Electrochemical Sensor for the Quantification of Dopamine Using Glassy Carbon Electrodes Modified with Single‐Wall Carbon Nanotubes Covalently Functionalized with Polylysine

We report a dopamine electrochemical sensor based on the modification of glassy carbon electrodes (GCE) with polylysine‐functionalized single‐wall carbon nanotubes (SWCNT‐PLys). The resulting electrodes (GCE/SWCNT‐PLys) showed a significant improvement in the electrooxidation of dopamine with drastic decrease in the peak potentials separation and important enhancement in the associated currents. Dopamine was detected by differential pulse voltammetry‐adsorptive stripping with medium exchange at nanomolar levels even in the presence of high excess of ascorbic and uric acids. The sensor was successfully used for the quantification of dopamine in urine samples enriched with the neurotransmitter.     

Kondo‐like resonance in ZnO:Eu

Doping ZnO with Eu results in the hybridization of the f atomic orbitals of the Eu with the bands of the host material. The strongest interaction turns out to be with the oxygen s‐p band. This hybridization manifests itself as a Kondo‐like resonance, namely, the appearance of a narrow resonant f band close to the Fermi level. Our aim in the present work is to calculate the electronic structure of ZnO:Eu in which the lanthanide ion replaces one of the Zn ions inducing a geometric relaxation on the system. We have used two reliable crystal electronic structure codes for our calculation. The program WIEN2k [Blaha, P., et al. WIEN2k, An Augmented Plane Wave + Local Orbitals Program for Calculating Crystal Properties, 2001] allows us to include the effects of the f the GGA + U model (generalized gradient approximation plus U) for the relaxed configuration. On the other hand, the program CRYSTAL06 [ http://www.crystal.unito.it/ ] allows us to monitor the charge of the Eu ion using a judicious mix of the Hartree‐Fock nonlocal exchange term with the density functional exchange‐correlation potential. Results are presented for the density of states (both the total and the partial contribution from the f electrons), as well as maps of the spin density around the Eu ion, both clearly showing the presence of the resonant f bands. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Metal-ion retention properties of water-soluble amphiphilic block copolymer in double emulsion systems (w/o/w) stabilized by non-ionic surfactants

Metal-ion retention properties of water-soluble amphiphilic polymers in presence of double emulsion were studied by diafiltration. Double emulsion systems, water-in-oil-in-water, with a pH gradient between external and internal aqueous phases were prepared. A poly(styrene-co-maleic anhydride) (PSAM) solution at pH 6.0 was added to the external aqueous phase of double emulsion and by application of pressure a divalent metal-ion stream was continuously added. Metal-ions used were Cu(2+) and Cd(2+) at the same pH of polymer solution. According to our results, metal-ion retention is mainly the result of polymer-metal interaction. Interaction between PSMA and reverse emulsion globules is strongly controlled by amount of metal-ions added in the external aqueous phase. In addition, as metal-ion concentration was increased, a negative effect on polymer retention capacity and promotion of flocculation phenomena were produced.     

Hard-soft magnetic ribbons with biased hysteresis curves

Nanocrystalline ribbons which present biased hysteresis loops have been obtained by annealing the rapidly quenched Co₆₉Si₁₂B₁₂Fe₄Mo₂Ni₁ amorphous alloy. With the adequate annealing conditions, the induced devitrification produces a soft material whose hysteresis loop biasing can be modified by simply applying an intense dc magnetic field at room temperature, with no field cooling. This anomalous magnetic behavior is analyzed in terms of the switching field distributions and related to the structural properties. It is concluded that a low concentration of individual nanoclusters, completely surrounded by the embedding amorphous matrix, rather than large agglomerates, favors the biasing effect preserving the soft magnetic behavior of the material.     

Magnetic nanoparticles for application in cancer therapy

Magnetic particles play nowadays an important role in different technological areas with potential applications in fields such as electronics, energy and biomedicine. In this report we will focus on the hyperthermia properties of magnetite nanoparticles and the effect of several chemical/physical parameters on their heating properties. We will discuss about the need of searching new smaller magnetic systems in order to fulfill the required physical properties which allow treating tumoral tissues more efficiently by means of magnetically induced heat. Preliminary results will be shown about the effect of a biocompatible shell of core–shell magnetite NPs on the heating properties by application of a RF magnetic field.     

Evaluation of generalized cross-correlation methods for direction of arrival estimation using two microphones in real environments

The localization of sound sources, and particularly speech, has a numerous number of applications to the industry. This has motivated a continuous effort in developing robust direction-of-arrival detection algorithms, in order to overcome the limitations imposed by real scenarios, such as multiple reflections and undesirable noise sources. Time difference of arrival-based methods, and particularly, generalized cross-correlation approaches have been widely investigated in acoustic signal processing, but there is considerable lack in the technical literature about their evaluation in real environments when only two microphones are used. In this work, four generalized cross-correlation methods for localization of speech sources with two microphones have been analyzed in different real scenarios with a stationary noise source. Furthermore, these scenarios have been acoustically characterized, in order to relate the behavior of these cross-correlation methods with the acoustic properties of noisy scenarios. The scope of this study is not only to assess the accuracy and reliability of a set of well-known localization algorithms, but also to determine how the different acoustic properties of the room under analysis have a determinant influence in the final results, by incorporating in the analysis additional factors to the reverberation time and signal-to-noise ratio. Results of this study have outlined the influence of the acoustic properties analysed in the performance of these methods.     

Study of static permittivity and density of the systems {(n-nonane + monoglyme or diglyme)} at various temperatures

Relative permittivity and density on mixing at atmospheric pressure and temperatures from (288.15 to 328.15) K have been measured over the whole composition range for {CH₃O(CH₂CH₂ O)_mCH₃ m = 1, 2 (also called monoglyme and diglyme) + n-nonane}. Excess permittivity and molar volume on mixing for the above systems have been calculated. The Redlich–Kister equation has been used to estimate the binary fitting parameters and standard deviations from the regression lines were calculated. The density and excess molar volume were fitted to a polynomial equation as a function of the mole fraction and temperature. The temperature dependences of derived magnitudes, ${\left(\frac{\mathrm{?}{V}_{\text{m}}^{\text{E}}}{\mathrm{?}T}\right)}_{P\text{,}x}$ and ${\left(\frac{\mathrm{?}{H}_{\text{m}}^{\text{E}}}{\mathrm{?}P}\right)}_{T\text{,}x}$, were computed, due to its importance in the study of specific molecular interactions. Different mixing rules have been applied to predict the permittivity of these mixtures and the results indicate that the predictions are better when the volume change on mixing is incorporated in calculations. In order to determine the dipolar moment of the glymes using Debye’s model at infinite dilution, their refraction index was measured. The values obtained agree with those in the literature for infinite dilution in hexane.     

Measurement uncertainty of shikimic acid in red wines produced in Chile

High-performance liquid chromatography (HPLC) to determine shikimic acid is used as a complementary tool to differentiate wine varieties. In order to correctly classify, measurement uncertainty of shikimic acid by HPLC in red wine was estimated considering the following components: uncertainty associated with the preparation of shikimic acid stock solution, uncertainty associated with quantification using a calibration curve, and uncertainty associated with precision. The most important contribution to total uncertainty was the method precision. The expanded uncertainty (U) for different wine varieties was between 2.6 and 8.5%. The method was applied to determine the concentration of shikimic acid in different emerging wine varieties cultivated in Chile, such as Carmenère, Shiraz, and Pinot Noir, comparing them with classical varieties, such as Cabernet Sauvignon and Merlot. Shiraz wines presented lower shikimic acid concentrations (between 27 and 86 mg L⁻¹ with U _(k=2) = 2.6%) than Cabernet Sauvignon wines (between 41 and 142 mg L⁻¹ with U _(k=2) = 8.1%), but their concentrations were higher than found in Merlot (from 9 to 41 mg L⁻¹ with U _(k=2) = 4.3%) and Carmenère wines (between 7 and 49 mg L⁻¹ with U _(k=2) = 5.8%). Pinot Noir was the variety with the lowest concentration of this acid (7–14 mg L⁻¹ with U _(k=2) = 8.5%). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.