Exact density-functional potentials for time-dependent quasiparticles

We calculate the exact Kohn-Sham potential that describes, within time-dependent density-functional theory, the propagation of an electron quasiparticle wavepacket of non-zero crystal momentum added to a ground-state model semiconductor. The potential is observed to have a highly nonlocal functional dependence on the charge density, in both space and time, giving rise to features entirely lacking in local or adiabatic approximations. The dependence of the non-equilibrium part of the Kohn-Sham electric field on the local current and charge density is identified as a key element of the correct Kohn-Sham functional.Comment: 4 pages, 3 figure

Intrinsic exchange-correlation magnetic fields in exact current-density functional theory for degenerate systems

We calculate the exact Kohn-Sham (KS) scalar and vector potentials that reproduce, within current-density functional theory, the steady-state density and current density corresponding to an electron quasiparticle added to the ground state of a model quantum wire. Our results show that, even in the absence of an external magnetic field, a KS description of a steady-state system in general requires a non-zero exchange-correlation magnetic field that is purely mechanical in origin. The KS paramagnetic current density is not, in general, that of the interacting system in any gauge.Comment: 6 pages, 2 figure

Narrative in adolescent specific language impairment (SLI): a comparison with peers across two different narrative genres

Background: Narrative may provide a useful way in which to assess the language ability of adolescents with specific language impairment and may be more ecologically valid than standardized tests. However, the language of this age group is seldom studied and, furthermore, the effect of narrative genre has not been explored in detail. Methods & Procedures: A total of 99 typically developing adolescents and 19 peers with specific language impairment were given two different types of narrative task: a story-telling condition and a conversational condition. Four areas of narrative (productivity, syntactic complexity, syntactic errors and performance) were assessed. Outcomes & Results: The group with specific language impairment was poorer on most aspects of narrative confirming recent research that specific language impairment is a long-term disorder. A number of measures also showed interactions between group and genre, with story-telling proving to be a disproportionately more difficult task for the specific language impairment group. Error analysis also suggested that the specific language impairment group was making qualitatively different errors to the typically developing group, even within a genre. Conclusions: Adolescents with specific language impairment are not only poorer at both types of narrative than peers, but also show different patterns of competence and error, and require more support from the narrative-partner. Clinical Implications: Assessments of adolescents are less frequent than at younger ages. This is partly because of the sparsity of tests available in this age range. Qualitative analysis of narrative might prove a useful alternative. The findings suggest that in every-day conversation, young people with specific language impairment manage their difficulties more discreetly and this might make them harder to identify in a mainstream setting

Myelin basic protein peptide 45–89 induces the release of nitric oxide from microglial cells.

Continuous (24 h) exposure of mixed oligodendrocyte/microglial cells to peptides 45–89 derived from citrullinated C8 isoforms of myelin basic protein (MBP) induces cell death. In contrast, MBP-C8 at the same molecular concentration is not toxic to oligodendrocyte/microglial cells as detected by the MTT test and trypan blue exclusion method. The loss of oligodendrocyte/microglial cells resulted in the release of cytochrome c from mitochondria, suggesting MBP 45–89-induced apoptosis. On the other hand, peptides 45–89 stimulated the secretion of nitric oxide from microglial cells only via induction of iNOS. The addition of peptide 45–89 to the microglial cells led to a decrease of the level of the inhibitory protein IkB, indicating that activation of the transcription factor NF-kB is involved in these processes. We propose that the immunodominant peptide 45–89 induces damage of oligodendrocytes by activation of microglial cells and subsequent generation of nitric oxide, and that this may be the first step in the initiation of autoimmunity

Emotional health in adolescents with and without a history of specific language impairment (SLI)

Objective:  This study examined the emotional health of adolescents with and without specific language impairment (SLI). Method:  One hundred and thirty-nine adolescents with a history of SLI (15;10 years) and a peer group of 124 adolescents with normal language development (NLD) (15;11 years) participated, who were in their final year of compulsory schooling. The risk of emotional difficulties was assessed using the Moods and Feelings Questionnaire (MFQ) and the Child Manifest Anxiety Scale-R (CMAS-R). Comprehensive language and cognition data were available for all participants (NLD and SLI) concurrently and also longitudinally for those with SLI. Results:  A clear increased risk of emotional health symptoms was found for the SLI group on both self- and parental-report. Girls scored less favourably than boys when groups were combined, but these were due to the effect of the NLD group, with no gender differences found in the SLI group. Direct links with language and cognition were not obvious. Instead, more diffuse factors such as family history of emotional health difficulties may warrant further investigation. Conclusion:  There is a marked higher rate of anxiety and depression symptoms in adolescents with SLI. However, these do not appear to be a direct result of impoverished communicative experiences

Electron localisation in static and time-dependent one-dimensional model systems

Electron localization is the tendency of an electron in a many-body system to exclude other electrons from its vicinity. Using a new natural measure of localization based on the exact manyelectron wavefunction, we find that localization can vary considerably between different ground-state systems, and can also be strongly disrupted, as a function of time, when a system is driven by an applied electric field. We use our new measure to assess the well-known electron localization function (ELF), both in its approximate single-particle form (often applied within density-functional theory) and its full many-particle form. The full ELF always gives an excellent description of localization, but the approximate ELF fails in time-dependent situations, even when the exact Kohn-Sham orbitals are employed.Comment: 7 pages, 4 figure

Sensitive imaging of electromagnetic fields with paramagnetic polar molecules

We propose a method for sensitive parallel detection of low-frequency electromagnetic fields based on the fine structure interactions in paramagnetic polar molecules. Compared to the recently implemented scheme employing ultracold $^{87}$Rb atoms [B{\"o}hi \textit{et al.}, Appl. Phys. Lett. \textbf{97}, 051101 (2010)], the technique based on molecules offers a 100-fold higher sensitivity, the possibility to measure both the electric and magnetic field components, and a probe of a wide range of frequencies from the dc limit to the THz regime

Associated reading skills in children with a history of Specific Language Impairment (SLI)

A large cohort of 200 eleven-year-old children with Specific Language Impairment (SLI) were assessed on basic reading accuracy and on reading comprehension as well as language tasks. Reading skills were examined descriptively and in relation to early language and literacy factors. Using stepwise regression analyses in which age and nonverbal IQ were controlled for, it was found that a single word reading measure taken at 7 years was unsurprisingly a strong predictor of the two different types of reading ability. However, even with this measure included, a receptive syntax task (TROG) entered when reading accuracy score was the DV. Furthermore, a test of expressive syntax/narrative and a receptive syntax task completed at 7 years entered into the model for word reading accuracy. When early reading accuracy was excluded from the analyses, early phonological skills also entered as a predictor of both reading accuracy and comprehension at 11 years. The group of children with a history of SLI were then divided into those with no literacy difficulties at 11 and those with some persisting literacy impairment. Using stepwise logistic regression, and again controlling for IQ and age, 7 years receptive syntax score (but not tests of phonology, expressive vocabulary or expressive syntax/narrative) entered as a positive predictor of membership of the ‘no literacy problems’ group regardless of whether early reading accuracy was controlled for in step one. The findings are discussed in relation to the overlap of SLI and dyslexia and the long term sequelae of language impairment