Turbulence Hierarchy in a Random Fibre Laser

Turbulence is a challenging feature common to a wide range of complex phenomena. Random fibre lasers are a special class of lasers in which the feedback arises from multiple scattering in a one-dimensional disordered cavity-less medium. Here, we report on statistical signatures of turbulence in the distribution of intensity fluctuations in a continuous-wave-pumped erbium-based random fibre laser, with random Bragg grating scatterers. The distribution of intensity fluctuations in an extensive data set exhibits three qualitatively distinct behaviours: a Gaussian regime below threshold, a mixture of two distributions with exponentially decaying tails near the threshold, and a mixture of distributions with stretched-exponential tails above threshold. All distributions are well described by a hierarchical stochastic model that incorporates Kolmogorov's theory of turbulence, which includes energy cascade and the intermittence phenomenon. Our findings have implications for explaining the remarkably challenging turbulent behaviour in photonics, using a random fibre laser as the experimental platform.Comment: 9 pages, 5 figure

Turbulent Intermittency in a Random Fiber Laser

In fluid turbulence, intermittency is the emergence of non-Gaussian tails in the distribution of velocity increments in small space and/or time scales. Intermittence is thus expected to gradually disappear as one moves from small to large scales. Here we study the turbulent-like intermittency effect experimentally observed in the distribution of intensity fluctuations in a disordered continuous-wave-pumped erbium-doped-based random fiber laser with specially-designed random fiber Bragg gratings. The intermittency effect is investigated as a crossover in the distribution of intensity increments from a heavy-tailed distribution (for short time scales), to a Gaussian distribution (for large time scales). The results are theoretically supported by a hierarchical stochastic model that incorporates Kolmogorov’s theory of turbulence. In particular, the discrete version of the hierachical model allows a general direct interpretation of the number of relevant scales in the photonic hierarchy as the order of the transitions induced by the non-linearities in the medium. Our results thus provide further statistical evidence for the interpretation of the turbulence-like emission previously observed in this system

Influence of fifth-order nonlinearities on the statistical fluctuations in emission intensities in a photonic open-cavity complex system

Este artículo contiene 6 páginas, 3 figuras.High-order nonlinear optical effects have become an important feature of photonic systems, both ordered and disordered. In this work, a very large and robust set of experimental data obtained from the emission spectra of a trivalent neodymium ion-based random laser, whose action mechanism relies upon gain and disorder, was characterized in detail. Using an effective model, it was possible to describe how the optical nonlinearities of the disordered gain medium affect the statistical behavior of the intensity fluctuations of the random laser for excitations close to and well above the laser threshold. A theoretical framework is presented and, in particular, in the regime well above threshold a nice fit to the experimental data is obtained with a distribution that incorporates nonlinearities up to fifth order, the Izrailev distribution.This work was supported by the Brazilian agencies Fundação de Amparo a Ciência e Tecnologia do Estado de Pernambuco (FACEPE), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The work was performed in the framework of the National Institute of Photonics (INCT de Fotônica-INFo) project.Peer reviewe

Nephroblastoma in a black-tufted marmoset (Callithrix penicillata)

ABSTRACT: A renal nephroblastoma is described in a free-living black-tufted marmoset (Callithrix penicillata) in Central Brazil. The monkey was found dead and subjected to necropsy. Gross anatomic changes consisted of a ruptured left kidney, which was almost completely effaced by a white to yellow, partially encapsulated friable mass. The left ureter was distended due to obstruction by a red, spherical, 2mm in diameter friable mass. The urinary bladder was also distended. Histologically the renal and ureteral masses consisted of a triphasic embryonal neoplasm composed of embryonic epithelium forming glomeruli and tubules, polygonal blastemal cells, and a mesenchymal stroma. The embryonic epithelium exhibited rare nuclear immunoreactivity for WT-1, whereas blastemal cells exhibited robust cytoplasmic and rare nuclear immunoreactivity for WT-1; blastemal cells were also immunoreactive for vimentin. No immunoreactivity was detected for pan-cytokeratin (AE1/AE3), actin, and desmin. Morphological and immunohistochemical features of the present neoplasm are consistent with those described for renal nephroblastoma

Identification of New Inhibitors with Potential Antitumor Activity from Polypeptide Structures via Hierarchical Virtual Screening.

Leukemias are neoplasms that affect hematopoietic cells, which are developed by genetic alterations (mutations) that lead to the loss of proliferation control mechanisms (maturation and/or cell death). The α4β1 integrin receptor is a therapeutic target for inflammation, autoimmune diseases and lymphoid tumors. This study was carried out to search through the antagonists-based virtual screening for α4β1 receptor. Initially, seventeen (17) structures were selected (based on the inhibitory activity values, IC50) and the structure with the best value was chosen as the pivot. The pharmacophoric pattern was determined from the online PharmaGist server and resulted in a model of score value equal to 97.940 with 15 pharmacophoric characteristics that were statistically evaluated via Pearson correlations, principal component analysis (PCA) and hierarchical clustering analysis (HCA). A refined model generated four pharmacophoric hypotheses totaling 1.478 structures set of Zinc_database. After, the pharmacokinetic, toxicological and biological activity predictions were realized comparing with pivot structure that resulted in five (ZINC72088291, ZINC68842860, ZINC14365931, ZINC09588345 and ZINC91247798) structures with optimal in silico predictions. Therefore, future studies are needed to confirm antitumor potential activity of molecules selected this work with in vitro and in vivo assays