Contribution à l'étude de l'impact du barrage de Garafiri sur la qualité des eaux et les écosystèmes aquatiques du Konkouré (Rép. de Guinée)

La mise en place d'un aménagement de grande envergure tel qu'un barrage a toujours des répercussions sur les écosystèmes naturels qu'il perturbe. L'objectif de la présente étude, est d'évaluer les impacts de la construction du barrage de Garafiri sur la qualité des eaux et les écosystèmes aquatiques du Konkouré (Rep. de Guinée). L'utilisation dans ce rapport des modèles développés par l'OCDE en 1982 et basés sur les flux de phosphore, met en évidence le risque d'eutrophisation des eaux de cette retenue (60% de risque). Les impacts d'un tel processus sur la faune aquatique sont nombreux (modification des peuplements, mortalité...). Il existe des solutions visant à éviter, ou du moins à diminuer l'impact d'un tel aménagement sur la vie aquatique. Elles sont nombreuses et plus ou moins coûteuses. L'intérêt de cette étude, outil d'aide à la décision est de sensibiliser le gestionnaire de la future retenue aux problèmes qu'il risque de rencontrer, pour être en mesure d'adopter des stratégies de gestion adéquates et ainsi éviter des surcoûts (réparation des ouvrages corrodés). (Résumé d'auteur

Does multifractal theory of turbulence have logarithms in the scaling relations?

The multifractal theory of turbulence uses a saddle-point evaluation in determining the power-law behaviour of structure functions. Without suitable precautions, this could lead to the presence of logarithmic corrections, thereby violating known exact relations such as the four-fifths law. Using the theory of large deviations applied to the random multiplicative model of turbulence and calculating subdominant terms, we explain here why such corrections cannot be present.Comment: 7 pages, 1 figur

Transaction costs in healthcare: empirical evidence from Portuguese hospitals

Transaction Cost Economics has been used in the healthcare context to discuss the make-or-buy dichotomy, focusing on minimizing production or governance costs, respectively. Nevertheless, it is important to recognize that there are other relevant costs, which influence these decisions in health care. Thus, the purpose of this research project was to study such additional variables which may significantly influence the dynamics of transaction costs in hospitals. Semi-structured interviewing was used to collect the data, complemented by some document analysis and observation in the visits made to the hospitals studied. The interviews were conducted during a period of three months, with directors and administrators of four Portuguese hospitals. A deeper study was developed in one of the hospitals where it was possible to get information from additional interviews and documents. Two important findings should be highlighted. Firstly, the internal transaction costs derived from the hospital’s own internal contracting process which generates retention costs of medical personnel and costs of control of the internal contract itself. Secondly, they were studied the intangible costs, particularly those related to the decision of carrying out a process that could deteriorate the patient’s health or her/his critical situation, making the total cost, including treatment and possible re-hospitalizations higher than the cost of having treated the patient internally since the initial cost was considered greater than treating the patient outside hospital facilities. These variables should be considered when studying or using TCE in hospitals, complementing and extending the traditional framework as it is discussed here.- (undefined

Mapping nonlinear gravity into General Relativity with nonlinear electrodynamics

We show that families of nonlinear gravity theories formulated in a metric-affine approach and coupled to a nonlinear theory of electrodynamics can be mapped into General Relativity (GR) coupled to another nonlinear theory of electrodynamics. This allows to generate solutions of the former from those of the latter using purely algebraic transformations. This correspondence is explicitly illustrated with the Eddington-inspired Born-Infeld theory of gravity, for which we consider a family of nonlinear electrodynamics and show that, under the map, preserve their algebraic structure. For the particular case of Maxwell electrodynamics coupled to Born-Infeld gravity we find, via this correspondence, a Born-Infeld-type nonlinear electrodynamics on the GR side. Solving the spherically symmetric electrovacuum case for the latter, we show how the map provides directly the right solutions for the former. This procedure opens a new door to explore astrophysical and cosmological scenarios in nonlinear gravity theories by exploiting the full power of the analytical and numerical methods developed within the framework of GR.Comment: 11 pages. v2: next discussions inserted, refs added; matches the version accepted for publication in EPJ

A correspondence between modified gravity and General Relativity with scalar fields

We describe a novel procedure to map the field equations of nonlinear Ricci-based metric-affine theories of gravity, coupled to scalar matter described by a given Lagrangian, into the field equations of General Relativity coupled to a different scalar field Lagrangian. Our analysis considers examples with a single and $N$ real scalar fields, described either by canonical Lagrangians or by generalized functions of the kinetic and potential terms. In particular, we consider several explicit examples involving $f(R)$ theories and the Eddington-inspired Born-Infeld gravity model, coupled to different scalar field Lagrangians. We show how the nonlinearities of the gravitational sector of these theories can be traded to nonlinearities in the matter fields, and how the procedure allows to find new solutions on both sides of the correspondence. The potential of this procedure for applications of scalar field models in astrophysical and cosmological scenarios is highlighted.Comment: 14 pages; v2: section IIID extended, some minor corrections, references update

Cost at Risk (CaR): a methodology for costing under uncertainty

Paper aims: This paper proposes Cost at Risk (CaR), a concept and a methodology that allows the computation of the risk of cost estimations within a costing system by means of the Monte Carlo Simulation, considering a predefined level of confidence and considering the worst expected result in terms of cost in a certain period. Originality: Traditionally, researchers and practitioners have been focused on deterministic costing models without recognizing and managing cost uncertainty. The proposed methodology is based on five steps that go from the determination of the parameters that generate uncertainty to the estimation of the risk. Research method: A Design Science Research (DSR) approach was followed based on mathematical modeling and computer simulation. Main findings: The model was applied to the imaging area of a hospital allowing to identify and quantify the risk of the most relevant costs and therefore, supporting the design and implementation of both operational and strategic decisions. Implications for theory and practice: The main contribution is the inclusion in costing systems of the uncertainty inherent in the estimation of costs, particularly in complex environments.- (undefined

Project management and costing systems: ABC SCRUM

In this article we advocate the use of project management principles and agile methodologies used mainly in software design to support the development of more effective costing systems. In this context, it is important to highlight two elements: the project with its phases, initiation, planning, execution, monitoring and control and closure, and the product, which would be within the execution phase of the project, design and implementation. The proposed scrum methodology for the design of activity-based costing (ABC) models is presented and discussed. Its advantages but also some use difficulties are presented. Namely, it facilitates the active participation of stakeholders, which increases the degree of acceptance of the costing system. On the other hand, among the problems encountered in applying the proposed ABC Scrum we highlight the need of regular meetings to give and receive feedback.- This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT - Fundacao para a Ciencia e Tecnologia within the Project Scope: UID/CEC/00319/2013