1,020 research outputs found

    Dynamic Mechanically Interlocked Dendrimers: Amplification in Dendritic Dynamic Combinatorial Libraries

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    In the context of constructing nonclassical mechanically interlocked dendrimers by employing a convergent templation procedure, the “clipping” thermodynamic approach has been explored to introduce sterically bulky Fre´chet-type dendrons with successive generations [G0] to [G3] onto a trivalent ammonium ion core using a seven-component self-assembly via imine bond formation. Four generations of mechanically interlocked dendrimers up to a molecular weight over 8800 Da were synthesized in a one-pot reaction by simply mixing the seven components together. The dendrimers form in excellent yield (>90%). The mechanically interlocked core of the [G0]-[G2] dendrimers can be modified and transformed into kinetically stable dendrimers by reduction of the imine bonds with borane-tetrahydrofuran complex. Moreover, the dynamic nature of the thermodynamically controlled self-assembly process is employed to obtain three dynamic combinatorial libraries of dendrimers by the treatment of the dendrons [G0]-[G3] with the complementary components in one pot. The inherent modularity of the overall process should allow for the rapid and straightforward access to many other analogues of mechanically interlocked systems for which either the branched core or the dendritic periphery can be modified to suit the needs of any potential application of these molecules

    Middle Miocene to Pliocene History of Antarctica and the Southern Ocean

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    This chapter explores the Middle Miocene to Pliocene terrestrial and marine records of Antarctica and the Southern Ocean. The structure of the chapter makes a clear distinction between terrestrial and marine records as well as proximal (on or around Antarctica) and more distal records (Southern Ocean). Particular geographical regions are identified that reflect the areas for which the majority of palaeoenvironmental and palaeoclimatic information exist. Specifically, the chapter addresses the terrestrial sedimentary and fjordal environments of the Transantarctic Mountains and Lambert Glacier region, the terrestrial fossil record of Antarctic climate, terrestrial environments of West Antarctica, and the marine records of the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (APIS), as well as the marine record of the Southern Ocean. Previous and current studies focusing on modelling Middle Miocene to Pliocene climate, environments and ice sheets are discussed.Published401-4631.8. Osservazioni di geofisica ambientale3.8. Geofisica per l'ambientereserve

    Effective suckling in relation to naked maternal-infant body contact in the first hour of life: an observation study

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    Background Best practice guidelines to promote breastfeeding suggest that (i) mothers hold their babies in naked body contact immediately after birth, (ii) babies remain undisturbed for at least one hour and (iii) breastfeeding assistance be offered during this period. Few studies have closely observed the implementation of these guidelines in practice. We sought to evaluate these practices on suckling achievement within the first hour after birth. Methods Observations of seventy-eight mother-baby dyads recorded newborn feeding behaviours, the help received by mothers and birthing room practices each minute, for sixty minutes. Results Duration of naked body contact between mothers and their newborn babies varied widely from 1 to 60 minutes, as did commencement of suckling (range = 10 to 60 minutes). Naked maternal-infant body contact immediately after birth, uninterrupted for at least thirty minutes did not predict effective suckling within the first hour of birth. Newborns were four times more likely to sustain deep rhythmical suckling when their chin made contact with their mother’s breast as they approached the nipple (OR 3.8; CI 1.03 - 14) and if their mothers had given birth previously (OR 6.7; CI 1.35 - 33). Infants who had any naso-oropharyngeal suctioning administered at birth were six times less likely to suckle effectively (OR .176; CI .04 - .9). Conclusion Effective suckling within the first hour of life was associated with a collection of practices including infants positioned so their chin can instinctively nudge the underside of their mother’s breast as they approach to grasp the nipple and attach to suckle. The best type of assistance provided in the birthing room that enables newborns to sustain an effective latch was paying attention to newborn feeding behaviours and not administering naso-oropharyngeal suction routinely

    Angular distributions in tt¯H(H→bb¯) reconstructed events at the LHC

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    The associated production of a Higgs boson and a top-quark pair, tt¯H, in proton-proton collisions is addressed in this paper for a center of mass energy of 13TeV at the LHC. Dileptonic final states of tt¯H events with two oppositely charged leptons and four jets from the decays t→bW+→bℓ+νℓ, t¯→b¯W−→b¯ℓ−ν¯ℓ and h→bb¯, are used. Signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed by applying a kinematic fit. New angular distributions of the decay products as well as angular asymmetries are explored in order to improve discrimination of tt¯H signal events over the dominant irreducible background contribution, tt¯bb¯. Even after the full kinematic fit reconstruction of the events, the proposed angular distributions and asymmetries are still quite different in the tt¯H signal and the dominant background (tt¯bb¯).This work was partially supported by Fundação para a Ciência e Tecnologia, FCT (projects CERN/FP/123619/2011 and EXPL/FIS-NUC/1705/2013, grants SFRH/BI/52524/2014 and SFRH/BD/73438/2010, and contracts IF/00050/2013 and IF/00014/2012). The work of M.C.N. Fiolhais was supported by LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Portugal (grant PestIC/FIS/LA007/2013). The work of R.S. is supported in part by FCT under contract PTDC/FIS/117951/2010. Special thanks go to Juan Antonio Aguilar-Saavedra for all the fruitful discussions and a long term collaboration

    Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

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    The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

    Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

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    The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

    Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

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    Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

    Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

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    The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry
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