Showing papers by "University of Sheffield published in 1993"

A Survey of the Nature and Extent of Bullying in Junior/Middle and Secondary Schools.

Abstract: Summary As part of a survey service developed to assess bullying in schools, anonymous questionnaires were given to over 6,000 pupils in 17 junior/middle and seven secondary schools in the Sheffield LEA. The results are analysed in terms of frequencies of being bullied, and bullying others; year differences; gender differences; types of bullying; where bullying occurs; whether teachers and parents are informed; and attitudes to bullying. Rates of reported bullying are disturbingly high; they vary with year, gender and school location, partly as a result of opportunities for bullying. With the addition of data from six other schools, it was found that school size, class size and ethnic mix were not linked with bullying. Social disadvantage is linked with bullying to a small extent, and schools with high bullying rates also tend to have pupils who dislike, or are alone at, playtime. Implications for intervention against bullying are briefly discussed.

Testing the validity of the Euroqol and comparing it with the SF-36 health survey questionnaire.

Abstract: There is an interest in the consequences of deriving a single index measure of health for validity and sensitivity. This paper presents the results of testing a recent example of a general health measure designed to derive a single index, the Euroqol (EQ), and presents a comparison with a new, influential profile measure, the Short Form 36 (SF-36) Health Survey Instrument. The EQ and an anglicised version of the SF-36 health survey, both designed for self-completion, were included in a postal survey of a random sample of 1980 patients from two practice lists in Sheffield, UK. The response rate for the EQ questionnaire was 83%, and the rate of completion over 95%. Evidence was found for the construct validity of the EQ dimension responses and the derived total EQ health score in terms of distinguishing between groups with expected health differences. Considerable agreement was found between EQ responses and the total EQ score, and the UK SF-36 profile scores. There was substantial evidence of EQ being less sensitive at the ceiling (i.e. low levels of perceived ill-health) and throughout the range of health states. A recent restructuring of the EQ, may help overcome some of the problems with the physical dimensions by reducing their skewness.

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. III. Effect of stator slotting

Abstract: For pt.II see ibid., vol.29, no.1, p.136-142 (1993). A method for modeling the effect of stator slotting on the magnetic field distribution in the airgap/magnet region of a radial-field brushless permanent-magnet DC motor equipped with a surface-mounted magnet rotor is presented to allow the analytical prediction of the open-circuit, armature-reaction, and consultant magnetic field distribution under any specified load condition. It is shown that the conventional 1D relative permeance model, which is used extensively in the analysis of induction and synchronous machines, is inappropriate for permanent magnet motors, for which the proposed analytical method accounts for stator slot openings by the application of the conformal transformation method and a 2-D relative permanence function. The results of predictions from the analysis are compared with corresponding finite element analyses. >

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. I. Open-circuit field

Abstract: An analytical technique for predicting the instantaneous magnetic field distribution in the airgap region of radial-field topologies of brushless permanent-magnet DC motors, under any specified load condition and accounting implicitly for the stator winding current waveform and the effect of stator-slot-openings, has been developed. It is based on the superposition of the component fields due to the permanent magnet and the stator excitation. A 2D analytical method for predicting the open-circuit airgap field distribution in both internal and external rotor radial-field motor topologies is presented. It involves the solution of the governing field equations in polar coordinates in the annular airgap/magnet region of a multipole slotless motor in which the magnets are assumed to have uniform radial magnetization and a constant relative recoil permeability. Results for various radial-field motors are compared with predictions from corresponding finite element analyses. >

A comparison of the information seeking patterns of researchers in the physical and social sciences

Abstract: The information seeking patterns of a group of research physicists and research chemists were analysed and the key features of those patterns identified. The aim was to use a similar methodology to that employed in a previous study of the information seeking activities of a group of social scientists and to effect a comparison between the information seeking patterns of the scientists and the social scientists. The information seeking patterns were derived from interviews with physicists at Manchester University and chemists at the University of Sheffield. The methodology adopted for the interviews and analysis was qualitative and based on the grounded theory approach. The results were then compared with the findings of the previous study of the social scientists to try and identify similarities and differences between the two groups. Certain minor variations concerned with awareness levels of facilities, the extent of usage of a source and the research stage at which a strategy may be employed were identified. Nonetheless, fundamental differences in information seeking behaviour could not be determined. Finally, the extent to which developments in electronic communication have had any impact on the information or communication patterns of the scientists and social scientists is considered.

Evidence of a feedback mechanism limiting plant response to elevated carbon dioxide

Abstract: IN short-term experiments under productive laboratory conditions, native herbaceous plants differ widely in their potential to achieve higher yields at elevated concentrations of atmospheric carbon dioxide1–8. The most responsive species appear to be large fast-growing perennials of recently disturbed fertile soils7,8. These types of plants are currently increasing in abundance9 but it is not known whether this is an effect of rising carbon dioxide or is due to other factors. Doubts concerning the potential of natural vegetation for sustained response to rising carbon dioxide have arisen from experiments on infertile soils, where the stimulus to growth was curtailed by mineral nutrient limitations2,3,10. Here we present evidence that mineral nutrient constraints on the fertilizer effect of elevated carbon dioxide can also occur on fertile soil and in the earliest stages of secondary succession. Our data indicate that there may be a feedback mechanism in which elevated carbon dioxide causes an increase in substrate release into the rhizosphere by non-mycorrhizal plants, leading to mineral nutrient sequestration by the expanded microflora and a consequent nutritional limitation on plant growth.

The assessment of vertebral deformity: a method for use in population studies and clinical trials

Abstract: The absence of specific criteria for the definition of vertebral fracture has major implications for assessing the apparent prevalence and incidence of vertebral deformity. Also, little is known of the effect of using different criteria for new vertebral fractures in clinical studies. We therefore developed radiological criteria for vertebral fracture in women for assessing both the prevalence and the incidence of vertebral osteoporosis in population and in prospective studies and compared these with several other published methods. Normal ranges for vertebral shape were obtained from radiographs in 100 women aged 45-50 years. These included ranges for the ratios of anterior/posterior, central/posterior and posterior/predicted posterior vertebral heights from T4 to L5. The predicted posterior height was calculated from adjacent vertebrae. In contrast to other methods, our definition of fracture required the fulfillment of two criteria at each vertebral site, and was associated with a lower apparent prevalence of fracture in the control women due to a lower false positive rate. The prevalence and incidence of vertebral deformity using different criteria were then compared in a series of women with skeletal metastases from breast cancer in whom radiographs were obtained 6 months apart. The prevalence of vertebral deformity and the specificity for deformity varied markedly with differing criteria. Using a cut-off of 3 standard deviations the prevalence of vertebral deformity in the women with breast cancer was 46%. Using other methods, the prevalences of deformity ranged from 33% to 74%. Over a 6-month interval 25% of patients with breast cancer sustained 61 deformities using our method, of which only 8% resulted from errors in reproducibility. The number of patients sustaining new deformities was increased twofold when assessed by other methods (45%-53%), but errors of reproducibility may have accounted for 21% of the new deformities. The magnitude and distribution of these errors have important implications for the apparent therapeutic efficacy of agents in clinical trials of osteoporosis. The rapid semi-automated technique for assessing vertebral deformities on lateral spine radiographs that we have developed has a high specificity, and reduces the impact of errors of reproducibility on estimates of prevalence and incidence. The method should prove a value in assessing vertebral deformity both in population studies and in prospective clinical trials.

Mega-scale glacial lineations and cross-cutting ice-flow landforms

Abstract: Landsat images reveal a previously unsuspected large-scale pattern of streamlining within drift that is assumed to reflect former phases of ice flow. Such a glacial grain can be regarded as a landform assemblage comprised of a number of components. Drumlins and megaflutes form part of the pattern, but in addition there are two previously undocumented ice-moulded landform elements: streamlined lineations of much greater proportions, referred to as mega-scale glacial lineations, and a distinctive cross-cutting topology within the grain. The ice-moulded landform assemblage is described and illustrated with reference to examples from Canada. Possible modes of genesis of such landforms are discussed and their glaciological implications outlined. The discovery of this pattern indicates the pervasive nature of subglacial deformation of sediment, and demands a radical re-interpretation of ice sheet dynamics.

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. II. Armature-reaction field

Abstract: For pt.I see ibid., vol.29, no.1, p.124-135 (1993). An analytical technique for predicting the open-circuit magnetic field distribution in the airgap/magnet region of a brushless permanent-magnet DC motor equipped with a surface mounted magnet rotor and a slotless stator was presented in Pt.I. In the present work, the analysis is extended to the prediction of the armature reaction field produced by the three-phase stator windings. As before, th motor model is formulated in polar coordinates and accounts for the large effective airgap, but it is not developed further to consider the effect of winding current harmonics on the airgap field distribution. Predicted instantaneous armature reaction field distributions are validated by a comparison with corresponding finite element calculations. >

Sexual selection and the temporal separation of reproductive events: sperm storage data from reptiles, birds and mammals

Abstract: The duration of sperm storage by females differs markedly between reptiles (maximum: 2555 d [7 years] and birds (maximum: 117 d), with mammals showing both very short (

Nonlinear rheology of wormlike micelles

Abstract: Certain viscoelastic surfactant solutions show unusual nonlinear rheology: In steady shear, the shear stress saturates to a constant value while the first normal stess increases roughly linearly with shear rate over several decades. Here we explain this behavior in terms of the ``reptation-reaction'' model for the dynamics of reversibly breakable, polymerlike micelles. The constitutive equation for this model leads to a flow instability of shear-banding type. The limiting shear stress is predicted to be ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$=0.67${\mathit{G}}_{0}$ (with ${\mathit{G}}_{0}$ the plateau modulus), in quantitative agreement with experiment.

The dissipation of excess excitation energy in British plant species

Abstract: The reversible dissipation of excitation energy in higher plants is believed to protect against light-induced damage to the photosynthetic apparatus. This dissipation is measured as the non-photochemical quenching of chlorophyll fluorescence. A method is described whereby the saturated capacity for rapidly reversible non-photochemical quenching can be compared between plant species. This method was applied to 22 common British plant species whose habitat was quantified using an index that describes shade tolerance. An association was found between occurrence in open habitats and a high capacity for non-photochemical quenching. It was found that, whilst this capacity was species dependent, it did not depend upon the conditions under which the plant was grown. The possible role of zeaxanthin as a determinant of quenching capacity was examined by measuring the contents of xanthophyll cycle carotenoids for each species. Comparing species, no correlation was seen between the saturated level of non-photochemical quenching and zeaxanthin content expressed relative to either total carotenoid or to chlorophyll. When zeaxanthin was expressed relative to the amount of xanthophyll cycle intermediates (zeaxanthin, antheraxanthin and violaxanthin), a weak correlation was seen.

‘Classical’ and ‘non-classical’ reproductive steroids in fish

Abstract: The nature of the steroids secreted by gonads of fish differs significantly from those of the mammals. The ‘classical teleost steroids’, oestradiol, testosterone, 11-ketotestosterone and 17,20βP, have been measured in a wide variety of teleosts but do not always reflect biological activities. There is increasing evidence that teleost gonads may produce a number of ‘non-classical steroids’ which may play an important role in their reproductive biology. Such products include metabolites reduced at C5 to 5α or 5β, at C3 to 3α or 3β, or hydroxylated at 6-, 7-, or 21. Conjugation, as either glucuronides or sulphates, may contribute either to localization of action within the gonad or to production of pheromones during the immediate pre-spawning period. Although it is often possible only to measure the steroids for which assays are readily available, it is important to recognize that there may be production of steroids that are not detected by such assays, but which nevertheless play a major role in reproductive activity. In evolutionary terms, the teleost hydroxylases probably originated in the very early fishes and show parallels with their analogues in amphibians and mammals. Gene sequencing may reveal a possible common ancestor for all vertebrate 6, 7 and 11-hydroxylases.

Anastomosis and the continuum of channel pattern

Abstract: Anastomosing rivers are characterized by multiple channels separated by islands excised from the floodplain. Their status relative to the continuum concept of channel pattern is assessed with channel pattern defined in terms of three variables—flow strength, bank erodibility and relative sediment supply. Using an ordinal scaling (L(ow)–M(oderate)–H(igh)), the traditional forms of straight, meandering and braided have respective representations of (L,L,L), (M,L/M,L/M) and (H,H,M/H) in terms of those variables. The anastomosing pattern is on average represented by (L,L,M/H) but not so definitively as other forms. Specification of the third element (sediment supply) is particularly hampered by the paucity of data but aggradation, a characteristic of many anastomosing rivers, can be thought of as symptomatic of a moderately high rate of supply relative to the ability for onward transport. A sufficiently high rate of supply to a channel with low flow strength and resistant banks would induce shoaling and/or lateral constriction that locally forces flow out of the main channel and ultimately leads to the cutting of anabranches. A flow regime characterized by concentrated floods of relatively large magnitude is also regarded as highly conducive to the formation of new channels where low bank erodibility constrains channel capacity. Anastomosis may in certain cases represent a transitional form of channel pattern but there is no denying the longevity of some anastomosing systems.

Oxygen, free radical processes and seed longevity

Abstract: The origin and significance of free radicals is described in the broad setting of animal and plant biology and in the specific context of seeds and seed viability. Evidence is given that free radicals play a central if not causal role in promoting molecular damage under the widest range of environmental stresses and induced ageing in mature plant tissuesIn ungerminated seeds, the evidence is less certain. The reason, we argue, is that many attempts to measure free radical processes in seeds are set not against gradients of damage or ageing (as they are in most other biological tissues) but against one of only two options, either seed germinability or mortality. Because free radical reactions differ quantitatively and qualitatively in living and dead tissues attempts to correlate radicalmediated damage with the viability of a population of seeds may be unreliable particularly when measurements are made at uncertain intervals after death. Despite this, the evidence that seeds, uniquely, are exempt from the ravages of oxygen assault is weak. Instead it ismore probable that oxygen plays a central role in seed mortality and may have significance in the evolution of seed persistence.

Modelling Auditory Processing and Organisation

Abstract: Acknowledgments 1. Introduction 2. The auditory periphery: physiology, function and a computer model 3. Auditory representations 4. Modelling auditory scene exploration 5. Implementation of auditory grouping principles 6. An evaluation of sound source separation in the model 7. Conclusions and further development Appendices Bibliography Index.

Pre- and postmortem influences on brain RNA

Abstract: Many potentially valuable techniques for the understanding of human neurobiological and neuropathological processes require the use of RNA obtained from postmortem tissue. As with earlier neurochemical studies, there are two particular problems posed by such tissue in comparison with tissue from experimental animals. These are the postmortem interval and the condition of the patient prior to death, referred to as the agonal state. We review the nature and extent of the effects of postmortem interval and agonal state on RNA in brain tissue, with particular reference to the study of neuropsychiatric disorders. Perhaps surprisingly, postmortem interval has at most a modest effect on RNA. Abundant intact and biologically active RNA is present in tissue frozen 36 h or more after death. Postmortem interval does not account for the marked variability observed among human brains in all RNA parameters. Despite the overall stability of RNA after death, some evidence suggests that individual RNAs may undergo postmortem decay. Less attention has been paid to the effects of agonal state. The existing data indicate that events in the premortem period such as hypoxia and coma can affect the amount of some messenger RNAs. The nature of agonal state influences depends on the messenger RNA in question, though the basis for this selective vulnerability is unknown. No agonal state effect on overall RNA level or activity has been found. The data show that postmortem brain tissue can be used for RNA research. However, considerable attention must be paid to controlling for the influences of pre- and postmortem factors, especially when quantitative analyses are performed.

Postmodernism, sociology and health

Abstract: Part 1 Power and inscription: inscribing the body organizing health. Part 2 Repetitions and resistance: repetition, desire and professional care resistance and the gift. Part 3 Difference and engagement: the politics of arche-health deterritorializing health and illness.

A path-independent parameter for fatigue under proportional and non-proportional loading

Abstract: -A path-independent multiaxial fatigue damage criterion is proposed based on critical plane concepts: fatigue crack growth is controlled by the maximum shear strain, and an important secondary effect is due to the normal strain excursion over one reversal of the maximum shear strain. The effect of loading path on fatigue endurance is quantified by the normal strain excursion. Only one multiaxial material constant is required in the model which can be determined from uniaxial test data plus one torsional result. The parameter can be easily integrated with a shear strain-life relationship to predict low cycle fatigue lifetime. Experimental data of four different materials: En1 5R steel, I% Cr-Mo-V steel, 304 stainless steel, and 316 stainless steel at two temperatures were used to verify the criterion. It is shown that the proposed parameter can satisfactorily correlate test results for various proportional and non-proportional straining paths. NOMENCLATURE

Identity of viridans streptococci isolated from cases of infective endocarditis

Abstract: Summary The oral streptococci have undergone considerable taxonomic revision in recent years but there is still little information concerning associations between the newly defined species and disease. This study examined the identities of 47 strains of oral streptococci collected from 42 confirmed cases of infective endocarditis. By means of recently described physiological schemes, the most common species identified were Streptococcus sanguis sensu stricto (31·9%), S. oralis (29·8%) and S. gordonii (12·7%). Other related species including S. mitis and “S. parasanguis” were less common. This indicates that attention should be focused on S. sanguis sensu stricto and S. oralis when considering possible pathogenic mechanisms involved in viridans streptococcal endocarditis.

Development of the PID controller

Abstract: In 1939, the Taylor Instrument Companies introduced a completely redesigned version of its Fulscope pneumatic controller. In addition to proportional and reset control actions, this new instrument provided an action which the Taylor Instrument Companies called pre-act. In the same year the Foxboro Instrument Company added Hyper-reset to the proportional and reset control actions provided by their Stabilog pneumatic controller. The pre-act and Hyper-reset actions each provide a control action proportional to the derivative of the error signal. Reset provides a control action proportional to the integral of the error signal and hence both controllers offered PID control. The historical development of these controllers is discussed. >

Female control of paternity.

Abstract: Of the two components of sexual selection, female choice is much less obvious than male—male competition, and hence has always been considered to be of secondary importance. However, recent field observations and new theory have brought about a radical change of emphasis. It now appears that although a female's choice of who fathers her offspring often occurs in a subtle manner, it may be widespread and take place through a variety of behavioural and physiological mechanisms, including the manipulation of male behaviour and the selection of sperm within the female reproductive tract.

A multicenter study of overdentures supported by Brånemark implants.

Abstract: Nine clinical centers participated in a prospective study of overdentures supported by Branemark implants in the maxilla or mandible. The study initially comprised 133 patients provided with 117 implants placed in the maxilla and 393 implants placed in the mandible. The preliminary results indicate a success rate in the mandible comparable with the reports on fixed prostheses. Conversely, overdenture treatment in the maxilla seems to be less favorable than previous reports of fixed restorations. The differences between the fixed and the present overdentures in the maxilla were mainly based on differences in patient selection and bone quality. A total of 32 implants was mobile and removed and another 29 implants were lost to follow-up because of patient dropout up to the first annual checkup after denture placement. A higher implant failure rate occurred in the maxilla. Mucosal reactions were also more unfavorable around implants placed in the maxilla.

Bully/Victim Problems Among Middle School Children

Abstract: Following the innovative research by Olweus (1978), there has been a growing concern among educators and researchers with bully-victim problems during childhood. Bullying, as a class of behaviors, can be conceptualized in a number of different ways. In this article, we agree with the way it is viewed by Smith and Thompson (1991). They stated, "bullying … can be taken to be a subset of aggressive behavior. As with aggressive behavior generally, bullying intentionally causes hurt to the recipient. This hurt can be both physical or psychological" (p. 1). In addition, they stated that three further criteria particularly distinguish bullying—that it is unprovoked, that it occurs repeatedly, and that the bully is stronger than the victim or is perceived to be stronger. Quantitative data on the extent of such problems in various European countries and elsewhere are disturbing. For example, Olweus (1987) developed an anonymous questionnaire, and in an extensive study involving 140,000 Norwegian students aged betw...

Instantaneous magnetic field distribution in permanent magnet brushless DC motors. IV. Magnetic field on load

Abstract: For pt.III see ibid., vol.29, no.1, p.143-151 (1993). An analytical technique is developed for predicting the instantaneous magnetic field distribution in the airgap-permanent magnet region of radial-field topologies of brushless DC motors equipped with a surface-mounted magnet rotor and operating under any specified load condition. It accounts implicitly for the stator winding current waveform and the effect of stator slot openings. The 2-D field analysis, in polar coordinates, combines the armature reaction field component, derived from an analytical determination of the relative temporal and spatial position of the two field components. The predicted open-circuit, armature-reaction, and load field distributions all show excellent agreement with results from corresponding finite element analyses. >

Induction of Nonphotochemical Energy Dissipation and Absorbance Changes in Leaves (Evidence for Changes in the State of the Light-Harvesting System of Photosystem II in Vivo)

Abstract: Simultaneous measurements of nonphotochemical quenching of chlorophyll fluorescence and absorbance changes in the 400- to 560-nm region have been made following illumination of dark-adapted leaves of the epiphytic bromeliad Guzmania monostachia. During the first illumination, an absorbance change at 505 nm occurred with a half-time of 45 s as the leaf zeaxanthin content rose to 14% of total leaf carotenoid. Selective light scattering at 535 nm occurred with a half-time of 30 s. During a second illumination, following a 5-min dark period, quenching and the 535-nm absorbance change occurred more rapidly, reaching a maximum extent within 30 s. Nonphotochemical quenching of chlorophyll fluorescence was found to be linearly correlated to the 535-nm absorbance change throughout. Examination of the spectra of chlorophyll fluorescence emission at 77 K for leaves sampled at intervals during this regime showed selective quenching in the light-harvesting complexes of photosystem II (LHCII). The quenching spectrum of the reversible component of quenching had a maximum at 700 nm, indicating quenching in aggregated LHCII, whereas the irreversible component represented a quenching of 680-nm fluorescence from unaggregated LHCII. It is suggested that this latter process, which is associated with the 505-nm absorbance change and zeaxanthin formation, is indicating a change in state of the LHCII complexes that is necessary to amplify or activate reversible pH-dependent energy dissipation, which is monitored by the 535-nm absorbance change. Both of the major forms of nonphotochemical energy dissipation in vivo are therefore part of the same physiological photoprotective process and both result from alterations in the LHCII system.

The radio structures of southern 2-Jy radio sources

Abstract: A subsample of the Wall & Peacock 2-Jy sample of radio sources, with redshift z<0.7 or unknown and declination δ<+10°, has been selected and observed in the radio at 6 cm (or information was obtained from the literature where appropriate) and in the optical with low-dispersion spectroscopy. Here we present the new radio data. We observed 66 sources with the Very Large Array and seven southern sources with the Australia Telescope Compact Array. Together with the data collected from the literature, we now have information about the radio structure of 107 sources. These data will be discussed along with optical spectra for the sample in a future paper