Showing papers by "Royal Holloway, University of London published in 1972"
TL;DR: In this article, a Monte Carlo method for the calculation of thermodynamic properties in the isothermal-isobaric ensemble is described, and the accuracy attainable in estimates of the excess properties is discussed in terms of statistical fluctuations in various calculated quantities and the advantages and disadvantages of the method are examined in relation to calculations by the more familiar constant-volume method.
Abstract: A Monte Carlo method for the calculation of thermodynamic properties in the isothermal-isobaric ensemble is described. Application is made to the calculation of excess thermodynamic properties (enthalpy, volume and Gibbs free energy) of binary mixtures of Lennard-Jones 12–6 liquids. Comparison is made with the predictions of a number of theories of liquid mixtures; the so-called van der Waals one-fluid model and the variational theory of Mansoori and Leland are both found to give excellent results. The accuracy attainable in estimates of the excess properties is discussed in terms of statistical fluctuations in various calculated quantities and the advantages and disadvantages of the method are examined in relation to calculations by the more familiar constant-volume method.
371 citations
363 citations
TL;DR: A recursive family of graphs is defined as a sequence of graphs whose Tutte polynomials satisfy a homogeneous linear recurrence relation as discussed by the authors, and necessary conditions for a family to be recursive are proved, and the theory is applied to the families of graphs known as the prisms and the Mobius ladders.
137 citations
TL;DR: In this paper, an empirical formula for the Helmholtz free energy of a system of particles interacting through the Lennard-Jones 12-6 potential is derived on the basis of Monte Carlo computations of the internal energy and pressure.
Abstract: An empirical formula for the Helmholtz free energy of a system of particles interacting through the Lennard-Jones 12-6 potential is derived on the basis of Monte Carlo computations of the internal energy and pressure. The calculations cover the reduced temperature range from [Ttilde] = 0·551 to [Ttilde] = 1·237 and reduced pressures up to [ptilde] = 1·6. The results are used to assess the adequacy of the 12-6 potential model for a number of simple liquids (Ar, Kr, Xe, CH4, N2, O2, CO) and values of the effective 12-6 potential parameters are proposed for each.
119 citations
TL;DR: In this paper, the vibrational frequencies of biphenyl and its 4,4'-dihalogen derivatives have been computed for various values of the dihedral angle between the two rings.
111 citations
TL;DR: It is concluded that hydrophobic bonds are a major factor in the stabilisation of collagen fibres after swelling in deionised water.
104 citations
TL;DR: In this paper, the effect of small deviations from the combination rules is examined and comparisons are carried out with the predictions of the van der Waals 1-and 2-fluid theories and with experimental data for 9 real mixtures.
Abstract: Calculations have been carried out for binary equimolar mixtures of Lennard-Jones (12-6) liquids conforming to the combination rules e12 2 = e11e22 and 2σ12 = σ11 + σ22. The results cover the parameter range with at 97 K and 117 K; they include free energies, enthalpies, volumes and chemical potentials. The effect of small deviations from the combination rules is examined and comparisons are carried out with the predictions of the van der Waals 1- and 2-fluid theories and with experimental data for 9 real mixtures.
89 citations
TL;DR: It is reasonable to suppose that those features of the pattern that are constant within living species or have persisted over long periods of time in mammalian evolution have been maintained by stabilizing selection because they have survival value.
Abstract: Theories of molar evolution have long been dominated by the cusp concept. In the 19th century the Concrescence Theory compared each cusp with a simple "reptilian cone" (see the review by Neuville, 1932). Cope (1873) ascribed the origin of the multicuspid molars to "anteroposterior repetitive acceleration" and "lateral repetition," by which he seems to imply that the process of development of a simple tooth is repeated in each cusp of the complex tooth. The idea that the molar is made up of cusps is deeply embedded in the Tritubercular Theory, even though the cingulum was recognised as an additional element. What sort of individuality does a cusp have? Strictly, a cusp can be recognised only at its tip, which stands on all sides higher than the adjacent tooth surface. More basally, it merges with adjacent cusps, and though in some cases grooves can be used to delimit cuspal areas, in others the surfaces of neighbouring cusps are continuous and boundary lines must be arbitrary. Moreover, when teeth of related animals are compared cusps seem to appear from (or disappear into) the surfaces of other cusps, most often from ridges running down their slopes, or from cingula. The same is observed when comparison is made between adjacent teeth in a dentition. The close relationship between cusps and ridges is shown also in ontogeny. The cusp appears as a separate centre of calcification, but sooner or later it joins with its neighbours: the shallower the intervening valley, the sooner the junction is made (Butler, 1956). Ridges develop in the same way as cusps (Butler, 1967), the only difference being that, as there is no intervening valley, their calcification is joined to that of a cusp from the beginning. When it is realised that the shape of the tooth surface is a result of the folding of a sheet of epithelium (the inner dental epithelium of the enamel organ), probably under the influence of the adjacent mesenchyme (Kollar and Baird, 1968), the difficulty of defining a cusp becomes understandable. It is a remarkable fact that tooth patterns, though they show much individual variation in minor detail, are sufficiently constant in their main features to provide useful taxonomic data. The manner of folding of the dental epithelium is evidently under genetic, and ultimately under selective control. The relation between genotype and tooth pattern is very complex (e.g., Griineberg, 1951, 1965) and much remains to be discovered about the genetic control of tooth development. Nevertheless, it is reasonable to suppose that those features of the pattern that are constant within living species or have persisted over long periods of time in mammalian evolution have been maintained by stabilizing selection because they have survival value. In other words, details of the molar pattern have functional significance. That cusps have functions was recognised by the trituberculists. Ryder (1878) and Cope (1889) related the shape and position of cusps to the direction of chewing movements and Osborn (1888) made use of occlusal diagrams to explain the origin of the tritubercular molar. It was believed that in primitive mammals jaw movements were vertical (orthal) due to a hinge action of the mandibular joint, and that occlusal relations could be adequately interpreted by superimposing drawings of upper and lower teeth seen in crown view. Many occlusal diagrams of this type were produced by Gregory (e.g., 1920a, 1920b,
88 citations
TL;DR: In this article, three natural cubes were examined by x-ray topography, each of edge length about 1·8 mm, and two possessed very similar internal structures, describable in terms of space-filling by fibrous or columnar single-crystal growth in directions, with branching and equal growth velocities in these symmetrically equivalent directions.
Abstract: Three natural cubes, each of edge length about 1·8 mm. were examined by x-ray topography. Two possessed very similar internal structures, describable in terms of space-filling by fibrous or columnar single-crystal growth in directions, with branching and equal growth velocities in these symmetrically equivalent directions. On a microscopic scale this structure appears similar to that of diamond coat: the cubic habit results from the branching mode of growth when the final crystal size is large compared with the dimensions of its core or nucleus. The internal structure of the third cube was entirely different. The record of growth horizons and dislocation trajectories showed that during most stages of its growth it had developed with a combination of forms: normal {111} faces plus hummocky, non-crystallographic surfaces of mean orientation {100}. The latter had become dominant in the outer parts of the crystal but the final overall cubic shape had been accentuated by solution following growth.
75 citations
TL;DR: Differences in the number, incidence and degree of infection of mice and voles with species of helminths is undoubtedly linked with differences in the feeding habits of the respective hosts but the present study has confirmed that infection levels in both leptospires and Helminths are influenced by the age/sex relationships of the host together with season and habitat.
Abstract: The occurrence of helminth parasites and leptospires from the Long-tailed field mouse, Apodemus sylvaticus, the Bank vole, Clethrionomys giareolus and the Short-tailed vole, Microtus agrestis has been studied from four woodland areas in Surrey. The composition of the helminth fauna of these rodents, particularly A. sylvaticus and C. giareolus, differs from that of previous studies carried out in the British Isles in consisting largely of cestodes and fewer species of digeneans and nematodes. On the other hand the degree of infection of the rodents with nematodes as in the case of A. sylvaticus infected with the trichostrongylid Nematospiroides dubius and theoxyurid Syphacia stroma and of C. giareolus with thecap-illarid Capillaria muris sylvatici is greater than the cestode and digenean infections and is probably linked with the monoxenous nature of the nematode life cycles.
Differences in the number, incidence and degree of infection of mice and voles with species of helminths is undoubtedly linked with differences in the feeding habits of the respective hosts but the present study has also confirmed that infection levels in both leptospires and helminths are influenced by the age/sex relationships of the host together with season and habitat. The relationship between the distribution of rodents infected with leptospires and some helminths suggests similarities in the mode of their transmission.
49 citations
TL;DR: In this paper, the standard enthalpies of formation of the condensed phases were derived and in combination with enthalps of transition obtained ebullioscopically, corresponding values for the gas phase were calculated.
01 Nov 1972
Abstract: In this paper we shall show how combinatorial methods can be applied to the study of maps on orientable surfaces. Our main concern is with maps which possess a certain kind of symmetry, called vertex-transitivity. We show how an extension of the well-known method of Cayley can be used to construct such maps, and we give conditions which suffice for the automorphism groups of these maps to have non trivial vertex-stabilizers. Finally, we investigate the special case when the skeleton of the map is a complete graph; a classical theorem of Frobenius then implies that all vertex-transitive maps are given by our extension of Cayley's construction.
TL;DR: In this paper, the results of Monte Carlo calculations in the isothermal-isobaric ensemble are reported for a series of binary mixtures of Lennard-Jones liquids at zero pressure and a temperature of 115·8 K.
Abstract: The results of Monte Carlo calculations in the isothermal-isobaric ensemble are reported for a series of binary mixtures of Lennard-Jones liquids at zero pressure and a temperature of 115·8 K. In the case of equimolar mixtures comparison is made with the predictions of several recently developed theories of liquid mixtures. Particularly good results for excess Gibbs free energy and enthalpy are obtained from the variational theory of Mansoori and Leland and for excess volume from the one-fluid version of the so-called van der Waals model.
TL;DR: In this article, the degree of hydration of excised podia changes but little upon immersion in 70% sea water, and reasons for the loss of neuromuscular co-ordination in dilute sea water are discussed.
TL;DR: The approximate number of terminal non-reducing d -glucose residues and those linked through positions 1 and 6, 1 and 3, as well as 1, 2, and 6 in the average repeating-unit of dextran S are 5, 4, 1, and 5.
TL;DR: The green seaweed Acetabularia crenulata was shown to synthesise d -glucose, fructose, sucrose, ribo-hexulose, myo-inositol and a second alcohol (tentatively identified as allo-quercitol) as mentioned in this paper.
TL;DR: In this article, the authors used nuclear double resonance (endor) to map the positions of the neighbouring ions around the center, and to discover the chemical nature of these ions, which is a powerful tool for investigating the immediate surroundings of a center with unpaired electrons.
Abstract: Electron nuclear double resonance (endor) is a powerful tool for investigating the immediate surroundings of a centre with unpaired electrons in a solid. One can determine the nature of all neighbouring nuclei with nuclear magnetic moments, and can often determine their precise position in the crystal structure. Hence this technique may be used to map the positions of the neighbouring ions around the centre, and to discover the chemical nature of these ions.
TL;DR: All stages in the life cycle of Pieris brassicae were studied for carotenoid content and it was found that the ova possess a large quantity of β-carotene which must have its origin from the female.
TL;DR: The quantitative determination of small algae by the sedimentation of samples to which have been added Lugol's iodine followed by observation with an inverted microscope is well known but few laboratories that have adopted the standard technique are known.
Abstract: The quantitative determination of small algae by the sedimentation of samples to which have been added Lugol's iodine followed by observation with an inverted microscope is well known and has been clearly described (LUND, KiPLING & LE CREN, 1958) . For about twelve years, modifications of the standard technique have been used and taught in the Botany Department of Royal Holloway College. The most important modification, which I shall refer to here as the "R.H.C . split-tube technique", has been described in various forms independently, elsewhere and more than ten years ago (DAWSON, 1960 ; LOVEGROVE, 1960) . However, despite the clear advantages of the modified method and its publication, I know of few laboratories that have adopted it . It would seem, therefore, in order and worthwhile to fully describe our standard method . Each sedimentation system consists of three parts (Fig . 1) . The upper part, constructed entirely of perspex, has a basal portion about 7 .5 x 2 .5 cm, with a central hole 9.5 mm in diameter. These dimensions are not critical but must match up with those of the other parts and the thickness should be about 3 mm . Symmetrically and permanently fixed with araldite, or fused on with perspex cement (perspex dissolved in chloroform), to this plate is a cylinder of perspex, cut from tube, which is 9.5 mm in internal diameter, 13 mm in external diameter and usually 3 .0 cm high . The middle part is similar to the upper but has no cylinder and has a shallow step fused onto the underside at each end . The third part consists simply of a No. 1 or No . 0 21 mm square cover slip. Before use all parts should be scrupulously clean . Immediately before the sedimentation procedure the underside of the upper part
TL;DR: In this article, the maximum diameter of an ad-polytope withn-facets was defined as Δ(d, n), where n is the number of facets in the polytope.
Abstract: Δ(d, n) is defined to be the maximum diameter of ad-polytope withn-facets. The main results of the work are an evaluation of Δ(4, 10) and Δ(5, 11). Also, improved upper bounds are found for Δ(6, 13) and Δ(7,14).
TL;DR: In this paper, the R f values of twenty-two carotenoids separated on Whatman paper Chromedia AH 81 and SG81 are given and reproducible in about half an hour.
TL;DR: In this article, the edge-colouring problem is formulated as an edge coloring problem, and the solution is shown to be NP-hard, but it is possible to solve it.
Abstract: (1972). An Edge-Colouring Problem. The American Mathematical Monthly: Vol. 79, No. 9, pp. 1018-1020.
TL;DR: Water-soluble acid polysaccharides containing variable proportions of galactose, rhamnose, xylose, 4- O -methylgalactose , and glucuronic acid were isolated from caps and stalks of the green seaweed Acetabularia crenulata, indicating a highly branched molecule.
TL;DR: The course of infection of Raillietina cesticllus in the chicken has been studied and information is presented on proglottid output, the dynamics of infection and the distribution and growth of the cestode.
Abstract: The course of infection of Raillietina cesticllus in the chicken has been studied and information is presented on proglottid output, the dynamics of infection and the distribution and growth of the cestode.
A posterior migration of young cestodes during the first 7 days of infection was confirmed and a progressive destrobilization of the worms was observed with complete destrobilization occurring 70 days after infection. No regeneration of strobilae occurs and the scolices are eventually eliminated. A marked difference in the rate of destrobilization in the two host sexes was noted.
TL;DR: In this article, the differences in the fine structure of these algal polysaccharides are described and the effect of these differences on the conformation of the macromolecules and consequently on the physical properties, in particular the gelling properties, of the individual polymers are discussed.
Abstract: The differences in the fine structure of these algal polysaccharides which are all polydisperse linear galactans are described. The effect of these differences on the conformation of the macromolecules and consequently on the physical properties, in particular the gelling properties, of the individual polymers is discussed. The evidence that gel formation occurs through the association of chain segments into a three dimensional framework which is held together by hydrogen bonds is reviewed.
TL;DR: The authors agree with TAYLOR that G. grandisonae is a very distinctive member of the genus.
TL;DR: Proof was obtained that the residual cell-wall comprises cellulose and it is possible that the various structural features are present in a single heteropolysaccharide.
Abstract: Glycerol, erythritol, xylitol, glucose and mannitol have been separated and characterised as low molecular weight carbohydrates of Tribonema aequale Pascher. Complex mixtures of water-soluble polysaccharides comprising glucose, galactose, mannose, rhamnose, fucose and traces of arabinose and xylose were also identified. The major alkali-soluble polysaccharides were characterised as a 1, 6-linked glucan and 1, 4- and 1, 3-linked xylans. These polysaccharides defied fractionation and it is possible that the various structural features are present in a single heteropolysaccharide. Evidence for the presence of a small proportion of 1, 3-linked glucose units was also obtained but enzymic studies failed to confirm the presence of a β-1, 3-linked glucan. Proof was obtained that the residual cell-wall comprises cellulose.