11,548 research outputs found
Room-Temperature Alternative to the Arbuzov Reaction: The Reductive Deoxygenation of Acyl Phosphonates
The reductive deoxygenation of acyl phosphonates using a Wolff−Kishner-like sequence is described. This transformation allows direct access to alkyl phosphonates from acyl phosphonates at room temperature. The method can be combined with acyl phosphonate synthesis into a one pot, four-step procedure for the conversion of carboxylic acids into alkyl phosphonates. The methodology works well for a variety of aliphatic acids and shows a functional group tolerance similar to that of other hydrazone-forming reactions
WR146 - observing the OB-type companion
We present new radio and optical observations of the colliding-wind system
WR146 aimed at understanding the nature of the companion to the Wolf-Rayet star
and the collision of their winds. The radio observations reveal emission from
three components: the WR stellar wind, the non-thermal wind-wind interaction
region and, for the first time, the stellar wind of the OB companion. This
provides the unique possibility of determining the mass-loss rate and terminal
wind velocity ratios of the two winds, independent of distance. Respectively,
these ratios are determined to be 0.20+/-0.06 and 0.56+/-0.17 for the
OB-companion star relative to the WR star. A new optical spectrum indicates
that the system is more luminous than had been believed previously. We deduce
that the ``companion'' cannot be a single, low luminosity O8 star as previously
suggested, but is either a high luminosity O8 star, or possibly an O8+WC binary
system.Comment: 9 pages, 5 figures,
ftp://fto.drao.nrc.ca/pub/smd/wr146/accepted.ps.gz To be published in Monthly
Notices of the Royal Astronomical Societ
Non-thermal X-ray and Gamma-ray Emission from the Colliding Wind Binary WR140
WR140 is the archetype long-period colliding wind binary (CWB) system, and is
well known for dramatic variations in its synchrotron emission during its
7.9-yr, highly eccentric orbit. This emission is thought to arise from
relativistic electrons accelerated at the global shocks bounding the
wind-collision region (WCR). The presence of non-thermal electrons and ions
should also give rise to X-ray and gamma-ray emission from several separate
mechanisms, including inverse-Compton cooling, relativistic bremsstrahlung, and
pion decay. We describe new calculations of this emission and make some
preliminary predictions for the new generation of gamma-ray observatories. We
determine that WR140 will likely require several Megaseconds of observation
before detection with INTEGRAL, but should be a reasonably strong source for
GLAST.Comment: 4 pages, 1 figure, contribution to "Massive Stars and High-Energy
Emission in OB Associations"; JENAM 2005, held in Liege (Belgium
The Effects of Federalism and Privatization on Productivity in Chinese Firms
This study offers empirical evidence about how the structure of government and private ownership affects productivity in Chinese firms. It uses the microdata of China's most recent decennial industrial census, covering all of the 23,000 large and medium industrial firms operating in China during 1995. The results show that government decentralization – 'federalism' – plays an important role in improving the performance of not just collective firms, but also state-owned and mixed public/private ownership firms. This result is strongly confirmatory of much of the recent theoretical work on transition economies that posits a key role for government in the efficient operation of markets. Privatization makes a big difference in performance for firms administered at the federal level, especially state-owned enterprises. Private ownership also makes a large difference for wholly foreign-owned firms, nearly all located in special districts. In local jurisdictions, however, there is little difference in productivity across the various nonstate ownership types, supporting the argument that the regulatory environment played a critical role in successful business performance.china productivity microdata ownership decentralization
Particle propagation channels in the solar wind
The intensities of low energy solar-interplanetary electrons and ions at 1 AU occasionally change in a square wave manner. The changes may be increases or decreases and they typically have durations of from one hour to a few hours. In some cases these channels are bounded by discontinuities in the interplanetary field and the plasma properties differ from the surrounding solar wind. In one case solar flare particles were confined to a channel of width 3 x 10 to the 6th km at Earth. At the Sun this dimension extrapolates to about 12,000 km, a size comparable to small flares
- …
