Tunable few electron quantum dots in InAs nanowires

Quantum dots realized in InAs are versatile systems to study the effect of spin-orbit interaction on the spin coherence, as well as the possibility to manipulate single spins using an electric field. We present transport measurements on quantum dots realized in InAs nanowires. Lithographically defined top-gates are used to locally deplete the nanowire and to form tunneling barriers. By using three gates, we can form either single quantum dots, or two quantum dots in series along the nanowire. Measurements of the stability diagrams for both cases show that this method is suitable for producing high quality quantum dots in InAs.Comment: 8 pages, 4 figure

Fast branching algorithm for Cluster Vertex Deletion

In the family of clustering problems, we are given a set of objects (vertices of the graph), together with some observed pairwise similarities (edges). The goal is to identify clusters of similar objects by slightly modifying the graph to obtain a cluster graph (disjoint union of cliques). Hueffner et al. [Theory Comput. Syst. 2010] initiated the parameterized study of Cluster Vertex Deletion, where the allowed modification is vertex deletion, and presented an elegant O(2^k * k^9 + n * m)-time fixed-parameter algorithm, parameterized by the solution size. In our work, we pick up this line of research and present an O(1.9102^k * (n + m))-time branching algorithm

More Than Forty Prominent Economists Urge Supreme Court to Allow EPA to Consider Costs and Consequences of Clean Air Regulations

More than forty prominent economists filed a Friend of the Court brief with the Supreme Court, asking the justices to overturn a lower court ruling that the Environmental Protection Agency (EPA) may not take into account the costs of regulations when setting standards under the Clean Air Act. Calling the lower court ruling "economically unsound," the economists argued that the EPA "should be allowed to consider explicitly the full consequences" of regulatory decisions, including costs, benefits, and any other relevant facts. In their Amici Curiae brief, the economists contended that the "plain aim" of the Clean Air Act "is protecting the public health&quo.t; That aim, they said, "is unlikely to be achieved without, at least, an implicit balancing of benefits and costs." The Supreme Court filing was organized by the American Enterprise Institute-Brookings Joint Center for Regulatory Studies. The bipartisan group of economists signing the brief included three Nobel laureates, seven former chairmen of the President's Council of Economic Advisers, and two former directors of the White House Office of Management and Budget. The case, American Trucking Association v. Carol M. Browner, Administrator of the Environmental Protection Agency , was appealed to the Supreme Court after a Federal Court in Washington D.C. ruled that the EPA was not permitted to consider costs in setting regulatory standards for enforcing the Clean Air Act. "We believe it would be imprudent for the EPA to ignore costs totally, particularly given their magnitude in this case," the economists stated in the brief. "The EPA estimates that those [clean air] standards could cost on the order of $50 billion annually." The brief argued, "Not considering costs makes it difficult to set a defensible standard, especially when there is no threshold below which health risks disappear." Ignoring costs, the economists said, "could lead to a decision to set the standard at zero pollution," which would threaten "the very economic prosperity on which public health primarily depends." The economists declared: "The importance of this issue cannot be overstated. Both direct benefits and costs of environmental, health, and safety regulations are substantial, estimated to be several hundred billion dollars annually." If the Supreme Court overturns the lower court ruling and allows the EPA to consider costs in establishing clear air regulations, the brief argued, it would be "a historic moment in the making of regulatory policy."Environment, Other Topics

Swiftly Computing Center Strings

Hufsky F, Kuchenbecker L, Jahn K, Stoye J, Böcker S. Swiftly Computing Center Strings. BMC Bioinformatics. 2011;12(1): 106

An Efficient Rank Based Approach for Closest String and Closest Substring

This paper aims to present a new genetic approach that uses rank distance for solving two known NP-hard problems, and to compare rank distance with other distance measures for strings. The two NP-hard problems we are trying to solve are closest string and closest substring. For each problem we build a genetic algorithm and we describe the genetic operations involved. Both genetic algorithms use a fitness function based on rank distance. We compare our algorithms with other genetic algorithms that use different distance measures, such as Hamming distance or Levenshtein distance, on real DNA sequences. Our experiments show that the genetic algorithms based on rank distance have the best results

Metal-Substituted Microporous Aluminophosphates

This chapter aims to present the zeotypes aluminophosphates (AlPOs) as a complementary alternative to zeolites in the isomorphic incorporation of metal ions within all-inorganic microporous frameworks as well as to discuss didactically the catalytic consequences derived from the distinctive features of both frameworks. It does not intend to be a compilation of either all or the most significant publications involving metal-substituted microporous aluminophosphates. Families of AlPOs and zeolites, which include metal ion-substituted variants, are the dominant microporous materials. Both these systems are widely used as catalysts, in particular through aliovalent metal ions substitution. Here, some general description of the synthesis procedures and characterization techniques of the MeAPOs (metal-contained aluminophosphates) is given along with catalytic properties. Next, some illustrative examples of the catalytic possibilities of MeAPOs as catalysts in the transformation of the organic molecules are given. The oxidation of the hardly activated hydrocarbons has probably been the most successful use of AlPOs doped with the divalent transition metal ions Co2+, Mn2+, and Fe2+, whose incorporation in zeolites is disfavoured. The catalytic role of these MeAPOs is rationalized based on the knowledge acquired from a combination of the most advanced characterization techniques. Finally, the importance of the high specificity of the structure-directing agents employed in the preparation of MeAPOs is discussed taking N,N-methyldicyclohexylamine in the synthesis of AFI-structured materials as a driving force. It is shown how such a high specificity could be predicted and how it can open great possibilities in the control of parameters as critical in catalysis as crystal size, inter-and intracrystalline mesoporosity, acidity, redox properties, incorporation of a great variety of heteroatom ions or final environment of the metal site (surrounding it by either P or Al)

On the Incentive Effect of Job Rotation

The longer an agent is employed in a job, the more the principal will have learned about his ability through the history of performance. With implicit incentives, influence perceptions and effort incentives decrease over time. Rotating agents to a different job deletes learning effects about ability, creating fresh impetus for effort. However, job rotation also reduces the time horizon, and thus reduces rents from working and also incentives. In this trade-off, we derive conditions for the desirability of job rotation and show how in the presence of career concerns job rotation may emerge endogenously. Finally, our model allows for more general comments on the optimal rotation frequency as well as the preferred organizational design of a firm

Comparison Wage in Trade Union Decision Making

The starting point of this paper is the idea that trade unions and individual workers pay attention to wage settlements in similar sectors of the economy. The foundations of this concept can be found in other social sciences and also in the literature of psychological economics. However, it has not received much attention in connection to union decision making. This comparison or reference wage enters the decision making of the union (i.e. the union utility function). In this paper, we employ a union utility function which incorporates this concept. The analysis is conducted in a bargaining framework and the results show the effects on the optimal wage of important variables like comparison wage, unemployment benefit, union power and of the weight that the union places on the comparison wag