For the Record: The Francis Crick Archive at the Wellcome Library

“This is an historic occasion”, announced Francis Crick on 2 June 1966, as he began the opening address of the annual meeting of molecular biologists at Cold Spring Harbor. “There have been many meetings”, he continued, “about the genetic code during the past ten or twelve years but this is the first important one to be held since the code became known.” Such bold pronouncements usually guarantee that an occasion will linger in history's footnotes and never shine centre-page. But, as the first public presentation of the complete genetic code, the moment had some claim to being historically complementary to the publication of James Watson and Crick's first paper in Nature. In April 1953, in fourteen paragraphs and a diagrammatic sketch (contributed by Odile Crick), they had announced—with a minimalism that came more of urgent certainty than of diffidence or reticence—not just a physical structure for DNA, but something far more. “It has not escaped our notice that the specific pairing [of purine and pyrimidine bases] we have postulated immediately suggests a possible copying mechanism for the genetic material.” The trajectory begun in 1953 with the suggestion of “a possible copying mechanism” completed its public arc at Cold Spring Harbor in 1966 with a very specific and (almost) complete table showing the genetic code. The occasion “marked”, as Crick later judged, “the end of classical molecular biology”.

Computer-Aided Analysis of Centrifugal Compressors

This paper describes computer-aided analysis of centrifugal compressors (CAACC), a micro-computer-based, interactive, and menu-driven software package for use as an educational tool by mechanical engineering students studying radial flow compressors. CAACC is written in the Pascal computer language and runs on IBM PC, or compatible, computers. In addition to solving for any unknown variables, the graphical utilities of the package allow the user to display a diagrammatic sketch of the compressor and to draw velocity diagrams at several locations. Furthermore, the program allows the investigation and plotting of the variation of any parameter versus any other parameter. Through this option, the package guides the student in learning the basics of centrifugal compressors by the various performance studies that can be undertaken and graphically displayed. The comprehensive example presented demonstrates the capabilities of the package as a teaching tool.

Model documentation

As is noted throughout this book, an information model does not merely consist of the formal model but also includes supporting editorial and technical material. Reading an uncommented EXPRESS model is like trying to decipher undocumented program code — possible, but error prone. Further, there are many things that cannot be expressed in EXPRESS — diagrams, for example, or references to the general literature, and so on. Two forms of documentation appear to be prevelant: the embedded and the partitioned style. We discuss both of these, although we prefer the former of the two. The model developer, though, should decide on a style that suits the purposes at hand. We also indicate how versions of a document could be produced in either style. This is based on the fact that an information model can be stored electronically (i.e., as computer files), and printed versions produced via a wordprocessor or other kind of desktop publishing system. The document style for an information model is typically much more detailed than is found for computer programs. On the other hand, it is usually less complex in its ordering than in the program documentation style known as literate programming. In addition to documenting the overall scope and purpose of the model, the content and relationship of the schemas in the model should be described in broad terms. A diagrammatic sketch of the major elements and relationships in the model is also useful. This overview material should also contain the definitions of terms that are used in the model. A section could also be included on the usage of the model, as seen by the authors. Each aspect of a model (i.e., schema, entity, attribute, function, rule, etc.) should have a related description. Each schema requires a description of its scope and its relationship, if any, to other schemas in the model. This sets the context for the entities and other constructs that form the schema content. The semantics of each type should be described. In particular, the meanings of enuneration items require a description — the meaning of a name may be obvious to the author, but not necessarily to the reader.

The isotherms of CO 2 in the neighbourhood of the critical point and round the coexistence line

The isotherms of CO 2 between 0 and 150°C. and up to 3000 atm. have been previously published by two of the authors (Michels, A. and C. 1935). The method used for these measurements was not suitable, however, for determinations in the neighbourhood of the critical point and the coexistence line. A second method has therefore been developed by which both the critical data and the coexistence line can be determined. This method and the results obtained are described in the present paper. The Method and Apparatus The method was based on the one developed by Michels and Nederbragt (1934) for the determination of the condensation points of a binary mixture. While, however, for the measurements of condensation points, it was not necessary to know the quantity of gas in the apparatus, this knowledge is essential for the determination of isotherms. A new apparatus was therefore constructed in which this quantity could be determined. A diagrammatic sketch showing the principle employed is given in fig. 1. In a steel vessel A , a glass bell B is suspended which is connected through the steel valve H and the capillary J to a cylinder containing a supply of the gas to be examined. A steel capillary C connects A with a second steel vessel D , placed on one scale pan of a balance. Inside D a steel tube E , which is coupled to C , reaches to the bottom. The capillary F is connected to the top of D and leads to a cylinder of pure nitrogen and to an apparatus for measuring the gas pressure. The capillaries C and F are flexible, and are supported at G at such a distance from the scale pan that the variations in the forces acting on the latter during the swinging can be neglected. Before starting the measurements, the vessels A , the glass bell B and the tube C are completely, and the vessel D is partly filled with mercury. The valve H is then opened and CO 2 gas admitted to the glass bell, driving mercury out of A into D . The pressure in D is balanced by nitrogen introduced through F . When sufficient CO 2 has entered the glass bell, the valve H is shut. As the filling operation is carried out at a temperature and pressure at which the isotherms of CO 2 are known, the amount of gas in B can be calculated from a knowledge of the volume.

The hard and soft states in ductile metals

In connection with the previous research attempts were made to break down the crystalline structure of the metal as completely as possible by wire drawing. On etching the surface of wires prepared in this way the structure disclosed appeared to be finely granular, no traces of crystalline grains or of patches of uniform orientation being visible. After the publication of the former paper the wires which had been then used were subjected to a more searching examination. Specimens were ground so as to expose longitudinal sections at various depths and these were etched till the true understructure was disclosed. At low magnifications the structure appeared to consist of parallel strands or fibres which became thinner and either pinched out or drew closer together at the point of fracture. The general character of this structure is shown on fig. 1, which is a diagrammatic sketch of the fractured end of a hard-drawn gold wire. For the proper resolution of the intimate structure of these strands or fibres, a lens of fairly high N. A. is necessary, and in the photomicrographs, figs. 2 and 3, a 4-mm. objective of 0·95 N. A. was found most suitable.