104 research outputs found
Canonical form of m-by-2-by-2 matrices over a field of characteristic other than two
We give a canonical form of m-by-2-by-2 matrices for equivalence over any
field of characteristic not two.Comment: 6 page
Recruitment dynamics in adaptive social networks
We model recruitment in adaptive social networks in the presence of birth and
death processes. Recruitment is characterized by nodes changing their status to
that of the recruiting class as a result of contact with recruiting nodes. Only
a susceptible subset of nodes can be recruited. The recruiting individuals may
adapt their connections in order to improve recruitment capabilities, thus
changing the network structure adaptively. We derive a mean field theory to
predict the dependence of the growth threshold of the recruiting class on the
adaptation parameter. Furthermore, we investigate the effect of adaptation on
the recruitment level, as well as on network topology. The theoretical
predictions are compared with direct simulations of the full system. We
identify two parameter regimes with qualitatively different bifurcation
diagrams depending on whether nodes become susceptible frequently (multiple
times in their lifetime) or rarely (much less than once per lifetime)
One-Pot 3D Printing of Robust Multimaterial Devices
Polymer 3D printing is a broad set of manufacturing methods that permit the
fabrication of complex architectures, and, as a result, numerous efforts focus
on formulating processible chemistries that produce desirable material behavior
in printed parts. However, current resin chemistries typically result in a
single fixed set of properties once fully polymerized, a fact that poses
significant engineering challenges to obtaining multimaterial devices. As an
alternative to single-property materials, we introduce a ternary sequential
reaction scheme that exhibits diverse multimaterial properties by profoundly
altering the polymer microstructure from within a single resin composition. In
this system, the photodosage during 3D printing sets both the shape and extent
of conversion for each subsequent reaction. This different polymerization
mechanisms of the subsequent stages yield disparate crosslink densities and
viscoelastic properties. As a result, our materials possess Young's Moduli
spanning over three orders of magnitude (400 kPa < E < 1.6 GPa) with smooth
transitions between soft and stiff regions. We successfully pattern a 500x
change in modulus in under a millimeter while the sequential assembly of our
polymer networks ensures robust interfaces and enhances toughness by 10x
compared to the single property materials. Most importantly, the final objects
remain stable to UV and thermal aging, a key limitation to applications of
previous multimaterial chemistries. We demonstrate the ability to 3D print
intricate multimaterial architectures by fabricating a soft, wearable braille
display.Comment: 54 pages including supplemental information, 5 main text figure
Formation of dislocations and hardening of LiF under high-dose irradiation with 5–21 MeV 12C ions
R. Zabels, I. Manika, J. Maniks, and R.Grants acknowledge the national project IMIS2, and A. Dauletbekova, M. Baizhumanov, and M. Zdorovets the Ministry of Education and Science of the Republic of Kazakhstan for the financial support.The emergence of dislocations and hardening of LiF crystals irradiated to high doses with 12C ions have been investigated using chemical etching, AFM, nanoindentation, and thermal annealing. At fluences ensuring the overlapping of tracks (Ф ≥6 × 1011 ions/cm2), the formation of dislocation-rich structure and ion-induced hardening is observed. High-fluence (1015 ions/cm2) irradiation with 12C ions causes accumulation of extended defects and induces hardening comparable to that reached by heavy ions despite of large differences in ion mass, energy, energy loss, and track morphology. The depth profiles of hardness indicate on a notable contribution of elastic collision mechanism (nuclear loss) in the damage production and hardening. The effect manifests at the end part of the ion range and becomes significant at high fluences (≥1014 ions/cm2).IMIS2; Ministry of Education and Science of the Republic of Kazakhstan; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Structure of magnetic fields in intracluster cavities
Observations of clusters of galaxies show ubiquitous presence of X-ray
cavities, presumably blown by the AGN jets. We consider magnetic field
structures of these cavities. Stability requires that they contain both
toroidal and poloidal magnetic fields, while realistic configurations should
have vanishing magnetic field on the boundary. For axisymmetric configurations
embedded in unmagnetized plasma, the continuity of poloidal and toroidal
magnetic field components on the surface of the bubble then requires solving
the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary
conditions. This leads to a double eigenvalue problem, relating the pressure
gradients and the toroidal magnetic field to the radius of the bubble. We have
found fully analytical stable solutions. This result is confirmed by numerical
simulation. We present synthetic X-ray images and synchrotron emission profiles
and evaluate the rotation measure for radiation traversing the bubble.Comment: 10 pages, 13 figures, accepted by MNRA
Accumulation of radiation defects and modification of micromechanical properties under MgO crystal irradiation with swift 132Xe ions
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. A.A. also acknowledges support via the project GF AP05134257 of Ministry of Education and Science of the Republic of Kazakhstan .Accumulation of F-type defects under irradiation of MgO crystals by 0.23-GeV 132Xe ions with fluence varying by three orders of magnitude has been investigated via the spectra of optical absorption and low-temperature cathodoluminescence. The number of single centers continuously increases with fluence without any marks of saturation. At the highest fluence, a mean volume concentration of 3.1 × 1019 and 3.35 × 1019 cm−3 is reached for F and F+ centers, respectively. The F+ emission strongly dominates in the cathodoluminescence of irradiated MgO and its enhancement with fluence is detected. However, the creation efficiency of the F2 aggregate centers is very low and fluence dependence has a complicated shape. Radiation-induced changes of micro-mechanical properties of the same samples have been analysed; the depth profiles of hardening correlate with the ion energy loss. A joint contribution of ionization and impact mechanisms in the formation of structural defects under MgO irradiation with Xe ions is considered.H2020 Euratom 2019-2020,633053,2014-2018,GF AP05134257; Ministry of Education and Science of the Republic of Kazakhstan GF AP05134257; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Epidemics in Adaptive Social Networks with Temporary Link Deactivation
Disease spread in a society depends on the topology of the network of social contacts. Moreover, individuals may respond to the epidemic by adapting their contacts to reduce the risk of infection, thus changing the network structure and affecting future disease spread. We propose an adaptation mechanism where healthy individuals may choose to temporarily deactivate their contacts with sick individuals, allowing reactivation once both individuals are healthy. We develop a mean-field description of this system and find two distinct regimes: slow network dynamics, where the adaptation mechanism simply reduces the effective number of contacts per individual, and fast network dynamics, where more efficient adaptation reduces the spread of disease by targeting dangerous connections. Analysis of the bifurcation structure is supported by numerical simulations of disease spread on an adaptive network. The system displays a single parameter-dependent stable steady state and non-monotonic dependence of connectivity on link deactivation rate
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
Pcl-PRC2 is needed to generate high levels of H3-K27 trimethylation at Polycomb target genes
PRC2 is thought to be the histone methyltransferase (HMTase) responsible for H3-K27 trimethylation at Polycomb target genes. Here we report the biochemical purification and characterization of a distinct form of Drosophila PRC2 that contains the Polycomb group protein polycomblike (Pcl). Like PRC2, Pcl-PRC2 is an H3-K27-specific HMTase that mono-, di- and trimethylates H3-K27 in nucleosomes in vitro. Analysis of Drosophila mutants that lack Pcl unexpectedly reveals that Pcl-PRC2 is required to generate high levels of H3-K27 trimethylation at Polycomb target genes but is dispensable for the genome-wide H3-K27 mono- and dimethylation that is generated by PRC2. In Pcl mutants, Polycomb target genes become derepressed even though H3-K27 trimethylation at these genes is only reduced and not abolished, and even though targeting of the Polycomb protein complexes PhoRC and PRC1 to Polycomb response elements is not affected. Pcl-PRC2 is thus the HMTase that generates the high levels of H3-K27 trimethylation in Polycomb target genes that are needed to maintain a Polycomb-repressed chromatin state
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