System-size convergence of point defect properties: The case of the silicon vacancy

We present a comprehensive study of the vacancy in bulk silicon in all its charge states from 2+ to 2-, using a supercell approach within plane-wave density-functional theory, and systematically quantify the various contributions to the well-known finite size errors associated with calculating formation energies and stable charge state transition levels of isolated defects with periodic boundary conditions. Furthermore, we find that transition levels converge faster with respect to supercell size when only the Gamma-point is sampled in the Brillouin zone, as opposed to a dense k-point sampling. This arises from the fact that defect level at the Gamma-point quickly converges to a fixed value which correctly describes the bonding at the defect centre. Our calculated transition levels with 1000-atom supercells and Gamma-point only sampling are in good agreement with available experimental results. We also demonstrate two simple and accurate approaches for calculating the valence band offsets that are required for computing formation energies of charged defects, one based on a potential averaging scheme and the other using maximally-localized Wannier functions (MLWFs). Finally, we show that MLWFs provide a clear description of the nature of the electronic bonding at the defect centre that verifies the canonical Watkins model.Comment: 10 pages, 6 figure

A cost comparison of traditional drainage and SUDS in Scotland

The Dunfermline Eastern Expansion (DEX) is a 350 ha mixed development which commenced in 1996. Downstream water quality and flooding issues necessitated a holistic approach to drainage planning and the site has become a European showcase for the application of Sustainable Urban Drainage Systems (SUDS). However, there is minimal data available regarding the real costs of operating and maintaining SUDS to ensure they continue to perform as per their design function. This remains one of the primary barriers to the uptake and adoption of SUDS. This paper reports on what is understood to be the only study in the UK where actual costs of constructing and maintaining SUDS have been compared to an equivalent traditional drainage solution. To compare SUDS costs with traditional drainage, capital and maintenance costs of underground storage chambers of analogous storage volumes were estimated. A whole life costing methodology was then applied to data gathered. The main objective was to produce a reliable and robust cost comparison between SUDS and traditional drainage. The cost analysis is supportive of SUDS and indicates that well designed and maintained SUDS are more cost effective to construct, and cost less to maintain than traditional drainage solutions which are unable to meet the environmental requirements of current legislation

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries Does the observational evidence support their existence?

Context. Period variations have been detected in a number of eclipsing close compact binary subdwarf B stars (sdBs) and these have often been interpreted as caused by circumbinary massive planets or brown dwarfs. Various evolutionary scenarios have been proposed for these stars, but a definite mechanism remains to be established. Equally puzzling is the formation of these putative circumbinary objects which must have formed either from the remaining post common envelope circumbinary disk or survived its evolution. Aims. In this paper we review the eclipse time variations (ETVs) exhibited by seven such systems and explore if there is conclusive evidence that the ETVs observed over the last two decades can reliably predict the presence of circumbinary bodies. Methods. We report 246 new observations of the seven sdB systems made between 2013 September and 2017 July using a worldwide network of telescopes. We combined our new data with previously published measurements to analyse the ETVs of these systems. Results. Our data shows that period variations cannot be modelled simply on the basis of circumbinary objects. This implies that more complex processes may be taking place in these systems. From eclipse time variations, it has historically been suggested that five of the seven binary systems reported herein had circumbinary objects. Based on our recent observations and analysis only three systems remain serious contenders. We find agreement with other observers that at least a decade of observations is required to establish reliable ephemeris. With longer observational baselines it is quite conceivable that the data will support the circumbinary object hypothesis of these binary systems. Also we generally agree with other observers that larger values of (O-C) residuals are found with secondary companions of spectral type M5/6 or earlier as a result of an Applegate type mechanismComment: 15 pages, 13 figures, 4 tables. 3 tables archived on CD

A Slight Excess of Large Scale Power from Moments of the Peculiar Velocity Field

The peculiar motions of galaxies can be used to infer the distribution of matter in the Universe. It has recently been shown that measurements of the peculiar velocity field indicates an anomalously high bulk flow of galaxies in our local volume. In this paper we find the implications of the high bulk flow for the power spectrum of density fluctuations. We find that analyzing only the dipole moment of the velocity field yields an average power spectrum amplitude which is indeed much higher than the LCDM value. However, by also including shear and octupole moments of the velocity field, and marginalizing over possible values for the growth rate, an average power spectrum amplitude which is consistent with LCDM is recovered. We attempt to infer the shape of the matter power spectrum from moments of the velocity field, and find a slight excess of power on scales ~ h-1 Gpc.Comment: 6 pages,6 figures, updated to match accepted versio

Underwater sounds from ribbon seal, Phoca (Histriophoca) fasciata

This paper is not subject to U.S. copyright. The definitive version was published in Fishery Bulletin 75 (1977): 450-453.Intense downward frequency "sweeps" and broadband "puffing" sounds were recorded underwater in the presence of ribbon seal, Phoca (Histriophoca) fasciata Zimmerman 1783. The recordings were made in the waters off Savoonga, St. Lawrence Island, Alaska, on 16, 17, 18, and 23 May 1967.Arctic Institute of North America under contractural agreements with the Office of Naval Research

Pesticide Application and Handling Technology: Proper Disposal of Empty Pesticide Containers

Recycling has become more and more popular as our awareness of environmental concerns grow. These environmental concerns have led to increased participation in recycling efforts among today\u27s farmers. Many farmers throughout Kentucky are now able to recycle their empty plastic pesticide containers (Five gallon or less) due to a statewide Rinse and Return program. Recycling of empty containers provides a safe means of disposal for applicators, reduces landfill space, and protects our valuable water resources

Pesticide Application and Handling Technology: Installing a Sprayer Tank Rinse Circuit

Proper tank rinsing techniques for agricultural sprayers are very important in order to protect against cross-contamination in subsequent loads and to ensure safe disposal of any excess chemicals and rinsate (rinse water). Spray tanks and other sprayer components should be cleaned after each use. In most situations, sprayer rinsate will have to be sprayed out in the field - either onto a reserved strip, or by over-spraying in the treated area (subject to the terms of the product label)

B840: Firm Formation, Firm Failure, and Competitiveness: An Overview of Maine\u27s Entrepreneurial Economy

The purpose of this paper is to establish a basic understanding of Maine\u27s entrepreneurial economy. The competitiveness of Maine\u27s small businesses, reflected in rates of firm formation and firm failure, is important to future economic growth and policy development. Previous research has pointed to the high proportion of small businesses operating in Maine, but questions concerning their entrepreneurial dynamism remain unanswered. Developing a useful policy response for future economic growth dictates that the following questions be fully explored: (1) What is the current state of Maine\u27s entrepreneurial base and how does this base compare with other states in the New England region? (2) How is this base changing with respect to firm formation and business failures, and are there sectors of emerging strength and competitiveness? (3) Are there rural/urban differences that form a potential basis for policy differentiation? (4) What are the crucial elements of entrepreneurship and associated policy development for economic growth in Maine?https://digitalcommons.library.umaine.edu/aes_bulletin/1018/thumbnail.jp

B845: The Cost of Doing Business and Economic Performance in Maine: A Regional Comparison

This study attempts to address the need for better understanding of those business climate factors that have a direct and measurable impact upon statewide economic performance by comparing several key costs faced by businesses in each of the New England states, and by examining how those costs relate to general economic conditions in each state.https://digitalcommons.library.umaine.edu/aes_bulletin/1007/thumbnail.jp

B804: The Growth and Change of High Technology Industries in the State of Maine: Implications for State and Local Development Policy

To shed light on Maine’s high-tech industries, employment and production data were gathered for 11O firms including 20 three-digit SIC (Standard Industrial Classification) categories. The time periods covered were 1970, 1976, and 1981. This data base was provided by the Bureau of Employment Security and the Bureau of Labor Standards of the Maine Department of Labor. The research was guided by the following questions: How are firms distributed among specific high technology industries and has this distribution changed over time? What is the geographic distribution of high technology firms within the state and how is this distribution changing? How dynamic have Maine\u27s high technology industries been with respect to plant openings, closings, and acquisitions? How is employment generation distributed by size, age, SIC, and type of firm? Does Maine show a potential comparative advantage for specific high technology SIC\u27s? and What implications can be drawn from the Maine data for rural communities seeking high technology development?https://digitalcommons.library.umaine.edu/aes_bulletin/1057/thumbnail.jp