Showing papers by "University of Salford published in 1986"

Optically nonlinear waves in thin films

Abstract: A new treatment of the behavior of TE nonlinear waves in an optically nonlinear film is given. The new mathematical results are expressed in terms of the physical parameters of the system and represent a straightforward way to introduce the necessary Jacobian elliptic functions. The optical nonlinearity is of the Kerr type and the numerical calculations are performed for a self-focusing medium. Dispersion curves labeled with optical power density at the lower film boundary, detailed plots of the variation of electric field amplitude as the wave number changes, and details of the power distribution across the guide are given. Since two values of a wave number can exist for the same power level and power thresholds exist, the system is of device interest in the area of optical switching.

Comparison of the structure of human intervertebral discs in the cervical, thoracic and lumbar regions of the spine

Abstract: Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4–5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3–4, T7–8 and L2–3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65°) than in the thoracic and lumbar discs (about 70°). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc.

Eigenstructure assignment in descriptor systems

Abstract: Coordinate free conditions are given for pole assignment by feedback in linear descriptor (singular) systems which guarantee closed-loop regularity. These conditions are shown to be both necessary and sufficient for assignment of the maximum possible number of finite poles. Transformation to special coordinates are not used and the results provide a robust algorithm for the computation of the required feedback.

Erosion and growth of solids stimulated by atom and ion beams

Abstract: The members of the organising Committee and their colleagues have, for many years been investigating the evol ution of the fas'cinating surface features which develop during sputtering erosion of solids. Such experimental, theoretical and computational studies have also been carried out in many international laboratories and, as well as much cow onality and agreement, substantial disagreements were unresolved. In view of the increasing importance of such processes in technological applications such as microlitho graphic etching for the patterning of solid state devices and in fusion technology it was felt opportune to hold a meeting in this area. Furthermore the use of energetic atomic and ion fluxes is also becoming of increasing importance in assisting or modifying the growth of thin films in a number of important industrial processes and it was therefore rational to combine the, study of both erosional and growth processes in a single meeting. These proceedings include 16 invited review and 15 oral or poster presented contributions to the NATO Advanced Study Institute on the "Erosion and Growth of Solids Stimulated by Atom and Ion Beams." The review contributions span the range from the fundamental concepts of ballistic sputtering, and how this influences surface morphology evolution, through processes involving entrapment of incident species to mechanisms involved in'the use of chemically reactive ion species. Further reviews outline the influence of energetic irradiation upon surface growth by atomic deposition whilst others discuss technologkal applications of both areas of growth and erosion."

The syntax of English genitive constructions

Abstract: As is well known, English has two genitive or possessive constructions, the ‘proposed’ and the ‘postposed’, exemplified in (1).In each case we have an NP, with a head N (book, office, dog, house, plants) modified by a possessive expression (John's, a man's, mine, etc.). This expression is itself an NP in the genitive Case, and I shall refer to it as the ‘genitive phrase’. By contrast with other familiar languages more highly inflected than English, genitive Case is hot marked by an inflection on the head of a genitive phrase, but by the clitic ’s, which is attached right at the end of the phrase. The exception is where the genitive phrase is not a full NP but a personal pronoun, in which case we get an inflected form (irregular in pattern) as in these other languages: I - my/mine, he - his, etc. These possessive forms of pronouns have almost identical distribution to that of full NPs in the genitive (there are some differences which I shall point to below), and so it seems clear that they are genitives, despite the morphological difference; personal pronouns are highly irregular morphologically anyway, and not only in English. This is assumed in all recent work I know of, and I shall take it to be uncontroversial.

Feeding behaviour of pathogen-infected vectors.

Abstract: Evidence from many sources indicates that, in several parasite–vector systems, flight ability, fecundity or gonotrophic concordance of vectors, are affected by parasites (including bacteria, rickettsia and viruses) and in some cases parasites cause well-documented pathogenic effects (see reviews, for example, by Lavoipierre (1958a) and Hawking & Worms (1961) on filaria; Molyneux (1977, 1983) for trypanosomatids; Killick-Kendrick (1979) for Leishmania).

Swelling properties of copolymeric hydrogels prepared by gamma irradiation

Abstract: Crosslinked xerogels in the form of rods have been prepared to > 99.9% conversion by the γ-ray initiated copolymerization in vacuo ob n-butyl acrylate (BA) with N-vinyl-2-pyrrolidone (VP) in the presence and absence of a crosslinking agent. Thin (about 0.5 mm) disks were swollen in water at 21°C, the final equilibrium swelling being the true water content only for copolymers of high BA content. At low-medium BA content, swelling was accompanied by the release of a small water-soluble fraction, leading to a slightly reduced apparent value for the water content. True water contents could be obtained more rapidly by prior Soxhlet extraction with boiling water. For xerogels containing > about 75% VP by weight, the resultant hydrogels had water contents > about 80%. The influences of dose, dose rate copolymer composition, and concentration of crosslinker on the water content, sol fraction, and extension ratio were investigated. A high level of reproducibility in properties of the hydrogels was obtained by numerous replicate experiments. The feasibility of scaling up the preparation to produce long (60 cm) xerogel rods of uniform properties has been demonstrated. For these copolymers, swelling in several common organic solvents generally exceeds that in water.

Surface-polariton solitons

Abstract: The propagation of surface or guided electromagnetic waves is considered for structures consisting of two or more dielectric media, at least one of which is nonlinear, that are separated by parallel, planar interfaces. The conditions are obtained under which bright envelope surface-polariton solitons can exist in these structures. Two physical systems are analyzed that can, in principle, sustain such nonlinear surface excitations.

Differentiation of anopheles culicifacies Giles (Diptera: Culicidae) sibling species by analysis of cuticular components

Abstract: Cuticular wax was extracted from adult females of Anopheles culicifacies Giles and analysed by gas liquid chromatography. The flies were taken from pure cage stocks of three sibling species: 56 individuals of species A, 43 of species B and 51 of species C. The three cytospecies were found to be significantly different in their cuticular hydrocarbon composition by a multivariate analysis of variance. Using discriminant analysis, each cytospecies was characterized by the amounts of C25-C33 hydrocarbons extracted from the cuticle, allowing criteria to be established for the identification of flies. By these criteria, specimens from stocks of known identity were allocated to the correct group with a high success rate. These results may reflect ecological differences among the sibling species.

Comparison between two finite‐difference schemes for computing the flow around a cylinder

Abstract: Separated flow past a circular cylinder is computed from two finite-difference Navier–Stokes models. Stream functions are calculated using a successive-over-relaxation (SOR) procedure. Alternating-direction-implicil (ADI) and ‘upwind’ directional difference explicit (DDE) numerical schemes for solving the vorticity-transport equation are compared. The ‘upwind’ differencing technique produces artificial viscosity which damps the wake and suppresses vortex shedding. It is shown to be unreliable and so the ADI approach is recommended.

Does testosterone affect the normal menstrual cycle

Abstract: In order to throw further light on the role of androgens in the aetiology of the polycystic ovary syndrome (PCO) we have examined the effect of artificially increasing serum testosterone levels on menstrual function in a group of ovulating women Six women were studied who had either severe premenstrual syndrome or loss of libido for which they were treated with 100 mg testosterone by sc implantation All had regular menstrual cycles For 1 month before implantation serum LH, FSH, oestradiol (E2), progesterone and testosterone were measured three times per week All women showed normal cyclical variation of LH, FSH, E2 and progesterone Following implantation, three times weekly blood samples were taken during the first and third cycles No patient had any disturbance of menstrual pattern All continued to show cyclical changes of LH, FSH, E2 and progesterone Serum E2 and progesterone were lower but not significantly so in the luteal phase of the treated cycles This was despite a mean serum testosterone which rose from 13 to 71 nmol/l at the end of the third week following implantation and to 41 nmol/l at the end of the third month Sex hormone binding globulin levels fell as expected by 185% during the first cycle The lack of significant effect of a markedly elevated serum testosterone level on cyclical hormone changes is indirect evidence that in PCO the primary cause of the menstrual disturbance is not excessive production of ovarian or adrenal testosterone

The Reagan Urban Policy and its Impacts

Abstract: The intent and effectiveness of the Reagan administration's urban policies have been the focus of much debate. This article analyzes Reagan's first-term urban policies and assesses their effects. Changes in budgetary requests, authorizations, and outlays during Reagan's first term are tracked for the full spectrum of urban programs. An attempt is also made to analyze the spatial and programmatic consequences of the changes in expenditure levels. Determination of the success or failure of the Reagan administration's urban policies is largely dependent on who is asking the questions and how they are asked.

Golytely: a new approach to faecal impaction in old age.

Abstract: Forty-five elderly subjects with faecal impaction were entered into a study of the efficacy of golytely. Twenty-three were treated with golytely 2 l/day for 2 days and then lactulose 30 ml b.d. and daily enemas. Twenty-two were treated with lactulose 30 ml b.d. and daily enemas alone. A good response was achieved in 13 (56%) within 1 week and in 20 (87%) within 2 weeks when golytely was used, as compared to only 5 (23%) within 1 week and 9 (41%) within 2 weeks when it was not used.

Viscosity of aqueous and alkaline solutions of poly(ethylene oxide)

Abstract: Viscosity measurements over a wide range of temperature were made on aqueous solutions of poly(ethylene oxide) samples of different molar mass and of low polydispersity. Above ca. 308 K the Mark-Houwink exponent decreases and tends to a value of 0,50 at a lower critical solution temperature of 376 ± 2 K. The same value for this θ-temperature is derived also as that at which the slope of Stockmayer-Fixman plots tends to zero. At 298 K the unperturbed dimensions [〈r2〉0/M]1/2 = 0,089 nm · g−1/2 · mol1/2 and their temperature coefficient d ln 〈r2〉0/dT ≈ − 1,5 (±0,5) · 10−3 K−1. In aq. KOH the intrinsic viscosity [η] is virtually uninfluenced by pH at low-medium pH, but at high pH, [η] falls sharply. Viscosity and phase separation measurements yield θ-conditions in 1,24 M aq. KOH at 298 K. The derived polymer-water interaction parameters χ increase from 0,449 at 276 K to 0,493 at 358 K, but the enthaplic component χH is incapable of yielding a meaningful value for the solubility parameter δ2 of the polymer in such a hydrogen-bonding system. The calculated value of χ2 was 18,9 (kJ · dm−3)1/2.

Factors determining radiation-induced mixing at interfaces

Abstract: A review is given of the principal mechanisms contributing to atomic mixing produced by ion beams at initially well-defined interfaces between solid phases. Their relative importance is discussed in the light of available experimental evidence, and a critical survey is given of current mathematical models. The case of a thin interior implant layer is included. Those aspects of surface sputtering of direct relevance to the construction of the mixing equations are examined. Mixing mechanisms considered are ballistic relocation, diffusion, radiation-induced segregation, and drifts induced by chemical affinities of the elements concerned, together with constraints on all these from packing (Kirkendall) effects. Ballistic terms are subdivided into direct-recoil and cascade contributions. A brief review is given of the established methods of modelling them by using relocation integral cross-sections, and also the limitations and advantages of their approximation by differential equations of Fokker-Plan...