Impact of van der Waals forces on the classical shuttle instability

The effects of including the van der Waals interaction in the modelling of the single electron shuttle have been investigated numerically. It is demonstrated that the relative strength of the vdW-forces and the elastic restoring forces determine the characteristics of the shuttle instability. In the case of weak elastic forces and low voltages the grain is trapped close to one lead, and this trapping can be overcome by Coulomb forces by applying a bias voltage $V$ larger than a threshold voltage $V_{\rm u}$. This allows for grain motion leading to an increase in current by several orders of magnitude above the transition voltage $V_{\rm u}$. Associated with the process is also hysteresis in the I-V characteristics.Comment: minor revisions, updated references, Article published in Phys. Rev. B 69, 035309 (2004

The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. I. Discovery of the optical counterpart using the Dark Energy Camera

We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational wave emission, GW170817. Our observations commenced 10.5 hours post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hours post-merger we detected a bright optical transient located 10:600 from the nucleus of NGC4993 at redshift z = 0:0098, consistent (for H0 = 70 km s-1 Mpc-1) with the distance of 40±8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes i=17.3 and z=17.4, and thus an absolute magnitude of Mi = -15.7, in the luminosity range expected for a kilonova. We identified 1,500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves, and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources

Integrating Civil Society and Economic Growth in Appalachia

Building from a framework that incorporates ideas from the civil society perspective into market-based sociological models of economic growth, this article examines the effects of three measures of civic engagement on measure of economic growth in Appalachian counties during the 1990-1995 period. The analysis shows that net of other market competition-based measures, civic engagement does have a net positive impact on economic growth (increases in private non-farm employment, private establishment, per capita income, earnings, etc.). The three measures of civic engagement are (1) percent of population in civically engaged denominations (1990), (2) number of national associations per capita (1990), (3) and number of third places per capita (1990). All three measures have significant positive effects in one or more models. Percent in civically engaged denominations has the most consistent effects. Implications are discussed. Copyright 2006 Blackwell Publishing.

Narrative, organizations and research

Given the rapid expansion of narrative approaches in management and organization theory in recent years, this paper investigates the contribution of this literature to the under-standing of organizations and processes of organizing. The paper tells the story of the development of narrative approaches in organizational theory. Narrative's contribution to substantive areas of organization theory is evaluated. These developments are then reviewed in relation to an ongoing tension between story and science. We conclude by contemplating some of the criticisms, and the future, of narrative research. © Blackwell Publishing Ltd 2005