Estuary Classification Revisited

This paper presents the governing equations of a tidally-averaged, width-averaged, rectangular estuary in completely nondimensionalized forms. Subsequently, we discover that the dynamics of an estuary is entirely controlled by only two variables: (i) the Estuarine Froude number, and (ii) a nondimensional number related to the Estuarine Aspect ratio and the Tidal Froude number. Motivated by this new observation, the problem of estuary classification is re-investigated. Our analysis shows that the two control variables are capable of completely determining the stratification at the estuary mouth, and therefore can specify the estuary type. The theoretical estuary classification scheme proposed in this paper is validated against real estuarine data collected from existing literature. Our classification scheme on comparison with the state-of-the-art theory shows significant improvement.Comment: 6 pages, 4 figure

neoKREEP: A new lunar component at Apollo 17

The Apollo 11 (Mare Tranquillitatis) and Apollo 17 (Mare Serenitatis) landing sites are important as the only sources of high-Ti basalt visited by the Apollo missions. The lunar high-Ti basalts (greater than 6 percent TiO2) have no volumetrically comparable analogs among terrestrial basalts and require the presence of ilmenite in the source region, probably representing cumulates produced late in the crystallization of the lunar magma ocean. Six principal groups of high-Ti basalts are described, three from each of the two sites

Melting of cognetic depleted and enriched reservoirs and the production of high Ti Mare basalts

Implicit in current understanding of the location of terrestrial enriched and depleted reservoirs is the notion that they are spatially separated. The depleted reservoir on Earth is situated in the upper mantle, and the complementary enriched reservoir is located in the crust. However, Earth reservoirs are continually being modified by recycling driven by mantle convection. The Moon is demonstrably different from Earth in that its evolution was arrested relatively early - effectively with 1.5 Ga of its formation. It is possible that crystallized trapped liquids (from the late stages of a magma ocean) have been preserved as LILE-enriched portions of the lunar mantle. This would lead to depleted (cumulate) and enriched (magma ocean residual liquid) reservoirs in the lunar upper mantle. There is no evidence for significant recycling from the highland crust back into the mantle. Therefore, reservoirs created at the Moon's inception may have remained intact for over 4.0 Ga. The topics discussed include the following: (1) radiogenic isotopes in high-Ti mare basalts; (2) formation of cogenetic depleted and enriched reservoirs; and (3) melting of the source to achieve high-Ti mare basalts

Constraints on the genesis and evolution of the Moon\u27s magma ocean and derivative cumulate sources as supported by lunar meteorites

It is generally considered that the outer portion of the Moon was molten in its early history. Antarctic lunar meteorites support this supposition, indicating the presence of a global plagioclase-rich crust derived from magma ocean flotation cumulates. Lunar meteorites also contain a significant very low-Ti (VLT) mare basalt component which was likely generated by the melting of a cumulate mantle formed in an early moon-wide magma ocean. Early in the evolution of the mantle, when the lunar magma ocean (LMO) still was largely liquid, it is likely that vigorous convection was an important factor in crystallization. Such convection would allow crystals to remain suspended and in equilibrium with the LMO liquid for relatively long periods of time. This extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust. The residual liquid after 80-90 percent crystallization was very evolved (in fact KREEPy) and, even in small proportions (1-5%), would have a noticeable effect on the trace-element chemistry of melts generated from these cumulates. This trapped residual liquid would elevate total REE abundances in the cumulate pile, while synchronously deepening the already negative Eu anomaly. The LMO liquid calculated after extensive crystallization (>99.5% crystallized) has a composition which is similar to that recorded in quartz monzodiorites. This evolved liquid could be represented by the sparse KREEP component found in lunar meteorites. The mare basalt component found in such meteorites as EET87521 can be generated by fractional crystallization of a more primitive magma similar in composition to Apollo VLT picritic glass beads. This picritic magma can be produced by melting of a cumulate source in the lunar upper mantle

Black hole evolution by spectral methods

Current methods of evolving a spacetime containing one or more black holes are plagued by instabilities that prohibit long-term evolution. Some of these instabilities may be due to the numerical method used, traditionally finite differencing. In this paper, we explore the use of a pseudospectral collocation (PSC) method for the evolution of a spherically symmetric black hole spacetime in one dimension using a hyperbolic formulation of Einstein's equations. We demonstrate that our PSC method is able to evolve a spherically symmetric black hole spacetime forever without enforcing constraints, even if we add dynamics via a Klein-Gordon scalar field. We find that, in contrast to finite-differencing methods, black hole excision is a trivial operation using PSC applied to a hyperbolic formulation of Einstein's equations. We discuss the extension of this method to three spatial dimensions.Comment: 20 pages, 17 figures, submitted to PR

Geochemical and isotopic evidence bearing on the origin of large, igneous-textured inclusions in ordinary chondrites

Geochemical and isotopic data for large, igneous-textured inclusions in ordinary chondrites suggest that the inclusions formed by the melting of diverse precursors, and that various inclusions had different origins. Some inclusions were metasomatized (chemically altered) and metamorphosed, and many appear to have degassed argon in late shock events. The inclusions can be subdivided into two chemical groups, Na-rich (Na/Al>0.35 at.) and Na-poor (≤0.35), which may have originated in different ways. The major-and trace-element abundances of Na-rich inclusions are best explained by these inclusions having formed by the shock-melting of ordinary chondrites, often accompanied by loss of FeNi-metal and sulfide and by preferential melting and accumulation of an albitic feldspar component. In contrast, there is no evidence that shock-melting was involved in the formation of Na-poor inclusions, which have compositions that were largely controlled by vapor-fractionation processes. It is suggested that the precursors to Na-poor inclusions consisted of mixtures of vapor-fractionated materials in a system of condensed phases that chemically resembled CI-chondrites, except for being depleted in volatile-lithophile elements and in metal and sulfide. Sodium-poor inclusions can be subdivided into two types, Trend A and Trend B, which differ in their trace-element characteristics, in the nature of their compositional variations, and in their inferred precursors. Trend A Na-poor inclusions are enriched in refractory elements, and could have formed by the melting of mixtures containing a chondritic (CI-like) component and a refractory (Al-rich, CAI-like) component. Trend B Na-poor inclusions are enriched in elements of intermediate volatility (Si) and appear to have formed from precursors that lost both a refractory (Mg-rich, olivine-rich) and a volatile component. The precursors to these inclusions could have been produced by the removal of an olivine-rich condensate during fractional condensation, or by the condensation of Si-rich gases during fractional vaporization

Stabilizing the Retromer Complex in a Human Stem Cell Model of Alzheimer's Disease Reduces TAU Phosphorylation Independently of Amyloid Precursor Protein.

Developing effective therapeutics for complex diseases such as late-onset, sporadic Alzheimer's disease (SAD) is difficult due to genetic and environmental heterogeneity in the human population and the limitations of existing animal models. Here, we used hiPSC-derived neurons to test a compound that stabilizes the retromer, a highly conserved multiprotein assembly that plays a pivotal role in trafficking molecules through the endosomal network. Using this human-specific system, we have confirmed previous data generated in murine models and show that retromer stabilization has a potentially beneficial effect on amyloid beta generation from human stem cell-derived neurons. We further demonstrate that manipulation of retromer complex levels within neurons affects pathogenic TAU phosphorylation in an amyloid-independent manner. Taken together, our work demonstrates that retromer stabilization is a promising candidate for therapeutic development in AD and highlights the advantages of testing novel compounds in a human-specific, neuronal system

Monitoring Turbidity in an Ultra-Ologotrophic Drinking Water Reservoir

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Brine rejection leads to salt-fingers in seasonally ice-covered lakes

When ice forms on the surface of lakes, dissolved salts are pushed out of the ice into the liquid water below. If enough salt is rejected from the ice, the excess weight of the salt can lead to long `fingers` of salty fluid moving from the ice into the water below. We ran a series of experiments to investigate these `fingers' and conclude that this process occurs in most freshwater lakes that freeze annually. This process is important for the evolution of lakes, and how they will be different as fewer lakes freeze