The MAGIC telescope   总被引：1，自引：0，他引：1  

Eckart Lorenz  Manel Martinez 《Astronomy& Geophysics》2005,46(6):6.21-6.25

The MAGIC telescope, the largest and most advanced single instrument to observe very-high-energy cosmic gamma rays from the ground, started regular operation in spring 2005. Eckart Lorenz and Manel Martinez report on progress observing the most distant and energetic universe; exciting results are just around the corner.  相似文献   

Authigenic carbonates in sediments from the Gulf of Mexico     

Reiner Botz  Eckhard Faber  Michael J. Whiticar  James M. Brooks 《Earth and Planetary Science Letters》1988,88(3-4)

The carbon isotopic composition of diagenetic dolomite and calcite in some sediments of the Gulf of Mexico varies between “normal-marine” (δ¹³C ca. 0‰) and −14.6‰ which suggests that biogenic CO₂ contributed to the carbonate formation. The δ¹³O values of dolomite and coexisting calcite are very similar but variable down-core.Dolomite and calcite precipitated early from pore water where SO₄²⁻ was not reduced. However, during (and after?) SO₄²⁻ reduction dolomite and calcite still formed and there are at least two generations of carbonate minerals present.  相似文献   

Methane oxidation in sediment and water column environments—Isotope evidence     

Michael J. Whiticar  Eckhard Faber 《Organic Geochemistry》1986,10(4-6)

Microbial anaerobic oxidation of methane in sediments is a kinetic process associated with a carbon isotope effect which enriches the remaining methane in ¹³C. Three, models: % residual methane, higher hydrocarbon enrichment, and CO₂-CH₄ coexisting pairs are used to independently calculate fractionation factors (αc) in the range of 1.002–1.014, which overlap the range determined by culture studies, αc is smaller than that associated with methanogenesis by CO₂ reduction or by acetate-type fermentation, and comparison of the coexisting CO₂-CH₄ pairs can distinguish between the formation and consumption processes. Methane oxidation in sediments continues to a threshold concentration of ca. 0.2 mM; the residual methane is either unavailable or unattractive to consumption. Minor amounts of methane may also be produced simultaneously in the methane consumption zone, influencing the apparent fractionation factor in this zone.  相似文献   

Seismically induced variations in Mariánské Lázně fault gas composition in the NW Bohemian swarm quake region, Czech Republic — A continuous gas monitoring     

Falk H. Weinlich  Eckhard Faber  Alena Bou&#x;kov  Josef Horlek  Manfred Teschner  Jürgen Poggenburg 《Tectonophysics》2006,421(1-2):89-110

A continuously operated gas monitoring station was emplaced within the epicentral area of the NW Bohemian swarm earthquakes overlying directly the active Mariánské Lázně fault. The recordings of 8-month continuous monitoring period are presented. The variations in radon concentrations are similarly to variations in CO₂, i.e. CO₂ is considered to be the carrier gas for radon. Very small diurnal variations in gas concentration are caused by the earth tides, as daily variations in meteorological conditions cannot explain a short daily minimum at midday times. Sudden changes in gas concentration, which clearly exceed these diurnal variations occur and are always linked with seismic activities. Decreased gas concentration may indicate compression resulting in reduced fault permeability as is implied by negative peaks following local earthquake swarms. A sudden increase in CO₂ and Rn concentration may indicate an increased fault permeability caused by stress redistribution, giving rise to opening of migration pathways. This implies a repeatedly sudden rise in gas concentration before local earthquake swarms. Several variations in gas concentration were monitored linked with remote earthquakes of ground motion amplitudes  >1 μm. These seismic events are accompanied by an interference of the diurnal gas concentration–stress-cycle along the Mariánské Lázně fault. However, if shocks of remote earthquake can alter properties of the migrating fluids or the fault properties it can be suggested that these are able to trigger local seismicity, as indicated in the case of the Slovenia earthquake on 12th July 2004.  相似文献   

Effective seed distribution pattern of an upward shift species in alpine tundra of Changbai Mountains     

Shengwei Zong  Jiawei Xu  Eckart Dege  Zhengfang Wu  Hongshi He 《中国地理科学(英文版)》2016,26(1):48-58

The vegetation of alpine tundra in the Changbai Mountains has experienced great changes in recent decades. Narrowleaf small reed(Deyeuxia angustifolia), a perennial herb from the birch forest zone had crossed the tree line and invaded into the alpine tundra zone. To reveal the driven mechanism of D. angustifolia invasion, there is an urgent need to figure out the effective seed distribution pattern, which could tell us where the potential risk regions are and help us to interpret the invasion process. In this study, we focus on the locations of the seeds in the soil layer and mean to characterize the effective seed distribution pattern of D. angustifolia. The relationship between the environmental variables and the effective seed distribution pattern was also assessed by redundancy analysis. Results showed that seeds of D. angustifolia spread in the alpine tundra with a considerable number(mean value of 322 per m2). They were mainly distributed in the low elevation areas with no significant differences in different slope positions. Effective seed number(ESN) occurrences of D. angustifolia were different in various plant communities. Plant communities with lower canopy cover tended to have more seeds of D. angustifolia. Our research indicated reliable quantitative information on the extent to which habitats are susceptible to invasion.  相似文献   

The Stellar Ages of Elliptical Galaxies     

S.M. Faber  S.C. Trager  J.J. Gonzalez  Guy Worthey 《Astrophysics and Space Science》1999,267(1-4):273-281

Integrated broad-band colors and metallic lines cannot discriminate clearly between the effects of age and Z in old stellar populations. Such data are more sensitive to Z than to age. The Hβ feature provides a way to break this degeneracy. New measurements indicate that the mean stellar ages of typical E galaxy nuclei are fairly young, ranging from 2 to ∼12 Gyr. The outer parts of E galaxies are both older and more metal-poor than nuclei, consistent with the formation of E galaxies via mergers and starbursts. Age effects contribute strongly to the classic color-line strength sequence of E galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A paleoclimate record for the past 250,000 years from Summer Lake, Oregon, USA. 1. chronology and magnetic proxies for lake level     

Robert Negrini  Daniel Erbes  Karin Faber  Adam Herrera  Andrew Roberts  Andrew Cohen  Peter Wigand  Franklin Foit 《Journal of Paleolimnology》2000,24(2):125-149

This study presents the age control and environmental magnetism components of a new, late Pleistocene paleoclimate record for the Great Basin of western North America. Two new cores from the Summer Lake sub-basin of pluvial Lake Chewaucan, Oregon, USA are correlated to basin margin outcrops on the basis of tephrochronology, lithostratigraphy, sediment magnetism and paleomagnetic secular variation. Eleven tephra layers were found in the cores that correlate to tephra identified previously in the outcrop. The Olema ash was also found in one of the cores; its stratigraphic position, relative to 3 dated tephra layers, indicates that its age is 50-55 ka, somewhat younger than has been previously reported. The Summer Lake sediments are divided into deep and shallow lake lithosomes based on sedimentary features. The stratigraphic position of these lithosomes support the tephra-based correlations between the outcrop and the cores. These sediments contain a well resolved record of the Mono Lake Excursion (MLE) and an earlier paleomagnetic excursion as well as a high quality replication of the paleosecular variation immediately above the MLE.Relative sedimentation rates increased dramatically toward the depocenter during intervals of low-lake level. In contrast, during intervals of high-lake level, relative sedimentation rates were comparable along the basin axis from the basin margin to the depocenter. The magnetic mineralogy of the Summer Lake sediments is dominated by pseudo-single domain (titano)magnetite and intervals of high/low magnetite concentration coincide with lithosomes that indicate high/low lake levels. Magnetic grain size also varies in accord with bulk sediment grain size as indicated by the silt/clay ratio. To a first order, variations in magnetic parameters, especially those attributable to the concentration of magnetic minerals, correlate well with global glacial/interglacial oscillations as indicated by marine oxygen isotope stages. This relationship can be explained by increased dissolution of (titano)magnetite minerals as lake level dropped and the lake became more productive biologically. This inference is supported by a correspondence between lower concentrations of magnetite with higher levels of total organic carbon and vice-versa.  相似文献   

The ALFA Laser and Analysis Tools     

S. Rabien  T. Ott  W. Hackenberg  A. Eckart  R. Davies  M. Kasper  A. Quirrenbach 《Experimental Astronomy》2000,10(1):75-88

The optimal performance of adaptive optics systems can only be maintainedif the wavefront reference is bright and compact.Experience has shown that both of these important criteria are remarkablydifficult to achieve with laser guide stars. This contribution gives an account of the methods by which ALFAattempts to reach them.First, the production of a high quality, high power laser beam isdescribed.However, this quality is unavoidably compromised along the path to thelaunch telescope.In order to rectify this, a new set of diagnostic tools which monitorthe quality of the out-going beam has been installed, and these arealso described.Lastly, we outline a number of possible modifications on which we areworking.If successful, these may allow a substantial improvement in the beamquality.  相似文献   

ALFA: The MPIA/MPE Laser Guide Star AO System     

A. Eckart  S. Hippler  A. Glindemann  W. Hackenberg  A. Quirrenbach  P. Kalas  M. Kasper  R. I. Davies  T. Ott  S. Rabien  D. Butler  H.-C. Holstenberg  D. Looze  R.-R. Rohloff  K. Wagner  N. Wilnhammer  D. Hamilton  S. V. W. Beckwith  I. Appenzeller  R. Genzel 《Experimental Astronomy》2000,10(1):1-3

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The Far‐Infrared Emission of Galaxies     

Carsten Kramer  Albrecht Poglitsch  Jürgen Stutzki  Andreas Eckart 《Astronomische Nachrichten》2005,326(7):523-534

C01 Study of local infrared bright galaxies with HERSHCEL‐PACS C02 PDR modeling of the COBE Far‐Infrared data of the Milky Way C03 MAMBO observations of BzK‐selected vigorous starburst galaxies at z ∼ 2 C04 Starburst galaxies in the far‐infrared. Modelling the line, PAH and dust continuum emission C05 The SED from isothermal clouds C06 PDRs in M83 and M51: The road to HIFI/Herschel and SOFIA C07 Large Scale Mapping of Molecular Gas in the Vicinity of 30 Doradus in the Large Magellanic Cloud C08 Modelling far‐infrared emission from dust in gas‐rich galaxies C09 [CII]/CO(1‐0) Line Ratio at low Metallicities C10 Gas, Stars and Dust in the Spiral Arms of M51 C11 The ISOPHOT 170 micron Serendipity Survey (ISOSS) catalog of optically identified galaxies C12 Spitzer Images of M33: A Probe to Radio‐FIR Correlation C13 Observations of far‐infrared emission from dust in gas‐rich galaxies C14 Dust and Gas in Nearby Galaxies: First Results from SINGS and THINGS C15 Sequential Starburst in Arp220?  相似文献