Imaging XPS. A Contribution to 3D X-ray Analysis

1990 ◽  
Vol 34 ◽  
pp. 201-211
Author(s):  
M. F. Ebel ◽  
H. Ebel ◽  
M. Mantler ◽  
R. Svagera
Keyword(s):  
Measured Signal ◽  
X Ray ◽  
Analytical Technique ◽  
Surface Analytical Technique

X-ray photoelectron spectrometry (XPS) has been a well established surface analytical technique for approximately 20 years. Fhotoelectrons are ejected by characteristic x-radiation. In our investigations we use Alκα-radiation. The depth from which l-l/e of the measured signal comes, is restricted to a few nanometers by inelastic mean free paths of photoelectrons in solids.

Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

1990 ◽  
Vol 48 (2) ◽  
pp. 388-389
Author(s):  
A. M. Bradshaw
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Reactivity ◽  
Target Material ◽  
Orbital Energy ◽  
Light Sources ◽  
Analytical Technique ◽  
Hartree Fock ◽  
Spatially Resolved ◽  
Koopmans Theorem ◽  
Surface Analytical Technique

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

scholarly journals Living-Cell Diffracted X-ray Tracking Analysis Confirmed Internal Salt Bridge Is Critical for Ligand-Induced Twisting Motion of Serotonin Receptors

2021 ◽  
Vol 22 (10) ◽  
pp. 5285
Author(s):  
Kazuhiro Mio ◽  
Shoko Fujimura ◽  
Masaki Ishihara ◽  
Masahiro Kuramochi ◽  
Hiroshi Sekiguchi ◽  
...  
Keyword(s):  
Serotonin Receptors ◽  
Serotonin Receptor ◽  
Frame Rate ◽  
Receptor Subtype ◽  
Transmembrane Segment ◽  
Hek 293 ◽  
Gold Nanocrystals ◽  
X Ray ◽  
Time Dynamics ◽  
Analytical Technique

Serotonin receptors play important roles in neuronal excitation, emotion, platelet aggregation, and vasoconstriction. The serotonin receptor subtype 2A (5-HT2AR) is a Gq-coupled GPCR, which activate phospholipase C. Although the structures and functions of 5-HT2ARs have been well studied, little has been known about their real-time dynamics. In this study, we analyzed the intramolecular motion of the 5-HT2AR in living cells using the diffracted X-ray tracking (DXT) technique. The DXT is a very precise single-molecular analytical technique, which tracks diffraction spots from the gold nanocrystals labeled on the protein surface. Trajectory analysis provides insight into protein dynamics. The 5-HT2ARs were transiently expressed in HEK 293 cells, and the gold nanocrystals were attached to the N-terminal introduced FLAG-tag via anti-FLAG antibodies. The motions were recorded with a frame rate of 100 μs per frame. A lifetime filtering technique demonstrated that the unliganded receptors contain high mobility population with clockwise twisting. This rotation was, however, abolished by either a full agonist α-methylserotonin or an inverse agonist ketanserin. Mutation analysis revealed that the “ionic lock” between the DRY motif in the third transmembrane segment and a negatively charged residue of the sixth transmembrane segment is essential for the torsional motion at the N-terminus of the receptor.

Investigation of low-energy ion scattering as a surface analytical technique

1972 ◽  
Vol 30 (1) ◽  
pp. 69-90 ◽  
Author(s):  
D.J. Ball ◽  
T.M. Buck ◽  
D. Macnair ◽  
G.H. Wheatley
Keyword(s):  
Low Energy ◽  
Ion Scattering ◽  
Analytical Technique ◽  
Low Energy Ion Scattering ◽  
Surface Analytical Technique

scholarly journals Evaluation of ash related problems during sewage sludge combustion

2019 ◽  
pp. 184-191
Author(s):  
Agnes Serbanescu ◽  
Mona Barbu ◽  
Ionut Cristea ◽  
Gina Catrina ◽  
Georgiana Cernica ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Combustion Process ◽  
Experimental Studies ◽  
Calorific Value ◽  
Waste To Energy ◽  
Mineral Matter ◽  
X Ray ◽  
Analytical Technique ◽  
Acid Ratio ◽  
Sludge Ash

A good function of waste-to-energy installation requires knowledge of the combustion characteristics of the fuel and fusion characteristics of the ash produced in the combustion process. Sewage sludge could be considered as renewable fuel due the high quantity of organics of sufficiently high calorific value. The combustion of sewage sludge can cause operating problems due to high ash content containing mineral compounds. This paper presents the oxide composition of three kinds of sewage sludge ashes and the influence on the slagging and fouling process in combustion. For comparation, two coal samples were selected, a low and a high rank coal. The mineral matter were investigated by the X-ray fluorescence analytical technique using the Rigaku CG X-ray Spectrofluorimeter. The evaluation of slagging and fouling process was performed on the basis of some indices: the basic oxides, the base-to-acid ratio, the slagging index and the fouling index. The conclusion based on experimental studies is that depending on mineral content the sewage sludge ash can cause high to moderate slagging and fouling hazard.

scholarly journals Multielement analysis of plant extracts with potential use in the treatment of peptic ulcers by synchrotron radiation total reflection X-ray fluorescence

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5375
Author(s):  
Leticia Diniz Vieira ◽  
Káthia Takeda da Silva ◽  
Rodrigo Sanchez Giarola ◽  
Guilherme Franco Inocente ◽  
Hélio Kushima ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Intermediate Stage ◽  
Total Reflection ◽  
New Drugs ◽  
Peptic Ulcers ◽  
X Ray ◽  
Analytical Technique ◽  
Methanolic Extracts ◽  
Synchrotron Light ◽  
Almost All

Some plants popularly employed for the treatment of peptic ulcers have proved to be attractive sources of new drugs. Despite extensive research, the pharmacological and toxicological potentials of these plants are not fully understood. In this context, the aim of this work was to analyze the multielemental composition of the methanolic extracts of three of those plants, Alchornea glandulosa (AG), Davilla elliptica (DE) and Davilla nitida (DN), with the intention of contributing to the understanding of the mechanisms of action of these extracts. For this purpose, we used the analytical technique of total reflection X-ray fluorescence (TXRF) by synchrotron radiation at the Brazilian Synchrotron Light Source (LNLS/CNPEM). It was possible to determine the concentrations of the elements: P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb and Br in all of the samples. Selenium (Se) was detected only in the DN extract. An inverse relationship between the concentrations of elements with proven effectiveness and the gastroprotective activity of extracts considering induction protocols with ethanol and non-steroidal anti-inflammatory drugs (NSAIDs) was obtained. This data suggests that the function of the extract is not only associated with providing the elements for restoring the gastric mucosa but that it also promotes the displacement of these elements from other parts of the mucosa to the damaged area. Correlations between the concentrations of the elements were also obtained. In the DE extract, which is the most effective extract for both induction protocols, the obtained correlations were above 70% among almost all of the elements, and no anticorrelations were found. For the other two extracts, in the less effective extract (AG) anticorrelations above 70% were predominantly found. Meanwhile, in the DN extract, a few high anticorrelations were found, which may explain its intermediate stage of effectiveness.

scholarly journals Visualizing a viral genome with contrast variation small angle X-ray scattering

2020 ◽  
Vol 295 (47) ◽  
pp. 15923-15932
Author(s):  
Josue San Emeterio ◽  
Lois Pollack
Keyword(s):  
Small Angle ◽  
Viral Genome ◽  
Viral Assembly ◽  
Measured Signal ◽  
Structural Rearrangements ◽  
Contrast Variation ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Despite the threat to human health posed by some single-stranded RNA viruses, little is understood about their assembly. The goal of this work is to introduce a new tool for watching an RNA genome direct its own packaging and encapsidation by proteins. Contrast variation small-angle X-ray scattering (CV-SAXS) is a powerful tool with the potential to monitor the changing structure of a viral RNA through this assembly process. The proteins, though present, do not contribute to the measured signal. As a first step in assessing the feasibility of viral genome studies, the structure of encapsidated MS2 RNA was exclusively detected with CV-SAXS and compared with a structure derived from asymmetric cryo-EM reconstructions. Additional comparisons with free RNA highlight the significant structural rearrangements induced by capsid proteins and invite the application of time-resolved CV-SAXS to reveal interactions that result in efficient viral assembly.

High energy resolution PIXE spectroscopy at the J. Stefan Institute, Ljubljana

2014 ◽  
Vol 24 (03n04) ◽  
pp. 205-215
Author(s):  
M. Kavčič
Keyword(s):  
Trace Element ◽  
Energy Resolution ◽  
Trace Element Analysis ◽  
High Energy ◽  
Energy Dispersive ◽  
High Energy Resolution ◽  
Pixe Analysis ◽  
X Ray ◽  
Analytical Technique ◽  
Stefan Institute

While traditional proton induced X-ray emission (PIXE) analytical technique is based on the energy dispersive solid state detectors used to collect the X-ray fluorescence from the sample, wavelength dispersive X-ray (WDX) spectrometers are applied in high energy resolution PIXE (HR-PIXE) analysis. The main drawback of the WDX spectroscopy is the relatively low efficiency making it less applicable for trace element PIXE analysis. However, the efficiency was enhanced significantly in modern spectrometers employing cylindrically or even spherically curved crystals combined with position sensitive X-ray detectors. The energy resolution of such a spectrometer may exceed the resolution of the energy dispersive detector by two orders of magnitude while keeping the efficiency at a high enough level to perform trace element analysis. In this paper, the recent history and the development of HR-PIXE spectroscopy at the J. Stefan Institute in Ljubljana is presented. Our current setup based on in-vacuum Johansson-type crystal spectrometer is presented in more details followed by some most recent applications.

X-Ray Powder Diffraction (XRPD)

2016 ◽  
pp. 326-341 ◽  
Author(s):  
Robert Heimann
Keyword(s):  
Powder Diffraction ◽  
X Rays ◽  
Powder Diffraction File ◽  
Thin Beam ◽  
Archaeological Ceramics ◽  
X Ray ◽  
Analytical Technique ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

X-ray powder diffraction (XRPD) is an important tool to determine the phase composition of archaeological ceramics. In principle, a thin beam of X-rays incident to a lattice plane of crystalline matter is scattered in specific directions and angles depending on the distances of atoms. This allows determination of characteristic unit cell dimensions and serves to unambiguously identify crystalline phases in the ceramics. In this chapter, generation of X-rays and the theory of diffraction will be briefly discussed as well as equipment, focusing conditions, and sample preparation procedures of common XRPD methods. The X-ray pattern obtained will provide an analytical fingerprint that can be matched against the Powder Diffraction File of the International Centre for Diffraction Data. Examples will be given of application of this analytical technique to archaeological clays and ceramics.

Small, Area X-Ray Diffraction Techniques: Errors in Strain Measurement

1987 ◽  
Vol 31 ◽  
pp. 77-85
Author(s):  
Thomas L. Nunes ◽  
Charles C. Goldsmith
Keyword(s):  
Lattice Distortion ◽  
Semiconductor Industry ◽  
Photon Counting ◽  
Random Errors ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analytical Technique ◽  
Beam Displacement ◽  
Counting Statistics ◽  
Area X

AbstractThe semiconductor industry is continually striving'for smaller, denser devices. Microdiffractometry is an analytical technique which endeavors to apply x-ray diffraction techniques for measuring strain and phase information to areas approaching 50 micrometers diameter or less.This study extends the work of Goldsmith and Walker in the measurement of strain using the lattice distortion or sin2(ψ) plot method.The systematic errors arising from both sample and beam displacement relative to the center of rotation of the cample ie examined. A relationship is derived which predicts the influence of these displacements upon the slope of a stress plot. The predictions are compared to experiment.The influence of random errors arising from particle size and photon counting statistics will also be discussed. Guidelines will be presented which will minimize both systematic and random errors.

X-Ray Absorption Spectroscopy Applied to Metal Accumulation

2009 ◽  
Vol 71-73 ◽  
pp. 613-616
Author(s):  
Regina Pinto de Carvalho ◽  
G.C. Silva ◽  
M. Sylvia S. Dantas ◽  
I.F. Vasconcelos ◽  
Virgínia S.T. Ciminelli
Keyword(s):  
Physical State ◽  
Unique Feature ◽  
Metal Accumulation ◽  
X Rays ◽  
Absorption Probability ◽  
X Ray ◽  
Analytical Technique ◽  
Absorption Phenomenon ◽  
Almost All ◽  
X Ray Absorption

X-Rays Absorption Fine Structure Spectroscopy (XAFS) is an analytical technique that can be used as a probe to characterize almost all elements, even if they appear in diluted or non-crystalline systems. This is due to the fact that the absorption probability of X-rays has a unique feature for each element, and is modulated by the chemical and physical state of that element, as well as by its neighborhood. This paper presents a brief description of the X-rays absorption phenomenon and the analytical technique involving this phenomenon, as well as the application of XAFS in biosorption studies. For more details on XAFS theory, refer to [1].

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