Cascades and self-organized criticality

We generalize the model of self-organized critical systems to cases where due to some internal degrees of freedom the local conservation law is violated. This can be realized by taking a transfer ratio different from the critical one in a sand pile model (global violation) or allowing fluctuations around the critical ratio (local violation). In the first case the deviation from the critical ratioR is a critical parameter and the characteristic avalanche size diverges as |R|^– . In the second case the global conservation assures criticality; however, our numerical results indicate that the model is in a new universality class.On leave from Institute for Experimental Physics, JATE University, Dóm tèr 9, Szeged, H-6720 Hungary.On leave from Institute for Technical Physics, H-1325 Budapest, Hungary.     

The role of defects in chemical sensing properties of carbon nanotube films

The electrical resistance of 24 different carbon nanotube (CNT) thin film samples in blowing ambient air and 10 different analyte vapor environments was measured. The effects of the CNT growth method, different chemical treatments, ball milling, sample preparation conditions and Ar⁺-ion irradiation are compared. Significant differences in the response signal curves as a function of time in the case of the studied sensor/vapor combinations show the important role of the defect structure and attached functional groups in the chemical sensing properties of CNTs.     

Trimodal imaging system capable of quantitative phase imaging without 2 pi ambiguities

A neoteric approach to interferometric phase imaging unencumbered by 2 pi phase ambiguities is presented. This technique utilizes an actively controlled angular displacement glass plate positioned in the reference arm of an environmentally stabilized pseudoheterodyne Mach-Zehnder interferometer. The plate is continually adjusted to maintain a constant interferometric output phase, as a phase object in the sample arm is raster scanned. Using a 632.8 nm source, unwrapped phase images of translucent samples ranging from approximately 150 nm to 1.5 microm thick were obtained. This system is incorporated into a conventional near-field scanning optical microscope, which permits simultaneous phase, intensity, and surface morphology studies.     

Force indeterminacy in the jammed state of hard disks

Granular packings of hard disks are investigated by means of contact dynamics which is an appropriate technique to explore the allowed force realizations in the space of contact forces. Configurations are generated for given friction coefficients, and then an ensemble of equilibrium forces is found for fixed contacts. We study the force fluctuations within this ensemble. In the limit of zero friction, the fluctuations vanish in accordance with the isostaticity of the packing. The magnitude of the fluctuations has a nonmonotonous friction dependence. The increase for small friction can be attributed to the opening of the angle of the Coulomb cone, while the decrease as friction increases is due to the reduction of connectivity of the contact network, leading to local, independent clusters of indeterminacy. We discuss the relevance of indeterminacy to packings of deformable particles and to the mechanical response properties.     

On projectively flat Finsler spaces

First we present a short overview of the long history of projectively flat Finsler spaces. We give a simple and quite elementary proof of the already known condition for the projective flatness, and we give a criterion for the projective flatness of a special Lagrange space (Theorem 1). After this we obtain a second-order PDE system, whose solvability is necessary and sufficient for a Finsler space to be projectively flat (Theorem 2). We also derive a condition in order that an infinitesimal transformation takes geodesics of a Finsler space into geodesics. This yields a Killing type vector field (Theorem 3). In the last section we present a characterization of the Finsler spaces which are projectively flat in a parameter-preserving manner (Theorem 4), and we show that these spaces over ${\mathbb {R}}^{n}$ are exactly the Minkowski spaces (Theorems 5 and 6).     

Isometries,submetries and distance coordinates on Finsler manifolds

This paper considers fundamental issues related to Finslerian isometries, submetries, distance and geodesics. It is shown that at each point of a Finsler manifold there is a distance coordinate system. Using distance coordinates, a simple proof is given for the Finslerian version of the Myers–Steenrod theorem and for the differentiability of Finslerian submetries.     

Comment on “Solitons in the Heimburg–Jackson model of sound propagation in lipid bilayers are enabled by dispersion of a stiff membrane” by M. Drab et al.

The European Physical Journal E - Inference problems for two-dimensional snapshots of rotating turbulent flows are studied. We perform a systematic quantitative benchmark of point-wise and...