Vibrational States of Glassy and Crystalline Orthotherphenyl

Low-frequency vibrations of glassy and crystalline orthoterphenyl are studied by means of neutron scattering. Phonon dispersions are measured along the main axes of a single crystal, and the corresponding longitudinal and transversal sound velocities are obtained. For glassy and polycrystalline samples, a density of vibrational states is determined and cross-checked against other dynamic observables. In the crystal, low-lying zone-boundary modes lead to an excess over the Debye density of states. In the glass, the boson peak is located at even lower frequencies. With increasing temperature, both glass and crystal show anharmonicity.Comment: 7 pages of LaTeX (svjour), 2 tables, 10 figures accepted in Eur. Phys. J.

Study of thermal conductivity design for thermal loaded geomaterials.

Soil thermal conductivity plays preponderant role in many geoengineering projects involving thermal effects, such as high voltage underground power cables, oil and gas pipelines, nuclear waste disposal facilities, ground heat energy storage and heat exchanger piles. A thorough understanding of thermal conductivity is necessary in heat transfer modelling. Depending upon the application and desired purpose of such projects, materials with either high or low thermal conductivity are used. Materials with high thermal conductivity are desirable in cases such as high voltage underground power cables to dissipate the generated heat rapidly to the surrounding soil. On the other hand, ground heat energy storage needs materials with low thermal conductivity and high heat capacity to hinder the heat energy loss. In this study, high conductive backfill materials for underground power cables were analysed based on existing knowledge of heat transfer mechanism in granular media and models of soil thermal conductivity in both dry and wet conditions (Yun and Santamarina, 2007, Cortes and Santamarina, 2009). Several researchers have developed theoretical, empirical and semi-empirical models to estimate the thermal conductivity of natural soils and crushed rock materials based on various factors such as particle shape and size, particle distribution, mineral composition, dry density, and wate

YAC contigs of the Rab1 and wobbler (wr) spinal muscular atrophy gene region on proximal mouse chromosome 11 and of the homologous region on human chromosome 2p

powerful tool to advance the identi®cation of gene com-Despite rapid progress in the physical characteriza- plexes and of disease genes. In this respect, the analysis tion of murine and human genomes, little molecular in- of human chromosomes 16 and 19 (Nowak, 1995) and formation is available on certain regions, e.g., proximal mouse chromosomes 1 (Hunter et al., 1994) and 17 (Cox mouse chromosome 11 (Chr 11) and human chromosome et al., 1993) as well as of human and murine X chromo-2p (Chr 2p). We have localized the wobbler spinal atrophy somes is particularly far advanced (Hamvas et al., 1993). gene wr to proximal mouse Chr 11, tightly linked toRab1, On the other hand, such extensive information is not a gene coding for a small GTP-binding protein, and Glns- available for mouse proximal chromosome 11 (Chr 11) ps1, an intronless pseudogene of the glutamine synthe- and human chromosome 2p (Chr 2p) (Fig. 1; cf. Berry et tase gene. We have now used these markers to construct al., 1995; Nowak, 1995), known to share at least the genesa 1.3-Mb yeast arti®cial chromosome (YAC) contig of the for the reticuloendotheliosis oncogene (Brownell et al.,Rab1 region on mouse Chr 11. Four YAC clones isolated 1985), for a brain-speci®cb-spectrin isoform (Bloom et al.,from two independent YAC libraries were characterized 1992), and for cytoplasmic malate dehydrogenase (Ball etby rare-cutting analysis, ¯uorescence in situ hybridiza-al., 1994). However, comparing the segregation map oftion (FISH), and sequence-tagged site (STS) isolation and the mouse with the human cytogenetic map, a colinearmapping. Rab1 and Glns-ps1 were found to be only 20

The Dynamic Transition of Protein Hydration Water

Thin layers of water on biomolecular and other nanostructured surfaces can be supercooled to temperatures not accessible with bulk water. Chen et al. [PNAS 103, 9012 (2006)] suggested that anomalies near 220 K observed by quasi-elastic neutron scattering can be explained by a hidden critical point of bulk water. Based on more sensitive measurements of water on perdeuterated phycocyanin, using the new neutron backscattering spectrometer SPHERES, and an improved data analysis, we present results that show no sign of such a fragile-to-strong transition. The inflection of the elastic intensity at 220 K has a dynamic origin that is compatible with a calorimetric glass transition at 170 K. The temperature dependence of the relaxation times is highly sensitive to data evaluation; it can be brought into perfect agreement with the results of other techniques, without any anomaly.Comment: 4 pages, 3 figures. Phys. Rev. Lett. (in press

Atomic Transport in Dense, Multi-Component Metallic Liquids

Pd43Ni10Cu27P0 has been investigated in its equilibrium liquid state with incoherent, inelastic neutron scattering. As compared to simple liquids, liquid PdNiCuP is characterized by a dense packing with a packing fraction above 0.5. The intermediate scattering function exhibits a fast relaxation process that precedes structural relaxation. Structural relaxation obeys a time-temperature superposition that extends over a temperature range of 540K. The mode-coupling theory of the liquid to glass transition (MCT) gives a consistent description of the dynamics which governs the mass transport in liquid PdNiCuP alloys. MCT scaling laws extrapolate to a critical temperature Tc at about 20% below the liquidus temperature. Diffusivities derived from the mean relaxation times compare well with Co diffusivities from recent tracer diffusion measurements and diffsuivities calculated from viscosity via the Stokes-Einstein relation. In contrast to simple metallic liquids, the atomic transport in dense, liquid PdNiCuP is characterized by a drastical slowing down of dynamics on cooling, a q^{-2} dependence of the mean relaxation times at intermediate q and a vanishing isotope effect as a result of a highly collective transport mechanism. At temperatures as high as 2Tc diffusion in liquid PdNiCuP is as fast as in simple liquids at the melting point. However, the difference in the underlying atomic transport mechanism indicates that the diffusion mechanism in liquids is not controlled by the value of the diffusivity but rather by that of the packing fraction

Harmonic behavior of metallic glasses up to the metastable melt

In two amorphous alloys ZrTiCuNiBe and ZrAlNiCu coherent neutron scattering has been measured over five decades in energy, including measurements in the metastable melt of a metallic alloy more than 80 K above Tg. In the vibrational spectra a pronounced "boson" peak is found: Even in crystallized samples the density of states exceeds the Debye ω2 model, and in the amorphous state low-frequency vibrations are further enhanced. The peak position shows no dispersion in q, while intensities are strongly correlated with the static structure factor. Over the full energy range the temperature dependence is strictly harmonic. From high-energy resolution measurements we establish lower bounds for the temperatures at which structural α and fast β relaxation become observable

Wavenumber dependence of structural alpha relaxation in a molecular liquid

Structural alpha relaxation in liquid orthoterphenyl is studied by means of coherent neutron time-of-flight and backscattering spectroscopy over a large temperature range. Not only amplitude and relaxation time but also the spectral line shape show a significant variation with wavenumber. As expected from mode coupling theory, these variations are correlated with the static structure factor. Even far above the melting point, alpha relaxation remains non-exponential.Comment: 6 pages of LaTeX, 4 figure

Supply chain finance: optimal introduction and adoption decisions

Supply chain finance (SCF) can improve supply chain performance by facilitating longer payment terms for buyers and better access to financing for suppliers. In spite of these clear benefits, there is empirical evidence for some hesitation and resistance to SCF adoption, manifesting in an often substantial time lag between a buyer's introduction of SCF and its adoption by all targeted suppliers. Observed adoption processes often resemble the s-shaped Bass-curve suggesting that successful early adoptions support adoption decisions by other suppliers. Based on these observations, we consider supplier SCF adoption decisions within a diffusion model, to obtain insights regarding a buyer's optimal SCF introduction decisions in terms of timing and payment terms. We find that initial payment terms and procurement volume strongly affect the optimal timing of SCF introduction and optimal payment term extensions. The degree to which the buyer can influence suppliers in their adoption decisions affects the optimal introduction timing, but not optimal payment terms. Interestingly, our results suggest that, in spite of the clear benefits, many buyers might be well-advised to postpone their SCF implementations

Depinning in a Random Medium

We develop a renormalized continuum field theory for a directed polymer interacting with a random medium and a single extended defect. The renormalization group is based on the operator algebra of the pinning potential; it has novel features due to the breakdown of hyperscaling in a random system. There is a second-order transition between a localized and a delocalized phase of the polymer; we obtain analytic results on its critical pinning strength and scaling exponents. Our results are directly related to spatially inhomogeneous Kardar-Parisi-Zhang surface growth.Comment: 11 pages (latex) with one figure (now printable, no other changes

Molecular mode-coupling theory applied to a liquid of diatomic molecules

We study the molecular mode coupling theory for a liquid of diatomic molecules. The equations for the critical tensorial nonergodicity parameters ${\bf F}_{ll'}^m(q)$ and the critical amplitudes of the $\beta$ - relaxation ${\bf H}_{ll'}^m(q)$ are solved up to a cut off $l_{co}$ = 2 without any further approximations. Here $l,m$ are indices of spherical harmonics. Contrary to previous studies, where additional approximations were applied, we find in agreement with simulations, that all molecular degrees of freedom vitrify at a single temperature $T_c$. The theoretical results for the non ergodicity parameters and the critical amplitudes are compared with those from simulations. The qualitative agreement is good for all molecular degrees of freedom. To study the influence of the cut off on the non ergodicity parameter, we also calculate the non ergodicity parameters for an upper cut off $l_{co}=4$. In addition we also propose a new method for the calculation of the critical nonergodicity parameterComment: 27 pages, 17 figure