| 1. |
- Aabel, Lise, et al.
(författare)
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A TDD Distributed MIMO Testbed Using a 1-bit Radio-Over-Fiber Fronthaul Architecture
- 2024
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- We present the uplink and downlink of a time-division duplex distributed multiple-input multiple-output (D-MIMO) testbed, based on a 1-bit radio-over-fiber architecture, which is low cost and scalable. The proposed architecture involves a central unit (CU) that is equipped with 1-bit digital-to-analog and analog-to-digital converters, operating at 10 GS/s. The CU is connected to multiple single-antenna remote radio heads (RRHs) via optical fibers, over which a binary radio frequency (RF) waveform is transmitted. In the uplink, a binary RF waveform is generated at the RRHs by a comparator, whose inputs are the received RF signal and a suitably designed dither signal. In the downlink, a binary RF waveform is generated at the CU via bandpass sigma-delta modulation. Our measurement results show that low error-vector magnitude (EVM) can be achieved in both the uplink and the downlink, despite 1-bit sampling at the CU. Specifically, for point-to-point over-cable transmission between a single user equipment (UE) and a CU equipped with a single RRH, we report, for a 10-MBd signal using single-carrier (SC) 16 quadratic-amplitude modulation (QAM) modulation, an EVM of 3.3% in the downlink, and of 4.5% in the uplink. We then consider a CU connected to three RRHs serving over the air two UEs, and show that, after over-the-air reciprocity calibration, a downlink zero-forcing precoder designed on the basis of uplink channel estimates at the CU achieves an EVM of 6.4% and 10.9% at UE 1 and UE 2, respectively. Finally, we investigate the ability of the proposed architecture to support orthogonal frequency-division multiplexing (OFDM) waveforms, and its robustness against both in-band and out-of-band interference.
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| 2. |
- Aas, Wenche, et al.
(författare)
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Trends in Air Pollution in Europe, 2000–2019
- 2024
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Ingår i: Aerosol and Air Quality Research. - 2071-1409 .- 1680-8584. ; 24:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper encompasses an assessment of air pollution trends in rural environments in Europe over the 2000–2019 period, benefiting from extensive long-term observational data from the EMEP monitoring network and EMEP MSC-W model computations. The trends in pollutant concentrations align with the decreasing emission patterns observed throughout Europe. Annual average concentrations of sulfur dioxide, particulate sulfate, and sulfur wet deposition have shown consistent declines of 3–4% annually since 2000. Similarly, oxidized nitrogen species have markedly decreased across Europe, with an annual reduction of 1.5–2% in nitrogen dioxide concentrations, total nitrate in the air, and oxidized nitrogen deposition. Notably, emission reductions and model predictions appear to slightly surpass the observed declines in sulfur and oxidized nitrogen, indicating a potential overestimation of reported emission reductions. Ammonia emissions have decreased less compared to other pollutants since 2000. Significant reductions in particulate ammonium have however, been achieved due to the impact of reductions in SOx and NOx emissions. For ground level ozone, both the observed and modelled peak levels in summer show declining trends, although the observed decline is smaller than modelled. There have been substantial annual reductions of 1.8% and 2.4% in the concentrations of PM10 and PM2.5, respectively. Elemental carbon has seen a reduction of approximately 4.5% per year since 2000. A similar reduction for organic carbon is only seen in winter when primary anthropogenic sources dominate. The observed improvements in European air quality emphasize the importance of comprehensive legislations to mitigate emissions.
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| 3. |
- Abadikhah, Marie, 1992
(författare)
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Microbial communities in biological electrochemical systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological electrochemical systems (BES) can be used as biosensors and for recovery of resources from waste streams. BES utilizes microbial communities that grow on the surface of electrodes in the form of biofilms. Electrogenic bacteria residing in the anode biofilm initiate oxidation reactions, resulting in the release of electrons and subsequent electrical current generation. The electrons flow to the cathode where reduction reactions take place. Microbial biofilms may also be involved in the catalysis of cathode reactions. Many factors are involved in shaping the composition and performance of the microbial communities in BES, most of which remain poorly understood. In this thesis, the impact of electrode material and biotic interactions on performance and microbial community assembly was investigated in microbial electrolysis cells (MECs) oxidizing volatile fatty acids at the anode. MECs are a type of BES that require an applied electric potential to generate products such as H2, CH4, and acetate at the cathode. MECs with mixed-culture biofilms on both the anode and the cathode were studied. Two experiments were conducted. The first was a comparison of MECs with three different cathode materials: carbon nanoparticles, titanium, and steel. The second was a comparison of MECs with three different anode materials: carbon cloth, graphene, and nickel. Furthermore, the effect of dispersal limitation as well as the presence of viruses and their associations with microorganisms was investigated. MECs with carbon cloth anodes had the highest current density and shortest lag time during startup. In contrast, no significant impact of cathode material on MEC performance was seen. The anode communities were dominated by electrogens from the Desulfobacterota phylum, while the cathodes were dominated by methanogens from the Methanobacteriaceae family. Stochastic initial attachment by competing electrogens on the anode explained variations in the startup time between replicate MECs. In each experiment at least two different Desulfobacterota species competed for dominance on the anode. MECs that enabled dispersal between the system tended to have the same dominating taxa. Biotic interactions also affected the microbial communities in the system. Network analysis showed that the anode communities had a greater number of negative interactions between taxa compared to the cathode. Due to the need for direct contact by electrogens to transfer electrons to the anode, there is a higher competitive element to the colonization of the anode biofilm. Viral infection is another type of biotic interaction. Analysis of the prokaryotic and viral communities resulted in the identification of CRISPR-based and prophage virus-host associations, indicating previous infections and prophage inductions of electrochemically active microorganisms. These findings suggest that while there is selective pressure for electrogenic bacteria on the anode, stochastic factors, and biotic interactions play a larger role compared to electrode material in shaping the anode community.
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| 4. |
- Abarenkov, Kessy, et al.
(författare)
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The UNITE database for molecular identification and taxonomic communication of fungi and other eukaryotes: sequences, taxa and classifications reconsidered
- 2024
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Ingår i: Nucleic Acids Research. - 0305-1048 .- 1362-4962. ; 52:D1, s. D791-D797
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Tidskriftsartikel (refereegranskat)abstract
- UNITE (https://unite.ut.ee) is a web-based database and sequence management environment for molecular identification of eukaryotes. It targets the nuclear ribosomal internal transcribed spacer (ITS) region and offers nearly 10 million such sequences for reference. These are clustered into similar to 2.4M species hypotheses (SHs), each assigned a unique digital object identifier (DOI) to promote unambiguous referencing across studies. UNITE users have contributed over 600 000 third-party sequence annotations, which are shared with a range of databases and other community resources. Recent improvements facilitate the detection of cross-kingdom biological associations and the integration of undescribed groups of organisms into everyday biological pursuits. Serving as a digital twin for eukaryotic biodiversity and communities worldwide, the latest release of UNITE offers improved avenues for biodiversity discovery, precise taxonomic communication and integration of biological knowledge across platforms. Graphical Abstract
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| 5. |
- Abbasi, R., et al.
(författare)
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Search for Continuous and Transient Neutrino Emission Associated with IceCube's Highest-energy Tracks: An 11 yr Analysis
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 964:1
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Tidskriftsartikel (refereegranskat)abstract
- IceCube alert events are neutrinos with a moderate-to-high probability of having astrophysical origin. In this study, we analyze 11 yr of IceCube data and investigate 122 alert events and a selection of high-energy tracks detected between 2009 and the end of 2021. This high-energy event selection (alert events + high-energy tracks) has an average probability of >= 0.5 of being of astrophysical origin. We search for additional continuous and transient neutrino emission within the high-energy events' error regions. We find no evidence for significant continuous neutrino emission from any of the alert event directions. The only locally significant neutrino emission is the transient emission associated with the blazar TXS 0506+056, with a local significance of 3 sigma, which confirms previous IceCube studies. When correcting for 122 test positions, the global p-value is 0.156 and compatible with the background hypothesis. We constrain the total continuous flux emitted from all 122 test positions at 100 TeV to be below 1.2 x 10-15 (TeV cm2 s)-1 at 90% confidence assuming an E -2 spectrum. This corresponds to 4.5% of IceCube's astrophysical diffuse flux. Overall, we find no indication that alert events in general are linked to lower-energetic continuous or transient neutrino emission.
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| 6. |
- Abbasi, R., et al.
(författare)
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Search for decoherence from quantum gravity with atmospheric neutrinos
- 2024
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Ingår i: Nature Physics. - 1745-2481 .- 1745-2473. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Neutrino oscillations at the highest energies and longest baselines can be used to study the structure of spacetime and test the fundamental principles of quantum mechanics. If the metric of spacetime has a quantum mechanical description, its fluctuations at the Planck scale are expected to introduce non-unitary effects that are inconsistent with the standard unitary time evolution of quantum mechanics. Neutrinos interacting with such fluctuations would lose their quantum coherence, deviating from the expected oscillatory flavour composition at long distances and high energies. Here we use atmospheric neutrinos detected by the IceCube South Pole Neutrino Observatory in the energy range of 0.5-10.0 TeV to search for coherence loss in neutrino propagation. We find no evidence of anomalous neutrino decoherence and determine limits on neutrino-quantum gravity interactions. The constraint on the effective decoherence strength parameter within an energy-independent decoherence model improves on previous limits by a factor of 30. For decoherence effects scaling as E2, our limits are advanced by more than six orders of magnitude beyond past measurements compared with the state of the art. Interactions of atmospheric neutrinos with quantum-gravity-induced fluctuations of the metric of spacetime would lead to decoherence. The IceCube Collaboration constrains such interactions with atmospheric neutrinos.
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| 7. |
- Abbasi, R., et al.
(författare)
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Search for Galactic Core-collapse Supernovae in a Decade of Data Taken with the IceCube Neutrino Observatory
- 2024
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 1538-4357 .- 0004-637X. ; 961:1
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Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory has been continuously taking data to search for O(0.5–10) s long neutrino bursts since 2007. Even if a Galactic core-collapse supernova is optically obscured or collapses to a black hole instead of exploding, it will be detectable via the O(10) MeV neutrino burst emitted during the collapse. We discuss a search for such events covering the time between 2008 April 17 and 2019 December 31. Considering the average data taking and analysis uptime of 91.7% after all selection cuts, this is equivalent to 10.735 yr of continuous data taking. In order to test the most conservative neutrino production scenario, the selection cuts were optimized for a model based on an 8.8 solar mass progenitor collapsing to an O–Ne–Mg core. Conservative assumptions on the effects of neutrino oscillations in the exploding star were made. The final selection cut was set to ensure that the probability to detect such a supernova within the Milky Way exceeds 99%. No such neutrino burst was found in the data after performing a blind analysis. Hence, a 90% C.L. upper limit on the rate of core-collapse supernovae out to distances of ≈25 kpc was determined to be 0.23 yr−1. For the more distant Magellanic Clouds, only high neutrino luminosity supernovae will be detectable by IceCube, unless external information on the burst time is available. We determined a model-independent limit by parameterizing the dependence on the neutrino luminosity and the energy spectrum.
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| 8. |
- Abbondanza, Giuseppe, 1991, et al.
(författare)
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Au-Pd Barcode Nanowires with Tailored Lattice Parameters and Segment Lengths for Catalytic Applications
- 2024
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 7:4, s. 3861-3874
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present a systematic investigation of the controlled fabrication of Au-Pd barcode nanowires within nanoporous anodic aluminum oxide (NP-AAO) templates. By using a combination of in situ X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and transmission electron microscopy (TEM), we elucidate the influence of template preparation methods on the resulting nanowire properties. The template treatment, involving either pore widening or barrier layer thinning, significantly impacts nanowire growth. Through the analysis of the XRD data, we observe sequential deposition of Au and Pd segments with lattice parameter variations and strain effects. Particularly, the lattice parameters of Au and Pd segments display intricate temporal dependencies, influenced by interfacial effects and strain caused by growth under confinement. FIB-SEM imaging reveals uniform and reproducible nanowire lengths in the template treated with pore widening. Furthermore, TEM analysis confirms the presence of distinct Au and Pd segments, while scanning TEM-energy-dispersive X-ray spectroscopy revealed minor evidence of interdiffusion between the first and the second electrodeposited segments. Our findings emphasize the potential of the electrodeposition process within nanoporous templates for producing barcode nanowires with precise segmental properties. The combination of in situ XRD and electron microscopy offers valuable insights into the growth dynamics and structural characteristics of the fabricated Au-Pd barcode nanowires. This controlled fabrication strategy opens doors to tailoring nanowire properties for diverse applications, particularly in catalysis.
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| 9. |
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| 10. |
- Abedin, Raschid, et al.
(författare)
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Topological Lie Bialgebras, Manin Triples and Their Classification Over g[[x]]
- 2024
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Ingår i: Communications in Mathematical Physics. - 1432-0916 .- 0010-3616. ; 405:1
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Tidskriftsartikel (refereegranskat)abstract
- The main result of the paper is classification of topological Lie bialgebra structures on the Lie algebra g[[x]] , where g is a finite-dimensional simple Lie algebra over an algebraically closed field F of characteristic 0. We introduce the notion of a topological Manin pair (L,g[[x]]) and present their classification by relating them to trace extensions of F[[x]] . Then we recall the classification of topological doubles of Lie bialgebra structures on g[[x]] and view it as a special case of the classification of Manin pairs. The classification of topological doubles states that up to an appropriate equivalence there are only three non-trivial doubles. It is proven that topological Lie bialgebra structures on g[[x]] are in bijection with certain Lagrangian Lie subalgebras of the corresponding doubles. We then attach algebro-geometric data to such Lagrangian subalgebras and, in this way, obtain a classification of all topological Lie bialgebra structures with non-trivial doubles. For F= C the classification becomes explicit. Furthermore, this result enables us to classify formal solutions of the classical Yang–Baxter equation.
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