Showing papers by "University of Manchester published in 1978"

Metal-semiconductor contacts

Abstract: A review is given of our present knowledge of metal-semiconductor contacts. Topics covered include the factors that determine the height of the Schottky barrier, its current/voltage characteristics, and its capacitance. A short discussion is also given of practical contacts and their application in semiconductor technology, and a comparison is made with p-n junctions.

Motion sickness adaptation: a neural mismatch model.

Abstract: Introduction In almost all susceptible individuals, continued exposure to a provocative motion stimulus leads to the diminution and eventual disappearance of established motion sickness reactions (see Reason & Brand 1975).This reduction in symptomatology takes place without any change in the nauseogenic stimulus; indeed, it is the absence of such variation that promotes its occurrence. These observations are clearly of considerable importance for elucidating the factors involved in the aetiology of motion sickness, as they demonstrate the existence of processes within the individual that are capable of counteracting the disturbing properties of the imposed motion without recourse to any external agency. It follows, therefore, that a better appreciation of how this vis medicatrix naturae operates must bring us closer to understanding how these curious and inappropriate reactions become established in the first place, since adaptation and provocation appear to be two sides of the same coin. The theoretical arguments presented here are directed toward answering two basic questions concerning the aetiology of motion sickness. First, what is the essential nature of the provocative stimulus? How do we explain the occurrence of motion sickness over such a wide range of apparently diverse circumstances? What, for example, do the conditions that elicit space sickness have in common with those that induce seasickness, airsickness, car sickness, camel sickness, swing sickness, simulator sickness, and so on? This question is dealt with briefly as a necessary prelude to the main concern of this paper, namely: what are the mechanisms underlying the acquisition of protective adaptation, and ofits sequel mal de debarquement ?The principal research findings relating to the efTects and after-effects of protective adaptation are summarized, and a neural mismatch model is described which attempts to account for these data.

Nucleation and growth of porous anodic films on aluminium

Abstract: POROUS anodic films on aluminium are of considerable interest, not only because of their important practical uses in architecture and industry but also because of their novel regular morphology. The simple explanation involving field-assisted dissolution1,2 has now been extended and an additional mechanism involving direct loss of Al3+ ions to solution has been proposed3. Ultramicrotomy4 and ion beam thinning5 of films, together with transmission electron microscopy and secondary ion mass spectrometry, have provided greater information on the film morphology and composition. Here we outline some of the more significant findings relating to the large-featured, regular films formed in phosphoric acid.

The Wakes of Cylindrical Bluff Bodies at Low Reynolds Number

Abstract: Experiments on the near wake of a cylinder will be discribed in an attempt to present a coherent picture of the events encountered as the Reynolds number increases from small values up to values of a few thousand. Much work on this subject has already been done, but there are gaps in our description of these flows as well as more fundamental deficiencies in our understanding of them. The subject has been reviewed several times and most recently by Berger & Wille (1972) whose paper covers much of the ground that will be discussed again here. The present work may be regarded as built upon this latest review. I remember with gratitude many helpful discussions with the late Rudolph Wille who contributed so much to this subject. The investigation has concentrated on circular cylinders, but the wakes of bluff cylinders of different cross sectional shapes have also been observed. Bluff cylinders in general are considered in §§4 and 5, together with the effect of splitter plates on circular cylinders in §9. The experiments concern, almost exclusively, flow visualization of the wakes by means of dye washed from the bodies. The patterns of dye observed are, therefore, filament line representations of the flow leaving the separation lines on the body. It must be stressed that the dye does not make visible the vorticity bearing fluid because at low Reynolds number, vorticity diffuses considerably more rapidly than does dye. The ratio of the molecular diffusivity of momentum to that of mass of dye is of the order of 100.

The Type Theoretic Interpretation of Constructive Set Theory

Abstract: By adding to Martin-LSf's intuitionistic theory of types a ‘type of sets’ we give a constructive interpretation of constructive set theory. constructive version of the classical conception of the cumulative hierarchy of sets. This interpretation is a

Linearized limb-darkening coefficients for use in analysis of eclipsing binary light curves

Abstract: Linear limb-darkening coefficientsu required in the analysis of eclipsing binary curves, are tabulated for a wide range of effective temperature (50 000° to 4000°), wavelength λ (02 μ≤λ≤22 μ), and gravitiesg (20≤logg≤50) The computation is based on the comprehensive range of model atmospheres of Carbon and Gingerich (1969) The results are compared with the theoretical values of Hosokawa (1957), Kopal (1959) and Grygaret al (1972), and examined in relation to empirically determined values ofu from analyses of eclipsing binary light curves An improved agreement between theory and observation for the calculated limb-darkening coefficients of the present work is noted

Cellular localisation of human urogastrone/epidermal growth factor

Abstract: HUMAN urogastrone (hUG) is a polypeptide prepared from urine and is chemically similar to mouse epidermal growth factor (mEGF) prepared from submandibular salivary glands. Both these substances stimulate fibroblast proliferation in tissue culture systems. hUG and mEGF inhibit gastric acid secretion in experimental animals and hUG produces an identical effect in man. We show here, using immunofluorescent techniques, that hUG is present in the duct cells of human submandibular gland and in Brunner's gland cells in the first part of the duodenum. This work suggests that these polypeptides may have a role in mucosal growth and control of gastrointestinal secretion.

The value of feedback in teaching interviewing skills to medical students.

Abstract: Forty-eight medical students took part in a study to assess the value of giving students some feedback about their interviewing skills. During the study they all received training from their clinical firms. In addition, 36 of the students received 1 of 3 types of feedback training. This was given by tutors who used television replays, audiotape replays or ratings of practice interviews conducted by the students.As in previous studies there was little improvement in the interviewing skills of those students who only received training from their clinical firms. In contrast, all 3 feedback groups improved their ability to elicit accurate and relevant information. However, only the television and audiotape groups also showed gains in techniques. While the differences between these 2 groups were not significant, they all favoured the television group.

DNA lesions occur with loss of viability in embryos of ageing rye seed

Abstract: In dry seeds, fragmentation of nuclear DNA and activation of DNases occur in vivo during embryo senescence. This loss of DNA integrity could be the source of chromosomal aberrations and impaired transcription observed when seeds of low viability germinate.

The film drainage problem in droplet coalescence

Abstract: A small drop of liquid 1 falls through a less dense liquid 2 and approaches the horizontal interface between liquid 2 and an underlying layer of liquid 1. After a short time the drop will be brought to rest (or nearly) in a hollow in the interface. Before the drop can coalesce with its bulk phase, the thin film of liquid 2 trapped between them must be squeezed out, and become sufficiently thin that rupture can occur. This is the film drainage problem. Early calculations, based on simple lubrication theory, fail to take proper account of two effects which are investigated here and shown to be decisive. They are the circulation induced in the drop and in the lower bulk fluid, which tends to speed up drainage, and the constriction in the film thickness at its periphery, which tends to slow it down. This constriction has been observed and some existing theories have attempted to model it in an ad hoc manner. We give here a physical explanation and calculate the minimum thickness explicitly. The effect of circulation in the adjacent fluids is also calculated.

Fuzzy relations in a control setting

Abstract: This brief paper considers the various possible mathematical operations on fuzzy sets that are required to implement a set of control rules as a fuzzy logic control element. The influence that these operations have on the characteristics of the final control element is a factor that is used to select those operations most suitable in the control context.

The distance and nature of the light-trap response of moths

Abstract: LIGHT TRAPS of various forms have been used to collect and study moths for well over 100 yr, but surprisingly little is known about how they attract moths. There has been some evaluation of the factors influencing the size of light trap catches1–5 and of the mechanics of the terminal phase of the moth's approach to a light6, but virtually nothing is understood about the light-trap response itself. Such an understanding is perhaps unnecessary when light traps are used solely to collect specimens, but becomes crucial as soon as they are used for quantitative sampling or survey work7. Of particular importance to the interpretation of such work is a knowledge of the distance from which moths orientate with respect to a light source; it seems intuitively that this distance should be fairly large. We present here the results of three experiments designed to determine the distance of response of free-flying moths to an artificial light source. Our results support Sotthibandhu's claim4 that the effective range of a 125 W mercury vapour (MV) lamp is about 3 m. They also lead to speculation concerning the behavioural meaning of the light trap response in moths.

The thermodynamic properties of reciprocal solid solutions

Abstract: A multisite solid solution of the type (A, B) (X, Y) has the four possible components AX, AY, BX, BY. Taking the standard state to be the pure phase at the pressure and temperature of interest, the mixing of these components is shown not to be ideal unless the condition: $$\Delta G^0 = (\mu _{AX}^0 + \mu _{BY}^0 - \mu _{AY}^0 - \mu _{BX}^0 = 0$$ applies. Even for the case in which mixing on each of the individual sublattices is ideal, ΔG 0 contributes terms of the following form to the activity coefficients of the constituent components: $$RT\ln \gamma _{AX} = - X_{B_1 } X_{Y_2 } \Delta G^0$$ (X Ji refers to the atomic fraction of J on sublattice i). The above equation, which assumes complete disorder on (A, B) sites and on (X, Y) sites is extended to the general n-component case. Methods of combining the “cross-site” or reciprocal terms with non-ideal terms for each of the individual sites are also described. The reciprocal terms appear to be significant in many geologically important solid solutions, and clinopyroxene, garnet and spinel solid solutions are all used as examples. Finally, it is shown that the assumption of complete disorder only applies under the condition: $$\Delta G^0 \ll zn_1 RT$$ where z is the number of nearest-neighbour (X, Y) sites around A and n 1 is the number of (A, B) sites in the formula unit. If ΔG 0 is relatively large, then substantial short range oder must occur and the activity coefficient is given by (ignoring individual site terms): $$\gamma _{AX} = \left( {\frac{{1 - X'_{Y_2 } }}{{1 - X_{Y_2 } }}} \right)^{zn_1 }$$ where X′Y2 is the equilibrium atomic fraction of Y atoms surrounding A atoms in the structure. The ordered model may be developed for multicomponent solutions and individual site interactions added, but numerical methods are needed to solve the simultaneous equations involved.

Bone metastasizing renal tumor of childhood. Morphological and clinical features, and differences from Wilms' tumor

Abstract: A bone metastasizing primary renal tumor of childhood is described, and five cases are presented. Although all five cases were originally diagnosed as nephroblastomata, there appear to be sufficient histological, ultrastructural and clinical differences to suggest that these tumors should comprise a separate and distinct entity. Using the data from the Manchester Children's Tumor Registry, the incidence of this tumor was found to be 2.3% of all primary renal neoplasms in childhood. Cancer 42:1922–1928, 1978.

11—an energy method for calculations in fabric mechanics part i: principles of the method

Abstract: An energy method for calculations in fabric mechanics is described. The aim behind the development of this method was to find an approach that could be applied in a uniform manner to a variety of fabric structures and types of deformation. In the first part of the paper, the principle of the method is described for the simplest case: that in which the fabric structure acts only as a load-bearing mechanism, whose changes in internal energy during deformation are negligible compared with changes in potential energy due to externally applied loads. In the second part, the method is extended to include the effects of strain energy in the component fibres and yarns.

The tritocerebral commissure giant (TCG): A bimodal interneurone in the locust,Schistocerca gregaria

Abstract: A large interneurone responding to stimulation both by wind on the head and to light is described in the locust,Schistocerca gregaria. The neurone has been filled with cobalt and intensified with silver. Its cell body lies in the brain. There is a tuft of fine branches in the tritocerebrum which receives input from the primary sensory projections of the sensory hairs on the head. The neurone descends to the suboesophageal and thoracic ganglia via the tritocerebral commissure and branches extensively in each ganglion on the side contralateral to the projection in the brain. The response of the neurone to both stimulus modes has been recorded at the tritocerebral commissure.

Proton-Dependent Solute Transport in Microorganisms

Abstract: Publisher Summary This chapter deals with the proton–dependent solute transport in microorganisms. This chapter reviews some of the more important evidence currently available on several microbial systems in which ionic gradients appear to be implicated in the transport of amino acids, carbohydrates, and other nutrients such as phosphate, sulfate, and succinate. The evolution of solute pumps that concentrated their substrates extensively, by a mechanism that tends to multiply the external concentration by a constant factor, required the simultaneous development of a means for regulating the amount of substrate absorbed. Moreover, the control of the biosynthesis of the pumps themselves provides a coarse control, and further controls are required on the operation of the pumps. The existence of leak pathways outside the main pump appears to be one way in which pumping is regulated, and transinhibition also serves this purpose. Finally, the size of the pool of retained substrate may also be regulated by metabolic degradation and by its replenishment through biosynthesis.

Accommodation and color

Abstract: Previous studies of the effects of color on the accommodation response are reviewed. The monocular, steady-state response to targets under various colors of illumination is investigated. It is shown that trained observers change their level of accommodation, when viewing a target at a constant distance, to compensate for the varying ocular longitudinal chromatic aberration as the color of the target is changed. Untrained subjects, however, may initially show inconsistent responses. Results in white and greeen are closely comparable. Dynamic aspects of these effects are illustrated and it is shown that the ocular longitudinal chromatic aberration increases slightly with accommodation. The results are related to current ideas on the accommodative system.

The prolongation structure of a higher order Korteweg-de Vries equation

Abstract: We have used Wahlquist & Estabrook's prolongation method to construct a Lie algebra for the higher order Korteweg de Vries (K. de V.) equation ($q\_{4x}$ + $\alpha qq\_{2x}$ + $\beta q\_{x}^{2}$ + $\gamma q^{3})\_{x}$ + $q$$\_{t}$ = 0 with ($q$$\_{nx}$ $\equiv $ $\equiv \_{x}^{n}q$). This has a single soliton solution when $\beta $ = 30 - $\alpha $; $\gamma $ = 2$\alpha $. The only closure for the algebra we have found fixes $\alpha $ at $\alpha $ = 20 or $\alpha $ = 30. These two values are the only ones for which this equation has been found to have $N$-soliton solutions. The case $\alpha $ = 20 gives the standard Lax higher order K. de V. equation. The case $\alpha $ = 30 produces the equation of Caudrey, Dodd & Gibbon (1976): 0 = $q$$\_{t}$ + ($q$$\_{4x}$ + 30$qq\_{2x}$ + 60$q^{3}$)$\_{x}$, for which no known inverse method has been found until now. By finding a realization for the algebra we have constructed a 3 $\times $ 3 eigenvalue problem for this latter case which can be trasformed into the Lax formulation: $\tilde{L}$$\_{t}$ = [$\tilde{A}$, $\tilde{L}$].

Estimating Irreversible Supply Functions

Abstract: The question of specifying and estimating irreversible functions has arisen most frequently in the context of agricultural supply. Theoretical arguments in favor of an asymmetric response of output to rising and falling prices were advanced by Johnson. A number of authors have attempted to estimate such relationships (Hartman, Houck, Saylor, Tweeten and Quance 1969). In this paper, we argue that the general lack of success of these studies is the result of a misunderstanding of the nature of the supply irreversibility. An alternative method of segmenting the price series is proposed and an empirical example presented.

Relationship between response rate and reinforcement frequency in variable-interval schedules: II. Effect of the volume of sucrose reinforcement.

Abstract: Four rats were exposed to variable-interval schedules specifying a range of different reinforcement frequencies, using sucrose of two different concentrations and distilled water as the reinforcer. With sucrose, the rates of responding of all four rats were increasing negatively accelerated functions of reinforcement frequency, the data conforming closely to Herrnstein's equation; this was also true of the data from three of the four rats when distilled water was used as the reinforcer. The values of both constants in Herrnstein's equation were related to the sucrose concentration: the asymptotic response rate decreased, and the reinforcement frequency corresponding to the half-maximal response rate increased, with decreasing sucrose concentration.