Showing papers by "Queen's University Belfast published in 1978"

Communicating sequential processes

Abstract: This paper suggests that input and output are basic primitives of programming and that parallel composition of communicating sequential processes is a fundamental program structuring method. When combined with a development of Dijkstra's guarded command, these concepts are surprisingly versatile. Their use is illustrated by sample solutions of a variety of a familiar programming exercises.

The symptoms of calcium deficiency in plants

Abstract: SUMMARY As the symptoms of calcium deficiency develop in plants, there is often a stage in which the tissues are water-soaked and one involving cell breakdown with loss of turgor (as in internal breakdown of apples). Eventually the tissue may become desiccated yielding a dry, more or less extensive area of necrosis. Two mechanisms are proposed. There is evidence that calcium deficiency renders membranes permeable which would account for a loss of turgor and permit cell fluids to invade intercellular spaces. An alternative situation may develop in soft, succulent fruits, the cells of which burst under hypotonic conditions in vitro. It is suggested that exogenous water may enter a fruit from the atmosphere or (in apple) through the phloem. Such exogenous water in the intercellular spaces of the fruit may cause cells to swell, so cracking the fruit or it may result in a bursting of the cells. A plea is made for further light microscope studies of the development of symptoms of calcium deficiency.

Depression of evoked potentials in brain slices by adenosine compounds.

Abstract: 1 A study has been made of the action of adenosine on surface slices of guinea-pig olfactory cortex in vitro. 2 With extracellular recordings from the pial surface and stimulation of the presynaptic input, the lateral olfactory tract (LOT) generated a monosynaptic negative wave representing dendritic excitatory potentials. This negative wave was depressed by bath application of 1 micron adenosine with increasing effect up to 1 mM. Adenosine 5'--triphosphate (ATP), adenosine 5'-monophosphate (AMP) and cyclic adenosine 3',5'-monophosphate (cyclic AMP) had similar depressant actions. Adenine and guanosine were very weak depressants. 3 Theophylline concentrations in the range 10 micron to 3 mM progressively antagonized the action of adenosine. 4 Dibuyryl cyclic AMP (100 micron) and agents which increase intracellular cyclic AMP were not depressants, suggesting that the action of adenosine was not cyclic AMP-mediated. 5 Intracellular recordings confirmed the depressant effect of adenosine on excitatory potentials generated by LOT stimulation and also showed that postsynatpic action potentials and the membrane of the soma were unaffected by adenosine. 6 Since presynaptic action potentials were also unaffected by adenosine, these experiments suggest that adenosine reduces excitatory transmission at LOT synapses and fortifies the idea that adenosine has a 'neurohumoral' action.

Mechanism of paraquat tolerance in perennial ryegrass

Abstract: The mechanism of paraquat tolerance was investigated in lines of perennial ryegrass (Lolium perenne L.) which had been selected for resistance to the herbicide. Uptake, metabolism and translocation of paraquat were studied. Susceptible cultivars and a tolerant line were not found to differ in uptake of radioactive paraquat applied to the leaf surface or supplied to the cut ends of excised leaves. Distribution of herbicide within leaf tissue was similar in tolerant and susceptible plants and no metabolites of 14C-paraquat were detected in tolerant or susceptible plants treated with sub-lethal concentrations of the herbicide. Autoradiography and quantitative determinations showed much variation in translocation of 14C-paraquat out of treated leaves of intact plants, but the variation was not related to the degree of susceptibility to the herbicide. It is concluded that paraquat tolerance in perennial ryegrass is unlikely to depend upon reduced uptake, enhanced metabolism or altered translocation of the herbicide.

A new type of convergence

Abstract: In his important paper (1), Lorentz defined the space f of almost convergent sequences, using the idea of Banach limits. If x ∈ l∞(R), the space of bounded real sequences, andwhere the inf is taken over all sets n(1), n(2), …, n(r) of natural numbers, then a Banach limit L may be defined as a linear functional on l∞(R) which satisfies

The influence of passive stretch on the growth and protein turnover of the denervated extensor digitorum longus muscle.

Abstract: At 7 days after cutting the sciatic nerve, the extensor digitorum longus muscle was smaller and contained less protein than its innervated control Correlating with these changes was the finding of elevated rates of protein degradation (measured in vitro) in the denervated tissue However, at this time, rates of protein synthesis (measured in vitro) and nucleic acid concentrations were also higher in the denervated tissue, changes more usually associated with an active muscle rather than a disused one These anabolic trends have, at least in part, been explained by the possible greater exposure of the denervated extensor digitorum longus to passive stretch When immobilized under a maintained influence of stretch the denervated muscle grew to a greater extent Although this stretch-induced growth appeared to occur predominantly through a stimulation of protein synthesis, it was opposed by smaller increases in degradative rates Nucleic acids increased at a similar rate to the increase in muscle mass when a continuous influence of stretch was imposed on the denervated tissue In contrast, immobilization of the denervated extensor digitorum longus in a shortened unstretched state reversed most of the stretch-induced changes; that is, the muscle became even smaller, with protein synthesis decreasing to a greater extent than breakdown after the removal of passive stretch The present investigation suggests that stretch will promote protein synthesis and hence growth of the extensor digitorum longus even in the absence of an intact nerve supply However, some factor(s), in addition to passive stretch, must contribute to the anabolic trends in this denervated muscle

The solution of sparse linear equations by the conjugate gradient method

Abstract: The convergence properties of the conjugate gradient method are discussed in relation to relaxation methods and Chebyshev accelerated Jacobi iteration when applied to the solution of large sets of linear equations which have a sparse, symmetric and positive definite coefficient matrix. The conclusion is reached that its convergence rate is unlikely to be much worse than these methods, and may be considerably better. The conjugate gradient method may either be applied to the basic unscaled or scaled equations or alternatively to various transformed equations. Preconditioning, block elimination and partial elimination methods of transforming equations are considered, and some comparative tests given for six problems.

Some Properties of Predicate Transformers

Abstract: This paper defines some "weakest precondltmn'" predicate transformers, Investigates their "healthi- ness" properties, and apphes them to Dljkstra's language of guarded commands It shows that Dljkstra's w~ function is not the weakest healthy one, but it ~s clearly the best one for practical programming, because it proves the absence of bhnd alleys from a nondetermmlsac program A previous paper (10) has suggested that a computer programming language should be given several separate formal definitions, which should be proved consistent with each other. The definitions should be complementary, m the sense that one of them should satisfy the need of the programmer to prove the correctness of his program, and another should assist in the construction and proof of a correct implementation. The suggestion was illustrated by a simple deterministic language, for which the axioms of conditional correctness were proved consistent with an abstract model of ~ts implementation. The results of that previous paper are here extended and improved m the following ways:

Anticholinergic drugs in anaesthesia. A survey of their present position.

Abstract: A survey was carried out amongst anaesthetists in the United Kingdom and Ireland regarding the use of anticholinergic drugs. Sixty-two per cent of these anaesthetists use these drugs routinely in premedication. The drugs are nearly always atropine or hyoscine and are used mainly for reducing secretions and protection against vagal stimulation. A longer-acting drug was desired by 22% and 60% would like to use an orally effective anticholinergic drug. Though quite a number of minor side effects are high-lighted, the majority do not consider these serious enough to stop routine use. There is now a tendency amongst many anaesthetists either not to use these drugs routinely or use them less often, more rationally and in reduced dosage.

Self-contained units in composite manuscripts of the Anglo-Saxon period

Abstract: Many medieval manuscripts are composite volumes, made up of a number of self-contained units which elsewhere I have called ‘booklets’. Such a unit originated as a small but structurally independent production containing a single work or a number of short works. Two of the earliest surviving examples, dating from the late eighth century, were produced on the continent. Each is a single gathering now bound with other gatherings into a codex: Merseburg, Stiftsbibliothek 105, fols. 85–105, containing Alcuin's Vita S. Vedasti and some of his homilies, and St Gall, Stiftsbibliothek 567, pp. 135–53, containing aVita S. Lucii. There is a fold in the centre of every page of both these quires, made after the text had been copied and not present in the other quires with which they are now bound. In both instances the completed quire was folded so that the verso of its last leaf became the outer pages or ‘cover’ of the resulting booklet. This ‘cover‘ is more soiled than the other pages in the quire, suggesting that the booklet once circulated independently of the other quires in the manuscript into which it is bound.

Biochemical Characteristics and Enterotoxigenicity of Staphylococcus aureus Strains Isolated from Poultry

Abstract: About half (49%) of strains of Staphylococcus aureus isolated from poultry were non-typable with the international human set of phages, and 55% were biotype B according to the biochemical identification scheme of Hajek & Marsalek (1971, 1973). A furthest neighbour clustering strategy and principal coordinate analysis based on 17 biochemical tests made clear distinctions between biotype B strains and a group of biotype A and intermediate strains. Overall 62% of strains were enterotoxigenic, the majority producing enterotoxin A. Significantly fewer intermediate strains than biotype A or B strains were enterotoxigenic. Starch gel zymograms of intracellular esterases showed a general correlation with the biotyping and phage typing results.

Pulsed-x-ray shadowgraphy of dense, cool, laser-imploded plasma

Abstract: Laser implosion of 87-bar neon-filled glass microballoon targets produces a dense, cool plasma whose development in time and space is recorded by pulsed-x-ray shadowgraphy with soft x rays from a separate laser-produced plasma. Compressed densities of 4 g ${\mathrm{cm}}^{\ensuremath{-}3}$ are estimated from the data by comparison with numerical simulations of the implosion.

Changes in auditory perception in the menstrual cycle.

Abstract: In an attempt to specify the critical functional components involved in the menstrual fluctuation of the upper frequency limit of the binaural beat we have obtained evidence of better performance in a variety of tasks at period and mid-cycle than at other times. These tasks include detection of physical beating, low-frequency octave matching, and lateralisation of clicks having interaural time delays in the 100 sec region. Continuous pure-tone frequency discrimination did not show a significant cyclical pattern overall but there was a tendency for low-frequency discrimination to show the described pattern. An attempt is made to reconcile some of these results with those of Wynn 1973 on absolute pitch, in terms of possible physiological and biochemical correlates. Three conclusions can be drawn: (1) The representations both of low-frequency tones and of the interaural time differences involved in some localisation tasks are particularly susceptible to alteration by the biochemical changes of the menstrual ...

Climatic signals in British Isles tree-ring chronologies

Abstract: INTERPRETATION of proxy records of past environmental conditions derived from dated geological or biological materials is of great importance for the extension of the climatic record1,2. Precisely dated, replicated tree-ring series have been particularly useful as they provide records (usually ring-widths) dated to the individual year, for hundreds or thousands of years. Each such series, or chronology, is derived from a particular known location. Thus a network of such chronologies may be developed for a particular region and used as a proxy record of spatial and temporal climatic variations. This has been achieved in North America by Fritts et al.3,4, using principally chronologies from semi-arid areas or from near altitudinal or polar tree-lines. We report evidence here that tree-ring chronologies from sites in the British Isles will provide suitable proxy records for the reconstruction of historical temporal and spatial variation of climate.

The effect of preslaughter lairage on serum thyroxine and cortisol levels at slaughter, and meat quality of boars, hogs and gilts

Abstract: Commercial crossbred hogs and gilts, and purebred Landrace boars and gilts were slaughtered after a lairage period of either 2 or 24 h. The meat quality of the carcasses was assessed by measuring the pH of the Longissimus dorsi and adductor muscles at 45 min and 20 h post mortem. Serum cortisol and thyroid parameters were measured in blood taken at slaughter. The incidence of the pale, soft and exudative (PSE) condition was slightly higher in purebred Landrace pigs killed after a short lairage period than in those held in lairage overnight. The PSE condition tended to be more prevalent in Landrace gilts than boars. The percentage of carcasses classified as dark, firm and dry (DFD) was much greater in both commercial crossbred and purebred Landrace pigs killed after overnight lairage. The incidence of the DFD condition was greater in Landrace boars than gilts, particularly after overnight lairage. Serum cortisol levels were higher and serum total thyroxine (T4) and free thyroxine indices (FTI) lower in pigs killed after a short lairage. Serum total T4 and FTI values at slaughter were lower in boars than gilts.

Control of photorespiration at RuBP carboxylase/oxygenase level in ryegrass cultivars

Abstract: PHOTORESPIRATION is probably a key intrinsic factor limiting photosynthetic productivity in C3 plants. Attempts to control photorespiration with inhibitors of the metabolism of various photorespiratory intermediates have yielded unsatisfactory results with whole plants. A logical endogenous control point would be the branch point between photosynthetic and photorespiratory pathways, as most if not all the substrate for photorespiration is formed by the oxygenase function of ribulose bisphosphate carboxylase (RuBP carboxylase). There is considerable direct and indirect evidence suggesting that the oxygenase and carboxylase functions of this enzyme are tightly linked1,2. However, temperature has been shown to have differential effects on the affinities of soybean RuBP carboxylase for CO2 and O2 (ref. 3), and mutant strains of Chlamydomonas and tobacco with altered carboxylase/oxygenase affinities have also been reported4,5. We present here evidence for genetically controlled variation in the relative affinities of the RuBP carboxylase from ryegrass for CO2 and O2.

Enhanced choice of familiar food in a food preference test after chlordiazepoxide administration.

Abstract: Chlordiazepoxide (5.0 and 10.0 mg/kg) increased the time spent eating familiar laboratory chow, in a food-choice test in which both familiar and novel food objects were available. Chlordiazepoxide did not affect the feeding response to the novel food. Prior handling of the rats and repeat testing affected feeding responses in the test, although in ways which were different from and independent of the effect of chlordiazepoxide. Chlordiazepoxide may facilitate feeding responses by a direct enhancement of feeding motivation, and not necessarily secondarily by either a release of suppression of feeding or as attenuation of anxiety evoked by unfamiliarity.

Etioplast Development in Dark-grown Leaves of Zea mays L.

Abstract: The ultrastructure of etioplasts and the acyl lipid and the fatty acid composition of sequential 2-centimeter sections cut from the base (youngest) to the top (oldest) of nonilluminated 5-day-old etiolated leaves of Zea mays L., and the acyl lipid and fatty acid composition of the etioplasts isolated from them have been investigated. There is a 2.5-fold increase in the size of the plastids from the base to the tip of the leaf, and an increase both in the size of the prolamellar body and in the length of lamellae attached to it. The etioplasts in the bundle sheath and mesophyll cells of the older, but not the younger leaf tissue, are morphologically distinct. The monogalactosyl and digalactosyldiglycerides, phosphatidylcholine, phosphatidylglycerol, and phosphatidylinositol were the only detectable acyl lipids in the isolated etioplast fractions. Together with phosphatidylethanolamine these were also the major acyl lipids in the whole leaf sections. With increasing age of the leaf tissue, increases occurred in two of the major plastid lipids, monogalactosyldiglyceride and phosphatidylglycerol, while the levels of essentially nonplastid lipids remained constant or declined slightly. The monogalactosyldiglyceride to digalactosyldiglyceride ratio increased from 0.4 to 1.1 in the tissue sections of increasing age and from 0.7 to 1.2 in the etioplasts isolated from them. Similarly, the galactolipid to phospholipid ratio increased from 0.8 to 1.4 in the tissue and from 0.5 to 4.5 in the isolated plastids. In the latter, the proportions of phosphatidylglycerol (as a per cent of total phospholipid) increased from 20 to 41% with increasing age of plastids. Linolenic acid was the major fatty acid in the total lipid of each of the etioplast fractions, but it was only the major fatty acid in the total lipid of the oldest leaf tissue. Its proportion in both total lipid extracts and individual lipids increased with age. The trans Δ 3 hexadecenoic acid was absent from all lipids. The protochlorophyllide content of the tissue increased with age. The results are discussed in relation to the use of illuminated etiolated leaves for studying chloroplast development.

Frequency of atopy and alelrgy in an anawesthetic patient population

Abstract: Ten thousand patients presenting for anaesthesia in the British Isles were questioned about a possible history of atopic or allergic disorders. The overall percentage frequency of atopy was 8.5, comprising eczema 2.4, hay fever 3.8 and asthma 3.5. The frequency of allergies was 13.5, of which penicillin was the most common (6.2). Females had a significantly greater frequency of atopy or allergy than males. Patients with a history of atopic disorders had a higher frequency of allergies than the non-atopic group (36.2% compared with 11.4%) and vice versa.

Report of a symposium: adverse responses to intravenous agents

Abstract: An International Symposium on \"Adverse Responses to Intravenous Agents\" held in Sheffield, July 6-7, 1978 attracted 137 registered participants, not only from a variety of countries, but also established representatives of a number of scientific disciplines. The Symposium, organized jointly by the University of Sheffield Departments of Immunology and Anaesthetics, also coincided with the 150th Anniversary of the founding of the Sheffield Medical School. Despite the intention of the scientific committee to consider the term \"adverse\" in its widest context to include all reactions mediated through the i.v. route, for the most part the participants showed a marked preference for \"anaphylactoid\" phenomena, which prompted a definition of the term anaphylactoid early in the proceedings. It was agreed that the term merely defined clinical manifestations (cutaneous, pulmonary and cardiovascular) which resembled those of immediate, immune-mediated, hypersensitivity reactions. In the absence of suitable laboratory tests (not denned) clinical reactions would not be ascribed to classical hypersensitivity mechanisms and would obviously include those produced pharmacologically by the direct action of the agent(s) on mast cells. The use of the terms histaminoid and allergoid (Lorenz, Marburg) to describe clinical manifestations restricted to the skin was also acceptable to the participants.