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Hydroxylation of wadsleyite, β-(Mg,Fe)2SiO4, is associated with divalent cation defects and well known to afect its physical properties. However, an atomic-scale understanding of the defect structure and hydrogen bonding at high pressures is needed to interpret the influence of water on the behavior of wadsleyite in the mantle transition zone. We have determined the pressure evolution of the wadsleyite crystal symmetry and structure, including all O∙∙∙O interatomic distances, up to 32 GPa using single-crystal X-ray difraction on two well-characterized, Fe-bearing (Fo90) samples containing 0.25(4) and 2.0(2) wt% H2O. Both compositions undergo a pressure-dependent monoclinic distortion from orthorhombic symmetry above 9 GPa, with the less hydrous sample showing a larger increase in distortion at increased pressures due to the diference in compressibility of the split M3 site in the monoclinic setting arising from preferred vacancy ordering at the M3B site. Although hydrogen positions cannot be modeled from the X-ray difraction data, the pressure evolution of the longer O1∙∙∙O4 distance in the structure characterizes the primary hydrogen bond length. We observe the hydrogen-bonded O1∙∙∙O4 distance shorten gradually from 3.080(1) Å at ambient pressure to about 2.90(1) Å at 25 GPa, being still much longer than is defined as strong hydrogen bonding (2.5–2.7 Å). Above 25 GPa and up to the maximum pressure of the experiment at 32.5 GPa, the hydrogen-bonded O1∙∙∙O4 distance decreases no further, despite the fact that previous spectroscopic studies have shown that the primary O-H stretching frequencies continuously drop into the regime of strong hydrogen bonding (<3200 cm–1) above ~15 GPa. We propose that the primary O1-H∙∙∙O4 hydrogen bond in wadsleyite becomes highly nonlinear at high pressures based on its deviation from frequency-distance correlations for linear hydrogen bonds. One possible explanation is that the hydrogen position shifts from being nearly on the long O1-O4 edge of the M3 site to a position more above O1 along the c-axis. [ABSTRACT FROM AUTHOR]

Recent research has indicated that conceptual development in a specific domain may not be independent of the way it is mapped linguistically. We explore this claim in the semantic domain of evidentiality by considering various sets of data from Turkish-speaking children between one and a half to six years. We present evidence for (1) the appropriate use of grammaticalized markers of direct experience, inference, and linguistic report by age three, (2) the understanding of knowledge source ("theory of knowledge") around age four, (3) the understanding of linguistic form and knowledge source relationship ("theory of evidentiality") by age six, and (4) a predictive relationship between the use of the reported speech marker and memory for knowledge source around age four. (Contains 2 tables and 1 figure.)

We have performed and analyzed the first combined 151Eu and 57Fe nuclear resonant vibrational spectroscopy (NRVS) for naturally abundant KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] complexes. Comparison of the observed 151Eu vs.57Fe NRVS spectroscopic features confirms that Eu(III) in both KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] occupies a position outside the [Fe(CN)6] core and coordinates to the N atoms of the CN− ions, whereas Fe(III) or Fe(II) occupies the site inside the [Fe(CN)6]4− core and coordinates to the C atoms of the CN− ions. In addition to the spectroscopic interest, the results from this study provide invaluable insights for the design and evaluation of the nanoparticles of such complexes as potential cellular contrast agents for their use in magnetic resonance imaging. The combined 151Eu and 57Fe NRVS measurements are also among the first few explorations of bi-isotopic NRVS experiments. [ABSTRACT FROM AUTHOR]

An investigation of the model compound chloro iron octaphenylporphyrin Fe(OEP)Cl, as a stepin understanding biologically significant dynamics in heme proteins is reported. A normal-mode analysis is employed to calculate the Fe(super 57) partial vibrational density of states (VDOS) and refined to absorption data from nuclear resonance vibrational spectroscopy.

Operando nuclear resonant inelastic X‐ray scattering (NRIXS) and X‐ray absorption fine‐structure spectroscopy (XAFS) measurements were used to gain insight into the structure and surface composition of FeCu and FeAg nanoparticles (NPs) during the electrochemical CO2 reduction (CO2RR) and to extract correlations with their catalytic activity and selectivity. The formation of a core–shell structure during CO2RR for FeAg NPs was inferred from the analysis of the operando NRIXS data (phonon density of states, PDOS) and XAFS measurements. Electrochemical analysis of the FeAg NPs revealed a faradaic selectivity of 36 % for CO in 0.1 M KHCO3 at −1.1 V vs. RHE, similar to that of pure Ag NPs. In contrast, a predominant selectivity towards H2 evolution is obtained in the case of the FeCu NPs, analogous to the results obtained for pure Fe NPs, although small Cu NPs have also been shown to favor H2 production. [ABSTRACT FROM AUTHOR]

Inelastic X‐ray scattering is a powerful and versatile technique for studying lattice dynamics in materials of scientific and technological importance. In this article, the design and capabilities of the momentum‐resolved high‐energy‐resolution inelastic X‐ray spectrometer (HERIX) at beamline 30‐ID of the Advanced Photon Source are reported. The instrument operates at 23.724 keV and has an energy resolution of 1.3–1.7 meV. It can accommodate momentum transfers of up to 72 nm−1, at a typical X‐ray flux of 4.5 × 109 photons s−1 meV−1 at the sample. A suite of in situ sample environments are provided, including high pressure, static magnetic fields and uniaxial strains, all at high or cryogenic temperatures. [ABSTRACT FROM AUTHOR]

The phonon propagation and damping along the axial direction of films of aligned 40 wt % calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S(Q,E) as a function of transferred energy E=hω, and the magnitude of the transferred wave vector Q. S(Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30 nm-1. A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q=4 nm-1. The high-frequency sound speed obtained in this Q range is 3100 m/s, which is about twice faster than the ultrasound speed of 1800 m/s, measured by Brillouin light scattering at Q∼0.01 nm-1 at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between ∼12.5 and ∼22.5 nm-1 are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4 ps. [ABSTRACT FROM AUTHOR]

A [super 57]Fe nuclear resonance vibrational spectroscopy (NRVS) was used to study the [Fe.sub.2][S.sub.2][(Cys).sub.4] sites in oxidized and reduced [2Fe-2S] ferredoxins from Rhodobacter capsulatus (Rc FdVI) and Aquifex aeolicus (Aa Fd5). The NRVS technique was found to be very useful for the observation and quantitative interpretation of the dynamical properties of Fe-S proteins.

A [super 57]Fe nuclear resonance vibrational spectroscopy (NRVS) was used to study the iron site in the iron-sulfur cluster-free hydrogenase Hmd from the methanogenic archaeon Methanothermobacter marburgensis. The data obtained for NRVS provided insights into the dynamics of the Fe site, revealing Fe-CO stretch and Fe-CO bend modes at 494, 562, 590, and 648 [cm.sup.-1], which are consistent with the proposed cis-Fe[(CO).sub.2] ligation.

The first information about vibrational modes of the Fe-S clusters in nitrogenase, using the technique of nuclear resonance vibrational spectroscopy (NRVS) is reported. The vibrational spectra derived from NRVS experiments support the presence of an interstitial atom in both isolated FeMoCo and in the Azotobacter vinelandii protein (Avl)-bound FeMo-cofactor.

The Fe(S(sub cys))4 site in reduced and oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf) is studied using (super 57)Fe nuclear resonance vibrational spectroscopy (NRVS). A normal mode analysis using a Urey-Bradley force field is undertaken to quantitatively interpret the NRVS spectra and to set the stage for analysis of seemingly more complex problems such as hydrogenase and nitrogenase.

The Fe nuclear resonance vibrational spectroscopy (NRVS) data for the FeCl(sub 4)(super -) ion in the solid state with NEt(sub 4)(super +) or P(C6H5)(sub 4)(super +) counterions and for the [Fe2S2Cl4](super 2-) cluster with NEt(sub 4)(super +) counterions and also their Raman and far-infrared (IR) spectra are described. The advantages of a combined NRVS, Raman, and IR approach to characterization of Fe-S complexes are discussed.

Nuclear resonant inelastic X-ray scatting (NRIXS) data on FeS4 and FeH(D)(sub 6) model systems is presented. Fe-H stretches have high frequencies and little Fe motion and both factors will reduce NIRXS intensity.

The reaction of protein-bound iron-sulfur (Fe-S) clusters with nitric oxide (NO) plays key roles in NO-mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe-S clusters has been hampered by a lack of information about the nature of the iron-nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe-4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe2(NO)4(Cys)2]) and Roussin's Black Salt (RBS, [Fe4(NO)7S3]. In the latter case, the absence of 32S/34S shifts in the Fe−S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates. [ABSTRACT FROM AUTHOR]

Blick ins Zentrum: Die Methode der inelastischen kernresonanten Streuung (NRVS) wurde genutzt, um 57Fe ‐ markierte [NiFe] ‐ Hydrogenase in unterschiedlichen Zuständen des Enzyms zu untersuchen. Damit gelang es, die Fe ‐ CO ‐ und Fe ‐ CN ‐ Beuge ‐ und ‐ Streckschwingung außerhalb des Spektralbereichs der Normalmoden der Fe ‐ S ‐ Cluster zu detektieren und zuzuordnen (siehe Spektrum). [ABSTRACT FROM AUTHOR]

Nuclear inelastic scattering of 57Fe labeled [NiFe] hydrogenase is shown to give information on different states of the enzyme. It was thus possible to detect and assign FeCO and FeCN bending and stretching vibrations of the active site outside the spectral range of the FeS cluster normal modes. [ABSTRACT FROM AUTHOR]

The electronic spin and valence states of iron in lower-mantle silicate perovskite have been previously investigated at high pressures using various experimental and theoretical techniques. However, experimental results and their interpretation remain highly debated. Here we have studied a well-characterized silicate perovskite starting sample [(Mg0.9,Fe0.1)SiO3] in a chemically inert Ne pressure medium at pressures up to 120 GPa using synchrotron Mössbauer spectra. Analyses of the Mössbauer spectra explicitly show a high-spin to low-spin transition of the octahedral-site Fe3+ occurring at ~13--24 GPa, as evidenced from a significant increase in the hyperfine quadrupole splitting. Two quadrupole doublets of the A-site Fe2+, with extremely high-QS values of 4.1 and 3.1 mm/s, occur simultaneously with the spin transition of the octahedral-site Fe3+ and continue to develop to 120 GPa. It is conceivable that the spin-pairing transition of the octahedral-site Fe3+ causes a volume reduction and a change in the local atomic-site configurations that result in a significant increase of the quadrupole splitting in the dodecahedral-site Fe2+ at 13--24 GPa. Our results here provide a coherent explanation for recent experimental and theoretical results on the spin and valence states of iron in perovskite, and assist in comprehending the effects of the spin and valence states of iron on the properties of the lower-mantle minerals. [ABSTRACT FROM AUTHOR]

Pressure, together with temperature, composition, or external fields, alone or in combination, can be used as principal variables in directing and controlling matter as well as for the synthesis of revolutionary new materials. The impact of extreme conditions to science, however, has been previously limited by the available vessels and probes. The last decade has witnessed a significant surge in extreme conditions science, thanks to the development of in situ synchrotron radiation (SR) probes and high-pressure (HP) instrumentation. Extreme conditions directly alter chemical, structural, mechanical, electronic, magnetic, and phonon properties of materials, revealing intriguing behaviors across boundaries between insulators and metals, ferromagnets and superconductors, ordered and disordered, and vigorously reactive and inert compounds. In Earth and planetary sciences, research from simulating experiments at high pressure and high temperature provides key information in understanding processes, dynamics, and formation of the deep interiors. For materials applications such as the search for new energy materials and superhard materials, extreme conditions remain a vast, unexplored field. [ABSTRACT FROM AUTHOR]

This article reports that a group from the University of Michigan, Ann Arbor, Michigan directly measured the transient strain in an ultrafast laser-excited germanium single crystal using time-resolved X-ray anomalous transmission at the MHATT/XOR sector 7-ID undulator beamline. Scientific research in the time domain using the pulsed structure of the X-ray beams from a third-generation synchrotron source, such as the Advanced Photon Source has become a major interest among synchrotron users. The traditional materials science, chemistry, and biology communities are getting an early glimpse of the potential impact of fast time-resolved X-ray studies. Technically, the turn-key-type femtosecond optical lasers with high peak power, used as pumps in many X-ray pump-probe experiments, have only recently become available.

Highlights the workshop on inelastic x-ray scattering, held on May 4-6, 2004 at Argonne National Laboratory in Chicago, Illinois. Purpose of the workshop; Keynote speakers; Topics discussed.