Multi-line Stokes inversion for prominence magnetic-field diagnostics

We present test results on the simultaneous inversion of the Stokes profiles of the He I lines at 587.6 nm (D_3) and 1083.0 nm in prominences (90-deg scattering). We created datasets of synthetic Stokes profiles for the case of quiescent prominences (B<200 G), assuming a conservative value of 10^-3 of the peak intensity for the polarimetric sensitivity of the simulated observations. In this work, we focus on the error analysis for the inference of the magnetic field vector, under the usual assumption that the prominence can be assimilated to a slab of finite optical thickness with uniform magnetic and thermodynamic properties. We find that the simultaneous inversion of the two lines significantly reduces the errors on the inference of the magnetic field vector, with respect to the case of single-line inversion. These results provide a solid justification for current and future instrumental efforts with multi-line capabilities for the observations of solar prominences and filaments.Comment: 14 pages, 5 figures, 1 tabl

Shaping electron wave functions in a carbon nanotube with a parallel magnetic field

A magnetic field, through its vector potential, usually causes measurable changes in the electron wave function only in the direction transverse to the field. Here we demonstrate experimentally and theoretically that in carbon nanotube quantum dots, combining cylindrical topology and bipartite hexagonal lattice, a magnetic field along the nanotube axis impacts also the longitudinal profile of the electronic states. With the high (up to 17T) magnetic fields in our experiment the wave functions can be tuned all the way from "half-wave resonator" shape, with nodes at both ends, to "quarter-wave resonator" shape, with an antinode at one end. This in turn causes a distinct dependence of the conductance on the magnetic field. Our results demonstrate a new strategy for the control of wave functions using magnetic fields in quantum systems with nontrivial lattice and topology.Comment: 5 figure

Planning intervention using dynamic assessments: A case study

Dynamic assessments (DA) of language have been shown to be a useful addition to the battery of tests used to diagnose language impairments in children, and to evaluate their skills. The current article explores the value of the information gained from a DA in planning intervention for a child with language impairment. A single case study was used to demonstrate the detailed qualitative information that can be derived from a DA procedure, and how that information may be used to elicit greater gains from intervention. The participant was a boy, aged 9, with a previously diagnosed language impairment. He was receiving language therapy regularly in a language resource base attached to his school. The CELF-3(UK) was used to monitor changes in his language, before and after two periods of intervention. The initial baseline phase consisted of regular ongoing language therapy. The second phase of therapy was modified by the speech and language therapist after receiving a report of the child’s performance on the Dynamic Assessment of Sentence Structure (DASS; Hasson et al., 2012), and observations of the child’s metalinguistic and metacognitive awareness. Greater gains observed in the second phase of therapy reflected the good modifiability shown by the child’s performance on the DASS

Improving storytelling and vocabulary in secondary school students with language disorder: a randomized controlled trial

Background: Although language and communication difficulties are common in secondary school students, there has been limited research into the efficacy of interventions for adolescents with language and communication difficulties. Aims: To investigate the efficacy of teaching assistant (TA)-delivered narrative and vocabulary interventions to mainstream secondary school-aged students with language disorder. Methods & Procedures: A randomized controlled trial (RCT) of a language and communication intervention was used to evaluate the efficacy of vocabulary and narrative interventions to improve the vocabulary and narrative performance of adolescents (mean age = 12.8 years) with language disorder. The language and communication programmes (narrative, vocabulary and combined narrative and vocabulary) were delivered by TAs in the classroom, three times per week, for 45–60 min each, over 6 weeks, totalling 18 sessions. Standardized and intervention-specific measures were used as outcomes. Outcomes & Results: Twenty-one schools with 358 eligible participants were recruited. The three intervention groups showed significant improvements (d =.296) on a narrative latent variable defined by a standardized narrative assessment (the Expression, Reception and Recall of Narrative Instrument—ERRNI), but there were no significant improvements on an overall vocabulary latent variable compared with the waiting control group. Differential effects were found on some non-standardized intervention-specific measures with the narrative group making significantly more progress on narrative tasks compared with the waiting control group, the vocabulary group showing the same pattern on specific vocabulary tasks, and the combined narrative and vocabulary group making significantly more progress on some of the intervention-specific narrative, and all the intervention-specific vocabulary outcomes compared with the waiting control group. Conclusions & Implications: It is possible to improve narrative but not vocabulary skills, as assessed by standardized measures, in secondary school students with a relatively brief group TA-delivered intervention. There were differential effects for both narrative and vocabulary with intervention-specific measures. Future work is required to explore whether more intensive and longer lasting interventions would be more effective and to identify which students in this age group are most likely to benefit from such interventions

Narrative skills in adolescents with a history of SLI in relation to non-verbal IQ scores

There is a debate about whether the language of children with primary language disorders and normal cognitive levels is qualitatively different from those with language impairments who have low or borderline non-verbal IQ (NVIQ). As children reach adolescence, this distinction may be even harder to ascertain, especially in naturalistic settings. Narrative may provide a useful, ecologically valid way in which to assess the language ability of adolescents with specific language impairment (SLI) who have intact or lowered NVIQ and to determine whether there is any discernable difference in every day language. Nineteen adolescents with a history of SLI completed two narrative tasks: a story telling condition and a conversational condition. Just under half the group (n = 8) had non-verbal IQs of 85. The remaining 11 had NVIQs in the normal range or above. Four areas of narrative (productivity, syntax, cohesion and performance) were assessed. There were no differences between the groups on standardized tests of language. However, the group with low NVIQ were poorer on most aspects of narrative, suggesting that cognitive level is important, even when language is the primary disorder. The groups showed similar patterns of differences between story telling and conversational narrative. It was concluded that adolescents with a history of SLI and poor cognitive levels have poorer narrative skills than those with normal range NVIQ even though these may not be detected by standardized assessment. Their difficulties present as qualitatively similar to those with normal range NVIQ and narratives appear impoverished rather than inaccurate

The first magnetic maps of a pre-main sequence binary star system - HD 155555

We present the first maps of the surface magnetic fields of a pre-main sequence binary system. Spectropolarimetric observations of the young, 18 Myr, HD 155555 (V824 Ara, G5IV + K0IV) system were obtained at the Anglo-Australian Telescope in 2004 and 2007. Both datasets are analysed using a new binary Zeeman Doppler imaging (ZDI) code. This allows us to simultaneously model the contribution of each component to the observed circularly polarised spectra. Stellar brightness maps are also produced for HD 155555 and compared to previous Doppler images. Our radial magnetic maps reveal a complex surface magnetic topology with mixed polarities at all latitudes. We find rings of azimuthal field on both stars, most of which are found to be non-axisymmetric with the stellar rotational axis. We also examine the field strength and the relative fraction of magnetic energy stored in the radial and azimuthal field components at both epochs. A marked weakening of the field strength of the secondary star is observed between the 2004 and 2007 epochs. This is accompanied by an apparent shift in the location of magnetic energy from the azimuthal to radial field. We suggest that this could be indicative of a magnetic activity cycle. We use the radial magnetic maps to extrapolate the coronal field (by assuming a potential field) for each star individually - at present ignoring any possible interaction. The secondary star is found to exhibit an extreme tilt (~75 deg) of its large scale magnetic field to that of its rotation axis for both epochs. The field complexity that is apparent in the surface maps persists out to a significant fraction of the binary separation. Any interaction between the fields of the two stars is therefore likely to be complex also. Modelling this would require a full binary field extrapolation.Comment: 17 pages, 12 figures, accepted for publication in MNRA

Vocabulary intervention for adolescents with language disorder: a systematic review

Background: Language disorder and associated vocabulary difficulties can persist into adolescence, and can impact on long-term life outcomes. Previous reviews have shown that a variety of intervention techniques can successfully enhance students’ vocabulary skills; however, none has investigated vocabulary intervention specifically for adolescents with language disorder. Aims: To carry out a systematic review of the literature on vocabulary interventions for adolescents with language disorder. Methods & Procedures: A systematic search of 14 databases and other sources yielded 1320 studies, of which 13 met inclusion criteria. Inclusion criteria were: intervention effectiveness studies with a focus on enhancing oral receptive and/or expressive vocabulary skills in the study's aims; participants in the age range 11;0–16;11 with receptive and/or expressive language difficulties of any aetiology. Main Contribution: There was a high degree of diversity between studies. Types of intervention included: semantic intervention (four studies); comparison of phonological versus semantic intervention (two); and combined phonological–semantic intervention (seven). The strongest evidence for effectiveness was found with a combined phonological–semantic approach. The evidence suggested a potential for all models of delivery to be helpful (individual, small group and whole class). Conclusions & Implications: Tentative evidence is emerging for the effectiveness of a phonological–semantic approach in enhancing the vocabulary skills of adolescents who have language disorder. Future research needs to refine and develop the methodologies used in this diverse group of studies in order to replicate their findings and to build consensus

Language and reading development in children learning English as an additional language in primary school in England

Children learning English as an additional language (EAL) are a growing population of learners in English primary schools. These children begin school with differing levels of English language proficiency and tend to underperform in relation to their non‐EAL peers on measures of English oral language and reading. However, little work has examined the developmental trajectories of these skills in EAL learners in England. EAL learners and 33 non‐EAL peers in Year 4 (age 8–9 years) were assessed at three time points over 18 months on measures of oral language (vocabulary, grammar and listening comprehension), phonological processing (spoonerisms and rapid automatised naming) and reading skills (single‐word decoding and passage reading). At t1, EAL learners scored significantly lower than non‐EAL peers in receptive and expressive vocabulary (breadth but not depth), spoonerisms and passage reading accuracy. Contrary to previous research, no significant group differences were found in listening or reading comprehension skills. With the exception of passage reading accuracy, there was no evidence for convergence or divergence between the groups in rate of progress over time. After three years of English‐medium classroom instruction, EAL learners continue to underperform relative to their non‐EAL peers in breadth of English vocabulary knowledge. This discrepancy in vocabulary knowledge does not appear to narrow as a result of regular classroom instruction in the run up to the final stages of primary school, pinpointing vocabulary as a key target for intervention

Limitations of Absolute Current Densities Derived from the Semel & Skumanich Method

Semel and Skumanich proposed a method to obtain the absolute electric current density, |Jz|, without disambiguation of 180 degree in the transverse field directions. The advantage of the method is that the uncertainty in the determination of the ambiguity in the magnetic azimuth is removed. Here, we investigate the limits of the calculation when applied to a numerical MHD model. We found that the combination of changes in the magnetic azimuth with vanishing horizontal field component leads to errors, where electric current densities are often strong. Where errors occur, the calculation gives |Jz| too small by factors typically 1.2 ~ 2.0.Comment: 10 pages, 4 figures. To appear on Science in China Series G: Physics, Mechanics & Astronomy, October 200