Peterhouse, The Royal Society and molecular biology

2000 ◽  
Vol 54 (3) ◽  
pp. 369-385 ◽  
Author(s):  
J. M. Thomas
Keyword(s):  
Molecular Biology ◽  
Royal Society ◽  
Rockefeller Foundation ◽  
Natural Sciences ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Subject ◽  
Warren Weaver

The term molecular biology was coined by Warren Weaver, a mathematician who was head of the natural sciences section of the Rockefeller Foundation, in his report to the president of the Foundation in 1938. The origins of the subject may be located in various places or periods, but Sir Peter Medawar used to argue that it was Sir William Bragg and W.T. Astbury at the Davy Faraday Laboratory in London who began it, when they investigated the structures of materials such as silk, wool and hair by X–ray diffraction. Others say that J.D. Bernal was the progenitor. Peterhouse, a Cambridge college, was a hothouse of the subject.

Crystallization of Vulcanized Rubber

1941 ◽  
Vol 14 (2) ◽  
pp. 347-355 ◽  
Author(s):  
Norman Bekkedahl ◽  
Lawrence A. Wood
Keyword(s):  
Practical Importance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Single Exception ◽  
Quantitative Results ◽  
The Subject ◽  
Low Sulfur Content ◽  
Low Sulfur

Abstract The formation of crystals at room temperature by stretching rubber, vulcanized or unvulcanized, has been the subject of considerable study. The crystallization of unstretched rubber at low temperatures is also well known, but with a single exception to be discussed later, the effect has commonly been considered to be limited to the unvulcanized material. In the present investigation, however, the crystallization of unstretched specimens of vulcanized rubber of low sulfur content has been accomplished. In commercial vulcanized rubber products, crystallization has not hitherto been recognized as a factor of practical importance. It is probably significant in cold climates, where some rubber products slowly undergo a great increase in rigidity and permanent set. Automobile traffic counters, for example, have been rendered inoperative by the hardening of the rubber tubing used with them. Laboratory tubing and other products made of a number of different commercial rubber compounds have become rigid after storage for some weeks in a refrigerator at about 0° C. Previous work on unvulcanized rubber showed that it can be crystallized at temperatures between + 10° and −40° C, the crystals melting in a range from about 6° to 16° C. Crystallization and fusion are accompanied by changes in volume, heat capacity, light absorption, birefringence, x-ray diffraction, and mechanical properties such as hardness. x-Ray diffraction and birefringence, of course, give the most direct evidence of crystalline structure, but in the present work change of volume, measured in a mercury-filled dilatometer, was chosen as the criterion of crystallization or fusion. Quantitative results are more easily obtained in this manner, and the experimental observations are simple. Furthermore, the method is well adapted to continuous observations over long periods of time, such as were found necessary in the present work.

Optical diffraction studies of myofibrillar structure

1971 ◽  
Vol 261 (837) ◽  
pp. 201-208 ◽  
Keyword(s):  
Electron Micrographs ◽  
Focal Length ◽  
Optical Diffraction ◽  
Myofibrillar Proteins ◽  
Electron Micrograph ◽  
X Ray Diffraction ◽  
Optical Filtering ◽  
X Ray ◽  
The Subject ◽  
Diffraction Patterns

We have used the techniques of optical diffraction and optical filtering to study electron micrographs of myofibrils and of paracrystals of myofibrillar proteins. The optical diffraction patterns provide information about periodic structure in the micrographs, and sometimes may reveal periodicities not apparent to the eye. We compare the optical diffraction patterns with the X-ray diffraction patterns obtained from living muscle, and this comparison can assist our interpretation of both the X-ray diffraction patterns and the electron micrographs. The optical diffractometer we have used is essentially similar to those described by Taylor & Lipson (1964), and by Klug & DeRosier (1966). The apparatus incorporates several refinements to facilitate operation. The recombining lens has a focal length, f , of about 1 m, and is placed so that the recombined image is formed at 2 f and has the same size as the subject. The diffraction subjects are not usually the electron micrographs themselves but copies on film. The film is of more uniform optical thickness than the glass electron micrograph, and is less fragile. Moreover, a set of films of varying contrast can be made from one micrograph.

scholarly journals The analysis of crystals by the X-ray spectrometer

1914 ◽  
Vol 89 (613) ◽  
pp. 468-489 ◽  
Keyword(s):  
Royal Society ◽  
Photographic Plate ◽  
Exact Nature ◽  
Photographic Method ◽  
X Rays ◽  
Alkaline Metal ◽  
Powerful Method ◽  
Narrow Beam ◽  
X Ray Diffraction ◽  
X Ray

In a former communication to the Royal Society, an attempt was made to determine for certain crystals the exact nature of the diffracting system which produces the Laue X-ray diffraction photographs. The crystals chosen for particular investigation were the isomorphous alkaline halides NaCl, KCl, KBr, and KI. As in the original experiments of Laue and his collaborators, a thin section of crystal was placed in the path of a narrow beam of X-rays, and the radiation diffracted by the crystal made its impression on a photographic plate. By noticing what differences were caused in the photograph by the substitution of heavier for lighter atoms in the crystal, a definite arrangement was decided on as that of the diffracting points of the crystalline grating. Though it was found possible in the case of these simple salts to determine the position of the atoms of alkaline metal and halogen, which constitute the elements of the dimensional diffraction grating, yet this method, which may be called the photographic method, is very limited in its range of applications. It was only the extremely simple nature of the NaCI structure which made its analysis possible. On the other hand, the X-ray spectrometer, which has been devised by W. H. Bragg for the purpose of studying the reflection of X-rays by crystals, affords a very much more powerful method of research into the structure of the crystal.

Diffuse scattering in protein crystallography

1995 ◽  
Vol 28 (2) ◽  
pp. 131-169 ◽  
Author(s):  
Jean-Pierre Benoit ◽  
Jean Doucet
Keyword(s):  
Molecular Biology ◽  
Active Site ◽  
Diffuse Scattering ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Physico Chemical ◽  
Chemical Conditions ◽  
Functional Mechanisms

The understanding of flexibility and deformability in proteins is one of the current major challenges of structural molecular biology. The knowledge of the average atomic positions of three-dimensional folding of proteins, which is obtained either by X-ray diffraction or n.m.r. spectroscopy, is generally not sufficient to explain their functional mechanisms. Very often it is necessary to consider the existence of other concerted atomic motions as, for example, in the well-known case of the CO molecule fixation at the active site of myoglobin which requires the concerted displacement of a large number of atoms in order to open a channel down to this site. This opening, which depends on the physico-chemical conditions, plays the role of a regulator in the biochemical reactions (Janin & Wodak, 1983; Tainer et al. 1984; Westhof et al. 1984; Ormos et al. 1988).

Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 1 December 1975

1976 ◽  
Vol 192 (1109) ◽  
pp. 371-391
Keyword(s):  
Molecular Biology ◽  
Coiled Coil ◽  
Helical Structure ◽  
X Ray Diffraction ◽  
Helical Structures ◽  
X Ray ◽  
Double Helical Structure ◽  
Leading Role ◽  
Replication Scheme ◽  
Related Proteins

The Copley Medal is awarded to Dr F. H. C. Crick, F. R. S. In 1953 Crick and Watson proposed the double-helical model for DNA, in which the bases are arranged in complementary pairs so that the molecule is capable of self-replication and is thus the essential carrier of genetic information in living cells. This proposal was based on an inspired interpretation of the results of X-ray diffraction analysis of DNA carried out by Wilkins, Franklin and their collaborators, and on the chemical analyses of Chargaff and others. The replication scheme inherent in the double-helical structure of DNA made it possible for the first time to discuss the mechanism of heredity in molecular terms; it has been the most fruitful concept in the whole of biology during the past 25 years, and has been the basis for the explosive development of molecular biology. Besides his part in this dramatic discovery, Crick played a very important part in increasing our understanding of the way in which the genetic message is carried on DNA (the ‘coding’ problem), and of the mechanisms by which it is translated into specific sequences of amino acids in the proteins synthesized by the cell. He has also continued to play a leading rôle in many other aspects of molecular biology, and has made important contributions to X-ray studies of crystalline proteins, fibrous proteins and viruses. These include the theory of diffraction from helical structures, the coiled-coil model of α-keratin and related proteins, the structure of collagen, and the theoretical basis of the construction of ‘spherical’ viruses. More recently, Crick has had an important influence on work in the fields of development and of chromosome structure.

scholarly journals Influence of Fluorine on Clinker burnability and mechanical properties of CPA Moroccan cement

2018 ◽  
Vol 149 ◽  
pp. 01075 ◽  
Author(s):  
A. Bouregba ◽  
A. Diouri ◽  
B. Elghattas ◽  
A. Boukhari ◽  
T. Guedira
Keyword(s):  
Mechanical Properties ◽  
Fluorescence Spectroscopy ◽  
Calcium Fluoride ◽  
X Ray Diffraction ◽  
Free Lime ◽  
X Ray ◽  
The Subject ◽  
Lower Temperature ◽  
The Impact ◽  
Cement Raw Mix

It has been found that the addition of certain components, despite their low concentration in raw mix, may accelerate and enhance the reactivity of the cement raw mix. The utilization of mineralizers to facilitate and quicken the process of clinkerization backpedals numerous years, the concept of using such mineralizers to burn normal raw mixes at a much lower temperature with the end goal of decreasing the fuel necessities of the furnace and to enhance the cement proprieties has become to be seriously considered over the most recent couple of years. The subject of this paper is to investigate the impact of calcium fluoride as mineralizer on addition during the clinkerization process of industrial raw mixtures and its effect on chemical, mineralogical, and mechanical properties of CPA Moroccan cement. Five different raw meals were utilized and were burned with 2% of calcium fluoride. The resulting clinker was analyzed by X-ray diffraction (XRD) and fluorescence spectroscopy to determine the chemical phases of the obtained clinker, and the mechanical properties of resulting CPA cement were determined. The results show that the addition of 2% of CaF2 to the clinker raw meal induced a decrease in the burning temperature and free lime, while improving the clinker phase formation and the mechanical properties of obtained cement.

scholarly journals Karakteristik dan kandungan mineral pasir pantai Lhok Mee, Beureunut dan Leungah, Kabupaten Aceh Besar

DEPIK ◽  
2015 ◽  
Vol 3 (3) ◽  
Author(s):  
Saniah . ◽  
Syahrul Purnawan ◽  
Sofyatuddin Karina
Keyword(s):  
Particle Size ◽  
Powder Diffraction ◽  
Sampling Method ◽  
Mineral Content ◽  
Color Difference ◽  
Natural Sciences ◽  
X Ray Diffraction ◽  
X Ray ◽  
Beach Sands ◽  
Coastal Sand

Abstract. The objective of this research was to determine the characteristics and mineral content of coastal sand from  Lhokmee, Beureunut, and Leungah Aceh Besar District. The sand analysis was conducted at Material Laboratory of Mathematics and Natural Sciences Faculty, Syiah Kuala University from March to April, 2014. Samples were collected using purpossive sampling method. The observed physical characteristics of this research were sand color, shape and particle size. The mineral content was analysed using X-Ray Diffraction (XRD) and Joint Committee for Powder Diffraction Standard (JCPDS) program. The result showed that Lhok Mee coastal sand was physically characterized as white, sub-angular rounded shape and 0.21 mm of size, while Beureunut coastal sand was light brown, rounded-well rounded shape and 0.19 mm of size, then Leungah coastal sand was black, angular-well rounded shape and 0.13 mm of size. Based on  mineral content showed that Lhok Mee, Beureunut, and Leungah coastal sand were dominated by SiO3, SO3 and Fe3O4, respectively. All identified minerals at all stations were classified as volcanic minerals of lithogenous sediment. Keywords: Beach sands; Color difference; Mineral content; Shape; Particle size. 

Surface Structural Techniques Applied to Interfaces

MRS Bulletin ◽  
1990 ◽  
Vol 15 (9) ◽  
pp. 38-41 ◽  
Author(s):  
I.K. Robinson
Keyword(s):  
Internal Surface ◽  
Amorphous Solid ◽  
Interface Roughness ◽  
Misfit Dislocations ◽  
Ion Scattering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Subject ◽  
Medium Energy Ion Scattering

An interface is an internal surface, the boundary between two media which may be crystalline, amorphous solid, or liquid. Its close similarity with a surface, a solid-vacuum boundary, suggests that many of the powerful techniques available for studying surfaces might be applied to the interface structure problem. The extent to which this is possible is the subject of this article.The techniques to be discussed in this article include low energy electron diffraction (LEED), medium energy ion scattering (MEIS), x-ray diffraction, and x-ray reflectivity. (The most widely used method, transmission electron microscopy (TEM), is the subject of a separate article in this issue of the MRS BULLETIN.) To summarize what we will find, surface methods were developed to be nonpenetrating in order to have surface sensitivity. This works against us in the interface situation by requiring the use of extremely thin samples, at least on one side of the interface. This means special handling of samples in some cases and raises the possibility of artifac-tual results. Of the three methods, x-ray diffraction is the most penetrating and least surface sensitive; it probably has the greatest potential for widespread use in interface science.This article defines structure as “atomic structure” for this purpose: we are interested in the coordinates of atoms at the interface and their relation to bulk structures on one or both sides. For this reason, we will consider only interfaces that are crystalline on at least one side. Since crystals are by far our strongest structural reference point, much less can be said about other interfaces. We will also consider the morphology of an interface, defined as the boundary of the crystal(s) that demarcates the interface, also at the atomic level. This is most apparent in the form of interface roughness. The roles of strain and misfit dislocations in interface formation, also studied by these techniques, are outside the scope of this article.

Photoluminescence and Physical Properties of the Nano-Zn2SiO4:Mn Phosphor Powder under the Nitrogen Atmosphere

2014 ◽  
Vol 602-603 ◽  
pp. 1009-1012
Author(s):  
Fann Wei Yang ◽  
Chien Min Cheng ◽  
Kai Huang Chen
Keyword(s):  
Grain Size ◽  
Grain Shape ◽  
Nitrogen Atmosphere ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
Phosphor Powder ◽  
Sintering Atmosphere ◽  
X Ray ◽  
The Subject

The subject of this work was to study the photoluminescence characteristics of nanoZnO and SiO2powders into Zn2SiO4phosphor, and to achieve better control on grain size and grain shape than traditional powder. The manganese elements were used to replace Zn2SiO4defects and to achieve better control on grain size and grain shape than traditional powder. With different sintering atmosphere conditions, the effect of the photoluminescence intensity due to sintering temperature and the concentration of activator were be discussed by the X-Ray diffraction, SEM and TEM were utilized in the characterization of phase purity and microstructure of phosphor particles.

Study of the Evolution of Phase Calcium Aluminate through the Method for Polymeric Precursors C12A7

2015 ◽  
Vol 820 ◽  
pp. 137-142
Author(s):  
Faili Cintia Tomsen Veiga ◽  
Flávio José Tomsen Veiga ◽  
Mário Lúcio Moreira ◽  
José Jurado ◽  
Vânia Caldas Sousa ◽  
...  
Keyword(s):  
Calcium Aluminate ◽  
Ceramic Materials ◽  
Vibrational Modes ◽  
X Ray Diffraction ◽  
Precursor Method ◽  
Crystalline Phases ◽  
Polymeric Precursors ◽  
X Ray ◽  
Pure Phase ◽  
The Subject

The synthesis of ceramic materials from polymeric precursors has been the subject of numerous studies due to lower energy cost compared to conventional processing. The study aims to research and develop synthesis of calcium aluminate powders via the polymeric precursor method, in order to obtain the pure phase of hepta-aluminate dodecálcio (C12A7) with mayenita mineral name, since it has applications like: special cements and components for high temperature fuel cells. A study of the evolution of crystalline phases by X-ray diffraction was performed, the vibrational modes of atomic location in crystalline phases were studied by micro-Raman spectroscopy was also performed and images from scanning electron microscopy. From the characterizations carried out on the material can be seen that the sintering temperature of 1200°C was obtained pure phase, so the choice of synthesis shown to be effective due to the complexity of obtaining this phase pure.

Sign in / Sign up

Export Citation Format

Share Document