[en] The Earth's iron-dominant core is known to contain nickel from cosmochemical analysis and some amount of light elements from geophysical constraints on density and seismic wave velocities. Although there have been several studies to constrain thermoelastic properties of iron-alloys, there has been no systematic study on the effects of nickel and light elements on properties of iron using the same experimental methods and data analysis approach. We conducted nuclear resonant inelastic X-ray scattering and X-ray diffraction experiments on body-centered cubic and hexagonal close-packed (hcp) Fe_0.91Ni_0.09 and Fe_0.8Ni_0.1Si_0.1 up to 104 GPa and 86 GPa, respectively, and compare to similar measurements conducted on hcp-Fe up to 171 GPa. Specifically, we determine the Debye sound velocity from the low-energy transfer region of the (partial) phonon density of states (DOS) using the equation of state determined for each material and a new approach which utilizes information criteria and probability distributions. Nickel decreases the shear velocity of iron, while 10 at% Si has little to no effect on the shear velocity of Fe_0.91Ni_0.09. We observe that the shape of the phonon DOS of these alloys remains similar with increasing pressure. In the measured compression range, we therefore apply a generalized scaling law to describe the volume dependence of the phonon DOS and find that the vibrational Grüneisen parameters of hcp-Fe_0.91Ni_0.09 are nearly indistinguishable from those hcp-Fe and those for Fe_0.8Ni_0.1Si_0.1 trend lower. From the vibrational free energy, we constrain the harmonic vibrational component of thermal pressure, which shows a significant positive deviation from theoretical calculations of hcp-Fe at pressures and temperatures of Earth's core. Collectively, our results demonstrate that the effects of nickel should be considered when modeling iron-rich planetary cores.

[en] A non-stationary stochastic model is proposed for seismic records of P-waves from underground nuclear explosions and natural earthquakes. When estimating the parameters of interest an asymptotically 'efficient' procedure is described and its statistical properties are derived. Numerical results are also provided in support of the model. By considering the relevant parameters in the model, two discriminating procedures are described and one is illustrated numerically using available records. Based on these parameters, 'complexity' is defined and its relation to the best linear discriminant function is pointed out. (orig.)

[en] It is shown that the paper 'Is the Tube Approach of Multiple Production on Nuclei Credible' by Azimov et al., misuses the Collective Tube Model (CTM), compares theoretical predictions with irrelevant experimental data while ignoring other relevant published experiments and consequently arrives at the wrong conclusions. (Auth.)

[en] It is proposed that in quantum chromodynamics the colour charge of gluons and of anything with zero triality is screened by a dynamic Higgs mechanism with Higgs scalars made out of gluons, but the center Z₃ of the gauge group SU(3) is left unbroken, and single quarks, which have nonzero triality, are not screened. Long range forces between them persist therefore. Given that the Higgs mechanism produces a mass gap, the most favourable configuration of field lines between e.g., quark and antiquark will be in strings analogous to magnetic field lines in a superconductor. The string confine the quarks. The screening mechanism, on the other hand, produces not only the mass gap (which leads to string formation) but is also responsible for saturation of forces, i.e. absence of bound states of six quarks, etc. (Auth.)

[en] It is argued that mass-singularities of inclusive cross sections in QCD factor to all orders in perturbation theory as required for a parton model interpretation. (Auth.)

[en] Acoustic wave velocities for synthetic polycrystalline pyrope (Mg3Al2Si3O12) were measured to 9 GPa and temperatures up to 1000 C by ultrasonic interferometry combined with energy-dispersive synchrotron X-ray diffraction in a cubic-anvil DIA-type apparatus (SAM-85). Specimen lengths at high pressures (P) and temperatures (T) are directly measured by X-radiographic methods. Elastic wave travel times and X-ray diffraction data were collected after heating and cooling at high pressures to minimize effect of non-hydrostatic stress on the measurements. A linear fit to the high P and T data set yields the elastic bulk and shear moduli [KS = 175 (2) GPa; G = 91 (1) GPa] and their pressure and temperature derivatives [K'S=3.9±0.3; G' = 1.7 ± 0.2 and (∂KS/∂T)P = -18 (2) MPa/K; (∂G/∂T)P = -10 (1) MPa/K]. In a separate analysis, the pressure-volume-temperature data collected during these acoustic experiments were fit to a high temperature Birch-Murnaghan (HTBM) equation [with K' fixed at 3.9] and to each isothermal P-V-T data yielding (∂KT/∂T)P = -22 (2) MPa/K and (∂KT/∂T)P = -20 (5) MPa/K, respectively. Comparison of Py100 data with those other Py-Mj compositions indicates that the thermo elastic properties are insensitive to majorite content in the garnet along the pyrope-majorite join.

[en] The effects of one photon exchange on an amplitude analysis of πN scattering at high energies are studied. The authors find large electromagnetic corrections to the elastic polarization, which have not previously been taken into account. If isospin invariance for the strong amplitudes is assumed, the hadronic charge exchange amplitudes show deviations from rho-Regge pole exchange. (Auth.)

[en] A new type of the quark confinement potential that previously led to the prediction of the 1110 MeV vector particle is applied to calculate the masses of the radial excitations of the rho,ω,phi-mesons. The values of the masses obtained are close to those of the recently discovered vector resonances below 2 GeV. (Auth.)

[en] Deformation experiments were carried out in a deformation-DIA high-pressure apparatus (D-DIA) on oriented San Carlos olivine single crystals, at pressure (P) ranging from 3.5 to 8.5 GPa, temperature (T) from 1373 to 1673 K, and in poor water condition. Oxygen fugacity (fO2) was maintained within the olivine stability field and contact with enstatite powder ensured an orthopyroxene activity aopx = 1. Two compression directions were tested, promoting either (1 0 0) slip alone or (0 0 1) slip alone in (0 1 0) crystallographic plane, here called, respectively, a-slip and c-slip. Constant applied stress (s) and specimen strain rates ((bar (var_epsilon))) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of run products revealed that dislocation creep was responsible for sample deformation. Comparison of the obtained high-P deformation data with the data obtained at room-P by Bai et al. (Bai, Q., Mackwell, S.L., Kohlstedt D.L., 1991, High-temperature creep of olivine single crystals. 1. Mechanical results for buffered samples, Journal of Geophysical Research, 96, 2441-2463) - on identical materials deformed at comparable T-sefO2-aopx conditions - allowed quantifying the P effect on a-slip and c-slip rheological laws. A slip transition with increasing pressure, from dominant a-slip to dominant c-slip, is documented. a-slip appears sensitive to pressure, which translates into the high activation volume V*_a = 12 ± 4 cm³/mol in the corresponding rheological law, while pressure has little effect on c-slip with V*_c = 3 ± 4 cm³/mol. These results may explain the discrepancy between olivine low-P and high-P deformation data which has been debated in the literature for more than a decade.

[en] Compressional (P) and shear (S) wave velocities have been measured for two synthetic polycrystalline specimens of pyrope-majorite garnets (Py60Mj40 and Py50Mj50) by ultrasonic interferometry to 8 GPa and 1000 K, in a DIA-type cubic anvil high pressure apparatus (SAM-85) interfaced with synchrotron X-radiation and X-ray imaging. Elastic bulk (KS) and shear (G) moduli data obtained at the end of the cooling cycles were fitted to functions of Eulerian strain to third order yielding pressure derivatives of the elastic moduli (?KS/?P)T = 4.3 (3); (?G/?P)T = 1.5 (1) for Py60Mj40 garnet and (?KS/?P)T = 4.4 (1); (?G/?P)T = 1.3 (1) for Py50Mj40 garnet. Both (?KS/?P)T and (?G/?P)T are identical for the two garnet compositions and are also consistent with Brillouin scattering data for polycrystalline Py50Mj50. Moreover, the new pressure derivatives of the elastic moduli are equal within experimental uncertainties to those of end-member pyrope garnet from ultrasonic studies.