Numerical Simulation of the Chemical Combination and Dissociation Reactions of Neutral Particles in a Rarefied Plasma Arc Jet

The expansion of neutral particles in a plasma arc jet is crucial for the distribution of the ions and electrons, especially in an unsteady rarefied plasma arc jet with chemical reactions. A 3-D unsteady investigation of neutral particles in a rarefied flow with chemical combination and dissociation reactions is numerically simulated based on an in-house direct simulation Monte Carlo (DSMC) code. The evolution of the neutral particles flow in vacuum cylinders is presented, and the influence of the chemical reactions has been investigated for the neutral particles. The predicted results imply that the dissociation reaction plays a key role in the expansion of the neutral particles process. In order to study the expansion of the neutral particles in an electric field, an electrostatic particle-in-cell (PIC) and DSMC are combined to simulate the axisymmetric rarefied plasma flows with chemical reactions. Two sets of grids are employed for the DSMC/PIC method by considering the different requirements of both the methods based on the molecule mean free path and the Debye length. The properties of both the flow and electric fields are analyzed in detail. It is found that the electric potential increases if the initial velocity of the ions from the inlet is sufficiently large, and accordingly, the number density of the ions in the flow field increases further

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

Developing sexual competence? Exploring strategies for the provision of effective sexualities and relationships education

School-based sexualities and relationships education (SRE) offers one of the most promising means of improving young people's sexual health through developing 'sexual competence'. In the absence of evidence on whether the term holds the same meanings for young people and adults (e.g. teachers, researchers, policy-makers), the paper explores 'adult' notions of sexual competence as construed in research data and alluded to in UK Government guidance on SRE, then draws on empirical research with young people on factors that affect the contexts, motivations and outcomes of sexual encounters, and therefore have implications for sexual competence. These data from young people also challenge more traditional approaches to sexualities education in highlighting disjunctions between the content of school-based input and their reported sexual experience. The paper concludes by considering the implications of these insights for developing a shared notion of what SRE is trying to achieve and suggestions for recognition in the content and approaches to SRE.</p

Understanding the effects of oxyfuel combustion and furnace scale on biomass ash deposition

Recycled wood oxyfuel combustion is attractive for the advantages of reusing the waste bioenergy and reducing the carbon emissions. However, the changes in the fuel properties and combustion conditions can lead to uncertainties in the ash deposition. In addition, the understanding of the differences in the ash deposition between the pilot-scale and full-scale furnaces is very limited. We have performed ash deposition experiments on a 250 kW pilot-scale furnace for recycled wood air and oxyfuel combustion along with the EI Cerrejon coal combustion as a reference. A CFD-based ash deposition model, which uses the excess energy based particle sticking model, has been developed and the predictions are in qualitative agreement with the measurement data. The results suggest that, besides furnace temperature, the aerodynamics and ash physicochemical properties dictate the ash deposition. The recycled wood has a much higher deposition rate than the coal in the pilot-scale furnace; however, the biomass can numerically have a lower deposition rate under high velocities close to the full-scale boilers. This is mainly due to the biomass having a much lower sticking efficiency since it has high calcium and silicon concentrations and low potassium concentration. Although the effect of oxyfuel combustion is small and within the experimental uncertainties, it is found that oxyfuel combustion can affect the particle impaction and sticking behaviours depending on the fly ash properties and these effects occur in different ways in the pilot-scale and full-scale conditions. Great care should be taken to perform the transfer of the deposition observations from the pilot scale to the full scale and this is because the furnace scale has an effect on the selective deposition behaviour. In this paper a relationship between the fly ash properties (ash composition, size, etc.) and ash deposition for the woody biomass has been proposed. Additionally, the uncertainty analysis of the CFD modelling is undertaken, which indicates that the fly ash size distribution and the heterogeneity are responsible for the major source of errors along with the experimental uncertainties

HE AMOT FAMILY OF PROTEINS BINDS AND ACTIVATES NEDD4 FAMILY LIGASES TO PROMOTE THE UBIQUITINATION OF LATS AND YAP

poster abstractAmot adaptor proteins bind and integrate signaling that controls cell po-larity and growth. All three Amot family members (Amot, AmotL1 and AmotL2) directly bind YAP; a transcriptional co-activator that controls the expression of genes involved in organ homeostasis and cell growth. Preven-tion of nuclear accumulation of YAP by either sequestration or degradation in the cytosol abolishes its transcriptional functions and is a major mechanism for growth arrest in response to cellular differentiation. This is mainly thought to be regulated by phosphorylation of YAP by the Hippo kinases LATS1/2. Recently, binding by the Amot proteins was also found to inhibit YAP by sequestering it in the cytosol through both LATS dependent and in-dependent mechanisms. This study identifies a novel mechanism whereby Amot proteins control YAP activation in a Hippo independent mechanism by coupling it to ubiquitination by Nedd4 family ligases. Amot proteins mediate the coupling of Nedd4 ligases with YAP by simultaneously binding both pro-teins via multiple PY motifs that are recognized by WW domains in both YAP and Nedd4. Binding of Nedd4 by Amot is also shown to relieve the auto-inhibition of its ligase activity. This may be a direct consequence of binding Amot or from being re-targeted in cells by Amot proteins to endosomes. Im-portantly, Amot induced ubiquitination of YAP by Nedd4 proteins is shown to enhance the residence of YAP in the nucleus and in YAP activated transcrip-tion. Taken together our data suggest that Amot couples Nedd4 family ubiq-uitin ligases with the transcriptional co-activator YAP to drive the ubiquitination and activation of YAP

'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

New Measurements of the Motion of the Zodiacal Dust

Using the Wisconsin H-Alpha Mapper (WHAM), we have measured at high spectral resolution and high signal-to-noise the profile of the scattered solar Mg I 5184 absorption line in the zodiacal light. The observations were carried out toward 49 directions that sampled the ecliptic equator from solar elongations of 48\dg (evening sky) to 334\dg (morning sky) plus observations near +47\dg and +90\dg ecliptic latitude. The spectra show a clear prograde kinematic signature that is inconsistent with dust confined to the ecliptic plane and in circular orbits influenced only by the sun's gravity. In particular, the broadened widths of the profiles, together with large amplitude variations in the centroid velocity with elongation angle, indicate that a significant population of dust is on eccentric orbits. In addition, the wide, flat-bottomed line profile toward the ecliptic pole indicates a broad distribution of orbital inclinations extending up to about 30\dg - 40\dg with respect to the ecliptic plane. The absence of pronounced asymmetries in the shape of the profiles limits the retrograde population to less than 10% of the prograde population and also places constraints on the scattering phase function of the particles. These results do not show the radial outflow or evening--morning velocity amplitude asymmetry reported in some earlier investigations. The reduction of the spectra included the discovery and removal of extremely faint, unidentified terrestrial emission lines that contaminate and distort the underlying Mg I profile. This atmospheric emission is too weak to have been seen in earlier, lower signal-to-noise observations, but it probably affected the line centroid measurements of previous investigations.Comment: 24 pages, 8 figures, 1 table, to appear in ApJ v612; figures appear low-res only on scree

Investigation of particle radiation and its effect on NO prediction in a pilot-scale facility for both air and oxy-coal combustion

Radiation heat transfer plays an important role in pulverised coal combustion, influencing the overall combustion efficiency, pollutant formation and flame ignition and propagation. In this paper, the radiation properties of the particles as well as gas property models on the overall influence of the prediction of the formation of NOx pollutants in a pulverised coal combustion have been investigated. The non-grey weighted sum of grey gases (WSGG) model has been employed to calculate the radiation of the gas phase coupled with the radiation interaction from the particulate phase. The Mie theory, as well as constant or linear models, have been employed to describe the particle radiative properties. The prediction results, calculated from the data from a 250 kW pilot scale combustion test facility (CTF), are compared against experimental measurements under air-fired condition and a range of oxyfuel conditions. The results show that the choice of radiation solution can have a considerable impact on the radiative heat transfer results, in which the Mie theory shows a significant improvement in the incident wall heat flux compared to the constant or linear models. Also, the more accurate solution employed for radiation of gases and particles considerably improves the NOx prediction in the flame region