Advantage of a quantum player over a classical one in 2x2 quantum games

We study a general $2 \times 2$ symmetric, entangled, quantum game. When one player has access only to classical strategies while the other can use the full range of quantum strategies, there are ``miracle'' moves available to the quantum player that can direct the result of the game towards the quantum player's preferred result regardless of the classical player's strategy. The advantage pertaining to the quantum player is dependent on the degree of entanglement. Below a critical level, dependent on the payoffs in the game, the miracle move is of no advantage.Comment: Revtex, 10 pages, 2 tables, 4 figures; v2 typo corrected in table 2, cosmetic changes to tables and figures, comment added to section VI E; v3 title changed to published title; minor mathematical errors in published version correcte

An introduction to quantum game theory

The application of the methods of quantum mechanics to game theory provides us with the ability to achieve results not otherwise possible. Both linear superpositions of actions and entanglement between the players' moves can be exploited. We provide an introduction to quantum game theory and review the current status of the subject.Comment: 8 pages, RevTeX; v2 minor changes to the text in light of referees comments, references added/update

Controlling Phalaris Minor in the Indian Rice-Wheat Belt

The ACIAR-managed project CS1/1996/013, Herbicide-resistant weeds of wheat in India and Australia: integrated management, was designed to find a long-term method of control of Phalaris minor, a problem weed of the rice–wheat cropping system of north-western India. By 1993, the weed had developed resistance to isoproturon, a herbicide which had delivered effective weed control for 15 years. The short-term solution, implemented before the ACIAR project commenced, involved identification and registration of a new set of herbicides. But these new herbicides were expensive. To ensure high adoption they needed to be combined with changes in wheat-growing techniques that would provide cost savings to help farmers pay for them. And to avoid the re-emergence of chemical resistance, they needed to be used sparingly as one element in a broader approach to weed management. The project team used these circumstances to field-test and encourage adoption of zero tillage, a technology that agronomists had been advocating for many years, but which had failed to capture the interest of Indian farmers. Zero tillage has the potential to deliver big cost savings. In addition, it provides prospects for yield increases by allowing early sowing of wheat and avoiding soil degradation. Project research established that zero tillage also provided effective weed control with only a moderate reliance on chemicals, making the re-emergence of herbicide resistance remote. We calculate a gain to the Indian economy of around $1800 million in net present value terms over the next 30 years from the adoption of zero tillage to control Phalaris minor infestation in the rice–wheat areas of north-western India. This leads to an extremely high ratio of benefits to project costs. Zero tillage by itself is clearly a profitable technology. It does not need a weed problem to justify its introduction. Without the ACIAR project, zero tillage would have been introduced to the region, though somewhat later than what has occurred. On the assumption that the ACIAR project has advanced the adoption profile of zero tillage by 3 years, we calculate gains that can be attributed to ACIAR’s role of$238 million in net present value terms over the next 30 years. This gain has been achieved with total expenditures on the ACIAR-managed project amounting to only $1.3 million in present values.herbicide-resistant weeds, wheat, weed, India, Australia, integrated management, phalaris minor, rice-wheat cropping systems, chemical resistance, weed management, zero tillage, cost saving, net present economy, high benefits, profitable technology, Agribusiness, Crop Production/Industries, Farm Management, Food Consumption/Nutrition/Food Safety, International Development, Production Economics,

X-ray Spectroscopy of the Contact Binary VW Cephei

Short-period binaries represent extreme cases in the generation of stellar coronae via a rotational dynamo. Such stars are important for probing the origin and nature of coronae in the regimes of rapid rotation and activity saturation. VW Cep (P=0.28 d) is a relatively bright, partially eclipsing, and very active object. Light curves made from Chandra/HETGS data show flaring and rotational modulation, but no eclipses. Velocity modulation of emission lines indicates that one component dominates the X-ray emission. The emission measure is highly structured, having three peaks. Helium-like triplet lines give electron densities of about 3.0E+10 - 18.0E+10 /cm^3. We conclude that the corona is predominantly on the polar regions of the primary star and compact.Comment: Accepted for publication in the Astropysical Journal, 23 June 2006; 22 pages, 15 figure

Optimizing the assessment of suicidal behavior: the application of curtailment techniques

Background: Given their length, commonly used scales to assess suicide risk, such as the Beck Scale for Suicide Ideation (SSI) are of limited use as screening tools. In the current study we tested whether deterministic and stochastic curtailment can be applied to shorten the 19-item SSI, without compromising its accuracy. Methods: Data from 366 patients, who were seen by a liaison psychiatry service in a general hospital in Scotland after a suicide attempt, were used. Within 24 h of admission, the SSI was administered; 15 months later, it was determined whether a patient was re-admitted to a hospital as the result of another suicide attempt. We fitted a Receiver Operating Characteristic curve to derive the best cut-off value of the SSI for predicting future suicidal behavior. Using this cut-off, both deterministic and stochastic curtailment were simulated on the item score patterns of the SSI. Results: A cut-off value of SSI≥6 provided the best classification accuracy for future suicidal behavior. Using this cut-off, we found that both deterministic and stochastic curtailment reduce the length of the SSI, without reducing the accuracy of the final classification decision. With stochastic curtailment, on average, less than 8 items are needed to assess whether administration of the full-length test will result in an SSI score below or above the cut-off value of 6. Limitations: New studies using other datasets should re-validate the optimal cut-off for risk of repeated suicidal behavior after being treated in a hospital following an attempt. Conclusions: Curtailment can be used to simplify the assessment of suicidal behavior, and should be considered as an alternative to the full scale