Photon correlation studies of single GaN quantum dots

We present measurements of the second-order coherence function on emission from single GaN quantum dots. In some cases a large degree of photon antibunching is observed, demonstrating isolation of a single quantum system. For a selected quantum dot, we study the dependence of photon antibunching on excitation power and temperature. Using pulsed excitation, we demonstrate an ultraviolet triggered single-photon source operating at a wavelength of 358 nm.Comment: 3 pages, 4 figure

Realization of two Fourier-limited solid-state single-photon sources

We demonstrate two solid-state sources of indistinguishable single photons. High resolution laser spectroscopy and optical microscopy were combined at T = 1.4 K to identify individual molecules in two independent microscopes. The Stark effect was exploited to shift the transition frequency of a given molecule and thus obtain single photon sources with perfect spectral overlap. Our experimental arrangement sets the ground for the realization of various quantum interference and information processing experiments.Comment: 6 page

Controlled photon transfer between two individual nanoemitters via shared high-Q modes of a microsphere resonator

We realize controlled cavity-mediated photon transfer between two single nanoparticles over a distance of several tens of micrometers. First, we show how a single nanoscopic emitter attached to a near-field probe can be coupled to high-Q whispering-gallery modes of a silica microsphere at will. Then we demonstrate transfer of energy between this and a second nanoparticle deposited on the sphere surface. We estimate the photon transfer efficiency to be about six orders of magnitude higher than that via free space propagation at comparable separations.Comment: accepted for publication in Nano Letter

A REPRESENTAÇÃO DE EDUCAÇÃO LINGUÍSTICA DE IMIGRANTES NO BRASIL

O presente artigo teve como objetivo explicar a representação de educação linguística de imigrantes no Brasil. A base teórica do estudo é a Historiografia Linguística (HL), cujas pesquisas visam à reconstrução do conhecimento sobre as línguas e linguagem humana em diferentes recortes temporais. Do tipo documental, o estudo tem como corpus as narrativas jornalísticas veiculadas durante o período de 1900 a 2015 na imprensa catarinense. Os jornais escolhidos como fontes para a obtenção dos dados foram: O Estado e Diário Catarinense. Adotou-se, para o tratamento dos dados, a técnica de análise de conteúdo. Os resultados foram analisados em três seções distintas. A primeira seção referiu-se ao período da Primeira Campanha de Nacionalização, na qual se discutiu a representação de educação linguística: escolas nacionalizadoras para assimilação do imigrante. A segunda referiu-se ao período da Segunda Campanha de Nacionalização, tendo como categorias: as práticas monoculturais e monolíngues nas escolas nacionalizadoras. A terceira intitulou-se a redemocratização, com as categorias: bilinguismo na escola e bilinguismo fora da escola. Os resultados indicam a superação de um passado em que se silenciava, por meio de medidas coercitivas, para dar lugar a um contexto em que se presenciam certa tolerância e proteção da diversidade linguístico-cultural existente no país

A REPRESENTAÇÃO DE IMIGRANTES NO BRASIL PELA IMPRENSA DO PAÍS AO LONGO DO PERÍODO DE 1900 A 2015

O presente artigo teve como objetivo explicar a representação de imigrantes no Brasil. A base teórica do estudo é a Historiografia Linguística e o tipo documental, o estudo tem como corpus narrativas jornalísticas veiculadas durante o período de 1900 a 2015 na imprensa catarinense. Os jornais escolhidos como fontes para a obtenção dos dados foram: O Estado e Diário Catarinense. Adotou-se, para o tratamento dos dados, a técnica de análise de conteúdo. Os resultados foram analisados em três seções distintas. A primeira seção referiu-se ao período da Primeira Campanha de Nacionalização, na qual se discutiu a representação de imigrantes e as categorias de análises foram: imigrante como trabalhador útil e imigrante como elemento indesejável. A segunda referiu-se ao período da Segunda Campanha de Nacionalização, tendo como categorias: imigrante como elemento indesejável. A terceira intitulou-se a redemocratização, com as categorias: imigrante como trabalhador útil e imigrante de países pobres. Os resultados indicam a superação de um passado em que se silenciava, por meio de medidas coercitivas, para dar lugar a um contexto em que se presenciam certa tolerância e proteção da diversidade linguístico-cultural existente no país

Estimation of uncertainty in flood forecasts - a comparison of methods

The scientific literature has many methods for estimating uncertainty, however, there is a lack of information about the characteristics, merits and limitations of the individual methods, particularly for making decisions in practice. This paper provides an overview of the different uncertainty methods for flood forecasting that are reported in literature, concentrating on two established approaches defined as the ensemble and the statistical approach. Owing to the variety of flood forecasting and warning systems in operation, the question ‘which uncertainty method is most suitable for which application’ is difficult to answer readily. The paper aims to assist practitioners in understanding how to match an uncertainty quantification method to their particular application using two flood forecasting system case studies in Belgium and Canada. These two specific applications of uncertainty estimation from the literature are compared, illustrating statistical and ensemble methods, and indicating the information and output that these two types of methods offer. The advantages, disadvantages and application of the two different types of method are identified. Although there is no one ‘best’ uncertainty method to fit all forecasting systems, this review helps to explain the current commonly used methods from the available literature for the non-specialist

Automated detection and cell density assessment of keratocytes in the human corneal stroma from ultrahigh resolution optical coherence tomograms

Keratocytes are fibroblast-like cells that maintain the optical clarity and the overall health of the cornea. The ability to measure precisely their density and spatial distribution in the cornea is important for the understanding of corneal healing processes and the diagnostics of some corneal disorders. A novel computerized approach to detection and counting of keratocyte cells from ultra high resolution optical coherence tomography (UHR-OCT) images of the human corneal stroma is presented. The corneal OCT data is first processed using a state-of-the-art despeckling algorithm to reduce the effect of speckle on detection accuracy. A thresholding strategy is then employed to allow for improved delineation of keratocyte cells by suppressing similarly shaped features in the data, followed by a second-order moment analysis to identify potential cell nuclei candidates. Finally, a local extrema strategy is used to refine the candidates to determine the locations and the number of keratocyte cells. Cell density distribution analysis was carried in 3D UHR-OCT images of the human corneal stroma, acquired in-vivo. The cell density results obtained using the proposed novel approach correlate well with previous work on computerized keratocyte cell counting from confocal microscopy images of human cornea

Cross-sectional prevalence of SARS-CoV-2 antibodies in healthcare workers in paediatric facilities in eight countries

Funding Information: DG receives support from the NIHR Great Ormond Street Biomedical Research Centre . HZ is supported by the South African Medical Research Council . Publisher Copyright: © 2021 The Author(s)Background: Healthcare workers (HCWs) have been disproportionately affected by coronavirus disease 2019 (COVID-19), which may be driven, in part, by nosocomial exposure. If HCW exposure is predominantly nosocomial, HCWs in paediatric facilities, where few patients are admitted with COVID-19, may lack antibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and be at increased risk during the current resurgence. Aim: To compare the seroprevalence of SARS-CoV-2 amongst HCWs in paediatric facilities in seven European countries and South Africa (N=8). Methods: All categories of paediatric HCWs were invited to participate in the study, irrespective of previous symptoms. A single blood sample was taken and data about previous symptoms were documented. Serum was shipped to a central laboratory in London where SARS-CoV-2 immunoglobulin G was measured. Findings: In total, 4114 HCWs were recruited between 1st May and mid-July 2020. The range of seroprevalence was 0–16.93%. The highest seroprevalence was found in London (16.93%), followed by Cape Town, South Africa (10.36%). There were no positive HCWs in the Austrian, Estonian and Latvian cohorts; 2/300 [0.66%, 95% confidence interval (CI) 0.18–2.4] HCWs tested positive in Lithuania; 1/124 (0.81%, 95% CI 0.14–4.3) HCWs tested positive in Romania; and 1/76 (1.3%, 95% CI 0.23–7.0) HCWs tested positive in Greece. Conclusion: Overall seroprevalence amongst paediatric HCWs is similar to their national populations and linked to the national COVID-19 burden. Staff working in paediatric facilities in low-burden countries have very low seroprevalence rates and thus are likely to be susceptible to COVID-19. Their susceptibility to infection may affect their ability to provide care in the face of increasing cases of COVID-19, and this highlights the need for appropriate preventative strategies in paediatric healthcare settings.publishersversionPeer reviewe

Calixarene alpha-ketoacetylenes: versatile platforms for reaction with hydrazine nucleophile

Late stage diversification of calix[4]arenes and thiacalix[4]arenes with heterocycles remains a significant synthetic challenge and hampers further exploitation of the scaffolds. Here we describe the development of a short and facile synthetic route to conformationally diverse novel calix[4]arene and thiacalix[4]arene ynones using a palladium cross coupling approach (5% Pd(II) + 10% Cu(I)) with benzoyl chloride. Their successful conversion to heterocycles to afford pyrazoles was demonstrated through treatment with hydrazine. Functionalisation is calixarene conformation and linker independent enabling access to a library of structures