Hydrogen burning: Study of the 22Ne(p,gamma)23Na, 3He(alpha,gamma)7Be and 7Be(p, gamma)8B reactions at ultra-low energies

The neon-sodium cycle (NeNa cycle) of hydrogen burning is active in stars of the Asymptotic Giant Branch, in classical novae, and in supernovae of type Ia. The thermonuclear reaction rate of the 22Ne(p,γ)23Na reaction is determined by a large number of resonances, and it represents the most uncertain rate in the NeNa cycle. This PhD thesis reports on an experiment to study tentative 22Ne(p,γ)23Na resonances at Elab = 71 and 105 keV, as well as the direct capture component of the reaction rate for Elab ≤ 400 keV. The measurements were performed deep underground at the Laboratory for Un- derground Nuclear Astrophysics - LUNA (Gran Sasso, Italy), taking advantage of the strong reduction in the cosmic ray induced background. The LUNA-400-kV electrostatic accelerator and a differentially pumped, windowless gas target of iso- topically enriched 22Ne gas were used. The γ-rays from the reaction were detected with a 4π bismuth germanate scintillator. The data show upper limits on the strengths of the resonances at Elab = 71 and 105 keV of 5.8 × 10−11 and 7.0 × 10−11 eV respectively. The resonances at Elab = 156.2, 189.5 and 259.7 keV have been re-studied and show 20% higher strength than the literature. The present experiment did not show any evidence for the direct capture process at the low energies studied. In addition to the experimental work at LUNA, the 3He(α, γ)7Be and 7Be(p, γ)8B reactions were studied using the most recent solar neutrino data available. Based on the standard solar model and the experimentally measured fluxes of solar 7Be and 8B neutrinos, the astrophysical S-factors of both reactions were evaluated directly in the solar Gamow peak

Cosmic-ray-induced background intercomparison with actively shielded HPGe detectors at underground locations

The main background above 3 MeV for in-beam nuclear astrophysics studies with γ-ray detectors is caused by cosmic-ray induced secondaries. The two commonly used suppression methods, active and passive shielding, against this kind of background were formerly considered only as alternatives in nuclear astrophysics experiments. In this work the study of the effects of active shielding against cosmic-ray induced events at a medium deep location is performed. Background spectra were recorded with two actively shielded HPGe detectors. The experiment was located at 148 m below the surface of the Earth in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data with the same detectors at the Earth’s surface, and at depths of 45 m and 1400 m, respectively

Determination of γ-ray widths in 15N using nuclear resonance fluorescence

Background: The stable nucleus 15N is the mirror of 15O, the bottleneck in the hydrogen burning CNO cycle. Most of the 15N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler shift attenuation method in 15O. As a reference and for testing the method, level lifetimes in 15N have also been determined in the same experiment. Purpose: The latest compilation of 15N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement to enable a comparison to the AGATA demonstrator data. The widths of several 15N levels have been studied with the NRF method. Method: The solid nitrogen compounds enriched in 15N have been irradiated with bremsstrahlung. The γ-rays following the deexcitation of the excited nuclear levels were detected with four high-purity germanium detectors. Results: Integrated photon-scattering cross sections of 10 levels below the proton emission threshold have been measured. Partial gamma-ray widths of ground-state transitions were deduced and compared to the literature. The photon scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced. Conclusions: Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision

Early prediction of acute necrotizing pancreatitis by artificial intelligence : a prospective cohort-analysis of 2387 cases

Pancreatic necrosis is a consistent prognostic factor in acute pancreatitis (AP). However, the clinical scores currently in use are either too complicated or require data that are unavailable on admission or lack sufficient predictive value. We therefore aimed to develop a tool to aid in necrosis prediction. The XGBoost machine learning algorithm processed data from 2387 patients with AP. The confidence of the model was estimated by a bootstrapping method and interpreted via the 10th and the 90th percentiles of the prediction scores. Shapley Additive exPlanations (SHAP) values were calculated to quantify the contribution of each variable provided. Finally, the model was implemented as an online application using the Streamlit Python-based framework. The XGBoost classifier provided an AUC value of 0.757. Glucose, C-reactive protein, alkaline phosphatase, gender and total white blood cell count have the most impact on prediction based on the SHAP values. The relationship between the size of the training dataset and model performance shows that prediction performance can be improved. This study combines necrosis prediction and artificial intelligence. The predictive potential of this model is comparable to the current clinical scoring systems and has several advantages over them

Detailed characteristics of post-discharge mortality in acute pancreatitis

The in-hospital survival of patients suffering from acute pancreatitis (AP) is 95-98%. However, there is growing evidence that patients discharged after AP may be at risk of serious morbidity and mortality. Here, we aimed to investigate the risk, causes, and predictors of the most severe consequence of the post-AP period: mortality.2,613, well-characterized patients from twenty-five centers were collected and followed by the Hungarian Pancreatic Study Group between 2012 and 2021. A general and a hospital-based population was used as the control group.After an AP episode patients have an approximately three-fold higher incidence rate of mortality than the general population (0.0404vs.0.0130 person-years). First-year mortality after discharge was almost double than in-hospital mortality (5.5%vs.3.5%), with 3.0% occurring in the first 90-day period. Age, comorbidities, and severity were the most significant independent risk factors for death following AP. Furthermore, multivariate analysis identified creatinine, glucose, and pleural fluid on admission as independent risk factors associated with post-discharge mortality. In the first 90-day period, cardiac failure and AP-related sepsis were among the main causes of death following discharge, while cancer-related cachexia and non-AP-related infection were the key causes in the later phase.Almost as many patients in our cohort die in the first 90-day period after discharge as during their hospital stay. Evaluation of cardiovascular status, follow-up of local complications, and cachexia-preventing oncological care should be an essential part of post-AP patient care. Future study protocols in AP must include at least a 90-day follow-up period after discharge

Invalidity of Tokyo guidelines in acute biliary pancreatitis : A multicenter cohort analysis of 944 pancreatitis cases

There is a noteworthy overlap between the clinical picture of biliary acute pancreatitis (AP) and the 2018 Tokyo guidelines currently used for the diagnosis of cholangitis (AC) and cholecystitis (CC). This can lead to significant antibiotic and endoscopic retrograde cholangiopancreatography (ERCP) overuse.We aimed to assess the on-admission prevalence of AC/CC according to the 2018 Tokyo guidelines (TG18) in a cohort of biliary AP patients, and its association with antibiotic use, ERCP and clinically relevant endpoints.We conducted a secondary analysis of the Hungarian Pancreatic Study Group's prospective multicenter registry of 2195 AP cases. We grouped and compared biliary cases (n = 944) based on the on-admission fulfillment of definite AC/CC according to TG18. Aside from antibiotic use, we evaluated mortality, AC/CC/AP severity, ERCP performance and length of hospitalization. We also conducted a literature review discussing each criteria of the TG18 in the context of AP.27.8% of biliary AP cases fulfilled TG18 for both AC and CC, 22.5% for CC only and 20.8% for AC only. Antibiotic use was high (77.4%). About 2/3 of the AC/CC cases were mild, around 10% severe. Mortality was below 1% in mild and moderate AC/CC patients, but considerably higher in severe cases (12.8% and 21.2% in AC and CC). ERCP was performed in 89.3% of AC cases, common bile duct stones were found in 41.1%.Around 70% of biliary AP patients fulfilled the TG18 for AC/CC, associated with a high rate of antibiotic use. Mortality in presumed mild or moderate AC/CC is low. Each of the laboratory and clinical criteria are commonly fulfilled in biliary AP, single imaging findings are also unspecific-AP specific diagnostic criteria are needed, as the prevalence of AC/CC are likely greatly overestimated. Randomized trials testing antibiotic use are also warranted