Nonradiating Photonics with Resonant Dielectric Nanostructures

Nonradiating sources of energy have traditionally been studied in quantum mechanics and astrophysics, while receiving a very little attention in the photonics community. This situation has changed recently due to a number of pioneering theoretical studies and remarkable experimental demonstrations of the exotic states of light in dielectric resonant photonic structures and metasurfaces, with the possibility to localize efficiently the electromagnetic fields of high intensities within small volumes of matter. These recent advances underpin novel concepts in nanophotonics, and provide a promising pathway to overcome the problem of losses usually associated with metals and plasmonic materials for the efficient control of the light-matter interaction at the nanoscale. This review paper provides the general background and several snapshots of the recent results in this young yet prominent research field, focusing on two types of nonradiating states of light that both have been recently at the center of many studies in all-dielectric resonant meta-optics and metasurfaces: optical {\em anapoles} and photonic {\em bound states in the continuum}. We discuss a brief history of these states in optics, their underlying physics and manifestations, and also emphasize their differences and similarities. We also review some applications of such novel photonic states in both linear and nonlinear optics for the nanoscale field enhancement, a design of novel dielectric structures with high-$Q$ resonances, nonlinear wave mixing and enhanced harmonic generation, as well as advanced concepts for lasing and optical neural networks.Comment: 22 pages, 9 figures, review articl

Non-scattering Metasurface-bound Cavities for Field Localization, Enhancement, and Suppression

We propose and analyse metasurface-bound invisible (non-scattering) partially open cavities where the inside field distribution can be engineered. It is demonstrated both theoretically and experimentally that the cavities exhibit unidirectional invisibility at the operating frequency with enhanced or suppressed field at different positions inside the cavity volume. Several examples of applications of the designed cavities are proposed and analyzed, in particular, cloaking sensors and obstacles, enhancement of emission, and "invisible waveguides". The non-scattering mode excited in the proposed cavity is driven by the incident wave and resembles an ideal bound state in the continuum of electromagnetic frequency spectrum. In contrast to known bound states in the continuum, the mode can stay localized in the cavity infinitely long, provided that the incident wave illuminates the cavity

Non-singular spacetimes with a negative cosmological constant: III. Stationary solutions with matter fields

Generalising the results in arXiv:1612.00281, we construct infinite-dimensional families of non-singular stationary space times, solutions of Yang-Mills-Higgs-Einstein-Maxwell-Chern-Simons-dilaton-scalar field equations with a negative cosmological constant. The families include an infinite-dimensional family of solutions with the usual AdS conformal structure at conformal infinity.Comment: 27 pages, v2: journal accepted versio

Beyond the photocycle-how cryptochromes regulate photoresponses in plants?

Cryptochromes (CRYs) are blue light receptors that mediate light regulation of plant growth and development. Land plants possess various numbers of cryptochromes, CRY1 and CRY2, which serve overlapping and partially redundant functions in different plant species. Cryptochromes exist as physiologically inactive monomers in darkness; photoexcited cryptochromes undergo homodimerization to increase their affinity to the CRY-signaling proteins, such as CIBs (CRY2-interacting bHLH), PIFs (Phytochrome-Interacting Factors), AUX/IAA (Auxin/INDOLE-3-ACETIC ACID), and the COP1-SPAs (Constitutive Photomorphogenesis 1-Suppressors of Phytochrome A) complexes. These light-dependent protein-protein interactions alter the activity of the CRY-signaling proteins to change gene expression and developmental programs in response to light. In the meantime, photoexcitation also changes the affinity of cryptochromes to the CRY-regulatory proteins, such as BICs (Blue-light Inhibitors of CRYs) and PPKs (Photoregulatory Protein Kinases), to modulate the activity, modification, or abundance of cryptochromes and photosensitivity of plants in response to the changing light environment

Evaluating the Oral Language Skills of English-Stream and French Immersion Students: Are the CLB/NCLC Applicable?

This study examined the oral language skills of grade-two anglophone children enrolled in French Immersion and English-stream programs. The study had two objectives: (a) to compare performance between the groups on measures of receptive vocabulary, narrative comprehension, and narrative production (i.e., structure and language) in English, and (b) to explore the applicability of the Canadian Language Benchmarks/Niveaux de compétences linguistiques canadiens (CLB/NCLC) to assessment of their conversational competency. All children (English-stream n = 27, French Immersion n = 33, aged 7-8 years) were tested in English. In addition, the French Immersion students were tested using equivalent measures in French. The results comparing performance in English revealed no differences between the groups on receptive vocabulary, narrative comprehension and narrative structure. However, the English-stream children outperformed their French Immersion peers in narrative language. Furthermore, CLB/NCLC listening and speaking criteria were applied to conversational samples yielding level scores in English (both groups) and French (French Immersion only). The range of benchmarks that are appropriate for this population is discussed in detail.Cette étude compare les habiletés langagières orales en anglais et en français d’élèves anglophones de deuxième année, scolarisés en anglais ou en immersion française. L’étude avait deux objectifs : (1) comparer les performances des deux groupes d’enfants sur un test de vocabulaire réceptif, de compréhension narrative et de production narrative (c.-à-d., structure et langage narratifs) en anglais (2) tester l’applicabilité des Niveaux de compétences linguistiques canadiens (CLB/NCLC) à l’évaluation de la fluidité conversationnelle chez les enfants en anglais et en français. Vingt-sept enfants scolarisés en anglais et 33 enfants scolarisés en immersion française, tous âgés de 7 à 8 ans, ont été évalués en anglais. Les enfants en immersion française ont aussi été évalués en français au moyen de tests de vocabulaire réceptif et de compétences narratives équivalents à ceux utilisés en anglais. Les résultats comparatifs en anglais ne révélaient aucune différence entre les deux groupes quant au vocabulaire réceptif et à la compréhension et la structure narratives en anglais. Cependant, la performance des élèves scolarisés en anglais était supérieure à celle des élèves en immersion française quant au langage narratif. De plus, les critères des CLB/NCLC portant sur la compréhension et l’expression orales ont été transposés aux échantillons de langage conversationnel recueillis, donnant des scores de niveau en anglais et en français. Enfin, la gamme de niveaux pouvant être transposés à cette population est discutée en détail.

Educators' experiences of the implementation of language policy affecting foreign nationals

The aim of this study was to understand educators' experiences of the implementation of language policy affecting foreign nationals. A body of relevant literature was reviewed and analysed to address the aim of this study. A qualitative phenomenological approach was used. Semi structured interviews were conducted in four different schools in Johannesburg East and Ekurhuleni North Districts of South Africa, with a total of 12 participants comprising of two educators and a principal in each school. This study was anticipated to make a significant contribution to the implementation of multilingual policies and practice in South Africa and elsewhere. The findings revealed that schools which offer English as Home language do not admit foreign learners without previous knowledge of English language. However, where such foreign learners were admitted, they receive school language interventions, translators, extra lessons, parental support and become resilience in order to cope and excel in schools’ language policy. The study also found that foreign learners who could not cope with the language of the school through the above interventions were withdrawn from schools. The recommendations arising from this study is an intervention from the Department of Education in providing translators for foreign learners This will help in relieving language teachers who seldom assist the foreign learners because of their teaching workload. Further recommendation is to understand the inclusivity, participation, and roles of teachers, and learners as student representative councils (SRC) in achieving an effective and workable language policy implementation. Keywords: Foreign learners; implementation of language policy; educators; Home language; first and second additional language; language of the school; schoolsDissertation (MEd)--University of Pretoria, 2021.Education Management and Policy StudiesMEdUnrestricte

Considering Parental Alienation When Assessing Best Interest of the Child

As the divorce rate in the United States remains steady at 50%, the last few decades have shown an increase in child custody disputes. Within these litigations, interparental conflict can reach high levels and incite behaviors that wreak havoc on the children who are caught in the middle. When considering custody arrangements, judges and other evaluators use the Best Interest of the Child Standard (BICS), a jurisdictionally-specific framework that examines several factors that contribute to a child’s health and well-being. Parents who allow their resentments to get the better of them sometimes engage in behavior that encourages their child to become alienated from the other parent, known as Parental Alienation (PA) —a form of psychological abuse that can result in emotional and behavioral consequences for the child. While some states investigate components relevant to PA during a BICS evaluation, none include criteria that directly addresses this construct. Therefore, to achieve the intended outcome of BICS, which is to create a custody arrangement that will best meet a child’s needs, recognizing and addressing the presence of PA within a family system is required