Nuclear isotope thermometry

We discuss different aspects which could influence temperatures deduced from experimental isotopic yields in the multifragmentation process. It is shown that fluctuations due to the finite size of the system and distortions due to the decay of hot primary fragments conspire to blur the temperature determination in multifragmentation reactions. These facts suggest that caloric curves obtained through isotope thermometers, which were taken as evidence for a first-order phase transition in nuclear matter, should be investigated very carefully.Comment: 9 pages, 7 figure

Bifurcated polarization rotation in bismuth-based piezoelectrics

ABO3 perovskite-type solid solutions display a large variety of structural and physical properties, which can be tuned by chemical composition or external parameters such as temperature, pressure, strain, electric, or magnetic fields. Some solid solutions show remarkably enhanced physical properties including colossal magnetoresistance or giant piezoelectricity. It has been recognized that structural distortions, competing on the local level, are key to understanding and tuning these remarkable properties, yet, it remains a challenge to experimentally observe such local structural details. Here, from neutron pair-distribution analysis, a temperature-dependent 3D atomic-level model of the lead-free piezoelectric perovskite Na0.5Bi0.5TiO3 (NBT) is reported. The statistical analysis of this model shows how local distortions compete, how this competition develops with temperature, and, in particular, how different polar displacements of Bi3+ cations coexist as a bifurcated polarization, highlighting the interest of Bi-based materials in the search for new lead-free piezoelectrics

Deep structure of the southern Rhinegraben area from seismic refraction investigations

A joint interpretation of all seismic-refraction profiles in the southern part of the Rhinegraben area is presented. A time-term analysis of all Pg-arrivals reveals the topography of the crystalline basement and provides an average velocity of 6.0 km/s for the uppermost crust. The crust-mantle boundary is clearly elevated in the Rhinegraben rift system forming an arch with a span of 150-180 km and reaching a depth of only 25 km at the flanks of the graben proper. The velocity of P-waves in the uppermost mantle is 8.0-8.1 km/s. Below the flanks of the graben, the crust-mantle boundary is formed by a first-order discontinuity. Within the graben proper it is replaced by a transition zone of 4 km thickness with the strongest velocity gradient at a depth of 21 km. This transition zone is regarded as region of crust-mantle interaction and seems to be confined to the graben proper.         ARK: https://n2t.net/ark:/88439/y074159 Permalink: https://geophysicsjournal.com/article/71 &nbsp

Isotopic Scaling in Nuclear Reactions

A three parameter scaling relationship between isotopic distributions for elements with Z$\leq 8$ has been observed that allows a simple description of the dependence of such distributions on the overall isospin of the system. This scaling law (termed iso-scaling) applies for a variety of reaction mechanisms that are dominated by phase space, including evaporation, multifragmentation and deeply inelastic scattering. The origins of this scaling behavior for the various reaction mechanisms are explained. For multifragmentation processes, the systematics is influenced by the density dependence of the asymmetry term of the equation of state.Comment: 10 Pages, 2 Figure

Seismicity and dynamics of the Upper Rhinegraben

In this paper we present the results of a 10-year period (1971-1980) of research on the seismicity of the Upper Rhinegraben. Our investigations are exclusively based on instrumentally recorded earthquakes with local magnitudes between 0.5 < ML < 5. The increase in the number of high-gain seismic stations during the past 2 decades improved the quality of the observations considerably, thus allowing detailed recognition of the spatial distribution of the earthquake loci in focal areas deduced from the analysis of historical events. No region, regarded up to now as aseismic, revealed itself as seismic, not even at the level of microearthquakes. Excluding the focal area of the Swabian Jura, the northernmost and southernmost parts of the Upper Rhinegraben show the highest degree of seismic activity. The middle part of the Rhinegraben, between Strasbourg and Karlsruhe, reveals only modest activity, somewhat in contrast to the historical record. The number of earthquakes increases towards the east of the river Rhine relative to the west. An even more pronounced asymmetry is shown in the southern graben by different maximum focal depths perpendicular to the strike of the Rhinegraben. In the Vosges mountains and in the graben proper, depths of 13 and 16 km, respectively, are not exceeded. Maximum depths down to about 20 km are found in the Black Forest. No earthquake was detected in the lower gabbroic crust or in the mantle. The maximum focal depth seems to be governed by variations in the temperature-depth distribution. Fault plane solutions of more than 30 earthquakes demonstrate that the seismic dislocations take place predominantly as strike slip mechanisms in the southern graben area whereas normal faulting prevails in the north. In the northern graben, most of the seismic dislocations occur on fault segments striking N30°W whereas in the south a strike ofN20°E or N60°W (the conjugate direction) is dominant. Furthermore, the fault plane solutions indicate a clockwise rotation of the principle stress directions from north to south by about 40°.         ARK: https://n2t.net/ark:/88439/y060010 Permalink: https://geophysicsjournal.com/article/81 &nbsp