Clay minerals in historic buildings

Although identified in heritage stones, clays are not always taken into full account in terms of negative effects due to their swelling ability (Delgado Rodrigues, Materiales de Construcción 51:183–195, 2001). The main purpose of this study is to identify clays in welded tuffs of three different historic monuments located in the city of Guanajuato, Mexico, and to establish the clays’ contribution to the deterioration of the monuments by their swelling behavior. Thermal analysis, differential thermal analysis (DTA), thermogravimetry (TG), and dynamic mechanical analysis (DMA), as well as supplementing data with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM), have been used. Data suggest that clays present in welded tuffs of the historic monuments studied contribute to increased deterioration through osmotic swelling in two of the three monuments.     

An Investigation of the N-Arylsulfonylation of 2-Azetidinones

N-Arylsulfonylation of 2-azetidinones can lead to the diastereoselective formation of oligomerization products. However, a simple increase of arylsulfonyl chloride concentration minimized oligomerization and allowed preparation of 1-arylsulfonyl-2-azetidinones in good yield.     

Preparation of Dithiolanes by Bentonitic Earth Catalysis

Treatment of ketones with ethanedithiol in the presence of bentonite as the catalyst affords dithiolanes. Reaction yields are good and work-up is very simple.     

Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

We have investigated the effect of solvent in the sol–gel process of tetraethylorthosilicate (TEOS) when di-n-butyltin dilaurate (DBTL) is used as polycondensation catalyst. Two sets of materials similar to those employed in the field of stone consolidation were prepared in the laboratory by using either protic or aprotic solvents: (1) xerogels from TEOS/DBTL, and (2) composites from TEOS/colloidal silica particles/DBTL. The results have shown that the solvent directly influences the aggregation pathway of the condensates. For a mixture of methyl ethyl ketone/acetone (aprotic solvents), gels with a higher degree of condensation were obtained. In the case of TEOS xerogels, the materials are essentially non-porous. Additionally, the incorporation of colloidal silica particles induces an important increase in porosity, which is even more dramatic when ethanol is used as solvent, through the formation of micro and mesoporous materials as the concentration of particles is increased. A TEOS polymerization pathway is suggested depending on which system of solvents is used. Various analytical techniques were used to characterize the materials obtained.     

Functional Magnetic Resonance Imaging Data Analysis by Autoregressive Estimator

The autoregressive (AR) estimator, a non-parametric method, is used to analyze functional magnetic resonance imaging (fMRI) data. The same method has been used, with success, in several other time series data analysis. It uses exclusively the available experimental data points to estimate the most plausible power spectra compatible with the experimental data and there is no need to make any assumption about non-measured points. The time series, obtained from fMRI block paradigm data, is analyzed by the AR method to determine the brain active regions involved in the processing of a given stimulus. This method is considerably more reliable than the fast Fourier transform or the parametric methods. The time series corresponding to each image pixel is analyzed using the AR estimator and the corresponding poles are obtained. The pole distribution gives the shape of power spectra, and the pixels with poles at the stimulation frequency are considered as the active regions. The method was applied in simulated and real data, its superiority is shown by the receiver operating characteristic curves which were obtained using the simulated data.     

Optimizing the resolution of nanohole arrays in metal films for refractive-index sensing

We optimized the resolution of nanohole arrays in metal films for refractive-index sensing by increasing the sensitivity with modifications to the hole-array parameters and by increasing the signal to noise ratio of the sensor system. The nanohole-array parameters (including film thickness, periodicity and diameter) were first optimized by finite-difference time-domain simulations, and then the arrays were fabricated and tested, showing good agreement between the two cases (theory and experiment) in terms of optimal parameters. To improve the sensitivity and to reduce the noise, the laser source wavelength was optimized (including the efficiency of the camera for detection) and the intensity was increased. A?bulk resolution of 6×10^?7 refractive-index units was demonstrated. Due to the collinear microscope geometry and potential for multiplexing of nanohole arrays, these results are encouraging for future biosensing applications.     

Study of Polymer-Solvent Interactions of Complex Polysiloxanes Using Dissipative Particle Dynamics

The mesoscopic modeling of three polysiloxanes in solution is reported in this work, with the purpose of predicting their physicochemical properties as functions of the quality of the solvent, so that a judicious choice of polymer/solvent can be made for various applications. The polymers studied were the following polysiloxanes: polydimethylsiloxane (PDMS), polysiloxane with a bulky alkyl side group (PMHS) and a siloxane copolymer with a hydrophilic polar side group (P2DMPAS). The model used and solved through numerical simulations is the one known as dissipative particle dynamics. Density profiles and radial distribution functions were calculated for each system. We analyzed how the polymers behave in the presence of solvents of varying quality and compared their behavior with experimental data. We observed that we could replicate the behavior in good solvents for PDMS and PMHS. We also observed in the simulation box the formation of pseudo-micelles for P2DMPAS.     

Benchmarking of laboratory evolved unspecific peroxygenases for the synthesis of human drug metabolites

By mimicking the role of human liver P450 monooxygenases, fungal unspecific peroxygenases (UPOs) can perform a range of highly selective oxyfunctionalization reactions on pharmacological compounds, including O-dealkylations and hydroxylations, thereby simulating drug metabolism. Here we have benchmarked human drug metabolite (HDM) synthesis by several evolved UPO mutants, focusing on dextromethorphan, naproxen and tolbutamide. The HDM from dextromethorphan was prepared at the semi-preparative scale as a proof of production. The structural analysis of mutations involved in the synthesis of HDMs highlights the heme access channel as the main feature on which to focus when designing evolved UPOs. These variants are becoming emergent tools for the cost-effective synthesis of HDMs from next-generation drugs.     

Achromatic reconstruction of femtosecond holograms in the planar optical waveguide

Holograms were recorded by 30 fs laser pulses in 20 microm film of dichromated gelatin on the polished quartz substrate and reconstructed in the waveguide mode. The geometric-optical regime of waveguide hologram reconstruction was obtained: the direction of the reconstructed beam was observed to be independent on the reconstructing wavelength within the hologram spectral selectivity band. We discuss the possibility of producing achromatic waveguide optical elements containing only a few periods.