4,310 research outputs found
Nuclear matrix element for two neutrino double beta decay from 136Xe
The nuclear matrix element for the two neutrino double beta decay (DBD) of
136Xe was evaluated by FSQP (Fermi Surface Quasi Particle model), where
experimental GT strengths measured by the charge exchange reaction and those by
the beta decay rates were used. The 2 neutrino DBD matrix element is given by
the sum of products of the single beta matrix elements via low-lying (Fermi
Surface) quasi-particle states in the intermediate nucleus. 136Xe is the
semi-magic nucleus with the closed neutron-shell, and the beta + transitions
are almost blocked. Thus the 2 neutrino DBD is much suppressed. The evaluated 2
neutrino DBD matrix element is consistent with the observed value.Comment: 7 pages 6 figure
The efficacy of aerosol–cloud radiative perturbations from near-surface emissions in deep open-cell stratocumuli
Aerosol–cloud radiative effects are determined and quantified in simulations
of deep open-cell stratocumuli observed during the VAMOS Ocean-Cloud-Atmosphere-Land
Study Regional Experiment (VOCALS-REx) campaign off
the west coast of Chile. The cloud deck forms in a boundary
layer 1.5 km deep, with cell sizes reaching 50 km in diameter. Global databases of ship
tracks suggest that these linear structures are seldom found in boundary
layers this deep. Here, we quantify the changes in cloud radiative properties
to a continuous aerosol point source moving along a fixed emission line
releasing 1017 particles per second. We show that a spatially coherent
cloud perturbation is not evident along the emission line. Yet our model
simulates an increase in domain-mean all-sky albedo of 0.05, corresponding to
a diurnally averaged cloud radiative effect of 20 W m−2, given the
annual mean solar insolation at the VOCALS-REx site. Therefore, marked
changes in cloud radiative properties in precipitating deep open cells may be
driven by anthropogenic near-surface aerosol perturbations, such as those
generated by ships.
Furthermore, we demonstrate that these changes in cloud radiative properties
are masked by the naturally occurring variability within the organised cloud
field. A clear detection and attribution of cloud radiative effects to a
perturbation in aerosol concentrations becomes possible when sub-filtering of
the cloud field is applied, using the spatio-temporal distribution of the
aerosol perturbation. Therefore, this work has implications for the detection
and attribution of effective cloud radiative forcing in marine stratocumuli,
which constitutes one of the major physical uncertainties within the climate
system. Our results suggest that ships may sometimes have a substantial
radiative effect on marine clouds and albedo, even when ship tracks are not
readily visible.</p
Aerosol Data Sources and Their Roles within PARAGON
We briefly but systematically review major sources of aerosol data, emphasizing suites of measurements that seem most likely to contribute to assessments of global aerosol climate forcing. The strengths and limitations of existing satellite, surface, and aircraft remote sensing systems are described, along with those of direct sampling networks and ship-based stations. It is evident that an enormous number of aerosol-related observations have been made, on a wide range of spatial and temporal sampling scales, and that many of the key gaps in this collection of data could be filled by technologies that either exist or are expected to be available in the near future. Emphasis must be given to combining remote sensing and in situ active and passive observations and integrating them with aerosol chemical transport models, in order to create a more complete environmental picture, having sufficient detail to address current climate forcing questions. The Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON) initiative would provide an organizational framework to meet this goal
Triangle-Free Penny Graphs: Degeneracy, Choosability, and Edge Count
We show that triangle-free penny graphs have degeneracy at most two, list
coloring number (choosability) at most three, diameter , and
at most edges.Comment: 10 pages, 2 figures. To appear at the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Beyond Outerplanarity
We study straight-line drawings of graphs where the vertices are placed in
convex position in the plane, i.e., convex drawings. We consider two families
of graph classes with nice convex drawings: outer -planar graphs, where each
edge is crossed by at most other edges; and, outer -quasi-planar graphs
where no edges can mutually cross. We show that the outer -planar graphs
are -degenerate, and consequently that every
outer -planar graph can be -colored, and this
bound is tight. We further show that every outer -planar graph has a
balanced separator of size . This implies that every outer -planar
graph has treewidth . For fixed , these small balanced separators
allow us to obtain a simple quasi-polynomial time algorithm to test whether a
given graph is outer -planar, i.e., none of these recognition problems are
NP-complete unless ETH fails. For the outer -quasi-planar graphs we prove
that, unlike other beyond-planar graph classes, every edge-maximal -vertex
outer -quasi planar graph has the same number of edges, namely . We also construct planar 3-trees that are not outer
-quasi-planar. Finally, we restrict outer -planar and outer
-quasi-planar drawings to \emph{closed} drawings, where the vertex sequence
on the boundary is a cycle in the graph. For each , we express closed outer
-planarity and \emph{closed outer -quasi-planarity} in extended monadic
second-order logic. Thus, closed outer -planarity is linear-time testable by
Courcelle's Theorem.Comment: Appears in the Proceedings of the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Metals and Bacteria Partitioning to Various Size Particles in Ballona Creek Storm Water Runoff
Many storm water best management practice (BMP) devices function primarily by capturing particulate matter to take advantage of the well‐documented association between storm water particles and pollutants. The hydrodynamic separation or settling methods used by most BMP devices are most effective at capturing medium to large particles; however, these may not be the most predominant particles associated with urban runoff. The present study examined particle size distribution in storm water runoff from an urban watershed in southern California and investigated the pollutant–particle associations of metals (Cu, Pb, Ni, and Zn) and bacteria (enterococci and Escherichia coli). During small storm events (≤0.7 cm rain), the highest concentration of pollutants were associated with a \u3c6‐µm filter fraction, which accounted for 70% of the per storm contaminant mass but made up more than 20% of the total particle mass. The pollutant–particle association changed with storm size. Most pollutant mass was associated with \u3e35 µm size particles during a 5‐cm rain event. These results suggest that much of the contaminant load in storm water runoff will not be captured by the most commonly used BMP devices, because most of these devices (e.g., hydrodynamic separators) are unable to capture particles smaller than 75 µm
On the Recognition of Fan-Planar and Maximal Outer-Fan-Planar Graphs
Fan-planar graphs were recently introduced as a generalization of 1-planar
graphs. A graph is fan-planar if it can be embedded in the plane, such that
each edge that is crossed more than once, is crossed by a bundle of two or more
edges incident to a common vertex. A graph is outer-fan-planar if it has a
fan-planar embedding in which every vertex is on the outer face. If, in
addition, the insertion of an edge destroys its outer-fan-planarity, then it is
maximal outer-fan-planar. In this paper, we present a polynomial-time algorithm
to test whether a given graph is maximal outer-fan-planar. The algorithm can
also be employed to produce an outer-fan-planar embedding, if one exists. On
the negative side, we show that testing fan-planarity of a graph is NP-hard,
for the case where the rotation system (i.e., the cyclic order of the edges
around each vertex) is given
Observing Spontaneous Strong Parity Violation in Heavy-Ion Collisions
We discuss the problem of observing spontaneous parity and CP violation in
collision systems. We discuss and propose observables which may be used in
heavy-ion collisions to observe such violations, as well as event-by-event
methods to analyze the data. Finally, we discuss simple monte-carlo models of
these CP violating effects which we have used to develop our techniques and
from which we derive rough estimates of sensitivities to signals which may be
seen at RHIC
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