1,721,137 research outputs found
A description of rodlet cells from the alimentary canal of Anguilla anguilla and their relationship with parasitic helminths
No full textRodlet cells in intestinal epithelia of infected and uninfected European eels Anguilla anguilla from brackish and fresh water were studied by light and electron microscopy. Deropristis inflata (Trematoda) was found in eels from brackish water, whereas eels from fresh water were infected with Acanthocephalus clavula (Acanthocephala). In a comparison between uninfected and infected eels from brackish water, a higher number of rodlet cells was recorded in the intestinal epithelia of infected fish. Evidence is presented that rodlet cells secrete their contents in a holocrine manner into the lumen of the eel intestine. The occurrence of organelles within the mature rodlet cell was rare
Forecasting the oil-gasoline price relationship : do asymmetries help?
No full textAccording to the Rockets and Feathers Hypothesis (RFH), the transmission mechanism of positive and negative
changes in the price of crude oil to the price of gasoline is asymmetric. Although there have been many
contributions documenting that downstreamprices are more reactive to increases than to decreases in upstream
prices, little is known about the forecasting performance of econometric models incorporating asymmetric price
transmission from crude oil to gasoline. In this paper we fill this gap by comparing point, sign and probability
forecasts from a variety of Asymmetric-ECM (A-ECM) and Threshold Autoregressive ECM (TAR-ECM)
specifications against a standard ECM. Forecasts from A-ECM and TAR-ECM subsume the RFH, while the ECM
implies symmetric price transmission from crude oil to gasoline. We quantify the forecast accuracy gains due
to incorporating the RFH in predictive models for the prices of gasoline and diesel. We show that, as far as
point forecasts are involved, the RFH does not lead to significant improvements, while it can be exploited to
produce more accurate sign and probability forecasts. Finally, we highlight that the forecasting performance of
the estimated models is time-varying
Ethanol and field crops : Is there a price connection?
No full textWe analyze the relationship between the prices of ethanol, corn, soybeans, wheat and cattle in Nebraska, U.S. We focus on long-run price relations, short-run Granger causality, in-sample and out-of-sample predictability linkages between returns on ethanol, field crops and cattle. Since the ethanol market has been subject to many policy interventions, our analysis takes structural breaks and parameter instabilities into account using modern statistical techniques. We find no evidence that ethanol returns Granger cause food price variations. Conversely, both in-sample and out-of-sample results suggest that ethanol is Granger caused and can be predicted by returns on corn. No linkages between ethanol and cattle are found
Consumption and precautionary saving: An empirical analysis under both financial and environmental risks
No full textThis paper studies the empirical relationship between consumption and saving under two different sources of
uncertainty: financial risk and environmental risk. The analysis is carried out using time series data for six advanced
economies in the period 1965–2007.
The results support the theoretical conclusions that both financial risk alone and the interaction between financial
and environmental risks influence consumption.Moreover,we suggest a solution to some shortcomingswhich affect
the empirical analysis performed with one-argument utility functions. Finally, we provide new estimates of
indexes of relative risk aversion and relative prudence, as well as relative preference of environmental qualit
Economic Impacts of El Niño Southern Oscillation: Evidence from the Colombian Coffee Market
Full text linkWe develop a structural econometric model to study the impacts of El Ni ̃no Southern Oscillation (ENSO) on Colombian coffee production, exports and price. Our empirical specification is consistent with an economic model of the coffee market that, in the short-run, is characterized by a downward-sloping demand curve and by a vertical supply curve. This allows to study the effects of unpredictable innovations to ENSO on the Colombian coffee price, while controlling for shocks arising from both the supply and the demand-side of the market. We show that El Ni ̃no events (i.e. positive shocks to ENSO) might be beneficial for production and exports and tend to decrease the price of coffee. On the contrary, La Ni ̃na conditions (i.e. negative shocks to ENSO) depress coffee production and exports and increase price. However, the overall impact of ENSO shocks is small. In the short-run, ENSO shocks explain 2% of the fluctuations of coffee production and 0.2% of the variability of the price of coffee. In the long-run, these percentages rise to 8% and 6%, respectively. Both in the short-run and in the long-run, demand-side shocks are more relevant than supply-side shocks in explaining the dynamics of the price of coffee
Forecasting the oil–gasoline price relationship: Do asymmetries help?
No full textAbstract According to the Rockets and Feathers Hypothesis (RFH), the transmission mechanism of positive and negative changes in the price of crude oil to the price of gasoline is asymmetric. Although there have been many contributions documenting that downstream prices are more reactive to increases than to decreases in upstream prices, little is known about the forecasting performance of econometric models incorporating asymmetric price transmission from crude oil to gasoline. In this paper we fill this gap by comparing point, sign and probability forecasts from a variety of Asymmetric-ECM (A-ECM) and Threshold Autoregressive \{ECM\} (TAR-ECM) specifications against a standard ECM. Forecasts from A-ECM and TAR-ECM subsume the RFH, while the \{ECM\} implies symmetric price transmission from crude oil to gasoline. We quantify the forecast accuracy gains due to incorporating the \{RFH\} in predictive models for the prices of gasoline and diesel. We show that, as far as point forecasts are involved, the \{RFH\} does not lead to significant improvements, while it can be exploited to produce more accurate sign and probability forecasts. Finally, we highlight that the forecasting performance of the estimated models is time-varying
How does stock market volatility react to oil price shocks?
Full text linkWe study the impact of oil price shocks on the U.S. stock market volatility. We jointly analyze three different structural oil market shocks (i.e., aggregate demand, oil supply, and oil-specific demand shocks) and stock market volatility using a structural vector autoregressive model. Identification is achieved by assuming that the price of crude oil reacts to stock market volatility only with delay. This implies that innovations to the price of crude oil are not strictly exogenous, but predetermined with respect to the stock market. We show that volatility responds significantly to oil price shocks caused by unexpected changes in aggregate and oil-specific demand, whereas the impact of supply-side shocks is negligible
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