Studien undersökte relationen mellan förskolebarns kognitiva förmåga och vilken typ av rörligmedia och mobila spel som barnen ägnade sig åt, samt relationen mellan föräldrarnas användningav mobila enheter och barnens kognitiva förmåga. Kognitiv förmåga undersöktes medtestbatteriet WPPSI-IV och medievariablerna undersöktes med en webbaserad enkät. Sammantaget visade resultaten att det fanns positiva samband mellan pojkars kognitiva förmågoroch att titta på viss typ av rörlig media, medan det för flickor fanns negativa sambandför viss rörlig media respektive spelande på mobila enheter. Gällande förälderns användningav mobila enheter hade flickorna bättre generell kognitiv förmåga och språklig förmåga omföräldern använde sådana i närvaro av barnet. Resultaten gick delvis mot och delvis i linje med tidigare forskning. Eftersom studien fannolika resultat för flickor och pojkar, bör detta undersökas mer noggrant i kommande studierför att bättre kunna uttala sig om relationen mellan digital media och barns kognitiva förmåga.

Syftet med projektet är att samla in data kring PV-modulers maxeffekt. Felmarginalen hos datan får vara högst ±2%. De PV-moduler som ska kopplas in har kortslutningsströmmar från 1.51A till 8.9A samt öppenkrets-spänningar från 15.7V till 98V. Ett IV-svep ska kunna genomföras och nya mätningar av maxeffekten ska skickas trådlöst var tionde sekund.  Automatisk kalibrering efter rådande ström- ochspänningskarakteristik kan initieras via applikationen Blynk, detta för att öka mätnoggrannheten till följd av det breda spann av PV-moduler mättekniken ska vara kompatibel med. Likaså kan en maxeffektföljande algoritm initieras via applikationen, där maxeffektens uppdateringsfrekvens ligger inom ett 10-sekundersintervall. IV-svep kan utföras med viss dataförlust närakortslutningsströmmen. Felmarginalen för spänningsmätningar uppgår till ±0.66% och felmarginalen för strömmätningar uppgår till ±1.23%. Felmarginalen för effekt uppgår till ±0.81% och felmarginalen för maxeffekt uppgår till ±0.89%. Data kan laddas ned som CSV-filer. Tester för de specifika PV-modulerna som ska kopplas in behöver genomföras. Ett annat val av OP-förstärkare kan förenkla kretsen. Resistansen hos Rshunt kan minskas för att öka det mätbara spänningsintervallet.

Several applications require the detection of terrestrial UV-C signatures. Efficiency, compactness, environmentally friendly and cost-effective requirements for UV-C–detectors resulted in a research interest in wide-bandgap (WBG) semiconductor-based photovoltaic diodes with a 280 nm cut-off wavelength. Advances in producing group-III-nitride materials allowed the growth of high quality Al[x]Ga[1−x]N, a direct-WBG ternary semiconductor in which the Al mole fraction (x) could be varied, allowing for a tuneable bandgap that made the semiconductor intrinsically 'blind' to longer wavelengths and responsive to selected wavelengths shorter than 360 nm. This dissertation reports on the development and characterization of a tuneable AlGaN-based solar-blind UV-sensitive Schottky photodiode. A fabrication procedure was established using optimized metallization techniques derived from literature. This included metallization schemes, metal thicknesses and annealing methods for metallization of both the ohmic and Schottky contacts for a front-irradiated photodiode. Characterization was done with a newly constructed optoelectronic characterization system. Electrical characterization was performed inside a light-tight shielded enclosure and a software routine aided in applying current–voltage and capacitance–voltage measurements on a Schottky diode. Spectral characterization made use of either a UV source or a visible-to-near-infrared source that was coupled to a monochromator that allowed for wavelength selection. The monochromatic electromagnetic radiation was guided by an optical fibre from the monochromator into the enclosure where the photodiode was irradiated. An additional software routine was developed that allowed for the automation of the spectral characterization. The system was calibrated against standards traceable to the National Institute of Standards and Technology (NIST) by following the photodetector substitution method. The study concluded with the manufacturing of an epoxy wire-bonded front-irradiated four-quadrant detector that was mounted on a commercial microchip carrier. Metal depositions were done through physical contact masks. The quadrants were surrounded with optimized layered ohmic contacts and a quadrant consisted of a thin-film iridium(IV) oxide (IrO₂) as Schottky contact that is UV transmissive with a Au contact on top to which a wire was bonded. Optoelectronic characterization verified that the four-quadrant detector was intrinsically solar-blind and showed good uniformity across the quadrants. Electrical parameters obtained included an average ideality factor of 1.97 ± 0.09, a Schottky barrier height of (1.22 ± 0.08) eV, a reverse leakage current density of (2.1 ± 3.3) nA/cm² and a series resistance of (120 ± 30) Ω. Spectral parameters obtained included a (275 ± 5) nm cut-off wavelength, an average current responsivity at 250 nm of (28 ± 1.0) mA/W with a quantum efficiency of (14 ± 0.5) % and an UV-to-visible and near-infrared rejection ratio between 10³ and 10⁵ for 400 nm to 1100 nm wavelengths. These characteristics allowed for the detector to be used in demonstrating a working solar-blind UV-sensitive electro-optic device. / Dissertation (MSc)--University of Pretoria, 2015. / Physics / Unrestricted

Orientador: Peter Hammer / Resumo: Este trabalho relata uma investigação detalhada das propriedades estruturais e eletroquímicas de revestimentos de polimetilmetacrilato (PMMA)-sílica. Espectroscopia Raman e análise térmica mostraram que o ajuste da quantidade de peróxido de benzoíla (BPO), como um parâmetro crítico de síntese, melhora a eficiência de polimerização do metilmetacrilato (MMA), levando a uma estrutura híbrida altamente reticulada. A espectroscopia de impedância eletroquímica (EIS) mostrou para revestimentos depositados sobre aço carbono (A1020) e liga de Al (AA7075) uma resposta de impedância capacitiva quase ideal, mantendo o módulo de impedância de baixa frequência de até 10 GΩ cm2 essencialmente inalterado durante 19 meses de imersão em NaCl 3,5%. Embora revestimentos passivos de alto desempenho tenham sido desenvolvidos, pites de corrosão podem afetar significativamente sua durabilidade. Assim, a inibição da corrosão ativa induzida por íons lítio e cério em revestimentos de sílica sol-gel de PMMA foi investigada. A adição de carbonato de lítio produziu revestimentos com melhor conectividade dos nós de sílica nanométricos e forte adesão ao substrato de alumínio. Os resultados de EIS mostraram que as concentrações de lítio mais altas resultam em um aumento no módulo de impedância e induzem a autorregeneração que aumenta significativamente sua vida útil dos revestimentos. Time-of-flight secondary ion mass spectrometry (ToFSIMS) e a espectroscopia de fotoelétrons excitados por raios-X (XPS) suger... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work reports on a detailed investigation of the structural and electrochemical properties of poly(methyl methacrylate) (PMMA)-silica coatings. Raman spectroscopy and thermal analysis showed that the fine-tuning of the benzoyl peroxide (BPO) amount, as a critical synthesis parameter, improves the polymerization efficiency of methyl methacrylate (MMA), leading to a highly cross-linked hybrid structure. Electrochemical impedance spectroscopy (EIS) showed for coatings deposited on carbon steel (A1020) and Al alloy (AA7075) a quasi-ideal capacitive impedance response, maintaining the low frequency impedance modulus of up to 10 GΩ cm2 essentially unchanged during 19 months of immersion in 3.5% NaCl. Although high performance passive coatings have been developed, pitting can significantly affect their durability. Hence, active corrosion inhibition induced by lithium and cerium ions in PMMA-silica sol-gel coatings was investigated. The addition of lithium carbonate yielded coatings with improved connectivity of nanometric silica cross-link nodes and stronger adhesion to the aluminum substrate. EIS results showed that higher lithium concentrations result in an increased impedance modulus and induce the self-healing ability, extending significantly the service life of the coatings. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) suggest that the regeneration process occurs by means of lithium ions leaching from the adjacent coat... (Complete abstract click electronic access below) / Doutor

Cognitive decline is one of the most common symptoms from neuropathology as well as a part of natural aging. While there may be a number of factors that contribute to age-related cognitive decline, previous research has shed a light on the role of chronic hypertension. The effect of hypertension on cognitive decline through small vessel disease is referred to as Vascular Cognitive Impairment and Dementia (VCID). However, the exact molecular pathology behind VCID is not very well understood. Using a non-human primate model of hypertensive aging with the Macaca mulatta, (more commonly known as the Rhesus Macaque) this project builds on previous research implicating collagen IV as part of the cascade of molecular changes that occur in VCID. This project evaluated collagen IV thickness around blood vessels in the corpus callosum and cingulum bundle of normotensive and hypertensive monkeys. as well as determined vessel properties such as total vessel area and perimeter length to evaluate the relationship to scores from the subjects cognitive testing batteries. The results from this project will allow for an examination of the effects on hypertension on vascular properties and possible mechanisms for the development of cognitive impairments. Data collected from this research shows significant differences of collagen IV thickness in the Corpus Callosum between hypertensive and normotensive groups. Similarly, in the cingulum bundle we see that the difference between these groups in collagen IV thickness is trending towards significance. The relationship between average collagen IV densities, blood pressure at perfusion, and cognitive testing scores also showed trending relationships in both the cingulum bundle and the corpus callosum. These results demonstrate how prolonged hypertension can negatively influence cognitive abilities and implicates increases in collagen IV around small vessels in white matter as a significant factor in the molecular cascade which results in cognitive impairment.

The purpose of this project was the modeling, optimization and prediction of a hybrid system composed of a fuel cell, a dc-dc converter and a supercapacitor in series. Lab tests were performed for each device to understand their behavior, and then each one was modeled using software (Simulink). The validation of the model was done by comparing its results with measured data; finally the model was used for the optimization and the prediction of the hybrid system

The goal of this work is to investigate the capabilities of two different commercial codes, OpenFOAM and ANSYS CFX, to predict forced convection heat transfer in low Prandtl number fluids and investigate the sensitivity of these predictions to the type of code and to several input parameters.The goal of the work is accomplished by predicting forced convection heat transfer in two different experimental setups with the codes OpenFOAM and ANSYS CFX using three different turbulence models and varying the input parameters in an extensive sensitivity analysis. The computational results are compared two the experimental data and analyzed for qualitative and quantitative parameters, such as shape of velocity and temperature profiles, thickness of the boundary layers and wall temperatures.The results show that predictions of the temperature and velocity field are generally sufficient to good, however, the sensitivity especially to the turbulent Prandtl number has to be taken into account when computing forced convection heat transfer in low Prandtl number fluids. The results also show that methods applied to OpenFOAM cannot directly be applied to ANSYS CFX. / <p>QC 20130531</p> / GENIUS

This is a study on crowns, wreaths and diadems as role symbols in Peter Paul Rubens’s 24 paintings for Marie de’Medici in Paris, 1622 – 1625. In these paintings, historic facts are shown with the addition of mythological gods and their symbols giving allegorical scenes, where sometimes also Christian symbols or subjects can be traced. A reader of these painted motifs therefore can choose to see the symbols as regal, Christian or mythological. The crown and the wreaths rarely present a challenge in modern interpretations, but the magnificent diadem does. Rubens chooses this diadem for higher goddesses, and for the queen a couple of times too. For some reason, this symbol is mostly misread in analyses. At this point in history, the crowns and the wreaths have been collected from divine spheres and turned into physical objects on earth used by the high and mighty. The large diadem has not; it is still only a symbol on a goddess. If and when put on a human in a portrait, the symbol gives the lady the abilities and characters of a goddess. Rubens uses his own design when turning this symbol into a physical picture;it is a high, pointed diadem with pearls and coloured gems set in gold. He has used it on goddesses both before and after the Medici commission. Today, we have seen numerous spectacular headpieces like this from late 18th century an onwards, wherefore it is an easy mistake to believe that Rubens copied what he saw instead of, as he actually did, foreboding a coming fashion. In addition to confirming this, I also suggest that it is the highest goddess Juno queen Marie is personifying. Juno is mostly known today as a goddess for women and childbirth. But she had far more masculine tasks in earlier days: she was seen as the saviour of the country and a special counsellor of the state. These two important roles are exactly what Marie de’ Medici took on when acting as regent for her young son, Louis XIII,after the murder of her husband, the late Henry IV. By putting Juno’s diadem on Marie’s head, when sitting on a throne, the divine abilities are manifested according to how a historic period could be transferred to the allegorical language in a painting at the time.

This study examines the Chicago Board Option Exchange (CBOE) Volatility Index (VIX) which is the implied volatility calculated from short-term option prices on the Standards & Poor’s 500 stock index (S&P 500). Findings suggest VIX overestimates average volatility by approximately 3% but explains 55% of S&P 500’s proceeding month’s volatility. The implied volatility (IV) from options on the VIX add additional explanatory power for the S&P’s 500 proceeding kurtosis values (a measure of tail risk). The VIX option’s volatility smirks did not add additional explanatory power for explaining the S&P 500 volatility or kurtosis. A simple trading rule based on buying the S&P 500 whether the VIX, IV from the options on the VIX, and the VIX option’s volatility smirk decline over the preceding month results in an additional 0.96% return in the following month. However, this only occurs approximately 10% of the time and does not outperform a simple buy-and-hold strategy as the strategy has the investor out of the market the majority of the time.

This thesis examines the role of grandchildren's existence in the retirement timing decision- making process of grandparents. Previous literature has focused mostly on other aspects of retirement and potential causes that can affect its timing. Using the Two-Stage least squares estimation on the SHARE dataset, representing 17 European countries and Israel, we estimate the desired effect with respect to various data limitations (age groups, gender, child existence). Residential proximity is used as the instrument for estimation. Having at least one grandchild yields a statistically significant result that increases on average the likelihood of retirement by 19% when compared to a non-grandparent while holding other factors constant. As a secondary outcome, the estimated effect of an additional child on retirement likelihood is negative. JEL Classification C36, C51, J26 Keywords grandchild, retirement, Instrumental variable, SHARE, IV, wide-ranging data, 2SLS Title The impact of grandchildren on retirement timing: evidence from SHARE data