Major Input (major + input)

Distribution by Scientific Domains

Selected Abstracts

Long-term synaptic depression in the adult entorhinal cortex in vivo

HIPPOCAMPUS, Issue 7 2003
Raby Bouras
Abstract The piriform cortex provides a major input to the entorhinal cortex. Mechanisms of long-term depression (LTD) of synaptic transmission in this pathway may affect olfactory and mnemonic processing. We have investigated stimulation parameters for the induction of homosynaptic LTD and depotentiation in this pathway using evoked synaptic field potential recordings in the awake rat. In this study, 15 min of 1-Hz stimulation induced a transient (<5 min) depression of evoked responses but did not induce LTD or depotentiation. To determine whether inhibitory and/or facilitatory mechanisms contribute to LTD induction, repetitive delivery of pairs of stimulation pulses was also assessed. Repetitive paired-pulse stimulation with a 10-ms interval between pulses, which activates inhibitory mechanisms during the second response, did not reliably induce LTD. However, repetitive paired-pulse stimulation using a 30-ms interval, which evokes marked paired-pulse facilitation, resulted in synaptic depression that lasted ,1 day, and which was reversible by tetanization. The selective induction of LTD by stimulation that evokes paired-pulse facilitation suggests that strong synaptic activation is required for LTD induction. The N -methyl- D -aspartate (NMDA) receptor antagonist MK-801 (0.1 mg/kg) blocked the induction of LTD, indicating that NMDA receptor activation is required for LTD induction in this pathway. These results indicate that LTD in piriform cortex inputs to the entorhinal cortex in the awake rat is effectively induced by strong repetitive synaptic stimulation, and that this form of LTD is dependent on activation of NMDA receptors. 2003 Wiley-Liss, Inc. [source]

Jumping hedges: An examination of movements in copper spot and futures markets

Wing H. Chan
Price risk is an important factor for both copper purchasers, who use the commodity as a major input in their production process, and copper refiners, who must deal with cash-flow volatility. Information from NYMEX cash and futures prices is used to examine optimal hedging behavior for agents in copper markets. A bivariate GARCH-jump model with autoregressive jump intensity is proposed to capture the features of the joint distribution of cash and futures returns over two subperiods with different dominant pricing regimes. It is found that during the earlier producerpricing regime this specification is not needed, whereas for the later exchange pricing era jump dynamics stemming from a common jump across cash and futures series are significant in explaining the dynamics in both daily and weekly data sets. Results from the model are used to under-take both within-sample and out-of-sample hedging exercises. These results indicate that there are important gains to be made from a time-varying optimal hedging strategy that incorporates the information from the common jump dynamics. 2006 Wiley Periodicals, Inc. Jrl Fut Mark 26:169,188, 2006 [source]

Demand Diversification Under Uncertainty and Market Power

John J. Y. Seo
This paper justifies theoretically and empirically the diversification behaviour of an importing firm when it chooses the mixture of potentially differentiated products of its major input under price uncertainty. The paper investigates an equilibrium relationship among three key explanatory variables, which are the expected price, the systematic risk of price, and monopolistic market power of the suppliers in the market. The theoretical section shows that there exists a conflict between the risk,diversification effect and the agent's preference over certain products when the importer chooses the vector of optimal quantity shares. The latter effect may disturb or even dominate the former, which can be represented in an equilibrium relationship similar to the framework of the CAPM. As an empirical application, the Chinese wheat import market is examined and analysed to answer the questions raised by the basic statistics. JEL classification: F12; F14; L22 [source]

Economic impacts of bio-refinery and resource cascading systems: An applied general equilibrium analysis for Poland

Adriana M. Ignaciuk Dr.
Abstract Due to more stringent energy and climate policies, it is expected that many traditional chemicals will be replaced by their biomass-based substitutes, bio-chemicals. These innovations, however, can influence land allocation since the demand for land dedicated to specific crops might increase. Moreover, it can have an influence on traditional agricultural production. In this paper, we use an applied general equilibrium framework, in which we include two different bio-refinery processes and incorporate so-called cascading mechanisms. The bio-refinery processes use grass, as one of the major inputs, to produce bio-nylon and propane-diol (1,3PDO) to substitute currently produced fossil fuel-based nylon and ethane-diol. We examine the impact of specific climate policies on the bioelectricity share in total electricity production, land allocation, and production quantities and prices of selected commodities. The novel technologies become competitive, with an increased stringency of climate policies. This switch, however, does not induce a higher share of bioelectricity. The cascade does stimulate the production of bioelectricity, but it induces more of a shift in inputs in the bioelectricity sector (from biomass to the cascaded bio-nylon and 1, 3PDO) than an increase in production level of bioelectricity. We conclude that dedicated biomass crops will remain the main option for bioelectricity production: the contribution of the biomass systems remains limited. Moreover, the bioelectricity sector looses a competition for land for biomass production with bio-refineries. [source]