Three-dimensional flow in the upper ocean

Measurements made from the Research Platform FLIP provide some of the first direct observations of three-dimensional flow within the surface mixed layer of the ocean. Relatively narrow regions of downwelling flow were found within the mixed layer, in coincidence with bands of convergent surface flow. At mid-depth in the mixed layer, the downwelling flow had magnitudes of up to 0.2 meter per second and was accompanied by a downwind, horizontal jet of comparable magnitude. There is some evidence that these motions transport heat and phytoplankton within the mixed layer.     

Thinning and flow of Tibetan crust constrained by seismic anisotropy

Intermediate-period Rayleigh and Love waves propagating across Tibet indicate marked radial anisotropy within the middle-to-lower crust, consistent with a thinning of the middle crust by about 30%. The anisotropy is largest in the western part of the plateau, where moment tensors of earthquakes indicate active crustal thinning. The preferred orientation of mica crystals resulting from the crustal thinning can account for the observed anisotropy. The middle-to-lower crust of Tibet appears to have thinned more than the upper crust, consistent with deformation of a mechanically weak layer that flows as if confined to a channel.     

Redox state of Mars' upper mantle and crust from Eu anomalies in shergottite pyroxenes

The oxidation state of basaltic martian meteorites is determined from the partitioning of europium (Eu) in their pyroxenes. The estimated redox conditions for these samples correlate with their initial neodymium and strontium isotopic compositions. This is interpreted to imply varying degrees of interaction between the basaltic parent melts, derived from a source in the martian mantle, and a crustal component. Thus, the mantle source of these martian basalts may have a redox state close to that of the iron-wüstite buffer, whereas the martian crust may be more oxidized (with a redox state higher than or equal to that of the quartz-fayalite-magnetite buffer). A difference in redox state of more than 3 log units between mantle and crustal reservoirs on Mars could result from oxidation of the crust by a process such as aqueous alteration, together with a subsequent lack of recycling of this oxidized crust through the reduced upper mantle.     

Viscoelastic flow in the lower crust after the 1992 landers, california, earthquake

Space geodesy showed that broad-scale postseismic deformation occurred after the 1992 Landers earthquake. Three-dimensional modeling shows that afterslip can only explain one horizontal component of the postseismic deformation, whereas viscoelastic flow can explain the horizontal and near-vertical displacements. The viscosity of a weak, about 10-km-thick layer, in the lower crust beneath the rupture zone that controls the rebound is about 10(18) pascal seconds. The viscoelastic behavior of the lower crust may help to explain the extensional structures observed in the Basin and Range province and it may be used for the analysis of earthquake hazard.     

Dating of multistage fluid flow in sandstones

Through ultraviolet laser argon-argon dating of potassium feldspar cements containing fluid inclusions, we determined temperature-composition-time data for paleofluids in a sedimentary basin, including data for an evolving episode of fluid flow recorded in distinct phases of cement. The fluid evolved from mixed aqueous oil 83 million years ago to purely aqueous by 76 million years ago, thus dating the time of oil charge in this reservoir.     

Seismic images of crust and upper mantle beneath Tibet: evidence for Eurasian plate subduction

Seismic data from central Tibet have been combined to image the subsurface structure and understand the evolution of the collision of India and Eurasia. The 410- and 660-kilometer mantle discontinuities are sharply defined, implying a lack of a subducting slab beneath the plateau. The discontinuities appear slightly deeper beneath northern Tibet, implying that the average temperature of the mantle above the transition zone is about 300 degrees C hotter in the north than in the south. There is a prominent south-dipping converter in the uppermost mantle beneath northern Tibet that might represent the top of the Eurasian mantle lithosphere underthrusting the northern margin of the plateau.     

New neurons follow the flow of cerebrospinal fluid in the adult brain

In the adult brain, neuroblasts born in the subventricular zone migrate from the walls of the lateral ventricles to the olfactory bulb. How do these cells orient over such a long distance and through complex territories? Here we show that neuroblast migration parallels cerebrospinal fluid (CSF) flow. Beating of ependymal cilia is required for normal CSF flow, concentration gradient formation of CSF guidance molecules, and directional migration of neuroblasts. Results suggest that polarized epithelial cells contribute important vectorial information for guidance of young, migrating neurons.     

Olivine and pyroxene diversity in the crust of Mars

Data from the Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) on the Mars Express spacecraft identify the distinct mafic, rock-forming minerals olivine, low-calcium pyroxene (LCP), and high-calcium pyroxene (HCP) on the surface of Mars. Olivine- and HCP-rich regions are found in deposits that span the age range of geologic units. However, LCP-rich regions are found only in the ancient Noachian-aged units, which suggests that melts for these deposits were derived from a mantle depleted in aluminum and calcium. Extended dark regions in the northern plains exhibit no evidence of strong mafic absorptions or absorptions due to hydrated materials.     

Phengite-based chronology of K- and Ba-rich fluid flow in two paleosubduction zones

Subduction recycles aqueous fluids from slab and sediment to the mantle. Subduction zones are long-lived, but time scales for fluid-rock interaction within subduction complexes are uncertain. Large-ion lithophile elements (potassium and barium) were added to eclogite (subducted basalt) during high pressure/temperature metamorphism via phengite crystallization from subduction zone fluids. Phengite grains from eclogite blocks and their metasomatic selvages yielded 40Ar/39Ar ages across grains and between samples that indicate 25 and 60 million years of fluid-rock interaction in the Samana Complex, Dominican Republic, and the Franciscan Complex, California, respectively.     

Biogenic carbon cycling in the upper ocean: effects of microbial respiration

Food-web processes are important controls of oceanic biogenic carbon flux and ocean-atmosphere carbon dioxide exchange. Two key controlling parameters are the growth efficiencies of the principal trophic components and the rate of carbon remineralization. We report that bacterial growth efficiency is an inverse function of temperature. This relationship permits bacterial respiration in the euphotic zone to be computed from temperature and bacterial production. Using the temperature-growth efficiency relationship, we show that bacterial respiration generally accounts for most community respiration. This implies that a larger fraction of assimilated carbon is respired at low than at high latitudes, so a greater proportion of production can be exported in polar than in tropical regions. Because bacterial production is also a function of temperature, it should be possible to compute euphotic zone heterotrophic respiration at large scales using remotely sensed information.     

上层土壤初始含水率对层状结构土壤中指流水分入渗的影响

为探明影响指流入渗特性的主要因素,通过室内物理模拟试验研究不同上层土壤初始质量含水率对层状结构土壤中指流水分运移的影响.结果表明:湿润锋到达指流层的转折时间与上层土壤初始含水率的相关性较高,且呈对数关系;分别运用分段函数模型和连续函数模型对累积入渗量与时间的关系进行拟合,发现运用分段函数模型拟合的结果虽整体与实测值相关性较高,但是该模型在进行分段拟合时,由于分段点处的不连续性,与实际中层状结构土壤水分入渗不一致,而连续函数模型随着入渗时间的延长,模拟结果越接近实测值,且连续函数模型符合实际中层状结构土壤水分入渗的连续性,因此,连续函数模型适用于长历时的水分入渗过程.     

古典舞上肢流动连接的运用分析

数千年来,汉唐古典舞因其深厚的文化底蕴及悠久的历史意义占据着人们生活的重要地位,在汉唐古典舞蹈中,极其强调上肢训练,重点是通过训练强化上肢的表现力和流动性,以达到与舞台的衔接,服务舞台,促进上下和谐,发挥舞蹈的运动特征和艺术文化,进而解决古典舞蹈上肢流动连接的问题。文章对古典舞上肢流动连接的概念、相互关系、表现对比以及运用进行分析,以期能为古典舞进行立体的、全面的研究做出贡献。     

Magnetic lineations in the ancient crust of mars

The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit, obtained vector magnetic field measurements above the surface of Mars (altitudes >100 kilometers). Crustal magnetization, mainly confined to the most ancient, heavily cratered martian highlands, is frequently organized in east-west-trending linear features, the longest extending over 2000 kilometers. Crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity were found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale. They may be a relic of an era of plate tectonics on Mars.     

新疆果园常见介壳虫的识别及防治

观察记载了新疆果园常见介壳虫12种,其中粉蚧科1种,绵蚧科2种,蚧科5种,盾蚧科4种.以雌成虫制定介壳虫检索表,并提出介壳虫综合防治方法.     

Composition of the ancient north american crust

Geochemical studies of Wyoming Precambrian graywackes derived from continental crust older than 3.2 x 10(9) years indicate that their source area was at least as highly differentiated as most younger Precambrian crust. The composition of this early crust (approximately that of calcium-rich granite) is not unlike that of the 2.5 to 3.2 x 10(9) year old North American crust. Limited geochemical data suggest that the composition of North America may not have changed significantly during the last 3.0 to 3.5 x 10(9) years.     

Probing the structure of the deep continental crust

Old, buried, deformed, crystalline rocks apparently make up most of the 40-kilometer-thick continental crust. This part of the earth is poorly explored and constitutes a major frontier of modern earth science. Two techniques, seismic reflection profiling and drilling, which were developed by industry for other purposes, offer special potential for such exploration. Seismic profiling of the deep crust by COCORP (the Consortium for Continental Reflection Profiling) has already produced important information, including evidence for extensive thin-skinned thrusting of older rocks over a continental margin as the corresponding ocean basin closed. Deep drilling of crystalline rocks of the continents for scientific purposes is so far relatively unexploited in the United States but is already being carried on elsewhere. In general, big science is likely to become more important in basic geology as this frontier is explored.     

Geothermal convection through oceanic crust and sediments in the Indian ocean

Closely spaced heat flow surveys at four sites on the flanks of the Central Indian Ridge and the Southeast Indian Ridge delineate a pattern of oscillatory heat flow which can only result from cellular convection of oceanic bottom water through the oceanic crust and overlying sediment. These cells have a wavelength of 5 to 10 kilometers and are presently active in sea floor 18 x 10(6), 25 x 10(6), and 45 x 10(6) years old of the Crozet Basin and in sea floor 55 x 10(6) years old of the Madagascar Basin. The precise measurement of nonlinear temperature profiles makes it possible to calculate the conductive and convective heat transfer components through the sea floor. Even in the oldest sites, geothermal convection is still a major component of heat transfer through both the crust and sedimentary layers. These observations coupled with the results of earlier oceanwide geothermal studies indicate that more than one-third of the entire surface area of the world's ocean floor contains presently active geothermal convection that is cellular in plan form.     

Overpressure and fluid flow in the new jersey continental slope: implications for slope failure and cold seeps

Miocene through Pleistocene sediments on the New Jersey continental slope (Ocean Drilling Program Site 1073) are undercompacted (porosity between 40 and 65%) to 640 meters below the sea floor, and this is interpreted to record fluid pressures that reach 95% of the lithostatic stress. A two-dimensional model, where rapid Pleistocene sedimentation loads permeable sandy silt of Miocene age, successfully predicts the observed pressures. The model describes how lateral pressure equilibration in permeable beds produces fluid pressures that approach the lithostatic stress where overburden is thin. This transfer of pressure may cause slope failure and drive cold seeps on passive margins around the world.     

鲢鱼鳞营养成分分析及营养学评价

[目的]了解鲢鱼鳞的营养成分,为鲢鱼鳞的食用和加工提供依据。[方法]采用生化成分分析方法对鲢鱼鳞的营养成分含量及组成进行了测定分析。[结果]鲢鱼鳞蛋白质含量为80.21%(干重),17种氨基酸总量为72.64%(干重),其中甘氨酸含量(15.98%)最高,脯氨酸含量(12.35%)次之;4种鲜味氨基酸总量为33.79%,3种支链氨基酸总量为6.36%,7种必需氨基酸总量为14.73%,占氨基酸总量20.27%。AAS和CS评分分别为0.30、0.24,必需氨基酸指数为33.34,其构成比例不符合FAO/WHO标准。鲢鱼鳞中共检测到13种脂肪酸,其中饱和脂肪酸4种,占23.18%;单不饱和脂肪酸5种,占37.78%;多不饱和脂肪酸4种,占31.55%。[结论]鲢鱼鳞中粗蛋白、氨基酸、不饱和脂肪酸含量较高,是一种良好的鱼鳞胶和保健食品源,同时也是一种良好的动物性饲料原料。