1,709 research outputs found

    Lateral Variations in Lower Crustal Strength Control the Temporal Evolution of Mountain Ranges: Examples From South-East Tibet

    Get PDF
    Controversy surrounds the rheology of the continental lithosphere, and how this rheology controls the evolution and behavior of mountain ranges. In this study, we investigate the effect of lateral contrasts in the strength of the lower crust, such as those between cratonic continental interiors and weaker rocks in the adjacent deforming regions, on the evolution of topography. We combine numerical modeling with recently published results from stable-isotope palaeoaltimetry in south-east Tibet. Stable-isotope palaeoaltimetry in this region provides constraints on vertical motions, which are required to distinguish between competing models for lithosphere rheology and deformation. We use numerical modeling to investigate the effect of lateral strength contrasts on the shape and temporal evolution of mountain ranges. In combination with palaeoaltimetry results, our modeling suggests that lateral strength contrasts provide a first-order control on the evolution of topography in south-east Tibet. We find that the evolution of topography in the presence of such strength contrasts leads to laterally varying topographic gradients, and to key features of the GPS- and earthquake-derived strain-rate field, without the need for a low-viscosity, lower-crustal channel. We also find that palaeoaltimetric samples may have been transported laterally for hundreds of kilometers, an effect which should be accounted for in their interpretation. Our results are likely to be applicable to the evolution of mountain ranges in general and provide an explanation for the spatial correlation between cratonic lowland regions and steep mountain range-fronts

    Neutron scattering study of a quasi-2D spin-1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure

    Full text link
    We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure. The spin gap {\Delta} becomes softened with the increase of the hydrostatic pressure up to P= 9.0 kbar. The observed threefold degenerate triplet excitation at P= 6.0 kbar is consistent with the theoretical prediction and the bandwidth of the dispersion relation is unaffected within the experimental uncertainty. At P= 9.0 kbar the spin gap is reduced to 0.55 meV from 1.0 meV at ambient pressure.Comment: 4 pages, 5 figure

    PWP2: A METHODOLOGY TO MEASURE PRODUCTIVITY OF HEALTH OUTCOMES GROUPS

    Get PDF

    A Key and check-list to Kenya Orchids

    Get PDF
    Volume: XXI
    • 

    corecore