Microbial community and activity shifts after soil transplantation in a glacier forefield     

Anita Zumsteg  Stefano M. Bernasconi  Josef Zeyer  Beat Frey 《Applied Geochemistry》2011

The majority of Alpine glaciers are currently receding because of global warming. Their forefields have become interesting sites to study primary microbial colonisation and microbial adaptation. Here, the structure and enzyme activity of microbial communities in exposed rock substrates and their changes in a gradient of temperature and soil moisture conditions within the forefield of the Damma glacier in the Swiss Central Alps are discussed. The temperature at the sites differed in the course of a day and also showed differing mean temperatures over the summer. Distinct bacterial communities inhabit the differing sites at the beginning of the experiment and even after transplantation they stay distinct. But a seasonal shift in the communities could be observed, which followed the same pattern for all the samples. Interestingly, microbial enzyme activity was highest at the site with the smallest temperature shifts.  相似文献   

Synthetic Spectra for Carbon Stars from Dynamica Model Atmospheres     

Rita Loidl  Josef Hron  Bernhard Aringer  Susanne Höfner  Uffe G. Jφrgensen 《Astrophysics and Space Science》1997,255(1-2):289-290

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Dust Features of Visually Bright AGB Variables as Seen by ISO and IRAS     

Josef Hron  Rita Loidl  Franz Kerschbaum 《Astrophysics and Space Science》1997,251(1-2):211-214

ISO-SWS spectra of two Mira variables (R Cas and T Dra), taken at two different pulsational phases, are presented. We describe the reduction of the data and the encountered problems. The dust features observed by ISO at different phases and with the Low Resolution Spectrometer of IRAS are compared. We briefly discuss the results in terms of current models for the circumstellar dust shells of AGB variables. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Observations of Jet Diameter, Density and Dynamics     

Francesca Bacciotti  Thomas P. Ray  Jochen Eislöffel  Jens Woitas  Josef Solf  Reinhard Mundt  Christopher J. Davis 《Astrophysics and Space Science》2003,287(1-4):3-13

Collimated jets are believed to be an essential ingredient of the star formation process, and we are now able for the first time to test observationally the theories for their formation and propagation. The major advances achieved in recent years are reviewed, regarding the observed morphology, kinematics and excitation properties of jets, from the parsec-scale `giant outflows' down to the `microjets' from T Tauri stars. High angular resolution images and spectra have provided valuable estimates of jet diameter, space velocity, temperature, ionization fraction, electron and total density, both along and across the flow. We can thus calculate key physical quantites, as the shock excitation parameters, or the mass and momentum fluxes in the flow. The results obtained appear to validate the popular magneto-centrifugal models for jet launching, although some important issues are still under debate, as to the cause of knotty structures, observed wind thermal properties, and the dynamical relationship between jets and molecular outflows. Among the most interesting recent findings, we mention the observed indications for jet rotation, with inferred toroidal velocities consistent with the prescribed angular momentum balance between infall and outflow.  相似文献   

Synthetic radii and visibilities for pulsating red giants     

Josef Hron  Walter Nowotny  Rita Gautschy-Loidl  Susanne Höfner 《Astrophysics and Space Science》2003,286(1-2):213-218

We present synthetic radii and visibilities in the IR, based on hydrostatic and dynamic model atmospheres of carbon stars. The differences between these two sets of input models and to uniform disc models are discussed and compared to the expected capabilities of the VLTI. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Effect of the Screen on the Mass, Momentum, and Energy Exchange Rates of a Uniform Crop Situated in an Extensive Screenhouse   总被引：2，自引：2，他引：0  

Mario B. Siqueira  Gabriel G. Katul  Josef Tanny 《Boundary-Layer Meteorology》2012,142(3):339-363

The area of crops cultivated in extensive screenhouses is rapidly growing, especially in semi-arid and arid regions. Water vapour, carbon dioxide, and sensible heat released or taken up by crops within such protected environments can substantially alter the immediate micro-environment, which in turn, affects these fluxes. This amplified interaction between plants and their microclimate challenges simple assessments on how partially covering the crop by a screen modifies plant water uptake and photosynthesis. Via a newly proposed higher-order closure model, the effects of a screen on the mean flow field, turbulent stresses, radiative and energy fluxes, as well as scalar sources, sinks, fluxes, and mean scalar concentration within screenhouses are explored. As a starting point, an extensive screenhouse is assumed thereby reducing the sensitivity of the model results to the precise geometric configuration of the screenhouse. The model findings for the screenhouse are presented and referenced against their open field counterpart. The radiation modulation and changes to turbulent transport due to the presence of the screen are investigated. In general, the presence of a screen results in a warmer and more humid environment inside the screenhouse, promoting reductions in both canopy photosynthesis and transpiration. However, the overall effect of the screen is to enhance water-use efficiency thereby resulting in water savings for the same amount of gross primary production.  相似文献   

Comparative Study of the Spherical Downward Continuation     

Josef Sebera  Martin Pitoňák  Eliška Hamáčková  Pavel Novák 《Surveys in Geophysics》2015,36(2):253-267

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克鲁格曼的新经济地理研究及其意义   总被引：11，自引：0，他引：11  

段学军  虞孝感  陆大道  Josef Nipper 《地理学报》2010,65(2):131-138

克鲁格曼在借鉴经典区位理论的基础上,引入了世界贸易、新经济增长理论的最新研究成果,改造并创新了传统区位理论,在此基础上构造出一套新的空间区位理论-称之为新经济地理学。克鲁格曼以在该领域及此前在国际贸易和世界经济形势预测方面的贡献,获得了2008年度诺贝尔经济学奖。克鲁格曼新经济地理学是经济地理学在新形势下取得的新成果,解决了许多传统区位理论未能解决的难题,而且使经典区位理论获得了新的发展动力。但是,长期以来克鲁格曼新经济地理学被认为与地理界所研究的经济地理学关系不大,未引起地理学界的足够重视。本文从地理学的角度对克鲁格曼所研究的新经济地理学的内涵、研究意义及其与传统区位论的关系等方面,重新解读和审视克鲁格曼的新经济地理学,分析该理论对经济地理学发展的影响,以期对中国经济地理学的创新研究和制订区域科学发展路线图提供参考。  相似文献   

Phyllocladane in brown coal from Handlová, Slovakia: Isolation and structural characterization     

Anton Zubrik  David Šaman  Soňa Vašíčková  Bernd R.T. Simoneit  L’udmila Turčániová  Michal Lovás  Josef Cvačka 《Organic Geochemistry》2009,40(1):126-134

Aliphatic diterpenes were isolated from brown coal from Handlová, Slovakia, using microwave assisted extraction of mechanically activated coal powder. The parameters of the extraction procedure were optimized to get the target compounds in high yield. The total extract was separated using adsorption chromatography. GC–MS revealed tetracyclic and tricyclic diterpanes in the aliphatic fraction; they were identified as 16α(H)-phyllocladane (83%), isopimarane (11%), 18-norisopimarane (4%), abietane (2%) and fichtelite (<0.1%). It was found that more than 2 g of the most abundant diterpane, 16α(H)-phyllocladane could be extracted from 1 kg of Handlová coal. Because of the scarcity of relevant analytical data, 16α(H)-phyllocladane was thoroughly characterized by spectroscopic and chromatographic methods. A complete set of ¹H and ¹³C NMR data is given including their comparison with published values and ab initio calculations. EI mass and IR spectra of 16α(H)-phyllocladane are shown and discussed. Kováts retention indices measured on two common GC stationary phases are also given.  相似文献   

Gravity Spectra from the Density Distribution of Earth’s Uppermost 435 km     

Josef Sebera  Roger Haagmans  Rune Floberghagen  Jörg Ebbing 《Surveys in Geophysics》2018,39(2):227-244

The Earth masses reside in a near-hydrostatic equilibrium, while the deviations are, for example, manifested in the geoid, which is nowadays well determined by satellite gravimetry. Recent progress in estimating the density distribution of the Earth allows us to examine individual Earth layers and to directly see how the sum approaches the observed anomalous gravitational field. This study evaluates contributions from the crust and the upper mantle taken from the LITHO1.0 model and quantifies the gravitational spectra of the density structure to the depth of 435 km. This is done without isostatic adjustments to see what can be revealed with models like LITHO1.0 alone. At the resolution of 290 km (spherical harmonic degree 70), the crustal contribution starts to dominate over the upper mantle and at about 150 km (degree 130) the upper mantle contribution is nearly negligible. At the spatial resolution \(<150\,\hbox {km},\) the spectra behavior is driven by the crust, the mantle lid and the asthenosphere. The LITHO1.0 model was furthermore referenced by adding deeper Earth layers from ak135, and the gravity signal of the merged model was then compared with the observed satellite-only model GOCO05s. The largest differences are found over the tectonothermal cold and old (such as cratonic), and over warm and young areas (such as oceanic ridges). The misfit encountered comes from the mantle lid where a velocity–density relation helped to reduce the RMS error by 40%. Global residuals are also provided in terms of the gravitational gradients as they provide better spatial localization than gravity, and there is strong observational support from ESA’s satellite gradiometry mission GOCE down to the spatial resolution of 80–90 km.  相似文献