Reconstrucing Richard Epstein

Presented at the 2005 Brigham-Kanner Property Rights Conference

A revised definition for copal and its significance for palaeontological and Anthropocene biodiversity‑loss studies

The early fossilization steps of natural resins and associated terminology are a subject of constant debate. Copal and resin are archives of palaeontological and historical information, and their study is critical to the discovery of new and/or recently extinct species and to trace changes in forests during the Holocene. For such studies, a clear, suitable definition for copal is vital and is herein established. We propose an age range for copal (2.58 Ma¿1760 AD), including Pleistocene and Holocene copals, and the novel term 'Defaunation resin', defined as resin produced after the commencement of the Industrial Revolution. Defaunation resin is differentiated from Holocene copal as it was produced during a period of intense human transformative activities. Additionally, the 'Latest Amber Bioinclusions Gap' (LABG) since the late Miocene to the end of the Pleistocene is hereby newly defined, and is characterized by its virtual absence of bioinclusions and the consequent lack of palaeontological information, which in part explains the historical differentiation between amber and copal. Crucial time intervals in the study of resin production, and of the biodiversity that could be contained, are now clarified, providing a framework for and focusing future research on bioinclusions preserved in copal and resin

Naturalistic visualization of reaching movements using head-mounted displays improves movement quality compared to conventional computer screens and proves high usability.

BACKGROUND The relearning of movements after brain injury can be optimized by providing intensive, meaningful, and motivating training using virtual reality (VR). However, most current solutions use two-dimensional (2D) screens, where patients interact via symbolic representations of their limbs (e.g., a cursor). These 2D screens lack depth cues, potentially deteriorating movement quality and increasing cognitive load. Head-mounted displays (HMDs) have great potential to provide naturalistic movement visualization by incorporating improved depth cues, reduce visuospatial transformations by rendering movements in the space where they are performed, and preserve eye-hand coordination by showing an avatar-with immersive VR (IVR)-or the user's real body-with augmented reality (AR). However, elderly populations might not find these novel technologies usable, hampering potential motor and cognitive benefits. METHODS We compared movement quality, cognitive load, motivation, and system usability in twenty elderly participants (>59 years old) while performing a dual motor-cognitive task with different visualization technologies: IVR HMD, AR HMD, and a 2D screen. We evaluated participants' self-reported cognitive load, motivation, and usability using questionnaires. We also conducted a pilot study with five brain-injured patients comparing the visualization technologies while using an assistive device. RESULTS Elderly participants performed straighter, shorter duration, and smoother movements when the task was visualized with the HMDs than screen. The IVR HMD led to shorter duration movements than AR. Movement onsets were shorter with IVR than AR, and shorter for both HMDs than the screen, potentially indicating facilitated reaction times due to reduced cognitive load. No differences were found in the questionnaires regarding cognitive load, motivation, or usability between technologies in elderly participants. Both HMDs proved high usability in our small sample of patients. CONCLUSIONS HMDs are a promising technology to be incorporated into neurorehabilitation, as their more naturalistic movement visualization improves movement quality compared to conventional screens. HMDs demonstrate high usability, without decreasing participants' motivation, and might potentially lower cognitive load. Our preliminary clinical results suggest that brain-injured patients may especially benefit from more immersive technologies. However, larger patient samples are needed to draw stronger conclusions.*

The variable radio-to-X-ray spectrum of the magnetar XTE J1810-197

We have observed the 5.54s anomalous X-ray pulsar XTE J1810-197 at radio, millimeter, and infrared (IR) wavelengths, with the aim of learning about its broad-band spectrum. At the IRAM 30m telescope, we have detected the magnetar at 88 and 144GHz, the highest radio-frequency emission ever seen from a pulsar. At 88GHz we detected numerous individual pulses, with typical widths ~2ms and peak flux densities up to 45Jy. Together with nearly contemporaneous observations with the Parkes, Nancay, and Green Bank telescopes, we find that in late 2006 July the spectral index of the pulsar was -0.5<alpha<0 over the range 1.4-144GHz. Nine dual-frequency Very Large Array and Australia Telescope Compact Array observations in 2006 May-September are consistent with this finding, while showing variability of alpha with time. We infer from the IRAM observations that XTE J1810-197 remains highly linearly polarized at millimeter wavelengths. Also, toward this pulsar, the transition frequency between strong and weak scattering in the interstellar medium may be near 50GHz. At Gemini, we detected the pulsar at 2.2um in 2006 September, at the faintest level yet observed, K_s=21.89+-0.15. We have also analyzed four archival IR Very Large Telescope observations (two unpublished), finding that the brightness fluctuated within a factor of 2-3 over a span of 3 years, unlike the monotonic decay of the X-ray flux. Thus, there is no correlation between IR and X-ray flux, and it remains uncertain whether there is any correlation between IR and radio flux.Comment: Accepted for publication in ApJ; contains improved discussion of infrared uncertaintie