Thermospheric/mesospheric temperatures on Venus: Results from ground-based high-resolution spectroscopy of CO2 in 1990/1991 and comparison to results from 2009 and between other techniques     

Guido Sonnabend  Peter Krötz  Frank Schmülling  Theodor Kostiuk  Jeff Goldstein  Manuela Sornig  Dušan Stupar  Timothy Livengood  Tilak Hewagama  Kelly Fast  Arnaud Mahieux 《Icarus》2012,217(2):856-862

We report temperatures in Venus’ upper mesosphere/lower thermosphere, deduced from reanalyzing very high resolution infrared spectroscopy of CO₂ emission lines acquired in 1990 and 1991. Kinetic temperatures at ～110 km altitude (0.15 Pa) are derived from the Doppler width of fully-resolved single line profiles measured near 10.4 μm wavelength using the NASA GSFC Infrared Heterodyne Spectrometer (IRHS) at the NASA IRTF on Mauna Kea, HI, close to Venus inferior conjunction and two Venus solstices. Measured temperatures range from ～200 to 240 K with uncertainty typically less than 10 K. Temperatures retrieved from similar measurement in 2009 using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) at the NOAO McMath Telescope at Kitt Peak, AZ are 10–20 K lower. Temperatures retrieved more recently from the SOIR instrument on Venus EXpress are consistent with these results when the geometry of observation is accounted for. It is difficult to compare ground-based sub-mm retrievals extrapolated to 110 km due to their much larger field of view, which includes the night side regions not accessible to infrared heterodyne observations. Temperature variability appears to be high on day-to-day as well as longer timescales. Observed short term and long term variability may be attributed to atmospheric dynamics, diurnal variability and changes over solar activity and seasons. The Venus International Reference Atmosphere (VIRA) model predicts cooler temperatures at the sampled altitudes in the lower thermosphere/upper mesosphere and is not consistent with these measurements.  相似文献   

Strength enhancement in particulate solids under high loading rates     

Dipankar Chandra  Theodor Krauthammer 《地震工程与结构动力学》1995,24(12):1609-1622

The so-called ‘strain-rate effect’ in any material has been investigated here from a structural dynamics point of view. Starting with lumped-mass models (SDOF and 2-DOF) and assuming a rate-independent failure criterion, it is shown here how a high loading rate produces an effect of strength enhancement in any massive elastic material and how failure takes place in a stronger component of a system as the loading rate increases. Extrapolating the concept of an equivalent elastic modulus as introduced in lumped-mass models and extending the analysis to a semi-infinite elastic continuum, an algorithm has been schematized to evaluate an overall equivalent elastic modulus of a concrete body under the influence of high loading rate treating the concrete as a two-component solid mixture consisting of cement paste matrix and aggregates.  相似文献   

Temporal and Spatial Variabilities of Chemical and Physical Parameters on the Heron Island Coral Reef Platform     

Kekuewa  Samuel A. H.  Courtney  Travis A.  Cyronak  Tyler  Kindeberg  Theodor  Eyre  Bradley D.  Stoltenberg  Laura  Andersson  Andreas J. 《Aquatic Geochemistry》2021,27(4):241-268

Globally, coral reefs are threatened by ocean warming and acidification. The degree to which acidification will impact reefs is dependent on the local hydrodynamics, benthic community composition, and biogeochemical processes, all of which vary on different temporal and spatial scales. Characterizing the natural spatiotemporal variability of seawater carbonate chemistry across different reefs is critical for elucidating future impacts on coral reefs. To date, most studies have focused on select habitats, whereas fewer studies have focused on reef scale variability. Here, we investigate the temporal and spatial seawater physicochemical variability across the entire Heron Island coral reef platform, Great Barrier Reef, Australia, for a limited duration of six days. Autonomous sensor measurements at three sites across the platform were complemented by reef-wide boat surveys and discrete sampling of seawater carbonate chemistry during the morning and evening. Variability in both temporal and spatial physicochemical properties were predominantly driven by solar irradiance (and its effect on biological activity) and the semidiurnal tidal cycles but were influenced by the local geomorphology resulting in isolation of the platform during low tide and rapid flooding during rising tides. As a result, seawater from previous tidal cycles was sometimes trapped in different parts of the reef leading to unexpected biogeochemical trends in space and time. This study illustrates the differences and limitations of data obtained from high-frequency measurements in a few locations compared to low-frequency measurements at high spatial resolution and coverage, showing the need for a combined approach to develop predictive capability of seawater physicochemical properties on coral reefs.

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Stand und Aufgaben einer Grundkarte der ozeanischen Lotungen im Maßstab 1∶5 Millionen     

Theodor Stocks 《International Journal of Earth Sciences》1939,30(3):373-381

Ohne Zusammenfassung  相似文献   

Intracontinental wedging and post-orogenic collapse in the mesohellenic trough     

T. Doutsos  J. Koukouvelas  A. Zelilidas  N. Kontopoulos 《International Journal of Earth Sciences》1994,83(2):257-275

The Mesohellenic Trough is a 130 km long and about 30 km wide subsiding area which contains a thick sequence of well exposed Late Cenozoic post-orogenic sediments. This intermontane basin, located at the contact between the Apulian and Pelagonian collided margins, provides a good example of the characteristics needed to study the chronology of late orogenic intracontinental structures.The Mesohellenic Trough was developed from the Middle Eocene to Middle Miocene as a piggy-back basin along the eastern flanks of a giant pop-up structure. This structure consists of west-verging, foreland-propagating thrusts within the Apulian plate and of east-verging backthrusts within the Pelagonian plate. As a result the eastern parts of the Apulian margin were thickened and uplifted, followed by post-orogenic collapse.Internal deformation of the sedimentary infill varies widely along the trough axis. At the northern and southern terminations of the trough, two small indentors induced a tectonic escape towards the central part of the basin until the Middle Miocene. During this process of convergent wrenching, reverse strike-slip faults and pure strike-slip faults formed. Towards the central part of the trough, convergent wrenching decreased gradually until it was replaced by a post-orogenic collapse with normal and oblique normal faults trending parallel and/or perpendicular to the trough axis.  相似文献   

II. Geophysik Die geophysikalische Erforschung Nordwestdeutschlands im Zeitraum 1932–1947, ein Überblick     

H. Reich  G. A. Schulze  Theodor Krey  Hans Closs  Bernt Paul 《International Journal of Earth Sciences》1948,35(2):171-172

Ohne Zusammenfassung  相似文献   

Thermal bifurcation in the upper photosphere inferred from heterodyne spectroscopy of OH rotational lines     

Drake Deming  John J. Hillman  Theodor Kostiuk  Michael J. Mumma  David M. Zipoy 《Solar physics》1984,94(1):57-74

We have obtained low noise (S/N > 10³), high spectral resolution (/ 10 ⁶) observations of two pure rotation transitions of OH from the solar photosphere. The observations were obtained using the technique of optically null-balanced infrared heterodyne spectroscopy, and consist of center-to-limb line profiles of a = 1 and a = 0 transition near 12 m. These lines should be formed in local thermodynamic equilibrium (LTE), and are diagnostics of the thermal structure of the upper photosphere. We find that the = 0R22(24.5)e line strengthens at the solar limb, in contradiction to the predictions of current one-dimensional photospheric models. Our data for this line support a two-dimensional model in which horizontal thermal fluctuations of order ±800 K occur in the region ₅₀₀₀ 10^–3–10^–2. This thermal bifurcation may be maintained by the presence of magnetic flux tubes, and may be related to the solar limb extensions observed in the 30–200 m region.Observations of the = 1R11(29.5)f line, at 885.643 cm^–1, show that it is anomalously weak in the photospheric spectrum. We argue that the source function in the core of this line has been substantially increased by interaction with the 9j-7i transition of Mgi at 885.524 cm^–1, which is itself too weak to appear in the disk center spectrum.Visiting Astronomer, Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.  相似文献   

Relativistic Rotational Darkening of Lightlike Radiation and Von Zeipel's Theorem for Radially Emitting Spheroids     

Andreas de Vries  Theodor Schmidt-Kaler 《Astrophysics and Space Science》1999,266(3):371-378

It is shown that an outgoing null radiation field in the outer space of a Kerr-Newman black hole is darkened by the rotation of the black hole. This rotational darkening is calculated for a spheroid emitting null radiation normally to its surface, yielding the von Zeipel-like effectthat the equatorial region is darkened more strongly than the polar regions.This effect is not confined to the case of black holes but is also observable for relativistically rotating fluid spheroids such as atmospheres of pulsars or neutron stars. Moreover, application to Hawking radiation suggests that the black hole cannot be viewed as a classical black body but that the Hawking radiationis a global geometric effect. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

An exhumation model of the south Peloponnesus, Greece   总被引：1，自引：0，他引：1  

T. Doutsos  I. Koukouvelas  G. Poulimenos  S. Kokkalas  P. Xypolias  K. Skourlis 《International Journal of Earth Sciences》2000,89(2):350-365

An exhumation model comprising forward and backward thrusting and late orogenic collapse is proposed in order to explain the kinematics of the tectonic windows in the south Peloponnesus. The model is based on mapping, mesoscopic structural data and strain analysis. Syn-compressional thickening took place throughout the Oligocene and Early Miocene which includes the subduction of the Pindos Ocean at the western margin of the Pelagonian microcontinent and the intracontinental subduction of the Phyllite–Quartzite and the Plattenkalk series. The latter subduction was associated with blueschist metamorphism, westward-directed ductile thrusting, and folding. The exhumation history of the deeper parts of the orogen began at the Oligocene–Miocene boundary with the progressive entrance of the low-density crust and the Plattenkalk carbonates in the subduction zone. Increased buoyancy caused: (a) the initiation of the Phyllite–Quartzite series extrusion; (b) vertical coaxial stretching; and (c) the evolution of two pop-up structures, i.e. the Parnon and Taygetos anticlines. This syn-compressional exhumation was taking place in the lower Miocene with decreasing rates from 7 to 1.5 mm/year. The change in the local stress field from compression to extension began in the middle Miocene with the formation of hinterland-dipping normal faults. The exhumation/denudation rate caused by the footwall uplift along these faults does not exceed 0.2 mm/year. Received: 16 April 1999 / Accepted: 19 January 2000  相似文献   

Using the SDIlight Approach in Teaching a Geoinformatics Master     

Barend Köbben  Rolf De By  Theodor Foerster  Otto Huisman  Rob Lemmens  Javier Morales 《Transactions in GIS》2010,14(Z1):25-37

ITC, the Faculty of Geo–Information Science and Earth Observation of the University of Twente, is an institute that aims at capacity building and institutional development, specifically in developing countries. In our Geoinformatics curriculum, we emphasise two principles. The first addresses the systematics of purposeful spatial data production and uptake into computerised systems; the second addresses the methodical construction of these computerised systems, applying principles of model – driven architecture, formal specification and transformational design of SDI nodes. The term Spatial Data Infrastructure (SDI) usually denotes large, complex systems, but its principles can also be applied in simple and cost–effective ways. This approach we have called SDI^light and it is of particular interest to our students that come from developing countries. We work with and build a software stack consisting of free and open source components. To achieve interoperability, we emphasise the use of open standards from the Open Geospatial Consortium and others. In this paper, we explain how our students apply the SDI^light approach in the GeoinformaticsMaster degree course. An important part of that course is a Case Study Application Building & Programming, in which students apply their knowledge in a ‘real–world’ project, with a focus on geo–information engineering skills. We conclude with a section that evaluates the effectiveness of using the SDI^light concept in teaching our Geoinformatics Master, and on the more general applicability of the methodology.  相似文献