Event-related potentials as indirect measures of recognition memory

Event-related potentials (ERPs) were recorded during an auditory word-recognition task to determine whether they can be used as indirect measures of recognition memory, defined as the ability to differentiate learned from unlearned material when no overt recognition response from the subject is required. A modified version of the two-choice reaction time task developed by Allen, Iacono and Danielson (Allen et al., 1992) was used. In three recognition tasks, administered on two consecutive days, subjects were instructed to indicate recognition of recently learned words. These words were presented along with unlearned words and along with previously learned words which both required a non-recognition response. Recently learned target words as well as previously learned nontarget words elicited a centro-parietal positivity around 500-1000 ms post-stimulus. The size and onset of this late positivity (P300) were affected by the requirement of an overt recognition response. The results suggest that ERPs are sensitive to differences between learned and unlearned words, to some extent independently of the behavioral response. ERPs may therefore be used as indirect measures of recognition memory. In addition, because the present results held for stimuli presented in the auditory modality and because recognition indices were still observed after a one-day interval between learning and testing, this procedure might prove useful in various applications when the integrity of memory is in question

Transverse instability and its long-term development for solitary waves of the (2+1)-Boussinesq equation

The stability properties of line solitary wave solutions of the (2+1)-dimensional Boussinesq equation with respect to transverse perturbations and their consequences are considered. A geometric condition arising from a multi-symplectic formulation of this equation gives an explicit relation between the parameters for transverse instability when the transverse wavenumber is small. The Evans function is then computed explicitly, giving the eigenvalues for transverse instability for all transverse wavenumbers. To determine the nonlinear and long time implications of transverse instability, numerical simulations are performed using pseudospectral discretization. The numerics confirm the analytic results, and in all cases studied, transverse instability leads to collapse.Comment: 16 pages, 8 figures; submitted to Phys. Rev.

Back-flow ripples in troughs downstream of unit bars: Formation, preservation and value for interpreting flow conditions

Back-flow ripples are bedforms created within the lee-side eddy of a larger bedform with migration directions opposed or oblique to that of the host bedform. In the flume experiments described in this article, back-flow ripples formed in the trough downstream of a unit bar and changed with mean flow velocity; varying from small incipient back-flow ripples at low velocities, to well-formed back-flow ripples with greater velocity, to rapidly migrating transient back-flow ripples formed at the greatest velocities tested. In these experiments back-flow ripples formed at much lower mean back-flow velocities than predicted from previously published descriptions. This lower threshold mean back-flow velocity is attributed to the pattern of velocity variation within the lee-side eddy of the host bedform. The back-flow velocity variations are attributed to vortex shedding from the separation zone, wake flapping and increases in the size of, and turbulent intensity within, the flow separation eddy controlled by the passage of superimposed bedforms approaching the crest of the bar. Short duration high velocity packets, whatever their cause, may form back-flow ripples if they exceed the minimum bed shear stress for ripple generation for long enough or, if much faster, may wash them out. Variation in back-flow ripple cross-lamination has been observed in the rock record and, by comparison with flume observations, the preserved back-flow ripple morphology may be useful for interpreting formative flow and sediment transport dynamics

Anaesthetic hazards of the 'passion gap' A case report

Dental abnormalities cause problems for both dentist and anaesthetist. The anaesthetic hazards associated with the 'passion gap' - a term used in the western Cape Province for removal of the top four incisor teeth, a practice widespread among members ot the Cape Coloured community - are discussed. Recommendations are made to assist the anaesthetist when dealing with such a patient

Soft range information for network localization

The demand for accurate localization in complex environments continues to increase despite the difficulty in extracting positional information from measurements. Conventional range-based localization approaches rely on distance estimates obtained from measurements (e.g., delay or strength of received waveforms). This paper goes one step further and develops localization techniques that rely on all probable range values rather than on a single estimate of each distance. In particular, the concept of soft range information (SRI) is introduced, showing its essential role for network localization. We then establish a general framework for SRI-based localization and develop algorithms for obtaining the SRI using machine learning techniques. The performance of the proposed approach is quantified via network experimentation in indoor environments. The results show that SRI-based localization techniques can achieve performance approaching the Cramer–Rao lower bound and significantly outperform the conventional techniques especially in harsh wireless environments.RYC-2016-1938

Convective Vortices on Mars: A Reanalysis of Viking Lander 2 Meteorological Data, Sols 1-50

On 7th August 1976 the Viking 2 lander touched down at Utopia Planitia, Mars. We have reanalysed Viking lander 2 meteorological data, and it is the object of this research to give not only annual but diurnal statistics of convective vortex formation for the Viking 2 landing site

Entanglement of photons

It is argued that the title of this paper represents a misconception. Contrary to widespread beliefs it is electromagnetic field modes that are ``systems'' and can be entangled, not photons. The amount of entanglement in a given state is shown to depend on redefinitions of the modes; we calculate the minimum and maximum over all such redefinitions for several examples.Comment: 5 pages ReVTe