Why do Hurst exponents of traded value increase as the logarithm of company size?

The common assumption of universal behavior in stock market data can sometimes lead to false conclusions. In statistical physics, the Hurst exponents characterizing long-range correlations are often closely related to universal exponents. We show, that in the case of time series of the traded value, these Hurst exponents increase logarithmically with company size, and thus are non-universal. Moreover, the average transaction size shows scaling with the mean transaction frequency for large enough companies. We present a phenomenological scaling framework that properly accounts for such dependencies.Comment: 10 pages, 4 figures, to appear in the Proceedings of the International Workshop on Econophysics of Stock Markets and Minority Games, Calcutta, 200

Nonuniversality in the pair contact process with diffusion

We study the static and dynamic behavior of the one dimensional pair contact process with diffusion. Several critical exponents are found to vary with the diffusion rate, while the order-parameter moment ratio m=\bar{rho^2} /\bar{rho}^2 grows logarithmically with the system size. The anomalous behavior of m is traced to a violation of scaling in the order parameter probability density, which in turn reflects the presence of two distinct sectors, one purely diffusive, the other reactive, within the active phase. Studies restricted to the reactive sector yield precise estimates for exponents beta and nu_perp, and confirm finite size scaling of the order parameter. In the course of our study we determine, for the first time, the universal value m_c = 1.334 associated with the parity-conserving universality class in one dimension.Comment: 9 pages, 5 figure

Percolation and epidemics in a two-dimensional small world

Percolation on two-dimensional small-world networks has been proposed as a model for the spread of plant diseases. In this paper we give an analytic solution of this model using a combination of generating function methods and high-order series expansion. Our solution gives accurate predictions for quantities such as the position of the percolation threshold and the typical size of disease outbreaks as a function of the density of "shortcuts" in the small-world network. Our results agree with scaling hypotheses and numerical simulations for the same model.Comment: 7 pages, 3 figures, 2 table

Integrating fluctuations into distribution of resources in transportation networks

We propose a resource distribution strategy to reduce the average travel time in a transportation network given a fixed generation rate. Suppose that there are essential resources to avoid congestion in the network as well as some extra resources. The strategy distributes the essential resources by the average loads on the vertices and integrates the fluctuations of the instantaneous loads into the distribution of the extra resources. The fluctuations are calculated with the assumption of unlimited resources, where the calculation is incorporated into the calculation of the average loads without adding to the time complexity. Simulation results show that the fluctuation-integrated strategy provides shorter average travel time than a previous distribution strategy while keeping similar robustness. The strategy is especially beneficial when the extra resources are scarce and the network is heterogeneous and lowly loaded.Comment: 14 pages, 4 figure

XY model in small-world networks

The phase transition in the XY model on one-dimensional small-world networks is investigated by means of Monte-Carlo simulations. It is found that long-range order is present at finite temperatures, even for very small values of the rewiring probability, suggesting a finite-temperature transition for any nonzero rewiring probability. Nature of the phase transition is discussed in comparison with the globally-coupled XY model.Comment: 5 pages, accepted in PR

Self-avoiding walks and connective constants in small-world networks

Long-distance characteristics of small-world networks have been studied by means of self-avoiding walks (SAW's). We consider networks generated by rewiring links in one- and two-dimensional regular lattices. The number of SAW's $u_n$ was obtained from numerical simulations as a function of the number of steps $n$ on the considered networks. The so-called connective constant, $\mu = \lim_{n \to \infty} u_n/u_{n-1}$, which characterizes the long-distance behavior of the walks, increases continuously with disorder strength (or rewiring probability, $p$). For small $p$, one has a linear relation $\mu = \mu_0 + a p$, $\mu_0$ and $a$ being constants dependent on the underlying lattice. Close to $p = 1$ one finds the behavior expected for random graphs. An analytical approach is given to account for the results derived from numerical simulations. Both methods yield results agreeing with each other for small $p$, and differ for $p$ close to 1, because of the different connectivity distributions resulting in both cases.Comment: 7 pages, 5 figure

Symptom variability over the course of the day in patients with stable COPD in Brazil: a real-world observational study

Objetivo: Analisar os sintomas em diferentes momentos do dia em pacientes com DPOC. Métodos: Estudo observacional multicêntrico de corte transversal em oito centros brasileiros. Foram avaliados os sintomas matinais, diurnos e noturnos em pacientes com DPOC estável. Resultados: Foram incluídos 593 pacientes em tratamento regular, sendo 309 (52,1%) do sexo masculino e 92 (15,5%) fumantes ativos. A média de idade foi de 67,7 anos, e a média de VEF1 foi de 49,4% do valor previsto. Os pacientes com sintomas mais graves (n = 183; 30,8%), em comparação com aqueles com sintomas leves e moderados, apresentaram pior nível de atividade física (p = 0,002), maior limitação ao fluxo aéreo (p < 0,001), exacerbações ambulatoriais (p = 0,002) e hospitalares (p = 0,043) mais frequentemente e piores resultados em instrumentos específicos. Os sintomas matinais e noturnos mais frequentes foram dispneia (em 45,2% e 33,1%, respectivamente), tosse (em 37,5% e 33,3%, respectivamente) e chiado (em 24,4% e 27,0%, respectivamente). Houve forte correlação da intensidade dos sintomas diurnos com sintomas matinais (r = 0,65, p < 0,001), sintomas noturnos (r = 0,60, p < 0,001), bem como com o escore do COPD Assessment Test (r = 0,62; p < 0,001); porém, houve uma correlação fraca com VEF1 (r = −0,205; p < 0,001). Conclusões: A dispneia foi mais frequente no período matinal do que no período noturno. Ter sintomas matinais e/ou noturnos foi associado à pior gravidade dos sintomas diurnos. A intensidade dos sintomas foi fortemente associada a pior qualidade de vida e frequência de exacerbações, mas fracamente associada à limitação ao fluxo aéreo.463Objective: To analyze symptoms at different times of day in patients with COPD. Methods: This was a multicenter, cross-sectional observational study conducted at eight centers in Brazil. We evaluated morning, daytime, and nighttime symptoms in patients with stable COPD. Results: We included 593 patients under regular treatment, of whom 309 (52.1%) were male and 92 (15.5%) were active smokers. The mean age was 67.7 years, and the mean FEV1 was 49.4% of the predicted value. In comparison with the patients who had mild or moderate symptoms, the 183 (30.8%) with severe symptoms were less physically active (p = 0.002), had greater airflow limitation (p < 0.001), had more outpatient exacerbations (p = 0.002) and more inpatient exacerbations (p = 0.043), as well as scoring worse on specific instruments. The most common morning and nighttime symptoms were dyspnea (in 45.2% and 33.1%, respectively), cough (in 37.5% and 33.3%, respectively), and wheezing (in 24.4% and 27.0%, respectively). The intensity of daytime symptoms correlated strongly with that of morning symptoms (r = 0.65, p < 0.001) and that of nighttime symptoms (r = 0.60, p < 0.001), as well as with the COPD Assessment Test score (r = 0.62; p < 0.001), although it showed only a weak correlation with FEV1 (r = −0.205; p < 0.001). Conclusions: Dyspnea was more common in the morning than at night. Having morning or nighttime symptoms was associated with greater daytime symptom severity. Symptom intensity was strongly associated with poor quality of life and with the frequency of exacerbations, although it was weakly associated with airflow limitation

Autoimmune hepatitis in 828 Brazilian children and adolescents: clinical and laboratory findings, histological profile, treatments, and outcomes

In this large clinical series of Brazilian children and adolescents, autoimmunehepatitis-1 was more frequent, and patients with autoimmune hepatitis-2 exhibited higherdisease remission rates with earlier response to treatment. Patients with autoimmune hepatitis-1 had a higher risk of death.sentation, laboratory findings, histological profile, treatments, and outcomes of children andadolescents with autoimmune hepatitis.Methods: The medical records of 828 children and adolescents with autoimmune hepatitiswere reviewed. A questionnaire was used to collect anonymous data on clinical presentation,biochemical and histological findings, and treatments.Results: Of all patients, 89.6% had autoimmune hepatitis-1 and 10.4% had autoimmunehepatitis-2. The female sex was predominant in both groups. The median age at symptomonset was 111.5 (6; 210) and 53.5 (8; 165) months in the patients with autoimmune hepatitis1 and autoimmune hepatitis-2, respectively. Acute clinical onset was observed in 56.1% and58.8% and insidious symptoms in 43.9% and 41.2% of the patients with autoimmune hepatitis-1and autoimmune hepatitis-2, respectively. The risk of hepatic failure was 1.6-fold higher forautoimmune hepatitis-2. Fulminant hepatic failure occurred in 3.6% and 10.6% of the patientswith autoimmune hepatitis-1 and autoimmune hepatitis-2, respectively; the risk was 3.1-foldhigher for autoimmune hepatitis-2. The gamma globulin and immunoglobulin G levels were sig-nificantly higher in autoimmune hepatitis-1, while the immunoglobulin A and C3 levels werelower in autoimmune hepatitis-2. Cirrhosis was observed in 22.4% of the patients; biochem-ical remission was achieved in 76.2%. The actuarial survival rate was 93.0%. A total of 4.6%underwent liver transplantation, and 6.9% died (autoimmune hepatitis-1: 7.5%; autoimmunehepatitis-2: 2.4%).Conclusions: In this large clinical series of Brazilian children and adolescents, autoimmunehepatitis-1 was more frequent, and patients with autoimmune hepatitis-2 exhibited higherdisease remission rates with earlier response to treatment. Patients with autoimmune hepatitis-1 had a higher risk of death.info:eu-repo/semantics/publishedVersio