bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variability in State-Dependent Plasticity of Intrinsic Properties during Cell-Autonomous Self-Regulation of Calcium Homeostasis in Hippocampal Model Neurons
Authors: Srikanth Sunandha , Narayanan Rishikesh 
Published: August 2015

AbstractHow do neurons reconcile the maintenance of calcium homeostasis with perpetual switches in patterns of afferent activity? Here, we assessed state-dependent evolution of calcium homeostasis in a population of hippocampal pyramidal neuron models, through an adaptation of a recent study on stomatogastric ganglion neurons. Calcium homeostasis was set to emerge through cell-autonomous updates to 12 ionic conductances, responding to different types of synaptically driven afferent activity. We first assessed the impact of theta-frequency inputs on the evolution of ionic conductances toward maintenance of calcium homeostasis. Although calcium homeostasis emerged efficaciously across all models in the population, disparate changes in ionic conductances that mediated this emergence resulted in variable plasticity to several intrinsic properties, also manifesting as significant differences in firing responses across models. Assessing the sensitivity of this form of plasticity, we noted that intrinsic neuronal properties and the firing response were sensitive to the target calcium concentration and to the strength and frequency of afferent activity. Next, we studied the evolution of calcium homeostasis when afferent activity was switched, in different temporal sequences, between two behaviorally distinct types of activity: theta-frequency inputs and sharp-wave ripples riding on largely silent periods. We found that the conductance values, intrinsic properties, and firing response of neurons exhibited differential robustness to an intervening switch in the type of afferent activity. These results unveil critical dissociations between different forms of homeostasis, and call for a systematic evaluation of the impact of state-dependent switches in afferent activity on neuronal intrinsic properties during neural coding and homeostasis.
Para a história da negação: o minimizador <i>homem</i> no português antigo
Authors: Pinto Clara 
Published: August 2015

Neste artigo apresentamos dados que pretendem contribuir para a compreensão da história da negação em português, partindo de textos datados entre os séculos XIII e XVI. Mostraremos que, a par dos indefinidos negativos, o português antigo dispunha de outro grupo de itens capazes de estabelecer concordância negativa: os minimizadores (Horn, 1989). No entanto, ao contrário de outras línguas como o francês, não há registo de minimizadores do português que tenham completado o ciclo de Jespersen (Jespersen, 1917), dando origem a um novo marcador de negação pós-verbal. Neste trabalho, propomos a existência de dois tipos diferentes de minimizadores no português antigo: os partitivos/valorativos e os indefinidos. Destes dois grupos, apenas o primeiro sobrevive em português contemporâneo, embora com baixa produtividade. O desaparecimento precoce dos minimizadores indefinidos do português, no final do século XVI, contrasta com o percurso seguido por itens equivalentes noutras línguas, como o italiano ou o francês. Exploraremos como hipótese de explicação para este desaparecimento a ideia de que existiu competição entre os indefinidos negativos e os minimizadores indefinidos, numa perspetiva de competição entre gramáticas (Kroch, 1989, 1994). Tomando como exemplo o minimizador homem, avançaremos a hipótese de que competisse com o indefinido nenhum, e mostraremos as diferenças e semelhanças entre ambos. A aplicação dos parâmetros propostos por Garzonio e Poletto (2008, 2009) permite verificar que homem e nenhum se encontravam em níveis de gramaticalização diferentes, e que, apesar de poderem competir para uma mesma posição, terá havido outros fatores acontribuirem para o desaparecimento de homem.
Semônides de Amorgos e Mimnermo (Fragmentos)
Authors: Assunção Teodoro Rennó , Brandão Jacyntho Lins 
Published: August 2015

Ao tentarmos estabelecer nosso critério de tradução, cremos dever antes de mais nada descrever minimamente o processo de sua formulação. Pois se aqui ele se mostra cristalizado em forma escrita e antecedendo a tradução mesma, é justo dizermos que não houve teorização a priori e nem mesmo escolha, a princípio, de um critério ao qual tivéssemos, durante a tradução, tentado nos conformar. Inversamente, a figura de um critério foi se delineando a medida em que a execução do trabalho o exigia, até que, tendo se tornado mais nítida, pôde iluminar retrospectivamente as dúvidas do começo que, por sua vez, são as linhas débeis que deram origem ao desenho da figura. O critério, portanto, é elemento ínsito e não separável do corpo da própria tradução e somente nesta poderemos verificar o seu maior ou menor acerto. A citação abaixo está pois presente menos como ponto de orientação do que como ilustração, à maneira das que aparecem nos livros infantis.
METACOGNIÇÃO ESTIMULA CARACTERÍSTICAS EMPREENDEDORAS? UMA ANÁLISE EM PROFISSIONAIS DE ADMINISTRAÇÃO
Authors: Lima Filho Raimundo Nonato , Bruni Adriano Leal 
Published: August 2015

<p>O objetivo deste estudo foi analisar a relação entre o nível metacognitivo e as características empreendedoras de profissionais de Administração por meio de três instrumentos psicométricos. Participaram do <em>survey</em> 851 profissionais cadastrados no Conselho Regional de Administração do Estado da Bahia. A hipótese desta pesquisa defendia que quanto maior fosse o nível de metacognição dos respondentes, maior seria o nível de suas características empreendedoras. A partir da Modelagem de Equações Estruturais (MEE), os resultados indicaram que maiores níveis de metacognição promovem maiores níveis de características empreendedoras, indicando que 42,79% das características empreendedoras podem ser explicadas pela perspectiva metacognitiva. As contribuições desta pesquisa não se restringem à perspectiva teórica e acadêmica, mas também aos contextos profissional, econômico e social, uma vez que este estudo promove a evolução da qualidade profissional e os impactos social e econômico se tornam uma consequência natural desse desenvolvimento. </p><p>Palavras-chave: Metacognição. Características empreendedoras. Modelagem de Equações Estruturais. Qualidade profissional.</p>
Developing Talent to Demand: Addressing the Skills Related Challenges Facing Oil and Gas Exploration in Frontier Markets
Authors: Strydom Adrian , Brown Fiona Cameron , Takolia Ebrahim 
Published: August 2015

Abstract
This presentation focuses on the skills related demand and challenges with specific reference to the West Coast of South Africa. The paper reflects on contextualising the oil and gas value chain with reference to South Africa, highlighting ‘blockages’ and ‘leaks’ in the ‘skills pipeline’ and putting forward recommendations for implementation. A SAOGA skills workshop and several research initiatives commissioned by stakeholders informs the paper.
The South African Oil and Gas value chain is unique and is broadly focused on Ship and Rig Repair and Fabrication (where skills are relatively readily available). Limited Oil and Gas exploration and production activities are currently evident locally, but growing interest in Oil and Gas exploration in the Southern African region promises to spill over to South Africa in many respects. This has implications for present and future skills demand in the region, related to Oil and Gas exploration. Future South African Oil and Gas exploration is evident from licenced exploration blocks as indicated by Petroleum Agency South Africa (PASA) maps.
The presentation will also focus on the extensive potential of Oil and Gas exploration and production on the continent and potential future scenarios.
Key systemic challenges and bottlenecks exist. While there is no specific project to address these, it is noted that the stakeholders consulted with each have spheres of influence. Potential solutions to the skills challenges are articulated in order to contribute to the development of a coherent and integrated skills development pipeline as envisaged in the South African Government's White Paper on Post School Education and Training.
A Blueprint for Maximising Economic Recovery
Authors: Hargreaves J. 
Published: August 2015

Abstract
For the majority of older oil and gas facilities, the production and processing environment has changed significantly since its early days, with increasing operational and maintenance overheads and obsolete control technology often threatening to bring lift costs above production revenues. As a result, Production and Operational Efficiency has significantly worsened in recent years with many of these assets performing well below optimum production, equating to approximately 500,000 barrels of lost production per day in the UKCS or £10bn/annum (based on Oil and Gas UK production availability figures)
Enquest's Thistle platform was one of these assets and was due to be decommissioned until the brave decision was taken to extend its life by putting in place the Late Life Extension Program (LLX).
Using groundbreaking Asset Life Extension techniques and methodologies, this old facility is in the process of being re-designed by simplifying the topsides which in turn, is leading to improved availability, increased production and reduced operating costs. A simplified, safer process in a controlled environment has been created whilst balancing the requirements of a capital budget, against reduced OPEX and process risk.
It is estimated that the modifications have added at least 15 years of safe, viable, profitable production to the Thistle's lifespan, a great example of deferring decommissioning and Maximising Economic Recovery.
Use Of Plasma-Based Tool For Plug And Abandonment
Authors: Gajdos Matus , Kristofic Tomas , Jankovic Slavomir , Horvath Gabriel , Kocis Igor 
Published: August 2015

Abstract
Plug and Abandonment (P&A) is the largest category in Decommissioning expenditures, representing 40-44 percent of the total investment that basically comes as mandatory cost with no expected return. If the well operator gets P&A inadequate, results may include water flows, gas or oil seeps from the seabed, or underground cross flow between formations with huge impact on environment and marine life. The objective of this paper is plasma-based technology for enhanced casing section milling addressing the P&A challenges.
According to some oilfield service providers, two main P&A challenges are as follows: Time and expense of casing milling - for example, Norwegian regulations call for cementing two 50-meter sections of casing above and below each hydrocarbon-bearing zone. Each section may take more than 10 days to mill and may generate four tons of swarf. The second challenge is swarf damaging blow out preventer (BOP) - Milling generates swarf, which then must be removed before cementing. However, swarf removal can damage the BOP. To avoid well integrity issues, BOP has to be dismantled, inspected and repaired at considerable expense.
The presented paper is focused on technology eliminating the P&A challenges. The core of the technology is based on plasma generator producing high temperature water steam plasma for rapid steel structural degradation. This approach brings a radical abandonment of the classic rotary approaches with connected tubes in long strings and generation of swarf which need to be removed. Besides elimination of aforementioned challenges, the technology advantages include also rigless operation since the system is designed for coiled tubing solution. This feature brings additional cost savings using Light Weight Intervention Vessel (LWIV). Moreover, fully automated coiled tubing goes hand in hand with enhanced safety of the operational staff.
Impact and potential of the technology is to change, simplify the process of P&A and therefore significantly cut the time of whole P&A. The technology is currently under development with expected commercialization within three-year period.
Understanding Variable Well Performance in a Chalk Reservoir
Authors: Kabir C. S. , Haftbaradaran R. , Asghari R. , Sastre J. P. 
Published: August 2015

Abstract
Analyzing well performance is a complex process that increases in difficulty when multiple reservoir-drive mechanisms are in play in the same reservoir. This paper explores an overpressured, compacting chalk reservoir with high porosity and high oil saturation at initial conditions. The diverse drive mechanisms, experienced through the long production history of Valhall field in Norway, are caused by different degrees of reservoir compaction across the field and the recent waterflood at the crest and northern areas of the field.
The purpose of this study is to illuminate the various drive mechanisms experienced in this field. The underlying objective is to understand widely varying Arps b-factors in decline-curve analysis (DCA) that support production forecasting and project evaluation. The performances of inactive wells with long production histories were used as analogs to analyze active wells. Other analytical tools were also used to augment overall understanding of a type well's performance, including rate-transient analysis (RTA) and capacitance-resistance modeling (CRM).
This study demonstrates that the proposed workflow for reservoir performance forecasting can be adopted in highly complex reservoirs with different rock mechanical properties, drive mechanisms, production scheduling, and field development strategies. Specifically, the workflow entails establishing energy support for individual wells using Arps b-factor with DCA; collapsing shut-in periods, if any, and using the cumulative production curve for DCA to retain solution objectivity; performing RTA to gauge pressure/rate coherence and system's linearity; and using CRM to establish injector-producer connectivity.
Overcoming the Perceived Risk of Multilateral Wells
Authors: Butler Ben , Grossmann Andreas , Parlin Joe , Sekhon Chet 
Published: August 2015

Abstract
Multilaterals are often cited as technology that can be implemented to maximize reservoir recovery rates. However, few operators have been willing to put multilaterals into practice. The most frequently cited reason for not considering multilaterals is risk. This paper presents a study of data from 22 years of actual multilateral well applications that demonstrate the reliability of the technology.
For the purpose of this study, failure has been defined as the loss of either the lateral or main bore or the loss of the junction (and therefore access to both legs). In the context of this study, reliability has been defined as the ability to successfully construct and complete the multilateral junction. Where failures have occurred, a study to determine root cause(s) has been undertaken. The records of one multilateral service provider have been analyzed from more than 800 actual multilateral installations to determine success and failure rates. The reliability of multilaterals has been compared to the reliability rates of other wellbore completion and construction technologies.
Multilateral technology (MLT), which was first implemented by Alexander Grigoryan in 1953, came into modern practice in the 1990s. Although it is not failure-free, the reliability of multilateral wells has improved remarkably during the past 22 years. This improvement in reliability has occurred as the complexities of multilateral installations have increased. This paper shows that successful completion rates of multilateral junctions have improved from slightly more than 87% for the period of 1995 to 1999 (with more than 100 junctions completed) to slightly more than 98% for the current five-year period (with more than 220 junctions completed). This improvement is the result of continuous planning, development of and adherence to procedures, management of change, communication, and continuous improvement.
This is the first known study of multilateral reliability that encompasses a large body of data over a significant time period. The results presented should enable operators to make fact-based decisions about the reliability of MLT and about whether or not this technology should be considered for implementation into resource development plans.
Designing and Testing ROVs for High Reliability
Authors: Dickson Andrew 
Published: August 2015

Abstract
Remotely Operated Vehicles (ROVs) are complex systems that incorporate electronics, electromechanical assemblies, computing equipment and their associated software systems, structural assemblies, hydraulics, and a variety of commercial off-the-shelf components and accessories. ROVs operate in the most severe of environments, yet they must be highly reliable systems. One necessary element in the design and manufacture of a reliable ROV system is a rigorous qualification test program to prove the existence of a robust design. This paper discusses the design of the qualification test program for a new ROV product line, how it was executed, and how the test results were used to meet and exceed project reliability design goals.
Detailed Approach for the Assessment of Accumulated Wellhead Fatigue
Authors: Sunday Kingsley , Ward Phil , Griffin Cary , Lorenson Peter 
Published: August 2015

Abstract
This paper presents a case study of the use of an enhanced analytical approach, combined with the use of structural monitoring, as an enabling technique in the planning of sidetrack operations on a well in 110m water depth in the Northern North Sea.
Subsea wellheads are fatigue sensitive structures due to their exposure to dynamic loading transferred from connected riser systems. Intervention and workover operations over the life span of the well each contribute to the total fatigue damage accumulated in components that cannot be readily inspected. Accurate assessment of fatigue damage accumulation in ageing wells using advanced analytical techniques is often necessary to quantify the residual life of these components. The ability to reliably estimate this life can greatly affect the planning and viability of operations to enhance the productivity of ageing wells, particularly in the North Sea.
A simplified screening approach to wave and current fatigue assessment, typically applied to new-drill wells, with comparatively fatigue resistant hardware is unlikely to be sufficient to provide the level of confidence required when planning intervention operations on a brownfield development featuring less fatigue resistant hardware. Further sophistication, more involved than the typical approach, is necessary to avoid over-conservatism and to provide confidence to proceed with the planned operations. To thoroughly assess the fatigue accumulation in an ageing well, a detailed operational history including hindcast or measured weather data is usually sourced. The assessment is conducted to ensure that the actual operational conditions during periods when risers were connected are as accurately represented as possible. However, this may not be sufficient to bring the resulting fatigue damage within the allowable limits set using the traditional code-defined factor of safety approach. In this scenario further analytical methods are required.
The use of pre and post-failure analysis and the development of a monitoring strategy to maximise both the likelihood of identifying a fatigue failure during the operations and the ability to subsequently calibrate the analytical models are discussed. The applicability of these techniques to other operations and geographical locations is also described.
The Evolution of Completion Practices and Reservoir Stimulation Techniques in the North Sea
Authors: Bocaneala B. , Barrett C. , Holland B. , Langford M. E. , McIntosh K. , Nitters G. , Norris M. R. , Orski K. 
Published: August 2015

Abstract
The objective of this paper is to collate and share with the industry the technical knowledge on hydraulic fracturing and related completion practices accumulated from both operating and service companies throughout the North Sea. We will follow the evolution of completion technologies and hydraulic fracturing techniques from the early 1980s, when hydraulic fracturing offshore was in its infancy, to present-day modern practices.
Although the North Sea hydrocarbon production has been in decline for the last 15 years, technologies exist that can improve production and transform resources into reserves in reservoirs previously believed uneconomic. Horizontal wells and hydraulic fracturing are two complementary technologies that, when combined, can reduce, halt, or even reverse this declining trend.
The first hydraulic fracturing treatment in the North Sea was conducted over 40 years ago; since then, the stimulation techniques and completion technologies have advanced significantly. Throughout the years, there have been several milestones in the evolution of stimulated well completions, with the most significant being the transition from single-stage fracturing of vertical wells to multistage fracturing of horizontal wells in the drive for ever-greater reservoir contact. Recently, this combination of technologies made possible the development of small stranded fields otherwise considered noncommercial.
The introduction of resin-coated proppants to minimize solids flowback, the evolution of fracturing fluids to meet the stringent environmental regulations, and the introduction of dedicated multistage completions to increase operational efficiency are further enabling innovations discussed in this paper.
The latest advances such as proppant channel placement within the fracture, dissolvable completion equipment, and environmentally friendly seawater-based fracturing fluids, have already been introduced and promise significant future improvements to production and the completion cycle efficiency.
The North Sea has been, and remains, at the forefront of safety, environmental awareness, and leading technology within the oil and gas industry. This paper reviews the historic evolution of hydraulic fracturing and well completions with the aim to create a clearer vision of the future by building on the past. Through this, we hope to inspire the new generation to find innovative solutions and continue the long history of hydrocarbon production in the North Sea.
Design Methodology for the Structural Capacity and Shakedown Assessment of Bolted Joint Connections in Subsea Open Water Systems
Authors: Chen Weihang , Orlando Michele , Roberts Simon 
Published: August 2015

Abstract
In this paper, a design methodology is presented for analysing a non-gasketed bolted flange connector, for subsea applications where the flange is subject to various combinations of mechanical loading. The proposed methodology is aligned with the API 17G 2nd Edition [API 2006] and ISO 13628-7:05 [ISO 2005] standards and combines linear elastic and elastic-plastic analysis approaches to determine structural capacity and assess shakedown. Structural analysis using the finite element method (FEM) was carried out for a bolted flange connection of an open water bore selector (OWBS), subjected to internal pressure, bending and temperature. Stress linearisation and classification were used to evaluate the structural capacity of the bolts modelled using linear-elastic material. Global and local strain based criteria were used to evaluate the structural capacity of the flanges modelled with elastic-plastic material. Analysis results of the OWBS are detailed for a normal operating condition and show the importance of prying. The analysis is compared with a hydrostatic pressure test for FAT (factory acceptance test) and analysis results obtained from a shakedown analysis indicate that crack initiation is located on the outer surface of the flanges. The proposed methodology provides guidance to ensure correct and safe application of non-gasketed bolted flange connectors, in offshore environments. In particular, the methodology addresses bolt prying, which is critical for preventing full separation and thread failure in bolted flange connectors subjected to combined mechanical loads.