Symmetry breaking and manipulation of nonlinear optical modes in an asymmetric double-channel waveguide

We study light-beam propagation in a nonlinear coupler with an asymmetric double-channel waveguide and derive various analytical forms of optical modes. The results show that the symmetry-preserving modes in a symmetric double-channel waveguide are deformed due to the asymmetry of the two-channel waveguide, yet such a coupler supports the symmetry-breaking modes. The dispersion relations reveal that the system with self-focusing nonlinear response supports the degenerate modes, while for self-defocusingmedium the degenerate modes do not exist. Furthermore, nonlinear manipulation is investigated by launching optical modes supported in double-channel waveguide into a nonlinear uniform medium.Comment: 10 page

SMART - Sediment Mitigation Actions for the River Rother, UK

The River Rother, West Sussex, is suffering from excess sediment which is smothering the river bed gravels. This is thought to be exacerbating issues of pollution and degradation of ecosystems. This project aims to identify the severity, extent, possible causes and potential mitigation options available to reduce these pressures on the river. Data have been collected from ten sites to investigate the amount of sediment stored in the river bed gravels and cores obtained from four small reservoirs to establish rates of sedimentation and contribute to the construction of a temporal sediment budget over the last 50–100 years. Evidence suggests that tributary streams have more stored sediment per m2 upstream of their confluence with the River Rother compared to the Rother itself. Reservoir core data indicate that sediment has accumulated more rapidly in the small reservoirs surrounded by mixed agricultural land compared to one surrounded by ancient woodland. These are preliminary results and work is continuing

Cold treatment enhances low-temperature flight performance in false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae)

1 In sterile insect technique programmes, temperatures experienced by insects during rearing and handling, along with cool temperatures after release, can negatively affect performance and activity levels. Phenotypic plasticity (trait modifications caused by prior stress exposure) can offset these effects but is poorly understood in many species and traits. 2 We investigated the effects of a cold treatment (2 ∘C for 16 h) on flight performance in adult false codling moth, Thaumatotibia leucotreta. Using diverse methods, flight performance was tested using flight assays in the laboratory and in the field under varying environmental conditions. 3 The flight performance of T. leucotreta in the laboratory was affected by cold treatment (relative to a 25 ∘C control group), test temperature and their interaction. Field recapture of released moths was significantly affected by the interaction between cold treatment and environmental conditions. 4 Field recapture counts depended on the ambient temperature upon release. For example, under warmer conditions (>17 ∘C), the recapture count of cold-treated moths was lower than that of the untreated control group, whereas the recapture count of cold-treated moths at cooler temperatures was significantly higher. 5 Our results suggest a temperature-dependent interaction between acute cold exposure and flight performance in adult T. leucotreta, which may be used to enhance the efficacy of the sterile insect technique under cooler environmental conditions

Comparison of three methods for materials identification and mapping with imaging spectroscopy

We are comparing three methods of mapping analysis tools for imaging spectroscopy data. The purpose of this comparison is to understand the advantages and disadvantages of each algorithm so others would be better able to choose the best algorithm or combinations of algorithms for a particular problem. The three algorithms are: (1) the spectralfeature modified least squares mapping algorithm of Clark et al (1990, 1991): programs mbandmap and tricorder; (2) the Spectral Angle Mapper Algorithm(Boardman, 1993) found in the CU CSES SIPS package; and (3) the Expert System of Kruse et al. (1993). The comparison uses a ground-calibrated 1990 AVIRIS scene of 400 by 410 pixels over Cuprite, Nevada. Along with the test data set is a spectral library of 38 minerals. Each algorithm is tested with the same AVIRIS data set and spectral library. Field work has confirmed the presence of many of these minerals in the AVIRIS scene (Swayze et al. 1992)

The Use of Sodium Pyrophosphate to Improve a Translucent Clay Simulate

In the ever expanding quest to understand the nature and behavior of soil, translucent and even transparent media have been developed to serve as soil simulates. These artificial soils can be used in experimental models to make visual measurement of phenomena such as geosystem kinematics, soil mass movement, soil particle motion, and pore fluid flow that would be nearly impossible to obtain in natural opaque soils without expensive equipment or boundary effects. One successful type of translucent clay simulate is lithium sodium magnesium silicate (LNM silicate); however, it’s low density/high void ratio results in higher than typical permeability, low undrained shear strength, and extremely long consolidation times. Until now, translucent soil simulates of only 4.5% by mass LNM silicate to total mass have been possible. This paper provides a method for creating mixtures of translucent LNM silicate gel/glass as high as 15% by mass with the additions of an emulsifier, sodium pyrophosphate decahydrate (SPP), which impedes gelation so additional silicate powder can be added. Further, digital image processing techniques are used to present a relationship between LNM silicate, SPP, and translucency and an analysis of the modified simulate’s permeability and consolidation properties, with comparisons to natural clays, is also included.The lead author would like to acknowledge the excellent work of the undergraduate researchers on this project: Elliese Shaughnessy for the laboratory work and MATLAB programming necessary to create the Laponite-SPP curve, Kristen Ewert for conducting and interpreting the consolidation experiments, Nicholas Boardman for mixing the testing specimens and conducting the permeability experiments, and Tom Anderson for assisting with the permeability experiments. We would also like to thank Dr. Cassandra Rutherford for her assistance on the project. This research was funded through the National Science Foundation, Award Number: 1041604.This is the author accepted manuscript. The final version is available from American Society of Civil Engineers via http://dx.doi.org/10.1061/9780784480151.00

Stable isotope values in modern bryozoan carbonate from New Zealand and implications for paleoenvironmental interpretation

Bryozoan carbonate contains useful geochemical evidence of temperate shelf paleoenvironments. Stable isotope values were determined for 103 modern marine bryozoan skeletons representing 30 species from New Zealand. δ18O values range from -1.4 to 2.8 VPDB, while δ13C range from -4.5 to 2.8 VPDB (values uncorrected for mineralogical variation). These values are distinct from those of both tropical marine skeletons and New Zealand Tertiary fossils. Most bryozoans secrete carbonate in or near isotopic equilibrium with sea water, except for Celleporina and Steginoporella. The complex and variable mineralogies of the bryozoans reported here make correction for mineralogical effects problematic. Nevertheless, mainly aragonitic forms display higher isotope values, as anticipated. Both temperature and salinity constrain δ18O and δ13C values, and vary with latitude and water depth. Ten samples from a single branch of Cinctipora elegans from the Otago shelf cover a narrow range, although the striking difference in carbon isotope values between the endozone and exozone probably reflects different mineralisation histories. Our stable isotope results from three different laboratories on a single population from a single location are encouragingly consistent. Monomineralic bryozoans, when carefully chosen to avoid species suspected of vital fractionation, have considerable potential as geochemical paleoenvironmental indicators, particularly in temperate marine environments where bryozoans are dominant sediment producers

Observation of surface gap solitons in semi-infinite waveguide arrays

We report on the first observation of surface gap solitons, recently predicted to exist at the interface between uniform and periodic dielectric media with defocusing nonlinearity [Ya.V. Kartashov et al., Phys. Rev. Lett. 96, 073901 (2006). We demonstrate strong self-trapping at the edge of a LiNbO_3 waveguide array and the formation of staggered surface solitons with propagation constant inside the first photonic band gap. We study the crossover between linear repulsion and nonlinear attraction at the surface, revealing the mechanism of nonlinearity-mediated stabilization of the surface gap modes.Comment: 4 pages, 5 figure