New classes of spectral densities for lattice processes and random fields built from simple univariate margins

Quasi arithmetic and Archimedean functionals are used to build new classes of spectral densities for processes defined on any d-dimensional lattice \mathbbZ^d{\mathbb{Z}^d} and random fields defined on the d-dimensional Euclidean space \mathbbR^d{\mathbb{R}^d}, given simple margins. We discuss the mathematical features of the proposed constructions, and show rigorously as well as through examples, that these new classes of spectra generalize celebrated classes introduced in the literature. Additionally, we obtain permissible spectral densities as linear combinations of quasi arithmetic or Archimedean functionals, whose associated correlation functions may attain negative values or oscillate between positive and negative ones. We finally show that these new classes of spectral densities can be used for nonseparable processes that are not necessarily diagonally symmetric.     

A review of definitions of the Himalayan Main Central Thrust

International Journal of Earth Sciences - Most workers regard the Main Central Thrust (MCT) as one of the key high strain zones in the Himalaya because it accommodated at least 90 km of...     

Nitrous oxide production and denitrification rates in estuarine intertidal saltmarsh and managed realignment zones

Increasing concerns over habitat loss and rising costs of sea defence maintenance due to rising sea levels, has seen increases in the practice of managed realignment and reflooding of former reclaimed areas of intertidal saltmarsh and mudflat around the world. These practices are taking place with little knowledge of their impact on soil biogeochemical processes. Rates of denitrification (using the acetylene inhibition technique) and nitrous oxide (N₂O) production were measured from a long-established saltmarsh (SM) and an adjacent, recently re-flooded managed realignment (MR) site comprising former arable land in the estuary of the River Torridge, Devon, UK. Incubations were carried out in closed chambers in which patterns of tidal flooding were simulated automatically. Measurements were made during periods of flood and non-flood over a total of four tidal inundations with estuarine water. During the latter two flooding episodes floodwater was amended with nitrate (NO₃⁻). Nitrous oxide production in the SM soil generally was lower than in the MR soil, with mean values and standard errors over the whole incubation of 0.27 ± 0.16 mg N₂O-N m⁻² h⁻¹ and 0.65 ± 0.15 mg N₂O-N m⁻² h⁻¹ respectively. Denitrification rates demonstrated a similar trend although generally were an order of magnitude higher than N₂O production, with mean rates and standard errors of 2.88 ± 1.12 mg N₂O-N m⁻² h⁻¹ in the SM soil and 3.39 ± 1.16 mg N₂O-N m⁻² h⁻¹ in the MR soil. The data suggest that both soils are net sinks for NO₃⁻ and net sources for N₂O. Both patterns of tidal inundation and floodwater chemistry affect the process rates in each soil differently. The impact of flooding with NO₃⁻ – amended water was greater on the SM soil than the MR soil, and it is likely that decomposing vegetation buried in the accreting sediments following reflooding at the MR site were supplying a source of N in the soil, and so process rates were less dependent upon external supplies. The act of managed realignment in intertidal zones could therefore result in an increase in mean production of N₂O in intertidal zones, at least in the short term.     

Origin of transverse folds in an extensional growth-fault setting: Evidence from an extensive seismic volume in the western Gulf of Mexico

Growth faults in gravity-driven extensional provinces are dominated by coast-parallel trends, but coast-perpendicular (transverse) trends are far less documented. The Clemente–Tomas fault in the inner Texas shelf has corrugations that are transverse to the fault and that plunge downdip. A large (8500 km²), high-quality, 3D seismic survey allows a uniquely encompassing perspective into hanging-wall deformation above this corrugated fault surface. Synextensional strata in the hanging wall are folded into alternating transverse ridges and synclines, typically spaced 10 km apart. Forward modelling in dip profiles of an extensional fault having three ramps produces ramp basin-rollover pairs that compare with the seismically revealed ridges and synclines. As they translated down the undulose fault plane, ramp basins and rollovers were juxtaposed along strike, forming the hanging-wall ridges and synclines observed offshore Texas. Fault-surface corrugations correlate broadly with footwall structure. We infer that corrugations on the Clemente–Tomas fault formed by evacuation of an allochthonous salt canopy emplaced in the late Eocene to early Oligocene. Early salt evacuation (Oligocene) created an undulose topography that influenced incipient Clemente-Tomas fault segments as they merged to form an inherently undulose fault. Late salt evacuation (early Miocene) further deformed this fault surface.     

A collective approach to Pacific islands fisheries management: Moving beyond regional agreements

The sustainable management and profitable development of the Pacific island tuna fisheries is the key ocean governance challenge for the Pacific islands region in the short and medium term. Resolving these challenges is fundamental to the long term future of the region and its ability to implement oceans governance across all resource and conservation concerns.     

Using Mean Sea Surface Topography for Determination of Height System Differences across the Baltic Sea

The mean sea surface topography in the Baltic Sea and adjacent waters is reliably known in the Nordic height system NH 60. Using this knowledge we estimate differences between NH 60, based on the Amsterdam zero point, and Russian, Polish, and German height systems along the southeastern coast of the Baltic Sea, based on the Kronstadt zero point. The differences agree within a few centimeters. We also make a simple study of the mean sea level difference between Kronstadt and Amsterdam (which is found to have been approximately 25 cm when sea level was still to be seen there).     

Relationship between turbidity and fish diets in Lakes Waahi and Whangape,New Zealand

Abstract

Stomach contents of Gobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, and Anguilla australis were compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m^?3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m^?3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m³) and submerged macrophytes had declined. The mysid Tenagomysis chiltoni was an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of Lake Whangape. Fish and mysids were the most important prey of shortfinned eels in both lakes, with mysids most important in Lake Waahi. High mysid densities in the turbid water bodies provide an alternative food resource apparently compensating for those lost by fish when water clarity declined and submerged macrophytes collapsed.     

Palynology and petroleum potential of the Kazhdumi Formation (Cretaceous: Albian–Cenomanian) in the South Pars field,northern Persian Gulf

The Kazhdumi Formation of the Bangestan Group is a well-known source rock that has produced abundant oil in most petroleum fields in the Zagros Basin, which stretches from northwest to southwest Iran over hundreds of kilometres. The formation reaches a thickness of 230 m at the type section in northwest Zagros but thins out to 40–50 m in wells studied from the South Pars giant petroleum field, where it comprises mainly grey shales with occasional intercalations of marls and sandstones. South Pars, best known as the Iranian part of the world's largest non-associated gas field, contains small quantities of oil above and below the Kazhdumi Formation.