23,404 research outputs found
Transport of quantum noise through random media
We present an experimental study of the propagation of quantum noise in a
multiple scattering random medium. Both static and dynamic scattering
measurements are performed: the total transmission of noise is related to the
mean free path for scattering, while the noise frequency correlation function
determines the diffusion constant. The quantum noise observables are found to
scale markedly differently with scattering parameters compared to classical
noise observables. The measurements are explained with a full quantum model of
multiple scattering
Exciton Trapping Is Responsible for the Long Apparent Lifetime in Acid-Treated MoS2
Here, we show that deep trapped "dark" exciton states are responsible for the
surprisingly long lifetime of band-edge photoluminescence in acid-treated
single-layer MoS2. Temperature-dependent transient photoluminescence
spectroscopy reveals an exponential tail of long-lived states extending
hundreds of meV into the band gap. These sub-band states, which are
characterized by a 4 microsecond radiative lifetime, quickly capture and store
photogenerated excitons before subsequent thermalization up to the band edge
where fast radiative recombination occurs. By intentionally saturating these
trap states, we are able to measure the "true" 150 ps radiative lifetime of the
band-edge exciton at 77 K, which extrapolates to ~600 ps at room temperature.
These experiments reveal the dominant role of dark exciton states in
acid-treated MoS2, and suggest that excitons spend > 95% of their lifetime at
room temperature in trap states below the band edge. We hypothesize that these
states are associated with native structural defects, which are not introduced
by the superacid treatment; rather, the superacid treatment dramatically
reduces non-radiative recombination through these states, extending the exciton
lifetime and increasing the likelihood of eventual radiative recombination
Examining the mortality effects of the Irish National Smoking Ban.
Secondhand smoke causes disease and death in those exposed, with cardiovascular and respiratory problems as the most likely outcomes. The purpose of this study was to examine the mortality effects of the Irish national smoking ban of 2004
Propagation of temporal entanglement
The equations that govern the temporal evolution of two photons in the
Schr{\"o}dinger picture are derived, taking into account the effects of loss,
group-velocity dispersion, temporal phase modulation, linear coupling among
different optical modes, and four-wave mixing. Inspired by the formalism, we
propose the concept of quantum temporal imaging, which uses dispersive elements
and temporal phase modulators to manipulate the temporal correlation of two
entangled photons. We also present the exact solution of a two-photon vector
soliton, in order to demonstrate the ease of use and intuitiveness of the
proposed formulation.Comment: 8 pages, 4 figure
Excess mortality during heat waves in Ireland
Ireland is not known for having extreme high temperatures, with values above 30C uncommon. Ireland has significant excess winter mortality compared to summer. The objective of this study is to estimate the impact of nation-wide heat waves on the total, cardiovascular and respiratory relationship, for the period 1981–2003, to determine if there are any periods of excess summer mortality
Beneficial or biohazard? How the media frame biosolids
This study looked at how the media framed biosolids, or treated sewage sludge, from 1994 to 2004 by analyzing the 13 media frames found in 286 biosolid-related articles from newspapers in Florida, Virginia, and California. The researchers found the articles framed biosolids as a regulatory or legal issue most often, and most of the frames’ tones were neutral (1,958). However, negative tone (507) happened three times more often than positive tone (149), and environmental, management, and public nuisance framing tended to be more negative than any of the other frames. Neither the frames themselves nor the tones had statistically significant changes over the past decade. Regarding the sources used in the stories, the most frequent source was local government officials, which were used twice as frequently as any other source, followed by corporations (16 percent) and citizens (14 percent). These findings should help biosolid producers and officials in developing a media strategy that is proactive toward shaping public opinion rather than reactive to an issue that makes its way to the media and spurs public concern
Helical Magnetorotational Instability in Magnetized Taylor-Couette Flow
Hollerbach and Rudiger have reported a new type of magnetorotational
instability (MRI) in magnetized Taylor-Couette flow in the presence of combined
axial and azimuthal magnetic fields. The salient advantage of this "helical''
MRI (HMRI) is that marginal instability occurs at arbitrarily low magnetic
Reynolds and Lundquist numbers, suggesting that HMRI might be easier to realize
than standard MRI (axial field only). We confirm their results, calculate HMRI
growth rates, and show that in the resistive limit, HMRI is a weakly
destabilized inertial oscillation propagating in a unique direction along the
axis. But we report other features of HMRI that make it less attractive for
experiments and for resistive astrophysical disks. Growth rates are small and
require large axial currents. More fundamentally, instability of highly
resistive flow is peculiar to infinitely long or periodic cylinders: finite
cylinders with insulating endcaps are shown to be stable in this limit. Also,
keplerian rotation profiles are stable in the resistive limit regardless of
axial boundary conditions. Nevertheless, the addition of toroidal field lowers
thresholds for instability even in finite cylinders.Comment: 16 pages, 2 figures, 1 table, submitted to PR
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