| 1. |
- Bouwmeester, Sjoerd, et al.
(författare)
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Registered Replication Report : Rand, Greene, and Nowak (2012)
- 2017
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Ingår i: Perspectives on Psychological Science. - : SAGE Publications. - 1745-6916 .- 1745-6924. ; 12:3, s. 527-542
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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
-
Ingår i: Perspectives on Psychological Science. - : Sage Publications. - 1745-6916 .- 1745-6924. ; 12:3, s. 527-542
-
Tidskriftsartikel (refereegranskat)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.
(författare)
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Decay-Out Of Superdeformed Bands By Coupling To Ordered Or Chaotic Spectra
- 2005
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 764:1, s. 27-33
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Order to Chaos Properties of the Decay-out Gamma Rays from Superdeformed Bands
- 2004
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 701, s. 164-168
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Observation of high-spin bands with large moments of inertia in Xe 124
- 2016
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Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 94:3
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Nuclear Structure Effects in Fission
- 2023. - 1
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Ingår i: Journal of Physics: Conference Series. - 1742-6588. ; 2586
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Konferensbidrag (refereegranskat)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.
(författare)
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Correlation studies of fission-fragment neutron multiplicities
- 2021
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Ingår i: Physical Review C. - 2469-9985. ; 103:1
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Excitation energy partition in fission
- 2020
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 803
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Formation of transfermium elements in reactions with 208Pb
- 2024
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Ingår i: Physical Review C. - 2469-9985. ; 110:1
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Tidskriftsartikel (refereegranskat)abstract
- Within the Langevin framework, we investigate the dynamics of the fusion process for production of transfermium elements in reactions of 48Ca, 50Ti, 54Cr, and 58Fe with 208Pb. After the reacting nuclei have made contact, the early dynamical stage is dominated by the dissipation of the initial radial kinetic energy, while the subsequent shape evolution is diffusive. The probability for surmounting the inner barrier and forming a compound system is obtained by simulating the evolution as a Metropolis random walk in a five-dimensional potential-energy landscape. Good agreement with the available data is obtained, especially for the maximal formation probability.
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| 10. |
- Albertsson, M., et al.
(författare)
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Super-short fission mode in fermium isotopes
- 2021
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Ingår i: Physical Review C. - 2469-9985. ; 104:6
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Tidskriftsartikel (refereegranskat)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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