Comparison of heavy-ion transport simulations: Collision integral with pions and Δ resonances in a box

We compare ten transport codes for a system confined in a box, aiming at improved handling of the production of $\Delta$ resonances and pions, which is indispensable for constraining high-density symmetry energy from observables such as the $\pi^-/\pi^+$ yield ratio in heavy-ion collisions. The system in a box is initialized with nucleons at saturation density and at 60 MeV temperature. The reactions $NN\leftrightarrow N\Delta$ and $\Delta\leftrightarrow N\pi$ are implemented, but the Pauli blocking and the mean-field potential are deactivated in the present comparison. Results are compared to those from the two reference cases of a chemically equilibrated ideal gas mixture and of the rate equation. In the results of the numbers of $\Delta$ and $\pi$, deviations from the reference values are observed in many codes, and they depend significantly on the size of the time step. These deviations are tied to different ways in ordering the sequence of collisions and decays, that take place in the same time step. Better agreements are seen in the reaction rates and the number ratios among the isospin species of $\Delta$ and $\pi$. These are, however, affected by the correlations, which are absent in the Boltzmann equation, but are induced by the way particle scatterings are treated in transport calculations. The uncertainty in the transport-code predictions of the $\pi^-/\pi^+$ ratio for the system initialized at n/p = 1.5, after letting the existing $\Delta$ resonances decay, is found to be within a few percent, which is sufficiently small so that it does not strongly impact constraining the high-density symmetry energy from heavy-ion collisions. Most of the sources of uncertainties have been understood, and individual codes may be further improved. This investigation will be extended in the future to heavy-ion collisions to ensure the problems identified here remain under control.Comment: 36 pages, 27 figures; a new Fig. 21 and revised results from some codes, achieving improved and consistent understandin

Bullying escolar: um fenômeno multifacetado

School bullying can involve children in different ways, making them play different roles, among them, victims, bullies and bully-victims. The aim of this study was to describe how bullying occurs in high social vulnerability schools of Florianópolis metropolitan area and the roles played by students in this phenomenon. Overall, 409 children and adolescents from the 3rd to 5th grades and of two public elementary schools aged 8-16 years (X = 11.14) participated in this study. As a tool, the Olweus Questionnaire adapted to the Brazilian population was used. For data analysis, descriptive statistics and inferential statistics were applied by the Mann Whitney and Kruskal Wallis tests. As for results, 29.8% of boys and 40.5% of girls reported being victims; 32.3% of boys and 24.6% of girls reported being bullies. Victims were the most willing to help a colleague who is suffering from bullying (X = 1.54; p> 0.001), even if they do not know the victims (X = 1.57; p> 0.004). Bullies are differentiated from the group that does not participate (X = 1.73) and the group of victims (X = 2.34), being those who felt less alone (x = 1.47; p> 0.001). It was concluded that the information obtained in this study is indispensable in the search for alternatives to reduce school bullying. The strengthening of relations between school and students and a better preparation of teachers and school staff are extremely necessary to try to minimize the effects of risk factors to which these children are exposed and consequently violence at school.O bullying escolar pode envolver crianças de diferentes maneiras, fazendo com que essas assumam papéis diferenciados. Dentre estes, têm-se vítimas, agressores e vítimas-agressoras. O objetivo deste estudo foi descrever como ocorre o bullying em escolas de alta vulnerabilidade social da Grande Florianópolis e os papéis assumidos pelos alunos nesse fenômeno. Quanto ao método, participaram 409 crianças e adolescentes do terceiro ao quinto ano e da quarta à sexta série do ensino fundamental, de duas escolas públicas municipais, com idades entre 8 e 16 anos (X=11,14). Como instrumento, utilizou-se o Questionário de Olweus adaptado à população brasileira. Para a análise dos dados, empregaram-se a estatística descritiva e estatística inferencial por meio dos testes Mann Whitney e Kruskal Wallis. Quanto aos resultados, 29,8% dos meninos e 40,5% das meninas relataram terem sido vítimas; já 32,3% dos meninos e 24,6% das meninas relataram terem sido agressores. As vítimas foram as que se mostraram mais dispostas a ajudar como podem um colega que esteja sofrendo agressão (X=1,54; p>0,001), mesmo que não o conheçam (X=1,57; p>0,004). Em contrapartida, os agressores se diferenciaram do grupo que não participa (X=1,73) e do grupo das vítimas (X=2,34), sendo aqueles que menos se sentiram sozinhos (X=1,47; p>0,001). Concluiu-se que as informações obtidas neste estudo são indispensáveis na busca de alternativas para redução do bullying escolar. O fortalecimento das relações entre escola e alunos, e um maior preparo dos professores e funcionários são extremamente necessários para tentar minimizar os efeitos dos fatores de risco a que essas crianças estão expostas e consequentemente a violência na escola.CAPES - Proc. nº 0815/14-4CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT)Projeto Estratégico da FCT: UID/CED/00317/201

Once bitten, not necessarily shy? Determinants of foreign market re-entry commitment strategies

We investigate foreign market re-entry commitment strategies, namely the changes in the modes of operation (commitment) undertaken by multinational enterprises (MNEs) as they return to foreign markets from which they had previously exited. We combine organisational learning theory with the institutional change literature to examine the antecedents of re-entry commitment strategies. From an analysis of 1,020 re-entry events between 1980 and 2016, we find that operation mode prior to exit is a strong predictor of subsequent re-entry mode. Contrary to the predictions of learning theory, we did not find support for the effect of experience accumulated during the initial market endeavour on the re-entry commitment strategies of MNEs. In turn, exit motives significantly impact on the re-entrants' decision to re-enter via a different mode of operation, by either increasing or decreasing their commitment to the market. We show that re-entrants do not replicate unsuccessful operation mode strategies if they had previously underperformed in the market. When favourable host institutional changes occur during the time-out period re-entrants tend to increase commitment in the host market irrespective of the degree of prior experience accumulated in the market

Genetic effects on gene expression across human tissues

Characterization of the molecular function of the human genome and its variation across individuals is essential for identifying the cellular mechanisms that underlie human genetic traits and diseases. The Genotype-Tissue Expression (GTEx) project aims to characterize variation in gene expression levels across individuals and diverse tissues of the human body, many of which are not easily accessible. Here we describe genetic effects on gene expression levels across 44 human tissues. We find that local genetic variation affects gene expression levels for the majority of genes, and we further identify inter-chromosomal genetic effects for 93 genes and 112 loci. On the basis of the identified genetic effects, we characterize patterns of tissue specificity, compare local and distal effects, and evaluate the functional properties of the genetic effects. We also demonstrate that multi-tissue, multi-individual data can be used to identify genes and pathways affected by human disease-associated variation, enabling a mechanistic interpretation of gene regulation and the genetic basis of diseas

Comparison of heart team vs interventional cardiologist recommendations for the treatment of patients with multivessel coronary artery disease

Abstract: Importance: Although the heart team approach is recommended in revascularization guidelines, the frequency with which heart team decisions differ from those of the original treating interventional cardiologist is unknown. Objective: To examine the difference in decisions between the heart team and the original treating interventional cardiologist for the treatment of patients with multivessel coronary artery disease. Design, setting, and participants: In this cross-sectional study, 245 consecutive patients with multivessel coronary artery disease were recruited from 1 high-volume tertiary care referral center (185 patients were enrolled through a screening process, and 60 patients were retrospectively enrolled from the center's database). A total of 237 patients were included in the final virtual heart team analysis. Treatment decisions (which comprised coronary artery bypass grafting, percutaneous coronary intervention, and medication therapy) were made by the original treating interventional cardiologists between March 15, 2012, and October 20, 2014. These decisions were then compared with pooled-majority treatment decisions made by 8 blinded heart teams using structured online case presentations between October 1, 2017, and October 15, 2018. The randomized members of the heart teams comprised experts from 3 domains, with each team containing 1 noninvasive cardiologist, 1 interventional cardiologist, and 1 cardiovascular surgeon. Cases in which all 3 of the heart team members disagreed and cases in which procedural discordance occurred (eg, 2 members chose coronary artery bypass grafting and 1 member chose percutaneous coronary intervention) were discussed in a face-to-face heart team review in October 2018 to obtain pooled-majority decisions. Data were analyzed from May 6, 2019, to April 22, 2020. Main outcomes and measures: The Cohen κ coefficient between the treatment recommendation from the heart team and the treatment recommendation from the original treating interventional cardiologist. Results: Among 234 of 237 patients (98.7%) in the analysis for whom complete data were available, the mean (SD) age was 67.8 (10.9) years; 176 patients (75.2%) were male, and 191 patients (81.4%) had stenosis in 3 epicardial coronary vessels. A total of 71 differences (30.3%; 95% CI, 24.5%-36.7%) in treatment decisions between the heart team and the original treating interventional cardiologist occurred, with a Cohen κ of 0.478 (95% CI, 0.336-0.540; P = .006). The heart team decision was more frequently unanimous when it was concordant with the decision of the original treating interventional cardiologist (109 of 163 cases [66.9%]) compared with when it was discordant (28 of 71 cases [39.4%]; P < .001). When the heart team agreed with the original treatment decision, there was more agreement between the heart team interventional cardiologist and the original treating interventional cardiologist (138 of 163 cases [84.7%]) compared with when the heart team disagreed with the original treatment decision (14 of 71 cases [19.7%]); P < .001). Those with an original treatment of coronary artery bypass grafting, percutaneous coronary intervention, and medication therapy, 32 of 148 patients [22.3%], 32 of 71 patients [45.1%], and 6 of 15 patients [40.0%], respectively, received a different treatment recommendation from the heart team than the original treating interventional cardiologist; the difference across the 3 groups was statistically significant (P = .002). Conclusions and relevance: The heart team's recommended treatment for patients with multivessel coronary artery disease differed from that of the original treating interventional cardiologist in up to 30% of cases. This subset of cases was associated with a lower frequency of unanimous decisions within the heart team and less concordance between the interventional cardiologists; discordance was more frequent when percutaneous coronary intervention or medication therapy were considered. Further research is needed to evaluate whether heart team decisions are associated with improvements in outcomes and, if so, how to identify patients for whom the heart team approach would be beneficial

Comparison of heavy-ion transport simulations: Collision integral in a box

Simulations by transport codes are indispensable to extract valuable physical information from heavy-ion collisions. In order to understand the origins of discrepancies among different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term; i.e., we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within 1 % or better) with analytical results, or completely controlled results of a basic cascade code. In orderto reach that goal, it was necessary to eliminate correlations within the same pair of colliding particles that can be present depending on the adopted collision prescription. In calculations with active Pauli blocking, the blocking probability was found to deviate from the expected reference values. The reason is found in substantial phase-space fluctuations and smearing tied to numerical algorithms and model assumptions in the representation of phase space. This results in the reduction of the blocking probability in most transport codes, so that the simulated system gradually evolves away from the Fermi-Dirac toward a Boltzmann distribution. Since the numerical fluctuations are weaker in the Boltzmann-Uehling-Uhlenbeck codes, the Fermi-Dirac statistics is maintained there for a longer time than in the quantum molecular dynamics codes. As a result of this investigation, we are able to make judgements about the most effective strategies in transport simulations for determining the collision probabilities and the Pauli blocking. Investigation in a similar vein of other ingredients in transport calculations, like the mean-field propagation or the production of nucleon resonances and mesons, will be discussed in the future publications

Students’ decision-making about postgraduate education at G University in China: the main factors and the role of family and of teachers

The paper draws on findings from a case study which explored factors influencing students’ decision-making of postgraduate (PG) education at G University in China. Both questionnaires and follow-up interviews were used for data collection. This paper reports the main reasons for students’ choices of subject and institution for PG education, and the influences of families and teachers, and of guanxi in their decision-making. The findings show that both families and teachers play important roles in shaping students’ decision-making about PG education. It provides insights into students’ decision-making about higher education embedded in the Chinese culture of Confucianism

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements