Showing papers by "Newcastle University published in 1975"

System structure for software fault tolerance

Abstract: The paper presents, and discusses the rationale behind, a method for structuring complex computing systems by the use of what we term “recovery blocks”, “conversations” and “fault-tolerant interfaces”. The aim is to facilitate the provision of dependable error detection and recovery facilities which can cope with errors caused by residual design inadequacies, particularly in the system software, rather than merely the occasional malfunctioning of hardware components.

System structure for software fault tolerance

Abstract: The paper presents, and discusses the rationale behind, a method for structuring complex computing systems by the use of what we term “recovery blocks”, “conversations” and “fault-tolerant interfaces”. The aim is to facilitate the provision of dependable error detection and recovery facilities which can cope with errors caused by residual design inadequacies, particularly in the system software, rather than merely the occasional malfunctioning of hardware components.

The Influence of Age and Sex on Skin Thickness, Skin Collagen and Density

Abstract: Forearm skin collagen, dermal thickness and collagen density were measured in a large number of normal subjects as a standard reference for future studies. Skin collagen decreased with age and was less in the females at all ages. There is a direct relationship between skin collagen and dermal thickness but variations in collagen density in disease limit the use of dermal thickness as a guide to changes in its collagen content.

Reinforced and Prestressed Concrete

Abstract: This highly successful textbook has been comprehensively revised for two main reasons: to bring the book up-to-date and make it compatible with BS8110 1985; and to take into account the increasing use made of microcomputers in civil engineering. An important new chapter on microcomputer applications has been added.

A unified approach to mean field electrodynamics

Abstract: Mit Hilfe der Korrelationsapproximation zweiter Ordnung und einer neuen Technik (doppelte Fouriertransformation und -entwicklung) wird eine Reihe von neuen und alten Ergebnissen in der Theorie der Elektrodynamik gemittelter Felder und der Magnetohydrodynamik durch eine systematische und allgemeine Ableitung dargestellt. Sie werden in Formen gebracht, die die Rolle des Helicity-Spektrums in Induktionsprozessen in neuem Licht erscheinen lassen. Die Situationen, in denen die Ergebnisse exakt gultig sind, werden angegeben. Neue Ausdrucke fur die Bestimmung der mittleren elektromotorischen Kraft, die durch die Wirkung der LORENTZ-Krafte auf die Turbulenz hervorgerufen werden, werden mitgeteilt. Using the first order smoothing approximation and a novel technique (double Fourier transformation and expansion) a number of results, new and old, in the theory of mean field electrodynamics and magnetohydrodynamics are given a systematic and general derivation. They are cast into forms which bring into new prominence the role of the helicity spectrum in induction processes. The situations in which the results may be expected to be accurate are delineated. New expressions are given for the reduction in the mean electromotive force created by the LORENTZ forces acting on the microscale turbulence.

Experiments on turbulence in a rotating fluid

Abstract: Experiments have been carried out to investigate the effect of rotation of the whole system on decaying turbulence, generally similar to grid turbulence, generated in air in an annular container on a rotating table. Measurements to determine the structure of the turbulence were made during its decay, mean quantities being determined by a mixture of time and ensemble averaging. Quantities measured (as functions of time after the turbulence generation) were turbulence intensities perpendicular to and parallel to the rotation axis, spectra of these two components with respect to a wavenumber perpendicular to the rotation axis, and some correlation coefficients, selected to detect differences in length scales perpendicular and parallel to the rotation axis. The intensity measurements were made for a wide range of rotation rates; the other measurements were made at a single rotation rate (selected to give a Rossby number varying during the decay from about 1 to small values) and, for comparison, at zero rotation. Subsidiary experiments were carried out to measure the spin-up time of the system, and to determine whether the turbulence produced any mean flow relative to the container.A principal result is that increasing the rotation rate produces faster decay of the turbulence; the nature of the additional energy sink is an important part of the interpretation. Other features of the results are as follows: the measurements with-outrotation can be satisfactorily related to wind-tunnel measurements; even with rotation, the ratio of the intensities in the two directions remains substantially constant; the normalized spectra for the rotating and the non-rotating cases show surprising similarity but do contain slight systematic differences, consistent with the length scales indicated by the correlations; rotation produces a large increase in the length scale parallel to the rotation axis and a smaller increase in that perpendicular to it; the turbulence produces no measurable mean flow.A model for the interpretation of the results is developed in terms of the action of inertial waves in carrying energy to the boundaries of the enclosure, where it is dissipated in viscous boundary layers. The model provides satisfactory explanations of the overall decay of the turbulence and of the decay of individual spectral components. Transfer of energy between wavenumbers plays a much less significant role in the dynamics of decay than in a non-rotating fluid. The relationship of the model to the interpretation of the length-scale difference in terms of the Taylor-Proudman theorem is discussed.The model implies that the overall dimensions of the system enter in an important way into the dynamics. This imposes a serious limitation on the application of the results to the geophysical situations at which experiments of this type are aimed.The paper includes some discussion of the possibility of energy transfer from the turbulence to a mean motion (the ‘vorticity expulsion’ hypothesis). It is possible, on the basis of the observations, to exclude this process as the additional turbulence energy sink. But this does not provide any evidence either for or against the hypothesis in the conditions for which it has been postulated.

A three-dimensional kinematic dynamo

Abstract: A number of steady (marginal) solutions of the induction equation governing the magnetic field created by a particular class of threedimensional flows in a sphere of conducting fluid surrounded by an insulator are derived numerically. These motions possess a high degree of symmetry which can be varied to confirm numerically that the corresponding asymptotic limit of Braginsky is attained. The effect of altering the spatial scale of the motions without varying their vigour can also be examined, and it is found that dynamo action is at first eased by decreasing their characteristic size. There are, however, suggestions that the regenerative efficiency does not persistently increase to very small length scales, but ultimately decreases. It is further shown that time varying motions, in which the asymmetric components of flow travel as a wave round lines of latitude, can sustain fields having co-rotating asymmetric parts. It is demonstrated that, depending on their common angular velocity, these may exist at slightly smaller magnetic Reynolds numbers than the corresponding models having steady flows and fields. The possible bearing of the integrations on the production of the magnetic field of the Earth is considered, and the implied ohmic dissipation of heat in the core of the Earth is estimated for different values of the parameters defining the model.

Sediment Transport in Smooth Fixed Bed Channels

Abstract: Incipient motion of discrete particles resting on a fixed smooth channel bed is investigated in different conveyance shapes. The results are compared with incipient motion studies in conveyances with movable beds. Higher critical velocities and shear stresses are obtained for smooth rectangular channels than for circular ones, but a single equation for all tested conveyance shapes is derived. The experimental results suggest that for normal sand as well as gravel much lower values of critical velocites are needed to avoid deposition than ususally adopted in sewer design. An analysis of the sediment transport parameter phi and flow parameter psi results in a relationship enabling the computation of sediment concentration C sub v for any conveyance for sediment transport as bed load without tendency for deposition. The results are again compared with similar functions for conveyances with movable beds. /ASCE/

The pattern of development of Anabaena in the Azolla-Anabaena symbiosis

Abstract: The development of Anabaena in the leaf cavities of Azolla (probably A. filiculoides) was studied. After the alga is installed in the cavity, heterocyst frequency rises to a maximum (20–30%) about 12 leaves from the apex, then remains constant until the leaf senesces. The size of vegetative cells of the alga increases with cell width apparently increasing linearly with increasing leaf age.

The interaction of magnesium ions with teichoic acid.

Abstract: The binding of Mg2+ to the wall teichoic acid of Lactobacillus buchneri N.C.I.B. 8007 was measured by equilibrium dialysis at controlled ionic concentration and pH. In an aqueous solution containing 10mM-NaCl at pH 5.0 one Mg2+ ion was bound for every two phosphate groups of the teichoic acid, with an apparent association constant, Kassoc. = 2.7 x 10(3) M-1. On lowering the pH below the pKa of the phosphate groups the amount of bound Mg2+ decreased concomitantly with decreasing ionization of the phosphate groups. Both the amount of Mg2+ bound to the teichoic acid and the apparent association constants were similar in the presence of 10 mM concentrations of NaCl or KCl but decreased markedly in the presence of 10 mM-CaCl2 because of competition between Ca2+ and Mg2+ for the binding sites. A similar effect was found when the concentration of NaCl was increased from 0 to 50 mM. The results are discussed in relation to the function of teichoic acid in the walls of Gram-positive bacteria.

Microbial metabolism of the pyridine ring. Metabolic pathways of pyridine biodegradation by soil bacteria.

Abstract: 1. Two bacteria, a Bacillus sp. and a Nocardia sp. (strain Z1) were isolated from soil by enrichment with 0.1 percent (v/v) pyridine and grew rapidly on this compound as sole C, N and energy source. The monohydroxypyridines, tetrahydropyridine, piperidine and some other analogues were not utilized for growth or oxidized by washed suspensions of either bacterium. 2. Cell-free extracts were unable to metabolize pyridine even after supplementation with a variety of cofactors or protecting agents. Treatment of cells with toluene led to rapid loss of the ability to oxidize pyridine. 3. In the presence of 10mM-semicarbazide at pH 6.0, Nocardia Z1 accumulated a semialdehyde idenditied as its 2,4-dinitrophenylhydrazone by chromatography, mixed melting point, mass spectrometry and isotope trapping from [2,6(-14)C]pyridine as glutarate semialdehyde. 4. Extracts of this bacterium prepared from cells grown with pyridine or exposed to the gratuitous inducer 2-picoline, contained high activities of a specific glutarate semialdehyde dehydrogenase. 5. Cells grown with pyridine or glutarate also contained a glutaric dialdehyde dehydrogenase, an acyl-CoA synthetase and elevated amounts of isocitrate lyase but no glutaryl-CoA dehydrogenase. 6. Bacillus 4 accumulated in the presence of 10mM-semicarbazide several acidic carbonyl compounds from pyridine among which was succinate semialdehyde. Extracts of this bacillus after growth of the cells with pyridine contained an inducible succinate semialdehyde dehydrogenase in amounts at least 50-fold over those found in succinate-grown cells. 7. Two mutants of this bacillus, selected for their inability to grow on pyridine were deficient in succinate semialdehyde dehydrogenase. 8. In the presence of 0.2mM-KCN, washed suspensions of Bacillus 4 accumulated formate and possibly formamide from pyridine. The use of [14C]pyridine showed that formate was derived from C-2 of the pyridine ring. 9. The organism had a specific formamide amidohydrolase cleaving formamide quantitatively to formate and NH3. 10. Formate was further oxidized by the particle fraction. There was no soluble formate dehydrogenase in extracts.

A new method for the measurement of itch and the response to treatment.

Abstract: SUMMARY Two new methods are described for the quantitative measurement of itch: the principle is to measure scratch which is the major objective correlate of itch. The first method is to record whole body movement at night by a vibration transducer on a bed leg; this gives qualitative and quantitative information. The second method is to measure limb movement with movement -sensitive meters; this gives only quantitative data but is quicker and more easily carried out. The subjective sensation of itch was found to correlate well with nocturnal scratch, confirming the basic assumption of the method. Itching as measured by scratch occurs throughout the night and increased severity of itch is accompanied by an increase in the number of bouts of itch and not in their duration. Nocturnal restlessness is associated with an increase in leg movement and so can be dissociated from itch-provoked scratch, which is mostly done by the hands. The response of pruritus to treatment was demonstrated by both methods.

Robust density estimation using distance methods

Abstract: SUMMARY Distance estimators of density may exhibit serious bias unless the population under consideration forms a completely random spatial pattern, i.e. the estimators are not robust. In this paper some new estimators are proposed, and their robustness is assessed analytically against two stochastic models, which together embrace a continuous range of spatial pattern, from extreme regularity, through randomness, to extreme aggregation.

Girvanella and other algae as depth indicators

Abstract: Girvarzella is interpreted to be the calcified sheath of a variety of filamentous blue-green algae. At present there are no clear limits which can be set on its depth of occurrence. The usefulness of benthic calcareous algae as depth indicators in palaeoenvironmental studies is dependent upon the level of identification. At high taxonomic levels it is very limited. Algae are not restricted to the euphotic zone (ka. 150 m). Calcareous green algae are restricted to shallower water (0-ca. 100 m) than are calcareous red algae (0-ca. 400 m) but they are prone to fragmentation and subsequent transportation. Narrower depth limits for lower taxonomic levels have been demonstrated in Recent green and red algae, but have yet to be recognized in ancient environments. In the Palaeozoic, problems of correctly identifying calcareous algae further restrict their use as depth indicators.

Influence of alanyl ester residues on the binding of magnesium ions to teichoic acids.

Abstract: The binding of Mg2+ to the ribitol teichoic acid of Staphylococcus aureus H walls was examined by equilibrium dialysis in solution and in the intact wall; the influence of alanyl ester groups on binding was determined. In solution the ribitol polymer had a lower affinity than did a glycerol teichoic acid and bound Mg2+ in the ratio Mg2+/P of 1:1. The presence of alanyl ester residues caused a decrease in the amount of cations bound in stoicheiometric proportion to the ratio Ala/P, but the affinity constant was unaltered. It is concluded that in solution the ribitol teichoic acid binds Mg2+ univalently to phosphate groups and univalently to a counter-ion. In the intact wall the binding of Mg2+ was different. The affinity constant was higher and resembled that of a glycerol teichoic acid. It is concluded that Mg2+ forms bridges across phosphate groups in teichoic acid chains lying adjacent to each other in the wall. The effect of alanyl esters was similar to that in solution, but Scatchard plots were not linear at low concentrations of Mg2+ where it was shown that the difference in affinities between walls with and without alanyl ester residues was much greater than it was at higher concentrations of Mg2+. Thus at very low concentrations of Mg2+ effective binding to the wall is markedly improved by loss of alanyl ester residues.

A study of thyroid stimulating activity in human serum with the highly sensitive cytochemical bioassay1

Abstract: The cytochemical bioassay is able to detect minute amounts of thyrotropin and thyroid stimulating immunoglobulins. Estimations of serum TSH by the cytochemical bioassay are in good agreement with values obtained by radioimmunoassay. In untreated hyperthyroid patients with Graves' disease the TSH levels are significantly lower than in control subjects. Thyroid stimulating immunoglobulins showed a delayed time course of action in the bioassay and this provided a convenient method of distinguishing between the two thyroid stimulators.

System Structure for Software Fault Tolerance

Abstract: The paper presents, and discusses the rationale behind, a method for structuring complex computing systems by the use of what we term “recovery blocks”, “conversations” and “fault-tolerant interfaces”. The aim is to facilitate the provision of dependable error detection and recovery facilities which can cope with errors caused by residual design inadequacies, particularly in the system software, rather than merely the occasional malfunctioning of hardware components.

Avascular Necrosis of Bone Following Renal Transplantation

Abstract: Assessment of 78 successful renal transplants carried out in Newcastle upon Tyne between October 1967 and March 1973, revealed avascular necrosis of bone (A.N.) in 11 patients (14 percent). Pain and restriction of movement were the cardinal symptoms, while the onset was from five to 35 months after transplantation. In some patients one joint only was affected but in seven patients (64 per cent) A.N. developed in other joints too in an additive and progressive fashion. A time lag was usually noted between the onset of symptoms and radiological proof. These 11 patients with A.N. were compared with two control groups of unaffected renal transplant patients. Taking into account the patients' body weight, the cumulative dose of prednisone received by affected patients during the first three post-transplant months was found to be significantly higher than that for both control groups (P less than 0.05). Patients with A.N. were found to have had an unusually high incidence of early post-transplant surgical complications and the length of their initial stay in hospital was significantly prolonged (P less than 0.02) when compared to both control groups. It is possible that excessive corticosteroid therapy is more deleterious in transplant patients weakened by peri-renal haematomas, urinary extravasations and stormy prolonged post-operative periods. Having emphasized the detrimental effects of excessive anti-rejection corticosteroid therapy it must be mentioned that occasionally patients develop avascular necrosis even after low doses of steroid therapy, while others, receiving high doses of steroid therapy and undergoing a stormy post-operative course, do not develop this complaint. It is suggested that although excessive steroid therapy is positively harmful, avascular necrosis is not an invariable complication and that ofther factors including possibly a genetic predisposition operate to produce avascular necrosis of bone in renal transplant patients.

Bacterial Glycolipids and Glycophospholipids

Abstract: Publisher Summary The chapter attempts to assess the developments in the area of bacterial glycolipids and glycophospholipids— that is, those lipids that contain carbohydrate residues. Bacterial glycolipids have been divided into two categories— namely, (i) glycosyl diglycerides, and (ii) acylated sugar derivatives. The glycosyl diglycerides are analogous to the phosphoglycerides— that is, they are derivatives of 1, 2-diacyl-sn-glycerol with the carbohydrate residue glycosidically bound at the 3-position of glycerol. Acylated sugars do not contain glycerol, and have the acyl groups esterified directly to the carbohydrate residue. The chapter discusses glycophospholipids, such as (a) phosphatidylinositol mannosides, (b) phosphatidylglycerol glycosides, (c) phosphatidylglucose, and (d) phosphoglycolipids: glycerylphosphoryl and phosphatidylglycosyl diglycerides. The term “glycophospholipid” may be applied to any lipid containing carbohydrate and phosphate residues, the latter not necessarily implying the presence of a phosphatidyl group. The term “phosphoglycolipid” will only be used for those lipids that are derived from glycolipids by the addition of a phosphate-containing residue. The generic term “lipopolysaccharides” has been given to this class of polymers, whose chemical and immunological properties have been extensively investigated. More recently other lipid-polysaccharide complexes have been isolated to which the name “lipopolysaccharides” could have been applied, but as they show many structural differences from the endotoxins, it would be inappropriate to use this term that has now acquired a particular connotation.