139 research outputs found
Measuring velocity of sound with nuclear resonant inelastic x-ray scattering
Nuclear resonant inelastic x-ray scattering is used to measure the projected
partial phonon density of states of materials. A relationship is derived
between the low-energy part of this frequency distribution function and the
sound velocity of materials. Our derivation is valid for harmonic solids with
Debye-like low-frequency dynamics. This method of sound velocity determination
is applied to elemental, composite, and impurity samples which are
representative of a wide variety of both crystalline and noncrystalline
materials. Advantages and limitations of this method are elucidated
Pressure-dependence of electron-phonon coupling and the superconducting phase in hcp Fe - a linear response study
A recent experiment by Shimizu et al. has provided evidence of a
superconducting phase in hcp Fe under pressure. To study the
pressure-dependence of this superconducting phase we have calculated the phonon
frequencies and the electron-phonon coupling in hcp Fe as a function of the
lattice parameter, using the linear response (LR) scheme and the full potential
linear muffin-tin orbital (FP-LMTO) method. Calculated phonon spectra and the
Eliashberg functions indicate that conventional s-wave
electron-phonon coupling can definitely account for the appearance of the
superconducting phase in hcp Fe. However, the observed change in the transition
temperature with increasing pressure is far too rapid compared with the
calculated results. For comparison with the linear response results, we have
computed the electron-phonon coupling also by using the rigid muffin-tin (RMT)
approximation. From both the LR and the RMT results it appears that
electron-phonon interaction alone cannot explain the small range of volume over
which superconductivity is observed. It is shown that
ferromagnetic/antiferromagnetic spin fluctuations as well as scattering from
magnetic impurities (spin-ordered clusters) can account for the observed values
of the transition temperatures but cannot substantially improve the agreeemnt
between the calculated and observed presure/volume range of the superconducting
phase. A simplified treatment of p-wave pairing leads to extremely small ( K) transition temperatures. Thus our calculations seem to rule out
both - and - wave superconductivity in hcp Fe.Comment: 12 pages, submitted to PR
Profiling microRNAs in individuals at risk of progression to rheumatoid arthritis
Background: Individuals at risk of rheumatoid arthritis (RA) demonstrate systemic autoimmunity in the form of anti-citrullinated peptide antibodies (ACPA). MicroRNAs (miRNAs) are implicated in established RA. This study aimed to (1) compare miRNA expression between healthy individuals and those at risk of and those that develop RA, (2) evaluate the change in expression of miRNA from "at-risk" to early RA and (3) explore whether these miRNAs could inform a signature predictive of progression from "at-risk" to RA. Methods: We performed global profiling of 754 miRNAs per patient on a matched serum sample cohort of 12 anti-cyclic citrullinated peptide (CCP) + "at-risk" individuals that progressed to RA. Each individual had a serum sample from baseline and at time of detection of synovitis, forming the matched element. Healthy controls were also studied. miRNAs with a fold difference/fold change of four in expression level met our primary criterion for selection as candidate miRNAs. Validation of the miRNAs of interest was conducted using custom miRNA array cards on matched samples (baseline and follow up) in 24 CCP+ individuals; 12 RA progressors and 12 RA non-progressors. Results: We report on the first study to use matched serum samples and a comprehensive miRNA array approach to identify in particular, three miRNAs (miR-22, miR-486-3p, and miR-382) associated with progression from systemic autoimmunity to RA inflammation. MiR-22 demonstrated significant fold difference between progressors and non-progressors indicating a potential biomarker role for at-risk individuals. Conclusions: This first study using a cohort with matched serum samples provides important mechanistic insights in the transition from systemic autoimmunity to inflammatory disease for future investigation, and with further evaluation, might also serve as a predictive biomarker
Cartels, managerial incentives, and productive efficiency in German coal mining, 1881-1913
In this paper, we evaluate the impact of cartelisation and managerial incentives on the productive efficiency of German coal mining corporations. We focus on coal mining in the Ruhr district, Germany’s main mining area. We use stochastic frontier analysis and an unbalanced dynamic panel data set for up to 28 firms for the years 1881-1913 to measure productive efficiency. We show that coal was mined with decreasing returns to scale. Moreover, it turns out that cartelisation did not affect productive efficiency. Controlling for corporate governance variables shows that stronger managerial incentives were significantly correlated with productive efficiency, whereas the debt-equity ratio did not influence it
The design of licensing contracts: Chemicals, Pharmaceuticals, and Electrical Engineering in Imperial Germany
We investigate a sample of 180 technology licensing contracts closed by German chemical, pharmaceutical, and electrical engineering companies between 1880 and 1913. Our empirical results suggest that strategic behaviour seems to be relevant for the design of licensing contracts, whereas inventor moral hazard and risk aversion of licensor or licensee seem to be irrelevant. Moreover, our results suggest that uncertainty regarding the profitability of licensed technology influenced the design of licensing contracts. More specifically, profit sharing agreements or producer milestones were typically included into licensing contracts
- …