Slowing of human arm movements during weightlessness : the role of vision

The prevalence of dental caries in children worldwide is very high. This PhD thesis investigated and compared the effectiveness of three oral healthcare protocols - the Conventional Restorative Treatment (CRT), the Atraumatic Restorative Treatment (ART), and the Ultra-conservative Treatment (UCT) - in preventing and treating dentine carious lesions in mixed-dentitions of 6-7-year-old schoolchildren from Paranoá, a deprived suburban area of Brasília, Brazil. This thesis presents clinical trials regarding: the survival of CRT and ART restorations in primary molars; the survival of primary molars that presented intact and defective restorations; the caries-preventive effect of supervised tooth brushing, composite resin and ART sealants; the survival of retained composite resin and ART sealants using different assessment criteria; and the long-term effect of supervised tooth brushing on levels of visible plaque and gingival bleeding among schoolchildren. The findings of this thesis support the use of ART restorations as a viable option to replace amalgam for managing cavitated dentine carious lesions in single-surfaces in primary molars and daily supervised tooth brushing at school and the application of ART sealants for preventing the occurrence of dentine carious lesions in first permanent molars. They further question the need to re-restore defective restorations in primary molars and show the benefit of supervised tooth brushing for obtaining a clean dentition in this age group. Oral healthcare protocols that are more accessible to the populations and that act on the causes of the disease, such as ART and UCT, seem to be the best options to reduce the burden of dental caries and to improve children’s oral health and quality of life

Near-infrared absorbing semitransparent organic solar cells

We present efficient, semitransparent small molecule organic solar cells. The devices employ an indium tin oxide-free top contact, consisting of thin metal films and an additional organic capping layer for enhanced light in/outcoupling. The solar cell encorporates a bulk heterojunction with the donor material Ph2-benz-bodipy, an infrared absorber. Combination of Ph2-benz-bodipy with C60 as acceptor leads to devices with high open circuit voltages of up to 0.81 V and short circuit current densities of 5–6 mA/cm2, resulting in efficiences of 2.2%–2.5%. At the same time, the devices are highly transparent, with an average transmittance in the visible range (400–750 nm) of up to 47.9%, with peaks at 538 nm of up to 64.2% and an average transmittance in the yellow-green range of up to 61.8%. © 2011 American Institute of Physics.</em

Reducing Voltage Losses in Cascade Organic Solar Cells while Maintaining High External Quantum Efficiencies

High photon energy losses limit the open-circuit voltage (VOC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimiza- tion route is presented which increases the VOC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha-sexithiophene (α-6T) (D) and chloroboron sub- naphthalocyanine (SubNc) (A) increases the VOC of an α-6T/SubNc/SubPc fullerene-free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D–A interface. By accurately measuring the optical gap (Eopt) and the energy of the charge-transfer state (ECT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. Eopt – qVOC losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the VOC-optimized devices, the low-energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low-voltage losses can be combined with a high EQE in organic photovoltaic devices

Trashcano: developing a quantitative teaching tool to understand ballistics accelerated by explosive volcanic eruptions

Accurate predictions of volcanological phenomena, such as the trajectory of blocks accelerated by volcanic explosions, require quantitative skills training. Large outdoor experiments can be useful to convey concepts of volcanic processes to students in an exciting way. Beyond the fun aspects, these experiments provide an opportunity to engage with the physics of projectile flight and help promote mathematical learning within the Earth Sciences. We present a quantitative framework required to interpret ballistic trajectories and the outdoor experiment known commonly as “trashcano”, taking a step-by-step approach to the physics of this problem, and deriving a range of mathematical solutions involving different levels of complexity. Our solutions are consistent with the predictions from established computer programs for volcanic ballistic trajectory modelling, but we additionally provide a nested set of simplified solutions, useful for a range of teaching scenarios as well as downloadable simulated datasets for use where the full experiment may not be possible