Origin of upper-mantle seismic scattering – evidence from Russian peaceful nuclear explosion data     

Lars Nielsen  Hans Thybo  Alan Levander  Leonid N. Solodilov 《Geophysical Journal International》2003,154(1):196-204

  相似文献   

Rapid and rhythmic ice sheet fluctuations in western Scandinavia 15-40 Kya–a review     

Lars Olsen  Harald Sveian  Klaas van der  Borg  Bjørn Bergstram  Maarten Broekmans 《Polar research》2002,21(2):235-242

The onshore record of Middle to Late Weichselian sediments and glacial history in Norway indicates a succession of four major ice advances alternating with rapid, considerable ice recessions and interstadial conditions. During all the glacial advances the ice sheet expanded from onshore/inland positions to the shelf areas. The basis for visualizing these variations in glaciation curves constructed along nine transects from inland to shelf, and for interpretation of the palaeoclimatic history, is the regional Quaternary stratigraphy, more than 300 datings, fossil content and some palaeomagnetic data. The methods applied in recent years for AMS radiocarbon dating of glacial sediments with low organic carbon content have given promising results with respect to accuracy and precision, and the results of such datings were an important tool for our reconstructions and for timing of the ice oscillations. The rapid and rhythmic ice fluctuations, as reconstructed in our new model, have been fairly synchronous in most parts of Norway. Ice advances commenced and culminated at 40, 30-28, 24-21 and 18-15 (¹⁴C) Kya. We describe three intervening interstadials from inland sites: Hattfjelldal I, Hattfjelldal II and Trofors. Our stratigraphical record also includes many indications of high, pre-Holocene, relative sea levels, suggesting a considerable glacioisostatic depression of western Scandinavia during the interstadials. In our glaciation model we suggest that, in addition to precipitation, the mountainous fjord and valley topography, glacial isostasy and relative sea level changes were probably more important for the size of the glacial fluctuations than were air temperature changes.  相似文献   

Moving Code in Spatial Data Infrastructures – Web Service Based Deployment of Geoprocessing Algorithms     

Matthias Müller  Lars Bernard  Johannes Brauner 《Transactions in GIS》2010,14(Z1):101-118

This article proposes a concept for offering complex geoprocessing functionality in service‐based Spatial Data Infrastructures (SDI). Today, geoprocessing in SDI is typically realized in a data driven manner. Applying the suggested “moving code” approach in a case study in the field of Spatial Decision Support proves its applicability. The proposed solution is analyzed and assessed in terms of gained efficiency, performance behavior and support for distributed development of geoprocessing functionality. In data and computation intensive SDI applications the deployment of moving code proves to be beneficial.  相似文献   

An evaluation of measures for quantifying map information     

Lars Harrie  Hanna Stigmar 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(3):266-274

A real-time map must not contain too much information. Therefore, we need measures of map information that could be guidelines for the selection of data layers and the real-time generalisation process. In this paper we evaluate measures of the amount of information and the distribution of information. The evaluation is performed by (1) defining measures, (2) implementing the measures, (3) computing the measures for some test maps, and finally (4) comparing the values of the measures with human judgement of the map information. For amount of information, we found that the measures number of objects, number of points and object line length had better correspondence with human judgement than object area. We also found that measures based on the size of Voronoi regions of objects (respectively points) can be used for identifying the distribution of information. The results are based on the testing of only building objects. Future work should extend the test, using all object types.  相似文献   

Spatial variability of soil water content in the covered catchment at Gårdsjön,Sweden     

Lars Nyberg 《水文研究》1996,10(1):89-103

The spatial variability of soil water content was investigated for a 6300 m² covered catchment on the Swedish west coast. The catchment podzol soil is developed in a sandy—silty till with a mean depth of 43 cm and the dominant vegetation is Norway spruce. The acid precipitation is removed by a plastic roof and replaced with lake water irrigated under the tree canopies. On two occasions, in April and May 1993, TDR measurements were made at 57–73 points in the catchment using 15 and 30 cm long vertically installed probes. The water content pattern at the two dates, which occurred during a relatively dry period, were similar. The range of water content was large, from 5 to 60%. In May 1993 measurements also were made in areas of 10 × 10 m, 1 × 1 m and 0·2 × 0·2 m. The range and standard deviation for the 10 × 10 m area, which apart from a small-scale variability in soil hydraulic properties and fine root distribution also had a heterogeneous micro- and macro-topography, was similar to the range and standard deviation for the catchment. The 1 × 1 m and 0·2 × 0·2 m areas had considerably lower variability. Semi-variogram models for the water content had a range of influence of about 20 m. If data were paired in the east-–west direction the semi-variance reflected the topography of the central valley and had a maximum for data pairs with internal distances of 20–40 m. The correlation between soil water content and topographic index, especially when averaged for the eight topographically homogeneous subareas, indicated the macro-topography as the cause of a large part of the water content variability.  相似文献   

A new look at population change and regional development in Aotearoa New Zealand     

Lars Brabyn  Natalie O. Jackson 《New Zealand geographer》2019,75(3):116-129

In New Zealand, population change is interlinked with regional development. Places growing in population attract regional investment, while regional investment—or lack thereof—can change migration patterns. However, to determine the appropriate response to population change for a community, it is important to understand that population change involves much more than “just” migration. Specifically, it involves interactions between the three components of population change: natural change (births minus deaths), net migration (international and internal) and population ageing (changing cohort size). For example, migration can be negative, but growth can be positive due to underlying natural increase or growth in cohort size. Responses need to differ, depending on these drivers. The goal of this article is to provide new insights into these interactions using data for 275 cities, towns and rural centres (hereafter “urban places”) in New Zealand for the period 1976 to 2013. The results show that natural change has been consistently positive for most urban places up to the present, although projections indicate that in the future this component will become negative across much of the country. At the same time, net migration shows considerable spatial variation, not only in terms of volume, but also direction (negative or positive), which differs markedly by age. A net gain of people of retirement age can offset a net loss of young adults to deliver overall growth, and vice‐versa, but the two have very different implications for longer term growth. An analysis of the drivers of net migration using GIS and machine learning techniques provides an indication of the importance of economic conditions (land‐use and access to markets), lifestyle, access to essential services (hospitals and education) and their interaction with age in regional change. The results show that population age is the best predictor of migration. Younger people are moving to cities for tertiary education and work and older people near or in retirement are moving to smaller lifestyle towns but also want to be close to amenities such as hospitals and international airports. The research also shows that natural lifestyle characteristics (landscape and climate), in combination with age are just as important as economic conditions for understanding migration. Regional development, such as infrastructure that helps business (ports and services) is important for the working age population but not necessarily the retirement age group. When regional development, age/life‐cycle stage and lifestyle come together, such as in Queenstown and Tauranga, net migration gain is high.  相似文献   

Phase transitions of α-quartz at elevated temperatures under dynamic compression using a membrane-driven diamond anvil cell: Clues to impact cratering?     

Eva-Regine Carl  Hanns-Peter Liermann  Lars Ehm  Andreas Danilewsky  Thomas Kenkmann 《Meteoritics & planetary science》2018,53(8):1687-1695

Coesite and stishovite are high-pressure silica polymorphs known to have been formed at several terrestrial impact structures. They have been used to assess pressure and temperature conditions that deviate from equilibrium formation conditions. Here we investigate the effects of nonhydrostatic, dynamic stresses on the formation of high-pressure polymorphs and the amorphization of α-quartz at elevated temperatures. The obtained disequilibrium states are compared with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We analyzed phase transformations starting with α-quartz in situ under dynamic loading utilizing a membrane-driven diamond anvil cell. Using synchrotron powder X-ray diffraction, the phase transitions of SiO₂ are identified up to 77.2 GPa and temperatures of 1160 K at compression rates ranging between 0.10 and 0.37 GPa s⁻¹. Coesite starts forming above 760 K in the pressure range between 2 and 11 GPa. At 1000 K, coesite starts to transform to stishovite. This phase transition is not completed at 1160 K in the same pressure range. Therefore, the temperature initiates the phase transition from α-quartz to coesite, and the transition from coesite to stishovite. Below 1000 K and during compression, α-quartz becomes amorphous and partially converts to stishovite. This phase transition occurs between 25 and 35 GPa. Above 1000 K, no amorphization of α-quartz is observed. High temperature experiments reveal the strong thermal dependence of the formation of coesite and stishovite under nonhydrostatic and disequilibrium conditions.  相似文献   

Oxidative damage in rainbow trout caged in a polluted river   总被引：1，自引：0，他引：1  

Carney Almroth B  Sturve J  Förlin L 《Marine environmental research》2008,66(1):90-91

Sewage treatment works (STWs) are a common source of chemicals entering into the aquatic environment. In order to assess effects of these effluents on oxidative stress parameters in aquatic organisms, we caged rainbow trout at five sites: upstream, near an STW effluent, and three sites downstream in the river Viskan in western Sweden for 14 days during autumn, 2006. We then measured protein carbonyls in plasma as well as 20S proteosome activity and lipid peroxidation products, i.e. MDA and 4-HNE, in liver samples. Levels of both lipid and protein oxidative damage products were elevated in fish caged near the STW effluent while 20S activity showed no differences. This argues that complex mixtures of chemicals entering into the aquatic environment do have deleterious effects on fish. Additionally, oxidative stress parameters can serve as a biomarker in aquatic organisms.  相似文献   

Seasonal changes in the distribution and exchange of inorganic nitrogen between sediment and water in the Northern Baltic (Gulf of Bothnia)     

David B. Nedwell  Sven-Eric Hall  Agneta Andersson  Åke F. Hagström  E.Börje Lindström 《Estuarine, Coastal and Shelf Science》1983,17(2):169-179

The concentration profiles of nitrate plus nitrite, ammonium, and redox potential in sediment and water column were determined in late winter and summer at a sampling site off Norrbyn, northern Sweden, in the Gulf of Bothnia. The sediment had an oxidized surface layer during winter and spring, and nitrification occurred. Nitrate but not ammonium was present in the water column at this time. During summer a layer of planktonic detritus was deposited onto the sediment and led to its deoxygenation and reduction. Ammonium was then the predominant form of inorganic nitrogen in the water column.Laboratory experiments confirmed that nitrification in the surface layer of sediment prevented ammonium export during winter. Enhanced temperature or organic detritus deoxygenated the surface sediment and inhibited nitrification, and export of ammonium from the sediment increased. Although nitrification was important in determining the flow of nitrogen in the sediment it accounted for at most only 5% of the total oxygen uptake by the sediment.  相似文献   

Black-body temperature of a closed Universe     

Lars Wåhlin 《Astrophysics and Space Science》1981,76(1):259-260

In a closed gravitationally-bound Universe we are subject to an inward accelerationa ₀. One consequence of this acceleration is that matter will radiate and create a black-body spectrum throughout the Universe. Using the valuea ₀=7.623×10^–12 ms^–2 and a radiation formula from a previously-described cosmological model (Wåhlin, 1981), we obtain a black-body temperature of 2.766 K.  相似文献