Microsaccades and Visual-Spatial Working Memory

Observers performed working memory tasks at varying retinal eccentricities, fixating centrally while microsaccade rates and directions were monitored. We show that microsaccades generate no interference in a working memory task, indicating that spatial working memory is at least partially insulated from oculomotor activity. Intervening tasks during the memory interval affected memory as well as microsaccade patterns. Average microsaccade rate peaks after appearance of a fixation cross at the start of a trial, and dips at cue onset and offset. Direction of stimuli in choice tasks did not influence micro-saccade direction, however. Poorer memory accuracy for locations at greater retinal eccentricity calls for revising ideas of short-term spatial representations to include retinotopic or allocentric code

Visual vs. Spatial Contributions to Microsaccades and Visual-Spatial Working Memory

Microsaccade rates and directions were monitored while observers performed a visual working memory task at varying retinal eccentricities. We show that microsaccades generate no interference in a working memory task, indicating that spatial working memory is at least partially insulated from oculomotor activity. Intervening tasks during the memory interval affected microsaccade patterns; microsaccade frequency was consistently higher during concurrent spatial tapping (no visual component) than during exposure to dynamic visual noise (no task). Average microsaccade rate peaked after appearance of a fixation cross at the start of a trial, and dipped at cue onset and offset, consistent with previous results. Direction of stimuli in choice tasks did not influence microsaccade direction,however

Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO2_2

By evaluating multipole susceptibility of a seven-orbital impurity Anderson model with the use of a numerical renormalization group method, we discuss possible multipole states of actinide dioxides at low temperatures. In particular, here we point out a possible scenario for multipole ordering in americium dioxide. For Am$^{4+}$ ion with five $5f$ electrons, it is considered that the ground state is $\Gamma_7^{-}$ doublet and the first excited state is $\Gamma_8^{-}$ quartet, but we remark that the $f^5$ ground state is easily converted due to the competition between spin-orbit coupling and Coulomb interactions. Then, we find that the $\Gamma_8^-$ quartet can be the ground state of AmO$_2$ even for the same crystalline electric field potential. In the case of $\Gamma_8^-$ quartet ground state, the numerical results suggest that high-order multipoles such as quadrupole and octupole can be relevant to AmO$_2$.Comment: 8 pages, 4 figures. To appear in Phys. Rev.

Probabilistic Analysis of Power Network Susceptibility to GICs

As reliance on power networks has increased over the last century, the risk of damage from geomagnetically induced currents (GICs) has become a concern to utilities. The current state of the art in GIC modelling requires significant geophysical modelling and a theoretically derived network response, but has limited empirical validation. In this work, we introduce a probabilistic engineering step between the measured geomagnetic field and GICs, without needing data about the power system topology or the ground conductivity profiles. The resulting empirical ensembles are used to analyse the TVA network (south-eastern USA) in terms of peak and cumulative exposure to 5 moderate to intense geomagnetic storms. Multiple nodes are ranked according to susceptibility and the measured response of the total TVA network is further calibrated to existing extreme value models. The probabilistic engineering step presented can complement present approaches, being particularly useful for risk assessment of existing transformers and power systems.Comment: 6 pages, 7 figures, accepted for PMAPS 202

Improvement in the modelling of geomagnetically induced currents in Southern Africa

One of the consequences of the geomagnetic storms resulting from adverse space weather is the induction of geomagnetically induced currents (GICs) in power lines. The GICs that flow in a power transmission network are driven by the induced electric field at the Earth's surface. The electric field, in turn, is affected by the changing magnetic field during a magnetic storm. These GICs can cause extensive and expensive damage to transformers in the power transmission system. Understanding the behaviour of the magnetic field during a magnetic storm is a crucial step in modelling and predicting the electric field and ultimately the GICs in a power transmission network. We present a brief overview of the present status of GIC modelling in southern Africa and then discuss whether it is sufficient to use geomagnetic data from a single magnetic observatory alone to model GICs over the subcontinent. A geomagnetic interpolation method is proposed to improve the modelling of GICs in southern Africa. This improved model is one step closer to our being able to predict GICs accurately in the subcontinent, which will enable power distribution companies to take the necessary precautions to minimize possible transformer damage

The Universlity Class of Monopole Condensation in Non-Compact, Quenched Lattice QED

Finite size scaling studies of monopole condensation in noncompact quenched lattice $QED$ indicate an authentic second order phase transition lying in the universality class of four dimensional percolation. Since the upper critical dimension of percolation is six, the measured critical indices are far from mean-field values. We propose a simple set of ratios as the exact critical indices for this transition. The implication of these results for critical points in Abelian gauge theories are discussed.Comment: ILL-(TH)-92-6, CERN-TH.6515/92, 10 pages, no figures available as PS fil

The REBOA window: a cadaveric study delineating the optimum site for austere cannulation of the femoral artery for resuscitative endovascular balloon occlusion of the aorta

Introduction: Haemorrhage is the major cause of early mortality following traumatic injury. Patients suffering from non-compressible torso haemorrhage are more likely to suffer early death. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) can be effective in initial resuscitation; however, establishing swift arterial access is challenging, particularly in a severe shock. This is made more difficult by anatomical variability of the femoral vessels. Methods: The femoral vessels were characterised in 81 cadaveric lower limbs, measuring specifically the distance from the inferior border of the inguinal ligament to the distal part of the origin of the profunda femoris artery (PFA), and from the distal part of the origin of the PFA to where the femoral vein lies posterior to and is completely overlapped by the femoral artery. Results: The femoral vein lay deep to the femoral artery at a mean distance of 105 mm from the inferior border of the inguinal ligament. The PFA arose from the femoral artery at a mean distance of 51.1 mm from the inguinal ligament. From the results, it is predicted that the PFA originates from the common femoral artery approximately 24 mm from the inguinal ligament, and the femoral vein is completely overlapped by the femoral artery by 67.7 mm distal from the inguinal ligament, in 95% of subjects. Conclusions: Based on the results, proposed is an ‘optimal access window’ of up to 24 mm inferior to the inguinal ligament for common femoral arterial catheterisation for pre-hospital REBOA, or more simply within one finger breadth