An APL approach to the representation and manipulation of data structures

One of the important characteristics of a programming language is the manner in which commonly used data structures can be represented and manipulated. Methods for the representation of complex data structures in APL, a programming language based on rectangular arrays and a multiplicity of functions, are presented in this paper. Data structures considered are: strings and sets, stacks and queues, tables, linked lists, and sort trees. The material provides insight into the nature of data structures and should aid in establishing future requirements for primal and base languages.     

The Preparation and Assessment of a Series of Pure Dye Acids

High-load paper chromatography has shown previous preparations of the free acids of C.I. Acid Red 88, 13, and 27 to have been impure, although their purity, like that of the free acids of C.I. Acid Orange 7 and 8, had seemed satisfactory according to spectrophotometric examination and titration with alkali and titanous chloride. Reasons are given for the lack of sensitivity of these latter methods when used without supporting data from high-load paper chromatography. The preparation of pure samples of these dye acids is described, together with appropriate analytical data.     

An approach to evaluating and maintaining sprinkler performance

The author presents a conceptual framework for hydraulically calculating sprinkler demand curves based upon a modular loss system. He establishes an interrelationship between a loss module and the demand requirements of a sprinkler system in terms of water density required to control a fire at the modular level and to supply supplemental hose streams for completing extinguishment. This paper was presented at the annual meeting of the Society of Fire Protection Engineers at Atlanta, Ga., May 23, 1968, as part of a program arranged by the Chesapeake Chapter of the SFPE.     

The separation of zirconium and hafnium in a molten salt-molten zinc system

The commercial separation of zirconium and hafniumvia aqueous/organic extraction procedures is both difficult and expensive. The principal objective of the present work was to study an alternative procedure involving the oxidation-reduction equilibria of zir-conium and hafnium between a molten salt phase and molten zincvia the displacement reaction: Zr(IV)_{molten salt} + Hf_{molten zink} ⇌ Hf(IV)_{molten salt} + Zr_{molten zink} The reaction goes strongly to the right with an equilibrium constant: logK =0.432 ×10⁴/T - 1.565 for Na₂Zr(Hf)F₆ dissolved in NaKCl₂ solvent, thus showing promise as the basis for an anhydrous process for separating zirconium and hafnium. The rate of approach to chemi-cal equilibrium was studied in a baffled stirred reactor. The equilibration rate was found to be controlled by the hafnium mass transfer rate from the molten zinc to the metal-salt interface. The mass transfer rate could be estimated from the physical properties of the molten metal and the salt phases, using the Mayer correlation. Formerly with the Teledyne Wah Chang Cor-poration, Albany, OR.     

Studies of structure in carbonized composites from a phenolic resin and oxidized PAN fibres using chromic acid as an etchant

Composites have been prepared from a phenolic resin (49 vol%) and oxidized PAN fibres (51vol%) with heat treatment to 423, 573, 873, 973, 1073 and 1173 K. Optical and scanning microscopy of polished surfaces indicate a fusing of these two materials into a homogeneous matrix. However, SEM of samples etched with chromic acid shows that the identity of materials is preserved. Initially the resin is less reactive than the PAN fibres. Upon carbonization, the carbon from the resin and the PAN have approximately equal reactivities. Enhanced etching occurs at the curved interfaces of the two carbons. The transverse sections of PAN fibres, HTT>973 K exhibit selective etching suggesting the existence of skin/core components in the fibre. It is the more graphitic components of the skin region which are oxidized preferentially.     

Diffusion-related implications for langasite resonator operation

Oxygen and gallium diffusivities in langasite were experimentally determined by analysis of diffusion profiles of 18O and 71Ga tracers by SIMS analysis as functions of temperature and doping. Strontium-enhanced diffusivities and activation energies of approximately 1.2+/-0.2 eV confirm the predominant role of oxygen vacancies in controlling the electrical conductivity of langasite at elevated temperature and oxygen partial pressure. The potential impact of high levels of porosity and the use of an oxygen primary ion beam on the accuracy of some of the data is discussed. The gallium diffusivity, with activation energy of 3.13 eV, was found to be more than two orders of magnitude lower than that of oxygen. Surface exchange measurements enabled estimation of gallium loss at elevated temperatures and oxygen partial pressure; the level is not believed to be of major concern for resonator performance.     

Co-carbonization of solvent fractions of hydrogenated and alkylated SRC pitches in studies of formation of needle-cokes

The optical texture of cokes from two SRC pitches of different coking properties, from co-carbonizations of these materials and of hydrogenated and alkylated products has been studied. The objective, relative to formation of needle-cokes, is to correlate the optical texture of cokes with the chemical structure of the pitch materials using both benzene-soluble (BS) and insoluble (BI) fractions of the pitches. Hydrogenation improved the compatibility of the BS fraction of the inferior SRC pitch (No. 2) with the BI fractions of the two pitches (non-hydrogenated) using a ratio of only 1 to 9. Before hydrogenation, a ratio of BS to BI of 8 to 2 did not give a needle-coke. In contrast, alkylation destroyed the compatibility of the BS fraction of the superior SRC pitch (No. 1) with the BI fraction (non-alkylated) using a ratio of 6 to 4, and which gave a needle-coke before alkylation. Hydrogenation of the alkylated material restored the compatability. The relevance of these studies to industrial carbonization processes is discussed in terms of chemical treatment and the hydrogen economy.     

The dietary potential of the common nettle

A leaf protein concentrate prepared from the young leaves of the common nettle (Urtica dioica) failed to support normal growth in young rats; supplementation with methionine produced a protein efficiency ratio greater than that of casein. A nettle leaf wholemeal, providing 66% of the dietary protein, supported normal growth in young guinea-pigs, mice and rats. Chicks receiving the whole nettle meal as their sole dietary protein grew at only half the rate of chicks given a standard commercial diet. A nettle meal-induced hypercholesterolaemia in mature guinea-pigs and kidney hypertrophy in mice and guinea-pigs should perhaps be interpreted as a caution against the indiscriminate introduction of nettles into the human diet.