scholarly journals The structure of some crystals as indicated by their diffraction of X-rays

1913 ◽  
Vol 89 (610) ◽  
pp. 248-277 ◽  
Keyword(s):  
Electromagnetic Waves ◽  
Regular Point ◽  
Short Wave ◽  
Point System ◽  
X Rays ◽  
Original Memoir ◽  
Homogeneous Wave ◽  
Wide Range ◽  
Wave Trains ◽  
Narrow Bands

A new method of investigating the structure of a crystal has been afforded by the work of Laue* and his collaborators on the diffraction of X-rays by crystals. The phenomena which they were the first to investigate, and which have since been observed by many others, lend themselves readily to the explanation proposed by Laue, who supposed that electromagnetic waves of very short wave-lengths were diffracted by a set of small obstacles arranged on a regular point system in space. In analysing the interference pattern obtained with a zincblende crystal, Laue, in his original memoir, came to the conclusion that the primary radiation possessed a spectrum consisting of narrow bands, in fact, that it was composed of a series of six or seven approximately homogeneous wave trains. In a recent paper I tried to show that the need for assuming this complexity was avoided by the adoption of a point system for the cubic crystal of zincblende which differed from the system considered by Laue. I supposed the diffracting centres to be arranged in a simple cubic space lattice, the element of the pattern being a cube with a point at each corner, and one at the centre of each cube face. A simpler conception of the radiation then became possible. It might be looked on as continuous over a wide range of wave-lengths, or as a series of independent pulses, and there was no longer any need to assume the existence of lines or narrow bands in its spectrum.

scholarly journals On the interpretation of the indications of atomic structure presented by crystals when interposed in the path of X-rays

1914 ◽  
Vol 91 (623) ◽  
pp. 1-16 ◽  
Keyword(s):  
Regular Point ◽  
Lower Class ◽  
Trigonal Axis ◽  
Point System ◽  
X Rays ◽  
Simple Modification ◽  
Cubic Symmetry ◽  
X Ray ◽  
Space Lattice ◽  
Three Space

W. L. Bragg states in his exposition of the method of investigating the structure of crystals by means of X-rays, that a slight symmetrical distortion of the arrangement of the atoms, which would reduce the crystal symmetry, would not affect any of the results that he had just been describing. Advancing considerably beyond this conclusion, it is proposed to show that a large amount of a certain kind of deformation of an atomic system arranged according to either of the three space-lattices possessing cubic symmetry, considerable enough to profoundly alter the nature of the arrangement, can take place with out any appreciable evidence of this deformation being presented by the X-ray results. The argument consists of the proofs of the following propositions:— Proposition 1.—Each of the three space-lattices which posses cubic symmetry can, by a simple modification, be converted into a regular point-system having this symmetry, but the system of trigonal axes of which, unlike that of the space-lattice, is of non-intersecting kind. The method employed to effect this modification is to so select one-fourth of the trigonal axes of the space-lattice concerned that no two of the selected axes intersect, and then to destroy the remaining three-fourths by symmetrically shifting each point of the space-lattice to the same extent in the appropriate direction along the selected trigonal axis on which it lies, and consequently away from the three other trigonal axes which passed through it. In the cases of the cubic space-lattice and the cube-centred space-lattice, the shifts, can take place in both directions on an axis or in one only. The effect of axes continues to be a trigonal axis of the system of points is that each of the selected axes continues to be a trigonal axis of the system of points, while each of the remaining three-fourths of the trigonal axes ceases to be so. The system of points resulting has cubic symmetry, but in nearly all the cases this is of a lower class than that of the space-lattice from which it is derived.

scholarly journals Morphophysiological and Proteomic Responses on Plants of Irradiation with Electromagnetic Waves

2021 ◽  
Vol 22 (22) ◽  
pp. 12239
Author(s):  
Zhuoheng Zhong ◽  
Xin Wang ◽  
Xiaojian Yin ◽  
Jingkui Tian ◽  
Setsuko Komatsu
Keyword(s):  
Gamma Rays ◽  
Communication Systems ◽  
Electromagnetic Waves ◽  
Insect Pests ◽  
Electromagnetic Energy ◽  
Fertilizer Efficiency ◽  
Future Research ◽  
X Rays ◽  
Radio Waves ◽  
Wide Range

Electromagnetic energy is the backbone of wireless communication systems, and its progressive use has resulted in impacts on a wide range of biological systems. The consequences of electromagnetic energy absorption on plants are insufficiently addressed. In the agricultural area, electromagnetic-wave irradiation has been used to develop crop varieties, manage insect pests, monitor fertilizer efficiency, and preserve agricultural produce. According to different frequencies and wavelengths, electromagnetic waves are typically divided into eight spectral bands, including audio waves, radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. In this review, among these electromagnetic waves, effects of millimeter waves, ultraviolet, and gamma rays on plants are outlined, and their response mechanisms in plants through proteomic approaches are summarized. Furthermore, remarkable advancements of irradiating plants with electromagnetic waves, especially ultraviolet, are addressed, which shed light on future research in the electromagnetic field.

A Color Coded STEM/SEM Image Storage System

1981 ◽  
Vol 39 ◽  
pp. 272-273
Author(s):  
Y. Kokubo ◽  
W. H. Hardy ◽  
J. Dance ◽  
K. Jones
Keyword(s):  
Image Processing ◽  
Electron Beam ◽  
Storage System ◽  
Particle Analysis ◽  
Specific Information ◽  
X Rays ◽  
Sem Image ◽  
Backscattered Electrons ◽  
Wide Range ◽  
Scanning Electron

A color coded digital image processing is accomplished by using JEM100CX TEM SCAN and ORTEC’s LSI-11 computer based multi-channel analyzer (EEDS-II-System III) for image analysis and display. Color coding of the recorded image enables enhanced visualization of the image using mathematical techniques such as compression, gray scale expansion, gamma-processing, filtering, etc., without subjecting the sample to further electron beam irradiation once images have been stored in the memory.The powerful combination between a scanning electron microscope and computer is starting to be widely used 1) - 4) for the purpose of image processing and particle analysis. Especially, in scanning electron microscopy it is possible to get all information resulting from the interactions between the electron beam and specimen materials, by using different detectors for signals such as secondary electron, backscattered electrons, elastic scattered electrons, inelastic scattered electrons, un-scattered electrons, X-rays, etc., each of which contains specific information arising from their physical origin, study of a wide range of effects becomes possible.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

scholarly journals Status of Phenological Research Using Sentinel-2 Data: A Review

2020 ◽  
Vol 12 (17) ◽  
pp. 2760
Author(s):  
Gourav Misra ◽  
Fiona Cawkwell ◽  
Astrid Wingler
Keyword(s):  
Vegetation Index ◽  
Temporal Frequency ◽  
Short Wave ◽  
Current State ◽  
Red Edge ◽  
Natural Grasslands ◽  
Wide Range ◽  
Normalised Difference Vegetation Index ◽  
Satellite Sensors ◽  
Sentinel 2

Remote sensing of plant phenology as an indicator of climate change and for mapping land cover has received significant scientific interest in the past two decades. The advancing of spring events, the lengthening of the growing season, the shifting of tree lines, the decreasing sensitivity to warming and the uniformity of spring across elevations are a few of the important indicators of trends in phenology. The Sentinel-2 satellite sensors launched in June 2015 (A) and March 2017 (B), with their high temporal frequency and spatial resolution for improved land mapping missions, have contributed significantly to knowledge on vegetation over the last three years. However, despite the additional red-edge and short wave infra-red (SWIR) bands available on the Sentinel-2 multispectral instruments, with improved vegetation species detection capabilities, there has been very little research on their efficacy to track vegetation cover and its phenology. For example, out of approximately every four papers that analyse normalised difference vegetation index (NDVI) or enhanced vegetation index (EVI) derived from Sentinel-2 imagery, only one mentions either SWIR or the red-edge bands. Despite the short duration that the Sentinel-2 platforms have been operational, they have proved their potential in a wide range of phenological studies of crops, forests, natural grasslands, and other vegetated areas, and in particular through fusion of the data with those from other sensors, e.g., Sentinel-1, Landsat and MODIS. This review paper discusses the current state of vegetation phenology studies based on the first five years of Sentinel-2, their advantages, limitations, and the scope for future developments.

Detector commissioning and development for PETRA-III

2010 ◽  
Vol 1 (SRMS-7) ◽  
Author(s):  
David Pennicard ◽  
Heinz Graafsma ◽  
Michael Lohmann
Keyword(s):  
High Speed ◽  
Materials Science ◽  
Dynamic Range ◽  
Photon Counting ◽  
High Energy ◽  
X Rays ◽  
Silicon Detectors ◽  
Time Resolved ◽  
Wide Range ◽  
Synchrotron Light

The new synchrotron light source PETRA-III produced its first beam last year. The extremely high brilliance of PETRA-III and the large energy range of many of its beamlines make it useful for a wide range of experiments, particularly in materials science. The detectors at PETRA-III will need to meet several requirements, such as operation across a wide dynamic range, high-speed readout and good quantum efficiency even at high photon energies. PETRA-III beamlines with lower photon energies will typically be equipped with photon-counting silicon detectors for two-dimensional detection and silicon drift detectors for spectroscopy and higher-energy beamlines will use scintillators coupled to cameras or photomultiplier tubes. Longer-term developments include ‘high-Z’ semiconductors for detecting high-energy X-rays, photon-counting readout chips with smaller pixels and higher frame rates and pixellated avalanche photodiodes for time-resolved experiments.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A18 ◽  
Author(s):  
C. H. A. Logan ◽  
B. J. Maughan ◽  
M. N. Bremer ◽  
P. Giles ◽  
M. Birkinshaw ◽  
...  
Keyword(s):  
Angular Resolution ◽  
False Positive Rate ◽  
High Sensitivity ◽  
Point Sources ◽  
Selection Function ◽  
X Rays ◽  
Cluster Emission ◽  
X Ray ◽  
Wide Range ◽  
Function Modelling

Context. The XMM-XXL survey has used observations from the XMM-Newton observatory to detect clusters of galaxies over a wide range in mass and redshift. The moderate PSF (FWHM ~ 6″ on-axis) of XMM-Newton means that point sources within or projected onto a cluster may not be separated from the cluster emission, leading to enhanced luminosities and affecting the selection function of the cluster survey. Aims. We present the results of short Chandra observations of 21 galaxy clusters and cluster candidates at redshifts z > 1 detected in the XMM-XXL survey in X-rays or selected in the optical and infra-red. Methods. With the superior angular resolution of Chandra, we investigate whether there are any point sources within the cluster region that were not detected by the XMM-XXL analysis pipeline, and whether any point sources were misclassified as distant clusters. Results. Of the 14 X-ray selected clusters, 9 are free from significant point source contamination, either having no previously unresolved sources detected by Chandra or with less than about 10% of the reported XXL cluster flux being resolved into point sources. Of the other five sources, one is significantly contaminated by previously unresolved AGN, and four appear to be AGN misclassified as clusters. All but one of these cases are in the subset of less secure X-ray selected cluster detections and the false positive rate is consistent with that expected from the XXL selection function modelling. We also considered a further seven optically selected cluster candidates associated with faint XXL sources that were not classed as clusters. Of these, three were shown to be AGN by Chandra, one is a cluster whose XXL survey flux was highly contaminated by unresolved AGN, while three appear to be uncontaminated clusters. By decontaminating and vetting these distant clusters, we provide a pure sample of clusters at redshift z > 1 for deeper follow-up observations, and demonstrate the utility of using Chandra snapshots to test for AGN in surveys with high sensitivity but poor angular resolution.

A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

2013 ◽  
Vol 46 (5) ◽  
pp. 1508-1512 ◽  
Author(s):  
Byron Freelon ◽  
Kamlesh Suthar ◽  
Jan Ilavsky
Keyword(s):  
Small Angle ◽  
Soft Matter ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
And Performance ◽  
New Facility ◽  
Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

scholarly journals Recurrent Novae — A Review

2015 ◽  
Vol 2 (1) ◽  
pp. 246-251 ◽  
Author(s):  
K. Mukai
Keyword(s):  
Accretion Rate ◽  
Current Understanding ◽  
X Rays ◽  
Symbiotic Star ◽  
Classical Novae ◽  
Extensive Data ◽  
Star Evolution ◽  
Wide Range ◽  
Multi Wavelength ◽  
Recurrent Nova

In recent years, recurrent nova eruptions are often observed very intensely in wide range of wavelengths from radio to optical to X-rays. Here I present selected highlights from recent multi-wavelength observations. The enigma of T Pyx is at the heart of this paper. While our current understanding of CV and symbiotic star evolution can explain why certain subset of recurrent novae have high accretion rate, that of T Pyx must be greatly elevated compared to the evolutionary mean. At the same time, we have extensive data to be able to estimate how the nova envelope was ejected in T Pyx, and it turns to be a rather complex tale. One suspects that envelope ejection in recurrent and classical novae in general is more complicated than the textbook descriptions. At the end of the review, I will speculate that these two may be connected.

scholarly journals The Use of Synchrotron Radiation in the Energy Calibration of Astronomical Apparatus

1972 ◽  
Vol 14 ◽  
pp. 642-646
Author(s):  
G. A. Gurzadyan ◽  
J. B. Ohanesyan
Keyword(s):  
Thin Films ◽  
Synchrotron Radiation ◽  
Electron Energy ◽  
Electron Accelerator ◽  
Energy Calibration ◽  
Ideal Solution ◽  
X Rays ◽  
Special Equipment ◽  
Physics Institute ◽  
Wide Range

The problem of energy calibration of astrophysical apparatus is essential for every or almost every space experiment. The utilization of synchrotron radiation from an electronic accelerator should perhaps be taken as an ideal solution of this problem, if of course, such a possibility is available.Special equipment for the extraction of synchrotron radiation has been devised at the circular electron accelerator with a maximum electron energy of 6 GeV, in the Physics Institute of Erevan (Gurzadyan and Ohanesyan, 1972). The equipment is designed primarily for the energy calibration of astronomical apparatus operating in a vacuum and hard ultraviolet and X rays. However, the equipment can also be applied to a wide range of experiments relating to the physics of solids, crystallography, physics of thin films, X rays, etc.

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