Showing papers by "Trinity College, Dublin published in 1982"

A bifunctional gene product involved in two phases of the yeast cell cycle

Abstract: The cell cycle in Saccharomyces cerevisiae is divided into two distinct phases. Unbudded, mononucleate cells in the G1 phase can react to relevant environmental changes by mating1, sporulating2, or by entering stationary phase3. DNA synthesis and bud initiation occur almost simultaneously and mark ‘commitment’ to the completion of mitosis. Temperature-sensitive mutations at the cdc28 locus are known to cause arrest in the G1 phase of the cell cycle at the restrictive temperature4,5. Here we show that the cdc28 gene product is also active in post-G1 cell cycle functions, and that a different property of the gene product may be required for each phase of the cycle in which it acts.

Deamination of 5-hydroxytryptamine by both forms of monoamine oxidase in the rat brain.

Abstract: Km and Vmax values of monoamine oxidase (MAO) A and B towards 5-hydroxytryptamine were determined for rat brain homogenates after the in vitro inhibition of one of the two forms by the selective inhibitors clorgyline and l-deprenyl. Km values of 178 and 1170 microM, and Vmax values of 0.73 and 0.09 nmol . mg protein-1 . min-1 towards 5-hydroxytryptamine were found for MAO-A and -B, respectively. The Ki for 5-hydroxytryptamine as a competitive inhibitor of beta-phenethylamine oxidation by MAO-B was found to be 1400 microM. The significance of these findings is discussed.

The ultrastructure of cat fusimotor endings and their relationship to foci of sarcomere convergence in intrafusal fibres

Abstract: 1. Six muscle spindle poles, five from experiments in which foci of sarcomere convergence had been observed during stimulation of fusimotor axons, were serially sectioned for light and electron microscopy. Every somatic motor terminal was studied in ultrathin sections at several levels.2. In all six poles static gamma axons, or presumed static gamma axons, supplying the static bag(2) fibre and/or chain fibres had no terminations on the dynamic bag(1) fibre. In five poles, the dynamic bag(1) fibre was selectively innervated by dynamic gamma or beta axons save in one case where a dynamic gamma axon also innervated one chain fibre.3. Seventy-seven motor endings were of four distinct ultrastructural types: ;m(a) plates' lay superficially on the surface of static bag(2) or chain fibres; ;m(b) plates' were deeply indented into dynamic bag(1) fibres; in ;m(c) plates', found on chain fibres only, the muscle surface was thrown into projecting fingers between which the axon terminals were embedded; one type ;m(d) plate' was found, fully indented into a long chain fibre. A few plates of intermediate form (m(ab)) were variants of m(a) and m(b) plates.4. The muscle membrane beneath both m(a) and m(b) plates was smooth, or had a few wide, shallow folds; m(c) plates usually had wide, shallow subjunctional folds; numerous deep, narrow folds were characteristic of the m(d) plate. The length of unmyelinated pre-terminal axon or the number of sole plate nuclei were not useful diagnostic features.5. Obvious foci of sarcomere convergence in the capsular sleeve region of dynamic bag(1) and static bag(2) fibres coincided with the location of motor plates. Additional contraction foci were observed in the extracapsular region of dynamic bag(1) fibres where there was no motor innervation; contraction occurs principally in the outer half of these fibres. No foci of contraction or motor plates were observed in the extracapsular region of static bag(2) fibres; contraction in these fibres is typically mid-polar.6. In some poles local contraction of chain fibres centred on the location of m(c) plates. In others, very localized contraction occurred distal to the sites of m(a) plates. Both m(a) and m(c) plates were never found on the same pole of a chain fibre.7. Dynamic gamma or beta axons end in m(b) plates, probably equivalent to p(2) plates. The concept of distinctly different p(1) and p(2) plates on dynamic bag(1) fibres, supplied by dynamic beta and gamma axons, respectively, is not supported by ultrastructural evidence.8. Some static gamma axons end in multiple m(a) plates which correspond with ;trail endings', or in single large m(a) plates, on static bag(2) or chain fibres. The m(c) plates are the terminations of other static gamma, or occasionally dynamic gamma, axons on chain fibres. Static beta axons probably end in m(d) plates on long chain fibres which may correspond with p(1) plates.9. It is proposed that there are two types of static gamma motoneurone, one terminating in m(a) plates and the other in m(c) plates, possibly directed preferentially towards static bag(2) fibres and chain fibres, respectively.

House Members' Communication Styles: Newsletters and Press Releases

Abstract: The literature on Congress offers no systematic analysis of representatives' communications with their constituents This paper argues that such communications constitute an important linkage between representative and represented and, as such, are indicators of House members' interelection reelection strategies Mayhew's categories of member activities were used for classifying communication styles in House members' newsletters and press releases; however, in order to delineate styles which discriminate among members in different electoral circumstances, it proved necessary to modify those categories to include consideration of geographic focus The distinction between nationally oriented and locally oriented position taking was found to be particularly important Thus, communication style was found to be a function of district and member characteristics; more ideologically extreme members from affluent suburban districts emphasize position taking on national issues; while relatively senior members from

A General Axiom of Assignment

Abstract: The axiomatic method of Floyd [1] and Hoare [2] has become the most popular formal method for reasoning about programs. Axiomatic semantics, more or less complete, exist for various programming languages [3, 4] and the method is widely used in deriving and verifying programs. Some areas of programming, however, have thus far defied a general axiomatic treatment. One such area is that of pointers and linked data structures, which will be the subject of this and the following two papers. The goal is to make manageable the formal verification of list-processing programs, using axiomatic semantics. The present work does not claim to be complete, but is more systematic than previous treatments [5, 6, 7, 8], and is more general. These advantages accrue from the use of Dijkstra’s “weakest preconditions” [9] rather than Hoare’s “sufficient preconditions”.

The Probability Distribution of Wind Power From a Dispersed Array of Wind Turbine Generators

Abstract: A method is presented for estimating the probability distribution of wind power from a dispersed array of wind turbine sites where the correlation between wind speeds at distinct sites is less than unity. The distribution is obtained from a model for the joint probability distribution of wind speeds. This is able to incorporate arbitrary inter-site correlations. It is shown that this joint distribution reduces in the single site case to a wind speed distribution closely approximating the widely used Weibull; the multiple site power distribution is also shown to fit adequately to data on wind speeds from four sites in Western Australia. Results presented in graphical and tabular form for a range of representative cases show that a significant reduction in the variability of total wind power output may result from dispersion of aerogenerator sites; a quantitative guide to the magnitude of these effects is also provided.

Waves on glaciers

Abstract: This paper is an attempt at a mathematical synopsis of the theory of wave motions on glaciers. These comprise surface waves (analogous to water waves) and seasonal waves (more like compression waves). Surface waves have been often treated and are well understood, but seasonal waves, while observed, do not seem to have attracted any theoretical explanation. Additionally, the spectacular phenomenon of glacier surges, while apparently a dynamic phenomenon, has not been satisfactorily explained. The present thesis is that the two wave motions (and probably also surging, though a discussion of this is not developed here) can both be derived from a rational theory based on conservation laws of mass and momentum, provided that the basal kinematic boundary condition involving boundary slip is taken to have a certain reasonable form. It is the opinion of this author that the form of this ‘sliding law’ is the crux of the difference between seasonal and surface waves, and that a further understanding of these motions must be based on a more satisfactory analysis of basal sliding. Since ice is here treated in the context of a slow, shallow, non-Newtonian fluid flow, the theory that emerges is that of non-Newtonian viscous shallow-water theory; rather than balance inertia terms with gravity in the momentum equation, we balance the shear-stress gradient. The resulting set of equationsis, in essence, a first-order nonlinear hyperbolic (kinematic) wave equation, and susceptible to various kinds of analysis. We show how both surface and seasonal waves are naturally described by such a model when the basal boundary condition is appropriately specified. Shocks can naturally occur, and we identify the (small) diffusive parameters that are present, and give the shock structure: in so doing, we gain a useful understanding of the effects of surface slope and longitudinal stress in these waves.

The Conduct of Integration

Abstract: A method is presented for integrating psychological and theological facts. Based on a definition of integration as a process of discovering, verifying, relating, and applying God's truths, the proc...

Semliki forest virus neurovirulence mutants have altered cytopathogenicity for central nervous system cells.

Abstract: We have analyzed the pathogenicity and host range properties of four neurovirulence mutants of Semliki Forest virus which, unlike the wild type (WT), allow the survival of weanling mice injected intraperitoneally with 102 PFU. The mutant M9 showed a sustained multiplication in the brains of infected mice. It produced paralysis in 35%, and 8% died. Demyelination occurred in 94% of the surviving mice and was associated with the destruction of oligodendrocytes. All of the mutants showed a restricted ability to multiply in BHK, C1300 (neuroblastoma), and G26-24 (oligodendroglioma) cells as compared with the WT, and this was not associated with differential interferon production or action. C1300 cells infected with the mutants survived, whereas WT-infected cells were killed. In G26-24 cells all of the mutants and the WT produced a rapid cytopathic effect which was inhibited by pretreatment with 10 U of mouse interferon. Extensive RNA synthesis was detected for all of the mutants and the WT in BHK and C1300 cells, but it was only detectable in G26-24 cells in small amounts early in the infection. The mutant M4 had a defect in the nucleocapsid assembly, whereas M9 had a defect in total RNA synthesis. M136 was defective in the synthesis of 26S RNA, and M103 showed defective synthesis of viral core protein in C1300 cells. It is concluded that C1300 cells can tolerate viral RNA synthesis by a defective virus without showing a cytopathic effect, but the fully virulent WT virus is cytopathic. G26-24 cells are sensitive to small amounts of viral RNA synthesis. These properties of the WT and mutant viruses correlate with changes produced in the neurons and oligodendrocytes of the central nervous system: the virulence of the WT is due to its ability to destroy both neurons and oligodendrocytes, whereas the demyelination produced by the mutants M9 and M136 is due to the destruction of oligodendrocytes alone.

A Proof of the Schorr-Waite Algorithm

Abstract: The preceding two papers laid a theoretical foundation for verifying list-processing programs. The present paper exercises the formalism in a verification of that most recalcitrant algorithm, the Schorr-Waite graph-marking algorithm.

Möussbauer spectroscopy of nafion polymer membranes exchanged with Fe2+, Fe3+, and Eu3+

Abstract: Mossbauer spectra of “Nafion” perfluoronated acid membranes exchanged with iron or europium have been studied as a function of ion concentration, water content, temperature, and applied magnetic field in order to characterize the ionic phase in these materials In every sample, the recoil-free fraction falls to zero at a temperature which decreases from 280 to 220 K with increasing water content The sudden fall in recoil-free fraction corresponds to a glass transition in the ionic phase rather than its melting point In Fe2+ Nafion, the spectrum is independent of water content above 6 wt%, and is typical of fully hydrated, isolated Fe2+(H2O)6 species The isomer shift, quadrupole splitting, and linewidth all change continuously below 6 wt % water, indicating a range of environments for the iron For Fe3+ Nafion, ions in several distinct environments can be identified on the basis of their magnetic properties Isolated Fe3+ species (Fe–Fe distances greater than 12 A) showing paramagnetic hyperfine structure in their 42-K spectra predominate in slightly neutralized samples, and in those with high water content The proportion of dimers, whose quadrupole splitting is about 17 mm/s, increases with increasing iron content or decreasing water content A third component of the spectra has a quadrupole splitting of 04 mm/s It is associated with paramagnetic iron having other iron ions in the neighborhood, and also with iron ions located in the interior of small groups or chains formed from dimers There is no iron belonging to magnetically ordered clusters involving hundreds of ferric ions of the type found in some other ionomers All the exchanged ions belong to the ionic phase, and none are associated with the polymer backbone

Yield functions that account for the effects of initial and subsequent plastic anisotropy

Abstract: A descriptive initial yield function is presented from an examination of experimentally determined yield loci, component plastic strain paths and Lode's parameters that indicate either a severe textural anisotropy in a material or a slight departure from the von Mises condition. The transition from the initial function to one that describes a subsequent yield surface which translates with the stress vector is developed and compared with experimental results. Observations on the Bauschinger, Swift and hardening effects in subsequent yield loci, defined at the limit of proportionality, are adequately represented through Ziegler's translation law when modified for non-linear work hardening. It is shown that the marked distortion, particularly apparent, in the presence of shear stress, may be represented by considering separately the translation for each quadrant of the initial yield locus.