Toward a systems understanding of plant–microbe interactions

Plants are closely associated with microorganisms including pathogens and mutualists that influence plant fitness. Molecular genetic approaches have uncovered a number of signaling components from both plants and microbes and their mode of actions. However, signaling pathways are highly interconnected and influenced by diverse sets of environmental factors. Therefore, it is important to have systems views in order to understand the true nature of plant–microbe interactions. Indeed, systems biology approaches have revealed previously overlooked or misinterpreted properties of the plant immune signaling network. Experimental reconstruction of biological networks using exhaustive combinatorial perturbations is particularly powerful to elucidate network structure and properties and relationships among network components. Recent advances in metagenomics of microbial communities associated with plants further point to the importance of systems approaches and open a research area of microbial community reconstruction. In this review, we highlight the importance of a systems understanding of plant–microbe interactions, with a special emphasis on reconstruction strategies

Do higher oil prices still benefit Texas?

Petroleum industry and trade

What drives natural gas prices?

For many years, fuel switching between natural gas and residual fuel oil kept natural gas prices closely aligned with those for crude oil. More recently, however, the number of U.S. facilities able to switch between natural gas and residual fuel oil has declined, and over the past five years, U.S. natural gas prices have been on an upward trend with crude oil prices but with considerable independent movement. Natural gas market analysts generally emphasize weather and inventories as drivers of natural gas prices. Using an error-correction model, we show that when these and other additional factors are taken into account, movements in crude oil prices have a prominent role in shaping natural gas prices. Our findings imply a continuum of prices at which natural gas and petroleum products are substitutes.

Energy prices and aggregate economic activity: an interpretive survey

In this paper, we survey the theory and evidence linking fluctuations in energy prices to aggregate economic activity. We then briefly examine the implications of this research for both monetary policy and energy policy in response to oil price shocks. Research seems to provide relatively reliable guidance for monetary policy. Because the precise channels through which oil price shocks affect economic activity are only partially known, however, research offers less guidance about how energy policy should cope with oil price shocks.Energy policy ; Monetary policy ; Petroleum industry and trade

Gasoline and crude oil prices: why the asymmetry?

Many consumers complain that gasoline and crude oil prices have an asymmetric relationship in which gasoline prices raise more quickly when crude oil prices are rising than they fall when crude oil prices are falling. Many also regard the asymmetry they observe as evidence of market power in the petroleum industry. Most previous research provides econometric evidence of the asymmetry, confirming at least part of what consumers suspect. In this article Stephen Brown and Mine Yucel extend the inquiry by examining the market conditions underlying the asymmetric relationship between gasoline and crude oil prices. They find the observed asymmetry is unlikely to be the result of monopoly power. The remaining explanations for the asymmetry suggest that policies to prevent an asymmetric relationship between gasoline and crude oil prices are likely to reduce economic efficiency.

Nematic elastomers with aligned carbon nanotubes: new electromechanical actuators

We demonstrate, for the first time, the large electromechanical response in nematic liquid crystalline elastomers filled with a very low (~0.01%) concentration of carbon nanotubes, aligned along the nematic director at preparation. The nanotubes create a very large effective dielectric anisotropy of the composite. Their local field-induced torque is transmitted to the rubber-elastic network and is registered as the exerted uniaxial stress of order ~1kPa in response to a constant field of order ~1MV/m. We investigate the dependence of the effect on field strength, nanotube concentration and reproducibility under multiple field-on and -off cycles. The results indicate the potential of the nanotube-nematic elastomer composites as electrically driven actuators

Crude oil and gasoline prices: an asymmetric relationship?

Gasoline is the petroleum product whose price is most visible and, therefore, always under public scrutiny. Many claim there is an asymmetric relationship between gasoline and oil prices - specifically, gasoline price changes follow oil price changes more quickly when oil prices are rising than when they are falling. To explore this issue, Nathan Balke, Stephen Brown and Mine Yucel use several different model specifications to analyze the relationship between oil prices and the spot, wholesale, and retail prices of gasoline. They find asymmetry is sensitive to model specification but is pervasive with the most general model.Petroleum industry and trade ; Prices

Oil price shocks and the U.S. economy: where does the asymmetry originate?

Rising oil prices appear to retard aggregate U.S. economic activity by more than falling oil prices stimulate it. Past research suggests adjustment costs and/or monetary policy may be possible explanations ofthe asymmetric response. This paper uses a quasi-vector autoregressive model of U. S. economy to examine from where the asymmetry might originate. The analysis uses counterfactual impulse response experiments to detennine that monetary policy alone cannot account for the asymmetry. The robustness ofshort-lived asymmetry across the base case and counterfactuals is consistent with the adjustment-cost explanation.Petroleum industry and trade

Business cycles: the role of energy prices

Oil price shocks have figured prominently U.S. business cycles since the end of World War II—although the relationship seems to have weakened during the 1990s. In addition the economy appears to respond asymmetrically to oil price shocks, rising oil prices hurt economic activity more than falling oil prices help it. This section of the Encyclopedia of Energy sorts through an extensive economics literature that relates oil price shocks to aggregate economic activity. It examines how oil price shocks create business cycles, why they seem to have a disproportionate effect on economic activity, why the economy responds asymmetrically to oil prices, and why the relationship between oil prices and economic activity may have weakened. It also addresses the issue of developing energy policy to mitigate the economic effects of oil price shocks.Petroleum industry and trade

An international perspective on oil price shocks and U.S. economic activity

The effect of oil price shocks on U.S. economic activity seems to have changed since the mid-1990s. A variety of explanations have been offered for the seeming change—including better luck, the reduced energy intensity of the U.S. economy, a more flexible economy, more experience with oil price shocks and better monetary policy. These explanations point to a weakening of the relationship between oil prices shocks and economic activity rather than the fundamentally different response that may be evident since the mid-1990s.> ; Using a dynamic stochastic general equilibrium model of world economic activity, we employ Bayesian methods to assess how economic activity responds to oil price shocks arising from supply shocks and demand shocks originating in the United States or elsewhere in the world. We find that both oil supply and oil demand shocks have contributed significantly to oil price fluctuations and that U.S. output fluctuations are derived largely from domestic shocks.Petroleum industry and trade ; Petroleum products - Prices ; International trade ; Economic conditions - United States