There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. This paper describes the LAT, its pre-flight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4x4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 x,y tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an 8 layer hodoscopic configuration with a total depth of 8.6 radiation lengths. The aspect ratio of the tracker (height/width) is 0.4 allowing a large field-of-view (2.4 sr). Data obtained with the LAT are intended to (i) permit rapid notification of high-energy gamma-ray bursts (GRBs) and transients and facilitate monitoring of variable sources, (ii) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (iii) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (iv) localize point sources to 0.3 - 2 arc minutes, (v) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (vi) measure the diffuse isotropic gamma-ray background up to TeV energies, and (vii) explore the discovery space for dark matter.

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission

The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

/pdf/the-confrontation-between-general-relativity-and-experiment-5dqdube5p9.pdf

The Confrontation Between General Relativity and Experiment

Carbonylation of methanol and methyl acetate to acetic acid and acetic anhydride are the only current examples of C 1 processes displacing petrochemical routes for the manufacture of commodity chemicals. Modem carbonylation processes are based upon an iodide promoted, homogeneous rhodium catalyst operating under mild reaction conditions (150°C–200°C, 25–45 bar). This highly selective catalytic cycle is described, and contrasted with other catalytic metals. The embodiment of Rh/I catalysis in commercial BP Chemicals methanol and methyl acetate carbonylation processes is also described, illustrating the process simplicity arising from high selectivity. The now extensive literature on attempts to support the rhodium catalyst in iodide promoted systems is reviewed. In the liquid phase, catalytic behaviour similar to that for the homogeneous system is claimed, although proper comparative data and conclusive evidence for catalyst immobilisation is generally lacking. A number of supported rhodium systems are reported to be active under vapour phase conditions, and activated carbon is also found to promote carbonylation activity of certain base metals, notably nickel. Issues affecting commercial viability include catalyst lifetime, gaseous by-product formation and efficiency of utilisation of precious metal components. Literature on carbonylation in the absence of iodide promoter, and on direct routes to acetyls from synthesis gas or methanol only is also reviewed. All require step changes in catalytic performance in order to approach commercial viability.

C1 to Acetyls: Catalysis and Process.

https://robots.iopscience.iop.org/article/10.1088/1742-6596/869/1/012071/pdf

A search for extragalactic pulsars in the local group galaxies IC 10 and Barnard's galaxy

Diagnostic accuracy, concordance and certainty with 68Ga-PSMA-11 PET/MRI fusion compared to mpMRI and 68Ga-PSMA-11 PET/CT alone for prostate cancer diagnosis: A PRIMARY trial sub-study

There is growing evidence that some pulsar wind nebulae (PWN) are significant sources of variable emission above 100 MeV. We review the observational evidence associating five PWN and candidate PWN with the four sources showing the most >100 MeV variability among Galactic sources that are bright above 1 GeV. We discuss potential physical mechanisms for such variability, examine the apparent X-ray and radio efficiencies, and place limits on the magnetic field required for variable synchrotron emission at such high energies.

Variable high-energy γ-ray emission from pulsar wind nebulae

PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multi-frequency study of the pulsed radio flux variability which suggests that this phenomenon is extrinsic to the pulsar and possibly tied to the companion, although not strongly correlated with orbital phase. The pulsar has an unusual combination of characteristics compared to typical recycled pulsars: a long spin period (172 ms); a relatively high magnetic field strength (1.7x10^10 G); a very circular, compact orbit of 4.6 hours; and a low-mass companion (0.08 Msun). These spin and orbital properties are likely inconsistent with standard evolutionary models. We find similarities between the properties of the PSR J1744-3922 system and those of several other known binary pulsar systems, motivating the identification of a new class of binary pulsars. We suggest that this new class could result from either: a standard accretion scenario of a magnetar or a high-magnetic field pulsar; common envelope evolution with a low-mass star and a neutron star, similar to what is expected for ultra-compact X-ray binaries; or, accretion induced collapse of a white dwarf. We also report the detection of a possible K'=19.30(15) infrared counterpart at the position of the pulsar, which is relatively bright if the companion is a helium white dwarf at the nominal distance, and discuss its implications for the pulsar's companion and evolutionary history.

https://arxiv.org/pdf/astro-ph/0702347.pdf

Mallory S. E. Roberts

Papers

C1 to Acetyls: Catalysis and Process.

A search for extragalactic pulsars in the local group galaxies IC 10 and Barnard's galaxy

Diagnostic accuracy, concordance and certainty with 68Ga-PSMA-11 PET/MRI fusion compared to mpMRI and 68Ga-PSMA-11 PET/CT alone for prostate cancer diagnosis: A PRIMARY trial sub-study

Variable high-energy γ-ray emission from pulsar wind nebulae

The Unusual Binary Pulsar PSR J1744-3922: Radio Flux Variability, Near-infrared Observation and Evolution