ABSTRACT
Erratum to the article published on December 27th 2015 in Issue 52 of Orvosi Hetilap [Orv. Hetil., 2015, 156(52), 2120-2126, DOI: 10.1556/650.2015.30329]. The name of Dávid Mezey was not correctly typed. The corresponding author asked for the following correction to be published.
ABSTRACT
INTRODUCTION: Two-photon microscopy is the ideal tool to study how signals are processed in the functional brain tissue. However, early raster scanning strategies were inadequate to record fast 3D events like action potentials. AIM: The aim of the authors was to record various neuronal activity patterns with high signal-to-noise ratio in an optical manner. METHOD: Authors developed new data acquisition methods and microscope hardware. RESULTS: Multiple Line Scanning enables the experimenter to select multiple regions of interests, doing this not just increases repetition speed, but also the signal-to-noise ratio of the fluorescence transients. On the same principle, an acousto-optical deflector based 3D scanning microscope has been developed with a sub-millisecond temporal resolution and a millimeter z-scanning range. Its usability is demonstrated by obtaining 3D optical recordings of action potential backpropagation in several hundred micrometers long neuronal processes of single neurons and by 3D random-access scanning of Ca(2+) transients in hundreds of neurons in the mouse visual cortex. CONCLUSIONS: Region of interest scanning enables high signal-to-noise ratio and repetition speed, while keeping good depth penetration of the two-photon microscopes.
Subject(s)
Imaging, Three-Dimensional , Microscopy, Confocal , Nerve Net/physiology , Neurons/physiology , Photons , Action Potentials , Animals , Humans , Mice , Tomography, Emission-Computed, Single-PhotonABSTRACT
The existence of a well-defined yield stress, where a macroscopic crystal begins to plastically flow, has been a basic observation in materials science. In contrast with macroscopic samples, in microcrystals the strain accumulates in random bursts, which makes controlled plastic formation difficult. Here we study by 2D and 3D simulations the plastic deformation of submicron objects under increasing stress. We show that, while the stress-strain relation of individual samples exhibits jumps, its average and mean deviation still specify a well-defined critical stress. The statistical background of this phenomenon is analyzed through the velocity distribution of dislocations, revealing a universal cubic decay and the appearance of a shoulder due to dislocation avalanches.
ABSTRACT
Under stress, many crystalline materials exhibit irreversible plastic deformation caused by the motion of lattice dislocations. In plastically deformed microcrystals, internal dislocation avalanches lead to jumps in the stress-strain curves (strain bursts), whereas in macroscopic samples plasticity appears as a smooth process. By combining three-dimensional simulations of the dynamics of interacting dislocations with statistical analysis of the corresponding deformation behavior, we determined the distribution of strain changes during dislocation avalanches and established its dependence on microcrystal size. Our results suggest that for sample dimensions on the micrometer and submicrometer scale, large strain fluctuations may make it difficult to control the resulting shape in a plastic-forming process.