2,498 research outputs found

    Absorption and Emission in the non-Poisson case

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    This letter adresses the challenging problems posed to the Kubo-Anderson (KA) theory by the discovery of intermittent resonant fluorescence with a non-exponential distribution of waiting times. We show how to extend the KA theory from aged to aging systems, aging for a very extended time period or even forever, being a crucial consequence of non-Poisson statistics.Comment: 4 pages 3 figures. accepted for publication on Physical Review Letter

    Brownian motion of a charged particle driven internally by correlated noise

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    We give an exact solution to the generalized Langevin equation of motion of a charged Brownian particle in a uniform magnetic field that is driven internally by an exponentially-correlated stochastic force. A strong dissipation regime is described in which the ensemble-averaged fluctuations of the velocity exhibit transient oscillations that arise from memory effects. Also, we calculate generalized diffusion coefficients describing the transport of these particles and briefly discuss how they are affected by the magnetic field strength and correlation time. Our asymptotic results are extended to the general case of internal driving by correlated Gaussian stochastic forces with finite autocorrelation times.Comment: 10 pages, 4 figures with subfigures, RevTeX, v2: revise

    Rural-urban migration in d-dimensional lattices

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    The rural-urban migration phenomenon is analyzed by using an agent-based computational model. Agents are placed on lattices which dimensions varying from d=2 up to d=7. The localization of the agents in the lattice define their social neighborhood (rural or urban) not being related to their spatial distribution. The effect of the dimension of lattice is studied by analyzing the variation of the main parameters that characterizes the migratory process. The dynamics displays strong effects even for around one million of sites, in higher dimensions (d=6, 7).Comment: 9 pages, 7 figures, to be published in International Journal of Modern Physics C 1

    Peruvian Red Uakaris (Cacajao calvus ucayalii) Are Not Flooded-Forest Specialists

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    In the literature, particularly in primatological books, the Peruvian red uakari (Cacajao calvus ucayalii) is generally considered as a species that is specialized on living in flooded forest, despite existing evidence to the contrary. Here we review all available information on habitats where Cacajao calvus ucayalii have been observed. Most sightings are from terra firme, including palm swamps, or from mixed habitats, including terra firme and flooded forest. Therefore, we conclude that the species is not a flooded-forest specialist, but is flexible in its habitat requirements and generally uses terra firme forests or a mixture of habitats. Proper recognition of habitat requirements is important for understanding the ecoethological adaptations of a species and for appropriate conservation measures

    Avaliação do efeito do fipronil sobre a germinação, número de perfilhos e produção de massa seca de Paspalum regnellii.

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    A pesquisa foi desenvolvida na EMBRAPA Pecuária Sudeste, São Carlos, SP, com o objetivo de avaliar os efeitos do tratamento de sementes de Paspalum Regnellii com o inseticida Fipronil 250g/L (Standak), sobre a germinação, número de perfilhos e massa seca. As dosagens aplicadas foram 0, 10, 20, 40, 80 mL p.c./ha. O delineamento utilizado foi de blocos completos ao acaso, com quatro repetições. As sementes foram semeadas em canteiros de 1,5m x 1,5 m, com espaçamento de 15 cm entre linhas. A germinação foi afetada positivamente por todas as doses de fipronil. O número de perfilhos foi afetado pelas doses, sendo as doses de 10 e 20 mL, as que apresentaram melhores resultados. As doses não afetaram a produção de massa seca. A dosagem de 10 mL apresentou melhores resultados que as doses recomendadas pelo fabricante

    Comparison between the comet assay and pimonidazole binding for measuring tumour hypoxia

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    Pimonidazole is finding increasing use in histochemical analyses of hypoxia in tumours. Whether it can identify every hypoxic cell in a tumour, and whether the usual subjective criteria used to define ‘positive’ cells are optimal, are less certain. Therefore, our aim was to develop an objective flow cytometry procedure for quantifying pimonidazole binding in tumours, and to validate this method by using a more direct indicator of radiobiologic hypoxia, the comet assay. SCCVII tumours in C3H mice were analysed for pimonidazole binding using flow cytometry and an iterative curve-fitting procedure, and the results were compared to the comet assay for the same cell suspensions. On average, cells defined as anoxic by flow analysis (n = 43 tumours) bound 10.8 ± 0.95 times more antibody than aerobic cells. In samples containing known mixtures of aerobic and anoxic cells, hypoxic fractions as low as 0.5% could easily be detected. To assess the flow cytometry assay under a wider range of tumour oxygen contents, mice were injected with hydralazine to reduce tumour blood flow, or allowed to breathe various gas mixtures during the 90 min exposure to pimonidazole. Hypoxic fraction estimated by the pimonidazole binding method agreed well with the hypoxic fraction measured using the comet assay in SCCVII tumours (r2 = 0.87, slope = 0.98), with similar results in human U87 glioma cells and SiHa cervical carcinoma xenografts. We therefore conclude that this objective analysis of pimonidazole labelling by flow cytometry gives a convenient and accurate estimate of radiobiological hypoxia. Preliminary analyses of biopsies from 3 patients given 0.5 g m–2 pimonidazole also suggest the suitability of this approach for human tumours. © 2000 Cancer Research Campaign http://www.bjcancer.co

    Resposta do cajueiro anão precoce à correção e adubação em solos de cerrados no Sul do Piauí.

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    Subcutaneous Plasmacytoma Metastasis Precipitated by Tunneled Central Venous Catheter Insertion

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    Extramedullary plasmacytomas are tumors of monoclonal plasma cells arising within soft tissue that uncommonly occur in multiple myeloma patients. While sporadic development of these tumors at cutaneous trauma sites, including venous catheter access sites, has been reported, interventional radiologists seldom encounter this disease. Herein, we describe a case of metastatic subcutaneous plasmacytoma precipitated by tunneled central venous catheter insertion in a male patient undergoing stem cell therapy for treatment of multiple myeloma. In addition, we review the identification, diagnostic pitfalls, pathogenesis, and treatment of this rare entity
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