| 1. |
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2021 Vehicle Dynamics seminar
- 2021
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Editorial proceedings (other academic/artistic)abstract
- The seminar is held annually. The full title of this year's seminar was "2021 Vehicle Dynamics seminar -- for Future Mobility ...and not only Lateral".
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| 2. |
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| 3. |
- A, Lavanya, et al.
(author)
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Smart energy monitoring and power quality performance based evaluation of 100-kW grid tied PV system
- 2023
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In: Heliyon. - 2405-8440. ; 9:6
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Journal article (peer-reviewed)abstract
- Globally, the demand for energy from renewable sources is growing due to the increasing electricity consumption and the pollution of fossil fuels. The government has framed various policies to facilitate green energy generation, encouraging renewable energy source usage through PV installations in multiple sectors, including educational institutions. The primary objective of this paper is to propose a methodological approach for analysing the performance of the installed PV system on the rooftop of a university building in Tamil Nadu, India. The site selected is favourable for electricity generation from PV systems with an average global solar radiation of 5.82 kWh/m2day. Solar energy changes periodically with annual and daily variations and is not steady due to seasonal changes. The step-by-step performance assessment and the annual performance of the 100-kW solar PV system, which was instituted in 2019, with the forecasted parameters, are presented in this paper. Therefore, the assessment analysis is carried out in four phases: feasibility assessment, Energy yield assessment, Life cycle assessment, and Power quality assessment. To improve the solar PV output and efficiency, considering the solar irradiation, temperature, wind velocity, etc., PV yield is measured to evaluate the PV system's energy metrics. This paper also considers the carbon credits earned, solar power generated in the location, and the payback period. The power quality assessment is carried out in this paper to test the PV plant's compliance with effective grid integration.
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| 4. |
- Aabel, Lise, et al.
(author)
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A TDD Distributed MIMO Testbed Using a 1-bit Radio-Over-Fiber Fronthaul Architecture
- 2024
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In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; In Press
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Journal article (peer-reviewed)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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| 5. |
- Aabel, Lise, 1992, et al.
(author)
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Distributed Massive MIMO via all-Digital Radio Over Fiber
- 2020
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In: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 319-323
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Conference paper (peer-reviewed)abstract
- A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed.
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| 6. |
- Aaboen, Lise, 1978, et al.
(author)
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Relationship development patterns of university-based start-ups
- 2021
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In: A Research Agenda for the Entrepreneurial University. ; , s. 207-228
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Book chapter (other academic/artistic)abstract
- In the present chapter, we focus on how start-ups become embedded in the university and industry context(s) in order to suggest a research agenda for a more systemic approach to university and industry actors when studying start-up development in entrepreneurial universities. More specifically, the story should not end in business formation but an entrepreneurial university also has roles in the further development of start-ups originating both from the university and industry. We base our suggested research agenda on a case study of the automotive and transport cluster in Western Sweden, which is established as both an academic context and an industry context. We relied both on secondary data about the case as such as well as primary data about the relationship development patterns of the 9 start-ups in the cluster. We identified 5 different patterns of how start-ups become embedded. Arguing that the development and success of university-based start-ups have to be understood in terms of how they embed in their context(s) entails several important implications for further studies connected to additional details of the development patterns, the roles universities play in the networking and embedding of start-ups and the design of collaborative platforms for collaboration between various actors.
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| 7. |
- Aadland, Torgeir, et al.
(author)
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Levelling the playing field: Could entrepreneurship education compensate the lack of entrepreneurial pedigree and prior experience?
- 2022
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Conference paper (other academic/artistic)abstract
- Questions we care about: In the last four decades, the importance of entrepreneurship education for societal renewal has seen a dramatic rise. Policy arguments state that to spur economic development, a more entrepreneurially oriented workforce is needed. To increase our understanding of how entrepreneurship education impacts entrepreneurial careers, the purpose of this paper is to investigate how entrepreneurship education, in the form of venture creation programs (VCPs), mitigate or surpass a lack of entrepreneurial career antecedents, such as entrepreneurial pedigree or prior entrepreneurial experience. We ask: What role do VCPs play in the subsequent career choice of graduates regarding career impact relative to prior entrepreneurial experience and entrepreneurial pedigree? Approach: This paper investigates the role of VCPs, entrepreneurial pedigree, and prior entrepreneurial experience regarding early career choice. A broad perspective of entrepreneurial career is considered, across four occupational forms: self-employed, entrepreneurial employment (intrapreneur), hybrid (self-employed and employed in parallel), and conventional employment. To investigate career choice, data from graduates of VCPs at three universities in Northern Europe was collected through an online survey. Questions addressed graduate background prior to education, yearly occupational employment subsequent to graduation, and graduates’ own perception of entrepreneurial activity in employment positions. The survey was sent to 1326 graduates (total graduate population = 1568) and received 692 responses (52.2% response rate). Results: The educational context of VCPs, whether Ind-VCP or Corp-VCP, mitigated prior entrepreneurial experience. Although prior entrepreneurial experience interacted with Ind-VCP in making a career as self-employed more likely, this was not the case for Corp-VCP, in subsequently choosing intrapreneurial careers. Entrepreneurial pedigree had no significant effect on career choice other than for hybrid careers. Implications: Entrepreneurial experience gained from VCPs seems to influence graduates towards future entrepreneurial careers. For some, a VCP is the first entrepreneurial experience, while others are building existing entrepreneurial experiences. Evidence supports the conclusion that many VCP graduates lacking prior entrepreneurial experience instead develop entrepreneurial competencies (knowledge, skills, and judgmental abilities) through the program, which prepares them to engage in subsequent entrepreneurial careers. For policy and practice, entrepreneurship education can level the playing field for students aspiring to an entrepreneurial career but lacking prior entrepreneurial experience or entrepreneurial pedigree. This is an important insight when considering the need to spur innovativeness among businesses transitioning towards sustainable futures and/or recouping from the economic downturns created and perpetuated by the pandemic. Our evidence illustrates that action-based, contextualized education in entrepreneurship creates graduates that engage either as self-employed or as change agents (working with initiating and developing new opportunities) in established businesses. Value/Originality: This study offers novel evidence that entrepreneurship education can level the playing field for students preparing for entrepreneurial careers but lacking prior entrepreneurial experience or an entrepreneurial pedigree.
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| 8. |
- Aadland, Torgeir, et al.
(author)
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Mitigating the lack of prior entrepreneurial experience and exposure through entrepreneurship education programs
- 2023
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In: International Journal of Entrepreneurial Behaviour and Research. - 1355-2554. ; 30:11, s. 19-44
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Journal article (peer-reviewed)abstract
- Purpose : To increase the understanding of how entrepreneurship education impacts entrepreneurial careers, the purpose of the paper is to investigate the role that a venture creation program (VCP) might have in mitigating or surpassing a lack of other antecedents of entrepreneurial careers. In particular, the authors focus on entrepreneurial pedigree and prior entrepreneurial experience. Design/methodology/approach : Data from graduates of VCPs at three universities in Northern Europe were collected through an online survey. Questions addressed graduate background prior to education, yearly occupational employment subsequent to graduation and graduates' own perceptions of entrepreneurial activity in employment positions. The survey was sent to 1,326 graduates and received 692 responses (52.2% response rate). Findings : The type of VCP, either independent (Ind-VCP) or corporate venture creation (Corp-VCP), influenced the mitigation of prior entrepreneurial experience. Prior entrepreneurial experience, together with Ind-VCP, made a career as self-employed more likely. However, this was not the case for Corp-VCP in subsequently choosing intrapreneurial careers. Entrepreneurial pedigree had no significant effect on career choice other than for hybrid careers. Research limitations/implications : Entrepreneurial experience gained from VCPs seems to influence graduates toward future entrepreneurial careers. Evidence supports the conclusion that many VCP graduates who lack prior entrepreneurial experience or entrepreneurial pedigree can develop sufficient entrepreneurial competencies through the program. Originality/value : This study offers novel evidence that entrepreneurship education can compensate for a lack of prior entrepreneurial experience and exposure for students preparing for entrepreneurial careers.
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| 9. |
- Aadland, Torgeir, et al.
(author)
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The gender gap in entrepreneurship: The role of the relative pay off from entrepreneurship
- 2022
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In: RENT Proceedings. - 2219-5572. ; 2022
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Conference paper (peer-reviewed)abstract
- Objectives Entrepreneurship education garners increasing interest, with current trends showing a greater number of women applying. However, less is known about how attendees experience the use of their education post-education in general, in regard to the relative pay-off in graduates’ subsequent careers. Similarly, the extent to which applied entrepreneurial competencies gained may differentiate in careers of women compared to men is also understudied. Research on the distinct gender populations, focusing on occupational differences have limited space in literature. The objective of this paper is to investigate the career metrics in income and work-life balance, comparing and contrasting a population of entrepreneurship education graduates, along gender lines. Literature review Literature points an underlying gender bias in entrepreneurship, where opportunity-based entrepreneurial careers and self-concept of an entrepreneur has predominantly been studied from a male perspective. For example, studies have highlighted aspects of gender bias towards women engaging in opportunity-based entrepreneurship such as difficulty in obtaining necessary funding for growth, challenges in accessing entrepreneurial networks, lower levels of self-belief and self-efficacy regarding entrepreneurial activity, differences in education, and imbalance in work expectations relative to home life. However, these studies have predominantly focused on a new firm formation definition of entrepreneurship. The utilization of entrepreneurial competencies, as developed through entrepreneurship education that focuses on experience- and reflection-based approaches to learning, have in recent studies shown to be equally important for intrapreneurs as self-employed entrepreneurs. This reflects the broader contextual spread of applied entrepreneurial competence in graduate careers. The entrepreneurial careers of the female graduates who engage in ideation and implementation of new business activity after an entrepreneurship education, may it be in firm formation or in employed roles, remains understudied. Therefore, the question is raised: What is the relative pay-off (i.e., income and work-life balance) of entrepreneurship in relation to occupational choice and gender for graduates of entrepreneurship educations? Approach/Method Alumni from three master-level venture creation programs at three universities in Northern Europe were contacted for this study. From a total population of 1103 (graduating between 1997-2018),531 graduates responded, resulting in a response rate of 48.1 percent. The gender distribution in the total population is 28.5 percent female, and within the respondent sample it is 29.5 percent female. Two dimensions of career progress: income and work-life balance, was then analyzed with a set of dependent variables and control variables in ordinal regression. These regressors include career start-up experience and to what extent ideation and implementation of new business activity in employed occupations impacts the independent variables. Models are based on separate regressions on men and women with the purpose to highlight gendered differences in career progression and what regressors contributes to this. Results/Findings The findings were divided into separate sets by the two dependent variables, income and work-life balance. For income levels, career length is shared by both men and women as being a strong predictor. Beyond that, the regression analysis gives different versions for women and men of what contributes to a high income. Men in paid employment (as conventional employees or intrapreneurs) earns more than their self-employed and hybrid (combining employment and self-employment) peers. For women, there is no significant differences among the occupations. For both genders, type of industry is also influential towards the income level. Work-life balance generated regressions that points towards small influences of the regressors for women. For men, having a partner indicates a higher work-life balance, which is not significant for women. Also, having less work related to entrepreneurial competencies (i.e., being conventional employed), results in a more positive work-life balance. Value & Implications Entrepreneurship education is shown to have many positive impacts on subsequent careers. However, entrepreneurial competencies developed through education do not appear to counteract the general gender differences seen in society, as differentiation between male and female graduates is evident through the study. Where previous research has focused on studying these differences, this study instead focuses on how income and work-life balance unfolds across gender categories of venture creation program graduates. These programs have shown to produce graduates who have developed and later utilized entrepreneurial competencies to a high degree in both employed and self-employed contexts. Though in the subsequent careers, the progression of income and work-life balance falls under different mechanisms depending on the gender of the graduate. Women seems to have more stable progression compared to men, with less variation between occupations. Though a limitation lies within that the regressors builds lesser models for women compared to men. This indicates that future research should consider an expanded set of variables or focus on designing qualitative studies target towards career progression of female entrepreneurs. In conclusion this study informs the need to consider the entrepreneurial career progression of women as different compared to their male graduates.
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| 10. |
- Aalbers, J., et al.
(author)
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A next-generation liquid xenon observatory for dark matter and neutrino physics
- 2023
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In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1
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Research review (peer-reviewed)abstract
- The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
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| 11. |
- Aalto, Susanne, 1964, et al.
(author)
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ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377
- 2020
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
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Journal article (peer-reviewed)abstract
- Submillimetre and millimetre line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs) and their mechanical feedback. With very high-resolution (0.'' 02x0.'' 03 (2x3 pc)) ALMA 345 GHz observations of CO 3-2, HCO+ 4-3, vibrationally excited HCN 4-3 nu (2)=1f, and continuum we have studied the remarkable, extremely radio-quiet, molecular jet and wind of the lenticular galaxy NGC 1377. The outflow structure is resolved, revealing a 150 pc long, clumpy, high-velocity (similar to 600 km s(-1)), collimated molecular jet where the molecular emission is emerging from the spine of the jet with an average diameter of 3-7 pc. The jet widens to 10-15 pc about 25 pc from the centre, which is possibly due to jet-wind interactions. A narrow-angle (50 degrees -70 degrees), misaligned and rotating molecular wind surrounds the jet, and both are enveloped by a larger-scale CO-emitting structure at near-systemic velocity. The jet and narrow wind have steep radial gas excitation gradients and appear turbulent with high gas dispersion (sigma> 40 km s(-1)). The jet shows velocity reversals that we propose are caused by precession, or more episodic directional changes. We discuss the mechanisms powering the outflow, and we find that an important process for the molecular jet and narrow wind is likely magneto-centrifugal driving. In contrast, the large-scale CO-envelope may be a slow wind, or cocoon that stems from jet-wind interactions. An asymmetric, nuclear r similar to 2 pc dust structure with a high inferred molecular column density N(H-2) similar or equal to 1.8x10(24) cm(-2) is detected in continuum and also shows compact emission from vibrationally excited HCN. The nuclear dust emission is hot (T-d> 180 K) and its luminosity is likely powered by a buried AGN. The lopsided structure appears to be a warped disk, which is responsible for a significant part of the nuclear obscuration and possibly formed as a result of uneven gas inflows. The dynamical mass inside r=1.4 pc is estimated to 9(-3)(+2) x 10(6)M(circle dot) 9 - 3 + 2 x 10 6 M circle dot , implying that the supermassive black hole (SMBH) has a high mass with respect to the stellar velocity dispersion of NGC 1377. We suggest that the SMBH of NGC 1377 is currently in a state of moderate growth, at the end of a more intense phase of accretion and also evolving from a state of more extreme nuclear obscuration. The nuclear growth may be fuelled by low-angular momentum gas inflowing from the gas ejected in the molecular jet and wind. Such a feedback-loop of cyclic outflows and central accretion could explain why there is still a significant reservoir of molecular gas in this ageing, lenticular galaxy. A feedback-loop would be an effective process in growing the nuclear SMBH and thus would constitute an important phase in the evolution of NGC 1377. This also invites new questions as to SMBH growth processes in obscured, dusty galaxies.
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| 12. |
- Aalto, Susanne, 1964, et al.
(author)
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Extragalactic Science with the Orbiting Astronomical Satellite Investigating Stellar Systems (OASIS) Observatory
- 2023
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In: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 219:1
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Research review (peer-reviewed)abstract
- The Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS), a proposed Astrophysics MIDEX-class mission concept, has an innovative 14-meter diameter inflatable primary mirror that will provide the sensitivity to study far-infrared continuum and line emission from galaxies at all redshifts with high spectral resolution heterodyne receivers. OASIS will have the sensitivity to follow the water trail from galaxies to the comets that create oceans. It will bring an understanding of the role of water in galaxy evolution and its part of the oxygen budget, by measuring water emission from local to intermediate redshift galaxies, observations that have not been possible from the ground. Observation of the ground-state HD line will accurately measure gas mass in a wide variety of astrophysical objects. Thanks to its exquisite spatial resolution and sensitivity, OASIS will, during its one-year baseline mission, detect water in galaxies with unprecedented statistical significance. This paper reviews the extragalactic science achievable and planned with OASIS.
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| 13. |
- Aalto, Susanne, 1964, et al.
(author)
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OH megamaser emission in the outflow of the luminous infrared galaxy Zw049.057
- 2022
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In: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 18, s. 40-44
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Conference paper (peer-reviewed)abstract
- High resolution (0.”26 × 0.”13 (70 × 35 pc)) L-band (18 cm) OH megamaser (OHM) e-Merlin observations of the LIRG Zw049.057 show that the emission is emerging from a low velocity outflowing structure - which is foreground to a fast, dense and collimated molecular outflow detected by ALMA. The extremely dusty compact obscured nucleus (CON) of Zw049.057 has no (or only little) OHM emission associated with it - possibly because of too high number densities that quench the OHM. In contrast we detect 6 cm H2CO emission primarily from the CON-region. We suggest that the OHM-region of Zw049.057 is not directly associated with star formation, but instead occurs in a wide-angle, slow outflow that surrounds the fast and dense outflow. The OHM is pumped by IR emission that likely stems from activities in the nucleus. We briefly discuss how OHM emission can be used as a probe of LIRG-CON galaxies.
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| 14. |
- Aarrestad, Thea, et al.
(author)
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Fast convolutional neural networks on FPGAs with hls4ml
- 2021
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In: Machine Learning: Science and Technology. - : IOP Publishing. - 2632-2153. ; 2:4
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Journal article (peer-reviewed)abstract
- We introduce an automated tool for deploying ultra low-latency, low-power deep neural networks with convolutional layers on field-programmable gate arrays (FPGAs). By extending the hls4ml library, we demonstrate an inference latency of 5 mu s using convolutional architectures, targeting microsecond latency applications like those at the CERN Large Hadron Collider. Considering benchmark models trained on the Street View House Numbers Dataset, we demonstrate various methods for model compression in order to fit the computational constraints of a typical FPGA device used in trigger and data acquisition systems of particle detectors. In particular, we discuss pruning and quantization-aware training, and demonstrate how resource utilization can be significantly reduced with little to no loss in model accuracy. We show that the FPGA critical resource consumption can be reduced by 97% with zero loss in model accuracy, and by 99% when tolerating a 6% accuracy degradation.
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| 15. |
- Aas, Wenche, et al.
(author)
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Trends in Air Pollution in Europe, 2000–2019
- 2024
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In: Aerosol and Air Quality Research. - 2071-1409 .- 1680-8584. ; 24:4
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Journal article (peer-reviewed)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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| 16. |
- Abad, Tahereh, 1989, et al.
(author)
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Universal Fidelity Reduction of Quantum Operations from Weak Dissipation
- 2022
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 129:15
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Journal article (peer-reviewed)abstract
- Quantum information processing is in real systems often limited by dissipation, stemming from remaining uncontrolled interaction with microscopic degrees of freedom. Given recent experimental progress, we consider weak dissipation, resulting in a small error probability per operation. Here, we find a simple formula for the fidelity reduction of any desired quantum operation, where the ideal evolution is confined to the computational subspace. Interestingly, this reduction is independent of the specific operation; it depends only on the operation time and the dissipation. Using our formula, we investigate the situation where dissipation in different parts of the system has correlations, which is detrimental for the successful application of quantum error correction. Surprisingly, we find that a large class of correlations gives the same fidelity reduction as uncorrelated dissipation of similar strength.
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| 17. |
- Abadikhah, Marie, 1992, et al.
(author)
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Effect of anode material and dispersal limitation on the performance and biofilm community in microbial electrolysis cells
- 2023
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In: Biofilm. - 2590-2075. ; 6
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Journal article (peer-reviewed)abstract
- In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54–80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10–16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61–98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0–20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64–89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.
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| 18. |
- Abadikhah, Marie, 1992, et al.
(author)
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Evidence of competition between electrogens shaping electroactive microbial communities in microbial electrolysis cells
- 2022
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In: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 13
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Journal article (peer-reviewed)abstract
- In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by hydrogen-utilizing taxa such as Methanobacterium and had a much lower proportion of negative correlations than the anodes. This could be explained by the diffusion of hydrogen throughout the cathode biofilms, reducing the need to compete for space.
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| 19. |
- Abadikhah, Marie, 1992
(author)
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Influence of electrode material and stochastic factors on the performance and microbial community assembly in microbial electrochemical systems
- 2022
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Licentiate thesis (other academic/artistic)abstract
- Microbial electrolysis cells (MECs) are systems with microbial communities in the form of biofilms on electrode surfaces. The electrogenic bacteria in the anode biofilm act as catalysts for the oxidization of organic compounds, leading to release of electrons, generation of electrical current, and production of hydrogen and methane at the cathode. In addition to production of energy carriers, MECs can be used for other applications as well; for example, as biosensors to monitor biochemical oxygen demand or toxicity. The performance of MECs is determined by both deterministic and stochastic factors influencing the microbial communities on the electrode surfaces, most of which as still poorly understood. In this thesis, the effects of electrode materials on microbial community assembly and MEC performance was investigated. Two experiments were carried out. In the first, three cathode materials (carbon nanoparticles, titanium, and steel) were compared. In the second, three anode materials (carbon cloth, graphene, and nickel) were compared. The cathode materials had no significant effect on the performance of the MECs, as opposed to the anode materials where carbon cloth MECs had the highest current density and the shortest lag time during startup. The differences seen in lag time of replicate systems at the start of the experiment indicated a stochastic initial attachment of the electrogenic bacteria on the anode. Different microbial communities develop in the biofilms on the anodes and cathodes. Electrogens from the Desulfobacterota phylum dominated the anode, while various hydrogenotrophic methanogens, e.g., Methanobacterium, were found to dominate on the cathodes. Diversity and null model analysis of the electrode communities highlighted stochasticity and not electrode material as the important factor in the community assembly. Network analysis showed that the cathode communities had fewer negative interactions between taxa in comparison to the anode. Since hydrogen gas generated at the cathode surface can diffuse through the biofilm, all microorganisms on the cathode have access to the substrate, reducing the need for competition between species. In contrast, electrogens require a short distance to the anode to be able to use it as electron acceptor. Limited space on the anode and competition between electrogens shaped the anode communities and explain the higher number of negative interactions observed. Based on the findings in this thesis, it is suggested that stochastic factors have more influence than electrode material on the anode community even though there is a selective pressure for electrogenic bacteria.
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| 20. |
- Abadikhah, Marie, 1992
(author)
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Microbial communities in biological electrochemical systems
- 2024
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Doctoral thesis (other academic/artistic)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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| 22. |
- Abadpour, Shadab, et al.
(author)
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Adipose-Derived Stromal Cells Preserve Pancreatic Islet Function in a Transplantable 3D Bioprinted Scaffold
- 2023
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In: Advanced healthcare materials. - 2192-2640 .- 2192-2659. ; 12:32
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Journal article (peer-reviewed)abstract
- Intra-portal islet transplantation is currently the only clinically approved beta cell replacement therapy, but its outcome is hindered by limited cell survival due to a multifactorial reaction against the allogeneic tissue in liver. Adipose-derived stromal cells (ASCs) can potentially improve the islet micro-environment by their immunomodulatory action. The challenge is to combine both islets and ASCs in a relatively easy and consistent long-term manner in a deliverable scaffold. Manufacturing the 3D bioprinted double-layered scaffolds with primary islets and ASCs using a mix of alginate/nanofibrillated cellulose (NFC) bioink is reported. The diffusion properties of the bioink and the supportive effect of human ASCs on islet viability, glucose sensing, insulin secretion, and reducing the secretion of pro-inflammatory cytokines are demonstrated. Diabetic mice transplanted with islet-ASC scaffolds reach normoglycemia seven days post-transplantation with no significant difference between this group and the group received islets under the kidney capsules. In addition, animals transplanted with islet-ASC scaffolds stay normoglycemic and show elevated levels of C-peptide compared to mice transplanted with islet-only scaffolds. The data present a functional 3D bioprinted scaffold for islets and ASCs transplanted to the extrahepatic site and suggest a possible role of ASCs on improving the islet micro-environment.
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| 23. |
- Abarenkov, Kessy, et al.
(author)
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The curse of the uncultured fungus
- 2022
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In: MycoKeys. - 1314-4057 .- 1314-4049. ; 86, s. 177-194
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Journal article (peer-reviewed)abstract
- The international DNA sequence databases abound in fungal sequences not annotated beyond the kingdom level, typically bearing names such as “uncultured fungus”. These sequences beget low-resolution mycological results and invite further deposition of similarly poorly annotated entries. What do these sequences represent? This study uses a 767,918-sequence corpus of public full-length fungal ITS sequences to estimate what proportion of the 95,055 “uncultured fungus” sequences that represent truly unidentifiable fungal taxa – and what proportion of them that would have been straightforward to annotate to some more meaningful taxonomic level at the time of sequence deposition. Our results suggest that more than 70% of these sequences would have been trivial to identify to at least the order/family level at the time of sequence deposition, hinting that factors other than poor availability of relevant reference sequences explain the low-resolution names. We speculate that researchers’ perceived lack of time and lack of insight into the ramifications of this problem are the main explanations for the low-resolution names. We were surprised to find that more than a fifth of these sequences seem to have been deposited by mycologists rather than researchers unfamiliar with the consequences of poorly annotated fungal sequences in molecular repositories. The proportion of these needlessly poorly annotated sequences does not decline over time, suggesting that this problem must not be left unchecked.
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| 24. |
- Abarenkov, Kessy, et al.
(author)
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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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In: Nucleic Acids Research. - 0305-1048 .- 1362-4962. ; 52:D1, s. D791-D797
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Journal article (peer-reviewed)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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| 25. |
- Abayazid, Fady, et al.
(author)
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A New Assessment of Bicycle Helmets: The Brain Injury Mitigation Effects of New Technologies in Oblique Impacts
- 2021
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In: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 49:10, s. 2716-2733
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Journal article (peer-reviewed)abstract
- New helmet technologies have been developed to improve the mitigation of traumatic brain injury (TBI) in bicycle accidents. However, their effectiveness under oblique impacts, which produce more strains in the brain in comparison with vertical impacts adopted by helmet standards, is still unclear. Here we used a new method to assess the brain injury prevention effects of 27 bicycle helmets in oblique impacts, including helmets fitted with a friction-reducing layer (MIPS), a shearing pad (SPIN), a wavy cellular liner (WaveCel), an airbag helmet (Hövding) and a number of conventional helmets. We tested whether helmets fitted with the new technologies can provide better brain protection than conventional helmets. Each helmeted headform was dropped onto a 45° inclined anvil at 6.3 m/s at three locations, with each impact location producing a dominant head rotation about one anatomical axes of the head. A detailed computational model of TBI was used to determine strain distribution across the brain and in key anatomical regions, the corpus callosum and sulci. Our results show that, in comparison with conventional helmets, the majority of helmets incorporating new technologies significantly reduced peak rotational acceleration and velocity and maximal strain in corpus callosum and sulci. Only one helmet with MIPS significantly increased strain in the corpus collosum. The helmets fitted with MIPS and WaveCel were more effective in reducing strain in impacts producing sagittal rotations and a helmet fitted with SPIN in coronal rotations. The airbag helmet was effective in reducing brain strain in all impacts, however, peak rotational velocity and brain strain heavily depended on the analysis time. These results suggest that incorporating different impact locations in future oblique impact test methods and designing helmet technologies for the mitigation of head rotation in different planes are key to reducing brain injuries in bicycle accidents.
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