Magnetic and electric phase control in epitaxial EuTiO3_3 from first principles

We propose a design strategy - based on the coupling of spins, optical phonons, and strain - for systems in which magnetic (electric) phase control can be achieved by an applied electric (magnetic) field. Using first-principles density-functional theory calculations, we present a realization of this strategy for the magnetic perovskite EuTiO$_3$.Comment: Significantly revised for clarit

Simulation of factors impeding water quality trading market performance

Over the past several decades, market-based approaches to natural resource management have received increased attention as a means to cost-effectively achieve environmental quality goals. Following on what has been hailed a success for reducing air pollution, water quality trading (WQT) has more recently been seen as the next great opportunity for reducing water pollution, especially for nutrient loading. Numerous trading programs have been pilot tested and/or adopted in states throughout the nation, with more than 70 programs now in operation (Breetz et al., 2004). WQT would allow multiple contributors to surface water degradation to determine how best to meet an overarching collective goal related to pollution reduction. WQT takes advantage of differences in pollution abatement costs. In the case of point/nonpoint source trading, such as between wastewater treatment plants (WWTPs) and agricultural producers, it is often the agricultural producers who can achieve a given level of nutrient reduction at less cost through their adoption of various best management practices that reduce sedimentation and nutrient loading to surface waters. Trading would allow WWTPs to purchase “credits” generated by producers who reduced their pollution loading to achieve an equivalent level of reduction as might be required by a regulatory discharge permit at a lower overall cost. While there is substantial evidence that nonpoint sources have lower nutrient reduction costs than point sources, experience with WQT reveals a common theme: little or no trading activity. The success of WQT seems, in part, to depend on the structure of the market created to bring buyers and sellers together to transact exchanges. These outcomes suggest the presence of obstacles to trading that were not recognized in the design of existing programs. To examine the ways that various market imperfections may impact the performance of a WQT market, an agent-based model was constructed which simulated a hypothetical point-nonpoint market. In particular, the market was modeled using a variant of the sequential, bilateral trading algorithm proposed by Atkinson and Tietenberg (1991). Our proposed paper first presents an overview of the simulation modeling technique and then analyzes the effects of two prominent market impediments identified in the WQT literature: information levels and trading ratios. Information levels refer to buyers’ and sellers’ knowledge of each others’ bid prices. A frictionless WQT market would be one where all of the potential buyers (i.e., point sources) would know all of the sellers’ (i.e., nonpoint sources) offer prices and vice versa. In this full information environment, we can expect that trades would be consummated in the order of their gains. That is, first buyers and sellers to be paired together for trading would be the buyers with the highest offer prices and the sellers with the lowest bid prices. Successive trades will have successively smaller gains until the gap between bid and offer prices reaches zero. This is the textbook Walrasian market and would closely approximate a double auction institution, where all buyers and sellers submit their offers and bids, which are then sorted and matched by a centralized market manager. While the full information scenario serves as a useful benchmark, most existing WQT markets are decentralized in nature, so that limited information causes traders to be matched in a less efficient sequence. A variety of information levels are possible. One side of the market may have more information than the other (limited information) or neither side having any knowledge of the other side’s bid or offer prices (low information). Each of these scenarios leads to a different sequencing of trades. This paper analyzes the effect of different information levels on market performance. Market performance is measured in terms of cost savings, the number of credits traded, and the average reduction costs under different information scenarios. Trading ratios are a common component of many existing WQT programs. A typical trading ratio of 2:1 requires a nonpoint source to reduce two pounds of expected nutrient loading in order to receive one pound of trading credit. These ratios serve as a “safety factor” and are incorporated to account for the uncertainty in the measurement and monitoring of nonpoint source loading. Because nonpoint traders must reduce loading by 2 pounds for every 1 pound emitted by point source traders, there will be a net reduction of 1 pound of expected loading for each trade. So, while inhibiting some trades from ever occurring, trading ratios also have the potential to improve water quality beyond trading with a 1:1 trading ratio. This paper examines these tradeoffs in terms of effects on market performance and then describes procedures that can be used to characterize an optimal trading ratio if one exists. Because WQT programs, by nature, involve complex interactions between economics and the biophysical world, accurately simulating a real-world WQT market requires at minimum a basic understanding of the types of data that watershed models can provide. This paper concludes by briefly discussing data requirements, points of consideration, and integrative techniques used in the simulation of WQT in real-world watersheds.water quality trading, market based, trading ratio, information levels, point source, nonpoint source, simulation, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials

Previous studies indicate that elasmobranch fishes (sharks, skates and rays) detect the Earth’s geomagnetic field by indirect magnetoreception through electromagnetic induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of elasmobranchs overall in comparison with control and procedural control hooks in the hook-and-line experiment. Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were signif icantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not. Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish (Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-and-line or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations

Choice Experiments to Assess Farmers' Willingness to Participate in a Water Quality Trading Market

Interest has grown in Water Quality Trading (WQT) as a means to achieve water quality goals, with more than 70 such programs now in operation in the United States. Substantial evidence exists that nonpoint sources can reduce nutrient loading at a much lower cost than point sources, implying the existence of gains from trade. Despite the potential gains, however, the most commonly noted feature of existing WQT markets is low trading volume, with many markets resulting in zero trades. This paper evaluates one explanation for the lack of participation from agricultural nonpoint sources. We test for and quantify the intangible costs that may deter farmers from trading even if the monetary benefits from doing so outweigh the observable out-of-pocket costs. We do so by designing and implementing a series of choice experiments to elicit WQT trading behavior of Great Plains crop producers in different situations. Attributes of the choice experiment included market rules and features (e.g., application time and effort, penalties for violations, means of monitoring compliance) that may affect farmers willingness to trade. The choice experiments were conducted with a total of 135 producers at four locations in the state of Kansas between August 2006 and January 2007. A Random Parameters Logit model is appropriate to analyze the resulting data, revealing diversity in the way that the attributes affect farmers choices.Resource /Energy Economics and Policy,

The Toxoplasma gondii plastid replication and repair enzyme complex, PREX

A plastid-like organelle, the apicoplast, is essential to the majority of medically and veterinary important apicomplexan protozoa including Toxoplasma gondii and Plasmodium. The apicoplast contains multiple copies of a 35 kb genome, the replication of which is dependent upon nuclear-encoded proteins that are imported into the organelle. In P. falciparum an unusual multi-functional gene, pfprex, was previously identified and inferred to encode a protein with DNA primase, DNA helicase and DNA polymerase activities. Herein, we report the presence of a prex orthologue in T. gondii. The protein is predicted to have a bi-partite apicoplast targeting sequence similar to that demonstrated on the PfPREX polypeptide, capable of delivering marker proteins to the apicoplast. Unlike the P. falciparum gene that is devoid of introns, the T. gondii prex gene carries 19 introns, which are spliced to produce a contiguous mRNA. Bacterial expression of the polymerase domain reveals the protein to be active. Consistent with the reported absence of a plastid in Cryptosporidium species, in silico analysis of their genomes failed to demonstrate an orthologue of prex. These studies indicate that prex is conserved across the plastid-bearing apicomplexans and may play an important role in the replication of the plastid genome

Photocurable Bioink for the Inkjet 3D Pharming of Hydrophilic Drugs.

Novel strategies are required to manufacture customized oral solid dosage forms for personalized medicine applications. 3D Pharming, the direct printing of pharmaceutical tablets, is an attractive strategy, since it allows for the rapid production of solid dosage forms containing custom drug dosages. This study reports on the design and characterization of a biocompatible photocurable pharmaceutical polymer for inkjet 3D printing that is suitable for hydrophilic active pharmaceutical ingredients (API). Specifically, hyaluronic acid was functionalized with norbornene moieties that, in the presence of poly(ethylene) glycol dithiol, Eosin Y as a photoinitiator, and a visible light source, undergoes a rapid step-growth polymerization reaction through thiol-ene chemistry. The engineered bioink was loaded with Ropinirole HCL, dispensed through a piezoelectric nozzle onto a blank preform tablet, and polymerized. Drug release analysis of the tablet resulted in 60% release within 15 min of tablet dissolution. The study confirms the potential of inkjet printing for the rapid production of tablets through the deposition of a photocurable bioink designed for hydrophilic APIs

Model-based spacecraft and mission design for the evaluation of technology

In order to meet the future vision of robotic missions, engineers will face intricate mission concepts, new operational approaches, and technologies that have yet to be developed. The concept of smaller, model driven projects helps this transition by including life-cycle cost as part of the decision making process. For example, since planetary exploration missions have cost ceilings and short development periods, heritage flight hardware is utilized. However, conceptual designs that rely solely on heritage technology will result in estimates that may not be truly representative of the actual mission being designed and built. The Laboratory for Spacecraft and Mission Design (LSMD) at the California Institute of Technology is developing integrated concurrent models for mass and cost estimations. The purpose of this project is to quantify the infusion of specific technologies where the data would be useful in guiding technology developments leading up to a mission. This paper introduces the design-to-cost model to determine the implications of various technologies on the spacecraft system in a collaborative engineering environment. In addition, comparisons of the benefits of new or advanced technologies for future deep space missions are examined