Screening for Parkinson’s Disease with Response Time Barriers: A Pilot Study

Background: Although significant response time deficits (both reaction time and movement time) have been identified in numerous studies of patients with Parkinson’s disease (PD), few attempts have been made to evaluate the use of these measures in screening for PD. Methods: Receiver operator characteristic curves were used to identify cutoff scores for a unitweighted composite of two choice response tasks in a sample of 40 patients and 40 healthy participants. These scores were then cross-validated in an independent sample of 20 patients and 20 healthy participants. Results: The unit-weighted movement time composite demonstrated high sensitivity (90%) and specificity (90%) in the identification of PD. Movement time was also significantly correlated (r = 0.59, p \u3c 0.025) with the motor score of the Unified Parkinson’s Disease Rating Scale (UPDRS). Conclusions: Measures of chronometric speed, assessed without the use of biomechanically complex movements, have a potential role in screening for PD. Furthermore, the significant correlation between movement time and UPDRS motor score suggests that movement time may be useful in the quantification of PD severity

Design and Analysis of Soft-Error Resilience Mechanisms for GPU Register File

Modern graphics processing units (GPUs) are using increasingly larger register file (RF) which occupies a large fraction of GPU core area and is very frequently access ed. This makes RF vulnerable to soft-errors (SE). In this paper, we present two techniques for improving SE resilience of GPU RF . First, we propose compressing the RF values for reducing the number of vulnerable bits. We leverage value similarity and the presence of narrow-width values to perform compression at warp or thread-level, respectively. Second, we propose sel ective hardening to design a portion of register entry with SE immun e circuits. By collectively using these techniques, higher r esilience can be provided with lower overhead. Without hardening, our warp and thread-level compression techniques bring 47.0% and 40.8% reduction in SE vulnerability, respectively

Isotropic reconstruction of 3D fluorescence microscopy images using convolutional neural networks

Fluorescence microscopy images usually show severe anisotropy in axial versus lateral resolution. This hampers downstream processing, i.e. the automatic extraction of quantitative biological data. While deconvolution methods and other techniques to address this problem exist, they are either time consuming to apply or limited in their ability to remove anisotropy. We propose a method to recover isotropic resolution from readily acquired anisotropic data. We achieve this using a convolutional neural network that is trained end-to-end from the same anisotropic body of data we later apply the network to. The network effectively learns to restore the full isotropic resolution by restoring the image under a trained, sample specific image prior. We apply our method to $3$ synthetic and $3$ real datasets and show that our results improve on results from deconvolution and state-of-the-art super-resolution techniques. Finally, we demonstrate that a standard 3D segmentation pipeline performs on the output of our network with comparable accuracy as on the full isotropic data

Starbursting Nuclear CO Disks of Early-type Spiral Galaxies

We have initiated the first CO interferometer survey of early-type spiral galaxies (S0-Sab). We observed five early-type spiral galaxies with HII nuclei (indicating circumnuclear starburst activities). These observations indicate gas masses for the central kiloparsec of \sim 1-5% of the dynamical masses. Such low gas mass fractions suggest that large-scale gravitational instability in the gas is unlikely to be the driving cause for the starburst activities. The Toomre Q values were >1 (mostly >3) within the central kiloparsec, indicating that the gas disks are globally gravitationally stable. The area filling factor of the gas disks is estimated to be about 0.05. This small value indicates the existence of lumpy structure, i.e. molecular clouds, in the globally-gravitationally stable disks. The typical surface density of the molecular clouds is as high as \sim 3000 Msun pc^{-2}. We reconsider the nature of the Toomre Q criterion, and conclude that the Q derived from CO observations indicates neither star formation nor molecular cloud formation. This argument should be valid not only for the circumnuclear disks but also for any region in galactic disks. We tentatively explore an alternative model, i.e. cloud-cloud collisions, as an initiating mechanism of star formation.Comment: 7pages, including 2 figures ; A&A accepted (19 Oct. 2004

Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions

We invoke star formation triggered by cloud-cloud collisions to explain global star formation rates of disk galaxies and circumnuclear starbursts. Previous theories based on the growth rate of gravitational perturbations ignore the dynamically important presence of magnetic fields. Theories based on triggering by spiral density waves fail to explain star formation in systems without such waves. Furthermore, observations suggest gas and stellar disk instabilities are decoupled. Following Gammie, Ostriker & Jog (1991), the cloud collision rate is set by the shear velocity of encounters with initial impact parameters of a few tidal radii, due to differential rotation in the disk. This, together with the effective confinement of cloud orbits to a two dimensional plane, enhances the collision rate above that for particles in a three dimensional box. We predict Sigma_{SFR}(R) proportional to Sigma_{gas} Omega (1-0.7 beta). For constant circular velocity (beta = 0), this is in agreement with recent observations (Kennicutt 1998). We predict a B-band Tully-Fisher relation: L_{B} proportional to v_{circ}^{7/3}, also consistent with observations. As additional tests, we predict enhanced star formation in regions with relatively high shear rates, and lower star formation efficiencies in clouds of higher mass.Comment: 27 pages including 3 figures and 2 tables. Accepted to ApJ. Expanded statistical analysis of cloud SF efficiency test. Stylistic changes. Data for figures available electronically at http://astro.berkeley.edu/~jt/disksfr.htm

Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs

In a composite system of gravitationally coupled stellar and gaseous discs, we perform linear stability analysis for axisymmetric coplanar perturbations using the two-fluid formalism. The background stellar and gaseous discs are taken to be scale-free with all physical variables varying as powers of cylindrical radius $r$ with compatible exponents. The unstable modes set in as neutral modes or stationary perturbation configurations with angular frequency $\omega=0$.Comment: 7 pages using AAS styl