Influence of molecular weight on some properties of poly(vinyl chloride)

Several fractions obtained from a large-scale fractionation and several unfractionated PVC polymers and blends have been processed both as rigid and plasticized compounds. The latter have been studied by stress–strain, creep, and recovery tests. The recoverable character of the creep results show that a relatively stable network must be present in the samples. The crosslink density is little influenced by molecular weight, as shown by the modulus and compliance results. On the contrary, the ultimate tensile properties depend strongly on molecular weight, which is interpreted as evidence that the stability of the crosslinks increases with increasing chain length of the polymers.     

Health risk of coplanar polychlorinated biphenyl congeners in edible fish from the Mediterranean Sea

The muscle tissue of different species of fish was analyzed for polychlorinated biphenyls (PCBs) in order to estimate the daily intake of these contaminants. Contamination levels among the different species varied between 108 and 678 ng/g lipid weight. Isomer-specific analysis in the muscle tissue of the various fish revealed a profile dominated by hexa- and pentachlorobiphenyls, followed by hepta- and tetrachlorobiphenyls. Other congeners, including those with fewer than four or more than nine chlorine atoms, were below the instrumental limit of detection in all samples. PCB dietary intake was below the range of 1 to 4 pg 2,3,7,8-tetrachloro-p-dioxin equivalents per kg body weight per day set by the World Health Organization. From a public health point of view, there is no indication of important risks associated with the consumption of these seafoods.     

Diffusion boundaries behaviour during a parabolic flight

The behaviour of a diffusion boundary between distilled water and a 1% sodium chloride solution during a parabolic flight has been observed. The presence of a few percent of Earth gravity pulses during the micro gravity conditions is sufficient to largely perturb the diffusion boundary that stabilises again during the subsequent normal gravity conditions present inside the aircraft at the end of each parabola. A numerical simulation of the boundary behaviour agrees with the experimental observation. Student flying team     

Simple portable lens meter

A device measuring the optical power of simple lenses by means of moiré phenomena is described. The relevant equations are derived, and a working instrument is presented. A power measuring accuracy better than 0.25 m(-1) in the range of +/- 10 m(-1) is demonstrated.     

Method for measuring the refractive index and the thickness of transparent plates with a lateral-shear,wavelength-scanning interferometer

A new method for measuring simultaneously the thickness and the refractive index of a transparent plate is proposed. The method is based on a simple, variable lateral-shear, wavelength-scanning interferometer. To achieve highly accurate measurements of both refractive index n and thickness d we use several means to determine these two quantities. We finely tune a distributed-feedback diode laser light source to introduce a phase shift into the detected signal, whereas we make the sample rotate to produce variable lateral shearing. Phase shifting permits precise determination of the optical thickness, nd, whereas refractive index n is obtained from the retrieved phase of the overall interference signal for all incidence angles.     

Measured and modeled radiometric quantities in coastal waters: toward a closure

Accurate radiative transfer modeling in the coupled atmosphere-sea system is increasing in importance for the development of advanced remote-sensing applications. Aiming to quantify the uncertainties in the modeling of coastal water radiometric quantities, we performed a closure experiment to intercompare theoretical and experimental data as a function of wavelength lambda and water depth z. Specifically, the study focused on above-water downward irradiance E(d)(lambda, 0+) and in-water spectral profiles of upward nadir radiance L(u)(lambda, z), upward irradiance E(u)(lambda, z), downward irradiance E(d)(lambda, z), the E(u)(lambda, z)/L(u)(lambda, z) ratio (the nadir Q factor), and the E(u)(lambda, z)/E(d)(lambda, z) ratio (the irradiance reflectance). The theoretical data were produced with the finite-element method radiative transfer code ingesting in situ atmospheric and marine inherent optical properties. The experimental data were taken from a comprehensive coastal shallow-water data set collected in the northern Adriatic Sea. Under various measurement conditions, differences between theoretical and experimental data for the above-water E(d)(lambda, 0+) and subsurface E(d)(lambda, 0-) as well as for the in-water profiles of the nadir Q factor were generally less than 15%. In contrast, the in-water profiles of L(u)(lambda, z), E(d)(lambda, z), E(u)(lambda, z) and of the irradiance reflectance exhibited larger differences [to approximately 60% for L(u)(lambda, z) and E(u)(lambda, z), 30% for E(d)(lambda, z), and 50% for the irradiance reflectance]. These differences showed a high sensitivity to experimental uncertainties in a few input quantities used for the simulations: the seawater absorption coefficient; the hydrosol phase function backscattering probability; and, mainly for clear water, the bottom reflectance.     

The evolution of vesicles from bulk lamellar gels

The remarkable ability of phospholipids to generate vesicles and lamellar morphologies has been mimicked by amphiphilic block copolymers and both classes of amphiphiles have been extensively studied in bulk and in dilute solution. The most common vesicle preparation method involves diffusion of water into a lamellar gel. The transformation proceeds from a collection of water-poor planar lamellae, to a water-rich interconnected layer-phase and then a collection of closed lamellae (vesicles) that form a close-packed gel. This is demonstrated by scattering and microscopy with the evolution of the gel structure being driven by increasing curvature. Vesicles have been observed to form when the copolymer-water system still has long-range order, with a discrete, clustered-vesicle structure leading to a turbid dispersion. Eventually, at very low concentration, the packed vesicles separate, generating very stable isotropic dispersions that are transparent. This phase sequence, involving a dispersion of close-packed vesicles, accounts for the formation of a narrow size distribution in these systems.     

Spatially resolved stress analysis in Al2O3/3Y-TZP multilayered composite using confocal fluorescence spectroscopy

Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al(2)O(3)/3Y-TZP (3 mol% Y(2)O(3)-stabilized ZrO(2)) composite using the chromophoric fluorescence spectra of Al(2)O(3). The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.