Publications associées à Coherent diffraction imaging

Phase Retrieval: From Computational Imaging to Machine Learning: A tutorial

Michaël Unser, Thanh-An Michel Pham, Jonathan Yuelin Dong

Phase retrieval consists in the recovery of a complex-valued signal from intensity-only measurements. As it pervades a broad variety of applications, many researchers have striven to develop phase-retrieval algorithms. Classical approaches involve techniqu ...

2023

Une version polyatomique de l'algorithme Frank-Wolfe pour résoudre le problème LASSO en grandes dimensions

Adrian Thibault Etienne Jarret, Matthieu Martin Jean-André Simeoni, Julien René Pierre Fageot

Nous nous intéressons à la reconstruction parcimonieuse d’images à l’aide du problème d’optimisation régularisé LASSO. Dans de nombreuses applications pratiques, les grandes dimensions des objets à reconstruire limitent, voire empêchent, l’utilisation des ...

2022

Phase Reconstruction of Low-Energy Electron Holograms of Individual Proteins

Klaus Kern, Stephan Rauschenbach, Sven Alexander Szilagyi, Hannah Julia Ochner

Low-energy electron holography (LEEH) is one of the few techniques capable of imaging large and complex three-dimensional molecules, such as proteins, on the single molecule level at subnanometer resolution. During the imaging process, the structural infor ...

AMER CHEMICAL SOC2022

Stochasticity helps to navigate rough landscapes: comparing gradient-descent-based algorithms in the phase retrieval problem

Lenka Zdeborová, Francesca Mignacco

In this paper we investigate how gradient-based algorithms such as gradient descent (GD), (multi-pass) stochastic GD, its persistent variant, and the Langevin algorithm navigate non-convex loss-landscapes and which of them is able to reach the best general ...

2021

Refinement for single-nanoparticle structure determination from low-quality single-shot coherent diffraction data

Christoph Bostedt, Christophe Nicolas

With the emergence of X-ray free-electron lasers, it is possible to investigate the structure of nanoscale samples by employing coherent diffractive imaging in the X-ray spectral regime. In this work, we developed a refinement method for structure reconstr ...

INT UNION CRYSTALLOGRAPHY2020

Monitoring Spontaneous Charge-Density Fluctuations by Single-Molecule Diffraction of Quantum Light

Jérémy Raymond Jean Maurice Rouxel

Homodyne X-ray diffraction signals produced by classical light and classical detectors are given by the modulus square of the charge density in momentum space vertical bar sigma(q)vertical bar(2), missing its phase, which is required in order to invert the ...

2019

Color neutral nanocomposite nickel-tantalum oxide for electrochromic windows

Andreas Schueler, Josef Andreas Schuler, Olivia Valérie Charlotte Bouvard

Electrochromic windows can darken on demand to limit the solar gains entering a building to reduce the risk of overheating, while preserving the view towards the exterior. Yet, the switching speed and contrast as well as the durability of commercial produc ...

IOP2019

Incommensurate atomic density waves in the high-pressure IVb phase of barium

Gervais Chapuis, Alla Arakcheeva, Philip Pattison, Vladimir Dmitriev

The host–guest structures of elements at high pressure discovered a decade ago still leave many open questions due to the lack of precise models based on full exploitation of the diffraction data. This concerns in particular Ba IV, which is stable in the r ...

Int Union Crystallography2017

Structural characterization of framework-gas interactions in the metal-organic framework Co-2(dobdc) by in situ single-crystal X-ray diffraction

Wendy Lee Queen, Miguel Gonzalez

The crystallographic characterization of framework-guest interactions in metal-organic frameworks allows the location of guest binding sites and provides meaningful information on the nature of these interactions, enabling the correlation of structure with ...

2017

Deformation behavior of nanoporous polycrystalline silver layers sintered by low temperature bonding: experiment and simulation

Saba Zabihzadeh

Integrated circuit packaging technology has become a prime design consideration for the develop-ment of electronic system concepts. One key issue is the bonding layer between chip and substrate. Currently, high-lead solder materials are being used, which a ...

EPFL2016

Gold nanoparticles: BSA (Bovine Serum Albumin) coating and X-ray irradiation produce variable-spectrum photoluminescence

Giorgio Margaritondo

We show that by using different x-ray irradiation times of BSA-coated Au nanoparticles (NPs) we can change their ultraviolet-stimulated photoluminescence and shift the spectral weight over the visible spectral range. This is due to the interplay of two emi ...

Elsevier Science Sa2015

Combining Monte Carlo methods with coherent wave optics for the simulation of phase-sensitive X-ray imaging

Peter Modregger, Marco Stampanoni

Phase-sensitive X-ray imaging shows a high sensitivity towards electron density variations, making it well suited for imaging of soft tissue matter. However, there are still open questions about the details of the image formation process. Here, a framework ...

International Union of Crystallography2014

Parametric Polytope Reconstruction, an Application to Crystal Shape Estimation

Colin Neil Jones, Jean-Hubert Hours

In situ imaging techniques are a promising direction for monitoring the distribution of crystal sizes and shapes during a crystallization process. Nevertheless, no tractable method yet exists for estimating complex crystal shapes. In this paper, an in situ ...

Institute of Electrical and Electronics Engineers2014

Low Complexity Image Recognition Algorithms for Handheld devices

Pradyumna Ayyalasomayajula

Content Based Image Retrieval (CBIR) has gained a lot of interest over the last two decades. The need to search and retrieve images from databases, based on information (“features”) extracted from the image itself, is becoming increasingly important. CBIR ...

EPFL2013

A Reciprocal Sampling Algorithm for Lightweight Distributed Multi-Robot Localization

Alcherio Martinoli, Amanda Stella Markowska Prorok

This work is situated in the context of collaboratively solving the localization problem for unknown initial conditions. We address this problem with a novel, fully decentralized, real-time particle filter algorithm, designed to accommodate realistic robot ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2011

Cellular Dynamics and Three-Dimensional Refractive Index Distribution Studied with Quantitative Phase Imaging

Nicolas Pavillon

We present in this PhD thesis work various applications of digital holographic microscopy (DHM), an imaging technique based on coherent illumination which enables the recovery of the full complex wavefront, i.e. the amplitude and phase of a wave field whic ...

EPFL2011

Picosecond dynamics of laser-induced strain in graphite

Paul Beaud

We report on the use of grazing-incidence time-resolved x-ray diffraction to investigate the evolution of strain in natural graphite excited by femtosecond-laser pulses in the fluence range of 6-35 mJ/cm(2). Strains corresponding to up to similar to 2.8% c ...

2011

Ab initio structure solution by iterative phase-retrieval methods: performance tests on charge flipping and low-density elimination

Thomas Alois Weber

Comprehensive tests on the density-modification methods charge flipping [Oszlanyi & Suto (2004). Acta Cryst. A60, 134-141] and low-density elimination [Shiono & Woolfson (1992). Acta Cryst. A48, 451-456] for solving crystal structures are performed on simu ...

2010

The potential for two-dimensional crystallography of membrane proteins at future x-ray free-electron laser sources

Ultrashort pulses from x-ray free-electron laser (XFEL) sources promise to assist in obtaining the structures of membrane proteins at high resolution. We have reconstructed the electron density distribution of a two-dimensional (2D) aquaporin crystal from ...

2010

Coherence and wavefront characterization of Si-111 monochromators using double-grating interferometry

Christian David

A study of the coherence and wavefront properties of a pseudo-channel-cut monochromator in comparison with a double-crystal monochromator is presented. Using a double-grating interferometer designed for the hard X-ray regime, the complex coherence factor w ...

2010