Showing papers by "University of Manchester published in 1982"

The serum transport of steroid hormones.

Abstract: Publisher Summary This chapter discusses the serum transport of steroid hormones Steroid hormones are extensively bound to plasma proteins including albumin, corticosteroid binding globulin (CBG), and sex hormone binding globulin (SHBG) Because of its high concentration, albumin binding is important in determining the magnitude of the nonprotein bound or free fraction of a steroid in plasma The generally accepted model of steroid hormone action suggests that free steroid (in equilibrium with circulating binding proteins) diffuses passively through target cell membranes and binds to a soluble intracellular receptor The steroid-receptor complex apparently moves into the nucleus where it modifies the chromatin transcriptional activity which results in, among other things, altered levels of protein synthesis CBG has been differentiated from the intracellular glucocorticoid and progesterone receptors by its inability to bind synthetic glucocorticoids and progestins

Making ends meet: a model for RNA splicing in fungal mitochondria

Abstract: On the basis of available nucleotide sequence and genetic data, we present a model for RNA splicing in fungal mitochondria. Seven intron RNAs of two fungal species can form identical secondary structures, involving four conserved sequences, which bring the ends of each intron together and allow an internal guide RNA sequence to pair with exon bases adjacent to the splice junctions. The splicing sites are thus aligned precisely within a conserved structure, which we suggest could present specific recognition signals to the proteins that catalyse the splicing reaction.

Selenium: toxicity and tolerance in higher plants

Abstract: Summary 1. Different plant species show considerable variation in their selenium content. Primary indicators, also termed selenium accumulators, many of which are members of the genus Astragalus, are highly tolerant of selenium; they are known to contain tissue levels of several thousand µg selenium/g. Secondary indicators, tolerant to low concentrations of the element, may absorb up to 1000 µg selenium/g. Non-accumulators are poisoned by selenium. 2. The toxicity of selenate (SeO4-) and selenite (SeO3-) to most plants can be attributed to a combination of three factors. Firstly, selenate and selenite are readily absorbed from the soil by roots and translocated to other parts of the plant. Secondly, metabolic reactions convert these anions into organic forms of selenium. Thirdly, the organic selenium metabolites, which act as analogues of essential sulphur compounds, interfere with cellular biochemical reactions. 3. Incorporation into proteins of the amino acid analogues selenocysteine and selenomethionine, in place of the equivalent sulphur amino acids, is considered to be the underlying cause of selenium toxicity. The physical and chemical differences between selenium and sulphur will result in small, but significant, changes in the biological properties of a selenium-substituted protein. 4. Selenium-tolerant accumulator plants differ in at least two respects from sensitive species. Large quantities of Se-methylselenocysteine and selenocystathionine, two non-protein selenoamino acids rarely detected in non-accumulators, have been isolated from the tissues of selenium accumulators. In addition, selenium is kept from entering proteins so that the selenium levels in proteins of accumulator plants is significantly lower than the levels in selenium-sensitive plants. 5. Exclusion of selenium from the proteins of accumulators is thought to be the basis of selenium tolerance. Discrimination against selenocysteine during protein synthesis seems to prevent incorporation of this selenoamino acid into proteins of accumulators. Furthermore, synthesis of Se-methylselenocysteine and selenocystathionine, which results in diversion of selenium away from the synthesis of selenomethionine, will restrict the amount of this compound available for protein synthesis. 6. Selenium accumulation among unrelated plant genera is a striking example of convergent evolution. The possibility that accumulation of this element is associated with a nutritional requirement for selenium, although explored in the past, is still in need of further clarification.

Skin thickness measurement by pulsed ultrasound; its reproducibility, validation and variability

Abstract: The reproducibility of the pulsed ultrasound technique for the determination of skin thickness was investigated, using two independent observers. No systematic difference was found and a high correlation was obtained. Studies were also undertaken to validate the pulsed ultrasound technique as a measure of true skin thickness. Skin thickness determined in vitro was found to be greater than when in vivo determinations were made by either the pulsed ultrasound or a xeroradiographic technique, probably due to the release of in vivo tension within the dermis after excision. Skin thickness was found to increase linearly with age up to the age of 20 years and to decrease linearly with age subsequently. Differences in skin thickness between the sexes and in different sites of the body were demonstrated.

Production of strontium-substituted lanthanum manganite perovskite powder by the amorphous citrate process

Abstract: The amorphous citrate process has been used to produce Mn2O3, Mn3O4, LaMnO3, SrMnO3 and strontium-substituted LaMnO3. The citrate-nitrate gels were dehydrated at 70‡ C to yield solid precursor materials. The decomposition/oxidation of the precursors have been studied using thermogravimetry and evolved gas analysis. The products of decomposition have been characterized by X-ray diffraction analysis, scanning electron microscopy and, in the case of the strontium-substituted LaMnO3, by analytical electron microscopy. The surface area and residual carbon content of the strontium-substituted LaMnO3 have been determined as a function of the decomposition/oxidation temperature. Both the process yield and compositional homogeneity of the strontium-substituted LaMnO3 have been shown to increase as the decomposition temperature increases. The residual carbon content has been shown to decrease as decomposition temperature increases. However, the surface areas of the powders decrease significantly as decomposition temperature increases. Consequently, it is evident that there is a conflict in the experimental conditions required for optimum yield, homogeneity and residual carbon content compared to those required for maximum surface area.

The wave forces acting on a floating hemisphere undergoing forced periodic oscillations

Abstract: The object of this paper is to derive the added mass and damping coefficients associated with the periodic motions of a floating hemisphere. Two physically distinct cases are considered; namely those of heave and surge, where these nautical terms refer respectively to a vertical or horizontal oscillation of the body. Computations have been done and the values found for the various force coefficients are presented in tabulated form. A brief derivation of the long- and short-wave asymptotics of these coefficients has also been included.

Accessible Independence Results for Peano Arithmetic

Abstract: Recently some interesting first-order statements independent of Peano Arithmetic (P) have been found. Here we present perhaps the first which is, in an informal sense, purely number-theoretic in character (as opposed to metamathematical or combinatorial). The methods used to prove it, however, are combinatorial. We also give another independence result (unashamedly combinatorial in character) proved by the same methods.

The drag-out problem in film coating theory

Abstract: An important step towards the understanding of many industrial coating processes is a solution of the dragout problem, which is to determine the thickness of the film of liquid which clings to a plate when it is drawn steadily out of a bath of the liquid. An approximate solution, valid for small capillary numbers, was given by Landau and Levich, and considerable effort has been exerted to extend or refine this work. In this paper we show that the Landau-Levich result is an asymptotic solution valid as the capillary number tends to zero, a fact not properly appreciated hitherto, and show how correction terms may be obtained by the method of matched expansions. We also show how the results may be applied to the coating of a horizontal roller.

Is the Universe rotating

Abstract: From the study of the position angles and polarization of high luminosity classical-double radio sources, it appears that the difference between the position angles of elongation and of polarization are highly organized, being generally positive in one half of the sky and negative in the other. The effect was first noticed amongst a sample of 94 3CR sources and later confirmed in three independent samples. Such a phenomenon can only have a physical explanation on a cosmic scale; an attractive theory is that it demonstrates the existence of a universal vorticity, that is, that the Universe is rotating with an angular velocity ∼10−13 rad yr−1. This would have drastic cosmological consequences, since it would violate Mach's principle1,2 and the widely held assumption of large-scale isotropy.

The morphology, crystallography, and chemistry of phases in as-cast nickel-aluminum bronze

Abstract: The morphology, crystallography, and composition of the phases present in as-cast nickel-aluminum bronze of nominal composition copper-10 wt pct aluminum-5 wt pct nickel-5 wt pct iron have been investigated using optical, electron optical, and microprobe analysis techniques. The as-cast microstructure consists of copper-rich α, martensitic β, and κ-phases based on Fe3Al and NiAl. The κz precipitates have a dendritic morphology and are cored; the composition ranges from iron-rich solid solution to Fe3Al. The κII and κiv precipitates have, respectively, a dendritic and an equiaxed/dendritic morphology, and are based on Fe3Al, while κIII is a eutectoidal decomposition product of lamellar or globular morphology based on NiAl. The κI, κII, and κIII precipitates have the Kurdjumov-Sachs orientation relationship with α matrix. Small κIV precipitates exhibit the Nishiyama-Wasserman orientation relationship with the α matrix, while large κiv precipitates have an orientation relationship which lies between Kurdjumov-Sachs and Nishiyama-Wasserman.

Mechanisms of solute transport in selected eukaryotic micro-organisms.

Abstract: Publisher Summary This chapter considers the chemiosmotic interpretation of the synthesis of ATP, which takes place in the mitochondria and chloroplasts of eukaryotic micro-organisms The evidence that is available indicates that the ionic pumps of the plasma membranes of these organisms are not involved in ATP synthesis Thus the plasma membrane of yeast lacks a typical electron-transport chain, resembling in this respect the plasma membrane of anaerobic organisms such as Streptococcus faecalis rather than the plasma membrane of facultative aerobes like Escherichia coli, which carry out oxidative phosphorylation It discusses that a further comparison concerns the extensively studied transport systems of mammalian cells, which include the sodium pump based on a Na/K-ATPase A wide range of such cells involve Na + ions in secondary active transport of various carbohydrates and amino acids Similar coupled mechanisms are found in certain bacteria Their occasional occurrences in eukaryotic microorganisms are also considered in this chapter

Serum concentrations of total and non-protein-bound oestradiol in patients with breast cancer and in normal controls.

Abstract: In premenopausal women with breast cancer, total serum oestradiol (E2) concentrations are normal but nonprotein-bound E2 concentration are significantly raised This is not due to low sex-hormone-binding-globulin (SHBG) binding capacities which are within the normal range and is unlikely to be due to the small but significant decrease in albumin concentrations In post-menopausal patients, both total and non-protein-bound E2 are significantly raised: this may be explained partially by lower SHBG binding capacities In patients and controls there is a highly significant correlation between non-protein-bound E2 and SHBG but, for a given SHBG binding capacity, the patients have more non-bound E2 than controls It is concluded that the breast in women with breast cancer may be exposed to elevated levels of biologically active E2 although the reasons for this remain obscure

Modelling the joint determination of household labour supplies and commodity demands

Abstract: In addition to choosing the allocation of total expenditure between commodities, households may also be able to make decisions over the allocation of their time between market work and leisure. In both theoretical and empirical work it has often been the case that these decisions have been analysed separately. In this paper we stress the theoretical attractions of considering the joint determination of the allocation of time between work and leisure and the allocation of total expenditure between commodities in a utility maximising framework. Using a sample of individual households we attempt to evaluate the empirical importance of the joint determination model over the separate determination of labour supplies and commodity demands. Our approach follows that of Abbott and Ashenfelter (I976), Phlips (I978), Barnett (I979), Deaton and Muellbauer (I980), and Atkinson and Stern (I980). Here we pay particular attention to the following four important aspects of household decision-making over commodity demand and labour supply. The first concerns the commonly assumed restriction on the household's preferences of (weak) separability between goods and leisure. This assumption allows the estimation of commodity demand systems and Engel curves that exclude wage-rate variables. In cross-section household budget data with large variation in wage rates across the sample the invalidity of this assumption would involve a serious mis-specification. Any correlation between the excluded wage variable and the included price, income and demographic variables would lead to biased parameter estimates and hence biased estimated elasticities. Similarly, this assumption allows the estimation of labour supply curves that exclude relative price variables and its invalidity could produce biased labour supply elasticities. A second aspect of household decision-making which we wish to highlight arises from the suspicion, commonly alluded to in labour economics texts, that primary male workers may not be free to choose their hours of work. Thus we estimate a matched pair of rationed and unrationed systems following the work of Neary and Roberts (i 980) and Deaton and Muellbauer (I 979). The separability restriction is not unrelated to this point, since without it we will see that the rationed hours of work enter demand systems in a complex fashion. In effect,

A Practical Data Flow Computer

Abstract: Based on a tagged dynamic data flow model, this prototype machine has eight unusual matching functions for handling incoming data tokens at its computational nodes. 10 references.

The social implications of embarrassment displays and restitution behavior

Abstract: The present study examines the evaluative consequences of two kinds of reaction to committing a social transgression. In an experimental study, embarrassment display and restitution behaviour were manipulated orthogonally in the context of a videotaped incident in which an actor was seen to upset a sales display in a store. Subjects were shown one of the four versions of this incident and asked to rate the actor responsible for the mishap. It was reasoned that both appearing embarrassed and engaging in restitution would have positive, but distinct, effects on social evaluation, and that the beneficial effect of restitution would be mitigated by embarrassment display. Results were consistent with these expectations. Discussion focuses on the implications of these findings for the social function of embarrassment displays.

Matching since Baum (1979).

Abstract: Data from recent studies employing concurrent variable-interval schedules are reviewed. Subject species employed in different experiments have included rats, pigeons, and humans, and reinforcers have varied from food and shock avoidance to points exchangeable for money. Undermatching (a greater preference for the schedule of the concurrent pair that delivers the lower rate of reinforcement than the Matching Law predicts) has been preponderant in recent studies, irrespective of whether behavior has been measured in terms of response ratios or time allocation, with the possible exception of data produced by human subjects. Little difference in the degree of undermatching exhibited by response and time measures has been found, except in the results from a single laboratory, in which time-allocation measures have tended to undermatch less than response measures. Procedural features, such as type of manipulandum used and changeover delay, seem to have little effect on the degree of undermatching exhibited, but asymmetrical response manipulanda (such as lever and key) for the different concurrent schedules, or other asymmetries in the experimental situation, show up clearly in bias measures, in a manner consistent with previous analyses.

The Type Theoretic Interpretation of Constructive Set Theory: Choice Principles

Abstract: In an earlier paper I gave an interpretation of a system CZF of constructive set theory within an extension of Martin-Lof's intuitionistic theory of types. In this paper some additional axioms, each a consequence of the axiom of choice, are shown to hold in the interpretation. The mathematical deductions are presented in an informal, but I hope rigorous style.

Optimality and efficiency

Abstract: Given a set of alternatives, X and a set of value, or utility, functions, V , on X , contemporary work in the Decision Theory field deals with the reduction of X to some acceptable subset Y . This paper deals with the various ways in which this may be done, more specifically with the optimal set, M ( X , V ), the efficient set E ( X , V ) and efficient sets ϵ ( X , f ), ϵ ( X , f ), ϵ ( X , f ), when the value of an alternative can be expressed in terms of a multi-objective vector f on X . Relationships between these various sets are explained. The importance of the differences and similarities is seen to depend on the nature of the circumstances faced by the decision analyst at each stage of the evolutionary process of analysis, and upon their use for computational purposes. Some contemporary work (e.g. portfolio analysis) is examined within this framework.

Work sample tests: Validity, adverse impact and applicant reaction

Abstract: Work sample tests are assigned to one of four categories: (i) psychomotor, (ii) individual, situational decision making, (iii) job-related information and (iv) group discussion/decision making. Validity data drawn from over 60 studies are presented and show that psychomotor work sample tests and group discussions predict job performance relatively well when compared with more conventional forms of psychological testing, such as intelligence or personality tests. Data showing other validity relationships are presented, and the importance of point-to-point correspondence between predictors and criteria is discussed. Research on the adverse impact of work sample tests and the applicant reaction to such tests is reviewed and suggests that the tests may help to reduce adverse impact and produce positive reactions from candidates.

Tempering of 2.25 Pct Cr-1 Pct Mo Low Carbon Steels

Abstract: The effect of carbon level on the tempering behavior at 700°C of 2.25 pct Cr-1 pct Mo steels having typical weld metal compositions has been investigated using analytical electron microscopy and X-ray diffraction techniques. The morphology, crystallography and chemistry, of each of the various types of carbides observed, has been established. It has been shown that each carbide type can be readily identified in terms of the relative heights of the EPMA spectra peaks for iron, chromium, molybdenum, and silicon. A decrease in the carbon level of the steel increases the rate at which the carbide precipitation reactions proceed, and also influences the final product. Of the carbides detected, M23C6 and M7C3 were found to be chromium-based, and their compositions were independent of both the carbon level of the steel and the tempering time. The molybdenum-based carbides, M2C and M6C, however, showed an increase in their molybdenum contents as the tempering time was increased. The rate of this increase became greater as the carbon content of the steel was lowered.