| 1. |
- Andersson, David A., et al.
(författare)
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TRPA1 mediates spinal antinociception induced by acetaminophen and the cannabinoid Delta(9)-tetrahydrocannabiorcol
- 2011
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- TRPA1 is a unique sensor of noxious stimuli and, hence, a potential drug target for analgesics. Here we show that the antinociceptive effects of spinal and systemic administration of acetaminophen (paracetamol) are lost in Trpa1(-/-) mice. The electrophilic metabolites N-acetyl-p-benzoquinoneimine and p-benzoquinone, but not acetaminophen itself, activate mouse and human TRPA1. These metabolites also activate native TRPA1 and, as a consequence, reduce voltage-gated calcium and sodium currents in primary sensory neurons. The N-acetyl-p-benzoquinoneimine metabolite l-cysteinyl-S-acetaminophen was detected in the mouse spinal cord after systemic acetaminophen administration. In the hot-plate test, intrathecal administration of N-acetyl-p-benzoquinoneimine, p-benzoquinone and the electrophilic TRPA1 activator cinnamaldehyde produced antinociception that was lost in Trpa1(-/-) mice. Intrathecal injection of a non-electrophilic cannabinoid, Delta(9)-tetrahydrocannabiorcol, also produced TRPA1-dependent antinociception in this test. Our study provides a molecular mechanism for the antinociceptive effect of acetaminophen and discloses spinal TRPA1 activation as a potential pharmacological strategy to alleviate pain.
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| 2. |
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| 3. |
- Hagey, Daniel W., et al.
(författare)
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Distinct transcription factor complexes act on a permissive chromatin landscape to establish regionalized gene expression in CNS stem cells
- 2016
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 26:7, s. 908-917
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Tidskriftsartikel (refereegranskat)abstract
- Spatially distinct gene expression profiles in neural stem cells (NSCs) are a prerequisite to the formation of neuronal diversity, but how these arise from the regulatory interactions between chromatin accessibility and transcription factor activity has remained unclear. Here, we demonstrate that, despite their distinct gene expression profiles, NSCs of the mouse cortex and spinal cord share the majority of their DNase I hypersensitive sites (DHSs). Regardless of this similarity, domain-specific gene expression is highly correlated with the relative accessibility of associated DHSs, as determined by sequence read density. Notably, the binding pattern of the general NSC transcription factor SOX2 is also largely cell type specific and coincides with an enrichment of LHX2 motifs in the cortex and HOXA9 motifs in the spinal cord. Interestingly, in a zebrafish reporter gene system, these motifs were critical determinants of patterned gene expression along the rostral-caudal axis. Our findings establish a predictive model for patterned NSC gene expression, whereby domain-specific expression of LHX2 and HOX proteins act on their target motifs within commonly accessible cis-regulatory regions to specify SOX2 binding. In turn, this binding correlates strongly with these DHSs relative accessibility-a robust predictor of neighboring gene expression.
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| 4. |
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| 5. |
- Alenmyr, Lisa, et al.
(författare)
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Effect of Mucosal TRPV1 Inhibition in Allergic Rhinitis.
- 2012
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Ingår i: Basic & Clinical Pharmacology & Toxicology. - : Wiley. - 1742-7843 .- 1742-7835. ; 110, s. 264-268
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Tidskriftsartikel (refereegranskat)abstract
- Transient receptor potential vanilloid-1 (TRPV1) has been implicated as a mediator of itch in allergic rhinitis. To address this possibility, we synthesized a TRPV1 blocker (SB-705498) for nasal administration in patients with seasonal allergic rhinitis. The pharmacological activity of SB-705498 was confirmed on human TRPV1-expressing HEK293 cells, using fluorometric calcium imaging, and in patients with allergic rhinitis subjected to nasal capsaicin challenges. The effect of SB-705498 was studied in patients with seasonal allergic rhinitis subjected to daily allergen challenges for seven days, using a double-blind, placebo-controlled, randomized and cross-over design. SB-705498 was delivered by nasal lavage 10 min. before each allergen challenge. Primary end-point was total nasal symptom score on days 5 to 7. Nasal peak inspiratory flow and eosinophil cationic protein content in nasal lavages were also monitored. Daily topical applications of SB-705498 at a concentration that inhibited capsaicin-induced nasal symptoms had no effect on total symptom score, nasal peak inspiratory flow and eosinophil cationic protein levels in allergen-challenged patients with seasonal allergic rhinitis. The individual symptom nasal itch or sneezes was also not affected. These findings may indicate that TRPV1 is not a key mediator of the symptoms in allergic rhinitis. However, additional studies, using drug formulations with a prolonged duration of action, should be conducted before TRPV1 is ruled out as a drug target in allergic rhinitis.
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| 6. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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A Survey of Secure Internet of Things in Relation to Blockchain
- 2020
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Ingår i: Journal of Internet Services and Information Security (JISIS). - Seoul, Republic of Korea : Innovative Information Science & Technology Research Group (ISYOU). - 2182-2069 .- 2182-2077. ; 10:3, s. 47-75
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Tidskriftsartikel (refereegranskat)abstract
- Distributed ledgers and blockchain technologies can improve system security and trustworthiness by providing immutable replicated histories of data. Blockchain is a linked list of blocks containing digitally signed transactions, a cryptographic hash of the previous block, and a timestamp stored in a decentralized and distributed network. The Internet of Things (IoT) is one of the application domains in which security based on blockchain is discussed. In this article, we review the structure and architectures of distributed IoT systems and explain the motivations, challenges, and needs of blockchain to secure such systems. However, there are substantial threats and attacks to blockchain that must be understood, as well as suitable approaches to mitigate them. We, therefore, survey the most common attacks to blockchain systems and the solutions to mitigate them, with the objective of assessing how malicious these attacks are in the IoT context.
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| 7. |
- Alizadeh, Morteza, 1987-
(författare)
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Architectural Aspects of Identification in Decentralized Systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High-level systems need identification techniques, where higher security and scalability are considered requirements. Identification plays a significant role in systems where smart electronic devices increase in zero trust and open environments like decentralized systems. Also, decentralization has emerged as one of the most exciting domains in recent years, again after the first Internet was invented. Besides, decentralization in identification systems has gained popularity worldwide since cryptocurrencies became part of businesses. Distributed Ledger Technology (DLT) and Distributed Hash Tables (DHT) can be appropriate decentralized solutions that improve identification to be much more secure, scalable, and trustworthy.The decentralized nature of DLT and DHT ensures no single point of failure, making them highly resilient to attacks. Blockchain as a DLT solution can help devices communicate with each other securely and trustably by storing an immutable history of transactions, providing an additional layer of security to identification systems. DHT senable applications to keep files and information immutable in a decentralized manner. DHTs ensure that the data is replicated across multiple nodes, making it highly resilient to data loss. Moreover, mitigating high storage costs without memory limitations is the target of these technologies. In this context, a decentralized system paradigm that combines systems with DLT and DHTs can be highly beneficial.This thesis argues for such a paradigm, and the contributions include introducing the term decentralized networks and architectures and demonstrating the feasibility of using blockchain as a DLT solution in real-world scenarios. These scenarios can be applied to the Internet of Things (IoT) or other Peer to Peer networked systems. We explore different architectures in various systems and analyze the interaction in blockchain. This thesis contributes to developing decentralized identification systems that provide users’ trust in an open environment. It presents the challenges associated with decentralized identification, including registry and storage issues, and proposes solutions using DLT and DHT. The immutability of DLT and DHTs provides fast and secure solutions for decentralized identification systems. In particular, we show that a DHT-based architecture is feasible to maintain decentralization while avoiding memory constraints. However, there is still room for improvement in terms of performance. Our investigation shows that combining DHTs with blockchain in decentralized identifiers improves performance.By concealing blocks in the private blockchain, we show that query performance is better than other DHT and public blockchain-based solutions without concealed information. Moreover, our results show that DHT performs better than the public blockchain for scenarios with many records.These findings highlight the importance of selecting the appropriate technology for decentralized identification systems, considering the specific use case and the number of records to be stored.We also consider different decentralized identification systems and platforms built based on the recommendation of W3C Decentralized Identifiers (DIDs). We found low-efficiency issues using this technology, resulting from leveraging public DLT in the data registry part of DIDs. That model has searching time problems if the DLT grows. Finally, this thesis helps to analyze these issues and find better solutions. By choosing the right technology, we can ensure that decentralized identifiers are efficient, secure, and scalable, which enables users to trust them in an open environment.
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| 8. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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Comparative Analysis of Decentralized Identity Approaches
- 2022
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Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 10, s. 92273-92283
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Tidskriftsartikel (refereegranskat)abstract
- Decentralization is essential when trust and performance must not depend on a single organization. Distributed Ledger Technologies (DLTs) and Decentralized Hash Tables (DHTs) are examples where the DLT is useful for transactional events, and the DHT is useful for large-scale data storage. The combination of these two technologies can meet many challenges. The blockchain is a DLT with immutable history protected by cryptographic signatures in data blocks. Identification is an essential issue traditionally provided by centralized trust anchors. Self-sovereign identities (SSIs) are proposed decentralized models where users can control and manage their identities with the help of DHT. However, slowness is a challenge among decentralized identification systems because of many connections and requests among participants. In this article, we focus on decentralized identification by DLT and DHT, where users can control their information and store biometrics. We survey some existing alternatives and address the performance challenge by comparing different decentralized identification technologies based on execution time and throughput. We show that the DHT and machine learning model (BioIPFS) performs better than other solutions such as uPort, ShoCard, and BBID.
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| 9. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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Decentralized Identifiers using Distributed Ledger Technologies
- 2023
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Ingår i: 2023 IEEE Asia-Pacific Conference on Computer Science and Data Engineering (CSDE). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- Decentralized identification is an interesting topic for Internet-based systems. Although the use of centralized systems for identification is prevalent, there is still a need for decentralized identification systems that do not rely on a centralized entity. We propose using Distributed Ledger Technology (DLT) to fulfill the needs. Although DLT and Distributed Hash Table (DHT) can be used as technologies in Decentralized Identifiers (DIDs), immutability and the growth of transactions are still challenging. This paper investigates DIDs under the W3C standard and DLT-based technology as one of the solutions for verifiable data registries in DIDs. We evaluate our proposed solution by comparing three models wrt. query time for verifiable data registries. Our proposed architecture for data registry achieves better query time by concealing old transactions from the main DLT.
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| 10. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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DHT- and Blockchain-based Smart Identification for Video Conferencing
- 2022
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Ingår i: Blockchain: Research and Applications. - : Elsevier. - 2096-7209. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Video conferencing applications help people communicate via the Internet and provide a significant and consistent basis for virtual meetings. However, integrity, security, identification, and authentication problems are still universal. Current video conference technologies typically rely on cloud systems to provide a stable and secure basis for executing tasks and processes. At the same time, video conferencing applications are being migrated from centralized to decentralized solutions for better performance without the need for third-party interactions. This article demonstrates a decentralized smart identification scheme for video conferencing applications based on biometric technology, machine learning, and a decentralized hash table combined with blockchain technology. We store users' information on a distributed hash table and transactional events on the distributed ledger after identifying users by implementing machine learning functions. Furthermore, we leverage distributed ledger technology's immutability and traceability properties and distributed hash table unlimited storage feature to improve the system's storage capacity and immutability by evaluating three possible architectures. The experimental results show that an architecture based on blockchain and distributed hash table has better efficiency but needs a longer time to execute than the two other architectures using a centralized database.
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| 11. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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Efficient Decentralized Data Storage Based on Public Blockchain and IPFS
- 2020
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Ingår i: 2020 IEEE Asia-Pacific Conference on Computer Science and Data Engineering (CSDE). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- Blockchain technology has enabled the keeping of a decentralized, tamper-proof, immutable, and ordered ledger of transactional events. Efforts to leverage such a ledger may be challenging when data storage requirements exceed most blockchain protocols’ current capacities. Storing large amounts of decentralized data while maintaining system efficiency is the challenge that we target. This paper proposes using the IPFS distributed hash table (DHT) technology to store information immutably and in a decentralized manner to mitigate the high cost of storage. A storage system involving blockchain and other storage systems in concert should be based on immutable data and allow removal of data from malicious users in the DHT. Efficiency is improved by decreasing the overall processing time in the blockchain with the help of DHT technology and introducing an agreement service that communicate with the blockchain via a RESTful API. We demonstrate the applicability of the proposed method and conclude that the combination of IPFS and blockchain provides efficient cryptographic storage, immutable history and overall better efficiency in a decentralized manner.
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| 12. |
- Alizadeh, Morteza, 1987-, et al.
(författare)
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Performance Analysis of Verifiable Data Registry Solutions for Decentralized Identifiers
- 2022
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Ingår i: 2022 IEEE Asia-Pacific Conference on Computer Science and Data Engineering (CSDE). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- User identification in decentralized systems is a demanding task. Identification systems should work resiliently and have efficient performance. Moreover, identification systems should protect the data that they must store against hackers and saboteurs. Keeping a system with decentralized identification without any intervention in the middle has attracted attention to improve earlier centralized identification systems. Decentralized Identifiers (DIDs) constitute a solution for identification divided into different modules. The verifiable data registry is one of the main parts of this technology, which is distributed storage of identity properties. We analyze the decentralized identification data registry and compare the performance of verifiable data registry based on blockchain and the Distributed Hash Table (DHT) on different scales of systems. Our evaluation results show that DHT has better performance. Furthermore, a model based on DHT shows that in addition to immutable storage and faster query time, it makes systems handle or search in data storage with lower searching time compared to Ethereum Blockchain as another immutable secure technology. Finally, our results show that DHT is a better solution than other models in different scenarios. Although blockchain has promising results on a small scale, it still has problems with storage and query time in large-scale systems.
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| 13. |
- Altmann, Peter, et al.
(författare)
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Creating a Traceable Product Story in Manufacturing Supply Chains Using IPFS
- 2020
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Ingår i: 2020 IEEE 19th International Symposium on Network Computing and Applications (NCA). - Boston/New York : IEEE. ; , s. 11-18
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Konferensbidrag (refereegranskat)abstract
- Evolving traceability requirements increasingly challenge manufacturing supply chain actors to collect tamperproof and auditable evidence about what inputs they process, in what way these inputs are used, and what the resulting process outputs are. Traceability solutions based on blockchain technology have shown ways to satisfy the requirements of creating a tamper-proof and auditable trail of traceability data. However, the existing solutions struggle to meet the increasing storage requirements necessary to create an evidence trail using manufacturing data. In this paper, we show a way to create a tamper-proof and auditable evolving product story that uses a decentralized file system called the InterPlanetary File System (IPFS). We also show how using linked data can help auditors derive a traceable product story from such an accumulating evidence trail. The solution proposed herein can supplement existing blockchain-based traceability solutions and enable traceability in global manufacturing supply chains where forming a consortium incurs prohibitive costs and where storage requirements are high.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Andersson, Jenny, et al.
(författare)
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Att skapa läkare i glesbygd
- 2018
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Ingår i: Allmänmedicin : tidskrift för Svensk förening för allmänmedicin. - Stockholm : Svensk förening för allmänmedicin (SFAM). - 0281-3513 .- 2001-8169. ; :3, s. 26-27
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 18. |
- Andersson, Jan-Olov, 1966-
(författare)
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A GIS-based landscape analysis of dissolved organic carbon in boreal headwater streams
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In boreal catchments, stream water chemistry is influenced and controlled by several landscape factors. The influence of spatially distributed variables is in turn dependent on the hydrological scale. Headwater streams have larger variability of water chemistry, and thus together represent a large biodiversity, and therefore need to be monitored in official environmental assessments. One objective of this study was, using Geographical Information Systems (GIS), to analyse co-variation between landscape variables and water chemistry and to determine which of the landscape variables have a major influence on the concentration of dissolved organic carbon (DOC) in headwater streams. Another objective was to find a simple method for predicting sources of DOC, using official map data and publically available GIS applications. Totally 85 headwater catchments (0.1-4 km2) in the county of Värmland, western south Sweden, were used in the study. Water chemistry was analysed for water sampled at low, medium and high flows, and landscape variables were extracted from official map data sources: topographic maps, a digital elevation model (DEM, 50 m grid), and vegetation data. Statistical analyses showed that topography (mean slope and mean topographic wetness index (TWI)) and wetland cover often correlated well with DOC in headwater catchments. Official map data could satisfactorily extract landscape variables (mean slope, mean TWI) that were useful in predicting stream water chemistry (DOC). A high-resolution elevation model, which was generated by interpolation of photogrammetric data, was used to calculate and evaluate two different wetness indices and their ability to predict the occurrence of wetlands in six catchments of different sizes and topography. The SAGA (System for Automated Geoscientific Analyses) wetness index (SWI) gave substantially better results than the TWI. The effects of resolution of DEMs on calculations of the SWI were investigated using 5, 10, 25 and 50 m grids. The results showed that SWI values increased with increasing cell size. The near linear increment of mean values for resolutions 10-50 m suggests a independence of terrain type and catchment size, which supported previous findings that indicated that mean slope and mean wetness index calculated from coarse elevation models may be used for prediction of DOC in headwater streams.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Andersson, Jan-Olov, et al.
(författare)
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Kartering av översvämningsrisker vid Vänern
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna studie genomfördes en översvämningskartering och -analys som utgick från fyraextrema vattennivåer i Vänern. Baserat på höjddata från den Nya Nationella Höjdmodellen(NNH) generades utbredningspolygoner med hjälp av GIS för de fyra översvämningsnivåerna.Överlagringsanalyser gjordes sedan med kartskikt för väg, mark och byggnadersamt för vissa kommuner även befolkning för att urskilja vägsträckor, markområden,byggnader och boende inom översvämningsutbredningen vid de fyra nivåerna.Översvämningskartor togs fram i pdf-format och Google Earth-format. GIS-analysen hargenererat kvantitativa data för översvämmade vägsträckor, markytor antal byggnader etc.Vidare har en objektsbaserad analys genomförts utifrån kartmaterial och kommunala dataöver sårbara anläggningar och funktioner. Resultaten har sammanställts kommunvis ochför Vänerområdet i sin helhet i form av text, tabeller och diagram.Det som drabbas först vid en översvämning i Vänern är dels objekt som utifrån sinafunktioner ligger vattennära t.ex. fritidsanläggningar, men även viktiga vägar som E18 ochE45. Järnvägsträckan Göteborg-Karlstad-Stockholm översvämmas redan vid 100-årsnivån.Med stigande vattennivå drabbas allt fler objekt och samhällsviktiga funktioner. De städersom påverkas mest är Karlstad, Kristinehamn, Mariestad, Lidköping och Vänersborg.De direkta skadekostnaderna för en 100-årsnivå i Vänern har beräknats till 100-240 Mkr,där en möjlig vindeffekt kan ge ytterligare upp till 120 Mkr i skadekostnader. För endimensionerande nivå skulle skadekostnaderna bli av en helt annan storleksordning ochuppgå till ca 9,8 miljarder kr. Vid denna nivå skulle stora indirekta skador uppstå som viinte har haft möjlighet att värdera ekonomiskt. De största kostnaderna kan kopplas tillöversvämmade byggnader.I en absolut jämförelse med Mälaren av kvantitativa data för översvämmade vägar,markområden och antal byggnader är konsekvenserna vid Vänern något lägre.Studien genomfördes på uppdrag av och i samarbete medVänerkommunerna i samverkan omVänerns reglering.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Andersson, Jan-Olov, 1966-, et al.
(författare)
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Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; :22, s. 1965-1975
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the relation between water chemistry and functional landscape elements, spatial data sets of characteristics for 68 small (0·2–1·5 km2) boreal forest catchments in western central Sweden were analysed in a geographical information system (GIS). The geographic data used were extracted from official topographic maps. Water sampled four times at different flow situations was analysed chemically. This paper focuses on one phenomenon that has an important influence on headwater quality in boreal, coniferous forest streams: generation and export of dissolved organic carbon (DOC). It is known that wetland cover (bogs and fens) in the catchment is a major source of DOC. In this study, a comparison was made between a large number of headwater catchments with varying spatial locations and areas of wetlands. How this variation, together with a number of other spatial variables, influences the DOC flux in the streamwater was analysed by statistical methods. There were significant, but not strong, correlations between the total percentages of wetland area and DOC flux measured at a medium flow situation, but not at high flow. Neither were there any significant correlations between the percentage of wetland area connected to streams, nor the percentage of wetland area within a zone 50 m from the stream and the DOC flux. There were, however, correlations between catchment mean slope and the DOC flux in all but one flow situations. This study showed that, considering geographical data retrieved from official sources, the topography of a catchment better explains the variation in DOC flux than the percentage and locations of distinct wetland areas. This emphasizes the need for high-resolution elevation models accurate enough to reveal the sources of DOC found in headwater streams.
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| 31. |
- Andersson, Jan-Olov, 1966-, et al.
(författare)
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Using official map data on topography, wetlands and vegetation cover for prediction of stream water chemistry in boreal headwater catchments
- 2009
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 13, s. 537-549
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. A large part of the spatial variation of stream water chemistry can be related to inputs from headwater streams. In order to understand and analyse the dominant processes taking place in small and heterogeneous catchments, accurate data with high spatial and temporal resolution is necessary. In most cases, the quality and resolution of available map data are considered too poor to be used in environmental assessments and modelling of headwater stream chemistry. In this study 18 forested catchments (1–4 km2) were selected within a 120×50 km region in the county of Värmland in western Sweden. The aim was to test if topographic and vegetation variables derived from official datasets were correlated to stream water chemistry, primarily the concentration of dissolved organic carbon (DOC), but also Al, Fe and Si content. GIS was used to analyse the elevation characteristics, generate topographic indices, and calculate the percentage of wetlands and a number of vegetation classes. The results clearly show that topography has a major influence on stream water chemistry. There were strong correlations between mean slope and percentage wetland, percentage wetland and DOC, mean slope and DOC, and a very strong correlation between mean topographic wetness index (TWI) and DOC. The conclusion was that official topographic data, despite uncertain or of low quality and resolution, could be useful in the prediction of headwater DOC-concentration in boreal forested catchments.
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| 32. |
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| 33. |
- Andersson, Joel
(författare)
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On Invertibility of the Radon Transform and Compressive Sensing
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contains three articles. The first two concern inversion andlocal injectivity of the weighted Radon transform in the plane. The thirdpaper concerns two of the key results from compressive sensing.In Paper A we prove an identity involving three singular double integrals.This is then used to prove an inversion formula for the weighted Radon transform,allowing all weight functions that have been considered previously.Paper B is devoted to stability estimates of the standard and weightedlocal Radon transform. The estimates will hold for functions that satisfy an apriori bound. When weights are involved they must solve a certain differentialequation and fulfill some regularity assumptions.In Paper C we present some new constant bounds. Firstly we presenta version of the theorem of uniform recovery of random sampling matrices,where explicit constants have not been presented before. Secondly we improvethe condition when the so-called restricted isometry property implies the nullspace property.
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| 34. |
- Andersson, Joel, et al.
(författare)
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On the Theorem of Uniform Recovery of Random Sampling Matrices
- 2014
-
Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 60:3, s. 1700-1710
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Tidskriftsartikel (refereegranskat)abstract
- We consider two theorems from the theory of compressive sensing. Mainly a theorem concerning uniform recovery of random sampling matrices, where the number of samples needed in order to recover an s-sparse signal from linear measurements (with high probability) is known to be m greater than or similar to s(ln s)(3) ln N. We present new and improved constants together with what we consider to be a more explicit proof. A proof that also allows for a slightly larger class of m x N-matrices, by considering what is called effective sparsity. We also present a condition on the so-called restricted isometry constants, delta s, ensuring sparse recovery via l(1)-minimization. We show that delta(2s) < 4/root 41 is sufficient and that this can be improved further to almost allow for a sufficient condition of the type delta(2s) < 2/3.
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| 35. |
- Andersson, Kristina E., et al.
(författare)
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Wholegrain oat diet changes the expression of genes associated with intestinal bile acid transport
- 2017
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Ingår i: Molecular Nutrition and Food Research. - : Wiley. - 1613-4125 .- 1613-4133. ; 61:7
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Tidskriftsartikel (refereegranskat)abstract
- Scope: The molecular mechanisms underlying the cholesterol-lowering properties of oats are only partly known. To study possible pathways involved, we investigated gene expressions in the liver and small intestine of mice fed oats. Method and results: Cholesterol and bile acids were analyzed in plasma and feces from LDL-receptor deficient (LDLr-/-) mice fed Western diet with wholegrain oats. A transcriptome analysis of mRNA from liver and jejunum was performed together with quantitative RT-PCR. Oat-fed mice had lower levels of plasma lipids and increased levels of bile acids and cholesterol in feces compared with controls. Two hundred thirty nine genes in jejunum and 25 genes in liver were differentially expressed (FDR corrected p < 0.05). The most affected biological process in jejunum was lipid biosynthesis and regulation. The apical sodium-dependent bile acid transporter (ASBT, Slc10a) and the intracellular bile acid binding protein (Fabp6) were both upregulated, whereas small heterodimer partner-1 (Shp-1) and apolipoprotein CII (Apoc2) were downregulated. Conclusions: Whole oats attenuated responses typically induced by high-fat diet. Increased expression of genes for intestinal bile acid uptake following oat consumption suggests retention in the gut lumen rather than decreased uptake capacity as cause for the increased bile acid excretion and the concomitant reduction of plasma cholesterol.
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| 36. |
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| 37. |
- Andersson, Martin, et al.
(författare)
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Betydelsen av unga och växande företag : En politik för ett mer dynamiskt näringsliv
- 2024
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Rapport (populärvet., debatt m.m.)abstract
- Syftet med denna rapport är att studera betydelsen av unga växande företag i Sverige underperioden 2003 till 2022. Vi studerar relationen mellan tillväxt i antal anställda och företagensålder och storlek med hjälp av registerdata över svenska privata aktiebolag. Mer specifiktbesvarar vi följande frågeställningar: Vilken betydelse har de unga företagen för jobbtillväxten i Sverige? Hur har nyföretagande och unga snabbväxande företag utvecklats över tid? Bör politiken fokusera på att stimulera framväxt av nya företag i Sverige och vilkareformer är effektiva för att utveckla ett dynamiskt näringsliv i Sverige med fler ungaväxande företag?
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| 38. |
- Andersson, Maria, et al.
(författare)
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Inhibition of kainic acid binding to glutamate receptors by extracts of Gastrodia
- 1995
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Ingår i: Phytochemistry. - 0031-9422. ; 38:4, s. 835-836
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Tidskriftsartikel (refereegranskat)abstract
- S-(4-hydroxybenzyl)glutathione was isolated as the major principle responsible for the inhibition of the in vitro binding of kainic acid to brain glutamate receptors by water extracts of the plant Gastrodia elata. The affinity (IC50 value) of the compound is slightly lower compared to glutamate and glutathione.
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| 39. |
- Andersson, Maria, et al.
(författare)
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Minor components with smooth muscle relaxing properties from scented myrrh (Commiphora guidotti)
- 1997
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Ingår i: Planta Medica. - : Georg Thieme Verlag KG. - 0032-0943 .- 1439-0221. ; 63:3, s. 251-254
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Tidskriftsartikel (refereegranskat)abstract
- All sesquiterpenes present in a sample of scented myrrh were isolated and characterised. Seven compounds, with cadinane, guaiane, oplopane, and eudesmane skeletons, were obtained, of which two are new and two are reported from a natural source for the first time. The major component, T-cadinol, has previously been shown to possess smooth muscle-relaxing properties, and the major purpose of the investigation was to compare the effects of the minor and more polar sesquiterpenes with that of T-cadinol in the rat aorta. Like T-cadinol, the minor sesquiterpenes are more efficient in reducing K(+)-induced contractions than those induced by the alpha-adrenoceptor agonist phenylephrine, however, they were all less potent than T-cadinol.
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| 40. |
- Andersson, Niklas, 1970, et al.
(författare)
-
A variant near the interleukin-6 gene is associated with fat mass in Caucasian men
- 2010
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 34:6, s. 1011-9
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: Regulation of fat mass appears to be associated with immune functions. Studies of knockout mice show that endogenous interleukin (IL)-6 can suppress mature-onset obesity. OBJECTIVE: To systematically investigate associations of single nucleotide polymorphisms (SNPs) near the IL-6 (IL6) and IL-6 receptor (IL6R) genes with body fat mass, in support for our hypothesis that variants of these genes can be associated with obesity. DESIGN AND STUDY SUBJECTS: The Gothenburg Osteoporosis and Obesity Determinants (GOOD) study is a population-based cross-sectional study of 18- to 20-year-old men (n=1049), from the Gothenburg area (Sweden). Major findings were confirmed in two additional cohorts consisting of elderly men from the Osteoporotic Fractures in Men (MrOS) Sweden (n=2851) and MrOS US (n=5611) multicenter population-based studies. MAIN OUTCOME: The genotype distributions and their association with fat mass in different compartments, measured with dual-energy X-ray absorptiometry. RESULTS: Out of 18 evaluated tag SNPs near the IL6 and IL6R genes, a recently identified SNP rs10242595 G/A (minor allele frequency=29%) 3' of the IL6 gene was negatively associated with the primary outcome total body fat mass (effect size -0.11 standard deviation (s.d.) units per A allele, P=0.02). This negative association with fat mass was also confirmed in the combined MrOS Sweden and MrOS US cohorts (effect size -0.05 s.d. units per A allele, P=0.002). When all three cohorts were combined (n=8927, Caucasian subjects), rs10242595(*)A showed a negative association with total body fat mass (effect size -0.05 s.d. units per A allele, P<0.0002). Furthermore, the rs10242595(*)A was associated with low body mass index (effect size -0.03, P<0.001) and smaller regional fat masses. None of the other SNPs investigated in the GOOD study were reproducibly associated with body fat. CONCLUSIONS: The IL6 gene polymorphism rs10242595(*)A is associated with decreased fat mass in three combined cohorts of 8927 Caucasian men.
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| 41. |
- Andersson, Niklas, 1970, et al.
(författare)
-
Variants of the interleukin-1 receptor antagonist gene are associated with fat mass in men
- 2009
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 33:5, s. 525-533
-
Tidskriftsartikel (refereegranskat)abstract
- Context: Immune functions seem to have connections to variations in body fat mass. Studies of knockout mice indicate that endogenous interleukin (IL)-1 can suppress mature-onset obesity. Objective: To systematically investigate our hypotheses that single- nucleotide polymorphisms (SNPs) and/or haplotypes variants in the IL-1 gene system are associated with fat mass. Subjects: The Gothenburg osteoporosis and obesity determinants (GOOD) study is a population-based cross-sectional study of 18-20 year-old men (n = 1068), from Gothenburg, Sweden. Major findings were confirmed in elderly men (n = 3014) from the Swedish part of the osteoporotic fractures in men (MrOS) multicenter population-based study. Main Outcome Measure: The genotype distributions and their association with body fat mass in different compartments, measured with dual-energy X-ray absorptiometry (DXA). Results: Out of 15 investigated SNPs in the IL-1 receptor antagonist (IL1RN) gene, a recently identified 30 untranslated region C4T (rs4252041, minor allele frequency 4%) SNP was associated with the primary outcome total fat mass (P = 0.003) and regional fat masses, but not with lean body mass or serum IL-1 receptor 1 (IL1RN) levels. This SNP was also associated with body fat when correcting the earlier reported IL1RN_2018 T4C (rs419598) SNP (in linkage disequilibrium with a well-studied variable number tandem repeat of 86 bp). The association between rs4252041 SNP and body fat was confirmed in the older MrOS population (P = 0.03). The rs4252041 SNP was part of three haplotypes consisting of five adjacent SNPs that were identified by a sliding window approach. These haplotypes had a highly significant global association with total body fat (P < 0.001). None of the other investigated members of the IL-1 gene family displayed any SNPs that have not been described previously to be significantly associated with body fat. Conclusions: The IL1RN gene, shown to enhance obesity by suppressing IL-1 effects in experimental animals, have no previously described gene polymorphisms and haplotypes that are associated with fat, but not lean mass in two populations of men. International Journal of Obesity (2009) 33, 525-533; doi: 10.1038/ijo.2009.47; published online 17 March 2009
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| 42. |
- Andersson, Olov, 1979-, et al.
(författare)
-
Deep Learning Quadcopter Control via Risk-Aware Active Learning
- 2017
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Ingår i: Proceedings of The Thirty-first AAAI Conference on Artificial Intelligence (AAAI). - : AAAI Press. - 9781577357841 ; , s. 3812-3818
-
Konferensbidrag (refereegranskat)abstract
- Modern optimization-based approaches to control increasingly allow automatic generation of complex behavior from only a model and an objective. Recent years has seen growing interest in fast solvers to also allow real-time operation on robots, but the computational cost of such trajectory optimization remains prohibitive for many applications. In this paper we examine a novel deep neural network approximation and validate it on a safe navigation problem with a real nano-quadcopter. As the risk of costly failures is a major concern with real robots, we propose a risk-aware resampling technique. Contrary to prior work this active learning approach is easy to use with existing solvers for trajectory optimization, as well as deep learning. We demonstrate the efficacy of the approach on a difficult collision avoidance problem with non-cooperative moving obstacles. Our findings indicate that the resulting neural network approximations are least 50 times faster than the trajectory optimizer while still satisfying the safety requirements. We demonstrate the potential of the approach by implementing a synthesized deep neural network policy on the nano-quadcopter microcontroller.
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| 43. |
- Andersson, Olov, 1979-, et al.
(författare)
-
Deep RL for Autonomous Robots: Limitations and Safety Challenges
- 2019
-
Ingår i: <em>ESANN 2019 - Proceedings, 27th European Symposium on Artificial Neural Networks, Computational Intelligence and Machine Learning</em>. - : ESANN. - 9782875870650 ; , s. 489-495
-
Konferensbidrag (refereegranskat)abstract
- With the rise of deep reinforcement learning, there has also been a string of successes on continuous control problems using physics simulators. This has lead to some optimism regarding use in autonomous robots and vehicles. However, to successful apply such techniques to the real world requires a firm grasp of their limitations. As recent work has raised questions of how diverse these simulation benchmarks really are, we here instead analyze a popular deep RL approach on toy examples from robot obstacle avoidance. We find that these converge very slowly, if at all, to safe policies. We identify convergence issues on stochastic environments and local minima as problems that warrant more attention for safety-critical control applications.
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| 44. |
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| 45. |
- Andersson, Olov
(författare)
-
Genetic analysis of ligand-receptor interactions in the TGF-beta superfamily during early embryonic development
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During early development, cells differentiate and acquire specific fates according to their position in concentration gradients of morphogens. These substances often spread from a local region, termed an organizer, and exert different effects at distinct thresholds. The transforming growth factor beta (TGF-β) superfamily comprises more than 30 factors that have previously been shown to induce specific cell-types and to act as morphogens. The work presented here identified critical roles for ligand-receptor interactions within the TGF-β superfamily during formation and functioning of organizing centers in the mouse embryo. TGF-β ligands bind and signal through a heteromeric receptor complex consisting of type I and type II receptors. Although most of the TGF-β ligands were identified more than ten years ago, interactions with their cognate receptors remain largely unknown. The number of ligands exceeds the number of receptors, indicating the existence of redundancy among the ligands. Indeed, in vitro experiments performed during the course of these studies revealed that three ligands, Nodal, GDFI, and GDF3 could all signal through the type 1 receptors ALK4 and ALK7 in a complex with the type II receptors Acvr2 and Acvr2b. The most critical time during embryogenesis is prior to- and during gastrulation, which is a phase of development that is characterized by extensive cell migration and morphological change. Data presented here show that, in the pre-gastrulation embryo, GDF1 and GDF3 cooperate during formation of anterior visceral endoderm, a tissue that is responsible for initiation of the anterior-posterior axis and forebrain induction. At gastrulation, GDF1 and GDF3 was shown to synergize with Nodal during the specific allocation of mesendoderm precursors into prechordal plate and foregut endoderm, tissues that are necessary for maintenance of the anterior axis and forebrain identity. Despite the ability of these ligands to signal through both ALK4 and ALK7 in vitro, analysis of compound mutants indicated that ALK4, but not ALK7, was responsible for anterior axis development. Since these three ligands have overlapping expression patterns and signal through a common pathway, it was not surprising that functional redundancy occurred at multiple sites, as revealed by genetic interactions in mutant mice. Thus, Nodal, GDF1 and GDF3 form a robust signaling network of major importance during early embryonic development. Given the high degree of convergence on a limited set of receptors, this mode of action may be widespread among other members of the TGF-β superfamily. Subsequent to gastrulation, during which the basic body plan is set up, elongation and regionalization of the embryo is coordinated by structures in the tail bud. GDF11 is a ligand that is expressed in the tail bud, and has been shown to affect these processes in a dosedependent manner by signaling through Acvr2b, although the identity of the corresponding type I receptor was unknown. Therefore, several distinct biochemical assays were undertaken to examine ligand binding and signaling properties, and complemented with in vivo experiments to establish physiological relevance. Despite in vitro evidence showing that GDF11 can signal promiscuously, signaling specificity was revealed in vivo by a genetic interaction between Alk5 and Acvr2b, which resulted in an enhanced homeotic transformation. Thus, functional specificity was only observed when taking a genetic approach to a mechanistic question. Taken together, this thesis provides insight into the mechanisms by which TGF-β ligands cooperate and are functionally integrated during embryonic development.
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| 46. |
- Andersson, Olov, 1979-
(författare)
-
Learning to Make Safe Real-Time Decisions Under Uncertainty for Autonomous Robots
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Robots are increasingly expected to go beyond controlled environments in laboratories and factories, to act autonomously in real-world workplaces and public spaces. Autonomous robots navigating the real world have to contend with a great deal of uncertainty, which poses additional challenges. Uncertainty in the real world accrues from several sources. Some of it may originate from imperfect internal models of reality. Other uncertainty is inherent, a direct side effect of partial observability induced by sensor limitations and occlusions. Regardless of the source, the resulting decision problem is unfortunately computationally intractable under uncertainty. This poses a great challenge as the real world is also dynamic. It will not pause while the robot computes a solution. Autonomous robots navigating among people, for example in traffic, need to be able to make split-second decisions. Uncertainty is therefore often neglected in practice, with potentially catastrophic consequences when something unexpected happens. The aim of this thesis is to leverage recent advances in machine learning to compute safe real-time approximations to decision-making under uncertainty for real-world robots. We explore a range of methods, from probabilistic to deep learning, as well as different combinations with optimization-based methods from robotics, planning and control. Driven by applications in robot navigation, and grounded in experiments with real autonomous quadcopters, we address several parts of this problem. From reducing uncertainty by learning better models, to directly approximating the decision problem itself, all the while attempting to satisfy both the safety and real-time requirements of real-world autonomy.
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| 47. |
- Andersson, Olov, 1979-
(författare)
-
Methods for Scalable and Safe Robot Learning
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Robots are increasingly expected to go beyond controlled environments in laboratories and factories, to enter real-world public spaces and homes. However, robot behavior is still usually engineered for narrowly defined scenarios. To manually encode robot behavior that works within complex real world environments, such as busy work places or cluttered homes, can be a daunting task. In addition, such robots may require a high degree of autonomy to be practical, which imposes stringent requirements on safety and robustness. \setlength{\parindent}{2em}\setlength{\parskip}{0em}The aim of this thesis is to examine methods for automatically learning safe robot behavior, lowering the costs of synthesizing behavior for complex real-world situations. To avoid task-specific assumptions, we approach this from a data-driven machine learning perspective. The strength of machine learning is its generality, given sufficient data it can learn to approximate any task. However, being embodied agents in the real-world, robots pose a number of difficulties for machine learning. These include real-time requirements with limited computational resources, the cost and effort of operating and collecting data with real robots, as well as safety issues for both the robot and human bystanders.While machine learning is general by nature, overcoming the difficulties with real-world robots outlined above remains a challenge. In this thesis we look for a middle ground on robot learning, leveraging the strengths of both data-driven machine learning, as well as engineering techniques from robotics and control. This includes combing data-driven world models with fast techniques for planning motions under safety constraints, using machine learning to generalize such techniques to problems with high uncertainty, as well as using machine learning to find computationally efficient approximations for use on small embedded systems.We demonstrate such behavior synthesis techniques with real robots, solving a class of difficult dynamic collision avoidance problems under uncertainty, such as induced by the presence of humans without prior coordination. Initially using online planning offloaded to a desktop CPU, and ultimately as a deep neural network policy embedded on board a 7 quadcopter.
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| 48. |
- Andersson, Olov, 1979-, et al.
(författare)
-
Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization
- 2015
-
Ingår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI). - : AAAI Press. - 9781577356981 ; , s. 2497-2503
-
Konferensbidrag (refereegranskat)abstract
- Reinforcement learning for robot control tasks in continuous environments is a challenging problem due to the dimensionality of the state and action spaces, time and resource costs for learning with a real robot as well as constraints imposed for its safe operation. In this paper we propose a model-based reinforcement learning approach for continuous environments with constraints. The approach combines model-based reinforcement learning with recent advances in approximate optimal control. This results in a bounded-rationality agent that makes decisions in real-time by efficiently solving a sequence of constrained optimization problems on learned sparse Gaussian process models. Such a combination has several advantages. No high-dimensional policy needs to be computed or stored while the learning problem often reduces to a set of lower-dimensional models of the dynamics. In addition, hard constraints can easily be included and objectives can also be changed in real-time to allow for multiple or dynamic tasks. The efficacy of the approach is demonstrated on both an extended cart pole domain and a challenging quadcopter navigation task using real data.
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| 49. |
- Andersson, Olov, 1979-, et al.
(författare)
-
Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization
- 2016
-
Ingår i: IEEE International Conference on Robotics and Automation (ICRA), 2016. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 4597-4604
-
Konferensbidrag (refereegranskat)abstract
- Robots are increasingly expected to move out of the controlled environment of research labs and into populated streets and workplaces. Collision avoidance in such cluttered and dynamic environments is of increasing importance as robots gain more autonomy. However, efficient avoidance is fundamentally difficult since computing safe trajectories may require considering both dynamics and uncertainty. While heuristics are often used in practice, we take a holistic stochastic trajectory optimization perspective that merges both collision avoidance and control. We examine dynamic obstacles moving without prior coordination, like pedestrians or vehicles. We find that common stochastic simplifications lead to poor approximations when obstacle behavior is difficult to predict. We instead compute efficient approximations by drawing upon techniques from machine learning. We propose to combine policy search with model-predictive control. This allows us to use recent fast constrained model-predictive control solvers, while gaining the stochastic properties of policy-based methods. We exploit recent advances in Bayesian optimization to efficiently solve the resulting probabilistically-constrained policy optimization problems. Finally, we present a real-time implementation of an obstacle avoiding controller for a quadcopter. We demonstrate the results in simulation as well as with real flight experiments.
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| 50. |
- Andersson, Olov, 1979-, et al.
(författare)
-
Real-Time Robotic Search using Structural Spatial Point Processes
- 2020
-
Ingår i: 35TH UNCERTAINTY IN ARTIFICIAL INTELLIGENCE CONFERENCE (UAI 2019). - : Association For Uncertainty in Artificial Intelligence (AUAI). ; , s. 995-1005
-
Konferensbidrag (refereegranskat)abstract
- Aerial robots hold great potential for aiding Search and Rescue (SAR) efforts over large areas, such as during natural disasters. Traditional approaches typically search an area exhaustively, thereby ignoring that the density of victims varies based on predictable factors, such as the terrain, population density and the type of disaster. We present a probabilistic model to automate SAR planning, with explicit minimization of the expected time to discovery. The proposed model is a spatial point process with three interacting spatial fields for i) the point patterns of persons in the area, ii) the probability of detecting persons and iii) the probability of injury. This structure allows inclusion of informative priors from e.g. geographic or cell phone traffic data, while falling back to latent Gaussian processes when priors are missing or inaccurate. To solve this problem in real-time, we propose a combination of fast approximate inference using Integrated Nested Laplace Approximation (INLA), and a novel Monte Carlo tree search tailored to the problem. Experiments using data simulated from real world Geographic Information System (GIS) maps show that the framework outperforms competing approaches, finding many more injured in the crucial first hours.
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