Influence of the geometry on a field-road model : the case of a conical field

Field-road models are reaction-diffusion systems which have been recently introduced to account for the effect of a road on propagation phenomena arising in epidemiology and ecology. Such systems consist in coupling a classical Fisher-KPP equation to a line with fast diffusion accounting for a road. A series of works investigate the spreading properties of such systems when the road is a straight line and the field a half-plane. Here, we take interest in the case where the field is a cone. Our main result is that the spreading speed is not influenced by the angle of the cone

Oral cancer: a descriptive analysis from a single institution (Centro Hospitalar de São João, Porto, PORTUGAL)

O cancro da cavidade oral é a sexta causa mais comum de cancro em todo o mundo e a forma mais comum de cancro da cabeça e pescoço. A sobrevida aos 5 anos pode ser bastante variável e é um fator da variabilidade do período de observação, caraterísticas dos doentes, experiência dos cirurgiões, percentagem de tumores iniciais comparada com mais avançados, qualidade da radioterapia e uso de tratamentos adjuvantes. Este estudo analisou os resultados de doentes submetidos a tratamento de tumores da cavidade oral para identificar o valor dos fatores de prognóstico. Um total de 125 doentes submetidos a tratamento de carcinoma da cavidade oral foram estudados entre 2007 e 2011. Para cada doente, os dados pessoais, achados histológicos, tratamento e resultado foram registados e analisados estatisticamente. As curvas de sobrevida foram calculadas usando o algoritmo de Kaplan-Meier e a diferença de sobrevida entre grupos examinada. A sobrevida global aos 5 anos nos 125 doentes foi de 52%. As diferenças na sobrevida global e na sobrevida específica aos 5 anos foi significativa (p < 0,05) para o género, o estadio tumoral, o envolvimento ganglionar a invasão perineural e a invasão óssea medular.Oral cancer is the sixth most common cancer worldwide and the most common form of head and neck cancer. The 5-year survival rate can be quite different as it is a factor of variability of observation period, patients' features, surgeons' expertise, percentage of starting tumors compared with advanced ones, quality of radiotherapy, and the use of adjuvant treatments. This report analyzed the outcomes of patients undergoing treatment for oral cancer to identify the value of prognostic factors. A total of 125 patients were studied who had undergone treatment for oral cancer between 2007 and 2011. For each patient, personal data, histological findings, treatment and outcome were recorded and analyzed statistically. Survival curves were calculated using the Kaplan-Meier algorithm, and the difference in survival among subgroups was examined. The overall 5-year survival rate in the 125 patients was 52%. The differences in the overall survival and disease-specific 5-year survival were significant (p < 0.05) for gender, tumor staging, lymph node involvement, perineural invasion, and bone medullary invasion

Nonequilibrium free energy, H theorem and self-sustained oscillations for Boltzmann-BGK descriptions of semiconductor superlattices

Semiconductor superlattices (SL) may be described by a Boltzmann-Poisson kinetic equation with a Bhatnagar-Gross-Krook (BGK) collision term which preserves charge, but not momentum or energy. Under appropriate boundary and voltage bias conditions, these equations exhibit time-periodic oscillations of the current caused by repeated nucleation and motion of charge dipole waves. Despite this clear nonequilibrium behavior, if we `close' the system by attaching insulated contacts to the superlattice and keeping its voltage bias to zero volts, we can prove the H theorem, namely that a free energy $\Phi(t)$ of the kinetic equations is a Lyapunov functional ($\Phi\geq 0$, $d\Phi/dt\leq 0$). Numerical simulations confirm that the free energy decays to its equilibrium value for a closed SL, whereas for an `open' SL under appropriate dc voltage bias and contact conductivity $\Phi(t)$ oscillates in time with the same frequency as the current self-sustained oscillations.Comment: 15 pages, 3 figures, minor revision of latex fil

Correlations and invariance of seismicity under renormalization-group transformations

The effect of transformations analogous to those of the real-space renormalization group are analyzed for the temporal occurrence of earthquakes. The distribution of recurrence times turns out to be invariant under such transformations, for which the role of the correlations between the magnitudes and the recurrence times are fundamental. A general form for the distribution is derived imposing only the self-similarity of the process, which also yields a scaling relation between the Gutenberg-Richter b-value, the exponent characterizing the correlations, and the recurrence-time exponent. This approach puts the study of the structure of seismicity in the context of critical phenomena.Comment: Short paper. I'll be grateful to get some feedbac

Real-time evolution of a large-scale relativistic jet

Context. Astrophysical jets are ubiquitous in the Universe on all scales, but their large-scale dynamics and evolution in time are hard to observe since they usually develop at a very slow pace. Aims. We aim to obtain the first observational proof of the expected large-scale evolution and interaction with the environment in an astrophysical jet. Only jets from microquasars offer a chance to witness the real-time, full-jet evolution within a human lifetime, since they combine a 'short', few parsec length with relativistic velocities. Methods. The methodology of this work is based on a systematic recalibraton of interferometric radio observations of microquasars available in public archives. In particular, radio observations of the microquasar GRS 1758-258 over less than two decades have provided the most striking results. Results. Significant morphological variations in the extended jet structure of GRS 1758-258 are reported here that were previously missed. Its northern radio lobe underwent a major morphological variation that rendered the hotspot undetectable in 2001 and reappeared again in the following years. The reported changes confirm the Galactic nature of the source. We tentatively interpret them in terms of the growth of instabilities in the jet flow. There is also evidence of surrounding cocoon. These results can provide a testbed for models accounting for the evolution of jets and their interaction with the environment.Comment: 5 pages, 3 figures, 2 tables. Accepted for publication in Astronomy and Astrophysics Letter

Genomic Evolution of Two Acinetobacter baumannii Clinical Strains from ST-2 Clones Isolated in 2000 and 2010 (ST-2_clon_2000 and ST-2_clon_2010)

Acinetobacter baumannii is a successful nosocomial pathogen due to its ability to persist in hospital environments by acquiring mobile elements such as transposons, plasmids, and phages. In this study, we compared two genomes of A. baumannii clinical strains isolated in 2000 (ST-2_clon_2000) and 2010 (ST-2_clon_2010) from GenBank project PRJNA308422