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1.
Birgitta NordstrÖm 《Astrophysics and Space Science》2003,284(2):779-782
New, precise abundance data for a large number of elements in a growing sample of extremely metal-poor stars are accumulating
from the new 8-m telescopes. Combined with theoretical models, these results advance our understanding of the first generations
of stars, whose nucleosynthesis products are fossilised in the oldest stars we see today and thus give clues to the earliest
phases of evolution in the Galaxy. In particular, the heaviest elements give us insight into the different neutron capture
mechanisms and the stellar sites where such elements could be produced. They also afford an independent way to determine the
age of the Galaxy, by radioactive chronology.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Perch (Perca fluviatilis), were sampled from unpolluted and polluted areas in Swedish coastal waters. The level of aromatic/hydrophobic DNA adducts in liver tissue was analyzed using the nucleas P1 version of the32P-post-labeling assay. The level of total adducts measured in the individual fish from polluted areas was between 6 and 22 nmol of adducts/mol of nucleotides, and in the fish from the reference area between 0.2 and 0.6 nmol of adducts/mol of nucleotides. 相似文献
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Cecilia Möller Eva Alfredsson-Olsson Birgitta Ericsson Kjell Overvåg 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(4):217-233
The purpose of the study was to analyse how cross-border commuting differed from intranational commuting in Sweden, and how cross-border mobilities affected spatial integration. The authors analysed patterns and spatial flows of cross-border commuting by comparing them with characteristics of intranational commuting. In the article, they explore the assumption that the border constitutes an ‘engine’ for work-related mobility, which affects processes of spatial integration in cross-border areas. The empirical material comprised data from surveys of commuting from the Swedish county of Värmland to Norway and commuting within Värmland. The findings showed that cross-border commuting shared common features with intranational commuting, including how the frequency of commuting was dependent on distance. The motives for commuting differed, and the reasons for working in Norway were economic rather than professional. In terms of spatial integration, cross-border commuting was mainly one-directional, from Sweden to Norway, while leisure mobility and migration tended to be in the opposite direction. The authors conclude that the border region is characterised by integration through specialisation, which involves a permanent state of ‘transient’ mobility. Thus, a win-win situation can be distinguished, in which the border serves as a resource and an ‘engine’ for cross-border integration, mobility and economic activities. 相似文献
5.
Lucas J. Stal Patrizia Albertano Birgitta Bergman Klaus von Brckel John R. Gallon Paul K. Hayes Kaarina Sivonen Anthony E. Walsby 《Continental Shelf Research》2003,23(17-19):1695
The blooms of cyanobacteria that develop each summer in the Baltic Sea are composed of two functional groups, namely the small-sized picocyanobacteria (Synechococcus sp.) and the larger, colony-forming, filamentous N2-fixing cyanobacteria. The former encompassed both red (phycoerythrin-rich) and blue-green (phycocyanin-rich) species. The majority of the picocyanobacteria measured less than 1 μm and this size fraction comprised as much as 80% of the total cyanobacterial biomass and contributed as much as 50% of the total primary production of a cyanobacterial bloom. The picocyanobacteria are incapable of fixing N2, do not possess gas vesicles and are not toxic. However, a small filamentous Pseudanabaena sp. that could potentially fix N2 was isolated from the picocyanobacteria fraction. The larger cyanobacteria may form surface scums because they possess gas vesicles that make them buoyant. Although their biomass was less than the picocyanobacteria, they therefore form the more conspicuous and nuisance-forming part of the bloom. The larger cyanobacteria were composed mainly of three different species: Nodularia spumigena, Aphanizomenon flos-aquae and Anabaena sp. These all belong to the heterocystous, N2-fixing cyanobacteria. N. spumigena and A. flos-aquae were the dominant species; only N. spumigena was toxic. Although individual Nodularia filaments showed a range of different phenotypes, they all belong to one species as judged from 16S rDNA sequencing. Through determination of the genotypes of many individual Nodularia filaments, it was shown that this population was not clonal and that horizontal exchange of genetic information occurs. N. spumigena and A. flos-aquae were different with respect to their photosynthetic and N2-fixing potentials. Depending on prevailing environmental conditions, these differences would promote the proliferation of one species over the other and hence would determine overall the toxicity of a bloom. Daily integrals of photon irradiance rather than temperature determined the onset of bloom formation. During a bloom, the diazotrophic cyanobacteria fixed N2 at a rate that was 10–20% in excess of their own demand for N. Picocyanobacteria assimilated most of this excess N as shown by 15N incorporation. During bloom conditions, the diazotrophic cyanobacteria met about 50% of the N demand of the total cyanobacterial community. The picocyanobacteria were predominantly N-limited while the diazotrophic cyanobacteria were probably iron limited. These findings allow us to understand the formation of toxic cyanobacterial blooms and also to develop tools to predict bloom formation. 相似文献
6.
Johan Holmberg Birgitta NordstrÖm Bjarne Rosenkilde Jørgensen Johannes Andersen 《Astrophysics and Space Science》2003,284(2):685-688
The evolution of the Solar neighbourhood is followed using a unique, magnitude complete and kinematically unbiased sample
of 14,000 F, G, and K dwarfs. Metallicity, age, space motion and galactic orbits have been determined for all stars. The result
is a detailed view of the complex evolution of the local Milky Way, which must be matched by any model for the chemical and
dynamical evolution of the Galactic disk. E.g., such models must explain the shape and large scatter in the age-metallity
relation as well as the overall metallicity distribution; the evolution of stellar kinematics with age; the distribution of
stars in velocity space; and the contributions from the thick and thin disks to all these relations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Linderoth M Hansson T Liewenborg B Sundberg H Noaksson E Hanson M Zebühr Y Balk L 《Marine pollution bulletin》2006,53(8-9):437-450
By measuring a battery of basic physiological biomarkers and the concentration of SigmaDDT in adult female perch (Perca fluviatilis), an assumed aquatic pollution gradient was confirmed, with the city of Stockholm (Sweden) as a point source of anthropogenic substances. The investigation included an upstream gradient, westwards through Lake M?laren (46 km), and a downstream gradient, eastwards through the Stockholm archipelago (84 km). The results indicated a severe pollution situation in central Stockholm, with poor health status of the perch: retarded growth, increased frequency of sexually immature females, low gonadosomatic index, and disturbed visceral fat metabolism. SigmaDDT, measured as a pollution indicator, was 10-28 times higher than the background in perch from the Baltic Proper. Besides the main gradient other sources of pollution also influenced the response pattern of the measured biomarkers. In particular, there were strong indications of pollution coming from the Baltic Sea. 相似文献
8.
Birgitta Hässler 《International Journal of Mineral Processing》1974,1(3):193-213
The paper deals with the reduction strength of iron-ore agglomerates, especially under the conditions in the blast furnace. As an introduction, the reduction zones, temperature zones and pressures exerted on the charge are covered.Special attention has been paid to the reasons for the often very large decrease in strength during heating and reduction. The plasticity of the wüstite is, in this case, of special interest. A number of testing methods for investigation of stresses and strains of the agglomerates during reduction are introduced. The test methods cover different procedures in the blast furnace — isothermal as well as blast furnace simulating.A method of measuring the pressure strength during reduction has been worked out which comprises testing the agglomerates at high temperature during the reduction. It was originally developed in order to study the cold-bound balls during the reducing process. With the aid of this test method the necessary conditions were established for the development of perfect agglomerates according to the COBO method.A series of results from investigations made with these tests are given both for cold-bonded COBO balls of various compositions and for commercial types of burnt pellets. 相似文献
9.
A simplified version of a model of the internalboundary layer evolution is compared with aircraftmeasurements across the southern part of the east coast ofSweden (Blekinge). The two flight occasions used hererepresent relatively high wind velocities and negligiblesurface heat flux. Both the vertical potential temperaturegradient and the surface temperaturedifference between land and sea are small. Modelpredictions of the internal boundary-layer (IBL)height agree well with data, for both short and largerdistances from the coastline. The contributions to theIBL growth from the mechanical turbulence and theZilitinkevich correction are discussed, as are thesensitivities of the growth to a number of physicalparameters. In near neutralconditions, the vertical potential temperaturegradient is found to be an important parameter for thegrowth of the IBL.A comparison with several simple model estimates forthe height of the IBL is presented. The majority ofthe models overestimate the IBL height. Some of themodels give reasonable results close to the coast, butgenerally the simple models perform less well atlarger distances. 相似文献
10.
Birgitta Källstrand Hans Bergström Jørgen Højstrup Ann-Sofi Smedman 《Boundary-Layer Meteorology》2000,95(2):161-188
For two consecutive days during spring 1997, the windfield over the Baltic Sea has been studied. Thestrength of the geostrophic wind speed is the majordifference in synoptic conditions between these twodays. During both days, the mesoscale wind field overmost of the Baltic Sea is quite heterogeneous; themodifications primarily being caused by the land-seacontrasts. On the day with the weaker wind speed,sea-breeze circulations develop. As a consequence, thewind direction at lower levels is more or lessopposite to the geostrophic over large areas of theBaltic Sea and the surface wind speed decreases withoffshore distance. Wind speed maxima caused by the seabreezes are found along the east coasts in the studiedarea. For the other day, the slow growth of a stableinternal boundary layer over the sea also gives asurface wind speed decrease with offshore distancefrom the coast. 相似文献