1,473 research outputs found

    Lithographic technology for microwave integrated circuits

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    Conductive lithographic films (CLFs) have been developed primarily as substitutes for resin/laminate boards, which share properties with the metallisation patterns used in planar microwave integrated circuits (MICs). The authors examine the microwave properties of the films and show that, although the losses are greater, they have potential as an alternative to the traditional manufacturing process of MICs

    Microsatellites retain phylogenetic signals across genera in eucalypts (Myrtaceae)

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    The utility of microsatellites (SSRs) in reconstructing phylogenies is largely confined to studies below the genus level, due to the potential of homoplasy resulting from allele size range constraints and poor SSR transferability among divergent taxa. The eucalypt genus Corymbia has been shown to be monophyletic using morphological characters, however, analyses of intergenic spacer sequences have resulted in contradictory hypotheses- showing the genus as either equivocal or paraphyletic. To assess SSR utility in higher order phylogeny in the family Myrtaceae, phylogenetic relationships of the bloodwood eucalypts Corymbia and related genera were investigated using eight polymorphic SSRs. Repeat size variation using the average square and Nei’s distance were congruent and showed Corymbia to be a monophyletic group, supporting morphological characters and a recent combination of the internal and external transcribed spacers dataset. SSRs are selectively neutral and provide data at multiple genomic regions, thus may explain why SSRs retained informative phylogenetic signals despite deep divergences. We show that where the problems of size-range constraints, high mutation rates and size homoplasy are addressed, SSRs might resolve problematic phylogenies of taxa that have diverged for as long as three million generations or 30 million years. Key word

    Synchronized dynamics of cortical neurons with time-delay feedback

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    The dynamics of three mutually coupled cortical neurons with time delays in the coupling are explored numerically and analytically. The neurons are coupled in a line, with the middle neuron sending a somewhat stronger projection to the outer neurons than the feedback it receives, to model for instance the relay of a signal from primary to higher cortical areas. For a given coupling architecture, the delays introduce correlations in the time series at the time-scale of the delay. It was found that the middle neuron leads the outer ones by the delay time, while the outer neurons are synchronized with zero lag times. Synchronization is found to be highly dependent on the synaptic time constant, with faster synapses increasing both the degree of synchronization and the firing rate. Analysis shows that presynaptic input during the interspike interval stabilizes the synchronous state, even for arbitrarily weak coupling, and independent of the initial phase. The finding may be of significance to synchronization of large groups of cells in the cortex that are spatially distanced from each other.Comment: 21 pages, 11 figure

    New insights into the classification and nomenclature of cortical GABAergic interneurons.

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    A systematic classification and accepted nomenclature of neuron types is much needed but is currently lacking. This article describes a possible taxonomical solution for classifying GABAergic interneurons of the cerebral cortex based on a novel, web-based interactive system that allows experts to classify neurons with pre-determined criteria. Using Bayesian analysis and clustering algorithms on the resulting data, we investigated the suitability of several anatomical terms and neuron names for cortical GABAergic interneurons. Moreover, we show that supervised classification models could automatically categorize interneurons in agreement with experts' assignments. These results demonstrate a practical and objective approach to the naming, characterization and classification of neurons based on community consensus

    An FPGA-based track finder for the L1 trigger of the CMS experiment at the high luminosity LHC

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    A new tracking system is under development for operation in the CMS experiment at the High Luminosity LHC. It includes an outer tracker which will construct stubs, built by correlating clusters in two closely spaced sensor layers for the rejection of hits from low transverse momentum tracks, and transmit them off-detector at 40 MHz. If tracker data is to contribute to keeping the Level-1 trigger rate at around 750 kHz under increased luminosity, a crucial component of the upgrade will be the ability to identify tracks with transverse momentum above 3 GeV/c by building tracks out of stubs. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are identified using a projective binning algorithm based on the Hough Transform. A hardware system based on the MP7 MicroTCA processing card has been assembled, demonstrating a realistic slice of the track finder in order to help gauge the performance and requirements for a full system. This paper outlines the system architecture and algorithms employed, highlighting some of the first results from the hardware demonstrator and discusses the prospects and performance of the completed track finder

    Measurement of the B+ and B-0 lifetimes and search for CP(T) violation using reconstructed secondary vertices

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    The lifetimes of the B+ and B-0 mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z(0) decays recorded at LEP. Z(0) --> b (b) over bar decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results aretau(B+) = 1.643 +/- 0.037 +/- 0.025 pstau(Bo) = 1.523 +/- 0.057 +/- 0.053 pstau(B+)/tau(Bo) = 1.079 +/- 0.064 +/- 0.041,where in each case the first error is statistical and the second systematic.A larger data sample of 3.1 million hadronic Z(o) decays has been used to search for CP and CPT violating effects by comparison of inclusive b and (b) over bar hadron decays, No evidence fur such effects is seen. The CP violation parameter Re(epsilon(B)) is measured to be Re(epsilon(B)) = 0.001 +/- 0.014 +/- 0.003and the fractional difference between b and (b) over bar hadron lifetimes is measured to(Delta tau/tau)(b) = tau(b hadron) - tau((b) over bar hadron)/tau(average) = -0.001 +/- 0.012 +/- 0.008

    A Measurement of Rb using a Double Tagging Method

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    The fraction of Z to bbbar events in hadronic Z decays has been measured by the OPAL experiment using the data collected at LEP between 1992 and 1995. The Z to bbbar decays were tagged using displaced secondary vertices, and high momentum electrons and muons. Systematic uncertainties were reduced by measuring the b-tagging efficiency using a double tagging technique. Efficiency correlations between opposite hemispheres of an event are small, and are well understood through comparisons between real and simulated data samples. A value of Rb = 0.2178 +- 0.0011 +- 0.0013 was obtained, where the first error is statistical and the second systematic. The uncertainty on Rc, the fraction of Z to ccbar events in hadronic Z decays, is not included in the errors. The dependence on Rc is Delta(Rb)/Rb = -0.056*Delta(Rc)/Rc where Delta(Rc) is the deviation of Rc from the value 0.172 predicted by the Standard Model. The result for Rb agrees with the value of 0.2155 +- 0.0003 predicted by the Standard Model.Comment: 42 pages, LaTeX, 14 eps figures included, submitted to European Physical Journal

    Search for the standard model Higgs boson at LEP

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