Tectonic evolution of the terrestrial planets

The style and evolution of tectonics on the terrestrial planets differ substantially. The style is related to the thickness of the lithosphere and to whether the lithosphere is divided into distinct, mobile plates that can be recycled into the mantle, as on Earth, or is a single spherical shell, as on the moon, Mars, and Mercury. The evolution of a planetary lithosphere and the development of plate tectonics appear to be influenced by several factors, including planetary size, chemistry, and external and internal heat sources. Vertical tectonic movement due to lithospheric loading or uplift is similar on all of the terrestrial planets and is controlled by the local thickness and rheology of the lithosphere. The surface of Venus, although known only at low resolution, displays features both similar to those on Earth (mountain belts, high plateaus) and similar to those on the smaller planets (possible impact basins). Improved understanding of the tectonic evolution of Venus will permit an evaluation of the relative roles of planetary size and chemistry in determining evolutionary style.     

Frequencies of occultations of stars by planets, satellites, and asteroids

Calculations show that several occultations of stars by the large satellites of the outer planets, Pluto, and the large asteroids could be observed each decade with existing equipment at Earth-based telescopes. A systematic program of occultation predictions and observations is urged in order to improve our knowledge about the atmospheres, sizes, shapes, topography, and positions of these poorly understood bodies, in support of forthcoming spacecraft missions to the outer solar system.     

Occurrence of giant impacts during the growth of the terrestrial planets

Three-dimensional Monte Carlo simulations of the accumulation of the terrestrial planets in the absence of gas drag produced results that are in general agreement with the number and distribution of the present planets. The accumulation process appears to be characterized by impact of bodies as large as three times the mass of Mars at velocities of about 9 kilometers per second. These giant impacts on Earth may have supplied the material and angular momentum that formed the moon, should have heated Earth to the melting point, and may have been responsible for the differences in the content of inert gases of the atmospheres of Earth and Venus.     

The use of transit timing to detect terrestrial-mass extrasolar planets

Future surveys for transiting extrasolar planets are expected to detect hundreds of jovian-mass planets and tens of terrestrial-mass planets. For many of these newly discovered planets, the intervals between successive transits will be measured with an accuracy of 0.1 to 100 minutes. We show that these timing measurements will allow for the detection of additional planets in the system (not necessarily transiting) by their gravitational interaction with the transiting planet. The transit-time variations depend on the mass of the additional planet, and in some cases terrestrial-mass planets will produce a measurable effect. In systems where two planets are seen to transit, the density of both planets can be determined without radial-velocity observations.     

Evidence of thermal metamorphism on the C, g, B, and f asteroids

Reflectance spectra (0.3 to 2.6 micrometers) of 14 C, G, B, and F asteroids and 21 carbonaceous chondrite powders are compared in detail. Only three thermally metamorphosed CM-Cl chondrites that have a weak ultraviolet absorption are shown to have close counterparts among those asteroids. Reflectance spectra of heated Murchison CM2 chondrite are compared with the average C and G type asteroid spectra. Murchison heated at 600 degrees to 1000 degrees C exhibits a similar weak ultraviolet absorption and provides the best analog for those spectra. Comparison of ultraviolet absorption strengths between 160 C, G, B, and F asteroids and carbonaceous chondrites suggests that surface minerals of most of those asteroids are thermally metamorphosed at temperatures around 600 degrees to 1000 degrees C.     

橡胶苗不同器官渗透调节物质组成及其对渗透势的贡献

为研究橡胶苗不同器官渗透调节物质对渗透势的贡献及其与物质运输的关系,进而为进一步研究橡胶树不同器官渗透调节过程与光合作用、木质部—韧皮部水分平衡、胶乳产量等之间的关系提供依据,以橡胶树'热研7-33-97'袋育组培苗为材料,测定了其根、叶渗透势和可溶性糖、游离氨基酸、有机酸、Ca2+、Mg2+、K+、Na+、NO3?、...     

Helium loss, tectonics, and the terrestrial heat budget

It has been known for the last decade that primordial helium incorporated in Earth at the time of its formation is still being degassed during the formation of new ocean crust at spreading ocean ridges. It is now clear that somewhat contrary to expectation, substantial degassing is also taking place through the continental crust. In western Europe the escape of mantle volatiles seems to occur largely where the crust is undergoing active extension. Although it is known that melting is the principal process for extracting and concentrating helium from the mantle at ocean ridges, the equivalent subcontinental process remains poorly understood. The same elements that are responsible for most of Earth's radiogenic heating (uranium and thorium) are also responsible for the generation of radiogenic helium. The present rate of mantle heat loss, however, is out of equilibrium with the rate of helium loss-too large by about a factor of 20. Either radiogenic helium is accumulated in the mantle while heat escapes or current models for the bulk chemistry of Earth are in error and much of the terrestrial heat loss is nonradiogenic.     

Thermal conductivity of lunar and terrestrial igneous rocks in their melting range

The thermal conductivity of a synthetic lunar rock in its melting range is about half that of a terrestrial basalt. The low conductivity and increased efficiency of insulating crusts on lunar lavas will enable flows to cover great distances without being quenched by high radiant heat losses from the surface. For a given rate of heat production, the thermal gradient of the moon would be significantly steeper than that of the earth.     

不同花香化合物对棉铃虫成虫触角电位的影响及诱蛾效果

测定了棉铃虫雌、雄蛾对7种花香化合物的触角电位(EAG)反应．结果表明,各种花香化合物均能引起棉铃虫较强的触角电位反应,雌、雄蛾对花香混合物(苯甲醛30％ 苯乙醇30％ 苯甲酸乙酯40％)的反应最强,相对反应值分别为220．176;对苯乙醇的反应次之;棉铃虫雌虫对不同剂量花香混合物的触角电位反应随剂量增加而增加．不同花香混合物在田间的诱蛾效果以配方G(苯甲醛100μL 苯甲醇100μL 苯乙醇200pL 乙酸苯甲酯600μL)最好,累计诱蛾量达到了196头．     

南亚热带富营养化浅水湖泊底泥磷的赋存形态及其对湖水的贡献

以南亚热带富营养化湖泊星湖为研究对象,对其4个子湖区底泥磷进行连续分级提取与测定．结果表明,星湖底泥总磷（Total phosphorus,TP）含量为352．32—710．33mg／kg,平均含量为505．82mg／kg,其含量大小依次为波海湖〉青莲湖〉仙女湖〉中心湖,其中生物可利用磷（Bio—available pbospborus,BAP）占TP的39．12％-52．59％,底泥TP主要由有机磷（Organic phosphorus,Org-P）、金属氧化物结合态磷（Metal oxides bound phosphorus,NaOH-P）和钙结合态磷（Calcium bound phosphoms,HCl-P）组成,其次还有少量可还原态磷（Redueible phosphorus,BD-P）和弱吸附态磷（Loosely absorbed phosphorus,NH4Cl-P）．不同形态磷的含量依次为：Org-P〉NaOH-P〉HCl-P〉BD-P〉NH4Cl-P．在底泥水-土界面存在一个明显的可溶性磷浓度梯度,为底泥磷向湖水释放提供了条件．     

千年桐种源叶片内源激素比较及其与碳氮关系

以11个不同种源千年桐叶片为试验材料,测定4种内源激素———赤酶素(GA)、玉米核苷(ZR)、吲哚乙酸(IAA)、脱落酸(ABA)的含量。结果表明:11个种源千年桐叶片的GA、IAA、ZR、ABA存在极显著差异,从变异系数的离散程度看,4种内源激素的差异程度为GA>ZR>IAA>ABA。IAA与ABA之间呈现出显著的相关关系(P<0.05),GA与IAA之间呈现出较明显的相关关系(P<0.1)。各种源内源激素平衡性具有一定差异,体现了不同种源适应能力的不同。在叶片C、N含量的相关性中,GA/ABA和GA与叶N含量呈一定程度的负相关,与C/N呈极显著正相关。     

3个品种梨香气感官品质与挥发性物质关联分析

为探究梨果皮挥发性物质和感官属性之间的潜在联系,为梨的风味品质育种和采后贮藏等提供理论支持,采用气相色谱-质谱联用仪测定库尔勒香梨（Pyrus sinkiangensis）、雪花梨（P. bretschneideri）及黄冠梨（P. bretschneideri）果皮挥发性物质;组建15人的感官评价小组对3个品种梨果实香气品质进行快闪剖面分析;并进行感官评分与挥发性物质的相关性分析。结果显示：3个品种梨果实中分别检测到50、48和37种挥发性物质,且均以醛类、萜烯类和脂肪酸类为主,占总挥发性物质的85%左右;库尔勒香梨以脂肪酸类及醛类含量占优,雪花梨以萜烯类含量占优,黄冠梨中各类物质含量均为最低。3个品种梨果实中属性强度最高的均为果香,属性强度最低的则为酸味;库尔勒香梨中,仅甜香属性显著高于雪花梨,而除莲雾味外的其他香气属性均显著高于黄冠梨。感官评分与挥发性物质的相关性分析表明,戊二酸二甲酯、丁香酚、2-十一烯醛、2-乙基-3-羟基己基-2-甲基丙酸酯、3-亚甲基-1-氧代螺环［4.5］癸-2-酮等8种挥发性物质的含量与花香、青草香和果香等多种感官属性的评分呈显著正相关。感官评价和代谢物的关联分析有助于解析影响梨果实风味的关键化合物。     

The novel use of proximal photogrammetry and terrestrial LiDAR to quantify the structural complexity of orchard trees

Precision Agriculture - Within the agrifood sector, the production of high yields is a driver for UK orchard husbandry. Currently, orchard tree management is typically a non-discriminatory method...     

柑橘木虱对几种非嗜食植物挥发油的趋性反应测定

应用四臂嗅觉仪测定了柑橘木虱Diaphorina citri对假臭草Eupatorium catarium、马樱丹Lantana camera、蟛蜞菊Wedelia chinensis、薇苷菊Mikania micrantha、柠檬桉Eucalyptus citriodora5种非嗜食植物挥发油和机油乳剂的趋性反应．结果表明：薇苷菊、马樱丹、蟛蜞菊、假臭草4种植物挥发油对柑橘木虱成虫都有显著的驱避作用,其中薇苷菊挥发油的驱避作用最强;桉油和机油乳剂对柑橘木虱成虫既无明显的驱避作用也没有吸引作用;雌雄成虫对测试的5种挥发油和机油乳剂的趋性反应没有差异．