Ahmet Alatas

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Compressional wave velocity-density (V(P)--ρ) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earth's core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planet's remotest region. Specifically, comparison between seismic V(P)--ρ profiles of the core and candidate Fe alloys(More)
Elastic neutron-scattering, inelastic x-ray scattering, specific-heat, and pressure-dependent electrical transport measurements have been made on single crystals of AuZn and Au0.52Zn0.48. Elastic neutron scattering detects new commensurate Bragg peaks (modulation) appearing at Q =(1.33,0.67,0) at temperatures corresponding to each sample's transition(More)
We summarize a series of experimental results made with the newly developed high resolution X-ray scattering (IXS) instrument on two pure lipid bilayers, including dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) in both gel and liquid crystal phases, and lipid bilayers containing cholesterol. By analyzing the IXS data based on(More)
Sediments from relic Lake Golbasi were analyzed by X-ray fluorescence with synchrotron radiation to determine changes in element concentrations over time with selected elements serving as proxies for environmental change. Increases in Ca and Sr suggest soil formation during a dry period, from ca. 4500 BC to ca. AD 200 at which point K, Rb, Zr, Ti, and Y(More)
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=variant Planck's(More)
Molecular dynamics simulations and neutron scattering experiments have shown that many hydrated globular proteins exhibit a universal dynamic transition at TD = 220 K, below which the biological activity of a protein sharply diminishes. We studied the phononlike low-energy excitations of two structurally very different proteins, lysozyme and bovine serum(More)
An in-line monochromatization scheme suitable for 10-40 keV synchrotron radiation is presented based on the use of six crystal reflections that achieves meV and sub-meV bandwidths with high efficiency. The theoretical spectral efficiency surpasses all previous multicrystal designs and approaches that of single room-temperature back-reflecting crystals. This(More)
Flexibility is an important property of porphyrins, both natural and synthetic. We applied two synchrotron-based techniques, nuclear resonance vibrational spectroscopy and inelastic X-ray scattering, to quantify this property by measuring the bulk modulus of a protein active-site mimic [chloro(octaethylporphyrinato)iron(III)] and the resilience of the iron(More)
We report high-resolution inelastic x-ray measurements of the soft phonon mode in the charge-density-wave compound TiSe(2). We observe a complete softening of a transverse optic phonon at the L point, i.e., q=(0.5, 0, 0.5), at T≈T(CDW). Detailed ab initio calculations for the electronic and lattice dynamical properties of TiSe(2) are in quantitative(More)
Phonon dispersion curves were obtained from inelastic x-ray and neutron scattering measurements on alpha-uranium single crystals at temperatures from 298 to 573 K. Both measurements showed a softening and an abrupt loss of intensity in the longitudinal optic branch along [00zeta] above 450 K. Above the same temperature a new dynamical mode of comparable(More)