Publications associées à Phase problem

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

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

Super Resolution Phase Retrieval for Sparse Signals

Martin Vetterli, Juri Ranieri, Gilles Baechler, Amina Chebira, Miranda Krekovic

In a variety of fields, in particular those involving imaging and optics, we often measure signals whose phase is missing or has been irremediably distorted. Phase retrieval attempts to recover the phase information of a signal from the magnitude of its Fo ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2018

Phase Retrieval for Sparse Signals: Uniqueness Conditions

Martin Vetterli, Yue Lu, Juri Ranieri, Amina Chebira

In a variety of fields, in particular those involving imaging and optics, we often measure signals whose phase is missing or has been irremediably distorted. Phase retrieval attempts the recovery of the phase information of a signal from the magnitude of i ...

2013

The success story of crystallography

Dieter Schwarzenbach

Diffractionists usually place the birth of crystallography in 1912 with the first X-ray diffraction experiment of Friedrich, Knipping and Laue. This discovery propelled the mathematical branch of mineralogy to global importance and enabled crystal structur ...

2012

The success story of crystallography

Dieter Schwarzenbach

Diffractionists usually place the birth of crystallography in 1912 with the first X-ray diffraction experiment of Friedrich, Knipping and Laue. This discovery propelled the mathematical branch of mineralogy to global importance and enabled crystal structur ...

2012

Development of X-Ray Powder Diffraction Methods for Biomolecules

Sebastian Basso

The comparable order of magnitude between interatomic distances in a crystal and the wavelength of X-rays make X-ray crystallography the ideal analytical tool to gain insight into the structure of crystalline material, including biomolecules. Nevertheless, ...

EPFL2011

Phase retrieval from integrated near-field diffraction intensity

Giorgio Margaritondo

We discuss a near-field phase retrieval algorithm working with integrated diffraction intensity as well as a series of tests of its characteristics. Numerical simulations show improved performances compared to the previous algorithm. ...

2011

Three-Dimensional Multiple-Order Twinning of Self-Catalyzed GaAs Nanowires on Si Substrates

Anna Fontcuberta i Morral, François Morier-Genoud, Martin Heiss, Emanuele Uccelli, Eleonora Russo, Gabriel Mugny

In this paper we introduce a new paradigm for nanowire growth that explains the unwanted appearance of parasitic nonvertical nanowires. With a crystal structure polarization analysis of the initial stages of GaAs nanowire growth on Si substrates, we demons ...

American Chemical Society2011

Features of the secondary structure of a protein molecule from powder diffraction data

Philip Pattison, Sebastian Basso

Protein powder diffraction is shown to be suitable for obtaining de novo solutions to the phase problem at low resolution via phasing methods such as the isomorphous replacement method. Two heavy-atom derivatives (a gadolinium derivative and a holmium deri ...

International Union of Crystallography2010

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

Molecular envelopes derived from protein powder diffraction Molecular envelopes derived from protein powder diffraction data

Philip Pattison, Sebastian Basso

The preparation of single crystals suitable for X-ray analysis is frequently the most difﬁcult step in structural studies of proteins.With the aid of two examples, it is shown that de novo solution of the crystallographic phase problem can be achieved at l ...

2008

Exploiting the anisotropy of anomalous scattering boosts the phasing power of SAD and MAD experiments

The X-ray polarization anisotropy of anomalous scattering in crystals of brominated nucleic acids and selenated proteins is shown to have signiﬁcant effects on the diffraction data collected at an absorption edge. For conventionally collected single- or mu ...

2008

Polarization-dependence of anomalous scattering in brominated DNA and RNA molecules, and importance of crystal orientation in single- and multiple-wavelength anomalous diffraction phasing

Philip Pattison, Marc Fleurant

In this paper the anisotropy of anomalous scattering at the Br K-absorption edge in brominated nucleotides is investigated, and it is shown that this effect can give rise to a marked directional dependence of the anomalous signal strength in X-ray diffract ...

2007

Exploiting X-ray induced anisotropic lattice changes to improve intensity extraction in protein powder diffraction: Application to heavy atom detection

Philip Pattison, Marc Fleurant, Annasara Dahlström

X-ray induced anisotropic variations of cell parameters in porcine pancreatic elastase (PPE) were used in a multi-Pawley refinement in order to improve the deconvolution of overlapping peaks occurring in the high-angle region of the powder pattern. The ben ...

2007

Modelling and refining site-specific radiation damage in SAD/MAD phasing

Site-specific radiation damage on anomalously scattering sites can be used to generate additional phase information in standard single- or multi-wavelength anomalous diffraction (SAD or MAD) experiments. In this approach the data are kept unmerged, down to ...

2007

Diffractive imaging for periodic samples: retrieving one-dimensional concentration profiles across microfluidic channels

Christian David

A technique has been developed that allows determination of the concentration profiles of colloidal solutions or any kind of fluid under confinement. Currently, submicrometre-wide channels are sampled with a resolution in the 10 nm range. The method compri ...

International Union of Crystallography2007

Experimental and theoretical characterization of the Zn-Zn bond in [Zn2([eta]5-C5Me5)2]

Philip Pattison

The experimental electron density obtained from a multipole refinement of the synchrotron X-ray data for the title complex, together with theoretical ab initio calculations of the electron density at the molecular geometry obtained from neutron diffraction ...

2007

Crystallization and halide phasing of the C-terminal domain of human KIN17

Here, the crystallization and initial phasing of the C-terminal domain of human KIN17, a 45 kDa protein mainly expressed in response to ionizing radiation and overexpressed in certain tumour cell lines, are reported. Crystals diffracting to 1.4 Å resolutio ...

2006

X-ray absorption, refraction and resonant scattering tensors in selenated protein crystals: implications for data collection strategies in macromolecular crystallography

Philip Pattison

Polarized fluorescence spectra were recorded in the vicinity of the Se and Br K edges on crystals of the selenated protein aldose reductase in complex with a brominated inhibitor molecule. The X-ray absorption, refraction and resonant scattering tensors as ...

2005

Crystal structure of yeast YER010Cp, a knotable member of the RraA protein family

We present here the structure of Yer0l0c protein of unknown function, solved by Multiple Anomalous Diffraction and revealing a common fold and oligomerization state with proteins of the regulator of ribonuclease activity A (RraA) family. In Escherichia col ...

2005