Showing 1–11 of 11 results for author: Simon, B

Developing a Compact SWIR Imaging Spectrometer for CO2 and CH4 Retrieval Using Photonic Crystal Filters

Authors: Marijn Siemons, Brecht Simon, Irina Malysheva, Ralf Kohlhaas

Abstract: The need for atmospheric measurements with higher spatial and temporal resolution is driving the development of satellites and satellite constellations to complement existing flagship missions. We are developing an instrument concept based on photonic crystal filters with tailored spectral transmission for trace gas retrieval. These filters can be integrated directly with the detector module, enab… ▽ More The need for atmospheric measurements with higher spatial and temporal resolution is driving the development of satellites and satellite constellations to complement existing flagship missions. We are developing an instrument concept based on photonic crystal filters with tailored spectral transmission for trace gas retrieval. These filters can be integrated directly with the detector module, enabling a highly compact system architecture. In this work, we present performance simulations for methane and carbon dioxide retrieval in the 1.6 um SWIR band for a medium-resolution global coverage mission with an approximately 250 m spatial resolution and a 150 km swath. We furthermore introduce an improved retrieval algorithm that substantially reduces retrieval bias. These results demonstrate the potential of the proposed architecture for medium-resolution global greenhouse-gas mapping, with retrieval performance comparable to state-of-the-art global mapping missions such as the planned CO2M mission at substantially finer spatial resolution. This measurement approach also inherently compresses the acquired spectral information, reducing the need for high downlink data rates. In the coming year, these filters will be fabricated by NIL Technology, followed by mechanical integration and experimental validation in a breadboard system. △ Less

Submitted 20 August, 2026; originally announced August 2026.

Comments: ICSO 2026

A Comparative Study of the Streaming Instability: Unstratified Models with Marginally Coupled Grains

Authors: Stanley A. Baronett, Wladimir Lyra, Hossam Aly, Olivia Brouillette, Daniel Carrera, Victoria I. De Cun, Linn E. J. Eriksson, Mario Flock, Pinghui Huang, Leonardo Krapp, Geoffroy Lesur, Rixin Li, Shengtai Li, Jeonghoon Lim, Sijme-Jan Paardekooper, David G. Rea, Debanjan Sengupta, Jacob B. Simon, Prakruti Sudarshan, Orkan M. Umurhan, Chao-Chin Yang, Andrew N. Youdin

Abstract: The streaming instability is a leading mechanism for concentrating solids and initiating planetesimal formation in protoplanetary disks. Although numerous studies have explored its linear growth, nonlinear evolution, and implications for planet formation, the diversity of numerical methods and dust treatments used across the literature has made it difficult to assess which features of the instabil… ▽ More The streaming instability is a leading mechanism for concentrating solids and initiating planetesimal formation in protoplanetary disks. Although numerous studies have explored its linear growth, nonlinear evolution, and implications for planet formation, the diversity of numerical methods and dust treatments used across the literature has made it difficult to assess which features of the instability are physically robust and which arise from code-dependent choices. We present the first systematic comparison of seven hydrodynamic codes--spanning finite-volume and finite-difference schemes and modeling dust either as Lagrangian particles or as a pressureless fluid--applied to the unstratified streaming instability with a dimensionless stopping time of unity. All codes reproduce the characteristic sequence of exponential growth, filament formation, and turbulent saturation, demonstrating broad agreement in the qualitative behavior of the instability. Quantitatively, however, the dust model remains the dominant source of variation at moderate resolution: particle-based simulations reach higher peak densities and exhibit broader high-density tails than fluid-based models at $512^2$ resolution, although increasing the number of particles brings their initial maximum density evolution into close agreement with that of dust-fluid models. At $1024^2$, these differences diminish substantially, indicating better agreement of the saturated-state statistics across dust treatments. In terms of computational performance, most particle implementations suffer from imbalanced parallelized loads, while execution on a GPU is at least two to three times more energy efficient and scales better at higher resolutions than on CPUs. Given the intrinsic stochasticity of this nonlinear system, only statistical diagnostics remain meaningful across codes. △ Less

Submitted 4 April, 2026; v1 submitted 4 March, 2026; originally announced March 2026.

Comments: 25 pages, 14 figures, under revision; for associated repository, see https://github.com/pfitsplus/sicc

Enzyme-free in situ polymerization of conductive polymers catalyzed by porous Au@Ag nanowires for stretchable neural electrodes

Authors: Yuyang Li, Changbai Li, Yangpeiqi Yi, Nader Marzban, Chengzhuo Yu, Tobias Abrahamsson, Zesheng Liu, Justinas Palisaitis, Xianjie Liu, Zhixing Wu, Eylul Ceylan, Per O. Å. Persson, Mats Fahlman, Xenofon Strakosas, Magnus Berggren Daniel T. Simon, Klas Tybrandt

Abstract: In situ polymerization of conductive polymers (CPs) represents a transformative approach in bioelectronics, by enabling the controlled growth of electrically active materials right at the tissue or device surface to create seamless biotic-abiotic interfaces. Traditional CP deposition techniques often use high anodic potentials, non-physiological electrolytes, or strong oxidants, making them harmfu… ▽ More In situ polymerization of conductive polymers (CPs) represents a transformative approach in bioelectronics, by enabling the controlled growth of electrically active materials right at the tissue or device surface to create seamless biotic-abiotic interfaces. Traditional CP deposition techniques often use high anodic potentials, non-physiological electrolytes, or strong oxidants, making them harmful to adjacent tissues. A possible solution is enzymatic polymerization which operates under milder conditions, but it is limited by the stability and activity window of the enzyme catalysts, low throughput, and challenges in spatially confining polymer growth. To resolve these issues, here we developed one-dimensional porous Au-coated Ag nanowires with horseradish peroxidase (HRP)-like catalytic properties, thereby for the first time enabling mild in situ enzyme-free polymerization of conductive polymers near neutral pH. The enzyme-free polymerization is demonstrated both in aqueous dispersions at pH=6 and in situ onto porous Au coated Ag nanowire based stretchable electrodes. Following enzyme-free catalytic polymerization, the electrically conducting polymer coating on the electrode greatly improves the impedance and achieves an impedance of 2.6 kOhm at 1 kHz for 50x50 um large electrodes. △ Less

Submitted 25 August, 2025; originally announced August 2025.

Comments: 13 pages, 4 figures

Quantitative real-time measurements of dose and dose rate in UHDR proton pencil beams via scintillation imaging system

Authors: Megan Clark, Joseph Harms, Roman Vasyltsiv, Austin Sloop, Jakub Kozelka, Bill Simon, Rongxiao Zhang, David Gladstone, Petr Bruza

Abstract: Purpose: Ultra-fast scintillation imaging has been shown to provide a unique tool for spatio-temporal dosimetry of conventional cyclotron and synchrocyclotron pencil beam scanning (PBS) deliveries, indicating the potential use for characterization of ultra-UHDR PBS proton beams. The goal of this work is to introduce this novel concept and demonstrate its capabilities in recording complex dose rate… ▽ More Purpose: Ultra-fast scintillation imaging has been shown to provide a unique tool for spatio-temporal dosimetry of conventional cyclotron and synchrocyclotron pencil beam scanning (PBS) deliveries, indicating the potential use for characterization of ultra-UHDR PBS proton beams. The goal of this work is to introduce this novel concept and demonstrate its capabilities in recording complex dose rate maps at FLASH-capable proton beam currents, as compared to log-based dose rate calculation, internally developed UHDR beam simulation, and a fast point detector (EDGE diode). Methods: The light response of a scintillator sheet located at isocenter and irradiated by pencil beam scanning proton fields (40-210 nA, 250 MeV) was imaged by an ultra-fast iCMOS camera at 4.5-12 kHz sampling frequency. Image intensity was calibrated to dose with film and the recorded spatio-temporal data was compared to a PPC05 ion chamber, log-based reconstruction, and EDGE diode. Calculation of full-field mean and PBS dose rate maps were used to highlight the importance of high resolution, full-field information in UHDR studies. Results: Camera response was linear with dose (R2 = 0.997) and current (R2 = 0.98) in the range from 2-22 Gy and 40-210 nA, respectively, when compared to ion chamber readings. Planned and delivered spot positions agreed within 0.2+/-0.1 mm and total irradiation time agreed within 0.2+/-0.2 ms when compared with the log files, indicating the high concurrent spatial and temporal resolution. For all deliveries, the PBS dose rate measured at the diode location agreed between the imaging and the diode within 3+/-2% and with the simulation within 5+/-3%. Conclusion: The high linearity and various spatiotemporal metric reporting capabilities confirm the continued use of this camera system for UHDR beam characterization, especially for spatially resolved dose rate information. △ Less

Submitted 22 December, 2023; originally announced December 2023.

Nitrogen-vacancy magnetometry of CrSBr by diamond membrane transfer

Authors: Talieh S. Ghiasi, Michael Borst, Samer Kurdi, Brecht G. Simon, Iacopo Bertelli, Carla Boix-Constant, Samuel Mañas-Valero, Herre S. J. van der Zant, Toeno van der Sar

Abstract: Magnetic imaging using nitrogen-vacancy (NV) spins in diamonds is a powerful technique for acquiring quantitative information about sub-micron scale magnetic order. A major challenge for its application in the research on two-dimensional (2D) magnets is the positioning of the NV centers at a well-defined, nanoscale distance to the target material required for detecting the small magnetic fields ge… ▽ More Magnetic imaging using nitrogen-vacancy (NV) spins in diamonds is a powerful technique for acquiring quantitative information about sub-micron scale magnetic order. A major challenge for its application in the research on two-dimensional (2D) magnets is the positioning of the NV centers at a well-defined, nanoscale distance to the target material required for detecting the small magnetic fields generated by magnetic monolayers. Here, we develop a diamond 'dry-transfer' technique, akin to the state-of-the-art 2D-materials assembly methods, and use it to place a diamond micro-membrane in direct contact with the 2D interlayer antiferromagnet CrSBr. We harness the resulting NV-sample proximity to spatially resolve the magnetic stray fields generated by the CrSBr, present only where the CrSBr thickness changes by an odd number of layers. From the magnetic stray field of a single uncompensated ferromagnetic layer in the CrSBr, we extract a monolayer magnetization of $M_\mathrm{CSB}$ = 0.46(2) T, without the need for exfoliation of monolayer crystals or applying large external magnetic fields. The ability to deterministically place NV-ensemble sensors into contact with target materials and detect ferromagnetic monolayer magnetizations paves the way for quantitative analysis of a wide range of 2D magnets assembled on arbitrary target substrates. △ Less

Submitted 3 July, 2023; originally announced July 2023.

Journal ref: npj 2D Materials and Applications (2023)

Interleaved Electro-Optic Dual Comb Generation to Expand Bandwidth and Scan Rate for Molecular Spectroscopy and Dynamics Studies near 1.6 μm

Authors: Jasper R. Stroud, James B. Simon, Gerd A. Wagner, David F. Plusquellic

Abstract: A chirped-pulse interleaving method is reported for generation of dual optical frequency combs based on electro-optic phase modulators (EOM) in a free-running all-fiber based system. Methods are discussed to easily modify the linear chirp rate and comb resolution by more than three orders of magnitude and to significantly increase the spectral bandwidth coverage. The agility of the technique is sh… ▽ More A chirped-pulse interleaving method is reported for generation of dual optical frequency combs based on electro-optic phase modulators (EOM) in a free-running all-fiber based system. Methods are discussed to easily modify the linear chirp rate and comb resolution by more than three orders of magnitude and to significantly increase the spectral bandwidth coverage. The agility of the technique is shown to both capture complex line shapes and to magnify rapid passage effects in spectroscopic and molecular dynamics studies of CO2. These methods are well-suited for applications in the areas of remote sensing, reaction dynamics, and sub-Doppler studies across the wide spectral regions accessible to EOMs. △ Less

Submitted 21 June, 2021; originally announced June 2021.

Comparing methods of modeling depth-induced breaking of irregular waves with a fully nonlinear potential flow approach

Authors: Bruno Simon, Christos E. Papoutsellis, Michel Benoit, Marissa L. Yates

Abstract: The modeling of wave breaking dissipation in coastal areas is investigated with a fully nonlinear and dispersive wave model. The wave propagation model is based on potential flow theory, which initially assumes non-overturning waves. Including the impacts of wave breaking dissipation is however possible by implementing a wave breaking initiation criterion and dissipation mechanism. Three criteria… ▽ More The modeling of wave breaking dissipation in coastal areas is investigated with a fully nonlinear and dispersive wave model. The wave propagation model is based on potential flow theory, which initially assumes non-overturning waves. Including the impacts of wave breaking dissipation is however possible by implementing a wave breaking initiation criterion and dissipation mechanism. Three criteria from the literature, including a geometric, kinematic, and dynamic-type criterion, are tested to determine the optimal criterion predicting the onset of wave breaking. Three wave breaking energy dissipation methods are also tested: the first two are based on the analogy of a breaking wave with a hydraulic jump, and the third one applies an eddy viscosity dissipative term. Numerical simulations are performed using combinations of the three breaking onset criteria and three dissipation methods. The simulation results are compared to observations from four laboratory experiments of regular and irregular waves breaking over a submerged bar, irregular waves breaking on a beach, and irregular waves breaking over a submerged slope. The different breaking approaches provide similar results after proper calibration. The wave transformation observed in the experiments is reproduced well, with better results for the case of regular waves than irregular waves. Moreover, the wave statistics and wave spectra are predicted well in general, and in particular for regular waves. Some differences are observed for irregular wave cases, in particular in the low-frequency range. This is attributed to incomplete absorption of the long waves in the numerical model. Otherwise, the wave spectra in the range $[0.5f_p,\: 5f_p]$ are reproduced well, before, inside, and after the breaking zone for the three irregular wave experiments. △ Less

Submitted 4 December, 2019; originally announced December 2019.

Comments: 25 pages, 14 figures, 5 tables. J. Ocean Eng. Mar. Energy (2019)

Modeling of depth-induced wave breaking in a fully nonlinear free-surface potential flow model

Authors: Christos E. Papoutsellis, Marissa L. Yates, Bruno Simon, Michel Benoit

Abstract: Two methods to treat wave breaking in the framework of the Hamiltonian formulation of free-surface potential flow are presented, tested, and validated. The first is an extension of Kennedy et al (2000)'s eddy-viscosity approach originally developed for Boussinesq-type wave models. In this approach, an extra term, constructed to conserve the horizontal momentum for waves propagating over a flat bot… ▽ More Two methods to treat wave breaking in the framework of the Hamiltonian formulation of free-surface potential flow are presented, tested, and validated. The first is an extension of Kennedy et al (2000)'s eddy-viscosity approach originally developed for Boussinesq-type wave models. In this approach, an extra term, constructed to conserve the horizontal momentum for waves propagating over a flat bottom, is added in the dynamic free-surface condition. In the second method, a pressure distribution is introduced at the free surface that dissipates wave energy by analogy to a hydraulic jump (Guignard and Grilli, 2001). The modified Hamiltonian systems are implemented using the Hamiltonian Coupled-Mode Theory, in which the velocity potential is represented by a rapidly convergent vertical series expansion. Wave energy dissipation and conservation of horizontal momentum are verified numerically. Comparisons with experimental measurements are presented for the propagation of a breaking dispersive shock wave following a dam break, and then incident regular waves breaking on a mildly sloping beach and over a submerged bar. △ Less

Submitted 20 October, 2019; originally announced October 2019.

Human brain ferritin studied by muon Spin Rotation: a pilot study

Authors: Lucia Bossoni, Laure Grand Moursel, Marjolein Bulk, Brecht G. Simon, Andrew Webb, Louise van der Weerd, Martina Huber, Pietro Carretta, Alessandro Lascialfari, Tjerk H. Oosterkamp

Abstract: Muon Spin Rotation is employed to investigate the spin dynamics of ferritin proteins isolated from the brain of an Alzheimer's disease (AD) patient and of a healthy control, using a sample of horse-spleen ferritin as a reference. A model based on the Néel theory of superparamagnetism is developed in order to interpret the spin relaxation rate of the muons stopped by the core of the protein. Using… ▽ More Muon Spin Rotation is employed to investigate the spin dynamics of ferritin proteins isolated from the brain of an Alzheimer's disease (AD) patient and of a healthy control, using a sample of horse-spleen ferritin as a reference. A model based on the Néel theory of superparamagnetism is developed in order to interpret the spin relaxation rate of the muons stopped by the core of the protein. Using this model, our preliminary observations show that ferritins from the healthy control are filled with a mineral compatible with ferrihydrite, while ferritins from the AD patient contain a crystalline phase with a larger magnetocrystalline anisotropy, possibly compatible with magnetite or maghemite. △ Less

Submitted 22 May, 2017; v1 submitted 21 February, 2017; originally announced February 2017.

Comments: 16 pages, 9 figures

Journal ref: Journal of Physics: Condensed Matter, Volume 29, Number 41 (2017)

Hamilton's turns as visual tool-kit for designing of single-qubit unitary gates

Authors: B. Neethi Simon, C. M. Chandrashekar, Sudhavathani Simon

Abstract: Unitary evolutions of a qubit are traditionally represented geometrically as rotations of the Bloch sphere, but the composition of such evolutions is handled algebraically through matrix multiplication [of SU(2) or SO(3) matrices]. Hamilton's construct, called turns, provides for handling the latter pictorially through the as addition of directed great circle arcs on the unit sphere S… ▽ More Unitary evolutions of a qubit are traditionally represented geometrically as rotations of the Bloch sphere, but the composition of such evolutions is handled algebraically through matrix multiplication [of SU(2) or SO(3) matrices]. Hamilton's construct, called turns, provides for handling the latter pictorially through the as addition of directed great circle arcs on the unit sphere S$^2 \subset \mathbb{R}^3$, resulting in a non-Abelian version of the parallelogram law of vector addition of the Euclidean translation group. This construct is developed into a visual tool-kit for handling the design of single-qubit unitary gates. As an application, it is shown, in the concrete case wherein the qubit is realized as polarization states of light, that all unitary gates can be realized conveniently through a universal gadget consisting of just two quarter-wave plates (QWP) and one half-wave plate (HWP). The analysis and results easily transcribe to other realizations of the qubit: The case of NMR is obtained by simply substituting $π/2$ and $π$ pulses respectively for QWPs and HWPs, the phases of the pulses playing the role of the orientation of fast axes of these plates. △ Less

Submitted 19 February, 2012; v1 submitted 14 October, 2011; originally announced October 2011.

Comments: 16 Pages, 14 Figures, Published version

Journal ref: Phys. Rev. A 85, 022323 (2012)

Charge Deficiency, Charge Transport and Comparison of Dimensions

Authors: Joseph E. Avron, Ruedi Seiler, Barry Simon

Abstract: We study the relative index of two orthogonal infinite dimensional projections which, in the finite dimensional case, is the difference in their dimensions. We relate the relative index to the Fredholm index of appropriate operators, discuss its basic properties, and obtain various formulas for it. We apply the relative index to counting the change in the number of electrons below the Fermi ener… ▽ More We study the relative index of two orthogonal infinite dimensional projections which, in the finite dimensional case, is the difference in their dimensions. We relate the relative index to the Fredholm index of appropriate operators, discuss its basic properties, and obtain various formulas for it. We apply the relative index to counting the change in the number of electrons below the Fermi energy of certain quantum systems and interpret it as the charge deficiency. We study the relation of the charge deficiency with the notion of adiabatic charge transport that arises from the consideration of the adiabatic curvature. It is shown that, under a certain covariance, (homogeneity), condition the two are related. The relative index is related to Bellissard's theory of the Integer Hall effect. For Landau Hamiltonians the relative index is computed explicitly for all Landau levels. △ Less

Submitted 10 March, 1998; originally announced March 1998.

Comments: 23 pages, no figures

Journal ref: Comm.Math.Phys. 159, 399-422, (1994)