We describe the use of near-infrared spectroscopy (NIRS) as a suitable means of assessing hemodynamic changes in the cerebral cortex of awake and behaving monkeys. NIRS can be applied to animals ...performing cognitive tasks in conjunction with electrophysiological methods, thus offering the possibility of investigating cortical neurovascular coupling in cognition. Because it imposes fewer constraints on behavior than fMRI, NIRS appears more practical than fMRI for certain studies of cognitive neuroscience on the primate cortex. In the present study, NIRS and field potential signals were simultaneously recorded from the association cortex (posterior parietal and prefrontal) of monkeys performing two delay tasks, one spatial and the other non-spatial. Working memory was accompanied by an increase in oxygenated hemoglobin mirrored by a decrease in deoxygenated hemoglobin. Both the trends and the amplitudes of these changes differed by task and by area. Field potential records revealed slow negative potentials that preceded the task trials and persisted during their memory period. The negativity during that period was greater in prefrontal than in parietal cortex. Between tasks, the potential differences were less pronounced than the hemodynamic differences. The present feasibility study lays the groundwork for future correlative studies of cognitive function and neurovascular coupling in the primate.
Many extensions of the Standard Model predict the existence of charged heavy long-lived particles, such as
-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be ...moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex provides sensitivity to metastable particles with lifetimes from 0.6 ns to 30 ns. A search for such particles with the ATLAS detector at the Large Hadron Collider is presented, based on a data sample corresponding to an integrated luminosity of Formula: see text fbFormula: see text of
collisions at Formula: see text TeV. No significant deviation from the Standard Model background expectation is observed, and lifetime-dependent upper limits on
-hadrons and chargino production are set. Gluino
-hadrons with 10 ns lifetime and masses up to 1185 GeV are excluded at 95 Formula: see text confidence level, and so are charginos with 15 ns lifetime and masses up to 482 GeV.
A search for Higgs boson pair production Formula: see text is performed with 19.5 fbFormula: see text of proton-proton collision data at Formula: see text TeV, which were recorded by the ATLAS ...detector at the Large Hadron Collider in 2012. The decay products of each Higgs boson are reconstructed as a high-momentum Formula: see text system with either a pair of small-radius jets or a single large-radius jet, the latter exploiting jet substructure techniques and associated
-tagged track-jets. No evidence for resonant or non-resonant Higgs boson pair production is observed. The data are interpreted in the context of the Randall-Sundrum model with a warped extra dimension as well as the two-Higgs-doublet model. An upper limit on the cross-section for Formula: see text of 3.2 (2.3) fb is set for a Kaluza-Klein graviton Formula: see text mass of 1.0 (1.5) TeV, at the 95 % confidence level. The search for non-resonant Standard Model
production sets an observed 95 % confidence level upper limit on the production cross-section Formula: see text of 202 fb, compared to a Standard Model prediction of Formula: see text fb.
A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at Formula: see text TeV from
collisions corresponding to an integrated ...luminosity of 20.3 fbFormula: see textare examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from Formula: see text to Formula: see text are searched for. No signal candidate events are observed, and 95 % confidence level cross-section upper limits are interpreted as lower mass limits for a Drell-Yan production model. The mass limits range between 660 and 785 GeV.
Double-differential three-jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of Formula: see text using the ATLAS detector at the large hadron collider. ...The measurements are presented as a function of the three-jet mass Formula: see text, in bins of the sum of the absolute rapidity separations between the three leading jets Formula: see text. Invariant masses extending up to 5 TeV are reached for Formula: see text. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of Formula: see text. Jets are identified using the anti-Formula: see text algorithm with two different jet radius parameters, Formula: see text and Formula: see text. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values.
A search for Higgs boson decays to invisible particles is performed using 20.3 Formula: see text of
collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the Large ...Hadron Collider. The process considered is Higgs boson production in association with a vector boson (Formula: see text or
) that decays hadronically, resulting in events with two or more jets and large missing transverse momentum. No excess of candidates is observed in the data over the background expectation. The results are used to constrain
production followed by
decaying to invisible particles for the Higgs boson mass range Formula: see text GeV. The 95 % confidence-level observed upper limit on Formula: see text varies from 1.6 pb at 115 GeV to 0.13 pb at 300 GeV. Assuming Standard Model production and including the Formula: see text contribution as signal, the results also lead to an observed upper limit of 78 % at 95 % confidence level on the branching ratio of Higgs bosons decays to invisible particles at a mass of 125 GeV.
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