Determination of refractive indices of quarter-wavelength Bragg reflectors by reflectance measurements in wavelength and angular domains

We show that all the structural properties of periodic dielectric multilayers can be accurately determined by a combined measurement of the transmission as a function of the wavelength and of the reflection as a function of the angle of incidence when the wavelength of the incident light is fixed. This method is applied to determine the structural properties of two commercial dielectric mirrors, and the results obtained are compared with a measurement of the same structural parameters by use of another technique based on the more standard optical guiding method.     

Regulatory Changes Affecting the Production and Use of Fats and Oils: Focus on Partially Hydrogenated Oils

Partially hydrogenated oils (PHO), the products of incomplete catalytic hydrogenation of food oils, have been widely employed by the food industry for more than a century. Their exceptional stability and technologic characteristics made them the preferred choice for the production of several food products including margarines, bakery goods, and frying oils. Some of these highly prized characteristics were provided by the high content in trans fatty acids (TFA), defined as fatty acids with one or more isolated double bond in trans configuration. The discovery of negative health effects associated with dietary intake of TFA triggered world-wide a wave of regulatory actions aimed to curb their consumption. PHO became the main target of most campaigns aimed to reduce consumption of TFA, and their fortune in the food industry progressively faded. At the 2017, AOCS Annual Meeting in Orlando, a group of experts from regulatory agencies and industry from North America and Europe met to discuss the current status of government regulations and industry adaptations regarding the productions and use of PHO. The discussion was enriched by including the impact on fats and oils production of the 2016 amendment of the Toxic Substances Control Act of 1976 (TSCA). The present publication may not include all regulatory changes that took place after this symposium, in 2017.     

Oxidation Rates of Triacylglycerol and Ethyl Ester Fish Oils

Fish oil is available primarily as triacylglycerols (TAG) or ethyl esters (EE). Anecdotal evidence suggests that TAG have superior bioavailability and oxidative stability compared to EE. In this work, peroxide value (PV) and p‐anisidine value (AV) were used to monitor oxidation in commercially available TAG and EE fish oils incubated at temperatures from 5 to 60 °C. Pseudo first‐order kinetics were assumed and rate constants were calculated for each temperature. At all temperatures, the rates of oxidation were higher for EE oils than TAG oils. For PV and AV measured in both oils, non‐linear Arrhenius models were plotted, generating activation energies that ranged from 7 to 103 and 2 to 159 kJ/mol for PV and AV, respectively. Although TAG were more resistant to oxidation than EE, they had lower activation energies (E_a) at ≤15 °C for reactions measured with PV and AV. The E_a for EE was negative at temperatures ≥45 °C, indicating that reaction rate was influenced by factors in addition to temperature.     

Stearic acid as interface modifier and lubricant agent of the system: Polypropylene/calcium carbonate nanoparticles

The toughness and the rheology of polypropylene (PP)‐calcium carbonate (CaCO₃) nanocompounds using stearic acid as an interface modifier were studied in this work. Compounding of the nanocomposites was carried out with a twin‐screw extruder. The benchmark samples (untreated) and stearic acid‐treated CaCO₃ nanoparticles were characterized by Fourier transform infrared (FTIR) spectroscopy. The nanocompounds were characterized by impact test, tensile test, scanning electron microscopy (SEM), rheological analysis, and differential scanning calorimetry (DSC). The elongation‐at‐break and impact resistance were increased in nanocompounds with interface modifier (stearic acid in hopper of the extruder). Nanocompounds with stearic acid showed the best dispersion state. Stearic acid helps to reduce complex viscosity acting as a lubricant, reducing frictional forces between nanoparticles of calcium carbonate (NCC) and PP chains. Nanocompounds with better dispersion state had crystallization temperatures very similar to the PP homopolymer. POLYM. ENG. SCI., 59:E279–E285, 2019. © 2019 Society of Plastics Engineers     

Plasma amino acids in anorexia nervosa

OBJECTIVE: To evaluate the amino acid profile in a group of adolescents with anorexia nervosa, and to apply alternative ways of presenting and assessing results, so as to increase the information available for understanding the metabolic abnormalities developed in these patients. DESIGN: Plasma amino acid concentrations of a random group of patients with anorexia nervosa compared with values obtained from a 'healthy' adolescent population. SETTING: The study was performed at the tertiary children's Hospital Sant Joan de Deu. SUBJECTS: Female adolescents (n = 92, age: 15+/-1.8 y) at diagnosis of anorexia nervosa. Reference values for amino acids were obtained from apparently healthy adolescents (by history and analytical data) who underwent presurgical analysis for minor operations. Interventions: Plasma amino acid concentrations were measured by ion exchange chromatography. Basic laboratory analysis, carnitine and IGF-I were also determined. RESULTS: In anorexic patients plasma concentrations of taurine, asparagine, glutamine, glycine, methionine, phenylalanine, ornithine, and histidine were significantly higher than reference values (Mann-Whitney, P < 0.01-0.0001), whereas arginine and cystine were lower than our reference values (P < 0.0001). Relative amino acid values (the molar fraction of the patient medians relative to control medians) were plotted. The ratios of some amino acids were significantly greater than those obtained from the reference population: Phe/Tyr (P < 0.001), Met/Cys (P < 0.0001), and Gly/Val (P < 0.01). CONCLUSIONS: A trend to hyperaminoacidemia is a common feature in anorexia nervosa. Although absolute amino acid values cannot play a significant role in the assessment of nutritional status in this condition, the calculation of some ratios (Phe/Tyr, Met/Cys and Gly/Val) and the graphical representation of relative values may be useful. The plasma amino acid profile in anorexia nervosa is different from those of other severe malnutrition states, showing a marasmic pattern of balanced protein-energy undernutrition. Cystine and arginine may be considered limiting amino acids in this disease, and the consequences of their deficient concentrations for oxidative damage should be further evaluated.     

Iris color and texture: A comparative analysis of real irises,ocular prostheses,and colored contact lenses

In this work, we analyzed the color and texture of irises, ocular prostheses, and cosmetic colored contact lenses measured by means of a multispectral system, which provides the CIE L*a*b* colorimetric coordinates of a high resolution image pixel by pixel. The same subject, who has dark brown irises, participated in the measurement of all the contact lenses. The CIE L*a*b* colorimetric coordinates were analyzed to classify the samples into three major groups (brown, blue and green) using a new algorithm developed for this purpose. This classification allowed us to carry out a comparison of the color associated with each set of samples, using the corresponding color gamuts in the CIE L*a*b* color space. Furthermore, we analyzed the iris color reproduction achieved by prostheses and contact lenses in terms of CIEDE2000 color differences, and obtained closer results with prostheses. In addition, we performed an analysis of texture by means of the color spatial distribution of all samples. This was achieved by means of two statistical approaches: first order statistics of image histograms and second order statistics using co‐occurrence matrices. The results suggest that the texture associated with real irises, ocular prostheses and colored contact lenses is very different. This study provides useful information about the color and texture of irises that may help to establish a strategy for improving the techniques used in the manufacturing process of prostheses and colored contact lenses to obtain a better and more realistic appearance. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

Repeatability,reproducibility, and accuracy of a novel pushbroom hyperspectral system

This study analyzes the repeatability, reproducibility and accuracy of a new hyperspectral system based on a pushbroom sensor as a means of measuring spectral features and color of materials and objects. The hyperspectral system consisted of a CCD camera, a spectrograph and an objective lens. An additional linear moving system allowed the mechanical scanning of the complete scene. A uniform overhead luminaire with daylight configuration was used to irradiate the scene using d:45 geometry. We followed the guidelines of the ASTM E2214‐08 Standard Practice for Specifying and Verifying the Performance of Color‐Measuring Instruments that define the standards and latest multidimensional procedures. The results obtained are analyzed in‐depth and compared to those recently reported by other authors for spectrophotometers and multispectral systems. It can be concluded that hyperspectral systems are reliable and can be used in the industry to perform spectral and color readings with a high spatial resolution. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 549–558, 2014     

Towards the understanding of plasma polymer film behaviour in ethanol: A multi-technique investigation

Plasma polymer films (PPFs) of allylamine are prepared varying the mean power injected in the plasma (P_mean). The PPF behaviour in ethanol is studied through the analysis of the PPF physico-chemistry and the composition of the resulting ethanol solutions. By Visible light Spectroscopic Ellipsometry (VISSE), it is observed that the well-known decrease of the PPF thickness (Δd) upon immersion decreases as a function of P_mean. This behaviour is attributed to an increase of the PPF cross-linking density (χ). By means of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and further statistical processing of the data by principal component analysis (PCA), we propose a method to discriminate the samples according to χ. A significant increase in the PPF oxygen content is also observed after immersion which is ascribed to reaction between ethanol molecules and trapped radicals of the PPF network. On the other hand, taking into account the specificities of the gas chromatography–mass spectrometry (GC–MS) method, the resulting ethanol solutions are demonstrated to be free of chemical species containing a number of carbon atoms ranging from 7 to 40. However, Δd (accounting for PPF restructuring) might come with the dissolution of PPF materials having less than 7 carbon atoms.     

The minimum number of measurements for colour,sparkle, and graininess characterisation in gonio‐apparent panels

Materials with new visual appearances have emerged over the last few years. In the automotive industry in particular there is a growing interest in materials with new effect finishes, such as metallic, pearlescent, sparkle, and graininess effects. Typically, for solid colours the mean of three measurements with repetitions is sufficient to obtain a representative measurement for colour characterisation. However, gonio‐apparent panels have non‐homogeneous colours, and there are no studies that recommend the minimum number of repetitions for colour, sparkle, and graininess characterisation of this type of panel. We assume that colour panels incorporating special‐effect pigments in their colour recipes will require a higher minimum number of measurements than solid colour panels. Therefore, the purpose of this study is to verify this assumption by using a multiangle BYK‐mac spectrophotometer, given that it is currently the only commercial device that can measure colour, sparkle, and graininess values simultaneously. In addition, a possible methodology is given for establishing the minimum number of measurements when characterising gonio‐apparent materials using a specific instrument, able to be implemented in future instruments when determining multiple appearance attributes (colour, gloss, sparkle, etc.) for many coloration technologies. Thus, we studied the minimum number of measurements needed to characterise the colour, sparkle, and graininess of three types of sample with solid, metallic, and pearlescent coatings respectively. Twenty measurements were made at twenty random positions (different target areas) of 90 samples. The minimum number of measurements for all these variables was determined on the basis of the point at which the cumulative mean value became constant. Thus, applying new statistical tools, it is clearly shown that metallic and pearlescent panels require more colour measurements than solid panels, in particular when geometries are being measured in a specular direction. As regards texture (sparkle and graininess), more measurements are needed for graininess than for sparkle, and more for metallic panels than for pearlescent panels.