4,280 research outputs found
Waveguide photonic limiters based on topologically protected resonant modes
We propose a concept of chiral photonic limiters utilising topologically
protected localised midgap defect states in a photonic waveguide. The chiral
symmetry alleviates the effects of structural imperfections and guaranties a
high level of resonant transmission for low intensity radiation. At high
intensity, the light-induced absorption can suppress the localised modes, along
with the resonant transmission. In this case the entire photonic structure
becomes highly reflective within a broad frequency range, thus increasing
dramatically the damage threshold of the limiter. Here we demonstrate
experimentally the principle of operation of such photonic structures using a
waveguide consisting of coupled dielectric microwave resonators.Comment: 6 pages, 4 figure
Enhancement of localization in one-dimensional random potentials with long-range correlations
We experimentally study the effect of enhancement of localization in weak
one-dimensional random potentials. Our experimental setup is a single mode
waveguide with 100 tuneable scatterers periodically inserted into the
waveguide. By measuring the amplitudes of transmitted and reflected waves in
the spacing between each pair of scatterers, we observe a strong decrease of
the localization length when white-noise scatterers are replaced by a
correlated arrangement of scatterers.Comment: 4 pages, 6 figure
An in situ instrument for planar O2 optode measurements at benthic interfaces
A new in situ instrument for twoâdimensional mapping of oxygen in coastal sediments is presented. The measuring principle is described, and potential mechanical disturbances, solute and particle smearing associated with the measurements, and calibration routines are evaluated. The first in situ measurements obtained in two different benthic communities are presented. In a shallow photosynthetic sediment (1 m of water depth), an extensive horizontal and temporal variation in the O2 distribution caused by benthic photosynthesis and irrigating fauna was resolved. Repetitive planar optode measurements performed along a transect in central Ăresund, Denmark (17 m of water depth) revealed a positive correlation between the apparent O2 penetration depths (OP) measured with a lateral distance <5.0 mm, whereas OP measured with a larger horizontal distance (up to 50 m) were not correlated. Consequently, the OP varied in patches with a characteristic size of 5.0 mm. The instrument described is a powerful new tool for in situ characterization of spatiotemporal variations in O2 distributions within benthic communities. The instrument can be adapted for use at full ocean depths, e.g., on deepâsea landers or remote operating vehicles
Utilization of Drought-Stricken Corn Silage by Yearling Steers
Corn silage is a very versatile and palatable feed that fits well into many cattle feeding programs. Insufficient rainfall in several areas of the country in recent years has resulted in many additional acres of corn being ensiled due to the low potential grain yield. Harvesting drought-stricken corn silage results in at least partial salvage of the crop. However, many farmers have expressed concern about the feeding value of drought-damaged corn silage and how it can be best incorporated into feedlot rations for optimal performance and maximal economic return
Two-Dimensional Magnetic Resonance Tomographic Microscopy using Ferromagnetic Probes
We introduce the concept of computerized tomographic microscopy in magnetic
resonance imaging using the magnetic fields and field gradients from a
ferromagnetic probe. We investigate a configuration where a two-dimensional
sample is under the influence of a large static polarizing field, a small
perpendicular radio-frequency field, and a magnetic field from a ferromagnetic
sphere. We demonstrate that, despite the non-uniform and non-linear nature of
the fields from a microscopic magnetic sphere, the concepts of computerized
tomography can be applied to obtain proper image reconstruction from the
original spectral data by sequentially varying the relative sample-sphere
angular orientation. The analysis shows that the recent proposal for atomic
resolution magnetic resonance imaging of discrete periodic crystal lattice
planes using ferromagnetic probes can also be extended to two-dimensional
imaging of non-crystalline samples with resolution ranging from micrometer to
Angstrom scales.Comment: 9 pages, 11 figure
Perception of nonnative tonal contrasts by Mandarin-English and English-Mandarin sequential bilinguals
This study examined the role of acquisition order and crosslinguistic similarity in influencing transfer at the initial stage of perceptually acquiring a tonal third language (L3). Perception of tones in Yoruba and Thai was tested in adult sequential bilinguals representing three different first (L1) and second language (L2) backgrounds: L1 Mandarin-L2 English (MEBs), L1 English-L2 Mandarin (EMBs), and L1 English-L2 intonational/non-tonal (EIBs). MEBs outperformed EMBs and EIBs in discriminating L3 tonal contrasts in both languages, while EMBs showed a small advantage over EIBs on Yoruba. All groups showed better overall discrimination in Thai than Yoruba, but group differences were more robust in Yoruba. MEBsâ and EMBsâ poor discrimination of certain L3 contrasts was further reflected in the L3 tones being perceived as similar to the same Mandarin tone; however, EIBs, with no knowledge of Mandarin, showed many of the same similarity judgments. These findings thus suggest that L1 tonal experience has a particularly facilitative effect in L3 tone perception, but there is also a facilitative effect of L2 tonal experience. Further, crosslinguistic perceptual similarity between L1/L2 and L3 tones, as well as acoustic similarity between different L3 tones, play a significant role at this early stage of L3 tone acquisition.Published versio
Characteristics of 454 pyrosequencing dataâenabling realistic simulation with flowsim
Motivation: The commercial launch of 454 pyrosequencing in 2005 was a milestone in genome sequencing in terms of performance and cost. Throughout the three available releases, average read lengths have increased to âŒ500 base pairs and are thus approaching read lengths obtained from traditional Sanger sequencing. Study design of sequencing projects would benefit from being able to simulate experiments
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