5,348 research outputs found
Tidal disruptions in circumbinary disks. II: Observational signatures in the reverberation spectra
Supermassive Binary Black Holes (SMBBHs) with sub-pc separations form in the
course of galaxy mergers, if both galaxies harbour massive black holes. Clear
observational evidence for them however still eludes us. We propose a novel
method of identifying these systems by means of reverberation mapping their
circumbinary disk after a tidal disruption event has ionized it. The tidal
disruption of a star at the secondary leads to strong asymmetries in the disk
response. We model the shape of the velocity--delay maps for various toy disk
models and more realistic gas distributions obtained by SPH simulations. The
emissivity of the ionized disk is calculated with {\em Cloudy}. We find
peculiar asymmetries in the maps for off center ionizing sources that may help
us constrain geometrical parameters of a circumbinary disk such as semi-major
axis and orbital phase of the secondary, as well as help strengthen the
observational evidence for sub-parsec SMBBHs as such.Comment: 10 pages, 5 figures. Accepted for publication in Ap
Organic substances against Monilia laxa on apricot – in-vitro and on-farm experiments
Natural substances against Monilia laxa were onfarm and in-vitro tested. According to on-farm tests, some products reached interesting efficacies. The fluctuation of the year and parcel pressures, makes it difficult to perform the results
Glass and Jamming Transitions: From Exact Results to Finite-Dimensional Descriptions
Despite decades of work, gaining a first-principle understanding of amorphous
materials remains an extremely challenging problem. However, recent theoretical
breakthroughs have led to the formulation of an exact solution in the
mean-field limit of infinite spatial dimension, and numerical simulations have
remarkably confirmed the dimensional robustness of some of the predictions.
This review describes these latest advances. More specifically, we consider the
dynamical and thermodynamic descriptions of hard spheres around the dynamical,
Gardner and jamming transitions. Comparing mean-field predictions with the
finite-dimensional simulations, we identify robust aspects of the description
and uncover its more sensitive features. We conclude with a brief overview of
ongoing research.Comment: 5 figures, 26 page
Exact theory of dense amorphous hard spheres in high dimension. III. The full RSB solution
In the first part of this paper, we derive the general replica equations that
describe infinite-dimensional hard spheres at any level of replica symmetry
breaking (RSB) and in particular in the fullRSB scheme. We show that these
equations are formally very similar to the ones that have been derived for spin
glass models, thus showing that the analogy between spin glasses and structural
glasses conjectured by Kirkpatrick, Thirumalai, and Wolynes is realized in a
strong sense in the mean field limit. We also suggest how the computation could
be generalized in an approximate way to finite dimensional hard spheres. In the
second part of the paper, we discuss the solution of these equations and we
derive from it a number of physical predictions. We show that, below the
Gardner transition where the 1RSB solution becomes unstable, a fullRSB phase
exists and we locate the boundary of the fullRSB phase. Most importantly, we
show that the fullRSB solution predicts correctly that jammed packings are
isostatic, and allows one to compute analytically the critical exponents
associated with the jamming transition, which are missed by the 1RSB solution.
We show that these predictions compare very well with numerical results.Comment: 58 pages, 13 figures -- Final version to appear on JSTA
Fractal free energy landscapes in structural glasses
Glasses are amorphous solids whose constituent particles are caged by their
neighbors and thus cannot flow. This sluggishness is often ascribed to the free
energy landscape containing multiple minima (basins) separated by high
barriers. Here we show, using theory and numerical simulation, that the
landscape is much rougher than is classically assumed. Deep in the glass, it
undergoes a "roughness transition" to fractal basins. This brings about
isostaticity at jamming and marginality of glassy states near jamming. Critical
exponents for the basin width, the weak force distribution, and the spatial
spread of quasi-contacts at jamming can be analytically determined. Their value
is found to be compatible with numerical observations. This advance therefore
incorporates the jamming transition of granular materials into the framework of
glass theory. Because temperature and pressure control which features of the
landscape are experienced, glass mechanics and transport are expected to
reflect the features of the topology we discuss here. Hitherto mysterious
properties of low-temperature glasses could be explained by this approach.Comment: 13 pages, 4 figures. This version was initially submitted to Nature
Communications in December 2013. The (much improved) final version is
available on the Nature Communications website (see DOI below). A detailed
version of this work is available on arXiv:1310.254
Sports Participation and Physical Education in American Secondary Schools: Current Levels of Racial/Ethnic and Socioeconomic Disparities
Summarizes findings from a study of physical education requirements and school-based physical activity among American schoolchildren. Analyzes data by gender, grade, race/ethnicity and socioeconomic status
The Challenge of Non-Technical Loss Detection using Artificial Intelligence: A Survey
Detection of non-technical losses (NTL) which include electricity theft,
faulty meters or billing errors has attracted increasing attention from
researchers in electrical engineering and computer science. NTLs cause
significant harm to the economy, as in some countries they may range up to 40%
of the total electricity distributed. The predominant research direction is
employing artificial intelligence to predict whether a customer causes NTL.
This paper first provides an overview of how NTLs are defined and their impact
on economies, which include loss of revenue and profit of electricity providers
and decrease of the stability and reliability of electrical power grids. It
then surveys the state-of-the-art research efforts in a up-to-date and
comprehensive review of algorithms, features and data sets used. It finally
identifies the key scientific and engineering challenges in NTL detection and
suggests how they could be addressed in the future
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