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Sample records for mixed-valence iron dimers

  1. Simulating Ru L3-edge X-ray absorption spectroscopy with time-dependent density functional theory: model complexes and electron localization in mixed-valence metal dimers.

    Science.gov (United States)

    Van Kuiken, Benjamin E; Valiev, Marat; Daifuku, Stephanie L; Bannan, Caitlin; Strader, Matthew L; Cho, Hana; Huse, Nils; Schoenlein, Robert W; Govind, Niranjan; Khalil, Munira

    2013-05-30

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of Ru(II) and Ru(III) complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6](4-) and Ru(II) polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5M(II)-CN-Ru(III)(NH3)5](-) (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  2. Moessbauer spectroscopic study on valence-detrapping and trapping of mixed-valence trinuclear iron (III, III, II) fluorine-substitute benzoate complexes

    International Nuclear Information System (INIS)

    Sakai, Y.; Onaka, S.; Ogiso, R.; Takayama, T.; Takahashi, M.; Nakamoto, T.

    2012-01-01

    Four mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes were synthesized; Fe 3 O(C 6 F 5 COO) 6 (C 5 H 5 N) 3 ·CH 2 Cl 2 (1), Fe 3 O(C 6 F 5 COO) 6 (C 5 H 5 N) 3 (2), Fe 3 O(2H-C 6 F 4 COO) 6 (C 5 H 5 N) 3 (3), and Fe 3 O(4H-C 6 F 4 COO) 6 (C 5 H 5 N) 3 (4). By means of 57 Fe-Moessbauer spectroscopy, valence-detrapping and trapping phenomena have been investigated for the four mixed-valence complexes. The valence state of three iron ions is trapped at lower temperatures while it is fully detrapped at higher temperatures for 1. Valence detrapping is not observed for 2, 3, and 4 even at room temperature, although Moessbauer spectra for 3 and 4 show a complicated temperature dependence. (author)

  3. Simulating Ru L 3 -Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    Energy Technology Data Exchange (ETDEWEB)

    Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.; Bannan, Caitlin; Strader, Matthew L.; Cho, Hana; Huse, Nils; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

    2013-05-30

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  4. Valence-delocalization of the mixed-valence oxo-centered trinuclear iron propionates [FeIII2FeIIO(C2H5CO2)6(py)3[npy; n = 0, 1.5

    International Nuclear Information System (INIS)

    Nakamoto, Tadahiro; Katada, Motomi; Kawata, Satoshi; Kitagawa, Susumu; Sano, Hirotoshi; Konno, Michiko

    1994-01-01

    Mixed-valence trinuclear iron propionates [Fe III 2 Fe II O(C 2 H 5 CO 2 ) 6 (py) 3 [npy, where n = 0, 1.5, were synthesized and the structure of the pyridine-solvated complex was determined by single-crystal X-ray diffraction. Moessbauer spectra of the solvated propionate complex showed a temperature-dependent mixed-valence state related to phase transitions, reaching an almost delocalized valence state at room temperature. On the other hand, the non-solvated propionate showed a remarkable change of the spectral shape related to a phase transition, remaining in a localized valence state at higher temperatures up to room temperature. (orig.)

  5. Mössbauer spectroscopic and powder X-ray diffraction studies on incorporation of gaseous organic molecules into intermolecular nano-voids of mixed-valence trinuclear iron pentafluorobenzoate complex

    International Nuclear Information System (INIS)

    Sakai, Yoichi; Onaka, Satoru; Ogiso, Ryo; Takayama, Tsutomu; Takahashi, Masashi; Nakamoto, Tadahiro

    2013-01-01

    Incorporation of gaseous organic molecules into polycrystalline mixed-valence trinuclear iron (Fe 3+ ,Fe 3+ ,Fe 2+ ) pentafluorobenzoate complex Fe 3 O(C 6 F 5 COO) 6 (C 5 H 5 N) 3 with intermolecular nano-voids was studied by 57 Fe-Mössbauer spectroscopic and powder XRD measurements. Organic-molecule incorporation was mainly chased by using iron-valence fluctuation observed in a Mössbauer spectrum, and also researched supportively by a powder XRD technique. (author)

  6. The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

    Science.gov (United States)

    Cañadillas-Delgado, Laura; Fabelo, Oscar; Rodríguez-Velamazán, J Alberto; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Pardo, Emilio; Lloret, Francesc; Zhao, Jiong-Peng; Bu, Xian-He; Simonet, Virginie; Colin, Claire V; Rodríguez-Carvajal, Juan

    2012-12-05

    Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

  7. Theory for the mixed-valence state

    International Nuclear Information System (INIS)

    Varma, C.M.

    1979-01-01

    A theory is presented which explains why mixed-valence compounds behave as two component Fermi liquids, and why TmSe orders magnetically while the other known mixed-valence compounds do not. The variation of Tsub(N) and the field Hsub(T) to obtain ferromagnetic alignment with changing Tm 2+ /Tm 3+ ratio is quantitatively explained. For Tm 2+ concentration > = 0.3, TmSe is predicted to order ferromagnetically

  8. Mixed-valence, layered, cation radical salts of the ethane-bridged dimeric tetrathiafulvalene [(EDT-TTF-CH2-)2#centre dot#+] [X-][THF]0.5, X-=FeCl4-, GaCl4-

    DEFF Research Database (Denmark)

    Mézière, C.; Fourmigué, M.; Canadell, E.

    2000-01-01

    The synthesis and X-ray crystal structure of the ethane-linked dimeric tetrathiafulvalene [(EDT-TTF-CH2)(2)], 1,2-bis(ethylenedithiotetrathiafulvalenyl)ethane (1), is reported. It oxidizes reversibly at 0.45 and 0.90 V vs SCE. Electrocrystallization in the presence of [n-Bu4N][FeCl4] or [n-Bu4N...

  9. Intersite interactions and susceptibility in mixed valence systems

    International Nuclear Information System (INIS)

    Xiaoqian Wang; Gao Lin; Bingjian Ni; Fusui Liu.

    1985-10-01

    This paper considers the effect of intersite processes on the susceptibility in mixed valence system. The method of thermodynamical perturbation used in this paper can also be generalized to study other properties of mixed valence system. The general formula of partition function of two-site interactions for the mixed valence system is given. The numerical calculations show that the intersite interaction is large enough to explain the minimum of susceptibility discovered in experiments. The different types of our theoretical curves predict that the susceptibility should exhibit a rich variety of behaviour at low temperature for various materials. (author)

  10. RKKY interaction in mixed valence system and heavy fermion superconductivity

    International Nuclear Information System (INIS)

    Fusui Liu; Gao Lin; Lin Zonghan

    1985-11-01

    The 1-D RKKY interaction of mixed valence system is given by using the thermodynamic perturbation theory. The numerical comparisons of 1-D and 3-D RKKY interaction between systems with localized magnetic moments of mixed valence and non-mixed valence show that the former is much stronger than the latter. From some analyses we propose that the heavy Fermion superconductivity comes from the RKKY interaction between two local f electrons which hop off the impurity site to become two continuum electrons. The source of the two impurity electrons hopping is the Coulomb interaction. It is also emphasized that the RKKY interaction does not disappear for the Kondo lattice, when the temperature is less than the Kondo temperature. (author)

  11. Persistent low-temperature spin dynamics in the mixed-valence iridate Ba3InIr2O9

    Science.gov (United States)

    Dey, Tusharkanti; Majumder, M.; Orain, J. C.; Senyshyn, A.; Prinz-Zwick, M.; Bachus, S.; Tokiwa, Y.; Bert, F.; Khuntia, P.; Büttgen, N.; Tsirlin, A. A.; Gegenwart, P.

    2017-11-01

    Using thermodynamic measurements, neutron diffraction, nuclear magnetic resonance, and muon spin relaxation, we establish putative quantum spin-liquid behavior in Ba3InIr2O9 , where unpaired electrons are localized on mixed-valence Ir2O9 dimers with Ir4.5 + ions. Despite the antiferromagnetic Curie-Weiss temperature on the order of 10 K, neither long-range magnetic order nor spin freezing are observed down to at least 20 mK, such that spins are short-range correlated and dynamic over nearly three decades in temperature. Quadratic power-law behavior of both the spin-lattice relaxation rate and specific heat indicates the gapless nature of the ground state. We envisage that this exotic behavior may be related to an unprecedented combination of the triangular and buckled honeycomb geometries of nearest-neighbor exchange couplings in the mixed-valence setting.

  12. Spin Dynamics and Magnetic Ordering in Mixed Valence Systems

    DEFF Research Database (Denmark)

    Shapiro, S. M.; Bjerrum Møller, Hans; Axe, J. D.

    1978-01-01

    . 0 meV at the transition to the alpha phase. The temperature independence of the susceptibility within the gamma phase cannot be simply reconciled with the temperature dependence of the valence within the gamma phase. TmSe is shown to order in a type I antiferromagnetic structure below T//N similar 3....... 2 K. The magnetic phase diagram is understood as a successive domain reorientation and a metamagnetic phase transition for T less than 3 K with increasing field. The mixed valence nature manifests itself in a reduced moment and a markedly altered crystal field. Another sample of TmSe with a lattice...

  13. Kondo and mixed-valence regimes in multilevel quantum dots

    International Nuclear Information System (INIS)

    Chudnovskiy, A. L.; Ulloa, S. E.

    2001-01-01

    We investigate the dependence of the ground state of a multilevel quantum dot on the coupling to an external fermionic system and on the interactions in the dot. As the coupling to the external system increases, the rearrangement of the effective energy levels in the dot signals the transition from the Kondo regime to a mixed-valence (MV) regime. The MV regime in a two-level dot is characterized by an intrinsic mixing of the levels in the dot, resulting in nonperturbative subtunneling and supertunneling phenomena that strongly influence the Kondo effect

  14. Isotopic exchange in mixed valence compounds in the solid state

    International Nuclear Information System (INIS)

    Fernandez Valverde, S.M.

    1986-01-01

    This work aims at the determination of isotopic exchange kinetics and mechanism in two mixed valence compounds: Cs 10 (Sbsup(V)Cl 6 ) (Sbsup(III)Cl 6 ) 3 and Tl 3 sup(I)(Tlsup(III)Cl 6 ). The synthesis of the first compound is very difficult because in most of the cases mixtures of chloroantimoniates are obtained. Exchange in Tl 4 Cl 6 labelled on Tlsup(III) is studied in detail by radiochemical analysis and physical techniques: ionic conductivity and positon annihilation. Cation vacancies are easily created in the lattice with formation enthalpy of 0.35 eV and migration enthalpy of 0.52 eV. Isochronic and isothermal exchange curves are described by a kinetic based on species diffusion. Models are given. Exchange is increased by grinding probably because extrinseque defects are introduced [fr

  15. Spin dynamics and magnetic ordering in mixed valence systems

    International Nuclear Information System (INIS)

    Shapiro, S.M.; Moller, H.B.; Axe, J.D.; Birgeneau, R.J.; Bucher, E.

    1977-01-01

    Neutron scattering measurements are reported on the mixed valence compounds Ce/sub 1-x/Th/sub x/ and TmSe. The Chi''(Q,ω) as derived from the inelastic spectra of Ce 0 . 74 Th 0 . 26 shows a peak in the γ phase near 20.0 meV and shifts abruptly to greater than 70.0 meV at the transition to the α phase. The temperature independence of the susceptibility within the γ phase cannot be simply reconciled with the temperature dependence of the valence within the γ phase. TmSe is shown to order in a type I antiferromagnetic structure below T/sub N/ approx. 3.2 K. The magnetic phase diagram is understood as a successive domain reorientation and a metamagnetic phase transition for T 3+ orders in a type II structure but never achieves long range order

  16. Neutron scattering studies of mixed-valence semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mignot, J M [Laboratoire Leon Brillouin (LLB) - Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France); Alekseev, P A [Kurchatov Institute, Moscow (Russian Federation)

    1994-12-31

    Neutron scattering experiments on the mixed-valence (MV) compounds SmB{sub 6} are reported. The inelastic magnetic response of SmB{sub 6} at T = 2 K, measured on a double-isotope single crystal,displays a strongly damped peak at 35 meV corresponding to the inter multiplet transition of Sm{sup 2+}. At lower energies ( h.{omega} {approx_equal} 14 meV), a narrow magnetic excitation is observed, with remarkable scattering-vector and temperature dependences of its intensity. This novel feature is discussed in terms of recent theoretical works describing the formation of an anisotropic local bound state in semiconducting MV materials. If the average samarium valence is decreased by substituting La for Sm, a peak is found to appear at high energies. The elastic magnetic form factor of SmB{sub 6} was determined using polarised neutrons and no significant difference is observed in its Q-dependence with respect to that of pure divalent samarium. This surprising behaviour is constant with previous measurements on the gold (high-pressure) phase of SmS. The above results are compared to those already reported for other MV materials. In particular existing information for TmSe is supplemented by recent inelastic scattering measurements carried out on a large stoichiometric single crystal. (author). 44 refs., 7 figs.

  17. Synthesis of the iron phthalocyaninate radical cation μ-nitrido dimer and its interaction with hydrogen peroxide

    Science.gov (United States)

    Grishina, E. S.; Makarova, A. S.; Kudrik, E. V.; Makarov, S. V.; Koifman, O. I.

    2016-03-01

    The iron phthalocyaninate μ-nitrido dimer radical cation, as well as the μ-nitrido dimer complexes of iron phthalocyaninate, was found to have high catalytic activity in the oxidation of organic compounds. It was concluded that this compound is of interest as a model of active intermediates—catalase and oxidase enzymes.

  18. In Situ Structural Characterization of Ferric Iron Dimers in Aqueous Solutions

    DEFF Research Database (Denmark)

    Zhu, Mengqiang; Puls, Brendan W.; Frandsen, Cathrine

    2013-01-01

    The structure of ferric iron (Fe3+) dimers in aqueous solutions has long been debated. In this work, we have determined the dimer structure in situ in aqueous solutions using extended X-ray absorption fine structure (EXAFS) spectroscopy. An Fe K-edge EXAFS analysis of 0.2 M ferric nitrate solutions...... at pH 1.28–1.81 identified a Fe–Fe distance at ∼3.6 Å, strongly indicating that the dimers take the μ-oxo form. The EXAFS analysis also indicates two short Fe–O bonds at ∼1.80 Å and ten long Fe–O bonds at ∼2.08 Å, consistent with the μ-oxo dimer structure. The scattering from the Fe–Fe paths interferes...... confirmed by Mössbauer analyses of analogous quick frozen solutions. This work also explores the electronic structure and the relative stability of the μ-oxo dimer in a comparison to the dihydroxo dimer using density function theory (DFT) calculations. The identification of such dimers in aqueous solutions...

  19. Metal-porphyrin interactions. V. Kinetics of cyanide addition to a water soluble iron porphyrin dimer(1)

    Energy Technology Data Exchange (ETDEWEB)

    Hambright, P; Rishnamurthy, M K

    1975-01-01

    The kinetics of cyanide addition to the water-soluble oxybridged iron dimer of tetra (p-sulophenyl) porphin indicate that HCN is the reactant. The rate law is of the form: Rate = (3.8 +- 0.2) x 10/sup 4/ (Fe dimer) (HCN)/(1 + (3.1 +- 0.3) x 10/sup 10/ (H/sup +/)) at 25/sup 0/ ..mu.. = 0.7 (NaNO/sub 3/). The cyano iron dimer dissociates into dicyano iron monomers by two pathways, one first order in (H/sup +/), and one proportional to (H/sup +/)(CN/sup -/)/sup 2/. The mechanism of this dimer reaction is compared to iron porphyrin monomer systems.

  20. Structure and Magnetic Properties of a Mixed-Valence Heptanuclear Manganese Cluster.

    Science.gov (United States)

    Abbati, Gian Luca; Cornia, Andrea; Fabretti, Antonio C.; Caneschi, Andrea; Gatteschi, Dante

    1998-07-27

    Two novel polynuclear manganese(II,III) complexes have been synthesized by exploiting controlled methanolysis. A one-pot reaction of MnCl(2), NaOMe, dibenzoylmethane (Hdbm), and O(2) in anhydrous methanol, followed by recrystallization from MeOH/CHCl(3) mixtures, afforded the alkoxomanganese complexes [Mn(7)(OMe)(12)(dbm)(6)].CHCl(3).14MeOH (2) and [Mn(2)(OMe)(2)(dbm)(4)] (3). Complex 2 crystallizes in trigonal space group R&thremacr; with a = 14.439(2) Å, alpha = 86.34(1) degrees, and Z = 1. Complex 3 crystallizes in triclinic space group P&onemacr; with a = 9.612(1) Å, b = 10.740(1) Å, c = 13.168(1) Å, alpha = 80.39(1) degrees, beta = 87.66(1) degrees, gamma = 83.57(1) degrees, and Z = 1. The solid-state structure of 2 comprises a [Mn(6)(OMe)(12)(dbm)(6)] "crown" with crystallographically imposed 6-fold symmetry plus a central manganese ion. The layered Mn/O core mimics a fragment of the manganese oxide mineral lithiophorite. Conductivity measurements confirmed the nonionic character of 2 and suggested a mixed-valence Mn(II)(3)Mn(III)(4) formulation. The metrical parameters of the core were analyzed with the aid of bond-valence sum calculations. The central ion is essentially a valence-trapped Mn(II) ion, whereas the average Mn-O distances for the manganese ions of the "crown" are consistent with the presence of two Mn(II) and four Mn(III) ions. However, (1)H NMR spectra in solution strongly support valence localization and suggest that the observed solid-state structure may be a result of static disorder effects. Magnetic susceptibility vs T and magnetization vs field data at low temperature are consistent with an S = (17)/(2) ground state. Complex 3 is a symmetric alkoxo-bridged dimer. The two high-spin Mn(III) ions are antiferromagnetically coupled with J = 0.28(4) cm(-)(1), g = 1.983(2), and D = -2.5(4) cm(-)(1).

  1. Inelastic neutron scattering on a mixed-valence dodecanuclear polyoxovanadate cluster

    CERN Document Server

    Basler, R; Andrés, H; Güdel, H U; Koegerler, P; Krickemeier, E; Bögge, H; Müller, A; Mutka, H

    2002-01-01

    The magnetic exchange interactions in the mixed-valence dodecanuclear polyoxovanadate cluster compound (NHEt sub 3) sub 4 [V sub 1 sub 2 As sub 8 O sub 4 sub 0 (H sub 2 O)] x H sub 2 O were investigated by a detailed inelastic neutron scattering study using cold neutrons. The data show clear evidence for the presence of a magnetic anisotropy within the cluster. Exchange parameters are accurately determined. (orig.)

  2. Spin and spinless conductivity in polypyrrole. Evidence for mixed-valence conduction

    Energy Technology Data Exchange (ETDEWEB)

    Zotti, G.; Schiavon, G. (Ist. di Polarografia ed Elettrochimica Preparativa, Padova (Italy))

    In situ conductivity of polypyrrole (as tosylate) as a function of oxidative doping level attains a maximum at three-quarters the total oxidation charge and the relevant in situ ESR signal corresponds to an equal concentration of spin-carrying (polaron) and spinless (bipolaron) species. Results are explained on the basis of mixed-valence conduction. Bipolaron conduction, taking the place of polaron-bipolaron conductivity at higher oxidation levels, accounts for persisting conductivity in the high-oxidation state.

  3. Optical and electronic properties of polyvinyl alcohol doped with pairs of mixed valence metal ions

    International Nuclear Information System (INIS)

    Bulinski, Mircea; Kuncser, Victor; Plapcianu, Carmen; Krautwald, Stefan; Franke, Hilmar; Rotaru, P; Filoti, George

    2004-01-01

    The electronic mechanisms induced by the UV exposure of thin films of polyvinyl alcohol doped with pairs of mixed valence metal ions were studied in relation to their optical behaviour by Moessbauer spectroscopy and optical absorption. The results obtained definitely point to the role of each element from the pair in the electronic mechanism involved, with influence on the optical properties regarding applications in real-time holography and integrated optics

  4. On the electrical conductivity for the mixed-valence model with d-f correlations

    International Nuclear Information System (INIS)

    Borgiel, W.; Matlak, M.

    1984-08-01

    The static electrical conductivity of mixed-valence systems is calculated in the model of Matlak and Nolting [Solid State Commun., 47, 11 (1983); Z. Phys., B55, 103 (1984)]. The method takes into account the atomic properties more exactly than those connected with bands, and hence emphasizes the ionic aspect of the problem in some way; indeed, the calculations overestimate the atomic properties. Some results are presented in a graph. It is found that the electrical conductivity depends strongly on temperature and the electron-hole attraction constant

  5. Non-Fermi Liquid Behavior in the Single-Impurity Mixed Valence Problem

    Science.gov (United States)

    Zhang, Guang-Ming; Su, Zhao-Bin; Yu, Lu

    An effective Hamiltonian of the Anderson single-impurity model with finite-range Coulomb interactions is derived near a particular limit, which is analogous to the Toulouse limit of the ordinary Kondo problem, and the physical properties around the mixed valence quantum critical point are calculated. At this quantum critical point, the local moment is only partially quenched and X-ray edge singularities are exhibited. Around this point, a new type of non-Fermi liquid behavior is predicted with an extra specific heat Cimp ~ T1/4 + AT ln T and spin-susceptibility χimp ~T-3/4 + B ln T.

  6. Universality class of non-Fermi liquid behaviour in mixed valence systems

    International Nuclear Information System (INIS)

    Zhang Guangming; Su Zhaobin; Lu Yu

    1995-11-01

    A generalized Anderson single-impurity model with off-site Coulomb interactions is derived from the extended three-band Hubbard model, originally proposed to describe the physics of the copper-oxides. Using the abelian bosonization technique and canonical transformations, an effective Hamiltonian is derived in the strong coupling limit, which is essentially analogous to the Toulouse limit of the ordinary Kondo problem. In this limit, the effective Hamiltonian can be exactly solved, with a mixed valence quantum critical point separating two different Fermi liquid phases, i.e. the Kondo phase and the empty orbital phase. In the mixed valence quantum critical regime, the local moment is only partially quenched and X-ray edge singularities are generated. Around the quantum critical point, a new type of non-Fermi liquid behaviour is predicted with an extra specific heat C imp ∼ T 1/4 and a singular spin-susceptibility χ imp ∼ T -3/4 . At the same time, the effective Hamiltonian under single occupancy is transformed into a resonant-level model, from which the correct Kondo physical properties (specific heat, spin susceptibility, and an enhanced Wilson ratio) are easily rederived. Finally, a brief discussion is given to relate these theoretical results to observations in U Pd x Cu 5-x (x=1, 1.5) alloys, which show single-impurity critical behaviour consistent with our predictions. (author). 30 refs

  7. Universality class of non-Fermi-liquid behavior in mixed-valence systems

    Science.gov (United States)

    Zhang, Guang-Ming; Su, Zhao-Bin; Yu, Lu

    1996-01-01

    A generalized Anderson single-impurity model with off-site Coulomb interactions is derived from the extended three-band Hubbard model, originally proposed to describe the physics of the copper oxides. Using the Abelian bosonization technique and canonical transformations, an effective Hamiltonian is derived in the strong-coupling limit, which is essentially analogous to the Toulouse limit of the ordinary Kondo problem. In this limit, the effective Hamiltonian can be exactly solved, with a mixed-valence quantum critical point separating two different Fermi-liquid phases, i.e., the Kondo phase and the empty orbital phase. In the mixed-valence quantum critical regime, the local moment is only partially quenched and x-ray edge singularities are generated. Around the quantum critical point, a type of non-Fermi-liquid behavior is predicted with an extra specific heat Cimp~T1/4 and a singular spin susceptibility χimp~T-3/4. At the same time, the effective Hamiltonian under single occupancy is transformed into a resonant-level model, from which the correct Kondo physical properties (specific heat, spin susceptibility, and an enhanced Wilson ratio) are easily rederived. Finally, a brief discussion is given to relate these theoretical results to observations in UPdxCu5-x (x=1,1.5) alloys, which show single-impurity critical behavior consistent with our predictions.

  8. NATO Advanced Study Institute on Mixed-Valence Compounds : Theory and Applications in Chemistry, Physics, Geology, and Biology

    CERN Document Server

    1980-01-01

    It has been a decade since two seminal reviews demonstrated that mixed-valence compounds share many unique and fascinating features. The insight pro­ vided by those early works has promoted a great deal of both experimental and theoretical study. As a result of extensive efforts, our understanding of the bonding and properties of mixed-valence compounds has advanced substantially. There has been no compre­ hensive treatment of mixed-valence compounds since 1967, and the meeting convened at Oxford in September, 1979, provided a unique opportunity to examine the subject and its many ramifications. Mixed-valence compounds play an important role in many fields. Although the major impact of the subject has been in chemistry, its importance has become increasingly clear in solid state physics, geology, and biology. Extensive interest and effort in the field of molecular metals has demonstrated that mixed-valency is a prerequisite for high elec­ trical conductivity. The intense colors of many minerals have been s...

  9. Mixed valence and metamagnetism in a metal flux grown compound Eu2Pt3Si5

    International Nuclear Information System (INIS)

    Sarkar, Sumanta; Subbarao, Udumula; Joseph, Boby; Peter, Sebastian C.

    2015-01-01

    A new compound Eu 2 Pt 3 Si 5 with plate shaped morphology has been grown from excess In flux. The compound crystallizes in the orthorhombic U 2 Co 3 Si 5 structure type, Ibam space group and the lattice parameters are a=10.007(2) Å, b=11.666(2) Å and c=6.0011(12) Å. The crystal structure of this compound can be conceived as inter-twinned chains of [Pt 2 Si 2 ] and [PtSi 3 ] tetrahedra connected along [100] direction to give rise to a complex three dimensional [Pt 3 Si 5 ] network. Temperature dependent magnetic susceptibility data suggests that Eu 2 Pt 3 Si 5 undergoes a strong antiferromagnetic ordering (T N =19 K) followed by a weak ferromagnetic transition (T C =5.5 K). The effective magnetic moment/Eu obtained from susceptibility data is 6.78 μ B accounts mixed valent Eu with almost 85% divalent Eu, which is supported by X-ray absorption near edge spectroscopy. The compound undergoes a metamagnetic transition under applied magnetic field through a probable spin flop mechanism. - Graphical abstract: Eu 2 Pt 3 Si 5 , a new member in the U 2 Co 3 Si 5 (Ibam) family undergoes metamagnetic transition at high magnetic field and Eu is in mixed valence state. - Highlights: • A new compound Eu 2 Pt 3 Si 5 has been synthesized using indium as an inactive metal flux. • The compound undergoes metamagnetic transition at higher field. • Eu in this compound resides in a mixed valence state

  10. Femtosecond dynamics of electron transfer in a neutral organic mixed-valence compound

    International Nuclear Information System (INIS)

    Maksimenka, Raman; Margraf, Markus; Koehler, Juliane; Heckmann, Alexander; Lambert, Christoph; Fischer, Ingo

    2008-01-01

    In this article we report a femtosecond time-resolved transient absorption study of a neutral organic mixed-valence (MV) compound with the aim to gain insight into its charge-transfer dynamics upon optical excitation. The back-electron transfer was investigated in five different solvents, toluene, dibutyl ether, methyl-tert-butyl ether (MTBE), benzonitrile and n-hexane. In the pump step, the molecule was excited at 760 nm and 850 nm into the intervalence charge-transfer band. The resulting transients can be described by two time constant. We assign one time constant to the rearrangement of solvent molecules in the charge-transfer state and the second time constant to back-electron transfer to the electronic ground state. Back-electron transfer rates range from 1.5 x 10 12 s -1 in benzonitrile through 8.3 x 10 11 s -1 in MTBE, around 1.6 x 10 11 s -1 in dibutylether and toluene and to 3.8 x 10 9 s -1 in n-hexane

  11. Fe II/Fe III mixed-valence state induced by Li-insertion into the metal-organic-framework Mil53(Fe): A DFT+U study

    Science.gov (United States)

    Combelles, C.; Ben Yahia, M.; Pedesseau, L.; Doublet, M.-L.

    The iron-based metal-organic-framework MIL53(Fe) has recently been tested as a cathode materials for Li-Ion batteries, leading to promising cycling life and rate capability. Despite a poor capacity of 70 mAh g -1 associated with the exchange of almost 0.5Li/Fe, this result is the first evidence of a reversible lithium insertion never observed in a MOF system. In the present study, the MIL53(Fe) redox mechanism is investigated through first-principles DFT+U calculations. The results show that MIL53(Fe) is a weak antiferromagnetic charge transfer insulator at T = 0 K, with iron ions in the high-spin S = 5/2 state. Its reactivity vs elemental lithium is then investigated as a function of lithium composition and distribution over the most probable Li-sites of the MOF structure. The redox mechanism is fully interpreted as a two-step insertion/conversion mechanism, associated with the stabilization of the Fe 3+/Fe 2+ mixed-valence state prior to the complete decomposition of the inorganic-organic interactions within the porous MOF architecture.

  12. Lithium Storage in Microstructures of Amorphous Mixed-Valence Vanadium Oxide as Anode Materials.

    Science.gov (United States)

    Zhao, Di; Zheng, Lirong; Xiao, Ying; Wang, Xia; Cao, Minhua

    2015-07-08

    Constructing three-dimensional (3 D) nanostructures with excellent structural stability is an important approach for realizing high-rate capability and a high capacity of the electrode materials in lithium-ion batteries (LIBs). Herein, we report the synthesis of hydrangea-like amorphous mixed-valence VOx microspheres (a-VOx MSs) through a facile solvothermal method followed by controlled calcination. The resultant hydrangea-like a-VOx MSs are composed of intercrossed nanosheets and, thus, construct a 3 D network structure. Upon evaluation as an anode material for LIBs, the a-VOx MSs show excellent lithium-storage performance in terms of high capacity, good rate capability, and long-term stability upon extended cycling. Specifically, they exhibit very stable cycling behavior with a highly reversible capacity of 1050 mA h g(-1) at a rate of 0.1 A g(-1) after 140 cycles. They also show excellent rate capability, with a capacity of 390 mA h g(-1) at a rate as high as 10 A g(-1) . Detailed investigations on the morphological and structural changes of the a-VOx MSs upon cycling demonstrated that the a-VOx MSs went through modification of the local VO coordinations accompanied with the formation of a higher oxidation state of V, but still with an amorphous state throughout the whole discharge/charge process. Moreover, the a-VOx MSs can buffer huge volumetric changes during the insertion/extraction process, and at the same time they remain intact even after 200 cycles of the charge/discharge process. Thus, these microspheres may be a promising anode material for LIBs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Magnetic properties of mixed valence La2/3Sr1/3Mn1−xTxO3 (T ...

    Indian Academy of Sciences (India)

    (T = Fe,Cr) manganites obtained by Pechini method. I BETANCOURT. ∗ ... structure. Keywords. Mixed valence manganites; magnetic manganites; magnetocaloric effect; Pechini method. 1. ..... IB thanks for financial support from research grant.

  14. Dimerization of Terminal Aryl Alkynes Catalyzed by Iron(II) Amine-Pyrazolyl Tripodal Complexes with E/Z Selectivity Controlled by tert-Butoxide

    KAUST Repository

    Xue, Fei

    2018-05-09

    The catalytic activity of iron(II) complexes with functionalized amine-pyrazolyl tripodal ligands toward dimerization of terminal alkynes in the presence a base (KOtBu or NaOtBu) has been studied. An unusual E/Z selectivity of the reaction determined by tert-butoxide was observed.

  15. Dimerization of Terminal Aryl Alkynes Catalyzed by Iron(II) Amine-Pyrazolyl Tripodal Complexes with E/Z Selectivity Controlled by tert-Butoxide

    KAUST Repository

    Xue, Fei; Song, Xiaolu; Lin, Ting Ting; Munkerup, Kristin; Albawardi, Saad Fahad; Huang, Kuo-Wei; Hor, T. S. Andy; Zhao, Jin

    2018-01-01

    The catalytic activity of iron(II) complexes with functionalized amine-pyrazolyl tripodal ligands toward dimerization of terminal alkynes in the presence a base (KOtBu or NaOtBu) has been studied. An unusual E/Z selectivity of the reaction determined by tert-butoxide was observed.

  16. Exchange Coupling Interactions from the Density Matrix Renormalization Group and N-Electron Valence Perturbation Theory: Application to a Biomimetic Mixed-Valence Manganese Complex.

    Science.gov (United States)

    Roemelt, Michael; Krewald, Vera; Pantazis, Dimitrios A

    2018-01-09

    The accurate description of magnetic level energetics in oligonuclear exchange-coupled transition-metal complexes remains a formidable challenge for quantum chemistry. The density matrix renormalization group (DMRG) brings such systems for the first time easily within reach of multireference wave function methods by enabling the use of unprecedentedly large active spaces. But does this guarantee systematic improvement in predictive ability and, if so, under which conditions? We identify operational parameters in the use of DMRG using as a test system an experimentally characterized mixed-valence bis-μ-oxo/μ-acetato Mn(III,IV) dimer, a model for the oxygen-evolving complex of photosystem II. A complete active space of all metal 3d and bridge 2p orbitals proved to be the smallest meaningful starting point; this is readily accessible with DMRG and greatly improves on the unrealistic metal-only configuration interaction or complete active space self-consistent field (CASSCF) values. Orbital optimization is critical for stabilizing the antiferromagnetic state, while a state-averaged approach over all spin states involved is required to avoid artificial deviations from isotropic behavior that are associated with state-specific calculations. Selective inclusion of localized orbital subspaces enables probing the relative contributions of different ligands and distinct superexchange pathways. Overall, however, full-valence DMRG-CASSCF calculations fall short of providing a quantitative description of the exchange coupling owing to insufficient recovery of dynamic correlation. Quantitatively accurate results can be achieved through a DMRG implementation of second order N-electron valence perturbation theory (NEVPT2) in conjunction with a full-valence metal and ligand active space. Perspectives for future applications of DMRG-CASSCF/NEVPT2 to exchange coupling in oligonuclear clusters are discussed.

  17. A THIOLATO-BRIDGED OCTANUCLEAR COPPER(I,II MIXED- VALENCE COMPLEX WITH N,N,S-TRIDENTATE LIGAND

    Directory of Open Access Journals (Sweden)

    Takanori Kotera

    2007-06-01

    Full Text Available Thiolato-bridged complex [CuI4CuII4(peampt4Cl8]·2H2O (Hpeampt = 1-(2-pyridylethylamino methylpropane-2-thiol has been synthesized and characterized by the elemental analysis, IR and UV-vis spectroscopies and magnetic susceptibility measurement. The X-ray crystal structure analysis of this complex shows a localized mixed-valence octanuclear cage structure made up of four trigonal-bipyramidal CuIIN2SCl2, two trigonal CuIS2Cl, and two tetrahedral CuIS2Cl2 coordination sites. Temperature dependence of magnetic susceptibility (4.5— 300 K shows that a fairly strong antiferromagnetic interaction is operating between the four CuII ions.

  18. Transient dynamics of a quantum-dot: From Kondo regime to mixed valence and to empty orbital regimes

    Science.gov (United States)

    Cheng, YongXi; Li, ZhenHua; Wei, JianHua; Nie, YiHang; Yan, YiJing

    2018-04-01

    Based on the hierarchical equations of motion approach, we study the time-dependent transport properties of a strongly correlated quantum dot system in the Kondo regime (KR), mixed valence regime (MVR), and empty orbital regime (EOR). We find that the transient current in KR shows the strongest nonlinear response and the most distinct oscillation behaviors. Both behaviors become weaker in MVR and diminish in EOR. To understand the physical insight, we examine also the corresponding dot occupancies and the spectral functions, with their dependence on the Coulomb interaction, temperature, and applied step bias voltage. The above nonlinear and oscillation behaviors could be understood as the interplay between dynamical Kondo resonance and single electron resonant-tunneling.

  19. Nature of the magnetic ground state in the mixed valence compound CeRuSn: a single-crystal study

    International Nuclear Information System (INIS)

    Fikáček, J; Prokleška, J; Prchal, J; Custers, J; Sechovský, V

    2013-01-01

    We report on detailed low-temperature measurements of the magnetization, the specific heat and the electrical resistivity on high-quality CeRuSn single crystals. The compound orders antiferromagnetically at T N = 2.8 K with the Ce 3+ ions locked within the a–c plane of the monoclinic structure. Magnetization shows that below T N CeRuSn undergoes a metamagnetic transition when applying a magnetic field of 1.5 and 0.8 T along the a- and c-axis, respectively. This transition manifests in a tremendous negative jump of ∼25% in the magnetoresistance. The value of the saturated magnetization along the easy magnetization direction (c-axis) and the magnetic entropy above T N derived from specific heat data correspond to the scenario of only one third of the Ce ions in the compound being trivalent and carrying a stable Ce 3+ magnetic moment, whereas the other two thirds of the Ce ions are in a nonmagnetic tetravalent and/or mixed valence state. This is consistent with the low-temperature CeRuSn crystal structure i.e., a superstructure consisting of three unit cells of the CeCoAl type piled up along the c-axis, and in which the Ce 3+ ions are characterized by large distances from the Ru ligands while the Ce–Ru distances of the other Ce ions are much shorter causing a strong 4f-ligand hybridization and hence leading to tetravalent and/or mixed valence Ce ions. (paper)

  20. Theoretical and experimental study of high-magnetic-field XMCD spectra at the L2,3 absorption edges of mixed-valence rare-earth compounds

    International Nuclear Information System (INIS)

    Kotani, Akio; Matsuda, Yasuhiro H; Nojiri, Hiroyuki

    2009-01-01

    X-ray magnetic circular dichroism(XMCD) spectra at the L 2,3 edges of mixed-valence rare-earth compounds in high magnetic fields are studied both theoretically and experimentally. The theoretical study is based on a new framework proposed recently by Kotani. The Zeeman splitting of 4f states, the mixed-valence character of 4f states, and the 4f-5d exchange interaction are incorporated into a single impurity Anderson model. New XMCD experiments in high magnetic fields up to 40 T are carried out for the mixed-valence compounds EuNi 2 (Si 0.18 Ge 0.82 ) 2 and YbInCu 4 by using a miniature pulsed magnet, which was developed recently by Matsuda et al. The XMCD data are taken at 5 K by transmission measurements for incident X-rays with ± helicities at BL39XU in SPring-8. After giving a survey on recent developments in the theory of XMCD spectra for mixed-valence Ce and Yb compounds, we calculate the XMCD spectra of YbInCu 4 at the field-induced valence transition around 32 T by applying the recent theoretical framework and by newly introducing at 32 T a discontinuous change in the Yb 4f level and that in the hybridization strength between the Yb 4f and conduction electrons. The calculated results are compared with the experimental ones.

  1. Mechanism of pyridine-ligand exchanges at the different labile sites of 3d heterometallic and mixed valence mu3-oxo trinuclear clusters.

    Science.gov (United States)

    Novitchi, Ghenadie; Riblet, Fabrice; Scopelliti, Rosario; Helm, Lothar; Gulea, Aurelian; Merbach, André E

    2008-11-17

    The syntheses and single crystal X-ray structural analysis of five novel hetero- and homometallic mu 3-oxo trinuclear cluster with the formula [Fe (III) 2M (II)(mu 3-O)(mu-O 2CCH 3) 6(4-Rpy) 3]. x(4-Rpy). y(CH 3CN) where R = Ph for 1(Fe 2Mn), 2(Fe 2Fe), 3(Fe 2Co), 4(Fe 2Ni) and R = CF 3 for 5(Fe 2Co), are reported. The persistence of the structure for compounds 2- 5 in dichloromethane solution in the temperature range 190-320 K is demonstrated by (1)H and (19)F NMR spectroscopy. Even at the lowest temperature, the electron exchange in the homometallic mixed-valence compound 2(Fe 2Fe) is in the fast regime at the NMR time scale. Variable temperature and pressure NMR line broadening allowed quantifying the fast coordinated/free 4-Rpy exchanges at the two labile metal centers in these clusters: 2: Fe (III)( k (298)/10 (3) s (-1) = 16.6; Delta H (++) = 60.32 kJ mol (-1); Delta S (++) = + 34.8 J K (-1) mol (-1); Delta V (++) = + 12.5 cm (3) mol (-1)); 3: Fe (11.9; 58.92; +30.7; +10.6) and Co (2.8; 68.24; +49.8; +13.9); 4: Fe(12.2; 67.91; +61.0; -) and Ni (0.37; 78.62; +67.8; +12.3); 5: Fe (46; 58.21; +39.3; +14.2) and Co (4.7; 55.37; +11.2; +10.9). A limiting D mechanism is assigned to these exchange reactions. This assignment is based on a first-order rate law, the detection of intermediates, the positive and large entropies and volumes of activation. The order of reactivity k (Co) > k (Ni) is expected for a D mechanism at these metal centers: their low exchange rates are due to their strong binding with the 4-Rpy donor. Surrounded by oxygen donors the d (5) iron(III) usually reacts associatively; however, here due to low affinity of this ion for nitrogen the mechanism is D and the rate of exchange is very fast, even faster than on the divalent ions. There is no significant effect of the divalent ion in cluster 2, 3, and 5 on the exchange rates of 4-Phpy at the iron center, which seems to indicate that the specific electronic interactions between the three ions making

  2. Exchange Interactions on the Highest-Spin Reported Molecule: the Mixed-Valence Fe42 Complex

    Science.gov (United States)

    Aravena, Daniel; Venegas-Yazigi, Diego; Ruiz, Eliseo

    2016-04-01

    The finding of high-spin molecules that could behave as conventional magnets has been one of the main challenges in Molecular Magnetism. Here, the exchange interactions, present in the highest-spin molecule published in the literature, Fe42, have been analysed using theoretical methods based on Density Functional Theory. The system with a total spin value S = 45 is formed by 42 iron centres containing 18 high-spin FeIII ferromagnetically coupled and 24 diamagnetic low-spin FeII ions. The bridging ligands between the two paramagnetic centres are two cyanide ligands coordinated to the diamagnetic FeII cations. Calculations were performed using either small Fe4 or Fe3 models or the whole Fe42 complex, showing the presence of two different ferromagnetic couplings between the paramagnetic FeIII centres. Finally, Quantum Monte Carlo simulations for the whole system were carried out in order to compare the experimental and simulated magnetic susceptibility curves from the calculated exchange coupling constants with the experimental one. This comparison allows for the evaluation of the accuracy of different exchange-correlation functionals to reproduce such magnetic properties.

  3. Can the second order multireference perturbation theory be considered a reliable tool to study mixed-valence compounds?

    Science.gov (United States)

    Pastore, Mariachiara; Helal, Wissam; Evangelisti, Stefano; Leininger, Thierry; Malrieu, Jean-Paul; Maynau, Daniel; Angeli, Celestino; Cimiraglia, Renzo

    2008-05-07

    In this paper, the problem of the calculation of the electronic structure of mixed-valence compounds is addressed in the frame of multireference perturbation theory (MRPT). Using a simple mixed-valence compound (the 5,5(') (4H,4H('))-spirobi[ciclopenta[c]pyrrole] 2,2('),6,6(') tetrahydro cation), and the n-electron valence state perturbation theory (NEVPT2) and CASPT2 approaches, it is shown that the ground state (GS) energy curve presents an unphysical "well" for nuclear coordinates close to the symmetric case, where a maximum is expected. For NEVPT, the correct shape of the energy curve is retrieved by applying the MPRT at the (computationally expensive) third order. This behavior is rationalized using a simple model (the ionized GS of two weakly interacting identical systems, each neutral system being described by two electrons in two orbitals), showing that the unphysical well is due to the canonical orbital energies which at the symmetric (delocalized) conformation lead to a sudden modification of the denominators in the perturbation expansion. In this model, the bias introduced in the second order correction to the energy is almost entirely removed going to the third order. With the results of the model in mind, one can predict that all MRPT methods in which the zero order Hamiltonian is based on canonical orbital energies are prone to present unreasonable energy profiles close to the symmetric situation. However, the model allows a strategy to be devised which can give a correct behavior even at the second order, by simply averaging the orbital energies of the two charge-localized electronic states. Such a strategy is adopted in a NEVPT2 scheme obtaining a good agreement with the third order results based on the canonical orbital energies. The answer to the question reported in the title (is this theoretical approach a reliable tool for a correct description of these systems?) is therefore positive, but care must be exercised, either in defining the orbital

  4. Manganese L-edge X-ray absorption spectroscopy of manganese catalase from Lactobacillus plantarum and mixed valence manganese complexes

    Energy Technology Data Exchange (ETDEWEB)

    Grush, M.M.; Chen, J.; George, S.J. [Univ. of California, Davis, CA (United States)] [and others

    1996-01-10

    The first Mn L-edge absorption spectra of a Mn metalloprotein are presented in this paper. Both reduced and superoxidized Mn catalase have been examined by fluorescence-detected soft X-ray absorption spectroscopy, and their Mn L-edge spectra are dramatically different. The spectrum of reduced Mn(II)Mn(II) catalase has been interpreted by ligand field atomic multiplet calculations and by comparison to model compound spectra. The analysis finds a 10 Dq value of nearly 1.1 eV, consistent with coordination by predominately nitrogen and oxygen donor ligands. For interpretation of mixed valence Mn spectra, an empirical simulation procedure based on the addition of homovalent model compound spectra has been developed and was tested on a variety of Mn complexes and superoxidized Mn catalase. This routine was also used to determine the oxidation state composition of the Mn in [Ba{sub 8}Na{sub 2}ClMn{sub 16}(OH){sub 8}(CO{sub 3}){sub 4}L{sub 8}] .53 H{sub 2}O (L=1,3-diamino-2-hydroxypropane-N,N,N`N`-tetraacetic acid). 27 refs., 6 figs.

  5. Synthesis of a Neutral Mixed-Valence Diferrocenyl Carborane for Molecular Quantum-Dot Cellular Automata Applications.

    Science.gov (United States)

    Christie, John A; Forrest, Ryan P; Corcelli, Steven A; Wasio, Natalie A; Quardokus, Rebecca C; Brown, Ryan; Kandel, S Alex; Lu, Yuhui; Lent, Craig S; Henderson, Kenneth W

    2015-12-14

    The preparation of 7-Fc(+) -8-Fc-7,8-nido-[C2 B9 H10 ](-) (Fc(+) FcC2 B9 (-) ) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed-valence Fe(II) /Fe(III) complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis-NIR spectroscopic and TD-DFT computational studies indicate that electron transfer within Fc(+) FcC2 B9 (-) is achieved through a bridge-mediated mechanism. This electronic framework therefore provides the possibility of an all-neutral null state, a key requirement for the implementation of quantum-dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc(+) FcC2 B9 (-) on Au(111) has been observed by scanning tunneling microscopy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Ferromagnetic dinuclear mixed-valence Mn(II)/Mn(III) complexes: building blocks for the higher nuclearity complexes. structure, magnetic properties, and density functional theory calculations.

    Science.gov (United States)

    Hänninen, Mikko M; Välivaara, Juha; Mota, Antonio J; Colacio, Enrique; Lloret, Francesc; Sillanpää, Reijo

    2013-02-18

    A series of six mixed-valence Mn(II)/Mn(III) dinuclear complexes were synthesized and characterized by X-ray diffraction. The reactivity of the complexes was surveyed, and structures of three additional trinuclear mixed-valence Mn(III)/Mn(II)/Mn(III) species were resolved. The magnetic properties of the complexes were studied in detail both experimentally and theoretically. All dinuclear complexes show ferromagnetic intramolecular interactions, which were justified on the basis of the electronic structures of the Mn(II) and Mn(III) ions. The large Mn(II)-O-Mn(III) bond angle and small distortion of the Mn(II) cation from the ideal square pyramidal geometry were shown to enhance the ferromagnetic interactions since these geometrical conditions seem to favor the orthogonal arrangement of the magnetic orbitals.

  7. Synthesis of an S T = 7 [Mn 3 ] Mixed-Valence Complex Based on 1,3-Propanediol Ligand Derivatives and Its One-Dimensional Assemblies

    KAUST Repository

    Huang, Jian; Wu, Gang; Bai, Jiaquan; Jiang, Yuan; Li, Guanghua; Qiu, Shilun; Clé rac, Rodolphe

    2013-01-01

    . In this work, a new ST = 7 trinuclear mixed-valence Mn complex, [MnIIIMnII 2(LA) 2(Br)4(CH3OH)6] ·Br· (CH3OH)1.5·(H2O)0.5 (1), is reported using a pyridinium-functionalized 1,3-propanediol ligand (H 2LABr = 1-(3-bromo-2,2-bis

  8. Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Slenkamp, Karla M.; Lynch, Michael S.; Van Kuiken, Benjamin E.; Brookes, Jennifer F.; Bannan, Caitlin C.; Daifuku, Stephanie L.; Khalil, Munira, E-mail: mkhalil@chem.washington.edu [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States)

    2014-02-28

    Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (ν{sub CN}) vibrations found in [(NH{sub 3}){sub 5}Ru{sup III}NCFe{sup II}(CN){sub 5}]{sup −} (FeRu) dissolved in D{sub 2}O and formamide and [(NC){sub 5}Fe{sup II}CNPt{sup IV}(NH{sub 3}){sub 4}NCFe{sup II}(CN){sub 5}]{sup 4−} (FePtFe) dissolved in D{sub 2}O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the ν{sub CN} modes in the electronic ground state. The FTIR spectra of the ν{sub CN} modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic ν{sub CN} modes. The vibrational mode anharmonicities of the individual ν{sub CN} modes range from 14 to 28 cm{sup −1}. The mixed-mode anharmonicities range from 2 to 14 cm{sup −1}. In general, the bridging ν{sub CN} mode is most weakly coupled to the radial ν{sub CN} mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four ν{sub CN} modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D{sub 2}O. The ν{sub CN} modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm{sup −1}. This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the ν{sub CN} modes in cyanide-bridged transition metal mixed valence complexes.

  9. Catalytic Activity of μ-Carbido-Dimeric Iron(IV) Octapropylporphyrazinate in the 3,5,7,2',4'-Pentahydroxyflavone Oxidation Reaction with tert-Butyl Hydroperoxide

    Science.gov (United States)

    Tyurin, D. V.; Zaitseva, S. V.; Kudrik, E. V.

    2018-05-01

    It is found for the first time that μ-carbido-dimeric iron(IV) octapropylporphyrazinate displays catalytic activity in the oxidation reaction of natural flavonol morin with tert-butyl hydroperoxide, with the catalyst being stable under conditions of the reaction. The kinetics of this reaction are studied. It is shown the reaction proceeds via tentative formation of a complex between the catalyst and the oxidant, followed by O‒O bond homolytic cleavage. The kinetics of the reaction is described in the coordinates of the Michaelis-Menten equation. A linear dependence of the apparent reaction rate constant on the concentration of the catalyst is observed, testifying to its participation in the limiting reaction step. The equilibrium constants and rates of interaction are found. A mechanism is proposed for the reaction on the basis of the experimental data.

  10. Structural and magnetic characterization of mixed valence Co(II, III)xZn1−xO epitaxial thin films

    International Nuclear Information System (INIS)

    Negi, D.S.; Loukya, B.; Dileep, K.; Sahu, R.; Shetty, S.; Kumar, N.; Ghatak, J.; Pachauri, N.; Gupta, A.; Datta, R.

    2014-01-01

    In this article, we report on the Co atom incorporation, secondary phase formation and composition-dependent magnetic and optical properties of mixed valence Co(II, III) x Zn 1−x O epitaxial thin films grown by pulsed laser deposition. The intended total Co concentration is varied between ∼6–60 at.% with relatively higher concentration of +3 over +2 charge state. Mixed valence Co(II, III) shows high solubility in ZnO (up to 38 at.%) and ferromagnetism is observed in samples with total Co incorporation of ∼29 and 38 at.%. Electron diffraction pattern and high resolution transmission electron microscopy images reveal single crystalline nature of the thin films with wurtzite structure. Co oxide interlayer, with both rock salt and spinel structure, are observed to be formed between the substrate and wurtzite film for total Co concentration at ∼17 at.% and above. Magnetization shows composition dependence with a saturation moment value of ∼93 emu cm −3 and a coercive field of ∼285 Oe observed for ∼38 at.% Co:ZnO films. Ferromagnetism was not observed for films with Co concentration 17 and 9 at.%. The Co oxide interlayer does not show any ferromagnetism. All the films are n-type with carrier concentration ∼10 19 cm −3 . The observed magnetism is probably resulting from direct antiferromagntic exchange interaction between Co 2+ and Co 3+ ions favored by heavy Co alloying giving rise to ferrimagnetism in the system. - Highlights: • Mixed valence Co doped ZnO ferromagnetic single crystal thin film. • Secondary phase formation in terms of CoO and Co3O4 and magnetism is observed only for high Co alloying. • Cathodoluminescence (CL) data showing increase in band gap with Co concentrations

  11. Brillouin-Wigner theory of mixed-valence impurities in BCS superconductor: Tc/TcO and ΔC/ΔCO

    International Nuclear Information System (INIS)

    Li Jun; Gong Changde.

    1986-08-01

    The (lowest order) Brillouin-Wigner perturbational expansion theory is adopted to describe the mixed-valence impurities in the BCS superconductor. Two substantial quantities characterizing the superconducting state, i.e. the reduced transition temperature T c /T cO and the reduced specific heat jump ΔC/ΔC O are calculated numerically as a function of the impurity concentration x and the energy level difference E f between two 4f configurations. A comparison with the experimental data of the Th 1-x Ce x and Th 1-x U x alloy is also included with a more reasonable fitting than Kaiser's theory. (author)

  12. Electric Field Generation and Control of Bipartite Quantum Entanglement between Electronic Spins in Mixed Valence Polyoxovanadate [GeV14O40]8.

    Science.gov (United States)

    Palii, Andrew; Aldoshin, Sergey; Tsukerblat, Boris; Borràs-Almenar, Juan José; Clemente-Juan, Juan Modesto; Cardona-Serra, Salvador; Coronado, Eugenio

    2017-08-21

    As part of the search for systems in which control of quantum entanglement can be achieved, here we consider the paramagnetic mixed valence polyoxometalate K 2 Na 6 [GeV 14 O 40 ]·10H 2 O in which two electrons are delocalized over the 14 vanadium ions. Applying a homogeneous electric field can induce an antiferromagnetic coupling between the two delocalized electronic spins that behave independently in the absence of the field. On the basis of the proposed theoretical model, we show that the external field can be used to generate controllable quantum entanglement between the two electronic spins traveling over a vanadium network of mixed valence polyoxoanion [GeV 14 O 40 ] 8- . Within a simplified two-level picture of the energy pattern of the electronic pair based on the previous ab initio analysis, we evaluate the temperature and field dependencies of concurrence and thus indicate that the entanglement can be controlled via the temperature, magnitude, and orientation of the electric field with respect to molecular axes of [GeV 14 O 40 ] 8- .

  13. Finding possible transition states of defects in silicon-carbide and alpha-iron using the dimer method

    CERN Document Server

    Gao Fei; Weber, W J; Corrales, L R; Jonsson, H

    2003-01-01

    Energetic primary recoil atoms from ion implantation or fast neutron irradiation produce isolated point defects and clusters of both vacancies and interstitials. The migration energies and mechanisms for these defects are crucial to successful multiscale modeling of microstructural evolution during ion-implantation, thermal annealing, or under irradiation over long periods of time. The dimer method is employed to search for possible transition states of interstitials and small interstitial clusters in SiC and alpha-Fe. The method uses only the first derivatives of the potential energy to find saddle points without knowledge of the final state of the transition. In SiC, the possible migration pathway for the C interstitial is found to consist of the first neighbor jump via a Si site or second neighbor jump, but the relative probability for the second neighbor jump is very low. In alpha-Fe, the possible transition states are studied as a function of interstitial cluster size, and the lowest energy barriers corr...

  14. Scaling properties for the first RE-like mixed valence examples in uranium compounds: U2Ru2Sn and U2RuGa8

    International Nuclear Information System (INIS)

    Troc, Robert

    2006-01-01

    The present study was motivated by the scaling characterization of the first example of mixed valence (MV) RE-like behaviour found recently among intermetallic ternary uranium compounds. The χ(T) function for both title compounds has been fitted to the interconfigurational fluctuation (ICF) model of Sales and Wohlleben in order to determine the characteristic fluctuation temperatures T sf and interconfigurational excitation energies E ex . A good scaling, with similar values of T sf like from those derived from the ICF model, has been achieved for both these ternaries by plotting Tχ(T)/C against the reduced T/T sf . Moreover, this scaling follows almost exactly those found earlier in a number of MV- RE compounds

  15. Synthesis and characterization of a multifunctional inorganic-organic hybrid mixed-valence copper(I/II) coordination polymer: {[CuCN][Cu(isonic)2]}n

    Science.gov (United States)

    Liu, Dong-Sheng; Chen, Wen-Tong; Ye, Guang-Ming; Zhang, Jing; Sui, Yan

    2017-12-01

    A new multifunctional mixed-valence copper(I/II) coordination polymer, {[CuCN][Cu(isonic)2]}n(1) (Hisonic = isonicotinic acid), was synthesized by treating isonicotinic acid and 5-amino-tetrazolate (Hatz = 5-amino-tetrazolate) with copper(II) salts under hydrothermal conditions, and characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray diffraction, respectively. The X-ray diffraction analysis reveals that compound exhibit noncentrosymmetric polar packing arrangement. It is three-dimensional (3D) framework with (3,5)-connected 'seh-3' topological network constructed from metal organic framework {[Cu(isonic)2]}n and the inorganic linear chain{Cu(CN)}n subunits. A remarkable feature of 1 is the rhombic open channels that are occupied by a linear chain of {Cu(CN)}n. Impressively compound 1 displays not only a second harmonic generation (SHG) response, but also a ferroelectric behavior and magnetic properties.

  16. Synthesis, Crystal Structure, and Electroconducting Properties of a 1D Mixed-Valence Cu(I–Cu(II Coordination Polymer with a Dicyclohexyl Dithiocarbamate Ligand

    Directory of Open Access Journals (Sweden)

    Kenji Nakatani

    2015-04-01

    Full Text Available A new mixed-valence Cu(I–Cu(II 1D coordination polymer, [CuI4CuIIBr4(Cy2dtc2]n, with an infinite chain structure is synthesized by the reaction of Cu(Cy2dtc2 (Cy2dtc− = dicyclohexyl dithiocarbamate, C13H22NS2 with CuBr·S(CH32. The as-synthesized polymer consists of mononuclear copper(II units of CuII(Cy2dtc2 and tetranuclear copper(I cluster units, CuI4Br4. In the cluster unit, all the CuI ions have distorted trigonal pyramidal coordination geometries, and the CuI–CuI or CuI–CuII distances between the nearest copper ions are shorter than the sum of van der Waals radii for Cu–Cu.

  17. Investigation of thermal quenching and abnormal thermal quenching in mixed valence Eu co-doped LaAlO{sub 3} phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jingjing [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Zhao, Yang [China academy of civil aviation science and technology, Beijing 100028 (China); Mao, Zhiyong, E-mail: mzhy1984@163.com [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Wang, Dajian [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China); Bie, Lijian, E-mail: ljbie@tjut.edu.cn [Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2017-06-15

    Temperature dependent luminescence of mixed valence Eu co-doped LaAlO{sub 3} phosphors are deeply investigated in this work. Different temperature properties of Eu{sup 2+} and Eu{sup 3+} luminescence are observed as the phosphor excited by different incident light. Eu{sup 3+} luminescence shows normal thermal quenching when excited at 320 nm and abnormal thermal quenching as the excitation light changed into 365 nm, while Eu{sup 2+} luminescence exhibits a normal thermal quenching independent on the incident excitation lights. The origin of these novel normal/abnormal thermal quenching phenomena are analyzed and discussed by the excitation-emission processes in terms of the configuration coordinate model. The presented important experimental and analysis results give insights into the temperature properties of phosphors.

  18. cis-dioxovanadium(V) and mixed-valence divanadium(IV, V) complexes containing β-diketonate and heterocyclic nitrogen-base ligands

    International Nuclear Information System (INIS)

    Taguchi, Hiroshi; Isobe, Kiyoshi; Nakamura, Yukio; Kawaguchi, Shinichi

    1978-01-01

    Diamagnetic dioxovanadium(V) complexes, VO 2 (β-dik)(phen or bpy), were prepared by the direct reactions of VO(β-dik) 2 with 1,10-phenanthroline and 2,2'-bipyridine in dichloromethane under aerobic conditions as well as by two other methods. These compounds were concluded to have a cis configuration on the basis of the IR and Raman data. These complexes are solvolyzed to afford the di-μ-methoxo- or di-μ-hydroxo-divanadium(V) species, and are reduced by hydrogen bromide to the oxovanadium(IV) species in dichloromethane. In methanol instead of dichloromethane, VO(acac) 2 reacted with 2,2'-bipyridine to produce a novel mixed-valence divanadium(IV, V) complex, V 2 O 3 (acac) 3 (bpy), which was revealed by the magnetic, spectral, and polarographic data to be a trans adduct of VO(acac) 2 with VO 2 (acac)(bpy) via an oxide ligand. (auth.)

  19. Electronic interaction in an outer-sphere mixed-valence double salt: a polarized neutron diffraction study of K(3)(MnO(4))(2).

    Science.gov (United States)

    Cannon, Roderick D; Jayasooriya, Upali A; Tilford, Claire; Anson, Christopher E; Sowrey, Frank E; Rosseinsky, David R; Stride, John A; Tasset, Francis; Ressouche, Eric; White, Ross P; Ballou, Rafik

    2004-11-01

    The mixed-valence double salt K(3)(MnO(4))(2) crystallizes in space group P2(1)/m with Z = 2. The manganese centers Mn1 and Mn2 constitute discrete "permanganate", [Mn(VII)O(4)](-), and "manganate", [Mn(VI)O(4)](2-), ions, respectively. There is a spin-ordering transition to an antiferromagnetic state at ca. T = 5 K. The spin-density distribution in the paramagnetic phase at T = 10 K has been determined by polarized neutron diffraction, confirming that unpaired spin is largely confined to the nominal manganate ion Mn2. Through use of both Fourier refinement and maximum entropy methods, the spin on Mn1 is estimated as 1.75 +/- 1% of one unpaired electron with an upper limit of 2.5%.

  20. Cu(I)/Cu(II) mixed-valence surface complexes of S-[(2-hydroxyamino)-2-oxoethyl]-N,N-dibutyldithiocarbamate: Hydrophobic mechanism to malachite flotation.

    Science.gov (United States)

    Liu, Sheng; Zhong, Hong; Liu, Guangyi; Xu, Zhenghe

    2018-02-15

    Hydroxamate and sulfhydryl surfactants are effective collectors for flotation of copper minerals. The combination application of hydroxamate and sulfhydryl collectors has been proved to be an effective approach for improving the flotation recovery of non-sulfide copper minerals. A surfactant owing both hydroxamate and dithiocarbamate groups might exhibit strong affinity to non-sulfide copper minerals through double sites adsorption, rendering an enhanced hydrophobization to non-sulfide copper minerals flotation. The flotation performance of S-[(2-hydroxyamino)-2-oxoethyl]- N,N-dibutyldithiocarbamate (HABTC) to malachite, calcite and quartz were first evaluated through systematic micro-flotation experiments. HABTC's hydrophobic mechanism to malachite was further investigated and analyzed by zeta potential, Fourier transform infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The micro-flotation results demonstrated HABTC was an excellent collector for malachite flotation and exhibited favorable selectivity for flotation separation of malachite from quartz or calcite under pH 8.5-10.3. Zeta potential and FTIR implied that HABTC might bond with the surface copper atoms of malachite, with releasing the H + ions of its hydroxamate group into pulp. ToF-SIMS provided clear evidences that the Cu-hydroxamate and Cu-dithiocarbamate groups were formed on malachite surfaces after HABTC adsorption. XPS revealed that Cu(I)/Cu(II) mixed-valence surface complexes of HABTC anchored on malachite through formation of Cu(I)S and Cu(II)O bonds, accompanying with reduction of partial surface Cu(II) to Cu(I). The Cu(I)/Cu(II) mixed-valence double chelating character and "chair"-shape N,N-dibutyldithiocarbamate hydrophobic group, resulting in an enhanced affinity and hydrophobization of HABTC to malachite flotation. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Electronic, magnetic structure and water splitting reactivity of the iron-sulfur dimers and their hexacarbonyl complexes: A density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Uzunova, Ellie L., E-mail: ellie@svr.igic.bas.bg [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria); Mikosch, Hans [Institute for Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/E164-EC, 1060 Vienna (Austria)

    2014-07-28

    The iron sulfide dimers (FeS){sub 2} and their persulfide isomers with S–S bonds are studied with the B3LYP density functional as bare clusters and as hexacarbonyls. The disulfides are more stable than the persulfides as bare clusters and the persulfide ground state lies at 3.2 eV above the global minimum, while in the hexacarbonyl complexes this order is reversed: persulfides are more stable, but the energy gap between disulfides and persulfides becomes much smaller and the activation barrier for the transition persulfide → disulfide is 1.11 eV. Carbonylation also favors a non-planar Fe{sub 2}S{sub 2} ring for both the disulfides and the persulfides and high electron density in the Fe{sub 2}S{sub 2} core is induced. The diamagnetic ordering is preferred in the hexacarbonyls, unlike the bare clusters. The hexacarbonyls possess low-lying triplet excited states. In the persulfide, the lowest singlet-to-triplet state excitation occurs by electron transition from the iron centers to an orbital located predominantly at S{sub 2} via metal-to-ligand charge transfer. In the disulfide this excitation corresponds to ligand-to-metal charge transfer from the sulfur atoms to an orbital located at the iron centers and the Fe–Fe bond. Water splitting occurs on the hexacarbonyls, but not on the bare clusters. The singlet and triplet state reaction paths were examined and activation barriers were determined: 50 kJ mol{sup −1} for HO–H bond dissociation and 210 kJ mol{sup −1} for hydrogen evolution from the intermediate sulfoxyl-hydroxyl complexes Fe{sub 2}S(OH)(SH)(CO){sub 6} formed. The lowest singlet-singlet excitations in the hexacarbonyls, the water adsorption complexes and in the reaction intermediates, formed prior to dihydrogen release, fall in the visible light region. The energy barrier of 210 kJ mol{sup −1} for the release of one hydrogen molecule corresponds to one visible photon of 570 nm. The dissociation of a second water molecule, followed by H{sub 2

  2. Re-entrant spin glass and stepped magnetization in mixed-valence SrFe3(PO4)3

    International Nuclear Information System (INIS)

    Shang Mingyu; Chen Yan; Tian Ge; Yuan Hongming; Feng Shouhua

    2013-01-01

    The 2 D channel mixed-valent iron (II/III) monophosphate SrFe 3 (PO 4 ) 3 was synthesized via one step mild hydrothermal method at 210 °C and characterized by X-ray diffraction techniques and magnetization measurements. Coexistence of antiferromagnetic superexchange and ferromagnetic superexchange interactions was supposed to be in the lattice according to the Goodenough-Kanamori-Anderson rules. Temperature dependent DC magnetization measurement shows that SrFe 3 (PO 4 ) 3 is ferrimagnet with three magnetic transitions between 2 and 350 K. Through AC magnetization measurement, re-entrant spin glass was observed due to the competition between ferromagnetic and antiferromagnetic interactions. Furthermore, an interesting field induced stepped magnetization was observed in SrFe 3 (PO 4 ) 3 at 2 K with the saturation magnetization Ms=2.4 μ B /f.u. at 5 T.

  3. Iron

    Science.gov (United States)

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  4. The possibility of the mixed valence state in the uranium intermetallic compounds: UCoGa5, U2Ru2Sn and U2RuGa8

    International Nuclear Information System (INIS)

    Troc, Robert

    2007-01-01

    The mixed valence (MV) phenomenon has been observed so far in a large number of various compounds but containing only lanthanides. These properties are usually associated with the mixing of the localised f-state and the band states. The usual valence state for magnetic uranium intermetallics is the trivalent state 5f 3 or hybridised 5f 2 6d 1 , both are nearly degenerate in energy and can compete for a stability of the compound. In some cases a gain in an energy minimum may be achieved by very fast fluctuating between these two states with a time of 10 -14 s, which does not allow to yield the ordered state even if the exchange interactions (favourite the U-U distances) would be able for that. The latter cases seem to concern the described here intermetallics: one ternary compound based on Co, UCoGa 5 , and the two uranium ternary compounds based on Ru, namely U 2 Ru 2 Sn and U 2 RuGa 8 which all crystallize in a tetragonal unit cell. All these compounds show a maximum in their temperature dependences of the magnetic susceptibility measured along and perpendicular to the c-axis. Such a behaviour, which is reminiscent of a number of Ce (Sm, Eu) and Yb compounds for which χ(T) has in the past been considered by Sales and Wohlleben (SW) by applying their ICF model or by Lawrance et al. following their scaling procedure. It turned out that these phenomenological models can also be applied to the considered here two Ru-based uranium ternaries from which some reliable energy parameters could be found. In order to further support the mixing valence scenario for the first such cases in uranium compounds presented here, the transport and thermodynamic properties are also discussed. However, some of the most important results confirming the MV state, e.g., in U 2 RuGa 8 , has recently been achieved from the inelastic neutron scattering performed in the Rutherford Appleton Laboratory on the ISIS facility. From these measurements a characteristic gap of 60 meV has been

  5. Doubly end-on azido bridged mixed-valence cobalt trinuclear complex: Spectral study, VTM, inhibitory effect and antimycobacterial activity on human carcinoma and tuberculosis cells

    Science.gov (United States)

    Datta, Amitabha; Das, Kuheli; Sen, Chandana; Karan, Nirmal Kumar; Huang, Jui-Hsien; Lin, Chia-Her; Garribba, Eugenio; Sinha, Chittaranjan; Askun, Tulin; Celikboyun, Pinar; Mane, Sandeep B.

    2015-09-01

    Doubly end-on azido-bridged mixed-valence trinuclear cobalt complex, [Co3(L)2(N3)6(CH3OH)2] (1) is afforded by employing a potential monoanionic tetradentate-N2O2 Schiff base precursor (2-[{[2-(dimethylamino)ethyl]imino}methyl]-6-methoxyphenol; HL). Single crystal X-ray structure reveals that in 1, the adjacent CoII and CoIII ions are linked by double end-on azido bridges and thus the full molecule is generated by the site symmetry of a crystallographic twofold rotation axis. Complex 1 is subjected on different spectral analysis such as IR, UV-vis, emission and EPR spectroscopy. On variable temperature magnetic study, we observe that during cooling, the χMT values decrease smoothly until 15 K and then reaches to the value 1.56 cm3 K mol-1 at 2 K. Complex 1 inhibits the cell growth on human lung carcinoma (A549 cells), human colorectal (COLO 205 and HT-29 cells), and human heptacellular (PLC5 cells) carcinoma cells. Complex 1 exhibits anti-mycobacterial activity and considerable efficacy on Mycobacterium tuberculosis H37Rv ATCC 27294 and H37Ra ATCC 25177 strains.

  6. Evidence of dithionite contribution to the low-frequency resonance Raman spectrum of reduced and mixed-valence cytochrome c oxidase.

    Science.gov (United States)

    Centeno, J A

    1992-02-01

    The resonance Raman spectra of deoxygenated solutions of mixed-valence cyanide-bound and fully reduced cytochrome oxidase derivatives that have been reduced in the presence of aqueous or solid sodium dithionite exhibit two new low-frequency lines centered at 474 and 590 cm-1. These lines were not observed when the reductant system was changed to a solution containing ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). Under enzyme turnover conditions, the addition of dithionite to the reoxidized protein (the 428-nm or "oxygenated" form) increases the intensity of these lines, while reoxidation and rereduction of the enzyme in the presence of ascorbate/TMPD resulted in the absence of both lines. Our data suggest that both lines must have contributions from species formed from aqueous dithionite, presumably the SO2 species, since these two lines are also observed in the Raman spectrum of a solution of aqueous dithionite, but not in the spectrum of an ascorbate/TMPD solution. Since heme metal-ligand stretch vibrations are expected to appear in the low-frequency region from 215 to 670 cm-1, our results indicate that special care should be exercised during the interpretation of the cytochrome a3 resonance Raman spectrum.

  7. Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

    Science.gov (United States)

    El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

    2003-02-01

    The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

  8. EXAFS analysis of the L3 edge of Ce in CeO2: effects of multielectron excitations and final-state mixed valence

    International Nuclear Information System (INIS)

    Fonda, E.; Andreatta, D.; Colavita, P.E.; Vlaic, G.

    1999-01-01

    Cerium oxide (IV) (CeO 2 ) is extensively employed in heterogeneous catalysis, particularly as a promoter of noble metal action in three-way catalysts. For this reason there is a great scientific and economical interest in the development of any possible chemical or structural analysis technique that could provide information on these systems. EXAFS spectroscopy has revealed itself as a powerful technique for structural characterization of such catalysts. Unfortunately, good quality K-edge spectra of cerium are not yet easily obtainable because of the high photon energy required (>40 keV). On the other hand, at lower energies it is easy to collect very good spectra of the L 3 edge (5.5 keV), but L 3 -edge spectra of cerium (IV) are characterized by the presence of two undesired additional phenomena that interfere with EXAFS analysis: final-state mixed-valence behaviour and intense multi-electron excitations. Here, a comparative analysis of the K, L 3 , L 2 and L 1 edges of Ce in CeO 2 has been made and a procedure for obtaining structural parameters from L 3 -edge EXAFS, even in the presence of these features, has been developed. This procedure could allow further studies of catalytic compounds containing tetravalent cerium surrounded by oxygen ligands. (au)

  9. A novel extended architecture with 4 6·6 4 topology based on mixed-valence Wells-Dawson arsenotungstate and mixed-ligand Cu(I) units

    Science.gov (United States)

    Tong, Ruizhan; Ren, Xiaoyu; Li, Zuoxi; Liu, Bin; Hu, Huaiming; Xue, Ganglin; Fu, Feng; Wang, Jiwu

    2010-09-01

    A novel inorganic-organic hybrid compound based on mixed-valence Wells-Dawson arsenotungstate and mixed-ligand Cu(I) units, Cu 8I(imi) 4(bpy) 6(H 2O)[As 2VW 2VW 16VlO 62]·2H 2O ( 1) (bpy=4,4'-bipydine; imi=imidazole), has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, luminescent spectrum and single crystal X-ray diffraction. Single-crystal X-ray diffraction revealed that four terminal and three bridging oxygen atoms of the Wells-Dawson cluster are coordinated to Cu(I) ions and form an unprecedented hepta-supporting polyoxometalate. The functionalized arsenotungstates are further connected by two kinds of tridentate linkers, Imi-Cu-(bpy)-Cu-(bpy)-Cu-(bpy)-Cu-Imi and Imi-Cu-(bpy)-Cu-(bpy)-Cu-H 2O, to construct a 3D framework with 4 6·6 4 topology. The hybrid material has an intense emission at about 397 nm.

  10. Efficient solar-assisted O2 reduction by a cofacial iron porphyrin dimer integrated to a p-CuBi2O4 photocathode prepared by a simple novel method.

    Science.gov (United States)

    Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori; Haleem, Ashraf

    2017-10-04

    A cofacial iron porphyrin hetero-dimer, Fe2TPFPP-TMP showed high electro-catalytic activity, selectivity, and stability for the O2 reduction to H2O both in homogeneous non-aqueous and heterogeneous neutral aqueous solutions. Moreover, when it is integrated to FTO/p-CuBi2O4 (FTO = fluorine doped tin oxide) photocathode prepared by a simple novel method, a remarkable efficient solar-assisted O2 reduction is achieved in neutral potassium phosphate (KPi) or basic NaOH solutions saturated with O2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Synthesis of an S T = 7 [Mn 3 ] Mixed-Valence Complex Based on 1,3-Propanediol Ligand Derivatives and Its One-Dimensional Assemblies

    KAUST Repository

    Huang, Jian

    2013-10-07

    Controlled organization of high-spin complexes and single-molecule magnets is a great challenge in molecular magnetism in order to study the effect of the intercomplex magnetic interactions on the intrinsic properties of a given magnetic object. In this work, a new ST = 7 trinuclear mixed-valence Mn complex, [MnIIIMnII 2(LA) 2(Br)4(CH3OH)6] ·Br· (CH3OH)1.5·(H2O)0.5 (1), is reported using a pyridinium-functionalized 1,3-propanediol ligand (H 2LABr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)pyridinium bromide). Using azido anions as bridging ligands and different pyridinium-functionalized 1,3-propanediol ligands (H2LBBr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)-4-picolinium bromide; H 2LCBr = 1-(3-bromo-2,2-bis(hydroxymethyl)propyl)-3,5- lutidinium bromide), the linear [MnIIIMnII 2L2X4]+ building block has been assembled into one-dimensional coordination networks: [MnIIIMn II 2(LA)2(Br)4(CH 3OH)4(N3)]·((C2H 5)2O)1.25 (2∞), [MnIIIMn II 2(LB)2(Br)4(C 2H5OH)(CH3OH)(H2O) 2(N3)]·(H2O)0.25 (3∞), and [MnIIIMnII 2(LC) 2(Cl)3.8(Br)0.2(C2H 5OH)3(CH3OH)(N3)] (4∞). The syntheses, characterization, crystal structures, and magnetic properties of these new [Mn3]-based materials are reported. © 2013 American Chemical Society.

  12. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    International Nuclear Information System (INIS)

    Takahashi, Jumpei; Oka, Daichi; Hirose, Yasushi; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya; Nakao, Shoichiro; Harayama, Isao; Sekiba, Daiichiro

    2015-01-01

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO x N y ) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO x N y thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO x N y thin films monotonically decreased from the order of 10 5  Ω cm to 10 −4  Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO x N y phase, which has not yet been reported in Co 2+ /Co 3+ mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO x N y phase, on the 10 −3  Ω cm order, may have originated from the intermediate spin state of Co 3+ stabilized by the lowered crystal field symmetry of the CoO 6−n N n octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO x N y films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides

  13. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jumpei; Oka, Daichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [University of Tsukuba Tandem Accelerator Complex (UTTAC), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-12-07

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO{sub x}N{sub y}) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO{sub x}N{sub y} thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO{sub x}N{sub y} thin films monotonically decreased from the order of 10{sup 5} Ω cm to 10{sup −4} Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO{sub x}N{sub y} phase, which has not yet been reported in Co{sup 2+}/Co{sup 3+} mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO{sub x}N{sub y} phase, on the 10{sup −3} Ω cm order, may have originated from the intermediate spin state of Co{sup 3+} stabilized by the lowered crystal field symmetry of the CoO{sub 6−n}N{sub n} octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO{sub x}N{sub y} films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides.

  14. Structure, magnetism, and theoretical study of a mixed-valence Co(II)3Co(III)4 heptanuclear wheel: lack of SMM behavior despite negative magnetic anisotropy.

    Science.gov (United States)

    Chibotaru, Liviu F; Ungur, Liviu; Aronica, Christophe; Elmoll, Hani; Pilet, Guillaume; Luneau, Dominique

    2008-09-17

    A mixed-valence Co(II)/Co(III) heptanuclear wheel [Co(II)3Co(III)4(L)6(MeO)6] (LH2 = 1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one) has been synthesized and its crystal structure determined using single-crystal X-ray diffraction. The valence state of each cobalt ion was established by bond valence sum calculations. Studies of the temperature dependence of the magnetic susceptibility and the field dependence of the magnetization evidence ferromagnetic interactions within the compound. In order to understand the magnetic properties of this Co7 wheel, we performed ab initio calculations for each cobalt fragment at the CASSCF/CASPT2 level, including spin-orbit coupling effects within the SO-RASSI approach. The four Co(III) ions were found to be diamagnetic and to give a significant temperature-independent paramagnetic contribution to the susceptibility. The spin-orbit coupling on the three Co(II) sites leads to separations of approximately 200 cm(-1) between the ground and excited Kramers doublets, placing the Co7 wheel into a weak-exchange limit in which the lowest electronic states are adequately described by the anisotropic exchange interaction between the lowest Kramers doublets on Co(II) sites. Simulation of the exchange interaction was done within the Lines model, keeping the fully ab initio treatment of magnetic anisotropy effects on individual cobalt fragments using a recently developed methodology. A good description of the susceptibility and magnetization was obtained for nearest-neighbor (J1) and next-nearest-neighbor (J2) exchange parameters (1.5 and 5.5 cm(-1), respectively). The strong ferromagnetic interaction between distant cobalt ions arises as a result of low electron-promotion energies in the exchange bridges containing Co(III) ions. The calculations showed a large value of the magnetization along the main magnetic axis (10.1 mu(B)), which is a combined effect of the ferromagnetic exchange interaction and negative magnetic anisotropy on

  15. Mixed-valence molecular four-dot unit for quantum cellular automata: Vibronic self-trapping and cell-cell response.

    Science.gov (United States)

    Tsukerblat, Boris; Palii, Andrew; Clemente-Juan, Juan Modesto; Coronado, Eugenio

    2015-10-07

    Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of mixed-valence (MV) tetra-ruthenium (2Ru(ii) + 2Ru(iii)) derivatives (assembled as two coupled Creutz-Taube complexes) for which molecular implementations of quantum cellular automata (QCA) was proposed. The cell based on this molecule includes two holes shared among four spinless sites and correspondingly we employ the model which takes into account the two relevant electron transfer processes (through the side and through the diagonal of the square) as well as the difference in Coulomb energies for different instant positions of localization of the hole pair. The combined Jahn-Teller (JT) and pseudo JT vibronic coupling is treated within the conventional Piepho-Krauzs-Schatz model adapted to a bi-electronic MV species with the square-planar topology. The adiabatic potentials are evaluated for the low lying Coulomb levels in which the antipodal sites are occupied, the case just actual for utilization in mQCA. The conditions for the vibronic self-trapping in spin-singlet and spin-triplet states are revealed in terms of the two actual transfer pathways parameters and the strength of the vibronic coupling. Spin related effects in degrees of the localization which are found for spin-singlet and spin-triplet states are discussed. The polarization of the cell is evaluated and we demonstrate how the partial delocalization caused by the joint action of the vibronic coupling and electron transfer processes influences polarization of a four-dot cell. The results obtained within the adiabatic approach are compared with those based on the numerical solution of the dynamic vibronic problem. Finally, the Coulomb interaction between

  16. Mixed-Valence Molecular Unit for Quantum Cellular Automata: Beyond the Born-Oppenheimer Paradigm through the Symmetry-Assisted Vibronic Approach.

    Science.gov (United States)

    Clemente-Juan, Juan Modesto; Palii, Andrew; Coronado, Eugenio; Tsukerblat, Boris

    2016-08-09

    In this article, we focus on the electron-vibrational problem of the tetrameric mixed-valence (MV) complexes proposed for implementation as four-dot molecular quantum cellular automata (mQCA).1 Although the adiabatic approximation explored in ref 2 is an appropriate tool for the qualitative analysis of the basic characteristics of mQCA, like vibronic trapping of the electrons encoding binary information and cell-cell response, it loses its accuracy providing moderate vibronic coupling and fails in the description of the discrete pattern of the vibronic levels. Therefore, a precise solution of the quantum-mechanical vibronic problem is of primary importance for the evaluation of the shapes of the electron transfer optical absorption bands and quantitative analysis of the main parameters of tetrameric quantum cells. Here, we go beyond the Born-Oppenheimer paradigm and present a solution of the quantum-mechanical pseudo Jahn-Teller (JT) vibronic problem in bielectronic MV species (exemplified by the tetra-ruthenium complexes) based on the recently developed symmetry-assisted approach.3,4 The mathematical approach to the vibronic eigenproblem takes into consideration the point symmetry basis, and therefore, the total matrix of the JT Hamiltonian is blocked to the maximum extent. The submatrices correspond to the irreducible representations (irreps) of the point group. With this tool, we also extend the theory of the mQCA cell beyond the limit of prevailing Coulomb repulsion in the electronic pair (adopted in ref 2), and therefore, the general pseudo-JT problems for spin-singlet ((1)B1g, 2(1)A1g, (1)B2g, (1)Eu) ⊗ (b1g + eu) and spin-triplet states ((3)A2g, (3)B1g, 2(3)Eu) ⊗ (b1g + eu) in a square-planar bielectronic system are solved. The obtained symmetry-adapted electron-vibrational functions are employed for the calculation of the profiles (shape functions) of the charge transfer absorption bands in the tetrameric MV complexes and for the discussion of the

  17. Iron

    DEFF Research Database (Denmark)

    Hansen, Jakob Bondo; Moen, I W; Mandrup-Poulsen, T

    2014-01-01

    and discuss recent evidence, suggesting that iron is a key pathogenic factor in both type 1 and type 2 diabetes with a focus on inflammatory pathways. Pro-inflammatory cytokine-induced β-cell death is not fully understood, but may include iron-induced ROS formation resulting in dedifferentiation by activation...... of transcription factors, activation of the mitochondrial apoptotic machinery or of other cell death mechanisms. The pro-inflammatory cytokine IL-1β facilitates divalent metal transporter 1 (DMT1)-induced β-cell iron uptake and consequently ROS formation and apoptosis, and we propose that this mechanism provides...

  18. Iron

    Science.gov (United States)

    ... Share: Search the ODS website Submit Search NIH Office of Dietary Supplements Consumer Datos en español Health ... eating a variety of foods, including the following: Lean meat, seafood, and poultry. Iron-fortified breakfast cereals ...

  19. Electronic structure and nature of the ground state of the mixed-valence binuclear tetra(mu-1,8-naphthyridine-N,N')-bis(halogenonickel) tetraphenylborate complexes: experimental and DFT characterization.

    Science.gov (United States)

    Bencini, Alessandro; Berti, Elisabetta; Caneschi, Andrea; Gatteschi, Dante; Giannasi, Elisa; Invernizzi, Ivana

    2002-08-16

    The ground state electronic structure of the mixed-valence systems [Ni(2)(napy)(4)X(2)](BPh(4)) (napy=1,8-naphthyridine; X=Cl, Br, I) was studied with combined experimental (X-ray diffraction, temperature dependence of the magnetic susceptibility, and high-field EPR spectroscopy) and theoretical (DFT) methods. The zero-field splitting (zfs) ground S=3/2 spin state is axial with /D/ approximately 3 cm(-1). The iodide derivative was found to be isostructural with the previously reported bromide complex, but not isomorphous. The compound crystallizes in the monoclinic system, space group P2(1)/n, with a=17.240(5), b=26.200(5), c=11.340(5) A, beta=101.320(5) degrees. DFT calculations were performed on the S=3/2 state to characterize the ground state potential energy surface as a function of the nuclear displacements. The molecules can thus be classified as Class III mixed-valence compounds with a computed delocalization parameter, B=3716, 3583, and 3261 cm(-1) for the Cl, Br, and I derivatives, respectively.

  20. Liquid crystal dimers

    CERN Document Server

    Kumar Pal, Santanu

    2017-01-01

    This book covers in-depth discussion of design principles, synthesis and thermal behavior of all types of liquid crystal (LC) dimers. The text presents recent advances in the field of LC dimers consisting of different mesogenic units such as calamitic, discotic and bent-core molecules. It starts with a chapter on the introduction of liquid crystal dimers, including their odd-even behavior, basic classification of dimers and common mesophases in dimers. The text shows how the molecular architectures are being used to develop new materials to study a range of interesting phenomena such as the biaxial nematic phase containing rod-like and disc-like mesogenic units. Finally, the text presents perspectives related to technological relevance of these dimers such as dopants in LC display mixtures exhibiting faster relaxation time, strong flexoelectric coupling and others to effect control over the properties of these materials.

  1. Novel Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N‧-bis(3-aminopropyl)ethane-1,2-diamine): Synthesis, crystal structure and magnetic properties

    Science.gov (United States)

    Smolko, Lukáš; Černák, Juraj; Kuchár, Juraj; Miklovič, Jozef; Boča, Roman

    2016-09-01

    Green crystals of Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N‧-bis(3-aminopropyl)ethane-1,2-diamine) were isolated from the aqueous system CoBr2 - bapen - HBr, crystallographically studied and characterized by elemental analysis and IR spectroscopy. Its ionic crystal structure is built up of [Co(bapen)Br2]+ cations and [CoBr4]2- anions. The Co(III) central atoms within the complex cations are hexacoordinated (donor set trans-N4Br2) with bromido ligands placed in the axial positions. The Co(II) atoms exhibit distorted tetrahedral coordination. Beside ionic forces weak Nsbnd H⋯Br intermolecular hydrogen bonding interactions contribute to the stability of the structure. Temperature variable magnetic measurements confirm the S = 3/2 behavior with the zero-field splitting of an intermediate strength: D/hc = 8.7 cm-1.

  2. Mixed dimers, ch. 7

    International Nuclear Information System (INIS)

    Deursen, A.P.J. van; Reuss, J.

    1976-01-01

    An attempt has been made to detect mixed dimers in nozzle beams of mixtures; NeAr and HeNe dimers were observed with sufficient intensity to determine the total collision cross section. A similar attempt for H 2 Ar was partially hampered by the circumstance that the corresponding HAr + ion must be detected on the wing of the thousand times larger Ar + peak. The search for H 2 He, H 2 Ne and HeAr dimers was not successful, due to masking ion peaks, H 5 + for HHe + , 21 Ne + for H 20 Ne + , and CO 2 + for HeAr + . (Auth.)

  3. 2-Ethynylpyridine dimers

    DEFF Research Database (Denmark)

    Bakarić, Danijela; Spanget-Larsen, Jens

    2018-01-01

    are used to study possible 2-EP dimer structures as well as their distribution in an inert solvent such as tetrachloroethene. Experimentally, the ≡C–H stretching vibration of the 2-EPmonomer absorbs close to 3300 cm−1, whereas a broad band withmaximum around 3215 cm−1 emerges as the concentration rises...... model with counterpoise correction predict that the two most stable dimers are of the pi-stacked variety, closely followed by dimers with intermolecular ≡C–H···N hydrogen bonding; the predicted red shifts of the ≡C–H stretching wavenumbers due to hydrogen bonding are in the range 54 – 120 cm–1...

  4. D-dimer Test

    Science.gov (United States)

    ... 1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition]. Pagana, Kathleen D. & Pagana, ... www.itxm.org . Titus, K. (2003 January). Identity crisis persists: which D-dimer? CAP Today , In the ...

  5. Dimers in nucleating vapors

    Science.gov (United States)

    Lushnikov, A. A.; Kulmala, M.

    1998-09-01

    The dimer stage of nucleation may affect considerably the rate of the nucleation process at high supersaturation of the nucleating vapor. Assuming that the dimer formation limits the nucleation rate, the kinetics of the particle formation-growth process is studied starting with the definition of dimers as bound states of two associating molecules. The partition function of dimer states is calculated by summing the Boltzmann factor over all classical bound states, and the equilibrium population of dimers is found for two types of intermolecular forces: the Lennard-Jones (LJ) and rectangular well+hard core (RW) potentials. The principle of detailed balance is used for calculating the evaporation rate of dimers. The kinetics of the particle formation-growth process is then investigated under the assumption that the trimers are stable with respect to evaporation and that the condensation rate is a power function of the particle mass. If the power exponent λ=n/(n+1) (n is a non-negative integer), the kinetics of the process is described by a finite set of moments of particle mass distribution. When the characteristic time of the particle formation by nucleation is much shorter than that of the condensational growth, n+2 universal functions of a nondimensional time define the kinetic process. These functions are calculated for λ=2/3 (gas-to-particle conversion in the free molecular regime) and λ=1/2 (formation of islands on surfaces).

  6. (NH4)[V1-xIIIVxIV(AsO4)F1-xOx]: A new mixed valence vanadium(III,IV) fluoro-arsenate with ferromagnetic interactions and electronic conductivity

    International Nuclear Information System (INIS)

    Berrocal, Teresa; Mesa, Jose L.; Pizarro, Jose L.; Bazan, Begona; Ruiz de Larramendi, Idoia; Arriortua, Maria I.; Rojo, Teofilo

    2009-01-01

    A new mixed valence vanadium(III,IV) fluoro-arsenate compound, with formula (NH 4 )[V 1-x III V x IV (AsO 4 )F 1-x O x ] and KTP structure-type, has been synthesized by mild hydrothermal techniques. The crystal structure has been solved from single crystal X-ray diffraction data in the Pna2 1 orthorhombic space group. The unit-cell parameters are a=13.196(2) A, b=6.628(1) A and c=10.7379(7) A with Z=8. The final R factors were R1=0.0438 and wR2=0.0943 [all data]. The crystal structure consists of a three-dimensional framework formed by (V III,IV O 4 F 2 ) octahedra and (AsO 4 ) 3- tetrahedra arsenate oxoanions. The vanadium(III,IV) cations, from the (V III,IV O 4 F 2 ) octahedra, are linked through the fluorine atoms giving rise to zigzag chains. The ammonium cations are located in the cavities of the structure compensating the anionic charge of the [V 1-x III V x IV (AsO 4 )F 1-x O x ] - inorganic skeleton. The thermal stability limit of the phase is 345 deg. C, around to this temperature the ammonium cation and fluoride anion are lost. The IR spectrum shows the characteristic bands of the (NH 4 ) + and (AsO 4 ) 3- ions. Magnetic measurements indicate the existence of weak ferromagnetic interactions. Electronic conductivity, via a hopping mechanism, occurs with an activation energy of 0.66 eV. - Graphical abstract: Polyhedral view of the crystal structure of (NH 4 )[V III 1-x V IV x (AsO 4 )F 1-x O x

  7. Synthesis, Magnetism, and X-ray Molecular Structure of the Mixed-Valence Vanadium(IV/V)-Oxygen Cluster [VO(4) subset(V(18)O(45))](9-).

    Science.gov (United States)

    Suber, Lorenza; Bonamico, Mario; Fares, Vincenzo

    1997-05-07

    Within the transition metal oxide systems, vanadium presents a unique chemistry due to its capacity to form a great number of mixed-valence oxo clusters which often have the peculiarity to incorporate species that function, for size, shape, and charge, as templates. Prismatic, lustrous dark brown crystals of [(n-C(4)H(9))NH(3)](9)[V(19)O(49)].7H(2)O are obtained by reacting (n-C(4)H(9)NH(3))VO(3), VOSO(4), and (n-C(4)H(9))NH(2) in H(2)O. The X-ray crystal structure shows an ellipsoidal metal-oxo cluster formed by 15 VO(5) and 3 VO(4) polyhedra surrounding an almost regular VO(4) tetrahedron located on the 3-fold axis of a trigonal cell of dimensions a = 19.113(5) Å and c = 13.743(5) Å with space group P&thremacr; and Z = 2. Exponentially weighted bond valence sum calculations, manganometric titration of the V(IV) centers, and magnetic measurements are consistent with the presence of three localized and three delocalized electrons. Variable-temperature solid-state susceptibility studies indicate antiferromagnetic coupling between V(IV) centers. Cyclic voltammetry in acetonitrile shows a irreversible reduction at -1.24 V and a reversible oxidation at +0.17 V (vs Ag/AgCl). The title compound converts quantitatively to the metal oxide K(2)V(3)O(8) with an extended layered structure as soon as a potassium salt is added to a neutral aqueous solution of the polyoxoanion.

  8. Photoionization of helium dimers

    International Nuclear Information System (INIS)

    Havermeier, Tilo

    2010-01-01

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  9. Iron valence in double-perovskite (Ba,Sr,Ca)2FeMoO6: isovalent substitution effect

    International Nuclear Information System (INIS)

    Yasukawa, Y.; Linden, J.; Chan, T.S.; Liu, R.S.; Yamauchi, H.; Karppinen, M.

    2004-01-01

    In the Fe-Mo based B-site ordered double-perovskite, A 2 FeMoO 6.0 , with iron in the mixed-valence II/III state, the valence value of Fe is not precisely fixed at 2.5 but may be fine-tuned by means of applying chemical pressure at the A-cation site. This is shown through a systematic 57 Fe Moessbauer spectroscopy study using a series of A 2 FeMoO 6.0 [A=(Ba,Sr) or (Sr,Ca)] samples with high degree of Fe/Mo order, the same stoichiometric oxygen content and also almost the same grain size. The isomer shift values and other hyperfine parameters obtained from the Moessbauer spectra confirm that Fe remains in the mixed-valence state within the whole range of A constituents. However, upon increasing the average cation size at the A site the precise valence of Fe is found to decrease such that within the A=(Ba,Sr) regime the valence of Fe is closer to II, while within the A=(Sr,Ca) regime it is closer to the actual mixed-valence II/III state. As the valence of Fe approaches II, the difference in charges between Fe and Mo increases, and parallel with this the degree of Fe/Mo order increases. Additionally, for the less-ordered samples an increased tendency of clustering of the antisite Fe atoms is deduced from the Moessbauer data

  10. Alkane dimers interaction

    DEFF Research Database (Denmark)

    Ferrighi, Lara; Madsen, Georg Kent Hellerup; Hammer, Bjørk

    2010-01-01

    The interaction energies of a series of n-alkane dimers, from methane to decane, have been investigated with Density Functional Theory (DFT), using the MGGA-M06-L density functional. The results are compared both to the available wavefunction-based values as well as to dispersion corrected DFT...... values. The MGGA-M06-L density functional is a semi-local functional designed and has proven to provide accurate estimates of dispersion interactions for several systems at moderate computational cost. In the present application, it reproduces the trends obtained by the more expensive wavefunction...

  11. Selective amine catalysed steroidal dimerization

    Indian Academy of Sciences (India)

    of cholesterol is the formation of a green colour in concentrated sulphuric acid, and this was shown to be due to a polyenyl steroidal dimer carbocation.7–9 Many dimeric and oligomeric steroids exhibit interesting micellular, detergent and liquid crystal behaviour.10,11. Most of the steroidal dimmers are also well-known.

  12. Collisional properties of weakly bound heteronuclear dimers

    NARCIS (Netherlands)

    Marcelis, B.; Kokkelmans, S.J.J.M.F.; Shlyapnikov, G.V.; Petrov, D.S.

    2008-01-01

    We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating

  13. Rate and extent of aqueous perchlorate removal by iron surfaces.

    Science.gov (United States)

    Moore, Angela M; De Leon, Corinne H; Young, Thomas M

    2003-07-15

    The rate and extent of perchlorate reduction on several types of iron metal was studied in batch and column reactors. Mass balances performed on the batch experiments indicate that perchlorate is initially sorbed to the iron surface, followed by a reduction to chloride. Perchlorate removal was proportional to the iron dosage in the batch reactors, with up to 66% removal in 336 h in the highest dosage system (1.25 g mL(-1)). Surface-normalized reaction rates among three commercial sources of iron filings were similar for acid-washed samples. The most significant perchlorate removal occurred in solutions with slightly acidic or near-neutral initial pH values. Surface mediation of the reaction is supported by the absence of reduction in batch experiments with soluble Fe2+ and also by the similarity in specific reaction rate constants (kSA) determined for three different iron types. Elevated soluble chloride concentrations significantly inhibited perchlorate reduction, and lower removal rates were observed for iron samples with higher amounts of background chloride contamination. Perchlorate reduction was not observed on electrolytic sources of iron or on a mixed-phase oxide (Fe3O4), suggesting that the reactive iron phase is neither pure zerovalent iron nor the mixed oxide alone. A mixed valence iron hydr(oxide) coating or a sorbed Fe2+ surface complex represent the most likely sites for the reaction. The observed reaction rates are too slow for immediate use in remediation system design, but the findings may provide a basis for future development of cost-effective abiotic perchlorate removal techniques.

  14. Adventures in holographic dimer models

    International Nuclear Information System (INIS)

    Kachru, Shamit; Karch, Andreas; Yaida, Sho

    2011-01-01

    We abstract the essential features of holographic dimer models, and develop several new applications of these models. Firstly, semi-holographically coupling free band fermions to holographic dimers, we uncover novel phase transitions between conventional Fermi liquids and non-Fermi liquids, accompanied by a change in the structure of the Fermi surface. Secondly, we make dimer vibrations propagate through the whole crystal by way of double trace deformations, obtaining nontrivial band structure. In a simple toy model, the topology of the band structure experiences an interesting reorganization as we vary the strength of the double trace deformations. Finally, we develop tools that would allow one to build, in a bottom-up fashion, a holographic avatar of the Hubbard model.

  15. Study of DNA Origami Dimerization and Dimer Dissociation Dynamics and of the Factors that Limit Dimerization.

    Science.gov (United States)

    Liber, Miran; Tomov, Toma E; Tsukanov, Roman; Berger, Yaron; Popov, Mary; Khara, Dinesh C; Nir, Eyal

    2018-06-01

    Organizing DNA origami building blocks into higher order structures is essential for fabrication of large structurally and functionally diverse devices and molecular machines. Unfortunately, the yields of origami building block attachment reactions are typically not sufficient to allow programed assembly of DNA devices made from more than a few origami building blocks. To investigate possible reasons for these low yields, a detailed single-molecule fluorescence study of the dynamics of rectangular origami dimerization and origami dimer dissociation reactions is conducted. Reactions kinetics and yields are investigated at different origami and ion concentrations, for different ion types, for different lengths of bridging strands, and for the "sticky end" and "weaving welding" attachment techniques. Dimerization yields are never higher than 86%, which is typical for such systems. Analysis of the dynamic data shows that the low yield cannot be explained by thermodynamic instability or structural imperfections of the origami constructs. Atomic force microscopy and gel electrophoresis evidence reveal self-dimerization of the origami monomers, likely via blunt-end interactions made possible by the presence of bridging strands. It is suggested that this mechanism is the major factor that inhibits correct dimerization and means to overcome it are discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Kinetics of DNA tile dimerization.

    Science.gov (United States)

    Jiang, Shuoxing; Yan, Hao; Liu, Yan

    2014-06-24

    Investigating how individual molecular components interact with one another within DNA nanoarchitectures, both in terms of their spatial and temporal interactions, is fundamentally important for a better understanding of their physical behaviors. This will provide researchers with valuable insight for designing more complex higher-order structures that can be assembled more efficiently. In this report, we examined several spatial factors that affect the kinetics of bivalent, double-helical (DH) tile dimerization, including the orientation and number of sticky ends (SEs), the flexibility of the double helical domains, and the size of the tiles. The rate constants we obtained confirm our hypothesis that increased nucleation opportunities and well-aligned SEs accelerate tile-tile dimerization. Increased flexibility in the tiles causes slower dimerization rates, an effect that can be reversed by introducing restrictions to the tile flexibility. The higher dimerization rates of more rigid tiles results from the opposing effects of higher activation energies and higher pre-exponential factors from the Arrhenius equation, where the pre-exponential factor dominates. We believe that the results presented here will assist in improved implementation of DNA tile based algorithmic self-assembly, DNA based molecular robotics, and other specific nucleic acid systems, and will provide guidance to design and assembly processes to improve overall yield and efficiency.

  17. Dimers in Piecewise Temperleyan Domains

    Science.gov (United States)

    Russkikh, Marianna

    2018-03-01

    We study the large-scale behavior of the height function in the dimer model on the square lattice. Richard Kenyon has shown that the fluctuations of the height function on Temperleyan discretizations of a planar domain converge in the scaling limit (as the mesh size tends to zero) to the Gaussian Free Field with Dirichlet boundary conditions. We extend Kenyon's result to a more general class of discretizations. Moreover, we introduce a new factorization of the coupling function of the double-dimer model into two discrete holomorphic functions, which are similar to discrete fermions defined in Smirnov (Proceedings of the international congress of mathematicians (ICM), Madrid, Spain, 2006; Ann Math (2) 172:1435-1467, 2010). For Temperleyan discretizations with appropriate boundary modifications, the results of Kenyon imply that the expectation of the double-dimer height function converges to a harmonic function in the scaling limit. We use the above factorization to extend this result to the class of all polygonal discretizations, that are not necessarily Temperleyan. Furthermore, we show that, quite surprisingly, the expectation of the double-dimer height function in the Temperleyan case is exactly discrete harmonic (for an appropriate choice of Laplacian) even before taking the scaling limit.

  18. Rubidium dimers in paraffin-coated cells

    International Nuclear Information System (INIS)

    Acosta, V M; Windes, D; Corsini, E; Ledbetter, M P; Karaulanov, T; Budker, D; Jarmola, A; Auzinsh, M; Rangwala, S A; Jackson Kimball, D F

    2010-01-01

    Measurements were made to determine the density of rubidium dimer vapor in paraffin-coated cells. The number density of dimers and atoms in similar paraffin-coated and uncoated cells was measured by optical spectroscopy. Due to the relatively low melting point of paraffin, a limited temperature range of 43-80 0 C was explored, with the lower end corresponding to a dimer density of less than 10 7 cm -3 . With 1 min integration time, a sensitivity to dimer number density of better than 10 6 cm -3 was achieved. No significant difference in dimer density between the cells was observed.

  19. Synthesis, crystal structure and magnetic studies of tetranuclear hydroxo and ligand bridged [Co4(μ3-OH)2(μ2-dea)2(L-L)4]4Cl·8H2O [L-L = 2,2'-bipyridine or 1,10-phenanthroline] complexes with mixed valence defect dicubane core.

    Science.gov (United States)

    Siddiqi, Zafar A; Siddique, Armeen; Shahid, M; Khalid, Mohd; Sharma, Prashant K; Anjuli; Ahmad, Musheer; Kumar, Sarvendra; Lan, Yanhua; Powell, Annie K

    2013-07-14

    X-ray crystallography of the title complexes indicates a discrete mixed valence (Co2(II)-Co2(III)) defect dicubane molecular unit where each cobalt nucleus attains a distorted octahedral geometry. The α-diimine (L-L) chelator coordinated to each cobalt ion stops further polymerization or nuclearization. The water molecules in the lattice play a crucial role in the formation of the supramolecular architectures. Magnetic data were analyzed using the effective spin-1/2 Hamiltonian approach and the parameters are, J = 115(6) K, ΔJ = -57.0(1.2) K, g(xy) = 3.001(25), and g(z) = 7.214(7) for 1 and J = 115(12) K, ΔJ = -58.5(2.5) K, g(xy) = 3.34(5), and g(z) = 6.599(12) for 2 suggesting that only the g matrices are prone to the change of α-diimine chelator.

  20. From iron coordination compounds to metal oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    Mihail Iacob

    2016-12-01

    Full Text Available Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe2IIIFeIIO(CH3COO6(H2O3]·2H2O (FeAc1, μ3-oxo trinuclear iron(III acetate, [Fe3O(CH3COO6(H2O3]NO3∙4H2O (FeAc2, iron furoate, [Fe3O(C4H3OCOO6(CH3OH3]NO3∙2CH3OH (FeF, iron chromium furoate, FeCr2O(C4H3OCOO6(CH3OH3]NO3∙2CH3OH (FeCrF, and an iron complex with an original macromolecular ligand (FePAZ were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination or using a nonconventional energy source (i.e., microwave or ultrasonic treatment to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

  1. From iron coordination compounds to metal oxide nanoparticles.

    Science.gov (United States)

    Iacob, Mihail; Racles, Carmen; Tugui, Codrin; Stiubianu, George; Bele, Adrian; Sacarescu, Liviu; Timpu, Daniel; Cazacu, Maria

    2016-01-01

    Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe 2 III Fe II O(CH 3 COO) 6 (H 2 O) 3 ]·2H 2 O (FeAc1), μ 3 -oxo trinuclear iron(III) acetate, [Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ]NO 3 ∙4H 2 O (FeAc2), iron furoate, [Fe 3 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeF), iron chromium furoate, FeCr 2 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

  2. Fiber optic D dimer biosensor

    Science.gov (United States)

    Glass, Robert S.; Grant, Sheila A.

    1999-01-01

    A fiber optic sensor for D dimer (a fibrinolytic product) can be used in vivo (e.g., in catheter-based procedures) for the diagnosis and treatment of stroke-related conditions in humans. Stroke is the third leading cause of death in the United States. It has been estimated that strokes and stroke-related disorders cost Americans between $15-30 billion annually. Relatively recently, new medical procedures have been developed for the treatment of stroke. These endovascular procedures rely upon the use of microcatheters. These procedures could be facilitated with this sensor for D dimer integrated with a microcatheter for the diagnosis of clot type, and as an indicator of the effectiveness, or end-point of thrombolytic therapy.

  3. Singlet fission in pentacene dimers

    Science.gov (United States)

    Zirzlmeier, Johannes; Lehnherr, Dan; Coto, Pedro B.; Chernick, Erin T.; Casillas, Rubén; Basel, Bettina S.; Thoss, Michael; Tykwinski, Rik R.; Guldi, Dirk M.

    2015-01-01

    Singlet fission (SF) has the potential to supersede the traditional solar energy conversion scheme by means of boosting the photon-to-current conversion efficiencies beyond the 30% Shockley–Queisser limit. Here, we show unambiguous and compelling evidence for unprecedented intramolecular SF within regioisomeric pentacene dimers in room-temperature solutions, with observed triplet quantum yields reaching as high as 156 ± 5%. Whereas previous studies have shown that the collision of a photoexcited chromophore with a ground-state chromophore can give rise to SF, here we demonstrate that the proximity and sufficient coupling through bond or space in pentacene dimers is enough to induce intramolecular SF where two triplets are generated on one molecule. PMID:25858954

  4. Viscosity and sedimentation behaviors of the magnetorheological suspensions with oleic acid/dimer acid as surfactants

    Science.gov (United States)

    Yang, Jianjian; Yan, Hua; Hu, Zhide; Ding, Ding

    2016-11-01

    This work deals with the role of polar interactions on the viscosity and sedimentation behaviors of magnetorheological suspensions with micro-sized magnetic particles dispersed in oil carriers. The oleic acid and dimer acid were employed to make an adjustment of the hydrophobicity of iron particles, in the interest of performing a comparative evaluation of the contributions of the surface polarity. The viscosity tests show that the adsorbed surfactant layer may impose a hindrance to the movement of iron particles in the oil medium. The polar attractions between dimer acid covered particles gave rise to a considerable increase in viscosity, indicating flocculation structure developed in the suspensions. The observed plateau-like region in the vicinity of 0.1 s-1 for MRF containing dimer acid is possibly due to the flocculation provoked by the carboxylic polar attraction, in which the structure is stable against fragmentation. Moreover, a quick recovery of the viscosity and a higher viscosity-temperature index also suggest the existence of particle-particle polar interaction in the suspensions containing dimer acid. The sedimentation measurements reveal that the steric repulsion of oleic acid plays a limited role in the stability of suspensions only if a large quantity of surfactant was used. The sedimentation results observed in the dimer acid covered particles confirm that loose and open flocculation was formed and enhanced sedimentation stability.

  5. Iron(III) species formed during iron(II) oxidation and iron-core formation in bacterioferritin of Escherichia coli

    International Nuclear Information System (INIS)

    Hawkins, C.; Treffry, A.; Mackey, J.; Williams, J.M.; Andrews, S.C.; Guest, J.R.; Harrison, P.M.

    1996-01-01

    This paper describes a preliminary investigation of the mechanisms of Fe(II) oxidation and storage of Fe(III) in the bacterioferritin of Escherichia coli (EcBFR). Using Moessbauer spectroscopy to examine the initial oxidation of iron by EcBFR it is confirmed that this ferritin exhibits 'ferroxidase' activity and is shown that dimeric and monomeric iron species are produced as intermediates. The characteristics of ferroxidase activity in EcBFR is compare d with those of human H-chain ferritin (HuHF) and discuss the different Moessbauer parameters of their dimeric iron with reference to the structures of their di-metal sites. In addition, it is presented preliminary findings suggesting that after an initial 'burst', the rate of oxidation is greatly reduced, possibly due to blockage of the ferroxidase centre by bound iron. A new component, not found in HuHF and probably representing a small cluster of Fe(III) atoms, is reported

  6. Crystal structure and Mössbauer spectroscopy of a new iron phosphate Mg{sub 2.88}Fe{sub 4.12}(PO{sub 4}){sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Saad, Y. [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia); Hidouri, M., E-mail: mourad_hidouri@yahoo.fr [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia); Álvarez-Serrano, I.; Veiga, M.L. [Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid (Spain); Wattiaux, A. [Institut de Chimie de la Matière Condensée de Bordeaux, CNRS, Université de Bordeaux I, 87 Avenue du Dr. A. Schweitzer, 33608 Pessac-Cedex (France); Amara, Mongi B. [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia)

    2014-01-25

    Highlights: • This study reports the synthesis and characterization of a new iron phosphate. • The cationic distribution is supported by a Mössbauer spectroscopy study. • The magnetic susceptibility results are discussed. -- Abstract: A new mixed valence iron phosphate Mg{sub 2.88}Fe{sub 4.12}(PO{sub 4}){sub 6} has been prepared as single crystals by the flux method and as a powder by solid state reaction and its crystal structure has been determined by X-ray diffraction. This compound crystallises in the triclinic system with space group P1{sup ¯} and a = 6.325(5) Å, b = 7.911(3) Å, c = 9.271(3) Å, α = 104.62(1)°, β = 108.41(1)° and γ = 101.24(1)° and Z = 1. Its structure is similar to that of the mineral howardevansite. It consists of Fe{sub 2}O{sub 10} bioctahedral units and MgO{sub 5} trigonal bipyramids sharing edges to form infinite zigzag chains. Such chains are linked to each other by MO{sub 6} (0.88 Mg{sup 2+} + 0.12 Fe{sup 2+}) octahedra and PO{sub 4} tetrahedra resulting in a 3D covalent framework. Magnetic measurements indicated two successive transitions at 46 K and 22 K. Mössbauer spectroscopy confirmed the mixed valence of iron and gave accurate information about its local environment.

  7. Strain mediated interaction of adatom dimers

    OpenAIRE

    Kappus, Wolfgang

    2013-01-01

    An earlier model for substrate strain mediated interactions between monomer adatoms is extended to the interaction of monomers with dimers and the interaction of dimers. While monomers (sitting on high symmetric sites) are supposed to create isotropic stress on the substrate, dimers would create anisotropic stress caused by stretching their bond. Resulting interactions are strongly angle dependent and also reflect the elastic anisotropy of the substrate. The applicability of a continuum elast...

  8. Formic acid dimers in a nitrogen matrix

    Science.gov (United States)

    Lopes, Susy; Fausto, Rui; Khriachtchev, Leonid

    2018-01-01

    Formic acid (HCOOH) dimers are studied by infrared spectroscopy in a nitrogen matrix and by ab initio calculations. We benefit from the use of a nitrogen matrix where the lifetime of the higher-energy (cis) conformer is very long (˜11 h vs. 7 min in an argon matrix). As a result, in a nitrogen matrix, a large proportion of the cis conformer can be produced by vibrational excitation of the lower-energy (trans) conformer. Three trans-trans, four trans-cis, and three cis-cis dimers are found in the experiments. The spectroscopic information on most of these dimers is enriched compared to the previous studies in an argon matrix. The cis-cis dimers of ordinary formic acid (without deuteration) are reported here for the first time. Several conformational processes are obtained using selective excitation by infrared light, some of them also for the first time. In particular, we report on the formation of cis-cis dimers upon vibrational excitation of trans-cis dimers. Tunneling decays of several dimers have been detected in the dark. The tunneling decay of cis-cis dimers of formic acid as well as the stabilization of cis units in cis-cis dimers is also observed for the first time.

  9. Preparation, Characterization, and Selectivity Study of Mixed-Valence Sulfites

    Science.gov (United States)

    Silva, Luciana A.; de Andrade, Jailson B.

    2010-01-01

    A project involving the synthesis of an isomorphic double sulfite series and characterization by classical inorganic chemical analyses is described. The project is performed by upper-level undergraduate students in the laboratory. This compound series is suitable for examining several chemical concepts and analytical techniques in inorganic…

  10. Intervalence charge transfer transition in mixed valence complexes ...

    Indian Academy of Sciences (India)

    Unknown

    volume of the reaction mixture was reduced to about 2 ml and by adding ..... obtained values for wave number (ν), molar absorbance at λIVCT (ε) and ... ∆ν1/2 values allow us to calculate values for ground state delocalisation (α2) and the.

  11. Mixed valence nanostructured Mn3O4 for supercapacitor applications

    Indian Academy of Sciences (India)

    respectively, were obtained for charge–discharge cycles at a constant current of 12.74 mA cm−2. Keywords. ... power using a Electrolux EM 18EG70SL (1000 W) oven for. 15 min at .... 22, 400), where Vm is the volume of gas adsorbed at STP,.

  12. Electron localization in a mixed-valence diniobium benzene complex.

    Science.gov (United States)

    Gianetti, Thomas L; Nocton, Grégory; Minasian, Stefan G; Kaltsoyannis, Nikolas; Kilcoyne, A L David; Kozimor, Stosh A; Shuh, David K; Tyliszczak, Tolek; Bergman, Robert G; Arnold, John

    2015-02-01

    Reaction of the neutral diniobium benzene complex {[Nb(BDI)N t Bu] 2 (μ-C 6 H 6 )} (BDI = N , N '-diisopropylbenzene-β-diketiminate) with Ag[B(C 6 F 5 ) 4 ] results in a single electron oxidation to produce a cationic diniobium arene complex, {[Nb(BDI)N t Bu] 2 (μ-C 6 H 6 )}{B(C 6 F 5 ) 4 }. Investigation of the solid state and solution phase structure using single-crystal X-ray diffraction, cyclic voltammetry, magnetic susceptibility, and multinuclear NMR spectroscopy indicates that the oxidation results in an asymmetric molecule with two chemically inequivalent Nb atoms. Further characterization using density functional theory (DFT) calculations, UV-visible, Nb L 3,2 -edge X-ray absorption near-edge structure (XANES), and EPR spectroscopies supports assignment of a diniobium complex, in which one Nb atom carries a single unpaired electron that is not largely delocalized on the second Nb atom. During the oxidative transformation, one electron is removed from the δ-bonding HOMO, which causes a destabilization of the molecule and formation of an asymmetric product. Subsequent reactivity studies indicate that the oxidized product allows access to metal-based chemistry with substrates that did not exhibit reactivity with the starting neutral complex.

  13. Moessbauer spectroscopy-nuclear hyperfine technique for studying dynamic chemical states of iron complexes

    International Nuclear Information System (INIS)

    Maeda, Y.

    2005-01-01

    A brief introduction of Moessbauer spectroscopy will be presented, followed by a discussion of the Moessbauer parameters, isomer shifts, quadrupole splittings, and spectral shapes of complexes in the presence of relaxation of the electronic states of the iron atoms. The usefulness of Moessbauer spectroscopy to demonstrate the dynamic phenomena of electronic states will be discussed in this lecture. (1) The Moessbauer spectra of mixed valence dinuclear and trinuclear iron complexes will be discussed in connection with the chemical structure of the complexes: The values of the quadrupole splittings and isomer shifts of [Fe II Fe III (bpmp) (ppa) 2 ](BF 4 ) 2 increase on raising the temperature, where Hbpmp represents 2,6-bis[bis(2- pyridylmethyl)aminoethyl]-4-methylphenol and ppa is 3-n-phenylpropionic acid. The spectra can be accounted for by postulating intramolecular electron exchange between two energetically inequivalent vibronic states Fe A 2+ Fe B 3+ and Fe A 3+ Fe B 2+ : The apparent time averaged valence states of the iron atoms are 2.2 and 2.8 on the Moessbauer time scale at 293 K. (2) The Moessbauer spectra of iron(III) spin-crossover complexes will be discussed in connection with the spin-transition rate and chemical structure of the complexes. The Moessbauer spectra of spin-crossover iron(III) complexes with LIESST (Light Induced Electronic Spin-State Transition) and of metallomesogens will be discussed to illustrate the extension of this research area by the use of Moessbauer spectroscopy.

  14. Molecular mechanics calculations on cobalt phthalocyanine dimers

    NARCIS (Netherlands)

    Heuts, J.P.A.; Schipper, E.T.W.M.; Piet, P.; German, A.L.

    1995-01-01

    In order to obtain insight into the structure of cobalt phthalocyanine dimers, molecular mechanics calculations were performed on dimeric cobalt phthalocyanine species. Molecular mechanics calculations are first presented on monomeric cobalt(II) phthalocyanine. Using the Tripos force field for the

  15. Mahler Measure, Eisenstein Series and Dimers

    NARCIS (Netherlands)

    Stienstra, J.

    2007-01-01

    This note reveals a mysterious link between the partition function of certain dimer models on 2-dimensional tori and the L-function of their spectral curves. It also relates the partition function in certain families of dimer models to Eisenstein series. http://www.arxiv.org/abs/math.NT/0502197

  16. Statistical transmutation in doped quantum dimer models.

    Science.gov (United States)

    Lamas, C A; Ralko, A; Cabra, D C; Poilblanc, D; Pujol, P

    2012-07-06

    We prove a "statistical transmutation" symmetry of doped quantum dimer models on the square, triangular, and kagome lattices: the energy spectrum is invariant under a simultaneous change of statistics (i.e., bosonic into fermionic or vice versa) of the holes and of the signs of all the dimer resonance loops. This exact transformation enables us to define the duality equivalence between doped quantum dimer Hamiltonians and provides the analytic framework to analyze dynamical statistical transmutations. We investigate numerically the doping of the triangular quantum dimer model with special focus on the topological Z(2) dimer liquid. Doping leads to four (instead of two for the square lattice) inequivalent families of Hamiltonians. Competition between phase separation, superfluidity, supersolidity, and fermionic phases is investigated in the four families.

  17. Novel covalently linked insulin dimer engineered to investigate the function of insulin dimerization

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Norrman, Mathias; Strauss, Holger M.

    2012-01-01

    An ingenious system evolved to facilitate insulin binding to the insulin receptor as a monomer and at the same time ensure sufficient stability of insulin during storage. Insulin dimer is the cornerstone of this system. Insulin dimer is relatively weak, which ensures dissociation into monomers...... in the circulation, and it is stabilized by hexamer formation in the presence of zinc ions during storage in the pancreatic ß-cell. Due to the transient nature of insulin dimer, direct investigation of this important form is inherently difficult. To address the relationship between insulin oligomerization...... and insulin stability and function, we engineered a covalently linked insulin dimer in which two monomers were linked by a disulfide bond. The structure of this covalent dimer was identical to the self-association dimer of human insulin. Importantly, this covalent dimer was capable of further oligomerization...

  18. Directed diffusion of reconstituting dimers

    International Nuclear Information System (INIS)

    Barma, Mustansir; Grynberg, Marcelo D; Stinchcombe, Robin B

    2007-01-01

    We discuss the dynamical aspects of an asymmetric version of assisted diffusion of hard core particles on a ring studied by Menon et al (1997 J. Stat. Phys. 86 1237). The asymmetry brings in phenomena like kinematic waves and effects of the Kardar-Parisi-Zhang non-linearity, which combine with the feature of strongly broken ergodicity, a characteristic of the model. A central role is played by a single non-local invariant, the irreducible string, whose interplay with the driven motion of reconstituting dimers, arising from the assisted hopping, determines the asymptotic dynamics and scaling regimes. These are investigated both analytically and numerically through sector-dependent mappings to the asymmetric simple exclusion process

  19. Directed diffusion of reconstituting dimers

    Energy Technology Data Exchange (ETDEWEB)

    Barma, Mustansir [Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400005 (India); Grynberg, Marcelo D [Departamento de Fisica, Universidad Nacional de La Plata (1900) La Plata (Argentina); Stinchcombe, Robin B [Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, Cambridge CB3 0EH (United Kingdom)

    2007-02-14

    We discuss the dynamical aspects of an asymmetric version of assisted diffusion of hard core particles on a ring studied by Menon et al (1997 J. Stat. Phys. 86 1237). The asymmetry brings in phenomena like kinematic waves and effects of the Kardar-Parisi-Zhang non-linearity, which combine with the feature of strongly broken ergodicity, a characteristic of the model. A central role is played by a single non-local invariant, the irreducible string, whose interplay with the driven motion of reconstituting dimers, arising from the assisted hopping, determines the asymptotic dynamics and scaling regimes. These are investigated both analytically and numerically through sector-dependent mappings to the asymmetric simple exclusion process.

  20. Thermodynamic data for modeling acid mine drainage problems: compilation and estimation of data for selected soluble iron-sulfate minerals

    Science.gov (United States)

    Hemingway, Bruch S.; Seal, Robert R.; Chou, I-Ming

    2002-01-01

    Enthalpy of formation, Gibbs energy of formation, and entropy values have been compiled from the literature for the hydrated ferrous sulfate minerals melanterite, rozenite, and szomolnokite, and a variety of other hydrated sulfate compounds. On the basis of this compilation, it appears that there is no evidence for an excess enthalpy of mixing for sulfate-H2O systems, except for the first H2O molecule of crystallization. The enthalpy and Gibbs energy of formation of each H2O molecule of crystallization, except the first, in the iron(II) sulfate - H2O system is -295.15 and -238.0 kJ?mol-1, respectively. The absence of an excess enthalpy of mixing is used as the basis for estimating thermodynamic values for a variety of ferrous, ferric, and mixed-valence sulfate salts of relevance to acid-mine drainage systems.

  1. Dynamic interplay between adhesive and lateral E-cadherin dimers

    DEFF Research Database (Denmark)

    Klingelhöfer, Jörg; Laur, Oscar Y; Troyanovsky, Regina B

    2002-01-01

    M. The disappearance of adhesive dimers was counterbalanced by an increase in Trp156-dependent lateral dimers. Increasing the calcium concentration to a normal level rapidly restored the original balance between adhesive and lateral dimers. We also present evidence that E-cadherin dimers in vivo have a short lifetime...

  2. The two-state dimer receptor model: a general model for receptor dimers.

    Science.gov (United States)

    Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferrada, Carla; Ferré, Sergi; Fuxe, Kjell; Cortés, Antoni; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

    2006-06-01

    Nonlinear Scatchard plots are often found for agonist binding to G-protein-coupled receptors. Because there is clear evidence of receptor dimerization, these nonlinear Scatchard plots can reflect cooperativity on agonist binding to the two binding sites in the dimer. According to this, the "two-state dimer receptor model" has been recently derived. In this article, the performance of the model has been analyzed in fitting data of agonist binding to A(1) adenosine receptors, which are an example of receptor displaying concave downward Scatchard plots. Analysis of agonist/antagonist competition data for dopamine D(1) receptors using the two-state dimer receptor model has also been performed. Although fitting to the two-state dimer receptor model was similar to the fitting to the "two-independent-site receptor model", the former is simpler, and a discrimination test selects the two-state dimer receptor model as the best. This model was also very robust in fitting data of estrogen binding to the estrogen receptor, for which Scatchard plots are concave upward. On the one hand, the model would predict the already demonstrated existence of estrogen receptor dimers. On the other hand, the model would predict that concave upward Scatchard plots reflect positive cooperativity, which can be neither predicted nor explained by assuming the existence of two different affinity states. In summary, the two-state dimer receptor model is good for fitting data of binding to dimeric receptors displaying either linear, concave upward, or concave downward Scatchard plots.

  3. The water dimer II: Theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, Anamika; Xantheas, Sotiris S.; Saykally, Richard J.

    2018-03-29

    As the archetype of hydrogen bonding between water molecules, the water dimer has been extensively studied by both theory and experiment for nearly seven decades. In this article, we present a detailed chronological review of the theoretical advances using electronic structure methods pertaining to the structure, hydrogen bonding and vibrational spectroscopy of the water dimer as well as the role of its potential energy surface in the development of classical force fields to describe intermolecular interaction in clusters and liquid water.

  4. Viscosity and sedimentation behaviors of the magnetorheological suspensions with oleic acid/dimer acid as surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jianjian; Yan, Hua; Hu, Zhide; Ding, Ding

    2016-11-01

    This work deals with the role of polar interactions on the viscosity and sedimentation behaviors of magnetorheological suspensions with micro-sized magnetic particles dispersed in oil carriers. The oleic acid and dimer acid were employed to make an adjustment of the hydrophobicity of iron particles, in the interest of performing a comparative evaluation of the contributions of the surface polarity. The viscosity tests show that the adsorbed surfactant layer may impose a hindrance to the movement of iron particles in the oil medium. The polar attractions between dimer acid covered particles gave rise to a considerable increase in viscosity, indicating flocculation structure developed in the suspensions. The observed plateau-like region in the vicinity of 0.1 s{sup −1} for MRF containing dimer acid is possibly due to the flocculation provoked by the carboxylic polar attraction, in which the structure is stable against fragmentation. Moreover, a quick recovery of the viscosity and a higher viscosity-temperature index also suggest the existence of particle-particle polar interaction in the suspensions containing dimer acid. The sedimentation measurements reveal that the steric repulsion of oleic acid plays a limited role in the stability of suspensions only if a large quantity of surfactant was used. The sedimentation results observed in the dimer acid covered particles confirm that loose and open flocculation was formed and enhanced sedimentation stability. - Highlights: • Surfactants were employed to make adjustments of the hydrophobicity of particles. • Polar attractions between particles increased the viscosity considerably. • Loose and open flocculation was formed in CI/DA suspension. • The steric repulsion of oleic acid played a limited role in the stability.

  5. Adsorption of dimeric surfactants in lamellar silicates

    Energy Technology Data Exchange (ETDEWEB)

    Balcerzak, Mateusz; Pietralik, Zuzanna [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Domka, Ludwik [Department of Metalorganic Chemistry, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań (Poland); Skrzypczak, Andrzej [Institute of Chemical Technology, Poznań University of Technology, Berdychowo 4, 60-965 Poznań (Poland); Kozak, Maciej, E-mail: mkozak@amu.edu.pl [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-12-01

    Highlights: • The intercalation of dimeric surfactants changed the morphology of MMT samples. • XRD indicated structures formed by surfactant molecules in interlayer space. • The four-step thermal decomposition of dimeric surfactant, confirms intercalation. - Abstract: The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d{sub 001}) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH{sub 2} and CH{sub 3} groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  6. Retroviral RNA Dimerization: From Structure to Functions

    Directory of Open Access Journals (Sweden)

    Noé Dubois

    2018-03-01

    Full Text Available The genome of the retroviruses is a dimer composed by two homologous copies of genomic RNA (gRNA molecules of positive polarity. The dimerization process allows two gRNA molecules to be non-covalently linked together through intermolecular base-pairing. This step is critical for the viral life cycle and is highly conserved among retroviruses with the exception of spumaretroviruses. Furthermore, packaging of two gRNA copies into viral particles presents an important evolutionary advantage for immune system evasion and drug resistance. Recent studies reported RNA switches models regulating not only gRNA dimerization, but also translation and packaging, and a spatio-temporal characterization of viral gRNA dimerization within cells are now at hand. This review summarizes our current understanding on the structural features of the dimerization signals for a variety of retroviruses (HIVs, MLV, RSV, BLV, MMTV, MPMV…, the mechanisms of RNA dimer formation and functional implications in the retroviral cycle.

  7. D-dimers (DD) in CVST.

    Science.gov (United States)

    Wang, Hui Fang; Pu, Chuan Qiang; Yin, Xi; Tian, Cheng Lin; Chen, Ting; Guo, Jun Hong; Shi, Qiang

    2017-06-01

    We were interested in further confirming whether D-dimers (DD) are indeed elevated in cerebral venous sinus thrombosis (CVST) as reported in those studies. CVST patients who had a plasma D-dimer test (139 cases) were included and divided into two groups: elevated D-dimer group (EDG) (>0.5 μg/mL; 65 cases) and normal D-dimer group (NDG) (≤0.5 μg/mL; 74 cases). The two groups were compared in terms of demographic data, clinical manifestation, laboratory and imaging data, using inferential statistical methods. The chi-squared and Fisher exact test showed that, compared to the NDG (74 cases), patients with elevated D-dimer levels were more likely to have a shorter symptom duration (SD) (30 ± 83.9 versus 90 ± 58.9 d, p = 0.003), more risk factors (75.4% versus 52.7%, p = 0.006), higher multiple venous sinus involvement (75.4% versus 59.5%, p = 0.037), increased fibrinogen (43.1% versus 18.9%, p = 0.037) and higher levels of blood glucose (18.3% versus 11%, p = 0.037). According to correlation analyses, D-dimer levels were positively correlated with number of venous sinuses involvement (NVS) (r = 0.321, p = 0.009) in the EDG. Multivariate logistic regression analysis showed that SD (OR, 0.025; 95% CI, 1.324-6.043; p = 0.000), NVS (OR, 1.573; 95% CI, 1.15-2.151; p = 0.005) and risk factors (OR, 3.321; 95% CI, 1.451-7.564; p = 0.004) were significantly different between the two groups. D-dimer is elevated in patients with acute/subacute CVST.

  8. Novel covalently linked insulin dimer engineered to investigate the function of insulin dimerization.

    Directory of Open Access Journals (Sweden)

    Tine N Vinther

    Full Text Available An ingenious system evolved to facilitate insulin binding to the insulin receptor as a monomer and at the same time ensure sufficient stability of insulin during storage. Insulin dimer is the cornerstone of this system. Insulin dimer is relatively weak, which ensures dissociation into monomers in the circulation, and it is stabilized by hexamer formation in the presence of zinc ions during storage in the pancreatic β-cell. Due to the transient nature of insulin dimer, direct investigation of this important form is inherently difficult. To address the relationship between insulin oligomerization and insulin stability and function, we engineered a covalently linked insulin dimer in which two monomers were linked by a disulfide bond. The structure of this covalent dimer was identical to the self-association dimer of human insulin. Importantly, this covalent dimer was capable of further oligomerization to form the structural equivalent of the classical hexamer. The covalently linked dimer neither bound to the insulin receptor, nor induced a metabolic response in vitro. However, it was extremely thermodynamically stable and did not form amyloid fibrils when subjected to mechanical stress, underlining the importance of oligomerization for insulin stability.

  9. Calix[4]arene supported clusters: a dimer of [Mn(III)Mn(II)] dimers

    DEFF Research Database (Denmark)

    Taylor, Stephanie M; McIntosh, Ruaraidh D; Beavers, Christine M

    2011-01-01

    Phosphinate ligands allow for the transformation of a calix[4]arene supported [Mn(III)(2)Mn(II)(2)] tetramer cluster motif into an unusual [Mn(III)Mn(II)](2) dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates....

  10. Plasmonic nanospherical dimers for color pixels

    KAUST Repository

    Alrasheed, Salma

    2018-04-20

    Display technologies are evolving more toward higher resolution and miniaturization. Plasmonic color pixels can offer solutions to realize such technologies due to their sharp resonances and selective scattering and absorption at particular wavelengths. Metal nanosphere dimers are capable of supporting plasmon resonances that can be tuned to span the entire visible spectrum. In this article, we demonstrate numerically bright color pixels that are highly polarized and broadly tuned using periodic arrays of metal nanosphere dimers on a glass substrate. We show that it is possible to obtain RGB pixels in the reflection mode. The longitudinal plasmon resonance of nanosphere dimers along the axis of the dimer is the main contributor to the color of the pixel, while far-field diffractive coupling further enhances and tunes the plasmon resonance. The computational method used is the finite-difference time-domain method. The advantages of this approach include simplicity of the design, bright coloration, and highly polarized function. In addition, we show that it is possible to obtain different colors by varying the angle of incidence, the periodicity, the size of the dimer, the gap, and the substrate thickness.

  11. Radiation chemistry of aromatic dimer radical cations

    International Nuclear Information System (INIS)

    Okamoto, Kazumasa; Tagawa, Seiichi

    2009-01-01

    π-π Interactions of aromatic molecules are paid attention much in many fields, especially biology, chemistry, and applied physics, represented as protein, DNA, electron donor-accepter complexes, charge transfers, and self assembly molecules. Aromatic molecules including benzene rings are the simplest case to study the π-π interactions. To interpret the charge resonance (CR) structure in the dimer radical cations, spectroscopic and ESR methods have been carried out. The spectroscopic study on the dimer radical ion of molecules with two chromophores would be profitable to identify the electronic and configurational properties. In this article, dynamics of the dimer radical cation of benzenes, polystyrenes, and resist polymers is described on the basis of direct observation of CR band by the nanosecond pulse radiolysis and low temperature γ-radiolysis methods. (author)

  12. Photoionization of helium dimers; Photoionisation von Heliumdimeren

    Energy Technology Data Exchange (ETDEWEB)

    Havermeier, Tilo

    2010-06-09

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  13. Hyperfine interactions of iron implanted into aluminium

    International Nuclear Information System (INIS)

    Sawicka, B.D.; Drwiega, M.; Sawicki, J.; Stanek, J.

    1976-01-01

    Systematical investigations of the stable 57 Fe implanted into Al at energies of 10 to 70 keV and doses of 10 14 to 2.10 17 ions/cm 2 were performed by means of conversion electron Moessbauer spectroscopy at room and liquid nitrogen temperatures. The spectra measured were interpreted as originated by iron monomers (single line) and by iron associations, mostly dimers (dublet). The isomer shifts of both components differ considerably and are constant against iron concentration. The ratio of both components depends strongly on the iron concentration. The quadrupole splitting of the doublet rises with the concentration, the rise being reproduced by computer simulations of efg distributions in densely packed random charge defected lattices. The annealing processes were investigated. The spectra of the Fe-Al samples made by ion implantation and by a splat-cooling technique are well comparable. (author)

  14. Photon Propagation through Linearly Active Dimers

    Directory of Open Access Journals (Sweden)

    José Delfino Huerta Morales

    2017-06-01

    Full Text Available We provide an analytic propagator for non-Hermitian dimers showing linear gain or losses in the quantum regime. In particular, we focus on experimentally feasible realizations of the PT -symmetric dimer and provide their mean photon number and second order two-point correlation. We study the propagation of vacuum, single photon spatially-separable, and two-photon spatially-entangled states. We show that each configuration produces a particular signature that might signal their possible uses as photon switches, semi-classical intensity-tunable sources, or spatially entangled sources to mention a few possible applications.

  15. On the asymptotics of dimers on tori

    OpenAIRE

    Kenyon, Richard W.; Sun, Nike; Wilson, David B.

    2013-01-01

    We study asymptotics of the dimer model on large toric graphs. Let $\\mathbb L$ be a weighted $\\mathbb{Z}^2$-periodic planar graph, and let $\\mathbb{Z}^2 E$ be a large-index sublattice of $\\mathbb{Z}^2$. For $\\mathbb L$ bipartite we show that the dimer partition function on the quotient $\\mathbb{L}/(\\mathbb{Z}^2 E)$ has the asymptotic expansion $\\exp[A f_0 + \\text{fsc} + o(1)]$, where $A$ is the area of $\\mathbb{L}/(\\mathbb{Z}^2 E)$, $f_0$ is the free energy density in the bulk, and $\\text{fsc...

  16. Sigma- versus Pi-Dimerization Modes of Triangulene.

    Science.gov (United States)

    Mou, Zhongyu; Kertesz, Miklos

    2018-04-20

    We show that the diradicaloid triangulene, a graphene nano-flake molecule, can aggregate in a variety of dimerization modes. We found by density functional theory modeling a number of triangulene dimers including six doubly bonded σ-dimers in addition to the previously reported six pancake bonded π-dimer isomers. The σ-dimers display a wide range of stabilities: the interaction energy of the most stable σ-dimer is -25.17 kcal mol -1 . Besides the doubly bonded σ-dimers with closed shell ground states, we also found an open-shell singly σ-bonded diradicaloid dimer. We found an interesting isomerization route between a doubly bonded σ-dimer, a singly bonded σ-dimer with a low-lying triplet state and two π-bonded dimers with low-lying quintet states. Derivatives of triangulene, trioxo-triangulenes (TOTs) have been previously characterized experimentally. Here, we show the reasons why so far only the π-dimer but not the σ-dimer was experimentally observed for all TOTs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Structural insights into the intertwined dimer of fyn SH2.

    Science.gov (United States)

    Huculeci, Radu; Garcia-Pino, Abel; Buts, Lieven; Lenaerts, Tom; van Nuland, Nico

    2015-12-01

    Src homology 2 domains are interaction modules dedicated to the recognition of phosphotyrosine sites incorporated in numerous proteins found in intracellular signaling pathways. Here we provide for the first time structural insight into the dimerization of Fyn SH2 both in solution and in crystalline conditions, providing novel crystal structures of both the dimer and peptide-bound structures of Fyn SH2. Using nuclear magnetic resonance chemical shift analysis, we show how the peptide is able to eradicate the dimerization, leading to monomeric SH2 in its bound state. Furthermore, we show that Fyn SH2's dimer form differs from other SH2 dimers reported earlier. Interestingly, the Fyn dimer can be used to construct a completed dimer model of Fyn without any steric clashes. Together these results extend our understanding of SH2 dimerization, giving structural details, on one hand, and suggesting a possible physiological relevance of such behavior, on the other hand. © 2015 The Protein Society.

  18. Synthesis and characterization of the Bis- Cyclometalating Ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl and its use in the preparation of bimetallic M(II), M(IV) (M = Pt, Pd) and mixed-valence Pt(II)-Pt(IV) complexes via a dilithio-derivative. Crystal structure of the Pd dimer [ClPd{2,6-(Me2NCH2)2C6H2}]2,

    NARCIS (Netherlands)

    Koten, G. van; Lagunas, M.C.; Gossage, R.A.; Spek, A.L.

    1998-01-01

    The potentially bis-cyclometalating ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl, was prepared from 3,5-(Me2NCH2)2C6H3Br in a one-pot synthesis involving lithium-halogen exchange, transmetalation, and reductive-elimination reactions. This ligand undergoes selective dilithiation in the 4

  19. Synthesis and characterization of monomeric and dimeric ...

    African Journals Online (AJOL)

    The two complexes are isostructural, with the central metal atom lying on a crystallographic 2-fold axis. Both complexes are approximately octahedral, the coordination being provided by two trans pyridine nitrogen atoms and two cis amine nitrogen atoms from the oxime ligands, and by two cis chlorides. The dimeric ...

  20. The hyperfine spectrum of hydrogen dimers

    International Nuclear Information System (INIS)

    Verberne, J.F.C.

    1979-01-01

    The authors' aim was to obtain the level scheme for the hydrogen dimers and to investigate the angle dependent interactions by analyzing the zero magnetic field hyperfine spectrum of the ortho-ortho and ortho-para species. The results were tested by several recent semi-empirical and ab initio potentials. (Auth.)

  1. What factors control dimerization of coniferyl alcohol?

    Science.gov (United States)

    Carl J. Houtman

    1999-01-01

    Data suggest that the dimerization of coniferyl alcohol is not under thermodynamic control. In this study, molecular dynamics calculations were used to estimate the effect of the solvent environment. In water, the coniferyl alcohol radicals were forced to associate by the formation of a solvent cage. In glycerol, the solvent cage effect appeared to be absent. These...

  2. Determination of the Tetramer-Dimer Equilibrium Constant of Rabbit ...

    African Journals Online (AJOL)

    Hemoglobin is a tetrameric protein which is able to dissociate into dimers. The dimers can in turn dissociate into tetramers. It has been found that dimers are more reactive than tetramers. The difference in the reactivity of these two species has been used to determine the tetramerdimer dissociation constant of various ...

  3. Stochastic optimization-based study of dimerization kinetics

    Indian Academy of Sciences (India)

    To this end, we study dimerization kinetics of protein as a model system. We follow the dimerization kinetics using a stochastic simulation algorithm and ... optimization; dimerization kinetics; sensitivity analysis; stochastic simulation ... tion in large molecules and clusters, or the design ..... An unbiased strategy of allocating.

  4. Cast irons

    CERN Document Server

    1996-01-01

    Cast iron offers the design engineer a low-cost, high-strength material that can be easily melted and poured into a wide variety of useful, and sometimes complex, shapes. This latest handbook from ASM covers the entire spectrum of one of the most widely used and versatile of all engineered materials. The reader will find the basic, but vital, information on metallurgy, solidification characteristics, and properties. Extensive reviews are presented on the low-alloy gray, ductile, compacted graphite, and malleable irons. New and expanded material has been added covering high-alloy white irons used for abrasion resistance and high-alloy graphitic irons for heat and corrosion resistance. Also discussed are melting furnaces and foundry practices such as melting, inoculation, alloying, pouring, gating and rising, and molding. Heat treating practices including stress relieving, annealing, normalizing, hardening and tempering, autempering (of ductile irons), and surface-hardening treatments are covered, too. ASM Spec...

  5. Transformation of vivianite by anaerobic nitrate-reducing iron-oxidizing bacteria.

    Science.gov (United States)

    Miot, J; Benzerara, K; Morin, G; Bernard, S; Beyssac, O; Larquet, E; Kappler, A; Guyot, F

    2009-06-01

    In phosphate-rich environments, vivianite (Fe(II)(3)(PO(4))(2), 8H(2)O) is an important sink for dissolved Fe(II) and is considered as a very stable mineral due to its low solubility at neutral pH. In the present study, we report the mineralogical transformation of vivianite in cultures of the nitrate-reducing iron-oxidizing bacterial strain BoFeN1 in the presence of dissolved Fe(II). Vivianite was first transformed into a greenish phase consisting mostly of an amorphous mixed valence Fe-phosphate. This precipitate became progressively orange and the final product of iron oxidation consisted of an amorphous Fe(III)-phosphate. The sub-micrometer analysis by scanning transmission X-ray microscopy of the iron redox state in samples collected at different stages of the culture indicated that iron was progressively oxidized at the contact of the bacteria and at a distance from the cells in extracellular minerals. Iron oxidation in the extracellular minerals was delayed by a few days compared with cell-associated Fe-minerals. This led to strong differences of Fe redox in between these two types of minerals and finally to local heterogeneities of redox within the sample. In the absence of dissolved Fe(II), vivianite was not significantly transformed by BoFeN1. Whereas Fe(II) oxidation at the cell contact is most probably directly catalyzed by the bacteria, vivianite transformation at a distance from the cells might result from oxidation by nitrite. In addition, processes leading to the export of Fe(III) from bacterial oxidation sites to extracellular minerals are discussed including some involving colloids observed by cryo-transmission electron microscopy in the culture medium.

  6. Compositional and structural variabilities of Mg-rich iron oxide spinels from tuffite

    Directory of Open Access Journals (Sweden)

    W. N. Mussel

    1999-12-01

    Full Text Available Maghemite (γFe2O3 from tuffite is exceptionally rich in Mg, relatively to most of those reportedly found in other mafic lithosystems. To investigate in detail the compositional and structural variabilities of this natural magnetic iron oxide, sets of crystals were isolated from samples collected at different positions in a tuffite weathering mantle. These sets of crystal were individually powdered and studied by X-ray diffractometry, Mössbauer spectroscopy, magnetization measurements and chemical analysis. Lattice parameter of the cubic cell (a0 was found to vary from 0.834(1 to 0.8412(1 nm. Lower a0-values are characteristic of maghemite whereas higher ones are related to a magnetite precursor. FeO content ranges up to 17 mass % and spontaneous magnetization ranges from 8 to 32 J T-1 kg-1. Zero-field room temperature Mössbauer spectra are rather complex, indicating that the hyperfine field distributions due to Fe3+ and mixed valence Fe3+/2+ overlap. The structural variabilities of the (Mg, Ti-rich iron oxide spinels is essentially related to the range of chemical composition of its precursor (Mg, Ti-rich magnetite, and probably to the extent to which it has been oxidized during transformation in soil.

  7. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... risk for iron-deficiency anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron-rich foods, ... iron-fortified foods that have iron added. Vegetarian diets can provide enough iron if you choose nonmeat ...

  8. Pyrimidine dimer formation and repair in human skin

    International Nuclear Information System (INIS)

    Sutherland, B.M.; Harber, L.C.; Kochevar, I.E.

    1980-01-01

    Cyclobutyl pyrimidine dimers have been detected in the DNA of human skin following in vivo irradiation with suberythermal doses of ultraviolet (UV) radiation from FS-20 sun lamp fluorescent tubes. Dimers were assayed by treatment of extracted DNA with Micrococus luteus UV-specific endonuclease, alkaline agarose electrophoresis, and ethidum bromide staining. This technique, in contrast to conventional dimer assays, can be used with nonradioactive DNA and is optimal at low UV light doses. These data suggest that some dimer disappearance by excision repair occurs within 20 min of UV irradiation and that photoreactivation of dimers can make a contribution to the total repair process

  9. Fibrillar dimer formation of islet amyloid polypeptides

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Chi-cheng [Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States); de Pablo, Juan J. [Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  10. An introduction to the dimer model

    International Nuclear Information System (INIS)

    Kenyon, R.

    2004-01-01

    A perfect matching of a graph is a subset of edges which covers every vertex exactly once, that is, for every vertex there is exactly one edge in the set with that vertex as endpoint. The dimer model is the study of the set of perfect matchings of a (possibly infinite) graph. The most well-known example is when the graph is Z 2 , for which perfect matchings are equivalent (via a simple duality) to domino tilings, that is, tilings of the plane with 2 x 1 and 1 x 2 rectangles. In the first three sections we study domino tilings of the plane and of finite polygonal regions, or equivalently, perfect matchings on Z 2 and subgraphs of Z 2 . In the last two sections we study the FK-percolation model and the dimer model on a more general family of planar graphs

  11. Revisiting the Optical PT-Symmetric Dimer

    Directory of Open Access Journals (Sweden)

    José Delfino Huerta Morales

    2016-08-01

    Full Text Available Optics has proved a fertile ground for the experimental simulation of quantum mechanics. Most recently, optical realizations of PT -symmetric quantum mechanics have been shown, both theoretically and experimentally, opening the door to international efforts aiming at the design of practical optical devices exploiting this symmetry. Here, we focus on the optical PT -symmetric dimer, a two-waveguide coupler where the materials show symmetric effective gain and loss, and provide a review of the linear and nonlinear optical realizations from a symmetry-based point of view. We go beyond a simple review of the literature and show that the dimer is just the smallest of a class of planar N-waveguide couplers that are the optical realization of the Lorentz group in 2 + 1 dimensions. Furthermore, we provide a formulation to describe light propagation through waveguide couplers described by non-Hermitian mode coupling matrices based on a non-Hermitian generalization of the Ehrenfest theorem.

  12. Palmitoylated APP Forms Dimers, Cleaved by BACE1.

    Directory of Open Access Journals (Sweden)

    Raja Bhattacharyya

    Full Text Available A major rate-limiting step for Aβ generation and deposition in Alzheimer's disease brains is BACE1-mediated cleavage (β-cleavage of the amyloid precursor protein (APP. We previously reported that APP undergoes palmitoylation at two cysteine residues (Cys186 and Cys187 in the E1-ectodomain. 8-10% of total APP is palmitoylated in vitro and in vivo. Palmitoylated APP (palAPP shows greater preference for β-cleavage than total APP in detergent resistant lipid rafts. Protein palmitoylation is known to promote protein dimerization. Since dimerization of APP at its E1-ectodomain results in elevated BACE1-mediated cleavage of APP, we have now investigated whether palmitoylation of APP affects its dimerization and whether this leads to elevated β-cleavage of the protein. Here we report that over 90% of palAPP is dimerized while only ~20% of total APP forms dimers. PalAPP-dimers are predominantly cis-oriented while total APP dimerizes in both cis- and trans-orientation. PalAPP forms dimers 4.5-times more efficiently than total APP. Overexpression of the palmitoylating enzymes DHHC7 and DHHC21 that increase palAPP levels and Aβ release, also increased APP dimerization in cells. Conversely, inhibition of APP palmitoylation by pharmacological inhibitors reduced APP-dimerization in coimmunoprecipitation and FLIM/FRET assays. Finally, in vitro BACE1-activity assays demonstrate that palmitoylation-dependent dimerization of APP promotes β-cleavage of APP in lipid-rich detergent resistant cell membranes (DRMs, when compared to total APP. Most importantly, generation of sAPPβ-sAPPβ dimers is dependent on APP-palmitoylation while total sAPPβ generation is not. Since BACE1 shows preference for palAPP dimers over total APP, palAPP dimers may serve as novel targets for effective β-cleavage inhibitors of APP as opposed to BACE1 inhibitors.

  13. Oxidation of NAD dimers by horseradish peroxidase.

    OpenAIRE

    Avigliano, L; Carelli, V; Casini, A; Finazzi-Agrò, A; Liberatore, F

    1985-01-01

    Horseradish peroxidase catalyses the oxidation of NAD dimers, (NAD)2, to NAD+ in accordance with a reaction that is pH-dependent and requires 1 mol of O2 per 2 mol of (NAD)2. Horseradish peroxidase also catalyses the peroxidation of (NAD)2 to NAD+. In contrast, bacterial NADH peroxidase does not catalyse the peroxidation or the oxidation of (NAD)2. A free-radical mechanism is proposed for both horseradish-peroxidase-catalysed oxidation and peroxidation of (NAD)2.

  14. On the dimerization of linear polymers

    International Nuclear Information System (INIS)

    Aragao Carvalho, C. de.

    1988-08-01

    We use the continuum limit of the Su-Schrieffer-Heeger model for linear polymers to construct its effective potential (Gibbs free energy) both at zero and finite temperature. We study both trans and cis-polymers. Our results show that, depending on a renormalization condition to be extracted from experiment, there are several possibilities for the minima of the dimerized ground state of cis-polymers. All calculations are done in the one-loop approximation. (author). 16 refs, 3 figs

  15. Entanglement in a Dimerized Antiferromagnetic Heisenberg Chain

    OpenAIRE

    Hao, Xiang; Zhu, Shiqun

    2008-01-01

    The entanglement properties in an antiferromagnetic dimerized Heisenberg spin-1/2 chain are investigated. The entanglement gap, which is the difference between the ground-state energy and the minimal energy that any separable state can attain, is calculated to detect the entanglement. It is found that the entanglement gap can be increased by varying the alternation parameter. Through thermal energy, the witness of the entanglement can determine a characteristic temperature below that an entan...

  16. Dimer monomer transition and dimer re-formation play important role for ATM cellular function during DNA repair

    International Nuclear Information System (INIS)

    Du, Fengxia; Zhang, Minjie; Li, Xiaohua; Yang, Caiyun; Meng, Hao; Wang, Dong; Chang, Shuang; Xu, Ye; Price, Brendan; Sun, Yingli

    2014-01-01

    Highlights: • ATM phosphorylates the opposite strand of the dimer in response to DNA damage. • The PETPVFRLT box of ATM plays a key role in its dimer dissociation in DNA repair. • The dephosphorylation of ATM is critical for dimer re-formation after DNA repair. - Abstract: The ATM protein kinase, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, mediates responses to ionizing radiation in mammalian cells. Here we show that ATM is held inactive in unirradiated cells as a dimer and phosphorylates the opposite strand of the dimer in response to DNA damage. Cellular irradiation induces rapid intermolecular autophosphorylation of serine 1981 that causes dimer dissociation and initiates cellular ATM kinase activity. ATM cannot phosphorylate the substrates when it could not undergo dimer monomer transition. After DNA repair, the active monomer will undergo dephosphorylation to form dimer again and dephosphorylation is critical for dimer re-formation. Our work reveals novel function of ATM dimer monomer transition and explains why ATM dimer monomer transition plays such important role for ATM cellular activity during DNA repair

  17. IRON DOME

    African Journals Online (AJOL)

    6 Israeli Navy 'First Arm of the Sea: The Successful Interception of the Iron Dome Rocket .... sky to destroy them whilst in flight to minimise civilian casualties. ..... Including The Moon and Celestial Bodies.53 Demeyere further emphasises the.

  18. Iron overdose

    Science.gov (United States)

    ... tracing) X-ray to detect and track iron tablets through the stomach and intestines Treatment may include: ... BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics . 20th ed. Philadelphia, PA: Elsevier; 2016: ...

  19. Peptides Interfering 3A Protein Dimerization Decrease FMDV Multiplication.

    Directory of Open Access Journals (Sweden)

    Mónica González-Magaldi

    Full Text Available Nonstructural protein 3A is involved in relevant functions in foot-and-mouth disease virus (FMDV replication. FMDV 3A can form homodimers and preservation of the two hydrophobic α-helices (α1 and α2 that stabilize the dimer interface is essential for virus replication. In this work, small peptides mimicking residues involved in the dimer interface were used to interfere with dimerization and thus gain insight on its biological function. The dimer interface peptides α1, α2 and that spanning the two hydrophobic α-helices, α12, impaired in vitro dimer formation of a peptide containing the two α-helices, this effect being higher with peptide α12. To assess the effect of dimer inhibition in cultured cells, the interfering peptides were N-terminally fused to a heptaarginine (R7 sequence to favor their intracellular translocation. Thus, when fused to R7, interference peptides (100 μM were able to inhibit dimerization of transiently expressed 3A, the higher inhibitions being found with peptides α1 and α12. The 3A dimerization impairment exerted by the peptides correlated with significant, specific reductions in the viral yield recovered from peptide-treated FMDV infected cells. In this case, α2 was the only peptide producing significant reductions at concentrations lower than 100 μM. Thus, dimer interface peptides constitute a tool to understand the structure-function relationship of this viral protein and point to 3A dimerization as a potential antiviral target.

  20. Iron Hydroxide Minerals Drive Organic and Phosphorus Chemistry in Subsurface Redox / pH Gradients

    Science.gov (United States)

    Flores, E.; Barge, L. M.; VanderVelde, D.; Baum, M.

    2017-12-01

    Iron minerals, particularly iron oxides and oxyhydroxides, are prevalent on Mars and may exist in mixed valence or even reduced states beneath the oxidized surface. Iron (II,III) hydroxides, including green rust, are reactive and potentially catalytic minerals that can absorb and concentrate charged species, while also driving chemical reactions. These minerals are highly redox-sensitive and the presence of organics and/or phosphorus species could affect their mineralogy and/or stability. Conversely, the minerals might be able to drive chemical processes such as amino acid formation, phosphorus oxyanion reactions, or could simply selectively preserve organic species via surface adsorption. In an open aqueous sediment column, soluble products of mineral-driven reactions could also diffuse to sites of different chemical conditions to react even further. We synthesized Fe-hydroxide minerals under various conditions relevant to early Earth and ancient Mars (>3.0 Gyr), anoxically and in the presence of salts likely to have been present in surface or ground waters. Using these minerals we conducted experiments to test whether iron hydroxides could promote amino acid formation, and how the reaction is affected by subsurface gradients of redox, pH, and temperature. We also tested the adsorption of organic and phosphorus species onto Fe-hydroxide minerals at different conditions within the gradients. The suite of organic or phosphorus signatures that may be found in a particular mineral system is a combination of what is synthesized there, what is preferentially concentrated / retained there, and what is preserved against degradation. Further work is needed to determine how these processes could have proceeded on Mars and what mineral-organic signatures, abiotic or otherwise, would be produced from such processes.

  1. Dimerization in the Grb7 Protein

    OpenAIRE

    Peterson, Tabitha A.; Benallie, Renee L.; Bradford, Andrew M.; Pias, Sally C.; Yazzie, Jaron.; Lor, Siamee N.; Haulsee, Zachary M.; Park, Chad K.; Johnson, Dennis L.; Rohrschneider, Larry R.; Spuches, Anne.; Lyons, Barbara A.

    2012-01-01

    In previous studies, we showed that the tyrosine phosphorylation state of growth factor receptor–bound protein 7 (Grb7) affects its ability to bind to the transcription regulator FHL2 and the cortactin-interacting protein, human HS-1-associated protein-1. Here, we present results describing the importance of dimerization in the Grb7–Src homology 2 (SH2) domain in terms of its structural integrity and the ability to bind phosphorylated tyrosine peptide ligands. A tyrosine phosphorylation-mimic...

  2. Dimerization and oligomerization of the chaperone calreticulin

    DEFF Research Database (Denmark)

    Jørgensen, Charlotte S; Ryder, L Rebekka; Steinø, Anne

    2003-01-01

    protein. Using PAGE, urea gradient gel electrophoresis, capillary electrophoresis and MS, we show that dimerization through the SH group can be induced by lowering the pH to 5-6, heating, or under conditions that favour partial unfolding such as urea concentrations above 2.6 m or SDS concentrations above...... that favour partial unfolding or an intramolecular local conformational change that allows oligomerization, resulting in a heterogeneous mixture of oligomers consisting of up to 10 calreticulin monomers. The oligomeric calreticulin was very stable, but oligomerization was partially reversed by addition of 8 m...

  3. Dimeric assembly of enterocyte brush border enzymes

    DEFF Research Database (Denmark)

    Danielsen, E M

    1994-01-01

    The noncovalent, dimeric assembly of small intestinal brush border enzymes was studied by sedimentation analysis in density gradients of extracts of pulse-labeled pig jejunal mucosal explants. Like aminopeptidase N (EC 3.4.11.2), sucrase-isomaltase (EC 3.2.1.48-10), aminopeptidase A (EC 3...... appearance of the liposome-reconstituted enzyme [Norén et al. (1986) J. Biol. Chem. 261, 12306-12309], showing only the inner, membrane-anchored domains of the monomers to be in close contact with one another while the outer domains are far apart. In contrast to the other brush border enzymes studied...

  4. Dimer pair correlations on the brick lattice

    International Nuclear Information System (INIS)

    Yokoi, C.S.O.; Nagle, J.F.; Sulinas, S.R.

    1986-01-01

    Using exact methods, pair-correlation functions are studied in the dimer model defined on a brick lattice. At long distances these functions exhibit strongly anisotropic algebraic decay and, near criticality, the length scales diverge differently in the two principal directions. The critical exponents are v /sub x/ =1/2 and v /sub y/ =1. These results are in agreement with deductions drawn from recent exact finite-size scaling calculations. We also interpret our results in the light of domain wall theories of commensurate-incommensurate transitions, and in particular we study the relation of the present model to the discrete version of the Pokrovsky-Talapov model introduced by Villain

  5. Tunneling anisotropic magnetoresistance via molecular π orbitals of Pb dimers

    Science.gov (United States)

    Schöneberg, Johannes; Ferriani, Paolo; Heinze, Stefan; Weismann, Alexander; Berndt, Richard

    2018-01-01

    Pb dimers on a ferromagnetic surface are shown to exhibit large tunneling anisotropic magnetoresistance (TAMR) due to molecular π orbitals. Dimers oriented differently with respect to the magnetization directions of a ferromagnetic Fe double layer on W(110) were made with a scanning tunneling microscope. Depending on the dimer orientations, TAMR is absent or as large as 20% at the Fermi level. General arguments and first-principles calculations show that mixing of molecular orbitals due to spin-orbit coupling, which leads to TAMR, is maximal when the magnetization is oriented parallel to the dimer axis.

  6. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... iron-rich foods, especially during certain stages of life when more iron is needed, such as childhood and pregnancy. Good sources of iron are meat, poultry, fish, and iron- ...

  7. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... that are good sources of iron include dried beans, dried fruits, eggs, lean red meat, salmon, iron- ... of iron, including iron-fortified breads and cereals, beans, tofu, dried fruits, and spinach and other dark ...

  8. Iron in diet

    Science.gov (United States)

    ... Reasonable amounts of iron are also found in lamb, pork, and shellfish. Iron from vegetables, fruits, grains, ... strawberries, tomatoes, and potatoes) also increase iron absorption. Cooking foods in a cast-iron skillet can also ...

  9. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... from developing iron-deficiency anemia. Foods that are good sources of iron include dried beans, dried fruits, ... iron is needed, such as childhood and pregnancy. Good sources of iron are meat, poultry, fish, and ...

  10. Iron-Deficiency Anemia

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    Full Text Available ... you are diagnosed with iron-deficiency anemia. Risk Factors You may have an increased risk for iron- ... iron-deficiency anemia if you have certain risk factors , including pregnancy. To prevent iron-deficiency anemia, your ...

  11. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... for your body to absorb iron from the gastrointestinal tract (GI tract). Blood loss When you lose blood, ... iron deficiency. Endurance athletes lose iron through their gastrointestinal tracts. They also lose iron through the breakdown of ...

  12. Iron-Deficiency Anemia

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    Full Text Available ... iron in your body is low. For this reason, other iron tests are also done. Ferritin measure ... iron is needed, such as childhood and pregnancy. Good sources of iron are meat, poultry, fish, and ...

  13. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... develop new therapies for conditions that affect the balance of iron in the body and lead to ... Disease Control and Prevention) Iron - Health Professional Fact Sheet (NIH) Iron Dietary Supplement Fact Sheet (NIH) Iron- ...

  14. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... to moderate iron-deficiency anemia, or red blood cell transfusion for severe iron-deficiency anemia. You may ... body needs iron to make healthy red blood cells. Iron-deficiency anemia usually develops over time because ...

  15. Iron-Deficiency Anemia

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    Full Text Available ... enough iron-rich foods, such as meat and fish, may result in you getting less than the ... pregnancy. Good sources of iron are meat, poultry, fish, and iron-fortified foods that have iron added. ...

  16. Iron Dextran Injection

    Science.gov (United States)

    Iron dextran injection is used to treat iron-deficiency anemia (a lower than normal number of red blood cells ... treated with iron supplements taken by mouth. Iron dextran injection is in a class of medications called ...

  17. Iron-Deficiency Anemia

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    Full Text Available ... and severity. Treatments may include iron supplements, procedures, surgery, and dietary ... iron supplements, also called iron pills or oral iron, by mouth once or several times a ...

  18. Iron-Deficiency Anemia

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    Full Text Available ... developing iron-deficiency anemia. Foods that are good sources of iron include dried beans, dried fruits, eggs, ... is needed, such as childhood and pregnancy. Good sources of iron are meat, poultry, fish, and iron- ...

  19. Iron deficiency

    DEFF Research Database (Denmark)

    Schou, Morten; Bosselmann, Helle; Gaborit, Freja

    2015-01-01

    BACKGROUND: Both iron deficiency (ID) and cardiovascular biomarkers are associated with a poor outcome in heart failure (HF). The relationship between different cardiovascular biomarkers and ID is unknown, and the true prevalence of ID in an outpatient HF clinic is probably overlooked. OBJECTIVES.......043). CONCLUSION: ID is frequent in an outpatient HF clinic. ID is not associated with cardiovascular biomarkers after adjustment for traditional confounders. Inflammation, but not neurohormonal activation is associated with ID in systolic HF. Further studies are needed to understand iron metabolism in elderly HF...

  20. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Research Home / < Back To Health Topics / Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer en español Iron-deficiency ... iron-deficiency anemia. Blood tests to screen for iron-deficiency anemia To screen for iron-deficiency anemia, your doctor ...

  1. Fibrillar dimer formation of islet amyloid polypeptides

    Directory of Open Access Journals (Sweden)

    Chi-cheng Chiu

    2015-09-01

    Full Text Available Amyloid deposits of human islet amyloid polypeptide (hIAPP, a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  2. Iron and iron derived radicals

    International Nuclear Information System (INIS)

    Borg, D.C.; Schaich, K.M.

    1987-04-01

    We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fast! Think small! In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab

  3. Excitonic Behavior of Rhodamine Dimers: A Single-Molecule Study

    NARCIS (Netherlands)

    Hernando Campos, J.; van der Schaaf, Martijn; van Dijk, E.M.H.P.; Sauer, Markus; Garcia Parajo, M.F.; van Hulst, N.F.

    2003-01-01

    The optical behavior of a dimer of tetramethylrhodamine-5-isothiocyanate has been investigated by means of single-molecule measurements. Bulk absorption and fluorescence spectra show the existence of two populations of the dimer molecule that exhibit distinct excitonic interactions (strong and weak

  4. Two Populations Mean-Field Monomer-Dimer Model

    Science.gov (United States)

    Alberici, Diego; Mingione, Emanuele

    2018-04-01

    A two populations mean-field monomer-dimer model including both hard-core and attractive interactions between dimers is considered. The pressure density in the thermodynamic limit is proved to satisfy a variational principle. A detailed analysis is made in the limit of one population is much smaller than the other and a ferromagnetic mean-field phase transition is found.

  5. On the diffusion and self-trapping of surface dimers

    Science.gov (United States)

    Kappus, W.

    1982-03-01

    The theory of elastic interactions between surface atoms which are caused by substrate strains is applied to the interaction of dimers on the (211) surface of tungsten. From the comparison of theoretical and experimental interactions which were derived from the diffusion behaviour of dimers, conclusions are drawn on the nature of the adatom-substrate bond.

  6. Asymmetric monometallic nanorod nanoparticle dimer and related compositions and methods

    KAUST Repository

    Han, Yu; Huang, Jianfeng; Zhu, Yihan

    2016-01-01

    and three-dimensional morphology of the dimer, as well as the growth pathway of the AuNP on the AuNR seed, was investigated for this example. The dimer exhibits an extraordinary broadband optical extinction spectrum spanning the UV, visible, and near

  7. Exact Solution of a Generalized Nonlinear Schrodinger Equation Dimer

    DEFF Research Database (Denmark)

    Christiansen, Peter Leth; Maniadis, P.; Tsironis, G.P.

    1998-01-01

    We present exact solutions for a nonlinear dimer system defined throught a discrete nonlinear Schrodinger equation that contains also an integrable Ablowitz-Ladik term. The solutions are obtained throught a transformation that maps the dimer into a double Sine-Gordon like ordinary nonlinear...... differential equation....

  8. Dimers at Ge/Si(001) surfaces: Ge coverage dependent quenching, reactivation of flip-flop motion, and interaction with dimer vacancy lines

    International Nuclear Information System (INIS)

    Hirayama, H.; Mizuno, H.; Yoshida, R.

    2002-01-01

    We studied Ge coverage (θ Ge ) dependent quenching, reactivation of the flip-flop motion, and interaction with dimer vacancy lines (DVLs) of dimers on Ge/Si(001) surfaces using a scanning tunneling microscope (STM) combined with a molecular beam epitaxy apparatus. Deposition of ∼0.3 ML (monolayer) Ge quenched the flip-flop motion, making all dimers asymmetric. Further deposition introduced DVLs at θ Ge ≥∼0.5 ML, and symmetric dimer domains appeared again locally at θ≥1.5 ML. High-resolution STM images indicated that asymmetric dimer rows always invert their phase in alternation with buckled dimer's up-end at the DVLs. Low-temperature STM images indicated that the symmetric dimer domains were due to flip-flopping of asymmetric dimers activated by large θ Ge at room temperature. The symmetric dimer domains extended along the dimer rows over the DVLs due to the phase correlation

  9. Iron and stony-iron meteorites

    DEFF Research Database (Denmark)

    Ruzicka, Alex M.; Haack, Henning; Chabot, Nancy L.

    2017-01-01

    By far most of the melted and differentiated planetesimals that have been sampled as meteorites are metal-rich iron meteorites or stony iron meteorites. The parent asteroids of these meteorites accreted early and differentiated shortly after the solar system formed, producing some of the oldest...... and interpretations for iron and stony iron meteorites (Plate 13.1). Such meteorites provide important constraints on the nature of metal-silicate separation and mixing in planetesimals undergoing partial to complete differentiation. They include iron meteorites that formed by the solidification of cores...... (fractionally crystallized irons), irons in which partly molten metal and silicates of diverse types were mixed together (silicate-bearing irons), stony irons in which partly molten metal and olivine from cores and mantles were mixed together (pallasites), and stony irons in which partly molten metal...

  10. Dualism of Sensitivity and Selectivity of Porphyrin Dimers in Electroanalysis.

    Science.gov (United States)

    Lisak, Grzegorz; Tamaki, Takashi; Ogawa, Takuji

    2017-04-04

    This work uncovers the application of porphyrin dimers for the use in electroanalysis, such as potentiometric determination of ions. It also puts in question a current perception of an occurrence of the super-Nernstian response, as a result of the possible dimerization of single porphyrins within an ion-selective membrane. To study that, four various porphyrin dimers were used as ionophores, namely, freebase-freebase, Zn-Zn, Zn-freebase, and freebase-Zn. Since the Zn-freebase and freebase-Zn porphyrin dimers carried both anion- and cation-sensitive porphyrin units, their application in ISEs was utilized in both anion- and cation-sensitive sensors. With respect to the lipophilic salt added, both porphyrins dimers were found anion- and cation-sensitive. This allowed using a single molecule as novel type of versatile ionophore (anion- and cation-selective), simply by varying the membrane composition. All anion-sensitive sensors were perchlorate-sensitive, while the cation-selective sensors were silver-sensitive. The selectivity of the sensors depended primarily on the porphyrin dimers in the ion-selective membrane. Furthermore, the selectivity of cation-sensitive dimer based sensors was found significantly superior to the ones measured for the single porphyrin unit based sensors (precursors of the porphyrin dimers). Thus, the dimerization of single porphyrins may actually be a factor to increase or modulate porphyrin selectivity. Moreover, in the case of cation-sensitive sensors, the selectivity vastly depended on the order of porphyrin units in the dimer. This opens a new approach of regulating and adjusting sensitivity and selectivity of the sensor through the application of complex porphyrin systems with more than one porphyrin units with mix sensitive porphyrins.

  11. Electron-beam-induced reduction of Fe3+ in iron phosphate dihydrate, ferrihydrite, haemosiderin and ferritin as revealed by electron energy-loss spectroscopy

    International Nuclear Information System (INIS)

    Pan, Ying-Hsi; Vaughan, Gareth; Brydson, Rik; Bleloch, Andrew; Gass, Mhairi; Sader, Kasim; Brown, Andy

    2010-01-01

    The effect of high-energy electron irradiation on ferritin/haemosiderin cores (in an iron-overloaded human liver biopsy), its mineral analogue; six-line ferrihydrite (6LFh), and iron phosphate dihydrate (which has similar octahedral ferric iron to oxygen coordination to that in ferrihydrite and ferritin/haemosiderin cores) has been investigated using electron energy-loss spectroscopy (EELS). Fe L 2,3 -ionisation edges were recorded on two types of electron microscope: a 200 keV transmission electron microscope (TEM) and a 100 keV scanning transmission electron microscope (STEM), in order to investigate the damage mechanisms in operation and to establish a methodology for minimum specimen alteration during analytical electron microscopic characterisation. A specimen damage mechanism dominated by radiolysis that results in the preferential loss of iron co-ordinating ligands (O, OH and H 2 O) is discussed. The net result of irradiation is structural re-organisation and reduction of iron within the iron hydroxides. At sufficiently low electron fluence and particularly in the lower incident energy, finer probe diameter STEM, the alteration is shown to be minimal. All the materials examined exhibit damage which as a function of cumulative fluence is best fitted by an inverse power-law, implying that several chemical and structural changes occur in response to the electron beam and we suggest that these are governed by secondary processes arising from the primary ionisation event. This work affirms that electron fluence and current density should be considered when measuring mixed valence ratios with EELS.

  12. Electron-beam-induced reduction of Fe{sup 3+} in iron phosphate dihydrate, ferrihydrite, haemosiderin and ferritin as revealed by electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Ying-Hsi; Vaughan, Gareth; Brydson, Rik [Institute for Materials Research, SPEME, University of Leeds, Leeds LS2 9JT (United Kingdom); Bleloch, Andrew; Gass, Mhairi [SuperSTEM, Daresbury Laboratories, Warrington WA4 4AD (United Kingdom); Sader, Kasim [Institute for Materials Research, SPEME, University of Leeds, Leeds LS2 9JT (United Kingdom); SuperSTEM, Daresbury Laboratories, Warrington WA4 4AD (United Kingdom); Brown, Andy, E-mail: a.p.brown@leeds.ac.uk [Institute for Materials Research, SPEME, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2010-07-15

    The effect of high-energy electron irradiation on ferritin/haemosiderin cores (in an iron-overloaded human liver biopsy), its mineral analogue; six-line ferrihydrite (6LFh), and iron phosphate dihydrate (which has similar octahedral ferric iron to oxygen coordination to that in ferrihydrite and ferritin/haemosiderin cores) has been investigated using electron energy-loss spectroscopy (EELS). Fe L{sub 2,3}-ionisation edges were recorded on two types of electron microscope: a 200 keV transmission electron microscope (TEM) and a 100 keV scanning transmission electron microscope (STEM), in order to investigate the damage mechanisms in operation and to establish a methodology for minimum specimen alteration during analytical electron microscopic characterisation. A specimen damage mechanism dominated by radiolysis that results in the preferential loss of iron co-ordinating ligands (O, OH and H{sub 2}O) is discussed. The net result of irradiation is structural re-organisation and reduction of iron within the iron hydroxides. At sufficiently low electron fluence and particularly in the lower incident energy, finer probe diameter STEM, the alteration is shown to be minimal. All the materials examined exhibit damage which as a function of cumulative fluence is best fitted by an inverse power-law, implying that several chemical and structural changes occur in response to the electron beam and we suggest that these are governed by secondary processes arising from the primary ionisation event. This work affirms that electron fluence and current density should be considered when measuring mixed valence ratios with EELS.

  13. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer en español Iron-deficiency anemia is a ... address the cause of your iron deficiency, such as any underlying bleeding. If undiagnosed or untreated, iron- ...

  14. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... To Health Topics / Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer en español Iron-deficiency ... anemia. Blood tests to screen for iron-deficiency anemia To screen for iron-deficiency anemia, your doctor ...

  15. Iron-Deficiency Anemia

    Science.gov (United States)

    ... To Health Topics / Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer en español Iron-deficiency ... anemia. Blood tests to screen for iron-deficiency anemia To screen for iron-deficiency anemia, your doctor ...

  16. Asymmetric monometallic nanorod nanoparticle dimer and related compositions and methods

    KAUST Repository

    Han, Yu

    2016-03-31

    The fabrication of asymmetric monometallic nanocrystals with novel properties for plasmonics, nanophotonics and nanoelectronics. Asymmetric monometallic plasmonic nanocrystals are of both fundamental synthetic challenge and practical significance. In an example, a thiol-ligand mediated growth strategy that enables the synthesis of unprecedented Au Nanorod-Au Nanoparticle (AuNR-AuNP) dimers from pre-synthesized AuNR seeds. Using high-resolution electron microscopy and tomography, crystal structure and three-dimensional morphology of the dimer, as well as the growth pathway of the AuNP on the AuNR seed, was investigated for this example. The dimer exhibits an extraordinary broadband optical extinction spectrum spanning the UV, visible, and near infrared regions (300 - 1300 nm). This unexpected property makes the AuNR-AuNP dimer example useful for many nanophotonic applications. In two experiments, the dimer example was tested as a surface- enhanced Raman scattering (SERS) substrate and a solar light harvester for photothermal conversion, in comparison with the mixture of AuNR and AuNP. In the SERS experiment, the dimer example showed an enhancement factor about 10 times higher than that of the mixture, when the excitation wavelength (660 nm) was off the two surface plasmon resonance (SPR) bands of the mixture. In the photothermal conversion experiment under simulated sunlight illumination, the dimer example exhibited an energy conversion efficiency about 1.4 times as high as that of the mixture.

  17. Role of cyclobutane dimers in UV-denaturation of DNA

    International Nuclear Information System (INIS)

    Zavil'gel'skij, G.B.; Zuev, A.V.

    1978-01-01

    UV irradiation of double-stranded DNA produces local denatured regions. The evidence presented indicates that these single-stranded regions arise from photoproducts other than pyrimidine dimers. The irradiation of T2 DNA at 8x10 4 erg/mm 2 (254 nm) produces 6-8% thymine dimers, amd Tsub(mel) drops by 12-14 deg C, accompanied by a significant broadening of the transition profile. The kinetics of denatured region formation and lowering Tsub(mel) corresponds to that of formation of crosslinkages and differs markedly from the kinetics of formation of cyclobutane pyrimidine dimers. Treatment of UV-irradiated DNA with light in the presence of yeast photoreactivating enzyme monomerizes almost all thymine dimers but does not change the Tsub(mel). Local denatured regions are detected in UV-irradiated DNA and are absent from AcPhM-sensibilized DNA, which contains 20-25% thymine dimers, as determined by the accridine orange fluorescence technique. S1 nuclease from Aspergillis oryzae produces single-strand breaks in UV-irradiated DNA of phage PM2 but is not active on AcPhM-treated PM2 DNA, which contains about 50 thymine dimers. It is supposed that the formation of a cyclobutane dimer only weakens the hydrogen bonds in the AT base pair rather than breaks them. Local denatured regions are thought to arise from the accumulation in UV-irradiated DNA (254 nm) of the sufficient number of photoproducts with impaired ability to base pairing

  18. Quantum dissipative dynamics and decoherence of dimers on helium droplets

    International Nuclear Information System (INIS)

    Schlesinger, Martin

    2011-01-01

    In this thesis, quantum dynamical simulations are performed in order to describe the vibrational motion of diatomic molecules in a highly quantum environment, so-called helium droplets. We aim to reproduce and explain experimental findings which were obtained from dimers on helium droplets. Nanometer-sized helium droplets contain several thousands of 4 He atoms. They serve as a host for embedded atoms or molecules and provide an ultracold ''refrigerator'' for them. Spectroscopy of molecules in or on these droplets reveals information on both the molecule and the helium environment. The droplets are known to be in the superfluid He II phase. Superfluidity in nanoscale systems is a steadily growing field of research. Spectra obtained from full quantum simulations for the unperturbed dimer show deviations from measurements with dimers on helium droplets. These deviations result from the influence of the helium environment on the dimer dynamics. In this work, a well-established quantum optical master equation is used in order to describe the dimer dynamics effectively. The master equation allows to describe damping fully quantum mechanically. By employing that equation in the quantum dynamical simulation, one can study the role of dissipation and decoherence in dimers on helium droplets. The effective description allows to explain experiments with Rb 2 dimers on helium droplets. Here, we identify vibrational damping and associated decoherence as the main explanation for the experimental results. The relation between decoherence and dissipation in Morse-like systems at zero temperature is studied in more detail. The dissipative model is also used to investigate experiments with K 2 dimers on helium droplets. However, by comparing numerical simulations with experimental data, one finds that further mechanisms are active. Here, a good agreement is obtained through accounting for rapid desorption of dimers. We find that decoherence occurs in the electronic manifold of the

  19. Subsurface dimerization in III-V semiconductor (001) surfaces

    DEFF Research Database (Denmark)

    Kumpf, C.; Marks, L.D.; Ellis, D.

    2001-01-01

    We present the atomic structure of the c(8 X 2) reconstructions of InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on the surface, instead subsurface dimerization of group m atoms ...... takes place in the second bilayer, accompanied by a major rearrangement of the surface atoms above the dimers to form linear arrays. By varying the occupancies of four surface sites the (001)-c(8 X 2) reconstructions of III-V semiconductors can be described in a unified model....

  20. Dimeric Surfactants: Promising Ingredients of Cosmetics and Toiletries

    Directory of Open Access Journals (Sweden)

    Naveen Kumar

    2013-11-01

    Full Text Available Surfactants are an essential ingredient for cosmetic, toiletries and personal care products for enhancing their performance. Dimeric surfactants demonstrate superiority compared to conventional surfactants in all areas of application. Dimeric surfactants are extremely promising for utilization in various cosmetic formulations viz. shampoo, lotions, creams, conditioners etc. These surfactants possess extremely unique surface properties viz. lower surface tension, unique micellization, low critical micelle concentration (CMC and antimicrobial activity, higher solubilization etc. Dimerics enhance the performances of cosmetics in an extraordinary manner and provide eco-friendly preparations for human epidermis.

  1. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... making new blood cells. Visit our Aplastic Anemia Health Topic to learn more. ... recommend that you take iron supplements, also called iron pills or oral iron, by mouth once or several times a ...

  2. Iron-Deficiency Anemia

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    Full Text Available ... red meat, salmon, iron-fortified breads and cereals, peas, tofu, dried fruits, and dark green leafy vegetables. ... stored iron has been used. Ferritin is a protein that helps store iron in your body. Reticulocyte ...

  3. Iron-Deficiency Anemia

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    Full Text Available ... drinking black tea, which reduces iron absorption. Other treatments If you have chronic kidney disease and iron- ... and lifestyle changes to avoid complications. Follow your treatment plan Do not stop taking your prescribed iron ...

  4. Iron-Deficiency Anemia

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    Full Text Available ... diagnoses you with iron-deficiency anemia, your treatment will depend on the cause and severity of the ... of iron. The recommended daily amounts of iron will depend on your age, sex, and whether you ...

  5. Iron-Deficiency Anemia

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    Full Text Available ... heart failure . Increased risk of infections Motor or cognitive development delays in children Pregnancy complications, such as ... iron-deficiency anemia may require intravenous (IV) iron therapy or a blood transfusion . Iron supplements Your doctor ...

  6. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... for iron-deficiency anemia. Lifestyle habits Certain lifestyle habits may increase your risk for iron-deficiency anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron-rich foods, such ...

  7. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... because your body’s intake of iron is too low. Low intake of iron can happen because of blood ... delivery or giving birth to a baby with low birth weight In people with chronic conditions, iron- ...

  8. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... breastfeeding. Recommended daily iron intake for children and adults. The table lists the recommended amounts of iron, ... increased need for iron during growth spurts. Older adults, especially those over age 65. Unhealthy environments Children ...

  9. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... girls. From birth to 6 months, babies need 0.27 mg of iron. This number goes up ... screen blood donors for low iron stores. Reliable point-of-care testing may help identify iron deficiency ...

  10. Iron metabolism and toxicity

    International Nuclear Information System (INIS)

    Papanikolaou, G.; Pantopoulos, K.

    2005-01-01

    Iron is an essential nutrient with limited bioavailability. When present in excess, iron poses a threat to cells and tissues, and therefore iron homeostasis has to be tightly controlled. Iron's toxicity is largely based on its ability to catalyze the generation of radicals, which attack and damage cellular macromolecules and promote cell death and tissue injury. This is lucidly illustrated in diseases of iron overload, such as hereditary hemochromatosis or transfusional siderosis, where excessive iron accumulation results in tissue damage and organ failure. Pathological iron accumulation in the liver has also been linked to the development of hepatocellular cancer. Here we provide a background on the biology and toxicity of iron and the basic concepts of iron homeostasis at the cellular and systemic level. In addition, we provide an overview of the various disorders of iron overload, which are directly linked to iron's toxicity. Finally, we discuss the potential role of iron in malignant transformation and cancer

  11. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... amount of iron, and medical conditions that make it hard for your body to absorb iron from ... hepcidin. Hepcidin prevents iron from leaving cells where it is stored or from being absorbed in the ...

  12. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... bleeding. If undiagnosed or untreated, iron-deficiency anemia can cause serious complications, including heart failure and development ... iron is too low. Low intake of iron can happen because of blood loss, consuming less than ...

  13. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... iron-fortified foods that have iron added. Vegetarian diets can provide enough iron if you choose nonmeat ... Anemia in Chronic Kidney Disease (National Institute of Diabetes and Digestive and Kidney Diseases) Avoiding Anemia (National ...

  14. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... lean red meat, salmon, iron-fortified breads and cereals, peas, tofu, dried fruits, and dark green leafy ... sources of iron, including iron-fortified breads and cereals, beans, tofu, dried fruits, and spinach and other ...

  15. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... starch. Restless legs syndrome Shortness of breath Weakness Complications Undiagnosed or untreated iron-deficiency anemia may cause ... as complete blood count and iron studies. Prevent complications over your lifetime To prevent complications from iron- ...

  16. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... you do not have enough iron in your body. People with mild or moderate iron-deficiency anemia ... and where to find more information. Causes Your body needs iron to make healthy red blood cells. ...

  17. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... from developing iron-deficiency anemia. Foods that are good sources of iron include dried beans, dried fruits, eggs, lean red meat, ... signs of iron-deficiency anemia include: Brittle nails ...

  18. Taking iron supplements

    Science.gov (United States)

    ... medlineplus.gov/ency/article/007478.htm Taking iron supplements To use the sharing features on this page, ... levels. You may also need to take iron supplements as well to rebuild iron stores in your ...

  19. Iron-Deficiency Anemia

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    Full Text Available ... fruits, eggs, lean red meat, salmon, iron-fortified breads and cereals, peas, tofu, dried fruits, and dark ... choose nonmeat sources of iron, including iron-fortified breads and cereals, beans, tofu, dried fruits, and spinach ...

  20. Iron-Deficiency Anemia

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    Full Text Available ... ESAs are usually used with iron therapy or IV iron, or when iron therapy alone is not enough. Look for Living With will discuss what your doctor may recommend, including lifelong lifestyle changes ...

  1. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... and pregnancy. Good sources of iron are meat, poultry, fish, and iron-fortified foods that have iron ... Anemia Restless Legs Syndrome Von Willebrand Disease Other Resources NHLBI resources Your Guide to Anemia [PDF, 1. ...

  2. Genetics Home Reference: iron-refractory iron deficiency anemia

    Science.gov (United States)

    ... refractory iron deficiency anemia Iron-refractory iron deficiency anemia Printable PDF Open All Close All Enable Javascript ... expand/collapse boxes. Description Iron-refractory iron deficiency anemia is one of many types of anemia , which ...

  3. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... increased need for iron during growth spurts. Older adults, especially those over age ... athletes. Athletes, especially young females, are at risk for iron deficiency. Endurance ...

  4. Iron and stony-iron meteorites

    DEFF Research Database (Denmark)

    Benedix, Gretchen K.; Haack, Henning; McCoy, T. J.

    2014-01-01

    Without iron and stony-iron meteorites, our chances of ever sampling the deep interior of a differentiated planetary object would be next to nil. Although we live on a planet with a very substantial core, we will never be able to sample it. Fortunately, asteroid collisions provide us with a rich...... sampling of the deep interiors of differentiated asteroids. Iron and stony-iron meteorites are fragments of a large number of asteroids that underwent significant geological processing in the early solar system. Parent bodies of iron and some stony-iron meteorites completed a geological evolution similar...... to that continuing on Earth – although on much smaller length- and timescales – with melting of the metal and silicates; differentiation into core, mantle, and crust; and probably extensive volcanism. Iron and stony-iron meteorites are our only available analogues to materials found in the deep interiors of Earth...

  5. DFT Study of dimers of dimethyl sulfoxide in gas phase

    Directory of Open Access Journals (Sweden)

    Reza Fazaeli

    2014-10-01

    Full Text Available Density functional (DFT calculations at M05-2x/aug-cc-pVDZ level were used to analyze the interactions between dimethyl sulfoxide (DMSO dimers. The structures obtained have been ana-lyzed with the Atoms in Molecules (AIMs and Natural Bond Orbital (NBO methodologies. Four minima were located on the potential energy surface of the dimers. Three types of interac-tions are observed, CH•••O, CH•••S hydrogen bonds and orthogonal interaction between the lone pair of the oxygen with the electron-deficient region of the sulfur atom. Stabilization energies of dimers including BSSE and ZPE are in the range 27–40 kJmol-1. The most stable conformers of dimers at DFT level is cyclic structure with antiparallel orientation of S=O groups pairing with three C–H∙∙∙O and a S∙∙∙O interactions.

  6. 21 CFR 176.120 - Alkyl ketene dimers.

    Science.gov (United States)

    2010-04-01

    ..., processing, preparing, treating, packaging, transporting, or holding food, subject to the provisions of this... paperboard. (c) The alkyl ketene dimers may be used in the form of an aqueous emulsion which may contain...

  7. Dimer-based model for heptaspanning membrane receptors.

    Science.gov (United States)

    Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferré, Sergi; Fuxe, Kjell; Cortés, Antonio; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

    2005-07-01

    The existence of intramembrane receptor-receptor interactions for heptaspanning membrane receptors is now fully accepted, but a model considering dimers as the basic unit that binds to two ligand molecules is lacking. Here, we propose a two-state-dimer model in which the ligand-induced conformational changes from one component of the dimer are communicated to the other. Our model predicts cooperativity in binding, which is relevant because the other current models fail to address this phenomenon satisfactorily. Our two-state-dimer model also predicts the variety of responses elicited by full or partial agonists, neutral antagonists and inverse agonists. This model can aid our understanding of the operation of heptaspanning receptors and receptor channels, and, potentially, be important for improving the treatment of cardiovascular, neurological and neuropsychyatric diseases.

  8. Family C 7TM receptor dimerization and activation

    DEFF Research Database (Denmark)

    Bonde, Marie Mi; Sheikh, Søren P; Hansen, Jakob Lerche

    2006-01-01

    The family C seven transmembrane (7TM) receptors constitutes a small and especially well characterized subfamily of the large 7TM receptor superfamily. Approximately 50% of current prescription drugs target 7TM receptors, this biologically important family represents the largest class of drug...... to be fully defined. This review presents the biochemical support for family C 7TM receptor dimerization and discusses its importance for receptor biosynthesis, surface expression, ligand binding and activation, since lessons learnt here may well be applicable to the whole superfamily of 7TM receptors.......-targets today. It is well established that family C 7TM receptors form homo- or hetero-dimers on the cell surface of living cells. The large extra-cellular domains (ECD) have been crystallized as a dimer in the presence and absence of agonist. Upon agonist binding, the dimeric ECD undergoes large conformational...

  9. Iron-reducing bacteria accumulate ferric oxyhydroxide nanoparticle aggregates that may support planktonic growth.

    Science.gov (United States)

    Luef, Birgit; Fakra, Sirine C; Csencsits, Roseann; Wrighton, Kelly C; Williams, Kenneth H; Wilkins, Michael J; Downing, Kenneth H; Long, Philip E; Comolli, Luis R; Banfield, Jillian F

    2013-02-01

    Iron-reducing bacteria (FeRB) play key roles in anaerobic metal and carbon cycling and carry out biogeochemical transformations that can be harnessed for environmental bioremediation. A subset of FeRB require direct contact with Fe(III)-bearing minerals for dissimilatory growth, yet these bacteria must move between mineral particles. Furthermore, they proliferate in planktonic consortia during biostimulation experiments. Thus, a key question is how such organisms can sustain growth under these conditions. Here we characterized planktonic microbial communities sampled from an aquifer in Rifle, Colorado, USA, close to the peak of iron reduction following in situ acetate amendment. Samples were cryo-plunged on site and subsequently examined using correlated two- and three-dimensional cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission X-ray microscopy (STXM). The outer membranes of most cells were decorated with aggregates up to 150 nm in diameter composed of ∼3 nm wide amorphous, Fe-rich nanoparticles. Fluorescent in situ hybridization of lineage-specific probes applied to rRNA of cells subsequently imaged via cryo-TEM identified Geobacter spp., a well-studied group of FeRB. STXM results at the Fe L(2,3) absorption edges indicate that nanoparticle aggregates contain a variable mixture of Fe(II)-Fe(III), and are generally enriched in Fe(III). Geobacter bemidjiensis cultivated anaerobically in the laboratory on acetate and hydrous ferric oxyhydroxides also accumulated mixed-valence nanoparticle aggregates. In field-collected samples, FeRB with a wide variety of morphologies were associated with nano-aggregates, indicating that cell surface Fe(III) accumulation may be a general mechanism by which FeRB can grow while in planktonic suspension.

  10. The dimerization of the yeast cytochrome bc1 complex is an early event and is independent of Rip1.

    Science.gov (United States)

    Conte, Annalea; Papa, Benedetta; Ferramosca, Alessandra; Zara, Vincenzo

    2015-05-01

    In Saccharomyces cerevisiae the mature cytochrome bc1 complex exists as an obligate homo-dimer in which each monomer consists of ten distinct protein subunits inserted into or bound to the inner mitochondrial membrane. Among them, the Rieske iron-sulfur protein (Rip1), besides its catalytic role in electron transfer, may be implicated in the bc1 complex dimerization. Indeed, Rip1 has the globular domain containing the catalytic center in one monomer while the transmembrane helix interacts with the adjacent monomer. In addition, the lack of Rip1 leads to the accumulation of an immature bc1 intermediate, only loosely associated with cytochrome c oxidase. In this study we have investigated the biogenesis of the yeast cytochrome bc1 complex using epitope tagged proteins to purify native assembly intermediates. We showed that the dimerization process is an early event during bc1 complex biogenesis and that the presence of Rip1, differently from previous proposals, is not essential for this process. We also investigated the multi-step model of bc1 assembly thereby lending further support to the existence of bona fide subcomplexes during bc1 maturation in the inner mitochondrial membrane. Finally, a new model of cytochrome bc1 complex assembly, in which distinct intermediates sequentially interact during bc1 maturation, has been proposed. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Iron from Zealandic bog iron ore -

    DEFF Research Database (Denmark)

    Lyngstrøm, Henriette Syrach

    2011-01-01

    og geologiske materiale, metallurgiske analyser og eksperimentel arkæologiske forsøg - konturerne af en jernproduktion med udgangspunkt i den sjællandske myremalm. The frequent application by archaeologists of Werner Christensen’s distribution map for the occurrence of bog iron ore in Denmark (1966...... are sketched of iron production based on bog iron ore from Zealand....

  12. Dynamics of the water dimer + nitric oxide collision

    Energy Technology Data Exchange (ETDEWEB)

    Ree, Jong Baik [Dept. of Chemistry Education, Chonnam National University, Gwangju (Korea, Republic of); Kim, Yoo Hang [Dept. of Chemistry, Inha University, Incheon (Korea, Republic of); Shin, Hyung Kyu [Dept. of Chemistry, University of Nevada, Nevada (Korea, Republic of)

    2017-02-15

    Collision-induced intermolecular energy transfer and intramolecular vibrational redistribution in the collision of a water dimer and nitric oxide are studied by use of quasiclassical procedures. Intermolecular energy flow is shown to occur mainly through a direct-mode mechanism transferring relatively large amounts in strong collisions. About a quarter of the energy initially deposited in the dimer transfers to the ground state NO, while the rest redistributes among internal motions of the collision system. The main portion of initial energy deposited in the dimer redistributes in the stretches of the donor monomer through the 1:1 resonance followed by in the bend through the 1:2 resonance. Energy transfer from the excited NO to the ground-state dimer is equally efficient, transferring more than half the initial excitation to the donor monomer, the efficiency that is attributed to the internal modes operating as energy reservoirs. The hydrogen bond shares about 15% of the initial excitation stored in both dimer-to-NO and NO-to-dimer processes as a result of strong coupling of the hydrogen bond with the proton-donor OH bond of the monomer. A small fraction of collisions proceeds through a complex-mode mechanism and lead to NO dissociation, the dissociated O atom showing a propensity to form a new hydrogen bond.

  13. VUV spectroscopy of rare gas van der Waals dimers

    International Nuclear Information System (INIS)

    Dehmer, P.M.; Pratt, S.T.

    1982-01-01

    We have undertaken a systematic study of the photoionization spectra of the homonuclear and heteronuclear rare gas dimers in order to better understand the nature of the bonding in the Rydberg states adnd ions of these molecules. We have obtained results for Ar 2 , Kr 2 , Xe 2 , NeAr, NeKr, NeXe, ArKr, ArXe, and KrXe. Of the remaining dimer species (Ne 2 and the Herare gas dimers), only Ne 2 has been studied using photoionization mass spectrometry. The results of the present series of experiments provide information both on the excited states of the neutral dimers and on the ground and excited states of the dimer ions. Using the data obtained in these measurements, we are able to compile for the first time a nearly complete list of ground state dissociation energies for the homonuclear and heteronuclear rare gas dimer ions. Somewhat less complete results are obtained for the excited states of these species. The observed trends in binding energy provide an excellent example of the systematic changes that occur as a result of changes in atomic orbital energies, polarizability, and internuclear distance, and these trends can be explained qualitatively in terms of simple molecular orbital theory

  14. Optical properties of electrically connected plasmonic nanoantenna dimer arrays

    Science.gov (United States)

    Zimmerman, Darin T.; Borst, Benjamin D.; Carrick, Cassandra J.; Lent, Joseph M.; Wambold, Raymond A.; Weisel, Gary J.; Willis, Brian G.

    2018-02-01

    We fabricate electrically connected gold nanoantenna arrays of homodimers and heterodimers on silica substrates and present a systematic study of their optical properties. Electrically connected arrays of plasmonic nanoantennas make possible the realization of novel photonic devices, including optical sensors and rectifiers. Although the plasmonic response of unconnected arrays has been studied extensively, the present study shows that the inclusion of nanowire connections modifies the device response significantly. After presenting experimental measurements of optical extinction for unconnected dimer arrays, we compare these to measurements of dimers that are interconnected by gold nanowire "busbars." The connected devices show the familiar dipole response associated with the unconnected dimers but also show a second localized surface plasmon resonance (LSPR) that we refer to as the "coupled-busbar mode." Our experimental study also demonstrates that the placement of the nanowire along the antenna modifies the LSPR. Using finite-difference time-domain simulations, we confirm the experimental results and investigate the variation of dimer gap and spacing. Changing the dimer gap in connected devices has a significantly smaller effect on the dipole response than it does in unconnected devices. On the other hand, both LSPR modes respond strongly to changing the spacing between devices in the direction along the interconnecting wires. We also give results for the variation of E-field strength in the dimer gap, which will be important for any working sensor or rectenna device.

  15. Hydrodynamic Torques and Rotations of Superparamagnetic Bead Dimers

    Science.gov (United States)

    Pease, Christopher; Etheridge, J.; Wijesinghe, H. S.; Pierce, C. J.; Prikockis, M. V.; Sooryakumar, R.

    Chains of micro-magnetic particles are often rotated with external magnetic fields for many lab-on-a-chip technologies such as transporting beads or mixing fluids. These applications benefit from faster responses of the actuated particles. In a rotating magnetic field, the magnetization of superparamagnetic beads, created from embedded magnetic nano-particles within a polymer matrix, is largely characterized by induced dipoles mip along the direction of the field. In addition there is often a weak dipole mop that orients out-of-phase with the external rotating field. On a two-bead dimer, the simplest chain of beads, mop contributes a torque Γm in addition to the torque from mip. For dimers with beads unbound to each other, mop rotates individual beads which generate an additional hydrodynamic torque on the dimer. Whereas, mop directly torques bound dimers. Our results show that Γm significantly alters the average frequency-dependent dimer rotation rate for both bound and unbound monomers and, when mop exceeds a critical value, increases the maximum dimer rotation frequency. Models that include magnetic and hydrodynamics torques provide good agreement with the experimental findings over a range of field frequencies.

  16. Pair Interaction of Catalytical Sphere Dimers in Chemically Active Media

    Directory of Open Access Journals (Sweden)

    Jing-Min Shi

    2018-01-01

    Full Text Available We study the pair dynamics of two self-propelled sphere dimers in the chemically active medium in which a cubic autocatalytic chemical reaction takes place. Concentration gradient around the dimer, created by reactions occurring on the catalytic sphere surface and responsible for the self-propulsion, is greatly influenced by the chemical activities of the environment. Consequently, the pair dynamics of two dimers mediated by the concentration field are affected. In the particle-based mesoscopic simulation, we combine molecular dynamics (MD for potential interactions and reactive multiparticle collision dynamics (RMPC for solvent flow and bulk reactions. Our results indicate three different configurations between a pair of dimers after the collision, i.e., two possible scenarios of bound dimer pairs and one unbound dimer pair. A phase diagram is sketched as a function of the rate coefficients of the environment reactions. Since the pair interactions are the basic elements of larger scale systems, we believe the results may shed light on the understanding of the collective dynamics.

  17. Metal membrane with dimer slots as a universal polarizer

    Science.gov (United States)

    Zhukovsky, Sergej; Zalkovskij, Maksim; Malureanu, Radu; Kremers, Christian; Chigrin, Dmitry; Tang, Peter T.; Jepsen, Peter U.; Lavrinenko, Andrei V.

    2014-03-01

    In this work, we show theoretically and confirm experimentally that thin metal membranes patterned with an array of slot dimers (or their Babinet analogue with metal rods) can function as a versatile spectral and polarization filter. We present a detailed covariant multipole theory for the electromagnetic response of an arbitrary dimer based on the Green functions approach. The theory confirms that a great variety of polarization properties, such as birefringence, chirality and elliptical dichroism, can be achieved in a metal layer with such slot-dimer patterning (i.e. in a metasurface). Optical properties of the metasurface can be extensively tuned by varying the geometry (shape and dimensions) of the dimer, for example, by adjusting the sizes and mutual placement of the slots (e.g. inter-slot distance and alignment angle). Three basic shapes of dimers are analyzed: II-shaped (parallel slots), V-shaped, and T-shaped. These particular shapes of dimers are found to be sensitive to variations of the slots lengths and orientation of elements. Theoretical results are well supported by full-wave three-dimensional simulations. Our findings were verified experimentally on the metal membranes fabricated using UV lithography with subsequent Ni growth. Such metasurfaces were characterized using time-domain THz spectroscopy. The samples exhibit pronounced optical activity (500 degrees per wavelength) and high transmission: even though the slots cover only 4.3 % of the total membrane area the amplitude transmission reaches 0.67 at the resonance frequency 0.56 THz.

  18. Native iron

    DEFF Research Database (Denmark)

    Brooks, Charles Kent

    2015-01-01

    System, was reduced. The oxidized outer layers of the Earth have formed by two processes. Firstly, water is decomposed to oxygen and hydrogen by solar radiation in the upper parts of the atmosphere, the light hydrogen diffusing to space, leaving oxygen behind. Secondly, plants, over the course......, hematite, or FeO.Fe2O3, magnetite), with carbon in the form of coke. This is carried out in a blast furnace. Although the Earth's core consists of metallic iron, which may also be present in parts of the mantle, this is inaccessible to us, so we must make our own. In West Greenland, however, some almost......We live in an oxidized world: oxygen makes up 22 percent of the atmosphere and by reacting with organic matter produces most of our energy, including the energy our bodies use to function: breathe, think, move, etc. It has not always been thus. Originally the Earth, in common with most of the Solar...

  19. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... blocks the intestine from taking up iron. Other medical conditions Other medical conditions that may lead to iron-deficiency anemia ... daily amount of iron. If you have other medical conditions that cause iron-deficiency anemia , such as ...

  20. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Home / < Back To Health Topics / Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer en español ... bleeding Consuming less than recommended daily amounts of iron Iron-deficiency anemia can be caused by getting ...

  1. Serum iron test

    Science.gov (United States)

    Fe+2; Ferric ion; Fe++; Ferrous ion; Iron - serum; Anemia - serum iron; Hemochromatosis - serum iron ... A blood sample is needed. Iron levels are highest in the morning. Your health care provider will likely have you do this test in the morning.

  2. Nutritional iron deficiency

    NARCIS (Netherlands)

    Zimmermann, M.B.; Hurrell, R.F.

    2007-01-01

    Iron deficiency is one of the leading risk factors for disability and death worldwide, affecting an estimated 2 billion people. Nutritional iron deficiency arises when physiological requirements cannot be met by iron absorption from diet. Dietary iron bioavailability is low in populations consuming

  3. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... also are hoping to determine which iron supplements work best to treat iron-deficiency anemia in children who do not consume the daily recommended amount of iron. Read less Participate in NHLBI Clinical Trials We lead or sponsor many studies related to iron-deficiency anemia. See if you ...

  4. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... peas, tofu, dried fruits, and dark green leafy vegetables. Foods rich in vitamin C, such as oranges, strawberries, ... iron are meat, poultry, fish, and iron-fortified foods that have iron ... green leafy vegetables. You can also take an iron supplement. Follow ...

  5. Iron deficiency anemia

    Science.gov (United States)

    Anemia - iron deficiency ... iron from old red blood cells. Iron deficiency anemia develops when your body's iron stores run low. ... You may have no symptoms if the anemia is mild. Most of the time, ... slowly. Symptoms may include: Feeling weak or tired more often ...

  6. Dimer coverings on random multiple chains of planar honeycomb lattices

    International Nuclear Information System (INIS)

    Ren, Haizhen; Zhang, Fuji; Qian, Jianguo

    2012-01-01

    We study dimer coverings on random multiple chains. A multiple chain is a planar honeycomb lattice constructed by successively fusing copies of a ‘straight’ condensed hexagonal chain at the bottom of the previous one in two possible ways. A random multiple chain is then generated by admitting the Bernoulli distribution on the two types of fusing, which describes a zeroth-order Markov process. We determine the expectation of the number of the pure dimer coverings (perfect matchings) over the ensemble of random multiple chains by the transfer matrix approach. Our result shows that, with only two exceptions, the average of the logarithm of this expectation (i.e., the annealed entropy per dimer) is asymptotically nonzero when the fusing process goes to infinity and the length of the hexagonal chain is fixed, though it is zero when the fusing process and the length of the hexagonal chain go to infinity simultaneously. Some numerical results are provided to support our conclusion, from which we can see that the asymptotic behavior fits well to the theoretical results. We also apply the transfer matrix approach to the quenched entropy and reveal that the quenched entropy of random multiple chains has a close connection with the well-known Lyapunov exponent of random matrices. Using the theory of Lyapunov exponents we show that, for some random multiple chains, the quenched entropy per dimer is strictly smaller than the annealed one when the fusing process goes to infinity. Finally, we determine the expectation of the free energy per dimer over the ensemble of the random multiple chains in which the three types of dimers in different orientations are distinguished, and specify a series of non-random multiple chains whose free energy per dimer is asymptotically equal to this expectation. (paper)

  7. Iron absorption in relation to iron status

    International Nuclear Information System (INIS)

    Magnusson, B.; Bjoern-Rasmussen, E.; Hallberg, L.; Rossander, L.

    1981-01-01

    The absorption from a 3 mg dose of ferrous iron was measured in 250 male subjects. The absorption was related to the log concentration of serum ferritin in 186 subjects of whom 99 were regular blood donors (r= -0.76), and to bone marrow haemosiderin grading in 52 subjects with varying iron status. The purpose was to try and establish a percentage absorption from such a dose that is representative of subjects who are borderline iron deficient. This information is necessary for food iron absorption studies in order (1) to calculate the absorption of iron from the diet at a given iron status and (2) compare the absorption of iron from different meals studied in different groups of subjects by different investigarors. The results suggest that an absorption of about 40% of a 3 mg reference dose of ferrous iron is given in a fasting state, roughly corresponds to the absorption in borderline-iron-deficient subjects. The results indicate that this 40% absorption value corresponds to a serum ferritin level of 30 μg/l and that food iron absorption in a group of subjects should be expressed preferably as the absorption corresponding to a reference-dose absorption of 45%, or possibly a serum ferritin level of 30 μg/l. (author)

  8. Glycine transporter dimers: evidence for occurrence in the plasma membrane.

    Science.gov (United States)

    Bartholomäus, Ingo; Milan-Lobo, Laura; Nicke, Annette; Dutertre, Sébastien; Hastrup, Hanne; Jha, Alok; Gether, Ulrik; Sitte, Harald H; Betz, Heinrich; Eulenburg, Volker

    2008-04-18

    Different Na(+)/Cl(-)-dependent neurotransmitter transporters of the SLC6a family have been shown to form dimers or oligomers in both intracellular compartments and at the cell surface. In contrast, the glycine transporters (GlyTs) GlyT1 and -2 have been reported to exist as monomers in the plasma membrane based on hydrodynamic and native gel electrophoretic studies. Here, we used cysteine substitution and oxidative cross-linking to show that of GlyT1 and GlyT2 also form dimeric complexes within the plasma membrane. GlyT oligomerization at the cell surface was confirmed for both GlyT1 and GlyT2 by fluorescence resonance energy transfer microscopy. Endoglycosidase treatment and surface biotinylation further revealed that complex-glycosylated GlyTs form dimers located at the cell surface. Furthermore, substitution of tryptophan 469 of GlyT2 by an arginine generated a transporter deficient in dimerization that was retained intracellulary. Based on these results and GlyT structures modeled by using the crystal structure of the bacterial homolog LeuT(Aa), as a template, residues located within the extracellular loop 3 and at the beginning of transmembrane domain 6 are proposed to contribute to the dimerization interface of GlyTs.

  9. Effects of Dimerization of Serratia marcescens Endonuclease on Water Dynamics.

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chuanying; Beck, Brian W.; Krause, Kurt; Weksberg, Tiffany E.; Pettitt, Bernard M.

    2007-02-15

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The dynamics and structure of Serratia marcescens endonuclease and its neighboring solvent are investigated by molecular dynamics (MD). Comparisons are made with structural and biochemical experiments. The dimer form is physiologic and functions more processively than the monomer. We previously found a channel formed by connected clusters of waters from the active site to the dimer interface. Here, we show that dimerization clearly changes correlations in the water structure and dynamics in the active site not seen in the monomer. Our results indicate that water at the active sites of the dimer is less affected compared with bulk solvent than in the monomer where it has much slower characteristic relaxation times. Given that water is a required participant in the reaction, this gives a clear advantage to dimerization in the absence of an apparent ability to use both active sites simultaneously.

  10. Artificial light harvesting by dimerized Möbius ring

    Science.gov (United States)

    Xu, Lei; Gong, Z. R.; Tao, Ming-Jie; Ai, Qing

    2018-04-01

    We theoretically study artificial light harvesting by a Möbius ring. When the donors in the ring are dimerized, the energies of the donor ring are split into two subbands. Because of the nontrivial Möbius boundary condition, both the photon and acceptor are coupled to all collective-excitation modes in the donor ring. Therefore, the quantum dynamics in the light harvesting is subtly influenced by dimerization in the Möbius ring. It is discovered that energy transfer is more efficient in a dimerized ring than that in an equally spaced ring. This discovery is also confirmed by a calculation with the perturbation theory, which is equivalent to the Wigner-Weisskopf approximation. Our findings may be beneficial to the optimal design of artificial light harvesting.

  11. Characterization of oxygen dimer-enriched silicon detectors

    CERN Document Server

    Boisvert, V; Moll, M; Murin, L I; Pintilie, I

    2005-01-01

    Various types of silicon material and silicon p+n diodes have been treated to increase the concentration of the oxygen dimer (O2i) defect. This was done by exposing the bulk material and the diodes to 6 MeV electrons at a temperature of about 350 °C. FTIR spectroscopy has been performed on the processed material confirming the formation of oxygen dimer defects in Czochralski silicon pieces. We also show results from TSC characterization on processed diodes. Finally, we investigated the influence of the dimer enrichment process on the depletion voltage of silicon diodes and performed 24 GeV/c proton irradiations to study the evolution of the macroscopic diode characteristics as a function of fluence.

  12. Fano resonances in heterogeneous dimers of silicon and gold nanospheres

    Science.gov (United States)

    Zhao, Qian; Yang, Zhong-Jian; He, Jun

    2018-06-01

    We theoretically investigate the optical properties of dimers consisting of a gold nanosphere and a silicon nanosphere. The absorption spectrum of the gold sphere in the dimer can be significantly altered and exhibits a pronounced Fano profile. Analytical Mie theory and numerical simulations show that the Fano profile is induced by constructive and destructive interference between the incident electric field and the electric field of the magnetic dipole mode of the silicon sphere in a narrow wavelength range. The effects of the silicon sphere size, distance between the two spheres, and excitation configuration on the optical responses of the dimers are studied. Our study reveals the coherent feature of the electric fields of magnetic dipole modes in dielectric nanostructures and the strong interactions of the coherent fields with other nanophotonic structures.

  13. Pyrimidine dimers in Drosophila chromatin become increasingly accessible after irradiation

    International Nuclear Information System (INIS)

    Harris, P.V.; Boyd, J.B.

    1987-01-01

    A prokaryotic DNA-repair enzyme has been utilized as a probe for changes in the accessibility of pyrimidine dimers in Drosophila chromatin following UV irradiation. The results demonstrate a rapid cellular response to physiologically relevant doses of radiation which results in at least a 40% increase in accessible dimers. This increase occurs in two incision-deficient mutants which indicates that the excision-repair process, at or beyond the incision step, is not required or responsible for the increase. In the absence of excision the increase in accessibility persists for a least 2 days following irradiation. The observed increase in accessibility is inhibited by both novobiocin and coumermycin. These inhibitors do not inhibit the initial rate of incision, but do reduce dimer excision measured over more extended periods. A pre-incision process is proposed which actively exposes DNA lesions to excision repair. A fraction of the genome is postulated to be accessible without the intervention of that process. (Auth.)

  14. Disintegration and dimerization of δ-tocopherol under radiation effect

    International Nuclear Information System (INIS)

    Jasinska-Stepniak, A.; Gogolewski, M.; Zabielski, J.

    1996-01-01

    The goal of the work was to recognize scala changes of δ-tocopherol in model system (diluted in benzene, ethanol and ''in substantia'') after 2.5, 5, 10 and 20 kGy dose irradiation. δ-tocopherol and its mild oxidation products (dimers) after TLC separation were quantitatively determined with Emmerie-Engel method. Relations dose-effect have been defined and radiation capacity has been calculated. The results show that disintegration of δ-tocopherol diluted in ethanol is about ten times stronger the diluted in benzene. δ-tocopherol in benzene was dimerized. The most stable after irradiation was δ-tocopherol ''in substantia''. (author)

  15. Dimer-flipping-assisted diffusion on a Si(001) surface

    International Nuclear Information System (INIS)

    Zi, J.; Min, B. J.; Lu, Y.; Wang, C. Z.; Ho, K. M.

    2000-01-01

    The binding sites and diffusion pathways of Si adatoms on a c(4x2) reconstructed Si(001) surface are investigated by a tight-binding method with an environment-dependent silicon potential in conjunction with ab initio calculations using the Car--Parrinello method. A new diffusion pathway along the trough edge driven by dimer flipping is found with a barrier of 0.74 eV, comparable to that of 0.68 eV along the top of the dimer rows

  16. Pyrimidine dimer excision in human cells and skin cancer

    International Nuclear Information System (INIS)

    Regan, J.D.; Carrier, W.L.; Smith, D.P.; Waters, R.

    1977-01-01

    We have compared three different methods for estimating the induction and removal of uv induced pyrimidine dimers from the DNA of human fibroblasts. Results indicate that after uv doses of 5-20 J/m 2 50% of the dimers are removed by 24 hours after irradiation. Almost complete excision can be observed if the cells are incubated for periods not less than 72 hours after 5 J/m 2 . After higher doses it probably takes even longer fr such complete removal to be seen

  17. Construction of covalently coupled, concatameric dimers of 7TM receptors

    DEFF Research Database (Denmark)

    Terpager, Marie; Scholl, D Jason; Kubale, Valentina

    2009-01-01

    -Ala repeats flanked by flexible spacers and positively charged residues to ensure correct inside-out orientation plus an extracellular HA-tag to construct covalently coupled dimers of 7TM receptors. Such 15 TM concatameric homo- and heterodimers of the beta(2)-adrenergic and the NK(1) receptors, which...... for either of the protomers, which was not observed upon simple coexpression of the two receptors. It is concluded that covalently joined 7TM receptor dimers with surprisingly normal receptor properties can be constructed with use of an artificial transmembrane connector, which perhaps can be used to fuse...

  18. Metal membrane with dimer slots as a universal polarizer

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Zalkovskij, Maksim; Malureanu, Radu

    2014-01-01

    In this work, we show theoretically and confirm experimentally that thin metal membranes patterned with an array of slot dimers (or their Babinet analogue with metal rods) can function as a versatile spectral and polarization filter. We present a detailed covariant multipole theory for the electr......In this work, we show theoretically and confirm experimentally that thin metal membranes patterned with an array of slot dimers (or their Babinet analogue with metal rods) can function as a versatile spectral and polarization filter. We present a detailed covariant multipole theory...

  19. Analytical study of avian reticuloendotheliosis virus dimeric RNA generated in vivo and in vitro.

    Science.gov (United States)

    Darlix, J L; Gabus, C; Allain, B

    1992-12-01

    The retroviral genome consists of two identical RNA molecules associated at their 5' ends by a stable structure called the dimer linkage structure. The dimer linkage structure, while maintaining the dimer state of the retroviral genome, might also be involved in packaging and reverse transcription, as well as recombination during proviral DNA synthesis. To study the dimer structure of the retroviral genome and the mechanism of dimerization, we analyzed features of the dimeric genome of reticuloendotheliosis virus (REV) type A and identified elements required for its dimerization. Here we report that the REV dimeric genome extracted from virions and infected cells, as well as that synthesized in vitro, is more resistant to heat denaturation than avian sarcoma and leukemia virus, murine leukemia virus, or human immunodeficiency virus type 1 dimeric RNA. The minimal domain required to form a stable REV RNA dimer in vitro was found to map between positions 268 and 452 (KpnI and SalI sites), thus corresponding to the E encapsidation sequence (J. E. Embretson and H. M. Temin, J. Virol. 61:2675-2683, 1987). In addition, both the 5' and 3' halves of E are necessary in cis for RNA dimerization and the extent of RNA dimerization is influenced by viral sequences flanking E. Rapid and efficient dimerization of REV RNA containing gag sequences in addition to the E sequences and annealing of replication primer tRNA(Pro) to the primer-binding site necessitate the nucleocapsid protein.

  20. Mixed Valence in Conjugated Anion Radicals. Solution and Solid State Studies

    Science.gov (United States)

    1991-05-24

    voltammetry was performed using a BAS-100 electrochemical analyzer. Bulk electrolyses were performed with a Princeton Applied Research (PAR) model 173...extracted with several small portions of CH 2 CI 2. The combined organic layers are then washed once again with water . After drying over Na2 SO4 the

  1. Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes

    Czech Academy of Sciences Publication Activity Database

    Schweinfurth, D.; Rechkemmer, Y.; Hohloch, S.; Deibel, N.; Peremykin, I.; Fiedler, Jan; Marx, R.; Neugebauer, P.; van Slageren, J.; Sarkar, B.

    2014-01-01

    Roč. 20, č. 12 (2014), s. 3475-3486 ISSN 0947-6539 R&D Projects: GA ČR GA203/09/0705 Institutional support: RVO:61388955 Keywords : bridging ligand s * mixed -valent compounds * non-innocent ligand s Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.731, year: 2014

  2. Effect of Tb.sup.3+./sup. doping in mixed-valence manganites and cobaltites

    Czech Academy of Sciences Publication Activity Database

    Knížek, Karel; Jirák, Zdeněk; Kaman, Ondřej; Maryško, Miroslav; Damay, F.

    2017-01-01

    Roč. 29, č. 40 (2017), s. 1-9, č. článku 405802. ISSN 0953-8984 R&D Projects: GA ČR GA15-10088S Institutional support: RVO:68378271 Keywords : cobalt perovskite * manganese perovskite * neutron diffraction * magnetic order ing * Ising moments Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.649, year: 2016

  3. Tetrathiafulvalene-Oligo(para-phenyleneethynylene) Conjugates: Formation of Multiple Mixed-Valence Complexes upon Electrochemical Oxidation

    Czech Academy of Sciences Publication Activity Database

    Lipnická, Šárka; Bělohradský, Martin; Kolivoška, Viliam; Pospíšil, Lubomír; Hromadová, Magdaléna; Pohl, Radek; Vacek Chocholoušová, Jana; Vacek, Jaroslav; Fiedler, Jan; Stará, Irena G.; Starý, Ivo

    2013-01-01

    Roč. 19, č. 19 (2013), s. 6108-6121 ISSN 0947-6539 R&D Projects: GA ČR GAP207/10/2214; GA ČR GA203/09/0705; GA ČR GA203/09/1802; GA MŠk 7E09054; GA AV ČR IAA400400802 EU Projects: European Commission(XE) 213382 - FUNMOL Institutional support: RVO:61388963 ; RVO:61388955 Keywords : cross - coupling * donor-acceptor systems * tetrathiofulvalene * oligomers * electrochemistry Subject RIV: CC - Organic Chemistry; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 5.696, year: 2013

  4. Electrochemistry and Spectroelectrochemistry of Polynuclear Zinc Phthalocyanines: Formation of Mixed Valence Cation Radical Species.

    Science.gov (United States)

    1988-02-25

    No. No. Copies Cpe Office of Naval Research 2 Dr. David You.)g Attn: Code 1113 Code 334 800 N. Quinc’ Street NORDA Arlington, Virginia 22217-5000 NSTL...Naval Surface Weapons Center Chapel Hill, North Carolina 27514 Silver Spring, Maryland 20910 Or. R. A. Marcus Dr. Michael J. Weaver Department of...Microprocessor model 340 spectrometer. Cyclic and dif, rential pulse voltammetry were performed with a Princeton Applied Research (PARC) model 174A

  5. Mixed valence transition metal 2D-oxides: Comparison between delafossite and crednerite compounds

    Science.gov (United States)

    Martin, Christine; Poienar, Maria

    2017-08-01

    Transition metal oxides offer large opportunities to study relationships between structures and properties. Indeed these compounds crystallize in numerous frameworks corresponding to different dimensionalities and, accordingly, show a huge variety of properties (as high Tc superconductivity, colossal magnetoresistivity, multiferroicity..). The control of the oxidation state of the transition metal, via the monitoring of the oxygen content, is of prime importance to understand and optimize the properties, due to the strong coupling that exists between the lattice and the charges and spins of the transition metals. In this large playground for chemists, we reinvestigated several 2D-compounds derived from delafossite structure. Considering this paper as a very short review, we report here the results obtained on CuMO2 compounds (with M = Cr, Mn or Mn+Cu) by using a combination of techniques, as X-ray, neutrons and/or electrons diffraction on poly-crystals for structural characterisations that are correlated with electrical and/or magnetic properties. The complementarity of studies is also addressed by the synthesis and characterization of single crystals in addition to poly-crystals. Moreover the comparison of the structures of similar Cr and Mn based oxides highlights the crucial role of the Jahn-Teller effect of trivalent manganese to lift the degeneracy, which is responsible of the magnetic frustration in CuCrO2.

  6. RESONANT MAGNETIC-X-RAY SCATTERING FROM MIXED-VALENCE TMSE

    NARCIS (Netherlands)

    MCWHAN, DB; ISAACS, ED; CARRA, P; SHAPIRO, SM; THOLE, BT; HOSHINO, S

    1993-01-01

    The mixed-valent compound TmSe has been studied in its antiferromagnetic state (T

  7. Iron-Deficiency Anemia

    Medline Plus

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  8. Iron-Deficiency Anemia

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  10. Iron-Deficiency Anemia

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    Full Text Available ... heart failure . Increased risk of infections Motor or cognitive development delays in children Pregnancy complications, such as ... for iron-deficiency anemia. Learn about exciting research areas that NHLBI is exploring about iron-deficiency anemia. ...

  11. Iron-Deficiency Anemia

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  14. Iron-Deficiency Anemia

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    Full Text Available ... same for boys and girls. From birth to 6 months, babies need 0.27 mg of iron. ... for iron deficiency at certain ages: Infants between 6 and 12 months, especially if they are fed ...

  15. Iron-Deficiency Anemia

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    Full Text Available ... Disorders Lung Diseases Heart and Vascular Diseases Precision Medicine Activities Obesity, Nutrition, and Physical Activity Population and ... lose blood, you lose iron. Certain conditions or medicines can cause blood loss and lead to iron- ...

  18. Iron-Deficiency Anemia

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  19. Iron-Deficiency Anemia

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  20. Iron-Deficiency Anemia

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  1. Iron-Deficiency Anemia

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    Full Text Available ... may be diagnosed with iron-deficiency anemia if you have low iron or ferritin levels in your blood. More testing may be needed to rule out other types of anemia. Tests for gastrointestinal ...

  2. Iron-Deficiency Anemia

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    Full Text Available ... were born prematurely may be at an even higher risk, as most of a newborn’s iron stores ... men of the same age. Women are at higher risk for iron-deficiency anemia under some circumstances, ...

  3. Iron supplements (image)

    Science.gov (United States)

    The mineral iron is an essential nutrient for humans because it is part of blood cells, which carry oxygen to all body cells. There is no conclusive evidence that iron supplements contribute to heart attacks.

  4. Total iron binding capacity

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003489.htm Total iron binding capacity To use the sharing features on this page, please enable JavaScript. Total iron binding capacity (TIBC) is a blood test to ...

  5. Iron-Deficiency Anemia

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  6. Iron-Deficiency Anemia

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  7. Iron-Deficiency Anemia

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    Full Text Available ... iron-rich foods, especially during certain stages of life when more iron is needed, such as ... to advancing science and translating discoveries into clinical practice to promote ...

  8. Iron-Deficiency Anemia

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    Full Text Available ... also often take other medicines—such as proton pump inhibitors, anticoagulants, or blood thinners—that may cause iron-deficiency anemia. Proton pump inhibitors interfere with iron absorption, and blood thinners ...

  9. Iron-Deficiency Anemia

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  10. Iron-Deficiency Anemia

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    Full Text Available ... striking the ground, such as with marathon runners. Sex Girls and women between the ages of 14 ... developing iron-deficiency anemia. Foods that are good sources of iron include dried beans, dried fruits, eggs, ...

  11. Iron-Deficiency Anemia

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    Full Text Available ... increase your risk for iron-deficiency anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron- ... factors , such as if you are following a vegetarian eating pattern, your doctor may recommend changes to ...

  12. Iron-Deficiency Anemia

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    Full Text Available ... deficiency anemia. Proton pump inhibitors interfere with iron absorption, and blood thinners increase the likelihood of bleeding ... oranges, strawberries, and tomatoes, may help increase your absorption of iron. If you are pregnant, talk to ...

  13. Iron-Deficiency Anemia

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    Full Text Available ... Not eating enough iron-rich foods, such as meat and fish, may result in you getting less ... include dried beans, dried fruits, eggs, lean red meat, salmon, iron-fortified breads and cereals, peas, tofu, ...

  14. Iron-Deficiency Anemia

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    Full Text Available ... mg and women need 18 mg. After age 51, both men and women need 8 mg. Pregnant ... for iron-deficiency anemia. Learn about exciting research areas that NHLBI is exploring about iron-deficiency anemia. ...

  15. Iron-Deficiency Anemia

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    Full Text Available ... iron-deficiency anemia. These conditions include: Intestinal and digestive conditions, such as celiac disease; inflammatory bowel diseases, ... iron-deficiency anemia , such as bleeding in the digestive or urinary tract or heavy menstrual bleeding, your ...

  16. Iron-Deficiency Anemia

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    Full Text Available ... prevent complications such as abnormal heart rhythms and depression. Learn the warning signs of serious complications and ... donors for low iron stores. Reliable point-of-care testing may help identify iron deficiency before potentially ...

  17. Iron-Deficiency Anemia

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    Full Text Available ... breastfeeding women older than 18 need 9 mg. Problems absorbing iron Even if you consume the recommended ... interested in learning how having iron-deficiency anemia early in life affects later behavior, thinking, and mood ...

  18. Iron-Deficiency Anemia

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    Full Text Available ... conditions that can cause iron-deficiency anemia. Blood tests to screen for iron-deficiency anemia To screen ... the size of your liver and spleen. Blood tests Based on results from blood tests to screen ...

  19. Iron-Deficiency Anemia

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    Full Text Available ... as most of a newborn’s iron stores are developed during the third trimester of pregnancy. Children between ... This makes it harder to stop bleeding and can increase the risk of iron-deficiency anemia from ...

  20. Iron-Deficiency Anemia

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    Full Text Available ... your doctor may recommend you eat heart-healthy foods or control other conditions that can cause iron-deficiency anemia. Blood tests to screen for iron-deficiency anemia To screen ...

  1. Iron-Deficiency Anemia

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    Full Text Available ... have less hemoglobin than normal. Hemoglobin is a protein inside red blood cells that carries oxygen from ... stored iron has been used. Ferritin is a protein that helps store iron in your body. Reticulocyte ...

  2. Iron-Deficiency Anemia

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    Full Text Available ... and Strategic Vision Leadership Scientific Divisions Operations and Administration Advisory Committees Budget and Legislative Information Jobs and ... blood cells. Iron-deficiency anemia usually develops over time because your body’s intake of iron is too ...

  3. Iron-Deficiency Anemia

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    Full Text Available ... vegan eating patterns. Not eating enough iron-rich foods, such as meat and fish, may result in ... be hard to get the recommended amount from food alone. Pregnant women need more iron to support ...

  4. Iron-Deficiency Anemia

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    Full Text Available ... learning how having iron-deficiency anemia early in life affects later behavior, thinking, and mood during adolescence. ... iron-deficiency anemia in blood donors affects the quality of donated red blood cells, such as how ...

  5. Iron-Deficiency Anemia

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    Full Text Available ... iron-deficiency anemia in blood donors affects the quality of donated red blood cells, such as how ... Cells From Iron-deficient Donors: Recovery and Storage Quality. Learn more about participating in a clinical trial . ...

  6. Iron-Deficiency Anemia

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    Full Text Available ... endoscopy or colonoscopy, to stop bleeding. Healthy lifestyle changes To help you meet your daily recommended iron ... iron-deficiency anemia early in life affects later behavior, thinking, and mood during adolescence. Treating anemia in ...

  7. Iron-Deficiency Anemia

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    Full Text Available ... family history and genetics , lifestyle habits, or sex. Age You may be at increased risk for iron ... Signs, Symptoms, and Complications Iron-deficiency anemia can range from mild to severe. People with mild or ...

  8. Iron-Deficiency Anemia

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    Full Text Available ... leaving cells where it is stored or from being absorbed in the duodenum, the first part of ... treatments for iron-deficiency anemia. Living With After being diagnosed with iron-deficiency anemia, it is important ...

  9. Iron-Deficiency Anemia

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    Full Text Available ... iron to prepare for blood loss during delivery. Screening and Prevention Your doctor may screen you for ... and symptoms of iron-deficiency anemia. Return to Screening and Prevention to review tests to screen for ...

  10. Iron-Deficiency Anemia

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    Full Text Available ... Teens, who have increased need for iron during growth spurts. Older adults, especially those over age 65. ... need for iron increases during these periods of growth and development, and it may be hard to ...

  11. Iron-Deficiency Anemia

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    Full Text Available ... endoscopy or colonoscopy, to stop bleeding. Healthy lifestyle changes To help you meet your daily recommended iron ... tofu, dried fruits, and spinach and other dark green leafy vegetables. You can also take an iron ...

  12. Iron absorption studies

    International Nuclear Information System (INIS)

    Ekenved, G.

    1976-01-01

    The main objective of the present work was to study iron absorption from different iron preparations in different types of subjects and under varying therapeutic conditions. The studies were performed with different radioiron isotope techniques and with a serum iron technique. The preparations used were solutions of ferrous sulphate and rapidly-disintegrating tablets containing ferrous sulphate, ferrous fumarate and ferrous carbonate and a slow-release ferrous sulphate tablet of an insoluble matrix type (Duroferon Durules). The serum iron method was evaluated and good correlation was found between the serum iron response and the total amount of iron absorbed after an oral dose of iron given in solution or in tablet form. New technique for studying the in-vivo release properties of tablets was presented. Iron tablets labelled with a radio-isotope were given to healthy subjects. The decline of the radioactivity in the tablets was followed by a profile scanning technique applied to different types of iron tablets. The release of iron from the two types of tablets was shown to be slower in vivo than in vitro. It was found that co-administration of antacids and iron tablets led to a marked reduction in the iron absorption and that these drugs should not be administered sumultaneously. A standardized meal markedly decreased the absorbability of iron from iron tablets. The influence of the meal was more marked with rapidly-disintegrating than with slow-release ferrous sulphate tablets. The absorption from rapidly-disintegrating and slow-release ferrous sulphate tablets was compared under practical clinical conditions during an extended treatment period. The studies were performed in healthy subjects, blood donors and patients with iron deficiency anaemia and it was found that the absorption of iron from the slow-release tablets was significantly better than from the rapidly-disintegrating tablets in all three groups of subjects. (author)

  13. Structure of an RNA dimer of a regulatory element from human thymidylate synthase mRNA

    OpenAIRE

    Dibrov, Sergey; McLean, Jaime; Hermann, Thomas

    2011-01-01

    An oligonucleotide representing a regulatory element of human thymidylate synthase mRNA has been crystallized as a dimer. The structure of the asymmetric dimer has been determined at 1.97 Å resolution.

  14. Iron-Deficiency Anemia

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    Full Text Available ... iron, in milligrams (mg) at different ages and stages of life. Until the teen years, the recommended amount of ... and choosing iron-rich foods, especially during certain stages of life when more iron is needed, such as childhood ...

  15. Iron-Deficiency Anemia

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    Full Text Available ... iron-fortified breads and cereals, peas, tofu, dried fruits, and dark green leafy vegetables. Foods rich in vitamin C, such as oranges, ... iron-fortified breads and cereals, beans, tofu, dried fruits, and spinach and other dark green leafy vegetables. You can also take an iron supplement. Follow ...

  16. Iron-Deficiency Anemia

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    Full Text Available ... because your body’s intake of iron is too low. Low intake of iron can happen because of blood ... a lot of cow’s milk. Cow’s milk is low in iron. Teens, who have increased need for ...

  17. Iron-Deficiency Anemia

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    Full Text Available ... This is sometimes used to deliver iron through a blood vessel to increase iron levels in the blood. One benefit of IV iron ... over 65 years of age had low hemoglobin levels. This was associated with a greater risk of death even with mild anemia. ...

  18. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Heart and Vascular Diseases Precision Medicine Activities Obesity, Nutrition, and Physical Activity Population and Epidemiology Studies Women’s ... making new blood cells. Visit our Aplastic Anemia Health Topic to learn more. ... recommend that you take iron supplements, also called iron pills or oral iron, by mouth once or several times a ...

  19. Iron-Deficiency Anemia

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    Full Text Available ... supplements. Iron supplements can change how certain medicines work. Your doctor may suggest check-ups to make sure your ... To prevent complications from iron-deficiency anemia, your doctor may ... during certain stages of life when more iron is needed, such as childhood ...

  20. Iron-Deficiency Anemia

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    Full Text Available ... if you are diagnosed with iron-deficiency anemia. Risk Factors You may have an increased risk for iron-deficiency anemia because of your age, ... or sex. Age You may be at increased risk for iron deficiency at certain ages: Infants between ...

  1. Iron and Immunity

    NARCIS (Netherlands)

    Verbon, E.H.|info:eu-repo/dai/nl/413534049; Trapet, P.L.; Stringlis, I.|info:eu-repo/dai/nl/41185206X; Kruijs, Sophie; Bakker, P.A.H.M.|info:eu-repo/dai/nl/074744623; Pieterse, C.M.J.|info:eu-repo/dai/nl/113115113

    2017-01-01

    Iron is an essential nutrient for most life on Earth because it functions as a crucial redox catalyst in many cellular processes. However, when present in excess iron can lead to the formation of harmful hydroxyl radicals. Hence, the cellular iron balance must be tightly controlled. Perturbation of

  2. Glutathione, Glutaredoxins, and Iron.

    Science.gov (United States)

    Berndt, Carsten; Lillig, Christopher Horst

    2017-11-20

    Glutathione (GSH) is the most abundant cellular low-molecular-weight thiol in the majority of organisms in all kingdoms of life. Therefore, functions of GSH and disturbed regulation of its concentration are associated with numerous physiological and pathological situations. Recent Advances: The function of GSH as redox buffer or antioxidant is increasingly being questioned. New functions, especially functions connected to the cellular iron homeostasis, were elucidated. Via the formation of iron complexes, GSH is an important player in all aspects of iron metabolism: sensing and regulation of iron levels, iron trafficking, and biosynthesis of iron cofactors. The variety of GSH coordinated iron complexes and their functions with a special focus on FeS-glutaredoxins are summarized in this review. Interestingly, GSH analogues that function as major low-molecular-weight thiols in organisms lacking GSH resemble the functions in iron homeostasis. Since these iron-related functions are most likely also connected to thiol redox chemistry, it is difficult to distinguish between mechanisms related to either redox or iron metabolisms. The ability of GSH to coordinate iron in different complexes with or without proteins needs further investigation. The discovery of new Fe-GSH complexes and their physiological functions will significantly advance our understanding of cellular iron homeostasis. Antioxid. Redox Signal. 27, 1235-1251.

  3. Iron Stain on Wood

    Science.gov (United States)

    Mark Knaebe

    2013-01-01

    Iron stain, an unsightly blue–black or gray discoloration, can occur on nearly all woods. Oak, redwood, cypress, and cedar are particularly prone to iron stain because these woods contain large amounts of tannin-like extractives. The discoloration is caused by a chemical reaction between extractives in the wood and iron in steel products, such as nails, screws, and...

  4. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... amounts of iron, in milligrams (mg) at different ages and stages of life. Until the teen years, the recommended amount of iron is the same for boys and girls. From birth to 6 months, babies need 0.27 mg of iron. This number goes up to 11 mg for children ages 7 to 12 months, and down to 7 ...

  5. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... bleeding or other abnormalities, such as growths or cancer of the lining of the colon. For this test, a ... that you take iron supplements, also called iron pills or oral iron, by mouth once or several times a ...

  6. Iron homeostasis during pregnancy.

    Science.gov (United States)

    Fisher, Allison L; Nemeth, Elizabeta

    2017-12-01

    During pregnancy, iron needs to increase substantially to support fetoplacental development and maternal adaptation to pregnancy. To meet these iron requirements, both dietary iron absorption and the mobilization of iron from stores increase, a mechanism that is in large part dependent on the iron-regulatory hormone hepcidin. In healthy human pregnancies, maternal hepcidin concentrations are suppressed in the second and third trimesters, thereby facilitating an increased supply of iron into the circulation. The mechanism of maternal hepcidin suppression in pregnancy is unknown, but hepcidin regulation by the known stimuli (i.e., iron, erythropoietic activity, and inflammation) appears to be preserved during pregnancy. Inappropriately increased maternal hepcidin during pregnancy can compromise the iron availability for placental transfer and impair the efficacy of iron supplementation. The role of fetal hepcidin in the regulation of placental iron transfer still remains to be characterized. This review summarizes the current understanding and addresses the gaps in knowledge about gestational changes in hematologic and iron variables and regulatory aspects of maternal, fetal, and placental iron homeostasis. © 2017 American Society for Nutrition.

  7. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Topics section only, or the News and Resources section. NHLBI Entire Site NHLBI Entire Site Health ... español Iron-deficiency anemia is a common type of anemia that occurs if you do not have enough iron in your body. People with mild or moderate iron-deficiency anemia ...

  8. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... for iron-deficiency anemia. Lifestyle habits Certain lifestyle habits may increase your risk for iron-deficiency anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron-rich foods, such as meat and fish, may result in ...

  9. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... blood cells. Iron-deficiency anemia usually develops over time because your body’s intake of iron is too ... clamping of your newborn’s umbilical cord at the time of delivery. This may help prevent iron-deficiency ...

  10. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... severity of the condition. Your doctor may recommend healthy eating changes, iron supplements, intravenous iron therapy for mild ... you: Adopt healthy lifestyle changes such as heart-healthy eating patterns. Increase your daily intake of iron-rich ...

  11. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... iron-deficiency anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron-rich foods, such as meat and fish, may result in you getting less than the recommended daily amount of iron. Frequent blood donation. Individuals who donate blood often may be ...

  12. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Topics News & Resources Intramural Research Home / < Back To Health Topics / Iron-Deficiency Anemia Iron-Deficiency Anemia Also known as Leer ... and symptoms as well as complications from iron-deficiency anemia. Research for Your Health The NHLBI is part of the U.S. Department ...

  13. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... anemia, your doctor may order the following blood tests to diagnose iron-deficiency anemia: Complete blood count (CBC) to ... than normal when viewed under a microscope. Different tests help your doctor diagnose iron-deficiency anemia. In iron-deficiency anemia, blood ...

  14. Iron-Deficiency Anemia

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    Full Text Available ... for iron-deficiency anemia if you have certain risk factors , including pregnancy. To prevent iron-deficiency anemia, your doctor may recommend you eat heart-healthy foods or control other conditions that can cause iron-deficiency anemia. ...

  15. Iron and Your Child

    Science.gov (United States)

    ... deficiency isn't corrected, it can lead to iron-deficiency anemia (a decrease in the number of red blood ... Parents Kids Teens Anemia Blood Test: Ferritin (Iron) Iron-Deficiency Anemia Vegetarianism Menstrual Problems Pregnant or Breastfeeding? Nutrients You ...

  16. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... normally stores but has used up. Increase your intake of vitamin C to help your body absorb iron. Avoid drinking black tea, which reduces iron absorption. Other treatments If you have chronic kidney disease and iron-deficiency anemia, your doctor may recommend ...

  17. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... different ages and stages of life. Until the teen years, the recommended amount of iron is the ... cow’s milk. Cow’s milk is low in iron. Teens, who have increased need for iron during growth ...

  18. Adsorption, mobility, and dimerization of benzaldehyde on Pt(111)

    DEFF Research Database (Denmark)

    Rasmussen, Anton Michael Havelund; Hammer, Bjørk

    2012-01-01

    to have low energy barriers. Aggregation of molecules in dimers bound by aryl C–H⋯O hydrogen bonds is investigated, and specific configurations are found to be up to 0.15 eV more favorable than optimally configured, separated adsorbates. The binding is significantly stronger than what is found for gas...

  19. Synthesis and Dimerization Behavior of Five Metallophthalocyanines in Different Solvents

    Directory of Open Access Journals (Sweden)

    Zhenhua Cheng

    2014-01-01

    Full Text Available Metallophthalocyanine (MPc has become one of the metal organic compounds with the largest production and the most widely application, because of its excellent performance in catalytic oxidation. However, aggregation of the MPc in solution, resulting in decreased solubility, greatly limits the performance of application. Studying the behavior of dimerization of MPcs can provide a theoretical basis for solving the problem of the low solubility. So five metallophthalocyanines (FePc, CoPc, NiPc, CuPc, and ZnPc were prepared with improved method and characterized. Dimerization of the five MPcs was measured by UV-Vis spectroscopy separately in N,N-dimethyl formamide (DMF and dimethylsulfoxide (DMSO. The red-shift of maximum absorption wavelength and deviations from Lambert-Beer law with increasing the concentration were observed for all the five MPcs. The dimerization equilibrium constants (K of the five MPcs in DMF were arranged in order of CoPc > ZnPc > CuPc > FePc > NiPc, while in DMSO they were arranged in order of ZnPc > CoPc > FePc > CuPc > NiPc. The type of the central metal and nature of the solvent affect the dimerization of the MPcs.

  20. Unphosphorylated rhabdoviridae phosphoproteins form elongated dimers in solution.

    Science.gov (United States)

    Gerard, Francine C A; Ribeiro, Euripedes de Almeida; Albertini, Aurélie A V; Gutsche, Irina; Zaccai, Guiseppe; Ruigrok, Rob W H; Jamin, Marc

    2007-09-11

    The phosphoprotein (P) is an essential component of the replication machinery of rabies virus (RV) and vesicular stomatitis virus (VSV), and the oligomerization of P, potentially controlled by phosphorylation, is required for its function. Up to now the stoichiometry of phosphoprotein oligomers has been controversial. Size exclusion chromatography combined with detection by multiangle laser light scattering shows that the recombinant unphosphorylated phosphoproteins from VSV and from RV exist as dimers in solution. Hydrodynamic analysis indicates that the dimers are highly asymmetric, with a Stokes radius of 4.8-5.3 nm and a frictional ratio larger than 1.7. Small-angle neutron scattering experiments confirm the dimeric state and the asymmetry of the structure and yield a radius of gyration of about 5.3 nm and a cross-sectional radius of gyration of about 1.6-1.8 nm. Similar hydrodynamic properties and molecular dimensions were obtained with a variant of VSV phosphoprotein in which Ser60 and Thr62 are substituted by Asp residues and which has been reported previously to mimic phosphorylation by inducing oligomerization and activating transcription. Here, we show that this mutant also forms a dimer with hydrodynamic properties and molecular dimensions similar to those of the wild type protein. However, incubation at 30 degrees C for several hours induced self-assembly of both wild type and mutant proteins, leading to the formation of irregular filamentous structures.

  1. Fe65-PTB2 Dimerization Mimics Fe65-APP Interaction

    Directory of Open Access Journals (Sweden)

    Lukas P. Feilen

    2017-05-01

    Full Text Available Physiological function and pathology of the Alzheimer’s disease causing amyloid precursor protein (APP are correlated with its cytosolic adaptor Fe65 encompassing a WW and two phosphotyrosine-binding domains (PTBs. The C-terminal Fe65-PTB2 binds a large portion of the APP intracellular domain (AICD including the GYENPTY internalization sequence fingerprint. AICD binding to Fe65-PTB2 opens an intra-molecular interaction causing a structural change and altering Fe65 activity. Here we show that in the absence of the AICD, Fe65-PTB2 forms a homodimer in solution and determine its crystal structure at 2.6 Å resolution. Dimerization involves the unwinding of a C-terminal α-helix that mimics binding of the AICD internalization sequence, thus shielding the hydrophobic binding pocket. Specific dimer formation is validated by nuclear magnetic resonance (NMR techniques and cell-based analyses reveal that Fe65-PTB2 together with the WW domain are necessary and sufficient for dimerization. Together, our data demonstrate that Fe65 dimerizes via its APP interaction site, suggesting that besides intra- also intermolecular interactions between Fe65 molecules contribute to homeostatic regulation of APP mediated signaling.

  2. Fe65-PTB2 Dimerization Mimics Fe65-APP Interaction.

    Science.gov (United States)

    Feilen, Lukas P; Haubrich, Kevin; Strecker, Paul; Probst, Sabine; Eggert, Simone; Stier, Gunter; Sinning, Irmgard; Konietzko, Uwe; Kins, Stefan; Simon, Bernd; Wild, Klemens

    2017-01-01

    Physiological function and pathology of the Alzheimer's disease causing amyloid precursor protein (APP) are correlated with its cytosolic adaptor Fe65 encompassing a WW and two phosphotyrosine-binding domains (PTBs). The C-terminal Fe65-PTB2 binds a large portion of the APP intracellular domain (AICD) including the GYENPTY internalization sequence fingerprint. AICD binding to Fe65-PTB2 opens an intra-molecular interaction causing a structural change and altering Fe65 activity. Here we show that in the absence of the AICD, Fe65-PTB2 forms a homodimer in solution and determine its crystal structure at 2.6 Å resolution. Dimerization involves the unwinding of a C-terminal α-helix that mimics binding of the AICD internalization sequence, thus shielding the hydrophobic binding pocket. Specific dimer formation is validated by nuclear magnetic resonance (NMR) techniques and cell-based analyses reveal that Fe65-PTB2 together with the WW domain are necessary and sufficient for dimerization. Together, our data demonstrate that Fe65 dimerizes via its APP interaction site, suggesting that besides intra- also intermolecular interactions between Fe65 molecules contribute to homeostatic regulation of APP mediated signaling.

  3. Core-to-core dimers forming switchable mesophase

    Czech Academy of Sciences Publication Activity Database

    Horčic, M.; Svoboda, J.; Novotná, Vladimíra; Pociecha, D.; Gorecka, E.

    2017-01-01

    Roč. 53, č. 18 (2017), s. 2721-2724 ISSN 1359-7345 R&D Projects: GA ČR GA15-02843S Institutional support: RVO:68378271 Keywords : liquid crystals * bent- core mesogens * dimers Subject RIV: JJ - Other Materials OBOR OECD: Nano-materials (production and properties) Impact factor: 6.319, year: 2016

  4. Plasma D-dimer concentration in patients with systemic sclerosis

    Directory of Open Access Journals (Sweden)

    Montagnana Martina

    2006-01-01

    Full Text Available Abstract Background Systemic sclerosis (SSc is an autoimmune disorder of the connective tissue characterized by widespread vascular lesions and fibrosis. Little is known so far on the activation of the hemostatic and fibrinolytic systems in SSc, and most preliminary evidences are discordant. Methods To verify whether SSc patients might display a prothrombotic condition, plasma D-dimer was assessed in 28 consecutive SSc patients and in 33 control subjects, matched for age, sex and environmental habit. Results and discussion When compared to healthy controls, geometric mean and 95% confidence interval (IC95% of plasma D-dimer were significantly increased in SSc patients (362 ng/mL, IC 95%: 361–363 ng/mL vs 229 ng/mL, IC95%: 228–231 ng/mL, p = 0.005. After stratifying SSc patients according to disease subset, no significant differences were observed between those with limited cutaneous pattern and controls, whereas patients with diffuse cutaneous pattern displayed substantially increased values. No correlation was found between plasma D-dimer concentration and age, sex, autoantibody pattern, serum creatinine, erythrosedimentation rate, nailfold videocapillaroscopic pattern and pulmonary involvement. Conclusion We demonstrated that SSc patients with diffuse subset are characterized by increased plasma D-dimer values, reflecting a potential activation of both the hemostatic and fibrinolytic cascades, which might finally predispose these patients to thrombotic complications.

  5. Dimeric Complexes of Tryptophan with M2+ Metal Ions

    NARCIS (Netherlands)

    Dunbar, R. C.; Steill, J. D.; Polfer, N. C.; Oomens, J.

    2009-01-01

    IRMPD spectroscopy using the FELIX free electron laser and a Fourier transform ICR mass spectrometer was used to characterize the structures of electrosprayed dimer complexes M(2+)Trp(2) of tryptophan with a series of eight doubly charged metal ions, including alkaline earths Ca, Sr, and Ba, and

  6. Density variations in a reactor during liquid full dimerization

    NARCIS (Netherlands)

    Golombok, M.; Bruijn, J.

    2000-01-01

    In a liquid full plug flow reactor during lower olefin dimerization, the assumption of constant density is not valid—the volume of a plug changes as it proceeds along the reactor. The observed kinetics depend on the density variation in the reactor as the conversion proceeds towards a distribution

  7. Cyclodextrin dimers as receptor molecules for steroid sensors

    NARCIS (Netherlands)

    de Jong, M.R.; Engbersen, Johannes F.J.; Huskens, Jurriaan; Reinhoudt, David

    2000-01-01

    The dansyl-modified dimer 9 complexes strongly with the steroidal bile salts. Relative to native -cyclodextrin, the binding of cholate (1 a) and deoxycholate (1 b) salts is especially enhanced. These steroids bind exclusively in a 1:1 fashion. For other bile salts (1 c-1 e) both 1:1 and 1:2

  8. Stepwise "Dark Photoswitching" of Photochromic Dimers in a Junction

    DEFF Research Database (Denmark)

    Olsen, Stine Tetzschner; Hansen, Thorsten; Nielsen, Mogens Brøndsted

    2017-01-01

    -induced switching) has been termed dark photoswitching and was observed for the dihydroazulene–vinylheptafulvene couple in a junction. In this theoretical study, we expand this concept to dimeric structures containing two dihydroazulene units linked through meta- or para-phenylene bridges and anchored...

  9. pi-Dimers of end-capped oligopyrrole cation radicals

    NARCIS (Netherlands)

    Haare, van J.A.E.H.; Groenendaal, L.; Havinga, E.E.; Janssen, R.A.J.; Meijer, E.W.

    1996-01-01

    In two consecutive one-electron oxidations, oligopyrroles substituted with phenyl capping groups (PhPynPh, n = 2–4) can be oxidized reversibly to give stable cation radicals and dications. Spectroelectrochemical studies give direct evidence that diamagnetic p-dimers of cation radicals are formed in

  10. Determining the nucleation rate from the dimer growth probability

    NARCIS (Netherlands)

    Ter Horst, J.H.; Kashchiev, D.

    2005-01-01

    A new method is proposed for the determination of the stationary one-component nucleation rate J with the help of data for the growth probability P2 of a dimer which is the smallest cluster of the nucleating phase. The method is based on an exact formula relating J and P2, and is readily applicable

  11. Dimerization of Carboxylic Acids: An Equation of State Approach

    DEFF Research Database (Denmark)

    Tsivintzelis, Ioannis; Kontogeorgis, Georgios; Panayiotou, Costas

    2017-01-01

    The association term of the nonrandom hydrogen bonding theory, which is an equation of state model, is extended to describe the dimerization of carboxylic acids in binary mixtures with inert solvents and in systems of two different acids. Subsequently, the model is applied to describe the excess...

  12. Designer interface peptide grafts target estrogen receptor alpha dimerization

    International Nuclear Information System (INIS)

    Chakraborty, S.; Asare, B.K.; Biswas, P.K.; Rajnarayanan, R.V.

    2016-01-01

    The nuclear transcription factor estrogen receptor alpha (ERα), triggered by its cognate ligand estrogen, regulates a variety of cellular signaling events. ERα is expressed in 70% of breast cancers and is a widely validated target for anti-breast cancer drug discovery. Administration of anti-estrogen to block estrogen receptor activation is still a viable anti-breast cancer treatment option but anti-estrogen resistance has been a significant bottle-neck. Dimerization of estrogen receptor is required for ER activation. Blocking ERα dimerization is therefore a complementary and alternative strategy to combat anti-estrogen resistance. Dimer interface peptide “I-box” derived from ER residues 503–518 specifically blocks ER dimerization. Recently using a comprehensive molecular simulation we studied the interaction dynamics of ERα LBDs in a homo-dimer. Based on this study, we identified three interface recognition peptide motifs LDKITDT (ERα residues 479–485), LQQQHQRLAQ (residues 497–506), and LSHIRHMSNK (residues 511–520) and reported the suitability of using LQQQHQRLAQ (ER 497–506) as a template to design inhibitors of ERα dimerization. Stability and self-aggregation of peptide based therapeutics poses a significant bottle-neck to proceed further. In this study utilizing peptide grafted to preserve their pharmacophoric recognition motif and assessed their stability and potential to block ERα mediated activity in silico and in vitro. The Grafted peptides blocked ERα mediated cell proliferation and viability of breast cancer cells but did not alter their apoptotic fate. We believe the structural clues identified in this study can be used to identify novel peptidometics and small molecules that specifically target ER dimer interface generating a new breed of anti-cancer agents. - Highlights: • Designer peptide grafts retain core molecular recognition motif during MD simulations. • Designer peptide grafts with Poly-ALA helix form stable

  13. Tricriticality for dimeric Coulomb molecular crystals in ground state

    Science.gov (United States)

    Travěnec, Igor; Šamaj, Ladislav

    2017-12-01

    We study the ground-state properties of a system of dimers. Each dimer consists in a pair of equivalent charges at a fixed distance, immersed in a neutralizing homogeneous background. All charges interact pairwisely by Coulomb potential. The dimer centers form a two-dimensional rectangular lattice with the aspect ratio α\\in [0, 1] and each dimer is allowed to rotate around its center. The previous numerical simulations, made for the more general Yukawa interaction, indicate that only two basic dimer configurations can appear: either all dimers are parallel or they have two different angle orientations within alternating (checkerboard) sublattices. As the dimer size increases, two second-order phase transitions, related to two kinds of the symmetry breaking in dimer’s orientations, were reported. In this paper, we use a recent analytic method based on an expansion of the interaction energy in Misra functions which converges quickly and provides an analytic derivation of the critical behaviour. Our main result is that there exists a specific aspect ratio of the rectangular lattice α^*=0.714 106 840 000 71\\ldots which divides the space of model’s phases onto two distinct regions. If the lattice aspect ratio α>α* , we recover both types of the second-order phase transitions and find that they are of mean-field type with the critical exponent β = 1/2 . If 0.711 535≤slantα<α* , the phase transition associated with the discontinuity of dimer’s angles on alternating sublattices becomes of first order. For α=α* , the first- and second-order phase transitions meet at the tricritical point, characterized by the different critical index β = 1/4 . Such phenomenon is known from literature about the Landau theory of one-component fields, but in our two-component version the scenario is more complicated: the component which is already in the symmetry-broken state at the tricritical point also interferes and exhibits unexpectedly the mean-field singular

  14. Designer interface peptide grafts target estrogen receptor alpha dimerization

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, S. [Laboratory of Computational Biophysics & Bioengineering, Department of Physics, Tougaloo College, Tougaloo, MS 39174 (United States); Asare, B.K. [Department of Pharmacology and Toxicology, University of Buffalo, Buffalo, NY 14214 (United States); Biswas, P.K., E-mail: pbiswas@tougaloo.edu [Laboratory of Computational Biophysics & Bioengineering, Department of Physics, Tougaloo College, Tougaloo, MS 39174 (United States); Rajnarayanan, R.V., E-mail: rajendra@buffalo.edu [Department of Pharmacology and Toxicology, University of Buffalo, Buffalo, NY 14214 (United States)

    2016-09-09

    The nuclear transcription factor estrogen receptor alpha (ERα), triggered by its cognate ligand estrogen, regulates a variety of cellular signaling events. ERα is expressed in 70% of breast cancers and is a widely validated target for anti-breast cancer drug discovery. Administration of anti-estrogen to block estrogen receptor activation is still a viable anti-breast cancer treatment option but anti-estrogen resistance has been a significant bottle-neck. Dimerization of estrogen receptor is required for ER activation. Blocking ERα dimerization is therefore a complementary and alternative strategy to combat anti-estrogen resistance. Dimer interface peptide “I-box” derived from ER residues 503–518 specifically blocks ER dimerization. Recently using a comprehensive molecular simulation we studied the interaction dynamics of ERα LBDs in a homo-dimer. Based on this study, we identified three interface recognition peptide motifs LDKITDT (ERα residues 479–485), LQQQHQRLAQ (residues 497–506), and LSHIRHMSNK (residues 511–520) and reported the suitability of using LQQQHQRLAQ (ER 497–506) as a template to design inhibitors of ERα dimerization. Stability and self-aggregation of peptide based therapeutics poses a significant bottle-neck to proceed further. In this study utilizing peptide grafted to preserve their pharmacophoric recognition motif and assessed their stability and potential to block ERα mediated activity in silico and in vitro. The Grafted peptides blocked ERα mediated cell proliferation and viability of breast cancer cells but did not alter their apoptotic fate. We believe the structural clues identified in this study can be used to identify novel peptidometics and small molecules that specifically target ER dimer interface generating a new breed of anti-cancer agents. - Highlights: • Designer peptide grafts retain core molecular recognition motif during MD simulations. • Designer peptide grafts with Poly-ALA helix form stable

  15. 2-Ethynylpyridine dimers: IR spectroscopic and computational study

    Science.gov (United States)

    Bakarić, Danijela; Spanget-Larsen, Jens

    2018-04-01

    2-ethynylpyridine (2-EP) presents a multifunctional system capable of participation in hydrogen-bonded complexes utilizing hydrogen bond donating (tbnd Csbnd H, Aryl-H) and hydrogen bond accepting functions (N-atom, Ctbnd C and pyridine π-systems). In this work, IR spectroscopy and theoretical calculations are used to study possible 2-EP dimer structures as well as their distribution in an inert solvent such as tetrachloroethene. Experimentally, the tbnd Csbnd H stretching vibration of the 2-EP monomer absorbs close to 3300 cm-1, whereas a broad band with maximum around 3215 cm-1 emerges as the concentration rises, indicating the formation of hydrogen-bonded complexes involving the tbnd Csbnd H moiety. The Ctbnd C stretching vibration of monomer 2-EP close to 2120 cm-1 is, using derivative spectroscopy, resolved from the signals of the dimer complexes with maximum around 2112 cm-1. Quantum chemical calculations using the B3LYP + D3 model with counterpoise correction predict that the two most stable dimers are of the π-stacked variety, closely followed by dimers with intermolecular tbnd Csbnd H⋯N hydrogen bonding; the predicted red shifts of the tbnd Csbnd H stretching wavenumbers due to hydrogen bonding are in the range 54-120 cm-1. No species with obvious hydrogen bonding involving the Ctbnd C or pyridine π-systems as acceptors are predicted. Dimerization constant at 25 °C is estimated to be K2 = 0.13 ± 0.01 mol-1 dm3.

  16. Dimerization of human immunodeficiency virus (type 1) RNA: stimulation by cations and possible mechanism.

    Science.gov (United States)

    Marquet, R; Baudin, F; Gabus, C; Darlix, J L; Mougel, M; Ehresmann, C; Ehresmann, B

    1991-05-11

    The retroviral genome consists of two identical RNA molecules joined close to their 5' ends by the dimer linkage structure. Recent findings indicated that retroviral RNA dimerization and encapsidation are probably related events during virion assembly. We studied the cation-induced dimerization of HIV-1 RNA and results indicate that all in vitro generated HIV-1 RNAs containing a 100 nucleotide domain downstream from the 5' splice site are able to dimerize. RNA dimerization depends on the concentration of RNA, mono- and multivalent cations, the size of the monovalent cation, temperature, and pH. Up to 75% of HIV-1 RNA is dimeric in the presence of spermidine. HIV-1 RNA dimer is fairly resistant to denaturing agents and unaffected by intercalating drugs. Antisense HIV-1 RNA does not dimerize but heterodimers can be formed between HIV-1 RNA and either MoMuLV or RSV RNA. Therefore retroviral RNA dimerization probably does not simply proceed through mechanisms involving Watson-Crick base-pairing. Neither adenine and cytosine protonation, nor quartets containing only guanines appear to determine the stability of the HIV-1 RNA dimer, while quartets involving both adenine(s) and guanine(s) could account for our results. A consensus sequence PuGGAPuA found in the putative dimerization-encapsidation region of all retroviral genomes examined may participate in the dimerization process.

  17. A first principles study of fluorescence quenching in rhodamine B dimers : how can quenching occur in dimeric species?

    NARCIS (Netherlands)

    Setiawan, Dani; Kazaryan, Andranik; Martoprawiro, Muhamad Abdulkadir; Filatov, Michael

    2010-01-01

    Rhodamine B (RhB) is widely used in chemistry and biology due to its high fluorescence quantum yield. In high concentrations, the quantum yield of fluorescence decreases considerably which is attributed to the formation of RhB dimers. In the present work, a possible mechanism of fluorescence

  18. Quantum-statistical mechanics of an atom-dimer mixture: Lee-Yang cluster expansion approach

    International Nuclear Information System (INIS)

    Ohkuma, Takahiro; Ueda, Masahito

    2006-01-01

    We use the Lee-Yang cluster expansion method to study quantum-statistical properties of a mixture of interconvertible atoms and dimers, where the dimers form in a two-body bound state of the atoms. We point out an infinite series of cluster diagrams whose summation leads to the Bose-Einstein condensation of the dimers below a critical temperature. Our theory captures some important features of a cold atom-dimer mixture such as interconversion of atoms and dimers and properties of the mixture at the unitarity limit

  19. Interaction of aromatic amines with iron oxides: implications for prebiotic chemistry.

    Science.gov (United States)

    Shanker, Uma; Singh, Gurinder; Kamaluddin

    2013-06-01

    The interaction of aromatic amines (aniline, p-chloroaniline, p-toludine and p-anisidine) with iron oxides (goethite, akaganeite and hematite) has been studied. Maximum uptake of amines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was found to be a better adsorbate probably due to its higher basicity. In alkaline medium (pH > 8), amines reacted on goethite and akaganeite to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-iron oxide hydroxide adduct suggests that the surface acidity of iron oxide hydroxides is responsible for the interaction. The present study suggests that iron oxide hydroxides might have played a role in the stabilization of organic molecules through their surface activity and in prebiotic condensation reactions.

  20. A short autocomplementary sequence plays an essential role in avian sarcoma-leukosis virus RNA dimerization.

    Science.gov (United States)

    Fossé, P; Motté, N; Roumier, A; Gabus, C; Muriaux, D; Darlix, J L; Paoletti, J

    1996-12-24

    Retroviral genomes consist of two identical RNA molecules joined noncovalently near their 5'-ends. Recently, two models have been proposed for RNA dimer formation on the basis of results obtained in vitro with human immunodeficiency virus type 1 RNA and Moloney murine leukemia virus RNA. It was first proposed that viral RNA dimerizes by forming an interstrand quadruple helix with purine tetrads. The second model postulates that RNA dimerization is initiated by a loop-loop interaction between the two RNA molecules. In order to better characterize the dimerization process of retroviral genomic RNA, we analyzed the in vitro dimerization of avian sarcoma-leukosis virus (ASLV) RNA using different transcripts. We determined the requirements for heterodimer formation, the thermal dissociation of RNA dimers, and the influence of antisense DNA oligonucleotides on dimer formation. Our results strongly suggest that purine tetrads are not involved in dimer formation. Data show that an autocomplementary sequence located upstream from the splice donor site and within a major packaging signal plays a crucial role in ASLV RNA dimer formation in vitro. This sequence is able to form a stem-loop structure, and phylogenetic analysis reveals that it is conserved in 28 different avian sarcoma and leukosis viruses. These results suggest that dimerization of ASLV RNA is initiated by a loop-loop interaction between two RNA molecules and provide an additional argument for the ubiquity of the dimerization process via loop-loop interaction.

  1. Effects of Dimers on Cooperation in the Spatial Prisoner's Dilemma Game

    International Nuclear Information System (INIS)

    Li Haihong; Cheng Hongyan; Dai Qionglin; Ju Ping; Yang Junzhong; Zhang Mei

    2011-01-01

    We investigate the evolutionary prisoner's dilemma game in structured populations by introducing dimers, which are defined as that two players in each dimer always hold a same strategy. We find that influences of dimers on cooperation depend on the type of dimers and the population structure. For those dimers in which players interact with each other, the cooperation level increases with the number of dimers though the cooperation improvement level depends on the type of network structures. On the other hand, the dimers, in which there are not mutual interactions, will not do any good to the cooperation level in a single community, but interestingly, will improve the cooperation level in a population with two communities. We explore the relationship between dimers and self-interactions and find that the effects of dimers are similar to that of self-interactions. Also, we find that the dimers, which are established over two communities in a multi-community network, act as one type of interaction through which information between communities is communicated by the requirement that two players in a dimer hold a same strategy. (general)

  2. Association of atoms into universal dimers using an oscillating magnetic field.

    Science.gov (United States)

    Langmack, Christian; Smith, D Hudson; Braaten, Eric

    2015-03-13

    In a system of ultracold atoms near a Feshbach resonance, pairs of atoms can be associated into universal dimers by an oscillating magnetic field with a frequency near that determined by the dimer binding energy. We present a simple expression for the transition rate that takes into account many-body effects through a transition matrix element of the contact. In a thermal gas, the width of the peak in the transition rate as a function of the frequency is determined by the temperature. In a dilute Bose-Einstein condensate of atoms, the width is determined by the inelastic scattering rates of a dimer with zero-energy atoms. Near an atom-dimer resonance, there is a dramatic increase in the width from inelastic atom-dimer scattering and from atom-atom-dimer recombination. The recombination contribution provides a signature for universal tetramers that are Efimov states consisting of two atoms and a dimer.

  3. Controlled Patterning of Plasmonic Dimers by Using an Ultrathin Nanoporous Alumina Membrane as a Shadow Mask.

    Science.gov (United States)

    Hao, Qi; Huang, Hao; Fan, Xingce; Yin, Yin; Wang, Jiawei; Li, Wan; Qiu, Teng; Ma, Libo; Chu, Paul K; Schmidt, Oliver G

    2017-10-18

    We report on design and fabrication of patterned plasmonic dimer arrays by using an ultrathin anodic aluminum oxide (AAO) membrane as a shadow mask. This strategy allows for controllable fabrication of plasmonic dimers where the location, size, and orientation of each particle in the dimer pairs can be independently tuned. Particularly, plasmonic dimers with ultrasmall nanogaps down to the sub-10 nm scale as well as a large dimer density up to 1.0 × 10 10 cm -2 are fabricated over a centimeter-sized area. The plasmonic dimers exhibit significant surface-enhanced Raman scattering (SERS) enhancement with a polarization-dependent behavior, which is well interpreted by finite-difference time-domain (FDTD) simulations. Our results reveal a facile approach for controllable fabrication of large-area dimer arrays, which is of fundamental interest for plasmon-based applications in surface-enhanced spectroscopy, biochemical sensing, and optoelectronics.

  4. GLYCOLALDEHYDE FORMATION VIA THE DIMERIZATION OF THE FORMYL RADICAL

    Energy Technology Data Exchange (ETDEWEB)

    Woods, Paul M.; Viti, Serena [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Slater, Ben; Raza, Zamaan; Brown, Wendy A.; Burke, Daren J., E-mail: p.woods@qub.ac.uk [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2013-11-10

    Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low- and high-mass star-forming cores. Following our previous investigation into glycolaldehyde formation, we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerization of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerization process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints.

  5. GLYCOLALDEHYDE FORMATION VIA THE DIMERIZATION OF THE FORMYL RADICAL

    International Nuclear Information System (INIS)

    Woods, Paul M.; Viti, Serena; Slater, Ben; Raza, Zamaan; Brown, Wendy A.; Burke, Daren J.

    2013-01-01

    Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low- and high-mass star-forming cores. Following our previous investigation into glycolaldehyde formation, we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerization of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerization process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints

  6. Acylphenols and dimeric acylphenols from Myristica maxima Warb.

    Science.gov (United States)

    Othman, Muhamad Aqmal; Sivasothy, Yasodha; Looi, Chung Yeng; Ablat, Abdulwali; Mohamad, Jamaludin; Litaudon, Marc; Awang, Khalijah

    2016-06-01

    Giganteone E (1), a new dimeric acylphenol was isolated as a minor constituent from the bark of Myristica maxima Warb. The structure of 1 was established on the basis of 1D and 2D NMR techniques and LCMS-IT-TOF analysis. Malabaricones A-C (2-4), giganteones A and C (5 and 6), maingayones A and B (7 and 8), maingayic acid B (9) and β-sitosteryl oleate (10) were also characterized in this plant for the first time. Compound 10 was identified for the first time in the Myristicaceae. Compounds 2 and 5 were active against human prostate cancer cell-lines, thus making this the first report on the prostate cancer inhibiting potential of acylphenols and dimeric acylphenols. Compounds 1, 4, 5, 7 and 8 exhibited potent DPPH free radical scavenging activity. This is the first report on their free radical scavenging capacity. Copyright © 2016. Published by Elsevier B.V.

  7. Cytotoxic bibenzyl dimers from the stems of Dendrobium fimbriatum Hook.

    Science.gov (United States)

    Xu, Feng-Qing; Xu, Fang-Cheng; Hou, Bo; Fan, Wei-Wei; Zi, Cheng-Ting; Li, Yan; Dong, Fa-Wu; Liu, Yu-Qing; Sheng, Jun; Zuo, Zhi-Li; Hu, Jiang-Miao

    2014-11-15

    The bioassay-guided chemical investigation of the stems of Dendrobium fimbriatum Hook led to the isolation of seven first reported bibenzyl dimers with a linkage of a methylene moiety, fimbriadimerbibenzyls A-G (1-7), together with a new dihydrophenanthrene derivative (S)-2,4,5,9-tetrahydroxy-9,10-dihydrophenanthrene (8) and thirteen known compounds (9-21). The structure of the new compound was established by spectroscopic analysis. Biological evaluation of bibenzyl derivatives against five human cell lines indicated that seven of those compounds exhibited broad-spectrum and cytotoxic activities with IC50 values ranging from 2.2 to 21.2 μM. Those rare bibenzyl dimers exhibited cytotoxic activities in vitro and the cytotoxicity decreased as the number of oxygen-containing groups in the structure decreases. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Solution structure of the dimeric cytoplasmic domain of syndecan-4

    DEFF Research Database (Denmark)

    Shin, J; Lee, W; Lee, D

    2001-01-01

    The syndecans, transmembrane proteoglycans which are involved in the organization of cytoskeleton and/or actin microfilaments, have important roles as cell surface receptors during cell-cell and/or cell-matrix interactions. Since previous studies indicate that the function of the syndecan-4...... between peptides at physiological pH. Commensurately, the NMR structures demonstrate that syndecan-4L is a compact intertwined dimer with a symmetric clamp shape in the central variable V region with a root-mean-square deviation between backbone atom coordinates of 0.95 A for residues Leu(186)-Ala(195...... in the center of the dimeric twist similar to our previously reported 4V structure. The overall topology of the central variable region within the 4L structure is very similar to that of 4V complexed with the phosphatidylinositol 4,5-bisphosphate; however, the intersubunit interaction mode is affected...

  9. Antagonizing STAT3 dimerization with a rhodium(III) complex.

    Science.gov (United States)

    Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

    2014-08-25

    Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Stability of gold atoms and dimers adsorbed on graphene

    International Nuclear Information System (INIS)

    Varns, R; Strange, P

    2008-01-01

    We report density functional theory (DFT) calculations for gold atoms and dimers on the surface of graphene. The calculations were performed using the plane wave pseudopotential method. Calculations were performed for a variety of geometries, and both the graphene surface and gold atoms were allowed to fully relax. In agreement with experiment, our results show that the gold-gold interaction is considerably stronger than the gold-graphene interaction, implying that uniform coverage could not be attained. The minimum energy configuration for a single gold atom is found to be directly above a carbon atom, while for the dimer it is perpendicular to the surface and directly above a carbon-carbon bond. Our results are consistent with previous similar calculations

  11. Glycine transporter dimers: evidence for occurrence in the plasma membrane

    DEFF Research Database (Denmark)

    Bartholomäus, Ingo; Milan-Lobo, Laura; Nicke, Annette

    2008-01-01

    membrane based on hydrodynamic and native gel electrophoretic studies. Here, we used cysteine substitution and oxidative cross-linking to show that of GlyT1 and GlyT2 also form dimeric complexes within the plasma membrane. GlyT oligomerization at the cell surface was confirmed for both GlyT1 and GlyT2......Different Na(+)/Cl(-)-dependent neurotransmitter transporters of the SLC6a family have been shown to form dimers or oligomers in both intracellular compartments and at the cell surface. In contrast, the glycine transporters (GlyTs) GlyT1 and -2 have been reported to exist as monomers in the plasma...

  12. Data on dimer formation between importin α subtypes

    Directory of Open Access Journals (Sweden)

    Yoichi Miyamoto

    2016-06-01

    Full Text Available This article describes data related to the research article titled “Functional characterization of importin α8 as a classical nuclear localization signal receptor” [1]. A GST pull-down assay showed that both importin α1 and α8, which are classical nuclear localization signal (cNLS receptors, can form a dimer with importin α6, α7, or α8. Importin α8 has higher dimer-forming ability than importin α1. In addition, our data show that either importin α1 or importin α8 can form a heterodimer with importin α3, which exists in a preformed complex with cNLS substrates such as the conventional SV40TNLS or the p53 protein, resulting in the release of the cNLS substrates from importin α3.

  13. SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY.

    Directory of Open Access Journals (Sweden)

    Mostafa Fekry

    Full Text Available Frataxin is a highly conserved protein found in both prokaryotes and eukaryotes. It is involved in several central functions in cells, which include iron delivery to biochemical processes, such as heme synthesis, assembly of iron-sulfur clusters (ISC, storage of surplus iron in conditions of iron overload, and repair of ISC in aconitase. Frataxin from different organisms has been shown to undergo iron-dependent oligomerization. At least two different classes of oligomers, with different modes of oligomer packing and stabilization, have been identified. Here, we continue our efforts to explore the factors that control the oligomerization of frataxin from different organisms, and focus on E. coli frataxin CyaY. Using small-angle X-ray scattering (SAXS, we show that higher iron-to-protein ratios lead to larger oligomeric species, and that oligomerization proceeds in a linear fashion as a results of iron oxidation. Native mass spectrometry and online size-exclusion chromatography combined with SAXS show that a dimer is the most common form of CyaY in the presence of iron at atmospheric conditions. Modeling of the dimer using the SAXS data confirms the earlier proposed head-to-tail packing arrangement of monomers. This packing mode brings several conserved acidic residues into close proximity to each other, creating an environment for metal ion binding and possibly even mineralization. Together with negative-stain electron microscopy, the experiments also show that trimers, tetramers, pentamers, and presumably higher-order oligomers may exist in solution. Nano-differential scanning fluorimetry shows that the oligomers have limited stability and may easily dissociate at elevated temperatures. The factors affecting the possible oligomerization mode are discussed.

  14. Cellular iron transport.

    Science.gov (United States)

    Garrick, Michael D; Garrick, Laura M

    2009-05-01

    Iron has a split personality as an essential nutrient that also has the potential to generate reactive oxygen species. We discuss how different cell types within specific tissues manage this schizophrenia. The emphasis in enterocytes is on regulating the body's supply of iron by regulating transport into the blood stream. In developing red blood cells, adaptations in transport manage the body's highest flux of iron. Hepatocytes buffer the body's stock of iron. Macrophage recycle the iron from effete red cells among other iron management tasks. Pneumocytes provide a barrier to prevent illicit entry that, when at risk of breaching, leads to a need to handle the dangers in a fashion essentially shared with macrophage. We also discuss or introduce cell types including renal cells, neurons, other brain cells, and more where our ignorance, currently still vast, needs to be removed by future research.

  15. Photomonomerization of pyrimidine dimers by indoles and proteins

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.; Huang, C.W.; Hinman, L.; Gordon, M.P.; Deranleau, D.A.

    1976-01-01

    Model systems for the study of photoreactivation have been developed that utilize a variety of indole derivatives. These systems can split uracil cis-syn cyclobutadipyrimidine, either free or in RNA, when irradiated at wavelengths absorbed only by the indole moiety. The ability of indole compounds to split dimers is closely related to their electronic properties. Those of high electron-donor capacity such as indole, 3-methylindole, indole-3-acetic acid, 5-hydroxytryptophan and tryptophan are good photosensitizers, with efficacy in that order. Indoles with electron-withdrawing substituents such as indole-3-carboxylic acid, indole-3-aldehyde and oxindole are inactive in the monomerization reaction. These findings support the proposed mechanism that the photosensitized monomerization occurs as a result of electron transfer from the excited indole molecules to the pyrimidine bases. Proteins containing fully exposed tryptophan residues (chicken egg white lysozyme and bovine diisopropylphosphoryltrypsin) also cause the splitting of the /sup 14/C-labeled dimers under the same conditions. In the case of lysozyme the quantum yield of monomerization is similar to that of free tryptophan. Much of the monomerization ability of lysozyme was lost after the solvent-available tryptophan had been oxidized by treatment with N-bromosuccinimide. Bovine pancreatic ribonuclease A, a protein devoid of tryptophan, failed to exhibit photosensitized monomerization of uracil dimers. The biological implication of these reactions involving a protein with an exposed tryptophan residue is discussed. Although indoles are able to split the dimers in RNA, they fail to photoreactivate uv-damaged TMV-RNA. Indole-3-acetic acid, 3-methylindole and 5-hydroxytryptophan rapidly inactive viral RNA when irradiated at 313 nm, possibly because of side reactions.

  16. A new hydroxychavicol dimer from the roots of Piper betle.

    Science.gov (United States)

    Lin, Chwan-Fwu; Hwang, Tsong-Long; Chien, Chun-Chien; Tu, Huei-Yu; Lay, Horng-Liang

    2013-02-26

    A new hydroxychavicol dimer, 2-(g'-hydroxychavicol)-hydroxychavicol (1), was isolated from the roots of Piper betle Linn. along with five known compounds, hydroxychavicol (2), aristololactam A II (3), aristololactam B II (4), piperolactam A (5) and cepharadione A (6). The structures of these isolated compounds were elucidated by spectroscopic methods. Compounds 1 and 2 exhibited inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

  17. A New Hydroxychavicol Dimer from the Roots of Piper betle

    Directory of Open Access Journals (Sweden)

    Huei-Yu Tu

    2013-02-01

    Full Text Available A new hydroxychavicol dimer, 2-(g'-hydroxychavicol-hydroxychavicol (1, was isolated from the roots of Piper betle Linn. along with five known compounds, hydroxychavicol (2, aristololactam A II (3, aristololactam B II (4, piperolactam A (5 and cepharadione A (6. The structures of these isolated compounds were elucidated by spectroscopic methods. Compounds 1 and 2 exhibited inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

  18. Synthesis and anti-inflammatory activity of phenylbutenoid dimer analogs

    International Nuclear Information System (INIS)

    Kim, Sung Soo; Fang, Yuan Ying; Park, Hae Eil

    2015-01-01

    Several phenylbutenoid dimer (PBD) analogs were synthesized and evaluated for their inhibitory activities against nitric oxide (NO) production and TNF-α release. The PBD analogs were synthesized via Diels–Alder and subsequent Schlosser reactions as key steps. Among the tested compounds, two analogs (8c, 8f) exhibited much stronger inhibitory activity against LPS-stimulated NO production and TNF-α release in RAW 264.7 cells than that of wogonin

  19. Formation and Dimerization of NO2 A General Chemistry Experiment

    Science.gov (United States)

    Hennis, April D.; Highberger, C. Scott; Schreiner, Serge

    1997-11-01

    We have developed a general chemistry experiment which illustrates Gay-Lussac's law of combining volumes. Students are able to determine the partial pressures and equilibrium constant for the formation and dimerization of NO2. The experiment can be carried out in about 45 minutes with students working in groups of two. The experiment readily provides students with data that can be manipulated with a common spreadsheet.

  20. A new dimeric anthraquinone from endophytic Talaromyces sp. YE3016.

    Science.gov (United States)

    Xie, Xiao-Song; Fang, Xiao-Wei; Huang, Rong; Zhang, Shou-Peng; Wei, Hong-Xia; Wu, Shao-Hua

    2016-08-01

    A new unsymmetrical dimeric anthraquinone, 3-demethyl-3-(2-hydroxypropyl)-skyrin (1) was isolated from the solid-state fermentation extract of an endophytic fungal strain Talaromyces sp. YE 3016, together with five known compounds, skyrin (2), oxyskyrin (3), emodin (4), 1,3,6-trihydroxy-8-methyl-anthraquinone (5) and ergosterol (6). The structure of the new compound was elucidated on the basis of spectroscopic analysis. Compounds 1-3 exhibited moderate cytotoxic activities against MCF-7 cell line.

  1. Dimeric spectra analysis in Microsoft Excel: a comparative study.

    Science.gov (United States)

    Gilani, A Ghanadzadeh; Moghadam, M; Zakerhamidi, M S

    2011-11-01

    The purpose of this work is to introduce the reader to an Add-in implementation, Decom. This implementation provides the whole processing requirements for analysis of dimeric spectra. General linear and nonlinear decomposition algorithms were integrated as an Excel Add-in for easy installation and usage. In this work, the results of several samples investigations were compared to those obtained by Datan. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  2. Theory and simulations of adhesion receptor dimerization on membrane surfaces.

    Science.gov (United States)

    Wu, Yinghao; Honig, Barry; Ben-Shaul, Avinoam

    2013-03-19

    The equilibrium constants of trans and cis dimerization of membrane bound (2D) and freely moving (3D) adhesion receptors are expressed and compared using elementary statistical-thermodynamics. Both processes are mediated by the binding of extracellular subdomains whose range of motion in the 2D environment is reduced upon dimerization, defining a thin reaction shell where dimer formation and dissociation take place. We show that the ratio between the 2D and 3D equilibrium constants can be expressed as a product of individual factors describing, respectively, the spatial ranges of motions of the adhesive domains, and their rotational freedom within the reaction shell. The results predicted by the theory are compared to those obtained from a novel, to our knowledge, dynamical simulations methodology, whereby pairs of receptors perform realistic translational, internal, and rotational motions in 2D and 3D. We use cadherins as our model system. The theory and simulations explain how the strength of cis and trans interactions of adhesive receptors are affected both by their presence in the constrained intermembrane space and by the 2D environment of membrane surfaces. Our work provides fundamental insights as to the mechanism of lateral clustering of adhesion receptors after cell-cell contact and, more generally, to the formation of lateral microclusters of proteins on cell surfaces. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. On the photophysics and photochemistry of the water dimer

    Energy Technology Data Exchange (ETDEWEB)

    Segarra-Marti, Javier; Merchan, Manuela [Instituto de Ciencia Molecular, Universitat de Valencia, P.O. Box 22085, 46071 Valencia (Spain); Roca-Sanjuan, Daniel; Lindh, Roland [Department of Chemistry - Angstroem, Theoretical Chemistry Program, Uppsala University, Box 518, 75120 Uppsala (Sweden)

    2012-12-28

    The photochemistry of the water dimer irradiated by UV light is studied by means of the complete active space perturbation theory//complete active space self-consistent field (CASPT2//CASSCF) method and accurate computational approaches like as minimum energy paths. Both electronic structure computations and ab initio molecular dynamics simulations are carried out. The results obtained show small shifts relative to a single water molecule on the vertical excitation energies of the dimer due to the hydrogen bond placed between the water donor (W{sub D}) and the water acceptor (W{sub A}). A red-shift and a blue-shift are predicted for the W{sub D} and W{sub A}, respectively, supporting previous theoretical and experimental results. The photoinduced chemistry of the water dimer is described as a process occurring between two single water molecules in which the effect of the hydrogen bond plays a minor role. Thus, the photoinduced decay routes correspond to two photodissociation processes, one for each water molecule. The proposed mechanism for the decay channels of the lowest-lying excited states of the system is established as the photochemical production of a hydrogen-bonded H{sub 2}O Horizontal-Ellipsis HO species plus a hydrogen H atom.

  4. Structures of closed and open conformations of dimeric human ATM

    Science.gov (United States)

    Baretić, Domagoj; Pollard, Hannah K.; Fisher, David I.; Johnson, Christopher M.; Santhanam, Balaji; Truman, Caroline M.; Kouba, Tomas; Fersht, Alan R.; Phillips, Christopher; Williams, Roger L.

    2017-01-01

    ATM (ataxia-telangiectasia mutated) is a phosphatidylinositol 3-kinase–related protein kinase (PIKK) best known for its role in DNA damage response. ATM also functions in oxidative stress response, insulin signaling, and neurogenesis. Our electron cryomicroscopy (cryo-EM) suggests that human ATM is in a dynamic equilibrium between closed and open dimers. In the closed state, the PIKK regulatory domain blocks the peptide substrate–binding site, suggesting that this conformation may represent an inactive or basally active enzyme. The active site is held in this closed conformation by interaction with a long helical hairpin in the TRD3 (tetratricopeptide repeats domain 3) domain of the symmetry-related molecule. The open dimer has two protomers with only a limited contact interface, and it lacks the intermolecular interactions that block the peptide-binding site in the closed dimer. This suggests that the open conformation may be more active. The ATM structure shows the detailed topology of the regulator-interacting N-terminal helical solenoid. The ATM conformational dynamics shown by the structures represent an important step in understanding the enzyme regulation. PMID:28508083

  5. Dimerization effect of sucrose octasulfate on rat FGF1

    International Nuclear Information System (INIS)

    Kulahin, N.; Kiselyov, V.; Kochoyan, A.; Kristensen, O.; Kastrup, Jette S.; Berezin, V.; Bock, E.; Gajhede, M.

    2008-01-01

    The work describes the sucrose octasulfate-mediated dimerization of rat FGF1 by gel-filtration experiments and crystal structure determination. Fibroblast growth factors (FGFs) constitute a family of at least 23 structurally related heparin-binding proteins that are involved in regulation of cell growth, survival, differentiation and migration. Sucrose octasulfate (SOS), a chemical analogue of heparin, has been demonstrated to activate FGF signalling pathways. The structure of rat FGF1 crystallized in the presence of SOS has been determined at 2.2 Å resolution. SOS-mediated dimerization of FGF1 was observed, which was further supported by gel-filtration experiments. The major contributors to the sulfate-binding sites in rat FGF1 are Lys113, Lys118, Arg122 and Lys128. An arginine at position 116 is a consensus residue in mammalian FGF molecules; however, it is a serine in rat FGF1. This difference may be important for SOS-mediated FGF1 dimerization in rat

  6. Correlative SEM SERS for quantitative analysis of dimer nanoparticles.

    Science.gov (United States)

    Timmermans, F J; Lenferink, A T M; van Wolferen, H A G M; Otto, C

    2016-11-14

    A Raman microscope integrated with a scanning electron microscope was used to investigate plasmonic structures by correlative SEM-SERS analysis. The integrated Raman-SEM microscope combines high-resolution electron microscopy information with SERS signal enhancement from selected nanostructures with adsorbed Raman reporter molecules. Correlative analysis is performed for dimers of two gold nanospheres. Dimers were selected on the basis of SEM images from multi aggregate samples. The effect of the orientation of the dimer with respect to the polarization state of the laser light and the effect of the particle gap size on the Raman signal intensity is observed. Additionally, calculations are performed to simulate the electric near field enhancement. These simulations are based on the morphologies observed by electron microscopy. In this way the experiments are compared with the enhancement factor calculated with near field simulations and are subsequently used to quantify the SERS enhancement factor. Large differences between experimentally observed and calculated enhancement factors are regularly detected, a phenomenon caused by nanoscale differences between the real and 'simplified' simulated structures. Quantitative SERS experiments reveal the structure induced enhancement factor, ranging from ∼200 to ∼20 000, averaged over the full nanostructure surface. The results demonstrate correlative Raman-SEM microscopy for the quantitative analysis of plasmonic particles and structures, thus enabling a new analytical method in the field of SERS and plasmonics.

  7. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs. Our ... more information about Donor Iron Deficiency Study - Red Blood Cells ...

  8. Mineralogy and geochemistry of banded iron formation and iron ...

    Indian Academy of Sciences (India)

    The geological complexities of banded iron formation (BIF) and associated iron ores of Jilling–. Langalata iron ore ...... sure to sea water. Uranium in these samples varies ..... Ce oxidation and removal (Elderfield and Greaves. 1982; De Baar et ...

  9. Iron Refractory Iron Deficiency Anaemia: A Rare Cause of Iron Deficiency Anaemia

    LENUS (Irish Health Repository)

    McGrath, T

    2018-01-01

    We describe the case of a 17-month-old boy with a hypochromic microcytic anaemia, refractory to oral iron treatment. After exclusion of dietary and gastrointestinal causes of iron deficiency, a genetic cause for iron deficiency was confirmed by finding two mutations in the TMPRSS6 gene, consistent with a diagnosis of iron-refractory iron deficiency anaemia (IRIDA).

  10. Neutral dipole-dipole dimers: A new field in science

    Science.gov (United States)

    Kosower, Edward M.; Borz, Galina

    2018-03-01

    Dimer formation with dipole neutralization produces species such as low polarity water (LPW) compatible with hydrophobic surfaces (Phys. Chem. Chem. Phys. 2015, 17, 24895-24900) Dimerization and dipole neutralization occurs for N-methylacetamide on polyethylene, a behavior drastically different from its contortions in acetonitrile on AgBr:AgCl planar crystals (AgX) (ChemPhysChem 2014, 15, 3598-3607). The weak infrared absorption of the amide dimer on polyethylene is shown experimentally. Dimerization of palmitic acid is shown along with some of the many ramifications for intracellular systems. Polyoligomers of water are present on polyethylene surfaces. Some high resolution spectra of three of the polyoligomers of water are shown along with a mechanistic scheme for polyoligomer formation and dissolution. The structures of some of the oligomers are known from spectroscopic studies of water on AgX. The scope of the article begins with PE, generally accepted as hydrophobic. The IR of PE revealed not only that water was present but that it appeared in two forms, oligomers (O) and polyoligomers (PO). How did we recognize what they were? These species had been observed as especially strong "marker" peaks in the spectra1 of water placed on planar AgX, a platform developed by Katzir and his coworkers [6]. But there was a problem: the proximity to PE of oligomers with substantial (calculated) dipole moments and thus polarity, including cyclic hexamers of water (chair and boat forms), the cyclic pentamer, the books I and II, and the cyclic trimer [7a]. Another link was needed, a role perfectly fit by the already cited low polarity water (LPW). The choice was experimentally supported by the detection of low intensity absorption in the bending region.Some important generalities flow from these results. What other dimers might be present in the biological or chemical world? Palmitic acid dimer (PAD) would be a candidate for decreasing the polarity of the acid (PA). Another

  11. cis elements and trans-acting factors involved in dimer formation of murine leukemia virus RNA.

    Science.gov (United States)

    Prats, A C; Roy, C; Wang, P A; Erard, M; Housset, V; Gabus, C; Paoletti, C; Darlix, J L

    1990-02-01

    The genetic material of all retroviruses examined so far consists of two identical RNA molecules joined at their 5' ends by the dimer linkage structure (DLS). Since the precise location of the DLS as well as the mechanism and role(s) of RNA dimerization remain unclear, we analyzed the dimerization process of Moloney murine leukemia virus (MoMuLV) genomic RNA. For this purpose we derived an in vitro model for RNA dimerization. By using this model, murine leukemia virus RNA was shown to form dimeric molecules. Deletion mutagenesis in the 620-nucleotide leader of MoMuLV RNA showed that the dimer promoting sequences are located within the encapsidation element Psi between positions 215 and 420. Furthermore, hybridization assays in which DNA oligomers were used to probe monomer and dimer forms of MoMuLV RNA indicated that the DLS probably maps between positions 280 and 330 from the RNA 5' end. Also, retroviral nucleocapsid protein was shown to catalyze dimerization of MoMuLV RNA and to be tightly bound to genomic dimer RNA in virions. These results suggest that MoMuLV RNA dimerization and encapsidation are probably controlled by the same cis element, Psi, and trans-acting factor, nucleocapsid protein, and thus might be linked during virion formation.

  12. Comparison of clinical probability-adjusted D-dimer and age-adjusted D-dimer interpretation to exclude venous thromboembolism.

    Science.gov (United States)

    Takach Lapner, Sarah; Julian, Jim A; Linkins, Lori-Ann; Bates, Shannon; Kearon, Clive

    2017-10-05

    Two new strategies for interpreting D-dimer results have been proposed: i) using a progressively higher D-dimer threshold with increasing age (age-adjusted strategy) and ii) using a D-dimer threshold in patients with low clinical probability that is twice the threshold used in patients with moderate clinical probability (clinical probability-adjusted strategy). Our objective was to compare the diagnostic accuracy of age-adjusted and clinical probability-adjusted D-dimer interpretation in patients with a low or moderate clinical probability of venous thromboembolism (VTE). We performed a retrospective analysis of clinical data and blood samples from two prospective studies. We compared the negative predictive value (NPV) for VTE, and the proportion of patients with a negative D-dimer result, using two D-dimer interpretation strategies: the age-adjusted strategy, which uses a progressively higher D-dimer threshold with increasing age over 50 years (age in years × 10 µg/L FEU); and the clinical probability-adjusted strategy which uses a D-dimer threshold of 1000 µg/L FEU in patients with low clinical probability and 500 µg/L FEU in patients with moderate clinical probability. A total of 1649 outpatients with low or moderate clinical probability for a first suspected deep vein thrombosis or pulmonary embolism were included. The NPV of both the clinical probability-adjusted strategy (99.7 %) and the age-adjusted strategy (99.6 %) were similar. However, the proportion of patients with a negative result was greater with the clinical probability-adjusted strategy (56.1 % vs, 50.9 %; difference 5.2 %; 95 % CI 3.5 % to 6.8 %). These findings suggest that clinical probability-adjusted D-dimer interpretation is a better way of interpreting D-dimer results compared to age-adjusted interpretation.

  13. Current understanding of iron homeostasis.

    Science.gov (United States)

    Anderson, Gregory J; Frazer, David M

    2017-12-01

    Iron is an essential trace element, but it is also toxic in excess, and thus mammals have developed elegant mechanisms for keeping both cellular and whole-body iron concentrations within the optimal physiologic range. In the diet, iron is either sequestered within heme or in various nonheme forms. Although the absorption of heme iron is poorly understood, nonheme iron is transported across the apical membrane of the intestinal enterocyte by divalent metal-ion transporter 1 (DMT1) and is exported into the circulation via ferroportin 1 (FPN1). Newly absorbed iron binds to plasma transferrin and is distributed around the body to sites of utilization with the erythroid marrow having particularly high iron requirements. Iron-loaded transferrin binds to transferrin receptor 1 on the surface of most body cells, and after endocytosis of the complex, iron enters the cytoplasm via DMT1 in the endosomal membrane. This iron can be used for metabolic functions, stored within cytosolic ferritin, or exported from the cell via FPN1. Cellular iron concentrations are modulated by the iron regulatory proteins (IRPs) IRP1 and IRP2. At the whole-body level, dietary iron absorption and iron export from the tissues into the plasma are regulated by the liver-derived peptide hepcidin. When tissue iron demands are high, hepcidin concentrations are low and vice versa. Too little or too much iron can have important clinical consequences. Most iron deficiency reflects an inadequate supply of iron in the diet, whereas iron excess is usually associated with hereditary disorders. These disorders include various forms of hemochromatosis, which are characterized by inadequate hepcidin production and, thus, increased dietary iron intake, and iron-loading anemias whereby both increased iron absorption and transfusion therapy contribute to the iron overload. Despite major recent advances, much remains to be learned about iron physiology and pathophysiology. © 2017 American Society for Nutrition.

  14. Iron-Deficiency Anemia

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    Full Text Available ... exploring about iron-deficiency anemia. Read more New treatments for disorders that lead to iron-deficiency anemia. We are ... and other pathways. This could help develop new therapies for conditions that ... behavior, thinking, and mood during adolescence. Treating anemia in ...

  15. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... grams per deciliter (g/dl) for men and less than 12 g/dl for women is diagnostic of anemia. In iron-deficiency anemia, ... blood levels of iron will be low, or less than 10 micromoles per liter (mmol/L) for both men and women. Normal levels are 10 to 30 mmol/L. ...

  16. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... is blood loss during dialysis. People who have chronic kidney disease also often take other medicines—such as proton ... reduces iron absorption. Other treatments If you have chronic kidney disease and iron-deficiency anemia, your doctor may recommend ...

  17. Iron-Deficiency Anemia

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    Full Text Available ... loss and lead to iron-deficiency anemia. Common causes of blood loss that lead to iron-deficiency anemia include: Bleeding in your GI tract, from an ulcer, colon cancer, or regular use of medicines such as aspirin ...

  18. Iron-Deficiency Anemia

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    Full Text Available ... ages and stages of life. Until the teen years, the recommended amount of iron is the same for boys and girls. From birth to 6 months, babies need 0.27 mg of iron. This number goes up to 11 mg for children ages 7 to 12 months, and down to 7 mg for children ...

  19. Iron-Deficiency Anemia

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    Full Text Available ... have less hemoglobin than normal. Hemoglobin is a protein inside red blood cells that carries oxygen from the lungs to tissues ... stored iron has been used. Ferritin is a protein that helps store iron in your ... very young red blood cells. Peripheral smear to see if your red blood ...

  20. Iron-Deficiency Anemia

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    Full Text Available ... iron supplements work best to treat iron-deficiency anemia in children who do not consume the daily recommended amount ... and Clinical Studies to hear experts, parents, and children talk about their experiences with clinical ... Anemia Arrhythmia Blood Donation Blood Tests Blood ...

  1. Iron-Deficiency Anemia

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    Full Text Available ... iron-deficiency anemia. Search the NIH Research Portfolio Online Reporting Tools (RePORT) to learn about research that ... iron-deficiency anemia in blood donors affects the quality of donated red blood cells, such as how ...

  2. Iron-Deficiency Anemia

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    Full Text Available ... or oral iron, by mouth once or several times a day to increase the iron in your body. This is ... and newer recommendations to increase the length of time between donations to protect blood donors. Cardiovascular Health Study identifies predictors ...

  3. Iron-Deficiency Anemia

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    Full Text Available ... or oral iron, by mouth once or several times a day to increase the iron in your body. This is the most common treatment ... and newer recommendations to increase the length of time between donations to protect ... in older adults. The NHLBI-sponsored Cardiovascular Health Study ...

  4. Iron deficiency in children

    African Journals Online (AJOL)

    cell and excess iron is stored as ferritin to protect the cell from oxidative ... iron deficiency has negative effects during pregnancy and in the postpartum period, which affects maternal health ... use of undiluted cow's milk and a predominant cow's milk intake in .... on bone marrow smear or biopsy for the definitive diagnosis of.

  5. Iron-Deficiency Anemia

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    Full Text Available ... Certain conditions or medicines can decrease your body’s ability to absorb iron and lead to iron-deficiency ... environment or water. Lead interferes with the body’s ability to make hemoglobin. Family history and genetics Von ...

  6. Iron-Deficiency Anemia

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    Full Text Available ... anemia if you have certain risk factors , including pregnancy. To prevent iron-deficiency anemia, your doctor may recommend you eat heart-healthy foods or control other conditions that can cause iron-deficiency anemia. Blood tests to screen for ...

  7. Iron-Deficiency Anemia

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    Full Text Available ... Services’ National Institutes of Health (NIH)—the Nation’s biomedical research agency that makes important scientific discoveries to improve ... efforts for iron-deficiency anemia. Learn about exciting research areas that ... This could help develop new therapies for conditions that affect the balance of iron ...

  8. Iron-Deficiency Anemia

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    Full Text Available ... Are you curious about how inflammation from chronic diseases can cause iron-deficiency anemia? Read more When there is ... DBDR) is a leader in research on the causes, prevention, and treatment of blood diseases, including iron-deficiency anemia. Search the NIH Research ...

  9. Iron-Deficiency Anemia

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    Full Text Available ... the Eunice Kennedy Shriver National Institute of Child Health and Human Development, we are investigating how best to treat premature newborns with low hemoglobin levels. We also are hoping to determine which iron supplements work best to treat iron-deficiency anemia in children ...

  10. Iron-Deficiency Anemia

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    Full Text Available ... do not have enough iron in your body. People with mild or moderate iron-deficiency anemia may ... as a TMRPSS6 gene mutation that causes a person’s body to make too much of a hormone ...

  11. Iron-Deficiency Anemia

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    Full Text Available ... during the third trimester of pregnancy. Children between ages 1 and 2, especially if they drink a lot of cow’s milk. Cow’s milk is low in iron. Teens, who have increased need for iron during growth spurts. Older adults, especially those ... environments Children who have lead in ...

  12. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... anemia, including: Vegetarian or vegan eating patterns. Not eating enough iron-rich foods, such as meat and fish, may result in ... deficiency anemia, your doctor may recommend heart-healthy eating and choosing iron-rich foods, especially during certain stages of life when more ...

  13. [Iron deficiency and pica].

    Science.gov (United States)

    Muñoz, J A; Marcos, J; Risueño, C E; de Cos, C; López, R; Capote, F J; Martín, M V; Gil, J L

    1998-02-01

    To study the relationship between pica and iron-lack anaemia in a series of iron-deficiency patients in order to establish the pathogenesis of such relationship. Four-hundred and thirty-three patients were analysed. Pica was studied by introducing certain diet queries into the clinical history. All patients received oral iron and were periodically controlled with the usual clinico-haematological procedures. Pica was present in 23 patients (5.3%). Eight nourishing (namely, coffee grains, almonds, chocolate, ice, lettuce, carrots, sunflower seeds and bread) and 2 non-nourishing (clay and paper) substances were involved. A second episode of pica appeared in 9 cases upon relapsing of iron deficiency. Both anaemia and pica were cured by etiologic and substitutive therapy in all instances. No clear correlation was found with either socio-economic status or pathogenetic causes of iron deficiency and pica, and no haematological differences were seen between patients with pica and those without this alteration. (1) The pathogenesis of pica is unclear, although it appears unrelated to the degree of iron deficiency. (2) According to the findings in this series, pica seems a consequence of iron deficiency rather than its cause. (3) Adequate therapy can cure both conditions, although pica may reappear upon relapse of iron deficiency.

  14. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... stores are developed during the third trimester of pregnancy. Children between ages 1 and 2, especially if they drink a lot of cow’s milk. Cow’s milk is low in iron. Teens, who have increased need for iron during growth ...

  15. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... other conditions that can cause iron-deficiency anemia. Blood tests to screen for iron-deficiency anemia To screen ... check the size of your liver and spleen. Blood tests Based on results from blood tests to screen ...

  16. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... en español Iron-deficiency anemia is a common type of anemia that occurs if you do not ... iron-deficiency anemia and help rule out other types of anemia. Treatment will explain treatment-related complications ...

  17. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... with the Eunice Kennedy Shriver National Institute of Child Health and Human Development, we are investigating how best to treat premature newborns with low hemoglobin levels. We also are hoping to determine which iron supplements work best to treat iron-deficiency anemia in children ...

  18. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... Precision Medicine Activities Obesity, Nutrition, and Physical Activity Population and Epidemiology Studies Women’s Health All Science A- ... to help your body absorb iron. Avoid drinking black tea, which reduces iron ... was associated with a greater risk of death even with mild anemia. Now, anemia in older ...

  19. Iron deficiency in childhood

    NARCIS (Netherlands)

    Uijterschout, L.

    2015-01-01

    Iron deficiency (ID) is the most common micronutrient deficiency in the world. Iron is involved in oxygen transport, energy metabolism, immune response, and plays an important role in brain development. In infancy, ID is associated with adverse effects on cognitive, motor, and behavioral development

  20. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... anemia. Return to Signs, Symptoms, and Complications to review signs and symptoms as well as complications from iron-deficiency ... NIH]) Heavy Menstrual Bleeding (Centers for Disease Control and ... Dietary Supplement Fact Sheet (NIH) Iron-Deficiency Anemia (National Library ...

  1. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... be at risk for iron-deficiency anemia. Lifestyle habits Certain lifestyle habits may increase your risk for iron-deficiency anemia, ... you are experiencing side effects such as a bad metallic taste, vomiting, diarrhea, constipation, or upset stomach. ...

  2. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... age, sex, and whether you are pregnant or breastfeeding. Recommended daily iron intake for children and adults. The table lists the recommended amounts of iron, in milligrams (mg) at different ages and stages of life. Until the teen years, the recommended amount of ...

  3. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... how we are using current research and advancing research to prevent iron-deficiency anemia. Participate in NHLBI Clinical Trials will explain our ongoing clinical studies that are investigating prevention strategies for iron-deficiency anemia. Signs, Symptoms, and Complications ...

  4. Unusual metal-ligand charge transfer in ferrocene functionalized μ3-O iron carboxylates observed with Mössbauer spectroscopy

    International Nuclear Information System (INIS)

    Mereacre, Valeriu; Schlageter, Martin; Eichhöfer, Andreas; Bauer, Thomas; Wolny, Juliusz A.; Schünemann, Volker; Powell, Annie K.

    2016-01-01

    Temperature dependent Mössbauer studies of two ferrocenecarboxylate functionalized {Fe 3 O} complexes in solid state are reported. It was found that conjugation of ferrocene ring orbitals with the π orbitals of the adjacent carboxylic group promotes a shift of electron density from the ferrocene Fe II ion to the cyclopentadienide rings with π-orbital character giving rise to a new type of mixed-valence compound. - Highlights: • In this manuscript we describe a mechanism of electron density shift which stabilizes the trapped mixed-valence state. • The coexistence of ferrocene and ferrocenium in solid state was determined. • A mixed-valence state at room-temperature and a thermally induced electron transfer with gradual interconversion were observed.

  5. Iron replacement therapy

    DEFF Research Database (Denmark)

    Nielsen, Ole Haagen; Coskun, Mehmet; Weiss, Günter

    2016-01-01

    PURPOSE OF REVIEW: Approximately, one-third of the world's population suffers from anemia, and at least half of these cases are because of iron deficiency. With the introduction of new intravenous iron preparations over the last decade, uncertainty has arisen when these compounds should...... be administered and under which circumstances oral therapy is still an appropriate and effective treatment. RECENT FINDINGS: Numerous guidelines are available, but none go into detail about therapeutic start and end points or how iron-deficiency anemia should be best treated depending on the underlying cause...... of iron deficiency or in regard to concomitant underlying or additional diseases. SUMMARY: The study points to major issues to be considered in revisions of future guidelines for the true optimal iron replacement therapy, including how to assess the need for treatment, when to start and when to stop...

  6. Aqueous corrosion of phosphide minerals from iron meteorites: a highly reactive source of prebiotic phosphorus on the surface of the early Earth.

    Science.gov (United States)

    Pasek, Matthew A; Lauretta, Dante S

    2005-08-01

    We present the results of an experimental study of aqueous corrosion of Fe-phosphide under conditions relevant to the early Earth. The results strongly suggest that iron meteorites were an important source of reactive phosphorus (P), a requirement for the formation of P-based life. We further demonstrate that iron meteorites were an abundant source of phosphide minerals early in Earth history. Phosphide corrosion was studied in five different solutions: deionized water, deionized water buffered with sodium bicarbonate, deionized water with dissolved magnesium and calcium chlorides, deionized water containing ethanol and acetic acid, and deionized water containing the chlorides, ethanol, and acetic acid. Experiments were performed in the presence of both air and pure Ar gas to evaluate the effect of atmospheric chemistry. Phosphide corrosion in deionized water results in a metastable mixture of mixed-valence, P-bearing ions including pyrophosphate and triphosphate, key components for metabolism in modern life. In a pH-buffered solution of NaHCO(3), the condensed and reduced species diphosphonate is an abundant corrosion product. Corrosion in ethanol- and acetic acid-containing solutions yields additional P-bearing organic molecules, including acetyl phosphonate and a cyclic triphosphorus molecule. Phosphonate is a major corrosion product of all experiments and is the only P-bearing molecule that persists in solutions with high concentrations of magnesium and calcium chlorides, which suggests that phosphonate may have been a primitive oceanic source of P. The stability and reactivity of phosphonate and hypophosphite in solution were investigated to elucidate reaction mechanisms and the role of mineral catalysts on P-solution chemistry. Phosphonate oxidation is rapid in the presence of Fe metal but negligible in the presence of magnetite and in the control sample. The rate of hypophosphite oxidation is independent of reaction substrate.

  7. Factors associated with D-dimer levels in HIV-infected individuals

    DEFF Research Database (Denmark)

    Borges, Alvaro H; O'Connor, Jemma L; Phillips, Andrew N

    2014-01-01

    BACKGROUND: Higher plasma D-dimer levels are strong predictors of mortality in HIV+ individuals. The factors associated with D-dimer levels during HIV infection, however, remain poorly understood. METHODS: In this cross-sectional study, participants in three randomized controlled trials...... with measured D-dimer levels were included (N = 9,848). Factors associated with D-dimer were identified by linear regression. Covariates investigated were: age, gender, race, body mass index, nadir and baseline CD4+ count, plasma HIV RNA levels, markers of inflammation (C-reactive protein [CRP], interleukin-6...... viruses, was positively correlated with D-dimer. Other factors independently associated with higher D-dimer levels were black race, higher plasma HIV RNA levels, being off ART at baseline, and increased levels of CRP, IL-6 and cystatin C. In contrast, higher baseline CD4+ counts and higher high...

  8. Photoreactivation of pyrimidine dimers in the DNA of normal and xeroderma pigmentosum cells

    International Nuclear Information System (INIS)

    Sutherland, B.M.; Oliver, R.; Fuselier, C.O.; Sutherland, J.C.

    1976-01-01

    Photoproducts formed in the DNA of human cells irradiated with ultraviolet light (uv) were identified as cyclobutyl pyrimidine dimers by their chromatographic mobility, reversibility to monomers upon short wavelength uv irradiation, and comparison of the kinetics of this monomerization with that of authentic cis--syn thymine--thymine dimers prepared by irradiation of thymine in ice. The level of cellular photoreactivation of these dimers reflects the level of photoreactivating enzyme measured in cell extracts. Action spectra for cellular dimer photoreactivation in the xeroderma pigmentosum line XP12BE agree in range (300 nm to at least 577 nm) and maximum (near 400 nm) with that for photoreactivation by purified human photoreactivating enzyme. Normal human cells can also photoreactivate dimers in their DNA. The action spectrum for the cellular monomerization of dimers is similar to that for photoreactivation by the photoreactivating enzyme in extracts of normal human fibroblasts

  9. Role of glutaredoxin 3 in iron homeostasis

    Science.gov (United States)

    Iron is an essential mineral nutrient that is tightly regulated through mechanisms involving iron regulatory genes, intracellular storage, and iron recycling. Dysregulation of these mechanisms often results in either excess tissue iron accumulation (overload) or iron deficiency (anemia). Many bioche...

  10. Dimerization of 3He in 3He-4He mixture films

    International Nuclear Information System (INIS)

    Bashkin, E.

    1994-01-01

    3 He atoms dissolved in superfluid 4 He may form dimers ( 3 He) 2 in two-dimensional geometries. Dimer formation is studied in films of dilute 3 He- 4 He mixture. After designing a schematic 3 He- 3 He interaction potential, the dimer binding energy is calculated for various substrates. It is shown that 3 He impurity states localized near the substrate give rise to the highest magnitudes of the binding energy. (author). 32 refs., 6 figs.,; 1 tab

  11. Species A rotavirus NSP3 acquires its translation inhibitory function prior to stable dimer formation.

    Directory of Open Access Journals (Sweden)

    Hugo I Contreras-Treviño

    Full Text Available Species A rotavirus non-structural protein 3 (NSP3 is a translational regulator that inhibits or, under some conditions, enhances host cell translation. NSP3 binds to the translation initiation factor eIF4G1 and evicts poly-(A binding protein (PABP from eIF4G1, thus inhibiting translation of polyadenylated mRNAs, presumably by disrupting the effect of PABP bound to their 3'-ends. NSP3 has a long coiled-coil region involved in dimerization that includes a chaperone Hsp90-binding domain (HS90BD. We aimed to study the role in NSP3 dimerization of a segment of the coiled-coil region adjoining the HS90BD. We used a vaccinia virus system to express NSP3 with point mutations in conserved amino acids in the coiled-coil region and determined the effects of these mutations on translation by metabolic labeling of proteins as well as on accumulation of stable NSP3 dimers by non-dissociating Western blot, a method that separates stable NSP3 dimers from the monomer/dimerization intermediate forms of the protein. Four of five mutations reduced the total yield of NSP3 and the formation of stable dimers (W170A, K171E, R173E and R187E:K191E, whereas one mutation had the opposite effects (Y192A. Treatment with the proteasome inhibitor MG132 revealed that stable NSP3 dimers and monomers/dimerization intermediates are susceptible to proteasome degradation. Surprisingly, mutants severely impaired in the formation of stable dimers were still able to inhibit host cell translation, suggesting that NSP3 dimerization intermediates are functional. Our results demonstrate that rotavirus NSP3 acquires its function prior to stable dimer formation and remain as a proteasome target throughout dimerization.

  12. Electron-nuclear corellations for photoinduced dynamics in molecular dimers

    Science.gov (United States)

    Kilin, Dmitri S.; Pereversev, Yuryi V.; Prezhdo, Oleg V.

    2003-03-01

    Ultrafast photoinduced dynamics of electronic excitation in molecular dimers is drastically affected by dynamic reorganization of of inter- and intra- molecular nuclear configuration modelled by quantized nuclear degree of freedom [1]. The dynamics of the electronic population and nuclear coherence is analyzed with help of both numerical solution of the chain of coupled differential equations for mean coordinate, population inversion, electronic-vibrational correlation etc.[2] and by propagating the Gaussian wavepackets in relevant adiabatic potentials. Intriguing results were obtained in the approximation of small energy difference and small change of nuclear equilibrium configuration for excited electronic states. In the limiting case of resonance between electronic states energy difference and frequency of the nuclear mode these results have been justified by comparison to exactly solvable Jaynes-Cummings model. It has been found that the photoinduced processes in dimer are arranged according to their time scales:(i) fast scale of nuclear motion,(ii) intermediate scale of dynamical redistribution of electronic population between excited states as well as growth and dynamics of electronic -nuclear correlation,(iii) slow scale of electronic population approaching to the quasiequilibrium distribution, decay of electronic-nuclear correlation, and diminishing the amplitude of mean coordinate oscillations, accompanied by essential growth of the nuclear coordinate dispersion associated with the overall nuclear wavepacket width. Demonstrated quantum-relaxational features of photoinduced vibronic dinamical processess in molecular dimers are obtained by simple method, applicable to large biological systems with many degrees of freedom. [1] J. A. Cina, D. S. Kilin, T. S. Humble, J. Chem. Phys. (2003) in press. [2] O. V. Prezhdo, J. Chem. Phys. 117, 2995 (2002).

  13. Transport properties of a ladder with two random dimer chains

    International Nuclear Information System (INIS)

    Hu Dong-Sheng; Zhu Chen-Ping; Zhang Yong-Mei

    2011-01-01

    We investigate the transport properties of a ladder with two random dimer (RD) chains. It is found that there are two extended states in the ladder with identical RD chains and a critical state regarded as an extended state in the ladder with pairing RD chains. Such a critical state is caused by the chiral symmetry. The ladder with identical RD chains can be decoupled into two isolated RD chains and the ladder with pairing RD chains can not. The analytic expressions of the extended states are presented for the ladder with identical RD chains. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  14. Laccase-mediated dimerization of the flavonolignan silybin

    Czech Academy of Sciences Publication Activity Database

    Gažák, Radek; Sedmera, Petr; Marzorati, M.; Riva, S.; Křen, Vladimír

    2008-01-01

    Roč. 50, 2-4 (2008), s. 87-92 ISSN 1381-1177 R&D Projects: GA AV ČR KJB400200701; GA MŠk OC D25.001; GA MŠk(CZ) LC06010; GA MŠk OC 170; GA MŠk ME 922 Grant - others:CZ(CZ) Bilateral Czech-Italian inter-academic projec Institutional research plan: CEZ:AV0Z50200510 Keywords : silybin * silymarin * dimer formation Subject RIV: EE - Microbiology, Virology Impact factor: 2.015, year: 2008

  15. The (6-4) Dimeric Lesion as a DNA Photosensitizer

    OpenAIRE

    Vendrell Criado, Victoria; Rodríguez Muñiz, Gemma María; Lhiaubet ., Virginie Lyria; Cuquerella Alabort, Maria Consuelo; Miranda Alonso, Miguel Ángel

    2016-01-01

    [EN] Based on our previous investigations into the photophysical properties of the 5-methyl-2-pyrimidone (Pyo) chromophore, we now extend our studies to the photobehavior of the dimeric (6-4) thymine photoproducts (6-4 PP) to evaluate their capability to act as instrinsic DNA photosensitizers. The lesion presents significant absorption in the UVB/UVA region, weak fluorescence emission, a singlet-excited-state energy of approximately 351 kJ mol(-1), and a triplet-excited-state energy of 297 kJ...

  16. Revealing the Dimeric Crystal and Solution Structure of β-Lactoglobulin at pH 4 and Its pH and Salt Dependent Monomer–Dimer Equilibrium

    DEFF Research Database (Denmark)

    Khan, Sanaullah; Ipsen, Richard; Almdal, Kristoffer

    2018-01-01

    The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 Å resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6%) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH...... and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20%, 50/50%, and 25/75%, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic...... shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications....

  17. Liver Iron Contents in Rats after Administration of Certain Iron ...

    African Journals Online (AJOL)

    The effect of consumption of certain iron compounds on liver iron deposition was ... extra iron probably depends on the type of food prepared, .... main groups. Each main group consisted of 4 subgroups. (8 rats per subgroup) which received the same basic diet but differing amounts of iron of a specific type. Each animal was ...

  18. Dimer and String Formation during Low Temperature Silicon Deposition on Si(100)

    DEFF Research Database (Denmark)

    Smith, A. P.; Jonsson, Hannes

    1996-01-01

    We present theoretical results based on density functional theory and kinetic Monte Carlo simulations of silicon deposition and address observations made in recently reported low temperature scanning tunneling microscopy studies. A mechanism is presented which explains dimer formation on top...... of the substrate's dimer rows at 160 K and up to room temperature, while between-row dimers and longer strings of adatoms (''diluted dimer rows'') form at higher temperature. A crossover occurs at around room temperature between two different mechanisms for adatom diffusion in our model....

  19. Radiation-induced tetramer-to-dimer transition of Escherichia coli lactose repressor

    International Nuclear Information System (INIS)

    Goffinont, S.; Davidkova, M.; Spotheim-Maurizot, M.

    2009-01-01

    The wild type lactose repressor of Escherichia coli is a tetrameric protein formed by two identical dimers. They are associated via a C-terminal 4-helix bundle (called tetramerization domain) whose stability is ensured by the interaction of leucine zipper motifs. Upon in vitro γ-irradiation the repressor losses its ability to bind the operator DNA sequence due to damage of its DNA-binding domains. Using an engineered dimeric repressor for comparison, we show here that irradiation induces also the change of repressor oligomerisation state from tetramer to dimer. The splitting of the tetramer into dimers can result from the oxidation of the leucine residues of the tetramerization domain.

  20. Solid-phase synthesis of 2{sup '}-O-methoxyethyl oligonucleotides using dimeric phosphoramidate blocks

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Gi Weon; Kang, Yong Han [Dept. of Applied Chemistry, Hanyang University, Ansan (Korea, Republic of)

    2016-11-15

    This research focused on the method of using dimeric phosphoramidite blocks to synthesize oligonucleotides for development as oligonucleotide drugs. A 16-mer oligonucleotide with the randomly selected sequence of C*C*T*C*G*C *T*C*T*C*G*C*C* C*G*C was synthesized using CC, GC, and TC dimers, a combination of monomers and dimers, or only monomers as building blocks. Using dimer blocks in this synthetic method provided a significant decrease in critical impurities that had similar properties to the main product, which was confirmed by LC-MS and HPLC analysis.

  1. Dimerization of a flocculent protein from Moringa oleifera: experimental evidence and in silico interpretation.

    Science.gov (United States)

    Pavankumar, Asalapuram R; Kayathri, Rajarathinam; Murugan, Natarajan A; Zhang, Qiong; Srivastava, Vaibhav; Okoli, Chuka; Bulone, Vincent; Rajarao, Gunaratna K; Ågren, Hans

    2014-01-01

    Many proteins exist in dimeric and other oligomeric forms to gain stability and functional advantages. In this study, the dimerization property of a coagulant protein (MO2.1) from Moringa oleifera seeds was addressed through laboratory experiments, protein-protein docking studies and binding free energy calculations. The structure of MO2.1 was predicted by homology modelling, while binding free energy and residues-distance profile analyses provided insight into the energetics and structural factors for dimer formation. Since the coagulation activities of the monomeric and dimeric forms of MO2.1 were comparable, it was concluded that oligomerization does not affect the biological activity of the protein.

  2. Magnetic and superconducting competition within the Hubbard dimer. Exact solution

    International Nuclear Information System (INIS)

    Matlak, M.; Slomska, T.; Grabiec, B.

    2005-01-01

    We express the Hubbard dimer Hamiltonian H d =Σ 16 α=1 E α vertical stroke E α right angle left angle E α vertical stroke in the second quantization with the use of the Hubbard and spin operators. We consider the case of positive and negative U. We decompose the resulting Hamiltonian into several parts collecting all the terms belonging to the same energy level. Such a decomposition visualizes explicitly all intrinsic interactions competing together and deeply hidden in the original form of the dimer Hamiltonian. Among them are competitive ferromagnetic and antiferromagnetic interactions. There are also hopping terms present which describe Cooper pairs hopping between sites 1 and 2 with positive and negative coupling constants (similar as in Kulik-Pedan, Penson-Kolb models). We show that the competition between intrinsic interactions strongly depends on the model parameters and the averaged occupation number of electrons n element of [0, 4] resulting in different regimes of the model (as e.g. t-J model regime, etc.). (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Dimerization deficiency of enigmatic retinitis pigmentosa-linked rhodopsin mutants

    Science.gov (United States)

    Ploier, Birgit; Caro, Lydia N.; Morizumi, Takefumi; Pandey, Kalpana; Pearring, Jillian N.; Goren, Michael A.; Finnemann, Silvia C.; Graumann, Johannes; Arshavsky, Vadim Y.; Dittman, Jeremy S.; Ernst, Oliver P.; Menon, Anant K.

    2016-10-01

    Retinitis pigmentosa (RP) is a blinding disease often associated with mutations in rhodopsin, a light-sensing G protein-coupled receptor and phospholipid scramblase. Most RP-associated mutations affect rhodopsin's activity or transport to disc membranes. Intriguingly, some mutations produce apparently normal rhodopsins that nevertheless cause disease. Here we show that three such enigmatic mutations--F45L, V209M and F220C--yield fully functional visual pigments that bind the 11-cis retinal chromophore, activate the G protein transducin, traffic to the light-sensitive photoreceptor compartment and scramble phospholipids. However, tests of scramblase activity show that unlike wild-type rhodopsin that functionally reconstitutes into liposomes as dimers or multimers, F45L, V209M and F220C rhodopsins behave as monomers. This result was confirmed in pull-down experiments. Our data suggest that the photoreceptor pathology associated with expression of these enigmatic RP-associated pigments arises from their unexpected inability to dimerize via transmembrane helices 1 and 5.

  4. Pyrimidine dimers block simian virus 40 replication forks

    International Nuclear Information System (INIS)

    Berger, C.A.; Edenberg, H.J.

    1986-01-01

    UV light produces lesions, predominantly pyrimidine dimers, which inhibit DNA replication in mammalian cells. The mechanism of inhibition is controversial: is synthesis of a daughter strand halted at a lesion while the replication fork moves on and reinitiates downstream, or is fork progression itself blocked for some time at the site of a lesion? We directly addressed this question by using electron microscopy to examine the distances of replication forks from the origin in unirradiated and UV-irradiated simian virus 40 chromosomes. If UV lesions block replication fork progression, the forks should be asymmetrically located in a large fraction of the irradiated molecules; if replication forks move rapidly past lesions, the forks should be symmetrically located. A large fraction of the simian virus 40 replication forks in irradiated molecules were asymmetrically located, demonstrating that UV lesions present at the frequency of pyrimidine dimers block replication forks. As a mechanism for this fork blockage, we propose that polymerization of the leading strand makes a significant contribution to the energetics of fork movement, so any lesion in the template for the leading strand which blocks polymerization should also block fork movement

  5. Structures of DNA containing psoralen crosslink and thymine dimer

    International Nuclear Information System (INIS)

    Kim, S.H.; Pearlman, D.A.; Holbrook, S.R.; Pirkle, D.

    1985-01-01

    UV irradiation by itself or in conjunction with other chemicals can cause covalent damages to DNA in living cells. To overcome the detrimental effect of DNA damage, cells developed a repair mechanism by which damaged DNA is repaired. In the absence of such repair, cell malfunction or cell death can occur. Two most studied radiation-induced DNA damage are thymine dimer formation by UV irradiation and psoralen crosslink by combination of psoralens and UV: In the former, two adjacent thymine bases on a strand of DNA are fused by forming cyclobutane ring, and in the latter, one pyrimidine on one DNA strand is crosslinked to another pyrimidine on the other strand via a psoralen. The authors' objective is to deduce the structure of DNA segment which contains a psoralen crosslink or a thymine dimer using the combination of results of X-ray crystallographic studies, molecular model building, and energy minimization. These structural features may be important for understanding the biological effects of such damages and for the recognition by the repair enzymes

  6. How Does Thymine DNA Survive Ultrafast Dimerization Damage?

    Directory of Open Access Journals (Sweden)

    Hongjuan Wang

    2016-12-01

    Full Text Available The photodimerization reaction between the two adjacent thymine bases within a single strand has been the subject of numerous studies due to its potential to induce DNA mutagenesis and possible tumorigenesis in human skin cells. It is well established that the cycloaddition photoreaction takes place on a picosecond time scale along barrierless or low barrier singlet/triplet pathways. However, the observed dimerization quantum yield in different thymine multimer is considerable lower than might be expected. A reasonable explanation is required to understand why thymine in DNA is able to survive ultrafast dimerization damage. In this work, accurate quantum calculations based on the combined CASPT2//CASSCF/AMBER method were conducted to map the excited state relaxation pathways of the thymine monomer in aqueous solution and of the thymine oligomer in DNA. A monomer-like decay pathway, induced by the twisting of the methyl group, is found to provide a bypass channel to ensure the photostability of thymine in single-stranded oligomers. This fast relaxation path is regulated by the conical intersection between the bright SCT(1ππ* state with the intra-base charge transfer character and the ground state to remove the excess excitation energy, thereby achieving the ground-state recovery with high efficiency.

  7. A multistep single-crystal-to-single-crystal bromodiacetylene dimerization

    Science.gov (United States)

    Hoheisel, Tobias N.; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K.; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W. Bernd; Frauenrath, Holger

    2013-04-01

    Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations.

  8. Dimerization of a Viral SET Protein Endows its Function

    Energy Technology Data Exchange (ETDEWEB)

    H Wei; M Zhou

    2011-12-31

    Histone modifications are regarded as the most indispensible phenomena in epigenetics. Of these modifications, lysine methylation is of the greatest complexity and importance as site- and state-specific lysine methylation exerts a plethora of effects on chromatin structure and gene transcription. Notably, paramecium bursaria chlorella viruses encode a conserved SET domain methyltransferase, termed vSET, that functions to suppress host transcription by methylating histone H3 at lysine 27 (H3K27), a mark for eukaryotic gene silencing. Unlike mammalian lysine methyltransferases (KMTs), vSET functions only as a dimer, but the underlying mechanism has remained elusive. In this study, we demonstrate that dimeric vSET operates with negative cooperativity between the two active sites and engages in H3K27 methylation one site at a time. New atomic structures of vSET in the free form and a ternary complex with S-adenosyl homocysteine and a histone H3 peptide and biochemical analyses reveal the molecular origin for the negative cooperativity and explain the substrate specificity of H3K27 methyltransferases. Our study suggests a 'walking' mechanism, by which vSET acts all by itself to globally methylate host H3K27, which is accomplished by the mammalian EZH2 KMT only in the context of the Polycomb repressive complex.

  9. Monomer-dimer problem on random planar honeycomb lattice

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Haizhen [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China); Department of Mathematics, Qinghai Normal University, Xining 810008, Qinghai (China); Zhang, Fuji; Qian, Jianguo, E-mail: jqqian@xmu.edu.cn [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China)

    2014-02-15

    We consider the monomer-dimer (MD) problem on a random planar honeycomb lattice model, namely, the random multiple chain. This is a lattice system with non-periodic boundary condition, whose generating process is inspired by the growth of single walled zigzag carbon nanotubes. By applying algebraic and combinatorial techniques we establish a calculating expression of the MD partition function for bipartite graphs, which corresponds to the permanent of a matrix. Further, by using the transfer matrix argument we show that the computing problem of the permanent of high order matrix can be converted into some lower order matrices for this family of lattices, based on which we derive an explicit recurrence formula for evaluating the MD partition function of multiple chains and random multiple chains. Finally, we analyze the expectation of the number of monomer-dimer arrangements on a random multiple chain and the asymptotic behavior of the annealed MD entropy when the multiple chain becomes infinite in width and length, respectively.

  10. The (6-4) Dimeric Lesion as a DNA Photosensitizer.

    Science.gov (United States)

    Vendrell-Criado, Victoria; Rodríguez-Muñiz, Gemma M; Lhiaubet-Vallet, Virginie; Cuquerella, M Consuelo; Miranda, Miguel A

    2016-07-04

    Based on our previous investigations into the photophysical properties of the 5-methyl-2-pyrimidone (Pyo) chromophore, we now extend our studies to the photobehavior of the dimeric (6-4) thymine photoproducts (6-4 PP) to evaluate their capability to act as instrinsic DNA photosensitizers. The lesion presents significant absorption in the UVB/UVA region, weak fluorescence emission, a singlet-excited-state energy of approximately 351 kJ mol(-1) , and a triplet-excited-state energy of 297 kJ mol(-1) . Its triplet transient absorption has a maximum at 420-440 nm, a lifetime of around 7 μs, and a high formation quantum yield, ΦISC =0.86. This species is efficiently quenched by thymidine. Its DNA photosensitizing properties are demonstrated by a series of experiments run on a pBR322 plasmid. The lesion photoinduces both single-strand breaks and the formation of cyclobutane thymine dimers. Altogether, these results show that, the substitution of the pyrimidone ring at C4 by a 5-hydroxy-5,6-dihydrothymine does not cancel out the photosensitization properties of the chromophore. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Biocompatible Amphiphilic Hydrogel-Solid Dimer Particles as Colloidal Surfactants.

    Science.gov (United States)

    Chen, Dong; Amstad, Esther; Zhao, Chun-Xia; Cai, Liheng; Fan, Jing; Chen, Qiushui; Hai, Mingtan; Koehler, Stephan; Zhang, Huidan; Liang, Fuxin; Yang, Zhenzhong; Weitz, David A

    2017-12-26

    Emulsions of two immiscible liquids can slowly coalesce over time when stabilized by surfactant molecules. Pickering emulsions stabilized by colloidal particles can be much more stable. Here, we fabricate biocompatible amphiphilic dimer particles using a hydrogel, a strongly hydrophilic material, and achieve large contrast in the wetting properties of the two bulbs, resulting in enhanced stabilization of emulsions. We generate monodisperse single emulsions of alginate and shellac solution in oil using a flow-focusing microfluidics device. Shellac precipitates from water and forms a solid bulb at the periphery of the droplet when the emulsion is exposed to acid. Molecular interactions result in amphiphilic dimer particles that consist of two joined bulbs: one hydrogel bulb of alginate in water and the other hydrophobic bulb of shellac. Alginate in the hydrogel compartment can be cross-linked using calcium cations to obtain stable particles. Analogous to surfactant molecules at the interface, the resultant amphiphilic particles stand at the water/oil interface with the hydrogel bulb submerged in water and the hydrophobic bulb in oil and are thus able to stabilize both water-in-oil and oil-in-water emulsions, making these amphiphilic hydrogel-solid particles ideal colloidal surfactants for various applications.

  12. Proteolysis of truncated hemolysin A yields a stable dimerization interface

    Energy Technology Data Exchange (ETDEWEB)

    Novak, Walter R.P.; Bhattacharyya, Basudeb; Grilley, Daniel P.; Weaver, Todd M. (Wabash); (UW)

    2017-02-21

    Wild-type and variant forms of HpmA265 (truncated hemolysin A) fromProteus mirabilisreveal a right-handed, parallel β-helix capped and flanked by segments of antiparallel β-strands. The low-salt crystal structures form a dimeric structureviathe implementation of on-edge main-chain hydrogen bonds donated by residues 243–263 of adjacent monomers. Surprisingly, in the high-salt structures of two variants, Y134A and Q125A-Y134A, a new dimeric interface is formedviamain-chain hydrogen bonds donated by residues 203–215 of adjacent monomers, and a previously unobserved tetramer is formed. In addition, an eight-stranded antiparallel β-sheet is formed from the flap regions of crystallographically related monomers in the high-salt structures. This new interface is possible owing to additional proteolysis of these variants after Tyr240. The interface formed in the high-salt crystal forms of hemolysin A variants may mimic the on-edge β-strand positioning used in template-assisted hemolytic activity.

  13. Iron-Deficiency Anemia

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  16. Iron-Deficiency Anemia

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  11. Iron-Deficiency Anemia

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    Full Text Available ... improve health through research and scientific discovery. Improving health with current research Learn about the following ways ... from needing iron supplementation. Advancing research for improved health In support of our mission , we are committed ...

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    Full Text Available ... research and scientific discovery. Improving health with current research Learn about the following ways that NHLBI continues ... and protect individuals from needing iron supplementation. Advancing research for improved health In support of our mission , ...

  13. Iron-Deficiency Anemia

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    Full Text Available ... Are you a frequent blood donor living in New York City? This study is looking at how iron- ... donate blood frequently. This study is located in New York City, and is recruiting by invitation only. View ...

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  19. Iron-Deficiency Anemia

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  1. Iron-Deficiency Anemia

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  2. Iron-Deficiency Anemia

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    Full Text Available ... may recommend erythropoiesis stimulating agents (esa) . These medicines stimulate the bone marrow to make more red blood ... NHLBI is funding on iron-deficiency anemia. We stimulate high-impact research. Our Trans-Omics for Precision ...

  3. Iron-Deficiency Anemia

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    Full Text Available ... lifestyle changes to avoid complications. Follow your treatment plan Do not stop taking your prescribed iron supplements ... warning signs of serious complications and have a plan Tell your doctor if you have any new ...

  4. Banded Iron Formations

    DEFF Research Database (Denmark)

    Posth, Nicole R; Konhauser, Kurt O; Kappler, Andreas

    2011-01-01

    Sedimentary deposits of alternating iron-rich (20–40% Fe) and iron-poor, siliceous (40–50% SiO2) mineral layers that primarily precipitated throughout much of the late Archean (2.7–2.5 Ga) and Paleoproterozoic (2.5– 1.8 Ga), but then remerged in the Neoproterozoic (0.8 Ga).......Sedimentary deposits of alternating iron-rich (20–40% Fe) and iron-poor, siliceous (40–50% SiO2) mineral layers that primarily precipitated throughout much of the late Archean (2.7–2.5 Ga) and Paleoproterozoic (2.5– 1.8 Ga), but then remerged in the Neoproterozoic (0.8 Ga)....

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  11. Ocean iron fertilization

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Smetacek, V.

    In 2009 and 2010, an Indo-German scientific expedition dusted the ocean with iron to stimulate the biological pump that captures atmosphereic carbon dioxide. Two onboard scientists tell the story of this controversial project. Besides raising...

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  20. Iron-Deficiency Anemia

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    Full Text Available ... improved health for people with iron-deficiency anemia. Recipient Epidemiology Donor Studies program findings help to protect blood donors . NHLBI’s Recipient Epidemiology Donor Studies (REDS) program , which began in ...