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- Waschitz, Y., et al.
(författare)
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Independent isotopic fission yields of Cf-252 spontaneous fission via mass measurements at the FRS Ion Catcher
- 2023
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Ingår i: 15th International Conference on Nuclear Data for Science and Technology, ND2022. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- We present first preliminary results of a novel method for measuring independent isotopic fission yields (IIFYs) of spontaneous fission (SF) via direct mass measurements, at the FRS Ion Catcher (FRS -IC) at GSI. Fission products were generated from a Cf-252 source installed in a cryogenic stopping cell, and were identified and counted with the multiple-reflection time-of-flight mass spectrometer (MR-TOR-MS) of the FRS-IC, utilizing well-established measurement and data analysis methods. The MR-TOR-MS resolves isobars unambiguously, even with limited statistics, and its non-scanning nature ensures minimal relative systematic uncertainties amongst fission products. The analysis for extracting IIFYs includes isotope-dependent efficiency corrections for all components of the FRS -IC. In particular, we applied a self-consistent technique that takes into account the element-dependent survival efficiencies in the CSC, due to chemical reactions with the buffer gas. Our IIFY results, which cover several tens of fission products in the less -accessible high-mass peak (Z = 56 to 63) down to fission yields at the level of 10(-5), are generally similar to those of the nuclear database ENDF/B-VII.O. Nevertheless, they reveal some structures that are not observed in the database smooth trends. These are the first results of a planned campaign to investigate IIFY distributions of spontaneous fission at the FRS-IC. Upcoming experiments will extend our results to wider Z and N ranges, lower fission yields, and other spontaneously-fissioning actinides.
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- Andreasson, M., et al.
(författare)
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Parkinson's disease with restless legs syndrome-an in vivo corneal confocal microscopy study
- 2021
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Ingår i: npj Parkinson's Disease. - : Springer Science and Business Media LLC. - 2373-8057. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Small fiber neuropathy (SFN) has been suggested as a trigger of restless legs syndrome (RLS). An increased prevalence of peripheral neuropathy has been demonstrated in Parkinson's disease (PD). We aimed to investigate, in a cross-sectional manner, whether SFN is overrepresented in PD patients with concurrent RLS relative to PD patients without RLS, using in vivo corneal confocal microscopy (IVCCM) and quantitative sensory testing (QST) as part of small fiber assessment. Study participants comprised of age- and sex-matched PD patients with (n = 21) and without RLS (n = 21), and controls (n = 13). Diagnosis of RLS was consolidated with the sensory suggested immobilization test. Assessments included nerve conduction studies (NCS), Utah Early Neuropathy Scale (UENS), QST, and IVCCM, with automated determination of corneal nerve fiber length (CNFL) and branch density (CNBD) from wide-area mosaics of the subbasal nerve plexus. Plasma neurofilament light (p-NfL) was determined as a measure of axonal degeneration. No significant differences were found between groups when comparing CNFL (p = 0.81), CNBD (p = 0.92), NCS (p = 0.82), and QST (minimum p = 0.54). UENS scores, however, differed significantly (p = 0.001), with post-hoc pairwise testing revealing higher scores in both PD groups relative to controls (p = 0.018 and p = 0.001). Analysis of all PD patients (n = 42) revealed a correlation between the duration of l-dopa therapy and CNBD (rho = -0.36, p = 0.022), and p-NfL correlated with UENS (rho = 0.35, p = 0.026) and NCS (rho = -0.51, p = 0.001). Small and large fiber neuropathy do not appear to be associated with RLS in PD. Whether peripheral small and/or large fiber pathology associates with central neurodegeneration in PD merits further longitudinal studies.
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- Al-Adili, Ali, et al.
(författare)
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Prompt fission neutron yields in thermal fission of U-235 and spontaneous fission of Cf-252
- 2020
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Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 102:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: The sharing of excitation energy between the fission fragments is one of the key issues in studying nuclear fission. One way to address this is by studying prompt-fission neutron multiplicities as a function of other fission observables such as the mass, (nu) over bar (A). These are vital benchmark data for both fission and nuclear deexcitation models, putting constrains on the fragment excitation energy and hence on the competing prompt neutron/gamma-ray emission. Despite numerous detailed studies, recent measurements done at JRC-Geel with the SCINTIA array in the epithermal region show surprisingly strong discrepancies to earlier thermal fission data and the Wahl systematics. Purpose: The purpose was to perform measurements of the prompt-fission neutron multiplicity, as a function of fragment mass and total kinetic energy (TKE), in U-235(n(th), f) and Cf-252(sf), to verify and extend the SCINTIA results. Another goal was to validate the analysis methods, and prepare for planned investigations at excitation energies up to 5.5 MeV. Methods: The experiments were conducted at the former 7 MV Van de Graaff facility in JRC-Geel, using a Twin Frisch-Grid Ionization Chamber and two liquid scintillation detectors. A neutron beam with an average energy of 0.5 MeV was produced via the Li-7(p,n) reaction. The neutrons were thermalized by a 12 cm thick block of paraffin. Digital data acquisition systems were utilized. Comprehensive simulations were performed to verify the methodology and to investigate the role of the mass and energy resolution on measured (nu) over bar (A) and (nu) over bar (TKE) values. The simulation results also revealed that the partial derivative(nu) over bar/partial derivative A and partial derivative(TKE) over bar/partial derivative(nu) over bar are affected by the mass and energy resolution. However, the effect is small for the estimated resolutions of this work. Detailed Fluka simulations were performed to calculate the fraction of thermal neutron-induced fission, which was estimated to be about 98%. Results: The experimental results on (nu) over bar (A) are in good agreement with earlier data for Cf-252(sf). For U-235(n(th), f), the (nu) over bar (A) data is very similar to the data obtained with SCINTIA, and therefore we verify these disclosed discrepancies to earlier thermal data and to the Wahl evaluation. The experimental results on (nu) over bar (TKE) are also in agreement with the data at epithermal energies. For Cf-252(sf) a slope value of partial derivative(TKE) over bar/partial derivative(nu) over bar = (-12.9 f 0.2) MeV/n was obtained. For U-235(n(th), f) the value is (-12.0 +/- 0.1) MeV/n. Finally, the neutron spectrum in the center-of-mass system was derived and plotted as a function of fragment mass. Conclusions: This work clearly proves the lack of accurate correlation between fission fragment and neutron data even in the best-studied reactions. The new results highlight the need of a new evaluation of the prompt-fission multiplicity for U-225(n(th), f).
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- Gao, Zhihao, et al.
(författare)
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Benchmark of a multi-physics Monte Carlo simulation of an ionguide for neutron-induced fission products
- 2022
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Ingår i: European Physical Journal. - : Springer Nature. - 1286-0042 .- 1286-0050. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- To enhance the production of medium-heavy,neutron-rich nuclei, and to facilitate measurements of independentyields of neutron-induced fission, a proton-toneutronconverter and a dedicated ion guide for neutroninducedfission have been developed for the IGISOL facilityat the University of Jyväskylä. The ion guide holds thefissionable targets, and the fission products emerging fromthe targets are collected in helium gas and transported to thedownstream experimental stations.Acomputer model, basedon a combination of MCNPX for modeling the neutron production,the fission code GEF, and GEANT4 for the transportof the fission products, was developed. The model willbe used to improve the setup with respect to the productionand collection of fission products. In this paper we benchmarkthe model by comparing simulations to a measurementin which fission products were implanted in foils located atdifferent positions in the ion guide. In addition, the productsfrom neutron activation in the titanium foil and the uraniumtargets are studied. The result suggests that the neutron fluxat the high-energy part of the neutron spectrum is overestimatedby approximately 40%.However, the transportation offission products in the uranium targets agrees with the experimentwithin 10%. Furthermore, the simulated transportationof fission products in the helium gas achieves almost perfectagreement with the measurement. Hence, we conclude thatthe model, after correction for the neutron flux, is well suitedfor optimization studies of future ion guide designs.
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- Gao, Zhihao, et al.
(författare)
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Fission studies at IGISOL/JYFLTRAP : Simulations of the ion guide for neutron-induced fission and comparison with experimental data
- 2020
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Ingår i: ND 2019. - : EDP Sciences. - 9782759891061
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Konferensbidrag (refereegranskat)abstract
- For the production of exotic nuclei at the IGISOL facility, an ion guide for neutron-induced fission has been developed and tested in experiments. Fission fragments are produced inside the ion guide and collected using a helium buffer gas. Meanwhile, a GEANT4 model has been developed to simulate the transportation and stopping of the charged fission products. In a recent measurement of neutron-induced fission yields, implantation foils were located at different positions in the ion guide. The gamma spectra from these foils and the fission targets are compared to the results from the GEANT4 simulation.In order to allow fission yield measurements in the low yield regions, towards the tails and in the symmetric part of the mass distribution, the stopping and extraction efficiency of the ion guide has to be significantly improved. This objective can be achieved by increasing the size while introducing electric field guidance using a combination of static electrodes and an RF-carpet. To this end, the GEANT4 model is used to optimise the design of such an ion guide.
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- Lindau, Robert, et al.
(författare)
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Decidual stromal cells support tolerance at the human foetal-maternal interface by inducing regulatory M2 macrophages and regulatory T-cells
- 2021
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Ingår i: Journal of Reproductive Immunology. - : Elsevier Ireland Ltd. - 0165-0378 .- 1872-7603. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- During pregnancy, the semi-allogeneic nature of the foetus requires maternal immune adaption and acquisition of tolerance at the foetal-maternal interface. Macrophages with regulatory properties and regulatory T (Treg) cells are central in promoting foetal tolerance and are enriched in the decidua (the uterine endometrium during pregnancy). Although tissue-resident decidual stromal cells (DSC) have been implicated in regulatory functions, it is not known if they are able to induce the regulatory phenotype of macrophages and T-cells. In this study we report that maternally derived DSC are able to induce homeostatic M2 macrophages and Treg cells. CD14+ monocytes and CD4+ T-cells from healthy non-pregnant women were cultured in the presence or absence of conditioned medium (CM) from DSC isolated from 1st trimester and term placentas. DSC-CM alone was able to promote the survival of macrophages and to induce a regulatory CD14brightCD163+CD209+CD86dim phenotype, typical for decidual macrophages and similar to that induced by M-CSF. Interestingly, DSC-CM was also able to overrule the pro-inflammatory effects of GM-CSF by upregulating CD14, CD163 and CD209. Protein-profiling showed that M-CSF was secreted by DSC, and blocking of M-CSF partially reversed the M2 phenotype and reduced viability. DSC-CM also expanded CD25brightFoxp3+ Treg cells, an expansion that was abolished by a SMAD3-inhibitor, indicating the contribution of TGF-beta signaling. In conclusion, our findings collectively emphasize the role of tissue-resident stromal cells in shaping the tolerogenic environment at the foetal-maternal interface.
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- Magalhaes, I, et al.
(författare)
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MAIT Cells in Health and Disease
- 2020
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Ingår i: Methods in molecular biology (Clifton, N.J.). - New York, NY : Springer US. - 1940-6029. ; 2098, s. 3-21
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Tidskriftsartikel (refereegranskat)
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| 15. |
- Neudecker, Denise, et al.
(författare)
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Templates of expected measurement uncertainties
- 2023
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Ingår i: EPJ NUCLEAR SCIENCES & TECHNOLOGIES. - : EDP Sciences. - 2491-9292. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The covariance committee of CSEWG (Cross Section Evaluation Working Group) established templates of expected measurement uncertainties for neutron-induced total, (n,gamma), neutron-induced charged-particle, and (n,xn) reaction cross sections as well as prompt fission neutron spectra, average prompt and total fission neutron multiplicities, and fission yields. Templates provide a list of what uncertainty sources are expected for each measurement type and observable, and suggest typical ranges of these uncertainties and correlations based on a survey of experimental data, associated literature, and feedback from experimenters. Information needed to faithfully include the experimental data in the nuclear-data evaluation process is also provided. These templates could assist (a) experimenters and EXFOR compilers in delivering more complete uncertainties and measurement information relevant for evaluations of new experimental data, and (b) evaluators in achieving a more comprehensive uncertainty quantification for evaluation purposes. This effort might ultimately lead to more realistic evaluated covariances for nuclear-data applications. In this topical issue, we cover the templates coming out of this CSEWG effort-typically, one observable per paper. This paper here prefaces this topical issue by introducing the concept and mathematical framework of templates, discussing potential use cases, and giving an example of how they can be applied (estimating missing experimental uncertainties of 235U(n,f) average prompt fission neutron multiplicities), and their impact on nuclear-data evaluations.
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