The Effect of Recurrent Floods on Genetic Composition of Marble Trout Populations

A changing global climate can threaten the diversity of species and ecosystems. We explore the consequences of catastrophic disturbances in determining the evolutionary and demographic histories of secluded marble trout populations in Slovenian streams subjected to weather extremes, in particular recurrent flash floods and debris flows causing massive mortalities. Using microsatellite data, a pattern of extreme genetic differentiation was found among populations (global FST of 0.716), which exceeds the highest values reported in freshwater fish. All locations showed low levels of genetic diversity as evidenced by low heterozygosities and a mean of only 2 alleles per locus, with few or no rare alleles. Many loci showed a discontinuous allele distribution, with missing alleles across the allele size range, suggestive of a population contraction. Accordingly, bottleneck episodes were inferred for all samples with a reduction in population size of 3–4 orders of magnitude. The reduced level of genetic diversity observed in all populations implies a strong impact of genetic drift, and suggests that along with limited gene flow, genetic differentiation might have been exacerbated by recurrent mortalities likely caused by flash flood and debris flows. Due to its low evolutionary potential the species might fail to cope with an intensification and altered frequency of flash flood events predicted to occur with climate change

Planar Cu and O hole densities in high-Tc cuprates determined with NMR

The electric hyperfine interaction observable in atomic spectroscopy for O and Cu ions in various configurations is used to analyze the quadrupole splitting of O and Cu nuclear magnetic resonance (NMR) in La2-xSrxCuO4 and YBa2Cu3O6+y and to determine the hole densities at both sites as a function of doping. It is found that in La2-xSrxCuO4 all doped holes (x) reside in the Cu-O plane but almost exclusively at O. For YBa2Cu3O6+y and y<0.6 doped holes are found at planar Cu as well as O. For y>0.6 further doping increases the hole content only for planar O. The phase diagram based on NMR data is presented. Further implications from the Cu A and B site in La2-xSrxCuO4 and the two planar O sites in YBa2Cu3O6+y and consequences for the phase diagram are discussed.Comment: 18 pages, 1 figure, 2 tables, 2 appendice

Guided wave propagation in three-layer pavement structures

A study on guided waves in a. layered half-space with large velocity contrasts and a decreasing velocity with depth is presented. Multiple mode dispersion curves are calculated in the complex wave number domain, taking into consideration the attenuation caused by leakage into the underlying half-space. The excitability of the modes by a vertical point force on the surface is also calculated. Results show that the measurable wave field at the surface of a pavement structure is dominated by leaky quasi-Lamb waves in the top and second layers. The fundamental antisymmetric mode of vibration is the dominating mode generated in the stiff top layer. This mode drives the complete system and continuity across the boundaries generates higher order modes in the embedded second layer. The interaction of leaky Lamb waves in the first two layers results in large variations in the excitability and the attenuation, so that only the waves corresponding to certain portions of the dispersion curves are measurable remote from the source at the pavement surface. It is concluded that these portions of dispersion curves can be individually resolved in practice, by using multichannel processing techniques. This holds the potential for a refined nondestructive testing technique for pavements