An investigation of nuclear collisions with a momentum-dependent Lattice Hamiltonian model

We formulate a Lattice Hamiltonian approach for the modeling of intermediate energy heavy ion collisions. After verifying stationary ground state solutions, we implement this in a calculation of nuclear stopping power and compare our results with experimental data. Our findings support a relatively soft nuclear equation of state, with a momentum-dependent self-consistent mean field.Comment: 8 pages including 2 figures. MRST '99 conference proceedings, Carleton University, Ottawa, Canad

Determination of the Mean-Field Momentum-Dependence using Elliptic Flow

Midrapidity nucleon elliptic flow is studied within the Boltzmann-equation simulations of symmetric heavy-ion collisions. The simulations follow a lattice Hamiltonian extended to relativistic transport. It is demonstrated that in the peripheral heavy-ion collisions the high-momentum elliptic flow is strongly sensitive to the momentum dependence of mean field at supranormal densities. The high transverse-momentum particles are directly and exclusively emitted from the high-density zone in the collisions, while remaining particles primarily continue along the beam axis. The elliptic flow was measured by the KaoS Collaboration as a function of the transverse momentum at a number of impact parameters in Bi + Bi collisions at 400, 700, and 1000 MeV/nucleon. The observed elliptic anisotropies in peripheral collisions, which quickly rise with momentum, can only be explained in simulations when assuming a strong momentum dependence of nucleonic mean field. This momentum dependence must strengthen with the rise of density above normal. The mean-field parametrizations, which describe the data in simulations with various success, are confronted with mean fields from microscopic nuclear-matter calculations. Two of the microscopic potentials in the comparisons have unacceptably weak momentum-dependencies at supranormal densities. The optical potentials from the Dirac-Brueckner-Hartree-Fock calculations, on the other hand, together with the UV14 + TNI potential from variational calculations, agree rather well within the region of sensitivity with the parametrized potentials that best describe the data.Comment: 44 pages, 17 figures, mostly minor editorial corrections, Nucl. Phys. A in pres

Trust within Sibling Relationships: Predicting Psychosocial Well-Being in Early Adolescence

Sibling relationships are a unique and critical context through which we can investigate early adolescent development and well-being. Positive sibling relationship qualities (e.g., warmth) are implicated in many facets of adolescents’ lives; for example, positive relationships promote positive self-worth (Noel et al., 2018) and fewer internalizing and externalizing symptoms (e.g., Dirks et al., 2015). An important, yet understudied, relational feature reflects the degree to which early adolescents feel that they can trust their sibling. Specifically, the extent to which they can rely on the behaviours or promises made by a sibling can have important implications for the sibling relationship and adolescent well-being. As such, the present three studies investigated the role of sibling trust and its value within the context of the sibling relationship and for adaptive and maladaptive adjustment. Study 1 reports on a new self-report measure of sibling trust that addressed the methodological limitations of previous measures of trust and examined its association with sibling relationship satisfaction. Findings revealed a two-factor structure based on reliability trust and trust honesty, which were each positively predictive of sibling relationship satisfaction. Regarding birth order, the effect of trust honesty was stronger for older siblings than younger siblings. Study 2 examined the predictive value of sibling trust on adolescent general self-worth in a cross-cultural sample from Canada and Colombia. Results indicated that sibling trust was positively predictive of general self-worth, social competence, and academic competence. Further, the effect of sibling trust on social competence was stronger for boys than girls, whereas no significant cultural differences were observed. Study 3 investigated the protective function of sibling trust on adolescent perceptions of depressed affect and the intolerance of uncertainty over a two-month period. Reliability trust and trust honesty differentially predicted the stability of depressed affect, such that high reliability trust weakened the association while high trust honesty strengthened it. Together, findings are discussed relation to established theoretical frameworks regarding the multidimensionality of trust (Rotenberg, 2010) and relationships theory (Hinde, 1979). Generally, these results supported the relative value of trust within the sibling relationship and its importance for maintaining a satisfactory relationship and individual well-being

The Use of Cooperative and Surrogate Alliances during Naturalistic Polyadic Family Conflicts

Polyadic family conflicts and the use of alliances were examined in 39 families during naturalistic home observations of mothers (M age = 32.8 years), fathers (M age = 34.6 years), older (M age = 6.3 years) and younger siblings (M age = 4.4 years). The data included transcripts of audio-recorded researcher notes and family member verbalizations for each of the six 90-minute sessions. Using these transcripts, conflict initiators, topics, and resolutions, as well as additional party roles (e.g., alliance, mediator; Black & Baumgartner, 1983) were coded. To distinguish between the amount of support that allies provided to the conflict, alliances were separated into two categories: Cooperative and surrogate alliances. The findings revealed that despite all family members being involved in polyadic conflicts, children tended to be initiators, while parents became involved as additional parties. Alliances occurred more often than the other additional party roles, were likely to be formed when conflicts arose about obnoxious behaviours, and often resulted in the alliance achieving their goals and winning the conflict. Intergenerational alliances (i.e., parent-child) were more likely to be formed than intra-generational alliances (e.g., parental). A preliminary content analysis found that cooperative and surrogate alliances were quantitatively different with respect to the number of turns that allies used when supporting a combatant. Moreover, rule enforcement, control, informational, repetition, and induction were identified as resources that allies used to support their side. Results are discussed relative to literature and theory, with respect to understanding each family member’s social and metacognitive skills and understanding

Excitation function of elliptic flow in Au+Au collisions and the nuclear matter equation of state

We present measurements of the excitation function of elliptic flow at midrapidity in Au+Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of elliptic flow is presented for the first time in this energy range, revealing a rapid change with incident energy below 0.4 AGeV, followed by an almost perfect scaling at the higher energies. The equation of state of compressed nuclear matter is addressed through comparisons to microscopic transport model calculations.Comment: 10 pages, 4 eps figures, submitted for publication. Data files will be available at http://www.gsi.de/~fopiwww/pub

Contextual variations in associations between measures of aggression and withdrawal and functioning with peers: A replication study

Data from 790 older school-age (Mage = 10.2 years, SD = 1.2 years) girls (N = 427) and boys from Barranquilla, Colombia (N = 449) and Montréal, Canada (N = 331) were used to replicate findings reported by Valdivia et al. (2005). This prior study revealed contextual variations in the association between two measures of social behavior, specifically aggression and withdrawal, and two measures of effective functioning with peers, specifically sociometric preference and friendship. The Montréal participants were primarily from families with European backgrounds. The ethnicity of the participants from Barranquilla can be described as Latinx/Caribbean. Multilevel analyses provided evidence of replication of place differences only for the associations between measures of aggression and sociometric preference. Stronger negative associations were observed between (a) measures of aggression and sociometric preference, (b) measures of withdrawal and sociometric preference, and (c) withdrawal and friendship in peer groups that were high in collectivism. These findings are interpreted as largely replicating the deep structure of the findings from the Valdivia et al. study

“Where’s your bum brain?” Humor, social understanding, and sibling relationship quality in early childhood

We investigated humor production in relation to social understanding and relationship quality in early childhood, by coding N = 72 5‐year‐olds’ (M = 5.78, SD = 0.41) spontaneous humor production during play with an older (n = 34; M age = 7.84 years, SD = 0.84) or younger sibling (M age = 3.72 years, SD = 0.54). Children who demonstrated better understanding of minds also produced more humor (preposterous statements and humorous anecdotes, and sound play). Types of humor were differentially associated with siblings’ ratings of positive rapport; associations were moderated by sibling constellation factors. Our findings highlight children’s humor production as an important marker of their understanding of minds and of their warm, positive relationships

Anisotropic distribution of nucleon participating in elliptical flow

Using the isospin dependent quantum molecular dynamics model, we study the effect of charge asymmetry and isospin dependent cross-section on $\frac{dN}{d()}$ and $\frac{dN}{p_tdp_t}$. Simulations have been carried out for the reactions of $^{124}X_{m}+^{124}X_{m}$, where m = (47, 50 and 59) and $^{40}S_{16}+^{40}S_{16}$. Our study shows that these parameters depend strongly on the isospin of cross-section and charge asymmetry. The distribution of nucleons and fragments is not symmetric around the beam axis