Dense optical flow software to quantify cellular contractility.

Cell membrane deformation is an important feature that occurs during many physiological processes, and its study has been put to good use to investigate cardiomyocyte function. Several methods have been developed to extract information on cardiomyocyte contractility. However, no existing computational framework has provided, in a single platform, a straightforward approach to acquire, process, and quantify this type of cellular dynamics.

Model for DNA Interactions with Proteins and Other Large Ligands: Extracting Physical Chemistry from Pure Mechanical Measurements.

We present a new model to describe DNA interactions with large ligands such as proteins, based on a quenched-disorder equation for ligand binding along the double helix and on Manning's description for the local changes of the persistence length at the binding sites. Such a model allows one to extract the physical chemistry of the interactions from pure mechanical measurements, such as those typically performed with DNA-protein complexes in force spectroscopy assays. We have tested the proposed methodology here to investigate the DNA interaction with the protein lysozyme, determining binding parameters such as the equilibrium association constant, the cooperativity degree of the binding reaction, and the fraction of neutralized charges on the phosphate backbone.

Fluorescence of a Natural Fluorophore as a Key to Improve Fingerprint Contrast Image.

The optical and morphological properties of resveratrol were investigated. This nontoxic fluorescent natural material, emitting in the visible blue light, was used as an optical marker, enabling the enhancement of the image contrast coming from relief pictures marked on challenging surfaces. By applying appropriated imaging softwares, this marker was verified to be very useful in the latent fingerprint recognition deposited on different wood surface types, mainly those with high level of roughness, where conventional forensic materials do not allow effective fingerprint image visualization.

Measurement of the refractive index profile of waveguides using defocusing microscopy.

Defocusing microscopy (DM) is a bright-field optical microscopy technique often used to obtain structural parameters of objects with low difference in refractive index in relation to the surrounding medium (phase objects). We show a use of this technique to measure the refractive index (n) profile of waveguides produced by femtosecond laser micromachining inside the bulk of a sodalime glass. The results are used to analyze the influence of production parameters on n.

Graph analysis of cell clusters forming vascular networks.

This manuscript describes the experimental observation of vasculogenesis in chick embryos by means of network analysis. The formation of the vascular network was observed in the of embryos from 40 to 55 h of development. In the endothelial cell clusters self-organize as a primitive and approximately regular network of capillaries.