Reducing thermal noise from optical coatings is crucial to reaching the required sensitivity in next generation interferometric gravitational-wave detectors. Here we show that adding TiO 2 to Ta 2 O 5 in Ta 2 O 5 /SiO 2 coatings reduces the internal friction and in addition present data confirming it reduces thermal noise. We also show that TiO 2 -doped Ta 2 O 5 /SiO 2 coatings are close to satisfying the optical absorption requirements of second generation gravitational-wave detectors.

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Carbon dioxide removal (CDR) is rising up the climate-policy agenda. Four principles for thinking about its role in climate policy can help ensure that CDR supports the kind of robust, abatement-focused long-term climate strategy that is essential to fair and effective implementation.

The Parties to the UNFCCC and Paris Agreement agreed to act "on the basis of equity" to protect the climate system. Equitable effort-sharing is an irreducibly normative matter, yet some influential studies have sought to create quantitative indicators of equitable effort that claim to be value-neutral (despite evident biases). Many of these studies fail to clarify the ethical principles underlying their indicators, some mislabel approaches which favour wealthy nations as 'equity approaches', and some combine contradictory indicators into composites we call 'derivative benchmarks'. This Perspective reviews influential climate effort sharing assessments and presents guidelines for developing and adjudicating policyrelevant (but not ethically neutral) equity research.