| 1. |
- Al-Adili, Ali, et al.
(författare)
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Neutron-multiplicity experiments for enhanced fission modelling
- 2017
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 9782759890200
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Konferensbidrag (refereegranskat)abstract
- The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A), as a function of the incident neutron energy (En) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc) is manifested through an increase of ν(A) for all fragments or for the heavy ones only. A systematic investigation of ν(A) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235U(nth,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A) and spectrum in correlation with FF properties are presented.
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| 2. |
- Al-Adili, Ali, et al.
(författare)
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Studying fission neutrons with 2E-2v and 2E
- 2018
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Ingår i: SCIENTIFIC WORKSHOP ON NUCLEAR FISSION DYNAMICS AND THE EMISSION OF PROMPT NEUTRONS AND GAMMA RAYS (THEORY-4). - : EDP Sciences. - 9782759890316
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Konferensbidrag (refereegranskat)abstract
- This work aims at measuring prompt-fission neutrons at different excitation energies of the nucleus. Two independent techniques, the 2E-2v and the 2E techniques, are used to map the characteristics of the mass-dependent prompt fission neutron multiplicity, 7(A), when the excitation energy is increased. The VERDI 2E-2v spectrometer is being developed at JRC-GEEL. The Fission Fragment (FF) energies are measured using two arrays of 16 silicon (Si) detectors each. The FFs velocities are obtained by time-of-flight, measured between micro-channel plates (MCP) and Si detectors. With MCPs placed on both sides of the fission source, VERDI allows for independent timing measurements for both fragments. Cf-252(sf) was measured and the present results revealed particular features of the 2E-2v technique. Dedicated simulations were also performed using the GEF code to study important aspects of the 2E-2v technique. Our simulations show that prompt neutron emission has a non-negligible impact on the deduced fragment data and affects also the shape of 17(A). Geometrical constraints lead to a total-kinetic energy-dependent detection efficiency. The 2E technique utilizes an ionization chamber together with two liquid scintillator detectors. Two measurements have been performed, one of Cf-252(sf) and another one of thermal-neutron induced fission in U-235(n,f). Results from Cf-252(sf) are reported here.
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| 3. |
- Andersson, Peter, 1981-, et al.
(författare)
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Coincidence spectroscopy for increased sensitivity in radionuclide monitoring
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The majority of the energy in a nuclear explosion is released in the immediate blast and the initial radiation accounts. The remaining fraction is released through radioactive decay of the explosion's fission products and neutron activation products over a longer time span. This allows for the detection of a nuclear explosion by detecting the presence of residual decay. Radionuclide monitoring stations for detection of radioactive emissions to the atmosphere is thereby an important tool in the verification of compliance with nuclear disarmament treaties. In particular, the globally spanning radionuclide station network of the International Monitoring System (IMS) has been implemented for verification of the Comprehensive Nuclear-Test-Ban Treaty.High Purity Germanium (HPGe) detectors are workhorses in radionuclide monitoring. The detection of characteristic gamma rays can be used to disclose the presence of signature nuclides produced innuclear weapon tests. A particular development that has potential to improve the sensitivity of radionuclide monitoring is the coincidence technique where decaying nuclides that emit several coincident gamma rays can be detected at much smaller activity concentrations than with conventional gamma spectroscopy.In this project, dedicated gamma-gamma coincidence detectors are being developed, utilizing electronically segmented HPGe detectors. These detectors are expected to be highly sensitive to low-activity samples of nuclides that present coincident emissions of gamma rays. In this paper we present the concept, define performance parameters, and explore the performance of such detectors to a subset of radionuclides of particular CTBT relevance. In addition, we discuss the path forward in developing a next generation gamma-gamma coincidence spectroscopy system of segmented HPGe.
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| 4. |
- Anselm, Jonas, et al.
(författare)
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Bannlys alla politiska beslut som ger mer klimatutsläpp
- 2014
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Ingår i: Dagens Nyheter.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Torftig valdebatt. Dagspolitiken klarar inte att hantera ödesfrågan om klimatet, vilket oroar oss. Vi föreslår därför ett ”utsläppsmoratorium”: inga beslut får tas som ökar utsläppen av växthusgaser. Principen måste kopplas till mål om exempelvis förnybar energi och grön infrastruktur, skriver 23 forskare och debattörer.
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| 5. |
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| 6. |
- Giovannucci, Tatiana A., et al.
(författare)
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Identification of a novel compound that simultaneously impairs the ubiquitin-proteasome system and autophagy
- 2022
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Ingår i: Autophagy. - : Taylor & Francis. - 1554-8627 .- 1554-8635. ; 18:7, s. 1486-1502
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Tidskriftsartikel (refereegranskat)abstract
- The ubiquitin-proteasome system (UPS) and macroautophagy/autophagy are the main proteolytic systems in eukaryotic cells for preserving protein homeostasis, i.e., proteostasis. By facilitating the timely destruction of aberrant proteins, these complementary pathways keep the intracellular environment free of inherently toxic protein aggregates. Chemical interference with the UPS or autophagy has emerged as a viable strategy for therapeutically targeting malignant cells which, owing to their hyperactive state, heavily rely on the sanitizing activity of these proteolytic systems. Here, we report on the discovery of CBK79, a novel compound that impairs both protein degradation by the UPS and autophagy. While CBK79 was identified in a high-content screen for drug-like molecules that inhibit the UPS, subsequent analysis revealed that this compound also compromises autophagic degradation of long-lived proteins. We show that CBK79 induces non-canonical lipidation of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) that requires ATG16L1 but is independent of the ULK1 (unc-51 like autophagy activating kinase 1) and class III phosphatidylinositol 3-kinase (PtdIns3K) complexes. Thermal preconditioning of cells prevented CBK79-induced UPS impairment but failed to restore autophagy, indicating that activation of stress responses does not allow cells to bypass the inhibitory effect of CBK79 on autophagy. The identification of a small molecule that simultaneously impairs the two main proteolytic systems for protein quality control provides a starting point for the development of a novel class of proteostasis-targeting drugs.
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| 7. |
- Grape, Sophie, 1982-, et al.
(författare)
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State-of-the-Art Report : Prepared by Working Group 4: Technical nuclear non-proliferation and safeguards under the Alva Myrdal Centre for nuclear disarmament
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Alva Myrdal Centre for nuclear disarmament (AMC) was established in 2021. AMC consists of six working Groups, and one of them - Working Group 4 - is called Technical nuclear non-proliferation and safeguards. This is the State-of-the-Art Report of that working group. The objective with the report is to provide an overview of the technical fields relevant to the working group and to highlight where research and activities within the working group may contribute to global nuclear disarmament. The report gives a brief explanation of actors in the field, introduces nuclear materials and assay techniques, and then continues to elaborate on challenges and needs associated with nuclear measurements and assessments in the fields of non-proliferation, nuclear safeguards and nuclear disarmament. A section is also devoted to the management of nuclear weapons materials after disarmament. Lastly, the report contains a section on interdisciplinary research and development in nuclear disarmament, and information about technical education and training in the non-proliferation and disarmament field.
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| 8. |
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| 10. |
- Gustavsson, Alf
(författare)
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Automatiska mjölkningssystem : så påverkas arbetstid och arbetsmiljö
- 2010
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Rapport (refereegranskat)abstract
- I häftet JTI-informerar nr 124 ”Automatiska mjölkningssystem – så påverkas mjölkningstid och arbetsmiljö” finns en lista på litteratur under rubriken Mer att läsa. Här saknas i den tryckta publikationen en rapport från Lantbrukets byggnadsteknik vid Sveriges Lantbruksuniversitet. I den uppdaterade digitala versionen av skriften har listan kompletterats med: Arbetsåtgång i mjölkproduktion beroende på besättningsstorlek samt mekaniserings och automatiseringsgrad. Sofia Hedlund. Rapport 2008:2. Institutionen för lantbrukets byggnadsteknik vid Sveriges lantbruksuniversitet.
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| 11. |
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| 12. |
- Gustavsson, Mattias, et al.
(författare)
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Numerical simulation of fluid dynamics in fluidized beds with horizontal heat exchanger tubes
- 2000
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 55:4, s. 857-866
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Tidskriftsartikel (refereegranskat)abstract
- A numerical code, Gemini, based on the implicit multifield method (IMF) of Harlow and Amsden for Eulerian two-fluid modelling, is used to simulate the fluid dynamics of bubbling fluidized beds, assuming no turbulence in the gas or solid phase. The paper gives a formulation of the equations of motion and empirical closure laws in general curvilinear coordinates for calculation of the fluid dynamics in beds with complex internal geometries. A special discretization method for general curvilinear structured grids with multiblock connectivity is implemented, and two-dimensional non-stationary calculations are performed for a bed with a cross-sectional width of 0.3 m, containing two horizontal heat exchanger tubes. The local visible bubble flow and the gas and particle motion around the tubes are briefly discussed and compared with experimental fluid dynamic results at different pressure levels.
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| 13. |
- Gustavsson, Mattias, et al.
(författare)
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Two-fluid modelling of cooling-tube erosion in a fluidized bed
- 2000
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 55:4, s. 867-879
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Tidskriftsartikel (refereegranskat)abstract
- The fluid dynamics of a bubbling fluidized bed is simulated in general curvilinear co-ordinates using an Eulerian two-fluid model. Computations are performed at different pressure levels for a bed with a cross-sectional width of 0.3 m in which two heat exchanger tubes were inserted. A monolayer kinetic energy dissipation model is implemented to simulate the erosion of cooling tube surfaces. The local visible bubble flow and particle motion close to the tubes are correlated with the modelled instantaneous erosion rate. Experiments were conducted in order to validate the erosion simulations, and fair qualitative agreement between experimental and numerical results was obtained.
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| 14. |
- Jansson, Kaj, 1987-, et al.
(författare)
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The new double energy-velocity spectrometer VERDI
- 2017
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Ingår i: ND 2016: INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY. - Les Ulis : EDP Sciences. - 9782759890200
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Konferensbidrag (refereegranskat)abstract
- VERDI (VElocity foR Direct particle Identification) is a fission-fragment spectrometer recently put into operation at JRC-Geel. It allows measuring the kinetic energy and velocity of both fission fragments simultaneously. The velocity provides information about the pre-neutron mass of each fission fragment when isotropic prompt-neutron emission from the fragments is assumed. The kinetic energy, in combination with the velocity, provides the post-neutron mass. From the difference between pre- and post-neutron masses, the number of neutrons emitted by each fragment can be determined. Multiplicity as a function of fragment mass and total kinetic energy is one important ingredient, essential for understanding the sharing of excitation energy between fission fragments at scission, and may be used to benchmark nuclear de-excitation models. The VERDI spectrometer design is a compromise between geometrical efficiency and mass resolution. The spectrometer consists of an electron detector located close to the target and two arrays of silicon detectors, each located 50 cm away from the target. In the present configuration pre-neutron and post-neutron mass distributions are in good agreement with reference data were obtained. Our latest measurements performed with spontaneously fissioning 252Cf is presented along with the developed calibration procedure to obtain pulse height defect and plasma delay time corrections.
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