1,667 research outputs found

    Surface roughness and height-height correlations dependence on thickness of YBaCuO thin films

    Get PDF
    For high Tc superconducting multilayer applications, smooth interfaces between the individual layers are required. However, in general, e.g., YBaCuO grows in a 3D screw-dislocation or island nucleation growth mode, introducing a surface roughness. In this contribution we study the surface layer roughness as a function of different deposition techniques as well as deposition parameters. Special attention will be paid to the increase in film roughness with increasing film thickness. For these studies we used scanning probe microscopy. From these experiments, we obtained an island density decreasing with a square root dependence on the film thickness. Furthermore, height-height correlations indicate that the film growth can be described by a ballistic growth process, with very limited effective surface diffusion. The correlation lengths ¿ are on the order of the island size, inferring that the island size forms the mean diffusion barrier. This results in a representation of non-correlated islands, which can be considered as autonomous systems

    On the Enumeration of Minimal Covers and Minimal Forbidden Sets

    Get PDF
    An independence system is a family I of subsets of a ground set V with the property that any subset of any member of I also belongs to I. The inclusion-minimal sets not in I are called minimal covers. We prove several complexity results related to computation, enumeration, and counting of the minimal covers of an independence system. Our motivation to study these problems is their importance in the solution of resource-constrained scheduling problems. There the minimal covers correspond to minimal subsets of jobs that must not be scheduled simultaneously, so-called minimal forbidden sets. In this context, minimal covers are the minimal infeasible 0/1-solutions of a linear inequality system. We propose and analyze a simple backtracking algorithm that generates a complete representation of all minimal covers of the independence system induced by a linear inequality system. The practical performance of this algorithm is evaluated on the basis of instances from the project scheduling library PSPLIB.computer science applications;

    Patterns of Second- and Third-Trimester Growth and Discordance in Twin Pregnancy: Analysis of the Southwest Thames Obstetric Research Collaborative (STORK) Multiple Pregnancy Cohort.

    Get PDF
    INTRODUCTION: This study investigates patterns of intertwin size discordance in dichorionic diamniotic (DCDA) and monochorionic diamniotic (MCDA) twin pregnancies. MATERIAL AND METHODS: Ultrasound measurements of twin pregnancies, from 14 weeks to term, were collected by 9 hospitals over a 10-year period. This analysis considers the modelled and observed levels of discordance in abdominal circumference (AC) and estimated fetal weight (EFW) in relation to gestational age. Fitted models were analysed to produce charts displaying the expected range of intertwin discordance in AC and EFW at any given examination. RESULTS: The dataset for analysis included a total of 9,866 ultrasound examinations in 1,802 DCDA and 323 MCDA twin pregnancies. The 95th percentile of intertwin discordance in EFW increased from 18.3% (95% CI, 17.8-18.7%) at 20 weeks to 21.9% (95% CI, 21.3-22.4%) at 30 weeks for DCDA pregnancies. The 95th percentile for intertwin discordance in AC was stable at 10-11% for this period. Slightly higher levels of discordance were observed for MCDA than for DCDA pregnancies. DISCUSSION: The expected range of intertwin discordance in EFW and AC shows differences with gestational age and between DCDA and MCDA pregnancies

    Enumeration of Circuits and Minimal Forbidden Sets

    Get PDF
    In resource-constrained scheduling, it is sometimes important to know all inclusion-minimal subsets of jobs that must not be scheduled simultaneously. These so-called minimal forbidden sets are given implicitly by a linear inequality system, and can be interpreted more generally as the circuits of a particular independence system. We present several complexity results related to computation, enumeration, and counting of the circuits of an independence system. On this account, we also propose a backtracking algorithm that enumerates all minimal forbidden sets for resource constrained scheduling problems

    Volatilization of fenpropimorph and clopyralid after spraying onto a sugar beet crop

    Get PDF
    Volatilization rates of pesticides were measured with two micrometeorological methods. For fenpropimorph, the highest rates (1.3-3.0% per hour) were measured in the first hours after application. The rate gradually declined to less than 0.01% per houron the sixth day. Clopyralid had much lower volatilization rates. They were highest (0.1% per hour) on the day after the day of application and declined below the detection limit (less than 0.01% per hour) on the sixth day after application. Rates calculated with the aerodynamic method were slightly higher than those calculated with the Bowen ratio

    Genetic and biochemical analyses of chromosome and plasmid gene homologues encoding ICL and ArCP domains in Vibrioanguillarum strain 775

    Get PDF
    Anguibactin, the siderophore produced by Vibrio anguillarum 775 is synthesized from 2,3-dihydroxybenzoic acid (DHBA), cysteine and hydroxyhistamine via a nonribosomal peptide synthetase (NRPS) mechanism. Most of the genes encoding anguibactin biosynthetic proteins are harbored by the pJM1 plasmid. In this work we report the identification of a homologue of the plasmid-encoded angB on the chromosome of strain 775. The product of both genes harbor an isochorismate lyase (ICL) domain that converts isochorismic acid to 2,3-dihydro-2,3-dihydroxybenzoic acid, one of the steps of DHBA synthesis. We show in this work that both ICL domains are functional in the production of DHBA in V. anguillarum as well as in E. coli. Substitution by alanine of the aspartic acid residue in the active site of both ICL domains completely abolishes their isochorismate lyase activity in vivo. The two proteins also carry an aryl carrier protein (ArCP) domain. In contrast with the ICL domains only the plasmid encoded ArCP can participate in anguibactin production as determined by complementation analyses and site-directed mutagenesis in the active site of the plasmid encoded protein, S248A. The site-directed mutants, D37A in the ICL domain and S248A in the ArCP domain of the plasmid encoded AngB were also tested in vitro and clearly show the importance of each residue for the domain function and that each domain operates independently.
    corecore