Recent developments in light alloys

This report is intended to cover the progress that has been made in both the manufacture and utility of light alloys in the United States since the first part of 1919. Duralumin is extensively discussed both as to manufacture and durability

"A most exquisite fellow" — William White and an Atlantic world perspective on the seventeenth-century chymical furnace

The seventeenth-century technologist and colonist William White (ca. 1600–73) has been cited as an alchemical tutor to Gabriel Plattes and George Starkey, and hailed as an early modern “wizard of industrial efficiency.” This study — the first that focuses on White individually — pays particular attention to White’s extraordinary reputation for furnace design and manufacture. By examining the sources of knowledge and social connections that enabled White to acquire and disseminate his knowledge of metallurgy, the authors develop a genealogy of fornacic design that extends from the continent to the Atlantic world and back again, connecting White to better known figures such as Cornelis Drebbel and Robert Boyle. By foregrounding, through White, the technology of early modern alchemy, the authors also hope to emphasise the importance of practical craft in the development of the chemical arts

Mechanistic Links Between the Sedimentary Redox Cycle and Marine Acid-Base Chemistry

The redox state of Earth's surface is controlled on geological timescales by the flow of electrons through the sedimentary rock cycle, mediated largely by the weathering and burial of C‐S‐Fe phases. These processes buffer atmospheric pO₂. At the same time, CO₂ influxes and carbonate burial control seawater acid‐base chemistry and climate over long timescales via the carbonate‐silicate cycle. However, these two systems are mechanistically linked and impact each other via charge balance in the hydrosphere. Here, we use a low‐order Earth system model to interrogate a subset of these connections, with a focus on changes that occur during perturbations to electron flow through the sedimentary rock cycle. We show that the net oxidation or reduction of the Earth's surface can play an important role in controlling acid‐base processes in the oceans and thus climate, and suggest that these links should be more fully integrated into interpretive frameworks aimed at understanding Earth system evolution throughout Precambrian and Phanerozoic time

Geochemical support for a climbing habit within the Paleozoic seed fern genus Medullosa

A long-standing problem in paleobotany is the accurate identification of the growth habits and statures of fossil plants. Tissue-specific analysis of stable carbon isotope ratios in plant fossils can provide an independent perspective on this issue. Lignin, a fundamental biopolymer providing structural support in plant tissues and the second most abundant organic material in plants, is ^(13)C depleted by several parts per thousand, averaging 4.1‰, relative to other plant constructional materials (e.g. cellulose). With this isotopic difference, the biochemical structural composition of ancient plants (and inferred stature) can be interrogated using microscale in situ isotope analysis between different tissues in fossils. We applied this technique to a well-preserved specimen of the Late Paleozoic seed plant Medullosa, an extinct genus with a variety of growth habits that includes several enigmatic yet abundant small-stemmed species widely found in calcium carbonate concretions (“coal balls”) in the Pennsylvanian coal beds of Iowa, USA. It remains unclear which of the medullosans were freestanding, and recent analysis of the medullosan vascular system has shown that this system provided little structural support to the whole plant. The leading hypothesis for small-stemmed medullosan specimens predicts that cortical tissues could have provided additional structural support, but only if they were lignified. The expected isotopic difference between lignified tissue and unlignified tissue is smaller than that expected from pure extracts, for the simple reason that even woody tissues maximally contain 40% lignin (by mass). This reduces the expected maximum difference between weakly and heavily lignified tissues by 60%, down to ~0.5‰–2‰. Analysis of the medullosan stem reveals a consistent difference in isotope ratios of 0.7‰–1.0‰ between lignified xylem and cortical tissues. This implies low abundances of lignin (between 0% and 11%) within the cortex. This inferred structural biochemistry supports hypotheses that the peripheral portions of these medullosan stems were not biomechanically reinforced to permit the plants to grow as freestanding, arborescent trees. A number of climbing or scandent medullosans have been identified in the fossil record, and this mode of growth has been suggested to be common within the group on the basis of observations from comparative biomechanics, hydraulics, and development. Finally, this mode of growth is common in several clades of stem group seed plants, including Lyginopteris and Callistophyton, along with Medullosa. This study provides further support for ideas that place a great portion of early seed plant diversity under the canopy, rather than forming it

An orbital window into the ancient Sun's mass

Models of the Sun's long-term evolution suggest that its luminosity was substantially reduced 2-4 billion years ago, which is inconsistent with substantial evidence for warm and wet conditions in the geological records of both ancient Earth and Mars. Typical solutions to this so-called "faint young Sun paradox" consider changes in the atmospheric composition of Earth and Mars, and while attractive, geological verification of these ideas is generally lacking-particularly for Mars. One possible underexplored solution to the faint young Sun paradox is that the Sun has simply lost a few percent of its mass during its lifetime. If correct, this would slow, or potentially even offset the increase in luminosity expected from a constant-mass model. However, this hypothesis is challenging to test. Here, we propose a novel observational proxy of the Sun's ancient mass that may be readily measured from accumulation patterns in sedimentary rocks on Earth and Mars. We show that the orbital parameters of the Solar system planets undergo quasi-cyclic oscillations at a frequency, given by secular mode g_2-g_5, that scales approximately linearly with the Sun's mass. Thus by examining the cadence of sediment accumulation in ancient basins, it is possible distinguish between the cases of a constant mass Sun and a more massive ancient Sun to a precision of greater than about 1 per cent. This approach provides an avenue toward verification, or of falsification, of the massive early Sun hypothesis.Comment: 7 pages, 4 Figures. Accepted to The Astrophysical Journal Letter

Effect of inflow control on inlet noise of a cut-on fan

The control of turbulence and other inflow disturbances in anechoic chambers for static turbofan noise studies was studied. A cut-on, high tip speed fan stage was acoustically tested with three configurations of an inflow control device in an anechoic chamber. Although this was a cut-on design, rotor inflow interaction appeared to be a much stronger source of blade passing tone radiated from the inlet than rotor stator interaction for the 1.6 mean rotor chord separation. Aft external suction applied to the area where the inflow control device joined the inlet produced a further reduction in blade passing tone, suggesting that disturbances in the forward flow on the outside of the inlet were superimposed on the inlet boundary layer and were a significant source of tone noise

Sulfate Burial Constraints on the Phanerozoic Sulfur Cycle

The sulfur cycle influences the respiration of sedimentary organic matter, the oxidation state of the atmosphere and oceans, and the composition of seawater. However, the factors governing the major sulfur fluxes between seawater and sedimentary reservoirs remain incompletely understood. Using macrostratigraphic data, we quantified sulfate evaporite burial fluxes through Phanerozoic time. Approximately half of the modern riverine sulfate flux comes from weathering of recently deposited evaporites. Rates of sulfate burial are unsteady and linked to changes in the area of marine environments suitable for evaporite formation and preservation. By contrast, rates of pyrite burial and weathering are higher, less variable, and largely balanced, highlighting a greater role of the sulfur cycle in regulating atmospheric oxygen

The care and feeding of slime

The care and feeding of slim