1,179 research outputs found
Train schedule coordination at an interchange station through agent negotiation
In open railway markets, coordinating train schedules at an interchange station requires negotiation between two independent train operating companies to resolve their operational conflicts. This paper models the stakeholders as software agents and proposes an agent negotiation model to study their interaction. Three negotiation strategies have been devised to represent the possible objectives of the stakeholders, and they determine the behavior in proposing offers to the proponent. Empirical simulation results confirm that the use of the proposed negotiation strategies lead to outcomes that are consistent with the objectives of the stakeholders
Asymmetric ephaptic inhibition between compartmentalized olfactory receptor neurons.
In the Drosophila antenna, different subtypes of olfactory receptor neurons (ORNs) housed in the same sensory hair (sensillum) can inhibit each other non-synaptically. However, the mechanisms underlying this underexplored form of lateral inhibition remain unclear. Here we use recordings from pairs of sensilla impaled by the same tungsten electrode to demonstrate that direct electrical ("ephaptic") interactions mediate lateral inhibition between ORNs. Intriguingly, within individual sensilla, we find that ephaptic lateral inhibition is asymmetric such that one ORN exerts greater influence onto its neighbor. Serial block-face scanning electron microscopy of genetically identified ORNs and circuit modeling indicate that asymmetric lateral inhibition reflects a surprisingly simple mechanism: the physically larger ORN in a pair corresponds to the dominant neuron in ephaptic interactions. Thus, morphometric differences between compartmentalized ORNs account for highly specialized inhibitory interactions that govern information processing at the earliest stages of olfactory coding
Arepo-MCRT: Monte Carlo Radiation Hydrodynamics on a Moving Mesh
We present Arepo-MCRT, a novel Monte Carlo radiative transfer (MCRT)
radiation-hydrodynamics (RHD) solver for the unstructured moving-mesh code
Arepo. Our method is designed for general multiple scattering problems in both
optically thin and thick conditions. We incorporate numerous efficiency
improvements and noise reduction schemes to help overcome efficiency barriers
that typically inhibit convergence. These include continuous absorption and
energy deposition, photon weighting and luminosity boosting, local packet
merging and splitting, path-based statistical estimators, conservative
(face-centered) momentum coupling, adaptive convergence between time steps,
implicit Monte Carlo algorithms for thermal emission, and discrete-diffusion
Monte Carlo techniques for unresolved scattering, including a novel advection
scheme. We primarily focus on the unique aspects of our implementation and
discussions of the advantages and drawbacks of our methods in various
astrophysical contexts. Finally, we consider several test applications
including the levitation of an optically thick layer of gas by trapped infrared
radiation. We find that the initial acceleration phase and revitalized second
wind are connected via self-regulation of the RHD coupling, such that the RHD
method accuracy and simulation resolution each leave important imprints on the
long-term behavior of the gas.Comment: 23 pages, 20 figures, ApJ, in pres
Synthesis, characterisation and performance of (TiO2)(0.18)(SiO2)(0.82) xerogel catalysts
The synthesis of high surface area xerogels has been achieved using the sol-gel route. Heptane washing was used during the stages of drying to minimise capillary pressures and hence preserve pore structure and maximise the surface area. SAXS data have identified that heptane washing during drying, in general, results in a preservation of the pore structure and surface areas of up to 450 m(2) g(-1). O-17 NMR showed that Ti is fully mixed into the silica network in all of the samples. XANES data confirm that reversible 4-fold Ti sites are more prevalent in samples with high surface areas, as expected. The calcined xerogels were tested for their catalytic activity using the epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) as a test reaction, with excellent selectivities and reasonable percentage conversions. FT-IR spectroscopy has revealed that the catalytic activity is correlated with the intensity of the Si-O-Ti signal, after accounting for variations in Si-OH and Si-O-Si. The most effective catalyst was produced with heptane washing, a calcination temperature of 500 degreesC, and a heating rate of 5 degreesC min(-1)
Stereotactic Body Radiotherapy re-irradiation for locally recurrent rectal cancer: outcomes and toxicity
Background:
Stereotactic body radiotherapy (SBRT) has emerged as a potential therapeutic option for locally recurrent rectal cancer (LRRC) but contemporaneous clinical data is limited. We aimed to evaluate the local control, toxicity and survival outcomes in a cohort of patients previously treated with neoadjuvant pelvic radiotherapy for non-metastatic LRRC, now treated with SBRT.
Methods:
Inoperable rectal cancer patients with ≤ 3 sites of pelvic recurrence and > 6 months since prior pelvic radiotherapy were identified from a prospective registry over 4 years. SBRT dose was 30Gy in 5 fractions, daily or alternate days, using cumulative organ at risk dose constraints. Primary outcome was local control (LC). Secondary outcomes were progression free survival (PFS), overall survival (OS), toxicity and patient reported Quality of Life scores (QoL) using EQ-VAS tool.
Results:
30 patients (35 targets) were included. Median GTV size was 14.3cm3. 27/30 (90%) previously received 45-50.4Gy in 25/28 fractions, with 10% receiving an alternative prescription. All patients received the planned re-irradiation SBRT dose. The median FU was 24.5 months (IQR 17.8 – 28.8). The 1-year LC was 84.9% (95% CI 70.6 – 99) and a 2-year LC was 69% (95% CI 51.8 – 91.9). The median PFS was 12.1 months (95% 8.6 – 17.66) and median OS was 28.3 months (95% CI 17.88 – 39.5 months). No patient experienced >G2 acute toxicity and only 1 patient experienced late G3 toxicity. Patient reported QoL outcomes were improved at 3 months following SBRT (Δ EQ-VAS, +10 points, Wilcoxon signed rank, p=0.009).
Conclusion:
Our study demonstrates that, for small volume pelvic disease relapses from rectal cancer, re-irradiation with 30Gy in 5 fractions is well tolerated and achieves an excellent balance between high local control rates with limited toxicity
TMT telescope structure system: design and development progress report
The Thirty Meter Telescope (TMT) project has revised the reference optical configuration from an Aplanatic Gregorian to a Ritchey-Chrétien design. This paper describes the revised telescope structural design and outlines the design methodology for achieving the dynamic performance requirements derived from the image jitter error budget. The usage of transfer function tools which incorporate the telescope structure system dynamic characteristics and the control system properties is described along with the optimization process for the integrated system. Progress on the structural design for seismic considerations is presented. Moreover, mechanical design progress on the mount control system hardware such as the hydrostatic bearings and drive motors, cable wraps and safety system hardware such as brakes and absorbers are also presented
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