3,292 research outputs found
New Information Response Functions.
We propose a new methodology for the analysis of impulse response functions in VAR or VARMA models. More precisely, we build our results on the non ambiguous notion of innovation of a stochastic process and we consider the impact of any kind of new information at a given date on the future values of the process. This methodology allows to take into account qualitative or quantitative information, either on the innovation or on the future responses, as well as informations on filters. We show, among other results, that our approach encompasses several standard methodologies found in the literature, such as the orthogonalization of shocks (Sims (1980)), the "structural" identification of shocks (Blanchard and Quah (1989)), the "generalized" impulse responses (Pesaran and Shin (1998)) or the impulse vectors (Uhlig (2005)).Impulse response functions ; innovation ; new information.
Parceria entre Embrapa Clima Temperado e Faculdade de Medicina Veterinária da UFPel obtém os primeiros embriões suÃnos viáveis pelo sistema de produção in vitro.
bitstream/item/58343/1/31-embrioes-Ligia.pd
Taking into account extreme events in European option pricing.
According to traditional option pricing models,1 financial markets underestimate the impact of tail risk. In this article, we put forward a European option pricing model based on a set of assumptions that ensure, inter alia, that extreme events are better taken into account. Using simulations, we compare the option prices obtained from the standard Black and Scholes model with those resulting from our model. We show that the traditional model leads to an overvaluation of at-the-money options, which are the most traded options, while the less liquid in-the-money and out-of-the-money options are undervalued.
Reciclagem em inseminação artificial de bovinos.
bitstream/CPACT-2009-09/12053/1/documento_246.pd
Transcriptional regulatory networks controlling woolliness in peach in response to preharvest gibberellin application and cold storage
BACKGROUND: Postharvest fruit conservation relies on low temperatures and manipulations of hormone metabolism to maintain sensory properties. Peaches are susceptible to chilling injuries, such as ‘woolliness’ that is caused by juice loss leading to a ‘wooly’ fruit texture. Application of gibberellic acid at the initial stages of pit hardening impairs woolliness incidence, however the mechanisms controlling the response remain unknown. We have employed genome wide transcriptional profiling to investigate the effects of gibberellic acid application and cold storage on harvested peaches. RESULTS: Approximately half of the investigated genes exhibited significant differential expression in response to the treatments. Cellular and developmental process gene ontologies were overrepresented among the differentially regulated genes, whereas sequences in cell death and immune response categories were underrepresented. Gene set enrichment demonstrated a predominant role of cold storage in repressing the transcription of genes associated to cell wall metabolism. In contrast, genes involved in hormone responses exhibited a more complex transcriptional response, indicating an extensive network of crosstalk between hormone signaling and low temperatures. Time course transcriptional analyses demonstrate the large contribution of gene expression regulation on the biochemical changes leading to woolliness in peach. CONCLUSION: Overall, our results provide insights on the mechanisms controlling the complex phenotypes associated to postharvest textural changes in peach and suggest that hormone mediated reprogramming previous to pit hardening affects the onset of chilling injuries. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-015-0659-2) contains supplementary material, which is available to authorized users
Transmission line parameters estimation in the presence of realistic PMU measurement error models
Proposals have been presented in literature to estimate line parameters and monitor their changes. Syn-chrophasor measurements from phasor measurement units (PMUs) have appeared as a possible breakthrough for accurate estimation. However, few methods consider a realistic measurement chain including PMUs and instrument transformers and their systematic and random error contributions. This paper proposes an improved method to simultaneously estimate line parameters and systematic measurement errors on multiple network lines. The algorithm is designed to deal with realistic PMU measurement errors and, in particular, with phase -angle errors caused by common time-base errors on multiple PMU channels. The impact of PMU measurement errors is investigated to achieve a comprehensive view of the performance under realistic conditions. The results obtained on an IEEE test network prove the advantages of the proposed method with respect to other recent methods and its robustness in the presence of mismatches in the error model
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