Impact of the preservation media on ex vivo bone samples for full field mechanical testing.

The preservation method to store bone tissue for posterior analysis is a widespread practice. However, the method's potential influence on the material's mechanical properties is often overlooked during single-point experimentation. Saline and formaldehyde solutions are the most common among the employed preservation media. A full field analysis of the mice femoral bone deformation using non-destructive optical techniques is conducted to assess the influence of the storage media on the viscoelastic properties of the tissue. Three different groups are subjected to a standard three-point bending test. The first group is the control, with fresh post-mortem samples. The second and third groups used saline and formaldehyde solutions, respectively. During the mechanical test, the bone's surface and internal deformation are monitored simultaneously using digital holographic interferometry and Fourier-domain optical coherence tomography. A mechanical comparison among the three groups is presented. The results show that after 48 h of immersion in saline solution, the mice bones keep their viscoelastic behavior similar to fresh bones. Meanwhile, 48 h in formaldehyde modifies the response and affects the marrow structure. The high sensitivity of the optical phase also makes it possible to observe changes in the anisotropy of the samples. As a comparison, Raman spectroscopy analyzes the three bone groups to prove that the preservation media does not affect a single-point inspection.

Flame analysis using a simple transmission digital holographic interferometer.

A digital holographic interferometer using a collimated beam in transmission mode to illuminate a flow coming from a diffusion flame is presented. The optical system proposes an indirect visualization of the flow to avoid saturation at the sensor. It can detect the intensity signal as a classical schlieren technique and the phase changes due to the presence of the flow. It is possible to retrieve a pseudo-3D flow's view and different gradient maps using the optical phase. According to the knife edge's position, these gradients could be observed in classical schlieren one at a time, but the proposed system could retrieve them all with a single image hologram. As proof of principle, a flame's flow is simultaneously observed with the optical system and a Z-type schlieren set up. A comparison of the visualized flows at different stages of the flame is presented and discussed. A temperature profile is obtained and validated with a thermocouple's point thermal measurements taking the resulting optical phase. Results from both optical techniques show a good agreement.

Electricity generation from Nopal biogas effluent using a surface modified clay cup (cantarito) microbial fuel cell.

A modified clay cup (cantarito) microbial fuel cell (C-MFCs) was designed to digest the biomass effluent from a nopal biogas (NBE). To improve the process, commercial acrylic varnish (AV) was applied to the C-MFCs. The experiment was performed as:Both-C-MFCs, painting of AV on both sides of the clay cup; In-C-MFCs, painting of AV on the internal side, and Out-C-MFCs painting of AV on the external side. The order for the maximum volumetric power densities were Both-C-MFCs (1841.99 mW/m3)>Out-C-MFCs (1023.74 mW/m3) >In-C-MFCs (448.90 mW/m3). The control experiment without applied varnish did not show a stable potential, supporting the idea that the acryloyl group in varnish could favor the performance. Finally, a 4-digits clock was powered with two, Both-C-MFCs connected in series; the microbial diversity in this format was explored and a well-defined bacterial community including members of the phyla Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, Synergistetes and candidate division TM7 was found.

Cortical bone quality affectations and their strength impact analysis using holographic interferometry.

It is now accepted that bone strength is a complex property determined mainly by three factors: quantity, quality and turnover of the bone itself. Most of the patients who experience fractures due to fragility could never develop affectations related to bone mass density (i.e. osteoporosis). In this work, the effect of secondary bone strength affectations are analyzed by simulating the degradation of one or more principal components (organic and inorganic) while they are inspected with a nondestructive optical technique. From the results obtained, a strong correlation among the hydroxyapatite, collagen and water is found that determines the bone strength.

Mach-Zehnder Stationary Two-Beam Spectroscopy Using Compound Prisms.

An interferometric optical setup for diffraction-less spectroscopy is tested as an optical design for control of interference frequency. Its design is based on a Mach-Zehnder interferometer in which a pair of compound prisms is introduced in the interferometer path to obtain interference patterns, which avoids the diffraction phenomena and nonlinear dispersion found on spectrometers that use gratings. Computer simulations of the interference patterns generated by the proposed optical setup are presented, and confirmed by the experimental results of the optical implementation. The theory that describes an ideal optical setup and the experimental results show that in order to reduce the combined uncertainties of wavelength measurement, a precise control in angle deviation and magnification are required for the reduction of measurement uncertainties.

Multiwavelength Raman Spectroscopic Analysis of Superficial Iron-Chromium Oxides Generated Using Laser Irradiation.

In order to characterize iron-chromium oxides generated by laser irradiation on the surface of stainless steel plates, an ultraviolet-visible (UV-Vis) near-infrared (NIR) multiwavelength excitation Raman analysis has been performed using both austenitic SS304 and ferritic SS430 stainless steel samples. Raman spectra were obtained using five different excitation wavelengths from blue (455 nm) to NIR (830 nm). These measurements have allowed us to observe and identify four Raman bands, among which two have not been previously observed for iron-chromium oxides, and characterize the existence of different resonant excitation conditions for the different excitation wavelengths. For example, when using 455 nm as excitation wavelength the band at 485 cm-1 did not show up, although that when using 830 nm as excitation wavelength is a clear characteristic band for iron-chromium oxide. In addition, the dependence of the spectra profile with the excitation wavelength for films and microspheres features was observed. This experimental Raman analysis shows the importance of the excitation wavelength for the characterization of metallic oxides with different features.

Raman spectroscopy study of calcium oxalate extracted from cacti stems.

To find markers that distinguish the different Cactaceae species, by using near infrared Raman spectroscopy and scanning electron microscopy, we studied the occurrence, in the stem, of solid deposits in five Cactaceae species (Coryphantha clavata, Ferocactus latispinus, Opuntia ficus-indica, O. robusta, and O. strepthacantha) collected from their natural habitats from a region of México. The deposits in the tissues usually occurred as spheroidal aggregates, druses, or prismatic crystals. From the Raman spectra, the crystals were identified either as calcium oxalate monohydrate (CaC2O4·H2O) or calcium oxalate dihydrate (CaC2O4·2H2O). Opuntia species (subfamily Opuntioideae) showed the presence of CaC2O4·H2O, and the deposition of CaC2O4·2H2O was present in C. clavata and F. latispinus (subfamily Cactoideae, Cacteae tribe). As a punctual technique, Raman spectroscopy seems to be a useful tool to identify crystal composition. In addition to allowing the analysis of crystal morphology, this spectroscopic technique can be used to identify Cactaceae species and their chemotaxonomy.

Knowledge discovery in spectral data by means of complex networks.

In the last decade, complex networks have widely been applied to the study of many natural and man-made systems, and to the extraction of meaningful information from the interaction structures created by genes and proteins. Nevertheless, less attention has been devoted to metabonomics, due to the lack of a natural network representation of spectral data. Here we define a technique for reconstructing networks from spectral data sets, where nodes represent spectral bins, and pairs of them are connected when their intensities follow a pattern associated with a disease. The structural analysis of the resulting network can then be used to feed standard data-mining algorithms, for instance for the classification of new (unlabeled) subjects. Furthermore, we show how the structure of the network is resilient to the presence of external additive noise, and how it can be used to extract relevant knowledge about the development of the disease.

Development of a method based on chemometric analysis of Raman spectra for the discrimination of heterofermentative lactobacilli.

In this work, a method based on Raman spectroscopy in combination with Principal Component Analysis (PCA) and Partial Least Square-Discriminant Analysis (PLS-DA) has been developed for the rapid differentiation of heterofermentative related lactobacilli. In a first approach, Lactobacillus kefir strains were discriminated from other species of heterofermentative lactobacilli: Lb. parakefir and Lb. brevis. After this first approach, PCA allowed for a clear differentiation between Lb. parakefir and Lb.brevis. For the first level of discrimination, PCA was performed on the whole spectra and also on delimited regions, defined taking into consideration the loading values. The best regions allowing a clear differentiation between Lb. kefir and non-Lb. kefir strains were found to be: the 1700-1500 cm(-1), 1500-1185 cm(-1) and 1800-400 (whole spectrum) cm(-1) Raman ranges. In order to develop a classification rule, PLS-DA was carried out on the mentioned regions. This method permitted the discrimination and classification of the strains under study in two groups: Lb. kefir and non-Lb. kefir. The model was further validated using lactobacilli strains from different culture collections or strains isolated from kefir grains previously identified using molecular methods. The second approach based on PCA was also performed on the whole spectra and on delimited regions, being the regions 1700-1500 cm(-1), 1500-1185 cm(-1) and 1185-1020 cm(-1), i.e., those allowing the clearest discrimination between Lb. parakefir and Lb. brevis. The results obtained in this work, allowed a clear discrimination within heterofermentative lactobacilli strains, proteins being the biological structures most determinant for this discrimination.

Detection of the presence of antibodies against Toxoplasma gondii in human colostrum by Raman spectroscopy and principal component analysis.

More than 60 million people in the United States and 23 million people in Mexico probably are infected with the Toxoplasma parasite, but very few have symptoms because the immune system usually keeps the parasite from causing illness. However, for people whose immune system is compromised, the consequences can be fatal. Toxoplasmosis is detected indirectly by different serological tests, where the sample requires a previous preparation. We analyze the feasibility to use Raman spectroscopy and principal component analysis (PCA) as an alternative method to detect the presence or absence of antibodies IgG (immunoglobulin G), IgM (immunoglobulin M), and IgA (immunoglobulin A), against Toxoplasma gondii, in a simple and fast way, in samples of human colostrum from a group of volunteers who were in contact with the parasite and others who were not in contact with the parasite.

Quantitative NIR Raman analysis in liquid mixtures.

The capability to obtain quantitative information of a simple way from Raman spectra is a subject of considerable interest. In this work, this is demonstrated for mixtures of ethanol with water and rhodamine-6G (R-6G) with methanol, which were analyzed directly in glass vessel. The Raman intensities and a simple mathematical model have been used and applied for the analysis of liquid samples. It is starting point to generate a general expression, from the experimental spectra, as the sum of the particular expression for each pure compound allow us to obtain an expression for the mixtures which can be used for determining concentrations, from the Raman spectrum, of the mixture.

Quantitative NIR-Raman analysis of methyl-parathion pesticide microdroplets on aluminum substrates.

The potential of Raman spectroscopy in the quantitative analysis of dilute organic contaminants on aluminum substrates is evidenced in this work. Methyl-parathion microdroplets, an organophosphorus pesticide, has been used as a probe for this purpose. The samples were analyzed on an aluminum foil, which is very easy to acquire and to adapt. Moreover, aluminum foil does not need a previous treatment. Linear and no-linear curves as a function of the concentration of methyl-parathion versus the Raman intensity of the 1345 and 1110 cm(-1) peaks were established by means of a simple mathematical expression. A comparison with calibration curves fits very well, allowing quantification at concentration levels as low as parts per million.