| 481. |
- Oberkofler, M., et al.
(författare)
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Nitrogen retention mechanisms in tokamaks with beryllium and tungsten plasma-facing surfaces
- 2016
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T167
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Tidskriftsartikel (refereegranskat)abstract
- Global gas balance experiments at ASDEX Upgrade (AUG) and JET have shown that a considerable fraction of nitrogen injected for radiative cooling is not recovered as N-2 upon regeneration of the liquid helium cryo pump. The most probable loss channels are ion implantation into plasma-facing materials, co-deposition and ammonia formation. These three mechanisms are investigated in laboratory and tokamak experiments and by numerical simulations. Laboratory experiments have shown that implantation of nitrogen ions into beryllium and tungsten leads to the formation of surface nitrides, which may decompose under thermal loads. On beryllium the presence of nitrogen at the surface has been seen to reduce the sputtering yield. On tungsten surfaces it has been observed that the presence of nitrogen can increase hydrogen retention. The global nitrogen retention in AUG by implantation into the tungsten surfaces saturates. At JET the steady state nitrogen retention is increased by co-deposition with beryllium. The tokamak experiments are interpreted in detail by simulations of the global migration with WallDYN. Mass spectrometry of the exhaust gas of AUG and JET has revealed the conversion of nitrogen to ammonia at percent-levels. Conclusions are drawn on the potential implications of nitrogen seeding on the operation of a reactor in a deuterium-tritium mix.
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| 482. |
- Obryk, B., et al.
(författare)
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TLD calibration for neutron fluence measurements at JET fusion facility
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER. - 0168-9002 .- 1872-9576. ; 904, s. 202-213
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of neutron streaming through penetrations in biological shields are being carried out at JET fusion device by means of thermoluminescence (TL) detectors with the objective to validate the neutronics codes and nuclear data widely applied in ITER nuclear analyses in a real fusion environment. TLDs response due to the neutron component of the radiation field is related to the neutron fluence in a well-defined neutron energy spectrum. Therefore, a TLDs calibration in real fusion radiation fields is necessary to allow neutron fluence from TL measurements at JET to be more precisely calculated. Hence, a MCP-N and MCP-7 TLDs produced at the IFJ PAN in Krakow were calibrated at the ENEA facilities of Frascati and Casaccia laboratories. The obtained results have been analysed and new calibration factors are proposed. The detection system based on TLDs developed and calibrated for JET experiments can then be generally applied not only to fusion neutron fields, but also to ITER to monitor the neutron fluence outside the biological shield.
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| 483. |
- Odar-Cederlöf, Ingegerd, et al.
(författare)
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Neuropeptide-Y and atrial natriuretic peptide as prognostic markers in patients on hemodialysis
- 2003
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Ingår i: ASAIO journal (1992). - Philadelphia, PA, United States : Lippincott Williams & Wilkins. - 1058-2916 .- 1538-943X. ; 49:1, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- We conducted a study of the influence of the vasoactive peptides atrial natriuretic peptide (ANP) and neuropeptide Y (NPY) on survival of patients on hemodialysis and their association and relative importance with cardiac and clinical variables. Thirty-three hemodialysis patients were characterized by age, sex, diagnosis, blood pressure, serum (S)-albumin, serum (S)-urea, hemoglobin, dialysis dose, weight gain, duration of dialysis, cardiac hypertrophy, volume, failure, and ischemia and plasma levels of ANP and NPY. The outcomes were analyzed for early deaths (<1 year) and for all deaths. The association of the variables to early deaths and all deaths, respectively, was studied in Cox proportional hazard analyses. The variables were also studied in three hierarchical steps: clinical variables only, clinical and cardiac variables, and all variables. For all deaths, the independent variables were plasma NPY (pmol/L) (hazard ratio [HR] = 1.035, p = 0.004), heart volume (ml/m2) (HR = 1.009, p = 0.001), and S-albumin (g/L) (HR = 0.750, p = 0.034). For early deaths, the independent variables were predialysis ANP (pmol/L) (HR = 1.008, p = 0.034) and NPY (pmol/L) (HR = 1.031, p = 0.026). In the hierarchical study, excluding the vasoactive peptides, heart volume, heart failure and S-albumin were independently associated with all deaths, and mean arterial blood pressure was associated with early death. When also excluding the cardiac parameters, S-albumin was associated with all deaths and mean arterial blood pressure with early death. In conclusion, plasma levels of the vasoactive peptides ANP and NPY are the most important group in a hierarchy of variables that predict imminent death in hemodialysis patients, and NPY is associated with late death. ANP and NPY apparently sum up the detrimental influence of many factors in hemodialysis patients.
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| 484. |
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| 485. |
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| 486. |
- Ojalehto, E., et al.
(författare)
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Influences of genetically predicted and attained education on geographic mobility and their association with mortality
- 2023
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Ingår i: Social Science and Medicine. - : Elsevier. - 0277-9536 .- 1873-5347. ; 324
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Both educational attainment and genetic propensity to education (PGSEdu) have been associated with geographic mobility. Socioeconomic conditions are, in turn, associated with individuals’ health. Geographic mobility could therefore lead to better health for some since it could provide better opportunities, like education. Our aim was to study how attained education and genetic predisposition for higher education are related to geographic mobility, and how they affect the association between geographic mobility and mortality. Methods: We used data from the Swedish Twin Registry (twins born 1926–1955; n = 14,211) in logistic regression models to test if attained education and PGSEdu predicted geographic mobility. Cox regression models were then performed to test if geographic mobility, attained education, and PGSEdu were associated with mortality. Results: The results show that both attained education and PGSEdu predicted geographic mobility, in both independent and joint effect models, with higher education associated with higher mobility. Geographic mobility was associated with lower mortality in the independent effect model, but joint effect models showed that this association was completely explained by attained education. Conclusions: To conclude, both attained education and PGSEdu were associated with geographic mobility. Moreover, attained education explained the relationship between geographic mobility and mortality.
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| 487. |
- Orsitto, F. P., et al.
(författare)
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Approximate analytic expressions using Stokes model for tokamak polarimetry and their range of validity
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 61:5
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Tidskriftsartikel (refereegranskat)abstract
- The analysis of the polarimetry measurements has the aim of validating models (De Marco and Segre 1972 Plasma Phys. 14 245), with a careful attention to the clarification of their limits of application. In this paper a new approximation method is introduced, the so-called special constant Omega direction (SCOD), which gives an analytical solution to the polarimetry exact Stokes model equations. The available approximate solutions (including SCOD) of the polarimetry propagation equations are presented, compared and their application limits determined, using a reference tokamak configuration, which is a simplified equilibrium for a circular tokamak. The SCOD approximation is compared successfully to the Stokes model in the context also of equilibria evaluated for two JET discharges. The approximation methods are analytical or very simple mathematical expressions which can also be used in equilibrium codes for their optimization.
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| 488. |
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| 489. |
- Pajuste, Elina, et al.
(författare)
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Comparison of the structure of the plasma-facing surface and tritium accumulation in beryllium tiles from JET ILW campaigns 2011-2012 and 2013-2014
- 2019
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Ingår i: Nuclear Materials and Energy. - : ELSEVIER. - 2352-1791. ; 19, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- In this study, beryllium tiles from Joint European Torus (JET) vacuum vessel wall were analysed and compared regarding their position in the vacuum vessel and differences in the exploitation conditions during two campaigns of ITER-Like-Wall (ILW) in 2011-2012 (ILW1) and 2013-2014 (ILW2) Tritium content in beryllium samples were assessed. Two methods were used to measure tritium content in the samples - dissolution under controlled conditions and tritium thermal desorption. Prior to desorption and dissolution experiments, scanning electron microscopy and energy dispersive x-ray spectroscopy were used to study structure and chemical composition of plasma-facing-surfaces of the beryllium samples. Experimental results revealed that tritium content in the samples is in range of 2.10(11)-2.10(13) tritium atoms per square centimetre of the surface area with its highest content in the samples from the outer wall of the vacuum vessel (up to 1.9.10(13) atoms/cm(2) in ILW1 campaign and 2.4.10(13) atoms/cm(2) in ILW2). The lowest content of tritium was found in the upper part of the vacuum vessel (2.0.10(12) atoms/cm(2) and 2.0.10(11) atoms/cm(2) in ILW1 and ILW2, respectively). Results obtained from scanning electron microscopy has shown that surface morphology is different within single tile, however if to compare two campaigns main tendencies remains similar.
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| 490. |
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