An Approach to the Use of Glycol Alkoxysilane-Polysaccharide Hybrids in the Conservation of Historical Building Stones.

Stone consolidants have been widely used to protect historical monuments. Consolidants and hydrophobic formulations based on the use of tetraethoxysilane (TEOS) and alkylalkoxysilanes as precursors have been widely applied, despite their lack of solubility in water and requirement to be applied in organic media. In the search for a "greener" alternative based on silicon that has potential use in this field, the use of tetrakis(2-hydroxyethyl)silane (THEOS) and tris(2-hydroxyethyl)methyl silane (MeTHEOS) as precursors, due their high water solubility and stability, is proposed in this paper. It is already known that THEOS and MeTHEOS possess remarkable compatibility with different natural polysaccharides. The investigated approach uses the water-soluble silanes THEOS-chitosan and MeTHEOS-chitosan as a basis for obtaining hybrid consolidants and hydrophobic formulations for the conservation of siliceous and calcareous stones. In the case of calcareous systems, their incompatibility with alkoxysilanes is known and is expected to be solved by the developed hybrid consolidant. Their application in the conservation of building stones from historical and archeological sites from Guanajuato, México was studied. The evaluation of the consolidant and hydrophobic formulation treatment was mainly conducted by determining the mechanical properties and contact angle measurements with satisfactory results in terms of the performance and compatibility with the studied stones.

Revisiting the System Silanes-Polysaccharides: The Cases of THEOS-Chitosan and MeTHEOS-Chitosan.

The glycol alkoxysilanes, tetrakis(2-hydroxyethyl)silane (THEOS), and tris(2-hydroxyethyl)methyl silane (MeTHEOS) are water soluble derivatives of tetraethoxysilane (TEOS) and methyltriethoxysilane (MeTEOS) and precursors of the system silane-chitosan reviewed in this work. The glycol modified alkoxysilanes are obtained by transesterification reaction of TEOS or MeTEOS with ethylene glycol. The reaction evolution is monitored by 29 Si NMR. It is possible to observe the formation of the various species of glycol alkoxysilanes in equilibrium as the reaction proceeds showing that the oligomers formation is favored at longer reaction times with the final product tendency to gel keeping the complete water solubility. The glycol alkoxysilanes are synthesized at moderated reaction conditions, by using the Piers-Rubinsztajn (PR) reaction. Additionally, it is already known that THEOS is compatible with different natural polysaccharides as chitosan and the same behavior has been demonstrated in this work for MeTHEOS. Several reports refer studies regarding the system THEOS-polysaccharides to synthesize hybrid materials. The system THEOS-chitosan is known but the characterization as well as the way silane-chitosan interact has not been studied in detail. In the present report, chemical evidence of the covalent interactions THEOS- and MeTHEOS-chitosan based on NMR studies (13 C and 29 Si) are presented as intended.

Feasibility of 3D-printed models of the proximal femur to real bone: a cadaveric study.

INTRODUCTION: 3D technology has increased popularity during the past decade due to recent advancements and has been described as a useful tool in several fields of medicine including orthopaedic surgery. Applications include preoperative planning, custom-made implants, patient-specific guides, etc. The aim of this study was to evaluate the similarity between 3D-printed models and cadaveric femoral heads, based on CT scans. METHODS: Cadaveric study of 12 male hips. Computed tomography (CT) was performed and through a semi-automatic segmentation process created the 3D model. Using a 3D printer, the model was printed in ABS plastic. 1 observer performed several measurements in the cadaver, and a 2nd observer performed the same measurements in the 3D-printed model. A 3rd observer compared both measurements and performed the statistical analysis. RESULTS: There were no significant differences in the measurements of bony structures between the cadaveric specimens and the 3D-printed model (p > 0.05 in all cases). We found significant differences when comparing measurements containing a soft tissue element, for example the dimensions of the cartilage covered femoral head (p < 0.0001). CONCLUSIONS: 3D-printed models of the hip are accurate and feasible to the real bone and can thus be reliable for preoperative planning or other uses that may arise in orthopaedic surgery. Presence of cartilage must be considered when creating the 3D model from CT that considers bone but not cartilage.

Atypical inguinal malignant peripheral nerve sheath tumour with arteriovenous fistula of the left femoral nerve in a child.

We report a 9-year-old girl who developed a malignant peripheral nerve sheath tumour (MPNST) with an arteriovenous fistula arising from the left femoral nerve and adjacent to the iliofemoral vessels in the ipsilateral groin, but without infiltrating them. We describe the MRI and MRA findings. Although MPNST is relatively well known and widely studied, the location of this mass is unique in a child. The mass was surgically removed.