30793 research outputs found
Sort by
Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at √ = 13 TeV
No full textA version of the article is available at arXiv:2401.14494v2 [hep-ex] (https://arxiv.org/abs/2401.14494). Comments: Submitted to Physical Review D. All figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/SMP-21-004 (CMS Public Pages). Report number: CMS-SMP-21-004, TOTEM-2024-001, CERN-EP-2023-279.The central exclusive production of charged-hadron pairs in collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high-* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, +−1.8 GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and +− are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities ||<2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton.SCOAP³
Si segregation deters prenucleation at the interfaces between liquid-aluminum and TiB2 substrates, the origin of ‘Si poisoning’
Get PDFSupplementary materials are available online at: https://www.sciencedirect.com/science/article/pii/S1359646224004809#sec0002 .The mechanism of ‘Si poisoning’ of Al-Ti-B based grain-refiners in Al-Si alloys has been a topic of intensive study for over half a century. We here investigate prenucleation of Al at the Si segregated interfaces between liquid Al and TiB2{0001} substrates using ab initio techniques. Our study reveals that chemical affinity between Ti and Si atoms empowers Si segregation at the Al(l)/substrate interface during solidification. The Si interfacial segregation curbs atomic ordering in the liquid Al adjacent to the substrate. Consequently, prenucleation of Al atoms at the Al(l)/{0001}TiB2 interface is deteriorated and thus, the subsequent nucleation process adversely affected, which causes the so-called ‘Si poisoning’ effect during the practice of grain refinement via inoculation with addition of TiB2 particles in Al-Si alloys.EPSRC (UK) under grant number EP/N007638/1 and EP/V011804/1
Guided Cooperation in Hierarchical Reinforcement Learning via Model-Based Rollout
Get PDFA preprint version of the article is available at arXiv:2309.13508v2 [cs.LG],
https://arxiv.org/abs/2309.13508 ([v2] Sat, 6 Apr 2024 17:07:13 UTC (4,747 KB)) . It is archived on this institutional repository but it has not been certified by peer review. Comments: Resubmitted a revised version, in which we provided more illustrative examples, corrected the writing errors, and added references.This article has supplementary downloadable material available at https://doi.org/10.1109/TNNLS.2024.3425809, provided by the authors.Goal-conditioned hierarchical reinforcement learning (HRL) presents a promising approach for enabling effective exploration in complex, long-horizon reinforcement learning (RL) tasks through temporal abstraction. Empirically, heightened interlevel communication and coordination can induce more stable and robust policy improvement in hierarchical systems. Yet, most existing goal-conditioned HRL algorithms have primarily focused on the subgoal discovery, neglecting interlevel cooperation. Here, we propose a novel goal-conditioned HRL framework named Guided Cooperation via Model-Based Rollout (GCMR; code is available at https://github.com/HaoranWang-TJ/GCMR_ACLG_official), aiming to bridge interlayer information synchronization and cooperation by exploiting forward dynamics. First, the GCMR mitigates the state-transition error within off-policy correction via model-based rollout, thereby enhancing sample efficiency. Second, to prevent disruption by the unseen subgoals and states, lower level Q -function gradients are constrained using a gradient penalty with a model-inferred upper bound, leading to a more stable behavioral policy conducive to effective exploration. Third, we propose a one-step rollout-based planning, using higher level critics to guide the lower level policy. Specifically, we estimate the value of future states of the lower level policy using the higher level critic function, thereby transmitting global task information downward to avoid local pitfalls. These three critical components in GCMR are expected to facilitate interlevel cooperation significantly. Experimental results demonstrate that incorporating the proposed GCMR framework with a disentangled variant of hierarchical reinforcement learning guided by landmarks (HIGL), namely, adjacency constraint and landmark-guided planning (ACLG), yields more stable and robust policy improvement compared with various baselines and significantly outperforms previous state-of-the-art (SOTA) algorithms
Learning multitasking in applied contexts
Get PDFThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThis thesis examined the learning of complex multitasking activities. Multitasking (MT) involves performing more than one task at a time and is commonplace in daily life.
Previous research has shown the benefits of dual-task training in comparison to single-task (ST) training, a phenomenon which has been termed Dual-Task Practice Advantage (DTPA). DTPA has been consistently demonstrated in MT studies comprising simple experimental designs; however, there is a lack of research into the ways in which people learn complex multitasking activities in real-life contexts, such as driving. Therefore, the aim of this thesis was to examine how people learn to multitask in everyday life and to identify potentially effective MT learning regimes.
In the first study, an online survey was conducted to explore 72 participants’ experiences of multitasking, their implicit and explicit multitasking learning strategies, and their opinions and attitudes towards MT. Participants’ data showed that, for everyday activities, particularly learning to drive, the most used and most preferred method was a mixture of MT and ST training conditions, the so-called mixed (Mix) learning regime.
In the second study, participants completed an online MT learning experiment in which they could choose their preferred learning regime (ST, MT, or Mix). The online MT study involved an auditory task with four differently pitched tones and a visual task with four different numbers. Participants were divided in two groups, the Fixed group trained in a pure MT regime, and the Choice group who had a free choice of training conditions. The results from both groups demonstrated significant learning effects, which did not differ significantly from each other. A further analysis of the Choice group showed a significant overall trend in choices (better performance leads to choosing more challenging tasks). The DTPA phenomenon was observed in the analysis of the MT learning effects, specifically in the positive correlation between the number of MT blocks chosen by participants and the MT learning effects obtained after the training phase.
The third study was conducted in a Driving Simulator Laboratory to compare three regimes (ST, MT, or Mix) and to identify the most effective MT learning regime. The study included four tasks – a driving task, a math task, a memory task and a monitoring task – performed separately as ST or in parallel as MT. Results showed that the most effective way to train a complex MT activity was the MT regime. The ST regime was the least effective. Moreover, the results supported the proposition that the DTPA phenomenon is applicable to learning challenging applied MT activities.
Overall, the results showed that while the most used and preferred MT learning approach was the Mix regime, training in MT is the most effective approach to learning MT activities
Thrombin Generation Is Associated With Extracellular Vesicle and Leukocyte Lipid Membranes in Atherosclerotic Cardiovascular Disease
Get PDFSupplemental Material isa available online at: https://doi.org/10.1161/ATVBAHA.124.320902 .BACKGROUND:
Clotting, leading to thrombosis, requires interactions of coagulation factors with the membrane aminophospholipids (aPLs) phosphatidylserine and phosphatidylethanolamine. Atherosclerotic cardiovascular disease (ASCVD) is associated with elevated thrombotic risk, which is not fully preventable using current therapies. Currently, the contribution of aPL to thrombotic risk in ASCVD is not known. Here, the aPL composition of circulating membranes in ASCVD of varying severity will be characterized along with the contribution of external facing aPL to plasma thrombin generation in patient samples.
METHODS:
Thrombin generation was measured using a purified factor assay on platelet, leukocyte, and extracellular vesicles (EVs) from patients with acute coronary syndrome (n=24), stable coronary artery disease (n=18), and positive risk factor (n=23) and compared with healthy controls (n=24). aPL composition of resting/activated platelet and leukocytes and EV membranes was determined using lipidomics.
RESULTS:
External facing aPLs were detected on EVs, platelets, and leukocytes, elevating significantly following cell activation. Thrombin generation was higher on the surface of EVs from patients with acute coronary syndrome than healthy controls, along with increased circulating EV counts. Thrombin generation correlated significantly with externalized EV phosphatidylserine, plasma EV counts, and total EV membrane surface area. In contrast, aPL levels and thrombin generation from leukocytes and platelets were not impacted by disease, although circulating leukocyte counts were higher in patients.
CONCLUSIONS:
The aPL membrane of EV supports an elevated level of thrombin generation in patient plasma in ASCVD. Leukocytes may also play a role although the platelet membrane did not seem to contribute. Targeting EV formation/clearance and developing strategies to prevent the aPL surface of EV interacting with coagulation factors represents a novel antithrombotic target in ASCVD.This work was supported by the Wellcome Trust (GW4-CAT fellowship to M.B. Protty, 216278/Z/19/Z) and the British Heart Foundation (program grant to P.W. Collins and V.B. O’Donnell, RG/F/20/110020). V.J. Tyrrell was supported, in part, by the Welsh Government/EU Ser Cymru Programme. A.A. Hajeyah is supported by a grant from the Kuwait University. P.V. Jenkins and A. Sharman were funded by the Government of Kingdom of Saudi Arabia
Integrating machine learning with a positioning mechanism for managing interference and power consumption in a multilayer fleet of unmanned aerial platforms
Get PDFData availability:
No datasets were generated or analysed during the current study.Acknowledgements:
This paper is an extended version of cited conference article [1]. Almalki, F.A., Angelides, M.C.: Deployment of an autonomous fleet of UAVs for Assessing the NDVI of Regenerative Farming, International Conference on Intelligent Computing, Communication, Networking and Services (ICCNS), Valencia, Spain, 2023, pp. 128–135, (2023). https://doi.org/10.1109/ICCNS58795.2023.10193565The soaring global demand for ubiquitous wireless connectivity, which epitomizes the digital era, can only be fulfilled with heterogenous networks that, increasingly, need to include aerial platform fleets for a more holistic approach. However, deploying aerial platforms to serve as a fleet would inevitably result in interference, especially for high frequency bands and increased power consumption. This work presents a framework that integrates Machine Learning with a fleet positioning mechanism to mitigate interference and reduce power consumption in a multilayer fleet of aerial platforms. In turn, this optimizes flight time in the short run and the sustainability of the holistic connectivity approach in the long run. Assessment of the post-optimisation Received Signal Strength Index reveals a 16% improvement to pre-optimisation. The work is validated with a proof-of-concept for smart agriculture.The research work presented in this manuscript was funded by Taif University in Saudi Arabia through Project No TU-DSPP-2024-139
Empirical Study of Autonomous Vehicles and V2V for Driver Acceptance in the UK
Get PDFTraffic levels have increased such that congestion is a major occurrence in many urban areas creating uncertainty around journey times as well as more incidents with significant damage and accidents placing lives at major risk. This has resulted in the onset of the development of mobile connective technology, such as vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) where vehicle manufacturers have begun to devise major ways to reduce the possibility of traffic delays and improve road safety. In this research, we supplement the Technology Acceptance Model (TAM) with driver context (from pervasive computing studies); technology attributes (compatibility; trust and safety) with some personal attributes to investigate nonprofessional and professional drivers’ perspectives. Based on a survey of 203 respondents, Structured Equation Modelling was used to analyse UK drivers’ perceptions of mobile connective technologies with findings of adoption factors for decision-makers at automotive manufactures
Standardisation efforts of ISO/TC 261 “Additive Manufacturing”. 24th Plenary Meeting of ISO/TC 261 “Additive Manufacturing”
Get PDFThe main objective of ISO/TC 261 is to standardise the processes of Additive Manufacturing, the process chains (Data, Materials, Processes, Hard- and Software, Applications), test procedures, quality parameters, supply agreements, environment, health and safety, fundamentals and vocabularies. This section provides readers with news regarding standardisation efforts of ISO/TC 261. Further up-to-date information regarding recently published documents, such as new standards, revised standards, and the status of standards, can be found in the ISO/TC261 webpages: https://www.iso.org/committee/629086.html and the committee webpages: https://committee.iso.org/sites/tc261/home/news.html.Not applicable
Comparative genomics of Metarhizium brunneum strains V275 and ARSEF 4556: unraveling intraspecies diversity
Get PDFData availability:
The genome of V275 has been submitted to the NCBI Genome Databank under BioProject Number PRJNA1057712 and Assembly Accession number GCA_039795395.1. The Supplementary Material for this article can be found online at “figshare” https://doi.org/10.6084/m9.figshare.26151751.v1 .
Supplemental material is available online at G3: https://academic.oup.com/g3journal/article/14/10/jkae190/7743223#485583742 .Entomopathogenic fungi belonging to the Order Hypocreales are renowned for their ability to infect and kill insect hosts, while their endophytic mode of life and the beneficial rhizosphere effects on plant hosts have only been recently recognized. Understanding the molecular mechanisms underlying their different lifestyles could optimize their potential as both biocontrol and biofertilizer agents, as well as the wider appreciation of niche plasticity in fungal ecology. This study describes the comprehensive whole genome sequencing and analysis of one of the most effective entomopathogenic and endophytic EPF strains, Metarhizium brunneum V275 (commercially known as Lalguard Met52), achieved through Nanopore and Illumina reads. Comparative genomics for exploring intraspecies variability and analyses of key gene sets were conducted with a second effective EPF strain, M. brunneum ARSEF 4556. The search for strain- or species-specific genes was extended to M. brunneum strain ARSEF 3297 and other species of genus Metarhizium, to identify molecular mechanisms and putative key genome adaptations associated with mode of life differences. Genome size differed significantly, with M. brunneum V275 having the largest genome amongst M. brunneum strains sequenced to date. Genome analyses revealed an abundance of plant-degrading enzymes, plant colonization-associated genes, and intriguing intraspecies variations regarding their predicted secondary metabolic compounds and the number and localization of Transposable Elements. The potential significance of the differences found between closely related endophytic and entomopathogenic fungi, regarding plant growth-promoting and entomopathogenic abilities, are discussed, enhancing our understanding of their diverse functionalities and putative applications in agriculture and ecology.The research work was supported by the Hellenic Foundation for Research and Innovation (HFRI) under the 3rd Call for HFRI PhD Fellowships (Fellowship Number: 5879)
Efficiency of Shoreline physical subsurface dam for mitigating the flooding of Sea level rise and saltwater in coastal aquifers
No full textData availability:
Upon request.Code availability:
Upon request.Fresh groundwater in arid and highly populated regions is limited. In coastal aquifers, the deterioration of fresh groundwater is accelerated by saltwater intrusion, primarily occurring through lateral encroachment and vertical movements in the proximity of discharging wells. Coastal regions have high salinity due to saline intrusion, where many abstraction wells are turned off by this high salinity, which leads to increased freshwater supply costs. This study investigates the performance of new approach using the shoreline subsurface dams (SSDs) for mitigating the saline water wedge in coastal aquifers, where the dams are installed at the shoreline (distance from shoreline = 0). Specifically, the current study's novelty is testing the effectiveness of SSDs by different relative heights ranging from 0.05 to 0.50 in the test case (Henry problem) and from 0.09 to 0.53 relative to the aquifer thickness in the field scale aquifer (Biscayne aquifer, Florida, USA). The results showed an exponential increase in salt repulsion for increasing SSDs height, reaching a maximum of + 0.70%, + 1.80%, + 3.25%, + 5.80%, + 10.45%, and + 18.40% for the dam height to aquifer thickness ratios of 0.09, 0.18, 0.26, 0.35, 0.44 and 0.53, respectively, in the field scale case. The SSDs increase the freshwater storage at the coastal zones where the low salinity occurs and reduces the freshwater supply cost. Despite the positive impact of height on repulsion, important factors such as economics, construction aspects, geographical suitability, and environmental impacts must be considered for real applications. This is crucial to develop feasible solutions applicable globally under the growing pressure of sea level rise.Alban Kuriqi is grateful for the Foundation for Science and Technology’s support through funding UIDB/04625/2020 from the research unit CERIS
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇