Supporting early oral language skills for English language learners in inner city preschool provision

BACKGROUND: A significant number of children now enter formal education in England with reduced levels of proficiency in oral language. Children who come from disadvantaged backgrounds and who are English language learners (ELL) are at risk of limited oral language skills in English which impacts on later educational achievement. AIMS: This paper reports the development of a theoretically motivated oral language intervention, Talking Time, designed to meet the needs of preschool children with poor language skills in typical preschool provision. SAMPLE: One hundred and forty-two 4-year-old children attending three inner city preschools in a disadvantaged area of London, England. METHOD: This is a quasi-experimental intervention study comparing children exposed to Talking Time with children exposed to a contrast intervention and children receiving the statutory early years curriculum. Measures were taken of both targeted and non-targeted language and cognitive skills. RESULTS: Data were analysed for the ELL. The intervention had a significant effect on vocabulary, oral comprehension, and sentence repetition but not narrative skills. As predicted, there were no effects on the skills which were not targeted. CONCLUSIONS: Regular evidence-based oral language interactions can make significant improvements in children's oral language. There is a need to examine the efficacy of more intensive interventions to raise language skills to allow learners to access the curriculum

A study of the high frequency limitations of series resonant converters

A transformer induced oscillation in series resonant (SR) converters is studied. It may occur in the discontinuous current mode. The source of the oscillation is an unexpected resonant circuit formed by normal resonance components in series with the magnetizing inductance of the output transformers. The methods for achieving cyclic stability are: to use a half bridge SR converter where q0.5. Q should be as close to 1.0 as possible. If 0.5q1.0, the instability will be avoided if psi2/3q-1/3. The second objective was to investigate a power field effect transistor (FET) version of the SR converter capable of operating at frequencies above 100 KHz, to study component stress and losses at various frequencies

Electrical performance characteristics of high power converters for space power applications

The first goal of this project was to investigate various converters that would be suitable for processing electric power derived from a nuclear reactor. The implementation is indicated of a 20 kHz system that includes a source converter, a ballast converter, and a fixed frequency converter for generating the 20 kHz output. This system can be converted to dc simply by removing the fixed frequency converter. This present study emphasized the design and testing of the source and ballast converters. A push-pull current-fed (PPCF) design was selected for the source converter, and a 2.7 kW version of this was implemented using three 900 watt modules in parallel. The characteristic equation for two converters in parallel was derived, but this analysis did not yield any experimental methods for measuring relative stability. The three source modules were first tested individually and then in parallel as a 2.7 kW system. All tests proved to be satisfactory; the system was stable; efficiency and regulation were acceptable; and the system was fault tolerant. The design of a ballast-load converter, which was operated as a shunt regulator, was investigated. The proposed power circuit is suitable for use with BJTs because proportional base drive is easily implemented. A control circuit which minimizes switching frequency ripple and automatically bypasses a faulty shunt section was developed. A nonlinear state-space-averaged model of the shunt regulator was developed and shown to produce an accurate incremental (small-signal) dynamic model, even though the usual state-space-averaging assumptions were not met. The nonlinear model was also shown to be useful for large-signal dynamic simulation using PSpice

A comparative study of electric power distribution systems for spacecraft

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems

STRUCTURE-FUNCTION STUDIES OF TRANSLOCATED EFFECTORS FROM THE LATE BLIGHT PATHOGEN

An almost universal feature of successful pathogens is the secretion of effector proteins, many of which translocate inside host cells. These effectors manipulate host processes for the pathogen’s benefit. However, in response to this manipulation, plants have evolved to monitor for effectors and trigger defence responses. Amongst plant pathogens, oomycetes of the genus Phytophthora have arguably caused almost unrivalled levels of human suffering and represent significant threats to global food security. The late blight pathogen, Phytophthora infestans, is the most devastating pathogen of potato – the fourth most important food crop worldwide. Effective and durable resistance against late blight is desperately needed; and will depend on an improved understanding of the mechanistic basis of disease. Determining the adaptive functions of effectors might reveal previously unexploited management strategies. This work details structure-function studies of two translocated effectors from the late blight pathogen; PexRD2, a representative RXLR effector, and CRN8, an effector with kinase activity. Efforts to heterologously express CRN8 were hampered by protein insolubility and low yields. However, the crystal structure of PexRD2 revealed that it homodimerises, and was crucial to the discovery of a conserved oomycete effector protein fold, the WY-domain fold. Yeast two-hybrid screening identified four PexRD2-interacting host proteins, including MAPKKKε, a known positive regulator of plant immunity. MAP-kinase cascades transduce the perception of invading pathogens into effective defence responses, and MAPKKKε is involved in resistance against P. infestans. PexRD2 specifically suppresses cell deaths that are either MAPKKKε-dependent or triggered by MAPKKKε overexpression. PexRD2 also inhibits MAPKKKε-triggered MAPK activation. Further, structure-led mutagenesis of PexRD2 suggests that this effector benefits the pathogen by interacting with MAPKKKε to inhibit the kinase’s signalling. Discovering the PexRD2-MAPKKKε interaction, and its implications for plant immunity, has suggested unexploited management strategies that could enhance crop resistance to this devastating pathogen

Generalised CP and A4A_4 Family Symmetry

We perform a comprehensive study of family symmetry models based on $A_4$ combined with the generalised CP symmetry $H_{\rm{CP}}$. We investigate the lepton mixing parameters which can be obtained from the original symmetry $A_4\rtimes H_{\rm{CP}}$ breaking to different remnant symmetries in the neutrino and charged lepton sectors. We find that only one case is phenomenologically viable, namely $G^{\nu}_{\rm{CP}}\cong Z^{S}_2\times H^{\nu}_{\rm{CP}}$ in the neutrino sector and $G^{l}_{\rm{CP}}\cong Z^{T}_3\rtimes H^{l}_{\rm{CP}}$ in the charged lepton sector, leading to the prediction of no CP violation, namely $\delta_{CP}$ and the Majorana phases $\alpha_{21}$ and $\alpha_{31}$ are all equal to either zero or $\pi$. We then propose an effective supersymmetric model based on the symmetry $A_4\rtimes H_{\rm{CP}}$ in which trimaximal lepton mixing is predicted together with either zero CP violation or $\delta_{CP}\simeq\pm \pi/2$ with non-trivial Majorana phases. An ultraviolet completion of the effective model yields a neutrino mass matrix which depends on only three real parameters. As a result of this, all three CP phases and the absolute neutrino mass scale are determined, the atmospheric mixing angle is maximal, and the Dirac CP can either be preserved with $\delta_{CP}=0,\pi$ or maximally broken with $\delta_{CP}=\pm \pi /2$ and sharp predictions for the Majorana phases and neutrinoless double beta decay.Comment: 38 pages, 3 figure

MatchIt: Nonparametric Preprocessing for Parametric Causal Inference

MatchIt implements the suggestions of Ho, Imai, King, and Stuart (2007) for improving parametric statistical models by preprocessing data with nonparametric matching methods. MatchIt implements a wide range of sophisticated matching methods, making it possible to greatly reduce the dependence of causal inferences on hard-to-justify, but commonly made, statistical modeling assumptions. The software also easily fits into existing research practices since, after preprocessing data with MatchIt, researchers can use whatever parametric model they would have used without MatchIt, but produce inferences with substantially more robustness and less sensitivity to modeling assumptions. MatchIt is an R program, and also works seamlessly with Zelig.