scholarly journals Macromolecular Nanocrystal Structural Analysis with Electron and X-Rays: A Comparative Review

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3490
Author(s):  
Krishna P. Khakurel ◽  
Borislav Angelov ◽  
Jakob Andreasson
Keyword(s):  
Structural Analysis ◽  
Structural Models ◽  
X Rays ◽  
High Quality ◽  
X Ray ◽  
Detection Techniques ◽  
Comparative Review

Crystallography has long been the unrivaled method that can provide the atomistic structural models of macromolecules, using either X-rays or electrons as probes. The methodology has gone through several revolutionary periods, driven by the development of new sources, detectors, and other instrumentation. Novel sources of both X-ray and electrons are constantly emerging. The increase in brightness of these sources, complemented by the advanced detection techniques, has relaxed the traditionally strict need for large, high quality, crystals. Recent reports suggest high-quality diffraction datasets from crystals as small as a few hundreds of nanometers can be routinely obtained. This has resulted in the genesis of a new field of macromolecular nanocrystal crystallography. Here we will make a brief comparative review of this growing field focusing on the use of X-rays and electrons sources.

scholarly journals Optimization of X-ray Investigations in Dentistry Using Optical Coherence Tomography

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4554
Author(s):  
Ralph-Alexandru Erdelyi ◽  
Virgil-Florin Duma ◽  
Cosmin Sinescu ◽  
George Mihai Dobre ◽  
Adrian Bradu ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Radiation Dose ◽  
Imaging Techniques ◽  
Image Resolution ◽  
Optical Coherence ◽  
X Rays ◽  
High Quality ◽  
X Ray

The most common imaging technique for dental diagnoses and treatment monitoring is X-ray imaging, which evolved from the first intraoral radiographs to high-quality three-dimensional (3D) Cone Beam Computed Tomography (CBCT). Other imaging techniques have shown potential, such as Optical Coherence Tomography (OCT). We have recently reported on the boundaries of these two types of techniques, regarding. the dental fields where each one is more appropriate or where they should be both used. The aim of the present study is to explore the unique capabilities of the OCT technique to optimize X-ray units imaging (i.e., in terms of image resolution, radiation dose, or contrast). Two types of commercially available and widely used X-ray units are considered. To adjust their parameters, a protocol is developed to employ OCT images of dental conditions that are documented on high (i.e., less than 10 μm) resolution OCT images (both B-scans/cross sections and 3D reconstructions) but are hardly identified on the 200 to 75 μm resolution panoramic or CBCT radiographs. The optimized calibration of the X-ray unit includes choosing appropriate values for the anode voltage and current intensity of the X-ray tube, as well as the patient’s positioning, in order to reach the highest possible X-rays resolution at a radiation dose that is safe for the patient. The optimization protocol is developed in vitro on OCT images of extracted teeth and is further applied in vivo for each type of dental investigation. Optimized radiographic results are compared with un-optimized previously performed radiographs. Also, we show that OCT can permit a rigorous comparison between two (types of) X-ray units. In conclusion, high-quality dental images are possible using low radiation doses if an optimized protocol, developed using OCT, is applied for each type of dental investigation. Also, there are situations when the X-ray technology has drawbacks for dental diagnosis or treatment assessment. In such situations, OCT proves capable to provide qualitative images.

scholarly journals X-Ray Superbubbles

1983 ◽  
Vol 6 ◽  
pp. 675-680
Author(s):  
Webster Cash
Keyword(s):  
Interstellar Medium ◽  
Collective Effects ◽  
Selection Effects ◽  
X Rays ◽  
High Quality ◽  
X Ray ◽  
Common Structure ◽  
The Galaxy ◽  
Gum Nebula

AbstractFour regions of the galaxy, the Cygnus Superbubble, the ƞ Carina complex, the Orion/Eridanus complex, and the Gum Nebula, are discussed as examples of collective effects in the interstellar medium. All four regions share certain features, indicating a common structure. We discuss the selection effects which determine the observable x-ray properties of the superbubbles and demonstrate that only a very few more in our galaxy can be detected in x-rays. X-ray observation of extragalactic superbubbles is shown to be possible but requires the capabilities of a large, high quality, AXAF class observatory.

scholarly journals IVAN PULUJ AND THE DISCOVERY OF X-RAYS

2021 ◽  
Vol 64 (1) ◽  
Author(s):  
Ulyana Pidvalna ◽  
◽  
Roman Plyatsko ◽  
Vassyl Lonchyna ◽  
◽  
...  
Keyword(s):  
International Exhibition ◽  
Bone Lesions ◽  
X Rays ◽  
High Quality ◽  
X Ray ◽  
Exact Date ◽  
Starting Point ◽  
The World ◽  
New Type ◽  
The Given

On January 5, 1896, the Austrian newspaper Die Presse published an article entitled “A Sensational Discovery”. It was dedicated to the discovery of X-rays made on November 8, 1895 by the German physicist Wilhelm Conrad Röntgen. Having taken into account the contribution of other scientists, the precondition of the given epochal, yet unexpected, discovery was, first and foremost, the work of the Ukrainian scientist Ivan Puluj. It was Puluj who laid the foundation for X-ray science. He explained the nature of X-rays, discovered that they can ionize atoms and molecules, and defined the place of X-ray emergence and their distribution in space. In 1881, Puluj constructed a cathode lamp (“Puluj’s tube”) which was fundamentally a new type of light source. In the same year, in recognition of this discovery, Puluj received an award at the International Exhibition in Paris. Investigating the processes in cathode-ray tubes, Ivan Puluj set the stage for two ground-breaking discoveries in physics, namely X-rays and electrons. Puluj used his cathode lamp in medicine as a source of intense X-rays which proved to be highly efficient. The exact date of the first X-ray images received by Puluj remains unknown. High-quality photographs of the hand of an eleven-year-old girl, taken on January 18, 1896, are preserved. Multiple X-ray images clearly visualized pathological changes in the examined structures (fractures, calluses, tuberculous bone lesions). High-quality images were obtained by means of the anticathode in the design of Puluj’s lamp, which was the first in the world. The image of the whole skeleton of a stillborn child (published on April 3, 1896 in The Photogram) is considered to be the starting point of using X-rays in anatomy.

Energy Dispersive Diffraction in a Diamond Anvil High Pressure Cell Using Synchrotron and Conventional X-Radiation

1983 ◽  
Vol 27 ◽  
pp. 331-337
Author(s):  
David R. Black ◽  
Carmen S. Menoni ◽  
Ian L. Spain
Keyword(s):  
High Pressure ◽  
Energy Dispersive ◽  
X Rays ◽  
High Pressure Cell ◽  
X Ray ◽  
Detection Techniques ◽  
Wide Range ◽  
Diamond Anvil ◽  
Experimental Geometry ◽  
Energy Dispersive Diffraction

A wide range of structural studies have been carried out in high pressure diamond anvil cells using x-rays. The most common experimental geometry is shown in Fig. 1a. The incident x-ray beam passes axially through the first diamond and enters the sample, typically 100-300 μm in diameter and 20-100 μm thick; the diffracted x-rays exit via the second diamond. Energy-dispersive detection techniques (EDXRD) have been used. However the intensity of diffracted radiation from the sample is weak, so that typical exposure times with a conventional, fixed anode, x-ray source are typically one to several days.Accordingly, higher intensity radiation from synchrotron sources has been used for these experiments.

Soft X-ray photochemistry beamline at SPring-8

1998 ◽  
Vol 5 (3) ◽  
pp. 545-547 ◽  
Author(s):  
I. Koyano ◽  
M. Okuyama ◽  
E. Ishiguro ◽  
A. Hiraya ◽  
H. Ohashi ◽  
...  
Keyword(s):  
High Resolution ◽  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
X Rays ◽  
High Quality ◽  
X Ray ◽  
Excitation Region ◽  
Linearly Polarized ◽  
Grating Monochromator

Design and construction of a soft X-ray beamline at SPring-8 is reported. The beamline utilizes high-quality linearly polarized soft X-rays obtainable from a figure-8 undulator for the study of photophysical and photochemical processes of atoms, molecules and surfaces in the inner-shell excitation region. It consists of two experimental stations, a photochemistry station and a chemical vapour deposition (CVD) station. A high-resolution grating monochromator is installed at the photochemistry station, while the intense undispersed undulator radiation is used at the CVD station. Unique features of the experimental chambers and of the analysis and characterization systems are described along with those of the monochromator.

Atmospheric coherent X-ray diffraction imaging for in situ structural analysis at SPring-8 Hyogo beamline BL24XU

2018 ◽  
Vol 25 (4) ◽  
pp. 1229-1237
Author(s):  
Yuki Takayama ◽  
Yuki Takami ◽  
Keizo Fukuda ◽  
Takamasa Miyagawa ◽  
Yasushi Kagoshima
Keyword(s):  
Structural Analysis ◽  
Control Device ◽  
Photon Flux ◽  
X Rays ◽  
Atmospheric Conditions ◽  
X Ray Diffraction ◽  
Macroporous Silica ◽  
X Ray ◽  
Diffraction Imaging

Coherent X-ray diffraction imaging (CXDI) is a promising technique for non-destructive structural analysis of micrometre-sized non-crystalline samples at nanometre resolutions. This article describes an atmospheric CXDI system developed at SPring-8 Hyogo beamline BL24XU for in situ structural analysis and designed for experiments at a photon energy of 8 keV. This relatively high X-ray energy enables experiments to be conducted under ambient atmospheric conditions, which is advantageous for the visualization of samples in native states. The illumination condition with pinhole-slit optics is optimized according to wave propagation calculations based on the Fresnel–Kirchhoff diffraction formula so that the sample is irradiated by X-rays with a plane wavefront and high photon flux of ∼1 × 1010 photons/16 µmø(FWHM)/s. This work demonstrates the imaging performance of the atmospheric CXDI system by visualizing internal voids of sub-micrometre-sized colloidal gold particles at a resolution of 29.1 nm. A CXDI experiment with a single macroporous silica particle under controlled humidity was also performed by installing a home-made humidity control device in the system. The in situ observation of changes in diffraction patterns according to humidity variation and reconstruction of projected electron-density maps at 5.2% RH (relative humidity) and 82.6% RH at resolutions of 133 and 217 nm, respectively, were accomplished.

scholarly journals What controls the UV-to-X-ray continuum shape in quasars?

2021 ◽  
Author(s):  
John D Timlin ◽  
W N Brandt ◽  
Ari Laor
Keyword(s):  
Physical Mechanism ◽  
Extreme Ultraviolet ◽  
Spectral Shape ◽  
Continuum Emission ◽  
X Rays ◽  
Spectral Slope ◽  
High Quality ◽  
Broad Absorption ◽  
X Ray ◽  
The Continuum

Abstract We present an investigation of the interdependence of the optical-to-X-ray spectral slope (αox), the  He ii equivalent-width (EW), and the monochromatic luminosity at 2500 Å (L2500). The values of αox and  He ii EW are indicators of the strength/shape of the quasar ionizing continuum, from the ultraviolet (UV; 1500–2500 Å), through the extreme ultraviolet (EUV; 300–50 Å), to the  X-ray (2 keV) regime. For this investigation, we measure the  He ii EW of 206 radio-quiet quasars devoid of broad absorption lines that have high-quality spectral observations of the UV and 2 keV X-rays. The sample spans wide redshift (≈ 0.13–3.5) and luminosity (log(L2500) ≈ 29.2–32.5 erg s−1 Hz−1) ranges. We recover the well-known αox–L2500 and  He ii EW–L2500 anti-correlations, and we find a similarly strong correlation between αox and  He ii EW, and thus the overall spectral shape from the UV, through the EUV, to the  X-ray regime is largely set by luminosity. A significant αox– He ii EW correlation remains after removing the contribution of L2500 from each quantity, and thus the emission in the EUV and the X-rays are also directly tied. This set of relations is surprising, since the UV, EUV, and  X-ray emission are expected to be formed in three physically distinct regions. Our results indicate the presence of a redshift-independent physical mechanism that couples the continuum emission from these three different regions, and thus controls the overall continuum shape from the UV to the  X-ray regime.

High-quality quasi-parallel X-ray beam obtained by a parabolic monocapillary X-ray lens with a square beam stop

2021 ◽  
pp. 1-13
Author(s):  
Peng Zhou ◽  
Jingduo Cui ◽  
Zelin Du ◽  
Tao Zhang ◽  
Zhiguo Liu
Keyword(s):  
Optical Path ◽  
X Rays ◽  
High Quality ◽  
Optimal Position ◽  
X Ray ◽  
Proposed Model ◽  
Beam Stop ◽  
Path System ◽  
New Applications ◽  
Study Designs

Parabolic monocapillary X-ray lens (PMXRL) is an ideal optical device for constraining the point divergent X-ray beams to quasi-parallel beams, but the overlap of direct X-rays and reflected X-rays through PMXRL deteriorates the outgoing beam divergence. Aiming to solve this problem, this study designs and tests a square-shaped lead occluder (SSLO) embedded in PMXRL to block the direct X-rays passing through the PMXRL. Python simulations are employed to determine the geometric parameters of the SSLO as well as the optimal position of the SSLO in the PMXRL according to our proposed model. The PMXRL with a conic parameter p of 0.000939 mm and a length L of 60.8 mm is manufactured and the SSLO with a size of 0.472 mm×0.472 mm×3.4 mm is embedded into it. An optical path system based on this PMXRL is built to measure the divergence of the outgoing X-ray beam. The experimental results show that the quasi-parallel X-ray beam reaches a divergence of 0.36 mrad in the range from 15–45 mm at the PMXRL outlet. This divergence is 10 times lower than the theoretical divergence without SSLO. Our work provides an alternative method for obtaining highly parallel X-ray beam and is beneficial to generate or facilitate new applications of monocapillary optics in X-ray technology.

Construction of a Multimode High Resolution X-Ray Powder Diffractometer and its Perfomance

1991 ◽  
Vol 35 (A) ◽  
pp. 375-381
Author(s):  
Masayasu Kurahashi ◽  
Kazumasa Honda ◽  
Midori Goto ◽  
Yu Inari ◽  
Chuji Katayama
Keyword(s):  
High Resolution ◽  
Organic Compound ◽  
Imaging Plate ◽  
Large Radius ◽  
X Rays ◽  
Parallel Beam ◽  
High Quality ◽  
X Ray ◽  
Powder Diffractometer ◽  
Beam Mode

AbstractRecently some of the above authors determined the structure of an unsolved organic compound employing X-rays from a Synchrotron, an Imaging Plate, and a large radius camera. It would be more desirable if the high quality powder diffaction data could be obtained by a diffractometer or a camera of laboratory use. Therefore a multimode X-ray powder diffractometer which can be used for various experimental geometries such as Bragg-Brentano mode, Guinier mode and parallel beam mode was constructed in order to find the highest resolution geometry. In this paper wc present the results of the measurements employing these three modes.

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.

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