Onion (<Emphasis Type="Italic">Allium cepa</Emphasis> L.) by-products as source of dietary fiber: physicochemical properties and effect on serum lipid levels in high-fat fed rats

The effect of industrial processes used to obtain onion by-products was evaluated. Fiber composition and physicochemical properties were assessed in order to choose the best process to obtain high-fiber ingredients. Moreover, the effect of the inclusion of the dietary fiber-rich onion by-products in a high-fat diet on serum lipids of rats was also evaluated. Bagasse was the best by-product since it showed the highest fiber content with a balanced soluble-to-insoluble fiber ratio and the best physicochemical properties. This fact is related to its high fiber content and also due to its composition, rich in uronic acids and polysaccharides, which explains its high cation exchange capacity, water-holding capacity and swelling capacity. In addition, the inclusion of Bagasse in a high-fat diet produced a reduction in the serum lipid and total cholesterol increases induced by high-fat diet. This effect could be related to the high cation exchange and swelling capacities that Bagasse showed, since these properties can create a concerted effect in reducing the number of intact micelles available, the transit time, and consequently the total time available for cholesterol and lipid absorption in the small intestine.     

Surface plasmon resonance sensors based on uniform-waist tapered fibers in a reflective configuration

We present a configuration for surface plasmon resonance sensors based on uniform-waist tapered optical fibers and reflective elements. Once the fiber is tapered fulfilling the adiabatic criterion, a multilayer including a metallic medium is asymmetrically deposited on the uniform waist of the fiber. This feature provides the resonant excitation of multiple surface plasma waves. In addition, a mirror is produced at the fiber tip by a chemical Tollens reaction. In this way, the sensor operates in a reflective mode, more convenient for dip probes. When these sensors are spectrally interrogated, a high sensitivity of 10-4 refractive index units per nanometer is attained. These devices can be advantageously used for any kind of chemical sensing and biosensing.     

Risks of using antifouling biocides in aquaculture

Biocides are chemical substances that can deter or kill the microorganisms responsible for biofouling. The rapid expansion of the aquaculture industry is having a significant impact on the marine ecosystems. As the industry expands, it requires the use of more drugs, disinfectants and antifoulant compounds (biocides) to eliminate the microorganisms in the aquaculture facilities. The use of biocides in the aquatic environment, however, has proved to be harmful as it has toxic effects on the marine environment. Organic booster biocides were recently introduced as alternatives to the organotin compounds found in antifouling products after restrictions were imposed on the use of tributyltin (TBT). The replacement products are generally based on copper metal oxides and organic biocides. The biocides that are most commonly used in antifouling paints include chlorothalonil, dichlofluanid, DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, Sea-nine 211^®), Diuron, Irgarol 1051, TCMS pyridine (2,3,3,6-tetrachloro-4-methylsulfonyl pyridine), zinc pyrithione and Zineb. There are two types of risks associated with the use of biocides in aquaculture: (i) predators and humans may ingest the fish and shellfish that have accumulated in these contaminants and (ii) the development of antibiotic resistance in bacteria. This paper provides an overview of the effects of antifouling (AF) biocides on aquatic organisms. It also provides some insights into the effects and risks of these compounds on non-target organisms.     

Sensing Cu2+ by controlling the aggregation properties of the fluorescent dye rhodamine 6G with the aid of polyelectrolytes bearing different linear aromatic density

The importance of the linear aromatic density of polyelectrolytes on the ability to bind and influence the state of aggregation of dyes such as rhodamine 6G is highlighted. The corresponding complexes present different interaction patterns with metal ions such as Cu²⁺, undergoing different spectroscopic changes. The chemical bases of these changes are discussed. The different polyelectrolytes studied, poly(sodium 4-styrenesulfonate), poly(sodium 4-styrenesulfonate-co-sodium maleate) at two different comonomer compositions (3:1 and 1:1), and poly(sodium acrylate-co-sodium maleate), bear different linear aromatic density and induce different R6G binding patterns, as seen by diafiltration and UV–vis spectroscopy of absorbance and fluorescence. As the linear aromatic density increases, smaller dye aggregates are induced in the systems. Thus, in the presence of a large excess of the polyelectrolyte showing the highest linear aromatic density, the dyes disperse on the polymer domain and no aggregation is detected. The interaction is less sensitive to the cleaving effect produced by the addition of NaCl 0.1M for the complexes that include the polyelectrolytes with the highest linear aromatic density. In the presence of Cu²⁺, the complexes formed with the polyelectrolytes showing the lowest linear aromatic density tend to cleave, producing the release of the dye from the polymer domain. On the contrary, the complexes formed with the polyelectrolytes showing the highest linear aromatic density effectively retain the dye in the presence of the divalent metal ion. Based on fluorescence changes by the addition of different amounts of Cu²⁺ to the solution, the potential of the polyelectrolyte/R6G complexes in applications as sensing materials is discussed.     

A generalized correlation for the viscosity of dextrans in aqueous solutions as a function of temperature,concentration, and molecular weight at low shear rates

An expression relating the viscosity of dextran solutions to polymer concentration (c), molecular weight (M), and temperature (T) has been derived from experimental data in the following ranges: 5 < c < 25% (wt/wt), 298.2 < T < 363.2 K, and 71,500 < M < 531,000 g/mol. The experimental work was based on capillary viscosimeters. Thermodynamic data (entropy and energy of activation for the viscous flow of a Newtonian fluid) are also presented as a function of polymer concentration for the three molecular weights studied. This thermodynamic analysis suggests that dextrans in aqueous solutions behave as flexible polymers. Application of our expression to existing viscosity data for ethylene/vinylacetate copolymers in paraffin has resulted in improved goodness of fit with respect to established correlations.     

Multivariate curve resolution as a tool to minimize the effects of electrodic adsorption in normal pulse voltammetry

Multivariate curve resolution by alternating least squares (MCR-ALS) was applied to normal pulse voltammograms (NPV) of heavy metal complexes that adsorb on the electrode. Adsorption usually causes: (i) a maximum superimposed on NPV waves, (ii) a decrease of the limiting current and (iii) a shift of half-wave potentials. Together, these effects result in excessively high stability constants when electrochemical methods of equilibrium calculation are applied. As an example of this behaviour, the Cd(II)-polymethacrylate (PMA) system was chosen.Despite the non-linearity of electrodic adsorption, MCR-ALS allows the decomposition of currents into three ca. linear contributions: (i) reduction of the free metal ion diffusing from the bulk solution, (ii) reduction of the metal complex also diffusing from the bulk and (iii) reduction of the metal ion accumulated by adsorption onto the electrode surface prior to pulse application. This almost ideal situation is achieved at high pulse times (which ensures that the adsorptive contribution is not much higher than the diffusive ones) and especially when NPV signals are analyzed in derivative form. Under these conditions, reasonable lacks of fit are obtained, as well as stability constants coincident with these determined by reverse pulse voltammetry (RPV), a technique especially unaffected by adsorption.     

Present and future of wastewater reuse in Spain

This article contains an analysis of the current situation in Spain with respect to the reuse of treated effluent, outlining the different experiences obtained together with the future prospects. In matters concerning reuse, Spanish Law places particular emphasis on the planning of basic State regulations that are now being drawn up by the Ministry of Environment, as well as developing other supplementary tools for hazard control and the breakthroughs that are in the process of being made in the planning area. Finally, an account is given of a series of observations that the authors believe to be relevant with respect to achieving sustainable progress for reuse in Spain.     

Signal splitting in the stripping analysis of heavy metals using bismuth film electrodes: Influence of concentration range and deposition parameters

The stripping signals of Pb(II), Cd(II) and Zn(II) in a bismuth film electrode (BiFE) ex situ plated on glassy carbon support were studied by differential pulse anodic stripping voltammetry and constant-current stripping chronopotentiometry. Regular signals were measured for Pb(II), with a good linearity inside a wide concentration range. In contrast, Cd(II) and Zn(II) produce two overlapping signals, one predominating at low metal concentrations and the other at high metal concentrations. For the detailed study of such peak splitting, multivariate curve resolution by alternating least squares has been used concluding that the total area becomes linear with metal concentration in both situations. The reasons of the peak splitting seem to be related to the accumulation of the reduced metal on BiFE in different ways. Even with that complication, the fact that the linear relationship total area versus concentration is hold reinforces the applicability of BiFE for the determination of total concentrations of metal ions inside a wider concentration range than that initially expected. However, the coexistence of signals at different characteristic potentials anticipates important difficulties in the analysis of potential shifts caused by heavy metal complexation.