A map for heavy inertial particles in fluid flows

We introduce a map which reproduces qualitatively many fundamental properties of the dynamics of heavy particles in fluid flows. These include a uniform rate of decrease of volume in phase space, a slow-manifold effective dynamics when the single parameter $s$ (analogous of the Stokes number) approaches zero, the possibility of fold caustics in the "velocity field", and a minimum, as a function of $s$, of the Lyapunov (Kaplan-Yorke) dimension of the attractor where particles accumulate.Comment: 10 pages, 5 figure

Competence pilus biogenesis in Streptococcus pneumoniae

Horizontal gene transfer drives bacterial evolution and is crucial for the pathogenicity of many bacteria that can exchange genetic material through distinct mechanisms such as natural transformation. S. pneumoniae, a common asymptomatic colonizer of the human nasopharynx, is naturally transformable, being able to take up naked DNA and integrate it into its genome. Natural transformation allows pneumococci to acquire new traits, which can provide fitness advantages and contribute to the modulation of carriage and invasive diseases such as pneumonia, meningitis or septicaemia. Natural transformation is a complex and highly regulated process, which requires bacteria to enter in a distinct metabolic state named competence. During this period, competent pneumococci express all proteins required for transformation. Among them, are the proteins encoded by the comG operon (comGA-G) implicated in the assembly of pneumococcal competence type IV pili (T4P), which were shown to directly bind DNA. Deciphering how these filaments are assembled is a crucial step in understanding pneumococcal natural transformation and the main focus of this thesis. Pneumococcal T4P can be several micrometres long and are composed of the major pilin ComGC. We demonstrated that ComGC has intrinsic capacity to polymerize and to assemble into pili. We also solved the high-resolution NMR structure of N-terminal truncated ComGC and found that ComGC has distinct structural features compared to other known type IV pilins and is highly flexible. Based on the structure of ComGC, we further identified a region with potential DNA binding properties, providing the basis to understand the function of competence pili. In addition to our investigation of the major pilin ComGC, we also studied the role of the minor pilins ComGD, ComGE, CopmGF and ComGG in pilus assembly and transformation. We showed that the pneumococcal minor pilins form a minor pilin complex likely to prime pilus assembly. Moreover, we visualized that ComGF is part of the filament and present strong evidence for the role of ComGG as the linker between the minor pilin complex and ComGC. Pneumococcal colonization and virulence can be influenced by different factors including induction of competence genes and cell morphology. We found that Deterministic Lateral Displacement is a suitable label-free microfluidics technique to sort S. pneumoniae into subpopulations based on morphological properties, which can be a relevant tool to understand the mechanisms governing colonization and how bacteria cause disease. In summary, here we provide a genetic and molecular characterization of the key components involved in pneumococcal pilus assembly and present a novel technique to study S. pneumoniae subpopulations

Fatigue-recovery simulation model to analyze the impact of nursing activities on fatigue level in an intensive care unit

[EMBARGOED UNTIL 6/1/2023] Although nursing is physically and mentally strenuous, not many studies have been done yet to find the impact of the key groups of tasks on nurses' average fatigue level and workflow. So, this study aims to understand the relationships among the key activities that impact the nurses' average fatigue level in an Intensive Care Unit (ICU). Nurses' time-study and real-time location data have been used to develop a simulation model in two different periods: February to March 2020 and July 2020. Two Hierarchical Task Analysis charts were generated from the collected data, one for each period, and used as the foundation for the fatigue-recovery simulation model. Both simulation models have been statistically tested and validated by comparing the time study observation data. Different scenarios of all nursing activities' frequencies (number of conducted tasks during a shift) and task sequences (number of times tasks are conducted continuously prior to a break) were simulated as independent variables. The dependent variable is their impacts on the nurses' predicted average fatigue levels during a shift. The main contribution of this work is that the model could provide a new way to estimate the nurses' fatigue levels in different workload conditions and to establish specific nursepatient ratios dynamically to improve patient care in a medical ICU. In this study, it was found that the major drivers for nurses' fatigue in an ICU shift is the number of times nurses conduct tasks in sequence without a break (number of task sequences), followed by the number of patient care or procedures, and peer support activities conducted in shift. However, the limitations in this study are the lack of the ratio number of nurses/number of patients during the shifts, the number of patients assigned to the assessed nurses, and regarding to the fatigue and recovery indexes. In this study, it is assumed three levels for the indexes, low, medium, and high, depending on the nature of the activity. It is recommended that, for the sake of more accurate results, in future studies, fatigue is monitored by a real-time method, in that way, there will be an estimated fatigue and/or recovery index for every single nurse task.Includes bibliographical references

Does Speculation Affect Oil Price Volatiliy?

O objetivo do presente estudo é tentar perceber se a atividade especulativa é o fator principal na repentina subida de preços do crude no spot market, especialmente no mais recente episódio especulativo que ocorreu entre 2003 e a primeira metade de 2008. A base do nosso estudo assenta num modelo já existente de vectores autoregressivos que foi proposto por Kilian e Murphy (2014); um modelo estrutural do mercado global do crude que permite uma análise de choques de procura e oferta e também choques especulativos. A originalidade do modelo apresentado nesta dissertação, relativamente ao daqueles autores, reside na introdução de um componente especulativo para medir os spreads usando contratos de futuros do crude. Com o output do modelo estrutural apresentado conseguimos excluir a teoria da especulação como fator na subida do preço do crude; no entanto, os nossos resultados sugerem que a subida se deve a um aumento na procura conduzido por um crescimento económico inesperado na economia global. As conclusões deste estudo permitem confirmar as de outras obras literárias da mesma natureza e revelam a importância dos futuros enquanto instrumentos preditivo

Multistability and Gibbs entropy in the planar dissipative spin-orbit problem

In this work, we numerically investigate and visually illustrate the dynamical properties of the dissipative spin-orbit problem such as the co-existence of multiple periodic and quasi-periodic attractors, and the complexity of the corresponding basins of attraction. Our model is composed by a triaxial satellite (planet) orbiting a planet (star) in a fixed Keplerian orbit with zero obliquity. A dissipative tidal torque that is proportional to its rotational angular velocity is assumed to be acting on the satellite. We use Hyperion as a toy model to characterize the methodology used, since this system has a very rich conservative dynamical scenario, and we later apply our methodology to the Moon and Mercury. Our results show that the basins of attraction may possess an intricate structure in all cases which changes with the orbital eccentricity, and that the Gibbs entropy is a good measure on how dominant one basin is over the others in the phase space.Comment: 20 pages, 12 figure

Firs under field extensions

Our main aim is to investigate the relation between free ideal rings (firs) which are algebras over a field and the rings obtained from them by a commutative field extension of scalars. Having in mind the monoid of projectives of these rings, we prove that commutative monoids with distinguished element which are conical and have the UGN property are strongly embedded in their coproduct and that the coproduct inherits some properties of its factors. This result, in conjunction with Bergman's coproduct theorems, is used to establish links between coproducts of skew fields and the rings obtained from them by extension of scalars. The notion of a power-free ideal ring is explored when looking at coproducts and, more generally, at rings obtained by matrix reduction of coproducts. We also look at firs of the form R = Fk(X), where F is either a finite Galois extension or a simple purely inseparable extension of k. These firs, when tensored with F over k, give rise to rings that are no longer firs, but they are very close to being full matrix rings over firs in the sense that the adjunction to R of a single inverse (in the purely inseparable case) or of finitely many inverses (in the Galois case) originates a ring which under the same extension of scalars is a full matrix ring over a fir. The universal field of fractions of a fir obtained by this construction is just the skew field component of the simple artinian ring obtained by extending the scalars of the universal field of fractions of R

Mergers & acquisitions : Portucel and Suzano Papel e Celulose

The pulp and paper industry is, nowadays, facing challenges associated with the lack of demand growth, pushing firms to adapt to intense competition and industry-wide overcapacity. In order to remain profitable and achieve sustainable competitive positions, industry players have relied on M&A to achieve scale and expand into growing markets in emerging countries. The industry concentration conducted through mergers has been able to deliver value to shareholders while changing the overall competitive landscape. This dissertation’s goal is to propose a merger between Suzano Papel e Celulose and Portucel. The proposition is supported by a review of the main literature on M&A, a thorough industry and company analysis, and a valuation of each individual firm and its combination. It is concluded that Suzano should acquire Portucel in an all-stock offer, valuing the Portuguese firm at €4.32, a premium of 55% over its 31 December 2013 market capitalization. Through the proposed takeover offer, Portucel would be entitled to 46% of the merged firm, with the remaining 54% allocated to Suzano’s shareholders