Model of a gravitating sphere set in rotation by internal stress

The systematic approximation technique of Synge is employed to construct a model of a spherical body at rest in the distant past and gradually attaining an angular velocity due to a modification of the internal stress. The calculations are carried out to include the second approximation so that, roughly speaking, there is an error of order m³ in Einstein's field equations wherem is the mass of the sphere.     

Colliding Plane Waves in Einstein–Maxwell Theory

Recently, a simple solution of the vacuum Einstein–Maxwell field equations was given describing a plane electromagnetic shock wave sharing its wave front with a plane gravitational impulse wave. We present here an exact solution of the vacuum Einstein–Maxwell field equations describing the head-on collision of such a wave with a plane gravitational impulse wave. The solution has the Penrose–Khan solution and a solution obtained by Griffiths as separate limiting cases.     

High-spectral-resolution stimulated Rayleigh-Brillouin scattering at 1 microm

We have demonstrated stimulated Rayleigh-Brillouin scattering at a wavelength of 1.064 microm , using an injection-seeded Nd:YAG laser as a pump laser and a tunable diode laser as a probe laser. Spectra with a good signal-to-noise ratio are obtained despite the low probe-beam power and small gain coefficient in the infrared. Stimulated Rayleigh scattering is readily observable in organic and many other liquids because of absorption by the OH and CH overtone or combination bands. The absorption also causes an asymmetry in the stimulated Brillouin peak. A Rayleigh linewidth of 8 MHz is measured with this approach.     

Breakdown limits on Gigavolt-per-meter electron-beam-driven wakefields in dielectric structures

First measurements of the breakdown threshold in a dielectric subjected to GV/m wakefields produced by short (30-330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100 microm inner diameter were exposed to a range of bunch lengths, allowing surface dielectric fields up to 27 GV/m to be generated. The onset of breakdown, detected through light emission from the tube ends, is observed to occur when the peak electric field at the dielectric surface reaches 13.8+/-0.7 GV/m. The correlation of structure damage to beam-induced breakdown is established using an array of postexposure inspection techniques.     

Comparison of homoleptic and heteroleptic 2,2′-bipyridine and 1,10-phenanthroline ruthenium complexes as chemiluminescence and electrochemiluminescence reagents in aqueous solution

We have conducted a comprehensive comparative study of Ru(bipy)₃²⁺, Ru(bipy)₂(phen)²⁺, Ru(bipy)(phen)₂²⁺, and Ru(phen)₃²⁺ as chemiluminescence and electrochemiluminescence (ECL) reagents, to address several previous conflicting observations and gain a greater insight into their potential for chemical analysis. Clear trends were observed in many of their spectroscopic and electrochemical properties, but the relative chemiluminescence or ECL intensity with a range of analytes/co-reactants is complicated by the contribution of numerous (sometimes opposing) factors. Significantly, the reversibility of cyclic voltammetric responses for the complexes decreased as the number of phenanthroline ligands was increased, due to the lower stability of their ruthenium(III) form in the aqueous solvent. This trend was also evident over a longer timescale when the ruthenium(III) form was spectrophotometrically monitored after chemical oxidation of the ruthenium(II) complexes. In general, the greater stability of Ru(bipy)₃³⁺ resulted in lower blank signals, although this effect was less pronounced with ECL, where the reagent is oxidised in the presence of the co-reactants. Nevertheless, this shows the need to compare signal-to-blank ratios or detection limits, rather than the more common comparisons of overall signal intensity for different ruthenium complexes. Furthermore, our results support previous observations that, compared to Ru(bipy)₃²⁺, Ru(phen)₃²⁺ provides greater ECL and chemiluminescence intensities with oxalate, which in some circumstances translates to superior detection limits, but they do not support the subsequent generalised notion that Ru(phen)₃²⁺ is a more sensitive reagent than Ru(bipy)₃²⁺ for all analytes.     

An atomic gravitational wave interferometric sensor in low earth orbit (AGIS-LEO)

We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of ${<10^{-18}/\sqrt{{\rm Hz}}}$ in the 50mHz?C10Hz frequency range, providing access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline $({\lesssim100\,{\rm m}})$ atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.     

History of Polyolefins

The history of polyolefins actually began in the 1890s with the synthesis of polymethylene from diazomethane. In the 1930s researchers in England discovered that ethylene at high pressure and in the presence of oxygen polymerized to a high molecular weight resin. Further research there and in the United States at still higher pressures yielded essentially straight chain, higher density polyethylenes. Early in the 1950s, groups in the United States and Europe independently discovered that linear, high-density polyethylenes could be made at low pressure over heterogeneous catalysts. Concurrently, groups catalytically produced polyolefin plastics from propylene and higher a-olefins. The inventorship of crystalline polypropylene was awarded to Phillips Petroleum Co. by United States courts in early 1980 (subject to final appeal). Commercial production of low-density polyethylene began in England (ICI) in 1939. High-pressure plants appeared in the United States (Du Pont and Union Carbide) and in Germany during World War II. Production of linear polyethylene started in late 1956 in the United States (Phillips). A semiworks Koppers plant began polyethylene production for commercial use earlier in 1956. Other plants quickly followed suit, using Phillips and Ziegler processes. Polypropylene production began in Europe and in the United States in 1957-1958. Two other polyolefin plastics have been produced in small commercial quantities, starting about 1965: poly(4-methyl-l-pentene) and poly-1-butene.     

Electrochemiluminescence of cyclometalated iridium (III) complexes

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