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2011 Rapporto tecnico metadata only access

Image plate reader postprocessing by HLSVD technique.

2007 Articolo in rivista metadata only access

Canonical Correlation and Quantitative Phase Analysis of Microdiffraction Patterns in Bone-tissue Engineering

A novel method is described that combines high-resolution scanning microdiffraction techniques, Rietveld quantitative phase analysis and a statistical method known as canonical correlation analysis (CCA). The method has been applied to a sample taken from a bone-tissue-engineered bioceramic porous scaffold implanted in a mouse for six months. The CCA technique allows the detection of those pixels throughout the investigated sample that best correlate with signal models. Besides the standard usage of this approach, which requires theoretical profiles as signal models, a novel application is presented here, which consists of picking the model spectra out of the experimental data set. Patterns representative of a reasonable range of phase compositions were selected among the huge number of two-dimensional patterns ( folded in onedimensional profiles) to extract quantitative phase fractions. At this stage, the CCA approach was also used to overcome the low Poisson statistic of signal models, so making Rietveld quantitative analysis more reliable. These patterns have been used as profile models for CCA. The final classification map, obtained by assigning the considered pixel to the model spectrum with the highest canonical coefficient, provides the spatial variation of phase concentration.

X-RAY-DIFFRACTION TRICALCIUM PHOSPHATE RIETVELD METHOD IMAGES POWDER DIFFRACTION
2007 Articolo in rivista metadata only access

Model independent pre-processing of X-ray powder diffraction profiles

Precise knowledge of X-ray diffraction profile shape is crucial in the investigation of the properties of matter in crystals powder. Line-broadening analysis is the fourth pre-processing step in most of the full powder pattern fitting softwares. The final result of line-broadening analysis strongly depends on three further steps: noise filtering, removal of background signal, and peak fitting. In this work a new model independent procedure for two of the aforementioned steps (background suppression and peak fitting) is presented. The former is dealt with by using morphological mathematics, while the latter relies on the Hankel–Lanczos singular value decomposition technique. Real X-ray powder diffraction (XRPD) intensity profiles of Ceria samples are used to test the performance of the proposed procedure. Results show the robustness of this approach and its capability of efficiently improving the disentangling of instrumental broadening. These features make the proposed approach an interesting and user-friendly tool for the pre-processing of XRPD data.

Hankel-Lanczos singular value decomposition (HLSVD) Morphological filtering X-ray powder diffraction
2007 Articolo in rivista metadata only access

Application of the HLSVD Technique to the Filtering of X-Ray Diffraction Data

A filter based on the Hankel-Lanczos singular value decomposition (HLSVD) technique is presented and applied for the first time to X-ray diffraction (XRD) data. Synthetic and real powder XRD intensity profiles of nanocrystals are used to study the filter performances with different noise levels. Results show the robustness of the HLSVD filter and its capability to extract easily and effciently the useful crystallographic information. These characteristics make the filter an interesting and user-friendly tool for processing of XRD data.

2007 Articolo in rivista metadata only access

Classification of Crystallographic Data Using Canonical Correlation Analysis

A reliable and automatic method is applied to crystallographic data for tissue typing. The technique is based on canonical correlation analysis, a statistical method which makes use of the spectral-spatial information characterizing X-ray diffraction data measured from bone samples with implanted tissues. The performance has been compared with a standard crystallographic technique in terms of accuracy and automation. The proposed approach is able to provide reliable tissue classification with a direct tissue visualization without requiring any user interaction.

2007 Rapporto tecnico metadata only access

Applying Canonical Correlation Analysis to bone tissue engineering

Guagliardi A ; Giannini C ; Ladisa M ; Lamura T ; Laudadio A ; Cedola A ; Lagomarsino S ; Cancedda R
2006 Rapporto tecnico metadata only access

Filtering of X-ray diffraction data by HLSVD technique

2006 Rapporto tecnico metadata only access

Determining solvent content in protein crystals by Independent Component Analysis

2006 Rapporto tecnico metadata only access

Pre-processing of X-ray powder diffraction profiles

2006 Rapporto tecnico metadata only access

Canonical Correlation Analysis as a new tool for classification of crystallographic data

2005 Articolo in rivista metadata only access

The independent Component Analysis as a new tool to determine solvent content in protein crystals

Estimating the solvent content in protein crystals is one of the first steps in a macromolecular structure determination. We apply a new statistical technique, the independent component analysis (ICA), to determine the volume fraction of the asymmetric unit of proteins occupied by the solvent. The results for several crystal forms are in good agreement with available ones and allow to validate the method. Its main advantage with respect to existing techniques is that it requires only the knowledge of crystallographic data of structure factors and no a priori information about protein.