An examination of atmospheric lids during COPS

Copyright @ 2009 E.Schweizerbart Science PublishersThe understanding of the nature, origin and prevalence of atmospheric lids is low. There is, therefore, an opportunity to contribute significantly to this area of meteorology - this is the goal of this work. The context for this paper is the Convective and Orographically-induced Precipitation Study (COPS). The COPS observational campaign, which was undertaken in 2007, was based around the Black Forest region with the aim of improving precipitation forecasts in low mountainous regions. However, the project also represents a great data archive with which to analyse isolated features, such as atmospheric lids. In short, lids play a vital role in the development of convective storms. For example, evidence from the Convective Storm Initiation Project (CSIP), which was run in the UK in 2005, has shown that lids are important not only in determining whether a storm occurs but also when and where they develop and how intense they are – sometimes, counterintuitively, they appear to increase the intensity. This extended abstract is intended as a brief overview of the previous literature on lids in order to place the work presented at ICAM-2009 in the wider scientific context.This work is funded by the Natural Environment Research Council (NERC)

The Jewish 'ghetto': formation and spatial structure

Research into patterns of immigrant settlement has consistently indicated that certain areas of cities are prone to settlement by immigrant groups. This paper proposes that immigrant settlement of such areas may have a particular spacial pattern. Taking the case of the settlement of Leeds, England by Jewish immigrants in the latter six decades of the nineteenth century, we describe the formation of the immigrant Jewish settlement in the area called Leylands.The paper shows first, that Leylands was spacially segregated in comparison with the city overall; and second, that the pattern of settlement was one of intensification of particular streets through time, whereby initially the main, relatively integrated streets were settled, with occupancy moving as time went on to more segregated streets.Analysis of social class defined by occupation suggests that the whole population of Leylands was much poorer than that of Leeds overall. This paper suggests that since the poverty difference was present and possibly more pronounced for the majority, non-Jewish population, that the socio-economic form of the area settlement in Leeds was more likely to have been related to its spacial sgregation than to the social and economic segregation of the immigrant group. It is suggested that the particular characteristics special to certain immigrant groups allowed the Jews of Leylands to overcome their spacial segregation by employing strong social networks on the one hand and through economic mutual help on the other

Phase Lags and Coherence of X-Ray Variability in Black Hole Candidates

The ``low'' (hard or ``non-thermal'') state of black hole candidates is sometimes modelled via an optically thick, hot Compton cloud that obscures a softer input source such as an accretion disk. In these models the observed output spectra consist entirely of photons reprocessed by the cloud, making it difficult to extract information about the input spectra. Recently Miller (1995) has argued that the Fourier phase (or time) lag between hard and soft X-ray photons in actuality represents the phase lags intrinsic to the input source, modulo a multiplicative factor. The phase lags thus would be a probe of the input photon source. In this paper we examine this claim and find that, although true for the limited parameter space considered by Miller, the intrinsic phase lag disappears whenever the output photon energy is much greater than the input photon energy. The remaining time lags represent a ``shelf'' due to differences between mean diffusion times across the cloud. As pointed out by Miller, the amplitude of this shelf -- which is present even when the intrinsic time lags remain -- is indicative of the size and temperature of the Compton cloud and is a function of the two energies being compared. However, we find that with previous instruments such as Ginga the shelf, if present, was likely obscured by counting noise. A more sensitive measure of Compton cloud parameters may be obtainable from the coherence function, which is derived from the amplitude of the Fourier cross power spectral density. This function has been seen to exponentially decrease at high Fourier frequencies in Cygnus X-1. Coherence loss is characteristic of Compton clouds that undergo large variations of size and/or temperature on time scales longer than about 10 seconds. We argue that observing phase lags and coherenceComment: 14 pages, uuencoded postscript, accepted for publication in Monthly Notice

Euclidean Supergravity in Five Dimensions

We construct a 5D, N = 2 Euclidean theory of supergravity coupled to vector multiplets. Upon reducing this theory over a circle we recover the action of 4D, N = 2 Euclidean supergravity coupled to vector multiplets.Comment: 13 page

Properties and Analysis of Thermally Aged Poly(ethylene oxide)

Recent studies have been performed into the use of polyethylene oxide (PEO) as a model system for observing the fundamental effects of adding micro and nano sized fillers to create polymeric composite systems. Many factors contribute to the successful creation of such a composite system, including dispersion of the filler and treatment of the material during creation. For example, while producing thin films of the materials for testing, high temperatures were used for short periods of time in open air to press the samples into small discs. It is well known that prolonged high temperature exposure can alter the chemistry and structure of polymeric materials and that small variations in the original chemistry, such as longer molecular weights or introduction of fillers, can reduce or possibly accelerate this 'ageing' effect. From these previous investigations many property changes were observed during addition of filler or variation of molecular weight, therefore to accurately attribute these changes to a cause the thermal ageing of the material should be observed. This investigation looks at the same 3 molecular weight PEO systems as those used in the previous investigations and analyses them for their vulnerability to thermal ageing. One thermally aged sample is then taken and tested alongside an unaged sample to observe the effects that the process has on the properties. This includes rheology in solution, differential scanning calorimetry (DSC), AC electrical breakdown, dielectric spectroscopy and Fourier transform infra-red (FTIR). By observing the property changes of aged samples it is possible to better understand the thermal ageing process occurring and possibly a way to reduce the effect, along with considering the effect with regard to the behaviour of the previously tested composite samples

A Raman Microprobe Study of Corona Ageing in a Controlled Atmosphere

Raman microprobe spectroscopy is widely used in the analysis of polymers due to its high spatial resolution and its ability to characterise the exact chemical composition of a material and, for this reason, it can be applied to study electrical ageing in solid dielectrics. For example, it enables us to probe the chemical processes involved in electrical treeing, whereby solid polymer is converted into decomposition products through a number of electrical processes [1]. This study takes a novel approach to this problem through ex-situ experiments that seek to reproduce the chemistry of electrical treeing in bulk. Plaque specimens of a range of polymers, including polyethylene, polystyrene, PEEK and silicone rubber, were subjected to surface ageing via corona discharge, and the residual products on both the sample surface and the high voltage electrode (as seen in figure 1) were characterised by Raman microprobe spectroscopy. These experiments were performed as a function of applied voltage, electrode geometry etc both in air and within a closed cell that enabled the atmosphere to be controlled and adjusted. The resulting Raman fingerprints were compared with those previously identified within electrical trees [2,3]. After corona discharge was applied to the samples, despite a large change in surface texture, no residues were seen on the sample and few chemical changes were detected via Raman spectroscopy, thus implying that erosion of the material occurs by fragmentation of the polymer. Analysis of the electrodes aged in air and nitrogen, revealed varying evidence of sp2 hybridized carbon, and fluorescence, both of which are products previously associated with the processes involved in electrical treeing. The similarity in these results and previous published works [2,3] suggest that there are common processes involved between corona surface ageing and electrical treeing especially when an inert atmosphere is used

An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. I. Evidence for a shocked outflow

An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 has revealed a rich absorption line spectrum indicating the presence of a photoionized outflow with a wide range of velocities and ionization parameter. At low continuum fluxes an emission line spectrum is well defined with both narrow and broad components of several abundant metal ions. The absorption line velocity structure and a broad correlation of velocity and ionization parameter are consistent with an outflow scenario where a highly ionized, high velocity wind, perhaps launched during intermittent super-Eddington accretion, runs into the interstellar medium or previous ejecta, losing much of its kinetic energy in the resultant strong shock. We explore the possibility that a quasi-constant soft X-ray emission component may be evidence of this post-shock cooling. This revised view of AGN outflows is consistent with multiple minor Eddington accretion episodes creating a momentum-driven feedback linking black hole and host galaxy growth.Comment: accepted for publication in Monthly Notices of the Royal Astronomical Societ

Graded Lie algebras of maximal class IV

We describe the isomorphism classes of certain infinite-dimensional graded Lie algebras of maximal class, generated by an element of weight one and an element of weight two, over fields of odd characteristic.Comment: 38 pages. See also http://www-math.science.unitn.it/~caranti/ and http://users.ox.ac.uk/~vlee