Leber's Hereditary Optic Neuropathy: A Case Report

Leber's hereditary optic neuropathy (LHON) is a maternally inherited mitochondrial disease that primarily affects the optic nerve, causing bilateral vision loss in juveniles and young adults. A 12-year-old boy had complained of blurred vision in both eyes for more than 1 year. His best-corrected visual acuity was 0.08 in the right eye and 0.1 in the left. Ophthalmologic examination showed bilateral optic disc hyperemia and margin blurring, peripapillary telangiectasis, and a relative afferent pupil defect in his right eye. Fluorescein angiography showed no stain or leakage around the optic disc in the late phase. Visual field analysis showed central scotoma in the left eye and a near-total defect in the right. Upon examination of the patient's mitochondrial DNA, a point mutation at nucleotide position 11778 was found, and the diagnosis of LHON was confirmed. Coenzyme Q10 was used to treat the patient

Probing gravitational non-minimal coupling with dark energy surveys

We investigate observational constraints on a specific one-parameter extension to the minimal quintessence model, where the quintessence field acquires a quadratic coupling to the scalar curvature through a coupling constant $\xi$. The value of $\xi$ is highly suppressed in typical tracker models if the late-time cosmic acceleration is driven at some field values near the Planck scale. We test $\xi$ in a second class of models in which the field value today becomes a free model parameter. We use the combined data from type-Ia supernovae, cosmic microwave background, baryon acoustic oscillations and matter power spectrum, to weak lensing measurements and find a best-fit value $\xi > 0.289$ where $\xi = 0$ is excluded outside the 95 per cent confidence region. The effective gravitational constant $G_{\rm eff}$ subject to the hint of a non-zero $\xi$ is constrained to $-0.003 < 1- G_{\rm eff}/G < 0.033$ at the same confidence level on cosmological scales, and can be narrowed down to $1- G_{\rm eff}/G < 2.2 \times 10^{-5}$ when combining with Solar System tests.Comment: Context extended, figures and references added, title changed to match with accepted version for publicatio

A process-driven approach to the understanding of developmental differences in cognitive flexibility in young children and adults

The ability to update one’s goal in a changing environment and adapt actions accordingly is often thought to reflect cognitive flexibility. Early childhood, from 3 to 6 years of age, is witness to a large improvement in this ability. In real life, environmental changes can be incredibly dynamic and fast, thus flexible behaviours need to happen in a timely manner. Moreover, attention operates in a multisensory environment so switching between tasks is often carried out cross-modally (e.g. stop doing the colouring exercise and put the story books away when being told to). Developmental studies with young children have generally focused on specific aspects of how the switch is initiated, if at all, in a unimodal, highly controlled framework. This approach may miss out aspects of task switching important for understanding cognitive flexibility in a wider context that relates better to real-world dynamics. Thus, the current thesis investigates young children’s task switching abilities in a temporally-driven and multisensory context. My thesis combines two approaches: (1) behavioural experiments with children and adults, and (2) computational modelling. Three behavioural experiments were carried out with 4-year-olds, 6-year-olds and adults. These experiments were unimodal task-switching (UTS), cross-modal task-switching with bimodal stimuli (bimodal CMTS) and cross-modal task-switching with unimodal stimuli (unimodal CMTS) respectively. In the cross-modal experiments, not only did the participants have to switch between tasks, but the stimuli associated with the tasks could be either visual or auditory. Past research has suggested that young children can exhibit cross-modal attention effects different from those observed in adults (e.g. modality dominance). However, it remains unclear how the developmental differences in cross-modal attention manifest in a highly task-oriented context. The task-switching procedures in these experiments draw heavily from established adult taskswitching paradigms. The computational models followed the principles of Interactive Activation as described in Gilbert and Shallice (2002). These are connectionist networks with units and connections between the units. The models were used to understand the behavioural results in the bimodal CMTS experiment. A series of computational models are used to understand what factors affect performance on different trial types, how task representations and responses can be triggered proactively and reactively, and how variations in performance can be modelled using a population modelling approach. The thesis combines the current understanding of the development of cognitive control with the literature on information processes in task-switching. Finally, the thesis proposes answers to questions such as what behaviours/measures are reflective of the development of cognitive function or constraints, of information processes associated with specific tasks, and of the inter-individual differences present at different ages

Robust Intrinsic Ferromagnetism and Half Semiconductivity in Stable Two-Dimensional Single-Layer Chromium Trihalides

Two-dimensional (2D) intrinsic ferromagnetic (FM) semiconductors are crucial to develop low-dimensional spintronic devices. Using density functional theory, we show that single-layer chromium trihalides (SLCTs) (CrX$_3$,X=F, Cl, Br and I) constitute a series of stable 2D intrinsic FM semiconductors. A free-standing SLCT can be easily exfoliated from the bulk crystal, due to a low cleavage energy and a high in-plane stiffness. Electronic structure calculations using the HSE06 functional indicate that both bulk and single-layer CrX$_3$ are half semiconductors with indirect gaps and their valence bands and conduction bands are fully spin-polarized in the same spin direction. The energy gaps and absorption edges of CrBr$_3$ and CrI$_3$ are found to be in the visible frequency range, which implies possible opt-electronic applications. Furthermore, SLCTs are found to possess a large magnetic moment of 3$\mu_B$ per formula unit and a sizable magnetic anisotropy energy. The magnetic exchange constants of SLCTs are then extracted using the Heisenberg spin Hamiltonian and the microscopic origins of the various exchange interactions are analyzed. A competition between a near 90$^\circ$ FM superexchange and a direct antiferromagnetic (AFM) exchange results in a FM nearest-neighbour exchange interaction. The next and third nearest-neighbour exchange interactions are found to be FM and AFM respectively and this can be understood by the angle-dependent extended Cr-X-X-Cr superexchange interaction. Moreover, the Curie temperatures of SLCTs are also predicted using Monte Carlo simulations and the values can further increase by applying a biaxial tensile strain. The unique combination of robust intrinsic ferromagnetism, half semiconductivity and large magnetic anisotropy energies renders the SLCTs as promising candidates for next-generation semiconductor spintronic applications.Comment: 12 pages, 14 figures. published in J. Mater. Chem.

Sosiaalisten ohjelmistojen käytön hyväksyminen

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Co-embedding attributed networks with external knowledge

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