Projected temperature changes indicate significant increase in interannual variability of U.S. maize yields     

Daniel Urban  Michael J. Roberts  Wolfram Schlenker  David B. Lobell 《Climatic change》2012,112(2):525-533

Climate change has the potential to be a source of increased variability if crops are more frequently exposed to damaging weather conditions. Yield variability could respond to a shift in the frequency of extreme events to which crops are susceptible, or if weather becomes more variable. Here we focus on the United States, which produces about 40% of the world’s maize, much of it in areas that are expected to see increased interannual variability in temperature. We combine a statistical crop model based on historical climate and yield data for 1950–2005 with temperature and precipitation projections from 15 different global circulation models. Holding current growing area constant, aggregate yields are projected to decrease by an average of 18% by 2030–2050 relative to 1980–2000 while the coefficient of variation of yield increases by an average of 47%. Projections from 13 out of 15 climate models result in an aggregate increase in national yield coefficient of variation, indicating that maize yields are likely to become more volatile in this key growing region without effective adaptation responses. Rising CO₂ could partially dampen this increase in variability through improved water use efficiency in dry years, but we expect any interactions between CO₂ and temperature or precipitation to have little effect on mean yield changes.  相似文献   

Darss Sill as a biological border in the fossil record of the Baltic Sea: evidence from diatoms   总被引：1，自引：0，他引：1  

Andrzej Witkowski  Anja Broszinski  Ole Bennike  Beata Janczak-Kostecka  Jrn Bo Jensen  Wolfram Lemke  Rudi Endler  Antoon Kuijpers 《Quaternary International》2005,130(1):97

Biostratigraphical and palaeoecological analyses of cores along a transect from Femer Belt to the Arkona Basin reveal that North Sea waters began to enter the western Baltic Sea between 8600 and 8400 calibrated years BP. Studies of diatoms indicate that Mecklenburg Bay was characterised by slightly brackish-water conditions between 8400 and 8000 cal. years BP. At around 8000 cal. years BP increasing salinity is indicated by a strong dominance of the diatoms Paralia sulcata and Dimeregramma minor. Some centuries later another diatom assemblage appeared and became dominant in Mecklenburg Bay. This assemblage includes Hyalinella lateripunctata and Pravifusus hyalinus species typical of shallow water areas along the Atlantic coast today. At this time the first marine molluscs made their appearance. The oldest shell of a marine mollusc found in our material is dated to 7600 cal. years BP. The associated assemblage that includes adult specimens of the gastropod Aporrhais pespelicani indicates higher salinities than today.During the Littorina Sea stage a marine diatom flora with P. sulcata, Catenula adhaerens and D. minor crossed the Darss Sill and became widely distributed in the Arkona Basin, Pomeranian Bay and the Baltic Sea proper. In contrast, taxa indicative of the Hyalinella lateripunctata/P. hyalinus assemblage are only found west of the Darss Sill in Femer Belt and Mecklenburg Bay. Apparently, the Darss Sill threshold has been acting as an important salinity border from around 7800 cal. years BP until today.  相似文献   

Loughlinit (Na-Sepiolith) und Analcim in neogenen Sedimenten Anatoliens     

Wolfram Echle 《Contributions to Mineralogy and Petrology》1967,14(2):86-101

Zusammenfassung Der Mineralbestand von Proben aus einem miozänen Tonhorizont der anatolischen Neogenformation bei Killik, Vilayet Eskiehir (Türkei), wird beschrieben und genetisch gedeutet. Hauptkomponenten bilden die Assoziationen Loughlinit-Analcim und Sepiolith-Analcim. Daneben sind Montmorillonit, Dolomit, Pyrit, Gips und — bei Anwesenheit von Loughlinit — wasserlösliche Na-Salze unbekannter Zusammensetzung vorhanden. Der Ton stellt das zweite bisher bekannte Loughlinitvorkommen dar. Analcim, Loughlinit und Sepiolith werden als diagenetische Bildungen im Sediment unter maßgeblicher Beteiligung Na- und Mg-reicher Porenwässer gedeutet. Die Möglichkeiten der Genese dieser Minerale werden durch Vergleich mit anderen Vorkommen und unter Berücksichtigung der geologischen Gegebenheiten diskutiert. Voraussetzung für die Bildung dieser Silikate ist ein enormes Na-Angebot aus einem eindampfenden Meeresbecken und/oder aus der Zersetzung sauren vulkanischen Materials und gleichzeitige Anlieferung von Mg, Al, Si in Form von Lösungen oder Detritus. Als wichtigste Liefergesteine werden die an den ehemaligen Beckenrändern verbreitet auftretenden Serpentinite betrachtet.

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The mineral content of specimens from a miocene clay horizon of the Anatolic Neogen formation near Killik, Vilayet Eskiehir (Turkey), has been described and a genetic interpretation has been given. The main components are the associations loughlinite-analcime and sepiolite-analcime. There are further montmorillonite, dolomite, pyrite, gypsum and watersoluble sodium salts of unknown composition, but the last ones apperently only if there is loughlinite. This clay is the second known occurrence of loughlinite. Analcime, loughlinite and sepiolite may have formed during diagenesis with an intensive interaction of sodium and magnesium rich pore solutions. The possibilities of the origin of these minerals have been discussed by comparing this occurrence with others and considering the geological environment.

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Frau Prof. Dr. D. Schachner danke ich für die Förderung der Arbeit und die Erlaubnis, die von der Deutschen Forschungsgemeinschaft zur Verfügung gestellte Röntgenapparatur benutzen zu können.  相似文献   

Waste Heat Balance in Aquifers Calculated by a Computer Programme     

Wolfram Kley  Winfried Heekmann 《Ground water》1981,19(2):144-148

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Modeling insulated borehole heat exchangers     

Daniel Otto Schulte  Bastian Welsch  Anke Boockmeyer  Wolfram Rühaak  Kristian Bär  Sebastian Bauer  Ingo Sass 《Environmental Earth Sciences》2016,75(10):910

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An Observational Case Study on the Influence of Atmospheric Boundary-Layer Dynamics on New Particle Formation     

Andreas Platis  Barbara Altstädter  Birgit Wehner  Norman Wildmann  Astrid Lampert  Markus Hermann  Wolfram Birmili  Jens Bange 《Boundary-Layer Meteorology》2016,158(1):67-92

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Diel Activity Patterns and Foraging Dynamics of the Sea Urchin Tripneustes ventricosus in a Tropical Seagrass Community and a Reef Environment (Virgin Islands)     

Wolfram P. Tertschnig 《Marine Ecology》1989,10(1):3-21

Abstract. Feeding and movement activity patterns and the foraging behavior of the sea urchin Tripneustes ventricosus were investigated in a Thalassia testudinum seagrass bed and on a patch reef at St. Croix, U.S. Virgin Islands.
Most of T. ventricosus in the seagrass bed fed during both the day and night. Consumption of seagrass blades amounted to 1.4 g dw · individual^-1· d^-1 (mean sea urchin size 12.1 cm ambitus diameter). The population consumed approximately 3.6% of the daily seagrass production.
The movement of T. ventricosus was diel with high nocturnal activity levels and rates of locomotion, and little activity during daylight hours. Foraging activity was reduced under turbulent conditions. Movement rates were not governed by food availability. T. ventricosus travelled 3.7 m · d^-1 on the patch reef. Individuals in the seagrass bed moved 8.8 m · d^-1, most of which was accomplished during the night. The area traversed contained more than one hundred times the amount of food consumed daily. It is assumed that this behavior requires high energy expenditures for locomotion, thus yielding a low net energy profit from feeding.
The high rate of movement in seagrass beds may represent an innate behavioral adaptation to predation by night-active helmet conchs ( Cassis spp.). Fitness optimization by T. ventricosus may have been achieved by minimizing the predation risk during night hours. In an evolutionary context, survival by means of an increased energy expenditure for locomotion may compensate for the lower net energy gain from foraging.  相似文献   

From mantle roots to surface eruptions: Cenozoic and Mesozoic continental basaltic magmatism     

Horst Kämpf  Karoly Németh Dr.  Jacek Puziewicz  Jan Mrlina  Wolfram H. Geissler 《International Journal of Earth Sciences》2015,104(8):1909-1912

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Upper mantle and lithospheric heterogeneities in central and eastern Europe as observed by teleseismic receiver functions     

Wolfram H. Geissler  Rainer Kind  Xiaohui Yuan 《Geophysical Journal International》2008,174(1):351-376

Data from 90 permanent broad-band stations spread over central and eastern Europe were analysed using Ps receiver functions to study the crustal and upper-mantle structure down to the mantle transition zone. Receiver functions provide valuable information on structural features, which are important for the resolution of European lithospheric dynamics. Moho depths vary from less than 25 km in extensional areas in central Europe to more than 50 km at stations in eastern Europe (Craton) and beneath the Alpine–Carpathian belt. A very shallow Moho depth can be observed at stations in the Upper Rhine Graben area ( ca. 25 km), whereas, for example, stations in the SW Bohemian Massif show a significantly deeper Moho interface at a depth of 38 km. V_p / V_s ratios vary between 1.60 and 1.96, and show no clear correlation to the major tectonic units, thus probably representing local variations in crustal composition. Delayed arrivals of converted phases from the mantle transition zone are observed at many stations in central Europe, whereas stations in the cratonic area show earlier arrivals compared with those calculated from the IASP91 Earth reference model. Differential delay times between the P₄₁₀s and P₆₆₀s phases indicate a thickened mantle transition zone beneath the eastern Alps, the Carpathians and the northern Balkan peninsula, whereas the transition zone thickness in eastern and central Europe agrees with the IASP91 value. The thickening of the mantle transition zone beneath the eastern Alps and the Carpathians could be caused by cold, deeply subducted oceanic slabs.  相似文献   

Active Galactic Nuclei     

Martin Haas  Peter Biermann  Rolf Chini  Jochen Heidt  Wolfram Kollatschny  Helmut Meusinger  Ralf Siebenmorgen 《Astronomische Nachrichten》2005,326(7):535-558

D01 Direct evidence of the receding ‘torus’ around active galactic nuclei of FRII radio galaxies and quasars D02 Infrared emission from a clumpy and dusty torus around AGN D03 Size and properties of AGN narrow–line regions from emission–line diagnostics D04 Structural Variability of Intraday Variable Sources D05 Stability of self‐gravitating accretion disks in galactic centers D06 Supermassive Binary Black Holes in AGN D07 The extreme flare in III Zw 2: Evolution of a radio jet in a Seyfert galaxy D08 Radio Linear and Circular Polarization from M81* D09 A fundamental relation between Supermassive Black Holes and Dark Matter Haloes D10 Hunting for radio‐quiet BL Lacs – the 2dF BL Lac survey D11 The Eddington limit in accretion discs D12 Molecular Tori in AGN: A search using excited states of OH D13 The X‐Ray Properties of Radio‐Loud Core‐Dominated AGN: The 2 cm‐X‐Sample D14 The X‐Ray Properties of Radio‐Loud Core‐Dominated AGN: Extension to the High Redshift Regime D15 Line Profile Variability in AGN D16 Jet Superwind Interaction D17 Radio Interferometric Observations of AGN – Probing the Nucleus of M87 with 20 Schwarzschild radii resolution D18 The ISO–2MASS AGN survey D19 Supermassive binary black holes driving the activity of galactic nuclei D20 Proton acceleration at quasi‐perpendicular shocks: A case study for Active Galactic Nuclei D21 Super‐luminal shocks in Active Galactic Nuclei D22 Unconventional quasars from the variability and proper motion survey D23 Radio observations of starburst and AGN activity in Ultraluminous Infrared Galaxies D24 Kinematics in Active Galactic Nuclei at Parsec Scales: the VLBA 2cm Survey D25 Three‐dimensional models of clumpy tori in Seyfert galaxies D26 Silicate emission in active galaxies ‐ From LINERs to QSOs D27 Discovery of 10 µm silicate emission in quasars. – Evidence of the AGN unification scheme. D28 Near‐IR adaptive optics imaging of luminous infrared galaxies D29 Interferometric observations of the Circinus galaxy with MIDI D30 Infrared Interferometry of the Seyfert Galaxy NGC 1068  相似文献