High-Q photonic crystal cavities in all-semiconductor photonic-crystal heterostructures

Photonic crystal cavities enable the realization of high Q-factor and low mode-volume resonators, with typical architectures consisting of a thin suspended periodically-patterned layer to maximize confinement of light by strong index guiding. We investigate a heterostructure-based approach comprising a high refractive index core and lower refractive index cladding layers. Whilst confinement typically decreases with decreasing index contrast between the core and cladding layers, we show that, counter-intuitively, due to the confinement provided by the photonic band structure in the cladding layers, it becomes possible to achieve Q-factors $>10^4$ with only a small refractive index contrast. This opens up new opportunities for implementing high Q-factor cavities in conventional semiconductor heterostructures, with direct applications to the design of electrically-pumped nano-cavity lasers using conventional fabrication approaches

The Cayley-Hilbert metric and positive operators

AbstractThe Cayley-Hilbert metric is defined for a real Banach space containing a closed cone. By restricting the domain of a particular type of positive nonlinear operator, the Banach contraction-mapping theorem is used to prove the existence of a unique fixed point of the operator with explicit upper and lower bounds. Applications to quasilinear elliptic partial differential equations and to matrix theory are considered

New Graduate Nurses\u27 Structural Empowerment and Their Experience of Co-worker Incivility and Burnout

Burnout among new graduate nurses [NGNs] is a risk to workplace retention and commitment to the nursing profession. With threats of nursing shortages, safeguarding and supporting NGN to maintain workplace allegiance and professional commitment is paramount. Research has highlighted the harmful effects of uncivil working environments and the deleterious effects it can have on working relationships. In this secondary analysis, Kanter’s (1977) theory of structural empowerment was tested using a predictive, non-experimental design in a sample of NGN working in acute care hospitals in Ontario. Two hypothesized models predicted that high levels of structural empowerment and low levels of coworker incivility are associated with low levels of emotional exhaustion and cynicism among NGN. Both workplace empowerment and incivility were significant strong predictors of lower levels of emotional exhaustion and cynicism. The overall findings suggest the combination of empowering workplaces and fewer incidences of incivility from co-workers influence NGN experiences of burnout

Living in the Moment: The Everyday in Woolf’s Mrs. Dalloway and Cunningham’s The Hours

In this essay the importance and effect of the everyday moment in Virginia Woolf's Mrs. Dalloway and Michael Cunningham's The Hours is discussed. Whether the everyday moment is shown as baking a cake, taking a sip of coffee or making hats, each moment has its own significant impact on the characters. The impact arouses both powerful feelings and illuminating possibilities in the lives of the characters, thus demonstrating that the ordinary moments in life often hold the greatest significance

Passive value capture through income taxation, and a beneficiaries-based funding model for infrastructure

Value capture is used to describe a range of mechanisms used to fund infrastructure projects. Active value capture mechanisms, specifically designed to raise revenue are well documented including land taxes, asset sales and other mechanisms with a direct nexus to the infrastructure that it funds. However passive value capture mechanisms exist, through extant government tax systems that capture value without being part of a specific program or policy to pay for infrastructure. These and their potential role in infrastructure investment are not well documented, with increased income tax collection representing a potentially significant stream of value capture funding for infrastructure investment. Through analysing current business cases with business beneficiaries, this paper documents income tax value capture and demonstrates how it may play a role in project funding. A beneficiary funding framework is developed to show how government investment levels may be structured to allow economically but non-financially viable projects to proceed to create value within the bounds of treasury constraints

Some properties of reaction: Bonded silicon nitride

Electron Spin Resonance, Pulse Echo Ultrasonics and electrical conductivity measurements have been used to study the effect of the unreacted silicon which is present in Reaction Bonded Silicon Nitride (RBSN) as a result of the manufacturing process. One of the techniques (ESR) has been found to be very sensitive to the unreacted silicon, and the PEG Ultrasonic measurements have suggested that weight gain should not be the sole criterion by which to judge RBSN for mechanical applications. ESR studies of unreacted silicon powder gave a signal, similar to that reported for amorphous silicon with g = 2.0055; the line is attributed to dangling bonds. ESR spectra have been found for both RBSN and Hot Pressed Silicon Nitride (HPSN) with g values closer to the free electron value. Measurements on partially reacted materials showed a complex signal whose shape changed considerably over the temperature range 4 to 300 K. The behaviour of this line, presumed to be the sum of the silicon and RBSN signals is probably attributably to differences in the relaxation rates of the two species. Determination of the elastic constants of the RLSN materials has shown that partially nitrided ceramics have lower strength than fully nitrided materials with similar densities, except in the region were the reaction is nearly complete (weight gain of 59% or more) when the effect of unreacted silicon is negligible, and the major factor governing strength is density. A.C.electrical measurements on high weight gain materials have shown dielectric constant (ɛ’) behaviour analagous to the mechanical strength in that the higher ɛ' has been found for the denser (less porous), but lower weight gain material. In contrast to this, however, the high weight gain material was found to have a lower tanδ this is consistent with the lower levels of silicon in the fully reacted ceramic. D.C. 'step response' measurements at room temperature gave results which fitted Jonscher's two stage relaxation theory. I(_D) (t) α (w(_p)t)(^n) + (w(_p)t)(^k) with n in the region 0.7 to 0.8 and k in the region 1.45 to 1.6. D.C. and A.C. results over the temperature range 100ºC to 900ºC suggested that the predominant conductivity up to 750ºC was hopping either in defect bands or localized states in the band tails