scholarly journals Non-negative matrix analysis for effective feature extraction in X-ray spectromicroscopy

2014 ◽  
Vol 171 ◽  
pp. 357-371 ◽  
Author(s):  
Rachel Mak ◽  
Mirna Lerotic ◽  
Holger Fleckenstein ◽  
Stefan Vogt ◽  
Stefan M. Wild ◽  
...  
Keyword(s):  
Large Scale ◽  
Environmental Science ◽  
Matrix Analysis ◽  
Matrix Approximation ◽  
New Approach ◽  
X Ray ◽  
Rich Information ◽  
Preliminary Study ◽  
X Ray Absorption ◽  
Calculated Image

X-Ray absorption spectromicroscopy provides rich information on the chemical organization of materials down to the nanoscale. However, interpretation of this information in studies of “natural” materials such as biological or environmental science specimens can be complicated by the complex mixtures of spectroscopically complicated materials present. We describe here the shortcomings that sometimes arise in previously-employed approaches such as cluster analysis, and we present a new approach based on non-negative matrix approximation (NNMA) analysis with both sparseness and cluster-similarity regularizations. In a preliminary study of the large-scale biochemical organization of human spermatozoa, NNMA analysis delivers results that nicely show the major features of spermatozoa with no physically erroneous negative weightings or thicknesses in the calculated image.

scholarly journals Finding and characterising WHIM structures using the luminosity density method

2014 ◽  
Vol 11 (S308) ◽  
pp. 368-371
Author(s):  
Jukka Nevalainen ◽  
L. J. Liivamägi ◽  
E. Tempel ◽  
E. Branchini ◽  
M. Roncarelli ◽  
...  
Keyword(s):  
Large Scale ◽  
Real Data ◽  
Sloan Digital Sky Survey ◽  
Physical Parameters ◽  
X Ray ◽  
Galaxy Surveys ◽  
Sky Survey ◽  
The Galaxy ◽  
Hydrodynamical Simulations ◽  
X Ray Absorption

AbstractWe have developed a new method to approach the missing baryons problem. We assume that the missing baryons reside in a form of Warm Hot Intergalactic Medium, i.e. the WHIM. Our method consists of (a) detecting the coherent large scale structure in the spatial distribution of galaxies that traces the Cosmic Web and that in hydrodynamical simulations is associated to the WHIM, (b) mapping its luminosity into a galaxy luminosity density field, (c) using numerical simulations to relate the luminosity density to the density of the WHIM, (d) applying this relation to real data to trace the WHIM using the observed galaxy luminosities in the Sloan Digital Sky Survey and 2dF redshift surveys. In our application we find evidence for the WHIM along the line of sight to the Sculptor Wall, at redshifts consistent with the recently reported X-ray absorption line detections. Our indirect WHIM detection technique complements the standard method based on the detection of characteristic X-ray absorption lines, showing that the galaxy luminosity density is a reliable signpost for the WHIM. For this reason, our method could be applied to current galaxy surveys to optimise the observational strategies for detecting and studying the WHIM and its properties. Our estimates of the WHIM hydrogen column density NH in Sculptor agree with those obtained via the X-ray analysis. Due to the additional NH estimate, our method has potential for improving the constrains of the physical parameters of the WHIM as derived with X-ray absorption, and thus for improving the understanding of the missing baryons problem.

In situ back-side illumination fluorescence XAFS (BI-FXAFS) studies on platinum nanoparticles deposited on a HOPG surface as a model fuel cell: a new approach to the Pt-HOPG electrode/electrolyte interface

2014 ◽  
Vol 16 (27) ◽  
pp. 13748-13754 ◽  
Author(s):  
Hiromitsu Uehara ◽  
Yohei Uemura ◽  
Takafumi Ogawa ◽  
Kentaro Kono ◽  
Ryoichi Ueno ◽  
...  
Keyword(s):  
Fine Structure ◽  
Fuel Cell ◽  
Back Side ◽  
New Approach ◽  
X Ray ◽  
Model Fuel ◽  
Fluorescence Xafs ◽  
X Ray Absorption ◽  
Side Illumination

We measured the in situ polarization-dependent X-ray absorption fine structure of PtNPs deposited on a flat HOPG substrate.

High-accuracy X-ray absorption spectra from mMsolutions of nickel (II) complexes with multiple solutions using transmission XAS

2015 ◽  
Vol 22 (4) ◽  
pp. 1008-1021 ◽  
Author(s):  
Christopher T. Chantler ◽  
M. Tauhidul Islam ◽  
Stephen P. Best ◽  
Lachlan J. Tantau ◽  
Chanh Q. Tran ◽  
...  
Keyword(s):  
Multiple Solutions ◽  
High Accuracy ◽  
Hybrid Technique ◽  
Edge Structure ◽  
New Approach ◽  
X Ray ◽  
Square Planar ◽  
Transmission Measurements ◽  
First Time ◽  
X Ray Absorption

A new approach is introduced for determining X-ray absorption spectroscopy (XAS) spectra on absolute and relative scales using multiple solutions with different concentrations by the characterization and correction of experimental systematics. This hybrid technique is a development of standard X-ray absorption fine structure (XAFS) along the lines of the high-accuracy X-ray extended range technique (XERT) but with applicability to solutions, dilute systems and cold cell environments. This methodology has been applied to determining absolute XAS of bis(N-n-propyl-salicylaldiminato) nickel(II) and bis(N-i-propyl-salicylaldiminato) nickel(II) complexes with square planar and tetrahedral structures in 15 mMand 1.5 mMdilute solutions. It is demonstrated that transmission XAS from dilute systems can provide excellent X-ray absorption near-edge structure (XANES) and XAFS spectra, and that transmission measurements can provide accurate measurement of subtle differences including coordination geometries. For the first time, (transmission) XAS of the isomers have been determined from low-concentration solutions on an absolute scale with a 1–5% accuracy, and with relative precision of 0.1% to 0.2% in the active XANES and XAFS regions after inclusion of systematic corrections.

scholarly journals Multi-probe methods for investigating ion hydration

2014 ◽  
Vol 70 (a1) ◽  
pp. C720-C720
Author(s):  
Sofia Diaz-Moreno ◽  
Daniel Bowron
Keyword(s):  
Large Scale ◽  
Biochemical Properties ◽  
X Ray Diffraction ◽  
Ion Hydration ◽  
Neutron Sources ◽  
X Ray ◽  
Chemical Systems ◽  
The Past ◽  
Hydration Shells ◽  
X Ray Absorption

Techniques developed at large scale facilities such as X-ray synchrotrons and pulsed or reactor based neutron sources have, over the past few decades, played a significant role in unravelling many of the mysteries that underpin the chemical, physical and biochemical properties of ions in solutions. In this presentation we will illustrate how the combination of X-ray diffraction, neutron diffraction and X-ray absorption spectroscopy can be applied to the investigation of the structure of ion hydration shells. Examples of hydration of di- and tri-valent ions will be shown. In particular we will present an investigation of the hydration structure of copper (II) ions using this multi-technique approach, and discuss the findings in the context of biological and chemical systems.

New approach to the x-ray-absorption problem

1981 ◽  
Vol 24 (8) ◽  
pp. 4863-4866 ◽  
Author(s):  
Luiz N. Oliveira ◽  
John W. Wilkins
Keyword(s):  
New Approach ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Neural network assisted analysis of bimetallic nanocatalysts using X-ray absorption near edge structure spectroscopy

2020 ◽  
Vol 22 (34) ◽  
pp. 18902-18910 ◽  
Author(s):  
Nicholas Marcella ◽  
Yang Liu ◽  
Janis Timoshenko ◽  
Erjia Guan ◽  
Mathilde Luneau ◽  
...  
Keyword(s):  
Neural Network ◽  
Local Structure ◽  
Bimetallic Nanoparticles ◽  
Edge Structure ◽  
X Ray ◽  
Coordination Numbers ◽  
Rich Information ◽  
Bimetallic Nanocatalysts ◽  
Assisted Analysis ◽  
X Ray Absorption

Trained neural networks are used to extract the first partial coordination numbers from XANES spectra. In bimetallic nanoparticles, the four local structure descriptors provide rich information on structural motifs.

scholarly journals Signatures of technetium oxidation states: a new approach

2020 ◽  
Vol 56 (67) ◽  
pp. 9608-9611
Author(s):  
Stephen Bauters ◽  
Andreas C. Scheinost ◽  
Katja Schmeide ◽  
Stephan Weiss ◽  
Kathy Dardenne ◽  
...  
Keyword(s):  
Oxidation State ◽  
Oxidation States ◽  
General Strategy ◽  
New Approach ◽  
X Ray ◽  
X Ray Absorption

A general strategy for the determination of Tc oxidation state by a new approach involving X-ray absorption near edge spectroscopy (XANES) at the Tc L3 edge is shown.

Calculating absorption dose when X-ray irradiation modifies material quantity and chemistry

2021 ◽  
Vol 28 (3) ◽  
Author(s):  
Viatcheslav Berejnov ◽  
Boris Rubinstein ◽  
Lis G. A. Melo ◽  
Adam P. Hitchcock
Keyword(s):  
Chemical Speciation ◽  
New Approach ◽  
X Ray ◽  
Scanning Transmission ◽  
Versatile Tool ◽  
Solid Film ◽  
Simplifying Assumptions ◽  
High Doses ◽  
Sensitive Parameters ◽  
X Ray Absorption

X-ray absorption is a sensitive and versatile tool for chemical speciation. However, when high doses are used, the absorbed energy can change the composition, amount and structure of the native material, thereby changing the aspects of the absorption process on which speciation is based. How can one calculate the dose when X-ray irradiation affects the chemistry and changes the amount of the material? This paper presents an assumption-free approach which can retrieve from the experimental data all dose-sensitive parameters – absorption coefficients, composition (elemental molecular units), material densities – which can then be used to calculate accurate doses as a function of irradiation. This approach is illustrated using X-ray damage to a solid film of a perfluorosulfonic acid fluoropolymer in a scanning transmission soft X-ray microscope. This new approach is compared against existing dose models which calculate the dose by making simplifying assumptions regarding the material quantity, density and chemistry. While the detailed measurements used in this approach go beyond typical methods to experimental analytical X-ray absorption, they provide a more accurate quantitation of radiation dose, and help to understand mechanisms of radiation damage.

Scanning Transmission X-ray Spectromicroscopy of Actinide Complexes

2008 ◽  
Vol 1104 ◽  
Author(s):  
David Shuh ◽  
Roy Copping ◽  
Tolek Tyliszczak ◽  
Ingrid Castro-Rodriguez ◽  
David K. Shuh
Keyword(s):  
Environmental Science ◽  
Light Element ◽  
Reference Spectrum ◽  
Donor Ligand ◽  
X Ray ◽  
Nitrogen Donor Ligand ◽  
Nitrogen Donor ◽  
Scanning Transmission ◽  
X Ray Absorption ◽  
Uranium Complex

AbstractThe fundamental characterization and understanding of 5f electron behavior in actinide complexes is imperative to provide an enhanced basis for the rational and accelerated development of improved processes relevant to nuclear energy. Soft x-ray absorption spectroscopy utilizing the scanning transmission x-ray microscope (STXM) at the Advanced Light Source-Molecular Environmental Science (ALS-MES) Beamline 11.0.2 has been used to probe the electronic characteristics of a nitrogen donor ligand 2,6-Bis(2-benzimidazyl)pyridine (BBP) and its resulting U(IV) complex. The nitrogen K- and carbon K-edges have been collected from both ligand and uranium complex, as well as the uranium 4d-edge from the complex. Upon complexation, the light element absorption spectra change markedly and the uranium spectra from the complex is compared to the reference spectrum obtained from U(IV)Cl4. The evolution of the spectral features are described and interpreted within a simple conceptual framework. Based on spectral evidence alone, the uranium is bound through the pyridine-like nitrogens and the oxidation state of the uranium is consistent with a U(IV) species.

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