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Stancu C.,Polytechnic University of Bucharest | Notingher P.V.,Polytechnic University of Bucharest | Ionita V.,Polytechnic University of Bucharest | Marinescu V.,Romanian National Institute for Research and Development in Electrical Engineering | Panaitescu D.,National Institute for R and D in Chemistry and Petrochemistry
2014 International Conference on Applied and Theoretical Electricity, ICATE 2014 - Proceedings | Year: 2014

Magnetic polymer composite materials have very good rheological (that are characteristic for polymers used as matrix) and magnetic properties superior to those of polymers (due to their magnetic filler) making them useful in many power applications (electromagnetic shielding, permanent magnets etc.). In this paper the results of an experimental study regarding the manufacture and characterization of some composites which have low density polyethylene (LDPE) as matrix and neodymium (Nd) and neodymium-iron-boron (NdFeB) as filler are presented. The manufacture process (with mass content between 0 and 15 %) and their structure (obtained by electronic and optical microscopy) are presented. It is shown that the samples are inhomogeneous and isotropic and the filler particles form clusters of variable dimensions and distances between them. Then, the first magnetization cycles obtained on neodymium (A) and neodymium-iron-boron (B) samples for three mass concentrations (5, 10 and 15 %) are presented. It is shown for both samples type (A and B) that the hysteresis area cycles increase with filler content being greater for samples B than A. It is shown, also, that the magnetic permeability values increase with filler content, but decrease very quickly with the magnetic field strength. © 2014 IEEE. Source

Hosu I.S.,Institut Universitaire de France | Hosu I.S.,National Institute for R and D in Chemistry and Petrochemistry | Wang Q.,Institut Universitaire de France | Wang Q.,Shandong University | And 10 more authors.
RSC Advances | Year: 2015

The quantification of peroxynitrite (ONOO-, PON) and hydrogen peroxide (H2O2) is intrinsically difficult as both species show similar oxidative features located within a narrow potential. The sub-second lifetime of ONOO- at neutral pH further complicates the analysis. In this paper, we examine the electrocatalytic activity of cobalt phthalocyanine tetracarboxylic acid (CoPc-COOH) loaded reduced graphene oxide (rGO) films towards peroxynitrite and hydrogen peroxide detection. The rGO/CoPc-COOH matrix is synthesized by the reaction of graphene oxide (GO) and CoPc-COOH at 90 °C for 5 h under ultrasonication. The integration of CoPc-COOH and the reduction of GO to rGO was confirmed by X-ray photoelectron spectroscopy, FTIR, Raman, UV-vis spectroscopy and electrochemistry. The rGO/CoPc-COOH film showed high electrocatalytic activity and specificity for ONOO- at anodic potential with a sensitivity of ≈11.5 ± 1 nA nM-1 and a peroxynitrite detection limit of ≈1.7 nM. The rGO/CoPc-COOH films further exhibited electrocatalytic reduction of H2O2 with a sensitivity of 14.5 μA mM-1 and a detection limit of ≈60 μM for H2O2. This journal is © The Royal Society of Chemistry 2015. Source

Vasilescu A.,International Center for Biodynamics Intrarea Portocalelor | Vezeanu A.,International Center for Biodynamics Intrarea Portocalelor | Liu Y.,Michigan State University | Hosu I.S.,National Institute for R and D in Chemistry and Petrochemistry | And 3 more authors.
ACS Symposium Series | Year: 2014

Typically, about $1 billion/year is lost when red meat loses freshness on the shelf. Consumer purchasing decisions depend on meat color and flavor, which are strongly influenced by complex nitro-oxidative events within meat muscle tissue. One goal of this chapter is to explain the loss in meat freshness linked to the action of peroxynitrite anion ONOO-, a strong nitro-oxidative agent. The toxicity of abnormally high ONOO-levels in vivo has been proven, and ONOO is also suspected of accelerating meat spoilage by two principal mechanisms: (1) oxidation of iron atoms in heme-containing globin proteins, leading to a color change from red to brown, and (2) peroxidation of unsaturated lipids, leading to flavor degradation. A second goal is to review electrochemical quantification methods for ONOO- and its oxidative effects on biologically relevant molecules, including unsaturated phospholipids within biological membranes and heme-containing molecules. A third goal is to examine the natural polyphenols that protect against peroxynitrite-induced oxidative damage. The final goal is to assess research advances and remaining research challenges related to ONOO-induced oxidative processes that reduce meat's shelf life. © 2014 American Chemical Society. Source

Constantinescu-Aruxandei D.,University of St. Andrews | Constantinescu-Aruxandei D.,National Institute for R and D in Chemistry and Petrochemistry | Petrovic-Stojanovska B.,University of St. Andrews | Penedo J.C.,University of St. Andrews | And 2 more authors.
Nucleic Acids Research | Year: 2016

The xeroderma pigmentosum group D (XPD) helicase is a component of the transcription factor IIH complex in eukaryotes and plays an essential role in DNA repair in the nucleotide excision repair pathway. XPD is a 5′ to 3′ helicase with an essential iron-sulfur cluster. Structural and biochemical studies of the monomeric archaeal XPD homologues have aided a mechanistic understanding of this important class of helicase, but several important questions remain open. In particular, the mechanism for DNA loading, which is assumed to require large protein conformational change, is not fully understood. Here, DNA binding by the archaeal XPD helicase from Thermoplasma acidophilum has been investigated using a combination of crystallography, cross-linking, modified substrates and biochemical assays. The data are consistent with an initial tight binding of ssDNA to helicase domain 2, followed by transient opening of the interface between the Arch and 4FeS domains, allowing access to a second binding site on helicase domain 1 that directs DNA through the pore. A crystal structure of XPD from Sulfolobus acidocaldiarius that lacks helicase domain 2 has an otherwise unperturbed structure, emphasizing the stability of the interface between the Arch and 4FeS domains in XPD. © 2016 The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research. Source

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