159 research outputs found
Closest string with outliers
Background: Given n strings s1, …, sn each of length ℓ and a nonnegative integer d, the CLOSEST STRING problem asks to find a center string s such that none of the input strings has Hamming distance greater than d from s. Finding a common pattern in many – but not necessarily all – input strings is an important task that plays a role in many applications in bioinformatics. Results: Although the closest string model is robust to the oversampling of strings in the input, it is severely affected by the existence of outliers. We propose a refined model, the CLOSEST STRING WITH OUTLIERS (CSWO) problem, to overcome this limitation. This new model asks for a center string s that is within Hamming distance d to at least n – k of the n input strings, where k is a parameter describing the maximum number of outliers. A CSWO solution not only provides the center string as a representative for the set of strings but also reveals the outliers of the set. We provide fixed parameter algorithms for CSWO when d and k are parameters, for both bounded and unbounded alphabets. We also show that when the alphabet is unbounded the problem is W[1]-hard with respect to n – k, ℓ, and d. Conclusions: Our refined model abstractly models finding common patterns in several but not all input strings
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
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)
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