Room-temperature transverse-electric polarized intersubband electroluminescence from InAs/AlInAs quantum dashes

We report the observation of transverse electric polarized electroluminescence from InAs/AlInAs quantum dash quantum cascade structures up to room temperature. The emission is attributed to the electric field confined along the shortest lateral dimension of the dashes, as confirmed by its dependence on crystallographic orientation both in absorption measurements on a dedicated sample and from electroluminescence itself. From the absorption we estimate a dipole moment for the observed transition of =1.7 nm. The electroluminescence is peaked at around 110 meV and increases with applied bias. Its temperature dependence shows a decrease at higher temperatures limited by optical phonon emission.Comment: 15 pages, 4 figures, submitted to Applied Physics Letter

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

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

Prognosis and longitudinal changes of physical activity in idiopathic pulmonary fibrosis

Background: Physical activity (PA) is associated with disease severity in idiopathic pulmonary fibrosis (IPF), but longitudinal studies evaluating its prognostic value and changes over time are lacking. Methods: We measured PA (steps per day, SPD) in a cohort of 46 IPF-patients (mean age, 67 years; mean FVC, 76.1%pred.) by accelerometry at baseline, recorded survival status during 3 years follow-up and repeated measurements in survivors. We compared the prognostic value of PA to established mortality predictors including lung function (FVC, DLCO) and 6-min walking-distance (6MWD). Results: During follow-up (median 34 months) 20 patients (43%) died. SPD and FVC best identified non-survivors (AUROC-curve 0.79, p < 0.01). After adjustment for confounders (sex, age, therapy), a standardized increase (i.e. one SD) in SPD, FVC%pred. or DLCO%pred. was associated with a more than halved risk of death (HR < 0.50; p < 0.01). Compared to baseline, SPD, FVC, and 6MWD annually declined in survivors by 973 SPD, 130 ml and 9 m, resulting in relative declines of 48.3% (p < 0.001), 13.3% (p < 0.001) and 7.8% (p = 0.055), respectively. Conclusion: While PA predicts mortality of IPF patients similar to established functional measures, longitudinal decline of PA seems to be disproportionally large. Our data suggest that the clinical impact of disease progression could be underestimated by established functional measures

Polynomial kernels for 3-leaf power graph modification problems

A graph G=(V,E) is a 3-leaf power iff there exists a tree T whose leaves are V and such that (u,v) is an edge iff u and v are at distance at most 3 in T. The 3-leaf power graph edge modification problems, i.e. edition (also known as the closest 3-leaf power), completion and edge-deletion, are FTP when parameterized by the size of the edge set modification. However polynomial kernel was known for none of these three problems. For each of them, we provide cubic kernels that can be computed in linear time for each of these problems. We thereby answer an open problem first mentioned by Dom, Guo, Huffner and Niedermeier (2005).Comment: Submitte

Swiftly Computing Center Strings

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

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