Analysis of Inclined Shear Waves in Vertical Bluffs

The effect of inclined shear waves on the seismic response of vertical bluffs is analyzed using the generalized hyperelement. The bluffs are modeled as a stepped halfspace in the frequency domain. It is shown that the response, normalized as a function of slope height (H) divided by wavelength (λ), is amplified for waves travelling into the slope and attenuation for waves travelling away from the slope. This amplification can be as much as twice the amplification for vertically propagating waves. The results of the analysis suggest that wave orientation and inclination in relation to the slope may need to be considered in performing stability analyses

Growth Of AlN Crystals On AlN/SiC Seeds By AlN Powder Sublimation In Nitrogen Atmosphere

AlN single crystals were grown on AlN/SiC seeds by sublimation of AlN powder in TaC crucibles in a nitrogen atmosphere. The seeds were produced by metallorganic chemical vapor deposition (MOCVD) of AlN on SiC crystals. The influence of growth temperature, growth time and source-toseed distance on the crystallinity and the crystal growth rate were investigated. Crystals were grown in an RF heated sublimation reactor at growth temperatures ranging from 1800-2000 °C, at a pressure of 600 Torr, nitrogen flow-rate of 100 sccm and source-to-seed distances of 10 and 35 mm. At 1870 °C and a source-to-seed distance of 35 mm, isolated crystals were observed with few instances of coalescence. At 1930 °C, a source-to-seed distance of 10 mm and longer growth times (~30 hrs), crystal coalescence was achieved. Above 1930 °C, the decomposition of SiC was evidently affecting the growth morphology and resulted in growth of polycrystalline AlN. After an initial nucleation period, the observed growth rates (10-30 μm/hr) were in close agreement with predictions of a growth model that assumed gas-phase diffusion controlled growth. Optical and electron microscope observations revealed step-flow growth, while X-ray diffraction results showed the single crystal nature of the grown material. Single crystalline AlN was grown over surface areas of 200-300 mm2 and was transparent and essentially colorless

Geotechnical Observations of the November 3, 2002 M7.9 Denali Fault Earthquake

The M 7.9 earthquake of November 3, 2002 event ruptured more than 340 kilometers on three fault, causing widespread liquefaction in the fluvial deposits of steep alpine valleys of the Alaska Range and eastern lowlands of the Tanana River. The event occurred in a remote and largely undeveloped portion of the rugged Alaskan central range, with few seismometer recordings. The areas affected by liquefaction are largely confined to native Holocene river deposits, areas bounded by stiffer ground moraine, Pleistocene uplands, and bedrock. Liquefaction affected areas of alluvial river valleys draining mountainous and glacier-proximal rivers. The most noteworthy observations are that liquefaction damage was focused towards the eastern end of the rupture area. In the western portion of the rupture zone, localized liquefaction developed in recent deposits of the Susitna and Delta rivers in the immediate vicinity of the surface rupture of the fault. More abundant and severe liquefaction occurred on the eastern Robertson, Slana, Tok, Chisana and, especially, Nabesna Rivers. In the Tanana lowland, liquefaction features were sparse on the western bars of the Tanana River in the vicinity of Fairbanks to west of Delta, but became pervasive throughout the eastern region from Delta to Northway. Though liquefaction observations were abundant, there was a dearth of instrumental recordings useful to relate damage effects to measured intensity. To characterize soil properties and stiffness of liquefaction evaluation sites, we used a portable spectral analysis of surface waves (SASW) apparatus to profile the shear wave velocity of the ground. On the Nabesna and Delta rivers that cross the fault, we only observe liquefaction features in soil deposits where normalized shear wave velocities fall below 230 m/s. Severity of sand boils, fissuring and lateral displacement of liquefied ground dramatically increase in soils of lower shear wave velocity, especially below 170 m/s. Some of the most pronounced ground failures are far from the fault zone (60-100 km) in extremely loose, low velocity (~120 m/s) fine sands of the bars of the Tanana River. Strong motion instrumentation was sparse within 150 kilometers of the fault rupture and the seismometers of Alyeska pump stations PS9 (PGA=0.09), PS10 (PGA=0.36g), and PS11 (PGA=0.09) serve as the principal strong motion recordings. Insufficient strong motion instrumentation is available to identify areas of amplified ground motio

\b{eta}-delayed three-proton decay of 31Ar

The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing to record decay events with emission of protons. In addition to \b{eta}-delayed emission of one and two protons we have clearly observed the beta-delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.

Search for {\eta}'(958)-nucleus bound states by (p,d) reaction at GSI and FAIR

The mass of the {\eta}' meson is theoretically expected to be reduced at finite density, which indicates the existence of {\eta}'-nucleus bound states. To investigate these states, we perform missing-mass spectroscopy for the (p, d) reaction near the {\eta}' production threshold. The overview of the experimental situation is given and the current status is discussed.Comment: 6 pages, 3 figures; talk at II Symposium on applied nuclear physics and innovative technologies, September 24th - 27th, 2014, Jagiellonian University, Krak\'ow Poland; to appear in Acta Physica Polonica

Phonon pressure coefficients and deformation potentials of wurtzite AlN determined by uniaxial pressure-dependent Raman measurements

© 2014 American Physical Society. We studied bulk crystals of wurtzite AlN by means of uniaxial pressure-dependent Raman measurements. As a result, we derive the phonon pressure coefficients and deformation potentials for all zone center optical phonon modes. For the A1 and E1 modes, we further experimentally determined the uniaxial pressure dependence of their longitudinal optical-transverse optical (LO-TO) splittings. Our experimental approach delivers new insight into the large variance among previously reported phonon deformation potentials, which are predominantly based on heteroepitaxial growth of AlN and the ball-on-ring technique. Additionally, the measured phonon pressure coefficients are compared to their theoretical counterparts obtained by density functional theory implemented in the siesta package. Generally, we observe a good agreement between the calculated and measured phonon pressure coefficients but some particular Raman modes exhibit significant discrepancies similar to the case of wurtzite GaN and ZnO, clearly motivating the presented uniaxial pressure-dependent Raman measurements on bulk AlN crystals

Spectroscopy of η′\eta'-nucleus bound states at GSI and FAIR --- very preliminary results and future prospects ---

The possible existence of \eta'-nucleus bound states has been put forward through theoretical and experimental studies. It is strongly related to the \eta' mass at finite density, which is expected to be reduced because of the interplay between the $U_A(1)$ anomaly and partial restoration of chiral symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as an overview of the experimental program at GSI and future plans at FAIR are discussed.Comment: 7 pages, 3 figures; talk at the International Conference on Exotic Atoms and Related Topics (EXA2014), Vienna, Austria, 15-19 September 2014. in Hyperfine Interactions (2015