| 1. |
- Baker, C. J., et al.
(författare)
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Laser cooling of antihydrogen atoms
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 592:7852, s. 35-42
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Ahmadi, M., et al.
(författare)
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Investigation of the fine structure of antihydrogen
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578:7795, s. 375-380
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Baker, C. J., et al.
(författare)
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Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)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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| 4. |
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| 5. |
- Jansen, Willemijn J, et al.
(författare)
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Prevalence Estimates of Amyloid Abnormality Across the Alzheimer Disease Clinical Spectrum.
- 2022
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Ingår i: JAMA neurology. - : American Medical Association (AMA). - 2168-6157 .- 2168-6149. ; 79:3, s. 228-243
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Tidskriftsartikel (refereegranskat)abstract
- One characteristic histopathological event in Alzheimer disease (AD) is cerebral amyloid aggregation, which can be detected by biomarkers in cerebrospinal fluid (CSF) and on positron emission tomography (PET) scans. Prevalence estimates of amyloid pathology are important for health care planning and clinical trial design.To estimate the prevalence of amyloid abnormality in persons with normal cognition, subjective cognitive decline, mild cognitive impairment, or clinical AD dementia and to examine the potential implications of cutoff methods, biomarker modality (CSF or PET), age, sex, APOE genotype, educational level, geographical region, and dementia severity for these estimates.This cross-sectional, individual-participant pooled study included participants from 85 Amyloid Biomarker Study cohorts. Data collection was performed from January 1, 2013, to December 31, 2020. Participants had normal cognition, subjective cognitive decline, mild cognitive impairment, or clinical AD dementia. Normal cognition and subjective cognitive decline were defined by normal scores on cognitive tests, with the presence of cognitive complaints defining subjective cognitive decline. Mild cognitive impairment and clinical AD dementia were diagnosed according to published criteria.Alzheimer disease biomarkers detected on PET or in CSF.Amyloid measurements were dichotomized as normal or abnormal using cohort-provided cutoffs for CSF or PET or by visual reading for PET. Adjusted data-driven cutoffs for abnormal amyloid were calculated using gaussian mixture modeling. Prevalence of amyloid abnormality was estimated according to age, sex, cognitive status, biomarker modality, APOE carrier status, educational level, geographical location, and dementia severity using generalized estimating equations.Among the 19097 participants (mean [SD] age, 69.1 [9.8] years; 10148 women [53.1%]) included, 10139 (53.1%) underwent an amyloid PET scan and 8958 (46.9%) had an amyloid CSF measurement. Using cohort-provided cutoffs, amyloid abnormality prevalences were similar to 2015 estimates for individuals without dementia and were similar across PET- and CSF-based estimates (24%; 95% CI, 21%-28%) in participants with normal cognition, 27% (95% CI, 21%-33%) in participants with subjective cognitive decline, and 51% (95% CI, 46%-56%) in participants with mild cognitive impairment, whereas for clinical AD dementia the estimates were higher for PET than CSF (87% vs 79%; mean difference, 8%; 95% CI, 0%-16%; P=.04). Gaussian mixture modeling-based cutoffs for amyloid measures on PET scans were similar to cohort-provided cutoffs and were not adjusted. Adjusted CSF cutoffs resulted in a 10% higher amyloid abnormality prevalence than PET-based estimates in persons with normal cognition (mean difference, 9%; 95% CI, 3%-15%; P=.004), subjective cognitive decline (9%; 95% CI, 3%-15%; P=.005), and mild cognitive impairment (10%; 95% CI, 3%-17%; P=.004), whereas the estimates were comparable in persons with clinical AD dementia (mean difference, 4%; 95% CI, -2% to 9%; P=.18).This study found that CSF-based estimates using adjusted data-driven cutoffs were up to 10% higher than PET-based estimates in people without dementia, whereas the results were similar among people with dementia. This finding suggests that preclinical and prodromal AD may be more prevalent than previously estimated, which has important implications for clinical trial recruitment strategies and health care planning policies.
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| 6. |
- Zaigham, S, et al.
(författare)
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An observational analysis on the influence of parental allergic rhinitis, asthma and smoking on exhaled nitric oxide in offspring.
- 2024
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Ingår i: Nitric oxide. - 1089-8603 .- 1089-8611.
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Parental allergic diseases and smoking influence respiratory disease in the offspring but it is not known whether they influence fractional exhaled nitric oxide (FeNO) in the offspring. We investigated whether parental allergic diseases, parental smoking and FeNO levels in parents were associated with FeNO levels in their offspring.METHODS: We studied 609 offspring aged 16-47 years from the Respiratory Health in Northern Europe, Spain and Australia generation (RHINESSA) study with parental information from the Respiratory Health in Northern Europe (RHINE) III study and the European Community Respiratory Health Survey (ECRHS) III. Linear regression models were used to assess the association between offspring FeNO and parental FeNO, allergic rhinitis, asthma and smoking, while adjusting for potential confounding factors.RESULTS: Parental allergic rhinitis was significantly associated with higher FeNO in the offspring, both on the paternal and maternal side (percent change: 20.3% [95%CI 5.0-37.7], p=0.008, and 13.8% [0.4-28.9], p=0.043, respectively). Parental allergic rhinitis with asthma in any parent was also significantly associated with higher offspring FeNO (16.2% [0.9-33.9], p=0.037). However, parental asthma alone and smoking were not associated with offspring FeNO. Parental FeNO was not associated with offspring FeNO after full adjustments for offspring and parental factors.CONCLUSIONS: Parental allergic rhinitis but not parental asthma was associated with higher levels of FeNO in offspring. These findings suggest that parental allergic rhinitis status should be considered when interpreting FeNO levels in offspring beyond childhood.
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| 7. |
- Zaigham, Suneela, et al.
(författare)
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An observational analysis on the influence of parental allergic rhinitis, asthma and smoking on exhaled nitric oxide in offspring
- 2024
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Ingår i: Nitric oxide. - : Elsevier. - 1089-8603 .- 1089-8611. ; 149, s. 60-66
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Parental allergic diseases and smoking influence respiratory disease in the offspring but it is not known whether they influence fractional exhaled nitric oxide (FeNO) in the offspring. We investigated whether parental allergic diseases, parental smoking and FeNO levels in parents were associated with FeNO levels in their offspring.METHODS: We studied 609 offspring aged 16-47 years from the Respiratory Health in Northern Europe, Spain and Australia generation (RHINESSA) study with parental information from the Respiratory Health in Northern Europe (RHINE) III study and the European Community Respiratory Health Survey (ECRHS) III. Linear regression models were used to assess the association between offspring FeNO and parental FeNO, allergic rhinitis, asthma and smoking, while adjusting for potential confounding factors.RESULTS: Parental allergic rhinitis was significantly associated with higher FeNO in the offspring, both on the paternal and maternal side (percent change: 20.3 % [95%CI 5.0-37.7], p = 0.008, and 13.8 % [0.4-28.9], p = 0.043, respectively). Parental allergic rhinitis with asthma in any parent was also significantly associated with higher offspring FeNO (16.2 % [0.9-33.9], p = 0.037). However, parental asthma alone and smoking were not associated with offspring FeNO. Parental FeNO was not associated with offspring FeNO after full adjustments for offspring and parental factors.CONCLUSIONS: Parental allergic rhinitis but not parental asthma was associated with higher levels of FeNO in offspring. These findings suggest that parental allergic rhinitis status should be considered when interpreting FeNO levels in offspring beyond childhood.
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| 8. |
- Krantz, Christina, et al.
(författare)
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Cross-sectional study on exhaled nitric oxide in relation to upper airway inflammatory disorders with regard to asthma and perennial sensitization
- 2022
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Ingår i: Clinical and Experimental Allergy. - : Wiley. - 0954-7894 .- 1365-2222. ; 52:2, s. 297-311
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Tidskriftsartikel (refereegranskat)abstract
- Background Fractional exhaled nitric oxide (FeNO) is a well-known marker of type-2 inflammation. FeNO is elevated in asthma and allergic rhinitis, with IgE sensitization as a major determinant. Objective We aimed to see whether there was an independent association between upper airway inflammatory disorders (UAID) and FeNO, after adjustment for asthma and sensitization, in a multi-centre population-based study. Methods A total of 741 subjects with current asthma and 4155 non-asthmatic subjects participating in the second follow-up of the European Community Respiratory Health Survey (ECRHS III) underwent FeNO measurements. Sensitization status was based on measurement of IgE against airborne allergens; information on asthma, UAID and medication was collected through interview-led questionnaires. Independent associations between UAID and FeNO were assessed in adjusted multivariate regression models and test for interaction with perennial sensitization and asthma on the relation between UAID and FeNO were made. Results UAID were associated with higher FeNO after adjusting for perennial sensitization, asthma and other confounders: with 4.4 (0.9-7.9) % higher FeNO in relation to current rhinitis and 4.8 (0.7-9.2) % higher FeNO in relation to rhinoconjunctivitis. A significant interaction with perennial sensitization was found in the relationship between current rhinitis and FeNO (p = .03) and between rhinoconjunctivitis and FeNO (p = .03). After stratification by asthma and perennial sensitization, the association between current rhinitis and FeNO remained in non-asthmatic subjects with perennial sensitization, with 12.1 (0.2-25.5) % higher FeNO in subjects with current rhinitis than in those without. Conclusions & Clinical Relevance Current rhinitis and rhinoconjunctivitis was associated with higher FeNO, with an interaction with perennial sensitization. This further highlights the concept of united airway disease, with correlations between symptoms and inflammation in the upper and lower airways and that sensitization needs to be accounted for in the relation between FeNO and rhinitis.
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| 9. |
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| 10. |
- Rhodes, Olin E., et al.
(författare)
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Integration of ecosystem science into radioecology : A consensus perspective
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 740
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Tidskriftsartikel (refereegranskat)abstract
- In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants. The participants also agreed that many such endpoints exit or are thought to exit and while many are used in ecological risk assessment currently, additional data need to be collected that link the causal mechanisms of radiological exposure to these endpoints. Finally, the participants agreed that radiological risk assessments must be designed and informed by rigorous statistical frameworks capable of revealing the causal inference tying radiological exposure to the endpoints selected for measurement.
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