Unanimity Rule on networks

We introduce a model for innovation-, evolution- and opinion dynamics whose spreading is dictated by unanimity rules, i.e. a node will change its (binary) state only if all of its neighbours have the same corresponding state. It is shown that a transition takes place depending on the initial condition of the problem. In particular, a critical number of initially activated nodes is needed so that the whole system gets activated in the long-time limit. The influence of the degree distribution of the nodes is naturally taken into account. For simple network topologies we solve the model analytically, the cases of random, small-world and scale-free are studied in detail.Comment: 7 pages 4 fig

Relaxation under outflow dynamics with random sequential updating

In this paper we compare the relaxation in several versions of the Sznajd model (SM) with random sequential updating on the chain and square lattice. We start by reviewing briefly all proposed one dimensional versions of SM. Next, we compare the results obtained from Monte Carlo simulations with the mean field results obtained by Slanina and Lavicka . Finally, we investigate the relaxation on the square lattice and compare two generalizations of SM, one suggested by Stauffer and another by Galam. We show that there are no qualitative differences between these two approaches, although the relaxation within the Galam rule is faster than within the well known Stauffer rule.Comment: 9 figure

Cultural selection drives the evolution of human communication systems

Human communication systems evolve culturally, but the evolutionary mechanisms that drive this evolution are not well understood. Against a baseline that communication variants spread in a population following neutral evolutionary dynamics (also known as drift models), we tested the role of two cultural selection models: coordination- and content-biased. We constructed a parametrized mixed probabilistic model of the spread of communicative variants in four 8-person laboratory micro-societies engaged in a simple communication game. We found that selectionist models, working in combination, explain the majority of the empirical data. The best-fitting parameter setting includes an egocentric bias and a content bias, suggesting that participants retained their own previously used communicative variants unless they encountered a superior (content-biased) variant, in which case it was adopted. This novel pattern of results suggests that (i) a theory of the cultural evolution of human communication systems must integrate selectionist models and (ii) human communication systems are functionally adaptive complex systems

Opinion Formation in Laggard Societies

We introduce a statistical physics model for opinion dynamics on random networks where agents adopt the opinion held by the majority of their direct neighbors only if the fraction of these neighbors exceeds a certain threshold, p_u. We find a transition from total final consensus to a mixed phase where opinions coexist amongst the agents. The relevant parameters are the relative sizes in the initial opinion distribution within the population and the connectivity of the underlying network. As the order parameter we define the asymptotic state of opinions. In the phase diagram we find regions of total consensus and a mixed phase. As the 'laggard parameter' p_u increases the regions of consensus shrink. In addition we introduce rewiring of the underlying network during the opinion formation process and discuss the resulting consequences in the phase diagram.Comment: 5 pages, eps fig

Perception of Radiation Exposure and Risk Among Patients, Medical Students, and Referring Physicians at a Tertiary Care Community Hospital

AbstractBackgroundIt is important for physicians to be aware of the radiation doses as well as the risks associated with diagnostic imaging procedures that they are ordering.MethodsA survey was administered to patients, medical students, and referring physicians from a number of specialties to determine background knowledge regarding radiation exposure and risk associated with commonly ordered medical imaging tests.ResultsA total of 127 patients, 32 referring physicians, and 30 medical students completed the survey. The majority of patients (92%) were not informed of the radiation risks associated with tests that they were scheduled to receive and had false perceptions about the use of radiation and its associated risks. Physicians and medical students had misconceptions about the use of ionizing radiation in a number of radiologic examinations; for example, 25% and 43% of physicians and medical students, respectively, were unaware that interventional procedures used ionizing radiation, and 28% of physicians were unaware that mammography used ionizing radiation. Computed tomographies and barium studies were thought to be associated with the least ionizing radiation among physicians.ConclusionThere is a need for educating the public, medical students, and referring physicians about radiation exposure and associated risk so that (1) patients receiving multiple medical imaging tests are aware of the radiation that they are receiving and (2) physicians and future physicians will make informed decisions when ordering such tests to limit the amount of radiation that patients receive and to promote informed consent among patients

Yield and risk associated with prolonged presurgical video-EEG monitoring: a systematic review

OBJECTIVE: Presurgical long-term video-EEG monitoring (LT-VEEG) is an important part of the presurgical evaluation in patients with focal epilepsy. Multiple seizures need to be recorded, often in limited time and with the need to taper anti-seizure medication (ASM). The aim of this study was to systematically study the yield – in terms of success – and risks associated with presurgical LT-VEEG, and to identify all previously reported contributing variables. METHODS: A systematic review of the databases of PubMed Medline, Embase, Cochrane Central, and the Cochrane Database of Systematic Reviews were searched following the Preferred Reporting Items for Systematic Reviews (PRISMA) guideline. Publications about presurgical LT-VEEG reporting on variables contributing to yield and risk were included. Study characteristics of all included studies were extracted following a standardized template. Within these articles, studies presenting multivariable analyses of factors contributing to the risk of adverse events or the success of LT-VEEG were identified. RESULTS: We found 36 articles reporting on LT-VEEG, including 4,703 presurgical patients, both children and adults. Presurgical LT-VEEG monitoring led to an average yield of 85%. Adverse events occurred with an averaged total event rate of 17%, but the type of included events was variable among studies. Factors reported to independently contribute to successful LT-VEEG were: baseline seizure frequency, a shorter interval from the most recent seizure, extratemporal lobe epilepsy, and no requirement for ASM reduction. Factors independently contributing to the occurrence of adverse events were: ASM tapering, a history of status epilepticus, a history of focal to bilateral tonic-clonic seizures, psychiatric comorbidity, and ASM taper rate. SIGNIFICANCE: This study reveals that the data on factors contributing to yield and risk of adverse events is significant and variable, and often reported with inadequate statistics. Future research is warranted to develop guidelines for ASM withdrawal during presurgical video-EEG monitoring, taking predefined factors for success and risks of adverse events into account

Field water dynamics in integrated systems in the Brazilian.

Agroforestry systems were established as a viable option for Brazilian farmers in recent decades. Shading is expected to affect the system?s microclimate and thus it is likely to alter water fluxes to the atmosphere via evapotranspiration. In this study we measured the evapotranspiration (ET) with micro-lysimeters in four different treatments as a proxy for different land use systems at EMBRAPA Beef Cattle, the Brazilian Agricultural Research Corporation, located in Campo Grande-MS, Brasil. The four treatments are: Integrated systems with rows of Eucalypt (Eucalyptus urograndis) trees (ICLF), integrated systems without Eucalypt trees (ICL), continuous pasture (CP) and native Cerrado (Savannah) vegetation. In the ICLF and ICL plots Bracchiaria brizantha was planted and in the CP plots Brachiaria decumbens. To measure the evapotranspiration lysimeters (diameter of 10 cm and a depth of 20 cm) were inserted into the ground and weighed daily during a period of 8 weeks. Within the ICLF systems, measurements were conducted in three different distances to the tree rows. In the treatments without trees the lysimeters were distributed randomly. Results were linked to data from the microclimate, i.e. wind speed, air humidity, and global radiation

Forecasting the behaviour of complex landslides with a spatially distributed hydrological model

International audienceThe relationships between rainfall, hydrology and landslide movement are often difficult to establish. In this context, ground-water flow analyses and dynamic modelling can help to clarify these complex relations, simulate the landslide hydrological behaviour in real or hypothetical situations, and help to forecast future scenarios based on environmental change. The primary objective of this study is to investigate the possibility of including more temporal and spatial information in landslide hydrology forecasting, by using a physically based spatially distributed model. Results of the hydrological and geomorphological investigation of the Super-Sauze earthflow, one of the persistently active landslide occurring in clay-rich material of the French Alps, are presented. Field surveys, continuous monitoring and interpretation of the data have shown that, in such material, the groundwater level fluctuates on a seasonal time scale, with a strong influence of the unsaturated zone. Therefore a coupled unsaturated/saturated model, incorporating Darcian saturated flow, fissure flow and meltwater flow is needed to adequately represent the landslide hydrology. The conceptual model is implemented in a 2.5-D spatially distributed hydrological model. The model is calibrated and validated on a multi-parameters database acquired on the site since 1997. The complex time-dependent and three-dimensional groundwater regime is well described, in both the short- and long-term. The hydrological model is used to forecast the future hydrological behaviour of the earthflow in response to potential environmental changes