Examining the Environmental Behavior and Treatment Efficacy of Titanium Dioxide Nanomaterials in Complex Systems

Metal oxide nanoparticles (MONPs) are manufactured at the greatest rate of any class of nanomaterial due to their wide variety of industrial, commercial, and environmental applications. The sustainable use of MONPs requires a balance of careful consideration of their potential negative environmental impacts with the effective exploitation of their unique properties in situations where the benefit of their use outweighs the risk. Currently, the study of the environmental behavior and toxicity of MONPs, as well as the understanding of their efficacy in environmental remediation applications, would benefit from the understanding of how MONPs behave in complex aquatic media. MONPs are particularly difficult to study in environmentally-relevant matrices like natural water samples or within organisms due to the presence of elevated levels of the naturally occurring metal oxide. In this dissertation, I directly address this challenge through the development of gold core-labeled TiO2 NPs (Au@TiO2 NPs). These labeled NPs were characterized and compared to their unlabeled counterparts, and it was determined that the size, crystal structure, and stability in media up to 500 mM was not significantly changed by the presence of the gold core label. The Au@TiO2 NPs were quantified at low concentrations in complex natural matrices containing elevated levels of background titanium, using both inductively-coupled plasma optical emission spectroscopy and instrumental neutron activation analysis. To contextualize these Au@TiO2 NPs within the broader context of the available MONP labeling strategies, I prepared a critical review of the current literature. Four major categories of labeling techniques are described: fluorescent dyes, radioactive isotopes, stable isotopes, and dopant and core/shell labels. The advantages and disadvantages of each technique are presented. Recommendations are made for characterization that should be performed on labeled and unlabeled MONPs to ensure mechanistic conclusions drawn in experiments are not affected by the presence of the label. Guidance is provided on choosing and applying a labeling strategy for a given study. Finally, I examine the properties and behavior of TiO2 NPs in water treatment applications. The relative influence of elemental surface composition, crystal structure, ROS generation capacity, aggregation state, and water chemistry on the photocatalytic degradation of methylene blue dye is presented. Due to sample contamination, no correlations were found between the molecular-level surface properties determined by x-ray photoelectron spectroscopy and overall treatment efficacy. The most important property determining the extent of decolorization of the dye solutions was the inherent ROS generation capacity of the TiO2 NPs, which in this study was controlled by the crystal structure. Other important properties were the aggregation state of the TiO2 NPs in solution, and the pH stability of the media during the treatment process. Overall, this dissertation provides both justification and methodologies for the study of TiO2 NPs in complex, environmentally-relevant aquatic matrices

O CONHECIMENTO EM CONSTRUÇÃO: DAS FORMULAÇÕES DE JEAN PIAGET À TEORIA DE SISTEMAS COMPLEXOS

Resenha crítica sobre o livro "O conhecimento em construção: das formulações de Jean Piaget à teoria de sistemas complexos", de Rolando García

Enforcing Programming Guidelines with Region Types and Effects

We present in this paper a new type and effect system for Java which can be used to ensure adherence to guidelines for secure web programming. The system is based on the region and effect system by Beringer, Grabowski, and Hofmann. It improves upon it by being parametrized over an arbitrary guideline supplied in the form of a finite monoid or automaton and a type annotation or mockup code for external methods. Furthermore, we add a powerful type inference based on precise interprocedural analysis and provide an implementation in the Soot framework which has been tested on a number of benchmarks including large parts of the Stanford SecuriBench.Comment: long version of APLAS'17 pape

Practical API Protocol Checking with Access Permissions

Reusable APIs often define usage protocols. We previously developed a sound modular type system that checks compliance with typestate-based protocols while affording a great deal of aliasing flexibility. We also developed Plural, a prototype tool that embodies our approach as an automated static analysis and includes several extensions we found useful in practice. This paper evaluates our approach along the following dimensions: (1) We report on experience in specifying relevant usage rules for a large Java standard API with our approach. We also specify several other Java APIs and identify recurring patterns. (2) We summarize two case studies in verifying third-party open-source code bases with few false positives using our tool. We discuss how tool shortcomings can be addressed either with code refactorings or extensions to the tool itself. These results indicate that our approach can be used to specify and enforce real API protocols in practice

CHEOPS launch in 2019! – Payload Capabilities and In-Orbit Commissioning Preview

ESA Science Programme Committee (SPC) selected CHEOPS as the first small class science mission in 2012. CHEOPS is considered as a pilot case for the implementation of “small science missions” and its success is key for the continuation of fast-paced, small missions. The mission has been developed and brought into a flight readiness state within 5-6 years from selection, which is about half the time of other ESA missions. This paper focuses on the CHEOPS payload and its predicted capabilities. The 300mm effective aperture Ritchey-Chretien telescope provided by the CHEOPS consortium has been tested and characterized on ground in a 2 months calibration campaign after the qualification for flight. The results have led to performance estimations, which are discussed here. We show that the performance requirements in flight are expected to be met by the instrument. A preview is given towards the 2 months lasting In Orbit Commissioning (IOC) phase of the CHEOPS payload after LEOP and platform check-out. The activities in orbit range from dark current measurements, PSF characterization and parasitic stray light determination to AOCS and instrument performance verifications to science validation using reference transits

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) - II. A broadened sodium feature on the ultra-hot giant WASP-76b

High-resolution optical spectroscopy is a powerful tool to characterise exoplanetary atmospheres from the ground. The sodium D lines, with their large cross sections, are especially suited to study the upper layers of atmospheres in this context. We report on the results from HEARTS, a spectroscopic survey of exoplanet atmospheres, performing a comparative study of hot gas giants to determine the effects of stellar irradiation. In this second installation of the series, we highlight the detection of neutral sodium on the ultra-hot giant WASP-76b. We observed three transits of the planet using the HARPS high-resolution spectrograph at the ESO 3.6m telescope and collected 175 spectra of WASP-76. We repeatedly detect the absorption signature of neutral sodium in the planet atmosphere ($0.371\pm0.034\%$; $10.75 \sigma$ in a $0.75$ \r{A} passband). The sodium lines have a Gaussian profile with full width at half maximum (FWHM) of $27.6\pm2.8$ km s$^{-1}$. This is significantly broader than the line spread function of HARPS ($2.7$ km s$^{-1}$). We surmise that the observed broadening could trace the super-rotation in the upper atmosphere of this ultra-hot gas giant.Comment: 11 pages, 9 figures; accepted by Astronomy and Astrophysics (29.01.2019