Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer

We present an analytical and numerical stability analysis of Soret-driven convection in a porous cavity saturated by a binary fluid. Both the mechanical equilibrium solution and the monocellular flow obtained for particular ranges of the physical parameters of the problem are considered. The porous cavity, bounded by horizontal infinite or finite boundaries, is heated from below or from above. The two horizontal plates are maintained at different constant temperatures while no mass flux is imposed. The influence of the governing parameters and more particularly the role of the separation ratio, characterizing the Soret effect and the normalized porosity, are investigated theoretically and numerically. From the linear stability analysis, we find that the equilibrium solution loses its stability via a stationary bifurcation or a Hopf bifurcation depending on the separation ratio and the normalized porosity of the medium. The role of the porosity is important, when it decreases, the stability of the equilibrium solution is reinforced. For a cell heated from below, the equilibrium solution loses its stability via a stationary bifurcation when the separation ratio >0(Le,), while for 0, while a stationary or an oscillatory bifurcation occurs if mono the monocellular flow loses stability via a Hopf bifurcation. As the Rayleigh number increases, the resulting oscillatory solution evolves to a stationary multicellular flow. For a cell heated from above and <0, the monocellular flow remains linearly stable. We verified numerically that this problem admits other stable multicellular stationary solutions for this range of parameters

Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems

Tungsten trioxide adopts a variety of structures which can be intercalated with charged species to alter the electronic properties, thus forming `tungsten bronzes'. Similar optical effects are observed upon removing oxygen from WO_3, although the electronic properties are slightly different. Here we present a computational study of cubic and hexagonal alkali bronzes and examine the effects on cell size and band structure as the size of the intercalated ion is increased. With the exception of hydrogen (which is predicted to be unstable as an intercalate), the behaviour of the bronzes are relatively consistent. NaWO_3 is the most stable of the cubic systems, although in the hexagonal system the larger ions are more stable. The band structures are identical, with the intercalated atom donating its single electron to the tungsten 5d valence band. Next, this was extended to a study of fractional doping in the Na_xWO_3 system (0 < x < 1). A linear variation in cell parameter, and a systematic change in the position of the Fermi level up into the valence band was observed with increasing x. In the underdoped WO_3-x system however, the Fermi level undergoes a sudden jump into the conduction band at around x = 0.2. Lastly, three compounds of a layered WO_4&#215;a,wdiaminoalkane hybrid series were studied and found to be insulating, with features in the band structure similar to those of the parent WO_3 compound which relate well to experimental UV-visible spectroscopy results.Comment: 12 pages, 16 figure

Out-of-plane behavior of one-way spanning unreinforced masonry walls

An analytical model is developed to describe the out-of-plane response of one-way spanning unreinforced masonry (URM) walls by investigating the effects of various parameters. Horizontal crack height, masonry compressive strength, and diaphragm support stiffness properties are assumed as variables, and sensitivity analyses are performed to study the influence of these parameters on the cracked wall characteristic behavior. The parametric studies show that crack height significantly influences wall stability by affecting both the instability displacement and the wall lateral resistance. The reduction in cracked wall lateral resistance and in the instability displacement caused by finite masonry compressive strength is shown to be significantly amplified by the applied overburden. A study using the typical configuration of flexible diaphragms and URM walls indicates that the wall top support flexibility does not significantly influence cracked wall out-of-plane response. An existing simplified wall behavioral model is improved, and a procedure is proposed for calculation of the wall out-of-plane response envelope.Hossein Derakhshan; Michael C. Griffith; and Jason M. Ingha

The Mersey Estuary : sediment geochemistry

This report describes a study of the geochemistry of the Mersey estuary carried out between April 2000 and December 2002. The study was the first in a new programme of surveys of the geochemistry of major British estuaries aimed at enhancing our knowledge and understanding of the distribution of contaminants in estuarine sediments. The report first summarises the physical setting, historical development, geology, hydrography and bathymetry of the Mersey estuary and its catchment. Details of the sampling and analytical programmes are then given followed by a discussion of the sedimentology and geochemistry. The chemistry of the water column and suspended particulate matter have not been studied, the chief concern being with the geochemistry of the surface and near-surface sediments of the Mersey estuary and an examination of their likely sources and present state of contamination

Quality and impact of appraisal for revalidation: the perceptions of London’s responsible officers and their appraisers

BACKGROUND: To evaluate NHS England London region's approach to the revalidation appraisal of responsible officers in London, exploring perceptions of the quality and impact of the appraisal process. Revalidation is the process which aims to ensure doctors in the UK are up-to-date and fit to practice medicine thus improving the quality of patient care. Revalidation recommendations are largely premised on the documentation included in annual appraisals, which includes the professional development a doctor has undertaken and supporting information about their practice. METHODS: A pan-London qualitative study exploring the views of responsible officers and their appraisers about the revalidation appraisal process. The study aimed to gain an in-depth understanding of the experiences and perceptions of the participants. Responsible officers were purposefully sampled to represent the broadest range of designated bodies. Data analysis generated themes pertaining to quality and impact of appraisal for revalidation with the potential to feed into and shape the evolving system under investigation. RESULTS: The central importance of highly skilled appraisers was highlighted. Both groups reported educational opportunities embedded within the appraisal process. Independent appraisers, not matched by clinical speciality or place of work, were considered to take a more objective view of a responsible officer's practice by providing an 'outsider perspective'. However, covering the breadth of roles, in sufficient depth, was challenging. Participants reported a bias favouring the appraisal of the responsible officer role above others including clinical work. Appraisal and revalidation was perceived to have the potential to improve the healthcare standards and support both personal development and institutional quality improvement. CONCLUSIONS: Responsible officers play a central role in the revalidation process. Getting responsible officer appraisal right is central to supporting those individuals to in turn support doctors and healthcare organisations in continuous quality improvement. The complexity and importance of the role of responsible officer may make achieving an appraisal of all roles of such individuals problematic. This evaluation suggests responsible officer appraisal was perceived as educational and effective

How to correct small quantum errors

The theory of quantum error correction is a cornerstone of quantum information processing. It shows that quantum data can be protected against decoherence effects, which otherwise would render many of the new quantum applications practically impossible. In this paper we give a self contained introduction to this theory and to the closely related concept of quantum channel capacities. We show, in particular, that it is possible (using appropriate error correcting schemes) to send a non-vanishing amount of quantum data undisturbed (in a certain asymptotic sense) through a noisy quantum channel T, provided the errors produced by T are small enough.Comment: LaTeX2e, 23 pages, 6 figures (3 eps, 3 pstricks

'Selling it as a holistic health provision and not just about condoms ?' Sexual health services in school settings: current models and their relationship with sex and relationships education policy and provision

In this article we discuss the findings from a recent study of UK policy and practice in relation to sexual health services for young people, based in - or closely linked with - schools. This study formed part of a larger project, completed in 2009, which also included a systematic review of international research. The findings discussed in this paper are based on analyses of interviews with 51 service managers and questionnaire returns from 205 school nurses. Four themes are discussed. First, we found three main service permutations, in a context of very diverse and uneven implementation. Second, we identified factors within the school context that shaped and often constrained service provision; some of these also have implications for sex and relationships education (SRE). Third, we found contrasting approaches to the relationship between SRE input and sexual health provision. Fourth, we identified some specific barriers that need to be addressed in order to develop 'young people friendly' services in the school context. The relative autonomy available to school head teachers and governors can represent an obstacle to service provision - and inter-professional collaboration - in a climate where, in many schools, there is still considerable ambivalence about discussing 'sex' openly. In conclusion, we identify areas worthy of further research and development, in order to address some obstacles to sexual health service and SRE provision in schools

Measuring the flow properties of small powder samples using an avalanche tester

The feasibility of using a small-scale avalanche tester to measure the flow properties of pharmaceutical lactose powders was examined. The modes of behaviour observed in larger systems were displayed and showed a clear distinction between angular, free-flowing particles and more spherical particles of similar flow characteristics. Angular Lactohale LH100 particles showed slumping behaviour at a rotational frequency of 0.33Hz which disappeared at higher frequencies. Spherical lactose powder with a similar flow function to LH100 only showed rolling behaviour under the same conditions, as did more cohesive powders LH200 and LH300. Further investigation of the LH100 data using Fast Fourier analysis showed that the slumping frequency was 1/10th of the rotational frequency

Sources of Sex Information Used by Young British Women Who Have Sex with Women (WSW) and Women Who Have Sex Exclusively with Men (WSEM): Evidence from the National Survey of Sexual Attitudes and Lifestyles

There is little consideration about the provision of information about sex to women who have sex with women (WSW). This study drew on data from the third National Survey of Sexual Attitudes and Lifestyle, a nationally representative survey of people in Great Britain. Logistic regression was undertaken to examine firstly the relationships between WSW and women who have sex exclusively with men (WSEM) and their main source of information about sex, and secondly between WSW/WSEM and unmet need for information about sex. Each source was included as the binary outcome indicating yes this was the main source, or no this was not the main source of information about sex. The results found that WSW had significantly lower odds of reporting lessons at schools as their main source of information, and significantly higher odds of reporting sources defined as ‘other’ (predominantly first girlfriend/boyfriend or sexual partner) as their main source of information. Reported levels of unmet need for information was also higher amongst young WSW compared with WSEM. This study provides new insights into the sex educational needs of young women and highlights the need for sex education in schools in Great Britain to include information on a full-range of sexual practices, including same-sex sexual relationships