52 research outputs found
Experimental characterization of a graded-index ring-core fiber supporting 7 LP mode groups
We design and characterize a graded-index-ring-core fiber supporting 7 LP modegroups (13 spatial modes) for mode multiplexed transmission with low MIMO processing complexity. Spatial and temporal modal properties are analyzed using an SLM-based mode multiplexer/demultiplexer
An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud
The local correlation between far-infrared (FIR) emission and radio-continuum
(RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales
from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc.
The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is
shown to be greatest in the most active star forming regions with a power law
slope of ~1.14 indicating that the RC emission increases faster than the FIR
emission. The slope of the other regions and the SMC are much flatter and in
the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the
regions which range from 0.5 to 0.95. The thermal fraction of the RC emission
alone can provide the expected FIR/RC correlation. The results are consistent
with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray
electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s
appear to escape the SMC so readily, the results here may not provide support
for coupling between the local gas density and the magnetic field intensity.Comment: 19 pages, 7 Figure
Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure
Ab initio total-energy density-functional methods with supercell models have
been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and
Au(100) surfaces. The atomic geometries of the surfaces and the preferred
bonding sites of the bromine have been determined. The bonding character of
bromine with the substrates has also been studied by analyzing the electronic
density of states and the charge transfer. The calculations show that while the
four-fold hollow-site configuration is more stable than the two-fold
bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on
the Au(100) surface. The one-fold on-top configuration is the least stable
configuration on both surfaces. It is also observed that the second layer of
the Ag substrate undergoes a small buckling as a consequence of the adsorption
of Br. Our results provide a theoretical explanation for the experimental
observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces
results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres
Project TENDR: Targeting environmental neuro-developmental risks. the TENDR consensus statement
Children in America today are at an unacceptably high risk of developing neurodevelopmental disorders that affect the brain and nervous system including autism, attention deficit hyperactivity disorder, intellectual disabilities, and other learning and behavioral disabilities. These are complex disorders with multiple causes—genetic, social, and environmental. The contribution of toxic chemicals to these disorders can be prevented. Approach: Leading scientific and medical experts, along with children’s health advocates, came together in 2015 under the auspices of Project TENDR: Targeting Environmental Neuro-Developmental Risks to issue a call to action to reduce widespread exposures to chemicals that interfere with fetal and children’s brain development. Based on the available scientific evidence, the TENDR authors have identified prime examples of toxic chemicals and pollutants that increase children’s risks for neurodevelopmental disorders. These include chemicals that are used extensively in consumer products and that have become widespread in the environment. Some are chemicals to which children and pregnant women are regularly exposed, and they are detected in the bodies of virtually all Americans in national surveys conducted by the U.S. Centers for Disease Control and Prevention. The vast majority of chemicals in industrial and consumer products undergo almost no testing for developmental neurotoxicity or other health effects. Conclusion: Based on these findings, we assert that the current system in the United States for evaluating scientific evidence and making health-based decisions about environmental chemicals is fundamentally broken. To help reduce the unacceptably high prevalence of neurodevelopmental disorders in our children, we must eliminate or significantly reduce exposures to chemicals that contribute to these conditions. We must adopt a new framework for assessing chemicals that have the potential to disrupt brain development and prevent the use of those that may pose a risk. This consensus statement lays the foundation for developing recommendations to monitor, assess, and reduce exposures to neurotoxic chemicals. These measures are urgently needed if we are to protect healthy brain development so that current and future generations can reach their fullest potential
Recent advances in the chemistry of gold(I) complexes with C-, N- and S-donor ligands part I: alkynyl, amino, imino and nitrido derivatives
Crosstalk in polarisation-maintaining fibres
We show that internal geometric imperfections have a negligible effect on polarisation cross-talk in a birefringent fibre. This is contrary to popular opinion and has considerable implications for the way in which polarisation maintaining fibres are specified
Gain equalization of a six-mode-group ring core multimode EDFA
We propose a 6-mode-group ring core multimode erbium doped fiber amplifier (RC-MMEDFA) capable of providing almost identical gain among the six mode groups within the C band using either core- or cladding-pumped implementations
Fibre-taper devices
In this paper I will review recent work at Southampton on tapered single mode optical fibre devices. In particular I will describe our recent work on single mode beam expanders and fused fibre couplers. It is well known that a gap of up to 100 µm in a single mode fibre results in about 1dB loss. By tapering the fibre so that the field expands into an LP cladding mode with increased spot size it is possible to introduce a larger gap of about one mm. This will allow the insertion of small electro-optic devices, such as a liquid crystal cell. By overjacketing the fibre with a silica capillary, or combination of Vycor and silica capillaries it should be possible to achieve a beam diameter of several hundred microns. This would allow a gap of about 1 cm and this would allow the insertion of a very wide range of optical devices, such as acousto optic modulators. Considerable progress has been made recently in the fabrication and analysis of long fused-taper 4-port directional couplers. This has resulted in several important devices, including polarization beam splitters, wavelength division multiplexers, optical fibre filters, and wavelength selective ring resonator
Predicted performance of Franz-Keldysh effect optical reflection modulators and comparisons with similar multiple quantum well-based devices
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