高斯加速振动试验剖面,其中x、y、z向PSD的RMS分别为3.34、6.28、3.85 m/s2,峰度分别为6.48、6.58、6.81,频率范围均为2~350 Hz。最后,采用超高斯加速试验剖面分别对2个LKJ主机进行超高斯振动试验验证。结果 试验共激发出7类故障模式,这与特定线路运行LKJ主机现场故障模式高度吻合。结论 该试验方法验证了LKJ主机超高斯加速振动试验的有效性。 相似文献
19.
不同碳源对两株真菌纤维素酶合成的诱导和调控 总被引:7,自引:0,他引:7
定时测定B-6(Aspergillus sp.)、AS3.3711(Trichoderma sp.)在各类碳源中的纤维素酶活力,结果发现,酶的合成受培养基中碳源性质的调节控制。结构相对完整的纤维类物质(α-纤维素粉、微晶纤维素)诱导活性较高,电泳结果表明,纤维素酶系是协同表达的,但酶系各组分的百分比在不同的诱导条件下却各不相同。在测定糖耗与酶活力的关系中发现纤维二糖直接诱导B-6纤维素酶的合成,对AS3.3711则起了间接诱导作用,其经菌体代谢后的某种转化产物才是AS3.3711纤维素酶合成的真正诱导源。图6表1参14 相似文献
20.