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- Barthelmi, K., et al.
(författare)
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Atomistic defects as single-photon emitters in atomically thin MoS2
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:7
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Tidskriftsartikel (refereegranskat)abstract
- Precisely positioned and scalable single-photon emitters (SPEs) are highly desirable for applications in quantum technology. This Perspective discusses single-photon-emitting atomistic defects in monolayers of MoS2 that can be generated by focused He-ion irradiation with few nanometers positioning accuracy. We present the optical properties of the emitters and the possibilities to implement them into photonic and optoelectronic devices. We showcase the advantages of the presented emitters with respect to atomistic positioning, scalability, long (microsecond) lifetime, and a homogeneous emission energy within ensembles of the emitters. Moreover, we demonstrate that the emitters are stable in energy on a timescale exceeding several weeks and that temperature cycling narrows the ensembles' emission energy distribution.
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| 3. |
- Bavinck, Maaike Bouwes, et al.
(författare)
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Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot
- 2016
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 16:2, s. 1081-1085
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Tidskriftsartikel (refereegranskat)abstract
- We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width. We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising quantum optical properties for single photon application and quantum optics.
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| 6. |
- Biström, M., et al.
(författare)
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Leptin levels are associated with multiple sclerosis risk
- 2019
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Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 25:Suppl. 2, s. 904-904
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: One environmental factor that in the last decade repeatedly has been linked to increased risk of developing multiple sclerosis (MS) is overweight, including obesity, early in life. The incidence of both MS and overweight are increasing, making elucidation of this connection important. The adipokine leptin is strongly correlated to both body mass index and total fat mass and the peptide hormone insulin is associated with obesity and type 2 diabetes, making leptin and insulin suitable biomarkers to investigate the connection between overweight and MS.Objectives: To determine if leptin or insulin are risk factors for developing relapsing MS.Aims: To further the understanding of how overweight influence MS risk.Methods: In this case-control study, we compared concentrations of leptin and insulin in 649 individuals that later developed relapsing-remitting MS with 649 matched controls. Cases were matched for biobank, sex, date of sampling and age with decreasing priority. Only prospectively collected samples from individuals below the age of 40 were included in the study. Conditional logistic regression was performed on log10 transformed and z-scored values for the entire group, separately for men and women and divided into age groups.Results: A 1-unit leptin z-score increase was associated with increased risk of MS in individuals below 20 years of age (odds ratio [OR] 1.4, 95% confidence interval [CI] 1.1–1.9) and for all men (OR 1.4, 95% CI 1.0–2.0). In contrast, for women aged 30-39 years there was a lower risk of MS with increased leptin levels (OR 0.74, 95% CI 0.54–1.0) when adjusting for insulin levels. No statistically significant association was found between insulin levels and MS risk.Conclusions: We show that the pro-inflammatory adipokine leptin is a risk factor for MS among young individuals. The age dependent relationship between leptin and MS risk in women - for whom leptin levels are several-fold higher than in men - suggests a possible role for leptin as being the link between MS risk and being overweight early in life.
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| 9. |
- Hummel, Thomas, et al.
(författare)
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Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:1, s. 610-625
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.
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| 11. |
- Jons, D., et al.
(författare)
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Increase in Epstein Barr virus serologies precedes neuroaxonal damage in pre-symptomatic multiple sclerosis
- 2022
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Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 28:Suppl. 3, s. 86-87
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Epstein-Barr virus (EBV) infection may be a pre-condition for the development of multiple sclerosis (MS). EBV antibodies, predominantly anti-EBNA1, develop in the presymp-tomatic phase of virtually all MS patients. Using material from a serum repository, studies in advance of MS onset indicated that EBV seropositivity preceded the first expression of incipient axonal lesions, serum Neurofilament Light (sNFL) .Objectives: To determine the onset and individual order of appearance of EBV seroreactivity and the serum neuroaxonal injury marker neurofilament light (sNfL) in a wide age spectrum of presymptomatic MS patients.Aims: To characterize the presymptomatic appearance of anti-bodies against an intranuclear (EBNA1) and a surface EBV anti-gen (gp350) and sNfL.Methods: A nested case-control study in 669 pre-symptomati-cally acquired blood samples from persons who later received an MS diagnosis, and from 1:1 matched control persons. Serum lev-els of EBNA1, VCA and gp350 IgG antibodies and sNFL (n=519) were measured in individual presymptomatic samples and expressed as delta scores with matched controls in relation to time until MS onset.Results: Serum levels expressed as delta scores for anti EBV and NfL IgG showed an incipient increase for anti EBNA1 and gp350 from 15-20 years before MS debut. Significant (p=0.001 and p=0.002) from 10-15 years, with consistent delta-scores succes-sively closer to MS onset. These findings contrasted to the level of sNfL which increasingly diverged from matched controls from 5-10 years before the onset of MS. None of the individual sam-ples negative for both EBNA1 and VCA IgG antibodies in the pre-MS group (n = 36) showed any elevation of the sNfL level.Conclusions: In a pre-MS material, the seroreactivity against EBNA1 was followed by VCA and gp350, before increased sNFL appeared, indicating incipient axonal injury. Together with its biological characteristics this temporal order confirms the role of EBV as a trigger of MS.
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