Elastic backbone defines a new transition in the percolation model

The elastic backbone is the set of all shortest paths. We found a new phase transition at $p_{eb}$ above the classical percolation threshold at which the elastic backbone becomes dense. At this transition in $2d$ its fractal dimension is $1.750\pm 0.003$, and one obtains a novel set of critical exponents $\beta_{eb} = 0.50\pm 0.02$, $\gamma_{eb} = 1.97\pm 0.05$, and $\nu_{eb} = 2.00\pm 0.02$ fulfilling consistent critical scaling laws. Interestingly, however, the hyperscaling relation is violated. Using Binder's cumulant, we determine, with high precision, the critical probabilities $p_{eb}$ for the triangular and tilted square lattice for site and bond percolation. This transition describes a sudden rigidification as a function of density when stretching a damaged tissue.Comment: 5 pages, 7 figure

Characterizing the intrinsic correlations of scale-free networks

Very often, when studying topological or dynamical properties of random scale-free networks, it is tacitly assumed that degree-degree correlations are not present. However, simple constraints, such as the absence of multiple edges and self-loops, can give rise to intrinsic correlations in these structures. In the same way that Fermionic correlations in thermodynamic systems are relevant only in the limit of low temperature, the intrinsic correlations in scale-free networks are relevant only when the extreme values for the degrees grow faster than the square-root of the network size. In this situation, these correlations can significantly affect the dependence of the average degree of the nearest neighbors of a given vertice on this vertices's degree. Here, we introduce an analytical approach that is capable to predict the functional form of this property. Moreover, our results indicate that random scale-free networks models are not self-averaging, that is, the second moment of their degree distribution may vary orders of magnitude among different realizations. Finally, we argue that the intrinsic correlations investigated here may have profound impact on the critical properties of random scale-free networks.Comment: 5 pages, 4 figure

Prevalence of lower limbs superficial venous insufficiency in obese and non-obese patients

BACKGROUND: Chronic venous insufficiency of the lower limbs is the most prevalent venous disease. There is an ongoing debate about its etiology and pathophysiology. Several risk factors have been associated with its development, such as age, sex and diet. Obesity is a public health problem and its prevalence has been increasing. Color Doppler ultrasonography is a useful method to evaluate the presence of reflux and/or obstruction of the venous system. OBJECTIVE: To compare the prevalence of superficial venous insufficiency and associated symptoms in obese and non-obese patients. METHODS: After weighing, height measurement and physical examination, patients with body mass index (BMI) 35 kg/m² and complaints compatible with venous insufficiency were divided into groups I and II, respectively. They underwent color Doppler ultrasonography of the lower limbs, in order to assess the presence or absence of reflux. RESULTS: A total of 311 limbs of 168 patients 25 to 72 years old were examined. For statistical analysis, complaints of varicose veins, pain, swelling, dermatitis, eczema and ulcers, associated or not, were considered. A total of 109 and 104 limbs with varicose veins were obtained in groups I and II, respectively. The prevalence of visible varicose veins (p35 kg/m² e queixas compatíveis com insuficiência venosa foram distribuídos nos grupos I e II, respectivamente. Foram submetidos à realização do ecocolor Doppler dos membros inferiores para avaliação da presença ou não de refluxo. RESULTADOS: Foram examinados 311 membros de 168 pacientes com 25-72 anos. Para análise estatística, foram consideradas queixas de varizes, dor, edema, dermatite, eczema e úlcera, associados ou não. Foi obtido um total de 109 e 104 membros com varizes nos grupos I e II, respectivamente. Queixas de varizes visíveis (p<0,001) e varizes visíveis com dor (p = 0,0118) foram mais prevalentes no grupo I. Queixas de varizes com edema (p<0,001), somente edema (p<0,001) e edema associado a dor (p<0,001) foram mais prevalentes no grupo II. Os dados não mostraram diferença estatisticamente significante na prevalência de varizes entre os grupos I e II. CONCLUSÃO: A prevalência de varizes é semelhante entre os obesos e não obesos; as queixas clínicas diferem entre os grupos e são compatíveis e dependentes da presença de insuficiência venosa.Universidade Estadual de MaringáUniversidade Federal de São Paulo (UNIFESP)UNIFESPSciEL

Uso da craniectomia descompressiva no tratamento do acidente vascular cerebral isquêmico hemisférico

Decompressive craniectomy (DC) has demonstrated efficacy in reducing mortality in hemispheric infarction of the middle cerebral artery. The aim of our study was to compare the outcome of patients submitted to DC to patients treated in a conservative way. Eighteen patients were submitted to DC and 14 received conservative treatment. Neurological status was assessed by the Glasgow Coma Score and National Institutes of Health Stroke Scale score. Mortality, modified Rankin Scale and Barthel Index scores were assessed at 90 days to evaluate outcome. We did not observe reduction in overall mortality and functional outcome in patients submitted to DC. The differences between our group and previously published series are probably related to the neurological status of the patients at the time of therapeutic decision.Craniectomia descompressiva (CD) tem demonstrado eficácia em reduzir a mortalidade em pacientes com infarto hemisférico (IH) da artéria cerebral média. Este estudo avaliou o prognóstico dos pacientes submetidos a CD comparando a pacientes com IH tratados de maneira conservadora. Dezoito pacientes foram submetidos a CD e 14 receberam tratamento conservador. Escala de Coma de Glasgow e Escala de AVC do National Institutes of Health foram utilizadas para graduar o déficit neurológico. A mortalidade, bem como os escores obtidos na escala modificada de Rankin e índice de Barthel foram avaliados em 90 dias. Não foi observada redução de mortalidade nos pacientes submetidos a CD. Essa diferença entre os nossos resultados e os estudos publicados previamente se deve, provavelmente, à decisão cirúrgica tardia em pacientes com sinais clínicos de herniação cerebral.Universidade Federal de São Paulo (UNIFESP) Department of Neurology and NeurosurgeryCentro de Medicina Diagnóstica FleuryUNIFESP, Department of Neurology and NeurosurgerySciEL

Phenomenology of production and decay of spinning extra-dimensional black holes at hadron colliders

We present results of CHARYBDIS2, a new Monte Carlo simulation of black hole production and decay at hadron colliders in theories with large extra dimensions and TeV-scale gravity. The main new feature of CHARYBDIS2 is a full treatment of the spin-down phase of the decay process using the angular and energy distributions of the associated Hawking radiation. Also included are improved modelling of the loss of angular momentum and energy in the production process as well as a wider range of options for the Planck-scale termination of the decay. The new features allow us to study the effects of black hole spin and the feasibility of its observation in such theories