Showing papers by "University College Dublin published in 1983"

A Survey of Recent Advances in Hierarchical Clustering Algorithms

Abstract: It has often been asserted that since hierarchical clustering algorithms require pairwise interobject proximities, the complexity of these clustering procedures is at least O(N 2 ). Recent work has disproved this by incorporating efficient nearest neighbour searching algorithms into the clustering algorithms. A general framework for hierarchical, agglomerative clustering algorithms is discussed here, which opens up the prospect of much improvement on current, widely-used algorithms. This 'progress report' details new algorithmic approaches in this area, and reviews recent results.

Glutamine Synthetases of Higher Plants Evidence for a Specific Isoform Content Related to Their Possible Physiological Role and Their Compartmentation within the Leaf

Abstract: The chromatographic properties of glutamine synthetase isoforms have been investigated in a wide range of higher plant leaves and shoots using ion exchange chromatography. Different patterns of glutamine synthetase isoform content were observed. Among higher plants, four patterns or groups could be recognized. The first group is characterized by having only cytosolic glutamine synthetase, whereas the second group is distinguished by having only chloroplastic glutamine synthetase. The third group is characterized by cytosolic glutamine synthetase being a minor component of the total leaf glutamine synthetase activity. The fourth group is distinct from the other groups in having high cytosolic and chloroplast glutamine synthetase activity. Immunological studies have been undertaken on a few species from each group to identify unambiguously both cytosolic and chloroplastic glutamine synthetases.

Computer simulation of a two-dimensional soap froth

Abstract: We have developed a computer program by means of which a two-dimensional soap froth may be simulated. This system is of interest in connection with theories of grain growth in polycrystalline solids, but only limited and somewhat contradictory experimental statistical data have hitherto been available. We present preliminary results for the evolution in time of a froth of 100 cells, with periodic boundary conditions.

Ro 15–1788 antagonizes the effects of diazepam in man without affecting its bioavailability

Abstract: In 8 double-blind, placebo-controlled three-way cross over study, the efficacy of Ro 15–1788 200 mg, a new benzodiazepine antagonist, in blocking the amnesic, cognitive, psychomotor and subjective effects of diazepam 20 mg, was investigated in a group of six healthy male volunteers. The amnesic effects of diazepam were markedly attenuated by the combined administration of Ro 15–1788. The psychomotor and subjective effects of diazepam by mouth were most pronounced 2.5 h after administration. Concurrent oral administration of Ro 15–1788 completely prevented these effects at 2.5 h. Plasma diazepam concentrations observed after administration of the combination of diazepam and the antagonist did not differ from those observed following diazepam alone.

Optimum Replacement of a System Subject to Shocks

Abstract: A system is subject to shocks that arrive according to a nonhomogeneous or homogeneous Poisson process. Since each shock weakens the system and makes it more expensive to run, it is desirable to determine a replacement policy for the system. We consider the possibility of periodic replacement of the system, and exhibit a necessary and sufficient condition for the existence of an optimal finite period. The problem is investigated for both finite and infinite time horizons. Finally, we study a particular model for a system that fails on the second shock.

Absence of central effects in man of the benzodiazepine antagonist Ro 15-1788.

Abstract: The benzodiazepines are typified by a profile of side effects which includes drowsiness, ataxia and incoordination. Ro 15-1788, an imidazodiazepine derivative, exhibits marked antagonism of the behavioural and biochemical effects of the benzodiazepines in animals and man. It is devoid of any behavioural activity in animals, except at very high doses. In the present study the effects of single rising oral doses of Ro 15-1788 on cognitive, psychomotor and subjective function in man have been assessed using a battery of psychometric tests designed to identify the sedative action of the benzodiazepines. At all doses up to 600 mg, Ro 15-1788 demonstrated none of the classical behavioural effects of the benzodiazepines.

Sweet itch: responses of clinically normal and affected horses to intradermal challenge with extracts of biting insects.

Abstract: Summary In a study of the skin reactivity of horses with lesions of sweet itch, six clinically normal horses and seven affected horses were challenged intradermally with extracts of Culicoides, Stomoxys, Tabanidae and Culex species. All the affected horses and three of the normal horses responded strongly to the culicoides extract. The skin reactions in the affected horses reached their maxima within 4 h in the majority of animals. Skin reactivity to culicoides was transferred to normal horses with serum from affected animals confirming that the reaction was an immediate hypersensitivity reaction. Three of the seven affected animals gave both immediate and delayed reactions when challenged with the culicoides extract. When the dermal reactions of 12 clinically normal and 10 affected horses were compared at 20 mins and 1 h after challenge, the reactions produced by the culicoides extract were significantly (P<0.025) greater in the affected than in the normal horses. Individual horses gave strong reactions to extracts of Stomoxys, Culex and Tabanidae species, but no consistent response was evident among the affected animals. Serum from horses with sweet itch sensitised the skin of normal horses to challenge with extracts of the biting flies and the transferred antibodies remained bound to the skin of the recipient horse for 72 h or longer. Although some variation among the affected horses occurred in passive transfer experiments, the response to Culicoides species extracts was consistently greater than for the other insect extracts tested. Resume Pour etudier la reactivite cutanee des chevaux atteint de dermite estivale recidivante, six chevaux normaux et sept malades furent intradermo inocules avec des extraits de Culicoides, de Stomoxys, de Tabanides et de Culex. Tous les chevaux malades et trois des chevaux normaux reagirent fortement a l'extrait de culicoides. Les reactions cutanees maximales furent atteints en moins de 4 heures chez la plupart des chevaux malades. La sensibilite cutanee aux culicoides fut conferee aux chevaux sains par l'administration de serum de chevaux malades. Cela confirmait l'existence d'une reaction immediate d'hypersensibilite. Trois des sept chevaux malades presenterent deux reactions aux extraits de culicoides, l'une immediate et l'autre differee. Lorsqu'on compara les reactions dermiques de 12 chevaux normaux et de 10 chevaux malades, 20 minutes, puis 1 heure apres l'injection declenchante, on observa que les reactions produites par l'extrait de culocoides etaient plus importantes de maniere significative (P<0.025) chez les chevaux malades. Certains chevaux eurent des reactions individuelles marquees aux extraits de Stomoxys, Culex et Tabanides, sans qu'aucune reaction ne puisse etre consideree comme interpretable. Le serum preleve sur des chevaux atteints de dermite estivale sensibilise — rait la peau des chevaux normaux a l'injection d'extraits de mouches piqueuses; les anticorps ainsi transferes restaient presents dans la peau des receveurs 72 heures et plus. A quelques variations pres constatees durant ces experiences d'immunosite passive conferee, on constatait une reponse immunitaire plus forte avec les extraits de Culicoides qu'avec les extraits provenant des autres especes utilisees. Zusammenfassung Anlasslich einer Untersuchung der Hautempfindlichkeit von Pferden mit Sommerekzemlasionen (“Sweet Itch”) wurden sechs klinisch gesunde und sieben erkrankte Pferde provoziert mit Extrakten von Culicoides, Stomoxys, Tabaniden und Culex sp. Alle kranken und drei normale Pferde reagierten stark auf Culicoidesextrakt. Die Hautreaktionen der erkrankten Tiere erreichten ihr Maximum innert vier Stunden bei der Mehrheit der Pferde. Die Hautreaktivitat gegen Culicoides konnte mit Serum kranker Pferde auf normale ubertragen werden, ein Beweis, dass es sich um eine Sofortreaktion handelt. Drei der sieben erkrankten Pferde wiesen sowohl Sofortreaktionen wie auch verzogerte Reaktionen gegen Culicoidesextrakt auf. Die Hautreaktionen von 12 klinisch gesunden und 10 erkrankten Pferde wurden 20 Minuten und 1 Stunde nach der Exposition verglichen; die Reaktionen gegen Culicoidesextrakt erwiesen sich bei affizierten Tieren als signifikant starker (p<0.025) als bei normalen Pferden. Einzeltiere reagierten heftig gegen Stomoxys-, Culex- und Tabanidenextrakte, aber es liess sich keine konsistente Antwort herauslesen. Serum von Pferden mit Sommerekzem vermochte die Haut normaler Pferde gegen Extrakte von Stechfliegen zu sensibilisieren und die ubertragenen Antikorper blieben wahrend 72 Stunden oder langer in der Haut nachweisbar. Obgleich eine gewisse Variation unter den erkrankten Pferden in diesen passiven Uebertragungsversuchen festzustellen war, ubertraf die Reaktion gegen Culicoidesextrakt immer diejenige gegen andere Insektenextrakte.

Ecology of nematophagous fungi: distribution and habitat

Abstract: SUMMARY A survey of 161 samples of soil and plant material collected from sites throughout Ireland has shown that nematophagous fungi exist in a wide range of habitats. 205 isolations were made consisting of 11 endoparasitic and 20 predatory species. The commonest endoparasites and their frequency of occurrence were Myzocytium spp. (9·3%), Acrostalagmus obovatus (6·8%) and Harposporium anguillulae (6·2%). Predators were equally abundant, the commonest being Dactylella bembicodes (8·7%), D. mammillata (6·8%) and D. ellipsospora (6·2%). Arthrobotrys oligospora and A. musiformis both had a highly restricted distribution. Adhesive knobs and constricting rings were significantly more abundant than the other trapping mechanisms. All the samples were classified into one of 10 broad habitat types. Of these temporary agricultural pasture, coastal vegetation and coniferous leaf litter had the greatest percentage of sites from which nematophagous fungi were isolated. A number of species showed distinct habitat associations, in particular Arthrobotrys robusta, A. musiformis and Dactylella cionopaga.

Spectra of Xe vii, viii, and ix in the extreme ultraviolet: 4d–mp, nf transitions

Abstract: The spectrum of a laser-produced plasma of Xe has been photographed in the 40–220-A region. Many lines arising from the transitions 4d105s2–4d95s2mp, 5f, 4d105s–4d95s mp, 5f, and 4d10–4d9mp, 5f (m = 5, 6) in Xe vii, viii, and ix have been identified with the aid of Hartree–Fock calculations.

The catholic parish, the catholic chapel and village development in ireland

Abstract: The Catholic Church in Ireland underwent profound transformations in the early modern period. Among the most significant of these was the need to reconstruct its parish network and to provide places of worship for its adherents. This reconstruction and rebuilding phase was largely compressed into the 1780–1860 period and gave rise to a radically new parish framework which was adapted to the demographic, social and economic conditions of that time. Chapels were also constructed in large numbers and their sites were determined by the attitudes of landlords, the wealth of the local Catholic community and the sponsorship of prominent Catholic families. The diffusion of chapel building shows pronounced regional biases. Associated with this reinvigorated parish and chapel network was the development of new villages, for which the chapel acted as a nucleus and focus. The term chapel-village is used to describe them and their economic, social and morphological characteristics are examined. Their distribution reve...

Purification and properties of a thermophilic amyloglucosidase from Aspergillus niger

Abstract: A thermophilic amyloglucosidase (EC 3.2.1.3) from a strain of Aspergillus niger was purified and separated from contaminating α-amylase (EC 3.2.1.1) and transglucosidase (EC 2.4.1.24) by ammonium sulphate fractionation, acetone precipitation and CM-BIO-GEL A chromatography. A 61-fold purification was achieved. The enzyme had highest affinity for starch (100), maltotriose (68) and maltose (31) and Km values of 0.025% and 1.42 mM with starch and maltose, respectively. It had a molecular weight of 63,000. The enzyme operated most efficiently on starch and maltose at pH 4.5 and surprisingly at the high temperature of 70°C. It possessed considerable pH stability, with 79% and 50% activity retained at pH 2.0 and pH 11.0, respectively, after 30 min at 40°C. The enzyme was 100% stable up to 50°C and 90% stable at 60°C for 30 min; above this latter temperature activity was rapidly destroyed. The presence of starch or glycerol improved the thermal stability of the enzyme. Polyvalent anions stimulated activity while the cations Cu2+ and Ag+ and to a lesser extent Ni2+ and Co2+ caused notable inhibitory effects. When incubated with high concentrations of glucose the enzyme formed small amounts of isomaltose as a reversion product.

Ontogeny of the photoreceptors in the embryonic retina of the viviparous guppy, Poecilia reticulata P. (Teleostei). An electron-microscopical study.

Abstract: Ultrastructural analyses of retinal development in the guppy embryo show that at midgestation all types of photoreceptors are differntiated in the fundus, and at birth differentiation extends over the whole retina. Formation of discs of outer segments is more rapid in rods than in cones. Double cones differentiate simultaneously with long single cones and are formed by the adhesion of two primordial inner segments; short single cones develop last. Wherever cones are differentiated, they are arranged in an adult-type square mosaic. The rods in the embryo, as opposed to the adult, are likewise regularly arranged within the mosaic unit. These results are at variance with the generally held opinion that adult teleosts which possess duplex retinae have larvae with pure cone retinae, and that rods, double cones and mosaics appear in late larval life or only at metamorphosis. In the double cones of the guppy embryo subsurface cisternae develop along the adjoining primordial inner segments. Additionally, regularly distributed subsurface cisternae are formed in the regions of intimate contact of long single cones with double cones and rods. We suggest that the early development of rods and double cones, and a square-mosaic with regular distribution of rods and subsurface cisternae, provide the newly born with a fully functional optical apparatus, especially suited to perception of movements. This is necessary for its survival against predatory, especially maternal, attacks.

The Σ- concept

Abstract: The "User's Conceptual Model" (UCM) plays an important role in determining the behaviour of a user at the user-computer interface. In this paper I consider a small well-defined group of users of computer systems - those who know some general-purpose programming language. Such users have a conceptual model of their own (favourite) "programming language as a problem-solving tool". Using the problem to compute the inner product of two vectors in En as a starting point, I develop that which I have called the Σ- concept and show how it fits into a formal model of the UCM of the "programming language as a problem-solving tool".

Fomannoxin, a phytotoxic metabolite of Fomes annosus: in vitro production, host toxicity and isolation from naturally infected Sitka spruce heartwood

Abstract: The effect of different culture conditions on growth and production of fomannoxin and the sesquiterpene phytotoxin fomannosin by a single isolate of Fomes annosus was studied. Whereas fomannoxin was produced by actively growing hyphae, fomannosin production was associated with the declinning growth phase of the fungus. The presence of fomannoxin in chloroform extracts from the stained stein heartwood zone of Fomes annosus diseased Sitka spruce trees was established. Fomannosin however was not detected. Toxicity of fomannoxin to germinating seeds and young seedlings of Sitka spruce was demonstrated.

The evolution of the structure of a two-dimensional soap froth

Abstract: We draw attention to the fact that the conclusions of Smith and others concerning the evolution of two-dimensional (2-D) soap froths, which were based on early experimental data, do not appear consistent with later data analysed by Aboav. This shows no stable limiting distribution of cell shapes within the range of the experimental samples. If this is accepted, the asymptotic evolution of the 2-D soap froth system (and any other physical system governed by analogous principles) must be radically different from what it is generally assumed to be.

Rotational Analysis of the 9877 and 8960 Å Bands of FeD

Abstract: The many-line infrared system of iron deuteride has been studied in absorption and thermal emission. Approximately 1000 lines in the (1, 0) and (0, 0) bands of a 4Δ - 4Δ transition have been assigned. All four subbands show Λ-doubling. The larger Λ-splitting occurs in the lower electronic state. Rotational analyses have been performed yielding the following rotational constants (in cm-1): for the lower 4Δ state: B''0 = 3.4357, D''0 = 8.49 × 10-5 for the upper 4Δ state: B'0 = 2.9846, D'0 = 9.20 × 10-5 B'1 = 2.9076, D'1 = 9.31 × 10-5 Both 4Δ states are inverted. Values of ω'e ≈ 1070 cm-1 and ω'ex'e ≈ 19 cm-1 are suggested for the Ω = 7/2 component of the upper state and similar values are anticipated in the other three spin components. Although the system appears in absorption at high temperatures, the lower 4Δ state does not seem to be the ground state.

Aetiology of chronic constrictive pericarditis.

Abstract: In a consecutive series of 32 cases of chronic constrictive pericarditis treated by pericardiectomy during the past 25 years, four were attributable to rheumatoid disease, two to trauma, one to sarcoidosis, and four, at a maximum, to tuberculosis. In the remaining 21 cases of undetermined aetiology there was no evidence of tuberculosis. It appears, therefore, that tuberculosis was not a common cause of chronic constrictive pericarditis during the period under review, which included the 1950s and early 1960s when tuberculosis was widespread.

Synergistic inhibition of [3H]muscimol binding to calf‐brain synaptic membranes in the presence of l‐homocysteine and pyridoxal 5′‐phosphate

Abstract: L-Homocysteine and pyridoxal 5'-phosphate (PxyP) inhibited [3H]muscimol binding to freeze-thawed, Triton-treated calf brain membranes (containing high-affinity muscimol-binding sites: Kd 9.5 +/- 0.6 nM, Bmax 5.2 +/- 0.2 pmol/mg protein). The homocysteine--pyridoxal-5'-phosphate (Hcy-PxyP) thiazine complex had no effect. L-Homocysteine was found to be a partially competitive inhibitor, thus demonstrating an allosteric inhibition with Ki value of 1.96 mM for free receptor and Ki of 13 mM for receptor-muscimol complex. PxyP was shown to be a two-site pure competitive inhibitor of [3H]muscimol binding with cooperativity of PxyP binding such that Ki values for PxyP of 20 mM and 2.1 mM were found. L-Homocysteine and PxyP when added simultaneously to binding assays, caused a greater degree of inhibition than that observed at the same total specific concentration of either inhibitor alone. This synergistic inhibitory effect was shown to be due to a homocysteine-induced increase in the affinity of PxyP-binding sites. Three alternative models are suggested to explain the observed synergistic effects whereby it is proposed that PxyP and [3H]muscimol binding is mutually exclusive, while L-homocysteine with PxyP and L-homocysteine with muscimol, exhibit non-exclusivity. Non-linear regression analysis of binding data was undertaken in order to substantiate conclusions drawn from graphical procedures and in an attempt to ascertain which mathematical model best fitted the experimental data describing the synergistic inhibitory effects of L-homocysteine and PxyP. This synergistic inhibitory effect of PxyP and L-homocysteine on the post-synaptic gamma-aminobutyric acid receptor may provide a basis for explanation of the mechanism of homocysteine-induced seizures.

Role of reflex responses of knee musculature during the swing phase of walking in man

Abstract: Muscle activation patterns of the quadriceps and hamstrings were studied in normal human subjects walking at comfortable speed on a treadmill. In addition knee angular velocity patterns and swing and stance phases of the step cycle were recorded. Data were collected from normal paces and from paces in which a momentary unexpected resistance was applied to the leg during swing. The application of the resistance caused an advance in the onset of both quadriceps and hamstrings activity. The latency of the onset of activity following the resistance in the quadriceps was 78.2±26.4 ms and this was considered to indicate a long latency stretch reflex. There was a close association between the onset of quadriceps and hamstrings activity both in the normal and resistance paces. The changes observed in knee angular velocity upon application of the resistance indicate tight control of angular velocity patterns. The results have important implications regarding neural control of muscle during purposive movement and the regulation of sensitivity of muscle receptors during such movements, especially during the periods when the muscle is normally inactive.

Polyvinylpyridine complexes of ruthenium(III) chloride

Abstract: SUMMARY: A series of polymeric materials were prepared by reacting poly(2-vinylpyridine) or poly(Cvinylpyridine) with ruthenium(II1) chloride in refluxing methanol. Mole ratio of RuCl, to vinylpyridine (Ru: PVP ratio) was varied from 2: 1 to 1 :20. From IR and UV/VIS spectroscopic data it is shown that several kinds of ruthenium-PVP complexes are present, their relative proportions depending on the Ru : PVP ratio of the original reaction mixture and on the reaction time. The spectroscopic properties of the polymer complexes are compared to those of methylpyridine complexes of ruthenium(II1) chloride.