Vitamin C and Phenolic Antioxidants of Jua (Ziziphus joazeiro M.) Pulp: A Rich Underexplored Brazilian Source of Ellagic Acid Recovered by Aqueous Ultrasound-Assisted Extraction

Jua (juá in Portuguese) is an underexplored fruit from Brazil’s northeast. This fruit is rich in antioxidant substances. However, there is a dearth of information about jua’s bioactive potential. The present study evaluated two extraction methods (continuous agitation and ultrasound-assisted extraction—UAE) and employed three different solvents (water, ethanol, and acetone) to efficiently recover soluble phenolic compounds. Aqueous extracts obtained by UAE showed the highest total phenolic content (TPC) and antiradical activity. Besides being an eco-friendly procedure, extraction and/or solubility in an aqueous medium is also important for food application. Ellagic acids were the predominant phenolics (80%) found in aqueous jua pulp extract obtained by UAE, as determined by HPLC, while its TPC was 405.8 gallic acid equivalent per gram of fruit. This extract also exhibited a higher scavenging activity towards peroxyl radicals when compared to that of several other fruits from the literature, including grape, strawberry, cranberry, and walnuts, which are known references in terms of antioxidants. This is the first report that demonstrates jua pulp’s potential as an alternative source of ellagic acid and other phenolic acids and flavonoids. Therefore, the outcome of this study provides new information that can be useful for functional food and nutraceutical industries.     

Bi-Lipschitz homeomorphic subanalytic sets have bi-Lipschitz homeomorphic tangent cones

We prove that if there exists a bi-Lipschitz homeomorphism (not necessarily subanalytic) between two subanalytic sets, then their tangent cones are bi-Lipschitz homeomorphic. As a consequence of this result, we show that any Lipschitz regular complex analytic set, i.e., any complex analytic set which is locally bi-Lipschitz homeomorphic to an Euclidean ball must be smooth. Finally, we give an alternative proof of S. Koike and L. Paunescu’s result about the bi-Lipschitz invariance of directional dimensions of subanalytic sets.     

Diagram,valence-to-core,and hypersatellite Kβ X-ray transitions in metallic chromium

We report on measurements of the Kβ diagram, valence-to-core (VtC), and hypersatellite X-ray spectra induced in metallic Cr by photon single and double K-shell ionization. The experiment was carried out at the Stanford Synchrotron Radiation Lightsource using the seven-crystal Johann-type hard X-ray spectrometer of the beamline 6-2. For the Kβ diagram and VtC transitions, the present study confirms the line shape features observed in previous works, whereas the K^hβ hypersatellite transition was found to exhibit a complex spectral line shape and a characteristic low-energy shoulder. The energy shift of the hypersatellite relative to the parent diagram line was deduced from the measurements and compared with the result of extensive multiconfiguration Dirac–Fock (MCDF) calculations. A very good agreement between experiment and theory was found. The MCDF calculations were also used to compute the theoretical line shape of the hypersatellite. A satisfactory agreement was obtained between the overall shapes of the experimental and theoretical spectra, but deviations were observed on the low- and high-energy flanks of the hypersatellite line. The discrepancies were explained by chemical effects, which were not considered in the MCDF calculations performed for isolated atoms.     

Electron capture rates on nuclei and implications for stellar core collapse

Supernova simulations to date have assumed that during core collapse electron captures occur dominantly on free protons, while captures on heavy nuclei are Pauli blocked and are ignored. We have calculated rates for electron capture on nuclei with mass numbers A=65-112 for the temperatures and densities appropriate for core collapse. We find that these rates are large enough so that, in contrast to previous assumptions, electron capture on nuclei dominates over capture on free protons. This leads to significant changes in core collapse simulations.     

Platinum–cadmium electrocatalyst for ethylene glycol electrochemical reaction in perchloric acid electrolyte

The electrooxidation of ethylene glycol was studied using platinum–cadmium electrocatalysts supported on high surface area carbon Vulcan XC-72. This is the first instance of Cd being used as an electrocatalyst for glycol oxidation reaction. The catalysts were prepared with various Pt:Cd atomic ratios of 90:10, 80:20, and 70:30. All the catalysts prepared were synthesized by the alcohol reduction method with 20 wt.% metal on carbon. These materials were characterized morphologically by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) and electrochemically by cyclic voltammetry and chronoamperometry. The electrochemical measurements were carried out at 25, 35, 45, and 55 °C, and the products of the electrochemical reaction were monitored by high-performance liquid chromatography (HPLC). The XRD patterns of all the PtCd catalysts presented cubic face-centered structures, and TEM revealed a homogeneous particle distribution on the carbon support with low agglomeration. The average particle size was assumed to be the maximum of the Gaussian distribution curve of particle size, at close to 2.5 nm. The presence of Cd results in an improvement in the glycol oxidation reaction, as observed by cyclic voltammetry; linear sweep voltammetry shows a lower onset potential compared to that of pure platinum. At a constant potential of 0.50 V (vs. RHE) at ambient temperature, HPLC showed glycolaldehyde to be the main byproduct formed from ethylene glycol oxidation at potential constant of 0.50 V.     

Tunable remote pinning of domain walls in magnetic nanowires

Domain wall (DW) pinning in ferromagnetic nanowires is in general a complex process. Distortions of the DW shape make quantitative agreement between modeling and experiment difficult. Here we demonstrate pinning using nanometer scale localized stray fields. This type of interaction gives well-characterized, tailorable potential landscapes that do not appreciably distort the DW. Our experimental results are in excellent quantitative agreement with an Arrhenius-Néel model of depinning--a result only possible when the modeled potential profile agrees fully with that experienced by the DW.     

Asymptotically stable periodic orbits of a coupled electromechanical system

In this paper an electromechanical system is analyzed. The existence and asymptotic stability of a periodic orbit are obtained in a mathematically rigorous way as well as an expansion of the period by using an adequate small parameter. For the analytical results the main tool used is the regular perturbation theory. Some results, such as the growing of the period according to some powers of the parameters and the relation 2:1 between the period of the cart, which is a part of the electromechanical system, and the period of the current, are compatible with earlier numerical findings.     

On duality theory for non-convex semidefinite programming

In this paper, with the help of convex-like function, we discuss the duality theory for nonconvex semidefinite programming. Our contributions are: duality theory for the general nonconvex semidefinite programming when Slater’s condition holds; perfect duality for a special case of the nonconvex semidefinite programming for which Slater’s condition fails. We point out that the results of Fan (Appl. Math. Lett. 18:1068–1073, 2005) can be regarded as a special case of our result.     

On the viscosities of liquid mixtures

There have been many empirical formulae proposed which would give the viscosity of a binary mixture of liquids in terms of the viscosities of the liquids and of the composition. Several years ago kinetic theory arguments were used to rederive an old formula due to Dolezalek and Schulze, which has the virtue of simplicity and, apparently, good accuracy. The parameters of this formula are the two fluid viscosities and a mutual viscosity. In this note we observe that such formulae fit exactly into the continuum theory of mixtures recently developed by us and others. We use Dolezalek's and Schulze's formula and thermodynamic restrictions, elsewhere derived, to present a generalized Navier-Stokes system for the flow of mixtures of liquids.

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Zusammenfassung Es sind viele empirische Formeln vorgeschlagen worden, die die Viskosität einer Mischung von zwei Flüssigkeiten als Funktion der Viskositäten der beiden Flüssigkeiten ausdrückt. Vor mehreren Jahren wurden Argumente aus der kinetischen Theorie benützt, um eine alte Formel von Dolezalek und Schulze wieder herzuleiten, die den Vorzug der Einfachheit hat und anscheinend ziemlich genau ist. In dieser Arbeit wird bemerkt, dass solche Formeln exakt in die Kontinuumstheorie von Mischungen passen, die vor kurzem von den Autoren und von andern entwickelt wurde. Wir benützten die Formel von Dolezalek und Schulze und thermodynamische Einschränkungen, die anderswo abgeleitet wurden, um eine verallgemeinertes Navier-Stokes-System für die Strömung von Mischungen von Flüssigkeiten anzugeben.