Application of visible and near infrared spectroscopy in non-destructive evaluation of cement materials

In the twenty-first century, there has been rapid urbanization in economically emerging countries. Many scientific research studies have proposed methods to monitor the quality of materials used in engineering works. Quality inspections are most often made of structure-related materials such as concrete. All the concrete used in construction work is subjected to a test that breaks the samples to evaluate its final mechanical strength. In this sense, remote sensing can contribute to mapping and monitoring construction materials, allowing investigation and identification of various properties such as mechanical strength and water content in a non-destructive manner. The materials can be inspected directly on site, in a rapid, non-invasive, and inexpensive manner; this is crucial for the ongoing process of construction. The spectral behaviour of four different mechanical strengths of two cement materials based on Portland cement, cement paste, and mortar was observed using a FieldSpec® 3 spectroradiometer. The spectral curves generated by recording the reflected and absorbed electromagnetic radiation of the samples were interpreted based on the theory of vibrational and electronic spectroscopy. The objective of this work is to show a novel technique for assisting in the analysis of solid samples using visible and near infrared spectroscopy. Through this study, a spectral contrast between different samples of the paste and mortar was found. Besides, it was possible to detect the presence and the corresponding proportion of water in the samples. Wavelet analysis enabled records of statistical evidence of spectral contrast, and showed that the depth of water absorption features is inversely proportional to compressive strength in the cement materials under study. This work is innovative, because there are no studies in the literature on the application of this technique as an aid tool for differentiating compressive strengths of Portland-cement-based materials.     

Vegetation responses to precipitation and temperature: a spatiotemporal analysis of ecoregions in the Colorado River Basin

Predicting vegetation response to precipitation and temperature anomalies, particularly during droughts, is of great importance in semi-arid regions, because ecosystem and hydrologic processes depend on vegetation conditions. This article studies vegetation responses to precipitation and temperature in 10 ecological regions within the semi-arid Colorado River Basin (CRB). The Normalized Difference Vegetation Index (NDVI) from Global Inventory Modeling and Mapping Studies (GIMMS) database and the Standardized Precipitation Index (SPI) and temperature series from Parameter-Elevation Regressions on Independent Slope Models (PRISM) database were jointly evaluated for the period 1986–2006, using Multichannel Singular Spectrum Analysis (MSSA) to determine common oscillations and significant lags in vegetation response to seasonal and annual precipitation and temperature. Results show high correlations between lagged SPI series and standardized NDVI: from 1-month lag in the warm deserts (Sonora, Chihuahua and Mojave) to two months in the Temperate Sierras and Semi-Arid Highlands and three months in the Colorado and Arizona/New Mexico Plateaus and the Western Cordillera. Temperature anomalies are negatively correlated to NDVI in the lower CRB and positively correlated in the upper CRB. Notably, we see a basin-wide response to SPI anomalies, and consequently, the identified latitudinal and altitudinal lags between SPI and NDVI will allow an early, basin-wide assessment of lagged vegetation responses to precipitation along the CRB ecoregions.     

Dye‐Doped Polyhedral Oligomeric Silsesquioxane (POSS)‐Modified Polymeric Matrices for Highly Efficient and Photostable Solid‐State Lasers

Here, the design, synthesis, and characterization of laser nanomaterials based on dye‐doped methyl methacrylate (MMA) crosslinked with octa(propyl‐methacrylate) polyhedral oligomeric silsesquioxane (8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl‐methacryl‐POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8‐hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid‐state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer‐sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon–oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action.     

Electrochemical treatment of the effluent of a fine chemical manufacturing plant

In this work, the electrochemical oxidation of an actual industrial wastewater with conductive-diamond anodes has been studied. The wastewater is the effluent of a fine chemicals plant. This effluent consists of an aqueous solution of solvents (ketones and alcohols) with a high concentration of aromatic compounds coming from the raw materials, intermediates and products of the different processes of the plant and its COD is around 6000 mg dm(-3). The electrolyses were carried out in a discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single compartment electrochemical flow cell. The conductive-diamond electrochemical oxidation (CDEO) allowed achieving the complete mineralization of the waste with high current efficiencies. These efficiencies seem to strongly depend on the concentration, pH and temperature but not on the current density (in the range studied). This confirms that besides the hydroxyl radicals mediated oxidation, CDEO combines other important oxidation processes such as the direct electrooxidation on the diamond surface and the oxidation mediated by other electrochemically formed compounds generated on this electrode. Other two advanced oxidation processes (ozonation and Fenton oxidation) have been also studied in this work for comparison purposes. Both technologies were able to treat the wastes, but they obtained very different results in terms of efficiency and mineralization. The efficiency of ozonation and electrochemical oxidation were very similar (especially during the first stages), although the energy consumption required by the electrochemical process to remove at fixed percentage of COD or TOC was significantly smaller than that of ozonation. The possible accumulation of carboxylic acid as final products excludes the use of Fenton oxidation as a sole treatment technology.     

Secondary bioreceptivity of granite: effect of salt weathering on subaerial biofilm growth

Salt crystallisation is a very common and powerful weathering agent that can modify the petrophysical properties of building stone such as granite. In addition, the weathering can affect the susceptibility of the stone to biological colonisation. The aims of the present study were to examine the properties of a granite weathered by sodium chloride crystallisation and to evaluate the effects of the weathering on the secondary bioreceptivity of the stone to subaerial phototrophic biofilms. For this purpose, granite samples were subjected to a laboratory-based accelerated salt weathering test, and changes in weight, open porosity, bulk density, capillary water content, abrasion pH and surface roughness of the samples were determined. Samples of both weathered and non-weathered granite were then inoculated with a multi-species phototrophic culture derived from a natural subaerial biofilm and incubated under standardised laboratory conditions for 3 months. The weight loss produced by the weathering process was consistent with significant changes in abrasion pH and surface roughness. The bioreceptivity of the stone was also altered. According to the bioreceptivity index, the granite under study was characterised by ‘mild primary bioreceptivity’, but ‘high secondary bioreceptivity’ after the salt weathering process. Study of the secondary bioreceptivity of stone materials can provide very useful information about response to weathering effects, and the findings can be used to improve the selection of materials for building purposes.     

A Review on the Fermentation of Foods and the Residues of Pesticides—Biotransformation of Pesticides and Effects on Fermentation and Food Quality

Residues of pesticides in food are influenced by processing such as fermentation. Reviewing the extensive literature showed that in most cases, this step leads to large reductions in original residue levels in the fermented food, with the formation of new pesticide by-products. The behavior of residues in fermentation can be rationalized in terms of the physical-chemical properties of the pesticide and the nature of the process. In addition, the presence of pesticides decrease the growth rate of fermentative microbiota (yeasts and bacterias), which provokes stuck and sluggish fermentations. These changes have in consequence repercussions on several aspects of food sensory quality (physical-chemical properties, polyphenolic content, and aromatic profile) of fermented food. The main aim of this review is to deal with all these topics to propose challenging needs in science-based quality management of pesticides residues in food.     

Electrochemical oxidation of several chlorophenols on diamond electrodes Part I. Reaction mechanism

The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C₄ carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols.     

Effect of irrigation level on yield and bioactive amine content of American lettuce

The influence of four levels (25, 50, 75 and 100%) of Class A pan evaporation replenishment (PER) on the marketable yield and bioactive amine content of American lettuce (Lactuca sativa cv Lucy Brown) grown under greenhouse conditions and drip irrigation was investigated. Lettuce was planted in 1.20 m × 2.10 m plots in a completely randomised block design with three replications. Lowest fresh head weights and diameters were obtained at 25% PER. Highest marketable yields and fresh head weights were obtained at 100% PER; however, no significant difference was observed when using 75% PER. The fresh head diameter was smaller only when using 25% PER. Four amines were detected in lettuce grown under 100% PER, with a total content of 7.60 mg kg^?1. Spermidine was the prevalent amine, followed by putrescine, cadaverine and agmatine. Higher spermidine and cadaverine levels were observed in the outer layers of leaves than in the intermediate and inner leaves. The contents of every amine except agmatine increased with water stress; however, a significant difference was observed only between 100 and 25% PER. The concentrations of accumulated putrescine were not capable of negatively affecting the sensory quality of the lettuce. Copyright © 2005 Society of Chemical Industry     

Analysis of the Content of Fatty Acid Methyl Esters in Biodiesel by Fourier-Transform Infrared Spectroscopy: Method and Comparison with Gas Chromatography

The increasing importance of sustainability in energy production has led to a global commitment to the use of fuels derived from renewable biological sources, such as biodiesel produced from plant crops or biomass residues, that do not compete with human food for their production. For a biofuel to be considered biodiesel, it must satisfy the specifications described in the UNE 14214, with the UNE-EN 14103 referring to the determination of fatty acid methyl ester content. This standard applies gas chromatography as an analytical technique. Gas chromatography is a widely used technique in the analysis of methyl ester although it has a number of drawbacks such as: long analysis times, a high consumption of high-quality gases and internal standards, does not allow the analysis of different compounds with the same column, etc. From an industrial production point of view, is necessary to know the fatty acid methyl ester content in biodiesel samples quickly. This paper studies the development of an analytical method using Fourier transform infrared spectroscopy (FTIR) as alternative to gas chromatography (GC), since it is a simple, rapid, and precise analytical technique to quantify fatty acid methyl ester content in biofuel samples.     

Mechanically driven syntheses of carbides and silcides

Most metal carbides or slicides may be synthesized at room temperature, by ball milling mixtures of elemental powders for some tens of hours with a vibratory mill. Both stable and metastable compounds containing a high density of defects can be obtained. In general, phases stable at low temperatures are synthesized. This observation allows us to confirm recent estimations for the maximum temperature (600 K) attained in these powders during mechanical alloying. Exceptions are found for some MSi₂ suicides with M = titanium, iron or molybdenum for which both low- and high-temperature phases are formed.