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Impacts of bridging nodes on the epidemic activation mechanisms
Authors:
José Carlos M. Silva,
Diogo H. Silva,
Wesley Cota,
Francisco A. Rodrigues,
Silvio C. Ferreira
Abstract:
Bridging nodes, which connect critical components of a network, play an important role in maintaining structural integrity and facilitating communication within the network, representing indirect yet relevant connections. Epidemic triggering mechanisms in networks often involve long-range mutual activation of hubs, mediated by paths composed of low-degree nodes. While low-degree nodes are abundant…
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Bridging nodes, which connect critical components of a network, play an important role in maintaining structural integrity and facilitating communication within the network, representing indirect yet relevant connections. Epidemic triggering mechanisms in networks often involve long-range mutual activation of hubs, mediated by paths composed of low-degree nodes. While low-degree nodes are abundant in networks, their role in bridging central nodes in epidemic activation mechanisms has not been thoroughly analyzed. Starting with a backbone network with a power-law degree distribution, we investigate the role of adding degree-2 bridging nodes that are preferentially attached to hubs. Our findings reveal that bridging nodes can mediate an indirect feedback interaction between hubs that modifies the epidemic localization and activation mechanisms of the epidemic processes with recurrent infections. In particular, the collective activation observed in the presence of waning immunity, which produces a finite epidemic threshold in power-law networks with degree exponent $γ>3$, is altered to a localized activation with a vanishing threshold. Our results are supported by the non-backtracking matrix properties that emerge in the recurrent dynamical message-passing theory.
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Submitted 16 November, 2025;
originally announced November 2025.
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Enhanced ammonia electro-oxidation reaction on platinum-iron oxide catalyst assisted by MagnetoElectroCatalysis
Authors:
Caio Machado Fernandes,
Eduardo M. Rodrigues,
Odivaldo C. Alves,
Flavio Garcia,
Yutao Xing,
Mauro C. Santos,
Julio Cesar M. Silva
Abstract:
Ammonia poses significant environmental challenges due to its role in water pollution, contributing to eutrophication and several detrimental environmental and ecological issues. Addressing the efficient removal or conversion of ammonia is, therefore, critical. Among various methods, the ammonia electro-oxidation reaction stands out due to its potential for direct energy conversion and environment…
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Ammonia poses significant environmental challenges due to its role in water pollution, contributing to eutrophication and several detrimental environmental and ecological issues. Addressing the efficient removal or conversion of ammonia is, therefore, critical. Among various methods, the ammonia electro-oxidation reaction stands out due to its potential for direct energy conversion and environment remediation. Here, we synthesize platinum-iron oxide magnetic nanoparticles (Pt-MNP) as electrocatalysts and apply an alternating magnetic field (AMF) to enhance their activity.. The AMF generates localized heat via Néel relaxation, accelerating ammonia oxidation kinetics at the catalytic surface.. Compared to conventional electro-oxidation methods, this technique demonstrates superior efficiency and stability, offering a promising alternative for ammonia treatment. This work uses the concept of MagnetoElectroCatalysis, showcasing the synergy between magnetic fields and the electrochemical process, leveraging the AMF to induce localized heating within the nanocatalyst, thereby improving its catalytic activity as shown in cyclic voltammetry and chronoamperometry experiments. By combining nanocatalyst design with innovative AMF application, this study provides a new avenue for enhancing electrochemical reactions, with broad implications for environmental remediation and sustainable energy solutions.
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Submitted 19 May, 2025;
originally announced May 2025.
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Magnetic field-enhanced two-electron oxygen reduction reaction using CeMnCo nanoparticles supported on different carbonaceous matrices
Authors:
Caio Machado Fernandes,
Joao Paulo C. Moura,
Aline B. Trench,
Odivaldo C. Alves,
Yutao Xing,
Marcos R. V. Lanza,
Julio Cesar M. Silva,
Mauro C. Santos
Abstract:
The current study illustrates the successful synthesis of Ce$_{1.0}$Mn$_{0.9}$Co$_{0.1}$ nanoparticles, characterized through XRD, EPR, magnetization curves, and TEM/HRTEM/EDX analyses. These nanoparticles were then loaded into the carbon Vulcan XC72 and the carbon Printex L6 matrices in varying amounts (1, 3, 5, and 10% w/w) via wet impregnation method to fabricate electrocatalysts for the 2-elec…
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The current study illustrates the successful synthesis of Ce$_{1.0}$Mn$_{0.9}$Co$_{0.1}$ nanoparticles, characterized through XRD, EPR, magnetization curves, and TEM/HRTEM/EDX analyses. These nanoparticles were then loaded into the carbon Vulcan XC72 and the carbon Printex L6 matrices in varying amounts (1, 3, 5, and 10% w/w) via wet impregnation method to fabricate electrocatalysts for the 2-electron ORR. Before experimentation, the material was characterized via XPS and contact angle measurements. The electrochemical results produced significant findings, indicating that the electrocatalysts with the nanostructures modifying both carbon blacks notably augmented currents in rotating ring-disk electrode measurements, signifying enhanced selectivity for H$_2$O$_2$ production. Moreover, our research underscored the significant impact of Magnetic Field-Enhanced Electrochemistry, employing a constant magnetic field strength of 2000 Oe, on 2-electron ORR experiments. Particularly noteworthy were the observed results surpassing the ones without the magnetic field, demonstrating heightened currents and improved selectivity for H$_2$O$_2$ production (more than 90 %) facilitated by CeMnCo nanoparticles. These significant findings in electrocatalytic efficiency have practical implications, suggesting the potential for developing more efficient and selective catalysts for the 2-electron ORR.
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Submitted 19 May, 2025;
originally announced May 2025.
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Magnetic field-enhanced oxygen reduction reaction for electrochemical hydrogen peroxide production with different cerium oxide nanostructures
Authors:
Caio Machado Fernandes,
Aila O. Santos,
Vanessa S. Antonin,
Joao Paulo C. Moura,
Aline B. Trench,
Odivaldo C. Alves,
Yutao Xing,
Julio Cesar M. Silva,
Mauro C. Santos
Abstract:
We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). It was used a continuous magnetic field (2000 Oe) for the first time in the literature. The best results were for 5% (w/w) CeO2 for all three different morphologies, more than doubling the ring current,…
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We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). It was used a continuous magnetic field (2000 Oe) for the first time in the literature. The best results were for 5% (w/w) CeO2 for all three different morphologies, more than doubling the ring current, enhancing the hydrogen peroxide selectivity from 51% (Vulcan XC-72) to 84-89%, and modifying the onset potential to lesser negative values. The presence of the magnetic field led to even higher ring currents with 5% (w/w) CeO$_2$, H$_2$O$_2$ selectivity from 54% (Vulcan XC-72) to 88-96% and changing even more the onset potential. Those results were correlated with the Zeeman effect, the Lorentz force, generating magnetohydrodynamic effects, the Kelvin force, and the formation of Bound Magnetic Polarons. This pioneering research introduces an innovative approach, highlighting the potential of an external continuous magnetic field.
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Submitted 19 May, 2025;
originally announced May 2025.
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Optimization of LYSO crystals and SiPM parameters for the CMS MIP timing detector
Authors:
F. Addesa,
T. Anderson,
P. Barria,
C. Basile,
A. Benaglia,
R. Bertoni,
A. Bethani,
R. Bianco,
A. Bornheim,
G. Boldrini,
A. Boletti,
A. Bulla,
M. Campana,
B. Cardwell,
P. Carniti,
F. Cetorelli,
F. De Guio,
K. De Leo,
F. De Riggi,
J. Dervan,
E. Fernandez,
A. Gaile,
M. Gallinaro,
A. Ghezzi,
C. Gotti
, et al. (46 additional authors not shown)
Abstract:
For the High-Luminosity (HL-LHC) phase, the upgrade of the Compact Muon Solenoid (CMS) experiment at CERN will include a novel MIP Timing Detector (MTD). The central part of MTD, the barrel timing layer (BTL), is designed to provide a measurement of the time of arrival of charged particles with a precision of 30 ps at the beginning of HL-LHC, progressively degrading to 60 ps while operating in an…
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For the High-Luminosity (HL-LHC) phase, the upgrade of the Compact Muon Solenoid (CMS) experiment at CERN will include a novel MIP Timing Detector (MTD). The central part of MTD, the barrel timing layer (BTL), is designed to provide a measurement of the time of arrival of charged particles with a precision of 30 ps at the beginning of HL-LHC, progressively degrading to 60 ps while operating in an extremely harsh radiation environment for over a decade. In this paper we present a comparative analysis of the time resolution of BTL module prototypes made of LYSO:Ce crystal bars read out by silicon photo-multipliers (SiPMs). The timing performance measured in beam test campaigns is presented for prototypes with different construction and operation parameters, such as different SiPM cell sizes (15, 20, 25 and 30 $\rm μm$), SiPM manufacturers and crystal bar thicknesses. The evolution of time resolution as a function of the irradiation level has been studied using non-irradiated SiPMs as well as SiPMs exposed up to $2\times 10^{14}~n_{eq}/cm^2$ fluence. The key parameters defining the module time resolution such as SiPM characteristics (gain, photon detection efficiency, radiation induced dark count rate) and crystal properties (light output and dimensions) are discussed. These results have informed the final choice of the MTD barrel sensor configuration and offer a unique starting point for the design of future large-area scintillator-based timing detectors in either low or high radiation environments.
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Submitted 11 October, 2024;
originally announced October 2024.
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Consequences of non-Markovian healing processes on epidemic models with recurrent infections on networks
Authors:
José Carlos M. Silva,
Diogo H. Silva,
Francisco A. Rodrigues,
Silvio C. Ferreira
Abstract:
Infections diseases are marked by recovering time distributions which can be far from the exponential one associated with Markovian/Poisson processes, broadly applied in epidemic compartmental models. In the present work, we tackled this problem by investigating a susceptible-infected-recovered-susceptible model on networks with $η$ independent infectious compartments (SI$_η$RS), each one with a M…
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Infections diseases are marked by recovering time distributions which can be far from the exponential one associated with Markovian/Poisson processes, broadly applied in epidemic compartmental models. In the present work, we tackled this problem by investigating a susceptible-infected-recovered-susceptible model on networks with $η$ independent infectious compartments (SI$_η$RS), each one with a Markovian dynamics, that leads to a Gamma-distributed recovering times. We analytically develop a theory for the epidemic lifespan on star graphs with a center and $K$ leaves showing that the epidemic lifespan scales with a non-universal power-law $τ_{K}\sim K^{α/μη}$ plus logarithm corrections, where $α^{-1}$ and $μ^{-1}$ are the mean waning immunity and recovering times, respectively. Compared with standard SIRS dynamics with $η=1$ and the same mean recovering time, the epidemic lifespan on star graphs is severely reduced as the number of stages increases. In particular, the case $η\rightarrow\infty$ leads to a finite lifespan. Numerical simulations support the approximated analytical calculations. For the SIS dynamics, numerical simulations show that the lifespan increases exponentially with the number of leaves, with a nonuniversal rate that decays with the number of infectious compartments. We investigated the SI$_η$RS dynamics on power-law networks with degree distribution $P(K)\sim k^{-γ}$. When $γ<5/2$, the epidemic spreading is ruled by a maximum $k$-core activation, the alteration of the hub activity time does not alter either the epidemic threshold or the localization pattern. For $γ>3$, where hub mutual activation is at work, the localization is reduced but not sufficiently to alter the threshold scaling with the network size. Therefore, the activation mechanisms remain the same as in the case of Markovian healing.
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Submitted 1 October, 2024;
originally announced October 2024.
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TOFHIR2: The readout ASIC of the CMS Barrel MIP Timing Detector
Authors:
E. Albuquerque,
M. Araújo,
A. Benaglia,
A. Boletti,
R. Bugalho,
T. Coutinho,
F. De Guio,
P. Faccioli,
L. Ferramacho,
M. Firlej,
T. Fiutowski,
R. Francisco,
M. Gallinaro,
A. Ghezzi,
J. Hollar,
M. Idzik,
H. Legoinha,
N. Leonardo,
C. Leong,
M. T. Lucchini,
M. Malberti,
G. Marozzo,
G. Da Molin,
J. Moron,
T. Niknejad
, et al. (16 additional authors not shown)
Abstract:
The CMS detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL respectively, providing precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillation crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30-60 ps for MIP signals at a rate of 2.…
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The CMS detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL respectively, providing precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillation crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30-60 ps for MIP signals at a rate of 2.5 Mhit/s per channel is expected along the HL-LHC lifetime. We present an overview of the TOFHIR2 requirements and design, simulation results and measurements with TOFHIR2 ASICs. The measurements of TOFHIR2 associated to sensor modules were performed in different test setups using internal test pulses or blue and UV laser pulses emulating the signals expected in the experiment. The measurements show a time resolution of 24 ps initially during Beginning of Operation (BoO) and 58 ps at End of Operation (EoO) conditions, matching well the BTL requirements. We also showed that the time resolution is stable up to the highest expected MIP rate. Extensive radiation tests were performed, both with x-rays and heavy ions, showing that TOFHIR2 is not affected by the radiation environment during the experiment lifetime.
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Submitted 1 April, 2024;
originally announced April 2024.
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Integration of thermo-electric coolers into the CMS MTD SiPM arrays for operation under high neutron fluence
Authors:
A. Bornheim,
W. Lustermann,
K. Stachon,
G. Reales Gutiérrez,
A. Benaglia,
F. De Guio,
A. Ghezzi,
M. T. Lucchini,
M. Malberti,
S. Palluotto,
T. Tabarelli de Fatis,
M. Benettoni,
R. Carlin,
M. Tosi,
R. Rossin,
P. Meridiani,
R. Paramatti,
F. Santanastasio,
J. C. Silva,
J. Varela,
A. Heering,
A. Karneyeu,
Y. Musienko,
M. Wayne,
T. Anderson
, et al. (5 additional authors not shown)
Abstract:
The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of $30-60$ ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about…
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The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of $30-60$ ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about $2\times10^{14}$ 1 MeV(Si) Eqv. n/cm$^2$, that will be integrated over a decade of operation of the High Luminosity Large Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to this level of radiation have shown a strong increase in dark count rate and radiation damage effects that also impact their gain and photon detection efficiency. For this reason during operations the whole detector is cooled down to about $-35^{\circ}$C. In this paper we illustrate an innovative and cost-effective solution to mitigate the impact of radiation damage on the timing performance of the detector, by integrating small thermo-electric coolers (TECs) on the back of the SiPM package. This additional feature, fully integrated as part of the SiPM array, enables a further decrease in operating temperature down to about $-45^{\circ}$C. This leads to a reduction by a factor of about two in the dark count rate without requiring additional power budget, since the power required by the TEC is almost entirely offset by a decrease in the power required for the SiPM operation due to leakage current. In addition, the operation of the TECs with reversed polarity during technical stops of the accelerator can raise the temperature of the SiPMs up to $60^{\circ}$C (about $50^{\circ}$C higher than the rest of the detector), thus accelerating the annealing of radiation damage effects and partly recovering the SiPM performance.
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Submitted 23 August, 2023; v1 submitted 1 June, 2023;
originally announced June 2023.
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Comparison of theoretical approaches for epidemic processes with waning immunity in complex networks
Authors:
José Carlos M. Silva,
Diogo H. Silva,
Francisco A. Rodrigues,
Silvio C. Ferreira
Abstract:
The role of waning immunity in basic epidemic models on networks has been undervalued while being noticeable fundamental for real epidemic outbreaks. One central question is which mean-field approach is more accurate in describing the epidemic dynamics. We tackled this problem considering the susceptible-infected-recovered-susceptible (SIRS) epidemic model on networks. Two pairwise mean-field theo…
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The role of waning immunity in basic epidemic models on networks has been undervalued while being noticeable fundamental for real epidemic outbreaks. One central question is which mean-field approach is more accurate in describing the epidemic dynamics. We tackled this problem considering the susceptible-infected-recovered-susceptible (SIRS) epidemic model on networks. Two pairwise mean-field theories, one based on recurrent dynamical message-passing (rDMP) and the other on the pair quenched mean-field theory (PQMF), are compared with extensive stochastic simulations on large networks of different levels of heterogeneity. For waning immunity times longer than or comparable with the recovering time, rDMP outperforms PQMF theory on power-law networks with degree distribution $P(k) \sim k^{-γ}$. In particular, for $γ> 3$, the epidemic threshold observed in simulations is finite, in qualitative agreement with rDMP, while PQMF leads to an asymptotically null threshold. The critical epidemic prevalence for $γ> 3$ is localized in a finite set of vertices in the case of the PQMF theory. In contrast, the localization happens in a subextensive fraction of the network in rDMP theory. Simulations, however, indicate that localization patterns of the actual epidemic lay between the two mean-field theories, and improved theoretical approaches are necessary to understanding the SIRS dynamics.
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Submitted 1 June, 2022;
originally announced June 2022.
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Test beam characterization of sensor prototypes for the CMS Barrel MIP Timing Detector
Authors:
R. Abbott,
A. Abreu,
F. Addesa,
M. Alhusseini,
T. Anderson,
Y. Andreev,
A. Apresyan,
R. Arcidiacono,
M. Arenton,
E. Auffray,
D. Bastos,
L. A. T. Bauerdick,
R. Bellan,
M. Bellato,
A. Benaglia,
M. Benettoni,
R. Bertoni,
M. Besancon,
S. Bharthuar,
A. Bornheim,
E. Brücken,
J. N. Butler,
C. Campagnari,
M. Campana,
R. Carlin
, et al. (174 additional authors not shown)
Abstract:
The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about…
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The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about 30 ps at the beginning of operation, and degrading to 50-60 ps at the end of the detector lifetime as a result of radiation damage. In this work, we present the results obtained using a 120 GeV proton beam at the Fermilab Test Beam Facility to measure the time resolution of unirradiated sensors. A proof-of-concept of the sensor layout proposed for the barrel region of the MTD, consisting of elongated crystal bars with dimensions of about 3 x 3 x 57 mm$^3$ and with double-ended SiPM readout, is demonstrated. This design provides a robust time measurement independent of the impact point of the MIP along the crystal bar. We tested LYSO:Ce bars of different thickness (2, 3, 4 mm) with a geometry close to the reference design and coupled to SiPMs manufactured by Hamamatsu and Fondazione Bruno Kessler. The various aspects influencing the timing performance such as the crystal thickness, properties of the SiPMs (e.g. photon detection efficiency), and impact angle of the MIP are studied. A time resolution of about 28 ps is measured for MIPs crossing a 3 mm thick crystal bar, corresponding to an MPV energy deposition of 2.6 MeV, and of 22 ps for the 4.2 MeV MPV energy deposition expected in the BTL, matching the detector performance target for unirradiated devices.
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Submitted 16 July, 2021; v1 submitted 15 April, 2021;
originally announced April 2021.
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Boosting spatial resolution by incorporating periodic boundary conditions into single-distance hard-x-ray phase retrieval
Authors:
David M. Paganin,
Vincent Favre-Nicolin,
Alessandro Mirone,
Alexander Rack,
Julie Villanova,
Margie P. Olbinado,
Vincent Fernandez,
Julio C. da Silva,
Daniele Pelliccia
Abstract:
A simple coherent-imaging method due to Paganin et al. is widely employed for phase-amplitude reconstruction of samples using a single paraxial x-ray propagation-based phase-contrast image. The method assumes that the sample-to-detector distance is sufficiently small for the associated Fresnel number to be large compared to unity. The algorithm is particularly effective when employed in a tomograp…
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A simple coherent-imaging method due to Paganin et al. is widely employed for phase-amplitude reconstruction of samples using a single paraxial x-ray propagation-based phase-contrast image. The method assumes that the sample-to-detector distance is sufficiently small for the associated Fresnel number to be large compared to unity. The algorithm is particularly effective when employed in a tomographic setting, using a single propagation-based phase-contrast image for each projection. Here we develop a simple extension of the method, which improves the reconstructed contrast of very fine sample features. This provides first-principles motivation for boosting fine spatial detail associated with high Fourier frequencies, relative to the original method, and was inspired by several recent works employing empirically-obtained Fourier filters to a similar end.
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Submitted 29 August, 2020; v1 submitted 7 May, 2020;
originally announced May 2020.
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A hierarchical approach for modelling X-ray beamlines. Application to a coherent beamline
Authors:
Manuel Sanchez del Rio,
Rafael Celestre,
Mark Glass,
Giovanni Pirro,
Juan Reyes-Herrera,
Ray Barrett,
Julio Cesar da Silva,
Peter Cloetens,
Xianbo Shi,
Luca Rebuffi
Abstract:
We consider different approaches to simulate a modern X-ray beamline. Several methodologies with increasing complexity are applied to discuss the relevant parameters that quantify the beamline performance. Parameters such as flux, dimensions and intensity distribution of the focused beam and coherence properties are obtained from simple analytical calculations to sophisticated computer simulations…
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We consider different approaches to simulate a modern X-ray beamline. Several methodologies with increasing complexity are applied to discuss the relevant parameters that quantify the beamline performance. Parameters such as flux, dimensions and intensity distribution of the focused beam and coherence properties are obtained from simple analytical calculations to sophisticated computer simulations using ray-tracing and wave optics techniques. A latest-generation X-ray nanofocusing beamline for coherent applications (ID16A at the ESRF) has been chosen to study in detail the issues related to highly demagnifying synchrotron sources and exploiting the beam coherence. The performance of the beamline is studied for two storage rings: the old ESRF-1 (emittance 4000~pm) and the new ESRF-EBS (emittance 150~pm). In addition to traditional results in terms of flux and beam sizes, an innovative study on the partial coherence properties based on the propagation of coherent modes is presented. The different algorithms and methodologies are implemented in the software suite OASYS. Those are discussed with emphasis placed upon the their benefits and limitations of each.
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Submitted 17 June, 2019;
originally announced June 2019.
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Online energy discrimination at DAQ front-end level on pixelated TOF-PET systems
Authors:
C. Zorraquino,
L. Ferramacho,
R. Bugalho,
M. Zvolsky,
T. Niknejad,
J. C. Silva,
S. Tavernier,
P. Guerra,
J. Varela,
A. Santos
Abstract:
Pixelated PET systems produce higher count rates as they integrate several detecting channels per detector module. An increased data flow from the detectors posses higher needs on the bandwidth requirements. We aim to optimize the bandwidth usage efficiency by filtering on the fly the detected events with non valid energies. PET systems with a SiPM-ASIC readout scheme are being extensively used to…
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Pixelated PET systems produce higher count rates as they integrate several detecting channels per detector module. An increased data flow from the detectors posses higher needs on the bandwidth requirements. We aim to optimize the bandwidth usage efficiency by filtering on the fly the detected events with non valid energies. PET systems with a SiPM-ASIC readout scheme are being extensively used to get enhanced images on Time-Of-Flight PET scanners. These kind of digital readout systems are specially interesting for the application of on-line processing techniques given the ease of access to each detected event digital information. This study purses the analysis of on-line processing techniques on the DAQ front-end level (on-detector electronics) for pixelated PET systems with SiPM-ASIC readout. In particular, we worked with a tunable on-line energy discriminating stage. For the optimization of its hardwired internal limits we analyzed the system energy space. We explored different solutions dependent or not on the system's energy calibration. Results obtained through the different filter versions confirm the minimal resources consumption of such processing techniques implemented at DAQ front-end level. Our experiences showed how the filtering process reduces the bandwidth needs excluding from the data stream all non valid energy events and thus improving the system sensitivity under saturation conditions. Additionally, these experiments highlight how setting proper energy limits we ensure the preservation of the system performance, which maintains its original energy and time resolution. Under the light of these findings, we see a great potential on the application of on-line processing techniques for Time-Of-Flight PET at the DAQ font-end level (on-detector electronics) and so we envisaged more complex processing methods.
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Submitted 4 April, 2018; v1 submitted 6 February, 2018;
originally announced February 2018.
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Soliton generation by internal tidal beams impinging on a pycnocline: laboratory experiments
Authors:
Matthieu J. Mercier,
Manikandan Mathur,
Louis Gostiaux,
Theo Gerkema,
Jorge M. Magalhães,
José C. B. Da Silva,
Thierry Dauxois
Abstract:
In this paper, we present the first laboratory experiments that show the generation of internal solitary waves by the impingement of a quasi-two-dimensional internal wave beam on a pycnocline. These experiments were inspired by observations of internal solitary waves in the deep ocean from synthetic aperture radar (SAR) imagery, where this so-called mechanism of 'local generation' was argued to be…
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In this paper, we present the first laboratory experiments that show the generation of internal solitary waves by the impingement of a quasi-two-dimensional internal wave beam on a pycnocline. These experiments were inspired by observations of internal solitary waves in the deep ocean from synthetic aperture radar (SAR) imagery, where this so-called mechanism of 'local generation' was argued to be at work, here in the form of internal tidal beams hitting the thermocline. Nonlinear processes involved here are found to be of two kinds. First, we observe the generation of a mean flow and higher harmonics at the location where the principal beam reflects from the surface and pycnocline; their characteristics are examined using particle image velocimetry (PIV) measurements. Second, we observe internal solitary waves that appear in the pycnocline, detected with ultrasonic probes; they are further characterized by a bulge in the frequency spectrum, distinct from the higher harmonics. Finally, the relevance of our results for understanding ocean observations is discussed.
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Submitted 20 May, 2015;
originally announced May 2015.
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Asymmetric Data Acquisition System for an Endoscopic PET-US Detector
Authors:
Carlos Zorraquino,
Ricardo Bugalho,
Manuel Rolo,
Jose C. Silva,
Viesturs Vecklans,
Rui Silva,
Catarina Ortigao,
Jorge A. Neves,
Stefaan Tavernier,
Pedro Guerra,
Joao Varela
Abstract:
According to current prognosis studies of pancreatic cancer, survival rate nowadays is still as low as 6% mainly due to late detections. Taking into account the location of the disease within the body and making use of the level of miniaturization in radiation detectors that can be achieved at the present time, EndoTOFPET-US collaboration aims at the development of a multimodal imaging technique f…
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According to current prognosis studies of pancreatic cancer, survival rate nowadays is still as low as 6% mainly due to late detections. Taking into account the location of the disease within the body and making use of the level of miniaturization in radiation detectors that can be achieved at the present time, EndoTOFPET-US collaboration aims at the development of a multimodal imaging technique for endoscopic pancreas exams that combines the benefits of high resolution metabolic information from Time-Of- Flight (TOF) Positron Emission Tomography (PET) and anatomical information from ultrasound (US). A system with such capabilities calls for an application-specific high-performance Data Acquisition System (DAQ) able to control and readout data from two different detectors.
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Submitted 3 November, 2015; v1 submitted 16 June, 2014;
originally announced June 2014.
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Computational Modelling with Modellus: An Enhancement Vector for the General University Physics Course
Authors:
Rui Gomes Neves,
Jorge Carvalho Silva,
Vítor Duarte Teodoro
Abstract:
In this paper we present a step forward to improve general physics as an educational experience: the implementation of a new course component composed by innovative workshop activities based on computational modelling in the general physics course taken by first year biomedical engineering students at the Faculty of Sciences and Technology of the New Lisbon University. The activities were created…
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In this paper we present a step forward to improve general physics as an educational experience: the implementation of a new course component composed by innovative workshop activities based on computational modelling in the general physics course taken by first year biomedical engineering students at the Faculty of Sciences and Technology of the New Lisbon University. The activities were created as interactive modelling experiments with Modellus, a computer software tool designed to construct and explore mathematical models based on functions, iterations and differential equations. Special emphasis was given to cognitive conflicts in the understanding of physical concepts, to the manipulation of multiple representations of mathematical models and to the interplay between analytical and numerical solutions of physical problems. In this work we describe these computational modelling activities and their educational aims. We also discuss their effective impact on the students learning of key physical and mathematical concepts of the course.
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Submitted 23 June, 2010;
originally announced June 2010.
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Improving Learning in Science and Mathematics with Exploratory and Interactive Computational Modelling
Authors:
Rui Gomes Neves,
Jorge Carvalho Silva,
Vítor Duarte Teodoro
Abstract:
Scientific research involves mathematical modelling in the context of an interactive balance between theory, experiment and computation. However, computational methods and tools are still far from being appropriately integrated in the high school and university curricula in science and mathematics. In this chapter, we present a new way to develop computational modelling learning activities in scie…
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Scientific research involves mathematical modelling in the context of an interactive balance between theory, experiment and computation. However, computational methods and tools are still far from being appropriately integrated in the high school and university curricula in science and mathematics. In this chapter, we present a new way to develop computational modelling learning activities in science and mathematics which may be fruitfully adopted by high school and university curricula. These activities may also be a valuable instrument for the professional development of teachers. Focusing on mathematical modelling in the context of physics, we describe a selection of exploratory and interactive computational modelling activities in introductory mechanics and discuss their impact on student learning of key physical and mathematical concepts in mechanics.
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Submitted 23 June, 2010;
originally announced June 2010.