106,757 research outputs found

    Insights into secondary reactions occurring during atmospheric ablation of micrometeoroids

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    Ablation of micrometeoroids during atmospheric entry yields volatile gases such as water, carbon dioxide, and sulfur dioxide, capable of altering atmospheric chemistry and hence the climate and habitability of the planetary surface. While laboratory experiments have revealed the yields of these gases during laboratory simulations of ablation, the reactions responsible for the generation of these gases have remained unclear, with a typical assumption being that species simply undergo thermal decomposition without engaging in more complex chemistry. Here, pyrolysis–Fourier transform infrared spectroscopy reveals that mixtures of meteorite-relevant materials undergo secondary reactions during simulated ablation, with organic matter capable of taking part in carbothermic reduction of iron oxides and sulfates, resulting in yields of volatile gases that differ from those predicted by simple thermal decomposition. Sulfates are most susceptible to carbothermic reduction, producing greater yields of sulfur dioxide and carbon dioxide at lower temperatures than would be expected from simple thermal decomposition, even when mixed with meteoritically relevant abundances of low-reactivity Type IV kerogen. Iron oxides were less susceptible, with elevated yields of water, carbon dioxide, and carbon monoxide only occurring when mixed with high abundances of more reactive Type III kerogen. We use these insights to reinterpret previous ablation simulation experiments and to predict the reactions capable of occurring during ablation of carbonaceous micrometeoroids in atmospheres of different compositions

    Different approaches to sharing school leadership : full report

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    Walmart Sweatshop Litigation Dismissed

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    Document from the 9th Circuit Court in California dismissing charges brought up by employees of Wal-Mart\u27s foreign suppliers. The case was dismissed on the grounds that the plaintiffs did not state a claim against Wal-Mart, only its suppliers, which Wal-Mart had no legal duty to monitor

    The Tryal Between J.G. Biker, Plaintiff; and M. Morley, Doctor of Phyfic, Defendant; for Criminal Conversation with the Plaintiff’s Wife; on Tuefday the 30th of June at Guildhall, London

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    An account of a civil suit, including witness testimony, of charges of assault and criminal conversation against the defendant for having unlawful martial relations with the plaintiff’s wife. The evidence presented during the trial suggests witness tampering took place on the part of the plaintiff, which resulted in a verdict for the defendant. Printed for J. Huggonson in Sword and Buckler Court, Ludgate-Hill. 1741

    Optimal Control for a Class of Infinite Dimensional Systems Involving an LL^\infty-term in the Cost Functional

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    An optimal control problem with a time-parameter is considered. The functional to be optimized includes the maximum over time-horizon reached by a function of the state variable, and so an LL^\infty-term. In addition to the classical control function, the time at which this maximum is reached is considered as a free parameter. The problem couples the behavior of the state and the control, with this time-parameter. A change of variable is introduced to derive first and second-order optimality conditions. This allows the implementation of a Newton method. Numerical simulations are developed, for selected ordinary differential equations and a partial differential equation, which illustrate the influence of the additional parameter and the original motivation.Comment: 21 pages, 8 figure
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