Showing papers by "University of Warwick published in 1970"

The theory of induced voltage electromagnetic flowmeters

Abstract: The performance of an electromagnetic flowmeter head is assessed in terms of a weight vector W such that the output voltage ∝ ∫ v. Wdτ, where v is the velocity and τ the flowmeter volume. The condition curl W = 0 with W → 0 at ∞ is shown to be necessary and sufficient for the velocity to depend only on the flow rate and not on the flow pattern. A class of such ‘ideal’ meters is described. It is shown that meters with point electrodes can never be ideal but may, with considerable complication of the magnetic field, be made immune to asymmetric velocity-profile variations if the flow is rectilinear.

Effect of sulphate nutrition on flavour components of onion (Allium cepa)

Abstract: It is known that the volatile components of raw and cooked onions contain mono-, di- and tri-sulphides and other flavour-contributing sulphur compounds. The relationship between the sulphate nutrition of spring (salad) onion (Allium cepa) and its flavour strength determined by sensory, biochemical and chromatographic methods has been investigated. The plants were grown in sand culture in a glasshouse and the nutrient solutions contained five levels of sulphate from zero to an adequate amount. In their growth response, total sulphur content and visual symptoms, the plants showed characteristic essential nutrient deficiency. The sensory tests, and instrumental and biochemical assays showed that flavour strength increased approximately in proportion to sulphate concentration in the medium; lachrymatory potency also increased. There were significant coefficients of correlation between sulphate concentration of the nutrient medium and some aspects of flavour strength. The correlation coefficients between total sulphur content (% of the edible portion) and total peak area, n-propyl disulphide peak area and total pyruvate were also high. These observations suggest the possibility of control of onion flavour strength and lachrymatory potency, under field conditions, by control of sulphate nutrition. The question of loss of maximum potential onion flavour as a consequence of sulphur deficiency in soils is discussed. A headspace method for sampling onion flavour volatiles and for their introduction into gas chromatographs is described.

Weed plants as sources of cucumber mosaic virus.

Abstract: SUMMARY Severe yellowing and stunting was widespread in lettuce crops in Britain in 1968. Cucumber mosaic virus was consistently obtained from affected plants and from weeds which were prevalent in lettuce fields. Infection was most frequent in Stellaria media but also occurred, more or less commonly, in Senecio vulgaris, Urtica urens, Tripleurospermum maritimum ssp. inodorum, Capsella bursa-pastoris, Lamium purpureum and Sonchus oleraceus. Most infected weeds were symptomless. Infected weeds were still common in January-April 1969 and are considered to be a major overwintering source of the virus for aphid transmission to lettuce.

Studies on the seed transmission of cucumber mosaic virus in chickweed (Stellaria media) in relation to the ecology of the virus

Abstract: SUMMARY Cucumber mosaic virus (CMV) was transmitted in the seed of infected Stellaria media plants. The rate of seed transmission varied both in manually infected plants (3–21%) and in plants grown from infected seed (21–40%). In naturally infected plants the rates of transmission found were 4–29%. Seeds recovered from field soil carried 4–5% infection and in infected seed placed in the soil the virus persisted for at least 5 months. Seed transmission of CMV also occurred in infected Lamium purpureum (4%), Cerastium holosteoides (2%) and Spergula arvensis (2%) but it could not be demonstrated in six other more common weed species in five botanical families. Seed transmission in Stellaria media occurred with a British (W) and an American (Y) strain of CMV. The virus was shown to occur in S. media pollen. The importance of CMV-infected S. media seed in the soil in relation to the epidemiology of the virus is discussed.

Fluid motions due to an electric current source

Abstract: A concentrated electric current enters a region of fluid through an interface. It is shown that the magnetic field due to the current in general gives rise to rotational magnetic forces which must cause motions of the fluid. In particular the paper solves the axisymmetric non-linear problem in which a concentrated current enters a semi-infinite region of inviscid conducting fluid of constant density, inducing an inwards flow along the wall and a jet away from the wall opposite the current source. The case treated is the practically realistic one in which the effective magnetic Reynolds number is small and the current flows isotropically from the source. The first-order perturbation of this current distribution by electromagnetic induction is also calculated.An analytical solution is possible because the non-linear equation of motion happens to be a linear equation in the square of the Stokes stream function. The motion is analytically related to viscous jet flows discussed by Slezkin, Landau and Squire.

The quantitative estimation of the infection of bean seed with Pseudomonas phaseolicola (Burkh.) Dowson.

Abstract: SUMMARY A routine laboratory method for the detection of Pseudomonas phaseolicola in bean seed is described. The method will detect low levels of seed-borne infection and has been used in a statistical procedure (the most probable number method) to give an estimate of percentage infection. Infection in seeds harvested from heavily infected crops varied from 10 to 1%, compared with from 1% to less than 0.1% in commercial seed stocks. A high proportion of infected seeds failed to produce infected plants and this may account for the very low levels of primary infection reported in the field. Removal of seeds showing possible ‘symptoms’ of disease reduced, but did not eliminate, infection from seed stocks.

Bacteriophage and serological methods for the identification of Pseudomonas phaseolicola (Burkh.) Dowson

Abstract: SUMMARY Rapid phage and serological methods were compared with biochemical and bean-pod inoculation tests for the identification of Pseudomonas phaseolicola. Phages II P, 12 P and 48 P were highly specific and did not lyse any of forty-five other isolates from bean or the sixteen species of Pseudomonas tested. They were also, however, unable to lyse the rough colony forms of P. phaseolicola which were occasionally isolated. Phage 12 S lysed a wide range of Pseudomonas spp., including a proportion of P. phaseolicola isolates, the majority of which were race 2. Serological tests showed that the heat-labile antigen possessed by P. phaseolicola was common to twelve other species of plant pathogenic pseudomonads. The heat-stable antigen was more specific and was detected only in P. mors-prunorum and P. primulae, neither of which occurs on bean. The two races of P. phaseolicola were indistinguishable in serological tests. It was concluded that both phage and antiserum tests provide specific, rapid and easily applied methods for the routine identification of P. phaseolicola isolates from plant and seed material.

Rapid clonal multiplication of cauliflower by shake culture

Abstract: SummaryShake culture has been used to induce cauliflower curd to produce proliferating units from which large numbers of plants can be grown clonally.

Macrolide antibiotic studies. xv

Abstract: Macrolide antibiotics of the polyene antifimgal subgroup undergo aerial autoxidation in methanol solution by a radical addition process which can be inhibited by antioxidants. The related pentaenes of the filipin complex, which has the main component (I), and lagosin (II) yield as the major primary products the corresponding tetraene epoxides (III) and (IV), which are probably mixtures of diastereoisomers. The structures of the products were established by spectroscopy and chemical degradation. Extended autoxidation leads to higher oxidation products and ultimately to polymeric materials.

The development of serial completion strategies: an information processing analysis

Abstract: An information processing model of a complex task involving several important Piagetian concepts is introduced and then extended to a more difficult class of problems often used to test adult cognitive abilities In comparing this extended model both to human performance and to the process model by Simon & Kotovsky, the criterion of developmental tractability is introduced A detailed study of a child's performance during a crucial transition from one stage of problem complexity to another indicates that a mixture of both models seems to provide the best explanation of problem-solving behaviour

Schauder decompositions in locally convex spaces

Abstract: A decomposition of a topological vector space E is a sequence of non-trivial subspaces of E such that each x in E can be expressed uniquely in the form , where yi∈Ei for each i. It follows at once that a basis of E corresponds to the decomposition consisting of the one-dimensional subspaces En = lin{xn}; the theory of bases can therefore be regarded as a special case of the general theory of decompositions, and every property of a decomposition may be naturally denned for a basis.

Representable Functors and Operations on Rings

Abstract: Introduction The main aim of this article is to describe the mechanics of certain types of operations on rings (e.g. A-operations on special A-rings or differentiation operators on rings with derivation). En route we meet the very useful notion of a representable functor from rings to rings. If B, R are rings, then the set Hom^(J5,i2) of ring homomorphisms does not, in general, have a ring structure (unlike, for instance, the case where G, H are abelian groups, in which case Homg(G,H) is naturally an abelian group). However, we shall show in § 1 that, if B also has a 'co-ring' structure (in which case we call it a hiring) then this induces a natural ring structure on Homg?(J5,i2). In this case, the functor R \\-> Hom^jB, R) is said to be represented by the biring B. In §2, we demonstrate that this functor has a left adjoint, which we denote by R h-» B © R to bring out the analogy with the abelian group case (where H h» G® H is left adjoint to H h> Homg((r,fi)). When, in §4, we come to discuss natural operations on a certain class of rings, there are many constructions we may perform. Given a collection T of operations on a ring, we may give T a ring structure by addition and multiplication of the values of operations. We are also interested in the value of an operation on the sum and product of two elements in terms of its value on those elements. This may be given by imposing a co-ring structure on T in which, for example, the effect of an operation on the sum of two elements is determined by the co-sum' of that operation on the tensor product of the elements. Finally, given two operations on a ring, we may form the composite of one followed by the other. We insist that the identity operation is in T. All these requirements add up to the notion of a 'biring triple' in § 3. In § 4 we discuss the class of rings on which the operations in T act and in §§5, 6 we concentrate on the particular examples afforded by special A-rings and rings with derivation. There follow three appendices which contain material supplementary to that in the main text which would otherwise have interrupted the flow of the exposition.

The Effect of Age, Sex, Parity, Haemoglobin Level, and Oral Contraceptive Preparations on the Normal Leucocyte Count

Abstract: Leucocyte counts of 408 male and 789 female blood donors aged 18-65 were studied at the Birmingham Regional Blood Transfusion Service. 2 separate 2.5 ml samples were taken from each donor at the end of the blood donation either in the morning or early afternoon. On each slide 200 cells were counted. Total and differential counts in males were the same at different ages. In females neutrophil and lymphocyte counts decreased with age particularly after menopause (neutrophil p less than .001 and lymphocytes p less than .01). Use of oral contraceptives was associated with an increase in the neutrophil count. With increasing parity increases in total cell and neutrophil counts were noted only in those not using the pill. Lymphocyte counts varied directly with hemoglobin concentration in women (p less than .001). In men the variation was less marked;y Monocyte counts were not altered. It is suggested that the age effects in women may be due to estrogens. The variation with hemoglobin levels is possibly explicable as due to the influence of nutritional and other environmental factors.

The temperature dependence of the magnitudes and positions of the peaks in LEED intensity-energy plots

Abstract: Measurements of the temperature dependences of the intensities and energies of LEED peaks in the intensity plots for the specular beam from a (111) copper surface are reported. An analysis is made, for the peak shifts as a function of temperature, in order to attempt to deduce the thermal expansion coefficient for the surface layers normal to the surface. Several additional effects are accounted for but the shifts appear to be dominated by an unknown process and no deductions are drawn concerning the expansion coefficient. The temperature dependence of the intensities of the Bragg peaks in the intensity plots give values for the Debye temperature as a function of primary electron energy. The results indicate that this is not strongly dependent on diffraction condition. From the Debye temperature, the ratio of the mean square vibrational amplitude of the surface atoms perpendicular to the surface to that for the bulk is found to be 1.9 ± 0.1, in agreement with theoretical predictions.

Secondary metal/air cell

Abstract: An electrically rechargeable metal/air or metal/oxygen depolarized electrochemical cell and a method of generating electricity therefrom are described. The electrochemical cell comprises an anode capable of being regenerated and a composite cathode having an oxygen-permeable, hydrophobic member layered with catalyst and a bi-porous unit. The coarse pore layer of the bi-porous unit is in contact with the catalyst. A bubble barrier which can be integral with either the anode or composite cathode is in contact with the fine pore layer of the bi-porous unit. During discharge of the cell, the bi-porous unit is flooded with electrolyte and merely acts as a current collector. When charging, oxygen evolution occurs at the fine pore layer and, due to the bubble barrier, the evolved oxygen is forced into the coarse pore layer displacing the electrolyte, thereby protecting the catalyst layer from damage due to oxygen evolution and the high charging potential.

Distribution of carbon dioxide in the aqueous phase of aerobic soils.

Abstract: Summary Theory predicts that in the aqueous phase of aerobic soils carbon dioxide concentration/distance gradients are 1·35 times as large as those for oxygen. Because of differences in solubility, the partial pressure/distance gradients of carbon dioxide should be less than one-twentieth of the gradients of oxygen partial pressure. Experiments were carried out to test this prediction. In some experiments oxygen partial pressures were measured directly by means of a micro-electrode and carbon dioxide indirectly by methods involving microelectrode determinations of specific conductance in agar-CaCO3 gel. Measurements were made in models of water-saturated soil consisting of yeast cells embedded in agar-CaCO3 gel, around plant roots in agar-CaCO3 gel and within water-saturated soil. Oxygen partial pressures fell by 5–15 per cent of an atmosphere over distances of 0·2–0·4 cm whereas carbon dioxide partial pressures increased by less than 0·3 per cent of an atmosphere over the same distance. In other experiments different thicknesses of water-saturated soil were incubated with their upper surfaces exposed to air. The mean oxygen partial pressure fell by 7–13 per cent of an atmosphere with increasing the thickness from 0·2 to 0·4 cm whereas the carbon dioxide partial pressure never increased by more than 0·2 per cent of an atmosphere. Both sets of evidence confirm the theoretical prediction. It is concluded that the partial pressure of carbon dioxide in the aqueous phase of soils containing no oxygen-free zones, would never, even at the surfaces of roots, be more than 1 per cent of atmosphere greater than in the gas phase.

Conjugacy properties of affine transformations of nilmanifolds

Abstract: Introduction. Automorphisms and, more generally, affine transformations of nilmanifolds exhibit many interesting properties. For example, hyperbolic automorphisms serve as basic examples of Anosov diffeomorphisms [6], ergodic automorphisms are Kolmogorov automorphisms [5], and ergodic rotations are examples of transformations with mixed spectrum which do not have quasidiscrete spectrum [2]. In this paper we consider conjugacy properties of affine transformations of nilmanifolds. Our main result, Theorem 2, gives necessary and sufficient conditions for the existence of a non-affine continuous conjugacy between two affine transformations. Among the corollaries of Theorem 2 we show that if all continuous maps commuting with an affine transformation T are affine then T is ergodic, and if T is weak-mixing then all continuous maps commuting with T are affine. In particular, an automorphism of a nilmanifold is ergodic if and only if all the continuous maps commuting with it are affine. The results of this paper were obtained in the special case of mappings of finitedimensional tori in the paper [7]. Applications of the results of this paper will appear in [8]. R, Z, C will denote the real numbers, the integers and the complex numbers, respectively. Let N be a connected, simply-connected, nilpotent Lie group and I' a uniform discrete subgroup of N. Uniform means that the space N/F of cosets Ex, x E N, is compact. N/E is called a nilmanifold. The simplest examples are finite-dimensional tori (N = R\", P = Z\"). The basic theory of nilmanifolds can be found in [4] (summarised in [1]). If N 1 is the commutator subgroup of N then N/N 1 is abelian and N/N ~. I\" is a finite-dimensional torus, where N 1I' denotes the semi-direct product of N ~ and F. Suppose that N/E and M/£x are nilmanifolds and that L: N ~ M is a continuous isomorphism with LE ~ A. If c ~ M the mapping x ~ L(x). c of N onto M induces a map of N/P onto M/A which is called an affine transformation. If c is the identity element of M, the induced map is called a homomorphism, and an isomorphism if LE = A. Endomorphism and automorphism are defined in the obvious way. By a rotation of a nilmanifold N/F we mean the map of