scholarly journals 3D multi-scale modelling of plasma-based seeded soft X-ray lasers

2021 ◽  
Vol 75 (11) ◽  
Author(s):  
Eduardo Oliva ◽  
Elisa V. Fernández-Tello ◽  
Manuel Cotelo ◽  
Pablo Martínez Gil ◽  
José Antonio Moreno ◽  
...  
Keyword(s):  
Inhomogeneous Plasma ◽  
X Rays ◽  
Electron Collisions ◽  
X Ray ◽  
Multi Scale ◽  
High Order Harmonic ◽  
Hydrodynamic Evolution ◽  
Scale Modelling ◽  
Computational Paradigm ◽  
Spatio Temporal

AbstractModelling plasma-based seeded soft X-ray lasers from the creation of the plasma to the propagation of a femtosecond high-order harmonic (HOH) seed throughout several millimetres of inhomogeneous plasma is a complex challenge. Different spatio-temporal scales from the hydrodynamic evolution of the plasma (hundreds of micrometres and nanoseconds) to the propagation of pulses through the plasma (millimetres and tens of picoseconds), electron collisions (picoseconds or even shorter) and the evolution of the envelope of the seeded HOH (tens of femtoseconds) must be tackled in order to fully understand these systems. In this paper, we will present the multi-scale computational paradigm that we have used to perform a full ab initio simulation of a dense, Ni-like Krypton plasma amplifier of soft X-rays. Results of the modelling and expected future applications will also be shown.

scholarly journals Automated segmentation and diagnosis of pneumothorax on chest X-rays with fully convolutional multi-scale ScSE-DenseNet: a retrospective study

2020 ◽  
Vol 20 (S14) ◽  
Author(s):  
Qingfeng Wang ◽  
Qiyu Liu ◽  
Guoting Luo ◽  
Zhiqin Liu ◽  
Jun Huang ◽  
...  
Keyword(s):  
Retrospective Study ◽  
Automatic Segmentation ◽  
Medical Emergency ◽  
Dice Similarity Coefficient ◽  
X Rays ◽  
X Ray ◽  
Learning Framework ◽  
Multi Scale ◽  
Life Threatening ◽  
Chest X Ray

Abstract Background Pneumothorax (PTX) may cause a life-threatening medical emergency with cardio-respiratory collapse that requires immediate intervention and rapid treatment. The screening and diagnosis of pneumothorax usually rely on chest radiographs. However, the pneumothoraces in chest X-rays may be very subtle with highly variable in shape and overlapped with the ribs or clavicles, which are often difficult to identify. Our objective was to create a large chest X-ray dataset for pneumothorax with pixel-level annotation and to train an automatic segmentation and diagnosis framework to assist radiologists to identify pneumothorax accurately and timely. Methods In this study, an end-to-end deep learning framework is proposed for the segmentation and diagnosis of pneumothorax on chest X-rays, which incorporates a fully convolutional DenseNet (FC-DenseNet) with multi-scale module and spatial and channel squeezes and excitation (scSE) modules. To further improve the precision of boundary segmentation, we propose a spatial weighted cross-entropy loss function to penalize the target, background and contour pixels with different weights. Results This retrospective study are conducted on a total of eligible 11,051 front-view chest X-ray images (5566 cases of PTX and 5485 cases of Non-PTX). The experimental results show that the proposed algorithm outperforms the five state-of-the-art segmentation algorithms in terms of mean pixel-wise accuracy (MPA) with $$0.93\pm 0.13$$ 0.93 ± 0.13 and dice similarity coefficient (DSC) with $$0.92\pm 0.14$$ 0.92 ± 0.14 , and achieves competitive performance on diagnostic accuracy with 93.45% and $$F_1$$ F 1 -score with 92.97%. Conclusion This framework provides substantial improvements for the automatic segmentation and diagnosis of pneumothorax and is expected to become a clinical application tool to help radiologists to identify pneumothorax on chest X-rays.

scholarly journals Recent advances in ultrafast X-ray sources

2019 ◽  
Vol 377 (2145) ◽  
pp. 20180384 ◽  
Author(s):  
Robert Schoenlein ◽  
Thomas Elsaesser ◽  
Karsten Holldack ◽  
Zhirong Huang ◽  
Henry Kapteyn ◽  
...  
Keyword(s):  
Structural Dynamics ◽  
Materials Science ◽  
X Rays ◽  
X Ray ◽  
High Order Harmonic ◽  
Recent Advances ◽  
Electronic Motion ◽  
Femtosecond Regime ◽  
Indispensable Tool ◽  
And Function

Over more than a century, X-rays have transformed our understanding of the fundamental structure of matter and have been an indispensable tool for chemistry, physics, biology, materials science and related fields. Recent advances in ultrafast X-ray sources operating in the femtosecond to attosecond regimes have opened an important new frontier in X-ray science. These advances now enable: (i) sensitive probing of structural dynamics in matter on the fundamental timescales of atomic motion, (ii) element-specific probing of electronic structure and charge dynamics on fundamental timescales of electronic motion, and (iii) powerful new approaches for unravelling the coupling between electronic and atomic structural dynamics that underpin the properties and function of matter. Most notable is the recent realization of X-ray free-electron lasers (XFELs) with numerous new XFEL facilities in operation or under development worldwide. Advances in XFELs are complemented by advances in synchrotron-based and table-top laser-plasma X-ray sources now operating in the femtosecond regime, and laser-based high-order harmonic XUV sources operating in the attosecond regime. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

scholarly journals X-ray emission from the solar wind

1970 ◽  
Vol 37 ◽  
pp. 408-412
Author(s):  
E. Boldt ◽  
A. Klimas ◽  
G. Sandri
Keyword(s):  
Solar Wind ◽  
Mean Free Path ◽  
Ecliptic Plane ◽  
Line Of Sight ◽  
Astronomical Unit ◽  
The Sun ◽  
X Rays ◽  
Electron Collisions ◽  
X Ray ◽  
Recent Developments

Recent developments have made it possible to detect cosmic X-rays with energies as low as several hundred eV. Several measurements of the diffuse X-radiation in this range have been reported (Baxter et al., 1969; Bowyer et al., 1968; Henry et al., 1968). In this note we investigate the possibility that these observers have detected X-radiation emitted by the solar wind. We conclude that they probably have not. However, we also find that bremsstrahlung may be detectable from a region of the sky near the sun. If this measurement is possible, it would represent an important method for determining some characteristics of the solar wind away from the ecliptic plane of the solar system. Even though the mean free path for electron collisions is large compared with the astronomical unit, the collision frequency, electron density, and energy released per encounter are sufficient to yield detectable soft X-radiation for lines of sight close to the sun. We have estimated the expected X-ray intensity in the vicinity of the earth on the basis of two models of the solar wind flow pattern; in the first, the flow is radial in all directions away from the sun, and in the second, the flow is confined to a disc of uniform thickness near the ecliptic. In both cases, we neglect temperature gradients for the electrons and compute the total flux received from interplanetary plasma along the line of sight. Most of the received intensity comes from the segment of the line of sight which is nearest the sun. The results are insensitive with respect to the position of the boundary of the solar cavity. Accordingly, we neglect the boundary and consider an infinitely large solar cavity.

scholarly journals Dynamic nanoimaging of extended objects via hard X-ray multiple-shot coherent diffraction with projection illumination optics

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuki Takayama ◽  
Keizo Fukuda ◽  
Motoki Kawashima ◽  
Yuki Aoi ◽  
Daiki Shigematsu ◽  
...  
Keyword(s):  
Phase Retrieval ◽  
Frame Rate ◽  
Retrieval Algorithm ◽  
X Rays ◽  
Full Field ◽  
X Ray ◽  
Cell Functions ◽  
Multiple Shot ◽  
Spatio Temporal ◽  
Diffraction Patterns

AbstractThe quest for understanding the structural mechanisms of material properties and biological cell functions has led to the active development of coherent diffraction imaging (CDI) and its variants in the hard X-ray regime. Herein, we propose multiple-shot CDI, a full-field CDI technique dedicated to the visualisation of local nanostructural dynamics in extended objects at a spatio-temporal resolution beyond that of current instrumentation limitations. Multiple-shot CDI reconstructs a “movie” of local dynamics from time-evolving diffraction patterns, which is compatible with a robust scanning variant, ptychography. We developed projection illumination optics to produce a probe with a well-defined illumination area and a phase retrieval algorithm, establishing a spatio-temporal smoothness constraint for the reliable reconstruction of dynamic images. The numerical simulations and proof-of-concept experiment using synchrotron hard X-rays demonstrated the capability of visualising a dynamic nanostructured object at a frame rate of 10 Hz or higher.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

Influence of X-Ray Induced Fluorescence on Energy Dispersive X-Ray Analysis of Thin Foils

1977 ◽  
Vol 35 ◽  
pp. 328-329
Author(s):  
E. A. Kenik ◽  
J. Bentley
Keyword(s):  
Thin Foil ◽  
Electron Excitation ◽  
Simple Approach ◽  
Foil Thickness ◽  
X Rays ◽  
X Ray ◽  
Hole Spectrum ◽  
Illumination System ◽  
Thin Foils ◽  
Intensity Ratios

Cliff and Lorimer (1) have proposed a simple approach to thin foil x-ray analy sis based on the ratio of x-ray peak intensities. However, there are several experimental pitfalls which must be recognized in obtaining the desired x-ray intensities. Undesirable x-ray induced fluorescence of the specimen can result from various mechanisms and leads to x-ray intensities not characteristic of electron excitation and further results in incorrect intensity ratios.In measuring the x-ray intensity ratio for NiAl as a function of foil thickness, Zaluzec and Fraser (2) found the ratio was not constant for thicknesses where absorption could be neglected. They demonstrated that this effect originated from x-ray induced fluorescence by blocking the beam with lead foil. The primary x-rays arise in the illumination system and result in varying intensity ratios and a finite x-ray spectrum even when the specimen is not intercepting the electron beam, an ‘in-hole’ spectrum. We have developed a second technique for detecting x-ray induced fluorescence based on the magnitude of the ‘in-hole’ spectrum with different filament emission currents and condenser apertures.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

X-ray diffraction properties of curved crystal diffractors

1992 ◽  
Vol 50 (2) ◽  
pp. 1734-1735
Author(s):  
W. Z. Chang ◽  
D. B. Wittry
Keyword(s):  
Diffraction Theory ◽  
X Rays ◽  
Diffraction Image ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Bent Crystal ◽  
Diffraction Geometry ◽  
Crystal Parameter ◽  
Quantitative Procedure

Since Du Mond and Kirkpatrick first discussed the principle of a bent crystal spectrograph in 1930, curved single crystals have been widely utilized as spectrometric monochromators as well as diffractors for focusing x rays diverging from a point. Curved crystal diffraction theory predicts that the diffraction parameters - the rocking curve width w, and the peak reflection coefficient r of curved crystals will certainly deviate from those of their flat form. Due to a lack of curved crystal parameter data in current literature and the need for optimizing the choice of diffraction geometry and crystal materials for various applications, we have continued the investigation of our technique presented at the last conference. In the present abstract, we describe a more rigorous and quantitative procedure for measuring the parameters of curved crystals.The diffraction image of a singly bent crystal under study can be obtained by using the Johann geometry with an x-ray point source.

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