1,043 research outputs found
Oscillatory long-wave Marangoni convection in a layer of a binary liquid: Hexagonal patterns
We consider a long-wave oscillatory Marangoni convection in a layer of a binary liquid in the presence of the Soret effect. A weakly nonlinear analysis is carried out on a hexagonal lattice. It is shown that the derived set of cubic amplitude equations is degenerate. A three-parameter family of asynchronous hexagons (AH), representing a superposition of three standing waves with the amplitudes depending on their phase shifts, is found to be stable in the framework of this set of equations. To determine a dominant stable pattern within this family of patterns, we proceed to the inclusion of the fifth-order terms. It is shown that depending on the Soret number, either wavy rolls 2 (WR2), which represents a pattern descendant of wavy rolls (WR) family, are selected or no stable limit cycles exist. A heteroclinic cycle emerges in the latter case: the system is alternately attracted to and repelled from each of three unstable solutions
Fiber amplification of radially and azimuthally polarized laser light
The results on amplifying either radially or azimuthally polarized light with
a fiber amplifier are presented. Experimental results reveal that more than 85%
polarization purity can be retained at the output even with 40dB amplification,
and that efficient conversion of the amplified light to linear polarization can
be obtained.Comment: 3 pages, 4 figures, submitted to optics letter
Creating research spaces for underserved communities: Expanding and extending intersectionality in contemporary educational contexts
Methods: Intersectionality has extended beyond the tenets of race, gender and class to include queer communities, religious issues, literacy concerns, pedagogical styles, etc. in South Africa, the European Union and beyond. Intersectionality is no longer solely relegated to the needs of African American women germane to the United States.
Aim(s): This paper is also aimed at engaging researchers and practitioners in an intellectual dialog that may contribute to the ever-expanding research on intersectionality to include the United States, European Union, South Africa and other global communities.
Background: Educators are cognisant of the dense demographic shifts and inequities in primary and secondary schools. The call for guidance, resources and policy is critically needed; the disproportionalities consistent in schools have manifested themselves in school disciplinary practices and student achievement. The manuscript encourages discourse and provides a roadmap to examine intersectionality’s expansion critically and how that expansion can aid in improving the lives of K-12 public education students on an international scale. Additionally, the manuscript addresses whether intersectionality or its expansion served as a pivotal voice for marginalised communities and structures domestically and abroad
Theory of selective excitation in Stimulated Raman Scattering
A semiclassical model is used to investigate the possibility of selectively
exciting one of two closely spaced, uncoupled Raman transitions. The duration
of the intense pump pulse that creates the Raman coherence is shorter than the
vibrational period of a molecule (impulsive regime of interaction). Pulse
shapes are found that provide either enhancement or suppression of particular
vibrational excitations.Comment: RevTeX4,10 pages, 5 figures, submitted to Phys.Rev.
A Large Blue Shift of the Biexciton State in Tellurium Doped CdSe Colloidal Quantum Dots
The exciton-exciton interaction energy of Tellurium doped CdSe colloidal
quantum dots is experimentally investigated. The dots exhibit a strong Coulomb
repulsion between the two excitons, which results in a huge measured biexciton
blue shift of up to 300 meV. Such a strong Coulomb repulsion implies a very
narrow hole wave function localized around the defect, which is manifested by a
large Stokes shift. Moreover, we show that the biexciton blue shift increases
linearly with the Stokes shift. This result is highly relevant for the use of
colloidal QDs as optical gain media, where a large biexciton blue shift is
required to obtain gain in the single exciton regime.Comment: 9 pages, 4 figure
Single-shot non-interferometric measurement of the phase transmission matrix in multicore fibers
A simple technique for far-field single-shot non-interferometric
determination of the phase transmission matrix of a multicore fiber with over
100 cores is presented. This phase retrieval technique relies on the aperiodic
arrangement of the cores.Comment: Submitted to Optics Letter
Dynamics of Perfectly Wetting Drops under Gravity
We study the dynamics of small droplets of polydimethylsiloxane (PDMS)
silicone oil on a vertical, perfectly-wetting, silicon wafer. Interference
videomicroscopy allows us to capture the dynamics of these droplets. We use
droplets with a volumes typically ranging from 100 to 500 nanolitres
(viscosities from 10 to 1000 centistokes) to understand long time derivations
from classical solutions. Past researchers used one dimensional theory to
understand the typical scaling for the position of the tip of the
droplet in time . We observe this regime in experiment for intermediate
times and discover a two-dimensional, similarity solution of the shape of the
droplet. However, at long times our droplets start to move more slowly down the
plane than the scaling suggests and we observe deviations in droplet
shape from the similarity solution. We match experimental data with simulations
to show these deviations are consistent with retarded van der Waals forcing
which should become significant at the small heights observed
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