Development of paper based electrodes: From air-breathing to paintable enzymatic cathodes

This work presents the results from the development of bio-cathodes for the application on paper-based biofuel cells. Our main goal here is to demonstrate the possibility of using different designs of air-breathing bio-cathodes and ink-based bio-cathodes for this new type of paper based electrochemical cell. The electrochemical performance for the bio-electrocatalytic oxygen reduction reaction was studied by using open circuit voltage and amperometry measurements, as well as polarization curves to probe the four-electron reduction reaction of ambient oxygen catalyzed by bilirubin oxidase (BOx). The electrochemical measurements showed that all procedures allowed the direct electron transfer from the active site of the bilirubin oxidase to the electrode surface with a limiting current density of almost 500 mu A cm(-2) for an air-breathing BOx cathode and 150 mu A cm(-2) for an ink based BOx cathode. Under a load of 300 mV a stable current density was obtained for 12 h of continuous operation. (C) 2012 Elsevier Ltd. All rights reserved.

Comparison of predicted and experimental DSC curves for vegetable oils

We compare experimental and predicted differential scanning calorimetry (DSC) curves for palm oil (PO), peanut oil (PeO) and grapeseed oil (GO). The predicted curves are computed from the solid-liquid equilibrium modelling and direct minimization of the Gibbs free energy. For PO, the lower the scan rate, the better the agreement. The temperature transitions of PeO and GO were predicted with an average deviation of -0.72 degrees C and -1.29 degrees C respectively, in relation to experimental data from literature. However, the predicted curves showed other peaks not reported experimentally, as computed DSC curves correspond to equilibrium hypothesis which is reached experimentally for an infinitely small scan rate. The results revealed that predicted transitions temperatures using equilibrium hypotheses can be useful in pre-experimental evaluation of vegetable oils formulations seeking for desired melting profiles. (C) 2012 Elsevier B.V. All rights reserved.

Curves in the Minkowski plane and their contact with pseudo-circles

We study the caustic, evolute, Minkowski symmetry set and parallels of a smooth and regular curve in the Minkowski plane.

J/psi Polarization in pp Collisions at root s=7 TeV

The ALICE Collaboration has studied J/psi production in pp collisions at root s = 7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/psi polarization parameters lambda(theta) and lambda(phi) were obtained. The study was performed in the kinematic region 2: 5 < y < 4, 2 < p(t) < 8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.

Case study: a 3D resistivity and induced polarization imaging from downstream a waste disposal site in Brazil

A contaminated site from a downstream municipal solid waste disposal site in Brazil was investigated by using a 3D resistivity and induced polarization (IP) imaging technique. This investigation purpose was to detect and delineate contamination plume produced by wastes. The area was selected based on previous geophysical investigations, and chemical analyses carried out in the site, indicating the presence of a contamination plume in the area. Resistivity model has successfully imaged waste presence (rho < 20 Omega m), water table depth, and groundwater flow direction. A conductive anomaly (rho < 20 Omega m) outside wastes placement was interpreted as a contamination plume. Chargeability model was also able to imaging waste presence (m > 31 mV/V), water table depth, and groundwater flow direction. A higher chargeability zone (m > 31 mV/V) outside wastes placement and following conductive anomaly was interpreted as a contamination plume. Normalized chargeability (MN = m/rho) confirmed polarizable zone, which could be an effect of a salinity increase (contamination plume), and the clay presence in the environment.

Fluorescence polarization assay, competitive enzyme-linked immunosorbent assay (ELISA-C) and indirect ELISA for the diagnosis of brucellosis in buffaloes (Bubalus bubalis)

The objective of the present study was to compare the performance of three serological tests for diagnosis of Brucella abortus infections in buffaloes (Bubalus bubalis). Serum samples collected from 696 adult females were submitted to the competitive enzyme-linked immunosorbent assay (ELISAC), (I-ELISA), fluorescence polarization test (FPA), 2-mercaptoethanol test (2-ME) and complement fixation test (CFT). The gold standard was the combination of CFT and 2-ME, considering as positive the reactors in both CFT and 2-ME, and as negative those non-reactors. ROC analyses were done for C-ELISA, I-ELISA and FPA and the Kappa agreement index were also calculated. The best combinations of relative sensitivity (SEr) and relative specificity (SPr) and Kappa were given by C-ELISA (96.9%, 99.1%, and 0.932, respectively) and FPA (92.2%, 97.6 and 0.836, respectively). The C-ELISA and FPA were the most promising confirmatory tests for the serological diagnosis of brucellosis in buffaloes, and for these tests, cut-off values for buffaloes may be the same as those used for bovines.

Spectral Induced Polarization (SIP) signatures of clayey soils containing toluene

We performed laboratory experiments to investigate the sensitivity of the Spectral Induced Polarization (SIP) method to toluene contamination in clayey soils. We used mixtures of quartzitic sand and montmorillonite as soil samples, artificially contaminated with varying amounts of toluene. Care was taken to quantify the experimental uncertainty resulting from packing since such effects must be quantified if variations in SIP signatures between samples are to be reliably interpreted in terms of the effects of hydrocarbon concentration. The SIP response of all samples following addition of toluene was monitored for a period of 40 days following sample preparation. Stepwise regression was used to examine the statistical significance of correlations between (i) clay content and (ii) toluene concentration and SIP parameters. Both single-frequency real and imaginary conductivity measurements, along with the integral chargeability, normalized chargeability, DC conductivity and time constant obtained from a Debye decomposition fitting, were examined in this regression analysis. The SIP measurements show a clear time dependence following sample preparation, indicating that samples containing toluene may take significant time to reach an equilibrium electrical response. SIP measurements are significantly related to toluene content shortly after sample preparation, when the expected dependence of SIP on clay concentration is apparently suppressed. However, for the state of electrical equilibrium after 40 days (interpreted to indicate surface chemistry at equilibrium) there is no significant relation between SIP measurements and toluene content; instead SIP measurements are then significantly correlated with clay concentration. The total chargeability, normalized chargeability and relaxation time obtained from the Debye decomposition show no correlation with toluene content, indicating that this procedure, which likely integrates over multiple mechanisms, may not be suitable for understanding relationships between SIP and hydrocarbon contamination. We find only small low-frequency polarization signals observed in relation to toluene concentration (2 mrad at 0.01 Hz), which initially decreases the interfacial polarization. Unlike earlier works, our results do not support the use of the SIP method as a tool for monitoring toluene contamination in clay soils.

Polarization effect on the two-photon absorption of a chiral compound

In this report, we investigate the polarization effect (linear, elliptical and circular) on the two-photon absorption (2PA) properties of a chiral compound based in azoaromatic moieties using the femtosecond Z-scan technique with low repetition rate and low pulse energy. We observed a strong 2PA modulation between 800 nm and 960 nm as a function the polarization changes from linear through elliptical to circular. Such results were interpreted employing the sum-over-essential states approach, which allowed us to model the 2PA circular-linear dichroism effect and to identifier the overlapping of the excited electronic states responsible by the 2PA allowed band. (C) 2012 Optical Society of America

On Fermat's principle for causal curves in time oriented Finsler spacetimes

In this work, a version of Fermat's principle for causal curves with the same energy in time orientable Finsler spacetimes is proved. We calculate the second variation of the time arrival functional along a geodesic in terms of the index form associated with the Finsler spacetime Lagrangian. Then the character of the critical points of the time arrival functional is investigated and a Morse index theorem in the context of Finsler spacetime is presented. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4765066]

MATHEMATICAL ANALYSIS OF MAXIMUM POWER GENERATED BY PHOTOVOLTAIC SYSTEMS AND FITTING CURVES FOR STANDARD TEST CONDITIONS

The rural electrification is characterized by geographical dispersion of the population, low consumption, high investment by consumers and high cost. Moreover, solar radiation constitutes an inexhaustible source of energy and in its conversion into electricity photovoltaic panels are used. In this study, equations were adjusted to field conditions presented by the manufacturer for current and power of small photovoltaic systems. The mathematical analysis was performed on the photovoltaic rural system I- 100 from ISOFOTON, with power 300 Wp, located at the Experimental Farm Lageado of FCA/UNESP. For the development of such equations, the circuitry of photovoltaic cells has been studied to apply iterative numerical methods for the determination of electrical parameters and possible errors in the appropriate equations in the literature to reality. Therefore, a simulation of a photovoltaic panel was proposed through mathematical equations that were adjusted according to the data of local radiation. The results have presented equations that provide real answers to the user and may assist in the design of these systems, once calculated that the maximum power limit ensures a supply of energy generated. This real sizing helps establishing the possible applications of solar energy to the rural producer and informing the real possibilities of generating electricity from the sun.

Electrostatic potentials and polarization effects in proton-molecule interactions by means of multipoles from the quantum theory of atoms in molecules

Some atomic multipoles (charges, dipoles and quadrupoles) from the Quantum Theory of Atoms in Molecules (QTAIM) and CHELPG charges are used to investigate interactions between a proton and a molecule (F2, Cl2, BF, AlF, BeO, MgO, LiH, H2CO, NH3, PH3, BF3, and CO2). Calculations were done at the B3LYP/6-311G(3d,3p) level. The main aspect of this work is the investigation of polarization effects over electrostatic potentials and atomic multipoles along a medium to long range of interaction distances. Large electronic charge fluxes and polarization changes are induced by a proton mainly when this positive particle approaches the least electronegative atom of diatomic heteronuclear molecules. The search for simple equations to describe polarization on electrostatic potentials from QTAIM quantities resulted in linear relations with r-4 (r is the interaction distance) for many cases. Moreover, the contribution from atomic dipoles to these potentials is usually the most affected contribution by polarization what reinforces the need for these dipoles to a minimal description of purely electrostatic interactions. Finally, CHELPG charges provide a description of polarization effects on electrostatic potentials that is in disagreement with physical arguments for certain of these molecules. (c) 2012 Wiley Periodicals, Inc.

Quantum oscillations of spin polarization in a GaAs/AlGaAs double quantum well

5 We employ the circular-polarization-resolved magnetophotoluminescence technique to probe the spin character of electron and hole states in a GaAs/AlGaAs strongly coupled double-quantum-well system. The photoluminescence (PL) intensities of the lines associated with symmetric and antisymmetric electron states present clear out-of-phase oscillations between integer values of the filling factor. and are caused by magnetic-field-induced changes in the population of occupied Landau levels near to the Fermi level of the system. Moreover, the degree of circular polarization of these emissions also exhibits the oscillatory behavior with increasing magnetic field. Both quantum oscillations observed in the PL intensities and in the degree of polarizations may be understood in terms of a simple single-particle approach model. The k . p method was used to calculate the photoluminescence peak energies and the degree of circular polarizations in the double-quantum-well structure as a function of the magnetic field. These calculations prove that the character of valence band states plays an important role in the determination of the degree of circular polarization and, thus, resulting in a magnetic-field-induced change of the polarization sign.

Double point curves for corank 2 map germs from C-2 to C-3

We characterize finite determinacy of map germs f : (C-2, 0) -> (C-3, 0) in terms of the Milnor number mu(D(f)) of the double point curve D(f) in (C-2, 0) and we provide an explicit description of the double point scheme in terms of elementary symmetric functions. Also we prove that the Whitney equisingularity of 1-parameter families of map germs f(t) : (C-2, 0) -> (C-3, 0) is equivalent to the constancy of both mu(D(f(t))) and mu(f(t)(C-2)boolean AND H) with respect to t, where H subset of C-3 is a generic plane. (C) 2011 Elsevier B.V. All rights reserved.

Simplified approach to low-cost multiparameter monitoring based on low frequency polarization modulation

We experimentally revisit a technique of low-cost multiparameter monitor for optical performance monitoring based on low frequency polarization modulation. A simplified calibration procedure, which significantly reduces the mathematical complexity and processing effort is proposed. Validation is achieved by carrying out relative optical power, wavelength, and differential group delay measurements. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:18201824, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26956

Simultaneous optical signal-to-noise ratio and differential group delay monitoring based on degree of polarization measurements in optical communications systems

We present a simultaneous optical signal-to-noise ratio (OSNR) and differential group delay (DGD) monitoring method based on degree of polarization (DOP) measurements in optical communications systems. For the first time in the literature (to our best knowledge), the proposed scheme is demonstrated to be able to independently and simultaneously extract OSNR and DGD values from the DOP measurements. This is possible because the OSNR is related to maximum DOP, while DGD is related to the ratio between the maximum and minimum values of DOP. We experimentally measured OSNR and DGD in the ranges from 10 to 30 dB and 0 to 90 ps for a 10 Gb/s non-return-to-zero signal. A theoretical analysis of DOP accuracy needed to measure low values of DGD and high OSNRs is carried out, showing that current polarimeter technology is capable of yielding an OSNR measurement within 1 dB accuracy, for OSNR values up to 34 dB, while DGD error is limited to 1.5% for DGD values above 10 ps. For the first time to our knowledge, the technique was demonstrated to accurately measure first-order polarization mode dispersion (PMD) in the presence of a high value of second-order PMD (as high as 2071 ps(2)). (C) 2012 Optical Society of America