Dust grain dynamics in C-Type shock waves in molecular clouds

We investigate the role and behaviour of dust grains in C-type MHD shock waves in weakly ionized, dense molecular clouds. New shock models are presented for steady, oblique C-type shock structures with shock speed v_s=18km/s, n_H=10^5cm^-3, and a grain population represented by either a single grain species or a MRN grain size distribution. The grain size distribution is calculated using Gauss-Legendre weights and the integrals over the continuous distribution of grain sizes are represented by a number of grain bins. The grain population can then be thought of as a series of separate grain size classes, each with uniquely specified properties. The dynamics of each grain size class is different through the shock front, with the smaller grain classes remaining coupled to the magnetic field and larger grains becoming partially decoupled from the magnetic field due to collisions with the neutrals. The importance of grain charging is also demonstrated. The effects of the orientation of the pre-shock magnetic field B_0 are also considered. It is found that there are critical orientations for B_0 in which the shock is no longer C-type and the transition becomes C$^*$ or J-type. The degree of non-coplanarity of the shock solution depends upon the grain model chosen, as well as the orientation of B_0.Comment: 27 pages, 17 figures, submitted to MNRAS July 200

Frequency-dependent AVO attribute: theory and example

Fluid-saturated rocks generally have seismic velocities that depend upon frequency. Exploring this property may help us discriminate different fluids from seismic data. In this paper, we introduce a scheme to calculate a frequency-dependent AVO attribute in order to estimate seismic dispersion from pre-stack data, and apply it to North Sea data. The scheme essentially combines the two-term approximation of Smith and Gidlow (1987) with the method of spectral decomposition based on the Wigner-Ville distribution, which is used to achieve high resolution. The result suggests the potential of this method for detection of seismic dispersion due to fluid saturation

An Analysis of FEE-HELP in the Vocational Education and Training Sector

The public vocational education and training (VET) system is now one of the few areas in Australia’s tertiary education system where students are required to pay up-front fees without access to loan assistance. These arrangements may lead to sub-optimal educational outcomes to the extent that prospective students reject a VET education on the basis of short-term financial constraints. In this paper we analyse some of the important issues related to the adoption of FEE-HELP (a 2005 Federal Government financial instrument based on the Higher Education Contribution Scheme (HECS)). It is argued that income contingent loans of this kind are associated with the advantages of both default-protection and consumption smoothing. Using data from the first three waves of the Household Income and Labour Dynamics in Australia (HILDA) survey, we examine various empirical issues associated with the adoption of FEE-HELP in VET, including the extent of private salary returns to VET qualifications. As well, we explore issues related to the public subsidies inherent in the adoption of FEE-HELP in VET, and illustrate the time periods involved in loan repayments for various assumptions concerning the size of the charge and the future income of VET graduates. Administrative issues are considered, as are the implications for the Commonwealth Government with respect to potential subsidies associated with the design parameters.educational finance, educational economics, vocational education

Transcriptome sequencing and marker development for four underutilized legumes

PREMISE OF THE STUDY:Combating threats to food and nutrition security in the context of climate change and global population increase is one of the highest priorities of major international organizations. Hundreds of species are grown on a small scale in some of the most drought/flood-prone regions of the world and as such may harbor some of the most environmentally tolerant crops (and alleles). •METHODS AND RESULTS:In this study, transcriptomes were sequenced, assembled, and annotated for four underutilized legume crops. Microsatellite markers were identified in each species, as well as a conserved orthologous set of markers for cross-family phylogenetics and comparative mapping, which were ground-truthed on a panel of diverse legume germplasm. •CONCLUSIONS:An understanding of these underutilized legumes will inform crop selection and breeding by allowing the investigation of genetic variation and the genetic basis of adaptive traits to be established

Multiscale reaction-diffusion algorithms: PDE-assisted Brownian dynamics

Two algorithms that combine Brownian dynamics (BD) simulations with mean-field partial differential equations (PDEs) are presented. This PDE-assisted Brownian dynamics (PBD) methodology provides exact particle tracking data in parts of the domain, whilst making use of a mean-field reaction-diffusion PDE description elsewhere. The first PBD algorithm couples BD simulations with PDEs by randomly creating new particles close to the interface which partitions the domain and by reincorporating particles into the continuum PDE-description when they cross the interface. The second PBD algorithm introduces an overlap region, where both descriptions exist in parallel. It is shown that to accurately compute variances using the PBD simulation requires the overlap region. Advantages of both PBD approaches are discussed and illustrative numerical examples are presented.Comment: submitted to SIAM Journal on Applied Mathematic

The effect of the prompt on writing product and process: a mixed methods approach

A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyThe aim of this thesis is to investigate the effect of the writing prompt on test takers in terms of their test taking processes and the final written product in a second language writing assessment context. The study employs a mixed methods approach, with a quantitative and a qualitative strand. The quantitative study focuses on an analysis of the responses to six different writing prompts, with the responses being analyzed for significant differences in a range of key textual features, such as syntactic complexity, lexical sophistication, fluency and cohesion. The qualitative study incorporates stimulated recall interviews with test takers to learn about the aspects of the writing prompt that can have an effect on test taking processes, such as selecting a prompt, planning a response, and composing a response. The results of the quantitative study indicate that characteristics of the writing prompt (domain, response mode, focus, number of rhetorical cues) have an effect on numerous textual features of the response; for example, fluency, syntactic complexity, lexical sophistication, and cohesion. The qualitative results indicate that similar characteristics of the writing prompt can have an effect on how test takers select a prompt, and that the test time constraint interacts with the prompt characteristics to affect how test takers plan and compose their responses. The topic and the number of rhetorical cues are the prompt characteristics that have the greatest effect on test taking processes. The main conclusion drawn from the study findings are that several prompt characteristics should be controlled if prompts are to be considered equivalent. Without controlling certain prompt characteristics, both test taking processes and the written product will vary as a result of the prompt. The findings raise some serious questions regarding the inferences that may legitimately be drawn from writing scores. The findings provide clear guidance on prompt characteristics that should be controlled to help ensure that prompts present an equivalent challenge and opportunity to test takers to demonstrate their writing proficiency. This thesis makes an original contribution to the second language writing assessment literature in the detailed understanding of the relationships between specific prompt characteristics and textual features of the response