Academic literature on the topic 'DP-1'

The cellular transcription factor DRTF1/E2F and the tumor suppressor protein p53 play important roles in controlling early cell cycle events. DRTF1/E2F is believed to coordinate and integrate the transcription of cell cycle-regulating genes, for example, those involved in DNA synthesis, with the activity of regulatory proteins, such as the retinoblastoma tumor suppressor gene product (pRb), which modulate its transcriptional activity. In contrast, p53 is thought to monitor the integrity of chromosomal DNA and when appropriate interfere with cell cycle progression, for example, in response to DNA damage. Generic DRTF1/E2F DNA binding activity and transcriptional activation arise when members of two distinct families of proteins, such as DP-1 and E2F-1, interact as DP/E2F heterodimers. In many cell types, DP-1 is a widespread component of DRTF1/E2F DNA binding activity which when expressed at high levels oncogenically transforms embryonic fibroblasts. Here, we document an association between DP-1 and p53 and demonstrate its presence in mammalian cell extracts. In vitro p53 interacts with an immunochemically distinct form of DP-1 and in vivo can regulate transcription driven by the DP-1/E2F-1 heterodimer. At the biochemical level, p53 competes with E2F-1 for DP-1, with a consequent reduction in DNA binding activity. Mutational analysis defines within DP-1 a C-terminal region required for the interaction with p53 and within p53 an N-terminal region distinct from that required to bind to MDM2. Our results establish DRTF1/E2F as a common cellular target in growth control mediated through the activities of pRb and p53 and suggest an alternative mechanism through which p53 may regulate cellular proliferation.

We construct Spin (p + 1, p + 1) covariant D p-brane bound states by using the fact that the potentials in the RR sector of toroidically compactified type II supergravity transform as a chiral spinor of the T duality group. As an application, we show the invariance of the zero-force condition for a probe D-brane under noncommutative deformations of the background, which gives a holographic proof of the stability of the corresponding field theory ground state under noncommutative deformations. We also identify the Spin (p + 1, p + 1) transformation laws by examining the covariance of the D-brane Lagrangians.

Unregulated expression of the transcription factor E2F promotes the G1-to-S phase transition in cultured mammalian cells. However, there has been no direct evidence for an E2F requirement in this process. To demonstrate that E2F is obligatory for cell cycle progression, we attempted to inactivate E2F by overexpressing dominant-negative forms of one of its heterodimeric partners, DP-1. We dissected the functional domains of DP-1 and separated the region that facilitate heterodimer DNA binding from the E2F dimerization domain. Various DP-1 mutants were introduced into cells via transfection, and the cell cycle profile of the transfected cells was analyzed by flow cytometry. Expression of wild-type DP-1 or DP-1 mutants that bind to both DNA and E2F drove cells into S phase. In contrast, DP-1 mutants that retained E2F binding but lost DNA binding arrested cells in the G1 phase of the cell cycle. The DP-1 mutants that were unable to bind DNA resulted in transcriptionally inactive E2F complexes, suggesting that the G1 arrest is caused by formation of defective E2F heterodimers. Furthermore, the G1 arrest instigated by these DP-1 mutants could be rescued by coexpression of wild-type E2F or DP protein. These experiments define functional domains of DP and demonstrate a requirement for active E2F complexes in cell cycle progression.

Let G be a group. Dp(G)=⋂H≤GNG(H′(p)) is defined and, the properties of Dp(G) are investigated. It is proved that Dp(G)=P[A], where P=D(P) is the Sylow p-subgroup and A=N(A) is a Hall p′-subgroup of Dp(G), respectively. Furthermore, it is proved in a group G that (1) Dp(G)=1 if and only if CG(G′(p))=1; (2) Op′(Dp(G))≤Z∞(Op(G)) and (3) if Z(G′(p))=1, then CG(G′(p))=Dp(G).

It is widely believed that in mammalian cells the cellular transcription factor (DRTF1/E2F integrates cell-cycle events with the transcription apparatus by interacting with important regulators of the cell cycle, such as the retinoblastoma gene product (pRb) and related proteins, cyclins, and cyclin-dependent kinases. Here, we have defined DRTF1/E2F in Xenopus laevis that, like its mammalian counterpart, specifically binds to the E2F site, is regulated during development, and interacts with pRb and related proteins. We have isolated cDNAs that encode the functional homologue of mammalian DP-1, X1 DP-1, together with a close relative, X1 DP-2. X1 DP-1, which is highly conserved with murine DP-1, is a major DNA binding component of X1 DRTF1/E2F. Both DP-1 and DP-2 synergistically interact with members of the E2F family of proteins, E2F-1, E2F-2, and E2F-3, to generate DNA binding complexes that specifically recognize the E2F site and functionally interact with E2F-1 in E2F site-dependent transcriptional activation of cellular genes. DP-1 and DP-2 encode maternally stored transcripts that are expressed during early development. In the adult however, the expression of DP-1 and DP-2 is tissue restricted. This study therefore defines a new family of transcription factors, the DP proteins, members of which can interact combinatorially with E2F proteins to generate an array of DNA binding complexes that integrate cell-cycle progression with the transcription apparatus through the E2F binding site. The tissue-specific expression of DP family members suggests that the combination of DP/E2F heterodimers that constitute DRTF1/E2F is influenced by the phenotype of the cell.

The E2F DNA binding activity consists of a heterodimer between E2F and DP family proteins, and these interactions are required for association of E2F proteins with pRb and the pRb-related proteins p107 and p130, which modulate E2F transcriptional activities. E2F-1 expression is sufficient to release fibroblasts from G0 and induce entry into S phase, yet it also initiates apoptosis. To investigate the mechanisms of E2F-induced apoptosis, we utilized interleukin-3 (IL-3)-dependent 32D.3 myeloid cells, a model of hematopoietic progenitor programmed cell death. In the absence of IL-3, E2F-1 alone was sufficient to induce apoptosis, and p53 levels were diminished. DP-1 alone was not sufficient to induce cell cycle progression or alter rates of death following IL-3 withdrawal. However, overexpression of both E2F-1 and DP-1 led to the rapid death of cells even in the presence of survival factors. In the presence of IL-3, levels of endogenous wild-type p53 increased in response to E2F-1, and coexpression of DP-1 further augmented p53 levels. These results provide evidence that E2F is a functional link between the tumor suppressors p53 and pRb. However, induction of p53 alone was not sufficient to trigger apoptosis, suggesting that the ability of E2F to override survival factors involves additional effectors.

Cette thèse est consacrée à l’étude d’expansions de certaines structures algébriques et leur place dans la classification modèle-théorique des structures, initiée par Shelah. La première partie aborde de manière abstraite l’expansion d’une théorie par un prédicat aléatoire –ou générique– pour une sous-structure modèle d’un réduit de la théorie. Nous éla- borons un critère pour l’existence d’une telle expansion, qui est vérifié pour certaines théories de structures algébriques. En particulier, nous montrons l’existence de sous-groupes additifs génériques pour certaines théories de corps, ainsi que de sous-groupes multiplicatifs génériques pour les corps algébriquement clos en toute caractéristique. Nous étudions aussi la conservation de diverses notions de néostabilité, en particulier nous montrons que cette expansion préserve la propriété NSOP 1 , mais en général ne préserve pas la simplicité. Nous produisons par cette construction de nouveaux exemples de structures NSOP 1 non simples, et faisons une étude toute particulière de l’une d’entre elles : l’expansion d’un corps algébriquement clos de caractéristique positive par un sous-groupe additif générique. La deuxième partie étudie les expansions du groupe des entiers par des valuations p-adiques. Nous montrons l’élimination des quantificateurs dans un langage naturel et calculons le dp-rang d’une telle expansion : il est égal au nombre de valuations considérées. L’expansion du groupe des entiers par une seule valuation p-adique est donc une nouvelle expansion dp-minimale du groupe des entiers. Enfin, nous montrons que cette dernière n’admet pas de structures intermédiaires : tout ensemble définissable dans l’expansion est soit définissable dans le groupe des entiers, soit capable de “reconstruire” la valuation en utilisant seulement la structure additive
This thesis is concerned with the expansions of some algebraic structures and their fit in Shelah’s classification landscape. The first part deals with the expansion of a theory by a random –or generic– predicate for a substructure model of a reduct of the theory. We describe a setup allowing such an expansion to exist, which is suitable for several algebraic structures. In particular, we obtain the existence of additive generic subgroups of some theories of fields and multiplicative generic subgroups of algebraically closed fields in all characteristic. We also study the preservation of certain neostability notions, for instance, the NSOP 1 property is preserved but the simplicity is not in general. Thus, this construction produces new examples of NSOP 1 not simple theories, and we study in depth a particular example: the expansion of an algebraically closed field of positive characteristic by a generic additive subgroup. The second part studies expansions of the groups of integers by p-adic valuations. We prove quantifier elimination in a natural language and compute the dp-rank of these expansions: it equals the number of distinct p-adic valuations considered. Thus, the expansion of the integers by one p-adic valuation is a new dp-minimal expansion of the group of integers. Finally, we prove that the latter expansion does not admit intermediate structures: any definable set in the expansion is either definable in the group structure or is able to "reconstruct" the valuation using only the group operation

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
SLAM (Mapeamento e Localização Simultânea) é uma das áreas mais pesquisadas na Robótica móvel. Trata-se do problema, num robô móvel, de construir um mapa sem conhecimento prévio do ambiente e ao mesmo tempo manter a sua localização nele. Embora a tecnologia ofereça sensores cada vez mais precisos, pequenos erros na medição são acumulados comprometendo a precisão na localização, sendo estes evidentes quando o robô retorna a uma posição inicial depois de percorrer um longo caminho. Assim, para melhoria do desempenho do SLAM é necessário representar a sua formulação usando teoria das probabilidades. O SLAM com Filtro Extendido de Kalman (EKF-SLAM) é uma solução básica, e apesar de suas limitações é a técnica mais popular. O Fast SLAM, por outro lado, resolve algumas limitações do EKF-SLAM usando uma instância do filtro de partículas conhecida como Rao-Blackwellized. Outra solução bem sucedida é o DP-SLAM, o qual usa uma representação do mapa em forma de grade de ocupação, com um algoritmo hierárquico que constrói mapas 2D bastante precisos. Todos estes algoritmos usam informação de dois tipos de sensores: odômetros e sensores de distância. O Laser Range Finder (LRF) é um medidor laser de distância por varredura, e pela sua precisão é bastante usado na correção do erro em odômetros. Este trabalho apresenta uma detalhada implementação destas três soluções para o SLAM, focalizado em ambientes fechados e estruturados. Apresenta-se a construção de mapas 2D e 3D em terrenos planos tais como em aplicações típicas de ambientes fechados. A representação dos mapas 2D é feita na forma de grade de ocupação. Por outro lado, a representação dos mapas 3D é feita na forma de nuvem de pontos ao invés de grade, para reduzir o custo computacional. É considerado um robô móvel equipado com apenas um LRF, sem nenhuma informação de odometria. O alinhamento entre varreduras laser é otimizado fazendo o uso de Algoritmos Genéticos. Assim, podem-se construir mapas e ao mesmo tempo localizar o robô sem necessidade de odômetros ou outros sensores. Um simulador em Matlab é implementado para a geração de varreduras virtuais de um LRF em um ambiente 3D (virtual). A metodologia proposta é validada com os dados simulados, assim como com dados experimentais obtidos da literatura, demonstrando a possibilidade de construção de mapas 3D com apenas um sensor LRF.
Simultaneous Localization and Mapping (SLAM) is one of the most widely researched areas of Robotics. It addresses the mobile robot problem of generating a map without prior knowledge of the environment, while keeping track of its position. Although technology offers increasingly accurate position sensors, even small measurement errors can accumulate and compromise the localization accuracy. This becomes evident when programming a robot to return to its original position after traveling a long distance, based only on its sensor readings. Thus, to improve SLAM s performance it is necessary to represent its formulation using probability theory. The Extended Kalman Filter SLAM (EKF-SLAM) is a basic solution and, despite its shortcomings, it is by far the most popular technique. Fast SLAM, on the other hand, solves some limitations of the EKFSLAM using an instance of the Rao-Blackwellized particle filter. Another successful solution is to use the DP-SLAM approach, which uses a grid representation and a hierarchical algorithm to build accurate 2D maps. All SLAM solutions require two types of sensor information: odometry and range measurement. Laser Range Finders (LRF) are popular range measurement sensors and, because of their accuracy, are well suited for odometry error correction. Furthermore, the odometer may even be eliminated from the system if multiple consecutive LRF scans are matched. This works presents a detailed implementation of these three SLAM solutions, focused on structured indoor environments. The implementation is able to map 2D environments, as well as 3D environments with planar terrain, such as in a typical indoor application. The 2D application is able to automatically generate a stochastic grid map. On the other hand, the 3D problem uses a point cloud representation of the map, instead of a 3D grid, to reduce the SLAM computational effort. The considered mobile robot only uses a single LRF, without any odometry information. A Genetic Algorithm is presented to optimize the matching of LRF scans taken at different instants. Such matching is able not only to map the environment but also localize the robot, without the need for odometers or other sensors. A simulation program is implemented in Matlab to generate virtual LRF readings of a mobile robot in a 3D environment. Both simulated readings and experimental data from the literature are independently used to validate the proposed methodology, automatically generating 3D maps using just a single LRF.

In this thesis, we attempt to obtain a class of generalized bilinear differential equations in (3+1)-dimensions by Dp-operators with p = 5, which have resonant solutions. We construct resonant solutions by using the linear superposition principle and parameterizations of wave numbers and frequencies. We test different values of p in Maple computations, and generate three classes of generalized bilinear differential equations and their resonant solutions when p = 5.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho consiste em uma caracterização inicial das habilidades de processamento presentes nas crianças que adquirem o sistema de número gramatical em português. Foi realizada uma coleta longitudinal de dados de produção durante 4 meses com 2 crianças de 24-28 meses e 21-25 meses, cujo objetivo foi obter dados de produção lingüística semi-espontânea que permitissem identificar exemplos de produção de formas flexionadas em número. Realizaram-se também 3 experimentos de reconhecimento de imagens, com crianças de 18 a 28 meses e 30 a 42 meses, os quais visavam a verificar (i) se a criança distingue nome flexionado em número de nome não-flexionado; (ii) se a criança percebe onde se localiza a marca de número no português em palavras de seu vocabulário e em pseudo- palavras que remetem a objetos inventados; e, por fim, contrastar dados de experimentos semelhantes relativos a gênero gramatical, de modo a averiguar se crianças processam concordância de número no DP. A hipótese de trabalho que orienta esta dissertação é a de que a informação relativa a número contida nos elementos que formam a categoria funcional Determinante (D) é crucial para a identificação do sistema de número no português. Os valores relativos a número identificados nos elementos da categoria D como marcado/não marcado são interpretados semanticamente como singular e plural por meio do mecanismo da concordância, sendo a identificação do número gramatical mais custosa do que a do gênero gramatical em virtude de o número ser um traço opcional e de este traço veicular informação semântica a ser associada a classes morfofonológicas identificadas no Det e no Nome. O modelo de língua assumido nesse estudo é o sugerido pelo Programa Minimalista (Chomsky, 1995).
This work is concerned with the acquisition of the Portuguese number system. Longitudinal production data of two children (24-28 months and 21-25 months) were collected for 4 months in order to verify whether there is evidence of the use of number inflected forms. 3 picture- identification experiments were carried out with children ranging from 18 to 28 months and 30 to 42 months, whose aim was to verify (i) whether children would distinguish number inflected from number uninflected nouns (ii) whether they would process number agreement in the DP and the extent to which they would perceive number incongruence and ungrammaticality as far as number agreement in the DP is concerned. Both nouns from children`s vocabulary and pseudo- nouns were used. The latter was indented to constraint semantic information to the number affix. These data were contrasted with the results on gender (Name, 2002), which suggest that young children (mean age 24 months) perceive gender incongruence between D and N in the processing of a DP. The working hypothesis of this study is that children identify morphological information concerning number and gender within the closed class of determiners. The fact that number is basically an optional feature, which can be expressed in the Noun, would nevertheless, make the acquisition of grammatical number to be relatively more demanding than the identification of grammatical gender. The linguistic framework assumed here is the Minimalist Program (Chomsky, 1995).

This study aimed to review the specialized literature on respiratory, postural and vocal manifestations, associated to stages in Parkinson´s Disease and its possible interrelations, as well as, aging in phonation. Method: Some researches were carried based in articles in some databases: Lilacs, Bireme, PubMed, MedLine, Scielo and Google Schoolar, besides books, theses, dissertations and the Internet. Results: senescence is a physiological process to all human beings, generating anatomical and functional changes, especially at the age of 60, as muscular atrophy, calcification of the laryngeal cartilage, and reduction in respiratory capacity, reflecting on the voice through changes in pitch, instability, decrease in the maximum phonation time and restriction of vocal intensity. Parkinson´s Disease causes a series of functional alterations, e.g., rigidity, shaking, bradikinesia, reduction in the respiratory muscular strength, in maximum phonation time and vocal intensity, as well as postural changes. Its repercussions occur simultaneously, due to the muscle chains, body posture, respiratory and, consequently, phonation. Postural deviations, as the head forward positioning, shoulder protrusion and chest hyperciphosis are common in aging and PD and contribute to vocal disturbances through biomechanic disadvantages, especially in the cervical-scapular segment. Associated to postural alterations, is the decreasing in the respiratory muscular strength, causing the chest to expand less, reduction in the lungs volume and capacity, interfering in vocal production. There is a tendency for these disturbances to occur more frequently and with more gravity according to the stage in which the parkinsonian is. Conclusion: Based in the premisse that the human movement and its disorders, as well as the comunication disturbances, from aging and neurological diseases are interrelated by means of complex neural and muscle-skeleton nets, it becomes essential for a better understanding of the integration of physiotherapy and speech therapy, in order to have a complementarity, aiming the Parksonian's well-being.
Este estudo objetivou realizar uma revisão de literatura sobre as manifestações respiratórias, posturais e vocais, associadas aos estágios da Doença de Parkinson e suas possíveis inter-relações, bem como, o envelhecimento na fonação. Método: Realizaram-se buscas a partir de publicações nas bases de dados Lilacs, Bireme, PubMed, MedLine, Scielo e Google Schoolar, tendo sido utilizados também livros, teses, dissertações e Internet. Resultados: a senescência é um processo fisiológico a todos os seres humanos, gerando modificações anátomo-funcionais, especialmente a partir dos 60 anos, como atrofia muscular, calcificação das cartilagens laríngeas, e redução na capacidade respiratória, refletindo-se na voz através de alterações no pitch, instabilidade, decréscimo dos tempos máximos de fonação e restrição à intensidade vocal. A Doença de Parkinson ocasiona uma série de alterações funcionais, por exemplo, rigidez, tremor, bradicinesia, redução na força muscular respiratória, nos tempos máximos de fonação e na intensidade vocal, bem como alterações posturais. Suas repercussões ocorrem simultaneamente, devido às cadeias musculares, na postura corporal, na respiração e, conseqüentemente, na fonação. Desvios posturais, como anteriorização da cabeça, protrusão de ombros e hipercifose torácica são comuns no envelhecimento e na DP e contribuem para os distúrbios vocais, por meio de desvantagens biomecânicas, especialmente no segmento cérvico-escapular. Associado às alterações posturais, ocorre o decréscimo na força muscular respiratória que propicia menor expansibilidade da caixa torácica, redução nos volumes e capacidades pulmonares, interferindo na produção vocal. Há uma tendência de que esses distúrbios ocorram com maior freqüência e gravidade de acordo com o estágio em que o parkinsoniano se encontra. Conclusão: Baseado na premissa de que o movimento humano e suas desordens, assim como os distúrbios da comunicação advindos tanto do envelhecimento quanto de doenças neurológicas apresentam-se inter-relacionados por meio de complexas redes neurais e músculoesqueléticas, torna-se essencial uma melhor compreensão da fisioterapia e da fonoaudiologia acerca dessas interações, a fim de que haja complementaridade, visando ao bem-estar do indivíduo.

Genomic imprinting is an epigenetic phenomenon whereby the expression of a gene, chromosomal region, or entire chromosome, depends on the sex of the transmitting parent. Imprinting results in an otherwise fully functional gene being transcriptionally silenced when transmitted by one parent, yet the same gene, with identical DNA sequence, is active when transmitted by the other. Thus, the gene retains an imprint or “memory” of its genetic history, which is reversible and reset each successive generation by passage through the germline. Within this thesis, I present my findings that show genomic imprinting in Drosophila is regulated by distinct epigenetic mechanisms at different stages of embryogenesis, suggesting the requirement of a transitional stage to stabilize the imprint between establishment in the germline and maintenance in the soma. I futher show that Drosophila utilize epigenetic mechanisms that are involved in regulating genomic imprinting in mammals and plants, such as DNA methylation, histone modification, antisense RNA, and chromatin insulators. These findings demonstrate convergence of the epigenetic mechanisms that regulate genomic imprinting in diverse organisms.

Chapter 4 investigates the dissimilar behavior of appositive relative clauses introduced by the complex relative pronoun o qual in Contemporary European Portuguese and earlier stages of Portuguese. From a descriptive point of view, eight contrasting properties are identified, relative to: (1) additional internal head; (2) extraposition; (3) pied-piping; (4) clausal antecedents; (5) split antecedents; (6) coordination of the wh-pronoun with another DP; (7) illocutionary force; and (8) the presence of a coordinator. From a theoretical point of view, it is argued that the same structural analysis cannot alone derive the contrasting properties of appositive relativization. To account for the variation found in the diachronic and cross-linguistic dimensions, it is claimed that appositive relatives might involve two different structures: specifying coordination and head raising.

This paper reports in-plane electrostatic comb-drive actuators with stroke as large as 245 μm, achieved by employing a novel Clamped Paired Double Parallelogram (C-DP-DP) flexure mechanism. For a given flexure beam length (L1), comb gap (G), and actuation voltage (V), this is currently the largest comb-drive actuator stroke reported in the literature. The C-DP-DP flexure mechanism design offers high bearing direction stiffness (Kx) while maintaining low motion direction stiffness (Ky), over a large range of motion direction displacement. The resulting high (Kx /Ky) ratio mitigates the on-set of sideways snap-in instability, thereby offering significantly greater actuation stroke compared to existing designs. Further improvement is achieved by reinforcing the individual beams in this flexure mechanism. While the traditional Paired Double Parallelogram (DP-DP) flexure design with G = 3 μm, L1 = 1 mm results in a 50 μm stroke before snap-in, the reinforced C-DP-DP design with G = 3μm achieves a stroke of 141 μm. The same C-DP-DP flexure design provides a 215 μm stroke with G = 4 μm, and a 245 μm stroke with G = 6 μm. The presented work includes closed-form stiffness values for the reinforced C-DP-DP flexure, a design procedure for selecting dimensions of the overall comb-drive actuator, micro-fabrication of some representative actuators, and experimental measurements demonstrating the large stroke.

Dynamically positioned (DP) vessels are widely used in marine operations in the offshore oil & gas industry. The risk caused by DP vessels’ position loss is not negligible, and managing DP safety in marine operations is indispensable. This paper presents an overall framework for DP safety management in offshore marine operations. It consists of the following three key steps, i.e. 1) Identification of position loss scenarios, 2) Risk analysis in terms of position loss frequency and consequences, and risk evaluation, 3) Mitigation of risk via measures to eliminate the risk, or to reduce the likelihood of position loss, as well as to mitigate the consequence in marine operations given DP vessel position losses. Case studies from DP shuttle tankers and DP mobile offshore drilling units are presented to illustrate key principles in each of the above three steps. Quantitative risk analysis and evaluation approach is highlighted, and the associated challenges are described. Recommendations to further improve DP safety management in offshore marine operations are proposed.

This paper presents a numerical station-keeping simulation in waves (regular and irregular waves) for a simplified FPSO with two DP systems. The main difference of the simulation with these two DP systems was that the first DP system (called MOT DP in this paper) was included in a seakeeping simulation code (MOTSIM) while another DP system (called IOT DP, developed by NRC/IOT) was an external system and installed on another computer (which was the same as the one used to control the vessel in physical model experiments). In order to exchange command messages between the simulation code (MOTSIM) and the IOT DP system, a communication code executed in the same time step was developed by using Windows™ socket functions. By using these two DP systems a station-keeping simulation for a 1:40 scale model FPSO with six azimuthing thrusters was conducted in regular and irregular waves and wind. The seakeeping RAO results in regular waves were compared between these two DP systems, and also with physical model experiments with external IOT DP system and analysis using a commercial linear, 3-dimensional panel code, HydroStar. In irregular waves a mean station keeping force Fx, Fy in horizontal plane was calculated and its total mean force was compared with results from the physical model experiments. Finally, a discussion between these two DP systems was provided.

Utilization of Dynamic Positioning (DP) systems for offshore exploration and production of hydrocarbons is increasing due to the need to exploit deeper water depths, where mooring becomes less feasible. In conducting analysis or predictions for DP System performance, there are two common techniques used: Either an experimental investigation at reduced scale using a simplified mooring system without thrusters; or, a similarly scaled experiment using active DP thrusters. This paper identifies differences in the DP system performance estimates for each method by assessing the same system in identical wind–wave environments. Experiments were completed using a 1:40 scale model of a typical 99,000t monohull drillship equipped with an active DP system consisting of six azimuthing thrusters. These experiments were repeated with the vessel unpowered on two mooring systems with different stiffnesses. A comparison of system performance predictions provided by each method is presented.

The effect of rotation on smooth narrow rectangular channels and narrow rectangular channels with pin-fins is investigated in this study. Pin-fins are commonly used in the narrow sections within the trailing edge of the turbine blade; the pin-fins act as turbulators to enhance internal cooling while providing structural support in this narrow section of the blade. The rectangular channel is oriented at 150° with respect to the plane of rotation, and the focus of the study involves narrow channels with aspect ratios of 4:1 and 8:1. The enhancement due to both conducting (copper) pin-fins and non-conducting (plexi-glass) pins is investigated. Due to the varying aspect ratio of the channel, the height-to-diameter ratio (hp/Dp) of the pins varies from two, for an aspect ratio of 4:1, to unity, for an aspect ratio of 8:1. A staggered array of pins with uniform streamwise and spanwise spacing (xp/Dp = sp/Dp = 2.0) is studied. With this array, 42 pin-fins are used, giving a projected surface density of 3.5 pins/in2 (0.543 pins/cm2), for the leading or trailing surfaces. The range of flow parameters include Reynolds number (ReDh = 5000–20000), rotation number (Ro = 0.0–0.302), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). Heat transfer in a stationary pin-fin channel can be enhanced up to 3.8 times that of a smooth channel. Rotation enhances the heat transferred from the pin-fin channels 1.5 times that of the stationary pin-fin channels. Overall, rotation enhances the heat transfer from all surfaces in both the smooth and pin-fin channels. Finally, as the rotation number increases, spanwise variation increases in all channels.

As of March 2010, Bluewater’s FPSO Munin has been operating on Dynamic Positioning (DP) in the South China Sea. The station keeping is performed by the vessel’s DP system only; no anchor leg mooring is used. Offloading from the FPSO is done to conventional (non-DP) shuttle tankers. See Fig. 1. This means that the DP system has to deal with a relatively large external force, and that the tandem has to respond appropriately to changing environmental conditions. To prepare for this operation, extensive FMEA proving trials have been performed prior to start-up of production. Furthermore a bridge simulation program has been conducted in which the offloading operations have been trained. From the FMEA (Failure Mode and Effect Analysis) proving trials, the offloading simulations and operational experience, a lot of knowledge has been gained on this specific DP operation. This knowledge is not only applicable to this single operation, but can also be used to enhance many other DP operations. This paper describes the Munin’s unique DP operations and the lessons learned from the FMEA proving trials, the offloading simulation program and operations in the field.

1.1 Resumen macroeconómico En el segundo trimestre la economía enfrentó varios choques, principalmente de oferta y de costos, la mayoría de los cuales no fueron anticipados, o los previstos fueron más persistentes de lo esperado, y que en conjunto interrumpieron la recuperación de la actividad económica observada a comienzos de año y llevaron la inflación total a niveles superiores a la meta. La inflación básica (sin alimentos ni regulados: SAR) aumentó, pero se mantuvo baja y acorde con lo esperado por el equipo técnico. A comienzos de abril se inició una tercera ola de pandemia, más acentuada y prolongada que la anterior, con un elevado costo en vidas humanas y algún impacto negativo en la recuperación económica. Entre mayo y mediados de junio los bloqueos de las carreteras y los problemas de orden público tuvieron un fuerte efecto negativo sobre la actividad económica y la inflación. Se estima que la magnitud de estos dos choques combinados habría generado una caída en niveles en el producto interno bruto (PIB) con respecto al primer trimestre del año. Adicionalmente, los bloqueos causaron un aumento significativo de los precios de los alimentos. A estos choques se sumaron los efectos acumulados de la disrupción global en algunas cadenas de valor y el incremento en los fletes internacionales que desde finales de 2020 vienen generando restricciones de oferta y aumentos de costos. Todos estos factores, que afectaron principalmente el índice de precios al consumidor (IPC) de bienes y de alimentos, explicaron la mayor parte del error de pronóstico del equipo técnico y el aumento de la inflación total a niveles superiores a la meta del 3 %. El incremento en la inflación básica y de los precios de los regulados fue acorde con lo esperado por el equipo técnico, y se explica principalmente por la eliminación de varios alivios de precios otorgados un año atrás. A todo esto se suma la mayor percepción de riesgo soberano y las presiones al alza que esto implica sobre el costo de financiamiento externo y la tasa de cambio. A pesar de los fuertes choques negativos, el crecimiento económico esperado para la primera mitad del año (9,1%), es significativamente mayor que lo proyectado en el informe de abril (7,1%), signo de una economía más dinámica que se recuperaría más rápido de lo previsto. Desde finales de 2020 las diferentes cifras de actividad económica han mostrado un crecimiento mayor que el esperado. Esto sugiere que los efectos negativos sobre el producto de las recurrentes olas de contagio estarían siendo cada vez menos fuertes y duraderos. No obstante, la tercera ola de contagio del Covid-19, y en mayor medida los bloqueos a las vías y los problemas de orden público, habrían generado una caída del PIB durante el segundo trimestre, frente al primero. Pese a lo anterior, los datos del índice de seguimiento a la economía (ISE) de abril y mayo han resultado mayores que lo esperado, y las nuevas cifras de actividad económica sectoriales sugieren que el impacto negativo de la pandemia sobre el producto se sigue moderando, en un entorno de menores restricciones a la movilidad y de mayor avance en el ritmo de vacunación. Los registros de transporte de carga (junio) y la demanda de energía no regulada (julio), entre otros, indican una recuperación importante después de los bloqueos en mayo. Con todo lo anterior, el incremento anual del PIB del segundo trimestre se habría situado alrededor del 17,3 % (antes 15,8 %), explicado en gran parte por una base baja de comparación. Para todo 2021 el equipo técnico incrementó su proyección de crecimiento desde un 6 % hasta el 7,5 %. Este pronóstico, que está rodeado de una incertidumbre inusualmente elevada, supone que no se presentarán problemas de orden público y que posibles nuevas olas de contagio del Covid-19 no tendrán efectos negativos adicionales sobre la actividad económica. Frente al pronóstico del informe pasado, la recuperación de la demanda externa, los niveles de precios de algunos bienes básicos que exporta el país y la dinámica de las remesas de trabajadores han sido mejores que las esperadas y seguirían impulsando la recuperación del ingreso nacional en lo que resta del año. A esto se sumaría la aún amplia liquidez internacional, la aceleración en el proceso de vacunación y las bajas tasas de interés, factores que continuarían favoreciendo la actividad económica. La mejor dinámica del primer semestre, que llevó a una revisión al alza en el crecimiento de todos los componentes del gasto, continuaría hacia adelante y, antes de lo esperado en abril, la economía recuperaría los niveles de producción de 2019 a finales de 2021. El pronóstico continúa incluyendo efectos de corto plazo sobre la demanda agregada de una reforma tributaria de magnitud similar a la proyectada por el Gobierno. Con todo eso, en el escenario central de este informe, el pronóstico de crecimiento para 2021 es del 7,5 % y para 2022 del 3,1 %. A pesar de esto, el nivel de la actividad económica seguiría siendo inferior a su potencial. La mejora en estas proyecciones, sin embargo, está rodeada de una alta incertidumbre. En junio la inflación anual (3,63 %) aumentó más de lo esperado debido al comportamiento del grupo de alimentos, mientras que la inflación básica (1,87 %) fue similar a la proyectada. En lo que resta del año el mayor nivel del IPC de alimentos persistiría y contribuiría a mantener la inflación por encima de la meta. A finales de 2022 la inflación total y básica retornarían a tasas cercanas al 3 %, en un entorno de desaceleración del IPC de alimentos y de menores excesos de capacidad productiva. En los meses recientes el aumento en los precios internacionales de los fletes y de los bienes agrícolas, y las mayores exportaciones de carne y el ciclo ganadero han ejercido presiones al alza sobre el precio de los alimentos, principalmente de los procesados. A estas fuerzas persistentes se sumaron los bloqueos de las vías nacionales y los problemas de orden público en varias ciudades registrados en mayo y parte de junio, los cuales se reflejaron en una fuerte restricción en la oferta y en un aumento anual no esperado del IPC de alimentos (8,52 %). El grupo de regulados (5,93 %) también se aceleró, debido a la baja base de comparación en los precios de la gasolina y a la disolución de parte de los alivios a las tarifas de servicios públicos otorgados en 2020. Como se proyectaba, la inflación SAR repuntó al 1,87 %, debido a la reactivación de los impuestos indirectos de algunos bienes y servicios eliminados un año atrás, y por las presiones al alza que ejercieron los alimentos sobre las comidas fuera del hogar (CFH), entre otros. En lo que resta del año se espera que el aumento en los alimentos perecederos se revierta, siempre y cuando no se registren nuevos bloqueos duraderos a las vías nacionales. El mayor nivel de precios de los alimentos procesados persistiría y contribuiría a mantener la inflación por encima de la meta a finales de año. La inflación SAR continuaría con una tendencia creciente, en la medida en que los excesos de capacidad productiva se sigan cerrando y registraría un aumento transitorio en marzo de 2022, debido principalmente al restablecimiento del impuesto al consumo en las CFH. Con todo esto, para finales de 2021 y 2022 se estima una inflación total del 4,1 % y 3,1 %, y una inflación básica del 2,6 % y 3,2 %, respectivamente. El comportamiento conjunto de los precios del IPC SAR, junto con continuas sorpresas al alza en la actividad económica, son interpretados por el equipo técnico como señales de amplios excesos de capacidad productiva de la economía. Estos persistirían en los siguientes dos años, al final de los cuales la brecha del producto se cerraría. El mayor crecimiento económico sugiere una brecha del producto menos negativa que la estimada hace un trimestre. Sin embargo, el comportamiento de la inflación básica, especialmente en servicios, indica que el PIB potencial se ha recuperado de forma sorpresiva y que los excesos de capacidad siguen siendo amplios, con una demanda agregada afectada de forma persistente. Esta interpretación encuentra soporte en el mercado laboral, en donde persiste un desempleo alto y la recuperación de los empleos perdidos se estancó. Adicionalmente, los aumentos en la inflación en buena medida están explicados por choques de oferta y de costos y por la disolución de algunos alivios de precios otorgados un año atrás. Los pronósticos de crecimiento y de inflación descritos son coherentes con una brecha del producto que se cierra más rápido y es menos negativa en todo el horizonte de pronóstico con respecto al informe de abril. No obstante, la incertidumbre sobre los excesos de capacidad es muy alta y es un riesgo sobre el pronóstico. Las perspectivas de las cuentas fiscales de Colombia se deterioraron, Standard & Poor’s Global Ratings (S&P) y Fitch Ratings (Fitch) redujeron su calificación crediticia, los bloqueos y problemas de orden público afectaron el producto y el país enfrentó una nueva ola de contagios de Covid-19 más acentuada y prolongada que las pasadas. Todo lo anterior se ha reflejado en un aumento de las primas de riesgo y en una depreciación del peso frente al dólar. Esto ha ocurrido en un entorno favorable de ingresos externos. Los precios internacionales del petróleo, del café y de otros bienes básicos que exporta el país aumentaron y han contribuido a la recuperación de los términos de intercambio y del ingreso nacional, y han mitigado las presiones al alza sobre las primas de riesgo y la tasa de cambio. En el presente informe se incrementó el precio esperado del petróleo para 2021 a USD 68 por barril (antes USD 61 bl) y para 2022 a USD 66 bl (antes USD 60 bl). Esta mayor senda presenta una convergencia hacia precios menores que los observados recientemente, como resultado de una mayor oferta mundial esperada de petróleo, la cual más que compensaría el incremento en la demanda de este bien básico. Por ende, se supone que el aumento reciente de los precios tiene un carácter transitorio. En el escenario macroeconómico actual se espera que las condiciones financieras internacionales sean algo menos favorables, a pesar de la mejora en los ingresos externos por cuenta de una mayor demanda y unos precios del petróleo y de otros productos de exportación más altos. Frente al informe de abril el crecimiento de la demanda externa fue mejor que el esperado, y las proyecciones para 2021 y 2022 aumentaron del 5,2 % al 6,0 % y del 3,4 % al 3,5 %, respectivamente. En lo corrido del año las cifras de actividad económica muestran una demanda externa más dinámica de la esperada. En los Estados Unidos y China la recuperación del producto ha sido más rápida que la registrada en los países de la región. En estos últimos la reactivación económica ha estado limitada por los rebrotes del Covid-19, las limitaciones en la oferta de vacunas y el poco espacio fiscal para enfrentar la pandemia, entre otros factores. La buena dinámica en el comercio externo de bienes se ha dado en un entorno de deterioro en las cadenas de valor y de un aumento importante en los precios de las materias primas y en el costo de los fletes. En los Estados Unidos la inflación sorprendió al alza y su valor observado y esperado se mantiene por encima de la meta, al tiempo que se incrementó la proyección de crecimiento económico. Con esto, el inicio de la normalización de la política monetaria en ese país se daría antes de lo proyectado. En este informe se estima que el primer incremento en la tasa de interés de la Reserva Federal de los Estados Unidos se dé a finales de 2022 (antes del primer trimestre de 2023). Para Colombia se supone una mayor prima de riesgo frente al informe de abril y se sigue esperando que presente una tendencia creciente, dada la acumulación de deuda pública y externa del país. Todo esto contribuiría a un incremento en el costo del financiamiento externo en el horizonte de pronóstico. La postura expansiva de la política monetaria sigue soportando unas condiciones financieras internas favorables. En el segundo trimestre la tasa de interés interbancaria y el índice bancario de referencia (IBR) se han mantenido acordes con la tasa de interés de política. Las tasas de interés promedio de captación y crédito continuaron históricamente bajas, a pesar de algunos incrementos observados a finales de junio. La cartera en moneda nacional detuvo su desaceleración anual y, entre marzo y junio, el crédito a los hogares se aceleró, principalmente para compra de vivienda. La recuperación de la cartera comercial y de los desembolsos a ese sector fue importante, y se alcanzó de nuevo el elevado saldo observado un año atrás, cuando las empresas requirieron niveles significativos de liquidez para enfrentar los efectos económicos de la pandemia. El riesgo de crédito aumentó, las provisiones se mantienes altas y algunos bancos han retirado de su balance una parte de su cartera vencida. No obstante, las utilidades del sistema financiero se han recuperado y sus niveles de liquidez y solvencia se mantienen por encima del mínimo regulatorio. A partir de este informe se implementará una nueva metodología para cuantificar y comunicar la incertidumbre que rodea los pronósticos del escenario macroeconómico central, en un entorno de política monetaria activa. Esta metodología se conoce como densidades predictivas (DP) y se explica en detalle en el Recuadro 1. Partiendo del balance de riesgos que contiene los principales factores que, de acuerdo con el juicio del equipo técnico, podrían afectar a la economía en el horizonte de pronóstico, la metodología DP produce distribuciones de probabilidad sobre el pronóstico de las principales variables (v. g.: crecimiento, inflación). Estas distribuciones reflejan el resultado de los posibles choques (a variables externas, precios y actividad económica) que podría recibir la economía y su transmisión, considerando la estructura económica y la respuesta de política monetaria en el futuro. En este sentido, permiten cuantificar la incertidumbre alrededor del pronóstico y su sesgo. El ejercicio DP muestra un sesgo a la baja en el crecimiento económico y en la brecha del producto, y al alza en la inflación. El balance de riesgos indica que las disyuntivas para la política monetaria serán potencialmente más complejas que lo contemplado en el pasado. Por el lado de las condiciones de financiamiento externo, se considera que el mayor riesgo es que se tornen un poco menos favorables, en un escenario en el cual la Reserva Federal de los Estados Unidos incremente con mayor prontitud su tasa de interés. Esto último, ante un crecimiento económico y del empleo mayor que el esperado en los Estados Unidos que genere presiones significativas sobre la inflación de ese país. A esto se suma la incertidumbre sobre el panorama fiscal en Colombia y sus efectos sobre la prima de riesgo y el costo del financiamiento externo. En el caso del crecimiento, la mayoría de los riesgos son a la baja, destacándose los efectos de la incertidumbre política y fiscal sobre las decisiones de consumo e inversión, la aparición de nuevas olas de contagio de la pandemia del Covid-19 y sus impactos sobre la actividad económica. En el caso de la inflación, se incorporó el riesgo de una mayor persistencia de los choques asociados con la disrupción de las cadenas de valor, mayores precios internacionales de las materias primas y de los alimentos, y una recuperación más lenta que la esperada de la cadena agrícola nacional afectada por los pasados bloqueos a las vías. Estos riesgos presionarían al alza principalmente los precios de los alimentos y de los bienes. Como principal riesgo a la baja se incluyó un alza de los arriendos menor que el esperado en el escenario central, explicada por una demanda débil y por una mayor oferta en 2022 dadas las altas ventas de vivienda observadas en el presente año. Con todo, el crecimiento económico presenta un sesgo a la baja y, con el 90 % de confianza, se encontraría entre un 6,1 % y 9,1 % para 2021 y entre el 0,5 % y 4,1 % para 2022. La brecha del producto tendría un sesgo a la baja, principalmente en 2022. El sesgo de la inflación es al alza, y se encontraría entre el 3,7 % y 4,9 % en 2021, y el 2,2 % y 4,7 % en 2022, con un 90 % de probabilidad. 1.2 Decisión de política monetaria En las reuniones de junio y julio la JDBR decidió mantener la tasa de política monetaria inalterada en 1,75 %.