| 1. |
- Bouwmeester, Sjoerd, et al.
(author)
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Registered Replication Report : Rand, Greene, and Nowak (2012)
- 2017
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In: Perspectives on Psychological Science. - : SAGE Publications. - 1745-6916 .- 1745-6924. ; 12:3, s. 527-542
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Journal article (peer-reviewed)abstract
- In an anonymous 4-person economic game, participants contributed more money to a common project (i.e., cooperated) when required to decide quickly than when forced to delay their decision (Rand, Greene & Nowak, 2012), a pattern consistent with the social heuristics hypothesis proposed by Rand and colleagues. The results of studies using time pressure have been mixed, with some replication attempts observing similar patterns (e.g., Rand et al., 2014) and others observing null effects (e.g., Tinghög et al., 2013; Verkoeijen & Bouwmeester, 2014). This Registered Replication Report (RRR) assessed the size and variability of the effect of time pressure on cooperative decisions by combining 21 separate, preregistered replications of the critical conditions from Study 7 of the original article (Rand et al., 2012). The primary planned analysis used data from all participants who were randomly assigned to conditions and who met the protocol inclusion criteria (an intent-to-treat approach that included the 65.9% of participants in the time-pressure condition and 7.5% in the forced-delay condition who did not adhere to the time constraints), and we observed a difference in contributions of −0.37 percentage points compared with an 8.6 percentage point difference calculated from the original data. Analyzing the data as the original article did, including data only for participants who complied with the time constraints, the RRR observed a 10.37 percentage point difference in contributions compared with a 15.31 percentage point difference in the original study. In combination, the results of the intent-to-treat analysis and the compliant-only analysis are consistent with the presence of selection biases and the absence of a causal effect of time pressure on cooperation.
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| 2. |
- Bouwmeester, S, et al.
(author)
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Registered Replication Report: Rand, Greene, and Nowak (2012) : Multilab direct replication of: Study 7 from Rand, D. G., Greene, J. D., & Nowak, M. A. (2012) Spontaneous giving and calculated greed. Nature, 489, 427–430.
- 2017
-
In: Perspectives on Psychological Science. - : Sage Publications. - 1745-6916 .- 1745-6924. ; 12:3, s. 527-542
-
Journal article (peer-reviewed)abstract
- In an anonymous 4-person economic game, participants contributed more money to a common project (i.e., cooperated) when required to decide quickly than when forced to delay their decision (Rand, Greene & Nowak, 2012), a pattern consistent with the social heuristics hypothesis proposed by Rand and colleagues. The results of studies using time pressure have been mixed, with some replication attempts observing similar patterns (e.g., Rand et al., 2014) and others observing null effects (e.g., Tinghög et al., 2013; Verkoeijen & Bouwmeester, 2014). This Registered Replication Report (RRR) assessed the size and variability of the effect of time pressure on cooperative decisions by combining 21 separate, preregistered replications of the critical conditions from Study 7 of the original article (Rand et al., 2012). The primary planned analysis used data from all participants who were randomly assigned to conditions and who met the protocol inclusion criteria (an intent-to-treat approach that included the 65.9% of participants in the time-pressure condition and 7.5% in the forced-delay condition who did not adhere to the time constraints), and we observed a difference in contributions of −0.37 percentage points compared with an 8.6 percentage point difference calculated from the original data. Analyzing the data as the original article did, including data only for participants who complied with the time constraints, the RRR observed a 10.37 percentage point difference in contributions compared with a 15.31 percentage point difference in the original study. In combination, the results of the intent-to-treat analysis and the compliant-only analysis are consistent with the presence of selection biases and the absence of a causal effect of time pressure on cooperation.
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| 3. |
- Døssing, T, et al.
(author)
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Decay-Out Of Superdeformed Bands By Coupling To Ordered Or Chaotic Spectra
- 2005
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In: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 764:1, s. 27-33
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Journal article (peer-reviewed)abstract
- Different treatments of the decay-out of superdeformed bands are reviewed, focusing on the role of the normally deformed doorway states to which the superdeformed band primarily couples at decay-out. A schematic description based on sparse GOE matrices is formulated for the normally deformed states including one doorway state. This allows for a gradual change of the normally deformed spectrum from an ordered to a chaotic situation by means of the effective dimensionality parameter. It is found that the distribution of the small normally deformed admixtures into the superdeformed band, through which it decays, depends sensitively on the effective dimensionality parameter. Analyzing the measured distribution of transition strength of decay-out gamma-ray lines in 194Hg, it is concluded that the spectrum of normally deformed states is closer to the chaotic than the ordered situation at the energy and angular momentum of the superdeformed band. ©2005 American Institute of Physics
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| 4. |
- Døssing, T, et al.
(author)
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Order to Chaos Properties of the Decay-out Gamma Rays from Superdeformed Bands
- 2004
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In: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 701, s. 164-168
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Journal article (peer-reviewed)abstract
- Based on GOE sparse matrices, a model for decay-out of superdeformed bands is formulated, with focus on the degree of chaoticity of the spectrum of normally deformed states, to which the superdeformed band couples at decay-out. By means of the effective dimensionality parameter, the spectrum may be varied between the two limiting situations of complete order and complete chaos. The model is applied to the measured distribution of transition strength of decay-out gamma-ray lines in 194Hg, and it is found that the normally deformed states should be closer to the chaotic than the ordered situation, with GOE-type spectral correlations extending over at least 10 levels. ©2004 American Institute of Physics
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| 5. |
- Nag, Somnath, et al.
(author)
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Observation of high-spin bands with large moments of inertia in Xe 124
- 2016
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 94:3
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Journal article (peer-reviewed)abstract
- High-spin states in Xe124 have been populated using the Se80(Ca48,4n) reaction at a beam energy of 207 MeV and high-multiplicity, γ-ray coincidence events were measured using the Gammasphere spectrometer. Six high-spin bands with large moments of inertia, similar to those observed in neighboring nuclei, have been observed. The experimental results are compared with calculations within the framework of the cranked Nilsson-Strutinsky model. It is suggested that the configurations of the bands involve excitations of protons across the Z=50 shell gap coupled to neutrons within the N=50-82 shell or excited across the N=82 shell closure.
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| 6. |
- Aberg, S., et al.
(author)
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Nuclear Structure Effects in Fission
- 2023. - 1
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In: Journal of Physics: Conference Series. - 1742-6588. ; 2586
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Conference paper (peer-reviewed)abstract
- Three examples of nuclear structure effects in fission dynamics are discussed: (i) The appearance of a super-short symmetric mode in the fission of nuclei around 264Fm leading to two double-magic 132Sn, (ii) Fission of some super-heavy elements where the heavy cluster is focused around double-magic 208Pb, and (iii) A saw-tooth distribution in angular momenta versus the fission fragment mass in the fission of 239U. The Metropolis random walk method is used to simulate the strongly damped fission dynamics on a 5D deformation grid. The dynamics is driven by pairing-, shape- and energy-dependent level densities. When available, a good agreement with experimental data is obtained.
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| 7. |
- Albertsson, M., et al.
(author)
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Correlation studies of fission-fragment neutron multiplicities
- 2021
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In: Physical Review C. - 2469-9985. ; 103:1
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Journal article (peer-reviewed)abstract
- We calculate neutron multiplicities from fission fragments with specified mass numbers for events having a specified total fragment kinetic energy. The shape evolution from the initial compound nucleus to the scission configurations is obtained with the metropolis walk method on the five-dimensional potential-energy landscape, calculated with the macroscopic-microscopic method for the three-quadratic-surface shape family. Shape-dependent microscopic level densities are used to guide the random walk, to partition the intrinsic excitation energy between the two proto-fragments at scission, and to determine the number of neutrons evaporated from the fragments. The contribution to the total excitation energy of the resulting fragments from statistical excitation and shape distortion at scission is studied. Good agreement is obtained with available experimental data on neutron multiplicities in correlation with fission fragments from U235(nth,f). With increasing neutron energy a superlong fission mode grows increasingly prominent, which affects the dependence of the observables on the total fragment kinetic energy.
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| 8. |
- Albertsson, M., et al.
(author)
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Excitation energy partition in fission
- 2020
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 803
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Journal article (peer-reviewed)abstract
- The transformation of an atomic nucleus into two excited fission fragments is modeled as a strongly damped evolution of the nuclear shape. As in previous studies, it is assumed that the division of mass and charge is frozen in at a critical neck radius of c0=2.5fm. In order to also determine the energetics, we follow the system further until scission occurs at a smaller neck radius, at which point the shapes of the proto-fragments are extracted. The statistical energy available at scission is then divided on the basis of the respective microscopic level densities. This approach takes account of important (and energy-dependent) finite-size effects. After the fragments have been fully accelerated and their shapes have relaxed to their equilibrium forms, they undergo sequential neutron evaporation. The dependence of the resulting mean neutron multiplicity on the fragment mass, ν¯(A), including the dependence on the initial excitation energy of the fissioning compound nucleus, agrees reasonably well with observations, as demonstrated here for 235U(n, f), and the sawtooth appearance of ν¯(A) can be understood from shell-structure effects in the level densities.
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| 9. |
- Albertsson, M., et al.
(author)
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Super-short fission mode in fermium isotopes
- 2021
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In: Physical Review C. - 2469-9985. ; 104:6
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Journal article (peer-reviewed)abstract
- The so-called super-short fission mode, in which a nucleus divides nearly symmetrically into two unusually energetic fragments, competes favorably with the standard asymmetric fission mode for spontaneous fission of a limited number of nuclei near Fm264 but it quickly fades away at finite excitations. We investigate the energy-dependent competition between those two fission modes for even fermium isotopes from Fm254 to Fm268, using the Metropolis method to simulate the strongly damped fission dynamics being driven by shape- and energy-dependent level densities. The origin of the super-short mode is discussed and its effects on the fragment mass distribution, the total fragment kinetic energy, and the neutron multiplicity are calculated. Generally good agreement with the available data is obtained.
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| 10. |
- Døssing, Arne, et al.
(author)
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UAV-Towed scalar magnetic gradiometry: A case study in relation to iron oxide copper-gold mineralization, Nautanen (Arctic Sweden)
- 2023
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In: The Leading Edge. - : Society of Exploration Geophysicists. - 1070-485X .- 1938-3789. ; 42:2, s. 103-111
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Journal article (peer-reviewed)abstract
- Scalar magnetic surveying using unmanned aerial vehicle (UAV) platforms is slowly gaining momentum within geophysical applications. So far, only a handful of studies have dealt with UAV-Towed scalar field measurements, while even fewer have considered towed scalar difference measurements (or gradients). In this paper, we demonstrate the possibilities and benefits of deploying precisely positioned noise-minimized UAV-Towed scalar transverse horizontal difference (THD) measurements for mineral exploration purposes. UAV-Towed gradiometry bird data are presented from the Nautanen area in northern Sweden and compared with ground magnetic surveys. This area is known for its iron oxide copper-gold mineralizations. The UAV survey spans a total area of 2.5 km2. It was covered using an average line spacing of 30 m and a constant flight altitude above ground level of 30 m. High-quality scalar total-field and THD data were collected with a dynamic noise level of the raw scalar data of about ±0.05 nT. Comparison with the ground magnetic data shows a strong correlation between magnetic anomaly lows and highs across the survey areas. A map with new structural information is presented based on subtle magnetic structures identified in discrete derivatives of the total magnetic intensity anomaly and THD data. Such systems may replace high-quality heliborne systems and reduce costs of the geophysical exploration phase. However, mapping with UAV-Towed systems is not straightforward. With typical UAV flight speeds of only 10-12 m/s, the wind often disturbs the 3D attitude of the bird during flights. Hence, advanced processing is required to obtain the intended gradients. Similar challenges are less important in surveying, where the survey speed often greatly exceeds the wind speed.
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| 11. |
- Døssing, T., et al.
(author)
-
Angular momentum in fission fragments
- 2024
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In: Physical Review C. - 2469-9985. ; 109:3
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Journal article (peer-reviewed)abstract
- We suggest that the angular momentum in fission fragments is generated by statistical excitation at scission. The magnitude of the angular momentum is determined by excitation energy and shell structure in the level density. Treating the prescission shape evolution as a diffusive process, implemented as a Metropolis walk on a five-dimensional potential-energy surface, the average magnitudes of the fission fragment angular momenta are calculated for U235(nth,f), assuming that they are perpendicular to the fission axis. The sawtooth behavior of the average angular momentum magnitude as function of mass number is discussed in connection with the similar observed behavior of the average neutron multiplicity, and a good understanding is achieved. The magnitudes of the angular momenta of light and heavy fragments are found to have a weak negative correlation, in accordance with recent experimental results. This correlation arises from the microcanonical sharing of excitation energy by the fragments at scission, where each energy provides a distribution of angular momenta.
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| 12. |
- Kardan, A., et al.
(author)
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High-spin rotational bands in Nd 137
- 2023
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In: Physical Review C. - 2469-9985. ; 107:4
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Journal article (peer-reviewed)abstract
- We have employed the cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov methods to predict the structure of the observed high-spin rotational bands in Nd137. Our study is motivated in particular by a previous observation of a rotational band more than 4 MeV above yrast. We discuss both possible interpretations of this band and in this connection also the HD band and the terminating states expected around I=45.
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| 13. |
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| 14. |
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| 15. |
- Ward, D. E., et al.
(author)
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Nuclear shape evolution based on microscopic level densities
- 2017
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In: Physical Review C. - 2469-9985. ; 95:2
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Journal article (peer-reviewed)abstract
- By combining microscopically calculated level densities with the Metropolis walk method, we develop a consistent framework for treating the energy and angular-momentum dependence of the nuclear shape evolution in the fission process. For each nucleus under consideration, the level density is calculated microscopically for each of more than five million shapes with a recently developed combinatorial method. The method employs the same single-particle levels as those used for the extraction of the pairing and shell contributions to the macroscopic-microscopic potential-energy surface. Containing no new parameters, the treatment is suitable for elucidating the energy dependence of the dynamics of warm nuclei on pairing and shell effects. It is illustrated for the fission fragment mass distribution for several uranium and plutonium isotopes of particular interest.
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