Spontaneous Emission of Gravity Waves by Interacting Vortex Dipoles in a Stratified Fluid: Laboratory Experiments

Results from a new series of experiments on the geophysically important issue of spontaneous emission of internal gravity waves during unsteady interactions of vortical structures are presented. Vortex dipoles are a common element of a quasi-two-dimensional turbulent flow. Vortex dipoles perform translational motion and can collide with other vortices. During collision events the flow is unsteady and unbalanced and a further adjustment process associated with these events can therefore result in the spontaneous emission of gravity waves. Our laboratory experiments demonstrate that gravity waves are emitted when two translating vortex dipoles interact (collide) in a layered fluid, in accord with the current theoretical results. The emission was evident both in a two-layer system and in a fluid with a linear distribution of density with depth. The waves were generated during the period of deceleration of the secondary dipoles which constitute a vortex quadrupole emerging immediately after the collision of the primary dipoles.     

Kampelite,Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O,a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula,Russia)

Mineralogy and Petrology - Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma,...     

The Study Internal Structure of the Annual Layers in Lake Sediments Using Synchrotron Radiation with X-ray Focusing Optics

正1 Introduction Annually laminated(varve)sedimentary deposits are considered as one of the most important archives,since they offer precise temporal information(years)in combination with high time resolutions.Bottom sediments of the lakes contain detailed geochemical information on     

Stability of the boundary layer between the lithosphere and convecting mantle and the steady-state lithospheric geotherm

In the steady state, the convective boundary layer (CBL) (the transition from the lithosphere to the convecting mantle, the lithosphere-asthenosphere boundary) is on the verge of stability. This determines its depth, thickness, and the steady-state temperature distribution in the lithosphere. Had the mantle been homogeneous, the base of the lithosphere at the current potential temperature would lie globally at the same depth H _rh of 50 to 70 km. Actually, the regime of interaction of the mantle convection with the lithosphere is determined by the relationship between this depth and the thickness H _depl of the chemical boundary layer including the crust and the layer of the depleted rock. If the thickness of the chemical boundary layer is small H _depl < H _rh, as it is the case in the present-day oceanic mantle, the suboceanic regime is established with the mantle convection that does not reach the base of the chemical boundary layer. In this case, the top of CBL is located at depth H _rh, while the oceanic heat flow and the depth of the seafloor only depend on the potential temperature T _p and, within the areas where the crust is older than 60 to 70 Ma, are the same everywhere far from the disturbed territories (the hot points and the subduction zones). The absence of noticeable distinctions between the heat flow in the different oceanic basins suggests a global constancy of the potential temperature. If H _depl > H _rh, the subcontinental regime of the interaction of the mantle convection with the lithosphere is established. In this case, the CBL is immediately adjacent to the depleted lithosphere, its top is located at depth H _depl, and the surface heat flow q(T _p, H _depl) not only depends on the potential temperature T _p but also on the the thickness of the depleted lithosphere H _depl; it decreases with increasing H _depl and, therefore, with the age of the lithosphere. Given the potential temperature, the dependence q(T _p, H _depl) agrees well with the envelope of the results of kimberlite xenolith thermobarometry presented in the diagram of the deepest xenolith depth as a function of the heat flow. It is likely that in the lowest part of the continental lithosphere there is a zone of horizontal shear deformation, from where kimberlites entrain the strongly deformed and, at the same time, the deepest xenoliths. Besides, the azimuthal anisotropy of seismic velocities can be associated with this zone. The change in its direction with depth can be observed as the Lehmann discontinuity.     

Melt segregation inside a partially molten zone: Theory,numerical models and implications

For the problem of matrix compaction and melt segregation a general mush continuity equation is derived, which explicitly expresses the coupling between the melt percolation and the inelastic matrix deformation and closes the governing equation set. Besides, a general equation is obtained, which describes the change in the volume of pore space due to all the possible reasons (inelastic matrix deformation, the phase transitions, and the advection of porosity by the matrix flow). The features of the isothermal melt segregation inside a partially molten zone are demonstrated using one-dimensional (1D) numerical solutions. It follows from the solutions that the pattern and the characteristic time of the melt segregation inside a partially molten zone of thickness L are controlled by the segregation parameter γ _c = (L/δ _c )², where the compaction length δ _c = k(φ₀)η/(φ₀μ) depends on the permeability, k, the value of characteristic porosity, φ₀, and the viscosities of the matrix, η, and melt, μ. The solutions demonstrate that at any value of γ _c , layers that are highly enriched in melt compared to the maximum initial porosity are formed in the upper part of the zone. At the same time, the evolution of the system and the segregation time differ considerably in the limits of γ _c ≪ γ* and γ _c ≫ γ*, where γ* depends on the boundary and initial conditions of the problem, and γ* is about 80 for the problem of melt segregation inside a partially molten zone with the maximum in the initial melt distribution located in the middle of the zone. At γ _c ≪ γ*, which corresponds to the segregation of low-viscosity ultrabasic melts (kimberlites, carbonatites), all the melt accumulates to the roof of the zone, and the segregation time does not depend on the matrix permeability and melt viscosity and decreases with an increase in the thickness of the zone as L ⁻¹. The latter can be the reason for the formation of clusters of the same age and same composition eruptions characteristic of the kimberlite provinces. In the opposite limiting case, γ _c ≫ γ*, the segregation time does not depend on the matrix viscosity and scales as L with a wave sequence forming in the upper part of the zone, which, probably, elucidates the origin of the rhythmical layering of the large tholeiitic basalt plutons.     

Deformation zones under square footings supported by clayey soils

Footing settlements depend not only on physical and mechanical properties of base soils, but also on applied load intensities and their distributions with depth, as well as on footing rigidity, shape and dimensions. An analytical expression relating rigid bearing plate and/or footing settlements to thicknesses of deformation (active) zones, which form below footing bottoms, has been previously offered by the author. The results of tests performed with 0.5, 1.0 and 4.0 m²-area square footings, constructed on undisturbed clayey soils and containing data describing active zone development, were collected from literature and analyzed. This paper presents graphical relationships between square footing settlements, active zone thicknesses and footing dimensions, which are verified by published test results performed with experimental square footings, having areas different than the ones selected for statistical analyses.     

Rainfall–runoff model parameter estimation and uncertainty evaluation on small plots

Four seasonal rainfall simulations in 2009 and 2010 were applied to a field containing 36 plots (0.75 × 2 m each), resulting in 144 runoff events. In all simulations, a constant rate of rainfall was applied then halted 60 min after initiation of runoff, with plot‐scale monitoring of runoff every 5 min during that period. Runoff was simulated with the Kinematic Runoff and Erosion/Simulator of Transport with Infiltration and Runoff (KINEROS2/STWIR) field‐scale model, whose hydrodynamics are based on the kinematic wave equation. Because of the non‐linear nature of the model and a highly parameterized model with respect to the available data, several approaches were investigated to upscale nine runoff‐related parameters from a series of small monitored plots to the field scale. Inverse modeling was performed using the model‐independent Parameter ESTimation (PEST) algorithm to individually calibrate the nine KINEROS2/STWIR parameters on 36 plots. The parameters were averaged, and bootstrapping was used to assess uncertainty of the parameters via estimation of confidence intervals (CI). A Monte Carlo simulation using the bootstrap results showed reasonable field‐scale representation of flow rates. Median values of calibrated parameters were within the 95% CI obtained with bootstrapping. The simulated results for the median values associated with the 90% CI flow rates produced similar trends as those exhibited with the observed data, suggesting that median values of the calibrated parameters from the PEST inverse modeling could be used to represent the field scale. Copyright © 2013 John Wiley & Sons, Ltd.