Pair production rates in mildly relativistic, magnetized plasmas

Electron-positron pairs may be produced by either one or two photons in the presence of a strong magnetic field. In magnetized plasmas with temperatures kT approximately sq mc, both of these processes may be important and could be competitive. The rates of one-photon and two-photon pair production by photons with Maxwellian, thermal bremsstrahlung, thermal synchrotron and power law spectra are calculated as a function of temperature or power law index and field strength. This allows a comparison of the two rates and a determination of the conditions under which each process may be a significant source of pairs in astrophysical plasmas. It is found that for photon densities n(gamma) or = 10 to the 25th power/cu cm and magnetic field strengths B or = 10 to the 12th power G, one-photon pair production dominates at kT approximately sq mc for a Maxwellian, at kT approximately 2 sq mc for a thermal bremsstrahlung spectrum, at all temperatures for a thermal synchrotron spectrum, and for power law spectra with indices s approximately 4

The disappearing women: North West ICT project final report

Project Context The Disappearing Women: Northwest ICT project was embarked upon to further understand why more women leave the sector than are being recruited, 36% of new ICT recruits in the UK (in the first quarter of 2002) were women, yet in the same period, women accounted for 46% of all leavers or ‘disappearing’ women (The DTI Women in IT Champions report 2003, Grey and Healy 2004). This continuing trend shows a decline from 27% of women making up the ICT workforce in 1997 with a drop to 21% in 2004 (The DTI Women in IT Industry report 2005b). The number of women in the ICT sector remains disappointingly small considering that women make up around 50% of the total UK workforce and significantly this figure has gradually continued to fall despite numerous initiatives to attract more women into the sector (see Griffiths and Moore 2006 for a list of high profile ‘women in ICT’ initiatives). The research team’s first gender research project - Women in IT (WINIT) - ran for two years from January 2004 until March 2006 at the Information Systems Institute at The University of Salford and dealt solely with women who worked in the ICT sector in England. The WINIT Project via an online questionnaire and in-depth interviews gathered the stories and experiences of up to 500 participants and 19 interviewees respectively. The project enabled these women’s voices to be heard but the research team were constantly aware that a certain part of the female ICT workforce - the ‘disappearing’ women who had left ICT vowing never to return - had been overlooked and effectively silenced. It was these women who once found, may be able to facilitate a more in-depth understanding of why women were leaving the ICT sector. Having amassed skills and expertise, qualifications in ICT and crossed ICT recruitment barriers (DTI 2005a) the ‘disappearing’ women for whatever reasons decided to change their career trajectories and leave the sector. What ‘chilly’ (Falkner 2004) workplaces, disinterested organisational cultures and indifferent working conditions had these women encountered that became determining factors in leaving the ICT sector? There has been little (if any) research conducted involving this specific cohort of women and The Disappearing Women: North West ICT (DW: NW ICT) project seeks to make a research contribution to what is a continuing statistical and symbolic under-representation of women in the ICT labour market. The DW: NW ICT project was partly funded by the European Social Fund (ESF) from April 2006 until December 2006 under ESF Objective 3, Policy Field 5.1: Improving the Participation of Women. The DW: NW ICT project contributes research to priority 5 and its strategic objective to reduce the level of disadvantage faced by women in the labour market. The project was run in the Information Systems Group, Salford Business School of The University of Salford, Greater Manchester, UK. The report is structured as follows. The first section presents the backdrop for the research, looking in general at women in the ICT labour market in England and then women leaving the ICT sector focussing on the North West of England and more explicitly women leaving ICT employment in the North West of England. The research aims of the project form the following section; they have been loosely classified in to two groupings, the push and pull factors that are contributing to the high attrition rate of women leaving ICT. The methodology follows with the route taken in how this ‘hard to reach’ target sample were finally located, once contacted the life history interview process and procedures adopted is explained in full. The vignettes of the ‘disappearing’ women are included to allow the reader an opportunity to ‘get to know’ these women a little more closely. Key themes that have naturally emerged throughout the interview data analysis process are presented, including hostilities in the ICT workplace, significant events and the process of leaving ICT workplaces and finally stories of the ‘appearing’ women and their current situations are heard. A discussion regarding the findings of the DW: NW ICT project concludes this report

Topological entropy and blocking cost for geodesics in riemannian manifolds

For a pair of points $x,y$ in a compact, riemannian manifold $M$ let $n_t(x,y)$ (resp. $s_t(x,y)$) be the number of geodesic segments with length $\leq t$ joining these points (resp. the minimal number of point obstacles needed to block them). We study relationships between the growth rates of $n_t(x,y)$ and $s_t(x,y)$ as $t\to\infty$. We derive lower bounds on $s_t(x,y)$ in terms of the topological entropy $h(M)$ and its fundamental group. This strengthens the results of Burns-Gutkin \cite{BG06} and Lafont-Schmidt \cite{LS}. For instance, by \cite{BG06,LS}, $h(M)>0$ implies that $s$ is unbounded; we show that $s$ grows exponentially, with the rate at least $h(M)/2$.Comment: 13 page

Integrated gasifier combined cycle polygeneration system to produce liquid hydrogen

An integrated gasifier combined cycle (IGCC) system which simultaneously produces electricity, process steam, and liquid hydrogen was evaluated and compared to IGCC systems which cogenerate electricity and process steam. A number of IGCC plants, all employing a 15 MWe has turbine and producing from 0 to 20 tons per day of liquid hydrogen and from 0 to 20 MWt of process steam were considered. The annual revenue required to own and operate such plants was estimated to be significantly lower than the potential market value of the products. The results indicate a significant potential economic benefit to configuring IGCC systems to produce a clean fuel in addition to electricity and process steam in relatively small industrial applications

Comparison of Integrated Gasifier-Combined Cycle and AFB-steam turbine systems for industrial cogeneration

In the cogeneration technology alternatives study (CTAS) a number of advanced coal fired systems were examined and systems using a integrated coal gasifier IGCC or a fluid bed combustor AFB were found to yield attractive cogeneration results in industrial cogeneration applications. A range of site requirements and cogeneration sizing strategies using ground rules based on CTAS were used in comparing an IGCC and an AFB. The effect of time variations in site requirements and the sensitivity to fuel and electricity price assumptions are examined. The economic alternatives of industrial or utility ownership are also considered. The results indicate that the IGCC system has potentially higher fuel and emission savings and could be an attractive option for utility ownership. The AFB steam turbine system has a potentially higher return on investment and could be attractive assuming industrial ownership

Mobilising communities to address alcohol harm : an Alcohol Health Champion approach

In this article, Cathy Ure et al. look at engaging communities in order to reduce alcohol harms. By training Alcohol Health Champions, individuals can support vulnerable friends and family, and work within their communities to influence policy and promote change

Surface Landing Site Weather Analysis for NASA's Constellation Program

Weather information is an important asset for NASA's Constellation Program in developing the next generation space transportation system to fly to the International Space Station, the Moon and, eventually, to Mars. Weather conditions can affect vehicle safety and performance during multiple mission phases ranging from pre-launch ground processing of the Ares vehicles to landing and recovery operations, including all potential abort scenarios. Meteorological analysis is art important contributor, not only to the development and verification of system design requirements but also to mission planning and active ground operations. Of particular interest are the surface weather conditions at both nominal and abort landing sites for the manned Orion capsule. Weather parameters such as wind, rain, and fog all play critical roles in the safe landing of the vehicle and subsequent crew and vehicle recovery. The Marshall Space Flight Center (MSFC) Natural Environments Branch has been tasked by the Constellation Program with defining the natural environments at potential landing zones. This paper wiI1 describe the methodology used for data collection and quality control, detail the types of analyses performed, and provide a sample of the results that cab be obtained

Integral constraints on the monodromy group of the hyperkahler resolution of a symmetric product of a K3 surface

Let M be a 2n-dimensional Kahler manifold deformation equivalent to the Hilbert scheme of length n subschemes of a K3 surface S. Let Mon be the group of automorphisms of the cohomology ring of M, which are induced by monodromy operators. The second integral cohomology of M is endowed with the Beauville-Bogomolov bilinear form. We prove that the restriction homomorphism from Mon to the isometry group O[H^2(M)] is injective, for infinitely many n, and its kernel has order at most 2, in the remaining cases. For all n, the image of Mon in O[H^2(M)] is the subgroup generated by reflections with respect to +2 and -2 classes. As a consequence, we get counter examples to a version of the weight 2 Torelli question, when n-1 is not a prime power.Comment: Version 3: Latex, 54 pages. Expository change