2011
Authors
Lima, D; Reis Henriques, MA; Silva, R; Santos, AI; Castro, LFC; Santos, MM;
Publication
AQUATIC TOXICOLOGY
Abstract
Despite the large number of studies on the phenomenon of imposex, the mechanism underlying the abnormal growth of male sexual characters onto females in numerous gastropod species is yet to be fully elucidated. Although several hypotheses have been raised over the years, a convincing body of evidence indicates that tributyltin-induced imposex involves the abnormal modulation of the retinoid X receptor (RXR). Here, we investigate the RXR gene transcription at different timings and tissues upon exposure to environmentally relevant concentrations of tributyltin (TOT) (100 ng Sn/L TBT) in both genders of the imposex susceptible gastropod Nucella lapillus. RXR gene transcription was determined at two time-points (i.e., before and after imposex initiation) by quantitative Real Time PCR in potential target tissues: the central nervous system (CNS), penis/penis forming area (PFA), gonads and digestive gland. TBT-exposure altered transcription of RXR gene in a tissue and sex specific manner. In the CNS, a significant down-regulation was observed in females both before and after imposex initiation (P <= 0.01 and P <= 0.05, respectively). A similar trend was observed in male CNS at the first time-point, although differences between control and the TBT-exposed group were just above significance (P=0.059). The penis/PFA showed no differences in transcription of RXR gene between control and TBT exposed female snails before imposex induction, or before and after imposex initiation for males. However, male penis showed higher transcription of RXR gene in comparison to the PFA of females. After imposex has been induced, a significant (P <= 0.001) increase in transcription of RXR gene was observed in penis of females with vas deference sequence index (VDS) levels of 3-4 in comparison with the PFA of both control and imposex females with VDS 1-2. At advanced stages of imposex, females displayed RXR transcription patterns in penis identical to those of males, which points to a functional role of RXR in the penis of both genders. In the other tissues, gonads and digestive gland. RXR gene transcription was not affected by TBT, at any of the analysed time-points. These patterns of RXR gene transcription upon TOT exposure highlight the pivotal involvement of the CNS in the mechanism of imposex induction. We integrate the results in a conceptual model, and discuss the central role of RXR and the retinoic acid signalling pathways in imposex and male genitalia formation in gastropods.
2010
Authors
Fidalgo, JN; Matos, MA; Jorge, H;
Publication
IET Conference Publications
Abstract
This paper describes the methodology and results obtained in the studies developed for deriving loss profiles for the Portuguese electricity market. For each voltage level (LV, MV, HV and VHV) the losses were distributed by the corresponding global load diagram, proportionally to the square of the hourly consumption. Transformer losses are assigned to the consumers of voltage levels equal or smaller to the secondary voltage. Loss profiles (like load profiles) were developed for each specific year, with its calendar particularities, and the global energy balance expected for that year. A subsequent product of the adopted methodology is the set of loss factors, which are directly driven from these profiles. The methodology was developed in a project with EDP (the Portuguese distribution system operator) and the result was approved by the regulatory authority that adopted the proposed loss profiles for market use.
2010
Authors
Botterud, A; Wang, J; Miranda, V; Bessa, RJ;
Publication
Electricity Journal
Abstract
Wind power forecasting is becoming an important tool in electricity markets, but the use of these forecasts in market operations and among market participants is still at an early stage. The authors discuss the current use of wind power forecasting in U.S. ISO/RTO markets, and offer recommendations for how to make efficient use of the information in state-of-the-art forecasts. © 2010 Elsevier Inc.
2010
Authors
Botterud, A; Wang, J; Bessa, RJ; Keko, H; Miranda, V;
Publication
IEEE POWER AND ENERGY SOCIETY GENERAL MEETING 2010
Abstract
This paper discusses risk management, contracting, and bidding for a wind power producer. A majority of the wind power in the United States is sold on long-term power purchase agreements, which hedge the wind power producer against future price risks. However, a significant amount is sold as merchant power and therefore is exposed to fluctuations in future electricity prices (day-ahead and real-time) and potential imbalance penalties. Wind power forecasting can serve as a tool to increase the profit and reduce the risk from participating in the wholesale electricity market. We propose a methodology to derive optimal day-ahead bids for a wind power producer under uncertainty in realized wind power and market prices. We also present an initial illustrative case study from a hypothetical wind site in the United States, where we compare the results of different day-ahead bidding strategies. The results show that the optimal day-ahead bid is highly dependent on the expected day-ahead and real-time prices, and also on the risk preferences of the wind power producer. A deviation penalty between day-ahead bid and real-time delivery tends to drive the bids closer to the expected generation for the next day.
2010
Authors
Bessa, RJ; Miranda, V; Principe, JC; Botterud, A; Wang, J;
Publication
2010 INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS IJCNN 2010
Abstract
This paper reports new results in adopting information theoretic learning concepts in the training of neural networks to perform wind power forecasts. The forecast "goodness" is discussed under two paradigms: one is only concerned in measuring the deviation between the forecasted and realized values, the other is related with the value of the forecast in the electricity market for different agents. The results and conclusions are supported by a real case example.
2010
Authors
Lima, SEU; Frazao, O; Farias, RG; Araujo, FM; Ferreira, LA; Santos, JL; Miranda, V;
Publication
IEEE TRANSACTIONS ON POWER DELIVERY
Abstract
Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in high-voltage apparatus. Partial discharges are a source of failure in power transformers, and the differentiation from other sources of acoustic emissions is of the utmost importance. This paper reports the development of a new sensor concept-mandrel-based fiber-optic sensor-for the detection of incipient faults in oil-filled power transformers, taking direct measurements inside a transformer. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure, and improving fault detection and location. The applicability of these acoustic sensors in air, water, and oil is investigated and the paper presents the promising results obtained, which will enable the industrial development of practical solutions.
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