118 results on '"Per Bergström"'
Search Results
2. Investigating survival, quality of life and cognition in PROton versus photon therapy for IDH-mutated diffuse grade 2 and 3 GLIOmas (PRO-GLIO): a randomised controlled trial in Norway and Sweden
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Inge C Olsen, Thomas Henry, Corina Silvia Rueegg, Asgeir S Jakola, Hanne Blakstad, Petter Brandal, Liv Cathrine Heggebø, Ida Maria Henriksen Borgen, Hillevi Rylander, Cecilie Kiserud, Tonje Haug Nordenmark, Taran Paulsen Hellebust, Morten Egeberg Evensen, Magnus Gustavsson, Christina Ramberg, Mette Sprauten, Henriette Magelssen, Janani Moorthy, Karin Andersson, Ingela Raunert, Cecilie Moe, Carin Granlund, Dorota Goplen, Jorunn Brekke, Tor-Christian Aase Johannessen, Tora Skeidsvoll Solheim, Kirsten Marienhagen, Øyvind Humberset, Per Bergström, Måns Agrup, Ludvig Dahl, Michael Gubanski, Helene Gojon, Carl-Johan Brahme, Isabelle Rydén, Einar O Vik-Mo, Hanne C. Lie, Lars Asphaug, Maziar Hervani, Ingrid Kristensen, Rolf J Ledal, Eskil Degsell, Katja Werlenius, and Malin Blomstrand
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Medicine - Abstract
Introduction The use of proton therapy increases globally despite a lack of randomised controlled trials demonstrating its efficacy and safety. Proton therapy enables sparing of non-neoplastic tissue from radiation. This is principally beneficial and holds promise of reduced long-term side effects. However, the sparing of seemingly non-cancerous tissue is not necessarily positive for isocitrate dehydrogenase (IDH)-mutated diffuse gliomas grade 2–3, which have a diffuse growth pattern. With their relatively good prognosis, yet incurable nature, therapy needs to be delicately balanced to achieve a maximal survival benefit combined with an optimised quality of life.Methods and analysis PRO-GLIO (PROton versus photon therapy in IDH-mutated diffuse grade 2 and 3 GLIOmas) is an open-label, multicentre, randomised phase III non-inferiority study. 224 patients aged 18–65 years with IDH-mutated diffuse gliomas grade 2–3 from Norway and Sweden will be randomised 1:1 to radiotherapy delivered with protons (experimental arm) or photons (standard arm). First intervention-free survival at 2 years is the primary endpoint. Key secondary endpoints are fatigue and cognitive impairment, both at 2 years. Additional secondary outcomes include several survival measures, health-related quality of life parameters and health economy endpoints.Ethics and dissemination To implement proton therapy as part of standard of care for patients with IDH-mutated diffuse gliomas grade 2–3, it should be deemed safe. With its randomised controlled design testing proton versus photon therapy, PRO-GLIO will provide important information for this patient population concerning safety, cognition, fatigue and other quality of life parameters. As proton therapy is considerably more costly than its photon counterpart, cost-effectiveness will also be evaluated. PRO-GLIO is approved by ethical committees in Norway (Regional Committee for Medical & Health Research Ethics) and Sweden (The Swedish Ethical Review Authority) and patient inclusion has commenced. Trial results will be published in international peer-reviewed journals, relevant conferences, national and international meetings and expert forums.Trial registration number ClinicalTrials.gov Registry (NCT05190172).
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- 2023
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3. Estimating and scaling-up biomass and abundance of epi- and infaunal bivalves in a Swedish archipelago region: Implications for ecological functions and ecosystem services
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Youk Greeve, Per Bergström, Åsa Strand, and Mats Lindegarth
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survey ,biodiversity ,infauna ,epifauna ,invasive species ,mussels ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
IntroductionAs suspension-feeders, bivalves play a key role in maintaining regulatory functions of coastal ecosystems, which are linked to important ecosystem services. The functions attributed to bivalves depend on the life habits of a species (epi- or infauna) and their abundance and biomass. To properly quantify and assess these functions, detailed information the distribution, abundance and biomass at the ecosystem scale is critical. Amongst others, this requires an understanding on how environmental conditions shape special patterns in distribution. In this study we investigate this fundamental information on the Swedish west coast, an area where this information is lacking.MethodsA survey which was designed to representatively sample both epi- and infaunal bivalves from randomized locations in various habitat types was conducted. Specifically, abundance and biomass of all species were recorded in the intertidal (0-0.5 m) and the shallow subtidal zone (0.5-2 m). The sites were distributed over an offshore gradient and at two exposure levels. This sampling structure allowed to extrapolate the results to an ecosystem level though information on the areal extent of these habitats using GIS layers.ResultsIt was found that even though there exist a great variability among sites, in general epifaunal bivalves outweigh infaunal bivalves approximately 3 to 1. In terms of abundance, the ratio is more or less reversed and infaunal species occur in greater numbers. Most bivalves were found at an intermediate level of exposure, but due to the areal extend of the sheltered inner-archipelago this was the most important habitat for bivalve abundance and biomass. It was also found that invasive epifaunal oyster Magallana gigas and the invasive infaunal clam Ensis leei both dominated their respective groups in terms of biomass.DiscussionThough the survey was relatively small, these results serve as a valuable insight of the relative importance of epi- and infaunal bivalves in this region. This gives understanding on which species and habitats are particularly important for ecosystem functions and services related to bivalves. This also provide a starting baseline for attempts to quantify ecosystem services provided by certain species or groups of bivalves in the future.
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- 2023
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4. Identifying high‐density areas of oysters using species distribution modeling: Lessons for conservation of the native Ostrea edulis and management of the invasive Magallana (Crassostrea) gigas in Sweden
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Per Bergström, Linnea Thorngren, Åsa Strand, and Mats Lindegarth
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conservation ,distribution ,ensemble modeling ,management ,oyster ,protection ,Ecology ,QH540-549.5 - Abstract
Abstract Aim Understanding spatial patterns of the distribution of adult native oyster, Ostrea edulis, and the invasive Magallana (Crassostrea) gigas is important for management of these populations. The aim of this study was to use ensemble SDM’s to (a) identify and predict conservation hotspots, (b) assess the current level of protection for O. edulis, and (c) quantify the amount of overlap between the two species where interactions with M. gigas are most likely. Location Skagerrak, Sweden. Methods We used data collected by video at depths from 0.5 to 10 m in 436 sites. Models of occurrence and densities >1 m−2 were fitted and assessed using ensemble methods (“biomod2” package). Models of high‐density hotspots were used to predict, map, and quantify areal extent of the species in order to assess the degree of overlap with protected areas and the potential for interactions between the two species. Results Both species were widely distributed in the region. Observations of high‐density habitats, mainly occurring at depths of ≈3 and 0.5 m for O. edulis and M. gigas, respectively, were found in 4% and 2% of the sites. Models provided useful predictions for both species (AUC = 0.85–0.99; sensitivity = 0.74–1.0; specificity = 0.72–0.97). High‐density areas occupy roughly 15 km2 each with substantial overlap between species. 50% of these are protected only by fisheries regulations, 44% are found in Natura 2000 reserves and 6% of the predicted O. edulis enjoys protection in a national park. Main conclusions Data collection by video in combination with SDM’s provides a realistic approach for large‐scale quantification of spatial patterns of marine population and habitats. O. edulis and M. gigas are common in the area, but a large proportion of the most valuable O. edulis habitats are not found in protected areas. The overlap between species suggests that efforts to manage the invasive M. gigas need to be integrated with management actions to conserve the native O. edulis.
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- 2021
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5. An open-source, citizen science and machine learning approach to analyse subsea movies
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Victor Anton, Jannes Germishuys, Per Bergström, Mats Lindegarth, and Matthias Obst
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marine biodiversity ,autonomous underwater vehicle ,Biology (General) ,QH301-705.5 - Abstract
This paper describes a data system to analyse large amounts of subsea movie data for marine ecological research. The system consists of three distinct modules for data management and archiving, citizen science, and machine learning in a high performance computation environment. It allows scientists to upload underwater footage to a customised citizen science website hosted by Zooniverse, where volunteers from the public classify the footage. Classifications with high agreement among citizen scientists are then used to train machine learning algorithms. An application programming interface allows researchers to test the algorithms and track biological objects in new footage. We tested our system using recordings from remotely operated vehicles (ROVs) in a Marine Protected Area, the Kosterhavet National Park in Sweden. Results indicate a strong decline of cold-water corals in the park over a period of 15 years, showing that our system allows to effectively extract valuable occurrence and abundance data for key ecological species from underwater footage. We argue that the combination of citizen science tools, machine learning, and high performance computers are key to successfully analyse large amounts of image data in the future, suggesting that these services should be consolidated and interlinked by national and international research infrastructures.Novel information system to analyse marine underwater footage.
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- 2021
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6. Recent change in spatial distribution of the European flat oyster (Ostrea edulis) inferred from field data and empirical models of living oysters and empty shells
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Per Bergström, Linnea Thorngren, and Mats Lindegarth
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conservation ,distribution ,management ,modeling ,Ostrea edulis ,Shell ,Ecology ,QH540-549.5 - Abstract
Abstract Marine coastal areas are increasingly affected by human activities resulting in changes in species and habitat distributions. Understanding these patterns and its causes and consequences is important for conservation and restoration of such changing habitats. One habitat that has been heavily affected by human use are the North Sea oyster beds which once were abundant but have lost large parts of its coastal distribution due to overexploitation. Based on data of living and dead assemblages of Ostrea edulis collected using video transects, we used an ensemble modeling technique to model and predict current and recent distribution of O. edulis along the Swedish west coast where its distribution is, in relative terms, still rather unaffected. We could detect a recent change in the distribution of O. edulis along the coast which to a large extent could be attributed to a change in depth distribution, suggesting that the population of O. edulis have a slightly shallower distribution today than in the past. Although a potential mismatch between living and dead assemblages, caused by a complex combination of biological and environmental conditions, needs to be considered in the interpretations drawn, it may be a way around the lack of suitable background data in management decisions. This provides important information for management and conservation of the native oyster beds. Furthermore, this study illustrates a method for identifying recent changes in species distribution using dead assemblages of bivalves.
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- 2022
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7. Assessment of the population of Ostrea edulis in Sweden: A marginal population of significance?
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Linnea Thorngren, Per Bergström, Thomas Dunér Holthuis, and Mats Lindegarth
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benthic habitat ,conservation ,Ostrea edulis ,sampling methods ,sustainable management ,towed video ,Ecology ,QH540-549.5 - Abstract
Abstract The European flat oyster Ostrea edulis is an economically and ecologically important species subjected to extensive protection and restoration efforts, due to sharp population declines in Europe. In Sweden, O. edulis occurs at the northern fringe of its range. Knowledge of the distribution and abundance of the species is limited, and the size of the population has never been estimated. Oyster fishery sustainability has never been assessed. Using a random sampling approach and towed video, we collected data on oyster occurrence at 435 sites to estimate abundance and distribution of O. edulis in the Swedish Skagerrak region. Furthermore, the size of the population was assessed and the current management and legislation strategy of the species was analyzed. Living O. edulis was found in 27% of all sampled sites above 6 m, and the size of the population was estimated to 36.6 ± 16.3 million individuals (total population ± SE). The distribution was patchy, and approximately 60% of the population was found in oyster bed densities (≥5 oysters/m2), which corresponds to around 1% of the sampled sites. The nondestructive sampling method and representative design provided useful estimates of population size and error, which indicate that the marginal population of O. edulis in Sweden constitutes a significant part of the remaining European population. We argue that the relatively good status of the Swedish population can be explained by (a) private ownership of fishing rights, (b) a small‐scale fishery that exploits
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- 2019
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8. Nitrogen and Phosphorous Content in Blue Mussels (Mytilus spp.) Across the Baltic Sea
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Anna-Lucia Buer, Daniel Taylor, Per Bergström, Lukas Ritzenhofen, and Annemarie Klemmstein
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Mytilus spp. ,Baltic Sea ,nitrogen ,phosphorus ,salinity ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
To support the ongoing discussion about mussel farming and the potential to extract nutrients from the sea, this study investigated the phosphorus (P) and nitrogen (N) content of blue mussels (Mytilus spp.) under different abiotic and biotic parameters. The focus of this survey was on the highly eutrophied Baltic Sea, where salinity ranges from 4 to 27 psu, and is a major contributing factor to differential mussel growth. We observed that nutrient content was not linearly correlated to salinity, but if categorized, decreased at higher salinities. Chlorophyll-a and temperature did not significantly correlate with nutrient content, but season of harvest and mussel size did. Furthermore, habitat was a strong driver of nutrient content, indicating higher nutrient density if mussels are grown in mussel farms (i.e., in the water column) instead of on mussel culture beds or harvested from wild beds (on the sea bed). Values of N and P averaged 5.85% N and 0.83% P of tissue dry weight in mussels at the sea bed and 9.43% N and 0.96% P of tissue dry weight in mussels from longline cultivation. These results will be useful in refining estimations about mussel farming as a nutrient mitigation measure and the extraction potential, as well as related costs.
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- 2020
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9. Robust registration of surfaces using a refined iterative closest point algorithm with a trust region approach.
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Per Bergström and Ove Edlund
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- 2017
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10. Reliable updates of the transformation in the iterative closest point algorithm.
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Per Bergström
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- 2016
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11. Uniaxial compression of fibre networks – the synergetic effect of adhesion and elastoplasticity on non-reversible deformation
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Henrik Ström, Per Bergström, Charlotta Hanson, and Srdjan Sasic
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Materials science ,Yield (engineering) ,General Chemical Engineering ,Uniaxial compression ,Discrete element model ,Adhesion ,Composite material ,Deformation (meteorology) ,Anisotropy ,Compression (physics) ,Volume (compression) - Abstract
In this paper we study numerically and experimentally non-reversible deformation of anisotropic, semi-flexible fibre networks. We formulate a Discrete Element Model (DEM) with bonded particles to simulate uniaxial compression of such networks and use this model to describe and quantify the effect of elasto-plastic fibre contacts and fibre-fibre adhesion on non-reversible deformation. Our results show that inter-fibre adhesion plays a role for compression in a low solid volume fraction range where adhesive forces can overcome fibre deformation forces and moments. Also, elasto-plastic contacts between fibres become important at higher solid volume fractions when the yield criterion is exceeded. The combined case of fibres having elasto-plastic contacts and adhesion shows a significant synergetic effect leading to a degree of non-reversible deformation of the network far beyond that of networks with only elasto-plastic fibre contacts or inter-fibre adhesion.
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- 2022
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12. Robust registration of point sets using iteratively reweighted least squares.
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Per Bergström and Ove Edlund
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- 2014
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13. Fitting NURBS using separable least squares techniques.
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Per Bergström and Inge Söderkvist
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- 2012
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14. Deposition of shells modify nutrient fluxes in marine sediments: effects of nutrient enrichment and mitigation by bioturbation below mussel farms
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Mats Lindegarth, Ylva Durland, and Per Bergström
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0106 biological sciences ,Ecology ,010604 marine biology & hydrobiology ,fungi ,SH1-691 ,Nutrient flux ,Mussel ,010501 environmental sciences ,Management, Monitoring, Policy and Law ,Aquatic Science ,01 natural sciences ,Nutrient ,Environmental chemistry ,Aquaculture. Fisheries. Angling ,Environmental science ,Deposition (chemistry) ,Bioturbation ,QH540-549.5 ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
Farming of extractive species such as filter feeding bivalves has been proposed as a potential method to mitigate impacts of eutrophication in marine environments. For such efforts to be sustainable, potential negative effects from mussel farms, such as accumulation of biodeposits in sediment below them, need to be considered and addressed. Benthic burrowing macrofauna strongly influence biogeochemical processes in soft bottom marine habitats by sediment reworking and irrigation and, thus, have the potential to mitigate some of the negative impacts. However, not all biodeposits are organic matter; shells that accumulate on and in the sediment below mussel farms also have the potential to influence processes in the sediment, the activity of bioturbators and the fluxes across the sediment-water interface. In this study, we evaluated the mitigation potential of the bioturbating polychaeteHediste diversicolorin sediments enriched with mussel waste material and the relative impact of mussel shells within the sediment matrix. The polychaetes generally increased fluxes and sediment oxygen uptake. With an observed tendency of increased fluxes of nutrients in sediments containing shells compared to sediments without, the results indicate that the accumulation of shell has a potential to further increase the mitigative effect of the polychaetes by influencing the solute fluxes across the sediment-water interface.
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- 2020
15. Spatio-temporal processing of surface EMG signals from the sternocleidomastoideus muscle to assess effects of radiotherapy on motor unit conduction velocity and firing rate - A pilot study.
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Christer Grönlund, Nils östlund, Jack Lindh, Per Bergström, and J. Stefan Karlsson
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- 2008
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16. Assessing the potential for sea-based macroalgae cultivation and its application for nutrient removal in the Baltic Sea
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Jonne Kotta, Urmas Raudsepp, Robert Szava-Kovats, Robert Aps, Aurelija Armoskaite, Ieva Barda, Per Bergström, Martyn Futter, Fredrik Gröndahl, Matthew Hargrave, Magdalena Jakubowska, Holger Jänes, Ants Kaasik, Patrik Kraufvelin, Nikolai Kovaltchouk, Peter Krost, Tomasz Kulikowski, Anneliis Kõivupuu, Ilmar Kotta, Liisi Lees, Sander Loite, Ilja Maljutenko, Göran Nylund, Tiina Paalme, Henrik Pavia, Ingrida Purina, Moona Rahikainen, Verena Sandow, Wouter Visch, Baoru Yang, and Francisco R. Barboza
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Baltic States ,Environmental Engineering ,Seaweed farming ,Oceans and Seas ,Water ,Aquaculture ,Nutrients ,Eutrophication ,Eutrophication control ,Seaweed ,Pollution ,Blue growth ,Fucus ,Environmental Chemistry ,Waste Management and Disposal - Abstract
Marine eutrophication is a pervasive and growing threat to global sustainability. Macroalgal cultivation is a promising circular economy solution to achieve nutrient reduction and food security. However, the location of production hotspots is not well known. In this paper the production potential of macroalgae of high commercial value was predicted across the Baltic Sea region. In addition, the nutrient limitation within and adjacent to macroalgal farms was investigated to suggest optimal site-specific configuration of farms. The production potential of Saccharina latissima was largely driven by salinity and the highest production yields are expected in the westernmost Baltic Sea areas where salinity is >23. The direct and interactive effects of light availability, temperature, salinity and nutrient concentrations regulated the predicted changes in the production of Ulva intestinalis and Fucus vesiculosus. The western and southern Baltic Sea exhibited the highest farming potential for these species, with promising areas also in the eastern Baltic Sea. Macroalgal farming did not induce significant nutrient limitation. The expected spatial propagation of nutrient limitation caused by macroalgal farming was less than 100–250 m. Higher propagation distances were found in areas of low nutrient and low water exchange (e.g. offshore areas in the Baltic Proper) and smaller distances in areas of high nutrient and high water exchange (e.g. western Baltic Sea and Gulf of Riga). The generated maps provide the most sought-after input to support blue growth initiatives that foster the sustainable development of macroalgal cultivation and reduction of in situ nutrient loads in the Baltic Sea.
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- 2022
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17. Evaluation of NURBS Surfaces for Regular Structured Parameter Values.
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Per Bergström
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- 2015
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18. Metabolic response patterns in brain microdialysis fluids and serum during interstitial cisplatin treatment of high-grade glioma
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Pär Jonsson, Thomas Asklund, Per Bergström, Benny Björkblom, Henrik Antti, A. Tommy Bergenheim, Mikael Johansson, and Pedram Tabatabaei
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Adult ,Male ,Oncology ,Cancer Research ,Microdialysis ,medicine.medical_specialty ,Poor prognosis ,Cancer therapy ,Tumour heterogeneity ,Antineoplastic Agents ,Article ,Prognostic markers ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Humans ,Medicine ,Effective treatment ,Lactic Acid ,Aged ,Neoplasm Staging ,030304 developmental biology ,High-Grade Glioma ,Aged, 80 and over ,Cisplatin ,Cancer och onkologi ,0303 health sciences ,Brain Neoplasms ,business.industry ,Brain ,Glioma surgery ,Glioma ,Middle Aged ,Cancer metabolism ,Glucose ,Cancer and Oncology ,030220 oncology & carcinogenesis ,Female ,Neoplasm staging ,business ,medicine.drug - Abstract
Background High-grade gliomas are associated with poor prognosis. Tumour heterogeneity and invasiveness create challenges for effective treatment and use of systemically administrated drugs. Furthermore, lack of functional predictive response-assays based on drug efficacy complicates evaluation of early treatment responses. Methods We used microdialysis to deliver cisplatin into the tumour and to monitor levels of metabolic compounds present in the tumour and non-malignant brain tissue adjacent to tumour, before and during treatment. In parallel, we collected serum samples and used multivariate statistics to analyse the metabolic effects. Results We found distinct metabolic patterns in the extracellular fluids from tumour compared to non-malignant brain tissue, including high concentrations of a wide range of amino acids, amino acid derivatives and reduced levels of monosaccharides and purine nucleosides. We found that locoregional cisplatin delivery had a strong metabolic effect at the tumour site, resulting in substantial release of glutamic acid, phosphate, and spermidine and a reduction of cysteine levels. In addition, patients with long-time survival displayed different treatment response patterns in both tumour and serum. Longer survival was associated with low tumour levels of lactic acid, glyceric acid, ketoses, creatinine and cysteine. Patients with longer survival displayed lower serum levels of ketohexoses, fatty acid methyl esters, glycerol-3-phosphate and alpha-tocopherol, while elevated phosphate levels were seen in both tumour and serum during treatment. Conclusion We highlight distinct metabolic patterns associated with high-grade tumour metabolism, and responses to cytotoxic cisplatin treatment.
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- 2019
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19. Scaling behaviour of strength of 3D-, semi-flexible-, cross-linked fibre network
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Shakhawath Hossain, Per Bergström, and Tetsu Uesaka
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Materials science ,Applied Mathematics ,Mechanical Engineering ,Modulus ,Stiffness ,02 engineering and technology ,Bending ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Shear (sheet metal) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Modeling and Simulation ,medicine ,General Materials Science ,Composite material ,Deformation (engineering) ,medicine.symptom ,0210 nano-technology ,Scaling ,Elastic modulus ,Beam (structure) - Abstract
Anisotropic, semi-flexible, cross-linked, random fibre networks are ubiquitous both in nature and in a wide variety of industrial materials. Modelling mechanical properties of such networks have been done extensively in terms of criticality, mechanical stability, and scaling of network stiffnesses with structural parameters, such as density. However, strength of the network has received much less attention. In this work we have constructed 3D-planar fibre networks where fibres are, more or less, oriented in the in-plane direction, and we have investigated the scaling of network strength with density. Instead of modelling fibres as 1D element (e.g., a beam element with stretching, bending and/or shear stiffnesses), we have treated fibres as a 3D-entity by considering the features like twisting stiffness, transverse stiffness, and finite cross-link (or bond) strength in different deformation modes. We have reconfirmed the previous results of elastic modulus in the literature that, with increasing density, the network modulus indeed undergoes a transition from bending-dominated deformation to stretching-dominated with continuously varying scaling exponent. Network strength, on the other hand, scales with density with a constant exponent, i.e., showing no obvious transition phenomena. Using material parameters for wood fibres, we have found that the predicted results for stiffness and strength agree very well with experimental data of fibre networks of varying densities reported in the literature.
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- 2019
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20. In situ characterization of benthic fluxes and denitrification efficiency in a newly re-established mussel farm
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Astrid Hylén, Mats Lindegarth, Mikhail Kononets, Per Bergström, Anna Stedt, Daniel P. Taylor, and Stefano Bonaglia
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Geologic Sediments ,Biogeochemical cycle ,Environmental Engineering ,Denitrification ,010504 meteorology & atmospheric sciences ,Mitigation ,Nitrogen ,Aquaculture ,010501 environmental sciences ,01 natural sciences ,chemistry.chemical_compound ,Nitrate ,Animals ,Environmental Chemistry ,Organic matter ,SDG 14 - Life Below Water ,Waste Management and Disposal ,0105 earth and related environmental sciences ,chemistry.chemical_classification ,Sediment ,Biogeochemistry ,Nutrients ,Sedimentation ,Eutrophication ,Pollution ,Carbon ,Bivalvia ,chemistry ,Environmental chemistry ,Environmental science - Abstract
Mussel farming has been proposed as a mechanism to mitigate eutrophication in coastal waters. However, localizing the intensive filtration of organic matter by mussels can cause a concomitant enrichment of organic matter in sediments below farms, which may influence biogeochemical processes and fates of nutrients in the system. In the context of mitigating eutrophication, it is important to quantify sedimentary changes induced at early life stages of mussel farms. Accordingly, this study investigated how a newly re-established mussel farm affected sedimentation rates, sediment characteristics, sediment-water solute fluxes and nitrate (NO3−) reduction rates (measured in situ) during the first year of production. Sedimentation rates were enhanced at the farm relative to a reference station, and both organic and inorganic carbon accumulated in the sediment with time. Increased organic matter input likely drove the slightly elevated sedimentary effluxes of ammonium (NH4+) and dissolved inorganic phosphorus (DIP) in the farm. Denitrification was the main NO3− reduction process, however, there was a relative increase in the remobilization of bioavailable nitrogen underneath the farm as dissimilatory nitrate reduction to ammonium (DNRA) rates were enhanced by >200% and the denitrification efficiency was 49% lower compared to the reference station. The sedimentary methane (CH4) release tended to be higher at the farm, but fluxes were not significantly different from reference conditions. Low sedimentary pigment concentrations indicated a reduced presence of benthic microalgae at the farm, which likely influenced sediment-water solute fluxes. Over the production cycle, the release of dissolved inorganic nitrogen (DIN) and DIP underneath the farm were respectively 426% and 510% relative to reference conditions. Impacts of the mussel farm were thus measurable already during the first year of establishment. These immediate changes to the sediment biogeochemistry, as well as long-term effects, should be considered when estimating the environmental impact of mussel aquaculture.
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- 2021
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21. Recent change in spatial distribution of the European flat oyster (
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Per, Bergström, Linnea, Thorngren, and Mats, Lindegarth
- Abstract
Marine coastal areas are increasingly affected by human activities resulting in changes in species and habitat distributions. Understanding these patterns and its causes and consequences is important for conservation and restoration of such changing habitats. One habitat that has been heavily affected by human use are the North Sea oyster beds which once were abundant but have lost large parts of its coastal distribution due to overexploitation. Based on data of living and dead assemblages of
- Published
- 2021
22. Perspective Depth Extraction of Points on a Surface Under an Instantaneous Rigid Body Transformation.
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Per Bergström
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- 2012
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23. The HILUS-Trial : a prospective Nordic multicenter phase 2 study of ultracentral lung tumors treated with stereotactic body radiotherapy
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Jörgen Olofsson, Charlotte Kristiansen, Mirjana Josipovic, Rolf Lewensohn, Charlotte Billiet, Tine Bjørn Nielsen, Kristin Karlsson, Hans-Olov Rosenbrand, Christina Ramberg, Ninni Drugge, Sara Lindberg, Ingmar Lax, Lotte Rogg, Jan Nyman, André Haraldsson, Stefan Starup Jeppesen, Karin Lindberg, Peter Wersäll, Per Bergström, Gitte F. Persson, Britta Lödén, D.S. Moeller, Vitali Grozman, Silke Engelholm, and Azza A. Khalil
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0301 basic medicine ,Pulmonary and Respiratory Medicine ,medicine.medical_specialty ,Fistula ,Phases of clinical research ,Group B ,TOXICITY ,8 FRACTIONS ,03 medical and health sciences ,0302 clinical medicine ,60 GY ,RADIATION-THERAPY ,ABLATIVE RADIOTHERAPY ,medicine ,Clinical endpoint ,Central ,Pneumonitis ,RISK ,Univariate analysis ,OUTCOMES ,Lung ,SBRT ,business.industry ,respiratory system ,medicine.disease ,CANCER ,Ultracentral ,030104 developmental biology ,medicine.anatomical_structure ,Oncology ,Lung tumors ,030220 oncology & carcinogenesis ,Toxicity ,Stereotactic ,EARLY-STAGE ,Radiology ,Human medicine ,business - Abstract
Introduction: Stereotactic body radiation therapy of thoracic tumors close to the central airways implies risk of severe toxicity. We report a prospective multicenter phase 2 trial for tumors located less than or equal to 1 cm from the proximal bronchial tree with primary end point of local control and secondary end point of toxicity. Methods: Stereotactic body radiation therapy with 7 Gy x 8 was prescribed to the 67% isodose encompassing the planning target volume. The patients were stratified to group A (tumors < 1 cm from the main bronchi and trachea) or group B (all other tumors). Risk factors for treatment-related death were tested in univariate analysis, and a logistic regression model was developed for fatal bronchopulmonary bleeding versus dose to the main bronchi and trachea. Results: A total of 65 patients (group A/group B, n = 39/ 26) were evaluated. The median distance between the tumor and the proximal bronchial tree was 0 mm (0 & ndash;10 mm). The 2-year local control was 83%. Grade 3 to 5 toxicity was noted in 22 patients, including 10 cases of treatment related death (bronchopulmonary hemorrhage, n = 8; pneumonitis, n = 1; fistula, n = 1). Dose to the combined structure main bronchi and trachea and tumor distance to the main bronchi were important risk factors. Dose modeling revealed minimum dose to the & ldquo;hottest & rdquo; 0.2 cc to the structure main bronchi and trachea as the strongest predictor for lethal bronchopulmonary hemorrhage. Conclusions: On the basis of the presented data, 7 Gy x 8, prescribed to the planning target volume-encompassing isodose, should not be used for tumors located within 1 cm from the main bronchi and trachea. Group B-type tumors may be considered for the treatment on the basis of an individual risk-benefit assessment and a maximum dose to the main bronchi and trachea in the order of 70 to 80 Gy (equivalent dose in 2 Gy fractions). (c) 2021 International Association for the Study of Lung Cancer. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).
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- 2021
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24. Photogrammetry for Free Surface Flow Velocity Measurement : From Laboratory to Field Measurements
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Hang Trieu, Per Bergström, Mikael Sjödahl, J. Gunnar I. Hellström, Patrik Andreasson, and Henrik Lycksam
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3D PTV ,surface velocity ,Water supply for domestic and industrial purposes ,Fluid Mechanics and Acoustics ,Strömningsmekanik och akustik ,Hydraulic engineering ,TC1-978 ,photogrammetry ,camera calibration ,TD201-500 ,particle tracking - Abstract
This study describes a multi-camera photogrammetric approach to measure the 3D velocityof free surface flow. The properties of the camera system and particle tracking velocimetry (PTV)algorithm were first investigated in a measurement of a laboratory open channel flow to prepare forfield measurements. The in situ camera calibration methods corresponding to the two measurementsituations were applied to mitigate the instability of the camera mechanism and camera geometry.There are two photogrammetry-based PTV algorithms presented in this study regarding differenttypes of surface particles employed on the water flow. While the first algorithm uses the particletracking method applied for individual particles, the second algorithm is based on correlation-basedparticle clustering tracking applied for clusters of small size particles. In the laboratory, referencedata are provided by particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Thedifferences in velocities measured by photogrammetry and PIV, photogrammetry and LDV are 0.1%and 3.6%, respectively. At a natural river, the change of discharges between two measurement timesis found to be 15%, and the corresponding value reported regarding mass flow through a nearbyhydropower plant is 20%. The outcomes reveal that the method can provide a reliable estimation of3D surface velocity with sufficient accuracy. Validerad;2021;Nivå 2;2021-06-18 (beamah);Forskningsfinansiär: Svenskt Vattenkraftcentrum (SVC)
- Published
- 2021
25. Identifying high-density areas of oysters using species distribution modeling: Lessons for conservation of the native
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Per, Bergström, Linnea, Thorngren, Åsa, Strand, and Mats, Lindegarth
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oyster ,conservation ,distribution ,protection ,ensemble modeling ,management ,Original Research - Abstract
Aim Understanding spatial patterns of the distribution of adult native oyster, Ostrea edulis, and the invasive Magallana (Crassostrea) gigas is important for management of these populations. The aim of this study was to use ensemble SDM’s to (a) identify and predict conservation hotspots, (b) assess the current level of protection for O. edulis, and (c) quantify the amount of overlap between the two species where interactions with M. gigas are most likely. Location Skagerrak, Sweden. Methods We used data collected by video at depths from 0.5 to 10 m in 436 sites. Models of occurrence and densities >1 m−2 were fitted and assessed using ensemble methods (“biomod2” package). Models of high‐density hotspots were used to predict, map, and quantify areal extent of the species in order to assess the degree of overlap with protected areas and the potential for interactions between the two species. Results Both species were widely distributed in the region. Observations of high‐density habitats, mainly occurring at depths of ≈3 and 0.5 m for O. edulis and M. gigas, respectively, were found in 4% and 2% of the sites. Models provided useful predictions for both species (AUC = 0.85–0.99; sensitivity = 0.74–1.0; specificity = 0.72–0.97). High‐density areas occupy roughly 15 km2 each with substantial overlap between species. 50% of these are protected only by fisheries regulations, 44% are found in Natura 2000 reserves and 6% of the predicted O. edulis enjoys protection in a national park. Main conclusions Data collection by video in combination with SDM’s provides a realistic approach for large‐scale quantification of spatial patterns of marine population and habitats. O. edulis and M. gigas are common in the area, but a large proportion of the most valuable O. edulis habitats are not found in protected areas. The overlap between species suggests that efforts to manage the invasive M. gigas need to be integrated with management actions to conserve the native O. edulis., Understanding spatial patterns of the native oyster, Ostrea edulis, and the invasive Magallana gigas is important for management of these populations. We used data collected by video at depths from 0.5 to 10 m in 436 sites. Models of occurrence and densities > 1 m−2 were fitted and assessed using ensemble methods. Data collection by video in combination with SDM’s provides a realistic approach for large‐scale quantification of spatial patterns of marine population and habitats.
- Published
- 2020
26. Intratumoral retrograde microdialysis treatment of high-grade glioma with cisplatin
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Pedram Tabatabaei, Per Bergström, Thomas Asklund, A. Tommy Bergenheim, Erik Björn, and Mikael Johansson
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Adult ,Glycerol ,Male ,medicine.medical_specialty ,Microdialysis ,Neurology ,medicine.medical_treatment ,Glutamic Acid ,Antineoplastic Agents ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,High-Grade Glioma ,Neuroradiology ,Aged ,Cisplatin ,Aged, 80 and over ,Chemotherapy ,medicine.diagnostic_test ,business.industry ,Brain Neoplasms ,Brain ,Interventional radiology ,Glioma ,Middle Aged ,Glucose ,Treatment Outcome ,Quality of Life ,Surgery ,Female ,Neurology (clinical) ,Radiology ,Neurosurgery ,Neoplasm Recurrence, Local ,business ,030217 neurology & neurosurgery ,medicine.drug - Abstract
This study evaluates the application of a microdialysis technique for interstitial chemotherapy using cisplatin in high-grade glioma.An in vitro study demonstrated that cisplatin can be administered through retrograde microdialysis and defined the recovery for cisplatin. In a subsequent phase I study, 1-4 microdialysis catheters were implanted in tumor tissue, brain adjacent to tumor (BAT) tissue, and subcutaneous tissue in 10 patients with recurrent high-grade glioma. Cisplatin was administered continuously in daily doses between 0.3 and 3.9 mg for 4 to12 days. Microdialysis samples were continuously collected and analyzed for glucose metabolites, glutamate, glycerol, and cisplatin concentrations. Treatment tolerability was evaluated through clinical monitoring. Quality of life was assessed using the EORTC-QLQ-C30 questionnaire for up to 3 months after treatment.This in vitro study showed that cisplatin could be administrated with a recovery of 41-97%, depending on flowrate, type of catheter, and cisplatin concentration. During the treatment, patients were exposed to a total dose of 1.2-36.8 mg cisplatin. The concentration of cisplatin in BAT, serum, and subcutaneous tissue was close to detection level in all but two patients. A transient neurologic deterioration due to edema was commonly observed, but no systemic side effects were recorded. After onset of treatment, concentrations of glutamate and glycerol were significantly increased in tumor tissue but not in BAT, with a peak after 3 days, and consistent for the rest of the treatment. Five of the patients survived between 153 and 492 days after treatment.This phase I study demonstrates that retrograde microdialysis can be used to administer cisplatin interstitially into high-grade glioma tissue. A high cytotoxicity was detected in tumor tissue, but not in the surrounding brain. Retrograde microdialysis appears to be a clinically useful method for intratumoral drug administration in high-grade glioma.
- Published
- 2020
27. Biodeposits from Mytilus edulis: a potentially high-quality food source for the polychaete, Hediste diversicolor
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Niklas Hällmark, Karl-Johan Larsson, Per Bergström, and Mats Lindegarth
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0106 biological sciences ,chemistry.chemical_classification ,biology ,Chemistry ,010604 marine biology & hydrobiology ,Sediment ,Mussel ,Aquatic Science ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Nutrient ,Ashing ,Benthic zone ,Environmental chemistry ,Hediste diversicolor ,Organic matter ,Agronomy and Crop Science ,Bioturbation - Abstract
Previous studies have shown clearly that the deposit feeding polychaete, Hediste diversicolor, can promote oxygenation of sediments exposed to excess loads of mussel faeces. In this experimental study, we explicitly test their utility as food for H. diversicolor to survive and grow on. Furthermore, in order to understand the consequences of experimental manipulations, we also evaluated effects on chemical fluxes in and out of the sediment. The results show strong differences in growth but no difference in short-term survival. Fed only on mussel faeces, the polychaetes grew on average 17% in wet weight after a period of 10 days, compared to 3% when given equivalent amounts of organic matter from the natural sediments. Addition of faeces to natural sediments resulted in 19–20% growth, thus suggesting an approximate additive effect of the two food sources. Chemical analyses showed that, oxygen consumption increased with load of organic material irrespective of origin, faecal material caused higher fluxes of ammonia compared to natural organic material, but neither oxygen consumption nor nutrient fluxes were affected by the ashing of sediments. In contrast, fluxes of silicate increased as a consequence of ashing but were not affected by the addition of mussel faeces. Thus, despite risks of experimental artefacts due to ashing of sediments, the results show that oxygen and nutrient dynamics responded to manipulations of organic material and not to the potential modification of sediment structure. Therefore, the observed effects on growth of H. diversicolor can be safely interpreted as caused by differences in amount and quality of organic material. Mussel faeces is a high-quality food source for this species of polychaete and, in combination with ample evidence from previous studies that bioturbation, we conclude that H. diversicolor is a suitable candidate in further efforts to develop technical solutions based on bioturbation for mitigation of adverse effects on benthic environments in connection with mussel-farming.
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- 2018
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28. The effects of small-scale coastal development on the eelgrass ( Zostera marina L.) distribution along the Swedish west coast – Ecological impact and legal challenges
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Kristjan Laas, Per Bergström, Louise Eriander, Lena Gipperth, and Per-Olav Moksnes
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0106 biological sciences ,biology ,Overfishing ,business.industry ,Ecology ,010604 marine biology & hydrobiology ,Distribution (economics) ,Management, Monitoring, Policy and Law ,Aquatic Science ,Oceanography ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Current (stream) ,Fishery ,Habitat ,Zostera marina ,Environmental science ,Ecosystem ,Marine protected area ,Eutrophication ,business - Abstract
Anthropogenic impacts on coastal areas have led to an increased degradation of marine environments globally. Eelgrass ecosystems are particularly susceptible to human induced stressors as they are sensitive to low light conditions and usually grow in shallow protected areas where pressure from coastal development is high. The extensive decline in coverage of eelgrass along the Swedish Northwest coast since the 1980s has largely been attributed to the effects of coastal eutrophication and overfishing. However, the impact on eelgrass from small-scale coastal development (docks and marinas) has never been investigated in this area. The aim of this study was to assess the local and large-scale effect of shading by docks and marinas on eelgrass habitats along the Swedish NW coast and to investigate the decision process behind small-scale exploitation to identify problems with the current legislation, which allows for continued exploitation of eelgrass. Through field assessments of eelgrass around docks and analysis of available data on eelgrass and dock distribution along the coast, the present study demonstrates that shading from docks reduced eelgrass coverage with on average 42–64% under and adjacent to the docks, and that floating docks affected larger areas and caused a much stronger reduction in eelgrass coverage (up to 100% loss) compared to docks elevated on poles (up to 70% reduction in coverage). The total eelgrass area negatively affected by docks and marinas along the NW coast was estimated to approximately 480 ha, an area corresponding to over 7% of the present areal coverage of eelgrass in the region. The analysis of decisions for dock construction showed that eelgrass was generally not assessed or considered in the decision process and that 69–88% of the applications were approved also in areas where eelgrass was present. Furthermore, marine protected areas only marginally reduced the approval of applications in eelgrass habitats. The continued small-scale development along the Swedish NW coast constitutes a significant threat to the already decimated coverage of eelgrass along the coast and changes in the management practices are needed in order to achieve both national and international goals on environmental status.
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- 2017
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29. Cleaning up seas using blue growth initiatives: Mussel farming for eutrophication control in the Baltic Sea
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Patrik Kraufvelin, Martyn N. Futter, Aleksandar Vidakovic, Per Bergström, Samuli Korpinen, Henrik Skov, Elina Virtanen, Merli Rätsep, Maren Moltke Lyngsgaard, Helen Orav-Kotta, Jouko Rissanen, Peter Krost, Marina I. Orlova, Andrius Šiaulys, Francisco R. Barboza, Eliecer Díaz, Jonne Kotta, Ivo Bobsien, Martina Mühl, Odd Lindahl, Ants Kaasik, Kristjan Herkül, Antonia Nyström Sandman, Mats Lindegarth, Per R. Jonsson, Kiran Liversage, and Lena Bergström
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Baltic States ,010504 meteorology & atmospheric sciences ,Cost effectiveness ,010501 environmental sciences ,01 natural sciences ,sininen kasvu ,Nutrient ,Aquaculture ,eutrophication control ,Waste Management and Disposal ,mussel farming ,geography.geographical_feature_category ,Aquatic ecosystem ,rehevöityminen ,Agriculture ,Phosphorus ,Eutrophication ,Pollution ,6. Clean water ,humanities ,aquaculture ,blue growth ,internal measures ,Baltic Sea ,meret ,geographic locations ,Environmental Engineering ,Nitrogen ,Oceans and Seas ,Environmental Chemistry ,Animals ,14. Life underwater ,biologiset menetelmät ,0105 earth and related environmental sciences ,geography ,Brackish water ,business.industry ,fungi ,Estuary ,puhdistus ,Mussel ,simpukat ,Bivalvia ,Fishery ,vesiviljely ,13. Climate action ,Itämeri ,sininen talous ,Environmental science ,business - Abstract
Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread oxygen free “dead zones” and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere. Highlights • Mussel farming is a viable internal measure to address Baltic Sea eutrophication. • Rates of nutrient removal depend on salinity at the regional scale and food availability at the local scale. • Cost effectiveness of nutrient removal by mussel farming depends also on farm type. • Total farm area needed for achieving HELCOM nutrient reduction targets is realistic.
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- 2020
30. Stochastic modelling of 3D fiber structures imaged with X-ray microtomography
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Tobias Gebäck, Philip Townsend, Malin Lundman, Emanuel Larsson, Per Bergström, Niklas Lorén, Tomas Karlson, Charlotta Hanson, Stephen Hall, Aila Särkkä, and Magnus Röding
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Materials science ,General Computer Science ,Estimation theory ,Stochastic modelling ,Lattice Boltzmann methods ,General Physics and Astronomy ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Computational Mathematics ,Permeability (earth sciences) ,Mechanics of Materials ,Consistency (statistics) ,General Materials Science ,Fiber ,0210 nano-technology ,Biological system ,Parametric statistics ,Virtual fiber - Abstract
Many products incorporate into their design fibrous material with particular levels of permeability as a way to control the retention and flow of liquid. The production and experimental testing of these materials can be expensive and time consuming, particularly if it needs to be optimised to a desired level of absorbency. We consider a parametric virtual fiber model as a replacement for the real material to facilitate studying the relationship between structure and properties in a cheaper and more convenient manner. 3D image data sets of a sample fibrous material are obtained using X-ray microtomography and the individual fibers isolated. The segmented fibers are used to estimate the parameters of a 3D stochastic model for generating softcore virtual fiber structures. We use several spatial measures to show the consistency between the real and virtual structures, and demonstrate with lattice Boltzmann simulations that our virtual structure has good agreement with respect to the permeability of the physical material.
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- 2021
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31. SPACE – A randomized study of SBRT vs conventional fractionated radiotherapy in medically inoperable stage I NSCLC
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Rolf Lewensohn, Jo-Åsmund Lund, Per Bergström, Odd Terje Brustugun, Bengt Bergman, Signe Friesland, Jan Nyman, Andreas Hallqvist, Ingmar Lax, and Erik Holmberg
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Male ,medicine.medical_specialty ,Lung Neoplasms ,Radiosurgery ,Chest pain ,030218 nuclear medicine & medical imaging ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,Randomized controlled trial ,law ,Carcinoma, Non-Small-Cell Lung ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aged ,Pneumonitis ,Aged, 80 and over ,COPD ,business.industry ,Standard treatment ,Hematology ,Middle Aged ,medicine.disease ,Survival Analysis ,Comorbidity ,Surgery ,Treatment Outcome ,Oncology ,030220 oncology & carcinogenesis ,Toxicity ,Female ,Dose Fractionation, Radiation ,Radiology ,Radiotherapy, Conformal ,medicine.symptom ,business ,Esophagitis - Abstract
Background Stereotactic body radiotherapy (SBRT) has been introduced for small lung tumors due to excellent local control and few side effects, even though there are no comparative studies. SPACE (Stereotactic Precision And Conventional radiotherapy Evaluation) is the first randomized phase II trial comparing SBRT and conventional fractionated radiotherapy (3DCRT). Methods Patients with stage I medically inoperable NSCLC were randomized to receive SBRT to 66Gy in 3 fractions (one week) or 3DCRT to 70Gy (7weeks). Patients were followed to assess efficacy, toxicity and HRQL. Findings Between 2007 and 2011, 102 patients were randomized. Mean age 74 (57-86), 60% women, the vast majority (92%) had COPD or cardiovascular comorbidity. The SBRT arm included more patients with T2-tumors (p=0.02) and male gender (p=0.35). The median follow-up was 37months with a 1-, 2- and 3-year PFS of: SBRT: 76%, 53%, 42% and 3DCRT: 87%, 54% 42%, HR=0.85 (95% CI 0.52-1.36) with no difference between the groups and no difference in OS (HR=0.75, 95% CI 0.43-1.30). At the end of the study 70% of SBRT patients had not progressed compared to 59% (3DCRT, p=0.26). Toxicity was low with no grade 5 events. Pneumonitis of any grade was observed in 19% (SBRT) and 34% (3DCRT, p=0.26), and esophagitis in 8% and 30% respectively (p=0.006). HRQL was evaluated with the EORTC QLQ 30 and LC14 module and patients treated with 3DCRT experienced worse dyspnea (p=0.01), chest pain (p=0.02) and cough (>10 points difference). Interpretation There was no difference in PFS and OS between SBRT and conventionally treated patients despite an imbalance of prognostic factors. We observed a tendency of an improved disease control rate in the SBRT group and they experienced better HRQL and less toxicity. SBRT is convenient for patients and should be considered standard treatment for patients with inoperable stage I NSCLC.
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- 2016
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32. Environmental influence on mussel ( Mytilus edulis ) growth – A quantile regression approach
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Per Bergström and Mats Lindegarth
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0106 biological sciences ,biology ,business.industry ,Ecology ,Range (biology) ,010604 marine biology & hydrobiology ,Aquatic Science ,Oceanography ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Ecosystem-based management ,Mytilus ,Quantile regression ,Fishery ,Aquaculture ,Sustainable management ,Threatened species ,Ecosystem ,business - Abstract
The need for methods for sustainable management and use of coastal ecosystems has increased in the last century. A key aspect for obtaining ecologically and economically sustainable aquaculture in threatened coastal areas is the requirement of geographic information of growth and potential production capacity. Growth varies over time and space and depends on a complex pattern of interactions between the bivalve and a diverse range of environmental factors (e.g. temperature, salinity, food availability). Understanding these processes and modelling the environmental control of bivalve growth has been central in aquaculture. In contrast to the most conventional modelling techniques, quantile regression can handle cases where not all factors are measured and provide the possibility to estimate the effect at different levels of the response distribution and give therefore a more complete picture of the relationship between environmental factors and biological response. Observation of the relationships between environmental factors and growth of the bivalve Mytilus edulis revealed relationships that varied both among level of growth rate and within the range of environmental variables along the Swedish west coast. The strongest patterns were found for water oxygen concentration level which had a negative effect on growth for all oxygen levels and growth levels. However, these patterns coincided with differences in growth among periods and very little of the remaining variability within periods could be explained indicating that interactive processes masked the importance of the individual variables. By using quantile regression and local regression (LOESS) this study was able to provide valuable information on environmental factors influencing the growth of M. edulis and important insight for the development of ecosystem based management tools of aquaculture activities, its use in mitigation efforts and successful management of human use of coastal areas.
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- 2016
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33. Spatial differences in growth rate and nutrient mitigation of two co-cultivated, extractive species: The blue mussel (Mytilus edulis) and the kelp (Saccharina latissima)
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Henrik Pavia, My Peterson, Wouter Visch, Per Bergström, Mats Lindegarth, and Göran M. Nylund
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,biology ,business.industry ,010604 marine biology & hydrobiology ,fungi ,Kelp ,Aquatic Science ,Oceanography ,biology.organism_classification ,Saccharina latissima ,01 natural sciences ,Mytilus ,Nutrient ,Aquaculture ,Agronomy ,Saccharina ,Environmental science ,Eutrophication ,business ,Blue mussel ,0105 earth and related environmental sciences - Abstract
Cultivation of extractive species, such as bivalves and seaweeds, provides opportunities for food production while removing excess nutrients in eutrophic coastal waters. However, to optimize these ecosystem services, selecting aquaculture sites that affect growth and nutrient uptake is important. In a transplant experiment we assessed spatial growth patterns of the blue mussel Mytilus edulis and the kelp Saccharina latissima, which were used to estimate nutrient removal. Optimal locations for growth and nutrient extraction differed, mussels grew better in relatively sheltered inner coastal areas, whereas seaweed growth increased in outer more exposed coastal areas. Estimates of mitigatory capacity indicated that under the best available conditions, mussels remove approximately 700 kg N and 6600 kg C ha−1yr−1, whereas seaweed removes approximately 100 kg N and 1000 kg C ha−1yr−1. We identified the importance of site selection for the overall capacity of two extractive species (bivalves and seaweeds) in order to synergistically maximise their growth and nutrient mitigation.
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- 2020
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34. Response to a letter to editor regarding Kotta et al. 2020: Cleaning up seas using blue growth initiatives: Mussel farming for eutrophication control in the Baltic Sea
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Samuli Korpinen, Jouko Rissanen, Jonne Kotta, Odd Lindahl, Lena Bergström, Per Bergström, Peter Krost, Per R. Jonsson, Merli Rätsep, Andrius Šiaulys, Aleksandar Vidakovic, Elina Virtanen, Kiran Liversage, Martyn N. Futter, Martina Mühl, Mats Lindegarth, Eliecer Díaz, Marina I. Orlova, Antonia Nyström Sandman, Henrik Skov, Ants Kaasik, Francisco R. Barboza, Ivo Bobsien, Kristjan Herkül, Maren Moltke Lyngsgaard, Patrik Kraufvelin, and Helen Orav-Kotta
- Subjects
Baltic States ,Environmental Engineering ,business.industry ,Oceans and Seas ,Agriculture ,Mussel ,Eutrophication ,Pollution ,Bivalvia ,Fishery ,Baltic sea ,Animals ,Environmental Chemistry ,Environmental science ,business ,Waste Management and Disposal - Published
- 2020
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35. Comparison between process simulation and deformation measured by defocused speckle photography
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Per Bergström, Mikael Sjödahl, Kristina Domeij, Per Gren, Joel Wahl, Torbjörn Lindbäck, and Malin Magnusson
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Materials science ,business.industry ,Photography ,Measure (physics) ,Physics::Optics ,Deformation (meteorology) ,Speckle pattern ,Optics ,Speckle photography ,Physics::Atomic Physics ,Process simulation ,Laser heating ,business ,A titanium - Abstract
Defocused laser speckle photography is used as a tool to measure the heat responses in a titanium component during laser heating. The evolution of the response is compared with a set of preprocesse ...
- Published
- 2018
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36. Modeling and predicting the growth of the mussel, Mytilus edulis: implications for planning of aquaculture and eutrophication mitigation
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Susanne Lindegarth, Mats Lindegarth, and Per Bergström
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Ecology ,Operations research ,business.industry ,Mytilus edulis ,growth ,Environmental resource management ,Bivalve ,Sampling (statistics) ,Marine spatial planning ,Context (language use) ,Biology ,Sustainable management ,ecosystem function ,Marine ecosystem ,Ecosystem ,mapping ,marine spatial planning ,business ,Spatial analysis ,predictive modeling ,Ecology, Evolution, Behavior and Systematics ,Spatial planning ,Nature and Landscape Conservation ,Original Research - Abstract
The increased pressure on the marine ecosystems highlights the need for policies and integrated approaches for sustainable management of coastal areas. Spatial planning based on geographic information of human activities, ecological structures and functions, and their associated goods and services is a fundamental component in this context. Here, we evaluate the potential of predictive modeling to provide spatial data on one ecosystem function, mussel growth for use in such processes. We developed a methodology based on statistical modeling, spatial prediction, and mapping for the relative growth of the blue mussel, Mytilus edulis. We evaluated the performance of different modeling techniques and classification schemes using empirical measurements of growth from 144 sampling sites and data on biological, chemical, and physical predictors. Following comparisons of the different techniques and schemes, we developed random forest models to predict growth along the Swedish west coast. Implemented into GIS the best model produced in this study predicts that low, intermediate, and high growth rates can be expected in 53%, 32%, and 15% of modeled area, respectively. The results of this study also suggest that the nature and quality of predictor data hold the key to improving the predictive power of models. On a more general note, this study exemplifies a feasible approach based on measuring, modeling, and mapping for obtaining scientifically based spatial information on ecosystem functions and services affected by a complex set of factors. Such information is fundamental for maritime spatial planning and ecosystem‐based management and its importance is likely to increase in the future. Because of its close link to nutrient assimilation and production yield, site‐specific information of soft tissue growth such as the map of predicted growth rate developed in this study can be used as a tool for optimizing actions aimed at mitigating eutrophication and aquaculture operations and in maritime spatial planning processes of coastal areas.
- Published
- 2015
37. Monitoring Recruitment Patterns of Mussels and Fouling Tunicates in Mariculture
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Thomas Dunér Holthuis, Susanne Lindegarth, Per Bergström, and Mats Lindegarth
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Larva ,biology ,Fouling ,business.industry ,Ecology ,Mussel ,Aquatic Science ,biology.organism_classification ,Tunicate ,Biofouling ,Fishery ,Aquaculture ,Settling ,Mariculture ,business - Abstract
Methods to increase the precision of spat collection and strategies to mitigate fouling are greatly needed in aquaculture production. As such, larval recruitment of mussels and a common tunicate species was investigated. Recruitment was measured in shallow (1–2 m) and deeper (4–5 m) water at three sites during the summer of 2012. In addition, to evaluate the importance of timing in deployment of mussel ropes, differences in mussel yield were examined. The settlement plates provided a good description of the settling community with high temporal resolution. Peaks in recruitment were observed for both mussels and tunicates but recruitment rates and the timing of peaks differed among sites. Although mussel larvae preferred shaded substrates at some sites and times, these substrates were consistently preferred by tunicates. Mussels preferred to settle at shallow depths, whereas tunicates were consistently more abundant deeper. In contrast to predictions, there was no positive relationship between the...
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- 2015
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38. Hypofractionated stereotactic radiotherapy in medium-sized to large arteriovenous malformations
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David Grayson, Peter Lindvall, Per Bergström, and A. Tommy Bergenheim
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Adult ,Intracranial Arteriovenous Malformations ,Male ,medicine.medical_specialty ,Neurology ,Adolescent ,medicine.medical_treatment ,Treatment results ,Radiosurgery ,Stereotactic radiotherapy ,Young Adult ,Physiology (medical) ,medicine ,Humans ,Radiation Injuries ,Aged ,Retrospective Studies ,business.industry ,General Medicine ,Middle Aged ,Cerebral arteriovenous malformations ,Treatment Outcome ,Female ,Radiation Dose Hypofractionation ,Surgery ,Neurology (clinical) ,Nuclear medicine ,business ,Follow-Up Studies - Abstract
We have reviewed treatment results in terms of obliteration and complications in 24 patients with medium to large sized cerebral arteriovenous malformations (AVMs) (mean volume 18.5±8.9cm(3); range: 10-42) treated with hypofractionated stereotactic radiotherapy (HSRT). AVMs are congenital lesions associated with a high morbidity and mortality. Radiosurgery is one option for treatment. However, in larger AVMs with volumes exceeding 10cm(3) obliteration rates are less favourable and radiation induced complications more frequent. For larger AVMs, volume-staged radiosurgery is one option while another option may be the use of HSRT. Patients were treated with 6-7Gy in five fractions to a total dose of 30-35Gy (mean total dose 32.9±1.6Gy [standard error of the mean]). Sixteen patients (69.6%) showed obliteration after a mean time of 35.2±14.8 months (range: 24-60). Only one patient (4.2%) experienced symptomatic radionecrosis. Our treatment with HSRT seems safe and efficient for treatment of medium to large sized AVMs. Treatment results seem to be in line with volume-staged radiosurgery and may be an alternative for AVMs not suitable for single fraction radiosurgery.
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- 2015
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39. Single Shot Dual-Wavelength Digital Holography: Calibration Based on Speckle Displacements
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Davood Khodadad, Mikael Sjödahl, Per Bergström, and Emil Hällstig
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Carrier signal ,Signal processing ,business.industry ,Computer science ,Mechanical Engineering ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Single shot ,Computational mathematics ,Speckle pattern ,Optics ,Hardware_GENERAL ,Calibration ,Dual wavelength ,Electrical and Electronic Engineering ,business ,Instrumentation ,Digital holography - Abstract
We present a calibration method which allows single shot dual wavelength online shape measurement in a disturbed environment. Effects of uncontrolled carrier frequency filtering are discussed as we ...
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- 2014
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40. Assessment of volume segmentation in radiotherapy of adolescents; a treatment planning study by the Swedish Workgroup for Paediatric Radiotherapy
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Måns Agrup, Ulla Martinsson, Per Nilsson, Zahra Taheri-Kadkhoda, Jacob Engellau, Per Bergström, Hedda Haugen, Jack Lindh, Kristina Nilsson, and Ingrid Kristensen
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Male ,medicine.medical_specialty ,Adolescent ,medicine.medical_treatment ,Concordance ,Planning target volume ,Pediatrics ,Skull Base Neoplasms ,Wilms Tumor ,Rhabdomyosarcoma ,Chordoma ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Segmentation ,Medical physics ,Radiation treatment planning ,Sweden ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Prostatic Neoplasms ,Radiotherapy Dosage ,Hematology ,General Medicine ,Prognosis ,medicine.disease ,Hodgkin Disease ,Kidney Neoplasms ,Radiation therapy ,Oncology ,Cancer and Oncology ,Female ,Radiotherapy, Conformal ,business ,Quality assurance - Abstract
Background and purpose. The variability in target delineation for similar cases between centres treating paediatric and adolescent patients, and the apparent differences in interpretation of radiotherapy guidelines in the treatment protocols encouraged us to perform a dummy-run study as a part of our quality assurance work. The aim was to identify and quantify differences in the segmentation of target volumes and organs at risk (OARs) and to analyse the treatment plans and dose distributions. Materials and methods. Four patient cases were selected: Wilm's tumour, Hodgkin's disease, rhabdomyosarcoma of the prostate and chordoma of the skull base. The five participating centres received the same patient-related material. They introduced the cases in their treatment planning system, delineated target volumes and OARs and created treatment plans. Dose-volume histograms were retrieved for relevant structures and volumes and dose metrics were derived and compared, e.g. target volumes and their concordance, dose homogeneity index (HI), treated and irradiated volumes, remaining volume at risk and relevant Vx and Dx values. Results. We found significant differences in target segmentation in the majority of the cases. The planning target volumes (PTVs) varied two- to four-fold and conformity indices were in the range of 0.3–0.6. This resulted in large variations in dose distributions to OARs as well as in treated and irradiated volumes even though the treatment plans showed good conformity to the PTVs. Potential reasons for the differences in target delineation were analysed. Conclusion. Considerations of the growing child and difficulties in interpretation of the radiotherapy information in the treatment protocols were identified as reasons for the variation. As a result, clarified translated detailed radiotherapy guidelines for paediatric/adolescent patients have been recognised as a way to reduce this variation.
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- 2013
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41. Testing the potential for improving quality of sediments impacted by mussel farms using bioturbating polychaete worms
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Marita Sundstein Carlsson, Marianne Holmer, Per Bergström, Jens Kjerulf Petersen, Mats Lindegarth, and Susanne Lindegarth
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0106 biological sciences ,Polychaete ,Nutrient cycle ,Ecology ,010604 marine biology & hydrobiology ,Biogeochemistry ,Sediment ,04 agricultural and veterinary sciences ,Mussel ,Aquatic Science ,Biology ,Sedimentation ,biology.organism_classification ,01 natural sciences ,Benthic zone ,040102 fisheries ,Hediste diversicolor ,0401 agriculture, forestry, and fisheries - Abstract
Biodeposits from farmed mussels severely influencethe biogeochemistry of sediments by increasing thelevels of organic matter (OM). Mitigation of suchnegative impacts is important for the developmentof sustainable aquaculture operations. As a steptowards developing methods for remediation ofcoastal sediments affected by mussel farming, theeffects of the polychaete, Hediste diversicolor wasevaluated experimentally. In a series of field- andlaboratory experiments we tested hypotheses aboutthe effects of polychaetes on sediment oxygen con-sumption, nutrient fluxes and sulphide pools underdifferent polychaete densities and sedimentationregimes. The experimental results support the ideathat polychaetes can mitigate negative effects onthe benthic environment beneath mussel farms.H. diversicolor oxidized the sediment and generallyenhanced the oxygen consumption, and thus thedecomposition of OM. The accumulation of porewater sulphides were reduced and fluxes of nutri-ents across the sediment-water interface increased.Additional calculations suggest that the effects ofpolychaetes were mainly indirect and driven byincreased microbial activity due to the borrowingactivity of the polychaetes. Trends of increasingdecomposition with increasing polychaete densitysuggest that the decomposition could be furtherenhanced by higher densities. Overall, we con-cluded that H. diversicolor is a potentially strongcandidate for remediation of mussel farm sedi-ments. The results show that sediments inhabitedby H. diversicolor have high assimilative capacityof OM and oxygen conditions are significantlyimproved following the addition of polychaetes atnaturally occurring densities. However, technologi-cal developments are needed in order to allow theapproach to be used in practice.Keywords: sediment remediation, oxygenconsumption, biogeochemistry, Hediste diversi-color, mussel faecesIntroductionAquaculture is well known to cause environmen-tal impacts due to increased sedimentation andaltered nutrient cycling (Holmer, Duarte, Heilskov,Olesen & Terrados 2003; Giles, Pilditch & Bell2006; Nizzoli, Welsh, Fano & Viaroli 2006;Richard, Archambault, Thouzeau, McKindsey D Robert, McKindsey, Chaillou A Callier, Richard, McKindsey, Archam-bault & Desrosiers 2009; Carlsson, Glud P Robert et al. 2013), which stimu-late O
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- 2017
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42. Radiotherapy induces an immediate inflammatory reaction in malignant glioma : a clinical microdialysis study
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Pedram Tabatabaei, Thomas Brännström, A. Tommy Bergenheim, Peter Siesjö, Edward Visse, and Per Bergström
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Glycerol ,Male ,Cancer Research ,Pathology ,medicine.medical_specialty ,Microdialysis ,Neurologi ,medicine.medical_treatment ,Clinical Neurology ,Glutamic Acid ,Inflammation ,Statistics, Nonparametric ,03 medical and health sciences ,0302 clinical medicine ,Glioma ,medicine ,Humans ,Cytokine ,Aged ,Aged, 80 and over ,Cancer och onkologi ,Radiotherapy ,business.industry ,CD68 ,Brain Neoplasms ,Middle Aged ,medicine.disease ,Radiation therapy ,Glucose ,Oncology ,Neurology ,030220 oncology & carcinogenesis ,Cancer and Oncology ,Clinical Study ,Immunohistochemistry ,Cytokines ,Female ,Neurology (clinical) ,medicine.symptom ,business ,Glioblastoma ,CD163 ,030217 neurology & neurosurgery - Abstract
The knowledge of response to radiation in the immuno-microenvironment of high grade gliomas is sparse. In vitro results have indicated an inflammatory response of myeloid cells after irradiation. Therefore, microdialysis was used to verify whether this is operative in tumor tissue and brain adjacent to tumor (BAT) after clinical radiotherapy of patients with high grade glioma. Stereotactic biopsies and implantation of microdialysis catheters in tumor tissue and BAT were performed in eleven patients with high-grade glioma. The patients were given daily radiation fractions of 2–3.4 Gy. Microdialysis samples were collected before radiotherapy and during the first five days of radiation. Cytokines, glucose metabolites, glutamate and glycerol were analyzed. Immunohistochemistry was performed to detect macrophages (CD68) and monocytes (CD163) as well as IL-6, IL-8 and MCP-1. A significant increase of IL-8, MCP-1 and MIP-1a were detected in tumor tissue already after the first dose of radiation and increased further during 5 days of radiation. IL-6 did also increase but after five fractions of radiation. In BAT, the cytokine response was modest with significant increase of IL-8 after third dose of radiation. We found a positive correlation between baseline IL-8 and IL-6 microdialysis levels in tumor tissue and survival. Glucose metabolites or glycerol and glutamate did not change during radiation. In all tumors staining for macrophages was demonstrated. IL-6 was found in viable tumor cells while MCP-1 was demonstrated in macrophages or tumor matrix. Our findings suggest that radiation induces a rapid enhancement of the prevailing inflammation in high-grade glioma tissue. The microdialysis technique is feasible for this type of study and could be used to monitor metabolic changes after different interventions. Electronic supplementary material The online version of this article (doi:10.1007/s11060-016-2271-1) contains supplementary material, which is available to authorized users.
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- 2017
43. Computational high-throughput screening of fluid permeability in heterogeneous fiber materials
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Charlotta Hanson, Tobias Gebäck, Per Bergström, Magnus Röding, Niklas Lorén, Erich Schuster, Katarina Logg, and Malin Lundman
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Diffusion ,Isotropy ,Lattice Boltzmann methods ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Volume (thermodynamics) ,Permeability (electromagnetism) ,Volume fraction ,Fiber ,Composite material ,0210 nano-technology ,Porous medium - Abstract
We explore computational high-throughput screening as a design strategy for heterogeneous, isotropic fiber materials. Fluid permeability, a key property in the design of soft porous materials, is systematically studied using a multi-scale lattice Boltzmann framework. After characterizing microscopic permeability as a function of solid volume fraction in the microstructure, we perform high-throughput computational screening of in excess of 35 000 macrostructures consisting of a continuous bulk interrupted by spherical/elliptical domains with either lower or higher microscopic permeability (hence with two distinct microscopic solid volume fractions and therefore two distinct microscopic permeabilities) to assess which parameters determine macroscopic permeability for a fixed average solid volume fraction. We conclude that the fractions of bulk and domains and the distribution of solid volume fraction between them are the primary determinants of macroscopic permeability, and that a substantial increase in permeability compared to the corresponding homogenous material is attainable.
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- 2016
44. Efficient computation of the Gauss-Newton direction when fitting NURBS using ODR
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Inge Söderkvist, Ove Edlund, and Per Bergström
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Mathematical optimization ,Computer Networks and Communications ,Applied Mathematics ,Computational mathematics ,Least squares ,Levenberg–Marquardt algorithm ,Overdetermined system ,Computational Mathematics ,symbols.namesake ,Data point ,Jacobian matrix and determinant ,symbols ,Curve fitting ,Applied mathematics ,Computational problem ,Software ,Mathematics - Abstract
We consider a subproblem in parameter estimation using the Gauss-Newton algorithm with regularization for NURBS curve fitting. The NURBS curve is fitted to a set of data points in least-squares sense, where the sum of squared orthogonal distances is minimized. Control-points and weights are estimated. The knot-vector and the degree of the NURBS curve are kept constant. In the Gauss-Newton algorithm, a search direction is obtained from a linear overdetermined system with a Jacobian and a residual vector. Because of the properties of our problem, the Jacobian has a particular sparse structure which is suitable for performing a splitting of variables. We are handling the computational problems and report the obtained accuracy using different methods, and the elapsed real computational time. The splitting of variables is a two times faster method than using plain normal equations.
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- 2012
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45. Interaction between classification detail and prediction of community types: implications for predictive modelling of benthic biotopes
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Genoveva Gonzalez-Mirelis, Mats Lindegarth, and Per Bergström
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0106 biological sciences ,Biotope ,Geography ,Ecology ,Benthic zone ,010604 marine biology & hydrobiology ,Aquatic Science ,010603 evolutionary biology ,01 natural sciences ,Ecology, Evolution, Behavior and Systematics ,Predictive modelling ,Community types - Published
- 2011
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46. Shape verification aimed for manufacturing process control
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Sara Rosendahl, Per Bergström, and Mikael Sjödahl
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Surface (mathematics) ,Computer science ,Manufacturing process ,business.industry ,Mechanical Engineering ,Control (management) ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Computational mathematics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Image (mathematics) ,Fringe pattern ,Active shape model ,Computer vision ,Artificial intelligence ,Electrical and Electronic Engineering ,Representation (mathematics) ,business - Abstract
We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 μ m . Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.
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- 2011
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47. Uniaxial compression of three-dimensional entangled fibre networks: impacts of contact interactions
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Tetsu Uesaka, Shakhawath Hossain, and Per Bergström
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010302 applied physics ,chemistry.chemical_classification ,Textile ,Materials science ,Deformation (mechanics) ,business.industry ,Fiber network ,Uniaxial compression ,02 engineering and technology ,Polymer ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Computer Science Applications ,chemistry ,Mechanics of Materials ,Modeling and Simulation ,0103 physical sciences ,General Materials Science ,Composite material ,0210 nano-technology ,business ,Anisotropy - Abstract
This paper concerns uniaxial compression of anisotropic fibre network, as typically seen in the end use of nonwoven and textile fibre assemblies. The constitutive relationship and deformation mecha ...
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- 2018
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48. Repeated surface registration for on-line use
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Inge Söderkvist, Ove Edlund, and Per Bergström
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Surface (mathematics) ,Mathematical optimization ,Matching (graph theory) ,Mechanical Engineering ,Iterative closest point ,Grid ,Data structure ,Industrial and Manufacturing Engineering ,Computer Science Applications ,Regular grid ,Control and Systems Engineering ,Line (geometry) ,Point (geometry) ,Algorithm ,Software ,Mathematics - Abstract
We consider the problem of matching sets of 3D points from a measured surface to the surface of a corresponding computer-aided design (CAD) object. The problem arises in the production line where the shape of the produced items is to be compared on-line with its pre-described shape. The involved registration problem is solved using the iterative closest point (ICP) method. In order to make it suitable for on-line use, i.e., make it fast, we pre-process the surface representation of the CAD object. A data structure for this purpose is proposed and named Distance Varying Grid tree. It is based on a regular grid that encloses points sampled from the CAD surfaces. Additional finer grids are added to the vertices in the grid that are close to the sampled points. The structure is efficient since it utilizes that the sampled points are distributed on surfaces, and it provides fast identification of the sampled point that is closest to a measured point. A local linear approximation of the surface is used for improving the accuracy. Experiments are done on items produced for the body of a car. The experiments show that it is possible to reach good accuracy in the registration and decreasing the computational time by a factor 700 compared with using the common kd-tree structure.
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- 2010
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49. Virtual projective shape matching in targetless CAD-based close-range photogrammetry for efficient estimation of specific deviations
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Mikael Sjödahl, Michael Fergusson, and Per Bergström
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0209 industrial biotechnology ,business.industry ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,General Engineering ,CAD ,02 engineering and technology ,Solid modeling ,Object (computer science) ,computer.software_genre ,3D modeling ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,020901 industrial engineering & automation ,Photogrammetry ,0103 physical sciences ,Computer Aided Design ,Computer vision ,Artificial intelligence ,business ,computer ,Projective geometry - Abstract
A concept for targetless, computer-aided design (CAD)-based, close-range photogrammetry for online shape inspection is introduced. The shape of an object, which is arbitrarily located on a conveyor belt, is to be measured and compared with its nominal shape as defined by a CAD model. For most manufactured objects, deviations are only measured at a few given comparison points. These deviations can be estimated using local photogrammetry based on a priori geometrical information given by the CAD model and the comparison points. Our method results in faster output with higher precision, because we do not generate a shape representation of the entire measured object using typical photogrammetric methods. Images depicting the object from convergent angles are captured by an array of cameras in a precalibrated network, and the CAD model is matched and aligned, within the projective geometry of the camera network, to the depicted object in the images without the use of targets. An algorithm for solving this virtual projective targetless shape matching problem is presented.
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- 2018
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50. Metabolomic Patterns in Glioblastoma and Changes during Radiotherapy: A Clinical Microdialysis Study
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Izabella Surowiec, Per Bergström, Carl Wibom, Mikael Johansson, A. Tommy Bergenheim, Lina Mörén, and Henrik Antti
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Treatment response ,Microdialysis ,Pathology ,medicine.medical_specialty ,medicine.medical_treatment ,Bioinformatics ,Biochemistry ,Catheters, Indwelling ,Conventional radiotherapy ,Metabolomics ,Extracellular fluid ,Tumor Microenvironment ,medicine ,Humans ,Least-Squares Analysis ,Brain Neoplasms ,Chemistry ,Computational Biology ,Reproducibility of Results ,Extracellular Fluid ,General Chemistry ,medicine.disease ,Radiation therapy ,ROC Curve ,Multivariate Analysis ,Metabolome ,Glioblastoma - Abstract
We employed stereotactic microdialysis to sample extracellular fluid intracranially from glioblastoma patients, before and during the first five days of conventional radiotherapy treatment. Microdialysis catheters were implanted in the contrast enhancing tumor as well as in the brain adjacent to tumor (BAT). Reference samples were collected subcutaneously from the patients' abdomen. The samples were analyzed by gas chromatography-time-of-flight mass spectrometry (GC-TOF MS), and the acquired data was processed by hierarchical multivariate curve resolution (H-MCR) and analyzed with orthogonal partial least-squares (OPLS). To enable detection of treatment-induced alterations, the data was processed by individual treatment over time (ITOT) normalization. One-hundred fifty-one metabolites were reliably detected, of which 67 were identified. We found distinct metabolic differences between the intracranially collected samples from tumor and the BAT region. There was also a marked difference between the intracranially and the subcutaneously collected samples. Furthermore, we observed systematic metabolic changes induced by radiotherapy treatment among both tumor and BAT samples. The metabolite patterns affected by treatment were different between tumor and BAT, both containing highly discriminating information, ROC values of 0.896 and 0.821, respectively. Our findings contribute to increased molecular knowledge of basic glioblastoma pathophysiology and point to the possibility of detecting metabolic marker patterns associated to early treatment response.
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- 2010
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