| 1. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Aas, Wenche, et al.
(författare)
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Trends in Air Pollution in Europe, 2000–2019
- 2024
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Ingår i: Aerosol and Air Quality Research. - 2071-1409 .- 1680-8584. ; 24:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper encompasses an assessment of air pollution trends in rural environments in Europe over the 2000–2019 period, benefiting from extensive long-term observational data from the EMEP monitoring network and EMEP MSC-W model computations. The trends in pollutant concentrations align with the decreasing emission patterns observed throughout Europe. Annual average concentrations of sulfur dioxide, particulate sulfate, and sulfur wet deposition have shown consistent declines of 3–4% annually since 2000. Similarly, oxidized nitrogen species have markedly decreased across Europe, with an annual reduction of 1.5–2% in nitrogen dioxide concentrations, total nitrate in the air, and oxidized nitrogen deposition. Notably, emission reductions and model predictions appear to slightly surpass the observed declines in sulfur and oxidized nitrogen, indicating a potential overestimation of reported emission reductions. Ammonia emissions have decreased less compared to other pollutants since 2000. Significant reductions in particulate ammonium have however, been achieved due to the impact of reductions in SOx and NOx emissions. For ground level ozone, both the observed and modelled peak levels in summer show declining trends, although the observed decline is smaller than modelled. There have been substantial annual reductions of 1.8% and 2.4% in the concentrations of PM10 and PM2.5, respectively. Elemental carbon has seen a reduction of approximately 4.5% per year since 2000. A similar reduction for organic carbon is only seen in winter when primary anthropogenic sources dominate. The observed improvements in European air quality emphasize the importance of comprehensive legislations to mitigate emissions.
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| 3. |
- Alling, Vanja, 1978-
(författare)
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Terrestrial organic carbon dynamics in Arctic coastal areas : budgets and multiple stable isotope approaches
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Arctic rivers transport 31-42 Tg organic carbon (OC) each year to the Arctic Ocean, which is equal to 10% of the global riverine OC discharge. Since the Arctic Ocean only holds approximately 1% of the global ocean volume, the influence of terrestrially derived organic carbon (OCter) in the Arctic Ocean is relatively high. Despite the global importance of this region the behavior of the, by far largest fraction of the OCter, the dissolved organic carbon (DOC) in Arctic and sub-arctic estuaries is still a matter of debate. This thesis describes data originating from field cruises in Arctic and sub-arctic estuaries and coastal areas with the aim to improve the understanding of the fate of OCter in these areas, with specific focus on DOC. All presented studies indicate that DOCter and terrestrially derived particulate organic carbon (POCter) are subjected to substantial degradation in high-latitude estuaries, as shown by the non-conservative behavior of DOC in the East Siberian Arctic Shelf Seas (ESAS) (paper I) and the even more rapid degradation of POC in the same region (paper II). The removals of OCter in Arctic shelf seas were further supported by multiple isotope studies (paper III and IV), which showed that a use of 13C/12C in both OC and DIC, together with 34S/32S is a powerful tool to describe the sources and fate of OCter in estuaries and coastal seas. High-latitude estuaries play a key role in the coupling between terrestrial and marine carbon pools. In contrast to the general perception, this thesis shows that they are not only transportation areas for DOCter from rivers to the ocean, but are also active sites for transformation, degradation and sedimentation of DOCter, as well as for POCter. In a rapidly changing climate, the importance of these areas for the coupling between inorganic and organic carbon pools cannot be underestimated.
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| 4. |
- Bittersohl, Bernd, et al.
(författare)
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Advanced Imaging in Femoroacetabular Impingement: Current State and Future Prospects.
- 2015
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Ingår i: Frontiers in surgery. - : Frontiers Media SA. - 2296-875X. ; 2, s. 34-34
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Forskningsöversikt (refereegranskat)abstract
- Symptomatic femoroacetabular impingement (FAI) is now a known precursor of early osteoarthritis (OA) of the hip. In terms of clinical intervention, the decision between joint preservation and joint replacement hinges on the severity of articular cartilage degeneration. The exact threshold during the course of disease progression when the cartilage damage is irreparable remains elusive. The intention behind radiographic imaging is to accurately identify the morphology of osseous structural abnormalities and to accurately characterize the chondrolabral damage as much as possible. However, both plain radiographs and computed tomography (CT) are insensitive for articular cartilage anatomy and pathology. Advanced magnetic resonance imaging (MRI) techniques include magnetic resonance arthrography and biochemically sensitive techniques of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T1rho (T1ρ), T2/T2* mapping, and several others. The diagnostic performance of these techniques to evaluate cartilage degeneration could improve the ability to predict an individual patient-specific outcome with non-surgical and surgical care. This review discusses the facts and current applications of biochemical MRI for hip joint cartilage assessment covering the roles of dGEMRIC, T2/T2*, and T1ρ mapping. The basics of each technique and their specific role in FAI assessment are outlined. Current limitations and potential pitfalls as well as future directions of biochemical imaging are also outlined.
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| 5. |
- Budimir, Sanja, et al.
(författare)
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Reasons for Discontinuing Active Participation on the Internet Forum Tinnitus Talk : Mixed Methods Citizen Science Study
- 2021
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Ingår i: JMIR Formative Research. - : JMIR Publications. - 2561-326X. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Tinnitus Talk is a nonprofit online self-help forum. Asking inactive users about their reasons for discontinued usage of health-related online platforms such as Tinnitus Talk is important for quality assurance. Objective: The aim of this study was to explore reasons for discontinued use of Tinnitus Talk, and their associations to the perceptions of Tinnitus Talk and the age of users who ceased logging on to the platform. Methods: Initially, 13,745 users that did not use Tinnitus Talk within the previous 2 months were contacted and the response rate was 20.47% (n=2814). After dataset filtering, a total of 2172 past members of Tinnitus Talk were included in the analyses. Nine predefined reasons for discontinued usage of Tinnitus Talk were included in the survey as well as one open question. Moreover, there were 14 predefined questions focusing on perception of Tinnitus Talk (usefulness, content, community, and quality of members' posts). Mixed methods analyses were performed. Frequencies and correlation coefficients were calculated for quantitative data, and grounded theory methodology was utilized for exploration of the qualitative data. Results: Quantitative analysis revealed reasons for discontinued use of Tinnitus Talk as well as associations of these reasons with perceptions of Tinnitus Talk and age. Among the eight predefined reasons for discontinued use of Tinnitus Talk, the most frequently reported was not finding the information they were looking for (451/2695, 16.7%). Overall, the highest rated perception of Tinnitus Talk was content-related ease of understanding (mean 3.9, SD 0.64). A high number (nearly 40%) of participants provided additional free text explaining why they discontinued use. Qualitative analyses identified a total of 1654 specific reasons, more than 93% of which (n=1544) could be inductively coded. The coding system consisted of 33 thematically labeled codes clustered into 10 categories. The most frequent additional reason for discontinuing use was thinking that there is no cure or help for tinnitus symptoms (375/1544, 24.3%). Significant correlations (P<.001) were observed between reasons for discontinued usage and perception of Tinnitus Talk. Several reasons for discontinued usage were associated with the examined dimensions of perception of Tinnitus Talk (usefulness, content, community, as well as quality of members' posts). Moreover, significant correlations (P<.001) between age and reasons for discontinued use were found. Older age was associated with no longer using Tinnitus Talk because of not finding what they were looking for. In addition, older participants had a generally less positive perception of Tinnitus Talk than younger participants (P<.001). Conclusions: This study contributes to understanding the reasons for discontinued usage of online self-help platforms, which are typically only reported according to the dropout rates. Furthermore, specific groups of users who did not benefit from Tinnitus Talk were identified, and several practical implications for improvement of the structure, content, and goals of Tinnitus Talk were suggested.
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| 6. |
- Dorigo, Wouter, et al.
(författare)
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The International Soil Moisture Network : Serving Earth system science for over a decade
- 2021
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 25:11, s. 5749-5804
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Forskningsöversikt (refereegranskat)abstract
- In 2009, the International Soil Moisture Network (ISMN) was initiated as a community effort, funded by the European Space Agency, to serve as a centralised data hosting facility for globally available in situ soil moisture measurements . The ISMN brings together in situ soil moisture measurements collected and freely shared by a multitude of organisations, harmonises them in terms of units and sampling rates, applies advanced quality control, and stores them in a database. Users can freely retrieve the data from this database through an online web portal (https://ismn.earth/en/, last access: 28 October 2021). Meanwhile, the ISMN has evolved into the primary in situ soil moisture reference database worldwide, as evidenced by more than 3000 active users and over 1000 scientific publications referencing the data sets provided by the network. As of July 2021, the ISMN now contains the data of 71 networks and 2842 stations located all over the globe, with a time period spanning from 1952 to the present. The number of networks and stations covered by the ISMN is still growing, and approximately 70 % of the data sets contained in the database continue to be updated on a regular or irregular basis. The main scope of this paper is to inform readers about the evolution of the ISMN over the past decade, including a description of network and data set updates and quality control procedures. A comprehensive review of the existing literature making use of ISMN data is also provided in order to identify current limitations in functionality and data usage and to shape priorities for the next decade of operations of this unique community-based data repository.
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| 7. |
- Holst, Christoph, et al.
(författare)
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Investigating the gravitational stability of a radio telescope’s reference point using a terrestrial laser scanner: Case study at the Onsala Space Observatory 20-m radio telescope
- 2019
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Ingår i: ISPRS Journal of Photogrammetry and Remote Sensing. - : Elsevier BV. - 0924-2716. ; 149, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- In geodetic very long baseline interferometry, pairs of radio telescopes simultaneously observe signals from quasi stellar objects to estimate the baseline between their reference points. Gravity-dependent variations of the radio telescopes’ reference points deteriorate the estimated baseline's accuracy since they lead to signal path variations in the radio telescopes. This study investigates a new concept for determining the stability of a radio telescope's reference point. Differing to previously used strategies, this concept is able to reveal instabilities due to an elevation-dependent tumbling of the telescope independent from the part of the axis offset that is constant for all elevation angles. The new concept is exclusively based on terrestrial laser scanning that at the same time is used for analyzing the main reflector's shape deformation. We applied this concept to the Onsala Space Observatory (OSO) 20-m radio telescope: The results show that we cannot disprove the reference point's stability. In general, our new strategy can be transferred to also investigate the stability of other radio telescopes’ reference points. A prerequisite for this strategy is that the laser scanner – that moves between the elevation angles – observes identical objects from different stations. These objects need to be stable during all measurements. In the case of the OSO 20-m radio telescope, the radome is used for this purpose.
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| 8. |
- Holst, Christoph, et al.
(författare)
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Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope’s Main Reflector in a Bundle Adjustment
- 2017
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 17:1833, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 by the authors. Licensee MDPI, Basel, Switzerland. For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes’ main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85° to 5° elevation angle. Further local deformations of the main r eflector are not detected.
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| 9. |
- Kaufmann, Thomas, et al.
(författare)
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Meshless eigenvalue analysis for resonant structures based on the radial point interpolation method
- 2009
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Ingår i: Microwave conference. - : IEEE. - 9781424428021 - 9781424428014 ; , s. 818-821
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Konferensbidrag (refereegranskat)abstract
- Meshless methods are a promising field of numerical methods recently introduced to computational electromagnetics. The potential of conformal and multi-scale modeling and the possibility of dynamic grid refinements are very attractive features that appear more naturally in meshless methods than in classical methods. The radial point interpolation method (RPIM) uses radial basis functions for the approximation of spatial derivatives. In this publication an eigenvalue solver is introduced for RPIM in electromagnetics. Eigenmodes are calculated on the example of a cylindrical resonant cavity. It is demonstrated that the computed resonance frequencies converge to the analytical values for increasingly fine spatial discretization. The computation of eigenmodes is an important tool to support research on a time-domain implementation of RPIM. It allows a characterization of the method's accuracy and to investigate stability issues caused by the possible occurrence of non-physical solutions
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| 10. |
- Lindström, Björn, et al.
(författare)
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Dynamics of the interaction of dust particles with the LHC beam
- 2020
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Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 23:12
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Tidskriftsartikel (refereegranskat)abstract
- Micrometer-sized dust particles present in the Large Hadron Collider (LHC) beam pipe are believed to have caused many thousands of sporadic beam loss events around the LHC. These so-called unidentified falling objects (UFOs) have been under continuous study since the start of high intensity beam operation in the LHC due to their impact on the LHC availability: 139 beam dumps and 12 magnet quenches during Run II (2015–2018) alone. To mitigate the impact of UFOs on future accelerators such as the High Luminosity LHC and the Future Circular Collider, it is fundamental to foster a better understanding of these beam loss events. In this paper, key observations made since the start of LHC operation are summarized and the prevailing UFO hypothesis is confronted by a compilation of observations acquired during Run II. In particular, it is shown that UFOs must carry an initial negative charge before entering the proton beam, or that they are by some other means accelerated toward the beam not only by gravity. A simulation model for the dynamics of the dust particles and their interaction with the beam was developed over the years. This model is improved and validated by measurements. It is however also shown that a subset of observed beam losses, which contain a positive time profile skewness, cannot be explained by it.
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