On the mixing properties of piecewise expanding maps under composition with permutations

This is the author accepted manuscript. The final version is available from American Institute of Mathematical Sciences via the DOI in this record.We consider the effect on the mixing properties of a piecewise smooth interval map f when its domain is divided into N equal subintervals and f is composed with a permutation of these. The case of the stretch-and-fold map f(x)=mxmod1 for integers m≥2 is examined in detail. We give a combinatorial description of those permutations σ for which σ∘f is still (topologically) mixing, and show that the proportion of such permutations tends to 1 as N→∞. We then investigate the mixing rate of σ∘f (as measured by the modulus of the second largest eigenvalue of the transfer operator). In contrast to the situation for continuous time diffusive systems, we show that composition with a permutation cannot improve the mixing rate of f, but typically makes it worse. Under some mild assumptions on m and N, we obtain a precise value for the worst mixing rate as σ ranges through all permutations; this can be made arbitrarily close to 1 as N→∞ (with m fixed). We illustrate the geometric distribution of the second largest eigenvalues in the complex plane for small m and N, and propose a conjecture concerning their location in general. Finally, we give examples of other interval maps f for which composition with permutations produces different behaviour than that obtained from the stretch-and-fold map

Provenance-Centered Dataset of Drug-Drug Interactions

Over the years several studies have demonstrated the ability to identify potential drug-drug interactions via data mining from the literature (MEDLINE), electronic health records, public databases (Drugbank), etc. While each one of these approaches is properly statistically validated, they do not take into consideration the overlap between them as one of their decision making variables. In this paper we present LInked Drug-Drug Interactions (LIDDI), a public nanopublication-based RDF dataset with trusty URIs that encompasses some of the most cited prediction methods and sources to provide researchers a resource for leveraging the work of others into their prediction methods. As one of the main issues to overcome the usage of external resources is their mappings between drug names and identifiers used, we also provide the set of mappings we curated to be able to compare the multiple sources we aggregate in our dataset.Comment: In Proceedings of the 14th International Semantic Web Conference (ISWC) 201

The incidence of total hip arthroplasty after hip arthroscopy in osteoarthritic patients

<p>Abstract</p> <p>Objective</p> <p>To assess the incidence of total hip arthroplasty (THA) in osteoarthritic patients who were treated by arthroscopic debridement and to evaluate factors that might influence the time interval from the first hip arthroscopy to THA.</p> <p>Design</p> <p>Retrospective clinical series</p> <p>Methods</p> <p>Follow-up data and surgical reports were retrieved from 564 records of osteoarthritic patients that have had hip arthroscopy between the years 2002 to 2009 with a mean follow-up time of 3.2 years (range, 1-6.4 years). The time interval between the first hip arthroscopy to THA was modelled as a function of patient age; level of cartilage damage; procedures performed and repeated arthroscopies with the use of multivariate regression analysis.</p> <p>Results</p> <p>Ninety (16%) of all participants eventually required THA. The awaiting time from the first arthroscopy to a hip replacement was found to be longer in patients younger than 55 years and in a milder osteoarthritic stage. Patients that experienced repeated hip scopes had a longer time to THA than those with only a single procedure. Procedures performed concomitant with debridement and lavage did not affect the time interval to THA.</p> <p>Conclusions</p> <p>In our series of arthroscopic treatment of hip osteoarthritis, 16% required THA over a period of 7 years. Factors that influence the time to arthroplasty were age, degree of osteoarthritis and recurrent procedures.</p

Gate-tuned normal and superconducting transport at the surface of a topological insulator

Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulator.Comment: 28 pages, 5 figure

Ori-Finder: A web-based system for finding oriCs in unannotated bacterial genomes

<p>Abstract</p> <p>Background</p> <p>Chromosomal replication is the central event in the bacterial cell cycle. Identification of replication origins (<it>oriC</it>s) is necessary for almost all newly sequenced bacterial genomes. Given the increasing pace of genome sequencing, the current available software for predicting <it>oriC</it>s, however, still leaves much to be desired. Therefore, the increasing availability of genome sequences calls for improved software to identify <it>oriC</it>s in newly sequenced and unannotated bacterial genomes.</p> <p>Results</p> <p>We have developed Ori-Finder, an online system for finding <it>oriC</it>s in bacterial genomes based on an integrated method comprising the analysis of base composition asymmetry using the <it>Z</it>-curve method, distribution of DnaA boxes, and the occurrence of genes frequently close to <it>oriC</it>s. The program can also deal with unannotated genome sequences by integrating the gene-finding program ZCURVE 1.02. Output of the predicted results is exported to an HTML report, which offers convenient views on the results in both graphical and tabular formats.</p> <p>Conclusion</p> <p>A web-based system to predict replication origins of bacterial genomes has been presented here. Based on this system, <it>oriC </it>regions have been predicted for the bacterial genomes available in GenBank currently. It is hoped that Ori-Finder will become a useful tool for the identification and analysis of <it>oriC</it>s in both bacterial and archaeal genomes.</p

T-Bet and Eomes Regulate the Balance between the Effector/Central Memory T Cells versus Memory Stem Like T Cells

Memory T cells are composed of effector, central, and memory stem cells. Previous studies have implicated that both T-bet and Eomes are involved in the generation of effector and central memory CD8 T cells. The exact role of these transcription factors in shaping the memory T cell pool is not well understood, particularly with memory stem T cells. Here, we demonstrate that both T-bet or Eomes are required for elimination of established tumors by adoptively transferred CD8 T cells. We also examined the role of T-bet and Eomes in the generation of tumor-specific memory T cell subsets upon adoptive transfer. We showed that combined T-bet and Eomes deficiency resulted in a severe reduction in the number of effector/central memory T cells but an increase in the percentage of CD62LhighCD44low Sca-1+ T cells which were similar to the phenotype of memory stem T cells. Despite preserving large numbers of phenotypic memory stem T cells, the lack of both of T-bet and Eomes resulted in a profound defect in antitumor memory responses, suggesting T-bet and Eomes are crucial for the antitumor function of these memory T cells. Our study establishes that T-bet and Eomes cooperate to promote the phenotype of effector/central memory CD8 T cell versus that of memory stem like T cells. © 2013 Li et al

STM and RHEED study of the Si(001)-c(8x8) surface

The Si(001) surface deoxidized by short annealing at T~925C in the ultrahigh vacuum molecular beam epitaxy chamber has been in situ investigated by high resolution scanning tunnelling microscopy (STM) and reflected high energy electron diffraction (RHEED). RHEED patterns corresponding to (2x1) and (4x4) structures were observed during sample treatment. The (4x4) reconstruction arose at T<600C after annealing. The reconstruction was observed to be reversible: the (4x4) structure turned into the (2x1) one at T>600C, the (4x4) structure appeared again at recurring cooling. The c(8x8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8x8) structure decreased as the sample cooling rate was reduced. The (2x1) structure was observed on the surface free of the c(8x8) one. The c(8x8) structure has been evidenced to manifest itself as the (4x4) one in the RHEED patterns. A model of the c(8x8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.Comment: 26 pages, 12 figure

Critical change in the Fermi surface of iron arsenic superconductors at the onset of superconductivity

The phase diagram of a correlated material is the result of a complex interplay between several degrees of freedom, providing a map of the material's behavior. One can understand (and ultimately control) the material's ground state by associating features and regions of the phase diagram, with specific physical events or underlying quantum mechanical properties. The phase diagram of the newly discovered iron arsenic high temperature superconductors is particularly rich and interesting. In the AE(Fe1-xTx)2As2 class (AE being Ca, Sr, Ba, T being transition metals), the simultaneous structural/magnetic phase transition that occurs at elevated temperature in the undoped material, splits and is suppressed by carrier doping, the suppression being complete around optimal doping. A dome of superconductivity exists with apparent equal ease in the orthorhombic / antiferromagnetic (AFM) state as well as in the tetragonal state with no long range magnetic order. The question then is what determines the critical doping at which superconductivity emerges, if the AFM order is fully suppressed only at higher doping values. Here we report evidence from angle resolved photoemission spectroscopy (ARPES) that critical changes in the Fermi surface (FS) occur at the doping level that marks the onset of superconductivity. The presence of the AFM order leads to a reconstruction of the electronic structure, most significantly the appearance of the small hole pockets at the Fermi level. These hole pockets vanish, i. e. undergo a Lifshitz transition, at the onset of superconductivity. Superconductivity and magnetism are competing states in the iron arsenic superconductors. In the presence of the hole pockets superconductivity is fully suppressed, while in their absence the two states can coexist.Comment: Updated version accepted in Nature Physic