Formal verification of a real-time operating system

Errors caused by the interaction of computer systems with the physical world are hard to mitigate but errors related to the underlying software can be prevented by a more rigorous development of software code. In the context of critical systems, a failure caused by software errors could lead to consequences that are determined to be unacceptable. At the heart of a critical system, a real-time operating system is commonly found. Since the reliability of the entire system depends upon having a reliable operating system, verifying that the operating systems functions as desired is of prime interest. One solution to verify the correctness of significant properties of an existing real-time operating system microkernel (FreeRTOS) applies assisted proof checking to its formalized specification description. The experiment consists of describing real-time operating system characteristics, such as memory safety and scheduler determinism, in Separation Logic — a formal language that allows reasoning about the behaviour of the system in terms of preconditions and postconditions. Once the desired properties are defined in a formal language, a theorem can be constructed to describe the validity of such formula for the given FreeRTOS implementation. Then, by using the Coq proof assistant, a machine-checked proof that such properties hold for FreeRTOS can be carried out. By expressing safety and deterministic properties of an existing real-time operating systems and proving them correct we demonstrate that the current state-of-the-art in theorem-based formal verification, including appropriate logics and proof assistants, make it possible to provide a machine-checked proof of the specification of significant properties for FreeRTOS

Wettability characterization of coquinas from Coqueiro Seco formation

Orientador: Rosângela Barros Zanoni Lopes MorenoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de GeociênciasResumo: A molhabilidade tem sido reconhecida como um fator importante controlando a localização microscópica, distribuição e escoamento de fluidos em um meio poroso. Afeta a saturação de água irredutível e de óleo residual assim como as curvas de permeabilidade relativa e pressão capilar do meio poroso, impactando significativamente na recuperação final de óleo. Evidencias de estudos de laboratório têm mostrado que as rochas carbonáticas são de molhabilidade mista a preferencialmente molhadas por óleo. Estas condições são desfavoráveis para a embebição espontânea da água e, portanto, para projetos de injeção de água como método de recuperação. Conforme estudos sobre interações óleo/água/rocha, a composição e propriedades da água injetada podem alterar as propriedades de molhabilidade das rochas durante processos de injeção de água, melhorando a recuperação de petróleo. O principal objetivo deste trabalho é caracterizar a molhabilidade de um bloco de coquinas de afloramento provenientes da Formação Coqueiro Seco - Bacia Sergipe-Alagoas, que são equivalentes às rochas dos reservatórios do pré sal. As medidas do índice de molhabilidade foram realizadas pelo método de Amott, que combina a embebição espontânea e forçada de fluidos para determinar a molhabilidade média das amostras carbonáticas. Óleo mineral e soluções aquosas com salinidade variando de 10000 a 140000 ppm de NaCl foram usadas para representar o óleo e a água de injeção, respectivamente. Os resultados obtidos dos testes realizados neste estudo evidenciam que este tipo de rocha é de molhabilidade mista a preferencialmente molhadas por óleoAbstract: Wettability has been recognized as an important factor controlling the microscopic location, distribution and fluid flow through a porous medium. It affects the irreducible water saturation and residual oil saturation as well as the relative permeability curves and capillary pressure impacting the ultimate recovery oil. Evidence from laboratory studies have shown that carbonate rocks are mixed wettability to preferentially oil wet which are unfavorable conditions for spontaneous imbibition of water and therefore in the design of a waterflooding process as a recovery method. As studies on oil/water/rock interactions the composition and properties of the injected water can alter the wetting properties of rocks during a waterflooding improving oil recovery. The main objective of this work is to measure the wettability of coquina outcrops from the Coqueiro Seco Formation - Sergipe-Alagoas Basin, which are equivalent to pre-salt reservoir rocks. Wettability index measurements were carried out with the Amott method which combines spontaneous and forced imbibition of fluids to determine the average wettability of carbonate cores. Mineral oil and brines with salinity ranging from 10.000 to 140.000 ppm of NaCl were used to represent crude oil and the injection brine respectively. The results of the tests addressed in this study provided evidences that these rocks are mixed-wet to preferentially oil-wetMestradoReservatórios e GestãoMestre em Ciências e Engenharia de Petróle

La expresión corporal como puesta lúdico-didáctica para el aprendizaje significativo en primera infancia

1. Formato I: Pienso y ahora me pregunto. Documento que utilizaron los docentes para registrar anotaciones y preguntas que surgían a lo largo de la exposición teórica y metodológica de la EC. Enlace de acceso: https://drive.google.com/drive/folders/1Ge_5OMnbFLYbvHPtBPtninps2einEeuU?usp=sharing Formato I:01_Heidy Paola Ortiz. Formato I:02_Claudia Castañeda. Formato I:03_Astrid Cepeda. Formato I:04_Diana Carolina Peñuela. Formato I:05_Natalia Maffiold. Formato I:06_Natalie Castillo. Formato I:07_María Mercedes Acero. 2. Grabación del Taller Expresión Corporal Momento 1 [G1]: Grabación de la primera sesión, al igual que las intervenciones de los docentes frente a los temas. Enlace de acceso: https://www.youtube.com/watch?v=qMOSABFYJLY&t=2274s Diapositivas hechas por el moderador de la reunión (Walton León Espinosa). Enlace de acceso: https://drive.google.com/file/d/14--vqBGMrbtudyN4iuDqUp7Q5PxNyja3/view?usp=sharing Formato_Planeación_K4 FPK4 Enlace de acceso: https://drive.google.com/file/d/1uRRCKXNBlHIsh1bDBBjm91x1wt5VUFlS/view?usp=sharing Formato_Planeación_K5 FPK5 Enlace de acceso: https://drive.google.com/file/d/19Q0_fGUru3608_W6VlxcQ7g3Q1RL-5xC/view?usp=sharing Formato_Planeación_TR FPTR Enlace de acceso: https://drive.google.com/file/d/1dzaDtSifN2SX5jH_CHuB8ZOQc-ehW2ru/view?usp=sharing Presentación Power Point PPT1 Enlace de acceso: https://drive.google.com/file/d/14--vqBGMrbtudyN4iuDqUp7Q5PxNyja3/view?usp=sharing 3. Soporte Audiovisual: Enlace de acceso: https://www.youtube.com/watch?v=wG81Ieez0oE&feature=youtu.beEn el ámbito educativo, la Expresión Corporal ha sido considerada como un campo de conocimiento disciplinar, totalmente alejada de las demás áreas. Tanto así que, es enseñada –y evaluada– como una asignatura más dentro de los programas educativos tanto oficiales como internacionales, incluso en la educación preescolar. En consecuencia, esta investigación pretende, a través de una búsqueda de literatura y de diferentes escenarios prácticos, posicionar la Expresión Corporal como una herramienta lúdico-didáctica para el aprendizaje significativo de los estudiantes en edad preescolar, capaz de combinar todos los conocimientos disciplinares y la maestría de un docente creativo en innovador para una formación y desarrollo integral del ser. A partir de una amplia revisión bibliográfica, y de las vivencias recogidas dentro del ámbito de la educación infantil, se creó un taller de capacitación para los docentes de edades preescolares, del colegio Bilingüe Internacional CIEDI, con el fin de que, desde un conocimiento metodológico y epistemológico, se pueda incluir el juego y el movimiento –bases fundamendoras de la Expresión Corporal– como fuerza integradora y transdisciplinar dentro de las demás áreas disciplinares, que desencadene y facilite la apropiación de conceptos, y en últimas el desarrollo de habilidades no sólo disciplinares sino también habilidades para la vida. Teniendo en cuenta los talleres desarrollados, los resultados de esta propuesta investigativa muestran la gran importancia de la Expresión Corporal como dinamizadora dentro de los procesos de aprendizaje significativo de los estudiantes en edad preescolar y el éxito de ésta como Puesta Lúdico-Didáctica, al haber logrado modificar el pensamiento de los docentes participantes de manera exitosa, no sólo a través del conocimiento innovador acerca del área en cuestión, sino de la inclusión de la misma dentro de la práctica pedagógica reflexiva.In Education, Corporal Expression has always been a disciplinary area, completely separated from the other subjects. It is actually taught –and evaluated- as a different area of study among the official Education Policies, as well as the International ones, even in preschool. This study, through a thorough literary review and implementing diverse practical scenarios, wants to show Corporal Expression as a didactic tool for the significant learning of Preschool students, that contributes to the full development of human beings. Through a vast bibliographic review, and several practical experiences within early childhood education, we created a workshop for preschool teachers from the bilingual school CIEDI, so that they could include movement –foundation of Corporal Expression- in the planning of other content subjects as an integrating and transdisciplinary element, to foster concept appropriation and disciplinary, and life skills development. Results of this research show the importance of Corporal Expression as a fundamental tool in the significant learning processes of Preschool students and its success as a didactic setting, due to its great success in transforming the participants’ way of thinking in relation to innovative knowledge of movement, and its inclusion inside their pedagogical reflexive exercises

Automatically Verifying Temporal Properties of Heap Programs with Cyclic Proof

This work proposes a deductive reasoning approach to the automatic verification of temporal properties of pointer programs, based on cyclic proof. We present a proof system whose judgements express that a program has a certain temporal property, given a suitable precondition, and whose rules operate directly on the temporal modalities as well as symbolically executing programs. Cyclic proofs in our system are, as elsewhere, finite rooted proof graphs subject to a natural, decidable sound ness condition, encoding a form of proof by infinite descent. We present two variants of our proof system, one for CTL (branching time) properties and one for LTL (linear time) properties, and show them both to be sound. We have implemented both variants in the C YCLIST theorem prover, yielding an automated tool that is capable of automatically discovering proofs of temporal properties of our programs. Evaluation of our tool on well-known benchmarks in the model checking community indicates that our approach is viable, and offers an interesting alternative to traditional model checking techniques

In vivo TssA proximity labeling reveals temporal interactions during Type VI secretion 1 biogenesis and TagA, a protein that stops and holds the sheath.

International audienceThe Type VI secretion system (T6SS) is a multiprotein weapon used by bacteria to destroy competitor cells. The T6SS contractile sheath wraps an effector-loaded syringe that is injected into the target cell. This tail structure assembles onto the baseplate that is docked to the membrane complex. In entero-aggregative Escherichia coli TssA plays a central role at each stage of the T6SS assembly pathway by stabilizing the baseplate and coordinating the polymerization of the tail. Here we adapted an assay based on APEX2-dependent biotinylation to identify the proximity partners of TssA in vivo. By using stage-blocking mutations, we define the temporal contacts of TssA during T6SS biogenesis. This proteomic mapping approach also revealed an additional partner of TssA, TagA. We show that TagA is a cytosolic protein tightly associated with the membrane. Analyses of sheath dynamics further demonstrate that TagA captures the distal end of the sheath to stop its polymerization and to maintain it under the extended conformation

RickA Expression Is Not Sufficient to Promote Actin-Based Motility of Rickettsia raoultii

Background: Rickettsia raoultii is a novel Rickettsia species recently isolated from Dermacentor ticks and classified within the spotted fever group (SFG). The inability of R. raoultii to spread within L929 cells suggests that this bacterium is unable to polymerize host cell actin, a property exhibited by all SFG rickettsiae except R. peacocki. This result led us to investigate if RickA, the protein thought to generate actin nucleation, was expressed within this rickettsia species. Methodology/Principal Findings: Amplification and sequencing of R. raoultii rickA showed that this gene encoded a putative 565 amino acid protein highly homologous to those found in other rickettsiae. Using immunofluorescence assays, we determined that the motility pattern (i.e. microcolonies or cell-to-cell spreading) of R. raoultii was different depending on the host cell line in which the bacteria replicated. In contrast, under the same experimental conditions, R. conorii shares the same phenotype both in L929 and in Vero cells. Transmission electron microscopy analysis of infected cells showed that non-motile bacteria were free in the cytosol instead of enclosed in a vacuole. Moreover, western-blot analysis demonstrated that the defect of R. raoultii actin-based motility within L929 cells was not related to lower expression of RickA. Conclusion/Significance: These results, together with previously published data about R. typhi, strongly suggest that another factor, apart from RickA, may be involved with be responsible for actin-based motility in bacteria from the Rickettsi

Dynamic subcellular localization of a respiratory complex controls bacterial respiration

International audienceRespiration, an essential process for most organisms, has to optimally respond to changes in the metabolic demand or the environmental conditions. The branched character of their respiratory chains allows bacteria to do so by providing a great metabolic and regulatory flexibility. Here, we show that the native localization of the nitrate reductase, a major respiratory complex under anaerobiosis in Escherichia coli, is submitted to tight spatiotemporal regulation in response to metabolic conditions via a mechanism using the transmembrane proton gradient as a cue for polar localization. These dynamics are critical for controlling the activity of nitrate reductase, as the formation of polar assemblies potentiates the electron flux through the complex. Thus, dynamic subcellular localization emerges as a critical factor in the control of respiration in bacteria

Estudio comparativo de la prevalencia de caries en dos escuelas de diferente nivel socioeconómico, Managua, julio-agosto, 1998

Tesis (Cirujano Dentista)--Universidad Americana, Managua, 1999El objetivo de esta tesis es determinar la prevalecía de caries dental y su relación con las condiciones socioeconómicas en estudiante con dentición permanente, matriculados en primer año de secundaria en los colegios Centroamérica y Benjamín Zeledón; ciudad de Managua 1998, establecer la relación entre el índice CPOD y el nivel socioeconómico de la población escolar en estudio