Risk factors for vulnerable youth in urban townships in South Africa: the potential contribution of reactive attachment disorder

Reactive attachment disorder (RAD) is a psychiatric disorder developing in early or middle childhood as a consequence of significant failures in the caregiving environment. RAD results in children failing to relate socially, either by exhibiting markedly inhibited behaviour or by indiscriminate social behaviour and is associated with significant socio-behavioural problems in the longer term. This study examined RAD in South Africa, a setting with high environmental risks. We recruited a sub-sample of 40 10-year-old children from a cohort enrolled during pregnancy for whom early attachment status was known. Children were purposefully selected to represent the four attachment categories using the data available on the strange situation procedure (SSP) at 18 months. The Manchester Child Attachment Story Task (MCAST) assessed current attachment and RAD was diagnosed using a standardised assessment package. A high proportion of the children (5/40% or 12.5%) fulfilled diagnostic criteria for RAD; all were boys and were displaying the disinhibited type. SSP classification at 18 months was not significantly associated with RAD symptoms at age of 10 years, while current MCAST classifications were. This suggests that children in this sample are at much higher risk of RAD than in high-income populations, and despite a fairly typical attachment distribution in this population at 18 months, RAD was evidenced in later childhood and associated with current attachment disorganisation. The strengths of this research include its longitudinal nature and use of diagnostic assessments. Given increasing evidence that RAD is relatively stable over time and introduces longer term socio-behavioural risks; the high rate of RAD in this sample (12.5%) highlights potential developmental threats to children in low- and middle-income countries (LMICs). Our results should be interpreted with caution given sample size and risk of selection bias. Further research is needed to confirm these findings

A Microservice Infrastructure for Distributed Communities of Practice

Non-formal learning in Communities of Practice (CoPs) makes up a significant portion of today’s knowledge gain. However, only little technological support is tailored specifically towards CoPs and their particular strengths and challenges. Even worse, CoPs often do not possess the resources to host or even develop a software ecosystem to support their activities. In this paper, we describe a distributed, microservice-based Web infrastructure for non-formal learning in CoPs. It mitigates the need for central infrastructures, coordination or facilitation and takes into account the constant change of these communities. As a real use case, we implement an inquiry-based learning application on-top of our infrastructure. Our evaluation results indicate the usefulness of this learning application, which shows promise for future work in the domain of community-hosted, microservice-based Web infrastructures for learning outside of formal settings

Association between changes in knee load and effusion-synovitis: evidence of mechano-inflammation in knee osteoarthritis using high tibial osteotomy as a model

Objective: Although mechanically-induced inflammation is an appealing explanation linking different etiologic factors in osteoarthritis (OA), clinical research investigating changes in both biomechanics and joint inflammation is limited. The purpose of this study was to evaluate the association between change in surrogate measures of knee load and knee effusion-synovitis in patients with medial compartment knee OA undergoing high tibial osteotomy (HTO). Methods: Thirty-six patients with medial compartment knee OA and varus alignment underwent 3D gait analysis and 3T magnetic resonance imaging (MRI) preoperatively and 1 year after medial opening wedge HTO. Primary outcome measures were the change in the external knee adduction moment impulse during walking and change in knee suprapatellar effusion-synovitis volume manually segmented on MRI by one blinded assessor. Results: Mean (SD) knee adduction moment impulse [24.0 (6.5) Nm•s] and knee effusion-synovitis volume [8976.7 (8016.9) mm3] suggested substantial preoperative medial knee load and inflammation. 1-year postoperative changes in knee adduction moment impulse [−10.1 Nm•s (95%CI: −12.7, −7.4)], and knee effusion-synovitis volume [−1856 mm3 (95%CI: −3830, 117)] were positively correlated [r = 0.60 (95% CI 0.34, 0.78)]. Simple linear regression suggested a 448 mm3 (95%CI: 241, 656) reduction in knee effusion-synovitis volume per 1 Nm•s reduction in knee adduction moment impulse. Change in knee adduction moment impulse explained 36% (R2 = 0.36) of the variance of change in knee effusion-synovitis volume. Conclusions: Reduction in medial knee load is positively associated with reduction in knee inflammation after HTO, suggesting the phenomenon of mechano-inflammation in patients with knee OA

Simulating open quantum systems: from many-body interactions to stabilizer pumping

In a recent experiment, Barreiro et al. demonstrated the fundamental building blocks of an open-system quantum simulator with trapped ions [Nature 470, 486 (2011)]. Using up to five ions, single- and multi-qubit entangling gate operations were combined with optical pumping in stroboscopic sequences. This enabled the implementation of both coherent many-body dynamics as well as dissipative processes by controlling the coupling of the system to an artificial, suitably tailored environment. This engineering was illustrated by the dissipative preparation of entangled two- and four-qubit states, the simulation of coherent four-body spin interactions and the quantum non-demolition measurement of a multi-qubit stabilizer operator. In the present paper, we present the theoretical framework of this gate-based ("digital") simulation approach for open-system dynamics with trapped ions. In addition, we discuss how within this simulation approach minimal instances of spin models of interest in the context of topological quantum computing and condensed matter physics can be realized in state-of-the-art linear ion-trap quantum computing architectures. We outline concrete simulation schemes for Kitaev's toric code Hamiltonian and a recently suggested color code model. The presented simulation protocols can be adapted to scalable and two-dimensional ion-trap architectures, which are currently under development.Comment: 27 pages, 9 figures, submitted to NJP Focus on Topological Quantum Computatio

Soliton-Like Solutions of the Grad-Shafranov Equation

A new class of soliton-like solutions is derived for the Grad-Shafranov (GS) equations. A mathematical analogy between the GS equation for MHD equilibria and the cubic Schr\"odinger (CS) equation for non-linear wave propagation forms the basis to derive the new class of solutions. The soliton-like solutions are considered for their possible relevance to astrophysics and solar physics problems. We discuss how a soliton-like solution can be generated by a repetitive process of magnetic arcade stretching and plasmoid formation induced by the differential rotation of the solar photosphere or of an accretion disk.Comment: Accepted for publication on Physical Review Letter

Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence

Using kinetic particle-in-cell (PIC) simulations, we simulate reconnection conditions appropriate for the magnetosheath and solar wind, i.e., plasma beta (ratio of gas pressure to magnetic pressure) greater than 1 and low magnetic shear (strong guide field). Changing the simulation domain size, we find that the ion response varies greatly. For reconnecting regions with scales comparable to the ion Larmor radius, the ions do not respond to the reconnection dynamics leading to ''electron-only'' reconnection with very large quasi-steady reconnection rates. The transition to more traditional ''ion-coupled'' reconnection is gradual as the reconnection domain size increases, with the ions becoming frozen-in in the exhaust when the magnetic island width in the normal direction reaches many ion inertial lengths. During this transition, the quasi-steady reconnection rate decreases until the ions are fully coupled, ultimately reaching an asymptotic value. The scaling of the ion outflow velocity with exhaust width during this electron-only to ion-coupled transition is found to be consistent with a theoretical model of a newly reconnected field line. In order to have a fully frozen-in ion exhaust with ion flows comparable to the reconnection Alfv\'en speed, an exhaust width of at least several ion inertial lengths is needed. In turbulent systems with reconnection occurring between magnetic bubbles associated with fluctuations, using geometric arguments we estimate that fully ion-coupled reconnection requires magnetic bubble length scales of at least several tens of ion inertial lengths

Schizophrenia-risk variant rs6994992 in the neuregulin-1 gene on brain developmental trajectories in typically developing children

The neuregulin-1 (NRG1) gene is one of the best-validated risk genes for schizophrenia, and psychotic and bipolar disorders. The rs6994992 variant in the NRG1 promoter (SNP8NRG243177) is associated with altered frontal and temporal brain macrostructures and/or altered white matter density and integrity in schizophrenic adults, as well as healthy adults and neonates. However, the ages when these changes begin and whether neuroimaging phenotypes are associated with cognitive performance are not fully understood. Therefore, we investigated the association of the rs6994992 variant on developmental trajectories of brain macro- and microstructures, and their relationship with cognitive performance. A total of 972 healthy children aged 3–20 years had the genotype available for the NRG1-rs6994992 variant, and were evaluated with magnetic resonance imaging (MRI) and neuropsychological tests. Age-by-NRG1-rs6994992 interactions and genotype effects were assessed using a general additive model regression methodology, covaried for scanner type, socioeconomic status, sex and genetic ancestry factors. Compared with the C-carriers, children with the TT-risk-alleles had subtle microscopic and macroscopic changes in brain development that emerge or reverse during adolescence, a period when many psychiatric disorders are manifested. TT-children at late adolescence showed a lower age-dependent forniceal volume and lower fractional anisotropy; however, both measures were associated with better episodic memory performance. To our knowledge, we provide the first multimodal imaging evidence that genetic variation in NRG1 is associated with age-related changes on brain development during typical childhood and adolescence, and delineated the altered patterns of development in multiple brain regions in children with the T-risk allele(s)

Modelling the radio pulses of an ultracool dwarf

<b>Context:</b> Recently, unanticipated magnetic activity in ultracool dwarfs (UCDs, spectral classes later than M7) has emerged from a number of radio observations. The highly (up to 100%) circularly polarized nature and high brightness temperature of the emission have been interpreted as requiring an effective amplification mechanism of the high-frequency electromagnetic waves − the electron cyclotron maser instability (ECMI). <p/><b>Aims:</b> We aim to understand the magnetic topology and the properties of the radio emitting region and associated plasmas in these ultracool dwarfs, interpreting the origin of radio pulses and their radiation mechanism. <p/><b>Methods:</b> An active region model was built, based on the rotation of the UCD and the ECMI mechanism. <p/><b>Results:</b> The high degree of variability in the brightness and the diverse profile of pulses can be interpreted in terms of a large-scale hot active region with extended magnetic structure existing in the magnetosphere of TVLM 513-46546. We suggest the time profile of the radio light curve is in the form of power law in the model. Combining the analysis of the data and our simulation, we can determine the loss-cone electrons have a density in the range of 1.25 × 105−5 × 105 cm-3 and temperature between 107 and 5 × 107 K. The active region has a size <1 RJup, while the pulses produced by the ECMI mechanism are from a much more compact region (e.g. ~0.007 RJup). A surface magnetic field strength of ≈7000 G is predicted. <p/><b>Conclusions:</b> The active region model is applied to the radio emission from TVLM 513-46546, in which the ECMI mechanism is responsible for the radio bursts from the magnetic tubes and the rotation of the dwarf can modulate the integral of flux with respect to time. The radio emitting region consists of complicated substructures. With this model, we can determine the nature (e.g. size, temperature, density) of the radio emitting region and plasma. The magnetic topology can also be constrained. We compare our predicted X-ray flux with Chandra X-ray observation of TVLM 513-46546. Although the X-ray detection is only marginally significant, our predicted flux is significantly lower than the observed flux. Further multi-wavelength observations will help us better understand the magnetic field structure and plasma behavior on the ultracool dwarf

3D Magnetic Reconnection with a spatially confined X-line extent -- Implications for Dipolarizing Flux Bundles and the Dawn-Dusk Asymmetry

Using 3D particle-in-cell (PIC) simulations, we study magnetic reconnection with the x-line being spatially confined in the current direction. We include thick current layers to prevent reconnection at two ends of a thin current sheet that has a thickness on an ion inertial (di) scale. The reconnection rate and outflow speed drop significantly when the extent of the thin current sheet in the current direction is < O(10 di). When the thin current sheet extent is long enough, we find it consists of two distinct regions; an inactive region (on the ion-drifting side) exists adjacent to the active region where reconnection proceeds normally as in a 2D case. The extent of this inactive region is ~ O(10 di), and it suppresses reconnection when the thin current sheet extent is comparable or shorter. The time-scale of current sheet thinning toward fast reconnection can be translated into the spatial-scale of this inactive region; because electron drifts inside the ion diffusion region transport the reconnected magnetic flux, that drives outflows and furthers the current sheet thinning, away from this region. This is a consequence of the Hall effect in 3D. While this inactive region may explain the shortest possible azimuthal extent of dipolarizing flux bundles at Earth, it may also explain the dawn-dusk asymmetry observed at the magnetotail of Mercury, that has a global dawn-dusk extent much shorter than that of Earth.Comment: 9 pages, 9 figures, submitted to JGR on 01/23/201