Plastic Deformation of 2D Crumpled Wires

When a single long piece of elastic wire is injected trough channels into a confining two-dimensional cavity, a complex structure of hierarchical loops is formed. In the limit of maximum packing density, these structures are described by several scaling laws. In this paper it is investigated this packing process but using plastic wires which give origin to completely irreversible structures of different morphology. In particular, it is studied experimentally the plastic deformation from circular to oblate configurations of crumpled wires, obtained by the application of an axial strain. Among other things, it is shown that in spite of plasticity, irreversibility, and very large deformations, scaling is still observed.Comment: 5 pages, 6 figure

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

Boosting search by rare events

Randomized search algorithms for hard combinatorial problems exhibit a large variability of performances. We study the different types of rare events which occur in such out-of-equilibrium stochastic processes and we show how they cooperate in determining the final distribution of running times. As a byproduct of our analysis we show how search algorithms are optimized by random restarts.Comment: 4 pages, 3 eps figures. References update

Experimental investigation of linear-optics-based quantum target detection

The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent superpositions and quantum correlations, to increase measurement precision. Here we experimentally investigate a scheme for quantum target detection based on linear optical measurment devices, when the object is immersed in unpolarized background light. By comparing the quantum (polarization-entangled photon pairs) and the classical (separable polarization states), we found that the quantum strategy provides us an improvement over the classical one in our experiment when the signal to noise ratio is greater than 1/40, or about 16dB of noise. This is in constrast to quantum target detection considering non-linear optical detection schemes, which have shown resilience to extreme amounts of noise. A theoretical model is developed which shows that, in this linear-optics context, the quantum strategy suffers from the contribution of multiple background photons. This effect does not appear in our classical scheme. By improving the two-photon detection electronics, it should be possible to achieve a polarization-based quantum advantage for a signal to noise ratio that is close to 1/400 for current technology.Comment: comments are welcome, submitted to PR

Composição química e digestibilidade in vitro do pedúnculo de caju.

O presente trabalho se propõe a avaliar a composição química-bromatológica e a digestibilidade in vitro do pedúnculo de caju, um subproduto fibroso, tratado ou não tratado com ureia

Radiative Corrections to the Aharonov-Bohm Scattering

We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order $\alpha$, radiative correction, to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected Aharonov-Bohm potential and, in particular, verify that an induced magnetic field is generated outside of the flux tube.Comment: 14 pages, revtex, 3 figure