Lund, Sweden


Lund, Sweden
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Lund M.,University of Aarhus | Hansen B.U.,Copenhagen University | Pedersen S.H.,University of Aarhus | Stiegler C.,Solvegatan | Tamstorf M.P.,University of Aarhus
Tellus, Series B: Chemical and Physical Meteorology | Year: 2014

Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000-2010) record of summer-time energy balance components (net radiation, Rn; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G) from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD) during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (βH/LE) compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (Ds) was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/Rn and LE/Rn and decreasing G/Rn and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system. © 2014 M. Lund et al.

Avsar E.,Pennsylvania State University | Flensburg C.,Solvegatan | Hatta Y.,University of Tsukuba | Ollitrault J.-Y.,CEA Saclay Nuclear Research Center | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

It has been argued that high-multiplicity proton-proton collisions at the LHC may exhibit collective phenomena usually studied in the context of heavy-ion collisions, such as elliptic flow. We study this issue using DIPSY-a Monte Carlo event generator based on the QCD dipole model. We calculate the eccentricity of the transverse area defined by the spatial distribution of produced gluons. The resulting elliptic flow is estimated to be about 6%, comparable to the value in nucleus-nucleus collisions at RHIC and the LHC. Experimentally, elliptic flow is inferred from the azimuthal correlation between hadrons, which receives contributions from collective flow, and from various other effects referred to as "nonflow". We discuss how to identify in experiments the signal of flow in the presence of large nonflow effects. © 2011 Elsevier B.V.

Avsar E.,Pennsylvania State University | Hatta Y.,University of Tsukuba | Flensburg C.,Solvegatan | Ollitrault J.-Y.,CEA Saclay Nuclear Research Center | Ueda T.,Karlsruhe Institute of Technology
Journal of Physics G: Nuclear and Particle Physics | Year: 2011

High-multiplicity proton-proton collisions at the LHC may exhibit collective phenomena such as elliptic flow. We study this issue using DIPSY, a brand-new Monte Carlo event generator which features almost-NLO BFKL dynamics and describes the transverse shape of the proton including all fluctuations. We predict the eccentricity of the collision as a function of the multiplicity and estimate the magnitude of elliptic flow. We suggest that flow can be signaled by a sign change in the four-particle azimuthal correlation. © 2011 IOP Publishing Ltd.

Aubry M.-P.,Rutgers University | Rodriguez O.,Pdvsa | Bord D.,Rutgers University | Godfrey L.,Rutgers University | And 2 more authors.
Austrian Journal of Earth Sciences | Year: 2012

The Qreiya section (Upper Egypt) contains a well-preserved record of the first radiation of the fasciculiths, an evolutionary event that affected the coccolithophores of the Order Discoasterales during the late Danian. At Qreiya it unfolds across the so-called Neo-Duwi Event. We describe the morphostructural changes that affected coccoliths and document a trend towards increased surface area of the coccoliths of the Order Discoasterales. Our isotopic data do not support earlier interpretation(s) that the Neo-Duwi Event may correspond to a Paleocene hyperthermal. We interpret the first radiation of the fasciculiths as an adaptive response to increased oceanic oligotrophy through the appearance of coccoliths adapted to food collection in nutrient-poor oceanic waters.

Flensburg C.,Solvegatan
Proceedings - 38th International Symposium on Multiparticle Dynamics, ISMD 2008 | Year: 2012

A series of previous papers [1] develops a dipole model in initial state impact parameter space that includes subleading effects such as running αs, unitarity, confinement and saturation. Here some recent work [2] is presented, where the model is applied to a new set of data: vector meson production in γ*p, DVCS and dσ/dt in pp. This allows us to tune a more realistic model of the proton wavefunction from the pp data, and confirm the predictive power of the model in high Q2 of DVCS and vector meson production. For low Q2 vector meson resonances dominate the photon wavefunction, making our predictions depend on a tuned parametrisation in this range.

Late Svecofennian granite is frequent in the Bothnian Basin, especially in zones of rapidly changing metamorphic grade but also in areas, where the metamorphic grade is elevated. The granite is essentially undeformed, but weakly foliated or lineated rocks are common; more rarely are rocks strongly foliated. X-ray fluorescence was used for major-element and ICP-MS for trace-element analyses. The chemical composition is almost invariably peraluminous, calc-alkaline and strict granitic. The mean of the molecular ratio Al2O3/(CaO þ Na2O þ K2O) is 1.3 with an almost normal distribution. It straddles the boundary between S-and I-type granites (where the value 1.1 is used as the boundary). The source is made up of mixtures in any proportions of igneous and sedimentary rocks, and this boundary is not a strict boundary between source rocks. Trace-element variation is immense. Rare earth element patterns are somewhat different for I-and S-type granites, but otherwise no systematic difference depending on the I/S character has been found. The metasedimentary rocks in the source were probably enriched in Sr and show evidence of oxidation. Breakdown of biotite and, probably to some extent, muscovite delivered the necessary volatiles for melting. Volatiles were important for the evolution of the granite giving non-CHARAC effects among others tetrad effects to the low-temperature granite. Degrees of melting were moderate and probably variable but cannot be quantified. Zr-saturation temperatures vary (820 ±1488C (2s)), but are higher for I-type than for S-type granites. The lowest temperatures occur in low-grade areas probably representing high intrusion levels. © Geologiska Föreningen.

Kulma K.,Uppsala University | Low M.,Swedish University of Agricultural Sciences | Bensch S.,Solvegatan | Qvarnstrom A.,Uppsala University
Molecular Ecology | Year: 2013

Parasites may influence the outcome of interspecific competition between closely related host species through lower parasite virulence in the host with which they share the longer evolutionary history. We tested this idea by comparing the prevalence of avian malaria (Haemosporidia) lineages and their association with survival in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis) breeding in a recent contact zone on the Swedish island of Öland. A nested PCR protocol amplifying haemosporidian fragments of mtDNA was used to screen the presence of malaria lineages in 1048 blood samples collected during 6 years. Competitively inferior pied flycatchers had a higher prevalence of blood parasites, including the lineages that were shared between the two flycatcher species. Multistate mark-recapture models revealed a lower survival of infected versus uninfected female pied flycatchers, while no such effects were detected in male pied flycatchers or in collared flycatchers of either sex. Our results show that a comparatively new host, the collared flycatcher, appears to be less susceptible to a local northern European malarial lineage where the collared flycatchers have recently expanded their distribution. Pied flycatchers experience strong reproductive interference from collared flycatchers, and the additional impact of species-specific blood parasite effects adds to this competitive exclusion. These results support the idea that parasites can strongly influence the outcome of interspecific competition between closely related host species, but that the invading species need not necessarily be more susceptible to local parasites. © 2013 John Wiley & Sons Ltd.

Previous studies of mid-Ordovician limestone in Sweden have shown that over a stratigraphic interval representing a few million years there is a two orders-of-magnitude enrichment in fossil L-chondritic meteorites (Ø=1-21. cm) and sediment-dispersed extraterrestrial chromite (EC) grains (>63 μm). This has been interpreted as a dramatic increase in the flux of L-chondritic matter to Earth following the breakup of the L-chondrite parent body, which based on Ar-Ar gas retention ages (470 ± 6. Ma) of recently fallen meteorites occurred at about this time. Here we show that the general trend in the distribution of sediment-dispersed EC grains can be reproduced in the Puxi River section in central China. A total of 288. kg of limestone was searched for chrome spinels. In samples spanning the lower 8. m of the section, representing the Paroistodus originalis and Lenodus antivariabilis conodont zones, a total of 110. kg of limestone yielded only one EC grain. Similarly to the Swedish sections, EC grains begin to be common in the overlying L. variabilis Zone and remain common throughout the upper 9. m of the section, representing the L. variabilis, Yangtzeplacognathus crassus and L. pseudoplanus zones. In this part of the section 178. kg of limestone yielded 290 EC grains, with an average chemical composition very similar to chromite from recent L chondrites. In most of the beds over this interval one finds 1-4 EC grains per kilogram rock, a clear two orders-of-magnitude enrichment relative to the lower part of the section. Small bed-by-bed variations in the EC content over the upper interval most likely reflect small variations in sedimentation rates. The Puxi River section contains only very rare terrestrial chrome spinel grains, which can be distinguished already by their rounded, abraded appearance compared to the angular, pristine extraterrestrial spinels. In the mid-Ordovician, based on paleoplate reconstructions, the Puxi River site was positioned at mid-latitudes on the southern hemisphere a couple of thousand kilometers east of the Swedish sites. The prominent enrichment of EC grains over the same stratigraphic interval in China and Sweden is supporting evidence for a dramatic increase in the flux of L-chondritic matter to Earth shortly after the disruption of the L-chondrite parent body in the asteroid belt. © 2010 Elsevier Inc.

Van der Putten N.,Solvegatan | Mauquoy D.,University of Aberdeen | Verbruggen C.,Ghent University | Bjorck S.,Solvegatan
Quaternary International | Year: 2012

Subantarctic islands are located within the Antarctic Circumpolar Current and the southern westerly wind belt, the latter called Southern Westerlies, making them unique terrestrial archives to investigate past changes in oceanic and atmospheric circulation patterns in the southern mid-latitudes. The islands are characterised by a treeless, phanerogam-poor flora in which bryophytes are of major importance. Several peat-based Holocene palaeoenvironmental and palaeoclimatic studies have recently been published for South Georgia and Ile de la Possession (Iles Crozet). A range of techniques have been used in these studies, mainly plant macrofossil analysis, but also analyses of diatoms, pollen and non-pollen microfossils, geochemical and geomagnetic measurements. The records are chronologically constrained by radiocarbon dating. This paper brings together these data in order to give an overview of the Subantarctic peat-based palaeoclimatic records. A new plant macrofossil record for the island of South Georgia is added. Evidence for millennial scale Holocene climate variability was found for both islands of which the most striking one occurred in the late Holocene. However, within the uncertainty of the age/depth models, the timing for this climate shift to wetter and/or colder conditions on South Georgia and windier/wetter conditions on Ile de la Possession is different for both islands. Ile de la Possession (Iles Crozet) seems to follow the Northern Hemisphere climate evolution as the event was dated to ∼2800 cal BP, a well-known climate event present in many peat-based records in north-western Europe. In contrast, the South Georgian late Holocene climate records reveal a shift around ∼2200-2000 cal BP. © 2011 Elsevier Ltd and INQUA.

Flensburg C.,Solvegatan
AIP Conference Proceedings | Year: 2011

Diffractive excitation is usually described by the Good-Walker formalism for low masses, and by the triple-Regge formalism for high masses. In the Good-Walker formalism the cross section is determined by the fluctuations in the interaction. By taking the fluctuations in the BFKL ladder into account, it is possible to describe both low and high mass excitation in the Good-Walker formalism. In high energy pp collisions the fluctuations are strongly suppressed by saturation, which implies that pomeron exchange does not factorise between DIS and pp collisions. The Dipole Cascade Model reproduces the expected triple-Regge form for the bare pomeron, and the triple-pomeron coupling is estimated. © 2011 American Institute of Physics.

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