472 research outputs found

    A new species of tapeworm of the genus Proteocephalus from the Perch and the Rock Bass

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    http://deepblue.lib.umich.edu/bitstream/2027.42/56506/1/OP067.pd

    A Teacher\u27s Trouble: Risk, Responsibility and Rebellion

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    What follows is an edited transcript of a session at the 1995 Annual Meeting of the Association of American Law Schools, held in New Orleans, Louisiana, January 7, 1995. The meeting was a joint plenary session of the AALS Section on Professional Responsibility and the Section on Clinical Legal Education. The meeting was planned and the role plays were written by Professors Margaret Martin Barry and Lisa Lerman of The Catholic University of America and Professor Homer La Rue of Howard University. The purpose of the program was to foster interaction among teachers of professional responsibility and clinical teachers about issues that arise in both clinical and non-clinical teaching. As Professor Sandy Ogilvy of Catholic University said in introducing the session, the planners wanted to bring together the perspective on the profession of the professional responsibility teachers, with the expertise in teaching methodology of the clinicians, with the thought that each group would be interested in what the other group had to say. Interesting ethical issues arise daily in clinical programs, and the planners wanted to encourage cross-fertilization between these two fields and increased collaboration within law schools between clinical teachers and teachers of professional responsibility. In developing the three role plays presented in this program, the planners selected issues that raise ethical or professional dilemmas for the law teachers as well as for their students. The transcript of this discussion explores only some of the issues potentially raised by the role play scenarios. The editors of the Clinical Law Review invite readers to submit commentary reacting to the issues raised in this discussion, or raising other issues suggested by the role plays but not fully discussed by the participants. The Review will consider such submissions for possible publication in its next issue. Readers might also consider initiating further dialogue with colleagues through one of the relevant internet listservs (lawclinic, legalethics or lawprof); such dialogue also may be submitted for possible publication

    A compact two-dimensional grating coupler used as a polarization splitter

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    We demonstrate a novel polarization splitter based on a two-dimensional grating etched in a silicon-on-insulator waveguide. The device couples orthogonal modes from a single-mode optical fiber into identical modes of two planar ridge waveguides. The extinction ratio is better than 18 dB in the wavelength range of 1530-1560 nm and the coupling efficiency is approximately 20%. The device is very compact and couples light only to transverse-electric modes of the planar waveguides. Therefore, it may be used in a polarization diversity configuration to implement a polarization insensitive photonic integrated circuit based on photonic crystal waveguides

    Enhancement and reproducibility of high quality factor, one-dimensional photonic crystal/photonic wire (1D PhC/PhW) microcavities

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    Background: The production of compact and multi-functional photonic devices has become a topic of major research activity in recent years. Devices have emerged that can be used for functional requirements in high speed optical data processing, filtering, nonlinear optical functions such as all-optical switching - and many other applications. The combination of photonic crystal (PhC) structures consisting of a single row of holes embedded in a narrow photonic wire (PhW) waveguide realised in high index-contrast materials is a possible contender for provision of a range of compact devices on a single chip. This trend has been motivated by the availability of a silicon technology that can support monolithic integration to form fully functional devices on CMOS chips. Results: We have successfully demonstrated experimentally an enhancement of the quality factor of a one-dimensional (1D) photonic crystal/photonic wire (PhC/PhW) microcavity that can exhibit resonance quality factor (Q-factor) values as high as 800,000 - together with a low modal volume of approximately 0.5 (λ/n)3. These results are based on the use of a mode matching approach previously used for device design - through the engineering of tapered hole sections within and outside the cavity - and were achieved without removing the silica cladding layer below the silicon waveguide core. The simulation results obtained in this case also agree with the experimental results obtained. Conclusions: In this work we have demonstrated that the mode matching, as light enters the photonic crystal structure, can be further enhanced through the use of careful fine tuning of the third hole, t3 of the tapered hole region outside the cavity. The Q-factor value obtained was approximately four times greater than that achieved in our previous work on a similar structure

    Modelling of photonic wire Bragg Gratings

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    Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

    Modulational instability in a silicon-on-insulator directional coupler: Role of the coupling-induced group velocity dispersion

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    We report frequency conversion experiments in silicon-on-insulator (SOI) directional couplers. We demonstrate that the evanescent coupling between two subwavelength SOI waveguides is strongly dispersive and significantly modifies modulational instability (MI) spectra through the coupling induced group velocity dispersion (GVD). As the separation between two 380-nm-wide silicon photonic wires decreases, the increasing dispersion of the coupling makes the GVD in the symmetric supermode more normal and suppresses the bandwidth of the MI gain observed for larger separations

    Unusual raptor nests around the world

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    From surveys in many countries, we report using unusual nesting materials (e.g., paper money, rags, metal, antlers, and large bones) and unusual nesting situations. For example, we documented nests of Steppe Eagles [Aquila nipalensis] and Upland Buzzards [Buteo hemilasius] on the ground beside well-traveled roads, Saker Falcon [Falco cherrug] eyries in attics and a cistern, and Osprey [Pandian haliaetus] nests on the masts of boats and on a suspended automobile. Other records include a Golden Eagle [A. chrysaelos] nest 7.0 m in height, believed to be the tallest nest ever described, and, for the same species, we report nesting in rudimentary, nests. Some nest sites are within a Few meters of known predators or competitors. These unusual observations may be important in revealing the plasticity of a species' behavioral repertoire
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