Showing papers by "City University London published in 1978"

The fine structure of innervated myotendinous cylinders in extraocular muscles of rhesus monkeys.

Abstract: Many of the myelinated nerve fibres of the distal myotendinous region of rectus muscles terminate on muscle fibre tips The terminal expansions contain aggregated, small clear vesicles and mitochondria Neuromuscular clefts at the contacts measure 20–40 nm and are uninterrupted by a basal lamina; the sarcoplasm opposite the contacts is unmodified Some terminals invaginate the muscle fibre tips and others contact the sides of processes formed by splitting of the tips The muscle fibre termination, its tendon and the nerve fibre branches are encapsulated to form an end-organ averaging 125 μm in length and described as a myotendinous cylinder Approximately 350 innervated myotendinous cylinders were estimated to be present in the horizontal recti with rather fewer in the vertical rectus muscles Many of them occur shortly before the main myotendinous junction All muscle fibres contributing to myotendinous cylinders were identified as the compact, felderstruktur, multi-innervated variety with directly apposed myofibrils that are known to be non-twitch fibres All felderstruktur fibre terminations examined were encapsulated but 19% of them were not innervated The nerve terminals of myotendinous cylinders are similar to those described by Dogiel (1906) as palisade endings and it is argued that they meet the morphological criteria of sensory neuromuscular endings Their disposition suggests a capacity to monitor felderstruktur muscle fibre contraction

Ranking in principle

Abstract: It is often suggested that information retrieval systems should rank documents rather than simply retrieving a set. Two separate reasons are adduced for this: that relevance itself is a multi‐valued or continuous variable; and that retrieval is an essentially approximate process. These two reasons lead to different ranking principles, one according to degree of relevance, the other according to probability of relevance. This paper explores the possibility of combining the two principles, but concludes that while neither is adequate alone, nor can any single all‐embracing ranking principle be constructed to replace the two. The only general solution to the problem would be to find an optimal ranking by exploring the effect on the user of every possible ranking. However, some more practical approximate solutions appear possible.

The Reduction of Oxygen on Teflon‐Bonded Perovskite Oxide Electrodes

Abstract: The electrochemical reduction of oxygen on Teflon‐bonded electrodes in 45% was studied as a function of temperature and oxygen partial pressure. The activation energy was 10.75 kcal/mole and the relationship between and obeys the relationship , suggesting that the rate of oxygen chemisorption is the rate‐controlling step, Galvanostatic oxygen stripping showed that the surface coverage of oxygen was only 1% for both Sr‐doped and , and that the coverage was independent of temperature in the range 25°–80°C.

The effects of eccentricity on torque and load in Taylor-vortex flow

Abstract: This paper extends two earlier papers in which DiPrima & Stuart calculated first (1972b) the critical Taylor number to order e2, where the eccentricity e is proportional to the displacement of the axes of the circular cylinders, and second (1975) the torque and load to order e associated with nonlinear effects of Taylor vortices. In the latter paper, it was shown that to order e the torque arising from the Taylor vortices is identical with that for the concentric problem, which was first calculated, by a perturbation method, by Davey (1962). This deficiency is remedied in the present paper, where the calculation is taken to order e2. It is found that, as e rises, the torque associated with the Taylor vortices falls slightly when we keep constant the percentage elevation of the Taylor number above the e-dependent critical value. This result is in accordance with experimental observations by Vohr (1967, 1968). In addition, results of calculations of the pressure field developed by the Taylor-vortex flow in association with the eccentric geometry are presented; this is larger than in the concentric case owing to a Reynolds lubrication effect. Also given are the associated components of the load on the inner cylinder, but only for Taylor numbers close to the critical value.One additional observation by Vohr, for cylinders with a mean ratio of the gap to the inner radius of 0·099, was that the maximum Taylor-vortex strength with e = 0·475 occurred some 50° downstream of the maximum gap for a 20% elevation of the Taylor number above the critical value. Calculations in the two earlier papers (1972b, 1975) gave 90 and 76°, respectively, for that angle. Note that in the 1975 paper a geometrical correction of order e was included. Here, with an additional modification of order e due to the flow, this result is improved to 49° by the extended analysis presented, although the ‘small’ parameters are somewhat outside the range for which perturbation theory is expected to be valid.

Corneal nerve access in monkeys.

Abstract: Electron microscopical examination of corneal nerves in rhesus and cynomolgous monkeys revealed that limbal, subepithelial nerves gained direct access to the corneal epithelium. Epithelial axons occurred singly and infrequently and they were confined to the basal layer of cells.

The stopping power of water, water vapour and aqueous tissue equivalent solution for alpha particles over the energy range 0.5-8 MeV

Abstract: Experimental stopping power values are presented. The molecular stopping power of water is found to be significantly lower than that of water vapour at energies below 1.5 MeV and above 2.5 MeV. These results are compared with calculated stopping power values and discussed particularly with reference to the charge state of the alpha particle at various energies. The stopping power values for tissue equivalent liquid are found to be lower in general than calculated values or values obtained from tissue equivalent gases or solids except in the 2.5-3.25 MeV energy region.

Internally charged palladium hydride reference electrode--Part 1: The effect of charging current density on long-term stability.

Abstract: The diffusion of H2 in the α-and β-phase of palladium hydride was measured electrochemically and found to agree very well with results reported in the literature. The α-β phase transition on continuous electrolysis of Pd wire and Pd foil electrodes was found to be strongly dependent on both charging current and charging time. An internally-charged Pd wire electrode on continuous charging gave a stable open circuit voltage of+53·5±4 mV against r.h.e. over a test period of 330 h in N2 saturated 0·5M H2SO4 solution. The pH response and reproducibility of such an electrode was superior to conventional palladium hydride electrodes. The potential of this electrode can still be maintained in air saturated solutions, provided higher charging currents are used. It was also shown that β-phase palladium hybride gave an irreproducible pH response.

Aspects of nickel-cadmium cells in single cycle applications. I. The effects of long term storage

Abstract: The use of sealed nickel-cadmium cells for single duty cycle applications involves certain novel features for which little or no quantitative knowledge exists. The investigations presented in this series of papers have sought answers to the questions raised in broad terms. This first paper considers the effects of long term storage (up to 10 years), in the short-circuited condition, at temperatures ranging between −40–+70° C. An accelerated test procedure was formulated to determine charge acceptance degradation of cells after storage for any given period and temperature. The results indicate that storage effects will constitute a major problem area for nickel-cadmium cells in these applications.

The Formation and Destruction of Pentenes During the Combustion of Pentane

Abstract: Studies have been made of the quantitative role of pent-1-ene and pent-2-ene in the combustion of pentane at temperatures below 400 degrees C. The present results show that, under these conditions, pentenes are initial and direct products of pentane combustion and pent-2-ene is the principal conjugate alkene formed. $[1-^{14}$C$]$ Pent-1-ene and $[2-^{14}$C$]$ pent-2-ene have been synthesized and the combustion of pentane has also been investigated in the presence of small concentrations of these specifically labelled compounds; control experiments have shown that the pentenes, in the amounts added, do not interfere appreciably with the kinetics of pentane combustion. Measurements of the variation with time of the specific activities and concentrations of the pentenes enable the separate rates of formation and destruction of the conjugate alkenes to be determined. Hence it is possible to calculate the total quantities of these compounds formed at different stages of reaction and to show to what extent these are greater than the net amounts revealed by conventional analytical measurements; the differences are found to be most marked at small conversions. The reactivity ratios of pentane and the pentenes have also been determined. The rates of destruction of both pentenes are much greater than that of pentane; pent-2-ene is removed from the system roughly twice as fast as pent-1-ene. An important contrast between the behaviour of pentane and butane is that, between 300 and 400 degrees C, but-1-ene is a much more abundant product than but-2-ene. However, with both alkanes, the relative amounts of the alk-1-enes formed become greater as the temperature is increased; indeed, the rate of formation of pent-1-ene considerably exceeds that of pent-2-ene at the instant of the passage of a strong cool flame. Comparison of the total amounts of conjugate alkenes formed from the two alkanes at 315 degrees C shows that only ca. 30% of the pentane consumed is converted to pentenes, whereas nearly 75% of the butane which has reacted is converted to butenes. Thus there is clearly a sharp decrease in the quantitative importance of conjugate alkenes as the carbon chain length is increased from C$\_{4}$ to C$\_{5}$. This suggests that the predominant reaction of pentyl radicals, under the conditions used, is to add on oxygen to form pentylperoxy radicals.

Isotopic Tracer Studies of the Further Reactions of Pentenes in the Combustion of Pentane

Abstract: Detailed studies have been made of the mechanisms by which products other than the conjugate alkenes are formed when pentane undergoes combustion in the presence of small quantities of isotopically labelled pent-1-ene and pent-2-ene. Seven pentenes, specifically labelled with 14 C in different skeletal positions, have been synthesized and the fate of the labelled carbon atoms during combustion has been determined. Special attention has been paid to the formation and destruction of the pentadienes, acrolein and ethylene, as products derived from pent-1-ene. In particular, measurements have been made of the instantaneous fraction of the original pentene converted into each of these compounds and of the percentages have been shown to be derived exclusively from the pentenes, whilst acrolein and ethylene, which are complementary products resulting simultaneously from the same pentene molecule, are formed principally from the alkenes. It has also been possible to determine the distribution of the points of abstractive attack in the pentenes and the reactivity rations of pent-1-ene to secondary products. There are sharply defined changes in the relative rates for the pentadienes and pent-1-ene before and after the passage of cool flames; the results suggest that penta-1, 2-diene is oxidized to acrolein and ethylene. A significant amount of 2, 4-dimethyloxetan is formed from both pent-1-ene and pent-2-ene; this compound appears to be produced by a somewhat unusual route, involving the isomerization of one hydroperoxy radical to another through a peroxy radical. The majority of these compounds result from reactions involving free radial addition to the alkene molecule. However, abstractive modes of attack, although leading almost exclusively to the pentadienes, acrolein and ethylene, are quantitatively very important in terms of the total amount of attack on the pentenes. The principal products formed from the pentenes are only minor constituents of the combustion products of pentane. This shows that the coujugate alkenes do not play nearly as important a part in the combustion of pentane as they do in the case of alkanes of lower molecular mass.

Complex solitons and poles of the sine-Gordon equation

Abstract: We discuss the implications of a recently established equivalence between the lynamics of interacting sine-Gordon solitons and the motions of poles of the corresponding Hamiltonian density. The connection is traced to the existence of a ‘complex soliton’ whose limiting forms are the real soliton and a singular form.

N.M.R. Spectral Studies of Some Quinolone Derivatives. Part VII.1 Carbon-13 Magnetic Resonance Spectral Studies of N-Methyl-2-Quinolone Derivatives and an Examination of peri Substituent Effects

Abstract: The 13C n.m.r. spectra of a series of 1-methyl-2-quinolone derivatives are presented. The N-CH3 and 8-CH3 carbons each exhibit a characteristic peri deshielding effect. The substituent effects caused by a peri-methyl group have been discussed and compared with effects previously observed in the naphthalene series.

In vivo reference electrodes

Abstract: The electrochemical principles governing the application ofin vivo reference electrodes are discussed. It is shown that the currently usedin vivo reference electrodes are not very satisfactory and that the use of an internally charged palladium hydride electrode may provide a far more stable reference electrode which has a lower impedance and is less susceptible to poisoning by protein adsorption and metal/tissue reaction

Thermal studies of the reactions of vanadium(V) oxide with other transition metal oxides

Abstract: Studies of the thermal behaviour of binary oxide mixtures containing vanadium(V) oxide (V2O5-TiO2, V2,O5- MoO3, V2,O5-ZrO2 and V2O5-ZnO) have shown that the evolution of gaseous oxygen at fairly low temperatures is characteristic of those systems which are eflective catalysts for the oxidation of hydrocarbons No weight changes were observed with V2, O5-ZnO mixtures under these conditions and, in accordance with this, zinc(II) oxide does not enhance the catalytic activity of vanadium(V) oxide In V2O5-containing systems, evolution of oxygen occurs during the reduction of V2O5 to V2O4 This process is accelerated in the presence of certain metal oxides and such acceleration may be caused by structural interactions at the interface of the oxides Among the systems studied, the formation of compounds such as Mo6V9O40 is thought to be of little significance from the catalytic point of view

N.M.R. Spectral Studies of Some Quinolone Derivatives. Part VI.1 N-Methyl-2-Quinolone Derivatives

Abstract: The chemical shifts of the N-CH3 protons for a series of 1-methyl-2-quinolone derivatives has been studied. Compounds with an 8-methyl substituent exhibit a slight downfield shift.

Image Enhancement And Pre-Processing

Abstract: An outline of the principles of digital image processing is presented The considerations necessary in on-line, real time processing of images for industrial applications are then examined Image restoration, characterisation, the solution and efficient encoding of image features, and the effects of processing on a grid of cells are discussed