Effect of wave amplitude on turbulent flow in a wavy channel by direct numerical simulation

The present study numerically investigates the characteristics of three-dimensional turbulent flow in a wavy channel. For the purpose of a careful observation of the effect of the wave amplitude on the turbulent flow, numerical simulations are performed at a various range of the wave amplitude to wavelength ratio (0.01?α/λ?0.05), where the wavelength is fixed with the same value of the mean channel height (H). The immersed boundary method is used to handle the wavy surface in a rectangular grid system, using the finite volume method. The Reynolds number (Re=U_bH/ν) based on the bulk velocity (U_b) is fixed at 6760. The present computational results for a wavy surface are well compared with those of references. When α/λ=0.02, the small recirculating flow occurs near the trough at the instant, but the mean reverse flow is not observed. In the mean flow field, the reverse flow appears from α/λ=0.03 among the wave amplitude considered in this study. The domain of the mean reverse flow defined by the locations of separation and reattachment depends strongly on the wave amplitude. The pressure drag coefficient augments with increasing the wave amplitude. The friction drag coefficient shows the increase and decrease behavior according to the wave amplitude. The quantitative information about the flow variables such as the distribution of pressure and shear stress on the wavy surface is highlighted.     

Agglutinated abyssal foraminifers of the equatorial pacific

The quantitative study of the distribution and taxonomic composition of recent living and dead (without plasma) benthic foraminifers revealed three foraminiferal assemblages in the bottom sediments of the Pacific Ocean at depths of 3350 to 4981 m. The assemblage dominated by the epibenthic Lagenammina difflugiformis, Reophax dentaliniformis, and Saccorhiza ramosa occupies the slopes of underwater hills. The assemblage with a high share of the infaunal Cribrostomoides subglobosum, C. nitidum, and Ammobaculites agglutinans is registered on the abyssal plateau. The assemblage with a significant proportion of the large Astrorhiza and Reophax species, which are characterized by an active way of life, populates gentle slopes and narrow depressions with potentially strong bottom currents.     

European Phanerozoic metallogenesis

Phanerozoic metallogenesis in Europe displays divergent characteristics which may be related to the variable nature of the three great European Phanerozoic orogens: Caledonian, Variscan and Alpine. These reflect different geodynamic processes. The Caledonian orogen resulted from the interaction of essentially oceanic with continental lithosphere, whilst the Variscan and Alpine orogens evolved mainly from continent-continent collisions with the involvement of a series of smaller oceanic basins. Each major stage of the orogenic processes is characterised by a typical metallogeny. The occurrence of subduction-related processes in the Caledonian orogeny gave rise to extensive VHMS deposition with characteristic Zn:Cu ratio signatures. The relative lack of abundance of metal-rich, Andean-type porphyry-type mineralisation remains unexplained, unless present erosional levels have prevented the preservation of such deposits. Continent-continent collisions do not appear to result in extensive mineralisation unless elevated heat flows result, possibly as a result of lithospheric delamination at the peak collisional stage. The development of late stage and peri-orogenic sedimentary basins are characterised by extensive Pb-Zn-Ba-F mineralisation as expressions of basinal fluid flow of regional dimensions.     

Two-Dimensional Periodic Waves in an Inviscid Continuously Stratified Fluid

Izvestiya, Atmospheric and Oceanic Physics - In this paper we study the propagation of two-dimensional periodic waves in an inviscid continuously stratified fluid with a free surface in the...     

Lunar nomenclature: A dissenting note

This note reviews the nature of the traditional (Mädler) lunar nomenclature and the recent developments based on the use of more than 2000 named provinces. It appears that the new nomenclature is less efficient than the old in many cases and may lead to an impossible publication situation. The unnecessary break with the past is especially critized.     

Cosmogenic nuclide measurements in southernmost South America and implications for landscape change

We measured in situ ¹⁰Be, ²⁶Al and³⁶Cl on glacial deposits as old as 1.1 Myr in the southernmost part of Patagonia and on northern Tierra del Fuego to understand boulder and moraine and, by inference, landscape changes. Nuclide concentrations indicate that surface boulders have been exposed for far less time than the ages of moraines they sit upon. The moraine ages are themselves constrained by previously obtained ⁴⁰Ar/³⁹Ar ages on interbedded lava flows or U-series and amino acid measurements on related (non-glacial) marine deposits. We suggest that a combination of boulder erosion and their exhumation from the moraine matrix could cause the erratics to have a large age variance and often short exposure histories, despite the fact that some moraine landforms are demonstrably 1 Myr old. We hypothesize that fast or episodic rates of landscape change occurred during glacial times or near the sea during interglacials. Comparison with boulder erosion rates and exhumation histories derived for the middle latitudes of semi-arid Patagonia imply different geomorphic processes operating in southernmost South America. We infer a faster rate of landscape degradation towards the higher latitudes where conditions have been colder and wetter.     

Estimation of the Mode by the Dominant Cluster Method

A method is presented fop estimation of the mode of analytical data reported by cooperating analysts in the preparation of reference materials. The method is referred to as the dominant cluster method, and the nodal value obtained is the value that shows most agreement between analysts.
Several examples demonstrate that this mode (for which approximate confidence intervals have been estimated), is not inconsistent with the recommended values that have been assigned to well-known geochemical reference samples. Features in its favour are that the calculation is simple, it is independent of the type of distribution, and outliers are automatically excluded.