312 research outputs found

    Effect of Disorder and Notches on Crack Roughness

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    We analyze the effect of disorder and notches on crack roughness in two dimensions. Our simulation results based on large system sizes and extensive statistical sampling indicate that the crack surface exhibits a universal local roughness of ζloc=0.71\zeta_{loc} = 0.71 and is independent of the initial notch size and disorder in breaking thresholds. The global roughness exponent scales as ζ=0.87\zeta = 0.87 and is also independent of material disorder. Furthermore, we note that the statistical distribution of crack profile height fluctuations is also independent of material disorder and is described by a Gaussian distribution, albeit deviations are observed in the tails.Comment: 6 pages, 6 figure

    Measuring functional renormalization group fixed-point functions for pinned manifolds

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    Exact numerical minimization of interface energies is used to test the functional renormalization group (FRG) analysis for interfaces pinned by quenched disorder. The fixed-point function R(u) (the correlator of the coarse-grained disorder) is computed. In dimensions D=d+1, a linear cusp in R''(u) is confirmed for random bond (d=1,2,3), random field (d=0,2,3), and periodic (d=2,3) disorders. The functional shocks that lead to this cusp are seen. Small, but significant, deviations from 1-loop FRG results are compared to 2-loop corrections. The cross-correlation for two copies of disorder is compared with a recent FRG study of chaos.Comment: 4 pages, 4 figure

    Morphology of two dimensional fracture surface

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    We consider the morphology of two dimensional cracks observed in experimental results obtained from paper samples and compare these results with the numerical simulations of the random fuse model (RFM). We demonstrate that the data obey multiscaling at small scales but cross over to self-affine scaling at larger scales. Next, we show that the roughness exponent of the random fuse model is recovered by a simpler model that produces a connected crack, while a directed crack yields a different result, close to a random walk. We discuss the multiscaling behavior of all these models.Comment: slightly revise

    Congenital infiltrating lipoma of the upper limb in a patient with von Willebrand disease

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    Infiltrating lipoma is a rare variety of lipoma, characterized by an infiltration of the adipose tissue of the muscles. Infiltrating lipomas are usually classified in two groups: intermuscular infiltrating lipoma and intramuscular infiltrating lipoma. Most are acquired, and they usually appear in middle-aged individuals. Exceptionally, they are congenital. In such cases they are not related to other diseases. We report an 8-year-old boy with a congenital infiltrating lipoma of the upper limb and von Willebrand disease. Both diseases are linked to an alteration in chromosome 12, but this clinical association seems to be random rather than causal

    Ewing Family Tumors: Potential Prognostic Value of Reverse-Transcriptase Polymerase Chain Reaction Detection of Minimal Residual Disease in Peripheral Blood Samples

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    In more than 95% of patients, the Ewing family of tumors (ET) has chimeric transcripts caused by fusion of the EWS gene to either FLI1 or ERG. The presence of specific EWS-FLI1 or EWS-ERG transcripts in peripheral blood (PB) samples of patients being treated for ET was prospectively evaluated, and these data were correlated to their clinical status. The authors studied 113 PB samples from 28 patients with ET. Treatment included chemotherapy, radiotherapy, and surgical excision of tumor after induction therapy. PB samples were taken prospectively at least 2 weeks after resection of tumor. Nested reverse-transcriptase polymerase chain reaction (RT-PCR) followed by Southern blot was performed in all samples. Resected tumors were reviewed for the degree of response to chemotherapy and volume. Seventy-seven PB samples from 28 patients had EWS-FLI1/ERG transcripts. In 11 patients, PB samples became negative with treatment, and, in 5 of them, the samples remained negative throughout the study. Samples taken during progression were always positive and, in 4 patients, became positive before progression was clinically evident. All patients with transcripts other than EWS-FLI1 type 1 (n = 3) died from tumor progression. This is a sensitive assay to monitor circulating tumor cells in Ewing tumors. The preliminary data suggest that progression is preceded by positive samples and may be related to specific transcript types

    Insuficiencia respiratoria neonatal asociada a mutación en el gen de la proteína C del surfactante

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    La insuficiencia respiratoria en el recién nacido a término durante las primeras semanas de vida extrauterina es una situación poco frecuente. Entre sus causas se incluyen las enfermedades difusas del intersticio pulmonar, un grupo heterogéneo de enfermedades, la mayoría idiopáticas, caracterizadas por infiltrados difusos, alteraciones funcionales de tipo restrictivo y afectación del intercambio gaseoso. Una forma de enfermedad pulmonar intersticial que puede afectar a lactantes, niños o adultos jóvenes es la que se asocia al déficit congénito de proteínas B o C del surfactante pulmonar. En estos casos los procesos inflamatorios que evolucionan hacia la fibrosis pulmonar están precedidos por la acumulación de material proteináceo en el alvéolo. Se indagó la presencia de mutaciones en los genes de las proteínas B y C del surfactante en una familia española en la cual dos lactantes presentaron insuficiencia respiratoria progresiva desde el nacimiento, con alteraciones radiológicas y anatomopatológicas compatibles con enfermedad del intersticio pulmonar, y el padre refería historia de problemas respiratorios desde la infancia. Se encontró que los dos hermanos de esta familia afectados por la enfermedad presentaban una expresión anómala del precursor de la proteína C del surfactante y concentraciones muy bajas de proteína madura. Se describe además una mutación nueva en el gen que codifica la proteína C del surfactante y que cosegrega con la enfermedad en esta familia

    Prediction of sustained remission of chronic hepatitis C after a 12-month course of alfa interferon

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    alpha-Interferon therapy normalizes aminotransferase levels in approximately 50% of the patients with chronic hepatitis C, but post-therapy relapses are common and predictive factors of sustained response remain largely unknown. We retrospectively assessed several parameters as predictors of sustained remission after a 12-month course of lymphoblastoid alpha-interferon: the Knodell histological activity index, serum levels of procollagen type III peptide, serum HCV-RNA, anti-alpha-interferon antibodies, and anti-HCV antibodies (C-100-3), all at month 12. Thirty-seven patients were studied. Fourteen patients were non-responders (38%), 15 patients experienced a sustained response (40.5%) and eight patients responded similarly but relapsed after alpha-interferon withdrawal (21.5%). A decrease in the histological activity index above 5, normalization of procollagen type III peptide levels (< 12 ng/ml) and the absence of viremia after treatment were all significantly associated with a sustained response (p = 0.008, p = 0.007 and p = 0.037, respectively). Anti-interferon antibodies were detected in only one non-responder patient. Anti-C-100-3 antibodies became undetectable at month 12 in 5 of the 15 sustained responders. The best prediction of sustained response was obtained from the three variables independent of multivariate analysis according to the following equation: F = 0.872 + 0.067 x K (decrease of histological index) -0.052 x P (procollagen type III peptide levels at month 12) -0.28 x R (HCV-RNA at month 12; R = 2 when present and R = 1 when absent). A score higher than 0 predicted sustained remission with a 100% sensitivity and specificity in this series of patients

    Size effects in statistical fracture

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    We review statistical theories and numerical methods employed to consider the sample size dependence of the failure strength distribution of disordered materials. We first overview the analytical predictions of extreme value statistics and fiber bundle models and discuss their limitations. Next, we review energetic and geometric approaches to fracture size effects for specimens with a flaw. Finally, we overview the numerical simulations of lattice models and compare with theoretical models.Comment: review article 19 pages, 5 figure

    Shortest paths and load scaling in scale-free trees

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    The average node-to-node distance of scale-free graphs depends logarithmically on N, the number of nodes, while the probability distribution function (pdf) of the distances may take various forms. Here we analyze these by considering mean-field arguments and by mapping the m=1 case of the Barabasi-Albert model into a tree with a depth-dependent branching ratio. This shows the origins of the average distance scaling and allows a demonstration of why the distribution approaches a Gaussian in the limit of N large. The load (betweenness), the number of shortest distance paths passing through any node, is discussed in the tree presentation.Comment: 8 pages, 8 figures; v2: load calculations extende
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