2,389 research outputs found

    A Bio-Logical Theory of Animal Learning

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    This article provides the foundation for a new predictive theory of animal learning that is based upon a simple logical model. The knowledge of experimental subjects at a given time is described using logical equations. These logical equations are then used to predict a subject’s response when presented with a known or a previously unknown situation. This new theory suc- cessfully anticipates phenomena that existing theories predict, as well as phenomena that they cannot. It provides a theoretical account for phenomena that are beyond the domain of existing models, such as extinction and the detection of novelty, from which “external inhibition” can be explained. Examples of the methods applied to make predictions are given using previously published results. The present theory proposes a new way to envision the minimal functions of the nervous system, and provides possible new insights into the way that brains ultimately create and use knowledge about the world

    Overview of using visualisation in programming learning

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    There is a high demand for mechanisms that support programming teaching, particularly in finding a solution to the bottleneck in programming education. Nowadays, different methods of teaching can support the learning process and motivate students to learn. These methods improve the thinking and creativity that lead to defining and analysing the problem of supporting programming learning to devise ideal solutions. Approaches such as visualising the code or using a memory diagram to trace the program’s execution have made a vital contribution to the process of teaching and learning how to program. The purpose of this paper is to provide an overview of studies that have been conducted in visualisation to support programming learning. Moreover, tools that follow the visualisation and memory-referencing approach will be investigated in this paper

    Diet of the west coast rock lobster Jasus Lalandii: Influence of lobster size, sex, capture depth, latitude and moult stage

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    Diets of male and female West Coast rock lobster Jasus lalandii in South Africa were compared across a large size range of 10–85 mm carapace length (CL). The diets of male rock lobsters were compared betweentwo different depths, different seasons, across the moult cycle, and among eight sites along the South-Western Cape coast. There was no significant difference in diet between male and female rock lobsters for any of thesize-classes examined. Male rock lobsters showed large differences in diet between small and large size-classes. The diet of small lobsters (80mm CL) fed on few species, and fish and ribbed mussels were their most abundant prey items. There were some dietary differences between individuals captured at 20 m and those collected at 50 m, but these differences were less marked than between the two sampling sites (the Knol and Olifantsbos). There was seasonal variation in diet at the Dassen Island and Olifantsbos sites. Cannibalism was highest during the moulting periods. Gut fullness varied seasonally at Dassen Island, and was consistently high at Olifantsbos. However, the proportion of the population feeding showed marked seasonal trends at both sites, tracking the commercial catch per unit effort of rock lobster. Ribbed mussels were a ubiquitous and dominant component of the diet at the eight sites sampled. However, south of Dassen Island, black mussels Choromytilus meridionalis were scarce in the diet of rock lobster and sponges predominated. Gut fullness was lowest at the northernmostsites

    A nocturnal atmospheric loss of CH2I2 in the remote marine boundary layer.

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    Ocean emissions of inorganic and organic iodine compounds drive the biogeochemical cycle of iodine and produce reactive ozone-destroying iodine radicals that influence the oxidizing capacity of the atmosphere. Di-iodomethane (CH2I2) and chloro-iodomethane (CH2ICl) are the two most important organic iodine precursors in the marine boundary layer. Ship-borne measurements made during the TORERO (Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOC) field campaign in the east tropical Pacific Ocean in January/February 2012 revealed strong diurnal cycles of CH2I2 and CH2ICl in air and of CH2I2 in seawater. Both compounds are known to undergo rapid photolysis during the day, but models assume no night-time atmospheric losses. Surprisingly, the diurnal cycle of CH2I2 was lower in amplitude than that of CH2ICl, despite its faster photolysis rate. We speculate that night-time loss of CH2I2 occurs due to reaction with NO3 radicals. Indirect results from a laboratory study under ambient atmospheric boundary layer conditions indicate a k CH2I2+NO3 of ≤4 × 10-13 cm3 molecule-1 s-1; a previous kinetic study carried out at ≤100 Torr found k CH2I2+NO3 of 4 × 10-13 cm3 molecule-1 s-1. Using the 1-dimensional atmospheric THAMO model driven by sea-air fluxes calculated from the seawater and air measurements (averaging 1.8 +/- 0.8 nmol m-2 d-1 for CH2I2 and 3.7 +/- 0.8 nmol m-2 d-1 for CH2ICl), we show that the model overestimates night-time CH2I2 by >60 % but reaches good agreement with the measurements when the CH2I2 + NO3 reaction is included at 2-4 × 10-13 cm3 molecule-1 s-1. We conclude that the reaction has a significant effect on CH2I2 and helps reconcile observed and modeled concentrations. We recommend further direct measurements of this reaction under atmospheric conditions, including of product branching ratios.LJC acknowledges NERC (NE/J00619X/1) and the National Centre for Atmospheric Science (NCAS) for funding. The laboratory work was supported by the NERC React-SCI (NE/K005448/1) and RONOCO (NE/F005466/1) grants.This is the final version of the article. It was first available from Springer via http://dx.doi.org/10.1007/s10874-015-9320-

    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

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    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

    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

    Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using √s=8 TeV proton-proton collision data

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    A search for squarks and gluinos in final states containing high-p T jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in s√=8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb−1. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with tan β = 30, A 0 = −2m 0 and μ > 0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector

    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

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    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

    Search for dark matter in events with heavy quarks and missing transverse momentum in pp collisions with the ATLAS detector

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    This article reports on a search for dark matterpair production in association with bottom or top quarks in20.3fb−1ofppcollisions collected at√s=8TeVbytheATLAS detector at the LHC. Events with large missing trans-verse momentum are selected when produced in associationwith high-momentum jets of which one or more are identifiedas jets containingb-quarks. Final states with top quarks areselected by requiring a high jet multiplicity and in some casesa single lepton. The data are found to be consistent with theStandard Model expectations and limits are set on the massscale of effective field theories that describe scalar and tensorinteractions between dark matter and Standard Model par-ticles. Limits on the dark-matter–nucleon cross-section forspin-independent and spin-dependent interactions are alsoprovided. These limits are particularly strong for low-massdark matter. Using a simplified model, constraints are set onthe mass of dark matter and of a coloured mediator suitableto explain a possible signal of annihilating dark matter

    Measurement of the charge asymmetry in dileptonic Decays of top quark pairs in pp collisions at √ s = 7 TeV using the ATLAS detector

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    A measurement of the top-antitop (tt) charge asymmetry is presented using data corresponding to an integrated luminosity of 4.6 fb −1 of LHC pp collisions at a centre- of-mass energy of 7 TeV collected by the ATLAS detector. Events with two charged leptons, at least two jets and large missing transverse momentum are selected. Two observables are studied: A tt/C, based on the reconstructed tt final state. The asymmetries are measured to be A ll/C = 0.024 +/- 0.015 (stat.) +/- 0.009 (syst.) Att/C = 0.021 +/- 0.025 (stat.) +/- 0.017 (syst.) The measured values are in agreement with the Standard Model predictions
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