Elaboration of superparamagnetic cobalt–ferrite nanocomposites from films of chitosan chelates

Cobalt–ferrite nanocomposites were synthesized from polymeric films of chelates of Co(II) and Fe(III) ions within a chitosan matrix by a solid‐state coprecipitation reaction with weight content ratios of chitosan to cobalt–ferrite of 50/50 and 25/75 w/w. Morphological and crystalline studies of the composites were performed by high‐resolution transmission electron microscopy, X‐ray diffraction, and selected area electron diffraction with a nanobeam diffraction probe. The results show nanoparticles around 4 nm with a spinel structure, consistent with the cobalt–ferrite phase. The magnetic behavior was evaluated with curves of the applied‐field‐dependent magnetization [M(H)] and the temperature‐dependent magnetization [M(T)]. Both the M(H) and M(T) curves showed typical superparamagnetic behavior, depicting an absence of hysteretic characteristics and the characteristic peak at blocking temperature in the zero‐field‐cooled curve. There was also evidence of strong interparticle and intraparticle interactions, which suggested magnetic frustration in the particle magnetic moment alignment with the applied field. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Performance analysis of Hurst exponent estimators using surrogate-data and fractional lognormal noise models: Application to breathing signals from preterm infants

The use of the Hurst exponent (H) to quantify the fractal characteristics of biological signals and its potential to detect abnormalities has aroused, recently, the interest of many researchers. Numerous techniques to estimate H are described in the literature, yet the choice of the most performing one is not straightforward. In this paper, we proposed some tests using artificial signals from experimental data and stochastic models to evaluate the robustness of three estimation techniques. Different surrogate-data tests, including a novel method to parametrize the degree of correlation in experimental signals with H (Hurst-adjusted surrogates), were first carried out. Then, simulated signals with prescribed H were obtained from fractional Gaussian noise modified properly to follow the lognormal laws observed in empirical data. The tests were applied to examine detrended fluctuation analysis (DFA), discrete wavelet transform and least squares based on standard deviation (LSSD) methods in the particular case of inter-breath interval signals from preterm infants. Simulations showed that none of the estimators were robust for every breathing pattern (regular, erratic and periodic) and should not be applied blindly without performing the preliminary tests proposed here. The LSSD technique was the most precise in general, but DFA was more robust with highly spiked patterns.     

Maillard reaction products profile and intake from Spanish typical dishes

The Mediterranean diet is proposed as one of the healthiest dietary models, but its contribution to Maillard reaction products (MRP) intake is unknown. Several Spanish dishes typical of the Mediterranean diet (paella, Spanish omelette, salmorejo or churros) were selected to evaluate MR extension and the presence of MRP. CIELab colour, browning at different wavelengths, furosine, hydroxymethylfurfural, furfural and acrylamide were determined, and content/serving was calculated. Development of MR was affected by ingredients: when protein levels were high and carbohydrates low, early MRP were formed, regardless of the culinary process. There was found a correlation between acrylamide and hydroxymethylfurfural. The possible underestimation of deterministic calculations of acrylamide dietary exposure is discussed. This study presents a first approximation to enable the MRP intake from the Mediterranean diet to be calculated, taking into account the moisture content and the serving size of dishes.     

EPR Study of MnO and MnO2 Doped Barium Aluminoborate Glasses

An off-equilibrium redox condition study of Mn²⁺ and Mn⁴⁺ ions added to the batch is reported for the case of the preparation of the barium aluminoborate glasses, by considering that the out of equilibrium reactions started already on the melt. It is shown that for lower dopant concentrations the relative concentrations of the oxidation states of the manganese are found out of equilibrium up to the added amount of 0.3 mol% of MnO₂, but on doping with MnO, the equilibrium state is achieved at the MnO added amount of 0.07 mol%. The change of the redox condition of the manganese ions toward the equilibrium was studied by tracking the Mn²⁺ amount as a function of the doping concentration in the two cases of MnO and MnO₂.     

Reduction of sodium and increment of calcium and ω‐3 polyunsaturated fatty acids in dry fermented sausages: effects on the mineral content,lipid profile and sensory quality

BACKGROUND: A combined technological approach was applied in the development of healthier dry fermented sausages: a partial substitution of the pork back fat by pre‐emulsified linseed oil and a partial replacement of sodium chloride with calcium ascorbate at two different levels, leading to low amounts of salt (14gSalt and 10gSalt, with 14 g and 10 g NaCl per kg of mixture, respectively). RESULTS: The developed products (14gSalt and 10gSalt) showed adequate results for a_w (0.85 and 0.87) and pH (4.98 and 5.21), and low lipid oxidation values (1.4 × 10^?4 and 1.5 × 10^?5 g malondialdehyde (MDA) kg^?1). The lipid modification led to a significantly higher supply of ω‐3 (23.3 g kg^?1) compared to the control (3.2 g kg^?1). Simultaneously, reductions of 38% and 50% in sodium content and a calcium supply of 4 and 5.2 g kg^?1 were achieved in the 14gSalt and 10gSalt formulations, respectively, compared to the control products (26 g salt and 0.87 g kg^?1 Ca). Instrumental analysis of colour and texture and sensory studies demonstrated that the organoleptic quality of the new formulations was similar to that of traditional products. CONCLUSIONS: The developed dry fermented sausages showed healthier properties than traditional ones owing to their reduced sodium and higher calcium content and a significant supply of ω‐3 fatty acids. © 2012 Society of Chemical Industry     

Influence of processing conditions on the rheological behavior of crumb tire rubber‐modified bitumen

Traditional or technological studies about crumb tire rubber‐modified bitumens (CTRMBs) do not provide detailed rheological information. In that way, this article describes the influence of processing conditions on the linear viscoelastic and viscous behaviors of CTRMBs. The results of the study reveal an exponential increase in dissolved/dispersed rubber with processing temperature and, therefore, lower solid content that affect the rheological behavior in different ways. No influence of the processing device was observed, probably due to the fact that processing temperature (180°C) was not high enough to break up the crosslinked network of the rubber. The presence of rubber particles avoids the negative hardening effects observed for unmodified bitumens, resulting in a more flexible binder at low temperature. At high in‐service temperature, better rutting resistance would also be expected for CTRMBs. Flow results at 135°C indicates that modified bitumens can satisfy the AASHTO MP1 requirements if high‐enough shear rates are reached. All the CTRMBs studied present segregation, due to rubber settling during storage at high temperature, although an increase in processing temperature seems to enhance its stability. The results obtained seem to indicate that the optimum CTRMB processing temperature is 210°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1683–1691, 2007     

Consumption of highly processed foods: Effects on bioavailability and status of zinc and copper in adolescents

The effects of consuming diets with different Maillard reaction products (MRP) content on zinc and copper bioavailability and status were examined. In a 2-week randomised 2-period crossover trial, 18 male adolescents consumed two diets, named white diet (WD) and brown diet (BD), which were poor and rich in MRP, respectively. A 3-day balance was performed at the end of each period and fasting blood samples were collected. Zinc bioavailability did not vary significantly between the diets (%WD: 21.0 ± 5.0, %BD: 15.1 ± 5.1), but BD consumption increased copper faecal excretion (~ 1.8-fold) and significantly decreased its bioavailability (~ 3.0-fold). Biochemical parameters related to zinc metabolism remained unaltered whereas copper in serum and erythrocytes significantly decreased after consumption of the BD (72.47 ± 2.42 μg/dl and 0.93 ± 0.01 μg/ml in serum and erythrocytes with WD compared to 65.87 ± 3.11 μg/dl and 0.84 ±0.02 μg/ml with BD). The present results suggest that the high presence of MRP in the diet does not affect zinc but negatively affects copper bioavailability. As both minerals are essential trace elements involved in adolescents' growth and development, possible long-term effects of excessive MRP intake during adolescence warrant attention.     

Reduction reactions applied for synthesizing different nano-structured materials

Different materials have been synthesized by alternative routes: nitrates thermal decomposition to prepare oxide or co-formed oxides and reduction by hydrogen or graphite to obtain mixed oxides, composites or alloys. These chemical-based synthesis routes are described and thermodynamics studies and kinetics data are presented to support its feasibility. In addition, selective reduction reactions have been applied to successfully produce metal/ceramic composites, and alloys. Structural characterization has been carried out by X-ray Diffraction and, more extensively, Transmission Electron Microscopy operating in conventional diffraction contrast (CTEM) and high-resolution mode (HRTEM), indicated the possibility of obtaining oxide and alloy crystals of sizes ranging between 20 and 40 nm.