1,341 research outputs found
Controlling Marangoni induced instabilities in spin-cast polymer films: how to prepare uniform films
In both research and industrial settings spin coating is extensively used to
prepare highly uniform thin polymer films. However, under certain conditions,
spin coating results in films with non-uniform surface morphologies. Although
the spin coating process has been extensively studied, the origin of these
morphologies is not fully understood and the formation of non-uniform spincast
films remains a practical problem. Here we report on experiments demonstrating
that the formation of surface instabilities during spin coating is dependent on
temperature. Our results suggest that non-uniform spincast films form as a
result of the Marangoni effect, which describes flow due to surface tension
gradients. We find that both the wavelength and amplitude of the pattern
increase with temperature. Finally, and most important from a practical
viewpoint, the non-uniformities in the film thickness can be entirely avoided
simply by lowering the spin coating temperature.Comment: 8 pages, 6 figures. electronic supplementary material: 3 pages, 4
figure
New developments in FeynRules
The program FeynRules is a Mathematica package developed to facilitate the
implementation of new physics theories into high-energy physics tools. Starting
from a minimal set of information such as the model gauge symmetries, its
particle content, parameters and Lagrangian, FeynRules provides all necessary
routines to extract automatically from the Lagrangian (that can also be
computed semi-automatically for supersymmetric theories) the associated Feynman
rules. These can be further exported to several Monte Carlo event generators
through dedicated interfaces, as well as translated into a Python library,
under the so-called UFO model format, agnostic of the model complexity,
especially in terms of Lorentz and/or color structures appearing in the
vertices or of number of external legs. In this work, we briefly report on the
most recent new features that have been added to FeynRules, including full
support for spin-3/2 fermions, a new module allowing for the automated
diagonalization of the particle spectrum and a new set of routines dedicated to
decay width calculations.Comment: 6 pages. Contribution to the 15th International Workshop on advanced
computing and analysis techniques (ACAT 2013), 16-21 May, Beijing, Chin
Ultra-narrow (sub-MHz) linewidth emission from discrete mode laser diodes
A class of laser which exhibits ultra-narrow sub MHz linewidth emission necessary for numerous applications in optical communications and sensors is described. The spectral performance of commercial discrete mode (DM) and distributed feedback (DFB) lasers is compared. The devices used in this work are asymmetrically coated ridge waveguide Fabry Perot lasers which incorporated etched slot features and emitting around lambda = 1.55 mum. The active region of the devices consisted of a strained compensated InAlGaAs MQW structure
Lived experiences of students in a public school enthusiast in playing Mobile Legends
The research study comprises a pure qualitative approach bounded in grounded theory and thematic analysis – a system of qualitative research that based on the data of the participants, the researcher will come up with the suggested principles on how to remediate the live experiences of the Mobile Legend Players who are also learners, and to give some collected data to be discussed as an authentic approach of comparing and relating the lived experiences of both study habits and the playing habits of the Grade 12 Learners of Salcedo Vocational High School
System-performance analysis of optimized gain-switched pulse source employed in 40-and 80-Gb/s OTDM systems
The development of ultrashort optical pulse sources, exhibiting excellent temporal and spectral profiles, will play a crucial role in the performance of future optical time division multiplexed (OTDM) systems. In this paper, we demonstrate the difference in performance in 40- and 80-Gb/s OTDM systems between optical pulse sources based on a gain-switched laser whose pulses are compressed by a nonlinearly and linearly chirped fiber Bragg grating. The results achieved show that nonlinear chirp in the wings of the pulse leads to temporal pedestals formed on either side of the pulse when using the linearly chirped grating, whereas with the nonlinearly chirped grating, pedestals are essentially eliminated. In an OTDM system, these pedestals cause coherent interaction between neighboring channels, resulting in intensity fluctuations that lead to a power penalty of 1.5 dB (40 Gb/s) and 3.5 dB (80 Gb/s) in comparison to the case where the nonlinearly chirped grating is used. Simulations carried out with the aid of Virtual Photonics Inc. verify the results achieved
80-Gb/s OTDM system analysis of a vertical microcavity-based saturable absorber for the enhancement of pulse pedestal suppression
In future high-speed optical time-division-multiplexed (OTDM) systems, an important factor that needs to be considered for optical pulse generation schemes is the impact of pulse pedestals on the overall system performance. The results presented in this letter are two-fold; first, the impact due to the height of pulse pedestals in an 80-Gb/s OTDM system are established. Second, a solution is provided to overcome these high pedestal levels through the use of a vertical microcavity saturable absorber, which can significantly reduce the pulse pedestal level and give enhanced system performanc
Magellan LDSS3 emission confirmation of galaxies hosting metal-rich Lyman-alpha absorption systems
Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay
Telescope, we target {candidate absorption host galaxies} detected in deep
optical imaging {(reaching limiting apparent magnitudes of 23.0-26.5 in and filters) in the fields of three QSOs, each of which shows the
presence of high metallicity, high absorption systems in their
spectra (Q0826-2230: =0.9110, Q1323-0021: ,
Q1436-0051: ). We confirm three host galaxies {at
redshifts 0.7387, 0.7401, and 0.9286} for two of the Lyman- absorption
systems (one with two galaxies interacting). For these systems, we are able to
determine the star formation rates (SFRs); impact parameters (from previous
imaging detections); the velocity shift between the absorption and emission
redshifts; and, for one system, also the emission metallicity.} Based on
previous photometry, we find these galaxies have LL. The [O II]
SFRs for these galaxies are in the range M yr
{(uncorrected for dust)}, while the impact parameters lie in the range
kpc. {Despite the fact that we have confirmed galaxies at 50 kpc from the QSO,
no gradient in metallicity is indicated between the absorption metallicity
along the QSO line of sight and the emission line metallicity in the galaxies.}
We confirm the anti-correlation between impact parameter and from
the literature. We also report the emission redshift of five other galaxies:
three at , and two (LL) at not
corresponding to any known absorption systems.Comment: 14 pages, 7 figures, 4 tables, accepted to MNRA
Pulse source for 80 Gb/s systems using a gain-wwitched laser diode followed by a nonlinearly chirped grating
This work presents the generation of 3.5 ps pulses at a repetition rate of 10 GHz and the optimization of the pulse spectrum. The output pulses are near transform limited and have pulse pedestals that are virtually eliminated to 35 dB down from the peak of the pulse, thus providing a source suitable for use in 80 Gb/s OTDM systems
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