An HCMT model of optical microring-resonators

Analytical modes of the bus and cavity cores are combined into a 2-D hybrid analytical / numerical coupled mode theory (HCMT) model of integrated optical ring-resonators. The variational technique generates 1-D FEM-discretized solutions for the amplitude functions in their natural Cartesian and polar coordinates

Collective excitations in circular atomic configurations, and single-photon traps

Correlated excitations in a plane circular configuration of identical atoms with parallel dipole moments are investigated. The collective energy eigenstates, their level shifts and decay rates are computed utilizing a decomposition of the atomic state space into carrier spaces for the irreducible representations of the symmetry group \ZZ_N of the circle. It is shown that the index $p$ of these representations can be used as a quantum number analogously to the orbital angular momentum quantum number $l$ in hydrogen-like systems. Just as the hydrogen s-states are the only electronic wave functions which can occupy the central region of the Coulomb potential, the quasi-particle corresponding to a collective excitation of the atoms in the circle can occupy the central atom only for vanishing \ZZ_N quantum number $p$. If a central atom is present, the $p=0$ state splits into two and shows level-crossing at certain radii; in the regions between these radii, damped Rabi oscillations between two "extreme" $p=0$ configurations occur. The physical mechanisms behind super- and subradiance at a given radius and the divergence of the level shifts at small interatomic distances are discussed. It is shown that, beyond a certain critical number of atoms in the circle, the lifetime of the maximally subradiant state increases exponentially with the number of atoms in the configuration, making the system a natural candidate for a {\it single-photon trap}.Comment: Shortened version, accepted for publication in Phys. Rev.

Hybrid analytical/numerical coupled-mode modeling of guided-wave devices

A general version of coupled-mode-theory for frequency domain scattering problems in integrated optics is proposed. As a prerequisite a physically reasonable field template is required, that typically combines modes of the optical channels in the structure with coefficient functions of in principle arbitrary coordinates. Upon 1-D discretizations of these amplitude functions into finite elements, a Galerkin procedure reduces the problem to a system of linear equations in the element coefficients, where given input amplitudes are included. Smooth approximate solutions are obtained by solving the system in a least squares sense. The versatility of the approach is illustrated by means of a series of 2-D examples, including a perpendicular crossing of waveguides, and a grating-assisted rectangular resonator. As an appendix, we show that alternatively a similar procedure can be derived by variational means, i.e. by restricting a suitable functional representation of the full 2-D/3-D vectorial scattering problem (with transparent influx boundary conditions for inhomogeneous exterior) to the respective field templates.\u

Pathways to Accountability II

This report summarises the results of the 2009-2010 review process on the One World Trust Global Accountability Framework and the piloting of the draft framework during 2011, and presents the full One World Trust Pathways to Accountability II indicator framework. Our work in this field work is motivated by a concern about the persisting weakness and insufficient effectiveness of global organisations from all sectors in responding to the challenge of delivering global public goods to citizens and communities, the very people whom they claim to serve and benefit, and who are most often dependent on them

Xenotransplantation: Perspectives and limits

Xenotransplantation faces the dilemma of an unlimited supply of cells, tissues and organs on the one hand and severe obstacles and limits on the other. One reason for the limitations is that the source animal of choice, the pig, and the human recipient separated 90 million years ago during evolution, a time in which biological characteristics such as anatomy, physiology and immunology have had much time to drift far apart. The acceptance of such an evolutionary widely divergent organ, especially the heart of a pig, could evoke refusal of xenotransplantation in conservative and religious patients. New legal aspects of allocation of xenografts have therefore to be reflected upon and appropriate guidelines developed. Inquiries show, however, that the acceptance of all types of porcine organs would be high if the quality of life after receiving such a xenograft is comparable to that after receiving the same allograft. This individual benefit of a xenograft could lead to a disregard of the collective risk in terms of xenozoonoses, often presented as a catastrophic scenarium. Therefore, transplantation societies and ethics committees have published comments and even guidelines for handling future clinical xenotransplantation. All three monotheistic religions and Hinduism support the idea of saving and improving human life with the help of an animal organ. Copyrght (C) 2001 S. Karger AG, Basel

Opening up spaces for collegial, collaborative academic development practice within a strategic, centrally coordinated team-based support model

Academic development units do not always determine the orientation of their professional activity. This paper showcases an initiative to implement an institution-wide strategic, project and team-based, faculty support model in a regional, Australian university. The institution wished to broaden the impact of the academic development unit across five faculties and address growing staff need related to e-learning. Learning Innovation Teaching Enhancement(LITE) teams include academic developers, librarians, e-learning support and others. They work with faculty colleagues on learning and teaching projects, targeting improvement at the degree and discipline level. This study uses a participatory action research, mixed-methods approach to evaluate both the effectiveness of our centrally coordinated model, and our capacity to retain successful aspects of our previous practice, such as situatedness and collegiality. This stage of the evaluation locates our support model within existing academic development practice and assesses its alignment with good practice principles outlined in relevant literature. Based on a preliminary analysis of group reflection, faculty uptake, success of project outcomes and survey data I conclude that LITE team projects can be an effective model for academic development. This initial evaluation also suggests that individual team projects tend to open up more collegial academic development spaces under the following conditions: where there is faculty ownership of project aims; where there is a faculty leader within the project team; where there is horizontal interaction between faculty participants, and between faculty and support team participants; and, where the academic developer can leverage existing relationships and collegial networks to generate a more collegial environment

Quadridirectional eigenmode expansion scheme for 2-D modeling of wave propagation in integrated optics

Superpositions of two perpendicularly oriented bidirectional eigenmode propagation (BEP) fields, composed of basis modes that satisfy Dirichlet boundary conditions, can establish rigorous semianalytical solutions for problems of 2-D fixed-frequency wave propagation on unbounded, cross-shaped domains