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- Ahmadi, M., et al.
(author)
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Investigation of the fine structure of antihydrogen
- 2020
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578:7795, s. 375-380
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Journal article (peer-reviewed)abstract
- At the historic Shelter Island Conference on the Foundations of Quantum Mechanics in 1947, Willis Lamb reported an unexpected feature in the fine structure of atomic hydrogen: a separation of the 2S(1/2) and 2P(1/2) states(1). The observation of this separation, now known as the Lamb shift, marked an important event in the evolution of modern physics, inspiring others to develop the theory of quantum electrodynamics(2-5). Quantum electrodynamics also describes antimatter, but it has only recently become possible to synthesize and trap atomic antimatter to probe its structure. Mirroring the historical development of quantum atomic physics in the twentieth century, modern measurements on anti-atoms represent a unique approach for testing quantum electrodynamics and the foundational symmetries of the standard model. Here we report measurements of the fine structure in the n = 2 states of antihydrogen, the antimatter counterpart of the hydrogen atom. Using optical excitation of the 1S-2P Lyman-alpha transitions in antihydrogen(6), we determine their frequencies in a magnetic field of 1 tesla to a precision of 16 parts per billion. Assuming the standard Zeeman and hyperfine interactions, we infer the zero-field fine-structure splitting (2P(1/2)-2P(3/2)) in antihydrogen. The resulting value is consistent with the predictions of quantum electrodynamics to a precision of 2 per cent. Using our previously measured value of the 1S-2S transition frequency(6,7), we find that the classic Lamb shift in antihydrogen (2S(1/2)-2P(1/2) splitting at zero field) is consistent with theory at a level of 11 per cent. Our observations represent an important step towards precision measurements of the fine structure and the Lamb shift in the antihydrogen spectrum as tests of the charge-parity-time symmetry(8) and towards the determination of other fundamental quantities, such as the antiproton charge radius(9,10), in this antimatter system. Precision measurements of the 1S-2P transition in antihydrogen that take into account the standard Zeeman and hyperfine effects confirm the predictions of quantum electrodynamics.
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- Baker, C. J., et al.
(author)
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Laser cooling of antihydrogen atoms
- 2021
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 592:7852, s. 35-42
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Journal article (peer-reviewed)abstract
- The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision(1). Slowing the translational motion of atoms and ions by application of such a force(2,3), known as laser cooling, was first demonstrated 40 years ago(4,5). It revolutionized atomic physics over the following decades(6-8), and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen(9), the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-alpha laser radiation(10,11), we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic(11-13) and gravitational(14) studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
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- Baker, C. J., et al.
(author)
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Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be+ ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries. Positrons are key to the production of cold antihydrogen. Here the authors report the sympathetic cooling of positrons by interacting them with laser-cooled Be+ ions resulting in a three-fold reduction of the temperature of positrons for antihydrogen synthesis.
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- Skjerven, H. O., et al.
(author)
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Skin emollient and early complementary feeding to prevent infant atopic dermatitis (PreventADALL): a factorial, multicentre, cluster-randomised trial
- 2020
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In: The Lancet. - 0140-6736. ; 395:10228, s. 951-961
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Journal article (peer-reviewed)abstract
- Background: Skin emollients applied during early infancy could prevent atopic dermatitis, and early complementary food introduction might reduce food allergy in high-risk infants. The study aimed to determine if either regular skin emollients applied from 2 weeks of age, or early complementary feeding introduced between 12 and 16 weeks of age, reduced development of atopic dermatitis by age 12 months in the general infant population. Methods: This population-based 2×2 factorial, randomised clinical trial was done at Oslo University Hospital and Østfold Hospital Trust, Oslo, Norway; and Karolinska University Hospital, Stockholm, Sweden. Infants of women recruited antenatally at the routine ultrasound pregnancy screening at 18 weeks were cluster-randomised at birth from 2015 to 2017 to the following groups: (1) controls with no specific advice on skin care while advised to follow national guidelines on infant nutrition (no intervention group); (2) skin emollients (bath additives and facial cream; skin intervention group); (3) early complementary feeding of peanut, cow's milk, wheat, and egg (food intervention group); or (4) combined skin and food interventions (combined intervention group). Participants were randomly assigned (1:1:1:1) using computer- generated cluster randomisation based on 92 geographical living area blocks as well as eight 3-month time blocks. Carers were instructed to apply the interventions on at least 4 days per week. Atopic dermatitis by age 12 months was the primary outcome, based on clinical investigations at 3, 6 and 12 months by investigators masked to group allocation. Atopic dermatitis was assessed after completing the 12-month investigations and diagnosed if either of the UK Working Party and Hanifin and Rajka (12 months only) diagnostic criteria were fulfilled. The primary efficacy analyses was done by intention-to-treat analysis on all randomly assigned participants. Food allergy results will be reported once all investigations at age 3 years are completed in 2020. This was a study performed within ORAACLE (the Oslo Research Group of Asthma and Allergy in Childhood; the Lung and Environment). The study is registered at clinicaltrials.gov, NCT02449850. Findings: 2697 women were recruited between Dec 9, 2014, and Oct 31, 2016, from whom 2397 newborn infants were enrolled from April 14, 2015, to April 11, 2017. Atopic dermatitis was observed in 48 (8%) of 596 infants in the no intervention group, 64 (11%) of 575 in the skin intervention group, 58 (9%) of 642 in the food intervention group, and 31 (5%) of 583 in the combined intervention group. Neither skin emollients nor early complementary feeding reduced development of atopic dermatitis, with a risk difference of 3·1% (95% CI –0·3 to 6·5) for skin intervention and 1·0% (–2·1 to 4·1) for food intervention, in favour of control. No safety concerns with the interventions were identified. Reported skin symptoms and signs (including itching, oedema, exanthema, dry skin, and urticaria) were no more frequent in the skin, food, and combined intervention groups than in the no intervention group. Interpretation: Neither early skin emollients nor early complementary feeding reduced development of atopic dermatitis by age 12 months. Our study does not support the use of these interventions to prevent atopic dermatitis by 12 months of age in infants. Funding: The study was funded by several public and private funding bodies: The Regional Health Board South East, The Norwegian Research Council, Health and Rehabilitation Norway, The Foundation for Healthcare and Allergy Research in Sweden-Vårdalstiftelsen, Swedish Asthma and Allergy Association's Research Foundation, Swedish Research Council—the Initiative for Clinical Therapy Research, The Swedish Heart-Lung Foundation, SFO-V at the Karolinska Institute, Freemason Child House Foundation in Stockholm, Swedish Research Council for Health, Working Life and Welfare—FORTE, Oslo University Hospital, the University of Oslo, and Østfold Hospital Trust. © 2020 Elsevier Ltd
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| 9. |
- Andersen, T. C. B., et al.
(author)
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The SH3 domains of the protein kinases ITK and LCK compete for adjacent sites on T cell?specific adapter protein
- 2019
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In: Journal of Biological Chemistry. - 0021-9258. ; 294:42, s. 15480-15494
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Journal article (peer-reviewed)abstract
- T-cell activation requires stimulation of specific intracellular signaling pathways in which protein-tyrosine kinases, phosphatases, and adapter proteins interact to transmit signals from the T-cell receptor to the nucleus. Interactions of LCK proto-oncogene, SRC family tyrosine kinase (LCK), and the IL-2?inducible T cell kinase (ITK) with the T cell-specific adapter protein (TSAD) promotes LCK-mediated phosphorylation and thereby ITK activation. Both ITK and LCK interact with TSAD's proline-rich region (PRR) through their Src homology 3 (SH3) domains. Whereas LCK may also interact with TSAD through its SH2 domain, ITK interacts with TSAD only through its SH3 domain. To begin to understand on a molecular level how the LCK SH3 and ITK SH3 domains interact with TSAD in human HEK293T cells, here we combined biochemical analyses with NMR spectroscopy. We found that the ITK and LCK SH3 domains potentially have adjacent and overlapping binding sites within the TSAD PRR amino acids (aa) 239?274. Pulldown experiments and NMR spectroscopy revealed that both domains may bind to TSAD aa 239?256 and aa 257?274. Co-immunoprecipitation experiments further revealed that both domains may also bind simultaneously to TSAD aa 242?268. Accordingly, NMR spectroscopy indicated that the SH3 domains may compete for these two adjacent binding sites. We propose that once the associations of ITK and LCK with TSAD promote the ITK and LCK interaction, the interactions among TSAD, ITK, and LCK are dynamically altered by ITK phosphorylation status.
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| 10. |
- Carlsen, O. C. L., et al.
(author)
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Physical activity in pregnancy: a Norwegian-Swedish mother-child birth cohort study
- 2021
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In: AJOG Global Reports. - : Elsevier BV. - 2666-5778. ; 1:1
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Journal article (peer-reviewed)abstract
- BACKGROUND: Physical activity during pregnancy is important for maternal and offspring health. Optimal conditions during pregnancy may help reduce the burden of noncommunicable diseases. National and international guidelines recommend at least 150 minutes of physical activity of at least moderate intensity per week. To optimize physical activity in pregnant women, it is important to identify factors associated with higher levels of physical activity. OBJECTIVE: This study aimed to explore types and levels of physical activity in midpregnancy in Norway and Sweden and to identify factors associated with higher levels of physical activity. MATERIALS AND METHODS: From the population-based mother-child cohort Preventing Atopic Dermatitis and Allergies in Children study recruiting 2697 women in Norway and Sweden from 2014 to 2016, we included 2349 women who answered an electronic questionnaire at enrollment in midpregnancy. Women were asked about regular physical activity in the last 2 weeks of pregnancy and afterward for types and levels of physical activity in pregnancy and before pregnancy and socioeconomic status, lifestyle, and maternal health. Logistic regression analyses were used to identify factors associated with higher levels of physical activity in pregnancy, defined as >30 minutes per session of ≥2 times per week of moderate- or high-intensity brisk walking, strength training, jogging, and bicycling. RESULTS: No regular physical activity during the last 2 weeks before answering the questionnaire at midpregnancy was reported by 689 women (29%). In this study, 1787 women (76%) reported weekly strolling during pregnancy. Regular physical activity at least twice weekly in the first half of pregnancy was reported as brisk walking by 839 women (36%), bicycling by 361 women (15%), strength training by 322 women (14%), and other activities by <10% of women. Among the 1430 women with regular moderate- or high-intensity physical activity, the estimated median duration per week was 120 minutes. Higher physical activity levels were achieved in 553 women (23.5%) by brisk walking, 287 women (12.2%) by strength training, 263 women (11.2%) by bicycling, and 114 women (4.9%) by jogging. Higher physical activity levels were positively associated with regular physical activity before pregnancy, dog ownership, and atopic dermatitis and negatively associated with higher body mass index, study location in Østfold, previous pregnancy or pregnancies, non-Nordic origin, suburban living, and sick leave. CONCLUSION: At midpregnancy, 29% of women were inactive, and less than 50% of women had at least 2 hours of moderate-intensity physical activity weekly. Awareness of physical activity in pregnancy should be discussed at pregnancy follow-up visits, particularly among women with higher body mass index, sick leave, previous pregnancy or pregnancies, and non-Nordic origin.
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