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We have designed an improved algorithm that enables us to simulate the chemistry of cold dense interstellar clouds with a full gas-grain reaction network. The chemistry is treated by a unified microscopic-macroscopic Monte Carlo approach…

Earth and Planetary Astrophysics · Physics 2015-06-19 Qiang Chang , Eric herbst

The ability to directly measure radiative-association rate coefficients for reactions between ions and neutral molecules has long challenged chemical physics laboratories, yet radiative association is one of the most important processes…

We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment, in the molecular flow regime. The Geant4 toolkit was originally developed by the high energy physics community to simulate the…

Computational Physics · Physics 2013-10-07 J. Singal , J. Langton , R. Schindler

Treatment planning in ion beam therapy requires accurate knowledge of the relative stopping power (RSP) distribution within the patient. Currently, RSP maps are obtained via conventional x-ray computed tomography (CT) by converting the…

Current Lagrangian (particle-tracking) algorithms used to simulate diffusion-reaction equations must employ a certain number of particles to properly emulate the system dynamics---particularly for imperfectly-mixed systems. The number of…

Numerical Analysis · Mathematics 2017-03-08 Michael Schmidt , Stephen Pankavich , David Benson

The exact and phaseless variants of Auxiliary-Field Quantum Monte Carlo (AFQMC) have been shown to be capable of producing accurate ground-state energies for a wide variety of systems including those which exhibit substantial electron…

Chemical Physics · Physics 2017-07-25 James Shee , Shiwei Zhang , David R. Reichman , Richard A. Friesner

A Geant4 simulation code was developed to perform realistic simulations of the RIBRAS facility. A second order expansion of a finite solenoid field was included to describe the beam optics with a good precision. A systematic study of coil…

Accelerator Physics · Physics 2022-04-05 L. E. Tamayose , J. C. Zamora , G. F. Fortino , D. Flechas

Collider experiments, such as those at the Large Hadron Collider, use the Geant4 toolkit to simulate particle-detector interactions with high accuracy. However, these experiments increasingly require larger amounts of simulated data,…

Instrumentation and Detectors · Physics 2025-09-10 Piyush Raikwar , Anna Zaborowska , Peter McKeown , Renato Cardoso , Mikolaj Piorczynski , Kyongmin Yeo

Morphogenesis is central to biology but remains largely unexplored in chemistry. Reaction-diffusion (RD) mechanisms are, however, essential to understand how shape emerges in the living world. While numerical methods confirm the incredible…

Pattern Formation and Solitons · Physics 2014-07-17 Anton S. Zadorin , Yannick Rondelez , Jean-Christophe Galas , André Estevez-Torres

A combination of reaction-diffusion models with moving-boundary problems yields a system in which the diffusion (spreading and penetration) and reaction (transformation) evolve the system's state and geometry over time. These systems can be…

Computational Engineering, Finance, and Science · Computer Science 2020-08-26 Mojtaba Barzegari , Liesbet Geris

Multiple time-scale algorithms exploit the natural separation of time-scales in chemical systems to greatly accelerate the efficiency of molecular dynamics simulations. Although the utility of these methods in systems where the interactions…

Computational Physics · Physics 2015-06-18 Nathan Luehr , Thomas E. Markland , Todd J. Martinez

Numerical radiation-hydrodynamics (RHD) for non-relativistic flows is a challenging problem because it encompasses processes acting over a very broad range of timescales, and where the relative importance of these processes often varies by…

Instrumentation and Methods for Astrophysics · Physics 2024-07-29 Chong-Chong He , Benjamin D. Wibking , Mark R. Krumholz

A Geant4 based simulation platform of the Holland Proton Therapy Centre (HollandPTC, Netherlands) R&D beamline (G4HPTC-R&D) was developed to enable the planning, optimisation and advanced dosimetry for radiobiological studies. It…

Medical Physics · Physics 2023-06-01 C. F. Groenendijk , M. Rovituso , D. Lathouwers , J. M. C. Brown

This work considers the method of uniformisation for continuous-time Markov chains in the context of chemical reaction networks. Previous work in the literature has shown that uniformisation can be beneficial in the context of…

Quantitative Methods · Quantitative Biology 2019-04-18 Casper Beentjes , Ruth Baker

An air cargo inspection system combining two nuclear reaction based techniques, namely Fast-Neutron Resonance Radiography and Dual-Discrete-Energy Gamma Radiography is currently being developed. This system is expected to allow detection of…

For a theoretical understanding of the reactivity of complex chemical systems, relative energies of stationary points on potential energy hypersurfaces need to be calculated to high accuracy. Due to the large number of intermediates present…

Chemical Physics · Physics 2018-10-30 Gregor N. Simm , Markus Reiher

A spatio-temporal evolution of chemicals appearing in a reversible enzyme reaction and modelled by a four component reaction-diffusion system with the reaction terms obtained by the law of mass action is considered. The large time behaviour…

Analysis of PDEs · Mathematics 2016-10-25 Jan Elias

We present a new continuous time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on a stochastic sampling of a perturbation expansion in the impurity-bath hybridization parameter.…

Strongly Correlated Electrons · Physics 2009-11-11 Philipp Werner , Armin Comanac , Luca De Medici , Matthias Troyer , Andrew J. Millis

Modeling the response of gamma detectors has long been a challenge within the nuclear community. Significant research has been conducted to digitally replicate instruments that can cost over $100,000 and are difficult to operate outside a…

Instrumentation and Detectors · Physics 2024-06-21 Matthew Niichel , Stylianos Chatzidakis

Reaction-Diffusion (RD) systems provide a computational framework that governs many pattern formation processes in nature. Current RD system design practices boil down to trial-and-error parameter search. We propose a differentiable…

Neural and Evolutionary Computing · Computer Science 2021-07-15 Alexander Mordvintsev , Ettore Randazzo , Eyvind Niklasson