Skylab Trash Airlock

The Skylab Trash Airlock (TAL) used throughout the Skylab mission to transfer trash materials that could support microbial growth from the pressurized cabin to the unpressurized waste tank is described. The TAL, which uses several basic mechanisms, was successfully operated daily for the 170 days of manned missions for a total of 637 cycles

Gauge invariant formalism for second order perturbations of Schwarzschild spacetimes

The ``close limit,'' a method based on perturbations of Schwarzschild spacetime, has proved to be a very useful tool for finding approximate solutions to models of black hole collisions. Calculations carried out with second order perturbation theory have been shown to give the limits of applicability of the method without the need for comparison with numerical relativity results. Those second order calculations have been carried out in a fixed coordinate gauge, a method that entails conceptual and computational difficulties. Here we demonstrate a gauge invariant approach to such calculations. For a specific set of models (requiring head on collisions and quadrupole dominance of both the first and second order perturbations), we give a self contained gauge invariant formalism. Specifically, we give (i) wave equations and sources for first and second order gauge invariant wave functions; (ii) the prescription for finding Cauchy data for those equations from initial values of the first and second fundamental forms on an initial hypersurface; (iii) the formula for computing the gravitational wave power from the evolved first and second order wave functions.Comment: 18 pages, no figure

Society-wide scenarios for effective integration of Paris-aligned climate mitigation and adaptation in national and regional policy

Climate science (IPCC 2018) and economics (Emmerling et al. 2019; Burke, Hsiang, and Miguel 2015) indicates that achieving far earlier and deeper mitigation than pledged to date is likely now critical to effective climate action – particularly to ensure limits to adaptation are not breached. However, clear and coherent comparisons of national and regional climate action have been lacking. Therefore, here we summarise a benchmarking method (McMullin et al. 2019) to establish a prudent, fair share of the remaining global CO2 budget for any Party to the Paris Agreement. Using Ireland as a case study, we analyse current policy ambition relative to this benchmarked national CO2 quota, demonstrate early emergence of CO2 debt, and show tacit mitigation policy reliance on future large scale carbon dioxide removal (CDR). Toward society-wide scenarios for effective climate action, we further examine the crucial roles of non-CO2 mitigation and safeguarding land carbon stocks

CaSiO3 perovskite at lower mantle pressures

We investigate by first-principles the structural behavior of CaSiO3 perovskite up to lower mantle pressures. We confirm that the cubic perovskite modification is unstable at all pressures. The zero Kelvin structure is stabilized by SiO6 octahedral rotations that lower the symmetry to tetragonal, orthorhombic, rhombohedral, or to a cubic supercell. The resulting structures have comparable energies and equation of state parameters. This suggests that relatively small deviatoric/ shear stresses might induce phase transformations between these various structures softening some elastic moduli, primarily the shear modulus. The seismic signature accompanying a local increase in CaSiO3 content should be a positive density anomaly and a negative V-S anomaly

Rapid Bayesian position reconstruction for gravitational-wave transients

Within the next few years, Advanced LIGO and Virgo should detect gravitational waves from binary neutron star and neutron star-black hole mergers. These sources are also predicted to power a broad array of electromagnetic transients. Because the electromagnetic signatures can be faint and fade rapidly, observing them hinges on rapidly inferring the sky location from the gravitational-wave observations. Markov chain Monte Carlo methods for gravitational-wave parameter estimation can take hours or more. We introduce BAYESTAR, a rapid, Bayesian, non-Markov chain Monte Carlo sky localization algorithm that takes just seconds to produce probability sky maps that are comparable in accuracy to the full analysis. Prompt localizations from BAYESTAR will make it possible to search electromagnetic counterparts of compact binary mergers.Comment: 23 pages, 12 figures, published in Phys. Rev.

Russian nationalism: creating a civic identity

A shared sense of identity within a state is a stabilising structure allowing a focus for citizens to rally around. As a multi-ethnic state, Russia has always been faced with the problem of how to imbue its citizens with a sense of identity that strengthens the state without causing dissent among the majority ethnic Russians or the many differenct minorities encapsulated within its territory. The choice between a civic based identity and an ethnically based national identity has faced the ruling apparatus for hundreds of years, and still poses a problem for both the people and the government of today's Russia

Practical post-modernism: FM and socially constructed realities

The theme of the paper, with examples, is that strategic FM should engage not with elaborate structural functional models of building service supply but with the socially constructed realities of organisations and their results. Several, evidence based, examples of FM creating different conversations will be provided, viz: • The creation of excellent patient environments in English Hospitals is not a function of structure (whether or not there is an integrated FM Directorate), sourcing (in house or outsourced) or a particular business process. It is a function of leadership exercised through context specific conversations. • The creation of effective new ‘knowledge’ environments is not a function of a particular design or project structure. It is a reflection of FMs ability to create conversations for changes in business results. • The failure of FM to capture strategic attention deriving from an obsession with considerations of unit costs and building condition rather than overall costs and business outcomes. • The role of perceptions and assertions in creating or blocking effective business relationships between FM providers and clients In the process the paper will challenge academic FM, whether research or education, to stop being in thrall to ‘practice’ to a degree that is arguably greater than is found in other areas of business and management, let alone other established disciplines. FM has too many models, too little theory and too little empirical evidence of specific business contributions. It is too concerned with supplying facilities rather than considering the purpose for which a given facility is managed.</p

Modification of the one-dimensional REKAP program to allow for charring in three material layers Final report

Modified one-dimensional reaction kinetics program to allow for charring in three material layers of rocket nozzle throat insert cas

High repetition rate sealed CO2 TEA lasers using heterogeneous catalysts

The significant operational advantages offered by CO2 lasers, operating in the 10.6 micron region of the spectrum, over current solid state lasers, emitting in the near IR region, have prompted increased interest in the development of compact, reliable, rugged CO2 laser sources. Perhaps the most critical aspect associated with achieving a laser compatible with military use is the development of lasers which require no gas replenishment. Sealed, single shot, CO2 TEA lasers have been available for a number of years. Stark et al were first to demonstrate reliable sealed operation in single shot CO2 TEA lasers in 1975 using gas catalysis. GEC Avionics reported the compact, environmentally qualified, MKIII CO2 TEA laser with a pulse life of greater than 10 to the 6th power pulses in 1980. A sealed laser lifetime of greater than 10 to the 6th power pulses is acceptable for single shot cases, such as direct detection rangefinders for tank laser sights. However, in many other applications, such as tracking of fast moving targets, it is essential that a repetition rate of typically 30Hz to 100Hz is employed. In such cases, a pulse lifetime of 10 to the 6th power pulses is no longer sufficient and a minimum pulse lifetime 10 to the 7th power pulses is essential to ensure a useful service life. In 1983 Stark el al described a sealed, 100Hz CO2 TEA laser, with a life of greater than 2.6 x 10 to the 6th power, which employed heterogeneous catalysis. Following this pioneering work, GEC Avionics has been engaged in the development of sealed high repetition rate lasers with a pulse lifetime of 20 million pulses