RESUMO
A method to identify the azimuthal index of vortices and the radial parameter of axicons, as well as their associated spatial frequencies, is presented. These constructive parameters are employed to design parallel superimposed computer-generated holograms (PSCGHs). The diffraction patterns are studied in correspondence with the constructive parameters of the PSCGH. Another diffractive structure serving as identification key is inserted in the entire beam emerging from the PSCGH. The method identifies the parameters set in the first and second diffraction orders. The robustness and sensitivity of the method were checked against parameter mismatches. This method can be exploited as an authentication tool for holographic stamps incorporating PSCGHs.
RESUMO
The cell refractive index has been proposed as a putative cancer biomarker of great potential, being correlated with cell content and morphology, cell division rate and membrane permeability. We used digital holographic microscopy to compare the refractive index and dry mass density of two B16 murine melanoma sublines of different metastatic potential. Using statistical methods, the distribution of phase shifts within the reconstructed quantitative phase images was analyzed by the method of bimodality coefficients. The observed correlation of refractive index, dry mass density and bimodality profile with the metastatic potential of the cells was validated by real time impedance-based assay and clonogenic tests. We suggest that the refractive index and bimodality analysis of quantitative phase image histograms could be developed as optical biomarkers useful in label-free detection and quantitative evaluation of cell metastatic potential.
RESUMO
Using chaos game representation we introduce a novel and straightforward method for identifying similarities/dissimilarities between DNA sequences of the same type, from different organisms. A matrix is associated to each CGR pattern and the similarities result from the comparison between the matrices of the sequences of interest. Three different methods of analysis of the resulting difference matrix are considered: a 3-dimensional representation giving both local and global information, a numerical characterization by defining an n-letter word similarity measure and a statistical evaluation. The method is illustrated by implementation to the study of albumin nucleotides sequences from eight mammal species taking as reference the human albumin.
