Gravitational Radiation from Post-Newtonian Sources and Inspiralling Compact Binaries

The article reviews the current status of a theoretical approach to the problem of the emission of gravitational waves by isolated systems in the context of general relativity. Part A of the article deals with general post-Newtonian sources. The exterior field of the source is investigated by means of a combination of analytic post-Minkowskian and multipolar approximations. The physical observables in the far-zone of the source are described by a specific set of radiative multipole moments. By matching the exterior solution to the metric of the post-Newtonian source in the near-zone we obtain the explicit expressions of the source multipole moments. The relationships between the radiative and source moments involve many non-linear multipole interactions, among them those associated with the tails (and tails-of-tails) of gravitational waves. Part B of the article is devoted to the application to compact binary systems. We present the equations of binary motion, and the associated Lagrangian and Hamiltonian, at the third post-Newtonian (3PN) order beyond the Newtonian acceleration. The gravitational-wave energy flux, taking consistently into account the relativistic corrections in the binary moments as well as the various tail effects, is derived through 3.5PN order with respect to the quadrupole formalism. The binary's orbital phase, whose prior knowledge is crucial for searching and analyzing the signals from inspiralling compact binaries, is deduced from an energy balance argument.Comment: 109 pages, 1 figure; this version is an update of the Living Review article originally published in 2002; available on-line at http://www.livingreviews.org

The Pioneer Anomaly

Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living Reviews in Relativit

A revised age of ad 667–699 for the latest major eruption at Rabaul

The most recent major eruption at Rabaul was one of the largest known events at this complex system, having a VEI rating of 6. The eruption generated widespread airfall pumice lapilli and ash deposits and ignimbrites of different types. The total volume of pyroclastic material produced in the eruption exceeded 11 km3 and led to a new phase of collapse within Rabaul Caldera. Initial 14C dating of the eruptive products yielded an age of about 1400 yrs BP, and the eruption became known as the "1400 BP" eruption. Previous analyses of the timing of the eruption have linked it to events in AD 536 and AD 639. However, we have re-evaluated the age of the eruption using the Bayesian wiggle-match radiocarbon dating method, and the eruption is now thought tohave occurred in the interval AD 667-699. The only significant equatorial eruptions recorded in both Greenland and Antarctic ice during this interval are at AD 681 and AD 684, dates that coincide with frost rings in bristlecone pines of western USA in the same years. Definitively linking the Rabaul eruption to this narrow age range will require identification of Rabaul tephra in the ice records. However, it is proposed that a new working hypothesis for the timing of the most recent major eruption at Rabaul is that it occurred in the interval AD 681-684

Summit acid crater lakes and flank instability in composite volcanoes

Volcanic landslides, including flank and sector collapses, constitute a major hazard in many parts of the world. While composite volcanoes are innately unstable, the presence of a hydrothermal system maintained by a magmatic source at depth is recognized as a key factor increasing the risk of failure. This relates to the formation of hydrothermally altered rock masses within the core and upper flanks of the volcano which leads to heterogeneous distribution of rock strength properties and pore fluid pressures. Here an emphasis is placed on acid crater lakes perched high on active volcanoes. By acting as a trap for magmatic heat and gas flows, these lakes localize extreme acid attack on their surrounds, thereby creating a source of instability. We outline how acid crater lakes form in relation to magmatic hydrothermal systems hosted within composite volcanoes, and describe the associated hydrothermal alteration and its relationships to flank instability. The sustainability of a volcanic slope is partly governed by the degree of rock alteration, which in turn reflects the time-integrated flux of acidic gases (SO2 and HCl) released from the subsurface magmatic source. Transient or longer-term changes in pore fluid pressure linked to hydrothermal system activity also readily affect the slope stability of composite volcanoes. Such fluctuations can be initiated by both magmatic and external non-magmatic processes such as major rainfall events and regional seismicity. Kawah Ijen hyper-acid crater lake, Indonesia, is used as a case study to illustrate the cascade of effects that may ensue following slope rupture linked to hydrothermal alteration

A 3-Dimensional Trimeric β-Barrel Model for Chlamydia MOMP Contains Conserved and Novel Elements of Gram-Negative Bacterial Porins

Chlamydia trachomatis is the most prevalent cause of bacterial sexually transmitted diseases and the leading cause of preventable blindness worldwide. Global control of Chlamydia will best be achieved with a vaccine, a primary target for which is the major outer membrane protein, MOMP, which comprises ∼60% of the outer membrane protein mass of this bacterium. In the absence of experimental structural information on MOMP, three previously published topology models presumed a16-stranded barrel architecture. Here, we use the latest β-barrel prediction algorithms, previous 2D topology modeling results, and comparative modeling methodology to build a 3D model based on the 16-stranded, trimeric assumption. We find that while a 3D MOMP model captures many structural hallmarks of a trimeric 16-stranded β-barrel porin, and is consistent with most of the experimental evidence for MOMP, MOMP residues 320–334 cannot be modeled as β-strands that span the entire membrane, as is consistently observed in published 16-stranded β-barrel crystal structures. Given the ambiguous results for β-strand delineation found in this study, recent publications of membrane β-barrel structures breaking with the canonical rule for an even number of β-strands, findings of β-barrels with strand-exchanged oligomeric conformations, and alternate folds dependent upon the lifecycle of the bacterium, we suggest that although the MOMP porin structure incorporates canonical 16-stranded conformations, it may have novel oligomeric or dynamic structural changes accounting for the discrepancies observed