Essays on the demand for ethanol in the United States: willingness to pay for E85

This dissertation contains three studies that estimate the distribution of willingness to pay (WTP) for E85 as a substitute for E10 among flex motorists in the United States. The results are vital for estimating the demand for ethanol beyond the blend wall and for analysis of the Renewable Fuel Standard. The first study attempts to estimate the distribution of preference for E85 from data generated by a survey of E85 stations in Minnesota. The study uses an extensive sample of recent observations, but estimates of the WTP distribution vary substantially depending on model specification. The conclusion is that the data are not suitable to estimate the distribution of WTP for E85. The second and third studies collect primary data from E85 stations in different regions of the United States to more accurately estimate preferences for E85 and investigate locational differences. The studies obtain revealed-preference (RP) data from flex motorists refueling at E85 stations and stated-preference (SP) data from surveying the flex motorists and presenting hypothetical scenarios. The second study uses the RP data to estimate relative preferences for E85, and the third study incorporates the SP data to better capture the wide range of fuel-switching behavior. The estimation sample consists of about nine hundred flex motorists in six urban areas in the Midwest and California. The sample of flex motorists who refuel at E85 stations is endogenously stratified; the probability of a flex motorist appearing in the sample is correlated to the motorist\u27s WTP for E85. The models apply corrective probability weights so estimates reflect the population and not the sample. The results show that a $0.10 increase in the E85-E10 price difference decreases the probability of motorists choosing E85 by about 2.5 percent, on average, and preferences are spread over a broad range of fuel prices. In general, motorists are willing to pay more for E85 in California than in the Midwest, and when E85 and E10 are priced equally on a cost-per-mile basis, about 25 percent of flex motorists choose E85 in the Midwest compared to 75 percent in California

Beyond the single-atom response in absorption lineshapes: Probing a dense, laser-dressed helium gas with attosecond pulse trains

We investigate the absorption line shapes of laser-dressed atoms beyond the single-atom response, by using extreme ultraviolet (XUV) attosecond pulse trains to probe an optically thick helium target under the influence of a strong infrared (IR) field. We study the interplay between the IR-induced phase shift of the microscopic time-dependent dipole moment and the resonant-propagation-induced reshaping of the macroscopic XUV pulse. Our experimental and theoretical results show that as the optical depth increases, this interplay leads initially to a broadening of the IR-modified line shape, and subsequently to the appearance of new, narrow features in the absorption line.Comment: 5 pages, 5 figure

Motorists’ Willingness to Pay for E85 versus E10

In November 2016, the Environment Protection Agency (EPA) released the inal rule for biofuel volumes under the Renewable Fuel Standard (RFS) for 2017. The total renewable fuel volume requirement for 2017 is 19.28 billion gallons, up from 18.11 billion gallons in 2016. Of the total renewable fuel volume, 15 billion gallons may be met with conventional biofuel, establishing the implied mandate for ethanol

Willingness to Pay for Ethanol in Motor Fuel: Evidence from Revealed and Stated Preference for E85

This paper estimates the relative preferences of motorists for E10 and E85 in different regions of the United States. We conducted an intercept survey of motorists with flex-fuel vehicles at E85 fuel stations in Iowa, Colorado, Oklahoma, Arkansas and California. The information collected includes prices observed at fuel stations, fuel choices by flex motorists, and responses to a series of opinion questions about ethanol and gasoline. We also proposed a hypothetical scenario to each motorist where either the price of the fuel selected was increased or the price of the fuel not selected was decreased. We estimate fuel preferences first using the revealed preference data from the observed choices and second using the stated preference data from the hypothetical price scenario. The empirical models correct for endogenous stratification within the sample and for endogeneity from unobservable demand shifters that carry over to the stated preference empirical model. We find that motorists significantly discount E85 compared to E10 even when adjusting for the different energy content of the two fuels and that the distribution of willingness to pay for E85 does not vary significantly between regions, except that flex motorists in California are willing to pay more for E85

Design and Characterization of a Novel N-type, Organic Electronic Ratchet

Ionic-organic ratchets have the ability to rectify alternating electric fields into DC current to sustain low power electronics, such as RFID devices. Until now however, organic electronic ratchets have only been realized using p-type organic semiconductors. The development and performance of organic n-type devices have historically lagged far behind their p-type equivalents, largely due to the high susceptibility of n-type organic semiconductors to electron trapping. A previously developed charge pump model predicts an output current for ionic-organic ratchets that is linearly dependent on frequency, and agrees well with data from p-type devices. In this model, the capacitance of the device is assumed to be constant over the measured frequency range. N-type ratchets based on PCBM and N2200 exhibit output currents that deviate from a linear relationship with frequency. Impedance spectroscopy measurements suggest that this deviation is caused by the presence of ions and traps which modify the frequency dependence of the device capacitance. This work demonstrates the first n-type organic electronic ratchet, capable of producing an output power comparable to its p-type counterparts

Vertical profile engineering and reliability study of silicon-germanium heterojunction bipolar transistors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 133-141).by Kenneth S. Liao.Ph.D

A Positive Feedback Loop Between Myc and Aerobic Glycolysis Sustains Tumor Growth in a Drosophila Tumor Model

Cancer cells usually exhibit aberrant cell signaling and metabolic reprogramming. However, mechanisms of crosstalk between these processes remain elusive. Here, we show that in an in vivo tumor model expressing oncogenic Drosophila Homeodomain-interacting protein kinase (Hipk), tumor cells display elevated aerobic glycolysis. Mechanistically, elevated Hipk drives transcriptional upregulation of Drosophila Myc (dMyc; MYC in vertebrates) likely through convergence of multiple perturbed signaling cascades. dMyc induces robust expression of pfk2 (encoding 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase; PFKFB in vertebrates) among other glycolytic genes. Pfk2 catalyzes the synthesis of fructose-2,6-bisphosphate, which acts as a potent allosteric activator of Phosphofructokinase (Pfk) and thus stimulates glycolysis. Pfk2 and Pfk in turn are required to sustain dMyc protein accumulation post-transcriptionally, establishing a positive feedback loop. Disruption of the loop abrogates tumorous growth. Together, our study demonstrates a reciprocal stimulation of Myc and aerobic glycolysis and identifies the Pfk2-Pfk governed committed step of glycolysis as a metabolic vulnerability during tumorigenesis