Showing papers by "University of Reading published in 1973"

Halogenated Hydrocarbons in and over the Atlantic

Abstract: DURING the past few decades the production of the chlorofluorocarbons, the propellant solvents for aerosol dispensers, has grown exponentially. R. L. McCarthy (unpublished) estimates that the integrated production of CCl2F2 and of CCl3F, the two principal compounds of the class, was about one megaton of each in mid 1971; they are unusually stable chemically and only slightly soluble in water and might therefore persist and accumulate in the atmosphere. Preliminary tests in 1970 showed that CCl3F was present in the air over Ireland at concentrations exceeding 10−11 by volume1.

Ecological Studies on the Lactobacillus Flora Associated with the Crop Epithelium of the Fowl

Abstract: Summary. The lactobacillus flora lining the crop of the chicken became established soon after hatching and adhered to the crop epithelium throughout the life of the bird: adhesion was unaffected by drastic changes in diet and was of widespread occurrence. Adhering lactobacilli were isolated from birds but not from mammals. Only these avion lactobacilli adhered to chicken crop epithelial cells. It is suggested that these lactobacilli have formed a symbiotic relationship with the chicken and help to regulate the composition of its intestinal microflora.

Inelastic-Electron-Tunneling Spectroscopy of Metal-Insulator-Metal Junctions

Abstract: The inelastic tunneling of electrons in a metal-insulator-metal junction has been shown to be a spectroscopic method for studying the vibrational modes of the whole system. In the present paper we consider the possibility of deducing precise information from this spectroscopy. The low-voltage part of the spectrum (i.e., the $\frac{{d}^{2}I}{d{V}^{2}}\ensuremath{-}\mathrm{v}\mathrm{s}\ensuremath{-}V$ characteristic) gives information about the phonons of the electrodes. The phonon density, which is deduced for a Mg electrode, is critically compared with the density deduced from neutron scattering. The range of this phonon probe is then studied by tunneling into multilayer electrodes. The 40-90-meV range of the characteristic of a Mg-Pb junction exhibits a specific structure due to the lattice vibrations of the insulator. This structure is compared with the infrared spectrum and the phonon density of states of MgO, as well as with a theoretical calculation of the tunneling current in the transfer-Hamiltonian formalism. From the fit obtained, it is deduced that the 30-\AA{}-thick insulator, grown on Mg, is an oxide, in contrast with the insulator grown on Al, which was previously deduced to be a hydroxide. At higher energies (100-500 meV), the vibrational spectrum of molecules contained in the insulator region is observed. The identification of the lines is shown to be accurate and it gives precise information on these molecules, especially about their chemical binding with the insulator. This last point could be important in the future for studying the problem of adsorption on solid surfaces.

The anharmonic force field and equilibrium structure of HCN and HCP

Abstract: The quadratic, cubic, and quartic force field of HCN has been calculated by a least squares refinement to fit the most recent observed data on the vibration-rotation constants of HCN, DCN and H13CN. All of the observed parameters are fitted within their standard errors of observation. The corresponding parameters for other isotopic species are calculated. For HCP and DCP the more limited data available have been fitted to an anharmonic force field using constraints based on comparison with HCN. Using this force field the zero-point rotational constants B 0 have been corrected to obtain the equilibrium constants Be , and hence the equilibrium structure has been determined to be re (CH) = 1·0692(7) A, and re (CP) = 1·5398(2) A.

Trimethylamine metabolism in obligate and facultative methylotrophs

Abstract: 1. Twelve bacterial isolates that grow with trimethylamine as sole source of carbon and energy were obtained in pure culture. All the isolates grow on methylamine, dimethylamine and trimethylamine. One isolate, bacterium 4B6, grows only on these methylamines whereas another isolate, bacterium C2A1, also grows on methanol but neither grows on methane; these two organisms are obligate methylotrophs. The other ten isolates grow on a variety of Ci and other organic compounds and are therefore facultative methylotrophs. 2. Washed suspensions of the obligate methylotrophs bacteria 4B6 and C2A1, and of the facultative methylotrophs bacterium 5B1 and Pseudomonas 3A2, all grown on trimethylamine, oxidize trimethylamine, dimethylamine, formaldehyde and formate; only bacterium 5B1 and Ps. 3A2 oxidize trimethylamine N-oxide; only bacterium 4B6 does not oxidize methylamine. 3. Cell-free extracts of trimethylamine-grown bacteria 4B6 and C2A1 contain a trimethylamine dehydrogenase that requires phenazine methosulphate as primary hydrogen acceptor, and evidence is presented that this enzyme is important for the growth of bacterium 4B6 on trimethylamine. 4. Cell-free extracts of eight facultative methylotrophs, including bacterium 5B1 and Ps. 3A2, do not contain trimethylamine dehydrogenase but contain instead a trimethylamine monooxygenase and trimethylamine N-oxide demethylase. It is concluded that two different pathways for the oxidation of trimethylamine occur amongst the isolates.

Stability of the Rossby-Haurwitz wave

Abstract: A spectral method is used to integrate the primitive equations for the motion on a sphere of a shallow layer of fluid with a free surface. A simple Rossby-Haurwitz wave of zonal wavenumber 4 is found to change its form little over 24 days, whilst one of wavenumber 8 breaks down completely in 5 days. Inspired by the integrations, the barotropic stability of a wave to a perturbation composed of another wave and a zonal flow is considered. The theory suggests that waves of zonal wavenumber greater than 5 may be unstable because the feedback of the perturbation on itself is positive. Those of wavenumber 5 and less are stable, the feedback being negative. The theory and the general barotropic instability of Rossby waves is tested by integrations of the non-divergent barotropic model, in which the wave is perturbed by a zonal flow. Some agreement with theory is found. Waves of zonal wavenumber 8 rapidly break down to produce jets in the same direction as the perturbation zonal flow. The stability of these jets is also examined.

Degree of Gelatinisation of Cooked Rice

Abstract: A method for determining degree of gelatinisation of rice starch or rice flour, based on the amylose/iodine blue value after dispersion in alkali, has been developed. The method can be used to follow the course of cooking of rice under different conditions, and has been checked against a novel infrared technique for relating degree of gelatinisation to the phenomenon of hydrogen bonding.

The Neutral Vacancy in Diamond

Abstract: The GR 1 radiation damage centre in diamond has been studied by means of optical absorption and uniaxial stress. Two zero phonon lines at 1.665 and 1.673 eV have been associated with the defect, and an energy level scheme is proposed to explain the thermal behaviour of the lines. The energy level diagram facilitates the interpretation of the uniaxial stress data, and it is concluded that the defect possesses tetrahedral symmetry. Comparison of the energy level scheme derived experimentally with theoretical treatments of intrinsic defects in diamonds suggests that the GR 1 centre is probably the neutral vacancy.

Features of cross-stratified units due to random and other changes in bed forms

Abstract: Because cross-stratified units depend upon the movement of bed forms, any change in the shape, size and direction of travel of the forms is reflected in the geometry of the units, notably in their relative length, breadth and thickness, mode of termination upstream and downstream, and internal discontinuities. Most models of cross-stratification so far published are unsatisfactory because they ignore the fact that real bed forms are subject to change. The changes are thought to occur at two levels of detail independently. Those at the coarser level depend on the essential non-uniformity, unsteadiness and multi-directionality of natural flows, when assessed on a suitably large scale. At the finer level, change is related to the random behaviour of individual bed forms as they interact with the adjacent flow, and it proceeds even when the flow is an equilibrium one overall. Flume experiments on current ripples show that many features of cross-stratified units can be explained by the random behaviour of bed forms. The finite streamwise length of such units, and their upstream and downstream erosional termination, is governed by the life-span (finite) of individual ripples and by the extent of net deposition on the bed. Internal discontinuities, closely resembling features described as reactivation structures, were also found to depend on the relative motion of ripples, no change of flow discharge and stage being involved. The degree of relative motion in the ripple assemblages was substantial, as measured by the fluctuating component of the ripple celerity.

The managment of severe agoraphobia: a comparison of iproniazid and systematic desensitization.

Abstract: Sixty out-patients with severe agoraphobia took part in a controlled prospective clinical trial of combinations of methohexitone-assisted and standard systematic desensitization and monoamine oxidase inhibitor Severity of agoraphobia in terms of avoidance and anxiety was rated both by the patients themselves and by an independent assessor during the eight weeks of treatment The monoamine oxidase inhibitor produced a significant reduction in severity of anxiety but not of avoidance Methohexitone-assisted systematic desensitization appeared to produce significantly greater improvement than either standard systematic desensitization or no systematic desensitization in both anxiety and avoidance Assessors' ratings showed that the monoamine oxidase inhibitor used in conjunction with methohexitone-assisted systematic desnsitization produced slightly greater clinical improvement than the other treatment combinations

Physiology of seed yield in field beans ( Vicia faba L.): I. Yield and yield components

Abstract: The growth and yield of four varieties of field beans were studied in field experiments in 1967 and 1968. Seed yield of the varieties Albyn Tick, Herz Freya, Blue Rock and Maris Bead were similar (averaging 6600 kg/ha) in 1967, but in 1968 Albyn Tick and Herz Freya (averaging 6400 kg/ha) outyielded Maris Bead (5700 kg/ha). Yield in both seasons were substantially more than the national average yields for Britain (about 3000 kg/ha). In 1968, yields were 40% greater at 57 plants/m 2 (7100 kg/ha) than at 36 plants/m 2 (5100 kg/ha). Yield was closely correlated with number of pods/plant. The number of pods/node regulated this rather more than the numbers of nodes forming pods. Mean seed weight and seed number/pod varied little between plant densities but variety means were significantly different. Maximum numbers of immature pods were present in late June. By mid-July 35% of the immature pods had shed, mainly from the middle and top of the range of podbearing nodes.

Porphyrin-Accumulating Mutants of Escherichia coli

Abstract: Four mutants (pop-1, pop-6, pop-10, and pop-14) which accumulate a red water-insoluble pigment were obtained in Escherichia coli K-12 AB1621. For each mutant, the red pigment was shown to be protoporphyrin IX, a late precursor of heme. Mutagenic treatment of mutant pop-1 yielded a secondary mutant, pop-1 sec-20, which accumulated a brown water-soluble pigment. The brown pigment was shown to be coproporphyrin III. Mutant pop-1 resembled the parental strain in its cytochrome absorption spectrum, catalase activity, and ability to grow on nonfermentable carbon and energy sources; therefore, its ability to produce and utilize heme was unimpaired. Judged on the same criteria, the secondary mutant, pop-1 sec-20, was partially heme and respiratory deficient. Growth in anaerobic conditions decreased by 25% the accumulation of protoporphyrin by pop-1; under the same conditions, pop-1 sec-20 did not accumulate coproporphyrin or coproporphyrinogen. The mutations causing protoporphyrin accumulation in all four pop mutants were found to map in the lac to purE (10–13 min) region of the E. coli chromosome. In the case of mutant pop-1, the mutation was shown to be strongly linked to the tsx locus (12 min). In mutant pop-1 sec-20, the second mutation causing coproporphyrin accumulation was co-transducible with the gal locus at a frequency of 88 to 96%. The mechanism of porphyrin accumulation by the mutants is discussed.

The Wear of Diamond

Abstract: The wear of diamond when rubbing against materials softer than itself is investigated. It is shown that the rate of wear depends primarily on the hardness of the second member, varying as hardness to the power 3.5 for hardnesses above 200 V.p.n. When the hardness of the second member is high enough, the tensile stresses acting on the diamond reach the fracture stress, and the wear quickly becomes visible. Below this point, the rate of wear is small and there is an appreciable delay before its onset can be detected. For metals, such as copper, silver and gold, which are well below the critical hardness, the scale of the wear process becomes extremely small and the relation between wear rate and hardness changes. It is thought that in these conditions the rate of wear becomes affected by residual effects arising from the stressing of the surface during the initial processes of polishing.

Floral initiation in strawberry: Spectral evidence for the regulation of flowering by long-day inhibition.

Abstract: Floral initiation in strawberry cv. Cambridge Favourite, a facultative short-day plant, was inhibited by a daylength extension with red light (R) during the second half of a 16-hour night but not during the first half, and by far-red light (FR) in the first half but not during the second. Mixed R plus FR light was inhibitory to flowering at both times. This change in sensitivity to R and FR light in the evening and morning resembles the pattern for flower induction in long-day plants but differs from the pattern for flower inhibition in several other short-day plants, examples of which are given. These experiments afford further support for the hypothesis that the control of flower initiation in strawberry depends on the production of a flower inhibitor by leaves exposed to long photoperiods.

Polyploidy and Flavonoid Synthesis in Briza media L.

Abstract: POLYPLOIDY may increase the flexibility of a species and consequently its ecological range by extending physiological tolerance1,2. In Lycopersicon esculentum polyploidy is reported to raise ascorbic acid levels in the fruit3 and in Valeriana officinalis the polyploids have been shown to be better adapted to certain soil types than the diploids4. Little work, however, has been carried out on chemical differences between chromosome races, so it was of some interest, when we found that diploid and tetraploid plants of Briza media, which have different geographical distributions also have distinct leaf flavonoid patterns. Diploid plants accumulate the C-glycosylflavones vitexin and isovitexin, tetraploid plants orientin and iso-orientin (Fig. 1).

Recent Serpulid Reefs, Connemara, Eire

Abstract: A SHELTERED lagoon, Ardbear Lough, Clifden, Co. Galway (Irish National Grid L 66 49), provides a very favourable environment for the growth of fringing reefs of the calcareous tubed polychaete Serpula vermicularis L. As far as I am aware living serpulid reefs (as distinct from encrustations) have not been described previously. Fossil reefs are described from the Lower Carboniferous of Cumberland (ref. 1 and M. R. Leeder, in this issue) and sub-fossil reefs from Baffin Bay, Texas2. The occurrence of a living serpulid reef is of geological and biological importance and here I describe in outline the ecology of the reefs.

Oriented chain-extended polyethylene: I. formation and characterization

Abstract: Aggregates of polyethylene lamellae, whose average thickness can be increased progressively from about 200 to 2000 A and beyond have been produced by annealing drawn polymer hydrostatically. All la...

A yield-surface corner lowers the buckling stress of an elastic-plastic plate under compression

Abstract: The bifurcation stress is calculated for a simply-supported elastic-plastic plate in uniaxial compression, in the case when the stress is at a vertex of the yield surface which is locally similar to that of Tresca. The effect of coupled hardening between yield-surface facets which meet at the vertex is included. It is found that the bifurcation stress may be substantially lower than that associated with the von Mises yield surface. The latter is known to give results too high to be reconciled with experiment. Reductions of order 10–30 per cent are shown to be unexceptional, even with the retention of an elastic value for the shear modulus.

The anatomical basis of function in the buccal mass of prosobranch and amphineuran molluscs

Abstract: A comparative account is given of the muscular anatomy of the buccal mass in chitons and a number of species of prosobranch gastropods. From this can be deduced a basic muscular organization consisting of buccal constrictors and dilators, protractors and retractors of the odontophore, protractors and retractors of the subradular membrane and an approximator muscle of the supporting cartilages. In addition to these many ancillary muscles act as tensors: these are numerous in chitons, monoplacophorans and rhipidoglossan proso-branchs. In the first two groups, which have a poorly developed anterior end covered by a shell, they act in place of the muscles of the mobile wall of the head of gastropods; in the last they are necessary for the fine control of an odontophore brushing the substratum. In prosobranchs which forcibly rasp their food they are lost. The dominating influence in the evolution of the buccal mass in neogastropods is the proboscis. Its narrowness and elongation have had profound effects on the anatomy of the buccal mass.

Physiologic races of Rhynchosporium secalis on barley in Britain

Abstract: By using newly developed techniques, 12 varieties of barley were inoculated with 122 single spore isolates of Rhynchosporium secalis collected from British barley crops in 1967 Two distinct physiologic races were identified UK 1 was the predominant race (96 isolates); it infected only one out of the 12 varieties (Cambrinus), whereas race UK 2 (26 isolates) infected nine varieties Both races were widely distributed in Britain

On mass transport induced by interfacial oscillations at a single frequency

Abstract: The to method of matched asymptotic expansions is employed to calculate the mass tre sport velocity due to combinations of small amplitude oscillatory waves propagatir, at a single frequency in fluid systems with density and viscosity dis-continuities. Interfacial boundary layers are considered in terms of the curvilinear coordinate system described by Longuet-Higgins(1). The order of magnitude of the mass transport velocity calculated for a general oscillatory disturbance is the same as that calculated for interfacial progressive waves by Dore(2). For standing waves, the time-averaged motion of the fluid particles forms a cellular structure in each fluid layer; the mass transport velocity due to modal interactions is associated with a similar structure.