4,877 research outputs found
Pressure-induced commensurate stacking of graphene on boron nitride
Combining atomically-thin van der Waals materials into heterostructures
provides a powerful path towards the creation of designer electronic devices.
The interaction strength between neighboring layers, most easily controlled
through their interlayer separation, can have significant influence on the
electronic properties of these composite materials. Here, we demonstrate
unprecedented control over interlayer interactions by locally modifying the
interlayer separation between graphene and boron nitride, which we achieve by
applying pressure with a scanning tunneling microscopy tip. For the special
case of aligned or nearly-aligned graphene on boron nitride, the graphene
lattice can stretch and compress locally to compensate for the slight lattice
mismatch between the two materials. We find that modifying the interlayer
separation directly tunes the lattice strain and induces commensurate stacking
underneath the tip. Our results motivate future studies tailoring the
electronic properties of van der Waals heterostructures by controlling the
interlayer separation of the entire device using hydrostatic pressure.Comment: 17 pages, 4 figures and supplementary information. Updated to
published versio
Divergent Time Scale in Axelrod Model Dynamics
We study the evolution of the Axelrod model for cultural diversity. We
consider a simple version of the model in which each individual is
characterized by two features, each of which can assume q possibilities. Within
a mean-field description, we find a transition at a critical value q_c between
an active state of diversity and a frozen state. For q just below q_c, the
density of active links between interaction partners is non-monotonic in time
and the asymptotic approach to the steady state is controlled by a time scale
that diverges as (q-q_c)^{-1/2}.Comment: 4 pages, 5 figures, 2-column revtex4 forma
Conservation laws for the voter model in complex networks
We consider the voter model dynamics in random networks with an arbitrary
distribution of the degree of the nodes. We find that for the usual node-update
dynamics the average magnetization is not conserved, while an average
magnetization weighted by the degree of the node is conserved. However, for a
link-update dynamics the average magnetization is still conserved. For the
particular case of a Barabasi-Albert scale-free network the voter model
dynamics leads to a partially ordered metastable state with a finite size
survival time. This characteristic time scales linearly with system size only
when the updating rule respects the conservation law of the average
magnetization. This scaling identifies a universal or generic property of the
voter model dynamics associated with the conservation law of the magnetization.Comment: 5 pages, 4 figures; for related material please visit
http://www.imedea.uib.e
Selfsimilar Domain Growth, Localized Structures and Labyrinthine Patterns in Vectorial Kerr Resonators
We study domain growth in a nonlinear optical system useful to explore
different scenarios that might occur in systems which do not relax to
thermodynamic equilibrium. Domains correspond to equivalent states of different
circular polarization of light. We describe three dynamical regimes: a
coarsening regime in which dynamical scaling holds with a growth law dictated
by curvature effects, a regime in which localized structures form, and a regime
in which polarization domain walls are modulationally unstable and the system
freezes in a labyrinthine pattern.Comment: 13 pages, 6 figure
Evaluasi Keberhasilan Inseminasi Buatan Pada Sapi Simental – Po (Simpo) Di Kecamatan Patean Dan Plantungan, Kabupaten Kendal, Jawa Tengah (Evaluation of Artificial Insemination Simmental – Po (Simpo) Cow in the Sub-district of Patean and Plantungan, Kend
The purpose of this research was to find out about the success of IB implementation for SIMPO cows in both of district which have different temperature and humidity based on, non return rate (NRR), conception rate(CR) and service per conception (S/C).The materials of this research was secondary data of IB implementation from 2009 until 2013 and the primary data was 60 SIMPO cows. The method that used in this study was observational and drscriptive analysis, and has passed the proportional test in order to determine the difference between the two regions, then linier regression analysis to estimate various parameters of 2014. To make the counting procedure easier and prevent humman error this research used statistical shoftware conStat. The result proved that presumption value 2014 there was a different results fo successively wereNRR28-35 83,33%; CR 30,80%; S/C 2,9 times for Patean and for Plantungan were NRR28-35 86,66%; CR 57,2%; S/C 1,5 times. The result of proportion test for CR and S/C showed different (p<0,05) but there was no differences for NRR result. The conclusion of this research that reproduction capability based on evaluation to NRR, CR and S/C of SIMPO cows in Plantungan district was better than SIMPO cows in Patean Distric
COST ES0602: towards a European network on chemical weather forecasting and information systems
The COST ES0602 action provides a forum for benchmarking approaches and practices in data exchange and multi-model capabilities for chemical weather forecasting and near real-time information services in Europe. The action includes approximately 30 participants from 19 countries, and its duration is from 2007 to 2011 (<a href="http://www.chemicalweather.eu/" target="_blank">http://www.chemicalweather.eu/</a>). Major efforts have been dedicated in other actions and projects to the development of infrastructures for data flow. We have therefore aimed for collaboration with ongoing actions towards developing near real-time exchange of input data for air quality forecasting. We have collected information on the operational air quality forecasting models on a regional and continental scale in a structured form, and inter-compared and evaluated the physical and chemical structure of these models. We have also constructed a European chemical weather forecasting portal that includes links to most of the available chemical weather forecasting systems in Europe. The collaboration also includes the examination of the case studies that have been organized within COST-728, in order to inter-compare and evaluate the models against experimental data. We have also constructed an operational model forecasting ensemble. Data from a representative set of regional background stations have been selected, and the operational forecasts for this set of sites will be inter-compared and evaluated. The Action has investigated, analysed and reviewed existing chemical weather information systems and services, and will provide recommendations on best practices concerning the presentation and dissemination of chemical weather information towards the public and decision makers
Nonlinear oscillator with parametric colored noise: some analytical results
The asymptotic behavior of a nonlinear oscillator subject to a multiplicative
Ornstein-Uhlenbeck noise is investigated. When the dynamics is expressed in
terms of energy-angle coordinates, it is observed that the angle is a fast
variable as compared to the energy. Thus, an effective stochastic dynamics for
the energy can be derived if the angular variable is averaged out. However, the
standard elimination procedure, performed earlier for a Gaussian white noise,
fails when the noise is colored because of correlations between the noise and
the fast angular variable. We develop here a specific averaging scheme that
retains these correlations. This allows us to calculate the probability
distribution function (P.D.F.) of the system and to derive the behavior of
physical observables in the long time limit
Electric Field Control of Soliton Motion and Stacking in Trilayer Graphene
The crystal structure of a material plays an important role in determining
its electronic properties. Changing from one crystal structure to another
involves a phase transition which is usually controlled by a state variable
such as temperature or pressure. In the case of trilayer graphene, there are
two common stacking configurations (Bernal and rhombohedral) which exhibit very
different electronic properties. In graphene flakes with both stacking
configurations, the region between them consists of a localized strain soliton
where the carbon atoms of one graphene layer shift by the carbon-carbon bond
distance. Here we show the ability to move this strain soliton with a
perpendicular electric field and hence control the stacking configuration of
trilayer graphene with only an external voltage. Moreover, we find that the
free energy difference between the two stacking configurations scales
quadratically with electric field, and thus rhombohedral stacking is favored as
the electric field increases. This ability to control the stacking order in
graphene opens the way to novel devices which combine structural and electrical
properties
Effect of Shear Flow on the Stability of Domains in Two Dimensional Phase-Separating Binary Fluids
We perform a linear stability analysis of extended domains in
phase-separating fluids of equal viscosity, in two dimensions. Using the
coupled Cahn-Hilliard and Stokes equations, we derive analytically the
stability eigenvalues for long wavelength fluctuations. In the quiescent state
we find an unstable varicose mode which corresponds to an instability towards
coarsening. This mode is stabilized when an external shear flow is imposed on
the fluid. The effect of the shear is seen to be qualitatively similar to that
found in experiments.Comment: 13 pages, RevTeX, 8 eps figures included. Submitted to Phys. Rev.
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