| 1. |
- Hao, Jing, 1991, et al.
(författare)
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Non-contact method to reduce contact problems between sample and electrode in dielectric measurements
- 2020
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Ingår i: High Voltage. - : Institution of Engineering and Technology (IET). - 2397-7264. ; 5:6, s. 753-761
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Tidskriftsartikel (refereegranskat)abstract
- Dielectric response measurement is a widely used technique for characterising dielectric materials in terms of their capacitance and dielectric loss. However, the widely used approach with contact between samples and electrodes can in some cases limit the accuracy of the measurement. The authors introduce an easily realised electrode arrangement for non-contact measurements, which avoids these contact problems. The performance of the electrode arrangement in terms of the edge effect is assessed. The non-contact and contact methods are compared based on error-sensitivity analysis and experimental results. Differences are studied further, with attention to contact pressure. The non-contact method is also compared experimentally with the one-sided non-contact method. Air-reference measurements, comparing the sample to an air-gap for improved calibration, are used for all measurements. The results show that the non-contact method can be an alternative to reduce contact problems between the sample and electrodes, although error sensitivity can be higher when the non-contact method is used. The non- contact method can decrease the influence of the pressure applied to the sample compared to the contact method, and can also reduce the problem of poor contact that can arise from the absence of pressure in the one-sided non-contact method.
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| 2. |
- Kirsten, Franz, 1983, et al.
(författare)
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A link between repeating and non-repeating fast radio bursts through their energy distributions
- 2024
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Ingår i: Nature Astronomy. - 2397-3366. ; 8:3, s. 337-346
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts (FRBs) are extremely energetic, millisecond-duration radio flashes that reach Earth from extragalactic distances. Broadly speaking, FRBs can be classified as repeating or (apparently) non-repeating. It is still unclear, however, whether the two types share a common physical origin and differ only in their activity rate. Here we report on an observing campaign that targeted one hyperactive repeating source, FRB 20201124A, for more than 2,000 h using four 25–32 m class radio telescopes. We detected 46 high-energy bursts, many more than one would expect given previous observations of lower-energy bursts using larger radio telescopes. We find a high-energy burst distribution that resembles that of the non-repeating FRB population, suggesting that apparently non-repeating FRB sources may simply be the rarest bursts from repeating sources. Also, we discuss how FRB 20201124A contributes strongly to the all-sky FRB rate and how similar sources would be observable even at very high redshift.
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| 3. |
- Kirsten, Franz, 1983, et al.
(författare)
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Detection of two bright radio bursts from magnetar SGR 1935 + 2154
- 2021
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 5:4, s. 414-422
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts are millisecond-duration, bright radio signals (fluence 0.1-100 Jy ms) emitted from extragalactic sources of unknown physical origin. The recent CHIME/FRB and STARE2 detection of an extremely bright (fluence similar to MJy ms) radio burst from the Galactic magnetar SGR 1935+2154 supports the hypothesis that (at least some) fast radio bursts are emitted by magnetars at cosmological distances. In follow-up observations totalling 522.7 h on source, we detect two bright radio bursts with fluences of 112 +/- 22 Jy ms and 24 +/- 5 Jy ms, respectively. Both bursts appear to be affected by interstellar scattering and we measure significant linear and circular polarization for the fainter burst. The bursts are separated in time by similar to 1.4 s, suggesting a non-Poissonian, clustered emission process-similar to those seen in some repeating fast radio bursts. Together with the burst reported by CHIME/FRB and STARE2, as well as a much fainter burst seen by FAST (fluence 60 mJy ms), our observations demonstrate that SGR 1935+2154 can produce bursts with apparent energies spanning roughly seven orders of magnitude, and that the burst rate is comparable across this range. This raises the question of whether these four bursts arise from similar physical processes, and whether the fast radio burst population distribution extends to very low energies (similar to 10(30) erg, isotropic equivalent).
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| 4. |
- Lankhaar, Boy, 1991, et al.
(författare)
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Characterization of methanol as a magnetic field tracer in star-forming regions
- 2018
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 2, s. 145-150
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic fields play an important role during star formation1. Direct magnetic field strength observations have proven particularly challenging in the extremely dynamic protostellar phase2,3,4. Because of their occurrence in the densest parts of star-forming regions, masers, through polarization observations, are the main source of magnetic field strength and morphology measurements around protostars2. Of all maser species, methanol is one of the strongest and most abundant tracers of gas around high-mass protostellar disks and in outflows. However, as experimental determination of the magnetic characteristics of methanol has remained largely unsuccessful5, a robust magnetic field strength analysis of these regions could hitherto not be performed. Here, we report a quantitative theoretical model of the magnetic properties of methanol, including the complicated hyperfine structure that results from its internal rotation6. We show that the large range in values of the Landé g factors of the hyperfine components of each maser line lead to conclusions that differ substantially from the current interpretation based on a single effective g factor. These conclusions are more consistent with other observations7,8 and confirm the presence of dynamically important magnetic fields around protostars. Additionally, our calculations show that (nonlinear) Zeeman effects must be taken into account to further enhance the accuracy of cosmological electron-to-proton mass ratio determinations using methanol9,10,11,12.
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| 5. |
- Singh, Gyanendra, 1983, et al.
(författare)
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Gate-tunable pairing channels in superconducting non-centrosymmetric oxides nanowires
- 2022
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Ingår i: npj Quantum Materials. - : Springer Science and Business Media LLC. - 2397-4648. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional SrTiO3-based interfaces stand out among non-centrosymmetric superconductors due to their intricate interplay of gate-tunable Rashba spin-orbit coupling and multi-orbital electronic occupations, whose combination theoretically prefigures various forms of non-standard superconductivity. By employing superconducting transport measurements in nano-devices we present strong experimental indications of unconventional superconductivity in the LaAlO3/SrTiO3 interface. The central observations are the substantial anomalous enhancement of the critical current by small magnetic fields applied perpendicularly to the plane of electron motion, and the asymmetric response with respect to the magnetic field direction. These features cannot be accommodated within a scenario of canonical spin-singlet superconductivity. We demonstrate that the experimental observations can be described by a theoretical model based on the coexistence of Josephson channels with intrinsic phase shifts. Our results exclude a time-reversal symmetry breaking scenario and suggest the presence of anomalous pairing components that are compatible with inversion symmetry breaking and multi-orbital physics.
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| 6. |
- Öhman, Carl, 1991-, et al.
(författare)
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An ethical framework for the digital afterlife industry
- 2018
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Ingår i: Nature Human Bahavior. - : Springer Science and Business Media LLC. - 2397-3374. ; 2:5, s. 318-320
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Tidskriftsartikel (refereegranskat)abstract
- The web is increasingly inhabited by the remains of its departed users, a phenomenon that has given rise to a burgeoning digital afterlife industry. This industry requires a framework for dealing with its ethical implications. The regulatory conventions guiding archaeological exhibitions could provide the basis for such a framework.
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| 7. |
- Lara Avila, Samuel, 1983, et al.
(författare)
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Towards quantum-limited coherent detection of terahertz waves in charge-neutral graphene
- 2019
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 3:11, s. 983-988
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Spectacular advances in heterodyne astronomy1,2 have been largely due to breakthroughs in detector technology3. To exploit the full capacity of future terahertz (∼300 GHz–5 THz) telescope space missions4, new concepts of terahertz coherent receivers are needed, providing larger bandwidths and imaging capabilities with multipixel focal plane heterodyne arrays5. Here we show that graphene uniformly doped to the Dirac point, with material resistance dominated by quantum localization and thermal relaxation governed by electron diffusion, enables highly sensitive and wideband coherent detection of signals from 90 to 700 GHz and, prospectively, across the entire terahertz range. We measure on proof-of-concept graphene bolometric mixers an electron diffusion-limited gain bandwidth of 8 GHz (corresponding to a Doppler shift of 480 km s−1 at 5 THz) and intrinsic mixer noise temperature of 475 K (which would be equivalent to ~2 hν/kB at ν = 5 THz), limited by the residual thermal background in our setup. An optimized device will result in a mixer noise temperature as low as 36 K, with the gain bandwidth exceeding 20 GHz, and a local oscillator power of <100 pW. In conjunction with the emerging quantum-limited amplifiers at the intermediate frequency6,7, our approach promises quantum-limited sensing in the terahertz domain, potentially surpassing superconducting technologies, particularly for large heterodyne arrays
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| 8. |
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| 9. |
- Ament-Velásquez, S. Lorena, Ph.D. 1988-, et al.
(författare)
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Allorecognition genes drive reproductive isolation in Podospora anserina
- 2022
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Ingår i: Nature Ecology & Evolution. - : Springer Nature. - 2397-334X. ; 6:7, s. 910-923
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Tidskriftsartikel (refereegranskat)abstract
- Allorecognition, the capacity to discriminate self from conspecific non-self, is a ubiquitous organismal feature typically governed by genes evolving under balancing selection. Here, we show that in the fungus Podospora anserina, allorecognition loci controlling vegetative incompatibility (het genes), define two reproductively isolated groups through pleiotropic effects on sexual compatibility. These two groups emerge from the antagonistic interactions of the unlinked loci het-r (encoding a NOD-like receptor) and het-v (encoding a methyltransferase and an MLKL/HeLo domain protein). Using a combination of genetic and ecological data, supported by simulations, we provide a concrete and molecularly defined example whereby the origin and coexistence of reproductively isolated groups in sympatry is driven by pleiotropic genes under balancing selection.
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| 10. |
- Bengtsson, Mattias, 1978, et al.
(författare)
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A journey into the new employment service landscape of responsibilisation: Towards de-personalisation of the caseworker-jobseeker relationship
- 2024
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Ingår i: International Journal of Social Welfare. - : Wiley. - 1369-6866 .- 1468-2397. ; 33:1, s. 137-150
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Tidskriftsartikel (refereegranskat)abstract
- The article analyses a new culture of responsibilisation implicated in a recent management reform in the Swedish Public Employment Service. Based on an interview study and organisational documents, it is shown that the reform entails a new form of responsibilisation of jobseekers as well as caseworkers. As jobseekers are expected to ‘carry their own case’ through the administrative job-search process, they are obliged to manage tasks that used to be in the caseworker's area of responsibility. Furthermore, caseworkers are expected to regulate themselves in new ways and change their mind-set according to new organisational values and behavioural norms, requiring a restraining of their availability to clients. It is argued that the employment agency is increasingly turned into the agency of the active and responsible jobseeker, which entails one further shift towards individual responsibility in Swedish labour market policy and one further step towards the breakup of a personal caseworker–jobseeker relationship.
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