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Development of a predictive capability of short-pulse laser-driven broadband x-ray radiography
摘要： High intensity, short-pulse laser interaction with a solid metal target produces broadband hard x rays potentially for various applications of x-ray radiography. Here experimental benchmarking of numerical modelling for short-pulse laser-driven broadband x-ray radiography is presented. Angular dependent x-ray spectra are first calculated with a hybrid particle-in-cell code, Large Scale Plasma (LSP), using fast electron parameters inferred from an analysis of measured bremsstrahlung signals. Subsequently, a calculated x-ray spectrum in the direction of radiography is used in photon transport calculations using a Monte Carlo code, Particle and Heavy Ion Transport code System (PHITS), to simulate a radiographic image including a modelled 3D test object, an x-ray attenuation filter and an image plate detector. Simulated radiographic images are compared with measurements obtained in an experiment using a 50-TW Leopard short-pulse laser at the University of Nevada Reno. Results show that simulations reproduce the experimental images well for three different attenuation filters (plastic, aluminium, and brass), while one-dimensional transmission profiles for the plastic and aluminium filters are quantitatively in good agreement. The modelling approach established in this work could be used as a predictive tool to simulate radiographic images of complex 3D solid objects at any arbitrary angular position or to optimize experimental components such as the source spectrum, x-ray attenuation filters and a detector type depending on a radiographic object without carrying out radiographic experiments.
关键词： Monte Carlo simulations,hybrid particle-in-cell,broadband x-ray radiography,short-pulse laser-produced x rays
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Desynchronization of Pulsed Driving in the Formation of Soliton Kerr Frequency Combs
摘要： MRED is a Python-language scriptable computer application that simulates radiation transport. It is the computational engine for the on-line tool CRèME-MC. MRED is based on c++ code from Geant4 with additional Fortran components to simulate electron transport and nuclear reactions with high precision. We provide a detailed description of the structure of MRED and the implementation of the simulation of physical processes used to simulate radiation effects in electronic devices and circuits. Extensive discussion and references are provided that illustrate the validation of models used to implement specific simulations of relevant physical processes. Several applications of MRED are summarized that demonstrate its ability to predict and describe basic physical phenomena associated with irradiation of electronic circuits and devices. These include effects from single particle radiation (including both direct ionization and indirect ionization effects), dose enhancement effects, and displacement damage effects. MRED simulations have also helped to identify new single event upset mechanisms not previously observed by experiment, but since confirmed, including upsets due to muons and energetic electrons.
关键词： single event upset,single event effects,total ionizing dose,radiation effects,Displacement damage,Monte Carlo,radiation transport,MRED
更新于2025-09-23 15:21:01
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Unimolecular FRET sensors: Simple linker designs and properties
摘要： Protein activation and deactivation is central to a variety of biological mechanisms, including cellular signaling and transport. Unimolecular fluorescent resonance energy transfer (FRET) probes are a class of fusion protein sensors that allow biologists to visualize using an optical microscope whether specific proteins are activated due to the presence nearby of small drug-like signaling molecules, ligands or analytes. Often such probes comprise a donor fluorescent protein attached to a ligand binding domain, a sensor or reporter domain attached to the acceptor fluorescent protein, with these ligand binding and sensor domains connected by a protein linker. Various choices of linker type are possible ranging from highly flexible proteins to hinge-like proteins. It is also possible to select donor and acceptor pairs according to their corresponding F¨oster radius, or even to mutate binding and sensor domains so as to change their binding energy in the activated or inactivated states. The focus of the present work is the exploration through simulation of the impact of such choices on sensor performance.
关键词： FRET Microscopy,Fusion Proteins,Diagnostics,Monte Carlo Simulation,Coarse Graining,Cellular Signaling
更新于2025-09-23 15:21:01
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On the imprecisions that may be induced when applying the Blaugrund approximation for the analysis of Doppler-shift attenuation lifetime measurements
摘要： It is shown that the Blaugrund approximation could have led to some imprecise lifetime determinations in the past which used the Doppler-shift attenuation method (DSAM). Comparison with Monte Carlo simulations of the slowing-down process show that there is not an easy way to judge using them on the reliability of old data.
关键词： Lineshapes analysis in DSAM measurements,Monte Carlo simulations,Lifetime determination,Blaugrund approximation
更新于2025-09-23 15:21:01
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Stepped morphology on vicinal 3C- and 4H-SiC (0001) faces: A Kinetic Monte Carlo study
摘要： Stepped morphologies on vicinal 3C- and 4H-SiC (0001) surfaces with the miscut toward [1100] or [1120] directions have been studied with a three-dimensional kinetic Monte Carlo model. In the model, a three-dimensional lattice mesh was established based on the crystal lattice of 3C-and 4H-SiC to fix the positions of atoms and interatomic bonding. Periodic boundary conditions were applied in the lateral direction while helicoidal boundary conditions were used in the direction of crystal growth. Events, such as adatoms attachment, detachment and interlayer transport at the step edges, and adatoms adsorption and diffusion on the terraces were considered in the model. Effects of Ehrlich-Schwoebel barriers at downward step edges and incorporation barriers at upwards step edges were also considered. Moreover, the atoms of silicon and carbon were treated as the minimal diffusing species independently to achieve more elaborate information for the behavior of atoms in the crystal surface. The simulation results showed that multiple-height steps were formed on the vicinal 4H-SiC (0001) surfaces, whereas single bilayer-height stepped morphologies were observed on the vicinal 3C-SiC (0001) surfaces. Furthermore, zigzag shaped edges were observed for both of 3C- and 4H-SiC (0001) surfaces with the miscut toward [1120] direction. At last, the formation mechanism of the stepped morphology was also analyzed.
关键词： Computer simulation,Crystal morphology,Silicon Carbide,Surfaces,Kinetic Monte Carlo Model
更新于2025-09-23 15:21:01
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: <i>Ab initio</i> and Monte Carlo approaches
摘要： The effects of nonmagnetic impurity doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO2 are investigated by means of density functional theory calculations and Monte Carlo simulations. Density functional theory calculations show that replacing up to 30% of Cr3+ ions by Ga3+ ones does not significantly affect the remaining Cr-Cr superexchange interactions. Monte Carlo simulations show that CuCr1?xGaxO2 preserves its magnetoelectric properties up to x ≈ 0.15 with a spiral ordering, while it becomes disordered at higher fractions. Antiferromagnetic transition shifts towards lower temperatures with increasing x and eventually disappears at x ≈ 0.2. Our simulations show that Ga3+ doping increases the Curie-Weiss temperature of CuCr1?xGaxO2, which agrees well with experimental observations. Moreover, our results show that the incommensurate ground-state configuration is destabilized by Ga3+ doping under zero applied field associated with an increase of frustration. Finally, coupling between noncollinear magnetic ordering and electric field is reported for x ≤ 0.15 through simulating P -E hysteresis loops, which leads to ferroelectricity in the extended inverse Dzyaloshinskii-Moriya model.
关键词： CuCrO2,multiferroic,Monte Carlo simulations,ferroelectric properties,magnetic properties,density functional theory,delafossite,Ga doping
更新于2025-09-23 15:21:01
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Electron dynamics in low pressure capacitively coupled radio frequency discharges
摘要： In low temperature plasmas, the interaction of the electrons with the electric field is an important current research topic that is relevant for many applications. Particularly, in the low pressure regime ((cid:1)10 Pa), electrons can traverse a distance that may be comparable to the reactor dimensions without any collisions. This causes “nonlocal,” dynamics which results in a complicated space- and time-dependence and a strong anisotropy of the distribution function. Capacitively coupled radio frequency (CCRF) discharges, which operate in this regime, exhibit extremely complex electron dynamics. This is because the electrons interact with the space- and time-dependent electric field, which arises in the plasma boundary sheaths and oscillates at the applied radio frequency. In this tutorial paper, the fundamental physics of electron dynamics in a low pressure electropositive argon discharge is investigated by means of particle-in-cell/Monte Carlo collisions simulations. The interplay between the fundamental plasma parameters (densities, fields, currents, and temperatures) is explained by analysis (aided by animations) with respect to the spatial and temporal dynamics. Finally, the rendered picture provides an overview of how electrons gain and lose their energy in CCRF discharges.
关键词： low pressure,particle-in-cell/Monte Carlo collisions simulations,electron dynamics,plasma parameters,capacitively coupled radio frequency discharges
更新于2025-09-23 15:21:01
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Study of the germanium dead layer influence on HP(Ge) detector efficiency by Monte Carlo simulation
摘要： Introduction The dead layer thickness provided by the manufacturer increases with the aging of the HPGe detector; the increase of dead layer thickness leads to the decrease in the detector’s ef?ciency, not only due to gamma rays attenuation in the dead layer but also due to the reduction of the active volume of the detector. Purpose In this work, the dead layer in?uence on HPGe detector ef?ciency was studied by Monte Carlo simulation. Materials and methods The detector model was developed using Monte Carlo N Particle (MCNP5) code for adjustment of the dead layer thickness; the adjustment was performed according to a speci?c irradiation con?guration by collimation approach using three reference point sources: 241Am (59.5 keV), 137Cs (661.6 keV) and 60Co (1173.2 keV; 1332.5 keV). Result The calculated ef?ciencies were compared to the measured intrinsic ef?ciency ones for these point sources; a good agreement between Monte Carlo and measurements results was found after the experimental validation. Conclusion The results con?rm the variation in the dead layer thickness according to aging of the detector; the average change of dead layer is in order of 1.30 ± 0.05 mm after 9 years.
关键词： Dead layer thickness,Detector ef?ciency,Monte Carlo simulation,Point sources,HPGe detector
更新于2025-09-23 15:21:01
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Nanostructures for Cancer Therapy || Dose enhancement effect in radiotherapy: adding gold nanoparticles to tumor in cancer treatment
摘要： The rationale of radiation dose enhancement due to gold nanoparticle addition in radiotherapy is revealed from the basic particle interactions to Monte Carlo simulation. Our review of different radiobiological studies on Monte Carlo, cell line, and preclinical model confirms that cancer cell kill definitely benefits from the dose enhancement when gold nanoparticles were added. Moreover, such dose enhancement depends on the size, shape, and concentration of the gold nanoparticle, as well as the type and energy of the radiation beams. It is concluded that adding gold nanoparticles to the tumor can enhance both the dose and contrast at the target in radiotherapy.
关键词： radiotherapy,cancer treatment,Monte Carlo simulation,gold nanoparticles,dose enhancement
更新于2025-09-23 15:21:01
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Synthesis of “lotus root”-like mesoporous titanium dioxide and its effects on UV response to aconitine release
摘要： Mesoporous titanium dioxide with a “lotus root”-like structure was synthesized for the first time using an improved template-free method. The structure has a BET (Brunauer Emmett Teller) surface area of 688.11 m2/g, a pore volume of 0.743 cm3/g, and a pore size of 3.59 nm. Aconitine, a botanical insecticide, could be loaded onto the mesoporous titanium dioxide via simply soaking the structure and had a maximum loading of 17.6 %. UV spectroscopy was utilized to explore the drug release behaviors, and the results showed that aconitine-loaded mesoporous titanium dioxide particles UV irradiated could successfully release aconitine with a release rate of 46.24%, which was significantly higher than the samples lacking UV irradiation (36.80%). Meanwhile, the release rate of aconitine (48.94 %) for pH 5.5 was significantly higher than that for pH 7.0 (42.09 %). The results of microcalorimetry revealed that both the enthalpy change (?H) and entropy change (?S) were negative (?H < 0, ?S < 0) for the whole process of aconitine loading onto the “lotus root”-like mesoporous titanium dioxide support. Hydrogen bonding was the driving force for drug loading, and this was also verified using Monte Carlo simulations. These results show that the “lotus root”-like mesoporous titanium dioxide material has some potential applications such as the storage and use of plant pesticides.
关键词： “Lotus root”-like mesoporous titanium dioxide,Monte Carlo simulations,hydrogen bonding,UV-responsed drug release
更新于2025-09-23 15:21:01