Showing papers by "University of Manchester published in 1979"

A scaled version of the General Health Questionnaire

Abstract: This study reports the factor structure of the symptoms comprising the General Health Questionnaire when it is completed in a primary care setting. A shorter, 28-item GHQ is proposed consisting of 4 subscales: somatic symptoms, anxiety and insomnia, social dysfunction and severe depression. Preliminary data concerning the validity of these scales are presented, and the performance of the whole 28-item questionnaire as a screening test is evaluated. The factor structure of the symptomatology is found to be very similar for 3 independent sets of data.

0957 + 561 A, B: twin quasistellar objects or gravitational lens?

Abstract: 0957 + 561 A, B are two QSOs of mag 17 with 5.7 arc s separation at redshift 1.405. Their spectra leave little doubt that they are associated. Difficulties arise in describing them as two distinct objects and the possibility that they are two images of the same object formed by a gravitational lens is discussed.

An experimental study of Fe-Mg partitioning between garnet and olivine and its calibration as a geothermometer

Abstract: The partitioning of Fe and Mg between coexisting garnet and olivine has been studied at 30 kb pressure and temperatures of 900 ° to 1,400 °C. The results of both synthesis and reversal experiments demonstrate that K D (= (Fe/Mg)gt/(Fe/Mg)OI) is strongly dependent on Fe/Mg ratio and on the calcium content of the garnet. For example, at 1,000 °C/30 kb, K D varies from about 1.2 in very iron-rich compositions to 1.9 at the magnesium end of the series. Increasing the mole fraction of calcium in the garnet from 0 to 0.3 at 1,000 ° C increases K D in magnesian compositions from 1.9 to about 2.5. The observed temperature and composition dependence of K D has been formulated into an equation suitable for geothermometry by considering the solid solution properties of the olivine and garnet phases. It was found that, within experimental error, the simplest kind of nonideal solution model (Regular Solution) fits the experimental data adequately. The use of more complex models did not markedly improve the fit to the data, so the model with the least number of variables was adopted. Multiple linear regression of the experimental data (72 points) yielded, for the exchange reaction: 3Fe2SiO4+2Mg3Al2Si3O12 olivine garnet ⇌ 2Fe2Al2Si3O12+3Mg2SiO4 garnet olivine ΔH ° (30kb) of −10,750 cal and ΔS ° of −4.26 cal deg−1 mol−1. Absolute magnitudes of interaction parameters (W ij ) derived from the regression are subject to considerable uncertainty. The partition coefficient is, however, strongly dependent on the following differences between solution parameters and these differences are fairly well constrained: W FeMg ol -W FeMg gt ≃ 800 cal W CaMg gt -W CaFe gt ≃ 2,670 cal. The geothermometer is most sensitive in the temperature and composition regions where K D is substantially greater than 1. Thus, for example, peridotitic compositions at temperatures less than about 1,300 ° C should yield calculated temperatures within 60 °C of the true value. Iron rich compositions (at any temperature) and magnesian compositions at temperatures well above 1,300 °C could not be expected to yield accurate calculated temperatures. For a fixed K D the influence of pressure is to raise the calculated temperature by between 3 and 6 °C per kbar.

Determinants of the ability of general practitioners to detect psychiatric illness

Abstract: This study of psychiatric illness among 4098 patients attending 91 general practitioners compares 2 methods of case identification: 'conspicuous morbidity' by the doctor's own assessments, and 'probable prevalence' by the patients' responses to the General Health Questionnaire (GHQ). In general, the latter gives somewhat higher estimates than the former, but there are wide variations in morbidity between practices. The ability of each general practitioner to detect psychiatric illness was measured by computing Spearman's correlation coefficient between his assessments and the GHQ scores of his patients. The mean correlation coefficient was + 0.36, but the range was very wide (0.09-0.60). The first part of the study deals with various demographic characteristics of the patients themselves which are associated with an increased likelihood of the doctor detecting a psychiatric illness; such factors include unemployment, female sex, and marriages which have ended by separation, divorce or death. The second part of the study examines characteristics of the doctors themselves in an attempt to account for the wide variation between them in their ability to detect psychiatric illness. A research psychiatrist made detailed observations on 2098 interviews carried out by 55 general practitioners. Each doctor's verbal and non-verbal styles were recorded minutely, and in addition various global ratings were made. The doctors completed personality inventories and supplied details of training and professional background. It was possible to account for 67% of the variance of correlation coefficient mainly in terms of 2 dimensions: 'interest and concern' and 'conservatism'. The way in which the doctor interviews his patients is shown to be important, but there are interactions between interview style and the doctor's personality.

The Evolution of Bird Coloration

Abstract: The aims in this paper are first to review theories of the evolution of bird coloration and, in some cases, partly revise and extend them, secondly to analyse the coloration of all the birds of a given geographical region using multiple regression, and thirdly on the basis of this analysis to evaluate the various theories. Theories . There have been many discussions of the selective forces acting on the coloration of birds and we review the major proposals in some detail. The earliest suggestion (Darwin 1871) was that the bright coloration of many male birds originated through sexual selection by female choice of the most exotic variants in male plumage. A conflicting view (Hingston 1933) is that brightness has an intimidatory effect on opponents, and that bright male coloration arose through sexual selection but largely due to its advantages against other males in disputes concerning mating access to females. Bird coloration has also been considered in terms of predation (see, for example, Cott 1964 a ). Some birds with bright plumage patterns are known to be unpalatable compared to cryptic species, and certain other patterns have been interpreted as adaptations to confuse predators. Bright colours may commonly be favoured when an individual is anyhow obvious (e.g. through activity) and where it represents an 9unprofitable’ prey for a predator. This interpretation may be particularly relevant to lekking among polygamous males. A special case of unprofitable prey may be ‘perception advertisement’, where an animal signals (by flash patterns or alarm calls) that it has seen a predator (or opponent). It is also possible that bright coloration may serve to deflect predators away from the nest site; this requires in many ways conditions opposite to those for the unprofitable prey solution. Finally, bird colorations can act as a variety of social signals other than threat. Analysis . The coloration of the 516 species of birds that breed and/ or winter in the Western Palaearctic was analysed by multiple regression. Seven regions of a bird’s body plus two areas of flash coloration were recognized and scored for colour on a cryptic/conspicuous scale. Five different age/sex/season categories were recognized and scored separately for each species. These dependent variables were each analysed with respect to 17 independent variables that reflect different aspects of the reproductive biology and ecology of the birds. The advantages and disadvantages of multiple regression as an analytical technique are discussed. Results . The analysis identifies associations between the reproductive biology and ecology of the birds and the coloration of the different regions of the body of the different age/sex/season classes. Apparent exceptions to these associations are also identified and discussed. A relatively large proportion of the associations made sense in terms of the theories presented and usually there was a strong implication that for any specific association one theory was more relevant than any of the others. The results indicate that by far the most potent selective pressures to have shaped bird coloration are those related to predation risk. A number of the theories make use of predation risk, each in a different way, and for most of them some support can be gained for their involvement in the evolution of bird coloration. Of all the theories, however, it is the unprofitable prey model that seems to account for the major part of the variation in bird coloration. By contrast, no clear evidence for the involvement of sexual selection in the evolution of bird coloration could be found. Indeed, many associations, such as that between sexual dimorphism and polygamy, were more readily explicable in terms of selection pressures due to predation risk than of sexual pressures. The suggestion that bird coloration is shaped by predation rather than by sexual selection in no way prevents the coloration, as it evolves, being incorporated within the species and sex recognition system. Conclusions . It is concluded that bird coloration has evolved almost entirely in response to predation-based selective pressures. Although plumage and coloration are involved in species and sex recognition systems, they have not evolved in response to sexual selection pressures. In species that are sexually dimorphic, the male is not brightly coloured as a result of female choice or male: male competition but because he represents a less profitable prey to a predator than the females and juveniles. We predict that brightly coloured birds will most often be found to suffer less from predation than will comparable more cryptic birds (though one of the predation-risk theories does allow the converse to be true).

Pole assignment self-tuning regulator

Abstract: Existing self-tuning algorithms imply an optimal-control or -regulation objective. The paper describes a self-tuning technique which uses a classical pole-assignment method which is nonoptimal. The approach has the same `self-tuning' property as do optimal self-tuning regulators, but is fundamentally more robust. In particular, pole assignment can be applied to nonminimum-phase situations in which conventional self tuners will fail. This point is of great practical significance, since nonminumum-phase behaviour is commonly encountered in self-tuning applications. A second, but closely related, feature of the pole-assignment self tuner is its ability successfully to regulate systems with unknown, possibly varying, transport delays, in situations where other methods have great difficulty.

Unsaturated water flow within porous materials observed by NMR imaging

Abstract: Wetting, drying and permeation processes in various porous materials are of special interest to soil science and agriculture, building science and chemical engineering. Direct experimental study of unsaturated flow within such materials is hampered by the difficulty of detecting with precision changes in their internal water content distributions. In laboratory work on soils gravimetric sampling is widely used1. However, this is a destructive method which interferes with water flow processes and in any case is not easy to apply accurately to rigid materials such as permeable rocks, ceramics and building materials, γ-ray attenuation is the only established non-destructive instrumental method in laboratory use2,3. We report the first use of a nuclear magnetic resonance (NMR) imaging technique to monitor the dynamics of the internal water content distribution in several porous inorganic materials during capillary inflow.

The analysis of qualitative data

Abstract: But immediately a problem arises. Sociology is a pluralistic discipline, characterized by numerous alternative conceptions of theory, explanation and data, that is, by different sodological approaches (or perspectives or orientations or paradigms).* Each different approach has its own conception of what is qualitative about sodal data and what are the problems and possibilities for the analysis of qualitative data.

Ecological Aspects of Nitrogen Assimilation

Abstract: Publisher Summary Nitrogen assimilation has received considerable attention by plant physiologists in recent years, and this has resulted in a number of interesting and important discoveries. However, the majority of these investigations have been confined to crop plants and relatively little regard has been paid to ecological considerations. The growth of higher plants in many ecosystems is limited by nitrogen supply. Adaptation to low nitrogen availability presumably demands at least some modification of the assimilation processes shown by crop plants, if not different mechanisms of assimilation, and in many perennial species this is linked to the efficient conservation and recycling of nitrogen within the plant. Nitrogen is largely made available to plants through the activities of micro-organisms and because the soils may show marked seasonal variation in the supply and form of available nitrogen. Again this must demand specific adaptations by plants to utilize effectively the fluctuating supply. This chapter reviews the investigations performed on the nitrogen assimilation of crop plants with work in progress on ecological aspects of nitrogen metabolism. It also reviews the mass of information on the availability of nitrogen in different ecosystems and examines the variety of adaptations shown by plants to extremes of nitrogen supply.

Self-tuning pole/zero assignment regulators

Abstract: In this paper a class of self-tuning regulators is considered which combines a simple recursive least squares estimator with a pole/zero assignment design rule. Two such algorithms are shown to have the self-tuning property (i ) detuned minimum variance regulators ; (ii ) pole-asaignment regulators. The use of these regulators in self-tuning can be of considerable benefit. In particular, case (i ) is useful when minimum variance strategies need unrealistically high-loop gains, since they permit an engineering trade-off between optimality and practicality. Case (ii ) is of use in regulating non-minimum phase systems or systems involving unknown time delays. Such systems are frequently encountered in discrete time control and cannot be handled by direct minimum variance methods.

1,2-Dithiolene Complexes of Transition Metals

Abstract: Publisher Summary Over the past two decades there has been a phenomenal increase in the study of the chemistry of transition metal complexes containing sulfur ligands. There are a number of reasons for this, the major one being the revitalization of the chemistry of the unsaturated sulphur donor chelates. These were used as early as the 1930s as analytical reagents for various metals. The interest in complexes of these ligand systems now embraces areas ranging from purely academic syntheses to large-scale industrial production. Almost every available physical technique has been utilized for the elucidation of the molecular and electronic structures and the kinetics manifested in these systems. The spiraling interest in the complexes of sulfur donor ligands has prompted number of excellent and frequently exhaustive reviews. Other reasons for the expansion of the field of dithiochelate chemistry have undoubtedly included the correlations of model complexes with biological systems.

A Cybernetic Framework for Studying Occupational Stress

Abstract: In a report by the Joint Working Party of the Royal College of Physicians of London and the British Cardiac Society (1976), it was established that in 1975, coronary heart disease accounted for 52% of all deaths of men aged from 45 to 54, and 41% of those aged from 25 to 44. In contrast, in 1951, heart disease accounted for less than 20% of deaths in men aged from 45 to 49. This upward trend, in one of the major manifestations of stress-related illness in our society, is unmistakably continuing, which has created an enormous interest in research studying stress identification and prevention.

The relationships between plasma substrates and hormones and the severity of injury in 277 recently injured patients.

Abstract: 1. The plasma concentrations of glucose, lactate, amino acids, non-esterified fatty acids, glycerol, ketone bodies, ethanol, cortisol and insulin were measured in patients within a few hours of injury and before treatment. The severity of the injuries was assessed by the Injury Severity Score (ISS) method. 2. Plasma lactate and glucose concentrations both rose significantly with increasing ISS. 3. The concentrations of non-esterified fatty acids and glycerol were greater after moderate (ISS 7–12) than after minor (ISS 1–6) injuries. The glycerol concentrations were no higher and the non-esterified fatty acid concentrations were lower after severe (ISS > 12) than after moderate injuries. The concentrations of total ketone bodies tended to follow those of non-esterified fatty acids and there was a highly significant correlation between them. 4. The total concentration of amino acids was not affected by the severity of injury and there were no systematic changes in the concentrations of individual ones. 5. Plasma insulin concentrations were very variable and not related to severity. A weak correlation with the plasma glucose concentration seen after minor and moderate injuries was lost in the severely injured. 6. The plasma cortisol concentration was positively related to ISS up to ISS 12 but negatively so in the severely injured. 7. Factors such as age, sex and time after last meal were investigated. The most important factor modifying the response was intake of ethanol, which reduced the plasma concentrations of glucose, non-esterified fatty acids and alanine and raised that of lactate as well as the [β-hydroxybutyrate]/[acetoacetate] ratio.

The Evolution of Droplet Spectra and the Rate of Production of Embryonic Raindrops in Small Cumulus Clouds

Abstract: Calculations have been made of the evolution of droplet spectra within small cumulus clouds which are entraining undersaturated environmental air. The mixing process is assumed to be highly inhomogeneous. In the extreme situation considered, environmental air is entrained in discrete blobs or parcels, causing some droplets of all sizes to be completely removed from the condensate spectrum, while others do not change in size. This model, which is based on laboratory experiments, corresponds to a situation in which the time constant for droplet evaporation is small relative to that for turbulent mixing; in the classical (homogeneous) model, which has been used by other workers, the reverse applies. The calculations produce spectral shapes which agree well with those observed in cumulus by Warner (1969), and they indicate that favored droplets may grow very much faster through the condensate spectrum than is predicted classically.

Mass and energy transfer in multicomponent systems

Abstract: In this paper, which is essentially an interpretative review, we develop the theory of multicomponent mass transfer using the Bird, Stewart and Lightfoot approach to binary mass transfer as a consistent basis. Methods of solving the coupled diffusion equations are discussed and procedures for estimating interphase mass transfer coefficients considered. The developed formalisms are applied to a few examples in the areas of distillation, condensation and extraction to demonstrate the importance of considering coupled diffusion effects in multicomponent transfers.

Thermodynamics of water in cordierite and some petrologic consequences of cordierite as a hydrous phase

Abstract: The H2O content of cordierite is often regarded as incidental to its stability, probably because cordierite has substantial fields of stability at low pressures both in wet and dry experimental systems. In this paper we show that, in contrast, the molecular water content of cordierite has profound effects on many equilibria involving this phase. Mg-cordierite has been modelled as an ideal solid solution of the hydrous and anhydrous end-members Mg2Al4Si5O18·1.2H2O and Mg2Al4Si5O18 respectively. The H2O-solubility data of Mirwald and Schreyer (1977) fit this model within experimental uncertainty and yield 1 bar enthalpy and entropy changes for the reaction: $$\begin{gathered} Mg_2 Al_4 Si_5 O_{18} + 1.2H_2 O = Mg_2 Al_4 Si_5 O_{18} \cdot 1.2H_2 O \hfill \\ cordierite fluid codierite \hfill \\ \end{gathered} $$ of −12,300 cal and −32.87 cal/K. This implies that the partial molal entropy of H2O in cordierite at 298 K/l bar is almost exactly the same as the molar entropy of liquid water (16.9 cal/K as opposed to 16.7 cal/K) and that the interaction energy of liquid water with cordierite is only of the order of a few hundred calories per mole. Application of the model to the hydrous experiments of Fawcett and Yoder (1966) and Chernosky (1974) yields a value for ΔG f,298 0 of anhydrous Mgcordierite of between −2,062.71 and −2,074.21 Kcal per mole. This in in good agreement with the calorimetric data of Charlu, Newton and Kleppa (1975) which yield ΔG f,298 0 of −2,067.03±1.18 Kcal. Water pressure has a considerable influence on the (Mg, Fe) isopleths of coexisting cordierite and garnet, and hence, their use as geobarometric curves. Pressures estimated from the Mg/Fe ratios in the high-Mg range can vary by two kilobars or more, depending on the assumed $$P_{H_2 O} $$ , with highest estimates for $$P_{H_2 O} = P_{total} $$ . The stability field of the talc-kyanite “white-schist” assemblage (Schreyer, 1973) is found to expand appreciably as $$P_{H_2 O} $$ is lowered. Thus the minimum pressure required to form this assemblage can be considerably less than the 10 kb required under conditions of $$P_{H_2 O} = P_{total} $$ =P total, as anticipated by Schreyer (1977). The high partial molal entropy of H2O in cordierite results in small entropy changes coupled with large volume changes in dehydration reactions forming cordierite. This greatly influences the slopes and positions of univariant reactions involving cordierite. The stability of cordierite is promoted to higher pressures in H2O-bearing systems where none of the cordierite breakdown products is a hydrate. Cordierite-forming reactions from hydrates can have the H2O released on the relatively low-temperature sides of the reaction curves, an anomalous situation known only in zeolite stability curves. These considerations can have profound effects on model “petrogenetic grids” involving cordierite.

Biological particles of given size, shape, and density for use in biological reactors

Abstract: Novel biomass support particles containing growing cells have been developed for use in large-scale fermentation processes. The characteristic size of the entrapped biomass is identical to that of the physical structure of the support particle, and particles can be produced of any size, shape, and density with a wide variety of microorganisms. Use of the particles in fermentors leads to high biomass concentration independent of throughput, predetermined biomass concentrations, the use of novel types of fermentor with advantageous performance characteristics, possibilities for the optimization of advantageous diffusion effects, and new procedures for biomass recovery.