9,641 research outputs found
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Observation of Replica Symmetry Breaking in the 1D Anderson Localization Regime in an Erbium-Doped Random Fiber Laser
The analogue of the paramagnetic to spin-glass phase transition in disordered
magnetic systems, leading to the phenomenon of replica symmetry breaking, has
been recently demonstrated in a two-dimensional random laser consisting of an
organic-based amorphous solid-state thin film. We report here the first
demonstration of replica symmetry breaking in a one-dimensional photonic system
consisting of an erbium-doped random fiber laser operating in the
continuous-wave regime based on a unique random fiber grating system, which
plays the role of the random scatterers and operates in the Anderson
localization regime. The clear transition from a photonic paramagnetic to a
photonic spin glass phase, characterized by the probability distribution
function of the Parisi overlap, was verified and characterized. In this unique
system, the radiation field interacts only with the gain medium, and the fiber
grating, which provides the disordered feedback mechanism, does not interfere
with the pump
Optical limiting behavior of bismuth oxide-based glass in the visible range
The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for β, the two-photon absorption coefficient, and σe, the absorption cross section due to free carriers, were determined. The values for β and σe are dependent on the amount of bismuth oxide in the glass composition
Conhecendo espécies de plantas da Amazônia: imbaúba-vermelha (Cecropia palmata Willd. - Urticaceae).
bitstream/item/81613/1/Oriental-ComTec238.pd
Quebra de dormência de sementes de pequi (Caryocar coriaceum Wittm.).
O fruto do pequizeiro possui grande aceitação na culinária regional, sendo consumido com arroz, frango, feijão, podendo ser usado também na fabricação de licor, sorvetes e picolés (VERA, 2004). Contudo, sua exploração ocorre de forma totalmente extrativista (OLIVEIRA, 2009), tornando esta atividade de grande importância socioeconômica, gerando renda e emprego à população do cerrado. O objetivo deste trabalho foi avaliar tratamentos de quebra de dormência de sementes de pequi
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
- …