Extremism propagation in social networks with hubs

One aspect of opinion change that has been of academic interest is the impact of people with extreme opinions (extremists) on opinion dynamics. An agent-based model has been used to study the role of small-world social network topologies on general opinion change in the presence of extremists. It has been found that opinion convergence to a single extreme occurs only when the average number of network connections for each individual is extremely high. Here, we extend the model to examine the effect of positively skewed degree distributions, in addition to small-world structures, on the types of opinion convergence that occur in the presence of extremists. We also examine what happens when extremist opinions are located on the well-connected nodes (hubs) created by the positively skewed distribution. We find that a positively skewed network topology encourages opinion convergence on a single extreme under a wider range of conditions than topologies whose degree distributions were not skewed. The importance of social position for social influence is highlighted by the result that, when positive extremists are placed on hubs, all population convergence is to the positive extreme even when there are twice as many negative extremists. Thus, our results have shown the importance of considering a positively skewed degree distribution, and in particular network hubs and social position, when examining extremist transmission

Retrospect on Fifty Years of Geography in the Ohio Academy of Science

Author Institution: Department of Geography, The University of AkronResearch by Ohio geographers over the 50-year history of the Geography Section of The Ohio Academy of Science (OAS) has been varied with respect to regional and topical themes. Research has closely followed the pattern of world events and social concerns. In the early years the areas of conservation, economic, urban and physical geography were popular. While urban and economic geography remained significant concerns over the 50 years, the past 15 years have had social and cultural concerns come to the fore. The regional focus on Ohio and the United States has been strong throughout the years. Interest in other regions has tended to fluctuate in response to world events, especially in years of crises and change as evidenced by World War II and the independence movement in Africa. Whenever special sessions were organized on particular regions, interest, as gauged by papers presented at OAS meetings, sky-rocketed but then quickly subsided. In the near future it is likely that trends begun in the late 1970s in topical and regional themes will continue

Developing a methodology for social network sampling (abstract)

Researchers are increasingly turning to network theory to describe and understand the social nature of animal populations. To make use of the statistical tools of network theory, ecologists need to gather relational data, typically by sampling the social relations of a population of animals over a given time-period. Due to effort constraints and the practical difficulty involved in tracking animals, these sampled relational data are almost always a subset of the actual network. Measurements of the sample – such as average path length, clustering, and assortativity – are assumed to be informative as to the structure of the real-world social network. However, this assumption is problematic. Due to artefacts of the sampling process, the various network measures taken on the sample may be biased estimators of the true values. For example, just as we would get a biased estimate of mean human height by selecting for a sample those people who stood out in a crowd, we will get a biased estimate of a measure like mean connectivity if we sample individuals who are socially prominent. This problem can only be solved by developing a qualitative theory of network sampling, answering questions such as what proportion of the whole network needs to be sampled before a given level of accuracy is achieved, and what sampling procedures are least biased? To develop such a theory, we need to be able to generate networks from which to sample. Ideally, we need to perform a systematic study of sampling protocols on different known network structures. But currently available data on animal social networks are unsuitable as these networks were themselves sampled. The simulation methods of artificial life provide the way forward. We have developed a computational tool for generating artificial social networks that have user-defined distributions for network properties (such as the number of nodes, and the density) and for key the measures of interest to ecologists (such as the average degree, average path length, clustering, betweenness, and assortativity). This tool allows us to perform the required systematic analyses of the biases inherent in different sampling regimes (e.g., snowball sampling) applied to different network structures. We will present details of this system, and show we are using it to develop robust sampling methods for social network data. We see the system as the first in a series of works that will allow us to develop a qualitative theory of social network sampling to aid ecologists, and eventually social scientists, in their social network data collection

Evidence for strong evolution in galaxy environmental quenching efficiency between z = 1.6 and z = 0.9

Indexación: Web of Science; Scopus.We analyse the evolution of environmental quenching efficiency, the fraction of quenched cluster galaxies which would be star forming if they were in the field, as a function of redshift in 14 spectroscopically confirmed galaxy clusters with 0.87 < z < 1.63 from the Spitzer Adaptation of the Red-Sequence Cluster Survey. The clusters are the richest in the survey at each redshift. Passive fractions rise from 42-13 +10 per cent at z ~ 1.6 to 80-9 +12 per cent at z ~ 1.3 and 88-3 +4 per cent at z < 1.1, outpacing the change in passive fraction in the field. Environmental quenching efficiency rises dramatically from 16-19 +15 per cent at z ~ 1.6 to 62-15 +21 per cent at z~1.3 and 73-7 +8 per cent at z ≲ 1.1. This work is the first to show direct observational evidence for a rapid increase in the strength of environmental quenching in galaxy clusters at z ~ 1.5, where simulations show cluster-mass haloes undergo non-linear collapse and virialization.https://academic.oup.com/mnrasl/article/465/1/L104/241728

Does the structure of the medical consultation align with an educational model of clinical communication? A study of physicians’ consultations from a postgraduate examination

OBJECTIVE: This study examined whether the structure of consultations in which physicians were tasked with sharing information corresponded to the chronological stages proposed by an established educational model of clinical communication. METHOD: Seventy six simulated consultations from a postgraduate examination for general medical hospital physicians were transcribed verbatim and converted into diagrams showing consultation structure. All doctor-patient/relative talk was allocated into six phases: Initiating, Gathering information, Summary, Explanation, Planning and Closing, using the ‘communication process skills’ from the Calgary-Cambridge Guide to the Medical Interview. RESULTS: The majority of consultations included four or five of the expected phases, with most talk (41-92%) in Explanation and Planning. There was no discernible consistency of structure across the consultations or in consultations from the same scenario. Consultations varied in the presence, sequential order, size, location and reappearance of phases. CONCLUSIONS: The structure of consultations in this standardised setting bore little resemblance to the chronological order of phases predicted by an educational model. PRACTICE IMPLICATIONS: Educational guidance and interventions to support patients in preparing for consultations need to take account of doctors’ behaviour in practice. Assumptions about the organisation of medical consultations should be queried in the absence of an evidence base

Stellar mass function of cluster galaxies at z ~ 1.5: evidence for reduced quenching efficiency at high redshift

Indexación: Web of ScienceWe present the stellar mass functions (SMFs) of passive and star-forming galaxies with a limiting mass of 10(10.1) M-circle dot in four spectroscopically confirmed Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) galaxy clusters at 1 : 37 < z < 1 : 63. The clusters have 113 spectroscopically confirmed members combined, with 8-45 confirmed members each. We construct Ks-bandselected photometric catalogs for each cluster with an average of 11 photometric bands ranging from u to 8 mu m. We compare our cluster galaxies to a field sample derived from a similar Ks-band-selected catalog in the UltraVISTA / COSMOS field. The SMFs resemble those of the field, but with signs of environmental quenching. We find that 30 +/- 20% of galaxies that would normally be forming stars in the field are quenched in the clusters. The environmental quenching e ffi ciency shows little dependence on projected cluster-centric distance out to similar to 4 Mpc, providing tentative evidence of pre-processing and/or galactic conformity in this redshift range. We also compile the available data on environmental quenching efficiencies from the literature, and find that the quenching e ffi ciency in clusters and in groups appears to decline with increasing redshift in a manner consistent with previous results and expectations based on halo mass growth.http://www.aanda.org/articles/aa/abs/2016/08/aa28663-16/aa28663-16.htm

Comparing open and minimally invasive surgical procedures for oesophagectomy in the treatment of cancer: the ROMIO (Randomised Oesophagectomy: Minimally Invasive or Open) feasibility study and pilot trial

Localised oesophageal cancer can be curatively treated with surgery (oesophagectomy) but the procedure is complex with a risk of complications, negative effects on quality of life and a recovery period of 6-9 months. Minimal-access surgery may accelerate recovery.The ROMIO (Randomised Oesophagectomy: Minimally Invasive or Open) study aimed to establish the feasibility of, and methodology for, a definitive trial comparing minimally invasive and open surgery for oesophagectomy. Objectives were to quantify the number of eligible patients in a pilot trial; develop surgical manuals as the basis for quality assurance; standardise pathological processing; establish a method to blind patients to their allocation in the first week post surgery; identify measures of postsurgical outcome of importance to patients and clinicians; and establish the main cost differences between the surgical approaches.Pilot parallel three-arm randomised controlled trial nested within feasibility work.Two UK NHS departments of upper gastrointestinal surgery.Patients aged ≥ 18 years with histopathological evidence of oesophageal or oesophagogastric junctional adenocarcinoma, squamous cell cancer or high-grade dysplasia, referred for oesophagectomy or oesophagectomy following neoadjuvant chemo(radio)therapy.Oesophagectomy, with patients randomised to open surgery, a hybrid open chest and minimally invasive abdomen or totally minimally invasive access.The primary outcome measure for the pilot trial was the number of patients recruited per month, with the main trial considered feasible if at least 2.5 patients per month were recruited.During 21 months of recruitment, 263 patients were assessed for eligibility; of these, 135 (51%) were found to be eligible and 104 (77%) agreed to participate, an average of five patients per month. In total, 41 patients were allocated to open surgery, 43 to the hybrid procedure and 20 to totally minimally invasive surgery. Recruitment is continuing, allowing a seamless transition into the definitive trial. Consequently, the database is unlocked at the time of writing and data presented here are for patients recruited by 31 August 2014. Random allocation achieved a good balance between the arms of the study, which, as a high proportion of patients underwent their allocated surgery (69/79, 87%), ensured a fair comparison between the interventions. Dressing patients with large bandages, covering all possible incisions, was successful in keeping patients blind while pain was assessed during the first week post surgery. Postsurgical length of stay and risk of adverse events were within the typical range for this group of patients, with one death occurring within 30 days among 76 patients. There were good completion rates for the assessment of pain at 6 days post surgery (88%) and of the patient-reported outcomes at 6 weeks post randomisation (74%).Rapid recruitment to the pilot trial and the successful refinement of methodology indicated the feasibility of a definitive trial comparing different approaches to oesophagectomy. Although we have shown a full trial of open compared with minimally invasive oesophagectomy to be feasible, this is necessarily based on our findings from the two clinical centres that we could include in this small preliminary study.Current Controlled Trials ISRCTN59036820.This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 48. See the NIHR Journals Library website for further project information

Bifurcations of discrete breathers in a diatomic Fermi-Pasta-Ulam chain

Discrete breathers are time-periodic, spatially localized solutions of the equations of motion for a system of classical degrees of freedom interacting on a lattice. Such solutions are investigated for a diatomic Fermi-Pasta-Ulam chain, i. e., a chain of alternate heavy and light masses coupled by anharmonic forces. For hard interaction potentials, discrete breathers in this model are known to exist either as ``optic breathers'' with frequencies above the optic band, or as ``acoustic breathers'' with frequencies in the gap between the acoustic and the optic band. In this paper, bifurcations between different types of discrete breathers are found numerically, with the mass ratio m and the breather frequency omega as bifurcation parameters. We identify a period tripling bifurcation around optic breathers, which leads to new breather solutions with frequencies in the gap, and a second local bifurcation around acoustic breathers. These results provide new breather solutions of the FPU system which interpolate between the classical acoustic and optic modes. The two bifurcation lines originate from a particular ``corner'' in parameter space (omega,m). As parameters lie near this corner, we prove by means of a center manifold reduction that small amplitude solutions can be described by a four-dimensional reversible map. This allows us to derive formally a continuum limit differential equation which characterizes at leading order the numerically observed bifurcations.Comment: 30 pages, 10 figure