Thermal-Diffusivity Measurements of Mexican Citrus Essential Oils Using Photoacoustic Methodology in the Transmission Configuration

Photoacoustic methodology in the transmission configuration (PMTC) was used to study the thermophysical properties and their relation with the composition in Mexican citrus essential oils providing the viability of using photothermal techniques for quality control and for authentication of oils and their adulteration. Linear relations for the amplitude (on a semi-log scale) and phase, as functions of the sample’s thickness, for the PMTC was obtained through a theoretical model fit to the experimental data for thermal-diffusivity measurements in Mexican orange, pink grapefruit, mandarin, lime type A, centrifuged essential oils, and Mexican distilled lime essential oil. Gas chromatography for distilled lime essential oil and centrifuged lime essential oil type A is reported to complement the study. Experimental results showed close thermal-diffusivity values between Mexican citrus essential oils obtained by centrifugation, but a significant difference of this physical property for distilled lime oil and the corresponding value obtained by centrifugation, which is due to their different chemical compositions involved with the extraction processes.     

Energy transfer and compatibility analysis of PVK/MEH-PPV blends processed via electrospraying and electrospinning

Solution polymer blends of a high molecular weight and a low molecular weight poly(9-vinyl carbazole) PVK with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), at a fixed blend ratio of 95.5:0.5, were processed via electrospraying and electrospinning. SEM studies revealed that electrosprayed particles were produced when low molecular weight PVK was used, while electrospun fibers were successfully obtained from solutions containing high molecular weight PVK, over a concentration range of 4–10% (w/v). From the absorption spectra of the neat polymers it was determined that Urbach energy E_u increase and optical band gap E_g decreases due to the physical defects along the main chain introduced by these electrostatic processing methods. Photoluminescence spectroscopy revealed a particular applied voltage, which depends on concentration and molecular weight, where aggregation of PVK levels off. Luminescence quenching of MEH-PPV is also observed to increase with applied voltage consistent with possible energy transfer from shorter conjugation length segments to nearby longer conjugated segments. The ratio of the intensity of the excitation spectra of the PVK (donor, both PVK_L or PVK_H) and the MEH-PPV (acceptor), I_D/I_A, exhibited minima at this particular voltage and then levels off, indicating not only maximum interpenetration and thus compatibility of both polymers but also maximum energy transfer. Hence, we demonstrate that compatibility and energy transfer can be optimized varying concentration and applied voltage during both electrospraying and electrospinning processes.     

The effect of Li+ incorporation in Yb3+-Nd3+ co-doped CaF2 phosphors over the NIR photoluminescence emission excited under visible light

The structural and optical characteristics of Nd³⁺-Yb³⁺ doped CaF₂ phosphors with and without the addition of Li⁺ ions are described in this work. The phosphors synthetized by hydrothermal and co-precipitation methods showed near-infrared (NIR) luminescence emission associated with inter-electronic transition of the Yb³⁺ ion in the range of 900–1050 nm via energy transfer process from Nd³⁺ ions under visible light excitation. The addition of Li⁺ to these phosphors resulted in an improvement of the NIR luminescence intensity by a factor up to 5. The effect of the incorporation of Li⁺ ions into the CaF₂ crystallite structure, the reduction of luminescence quenching states, as well as the energy transfer mechanism involved are discussed.     

Authentication of Concentrated Orange Essential Oils Using Photoacoustic Spectroscopy

Photoacoustic spectroscopy (PS) was used to study the thermal diffusivity and its relation with the composition in folded (concentrated) cold-pressed Mexican orange essential oils. A linear relation between the amplitude (on a semi-log scale) and phase, as functions of the sample thickness, for PS was obtained through a theoretical model to fit the experimental data for thermal-diffusivity measurements in concentrated orange essential oils. Experimental results showed a linear increase in thermal-diffusivity values with the folding degree: 5-fold, 10-fold, 20-fold, and 35-fold due to a decrease in terpenes (mainly D-limonene) related with the folding process that can be correlated with the thermal diffusivity of the orange essential oils. The obtained values in this study and those previously reported (see Int. J. Thermophys. 32, 1066, 2011) showed the possibility of using this thermal property to make distinctions between citrus oils obtained by different extraction processes and also between concentrated citrus oils. This provides the viability of a new complementary method for this purpose, contrasting with the use of density and refraction index, physical properties commonly used in the authentication of citrus essential oils.     

Brain–computer interfacing: more than the sum of its parts

The performance of non-invasive electroencephalogram-based (EEG) brain–computer interfaces (BCIs) has improved significantly in recent years. However, remaining challenges include the non-stationarity and the low signal-to-noise ratio of the EEG, which limit the bandwidth and hence the available applications. Optimization of both individual components of BCIs and the interrelationship between them is crucial to enhance bandwidth. In other words, neuroscientific knowledge and machine learning need to be optimized by considering concepts from human–computer interaction research and usability. In this paper, we present results of ongoing relevant research in our lab that addresses several important issues for BCIs based on the detection of transient changes in oscillatory EEG activity. First, we report on the long-term stability and robustness of detection of oscillatory EEG components modulated by distinct mental tasks, and show that the use of mental task pairs “mental subtraction versus motor imagery” achieves robust and reliable performance (Cohen’s κ > 0.6) in seven out of nine subjects over a period of 4 days. Second, we report on restricted Boltzmann machines (RBMs) as promising tools for the recognition of oscillatory EEG patterns. In an off-line BCI simulation we computed average peak accuracies, averaged over ten subjects, of 80.8 ± 7.2 %. Third, we present the basic framework of the context-aware hybrid Graz-BCI that allows interacting with the massive multiplayer online role playing game World of Warcraft. We show how a more integrated design approach that considers all components of BCIs, their interrelationships, other input signals and contextual information can increase interaction efficacy.     

Properties of Portland Cement Pastes Incorporating Nanometer-Sized Franklinite Particles Obtained from Electric-Arc-Furnace Dust

The present work presents preliminary results concerning ordinary portland cement (OPC) blended with electric-arc-furnace dust (EAFD) obtained from steel-smelting plants. The powder obtained after acid treatment of the EAFD consisted basically of nanometer-sized particles of ZnFe₂O₄. Incorporation of the EAFD in the OPC produced retardation of the setting process. Nevertheless, after 7 d, the compressive strength of the OPC/EAFD pastes was superior to undoped OPC, and, after 28 d, the extent of hydration of the OPC/EAFD pastes was equivalent to undoped OPC. A compressive strength of 72 MPa was attained after 42 d for OPC doped with 10 wt% EAFD.     

Comparison of mesoscopic solvation pressure at constant density and at constant chemical potential

The solvation pressures arising from the confinement of a fluid by surfaces are calculated under two different thermodynamic conditions, namely at constant density and at constant chemical potential, through mesoscopic scale simulations. We consider two types of fluids, a model monomeric solvent on the one hand, and a fluid composed of linear polymers dissolved in a monomeric solvent, on the other. For these systems our simulations show that the prediction of the solvation (or disjoining) pressure when the chemical potential is kept fixed is different from that obtained when the total density is fixed. We find however, that the same trend between both types of simulations can be obtained when the value of the fixed density is chosen as the average value of the density obtained at constant chemical potential.     

Lupus susceptibility loci in New Zealand mice

Susceptibility to systemic lupus erythematosus has been unequivocally established to be an inherited trait, but the exact genes and how they confer susceptibility remain largely unknown. In this study of (NZB x NZW)F2 intercross mice, we used linkage analysis of markers covering > 90% of the autosomal genome and identified eight susceptibility loci (Lbw1 to -8, chromosomes 17, 4-7, 18, 1, 11, respectively) associated with antichromatin autoantibody production, glomerulonephritis, and/or mortality. Only one locus, the major histocompatibility complex, was linked to all three traits. Two other loci were associated with both glomerulonephritis and mortality, whereas the remaining loci were linked to one of the above traits. Two additional loci (Sbw1 and -2) that contributed to splenomegaly were also identified. The Sbw2 locus mapped to the identical region as Lbw2, a locus on chromosome 4 linked to glomerulonephritis and mortality, suggesting a single locus with pleiotropic effects. The results indicate that the immunopathologic features of lupus are affected by distinct, but additive, genetic contributions. Studies to determine the nature of the genes associated with these loci should help define the genetic mechanisms involved in this systemic autoimmune disease.     

Thermal diffusivity measurement of spherical gold nanofluids of different sizes/concentrations

ABSTRACT: In recent times nanofluids have been studied by their thermal properties due to their variety of applications which ranges from photo-thermal therapy and radiofrequency hyperthermia (which have proven their potential use as coadjutants in these medical treatments for cancer diseases) to next generation of thermo-fluids. In this work photoacoustic spectroscopy for a specific study of thermal diffusivity, as a function of particle size and concentration, on colloidal water based gold nanofluids is reported. Gold nanoparticles were synthetized in presence of hydroquinone through a seed-mediated growth with homogenous sizes and shape in a range 15-125 nm. The optical response; size and morphology of these nanoparticles were characterized using UV-VIS spectroscopy and TEM respectively. The thermal characterization show a decrease in the thermal diffusivity ratio as the nanoparticle size is increased and an enhancement in thermal diffusivity ratio as nanoparticles concentration is added in the nanofluids. Compared with other techniques in the literature such as thermal lens and hot wire method, this photoacoustic technique shows advantage in terms of precision and a small amount of sample required (500ul) for which this technique might be suitable for thermal diffusivity measurement of nanofluids and being a promising alternative to classical techniques.     

Critical micelle concentration of an ammonium salt through DPD simulations using COSMO‐RS–based interaction parameters

In order to determine the critical micelle concentration (CMC) of aqueous dodecyltrimethylammonium chloride (DTAC), a screening of the DTAC gathering process at different molalities by performing dissipative particle dynamics (DPD) simulations over mesomolecules whose beads interact via repulsive conservative forces was performed. Conductor‐like screening model for real solvent quantum methodology, applied to molecular segments that describe the DTAC chemistry and were mapped onto the DPD beads, allows us the computing of activity coefficients at infinite dilution to obtain thermodynamic Flory–Huggins interaction parameters, from which we calculated the maxima repulsive conservative forces, that is, the DPD interaction parameters. Results indicate that at room temperature the CMC is 0.0217 mol/kg, the aggregation number ranges from 46 to 54 molecules, and the aggregate radius varies from 19.58 to 22.02 Å; all values are in excellent agreement with literature reported experimental ones of 0.0213 mol/kg, 47 5 molecules, and 20.1 Å. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4413–4423, 2013