Browsing by Author "Unruh, T"

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    Hindered water motions in hardened cement pastes investigated over broad time and length scales.
    (American Chemical Society, 2009-10-28) Bordallo, HN; Aldridge, LP; Fouquet, P; Pardo, LC; Unruh, T; Wuttke, J; Yokaichiya, F
    We investigated the dynamics of confined water in different hydrated cement pastes with minimized contributions of capillary water. It was found that the water motions are extremely reduced compared to those of bulk water. The onset of water mobility, which was modified by the local environment, was investigated with elastic temperature scans using the high-resolution neutron backscattering instrument SPHERES. Using a Cauchy−Lorenz distribution, the quasi-elastic signal observed in the spectra obtained by the backscattering spectrometer was analyzed, leading to the identification of rotational motions with relaxation times of 0.3 ns. Additionally, neutron spin echo (NSE) spectroscopy was used to measure the water diffusion over the local network of pores. The motions observed in the NSE time scale were characterized by diffusion constants ranging from 0.6 to 1.1 × 10−9 m2 s−1 most likely related to water molecules removed from the interface. In summary, our results indicate that the local diffusion observed in the gel pores of hardened cement pastes is on the order of that found in deeply supercooled water. Finally, the importance of the magnetic properties of cement pastes were discussed in relation to the observation of a quasi-elastic signal on the dried sample spectra measured using the time-of-flight spectrometer. © 2009, American Chemical Society
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    New sources and instrumentation for neutrons in biology
    (Elsevier, 2008-04-18) Teixeira, SCM; Zaccai, G; Ankner, J; Bellissent-Funel, MC; Bewley, RI; Blakeley, MP; Callow, P; Coates, L; Dahint, R; Dalgliesh, R; Dencher, NA; Forsyth, VT; Fragneto, G; Frick, B; Gilles, R; Gutberlet, T; Haertlein, M; Hauß, T; Häußler, W; Heller, WT; Herwig, K; Holderer, O; Juranyi, F; Kampmann, R; Knott, RB; Krueger, S; Langan, P; Lechner, RE; Lynn, GW; Majkrzak, CF; May, RP; Meilleur, F; Mo, Y; Mortensen, K; Myles, DAA; Natali, F; Neylon, C; Niimura, N; Ollivier, J; Ostermann, A; Peters, J; Pieper, J; Rühm, A; Schwahn, D; Shibata, K; Soper, AK; Strässle, T; Suzuki, J; Tanaka, I; Tehei, M; Timmins, P; Torikai, N; Unruh, T; Urban, V; Vavrin, R; Weiss, K
    Neutron radiation offers significant advantages for the study of biological molecular structure and dynamics. A broad and significant effort towards instrumental and methodological development to facilitate biology experiments at neutron sources worldwide is reviewed. © 2008, Elsevier Ltd.
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    Non-classical behaviour in an S=5/2 chain with next nearest neighbour interactions observed from the inelastic neutron scattering of Mn-2(OD)(2)(C4O4)
    (Institute of Physics, 2009-02-18) Mole, RA; Stride, JA; Unruh, T; Wood, PT
    Low-dimensional and frustrated magnetic systems often show interesting quantum phenomena. The use of large moments such as S = 5/2 within such materials is uncommon, partly due to the evidence that the large manifold of states associated with these centres results in pseudo-classical behaviour. Here we report on the inelastic neutron scattering of Mn-2(OD)(2)(C4O4), a well-isolated chain with next nearest neighbour interactions. We observe a magnetic excitation spectrum below 30 K whose characteristics resemble those of quantum spin singlets. Inelastic neutron scattering from a powdered sample is shown to yield a great deal of information about the nature of these effects. © 2009, Institute of Physics
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    Picosecond dynamics in haemoglobin from different species: a quasielastic neutron scattering study
    (Elsevier, 2014-10) Stadler, AM; Garvey, CJ; Embs, JP; Koza, MM; Unruh, T; Artmann, GM; Zaccai, G
    Background Dynamics in haemoglobin from platypus (Ornithorhynchus anatinus), chicken (Gallus gallus domesticus) and saltwater crocodile (Crocodylus porosus) were measured to investigate response of conformational motions on the picosecond time scale to naturally occurring variations in the amino acid sequence of structurally identical proteins. Methods Protein dynamics was measured using incoherent quasielastic neutron scattering. The quasielastic broadening was interpreted first with a simple single Lorentzian approach and then by using the Kneller–Volino Brownian dynamics model. Results Mean square displacements of conformational motions, diffusion coefficients of internal dynamics and residence times for jump-diffusion between sites and corresponding effective force constants (resilience) and activation energies were determined from the data. Conclusions Modifications of the physicochemical properties caused by mutations of the amino acids were found to have a significant impact on protein dynamics. Activation energies of local side chain dynamics were found to be similar between the different proteins being close to the energy, which is required for the rupture of single hydrogen bond in a protein. General significance The measured dynamic quantities showed significant and systematic variations between the investigated species, suggesting that they are the signature of an evolutionary adaptation process stimulated by the different physiological environments of the respective protein. © 2014,Elsevier B.V.
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    A spectroscopic investigation of magnetic exchange between highly anisotropic spin centers
    (Wiley-Blackwell, 2011-04-18) Boeer, AB; Barra, AL; Chibotaru, LF; Collison, D; McInnes, EJL; Mole, RA; Simeoni, GG; Timco, GA; Ungur, L; Unruh, T; Winpenny, REP
    Structurally similar, magnetically diverse: The exchange and Zeeman parameters of two dimetallic, six-coordinate cobalt(II) compounds—i.e., with orbitally degenerate metal ions—have been determined by a combination of high-resolution EPR and INS spectroscopies, together with ab intio calculations. It is suggested that the correlation between the local crystal field about the CoII centers and the superexchange pathway controls the magnetic interaction. © 2011, Wiley-Blackwell.