Ionized polycyclic aromatic hydrocarbons in space

The mid-infrared spectrum of a continuously increasing number of stellar objects, planetary and reflection nebulae, H-II regions and extragalactic sources show a distinctive set of broad emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 micron known collectively as the unidentified infrared emission bands. A model is summarized in which the bands arise from positively charged polycyclic hydrocarbons (PAH's) on the basis of their low ionization potential and the excellent agreement between the emission bands and laboratory spectra of auto exhaust which contains these types of molecules. The proposed presence of PAHs in such a variety of objects points to their presence in the interstellar medium. Out of a previously published collection of solid state PAH radical cation spectra five were selected on the basis of the unique thermodynamic stability of their carrier and compared directly to the wavelengths of the DIB's. Although the match seems quite favorable, strongly suggesting that PAH radicals are the long sought after carrier of the diffuse interstellar absorption bands, much laboratory work must be done to test this hypothesis

Process improvement in BAe Systems and the wider aerospace sector

Purpose: To research the change management processes used to implement ‘world class’ improvements in a major aerospace company, BAE SYSTEMS, and to propose a model for process improvement in the wider aerospace sector. Design/methodology/approach: The research was undertaken as a longitudinal study over a period of five years. A variety of research methodologies were used at various stages of the research including action research and observation. Semi-structured and unstructured interviews were used to gather qualitative data along with documentary evidence of the processes being used. Findings: There are three key findings. Firstly, an understanding of the production stages in the aerospace sector: future project; new product; sustain and return to work. Secondly details of a matrix-based approach and the issues regarding its implementation in a large organisation are discussed. Thirdly, a generic set of principles to aid process improvement in the aerospace sector is proposed. Research limitations/implications: Given that the study is based in one company, there are issues regarding the generalisation of the results. A potential further research project would entail the implementation of the proposed generic principles in another aerospace organisation. Practical implications: For BAE SYSTEMS, this research project aided their understanding of the issues involved in rolling out a process improvement program in a large organisation.Originality/value: Until recently, most of the research into process improvement had either been universalistic or aimed at another type of industry, such as the automotive industry. This research helps to address the specific needs of the aerospace industry

Infrared absorption and emission characteristics of interstellar PAHs

The mid-infrared interstellar emission spectrum with features at 3.28, 6.2, 7.7, 8.7 and 11.3 microns is discussed in terms of the Polycyclic Aromatic Hydrocarbon (PAH) hypothesis, which is based on the suggestive, but inconclusive comparison between the interstellar emission spectrum with the infrared absorption and Raman spectra of a few PAHs. The fundamental vibrations of PAHs and PAH-like species which determine the IR and Raman properties are discussed. Interstellar IR band emission is due to relaxation from highly vibrationally excited PAHs excited by ultraviolet photons. The excitation/emission process is described and the IR fluorescence from one PAH, chrysene, is traced. Generally, there is sufficient energy to populate several vibrational levels in each mode. Molecular vibrational potentials are anharmonic and emission from these higher levels will fall at lower frequencies and produce weak features to the red of the stronger fundamentals. This process is also described and can account for some spectroscopic details of the interstellar emission spectra previously unexplained. Analysis of the interstellar spectrum shows that PAHs contain between 20 and 30 carbon atoms are responsible for the emission

The hydrogen coverage of interstellar PAHs

The rate at which the CH bond in interstellar Polycyclic Aromatic Hydrocarbons (PAHs) rupture due to the absorption of a UV photon has been calculated. The results show that small PAHs (less than or equal to 25 carbon atoms) are expected to be partially dehydrogenated in regions with intense UV fields, while large PAHs (greater than or equal to 25 atoms) are expected to be completely hydrogenated in those regions. Because estimate of the carbon content of interstellar PAHs lie in the range of 20 to 25 carbon atoms, dehydrogenation is probably not very important. Because of the absence of other emission features besides the 11.3 micrometer feature in ground-based 8 to 13 micrometer spectra, it has been suggested that interstellar PAHs are partially dehydrogenated. However, IRAS 8 to 22 micrometer spectra of most sources that show strong 7.7 and 11.2 micrometer emission features also show a plateau of emission extending from about 11.3 to 14 micrometer. Like the 11.3 micrometer feature, this new feature is attributed to the CH out of plane bending mode in PAHs. This new feature shows that interstellar PAHs are not as dehydrogenated as estimated from ground-based 8 to 13 micrometer spectra. It also constrains the molecular structure of interstellar PAHs. In particular, it seems that very condensed PAHs, such as coronene and circumcoronene, dominate the interstellar PAH mixture as expected from stability arguments

Troll or No Troll? Policing Patent Usage With an Open Post-Grant Review

In December 2004, a mystery business, JGR Acquisitions Inc., purchased the patent portfolio of bankrupt Commerce One at auction. Commerce One had not previously enforced the acquired patents and many companies were using the patented technologies at the time of the auction. Patent watchdog groups argued that JGR--a potential patent troll formed solely to purchase Commerce One\u27s patents--should not be able to use the patents as a vehicle to extract licensing fees and that the patents should lapse into the public domain. Under current law, however, there is no provision for patents to be invalidated merely because they are used in a manner that discourages innovation. This iBrief argues that in order to keep patent trolls from stifling innovation and to protect legitimate patent holders, the Patent and Trademark Office should require an open post-grant review whenever patents are renewed or sold

b-Hadron Physics at LEP

A personal overview of the current status of physics results from LEP using b-hadrons is presented. Emphasis is placed on those areas where analyses are not yet finalised and there remains significant activity. Results are presented in the areas of b-quark fragmentation, b-hadron lifetimes, charm counting in b-decays and Vcb.Comment: 4 pages TEX, 4 figure

Balloon borne humidity and aerosol sensors

Infrared detectors for balloon sensing of aerosols and atmospheric moistur