A Physical Model of Warped Galaxy Disks

Warped H I gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure almost certainly arises primarily as a result of differential precession in the H I disk as it settles toward a preferred orientation in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better understand the structure and evolution of these twisted, warped disk structures, we have adopted the "twist-equation" formalism originally developed by Petterson (1977) to study accretion onto compact objects. Utilizing more recent treatments of this formalism, we have generalized the twist-equation to allow for the treatment of non-Keplerian disks and from it have derived a steady-state structure of twisted disks that develops from free precession in a nonspherical, logarithmic halo potential. We have used this steady-state solution to produce H I maps of five galaxies (M83, NGC 300, NGC 2841, NGC 5033, NGC5055), which match the general features of the observed maps of these galaxies quite well. In addition, the model provides an avenue through which the kinematical viscosity of the H I disk and the quadrupole distortion of the dark halo in each galaxy can be quantified. This generalized equation can also be used to examine the time-evolutionary behavior of warped galaxy disks.Comment: 22 pages, 5 figures, to be published in The Astrophysical Journa

Functional Brain Imaging in the Clinical Assessment of Consciousness

Recent findings suggest that functional brain imaging might be used to identify consciousness in patients diagnosed with persistent vegetative state and minimally conscious state. Michael Rafii and James Brewer discuss the potential for fMRI's wider implementation in clinical practice, and associated caveats

Top-down contingent feature-specific orienting with and without awareness of the visual input

In the present article, the role of endogenous feature-specific orienting for conscious and unconscious vision is reviewed. We start with an overview of orienting. We proceed with a review of masking research, and the definition of the criteria of experimental protocols that demonstrate endogenous and exogenous orienting, respectively. Against this background of criteria, we assess studies of unconscious orienting and come to the conclusion that so far studies of unconscious orienting demonstrated endogenous feature-specific orienting. The review closes with a discussion of the role of unconscious orienting in action control

Dos and don’ts in response priming research

Response priming is a well-understood but sparsely employed paradigm in cognitive science. The method is powerful and well-suited for exploring early visuomotor processing in a wide range of tasks and research fields. Moreover, response priming can be dissociated from visual awareness, possibly because it is based on the first sweep of feedforward processing of primes and targets. This makes it a theoretically interesting device for separating conscious and unconscious vision. We discuss the major opportunities of the paradigm and give specific recommendations (e.g., tracing the time-course of priming in parametric experiments). Also, we point out typical confounds, design flaws, and data processing artifacts

Nuclear waste projections and source-term data for FY 1977

A description of the light-water reactor (LWR) fuel cycle and the nature of the radioactive wastes is basic to the design and evaluation of terminal waste repositories. For these projections, the fuel cycle is represented as a typical system of operations related to the back end of the LWR fuel cycle. Wastes, as prepared for disposal, are described in terms of form, volume, radioactivity, heat generation, and weight. To obtain these waste projections, three fuel management computer codes were used: ORIGEN, KWIKPLAN, and WASPR. A brief description of these codes and their usage is included. Also included are descriptions of the containers assumed to be used for the handling and geologic disposal of the various waste types. The data generated for the Office of Waste Isolation (OWI) and its subcontractors are documented. Projections of LWR fuel cycle wastes are based on OWI modification of the ERDA mid-case forecast of 1976 for nuclear power growth in the United States. In this case, the installed nuclear electric capacity rises from a nominal 50 GW(e) in year 1977 to a nominal 480 GW(e) in the year 2000. The power reactor grid is assumed to consist entirely of LWRs. The four basic fuel cycle scenarios considered follow the same growth curve. These fuel cycles range from spent unreprocessed fuel (SURF) through full recycle of both uranium and plutonium. The overall objective is to compare the impacts of the alternative fuel cycles rather than to describe the impacts of reactor growth scenarios or the use of raw materials for power generation

Ascending dose-controlled trial of beloranib, a novel obesity treatment for safety, tolerability, and weight loss in obese women

Objective: Evaluate the safety and tolerability of beloranib, a fumagillin-class methionine aminopetidase-2 (MetAP2) inhibitor, in obese women over 4 weeks