Novel resonant and light-guiding phenomena in photonics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 100-109).We investigate theoretically five novel resonant and light-guiding photonics phenomena. First, we develop a universal coupled mode theory (CMT) treatment of the freespace scattering of waves from resonant objects. This analytical framework very accurately models the scattering and absorption cross sections, as long as the resonant scatterer has spherical/cylindrical symmetry, or is sufficiently smaller than the resonant wavelength of the incident wave. We apply it to study the scattering of light from spherically symmetrical resonant objects and atoms, and also the neutron scattering off nuclei. Then, we propose an efficient weakly-radiative Wireless Energy Transfer (WET) scheme between two identical classical resonant objects, strongly coupled to an intermediate one having the same resonance frequency. The transfer mechanism, analyzed by CMT, relies on the adiabatic evolution of a dark eigenstate of the 3-object system. We explore its performance in various parameter regimes, and illustrate it by witricity-type WET between resonant inductively-coupled capacitively-loaded metallic loops. Third, we develop an analytical CMT model for the electric field generated by an arbitrary polarization source in a general photonic structure (that could involve loss, gain and/or nonlinearities). Based on this model, we investigate the criteria for enhancing the efficiency of nonlinear effects, and produce efficient terahertz sources. The results, validated by Finite-Difference Time-Domain (FDTD) calculations, suggest that this approach could potentially be a substitute for the more numerically intensive FDTD method. Next, we propose a 2D PhC structure that supports super-collimation over a large frequency range. We theoretically and numerically investigate the collimation mechanism in this 2D structure, in comparison to that of two other frequently used related PhC structures. We also point out the potential importance of this structure in designing super-collimation-based devices for monochromatic and polychromatic light. Finally, we present numerical simulations of anisotropic multilayers that strongly discriminate certain incidence angles of light, over a broad range of frequencies and irrespective of polarization. Such systems could improve the efficiency of solar cells.by Rafif E. Hamam.Ph.D

Improving Supports for Diverse Women Entering Executive Roles

We report on research identifying supports and barriers for women of diverse backgrounds entering executive roles in Canadian organizations. Intersectionality explains how different social categories such as gender, age and ethnoracial identity are interrelated and affect the professional lives of women. Family supports and networking are key to women\u27s success. The COVID-19 pandemic presents both problems and opportunities for working women. This research was conducted as a graduate student project in collaboration with the Women\u27s Executive Network. We offer recommendations for how organizations can better support women entering leadership roles

Efficient weakly-radiative wireless energy transfer: An EIT-like approach

Inspired by a quantum interference phenomenon known in the atomic physics community as electromagnetically induced transparency (EIT), we propose an efficient weakly radiative wireless energy transfer scheme between two identical classical resonant objects, strongly coupled to an intermediate classical resonant object of substantially different properties, but with the same resonance frequency. The transfer mechanism essentially makes use of the adiabatic evolution of an instantaneous (so called “dark”) eigenstate of the coupled 3-object system. Our analysis is based on temporal coupled mode theory (CMT), and is general enough to be valid for various possible sorts of coupling, including the resonant inductive coupling on which witricity-type wireless energy transfer is based. We show that in certain parameter regimes of interest, this scheme can be more efficient, and/or less radiative than other, more conventional approaches. A concrete example of wireless energy transfer between capacitively-loaded metallic loops is illustrated at the beginning, as a motivation for the more general case. We also explore the performance of the currently proposed EIT-like scheme, in terms of improving efficiency and reducing radiation, as the relevant parameters of the system are varied.U.S. Department of EnergyDARPAArmy Research OfficeNational Science Foundatio

On the Energy Transfer Performance of Mechanical Nanoresonators Coupled with Electromagnetic Fields

We study the energy transfer performance in electrically and magnetically coupled mechanical nanoresonators. Using the resonant scattering theory, we show that magnetically coupled resonators can achieve the same energy transfer performance as for their electrically coupled counterparts, or even outperform them within the scale of interest. Magnetic and electric coupling are compared in the Nanotube Radio, a realistic example of a nano-scale mechanical resonator. The energy transfer performance is also discussed for a newly proposed bio-nanoresonator composed of a magnetosomes coated with a net of protein fibers.Comment: 9 Pages, 3 Figure

Nursing lecturers’ perception and experience of teaching cultural competence: a european qualitative study

Cultural competence is an essential component in providing effective and culturally responsive healthcare services, reducing health inequalities, challenging racism in health care and improving patient safety, satisfaction and health outcomes. It is thus reasonable that undergraduate nursing students can develop cultural competency through education and training. The aim of this paper was to investigate nursing lecturers’ perception and experience of teaching cultural competence in four undergraduate nursing programs. A phenomenological approach was selected to illicit nursing lecturers’ perception of culture and experience of teaching cultural competence. Semi-struc-tured personal interviews were held with a sample of 24 lecturers from four European universities. The anonymized transcripts were analyzed qualitatively following Braun and Clark’s phases for thematic analysis. Six themes and fifteen subthemes emerged from thematic analysis of the tran-scripts. Cultural competence was not explicitly integrated in the nursing curricula. Instead, the lecturers used mainly examples and case studies to illustrate the theory. The integration of cultural content in the modules was unplanned and not based on a specific model. Nursing programs should be examined to establish how cultural content is integrated in the curricula; clear guidelines and standards for a systematic integration of cultural content in the nursing curriculum should be de-veloped

The Palomar Transient Factory: System Overview, Performance and First Results

The Palomar Transient Factory (PTF) is a fully-automated, wide-field survey aimed at a systematic exploration of the optical transient sky. The transient survey is performed using a new 8.1 square degree camera installed on the 48-inch Samuel Oschin telescope at Palomar Observatory; colors and light curves for detected transients are obtained with the automated Palomar 60-inch telescope. PTF uses eighty percent of the 1.2-m and fifty percent of the 1.5-m telescope time. With an exposure of 60-s the survey reaches a depth of approximately 21.3 in g' and 20.6 in R (5 sigma, median seeing). Four major experiments are planned for the five-year project: 1) a 5-day cadence supernova search; 2) a rapid transient search with cadences between 90 seconds and 1 day; 3) a search for eclipsing binaries and transiting planets in Orion; and 4) a 3-pi sr deep H-alpha survey. PTF provides automatic, realtime transient classification and follow up, as well as a database including every source detected in each frame. This paper summarizes the PTF project, including several months of on-sky performance tests of the new survey camera, the observing plans and the data reduction strategy. We conclude by detailing the first 51 PTF optical transient detections, found in commissioning data.Comment: 12 pages, 11 figures, 3 tables, submitted to PAS

Nursing students’ experience of learning cultural competence

Introduction European societies are rapidly becoming multicultural. Cultural diversity presents new challenges and opportunities to communities that receive immigrants and migrants, and highlights the need for culturally safe healthcare. Universities share a responsibility to build a fair and equitable society by integrating cultural content in the nursing curricula. This paper aims to analyze European student nurses´ experience of learning cultural competence and of working with patients from diverse cultural backgrounds. Materials and methods A phenomenological approach was selected through a qualitative research method. 7 semi-structured focus groups with 5–7 students took place at the participants’ respective universities in Spain, Belgium, Turkey and Portugal. Results 5 themes and 16 subthemes emerged from thematic analysis. Theme 1, concept of culture/ cultural diversity, describes the participants’ concept of culture; ethnocentricity emerged as a frequent element in the students’ discourse. Theme 2, personal awareness, integrates the students’ self-perception of cultural competence and their learning needs. Theme 3, impact of culture, delves on the participants’ perceived impact of cultural on both nursing care and patient outcomes. Theme 4, learning cultural competence, integrates the participants’ learning experiences as part of their nursing curricula, as part of other academic learning opportunities and as part of extra-academic activities. Theme 5, learning cultural competence during practice placements, addresses some important issues including witnessing unequal care, racism, prejudice and conflict, communication and language barriers, tools and resources and positive attitudes and behaviors witnesses or displayed during clinical practice. Conclusion The participants’ perceived level of cultural competence was variable. All the participants agreed that transcultural nursing content should be integrated in the nursing curricula, and suggested different strategies to improve their knowledge, skills and attitudes. It is important to listen to the students and take their opinion into account when designing cultural teaching and learning activities. © 2021 Antón-Solanas et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited