Showing papers by "Queen's University Belfast published in 1972"
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01 Jan 1972TL;DR: The first monograph has suggested that in analysing a problem and groping towards a solution, a programmer should take advantage of abstract concepts such as sets, sequences, and mappings; and judiciously postpone decisions on representation until he is constructing the more detailed code of the program.
Abstract: In recent years there has been an increasing interest in the art of computer programming, the conceptual tools available for the design of programs, and the prevention of programming oversights and error. The initial outstanding contribution to our understanding of this subject was made by E. W. Dijkstra, whose Notes on Structured Programming form the first and major section of this book. They clearly expound the reflections of a brilliant programmer on the methods which he has hitherto unconsciously applied; there can be no programmer of the present day who could not increase his skills by a study and conscious application of these principles.
In the second monograph I have tried to describe how similar principles can be applied in the design of data structures. I have suggested that in analysing a problem and groping towards a solution, a programmer should take advantage of abstract concepts such as sets, sequences, and mappings; and judiciously postpone decisions on representation until he is constructing the more detailed code of the program. The monograph also describes a range of useful ideas for data representation, and suggests the criteria relevant for their selection.
The third monograph provides a synthesis of the previous two, and expounds the close theoretical and practical connections between the design of data and the design of programs. It introduces useful additional methods for program and data structuring which may be unfamiliar to many programmers. The examples show that structured programming principles can be equally applied in "bottom-up" as in "top-down" program design. The original inspiration, insight, and all the examples were contributed by O.-J. Dahl; I have only assembled the material, and added some additional explanations where I found it difficult to understand.
1,238 citations
TL;DR: In this paper, a powerful method of simplifying the proofs of program correctness is suggested; and some new light is shed on the problem of functions with side-effects, and a new method for simplifying program correctness proofs is proposed.
Abstract: A powerful method of simplifying the proofs of program correctness is suggested; and some new light is shed on the problem of functions with side-effects.
875 citations
TL;DR: Examination of the wall structure of the above algae suggest a relationship between the presence of sporopollenin and the development of an outer, trilaminar wall component, and suggests that the ability to synthesise sporipollenin is related to the able to produce secondary carotenoids.
Abstract: Cells of Chlorella fusca var. vacuolata (Cambridge 211/8p) resisted efforts aimed at producing naked protoplasts by enzymatic degradation of the cell wall, and a study of the development and composition of the wall was therefore undertaken.
1.
After cytokinesis has produced naked autospores within the mother cell wall, cell wall formation commences outside the autospore plasma membrane with the appearance of small trilaminar plaques. These enlarge while inter-autospore granular material diminishes in quantity, and they eventually fuse to produce a complete trilaminar sheath around each autospore.
2.
A microfibrillar, cellulase digestible, layer is deposited between the trilaminar component and the plasma membrane. Meanwhile the corresponding microfibrillar component of the mother cell wall is digested leaving only its resistant trilaminar component.
3.
The trilaminar component includes a substance considered to be the polymerized carotenoid, sporopollenin, on the basis of its resistance to extreme extraction procedures including acetolysis, and its infra red absorption spectrum.
4.
Two phases of sporopollenin biosynthesis were detected by means of pulse and pulse-chase treatments with 14C-acetate at intervals during the cell cycle in synchronous cultures. One coincides with the formation of the sporopollenin-containing trilaminar wall component, and the other is 6–8 hours earlier while the cells are in karyokinesis. The former yields labelled sporopollenin directly and the latter probably represents formation of a precursor.
5.
Of five other strains of Chlorella tested, only one possesses sporopollenin, and so does one Scenedesmus and two out of three strains of Prototheca.
6.
Examination of the wall structure of the above algae suggest a relationship between the presence of sporopollenin and the development of an outer, trilaminar wall component.
7.
A survey of the literature gives support to this hypothesis and further suggests that the ability to synthesise sporopollenin is related to the ability to produce secondary carotenoids.
8.
The significance of the findings is discussed.
341 citations
07 Aug 1972
TL;DR: The axiomatic definition method proposed in reference [5] is extended and applied to define the meaning of the programming language PASCAL.
Abstract: The axiomatic definition method proposed in reference [5] is extended and applied to define the meaning of the programming language PASCAL [1]. The whole language is covered with the exception of real arithmetic and go to statements.
236 citations
TL;DR: Six out of eight female patients (all of whom developed amenorrhœa during cyclophosphamide therapy) had a return of menstruation when the drug was withdrawn.
183 citations
TL;DR: Amniotic fluid determinations were performed on 115 patients from 15 to 42 weeks' gestation by the para-aminohippurate method of Charles and Jacoby to show a wide normal range which increases as pregnancy progresses.
127 citations
TL;DR: A method suitable for programs containing functions, and a certain kind of jump, that is illustrated by the proof of a useful and efficient program for table lookup by logarithmic search is developed.
Abstract: Proof methods adequate for a wide range of computer programs have been expounded in [1] and [2]. This paper develops a method suitable for programs containing functions, and a certain kind Of jump. The method is illustrated by the proof of a useful and efficient program for table lookup by logarithmic search.
116 citations
TL;DR: In this article, a simple rate-equation theory is developed which indicates that the combination of nonlinear amplification and nonlinear absorption may be responsible for ultrashort pulse generation in a mode-locked quasi-continuous laser system in the absence of commensurately short relaxation times.
109 citations
TL;DR: It is concluded that catecholamines stimulate gastrin release and the intravenous infusion of adrenaline in dogs produced a rise in plasma-gastrin level.
100 citations
TL;DR: Plasma pancreatic glucagon was measured in controls and in untreated recently diagnosed diabetic patients during an oral glucose-tolerance test and severely insulin-deficient diabetics showed a significant rise in glucagon levels after oral glucose.
100 citations
TL;DR: Amnesia was not observed after saline or after 50 mg pethidine, and on questioning 6 h after a short operation many patients had no memory of an object which they clearly recognized and described 1 h after surgery.
Abstract: 1. The intravenous administration of 5 and 10 mg of diazepam caused anterograde amnesia in 50 and 90% of adults, the peak effect occurring in 2-3 min and action persisting for 20-30 minutes.2. Hyoscine (0.4 and 0.6 mg) caused amnesia in 35 and 50% of patients with peak effect not occurring until 50-80 min after injection and action persisting for at least 120 minutes.3. With neither drug was there any relationship between the incidence of amnesia and the degree of drowsiness.4. Amnesia was not observed after saline or after 50 mg pethidine.5. On questioning 6 h after a short operation many patients had no memory of an object which they clearly recognized and described 1 h after surgery.
TL;DR: The mineral skeleton of the remaining stenolaemates represented by extinct trepostomes, cystoporates and cyclostomes, is exclusively double-layered and coelocystic.
Abstract: Eighty species of living and extinct bryozoans have been studied to ascertain the mode of secretion of the skeleton and its structural diversity throughout geological time. In the growing tip of the cheilostomes Membranipora and Electra and the ctenostome Bowerbankia , periostracum secreted by a cap of palisade cells expands forwards by intussusception. Older periostracum, left behind by the advancing cell cap in cheilostomes and cyclostomes, becomes the seeding sheet of a calcitic layer (primary layer) of vertically disposed crystallites with minor banding, nodules and lenses, deposited by epithelium generated immediately proximal of the cell cap. The periostracum is composed of mucopolysaccharide and some chitin but its outer surface varies, being a fibrillar triple-unit membrane in cheilostomes and the cyclostomes Berenicea and Lichenopora , and a homogenous granular layer in Bowerbankia and the cyclostome Crisidia . The mineral skeleton of most cheilostomes is secreted on periostracum by succeeding epithelium. But coelocystic structures, deposited within folds of epithelium, also occur and vary from frontal walls and cryptocysts to almost complete skeletons of Cupuladria and Iodictyum . In some living cheilostomes and in most fossil species examined, only a primary shell, more commonly calcitic than aragonitic, is found, but in the majority of living species there occurs an organic-carbonate secondary layer usually composed of discrete laminar or lenticular aggregates of vertically disposed crystallites enclosed in proteinous sheets. In Celleporella , however, the laminae are more strongly defined because they consist of spirally growing calcitic plates separated from one another by simultaneously secreted proteinous sheets. More rarely, a tertiary layer is found in some species. It is almost entirely calcitic or aragonitic and may be banded, granular or composed of acicular crystallites. Puncta and basal kenozooids, as in Schizoporella and Cupuladria, penetrate the shell of some species and accommodate papillae with storage cells. The mineral skeleton of most cyclostomes, including the earliest known genera like the Ordovician Corynotrypa, has always been subperiostracal, and may also be pierced by puncta accommodating storage papillae and distally closed by periostracal plugs (e.g. Crisidia, Berenicea ). The skeleton of Heteropora , Hornera, Lichenopora and related genera which first appeared in early Mesozoic times, is coelocystic. It may also be ornamented by inwardly pointing cones of secondary shell (pseudopuncta) with or without axial rods of granular calcite (e.g. Hornera ) , or include vesicular tissue between radiating rows of zooecia as in Lichenopora . All cyclostomes, however, have always had a double-layered calcitic skeleton consisting of a primary layer of vertically disposed acicular crystallites, granules or tablets altered to a granular texture in the fossil state, and a laminar secondary layer with spirally growing plates and/or overlapping fibres coated by protein sheets. The mineral skeleton of the remaining stenolaemates represented by extinct trepostomes, cystoporates and cyclostomes, is exclusively double-layered and coelocystic. The primary layer is granular, the secondary composed of lenticular fibres. Pseudopuncta were almost invariably developed and interzooecial cavities (mesopores) commonly occurred and were filled with vesicular tissue as in Lichenopora . Phylogenetic considerations suggest that the prototypic bryozoans possessed a pseudopunctate coelocystic skeleton, indented by mesopores and composed of a chitinous or proteinous periostracum, a primary layer of acicular crystallites and a secondary layer of lenticular fibres. This structure was inherited by trepostomes, cystoporates and cryptostomes. It reappeared in Mesozoic cyclostomes subsequent to their divergence from a cystoporate-like ancestor by the development of a variably punctate subperiostracal skeleton which, however, was composed of the same shell types. The subperipheral skeleton of early cheilostomes may have evolved by extension of the ctenostome secretory regime. In any event a new type of secondary shell, composed of acicular crystallites arranged in proteinbound laminae and lentides, became characteristic mainly of Tertiary and Recent species. Nevertheless, a coelocystic skeleton and even a stenolaemate-like secondary shell have already appeared within the Order.
TL;DR: Feeding experiments using 15N2 or 15NO3 are described investigating the transport of nitrogen in the field pea, with the root appearing to be extremely inactive in transferring nitrogen from the downward translocation stream across to the stream of nitrogen leaving the root in the xylem.
Abstract: Feeding experiments using (15)N2 or (15)NO3 are described investigating the transport of nitrogen in the field pea (Pisum arvense L.). Nitrogen assimilated by root or nodules moves preferentially upwards to the shoot through the xylem. Parts of the root below or distal to a region of assimilation can benefit from this nitrogen but do so to a much greater extent when the shoot is left attached than when it has been removed. A considerable proportion of the nitrogen received by a shoot from the root or nodules is apparently returned to the root in the translocation stream, this "cycled" nitrogen being especially important in the nutrition of outlying parts of nodulated roots growing in media lacking combined nitrogen.Nitrogen from nitrate fed to a mature leaf is exported in quantity to all parts of the plant except older regions of the shoot. Leaf and stem segments immediately above the fed leaf, and the root and its nodules receive large shares of this nitrogen, although the root's share declines noticeably as the plant ages.The root appears to be extremely inactive in transferring nitrogen from the downward translocation stream across to the stream of nitrogen leaving the root in the xylem. This may act as a major obstacle to the free circulation and mixing of nitrogen within the plant body.A scheme is proposed embracing the main quantitative features of the transport system for nitrogen in the species.
TL;DR: It is suggested that the urine of adult mice contains an active substance(s) which can affect the growth of young female mice and that the effect is dependent on the reproductive state of the donor.
TL;DR: In red light at 15°C, female gametophytes of Laminaria saccharina continue to grow indefinitely without becoming fertile, but 6–12 hours' irradiation with blue light induces the production of eggs.
Abstract: In red light at 15°C, female gametophytes of Laminaria saccharina continue to grow indefinitely without becoming fertile, but 6–12 hours' irradiation with blue light induces the production of eggs. At lower temperatures, some gametophytes become fertile in red light, but blue irradiation increases the percentage of fertile gametophytes.
TL;DR: In this article, the effects of single photon absorption and stimulated emission from the S$\_{1}$ and S$2}$ excited singlet states of Rhodamine 6G and DPA were investigated by measurements of the two-photon fluorescence efficiencies of these dyes.
Abstract: Intensity dependent quenching and reversal of the two-photon fluorescence patterns in Rhodamine 6G and DPA, of picosecond pulses from a mode-locked ruby laser have been investigated by measurements of the two-photon fluorescence efficiencies of these dyes. While for Rhodamine 6G there was a marked departure from the square law dependence at high laser intensities, the experimental curve for DPA showed no evidence of quenching. When excited by a mode-locked neodymium: glass laser Rhodamine 6G fluorescence was not quenched at fluxes as high as $5\times 10^{30}$ photons cm$^{-2}$ s$^{-1}$ but in Rhodamine B quenching appeared at a laser flux of $3\times 10^{27}$ photons cm$^{-2}$ s$^{-1}$. These quenching results and measurements of the absorption of pulses by Rhodamine 6G, previously excited by second harmonic pulses, are explained by the effects of single photon absorption and stimulated emission from the S$\_{1}$ and S$\_{2}$ excited singlet states. A square pulse approximation has been employed to solve the general rate equations and the fitting of the calculated curves to the experimental results gave values for the stimulated emission and absorption cross-sections of the S$\_{1}$ and S$\_{2}$ states of Rhodamine 6G and for the relaxation time ($\sim 2$ ps) between the vibrational manifolds of these excited states. Taking into account random phase and amplitude fluctuations of the picosecond pulses, time and space averaged two-photon fluorescence profiles, using these values of the dye parameters, showed quenching and reversal of the patterns for the laser pulse intensities at which these effects were experimentally observed. The possibilities of frequency tunable pulses, of transform-limited durations, from mode-locked dye lasers employed with an electro-optical streak camera of time-resolution equal to that of the pulse durations ($\sim 2$ ps) for time-resolved excited state molecular spectroscopy are briefly considered.
TL;DR: An outline scheme for the ecological classification of heterotrophic microorganisms in fresh water is presented in the hope that it may help to indicate some gaps in knowledge and stimulate a search for precision and definition in future studies.
Abstract: An outline scheme for the ecological classification of heterotrophic microorganisms in fresh water is presented in the hope that it may help to indicate some gaps in our knowledge and stimulate a search for precision and definition in future studies.
TL;DR: A method of producing minor trauma by osmotic forces has been developed to enable the localiza- development of enzymes specifically concerned with phospholipid metabolism.
Abstract: The alveoli of the mammalian lung are lined by a film of surface-active material (surfactant) which is commonly believed to be a phospholipid (1, 5, 8, 11) . A considerable body of evidence has accumulated which suggests that surfactant is synthesized by the granular pneumonocytes (type II cells) of the alveolar epithelium (1, 9, 10) . Although a number of acid hydrolases have been demonstrated in the inclusion bodies of granular pneumonocytes (4, 6), no attempt has been made to localize enzymes specifically concerned with phospholipid metabolism. Phosphatidic acid phosphatase is of particular interest because of its key role in the biosynthesis of phosphatides . Unfortunately, this enzyme cannot be demonstrated by conventional histochemical methods because of the insolubility of the substrate (phosphatidic acid) in water . Stable emulsions of phosphatidic acid can be prepared but these do not diffuse into cells . One method of overcoming this difficulty is to inflict minor localized damage on cells and expose the organelles to an emulsion of phosphatidic acid in a suitable medium . A method of producing minor trauma by osmotic forces has been developed to enable the localiza-
TL;DR: Results were consistent with the hypothesis that physostigmine sulphate improved “attention” to the stimuli rather than response inhibition, and were thought to be the critical levels for neural facilitation.
Abstract: In order to assess the effects of physostigmine sulphate on stable discrimination performance, a group of rats were trained on a simple brightness discrimination and injected with saline and three doses of the drug according to a latin square design. Improved performance was obtained with 0.05 and 0.10 mg/kg doses of the drug while the highest dose of 0.20 mg/kg impaired the discrimination responding. The effects of the highest dose were similar to the results obtained after injections of scopolamine hydrobromide into the same animals. A signal detection analysis revealed that physostigmine sulphate at the two low doses increased the stimulus sensitivity index without changes in the response bias index. These results were consistent with the hypothesis that physostigmine sulphate improved “attention” to the stimuli rather than response inhibition. A biochemical assay of brain cholinesterase activity showed that these two doses produced between 40% and 60% inhibition of activity, which is thought to be the critical levels for neural facilitation.
TL;DR: This note discusses methods of defining the for statement in high level languages and suggests a proof rule intended to reflect the proper role of a for Statement in computer programming and a suggestion for possible generalisation.
Abstract: This note discusses methods of defining the for statement in high level languages and suggests a proof rule intended to reflect the proper role of a for statement in computer programming. It concludes with a suggestion for possible generalisation.
TL;DR: In this paper, the exact values of the two-photon absorption cross-sections of Rhodamine 6G, Rhodamine B, Acridine Red, Disodium Fluorescein and DODCI have been obtained by excitation with a neodymium: glass laser (1060 nm).
Abstract: Absolute values of the two-photon absorption cross-sections of Rhodamine 6G, Rhodamine B, Acridine Red, Disodium Fluorescein and DODCI have been obtained by excitation with a neodymium: glass laser (1060 nm). Measurements over eight orders of magnitude of the exciting light flux were carried out by employing the laser both Q-switched and mode-locked. The two-photon fluorescence flux measurements were calibrated by single-photon fluorescence generated by excitation with second-harmonic laser pulses. The experimental results are compared with values predicted by semi-empirical theoretical models and good agreement is obtained. Two-photon amplification of the mode-locked neodymium laser by organic dyes is shown not to be practicable at present. Other possible two-photon oscillators are discussed.
TL;DR: Evidence obtained would suggest that the processes involved in egg formation in Fasciola hepatica occur in the following sequence: the egg constituents pass through the proximal ootype and are smeared by the secretions of Mehlis' gland which have accumulated there.
TL;DR: In this article, the catalytic properties of clay surfaces have been investigated to determine the probable contribution of such reactions in petroleum genesis, and they concluded that surface catalytic-type reactions provide a feasible route to petroleum genesis and that such reactions may make a substantial contribution tothe formation and diagenesis of natural hydrocarbon deposits.
TL;DR: Observations were made of the fungi in eight unpolluted streams in Northern Ireland, using different techniques of isolation, and the results are recorded, suggesting that the systematic use of several methods of isolation can yield valuable information on the ecology of micro-organisms.
Abstract: Observations were made of the fungi in eight unpolluted streams in Northern Ireland, using different techniques of isolation, and the results are recorded. It is suggested that the systematic use of several methods of isolation can yield valuable information on the ecology of micro-organisms.
01 Feb 1972
TL;DR: Stable passive mode-locking of a cw rhodamine 6G dye laser has been achieved using a simple, end-pumped, internal lens cavity as mentioned in this paper, where the laser output consists of isolated picosecond pulses separated by the 8 nsec round-trip time of the cavity.
TL;DR: Diclidophora merlangi is a common parasite of whiting in the Irish Sea and the incidence of infection over an 18-month period of study varied between 43-59%.
Abstract: Diclidophora merlangi is a common parasite of whiting in the Irish Sea. The incidence of infection over an 18-month period of study varied between 43-59%. The majority of flukes in single worm infections are found on the 1st gill arch, although in infections of higher intensity increasing numbers of parasites are found on the remaining arches. The factors which may influence the distribution of Diclidophora on the host gills are discussed.