Haldane's Dilemma refers to the concern that the need for many "selective deaths" to complete a substitution (i.e. selective sweep) creates a speed limit to adaptation. However, discussion of this concern has been marked by confusion, especially with respect to the term "substitution load". Here we distinguish different historical lines of reasoning, and identify one, focused on finite reproductive excess and the proportion of deaths that are "selective" (i.e. causally contribute to adaptive allele frequency changes), that has not yet been fully addressed. We develop this into a more general theoretical model that can apply to populations with any life history, even those for which a generation or even an individual are not well defined. The actual speed of adaptive evolution is coupled to the proportion of deaths that are selective. The degree to which reproductive excess enables a high proportion of selective deaths depends on the details of when selection takes place relative to density regulation, and there is therefore no general expression for a speed limit. As proof of principle, we estimate both reproductive excess, and the proportion of deaths that are selective, from a dataset measuring survival of 517 different genotypes of Arabidopsis thaliana grown in eight different environmental conditions. These data suggest that a much higher proportion of deaths contribute to adaptation, in all environmental conditions, than the 10% cap that was anticipated as substantially restricting adaptation during historical discussions of speed limits.

Subduction of hydrous and carbonated oceanic lithosphere replenishes the mantle volatile inventory. Substantial uncertainties exist on the magnitudes of the recycled volatile fluxes and it is unclear whether Earth surface reservoirs are undergoing net-loss or net-gain of H2O and CO2. Here, we use noble gases as tracers for deep volatile cycling. Specifically, we construct and apply a kinetic model to estimate the effect of subduction zone metamorphism on the elemental composition of noble gases in amphibole a common constituent of altered oceanic crust. We show that progressive dehydration of the slab leads to the extraction of noble gases, linking noble gas recycling to H2O. Noble gases are strongly fractionated within hot subduction zones, whereas minimal fractionation occurs along colder subduction geotherms. In the context of our modelling, this implies that the mantle heavy noble gas inventory is dominated by the injection of noble gases through cold subduction zones. For cold subduction zones, we estimate a present-day bulk recycling efficiency, past the depth of amphibole breakdown, of 5-35% and 60-80% for 36Ar and H2O bound within oceanic crust, respectively. Given that hotter subduction dominates over geologic history, this result highlights the importance of cooler subduction zones in regassing the mantle and in affecting the modern volatile budget of Earth's interior. (C) 2017 Elsevier B.V. All rights reserved.

Diamond possesses extraordinary material properties, a result that has given rise to a broad range of scientific and technological applications. This study reports the successful production of high-quality single-crystal diamond with microwave plasma chemical vapor deposition (MPCVD) techniques. The diamond single crystals have smooth, transparent surfaces and other characteristics identical to that of high-pressure, high-temperature synthetic diamond. In addition, the crystals can be produced at growth rates from 50 to 150 mum/h, which is up to 2 orders of magnitude higher than standard processes for making polycrystalline MPCVD diamond. This high-quality single-crystal MPCVD diamond may find numerous applications in electronic devices as high-strength windows and in a new generation of high-pressure instruments requiring large single-crystal anvils.

Two experiments were conducted compressing Ta, Re, Pt, and an Fe-Si alloy to ultrahigh pressures using single-crystal chemical vapor deposition (CVD) and natural diamonds. In situ energy-dispersive and angle-dispersive x-ray diffraction were used to determine pressure from known equations of state. We demonstrate that CVD diamonds can be used in diamond anvil cells to reach pressures of nearly 200 GPa. (C) 2003 American Institute of Physics.

Gem-sized single crystals of diamond have been produced by very high growth rate microwave plasma chemical vapor deposition (CVD) and found to exhibit remarkable mechanical properties. The as-grown material has extremely high fracture toughness, and treatment by high-pressure/high-temperature annealing produces crystals that have exceptionally high intrinsic hardness. The annealing appears to induce a novel work hardening of CVD single-crystal diamond. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A 820 micron thick single crystal diamond layer epitaxially grown on a single crystal diamond seed (high pressure, high temperature grown synthetic) by microwave plasma chemical vapor deposition with added nitrogen is characterized by an array of analytical techniques before and after annealing the material at high pressures and temperatures. The most striking result is the conversion of the initially dark colored, highly absorbing CVD layer to clear, transparent material after a 1 hour anneal at 7 GPa and 2200 degreesC. IR absorption in the region of the CH stretching modes, 2800 to 3107 cm(-1) shows a remarkable sharpening and persistence of the observed modes. IR absorption in the one-phonon region also indicates the presence of significant concentrations of ionized single substitutional nitrogen in the as grown material. EPR indicates a concentration of neutral single substitutional nitrogen at lattice sites of ca. I ppm, and this changes by less then 30% when annealed at temperatures up to 2200 degreesC. EPR also detects 0.1 ppm of the negatively charged nitrogen-vacancy-hydrogen complex in the as grown diamond, but this anneals out by 1900 degreesC, the negatively charged nitrogen-vacancy complex is below the EPR detection limit in these samples of about 0.1 ppm. Photoluminescence detects the presence of neutral and negatively charged nitrogen-vacancy complexes in the as grown material, and the formation of new, unassigned bands principally in the 800 to 900 nm region. The total detected nitrogen concentration in the sample is ca. 1.5 ppm. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The synthesis of large single-crystal diamonds by chemical vapor deposition (CVD) at high growth rate has opened a new era for applications of the material. Large and thick single crystals can now be produced at very high growth rates, and the mechanical properties, chemistry, and optical and electronic properties of the material can be tuned over a wide range. The single crystals can have extremely high fracture toughness exceptionally high hardness following high-pressure/high-temperature annealing. CVD single-crystal diamonds will make possible a new generation of high-pressure-temperature experimentation to study Earth and planetary materials and should enable a variety of other new scientific and technological applications.

The detailed correlation of results from two dissimilar experimental techniques, transmission electron microscopy and micro-photoluminescence spectroscopy, has allowed us to obtain direct evidence of the interaction between linear and point defects in diamond as both 388.9 nm and 379 nm optical centers were found to be strongly related to dislocations. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The correlation of TEM imaging and micro-photoluminescence studies of electron irradiated areas of diamond, developed in Bristol, has been extended to new optical centres and defects. In this paper, we show new evidence of the interaction of point defects with dislocations and grain boundaries in diamond. Optical centres at 518.6 and 518.8 nm are directly correlated with dislocations and an optical centre at 519.1 nm was correlated with a grain boundary. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.