Geochemical evaluation of mineralization potential of the Somie-Ntem area within the Tikar plain,Cameroon: implication on petrogenesis

Acta Geochimica - Somie-Ntem area of the Tikar plain belongs to the western Cameroon Domain. The lithology of the plain has been characterized, and the mineral potential is still unclear despite...     

Multi-link laser interferometry architecture for interspacecraft displacement metrology

Targeting a future Gravity Recovery and Climate Experiment (GRACE) mission, we present a new laser interferometry architecture that can be used to recover the displacement between two spacecraft from multiple interspacecraft measurements. We show it is possible to recover the displacement between the spacecraft centers of mass in post-processing by forming linear combinations of multiple, spatially offset, interspacecraft measurements. By canceling measurement error due to angular misalignment of the spacecraft, we remove the need for precise placement or alignment of the interferometer, potentially simplifying spacecraft integration. To realize this multi-link architecture, we propose an all-fiber interferometer, removing the need for any ultrastable optical components such as the GRACE Follow-On mission’s triple mirror assembly. Using digitally enhanced heterodyne interferometry, the number of links is readily scalable, adding redundancy to our measurement. We present the concept, an example multi-link implementation and the signal processing required to recover the center of mass displacement from multiple link measurements. Finally, in a simulation, we analyze the limiting noise sources in a 9 link interferometer and ultimately show we can recover the \(80\;\text {nm}/\sqrt{\text {Hz}}\) displacement sensitivity required by the GRACE Follow-On laser ranging interferometer.     

The generalized Pareto sum

The generalized Pareto distribution has received much popularity as models for extreme events in hydrological sciences. In this note, the important problem of the sum of two independent generalized Pareto random variables is considered. Exact analytical expressions for the probability distribution of the sum are derived and a detailed application to drought data from Nebraska is provided. Copyright © 2007 John Wiley & Sons, Ltd.     

The Pioneer anomaly and a Machian universe

We discuss astronomical and astrophysical evidence, which we relate to the principle of zero-total energy of the Universe, that imply several relations among the mass M, the radius R and the angular momentum L of a “large” sphere representing a Machian Universe. By calculating the angular speed, we find a peculiar centripetal acceleration for the Universe. This is an ubiquituous property that relates one observer to any observable. It turns out that this is exactly the anomalous acceleration observed on the Pioneers spaceships. We have thus shown that this anomaly is to be considered a property of the Machian Universe. We discuss several possible arguments against our proposal.     

Discursive stability meets climate instability: A critical exploration of the concept of ‘climate stabilization’ in contemporary climate policy

The goals and objectives of ‘climate stabilization’ feature heavily in contemporary environmental policy and in this paper we trace the factors that have contributed to the rise of this concept and the scientific ideas behind it. In particular, we explore how the stabilization-based discourse has become dominant through developments in climate science, environmental economics and policymaking. That this discourse is tethered to contemporary policy proposals is unsurprising; but that it has remained relatively free of critical scrutiny can be associated with fears of unsettling often-tenuous political processes taking place at multiple scales. Nonetheless, we posit that the fundamental premises behind stabilization targets are badly matched to the actual problem of the intergenerational management of climate change, scientifically and politically, and destined to fail. By extension, we argue that policy proposals for climate stabilization are problematic, infeasible, and hence impede more productive policy action on climate change. There are gains associated with an expansion and reconsideration of the range of possible policy framings of the problem, which are likely to help us to more capably and dynamically achieve goals of decarbonizing and modernizing the energy system, as well as diminishing anthropogenic contributions to climate change.     

Utilizing soil geochemistry,ground magnetic,and radiometric surveys to outline a blue ridge,ultramafic body in North Carolina

A soil geochemical survey for Ni plus magnetic and radiometric surveys were used to outline a small dunite body on Rich Mountain, North Carolina. The dunite body is poorly exposed and is enclosed by garnet-bearing amphibolite of the Ashe Formation. Of the geophysical techniques used, the magnetic survey gives a better definition of the known extent of the body than the radiometric survey. However, the 400-ppm Ni contour from the soil program appears to best define the dunite and suggests that it extends farther to the north and east than was indicated from geologic mapping. Though HF digestion yields higher Ni values than HNO₃ + HCl digestion, the patterns are the same. The Mn content of the soil at the Rich Mountain locality probably could also be used to outline the dunite body.