Australian Group on Antimicrobial Resistance (AGAR) Australian Gram-negative Sepsis Outcome Programme (GnSOP) Annual Report 2020

The Australian Group on Antimicrobial Resistance (AGAR) performs regular period-prevalence studies to monitor changes in antimicrobial resistance in selected enteric gram-negative pathogens. The 2020 survey was the eighth year to focus on bloodstream infections caused by Enterobacterales, and the sixth year in which Pseudomonas aeruginosa and Acinetobacter species were included. Eight thousand seven hundred and fifty-two isolates, comprising Enterobacterales (7,871, 89.9%), P. aeruginosa (771, 8.8%) and Acinetobacter species (110, 1.3%), were tested using commercial automated methods. The results were analysed using Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints (January 2021). Of the key resistances, resistance to the third-generation cephalosporin ceftriaxone was found in 13.5%/13.5% (CLSI/EUCAST criteria) of Escherichia coli and 8.7%/8.7% of Klebsiella pneumoniae. Resistance rates to ciprofloxacin were 16.1%/16.1% for E. coli; 9.9%/9.9% for K. pneumoniae; 5.8%/5.8% for Enterobacter cloacae complex; and 4.5%/8.1% for P. aeruginosa. Resistance rates to piperacillin-tazobactam were 2.5%/6.6%; 3.9%/12.5%; 16.9%/26.3%; and 5.5%/14.4% for the same four species respectively. Thirty-two isolates from 32 patients were shown to harbour at least one carbapenemase gene: 19 blaIMP-4, three blaGES-5, two blaNDM-1, two blaNDM-5, two blaOXA-48, two blaOXA-181, one blaIMI-1, and one blaOXA-23+NDM-1

Experimental investigation of high strain-rate, large-scale crack bridging behaviour of z-pin reinforced tapered laminates

Significant research exists on small-scale, quasi-static failure behaviour of Z-pinned composite laminates. However, little work has been conducted on large-scale, high strain-rate behaviour of Z-pinned composites at structural level. Small-scale testing is often at an insufficient scale to invoke the full crack bridging effects of the Z-pins. Full-scale testing on real components involves large length scales, complex geometries and resulting failure mechanisms that make it difficult to identify the specific effect of Z-pins on the component failure behaviour. A novel cantilever soft body impact test has been developed which is of sufficient scale to invoke large-scale delamination, such that behaviour in Z-pin arrays at high strain-rates can be studied. Laminates containing Z-pin arrays were subjected to soft-body gelatine impact in high-speed light gas-gun tests. Detailed fractographic investigation was carried out to investigate the dynamic failure behaviour of Z-pins at the microscopic scale

Experimental investigation of large-scale high-velocity soft-body impact on composite laminates

High-performance aerospace laminated composite structures manufactured from carbon-fibre prepreg are very susceptible to delamination failure under in-flight impact conditions. Much testing has been conducted at small length scales and quasi-static strain-rates to characterise the delamination performance of different material systems and loading scenarios. Testing at this scale and strain-rate is not representative of the failure conditions experienced by a laminate in a real impact event. Full-scale testing has also been conducted, but much of this is not in the open literature due to intellectual property constraints. Testing at this scale is also prohibitively expensive and involves complex failure mechanisms that cause difficulty in the analysis of associated failure behaviour. A novel test is presented which provides a simple, affordable alternative to full-scale testing but which invokes failure at sufficient scale and velocity to be representative of real component failure. This test design is experimentally validated through a series of soft-body gelatine impact tests using a light gas-gun facility. A fractographic analysis using scanning-electron microscopy was undertaken to examine microscopic failure behaviour, showing a possible reduction in crack mode-ratio during propagation

Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits

The WWgamma triple gauge boson coupling parameters are studied using p-pbar -> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were collected with the DO detector from an integrated luminosity of 162 pb^{-1} delivered by the Fermilab Tevatron Collider. The cross section times branching fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum) pb. The one-dimensional 95% confidence level limits on anomalous couplings are -0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events

We present a measurement of the top quark pair ttbar production cross section in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1} of data collected by the DO detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the ttbar content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1} (syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging

We present a measurement of the top quark pair ($t\bar{t}$) production cross section ($\sigma_{t\bar{t}}$) in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using 230 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the $t\bar{t}$ purity of the selected sample. For a top quark mass of 175 GeV, we measure $\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.)$ pb, in agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let

Search for W' bosons decaying to an electron and a neutrino with the D0 detector

This Letter describes the search for a new heavy charged gauge boson W' decaying into an electron and a neutrino. The data were collected with the D0 detector at the Fermilab Tevatron proton-antiproton Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of about 1 inverse femtobarn. Lacking any significant excess in the data in comparison with known processes, an upper limit is set on the production cross section times branching fraction, and a W' boson with mass below 1.00 TeV can be excluded at the 95% C.L., assuming standard-model-like couplings to fermions. This result significantly improves upon previous limits, and is the most stringent to date.Comment: submitted to Phys. Rev. Let

Search for a scalar or vector particle decaying into Zgamma in ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for a narrow scalar or vector resonance decaying into Zgamma with a subsequent Z decay into a pair of electrons or muons. The data for this search were collected with the D0 detector at the Fermilab Tevatron ppbar collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0) fb-1 of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (sigma x B) into Zgamma. These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c^2 to 2.5 (3.1) pb for a mass of 140 GeV/c^2.Comment: Published by Phys. Lett.