Holocene eruptions of mauna kea volcano, hawaii

Postglacial lava flows, interstratified with thick locally derived sheets of tephra, cover some 27.5 square kilometers on the south slope of Mauna Kea. Most of the volcanics were erupted about 4500 years ago and overlie a regionally extensive paleosol which developed largely during the last glaciation.     

Buried caldera of mauna kea volcano, hawaii

An elliptical caldera (2.1 by 2.8 kilometers) at the summit of Mauna Kea volcano is inferred to lie buried beneath hawaiite lava flows and pyroclastic cones at an altitude of approximately 3850 meters. Stratigraphic relationships indicate that hawaiite eruptions began before a pre-Wisconsin period of ice-cap glaciation and that the crest of the mountain attained its present altitude and gross form during a glaciation of probable Early Wisconsin age.     

Volcanic gases: hydrogen burning at kilauea volcano, hawaii

Spectroscopic evidence for hydrogen burning in air was obtained at Kilauea Volcano. The abundance of hydrogen required to support combustion is consistent with that predicted for gases in equilibrium with typical Hawaiian tholeiitic basalt.     

Sandstone: secular trends in lithology in southwestern montana

Long-term secular trends in the composition and texture of sandstones in southwestern Montana reflect changing provenance and depositional environment, which in turn reflect changing tectonic patterns in the Cordilleran mobile belt just to the west.     

Global trends in total atmospheric ozone

Analyses of the mean monthly global distributions of total ozone for the 13-year period from 1957 through 1970 reveal an upward trend of about 7.5 percent per decade in the Northern Hemisphere and about 2.5 percent per decade in the Southern Hemisphere. The increase seems to have started about March 1961 in the Northern Hemisphere and about September 1961 in the Southern Hemisphere. The cause of these trends is at present unknown.     

Turbidity trends at tucson, Arizona

Variations in atmospheric turbidity at Tucson, Arizona, since 1956 are similar to those at Mauna Loa in Hawaii, especially before January 1970. The turbidity at both locations increased markedly in 1963 after the Bali eruption. Since January 1970, the turbidity has returned to its pre-1963 level at Mauna Loa, but has remained relatively high at Tucson.     

Argon-40: excess in submarine pillow basalts from kilauea volcano, hawaii

Submarine pillow basalts from Kilauea Volcano contain excess radiogenic argon-40 and give anomalously high potassium-argon ages. Glassy rims of pillows show a systematic increase in radiogenic argon-40 with depth, and a pillow from a depth of 2590 meters shows a decrease in radiogenic argon40 inward from the pillow rim. The data indicate that the amount of excess radiogenic argon-40 is a direct function of both hydrostatic pressure and rate of cooling, and that many submarine basalts are not suitable for potassium-argon dating.     

Cumulate xenolith in oahu, hawaii: implications for deep magma chambers and hawaiian volcanism

The maximum depth at which large (>1000 km(3)) terrestrial mafic magma chambers can form has generally been thought to be the Moho, which occurs at a mean depth of about 35 kilometers beneath the continents and 8 kilometers beneath ocean basins. However, the presence of layers of cumulus magnesium-rich spinel and olivine and intercumulus garnet in an unusual mantle xenolith from Oahu, Hawaii, suggests that this rock is a fragment of a large magma chamber that formed at a depth of about 90 kilometers; Hawaiian shield-building magmas may pond and fractionate in such magma chambers before continuing their ascent. This depth is at or near the base of the 90-million-year-old lithosphere beneath Oahu; thus, rejuvenated stage alkalic magmas containing mantle xenoliths evidently also originate below the lithosphere.     

National Radio Astronomy Observatory: The early history and development of the observatory at Green Bank,West Virginia,are reviewed

The existence of the National Radio Astronomy Observatory and the researches already accomplished there are the result of the foresight and wisdom of United States scientists, the National Science Board, and the Congress, who joined forces to make possible this new national asset. Continued effort will be needed td insure that the observatory will always have the finest possible research instruments and that the site will be a haven of radio quiet. Visiting scientists in some instances may wish to bring equipment with them for studying special problems. Within its means, the observatory will provide supporting facilities, including receivers and other electronic devices, computers, laboratories and shops, and housing. Scientists interested in more details concerning arrangements for visitors should direct their inquiries to the National Radio Astronomy Observatory, P. O. Box 2, Green Bank, West Virginia.     

Synaptic transmission at single glomeruli in the turtle cerebellum

We have recorded from the granular layer of the turtle cerebellum extracellular unitary potentials that appear to reflect pre- and postsynaptic events at the synapse between a single swelling of a mossy fiber and the dendritic tips of several granule cells. The presynaptic component is an all-or-none potential. It can be directly activated by spinal stimulation and is unaltered by repetitive activity or by high concentrations of magnesium. The postsynaptic component is a graded potential. It follows the presynaptic component by approximately 1 millisecond and is depressed by repetitive activity and by high concentrations of magnesium. The recording of large potentials produced by the flow of postsynaptic current within a single glomerulus suggests powerful transmission. Electron micrographs demonstrate large cerebellar glomeruli in the turtle and a substantial accumulation of mitochondria in the dendritic tips of granule cells.     

High-probability uniquantal transmission at excitatory synapses in barrel cortex

The number of vesicles released at excitatory synapses and the number of release sites per synaptic connection are key determinants of information processing in the cortex, yet they remain uncertain. Here we show that the number of functional release sites and the number of anatomically identified synaptic contacts are equal at connections between spiny stellate and pyramidal cells in rat barrel cortex. Moreover, our results indicate that the amount of transmitter released per synaptic contact is independent of release probability and the intrinsic release probability is high. These properties suggest that connections between layer 4 and layer 2/3 are tuned for reliable transmission of spatially distributed, timing-based signals.     

大众化教育阶段我国高校课程改革的基本趋势

对我国高等教育进入大众化阶段以来高校课程改革的研究与实践进行梳理、提炼。发现其基本趋势是发展性、多样化和综合化,以期为大众化阶段下我国高校课程改革的进一步深化提供有益的借鉴作用。     

Interpreting differential temperature trends at the surface and in the lower troposphere

Estimated global-scale temperature trends at Earth's surface (as recorded by thermometers) and in the lower troposphere (as monitored by satellites) diverge by up to 0.14 degrees C per decade over the period 1979 to 1998. Accounting for differences in the spatial coverage of satellite and surface measurements reduces this differential, but still leaves a statistically significant residual of roughly 0.1 degrees C per decade. Natural internal climate variability alone, as simulated in three state-of-the-art coupled atmosphere-ocean models, cannot completely explain this residual trend difference. A model forced by a combination of anthropogenic factors and volcanic aerosols yields surface-troposphere temperature trend differences closest to those observed.     

Recent trends in Arctic surface,cloud, and radiation properties from space

Trends in satellite-derived cloud and surface properties for 1982 to 1999 show that the Arctic has warmed and become cloudier in spring and summer but has cooled and become less cloudy in winter. The increase in spring cloud amount radiatively balances changes in surface temperature and albedo, but during summer, fall, and winter, cloud forcing has tended toward increased cooling. This implies that, if seasonal cloud amounts were not changing, surface warming would be even greater than that observed. Strong correlations with the Arctic Oscillation indicate that the rise in surface temperature and changes in cloud amount are related to large-scale circulation rather than to local processes.     

我国小浆果生产现状、问题和发展趋势

从我国蓝莓、树莓和黑加仑的栽培面积和产量、品种构成、加工和销售市场等方面深入详细的阐述了我国小浆果生产的现状;对目前我国在小浆果聍藏保鲜、栽培技术等方面存在的问题进行了总结;从营养保健、国内外市场需求及发展前景等方面细致分析了我国小浆果的未来发展趋势,并提出了小浆果的研究发展方向,对小浆果产业发展具有极为重要的意义.     

福建粮食安全：现状、趋势及其应对策略

粮食安全属于重要的战略性问题.在简要分析福建省粮食生产及其面临主要问题与矛盾的基础上,着重就福建粮食安全战略的构建及其实施问题进行初步研究探索,提出了防止耕地抛荒、稳定粮食生产以及建立和完善粮食安全机制等对策措施.     

国外设施园艺发展概况、特点及趋势分析

设施园艺是现代农业的重要标志。随着科学技术的进步,尤其是现代生物技术、信息技术和工程技术在设施园艺中的应用,设施园艺的发展步入了一个崭新的时代。本文在综述欧洲、非洲、中近东、亚洲、美州及设施园艺发达国家概况的基础上,总结了国外设施园艺发展的特点,分析了国外设施园艺发展的趋势,以期为我国设施园艺健康持续发展提供一些经验和启示。     

气调条件下采后番木瓜硬度与相关酶活性研究

将购买的新鲜夏威夷木瓜在非气调(大气)和气调(8%O2+3%CO2+89%N2)两种条件下低温贮藏(13℃),测定多聚半乳糖醛酸酶(PG)、β-葡萄糖苷酶和过氧化物酶(POD)活力以及硬度的大小,分析测定结果的相关性,并进行拟合。结果表明,13℃气调延迟了PG、β-葡萄糖苷酶和POD活力高峰的出现,有效降低了PG和β-葡萄糖苷酶活力;且PG、β-葡萄糖苷酶和POD与硬度具有线性相关性。     

杭州市大气环境质量评价、预测及防治对策研究

选用综合污染指数法对2001-2005年杭州市大气环境质量现状进行评价,采用灰色系统模型对大气环境质量变化趋势进行了预测分析,并剖析了杭州市大气污染的主要原因,提出了改善大气污染的防治对策,为防治大气污染提供科学依据.