Different Approaches to Proof Systems

The classical approach to proof complexity perceives proof systems as deterministic, uniform, surjective, polynomial-time computable functions that map strings to (propositional) tautologies. This approach has been intensively studied since the late 70’s and a lot of progress has been made. During the last years research was started investigating alternative notions of proof systems. There are interesting results stemming from dropping the uniformity requirement, allowing oracle access, using quantum computations, or employing probabilism. These lead to different notions of proof systems for which we survey recent results in this paper

Optimal algorithms and proofs (Dagstuhl Seminar 14421)

This report documents the programme and the outcomes of the Dagstuhl Seminar 14421 "Optimal algorithms and proofs". The seminar brought together researchers working in computational and proof complexity, logic, and the theory of approximations. Each of these areas has its own, but connected notion of optimality; and the main aim of the seminar was to bring together researchers from these different areas, for an exchange of ideas, techniques, and open questions, thereby triggering new research collaborations across established research boundaries

Development of an electrical resistance-based corrosion monitoring system for offshore applications.

La imagen de la página 62 está sujeta a confidencialidad por la autora. 124 p.El objetivo principal de la tesis es el desarrollo de un sistema de monitorización remota de la corrosión para estructuras off-shore (eólica y oil & gas). Mediante este sistema se pretende medir en forma remota la velocidad de corrosión de estructuras expuestas a un medio altamente agresivo como el marino, y así conocer en tiempo real el estado de salud de las estructuras en servicio, permitiendo reducir costes de mantenimiento y reparación, etc. Las condiciones de trabajo de las estructuras offshore representan diversos retos científico-tecnológicos: El ambiente corrosivo y los fenómenos combinados de corrosión-fatiga, corrosión bajo tensión, tribocorrosión, los esfuerzos mecánicos debido al viento, olas, bloques de hielo flotante, la fragilización por hidrógeno, el biofouling en la parte sumergida, son algunos de ellos. Si bien se han llevado a cabo múltiples trabajos en el diseño de materiales y componentes offshore con el objetivo principal de incrementar la vida útil de los mismos, las condiciones extremas de trabajo a la que están sometidos estos materiales siguen representando un desafío que necesita de nuevos desarrollos.En la presente tesis se recogen sendos estados del arte relacionados con las diversas estructuras marinas susceptibles de ser monitorizadas por este sistema, los fenómenos de corrosión y como afectan a los materiales de interés, y estrategias sobre la protección frente a la corrosión y la monitorización de la misma. Paralelamente, se hace hincapié en el efecto de las bacterias sulfatoreductoras en la aleación de acero al carbono HSLA de grado R5 escogido en el presente proyecto. Se detalla la caracterización del acero HSLA empleado, su comportamiento frente a la corrosión comparado con otras aleaciones, una caracterización metalográfica completa que avala el uso del presente material en líneas de fondeo.Finalmente, se detalla de manera cronológica el desarrollo del sensor de corrosión basado en la técnica de la resistencia eléctrica, así como la caracterización de fenómenos parásitos asociados a las medidas de baja y ultra-baja resistencia sobre el que se basa el funcionamiento del sensor

Funcionalització d’enllaços C–H catalitzada per pal·ladi per a la síntesi de tetrahidroisoquinolines

Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2022. Tutor: Xavier Ariza PiquerThe synthesis of new bioactive compounds is always a challenge for chemists, particularly in areas where the appearance of resistant strains to specific drugs is becoming important. Even with the technology and knowledge available, drug discovery is not trivial and hit rates tend to be unfavourable. For this reason, the discovery of privileged bioactive scaffolds that allow multiple structural variations seems to be an appropriate strategy to tackle these issues. In this sense, tetrahydroisoquinoline, a heterocycle that is present in many natural sources, is part of a family of compounds with multiple biological activities that fits with these features. One way to access these heterocycles is by metal-catalyzed cyclization of 2-phenylethylamine derivatives by a C–H activation process. However, the use of unprotected primary amines as a cyclization precursors was almost unprecedented: the elevated reactivity and strong coordination of primary amines to metals difficults their use in metal-catalyzed processes. In this context, to avoid the aforementioned coordination to the metal, the addition of steric hindrance next to the nitrogen was suggested and tested. The results showed that hindered primary amines can be used in this type of cyclization with Pd(II) as a catalyst. Thus, a general synthetic route for the obtention of tetrahydroisoquinoline derivatives coming from primary amines is reported in this project where the additional carbon atom necessary to form the THIQ is introduced through a conjugated addition of a C–H activated carbon to a phenyl vinyl sulfone. The synthetized compounds have a common THIQ skeleton and vary their aromatic substituents and the steric hindrance around the amine. In this work, two different methods for the preparation of the starting amines are reported as well as its cyclization to THIQs

Annual Report 2011 - Institute of Radiochemistry

The Institute of Radiochemistry (IRC) is one of the seven institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research activities are fully integrated into the “Nuclear Safety Research Program” of the Helmholtz Association and focused on the topic “Safety of Nuclear Waste Disposal”. The research objectives are to generate better process understanding and data for the long-term safety analysis of a nuclear waste disposal in the deep geological underground. A better knowledge about the dominating processes essential for radionuclide (actinide) mobilization and immobilization on the molecular level is needed for the assessment of the macroscopic processes which determine the transport and distribution of radioactivity in the environment. Special emphasis is put on the biological mediated transport of long-lived radionuclides in the geosphere and their interaction with different biosystems like biota and human organism for a better calculation of environmental and health risks. Advanced knowledge is needed for description of the processes dominating at the interfaces between geo- and bio-systems related to the distribution of long-lived radionuclides in various bio-systems along the food chain

Combinatorial–computational–chemoinformatics (C3) approach to finding and analyzing low-energy tautomers

Finding the most stable tautomer or a set of low-energy tautomers of molecules is critical in many aspects of molecular modelling or virtual screening experiments. Enumeration of low-energy tautomers of neutral molecules in the gas-phase or typical solvents can be performed by applying available organic chemistry knowledge. This kind of enumeration is implemented in a number of software packages and it is relatively reliable. However, in esoteric cases such as charged molecules in uncommon, non-aqueous solvents there is simply not enough available knowledge to make reliable predictions of low energy tautomers. Over the last few years we have been developing an approach to address the latter problem and we successfully applied it to discover the most stable anionic tautomers of nucleic acid bases that might be involved in the process of DNA damage by low-energy electrons and in charge transfer through DNA. The approach involves three steps: (1) combinatorial generation of a library of tautomers, (2) energy-based screening of the library using electronic structure methods, and (3) analysis of the information generated in step (2). In steps 1–3 we employ combinatorial, computational and chemoinformatics techniques, respectively. Therefore, this hybrid approach is named “Combinatorial*Computational*Chemoinformatics”, or just abbreviated as C3 (or C-cube) approach. This article summarizes our developments and most interesting methodological aspects of the C3 approach. It can serve as an example how to identify the most stable tautomers of molecular systems for which common chemical knowledge had not been sufficient to make definite predictions