The cost structure of transit in small urban and rural U.S. communities

The cost structure of transit agencies that provide service to small urban and rural communities in the United States is estimated, the justification for government support of these agencies on the basis of natural monopoly evaluated, and the cost implications of combining transit agencies investigated. Increasing returns to density are found at all levels of output suggesting that marginal cost pricing will not recover full costs, and that government intervention is justified. Increasing returns to size are also found suggesting that expanding transit service areas is beneficial. Economies of scope between demand-response service and fixed-route service are found for average-size agencies suggesting benefits to combining these services for mid-size organizations. In order to examine the cost implications of combining transit agencies, we investigate the necessary and sufficient condition for natural monopoly – cost subadditivity. Rural transit is found to be a natural monopoly when service to a fixed service area is considered, suggesting that combining transit agencies that have duplicative service areas is likely to be beneficial – particularly when such transit agencies provide one type of service. On the other hand, there is little evidence of rural transit being a natural monopoly when the alternative to single provision of transit service is two systems with smaller service areas. This suggests that combining transit agencies with smaller service areas into larger regional systems may not be beneficial. We also find that rural transit agencies have excess capacity, suggesting that federal guidelines regarding vehicle purchase should be reviewed

Public transit and alternative fuels – The costs associated with using biodiesel and CNG in comparison to diesel for U.S. public transit systems

This study addresses the dearth of research that examines the impacts of alternative fuel use on operational costs of public transit in the U.S. Specifically, the study examines the impact on operational costs of shifting diesel gallons to biodiesel or to compressed natural gas (CNG) for an unbalanced panel of 269 public transit systems in the U.S. from 2008 through 2012, using an econometric cost function approach. We find that shifting all diesel gallons to biodiesel results in operational cost increases ranging from 1 to 12 percent, with smaller cost increases being realized with increases in system size. Shifting all diesel gallons to CNG results in operational cost increases between 5 and 10 percent – again with smaller impacts for larger systems. These findings suggest that there are some economies of using biodiesel and CNG with large scale production. That is, the cost increases associated with increased fuel prices, decreased fuel economy, increased maintenance costs, and increased fueling costs associated with biodiesel and CNG are mitigated somewhat by large scale production. The findings of this study suggest that increased operational costs are an important consideration in policies aimed at encouraging the use of alternative fuels by U.S. public transit systems

INSURING AGAINST LOSSES FROM TRANSGENIC CONTAMINATION

Concerns about contamination of the food supply and the financial losses that would result have limited the promise of certain genetically engineered plants. This article addresses the situation by constructing an insurance pricing model to protect against those losses. The model first estimates the physical dispersal of corn pollen subject to a number of parameters. This physical distribution is then used to calculate the premium for fair valued insurance that would be necessary to destroy contaminated fields. The flexible framework can be readily adapted to other crops, management practices, and regions

Economics of Using Flared vs. Conventional Natural Gas to Produce Nitrogen Fertilizer: A Feasibility Analysis

The feasibility analysis begins by examining the economic potential of using flared natural gas as a feedstock to produce a low-cost, reliable, and sustainable supply of nitrogen fertilizer for North Dakota farmers. Specific objectives include • Determining the most profitable facility size, location, and configuration for a natural gas nitrogen fertilizer production facility in North Dakota. • Calculating the financial returns and capital requirements of gas-based nitrogen fertilizer production. • Identifying possible business structures for the fertilizer production facility. Project objectives are achieved by evaluating the technological and economic feasibility of alternative nitrogen fertilizer production and distribution systems. • Flared Gas Collection: the economics of flared gas collection in western North Dakota analyzes the availability of flared gas supplies. • Ammonia Plant Preliminary Design: several ammonia production plants based on commercially available technologies are used to estimate capital and operating cost. • Business Structure: the effect of alternative business structures, including new generation cooperatives, on incorporation, capitalization, taxation, and fertilizer marketing are investigated. • Facility Siting: factors in determining optimal plant site include fertilizer form (e.g. ammonia, urea), technological and economies of scale, transportation and utility infrastructure, and nitrogen fertilizer demand. The use of natural gas in western and eastern North Dakota and co-location by existing coal-fired power plants or refineries are considered. Topics originally intended to study but not yet completed or are no longer relevant include • Preparing a financial pro forma, including pro forma balance sheet, income and cash flow statements for the nitrogen fertilizer production plant to demonstrate the financial viability of the enterprise. • Incorporating a supply chain model to estimate storage and transportation costs and efficiencies, including capturing and retaining value, and reducing cost and risks. • Determining the willingness of food manufacturers, bioenergy producers, and other current and potential buyers of North Dakota crops to pay the premiums for green inputs. • Estimating the impact of using of green fertilizer on farm profit. The focus of the study was refined when initial findings revealed that initiating an enterprise to capture and process flared gas was not economical at this time, but that relying on the energy industry to supply conventional natural gas for fertilizer manufacturing is more feasible at the present time. However, a premium for crops produced with green inputs and need for carbon sequestration in the future should be subsequently studied at appropriate times

Insuring Against Losses from Transgenic Contamination: The Case of Pharmaceutical Maize

Concerns about the risk of food supply contamination and the resulting financial losses have limited the development and commercialization of certain pharmaceutical plants. This article develops an insurance pricing model that helps translate these concerns into a cost-benefit analysis. The model first estimates the physical dispersal of maize pollen subject to a number of weather parameters. This distribution is then validated with the limited amount of currently available field trial data. The physical distribution is then used to calculate the premium for a fair-valued insurance policy that would fund the destruction of possibly contaminated fields. The flexible framework can be readily adapted to other crops, management practices, and regions

Guidelines for Experimental Models of Myocardial Ischemia and Infarction

Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia/reperfusion and infarction models

Diversity of cells and signals in the cardiovascular system

This white paper is the outcome of the seventh UC Davis Cardiovascular Research Symposium on Systems Approach to Understanding Cardiovascular Disease and Arrhythmia. This biannual meeting aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2022 Symposium was \u27Cell Diversity in the Cardiovascular System, cell-autonomous and cell-cell signalling\u27. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies, and challenges in examining cell and signal diversity, co-ordination and interrelationships involved in cardiovascular function. This paper originates from the topics of formal presentations and informal discussions from the Symposium, which aimed to develop a holistic view of how the multiple cell types in the cardiovascular system integrate to influence cardiovascular function, disease progression and therapeutic strategies. The first section describes the major cell types (e.g. cardiomyocytes, vascular smooth muscle and endothelial cells, fibroblasts, neurons, immune cells, etc.) and the signals involved in cardiovascular function. The second section emphasizes the complexity at the subcellular, cellular and system levels in the context of cardiovascular development, ageing and disease. Finally, the third section surveys the technological innovations that allow the interrogation of this diversity and advancing our understanding of the integrated cardiovascular function and dysfunction

Diffusion MR tractography of the heart

Histological studies have shown that the myocardium consists of an array of crossing helical fiber tracts. Changes in myocardial fiber architecture occur in ischemic heart disease and heart failure, and can be imaged non-destructively with diffusion-encoded MR. Several diffusion-encoding schemes have been developed, ranging from scalar measurements of mean diffusivity to a 6-dimensional imaging technique known as diffusion spectrum imaging or DSI. The properties of DSI make it particularly suited to the generation of 3-dimensional tractograms of myofiber architecture. In this article we review the physical basis of diffusion-tractography in the myocardium and the attributes of the available techniques, placing particular emphasis on DSI. The application of DSI in ischemic heart disease is reviewed, and the requisites for widespread clinical translation of diffusion MR tractography in the heart are discussed.National Institutes of Health (NCRR P41RR14075