Gutenberg Open Science

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DissertationAccess status: Open Access ,
Nuclear structure corrections in muonic atoms
(2023) Li Muli, Simone Salvatore; Bacca, Sonia
Muonic hydrogen-like atoms, bound systems of a muon and an atomic nucleus, are excellent probes for nuclear physics, because the muon is much heavier than the electron and its wavefunction overlaps significantly more with the nuclear charge distribution. This increased sensitivity to nuclear physics allows for precise extractions of nuclear charge radii by measuring the Lamb-shift. The precision of this extraction is currently limited by the uncertainty of nuclear structure effects, which are not known as precisely as quantum electrodynamics effects, due to the non-perturbative nature of the strong force at the low-energy scale relevant to muonic atoms. This work addresses the calculation of the nuclear structure corrections to the Lamb-shift of muonic helium and lithium atoms. For muonic lithium, we calculate the nuclear structure corrections to the Lamb-shift using a simplified model of the nuclear force. This allows us to perform estimates, which are useful in view of the future planned experimental activities. For muonic helium, the novelty of this work comes from the use of nuclear interactions derived from the chiral effective field theory and of Bayesian inference for quantifying the uncertainties. This combination of techniques puts the problem of quantifying theoretical uncertainties in nuclear physics into a more solid statistical ground and defines a systematically improvable method for calculating observables. The main results of this work are new high-precision values for nuclear structure corrections in muonic atoms, which can be used to update the charge radii of 3 He and 4 He extracted from the recent muonic-atoms spectroscopy experiments in muonic helium. Due to partial cancellation of uncertainties, the squared difference in the nuclear charge radii, δr2 = rc2 (3 He) − rc2 (4 He) can be obtained with more precision than the nuclear charge radii itself. This quantity can also be precisely obtained from spectroscopy experiments in ordinary helium atoms, which allows to perform consistency checks between theory and experiments in electronic and muonic atoms. Two publications of δr2 , one using muonic atoms and the other using ordinary helium atoms, were recently published, which resulted in a disagreement at the level of 3.6σ. Our updated theory of the nuclear structure effects supports the previous value of δr2 coming from muonic atoms, and intensifies the current disagreement.
ZeitschriftenaufsatzAccess status: Open Access ,
Oscillometric, greyscale- and novel color-Doppler-ultrasound indices of macrovascular damage in Sjögren’s : the SICARD cohort study
(2025) Triantafyllias, Konstantinos; Bach, Mirjam; Bögel, Sebastian; Muthuraman, Muthuraman; Bertsias, George; Boumpas, Dimitrios; Bergner, Raoul; Schepers, Markus; Schwarting, Andreas
Background To assess for the first time a combination of oscillometric, greyscale- and novel color-Doppler ultrasound (US) indices of carotid and aortic damage in patients with primary Sjögren’s syndrome (pSS). Moreover, to examine associations of these markers with patient and disease-characteristics, as well as with a traditional cardiovascular (CV) risk score (SCORE) and its EULAR-modified version (mSCORE). Methods Greyscale and color-Doppler indices [resistance (RI)- and pulsatility (PI)-index], as well as markers of atherosclerosis [Intima-Media-Thickness (cIMT), plaques, and cumulative calcification surface], were examined in the common- (CCA) and internal- (ICA) carotid arteries of pSS patients and healthy controls. The gold standard oscillometric marker of aortic stiffness (carotid-femoral pulse wave velocity; cfPWV) and the traditional SCORE/mSCORE, were also assessed. Results We recruited 119 pSS-patients and 97 controls. Patients exhibited significantly higher cfPWV (padj = 0.025), cIMT (padj < 0.001), and calcification area (p = 0.013), compared to controls. According to mSCORE, 5.7% of the patients had high CV risk. However, cfPWV and carotid-sonography revealed increased aortic stiffness in 45.4% and carotid atherosclerosis in 69.2%, respectively. Among pSS-patients, cfPWV correlated with C-reactive-protein (rho = 0.325, p < 0.001), erythrocyte-sedimentation-rate (rho = 0.271, p = 0.003), and traditional CV-risk factors (age, cholesterol, systolic blood pressure: all; p < 0.01). ICA-RI and ICA-PI were higher in patients with further (non-rheumatological) autoimmune diseases (both; p < 0.05). Conclusion In the largest cfPWV/US-cohort examined to date, pSS-patients had significantly higher aortic stiffness and atherosclerosis than controls. Aortic stiffness was predicted by systemic inflammation, alongside traditional CV risk factors. cfPWV and carotid-US may help identify subclinical end-organ disease and atherosclerosis and thus assist CV/CVB-screening in pSS. Trial registration DRKS00031470.
ZeitschriftenaufsatzAccess status: Open Access ,
MR1-ligand cross-linking identifies vitamin B6 metabolites as TCR-reactive antigens
(2025) Schmidlin, Thierry; Behiry, Enas; Thomas, Hannah; Dolton, Garry; Marino, Fabio Marino; Hasan, Samiul; von Essen, Magdalena; Gathungu, Rose M.; Steigenberger, Barbara A.; Selvadurai, Hayden; Dukes, Joseph; Brennan, Paul E.; Spiller, Owen B.; Silk, Jonathan D.; Sewell, Andrew K.; Ternette, Nicola
Major histocompatibility complex class I-related protein 1 (MR1) plays a central role in the immune recognition of infected cells and can mediate T cell detection of cancer. Knowledge of the nature of the ligands presented by MR1 is still sparse and has been limited by a lack of efficient approaches for MR1 ligand discovery. Here, we present a cross-linking strategy to investigate Schiff base-bound MR1 ligands. Our methodology employs reductive amination to stabilize the labile Schiff base bond between MR1 and its ligand, allowing for the detection of ligands as covalent MR1 adducts by mass spectrometry-based proteomics. We apply our approach to identifying vitamin B6 vitamers pyridoxal and pyridoxal 5′-phosphate (PLP) as MR1 ligands and show that both compounds are recognized by T cells expressing either A-F7, a mucosal-associated invariant T (MAIT) cell T cell receptor (TCR), or MC.7.G5, an MR1-restricted TCR reported to recognize cancer cells, highlighting them as immunogenic MR1 ligands.