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Electrical characterization of electro-Ceramics
Published in Amit Sachdeva, Pramod Kumar Singh, Hee Woo Rhee, Composite Materials, 2021
X-ray crystallography is a technique in which the pattern produced by the diffraction of X-rays through the closely spaced atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice (Figure 6.1). Geometrically, one may imagine that a crystal is made up of lattice planes and that the scattering from a given set of planes will only be strong if the X-ray reflected by each plane arrives at the detector in phase. This leads to a relationship between the order of diffraction pattern n, X-ray wavelength λ, the spacing between lattice planes d, and the angle of incidence θ known as Bragg’s law [11, 12]: 2dsinθ=nλ
Therapeutic Strategies and Future Research
Published in Mark A. Mentzer, Mild Traumatic Brain Injury, 2020
X-ray crystallography provides another means to characterize the atomic structure of crystalline materials. (Rosalind Franklin used the technique to produce the famous demonstration that DNA is helical.) This characterization includes proteins and nucleic acids. While certain proteins are difficult to crystallize, nearly 50,000 proteins, nucleic acids and other biological macromolecules have now been measured with X-ray crystallography (Scapin, 2006; Lundstrom, 2006).
An Introduction to Crystal Structures
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
To understand the solid state, we need to have some insight into the structure of simple crystals and the forces that hold them together, so it is here that we start this book. Crystal structures are usually determined by the technique of X-ray crystallography. This technique relies on the fact that the distances between the atoms in the crystals are of the same order of magnitude as the wavelength of X-rays (of the order of 1 Å or 100 pm): a crystal thus acts as a three-dimensional diffraction grating to a beam of X-rays. The resulting diffraction pattern can be interpreted to give the internal positions of the atoms in the crystal very precisely, thus defining interatomic distances and angles. (Some of the principles underlying this technique are discussed in Chapter 2, where we review the physical methods available for characterising solids.) Most of the structures discussed in this book would have been determined in this way.
A comprehensive review on stability of therapeutic proteins treated by freeze-drying: induced stresses and stabilization mechanisms involved in processing
Published in Drying Technology, 2022
Zhe Wang, Linlin Li, Guangyue Ren, Xu Duan, Jingfang Guo, Wenchao Liu, Yuan Ang, Lewen Zhu, Xing Ren
At present, the main technology to determine the three-dimensional structure of molecules at the atomic resolution level is X-ray crystallography. X-ray is a kind of electromagnetic radiation like light, but it has a shorter wavelength, generally about 0.1 nm. X-rays interact weakly with biological substances, which make it difficult to use them to study individual protein complexes. But when multiple copies of the same protein are arranged in a 3D crystal, information about the protein's atomic structure can be obtained through it. This technique is called X-ray crystallography and is one of the most important tools in structural biology. Taschner et al [87] obtained the three-dimensional crystal structure of anti-idiotypic antibody MMA 383 by X-ray, although the assumed conformation in the crystal is only one of many conformations in the solution. Moreover, although X-ray has high requirements for the purity and crystallinity of proteins, it is still of great significance for the characterization of protein structures. The application of X-ray in the freeze-drying stability of therapeutic proteins needs further study.
Robust phase retrieval via median-truncated smoothed amplitude flow
Published in Inverse Problems in Science and Engineering, 2021
Qi Luo, Shijian Lin, Hongxia Wang
Phase retrieval (PR) is a problem about recovering a signal from its phaseless measurements. It has a wide range of applications including X-ray crystallography [1], molecular imaging [2], biological imaging [3] and astronomy [4]. Mathematically, phase retrieval can be formulated as finding a signal from the following system of phaseless equations: where gathers the measurements, and or is the sensing vector. In many optical scenarios, correspond to the Fourier transform matrix. For the convenience of theoretical analysis, recent studies also paid much attention to the generic measurement vectors [5]. Specifically, we consider the model that are independently sampled from the Gaussian distribution.
Extraction of Cr from CCLW and its utilisation in the development of composite by friction stir process
Published in Australian Journal of Mechanical Engineering, 2023
X-ray crystallography (XRC) is used to find out the atomic and molecular structure of a crystal. In this process, the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. Crystallographer of the materials produces with three-dimensional picture of the density of electrons within the crystal by measuring the angles and intensities of diffracted beams. The mean positions of the atoms in the crystal identified from this electron density. Usually, X-ray diffractometers consist three basic elements; X-ray detector, a sample holder and an X-ray tube. X-rays are generated in a cathode ray tube by heating a filament to produce electrons, accelerating the electrons towards a target by applying a voltage, and bombarding the target material with electrons. When electrons have sufficient energy to dislodge inner shell electrons of the target material, characteristic X-ray spectra are produced. The specific wavelengths are characteristic of the target material (Cu, Fe, Mo, Cr). These X-rays are collimated and directed onto the sample. As the sample and detector are rotated, the intensity of the reflected X-rays is recorded. When the geometry of the incident X-rays impinging the sample satisfies the Bragg Equation, constructive interference occurs and a peak in intensity occurs. A detector records and processes this X-ray signal and converts the signal to a count rate which is then output to a device such as a printer or computer monitor. The geometry of an X-ray diffractometer is such that the sample rotates in the path of the collimated X-ray beam at an angle θ while the X-ray detector is mounted on an arm to collect the diffracted X-rays and rotates at an angle of 2θ. The instrument used to maintain the angle and rotate the sample is termed a goniometer. Figure 10 shows the XRD behaviour of composite developed at optimum combination of FSP parameters in the present study. The XRD of the composite material was observed to identify the different phases in the developed composite material. XRD results showed the presence of Al, Al2O3, Cr and Cr2O3. Presence of hard phases such as Al2O3, Cr and Cr2O3 in the developed composite was responsible for enhancing the tensile strength and hardness of composite.