Encoding information into spatial modes of light

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, May 3, 2016.Spatial modes of light hold the possibility to power the next leap in classical and quantum communications. They provide the ability to pack more information into light, even into single photons themselves, while increasing the level of information security. In this quest, spatial modes carrying orbital angular momentum (OAM) have come under the spotlight due to their discrete in nite dimensional Hilbert space allowing, in theory, for an in nite amount of information to be carried by a photon. Here we study, theoretically and experimentally, spatial modes of two avours: scalar and vector modes. the dichotomy between the two avours is in their polarisation characteristics: scalar modes have spatially homogeneous polarisation elds, while vector modes do not. One facet of our work focusses on scalar mode carrying OAM; using digital holographic methods, we demonstrate the techniques used to tailor and analyse scalar optical elds. We discuss principles of generation and detection for scalar modes based on manipulations of the dynamic phase of light with spatial light modulators. We apply these techniques to characterise free-space and optical bre links, and demonstrate an increase in bandwidth with the additional modal channels. In the other facet of our work, we study vector vortex modes. A particular property exhibited by these modes is the non-separability of their degrees of freedom, a property traditionally associated with entangled quantum states. This raises the question: could quantum entangled systems be modelled with bright sources of vector vortex modes? We answer this question by applying vector vortex modes to the study of quantum transport of entangled states. We borrow techniques from quantum mechanics to evaluate the degree of non-separability of vector vortex modes, using the concurrence as our measure. By determining the evolution of the concurrence, and therefore the entanglement, of vector vortex modes in bres and free-space turbulent channels, we show that indeed, bright classical sources can be used to model the evolution of entangled quantum states in these channels.TG201

As Nações Unidas e a consolidação de um Estado Democrático de Direito na República Democrática do Congo

Cinco décadas após a acessão à independência, a situação sociopolítica na República Democrática do Congo permanece muito complexa. Os sucessivos conflitos armados sufocam qualquer iniciativa de desenvolvimento. Todas as tentativas de proteção e de promoção dos direitos humanos produzem resultados insignificantes, seguida de má governança e da ausência de autoridade do Estado em algumas partes do país. A chegada da MONUC/MONUSCO, a convite do governo congolês, foi e é benéfica em muitos aspectos, incluindo a participação ativa nas eleições presidenciais e legislativas de 2006 e no fortalecimento do sistema judiciário congolês. Alguns consideram que o sucesso das eleições presidenciais e legislativas de novembro de 2011 também dependeu, em grande parte, da ação da MONUSCO em vários níveis. Apesar do avanço promovido pela presença da MONUC/ MONUSCO em sua missão, as ONGs locais continuam a condenar o comportamento de certos efetivos acusados de violência sexual e envolvidos na exploração de minerais no leste da RDC. Certamente, para que a democracia seja uma realidade na RDC, a presença da MONUSCO se mostra necessária, mas o Congo deve deixar, então, a posição de um “Estado falido” e dar a seu povo a chance de sonhar com um futuro melhor

Low-Wavelengths SOI CMOS Photosensors for Biomedical Applications

INTRODUCTION : Biological agents may be characterized (in terms of quantity (or concentration), purity, nature) using optical ways like spectrometry, fluorometry and real-time PCR for example. Most of these techniques are based on absorbance or fluorescence. Indeed, many biological molecules can absorb the light when excited at wavelengths close to blue and ultraviolet (UV). For example, DNA, RNA and proteins feature an absorption peak in the deep UV, more precisely around 260 and 280 nm (Karczemska & Sokolowska, 2001). This work is widely focused on those wavelengths. A biological sample concentration measurement method can be based on UV light absorbance or transmittance, as already known and realized with high-cost and large-size biomedical apparatus. But, often, the difficulties come from the limitation for measuring very small concentrations (close to a few ng/µL or lower) since the measurement of such small light intensity variations at those low wavelengths requires a precise light source, and very efficient photodetectors. Reducing the dimensions of such a characterization system further requires a small light source, a miniaturized photosensor and a processing system with high precision to reduce the measurement variations. Some light-emitting diodes (LED) performing at those UV wavelengths have recently appeared and may be used to implement the light source. Concerning the optical sensor, while accurate but high-cost photosensors in technologies such as AlGaN and SiC provide high sensitivities in UV low wavelengths thanks to their semiconductor bandgap (Yotter & Wilson, 2003), the silicon-on-insulator (SOI) layers absorb the photons in that specific range thanks to an appropriate thickness of the silicon. Adding excellent performances of low power consumption, good temperature behavior and high speed (Flandre et al., 1999; 2001), the SOI technology allows the designers for integrating a specific signal processing integrated CMOS circuit to transform the photocurrent into a digital signal for example. This opens the possibility to build a low-cost, complete and portable microsystem, including the light source, the photodetector and a recipient for the sample to characterize […

Phytochemical Study and in Vitro Test of the Activity of Total Extracts of Cissampelos Mucronata (Menispermaceae) Leaves on Plasmodia Falciparum

Objectives: The objectives of the present work were to carry out a phytochemical and pharmacological study of total extracts of Cissampelos mucronata (Menispermaceae) leaves on Plasmodium falciparum. Methods: To achieve this we: harvested and dried the plant's leaves, and carried out phytochemical screening to detect the chemical substances contained in the plant; performed a chromatographic analysis to study the similarity of the chemical structures of these substances with modern antimalarial drugs; tested the in vitro antimalarial activity of extracts from this plant against modern antimalarial drugs: quinine, L-artem and Doxycycline. Results: The results obtained revealed that: the leaves of the Cissampelos mucronata plant (Menispermaceae) contain all the substances we're looking for, but at different levels; some of the active ingredients found in these leaves have chemical structures similar to those of the above-mentioned modern antimalarials, while others do not. Anti-malarial test confirms plant's activity against Plasmodim falciparum. Conclusion: alkaloids, flavonoids, glycosides, at 50%, terpenoids, lipoids, have a high concentration of active principle; saponins, phenols, terpenoids, are at 30%; steroids and quinones are at 20%. For thin-layer chromatology (TLC): In the aqueous extract of Cissampelos micronata(Menuspermaceae, there is one spot with a retention coefficient (Rf) equal to that of L-artm 0.9 and contains 5 different Rf spots; this means that the plant contains a single substance with a chemical structure similar to that of strong L-artm ; In the ethanolic extract of this plant, there is no substance with the same chemical structure as the antimalarial drugs in common use in the environment where they are used. Similarly, the ethanolic extract and the aqueous extract contain certain substances with the same chemical structure. In this plant, there is no active ingredient with the same chemical structure as doxycycline and cyprofloxacin. This has led us to conclude that the leaves of Cissampelos mucronata (Menispermaceae) need to be used by people in and around South Kivu province to treat malaria, but with caution, as the pharmaco-vigilance of this plant has not yet been elucidated

Integrated Transboundary Water-Climate Management Tools

The scholarly theme of the book lends itself to the discipline of earth and atmospheric sciences, with a specific focus on water-climate studies. The book is a scholarly discourse by researchers in the natural sciences, including Hydrologists, Climate Scientists, Environmental Engineers and Water Scientists. The purpose of the book is to address the limited complementarity between the water and climate studies; which is crucial in promoting scientific research that informs policy decisions and implementation of water security plans. The chapters were selected to represent water-climate models and policy research conducted in different river basins in the arid and semi-arid environments. Therefore, the water-climate management tools highlighted in this book include General Circulation Models (GCMs), Coupled Model Inter-comparison Project Phase 5 (CMIP5), Soil and Water Assessment Tool (SWAT), Africa Flood and Drought Monitor (AFDM), Extreme Precipitation Events (EPEs), R ClimDex, Mixed strategy game models, Standard Precipitation Indices (SPIs), Water Evaluation and Planning System (WEAP), Penman Calculator, and Saturated Volume Fluctuation (SVF)

Second trimester vaginal Candida colonization among pregnant women attending antenatal care in Bukavu, Democratic Republic of the Congo: prevalence, clinical correlates, risk factors and pregnancy outcomes

IntroductionVaginal Candida colonization (CC) can lead to vulvovaginal candidiasis, the second most prevalent vaginal condition worldwide, and has been associated with adverse birth outcomes. However, no data on CC in the Democratic Republic of the Congo are available. We investigated the prevalence, Candida species, clinical correlates, risk factors and pregnancy outcomes in women with CC in the second trimester of pregnancy.Material and methodsIn Bukavu, the Democratic Republic of the Congo, pregnant women were recruited during antenatal care between 16 and 20 weeks of gestation from January 2017 to October 2017 and followed until delivery. Sociodemographics, sexual behavioral, hygienic and clinical characteristics, microbiological data and pregnancy outcomes were collected. Candida detection and speciation was performed with microscopy (Gram-stained smears and wet-mount) and/or quantitative PCR. Multivariate regression models were used to estimate the different associations with CC.ResultsThe prevalence of CC by wet mount, microscopy of Gram-stain smears and qPCR was 27.9%, 28.1% and 38.2%, respectively. C. albicans was the most prevalent Candida species (91.0%). Previous genital infections, an intermediate vaginal microbiota, bacterial vaginosis, and the use of pit toilets were risk factors for CC. Clinically, CC was associated with itching only. Women with CC had twice the odds for preterm birth, if Candida concentration was high, the odds were four times higher.ConclusionsIn Bukavu, the Democratic Republic of the Congo, the prevalence of CC was high and associated with microbiological and modifiable risk factors. Screening and treatment for CC during antenatal care should be investigated as a possible strategy to reduce preterm birth