Inverse problem for the retarded field of an arbitrary moving charge

It is assumed that the Lienard-Wiechert fields of an arbitrary moving charge is measured or predefined as a function of time. The position of the charge is calculated as a function of the retarded time.Comment: LaTeX2e, 6 pages, published in Physics Letters

Metal-insulator transition at B=0 in an ultra-low density (rs=23r_{s}=23) two dimensional GaAs/AlGaAs hole gas

We have observed a metal-insulator transition in an ultra-low density two dimensional hole gas formed in a high quality GaAs-AlGaAs heterostructure at B=0. At the highest carrier density studied ($p_{s}=2.2x10^{10} cm^{-2}, r_{s}=16$) the hole gas is strongly metallic, with an exceptional mobility of $425,000 cm^{2}V^{-1}s^{-1}$. The low disorder and strength of the many-body interactions in this sample are highlighted by the observation of re-entrant metal insulator transitions in both the fractional ($\nu < 1/3$) and integer ($2 > \nu > 1$) quantum Hall regimes. On reducing the carrier density the temperature and electric field dependence of the resistivity show that the sample is still metallic at $p_{s}=1.3x10^{10} cm^{-2}$ ($r_{s}=21$), becoming insulating at $p_{s}{\simeq}1x10^{10} cm^{-2}$. Our results indicate that electron-electron interactions are dominant at these low densities, pointing to the many body origins of this metal-insulator transition. We note that the value of $r_{s}$ at the transition ($r_{s}=23 +/- 2$) is large enough to allow the formation of a weakly pinned Wigner crystal, and is approaching the value calculated for the condensation of a pure Wigner crystal.Comment: 4 pages, latex, 4 postscript figures, submitted to EP2DS-12 on 21st August 1997, to appear in Physica

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

A Very Early-Branching Staphylococcus aureus Lineage Lacking the Carotenoid Pigment Staphyloxanthin

Here we discuss the evolution of the northern Australian Staphylococcus aureus isolate MSHR1132 genome. MSHR1132 belongs to the divergent clonal complex 75 lineage. The average nucleotide divergence between orthologous genes in MSHR1132 and typical S. aureus is approximately sevenfold greater than the maximum divergence observed in this species to date. MSHR1132 has a small accessory genome, which includes the well-characterized genomic islands, νSAα and νSaβ, suggesting that these elements were acquired well before the expansion of the typical S. aureus population. Other mobile elements show mosaic structure (the prophage φSa3) or evidence of recent acquisition from a typical S. aureus lineage (SCCmec, ICE6013 and plasmid pMSHR1132). There are two differences in gene repertoire compared with typical S. aureus that may be significant clues as to the genetic basis underlying the successful emergence of S. aureus as a pathogen. First, MSHR1132 lacks the genes for production of staphyloxanthin, the carotenoid pigment that confers upon S. aureus its characteristic golden color and protects against oxidative stress. The lack of pigment was demonstrated in 126 of 126 CC75 isolates. Second, a mobile clustered regularly interspaced short palindromic repeat (CRISPR) element is inserted into orfX of MSHR1132. Although common in other staphylococcal species, these elements are very rare within S. aureus and may impact accessory genome acquisition. The CRISPR spacer sequences reveal a history of attempted invasion by known S. aureus mobile elements. There is a case for the creation of a new taxon to accommodate this and related isolates

Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology

notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations

Measurement of the View the tt production cross-section using eμ events with b-tagged jets in pp collisions at √s = 13 TeV with the ATLAS detector

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented

Search for strong gravity in multijet final states produced in pp collisions at √s=13 TeV using the ATLAS detector at the LHC

A search is conducted for new physics in multijet final states using 3.6 inverse femtobarns of data from proton-proton collisions at √s = 13TeV taken at the CERN Large Hadron Collider with the ATLAS detector. Events are selected containing at least three jets with scalar sum of jet transverse momenta (HT) greater than 1TeV. No excess is seen at large HT and limits are presented on new physics: models which produce final states containing at least three jets and having cross sections larger than 1.6 fb with HT > 5.8 TeV are excluded. Limits are also given in terms of new physics models of strong gravity that hypothesize additional space-time dimensions

Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt [ s ] = 13TeV

A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions

Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations