18 resultados para retardation
em Aston University Research Archive
Resumo:
The exchange of proteins and lipids between the trans-Golgi network (TGN) and the endosomal system requires multiple cellular machines, whose activities are coordinated in space and time to generate pleomorphic, tubulo-vesicular carriers that deliver their content to their target compartments. These machines and their associated protein networks are recruited and/or activated on specific membrane domains where they select proteins and lipids into carriers, contribute to deform/elongate and partition membrane domains using the mechanical forces generated by actin polymerization or movement along microtubules. The coordinated action of these protein networks contributes to regulate the dynamic state of multiple receptors recycling between the cell surface, endosomes and the TGN, to maintain cell homeostasis as exemplified by the biogenesis of lysosomes and related organelles, and to establish/maintain cell polarity. The dynamic assembly and disassembly of these protein networks mediating the exchange of membrane domains between the TGN and endosomes regulates cell-cell signalling and thus the development of multi-cellular organisms. Somatic mutations in single network components lead to changes in transport dynamics that may contribute to pathological modifications underlying several human diseases such as mental retardation.
Resumo:
Changes in DHPR activity in those aged 12 and under with a variety of mental disorders were investigated using dried blood spots on Guthrie cards. DHPR activity was found to be lowered in autism and Rett's syndrome. DHPR activity was unaffected in non specific mental retardation suggesting that the deficit seen in autism and Rett's syndrome does not arise secondary to the mental dysfunction. In Down's syndrome blood biopterin levels correlated with blood spot DHPR activity. Human brain BH4 synthetic activity was investigated in aging and senile dementia of the Alzheimer type (SDAT). BH4 synthetic activity and DHPR activity decline with age in non-demented controls. In SDAT, decreases in BH4 synthetic activity were seen in temporal and visual cortices and locus coeruleus. The site of the defect is probably at 6-pyruvoyl-tetrahydropterin synthase. Aluminium inhibits human brain BH4 synthesis in vitro and produces an `Alzheimeresque' pattern of abnormalities in rats chronically exposed to the acetate salt in drinking water. Aluminium appears to chiefly affect enzymes requiring a metal ion cofactor. Aluminium induced inhibition of BH4 synthesis can be reversed by treatment with transferrin, an aluminium chelator. Transferrin treatment improves BH4 synthetic activity in SDAT brains whilst having no effect on controls, further implicating aluminium as the key neurotoxin in SDAT. Lithium inhibits human brain BH4 synthesis in vitro and lowers rat brain total biopterins and inhibits rat brain BH4 synthesis on chronic exposure to the carbonate salt in drinking water. A possible mechanism for the anti-manic actions of lithium is suggested. Monoamine oxidase inhibitors decrease human brain BH4 synthetic activity in vitro. 5-methyl-tetrahydrofolate had no effect on human brain BH4 synthesis in vitro but methionine increased BH4 synthesis in vitro. Oxotremorine is a potent inhibitor of BH4 synthesis in man and the rat. This may prove useful as a tool for modelling BH4 deficiency.
Resumo:
Investigations concentrated on the styrene butadiene rubber (SBR) latex and formulations included standard carboxylated and special carboxylated latexes. The aqueous component, containing the stabilisers and antifoaming agent but not the polymer solids, was also used. For comparison, limited investigations were carried out using other polymer types e.g. acrylic, ethylene-vinyl acetate (EVA), and redispersible powders rather than emulsions. The major findings were: 1) All latex systems investigated acted as retarders for cement hydration. The extent of retardation depends on the type of polymer. The mechanism for cement hydration may be changed, and excessive retardation influences properties. 2) Polymer modified cements exhibited either similar or coarser pore structures compared with unmodified cements. Results suggest that polymer mainly exists in a mixture of cement hydrates and polymer phase. Very little evidence was found for the formation of a distinct polymer film phase. 3) During the first few days of curing the polymer solids are removed from the pore solution and concentrations of OH-, Na+ and K+ are reduced. These observations are probably a result of polymer-cement surface interactions since there was no evidence of any chemical reactions or degradation of the polymer. 4) Improved diffusional resistance of modified cements depends on the ability to achieve adequate workability at low w/c ratio, rather than modification of matrix structure.
Resumo:
The need to measure the response of the oculomotor system, such as ocular accommodation, accurately and in real-world environments is essential. New instruments have been developed over the past 50 years to measure eye focus including the extensively utilised and well validated Canon R-1, but in general these have had limitations such as a closed field-of-view, a poor temporal resolution and the need for extensive instrumentation bulk preventing naturalistic performance of environmental tasks. The use of photoretinoscopy and more specifically the PowerRefractor was examined in this regard due to its remote nature, binocular measurement of accommodation, eye movement and pupil size and its open field-of-view. The accuracy of the PowerRefractor to measure refractive error was on averaging similar, but more variable than subjective refraction and previously validated instrumentation. The PowerRefractor was found to be tolerant to eye movements away from the visual axis, but could not function with small pupil sizes in brighter illumination. The PowerRefractor underestimated the lead of accommodation and overestimated the slope of the accommodation stimulus response curve. The PowerRefractor and the SRW-5000 were used to measure the oculomotor responses in a variety of real-world environment: spectacles compared to single vision contract lenses; the use of multifocal contact lenses by pre-presbyopes (relevant to studies on myopia retardation); and ‘accommodating’ intraocular lenses. Due to the accuracy concerns with the PowerRefractor, a purpose-built photoretinoscope was designed to measure the oculomotor response to a monocular head-mounted display. In conclusion, this thesis has shown the ability of photoretinoscopy to quantify changes in the oculomotor system. However there are some major limitations to the PowerRefractor, such as the need for individual calibration for accurate measures of accommodation and vergence, and the relatively large pupil size necessary for measurement.
Resumo:
The present thesis tested the hypothesis of Stanovich, Siegel, & Gottardo (1997) that surface dyslexia is the result of a milder phonological deficit than that seen in phonological dyslexia coupled with reduced reading experience. We found that a group of adults with surface dyslexia showed a phonological deficit that was commensurate with that shown by a group of adults with phonological dyslexia (matched for chronological age and verbal and non-verbal IQ) and normal reading experience. We also showed that surface dyslexia cannot be accounted for by a semantic impairment or a deficit in the verbal learning and recall of lexical-semantic information (such as meaningful words), as both dyslexic subgroups performed the same. This study has replicated the results of our published study that surface dyslexia is not the consequence of a mild retardation or reduced learning opportunities but a separate impairment linked to a deficit in written lexical learning, an ability needed to create novel lexical representations from a series of unrelated visual units, which is independent from the phonological deficit (Romani, Di Betta, Tsouknida & Olson, 2008). This thesis also provided evidence that a selective nonword reading deficit in developmental dyslexia persists beyond poor phonology. This was shown by finding a nonword reading deficit even in the presence of normal regularity effects in the dyslexics (when compared to both reading and spelling-age matched controls). A nonword reading deficit was also found in the surface dyslexics. Crucially, this deficit was as strong as in the phonological dyslexics despite better functioning of the sublexical route for the former. These results suggest that a nonword reading deficit cannot be solely explained by a phonological impairment. We, thus, suggested that nonword reading should also involve another ability relating to the processing of novel visual orthographic strings, which we called 'orthographic coding'. We then investigated the ability to process series of independent units within multi-element visual arrays and its relationship with reading and spelling problems. We identified a deficit in encoding the order of visual sequences (involving both linguistic and nonlinguistic information) which was significantly associated with word and nonword processing. More importantly, we revealed significant contributions to orthographic skills in both dyslexic and control individuals, even after age, performance IQ and phonological skills were controlled. These results suggest that spelling and reading do not only tap phonological skills but also order encoding skills.
Resumo:
FULL TEXT: Like many people one of my favourite pastimes over the holiday season is to watch the great movies that are offered on the television channels and new releases in the movie theatres or catching up on those DVDs that you have been wanting to watch all year. Recently we had the new ‘Star Wars’ movie, ‘The Force Awakens’, which is reckoned to become the highest grossing movie of all time, and the latest offering from James Bond, ‘Spectre’ (which included, for the car aficionados amongst you, the gorgeous new Aston Martin DB10). It is always amusing to see how vision correction or eye injury is dealt with by movie makers. Spy movies and science fiction movies have a freehand to design aliens with multiples eyes on stalks or retina scanning door locks or goggles that can see through walls. Eye surgery is usually shown in some kind of day case simplified laser treatment that gives instant results, apart from the great scene in the original ‘Terminator’ movie where Arnold Schwarzenegger's android character encounters an injury to one eye and then proceeds to remove the humanoid covering to this mechanical eye over a bathroom sink. I suppose it is much more difficult to try and include contact lenses in such movies. Although you may recall the film ‘Charlie's Angels’, which did have a scene where one of the Angels wore a contact lens that had a retinal image imprinted on it so she could by-pass a retinal scan door lock and an Eddy Murphy spy movie ‘I-Spy’, where he wore contact lenses that had electronic gadgetry that allowed whatever he was looking at to be beamed back to someone else, a kind of remote video camera device. Maybe we aren’t quite there in terms of devices available but these things are probably not the behest of science fiction anymore as the technology does exist to put these things together. The technology to incorporate electronics into contact lenses is being developed and I am sure we will be reporting on it in the near future. In the meantime we can continue to enjoy the unrealistic scenes of eye swapping as in the film ‘Minority Report’ (with Tom Cruise). Much more closely to home, than in a galaxy far far away, in this issue you can find articles on topics much nearer to the closer future. More and more optometrists in the UK are becoming registered for therapeutic work as independent prescribers and the number is likely to rise in the near future. These practitioners will be interested in the review paper by Michael Doughty, who is a member of the CLAE editorial panel (soon to be renamed the Jedi Council!), on prescribing drugs as part of the management of chronic meibomian gland dysfunction. Contact lenses play an active role in myopia control and orthokeratology has been used not only to help provide refractive correction but also in the retardation of myopia. In this issue there are three articles related to this topic. Firstly, an excellent paper looking at the link between higher spherical equivalent refractive errors and the association with slower axial elongation. Secondly, a paper that discusses the effectiveness and safety of overnight orthokeratology with high-permeability lens material. Finally, a paper that looks at the stabilisation of early adult-onset myopia. Whilst we are always eager for new and exciting developments in contact lenses and related instrumentation in this issue of CLAE there is a demonstration of a novel and practical use of a smartphone to assisted anterior segment imaging and suggestions of this may be used in telemedicine. It is not hard to imagine someone taking an image remotely and transmitting that back to a central diagnostic centre with the relevant expertise housed in one place where the information can be interpreted and instruction given back to the remote site. Back to ‘Star Wars’ and you will recall in the film ‘The Phantom Menace’ when Qui-Gon Jinn first meets Anakin Skywalker on Tatooine he takes a sample of his blood and sends a scan of it back to Obi-Wan Kenobi to send for analysis and they find that the boy has the highest midichlorian count ever seen. On behalf of the CLAE Editorial board (or Jedi Council) and the BCLA Council (the Senate of the Republic) we wish for you a great 2016 and ‘may the contact lens force be with you’. Or let me put that another way ‘the CLAE Editorial Board and BCLA Council, on behalf of, a great 2016, we wish for you!’
Resumo:
Book revew: Marketinggeschichte: die Genese einer modernen Sozialtechnik [Marketing history: The genesis of a modern social technique], edited by Hartmut Berghoff, Frankfurt/Main, Campus Verlag, 2007, 409 pp., illus., [euro]30.00 (paperback), ISBN 978-3-593-38323-1. This edited volume is the result of a workshop at Göttingen University in 2006 and combines a number of different approaches to the research into the history of marketing in Germany's economy and society. The majority of contributions loosely focus around the occurrence of a ‘marketing revolution’ in the 1970s, which ties in with interpretations of the Americanisation of German business. This revolution replaced the indigenous German idea of Absatzwirtschaft (the economics of sales) with the American-influenced idea of Marketing, which was less functionally oriented and more strategic, and which aimed to connect processes within the firm in order to allow a greater focus on the consumer. The entire volume is framed by Hartmut Berghoff's substantial and informative introduction, which introduces a number of actors and trends beyond the content of the volume. Throughout the various contributions, authors provide explanations of the timing and nature of marketing revolutions. Alexander Engel identifies an earlier revolution in the marketing of dyes, which undergoes major change with the emergence of chemical dyes. While the natural dyestuff had been a commodity, with producers removed from consumers via a global network of traders, chemical dyes were products and were branded at an early stage. This was a fundamental change in the nature of production and sales. As Roman Rossfeld shows in his contribution on the Swiss chocolate industry (which focuses almost exclusively on Suchard), even companies that produced non-essential consumer goods which had always required some measure of labelling grappled for years with the need to develop fewer and higher impact brands, as well as an efficient sales operation. A good example for the classical ‘marketing revolution’ of the 1970s is the German automobile industry. Ingo Köhler convincingly argues that the crisis situation of German car manufacturers – the change from a seller's to a buyer's market, appreciation of the German mark which undermines exports, the oil crises coupled with higher inflation and greater frugality of consumers and the emergence of new competitors – lead companies to refocus from production to the demands of the consumer. While he highlights the role of Ford in responding most rapidly to these problems, he does not address whether the multinational was potentially transferring American knowledge to the German market. Similarly, Paul Erker illustrates that a marketing revolution in transport and logistics happened much later, because the market remained highly regulated until the 1980s. Both Paul Erker and Uwe Spiekermann in their contribution, present comparisons of two different sectors or companies (the tire manufacturer Continental and the logistics company Dachser, and agriculture and trade, respectively). In both cases, however, it remains unclear why these examples were chosen for comparison, as both seem to have little in common and are not always effectively used to demonstrate differences. The weakest section of the book is the development of marketing as an academic discipline. The attempt at sketching the phases in the evolution of marketing as an academic discipline by Ursula Hansen and Matthias Bode opens with an undergraduate-level explanation on the methodology of historical periodisation that seems extraneous. Considerably stronger is the section on the wider societal impact of marketing, and Anja Kruke shows how the new techniques of opinion research was accepted by politics and business – surprisingly more readily by politicians than their commercial counterparts. In terms of contemporary personalities, Hans Domizlaff emerges as one fascinating figure of German marketing history, which several contributors refer to and whose career as the German cigarette manufacturer Reemtsma is critically analysed by Tino Jacobs. Domizlaff was Germany's own ‘marketing guru’, whose successful campaigns led to the wide-ranging reception of his ideas about the nature of good branding and marketing. These are variously described as intuitive, elitist, and sachlich, a German concept of a sober, fact-based, and ‘no frills’ approach. Domizlaff did not believe in market research. Rather, he saw the genius of the individual advertiser as key to intuitively ascertaining the people's moods, wishes, and desires. This seems to have made him peculiarly suited to the tastes of the German middle class, according to Thomas Mergel's contribution on the nature of political marketing in the republic. Especially in politics, any form of hard sales tactics were severely frowned upon and considered to demean the citizen as incapable of making an informed choice, a mentality that he dates back to the traditions of nineteenth-century liberalism. Part of this disdain of ‘selling politics like toothpaste’ was also founded on the highly effective use of branding by the National Socialists, who identified their party through the use of an increasingly standardised image of Adolf Hitler and the swastika. Alexander Schug extends on previous research that criticised the simplistic notion of Hitler's charisma as the only explanation of the popular success and distances his approach from those who see it in terms of propaganda and demagogy. He argues that the NSDAP used the tools of advertising and branding precisely because they had to introduce their new ideology into a political marketplace dominated by more established parties. In this they were undoubtedly successful, more so than they intended: as bakers sold swastika cookies and butchers formed Führer heads out of lard, the NSDAP sought to regain control over the now effectively iconic images that constituted their brand, which was in danger of being trivialised and devalued. Key to understanding the history of marketing in Germany is on the one hand the exchange of ideas with the United States, and on the other the impact of national-socialist policies, and the question whether they were a force of modernisation or retardation. The general argument in the volume appears to favour the latter explanation. In the 1930s, some of the leading marketing experts emigrated to the USA, leaving German academia and business isolated. The aftermath of the Second World War left a country that needed to increase production to satisfy consumer demand, and there was little interest in advanced sales techniques. Although the Nazis were progressive in applying new marketing methods to their political campaign, this retarded the adoption of sales techniques in politics for a long time. Germany saw the development of idiosyncratic approaches by people like Domizlaff in the 1930s and 1940s, when it lost some leading thinkers, and only engaged with American marketing conceptions in the 1960s and 1970s, when consumers eventually became more important than producers.
Resumo:
Age-Related Macular Degeneration (AMD) is the UK’s leading cause of severe visual impairment amongst the elderly. It accounts for 16,000 blind/partial sight registrations per year and is the leading cause of blindness among people aged 55 years and older in western countries (Bressler, 2004). Our research aims to design and develop a self-monitoring, ability-reactive technology (SMART) for users with AMD to support their dietary-based AMD risk mitigation and progression retardation over time. In this paper, we reflect on our experience of adapting and applying a participatory design (PD) approach to support the effective design of our application with and for older adults with AMD. We introduce the outcome of a series of PD sessions with older adults with AMD - that is, a paper prototype of our proposed application which focuses on accessibility for our target users - and discuss implications for the eventual prototype development
Resumo:
Purpose: To describe the electroclinical features of subjects who presented with a photosensitive benign myoclonic epilepsy in infancy (PBMEI). Methods: The patients were selected from a group of epileptic subjects with seizure onset in infancy or early childhood. Inclusion criteria were the presence of photic-induced myoclonic seizures and a favorable outcome. Cases with less than 24 month follow up were excluded from the analysis. Results: Eight patients were identified (4 males, 4 females). Personal history was uneventful. All of them had familial antecedents of epilepsy. Psychomotor development was normal in 6 cases, both before and after seizure onset. One patient showed a mild mental retardation and a further patient showed some behavioral disturbances. Neuroradiological investigations, when performed (5 cases), gave normal results. The clinical manifestations were typical and could vary from upward movements of the eyes to myoclonic jerks of the head and shoulders, isolated or briefly repetitive, never causing a fall. Age of onset was between 11 months and 3 years and 2 months. Characteristically, the seizures were always triggered by photic stimulation. Non photo-induced spontaneous myoclonic attacks were reported in 2 cases during the follow-up. Other types of seizures were present at follow-up in 2 cases. The outcome was favorable, even if, usually, seizure control required high AED plasma levels. Since the clinical symptoms were not recognized early, some patients were treated only many years after the onset of symptoms. Conclusion: Among BMEI patients, our cases constitute a subgroup in which myoclonic jerks were always triggered by photostimulation, in particular at onset of their epilepsy. © 2006 International League Against Epilepsy.
Resumo:
The effect of brittle coating precracking on the fatigue behavior of a high-activity aluminide-coated single-crystal nickel-base superalloy has been studied using hollow cylindrical specimens at test temperatures of 600 °C, 800 °C, and 1000 °C. Three types of precrack were studied: narrow precracks formed at room temperature, wide precracks formed at room temperature, and narrow precracks formed at elevated temperature. The effect of precracking on fatigue life at 600 °C was found to depend strongly on the type of precrack. No failure was observed for specimens with narrow room-temperature precracks because of crack arrest via an oxidation-induced crack closure mechanism, while the behavior of wide precracks and precracks formed at elevated temperature mirrored the non-precracked behavior. Crack retardation also occurred for narrow room-temperature precracks tested at 800 °C - in this case, fatigue cracks leading to failure initiated in a layer of recrystallized grains on the inside surface of the specimen. A significant reduction in fatigue life at 800 °C relative to non-precracked specimens was observed for wide precracks and elevated temperature precracks. The presence of precracks bypassed the initiation and growth of coating fatigue cracks necessary for failure in non-precracked material. No effect of precracking was observed at 1000 °C.
Resumo:
Fatigue crack initiation and propagation in duplex stainless steels are strongly affected by microstructure in both inert and aggressive environments. Fatigue crack growth rates in wrought Zeron 100 duplex stainless steel in air were found to vary with orientation depending on the frequency of crack tip retardation at ferrite/austenite grain boundaries. Fatigue crack propagation rates in 3.5% NaCl solution and high purity water are increased by hydrogen assisted transgranular cyclic cleavage of the ferrite. The corrosion fatigue results are interpreted using a model for the cyclic cleavage mechanism.
Resumo:
The fatigue crack propagation behaviour of a low alloy, boron-containing steel has been examined after austenitizing at 900°C or 1250°C and tempering at a range of temperatures up to 400°C. Fatigue threshold values were found to vary with austenitizing and tempering treatment in a range between 3.3 to 6 MPa √m when tested at a stress ratio (R) of 0.2. Crack propagation rates in the Paris regime were insensitive to heat treatment variations. The crack propagation path was essentially transgranular in all conditions with small regions of intergranular facets appearing at growth rates around the knee of the da/dN vs ΔK curve. The crack front shape showed marked retardation in the centre of the specimen at low tempering temperatures. Experimental determinations and computer predictions of residual stress levels in the specimens indicated that this was due to a central residual compressive stress resulting from differential cooling rates and the volume change associated with the martensite transformation. The results are discussed in terms of microstructural and residual stress effects on fatigue behaviour. © 1987.