A γ-β frequency transition generated by inter-areal communication in the hippocampus in vitro

Gamma oscillations are generated in area CA3 of the hippocampus both in vitro and in vivo (Fisahn et al., 1998; Csicsvari et al., 2003). Here we present experimental and network simulation data to elucidate the mechanism of the generation of CA3-driven gamma and beta oscillations in area CA1. (1) The frequency of area CA1 output generated by gamma input from area CA3 was dependent on the degree of recruitment of CA1 principal cells. Passive involvement of area CA1 principal cells resulted in a gamma frequency oscillation. Active involvement of CA1 principal cells transformed this gamma oscillation into one at beta frequencies. (2) This beta oscillation in area CA1 was dependent on CA1 recurrent excitation. (3) It was also dependent on the temporal relationship between feedforward excitation of CA1 interneurons (by CA3 output) and feedback excitation of CA1 interneurons (by CA1 output). That is, the network beta oscillation in area CA1 depended on doublet firing of certain interneurons driven by area CA3. (4) The interneuron doublet rate during beta corresponded to whether or not dendrites are oriented horizontally or vertically: Interneurons with vertically oriented dendrites (eg. basket cells and - to a lesser extent - bistratified cells, all receiving input from CA3) fired considerably more doublets than interneurons with horizontally oriented dendrites (horizontal alveus cells or olm cells) which are not contacted by area CA3 and hardly ever fired doublets during beta. Taken together the findings demonstrate that different interneurons can serve different purposes during a given network oscillation, that single interneuron subtypes can mediate multiple network frequencies, and that the frequency of output from a cortical region serves to signal the degree of principal cell recruitment

A γ-β frequency transition generated by inter-areal communication in the hippocampus in vitro

Gamma oscillations are generated in area CA3 of the hippocampus both in vitro and in vivo (Fisahn et al., 1998; Csicsvari et al., 2003). Here we present experimental and network simulation data to elucidate the mechanism of the generation of CA3-driven gamma and beta oscillations in area CA1. (1) The frequency of area CA1 output generated by gamma input from area CA3 was dependent on the degree of recruitment of CA1 principal cells. Passive involvement of area CA1 principal cells resulted in a gamma frequency oscillation. Active involvement of CA1 principal cells transformed this gamma oscillation into one at beta frequencies. (2) This beta oscillation in area CA1 was dependent on CA1 recurrent excitation. (3) It was also dependent on the temporal relationship between feedforward excitation of CA1 interneurons (by CA3 output) and feedback excitation of CA1 interneurons (by CA1 output). That is, the network beta oscillation in area CA1 depended on doublet firing of certain interneurons driven by area CA3. (4) The interneuron doublet rate during beta corresponded to whether or not dendrites are oriented horizontally or vertically: Interneurons with vertically oriented dendrites (eg. basket cells and - to a lesser extent - bistratified cells, all receiving input from CA3) fired considerably more doublets than interneurons with horizontally oriented dendrites (horizontal alveus cells or olm cells) which are not contacted by area CA3 and hardly ever fired doublets during beta. Taken together the findings demonstrate that different interneurons can serve different purposes during a given network oscillation, that single interneuron subtypes can mediate multiple network frequencies, and that the frequency of output from a cortical region serves to signal the degree of principal cell recruitment

The position of graptolites within Lower Palaeozoic planktic ecosystems.

An integrated approach has been used to assess the palaeoecology of graptolites both as a discrete group and also as a part of the biota present within Ordovician and Silurian planktic realms. Study of the functional morphology of graptolites and comparisons with recent ecological analogues demonstrates that graptolites most probably filled a variety of niches as primary consumers, with modes of life related to the colony morphotype. Graptolite coloniality was extremely ordered, lacking any close morphological analogues in Recent faunas. To obtain maximum functional efficiency, graptolites would have needed varying degrees of coordinated automobility. A change in lifestyle related to ontogenetic changes was prevalent within many graptolite groups. Differing lifestyle was reflected by differing reproductive strategies, with synrhabdosomes most likely being a method for rapid asexual reproduction. Direct evidence in the form of graptolithophage 'coprolitic' bodies, as well as indirect evidence in the form of probable defensive adaptations, indicate that graptolites comprised a food item for a variety of predators. Graptolites were also hosts to a variety of parasitic organisms and provided an important nutrient source for scavenging organisms

A deep dive into the ecology of Gamay (Botany Bay, Australia): current knowledge and future priorities for this highly modified coastal waterway

Context: Gamay is a coastal waterway of immense social, cultural and ecological value. Since European settlement, it has become a hub for industrialisation and human modification. There is growing desire for ecosystem-level management of urban waterways, but such efforts are often challenged by a lack of integrated knowledge. Aim and methods: We systematically reviewed published literature and traditional ecological knowledge (TEK), and consulted scientists to produce a review of Gamay that synthesises published knowledge of Gamay’s aquatic ecosystem to identify knowledge gaps and future research opportunities. Key results: We found 577 published resources on Gamay, of which over 70% focused on ecology. Intertidal rocky shores were the most studied habitat, focusing on invertebrate communities. Few studies considered multiple habitats or taxa. Studies investigating cumulative human impacts, long-term trends and habitat connectivity are lacking, and the broader ecological role of artificial substrate as habitat in Gamay is poorly understood. TEK of Gamay remains a significant knowledge gap. Habitat restoration has shown promising results and could provide opportunities to improve affected habitats in the future. Conclusion and implications: This review highlights the extensive amount of knowledge that exists for Gamay, but also identifies key gaps that need to be filled for effective management

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

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters