Taxonomy and biogeography of the genera Oedaleus fieber and Gastrimargus saussure (Orthoptera: Acrididae)

Imperial Users onl

Global Agricultural Trade Negotiations and Their Potential Impact on Minnesota

The two main factors determining the financial well-being of our family farmers, market prices and government payments, are primarily established by Congress through federal legislation, commonly called the Farm Bill. Although these two factors are likely to remain the main economic ingredients in Minnesota\u27s farm economy for the foreseeable future, the political control over these issues appears to be shifting out of the hands of Congress and into the hands of our international trade negotiators. For the very first time, all price support, income subsidy, and supply management programs are on the table for alteration or elimination in this new Uruguay Round of General Agreement on Tariffs and Trade (GATT) negotiations

Ab initio modeling of the energy landscape for screw dislocations in body-centered cubic high-entropy alloys

In traditional body-centered cubic (bcc) metals, the core properties of screw dislocations play a critical role in plastic deformation at low temperatures. Recently, much attention has been focused on refractory high-entropy alloys (RHEAs), which also possess bcc crystal structures. However, unlike face-centered cubic high-entropy alloys (HEAs), there have been far fewer investigations on bcc HEAs, specifically on the possible effects of chemical short-range order (SRO) in these multiple principal element alloys on dislocation mobility. Here, using density functional theory, we investigate the distribution of dislocation core properties in MoNbTaW RHEAs alloys, and how they are influenced by SRO. The average values of the core energies in the RHEA are found to be larger than those in the corresponding pure constituent bcc metals, and are relatively insensitive to the degree of SRO. However, the presence of SRO is shown to have a large effect on narrowing the distribution of dislocation core energies and decreasing the spatial heterogeneity of dislocation core energies in the RHEA. It is argued that the consequences for the mechanical behavior of HEAs is a change in the energy landscape of the dislocations which would likely heterogeneously inhibit their motion

Tunable stacking fault energies by tailoring local chemical order in CrCoNi medium-entropy alloys

High-entropy alloys (HEAs) are an intriguing new class of metallic materials due to their unique mechanical behavior. Achieving a detailed understanding of structure-property relationships in these materials has been challenged by the compositional disorder that underlies their unique mechanical behavior. Accordingly, in this work, we employ first-principles calculations to investigate the nature of local chemical order and establish its relationship to the intrinsic and extrinsic stacking fault energy (SFE) in CrCoNi medium-entropy solid-solution alloys, whose combination of strength, ductility and toughness properties approach the best on record. We find that the average intrinsic and extrinsic SFE are both highly tunable, with values ranging from -43 mJ.m-2 to 30 mJ.m-2 and from -28 mJ.m-2 to 66 mJ.m-2, respectively, as the degree of local chemical order increases. The state of local ordering also strongly correlates with the energy difference between the face-centered cubic (fcc) and hexagonal-close packed (hcp) phases, which affects the occurrence of transformation-induced plasticity. This theoretical study demonstrates that chemical short-range order is thermodynamically favored in HEAs and can be tuned to affect the mechanical behavior of these alloys. It thus addresses the pressing need to establish robust processing-structure-property relationships to guide the science-based design of new HEAs with targeted mechanical behavior.Comment: 23 pages, 5 figure

A Flightless Grasshopper of the genus Uganda Bolivar, from the Aberdares National Park, Kenya (Orthoptera, Acrididae)

Volume: 8

That Smell in the Vaults

THAT SMELL IN THE VAULTS: THE DEGRADATION OF POLYMERS IN AV MATERIALS VINEGAR Syndrome(1), Rancid Butter Syndrome(2), Rotten Fish Syndrome -- evocative but accurate descriptions of the pervasive killers of our sound and moving image heritage. Leaving aside the well-known problems of nitrate film we are faced with the stability problems of our polymer-based supports. All polymers are subject to decay; and the cellulose nitrate, cellulose diacetate, cellulose butyrate, cellulose propionate and cellulose triacetate bases are no exception. The problem is not limited to film -- audiotape, videotape, computer tape, computer disk and other formats are subject to the same inevitable decay and destruction. Over the last few years it has come to the attention of archivists around the world that the life expectancy of our audio-visual heritage is not what we once thought it should be. Storage conditions naturally have dramatic impacts on life expectancy. We..

Principles- versus rules-based output statistical disclosure control in remote access environments

In recent years, the level of detail in confidential data made available to social scientists has increased dramatically. Much of this has been due to the growth in secure data access facilities, which allow access to the most detailed data under strictly controlled conditions.One element of that control is checking to ensure that statistical outputs do not present any residual disclosure risk. Traditionally this has been managed by specifying rules for researchers to follow, but it is increasingly recognised that a ‘principles-based’ approach can be both more secure and more cost-effective.The principles-based approach requires a higher level of expertise from the facility managers, and places the subjective assessment of risk at the forefront of decision-making; these two factors often make facility managers uncomfortable. In addition, knowledge of this approach is concentrated amongst a relatively small community, whereas the rules-based model has been the dominant approach for half a century; facility managers may not be aware that there is an alternative perspective.This paper reviews the arguments for the two different approaches. The two are not mutually exclusive: both take simple rules as a starting point, but the rules-based approach also finishes there. This has advantages in some circumstances, but this paper demonstrates that the value of the principles-based approach increases with the sensitivity of the data and gives more freedom to the researchers to innovate.The paper considers how the two approaches can be implemented. It notes that, although the principles-based model requires greater initial investment by both the facility managers and researchers, the necessary training can bring substantial auxiliary benefits to the facility manager. The paper therefore concludes that a principles-based approach has advantages in many circumstances, and it is essential for the remote research data centres which dominate access solutions for the most sensitive data