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H S Sousa, M S S Pereira, I N de Oliveira, J Strečka, M L Lyra
The degree of fermionic entanglement is examined in an exactly solvable Ising-Hubbard ladder, which involves interacting electrons on the ladder's rungs described by Hubbard dimers at half-filling on each rung, accounting for intrarung hopping and Coulomb terms. The coupling between neighboring Hubbard dimers is assumed to have an Ising-like nature. The ground-state phase diagram consists of four distinct regions corresponding to the saturated paramagnetic, the classical antiferromagnetic, the quantum antiferromagnetic, and the mixed classical-quantum phase...
May 2018: Physical Review. E
Milan Žukovič, Georgii Kalagov
Critical properties of the two-dimensional XY model involving solely nematic-like terms of the second and third orders are investigated by spin-wave analysis and Monte Carlo simulation. It is found that, even though neither of the nematic-like terms alone can induce magnetic ordering, their coexistence and competition leads to an extended phase of the magnetic quasi-long-range-order phase, wedged between the two nematic-like phases induced by the respective couplings. Thus, except for the multicritical point, at which all the phases meet, for any finite value of the coupling parameters ratio there are two phase transition: one from the paramagnetic phase to one of the two nematic-like phases followed by another one at lower temperatures to the magnetic phase...
May 2018: Physical Review. E
Debarshee Bagchi, Renato Pakter, Yan Levin
We introduce and study a one dimensional model of classical planar spins interacting self-consistently through magnetic field. The spins and the magnetic field evolve in time according to the Hamiltonian dynamics which mimics that of a free electron laser. We show that by rescaling the energy due to magnetic field inhomogeneity, in equilibrium, this system can be mapped onto a model very similar to the paradigmatic globally coupled Hamiltonian mean-field (HMF) model. The system exhibits a continuous equilibrium phase transition from paramagnetic to ferromagnetic phase, however unlike HMF, we do not see any magnetized quasistationary states...
May 2018: Physical Review. E
Yuan Ma, Qing Wang, Shengtao Xing
Magnetic γ-Fe2 O3 supported on mesoporous ZnFe2 O4 was synthesized by impregnation and deposition-precipitation methods. The obtained γ-Fe2 O3 /ZnFe2 O4 was found to be an effective catalyst for the degradation and mineralization of Orange II with H2 O2 under visible light irradiation, which can be attributed to the enhanced production of OH and particularly O2 - . The catalytic mechanism of γ-Fe2 O3 /ZnFe2 O4 for H2 O2 activation and the degradation pathway of Orange II were investigated. The result indicates that the loaded γ-Fe2 O3 could capture the electrons in the conductive band of ZnFe2 O4 , thus promoting the formation of O2 - from the reaction between H2 O2 and holes...
June 8, 2018: Journal of Colloid and Interface Science
Tsubasa Okamoto, Eiji Ohmichi, Yu Saito, Takahiro Sakurai, Hitoshi Ohta
We experimentally studied the pressure dependence of the zero-field splitting (ZFS) parameter of hemin (iron(III) protoporphyrin IX chloride), which is a model complex of hemoproteins, via high-frequency and high-field electron paramagnetic resonance (HFEPR) under pressure. Owing to the large ZFS, the pressure effect on the electronic structure of iron-porphyrin complexes has not yet been explored using EPR. Therefore, we systematically studied this effect using our newly developed sub-terahertz EPR spectroscopy system in the frequency range of 80-515 GHz, under magnetic fields up to 10 T and pressure up to 2 GPa...
June 14, 2018: Journal of Physical Chemistry. B
Ke Luo, Ki-Baek Jeong, Sang-Mook You, Da-Hee Lee, Young-Rok Kim
Herein, we report a fairly simple and environmentally friendly approach for the fabrication of starch-based magnetic polymer beads (SMPBs) with uniform shape and size through spontaneous rearrangement of short chain glucan (SCG) produced by enzymatic debranching of waxy maize starch. The paramagnetic materials, dextran-coated iron oxide nanoparticles (Dex@IONPs), were readily incorporated into the starch microstructure and rendered a superparamagnetic property to the SMPBs. The morphology and size of resulting SMPBs turned out to be modulated by Dex@IONPs in concentration dependent manner, of which Dex@IONPs was assumed to be acting as a seed inducing the epitaxial crystallization of SCG and further transforming it into homogeneous microparticles...
June 14, 2018: Journal of Agricultural and Food Chemistry
Bangaru Subban, Roobanguru Dhanraj
The luminescence properties of praseodymium (Pr3+ ) ion in potassium bromide (KBr) host have been investigated. The excitation bands observed in the region 220-300 nm are attributed to the transitions from 4f level to the 5d crystal field splitting levels of Pr3+ ion. Emission bands originated due to transition of 3 P2 →3 H6 (564 nm), 3 P0 →3 H6 (604 nm), 1 D2 →3 P4 (721 nm) and 3 P0 →3 F2 (659 nm) have been observed. Optical absorption, photoluminescence (PL) and thermoluminescence (TL) studies confirms the trivalent state of Pr3+ ion in KBr host...
June 13, 2018: Luminescence: the Journal of Biological and Chemical Luminescence
Tobias S Fischer, Sebastian Spann, Qi An, Burkhard Luy, Manuel Tsotsalas, James P Blinco, Hatice Mutlu, Christopher Barner-Kowollik
We pioneer the formation of self-reporting and refoldable profluorescent single-chain nanoparticles (SCNPs) via the light-induced reaction ( λ max = 320 nm) of nitroxide radicals with a photo-active crosslinker. Whereas the tethered nitroxide moiety in these polymers fully quenches the luminescence ( i.e. fluorescence) of the aromatic backbone, nitroxide trapping of a transient C-radical leads to the corresponding closed shell alkoxyamine thereby restoring luminescence of the folded SCNP. Hence, the polymer in the folded state is capable of emitting light, while in the non-folded state the luminescence is silenced...
May 28, 2018: Chemical Science
Michael Haimerl, Ute Probst, Stefanie Poelsterl, Lukas Beyer, Claudia Fellner, Michael Selgrad, Matthias Hornung, Christian Stroszczynski, Philipp Wiggermann
Gadoxetic acid (Gd-EOB-DTPA) is a paramagnetic MRI contrast agent with raising popularity and has been used for evaluation of imaging-based liver function in recent years. In order to verify whether liver function as determined by real-time breath analysis using the intravenous administration of 13 C-methacetin can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using signal intensity (SI) values. 110 patients underwent Gd-EOB-DTPA-enhanced 3-T MRI and, for the evaluation of liver function, a 13 C-methacetin breath test (13 C-MBT)...
June 13, 2018: Scientific Reports
Shahla Ahmadian-Fard-Fini, Masoud Salavati-Niasari, Davood Ghanbari
The aim of this work is preparing of a photoluminescence nanostructures for rapid detection of bacterial pathogens. Firstly, carbon dots (CDs) were synthesized by grape fruit, lemon, turmeric extracts and hydrothermal method. Then Fe3 O4 (magnetite) nanoparticles was achieved using these bio-compatible capping agents. Finally, magnetite-carbon dots were synthesized as a novel magnetic and photoluminescence nanocomposite. X-ray diffraction (XRD) confirms the crystallinity and phase of the products, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigate the morphology, shape and size of the magnetite, carbon dot and nanocomposites...
June 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Ralf Wunderlich, Jonas Kohlrautz, Bernd Abel, Juergen Haase, J Meijer
In this work we investigated the time behavior of the polarization of bulk 13C nuclei in diamond
 above the thermal equilibrium. This nonthermal nuclear hyperpolarization is achieved by cross
 relaxation between two nitrogen related paramagnetic defect species in diamond in combination with
 optical pumping. The decay of the hyperpolarization at four different magnetic fields is measured.
 Furthermore, we use the comparison with conventional nuclear resonance measurements to identify the involved distances of the nuclear spin with respect to the defects and therefore the coupling strengths...
June 13, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Weixiang Zhai, Yalan Feng, Huiqiang Liu, Antal Rockenbauer, Deni Mance, Shaoyong Li, Yuguang Song, Marc Baldus, Yangping Liu
The exchange ( J ) interaction of organic biradicals is a crucial factor controlling their physiochemical properties and potential applications and can be modulated by changing the nature of the linker. In the present work, we for the first time demonstrate the effect of chiral configurations of radical parts on the J values of trityl-nitroxide (TN) biradicals. Four diastereoisomers (TNT1 , TNT2 , TNL1 and TNL2 ) of TN biradicals were synthesized and purified by the conjugation of a racemic ( R / S ) nitroxide with the racemic ( M / P ) trityl radical via l-proline...
May 21, 2018: Chemical Science
Lisa M Galle, George E Cutsail Iii, Volker Nischwitz, Serena DeBeer, Ingrid Span
Pseudomonas putida rubredoxin-2 (Rxn2) is an essential member of the alkane hydroxylation pathway and transfers electrons from a reductase to the membrane-bound hydroxylase. The regioselective hydroxylation of linear alkanes is a challenging chemical transformation of great interest for the chemical industry. Herein, we report the preparation and spectroscopic characterization of cobalt-substituted P. putida Rxn2 and a truncated version of the protein consisting of the C-terminal domain of the protein. Our spectroscopic data on the Co-substituted C-terminal domain supports a high-spin Co(II) with a distorted tetrahedral coordination environment...
June 27, 2018: Biological Chemistry
Ivan V Kurganskii, Michael Yu Ivanov, Matvey V Fedin
Molecular-level properties of ionic liquids (ILs) draw an increasing interest. Several informative experimental approaches for investigation of nano/miscrostructuring phenomena and local viscosity/rigidity of ILs use probe molecules sensitive to microenvironment along with suitable detection techniques. In this work we for the first time investigate capabilities of photoexcited triplet fullerenes to probe local properties of ILs, with Time-Resolved Electron Paramagnetic Resonance (TR EPR) being a sensitive detection tool...
June 12, 2018: Journal of Physical Chemistry. B
Leidys French-Pacheco, Cesar L Cuevas-Velazquez, Lina Rivillas-Acevedo, Alejandra A Covarrubias, Carlos Amero
Late embryogenesis abundant (LEA) proteins accumulate in plants during adverse conditions and their main attributed function is to confer tolerance to stress. One of the deleterious effects of the adverse environment is the accumulation of metal ions to levels that generate reactive oxygen species, compromising the survival of cells. AtLEA4-5, a member of group 4 of LEAs in Arabidopsis , is an intrinsically disordered protein. It has been shown that their N -terminal region is able to undergo transitions to partially folded states and prevent the inactivation of enzymes...
2018: PeerJ
Elisabetta Mileo, Marianne Ilbert, Alessandro Barducci, Patricia Bordes, Marie-Pierre Castanié-Cornet, Cyrille Garnier, Pierre Genevaux, Reynald Gillet, Pierre Goloubinoff, Françoise Ochsenbein, Gilbert Richarme, Chantal Iobbi-Nivol, Marie-Thérèse Giudici-Orticoni, Brigitte Gontero, Olivier Genest
The "Bioénergétique et Ingénierie des Protéines (BIP)" laboratory, CNRS (France), organized its first French workshop on molecular chaperone proteins and protein folding in November 2017. The goal of this workshop was to gather scientists working in France on chaperone proteins and protein folding. This initiative was a great success with excellent talks and fruitful discussions. The highlights were on the description of unexpected functions and posttranslational regulation of known molecular chaperones (such as Hsp90, Hsp33, SecB, GroEL) and on state-of-the-art methods to tackle questions related to this theme, including Cryo-electron microscopy, Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR), simulation and modeling...
June 8, 2018: Biochimie
Alexander T Taguchi, Daijiro Ohmori, Sergei A Dikanov, Toshio Iwasaki
Interpretation of magnetic resonance data in the context of structural and chemical biology requires prior knowledge of the g-tensor directions for paramagnetic metallo-cofactors with respect to the protein structural frame. Access to this information is often limited by the strict requirement of suitable protein crystals for single-crystal electron paramagnetic resonance (EPR) measurements, or the reliance on protons (with ambiguous locations in crystal structures) near the paramagnetic metal site. Here we develop a novel pulsed EPR approach with selective 13 Cβ -cysteine labeling of model [2Fe-2S] proteins to help bypass these problems...
June 11, 2018: Biochemistry
Meshal Alzaid, Abu M N Taufique, Salim A Thomas, Clay Carufel, John M Harris, Alex J B Waters, Amal Altayyar, Sylvio May, Erik K Hobbie
Macroscopic single-wall carbon nanotube (SWCNT) films of nanoscale thickness have significant potential for an array of applications that demand thin, transparent, conductive coatings. Using macroscopic micrometer-thick polystyrene sheets as a reference, we characterize the elastic response of freestanding multifunctional SWCNT nanosheets possessing both exceptionally high Young's modulus and good durability. Thin SWCNT films (20 nm to 200 nm thick) asymmetrically 'doped' with dilute concentrations of super-paramagnetic colloids were suspended in ethanol as freestanding nanosheets...
June 11, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Line Munk, Mogens Larsen Andersen, Anne S Meyer
Laccases (EC catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O2 to H2 O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila, respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements...
September 2018: Enzyme and Microbial Technology
Anne Bertrand, Maria Baron, Dung M Hoang, Lindsay K Hill, Sebastian L Mendoza, Einar M Sigurdsson, Youssef Z Wadghiri
Manganese-enhanced MRI (MRI) is a technique that allows for a noninvasive in vivo estimation of neuronal transport. It relies on the physicochemical properties of manganese, which is both a calcium analogue being transported along neurons by active transport, and a paramagnetic compound that can be detected on conventional T1-weighted images. Here, we report a multi-session MEMRI protocol that helps establish time-dependent curves relating to neuronal transport along the olfactory tract over several days. The characterization of these curves via unbiased fitting enables us to infer objectively a set of three parameters (the rate of manganese transport from the maximum slope, the peak intensity, and the time to peak intensity)...
2018: Methods in Molecular Biology
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