26,851 research outputs found
Phase transition in conservative diffusive contact processes
We determine the phase diagrams of conservative diffusive contact processes
by means of numerical simulations. These models are versions of the ordinary
diffusive single-creation, pair-creation and triplet-creation contact processes
in which the particle number is conserved. The transition between the frozen
and active states was determined by studying the system in the subcritical
regime and the nature of the transition, whether continuous or first order, was
determined by looking at the fractal dimension of the critical cluster. For the
single-creation model the transition remains continuous for any diffusion rate.
For pair- and triplet-creation models, however, the transition becomes first
order for high enough diffusion rate. Our results indicate that in the limit of
infinite diffusion rate the jump in density equals 2/3 for the pair-creation
model and 5/6 for the triplet-creation model
Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS using multiphoton microscopy
We report second- and third-harmonic generation in monolayer MoS
as a tool for imaging and accurately characterizing the material's nonlinear
optical properties under 1560 nm excitation. Using a surface nonlinear optics
treatment, we derive expressions relating experimental measurements to second-
and third-order nonlinear sheet susceptibility magnitudes, obtaining values of
m V and for the first time for
monolayer MoS, m V.
These sheet susceptibilities correspond to effective bulk nonlinear
susceptibility values of m V and
m V, accounting for the sheet
thickness. Experimental comparisons between MoS and graphene are
also performed, demonstrating 3.4 times stronger third-order sheet
nonlinearity in monolayer MoS, highlighting the material's
potential for nonlinear photonics in the telecommunications C band.Comment: Accepted by 2D Materials, 28th Oct 201
PCA Tomography and its application to nearby galactic nuclei
With the development of modern technologies such as IFUs, it is possible to
obtain data cubes in which one produces images with spectral resolution. To
extract information from them can be quite complex, and hence the development
of new methods of data analysis is desirable. We briefly describe a method of
analysis of data cubes (data from single field observations, containing two
spatial and one spectral dimension) that uses Principal Component Analysis
(PCA) to express the data in the form of reduced dimensionality, facilitating
efficient information extraction from very large data sets. We applied the
method, for illustration purpose, to the central region of the low ionization
nuclear emission region (LINER) galaxy NGC 4736, and demonstrate that it has a
type 1 active nucleus, not known before. Furthermore, we show that it is
displaced from the centre of its stellar bulge.Comment: 4 pages, 1 figure, 1 table, to be published in the Proceedings of the
IAU Symposium no. 26
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