Robust optical tracking of individual ejecta particles in hypervelocity impact experiments          下载免费PDF全文

Max Gulde  Lukas Kortmann  Matthias Ebert  Erkai Watson  Jakob Wilk  Frank Schäfer 《Meteoritics & planetary science》2018,53(8):1696-1704

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“This venue is brought to you by…”: the diffusion of sports and entertainment facility name sponsorship in urban Europe     

Jani Vuolteenaho  Matthias Wolny  Guy Puzey 《Urban geography》2019,40(6):762-783

ABSTRACT

Drawing on a database of 193 football (soccer) grounds and 115 indoor arenas, as well as press releases and media reports associated with them, this study charts the diffusion of sporting and entertainment facility name sponsorship across metropolises, cities, towns, and smaller settlements in six European contexts. Our results show the emergence of naming rights deals in the 1990s, their peak in the mid-2000s, and the current situation with a steadier growth of name sponsorship. Thus far, the corporate re-branding of venues has remained less prevalent in Italy, Norway, and Scotland than in England and Wales, Finland, and above all Germany. In financing newly built venues, however, the corporatized landmark language in focus has become a practically invariable part of local growth, austerity and (re)branding policies. Despite voices of resistance in all regions studied here, pressure towards the corporate renaming of even hereditary, communally endorsed football stadiums is increasingly being felt by municipal and private-sector venue owners.  相似文献   

A review of the magnitude and response times for sediment yield reductions following the rehabilitation of gullied landscapes     

Rebecca Bartley  Jean Poesen  Scott Wilkinson  Matthias Vanmaercke 《地球表面变化过程与地形》2020,45(13):3250-3279

Gully erosion is a major driver of elevated sediment yields across many areas of the globe, and considerable rehabilitation has occurred to reduce the amount of sediment eroded from gullies. However, compared to other forms of erosion, there has been little systematic review of the effectiveness of gully rehabilitation on reducing sediment yields. This study reviewed the global literature to provide an understanding of the potential sediment yield reductions that can occur following the rehabilitation of gullied landscapes. We focused on studies reporting a measured response on how gully and catchment sediment yield has changed since treatment. A total of 37 studies were found that met this criterion. The studies were partitioned into three broad categories, including those focused on: (i) treating the catchment above the gully; (ii) installing treatments in the actual gully channel; and (iii) a combination of approaches which include treating both the catchment and the gully channel. All the studies demonstrated a reduction in sediment yield following gully rehabilitation, with reported values ranging between 12 and 94%. The timeframes associated with the reductions in sediment yield varied considerably (2–80 years). Applying a variety of rehabilitation measures, which generally includes treating both the hillslope above the gully, and trapping sediment within the gully, appears to result in shorter (median) timescales for sediment yield reduction. Overall, this review indicates that gully rehabilitation strategies combining both engineering and vegetation measures are often the most successful. Engineering measures such as check dams are important for stabilizing sites in the early phases to support the revegetation of gullies and adjacent hillslopes. However, vegetation is the key to the long-term success of gully rehabilitation. This is because many engineering structures eventually fail, or they have a limited life span as an active sediment trap. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Predicting gully densities at sub-continental scales: a case study for the Horn of Africa     

Matthias Vanmaercke  Yixian Chen  Nigussie Haregeweyn  Sofie De Geeter  Benjamin Campforts  Wouter Heyndrickx  Atsushi Tsunekawa  Jean Poesen 《地球表面变化过程与地形》2020,45(15):3763-3779

Despite its environmental and scientific significance, predicting gully erosion remains problematic. This is especially so in strongly contrasting and degraded regions such as the Horn of Africa. Machine learning algorithms such as random forests (RF) offer great potential to deal with the complex, often non-linear, nature of factors controlling gully erosion. Nonetheless, their applicability at regional to continental scales remains largely untested. Moreover, such algorithms require large amounts of observations for model training and testing. Collecting such data remains an important bottleneck. Here we help to address these gaps by developing and testing a methodology to simulate gully densities across Ethiopia, Eritrea and Djibouti (total area: 1.2 million km²). We propose a methodology to quickly assess the gully head density (GHD) for representative 1 km² study sites by visually scoring the presence of gullies in Google Earth and then converting these scores to realistic estimates of GHD. Based on this approach, we compiled GHD observations for 1,700 sites. We used these data to train sets of RF regression models that simulate GHD at a 1 km² resolution, based on topographic/geomorphic, land cover, soil and rainfall conditions. Our approach also accounts for uncertainties in GHD observations. Independent validations showed generally acceptable simulations of regional GHD patterns. We further show that: (i) model performance strongly depends on the amount of training data used, (ii) large prediction errors mainly occur in areas where also the predicted uncertainty is large and (iii) collecting additional training data for these areas results in more drastic model performance improvements. Analyses of the feature importance of predictor variables further showed that patterns of GHD across the Horn of Africa strongly depend on NDVI and annual rainfall, but also on normalized steepness index (k_sn) and distance to rivers. Overall, our work opens promising perspectives to assess gully densities at continental scales. © 2020 John Wiley & Sons, Ltd.  相似文献   

The effect of sewage plant effluent on brown trout (Salmo trutta fario): a cage experiment     

Matthias Escher  Thomas Wahli  Sabina Büttner  Willy Meier  Patricia Burkhardt-Holm 《Aquatic Sciences - Research Across Boundaries》1999,61(2):93-110

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The IWC and the decimation of whale stocks     

Matthias Tomczak 《Marine Policy》1980,4(1):79-82

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Interrelations between geostatistics and information theory and their practical use     

Gerald J. Peschel  Matthias Mokosch 《Mathematical Geology》1991,23(1):3-7

Well-defined analytical interrelations exist between the geostatistical estimation variance performing an expression of degree of geological exploration and the task-oriented entropy as a concept of information theory. The example of normal distribution shows that this relationship can be expressed in mathematical terms. An extensive practical use could consist in the improvement of exploration optimization on the common basis of continuous geological parameters as is demonstrated by means of an example.  相似文献   

Effects of hyperons on the vibrations of neutron stars     

William D. Langer  A. G. W. Cameron 《Astrophysics and Space Science》1969,5(2):213-253

We calculate the effects of hyperons and resonance particles on the vibrations of neutron stars. Vibrating neutron stars can store large amounts of energy in their vibrations; the interaction of the vibrations with the atmosphere would produce electromagnetic radiation. If any process damps out the vibrations rapidly on an astronomical time scale ( 1000 years) then vibrating neutron stars are not likely to be found. Previous work indicates that radiation by a neutrino URCA process (N+NP+N+e ^–+ ) does not rapidly damp many of the neutron star models. Some neutron stars are predicted to contain massive baryons; here we study thermal damping by nonequilibrium reactions involving these baryons.During vibrations the thermodynamic equilibrium state is changed and particle reactions attempt to restore equilibrium. If the reaction rates per particle are very rapid or slow compared to the frequency of vibration the system follows almost the same pressure-volume curve through both parts of the gas cycle, and very little work is done. In the intermediate case, when reaction rates are comparable to the frequency, damping is rapid.We find that the reaction rates for weak interactions such asN+NP+^– (the ^– is the first hyperon to appear with increasing density in degenerate neutron star matter) are of the right magnitude to cause rapid damping. If there is a hyperon region in the star then it cannot sustain vibrations. We also consider the much faster (and hence less important) processN+NP+^–.  相似文献   

Algen als Faziesindikatoren: Bioherme und Biostrome im Unter-Kambrium von SW-Sardinien     

Dr. Matthias Selg 《International Journal of Earth Sciences》1986,75(3):693-702

Archaeocythan limestones of the Lower Cambrian Nebida Fm. (SW-Sardinia) form bioherms (lower Nebida Fm. = Matoppa Mbr.) as well as biostromes (upper Nebida Fm. = Punta Manna Mbr.). In both cases algae are the main rock forming organisms; they act as sediment binding and sediment baffling organisms and thus are responsible for the growth of these carbonates.Both bioherms and biostromes derive from a low energy environment of shallow water depth. While the bioherms developed in an open marine setting, the biostromes belong to a restricted lagoonal area. Apparently, this is the reason for the growth of different algae:Renalcis andEpiphyton in the bioherms,Girvanella in the lagoonal biostromes. Moreover, facies analysis and occurence of archaeocyathans show that these organisms could flourish well above the water depth of 20–50 m mentioned byHill (1972).

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Zusammenfassung Archaeocyathen führende Kalke der unterkambrischen Nebida Fm. (SW-Sardinien) treten sowohl als Bioherme (tiefere Nebida Fm. = Matoppa Mbr.) auf, als auch in Form von Biostromen (höhere Nebida Fm. = Punta Manna Mbr.). Als Hauptgesteinsbildner treten in beiden Fällen Algen auf, die als Sediment bindende und Sediment fangende Organismen für die Entstehung dieser Karonate verantwortlich sind. Sowohl Bioherme wie auch Biostrome entstammen Bereichen geringer Wassertiefe und nur mä\iger Wasserbewegung. Während aber die Bioherme wohl in einem offen-marinen Bereich entstanden sind, lassen sich die Biostrome einem geschützten Lagunenbereich zuordnen. Hierin scheint der Grund für das Auftreten unterschiedlicher Algen zu liegen:Renalcis undEpiphyton in den Biohermen,Girvanella in den lagunären Biostromen. Faziesanalyse und Auftreten von Archaeocyathen legen ferner nahe, da\ diese auch oberhalb der vonHill (1972) als bevorzugt angegebenen Tiefe von 20–50 m recht gut existieren konnten.

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Résumé Les calcaires à Archéocyathes de la formation du Nedida au Cambrien inférieur (Sardaigne du Sud-Ouest) forment non seulement des bioherms (formation du Nebida inférieure = membre de Matoppa) mais encore des biostromes (formation du Nebida supérieure = membre de Punta Manna). On considère que les algues sont les organismes responsables de l'édification de ces calcaires, tant comme »cimenteurs« que comme capteurs des sédiments. Non seulement les biostromes, mais encores les-faible profondeur. Tandis que les bioherms se formaient dans un milieu marin ouvert, on peut attribuer les biostromes à un milieu confiné. Ceci semle Être la raison de la présence d'algues différentes:Renalcis etEpiphyton dans les bioherms,Girvanella dans les biostromes lagunaires. L'analyse du facies et la présence des Archéocythes indiquent que ceux-ci peuvent aussi exister au-dessus de la profondeur de 20 à 50 m proposée parHill (1972).

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Hydrothermal recrystallization and transformation of tridymite     

O. W. Flörke  K. Langer 《Contributions to Mineralogy and Petrology》1972,36(3):221-230

Well ordered tridymites containing atmost 0.016% Na (0.004% Na) were prepared at 1400° C from Na₂WO₄-(K₂WO₄-) fluxes using high purity amorphous silica as starting material. No further reduction of these Na-contents was attainable by soxhlet extraction. These tridymites were treated hydrothermally at temperatures between 815 and 950° C and 200 bars H₂O. The products obtained were investigated optically as well as by powder X-ray methods and were analyzed for Na-contents: the hydrothermal treatment resulted either in recrystallization of tridymite or transformation into quartz mostly depending on Na-contents. Na-contents below about 0.015% tend to favour recrystallization of tridymite within the quartz field (<870° C), Na-contents above about 0.03% tend to favour formation of quartz within the tridymite field (>870° C). This may be due to influences of Na-traces either on the kinetics or on the equilibrium temperature of tridymite-quartz transformation.  相似文献