138,476 research outputs found
Letter from Charles Noble to N. Silsbee
No full textA letter of Charles Noble to N. Silsbee, indicating that Silsbee sold the property to Van Raalte, and other matters including the information that the state government decided to place the seat of government in Lansing.https://digitalcommons.hope.edu/vrp_1840s/1106/thumbnail.jp
Noble gases in the Cameroon line and the He, Ne, and Ar isotopic compositions of high mu (HIMU) mantle
No full textUltramafic xenoliths, basaltic lavas, and CO2 gases from the Cameroon line volcanic chain provide the first characterization of combined He, Ne, and Ar isotopes in a high-time-integrated 238U/204Pb = μ (HIMU) magmatic system. Helium isotopic compositions typically range from 5.0 to 6.7 Ra, with an average of 6.3. These values are indistinguishable from the 3He/4He of other HIMU locales (Austral Islands, St. Helena). Neon isotopic compositions for xenoliths and CO2 gases are mid-ocean ridge basalt (MORB)-like, with a maximum 20Ne/22Ne of 11.87 and 21Ne/22Ne of 0.0508. Argon isotopic compositions in silicates range from atmospheric to 40Ar/36Ar = 4910±430 (crushing) and up to 16,300±1000 (single grain, laser step heating). The correlation between 20Ne/22Ne and 40Ar/36Ar in CO2 gases suggests a minimum 40Ar/36Ar = 1650±30 for the mantle-derived component. Uniform 3He/4He in silicates and in CO2 fluids across both the continental and oceanic sectors of the Cameroon line argues strongly for a negligible lithospheric contribution to noble gas isotopic compositions. This inference is supported by high 238U/3He in lherzolites, indicating that noble gases in these samples must have been recently introduced (<50,000 years ago) to the sample, most likely from the host magma. Ocean crust recycling models of mixing between MORB source regions and highly radiogenic slabs cannot produce the observed He and Ne isotopic compositions. Isolation and aging of MORB source mantle can generate the isotopic compositions but require extreme 3He/22Ne fractionation. Involvement of plume-derived gases, consistent with the lithophile element isotopic compositions, alleviates the need for strong 3He/22Ne fractionation. Closed-system aging of plume-derived heterogeneities can reproduce the data with minimum 3He/22Ne fractionation at reasonable 238U/3He ratios. However, diffusive exchange of He and to a lesser extent Ne between aged MORB source and aged plume veins could explain the occurrence of low 3He/4He compositions in all HIMU centers and the apparent low time-integrated 3He/22Ne of the Cameroon line
Study of Non-Noble-Metal-Based Metal–Nitrogen–Carbon Catalysts for Formic Acid Dehydrogenation
No full textFormic
acid (FA) is a safe, renewable, and promising hydrogen carrier.
A critical challenge is the effective screening of the suitable non-noble-metal-based
catalysts for FA dehydrogenation to substitute expensive noble-metal-based
ones. Here, a study of all possible catalysts with M–N–C
structures (M = 12 metals, −N–C = nitrogen-doped graphene-like
surface) for FA dehydrogenation has been conducted using density functional
theory (DFT) and followed by experimental analysis. Based on the adsorption
energy of critical intermediates, preliminary screening suggests Co
as a possible active metal for M–N–C. Experiment and
further DFT calculations suggest that atomically dispersed Co sites
(Co–N1–C3, Co–N2–C2, and Co–N3–C) are
preferable for FA dehydrogenation. The appropriate N contents are
critical to the catalytic activity, whose amount can be tuned by choosing
different sacrifice templates and the pyrolysis temperature
Warning signals and predator-prey coevolution
No full textTheories of the evolution of warning signals are typically expressed using analytic and computational models, most of which attribute aspects of predator psychology as the key factors facilitating the evolution of warning signals. Sherratt provides a novel and promising perspective with a model that considers the coevolution of predator and prey populations, showing how predators may develop a bias towards attacking cryptic prey in preference to conspicuous prey. Here, we replicate the model as an individual-based simulation and find, in accordance with Sherratt, that predators evolve a bias towards attacking cryptic prey. We then use a Monte Carlo simulation to calculate the relative survivorships of cryptic and conspicuous prey and stress that, as it stands, the model does not predict the evolution or stability of warning signals. We extend the model by giving predators continuous attack strategies and by allowing the evolution of prey conspicuousness: results are robust to the first modification but, in all cases, cryptic prey always enjoy a higher survivorship than conspicuous prey. When conspicuousness is allowed to evolve, prey quickly evolve towards crypsis, even when runaway coevolution is enabled. Sherratt's approach is promising, but other aspects of predator psychology, besides their innate response, remain vital to our understanding of warning signal
Noble-Metal–Metalloid Alloy Architectures: Mesoporous Amorphous Iridium–Tellurium Alloy for Electrochemical N<sub>2</sub> Reduction
No full textAmorphous noble metals with high surface areas have attracted
significant
interest as heterogeneous catalysts due to the numerous dangling bonds
and abundant unsaturated surface atoms created by the amorphous phase.
However, synthesizing amorphous noble metals with high surface areas
remains a significant challenge due to strong isotropic metallic bonds.
This paper describes the first example of a mesoporous amorphous noble
metal alloy [iridium–tellurium (IrTe)] obtained using a micelle-directed
synthesis method. The resulting mesoporous amorphous IrTe electrocatalyst
exhibits excellent performance in the electrochemical N2 reduction reaction. The ammonia yield rate is 34.6 μg mg–1 h–1 with a Faradaic efficiency
of 11.2% at −0.15 V versus reversible hydrogen electrode in
0.1 M HCl solution, outperforming comparable crystalline and Ir metal
counterparts. The interconnected porous scaffold and amorphous nature
of the alloy create a complementary effect that simultaneously enhances
N2 absorption and suppresses the hydrogen evolution reaction.
According to theoretical simulations, incorporating Te in the IrTe
alloy effectively strengthens the adsorption of N2 and
lowers the Gibbs free energy for the rate-limiting step of the electrocatalytic
N2 reduction reaction. Mesoporous chemistry enables a new
route to achieve high-performance amorphous metalloid alloys with
properties that facilitate the selective electrocatalytic reduction
of N2
Feasibility study of geospatial mapping of chronic disease risk to inform public health commissioning
No full textThis final article is available for use under the terms of the Creative Commons Attribution Non-Commercial 2.0 Licence; see http://bmjopen.bmj.co
Letter from John W. Noble to R[obert] U[nderwood] Johnson, 1891 Sep 14.
No full textDepartment of the Interior Washington, Sept. 14, 1891. Mr. R. U. Johnson, Associate Editor, Century Magazine, Union Square, N. Y.City, New York. Sir: In further reply to yours of July 7th, I have to say the question of timber reserves is receiving earnest attention and Mr. Muir\u27s suggestions would be very timely, if you can send me an advance copy. I return photo of cutting a Sequoia. With thanks, Yours truly, John W. Noble, Secretary.https://scholarlycommons.pacific.edu/jmcl/38816/thumbnail.jp
Homeostatic plasticity improves signal propagation in continuous time recurrent neural networks
No full textContinuous-time recurrent neural networks (CTRNNs) are potentially an excellent substrate for the generation of adaptive behaviour in artificial autonomous agents. However, node saturation effects in these networks can leave them insensitive to input and stop signals from propagating. Node saturation is related to the problems of hyper-excitation and quiescence in biological nervous systems, which are thought to be avoided through the existence of homeostatic plastic mechanisms. Analogous mechanisms are here implemented in a variety of CTRNN architectures and are shown to increase node sensitivity and improve signal propagation, with implications for robotics. These results lend support to the view that homeostatic plasticity may prevent quiescence and hyper-excitation in biological nervous systems
End of an ERA: lessons from negative clinical trials in idiopathic pulmonary fibrosis
No full textComment on "BUILD-3: a randomized, controlled trial of bosentan in idiopathic pulmonary fibrosis." [American Journal of Respiratory and Critical Care Medicine, 2011
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