It\u27s Not All in Your Head (or at Least Your Brain): Association of Traumatic Brain Lesion Presence and Location with Performance on Measures of Response Bias in Forensic Evaluation

This study examined the relationship between lesion presence and localization and performance on measures of cognitive response bias, specifically in individuals purporting to have a traumatic brain injury. Ninety-two participants, all of whom were involved in workers’ compensation or personal injury litigation, were administered an extensive neuropsychological battery, including neuroimaging (magnetic resonance imaging and computed tomography), at a neuropsychiatric clinic in Lexington, KY. Those with evidence of intracranial injury on neuroimaging findings were placed in the head injury lesion litigation group and were coded based on the anatomical location and type of intracranial injury. Results demonstrated no significant relationships between lesion location and performance on performance validity tests (PVTs), as well as the Response Bias Scale of the Minnesota Multiphasic Personality Inventory-2 Restructured Form. Given the lack of research concerning lesions and performance validity tests, this study addresses important questions about the validity of PVTs as specific measures of response bias in patients who have structural changes secondary to traumatic brain injury. Copyright#2013 John Wiley & Sons, Ltd

Effect of temperature anisotropy on various modes and instabilities for a magnetized non-relativistic bi-Maxwellian plasma

Using kinetic theory for homogeneous collisionless magnetized plasmas, we present an extended review of the plasma waves and instabilities and discuss the anisotropic response of generalized relativistic dielectric tensor and Onsager symmetry properties for arbitrary distribution functions. In general, we observe that for such plasmas only those electromagnetic modes whose magnetic field perturbations are perpendicular to the ambient magneticeld, i.e.,B1 \perp B0, are effected by the anisotropy. However, in oblique propagation all modes do show such anisotropic effects. Considering the non-relativistic bi-Maxwellian distribution and studying the relevant components of the general dielectric tensor under appropriate conditions, we derive the dispersion relations for various modes and instabilities. We show that only the electromagnetic R- and L- waves, those derived from them and the O-mode are affected by thermal anisotropies, since they satisfy the required condition B1\perpB0. By contrast, the perpendicularly propagating X-mode and the modes derived from it (the pure transverse X-mode and Bernstein mode) show no such effect. In general, we note that the thermal anisotropy modifies the parallel propagating modes via the parallel acoustic effect, while it modifies the perpendicular propagating modes via the Larmor-radius effect. In oblique propagation for kinetic Alfven waves, the thermal anisotropy affects the kinetic regime more than it affects the inertial regime. The generalized fast mode exhibits two distinct acoustic effects, one in the direction parallel to the ambient magnetic field and the other in the direction perpendicular to it. In the fast-mode instability, the magneto-sonic wave causes suppression of the firehose instability. We discuss all these propagation characteristics and present graphic illustrations

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products

Highly structured slow solar wind emerging from an equatorial coronal hole

International audienceDuring the solar minimum, when the Sun is at its least active, the solar wind(1,2) is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvenic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind(3) of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain(4); theories and observations suggest that they may originate at the tips of helmet streamers(5,6), from interchange reconnection near coronal hole boundaries(7,8), or within coronal holes with highly diverging magnetic fields(9,10). The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfven-wave turbulence(11,12), heating by reconnection in nanoflares(13), ion cyclotron wave heating(14) and acceleration by thermal gradients1. At a distance of one astronomical unit, the wind is mixed and evolved, and therefore much of the diagnostic structure of these sources and processes has been lost. Here we present observations from the Parker Solar Probe(15) at 36 to 54 solar radii that show evidence of slow Alfvenic solar wind emerging from a small equatorial coronal hole. The measured magnetic field exhibits patches of large, intermittent reversals that are associated with jets of plasma and enhanced Poynting flux and that are interspersed in a smoother and less turbulent flow with a near-radial magnetic field. Furthermore, plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities(10,16) that are associated with plasma heating and thermalization processes. Our measurements suggest that there is an impulsive mechanism associated with solar-wind energization and that micro-instabilities play a part in heating, and we provide evidence that low-latitude coronal holes are a key source of the slow solar wind

Satellite Observations of Separator Line Geometry of Three-Dimensional Magnetic Reconnection

Detection of a separator line that connects magnetic nulls and the determination of the dynamics and plasma environment of such a structure can improve our understanding of the three-dimensional (3D) magnetic reconnection process. However, this type of field and particle configuration has not been directly observed in space plasmas. Here we report the identification of a pair of nulls, the null-null line that connects them, and associated fans and spines in the magnetotail of Earth using data from the four Cluster spacecraft. With di and de designating the ion and electron inertial lengths, respectively, the separation between the nulls is found to be ~0.7di and an associated oscillation is identified as a lower hybrid wave with wavelength ~ de. This in situ evidence of the full 3D reconnection geometry and associated dynamics provides an important step toward to establishing an observational framework of 3D reconnection.Comment: 10 pages, 3 figures and 1 tabl