24,214 research outputs found
Mechanical modulation of single-electron tunneling through molecular-assembled metallic nanoparticles
We present a microscopic study of single-electron tunneling in nanomechanical
double-barrier tunneling junctions formed using a vibrating scanning nanoprobe
and a metallic nanoparticle connected to a metallic substrate through a
molecular bridge. We analyze the motion of single electrons on and off the
nanoparticle through the tunneling current, the displacement current and the
charging-induced electrostatic force on the vibrating nanoprobe. We demonstrate
the mechanical single-electron turnstile effect by applying the theory to a
gold nanoparticle connected to the gold substrate through alkane dithiol
molecular bridge and probed by a vibrating platinum tip.Comment: Accepted by Phys. Rev.
Millicharged Atomic Dark Matter
We present a simplified version of the atomic dark matter scenario, in which
charged dark constituents are bound into atoms analogous to hydrogen by a
massless hidden sector U(1) gauge interaction. Previous studies have assumed
that interactions between the dark sector and the standard model are mediated
by a second, massive Z' gauge boson, but here we consider the case where only a
massless gamma' kinetically mixes with the standard model hypercharge and
thereby mediates direct detection. This is therefore the simplest atomic dark
matter model that has direct interactions with the standard model, arising from
the small electric charge for the dark constituents induced by the kinetic
mixing. We map out the parameter space that is consistent with cosmological
constraints and direct searches, assuming that some unspecified mechanism
creates the asymmetry that gives the right abundance, since the dark matter
cannot be a thermal relic in this scenario. In the special case where the dark
"electron" and "proton" are degenerate in mass, inelastic hyperfine transitions
can explain the CoGeNT excess events. In the more general case, elastic
transitions dominate, and can be close to current direct detection limits over
a wide range of masses.Comment: 5 pages, 2 figures; v2: added references, and formula for dark
ionization fraction; published versio
GRB970228 and the class of GRBs with an initial spikelike emission: do they follow the Amati relation?
On the basis of the recent understanding of GRB050315 and GRB060218, we
return to GRB970228, the first Gamma-Ray Burst (GRB) with detected afterglow.
We proposed it as the prototype for a new class of GRBs with "an occasional
softer extended emission lasting tenths of seconds after an initial spikelike
emission". Detailed theoretical computation of the GRB970228 light curves in
selected energy bands for the prompt emission are presented and compared with
observational BeppoSAX data. From our analysis we conclude that GRB970228 and
likely the ones of the above mentioned new class of GRBs are "canonical GRBs"
have only one peculiarity: they exploded in a galactic environment, possibly
the halo, with a very low value of CBM density. Here we investigate how
GRB970228 unveils another peculiarity of this class of GRBs: they do not
fulfill the "Amati relation". We provide a theoretical explanation within the
fireshell model for the apparent absence of such correlation for the GRBs
belonging to this new class.Comment: 5 pages, 3 figures, in the Proceedings of the "4th Italian-Sino
Workshop on Relativistic Astrophysics", held in Pescara, Italy, July 20-28,
2007, C.L. Bianco, S.-S. Xue, Editor
Nonclassical photon pairs generated from a room-temperature atomic ensemble
We report experimental generation of non-classically correlated photon pairs
from collective emission in a room-temperature atomic vapor cell. The
nonclassical feature of the emission is demonstrated by observing a violation
of the Cauchy-Schwarz inequality. Each pair of correlated photons are separated
by a controllable time delay up to 2 microseconds. This experiment demonstrates
an important step towards the realization of the Duan-Lukin-Cirac-Zoller scheme
for scalable long-distance quantum communication.Comment: 4 pages, 2 figure
'To trust or not to trust': The impact of social media influencers on the reputation of corporate brands in crisis
Corporates often partner with social media influencers to bolster brand image after crises. Although existing evidence suggests that influencers have a largely positive effect on brands, yet there is paucity of research on the role of influencers in corporate crisis communications. Across two studies, we examine the impact of influencers on consumers’ perception of corporate brand in crisis. Drawing on persuasion knowledge theory, we identify pitfalls associated with influencers, such as inferences of manipulative intent, which negatively affect perceived trustworthiness and corporate reputation. The downside of engaging influencers in crisis communications can, however, be offset by influencer and the brand communicating values-driven motives of their partnership. Our findings imply that corporate brands should respond to crises through a bolstering strategy that promotes existing corporate goodwill, without influencer’s involvement. When leveraging on influencers’ support, however, brands should endeavor to inoculate manipulative inferences by communicating the values-driven motives behind the brand-influencer partnership
'To trust or not to trust': The impact of social media influencers on the reputation of corporate brands in crisis
Corporates often partner with social media influencers to bolster brand image after crises. Although existing evidence suggests that influencers have a largely positive effect on brands, yet there is paucity of research on the role of influencers in corporate crisis communications. Across two studies, we examine the impact of influencers on consumers’ perception of corporate brand in crisis. Drawing on persuasion knowledge theory, we identify pitfalls associated with influencers, such as inferences of manipulative intent, which negatively affect perceived trustworthiness and corporate reputation. The downside of engaging influencers in crisis communications can, however, be offset by influencer and the brand communicating values-driven motives of their partnership. Our findings imply that corporate brands should respond to crises through a bolstering strategy that promotes existing corporate goodwill, without influencer’s involvement. When leveraging on influencers’ support, however, brands should endeavor to inoculate manipulative inferences by communicating the values-driven motives behind the brand-influencer partnership
Global regularity for the supercritical dissipative quasi-geostrophic equation with large dispersive forcing
We consider the 2D quasi-geostrophic equation with supercritical dissipation
and dispersive forcing in the whole space. When the dispersive amplitude
parameter is large enough, we prove the global well-posedness of strong
solution to the equation with large initial data. We also show the strong
convergence result as the amplitude parameter goes to . Both results
rely on the Strichartz-type estimates for the corresponding linear equation.Comment: 26page
GRB 970228 Within the EMBH Model
We consider the gamma-ray burst of 1997 February 28 (GRB 970228) within the
ElectroMagnetic Black Hole (EMBH) model. We first determine the value of the
two free parameters that characterize energetically the GRB phenomenon in the
EMBH model, that is to say the dyadosphere energy,
ergs, and the baryonic remnant mass in units of ,
. Having in this way estimated the
energy emitted during the beam-target phase, we evaluate the role of the
InterStellar Medium (ISM) number density (n) and of the ratio between the effective emitting area and the total surface area of the GRB
source, in reproducing the observed profiles of the GRB 970228 prompt emission
and X-ray (2-10 keV energy band) afterglow. The importance of the ISM
distribution three-dimensional treatment around the central black hole is also
stressed in this analysis.Comment: 4 pages, 1 figure, to appear in the Proceedings of the Los Alamos
"Gamma Ray Burst Symposium" in Santa Fe, New Mexico, September 8-12 2003 (AIP
Conf. Ser.), CHAPTER: GRB Connection to Supernova
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