740 research outputs found

    VRU-TOO: Micro-Level Behavioural and Conflict Changes in the VRU-TOO Pilot Projects. Deliverable 15.

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    This report describes the results of an evaluation of pilot project pedestrian detection systems installed in three different European cities at in total six different sites. The implemented systems had the improvement of safety and comfort of pedestrians as objectives. The systems provided early detection of pedestrians approaching the crossing facility and detection of the presence of pedestrian on the crossing facility, allowing the onset of a pedestrian green phase or an extension of such a green phase. The evaluation involved the registration of pedestrian behaviour and pedestrian-vehicle encounters and conflicts. Pedestrian behaviour was recorded on videotape, conflicts were scored on the spot by trained observers. The behaviour recorded on videotape was later analysed using approach speed, nonnative behaviour and appropriate use of the crossing facilities as main indicators. In addition, pedestrian signal settings were recorded for each crossing. The evaluation design used a beforelafter measurement design with the after measurements being taken at least two weeks after the system implementation. The results indicated that although red light violations were reduced at some sites, they remained at a high level. The implementations had some positive effects on the normative behaviour of pedestrians. The percentage of pedestrians getting involved in encounters with motorized traffic was reduced at one site, increased at another and remained unchanged at the other sites. A significant reduction in conflicts was observed at several sites, but at other sites conflict occurrence remained unchanged. The system implementations had a very distinct positive effect on pedestrian delay. Required waiting times were reduced at all but one site and at some sites the reductions were substantial. Pedestrian comfort was also improved by an increase in the percentage of pedestrians arriving durhg the pedestrian green phase and the percentage being able to complete their crossing during pedestrian green. In summary, the evaluation study demonstrated that some safety effects and substantial effect on comfort were achieved by the implementation of the systems. The effects can be further optimized by selecting sites that fulfil specific requirements for successful implementation. Red light violation by pedestrian remains a serious safety problem and further studies should be undertaken how further reductions can be achieved by optimizing signal settings

    Anomaly Mediation, Fayet-Iliopoulos D-terms and the Renormalisation Group

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    We address renormalisation group evolution issues that arise in the Anomaly Mediated Supersymmetry Breaking scenario when the tachyonic slepton problem is resolved by Fayet-Iliopoulos term contributions. We present typical sparticle spectra both for the original formulation of this idea and an alternative using Fayet-Iliopoulos terms for a U(1) compatible with a straightforward GUT embedding.Comment: 20 pages, 2 figure

    Lasing on the D_2 line of sodium in helium atmosphere due to optical pumping on the D_1 line (up-conversion)

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    A new method is proposed to produce population inversion on transitions involving the ground state of atoms. The method is realized experimentally with sodium atoms. Lasing at the frequency corresponding to the sodium D_2 line is achieved in the presence of pump radiation resonant to the D_1 line with helium as a buffer gas.Comment: 4 pages, 4 figures, Late

    Do British birds conform to Bergmann's and Allen's rules? An analysis of body size variation with latitude for four species

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    Capsule: An analysis of body mass and wing length for four bird species shows trends broadly in line with predictions from Bergmann's and Allen's rules but with species- and sex-specific trends in terms of body size variation with latitude in Britain. Aims: To analyse body size characteristics for bird species with latitude in Britain and to test Bergmann’s and Allen’s rules (over a range of c. 740 km). Methods Body mass and wing length for four bird species (Blackbird Turdus merula, House Sparrow Passer domesticus, Robin Erithacus rubecula, and Song Thrush Turdus philomelos) were analysed using principal components regression analysis to investigate trends with latitude, longitude, or by sex and Julian day. Results: Evidence was found for latitudinal gradients in body mass for male Blackbird, female House Sparrow (both increasing in size northwards), and female Robin (decreasing in size northwards) and in wing length for female Robin and male Song Thrush (decreasing and increasing northwards, respectively). Conclusion: Trends were broadly in line with predictions from Bergmann's and Allen's rules except for Robin which had trends opposite to those expected. Differences in trends between sexes suggest a role for an interplay between natural and sexual selection with latitude that deserves further consideration

    Come back Marshall, all is forgiven? : Complexity, evolution, mathematics and Marshallian exceptionalism

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    Marshall was the great synthesiser of neoclassical economics. Yet with his qualified assumption of self-interest, his emphasis on variation in economic evolution and his cautious attitude to the use of mathematics, Marshall differs fundamentally from other leading neoclassical contemporaries. Metaphors inspire more specific analogies and ontological assumptions, and Marshall used the guiding metaphor of Spencerian evolution. But unfortunately, the further development of a Marshallian evolutionary approach was undermined in part by theoretical problems within Spencer's theory. Yet some things can be salvaged from the Marshallian evolutionary vision. They may even be placed in a more viable Darwinian framework.Peer reviewedFinal Accepted Versio

    Correction to: Effects of New Zealand blackcurrant extract on sport climbing performance

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    The authors would like to correct the following errors in the online publication of the article. Incorrect values for % changes for climb duration were provided in the abstract, results and discussion session. The  % changes in climb duration was 15% with intake of New Zealand blackcurrant extract and -15% for the placebo condition. This correction does not change the conclusions derived from the study

    Ab initio Quantum and ab initio Molecular Dynamics of the Dissociative Adsorption of Hydrogen on Pd(100)

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    The dissociative adsorption of hydrogen on Pd(100) has been studied by ab initio quantum dynamics and ab initio molecular dynamics calculations. Treating all hydrogen degrees of freedom as dynamical coordinates implies a high dimensionality and requires statistical averages over thousands of trajectories. An efficient and accurate treatment of such extensive statistics is achieved in two steps: In a first step we evaluate the ab initio potential energy surface (PES) and determine an analytical representation. Then, in an independent second step dynamical calculations are performed on the analytical representation of the PES. Thus the dissociation dynamics is investigated without any crucial assumption except for the Born-Oppenheimer approximation which is anyhow employed when density-functional theory calculations are performed. The ab initio molecular dynamics is compared to detailed quantum dynamical calculations on exactly the same ab initio PES. The occurence of quantum oscillations in the sticking probability as a function of kinetic energy is addressed. They turn out to be very sensitive to the symmetry of the initial conditions. At low kinetic energies sticking is dominated by the steering effect which is illustrated using classical trajectories. The steering effects depends on the kinetic energy, but not on the mass of the molecules. Zero-point effects lead to strong differences between quantum and classical calculations of the sticking probability. The dependence of the sticking probability on the angle of incidence is analysed; it is found to be in good agreement with experimental data. The results show that the determination of the potential energy surface combined with high-dimensional dynamical calculations, in which all relevant degrees of freedon are taken into account, leads to a detailed understanding of the dissociation dynamics of hydrogen at a transition metal surface.Comment: 15 pages, 9 figures, subm. to Phys. Rev.

    A detailed kinematic study of 3C 84 and its connection to Îł-rays

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    3C 84 (NGC 1275) is the bright radio core of the Perseus cluster. Even in the absence of strong relativistic effects, the source has been detected at Îł-rays up to TeV energies. Despite its intensive study, the physical processes responsible for the high-energy emission in the source remain unanswered. We present a detailed kinematics study of the source and its connection to Îł-ray emission. The subparsec-scale radio structure is dominated by slow-moving features in both the eastern and western lanes of the jet. The jet appears to have accelerated to its maximum speed within less than 125,000 gravitational radii. The fastest reliably detected speed in the jet was ∌0.9c. This leads to a minimum viewing angle to the source of ≳42° and a maximum Doppler factor of â‰Č1.5. Our analysis suggests the presence of multiple high-energy sites in the source. If Îł-rays are associated with kinematic changes in the jet, they are being produced in both eastern and western lanes in the jet. Three Îł-ray flares are contemporaneous with epochs where the slowly moving emission region splits into two subregions. We estimate the significance of these events being associated to be ∌2σ–3σ. We tested our results against theoretical predictions for magnetic-reconnection-induced mini-jets and turbulence and find them compatible.https://iopscience.iop.org/article/10.3847/1538-4357/abf6dd/pdfPublished versio

    Jet kinematics in the transversely stratified jet of 3C 84

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    3C 84 (NGC 1275) is one of the brightest radio sources in the millimetre radio bands, which led to a plethora of very-long-baseline interferometry (VLBI) observations at numerous frequencies over the years. They reveal a two-sided jet structure, with an expanding but not well-collimated parsec-scale jet, pointing southward. High-resolution millimetre-VLBI observations allow the study and imaging of the jet base on a sub-parsec scale. This could facilitate the investigation of the nature of the jet origin, also in view of the previously detected two-railed jet structure and east-west oriented core region seen withRadioAstronat 22 GHz. We produced VLBI images of this core and inner jet region, observed over the past twenty years at 15, 43, and 86 GHz. We determined the kinematics of the inner jet and ejected features at 43 and 86 GHz and compared their ejection times with radio andÎł-ray variability. For the moving jet features, we find an average velocity ofÎČappavg = 0.055−0.22c (ÎŒavg = 0.04 − 0.18 mas yr−1). From the time-averaged VLBI images at the three frequencies, we measured the transverse jet width along the bulk flow. On the ≀1.5 parsec scale, we find a clear trend of the jet width being frequency dependent, with the jet being narrower at higher frequencies. This stratification is discussed in the context of a spine-sheath scenario, and we compare it to other possible interpretations. From quasi-simultaneous observations at 43 and 86 GHz, we obtain spectral index maps, revealing a time-variable orientation of the spectral index gradient due to structural variability of the inner jet.https://www.aanda.org/articles/aa/pdf/2022/09/aa43343-22.pdfFirst author draf
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