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Overall summary and future thoughts

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

This chapter summarizes the state‐of‐the‐art in the field and discusses upcoming techniques to solve and to improve the current problems.

Macromolecular crystals and twinning

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

Macromolecular crystal structure analyses can be severely hampered by cases of twinning or of multiple crystals. However, increasingly, twinning can readily be recognized, notably when the X‐ray ... More

Macromolecular crystal structure analyses can be severely hampered by cases of twinning or of multiple crystals. However, increasingly, twinning can readily be recognized, notably when the X‐ray diffraction data are analyzed using intensity statistics. Remediation of such cases is possible via alteration of crystal‐growth conditions including use, mainly, of chemical additives. The case of multiple crystal growths likewise can hamper crystal‐structure analysis and although not necessarily associated with twinning is a crystal‐growth situation where similar remediation methods can be adopted, or portions of crystals ‘cut out’ or selected through use of X‐ray ‘microbeams’. There is also a nice body of case studies now in the crystallographic literature and several of these are highlighted in this chapter. Practical details of use of MAD, SAD or molecular replacement with different degrees of crystal twinning, as well as software to diagnose such cases, are described.Less

Introduction

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

Macromolecules are the machinery of life and their function is determined by their 3D structure. Visual observation with a light microscope is not possible as the sizes of macromolecules are well ... More

Macromolecules are the machinery of life and their function is determined by their 3D structure. Visual observation with a light microscope is not possible as the sizes of macromolecules are well below the wavelength of visible light. X‐rays and neutrons allow visualization but they cannot be focused, so diffraction techniques have to be used. An understanding of the three‐dimensional macromolecular structure gives us a deeper understanding of basic biological concepts and processes, and reveals the cause of diseases, helps rational pharmaceutical design and can lead to the design of macromolecules with novel properties. Visualizing these macromolecules is a complex ballet involving diverse but interrelated fields of endeavour. In this chapter we cover an introduction to crystallization and X‐ray and neutron diffraction techniques. We distinguish between long‐ and short‐range order and introduce the rest of the book.Less

Towards research

John Jenkin

in William and Lawrence Bragg, Father and Son: The Most Extraordinary Collaboration in Science

William explored teaching problems beyond the textbooks and was encouraged by AAAS meetings and the need to nominate students for the new 1851 Exhibition Research Scholarships. Lawrence began his ... More

William explored teaching problems beyond the textbooks and was encouraged by AAAS meetings and the need to nominate students for the new 1851 Exhibition Research Scholarships. Lawrence began his education, loved his grandparents' rambling home, and enjoyed family holidays by the sea. William led the development of a student union. His extension lectures were over-subscribed, particularly those on radio and the new X-rays. Willie fractured an elbow, which was X-rayed in his father's laboratory, a sign of the collaboration to come. William continued to facilitate University/School of Mines interaction and to foster teacher training and support. Ernest Rutherford, on his way to Cambridge, visited William at the university. Sir Thomas Elder's will funded a new Conservatorium of Music.Less

TOMOGRAPHY USING MAGNIFYING OPTICS

Yoshio Suzuki, Hiroyuki Toda, and Christian Schroer

in Advanced Tomographic Methods in Materials Research and Engineering

This chapter describes the principles of Fresnel zone-plate (FZP) optics and imaging properties of FZP microscopy in the context of tomographic application. The limitation of zone-plate optics is ... More

This chapter describes the principles of Fresnel zone-plate (FZP) optics and imaging properties of FZP microscopy in the context of tomographic application. The limitation of zone-plate optics is discussed, and some typical examples of tomographic imaging experiment are shown. A brief introduction to reflective and refractive X-ray optics is presented since they are used for X-ray microscopy in the hard X-ray range relevant for materials research.Less

THREE-DIMENSIONAL X-RAY DIFFRACTION

Henning Friis Poulsen

in Advanced Tomographic Methods in Materials Research and Engineering

Three-dimensional X-ray diffraction (3DXRD) is a novel technique aimed at quick and non-destructive characterization of the individual elements within millimetre- to centimetre-sized specimens. It is ... More

Three-dimensional X-ray diffraction (3DXRD) is a novel technique aimed at quick and non-destructive characterization of the individual elements within millimetre- to centimetre-sized specimens. It is based on two principles: the use of highly penetrating hard X-rays from a synchrotron source (X-ray energies above 30 keV) and the application of ‘tomographic” reconstruction algorithms for the analysis of the diffraction data. This chapter outlines the 3DXRD methodology with the focus on characterizing grains and orientations. The chapter is organized as follows. The 3DXRD setup is presented and 3DXRD strategies discussed. Then, the standard modes of operation are presented in more detail with emphasis on reconstruction principles and providing selected examples of use. Next, a novel method called diffraction contrast tomography is proposed — this is related to 3DXRD in the same way as bright-field and dark-field images are in transmission electron microscopy. Finally, the mathematics underlying the 3DXRD diffraction geometry and the representation of the crystallographic orientation are summarized.Less

Further research: X-rays and γ-rays

John Jenkin

in William and Lawrence Bragg, Father and Son: The Most Extraordinary Collaboration in Science

Radioactive ores discovered in outback South Australia were found by William to contain uranium minerals, and not developed commercially until many years later. At home he welcomed the birth of a ... More

Radioactive ores discovered in outback South Australia were found by William to contain uranium minerals, and not developed commercially until many years later. At home he welcomed the birth of a daughter, Gwendolen (‘Gwendy’), and began a new research project, the nature of X- and γ-rays, while at the university. European scientists believed they were waves, William suggested they were a neutral pair of positive and negative particles. The Englishman Charles Barkla vigorously promoted a wave picture of X-rays, while William defended his ‘neutral pair hypothesis’ for γ-rays, each presenting experimental evidence to support their position. A vigorous debate developed in the scientific literature, neither man giving way, and the dispute was unresolved.Less

Rules Relating to Other Specific Technologies

William H. Boothby

in Weapons and the Law of Armed Conflict

After a brief introduction to the topic, this chapter discusses three classes of weapon for which specific provision is made in Protocols to the Conventional Weapons Convention. In each case, the ... More

After a brief introduction to the topic, this chapter discusses three classes of weapon for which specific provision is made in Protocols to the Conventional Weapons Convention. In each case, the relevant protocol's provisions are given and their meaning is discussed. The participation of states in that protocol is revealed and the status of the relevant rule in customary law is explained. The applicability of the rule in non-international armed conflicts is then assessed, and the relevant section concludes with a brief discussion of the compliance arrangements relating to that Protocol. The weapons discussed in this chapter are weapons that primarily injure using fragments not detectable using X-rays, incendiary weapons, and blinding lasers. In each case, care is taken to explain which weapons are and are not caught by the relevant legal rules, noting that some of the rules prohibit the weapon affected by them while others consist of restrictions on the lawful use of such weapons.Less

The crystalline state and its study

Dennis Sherwood and Jon Cooper

in Crystals, X-rays and Proteins: Comprehensive Protein Crystallography

This chapter provides an introduction to the fundamental states of matter and the phenomenon of anisotropy which is attributable to the ordered solid state. Solids which possess molecular order over ... More

This chapter provides an introduction to the fundamental states of matter and the phenomenon of anisotropy which is attributable to the ordered solid state. Solids which possess molecular order over macroscopic distances are referred to as crystals. The remainder of the chapter introduces experimental methods of analysing the structure of crystals at the molecular level. The necessity for using electromagnetic radiation of a wavelength comparable to the dimensions of the molecule under study is explained, as is the need to use diffraction methods rather than microscopy for analysing their structures. The chapter concludes with a brief introduction to the properties of protein crystals, such as their fragility and high solvent content.Less

Principles of radiotherapy

Peter Hoskin and Wendy Makin

in Oncology for Palliative Medicine

This chapter provides an overview of radiotherapy. Radiotherapy is the method of treatment using ionizing radiation. Normally, radiation is in the form of X-rays or gamma rays which, when directed ... More

This chapter provides an overview of radiotherapy. Radiotherapy is the method of treatment using ionizing radiation. Normally, radiation is in the form of X-rays or gamma rays which, when directed through a cell, result in the ionization and destruction of DNA. Methods of delivering radiation include external X-ray beams and the use of radioisotopes. Radiation is potentially dangerous, hence administration of radiotherapy is usually done within a radiotherapy department. Radiotherapy plays a significant role in palliative care: it aids in the management of local symptoms such as pain, haemorrhage, and obstruction. Topics discussed in the chapter include the different kinds of radiation, radioisotope therapy, biological effects of radiation, and fractionation. The chapter also discusses the practicality of radiotherapy, and the practicality and efficiency of radiotherapy in palliative care.Less

X-ray and neutron sources

William Clegg

in Crystal Structure Analysis: Principles and Practice

Crystal structure determination by diffraction uses X-rays or neutrons. X-rays are readily available in laboratories from a standard X-ray tube, in which electron kinetic energy is converted to ... More

Crystal structure determination by diffraction uses X-rays or neutrons. X-rays are readily available in laboratories from a standard X-ray tube, in which electron kinetic energy is converted to X-rays by interaction with core electrons of a metal target, giving particular characteristic wavelengths (and much wasted heat). Enhancements of the basic X-ray tube include rotating anodes and microfocus tubes, and the extracted X-rays can be concentrated somewhat by modern optics methods. Far higher X-ray intensities, together with other special properties, are obtained from synchrotron storage rings, which are large-scale national and international facilities; some of the properties are described, and an account given of applications. Neutrons are available from nuclear reactors and spallation sources, in monochromatic or pulsed polychromatic modes. Some advantages and disadvantages of neutrons, compared with X-rays, are described, resulting from their different interaction with samples.Less

Diffraction

Jenny Pickworth Glusker and Kenneth N. Trueblood

in Title Pages

A common approach to crystal structure analysis by X-ray diffraction presented in texts that have been written for nonspecialists involves the Bragg ... More

A common approach to crystal structure analysis by X-ray diffraction presented in texts that have been written for nonspecialists involves the Bragg equation, and a discussion in terms of “reflection” of X rays from crystal lattice planes (Bragg, 1913). While the Bragg equation, which implies this “reflection,” has proved extremely useful, it does not really help in understanding the process of X-ray diffraction. Therefore we will proceed instead by way of an elementary consideration of diffraction phenomena generally, and then diffraction from periodic structures (such as crystals), making use of optical analogies (Jenkins and White, 1957; Taylor and Lipson, 1964; Harburn et al., 1975). The eyes of most animals, including humans, comprise efficient optical systems for forming images of objects by the recombination of visible radiation scattered by these objects. Many things are, of course, too small to be detected by the unaided human eye, but an enlarged image of some of them can be formed with a microscope—using visible light for objects with dimensions comparable to or larger than the wavelength of this light (about 6 × 10−7 m), or using electrons of high energy (and thus short wavelength) in an electron microscope. In order to “see” the fine details of molecular structure (with dimensions 10−8 to 10−10 m), it is necessary to use radiation of a wavelength comparable to, or smaller than, the dimensions of the distances between atoms. Such radiation is readily available (1) in the X rays produced by bombarding a target composed of an element of intermediate atomic number (for example, between Cr and Mo in the Periodic Table) with fast electrons, or from a synchrotron source, (2) in neutrons from a nuclear reactor or spallation source, or (3) in electrons with energies of 10–50 keV. Each of these kinds of radiation is scattered by the atoms of the sample, just as is ordinary light, and if we could recombine this scattered radiation, as a microscope can, we could form an image of the scattering matter. Less

Concatenation of fortunate circumstances: Cambridge, 1909–14

Graeme K. Hunter

in Light is a Messenger: The Life and Science of William Lawrence Bragg

This chapter details the life of William Lawrence Bragg from 1909–14. In the spring of 1910, Bragg competed in the Trinity scholarships examination. The Master of Trinity, Montagu Butler, read his ... More

This chapter details the life of William Lawrence Bragg from 1909–14. In the spring of 1910, Bragg competed in the Trinity scholarships examination. The Master of Trinity, Montagu Butler, read his essays and commented upon the ‘brilliant imagination’ shown in them. Bragg was awarded a College Senior Mathematical Scholarship. By the beginning of his second year Bragg had switched from the Mathematical Tripos to the Natural Sciences Tripos — in effect, dropping mathematics in favor of physics. Father and son joined forces during the Christmas holiday of 1912–13, studying the radiation reflected by crystals of rock salt.Less

Röntgen and the Discovery of X‐rays

André Authier

in Early Days of X-ray Crystallography

The circumstances surrounding Röntgen’s discovery of X-rays are related, as well as the detailed investigations he made on the properties of X-rays before announcing the discovery. An account of his ... More

The circumstances surrounding Röntgen’s discovery of X-rays are related, as well as the detailed investigations he made on the properties of X-rays before announcing the discovery. An account of his career in research before his discovery is also presented. The swift spreading of the news of the discovery throughout the world, and the general excitement it generated, are recounted. Further studies of Röntgen on the new radiation are then described, and prior observations by other investigators of what may have been X-rays are discussed. The last part of the chapter is devoted to the rays studied by Lenard, which were cathode rays. Lenard probably also observed X-rays, but he did not characterize them.Less

Reception and Early Developments

Helge Kragh

in Niels Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913–1925

Bohr’s theory was generally well received, although few physicists accepted the postulates on which it rested. It was found attractive because of its explanatory and predictive power. This chapter ... More

Bohr’s theory was generally well received, although few physicists accepted the postulates on which it rested. It was found attractive because of its explanatory and predictive power. This chapter details the reception of the theory from 1913 to about 1916, mostly in England, Germany, and the United States, including the opposition it met from conservative physicists and chemists. It is argued that this opposition was substantial and often justified, but also that it had little effect on the further development of Bohr’s theory. The Stark effect, discovered in 1913, had a major impact on how the theory was received in Germany, and its role is explained. In addition, the little known case of triatomic hydrogen is considered, and also the support that Bohr’s views received from H. Moseley’s pioneering research on characteristic X-rays.Less

The Nature of X‐Rays: Waves or Corpuscles?

André Authier

in Early Days of X-ray Crystallography

This chapter relates the discussions which took place before the discovery of X-ray diffraction as to the real nature, wave or corpuscular, of X-rays. Similar discussions as to the nature of ... More

This chapter relates the discussions which took place before the discovery of X-ray diffraction as to the real nature, wave or corpuscular, of X-rays. Similar discussions as to the nature of electrons are first reviewed. A pulse theory was proposed independently by Wiechert, Stokes, and Thomson for the nature of X-rays. The observation of secondary radiation by various authors is then recounted, and Thomson’s theory of X-ray scattering is summarized. The next steps were the observations by Barkla of the polarization of X-rays, and of characteristic X-rays. At the same time came W. H. Bragg’s suggestion that X-rays were in fact neutral pairs constituted by a positive and a negative particle. A sharp controversy between Bragg and Barkla ensued. In order to test the validity of the pulse theory, attempts were made to observe the diffraction of X-rays by a slit. From the results, Sommerfeld made an estimate of X-ray wavelengths. These were also estimated by Wien and Stark using the Planck—Einstein relation. Stark went further and elaborated a corpuscular theory for X-rays, about which he entered into a controversy with Sommerfeld.Less

Assassin or Look-Alike

Joe Nickell

in Real or Fake: Studies in Authentication

This chapter investigates if the photographs and videotapes of the assassin of President John F. Kennedy really depict ex-marine Lee Harvey Oswald. The first scientific attempt to identify felons ... More

This chapter investigates if the photographs and videotapes of the assassin of President John F. Kennedy really depict ex-marine Lee Harvey Oswald. The first scientific attempt to identify felons began in 1860. Fingerprints are the mainstay of identification. However, in some cases where there are too few ridge characteristics to make a positive fingerprint identification, the pattern of tiny pores along the ridges is employed, a method known as poroscopy. Like fingerprints, the patterns of the palms and the soles of the feet may prove valuable. Lip impressions, bite marks, and dental X-rays are other methods for identification. It examines Eddowes's theory explaining that Lee Harvey Oswald has a double. However this theory was contradicted by other experts.Less