植物挥发性有机物的分析方法   总被引：6，自引：0，他引：6  

Bai Jianhui  Wang Mingxing  Hu Fei  James P. Greenberg  Alex B. Guenther 《大气科学进展》2002,19(1):64-72

为了分析植物排放到大气中的挥发性有机物，在2000年1-6月期间，与美国国家大气研究中心（NCAR）的科学家共同发展和研究了一套自动的气相色谱系统和分析方法。该系统引入一个小型冰箱以除去空气样品进样时的水分，得到了对挥发性有机物样品进行分析时比较好的准确度。在5℃以及稳定的进样速率的条件下，可以得到比较好的除水效果。对NCAR附近的大气进行了采样，并利用此系统做了分析。本简单介绍此自动系统以及样品分析结果。实验结果表明，此套系统具有良好的重复性和稳定性，主要的挥发性有机物的成分如异戊二烯和单萜烯等具有明显的日变化。  相似文献   

Modeling the impacts of climate change on China’s agriculture     

LIU Hui  LI Xiu-bin  Guenther Fischer  SUN Lai-xiang 《地理学报》2001,11(2):149-160

The impacts of climate change on China’s agriculture are measured based on Ricardian model. By using county-level cross-sectional data on agricultural net revenue, climate, and other economic and geographical data for 1275 agriculture-dominated counties in the period of 1985-1991, we find that both higher temperature and more precipitation will have overall positive impact on China’s agriculture. However, the impacts vary seasonally and regionally. Higher temperature in all seasons except spring increases agricultural net revenue while more precipitation is beneficial in winter but is harmful in summer. Applying the model to five climate scenarios in the 2020s and 2050s shows that the North, the Northeast, the Northwest, and the Qinghai-Tibet Plateau would always benefit from climate change while the South and the Southwest may be negatively affected. For the East and the Central China, most scenarios show that they may benefit from climate change. In conclusion, climate change would be beneficial to the whole China.  相似文献   

Zahnmissbildungen und die Frage des Aussterbens der Diluvialen Elefanten in Mitteleuropa     

E. W. Guenther 《International Journal of Earth Sciences》1956,45(1):46-51

Zusammenfassung An den Molaren der pleistozänen mitteleuropäischen Elefanten finden sida verschiedene Arten von Fehlbildungen. In der Hauptsache sind dies: Knickung und Verwindung ganzer Zähne sowie Verdrückung von Lamellen oder geschwulstmäßige Fehlbildungen. Als Ursachen werden mechanische und genbedingte Faktoren in Erwägung gezogen. Zum Teil umweltbedingte Hemmungsmißbildungen sind in der Lage, die Lebenskraft der davon befallenen Tiere zu schwächen.  相似文献   

Implications of U–Pb SHRIMP zircon data on the age and evolution of the Felbertal tungsten deposit (Tauern Window, Austria)     

R. Eichhorn  R. Höll  G. Loth  A. Kennedy 《International Journal of Earth Sciences》1999,88(3):496-512

U–Pb SHRIMP analyses of zircons from various lithologies and ore bodies of the Felbertal scheelite deposit (western and eastern ore field) and neighbouring areas allow the reconstruction of the pre-Alpine magmatic and metamorphic processes responsible for the tungsten mineralization. The ore deposit belongs to the Magmatic Rock Formation, which is tectonically squeezed between the Habach Phyllite Formation and the Basal Schist Formation (all members of the Habach Group). In both the eastern and western ore field, the pre-mineralization geological processes are marked by the emplacement of basalts (547±27?Ma). Ensialic back-arc extension provided pathways for gabbroic and pyroxenitic melts as well as normal "I-type" granitoids (minimum crystallization age of 529±18?Ma). The rock assemblage forms a magmatic arc on an approximately 2?Ga continental Gondwana (?) margin. Post-emplacement tectonism and metamorphism have converted the basalts to fine-grained amphibolites, the gabbroic and pyroxenitic rocks to coarse-grained amphibolites and hornblendites, and the granitoids to leucocratic orthogneisses, respectively. Tungsten mineralization is intimately related to small patches and dikes of differentiated granitoids in the eastern ore field and the K2 ore body in the western ore field. The granitic melts have supposedly been generated by ongoing differentiation of calcalkaline magmas. They cut the older lithologies and intruded along the same pathways as the earlier melts. Fluids have been carried up along a major line in the eastern ore field. They caused the formation of an elongate ore body with a scheelite-quartz stockwork zone (scheelite-bearing quartz veinlets and veins) and an overlying, likewise elongate, 900-m-long, scheelite-rich quartzite lens. In the western ore field, accompanying fluids produced the K2 ore body. In this ore body, an eruption breccia occurs above a mineralized quartzite. The breccia (younger than 529±18?Ma) contains mineralized quartzite clasts as well as barren fine-grained amphibolite clasts and leucocratic orthogneiss-clasts that are similar to the surrounding host rock equivalents. The quartzite, which represents the main mineralization stage of the K2 ore body, is unsuitable for dating. However, the scheelite-rich quartzite lens of the eastern ore field is probably coeval. This lens locally lies on top of a differentiated and strongly mineralized gneiss. The crystallization age of this gneiss is 529±17?Ma, and marks the peak of tungsten input in the eastern ore field. Small, differentiated granitic dikes, which cut both the K2 eruption breccia and the K2 quartzite in the western ore field, contain only minor scheelite and mark a decrease in mineralization at 519±14?Ma. Thus, a period between 530 and 520?Ma and a setting between magmatic arc and (ensialic) back-arc may properly explain the likely scenario for the primary tungsten input (stage-1 scheelite) by differentiated granitic melts of calcalkaline character. Surprisingly, a second stage-2 scheelite formation was induced in the western ore field by a Variscan granite intrusion (K1–K3 gneiss; 336±19?Ma), the emplacement time of which is pre-dated by a cross-cutting dacitic dike of 340±5?Ma. This mineralization, which occurs in small quartz veins and within a quartz aureole atop the intrusion as well as an even younger mineralization in shear zones (yellowish-fluorescent stage-2 scheelite porphyroblasts), is bracketed between 355?Ma (the upper age limit of the K1–K3 gneiss precursor) and 335?Ma (the lower age limit of the dacitic dike, which is stage-2 scheelite free). Supposedly, long-lasting Variscan (amphibolite facies) metamorphic conditions till 282±2?Ma extended the scheelite remobilization. They caused a further dispersion of scheelite and induced the growth of individual grains and of rims around older grains (bluish-fluorescent stage-3 scheelite). The Alpine metamorphism of lower amphibolite to upper greenschist facies conditions caused a further, minor scheelite remobilization, especially along some faults and quartz veins, including sparse, but large, whitish-bluish-fluorescent crystals (stage-4 scheelite).  相似文献   

Surface inhomogeneities and line variability on DF Tau     

Y. C. Unruh  A. Collier Cameron  & E. Guenther 《Monthly notices of the Royal Astronomical Society》1998,295(4):781-798

We have mapped surface inhomogeneities on the classical T Tauri star DF Tau, using the Li  i doublet at 670.8 nm, the Ca  i lines at 612.2 nm and 643.9 nm and a calcium and iron blend at 646.3 nm. We find compelling evidence that there are hotspots with temperatures of more than 5000 K. Two of the hotspots produce line-profile deformations that can be traced as they move through the cross-correlated profiles. When one of the hotspots crosses the stellar disc, redshifted absorption components appear in the Na D lines. As these redshifted absorption features are usually tracers for mass-infall we interpret this hotspot as an accretion shock close to the stellar surface.   Parts of the surface of DF Tau are covered with a hot chromosphere that is visible in the Ca  ii infrared triplet lines and the narrow component of He  i . We find no correlation between the veiling and the lines that originate from the hot chromosphere, suggesting that the veiling and the chromospheric emission are produced in physically distinct regions.  相似文献   

Primary velocity dependence of impact ejecta parameters     

G. Eichhorn 《Planetary and Space Science》1978,26(5):469-471

From the light emitted during impacts of secondary particles produced during hypervelocity primary impacts, the velocities and relative masses of these ejecta were determined as a function of the angle between the ejection direction and the target surface. The velocity of the ejecta increases with increasing impact velocity and decreasing ejection angle. The ratio of the maximum ejecta velocity to the primary impact velocity decreases with increasing impact speed. The main fraction of the secondary particles is ejected in rather small angular intervals of about 10° width in elevation. The ejection angle of the main fraction of the ejecta mass increases with increasing impact velocity.  相似文献   

Calculation of the far field finite depth green's function     

H.T. Wang  R.B. Guenther 《Ocean Engineering》1997,24(1):83-94

This note presents a numerical method for calculating the far field part of the Green's function for a source in steady translation below the surface of fluid of finite depth. The principal steps of the numerical scheme are outlined, with emphasis on those aspects which are needed for a computer implementation of the scheme. Numerical results are given to show the behavior of the function in various parts of the computation domain, the computer requirements of the method, and its expected accuracy.  相似文献   

Astrometric confirmation of a wide low‐mass companion to the planet host star HD 89744     

M. Mugrauer  R. Neuhuser  T. Mazeh  E. Guenther  M. Fernndez 《Astronomische Nachrichten》2004,325(9):718-722

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Deep infrared imaging and spectroscopy of the nearby late M‐dwarf DENIS‐P J104814 –395606     

R. Neuhuser  E.W. Guenther  J. Alves  N. Grosso  Ch. Leinert  Th. Ratzka  Th. Ott  M. Mugrauer  F. Comern  A. Eckart  W. Brandner 《Astronomische Nachrichten》2002,323(5):447-452

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Traffic-related immissions and their impact on historic buildings: implications from a pilot study at two German cities   总被引：1，自引：1，他引：0  

Michael Auras  Silvia Beer  Petra Bundschuh  Joachim Eichhorn  Martin Mach  Dirk Scheuvens  Michael Schorling  Jonas von Schumann  Rolf Snethlage  Stephan Weinbruch 《Environmental Earth Sciences》2013,69(4):1135-1147

Besides the enormous improvement of air quality in Germany due to the reduction of sulphur dioxide emissions in the last decades, high immissions of nitrogen oxides and fine particulate matter are frequently observed at traffic-rich urban sites. The changed chemical composition of air pollution requires a new investigation of its impact on historic buildings constructed of natural stone. In a pilot study a multi-disciplinary approach was chosen to obtain information on the actual pollution situation of historic buildings and monuments at traffic hotspots in Germany. The study concentrated on the two German cities of Munich and Mainz of different size, traffic volume and stone inventory. Dose–response functions were calculated to demonstrate the change of impact of different pollutants over the last three decades, and for comparison of traffic hotspots and housing areas of both cities. Numeric modelling on a city-scale was used to identify the historic buildings and monuments affected by elevated traffic immissions. Because a relevant part of these pollutants is dominated by short-range transport, the differences of wind speed and deposition rates were calculated using a street-scale 3D flow and dispersion model regarding traffic volume, wind regime and adjacent buildings. Finally, particulate matter was sampled at different positions of two buildings heavily exposed to traffic emissions. Individual particles were investigated by environmental scanning electron microscopy. After classification of the particles into different chemical groups, the fraction of traffic-induced particulate matter was quantified. Summarizing the results, it must be stated that soiling by traffic-related particulate matter, deposition of nitrates deriving from exhaust emission and other diffusely emitted components bear a severe damage potential for natural building stone at least locally at traffic-rich urban sites.  相似文献