Brian F. Snyder

A REAPPRAISAL OF BATEMAN'S CLASSIC STUDY OF INTRASEXUAL SELECTION

Abstract Batemans (1948) study showing greater variances in number of mates and reproductive success in male than female Drosophila melanogaster is a foundational paper in sexual selection. Here we show for the first time that his methods had flaws, including the elimination of genetic variance, sampling biases, miscalculations of fitness variances, statistical pseudo-replication, and selective presentation of data. We conclude that Batemans results are unreliable, his conclusions are questionable, and his observed variances are similar to those expected under random mating. Despite our analysis, we do not intend this article as a criticism of Bateman; he accomplished his work without modern computational tools, and his approach was groundbreaking emphasizing the significance of fitness variance for sexual selection. However, this reanalysis has implications for what counts as evidence for sexual selection and we believe that our concerns should be of interest to contemporary students of sexual selection. We call for repetitions of Batemans study using modern statistical and molecular methods.

An empirical analysis of offshore service vessel utilization in the US Gulf of Mexico

Purpose – The offshore supply vessel (OSV) industry is critical to offshore oil and gas operations around the world and contributes to the economic and ecological impacts experienced by the local communities supporting the offshore oil and gas industries. The OSV industry has not been studied significantly and the economic and ecological impacts to local communities is generally unknown. This paper aims to address these issues.Design/methodology/approach – In this paper, the authors review the activities and logistical requirements involved in offshore exploration and development with special attention paid to workflows and the manner in which service vessels are utilized in the Gulf of Mexico. The authors estimate the OSV needs per stage of activity for offshore operations based on data collected from company planning documents, fleet utilization data from oil and gas companies and service providers, interviews and surveys. The statistical data is synthesized and reconciled and despite large variances th...

Offshore wind structure weight algorithms

Decommissioning requirements for offshore renewable energy facilities in US federal waters requires that all facilities be removed and the seafloor be cleared of all obstructions at the end of the life of the lease. Before construction activities are permitted, developers are required to post a bond based on the estimated cost of decommissioning to ensure that the federal government is protected in case of company default. The purpose of this note is to provide weight algorithms of offshore wind farm components to estimate the lift requirements in decommissioning, the scrap value of material, and disposal cost. Weight algorithms are calibrated and compared with North Sea project data and examples illustrate the procedures. The component weights at the Cape Wind farm offshore Massachusetts are estimated.

Capital Investment and Operational Decision Making in the Offshore Drilling Industry

Drilling contractors new build or idle rigs based on market conditions and business strategies. In theory, contractors invest in new building when the expected net present value of adding a rig to the fleet is positive, and idle capacity when the costs of operation are expected to exceed the costs of idling. We developed models of capacity decision making in the offshore contract drilling industry and found that high combinations of day rates and utilization are required to justify new build investment and that idling capacity may be preferred even if daily operating costs exceed daily revenue.

Empirical models of jackup rig lightship displacement

A jackup rig is a mobile offshore drilling unit used to drill wells to find and produce hydrocarbons. The weight of a rig is an important variable in cost estimation and determining the amount of steel required in construction. Rig weight is generally considered proprietary because it indicates design benchmarks and performance metrics that are central to the competitive nature of the construction industry. Methods to predict ship weight cannot be used for jackups because of the structural differences between jackup rigs and ships. The purpose of this note is to present an empirically-derived jackup lightship displacement function. We compile a dataset of jackup lightship displacements and develop a linear regression model that explains over 90% of the variation in rig weight.

Modeling impacts of sea-level rise, oil price, and management strategy on the costs of sustaining Mississippi delta marshes with hydraulic dredging

Over 25% of Mississippi River delta plain (MRDP) wetlands were lost over the past century. There is currently a major effort to restore the MRDP focused on a 50-year time horizon, a period during which the energy system and climate will change dramatically. We used a calibrated MRDP marsh elevation model to assess the costs of hydraulic dredging to sustain wetlands from 2016 to 2066 and 2016 to 2100 under a range of scenarios for sea level rise, energy price, and management regimes. We developed a subroutine to simulate dredging costs based on the price of crude oil and a project efficiency factor. Crude oil prices were projected using forecasts from global energy models. The costs to sustain marsh between 2016 and 2100 changed from

Modelling service vessel activity in the Outer Continental Shelf Gulf of Mexico

128,000/ha in the no change scenario to ~

Renewable Energy Potential and Renewable Portfolio Standard Adoption

1,010,000/ha in the worst-case scenario for sea level rise and energy price, an ~8-fold increase. Increasing suspended sediment concentrations, which is possible using managed river diversions, raised created marsh lifespan and decreased long term dredging costs. Created marsh lifespan changed nonlinearly with dredging fill elevation and suspended sediment level. Cost effectiveness of marsh creation and nourishment can be optimized by adjusting dredging fill elevation to the local sediment regime. Regardless of management scenario, sustaining the MRDP with hydraulic dredging suffered declining returns on investment due to the convergence of energy and climate trends. Marsh creation will likely become unaffordable in the mid to late 21st century, especially if river sediment diversions are not constructed before 2030. We recommend that environmental managers take into consideration coupled energy and climate scenarios for long-term risk assessments and adjust restoration goals accordingly.

Modeling Offshore Turbine Installation Vessel Dayrates in the U.S.

Supply vessels transport goods and provide services to support oil and gas exploration, development and production activity throughout the worlds offshore basins. The Outer Continental Shelf of the Gulf of Mexico is one of the oldest and largest offshore hydrocarbon producing regions in the world and is supported by an extensive offshore industry. The purpose of this paper is to model the activity level and spatial distribution of supply vessels operating in the Gulfs coastal regions in support of the oil and gas industry. The logistics network is modelled as a linear time-invariant deterministic system and implemented using an input–output model across 19 shorebases and 52 offshore area blocks. Historic activity levels and empirical data on vessel utilisation and shorebase allocation are used to parameterise the model. We estimate that about 80,000 trips per year are required to support the offshore industry with approximately 80% of trips in support of shallow water operations and 60% for production activity. Sensitivity analysis and model limitations are summarised.

Decommissioning Cost Estimation

Thirty states have adopted renewable portfolio standards (RPSs) that set targets for renewable energy generation by mandating electric power utilities obtain a minimum percentage of their power from renewable sources. To date, there have been a number of studies that have consistently found that political and economic factors impact RPS adoption. There have also been studies that examine the impact of the amount of renewable energy potential in a state on the probability of RPS adoption, but results have largely been statistically weak and inconclusive. After controlling for political and economic factors, we estimate that a one standard deviation increase in wind potential is associated with an approximately 4.2 percentage point increase in the probability of having an RPS, and a one standard deviation increase in solar potential is associated with a 6.1 percentage point increase in the probability of having an RPS.